EP3487890A1

EP3487890A1 - Method for producing modified rubber by anionic solution polymerization, rubber composition comprising said rubber and use thereof

Info

Publication number: EP3487890A1
Application number: EP16909626.0A
Authority: EP
Inventors: Alexey Mikhailovich AVERKOV; Svetlana Viktorovna TURENKO; Ekaterina Vasilievna KHARLAMOVA
Original assignee: Sibur Holding PJSC
Current assignee: Sibur Holding PJSC
Priority date: 2016-07-22
Filing date: 2016-07-22
Publication date: 2019-05-29
Also published as: WO2018016987A1; BR112019001004A2; CN109563196B; RU2707102C1; EP3487890A4; CN109563196A

Abstract

Present invention relates to a method for producing a rubber by an anionic solution (co)polymerization of a conjugated diene and/or a vinyl aromatic compound in an organic solvent in the presence of an organolithium N,N-disubstituted aminomethylstyrene oligomeric initiator, a special N,N-disubstituted aminomethylstyrene monomer, and an end-functionalizing agent of the general formula (CH3)2Hal2Si, wherein Hal is a halogen atom. The invention also relates to a rubber based on (co)polymers of a conjugated diene and/or a vinyl aromatic compound produced by said method, and to a rubber composition comprising such rubber. Rubber compositions of the present invention are useful in manufacturing of auto tire treads.

Description

METHOD FOR PRODUCING MODIFIED RUBBER BY ANIONIC SOLUTION POLYMERIZATION, RUBBER COMPOSITION COMPRISING SAID

RUBBER AND USE THEREOF

TECHNICAL FIELD

The present invention relates to the field of the production of modified rubbers by anionic solution polymerization and to the manufacture of vulcanizates based thereon, mechanical rubber goods and tires with improved hysteresis properties. In particular, the invention relates to a method for producing a modified rubber in the presence of an organolithium N,N-di substituted aminomethylstyrene oligomeric initiator, a special Ν,Ν-disubstituted aminomethylstyrene monomer, and an end- functionalizing agent of the general formula (CH3)₂Hal₂Si, wherein Hal is a halogen atom. This method provides butadiene, styrene-butadiene or styrene-isoprene-butadiene rubbers.

The rubbers produced by the claimed method are characterized by an average molecule weight (Mn) of from 50000 to 400000 g/mol, a polydispersity index of from 1 to 3, a content of 1 ,2-butadiene units of from 40 to 100 wt.% based on the rubber polydiene part, and from 0 to 50 wt.% based on the rubber vinyl aromatic units. Modified rubbers with such properties possess an enhanced compatibility with carbon black and precipitated colloidal silicic acid (silica, PSF), which provides vulcanizates with improved hysteresis characteristics, useful in tire industry for the manufacture of auto tire treads.

BACKGROUND OF THE INVENTION

Performance properties of vulcanizates for tire treads, such as rolling resistance, grip index and the like, mainly depend on the nature of a used rubber and, in particular, on the presence of functional groups in the rubber.

Functional ization of a rubber results in improved hysteresis properties of vulcanizates produced based on such a rubber. In particular, functionalization is widely practiced in the step of polymerization by using various initiators comprising functional groups, and special monomers. In addition, functionalization of chain ends by functionalizing, coupling or branching agents is also applicable.

The use of functionalized initiators is disclosed, for example, in patent US7405262 where an initiator is prepared by premixing cinnamyl hexamethyleneimine

wherein A is alkyl, dialkyl, cycloalkyl, or dicycloamine, or cyclic amine; R_1-6 are independently selected from the group consisting of alkyl, cycloalkyl, or aryl hydrocarbons having 1 to 12 carbon atoms. This initiator is used in solution (co)polymerization of conjugated dienes and/or vinyl aromatic compounds. A polymer prepared by using this initiator is characterized by a Mooney viscosity (ML 1+4 at 100°C) of 1 to 150, an average molecule weight of from 50000 to 1000000, and a molecular weight distribution of less than 2.

Patent US5393721 discloses a functionalized initiator of the general formula

ALi(SOL)_y, wherein A is alkyl, dialkyl, cycloalkyl, dicycloamine, or cyclic amine, SOL is a solubilizing component selected from the group of hydrocarbons, ethers, amines, or mixture thereof, which provides an initiator soluble in non-polar organic solvents. The initiator is prepared by premixing hexamethylenimine and an organolithium compound and is used in solution (co)polymerization of conjugated dienes. The inventors of US5393721 teach that the obtained polymer has a narrow range of molecular weights of from 20000 to 250000.

The use of special monomers in polymerization to provide articles with required performance characteristics is known from the prior art (see US6630552, US6790921 , US20100152364, and US6803462). The disclosed special monomers have the general formula:

wherein R is alkyl comprising 1 to 10 carbon atoms or a hydrogen atom, R₁ and R₂ may be the same or different and are a hydrogen atom or groups of formulas:

wherein R₃ radicals are the same or different alkyl groups comprising 1 to 4 carbon atoms or a hydrogen atom, R₄ is alkyl comprising 1 to 10 carbon atoms, aryl or allyl, Z is a nitrogen-containing heterocycle, n and x are integers from 1 to 10, in proviso that R₁ and R₂ both cannot be hydrogen. A rubber containing from 0.2 to 10 wt.% of special monomers are obtained most often. Thus, according to an example of the invention (US6630552), a vulcanizate based on a copolymer of butadiene, styrene, and 1 wt.% of l-[(4-vinylphenyl)methyl] -pyrrolidine as a special monomer has rolling resistance 38.7% less than that in a non-modified styrene-butadiene rubber.

US20100099810 and US20130303683 disclose a combined use of the above- mentioned special monomers and cross-linked silicon-based agents. A method for producing pneumatic tires having a good wet grip index and abrasion is described. Special monomers have the general formula:

wherein R₁ and R₂ are the same or different groups of general formulas:

wherein R₃ is an aliphatic hydrocarbon comprising 1 to 4 carbon atoms, Z is a bivalent hydrocarbon saturated radical optionally comprising nitrogen, oxygen, and sulfur, R₄-R₇ are aliphatic hydrocarbons comprising 1 to 30 carbon atoms, acyclic hydrocarbons comprising 3 to 30 carbon atoms, aromatic hydrocarbons comprising 5 to 30 carbon atoms, or a hydrocarbon atom. The cross-linking agent is characterized by the general formula:

wherein R₂i is -0-(R2₅-0)_t-R₂₆, wherein R₂₅ radicals are the same or different branched or linear bivalent Ci-C₃₀ hydrocarbon groups, R₂₆ is a branched or linear d-C₃₀-alkyl, linear C₂-C₃₀-alkenyl, C₆-C₃₀-aryl, or C₇-C₃₀-arylalkyl hydrocarbon radical; t is an integer of 1 to 30; R₂₂ and R₂₃ are the same or different aliphatic and/or aromatic branched or linear hydrocarbon radicals comprising up to 30 carbon atoms.

Thus, to date the prior art provides no information about a combined use of a functionalized initiator, special monomers, and end-functionalizing agents to produce a modified rubber by solution polymerization, which would provide a modified rubber, vulcanizates based thereon will have an improved complex of hysteresis properties.

The object of the present invention is to develop an industrial method for producing a modified rubber by solution polymerization in the presence of an organolithium Ν,Ν-disubstituted aminomethylstyrene oligomeric initiator of general formula (I):

a special Ν,Ν-disubstituted aminomethylstyrene monomer of general formula (II):

(II),

and an end-functionalizing agent of the general formula: (CH₃)₂Hal₂Si. The technical result of the present invention is in improvement of hysteresis characteristics of vulcanizates based on rubbers produced by the claimed method, which provides a reduced hysteresis loss of vulcanizates under dynamic conditions. This results in a reduction of mechanical loss tangent at 60°C (rolling resistance) by 14-19% and in a raise of mechanical loss tangent at 0°C (improved wet grip index) by 9-10%. Said technical result is achieved by a complex modification of a rubber at the polymerization step, in particular, by using a functionalized initiator, a special monomer, and an end-functionalizing agent.

DESCRIPTION OF THE INVENTION

A method for producing a modified rubber according to the present invention comprises anionic solution (co)polymerization of a conjugated diene and/or a vinyl aromatic compound in an organic solvent in the presence of an organolithium N,N- disubstituted aminomethylstyrene oligomeric initiator, a special N,N-disubstituted aminomethylstyrene monomer, and an end-functionalizing agent of the general formula: (CH₃)₂Hal₂Si, wherein Hal is a halogen atom, as shown in the scheme below:

wherein f-SM is a special monomer, f-InLi is an N,N-disubstituted aminomethylstyrene oligomeric initiator, and f-In is an N,N-disubstituted aminomethylstyrene functional group.

The initial monomer for producing rubbers may be a conjugated diene and a vinyl aromatic compound. Examples of conjugated dienes include conjugated dienes comprising 4 to 12 carbon atoms, such as 1,3 -butadiene, 2-methyl-l ,3-butadiene (isoprene), 2-ethyl- 1,3 -butadiene, 2,3-di(Ci-C₅ alkyl)- 1 ,3 -butadienes, such as 2,3- dimethyl- 1 ,3 -butadiene, 2,3-diethyl-l ,3-butadiene, 2-methyl-3-ethyl-l,3-butadiene, 2- methyl-3-isopropyl-l ,3-butadiene, phenyl- 1 ,3 -butadiene, 1 ,3-pentadiene, 2,4-hexadiene, 2-methyl-pentadiene, and 4-methyl-pentadiene. 1 ,3-Butadiene or isoprene is preferred.

Vinyl aromatic compounds are selected from styrene, a-methylstyrene, ortho-, meta-, and para-methylstyrene, 3-vinyltoluene, ethylvinylbenzene, 4-cyclohexylstyrene, para-tert-butylstyrene, methoxystyrene, vinylmesitylene, divinylbenzene, 1- vinylnaphthalene, and 2,4,6-trimethylstyrene. Styrene or a-methylstyrene is preferred.

Special Ν,Ν-disubstituted aminomethylstyrenes or a-aminomethylstyrenes are compounds of general formula (II):

wherein x is 1 , y is 0 or x is 0, y is 1 ;

R is -CH₂N(R₁)(R₂), wherein R₁ and R₂ may be the same or different and are independently alkyl or cycloalkyl optionally substituted with one or more substituents selected from hydroxy, dialkylamino, alkoxy, aryloxy, alkylsulfanyl, arylsulfanyl, and aryl;

or aryl optionally substituted with one or more substituents selected from halogen, alkyl, dialkylamino, alkoxy, aryloxy, alkylsulfanyl, arylsulfanyl, and aryl; or heteroaryl comprising one or more nitrogen atoms, wherein the heteroaryl is optionally substituted with one or more substituents selected from halogen, alkyl, dialkylamino, alkoxy, aryloxy, alkylsulfanyl, arylsulfanyl, and aryl;

or R₁ and R₂, taken together with a nitrogen atom, form a 5-6-membered heterocyclic or 5-membered heteroaromatic ring optionally containing one or more additional heteroatoms selected from nitrogen, oxygen, and sulfur.

Examples of such compounds are, but not are limited to, l-[(4- vinylphenyl)methyl]-pyrrolidine,4-(3-ethenylbenzyl)morpholine.

The inventors have found that the best result is obtained when the used special monomers are compounds in which R₁ and R₂, taken together with a nitrogen atom, form a 6-membered heterocyclic ring comprising one additional heteroatom, and the compounds where the heteroatom is oxygen are more preferred. An example of this monomer is 4-(3,4-ethenylbenzyl)morpholine.

The special monomer is added in an amount of 0 to 40 wt.%, preferably 0.1 to

10 wt.%, and more preferably 0.5 to 5 wt.% based on the polymer weight.

It is preferable to use conjugated dienes, vinyl aromatic compounds, and special monomers with a purity of 99.5% and more and a moisture content of 50 ppm and less. The solvent for polymerization is selected from saturated hydrocarbons, for example, pentane, hexane, heptane; cyclic hydrocarbons, for example, cyclopentane, cyclohexane, methylcyclopentane, and methylcyclohexane; aromatic hydrocarbons, such as benzene, toluene, p-xylene; and a mixture thereof in various ratios, with a purity of 99% or more. Solvents comprising 3 to 12 carbon atoms are preferred. Petroleum solvent is also applicable, for example, petroleum solvent of hexane-heptane fraction PI -65/75. The weight ratio of a solvent to the total amount of monomers is from 2 to 20, preferably 4 to 12, more preferably from 6 to 8.

According to present invention, the functionalized initiator is usually an oligomer of a selected special monomer, or so-called macromonomer. The use of an initiator with a controlled length of the oligomer chain allows the control of the properties of a resulting rubber. In particular, the functionalized initiator is an anionic polymerization initiator containing an amine functional group, prepared by reacting said organolithium compound and a secondary amine in situ, i.e. in a polymerization medium, or in advance, i.e. before the introduction to the polymerization medium. The organolithium compound is a compound of the general formula: R'Li, wherein R' is an alkyl or aryl hydrocarbon radical. Examples of the alkyl radical include, but are not limited to, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n- pentyl, neopentyl, isopentyl, n-hexyl, 2-ethylhexyl, heptyl, n-nonyl, n-decyl, and n- undecyl. A radical comprising 1 to 4 carbon atoms is preferred, and n-butyl and sec- butyl are most preferred. Examples of the aryl radical include, but are not limited to, phenyl, 2-benzyl, 3-benzyl, 4-benzyl, 2,3-xylyl, 2,4-xylyl, 2,5-xylyl, 2,6-xylyl, 3,4- xylyl, 3,5-xylyl, 2,3,4-trimethylphenyl, 2,3,5-trimethylphenyl, 2,3,6-trimethylphenyl, 2,4,6-trimethylphenyl, 3,4,5-trimethylphenyl, 2,3,4,5-tetramethylphenyl, and 2,3,4,6- tetramethylphenyl. Aryl radicals comprising 6 to 12 carbon atoms are preferred, and a phenyl radical is most preferred.

The Ν,Ν-disubstituted aminomethylstyrene compound is selected from the compounds described above as special monomers.

The initiator is prepared by using a solvent the same as used in the polymerization process. The reaction runs in inert atmosphere, for example, in nitrogen or argon atmosphere.

The synthesis of the initiator is carried out under continuous stirring at room temperature (from 15 to 30°C) or at heating to 100°C, preferably to 50°C, most preferably to 38°C. The duration of the reaction depends on the initial compounds and varies from several minutes to several hours.

The amount of the used initiator is determined by the required molecular weight of a rubber and by the presence of impurities in starting components. Preferably, the amount of the used initiator varies from 1 to 50 mol/t of the rubber, preferably from 2 to 25 mol/t of the rubber, more preferably from 3 to 10 mol/t of the rubber.

The polymerization process also involves an electron donor to increase the amount of 1 ,2- or 3,4-units. The electron donor used in the polymerization reaction may be any donor known in the prior art, for example, bis(2-oxolanyl)methane, l,l-bis(2- oxolanyl)ethane, 2,2-bis(2-oxolanyl)butane, 2,2-bis(5-methyl-2-oxolanyl)propane, 2,2- bis(3,4,5-trimethyl-2-oxolanyl)propane, tetrahydrofuran, dialkyl ethers of mono- and oligo-alkylene glycols, for example, ethylene glycol dimethyl ether, ethylene glycol dibutyl ether; or tertiary amines, for example, Ν,Ν,Ν',Ν'-tetramethylethylenediamine, or Ν,Ν,Ν',Ν'-tetraethylethylenediamine. Tetramethylenediamine, tetrahydrofuran, and 2,2-bis(2-oxolanyl)propane are preferably used.

The molar ratio of the electron donor to the initiator is from 0.5 to 4, preferably from 0.8 to 2, more preferably from 1 to 1.5.

The temperature mode of the polymerization method is determined by the heat of the exothermic reaction of copolymerization of a conjugated diene and/or a vinylaromatic compound. The temperature of polymerization ranges from (-30)°C to + 120°C, preferably from 0°C to 100°C, more preferably from 15°C to 80°C. The process runs in an inert atmosphere at pressure of 0 to 10 atm, preferably 0.5 to 5 atm, more preferably 1 to 3 atm.

In accordance with the claimed method, the duration of the polymerization depends on temperature and may range from 10 minutes to 120 minutes, preferably from 20 minutes to 80 minutes, more preferably from 30 minutes to 50 minutes.

The polymerization process preferably runs until the monomer conversion reaches 95%.

An initial monomer stock, a solvent, and an electron donor may be fed in any technically convenient sequence. The components are fed to a reactor in the following sequence: the solvent, monomers free of the solvent or in the form of a charge in the used solvent, the electron donor, and the initiator are fed first, and then monomer(s) are added batchwise until completion of the polymerization. The monomer(s) may be added once on reaching a conversion of 90 to 100%. It is preferable to feed the components in the following sequence: the solvent, the initial monomer stock, and the electron donor. The pre-prepared initiator or the components for its preparation in situ are fed at the end.

The polymerization process is carried out in any batch or continuous equipment known in the prior art, suitable for anionic polymerization.

When the monomer conversion reaches at least 95%, a modification process is carried out by reacting a "living" polymer with a end-functionalizing agent by adding to the polymerization reactor a solution of said agent.

The scheme 1 demonstrates, but is not limited to, the step of reacting a "living" polymer with a end-functionalizing agent, which is a compound of the general formula CH3)₂Hal₂Si, preferably dimethyldichlorosilane (SiMe₂C1₂):

Scheme 1 ,

wherein f-SM is a special monomer, f-In is N,N-disubstituted aminomethylstyrene functional group, f-polymer is a functionalized polymer.

The reaction between a "living" polymer and end-functionalizing agent is carried out at temperature of from 20°C to 120°C, preferably from 40°C to 100°C, more preferably from 60°C to 80°C in an inert atmosphere at a pressure of from 0 to 10 atm, preferably 0.5 to 5 atm, more preferably from 1 to 3 atm, under vigorous stirring.

The duration of the process ranges from 5 minutes to 100 minutes, preferably from 20 minutes to 60 minutes, more preferably from 30 minutes to 40 minutes. The time of the modification is determined by the modification temperature: the higher temperature, the less time is required for modification.

The claimed method provides a rubber with an average molecule weight of 50000 to 500000, preferably 100000 to 450000, more preferably 200000 to 400000 g/mol with a polydispersity index of 1 to 3, a content of 1,2- (or 3,4- depending on the type of a selected diene monomer) units of 40 to 100 wt.% based on the rubber polybutadiene part, preferably 50 to 80 wt.%, more preferably of 60 to 70 wt.%. The content of vinyl aromatic units in the rubber according to the present invention is 0 to 60 wt.%, preferably of 10 to 45 wt.%, more preferably of 15 to 40 wt.% based on the rubber.

At the end of the process, the polymerizate is mixed with an antioxidant, filled, if necessary, with an oil-filler, and then degassed; the rubber is separated and dried.

The antioxidant for the rubber may be a phenolic or amine-type compound or another antioxidant, including a composite antioxidant, recommended for the stabilization of rubbers. Examples of phenolic antioxidants are 2,6-di-tert-butyl-4- methylphenol (ionol, Agidol 1, Alkofen, Antioxidant 264); 2,2-di-(4-mefhyl-6-tert- butylphenol)methane (antioxidant 2246, Agidol 2, Bisalkofen), 2-mefhyl-4,6- bis(octylsulfanylmethyl)phenol (IRGANOX 1520L); pentaerythritol tetrakis(3-(3,5-di- tert-butyl-4-hydroxyphenyl)propionate) (IRGANOX 1010); ester of benzenpropanoic acid and 3,5-bis(l ,l-dimethyl-ethyl)-4-hydroxy-C₇-C₉ branched alkyl (IRGANOX 1 135); 2,6-di-tert-butyl-4-(4,6-bis(octylthio)-l,3,5-triazin-2-yl-amino)phenol (BNX™ 565, Mayzo Inc.); and octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (IRGANOX 1076). Examples of amine-type antioxydants include N-isopropyl-N'- phenyl-p-phenylenediamine (IPPD, VULCANOX 4010), N-(l,3-dimethyl-butyl)-N'- phenyl-p-phenylenediamine (Antioxidant 4020, 6PPD), N-(l ,3-dimethyl-phenyl)-N'- phenyl-p-phenylenediamine (7PPD), N-2-ethylhexyl-N'-phenyl-p-phenylenediamine (Novantox 8 PFDA Antioxidant S789), N,N'-diphenyl-p-phenylenediamine (DFFD), composite antioxidants such Santoflex™ 134PD, which are a 1 :2 mixture of products 6PPD and 7PPD. Antioxidants are introduced into the polymerizate in an amount of from 0.2 to 3.0 wt.% of the weight of resulting rubber. The most effective and advisable amount of the antioxidant is 0.3 to 1.5 wt.% based on the rubber.

The oil-fillers for the rubbers include oils of such types as TDAE (treated distillate aromatic extract), TRAE (treated residual aromatic extract), MES (mild extract solvate), and naphthenic oils (NAP). Rubbers can be also filled with vegetable oils, such as rapeseed. DAE oils (aromatic oils) can be also used, but they are not desirable because of a high content of carcinogenic substances. Mixtures of different oils are also applicable. The most common oil-fillers are oils of group TDAE. Examples of TDAE oils are NORMAN 346 ("Orgkhim", JSC), Vivatec 500 (Hansen&Rosental), and Nytex 840 (Nynas). Examples of MES oils include Vivatec 200 (Hansen&Rosental), Nytex 832 (Nynas), and NORMAN 132 ("Orgkhim", JSC). Example of DAE oils is PN-6 ("Orgkhim", JSC). Examples of NAP oils include Nytex 4700 (Nynas) and Octopus N317 (Petroyag, Turkey). Example of TRAE oil is NORMAN 583 ("Orgkhim", JSC). The oil-filler is fed in an amount of 5 to 80 weight parts per 100 rubber weight parts, depending on the processing properties of the rubber to be achieved. However, the most traditional rubber is a rubber with an oil content of 25 to 30 wt.% in a mixture, which corresponds to 34 to 44 oil weight parts per 100 rubber weight parts.

The rubber produced according to the present invention may be used in vulcanizates for various applications, providing them with a reduced hysteresis loss under dynamic conditions, including in tire treads, to increase a grip index and reduce rolling loss.

Persons skilled in the art are well aware of common requirements to the rubber compositions.

Vulcanizates according to the present invention differ from known compositions of the same intended purpose in that they include the rubbers produced by the claimed methods.

In accordance with the present invention, vulcanizates can be produced based on a mixture of several rubbers, preferably two or three, selected from the group of styrene-butadiene (A), butadiene (B) and isoprene (C), styrene-izoprene-butadiene (D), or other rubbers which can be used in the production of vulcanizates for a given purpose. One or more rubbers relating to group A, B or D and synthesized in a hydrocarbon solvent by anionic polymerization are produced according to the present invention.

Rubber compositions according to the invention may also contain the following ingredients, which are traditional for tires and, in particular, tread rubbers (weight parts per 100 rubber weight parts):

a) 0-150 wt. parts of silica;

b) 0-150 wt. parts of carbon black; c) 0-30 wt. parts of silanizing agent;

d) a vulcanizing system comprising sulfur or sulfur donors, accelerators such as sulfenamides, thiurams, thiazoles, guanidines, phosphates, and a combination thereof, which are used to accelerate the process of rubber vulcanization and obtain the optimal structure of a vulcanization network; activators, such as metal oxides, amines, among which zinc oxide is commonly used; vulcanization retarders, among which Santogard PVI is most commonly used;

e) processing additives improving dispersion of fillers and processability of rubber compositions;

f) plastisizers and softeners, in particular selected from the group including petrochemical products, plant oils, synthetic ether products, derivative products of the coal-mining industry, synthetic and oligomeric functionalized and non-functionalized products;

g) anti-aging agents/antiozonants/anti-fatigue agents of physical and chemical action;

h) other components providing the required complex of processing, vulcanized, mechanical and physical, and performance characteristics, for example, modifiers, fillers, including fibrous, layered, polymer fillers (such as cross-linked polymeric gels); agents that prevent reversion during vulcanization and enhance heat-resistant of the rubbers; and agents improving stickiness.

Vulcanizates can be produced by using butadiene and isoprene rubbers which are prepared by using various catalyst systems by solution polymerization in the presence of an initiator or a catalyst of polymerization and which comprise 1 ,4-cis units in an amount of not more than 90 wt.%. Vulcanizates also may comprise styrene- butadiene copolymers prepared in an emulsion (aqueous phase) or a solution (organic solvent).

The rubber compositions, which are a subject matter of the present invention, can be prepared by using natural rubbers of various manufactures, brands and grades, for example, RSS (Ribbed Smoked Sheet) and IRQPC (International Standards of Quality and Packing of Natural Rubber).

The elastomer part of a rubber composition also may include a terpolymer of styrene, isoprene, and butadiene, produced in the form of an emulsion or in a solution with a ratio of styrene:butadiene:isoprene units (wt.%) of 5-70:20-70:20-70. The total amount of 1 ,2-butadiene and 3,4-isoprene units ranging from 20 to 90 wt.% based on the butadiene and isoprene part is preferred, and from 40 to 70 wt.% is most preferred.

Other elastomers and copolymers can be also used, for example, an isoprene- butadiene copolymer, polybutadiene with a high content of 1 ,2-butadiene units, and polyisoprene with a high amount of 3,4-isoprene units.

Rubber compositions can also comprise oil-filed rubbers, for example, emulsion or solution butadiene-styrene or butadiene rubbers.

Each of the rubbers constituting the disclosed vulcanizates can have a branched structure, such as a star-shaped structure of the polymer chain. The branching may be achieved by using at the polymerization step a known branching agent such as SiCl₄, SnCl₄, and divinylbenzene.

According to the present invention, the main reinforcing filler for rubber compositions is synthetic amorphous silicon dioxide (colloidal silicic acid), preferably precipitated, and/or carbon black. It is possible to use a two-phase filler which is silicon dioxide with carbon black applied on its surface, silicon dioxide that has a surface impregnated with an addition agent or that is chemically modified, and precipitated colloidal silicic acid (silica, PSF) produced by a pyrogenic method.

The amount of carbon black may vary from 0 to 150 wt. parts per 100 rubber wt. parts. If the amount of carbon black higher than 150 wt. parts, the processing and performance properties of vulcanizates are deteriorated.

The amount of silicon dioxide in an elastomeric composition is 0 to 150 wt. parts per 100 rubber wt. parts, preferably 10 to 1 10 wt. parts, more preferably 30 to 95 wt. parts. If the amount of silicon dioxide is higher than 150 wt. parts, the processing and some performance properties of vulcanizates are deteriorated.

According to the present invention, silicon dioxide is characterized by a BET surface area within a range of 40 to 600 m²/g and an oil absorption (DBP) within a range of from 50 to 400 cm³/100 g. In a preferred embodiment, silicon dioxide has a BET surface area of 100 to 250 m²/g, a CTAB surface area of 100 to 250 m²/g, and an oil adsorption (DBP) of 150 to 250 cm³/l 00 g.

For this purpose there are applicable various commercially available brands of silicon dioxide, for example, Zeosil 1 165MP, Zeosil 1165 GR, Hi-Sil 210, Hi-Sil 243, Ultrasil VN2, Ultrasil VN3, Ultrasil VN3 GR, as well as other brands, preferably, of precipitated colloidal silicic acid, which are used for elastomer reinforcement.

Rubber compositions filled with silicon dioxide comprise silanizing agents (coupling agents of precipitated silica fillers and elastomers). Most frequently used coupling agents are bis(3-triethoxysilylpropyl)tetrasulfide, bis(2- triethoxysilylethyl)tetrasulfide, bis(3-trimethoxypropyl)tetrasulfide, bis(2- trimethoxysilylethyl)terasulfide, 3 -mercaptopropyltrimethoxysilane, 3 - mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, 2- mercaptoethyltriethoxysilane, 3-nitropropyltrimethoxysilane, 3- nitropropyltriethoxysilane, 3-chloropropyltrimethoxysilane, 3- chloropropyltriethoxysilane, 2-chloroethyltriethoxysilane, 3-trimethoxysilylpropyl-N, N-dimethylthiocarbamoyltetrasulfide, 3 -trimethoxysilylpropylbenzothiazol tetrasulfide, and 3-triethoxysilylpropylmethacrylate monosulfide. Among the above-recited components, bis(3-triethoxysilylpropyl)tetrasulfide and 3- trimethoxysilylpropylbenzothiazol tetrasulfide are most preferred.

In addition, coupling agents can be used which are compositions of the above- recited compounds, as well as other compounds intended to be used for this purpose with a powdered carrier, for example, carbon black.

Other coupling agents also can be used to improve compatibility of precipitated silicic fillers to a rubber, for example, such as NXT and NXT Z 100, produced by Momentive (USA).

The content of silanizing agents in vulcanizate is determined so that the amount of the main active agent, except a carrier in the case of composite silanizing agents, is within a range of 1 to 30% wt., most preferably from 5 to 25 wt.%, based on silicon dioxide.

Rubber compositions are vulcanized by using vulcanizing agents known in the prior art, for example, elemental sulfur, sulfur donors, such as Ν,Ν'- dimorpholyldisulfide, polymeric polysulfides, etc. Elemental sulfur and polymeric sulfur are most commonly used in the tire industry. An amount of vulcanizing agents in vulcanizate is known to be, in general, between 0.5 and 4.0 wt. parts, sometimes may reach 10 wt. parts per 100 rubber wt. parts. In general, sulfur is used together with such ingredients as vulcanization activators, in particular, oxides and hydroxides of alkaline- earth metals (Zn, Mg, Ca), metals in combination with fatty acids, accelerators (sulfenamides, thiazoles, thiurams, guanidines, urine derivatives), and vulcanization retarders (phthalic anhydride, N-nitrosodiphenylamine, cyclohexylthiophthalimide). Their amounts depend on the amount of a vulcanizing agent and requirements for vulcanization kinetics, as well as on the structure of a vulcanization network.

Silicon dioxide-filled rubber compositions, as a rule, also comprise processing additives improving the filler dispersion and processability of rubber compositions. Fatty acid derivatives (zinc salts and esters, and mixtures thereof), which enhance the dispersion of fillers and reduce the viscosity of the mixture, are considered to be such ingredients. In particular, products based on fatty acid derivatives known under the brand names Struktol E44, Struktol GTI, and Actiplast ST can be used.

Plastisizers and softeners include petrochemical products, plant, synthetic ether products, derivative products of the coal-mining industry.

A composition of tire rubbers includes, as a rule, ingredients of the following intended purpose: anti-aging agents, antiozonants, anti-fatigue agents and other components providing a required complex of processing, vulcanized, physical and mechanical, and performance characteristics, for example, modifiers, fillers, including fibrous, layered, and polymer fillers (such as cross-linked polymer gels); agents preventing reversion during vulcanization and increasing heat resistance of vulcanizates; and agents improving tackiness.

Rubber compositions are prepared by methods known in the art and disclosed, for example, by Jhon S. Dick in Rubber Technology. Compounding and Testing for Performance(pp.606-616), preferably by using closed rubber mixers, for example, Banbury or Intermix types. The process of mixing can be carried out in two or three steps, wherein the second and the third steps are intended to add components of the vulcanizing group to the mixture. The curing temperature is 130 to 180°C, preferably 140 to 170°C.

Rubber compositions prepared thereby are widely used as materials for tire treads and are characterized by an improved complex of elastic-hysteresis characteristics, in particular by an improved wet and icy grip indexes.

EMBODIMENTS OF THE INVENTION

Synthesis of an initiator based on DEAMS (diethylaminomethylstyrene) A 250 round-bottom flask was filled with 100 ml of a solvent (cyclohexane (70 wt.%) + petroleum solvent (30 wt.%)) and 18.8 ml (0.03 mol) of n-butyllithium (1.6 M in hexane) at 0°C under stirring, and 5.679 g (0.03 mol) of DEAMS was added for 30 minutes. Then the solution was allowed to heat to room temperature under stirring for 1 hour. The resulting solution was homogenous, transparent, and red colored. An aliquot of the resulting mixture was titrated with a solution of isopropanol in toluene. The resulting stopped solution was washed with 50 ml of water. The solvent was evaporated from the organic layer, the residue was dried in a vacuum oven and was analyzed by gel permeation chromatography (GPC); the results are given in Table 1. The calculated concentration of active lithium in the resulting solution was 0.22 mol/L. The actual concentration was 0.20 mol/L.

Synthesis of an initiator based on DIPAMS (diisopropylaminomethylstyrene)

A 250 round-bottom flask was filled with 100 ml of a solvent (cyclohexane (70 wt.%) + petroleum solvent (30 wt.%)) and 18.8 ml (0.03 mol) of n-butyllithium (1.6 M in hexane) at 0°C under stirring, and 6.52 g (0.03 mol) of DIPAMS was added for 30 minutes. After the whole amount of DIPAMS was added, the solution was allowed to heat under stirring for 60 minutes. Under stirring, the solution was colored red. An aliquot of the resulting mixture was titrated with a solution of isopropanol in toluene. The resulting stopped solution was washed with 50 ml of water. The solvent was evaporated from the organic layer, the residue was dried in a vacuum oven and was analyzed by gel permeation chromatography (GPC); the results are given in Table 1. The concentration of active lithium in the resulting solution was 0.22 mol/1. The actual concentration was 0.20 mol/L. Upon completion of the synthesis, the color of the solution became less intense than in the initiator based on DEAMS.

Table 1. Molecular weight characteristics of stopped oligomeric initiators

Example 1. Polymerization in the presence of n-butyllithium (n-BuLi)

The process for producing styrene-butadiene rubbers was carried out in a 2L reactor with a metal cup (company "Buchi"), equipped with a stirrer, a jacket for temperature control, fittings and special detachable metal feeders for feeding reagents.

Petroleum solvent (984 g), butadiene (92.62 g), styrene (30.98 g), and 6.18 ml a DTGFP (ditetrahydrofurylpropane or 2,2-bis(2-oxolonyl)propane) solution in petroleum solvent (0.2 M solution) were fed to the reactor cooled to -20°C (± 2°C) in a nitrogen flow at a stirrer rotary rate of 50 rpm. Further, the stirrer rotary rate was set to be 300 rpm, the temperature of the reaction mass began to increase to 55°C at a rate of 7°/min, and when the temperature reached 15°C, 4.94 ml of n-butyllithium in petroleum solvent (0.2 M solution) was fed. After reaching a required monomer conversion (100%), the polymer was poured to the cup and filled with antioxidant Novantox 8 PFDA (0.4 wt.% per 100 g of polymer). Further, the rubber was subjected to aqueous degassing in an oil bath at 150°C. The resulting rubber containing water was dried on rollers at a temperature of 85°C.

The characteristics of the resulting rubber are given in Table 2. The properties of the vulcanizates prepared from this rubber are shown in Tables 4-5.

Example 2. Polymerization in the presence of n-butyllithium and SiMe₂C1₂ The process for producing styrene-butadiene rubbers was carried out as disclosed in Example 1 , except that upon reaching 100% conversion, a solution of SiMe₂C1₂ (0.2 M) was added in an amount of 0.5 of molar amount of the used initiator. Modification with SiMe₂C1₂ was carried out at 60°C for 30 minutes.

The amounts of reagents in the synthesis of a rubber and the properties of the resulting rubber are given in Table 2. The properties of the vulcanizates prepared from this rubber are shown in Tables 4-5.

Example 3. Polymerization in the presence of n-butyllithium and a special monomer - MMS (morpholylmethylstyrene)

The process for producing styrene-butadiene rubbers was carried out as disclosed in Example 1, except that before feeding the initiator to a charge, a special monomer - MMS was added in an amount of 2.6 wt.% based on rubber.

Example 4 Polymerization in the presence of n-butyllithium, MMS, and

SiMe₂C1₂

The process for producing styrene-butadiene rubbers was carried out as disclosed in Example 1, except that before feeding the initiator to a charge, a special monomer - MMS was added in an amount of 2.6 wt.% based on rubber, and when the conversion reached 100%, a solution of SiMe₂C1₂ (0.2 M) was added in an amount of 0.5 of molar amount of the used initiator. Modification of SiMe₂C1₂ was carried out at 60°C for 30 minutes.

Example 5. Polymerization in the presence of an oligomeric initiator based on DEAMS-Li

The process for producing styrene-butadiene rubbers was carried out as disclosed in Example 1, except that the initiator was an oligomeric initiator based on DEAMS instead n-butyllithium.

Example 6. Polymerization in the presence of an oligomeric initiator based on DEAMS-Li and SiMe₂C1₂

The process for producing styrene-butadiene rubbers was carried out as disclosed in Example 1, except that the initiator was an oligomeric initiator based on DEAMS instead n-butyllithium, and when the conversion reached 100%, a solution of SiMe₂C1₂ (0.2 M) was added in an amount of 0.5 of molar amount of the used initiator. Modification of the rubber with SiMe₂C1₂ was carried out at 60°C for 30 minutes.

Example 7. Polymerization in the presence of an oligomeric initiator based on DEAMS-Li and special monomer MMS.

The process for producing styrene-butadiene rubbers was carried out as disclosed in Example 1, except that before feeding the initiator to a charge, a special monomer - MMS was added in an amount of 2.6 wt.% based on rubber, and the initiator was an oligomeric initiator based on DEAMS instead n-butyllithium.

Example 8. Polymerization in the presence of an oligomeric initiator based on DEAMS-Li, special monomer MMS, and SiMe₂C1₂

The process for producing styrene-butadiene rubbers was carried out as disclosed in Example 1 , except that before feeding the initiator to a charge, a special monomer - MMS was added in an amount of 2.6 wt.% based on rubber, and the initiator was an oligomeric initiator based on DEAMS instead n-butyllithium, and when the conversion reached 100%, a solution of SiMe₂C1₂ (0.2 M) was added in an amount of 0.5 of molar amount of the used initiator. Modification of the rubber with SiMe₂C1₂ was carried out at 60°C for 30 minutes.

Example 9. Polymerization in the presence of an oligomeric initiator based on DIPAMS-Li

The process for producing styrene-butadiene rubbers was carried out as disclosed in Example 1 , except that the initiator was an oligomeric initiator based on DIPAMS instead n-butyllithium.

The amounts of reagents in the synthesis of a rubber and the properties of the resulting rubber are given in Table 2. The properties of vulcanizates produced from this rubber are shown in Table 4.

Example 10. Polymerization in the presence of an oligomeric initiator based on DIPAMS-Li and special monomer MMS The process for producing styrene-butadiene rubbers was carried out as disclosed in Example 1 , except that before feeding the initiator to a charge, a special monomer - MMS was added in an amount of 2.6 wt.% based on rubber, and the initiator was an oligomeric initiator based on DIPAMS instead n-butyllithium.

Example 11. Polymerization in the presence of an oligomeric initiator based on DIPAMS-Li, special monomer MMS, and SiMe₂C1₂

Example 12 (comparative). Commercially available rubber

Properties of the commercially available rubber, which are branched and functionalized, are given in Table 2. The properties of vulcanizates produced from this rubber are shown in Tables 4-5.

Tests of rubbers produced according to examples 1-12, including comparative and commercially available samples, were performed as constituents of the a rubber composition for auto tire treads (Recipe 1) and a standard rubber composition (National State Standard ISO 2322-2013, Example A) filled with carbon black (Recipe 2). The formulation of rubber compositions are shown in Table 3. Rubber compositions were prepared in plasticorder Plastograph EC Plus, Model 2008 ("Brabender", Germany). The free volume of a mixing chamber with bump rotors N50 EHT was 80 cm . A rubber composition of Recipe 1 was prepared in three steps:

step 1 - comprised mixing all ingredients, except a vulcanized group (i.e. sulfur, DPG, SAC), at the initial temperature of the chamber walls of 130°C; the maximum temperature in the chamber during the mixing process was not higher than 165°C, and the rotary speed was 40 rpm;

step 2 comprised dispersing mixing of the mixture of step 1 without adding additional ingredients at the initial temperature of the chamber walls of 80°C; the maximum temperature was not higher than 130°C, and the rotary speed was 60 rpm; and step 3 comprised adding the vulcanizing group to the rubber composition at the initial temperature of the chamber walls of 80°C; the maximum temperature was not higher than 1 10°C, and the rotary speed was 40 rpm. Rubber compositions of Recipe 2 were prepared in an internal mixer in one step according to National State Standard ISO 2322-2013, Example A.

The rubber compositions were prepared for vulcanization, and the vulcanization process and the preparation of samples for testing were carried out in accordance with ASTM D 3182. Regimes for vulcanization of rubber compositions produced according to Recipe 1 were as follows: 160°C for 20 min to evaluate deformation-strength properties, and for 30 min to evaluate abrasion. Regimes for vulcanization of rubber compositions produced according to Recipe 2 are given in National State Standard ISO 2322-2013. Vulcanized properties (t_si - time of starting vulcanization, t₅₀ - time of reaching a 50% vulcanization, t₉₀ - optimal time of vulcanization, MH - maximum torque, ML - minimum torque, Rv - rate of vulcanization) were evaluated in an RPA

2000 device, 160°C ^χ 30 min, according to ASTM D 5289-07. The main tensile parameters of vulcanizates (fioo - conventional stress at 100% elongation, f₃₀o - conventional stress at 300% elongation, the f_p - modulus of rupture, e_rei - breaking elongation) were evaluated according to ASTM D 412-98. Shopper-Schlobach abrasion (ABR) (method B) was evaluated in accordance with National State Standard 23509-79. Hysteresis properties (mechanical loss tangent tgδ ) were evaluated in a DMA 242 C apparatus (NETZSCH). The test conditions in DMA 242 C were as follows: dual cantilever bending, the specimen dimensions 10.00 ^χ 6.50 ^χ 2.0 mm, amplitude of 40 μπι (1%), frequency of 10 Hz, and a load of 7 N. Test temperature ranged between (- 60)°C and 60°C, a rate of temperature rise was 2°/min. t_.t

Table 3. Formulation of rubber compositions

As can be seen from the results of the testing rubber compositions filled with carbon black (Table 4, Recipe 1), rubbers with triple functionalization (Examples 8 and 1 1) produced according to the present invention provide vulcanizates with the least hysteresis loss ( tgδ 60°C) at 60°C, which is better than that in non-functionalized rubber (Example 1), rubbers functionalized with one of modifying agents (Examples 2, 3, 5, and 9), and rubbers with double functionalization (Examples 6, 7, 10). Parameter tgδ _60°c characterizes a rolling loss value of tires in service. According to the parameter tgδ _0°c characterizing wet grip, the rubbers with triple functionalization (Examples 8 and 1 1) are on the level of other modified rubbers described in Examples 2, 3, 5, 9, 6, 7, and 10. Vulcanized parameters and physical and mechanical properties of vulcanizates do not undergo significant changes when used in vulcanizates based on rubbers with triple functionalization (Examples 8 and 1 1), which would limit the field of application of such vulcanizates.

As for tire rubbers (Table 5) comprising colloidal silicic acid, which is their main component, the use of a rubber with triple functionalization (Example 8) also has a positive effect on tgδ 60°C, as compared with both the non-functionalized rubber (Example 1) and functionalized rubbers, including commercially available rubber (Examples 2, 3, 4, 5, 6, 11 , and 12). The rest of the properties of the vulcanizate underwent no significant changes.

Claims

1. A method for producing a rubber by an anionic solution (co)polymerization of a conjugated diene and/or a vinyl aromatic compound in an organic solvent in the presence of an organolithium Ν,Ν-disubstituted aminomethylstyrene oligomeric initiator, a special Ν,Ν-disubstituted aminomethylstyrene monomer, and an end- functionalizing agent of the general formula (CH₃)₂Hal₂Si, wherein Hal is a halogen atom.

2. The method for producing a rubber of claim 1, wherein the special N,N- disubstituted aminomethylstyrene monomer is represented by formula (II)

wherein R is -CH₂N(R₁)(R₂), wherein R₁ and R₂ may be the same or different and independently are alkyl, cycloalkyl, aryl, or heteroaryl, or

R₁ and R₂, taken together with a nitrogen atom, form a 5-6-membered or 5- membered heteroaromatic ring optionally containing one or more additional heteroatoms selected from nitrogen, oxygen, and sulfur,

Hal is a halogen atom,

x is 1, y is 0 or x is 0, y is 1.

3. The method for producing a rubber of claim 2, wherein the alkyl has one or more substituents selected from hydroxy, dialkylamino, alkoxy, aryloxy, alkylsulfanyl, and arylsulfanyl.

4. The method for producing a rubber of claim 2, wherein the aryl has one or more substituents selected from halogen, alkyl, dialkylamino, alkoxy, aryloxy, alkylsulfanyl, arylsulfanyl, and aryl.

5. The method for producing a rubber of claim 2, wherein the heteroaryl has one or more substituents selected from halogen, alkyl, dialkylamino, alkoxy, aryloxy, alkylsulfanyl, arylsulfanyl, and aryl.

6. The method for producing a rubber of claim 1, wherein the organolithium Ν,Ν-disubstituted aminomethylstyrene oligomeric initiator is a product of reaction between an organolithium compound and a compound according to any one of claims 2 to 5.

7. The method for producing a rubber of claim 6, wherein the organolithium compound is represented by the formula: R'Li, wherein R' is an alkyl or aryl hydrocarbon radical.

8. The method for producing a rubber of claim 1, wherein the end- functionalizing agent is dimethyldichlorosilane.

9. The method for producing a rubber of claim 1, wherein the conjugated diene comprises 4 to 12 carbon atoms, and preferably is 1,3-butadiene and/or isoprene.

10. The method for producing a rubber of claim 1, wherein the vinyl aromatic compound is selected from the group consisting of styrene, a-methylstyrene, ortho-, meta-, and para-methylstyrene, 3-vinyltoluene, ethylvinylbenzene, 4-cyclohexylstyrene, para-tert-butylstyrene, methoxystyrene, vinylmesitylene, divinylbenzene, 1- vinylnaphthaline, and 2,4,6-trimethylstyrene, preferably from styrene and a- methyl styrene.

1 1. The method for producing a rubber of claim 1 , wherein the special monomer is added in an amount of 0 to 40 wt.%, preferably 0.1 to 10 wt.%, more preferably 0.5 to 5 wt.% based on the polymer weight.

12. The method for producing a rubber of claim 1, wherein the polymerization is carried out at a temperature of from (-30)°C to 120°C, preferably from 0°C to 100°C, more preferably from 15°C to 80°C.

13. The method for producing a rubber of claim 1, wherein an initiatonrubber molar ratio is from 1 to 50 mol/t of the rubber, preferably from 2 to 25 mol/t of the rubber, more preferably from 3 to 10 mol/t of the rubber.

14. The method for producing a rubber of claim 1, wherein the solvents of the anionic polymerization are saturated hydrocarbons preferably comprising from 3 to 12 carbon atoms, or a mixture thereof.

15. A rubber based on (co)polymers of a conjugated diene and/or a vinyl aromatic compound produced by the method according to claims 1 to 14.

16. A rubber composition comprising the rubber according to claim 15.

17. The rubber composition according to claim 16, further comprising components selected from the group comprising natural rubber; silica; carbon black; a silanizing agent; a vulcanizing agent; and traditional processing additives, such as additives improving dispersion of fillers and processability of rubber compositions; plastisizers, anti-aging agents/antiozonants/anti-fatigue agents of physical and chemical action; modifiers, fillers, including fibrous, layered, and polymer fillers; agents preventing reversion during vulcanization and increasing heat resistance of vulcanizates.

18. Use of the rubber composition according to claims 16 and 17 in the manufacture of auto tire treads.