JPH06107855A - Vulcanizable rubber composition - Google Patents

Abstract

PURPOSE:To obtain a vulcanizable rubber composition having improved resilien cy and low heat buildup by using a radicalpolymerized diene copolymer rubber containing repeating units derived from a monomer having a specified structure in the molecule. CONSTITUTION:The composition is obtained by mixing a radical-polymerized diene copolymer rubber containing repeating units derived from a monomer having a >C=N structure in the molecule (e.g. a copolymer rubber obtained by copolymerizing a monomer having a >C=N structure in the molecule such as 2-vinyl-2-oxazoline, with a conjugated diene monomer such as 1,3-butadiene or radical-copolymerizing them with a monoolefinic monomer such as styrene) with a vulcanization system (e.g. sulfur). This composition comprising the diene copolymer rubber has improved resiliency and reduced heat buildup without lowering the processability in kneading and molding.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vulcanizable rubber composition containing a radical-polymerized diene-based copolymer rubber having improved impact resilience and reduced internal exothermicity, and a vulcanizing agent.

[0002]

2. Description of the Related Art Recently, the tendency toward low fuel consumption of automobiles has become stronger and stronger. As a result, reduction of rolling resistance and reduction of heat generation of tires have been strongly demanded. In order to reduce the rolling resistance of the tire, it is necessary that the tread rubber material has a high impact resilience.
It is necessary that the impact resilience evaluated at temperatures up to around ℃ is high. Further, in order to reduce the energy loss when transmitting the driving force from the engine to the road surface, it is necessary that the tread rubber material has a low internal heat generation property.

Conventionally, as rubber materials satisfying such requirements, styrene-butadiene copolymer rubber (SBR) whose microstructure is controlled by solution polymerization and carbon black are used in order to improve dispersibility. The modified SBR etc. which introduced the functional group of were used.

In general, a styrene-butadiene copolymer rubber produced by anionic polymerization is capable of controlling the microstructure and modifying the end of the molecular chain, and as a result, it is possible to improve the impact resilience and reduce the internal exothermicity. Although it is advantageous to reduce the rolling resistance of the tire, it has a problem in extrusion workability due to the narrow molecular weight distribution. That is, there was a problem in the shape of the extrudate in the molding process using the extruder.

[0005]

DISCLOSURE OF THE INVENTION As a result of intensive studies to solve the above-mentioned drawbacks, the present inventors have found that radical copolymerization of a diene monomer with a monomer having a specific bond in the molecule is carried out. The diene-based copolymer rubber obtained by the present invention has been found to have good impact resilience and reduced internal exothermicity without deteriorating processability during kneading and molding. Is.

[0006]

Thus, according to the present invention, a radical-polymerized diene-based copolymer rubber containing a monomer unit having a> C = N-structure in the molecule in the copolymer chain, and A vulcanizable rubber composition including a vulcanization system is provided.

By carrying out the present invention, taking a tire as an example, it is possible to obtain a composition in which rolling resistance and processability, which are important for the recent tire performance, are matched at a high level. Hereinafter, the present invention will be described in detail.

The radically polymerized diene-based copolymer rubber of the present invention comprises a monomer having a> C = N-structure in the molecule and a conjugated diene-based monomer, or these and a monoolefin-based monomer. It is a copolymer rubber obtained by radically copolymerizing.

Examples of the monomer having a> C = N-structure in the molecule (hereinafter sometimes referred to as monomer I) include, for example, 2-vinyl-2-oxazoline and 2-vinyl-4.
-Methyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, 2-vinyl-4-ethyl-2-oxazoline, 2-isopropenyl-2-oxazoline,
2- (4-vinylphenyl) -2-oxazoline, 2-
Isopropenyl-4-methyl-2-oxazoline, 2-
Isopropenyl-5-methyl-2-oxazoline, 2-
Oxazoline group-containing monomers such as isopropenyl-4,5-dimethyl-2-oxazoline and the corresponding thiazoline group-containing monomers shown on the left; 1-vinylimidazole, 2-vinylimidazole, 1-methyl- 2-vinyl imidazo
1-vinyl-2,4-dimethylimidazole, 2-
An imidazole group-containing monomer such as isopropenyl imidazole and the corresponding thiazole group-containing monomer shown on the left;

1-vinyl-2-imidazoline, 1-vinyl-2-methyl-2-imidazoline, 2-vinyl-2-
Imidazoline, 2-vinyl-3-methyl-2-imidazoline and other imidazoline group-containing monomers; 2-vinylbenzoxazol, 2-vinylbenzothiazole, 2-vinylbenzimidazole and the like; 5 1,6-oxazine group-containing monomers such as 6,6-dihydro-2-vinyl-4H-1,3-oxazine and 5,6-dihydro-2-isopropenyl-4H-1,3-oxazine; 4-Dimethyl-6-vinyl-1,3,5-triazine, 2,4-diamino-6-vinyl-1,3,5-triazine, 2-anilino-4-amino-6-vinyl-1,3, 5-triazine, 2-N-vinylanilino-4-hydroxy-6-methoxy-1,3,5-
Triazine group-containing monomers such as triazine; acryloylguanidine, tetramethylacryloylguanidine, N
-Benzylidene vinylamine, N-butyl isomaleimide, etc. are mentioned. These monomers are used alone or in combination of two or more.

Examples of the conjugated diene monomer include, for example,
1,3-butadiene, 2-methyl-1,3 butadiene, 2
-Chloro-1,3 butadiene, 1,3-pentadiene and the like can be mentioned, and one or more of these can be used.

Examples of the monoolefin type monomer include styrene, α-methylstyrene, 2-methylstyrene and 3-methylstyrene.
Methylstyrene, 4-methylstyrene, 2,4-diisopropylstyrene, 2,4-dimethylstyrene, 4-t
-Aromatic vinyl monomers such as butyl styrene, 5-t-butyl-2-methylstyrene, monochlorostyrene, dichlorostyrene, monofluorostyrene, hydroxymethylstyrene; vinyl cyanide monomers such as acrylonitrile and methacrylonitrile. Methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, 2-ethylhexyl acrylate, methacrylic acid-
Ester of acrylic acid or methacrylic acid such as 2-ethylhexyl, hydroxyethyl acrylate and hydroxyethyl methacrylate; unsaturated amide compounds such as acrylamide, methacrylamide, N-methylol acrylamide, diacetone acrylamide; acrolein, vinyl chloride, vinyl acetate Vinyl monomers such as
These 1 type (s) or 2 or more types are used. Particularly preferred are aromatic vinyl monomers and vinyl cyanide monomers.

The amount of the monomer I used is in the range of 0.01 to 20% by weight in the total monomer mixture (the same applies to the following monomers). If it is less than 0.01% by weight, the effect of improving the impact resilience is reduced, and if it exceeds 20% by weight, the balance between workability and impact resilience is reduced. It is preferably 0.1 to 10% by weight, more preferably 0.5 to 5% by weight.

The amount of the conjugated diene monomer used is 40 to 9
It is 9.99% by weight. If it exceeds 99.99% by weight, improvement in impact resilience cannot be expected. Further, if it is less than 40% by weight, rubber elasticity is lowered, which is not preferable. From the viewpoint of the balance between wet skid resistance and impact resilience, it is preferably 55 to 85% by weight.

The amount of the monoolefin monomer used is 0 to 6
It is in the range of 0% by weight. If it exceeds 60% by weight, rubber elasticity is lowered, which is not preferable. From the viewpoint of strength characteristics and wet skid resistance, the range of 5 to 50% by weight is preferable. More preferably, it is in the range of 10 to 40% by weight.

The radical-polymerized diene polymer rubber of the present invention can be produced by radical polymerization of the above-mentioned monomer mixture. Although it can be produced by solution polymerization using a radical polymerization initiator, it is particularly preferably produced by emulsion polymerization. Emulsion polymerization may be carried out using a usual emulsion polymerization technique and is not particularly limited.

Therefore, the agents necessary for the polymerization such as the emulsifier and the radical polymerization initiator used in the emulsion polymerization can be those conventionally used and are not particularly limited. As the emulsifier, a long-chain fatty acid salt having 10 or more carbon atoms and / or a rosin acid salt or the like is usually used. For example, capric acid, lauric acid, myristic acid, palmitic acid, oleic acid,
Examples include 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;
Redox initiators such as a combination of ammonium persulfate and ferric sulfate, a combination of organic peroxide and ferric sulfate, and a combination of hydrogen peroxide and ferric sulfate are usually used. In particular, redox formulations consisting of organic peroxide, sodium formaldehyde sulfoxylate and ferric sulfate are common.

Examples of the chain transfer agent for controlling the molecular weight of the polymer include mercaptans such as n-dodecyl mercaptan and t-dodecyl mercaptan; carbon tetrachloride; thioglycolic acid; diterpene, terbinolene,
γ-Terpinenes are usually used.

The emulsion polymerization is usually carried out at a temperature of 0 to 100 ° C, preferably 0 to 60 ° C. The polymerization mode may be any of continuous polymerization, batch polymerization and the like. When the conversion rate of the monomer into the polymer increases, the produced polymer tends to gel. In order to obtain a polymer having a small amount of gel, the conversion rate is 80% or less, preferably 40 to 70.
It is preferable to terminate the polymerization at a point in the range of%. The polymerization is usually stopped by adding a polymerization terminator to the polymerization system when a predetermined conversion rate is reached. Examples of the polymerization terminator include amine compounds such as diethylhydroxylamine and hydroxylamine; hydroquinone,
Quinone compounds such as benzoquinone; sodium nitrate, sodium dithiocarbamate and the like are usually used.

After termination of the polymerization, unreacted monomers are recovered, if necessary, and an acid such as nitric acid or sulfuric acid is added to the obtained polymer latex to adjust the pH of the latex to a predetermined value.
Then, a salt such as sodium chloride, calcium chloride or potassium chloride is added and mixed as a coagulant to coagulate the polymer as a crumb, followed by dehydration and drying to obtain the diene polymer rubber of the present invention. From the viewpoint of processability, the diene polymer rubber of the present invention has a Mooney viscosity (ML1 + 4, 100 ° C.) in the range of 20 to 150, and further 3
It is preferably in the range of 0 to 100.

The diene polymer rubber of the present invention thus obtained contains a monomer unit having a> C = N-structure in the polymer chain. It is possible to ionize the structural part. Examples of the cationizing agent include methyl tosyl sulfonate, dimethyl sulfate, fluoroacetic acid, perchloric acid, sodium tetrafluoroborate and the like.

The vulcanizable rubber composition of the present invention is produced by mixing the above-described diene polymer rubber of the present invention and a vulcanizing system. At that time, depending on the intended use (application) of the rubber composition of the present invention, various compounding agents commonly used in the rubber industry together with the vulcanization system, for example, HA of various grades.
Carbon black such as F and ISAF, a reinforcing agent such as silica, a filler such as calcium carbonate, a process oil, a processing aid, a stabilizer and the like can be added.

As the vulcanization system used in the present invention, a vulcanization system usually used in the rubber industry can be used, and an optimum vulcanization system is selected according to the intended purpose (use) of the composition of the present invention. There is no particular limitation as long as it does. For example, as a sulfur-based vulcanization system, sulfur or tetramethylthiuram disulfide,
Sulfur-donating compounds such as morpholine disulfide, stearic acid, zinc white, various vulcanization accelerators (such as thiazole-based, thiuram-based and sulfenamide-based) are used as organic peroxide vulcanization systems such as dicumyl peroxide, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, 2,
Organic peroxides such as 5-dimethyl-2,5-di (t-butylperoxy) hexyne-3,2,5-dimethyl-2,5-di (benzoylperoxy) hexane or triallyl cyanurate , Triallyl isocyanurate
And trimethylol propane trimethacrylate, ethylene dimethacrylate, diallyl phthalate, divinylbenzene, toluylene bismaleimide, high vinyl polybutadiene and the like in combination with a crosslinking aid.

The rubber composition of the present invention may be used by blending the diene polymer rubber of the present invention with another diene polymer rubber rubber as long as the effect of the present invention is not impaired. Other diene polymer rubbers include natural rubber, polyisoprene rubber, polybutadiene rubber, styrene-butadiene copolymer rubber, acrylonitrile-butadiene copolymer rubber, butyl rubber, halogenated butyl rubber, ethylene-propylene-diene copolymer. Rubber (EPDM),
And epichlorohydrin gum. When a mixture of these diene polymer rubbers and the diene polymer rubber of the present invention is used as a rubber component, the diene polymer rubber of the present invention in the mixture is at least 10% by weight, preferably 20% by weight. As described above, it is necessary to use 30% by weight or more. If it is less than 10% by weight, the effect of the present invention cannot be expected.

The diene polymer rubber of the present invention is kneaded and mixed with the above-mentioned various compounding agents using a mixer such as a roll or Banbury to obtain a rubber composition. The vulcanizate of the rubber composition of the present invention has improved impact resilience and internal exothermicity, which is a feature of> C = N- introduced into the diene polymer rubber of the present invention. It is considered that this was caused by the fact that the rubber caused specific adsorption to carbon black due to its structure and improved the dispersibility of carbon black.

[0027]

EXAMPLES The present invention will be described in detail below with reference to examples. The parts and% in the examples are by weight unless otherwise specified.

Polymerization Example A polymerization vessel equipped with a stirrer was charged with 200 parts of water, 3 parts of rosin acid soap, 0.2 parts of t-dodecyl mercaptan as a chain transfer agent and the monomer mixture of Experiment No. 1. The temperature of the polymerization vessel was set to 5 ° C, and as a radical initiator system, 0.1 part of cumene hydroperoxide, 0.2 part of sodium formaldehyde sulfoxylate, and 0.02 part of ferric sulfate were used.
Polymerization was started by adding 1 part.

When the polymerization conversion rate reached 60%, diethylhydroxylamine was added to stop the reaction. Then, the unreacted monomer was recovered, the copolymer was coagulated with sulfuric acid and sodium chloride to form crumb, and dried under reduced pressure to obtain the intended diene copolymer rubber of the present invention. Further, in the same manner, a diene copolymer rubber was obtained by using the monomer mixture of Table 1 and Experiment Nos. 2 to 7.

[0030]

[Table 1]

The monomer composition and the polymer-n-viscosity (M
L1 + 4,100 ° C.) is shown in Table 3. The amount of styrene is determined from the refractive index, and the amount of monomer having a> C = N- structure in the molecule is determined by GPC equipped with a differential refractive index detection multi-wavelength detector and an ultraviolet absorption detector.
The wavelength of the ultraviolet absorption detector of the
To 330 nm), and the amount of acrylonitrile was determined by the Kjeldahl method from the calibration curve prepared in advance from the peak area ratios obtained by the refractive index detector and the ultraviolet absorption detector.

Examples 1 to 5 and Comparative Examples 1 and 2 Each of the seven diene copolymer rubbers obtained by the method of the above-mentioned polymerization example was prepared in accordance with the compounding recipe shown in Table 2 with each compounding agent and a volume of 250 ml. Each rubber compounding composition was obtained by kneading in a Brabender type mixer. These rubber compounding compositions were press-vulcanized at 160 ° C. for 20 minutes to prepare test pieces,
According to JIS K6301, the Muni-viscosity of the unvulcanized compounded composition and the strength characteristics and impact resilience of the vulcanized product (Lupke type, measurement temperature 60 ° C.) were measured according to JIS K6301, and the heat generation was goodrich flexo. Using a meter (test temperature 10
(0 ° C) was measured. The extrusion processability was evaluated by the 5-point method (5 excellent ← → inferior 1) in terms of the shape of the extruded product by the extruder, surface texture and winding property during roll processing. The above results are shown in Table 3.

[0033]

[Table 2]

[0034]

[Table 3]

Examples 6 to 8, Comparative Examples 3 and 4, SBR (styrene-butadiene copolymer rubber, styrene content 23.5%) of each of the copolymer rubbers of Examples 1 and 3 of Table 3: Japan Zeon Nipol 150
2), BR (high cis polybutadiene rubber: Nipol 1220 manufactured by Nippon Zeon Co., Ltd.) or NBR (acrylonitrile-butadiene copolymer rubber, acrylonitrile amount 22%; Nipol DN402 manufactured by Nippon Zeon Co., Ltd.) in a mixture of 1/1 in Table 2 A rubber compounding composition was prepared by adding each compounding agent of the compounding recipe described. Each rubber compound composition obtained was press-vulcanized at 160 ° C. for 20 minutes to prepare a test piece, which was tested in the same manner as in the above-mentioned Examples. The results are shown in Table 4.

[0036]

By carrying out the present invention, taking a tire as an example, it is possible to obtain a composition in which the rolling resistance and workability required for the recent tire performance described above are harmonized at a high level. It can also be used for shoe soles, flooring and the like.

[Table 4]

Claims (3)

[Claims] 1. A vulcanizable rubber composition comprising a radical-polymerized diene-based copolymer rubber containing a monomer unit having a> C═N-structure in the molecule in a copolymer chain and a vulcanized system. . 2. The vulcanizable rubber composition according to claim 1, wherein the content of the monomer unit is 0.01 to 20% by weight in the diene copolymer rubber. 3. The vulcanizable rubber composition according to claim 1, wherein the diene-based copolymer rubber is a copolymer rubber of a conjugated diene-based monomer and a monomer having the structure.