JPH07102117A - Vulcanizable rubber composition - Google Patents

Abstract

PURPOSE:To obtain a vulcanizable rubber composition good in repulsion resilience and abrasion resistance by blending a rubber-like copolymer prepared by carrying out the emulsion copolymerization of a tertiary-amino group- containing monomer with an aliphatic conjugated diolefin and an aromatic vinyl monomer with a vulcanization accelerator and carbon black. CONSTITUTION:This vulcanizable rubber composition is obtained by blending a rubber-like copolymer prepared by carrying out the emulsion copolymerization of a monomer mixture composed of 0.5-20wt.% polymerizable monomer, expressed by the formula (R1 and R2 are each a 1-10C alkyl, an aralkyl or an aryl; R3 is H or a 1-4C lower alkyl; n is an integer of 1-6) and having a tertiary-amino group such as an N-disubstituted aminoalkyl acrylate (e.g. dimethylaminomethyl acrylate) with 20-99.5wt.% aliphatic conjugated diolefin monomer (e.g. 1,3-butadiene) and 0-60wt.% aromatic vinyl monomer (e.g. styrene) with a vulcanization accelerator such as sulfur or a sulfenamide-based vulcanization accelerator and carbon black. The composition has excellent impact resilience and abrasion resistance and is suitable for tire treads, etc.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber composition, and more particularly to a rubber composition suitable for a tire tread having improved impact resilience and abrasion resistance after vulcanization using a sulfur vulcanization system. Regarding things.

[0002]

2. Description of the Related Art From the viewpoint of resource saving and environmental measures, the demand for low fuel consumption of automobiles is becoming more and more stringent, and even rubber materials for tires are resistant to rolling resistance, which is an index of impact resistance, and weight resistance. There is a strong demand for rubber with improved wear properties. In order to satisfy such requirements, various measures by the solution polymerization method (for example, high vinyl SBR, high vinyl SBR whose terminal is modified with a specific compound, use of high vinyl SBR having butadienyl-Sn bond in its molecule, etc.) have been made variously. Is coming. However, the study by the emulsion polymerization method has not been sufficiently conducted, and the use of a diene rubber obtained by copolymerizing a monomer having a tertiary amino group slightly has been proposed (JP-A-2-55747). ). According to this method, it is reported that a rubber vulcanizate excellent in abrasion resistance and wet skid resistance can be obtained by blending the above-mentioned diene rubber with carbon black in the range of pH 2 to 6 and vulcanizing it. . However, with this method, sufficient performance could not be expected in a system containing general-purpose carbon such as furnace black. Further, the effect of improving the impact resilience was not obtained even when channel black was used.

[0003]

An object of the present invention is to provide a rubber composition which is an emulsion polymerized rubber material and is excellent in impact resilience and abrasion resistance.

[0004]

The object of the present invention is as follows.
It is composed of 0.5 to 20% by weight of a polymerizable monomer having a tertiary amino group, 20 to 99.5% by weight of an aliphatic conjugated diolefin monomer, and 0 to 60% by weight of an aromatic vinyl monomer. It is achieved by using a vulcanizable rubber composition obtained by compounding a rubbery copolymer obtained by emulsion polymerization of a monomer mixture with sulfur, a sulfenamide-based vulcanization accelerator and carbon black. .

The polymerizable monomer having a tertiary amino group used in the present invention includes N-di-substituted aminoalkyl acrylate, N-di-substituted aminoalkyl acrylamide, N-di-substituted amino aromatic compound and pyridyl group. At least one monomer selected from the polymerizable monomers having

As the N-disubstituted aminoalkyl acrylate, compounds represented by the following general formula are used.

[Chemical 1] (In the formula, R ₁ and R ₂ are alkyl groups having 1 to 10 carbon atoms,
An aralkyl group or an aryl group, R ₃ is a hydrogen atom or a lower alkyl group having 1 to 4 carbon atoms, and n is an integer of 1 to 6. )

Specifically, dimethylaminomethyl acrylate, dimethylaminoethyl acrylate, dimethylaminoethyl (meth) acrylate, dimethylaminopropyl (meth) acrylate, dimethylaminobutyl (meth) acrylate, diethylaminoethyl acrylate, diethylaminoethyl (meth) ) Acrylate, diethylaminopropyl (meth) acrylate, diethylaminobutyl (meth) acrylate, methylethylaminoethyl (meth) acrylate, dipropylaminoethyl (meth) acrylate, dibutylaminoethyl (meth) acrylate, dibutylaminopropyl (meth) acrylate , Dibutylaminobutyl (meth) acrylate, dihexylaminoethyl (meth) acrylate, dioctylaminoethyl Examples thereof include compounds such as (meth) acrylate, and among these, preferred are dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, dipropylaminoethyl (meth) acrylate, dioctylaminoethyl (meth) acrylate, and methyl. Ethylaminoethyl (meta)
Examples thereof include acrylate.

As the N-disubstituted aminoalkylacrylamide, a compound represented by the following general formula is used.

[Chemical 2] (In the formula, R ₁ and R ₂ are alkyl groups having 1 to 10 carbon atoms,
An aralkyl group or an aryl group, R ₃ is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and n is an integer of 1 to 6. )

Specific compounds include dimethylaminomethylacrylamide, dimethylaminoethylacrylamide, dimethylaminoethyl (meth) acrylamide, dimethylaminopropylacrylamide, dimethylaminopropyl (meth) acrylamide, dimethylaminobutyl (meth) acrylamide, diethylamino. Ethyl acrylamide, diethylaminoethyl (meth) acrylamide, diethylaminopropyl acrylamide,
Diethylaminopropyl (meth) acrylamide, diethylaminobutyl (meth) acrylamide, methylethylaminoethyl (meth) acrylamide, dipropylaminoethyl (meth) acrylamide, dibutylaminoethyl (meth) acrylamide, dibutylaminopropylacrylamide, dibutylaminopropyl (meth) ) Acrylamide, dibutylaminobutyl (meth) acrylamide, dihexylaminoethylmethacrylamide, dihexylaminopropyl (meth) acrylamide, dioctylaminopropylacrylamide, dioctylaminopropyl (meth) acrylamide and the like, preferably dimethylaminopropyl (meth) Acrylamide, diethylaminopropyl (meth) acrylamide,
Dioctylaminopropyl (meth) acrylamide and the like.

As the N-disubstituted amino aromatic compound,
For example, styrene derivatives such as dimethylaminoethylstyrene, diethylaminoethylstyrene, dipropylaminoethylstyrene and dioctylaminoethylstyrene are used. In the present invention, a compound having a pyridyl group such as vinylpyridine can also be used as the polymerizable monomer having a tertiary amino group. Specifically, 2-vinylpyridine, 4-vinylpyridine, 5-
Methyl-2-vinyl pyridine, 5-ethyl-2-vinyl pyridine, etc. are mentioned, Preferably 2-vinyl pyridine and 4-vinyl pyridine are used.

The proportion of the polymerizable monomer having a tertiary amino group used is 0.5 to 20% by weight in the monomer mixture. If it is less than 0.5% by weight, the impact resilience and abrasion resistance are not improved, and if it exceeds 20% by weight, the improving effect is saturated and not only economically unfavorable, but also moldability is deteriorated. It is preferably in the range of 1 to 15% by weight, and more preferably in the range of 2 to 10% by weight.

Examples of the aliphatic conjugated diolefin monomer used in the present invention include 1,3-butadiene and 2
-Methyl-1,3-butadiene and 2-chloro-1,
3-butadiene etc. are mentioned. Particularly, 1,3-butadiene is preferable. These monomers are used to impart elasticity to the copolymer, and the amount used is 10 to 10 in the monomer mixture.
99.5% by weight, preferably 30 to 95% by weight,
More preferably, it is in the range of 40 to 90% by weight.

Examples of the aromatic vinyl monomer used in the present invention include styrene, α-methylstyrene,
2-methylstyrene, 3-methylstyrene, 4-methylstyrene, 2,4-diisopropylstyrene, 2,4-
Dimethylstyrene, 4-t-butylstyrene, 5-t-
Butyl-2-methylstyrene, monochlorostyrene, dichlorostyrene, monofluorostyrene, hydroxymethylstyrene and the like can be mentioned, with styrene being particularly preferred. Aromatic vinyl monomer content is 0-60% by weight
10 to 40% by weight on the strength characteristics of the obtained copolymer rubber.
Is preferred.

The rubbery copolymer of the present invention can be obtained by emulsion polymerization of the above monomer mixture. Emulsion polymerization may be carried out by a usual emulsion polymerization method and is not particularly limited. For example, it can be obtained by emulsion-dispersing a predetermined amount of a monomer in an aqueous medium in the presence of an emulsifier, and emulsion-polymerizing in the presence of a radical initiator.

As the emulsifier, a long-chain fatty acid salt having 10 or more carbon atoms and / or a rosin acid salt is usually used. For example, capric acid, lauric acid, myristic acid,
Examples thereof include palmitic acid, oleic acid, stearic acid and the like, and their potassium salts or sodium salts.

Examples of the radical polymerization initiator include persulfates such as ammonium persulfate and potassium persulfate, combinations of ammonium persulfate and ferric sulfate as redox type initiators, organic peroxides and ferric sulfate. A combination with iron, a combination of hydrogen peroxide and ferric sulfate, and the like are used.

Chain transfer agents can also be added to control the molecular weight of the polymer. Examples of chain transfer agents that can be used include mercaptans such as t-dodecyl mercaptan and n-dodecyl mercaptan, carbon tetrachloride, thioglycolic acid, diterpenes, terbinolene, and γ-terpinenes.

The polymerization temperature can be appropriately selected depending on the type of radical initiator used, but it is usually from -5 ° C to
It is 100 ° C., preferably 0 ° C. to 60 ° C. The polymerization mode may be any of continuous polymerization, batch polymerization and the like. When the conversion rate of emulsion polymerization increases, gelation tends to occur. Therefore, in order to obtain a polymer with a small amount of gel, it is preferable to suppress the polymerization conversion rate to 80% or less, and especially 4
It is preferable to terminate the polymerization in the range of 0 to 70%.
Usually, when a predetermined conversion rate is reached, the polymerization is stopped by adding a polymerization terminator to the polymerization system. Examples of the polymerization terminator include amine compounds such as ethylhydroxylamine and hydroxylamine, quinone compounds such as hydroquinone and benzoquinone, and compounds such as sodium nitrite and sodium dithiocarbamate.

After termination of the polymerization, unreacted monomers are removed from the obtained polymer latex as needed, and acids such as nitric acid and sulfuric acid are added and mixed as needed, and the latex p
Adjust H to a predetermined value, add and mix salts such as sodium chloride, calcium chloride, potassium chloride as a coagulant,
The synthetic polymer is solidified as crumb. The crumbs are washed,
After dehydration, the target rubber-like copolymer can be obtained by drying with a band dryer or the like.

It is also possible to add a cationizing agent to the latex as necessary before the coagulation to ionize the produced copolymer. As such a cationizing agent, for example, methyl decyl sulfonate, dimethyl sulfate, fluoroacetic acid, perchloric acid, sodium tetrafluoroborate and the like can be used.

The Mooney viscosity (ML _{1 + 4} , 100 ° C.) of the rubbery copolymer of the present invention is not particularly limited, but it is usually
It is in the range of 20 to 150 in terms of mechanical strength and workability. 15 when the copolymer is used as an oil-extended rubber
It may exceed 0.

The rubber composition of the present invention is obtained by mixing the above rubber-like copolymer with carbon black in a sulfur vulcanization system. In order to achieve the object of the present invention, a sulfur vulcanization system is used, but it is necessary to use a sulfenamide-based accelerator as a vulcanization accelerator. The sulfenamide-based accelerator is not particularly limited, but an N-substituted-2-benzothiazylsulfenamide-based compound is preferable. Specifically, N-cyclohexyl-2-benzothiazyl sulfenamide, N, N-diethyl-2-benzothiazyl sulfenamide, Nt-butyl-2-
Benzothiazyl sulfenamide, Nt-octyl-
2-benzothiazylsulfenamide, N-oxydiethylene-2-benzothiazylsulfenamide, 2-
(2,6-dimethyl-4-morpholinothia) benzothiazole, N, N-diesopropyl-2-benzothiazylsulfenamide, N, N-dicyclohexyl-2-benzothiazylsulfenamide and the like can be mentioned.

The sulfur vulcanization system used in the present invention may use sulfur as a vulcanizing agent, a vulcanization aid and the above-mentioned vulcanization accelerator. As sulfur, elemental sulfur and / or sulfur donating compounds are used. As the sulfur-donating compound, a thiurum-based compound containing tetramethylthiuram disulfide, tetraethylthiuram disulfide, dipentamethylenethiuram tetrasulfide, or the like,
Sulfur-donating compounds that release active sulfur by heat, including morpholine disulfide, monoforine-based compounds containing 2- (4-morpholinodithio) benzothiazole, etc., selenium dimethyldithiocarbamate, alkylphenol disulfide, aliphatic polysulfide polymers, etc. And so on. As the vulcanization aid, stearic acid, zinc white, or the like can be used. The amount of each component of the sulfur vulcanization system used is not particularly limited, but may be used within a range usually used. For example, the amounts of sulfur and vulcanization accelerator used are each 0.1 part with respect to 100 parts by weight of the rubbery polymer.
-3 parts by weight, 0.01-2 parts by weight, and is appropriately selected according to the properties required for the composition.

The carbon black used in the present invention is not particularly limited, and commonly used ones such as furnace black, acetylene black, thermal black and channel black can be used. According to JP-A-2-55747, pH 2
Only specific carbon blacks in the range of 6 to 6 could be used, but when the sulfenamide-based sulfur addition accelerator of the present invention is used, generally used carbon blacks are used without limitation to the pH range. be able to.
A particularly preferred carbon black is a furnace black that is widely used in rubber compositions for tires, and specifically, SAF, ISAF, ISAF-HS, ISAF.
-LS, IISAF-HS, HAF, HAF-HS, H
Carbon black such as AF-LS. The amount of carbon black used is not particularly limited as long as it is appropriately determined depending on the purpose of use or required characteristics, but is usually 20 to 150 parts by weight per 100 parts by weight of the rubbery copolymer.

In the composition of the present invention, a rubbery copolymer and another polymer rubber can be blended and used. The amount of the rubbery copolymer used is not particularly limited as long as it does not impair the effects of the present invention, but is preferably 1
It is 0% by weight or more, and more preferably 30% by weight or more. Examples of other polymer rubbers include natural rubber, polyisoprene rubber, polybutadiene rubber, solution-polymerized styrene-butadiene rubber, acrylonitrile-butadiene rubber, butyl rubber, halogenated butyl rubber, ethylene-propylene-diene rubber, and epichlorohydrin rubber. .

All or part of the rubber component used in the present invention can be used as an oil-extended rubber.

The rubber composition of the present invention comprises various compounding agents generally used in the rubber industry depending on the purpose and application, for example, reinforcing agents such as silica, fillers such as calcium carbonate, process oils, processing aids and stabilizers. Etc. can be added.

The rubber composition of the present invention is produced by kneading and mixing the rubber component and various compounding agents by using an ordinary mixer such as a roll or a Banbury mixer.

[0029]

EXAMPLES The effects of the present invention will be explained below with reference to examples, but these do not limit the present invention. The parts and% in the examples are by weight unless otherwise specified.

Example 1 200 parts of water and 3 parts of rosin acid soap were placed in a polymerization reactor equipped with a stirrer.
Parts, 71 parts of 1,3-butadiene as a monomer, 26 parts of styrene and 3 parts of 4-vinylpyridine, and 0.2 part of t-dodecyl mercaptan as a chain transfer agent. The reaction temperature was set to 5 ° C., and 0.1 part of cumene hydroperoxide, 0.2 part of sodium formaldehyde sulfoxylate and 0.01 part of ferric sulfate as a radical initiator were added to initiate polymerization.

When the conversion reached 60%, diethylhydroxylamine was added to stop the reaction. Then
The unreacted monomer was recovered by steam distillation, the copolymer was coagulated with sulfuric acid and sodium chloride, washed with water and dried under reduced pressure to obtain a rubbery copolymer.

The amount of bound styrene in the copolymer is determined from the refractive index, and the amount of bound 4-vinylpyridine is determined from the wavelength of the UV absorption detector of GPC equipped with a differential refractive index detector and an ultraviolet absorption detector. It was set to (250 to 275 nm), and it was determined from a calibration curve prepared in advance from the peak area ratio obtained from the refractive index detector and the ultraviolet absorber. The bound styrene content was 20.4% and the bound 4-vinylpyridine content was 3.7%, respectively.

Next, the obtained rubber-like copolymer and various compounding ingredients according to the compounding recipe of Compounding Example 1 shown in Table 1 were kneaded in a Brabender type mixer having a capacity of 250 ml to obtain each rubber compounding composition. It was These rubber compounding compositions were press-vulcanized at 160 ° C. for 20 minutes to prepare test pieces. The Mooney viscosity of the unvulcanized compounded rubber composition (Moonee viscosity of the compounded compound) and the strength characteristics of the vulcanized product are measured according to JIS K6301.
The rebound resilience of the vulcanizate at 60 ° C. was measured in accordance with the above method using a Rupke type tester. Pico wear index is ASTM
The amount of wear was measured according to -D-2228, and the value was expressed as an index with Comparative Example 1 in Table 1 being 100. The above results are shown in Table 2.

[0034]

[Table 1]

Examples 2 to 4 and Comparative Examples 1 to 2 Rubber-like copolymers were obtained by emulsion polymerization in the same manner as in Example 1 using the types and amounts of the monomers shown in Table 2. Vulcanization physical properties were measured in the same manner as in Example 1 according to the formulation shown in Table 1. The results are shown in Table 2. The amount of bound DEAM was determined by NMR measurement.

[0036]

[Table 2]

As is apparent from Table 2, Examples 1 to 4 are Comparative Example 1 (conventional styrene-butadiene copolymer rubber (S
BR)) and Comparative Example 2 (different vulcanization accelerators),
The impact resilience and wear resistance are significantly improved without changing the strength characteristics.

Example 5 50 parts by weight of the rubber-like copolymer obtained in Example 1 and SBR
(Nipol 1502 manufactured by Zeon Corporation; styrene content 2
Using 50% by weight of 3.5%, ML _{1 + 4} , 100 ° C. = 52) as a raw rubber, a rubber compounding composition was obtained according to the compounding formulation of Table 1 compounding 1. This rubber compounding composition was press-vulcanized at 160 ° C. for 20 minutes to prepare a test piece, and the vulcanized physical properties were measured in the same manner as in Example 1. The results are shown in Table 3.

Example 6 50 parts by weight of the rubbery copolymer obtained in Example 1 and polybutadiene (BR) (Nipol 122 manufactured by Nippon Zeon Co., Ltd.)
0; cis-1,4 bond unit amount 98%, ML _{1 + 4} , 100 ° C =
43) A rubber compounding composition was obtained by using 50 parts by weight as a raw material rubber and a compounding formulation of Table 1 compounding 1. This rubber compounding composition was press-vulcanized at 160 ° C. for 20 minutes to prepare a test piece, and the vulcanized physical properties were measured in the same manner as in Example 1. The results are shown in Table 3.

Example 7 50 parts by weight of the rubbery copolymer obtained in Example 1 and acrylonitrile-butadiene copolymer rubber (NBR) (Nipol DN402 manufactured by Zeon Corporation; acrylonitrile amount 22%, ML _{1 +} 4,100) A rubber compounding composition was obtained according to the compounding formulation of Table 1 compounding 1 using 50 parts by weight as a raw rubber. This rubber compounding composition was press-vulcanized at 160 ° C. for 20 minutes to prepare a test piece, and the vulcanized physical properties were measured in the same manner as in Example 1. The results are shown in Table 3.

Comparative Example 3 Nipol 1502 (styrene content 2
3.5%, 50 parts by weight of ML _{1 + 4} , 100 ° C. = 52) and 50 parts by weight of Nipol 1220 manufactured by Zeon Corporation (98% cis-1,4 bond unit amount, ML _{1 + 4} , 100 ° C. = 43) As a raw material rubber, a rubber compounding composition was obtained according to the compounding recipe shown in Table 1 Compounding 1. This rubber compounding composition was press-vulcanized at 160 ° C. for 20 minutes to prepare a test piece, and the vulcanized physical properties were measured in the same manner as in Example 1. The results are shown in Table 3.

Comparative Example 4 Nipol 1502 (styrene content 2 manufactured by Nippon Zeon Co., Ltd.)
50% by weight of 3.5%, ML _{1 + 4} , 100 ° C. = 52) and 50 parts by weight of Zeon Nippon Nipol DN402 (acrylonitrile amount 22%, ML _{1 + 4} , 100 ° C. = 55) are used as raw rubbers. A rubber compounding composition was obtained with the compounding formulation of Table 1 compounding 1. This rubber compounding composition was press-vulcanized at 160 ° C. for 20 minutes to prepare a test piece, and the vulcanized physical properties were measured in the same manner as in Example 1. The results are shown in Table 3.

[0043]

[Table 3]

From Table 3, it is clear from the comparison between Example 5 and Comparative Example 1 (described in Table 2), Example 6 and Comparative Example 3 and Example 7 and Comparative Example 4 that the conventional SBR was replaced. It can be seen that the vulcanized product obtained by blending the rubber copolymer of the present invention with other general-purpose rubbers exhibits high impact resilience and high abrasion resistance.

[0045]

Since the rubber composition of the present invention has excellent impact resilience and abrasion resistance, it is particularly suitable as a rubber material for automobile tire treads, but it is suitable for bicycle tires, shoe soles, and floors. It can also be used for applications such as wood.

Claims (2)

[Claims] 1. 0.5 to 20% by weight of a polymerizable monomer having a tertiary amino group, and an aliphatic conjugated diolefin monomer 2
0-99.5% by weight and aromatic vinyl monomer 0-60
A vulcanizable rubber composition comprising a rubber-like copolymer obtained by emulsion-polymerizing a monomer mixture containing 1% by weight and sulfur, a sulfenamide-based vulcanization accelerator, and carbon black. 2. A polymerizable monomer having a tertiary amino group, wherein the polymerizable monomer has an N-di-substituted aminoalkyl acrylate, an N-di-substituted aminoalkyl acrylamide, an N-di-substituted amino aromatic compound and a pyridyl group. The compound according to claim 1, which is at least one kind of monomer selected from monomers.
The rubber composition described.