EP4673320A1 - Tire tread rubber composition and related methods - Google Patents

Tire tread rubber composition and related methods

Info

Publication number
EP4673320A1
EP4673320A1 EP24715973.4A EP24715973A EP4673320A1 EP 4673320 A1 EP4673320 A1 EP 4673320A1 EP 24715973 A EP24715973 A EP 24715973A EP 4673320 A1 EP4673320 A1 EP 4673320A1
Authority
EP
European Patent Office
Prior art keywords
phr
tire tread
rubber composition
parts
tan
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
EP24715973.4A
Other languages
German (de)
French (fr)
Inventor
Takuya OGASAWARA
Kenny L. HOWMAN
Benjamin C. GALIZIO
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Bridgestone Americas Tire Operations LLC
Original Assignee
Bridgestone Americas Tire Operations LLC
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Bridgestone Americas Tire Operations LLC filed Critical Bridgestone Americas Tire Operations LLC
Publication of EP4673320A1 publication Critical patent/EP4673320A1/en
Pending legal-status Critical Current

Links

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60C—VEHICLE TYRES; TYRE INFLATION; TYRE CHANGING; CONNECTING VALVES TO INFLATABLE ELASTIC BODIES IN GENERAL; DEVICES OR ARRANGEMENTS RELATED TO TYRES
    • B60C1/00—Tyres characterised by the chemical composition or the physical arrangement or mixture of the composition
    • B60C1/0016—Compositions of the tread

Definitions

  • the present application is directed to tire tread rubber compositions and related methods.
  • Tires comprise many components including a road-contacting tread.
  • the particular ingredients used to prepare the rubber composition which comprises the tire tread may vary.
  • Formulation of tire tread rubber compositions is a complex science since changes to the formulation which result in an improvement in one property (e.g., wet performance) may result in deterioration of another property (e.g., dry traction).
  • a tire tread rubber composition is disclosed.
  • the composition is made of ingredients comprising: (a) 100 parts of an elastomer component comprising (i) 35-55 parts, preferably 35-49 parts, more preferably 40-49 parts of at least one styrene-butadiene rubber having a Tg of about -30 to about -50 °C, (ii) 45-65 parts, preferably 51- 65 parts, more preferably 51-60 parts of polybutadiene rubber having a cis bond content of at least 95%, a Tg of less than -101 °C, preferably -101 to -110 °C, and a silica-reactive functional group; (b) 70-99 phr of at least one reinforcing silica filler having a surface area of about 100 to about 300 m 2 /g, preferably about 150 to about 300 m 2 /g; (c) no more than 15 phr of carbon black, preferably no more than
  • a tire tread rubber composition is disclosed.
  • the composition is made of ingredients comprising: (a) 100 parts of an elastomer component comprising (i) 35-49 parts, preferably 40-49 parts, of at least one styrene-butadiene rubber having a Tg of about -30 to about -50 °C and a silica-reactive functional group, (ii) 51-65 parts, preferably 51-60 parts, of polybutadiene rubber having a cis bond content of at least 95%, a Tg of less than -101 °C, preferably -101 to -110 °C, and a silica-reactive functional group; (b)70-99 phr of at least one reinforcing silica filler having a surface area of about 100 to about 300 m 2 /g, preferably about 150 to about 300 m 2 /g; (c) no more than 15 phr of carbon black, preferably no more than 10 p
  • a tire tread rubber composition is disclosed.
  • the composition is made of ingredients comprising: (a) 100 parts of an elastomer component comprising (i) 35-55 parts, preferably 35-49 parts, more preferably 40-49 parts of at least one styrene-butadiene rubber having a Tg of about -30 to about -50 °C, (ii) 45-65 parts, preferably 51-65 parts, more preferably 51-60 parts of polybutadiene rubber having a cis bond content of at least 95%, a Tg of less than -101 °C, preferably -101 to - 110 °C, and a silica-reactive functional group; (b) 70-99 phr of at least one reinforcing silica filler having a surface area of about 100 to about 300 m 2 /g, preferably about 150 to about 300 m 2 /g; (c) no
  • the tire tread rubber composition has a value for tan 6 at 60 °C of 0.18 to 0.25, preferably 0.18 to 0.22, more preferably 0.18 to 0.2, and meets at least one of the following: (a) has a value for tan 6 at -30 °C of no more than 2.5 times the tan 6 at 60 °C value, preferably between 2.5 times and 2 times the tan 6 at 60 °C value; (b) has a value for tan 6 at 30 °C of at least 1.4 times the tan 6 at 60 °C value, preferably between 1.4 times and 2 times the tan 6 at 60 °C value, more preferably between 1.5 times and 1.8 times the tan 6 at 60 °C value; or (c) has a value for tan 6 at 0 °C of at least 2.2 times the tan 6 at 60 °C value, preferably between 2.2 times and 3 times the tan 6 at 60 °C value, more preferably between
  • a tire tread rubber composition is disclosed.
  • the composition is made of ingredients comprising: (a) 100 parts of an elastomer component comprising (i) 35-49 parts, preferably 40-49 parts, of at least one styrene-butadiene rubber having a Tg of about -30 to about -50 °C and a silicareactive functional group, (ii) 51-65 parts, preferably 51-60 parts, of polybutadiene rubber having a cis bond content of at least 95%, a Tg of less than -101 °C, preferably -101 to -110 °C, and a silica-reactive functional group; (b) 70-99 phr of at least one reinforcing silica filler having a surface area of about 100 to about 300 m 2 /g, preferably about 150 to about 300 m 2 /g; (c) no more than 15 p
  • the tire tread rubber composition has a value for tan 6 at 60 °C of 0.18 to 0.25, preferably 0.18 to 0.22, more preferably 0.18 to 0.2, and meets at least one of the following: (a) has a value for tan 6 at -30 °C of no more than 2.5 times the tan 6 at 60 °C value, preferably between 2.5 times and 2 times the tan 6 at 60 °C value; (b) has a value for tan 6 at 30 °C of at least 1.4 times the tan 6 at 60 °C value, preferably between 1.4 times and 2 times the tan 6 at 60 °C value, more preferably between 1.5 times and 1.8 times the tan 6 at 60 °C value; or (c) has a value for tan 6 at 0 °C of at least 2.2 times the tan 6 at 60 °C value, preferably between 2.2 times and 3 times the tan 6 at 60 °C value, more preferably between
  • a tire tread rubber composition is disclosed.
  • the composition is made of ingredients comprising: (a) 100 parts of an elastomer component comprising (i) 35-55 parts, preferably 35-49 parts, more preferably 40-49 parts of at least one styrene-butadiene rubber having a Tg of about -30 to about -50 °C, (ii) 45-65 parts, preferably 51- 65 parts, more preferably 51-60 parts of polybutadiene rubber having a cis bond content of at least 95%, a Tg of less than -101 °C, preferably -101 to -110 °C, and a silica-reactive functional group; (b) 70-99 phr of at least one reinforcing silica filler having a surface area of about 100 to about 300 m 2 /g, preferably about 150 to about 300 m 2 /g; (c) no more than 15 phr of carbon black, preferably no more than
  • a tire tread rubber composition is disclosed.
  • the composition is made of ingredients comprising: (a) 100 parts of an elastomer component comprising (i) 35-49 parts, preferably 40-49 parts, of at least one styrene-butadiene rubber having a Tg of about -30 to about -50 °C and a silica-reactive functional group, (ii) 51-65 parts, preferably 51-60 parts, of polybutadiene rubber having a cis bond content of at least 95%, a Tg of less than -101 °C, preferably -101 to -110 °C, and a silica-reactive functional group; (b)70-99 phr of at least one reinforcing silica filler having a surface area of about 100 to about 300 m 2 /g, preferably about 150 to about 300 m 2 /g; (c) no more than 15 phr of carbon black, preferably no more than 10 p
  • (e) is 36-54 phr, preferably 40-50 phr.
  • a tire tread rubber composition is disclosed.
  • the composition is made of ingredients comprising: (a) 100 parts of an elastomer component comprising (i) 35-55 parts, preferably 35-49 parts, more preferably 40-49 parts of at least one styrene-butadiene rubber having a Tg of about -30 to about -50 °C, (ii) 45-65 parts, preferably 51-65 parts, more preferably 51-60 parts of polybutadiene rubber having a cis bond content of at least 95%, a Tg of less than -101 °C, preferably -101 to - 110 °C, and a silica-reactive functional group; (b) 70-99 phr of at least one reinforcing silica filler having a surface area of about 100 to about 300 m 2 /g, preferably about 150 to about 300 m 2 /g; (c) no
  • the tire tread rubber composition has a value for tan 6 at 60 °C of 0.18 to 0.25, preferably 0.18 to 0.22, more preferably 0.18 to 0.2, and meets at least one of the following: (a) has a value for tan 6 at -30 °C of no more than 2.5 times the tan 6 at 60 °C value, preferably between 2.5 times and 2 times the tan 6 at 60 °C value; (b) has a value for tan 6 at 30 °C of at least 1.4 times the tan 6 at 60 °C value, preferably between 1.4 times and 2 times the tan 6 at 60 °C value, more preferably between 1.5 times and 1.8 times the tan 6 at 60 °C value; or (c) has a value for tan 6 at 0 °C of at least 2.2 times the tan 6 at 60 °C value, preferably between 2.2 times and 3 times the tan 6 at 60 °C value, more preferably between
  • a tire tread rubber composition is disclosed.
  • the composition is made of ingredients comprising: (a) 100 parts of an elastomer component comprising (i) 35-49 parts, preferably 40-49 parts, of at least one styrene-butadiene rubber having a Tg of about -30 to about -50 °C and a silicareactive functional group, (ii) 51-65 parts, preferably 51-60 parts, of polybutadiene rubber having a cis bond content of at least 95%, a Tg of less than -101 °C, preferably -101 to -110 °C, and a silica-reactive functional group; (b) 70-99 phr of at least one reinforcing silica filler having a surface area of about 100 to about 300 m 2 /g, preferably about 150 to about 300 m 2 /g; (c) no more than 15 p
  • the tire tread rubber composition has a value for tan 6 at 60 °C of 0.18 to 0.25, preferably 0.18 to 0.22, more preferably 0.18 to 0.2, and meets at least one of the following: (a) has a value for tan 6 at -30 °C of no more than 2.5 times the tan 6 at 60 °C value, preferably between 2.5 times and 2 times the tan 6 at 60 °C value; (b) has a value for tan 6 at 30 °C of at least 1.4 times the tan 6 at 60 °C value, preferably between 1.4 times and 2 times the tan 6 at 60 °C value, more preferably between 1.5 times and 1.8 times the tan 6 at 60 °C value; or (c) has a value for tan 6 at 0 °C of at least 2.2 times the tan 6 at 60 °C value, preferably between 2.2 times and 3 times the tan 6 at 60 °C value, more preferably between
  • Mn is used for number average molecular weight.
  • Mp is used for peak molecular weight.
  • Mw is used for weight average molecular weight.
  • Mooney viscosity refers to the Mooney viscosity, M LI+4. As those of skill in the art will understand, a rubber composition's Mooney viscosity is measured prior to vulcanization or curing.
  • natural rubber means naturally occurring rubber such as can be harvested from sources such as Hevea rubber trees and non-/7eveo sources (e.g., guayule shrubs and dandelions such as TKS).
  • sources such as Hevea rubber trees and non-/7eveo sources (e.g., guayule shrubs and dandelions such as TKS).
  • natural rubber should be construed so as to exclude synthetic polyisoprene.
  • the term “phr” means parts per one hundred parts rubber.
  • the one hundred parts rubber is also referred to herein as 100 parts of an elastomer component.
  • polyisoprene means synthetic polyisoprene.
  • the term is used to indicate a polymer that is manufactured from isoprene monomers, and should not be construed as including naturally occurring rubber (e.g., Hevea natural rubber, guayule-sourced natural rubber, or dandelion-sourced natural rubber).
  • polyisoprene should be construed as including polyisoprenes manufactured from natural sources of isoprene monomer.
  • the term "tread,” refers to both the portion of a tire that comes into contact with the road under normal inflation and load as well as any subtread.
  • the first-fourth embodiments disclosed herein are directed to tire tread rubber compositions made of specified ingredients.
  • the subject rubber compositions are used in preparing treads for tires, generally by a process which includes forming of a tread pattern by molding and curing one of the subject rubber compositions.
  • the tire treads will contain a cured form of one of the tire tread rubber compositions.
  • the tire tread rubber compositions may be present in the form of a tread which has been formed but not yet incorporated into a tire and/or they may be present in a tread which forms part of a tire.
  • the Tg of the overall rubber composition may vary.
  • the Tg of the overall rubber composition may be referred to as a compound Tg or as a rubber composition Tg.
  • the rubber composition has a compound Tg of -40 to -60 °C (e.g., -40, -42, -44, - 45, -46, -48, -50, -52, -54, -55, -56, -58, -60, -62, -64, -65, -66, -68, or -70 °C ), -50 to -70 °C (e.g., -50, -52, -54, -55, -56, -58, -60, -62, -64, -66, -68, or -70 °C ), -45 to -65 °C (e.g, -
  • the compound Tg of a rubber composition can be measured using a dynamic mechanical thermal spectrometer (such as the Gabo instrument described below, operating in tension mode) generally following the guidelines of ASTM D5992-96 (2011) and using a temperature sweep (from -70 to 65 °C), under specified test conditions (i.e., frequency 52 Hz, static strain of 6%, dynamic strain of 0.1%, sample geometry 4.75 mm wide x 29 mm long x 2 mm deep), with the measurement made on the sample after curing for 15 minutes at 170 °C, and using a vibratory method to estimate the Tg from the curve that results.
  • a dynamic mechanical thermal spectrometer such as the Gabo instrument described below, operating in tension mode
  • the tire tread rubber composition is made of ingredients comprising (including) 100 parts of an elastomer component.
  • the ingredients of the elastomer component include styrene-butadiene rubber and polybutadiene rubber.
  • the total amount of 100 parts of elastomer or rubber is used so that the amount of other ingredients may be listed in amounts of phr or the number of parts per hundred parts of rubber (or 100 parts of the elastomer component).
  • the amount of silica filler can also be described as 110 phr.
  • the 100 parts of elastomer component comprises (includes) (i) 35-55 parts (e.g., 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, or 55 parts), preferably 35-49 parts (e.g., 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49 parts), more preferably 40-49 parts (e.g., 40, 41, 42, 43, 44, 45, 46, 47, 48, 49 parts) of at least one styrene-butadiene rubber having a Tg of about -30 to about -50 °C or -30 to -50 °C (e.g., 30, 32, 34, 35, 36, 38, 40, 42, 44, 45, 46, 48, or 50 °C), and (ii) 45-65 parts (e.
  • 35-55 parts e.g., 35, 36,
  • °C preferably -101 to - 110 °C (e.g., -101, -102, -103, -104, -105, -106, -107, -108, -109, -110 °C) and a silica-reactive functional group.
  • the 100 parts of elastomer component comprises (includes) (i) 35-49 parts (e.g., 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49 parts), preferably 40-49 parts (e.g., 40, 41, 42, 43, 44, 45, 46, 47, 48, 49 parts) of at least one styrene-butadiene rubber having a Tg of about -30 to about -50 °C or -30 to -50 °C (e.g., 30, 32, 34, 35, 36, 38, 40, 42, 44, 45, 46, 48, or 50 °C) and a silica-reactive functional group, and (ii) 51-65 parts (e.g., 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64 or 65 parts), preferably 51-60 parts (e.g)
  • the elastomer component (a) includes no more than 9 parts (e.g., 9, 8, 7, 6, 5, 4, 3, 2, 1 or even 0 parts), preferably no more than 5 parts (e.g., 5, 4, 3, 2, 1 or even 0 parts) of natural rubber, polyisoprene, or a combination thereof.
  • the elastomer component (a) includes 0 parts of natural rubber, polyisoprene, or a combination thereof. In certain embodiments of the first -fourth embodiments, an amount of no more than 9 parts refers to 1-9 parts and in other embodiments 0-9 parts. Similarly, in certain embodiments of the first-fourth embodiments, an amount of no more than 5 parts refers to 1-5 parts and in other embodiments 0-5 parts.
  • the 100 parts of elastomer component consists (only) of (i) (i.e., the at least one styrene-butadiene rubber, as specified) and (ii) (i.e., the polybutadiene rubber, as specified), in amounts as discussed above.
  • the 100 parts of elastomer component includes in addition to (i) and (ii), one or more additional rubbers (iii).
  • the amount when one or more additional rubbers (iii) is present, the amount will generally be limited preferably to no more than 20 parts (e.g., 20 parts, 15 parts, 10 parts, 5 parts, or less), more preferably no more than 15 parts (e.g., 15 parts, 10 parts, 5 parts, or less), no more than 9 parts (e.g., 9, 8, 7, 6, 5, 4, 3, 2, 1 or even 0 parts), or no more than 5 parts (e.g., 5 parts, 4 parts, 3 parts, 2 parts, 1 part, or less).
  • an amount of no more than 20 parts refers to 1-20 parts and in other embodiments 0-20 parts.
  • an amount of no more than 15 parts refers to 1-15 parts and in other embodiments 0-15 parts. In certain embodiments of the first- fourth embodiments, an amount of no more than 9 parts refers to 1-9 parts and in other embodiments 0-9 parts. In certain embodiments of the first-fourth embodiments, an amount of no more than 5 parts refers to 1-5 parts and in other embodiments 0-5 parts.
  • one or more additional rubbers (iii) are selected from diene monomer-containing rubbers; in certain such embodiments, the one or more additional rubbers (iv) are selected from the group consisting of natural rubber, polyisoprene, styrene-isoprene rubber, butadiene-isoprene rubber, styrene-isoprene-butadiene rubber, butyl rubber (both halogenated and non-halogenated), ethylene-propylene rubber (EPR), ethylenebutylene rubber (EBR), ethylene-propylene-diene rubber (EPDM), and combinations thereof.
  • EPR ethylene-propylene rubber
  • EBR ethylenebutylene rubber
  • EPDM ethylene-propylene-diene rubber
  • the one or more additional rubbers are selected from natural rubber, polyisoprene, or a combination thereof; one or more styrenebutadiene rubbers other than the styrene-butadiene rubber (i), e.g., a SBR having a Tg of greater than -30 °C (e.g., -25 °C, -20 °C, -15 °C or higher) or having a Tg of less than -50 °C (e.g., -55, -60 °C or lower); or from a polybutadiene other than the polybutadiene (ii), e.g., a polybutadiene having a low cis 1,-4 bond content (e.g., of less than 50%, less than 45%, less than 40%, etc.), a non-functionalized polybutadiene rubber having a cis bond content of at least 95% and a Tg of
  • the elastomer component of the tire tread rubber composition includes less than 10 parts (e.g., 9, 8, 7, 6, 5, 4, 3, 2, 1, or 0 parts) of non-functionalized rubber, preferably less than 5 parts (e.g., 4, 3, 2, 1, or 0 parts) of non-functionalized rubber, even more preferably 0 parts of non-functionalized rubber.
  • the at least one styrene-butadiene rubber (i) and polybutadiene rubber (ii) are both functionalized, preferably both with a silica-reactive functional group.
  • the Tg values referred to herein for elastomers represent a Tg measurement made upon the elastomer without any oil-extension.
  • the Tg values above refer to the Tg prior to oil extension or to a non-oil-extended version of the same elastomer.
  • Elastomer or polymer Tg values may be measured using a differential scanning calorimeter (DSC) instrument, such as manufactured by TA Instruments (New Castle, Delaware), where the measurement is conducted using a temperature elevation of 10°C/minute after cooling at -120 °C. Thereafter, a tangent is drawn to the base lines before and after the jump of the DSC curve. The temperature on the DSC curve (read at the point corresponding to the middle of the two contact points) can be used as Tg.
  • DSC differential scanning calorimeter
  • the average Tg of the elastomer component is -70 to -90 °C (e.g., -70, -71, -72, -73, -74, -75, -76, -77, -78, -79, -80, -81, -82, -83, -84, -85, -86, -87, -88, -89, or -90 °C), preferably -75 to -85 °C (e.g., -75, -76, -77, -78, -79, -80, -81, -82, -83, -84, or -85 °C).
  • the average Tg of the elastomer component can be calculated using the Tg of each rubber present in the 100 parts of elastomer component and accounting for their relative weight percentage.
  • the amount of rubber /.e., excluding any amount of oil
  • the Tg of the oil- extended rubber in its non-oil-extended form is utilized in calculating the average Tg of the elastomer component.
  • the elastomer component of the tire tread rubber composition includes at least one styrene-butadiene rubber (i) having a Tg of about -30 to about -50 °C or -30 to -50 °C (e.g., -30, -31, -32, -33, -34, -35, -36, - 37, -38, -39, -40, -41, -42, -43, -44, -45, -46, -47, -48, -49, or -50 °C) and according to the second and fourth embodiments, the elastomer component of the tire tread rubber composition includes at least one styrene-butadiene rubber (i) having a Tg of about -30 to about -50 °C or -30 to -50 °C (e.g., -30, -31, -32, -33, -
  • the at least one styrene- butadiene rubber (i) has a Tg of about -40 to about -50 or -40 to -50 °C (e.g., -40, -41, -42, -43, - 44, -45, -46, -47, -48, -49, or -50 °C), in an amount as discussed above.
  • the styrene monomer content (i.e., weight percent of the polymer chain comprising styrene units as opposed to butadiene units) of the at least one styrene-butadiene rubber(i), as described above, may vary.
  • the at least one styrene-butadiene rubber(i), as described above, has a styrene monomer content of about 20 to about 35% or 20 to 35% (e.g., 20%, 25%, 20%, 35%, or 35%) by weight of the total monomer content (i.e., 1,3-butadiene + styrene), including about 25 to about 35%, and 25 to 35% (e.g., 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, or 35%) by weight.
  • styrene monomer content of about 20 to about 35% or 20 to 35% (e.g., 20%, 25%, 20%, 35%, or 35%) by weight of the total monomer content (i.e., 1,3-butadiene + styrene), including about 25 to about 35%, and 25 to 35% (e.g., 25%, 26%, 27%, 28%, 29%, 30%, 31%
  • the vinyl bond content (i.e., 1,2- microstructure) of the at least one styrene-butadiene rubber(i), as described above may vary.
  • the at least one styrene-butadiene rubber(i), as discussed above has a vinyl bond content of about 35 to about 55%, 35-55% (e.g., 35%, 40%, 45%, 50%, or 55%), preferably about 40 to about 55%, 40 to 55% (e.g., 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%, or 55%), more preferably about 45 to about 50%, or 45 to 50% (e.g., 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, or 50%).
  • the at least one styrene-butadiene rubber(i), as described above, may have a vinyl bond content within one of the foregoing ranges, optionally in combination with one or more of the Mw, Mn, and/or Mw/Mn ranges discussed below, and in certain preferred embodiments optionally in combination with one of the styrene monomer contents discussed above.
  • the vinyl bond contents referred to herein should be understood as being for the overall vinyl bond content in the styrene-butadiene rubber polymer chain rather than of the vinyl bond content in the butadiene portion of the styrene-butadiene rubber polymer chain, and can be determined by H 1 -NMR and C 13 -NMR (e.g., using a 300 MHz Gemini 300 NMR Spectrometer System (Varian)).
  • the styrene contents disclosed herein can be determined using a similar method and the same instrumentation.
  • the Mw of the at least one styrene-butadiene rubber (i), as described above, may vary.
  • the at least one styrene-butadiene rubber (i) (as described above), has a Mw of about 300,000 to about 550,000 grams/mole or 300,000 to 550,000 grams/mole (e.g., 300,000; 325,000; 350,000; 375,000; 400,000; 425,000; 450,000; 475,000; 500,000; 525,000; or 550,000 grams/mole), preferably about 300,000 to about 500,000 or 300,000 to 500,000 grams/mole (e.g., 300,000; 325,000; 350,000; 375,000; 400,000; 425,000; 450,000; 475,000; or 500,000 grams/mole), more preferably about 350,000 to about 450,000 or 350,000 to 450,000 grams/mole (e.g., 350,000; 375,000;
  • the Mn of the at least one styrene-butadiene rubber (i), as described above may vary.
  • the at least one styrene-butadiene rubber (i), as described above has a Mn of about 250,000 to about 450,000 grams/mole or 250,000 to 450,000 grams/mole (e.g., 250,000; 275,000; 300,000; 325,000; 350,000; 375,000; 400,000; 425,000; or 450,000 grams/mole), preferably about 300,000 to about 400,000 grams/mole or 300,000 to 400,000 grams/mole (e.g., 300,000; 325,000; 350,000; 375,000; or 400,000 grams/mole), according to a polystyrene standard (and as determined by GPC).
  • the at least one styrenebutadiene rubber (i), as described above, is a functionalized polymer (i.e., according to the second and fourth embodiments and in preferred embodiments of the first and third embodiments), it should be understood that the foregoing Mw and Mn values refer to coupled Mw and coupled Mn rather than base polymer values.
  • the at least one styrene-butadiene rubber of (i), as described above has a Mn within one of the foregoing ranges in combination with a Mw within one of the foregoing ranges, optionally in combination with a Mw/Mn value as discussed below.
  • the Mw/Mn of the at least one styrene-butadiene rubber (i), as described above may vary.
  • the at least one styrene-butadiene rubber(i), as described above has a Mw/Mn (polydispersity) of 1.2 to 2 (e.g., 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, or 2), preferably 1.2 to 1.5 (e.g., 1.2, 1.3, 1.4, or 1.5).
  • the at least one styrene- butadiene rubber (i), as described above has a Mw/Mn within one of the foregoing ranges, in combination with at least one of the Mw ranges or Mn ranges described above, preferably in combination with one of the Mw ranges and one of the Mn ranges described above.
  • the at least one styrene-butadiene rubber (i), as described above is an oil-extended rubber, incorporating oil in an amount as discussed further below.
  • the at least one styrene-butadiene rubber (i), as described above is a non oil-extended rubber (i.e., the SBR is not extended with any oil).
  • the at least one styrene-butadiene rubber (i) having a Tg of about -30 to about -50 °C has a silica-reactive functional group.
  • a styrene-butadiene rubber having a silica-reactive functional group can be considered to be a functionalized polymer or functionalized styrene-butadiene rubber.
  • Non-limiting examples of silica-reactive functional groups generally include nitrogen-containing functional groups, silicon-containing functional groups, oxygen- or sulfur-containing functional groups, and metal-containing functional groups, as discussed in more detail below.
  • the functionalization can be achieved during preparation of the polymer by adding a functional group to one or both terminus of the polymer, by adding a functional group to the backbone of the poly (or a combination of the foregoing) or by coupling more than one polymer chains to a coupling agent, or by a combination thereof.
  • Such effects can be achieved by treating a living polymer with coupling agents, functionalizing agents, or a combination thereof which serve to couple and/or functionalize other chains.
  • the at least one styrene-butadiene rubber (i) having a silica-reactive functional group contains one or more functional groups but is not coupled (/.e., does not contain any separate coupling agent).
  • a coupling agent and/or functionalizing agent can be used at various molar ratios.
  • the functionalized styrene-butadiene rubber of (i) may be silica-reactive merely from the result of using a coupling agent.
  • certain compounds may both couple and provide the polymer chains with a functional group.
  • the ability to couple polymer chains may depend upon the amount of coupling agent reacted with the polymer chains.
  • advantageous coupling may be achieved where the coupling agent is added in a one to one ratio between the equivalents of lithium on the initiator and equivalents of leaving groups (e.g., halogen atoms) on the coupling agent.
  • Non-limiting examples of coupling agents include metal halides, metalloid halides, alkoxysilanes, alkoxystannanes, and combinations thereof.
  • the at least one styrene-butadiene rubber (i) has a silica-reactive functional group (as discussed further, infra, as functional groups) but does not include any coupling agent selected from the group consisting of metal halides, metalloid halides, alkoxysilanes, alkoxystannanes, and combinations thereof.
  • Non-limiting examples of nitrogen-containing functional groups that can be utilized in certain embodiments of the first-fourth embodiments as a silica-reactive functional group in the at least one styrene-butadiene rubber include, but are not limited to, a substituted or unsubstituted amino group, an amide residue, an isocyanate group, an imidazolyl group, an indolyl group, an imino group, a nitrile group, a pyridyl group, and a ketimine group.
  • the at least one styrene-butadiene rubber (i) has a silica-reactive functional group including, an unsubstituted amino group, a substituted amino group, or substituted imino group.
  • a silica-reactive functional group including, an unsubstituted amino group, a substituted amino group, or substituted imino group.
  • the foregoing substituted or unsubstituted amino group should be understood to include a primary alkylamine, a secondary alkylamine, or a cyclic amine, and an amino group derived from a substituted or unsubstituted imine.
  • the at least one styrene- butadiene rubber (i) of the elastomer component comprises at one silica-reactive functional group selected from the foregoing list of nitrogen-containing functional groups.
  • the at least one styrene- butadiene rubber (i) includes a silica-reactive functional group from a compound which includes nitrogen in the form of an imino group.
  • Such an imino-containing functional group may be added by reacting the active terminal of a polymer chain with a compound having the following formula (I): wherein R, R', R", and R"' each independently are selected from a group having 1 to 18 carbon atoms (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, or 18 carbon atoms) selected from the group consisting of an alkyl group, an allyl group, and an aryl group; m and n are integers of 1 to 20 (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20) and 1 to 3 (1, 2, or 3), respectively.
  • R, R', R", and R"' each independently are selected from a group having 1 to 18 carbon atoms (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, or 18 carbon atoms) selected from the group consisting of an alkyl group, an allyl group, and an
  • each of R, R', R", and R'" are preferably hydrocarbyl and contain no heteroatoms.
  • each R and R' are independently selected from an alkyl group having 1 to 6 carbon atoms (e.g., 1, 2, 3, 4, 5, or 6 carbon atoms), preferably 1 to 3 carbon atoms (e.g., 1, 2, or 3 carbon atoms).
  • m is an integer of 2 to 6 (e.g., 2, 3, 4, 5, or 6), preferably 2 to 3.
  • R'" is selected from an alkyl group having 1 to 6 carbon atoms (e.g., 1, 2, 3, 4, 5, or 6 carbon atoms), preferably 2 to 4 carbon atoms (e.g., 2, 3, or 4 carbon atoms). In certain embodiments of the first-fourth embodiments, R" is selected from an alkyl group having 1 to 6 carbon atoms (e.g., 1, 2, 3, 4, 5, or 6 carbon atoms), preferably 1 to 3 carbon atoms (e.g., 1, 2, or 3 carbon atoms), most preferably 1 carbon atom (e.g., methyl).
  • n is 3 resulting in a compound with a trihydrocarboxysilane moiety such as a trialkoxysilane moiety.
  • compounds having an imino group and meeting formula (I) above, which are suitable for providing the silica-reactive functional group for the styrene-butadiene rubber of (i) include, but are not limited to, N-(l,3-dimethylbutylidene)-3-(triethoxysilyl)-l- propaneamine, N-(l-methylethylidene)-3-(triethoxysilyl)-l-propaneamine, N-ethylidene-3- (triethoxysilyl)-l-propaneamine, N-(l-methylpropylidene)-3-(triethoxysilyl)-l-propaneamine, and N-(4-N,N-dimethylaminobenzylidene
  • Non-limiting examples of silicon-containing functional groups that can be utilized in certain embodiments of the first-fourth embodiments as a silica-reactive functional group in the at least one styrene-butadiene rubber include, but are not limited to, an organic silyl or siloxy group, and more precisely, such a functional group may be selected from an alkoxysilyl group, an alkylhalosilyl group, a siloxy group, an alkylaminosilyl group, and an a I koxyhalosilyl group.
  • the organic silyl or siloxy group may also contain one or more nitrogens.
  • Suitable silicon-containing functional groups for use in functionalizing diene-based elastomers also include those disclosed in U.S. Patent No. 6,369,167, the entire disclosure of which is herein incorporated by reference.
  • the at least one styrene-butadiene rubber (i) comprises at least one silica-reactive functional group selected from the foregoing list of silicon-containing functional groups.
  • the at least one styrenebutadiene rubber (i) includes a silica-reactive functional group which includes a silicon-containing functional group having a siloxy group (e.g., a hydrocarbyloxysilane-containing compound), wherein the compound optionally includes a monovalent group having at least one functional group.
  • a silica-reactive functional group which includes a silicon-containing functional group having a siloxy group (e.g., a hydrocarbyloxysilane-containing compound), wherein the compound optionally includes a monovalent group having at least one functional group.
  • Such a silicon-containing functional group may be added by reacting the active terminal of a polymer chain with a compound having the following formula (II): wherein A 1 represents a monovalent group having at least one functional group selected from epoxy, isocyanate, imine, cyano, carboxylic ester, carboxylic anhydride, cyclic tertiary amine, non-cyclic tertiary amine, pyridine, silazane and sulfide; R c represents a single bond or a divalent hydrocarbon group having from 1 to 20 carbon atoms (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 carbon atoms); R d represents a monovalent aliphatic hydrocarbon group having 1 to 20 carbon atoms (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 carbon atoms), a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms (e.g., 6,
  • a partial condensation product refers to a product in which a part (not all) of a SiOR group in the hydrocarbyloxysilane compound is turned into a SiOSi bond by condensation.
  • R c represents a divalent hydrocarbon group having 1 to 12 carbon atoms (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, or 12 carbon atoms), 2 to 6 carbon atoms (e.g., 2, 3, 4, 5, or 6 carbon atoms), or 2 to 3 1 carbon atoms (e.g., 2 or 3 carbon atoms);
  • R e represents a monovalent aliphatic hydrocarbon group having 1 to 12 carbon atoms (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, or 12 carbon atoms), 2 to 6 carbon atoms (e.g., 2, 3, 4, 5, or 6 carbon atoms), or 1 to 2 carbon atoms or a monovalent hydrocarbon group having 1 to 12 carbon atoms (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10,
  • the silica-reactive functional group of the at least one styrene-butadiene rubber results from a compound represented by Formula (II) wherein A 1 has at least one epoxy group.
  • Non-limiting specific examples of such compounds include 2-glycidoxyethyltrimethoxysilane, 2- glycidoxyethyltriethoxysilane, (2-glycidoxyethyl)methyldimethoxysilane, 3- glycidoxypropyltri methoxysilane, 3-glycidoxypropyltriethoxysilane, (3-glycidoxypropyl)- methyldimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 2-(3,4- epoxycyclohexyl)ethyltriethoxysilane, 2-(3,4-epoxycyclohexyl)ethyl(methyl)dimethoxysilane and the like.
  • 3-glycidoxypropyltrimethoxysilane and 2-(3,4- epoxycyclohexyl)ethyltrimethoxysilane are particularly suited.
  • Non-limiting specific examples of such compounds include N-(l,3-dimethylbutylidene)-3-(triethoxysilyl)-l- propaneamine, N-(l-methylethylidene)-3-(triethoxysilyl)-l-propaneamine, N-ethylidene-3- (triethoxysilyl)-l-propaneamine, N-(l-methylpropylidene)-3-(triethoxysilyl)-l-propaneamine, N- (4-N,N-dimethylaminobenzylidene)-3-(triethoxysilyl)-l-propaneamine, N-(cyclohexylidene)-3- (triethoxysilyl)-l-propaneamine and trimethoxysilyl compounds, methyldiethoxysilyl compounds, ethyldimethoxysilyl compounds and the like each corresponding to the above triethoxysilyl compounds.
  • N-(l,3-dimethylbutylidene)-3-(triethoxysilyl)-l- propaneamine and N-(l-methylpropylidene)-3-(triethoxysilyl)-l-propaneamine are particularly suited.
  • the imine(amidine) group-containing compounds include preferably l-[3- trimethoxysilyl]propyl]-4,5-dihydroimidazole, 3-(l-hexamethyleneimino)propyl(triethoxy)silane, (l-hexamethyleneimino)methyl(trimethoxy)silane, N-(3-triethoxysilylpropyl)-4,5- dihydroimidazole, N-(3-isopropoxysilylpropyl)-4,5-dihydroimidazole, N-(3- methyldiethoxysilylpropyl)-4,5-dihydroimidazole and the like, and among them, N-(3- triethoxysilylpropyl)-4,5-dihydroimidazole and N-(3-isopropoxysilylpropyl)-4,5-dihydroimidazole are preferred.
  • the silica-reactive functional group of the styrene-butadiene rubber (i) results from a compound represented by Formula (II) wherein A 1 has at least one carboxylic ester group.
  • Non-limiting specific examples of such compounds include 3-methacryloyloxypropyltriethoxysilane, 3- methacryloyloxypropyltrimethoxysilane, 3-methacryloyloxypropylmethyldiethoxysilane, 3- methacryloyloxypropyltriisopropoxysilane and the like, and among them, 3- methacryloyloxypropyltriethoxysilane is preferred.
  • the silica-reactive functional group of the at least one styrene-butadiene rubber (i) results from a compound represented by Formula (II) wherein A 1 has at least one carboxylic anhydride group.
  • a 1 has at least one carboxylic anhydride group.
  • Non-limiting specific examples of such compounds include 3-trimethoxysilylpropylsuccinic anhydride, 3- triethoxysilylpropylsuccinic anhydride, 3-methyldiethoxysilylpropylsuccinic anhydride and the like, and among them, 3-triethoxysilylpropylsuccinic anhydride is preferred.
  • the silica-reactive functional group of the at least one styrene-butadiene rubber (i) results from a compound represented by Formula (II) wherein A 1 has at least one cyano group.
  • Non-limiting specific examples of such compounds include 2-cyanoethylpropyltriethoxysilane and the like.
  • the silica-reactive functional group of the at least one styrene-butadiene rubber (i) results from a compound represented by Formula (II) wherein A 1 has at least one cyclic tertiary amine group.
  • Non-limiting specific examples of such compounds include 3-(l-hexamethyleneimino)propyltriethoxysilane,
  • the silica-reactive functional group of the at least one styrene-butadiene rubber (i) results from a compound represented by Formula (II) wherein A 1 has at least one non-cyclic tertiary amine group.
  • Nonlimiting specific examples of such compounds include 3-dimethylaminopropyltriethoxysilane, 3- dimethylaminopropyltrimethoxysilane, 3-diethylami nopropyltriethoxysilane, 3- dimethylaminopropyltrimethoxysilane, 2-dimethylaminoethyltriethoxysilane, 2- dimethylaminoethyltri methoxysilane, 3-dimethylaminopropyldiethoxymethylsilane, 3- dibutylaminopropyltriethoxysilane and the like, and among them, 3- dimethylaminopropyltriethoxysilane and 3-diethylaminopropyltriethoxysilane are suited.
  • the silica-reactive functional group of the at least one styrene-butadiene rubber (i) results from a compound represented by Formula (II) wherein A 1 has at least one pyridine group.
  • Non-limiting specific examples of such compounds include 2-trimethoxysilylethylpyridine and the like.
  • the silicareactive functional group of the at least one styrene-butadiene rubber (i) results from a compound represented by Formula (II) wherein A 1 has at least one silazane group.
  • Non-limiting specific examples of such compounds include N,N-bis(trimethylsilyl)- a mi nopropylmethyldimethoxysilane, l-trimethylsilyl-2,2-dimethoxy-l-aza-2-silacyclopentane,
  • N,N-bis(trimethylsilyl)aminopropyltrimethoxysilane N,N- bis(trimethylsilyl)aminopropyltriethoxysilane, N,N- bis(trimethylsilyl)aminopropylmethyldiethoxysilane, N,N- bis(trimethylsilyl)aminoethyltrimethoxysilane, N,N-bis(trimethylsilyl)ami noethyltriethoxysilane, N,N-bis(trimethylsilyl)aminoethylmethyldimethoxysilane, N,N- bis(trimethylsilyl)aminoethylmethyldiethoxysilane and the like.
  • N,N- bis(trimethylsilyl)aminopropyltriethoxysilane, N,N- bis(trimethylsilyl)aminopropylmethyldiethoxysilane or l-trimethylsilyl-2,2-dimethoxy-l-aza-2- silacyclopentane are particularly preferred.
  • the nitrogen(s) may be deprotected or deblocked by hydrolysis or other procedures to convert the protected nitrogen(s) into a primary nitrogen.
  • a nitrogen bonded to two trimethylsilyl groups could be deprotected and converted to a primary amine nitrogen (such a nitrogen would still be bonded to the remainder of the formula (II) compound).
  • the functionalized polymer can be understood as containing a functional group resulting from a deprotected (or hydrolyzed) version of the compound.
  • Non-limiting examples of oxygen- or sulfur-containing functional groups that can be utilized in certain embodiments of the first -fourth embodiments as a silica-reactive functional group in the at least one styrene-butadiene rubber include, but are not limited to, a hydroxyl group, a carboxyl group, an epoxy group, a glycidoxy group, a diglycidylamino group, a cyclic dithiane-derived functional group, an ester group, an aldehyde group, an alkoxy group, a ketone group, a thiocarboxyl group, a thioepoxy group, a thioglycidoxy group, a thiodiglycidylamino group, a thioester group, a thioaldehyde group, a thioalkoxy group, and a thioketone group.
  • the foregoing alkoxy group may be an alcohol-derived alkoxy group derived from a benzophenone.
  • the at least one styrene-butadiene rubber (i) comprises at least one silicareactive functional group selected from the foregoing list of oxygen- or sulfur-containing functional groups.
  • the at least one styrene-butadiene rubber (i), whether having a silica-reactive functional group or not may be prepared by either solution polymerization or by emulsion polymerization.
  • the only styrene-butadiene rubber(s) present as (i), whether having a silica-reactive functional group or not is (are) prepared by solution polymerization.
  • the only styrene-butadiene rubber(s) present as (i), whether having a silica-reactive functional group or not is (are) prepared by emulsion polymerization.
  • the rubbers are a combination of solution polymerized styrene-butadiene rubber and emulsion polymerized styrene-butadiene rubber (e.g., one solution styrene-butadiene rubber and one emulsion styrene-butadiene rubber).
  • the only styrene-butadiene rubber(s) present in the elastomer component is (are) solution styrene-butadiene rubbers (Z.e., no emulsion styrene-butadiene rubber is present).
  • (ii) of the elastomer component consists of polybutadiene rubber having a cis bond content of at least 95% (e.g., 95%, 96%, 97%, 98%, 99%, or more), a Tg of less than -101 °C (e.g., -102, -103, -104, -105, -106, -107, -108, -109, -110, -111, -112 °C or less), preferably -101 or -110 °C (e.g., -102, -103, -104, -105, -106, -107, - 108, -109, or -110 °C), and a silica-reactive functional group.
  • a Tg of less than -101 °C (e.g., -102, -103, -104, -105, -106, -107, -108, -109, or -110
  • the Tg of the polybutadiene rubber (ii) is -101 to -110 °C.
  • the cis bond content refers to the cis 1,4- bond content.
  • the cis 1,4-bond contents and vinyl bond contents referred to herein for polybutadiene rubber are determined by FTIR (FourierTransform Infrared Spectroscopy) wherein a polymer sample is dissolved in CS2 and then subjected to FTIR.
  • the polybutadiene rubber of (ii) has a cis 1,4-bond content of at least 98% (e.g., 98%, 99%, or more) or at least 99% (e.g., 99%, 99.5%, or more). Since the cis bond content of the polybutadiene rubber (ii) is high (i.e., at least 95%, as discussed above), the vinyl bond content will be low.
  • the polybutadiene rubber of (ii) has a vinyl bond content of less than 4% (e.g., 3.9%, 3.5%, 3%, 2.5%, 2%, 1.5%, 1%, 0.5%, etc.), preferably less than 3% (e.g., 2.5%, 2%, 1.5%, 1%, 0.5%, etc.), more preferably less than 2% (e.g., 1.5%, 1.4%, 1.3%, 1.2%, 1.1%, 1%, 0.9%, 0.8%, 0.7%, 0.6%, 0.5%, 0.4%, etc.).
  • any polybutadiene rubber used in the tire tread rubber compositions has a Tg of -105 °C or less (e.g., -105, -106, -107, -108, -109 °C or less) such as -105 to -110 °C.
  • any polybutadiene rubber used in the tire tread rubber compositions contains less than 3% by weight (e.g., 3%, 2%, 1%, 0.5%, or less), preferably less than 1% by weight (e.g., 1%, 0.5%, or less) or 0% by weight syndiotactic 1,2-polybutadiene.
  • one or more than one polybutadiene rubber having a cis bond content of at least 95%, a Tg of less than -101 °C, and a silica-reactive functional group may be used for (ii).
  • (ii) consists of only one polybutadiene rubber having a cis bond content of at least 95% (e.g., 95%, 96%, 97%, 98%, 99%, or more), a Tg of less than -101 °C, and a silica-reactive functional group.
  • the amount of any polybutadiene rubber having a high vinyl content is limited (in the overall tread rubber composition) to less than 25 parts, more preferably less than 10 parts, even more preferably less than 5 parts or 0 parts.
  • 51-65 parts e.g., 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64 or 65 parts), preferably 51-65 parts (e.g., 51-65 parts), preferably 51-65 parts (e.g., 51-65 parts), preferably 51-65 parts (e.g., 51-65 parts), preferably 51-65 parts (e.g.,
  • the polybutadiene rubber having a cis bond content of at least 95%, a Tg of less than -101 °C, and a silica-reactive functional group is present as (ii).
  • the Tg of this polybutadiene rubber (ii) is -101 to -110 °C (e.g., -101, -102, -103, - 104, -105, -106, -107, -108, -109, or -110 °C), or -105 to -110 °C (e.g., -105, -106, -107, -108, -109, or -110 °C).
  • the Mw of the polybutadiene rubber having a cis bond content of at least 95%, a Tg of less than -101 °C, preferably -101 to -110 -101 °C, and a silica-reactive functional group of (ii) may vary.
  • the polybutadiene rubber having a cis bond content of at least 95%, a Tg of less than -101 °C, preferably -101 to -110 -101 °C, and a silicareactive functional group of (ii) has a Mw of 450,000 to 700,000 grams/mole (e.g., 450,000; 500,000; 550,000; 600,000; 650,000; or 700,000 grams/mole), preferably a Mw of 500,000 to 650,000 grams/mole (e.g., 500,000; 525,000; 550,000; 575,000; 600,000; 625,000; or 650,000 grams/mole).
  • Mw ranges falling within the foregoing ranges such as 500,000 to 600,000 grams/mole, 550,000 to 600,000 grams/mole, 450,000 to 600,000 grams/mole, and 500,000 to 700,000 grams/mole can also be utilized in certain embodiments of the first-fourth embodiments.
  • the polybutadiene rubber having a cis bond content of at least 95%, a Tg of less than -101 °C, preferably -101 to - 110 -101 °C, and a silica-reactive functional group of (ii) has a Mn of 180,000 to 300,000 grams/mole (e.g., 180,000; 200,000; 220,000; 240,000; 250,000; 260,000; 280,000; or 300,000 grams/mole), preferably a Mn of 200,000 to 280,000 grams/mole (e.g., 200,000; 210,000; 220,000; 230,000; 240,000; 250,000; 260,000; 270,000; or 280,000 grams/mole).
  • Mn ranges falling within the foregoing ranges such as 200,000 to 250,000 grams/mole, 230,000 to 280,000 grams/mole, 180,000 to 280,000 grams/mole, and 200,000 to 280,000 grams/mole can also be utilized in certain embodiments of the first-fourth embodiments.
  • the polybutadiene rubber having a cis bond content of at least 95%, a Tg of less than -101 °C, preferably -101 to -110 -101 °C, and a silica-reactive functional group of (ii) has a Mw of 450,000 to 700,000 grams/mole (or a range within the foregoing, as described above) and a Mn of 180,000 to 300,000 grams/mole (or a range within the foregoing, as described above).
  • the foregoing Mw and Mn values for the polybutadiene of (ii) refer to values measured by GPC using a polystyrene standard.
  • the foregoing Mw and Mn values for the polybutadiene of (ii) refer to coupled Mw and coupled Mn rather than base polymer values.
  • the at least one polybutadiene rubber (ii), as described above is an oil-extended rubber, incorporating oil in an amount as discussed further below.
  • the at least one polybutadiene rubber (ii), as described above is a non oil-extended rubber (i.e., the BR is not extended with any oil).
  • the tire tread rubber composition exhibits an improvement in wear of at least 5% (e.g., 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 5-14%, 5-13%, 5-10%, etc.), or even at least 10% (e.g., 10%, 11%, 12%, 13%, 14%, 10-13%, 10-14%, etc.).
  • an improvement in wear can be measured by DIN abrasion values wherein a lower value (i.e., less material lost) indicates better wear.
  • the tire tread rubber composition exhibits an improvement in rolling resistance (as evidenced by its value tan 6 at -60 °C, as discussed in more detail, infra) of at least 5% (e.g., 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 5-13%, 5-10%, etc.), or even at least 10% (e.g., 10%, 11%, 12%, 13%, 10-13%, etc.).
  • the polybutadiene rubber of (i) includes a silica-reactive functional group which includes a silicon-containing functional group having a siloxy group (e.g., a hydrocarbyloxysilane- containing compound), wherein the compound optionally includes a monovalent group having at least one functional group.
  • a silica-reactive functional group which includes a silicon-containing functional group having a siloxy group (e.g., a hydrocarbyloxysilane- containing compound), wherein the compound optionally includes a monovalent group having at least one functional group.
  • Such a silicon-containing functional group may be added by reacting the active terminal of a polymer chain with a compound having the following formula (II): wherein A 1 represents a monovalent epoxy group; R c represents a single bond or a divalent hydrocarbon group having from 1 to 20 carbon atoms (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 carbon atoms); R d represents a monovalent aliphatic hydrocarbon group having 1 to 20 carbon atoms (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 carbon atoms), a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms (e.g., 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, or 18 carbon atoms) or a reactive group; R e represents a monovalent aliphatic hydrocarbon group having 1 to 20 carbon atoms (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18,
  • a partial condensation product refers to a product in which a part (not all) of a SiOR group in the hydrocarbyloxysilane compound is turned into a SiOSi bond by condensation.
  • R c represents a divalent hydrocarbon group having 1 to 12 carbon atoms (e.g., 1, 2, 3, 4, 5, 6, 7, 8,
  • R e represents a monovalent aliphatic hydrocarbon group having 1 to 12 carbon atoms (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, or 12 carbon atoms), 2 to 6 carbon atoms (e.g., 2, 3, 4, 5, or 6 carbon atoms), or 1 to 2 carbon atoms or a monovalent aromatic hydrocarbon group having 6 to 8 carbon atoms
  • R d represents a monovalent aliphatic hydrocarbon group having 1 to 12 carbon atoms(e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, or 12 carbon atoms), 2 to 6 carbon atoms (e.g., 2, 3, 4, 5, or 6 carbon atoms), or 1 to 2 carbon atoms or a monovalent aromatic hydrocarbon group having 6 to 8 carbon atoms
  • R d represents a monovalent aliphatic hydrocarbon group having 1 to 12 carbon atoms(e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, or 12 carbon atoms), 2 to 6 carbon atoms (e.g
  • the particular epoxy group present in the formula (II) functionalizing compound can vary.
  • the epoxy group i.e., A 1 in formula (II), above
  • the epoxy group is selected from glycidoxy, 3,4-epoxycyclohexyl, or a glycidyl group having 3-8 (e.g., 3, 4, 5, 6, 7, or 8), preferably 3-6 (e.g., 3, 4, 5, or 6), carbons overall (with the 2 end carbons being within the epoxy ring and the other end of the carbon chain bonded to R c ).
  • the polybutadiene rubber of (ii) has a silica-reactive functional group resulting from use of a functionalizing compound of formula (II) where the epoxy group (i.e., A 1 ) is selected from glycidoxy. In certain embodiments of the first-fourth embodiments, the polybutadiene rubber of (ii) has a silica-reactive functional group resulting from use of a functionalizing compound of formula (II) where the epoxy group (i.e., A 1 ) is selected from 3,4-epoxycylohexyl.
  • the polybutadiene rubber of (ii) has a silica-reactive functional group resulting from use of a functionalizing compound of formula (II) where the epoxy group (i.e., A 1 ) is selected from a glycidyl group having 3-8 (e.g., 3, 4, 5, 6, 7, or 8), preferably 3-6 (e.g., 3, 4, 5, or 6), carbons overall (with the 2 end carbons being within the epoxy ring and the other end of the carbon chain bonded to R c ).
  • Non-limiting specific examples of such functionalizing compounds according to formula (II) which include an epoxy group include 2-glycidoxyethyltrimethoxysilane, 2-glycidoxyethyltriethoxysilane, (2- glycidoxyethyl)methyldimethoxysilane, (2-glycidoxyethyl)methyldiethoxysilane, 3- glycidoxypropyltri methoxysilane, 3-glycidoxypropyltriethoxysilane, (3-glycidoxypropyl)- methyldimethoxysilane, (3-glycidoxypropyl)-methyldiethoxysilane, 2-(3,4- epoxycyclohexyl)ethyltrimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane, 2-(3,4- epoxycyclohexyl)ethyl(methyl)dimethoxysilane, 2-(3,4
  • 3- glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, and 2-(3,4- epoxycyclohexyl)ethyltrimethoxysilane are particularly preferred.
  • the elastomer component may consist of (include) up to 9 parts (e.g., 9, 8, 7, 6, 5, 4, 3, 2, 1 or 0 parts) of natural rubber, polyisoprene, or a combination thereof, which can be referred to as (iii).
  • the amount of (iii) is 0-9 parts, and in other embodiments 1-9 parts.
  • (iii) of the elastomer component consists of up to 5 parts, 0-5 parts, or 1-5 parts of natural rubber, polyisoprene, or a combination thereof.
  • (iii) consists (only) of natural rubber. In other embodiments of the first-fourth embodiments, (iii) consists (only) of polyisoprene. In yet other embodiments of the first-fourth embodiments, as previously mentioned, no natural rubber or polyisoprene is present or used in the tire tread rubber composition.
  • natural rubber may include Hevea natural rubber, non-Hevea natural rubber (e.g., guayule natural rubber), or a combination thereof.
  • the natural rubber When natural rubber is utilized in the tire tread rubber compositions of the first-fourth embodiments, the natural rubber preferably has a Mw of 1,000,000 to 2,000,000 grams/mole (e.g., 1 million, 1.1 million, 1.2 million, 1.3 million, 1.4 million, 1.5 million, 1.6 million, 1.7 million, 1.8 million, 1.9 million, 2 million grams/mole); 1,250,000 to 2,000,000 grams/mole, or 1,500,000 to 2,000,000 grams/mole (as measured by GPC using a polystyrene standard).
  • the Tg of the natural rubber may vary.
  • the first-fourth embodiments when natural rubber is utilized it has a Tg of -65 to -80 °C (e.g., - 65, -66, -67, -68, -69, -70, -71-, -72, -73, -74, -75, -76, -77, -78, -79, or -80 °C), more preferably a Tg of -67 to -77 °C (e.g., -67, -68, -69, -70, -71, -72, -73, -74, -75, -76, or -77 °C).
  • the Tg of the polyisoprene may vary.
  • the Tg of the polyisoprene when polyisoprene is utilized it has a Tg of -55 to -75 °C (e.g., -55, -56, -57, -58, -59, -60, -61, -62, -63, - 64, -65, -66, -67, -68, -69, -70, -71, -72, -73, -74, or -75 °C), more preferably -58 to -74 °C (e.g., - 58, -59, -60, -61, -62, -63, -64, -65, -66, -67, -68, -69, -70, -71, -72, -73, -74, or -75 °C), more preferably -58 to -74 °C
  • the term "reinforcing filler” is used to refer to a particulate material that has a nitrogen absorption specific surface area (N2SA) of more than about 100 m 2 /g, and in certain instances more than 100 m 2 /g, more than about 125 m 2 /g, more than 125 m 2 /g, or even more than about 150 m 2 /g or more than 150 m 2 /g.
  • N2SA nitrogen absorption specific surface area
  • the traditional use of the term “reinforcing filler” can also be used to referto a particulate material that has a particle size of about 10 nm to about 50 nm (including 10 nm to 50 nm).
  • si-reinforcing filler is used to refer to a filler that is intermediary in either particle size, surface area (N2SA), or both, to a non-reinforcing filler (as discussed below) and a reinforcing filler.
  • the term "reinforcing filler” is used to refer to a particulate material that has a nitrogen absorption specific surface area (N2SA) of about 20 m 2 /g or greater, including 20 m 2 /g or greater, more than about 50 m 2 /g, more than 50 m 2 /g, more than about 100 m 2 /g, or more than 100 m 2 /g.
  • N2SA nitrogen absorption specific surface area
  • the term "reinforcing filler” is used to refer to a particulate material that has a particle size of about 10 nm up to about 1000 nm, including 10 nm to 1000 nm, about 10 nm up to about 50 nm and 10 nm to 50 nm.
  • the tire tread rubber compositions comprise (include) at least one reinforcing silica filler in an amount of 70-99 phr (e.g., 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 84, 85, 86, 88, or 90 phr), having a surface area of about 100 to about 300 m 2 /g (e.g., 110, 120, 130, 140, 150, 160, 180, 200, 220, 240, 260, 280, or 300 m 2 /g), preferably about 150 to about 300 m 2 /g, and more preferably about 180 to about 250 m 2 /g.
  • 70-99 phr e.g., 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 84, 85, 86, 88, or 90 phr
  • the tire tread rubber compositions comprise (include) at least one reinforcing silica filler in an amount of 80-90 phr (e.g., 80, 81, 82, 84, 85, 86, 88, or 90 phr), having a surface area of about 100 to about 300 m 2 /g (e.g., 110, 120, 130, 140, 150, 160, 180, 200, 220, 240, 260, 280, or 300 m 2 /g), preferably about 150 to about 300 m 2 /g, and more preferably about 180 to about 250 m 2 /g.
  • 80-90 phr e.g., 80, 81, 82, 84, 85, 86, 88, or 90 phr
  • the tire tread rubber composition comprises (includes) at least one reinforcing silica filler having a surface area of 150 to 300 m 2 /g (e.g., 150, 160, 180, 200, 220, 240, 260, 280, or 300 m 2 /g).
  • the tire tread rubber composition comprises (includes) at least one reinforcing silica filler having a surface area of 180 to 250 m 2 /g (e.g., 180, 185, 190, 195, 200, 205, 210, 215, 220, 225, 230, 235, 240, or 250 m 2 /g) which should be understood as including intermediary ranges such as 180-240, 180-230, 180-220, 180-210, 190-240, 190-230, 190-220, 190-210, etc.
  • at least one reinforcing silica filler having a surface area of 180 to 250 m 2 /g (e.g., 180, 185, 190, 195, 200, 205, 210, 215, 220, 225, 230, 235, 240, or 250 m 2 /g) which should be understood as including intermediary ranges such as 180-240, 180-230, 180-220, 180-210, 190-240, 190
  • one or more than one reinforcing silica filler having a surface area as discussed above may be utilized; in those embodiments where more than one such reinforcing silica filler is utilized, the foregoing amounts refer to the total amount of all reinforcing silica fillers. In certain embodiments of the first-fourth embodiments, only one reinforcing silica filler having a surface area as discussed above is utilized.
  • the only reinforcing silica filler(s) used in the tire tread rubber composition have a surface area as discussed above; in such embodiments, the tire tread rubber composition can be understood as being free of (/.e., contains 0 phr of) reinforcing silica filler having a surface area outside the above-discussed ranges.
  • the particular type of silica used for the at least one reinforcing silica filler having a surface area as discussed above may vary.
  • Nonlimiting examples of reinforcing silica fillers suitable for use in certain embodiments of the first- fourth embodiments include, but are not limited to, precipitated amorphous silica, wet silica (hydrated silicic acid), dry silica (anhydrous silicic acid), fumed silica, calcium silicate and the like.
  • suitable reinforcing silica fillers for use in certain embodiments of the first-fourth embodiments include, but are not limited to, aluminum silicate, magnesium silicate (Mg2SiO4, MgSiOs etc.), magnesium calcium silicate (CaMgSiO4), calcium silicate (Ca2SiO4 etc.), aluminum silicate (A ⁇ SiOs, AI4.3SiO4.5H2O etc.), aluminum calcium silicate (Al2O3.CaO2SiO2, etc.), and the like.
  • magnesium silicate Mg2SiO4, MgSiOs etc.
  • CaMgSiO4 magnesium calcium silicate
  • Ca2SiO4 etc. calcium silicate
  • Al silicate Al2O3.CaO2SiO2, etc.
  • precipitated amorphous wet-process hydrated silica fillers are preferred.
  • the tire tread rubber composition comprises a reinforcing silica filler having a surface area (as measured by the BET method), as discussed infra.
  • the tire tread rubber composition comprises reinforcing silica filler having a pH of about 5.5 to about 8, 5.5 to 8 (e.g., 5.5, 5.7, 5.9, 6.1, 6.3, 6.5, 6.7, 6.9, 7.1, 7.3, 7.5, 7.7, 7.9, or 8), about 6 to about 8, 6 to 8 (e.g., 6, 6.2, 6.4, 6.6, 6.8, 7, 7.2, 7.4, 7.6, 7.8, or 8), about 6 to about 7.5, 6 to 7.5, about 6.5 to about 8, 6.5 to 8, about 6.5 to about 7.5, 6.5 to 7.5, about 5.5 to about 6.8, or 5.5 to 6.8.
  • 5.5 to about 8 e.g., 5.5, 5.7, 5.9, 6.1, 6.3, 6.5, 6.7, 6.9, 7.1, 7.3, 7.5, 7.7, 7.9, or 8
  • about 6 to about 8, 6 to 8 e.g., 6, 6.2, 6.4, 6.6, 6.8, 7, 7.2, 7.
  • Some of the commercially available reinforcing silica fillers which can be used in certain embodiments of the first-fourth embodiments include, but are not limited to, Hi-Sil® EZ120G, Hi-Sil® EZ120G-D, Hi- Sil® 134G, Hi-Sil® EZ 160G, Hi-Sil®EZ 160G-D, Hi-Sil®190, Hi-Sil® 190G-D, Hi-Sil® EZ 200G, Hi-Sil® EZ 200G-D, Hi-Sil® 210, Hi-Sil® 233, Hi-Sil® 243LD, Hi-Sil® 255CG-D, Hi-Sil® 315-D, Hi-Sil® 315G-D, Hi- Sil® HDP 320G and the like, produced by PPG Industries (Pittsburgh, Pa.) As well, a number of useful commercial grades of different reinforcing silica fillers are also available from Evonik Corporation (e.g., Ultrasil®
  • one or more than one silica coupling agent may also (optionally) be utilized.
  • at least one silica coupling agent is utilized.
  • Silica coupling agents are useful in preventing or reducing aggregation of the silica filler in rubber compositions. Aggregates of the silica filler particles are believed to increase the viscosity of a rubber composition, and, therefore, preventing this aggregation reduces the viscosity and improves the processability and blending of the rubber composition.
  • any conventional type of silica coupling agent can be used, such as those having a silane and a constituent component or moiety that can react with a polymer, particularly a vulcanizable polymer.
  • the silica coupling agent acts as a connecting bridge between silica and the polymer.
  • Suitable silica coupling agents for use in certain embodiments of the first- fourth embodiments disclosed herein include those containing groups such as alkyl alkoxy, mercapto, blocked mercapto, sulfide-containing (e.g., monosulfide-based alkoxy-containing, disulfide-based alkoxy-containing, tetrasulfide-based alkoxy-containing), amino, vinyl, epoxy, and combinations thereof.
  • the silica coupling agent can be added to the rubber composition in the form of a pre-treated silica; a pre-treated silica has been pre-surface treated with a silane prior to being added to the rubber composition.
  • a pre-treated silica can allow for two ingredients (/.e., silica and a silica coupling agent) to be added in one ingredient, which generally tends to make rubber compounding easier.
  • Alkyl alkoxysilanes have the general formula R 10 p Si(OR 11 )4-p where each R 11 is independently a monovalent organic group, and p is an integer from 1 to 3, with the proviso that at least one R 10 is an alkyl group. Preferably p is 1.
  • each R 10 independently comprises Ci to C20 aliphatic, C5 to C20 cycloaliphatic, or Cg to C20 aromatic; and each R 11 independently comprises Ci to Cg aliphatic.
  • each R 10 independently comprises Cg to C15 aliphatic and in additional embodiments each R 10 independently comprises Cs to C14 aliphatic.
  • Mercapto silanes have the general formula HS-R 13 -Si(R 14 )(R 15 )2 where R 13 is a divalent organic group, R 14 is a halogen atom or an alkoxy group, each R 15 is independently a halogen, an alkoxy group or a monovalent organic group.
  • the halogen is chlorine, bromine, fluorine, or iodine.
  • the alkoxy group preferably has 1-3 carbon atoms.
  • Blocked mercapto silanes have the general formula B-S-R 16 -Si-X3 with an available silyl group for reaction with silica in a silica-silane reaction and a blocking group B that replaces the mercapto hydrogen atom to block the reaction of the sulfur atom with the polymer.
  • B is a block group which can be in the form of an unsaturated heteroatom or carbon bound directly to sulfur via a single bond
  • R 16 is Ci to Cg linearor branched alkylidene and each X is independently selected from the group consisting of Ci to C4 alkyl or Ci to C4 alkoxy.
  • alkyl alkoxysilanes suitable for use in certain embodiments of the first-fourth embodiments include, but are not limited to, octyltriethoxysilane, octyltrimethoxysilane, trimethylethoxysilane, cyclohexyltriethoxysilane, isobutyltriethoxy-silane, ethyltrimethoxysilane, cyclohexyl-tributoxysilane, dimethyldiethoxysilane, methyltriethoxysilane, propyltriethoxysilane, hexyltriethoxysilane, heptyltriethoxysilane, nonyltriethoxysilane, decyltriethoxysilane, dodecyltriethoxysilane, tetradecyltriethoxysilane, octadecyltrieth
  • Non-limiting examples of bis(trialkoxysilylorgano)polysulfides suitable for use in certain embodiments of the first -fourth embodiments include bis(trialkoxysilylorgano) disulfides and bis(trialkoxysilylorgano)tetrasulfides.
  • bis(trialkoxysilylorgano)disulfides include, but are not limited to, 3,3'-bis(triethoxysilylpropyl) disulfide, 3,3'-bis(trimethoxysilylpropyl)disulfide, 3, 3'-bis(tri butoxysilyl propyl [disulfide, 3,3'- bis(tri-t-butoxysilylpropyl)disulfide, 3, 3'-bis(tri hexoxysilyl propyl)disulfide, 2,2'- bis(dimethylmethoxysilylethyl)disulfide, 3,3'- bis(di phenylcyclo hexoxysilyl propyl [disulfide, 3,3'- bis(ethyl-di-sec-butoxysilylpropyl)disulfide, 3,3'-bis(propyldiethoxysilylpropyl)dis
  • Non-limiting examples of bis(trialkoxysilylorgano)tetrasulfide silica coupling agents suitable for use in certain embodiments of the first-fourth embodiments include, but are not limited to, bis(3-triethoxysilylpropyl)tetrasulfide, bis(2-triethoxysilylethyl) tetrasufide, bis(3-trimethoxysilylpropyl)tetrasulfide, 3- trimethoxysilylpropyl-N,N- dimethylthiocarbamoyl tetrasulfide, 3-triethoxysilylpropyl-N,N-dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilyl-N,N-dimethylthiocarbamoyl tetrasulfide, 3-tri methoxysilyl propylbenzothiazole tetrasulfide, 3-trie
  • the tire tread rubber composition includes a silica coupling agent in the form of a bis(trialkoxysilylorgano)polysulfides, more preferably a bis(trialkoxysilylorgano) disulfides.
  • Non-limiting examples of mercapto silanes suitable for use in certain embodiments of first-fourth embodiments disclosed herein include, but are not limited to, 1- mercaptomethyltriethoxysilane, 2- mercaptoethyltriethoxysilane, 3- mercaptopropyltriethoxysilane, 3- mercaptopropylmethyldiethoxysilane, 2- mercaptoethyltripropoxysilane, 18- mercaptooctadecyldiethoxychlorosilane, and mixtures thereof.
  • Non-limiting examples of blocked mercapto silanes suitable for use in certain embodiments of the first-fourth embodiments disclosed herein include, but are not limited to, those described in U.S. Pat. Nos. 6,127,468; 6,204,339; 6,528,673; 6,635,700; 6,649,684; and 6,683,135, the disclosures of which are hereby incorporated by reference.
  • blocked mercapto silanes include, but are not limited to, 2- triethoxysi lyl-1- ethylthioacetate; 2-trimethoxysilyl-l-ethylthioacetate; 2-(methyldimethoxysilyl)- 1- ethylthioacetate; 3-trimethoxysilyl-l-propylthioacetate; triethoxysilylmethyl-thioacetate; trimethoxysilylmethylthioacetate; triisopropoxysilylmethylthioacetate; methyldiethoxysilylmethylthioacetate; methyldimethoxysilylmethylthioacetate; methyldiisopropoxysilylmethylthioacetate; di methylethoxysilyl methylthioacetate; dimethylmethoxysilylmethylthioacetate; di methylisopropoxysilyl methylthioacetate; 2- triisopropoxysilyl-l-ethylthi
  • NXTTM silane (3- octanoylthio-l-propyltriethoxysilane), commercially available from Momentive Performance Materials Inc. of Albany, NY.
  • Non-limiting examples of pre-treated silicas (7. e. , silicas that have been pre-surface treated with a silane) suitable for use in certain embodiments of the first-fourth embodiments disclosed herein include, but are not limited to, Ciptane® 255 LD and Ciptane® LP (PPG Industries) silicas that have been pre-treated with a mercaptosilane, and Coupsil® 8113 (Degussa) that is the product of the reaction between organosilane bis(triethoxysilylpropyl) polysulfide (Si69) and Ultrasil® VN3 silica.
  • the pre-treated silica is used in an amount as previously disclosed for the silica filler (i.e., 81-120 phr or about 90 to about 120 phr, etc.).
  • the amount used may vary.
  • the rubber compositions do not contain any silica coupling agent.
  • the silica coupling agent is present in an amount sufficient to provide a ratio of the total amount of silica coupling agent to silica filler of about 0.1:100 to about 1:5 (i.e., about 0.1 to about 20 parts by weight per 100 parts of silica), including 0.1:100 to 1:5, about 1:100 to about 1:10, 1:100 to 1:10, about 1:100 to about 1:20, 1:100 to 1:20, about 1:100 to about 1:25, and 1:100 to 1:25 as well as about 1:100 to about 0:100 and 1:100 to 0:100.
  • the ratio of the total amount of silica coupling agent to silica filler falls within a ratio of 1:10 to 1:20 (i.e., 10 to 5 parts by weight per 100 parts of silica).
  • the rubber composition comprises about 0.1 to about 15 phr silica coupling agent, including 0.1 to 15 phr (e.g., 0.1, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15 phr), about 0.1 to about 12 phr, 0.1 to 12 phr, about 0.1 to about 10 phr, 0.1 to 10 phr, about 0.1 to about 7 phr, 0.1 to 7 phr, about 0.1 to about 5 phr, 0.1 to 5 phr, about 0.1 to about 3 phr, 0.1 to 3 phr, about 1 to about 15 phr, 1 to 15 phr (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15 phr), about 1 to about 12 phr, 1 to 12 phr (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15 phr), about 1 to
  • the amount of carbon black filler used in the tire tread rubber composition is limited. More specifically, according to the first-fourth embodiments disclosed herein, the tire tread rubber composition contains no more than 15 phr (e.g., 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, or even 0 phr) of carbon black filler, and in preferred embodiments of the first -fourth embodiments disclosed herein, the tire tread rubber composition contains no more than 10 phr (e.g., 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, or even 0 phr) of carbon black filler.
  • 15 phr e.g., 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, or even 0 phr
  • 10 phr e.g., 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, or even 0 phr
  • the tire tread rubber composition contains about 5 to about 10 phr of carbon black or 5- 10 phr (e.g., 5, 6, 7, 8, 9 or 10 phr) of carbon black. In certain embodiments of the first -fourth embodiments, the tire tread rubber composition contains 1-15 phr, 5-15 phr, 1-10 phr, 5-10 phr, 1-9 phr, 1-8 phr, no more than 8 phr (e.g., 8, 7, 6, 5, 4, 3, 2, 1 or even 0 phr), 0-9 phr, or 0-8 phr of carbon black filler.
  • 8 phr e.g., 8, 7, 6, 5, 4, 3, 2, 1 or even 0 phr
  • the tire tread rubber composition contains 0 phr of carbon black filler.
  • the foregoing limited amounts of carbon black filler should be understood to referto reinforcing carbon black filler.
  • the foregoing limited amounts of carbon black filler should be understood to refer to nonreinforcing carbon black filler.
  • the foregoing limited amounts of carbon black filler should be understood to referto all carbon black fillers (i.e., both reinforcing and non-reinforcing carbon black filler).
  • suitable carbon blacks for use as a reinforcing filler in the rubber composition of certain embodiments of the first-fourth embodiments include any of the commonly available, commercially-produced carbon blacks, including those having a surface area of at least about 20 m 2 /g (including at least 20 m 2 /g) and, more preferably, at least about 35 m 2 /g up to about 200 m 2 /g or higher (including 35 m 2 /g up to 200 m 2 /g).
  • useful carbon blacks are furnace black, channel blacks, and lamp blacks. More specifically, examples of useful carbon blacks include super abrasion furnace (SAF) blacks, high abrasion furnace (HAF) blacks, fast extrusion furnace (FEF) blacks, fine furnace (FF) blacks, intermediate super abrasion furnace (ISAF) blacks, semi-reinforcing furnace (SRF) blacks, medium processing channel blacks, hard processing channel blacks and conducting channel blacks.
  • SAF super abrasion furnace
  • HAF high abrasion furnace
  • FEF fast extrusion furnace
  • FF fine furnace
  • ISIF intermediate super abrasion furnace
  • SRF semi-reinforcing furnace
  • Other carbon blacks which can be utilized include acetylene blacks.
  • the rubber composition includes a mixture of two or more of the foregoing blacks.
  • a carbon black filler if a carbon black filler is present it consists of only one type (or grade) of reinforcing carbon black.
  • Typical suitable carbon blacks for use in certain embodiments of the first-fourth embodiments are N-110, N-220, N-339, N-330, N-351, N-550, and N-660, as designated by ASTM D-1765-82a.
  • the carbon blacks utilized can be in pelletized form or an unpelletized flocculent mass. Preferably, for more uniform mixing, unpelletized carbon black is preferred.
  • the tire tread rubber composition comprises a reinforcing filler other than carbon black or silica (/.e., an additional reinforcing filler). While one or more than one additional reinforcing filler may be utilized, their total amount is preferably limited to no more than 10 phr (e.g., 10, 9, 8, 7, 6, 5, 4, 3, 2, 1 or 0 phr), or no more than 5 phr (e.g., 5, 4, 3, 2, 1, or 0 phr).
  • 10 phr e.g., 10, 9, 8, 7, 6, 5, 4, 3, 2, 1 or 0 phr
  • 5 phr e.g., 5, 4, 3, 2, 1, or 0 phr
  • the tire tread rubber composition contains no additional reinforcing filler (/.e., 0 phr); in other words, in such embodiments no reinforcing filler other than silica and optionally carbon black are present.
  • the additional reinforcing filler or fillers may vary.
  • suitable additional reinforcing fillers for use in the tire tread rubber compositions of certain embodiments of the first-fourth embodiments include, but are not limited to, alumina, aluminum hydroxide, clay (reinforcing grades), magnesium hydroxide, boron nitride, aluminum nitride, titanium dioxide, reinforcing zinc oxide, and combinations thereof.
  • Non-Reinforcing Fillers include, but are not limited to, alumina, aluminum hydroxide, clay (reinforcing grades), magnesium hydroxide, boron nitride, aluminum nitride, titanium dioxide, reinforcing zinc oxide, and combinations thereof.
  • the tire tread rubber composition further comprises at least one non-reinforcing filler. In other preferred embodiments of the first-fourth embodiments, the tire tread rubber composition contains no non-reinforcing fillers (/.e., 0 phr).
  • the at least one non-reinforcing filler may be selected from clay (non-reinforcing grades), graphite, magnesium dioxide, aluminum oxide, starch, boron nitride (non-reinforcing grades), silicon nitride, aluminum nitride (non-reinforcing grades), calcium silicate, silicon carbide, ground rubber, and combinations thereof.
  • nonreinforcing filler is used to refer to a particulate material that has a nitrogen absorption specific surface area (N2SA) of less than about 20 m 2 /g (including less than 20 m 2 /g), and in certain embodiments less than about 10 m 2 /g (including less than 10 m 2 /g).
  • N2SA surface area of a particulate material can be determined according to various standard methods including ASTM D6556.
  • non-reinforcing filler is alternatively or additionally used to refer to a particulate material that has a particle size of greater than about 1000 nm (including greater than 1000 nm).
  • the total amount of nonreinforcing filler may vary but is preferably no more than 10 phr (e.g., 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 phr), and in certain embodiments 1-10 phr, no more than 5 phr (e.g., 5, 4, 3, 2, or 1 phr), 1-5 phr, or no more than 1 phr.
  • the tire tread rubber composition comprises (includes) as (d) 25-35 phr (e.g., 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, or 35 phr) of at least one hydrocarbon resin having a Tg of about 30 to about 50 °C or 30-50 °C (e.g., 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 42, 44, 45, 46, 48, or 50 °C).
  • 25-35 phr e.g., 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, or 35 phr
  • at least one hydrocarbon resin having a Tg of about 30 to about 50 °C or 30-50 °C (e.g., 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 42, 44, 45, 46, 48, or 50 °C).
  • the tire tread rubber composition comprises (includes) as (d) 25-35 phr (e.g., 25, 26, 1 , 28, 29, 30, 31, 32, 33, 34, or 35 phr) of at least one aromatic hydrocarbon resin having a Tg of about 30 to about 50 °C or 30-50 °C (e.g., 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 42, 44, 45, 46, 48, or 50 °C).
  • 25-35 phr e.g., 25, 26, 1 , 28, 29, 30, 31, 32, 33, 34, or 35 phr
  • aromatic hydrocarbon resin having a Tg of about 30 to about 50 °C or 30-50 °C (e.g., 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 42, 44, 45, 46, 48, or 50 °C).
  • the tire tread rubber composition comprises (includes) as (d) 30-35 phr (e.g., 30, 31, 32, 33, 34, or 35 phr) of at least one hydrocarbon resin, preferably an aromatic hydrocarbon resin, having a Tg of 30-50 °C, or a range within that range, as discussed infa.
  • Hydrocarbon resin Tg can be determined by DSC, according to the procedure discussed above for elastomer Tg measurements.
  • the at least one hydrocarbon resin of (d) has a Tg of about 35 to about 50 °C, 35- 50 °C (e.g., 30, 32, 34, 35, 36, 38, 40, 42, 44, 45, 46, 48, or 50 °C), about 35 to about 45 °C, or 35- 45 °C (e.g., 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, or 45 °C) and may be present in one of the foregoing discussed amounts.
  • the at least one hydrocarbon resin of (d) comprises an aromatic resin.
  • the hydrocarbon resin of (d) consists of (only) an aromatic hydrocarbon resin.
  • an aromatic resin is used, one or more than one aromatic hydrocarbon resin may be utilized.
  • the hydrocarbon resin of (d) includes less than 5 phr of terpene resin, and preferably excludes any terpene resin (i.e., 0 phrof terpene resin is present in the tire tread rubber composition).
  • aromatic resin or aromatic hydrocarbon resin should be understood to include both aromatic homopolymer resins and aromatic copolymer resins.
  • Non-limiting examples of aromatic resins suitable for use as the hydrocarbon resin (d) in certain embodiments of the first-fourth embodiments include coumarone-indene resins and alkylphenol resins as well as vinyl aromatic homopolymer or copolymer resins such as those including one or more of the following monomers: alpha-methylstyrene, styrene, ortho-methylstyrene, meta-methylstyrene, para-methylstyrene, vinyltoluene, para(tert-butyl)styrene, methoxystyrene, chlorostyrene, hydroxystyrene, vinylmesitylene, divinylbenzene, vinylnaphthalene or any vinyl aromatic monomer resulting from C9 fraction or C8-C10 fraction.
  • Non-limiting examples of vinylaromatic copolymer resins include vinylaromatic/terpene copolymer resins (e.g., limonene/styrene copolymer resins), vinylaromatic/C5 fraction resins (e.g., C5 fraction/styrene copolymer resin), vinylaromatic/aliphatic copolymer resins (e.g., CPD/styrene copolymer resin, and DCPD/styrene copolymer resin).
  • vinylaromatic/terpene copolymer resins e.g., limonene/styrene copolymer resins
  • vinylaromatic/C5 fraction resins e.g., C5 fraction/styrene copolymer resin
  • vinylaromatic/aliphatic copolymer resins e.g., CPD/styrene copolymer resin, and DCPD/styrene copolymer
  • alkyl-phenol resins include alkylphenol-acetylene resins such as p-tert-butylphenol-acetylene resins, alkylphenol-formaldehyde resins (such as those having a low degree of polymerization).
  • alkylphenol-acetylene resins such as p-tert-butylphenol-acetylene resins, alkylphenol-formaldehyde resins (such as those having a low degree of polymerization).
  • aromatic resins are commercially available from various companies including Chemfax, Dow Chemical Company, Eastman Chemical Company, Idemitsu, Neville Chemical Company, Nippon, Polysat Inc., Resinall Corp., and Zeon under various trade names.
  • the hydrocarbon resin (d) comprises an aromatic resin based upon one or more of the above-mentioned vinyl aromatic monomers (e.g., styrene, alpha-methylstyrene); in certain such embodiments at least 80% by weight, at least 85% by weight, at least 90% by weight, at least 95% by weight, at least 98% by weight, at least 99% by weight, or even 100% by weight of the monomers in the aromatic resin are aromatic monomers.
  • vinyl aromatic monomers e.g., styrene, alpha-methylstyrene
  • the hydrocarbon resin (d) consists of an aromatic resin based upon one or more of the above- mentioned vinyl aromatic monomers (e.g., styrene, alpha-methylstyrene); in certain such embodiments at least 80% by weight, at least 85% by weight, at least 90% by weight, at least 95% by weight, at least 98% by weight, at least 99% by weight, or even 100% by weight of the monomers in the aromatic resin are aromatic monomers.
  • the aromatic resin of (d) may include a hydrogenated form of one of the aromatic resins discussed above (i.e., a hydrogenated aromatic resin).
  • the aromatic resin of (d) excludes any hydrogenated aromatic resin; in other words, in such embodiments, the aromatic resin is not hydrogenated.
  • the at least one hydrocarbon resin of (d) comprises (i) an aromatic resin in combination with (ii) an aliphatic resin.
  • aliphatic resins include C5 fraction homopolymer and copolymer resins.
  • the amount of any aliphatic resin used in (d) is preferably limited.
  • the total amount of any aliphatic resin used in combination with the aromatic resin is preferably no more than 5 phr, less than 5 phr, less than 4 phr, less than 3 phr, less than 2 phr, or less than 1 phr (and in each instance no more than 20% by weight, preferably no more than 15% or no more than 10% by weight of the overall amount of hydrocarbon resin of (d)).
  • the at least one hydrocarbon resin of (d) comprises (i) an aromatic resin in combination with (ii) a cycloaliphatic resin.
  • cycloaliphatic resins include cyclopentadiene (“CPD”) homopolymer or copolymer resins, dicyclopentadiene (“DCPD”) homopolymer or copolymer resins, and combinations thereof.
  • CPD cyclopentadiene
  • DCPD dicyclopentadiene
  • the amount of any cycloaliphatic resin used in (d) is preferably limited.
  • the at least one hydrocarbon resin of (d) comprises (i) an aromatic resin in combination with (ii) a terpene resin.
  • terpene resins include alpha-pinene resins, beta-pinene resins, limonene resins (e.g., L-limonene, D-limonene, dipentene which is a racemic mixture of L- and D-isomers), beta-phellandrene, delta-3-carene, delta-2-carene, and combinations thereof.
  • the amount of any terpene resin used in (d) is preferably limited.
  • the total amount of any terpene resin used in combination with the aromatic resin is preferably no more than 5 phr, less than 5 phr, less than 4 phr, less than 3 phr, less than 2 phr, or less than 1 phr (and in each instance no more than 20% by weight, preferably no more than 15% or no more than 10% by weight of the overall amount of hydrocarbon resin of (d)).
  • the hydrocarbon resin (d) includes no terpene resin (i.e., 0 phr).
  • the hydrocarbon resin (d) has a softening point of about 70 to about 100 °C or 70-100 °C (e.g., 70, 75, 80, 85, 90, 95, or 100 °C), preferably about 75 to about 95 °C or 75-95 °C (e.g., 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, or 95 °C), more preferably about 80 to about 90 °C or 80-90 °C (e.g., 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, or 90 °C).
  • the softening point of a hydrocarbon resin will have a relationship to its Tg such that the Tg is lower than its softening point, and such that the lower the Tg the lower the softening point.
  • the resin with the Tg of 70 °C will have a lower softening point than the resin with the Tg of 100 °C.
  • the hydrocarbon resin (d) has a Mw according to one of the ranges provided above, in combination with a Mn according to one of the ranges provided above, further in combination with a Mw/Mn according to one of the ranges provided above; in certain such embodiments, the hydrocarbon resin (d) is an aromatic resin.
  • the hydrocarbon resin (d) comprises an aromatic resin (as discussed above) having an aromatic monomer content of at least about 40% by weight, at least 40% by weight (e.g., 40, 45, 50, 51, 55, 60% by weight, or more), about 40% to about 65% by weight, 40-65% by weight (e.g., 40, 42, 44, 45, 46, 48, 50, 52, 54, 55, 56, 58, 60, 62, 64, or 65% by weight), at least about 45% by weight, at least 45% by weight (e.g., 45, 50, 51, 55, 60% by weight, or more), about 45% to about 65% by weight, 45-65% by weight (e.g., 45, 47, 49, 50, 51, 53, 55, 57, 59, 60, 61, 63, or 65% by weight), at least 51% by weight (e.g., 51, 55, 60, 65% by weight, or more), about 51% to about weight (e.g., 51, 55, 60, 65% by
  • the amounts of aromatic monomer content are weight percentages based upon the total weight of the respective hydrocarbon resin.
  • Liquid Plasticizers including oils and non-oils
  • the tire tread rubber composition comprises 11-20 phr of liquid plasticizer (e.g., 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 phr), which preferably consists of at least one oil.
  • the 11-20 phr of liquid plasticizer comprises (includes) at least one oil, more preferably the 11-20 phr of liquid plasticizer consists of (only) at least one oil.
  • the tire tread rubber composition comprises 15- 20 phr of liquid plasticizer (e.g., 15, 16, 17, 18, 19, or 20 phr).
  • liquid plasticizer is used to refer to plasticizer ingredients which are liquid at room temperature (i.e., liquid at 25 °C and above) and to distinguish hydrocarbon resin plasticizers which will generally be solid at room temperature.
  • liquid plasticizers will have a Tg below 0 °C, generally well below such as less than -30 °C, less than -40 °C, or less than -50 °C.
  • the liquid plasticizer has a Tg of less than 0 °C to -100 °C, a Tg of -30 °C to -100 °C, or a Tg of -50 to -100 °C.
  • liquid plasticizers include both oils (e.g., petroleum oils as well as plant oils) and other non-oil liquid plasticizers including, but not limited to, ether plasticizers, ester plasticizers, phosphate plasticizers, and sulfonate plasticizers.
  • liquid plasticizer is meant to encompass both free liquid plasticizer (which is usually added during the compounding process) and extender oil (which is used to extend a rubber).
  • free liquid plasticizer which is usually added during the compounding process
  • extender oil which is used to extend a rubber.
  • the tire tread rubber composition contains only free liquid plasticizer in an amount of 11-20 phr. In other embodiments of the first and third embodiments and in certain embodiments of the second and fourth embodiments, the tire tread rubber composition contains only extender oil in an amount of 11-20 phr. In yet other embodiments of the first-fourth embodiments, the tire tread rubber composition includes both free liquid plasticizer and extender oil in a total amount of 11-20 phr. In those embodiments of the first-fourth embodiments wherein an oil-extended rubber is used, the amount of oil used to prepare the oil-extended rubber may vary.
  • the amount of oil used to prepare the oil-extended rubber may vary; in certain such embodiments, the amount of extender oil present in the oil-extended rubber (polymer) or SBR is 10-50 parts oil per 100 parts of rubber (e.g., 10, 15, 20, 25, 30, 35, 40, 45 or 50 parts of oil per 100 parts or rubber), preferably 10-40 parts oil per 100 parts or rubber or 20-40 parts oil per 100 parts of rubber.
  • extender oil could be used in an amount of 40 parts oil per 100 parts rubber in an SBR for (i) which SBR is used in an amount of 40 parts (the 40 parts being the amount of polymer of the oil-extended SBR, as discussed previously) in the overall tread rubber composition and, thus, the amount of oil contributed by the oil-extended SBR to the tire tread rubber composition would be 16 phr.
  • Oil-extension of rubbers can be beneficial to ease of processing or mixing when the SBR has a relatively high Mw and/or a relatively high Mooney viscosity.
  • the styrene-butadiene rubber as used in (i) is an oil-extended styrene-butadiene rubber having a polymer Mooney viscosity ML1+4 at 100 °C of at least 100.
  • polymer Mooney viscosity is meant the Mooney viscosity of the rubber or polymer before oilextension.
  • oil refers to both petroleum based oils (e.g., aromatic, naphthenic, and low PCA oils) as well as plant oils (such as can be harvested from vegetables, nuts, and seeds).
  • Plant oils will generally comprise triglycerides and the term should be understood to include synthetic triglycerides as well as those actually sourced from a plant.
  • various types of processing and extender oils may be utilized as the at least one liquid plasticizer, including, but not limited to aromatic, naphthenic, and low PCA oils (petroleum-sourced or plant-sourced).
  • Suitable low PCA oils include those having a polycyclic aromatic content of less than 3 percent by weight as determined by the IP346 method. Procedures for the IP346 method may be found in Standard Methods for Analysis & Testing of Petroleum and Related Products and British Standard 2000 Parts, 2003, 62nd edition, published by the Institute of Petroleum, United Kingdom.
  • Exemplary petroleum-sourced low PCA oils include mild extraction solvates (MES), treated distillate aromatic extracts (TDAE), TRAE, and heavy naphthenics.
  • Exemplary MES oils are available commercially as CATENEX SNR from SHELL, PROREX 15, and FLEXON 683 from EXXONMOBIL, VIVATEC 200 from BP, PLAXOLENE MS from TOTAL FINA ELF, TUDALEN 4160/4225 from DAHLEKE, MES-H from REPSOL, MES from Z8, and OLIO MES S201 from AGIP.
  • Exemplary TDAE oils are available as TYREX 20 from EXXONMOBIL, VIVATEC 500, VIVATEC 180, and ENERTHENE 1849 from BP, and EXTENSOIL 1996 from REPSOL.
  • Exemplary heavy naphthenic oils are available as SHELLFLEX 794, ERGON BLACK OIL, ERGON H2000, CROSS C2000, CROSS C2400, and SAN JOAQUIN 2000L.
  • Exemplary low PCA oils also include various plant-sourced oils such as can be harvested from vegetables, nuts, and seeds. Non-limiting examples include, but are not limited to, soy or soybean oil, sunflower oil (including high oleic sunflower oil), safflower oil, corn oil, linseed oil, cotton seed oil, rapeseed oil, cashew oil, sesame oil, camellia oil, jojoba oil, macadamia nut oil, coconut oil, and palm oil.
  • the foregoing processing oils can be used as an extender oil, i.e., to prepare an oil-extended polymer or copolymer, or as a processing or free oil.
  • the liquid plasticizer may in certain embodiments include a non-oil plasticizer, non-limiting examples of which include ether plasticizers, ester plasticizers, phosphate plasticizers, and sulfonate plasticizers.
  • a non-oil plasticizer preferably only a portion of the liquid plasticizer (e.g., less than 50%, no more than 40%, no more than 30%, no more than 20%, no more than 10%, or even no more than 5% is provided by the non-oil plasticizer).
  • Exemplary ether plasticizers include polyethylene glycols and polypropylene glycols.
  • Exemplary ester plasticizers include triesters and diesters in particular (which may be selected from the group consisting of di- and triesters of carboxylic acid, of phosphoric acid, or of sulphonic acid, and mixtures of these triesters). More specifically, exemplary carboxylic acid ester plasticizers include compounds selected from the group consisting of trimellitates, pyromellitates, phthalates, 1,2-cyclohexanedicarboxylates, adipates, azelates, sebacates, glyercol triesters, and mixtures of the foregoing.
  • glycerol triesters may include more than 50% by weight, more preferably more than 80% by weight of an unsaturated C18 fatty acid (e.g., oleic acid, linoleic acid, linolenic acid, and mixtures thereof).
  • unsaturated C18 fatty acid e.g., oleic acid, linoleic acid, linolenic acid, and mixtures thereof.
  • carboxylic acid ester plasticizers include stearic acid esters, ricinoleicacid esters, phthalic acid esters (e.g., di-2-ethylhexyl phthalate and diosodecyl phthalate), isophthalic acid esters, tetrahydrophthalic acid esters, adipic acid esters (e.g., di(2-ethylhexyl)adipate and diisooctyl adipate), malic acid esters, sebic acid esters (e.g., di(2-ethylhexyl)sebacate and diisooctyl sebacate), and fumaric acid esters.
  • stearic acid esters e.g., di-2-ethylhexyl phthalate and diosodecyl phthalate
  • isophthalic acid esters e.g., tetrahydrophthalic acid esters
  • Exemplary phosphate plasticizers include those with a tri-hydrocarbyl phosphate and di-hydrocarbyl phosphate structures (where each hydrocarbyl is independently selected from alkyl of Cl to C12, preferably Cl to C8, and aromatic of C6 to C12 both substituted and un-substituted, preferably when aromatic C6 either substituted or un-substituted).
  • exemplary phosphate plasticizers include trimethyl phosphate, triethyl phosphate, tributyl phosphate, trioctyl phosphate, dioctyl phosphate, 2- ethylhexyl diphenyl phosphate, tributoxyethyl phosphate, triphenyl phosphate, cresyl diphenyl phosphate, isodecyl diphenyl phosphate, tricresyl phosphate, tritolyl phosphate, trixylenyl phosphate, tris(chloroethyl) phosphate, and diphenyl mono-o-xenyl phosphate.
  • Exemplary sulfonate plasticizers include sulfonic acid esters such as sulfone butylamide, toluenesulfonamide, N-ethyl-toluenesulfonamide, and N-cyclohexyl-p-toluencesulfonamide.
  • sulfonic acid esters such as sulfone butylamide, toluenesulfonamide, N-ethyl-toluenesulfonamide, and N-cyclohexyl-p-toluencesulfonamide.
  • phosphate plasticizers in particular phosphoric acid derivatives (which can be understood as being phosphate esters) are preferred.
  • the Tg of the oil or oils used may vary.
  • any oil utilized has a Tg of about -40 to about -100 °C, -40 to -100 °C (e.g., -40, -45, -50, -55, -60, -65, -70, -75, -80, -85, -90, -95, or -100 °C), about -40 to about -90 °C, -40 to -90 °C (e.g., -40, -45, -50, -55, -60, -65, -70, -75, -80, -85, or -90 °C), about -45 to about -85 °C, -45 to -85 °C ⁇ e.g., -45, -50, -55, -60, -65, -70, -75, -80, -85, or -90 °C), about -45 to about
  • the tire tread rubber composition contains less than 5 phr (e.g., 4.5, 4, 3, 2, 1, or 0 phr) of MES orTDAE oil, or even no MES or TDAE oil (i.e., 0 phr).
  • the tire tread rubber composition contains no petroleum oil (i.e., 0 phr) and instead any oil utilized is a plant oil.
  • the tire tread rubber composition contains soybean oil in one of the above-mentioned amounts.
  • the tire tread rubber composition contains no sunflower oil (i.e., 0 phr).
  • the tire tread rubber composition includes one or more ester plasticizers.
  • Suitable ester plasticizers are known to those of skill in the art and include, but are not limited to, phosphate esters, phthalate esters, adipate esters and oleate esters (i.e., derived from oleic acid).
  • an ester is a chemical compound derived from an acid wherein at least one -OH is replaced with an -O- alkyl group
  • various alkyl groups may be used in suitable ester plasticizers for use in the tire tread rubber compositions, including generally linear or branched alkyl of Cl to C20 (e.g., Cl, C2, C3, C4, C5, C6, C7, C8, C9, CIO, Cll, C12, C13, C14, C15, C16, C17, C18, C19, C20), or C6 to C12.
  • esters are based upon acids which have more than one -OH group and, thus, can accommodate one or more than one O-alkyl group (e.g., trialkyl phosphates, dialkyl phthalates, dialkyl adipates).
  • suitable ester plasticizers include trioctyl phosphate, dioctyl phthalate, dioctyl adipate, nonyl oleate, octyl oleate, and combinations thereof.
  • ester plasticizer such as one or more of the foregoing may be beneficial to the snow or ice performance of a tire made from a tread rubber composition containing such ester plasticizer at least in part due to the relatively low Tg of ester plasticizers.
  • the tire tread rubber composition includes one or more ester plasticizers having a Tg of -40 °C to -70 °C (e.g., -40, -45, -50, -55, -60, -65, or -70 °C), or -50 °C to -65 °C (e.g., -50, -51, -52, -53, -54, -55, -56, -57, -58, -59, -60, -61, -62, -63, -64, or -65 °C ).
  • ester plasticizers having a Tg of -40 °C to -70 °C (e.g., -40, -45, -50, -55, -60, -65, or -70 °C), or -50 °C to -65 °C (e.g., -50, -51, -52, -53, -54, -55
  • the amount utilized may vary.
  • one or more ester plasticizers are utilized in a total amount of 1-12 phr (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, or 12 phr), 1-10 phr (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 phr), 2-6 phr (e.g., 2, 3, 4, 5, or 6 phr) or 2-5 phr (e.g., 2, 3, 4, or 5 phr).
  • one or more ester plasticizers is used in combination with oil in one of the foregoing amounts.
  • the total amount of at least one hydrocarbon resin (d) and at least one liquid plasticizer (e) is 36-50 phr (e.g., 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, or 50 phr).
  • the total amount of hydrocarbon resin (d) and liquid plasticizer (e) is 40-50 phr (e.g., 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, or 50 phr).
  • the total amount of hydrocarbon resin (d) and liquid plasticizer (e) is no more than 49 phr (e.g., 49, 48, 47, 46, 45, 44, 43, 42, 41, 40, 39, 38, 37, or 36 phr, or a range from the foregoing such as 36-49 phr, etc.).
  • 49 phr e.g., 49, 48, 47, 46, 45, 44, 43, 42, 41, 40, 39, 38, 37, or 36 phr, or a range from the foregoing such as 36-49 phr, etc.
  • the amount of hydrocarbon resin (d) is greater than the amount of liquid plasticizer (e).
  • the hydrocarbon resin (d) and liquid plasticizer (e) are present in a weight ratio of at least 1.5:1, preferably 1.5:1 to 3:1 (e.g., 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1, 2:1, 2.1:1, 2.2:1, 2.3:1, 2.4:1, 2.5:1, 2.6:1, 2.7:1, 2.8:1, 2.9:1, or 3:1), more preferably 1.6:1 to 2.8: (e.g., 1.6:1, 1.7:1, 1.8:1, 1.9:1, 2:1, 2.1:1, 2.2:1, 2.3:1, 2.4:1, 2.5:1, 2.6:1, 2.7:1, or 2.8:1).
  • the tire tread rubber composition includes (comprises) a cure package.
  • the contents of the cure package may vary according to the first -fourth embodiments, generally, the cure package includes at least one of: a vulcanizing agent; a vulcanizing accelerator; a vulcanizing activator (e.g., zinc oxide, stearic acid, and the like); a vulcanizing inhibitor; and an anti-scorching agent.
  • the cure package includes at least one vulcanizing agent, at least one vulcanizing accelerator, at least one vulcanizing activator and optionally a vulcanizing inhibitor and/or an anti-scorching agent.
  • Vulcanizing accelerators and vulcanizing activators act as catalysts for the vulcanization agent.
  • Various vulcanizing inhibitors and anti-scorching agents are known in the art and can be selected by one skilled in the art based on the vulcanizate properties desired.
  • Suitable types of vulcanizing agents for use in certain embodiments of the first-fourth embodiments include but are not limited to, sulfur or peroxidebased curing components.
  • the curative component includes a sulfur-based curative or a peroxide-based curative.
  • the vulcanizing agent is a sulfur-based curative; in certain such embodiments the vulcanizing agent consists of (only) a sulfur-based curative.
  • sulfur vulcanizing agents examples include "rubbermaker's" soluble sulfur; sulfur donating curing agents, such as an amine disulfide, polymeric polysulfide, or sulfur olefin adducts; and insoluble polymeric sulfur.
  • the sulfur vulcanizing agent is soluble sulfur or a mixture of soluble and insoluble polymeric sulfur.
  • suitable vulcanizing agents and other components used in curing e.g., vulcanizing inhibitor and anti-scorching agents, one can refer to Kirk-Othmer, Encyclopedia of Chemical Technology, 3rd ed., Wiley Interscience, N.Y. 1982, Vol. 20, pp.
  • Vulcanizing agents can be used alone or in combination.
  • the vulcanizing agents may be used in certain embodiments of the first -fourth embodiments in an amount ranging from 0.1 to 10 phr (e.g., 0.1, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 phr), including from 1 to 7.5 phr (e.g., 1, 2, 3, 4, 5, 6, 7, or 7.5 phr), including from 1 to 5 phr (e.g., 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, or 5 phr), and preferably from 1 to 3.5 phr (e.g., 1, 1.5, 2, 2.5, 3, or 3.5 phr).
  • 0.1 to 10 phr e.g., 0.1, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 phr
  • 1 to 7.5 phr e.g., 1, 2, 3, 4, 5, 6, 7, or 7.5 phr
  • 5 phr e.g., 1, 1.5, 2, 2.5, 3, 3.5,
  • Vulcanizing accelerators are used to control the time and/or temperature required for vulcanization and to improve properties of the vulcanizate.
  • suitable vulcanizing accelerators for use in certain embodiments of the first-fourth embodiments disclosed herein include, but are not limited to, thiazole vulcanization accelerators, such as 2- mercaptobenzothiazole, 2,2'-dithiobis(benzothiazole) (MBTS), N-cyclohexyl-2-benzothiazole- sulfenamide (CBS), N-tert-butyl-2-benzothiazole-sulfenamide (TBBS), and the like; guanidine vulcanization accelerators, such as diphenyl guanidine (DPG) and the like; thiuram vulcanizing accelerators; carbamate vulcanizing accelerators; and the like.
  • thiazole vulcanization accelerators such as 2- mercaptobenzothiazole, 2,2'-dithiobis
  • the amount of the vulcanization accelerator used ranges from 0.1 to 10 phr ⁇ e.g., 0.1, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 phr), preferably 0.5 to 5 phr ⁇ e.g., 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, or 5 phr).
  • any vulcanization accelerator used in the tire tread rubber compositions of the first-fourth embodiments excludes any thiurams such as thiuram monosulfides and thiuram polysulfides (examples of which include TMTM (tetramethyl thiuram monosulfide), TMTD (tetramethyl thiuram disulfide), DPTT (dipentamethylene thiuram tetrasulfide), TETD (tetraethyl thiuram disulfide), TiBTD (tetraisobutyl thiuram disulfide), and TBzTD (tetrabenzyl thiuram disulfide)); in other words, the tire tread rubber compositions of the first-fourth embodiments preferably contain no thiuram accelerators (/.e., 0 phr).
  • Vulcanizing activators are additives used to support vulcanization.
  • Generally vulcanizing activators include both an inorganic and organic component.
  • Zinc oxide is the most widely used inorganic vulcanization activator.
  • Various organic vulcanization activators are commonly used including stearic acid, palmitic acid, lauric acid, and zinc salts of each of the foregoing.
  • the amount of vulcanization activator used ranges from 0.1 to 6 phr ⁇ e.g., 0.1, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, or 6 phr), preferably 0.5 to 4 phr ⁇ e.g., 0.5, 1, 1.5, 2, 2.5, 3 3.5, or 4 phr).
  • one or more vulcanization activators are used which includes one or more thiourea compounds (used in one of the foregoing amounts), and optionally in combination with one or more of the foregoing vulcanization activators.
  • R 1 , R 2 , R 3 , and R 4 are independently selected from H, alkyl, aryl, and N-containing substituents ⁇ e.g., guanyl).
  • two of the foregoing structures can be bonded together through N (removing one of the R groups) in a dithiobiurea compound.
  • one of R 1 or R 2 and one of R 3 or R 4 can be bonded together with one or more methylene groups (-CH2-) therebetween.
  • the thiourea has one or two of R 1 , R 2 , R 3 and R 4 selected from one of the foregoing groups with the remaining R groups being hydrogen.
  • exemplary alkyl include C1-C6 linear, branched or cyclic groups such as methyl, ethyl, propyl, iso-propyl, butyl, iso-butyl, pentyl, hexyl, and cyclohexyl.
  • Exemplary aryl include C6-C12 aromatic groups such as phenyl, tolyl, and naphthyl.
  • Exemplary thiourea compounds include, but are not limited to, dihydrocarbylthioureas such as dialkylthioureas and diarylthioureas.
  • Non-limiting examples of particular thiourea compounds include one or more of thiourea, N,N'-diphenylthiourea, trimethylthiourea, N,N'- diethylthiourea (DEU), N,N'-dimethylthiourea, N,N'-dibutylthiourea, ethylenethiourea, N,N'- diisopropylthiourea, N,N'-dicyclohexylthiourea, l,3-di(o-tolyl)thiourea, l,3-di(p-tolyl)thiourea, l,l-diphenyl-2-thiourea, 2,5-dithiobiurea, guanylthiourea, l-(
  • the activator includes at least one thiourea compound selected from thiourea, N,N'-diethylthiourea, trimethylthiourea, N,N'-diphenylthiourea, and N-N'-dimethylthiourea.
  • Vulcanization inhibitors are used to control the vulcanization process and generally retard or inhibit vulcanization until the desired time and/or temperature is reached.
  • Common vulcanization inhibitors include, but are not limited to, PVI (cyclohexylthiophthalmide) from Santogard.
  • the amount of vulcanization inhibitor is 0.1 to 3 phr (e.g., 0.1, 0.5, 1, 1.5, 2, 2.5, or 3 phr), preferably 0.5 to 2 phr (e.g., 0.5, 1, 1.5, or 2 phr).
  • the particular steps involved in preparing the tire tread rubber compositions of the first-fourth embodiments disclosed herein are generally those of conventionally practiced methods comprising mixing the ingredients in at least one nonproductive master-batch stage and a final productive mixing stage.
  • the tire tread rubber composition is prepared by combining the ingredients for the rubber composition (as disclosed above) by methods known in the art, such as, for example, by kneading the ingredients together in a Banbury mixer or on a milled roll.
  • Such methods generally include at least one non-productive master-batch mixing stage and a final productive mixing stage.
  • non-productive master-batch stage is known to those of skill in the art and generally understood to be a mixing stage (or stages) where no vulcanizing agents or vulcanization accelerators are added.
  • final productive mixing stage is also known to those of skill in the art and generally understood to be the mixing stage where the vulcanizing agents and vulcanization accelerators are added into the rubber composition.
  • the tire tread rubber composition is prepared by a process comprising more than one non-productive master-batch mixing stage.
  • the tire tread rubber composition is prepared by a process wherein the master-batch mixing stage includes at least one of tandem mixing or intermeshing mixing.
  • Tandem mixing can be understood as including the use of a mixer with two mixing chambers with each chamber having a set of mixing rotors; generally, the two mixing chambers are stacked together with the upper mixer being the primary mixer and the lower mixer accepting a batch from the upper or primary mixer.
  • the primary mixer utilizes intermeshing rotors and in other embodiments the primary mixer utilizes tangential rotors.
  • the lower mixer utilizes intermeshing rotors.
  • Intermeshing mixing can be understood as including the use of a mixerwith intermeshing rotors.
  • Intermeshing rotors refers to a set of rotors where the major diameter of one rotor in a set interacts with the minor diameter of the opposing rotor in the set such that the rotors intermesh with each other. Intermeshing rotors must be driven at an even speed because of the interaction between the rotors.
  • tangential rotors refers to a set of rotors where each rotor turns independently of the other in a cavity that may be referred to as a side.
  • a mixer with tangential rotors will include a ram whereas a ram is not necessary in a mixer with intermeshing rotors.
  • the rubbers (or polymers) and at least one reinforcing filler will be added in a non-productive or master-batch mixing stage or stages.
  • at least the vulcanizing agent component and the vulcanizing accelerator component of a cure package will be added in a final or productive mixing stage.
  • the tire tread rubber composition is prepared using a process wherein at least one non-productive master batch mixing stage is conducted at a temperature of about 130 °C to about 200 °C.
  • the tire tread rubber composition is prepared using a final productive mixing stage conducted at a temperature below the vulcanization temperature in order to avoid unwanted pre-cure of the rubber composition. Therefore, the temperature of the productive or final mixing stage generally should not exceed about 120 °C and is typically about 40 °C to about 120 °C, or about 60 °C to about 110 °C and, especially, about 75 °C to about 100 °C.
  • the tire tread rubber composition is prepared according to a process that includes at least one non-productive mixing stage and at least one productive mixing stage.
  • the use of silica fillers may optionally necessitate a separate re-mill stage for separate addition of a portion or all of such filler. This stage often is performed at temperatures similar to, although often slightly lower than, those employed in the masterbatch stage, i.e., ramping from about 90°C to a drop temperature of about 150°C.
  • improved or desirable tread properties may include one or more of rolling resistance, snow or ice traction, wet traction, dry handling, or wear, preferably improved rolling resistance and wear. Additional improved or desirable properties may include elongation at break (Eb), tensile at break (Tb) and TbxEb. While these properties may be measured by various methods, the values referred to herein for rolling resistance, snow or ice traction, wet traction, and dry handling refer to tan 6 values measured at the following temperatures and according to the following procedures.
  • Tan 6 values can be measured with a dynamic mechanical thermal spectrometer (Eplexor® 500N from Gabo Qualimeter Testanlagen GmbH of Ahiden, Germany) generally following the guidelines of ASTM D5992-96 (2011) and under the following conditions: measurement mode: tensile test mode; measuring frequency: 52 Hz; applying 0.2% strain from -50 to -5 °C and 1% strain from -5 to 65 °C; collecting data approximately every 1 °C in order to provide measurements at temperatures of -30 °C, 0 °C, 30°C, and 60 °C; sample shape: 4.75 mm wide x 29 mm long x 2.0 mm thick. Measurement is made upon a cured sample of rubber (cured for 15 minutes at 170°C).
  • a rubber composition's tan 6 at -30 °C is indicative of its snow or ice traction (also referred to herein as winter performance) when incorporated into a tire tread
  • tan 6 at 0 °C is indicative of its wet traction when incorporated into a tire tread
  • tan 6 at 30 °C is indicative of its dry handling when incorporated into a tire tread
  • its tan 6 at 60 °C is indicative of its rolling resistance when incorporated into a tire tread.
  • the rubber composition has a value for tan 6 at 60 °C of 0.18 to 0.25 (e.g., 0.18, 0.19, 0.2, 0.21, 0.22, 0.23, 0.24, or 0.25), preferably 0.18 to 0.22 (e.g., 0.18, 0.19, 0.2, 0.21, or 0.22 times), more preferably 0.18 to 0.2 (e.g., 0.18, 0.19, 0.2).
  • a tan 6 at 60 °C within one of the foregoing ranges can be understood as being indicative of a tire (or more specifically, a tire tread) with moderate rolling resistance (as opposed to a tire with low rolling resistance which would generally be indicated by a tan 6 at 60 °C of less than or equal to 0.2).
  • the value for tan 6 at 60 °C is combined with at least one of the following: (a) a value for tan 6 at -30 °C of no more than 2.5 times the tan 6 at 60 °C value (e.g., 2.5, 2.4, 2.2, 2.1, 2, 1.9, 1.8, etc.
  • tan 6 at 60 °C value preferably between 2.5 times and 2 times (e.g., 2.5, 2.4, 2.3, 2.2, 2.1, or 2 times) the tan 6 at 60 °C value; (b) a value for tan 6 at 30 °C of at least 1.4 times the tan 6 at 60 °C value (e.g., 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2, 2.1, 2.2, etc.
  • tan 6 at 60 °C value preferably between 1.4 and 2 times (e.g., 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, or 2 times) the tan 6 at 60 °C value, more preferably between 1.5 and 1.8 times (e.g., 1.5, 1.6, 1.7, or 1.8 times) the tan 6 at 60 °C value; or (c) a value for tan 6 at 0 °C of at least 2.2 times the tan 6 at 60 °C value (e.g., 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3, 3.1, 3.2, etc. times), preferably 2.2 times to 3 times the tan 6 at 60 °C value (e.g., 2.2, 2.3,
  • the value for tan 6 at 60 °C is combined with each of (a), (b), and (c).
  • one of the foregoing values for tan 6 at 60 °C e.g., 0.18 to 0.25, 0.18 to 0.22, 0.18 to 0.2, etc.
  • one of the foregoing values for tan 6 at 60 °C (e.g., 0.18 to 0.25, 0.18 to 0.22, 0.18 to 0.2, etc.) is combined with (b) a value for 6 at 30 °C of 1.4 and 2 times (e.g., 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, or 2 times) the tan 6 at 60 °C value,.
  • one of the foregoing values for tan 6 at 60 °C (e.g., 0.18 to 0.25, 0.18 to 0.22, 0.18 to 0.2, etc.) is combined with (c) a value for 6 at 0 °C of 2.2 times to 3 times the tan 6 at 60 °C value (e.g., 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, or 3 times) the tan 6 at 60 °C value.
  • one of the foregoing values for tan 6 at 60 °C (e.g., 0.18 to 0.25, 0.18 to 0.22, 0.18 to 0.2, etc.) is combined with the more preferred values for tan 6 at -30 °C, the more preferred values for tan 6 at 30 °C, and the more preferred values for tan 6 at 30 °C.
  • the tire tread rubber composition has a value for tan 6 at 60 °C of 0.18 to 0.25, preferably 0.18 to 0.22, more preferably 0.18 to 0.2, and meets at least one of the following (i.e., (a)-(b), preferably each of the following: (a) has a value for tan 6 at -30 °C of no more than 2.5 times the tan 6 at 60 °C value, preferably between 2.5 times and 2 times the tan 6 at 60 °C value; (b) has a value for tan 6 at 30 °C of at least 1.4 times the tan 6 at 60 °C value, preferably between 1.4 times and 2 times the tan 6 at 60 °C value, more preferably between 1.5 times and 1.8 times the tan 6 at 60 °C value; or (c) has a value for tan 6 at 0 °C of at least 2.2
  • the wear performance of a tire tread rubber composition can be evaluated by various methods.
  • the absolute wear values provided herein refer to DIN abrasion values that can be measured using standard methods including DIN ISO 4649, 2017 edition, or more preferably DIN ISO 53516. According to such method, the values represent the amount of material lost (in mm 3 ) during the abrasion testing. When comparing two DIN abrasion values, a lower number indicates less material lost and corresponds to an improvement in wear. An improvement in wear can also be described as improved resistance to abrasion and is generally desirable in a tire tread since it leads to a tire having a longer lifespan (e.g., having a higher predicted mileage rating).
  • the tire tread rubber composition has a DIN abrasion (according to DIN ISO 4649, 2017 edition, more preferably DIN ISO 53516) of no more than no more than 95 mm 3 (e.g., 95, 94, 93, 92, 91, 90, 89, 88, 87, 86, 85, 84, 83, 82, 81, 80, 79, 78, 77, 76, 75, 74, 73, 72, 71, 70, 69, 68, 67, 66, 65, 64, 63, 62, 61, 60 mm 3 or less), preferably no more than 90 mm 3 (e.g., 90, 89, 88, 87, 86, 85, 84, 83, 82, 81, 80, 79, 78, 77, 76, 75, 74, 73, 72, 71, 70, 69, 68, 67, 66, 65, 64, 63, 62, 61, 60 mm 3
  • the tire tread rubber compositions of the first-fourth embodiments can be considered to be particularly useful in terms of providing a tire tread improved rolling resistance and wear performance.
  • the rolling resistance and wear performance are balanced is meant that the rolling resistance and wear performance are each improved by at least 5% as compared to a control while maintaining the wear performance, where the control refers to a tread rubber composition which replaces the silica-reactive functionalized polybutadiene (ii) with an equivalent amount of a non-functional high cis polybutadiene.
  • the wear performance is at least 101% of a control (e.g., 101%, 102%, 103%, 104%, 105%, etc.), and in certain instances an improvement in wear as compared to the control, e.g., of at least 5% (e.g., 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15% or higher, including ranges encompassing the foregoing such as 5-15% and 5-10%) or even at least 10% (e.g., 10%, 11%, 12%, 13%, 14%, 15% or higher, including ranges encompassing the foregoing such as 10-15%).
  • a control e.g., 101%, 102%, 103%, 104%, 105%, etc.
  • an improvement in wear as compared to the control, e.g., of at least 5% (e.g., 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15% or higher, including
  • the foregoing improvements can also be described as being at least 105% (with 105% being 5% higher than 100%) and at least 110% (with 110% being 10% higher than 100%) as compared to a control.
  • the sample could be described as having a wear performance that is 95% of its control and if a sample exhibited an abrasion loss of 0.0054 mg and its control exhibited an abrasion loss of 0.0060 mg, the sample could be described as having a wear performance that is improved by 10% as compared to its control.
  • a wear performance that is 100% of its control should be understood as having a wear performance that is equal to its control and the comparisons to control are calculated by dividing the control value by the sample value and multiplying by 100%.
  • the rolling resistance is improved is meant that the rolling resistance (as reflected by tan 6 measurements at 60 °C, as described further herein) is at least 101% of a control (e.g., 101%, 102%, 103%, 104%, 105%, etc.), and in certain instances an improvement in rolling resistance as compared to the control, e.g., of at least 5% (e.g., 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15% or higher, including ranges encompassing the foregoing such as 5-15% and 5-10%) or even at least 10% (e.g., 10%, 11%, 12%, 13%, 14%, 15% or higher, including ranges encompassing the foregoing such as 10-15%).
  • the foregoing improvements can also be described as being at least 105% (with 105% being 5% higher than 100%) and at least 110% (with 110% being 10% higher than 100%) as compared to a control.
  • the rolling resistance and wear performance are each improved by at least 5% as compared to a control is meant to encompass improvements of 5%, 6%, 7%, 8%, 9%, 10%, 11%, etc. (as discussed above) or even improvements of at least 10% (as also discussed above).
  • the rubber composition has a room temperature Eb of at least 475% (e.g., 475%, 480%, 485%, 490%, 495%, 500%, 505%, 510%, 515%, 520%, 525%, 530%, 535%, 540%, 545%, 550%, 555%, 560%, 565%, 570%, 575%, 580%, 585%, 590%, 595%, 600%, 605%, 610%, 615%, 620%, 625%, 630%, 635%, 640%, 645%, 650%, or more) or within the range of 475 to 650% or a sub-range within that range, preferably at least 500% (e.g., 500%, 505%, 510%, 515%, 520%, 525%, 530%, 535%, 540%, 545%, 550%, 555%, 560%, 565%, 570%, 575%, 580%, 585%, 590%, 595%, preferably at least 500% (e.g., 500%, 50
  • Eb values refer to measurements made at 23 ° C. Eb can be measured following the guidelines, but not restricted to, the standard procedure described in ASTM D-412, with dumbbell-shaped samples having a cross-section dimension of 4 mm in width and 1.9 mm in thickness at the center. During measurement, specimens may be strained at a constant rate (20% per second) and the resulting force recorded as a function of extension (strain).
  • the rubber composition has a hot Eb of at least 375%, (e.g., 375%, 380%, 385%, 390%, 395%, 400%, 405%, 410%, 415%, 420%, 425%, 430%, 435%, 440%, 445%, 450%, 455%, 460%, 465%, 470%, 475%, 480%, 485%, 490%, 495%, 499%, or more) or within a range of 375-499% or a sub-range within that range, preferably at least 400% (e.g., 400%, 405%, 410%, 415%, 420%, 425%, 430%, 435%, 440%, 445%, 450%, 455%, 460%, 465%, 470%, 475%, 480%, 485%, 490%, 495%, 499%, or more) or within a range of 400-499% or a sub-range within that range.
  • 375% e.g., 375%, 380%, 385%, 390%, 395%, 400%, 405%, 410%, 41
  • hot Eb values refer to measurements made at 100 °C. Eb can be measured following the guidelines, but not restricted to, the standard procedure described in ASTM D-412, with dumbbell-shaped samples having a cross-section dimension of 4 mm in width and 1.9 mm in thickness at the center. During measurement, specimens may be strained at a constant rate (20% per second) and the resulting force recorded as a function of extension (strain). Generally, a hot Eb value for a given tread rubber composition will be lower (i.e., less than) the room temperature Eb for that tread rubber composition.
  • the rubber composition has a hot EbxTb (both values determined at 100 °C) of at least 3600 (e.g., 3600, 3650, 3700, 3750, 3800, 3850, 3900, 3950, 4000, 4050, 4100, 41504200, 4250, 4300, 4350, 4400, 4450, 4500, 4550, 4600, 4650, 4700, 4750, 4800, 4850, 4900, or more) or 3600 to 4900 or a subrange within that range, preferably at least 3800 (e.g., 3700, 3750, 3800, 3850, 3900, 3950, 4000, 4050, 4100, 4150, 4200, 4250, 4300, 4350, 4400, 4450, 4500, 4550, 4600, 4650, 4700, 4750, 4800, 4850, 4900, or more) or 3800 to 4900 or a sub-range within that range.
  • 3600 e.g., 3600, 3650, 3
  • the hot TbxEb is calculated by multiplying the hot Tb with the hot Eb value and refers to measurements made at 100 ° C.
  • Tb can be measured following the guidelines, but not restricted to, the standard procedure described in ASTM D-412, with dumbbell-shaped samples having a cross-section dimension of 4 mm in width and 1.9 mm in thickness at the center. During measurement, specimens may be strained at a constant rate (20% per second) and the resulting force recorded as a function of extension (strain).
  • the tire tread rubber composition according to the first-fourth embodiments, as disclosed herein will be utilized in a tire tread.
  • a tire tread comprising (made from) the tire tread rubber composition according to the first-fourth embodiments, as discussed herein.
  • such a tire tread can be utilized in a tire (along with other components).
  • a tire having a tread comprising (made from) the tire tread rubber composition according to the first- fourth embodiments, as discussed herein.
  • the methods are for providing a tire tread having improved wear and/or rolling resistance performance (preferably both improved wear and improved rolling resistance) by utilizing a tire tread rubber composition according to the first-third embodiments disclosed herein.
  • the improvement in wear and/or rolling resistance can be measured according to the methods described herein.
  • tire tread rubber compositions according to the present disclosure can be made using different SBRs, different polybutadienes, different reinforcing silica filler, different (or no) carbon black, different hydrocarbon resin, and different liquid plasticizing agents, generally in connection with the teachings provided herein and as fully disclosed in the preceding paragraphs.
  • Table 1 contains a summary of information relating to an exemplary inventive tire tread rubber composition and two (2) exemplary control tire tread rubber compositions. As should be apparent from a detailed review of Table 1, the control compositions each differ from the inventive compound with respect to certain of the listed ingredients as well as with respect to their properties, i.e., tan 6 values, as described below.
  • a tire tread rubber composition having a tan 6 at 60 ° C within the range of 0.18-0.22, a tan 6 at -30 °C of no more than 2.5 times the tan 6 at 60 °C, a tan 6 at 0 °C that is at least 2.2 times larger than tan 6 at 60 °C, and a tan 6 at 30 °C that is at least 1.4 times the tan 6 at 60 °C.
  • neither of the control compositions have a tan 6 at 60 ° C within the range of 0.18-0.22, a tan 6 at 0 °C that is at least 2.2 times larger than tan 6 at 60 °C, or a tan 6 at 30 °C that is at least 1.4 times the tan 6 at 60 °C.

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Abstract

Disclosed herein are tire tread rubber compositions comprising a specified elastomer component, reinforcing silica filler, a specified hydrocarbon resin, liquid plasticizer, and a cure package. The elastomer component includes styrene-butadiene rubber and a high cis polybutadiene having a silica-reactive functional group. Use of the disclosed ingredients may result in a tire tread having particular properties, as discussed further herein.

Description

TIRE TREAD RUBBER COMPOSITION AND RELATED METHODS
FIELD
[0001] The present application is directed to tire tread rubber compositions and related methods.
BACKGROUND
[0002] Tires comprise many components including a road-contacting tread. The particular ingredients used to prepare the rubber composition which comprises the tire tread may vary. Formulation of tire tread rubber compositions is a complex science since changes to the formulation which result in an improvement in one property (e.g., wet performance) may result in deterioration of another property (e.g., dry traction).
SUMMARY
[0003] Disclosed herein are rubber compositions for tire treads and related methods.
[0004] In a first embodiment, a tire tread rubber composition is disclosed. The composition is made of ingredients comprising: (a) 100 parts of an elastomer component comprising (i) 35-55 parts, preferably 35-49 parts, more preferably 40-49 parts of at least one styrene-butadiene rubber having a Tg of about -30 to about -50 °C, (ii) 45-65 parts, preferably 51- 65 parts, more preferably 51-60 parts of polybutadiene rubber having a cis bond content of at least 95%, a Tg of less than -101 °C, preferably -101 to -110 °C, and a silica-reactive functional group; (b) 70-99 phr of at least one reinforcing silica filler having a surface area of about 100 to about 300 m2/g, preferably about 150 to about 300 m2/g; (c) no more than 15 phr of carbon black, preferably no more than 10 phr of carbon black; (d) 25-35 phr of at least one hydrocarbon resin having a Tg of about 30 to about 50 °C; (e) 11-20 phr of at least one liquid plasticizing agent, which preferably consists of at least one oil; and (f) a cure package, wherein the total amount of (d) and (e) is 36-54 phr.
[0005] In a second embodiment, a tire tread rubber composition is disclosed. The composition is made of ingredients comprising: (a) 100 parts of an elastomer component comprising (i) 35-49 parts, preferably 40-49 parts, of at least one styrene-butadiene rubber having a Tg of about -30 to about -50 °C and a silica-reactive functional group, (ii) 51-65 parts, preferably 51-60 parts, of polybutadiene rubber having a cis bond content of at least 95%, a Tg of less than -101 °C, preferably -101 to -110 °C, and a silica-reactive functional group; (b)70-99 phr of at least one reinforcing silica filler having a surface area of about 100 to about 300 m2/g, preferably about 150 to about 300 m2/g; (c) no more than 15 phr of carbon black, preferably no more than 10 phr of carbon black; (d) 25-35 phrof at least one aromatic hydrocarbon resin having a Tg of about 30 to about 50 °C; (e) 11-20 phr of at least one liquid plasticizing agent, which preferably consists of at least one oil; and (f) a cure package, wherein the total amount of (d) and (e) is 36-54 phr, preferably 40-50 phr.
[0006] In a third embodiment, which is a sub-embodiment of the first embodiment, a tire tread rubber composition is disclosed. The composition is made of ingredients comprising: (a) 100 parts of an elastomer component comprising (i) 35-55 parts, preferably 35-49 parts, more preferably 40-49 parts of at least one styrene-butadiene rubber having a Tg of about -30 to about -50 °C, (ii) 45-65 parts, preferably 51-65 parts, more preferably 51-60 parts of polybutadiene rubber having a cis bond content of at least 95%, a Tg of less than -101 °C, preferably -101 to - 110 °C, and a silica-reactive functional group; (b) 70-99 phr of at least one reinforcing silica filler having a surface area of about 100 to about 300 m2/g, preferably about 150 to about 300 m2/g; (c) no more than 15 phr of carbon black, preferably no more than 10 phr of carbon black; (d) 25- 35 phr of at least one hydrocarbon resin having a Tg of about 30 to about 50 °C; (e) 11-20 phr of at least one liquid plasticizing agent, which preferably consists of at least one oil; and (f) a cure package, wherein the total amount of (d) and (e) is 36-54 phr. Additionally, according to third embodiment, the tire tread rubber composition has a value for tan 6 at 60 °C of 0.18 to 0.25, preferably 0.18 to 0.22, more preferably 0.18 to 0.2, and meets at least one of the following: (a) has a value for tan 6 at -30 °C of no more than 2.5 times the tan 6 at 60 °C value, preferably between 2.5 times and 2 times the tan 6 at 60 °C value; (b) has a value for tan 6 at 30 °C of at least 1.4 times the tan 6 at 60 °C value, preferably between 1.4 times and 2 times the tan 6 at 60 °C value, more preferably between 1.5 times and 1.8 times the tan 6 at 60 °C value; or (c) has a value for tan 6 at 0 °C of at least 2.2 times the tan 6 at 60 °C value, preferably between 2.2 times and 3 times the tan 6 at 60 °C value, more preferably between 2.3 times and 2.8 times the tan 6 at 60 °C value. [0007] In a fourth embodiment, which is a sub-embodiment of the second embodiment, a tire tread rubber composition is disclosed. The composition is made of ingredients comprising: (a) 100 parts of an elastomer component comprising (i) 35-49 parts, preferably 40-49 parts, of at least one styrene-butadiene rubber having a Tg of about -30 to about -50 °C and a silicareactive functional group, (ii) 51-65 parts, preferably 51-60 parts, of polybutadiene rubber having a cis bond content of at least 95%, a Tg of less than -101 °C, preferably -101 to -110 °C, and a silica-reactive functional group; (b) 70-99 phr of at least one reinforcing silica filler having a surface area of about 100 to about 300 m2/g, preferably about 150 to about 300 m2/g; (c) no more than 15 phr of carbon black, preferably no more than 10 phr of carbon black; (d) 25-35 phr of at least one aromatic hydrocarbon resin having a Tg of about 30 to about 50 °C; (e) 11-20 phr of at least one liquid plasticizing agent, which preferably consists of at least one oil; and (f) a cure package, wherein the total amount of (d) and (e) is 36-54 phr, preferably 40-50 phr. Additionally, according to fourth embodiment, the tire tread rubber composition has a value for tan 6 at 60 °C of 0.18 to 0.25, preferably 0.18 to 0.22, more preferably 0.18 to 0.2, and meets at least one of the following: (a) has a value for tan 6 at -30 °C of no more than 2.5 times the tan 6 at 60 °C value, preferably between 2.5 times and 2 times the tan 6 at 60 °C value; (b) has a value for tan 6 at 30 °C of at least 1.4 times the tan 6 at 60 °C value, preferably between 1.4 times and 2 times the tan 6 at 60 °C value, more preferably between 1.5 times and 1.8 times the tan 6 at 60 °C value; or (c) has a value for tan 6 at 0 °C of at least 2.2 times the tan 6 at 60 °C value, preferably between 2.2 times and 3 times the tan 6 at 60 °C value, more preferably between 2.3 times and 2.8 times the tan 6 at 60 °C value.
DETAILED DESCRIPTION
[0008] Disclosed herein are rubber compositions for tire treads and related methods.
[0009] In a first embodiment, a tire tread rubber composition is disclosed. The composition is made of ingredients comprising: (a) 100 parts of an elastomer component comprising (i) 35-55 parts, preferably 35-49 parts, more preferably 40-49 parts of at least one styrene-butadiene rubber having a Tg of about -30 to about -50 °C, (ii) 45-65 parts, preferably 51- 65 parts, more preferably 51-60 parts of polybutadiene rubber having a cis bond content of at least 95%, a Tg of less than -101 °C, preferably -101 to -110 °C, and a silica-reactive functional group; (b) 70-99 phr of at least one reinforcing silica filler having a surface area of about 100 to about 300 m2/g, preferably about 150 to about 300 m2/g; (c) no more than 15 phr of carbon black, preferably no more than 10 phr of carbon black; (d) 25-35 phr of at least one hydrocarbon resin having a Tg of about 30 to about 50 °C; (e) 11-20 phr of at least one liquid plasticizing agent, which preferably consists of at least one oil; and (f) a cure package, wherein the total amount of
(d) and (e) is 36-54 phr.
[0010] In a second embodiment, a tire tread rubber composition is disclosed. The composition is made of ingredients comprising: (a) 100 parts of an elastomer component comprising (i) 35-49 parts, preferably 40-49 parts, of at least one styrene-butadiene rubber having a Tg of about -30 to about -50 °C and a silica-reactive functional group, (ii) 51-65 parts, preferably 51-60 parts, of polybutadiene rubber having a cis bond content of at least 95%, a Tg of less than -101 °C, preferably -101 to -110 °C, and a silica-reactive functional group; (b)70-99 phr of at least one reinforcing silica filler having a surface area of about 100 to about 300 m2/g, preferably about 150 to about 300 m2/g; (c) no more than 15 phr of carbon black, preferably no more than 10 phr of carbon black; (d) 25-35 phrof at least one aromatic hydrocarbon resin having a Tg of about 30 to about 50 °C; (e) 11-20 phr of at least one liquid plasticizing agent, which preferably consists of at least one oil; and (f) a cure package, wherein the total amount of (d) and
(e) is 36-54 phr, preferably 40-50 phr.
[0011] In a third embodiment, which is a sub-embodiment of the first embodiment, a tire tread rubber composition is disclosed. The composition is made of ingredients comprising: (a) 100 parts of an elastomer component comprising (i) 35-55 parts, preferably 35-49 parts, more preferably 40-49 parts of at least one styrene-butadiene rubber having a Tg of about -30 to about -50 °C, (ii) 45-65 parts, preferably 51-65 parts, more preferably 51-60 parts of polybutadiene rubber having a cis bond content of at least 95%, a Tg of less than -101 °C, preferably -101 to - 110 °C, and a silica-reactive functional group; (b) 70-99 phr of at least one reinforcing silica filler having a surface area of about 100 to about 300 m2/g, preferably about 150 to about 300 m2/g; (c) no more than 15 phr of carbon black, preferably no more than 10 phr of carbon black; (d) 25- 35 phr of at least one hydrocarbon resin having a Tg of about 30 to about 50 °C; (e) 11-20 phr of at least one liquid plasticizing agent, which preferably consists of at least one oil; and (f) a cure package, wherein the total amount of (d) and (e) is 36-54 phr. Additionally, according to third embodiment, the tire tread rubber composition has a value for tan 6 at 60 °C of 0.18 to 0.25, preferably 0.18 to 0.22, more preferably 0.18 to 0.2, and meets at least one of the following: (a) has a value for tan 6 at -30 °C of no more than 2.5 times the tan 6 at 60 °C value, preferably between 2.5 times and 2 times the tan 6 at 60 °C value; (b) has a value for tan 6 at 30 °C of at least 1.4 times the tan 6 at 60 °C value, preferably between 1.4 times and 2 times the tan 6 at 60 °C value, more preferably between 1.5 times and 1.8 times the tan 6 at 60 °C value; or (c) has a value for tan 6 at 0 °C of at least 2.2 times the tan 6 at 60 °C value, preferably between 2.2 times and 3 times the tan 6 at 60 °C value, more preferably between 2.3 times and 2.8 times the tan 6 at 60 °C value.
[0012] In a fourth embodiment, which is a sub-embodiment of the second embodiment, a tire tread rubber composition is disclosed. The composition is made of ingredients comprising: (a) 100 parts of an elastomer component comprising (i) 35-49 parts, preferably 40-49 parts, of at least one styrene-butadiene rubber having a Tg of about -30 to about -50 °C and a silicareactive functional group, (ii) 51-65 parts, preferably 51-60 parts, of polybutadiene rubber having a cis bond content of at least 95%, a Tg of less than -101 °C, preferably -101 to -110 °C, and a silica-reactive functional group; (b) 70-99 phr of at least one reinforcing silica filler having a surface area of about 100 to about 300 m2/g, preferably about 150 to about 300 m2/g; (c) no more than 15 phr of carbon black, preferably no more than 10 phr of carbon black; (d) 25-35 phr of at least one aromatic hydrocarbon resin having a Tg of about 30 to about 50 °C; (e) 11-20 phr of at least one liquid plasticizing agent, which preferably consists of at least one oil; and (f) a cure package, wherein the total amount of (d) and (e) is 36-54 phr, preferably 40-50 phr. Additionally, according to fourth embodiment, the tire tread rubber composition has a value for tan 6 at 60 °C of 0.18 to 0.25, preferably 0.18 to 0.22, more preferably 0.18 to 0.2, and meets at least one of the following: (a) has a value for tan 6 at -30 °C of no more than 2.5 times the tan 6 at 60 °C value, preferably between 2.5 times and 2 times the tan 6 at 60 °C value; (b) has a value for tan 6 at 30 °C of at least 1.4 times the tan 6 at 60 °C value, preferably between 1.4 times and 2 times the tan 6 at 60 °C value, more preferably between 1.5 times and 1.8 times the tan 6 at 60 °C value; or (c) has a value for tan 6 at 0 °C of at least 2.2 times the tan 6 at 60 °C value, preferably between 2.2 times and 3 times the tan 6 at 60 °C value, more preferably between 2.3 times and
2.8 times the tan 6 at 60 °C value.
Definitions
[0013] The terminology as set forth herein is for description of the embodiments only and should not be construed as limiting the invention as a whole.
[0014] As used herein, the term "majority" refers to more than 50%.
[0015] As used herein, the abbreviation Mn is used for number average molecular weight.
[0016] As used herein, the abbreviation Mp is used for peak molecular weight.
[0017] As used herein, the abbreviation Mw is used for weight average molecular weight.
[0018] Unless otherwise indicated herein, the term "Mooney viscosity" refers to the Mooney viscosity, M LI+4. As those of skill in the art will understand, a rubber composition's Mooney viscosity is measured prior to vulcanization or curing.
[0019] As used herein, the term "natural rubber" means naturally occurring rubber such as can be harvested from sources such as Hevea rubber trees and non-/7eveo sources (e.g., guayule shrubs and dandelions such as TKS). In other words, the term "natural rubber" should be construed so as to exclude synthetic polyisoprene.
[0020] As used herein, the term "phr" means parts per one hundred parts rubber. The one hundred parts rubber is also referred to herein as 100 parts of an elastomer component.
[0021] As used herein the term "polyisoprene" means synthetic polyisoprene. In other words, the term is used to indicate a polymer that is manufactured from isoprene monomers, and should not be construed as including naturally occurring rubber (e.g., Hevea natural rubber, guayule-sourced natural rubber, or dandelion-sourced natural rubber). However, the term polyisoprene should be construed as including polyisoprenes manufactured from natural sources of isoprene monomer.
[0022] As used herein, the term "tread," refers to both the portion of a tire that comes into contact with the road under normal inflation and load as well as any subtread.
Tire Tread Rubber Composition
[0023] As mentioned above, the first-fourth embodiments disclosed herein are directed to tire tread rubber compositions made of specified ingredients. The subject rubber compositions are used in preparing treads for tires, generally by a process which includes forming of a tread pattern by molding and curing one of the subject rubber compositions. Thus, the tire treads will contain a cured form of one of the tire tread rubber compositions. The tire tread rubber compositions may be present in the form of a tread which has been formed but not yet incorporated into a tire and/or they may be present in a tread which forms part of a tire.
[0024] According to the first -fourth embodiments disclosed herein, the Tg of the overall rubber composition may vary. The Tg of the overall rubber composition may be referred to as a compound Tg or as a rubber composition Tg. In certain embodiments of the first-fourth embodiments, the rubber composition has a compound Tg of -40 to -60 °C (e.g., -40, -42, -44, - 45, -46, -48, -50, -52, -54, -55, -56, -58, -60, -62, -64, -65, -66, -68, or -70 °C ), -50 to -70 °C (e.g., -50, -52, -54, -55, -56, -58, -60, -62, -64, -66, -68, or -70 °C ), -45 to -65 °C (e.g, -45, -46, -48, -50, -52, -54, -55, -56, -58, -60, -62, -64, or -65 °C ), -40 to -60 °C (e.g, -40, -42, -44, -45, -46, -48, -50, -52, -54, -55, -56, -58, or -60 °C), -40 to -50 °C (e.g, -40, -41, -42, -43, -44, -45, -46, -47, -48, -49, or -50 °C), -50 to -60 °C (e.g, -50, -51, -52, -53, -54, -55, -56, -57, -58, -59, or -60 °C), -60 to -70 °C (-60, -61, -62, -63, -64, -65, -66, -67, -68, -69, or -70 °C), -45 to -55 °C (-45, -46, -47, -48, -49, -50, -51, -52, -53, -54, or -55 °C), or -55 to -65 °C (e.g., -55, -56, -57, -58, -59, -60, -61, -62, -63, -64, or -64 °C) or a range within one of the foregoing ranges. The compound Tg of a rubber composition can be measured using a dynamic mechanical thermal spectrometer (such as the Gabo instrument described below, operating in tension mode) generally following the guidelines of ASTM D5992-96 (2011) and using a temperature sweep (from -70 to 65 °C), under specified test conditions (i.e., frequency 52 Hz, static strain of 6%, dynamic strain of 0.1%, sample geometry 4.75 mm wide x 29 mm long x 2 mm deep), with the measurement made on the sample after curing for 15 minutes at 170 °C, and using a vibratory method to estimate the Tg from the curve that results.
Elastomer Component
[0025] As mentioned above, according to the first-fourth embodiments, the tire tread rubber composition is made of ingredients comprising (including) 100 parts of an elastomer component. The ingredients of the elastomer component include styrene-butadiene rubber and polybutadiene rubber. The total amount of 100 parts of elastomer or rubber is used so that the amount of other ingredients may be listed in amounts of phr or the number of parts per hundred parts of rubber (or 100 parts of the elastomer component). As a non-limiting example, for a rubber composition containing 35 parts of styrene-butadiene rubber, 65 parts of polybutadiene rubber, and 110 parts of reinforcing silica filler, the amount of silica filler can also be described as 110 phr.
[0026] As mentioned above, according to the first and third embodiments, the 100 parts of elastomer component comprises (includes) (i) 35-55 parts (e.g., 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, or 55 parts), preferably 35-49 parts (e.g., 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49 parts), more preferably 40-49 parts (e.g., 40, 41, 42, 43, 44, 45, 46, 47, 48, 49 parts) of at least one styrene-butadiene rubber having a Tg of about -30 to about -50 °C or -30 to -50 °C (e.g., 30, 32, 34, 35, 36, 38, 40, 42, 44, 45, 46, 48, or 50 °C), and (ii) 45-65 parts (e.g., 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64 or 65 parts), preferably 51-65 parts (e.g., 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64 or 65 parts), more preferably 51-60 parts (e.g., 51, 52, 53, 54, 55, 56, 57, 58, 59, or 60 parts) of polybutadiene rubber having a cis bond content of at least 95%, a Tg of less than -101 °C (e.g., - 101, -102, -103, -104, -105, -106, -107, -108, -109, -110, -111, -112, etc. °C), preferably -101 to - 110 °C (e.g., -101, -102, -103, -104, -105, -106, -107, -108, -109, -110 °C) and a silica-reactive functional group. As mentioned above, according to the second and fourth embodiments, the 100 parts of elastomer component comprises (includes) (i) 35-49 parts (e.g., 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49 parts), preferably 40-49 parts (e.g., 40, 41, 42, 43, 44, 45, 46, 47, 48, 49 parts) of at least one styrene-butadiene rubber having a Tg of about -30 to about -50 °C or -30 to -50 °C (e.g., 30, 32, 34, 35, 36, 38, 40, 42, 44, 45, 46, 48, or 50 °C) and a silica-reactive functional group, and (ii) 51-65 parts (e.g., 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64 or 65 parts), preferably 51-60 parts (e.g., 51, 52, 53, 54, 55, 56, 57, 58, 59, or 60 parts) of polybutadiene rubber having a cis bond content of at least 95%, a Tg of less than -101 °C (e.g., - 101, -102, -103, -104, -105, -106, -107, -108, -109, -110, -111, -112, etc. °C), preferably -101 to - 110 °C (e.g., -101, -102, -103, -104, -105, -106, -107, -108, -109, -110 °C) and a silica-reactive functional group. [0027] In certain embodiments of the first-fourth embodiments, the elastomer component (a) includes no more than 9 parts (e.g., 9, 8, 7, 6, 5, 4, 3, 2, 1 or even 0 parts), preferably no more than 5 parts (e.g., 5, 4, 3, 2, 1 or even 0 parts) of natural rubber, polyisoprene, or a combination thereof. In certain embodiments of the first-fourth embodiments, the elastomer component (a) includes 0 parts of natural rubber, polyisoprene, or a combination thereof. In certain embodiments of the first -fourth embodiments, an amount of no more than 9 parts refers to 1-9 parts and in other embodiments 0-9 parts. Similarly, in certain embodiments of the first-fourth embodiments, an amount of no more than 5 parts refers to 1-5 parts and in other embodiments 0-5 parts.
[0028] In certain embodiments of the first-fourth embodiments, the 100 parts of elastomer component consists (only) of (i) (i.e., the at least one styrene-butadiene rubber, as specified) and (ii) (i.e., the polybutadiene rubber, as specified), in amounts as discussed above. In other embodiments of the first embodiment, the 100 parts of elastomer component includes in addition to (i) and (ii), one or more additional rubbers (iii). According to the first-fourth embodiments, when one or more additional rubbers (iii) is present, the amount will generally be limited preferably to no more than 20 parts (e.g., 20 parts, 15 parts, 10 parts, 5 parts, or less), more preferably no more than 15 parts (e.g., 15 parts, 10 parts, 5 parts, or less), no more than 9 parts (e.g., 9, 8, 7, 6, 5, 4, 3, 2, 1 or even 0 parts), or no more than 5 parts (e.g., 5 parts, 4 parts, 3 parts, 2 parts, 1 part, or less). In certain embodiments of the first-fourth embodiments, an amount of no more than 20 parts refers to 1-20 parts and in other embodiments 0-20 parts. In certain embodiments of the first-fourth embodiments, an amount of no more than 15 parts refers to 1-15 parts and in other embodiments 0-15 parts. In certain embodiments of the first- fourth embodiments, an amount of no more than 9 parts refers to 1-9 parts and in other embodiments 0-9 parts. In certain embodiments of the first-fourth embodiments, an amount of no more than 5 parts refers to 1-5 parts and in other embodiments 0-5 parts. In certain embodiments of the first-fourth embodiments, one or more additional rubbers (iii) are selected from diene monomer-containing rubbers; in certain such embodiments, the one or more additional rubbers (iv) are selected from the group consisting of natural rubber, polyisoprene, styrene-isoprene rubber, butadiene-isoprene rubber, styrene-isoprene-butadiene rubber, butyl rubber (both halogenated and non-halogenated), ethylene-propylene rubber (EPR), ethylenebutylene rubber (EBR), ethylene-propylene-diene rubber (EPDM), and combinations thereof. In yet other embodiments of the first -fourth embodiments, the one or more additional rubbers are selected from natural rubber, polyisoprene, or a combination thereof; one or more styrenebutadiene rubbers other than the styrene-butadiene rubber (i), e.g., a SBR having a Tg of greater than -30 °C (e.g., -25 °C, -20 °C, -15 °C or higher) or having a Tg of less than -50 °C (e.g., -55, -60 °C or lower); or from a polybutadiene other than the polybutadiene (ii), e.g., a polybutadiene having a low cis 1,-4 bond content (e.g., of less than 50%, less than 45%, less than 40%, etc.), a non-functionalized polybutadiene rubber having a cis bond content of at least 95% and a Tg of - 101 °C or lower, or a combination thereof; or a combination of the foregoing types of rubbers.
[0029] In certain embodiments of the first-fourth embodiments, the elastomer component of the tire tread rubber composition includes less than 10 parts (e.g., 9, 8, 7, 6, 5, 4, 3, 2, 1, or 0 parts) of non-functionalized rubber, preferably less than 5 parts (e.g., 4, 3, 2, 1, or 0 parts) of non-functionalized rubber, even more preferably 0 parts of non-functionalized rubber. According to such embodiments, the at least one styrene-butadiene rubber (i) and polybutadiene rubber (ii), are both functionalized, preferably both with a silica-reactive functional group.
[0030] The Tg values referred to herein for elastomers represent a Tg measurement made upon the elastomer without any oil-extension. In other words, for an oil-extended elastomer, the Tg values above refer to the Tg prior to oil extension or to a non-oil-extended version of the same elastomer. Elastomer or polymer Tg values may be measured using a differential scanning calorimeter (DSC) instrument, such as manufactured by TA Instruments (New Castle, Delaware), where the measurement is conducted using a temperature elevation of 10°C/minute after cooling at -120 °C. Thereafter, a tangent is drawn to the base lines before and after the jump of the DSC curve. The temperature on the DSC curve (read at the point corresponding to the middle of the two contact points) can be used as Tg.
[0031] In certain embodiments of the first-fourth embodiments, the average Tg of the elastomer component is -70 to -90 °C (e.g., -70, -71, -72, -73, -74, -75, -76, -77, -78, -79, -80, -81, -82, -83, -84, -85, -86, -87, -88, -89, or -90 °C), preferably -75 to -85 °C (e.g., -75, -76, -77, -78, -79, -80, -81, -82, -83, -84, or -85 °C). The average Tg of the elastomer component can be calculated using the Tg of each rubber present in the 100 parts of elastomer component and accounting for their relative weight percentage. When one (or more) of the rubbers is oil-extended, only the amount of rubber (/.e., excluding any amount of oil) is utilized in calculating the average Tg of the elastomer component. When one (or more) of the rubbers is oil-extended, the Tg of the oil- extended rubber in its non-oil-extended form (/.e., rubber only) is utilized in calculating the average Tg of the elastomer component.
Styrene-Butadiene Rubber (i)
[0032] As mentioned above, according to the first and third embodiments, the elastomer component of the tire tread rubber composition includes at least one styrene-butadiene rubber (i) having a Tg of about -30 to about -50 °C or -30 to -50 °C (e.g., -30, -31, -32, -33, -34, -35, -36, - 37, -38, -39, -40, -41, -42, -43, -44, -45, -46, -47, -48, -49, or -50 °C) and according to the second and fourth embodiments, the elastomer component of the tire tread rubber composition includes at least one styrene-butadiene rubber (i) having a Tg of about -30 to about -50 °C or -30 to -50 °C (e.g., -30, -31, -32, -33, -34, -35, -36, -37, -38, -39, -40, -41, -42, -43, -44, -45, -46, -47, - 48, -49, or -50 °C), and a silica-reactive functional group, in an amount as discussed above. In certain preferred embodiments of the first-fourth embodiments, the at least one styrene- butadiene rubber (i) has a Tg of about -40 to about -50 or -40 to -50 °C (e.g., -40, -41, -42, -43, - 44, -45, -46, -47, -48, -49, or -50 °C), in an amount as discussed above.
[0033] According to the first-fourth embodiments, the styrene monomer content (i.e., weight percent of the polymer chain comprising styrene units as opposed to butadiene units) of the at least one styrene-butadiene rubber(i), as described above, may vary. In certain embodiments of the first-fourth embodiments, the at least one styrene-butadiene rubber(i), as described above, has a styrene monomer content of about 20 to about 35% or 20 to 35% (e.g., 20%, 25%, 20%, 35%, or 35%) by weight of the total monomer content (i.e., 1,3-butadiene + styrene), including about 25 to about 35%, and 25 to 35% (e.g., 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, or 35%) by weight.
[0034] According to the first-fourth embodiments, the vinyl bond content (i.e., 1,2- microstructure) of the at least one styrene-butadiene rubber(i), as described above, may vary. In certain embodiments of the first-fourth embodiments, the at least one styrene-butadiene rubber(i), as discussed above, has a vinyl bond content of about 35 to about 55%, 35-55% (e.g., 35%, 40%, 45%, 50%, or 55%), preferably about 40 to about 55%, 40 to 55% (e.g., 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%, or 55%), more preferably about 45 to about 50%, or 45 to 50% (e.g., 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, or 50%). The at least one styrene-butadiene rubber(i), as described above, may have a vinyl bond content within one of the foregoing ranges, optionally in combination with one or more of the Mw, Mn, and/or Mw/Mn ranges discussed below, and in certain preferred embodiments optionally in combination with one of the styrene monomer contents discussed above. The vinyl bond contents referred to herein should be understood as being for the overall vinyl bond content in the styrene-butadiene rubber polymer chain rather than of the vinyl bond content in the butadiene portion of the styrene-butadiene rubber polymer chain, and can be determined by H1-NMR and C13-NMR (e.g., using a 300 MHz Gemini 300 NMR Spectrometer System (Varian)). The styrene contents disclosed herein can be determined using a similar method and the same instrumentation.
[0035] According to the first-fourth embodiments disclosed herein, the Mw of the at least one styrene-butadiene rubber (i), as described above, may vary. In certain embodiments of the first-fourth embodiments disclosed herein, the at least one styrene-butadiene rubber (i) (as described above), has a Mw of about 300,000 to about 550,000 grams/mole or 300,000 to 550,000 grams/mole (e.g., 300,000; 325,000; 350,000; 375,000; 400,000; 425,000; 450,000; 475,000; 500,000; 525,000; or 550,000 grams/mole), preferably about 300,000 to about 500,000 or 300,000 to 500,000 grams/mole (e.g., 300,000; 325,000; 350,000; 375,000; 400,000; 425,000; 450,000; 475,000; or 500,000 grams/mole), more preferably about 350,000 to about 450,000 or 350,000 to 450,000 grams/mole (e.g., 350,000; 375,000; 400,000; 425,000; or 450,000 grams/mole), according to a polystyrene standard (and as determined by GPC).
[0036] According to the first-fourth embodiments disclosed herein, the Mn of the at least one styrene-butadiene rubber (i), as described above, may vary. In certain embodiments of the first-fourth embodiments disclosed herein, the at least one styrene-butadiene rubber (i), as described above, has a Mn of about 250,000 to about 450,000 grams/mole or 250,000 to 450,000 grams/mole (e.g., 250,000; 275,000; 300,000; 325,000; 350,000; 375,000; 400,000; 425,000; or 450,000 grams/mole), preferably about 300,000 to about 400,000 grams/mole or 300,000 to 400,000 grams/mole (e.g., 300,000; 325,000; 350,000; 375,000; or 400,000 grams/mole), according to a polystyrene standard (and as determined by GPC). When the at least one styrenebutadiene rubber (i), as described above, is a functionalized polymer (i.e., according to the second and fourth embodiments and in preferred embodiments of the first and third embodiments), it should be understood that the foregoing Mw and Mn values refer to coupled Mw and coupled Mn rather than base polymer values. In certain embodiments of the first-fourth embodiments, the at least one styrene-butadiene rubber of (i), as described above, has a Mn within one of the foregoing ranges in combination with a Mw within one of the foregoing ranges, optionally in combination with a Mw/Mn value as discussed below.
[0037] According to the first -fourth embodiments disclosed herein, the Mw/Mn of the at least one styrene-butadiene rubber (i), as described above, may vary. In certain embodiments of the first-fourth embodiments disclosed herein, the at least one styrene-butadiene rubber(i), as described above, has a Mw/Mn (polydispersity) of 1.2 to 2 (e.g., 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, or 2), preferably 1.2 to 1.5 (e.g., 1.2, 1.3, 1.4, or 1.5). As mentioned above, in certain embodiments of the first-fourth embodiments disclosed herein, the at least one styrene- butadiene rubber (i), as described above, has a Mw/Mn within one of the foregoing ranges, in combination with at least one of the Mw ranges or Mn ranges described above, preferably in combination with one of the Mw ranges and one of the Mn ranges described above.
[0038] In certain embodiments of the first-fourth embodiments disclosed herein, the at least one styrene-butadiene rubber (i), as described above, is an oil-extended rubber, incorporating oil in an amount as discussed further below. In other preferred embodiments of the first-fourth embodiments disclosed herein, the at least one styrene-butadiene rubber (i), as described above, is a non oil-extended rubber (i.e., the SBR is not extended with any oil).
[0039] As mentioned above, according to the second and fourth embodiments and in preferred embodiments of the first and second embodiments disclosed herein, the at least one styrene-butadiene rubber (i) having a Tg of about -30 to about -50 °C, has a silica-reactive functional group. Generally, a styrene-butadiene rubber having a silica-reactive functional group can be considered to be a functionalized polymer or functionalized styrene-butadiene rubber. Non-limiting examples of silica-reactive functional groups generally include nitrogen-containing functional groups, silicon-containing functional groups, oxygen- or sulfur-containing functional groups, and metal-containing functional groups, as discussed in more detail below.
[0040] When the at least one styrene-butadiene rubber (i), as described above, has a silica-reactive functional group, the functionalization can be achieved during preparation of the polymer by adding a functional group to one or both terminus of the polymer, by adding a functional group to the backbone of the poly (or a combination of the foregoing) or by coupling more than one polymer chains to a coupling agent, or by a combination thereof. Such effects can be achieved by treating a living polymer with coupling agents, functionalizing agents, or a combination thereof which serve to couple and/or functionalize other chains. In certain preferred embodiments of the first-fourth embodiments, the at least one styrene-butadiene rubber (i) having a silica-reactive functional group contains one or more functional groups but is not coupled (/.e., does not contain any separate coupling agent). Generally, a coupling agent and/or functionalizing agent can be used at various molar ratios. Alternatively, in certain embodiments of the first-fourth embodiments, the functionalized styrene-butadiene rubber of (i) may be silica-reactive merely from the result of using a coupling agent. Although reference is made herein to the use of both coupling agents and functionalizing groups (and compounds used therefor), those skilled in the art appreciate that certain compounds may serve both functions. That is, certain compounds may both couple and provide the polymer chains with a functional group. Those skilled in the art also appreciate that the ability to couple polymer chains may depend upon the amount of coupling agent reacted with the polymer chains. For example, advantageous coupling may be achieved where the coupling agent is added in a one to one ratio between the equivalents of lithium on the initiator and equivalents of leaving groups (e.g., halogen atoms) on the coupling agent. Non-limiting examples of coupling agents include metal halides, metalloid halides, alkoxysilanes, alkoxystannanes, and combinations thereof. In preferred embodiments of the first-fourth embodiments, the at least one styrene-butadiene rubber (i) has a silica-reactive functional group (as discussed further, infra, as functional groups) but does not include any coupling agent selected from the group consisting of metal halides, metalloid halides, alkoxysilanes, alkoxystannanes, and combinations thereof. [0041] Non-limiting examples of nitrogen-containing functional groups that can be utilized in certain embodiments of the first-fourth embodiments as a silica-reactive functional group in the at least one styrene-butadiene rubber (i) include, but are not limited to, a substituted or unsubstituted amino group, an amide residue, an isocyanate group, an imidazolyl group, an indolyl group, an imino group, a nitrile group, a pyridyl group, and a ketimine group. In certain preferred embodiments of the first-fourth embodiments, the at least one styrene-butadiene rubber (i) has a silica-reactive functional group including, an unsubstituted amino group, a substituted amino group, or substituted imino group. The foregoing substituted or unsubstituted amino group should be understood to include a primary alkylamine, a secondary alkylamine, or a cyclic amine, and an amino group derived from a substituted or unsubstituted imine. In certain embodiments of the first-fourth embodiments, the at least one styrene- butadiene rubber (i) of the elastomer component comprises at one silica-reactive functional group selected from the foregoing list of nitrogen-containing functional groups.
[0042] In certain embodiments of the first-fourth embodiments, the at least one styrene- butadiene rubber (i) includes a silica-reactive functional group from a compound which includes nitrogen in the form of an imino group. Such an imino-containing functional group may be added by reacting the active terminal of a polymer chain with a compound having the following formula (I): wherein R, R', R", and R"' each independently are selected from a group having 1 to 18 carbon atoms (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, or 18 carbon atoms) selected from the group consisting of an alkyl group, an allyl group, and an aryl group; m and n are integers of 1 to 20 (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20) and 1 to 3 (1, 2, or 3), respectively. Each of R, R', R", and R'" are preferably hydrocarbyl and contain no heteroatoms. In certain embodiments of the first-fourth embodiments, each R and R' are independently selected from an alkyl group having 1 to 6 carbon atoms (e.g., 1, 2, 3, 4, 5, or 6 carbon atoms), preferably 1 to 3 carbon atoms (e.g., 1, 2, or 3 carbon atoms). In certain embodiments of the first-fourth embodiments, m is an integer of 2 to 6 (e.g., 2, 3, 4, 5, or 6), preferably 2 to 3. In certain embodiments of the first -fourth embodiments, R'" is selected from an alkyl group having 1 to 6 carbon atoms (e.g., 1, 2, 3, 4, 5, or 6 carbon atoms), preferably 2 to 4 carbon atoms (e.g., 2, 3, or 4 carbon atoms). In certain embodiments of the first-fourth embodiments, R" is selected from an alkyl group having 1 to 6 carbon atoms (e.g., 1, 2, 3, 4, 5, or 6 carbon atoms), preferably 1 to 3 carbon atoms (e.g., 1, 2, or 3 carbon atoms), most preferably 1 carbon atom (e.g., methyl). In certain embodiments of the first-fourth embodiments, n is 3 resulting in a compound with a trihydrocarboxysilane moiety such as a trialkoxysilane moiety. Non-limiting examples of compounds having an imino group and meeting formula (I) above, which are suitable for providing the silica-reactive functional group for the styrene-butadiene rubber of (i) include, but are not limited to, N-(l,3-dimethylbutylidene)-3-(triethoxysilyl)-l- propaneamine, N-(l-methylethylidene)-3-(triethoxysilyl)-l-propaneamine, N-ethylidene-3- (triethoxysilyl)-l-propaneamine, N-(l-methylpropylidene)-3-(triethoxysilyl)-l-propaneamine, and N-(4-N,N-dimethylaminobenzylidene )-3-( triethoxysilyl)-l-propaneamine.
[0043] Non-limiting examples of silicon-containing functional groups that can be utilized in certain embodiments of the first-fourth embodiments as a silica-reactive functional group in the at least one styrene-butadiene rubber (i) include, but are not limited to, an organic silyl or siloxy group, and more precisely, such a functional group may be selected from an alkoxysilyl group, an alkylhalosilyl group, a siloxy group, an alkylaminosilyl group, and an a I koxyhalosilyl group. Optionally, the organic silyl or siloxy group may also contain one or more nitrogens. Suitable silicon-containing functional groups for use in functionalizing diene-based elastomers also include those disclosed in U.S. Patent No. 6,369,167, the entire disclosure of which is herein incorporated by reference. In certain embodiments of the first-fourth embodiments, the at least one styrene-butadiene rubber (i) comprises at least one silica-reactive functional group selected from the foregoing list of silicon-containing functional groups. [0044] In certain embodiments of the first-fourth embodiments, the at least one styrenebutadiene rubber (i) includes a silica-reactive functional group which includes a silicon-containing functional group having a siloxy group (e.g., a hydrocarbyloxysilane-containing compound), wherein the compound optionally includes a monovalent group having at least one functional group. Such a silicon-containing functional group may be added by reacting the active terminal of a polymer chain with a compound having the following formula (II): wherein A1 represents a monovalent group having at least one functional group selected from epoxy, isocyanate, imine, cyano, carboxylic ester, carboxylic anhydride, cyclic tertiary amine, non-cyclic tertiary amine, pyridine, silazane and sulfide; Rc represents a single bond or a divalent hydrocarbon group having from 1 to 20 carbon atoms (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 carbon atoms); Rd represents a monovalent aliphatic hydrocarbon group having 1 to 20 carbon atoms (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 carbon atoms), a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms (e.g., 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, or 18 carbon atoms) or a reactive group; Re represents a monovalent aliphatic hydrocarbon group having 1 to 20 carbon atoms (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 carbon atoms) or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms (e.g., 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, or 18 carbon atoms); b is an integer of 0 to 2; when more than one Rd or ORe are present, each Rd and/or ORe may be the same as or different from each other; and an active proton is not contained in a molecule) and/or a partial condensation product thereof. As used herein, a partial condensation product refers to a product in which a part (not all) of a SiOR group in the hydrocarbyloxysilane compound is turned into a SiOSi bond by condensation. In certain embodiments of the first-fourth embodiments, at least one of the following is met: (a) Rc represents a divalent hydrocarbon group having 1 to 12 carbon atoms (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, or 12 carbon atoms), 2 to 6 carbon atoms (e.g., 2, 3, 4, 5, or 6 carbon atoms), or 2 to 3 1 carbon atoms (e.g., 2 or 3 carbon atoms); (b) Re represents a monovalent aliphatic hydrocarbon group having 1 to 12 carbon atoms (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, or 12 carbon atoms), 2 to 6 carbon atoms (e.g., 2, 3, 4, 5, or 6 carbon atoms), or 1 to 2 carbon atoms or a monovalent aromatic hydrocarbon group having 6 to 8 carbon atoms; (c) Rd represents a monovalent aliphatic hydrocarbon group having 1 to 12 carbon atoms(e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, or 12 carbon atoms), 2 to 6 carbon atoms (e.g., 2, 3, 4, 5, or 6 carbon atoms), or 1 to 2 carbon atoms or a monovalent aromatic hydrocarbon group having 6 to 8 carbon atoms; in certain such embodiments, each of (a), (b) and (c) are met and Rc, Re and Rd are selected from one of the foregoing groups.
[0045] In certain embodiments of the first-fourth embodiments, the silica-reactive functional group of the at least one styrene-butadiene rubber (i) results from a compound represented by Formula (II) wherein A1 has at least one epoxy group. Non-limiting specific examples of such compounds include 2-glycidoxyethyltrimethoxysilane, 2- glycidoxyethyltriethoxysilane, (2-glycidoxyethyl)methyldimethoxysilane, 3- glycidoxypropyltri methoxysilane, 3-glycidoxypropyltriethoxysilane, (3-glycidoxypropyl)- methyldimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 2-(3,4- epoxycyclohexyl)ethyltriethoxysilane, 2-(3,4-epoxycyclohexyl)ethyl(methyl)dimethoxysilane and the like. Among them, 3-glycidoxypropyltrimethoxysilane and 2-(3,4- epoxycyclohexyl)ethyltrimethoxysilane are particularly suited.
[0046] In certain embodiments of the first-fourth embodiments, the silica-reactive functional group of the at least one styrene-butadiene rubber (i) results from a compound represented by Formula (II) wherein A1 has at least one isocyanate group. Non-limiting specific examples of such compounds include 3-isocyanatopropyltrimethoxysilane, 3- isocyanatopropyltriethoxysilane, 3-isocyanatopropylmethyldiethoxysilane, 3- isocyanatopropyltriisopropoxysilane and the like, and among them, 3- isocyanatopropyltrimethoxysilane is particularly preferred.
[0047] In certain embodiments of the first-fourth embodiments, the silica-reactive functional group of the at least one styrene-butadiene rubber (i) results from a compound represented by Formula (II) wherein A1 has at least one imine group. Non-limiting specific examples of such compounds include N-(l,3-dimethylbutylidene)-3-(triethoxysilyl)-l- propaneamine, N-(l-methylethylidene)-3-(triethoxysilyl)-l-propaneamine, N-ethylidene-3- (triethoxysilyl)-l-propaneamine, N-(l-methylpropylidene)-3-(triethoxysilyl)-l-propaneamine, N- (4-N,N-dimethylaminobenzylidene)-3-(triethoxysilyl)-l-propaneamine, N-(cyclohexylidene)-3- (triethoxysilyl)-l-propaneamine and trimethoxysilyl compounds, methyldiethoxysilyl compounds, ethyldimethoxysilyl compounds and the like each corresponding to the above triethoxysilyl compounds. Among them, N-(l,3-dimethylbutylidene)-3-(triethoxysilyl)-l- propaneamine and N-(l-methylpropylidene)-3-(triethoxysilyl)-l-propaneamine are particularly suited. Also, the imine(amidine) group-containing compounds include preferably l-[3- trimethoxysilyl]propyl]-4,5-dihydroimidazole, 3-(l-hexamethyleneimino)propyl(triethoxy)silane, (l-hexamethyleneimino)methyl(trimethoxy)silane, N-(3-triethoxysilylpropyl)-4,5- dihydroimidazole, N-(3-isopropoxysilylpropyl)-4,5-dihydroimidazole, N-(3- methyldiethoxysilylpropyl)-4,5-dihydroimidazole and the like, and among them, N-(3- triethoxysilylpropyl)-4,5-dihydroimidazole and N-(3-isopropoxysilylpropyl)-4,5-dihydroimidazole are preferred.
[0048] In certain embodiments of the first-fourth embodiments, the silica-reactive functional group of the styrene-butadiene rubber (i) results from a compound represented by Formula (II) wherein A1 has at least one carboxylic ester group. Non-limiting specific examples of such compounds include 3-methacryloyloxypropyltriethoxysilane, 3- methacryloyloxypropyltrimethoxysilane, 3-methacryloyloxypropylmethyldiethoxysilane, 3- methacryloyloxypropyltriisopropoxysilane and the like, and among them, 3- methacryloyloxypropyltriethoxysilane is preferred.
[0049] In certain embodiments of the first-fourth embodiments, the silica-reactive functional group of the at least one styrene-butadiene rubber (i) results from a compound represented by Formula (II) wherein A1 has at least one carboxylic anhydride group. Non-limiting specific examples of such compounds include 3-trimethoxysilylpropylsuccinic anhydride, 3- triethoxysilylpropylsuccinic anhydride, 3-methyldiethoxysilylpropylsuccinic anhydride and the like, and among them, 3-triethoxysilylpropylsuccinic anhydride is preferred. [0050] In certain embodiments of the first-fourth embodiments, the silica-reactive functional group of the at least one styrene-butadiene rubber (i) results from a compound represented by Formula (II) wherein A1 has at least one cyano group. Non-limiting specific examples of such compounds include 2-cyanoethylpropyltriethoxysilane and the like.
[0051] In certain embodiments of the first-fourth embodiments, the silica-reactive functional group of the at least one styrene-butadiene rubber (i) results from a compound represented by Formula (II) wherein A1 has at least one cyclic tertiary amine group. Non-limiting specific examples of such compounds include 3-(l-hexamethyleneimino)propyltriethoxysilane,
3-(l-hexamethyleneimino)propyltrimethoxysilane, (1- hexamethyleneimino)methyltriethoxysilane, (l-hexamethyleneimino)methyltrimethoxysilane, 2-(l-hexamethyleneimino)ethyltriethoxysilane, 3-(l- hexamethyleneimino)ethyltrimethoxysilane, 3-(l-pyrrolidinyl)propyltrimethoxysilane, 3-(l- pyrrolidinyl) propyltriethoxysilane, 3-(l-heptamethyleneimino)propyltriethoxysilane, 3-(l- dodecamethyleneimino)propyltriethoxysilane, 3-(l- hexamethyleneimino)propyldiethoxymethylsilane, 3-(l- hexamethyleneimino)propyldiethoxyethylsilane, 3-[10-(triethoxysilyl)decyl]-4-oxazoline and the like. Among them, 3-(l-hexamethyleneimino)propyltriethoxysilane and (1- hexamethyleneimino)methyltriethoxysilane can preferably be listed.
[0052] In certain embodiments of the first-fourth embodiments, the silica-reactive functional group of the at least one styrene-butadiene rubber (i) results from a compound represented by Formula (II) wherein A1 has at least one non-cyclic tertiary amine group. Nonlimiting specific examples of such compounds include 3-dimethylaminopropyltriethoxysilane, 3- dimethylaminopropyltrimethoxysilane, 3-diethylami nopropyltriethoxysilane, 3- dimethylaminopropyltrimethoxysilane, 2-dimethylaminoethyltriethoxysilane, 2- dimethylaminoethyltri methoxysilane, 3-dimethylaminopropyldiethoxymethylsilane, 3- dibutylaminopropyltriethoxysilane and the like, and among them, 3- dimethylaminopropyltriethoxysilane and 3-diethylaminopropyltriethoxysilane are suited.
[0053] In certain embodiments of the first-fourth embodiments, the silica-reactive functional group of the at least one styrene-butadiene rubber (i) results from a compound represented by Formula (II) wherein A1 has at least one pyridine group. Non-limiting specific examples of such compounds include 2-trimethoxysilylethylpyridine and the like.
[0054] In certain preferred embodiments of the first-fourth embodiments, the silicareactive functional group of the at least one styrene-butadiene rubber (i) results from a compound represented by Formula (II) wherein A1 has at least one silazane group. Non-limiting specific examples of such compounds include N,N-bis(trimethylsilyl)- a mi nopropylmethyldimethoxysilane, l-trimethylsilyl-2,2-dimethoxy-l-aza-2-silacyclopentane,
N,N-bis(trimethylsilyl)aminopropyltrimethoxysilane, N,N- bis(trimethylsilyl)aminopropyltriethoxysilane, N,N- bis(trimethylsilyl)aminopropylmethyldiethoxysilane, N,N- bis(trimethylsilyl)aminoethyltrimethoxysilane, N,N-bis(trimethylsilyl)ami noethyltriethoxysilane, N,N-bis(trimethylsilyl)aminoethylmethyldimethoxysilane, N,N- bis(trimethylsilyl)aminoethylmethyldiethoxysilane and the like. N,N- bis(trimethylsilyl)aminopropyltriethoxysilane, N,N- bis(trimethylsilyl)aminopropylmethyldiethoxysilane or l-trimethylsilyl-2,2-dimethoxy-l-aza-2- silacyclopentane are particularly preferred.
[0055] In those embodiments of the first-fourth embodiments wherein the at least one styrene-butadiene rubber has a silica-reactive functional group according to formula (II) wherein A1 contains one or more protected nitrogens (as discussed in detail above), the nitrogen(s) may be deprotected or deblocked by hydrolysis or other procedures to convert the protected nitrogen(s) into a primary nitrogen. As a non-limiting example, a nitrogen bonded to two trimethylsilyl groups could be deprotected and converted to a primary amine nitrogen (such a nitrogen would still be bonded to the remainder of the formula (II) compound). Accordingly, in certain embodiments of the first -fourth embodiments wherein a silica-reactive functional group of the at least one styrene-butadiene rubber (i) results from use of a compound according to formula (II) wherein A1 contains one or more protected nitrogens, the functionalized polymer can be understood as containing a functional group resulting from a deprotected (or hydrolyzed) version of the compound. [0056] Non-limiting examples of oxygen- or sulfur-containing functional groups that can be utilized in certain embodiments of the first -fourth embodiments as a silica-reactive functional group in the at least one styrene-butadiene rubber (i) include, but are not limited to, a hydroxyl group, a carboxyl group, an epoxy group, a glycidoxy group, a diglycidylamino group, a cyclic dithiane-derived functional group, an ester group, an aldehyde group, an alkoxy group, a ketone group, a thiocarboxyl group, a thioepoxy group, a thioglycidoxy group, a thiodiglycidylamino group, a thioester group, a thioaldehyde group, a thioalkoxy group, and a thioketone group. In certain embodiments of the first-fourth embodiments, the foregoing alkoxy group may be an alcohol-derived alkoxy group derived from a benzophenone. In certain embodiments of the first- fourth embodiments, the at least one styrene-butadiene rubber (i) comprises at least one silicareactive functional group selected from the foregoing list of oxygen- or sulfur-containing functional groups.
[0057] According to the first-fourth embodiments, the at least one styrene-butadiene rubber (i), whether having a silica-reactive functional group or not may be prepared by either solution polymerization or by emulsion polymerization. In certain preferred embodiments of the first-fourth embodiments, the only styrene-butadiene rubber(s) present as (i), whether having a silica-reactive functional group or not is (are) prepared by solution polymerization. In other embodiments of the first-fourth embodiments, the only styrene-butadiene rubber(s) present as (i), whether having a silica-reactive functional group or not, is (are) prepared by emulsion polymerization. In certain embodiments of the first -fourth embodiments, when more than one styrene-butadiene rubber is used for (i) or when more than one styrene-butadiene rubber having a silica-reactive functional group is used for (i), the rubbers are a combination of solution polymerized styrene-butadiene rubber and emulsion polymerized styrene-butadiene rubber (e.g., one solution styrene-butadiene rubber and one emulsion styrene-butadiene rubber). In certain embodiments of the first-fourth embodiments, the only styrene-butadiene rubber(s) present in the elastomer component (including for the at least one styrene-butadiene rubber having a silica-reactive functional group) is (are) solution styrene-butadiene rubbers (Z.e., no emulsion styrene-butadiene rubber is present). Polybutadiene Rubber (ii)
[0058] According to the first-fourth embodiments, (ii) of the elastomer component consists of polybutadiene rubber having a cis bond content of at least 95% (e.g., 95%, 96%, 97%, 98%, 99%, or more), a Tg of less than -101 °C (e.g., -102, -103, -104, -105, -106, -107, -108, -109, -110, -111, -112 °C or less), preferably -101 or -110 °C (e.g., -102, -103, -104, -105, -106, -107, - 108, -109, or -110 °C), and a silica-reactive functional group. In certain such embodiments, the Tg of the polybutadiene rubber (ii) is -101 to -110 °C. The cis bond content refers to the cis 1,4- bond content. The cis 1,4-bond contents and vinyl bond contents referred to herein for polybutadiene rubberare determined by FTIR (FourierTransform Infrared Spectroscopy) wherein a polymer sample is dissolved in CS2 and then subjected to FTIR. In certain embodiments of the first-fourth embodiments, the polybutadiene rubber of (ii) has a cis 1,4-bond content of at least 98% (e.g., 98%, 99%, or more) or at least 99% (e.g., 99%, 99.5%, or more). Since the cis bond content of the polybutadiene rubber (ii) is high (i.e., at least 95%, as discussed above), the vinyl bond content will be low. In certain embodiments of the first-fourth embodiments, the polybutadiene rubber of (ii) has a vinyl bond content of less than 4% (e.g., 3.9%, 3.5%, 3%, 2.5%, 2%, 1.5%, 1%, 0.5%, etc.), preferably less than 3% (e.g., 2.5%, 2%, 1.5%, 1%, 0.5%, etc.), more preferably less than 2% (e.g., 1.5%, 1.4%, 1.3%, 1.2%, 1.1%, 1%, 0.9%, 0.8%, 0.7%, 0.6%, 0.5%, 0.4%, etc.). In certain embodiments of the first-fourth embodiments, any polybutadiene rubber used in the tire tread rubber compositions has a Tg of -105 °C or less (e.g., -105, -106, -107, -108, -109 °C or less) such as -105 to -110 °C. In certain embodiments of the first-fourth embodiments, any polybutadiene rubber used in the tire tread rubber compositions contains less than 3% by weight (e.g., 3%, 2%, 1%, 0.5%, or less), preferably less than 1% by weight (e.g., 1%, 0.5%, or less) or 0% by weight syndiotactic 1,2-polybutadiene. Generally, according to the first-fourth embodiments, one or more than one polybutadiene rubber having a cis bond content of at least 95%, a Tg of less than -101 °C, and a silica-reactive functional group may be used for (ii). In certain embodiments of the first-fourth embodiments, (ii) consists of only one polybutadiene rubber having a cis bond content of at least 95% (e.g., 95%, 96%, 97%, 98%, 99%, or more), a Tg of less than -101 °C, and a silica-reactive functional group. In preferred embodiments of the first-fourth embodiments, the amount of any polybutadiene rubber having a high vinyl content (i.e., above about 70%) is limited (in the overall tread rubber composition) to less than 25 parts, more preferably less than 10 parts, even more preferably less than 5 parts or 0 parts.
[0059] According to the first and fourth embodiments, the polybutadiene rubber (ii) having a cis bond content of at least 95% (e.g., 95%, 96%, 97%, 98%, 99%, or more), a Tg of less than -101 °C (e.g., -102, -103, -104, -105, -106, -107, -108, -109, -110, -111, -112 °C or less), preferably -101 or -110 °C (e.g., -102, -103, -104, -105, -106, -107, -108, -109, or -110 °C), and a silica-reactive functional group, is present in an amount of 45-65 parts (e.g., 45, 46, 47, 48, 49,
50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64 or 65 parts), preferably 51-65 parts (e.g.,
51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64 or 65 parts), more preferably 51-60 parts (e.g., 51, 52, 53, 54, 55, 56, 57, 58, 59, or 60 parts). According to the second and third embodiments, the polybutadiene rubber (ii) having a cis bond content of at least 95% (e.g., 95%, 96%, 97%, 98%, 99%, or more), a Tg of less than -101 °C (e.g., -102, -103, -104, -105, -106, -107, -108, -109, -110, -111, -112 °C or less), preferably -101 or -110 °C (e.g., -102, -103, -104, -105, -106, -107, -108, - 109, or -110 °C), and a silica-reactive functional group, is present in an amount of 51-65 parts (e.g., 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64 or 65 parts), preferably 51-60 parts (e.g., 51, 52, 53, 54, 55, 56, 57, 58, 59, or 60 parts).
[0060] As mentioned above, according to the first-fourth embodiments, the polybutadiene rubber having a cis bond content of at least 95%, a Tg of less than -101 °C, and a silica-reactive functional group is present as (ii). In certain embodiments of the first-fourth embodiments, the Tg of this polybutadiene rubber (ii) is -101 to -110 °C (e.g., -101, -102, -103, - 104, -105, -106, -107, -108, -109, or -110 °C), or -105 to -110 °C (e.g., -105, -106, -107, -108, -109, or -110 °C).
[0061] According to the first -fourth embodiments disclosed herein, the Mw of the polybutadiene rubber having a cis bond content of at least 95%, a Tg of less than -101 °C, preferably -101 to -110 -101 °C, and a silica-reactive functional group of (ii) may vary. In certain embodiments of the first-fourth embodiments, the polybutadiene rubber having a cis bond content of at least 95%, a Tg of less than -101 °C, preferably -101 to -110 -101 °C, and a silicareactive functional group of (ii) has a Mw of 450,000 to 700,000 grams/mole (e.g., 450,000; 500,000; 550,000; 600,000; 650,000; or 700,000 grams/mole), preferably a Mw of 500,000 to 650,000 grams/mole (e.g., 500,000; 525,000; 550,000; 575,000; 600,000; 625,000; or 650,000 grams/mole). Mw ranges falling within the foregoing ranges such as 500,000 to 600,000 grams/mole, 550,000 to 600,000 grams/mole, 450,000 to 600,000 grams/mole, and 500,000 to 700,000 grams/mole can also be utilized in certain embodiments of the first-fourth embodiments. In certain embodiments of the first-fourth embodiments, the polybutadiene rubber having a cis bond content of at least 95%, a Tg of less than -101 °C, preferably -101 to - 110 -101 °C, and a silica-reactive functional group of (ii) has a Mn of 180,000 to 300,000 grams/mole (e.g., 180,000; 200,000; 220,000; 240,000; 250,000; 260,000; 280,000; or 300,000 grams/mole), preferably a Mn of 200,000 to 280,000 grams/mole (e.g., 200,000; 210,000; 220,000; 230,000; 240,000; 250,000; 260,000; 270,000; or 280,000 grams/mole). Mn ranges falling within the foregoing ranges such as 200,000 to 250,000 grams/mole, 230,000 to 280,000 grams/mole, 180,000 to 280,000 grams/mole, and 200,000 to 280,000 grams/mole can also be utilized in certain embodiments of the first-fourth embodiments. In certain embodiments of the first-fourth embodiments, the polybutadiene rubber having a cis bond content of at least 95%, a Tg of less than -101 °C, preferably -101 to -110 -101 °C, and a silica-reactive functional group of (ii) has a Mw of 450,000 to 700,000 grams/mole (or a range within the foregoing, as described above) and a Mn of 180,000 to 300,000 grams/mole (or a range within the foregoing, as described above). The foregoing Mw and Mn values for the polybutadiene of (ii) refer to values measured by GPC using a polystyrene standard. As well, the foregoing Mw and Mn values for the polybutadiene of (ii) refer to coupled Mw and coupled Mn rather than base polymer values.
[0062] In certain embodiments of the first-fourth embodiments disclosed herein, the at least one polybutadiene rubber (ii), as described above, is an oil-extended rubber, incorporating oil in an amount as discussed further below. In other preferred embodiments of the first -fourth embodiments disclosed herein, the at least one polybutadiene rubber (ii), as described above, is a non oil-extended rubber (i.e., the BR is not extended with any oil).
[0063] The use of the claimed amounts of polybutadiene having a cis bond content of at least 95%, a Tg of less than -101 °C, preferably -101 to -110 -101 °C, and a silica-reactive functional group in the tire tread rubber compositions according to the first-fourth embodiments (preferably in combination with the other components of the tire tread rubber compositions according to the first-fourth embodiments) disclosed herein can in certain embodiments result in an improvement in wear and in rolling resistance as compared to a control rubber composition which uses a non-functionalized version of the polybutadiene having a cis bond content of at least 95% and a Tg of less than -101 °C. In certain embodiments of the first-fourth embodiments, the tire tread rubber composition exhibits an improvement in wear of at least 5% (e.g., 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 5-14%, 5-13%, 5-10%, etc.), or even at least 10% (e.g., 10%, 11%, 12%, 13%, 14%, 10-13%, 10-14%, etc.). As discussed further, infra, an improvement in wear can be measured by DIN abrasion values wherein a lower value (i.e., less material lost) indicates better wear. In certain embodiments of the first-fourth embodiments, the tire tread rubber composition exhibits an improvement in rolling resistance (as evidenced by its value tan 6 at -60 °C, as discussed in more detail, infra) of at least 5% (e.g., 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 5-13%, 5-10%, etc.), or even at least 10% (e.g., 10%, 11%, 12%, 13%, 10-13%, etc.).
[0064] According to certain embodiments of the first-fourth embodiments disclosed herein, the polybutadiene rubber of (i) includes a silica-reactive functional group which includes a silicon-containing functional group having a siloxy group (e.g., a hydrocarbyloxysilane- containing compound), wherein the compound optionally includes a monovalent group having at least one functional group. Such a silicon-containing functional group may be added by reacting the active terminal of a polymer chain with a compound having the following formula (II): wherein A1 represents a monovalent epoxy group; Rc represents a single bond or a divalent hydrocarbon group having from 1 to 20 carbon atoms (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 carbon atoms); Rd represents a monovalent aliphatic hydrocarbon group having 1 to 20 carbon atoms (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 carbon atoms), a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms (e.g., 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, or 18 carbon atoms) or a reactive group; Re represents a monovalent aliphatic hydrocarbon group having 1 to 20 carbon atoms (e.g., 1, 2, 3, 4, 5, 6, 7,
8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 carbon atoms) or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms {e.g., 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, or 18 carbon atoms); b is an integer of 0 to 2; when more than one Rd or ORe are present, each Rd and/or ORe may be the same as or different from each other; and an active proton is not contained in a molecule) and/or a partial condensation product thereof. As used herein, a partial condensation product refers to a product in which a part (not all) of a SiOR group in the hydrocarbyloxysilane compound is turned into a SiOSi bond by condensation. In certain embodiments of the first-fourth embodiments, at least one of the following is met: (a) Rc represents a divalent hydrocarbon group having 1 to 12 carbon atoms (e.g., 1, 2, 3, 4, 5, 6, 7, 8,
9, 10, 11, or 12 carbon atoms), 2 to 6 carbon atoms (e.g., 2, 3, 4, 5, or 6 carbon atoms), or 2 to 3 carbon atoms (e.g., 2 or 3 carbon atoms); (b) Re represents a monovalent aliphatic hydrocarbon group having 1 to 12 carbon atoms (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, or 12 carbon atoms), 2 to 6 carbon atoms (e.g., 2, 3, 4, 5, or 6 carbon atoms), or 1 to 2 carbon atoms or a monovalent aromatic hydrocarbon group having 6 to 8 carbon atoms; (c) Rd represents a monovalent aliphatic hydrocarbon group having 1 to 12 carbon atoms(e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, or 12 carbon atoms), 2 to 6 carbon atoms (e.g., 2, 3, 4, 5, or 6 carbon atoms), or 1 to 2 carbon atoms or a monovalent aromatic hydrocarbon group having 6 to 8 carbon atoms; in certain such embodiments, each of (a), (b) and (c) are met and Rc, Re and Rd are selected from one of the foregoing groups.
[0065] According to the first-fourth embodiments, the particular epoxy group present in the formula (II) functionalizing compound can vary. In certain preferred embodiments of the first-fourth embodiments, the epoxy group (i.e., A1 in formula (II), above) is selected from glycidoxy, 3,4-epoxycyclohexyl, or a glycidyl group having 3-8 (e.g., 3, 4, 5, 6, 7, or 8), preferably 3-6 (e.g., 3, 4, 5, or 6), carbons overall (with the 2 end carbons being within the epoxy ring and the other end of the carbon chain bonded to Rc). In certain embodiments of the first-fourth embodiments, the polybutadiene rubber of (ii) has a silica-reactive functional group resulting from use of a functionalizing compound of formula (II) where the epoxy group (i.e., A1) is selected from glycidoxy. In certain embodiments of the first-fourth embodiments, the polybutadiene rubber of (ii) has a silica-reactive functional group resulting from use of a functionalizing compound of formula (II) where the epoxy group (i.e., A1) is selected from 3,4-epoxycylohexyl. In certain embodiments of the first-fourth embodiments, the polybutadiene rubber of (ii) has a silica-reactive functional group resulting from use of a functionalizing compound of formula (II) where the epoxy group (i.e., A1) is selected from a glycidyl group having 3-8 (e.g., 3, 4, 5, 6, 7, or 8), preferably 3-6 (e.g., 3, 4, 5, or 6), carbons overall (with the 2 end carbons being within the epoxy ring and the other end of the carbon chain bonded to Rc).. Non-limiting specific examples of such functionalizing compounds according to formula (II) which include an epoxy group include 2-glycidoxyethyltrimethoxysilane, 2-glycidoxyethyltriethoxysilane, (2- glycidoxyethyl)methyldimethoxysilane, (2-glycidoxyethyl)methyldiethoxysilane, 3- glycidoxypropyltri methoxysilane, 3-glycidoxypropyltriethoxysilane, (3-glycidoxypropyl)- methyldimethoxysilane, (3-glycidoxypropyl)-methyldiethoxysilane, 2-(3,4- epoxycyclohexyl)ethyltrimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane, 2-(3,4- epoxycyclohexyl)ethyl(methyl)dimethoxysilane, 2-(3,4- epoxycyclohexyl)ethyl(methyl)diethoxysilane, and the like. Among them, 3- glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, and 2-(3,4- epoxycyclohexyl)ethyltrimethoxysilane are particularly preferred.
Natural Rubber, Polyisoprene, Or A Combination Thereof Of
[0066] In certain embodiments of the first-fourth embodiments, the elastomer component may consist of (include) up to 9 parts (e.g., 9, 8, 7, 6, 5, 4, 3, 2, 1 or 0 parts) of natural rubber, polyisoprene, or a combination thereof, which can be referred to as (iii). In certain embodiments of the first-fourth embodiments, the amount of (iii) is 0-9 parts, and in other embodiments 1-9 parts. In other embodiments of the first-fourth embodiments, (iii) of the elastomer component consists of up to 5 parts, 0-5 parts, or 1-5 parts of natural rubber, polyisoprene, or a combination thereof. In certain embodiments of the first-fourth embodiments, (iii) consists (only) of natural rubber. In other embodiments of the first-fourth embodiments, (iii) consists (only) of polyisoprene. In yet other embodiments of the first-fourth embodiments, as previously mentioned, no natural rubber or polyisoprene is present or used in the tire tread rubber composition. When natural rubber is present for (iii) of the elastomer component, it may include Hevea natural rubber, non-Hevea natural rubber (e.g., guayule natural rubber), or a combination thereof. When natural rubber is utilized in the tire tread rubber compositions of the first-fourth embodiments, the natural rubber preferably has a Mw of 1,000,000 to 2,000,000 grams/mole (e.g., 1 million, 1.1 million, 1.2 million, 1.3 million, 1.4 million, 1.5 million, 1.6 million, 1.7 million, 1.8 million, 1.9 million, 2 million grams/mole); 1,250,000 to 2,000,000 grams/mole, or 1,500,000 to 2,000,000 grams/mole (as measured by GPC using a polystyrene standard). When natural rubber is utilized in the tire tread rubber compositions of the first-fourth embodiments, the Tg of the natural rubber may vary. Preferably, according to the first-fourth embodiments, when natural rubber is utilized it has a Tg of -65 to -80 °C (e.g., - 65, -66, -67, -68, -69, -70, -71-, -72, -73, -74, -75, -76, -77, -78, -79, or -80 °C), more preferably a Tg of -67 to -77 °C (e.g., -67, -68, -69, -70, -71, -72, -73, -74, -75, -76, or -77 °C). When polyisoprene is utilized in the tire tread rubber compositions of the first-fourth embodiments, the Tg of the polyisoprene may vary. Preferably, according to the first-fourth embodiments, when polyisoprene is utilized it has a Tg of -55 to -75 °C (e.g., -55, -56, -57, -58, -59, -60, -61, -62, -63, - 64, -65, -66, -67, -68, -69, -70, -71, -72, -73, -74, or -75 °C), more preferably -58 to -74 °C (e.g., - 58, -59, -60, -61, -62, -63, -64, -65, -66, -67, -68, -69, -70, -71, -72, -73, or -74 °C).
Fillers
[0067] As used herein, the term "reinforcing" with respect to "reinforcing carbon black filler," "reinforcing silica filler," and "reinforcing filler" generally should be understood to encompass both fillers that are traditionally described as reinforcing as well as fillers that may traditionally be described as semi-reinforcing. Traditionally, the term "reinforcing filler" is used to refer to a particulate material that has a nitrogen absorption specific surface area (N2SA) of more than about 100 m2/g, and in certain instances more than 100 m2/g, more than about 125 m2/g, more than 125 m2/g, or even more than about 150 m2/g or more than 150 m2/g. Alternatively (or additionally), the traditional use of the term "reinforcing filler" can also be used to referto a particulate material that has a particle size of about 10 nm to about 50 nm (including 10 nm to 50 nm). Traditionally, the term "semi-reinforcing filler" is used to refer to a filler that is intermediary in either particle size, surface area (N2SA), or both, to a non-reinforcing filler (as discussed below) and a reinforcing filler. In certain embodiments of the first-fourth embodiments disclosed herein, the term "reinforcing filler" is used to refer to a particulate material that has a nitrogen absorption specific surface area (N2SA) of about 20 m2/g or greater, including 20 m2/g or greater, more than about 50 m2/g, more than 50 m2/g, more than about 100 m2/g, or more than 100 m2/g. In certain embodiments of the first-fourth embodiments disclosed herein, the term "reinforcing filler" is used to refer to a particulate material that has a particle size of about 10 nm up to about 1000 nm, including 10 nm to 1000 nm, about 10 nm up to about 50 nm and 10 nm to 50 nm.
Reinforcing Silica Filler
[0068] As mentioned above, according to the first-fourth embodiments disclosed herein, the tire tread rubber compositions comprise (include) at least one reinforcing silica filler in an amount of 70-99 phr (e.g., 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 84, 85, 86, 88, or 90 phr), having a surface area of about 100 to about 300 m2/g (e.g., 110, 120, 130, 140, 150, 160, 180, 200, 220, 240, 260, 280, or 300 m2/g), preferably about 150 to about 300 m2/g, and more preferably about 180 to about 250 m2/g. In certain preferred embodiments of the first-fourth embodiments disclosed herein, the tire tread rubber compositions comprise (include) at least one reinforcing silica filler in an amount of 80-90 phr (e.g., 80, 81, 82, 84, 85, 86, 88, or 90 phr), having a surface area of about 100 to about 300 m2/g (e.g., 110, 120, 130, 140, 150, 160, 180, 200, 220, 240, 260, 280, or 300 m2/g), preferably about 150 to about 300 m2/g, and more preferably about 180 to about 250 m2/g. In certain preferred embodiments of the first-fourth embodiments, the tire tread rubber composition comprises (includes) at least one reinforcing silica filler having a surface area of 150 to 300 m2/g (e.g., 150, 160, 180, 200, 220, 240, 260, 280, or 300 m2/g). In certain even more preferred embodiments of the first -fourth embodiments the tire tread rubber composition comprises (includes) at least one reinforcing silica filler having a surface area of 180 to 250 m2/g (e.g., 180, 185, 190, 195, 200, 205, 210, 215, 220, 225, 230, 235, 240, or 250 m2/g) which should be understood as including intermediary ranges such as 180-240, 180-230, 180-220, 180-210, 190-240, 190-230, 190-220, 190-210, etc. According to the first- fourth embodiments, one or more than one reinforcing silica filler having a surface area as discussed above may be utilized; in those embodiments where more than one such reinforcing silica filler is utilized, the foregoing amounts refer to the total amount of all reinforcing silica fillers. In certain embodiments of the first-fourth embodiments, only one reinforcing silica filler having a surface area as discussed above is utilized. In preferred embodiments of the first-fourth embodiments, the only reinforcing silica filler(s) used in the tire tread rubber composition have a surface area as discussed above; in such embodiments, the tire tread rubber composition can be understood as being free of (/.e., contains 0 phr of) reinforcing silica filler having a surface area outside the above-discussed ranges.
[0069] According to the first-fourth embodiments, the particular type of silica used for the at least one reinforcing silica filler having a surface area as discussed above may vary. Nonlimiting examples of reinforcing silica fillers suitable for use in certain embodiments of the first- fourth embodiments include, but are not limited to, precipitated amorphous silica, wet silica (hydrated silicic acid), dry silica (anhydrous silicic acid), fumed silica, calcium silicate and the like. Other suitable reinforcing silica fillers for use in certain embodiments of the first-fourth embodiments include, but are not limited to, aluminum silicate, magnesium silicate (Mg2SiO4, MgSiOs etc.), magnesium calcium silicate (CaMgSiO4), calcium silicate (Ca2SiO4 etc.), aluminum silicate (A^SiOs, AI4.3SiO4.5H2O etc.), aluminum calcium silicate (Al2O3.CaO2SiO2, etc.), and the like. Among the listed reinforcing silica fillers, precipitated amorphous wet-process, hydrated silica fillers are preferred. Such reinforcing silica fillers are produced by a chemical reaction in water, from which they are precipitated as ultrafine, spherical particles, with primary particles strongly associated into aggregates, which in turn combine less strongly into agglomerates. The surface area, as measured by the BET method, is a preferred measurement for characterizing the reinforcing character of different reinforcing silica fillers. In certain embodiments of the first- fourth embodiments disclosed herein, the tire tread rubber composition comprises a reinforcing silica filler having a surface area (as measured by the BET method), as discussed infra. In certain embodiments of the first-fourth embodiments disclosed herein, the tire tread rubber composition comprises reinforcing silica filler having a pH of about 5.5 to about 8, 5.5 to 8 (e.g., 5.5, 5.7, 5.9, 6.1, 6.3, 6.5, 6.7, 6.9, 7.1, 7.3, 7.5, 7.7, 7.9, or 8), about 6 to about 8, 6 to 8 (e.g., 6, 6.2, 6.4, 6.6, 6.8, 7, 7.2, 7.4, 7.6, 7.8, or 8), about 6 to about 7.5, 6 to 7.5, about 6.5 to about 8, 6.5 to 8, about 6.5 to about 7.5, 6.5 to 7.5, about 5.5 to about 6.8, or 5.5 to 6.8. Some of the commercially available reinforcing silica fillers which can be used in certain embodiments of the first-fourth embodiments include, but are not limited to, Hi-Sil® EZ120G, Hi-Sil® EZ120G-D, Hi- Sil® 134G, Hi-Sil® EZ 160G, Hi-Sil®EZ 160G-D, Hi-Sil®190, Hi-Sil® 190G-D, Hi-Sil® EZ 200G, Hi-Sil® EZ 200G-D, Hi-Sil® 210, Hi-Sil® 233, Hi-Sil® 243LD, Hi-Sil® 255CG-D, Hi-Sil® 315-D, Hi-Sil® 315G-D, Hi- Sil® HDP 320G and the like, produced by PPG Industries (Pittsburgh, Pa.) As well, a number of useful commercial grades of different reinforcing silica fillers are also available from Evonik Corporation (e.g., Ultrasil® 320 GR, Ultrasil® 5000 GR, Ultrasil® 5500 GR, Ultrasil® 7000 GR, Ultrasil® VN2 GR, Ultrasil® VN2, Ultrasil® VN3, Ultrasil® VN3 GR, Ultrasi l®7000 GR, Ultrasil® 7005, Ultrasil® 7500 GR, Ultrasil® 7800 GR, Ultrasil® 9500 GR, Ultrasil® 9000 G, Ultrasil® 9100 GR), and Solvay (e.g., Zeosil® 1115MP, Zeosil® 1085GR, Zeosil® 1165MP, Zeosil® 1200MP, Zeosil® Premium, Zeosil® 195HR, Zeosil® 195GR, Zeosil® 185GR, Zeosil® 175GR, and Zeosil® 165 GR).
Silica Coupling Agent
[0070] In certain embodiments of the first-fourth embodiments disclosed herein, one or more than one silica coupling agent may also (optionally) be utilized. In preferred embodiments of the first-fourth embodiments, at least one silica coupling agent is utilized. Silica coupling agents are useful in preventing or reducing aggregation of the silica filler in rubber compositions. Aggregates of the silica filler particles are believed to increase the viscosity of a rubber composition, and, therefore, preventing this aggregation reduces the viscosity and improves the processability and blending of the rubber composition.
[0071] Generally, any conventional type of silica coupling agent can be used, such as those having a silane and a constituent component or moiety that can react with a polymer, particularly a vulcanizable polymer. The silica coupling agent acts as a connecting bridge between silica and the polymer. Suitable silica coupling agents for use in certain embodiments of the first- fourth embodiments disclosed herein include those containing groups such as alkyl alkoxy, mercapto, blocked mercapto, sulfide-containing (e.g., monosulfide-based alkoxy-containing, disulfide-based alkoxy-containing, tetrasulfide-based alkoxy-containing), amino, vinyl, epoxy, and combinations thereof. In certain embodiments of the first-fourth, the silica coupling agent can be added to the rubber composition in the form of a pre-treated silica; a pre-treated silica has been pre-surface treated with a silane prior to being added to the rubber composition. The use of a pre-treated silica can allow for two ingredients (/.e., silica and a silica coupling agent) to be added in one ingredient, which generally tends to make rubber compounding easier.
[0072] Alkyl alkoxysilanes have the general formula R10 pSi(OR11)4-p where each R11 is independently a monovalent organic group, and p is an integer from 1 to 3, with the proviso that at least one R10 is an alkyl group. Preferably p is 1. Generally, each R10 independently comprises Ci to C20 aliphatic, C5 to C20 cycloaliphatic, or Cg to C20 aromatic; and each R11 independently comprises Ci to Cg aliphatic. In certain exemplary embodiments, each R10 independently comprises Cg to C15 aliphatic and in additional embodiments each R10 independently comprises Cs to C14 aliphatic. Mercapto silanes have the general formula HS-R13-Si(R14)(R15)2 where R13 is a divalent organic group, R14 is a halogen atom or an alkoxy group, each R15 is independently a halogen, an alkoxy group or a monovalent organic group. The halogen is chlorine, bromine, fluorine, or iodine. The alkoxy group preferably has 1-3 carbon atoms. Blocked mercapto silanes have the general formula B-S-R16-Si-X3 with an available silyl group for reaction with silica in a silica-silane reaction and a blocking group B that replaces the mercapto hydrogen atom to block the reaction of the sulfur atom with the polymer. In the foregoing general formula, B is a block group which can be in the form of an unsaturated heteroatom or carbon bound directly to sulfur via a single bond; R16 is Ci to Cg linearor branched alkylidene and each X is independently selected from the group consisting of Ci to C4 alkyl or Ci to C4 alkoxy.
[0073] Non-limiting examples of alkyl alkoxysilanes suitable for use in certain embodiments of the first-fourth embodiments include, but are not limited to, octyltriethoxysilane, octyltrimethoxysilane, trimethylethoxysilane, cyclohexyltriethoxysilane, isobutyltriethoxy-silane, ethyltrimethoxysilane, cyclohexyl-tributoxysilane, dimethyldiethoxysilane, methyltriethoxysilane, propyltriethoxysilane, hexyltriethoxysilane, heptyltriethoxysilane, nonyltriethoxysilane, decyltriethoxysilane, dodecyltriethoxysilane, tetradecyltriethoxysilane, octadecyltriethoxysilane, methyloctyldiethoxysilane, dimethyldimethoxysilane, methyltrimethoxysilane, propyltrimethoxysilane, hexyltrimethoxysilane, heptyltrimethoxysilane, nonyltrimethoxysilane, decyltrimethoxysilane, dodecyltrimethoxysilane, tetradecyltrimethoxysilane, octadecyl-trimethoxysilane, methyloctyl dimethoxysilane, and mixtures thereof. [0074] Non-limiting examples of bis(trialkoxysilylorgano)polysulfides suitable for use in certain embodiments of the first -fourth embodiments include bis(trialkoxysilylorgano) disulfides and bis(trialkoxysilylorgano)tetrasulfides. Specific non-limiting examples of bis(trialkoxysilylorgano)disulfides include, but are not limited to, 3,3'-bis(triethoxysilylpropyl) disulfide, 3,3'-bis(trimethoxysilylpropyl)disulfide, 3, 3'-bis(tri butoxysilyl propyl [disulfide, 3,3'- bis(tri-t-butoxysilylpropyl)disulfide, 3, 3'-bis(tri hexoxysilyl propyl)disulfide, 2,2'- bis(dimethylmethoxysilylethyl)disulfide, 3,3'- bis(di phenylcyclo hexoxysilyl propyl [disulfide, 3,3'- bis(ethyl-di-sec-butoxysilylpropyl)disulfide, 3,3'-bis(propyldiethoxysilylpropyl)disulfide, 12,12'- bis(triisopropoxysilyl propyljdisu Ifide, 3,3'-bis(dimethoxyphenylsilyl-2-methylpropyl)disulfide, and mixtures thereof. Non-limiting examples of bis(trialkoxysilylorgano)tetrasulfide silica coupling agents suitable for use in certain embodiments of the first-fourth embodiments include, but are not limited to, bis(3-triethoxysilylpropyl)tetrasulfide, bis(2-triethoxysilylethyl) tetrasufide, bis(3-trimethoxysilylpropyl)tetrasulfide, 3- trimethoxysilylpropyl-N,N- dimethylthiocarbamoyl tetrasulfide, 3-triethoxysilylpropyl-N,N-dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilyl-N,N-dimethylthiocarbamoyl tetrasulfide, 3-tri methoxysilyl propylbenzothiazole tetrasulfide, 3-triethoxysilylpropylbenzothiazole tetrasulfide, and mixtures thereof. Bis(3-triethoxysilylpropyl)tetrasulfide is sold commercially as Si69® by Evonik Degussa Corporation. In preferred embodiments of the first-fourth embodiments, the tire tread rubber composition includes a silica coupling agent in the form of a bis(trialkoxysilylorgano)polysulfides, more preferably a bis(trialkoxysilylorgano) disulfides.
[0075] Non-limiting examples of mercapto silanes suitable for use in certain embodiments of first-fourth embodiments disclosed herein include, but are not limited to, 1- mercaptomethyltriethoxysilane, 2- mercaptoethyltriethoxysilane, 3- mercaptopropyltriethoxysilane, 3- mercaptopropylmethyldiethoxysilane, 2- mercaptoethyltripropoxysilane, 18- mercaptooctadecyldiethoxychlorosilane, and mixtures thereof.
[0076] Non-limiting examples of blocked mercapto silanes suitable for use in certain embodiments of the first-fourth embodiments disclosed herein include, but are not limited to, those described in U.S. Pat. Nos. 6,127,468; 6,204,339; 6,528,673; 6,635,700; 6,649,684; and 6,683,135, the disclosures of which are hereby incorporated by reference. Representative examples of the blocked mercapto silanes include, but are not limited to, 2- triethoxysi lyl-1- ethylthioacetate; 2-trimethoxysilyl-l-ethylthioacetate; 2-(methyldimethoxysilyl)- 1- ethylthioacetate; 3-trimethoxysilyl-l-propylthioacetate; triethoxysilylmethyl-thioacetate; trimethoxysilylmethylthioacetate; triisopropoxysilylmethylthioacetate; methyldiethoxysilylmethylthioacetate; methyldimethoxysilylmethylthioacetate; methyldiisopropoxysilylmethylthioacetate; di methylethoxysilyl methylthioacetate; dimethylmethoxysilylmethylthioacetate; di methylisopropoxysilyl methylthioacetate; 2- triisopropoxysilyl-l-ethylthioacetate; 2-(methyldiethoxysilyl)-l-ethylthioacetate, 2- (methyldiisopropoxysilyl)-l- ethylthioacetate; 2-(dimethylethoxysilyl-l-ethylthioacetate; 2-
(dimethylmethoxysilyl)-l- ethylthioacetate; 2-(dimethylisopropoxysilyl)-l-ethylthioacetate; 3- triethoxysilyl-l-propylthioacetate; 3-triisopropoxysilyl-l-propylthioacetate; 3- methyldiethoxysilyl-l-propyl-thioacetate; 3-methyldimethoxysilyl-l-propylthioacetate; 3- methyldiisopropoxysilyl-l-propylthioacetate; 1- (2-triethoxysilyl-l-ethyl)-4- thioacetylcyclohexane; l-(2-triethoxysilyl-l-ethyl)-3- thioacetylcyclohexane; 2-triethoxysilyl-5- thioacetylnorbornene; 2-triethoxysilyl-4-thioacetylnorbornene; 2-(2-triethoxysilyl-l-ethyl)-5- thioacetylnorbornene; 2-(2-triethoxy-silyl-l- ethyl)-4-thioacetylnorbornene; l-(l-oxo-2-thia-5- triethoxysilylphenyl)benzoic acid; 6- triethoxysilyl-l-hexylthioacetate; l-triethoxysilyl-5- hexylthioacetate; 8-triethoxysilyl-l- octylthioacetate; l-triethoxysilyl-7-octylthioacetate; 6- triethoxysilyl-l-hexylthioacetate; 1- triethoxysilyl-5-octylthioacetate; 8-trimethoxysilyl-l- octylthioacetate; l-trimethoxysilyl-7- octylthioacetate; 10-triethoxysilyl-l-decylthioacetate; 1- triethoxysilyl-9-decylthioacetate; 1- triethoxysilyl-2-butylthioacetate; l-triethoxysilyl-3- butylthioacetate; l-triethoxysilyl-3-methyl-2- butylthioacetate; l-triethoxysilyl-3-methyl-3- butylthioacetate; 3-trimethoxysilyl-l- propylthiooctanoate; 3-triethoxysilyl-l-propyl-l- propylthiopalmitate; 3-triethoxysilyl-l- propylthioocta noate; 3-triethoxysi lyl-1- propylthiobenzoate; 3-triethoxysilyl-l-propylthio-2- ethylhexanoate; 3-methyldiacetoxysilyl-l- propylthioacetate; 3-triacetoxysilyl-l- propylthioacetate; 2-methyldiacetoxysilyl-l- ethylthioacetate; 2-triacetoxysilyl-l- ethylthioacetate; 1-methyldiacetoxysilyl-l- ethylthioacetate; 1-triacetoxysilyl-l-ethyl-thioacetate; tris-(3-triethoxysi lyl-1- propyl)trithiophosphate; bis-(3-triethoxysi lyl-1- propyl)methyldithiophosphonate; bis-(3- triethoxysilyl-l-propyl)ethyldithiophosphonate; 3- triethoxysilyl-1- propyldimethylthiophosphinate; 3-triethoxysilyl-l-propyldiethylthiophosphinate; tris-(3- triethoxysilyl-l-propyl)tetrathiophosphate; bis-(3-triethoxysilyl-l propyl)methyltrithiophosphonate; bis-(3-triethoxysilyl-l-propyl)ethyltrithiophosphonate; 3- triethoxysilyl-l-propyldimethyldithiophosphinate; 3-triethoxysilyl-l- propyldiethyldithiophosphinate; tris-(3-methyldimethoxysilyl-l-propyl)trithiophosphate; bis-(3- methyldi methoxysilyl- l-propyl)methyldithiophosphonate; bis-(3-methyldimethoxysilyl-l- propyl)-ethyldithiophosphonate; 3-methyldimethoxysilyl-l-propyldimethylthiophosphinate; 3- methyldimethoxysilyl-l-propyldiethylthiophosphinate; 3-triethoxysilyl-l- propylmethylthiosulfate; 3-triethoxysilyl-l-propyl ethanethiosulfonate; 3-triethoxysilyl-l- propylethanethiosulfonate; 3-triethoxysilyl-l-propylbenzenethiosulfonate; 3-triethoxysilyl-l- propyltoluenethiosulfonate; 3-triethoxysilyl-l-propylnaphthalenethiosulfonate; 3-triethoxysi lyl- 1-propylxylenethiosulfonate; triethoxysilylmethylmethylthiosulfate; triethoxysilylmethyl methanethiosulfonate; triethoxysilylmethylethanethiosulfonate; triethoxysilylmethylbenzenethiosulfonate; triethoxysilylmethyltoluenethiosulfonate; triethoxysilylmethylnaphthalenethiosulfonate; triethoxysilylmethylxylenethiosulfonate, and the like. Mixtures of various blocked mercapto silanes can be used. A further example of a suitable blocked mercapto silane for use in certain exemplary embodiments is NXT™ silane (3- octanoylthio-l-propyltriethoxysilane), commercially available from Momentive Performance Materials Inc. of Albany, NY.
[0077] Non-limiting examples of pre-treated silicas (7. e. , silicas that have been pre-surface treated with a silane) suitable for use in certain embodiments of the first-fourth embodiments disclosed herein include, but are not limited to, Ciptane® 255 LD and Ciptane® LP (PPG Industries) silicas that have been pre-treated with a mercaptosilane, and Coupsil® 8113 (Degussa) that is the product of the reaction between organosilane bis(triethoxysilylpropyl) polysulfide (Si69) and Ultrasil® VN3 silica. Coupsil 6508, Agilon 400™ silica from PPG Industries, Agilon 454® silica from PPG Industries, and 458® silica from PPG Industries. In those embodiments where the silica comprises a pre-treated silica, the pre-treated silica is used in an amount as previously disclosed for the silica filler (i.e., 81-120 phr or about 90 to about 120 phr, etc.).
[0078] When a silica coupling agent is utilized in an embodiment of the first-fourth embodiments, the amount used may vary. In certain embodiments of the first-fourth embodiments, the rubber compositions do not contain any silica coupling agent. In other preferred embodiments of the first-fourth embodiments, the silica coupling agent is present in an amount sufficient to provide a ratio of the total amount of silica coupling agent to silica filler of about 0.1:100 to about 1:5 (i.e., about 0.1 to about 20 parts by weight per 100 parts of silica), including 0.1:100 to 1:5, about 1:100 to about 1:10, 1:100 to 1:10, about 1:100 to about 1:20, 1:100 to 1:20, about 1:100 to about 1:25, and 1:100 to 1:25 as well as about 1:100 to about 0:100 and 1:100 to 0:100. In preferred embodiments of the first-fourth embodiments, the ratio of the total amount of silica coupling agent to silica filler falls within a ratio of 1:10 to 1:20 (i.e., 10 to 5 parts by weight per 100 parts of silica). In certain embodiments according to the first-fourth embodiments, the rubber composition comprises about 0.1 to about 15 phr silica coupling agent, including 0.1 to 15 phr (e.g., 0.1, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15 phr), about 0.1 to about 12 phr, 0.1 to 12 phr, about 0.1 to about 10 phr, 0.1 to 10 phr, about 0.1 to about 7 phr, 0.1 to 7 phr, about 0.1 to about 5 phr, 0.1 to 5 phr, about 0.1 to about 3 phr, 0.1 to 3 phr, about 1 to about 15 phr, 1 to 15 phr (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15 phr), about 1 to about 12 phr, 1 to 12 phr (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, or 12 phr), about 1 to about 10 phr, 1 to 10 phr (e.g., 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, or 10 phr), about 1 to about 7 phr, 1 to 7 phr, about 1 to about 5 phr, 1 to 5 phr, about 1 to about 3 phr, 1 to 3 phr, about 3 to about 15 phr, 3 to 15 phr, about 3 to about 12 phr, 3 to 12 phr, about 3 to about 10 phr, 3 to 10 phr, about 3 to about 7 phr, 3 to 7 phr, about 3 to about 5 phr, 3 to 5 phr, about 5 to about 15 phr, 5 to 15 phr, about 5 to about 12 phr, 5 to 12 phr, about 5 to about 10 phr, 5 to 10 phr, about 5 to about 7 phr, or 5 to 7 phr. In preferred embodiments of the first- fourth embodiments, the rubber composition comprises silica coupling agent in an amount of 8 to 12 phr or one of the foregoing ranges falling within this range. Carbon Black Filler
[0079] According to the first -fourth embodiments disclosed herein, the amount of carbon black filler used in the tire tread rubber composition is limited. More specifically, according to the first-fourth embodiments disclosed herein, the tire tread rubber composition contains no more than 15 phr (e.g., 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, or even 0 phr) of carbon black filler, and in preferred embodiments of the first -fourth embodiments disclosed herein, the tire tread rubber composition contains no more than 10 phr (e.g., 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, or even 0 phr) of carbon black filler. In certain embodiments of the first -fourth embodiments disclosed herein, the tire tread rubber composition contains about 5 to about 10 phr of carbon black or 5- 10 phr (e.g., 5, 6, 7, 8, 9 or 10 phr) of carbon black. In certain embodiments of the first -fourth embodiments, the tire tread rubber composition contains 1-15 phr, 5-15 phr, 1-10 phr, 5-10 phr, 1-9 phr, 1-8 phr, no more than 8 phr (e.g., 8, 7, 6, 5, 4, 3, 2, 1 or even 0 phr), 0-9 phr, or 0-8 phr of carbon black filler. In certain embodiments of the first-fourth embodiments, the tire tread rubber composition contains 0 phr of carbon black filler. In certain embodiments of the first- fourth embodiments, the foregoing limited amounts of carbon black filler should be understood to referto reinforcing carbon black filler. In other embodiments of the first-fourth embodiments, the foregoing limited amounts of carbon black filler should be understood to refer to nonreinforcing carbon black filler. In yet other embodiments of the first -fourth embodiments, the foregoing limited amounts of carbon black filler should be understood to referto all carbon black fillers (i.e., both reinforcing and non-reinforcing carbon black filler).
[0080] In those embodiments of the first-fourth embodiments where carbon black filler is present, the particular type or types of carbon black utilized may vary. Generally, suitable carbon blacks for use as a reinforcing filler in the rubber composition of certain embodiments of the first-fourth embodiments include any of the commonly available, commercially-produced carbon blacks, including those having a surface area of at least about 20 m2/g (including at least 20 m2/g) and, more preferably, at least about 35 m2/g up to about 200 m2/g or higher (including 35 m2/g up to 200 m2/g). Surface area values used herein for carbon blacks are determined by ASTM D-1765 using the cetyltri methyl-ammonium bromide (CTAB) technique. Among the useful carbon blacks are furnace black, channel blacks, and lamp blacks. More specifically, examples of useful carbon blacks include super abrasion furnace (SAF) blacks, high abrasion furnace (HAF) blacks, fast extrusion furnace (FEF) blacks, fine furnace (FF) blacks, intermediate super abrasion furnace (ISAF) blacks, semi-reinforcing furnace (SRF) blacks, medium processing channel blacks, hard processing channel blacks and conducting channel blacks. Other carbon blacks which can be utilized include acetylene blacks. In certain embodiments of the first-fourth embodiments, the rubber composition includes a mixture of two or more of the foregoing blacks. Preferably according to the first-fourth embodiments, if a carbon black filler is present it consists of only one type (or grade) of reinforcing carbon black. Typical suitable carbon blacks for use in certain embodiments of the first-fourth embodiments are N-110, N-220, N-339, N-330, N-351, N-550, and N-660, as designated by ASTM D-1765-82a. The carbon blacks utilized can be in pelletized form or an unpelletized flocculent mass. Preferably, for more uniform mixing, unpelletized carbon black is preferred.
Other Reinforcing Fillers
[0081] In certain embodiments of the first-fourth embodiments, the tire tread rubber composition comprises a reinforcing filler other than carbon black or silica (/.e., an additional reinforcing filler). While one or more than one additional reinforcing filler may be utilized, their total amount is preferably limited to no more than 10 phr (e.g., 10, 9, 8, 7, 6, 5, 4, 3, 2, 1 or 0 phr), or no more than 5 phr (e.g., 5, 4, 3, 2, 1, or 0 phr). In certain preferred embodiments of the first-fourth embodiments, the tire tread rubber composition contains no additional reinforcing filler (/.e., 0 phr); in other words, in such embodiments no reinforcing filler other than silica and optionally carbon black are present.
[0082] In those embodiments of the first-fourth embodiments wherein an additional reinforcing filler is utilized, the additional reinforcing filler or fillers may vary. Non-limiting examples of suitable additional reinforcing fillers for use in the tire tread rubber compositions of certain embodiments of the first-fourth embodiments include, but are not limited to, alumina, aluminum hydroxide, clay (reinforcing grades), magnesium hydroxide, boron nitride, aluminum nitride, titanium dioxide, reinforcing zinc oxide, and combinations thereof. Non-Reinforcing Fillers
[0083] In certain embodiments of the first-fourth embodiments, the tire tread rubber composition further comprises at least one non-reinforcing filler. In other preferred embodiments of the first-fourth embodiments, the tire tread rubber composition contains no non-reinforcing fillers (/.e., 0 phr). In embodiments of the first-fourth embodiments wherein at least one non-reinforcing filler is utilized, the at least one non-reinforcing filler may be selected from clay (non-reinforcing grades), graphite, magnesium dioxide, aluminum oxide, starch, boron nitride (non-reinforcing grades), silicon nitride, aluminum nitride (non-reinforcing grades), calcium silicate, silicon carbide, ground rubber, and combinations thereof. The term "nonreinforcing filler" is used to refer to a particulate material that has a nitrogen absorption specific surface area (N2SA) of less than about 20 m2/g (including less than 20 m2/g), and in certain embodiments less than about 10 m2/g (including less than 10 m2/g). The N2SA surface area of a particulate material can be determined according to various standard methods including ASTM D6556. In certain embodiments, the term "non-reinforcing filler" is alternatively or additionally used to refer to a particulate material that has a particle size of greater than about 1000 nm (including greater than 1000 nm). In those embodiments of the first-fourth embodiments, wherein a non-reinforcing filler is present in the rubber composition, the total amount of nonreinforcing filler may vary but is preferably no more than 10 phr (e.g., 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 phr), and in certain embodiments 1-10 phr, no more than 5 phr (e.g., 5, 4, 3, 2, or 1 phr), 1-5 phr, or no more than 1 phr.
Hydrocarbon Resins
[0084] As mentioned above, according to the first and third embodiments, the tire tread rubber composition comprises (includes) as (d) 25-35 phr (e.g., 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, or 35 phr) of at least one hydrocarbon resin having a Tg of about 30 to about 50 °C or 30-50 °C (e.g., 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 42, 44, 45, 46, 48, or 50 °C). As also mentioned above, according to the second and fourth embodiments, the tire tread rubber composition comprises (includes) as (d) 25-35 phr (e.g., 25, 26, 1 , 28, 29, 30, 31, 32, 33, 34, or 35 phr) of at least one aromatic hydrocarbon resin having a Tg of about 30 to about 50 °C or 30-50 °C (e.g., 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 42, 44, 45, 46, 48, or 50 °C). In certain embodiments of the first-fourth embodiments, the tire tread rubber composition comprises (includes) as (d) 30-35 phr (e.g., 30, 31, 32, 33, 34, or 35 phr) of at least one hydrocarbon resin, preferably an aromatic hydrocarbon resin, having a Tg of 30-50 °C, or a range within that range, as discussed infa. Hydrocarbon resin Tg can be determined by DSC, according to the procedure discussed above for elastomer Tg measurements. In certain preferred embodiments of the first-fourth embodiments, the at least one hydrocarbon resin of (d) has a Tg of about 35 to about 50 °C, 35- 50 °C (e.g., 30, 32, 34, 35, 36, 38, 40, 42, 44, 45, 46, 48, or 50 °C), about 35 to about 45 °C, or 35- 45 °C (e.g., 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, or 45 °C) and may be present in one of the foregoing discussed amounts. As discussed in more detail below, according to the second and fourth embodiments and in certain embodiments of the first and third embodiments, the at least one hydrocarbon resin of (d) comprises an aromatic resin.
[0085] As discussed further, infra, according to the first-fourth embodiments in addition to controlling the amount of hydrocarbon resin (d) used in the tire tread rubber compositions, it is also preferable to control the total (or combined) amount of plasticizers, i.e., the hydrocarbon resin (d) and the liquid plasticizer (e) to within the amounts discussed elsewhere herein.
[0086] According to the first-fourth embodiments, one or more than one hydrocarbon resin may be utilized in the tire tread rubber composition and the particular type or types of hydrocarbon resin may vary. When more than one hydrocarbon resin is utilized, the abovediscussed amounts should be understood to refer to the total amount of all hydrocarbon resins.
[0087] According to the second and fourth embodiments and in certain embodiments of the first and third embodiments, the hydrocarbon resin of (d) comprises an aromatic resin optionally in combination with one or more additional resins selected from aliphatic, cycloaliphatic, and terpene resins; in those embodiments of the first-fourth embodiments wherein one or more additional resins are present, the total amount of such additional resin(s) is preferably no more than 5 phr, less than 5 phr, less than 4 phr, less than 3 phr, less than 2 phr, or less than 1 phr (and in each instance no more than 10% by weight, preferably no more than 5% by weight of the overall amount of hydrocarbon resin of (d)). In other embodiments of the first-fourth embodiments, the hydrocarbon resin of (d) consists of (only) an aromatic hydrocarbon resin. When an aromatic resin is used, one or more than one aromatic hydrocarbon resin may be utilized. In preferred certain embodiments of the first-fourth embodiments, the hydrocarbon resin of (d) includes less than 5 phr of terpene resin, and preferably excludes any terpene resin (i.e., 0 phrof terpene resin is present in the tire tread rubber composition). As used herein, the term aromatic resin or aromatic hydrocarbon resin should be understood to include both aromatic homopolymer resins and aromatic copolymer resins. An aromatic copolymer resins refers to a hydrocarbon resin which comprises a combination of one or more aromatic monomers in combination with one or more other (non-aromatic) monomers, with the largest amount of any type of monomer being aromatic. An aromatic copolymer resin would include a hydrocarbon resin having 45% by weight aromatic monomers, in addition to 25% by weight cycloaliphatic monomers and 30% by weight aliphatic monomers as well as a hydrocarbon resin having 55% by weight aromatic monomers, in addition to 30% by weight cycloaliphatic monomers and 15% by weight aliphatic monomers. In certain embodiments of the first -fourth embodiments, the hydrocarbon resin of (d) comprises one or more aromatic copolymer resins having a majority by weight of all monomers being aromatic (e.g., 51%, 55%, 60%, 65%, etc.). Non-limiting examples of aromatic resins suitable for use as the hydrocarbon resin (d) in certain embodiments of the first-fourth embodiments include coumarone-indene resins and alkylphenol resins as well as vinyl aromatic homopolymer or copolymer resins such as those including one or more of the following monomers: alpha-methylstyrene, styrene, ortho-methylstyrene, meta-methylstyrene, para-methylstyrene, vinyltoluene, para(tert-butyl)styrene, methoxystyrene, chlorostyrene, hydroxystyrene, vinylmesitylene, divinylbenzene, vinylnaphthalene or any vinyl aromatic monomer resulting from C9 fraction or C8-C10 fraction. Non-limiting examples of vinylaromatic copolymer resins include vinylaromatic/terpene copolymer resins (e.g., limonene/styrene copolymer resins), vinylaromatic/C5 fraction resins (e.g., C5 fraction/styrene copolymer resin), vinylaromatic/aliphatic copolymer resins (e.g., CPD/styrene copolymer resin, and DCPD/styrene copolymer resin). Non-limiting examples of alkyl-phenol resins include alkylphenol-acetylene resins such as p-tert-butylphenol-acetylene resins, alkylphenol-formaldehyde resins (such as those having a low degree of polymerization). Exemplary such aromatic resins are commercially available from various companies including Chemfax, Dow Chemical Company, Eastman Chemical Company, Idemitsu, Neville Chemical Company, Nippon, Polysat Inc., Resinall Corp., and Zeon under various trade names.
[0088] In certain embodiments of the first-fourth embodiments, the hydrocarbon resin (d) comprises an aromatic resin based upon one or more of the above-mentioned vinyl aromatic monomers (e.g., styrene, alpha-methylstyrene); in certain such embodiments at least 80% by weight, at least 85% by weight, at least 90% by weight, at least 95% by weight, at least 98% by weight, at least 99% by weight, or even 100% by weight of the monomers in the aromatic resin are aromatic monomers. In certain embodiments of the first-fourth embodiments, the hydrocarbon resin (d) consists of an aromatic resin based upon one or more of the above- mentioned vinyl aromatic monomers (e.g., styrene, alpha-methylstyrene); in certain such embodiments at least 80% by weight, at least 85% by weight, at least 90% by weight, at least 95% by weight, at least 98% by weight, at least 99% by weight, or even 100% by weight of the monomers in the aromatic resin are aromatic monomers. In certain embodiments of the first- fourth embodiments, the aromatic resin of (d) may include a hydrogenated form of one of the aromatic resins discussed above (i.e., a hydrogenated aromatic resin). In other embodiments of the first-fourth embodiments, the aromatic resin of (d) excludes any hydrogenated aromatic resin; in other words, in such embodiments, the aromatic resin is not hydrogenated.
[0089] As mentioned above, in certain embodiments of the first-fourth embodiments, the at least one hydrocarbon resin of (d) comprises (i) an aromatic resin in combination with (ii) an aliphatic resin. Non-limiting examples of aliphatic resins include C5 fraction homopolymer and copolymer resins. The amount of any aliphatic resin used in (d) is preferably limited. According to the first-fourth embodiments, the total amount of any aliphatic resin used in combination with the aromatic resin is preferably no more than 5 phr, less than 5 phr, less than 4 phr, less than 3 phr, less than 2 phr, or less than 1 phr (and in each instance no more than 20% by weight, preferably no more than 15% or no more than 10% by weight of the overall amount of hydrocarbon resin of (d)).
[0090] As mentioned above, in certain embodiments of the first-fourth embodiments, the at least one hydrocarbon resin of (d) comprises (i) an aromatic resin in combination with (ii) a cycloaliphatic resin. Non-limiting examples of cycloaliphatic resins include cyclopentadiene ("CPD") homopolymer or copolymer resins, dicyclopentadiene ("DCPD") homopolymer or copolymer resins, and combinations thereof. The amount of any cycloaliphatic resin used in (d) is preferably limited. According to the first-fourth embodiments, the total amount of any cycloaliphatic resin used in combination with the aromatic resin is preferably no more than 5 phr, less than 5 phr, less than 4 phr, less than 3 phr, less than 2 phr, or less than 1 phr (and in each instance no more than 20% by weight, preferably no more than 15% or no more than 10% by weight of the overall amount of hydrocarbon resin of (d)).
[0091] As mentioned above, in certain embodiments of the first-fourth embodiments the at least one hydrocarbon resin of (d) comprises (i) an aromatic resin in combination with (ii) a terpene resin. Non-limiting examples of terpene resins include alpha-pinene resins, beta-pinene resins, limonene resins (e.g., L-limonene, D-limonene, dipentene which is a racemic mixture of L- and D-isomers), beta-phellandrene, delta-3-carene, delta-2-carene, and combinations thereof. The amount of any terpene resin used in (d) is preferably limited. According to the first-fourth embodiments, the total amount of any terpene resin used in combination with the aromatic resin is preferably no more than 5 phr, less than 5 phr, less than 4 phr, less than 3 phr, less than 2 phr, or less than 1 phr (and in each instance no more than 20% by weight, preferably no more than 15% or no more than 10% by weight of the overall amount of hydrocarbon resin of (d)). As mentioned above, in preferred embodiments of the first-fourth embodiments, the hydrocarbon resin (d) includes no terpene resin (i.e., 0 phr).
[0092] In certain preferred embodiments of the first-fourth embodiments, the hydrocarbon resin (d) has a softening point of about 70 to about 100 °C or 70-100 °C (e.g., 70, 75, 80, 85, 90, 95, or 100 °C), preferably about 75 to about 95 °C or 75-95 °C (e.g., 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, or 95 °C), more preferably about 80 to about 90 °C or 80-90 °C (e.g., 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, or 90 °C). Generally the softening point of a hydrocarbon resin will have a relationship to its Tg such that the Tg is lower than its softening point, and such that the lower the Tg the lower the softening point. As a nonlimiting example, for two hydrocarbon resins having Tg's of 70 and 100 °C, the resin with the Tg of 70 °C will have a lower softening point than the resin with the Tg of 100 °C. [0093] In certain embodiments of the first-fourth embodiments, the hydrocarbon resin (d) meets at least one of the following: (a) a Mw of 1000 to about 4000 grams/mole, 1000-4000 grams/mole (e.g., 1000, 1100, 1200, 1300, 1400, 1500, 1600, 1700, 1800, 1900, 2000, 2100, 2200, 2300, 2400, 2500, 2600, 2700, 2800, 2900, 3000, 3100, 3200, 3300, 3400, 3500, 3600, 3700, 3800, 3900, or 4000 grams/mole), about 1000 to about 3000 grams/mole, 1000-3000 grams/mole (e.g., 1000, 1100, 1200, 1300, 1400, 1500, 1600, 1700, 1800, 1900, 2000, 2100, 2200, 2300, 2400, 2500, 2600, 2700, 2800, 2900, or 3000 grams/mole), about 1000 to about 2500 grams/mole, 1000-2500 grams/mole (e.g., 1000, 1100, 1200, 1300, 1400, 1500, 1600, 1700, 1800, 1900, 2000, 2100, 2200, 2300, 2400, or 2500 grams/mole), about 1000 to about 2000 grams/mole, 1000-2000 grams/mole (e.g., 1000, 1100, 1200, 1300, 1400, 1500, 1600, 1700, 1800, 1900, or 2000 grams/mole), about 1100 to about 1800 grams/mole, or 1100-1800 grams/mole (e.g., 1100, 1200, 1300, 1400, 1500, 1600, 1700, or 1800 grams/mole); (b) a Mn of about 700 to about 1500 grams/mole, 700-1500 grams/mole (e.g., 700, 800, 900, 1000, 1100, 1200, 1300, 1400, or 1500 grams/mole), about 800 to about 1400 grams/mole, 800-1400 grams/mole (e.g., 800, 900, 1000, 1100, 1200, 1300, or 1400 grams/mole), about 800 to about 1300 grams/mole, 800-1300 grams/mole (e.g., 800, 900, 1000, 1100, 1200, or 1300 grams/mole), about 900 to about 1200 grams/mole, or 900-1200 grams/mole (e.g., 900, 950, 1000, 1050, 1100, 1150, or 1200 grams/mole); or (c) a polydispersity (Mw/Mn) of about 1 to about 2, 1-2 (e.g., 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, or 2), about 1.1 to about 1.8, 1.1-1.8 (e.g., 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, or 1.8), about 1.1 to about 1.7, 1.1-1.7 (e.g., 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, or 1.7), about 1.2 to about 1.5, or 1.2 to 1.5 (e.g., 1.2, 1.3, 1.4, or 1.5). In certain preferred embodiments of the first-fourth embodiments, the hydrocarbon resin (d) has a Mw according to one of the ranges provided above, in combination with a Mn according to one of the ranges provided above, further in combination with a Mw/Mn according to one of the ranges provided above; in certain such embodiments, the hydrocarbon resin (d) is an aromatic resin.
[0094] In certain embodiments of the first-fourth embodiments, the hydrocarbon resin (d) comprises an aromatic resin (as discussed above) having an aromatic monomer content of at least about 40% by weight, at least 40% by weight (e.g., 40, 45, 50, 51, 55, 60% by weight, or more), about 40% to about 65% by weight, 40-65% by weight (e.g., 40, 42, 44, 45, 46, 48, 50, 52, 54, 55, 56, 58, 60, 62, 64, or 65% by weight), at least about 45% by weight, at least 45% by weight (e.g., 45, 50, 51, 55, 60% by weight, or more), about 45% to about 65% by weight, 45-65% by weight (e.g., 45, 47, 49, 50, 51, 53, 55, 57, 59, 60, 61, 63, or 65% by weight), at least 51% by weight (e.g., 51, 55, 60, 65% by weight, or more), about 51% to about 65% (e.g., 51, 52, 53, 54,
55, 56, 57, 58, 59, 60, 61, 62, 63, 64, or 65%), 51-65%, about 51% to about 60%, 51-60% (e.g., 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, or 60%), about 51% to about 55%, or 51-55% (e.g, 51, 52, 53, 54, or 55%). The amounts of aromatic monomer content are weight percentages based upon the total weight of the respective hydrocarbon resin.
Liquid Plasticizers (including oils and non-oils)
[0095] As mentioned above, according to the first-fourth embodiments, the tire tread rubber composition comprises 11-20 phr of liquid plasticizer (e.g., 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 phr), which preferably consists of at least one oil. In preferred embodiments of the first-fourth embodiments, the 11-20 phr of liquid plasticizer comprises (includes) at least one oil, more preferably the 11-20 phr of liquid plasticizer consists of (only) at least one oil. In certain embodiments of the first-fourth embodiments, the tire tread rubber composition comprises 15- 20 phr of liquid plasticizer (e.g., 15, 16, 17, 18, 19, or 20 phr). The term liquid plasticizer is used to refer to plasticizer ingredients which are liquid at room temperature (i.e., liquid at 25 °C and above) and to distinguish hydrocarbon resin plasticizers which will generally be solid at room temperature. Generally, liquid plasticizers will have a Tg below 0 °C, generally well below such as less than -30 °C, less than -40 °C, or less than -50 °C. In certain embodiments of the first -fourth embodiments, the liquid plasticizer has a Tg of less than 0 °C to -100 °C, a Tg of -30 °C to -100 °C, or a Tg of -50 to -100 °C. As discussed in more detail below, liquid plasticizers include both oils (e.g., petroleum oils as well as plant oils) and other non-oil liquid plasticizers including, but not limited to, ether plasticizers, ester plasticizers, phosphate plasticizers, and sulfonate plasticizers. Moreover, the term liquid plasticizer is meant to encompass both free liquid plasticizer (which is usually added during the compounding process) and extender oil (which is used to extend a rubber). Thus, by stating that the tire tread rubber composition comprises 11-20 phr of liquid plasticizer it should be understood that the total amount of any free liquid plasticizer (both oil plasticizer and non-oil liquid plasticizer) and any extender oil is 11-20 phr. In certain embodiments of the first and third embodiments, the tire tread rubber composition contains only free liquid plasticizer in an amount of 11-20 phr. In other embodiments of the first and third embodiments and in certain embodiments of the second and fourth embodiments, the tire tread rubber composition contains only extender oil in an amount of 11-20 phr. In yet other embodiments of the first-fourth embodiments, the tire tread rubber composition includes both free liquid plasticizer and extender oil in a total amount of 11-20 phr. In those embodiments of the first-fourth embodiments wherein an oil-extended rubber is used, the amount of oil used to prepare the oil-extended rubber may vary. In those embodiments of the first and third embodiments wherein an oil-extended rubber is used (e.g., an oil-extended SBR for (i)) and according to the second and fourth embodiments wherein the SBR of (i) is oil-extended, the amount of oil used to prepare the oil-extended rubber may vary; in certain such embodiments, the amount of extender oil present in the oil-extended rubber (polymer) or SBR is 10-50 parts oil per 100 parts of rubber (e.g., 10, 15, 20, 25, 30, 35, 40, 45 or 50 parts of oil per 100 parts or rubber), preferably 10-40 parts oil per 100 parts or rubber or 20-40 parts oil per 100 parts of rubber. As a non-limiting example, extender oil could be used in an amount of 40 parts oil per 100 parts rubber in an SBR for (i) which SBR is used in an amount of 40 parts (the 40 parts being the amount of polymer of the oil-extended SBR, as discussed previously) in the overall tread rubber composition and, thus, the amount of oil contributed by the oil-extended SBR to the tire tread rubber composition would be 16 phr. Oil-extension of rubbers (especially styrenebutadiene rubbers) can be beneficial to ease of processing or mixing when the SBR has a relatively high Mw and/or a relatively high Mooney viscosity. In certain embodiments of the first-fourth embodiments disclosed herein, the styrene-butadiene rubber as used in (i) is an oil-extended styrene-butadiene rubber having a polymer Mooney viscosity ML1+4 at 100 °C of at least 100. By polymer Mooney viscosity is meant the Mooney viscosity of the rubber or polymer before oilextension. When an oil-extended rubber is used in the elastomer component of the tire tread rubber composition disclosed herein, the amounts specified for (i) (and (ii)) should be understood to refer to the amounts of rubber only rather than the amounts of oil-extended rubber. As used herein, oil refers to both petroleum based oils (e.g., aromatic, naphthenic, and low PCA oils) as well as plant oils (such as can be harvested from vegetables, nuts, and seeds). Plant oils will generally comprise triglycerides and the term should be understood to include synthetic triglycerides as well as those actually sourced from a plant.
[0096] According to the first-fourth embodiments, various types of processing and extender oils may be utilized as the at least one liquid plasticizer, including, but not limited to aromatic, naphthenic, and low PCA oils (petroleum-sourced or plant-sourced). Suitable low PCA oils include those having a polycyclic aromatic content of less than 3 percent by weight as determined by the IP346 method. Procedures for the IP346 method may be found in Standard Methods for Analysis & Testing of Petroleum and Related Products and British Standard 2000 Parts, 2003, 62nd edition, published by the Institute of Petroleum, United Kingdom. Exemplary petroleum-sourced low PCA oils include mild extraction solvates (MES), treated distillate aromatic extracts (TDAE), TRAE, and heavy naphthenics. Exemplary MES oils are available commercially as CATENEX SNR from SHELL, PROREX 15, and FLEXON 683 from EXXONMOBIL, VIVATEC 200 from BP, PLAXOLENE MS from TOTAL FINA ELF, TUDALEN 4160/4225 from DAHLEKE, MES-H from REPSOL, MES from Z8, and OLIO MES S201 from AGIP. Exemplary TDAE oils are available as TYREX 20 from EXXONMOBIL, VIVATEC 500, VIVATEC 180, and ENERTHENE 1849 from BP, and EXTENSOIL 1996 from REPSOL. Exemplary heavy naphthenic oils are available as SHELLFLEX 794, ERGON BLACK OIL, ERGON H2000, CROSS C2000, CROSS C2400, and SAN JOAQUIN 2000L. Exemplary low PCA oils also include various plant-sourced oils such as can be harvested from vegetables, nuts, and seeds. Non-limiting examples include, but are not limited to, soy or soybean oil, sunflower oil (including high oleic sunflower oil), safflower oil, corn oil, linseed oil, cotton seed oil, rapeseed oil, cashew oil, sesame oil, camellia oil, jojoba oil, macadamia nut oil, coconut oil, and palm oil. The foregoing processing oils can be used as an extender oil, i.e., to prepare an oil-extended polymer or copolymer, or as a processing or free oil.
[0097] As mentioned above, according to the first-fourth embodiments, the liquid plasticizer may in certain embodiments include a non-oil plasticizer, non-limiting examples of which include ether plasticizers, ester plasticizers, phosphate plasticizers, and sulfonate plasticizers. In those embodiments where a non-oil plasticizer is present, preferably only a portion of the liquid plasticizer (e.g., less than 50%, no more than 40%, no more than 30%, no more than 20%, no more than 10%, or even no more than 5% is provided by the non-oil plasticizer). Exemplary ether plasticizers include polyethylene glycols and polypropylene glycols. Exemplary ester plasticizers include triesters and diesters in particular (which may be selected from the group consisting of di- and triesters of carboxylic acid, of phosphoric acid, or of sulphonic acid, and mixtures of these triesters). More specifically, exemplary carboxylic acid ester plasticizers include compounds selected from the group consisting of trimellitates, pyromellitates, phthalates, 1,2-cyclohexanedicarboxylates, adipates, azelates, sebacates, glyercol triesters, and mixtures of the foregoing. More specifically as to glycerol triesters, these may include more than 50% by weight, more preferably more than 80% by weight of an unsaturated C18 fatty acid (e.g., oleic acid, linoleic acid, linolenic acid, and mixtures thereof). Other exemplary carboxylic acid ester plasticizers include stearic acid esters, ricinoleicacid esters, phthalic acid esters (e.g., di-2-ethylhexyl phthalate and diosodecyl phthalate), isophthalic acid esters, tetrahydrophthalic acid esters, adipic acid esters (e.g., di(2-ethylhexyl)adipate and diisooctyl adipate), malic acid esters, sebic acid esters (e.g., di(2-ethylhexyl)sebacate and diisooctyl sebacate), and fumaric acid esters. Exemplary phosphate plasticizers include those with a tri-hydrocarbyl phosphate and di-hydrocarbyl phosphate structures (where each hydrocarbyl is independently selected from alkyl of Cl to C12, preferably Cl to C8, and aromatic of C6 to C12 both substituted and un-substituted, preferably when aromatic C6 either substituted or un-substituted). More specifically, exemplary phosphate plasticizers include trimethyl phosphate, triethyl phosphate, tributyl phosphate, trioctyl phosphate, dioctyl phosphate, 2- ethylhexyl diphenyl phosphate, tributoxyethyl phosphate, triphenyl phosphate, cresyl diphenyl phosphate, isodecyl diphenyl phosphate, tricresyl phosphate, tritolyl phosphate, trixylenyl phosphate, tris(chloroethyl) phosphate, and diphenyl mono-o-xenyl phosphate. Exemplary sulfonate plasticizers include sulfonic acid esters such as sulfone butylamide, toluenesulfonamide, N-ethyl-toluenesulfonamide, and N-cyclohexyl-p-toluencesulfonamide. Of the foregoing non-oil liquid plasticizers, phosphate plasticizers, in particular phosphoric acid derivatives (which can be understood as being phosphate esters) are preferred.
[0098] According to first-fourth embodiments, the Tg of the oil or oils used may vary. In certain embodiments of the first-fourth embodiments, any oil utilized has a Tg of about -40 to about -100 °C, -40 to -100 °C (e.g., -40, -45, -50, -55, -60, -65, -70, -75, -80, -85, -90, -95, or -100 °C), about -40 to about -90 °C, -40 to -90 °C (e.g., -40, -45, -50, -55, -60, -65, -70, -75, -80, -85, or -90 °C), about -45 to about -85 °C, -45 to -85 °C {e.g., -45, -50, -55, -60, -65, -70, -75, -80, or -85 °C), about -50 to about -80 °C, or -50 to -80 °C (e.g., -50, -55, -60, -65, -70, -75, or -80 °C).
[0099] In certain embodiments of the first-fourth embodiments, the tire tread rubber composition contains less than 5 phr (e.g., 4.5, 4, 3, 2, 1, or 0 phr) of MES orTDAE oil, or even no MES or TDAE oil (i.e., 0 phr). In certain embodiments of the first -fourth embodiments, the tire tread rubber composition contains no petroleum oil (i.e., 0 phr) and instead any oil utilized is a plant oil. In certain embodiments of the first-fourth embodiments, the tire tread rubber composition contains soybean oil in one of the above-mentioned amounts. In certain embodiments of the first-fourth embodiments, the tire tread rubber composition contains no sunflower oil (i.e., 0 phr).
[00100] In certain embodiments of the first-fourth embodiments, the tire tread rubber composition includes one or more ester plasticizers. Suitable ester plasticizers are known to those of skill in the art and include, but are not limited to, phosphate esters, phthalate esters, adipate esters and oleate esters (i.e., derived from oleic acid). Taking into account that an ester is a chemical compound derived from an acid wherein at least one -OH is replaced with an -O- alkyl group, various alkyl groups may be used in suitable ester plasticizers for use in the tire tread rubber compositions, including generally linear or branched alkyl of Cl to C20 (e.g., Cl, C2, C3, C4, C5, C6, C7, C8, C9, CIO, Cll, C12, C13, C14, C15, C16, C17, C18, C19, C20), or C6 to C12. Certain of the foregoing esters are based upon acids which have more than one -OH group and, thus, can accommodate one or more than one O-alkyl group (e.g., trialkyl phosphates, dialkyl phthalates, dialkyl adipates). Non-limiting examples of suitable ester plasticizers include trioctyl phosphate, dioctyl phthalate, dioctyl adipate, nonyl oleate, octyl oleate, and combinations thereof. The use of an ester plasticizer such as one or more of the foregoing may be beneficial to the snow or ice performance of a tire made from a tread rubber composition containing such ester plasticizer at least in part due to the relatively low Tg of ester plasticizers. In certain embodiments of the first-fourth embodiments, the tire tread rubber composition includes one or more ester plasticizers having a Tg of -40 °C to -70 °C (e.g., -40, -45, -50, -55, -60, -65, or -70 °C), or -50 °C to -65 °C (e.g., -50, -51, -52, -53, -54, -55, -56, -57, -58, -59, -60, -61, -62, -63, -64, or -65 °C ). In those embodiments of the first-fourth embodiments wherein one or more ester plasticizers is utilized the amount utilized may vary. In certain embodiments of the first -fourth embodiments, one or more ester plasticizers are utilized in a total amount of 1-12 phr (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, or 12 phr), 1-10 phr (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 phr), 2-6 phr (e.g., 2, 3, 4, 5, or 6 phr) or 2-5 phr (e.g., 2, 3, 4, or 5 phr). In certain embodiments of the first-fourth embodiments, one or more ester plasticizers is used in combination with oil in one of the foregoing amounts.
Hydrocarbon Resin + Liquid Plasticizer
[00101] As mentioned above, according to the first-fourth embodiments disclosed herein, the total amount of at least one hydrocarbon resin (d) and at least one liquid plasticizer (e) is 36-50 phr (e.g., 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, or 50 phr). In certain preferred embodiments of the first-fourth embodiments, the total amount of hydrocarbon resin (d) and liquid plasticizer (e) is 40-50 phr (e.g., 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, or 50 phr). In certain embodiments of the first -fourth embodiments, the total amount of hydrocarbon resin (d) and liquid plasticizer (e) is no more than 49 phr (e.g., 49, 48, 47, 46, 45, 44, 43, 42, 41, 40, 39, 38, 37, or 36 phr, or a range from the foregoing such as 36-49 phr, etc.).
[00102] In certain preferred embodiments of the first-fourth embodiments, the amount of hydrocarbon resin (d) is greater than the amount of liquid plasticizer (e). In certain such embodiments, the hydrocarbon resin (d) and liquid plasticizer (e) are present in a weight ratio of at least 1.5:1, preferably 1.5:1 to 3:1 (e.g., 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1, 2:1, 2.1:1, 2.2:1, 2.3:1, 2.4:1, 2.5:1, 2.6:1, 2.7:1, 2.8:1, 2.9:1, or 3:1), more preferably 1.6:1 to 2.8: (e.g., 1.6:1, 1.7:1, 1.8:1, 1.9:1, 2:1, 2.1:1, 2.2:1, 2.3:1, 2.4:1, 2.5:1, 2.6:1, 2.7:1, or 2.8:1).
Cure Package
[00103] As discussed above, according to the first-fourth embodiments disclosed herein, the tire tread rubber composition includes (comprises) a cure package. Although the contents of the cure package may vary according to the first -fourth embodiments, generally, the cure package includes at least one of: a vulcanizing agent; a vulcanizing accelerator; a vulcanizing activator (e.g., zinc oxide, stearic acid, and the like); a vulcanizing inhibitor; and an anti-scorching agent. In certain embodiments of the first-fourth embodiments, the cure package includes at least one vulcanizing agent, at least one vulcanizing accelerator, at least one vulcanizing activator and optionally a vulcanizing inhibitor and/or an anti-scorching agent. Vulcanizing accelerators and vulcanizing activators act as catalysts for the vulcanization agent. Various vulcanizing inhibitors and anti-scorching agents are known in the art and can be selected by one skilled in the art based on the vulcanizate properties desired.
[00104] Examples of suitable types of vulcanizing agents for use in certain embodiments of the first-fourth embodiments, include but are not limited to, sulfur or peroxidebased curing components. Thus, in certain such embodiments, the curative component includes a sulfur-based curative or a peroxide-based curative. In preferred embodiments of the first- fourth embodiments, the vulcanizing agent is a sulfur-based curative; in certain such embodiments the vulcanizing agent consists of (only) a sulfur-based curative. Examples of specific suitable sulfur vulcanizing agents include "rubbermaker's" soluble sulfur; sulfur donating curing agents, such as an amine disulfide, polymeric polysulfide, or sulfur olefin adducts; and insoluble polymeric sulfur. Preferably, the sulfur vulcanizing agent is soluble sulfur or a mixture of soluble and insoluble polymeric sulfur. For a general disclosure of suitable vulcanizing agents and other components used in curing, e.g., vulcanizing inhibitor and anti-scorching agents, one can refer to Kirk-Othmer, Encyclopedia of Chemical Technology, 3rd ed., Wiley Interscience, N.Y. 1982, Vol. 20, pp. 365 to 468, particularly Vulcanization Agents and Auxiliary Materials, pp. 390 to 402, or Vulcanization by A. Y. Coran, Encyclopedia of Polymer Science and Engineering, Second Edition (1989 John Wiley & Sons, Inc.), both of which are incorporated herein by reference. Vulcanizing agents can be used alone or in combination. Generally, the vulcanizing agents may be used in certain embodiments of the first -fourth embodiments in an amount ranging from 0.1 to 10 phr (e.g., 0.1, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 phr), including from 1 to 7.5 phr (e.g., 1, 2, 3, 4, 5, 6, 7, or 7.5 phr), including from 1 to 5 phr (e.g., 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, or 5 phr), and preferably from 1 to 3.5 phr (e.g., 1, 1.5, 2, 2.5, 3, or 3.5 phr).
[00105] Vulcanizing accelerators are used to control the time and/or temperature required for vulcanization and to improve properties of the vulcanizate. Examples of suitable vulcanizing accelerators for use in certain embodiments of the first-fourth embodiments disclosed herein include, but are not limited to, thiazole vulcanization accelerators, such as 2- mercaptobenzothiazole, 2,2'-dithiobis(benzothiazole) (MBTS), N-cyclohexyl-2-benzothiazole- sulfenamide (CBS), N-tert-butyl-2-benzothiazole-sulfenamide (TBBS), and the like; guanidine vulcanization accelerators, such as diphenyl guanidine (DPG) and the like; thiuram vulcanizing accelerators; carbamate vulcanizing accelerators; and the like. Generally, the amount of the vulcanization accelerator used ranges from 0.1 to 10 phr {e.g., 0.1, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 phr), preferably 0.5 to 5 phr {e.g., 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, or 5 phr). Preferably, any vulcanization accelerator used in the tire tread rubber compositions of the first-fourth embodiments excludes any thiurams such as thiuram monosulfides and thiuram polysulfides (examples of which include TMTM (tetramethyl thiuram monosulfide), TMTD (tetramethyl thiuram disulfide), DPTT (dipentamethylene thiuram tetrasulfide), TETD (tetraethyl thiuram disulfide), TiBTD (tetraisobutyl thiuram disulfide), and TBzTD (tetrabenzyl thiuram disulfide)); in other words, the tire tread rubber compositions of the first-fourth embodiments preferably contain no thiuram accelerators (/.e., 0 phr).
[00106] Vulcanizing activators are additives used to support vulcanization. Generally vulcanizing activators include both an inorganic and organic component. Zinc oxide is the most widely used inorganic vulcanization activator. Various organic vulcanization activators are commonly used including stearic acid, palmitic acid, lauric acid, and zinc salts of each of the foregoing. Generally, in certain embodiments of the first-fourth embodiments the amount of vulcanization activator used ranges from 0.1 to 6 phr {e.g., 0.1, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, or 6 phr), preferably 0.5 to 4 phr {e.g., 0.5, 1, 1.5, 2, 2.5, 3 3.5, or 4 phr). In certain embodiments of the first-fourth embodiments, one or more vulcanization activators are used which includes one or more thiourea compounds (used in one of the foregoing amounts), and optionally in combination with one or more of the foregoing vulcanization activators. Generally, a thiourea compound can be understood as a compound having the structure (R1)(R2)NS(=C)N(R3)(R4) wherein each of R1, R2, R3, and R4 are independently selected from H, alkyl, aryl, and N-containing substituents {e.g., guanyl). Optionally, two of the foregoing structures can be bonded together through N (removing one of the R groups) in a dithiobiurea compound. In certain embodiments, one of R1 or R2 and one of R3 or R4 can be bonded together with one or more methylene groups (-CH2-) therebetween. In certain embodiments of the first- fourth embodiments, the thiourea has one or two of R1, R2, R3 and R4 selected from one of the foregoing groups with the remaining R groups being hydrogen. Exemplary alkyl include C1-C6 linear, branched or cyclic groups such as methyl, ethyl, propyl, iso-propyl, butyl, iso-butyl, pentyl, hexyl, and cyclohexyl. Exemplary aryl include C6-C12 aromatic groups such as phenyl, tolyl, and naphthyl. Exemplary thiourea compounds include, but are not limited to, dihydrocarbylthioureas such as dialkylthioureas and diarylthioureas. Non-limiting examples of particular thiourea compounds include one or more of thiourea, N,N'-diphenylthiourea, trimethylthiourea, N,N'- diethylthiourea (DEU), N,N'-dimethylthiourea, N,N'-dibutylthiourea, ethylenethiourea, N,N'- diisopropylthiourea, N,N'-dicyclohexylthiourea, l,3-di(o-tolyl)thiourea, l,3-di(p-tolyl)thiourea, l,l-diphenyl-2-thiourea, 2,5-dithiobiurea, guanylthiourea, l-(l-naphthyl)-2-thiourea, 1-phenyl- 2-thiourea, p-tolylthiourea, and o-tolylthiourea. In certain embodiments of the first-fourth embodiments, the activator includes at least one thiourea compound selected from thiourea, N,N'-diethylthiourea, trimethylthiourea, N,N'-diphenylthiourea, and N-N'-dimethylthiourea.
[00107] Vulcanization inhibitors are used to control the vulcanization process and generally retard or inhibit vulcanization until the desired time and/or temperature is reached. Common vulcanization inhibitors include, but are not limited to, PVI (cyclohexylthiophthalmide) from Santogard. Generally, in certain embodiments of the first-fourth embodiments the amount of vulcanization inhibitor is 0.1 to 3 phr (e.g., 0.1, 0.5, 1, 1.5, 2, 2.5, or 3 phr), preferably 0.5 to 2 phr (e.g., 0.5, 1, 1.5, or 2 phr).
Preparing The Rubber Compositions
[00108] The particular steps involved in preparing the tire tread rubber compositions of the first-fourth embodiments disclosed herein are generally those of conventionally practiced methods comprising mixing the ingredients in at least one nonproductive master-batch stage and a final productive mixing stage. In certain embodiments of the first-fourth embodiments, the tire tread rubber composition is prepared by combining the ingredients for the rubber composition (as disclosed above) by methods known in the art, such as, for example, by kneading the ingredients together in a Banbury mixer or on a milled roll. Such methods generally include at least one non-productive master-batch mixing stage and a final productive mixing stage. The term non-productive master-batch stage is known to those of skill in the art and generally understood to be a mixing stage (or stages) where no vulcanizing agents or vulcanization accelerators are added. The term final productive mixing stage is also known to those of skill in the art and generally understood to be the mixing stage where the vulcanizing agents and vulcanization accelerators are added into the rubber composition. In certain embodiments of the first-fourth embodiments, the tire tread rubber composition is prepared by a process comprising more than one non-productive master-batch mixing stage.
[00109] In certain embodiments of the first-fourth embodiments, the tire tread rubber composition is prepared by a process wherein the master-batch mixing stage includes at least one of tandem mixing or intermeshing mixing. Tandem mixing can be understood as including the use of a mixer with two mixing chambers with each chamber having a set of mixing rotors; generally, the two mixing chambers are stacked together with the upper mixer being the primary mixer and the lower mixer accepting a batch from the upper or primary mixer. In certain embodiments, the primary mixer utilizes intermeshing rotors and in other embodiments the primary mixer utilizes tangential rotors. Preferably, the lower mixer utilizes intermeshing rotors. Intermeshing mixing can be understood as including the use of a mixerwith intermeshing rotors. Intermeshing rotors refers to a set of rotors where the major diameter of one rotor in a set interacts with the minor diameter of the opposing rotor in the set such that the rotors intermesh with each other. Intermeshing rotors must be driven at an even speed because of the interaction between the rotors. In contrast to intermeshing rotors, tangential rotors refers to a set of rotors where each rotor turns independently of the other in a cavity that may be referred to as a side. Generally, a mixer with tangential rotors will include a ram whereas a ram is not necessary in a mixer with intermeshing rotors.
[00110] Generally, the rubbers (or polymers) and at least one reinforcing filler (as well as any silane coupling agent and liquid plasticizer) will be added in a non-productive or master-batch mixing stage or stages. Generally, at least the vulcanizing agent component and the vulcanizing accelerator component of a cure package will be added in a final or productive mixing stage.
[00111] In certain embodiments of the first -fourth embodiments, the tire tread rubber composition is prepared using a process wherein at least one non-productive master batch mixing stage is conducted at a temperature of about 130 °C to about 200 °C. In certain embodiments of the first-fourth embodiments, the tire tread rubber composition is prepared using a final productive mixing stage conducted at a temperature below the vulcanization temperature in order to avoid unwanted pre-cure of the rubber composition. Therefore, the temperature of the productive or final mixing stage generally should not exceed about 120 °C and is typically about 40 °C to about 120 °C, or about 60 °C to about 110 °C and, especially, about 75 °C to about 100 °C. In certain embodiments of the first-fourth embodiments, the tire tread rubber composition is prepared according to a process that includes at least one non-productive mixing stage and at least one productive mixing stage. The use of silica fillers may optionally necessitate a separate re-mill stage for separate addition of a portion or all of such filler. This stage often is performed at temperatures similar to, although often slightly lower than, those employed in the masterbatch stage, i.e., ramping from about 90°C to a drop temperature of about 150°C.
Tire Tread Properties
[00112] The use of the tire tread rubber composition of the first-fourth embodiments disclosed herein, preferably result in a tire having improved or desirable tread properties. These improved or desirable properties may include one or more of rolling resistance, snow or ice traction, wet traction, dry handling, or wear, preferably improved rolling resistance and wear. Additional improved or desirable properties may include elongation at break (Eb), tensile at break (Tb) and TbxEb. While these properties may be measured by various methods, the values referred to herein for rolling resistance, snow or ice traction, wet traction, and dry handling refer to tan 6 values measured at the following temperatures and according to the following procedures. Tan 6 values can be measured with a dynamic mechanical thermal spectrometer (Eplexor® 500N from Gabo Qualimeter Testanlagen GmbH of Ahiden, Germany) generally following the guidelines of ASTM D5992-96 (2011) and under the following conditions: measurement mode: tensile test mode; measuring frequency: 52 Hz; applying 0.2% strain from -50 to -5 °C and 1% strain from -5 to 65 °C; collecting data approximately every 1 °C in order to provide measurements at temperatures of -30 °C, 0 °C, 30°C, and 60 °C; sample shape: 4.75 mm wide x 29 mm long x 2.0 mm thick. Measurement is made upon a cured sample of rubber (cured for 15 minutes at 170°C). A rubber composition's tan 6 at -30 °C is indicative of its snow or ice traction (also referred to herein as winter performance) when incorporated into a tire tread, tan 6 at 0 °C is indicative of its wet traction when incorporated into a tire tread, tan 6 at 30 °C is indicative of its dry handling when incorporated into a tire tread and its tan 6 at 60 °C is indicative of its rolling resistance when incorporated into a tire tread.
[00113] In certain embodiments of the first -fourth embodiments, the rubber composition has a value for tan 6 at 60 °C of 0.18 to 0.25 (e.g., 0.18, 0.19, 0.2, 0.21, 0.22, 0.23, 0.24, or 0.25), preferably 0.18 to 0.22 (e.g., 0.18, 0.19, 0.2, 0.21, or 0.22 times), more preferably 0.18 to 0.2 (e.g., 0.18, 0.19, 0.2). A tan 6 at 60 °C within one of the foregoing ranges can be understood as being indicative of a tire (or more specifically, a tire tread) with moderate rolling resistance (as opposed to a tire with low rolling resistance which would generally be indicated by a tan 6 at 60 °C of less than or equal to 0.2). In certain embodiments of the first-fourth embodiments, the value for tan 6 at 60 °C is combined with at least one of the following: (a) a value for tan 6 at -30 °C of no more than 2.5 times the tan 6 at 60 °C value (e.g., 2.5, 2.4, 2.2, 2.1, 2, 1.9, 1.8, etc. times ), preferably between 2.5 times and 2 times (e.g., 2.5, 2.4, 2.3, 2.2, 2.1, or 2 times) the tan 6 at 60 °C value; (b) a value for tan 6 at 30 °C of at least 1.4 times the tan 6 at 60 °C value (e.g., 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2, 2.1, 2.2, etc. times), preferably between 1.4 and 2 times (e.g., 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, or 2 times) the tan 6 at 60 °C value, more preferably between 1.5 and 1.8 times (e.g., 1.5, 1.6, 1.7, or 1.8 times) the tan 6 at 60 °C value; or (c) a value for tan 6 at 0 °C of at least 2.2 times the tan 6 at 60 °C value (e.g., 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3, 3.1, 3.2, etc. times), preferably 2.2 times to 3 times the tan 6 at 60 °C value (e.g., 2.2, 2.3,
2.4, 2.5, 2.6, 2.7, 2.8, 2.9, or 3 times), more preferably 2.3 times to 2.8 times the tan 6 at 60 °C value (e.g., 2.3, 2.4, 2.5, 2.6, 2.7, or 2.8 times); in certain such embodiments, the value for tan 6 at 60 °C is combined with each of (a), (b), and (c). In certain embodiments of the first-fourth embodiments, one of the foregoing values for tan 6 at 60 °C (e.g., 0.18 to 0.25, 0.18 to 0.22, 0.18 to 0.2, etc.) is combined with (a) a value for 6 at -30 °C of between 2.5 times and 2 times (e.g.,
2.5, 2.4, 2.3, 2.2, 2.1, or 2 times) the tan 6 at 60 °C value. In certain embodiments of the first- fourth embodiments, one of the foregoing values for tan 6 at 60 °C (e.g., 0.18 to 0.25, 0.18 to 0.22, 0.18 to 0.2, etc.) is combined with (b) a value for 6 at 30 °C of 1.4 and 2 times (e.g., 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, or 2 times) the tan 6 at 60 °C value,. In certain embodiments of the first-fourth embodiments, one of the foregoing values for tan 6 at 60 °C (e.g., 0.18 to 0.25, 0.18 to 0.22, 0.18 to 0.2, etc.) is combined with (c) a value for 6 at 0 °C of 2.2 times to 3 times the tan 6 at 60 °C value (e.g., 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, or 3 times) the tan 6 at 60 °C value. In certain embodiments of the first-fourth embodiments, one of the foregoing values for tan 6 at 60 °C (e.g., 0.18 to 0.25, 0.18 to 0.22, 0.18 to 0.2, etc.) is combined with the more preferred values for tan 6 at -30 °C, the more preferred values for tan 6 at 30 °C, and the more preferred values for tan 6 at 30 °C.
[00114] In certain embodiments of the first and second embodiments, and according to the third and fourth embodiments, the tire tread rubber composition has a value for tan 6 at 60 °C of 0.18 to 0.25, preferably 0.18 to 0.22, more preferably 0.18 to 0.2, and meets at least one of the following (i.e., (a)-(b), preferably each of the following: (a) has a value for tan 6 at -30 °C of no more than 2.5 times the tan 6 at 60 °C value, preferably between 2.5 times and 2 times the tan 6 at 60 °C value; (b) has a value for tan 6 at 30 °C of at least 1.4 times the tan 6 at 60 °C value, preferably between 1.4 times and 2 times the tan 6 at 60 °C value, more preferably between 1.5 times and 1.8 times the tan 6 at 60 °C value; or (c) has a value for tan 6 at 0 °C of at least 2.2 times the tan 6 at 60 °C value, preferably between 2.2 times and 3 times the tan 6 at 60 °C value, more preferably between 2.3 times and 2.8 times the tan 6 at 60 °C value.
[00115] The wear performance of a tire tread rubber composition can be evaluated by various methods. However, the absolute wear values provided herein refer to DIN abrasion values that can be measured using standard methods including DIN ISO 4649, 2017 edition, or more preferably DIN ISO 53516. According to such method, the values represent the amount of material lost (in mm3) during the abrasion testing. When comparing two DIN abrasion values, a lower number indicates less material lost and corresponds to an improvement in wear. An improvement in wear can also be described as improved resistance to abrasion and is generally desirable in a tire tread since it leads to a tire having a longer lifespan (e.g., having a higher predicted mileage rating). In certain preferred embodiments of the first-fourth embodiments, the tire tread rubber composition has a DIN abrasion (according to DIN ISO 4649, 2017 edition, more preferably DIN ISO 53516) of no more than no more than 95 mm3 (e.g., 95, 94, 93, 92, 91, 90, 89, 88, 87, 86, 85, 84, 83, 82, 81, 80, 79, 78, 77, 76, 75, 74, 73, 72, 71, 70, 69, 68, 67, 66, 65, 64, 63, 62, 61, 60 mm3 or less), preferably no more than 90 mm3 (e.g., 90, 89, 88, 87, 86, 85, 84, 83, 82, 81, 80, 79, 78, 77, 76, 75, 74, 73, 72, 71, 70, 69, 68, 67, 66, 65, 64, 63, 62, 61, 60 mm3 or less), 95 to 80 mm3 (e.g., 95, 94, 93, 92, 91, 90, 89, 88, 87, 86, 85, 84, 83, 82, 81, or 80 mm3) including ranges within the foregoing), 95 to 85 mm3 (e.g., 95, 94, 93, 92, 91, 90, 89, 88, 87, 86, or 85 mm3), 90 to 80 mm3 (e.g., 90, 89, 88, 87, 86, 85, 84, 83, 82, 81, or 80 mm3), or 90 to 85 mm3 (e.g., 90, 89, 88, 87, 86, 85, 84, 83, 82, 81, or 80 mm3).
[00116] The tire tread rubber compositions of the first-fourth embodiments can be considered to be particularly useful in terms of providing a tire tread improved rolling resistance and wear performance. By stating that the rolling resistance and wear performance are balanced is meant that the rolling resistance and wear performance are each improved by at least 5% as compared to a control while maintaining the wear performance, where the control refers to a tread rubber composition which replaces the silica-reactive functionalized polybutadiene (ii) with an equivalent amount of a non-functional high cis polybutadiene. By stating that the wear performance is improved is meant that the wear performance (as measured by ISO 23337:2016)) is at least 101% of a control (e.g., 101%, 102%, 103%, 104%, 105%, etc.), and in certain instances an improvement in wear as compared to the control, e.g., of at least 5% (e.g., 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15% or higher, including ranges encompassing the foregoing such as 5-15% and 5-10%) or even at least 10% (e.g., 10%, 11%, 12%, 13%, 14%, 15% or higher, including ranges encompassing the foregoing such as 10-15%). Alternatively, the foregoing improvements can also be described as being at least 105% (with 105% being 5% higher than 100%) and at least 110% (with 110% being 10% higher than 100%) as compared to a control. As non-limiting examples, if a sample exhibited an abrasion loss of 0.0055 mg and its control exhibited an abrasion loss of 0.0050, the sample could be described as having a wear performance that is 95% of its control and if a sample exhibited an abrasion loss of 0.0054 mg and its control exhibited an abrasion loss of 0.0060 mg, the sample could be described as having a wear performance that is improved by 10% as compared to its control. According to the foregoing descriptions, a wear performance that is 100% of its control should be understood as having a wear performance that is equal to its control and the comparisons to control are calculated by dividing the control value by the sample value and multiplying by 100%. By stating that the rolling resistance is improved is meant that the rolling resistance (as reflected by tan 6 measurements at 60 °C, as described further herein) is at least 101% of a control (e.g., 101%, 102%, 103%, 104%, 105%, etc.), and in certain instances an improvement in rolling resistance as compared to the control, e.g., of at least 5% (e.g., 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15% or higher, including ranges encompassing the foregoing such as 5-15% and 5-10%) or even at least 10% (e.g., 10%, 11%, 12%, 13%, 14%, 15% or higher, including ranges encompassing the foregoing such as 10-15%). Alternatively, the foregoing improvements can also be described as being at least 105% (with 105% being 5% higher than 100%) and at least 110% (with 110% being 10% higher than 100%) as compared to a control. By stating that the rolling resistance and wear performance are each improved by at least 5% as compared to a control is meant to encompass improvements of 5%, 6%, 7%, 8%, 9%, 10%, 11%, etc. (as discussed above) or even improvements of at least 10% (as also discussed above).
[00117] In certain embodiments of the first -fourth embodiments, the rubber composition has a room temperature Eb of at least 475% (e.g., 475%, 480%, 485%, 490%, 495%, 500%, 505%, 510%, 515%, 520%, 525%, 530%, 535%, 540%, 545%, 550%, 555%, 560%, 565%, 570%, 575%, 580%, 585%, 590%, 595%, 600%, 605%, 610%, 615%, 620%, 625%, 630%, 635%, 640%, 645%, 650%, or more) or within the range of 475 to 650% or a sub-range within that range, preferably at least 500% (e.g., 500%, 505%, 510%, 515%, 520%, 525%, 530%, 535%, 540%, 545%, 550%, 555%, 560%, 565%, 570%, 575%, 580%, 585%, 590%, 595%, 600%, 605%, 610%, 615%, 620%, 625%, 630%, 635%, 640%, 645%, 650%, or more) or within the range of 500 to 650% or a sub-range within that range, more preferably at least 525% (e.g., 525%, 530%, 535%, 540%, 545%, 550%, 555%, 560%, 565%, 570%, 575%, 580%, 585%, 590%, 595%, 600%, 605%, 610%, 615%, 620%, 625%, 630%, 635%, 640%, 645%, 650%, or more) or within the range of 525 to 650% or a sub-range within that range. The foregoing room temperature Eb values refer to measurements made at 23 ° C. Eb can be measured following the guidelines, but not restricted to, the standard procedure described in ASTM D-412, with dumbbell-shaped samples having a cross-section dimension of 4 mm in width and 1.9 mm in thickness at the center. During measurement, specimens may be strained at a constant rate (20% per second) and the resulting force recorded as a function of extension (strain).
[00118] In certain embodiments of the first -fourth embodiments, the rubber composition has a hot Eb of at least 375%, (e.g., 375%, 380%, 385%, 390%, 395%, 400%, 405%, 410%, 415%, 420%, 425%, 430%, 435%, 440%, 445%, 450%, 455%, 460%, 465%, 470%, 475%, 480%, 485%, 490%, 495%, 499%, or more) or within a range of 375-499% or a sub-range within that range, preferably at least 400% (e.g., 400%, 405%, 410%, 415%, 420%, 425%, 430%, 435%, 440%, 445%, 450%, 455%, 460%, 465%, 470%, 475%, 480%, 485%, 490%, 495%, 499%, or more) or within a range of 400-499% or a sub-range within that range. The foregoing hot Eb values refer to measurements made at 100 °C. Eb can be measured following the guidelines, but not restricted to, the standard procedure described in ASTM D-412, with dumbbell-shaped samples having a cross-section dimension of 4 mm in width and 1.9 mm in thickness at the center. During measurement, specimens may be strained at a constant rate (20% per second) and the resulting force recorded as a function of extension (strain). Generally, a hot Eb value for a given tread rubber composition will be lower (i.e., less than) the room temperature Eb for that tread rubber composition.
[00119] In certain embodiments of the first -fourth embodiments, the rubber composition has a hot EbxTb (both values determined at 100 °C) of at least 3600 (e.g., 3600, 3650, 3700, 3750, 3800, 3850, 3900, 3950, 4000, 4050, 4100, 41504200, 4250, 4300, 4350, 4400, 4450, 4500, 4550, 4600, 4650, 4700, 4750, 4800, 4850, 4900, or more) or 3600 to 4900 or a subrange within that range, preferably at least 3800 (e.g., 3700, 3750, 3800, 3850, 3900, 3950, 4000, 4050, 4100, 4150, 4200, 4250, 4300, 4350, 4400, 4450, 4500, 4550, 4600, 4650, 4700, 4750, 4800, 4850, 4900, or more) or 3800 to 4900 or a sub-range within that range. The hot TbxEb is calculated by multiplying the hot Tb with the hot Eb value and refers to measurements made at 100 ° C. Tb can be measured following the guidelines, but not restricted to, the standard procedure described in ASTM D-412, with dumbbell-shaped samples having a cross-section dimension of 4 mm in width and 1.9 mm in thickness at the center. During measurement, specimens may be strained at a constant rate (20% per second) and the resulting force recorded as a function of extension (strain). Tires
[00120] It is specifically contemplated that the tire tread rubber composition according to the first-fourth embodiments, as disclosed herein, will be utilized in a tire tread. Thus, also disclosed herein is a tire tread comprising (made from) the tire tread rubber composition according to the first-fourth embodiments, as discussed herein. As well, such a tire tread can be utilized in a tire (along with other components). Thus, also disclosed herein is a tire having a tread comprising (made from) the tire tread rubber composition according to the first- fourth embodiments, as discussed herein.
Methods
[00121] Also disclosed herein, are methods for providing a tire tread. More specifically, the methods are for providing a tire tread having improved wear and/or rolling resistance performance (preferably both improved wear and improved rolling resistance) by utilizing a tire tread rubber composition according to the first-third embodiments disclosed herein. As discussed in detail above, the improvement in wear and/or rolling resistance can be measured according to the methods described herein.
EXAMPLES
[00122] The following examples are provided to illustrate specific and exemplary embodiments and/or features of the embodiments of the present disclosure. The examples are provided solely for the purposes of illustration and should not be construed as limitations of the present disclosure. Numerous variations over these specific examples are possible without departing from the spirit and scope of the presently disclosed embodiments. It should specifically be understood that tire tread rubber compositions according to the present disclosure can be made using different SBRs, different polybutadienes, different reinforcing silica filler, different (or no) carbon black, different hydrocarbon resin, and different liquid plasticizing agents, generally in connection with the teachings provided herein and as fully disclosed in the preceding paragraphs. It should also be understood that the foregoing ingredients can differ in relative amount, composition, or both from those used in the examples (/.e., as fully as disclosed in the preceding paragraphs). [00123] Table 1 contains a summary of information relating to an exemplary inventive tire tread rubber composition and two (2) exemplary control tire tread rubber compositions. As should be apparent from a detailed review of Table 1, the control compositions each differ from the inventive compound with respect to certain of the listed ingredients as well as with respect to their properties, i.e., tan 6 values, as described below. Use of ingredients according to the first-fourth embodiments, as described in detail in the above paragraphs, results in a tire tread rubber composition having a tan 6 at 60 ° C within the range of 0.18-0.22, a tan 6 at -30 °C of no more than 2.5 times the tan 6 at 60 °C, a tan 6 at 0 °C that is at least 2.2 times larger than tan 6 at 60 °C, and a tan 6 at 30 °C that is at least 1.4 times the tan 6 at 60 °C. In contrast, neither of the control compositions have a tan 6 at 60 ° C within the range of 0.18-0.22, a tan 6 at 0 °C that is at least 2.2 times larger than tan 6 at 60 °C, or a tan 6 at 30 °C that is at least 1.4 times the tan 6 at 60 °C.
[00124] This application discloses several numerical range limitations that support any range within the disclosed numerical ranges, even though a precise range limitation is not stated verbatim in the specification, because the embodiments of the compositions and methods disclosed herein could be practiced throughout the disclosed numerical ranges. With respect to the use of substantially any plural or singular terms herein, those having skill in the art can translate from the plural to the singular or from the singular to the plural as is appropriate to the context or application. The various singular or plural permutations may be expressly set forth herein for sake of clarity.
[00125] It will be understood by those within the art that, in general, terms used herein, and especially in the appended claims are generally intended as "open" terms. For example, the term "including" should be interpreted as "including but not limited to," the term "having" should be interpreted as "having at least," the term "includes" should be interpreted as "includes but is not limited to." It will be further understood by those within the art that if a specific number of an introduced claim recitation is intended, such an intent will be explicitly recited in the claim, and in the absence of such recitation no such intent is present. For example, as an aid to understanding, the following appended claims may contain usage of the introductory phrases "at least one" and "one or more" to introduce claim recitations. However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by the indefinite articles "a" or "an" limits any particular claim containing such introduced claim recitation to inventions containing only one such recitation, even when the same claim includes the introductory phrases "one or more" or "at least one" and indefinite articles such as "a" or "an" (e.g., "a" or "an" should typically be interpreted to mean "at least one" or "one or more"); the same holds true for the use of definite articles used to introduce claim recitations. In addition, even if a specific number of an introduced claim recitation is explicitly recited, those skilled in the art will recognize that such recitation should typically be interpreted to mean at least the recited number (e.g., the bare recitation of "two recitations," without other modifiers, typically means at least two recitations, or two or more recitations). Furthermore, in those instances where a convention analogous to "at least one of A, B, and C, etc." is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., " a system having at least one of A, B, and C" would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). It will be further understood by those within the art that virtually any disjunctive word or phrase presenting two or more alternative terms, whether in the description, claims, or drawings, should be understood to contemplate the possibilities of including one of the terms, either of the terms, or both terms. For example, the phrase "A or B" will be understood to include the possibilities of "A" or "B" or "A and B."
[00126] All references, including but not limited to patents, patent applications, and non-patent literature are hereby incorporated by reference herein in their entirety.
[00127] While various aspects and embodiments of the compositions and methods have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope and spirit being indicated by the claims.

Claims

What is claimed is:
1. A tire tread rubber composition comprising: a. 100 parts of an elastomer component comprising i. 35-55 parts, preferably 35-49 parts, more preferably 40-49 parts of at least one styrene-butadiene rubber having a Tg of about -30 to about -50 °C, ii. 45-65 parts, preferably 51-65 parts, more preferably 51-60 parts of polybutadiene rubber having a cis bond content of at least 95%, a Tg of less than -101 °C, preferably -101 to -110 °C, and a silica-reactive functional group; b. 70-99 phr of at least one reinforcing silica filler having a surface area of about 100 to about 300 m2/g, preferably about 150 to about 300 m2/g; c. no more than 15 phr of carbon black, preferably no more than 10 phr of carbon black; d. 25-35 phr of at least one hydrocarbon resin having a Tg of about 30 to about 50 °C; e. 11-20 phr of at least one liquid plasticizing agent, which preferably consists of at least one oil; and f. a cure package, wherein the total amount of (d) and (e) is 36-54 phr, preferably 40-50 phr.
2. The tire tread rubber composition of claim 1, wherein the at least one styrenebutadiene rubber of (a)(i ) is functionalized, preferably with a silica -reactive functional group.
3. The tire tread rubber composition of claim 1 or claim 2, wherein the at least one hydrocarbon resin of (d) is an aromatic hydrocarbon resin.
4. A tire tread rubber composition comprising: a. 100 parts of an elastomer component comprising I . 35-49 parts, preferably 40-49 parts, of at least one styrene-butadiene rubber having a Tg of about -30 to about -50 °C and a silica-reactive functional group, ii. 51-65 parts, preferably 51-60 parts, of polybutadiene rubber having a cis bond content of at least 95%, a Tg of less than -101 °C, preferably -101 to -110 °C, and a silica-reactive functional group; b. 70-99 phr of at least one reinforcing silica filler having a surface area of about 100 to about 300 m2/g, preferably about 150 to about 300 m2/g; c. no more than 15 phr of carbon black, preferably no more than 10 phr of carbon black; d. 25-35 phr of at least one aromatic hydrocarbon resin having a Tg of about 30 to about 50 °C; e. 11-20 phr of at least one liquid plasticizing agent, which preferably consists of at least one oil; and f. a cure package, wherein the total amount of (d) and (e) is 36-54 phr, preferably 40-50 phr.
5. The tire tread rubber composition of any one of claims 1-4, wherein at least one of (a) and (b) is met, preferably both (a) and (b): a. the at least one styrene-butadiene rubber of (a)(i) has a Mw of about 300,000 to about 500,000 grams/mole; preferably about 300,000 to about 500,000 grams/mole; more preferably about 350,000 to about 450,000 grams/mole; or b. the polybutadiene rubber of (a)(ii) has a Mw of about 450,000 to about 700,000 grams/mole, preferably about 500,000 to about 650,000 grams/mole.
6. The tire tread rubber composition of any one of claims 1-5, wherein the elastomer component includes less than 10 parts of non-functionalized rubber, preferably less than 5 parts of non-functionalized rubber, even more preferably 0 parts of non-functionalized rubber.
7. The tire tread rubber composition of any one of claims 1-6, wherein the at least one reinforcing silica filler of (b) is present in an amount of 80-90 phr.
8. The tire tread rubber composition of any one of claims 1-7, wherein the total amount of natural rubber, polyisoprene, or a combination thereof in the elastomer component is no more than 9 phr, preferably no more than 5 phr, more preferably 0 phr.
9. The tire tread rubber composition of any one of claims 1-8, wherein the polybutadiene of (ii) has less than 3% by weight syndiotactic 1,2-polybutadiene, preferably 0%.
10. The tire tread rubber composition of any one of claims 1-9, wherein the polybutadiene of (ii) has a silica-reactive functional group resulting from a functional compound having the following formula (II): wherein A1 represents a monovalent epoxy group, preferably selected from glycidoxy groups, 3,4-epoxycyclohexyl groups; or a glycidyl group having 3-8, preferably 3-6, carbons overall, with the 2 end carbons being within the epoxy ring and the other end of the carbon chain bonded to Rc; Rc represents a single bond or a divalent hydrocarbon group having from 1 to 20 carbon atoms (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 carbon atoms); Rd represents a monovalent aliphatic hydrocarbon group having 1 to 20 carbon atoms (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 carbon atoms), a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms (e.g., 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, or 18 carbon atoms) or a reactive group; Re represents a monovalent aliphatic hydrocarbon group having 1 to 20 carbon atoms (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 carbon atoms) or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms (e.g., 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, or 18 carbon atoms); b is an integer of 0 to 2; when more than one Rd or ORe are present, each Rd and/or ORe may be the same as or different from each other; and an active proton is not contained in a molecule) and/or a partial condensation product thereof.
11. The tire tread rubber composition of claim 10, wherein the monovalent epoxy group A1 is selected from glycidoxy groups.
12. The tire tread rubber composition of claim 10, wherein the monovalent epoxy group A1 is selected from 3,4-epoxycyclohexyl groups.
13. The tire tread rubber composition of claim 10, wherein the monovalent epoxy group A1 is selected from a glycidyl group having 3-8, preferably 3-6, carbons overall, with the 2 end carbons being within the epoxy ring and the other end of the carbon chain bonded to Rc.
14. The tire tread rubber composition of any one of claims 1-13, wherein the at least one hydrocarbon resin of (d) less than 5 phr of terpene resin, preferably 0 phr of terpene resin.
15. The tire tread rubber composition of any one of claims 1-14, wherein the at least one hydrocarbon resin of (d) is present in an amount of 30-35 phr.
16. The tire tread rubber composition of any one of claims 1-15, wherein the at least one liquid plasticizing agent of (e) is present in an amount of 15-20 phr.
17. The tire tread rubber composition of any one of claims 1-16, wherein the at least one liquid plasticizing agent of (e) is a non-petroleum oil, preferably a plant oil.
18. The tire tread rubber composition of any one of claims 1-17, wherein the rubber composition has a value for tan 6 at 60 °C of 0.18 to 0.25, preferably 0.18 to 0.22, more preferably 0.18 to 0.2, and meets at least one of the following, preferably each of the following: a. has a value for tan 6 at -30 °C of no more than 2.5 times the tan 6 at 60 °C value, preferably between 2.5 times and 2 times the tan 6 at 60 °C value; b. has a value for tan 6 at 30 °C of at least 1.4 times the tan 6 at 60 °C value, preferably between 1.4 times and 2 times the tan 6 at 60 °C value, more preferably between 1.5 times and 1.8 times the tan 6 at 60 °C value; or c. has a value for tan 6 at 0 °C of at least 2.2 times the tan 6 at 60 °C value, preferably between 2.2 times and 3 times the tan 6 at 60 °C value, more preferably between 2.3 times and 2.8 times the tan 6 at 60 °C value.
19. The tire tread rubber composition according to any one of claims 1-18, wherein the rubber composition meets at least one of the following, preferably each of the following: a. has a room temperature Eb of at least 475%, preferably at least 500%, more preferably at least 525%; b. has an Eb at 100 °C of at least 375%, preferably at least 400%; or c. has an Tb x Eb, both at 100 °C, of at least 3600, preferably at least 3800.
20. The tire tread rubber composition of any one of claims 1-19, wherein the rubber composition has a DIN abrasion of no more than 95 mm3, preferably no more than 90 mm3.
21. A tire having a tread comprising the tire tread rubber composition of any one of claims 1-20.
EP24715973.4A 2023-02-28 2024-02-27 Tire tread rubber composition and related methods Pending EP4673320A1 (en)

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US12365202B2 (en) 2018-05-04 2025-07-22 Bridgestone Americas Tire Operations, Llc Tire tread rubber composition
JP2021523260A (en) 2018-05-04 2021-09-02 ブリヂストン アメリカズ タイヤ オペレーションズ、 エルエルシー Tire tread rubber composition
US12103334B2 (en) 2018-05-04 2024-10-01 Bridgestone Americas Tire Operations, Llc Tire tread rubber composition
WO2019213226A1 (en) 2018-05-04 2019-11-07 Bridgestone Americas Tire Operations, Llc Tire tread rubber composition
EP3976393A1 (en) 2019-05-29 2022-04-06 Bridgestone Americas Tire Operations, LLC Tire tread rubber composition and related methods
JP2022535725A (en) 2019-05-29 2022-08-10 ブリヂストン アメリカズ タイヤ オペレーションズ、 エルエルシー Tire tread rubber composition and related methods
JP2022534568A (en) 2019-05-29 2022-08-02 ブリヂストン アメリカズ タイヤ オペレーションズ、 エルエルシー Tire tread rubber composition and related methods

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