JP2011074252A - Rubber composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber composition capable of reducing hardening due to aging with time. <P>SOLUTION: The rubber composition is prepared by mixing 1 to 30 pts.wt. of microcapsule which includes vegetable fat and oil containing naturally derived polyphenol to 100 pts.wt. diene-based rubber. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a rubber composition, and more particularly to a rubber composition that suppresses curing associated with aging.

  For rubber products constituting pneumatic tires and various industrial products, rubber compositions designed so that the rubber hardness is optimized in accordance with the purpose, application and use environment are used. However, even if the rubber hardness is optimal at the start of use of a tire or rubber product, it is known that the rubber is cured by aging over a long period of use. For this reason, for example, in a pneumatic tire, there is a problem that generated noise and riding comfort deteriorate with aging.

  As such an anti-aging measure, it is conceivable to increase the amount of the anti-aging agent blended in the rubber composition. However, even if the amount of the anti-aging agent is increased, the rubber curing due to aging cannot be sufficiently suppressed, or the anti-aging agent is transferred to the tire surface, so that the tire surface turns brown and the appearance There was a problem that was damaged.

  As a countermeasure against this, Patent Document 1 proposes a tire rubber composition in which a thermally expandable microcapsule containing a thermally expandable substance and a nonpolar oil is blended. However, with this rubber composition, although the oil contained in the capsule gradually migrates into the rubber, an increase in rubber hardness can be suppressed, but an improvement is required to suppress the rubber curing with aging. There was room for.

JP 2009-138181 A

  An object of the present invention is to provide a rubber composition in which the curing associated with aging is reduced.

  The rubber composition of the present invention that achieves the above object is characterized in that 1 to 30 parts by weight of microcapsules containing vegetable oils and fats containing natural polyphenols are blended in 100 parts by weight of diene rubber.

The vegetable oil / fat preferably contains 0.03 × 10 ⁻³ wt% or more of the polyphenol, and may be grape seed oil.

  In the rubber composition of the present invention, 1 to 30 parts by weight of microcapsules containing vegetable oils and fats containing naturally derived polyphenols are blended with 100 parts by weight of diene rubber. Since the vegetable oil containing polyphenol is gradually released from the microcapsule and the rubber component is prevented from aging due to the antioxidant action of this polyphenol, curing due to aging can be suppressed. In addition, since vegetable oils and fats containing polyphenols are encapsulated in microcapsules, the consumption of polyphenols during rubber composition molding and vulcanization can be suppressed, and the rubber component can be selectively prevented from aging. Can act.

  In the rubber composition of the present invention, the rubber component is a diene rubber. The diene rubber is not particularly limited, and examples thereof include natural rubber, isoprene rubber, butadiene rubber, styrene-butadiene rubber, acrylonitrile-butadiene rubber, and butyl rubber. Of these, natural rubber, isoprene rubber, butadiene rubber, and styrene-butadiene rubber are preferable. These diene rubbers can be used alone or as a blend of plural kinds.

  The rubber composition of the present invention blends a microcapsule containing a vegetable oil containing polyphenol as a naturally derived component, whereby the vegetable oil is gradually released from the microcapsule, and the antioxidant action of the polyphenol contained in the vegetable oil Prevents the rubber component from aging. In addition, since the vegetable oil containing polyphenol is encapsulated in the microcapsule, the polyphenol is prevented from being thermally decomposed or consumed in contact with oxygen during the molding process and vulcanization of the rubber composition. For this reason, polyphenol can be made to selectively act to prevent aging of the rubber component. Therefore, when the amount of vegetable oils and fats containing polyphenols is the same, it is better to contain vegetable oils and fats in microcapsules and to prevent aging than rubber oils and oils. Curing can be further reduced.

  In the present invention, since vegetable oils and fats containing naturally derived polyphenols are encapsulated in microcapsules, they are characterized by excellent safety and hygiene. That is, the vegetable fats and oils used in the present invention do not contain natural polyphenols and / or chemically synthesized polyphenol antioxidants by artificial manipulation.

The naturally-derived polyphenol content in the vegetable oil is preferably 0.03 × 10 ⁻³ wt% or more, more preferably 0.9 × 10 ⁻³ wt% or more. When the polyphenol content in the vegetable oil is less than 0.03 × 10 ⁻³ wt%, the antioxidant effect cannot be sufficiently obtained and the rubber component cannot be inhibited from curing. The polyphenol content in the vegetable oil was determined by the foreign-thiocult method. The foreign-thiocult method uses a foreign-thiocult reagent that develops a blue color under strong alkali against a reducing substance. Polyphenols in a sample (vegetable oil) are collectively collected by a colorimetric method (660 nm). It was measured as the amount of polyphenol. In addition, (+)-catechin was used as a standard sample, and the amount of polyphenol was determined from the calibration curve.

  Examples of vegetable oils and fats containing naturally derived polyphenols include grape seed oil, olive oil, safflower oil, sunflower oil, canola oil, walnut seed oil, sesame oil, and the like. These vegetable fats and oils can be used alone. A plurality of types may be blended and used.

As vegetable oils and fats, grape seed oil and olive oil are particularly preferable. Grape seed oil is produced all over the world, but chilean grape seed oil is particularly preferable because it has an extremely high polyphenol content of 1.1 × 10 ⁻³ wt% or more. However, in addition to Chilean grape seed oil, the same effect can be expected if it is a vegetable oil containing 0.9 × 10 ⁻³ wt% or more of polyphenol due to variety improvement or the like. Grape seed oil contains a large amount of naturally occurring polyphenols and also contains a lot of vitamin E. Since vitamin E has an antioxidant action, it works together with polyphenols to prevent aging of the rubber composition and to suppress hardening.

  The shell material of the microcapsule prevents vegetable oils and fats containing polyphenols from coming into contact with oxygen during molding and vulcanization of the rubber composition, and prevents polyphenols from being consumed by oxidation. In addition, after vulcanization, vegetable oil and fat containing polyphenol is gradually released into a rubber product such as a pneumatic tire so that the rubber component can be prevented from being cured by aging.

  Such a shell material for microcapsules can be formed of a thermoplastic resin useful as an ordinary microencapsulating agent. The thermoplastic resin is formed by polymerizing a polymerizable component in the presence of a polymerization initiator. The polymerizable component generally includes a monomer component called a (radical) polymerizable monomer having at least one polymerizable double bond. The monomer component is not particularly limited. For example, nitrile monomers such as acrylonitrile; carboxyl group-containing monomers such as acrylic acid and methacrylic acid; vinylidene chloride; vinyl halide monomers such as vinyl chloride Monomer; vinyl ester monomer such as vinyl acetate; (meth) acrylic acid ester monomer such as methyl (meth) acrylate and ethyl (meth) acrylate; styrene monomer such as styrene and α-methylstyrene Acrylamide monomers such as acrylamide; ethylenically unsaturated monoolefin monomers such as ethylene and propylene. These monomer components may be used alone or in combination of two or more.

  The polymerizable component may contain a polymerizable monomer (crosslinking agent) having two or more polymerizable double bonds in addition to the monomer component. By polymerizing using a cross-linking agent, the heat resistance and solvent resistance of the microcapsule shell material can be improved, and the release speed of vegetable oil and fat in the rubber product can be controlled.

  The cross-linking agent is not particularly limited. For example, aromatic divinyl compounds such as divinylbenzene and divinylnaphthalene; allyl methacrylate, triacryl formal, triallyl isocyanate, ethylene glycol di (meth) acrylate, diethylene glycol di (meth) Acrylate, triethylene glycol di (meth) acrylate, 1,4-butanediol di (meth) acrylate, 1,9-nonanediol di (meth) acrylate, 1,10-decanediol di (meth) acrylate, PEG # 200 Di (meth) acrylate, PEG # 400 di (meth) acrylate, PEG # 600 di (meth) acrylate, neopentyl glycol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, Trimethylo Propane trimethacrylate, glycerin dimethacrylate, dimethylol-tricyclodecane diacrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetraacrylate, dipentaerythritol hexaacrylate, neopentyl glycol acrylate benzoate, trimethylol propane benzoate Acid esters, 2-hydroxy-3-acryloyloxypropyl methacrylate, hydroxypivalate neopentyl glycol diacrylate, ditrimethylolpropane tetraacrylate, 2-butyl-2-ethyl-1,3-propanediol diacrylate and the like ( Mention may be made of (meth) acrylate compounds. These crosslinking agents may be used alone or in combination of two or more. In the above, a series of compounds described as “PEG # OOXX di (meth) acrylate” means polyethylene glycol di (meth) acrylate.

  In addition, the method for producing a microcapsule encapsulating the vegetable oil according to the present invention includes an aqueous dispersion medium, etc., in which a polymerizable component, vegetable oil, and water are essential, and an electrolyte, a water-soluble additive, and the like as necessary. The polymerization assistant, the dispersion stabilizer, the dispersion assistant stabilizer and the like are mixed to polymerize the polymerizable component. The order of blending these components is not particularly limited, and components that can be dissolved or dispersed in the aqueous dispersion medium may be blended in advance and blended with other components.

  In the method for producing a microcapsule, an oily mixture such as a polymerizable component and vegetable oil or fat is emulsified and dispersed in an aqueous dispersion medium so that spherical oil droplets having a predetermined particle diameter are prepared. Examples of the method for emulsifying and dispersing the oily mixture include, for example, a method of stirring with a homomixer (for example, manufactured by Special Machine Engineering Co., Ltd.), a homodisper (for example, manufactured by Special Machine Engineering Co., Ltd.), and the like, And general dispersion methods such as a method using a static dispersion device such as Noritake Engineering Co., Ltd., a membrane emulsification method, an ultrasonic dispersion method, a microchannel method, and the like.

  Next, suspension polymerization is started by heating the dispersion in which the oily mixture is dispersed as spherical oil droplets in the aqueous dispersion medium. Although superposition | polymerization temperature is freely set by the kind of polymerization initiator, Preferably it is 30-100 degreeC, More preferably, it is 40-90 degreeC, Most preferably, it controls in the range of 50-85 degreeC. The time for maintaining the reaction temperature is preferably about 0.1 to 20 hours.

  After completion of the polymerization reaction, the dispersion stabilizer is decomposed with hydrochloric acid or the like, if desired, and the resulting product (microcapsule) is isolated from the dispersion by an operation such as suction filtration, centrifugation, or centrifugal filtration. Furthermore, the obtained microcapsule hydrous cake can be washed with water and dried to obtain microcapsules.

  The content of vegetable oil in the microcapsule is preferably 10 to 70% by weight, more preferably 20 to 50% by weight. When the content of the vegetable oil in the microcapsule is less than 10% by weight, the period for suppressing the aging of the rubber composition is shortened. On the other hand, if the content of vegetable oil exceeds 70% by weight, it becomes difficult to produce microcapsules, and it becomes fragile during molding and vulcanization.

  In the present invention, the size of the microcapsules encapsulating the vegetable oil and fat is not particularly limited, but is preferably 1 to 100 μm in diameter, more preferably 5 to 50 μm in diameter. When the diameter of the microcapsule is less than 1 μm, the amount of vegetable oil / fat is reduced. Moreover, when the diameter of a microcapsule exceeds 100 micrometers, it will become difficult to include vegetable fats and oils, and it will become easy to break during rubber molding processing or vulcanization.

  The compounding quantity of the microcapsule which included the vegetable fat and oil containing polyphenol shall be 1-30 weight part with respect to 100 weight part of diene rubbers, Preferably it is 2-25 weight part. When the blending amount of the microcapsules is less than 1 part by weight, the antioxidant effect of the polyphenol cannot be sufficiently obtained, and the rubber component cannot be prevented from curing due to aging. Moreover, when the compounding quantity of a microcapsule exceeds 30 weight part, abrasion resistance falls and it becomes impossible to satisfy | fill sufficient performance as a tire.

  The rubber composition of the present invention may contain carbon black. By blending carbon black, the strength of the rubber composition can be increased and the wear resistance can be improved. The compounding amount of carbon black is preferably 10 to 100 parts by weight, more preferably 20 to 90 parts by weight with respect to 100 parts by weight of the diene rubber. When the compounding amount of the carbon black is less than 10 parts by weight, the rubber composition cannot be sufficiently reinforced and hardened and wear resistance is insufficient. Moreover, when the compounding quantity of carbon black exceeds 100 weight part, the viscosity of a rubber composition will become high and molding processability will deteriorate.

  In addition to carbon black, an inorganic filler can be blended in the rubber composition of the present invention. As the inorganic filler, for example, silica, clay, calcium carbonate, talc, mica, aluminum hydroxide, magnesium carbonate and the like can be blended as necessary. Of these, silica is preferable.

  Various additives generally used in rubber compositions such as vulcanization or crosslinking agents, vulcanization accelerators, processing aids, anti-aging agents, oils and plasticizers can be blended in the rubber composition. Such an additive can be kneaded by a general method to obtain a rubber composition which can be used for vulcanization or crosslinking. As long as the amount of these additives is not contrary to the object of the present invention, a conventional general amount can be used. The rubber composition can be produced by mixing each of the above components using a known rubber kneading machine, such as a Banbury mixer, a kneader, or a roll.

  The rubber composition of the present invention can be suitably used as a rubber product constituting a pneumatic tire or various industrial products. The rubber product constituted by the rubber composition of the present invention prevents the aging of the rubber component and suppresses the curing, so that the product life can be extended. When used in a pneumatic tire, it is suitable for constituting a tread portion or a sidewall portion, and durability such as fatigue can be improved.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further, the scope of the present invention is not limited to these Examples.

Manufacture of microcapsules Microcapsule 1 (microcapsule containing grape seed oil)
As an aqueous system, 40 g of colloidal silica having a solid content of 40%, 0.5 g of diethanolamine-adipic acid condensate, 150 g of sodium chloride, and 500 g of ion-exchanged water were mixed and adjusted to pH 3.5 to produce an aqueous dispersion medium. . As an oil system, 100 g of acrylonitrile, 50 g of methacrylonitrile, 50 g of methacrylic acid, 1 g of ethylene glycol dimethacrylate, 3 g of azobis (2,4-dimethylvaleronitrile) are added, and 90 g of grape seed oil is further added, did.

  The aqueous dispersion medium and the oily mixture were mixed, and the resulting mixture was dispersed with a homomixer (TK homomixer manufactured by Tokushu Kika Kogyo Co., Ltd.) at a rotation speed of 9000 rpm for 5 minutes to prepare a suspension. This suspension was charged into an autoclave, purged with nitrogen, and reacted at a reaction temperature of 60 ° C. and a reaction pressure of 0.5 MPa for 8 hours to obtain microcapsules 1. Microcapsule 1 contained 30% by weight of grape seed oil, and the average particle size was 19 μm.

Microcapsule 2 (Microcapsule containing naphthenic oil)
A microcapsule 2 was produced in the same procedure as in the production of the microcapsule 1 except that the grape seed oil was changed to naphthenic oil. Microcapsule 2 contained 30% by weight of naphthenic oil, and the average particle size was 22 μm.

Preparation and Evaluation of Rubber Composition Nine kinds of rubber compositions (Examples 1 to 4 and Comparative Examples 1 to 5) having the compositions shown in Tables 1 and 2 were blended except for vulcanization accelerator, sulfur and microcapsules, respectively. The components were weighed and kneaded for 5 minutes with a 1.7 L hermetic Banbury mixer, and the master batch was discharged at a temperature of 150 ° C. and cooled at room temperature. Thereafter, this master batch was subjected to a 1.7 L hermetic banbury mixer, and a vulcanization accelerator, sulfur and microcapsules were added and mixed for 2 minutes to prepare a rubber composition.

  Using the obtained nine types of rubber compositions, the rubber hardness increase rate (aging hardness increase rate) before and after the thermal aging test was measured by the method described below.

Aging hardness increase rate Using the obtained rubber composition, a test piece vulcanized into the shape of a Rupke sample (a cylindrical shape having a thickness of 12.5 mm and a diameter of 29 mm) was prepared. Each test piece was divided into two groups, and one of them was subjected to air heat aging treatment at 80 ° C. for 120 hours. Using the test specimens before and after the aging treatment, the rubber hardness at a temperature of 20 ° C. was measured by a durometer type A in accordance with JIS K6253, and each (rubber hardness after aging treatment / rubber hardness before aging treatment × 100) Was used to calculate the rate of increase in rubber hardness (%) accompanying heat aging. The obtained results are shown in Tables 1 and 2 as the rate of increase in aging hardness, with the value of Comparative Example 1 being 100 in Table 1 and the value of Comparative Example 5 being 100 in Table 2. A smaller index means that the curing of the rubber composition accompanying heat aging is suppressed.

The types of raw materials used in Tables 1 and 2 are shown below.
NR: natural rubber, RSS # 3
Carbon black: Toast carbon carbon seast 6
Zinc oxide: 3 types of zinc oxide manufactured by Shodo Chemical Industry Co., Ltd. Stearic acid: Beads manufactured by NOF Co., Ltd. Bead stearic acid anti-aging agent: SANTOFLEX 6PPD manufactured by Flexis
Wax: Paraffin wax process oil manufactured by Ouchi Shinsei Chemical Industry: Extract No. 4 S manufactured by Showa Shell Sekiyu KK
Grapeseed oil: Chilean grapeseed oil, edible grape oil manufactured by Catac Planners, natural polyphenol content of 1.3 x 10 ^-3 wt% (polyphenol content measured by the method described above)
Microcapsule 1: Microcapsule encapsulating grape seed oil, manufactured by the above-described method Microcapsule 2: Microcapsule encapsulating naphthenic oil, manufactured by the above-described method Sulfur: Fine powder with Jinhua seal oil manufactured by Tsurumi Chemical Co., Ltd. Sulfur vulcanization accelerator: Nouchira NS-P manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.

Claims (3)

  A rubber composition comprising 100 parts by weight of a diene rubber and 1 to 30 parts by weight of microcapsules encapsulating a vegetable oil containing natural polyphenols. The rubber composition according to claim 1, wherein the vegetable oil contains 0.03 × 10 ⁻³ wt% or more of the polyphenol.   The rubber composition according to claim 1 or 2, wherein the vegetable oil is grape seed oil.