JP2008189718A - Method for producing rubber composition, rubber composition obtained thereby and pneumatic tire using the same rubber composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a rubber composition by which rolling resistance can be reduced and all the processability, abrasion resistance, gripping performances and persistence can be improved to improve the gripping performances particularly under wide temperature conditions. <P>SOLUTION: The rubber composition is produced by the following steps: (A) a step of mixing a latex of a synthetic rubber (1) having 0-100°C glass transition temperature with a latex of a synthetic rubber (2) having 5-105°C glass transition temperature which is higher than that of the synthetic rubber (1) and 5-105°C difference in the glass transition temperature from the synthetic rubber (1) and at least one kind selected from the group consisting of water glass, a cationizing agent and a surfactant, (B) a step of coagulating the mixture obtained in the step (A) with an acid, then drying the mixture and affording a rubber master batch and (C) a step of mixing 100 pts.wt. of a rubber component containing ≥20 wt.% of a styrene-butadiene rubber obtained by a solution polymerization method or an emulsion polymerization method with 5-100 pts.wt. of the rubber master batch obtained in the step (B) in a hermetically closed type mixer. <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.

  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, improve processability, wear resistance, and grip performance, and can improve grip performance particularly in a wide temperature condition. With the goal.

  The present invention includes (A) a latex of synthetic rubber (1) having a glass transition temperature of 0 to 100 ° C., a glass transition temperature of 5 to 105 ° C. larger than that of synthetic rubber (1), and synthetic rubber (1). A step of mixing the latex of the synthetic rubber (2) having a glass transition temperature difference of 5 to 105 ° C. and at least one selected from the group consisting of water glass, a cationizing agent and a surfactant, (B) A step of acid coagulating the mixture obtained in step (A) and then drying to obtain a rubber master batch; and (C) a rubber containing 20% by weight or more of styrene butadiene rubber obtained by a solution polymerization method or an 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 rubber master batch obtained in step (B) with 100 parts by weight of a component in a closed mixer.

  In the step (A), it is preferable to mix 0.5 to 90 parts by weight of water glass in terms of silica solid content with respect to 100 parts by weight of rubber solid content in the total synthetic rubber latex.

  In the step (C), it is preferable to further mix 5 to 80 parts by weight of at least one filler selected from the group consisting of carbon black, silica, alumina and clay.

  In the step (C), it is preferable to further mix 1 to 20 parts by weight of a silane coupling agent.

  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, two or more types of predetermined synthetic rubber latex and at least one selected from the group consisting of water glass, a cationizing agent and a surfactant are mixed in advance to prepare a rubber master batch, By adding a certain amount to the rubber component, it is possible to reduce rolling resistance and improve all of workability, wear resistance and grip performance, and particularly to improve grip performance under a wide range of temperature conditions. A rubber composition can be produced.

  The method for producing the rubber composition of the present invention comprises at least one selected from the group consisting of (A) latex of synthetic rubber (1), latex of synthetic rubber (2), water glass, cationizing agent and surfactant. A step of mixing seeds, (B) a step of acid coagulating the mixture obtained by step (A) and then drying to obtain a rubber masterbatch, and (C) a rubber component and a step (B) Mixing the rubber masterbatch in a closed mixer.

  In the step (A), the latex of the synthetic rubber (1) and the latex of the synthetic rubber (2) are mixed with at least one selected from the group consisting of water glass, a cationizing agent and a surfactant. The lower glass transition temperature (Tg) is the synthetic rubber (1) latex, and the higher glass transition temperature (Tg) is the synthetic rubber (2) latex.

  Examples of the latex of the synthetic rubber (1) and the latex of the synthetic rubber (2) include styrene butadiene rubber (SBR) latex, butadiene rubber (BR) latex, isoprene rubber (IR) latex, and the like, and are particularly limited. However, SBR latex is preferred because of its excellent compatibility with NR and low cost. Further, as the latex of the synthetic rubber (1) and the latex of the synthetic rubber (2), two or more kinds of different synthetic rubber latex (for example, SBR latex and BR latex) may be used. Two or more types (for example, two or more types of SBR latex) are preferably used.

  When only one kind of synthetic rubber latex is used, the resulting rubber composition can produce a tan δ peak derived from latex only under a limited temperature condition, thus improving the grip performance only under a limited temperature condition. I can't. In the present invention, by using two or more kinds of predetermined synthetic rubber latexes having different Tg, the width of the tan δ peak derived from the latex can be widened in the rubber composition, and the grip performance is improved under a wide temperature condition. Can do.

  In the present invention, when SBR latex is used as the synthetic rubber latex, Tg can be changed by changing the styrene unit amount.

  The glass transition temperature (hereinafter referred to as Tg (1)) of the latex of the synthetic rubber (1) is 0 ° C. or higher. Moreover, Tg (1) is 100 degrees C or less. When Tg (1) exceeds 100 ° C., the properties as a resin become strong, and the resin cannot be kneaded and causes poor dispersion.

  The glass transition temperature (hereinafter referred to as Tg (2)) of the latex of the synthetic rubber (2) is 5 ° C. or higher. Moreover, Tg (2) is 105 degrees C or less.

  The difference between Tg (1) and Tg (2) is 5 ° C. or higher, preferably 20 ° C. or higher. When the difference between Tg (1) and Tg (2) is less than 5 ° C., the grip performance in a wide temperature range cannot be improved. The difference between Tg (1) and Tg (2) is 105 ° C. or less. If the difference between Tg (1) and Tg (2) exceeds 105 ° C., the tan δ curve cannot be broadened, resulting in a double mountain structure, and the grip performance in the intermediate temperature range cannot be improved.

  The rubber solid content in the latex of the synthetic rubber (1) and the rubber solid content in the latex of the synthetic rubber (2) are both preferably 10% by weight or more, and more preferably 30% by weight or more. When either the rubber solid content in the latex of the synthetic rubber (1) or the rubber solid content in the latex of the synthetic rubber (2) is less than 10% by weight, the amount of rubber that can be recovered after coagulation is very small There is a tendency to be slight. The rubber solid content in the latex of the synthetic rubber (1) and the rubber solid content in the latex of the synthetic rubber (2) are both preferably 75% by weight or less, and more preferably 60% by weight or less. If either of the rubber solid content in the latex of the synthetic rubber (1) or the rubber solid content in the latex of the synthetic rubber (2) exceeds 75% by weight, the rubber particles are stably present in water. There is a tendency to become impossible.

  In the present invention, the ratio of the amount of latex of synthetic rubber (1) (hereinafter referred to as mixing amount (1)) to the amount of latex of synthetic rubber (2) (hereinafter referred to as mixing amount (2)) ( The mixing amount (1) / mixing amount (2)) is preferably 5/95 or more, and more preferably 15/85 or more. When the mixing amount (1) / mixing amount (2) is less than 5/95, the latex characteristic of the synthetic rubber (1) is difficult to be obtained, and the grip performance of the synthetic rubber (1) near the tan δ peak temperature can be improved. In addition, the strength does not tend to improve. The mixing amount (1) / mixing amount (2) is preferably 95/5 or less, more preferably 85/15 or less. If the mixing amount (1) / mixing amount (2) exceeds 95/5, it is difficult to obtain the latex characteristics of the synthetic rubber (2), and the grip performance of the synthetic rubber (2) near the tan δ peak temperature can be improved. It cannot be done, and there is a tendency that strength is not 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. On the other hand, if 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.

  When water glass is used, the blending amount of water glass is 0.5 parts by weight or more, preferably 10 parts by weight or more in terms of silica solids with respect to 100 parts by weight of the total rubber solids in the synthetic rubber latex. It is. 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.

  There is no restriction | limiting in particular as a cationizing agent, Although what is marketed can be used, Specifically, the glycidyl trimethyl ammonium chloride by Yokkaichi synthesis 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 using a cationizing agent and / or a surfactant, the compounding 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 total rubber solid content in the synthetic rubber latex. 5 parts by weight or more is more preferable. 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.

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

  In step (B), the mixture obtained in step (A) is acid-coagulated and then dried to obtain a rubber master batch.

  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, the aqueous solution remains alkaline and the rubber tends not to coagulate. If the amount exceeds 5 parts by weight, when a strong acid is used as the reaction solution, the resulting rubber is It tends to take time to wash to neutrality.

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. When the drying temperature exceeds 60 ° C., the rubber tends to deteriorate.

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

  The rubber component 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 40% by weight or more. When the SBR content is less than 20% by weight, the heat resistance (aging resistance), ozone resistance, and wear resistance of the rubber are lowered. 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), butyl rubber (IIR), halogenated butyl rubber and the like can be mentioned, and these rubbers can be used alone or in combination of two or more with SBR.

  The compounding amount of the rubber master batch obtained by the step (B) is 5 parts by weight or more, preferably 10 parts by weight or more with respect to 100 parts by weight of the rubber component. When the compounding amount of the rubber master batch is less than 5 parts by weight, the tan δ peak does not increase and the effect of improving the grip performance is not observed. Moreover, the compounding quantity of a rubber masterbatch is 100 weight part or less, Preferably it is 50 weight part or less. When the blending amount of the rubber masterbatch exceeds 100 parts by weight, rubber elasticity is not exhibited.

  When mixing the rubber component and the rubber masterbatch, a closed mixer such as a Banbury mixer or a kneader is used.

  In the step (C), when the rubber component and the 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. The blending amount of the filler is preferably 80 parts by weight or less, more preferably 70 parts by weight or less, and further preferably 60 parts by weight or less. When the blending amount of the filler exceeds 80 parts by weight, workability and workability deteriorate.

  In the step (C), 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, rubber masterbatch, filler and silane coupling agent, the rubber composition produced by the production method of the present invention includes compounding agents conventionally used in the rubber industry, such as anti-aging agents. Vulcanizing agents such as stearic acid, zinc oxide, and sulfur, vulcanization accelerators, 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
Master batch (1): produced by the following production method (master batch comprising water glass and two types of SBR latex)
Master batch (2): produced by the following production method (master batch comprising water glass and one kind of SBR latex)
Master batch (3): produced by the following production method (master batch comprising water glass and one kind of SBR latex)
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 master batches (1) to (3))
In accordance with the mixed formulation shown in Table 1, No. 3 water glass (n: 2.1-3.1, silica solid content: 29.5% by weight) defined in JIS K 1408, SBR latex (1) (Nippon Zeon) Lx407K3 manufactured by Co., Ltd., rubber solid content: 40 wt%, Tg: 15 ° C.) and SBR latex (2) (Lx 433 manufactured by Nippon Zeon Co., Ltd., rubber solid content: 45 wt%, Tg: 50 ° C.) 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).

Example 1 and Comparative Examples 1-3
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 Example 1 and Comparative Examples 1-3. 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 test)
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 | exponent of the comparative example 1 was set to 100, and the volume loss amount of each mixing | blending was displayed as an index | exponent with the following formula. In addition, it shows that it is excellent in abrasion resistance, so that an abrasion resistance index | exponent is large.
(Abrasion resistance index) = (volume loss amount of Comparative Example 1) / (volume loss amount of each formulation) × 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

  The evaluation results are shown in Table 2.

Claims (6)

(A) a latex of synthetic rubber (1) having a glass transition temperature of 0 to 100 ° C .;
A latex of synthetic rubber (2) having a glass transition temperature larger than that of synthetic rubber (1) and 5 to 105 ° C., and a difference in glass transition temperature from synthetic rubber (1) of 5 to 105 ° C .;
Mixing at least one selected from the group consisting of water glass, a cationizing agent and a surfactant;
(B) A step of acid coagulating the mixture obtained in step (A) and then drying to obtain a rubber master batch; and (C) 20% by weight of styrene butadiene rubber obtained by a solution polymerization method or an emulsion polymerization method. A method for producing a rubber composition comprising a step of mixing 5 to 100 parts by weight of the rubber master batch obtained in the step (B) with 100 parts by weight of the rubber component contained above in a closed mixer. In the step (A), with respect to 100 parts by weight of the rubber solid content in the total synthetic rubber latex,
The method for producing a rubber composition according to claim 1, wherein 0.5 to 90 parts by weight of water glass is mixed in terms of silica solid content. The method for producing a rubber composition according to claim 1 or 2, wherein in the step (C), 5 to 80 parts by weight of at least one filler selected from the group consisting of carbon black, silica, alumina and clay is further mixed. The method for producing a rubber composition according to claim 1, 2 or 3, further comprising mixing 1 to 20 parts by weight of a silane coupling agent in the step (C). The rubber composition obtained by the manufacturing method of the rubber composition of Claim 1, 2, 3 or 4. A pneumatic tire using the rubber composition according to claim 5.