JP2003113287A - Rubber composition improved in wet gripping property - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a rubber composition improved in wet gripping properties without spoiling the breaking strength of a tire. SOLUTION: This rubber composition consists of a block copolymer (A) comprising a polymer block mainly comprising isobutylene and a polymer block mainly comprising an aromatic vinyl compound, an adhesiveness-imparting resin (B) and at least one species of rubber component (C) selected from a group comprising natural rubber, diene-based polymer rubber and olefin-based polymer rubber. The rubber component (C) is preferably crosslinked.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a rubber composition for tires containing an isobutylene block copolymer having improved wet grip properties.

[0002]

2. Description of the Related Art In recent years, there has been a strong demand for lower fuel consumption of automobiles, especially reduction of rolling resistance of tires, and from a safety point of view, it is possible to provide a tire having high grip performance on wet road surfaces, that is, high wet grip performance. A rubber composition is sought.

The wet grip property is related to the hysteresis loss (tan δ) of the tread rubber, and has a frequency of 1
It is known that the larger the tan δ at 0 ° C. at 0 Hz, the higher the wet grip property.

As a rubber composition for a tread used for such a pneumatic tire in the field of automobiles, Japanese Patent Application Laid-Open No. 11-80433 discloses polyisobutylene / p-.
A rubber composition for a tread comprising a bromide of a methylstyrene copolymer and a rubber component is disclosed. However, styrene-butadiene rubber (S
Since the vulcanization rates of BR), butadiene rubber (BR), and natural rubber (NR) are significantly different, there is a problem that processability and productivity are deteriorated. In addition, JP-A-11-3151
No. 71 discloses a rubber composition containing a styrene-isobutylene copolymer as a rubber component,
This is to add a styrene-isobutylene random copolymer as a plasticizer component, and improves the wet grip property by lowering the elastic modulus of the rubber composition. However, the addition of the plasticizer component has a problem that the hardness is lowered unlike the improvement of the wet grip property by selecting the rubber component. Further, the above publication does not describe a block copolymer.

On the other hand, regarding a rubber composition comprising a styrene-isobutylene block copolymer and a rubber component, W
Although described in O98 / 14518 and Japanese Patent Laid-Open No. 6-200098, all of these publications only disclose that they can be used as a general rubber material, and a rubber composition for a tread in the automobile field. No mention is made of use in applications requiring special properties such as. The present inventors have found that a styrene-isobutylene block copolymer is suitable as a wet grip improver for a rubber composition for tires.
However, as for the number of parts added, the effect of improving wet grip properties did not appear unless a large amount was added, and it was observed that physical properties such as fracture properties tend to deteriorate.

[0006]

That is, the problem to be solved by the present invention is to provide a rubber composition for a tire which improves wet grip properties without impairing the breaking strength of the tire.

[0007]

That is, the present invention provides a block copolymer (A) comprising a polymer block mainly containing isobutylene and a polymer block mainly containing an aromatic vinyl compound, and a tackifying resin ( A rubber composition comprising B) and at least one rubber component (C) selected from the group consisting of natural rubber, diene polymer rubber and olefin polymer rubber, wherein the rubber component (C) is crosslinked. What is formed is preferable.

Loss tangent (Tan δ) obtained by measuring the dynamic viscoelasticity of the mixture of the block copolymer (A) and the tackifying resin (B) in the tensile mode at 10 Hz.
Is preferably 0.5 or more at 0 ° C.

As the compounding amount, the block copolymer (A) is used.
It is preferable to add 10 parts by weight to 50 parts by weight of the tackifying resin (B) to 100 parts by weight, and as a whole rubber composition, the block copolymer (A) is added to 100 parts by weight of the rubber component (C). ) And tackifying resin (B) in total of 1 to 5
It is preferable to add 0 part by weight.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The rubber composition of the present invention comprises a block copolymer (A) comprising a polymer block mainly containing isobutylene and a polymer block mainly containing an aromatic vinyl compound, and a tackifying resin. A rubber composition comprising (B) and at least one rubber component (C) selected from the group consisting of natural rubber, diene polymer rubber and olefin polymer rubber. The rubber composition of the present invention shifts the peak point of loss tangent (Tan δ) obtained by dynamic viscoelasticity measurement in the tensile mode at 10 Hz of (A) to 0 ° C. by adding (B). Therefore, the wet grip property improving effect can be exhibited with a smaller amount of addition to (C). For this reason, the deterioration of the breaking characteristics of the rubber composition is reduced.

The isobutylene block copolymer (A) which can be used in the present invention has a structure called a block copolymer consisting of a polymer block mainly containing isobutylene and a polymer block mainly containing an aromatic vinyl compound. There is no particular limitation as long as it has, for example, a block copolymer, a diblock copolymer, a triblock copolymer, a multiblock copolymer having a linear, branched, or star structure. Any combination or the like can be selected, and one that meets the requirements of mechanical characteristics and workability may be selected.

The isobutylene-based polymer block of the present invention may contain a monomer component other than isobutylene, and the content of the monomer other than isobutylene is 30.
It is preferably not more than 10% by weight, more preferably not more than 10% by weight.

The monomers other than isobutylene in the isobutylene-based polymer block of the present invention are not particularly limited as long as they are cationically polymerizable monomer components, but aromatic vinyls and aliphatic olefins. Examples of the monomer include diene, vinyl ether, and β-pinene. These may be used alone or in combination of two or more.

Aromatic vinyl monomers include styrene, o-, m- or p-methylstyrene, α-methylstyrene, β-methylstyrene, 2,6-dimethylstyrene, 2,4-dimethylstyrene, α-methyl-o-methylstyrene, α-methyl-m-methylstyrene, α-methyl-p-methylstyrene, β-methyl-o-methylstyrene, β-methyl-m-methylstyrene, β-methyl-p -Methylstyrene, 2,4,6-trimethylstyrene, α-methyl-2,6-dimethylstyrene, α-methyl-2,4-dimethylstyrene, β-methyl-2,6-
Dimethylstyrene, β-methyl-2,4-dimethylstyrene, o-, m- or p-chlorostyrene, 2,6-dichlorostyrene, 2,4-dichlorostyrene, α-chloro-o-chlorostyrene, α- Chloro-m-chlorostyrene, α-chloro-p-chlorostyrene, β-chloro-
o-chlorostyrene, β-chloro-m-chlorostyrene, β-chloro-p-chlorostyrene, 2,4,6-trichlorostyrene, α-chloro-2,6-dichlorostyrene, α-chloro-2,4 -Dichlorostyrene, β-chloro-2,6-dichlorostyrene, β-chloro-2,4
-Dichlorostyrene, o-, m- or p-t-butylstyrene, o-, m- or p-methoxystyrene, o-,
m- or p-chloromethylstyrene, o-, m- or p
-Bromomethylstyrene, styrene derivatives substituted with a silyl group, indene, vinylnaphthalene and the like. These may be used alone or in combination of two or more.

Examples of the aliphatic olefinic monomer include ethylene, propylene, 1-butene, 2-methyl-1-butene, 3-methyl-1-butene, pentene, hexene, cyclohexene, 4-methyl-1-pentene. , Vinylcyclohexane, octene, norbornene and the like.
These may be used alone or in combination of two or more.

Examples of the diene-based monomer include butadiene, isoprene, hexadiene, cyclopentadiene, cyclohexadiene, dicyclopentadiene, divinylbenzene and ethylidene norbornene. These may be used alone or in combination of two or more.

The vinyl ether type monomers include methyl vinyl ether, ethyl vinyl ether, (n-, iso) propyl vinyl ether, (n-, sec-, te).
Examples include rt-, iso) butyl vinyl ether, methyl propenyl ether, ethyl propenyl ether and the like. These may be used alone or in combination of two or more.

The polymer block mainly composed of an aromatic vinyl compound of the present invention may or may not contain a monomer other than the aromatic vinyl compound, and the content of the aromatic vinyl compound is 60. It is desirable that the content is not less than wt%, preferably not less than 80 wt%. As the aromatic vinyl-based monomer, it is preferable to use at least one monomer selected from the group consisting of styrene, α-methylstyrene, p-methylstyrene, and indene. From the viewpoint of cost, styrene, α It is particularly preferred to use methylstyrene or mixtures thereof.

The aromatic vinyl compound of the polymer block mainly composed of the aromatic vinyl compound of the present invention is not particularly limited as long as it is a cationically polymerizable monomer. Etc.

The proportion of the polymer block mainly containing isobutylene and the polymer block mainly containing an aromatic vinyl compound is not particularly limited, but a polymer mainly containing isobutylene is used in view of the balance between physical properties and processability. It is preferable that the block is 98 to 40% by weight, the polymer block mainly containing an aromatic vinyl compound is 2 to 60% by weight, and the polymer block mainly containing isobutylene is 95 to 40% by weight.
It is particularly preferable that the content of the polymer block is 60% by weight and the amount of the polymer block mainly containing the aromatic vinyl compound is 5 to 40% by weight.
From the viewpoint of tire characteristics, when the proportion of the polymer block mainly containing isobutylene is increased, the wet grip property is improved, but the fracture properties, that is, the wear resistance and the rolling resistance tend to be decreased.

As a preferred structure of the isobutylene block copolymer of the present invention, a polymer block containing an aromatic vinyl compound as a monomer (b) is used in view of physical properties and processability of the resulting composition. And the polymer block mainly composed of isobutylene is (a). (B)-
A triblock copolymer having a structure of (a)-(b),
Alternatively, it is at least one selected from star-shaped polymers having a diblock copolymer having the structure of (a)-(b) as an arm.

The number average molecular weight of the isobutylene block copolymer is not particularly limited, but from the viewpoint of physical properties and processability, it is preferably 3,000 to 500,000.
Particularly preferably, it is 5,000 to 100,000.
The number average molecular weight of the isobutylene block copolymer is 3,
When it is less than 000, the physical properties of the composition are not sufficiently expressed, while when it exceeds 500,000, there is a tendency of being disadvantageous in terms of processability.

The method for producing the isobutylene block copolymer is not particularly limited, and a known polymerization method can be used. In order to obtain a block copolymer having a controlled structure, the following general formula ( It is preferable to polymerize a monomer containing isobutylene as a main component and a monomer component containing no isobutylene as a main component such as an aromatic vinyl-based monomer in the presence of the compound represented by 1). (CR ¹ R ² X) _n R ³ (1) [In the formula, X represents a substituent selected from the group consisting of a halogen atom, an alkoxyl group having 1 to 6 carbon atoms and an acyloxyl group having 1 to 6 carbon atoms. Represent R ¹ and R ² are respectively
It represents a hydrogen atom or a monovalent hydrocarbon group having 1 to 6 carbon atoms.
R ¹ and R ² may be the same or different. Further, a plurality of R ¹ and R ² may be the same or different. R ³ represents a polyvalent aromatic hydrocarbon group or a polyvalent aliphatic hydrocarbon group which can have n substituents. n represents a natural number of 1 to 6. Examples of the halogen atom include chlorine, fluorine, bromine, iodine and the like. The alkoxyl group having 1 to 6 carbon atoms is not particularly limited, and examples thereof include a methoxy group, an ethoxy group, an n- or isopropoxy group, and the like. The acyloxyl group having 1 to 6 carbon atoms is not particularly limited, and examples thereof include an acetyloxy group and a propionyloxy group. The hydrocarbon group having 1 to 6 carbon atoms is not particularly limited, and examples thereof include a methyl group, an ethyl group and n-
Alternatively, an isopropyl group and the like can be mentioned.

The compound represented by the above general formula (1) serves as an initiator and is considered to form a carbon cation in the presence of a Lewis acid or the like and serve as a starting point of cationic polymerization. Examples of the compound represented by the general formula (1) used in the present invention include the following compounds.

(1-chloro-1-methylethyl) benze
The C₆H_FiveC (CH₃)₂Cl 1,4-bis (1-chloro-1-methylethyl) benze
The 1,4-Cl (CH₃)₂CC₆H_FourC (CH₃)₂Cl 1,3-bis (1-chloro-1-methylethyl) benze
The 1,3-Cl (CH₃)₂CC₆H_FourC (CH₃)₂Cl 1,3,5-tris (1-chloro-1-methylethyl)
benzene 1,3,5- (ClC (CH₃)₂)₃C₆H₃ 1,3-bis (1-chloro-1-methylethyl) -5-
(Tert-butyl) benzene 1,3- (C (CH
₃)₂Cl)₂-5- (C (CH₃)₃) C₆H₃ Among these, particularly preferred is 1-chloro-1-methyl.
Luethylbenzene [C ₆H_FiveC (CH₃)₂Cl], bis
(1-Chloro-1-methylethyl) benzene [C ₆H
_Four(C (CH₃)₂Cl)₂], Tris (1-chloro-1-
Methylethyl) benzene [(ClC (CH₃)₂)₃C₆H
₃]. [Note that 1-chloro-1-methylethylben
Zen is α-chloroisopropylbenzene, 2-chloro
-2-Propylbenzene or cumyl chloride
Called bis (1-chloro-1-methylethyl) benze
Is bis (α-chloroisopropyl) benzene, bis
(2-chloro-2-propyl) benzene or dicum
Also called luchloride, tris (1-chloro-1-me
Tylethyl) benzene is tris (α-chloroisopropene).
Pill) benzene, tris (2-chloro-2-propyl)
Also called benzene or tricumyl chloride
]].

In the above polymerization reaction, a Lewis acid catalyst can coexist. Any Lewis acid can be used as long as it can be used for cationic polymerization, such as TiCl ₄ , TiBr.
₄ , BCl ₃ , BF ₃ , BF ₃ · OEt ₂ , SnCl ₄ , SbCl ₅ ,
SbF ₅ , WCl ₆ , TaCl ₅ , VCl ₅ , FeCl ₃ , ZnB
Metal halides such as r ₂ , AlCl ₃ , AlBr ₃ ; Et ₂
Organic metal halides such as AlCl and EtAlCl ₂ can be preferably used. Above all, considering the catalytic ability and industrial availability, TiCl ₄ , B
Cl ₃ and SnCl ₄ are preferred.

The amount of the Lewis acid catalyst used is not particularly limited and can be set in consideration of the polymerization characteristics or the polymerization concentration of the monomers used.

In the above polymerization reaction, if necessary, an electron donor component may coexist. This electron donor component is believed to have the effect of stabilizing the growing carbocation during cationic polymerization.
The addition of an electron donor produces a polymer with a controlled structure with a narrow molecular weight distribution. The electron donor component that can be used is not particularly limited, and examples thereof include pyridines, amines, amides, sulfoxides, esters, and metal compounds having an oxygen atom bonded to a metal atom.

The above polymerization reaction can be carried out in an organic solvent as the case requires, and the organic solvent can be used without particular limitation as long as it does not essentially inhibit the cationic polymerization. Specifically, halogenated hydrocarbons such as methyl chloride, dichloromethane, chloroform, ethyl chloride, dichloroethane, n-propyl chloride, n-butyl chloride and chlorobenzene; benzene, toluene, xylene,
Alkylbenzenes such as ethylbenzene, propylbenzene and butylbenzene; linear aliphatic hydrocarbons such as ethane, propane, butane, pentane, hexane, heptane, octane, nonane and decane; 2-methylpropane,
2-methylbutane, 2,3,3-trimethylpentane,
Branched aliphatic hydrocarbons such as 2,2,5-trimethylhexane; cycloaliphatic hydrocarbons such as cyclohexane, methylcyclohexane, ethylcyclohexane; paraffin oil obtained by hydrogenating and refining petroleum fractions. it can.

These solvents may be used alone or in combination of two or more in consideration of the balance between the polymerization characteristics of the monomers constituting the block copolymer and the solubility of the resulting polymer.

The amount of the above-mentioned solvent used is in the range of 1 to 1 in consideration of the viscosity of the resulting polymer solution and the ease of heat removal.
It is determined to be 50 wt%, preferably 3 to 35 wt%.

In carrying out the actual polymerization, the components are mixed under cooling, for example, at a temperature of -100 ° C or higher and lower than 0 ° C. In order to balance the energy cost and the stability of polymerization, a particularly preferable temperature range is -30 ° C to -80 ° C.

The tackifying resin (B) is a low molecular weight resin having a number average molecular weight of 300 to 3,000 and a softening point of 60 to 150 ° C. based on the ring and ball method defined in JIS K-2207, Rosin and rosin derivatives, polyterpene resins, aromatic modified terpene resins and their hydrides, terpene phenol resins, coumarone indene resins, aliphatic petroleum resins, alicyclic petroleum resins and their hydrides, aromatic petroleum resins And hydrides thereof, aliphatic aromatic copolymer-based petroleum resins and hydrides thereof, dicyclopentadiene-based petroleum resins and hydrides thereof, and low molecular weight polymers of styrene or substituted styrene. Specific examples include isobutylene. It is possible to add a tackifier resin compatible with the isobutylene-based polymer block in the block copolymer. Preferred, for example, alicyclic petroleum resin and hydrides thereof, aliphatic petroleum resins, hydrides aromatic petroleum resins, such as polyterpene resins.

Examples of the rubber component (C) include natural rubber, diene polymer rubber and olefin polymer rubber. Examples of the diene polymer rubber include isoprene rubber, butadiene rubber, 1,2-polybutadiene, styrene-butadiene rubber, chloroprene rubber, and nitrile rubber. Examples of the olefin rubber include butyl rubber, chlorinated butyl rubber, brominated butyl rubber, and ethylene-propylene-diene rubber. Among these, a homopolymer of a diene compound or a copolymer of a diene compound and an aromatic vinyl compound is preferable, and specifically, isoprene rubber, butadiene rubber, and styrene butadiene rubber are particularly preferable.

In addition to the above, the rubber composition of the present invention contains a compounding agent which is generally used in the rubber industry, such as a filler, a plasticizer, a vulcanizing agent, a vulcanization accelerator and an antioxidant. It can be appropriately blended according to the purpose and application. Examples of the filler include carbon black, silica, filler, calcium carbonate, mica, flake graphite and the like. Examples of the plasticizer include petroleum-based process oils such as paraffin-based process oils, naphthene-based process oils and aromatic process oils, dialkyl dibasic acid salts such as diethyl phthalate, dioctyl phthalate and dibutyl adipate, liquid polybutene, liquid poly A low molecular weight liquid polymer such as isoprene is exemplified, and among them, liquid polybutene, liquid polyisoprene, and aromatic process oil are preferable from the viewpoint of compatibility with the rubber component. Examples of the vulcanizing agent include sulfur, phenolic resins, metal oxides and peroxides. These are usually 100 parts by weight of the rubber component,
About 0.5 to 10 parts are used. As a vulcanization accelerator,
2,2-dithiobisbenzothiazole, 1,3-diphenylguanidine, tetramethylthiuram disulfide,
Examples are zinc dimethylthiocarbamate and mercaptobenzothiazyl disulfide. These are usually used in an amount of about 0.2 to 5 parts based on 100 parts by weight of the rubber component.

The wet grip property is considered to depend on the deformation near the surface of the tire. It is known that this deformation near the surface is vibration of a very high frequency, and using temperature-frequency conversion, the wet grip property is represented by tan δ of 0 ° C. at 10 Hz.

The rubber composition for a tire used in the present invention has a loss tangent (tan δ) of 0.5 or more at 0 ° C., which is obtained by dynamic viscoelasticity measurement of the composition in a 10 Hz tensile mode. Then, an isobutylene block copolymer (A) composed of a polymer block mainly containing isobutylene and a polymer block mainly containing an aromatic vinyl compound, a tackifying resin (B) and a rubber component (C)
Besides, any component may be blended.

As a component for controlling the temperature of the Tan δ peak of the polymer block mainly composed of isobutylene in the isobutylene block copolymer, a tackifying resin can be mentioned. The tackifying resin has the effect of shifting the temperature of the Tan δ peak of the polymer block mainly composed of isobutylene in the isobutylene block copolymer to the high temperature side and increasing tan δ at the peak temperature. The Tan δ peak temperature of the isobutylene-based block copolymer-based polymer block mainly containing isobutylene is -40 to
Since it is as low as −35 ° C., it is preferable to add a tackifying resin to move the peak to 0 ° C.

In order to achieve the object of the present invention, it is desirable to add a tackifier resin compatible with the polymer block mainly composed of isobutylene in the isobutylene block copolymer, for example, an alicyclic resin. Petroleum resin and its hydride, aliphatic petroleum resin, hydride of aromatic petroleum resin,
A polyterpene resin or the like is preferably used. Even in the same type of tackifier resin, the higher the softening point, the higher the effect of moving the Tan δ peak temperature of the polymer block mainly composed of isobutylene of the isobutylene-based block copolymer to the high temperature side, and the tackifier resin If it is desired to reduce the compounding amount of (1), those having a high softening point may be selected, and if it is desired to increase it, those having a low softening point may be selected. For example, when using Alcon (manufactured by Arakawa Chemical Industry Co., Ltd.), which is a hydride of a C9 alicyclic petroleum resin, P- having a softening point of 100 ° C. with respect to 100 parts by weight of an isobutylene block copolymer.
When 100 is 10 to 70 parts by weight, and when M-135 having a softening point of 135 ° C. is 10 to 55 parts by weight, the Tan δ peak temperature of the polymer block mainly composed of isobutylene of the isobutylene block copolymer is -15 ℃ ~ 1
It can be adjusted within the range of 5 ° C. The blending ratio of the isobutylene block copolymer (A) and the tackifying resin (B) used in the present invention is 10 Hz at 0 ° C. loss tangent obtained by dynamic viscoelasticity measurement of the composition in the tensile mode. Any mixing ratio may be used as long as (Tanδ) is 0.5 or more. In order to satisfy such a condition, as described above, it is necessary to set the blending ratio so that the Tan δ peak temperature of the polymer block mainly composed of isobutylene in the isobutylene block copolymer is around 0 ° C. preferable. For example, when 100 parts by weight of the isobutylene block copolymer is blended with the tackifying resin in a range of 1 to 100 parts by weight, preferably 10 to 50 parts by weight,
The desired composition is obtained. If less than 1 part by weight,
It becomes difficult to obtain the effect of improving the wet grip property, and if it exceeds 50 parts by weight, rolling resistance tends to increase, which is not preferable.

The compounding amounts of the isobutylene block copolymer (A) and the tackifying resin (B) used in the present invention are not particularly limited and can be appropriately selected according to the purpose. For example, for tires. When used in a rubber composition, it is preferable to add 1 to 50 parts by weight of the block copolymer (A) and the tackifying resin (B) in total to 100 parts by weight of the rubber component (C). It is most preferable to add 30 parts by weight. If the amount is less than 1 part by weight, it is difficult to obtain the effect of improving the wet grip property, and if it exceeds 50 parts by weight, rolling resistance tends to increase, which is not preferable.
As a method for preparing the rubber composition of the present invention, a conventionally known method may be adopted. For example, first, an isobutylene block copolymer (A), a tackifying resin (B) a rubber component (C) and a vulcanizing agent. After mixing various compounding agents other than the vulcanization accelerator with a tumbler, a Henschel mixer, a riboblender, or the like, they are kneaded with an extruder, bumper, roll, or the like. At this time, the kneading temperature is preferably appropriately changed from room temperature to 200 ° C. depending on the compounding ratio of the isobutylene block copolymer (A), the tackifying resin (B) and the rubber component (C). This is because the glass transition temperature of the polymer block containing the aromatic vinyl compound of the isobutylene-based block copolymer as a monomer is usually 100 ° C. or higher, so that the isobutylene-based block copolymer (A) If the percentage is high,
This is because the components do not mix well. Therefore,
It is preferable to knead at a higher temperature as the blending amount of (A) is higher. When obtaining vulcanized rubber, after kneading,
A vulcanizing agent and a vulcanization accelerator are added, and the mixture is further kneaded using the above apparatus. At this time, the kneading temperature is preferably 80 ° C. to 120 ° C. for the purpose of suppressing the reaction of the vulcanizing agent.
Furthermore, if necessary, the rubber composition can be molded and crosslinked using a press machine, an injection molding machine or the like.

The structure and size of the tire using the rubber composition of the present invention are not particularly limited and can be selected as required. The wet grip, which is the object of the present invention, is most required for tires for passenger cars, and it is desirable to use it for this. When the tire tread has a multi-layer structure, it is preferable to use the rubber composition of the present invention at least in the outermost layer. Further, since the rubber composition of the present invention has a good grip on a wet road surface, it is useful to use it for the sole of general footwear.

[0042]

The present invention will be described in more detail with reference to the following examples. It should be noted that the present invention is not limited to these embodiments, and various modifications can be made without departing from the scope of the invention. The viscoelasticity measuring method will be described prior to the examples.

(Measurement of Viscoelasticity) The dynamic viscoelastic properties of the mixture containing the isobutylene block copolymer and the rubber composition were measured by using the mixture and the composition described above (in the examples, the formulations shown in Table 1). A plastomill (manufactured by Toyo Seiki Co., Ltd.) was melt kneaded at 170 ° C. and 50 rpm for 10 minutes to form a sheet by hot press molding, and the obtained sheet was JIS K-6394 (vulcanized rubber and heat 40 mm x 5 according to the dynamic property test method for plastic rubber)
A test piece of mm × 2 mm is cut out and used at a frequency of 1
It was measured at 0 Hz and a strain of 0.1%. The device used was a dynamic viscoelasticity measuring device DVA-200 (manufactured by IT Measurement and Control Co., Ltd.). At this time, the frequency needs to be 10 Hz because this is because the wet grip characteristics are correlated with the tan δ value at 10 Hz and 0 ° C. when the time-temperature conversion rule of viscoelasticity is used. It is known that the larger is, the better the wet grip property is.

(Production Example: Production of styrene-isobutylene-styrene-triblock copolymer) In a 2 L reaction vessel equipped with a stirrer, 570 mL of methylcyclohexane (dried with molecular sieves) and n-butyl chloride (dried with molecular sieves) ) 590 mL,
0.400 g of dicumyl chloride was added. After cooling the reaction vessel to −70 ° C., 0.34 mL of α-picoline (2-methylpyridine) and 174 mL of isobutylene were added. Further, 10.3 mL of titanium tetrachloride was added to initiate polymerization, and the solution was reacted at -70 ° C for 2.0 hours with stirring. Then, 58 mL of styrene was added to the reaction solution, the reaction was continued for further 60 minutes, and then a large amount of methanol was added to stop the reaction. After removing the solvent and the like from the reaction solution, the polymer was dissolved in toluene and washed twice with water. This toluene solution was added to a methanol mixture to precipitate a polymer, and the obtained polymer was vacuum dried at 60 ° C. for 24 hours to obtain an isobutylene block copolymer (hereinafter abbreviated as SIBS).

The obtained isobutylene block copolymer has a number average molecular weight of 98,000 and a molecular weight distribution of 1.15.
The styrene content in the polymer was 29% by weight. The number average molecular weight was measured by Waters 510 type GPC system (chloroform was used as a solvent, and the flow rate was 1 mL / min), and the value in terms of polystyrene was shown. The styrene content in the polymer was calculated from the integration ratio of ¹ H NMR spectrum.

(Example) Styrene-butadiene copolymer rubber (JSRSL552, manufactured by JSR, hereinafter abbreviated as SBR), butadiene rubber (JSRBR01, manufactured by JSR, hereinafter abbreviated as BR), tackifying resin (C9 type). Alicyclic petroleum resin hydride Alcon P-100, softening point 1
00 ° C., molecular weight 610, manufactured by Arakawa Chemical Industry Co., Ltd.), and the compounding agent with SIBS produced in Production Example were set at 150 ° C. at the compounding ratio shown in Table 1 (unit in the table is part by weight). A composition was obtained by kneading with a Labo Plastomill (produced by Toyo Seiki Co., Ltd.) for 15 minutes. The rubber composition was compression molded at 150 ° C. to prepare a sheet. The moldability was extremely good.
A test piece measuring 6 mm in length × 5 mm in width × 2 mm in thickness was cut out from the sheet, and a loss tangent tan at 0 ° C. was measured using a dynamic viscoelasticity measuring device DVA-200 (manufactured by IT measurement control company).
δ was measured. The measurement frequency was 10 Hz.

(Comparative Examples 1 and 2) As a comparative example, a styrene-butadiene copolymer rubber without adding any tackifying resin,
SIBS was compression molded at 150 ° C. to prepare a sheet.
The loss tangent tan δ at 0 ° C. was measured in the same manner as in the example. The measurement frequency was 10 Hz.

(Comparative Example 3) As a comparative example, a tackifying resin,
SIBS was not added at all, and only styrene-butadiene copolymer rubber was compression molded at 150 ° C. to prepare a sheet. The loss tangent tan δ at 0 ° C. was measured in the same manner as in the example. The measurement frequency was 10 Hz.

[0049]

[Table 1]

In the examples, the addition of tackifying resin
The tan δ at 0 ° C. is higher than that of SIBS alone (Comparative Example 1), that is, the wet grip property is improved. Further, the breaking properties are almost the same as or slightly lower than those of the rubber component alone, that is, the breaking properties are the same as those of the rubber component alone.

[0051]

EFFECTS OF THE INVENTION The rubber composition of the present invention has a wet grip property and a tire breaking strength which are improved by adding an isobutylene block copolymer in which a tackifying resin is added to a rubber component which has been conventionally used for a tire. It can be used as a pneumatic tire with an excellent balance of contradictory properties.

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Claims (7)

[Claims] 1. A block copolymer (A) comprising a polymer block mainly containing isobutylene and a polymer block mainly containing an aromatic vinyl compound, and a tackifying resin (B).
And a rubber composition comprising at least one rubber component (C) selected from the group consisting of natural rubber, diene polymer rubber and olefin polymer rubber. 2. The rubber component (C) is crosslinked.
The rubber composition described. 3. The loss tangent (Tan δ) of the mixture of the block copolymer (A) and the tackifying resin (B) obtained by dynamic viscoelasticity measurement at 10 Hz in a tensile mode is 0.
The rubber composition according to claim 1, which is 0.5 or more at a temperature of ° C. 4. The rubber composition according to claim 1, wherein 10 parts by weight to 50 parts by weight of the tackifying resin (B) is mixed with 100 parts by weight of the block copolymer (A). 5. A total of 1 part of the block copolymer (A) and the tackifying resin (B) per 100 parts by weight of the rubber component (C).
The rubber composition according to any one of claims 1 to 4, which is compounded in an amount of -50 parts by weight. 6. A pneumatic tire tread comprising the rubber composition according to claim 1. 7. A shoe sole comprising the rubber composition according to claim 1.