JP5882021B2 - Rubber composition and pneumatic tire, and method for producing fine particle rubber powder - Google Patents

Description

  The present invention relates to a fine particle rubber powder suitable for blending into a polymer composition such as a rubber composition, and also relates to a polymer composition using the same and a pneumatic tire.

  Conventionally, in order to improve physical properties of polymer compositions, particularly rubber compositions, a blend system in which a plurality of types of rubber polymers are mixed, carbon black, silica, and other organic / inorganic fillers are mixed. Techniques are known.

  In addition, in order to improve wear resistance, heat build-up, etc., it has been proposed to blend fine rubber powders such as polybutadiene rubber gel and styrene butadiene rubber gel into the rubber composition (see Patent Documents 1 to 3 below). . In these conventional techniques, fine particle rubber powder based on synthetic rubber obtained by emulsion polymerization or the like is used.

Japanese Patent Laid-Open No. 06-057038 Japanese Patent No. 3606860 JP 2006-257160 A

  In a blend system in which rubber polymers are simply kneaded and crosslinked as in the conventional case, when rubber polymers are poorly compatible (that is, the solubility parameter SP value is extremely different), one rubber polymer becomes the other rubber polymer. It is difficult to obtain a finely dispersed uniform phase structure, and there is a problem that desired physical properties cannot be obtained. In addition, carbon black, silica, and other organic / inorganic fillers are inferior in compatibility with the rubber polymer, and surface treatment or a coupling agent may be required to improve physical properties.

  On the other hand, since the conventional fine particle rubber powder is composed of an emulsion polymer of synthetic rubber, there is a problem that the molecular weight is relatively small and the physical properties are inferior. There is a problem that it is large and the variation becomes large.

In view of the above points, the present invention uses a method for producing fine particle rubber powder that can improve the physical properties of the rubber composition when used in a polymer composition such as a rubber composition, and the fine particle rubber powder . An object is to provide a rubber composition.

The rubber composition according to the present invention, 100 parts by mass of the base polymer comprising a sulfur-cross-linkable rubber, epoxidized natural rubber viscosity average molecular weight average particle diameter of Ri der less 10μm is 500,000 to 1,500,000 1 to 300 parts by mass of a fine particle rubber powder made from the above, and the fine particle rubber powder is dispersed in the base polymer . The pneumatic tire according to the present invention has a rubber portion using the rubber composition.

  The present invention also provides the production of fine particle rubber powder comprising an epoxidized natural rubber, characterized in that a natural rubber latex prepared with DRC of 70 to 85% by mass is epoxidized with hydrogen peroxide. Provide a method.

  When the fine particle rubber powder according to the present invention is blended into the polymer composition, good physical properties can be imparted. In particular, when used in a pneumatic tire, it is possible to control viscoelasticity, hardness and the like by setting the epoxy group amount of the fine particle rubber powder, and for example, wet skid property and heat generation property can be improved.

  Hereinafter, matters related to the implementation of the present invention will be described in detail.

[Fine particle rubber powder]
The fine particle rubber powder according to the present invention is made of epoxidized natural rubber. In this way, natural rubber derived from nature is used for modification, so that a fine particle rubber powder having the characteristics of a natural rubber having a high molecular weight can be obtained, and the physical property improving effect is excellent.

Moreover, since the glass transition point and crystallinity change by changing the epoxidation rate, the hardness of the fine particle rubber powder and the viscoelasticity of the polymer composition can be controlled by the epoxidation rate. The epoxidation rate can be set within a range of 100 mol% or less. The lower the epoxidation rate, the closer to the rubber polymer, and the rubber composition can be used as a substitute for the rubber polymer. On the contrary, the higher the epoxidation rate, the harder the resin is approached, so that it can be used as a substitute for the filler in the rubber composition. Here, the epoxidation rate is a ratio of the number of moles of epoxy groups to the number of moles of all isoprene units, and is determined by proton nuclear magnetic resonance ( ¹ H-NMR) of proton peaks of isoprene double bonds and epoxy group bonds. Quantified by ratio.

  For example, when the epoxidation rate is 5 to 50% by mole, a pseudo phase structure having a uniform phase that cannot be obtained by a conventional polymer blend system using kneading / crosslinking by using fine particle rubber powder as a rubber polymer alternative It can be. That is, since the fine particle rubber powder is originally in the form of fine particles having a predetermined particle diameter, it is possible to form a sea-island structure in which the base polymer is the sea phase and the fine particle rubber powder is uniformly dispersed in the island phase. Therefore, physical properties such as dynamic viscoelasticity and tension can be improved. Thus, when using as a rubber polymer substitute, it is more preferable that an epoxidation rate is 10-40 mol%.

  Also, when the epoxidation rate is more than 50 mol% and 100 mol% or less, the use of fine particle rubber powder as a filler substitute gives excellent physical properties that cannot be achieved with a conventional rubber polymer / filler mixed system. Can do. That is, the fine particle rubber powder is made of natural rubber and has better compatibility with the rubber polymer than fillers such as carbon black and silica, so that aggregation can be suppressed and heat generation can be improved. . Also, the tensile properties can be improved. Moreover, since the specific gravity is smaller and lighter than conventional fillers, the weight of the polymer composition can be reduced. Thus, when using as a filler substitute, it is more preferable that an epoxidation rate is 60-80 mol%.

  The molecular weight of the epoxidized natural rubber constituting the fine particle rubber powder is not particularly limited, but the viscosity average molecular weight of 100,000 to 1,500,000 maintains the shape regardless of the surrounding polymer during kneading. It is preferable from the point which can be performed. The viscosity average molecular weight is more preferably 500,000 to 1,300,000, still more preferably 800,000 to 1,200,000.

  The average particle size of the fine particle rubber powder is preferably 10 μm or less. When the average particle diameter exceeds 10 μm, the reinforcing property is inferior, and when used in the polymer composition, the tensile strength, elongation, abrasion resistance, etc. are insufficient. The lower limit of the average particle diameter of the fine particle rubber powder is not particularly limited, but is preferably 0.001 μm or more. The average particle size of the fine particle rubber powder is more preferably 0.01 to 5 μm, still more preferably 0.1 to 1 μm. Here, the average particle diameter is a value measured using a laser diffraction particle size distribution measuring apparatus.

  Fine particle rubber powder made of epoxidized natural rubber can be obtained by epoxidizing natural rubber latex. Specifically, natural rubber latex in an emulsified state is prepared (concentrated) with DRC (Dry Rubber Content) to about 80% by mass (for example, 70 to 85% by mass), and epoxidized with hydrogen peroxide using this. By doing so, a fine particle state can be created by hydrogen bonding between the epoxy group and the polymer in the emulsified particles, and by adding water again there, a stable fine particle rubber latex can be obtained. Rubber powder can be obtained. The DRC is not limited to the above concentration, but when the latex concentration is low, there are few fine particles obtained, resulting in ordinary epoxidized natural rubber. On the other hand, when the concentration is higher than the above-mentioned concentration, the emulsified state becomes unstable, so that the fine particles are easily destroyed by chemicals or temperature environment.

  The fine particle rubber powder of the epoxidized natural rubber thus obtained has a low ratio of being formed into particles by internal crosslinking, and is formed into particles with a high degree of entanglement between molecules. Therefore, the fine particle rubber powder is dissolved in toluene, and therefore has a large toluene swelling index, and this point is also different from the rubber gels described in Patent Documents 1 to 3. Moreover, in spite of the low rate of internal cross-linking, the fine particle rubber powder has lost its thermoplasticity and retains its fine particle form as it is when mixed with the rubber polymer. The fine particle rubber powder is not limited to the case where it is not internally cross-linked as described above, and may form internal cross-links using sulfur, peroxide, etc. In that case, the degree of cross-linking is increased. The toluene swelling index becomes smaller as it goes.

[Polymer composition]
In the polymer composition according to the present invention, the base polymer is not particularly limited, and various polymers such as a rubber polymer, a thermoplastic resin, and a thermosetting resin can be used. For example, in the case of applications such as films and sheets, various thermoplastic resins such as nylon, polyethylene, polystyrene, polyvinyl chloride, and polypropylene can be used as the base polymer.

  Preferably, a rubber polymer is used as the base polymer, in which case the polymer composition is also referred to as a rubber composition. The rubber polymer may be non-sulfur crosslinkable rubber such as silicone rubber, fluorine rubber, acrylic rubber, etc., but preferably sulfur crosslinkable rubber is used. The sulfur crosslinkable rubber includes natural rubber (NR), polyisoprene rubber (IR), styrene butadiene rubber (SBR), polybutadiene rubber (BR), styrene-isoprene copolymer rubber, butadiene-isoprene copolymer rubber, styrene. -In addition to diene rubbers such as isoprene-butadiene copolymer rubber, nitrile rubber (NBR), and chloroprene rubber (CR), butyl rubber (IIR), halogenated butyl rubber, ethylene propylene diene copolymer rubber (EPDM), etc. These may be used alone or in combination of two or more. Moreover, the same effect is acquired also with respect to the modified polymer which gave some functional groups to these. Among these, at least one selected from the group consisting of natural rubber, polyisoprene rubber, styrene butadiene rubber, and polybutadiene rubber is particularly preferably used. More preferably, it is natural rubber and / or polyisoprene rubber, and these rubbers are excellent in compatibility with the fine particle rubber powder made of epoxidized natural rubber. Can be increased.

  The blending amount of the fine particle rubber powder is not particularly limited, but usually it is preferably blended at 1 to 300 parts by weight with respect to 100 parts by weight of the base polymer (here, 100 blending amount of the base polymer). The amount of fine rubber powder is not included in the weight part). The blending amount of the fine particle rubber powder is more preferably 5 to 200 parts by mass, and still more preferably 10 to 100 parts by mass. When the blending amount of the fine particle rubber powder exceeds 300 parts by mass, the ratio of the base polymer to the fine particle rubber powder becomes too low even when the fine particle rubber powder is considered as a polymer substitute, and the fine particle rubber powder is locked by the base polymer. It becomes difficult to maintain the shape.

  In particular, when the polymer composition is a tire rubber composition, the amount of the fine particle rubber powder is preferably 5 to 200 parts by mass with respect to 100 parts by mass of the sulfur crosslinkable rubber as the base polymer. More preferably, it is 10-100 mass parts. If the blending amount of the fine particle rubber powder is less than 5 parts by mass, the effect of addition may be insufficient. On the other hand, when the amount exceeds 200 parts by mass, when the fine particle rubber powder is used as a rubber polymer substitute, the amount of fine particle rubber powder that becomes an island phase becomes relatively large, and a pseudo-layer structure having a uniform phase is taken. In addition, when the fine particle rubber powder is used as a filler substitute, the amount of the filler is excessively increased, and the elongation and tear strength may be significantly reduced.

  The polymer composition according to the present invention can contain a filler such as carbon black or silica. The blending amount of the filler is not particularly limited, but in the case of a rubber composition, particularly a tire rubber composition, it is preferably 5 to 100 parts by mass with respect to 100 parts by mass of the base polymer (sulfur crosslinkable rubber). More preferably, it is 10-50 mass parts.

  The carbon black is not particularly limited. For example, SAF class (N100 series), ISAF class (N200 series), HAF class (N300 series), FEF (N500 series), GPF (N600 series) (both ASTM grade) Things. The silica is not particularly limited, and examples thereof include those having a silicon dioxide structure such as wet silica, dry silica, colloidal silica, and precipitated silica. It is particularly preferable to use wet silica containing hydrous silicic acid as a main component. In addition, when mix | blending a silica as a filler, it is preferable to use together silane coupling agents, such as sulfide silane and mercaptosilane, and a silane coupling agent is 2-25 mass parts normally with respect to 100 mass parts of silica. Can be used.

  Examples of fillers other than carbon black and silica include titanium oxide, clay, talc, and calcium carbonate. In addition, any one of the above-mentioned carbon black, silica, and other fillers may be used alone, or a plurality of fillers may be used in combination.

  In addition to the above components, the polymer composition according to the present invention may optionally contain various additives such as a softener, a plasticizer, an antiaging agent, zinc white, stearic acid, a vulcanizing agent, and a vulcanization accelerator. Can be blended. In a rubber composition using a sulfur crosslinkable rubber as a base polymer, sulfur or a sulfur-containing compound is usually blended as a vulcanizing agent. Although it does not specifically limit, it is preferable that the compounding quantity of a vulcanizing agent is 0.1-10 mass parts with respect to 100 mass parts of said sulfur crosslinkable rubber, More preferably, it is 0.5-5 mass parts. is there. In this case, a vulcanization accelerator is usually blended together with the vulcanizing agent, and the blending amount is preferably 0.1 to 7 parts by mass with respect to 100 parts by mass of the sulfur crosslinkable rubber. Preferably it is 0.5-5 mass parts. When the fine particle rubber powder is used as a substitute for the rubber polymer as described above, crosslinking is performed even inside the fine particle rubber powder during vulcanization of the rubber composition, and crosslinking is also performed between the fine particle rubber powder and the sulfur crosslinkable rubber. Done. Therefore, in this case, it is preferable to blend 0.1 to 10 parts by mass of the vulcanizing agent with respect to 100 parts by mass of the total amount based on the total amount of the sulfur crosslinkable rubber and the fine particle rubber powder, and more preferably Is to blend 0.5 to 5 parts by mass.

  The preparation method of the said polymer composition is not specifically limited, It can prepare using a normal mixing method. For example, in the case where the polymer composition is a rubber composition, it is prepared by kneading using a rubber kneader such as an ordinary Banbury mixer or kneader, and formed into a predetermined shape and crosslinked to form a tire, a vibration-proof rubber, Various rubber products such as belts can be obtained. Preferably, it is used as a rubber composition for tires, and various rubber parts such as tread rubber and sidewall rubber of a pneumatic tire are formed by vulcanization molding at 140 to 180 ° C. according to a conventional method. can do.

  Examples of the present invention will be described below, but the present invention is not limited to these examples.

  The average particle diameter, viscosity average molecular weight and specific gravity of the fine particle rubber powder were measured as follows.

Average particle size: Measured with a laser diffraction particle size distribution analyzer “SALD-2200” manufactured by Shimadzu Corporation using a red semiconductor laser (wavelength 680 nm) as a light source, and the average value of the particle size distribution was defined as the average particle size.

Viscosity average molecular weight: Viscosity was measured by “Viscosity measuring device PVS1” manufactured by LAUDA. Using 1,4-polyisoprene (molecular weight: 600, 1500, 7500, 21000, 80000, 210000, 750,000, 1000000) as standard samples, and calculating the coefficients K and α of [η] = KM ^α by the viscosity method (Where [η] is the intrinsic viscosity and M is the molecular weight), and the viscosity average molecular weight of each sample was determined from the equation using the coefficient.

Specific gravity: Measured using a hydrometer “MICROMERITICS” manufactured by Shimadzu Corporation.

[Fine particle rubber powder 1: fine particle rubber powder having an epoxidation rate of 10 mol%]
While adding 2.4 g of sodium dodecyl sulfate (SDS) as an emulsifier to 100 g of natural rubber latex (“LA-NR” manufactured by Regex, Inc., DRC = 60% by mass), the emulsified state is stabilized, while stirring at 50 rpm. It heated at 40 degreeC and the water | moisture content was blown until DRC = 80 mass%. Thereto, 14.2 g of 30% by mass hydrogen peroxide and 5.4 g of formic acid were added dropwise and reacted at 60 ° C. for 24 hours. 100 g of water was added to this, redispersed in water, stirred at room temperature for 1 hour, and then dried to obtain fine particle rubber powder 1. The obtained fine particle rubber powder 1 had an epoxidation rate of 10 mol%, an average particle size of 0.6 μm, a viscosity average molecular weight of 1,200,000, and a specific gravity of 0.92.

[Fine particle rubber powder 2: Fine particle rubber powder having an epoxidation rate of 25 mol%]
The amount of hydrogen peroxide water was 35.4 g, the amount of formic acid was 13.6 g, and the others were the same as the fine particle rubber powder 1 to obtain fine particle rubber powder 2. The obtained fine particle rubber powder 2 had an epoxidation rate of 25 mol%, an average particle diameter of 0.5 μm, a viscosity average molecular weight of 1,180,000, and a specific gravity of 0.93.

[Fine particle rubber powder 3: fine particle rubber powder having an epoxidation rate of 40 mol%]
The amount of hydrogen peroxide water was 56.6 g, the amount of formic acid was 21.7 g, and the other procedures were the same as those of the fine particle rubber powder 1 to obtain a fine particle rubber powder 3. The obtained fine particle rubber powder 3 had an epoxidation rate of 40 mol%, an average particle size of 0.5 μm, a viscosity average molecular weight of 11,120,000, and a specific gravity of 0.93.

[Fine particle rubber powder 4: fine particle rubber powder having an epoxidation rate of 60 mol%]
The amount of hydrogen peroxide water was 85.0 g, the amount of formic acid was 32.6 g, and the other procedures were the same as those of the fine particle rubber powder 1 to obtain a fine particle rubber powder 4. The obtained fine particle rubber powder 4 had an epoxidation rate of 60 mol%, an average particle diameter of 0.5 μm, a viscosity average molecular weight of 1,160,000, and a specific gravity of 0.93.

[Fine particle rubber powder 5: Fine particle rubber powder having an epoxidation rate of 80 mol%]
The amount of hydrogen peroxide water was 113 g, the amount of formic acid was 43.4 g, and the other procedures were the same as those of the fine particle rubber powder 1 to obtain a fine particle rubber powder 5. The obtained fine particle rubber powder 5 had an epoxidation rate of 80 mol%, an average particle diameter of 0.6 μm, a viscosity average molecular weight of 11,120,000, and a specific gravity of 0.93.

[First embodiment] (polymer substitute)
A rubber composition for a tire was prepared according to a conventional method according to the formulation (parts by mass) shown in Table 1 below using a Banbury mixer using the fine particle rubber powders 1 to 3 obtained above as a polymer substitute. Specifically, first, components except for sulfur and vulcanization accelerator are kneaded in the first mixing stage, and then sulfur and vulcanization accelerator are added and kneaded to the obtained kneaded product in the final mixing stage. A rubber composition was prepared. Each component in the table is as follows.

・ Natural rubber: RSS # 3
-Epoxidized natural rubber 1: “ENR-25” manufactured by MRB, Malaysia
-Epoxidized natural rubber 2: “ENR-50” manufactured by MRB, Malaysia
・ Silica: “Nip Seal AQ” manufactured by Tosoh Silica Co., Ltd.
Silane coupling agent: bis (3-triethoxysilylpropyl) tetrasulfide, “Si69” manufactured by Evonik Degussa
・ Zinc flower: “Zinc flower 1” manufactured by Mitsui Mining & Smelting Co., Ltd.
・ Stearic acid: “Lunac S-20” manufactured by Kao Corporation
・ Sulfur: "Sulfur powder for rubber 150 mesh" manufactured by Hosoi Chemical Co., Ltd.
・ Vulcanization accelerator: “Noxeller CZ” manufactured by Ouchi Shinsei Chemical Co., Ltd.

・ Polybutadiene rubber gel: A butadiene rubber latex “Nipol LX111A2” (DRC = 54% by mass) manufactured by Zeon Corporation was peroxide-crosslinked with benzoyl peroxide (BPO) at 80 ° C. and gelled. The dried product was dried to obtain a polybutadiene rubber gel. The obtained gel powder had a particle size of 0.3 μm and a specific gravity of 0.92.

Styrene butadiene rubber gel: styrene butadiene rubber latex “Nipol LX110” (DRC = 40.5 mass%) manufactured by Nippon Zeon Co., Ltd. was peroxide-crosslinked at 80 ° C. with benzoyl peroxide (BPO) while stirring at 100 rpm. The gelled product was dried to obtain a styrene butadiene rubber gel. The resulting gel powder had a particle size of 0.2 μm and a specific gravity of 0.95.

  Each rubber composition obtained was vulcanized at 160 ° C. for 20 minutes to prepare a test piece having a predetermined shape, and a dynamic viscoelasticity test was performed using the obtained test piece to obtain tan δ (0 ° C.). And tan δ (60 ° C.) were evaluated, a tensile test was performed, M300 and EB were evaluated, and hardness was further evaluated. Each evaluation method is as follows.

Tan δ (0 ° C.): Using a rheometer E4000 manufactured by USM, the loss factor tan δ was measured under the conditions of a frequency of 50 Hz, a static strain of 10%, a dynamic strain of 2%, and a temperature of 0 ° C. Expressed with an index of 100. Tan δ at 0 ° C. is generally used as an index of grip performance (wet performance) on a wet road surface, and the larger the index, the larger tan δ, and the better the wet performance.

Tan δ (60 ° C.): tan δ was measured in the same manner as tan δ (0 ° C.) except that the temperature was changed to 60 ° C., and the reciprocal number was expressed as an index with the value of Comparative Example 1 being 100. The tan δ at 60 ° C. is generally used as an index of low heat generation. The larger the index, the smaller the tan δ. Therefore, the tan δ is less likely to generate heat and is excellent in low fuel consumption as a tire.

M300, EB: A tensile test based on JIS K6251 was performed (dumbbell No. 3), and M300 (modulus at 300% elongation) and EB (elongation at break) were displayed as an index with the value of Comparative Example 1 being 100. . It shows that M300 and EB are large and the reinforcing property is excellent as the index is large.

Hardness: Measured according to JIS K6253 (type A durometer), and displayed as an index with the value of Comparative Example 1 being 100. The larger the index, the higher the hardness.

  The results are as shown in Table 1, and in Comparative Examples 2 and 3 using a general epoxidized natural rubber which is not a fine particle-shaped rubber powder, although the wet performance was slightly improved, the improvement effect was small, The improvement effect of the low fuel consumption was not obtained, and further, the reinforcing property, particularly the M300 was lowered.

  On the other hand, in Examples 1 to 7 using the fine particle rubber powder made of epoxidized natural rubber, the wet performance improvement effect was excellent, and the low fuel consumption improvement effect was also excellent. Further, the reinforcing property, particularly EB, was high, and the decrease in M300 was not observed.

[Second Example] (Filler replacement)
Using the fine rubber powders 4 and 5 obtained above as a substitute for a filler, a banbury mixer was used, and a rubber composition for tires was prepared according to a conventional method according to the formulation (parts by mass) shown in Table 2 below. Specifically, first, components except for sulfur and vulcanization accelerator are kneaded in the first mixing stage, and then sulfur and vulcanization accelerator are added and kneaded to the obtained kneaded product in the final mixing stage. A rubber composition was prepared. Each component in Table 2 is the same as in the first example.

  About each obtained rubber composition, tan-delta (0 degreeC), tan-delta (60 degreeC), M300, EB, and hardness were evaluated similarly to 1st Example (In addition, the comparative example 1 used as reference | standard is 1st implementation. Same as example).

  The results are shown in Table 2, and in Comparative Example 4 using a general epoxidized natural rubber that is not a fine particle-shaped rubber powder, the wet performance was improved, but the improvement effect of low fuel consumption was obtained. In addition, the reinforcing property, particularly M300, decreased in hardness. In Comparative Example 5 using polybutadiene rubber gel, the improvement effect was insufficient with respect to both wet performance and low fuel consumption, and the reinforcing property, particularly M300, was lowered. Also in Comparative Example 6 using styrene butadiene rubber gel, the effect of improving the fuel efficiency was insufficient, and the reinforcing property, particularly M300, was reduced. On the other hand, in Examples 8 to 12 using fine particle rubber powder made of epoxidized natural rubber, the fuel economy was excellent in the improvement effect without impairing the wet performance. Moreover, EB and M300 were improved, and an effect of improving the reinforcing property was observed.

[Third embodiment]
Using a Banbury mixer, a tire rubber composition was prepared according to a conventional method according to the formulation shown in Table 3 below. Specifically, first, components except for sulfur and vulcanization accelerator are kneaded in the first mixing stage, and then sulfur and vulcanization accelerator are added and kneaded to the obtained kneaded product in the final mixing stage. A rubber composition was prepared. SBR in the table is styrene butadiene rubber (“SBR1502” manufactured by JSR Corporation), and the others are the same as in Table 1.

  About each rubber composition obtained, tan δ (0 ° C.), tan δ (60 ° C.), M300, EB and hardness were evaluated in the same manner as in the first example (all evaluations were based on Comparative Example 7). It was indicated by an index for that).

  The results are as shown in Table 3, and in Comparative Examples 8 and 9 using a general epoxidized natural rubber that is not a fine particle-shaped rubber powder, although the wet performance was improved, the fuel efficiency was deteriorated. In addition, there was a decrease in reinforcing properties, particularly M300. In Comparative Example 10 using styrene-butadiene rubber, both wet performance and low fuel consumption were improved, but the reinforcement, particularly M300, was reduced. On the other hand, in Examples 13 and 15 in which fine particle rubber powder made of epoxidized natural rubber was used as a polymer substitute, the wet performance was improved and the fuel efficiency was improved. Moreover, reinforcement property, especially M300 was improving, and the fall like Comparative Examples 8-10 was not seen. Further, in Example 14 in which the fine particle rubber powder was used as a substitute for the filler, the effect of improving the fuel efficiency was excellent without impairing the wet performance. Moreover, EB and M300 were improved, and an effect of improving the reinforcing property was observed.

  The fine particle rubber powder according to the present invention can be used as a component to be blended in a resin molded product for various uses such as a film, a sheet, a paint, and a coating material. It can use as a component mix | blended with the rubber composition of the use of. Particularly preferably, it is used as a rubber composition for tires and can be suitably used for pneumatic tires for heavy loads such as trucks and buses as well as pneumatic tires for passenger cars.

Claims (5)

1 to 300 parts by mass of fine particle rubber powder made of epoxidized natural rubber having an average particle diameter of 10 μm or less and a viscosity average molecular weight of 500,000 to 1,500,000, based on 100 parts by mass of a base polymer made of sulfur-crosslinkable rubber Ri Na blended with a rubber composition in which the fine rubber powder is dispersed in the base polymer. The rubber composition according to claim 1 , wherein the fine particle rubber powder has an epoxidation rate of 5 mol% or more and 50 mol% or less. 2. The rubber composition according to claim 1 , wherein the fine particle rubber powder has an epoxidation ratio of more than 50 mol% and 100 mol% or less. The pneumatic tire which has a rubber part which uses the rubber composition of any one of Claims 1-3 .   A method for producing a fine particle rubber powder comprising an epoxidized natural rubber, wherein a natural rubber latex having DRC adjusted to 70 to 85% by mass is epoxidized using hydrogen peroxide.