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
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K3/00—Use of inorganic substances as compounding ingredients
  • C08K3/01—Use of inorganic substances as compounding ingredients characterized by their specific function
  • C08K3/013—Fillers, pigments or reinforcing additives
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K5/00—Use of organic ingredients
  • C08K5/54—Silicon-containing compounds
  • C08K5/5406—Silicon-containing compounds containing elements other than oxygen or nitrogen
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K5/00—Use of organic ingredients
  • C08K5/54—Silicon-containing compounds
  • C08K5/548—Silicon-containing compounds containing sulfur

Definitions

• the present disclosure relates to rubber compositions comprising unsaturated organic polymers, fillers and silane.
• the present disclosure also provides for a process of making said rubber composition as well as articles made therefrom.
• the polysulfurized alkoxysilanes such as bis(triethoxysilylpropyl)tetrasulfite (TESPT), and blocked mercapto-functional silanes such as 3-octanoylthio-l-propyltriethoxysilane, are currently regarded as the most effective and the most widely used coupling agents in rubber compositions for tires, especially those compositions containing styrene-butadiene rubber or butadiene rubber.
• the reinforcing efficiency and abrasion resistance of vulcanizates filled with silica are not good enough to justify the replacement of carbon black in formulations containing high levels of natural rubber.
• non-sulfur silanes are focused on the use of activated double bonds to improve the coupling between fillers and polymer, notably natural rubber. But these non-sulfur coupling agents have shown inadequate coupling performances or performances inferior to those offered by polysulfurized silanes such as bis(triethoxysilylpropyl)tetrasulfide.
• polysulfurized silanes such as bis(triethoxysilylpropyl)tetrasulfide.
• the known non-sulfur silanes are very reactive with conventional fillers and elastomers and are therefore difficult to use.
• the uncured filled elastomer typically exhibits poorly dispersed filler and short scorch times during curing. Both good filler dispersion and good filler reinforcing efficiency are required to achieve satisfactory end-use properties.
• a rubber composition comprising:
• a rubber composition comprising:
• each R 1 is independently selected from the group consisting of hydrogen, alkyl, alkenyl, aryl and aralkyl groups wherein each R 1 , other than hydrogen, contains from 1 to 18 carbon atoms and optionally at least one heteroatom selected from the group consisting of oxygen and sulfur;
• each occurrence of X 2 and X 3 is independently selected from X 1 and R 2 - groups wherein each R 2 is independently selected from the group consisting of hydrogen, straight, cyclic or branched alkyl, alkenyl, aryl and aralkyl groups wherein each R 2 , other than hydrogen, contains from 1 to 18 carbon atoms and optionally at least one heteroatom selected from the group consisting of oxygen and sulfur;
• each occurrence of G is independently a divalent or polyvalent hydrocarbon group of from 1 to about 18 carbon atoms that can optionally contain at least one heteroatom selected from the group consisting of oxygen, sulfur, phosphorous and silicon;
• each occurrence of Y is independently an unsaturated group;
• alkyl includes straight, branched and cyclic alkyl groups; "alkenyl' includes any straight, branched, or cyclic alkenyl group containing one or more carbon-carbon double bonds, where the point of substitution can be either at a carbon-carbon double bond or elsewhere in the group; "alkynyl” includes any straight, branched or cyclic alkynyl group containing one or more carbon-carbon triple bonds, where the point of substitution can be either at a carbon-carbon triple bond or elsewhere in the group; "aryl” includes the non- limiting group of any aromatic hydrocarbon from which one hydrogen atom has been removed; “aralkyl” includes, but is not limited to, any of the aforementioned alkyl groups in which one or more hydrogen atoms have been substituted by the same number of like and/or different aryl (as defined herein) substituents.
• alkyls include, but are not limited to, methyl, ethyl, propyl and isobutyl.
• alkenyls include, but are not limited to, vinyl, propenyl, allyl, methallyl, ethylidenyl norbornane, ethylidene norbornyl and ethylidene norornenyl.
• aryls include, but are not limited to, tolyl, xylyl, phenyl and naphthalenyl.
• aralkyls include, but are not limited to, benzyl and phenethyl.
• X 1 of the general Formula (1) is a hydrolyzable group.
• Some non-limiting representative examples of X 1 include alkoxy groups such as the non-limited examples methoxy, ethoxy, propoxy, isopropoxy, butoxy, phenoxy and benzyloxy; hydroxyl group; halo groups such as the non-limiting examples chloro, bromo and iodo; oximato groups such as the non-limiting examples methylethyloximato, phenylmethyloximato and dimethyloximato; amineoxy groups such as the non-limiting examples dimethylamineoxy, diethylamineoxy and methylphenyamineoxy; and, acyloxy groups such as the non-limiting examples formyloxy, acetoxy and propanoyloxy.
• Some representative non-limiting examples of X 2 and X 3 in Formula (1) include the representative examples listed above for X 1 as well as hydrogen, alkyl groups such as the non-limiting examples methyl, ethyl, propyl, isopropyl, sec-butyl and cyclohexyl; higher straight-chain alkyl such as butyl, hexyl, octyl, lauryl and octadecyl; alkenyl groups such as the non-limiting examples vinyl, allyl, methallyl and 3-butenyl; aryl groups such as the non-limiting examples phenyl and tolyl; and, aralkyl groups such as the non-limiting examples benzyl and phenethyl.
• alkyl groups such as the non-limiting examples methyl, ethyl, propyl, isopropyl, sec-butyl and cyclohexyl
• higher straight-chain alkyl such as butyl, he
• G of Formula (1) can be any divalent or polyvalent hydrocarbon and can optionally contain at least one heteroatom selected from the group consisting of oxygen, sulfur, phosphorus and silicon atoms.
• the numbers of carbon atoms in group G is specifically from 1 to 18, more specifically from 1 to 12, even more specifically from 1 to 8 and most specifically from 1 to 4.
• G include, but are not limited to, those selected from the group consisting of diethylene cyclohexane; 1,2,4-triethylene cyclohexane; diethylene benzene; phenylene; -(CH 2 ) g - wherein g is preferably 1 to 18, which represent terminal straight-chain alkyls further substituted terminally at the other end such as -CH 2 -, -CH 2 CH 2 -, -CH 2 CH 2 CH 2 - and
• Y of Formula (1) is a divalent or polyvalent unsaturated hydrocarbon group of from 2 to 12 carbon atoms containing at least one carbon-carbon double bond that is bonded to the -CR ⁇ Z e fragment or at least one carbon-carbon triple bond that is bonded to the -CR 3-6 Z e fragment of Formula (1).
• the carbon-carbon double bond or carbon-carbon triple bond can be conjugated or non- conjugated with other carbon-carbon double and/or triple bonds and can include aromatic ring structures.
• Z of Formula (1) is the halogen atom
• R of Formula (1) is hydrogen; a straight, branched or cyclic alkyl group of specifically up to 30 carbon atoms, more specifically up to 10 carbon atoms, even more specifically up to 6 carbon atoms and most specifically 3 carbon atoms; (a straight, branched or cyclic alkenyl group containing one or more carbon-carbon double bond where the point of substitution can be either at a carbon-carbon double bond or elsewhere in the group and where the alkenyl group contains specifically up to 30 carbon atoms, more specifically up to 10 carbon atoms, even more specifically up to 6 carbon atoms and most specifically up to 3 carbon atoms; an aryl group containing specifically up to 30 carbon atoms, more specifically up to 20 carbon atoms, even more specifically up to 12 carbon atoms and most specifically up to 8 carbon atoms.
• representative examples of R include alkyl groups such as the non-limiting examples methyl, ethyl, propyl and isobutyl; alkenyl groups such as the non-limiting examples vinyl, propenyl, allyl, methallyl, ethylidenyl norbornane, ethylidene norbornyl, ethylidenyl norbomene and ethylidene norbornenyl; aryl groups such as the non-limiting examples phenyl and naphthalenyl; and, aralkyl groups such as the non-limiting examples benzyl and phenethyl.
• alkyl groups such as the non-limiting examples methyl, ethyl, propyl and isobutyl
• alkenyl groups such as the non-limiting examples vinyl, propenyl, allyl, methallyl, ethylidenyl norbornane, ethylidene norbornyl, e
• cyclic alkyl and “cyclic alkenyl” include, but are not limited to, norbornyl, norbornenyl, ethylnorbornyl, ethylnorbornenyl, ethylcyclohexyl, ethylcyclohexenyl, cyclohexylcyclohexyl and cyclododecatrienyl.
• silane (d) is at least one silane selected from the group consisting of 3-chloroprop-l-ynyltriethoxysilane, 3-chloroprop- 1- enyltriethoxysilane, 3-chloroprop- 1 -enyltrimethoxysilane, 3-chloroprop-l-enylmethyldiethoxysilane, 3-chloroprop- 1-enyldimethylethoxysilane, 3-chloroprop- 1 -enyltributoxysilane, 3-bromoprop- 1 -enyltriethoxysilane,
• silane (d) is selected from the group consisting of
• the rubber composition of the present invention can optionally contain one or more other hydrolyzable organosilanes that hydrophobate and aid in the dispersion of silane-reactive filler (b).
• These hydrolyzable organosilanes contain at least one alkyl group, specifically of from 3 to 18 carbon atoms and more specifically from about 6 to 10 carbon atoms, and at least one R 3 O- hydrolyzable group wherein R 3 is hydrogen or an alkyl, alkenyl, aryl or aralkyl of from 1 to 10 carbon atoms.
• R 3 is hydrogen or an alkyl, alkenyl, aryl or aralkyl of from 1 to 10 carbon atoms.
• These hydrolyzable organosilanes can be used, e.g., specifically in amounts of from about 0.5 to about 10 phr and more specifically in amounts of from about 1 to about 5 phr.
• the rubber composition herein comprises the mixture and/or reaction product of components (a), (b), optionally (c), and (d).
• silane (d) bonds to silane-reactive filler (b) through one functionality and to rubber component (a) (e.g., diene polymer) through a different functionality.
• at least one activating agent can be used in the rubber compounding process to facilitate the coupling reactions between rubber component (a) and silane (d).
• the activating agent can be selected from among the transition metal salts. Transition metal salts are compounds that assist in the removal of the Z group on the silane of general Formula (1) and include metal oxides, metal halides, metal carboxylates, metal hydroxides and other suitable metal complexes.
• transition metal salts include metal oxides such as zinc oxide, aluminum oxide, and titanium oxide; metal halides, such as zinc chloride, zinc bromide, zinc iodide, aluminum chloride, aluminum bromide, titanium chloride, titanium bromide and stannic chloride; and, metal carboxylates such as zinc stearate, zinc acetate and stannic octanoate.
• metal oxides such as zinc oxide, aluminum oxide, and titanium oxide
• metal halides such as zinc chloride, zinc bromide, zinc iodide, aluminum chloride, aluminum bromide, titanium chloride, titanium bromide and stannic chloride
• metal carboxylates such as zinc stearate, zinc acetate and stannic octanoate.
• rubber component (a) can be an organic polymer selected from the group consisting of at least one diene based elastomer and rubber.
• rubber component (a) can be any of those that are well known in the art many of which are described in "The Vanderbilt Rubber Handbook", R.F. Ohm, ed.; R.T. Vanderbilt Company, Inc., Norwalk, CT, 1990 and "Manual For The Rubber Industry", T. Kempermann, S. Koch, J. Sumner, eds.; Bayer AG, Leverkusen, Germany, 1993.
• suitable rubber component (a) examples include natural rubber (NR), synthetic polyisoprene (IR), polybutadiene (BR), various copolymers of butadiene, the various copolymers of isoprene and mixtures of these elastomers; solution styrene-butadiene rubber (SSBR), emulsion styrene-butadiene rubber (ESBR), ethylene-propylene terpolymers (EPDM) and acrylonitrile-butadiene rubber (NBR).
• natural rubber NR
• synthetic polyisoprene IR
• polybutadiene BR
• various copolymers of butadiene the various copolymers of isoprene and mixtures of these elastomers
• SSBR solution styrene-butadiene rubber
• ESBR emulsion styrene-butadiene rubber
• EPDM ethylene-propylene terpolymers
• NBR acrylon
• rubber component (a) is comprised of at least one diene-based elastomer or rubber.
• suitable monomers for preparing the rubbers are conjugated dienes such as the non-limiting examples of isoprene and 1,3-butadiene, and suitable vinyl aromatic compounds such as the non-limiting examples of styrene and alpha methyl styrene, and combinations thereof.
• rubber component (a) is a sulfur-curable rubber.
• the diene based elastomer, or rubber can be selected from the non-limiting examples of at least one of cis-l,4-polyisoprene rubber (natural and/or synthetic), and preferably natural rubber, emulsion polymerization-prepared styrene/butadiene copolymer rubber, organic solution polymerization-prepared styrene/butadiene rubber, 3,4-polyisoprene rubber, isoprene/butadiene rubber, styrene/isoprene/butadiene terpolymer rubber, cis-l,4-polybutadiene, medium vinyl polybutadiene rubber (about 35- 50 percent vinyl), high vinyl polybutadiene rubber (about 50-75 percent vinyl), styrene/isoprene copolymers, emulsion polymerization-prepared styrene/butadiene/acrylonitrile terpolymer rubber and but
• An emulsion polymerization-derived styrene/butadiene (ESBR) is also contemplated as diene-based rubber for use herein such as one having a relatively low to medium styrene content of from about 20 to about 29 percent bound styrene or, for some applications, an ESBR having a medium to relatively high bound styrene content, in particular, a bound styrene content of from about 30 to about 45 percent.
• emulsion polymerization-prepared styrene/butadiene/acrylonitrile terpolymer rubbers containing from about 2 to about 40 weight percent bound acrylonitrile in the terpolymer are also contemplated as diene- based rubbers for use herein.
• polybutadiene elastomer typically has a bound styrene content in a range of specifically from about 5 to about 50, more specifically from about 9 to about 36 bound styrene and most specifically from about 20 to about 30 weight percent bound styrene.
• polybutadiene elastomer can be conveniently characterized, for example, by having at least about 90 weight percent cis-l,4-content.
• rubber component (a) is a diene polymer functionalized or modified by an alkoxysilane derivative.
• Silane-functionalized organic solution polymerization-prepared styrene-butadiene rubber and silane- functionalized organic solution polymerization-prepared 1,4-polybutadiene rubbers may be used. These rubber compositions are known; see, for example U.S. Patent No. 5,821,290 the entire contents of which are incorporated by reference herein.
• rubber component (a) is a diene polymer functionalized or modified by a tin derivative.
• Tin-coupled copolymers of styrene and butadiene may be prepared, for example, by introducing a tin coupling agent during the styrene and 1,3 -butadiene monomer copolymerization reaction in an organic solvent solution, usually at or near the end of the polymerization reaction.
• tin coupled styrene-butadiene rubbers are well known to those skilled in the art; see, for example U.S. Patent No. 5,268,439, the entire contents of which are incorporated by reference herein.
• At least about 50 percent, and more specifically from about 60 to about 85 percent, of the tin is bonded to the butadiene units of the styrene-butadiene rubbers to create a tin-dienyl bond.
• rubber component (a) is selected from the group comprising natural rubber and synthetic polyisoprene.
• silane-reactive filler shall be understood herein to mean a substance that is capable of reaction with silane (d) to form stable Si-O-filler bonds.
• the silane-reactive filler includes a substance that is added to rubber component (a) to reinforce the elastomeric network. Reinforcing fillers are materials whose moduli are higher than rubber component (a) of the rubber composition and are capable of absorbing stress from rubber component (a) when this component is strained.
• silane-reactive filler (b) includes fibers, particulates and sheet-like structures and can be composed of inorganic minerals, silicates, silica, clays, ceramics, carbon, organic polymers and diatomaceous earth.
• silane-reactive filler (b) can be a discrete particle or group of particles in the form of aggregates or agglomerates.
• Silane- reactive filler (b) can be mixed with other fillers that do not react with silane (d). These fillers are used to either extend rubber component (a) or to reinforce the elastomeric network.
• suitable silane-reactive filler (b) materials include at least one metal oxide such as silica (pyrogenic and/or precipitated), titanium dioxide, aluminosilicate, alumina and siliceous materials including clays and talc. In a specific embodiment herein, particulate precipitated silica is sometimes used in connection with a silane.
• silane-reactive filler (b) is a silica used alone or in combination with one or more other fillers.
• a combination of silica and carbon black is utilized, such as for reinforcing fillers for various rubber products, including the non-limiting example of treads for tires.
• alumina can be used either alone or in combination with silica.
• the term "alumina” herein refers to aluminum oxide, or Al 2 O 3 .
• the fillers can be hydrated or in anhydrous form. Use of alumina in rubber compositions is known; see, for example, U.S. Patent No. 5,116,886 and EP 631 982, the entire contents of both of which are incorporated by reference herein.
• the term "carrier” as used herein means a porous or high surface area filler or organic polymer that has a high adsorption or absorption capability and is capable of carrying up to about 75 percent liquid silane while maintaining its free- flowing and dry properties.
• the carrier filler or carrier polymer herein is essentially inert to the silane and is capable of releasing or deabsorbing the liquid silane when added to the elastomeric composition.
• silane-reactive filler (b) herein can be used as a carrier for liquid silanes and reinforcing fillers for elastomers in which silane (d) herein is capable of reacting or bonding with the surface.
• the fillers that are used as carriers are non-reactive with the silanes of this invention.
• the non-reactive nature of the fillers is demonstrated by the ability of silane (d) to be extracted at greater than about 50 percent of the loaded silane using an organic solvent.
• the extraction procedure is described in U. S. Patent No. 6,005,027, the entire contents of which are incorporated herein by reference.
• carriers include, but are not limited to, porous organic polymers, carbon black, diatomaceous earth and silicas that are characterized by a relatively low differential of less than 1.3 between the infrared absorbance at 3502 cm "2 of the silica when taken at 105 0 C and when taken at 500 0 C as described in U. S. Patent No. 6,005,027.
• the amount of silane (d) that can be loaded on the carrier is between about 0.1 and about 70 percent.
• silane (d) is loaded on the carrier at concentrations between about 10 and about 50 percent.
• silane-reactive filler (b) includes fillers in which the silane (d) is reactive with the surface of the filler.
• particulate precipitated silica is useful as silane-reactive filler (b), particularly when the silica has reactive surface silanols.
• the silane-reactive filler (b) herein may be in the hydrated form.
• the other fillers that may be mixed with silane-reactive filler (b) can be essentially inert to the silane (d) with which they are admixed as is the case with carbon black or organic polymers, or at least two silane-reactive fillers can be mixed together and can be reactive therewith, e.g., the case with carriers possessing metal hydroxyl surface functionality, e.g., silicas and other siliceous particulates which possess surface silanol functionality, in combination with reinforcing fillers containing metal hydroxyl surface functionality, e.g., alumina, silicas and other siliceous fillers.
• silica filler herein can be characterized by having a Brunauer, Emmett and Teller (BET) surface area, as measured using nitrogen gas, specifically in the range of from about 40 to about 600 m 2 /g, and more specifically in a range of from about 50 to about 300 m 2 /g and most specifically in a range of from about 100 to about 150 m 2 /g.
• BET Brunauer, Emmett and Teller
• the silica typically can also be characterized by having a dibutylphthalate (DBP) absorption value in a range of specifically from about 100 to about 350, more specifically from about 150 to about 300 and most specifically from about 200 to about 250.
• DBP dibutylphthalate
• silane-reactive fillers (b), as well as the aforesaid alumina and aluminosilicate fillers can be expected to have a CTAB surface area in a range of from about 100 to about 220 m 2 /g.
• the CTAB surface area is the external surface area as determined by cetyl trimethylammonium bromide with a pH of 9; the method for its measurement is described in ASTM D 3849.
• Mercury porosity surface area is the specific surface area determined by mercury porosimetry. In this technique, mercury is penetrated into the pores of the sample after a thermal treatment to remove volatiles.
• setup conditions use a 100 mg sample, remove volatiles over 2 hours at 105 0 C and ambient atmospheric pressure and employ a measuring range of from ambient to 2000 bars pressure.
• evaluation can be performed according to the method described in Winslow, et al. in ASTM bulletin, p.39 (1959) or according to DIN 66133; for such an evaluation, a CARLO-ERBA Porosimeter 2000 can be used.
• the average mercury porosity specific surface area for the selected silane- reactive filler (b) should be in a range of, specifically, from about 100 to about 300 m 2 /g, more specifically from about 150 to about 275 m 2 /g and most specifically from about 200 to about 250 m 2 /g.
• a suitable pore size distribution for the silane-reactive filler (b) (e.g. the non-limiting examples of silica, alumina and aluminosilicate) according to such mercury porosity evaluation is considered herein to be: five percent or less of its pores having a diameter of less than about 10 run; from about 60 to about 90 percent of its pores have a diameter of from about 10 to about 100 run; from 10 to about 30 percent of its pores having a diameter of from about 100 to about 1,000 nm; and from about 5 to about 20 percent of its pores have a diameter of greater than about 1,000 nm.
• silane-reactive filler (b) e.g. the non-limiting examples of silica, alumina and aluminosilicate
• the silane-reactive filler (b) e.g., silica
• the silane-reactive filler (b) can be expected to have an average ultimate particle size, for example, in the range of from about 0.01 to about 0.05 ⁇ m as determined by electron microscopy, although the particles (e.g., silica) can be even smaller, or possibly larger, in size.
• various commercially available silicas can be considered for use herein such as those available from PPG Industries under the HI-SIL trademark, in particular, HI-SIL 210, and 243; silicas available from Rhone-Poulenc, e.g., ZEOSIL 1165MP; silicas available from Degussa, e.g., VN2 and VN3, etc. and silicas available from Huber, e.g., HUBERSIL 8745.
• a rubber composition which contains both a siliceous filler such as silica, alumina and/or aluminosilicates and also carbon black reinforcing pigments, to be primarily reinforced with silica as the reinforcing pigment, it is often more specific that the weight ratio of such siliceous fillers to carbon black is at least about 3/1 and preferably at least about 10/1 and, thus, in a range of from about 3/1 to about 30/1.
• silane-reactive filler (b) can comprise from about 15 to about 95 weight percent precipitated silica, alumina and/or aluminosilicate and, correspondingly, from about 5 to about 85 weight percent carbon black having a CTAB value in a range of from about 80 to about 150.
• silane-reactive filler (b) can comprise from about 60 to about 95 weight percent of said silica, alumina and/or aluminosilicate and, correspondingly, from about 40 to about 5 weight percent of carbon black.
• the siliceous filler and carbon black can be pre-blended or blended together in the manufacture of the vulcanized rubber
• an effective amount of silane (d) is specifically from about 0.2 to about 20, more specifically from about 0.5 to about 15 and most specifically from about 2 to about 10 weight percent of silane (d) based on the total weight of rubber composition herein.
• an effective amount of silane-reactive filler (b) is specifically from about 2 to about 70, more specifically from about 5 to about 50 and most specifically from about 20 to about 40 weight percent of silane-reactive filler (b) wherein said weight percent is based on the total weight of rubber composition herein.
• an effective amount of rubber component (a) is specifically from about 30 to about 98, more specifically from about 50 to about 95 and most specifically from about 60 to about 80 weight percent of rubber component (a) based on the total weight of the rubber composition herein.
• the herein described process for preparing a rubber composition can further comprise curing the rubber composition, before, during and/or after molding the rubber composition.
• a vulcanized rubber composition should contain a sufficient amount of silane-reactive filler (b) to contribute a reasonably high modulus and high resistance to tear thereto.
• the combined weight of silane-reactive filler (b) can be as low as about 5 to about 100 parts per hundred of rubber (phi) component (a), but is more specifically from about 25 to about 85 phr, and most specifically from about 50 to about 70 phr.
• silane (d) can be premixed, or pre-reacted, with particles, aggregates and/or agglomerates of silane-reactive filler (b) or added to the rubber mix during the processing or mixing of rubber (a) and silane-reactive filler (b).
• silane (d) and silane-reactive filler (b) are added separately to the process mixture during the rubber component (a) and silane-reactive filler (b)
• silane (d) can be considered to couple in situ to silane-reactive filler (b).
• sulfur vulcanized rubber products typically are prepared by thermomechanically mixing rubber and various ingredients in a sequentially step-wise manner followed by shaping and curing the compounded rubber to form a vulcanized product.
• the rubber(s) and various rubber compounding ingredients are usually blended in at least one, and optionally two or more, preparatory thermomechanical mixing stage(s) in suitable mixers. Such preparatory mixing is referred to as non-productive mixing or non-productive mixing steps or stages.
• such preparatory mixing usually is conducted at temperatures specifically in the range of from about 13O 0 C to about 18O 0 C and more specifically in the range of from about 14O 0 C to about 16O 0 C.
• a final mixing stage sometimes referred to as a productive mixing stage
• curing agents, and, optionally, one or more additional ingredients are mixed with the rubber compound or composition, typically at a temperature in the range of from about 5O 0 C to about 13O 0 C which is a lower temperature than those utilized in the preparatory mixing stages, to prevent or retard premature curing of the sulfur-curable rubber, sometimes referred to as scorching of the rubber composition.
• the rubber composition typically is allowed to cool, sometimes after or during a process of intermediate mill mixing, between the aforesaid various mixing steps, for example, to a temperature of about 5O 0 C or lower.
• the rubber composition when it is desired to mold and to cure the rubber composition, the rubber composition is placed in the desired mold and heated to at least about 130°C and up to about 200°C causing the vulcanization of the rubber.
• thermomechanical mixing is meant that the rubber compound, or composition of rubber and rubber compounding ingredients, is mixed in a rubber mixer under high shear conditions where it autogenously heats up as a result of the mixing, primarily due to shear and associated friction within the rubber mixture in the rubber mixer.
• several chemical reactions can occur at various steps in the mixing and curing processes.
• the independent addition of a sulfur source can be manipulated by the amount of addition thereof and by sequence of addition relative to addition of other ingredients to the rubber mixture.
• the rubber composition herein can be prepared by a process comprising the steps of: a) thermomechanically mixing, in at least one preparatory mixing operation, in a first embodiment to a temperature of from about 140 0 C to about 180 0 C and in a second embodiment to a temperature of from about 150° to about 170° for a total mixing time in a first embodiment of from about 1 to about 20 minutes and in a second embodiment from about 4 to about 15 minutes, for such mixing operation(s): i) about 100 parts by weight of at least one sulfur vulcanizable rubber selected from the group consisting of conjugated diene homopolymers and copolymers and copolymers of at least one conjugated diene and aromatic vinyl compound, ii) from about 5 to about 100 parts by weight of silane-reactive filler (b) in a first embodiment and from about 25 to 80 parts by weight of silane-reactive filler (b) in a second embodiment, wherein the silane-reactive filler (b)
• the rubber composition herein can be compounded by methods known in the rubber compounding art such as mixing component (a) (the various sulfur- vulcanizable constituent rubbers) with various commonly used additive materials such as, for example, curing aids such as sulfur, activators, retarders and accelerators, processing additives such as oils, resins, e.g., tackifying resins, silicas, plasticizers, fillers, pigments, fatty acid, zinc oxide, waxes, antioxidants and antiozonants, peptizing agents, and reinforcing materials such as, for example, carbon black, and the like.
• curing aids such as sulfur, activators, retarders and accelerators
• processing additives such as oils, resins, e.g., tackifying resins, silicas, plasticizers, fillers, pigments, fatty acid, zinc oxide, waxes, antioxidants and antiozonants, peptizing agents, and reinforcing materials such as, for example, carbon black, and the like.
• Vulcanization can be conducted in the presence of an additional sulfur vulcanizing agent.
• suitable sulfur vulcanizing agents include, e.g., elemental sulfur (free sulfur) or sulfur-donating vulcanizing agents such as the non-limiting examples of amino disulfide, polymeric polysulfide or sulfur-olefin adducts, which are conventionally added in the final, i.e., productive, rubber composition mixing step.
• the sulfur vulcanizing agents (which are common in the art) are used, or added, in the productive mixing stage, in an amount ranging from about 0.4 to about 3 phr, or even in some circumstances, up to about 8 phr, with a range of from about 1.5 to about 2.5 phr, and in some cases from about 2 to about 2.5 phr, being generally suitable.
• Vulcanization accelerators i.e., additional sulfur donors, can also be used if desired.
• Non-limiting examples of vulcanization accelerators include benzothiazole, alkyl thiuram disulfide, guanidine derivatives and thiocarbamates.
• accelerators include, but are not limited to, mercapto benzothiazole, tetramethyl thiuram disulfide, benzothiazole disulfide, diphenylguanidine, zinc dithiocarbamate, alkylphenoldisulfide, zinc butyl xanthate, N-dicyclohexyl-2- benzothiazolesulfenamide, N-cyclohexyl-2-benzothiazolesulfenamide, N-oxydiethylenebenzothiazole-2-sulfenamide, N,N-diphenylthiourea, dithiocarbamylsulfenamide,
• other additional sulfur donors include, e.g., thiuram and morpholine derivatives.
• representative of such donors include, e.g., but are not limited to, dimorpholine disulfide, dimorpholine tetrasulfide, tetramethyl thiuram tetrasulfide, benzothiazyl-2,N-dithiomorpholide, thioplasts, dipentamethylenethiuram hexasulfide, disulfidecaprolactam and combinations thereof.
• Accelerators are used to control the time and/or temperature required for vulcanization and to improve the properties of the vulcanizate.
• a single accelerator system can be used, i.e., a primary accelerator.
• a primary accelerator(s) is used in total amounts ranging from about 0.5 to about 4, preferably from about 0.8 to about 1.5 phr.
• combinations of a primary and a secondary accelerator can be used with the secondary accelerator being used in smaller amounts (e.g., from about 0.05 to about 3 phr) in order to activate and to improve the properties of the vulcanizate.
• delayed action accelerators can also be used.
• vulcanization retarders can also be used.
• suitable types of accelerators are those such as the non-limiting examples of amines, disulfides, guanidines, thioureas, thiazoles, thiurams, sulfenamides, dithiocarbamates, xanthates and combinations thereof.
• the primary accelerator is a sulfenamide.
• the secondary accelerator is more specifically a guanidine, dithiocarbamate or thiuram compound.
• Optional tackifier resins can be used at levels of from about 0.5 to about
• typical amounts of processing aids comprise from about 1 to about 50 phr.
• Suitable processing aids can include, as non-limiting examples, aromatic, naphthenic and/or paraffinic processing oils and combinations thereof.
• typical amounts of antioxidants are from about 1 to about 5 phr. Representative antioxidants include, as non-limiting examples, diphenyl-p-phenylenediamine and others, e.g., those disclosed in the Vanderbilt Rubber Handbook (1978), pages 344-346.
• typical amounts of antiozonants are from about 1 to about 5 phr.
• Typical amounts of optional fatty acids are from about 0.5 to about 3 phr.
• typical amounts of zinc oxide are from about 2 to about 5 phr.
• typical amounts of waxes e.g., microcrystalline wax, are from about 1 to about 5 phr.
• Typical amounts of peptizers are from about 0.1 to about 1 phr. Suitable peptizers include, as non-limiting examples, pentachlorothiophenol, dibenzamidodiphenyl disulfide and combinations thereof.
• the rubber composition herein can be used for various purposes.
• an article of which at least one component is the herein described cured rubber composition.
• the rubber composition herein can be used for the manufacture of such articles as shoe soles, hoses, seals, cable jackets, gaskets and other industrial goods. Such articles can be built, shaped, molded and cured by various known and conventional methods as is readily apparent to those skilled in the art.
• a 250ml 3-neck round-bottom flask was equipped with a reflux condenser, addition funnel and stir bar.
• Propargyl chloride 50g, 0.67 lmol
• 0.15g of Platinum (0)-l,3-divinyl-l,l,3,3-tetramethyldisiloxane complex 3% Weight in xylenes
• Triethoxysilane 115.6g, 0.705mol was added dropwise from the addition funnel to the reaction mixture. The flask quickly became warm. After the completion of addition, the flask was kept at 100 0 C for one hour.
• a 250ml 3-neck round-bottom flask was equipped with a reflux condenser, addition funnel and stir bar.
• Vinylbenzyl chloride (76g, 0.5mol) and 0.15g of Pt-tetravinyl tetramethyl-cyclotetrasiloxane complex (0.104M) were added to the flask.
• Triethoxysilane (82g, 0.5mol) was added dropwise from the addition funnel to the reaction mixture. After the completion of addition, the flask was kept at 100 0 C for one hour.
• the amounts of reactants are parts per hundred of rubber (phr) unless otherwise indicated.
• the following rubber compositions were prepared based on natural rubber and reinforced with highly dispersible precipitated silica, the said compositions being intended for tread compounds in truck tires. Formulations for the rubber compositions of these examples are described below in Table 1.
• the rubber composition of Comp(arative) Ex(ample) 1 contains carbon black as the reinforcing filler.
• the remaining rubber compositions (Comp. Ex. 2-4 and Ex. 2-5) contain silica as the reinforcing filler.
• the silane coupling agents tested are used in equal molar amounts of silicon.
• the rubber compositions of Comp. Ex. 2-4 and Ex. 2-5 have the same formulations except for the silane component. Table 1. Formulations of the Rubber Compositions:
• silica Zeosil 1165MP from Rhodia
• CB carbon black (N-220)
• process oil Sundex 8125 from Sun Oil
• ZnO Kadox 720C from ZincCorp.
• stearic acid Industrene R from Witco, Crompton
• 6 PPD (Flexzone 7P from Uniroyal)
• Wax Sunproof Improved from Uniroyal, Crompton
• Naugurd Q from Uniroyal
• Sulfur Rubbermakers Sulfur 104 from Harwick
• TBBS Delac S from Uniroyal, Crompton
• DPG from Uniroyal, Crompton.
• Silanes (I)* Silquest A-1289 and (2)* 3-chloropropyltriethoxysilane are available from Momentive Performance Materials;
• the mixer throat was dusted down, and the mixer's mixing speed was increased to 90 rpm as required to raise the temperature of the rubber masterbatch to 140 0 C.
• the master batch was dumped (removed from the mixer), a sheet was formed on a roll mill set at about 60° to 65 0 C and the sheet allowed to cool to ambient temperature.
• the sheets from the first pass were added to the mixer and ram down mixed for 60 seconds.
• the rest of the ingredients except for the curatives were added together and ram down mixed for 60 seconds.
• the mixer throat was dusted down and the mixer's mixing speed was increased to 90 rpm as required to raise the temperature of the rubber master batch to between 135 0 C to 140°C.
• the rubber master batch was mixed for five minutes and the speed of the Krupp mixer as adjusted to maintain the temperature between 135°C and 140 0 C.
• the dynamic parameters, G'j n i t i a i, ⁇ G', G" maX and tan ⁇ max were extracted from the non-linear responses of the rubber compounds at small strains.
• steady state values of tan ⁇ were measured after 15 minutes of dynamic oscillations at strain amplitudes of 35% (at 6O 0 C).
• Temperature dependence of dynamic properties was also measured from about -8O 0 C to +80 0 C at small strain amplitudes (1 or 2%) at a frequency of 10 Hz.
• M300 moduli and M300/M100 ratio are appreciably higher indicating better reinforcement between the elastomer and the filler
• Tan delta 60 is appreciably smaller indicating better rolling resistance.
• Abrasion Loss (DIN) (mm 3 ) for the compositions of Ex. 3 and 4 are much lower than those of the control compositions (Comp. Ex. 1 for carbon black and Comp. Ex. 2 for silane A- 1289) indicating improved abrasion resistance.
• the rubber composition of this invention is particularly advantageous for use in the manufacture of tire treads exhibiting low rolling resistance and high wear resistance, especially when the treads are based on natural rubber or synthetic polyisoprene.

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