JP3216267B2 - Vulcanizable rubber composition - Google Patents

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 radically polymerized diene copolymer rubber having vulcanization characteristics such as improved processability, green strength and rebound resilience.

[0002]

2. Description of the Related Art Conventionally, rubbers having polar groups such as carboxyl groups introduced therein, for example, maleic anhydride or glyoxyza, have been used for the purpose of obtaining rubber compositions having improved green strength and adhesiveness of vulcanizates. And α, β
A method of copolymerizing an unsaturated dicarboxylic acid or a phosphorus-containing compound having an ethylenic double bond (JP-A-59-22)
No. 1316, Japanese Unexamined Patent Publication (Kokai) No. 59-187011, etc.)
It has been known. However, these rubbers have the disadvantage that during the modification reaction, secondary reactions such as gelation of the rubber and a decrease in the molecular weight occur, and even when introduced, the strength properties and dynamic properties of the vulcanized product are extremely reduced. Have.

[0003] In recent years, automobiles have become increasingly fuel-efficient, and as a result, there has been a strong demand especially for a reduction in tire rolling resistance and a reduction in heat generation. In order to reduce the rolling resistance of the tire, it is necessary for the tread rubber material to have a high rebound resilience.
It is necessary that the rebound resilience evaluated at a temperature up to the vicinity 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 internal heat generation of the tread rubber material is low.

Conventionally, rubber materials satisfying such requirements include styrene-butadiene copolymer rubber (SBR) whose microstructure is controlled by anionic polymerization, and modified SBR in which a specific functional group is introduced at a molecular chain terminal or the like. Was used.

In general, styrene-butadiene copolymer rubber obtained by anionic polymerization can control the microstructure and modify the molecular chain terminals, and as a result, can improve the rebound resilience and reduce the internal heat generation. Although it is advantageous to reduce the rolling resistance of the tire, there is a problem in the extrudability due to the narrow molecular weight distribution. When carbon black is blended with the above-mentioned modified SBR, the Mooney viscosity of the blend (usually referred to as compound Mu-viscosity) is the same as that when unmodified SBR is used. , And also has a problem in extrusion processability. Specifically, there is a problem in the shape of an extruded product in a forming process using an extruder.

[0006]

The inventors of the present invention have conducted intensive studies to solve the above-mentioned drawbacks and found that a radical copolymerization of a diene monomer and a monomer having a specific bond in the molecule. The use of the resulting diene-based copolymer rubber improves the green strength of the unvulcanized compound and improves the compound strength.
The present invention has been found to suppress the rise in viscosity and to have good rebound resilience and reduced internal heat generation without lowering the workability during kneading and molding.

[0007]

Thus, according to the present invention, a monomer unit having a structure of> C = N ⁺ <in a copolymer chain or a monomer having a carbocation group in a molecule is provided. Provided are a vulcanizable rubber composition containing a radical polymerized diene-based copolymer rubber containing a unit and a vulcanized system.

Hereinafter, the present invention will be described in detail. The radical polymerized diene-based copolymer rubber of the present invention comprises a monomer having a structure of> C = N ⁺ <in the molecule or a monomer having a carbocation group in the molecule and a conjugated diene-based monomer, Alternatively, it is a copolymer rubber obtained by radical copolymerization of these with a monoolefin-based monomer.

Examples of the monomer having a structure of> C = N ⁺ <in the molecule (hereinafter sometimes referred to as monomer I) include, for example, pyrroline-based monomers represented by the chemical formulas (1) to (3). Oxazoline monomer represented by chemical formulas (4) to (8); Oxazine monomer represented by chemical formula (9); Thiazole-based monomer represented by chemical formulas (10) to (13) Body; imidazoline-based monomers represented by chemical formulas (14) and (15); and dithiane-based monomers represented by chemical formula (16). R _{1 to} R ₃ in these chemical formulas represent hydrogen or a hydrocarbon group having 1 to 4 carbon atoms, and X ⁻ represents CF ₃ C
_{^{OO -, BF 4 -, ClO}} 4 -, OH -, Cl -, CH 3 -Ph
Represents an anion such as —SO ₃ ⁻ (Ph represents a benzene ring). One or two or more of these monomers are used.

[0010]

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[0020]

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[0021]

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[0022]

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[0023]

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[0024]

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[0025]

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A monomer having a carbocation group in the molecule (sometimes referred to as monomer II) has a chemical formula (1)
A monomer having the structure represented by 7) in the molecule, for example, monomers represented by chemical formulas (18) and (19) and the like. R ₁ and X ⁻ represent the same anions as described above.

[0027]

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[0028]

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[0029]

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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, and one or more of these are used.

Examples of the monoolefin monomer include styrene, α-methylstyrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene,
4-diisopropylstyrene, 2,4-dimethylstyrene, 4-t-butylstyrene, 5-t-butyl-2-
Aromatic vinyl monomers such as methylstyrene, monochlorostyrene, dichlorostyrene, monofluorostyrene, and hydroxymethylstyrene;

Vinyl cyanide monomers such as acrylonitrile and methacrylonitrile; methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate;
2-ethylhexyl acrylate, methacrylic acid-2-
Esters of acrylic acid or methacrylic acid such as ethylhexyl, hydroxyethyl acrylate, hydroxyethyl methacrylate; unsaturated amide compounds such as acrylamide, methacrylamide, N-methylolacrylamide, diacetone acrylamide; acrolein, vinyl chloride, vinyl acetate, etc. Vinyl monomers and the like,
One or more of these are used. Particularly preferred are aromatic vinyl monomers and vinyl cyanide monomers.

The amount of the monomer I or the monomer II used is from 0.01 to 0.01 in the total monomer mixture (the same applies to the following monomers).
It is in the range of 20% by weight. If it is less than 0.01% by weight, the effect of improving green strength and rebound resilience decreases, and if it exceeds 20% by weight, the balance between processability and rebound resilience decreases. Preferably from 0.1 to 10% by weight, more preferably from 0.5 to 10% by weight.
5% by weight.

The amount of the conjugated diene monomer used is 40 to 9
9.99% by weight. If it exceeds 99.99% by weight, improvement in green strength and rebound resilience cannot be expected. Also, 40
If it is less than the weight percentage, the rubber elasticity decreases, which is not preferable. From the viewpoint of the balance between wet skid resistance and rebound resilience, the content is preferably 55 to 85% by weight.

The amount of the monoolefin monomer used is from 0 to 6
The range is 0% by weight. If it exceeds 60% by weight, rubber elasticity is undesirably reduced. The range of 5 to 50% by weight is preferable from the viewpoint of strength characteristics and wet skid resistance. 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 subjecting the above monomer mixture to radical polymerization. Although it can be produced by solution polymerization using a radical polymerization initiator, production by emulsion polymerization is particularly preferred. Emulsion polymerization may be performed by a usual emulsion polymerization technique, and is not particularly limited.

The chemicals required for polymerization, such as an emulsifier and a 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 and / or a rosinate having 10 or more carbon atoms are usually used. Examples include capric acid, lauric acid, myristic acid, palmitic acid, oleic acid, stearic acid and the like, and potassium salts or sodium salts thereof.

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 an organic peroxide and ferric sulfate, and a combination of hydrogen peroxide and ferric sulfate are usually used. In particular, a redox formulation comprising an organic peroxide, sodium formaldehyde sulfoxylate and ferric sulfate is generally used.

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; diterpenes, tabino-lenes,
γ-terpinenes are usually used.

The emulsion polymerization is carried out usually at a temperature of 0 to 100 ° C., preferably at a temperature of 0 to 60 ° C. The polymerization mode may be any mode such as continuous polymerization or batch polymerization. When the conversion of the monomer into the polymer increases, the resulting polymer tends to gel. In order to obtain a polymer having a small amount of gel, the conversion is preferably from 40 to 70 when the conversion is 80% or less.
It is preferable to stop the polymerization at the time point in the range of%. The polymerization is usually stopped by adding a polymerization terminator to the polymerization system when a predetermined conversion is reached.

As the polymerization terminator, for example, amine compounds such as diethylhydroxylamine and hydroxylamine; quinone compounds such as hydroquinone and benzoquinone; sodium nitrate and sodium dithiocarbamate are usually used.

After termination of the polymerization, if necessary, unreacted monomers are recovered, 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, potassium chloride or the like is added and mixed as a coagulant to coagulate the polymer as crumb, dehydrated and dried to obtain the diene polymer rubber of the present invention. The diene polymer rubber of the present invention has a Mooney viscosity (ML1 + 4, 100 ° C.) in the range of 20 to 150, and more preferably 3 in view of processability.
It is preferably in the range of 0 to 100.

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

As the vulcanizing system used in the present invention, a vulcanizing system usually used in the rubber industry can be used, and an optimum vulcanizing system is selected according to the intended use (use) of the composition of the present invention. There is no particular limitation as long as it is performed. For example, sulfur-based vulcanization systems include sulfur or tetramethylthiuram disulfide,
Examples thereof include sulfur-donating compounds such as morpholine disulfide, stearic acid, zinc white, and various vulcanization accelerators (such as thiazole, thiuram, and sulfenamide).

The organic peroxide vulcanization system includes dicumyl peroxide, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, and 2,5-dimethyl-2,5-di (t- Organic peroxides such as butylperoxy) hexyne-3,2,5-dimethyl-2,5-di (benzoylperoxy) hexane or triallycyanurene
, Triallyl isocyanurate, trimethylolpropane trimethacrylate, ethylene dimethacrylate,
Use in combination with a cross-linking aid such as diallyl phthalate, divinylbenzene, toluylenebismaleimide, or high vinyl polybutadiene may be mentioned.

The rubber composition of the present invention can be used by blending the diene polymer rubber of the present invention with another diene polymer rubber rubber as long as the effects of the present invention are 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 rubber.

When a mixture of the diene polymer rubber and the diene polymer rubber of the present invention is used as the rubber component, the mixture contains at least 10% by weight, preferably at least 10% by weight of the diene polymer rubber of the present invention. It is necessary to use 20% by weight or more, more preferably 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 a Banbury to form a rubber composition. The vulcanizates of the rubber composition of the present invention have improved rebound resilience and internal heat build-up, which is characterized by> C = N ⁺ incorporated into the diene polymer rubber of the present invention. It is considered that the rubber caused specific adsorption to carbon black due to the structure or carbocation, and the dispersibility of carbon black was improved.

[0050]

The present invention will be described below in detail with reference to examples. The parts and percentages in the examples are on a weight basis unless otherwise specified.

Polymerization Example A polymerization vessel equipped with a stirrer was charged with 200 parts of water, 3 parts of a rosin acid soap, 0.2 parts of the monomer mixture of Table 1, Experiment No. 1, and t-dodecyl mercaptan as a chain transfer agent. The temperature of the polymerization vessel was set at 5 ° C., and 0.1 part of cumene hydroperoxide, 0.2 part of sodium formaldehyde sulfoxylate and 0.0 part of ferric sulfate were used as radical initiator systems.
One part was added to initiate the polymerization.

When the polymerization conversion reached 65%, the reaction was stopped by adding diethylhydroxylamine. Next, the unreacted monomer was recovered, and the copolymer was coagulated with sulfuric acid and sodium chloride to form a crumb. After drying under reduced pressure, the desired diene copolymer rubber of the present invention was obtained. Similarly, diene copolymer rubbers were obtained using the monomer mixtures shown in Table 1 and Experiment Nos. 2 to 4.

[0053]

[Table 1]

The four diene copolymer rubbers thus obtained had a monomer composition and a polymer-ny viscosity (M
L1 + 4,100 ° C.) are shown in Table 3. From the refractive index, the amount of the monomer having a structure of> C = N ⁺ <and the amount of the monomer having a carbocation are determined by the refractive index detection multi-wavelength detector and the GPC equipped with an ultraviolet absorption detector. The wavelength of the ultraviolet absorption detector is set to the absorption wavelength of the structure (290 to 330 nm)
, And each was obtained from a calibration curve prepared in advance from the peak area ratio obtained from the refractive index detector and the ultraviolet absorption detector.

Examples 1 to 3 and Comparative Example 1 Each of the four types of diene copolymer rubbers obtained by the method of the above polymerization example was mixed with each compounding agent according to the compounding formula shown in Table 2 and a Brabender having a capacity of 250 ml. Each rubber compounded composition was obtained by kneading in a type mixer. Test specimens were prepared by press vulcanizing these rubber compounded compositions at 160 ° C. The Mooney viscosity (compound Mooney viscosity) of the unvulcanized compounded composition and the strength properties and rebound resilience (Lupke method, measurement temperatures of 0 ° C., 23 ° C. and 6 ° C.) of the vulcanizate according to JIS K6301.
0 ° C.) was measured for wear resistance using a pico abrasion tester,
The result of Comparative Example 1 was indicated by an index with the value being 100 (the larger the value, the better the abrasion resistance).

The extrudability was evaluated by the five-point method (5 excellent ← → poor 1) of the shape of the extruded product by the extruder, the surface texture and the winding property during roll processing. The green strength was determined by pressing an unvulcanized rubber compounded composition at 100 ° C. for 5 minutes, and
A dumbbell-shaped JIS No. 3 test piece was punched out as a sheet having a thickness, and a tensile test was performed at 25 ° C. at a tensile speed of 500 mm / min.
Table 3 shows the above results.

[0057]

[Table 2]

[0058]

[Table 3]

Examples 4 to 6 and Comparative Example 2 Four kinds of diene polymer rubbers were obtained by using the respective monomer mixtures shown in Table 4 in the same manner as in the above polymerization examples. A rubber compounding composition was prepared using the compounding recipe shown in Table 2 in the same manner as in the above example, and the unvulcanized compounded rubber composition was prepared using this compound.
The viscosity, green strength, processability and vulcanization properties were measured.
Table 5 shows the results.

[0060]

[Table 5]

Examples 7 and 8, Comparative Examples 3 and 4 Each of the copolymer rubbers of Examples 1 and 6 was added to SB
R (styrene-butadiene copolymer rubber, styrene content 2
3.5%: Nipol 1502 manufactured by Zeon Corporation, BR
(High cis polybutadiene rubber: Nipo manufactured by Zeon Corporation)
l1220) or NBR (acrylonitrile-butadiene copolymer rubber, acrylonitrile content 22%; Nipol DN402 manufactured by Nippon Zeon Co., Ltd.) to a 1/1 mixture thereof with each compounding agent of the compounding formula shown in Table 2 and rubber compounding. A composition was made. Each of the obtained rubber compounding compositions was mixed with 16
A test piece was prepared by press vulcanization at 0 ° C. for 20 minutes, and tested in the same manner as in the above example. The results are shown in Table 6.

[0062]

[Table 6]

[0063]

According to the present invention, in the case of a tire as an example, a composition which balances the above-mentioned rolling resistance and workability required for recent tire performance at a high level can be obtained. It can also be used for applications such as shoe soles and flooring.

[Table 4]

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-6-107855 (JP, A) JP-A-4-300931 (JP, A) JP-A-4-300930 (JP, A) JP-A-2- 117939 (JP, A) JP-A-2-49040 (JP, A) JP-A-3-263468 (JP, A) JP-A-59-131681 (JP, A) JP-A-57-170912 (JP, A) JP-A-57-170910 (JP, A) JP-A-52-19727 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08L 9/00 C08J 3/24 C08K 5/14 C08K 5/36

Claims (4)

(57) [Claims] 1. A radically polymerized diene copolymer containing, in a copolymer chain, a monomer unit having a structure of> C = N ⁺ <in a molecule or a monomer unit having a carbocation group in a molecule. A vulcanizable rubber composition comprising a united rubber and a vulcanization 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 copolymer rubber is a copolymer rubber of a conjugated diene monomer and a monomer having the structure or the group. object. 4. The process according to claim 1, wherein the diene copolymer rubber is a copolymer rubber of a conjugated diene monomer, a monomer having the structure, and a monoolefin monomer. Vulcanizable rubber composition.