JP2008156503A - Method for producing rubber composition and rubber composition obtained thereby and pneumatic tire using the rubber composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a rubber composition, capable of reducing rolling resistance and improving all of processability, abrasion resistance, grip performance and persistency and capable of improving grip performance, especially in wide temperature conditions. <P>SOLUTION: The method for producing the rubber composition comprises (A) a step of preparing a polystyrene by coagulating a latex of a polystyrene having 90-150°C glass transition temperature with an acid and drying the coagulated latex and (B) a step of mixing 100 pts.wt. rubber component containing ≥20 wt.% styrene butadiene rubber obtained by a solution polymerization and/or an emulsion polymerization method with 5-100 pts.wt. polystyrene prepared in the step (A) in a closed mixer. The polystyrene latex may be mixed with at least one kind of material selected from the group consisting of water glass, a cationizing agent and a surfactant before coagulating the polystyrene latex with the acid. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for producing a rubber composition, a rubber composition obtained thereby, and a pneumatic tire using the rubber composition.

  In general, a rubber composition used as a tread for a high-performance tire such as a racing tire is required to have both high grip performance and wear resistance. However, in the conventional technology, heat sagging is caused particularly under severe conditions such as 100 ° C. or higher, and a rubber composition having sufficient grip performance and wear resistance under severe conditions has not been obtained.

  Conventionally, as a method for obtaining a tire exhibiting high grip performance, a method using a rubber composition using styrene butadiene rubber (SBR) having a high glass transition temperature (Tg) as a rubber component, a resin having a high softening point for process oil A method using a rubber composition substituted with an equal amount, a method using a rubber composition highly filled with a softener or carbon black, a method using a rubber composition using carbon black having a small particle diameter, and a high Tg A method using a rubber composition containing SBR, a resin having a high softening point, a softening agent and carbon black is known. However, the rubber composition using SBR having a high Tg has a problem that the temperature dependency is increased, the performance change with respect to the temperature change is large, and stable performance cannot be obtained. Further, when a large amount of process oil is replaced with a resin having a high softening point, there is a problem in that a temperature dependence is large due to the effect of the high softening point resin, and stable performance cannot be obtained. In addition, when the softener or carbon black is highly filled or when carbon black with a small particle size is filled, the dispersibility of the softener or carbon black may be reduced, and the fracture strength and wear resistance may be reduced. There was a problem to do.

  On the other hand, as a technique for obtaining a tire exhibiting high wear resistance, a technique of blending special carbon black as a filler (see, for example, Patent Document 1) is known. However, since the surface activity of carbon black is high, there is a problem that the energy loss is greatly changed due to tire fatigue and heat sagging occurs.

JP 2004-59803 A

  The present invention provides a method for producing a rubber composition that can reduce rolling resistance and improve all of workability, wear resistance, grip performance and sustainability, and in particular, can improve grip performance under a wide range of temperature conditions. The purpose is to provide.

  The present invention includes (A) a step of acid-coagulating and drying polystyrene latex having a glass transition temperature of 90 to 150 ° C. to obtain polystyrene, and (B) a styrene-butadiene rubber obtained by solution polymerization and / or emulsion polymerization. The present invention relates to a method for producing a rubber composition comprising a step of mixing 5 to 100 parts by weight of the polystyrene obtained in the step (A) with 100 parts by weight of a rubber component containing 20% by weight or more in a closed mixer.

  In the present invention, (A) a polystyrene latex having a glass transition temperature of 90 to 150 ° C. is mixed with at least one selected from the group consisting of water glass, a cationizing agent and a surfactant, and then coagulated and dried. Obtained in step (A) with respect to 100 parts by weight of a rubber component containing 20% by weight or more of styrene butadiene rubber obtained by (B) solution polymerization and / or emulsion polymerization method. The present invention relates to a method for producing a rubber composition comprising a step of mixing 5 to 100 parts by weight of a master batch in a closed mixer.

  The amount of the water glass is preferably 0.5 to 90 parts by weight in terms of silica solid content with respect to 100 parts by weight of the rubber component.

  The method for producing the rubber composition further comprises, in step (B), 5 to 80 at least one filler selected from the group consisting of carbon black, silica, alumina and clay with respect to 100 parts by weight of the rubber component. It is preferable to mix by weight.

  In the method for producing the rubber composition, it is preferable that 1 to 20 parts by weight of a silane coupling agent is mixed with 100 parts by weight of the rubber component in the step (B).

  Moreover, this invention relates to the rubber composition obtained by the manufacturing method of the said rubber composition.

  Furthermore, the present invention relates to a pneumatic tire using the rubber composition.

  According to the present invention, a predetermined polystyrene latex is acid-coagulated and dried, and a predetermined amount is blended with a predetermined rubber component, thereby reducing rolling resistance, workability, wear resistance, grip performance and sustainability. Thus, it is possible to produce a rubber composition that can improve the grip performance under a wide range of temperature conditions. In addition, if the polystyrene latex is mixed with at least one selected from the group consisting of water glass, a cationizing agent and a surfactant before acid coagulation, the physical properties can be further improved.

  The method for producing a rubber composition of the present invention comprises (A) a step of acid coagulating and drying polystyrene latex to obtain polystyrene, and (B) a rubber component and the polystyrene obtained in step (A) in a closed mixer. Mixing.

  In the step (A), polystyrene latex is acid-coagulated and then dried to obtain polystyrene.

  The glass transition temperature (Tg) of polystyrene used as the polystyrene latex is 90 ° C. or higher, preferably 100 ° C. or higher. When Tg is less than 90 ° C., the tan δ curve on the high temperature side is not flat, and thermal sagging cannot be prevented. Moreover, Tg is 150 degrees C or less, Preferably it is 130 degrees C or less, More preferably, it is 120 degrees C or less. When Tg exceeds 150 ° C., the resulting polystyrene and masterbatch are not dispersed in the rubber, and the physical properties are significantly lowered.

  Only one type of polystyrene latex may be used, but if two or more types of polystyrene obtained with different Tg are used, the width of the tan δ peak position can be widened, improving the grip performance in a wide temperature range. Can be made.

  When two types are used as the polystyrene latex, the difference in Tg of the obtained polystyrene is preferably 5 ° C. or more, and more preferably 10 ° C. or more. When the difference in Tg is less than 5 ° C., the width of the tan δ peak is not sufficient, and therefore there is a tendency that it is not much different from when one kind of polystyrene latex is used. Further, the difference in Tg is preferably 100 ° C. or less, and more preferably 50 ° C. or less. When the difference in Tg exceeds 100 ° C., the peak splits and becomes a two-peak peak, so that the intermediate grip performance tends not to be improved.

  As the acid used for acid coagulation, it is usually preferable to use an inorganic acid, and examples thereof include sulfuric acid and hydrochloric acid.

  The acid may be added in an amount sufficient to produce silanol groups from water glass, but specifically, it is preferably 2 to 5 parts by weight with respect to 100 parts by weight of water glass. If the amount of acid added is less than 2 parts by weight, silanol groups do not adhere to the negative charge of the latex, causing poor dispersion, and a sufficient reinforcing effect of silica tends not to be expected. When a strong acid is used as the reaction solution, it tends to take time to wash the resulting polystyrene to make it neutral.

  Examples of the drying method include ventilation drying and vacuum drying, but vacuum drying is preferable because the time can be shortened.

  The drying temperature is preferably 50 to 60 ° C. If the drying temperature is less than 50 ° C., it cannot be sufficiently dried, and moisture tends to remain when it is made into a rubber composition, and if it exceeds 60 ° C., polystyrene tends to deteriorate.

  In step (A), before acid coagulation, polystyrene latex and at least one selected from the group consisting of water glass, a cationizing agent, and a surfactant can be mixed. By mixing with at least one selected from the group consisting of water glass, a cationizing agent and a surfactant, the dispersibility in rubber, tensile strength, tear strength, etc. compared to when used alone with polystyrene latex The physical properties of can be improved.

The water glass is usually represented by the following general formula.
Na ₂ O · nSiO ₂ · mH ₂ O

In the above general formula, n represents a molecular ratio of SiO ₂ / Na ₂ O, and preferably 2.1 to 3.1. When n is outside the above range, it cannot exist as an aqueous solution and gelation tends to occur. In addition, when n is too large, condensation of silanol groups proceeds and there is a tendency that it cannot exist stably. The composition of water glass is specified in JIS K 1408.

  The content of silica solid content in the water glass is preferably 5% by weight or more, and more preferably 15% by weight or more. If the content of silica solids in the water glass is less than 5% by weight, the amount of silica is too small, it is difficult to handle with only water, and is not suitable for transportation, so it cannot be used in the manufacturing process of industrial products. There is. Moreover, 60 weight% or less is preferable and, as for the content rate of the silica solid content in water glass, 55 weight% or less is more preferable. When the content of the solid content of silica in the water glass exceeds 60% by weight, it cannot exist as an aqueous solution. Specifically, silica tends to precipitate and silica gel is generated.

  There is no restriction | limiting in particular as a cationizing agent, Although what is marketed can be used, Specifically, the Kathiomaster G (glycidyl trimethyl ammonium chloride) by Yokkaichi Gosei Co., Ltd. etc. are mention | raise | lifted. The surfactant is not particularly limited as long as it is a cationic surfactant or an anionic surfactant, and a commercially available one can be used.

  When water glass is used, the amount of water glass is 0.5 parts by weight or more, preferably 10 parts by weight or more in terms of silica solid content with respect to 100 parts by weight of a rubber component described later. When the blending amount of water glass is less than 0.5 parts by weight, the reinforcing effect by blending water glass and the effect as a tan δ control agent are not observed. Moreover, the compounding quantity of water glass is 90 weight part or less, Preferably it is 60 weight part or less. When the amount of water glass exceeds 90 parts by weight, the rubber elasticity is lost and kneading cannot be performed. Further, the shape of silica is large, and it becomes a foreign substance when kneaded in rubber.

  When a cationizing agent and / or a surfactant is used, the amount of the cationizing agent and / or the surfactant is preferably 2 parts by weight or more with respect to 100 parts by weight of the rubber component described later, and 5 parts by weight or more. More preferred. When the blending amount of the cationizing agent and / or surfactant is less than 2 parts by weight, the effect of blending the cationizing agent and the surfactant tends not to be observed. Further, the blending amount of the cationizing agent and / or the surfactant is preferably 30 parts by weight or less, and more preferably 20 parts by weight or less. When the blending amount of the cationizing agent and / or the surfactant exceeds 30 parts by weight, the adhesiveness of the rubber increases, which tends to cause a problem in the processing step.

  In the step (A), when the polystyrene latex is mixed with at least one selected from the group consisting of water glass, a cationizing agent and a surfactant before acid coagulation, the type of acid, the amount added, and the type of drying The drying temperature can be the same as in the case of using polystyrene latex alone.

  In step (A), animal polysaccharides such as chitosan and chitin derivatives can be mixed in addition to water glass, cationizing agent and surfactant before acid coagulation.

  In the step (B), the rubber component and the polystyrene or rubber master batch obtained in the step (A) are mixed in a closed mixer.

  The rubber component includes diene rubber, and includes styrene butadiene rubber (SBR) because wet grip performance and rolling resistance characteristics can be balanced to a high level.

  SBR includes those obtained by a solution polymerization method and those obtained by an emulsion polymerization method, but is not particularly limited.

  The content of SBR in the rubber component is 20% by weight or more, preferably 35% by weight or more. When the SBR content is less than 20% by weight, the wear resistance and wet grip performance deteriorate. The SBR content is most preferably 100% by weight.

  As rubber components, in addition to SBR, natural rubber (NR), butadiene rubber (BR), isoprene rubber (IR), ethylene propylene diene rubber (EPDM), chloroprene rubber (CR), acrylonitrile butadiene rubber (NBR), etc. Non-diene rubbers such as diene rubber, butyl rubber (IIR), and halogenated butyl rubber can be used. These rubbers can be used alone or in combination of two or more with SBR.

  The compounding amount of the polystyrene or rubber master batch obtained by the step (A) is 5 parts by weight or more, preferably 20 parts by weight or more with respect to 100 parts by weight of the rubber component. When the blending amount of the polystyrene or rubber master batch is less than 5 parts by weight, it does not function as a tan δ control agent. Moreover, the compounding quantity of a polystyrene or a rubber masterbatch is 100 weight part or less, Preferably it is 70 weight part or less. When the blending amount of the polystyrene or rubber masterbatch exceeds 100 parts by weight, the hardness of the rubber composition increases and becomes too hard to show rubber elasticity.

  When mixing a rubber component and polystyrene or a rubber master batch, a closed mixer such as a Banbury mixer or a kneader is used.

  In the step (B), when the rubber component and the polystyrene or rubber master batch are mixed, it is preferable to mix at least one filler selected from the group consisting of carbon black, silica, alumina and clay.

  Carbon black is not particularly limited, and grades such as SAF, ISAF, HAF, FEF, and GPF conventionally used in the rubber industry can be used.

  There is no restriction | limiting in particular also as a silica, It can select and use suitably from what was prepared by the dry process, and the thing prepared by the wet method.

  The blending amount of the filler is preferably 5 parts by weight or more, more preferably 10 parts by weight or more, and still more preferably 15 parts by weight or more with respect to 100 parts by weight of the rubber component. When the blending amount of the filler is less than 5 parts by weight, there is a tendency that sufficient low heat build-up and wet grip performance cannot be obtained. Moreover, 150 weight part or less is preferable, as for the compounding quantity of a silica, 120 weight part or less is more preferable, and 100 weight part or less is further more preferable. When the blending amount of the filler exceeds 150 parts by weight, workability and workability deteriorate.

  In the step (B), when the rubber component and the rubber master batch are mixed, it is preferable to further mix the silane coupling agent.

  In the present invention, a silane coupling agent conventionally used in the rubber industry can be preferably used. Specifically, bis (3-triethoxysilylpropyl) tetrasulfide, bis (2-triethoxysilylethyl) can be used. ) Tetrasulfide, bis (4-triethoxysilylbutyl) tetrasulfide, bis (3-trimethoxysilylpropyl) tetrasulfide, bis (2-trimethoxysilylethyl) tetrasulfide, bis (4-trimethoxysilylbutyl) tetra Sulfide, bis (3-triethoxysilylpropyl) trisulfide, bis (2-triethoxysilylethyl) trisulfide, bis (4-triethoxysilylbutyl) trisulfide, bis (3-trimethoxysilylpropyl) trisulfide, Bis (2-trimethoxysilyl Ethyl) trisulfide, bis (4-trimethoxysilylbutyl) trisulfide, bis (3-triethoxysilylpropyl) disulfide, bis (2-triethoxysilylethyl) disulfide, bis (4-triethoxysilylbutyl) disulfide, Bis (3-trimethoxysilylpropyl) disulfide, bis (2-trimethoxysilylethyl) disulfide, bis (4-trimethoxysilylbutyl) disulfide, 3-trimethoxysilylpropyl-N, N-dimethylthiocarbamoyl tetrasulfide, 3-triethoxysilylpropyl-N, N-dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilylethyl-N, N-dimethylthiocarbamoyl tetrasulfide, 2-trimethoxysilylethyl-N, N-dimethyl Ocarbamoyl tetrasulfide, 3-trimethoxysilylpropylbenzothiazolyl tetrasulfide, 3-triethoxysilylpropylbenzothiazole tetrasulfide, 3-triethoxysilylpropyl methacrylate monosulfide, 3-trimethoxysilylpropyl methacrylate monosulfide, etc. Sulfide type, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, 2-mercaptoethyltriethoxysilane and other mercaptotypes, vinyltriethoxysilane, vinyltrimethoxysilane, etc. Vinyl, 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3- (2-aminoethyl) aminopropyltri Amino type such as toxisilane, 3- (2-aminoethyl) aminopropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane , Glycidoxy type such as γ-glycidoxypropylmethyldimethoxysilane, nitro type such as 3-nitropropyltrimethoxysilane, 3-nitropropyltriethoxysilane, 3-chloropropyltrimethoxysilane, 3-chloropropyltriethoxysilane And chloro-based compounds such as 2-chloroethyltrimethoxysilane and 2-chloroethyltriethoxysilane. These silane coupling agents may be used alone or in combination of two or more. Of these, bis (3-triethoxysilylpropyl) tetrasulfide, bis (3-triethoxysilylpropyl) disulfide, and the like are more preferably used from the viewpoint of both the effect of adding a coupling agent and cost.

  The compounding amount of the silane coupling agent is preferably 1 part by weight or more, more preferably 2 parts by weight or more with respect to 100 parts by weight of the rubber component. If the amount of the silane coupling agent is less than 1 part by weight, the effect of incorporating the silane coupling agent tends to be insufficient. The amount of the silane coupling agent is preferably 20 parts by weight or less, and more preferably 15 parts by weight or less. When the compounding amount of the silane coupling agent exceeds 20 parts by weight, the rubber becomes soft and there is a tendency for problems in the process such as the rubber to stick to the roll.

  In addition to the rubber component, polystyrene or rubber masterbatch, filler and silane coupling agent, the rubber composition produced by the production method of the present invention includes a compounding agent conventionally used in the rubber industry, such as aging. An inhibitor, a vulcanizing agent such as stearic acid, zinc oxide and sulfur, a vulcanization accelerator, and the like can be appropriately blended as necessary.

  The rubber composition produced by the production method of the present invention is used for tires, and is particularly used as a tread because it has excellent grip performance under a wide range of temperature conditions and excellent wear resistance. It is preferable.

  The pneumatic tire of the present invention is produced by a usual method using the rubber composition of the present invention. That is, if necessary, the rubber composition containing the additive is extruded in accordance with the shape of each member of the tire at an unvulcanized stage, and molded by a normal method on a tire molding machine. Thus, an unvulcanized tire is formed. The unvulcanized tire is heated and pressurized in a vulcanizer to obtain a pneumatic tire.

  The present invention will be specifically described based on examples, but the present invention is not limited to these examples.

Hereinafter, various chemicals used in Examples and Comparative Examples will be described together.
Styrene butadiene rubber (SBR): SBR1502 manufactured by JSR Corporation (styrene unit amount: 23.5% by weight)
Carbon Black: Show Black N220 manufactured by Cabot Japan
Silica: Ultrazil VN3 manufactured by Degussa (N ₂ SA: 210 m ² / g)
Silane coupling agent: Si69 (bis (3-triethoxysilylpropyl) tetrasulfide) manufactured by Degussa
Aroma oil: Process X140 made by Japan Energy Co., Ltd.
Latex of polystyrene: Lx303 (polystyrene Tg: 100 ° C.) manufactured by Zeon Corporation
Styrene butadiene rubber latex (SBR latex): Lx433 (TBR of SBR: 50 ° C.) manufactured by Zeon Corporation
Water glass: No. 3 water glass defined in JIS K 1408 (n: 2.1-3.1, silica solid content: 29.5% by weight)
Cationizing agent: Kathiomaster G (Glycidyltrimethylammonium chloride) manufactured by Yokkaichi Gosei Co., Ltd.
Polystyrene: produced by the following production method (polystyrene latex is acid coagulated and dried)
Master batch (1): produced by the following production method (polystyrene latex and water glass mixture are acid coagulated and dried)
Master batch (2): produced by the following production method (a mixture of polystyrene latex and cationizing agent is acid coagulated and dried)
Master batch (3): produced by the following production method (a mixture of SBR latex and water glass is acid coagulated and dried)
Anti-aging agent: NOCRACK 6C (N- (1,3-dimethylbutyl) -N′-phenyl-p-phenylenediamine) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.
Stearic acid: Zinc stearate oxide manufactured by Nippon Oil & Fats Co., Ltd .: Zinc Hua No. 1 manufactured by Mitsui Mining & Smelting Co., Ltd. Sulfur: Powder sulfur vulcanization accelerator manufactured by Tsurumi Chemical Co., Ltd. TBBS: Ouchi Shinsei Chemical Industry Co., Ltd. Noxeller NS (N-tert-butyl-2-benzothiazolylsulfenamide) manufactured by KK
Vulcanization accelerator DPG: Noxeller D (N, N'-diphenylguanidine) manufactured by Ouchi Shinsei Chemical Co., Ltd.

(Production of polystyrene)
According to the mixed formulation shown in Table 1, the latex latex was salted out under neutral conditions at pH 6-7 while gradually adding polystyrene latex to the acid solution (0.1 M sulfuric acid), and the precipitated polystyrene was collected, Washed with water until neutral. Then, it was vacuum-dried at a temperature of 50 ° C. for 24 hours to produce polystyrene.

(Production of master batches (1) to (3))
According to the mixed formulation shown in Table 1, polystyrene latex, SBR latex, water glass and cationizing agent were mixed and stirred. The reaction solution is gradually added to an acid solution (0.1 M sulfuric acid) while salting out under neutral conditions at pH 6 to 7, and the precipitated rubber composite is collected, and then neutralized with water. Until washed. Then, it vacuum-dried at the temperature of 50 degreeC for 24 hours, and produced masterbatch (1)-(3).

  Table 1 shows the amounts added in the production of master batches (1) to (3).

Examples 1-3 and Comparative Examples 1-2
In accordance with the formulation shown in Table 2, the rubber component was masticated at a roll temperature of 50 ° C. for 5 minutes, and then sulfur and a vulcanization accelerator were added to the masticated rubber component using a closed Banbury mixer. The mixture was kneaded for 3 minutes at 150 ° C. to prepare a kneaded product. Next, sulfur and a vulcanization accelerator were added to the kneaded product obtained, and kneaded for 3 minutes under the condition of 80 ° C. using an open roll to obtain an unvulcanized rubber composition. Furthermore, it vulcanized for 20 minutes with the electric press heated at 170 degreeC, and obtained the vulcanized rubber composition of Examples 1-3 and Comparative Examples 1-2. The optimum vulcanization time is a time showing 90% torque of the time (T100) showing the maximum torque value after measuring the vulcanization torque curve at a heating temperature of 170 ° C. using a curast meter. Actually, since an open press is used, the optimal vulcanization time was determined by adding 5 minutes to the fear of insufficient vulcanization.

(Processability)
In accordance with the Mooney viscosity measurement method stipulated in JIS K 6300 “Testing method for unvulcanized rubber”, a small rotor is used at a temperature of 130 ° C. heated by preheating for 1 minute using a Mooney viscosity tester. The Mooney viscosity (ML _{1 + 4} ) of the unvulcanized rubber composition after 4 minutes was measured. Then, the Mooney viscosity index of Comparative Example 1 was set to 100, and the Mooney viscosity of each formulation was displayed as an index according to the following calculation formula. In addition, it shows that Mooney viscosity can be reduced and it is excellent in workability, so that Mooney viscosity index is large.
(Mooney viscosity index) = (ML _{1 + 4} of Comparative Example 1) / (ML _{1 + 4 of} each formulation) × 100

(Abrasion resistance (1))
Using a Lambourn abrasion tester, the amount of Lambourn abrasion of each formulation was measured under the conditions of a temperature of 20 ° C., a slip rate of 20%, and a test time of 5 minutes, and the volume loss was calculated. And the abrasion-resistance index (1) of the comparative example 1 was set to 100, and the volume loss amount of each combination was indicated by an index by the following calculation formula. In addition, it shows that it is excellent in abrasion resistance, so that an abrasion resistance index | exponent (1) is large.
(Abrasion resistance index (1)) = (volume loss amount of Comparative Example 1)
÷ (volume loss of each compound) x 100

(Rolling resistance)
Using a viscoelastic spectrometer VES manufactured by Iwamoto Seisakusho, tan δ of each formulation was measured under conditions of a temperature of 60 ° C., an initial strain of 10%, and a dynamic strain of 2%. And the rolling resistance index | exponent of the comparative example 1 was set to 100, and tan (delta) of each mixing | blending was index-displayed with the following formula. In addition, it shows that rolling resistance can be reduced and it is excellent, so that a rolling resistance index | exponent is large.
(Rolling resistance index) = (tan δ of Comparative Example 1) / (tan δ of each formulation) × 100

(Flat belt test)
Using a flat belt testing machine FR5010 manufactured by Ueshima Seisakusho Co., Ltd., changing the slip rate of the measurement sample to the road surface from 0 to 70% under the conditions of a road surface temperature of 20 ° C., a load of 4 kgf, and a test piece speed of 20 km / h. The maximum value of the friction coefficient of a cylindrical rubber test piece having a width of 20 mm and a diameter of 10 mm was read and used as the maximum friction coefficient. Furthermore, the grip performance index of Comparative Example 1 was set to 100, and the maximum friction coefficient of each formulation was displayed as an index according to the following formula. The larger the grip performance index, the higher the grip power and the better the grip performance.
(Grip performance index) = (Maximum friction coefficient of each formulation)
÷ (maximum friction coefficient of Comparative Example 1) × 100

(Low temperature grip performance and high temperature grip performance)
The unvulcanized rubber composition was formed into a tread shape, bonded together with other tire members on a tire molding machine, and press vulcanized under conditions of 150 ° C. and 25 kgf for 45 minutes to produce tires of various blends. .

  The manufactured tire was mounted on all the wheels of the test vehicle, and the grip performance was judged by sensory evaluation when the circuit traveled about 5 km per lap for 5 laps. The evaluation shows that the test driver has a perfect score of 100, the comparative example 1 is 50 points, and 70 points or more are good. The low temperature grip performance is measured at 15 ° C., and the high temperature grip performance is measured at 30 ° C.

(Persistence)
The manufactured tire was attached to all the wheels of the test vehicle, and the sustainability was determined by sensory evaluation when the circuit traveled about 5 km per lap for 5 laps. The evaluation shows that the test driver has a perfect score of 100, the comparative example 1 is 50 points, and 70 points or more are good.

(Abrasion resistance (2))
Wear resistance (2) was determined by sensory evaluation when the manufactured tire was mounted on all the wheels of the test vehicle and the circuit traveled about 5 km per lap for 5 laps. The evaluation shows that the test driver has a perfect score of 100, the comparative example 1 is 50 points, and 70 points or more are good.

  The evaluation results are shown in Table 2.

Claims (7)

(A) A step of acid-coagulating and drying polystyrene latex having a glass transition temperature of 90 to 150 ° C. to obtain polystyrene, and (B) 20% by weight of styrene-butadiene rubber obtained by solution polymerization and / or emulsion polymerization. For 100 parts by weight of the rubber component contained above,
A method for producing a rubber composition, comprising a step of mixing 5 to 100 parts by weight of the polystyrene obtained in the step (A) in a closed mixer. (A) A polystyrene latex having a glass transition temperature of 90 to 150 ° C. is mixed with at least one selected from the group consisting of water glass, a cationizing agent and a surfactant, and then solidified and dried to obtain a master batch. And (B) 100 parts by weight of a rubber component containing 20% by weight or more of styrene butadiene rubber obtained by solution polymerization and / or emulsion polymerization,
A method for producing a rubber composition, comprising a step of mixing 5 to 100 parts by weight of the master batch obtained in the step (A) in a closed mixer. The method for producing a rubber composition according to claim 2, wherein the blending amount of water glass is 0.5 to 90 parts by weight in terms of silica solid content with respect to 100 parts by weight of the rubber component. Furthermore, in step (B), with respect to 100 parts by weight of the rubber component,
The method for producing a rubber composition according to claim 1, 2 or 3, wherein 5 to 80 parts by weight of at least one filler selected from the group consisting of carbon black, silica, alumina and clay is mixed. Furthermore, in step (B), with respect to 100 parts by weight of the rubber component,
The manufacturing method of the rubber composition of Claim 1, 2, 3 or 4 which mixes 1-20 weight part of silane coupling agents. A rubber composition obtained by the production method according to claim 1, 2, 3, 4 or 5. A pneumatic tire using the rubber composition according to claim 6.