JP2012140510A - Antioxidant for rubber compounding, method for producing the same and rubber composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve sustainability of weather resistance while suppressing discoloration of a rubber surface and improving the appearance by improving sustained releasability of an antioxidant.SOLUTION: The antioxidant for rubber compounding use is produced by including an antioxidant in porous particles and fixing fine particles of a resin and/or metal oxide having an average particle diameter corresponding to 1/100 to 1/5 of the average particle diameter of the porous particles and infusible at ≤160°C to the surfaces of the porous particles using a high-speed airflow impact method.

Description

  The present invention relates to an antioxidant for rubber blending and a method for producing the same. The present invention also relates to a rubber composition containing the rubber composition anti-aging agent and a pneumatic tire using the rubber composition.

  A pneumatic tire is deteriorated by oxygen and ozone in the atmosphere during long-term use, and thus cracks are generated in the groove portions of the sidewall portions and the tread portion, which causes deterioration in durability. Therefore, various anti-aging agents are blended in the tire rubber composition in order to improve oxidation resistance and ozone resistance. Such an anti-aging agent works to suppress the deterioration of the rubber by blooming on the rubber surface, but simply increasing the blending amount causes excessive blooming and contamination of the rubber surface with the anti-aging agent. There is a problem that the appearance is impaired. On the other hand, if the blending amount of the anti-aging agent is decreased in order to ensure the appearance, the weather resistance is lowered.

  Patent Document 1 listed below discloses blending inorganic porous particles together with an anti-aging agent in order to provide a rubber composition that hardly changes color while maintaining weather resistance. However, since the anti-aging agent and the porous particles are added and mixed at the time of kneading the rubber composition, the anti-aging agent is hardly contained inside the porous particles. Therefore, the sustained release effect of gradually releasing the anti-aging agent from the porous particles is hardly obtained, and the weather resistance sustaining effect is poor. Moreover, even if an anti-aging agent enters the inside of the porous particles at the time of kneading, since the outlet of the pores of the porous particles is free, at the time of kneading and subsequent processing and molding, and further at the time of vulcanization The internal anti-aging agent elutes at the temperature, and the cost for improving the weather resistance is reduced.

  On the other hand, in Patent Document 2 below, as a technique related to a vulcanization accelerator, an amine compound is prepared by filling or impregnating a hollow portion of an inorganic porous particle with an amine compound and coating it with a resin that melts during vulcanization. A technique for gradually releasing heat into the heat during vulcanization is disclosed. However, unlike vulcanization accelerators that function during vulcanization, anti-aging agents function during normal use of rubber products that cannot be temperature controlled. Therefore, the technique of Patent Document 2 in which the coating film is melted by heat during vulcanization to control the release of inclusions cannot be applied to an anti-aging agent. In this document, coacervation method, submerged drying method, air suspension method, spray drying method, etc. are used to coat porous particles with resin. When applied to the agent, in the coacervation method or the submerged drying method, the internal anti-aging agent is dissolved in the solvent when the porous particles containing the anti-aging agent are immersed in the solvent. Further, in the air suspension method and the spray drying method, the inside of the tank is heated to a high temperature (for example, 60 to 80 ° C.) in order to dry the solvent, so that the anti-aging agent having a low melting point dissolves from the inside of the porous particles. Therefore, it is impossible to produce an anti-aging agent having excellent release properties.

JP 2002-037926 A JP 2001-151945 A

  The present invention provides an anti-aging agent for compounding rubber that has excellent weather resistance sustaining effects while improving appearance by suppressing discoloration of the rubber surface by improving the release of the anti-aging agent. With the goal.

  In view of the above-mentioned problems, the present inventor has made aging by encapsulating an anti-aging agent in porous particles and coating it with resin or metal oxide fine particles that do not melt during rubber processing. The release of the inhibitor can be improved, and the present invention has been completed by finding out that the appearance and weather resistance can both be increased and improved.

  That is, the anti-aging agent for compounding rubber according to the present invention includes the anti-aging agent in the porous particles, and further has an average particle size of 1/100 to 1/5 of the average particle size of the porous particles and 160 Resin and / or metal oxide fine particles that do not melt at a temperature below ℃ are fixed on the surface of the porous particles.

  In addition, the method for producing an anti-aging agent for blending rubber according to the present invention includes an anti-aging agent encapsulated in porous particles, and then an average particle size of 1/100 to 1/5 of the average particle size of the porous particles. And fine particles of resin and / or metal oxide that do not melt at 160 ° C. or lower are immobilized on the surface of the porous particles by the impact method in high-speed air current.

  Moreover, the rubber composition according to the present invention is characterized by blending the above-mentioned anti-aging agent for blending rubber. Moreover, the pneumatic tire according to the present invention is formed by using the rubber composition.

  According to the present invention, it is possible to improve the release property of the anti-aging agent, so that the anti-aging agent improves the appearance while suppressing discoloration caused by excessive bleeding of the anti-aging agent on the rubber surface. The weather resistance can be maintained for a long time by being gradually released.

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

  The anti-aging agent for compounding rubber according to the present embodiment includes an anti-aging agent in the pores and hollow portions of the porous particles, and further, a resin or metal oxide that does not melt during rubber processing on the surface of the porous particles. It is an anti-aging agent complex in which fine particles of an object are fixed as a film material. In this way, the surface of the porous particles encapsulating the anti-aging agent is coated with fine particles of resin and metal oxide that do not melt during rubber processing, so that the particles are covered with the fine particles even at the rubber product stage. can do. Therefore, since the release rate of the anti-aging agent from the inside of the porous particles is slowed down by the coating of the fine particles, it is possible to improve the controlled release property of being gradually released onto the rubber surface.

  The structure of the porous particles is not particularly limited as long as the anti-aging agent can be included by filling or impregnating the anti-aging agent. For example, it may be a porous hollow particle composed of a porous body (that is, a structure having innumerable pores) having a hollow as a hollow portion inside and a shell portion communicating with the hollow and the outside, or alternatively The particles may have a porous structure that does not have such a hollow portion and has innumerable pores as a whole. Preferably, porous hollow particles are used because the encapsulation rate of the anti-aging agent can be increased. The shape of the porous particles is not particularly limited, and may be spherical or elliptical such as oblong or oblate, but is preferably a hollow sphere.

  The porous particles are preferably inorganic porous particles made of an inorganic material. Such an inorganic material is not particularly limited, and examples thereof include silica, alumina, titanium oxide, sodium silicate, calcium silicate, aluminum silicate, magnesium silicate, calcium carbonate, magnesium carbonate, and carbon. These can be used alone or in combination of two or more. Specifically, porous hollow silica, porous hollow carbon and the like are particularly preferable.

  The size of the porous particles is not particularly limited, but the average particle size is preferably 0.1 to 200 μm, more preferably 0.5 to 100 μm. The average particle diameter of the porous particles is obtained by observing with a transmission electron microscope (TEM), obtaining an image, and using this image, measuring the diameter of 10 randomly extracted particles. Calculated as an arithmetic mean.

  Examples of the anti-aging agent include N-phenyl-N ′-(1,3-dimethylbutyl) -p-phenylenediamine (6PPD), N-isopropyl-N′-phenyl-p-phenylenediamine (IPPD), N, N′-diphenyl-p-phenylenediamine (DPPD), N, N′-di-2-naphthyl-p-phenylenediamine (DNPD), N- (3-methacryloyloxy-2-hydroxypropyl) -N ′ P-phenylenediamine-based antioxidants such as phenyl-p-phenylenediamine and N-cyclohexyl-N′-phenyl-p-phenylenediamine; p- (p-toluenesulfonylamido) diphenylamine, 4,4′-bis ( α, α-dimethylbenzyl) diphenylamine (CD), octylated diphenylamine (ODPA), Diphenylamine-based antioxidants such as styrenated diphenylamine; naphthylamine-based antioxidants such as N-phenyl-1-naphthylamine (PAN) and N-phenyl-2-naphthylamine (PBN); 2,2,4-trimethyl-1, Amine-ketone aging prevention such as 2-dihydroquinoline polymer (TMDQ), 6-ethoxy-2,2,4-trimethyl-1,2-dihydro-quinoline (ETMDQ), reaction product of diphenylamine and acetone (ADPAL) Agent; 2,6-di-tert-butyl-4-methylphenol (DTBMP), styrenated phenol (SP), 2,2′-methylene-bis (4-methyl-6-tert-butylphenol) (MBMBP), 2,2′-methylene-bis (4-ethyl-6-tert-butylphenol) (MB TB), 4,4′-butylidene-bis (3-methyl-6-tert-butylphenol) (BBMTBP), 4,4′-thio-bis (3-methyl-6-tert-butylphenol) (TBMTBP), 2 , 5-di-tert-butylhydroquinone (DBHQ), 2,5-di-tert-amylhydroquinone (DAHQ), and the like. These can be used alone or in combination of two or more. Among these, those having a melting point of 150 ° C. or lower are preferable, and those having a melting point of 80 ° C. or lower are more preferable from the viewpoint of excellent release from the inside of the porous particles coated with fine particles. In addition, amine-based antioxidants are preferable from the viewpoint of excellent weather resistance, and aromatic secondary amines, particularly p-phenylenediamine-based antioxidants are preferably used.

  A method for encapsulating the anti-aging agent in the porous particles is not particularly limited. For example, by mixing an anti-aging agent with porous particles at a temperature equal to or higher than its melting point, the anti-aging agent heated and melted can be impregnated or filled into the porous particles. More specifically, the anti-aging agent may be heated and melted in an oil bath or the like, and porous particles may be added to the heat-melted anti-aging agent and mixed with stirring. Alternatively, the porous particles are heated and melted while stirring. The anti-aging agent may be added and mixed, or the anti-aging agent may be mixed by stirring and mixing the anti-aging powder and the porous particles with a mixer during friction mixing or heating with a heater. May be melted. The anti-aging agent is not limited to melting due to such a temperature rise, but may be dissolved using a solvent, and the anti-aging agent is impregnated with the porous particles by mixing the anti-aging agent dissolved in the solvent with the porous particles. Or it may be filled. Moreover, anti-aging agent can be more effectively permeated into the porous particles by evacuation.

  When the porous hollow particles are used as the porous particles, the melted liquid anti-aging agent penetrates into the internal cavities through the pores of the shell of the porous hollow particles. A complex containing an anti-aging agent is obtained. The anti-aging agent is not limited to an embodiment in which only the hollow portion of the porous hollow particles is filled or impregnated, and is usually filled or impregnated in the shell portion together with the hollow portion. Naturally, it is included as an embodiment of the present invention. Moreover, the anti-aging agent may be impregnated only in the shell part of the porous hollow particle, or may be adhered to the particle surface together with the hollow part or the shell part.

  The encapsulation rate of the anti-aging agent is not particularly limited, but is preferably 10 to 70% by mass, and more preferably 20 to 50% by mass. Here, the encapsulation rate is a mass ratio of the encapsulated anti-aging agent to the total amount of the porous particles and the anti-aging agent.

  After encapsulating the anti-aging agent in the porous particles in this way, a resin and / or metal having an average particle size of 1/100 to 1/5 of the average particle size of the porous particles and not melting at 160 ° C. Oxide fine particles are immobilized on the surface of the porous particles.

  By using a fine particle having an average particle size that is 1/100 to 1/5 of the average particle size of the porous particle, the fine particle as the child particle is firmly fixed to the porous particle as the mother particle. Can do. That is, when the size of the fine particles with respect to the porous particles is larger than 1/5, the effect of preventing the release of the anti-aging agent by the fine particles is not sufficient, and the release property of the anti-aging agent cannot be improved. Further, if the size of the fine particles relative to the porous particles is smaller than 1/100, the coating film made of the fine particles becomes too dense, and the release rate of the anti-aging agent may be too low. The ratio of the average particle diameter of the fine particles to the average particle diameter of the porous particles is preferably 1/100 to 1/10, more preferably 1/50 to 1/10. Here, the average particle diameter of the fine particles is also observed with a transmission electron microscope (TEM) to obtain an image, and by using this image, the diameter of 10 randomly extracted particles is measured. Calculated as an arithmetic mean.

  The fine particles that do not melt (soften and melt) at 160 ° C. or lower are used because the fine particles that melt at 160 ° C. or lower melt at the temperature exposed during the processing of the rubber composition and are encapsulated in porous particles. This is because the anti-aging agent is eluted and the release property at the rubber product stage cannot be improved. More preferably, a material that does not melt at 180 ° C. or lower, more preferably a material that does not melt at 200 ° C. or lower is used. Further, a resin having no melting point, that is, not melting by heat may be used. In the case of a thermoplastic resin, the melting point is a value measured at a rate of temperature increase of 20 ° C./min by a differential scanning calorimetry (DSC) method according to JIS K7121, and a value exceeding 160 ° C. is used. More preferably, it is more than 180 ° C, more preferably more than 200 ° C.

  The resin constituting such fine particles is not particularly limited, and examples thereof include acrylic resins, styrene resins, guanamine resins (benzoguanamine resins, acetoguanamine resins, etc.), melamine resins, nylon resins, polyvinyl alcohol resins. Examples thereof include various thermoplastic resins such as resins and thermosetting resins, and these can be used alone or in combination of two or more. Moreover, it does not specifically limit as a metal oxide which comprises microparticles | fine-particles, For example, zinc oxide, a titanium oxide, etc. are mentioned, These can be used individually or in combination of 2 or more types, respectively.

  As a method for immobilizing the fine particles on the surface of the porous particles, it is preferable to use a high-speed air impact method. In the high-speed airflow impact method, particles collide with each other in a high-speed airflow, thereby solidifying other solid particles (child particles) smaller in size than the mother particles on the surface of the solid particles (mother particles) that are the core. This is a particle compounding method in which the particles are immobilized. By using the high-speed airflow impact method, the porous particles can be coated with the fine particles without eluting the anti-aging agent contained in the porous particles. In addition, according to the high-speed air-flow impact method, the fine particles can be firmly fixed on the surface of the porous particles, so that the fine particles can be prevented from falling off during kneading of the rubber composition. In addition, when the impact method is in a high-speed air current, a layer in which fine particles are relatively uniformly fixed can be provided on the surface of the porous particles, and the surface of the porous particles can be fixed by immobilizing the fine particles. Since it does not completely cover without gaps, it is advantageous for gradually releasing the anti-aging agent. The high-speed air-flow impact method itself is a known technique, and is described in, for example, Japanese Patent Application Laid-Open No. 10-113874. Examples of the apparatus utilizing the high-speed air-flow impact method include a hybridization system manufactured by Nara Machinery Co., Ltd. and a mechano-fusion system manufactured by Hosokawa Micron Corporation.

  The coating amount by the fine particles is preferably 10 to 50 parts by mass with respect to 100 parts by mass of the porous particles containing the antioxidant, that is, the coating rate is preferably 10 to 50% by mass. When the coating rate is less than 10% by mass, the effect of improving the release property of the antioxidant may be insufficient. Moreover, when it exceeds 50 mass%, an anti-aging agent will hardly be discharge | released and there exists a possibility that the original anti-aging function may be impaired.

  The rubber composition according to the present embodiment contains the anti-aging agent composite as described above. Examples of rubber components blended in the rubber composition include natural rubber (NR), polyisoprene rubber (IR), polybutadiene rubber (BR), styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber (NBR), and chloroprene. Various diene rubbers such as rubber (CR) and ethylene-propylene-diene rubber (EPDM) are exemplified. These can be used alone or in combination of two or more. The rubber component is preferably natural rubber, butadiene rubber, styrene-butadiene rubber, or a blend of two or more thereof.

  The content of the anti-aging agent complex in the rubber composition is not particularly limited, but the mass of the anti-aging agent included in the porous particles is 0.5 to 10 mass with respect to 100 parts by mass of the rubber component. Parts, preferably 1 to 6 parts by mass.

  In the rubber composition according to the present embodiment, a reinforcing filler that is generally blended in a rubber composition such as carbon black or silica can be blended. Although the compounding quantity of a reinforcing filler is not specifically limited, It is preferable that it is 10-200 mass parts with respect to 100 mass parts of rubber components, More preferably, it is 20-100 mass parts.

  In the rubber composition according to the present embodiment, in addition to the above-described components, various softeners such as oil, stearic acid, zinc white, wax, vulcanizing agent, vulcanization accelerator, and the like that are generally used in the rubber industry. An additive can be mix | blended as needed. Examples of the vulcanizing agent include sulfur and sulfur-containing compounds, and are not particularly limited. However, the blending amount is preferably 0.1 to 10 parts by mass with respect to 100 parts by mass of the rubber component. More preferably, it is 0.5-5 mass parts. Moreover, as a compounding quantity of a vulcanization accelerator, it is preferable that it is 0.1-7 mass parts with respect to 100 mass parts of said rubber components, More preferably, it is 0.5-5 mass parts.

  The rubber composition is prepared by kneading according to a conventional method using a rubber kneader such as a normal Banbury mixer or kneader. The use of the rubber composition thus obtained is not particularly limited, and can be used for various rubber compositions such as tires such as treads and sidewalls, conveyor belts, and vibration-proof rubbers.

  Preferably, it is used as a rubber composition for tires, and is particularly suitably used for sidewall rubber, and can form a pneumatic tire by vulcanization molding at 140 to 180 ° C., for example, according to a conventional method. it can.

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

[Preparation of anti-aging agent complex]
・ Anti-aging agent complex 1:
As an anti-aging agent, N-phenyl-N ′-(1,3-dimethylbutyl) -p-phenylenediamine (6PPD, “Nocrack 6C” manufactured by Ouchi Shinsei Chemical Co., Ltd.) is used. Porous hollow silica (“God Ball B-25C” manufactured by Suzuki Oil & Fat Co., Ltd., average particle size: 9 μm) was used. 45 parts by mass of the antioxidant was heated and melted at 110 ° C., 55 parts by mass of porous hollow silica was added thereto, and the mixture was stirred for 1 hour. Then, after carrying out suction filtration, the porous particle | grains which included the anti-aging agent by leaving it naturally were obtained. The encapsulation rate of the anti-aging agent was 40% by mass. Next, by using acrylic fine particles (“Chemisnow MR-2G” manufactured by Soken Chemical Co., Ltd., average particle size: 0.8 μm, melting point: insoluble) as the child particles, Immobilized on the surface. Specifically, using “hybridization system NHS-0” manufactured by Nara Machinery Co., Ltd. as an impact-type powder surface modification device in a high-speed air current, with respect to 100 parts by mass of porous particles containing an anti-aging agent The mixture was charged at a ratio of 15 parts by mass of the acrylic fine particles, and processed at a rotor rotational speed of 10000 rpm and a processing time of 5 minutes to obtain an anti-aging agent composite 1.

-Anti-aging agent complex 2:
The ratio of the acrylic fine particles to be charged into the powder surface modification device is changed to 40 parts by mass with respect to 100 parts by mass of the porous particles containing the anti-aging agent, and the others are the same as in the anti-aging agent composite 1. Thus, an anti-aging agent complex 2 was obtained.

・ Anti-aging agent complex 3:
As the child particles, melamine / formaldehyde condensate fine particles (“Eposter S” manufactured by Nippon Shokubai Co., Ltd., average particle size: 0.2 μm, melting point: insoluble) are used in place of the above acrylic fine particles, and other anti-aging agent composites In the same manner as for body 1, anti-aging agent complex 3 was obtained.

Anti-aging agent complex 4:
As the child particles, zinc oxide fine particles (“No. 1 Zinc Hana” manufactured by Mitsui Mining & Smelting Co., Ltd., average particle size: 0.6 μm) are used in place of the above acrylic fine particles. Thus, an anti-aging agent complex 4 was obtained.

Anti-aging agent complex 5 (comparative example):
As the child particles, acrylic fine particles (“Kemisnow MP-4409” manufactured by Soken Chemical Co., Ltd., average particle size: 0.6 μm, melting point: 105 ° C.) were used, and the others were aged in the same manner as the anti-aging agent composite 1. Inhibitor complex 5 was obtained.

Anti-aging agent complex 6 (comparative example):
As the child particles, benzoguanamine / formaldehyde condensate fine particles (“Eposter L15” manufactured by Nippon Shokubai Co., Ltd., average particle size: 10 μm, melting point: insoluble) were used. Agent complex 6 was obtained.

Anti-aging agent complex 7:
As the porous particles, porous hollow silica (“God Ball B-6C” manufactured by Suzuki Oil & Fat Co., Ltd., average particle size: 3 μm) was used, and the others were the same as in the anti-aging composite 3 and the anti-aging agent was used. Complex 7 was obtained. The encapsulation rate of the anti-aging agent was 40% by mass.

Anti-aging agent complex 8 (comparative example):
In the preparation of the anti-aging complex 1, an anti-aging complex 8 was prepared by encapsulating an anti-aging agent in porous particles (that is, before immobilizing fine particles).

The structure of the above anti-aging agent composites 1-8 is shown in Table 1 below.

[Preparation of rubber composition]
According to the composition (parts by mass) shown in Table 2 below, a rubber composition for a tire sidewall was prepared using a Banbury mixer according to a conventional method. Specifically, first, in the first mixing stage, components other than the vulcanization accelerator and sulfur are added and kneaded (discharge temperature 160 ° C.), and then the resulting mixture is vulcanized in the second mixing stage. An agent and a vulcanizing agent were added and kneaded (discharge temperature 100 ° C.). In addition, except for the comparative example 4, the anti-aging agent composites 1-8 are set so that 3 mass parts of anti-aging agents may be mix | blended with respect to 100 mass parts of rubber components, and in the comparative example 4, 6 mass parts and did.

Details of each component in Table 2 are as follows.
・ Natural rubber: RSS # 3
・ Butadiene rubber: “BR150” manufactured by Ube Industries, Ltd.
・ Carbon black: “Seast SO” manufactured by Tokai Carbon Co., Ltd.
・ Aroma oil: "Extract No. 4 S" manufactured by Showa Shell Sekiyu KK
・ Stearic acid: "Industrial stearic acid" manufactured by Kao Corporation
・ Zinc flower: “No. 1 Zinc flower” manufactured by Mitsui Mining & Smelting Co., Ltd.
・ Wax: Paraffin wax, “Ozoace 0355” manufactured by Nippon Seiwa Co., Ltd.
・ Vulcanization accelerator: N-tert-butyl-2-benzothiazolylsulfenamide ・ Sulfur: “5% oil-treated powdered sulfur” manufactured by Tsurumi Chemical Co., Ltd.

  Using each rubber composition obtained as a side wall rubber, a 195 / 65R15 pneumatic radial tire was produced according to a conventional method, and the weather resistance and appearance of each tire were evaluated. The evaluation method is as follows.

-Weather resistance: A tire was mounted on a passenger car, and the state of the surface of the side wall rubber part after traveling 50,000 km was evaluated by collating with the standard of JIS K6259. The evaluation is performed by combining the three levels of A, B, and C in order from the smallest with respect to the number of cracks, and the five levels of 1 to 5 in order from the smallest with respect to the size of the crack.

Appearance: Leave the tire outdoors for 4 months, and visually observe the surface of the sidewall rubber part, and “3: Almost no discoloration, 2: Slight discoloration, 1: Large discoloration” 3 Evaluated in stages.

  The results are as shown in Table 2, and in Examples 1 to 5, the surface of the porous particles encapsulating the anti-aging agent is applied to the resin and metal oxide fine particles that do not melt using the high-speed air current impact method. Since it was used and fixed, it was found that the appearance was excellent and the initial migration rate of the anti-aging agent was suppressed. Moreover, since it was excellent also in the weather resistance after 50,000 km driving | running | working, it was excellent also in the sustainability of the anti-aging effect over a long period of time. From these things, in Examples 1-5, the release property of the anti-aging agent has been improved. Therefore, while suppressing the discoloration of the rubber surface and improving the appearance, the weather resistance is sustained. It was excellent.

On the other hand, in Comparative Example 1, the anti-aging agent was only encapsulated in the porous particles, and since it was not coated with the fine particles, the initial appearance was inferior, and the weather resistance sustained effect was also inferior. . In Comparative Example 2, because the melting point of the fine particles covering the surface of the porous particles was as low as 105 ° C., the anti-aging agent was eluted by melting the fine particles during kneading or vulcanization of the rubber composition. It was an equivalent effect, and the effect of improving the controlled release of the anti-aging agent as in Examples was not obtained. In Comparative Example 3, since the particle diameter of the fine particles covering the surface of the porous particles was large, it was not possible to form a beautiful film using the high-speed air-flow impact method. The release improvement effect was not obtained. In Comparative Example 4, the same anti-aging agent complex not coated with the fine particles as in Comparative Example 1 was used, and by increasing the amount, the weather resistance could be improved, but the appearance was inferior and the appearance was poor. And weather resistance could not be achieved at the same time.

Claims (6)

  Resin and / or metal oxide fine particles having an anti-aging agent encapsulated in porous particles, and having an average particle size of 1/100 to 1/5 of the average particle size of the porous particles and not melting below 160 ° C. An anti-aging agent for compounding rubber, characterized in that it is fixed on the surface of the porous particles.   2. The anti-aging agent for compounding rubber according to claim 1, wherein the fine particles are immobilized on the surface of the porous particles by a high-speed air impact method.   The anti-aging agent for compounding rubber according to claim 1 or 2, wherein the coating amount by the fine particles is 10 to 50 parts by mass with respect to 100 parts by mass of the porous particles containing the anti-aging agent.   A rubber composition comprising the anti-aging agent for rubber compounding according to any one of claims 1 to 3.   A pneumatic tire using the rubber composition according to claim 4.   An anti-aging agent is encapsulated in the porous particles, and the resin and / or metal oxide has an average particle size of 1/100 to 1/5 of the average particle size of the porous particles and does not melt below 160 ° C. A method for producing an anti-aging agent for rubber compounding, characterized in that fine particles are immobilized on the surface of the porous particles by a high-speed air impact method.