JP2010059326A - Rubber composition, method for producing the same, and pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress the discoloration of a rubber surface by an amine-based age inhibitor and to improve the appearance, without reducing an ozone resistance improving effect produced by the amine-based age inhibitor. <P>SOLUTION: A rubber composition is provided by melting and mixing an amine-based age inhibitor and a bisphenolic compound and mixing the resultant mixture with a rubber component comprising a diene rubber so that 100 pts.wt. of the rubber component is blended with 0.5-8 pts.wt. of the amine-based age inhibitor and 0.5-8 pts.wt. of the bisphenolic compound. A pneumatic tire using the rubber composition is also provided. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a rubber composition and a method for producing the same. The present invention also relates to a pneumatic tire using the rubber composition.

  A pneumatic tire is deteriorated by oxygen or ozone in the atmosphere during long-term use, so that cracks are generated in the groove bottoms of the sidewall portion 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. Among them, the amine-based anti-aging agent has an effect of effectively preventing oxidative degradation and ozone degradation of tire sidewall rubber and the like. However, the amine-based anti-aging agent discolors the tire to brown or brown, so that there is a problem that the appearance is deteriorated and the commercial value of the tire is lowered.

  On the other hand, although phenolic anti-aging agents have an effect of oxidation deterioration resistance, they are not as effective as amine type anti-aging agents and are not effective in ozone resistance. This is the current situation.

  Conventionally, in order to prevent discoloration due to an amine anti-aging agent, it has been proposed to use an ultraviolet absorber, a resin, a surfactant or the like together with the amine anti-aging agent. For example, in Patent Documents 1 and 2 listed below, diene rubber, diamine anti-aging agent, benzophenone compound, salicylate compound, acrylate compound, benzotriazole compound, benzoate compound, triazine compound, etc. It is disclosed to incorporate a UV absorber. Patent Document 3 below discloses a rubber composition obtained by blending a granular material obtained by mixing an anti-aging agent and a thermoplastic resin. Patent Document 4 listed below discloses a rubber composition comprising a polyoxyethylene ether-type nonionic surfactant together with an amine-based antioxidant.

  On the other hand, in Patent Document 5 described below, rubber aging, particularly rubber, is obtained by blending a biphenol derivative that is directly bonded to each other and has a substituent on each ring together with an amine-based anti-aging agent. The point which prevents the aging by repeated bending elongation fatigue | exhaustion is disclosed.

  As described above, in Patent Documents 1 to 4, in order to prevent coloring without impairing the anti-aging effect of the amine anti-aging agent, it is possible to use an amine anti-aging agent and an additive such as an ultraviolet absorber in combination. In addition, Patent Document 5 discloses that an amine anti-aging agent and a biphenol derivative are used in combination in order to enhance the anti-aging effect. However, these documents do not disclose mixing an amine-based antioxidant and a bisphenol-based compound with a rubber component after being melt-mixed in advance.

Patent Document 6 below discloses that an aromatic ring-containing secondary amine, which is generally used as an amine-based antioxidant, and a phenol derivative such as a bisphenol derivative are used in combination. However, this document is intended to improve the grip performance and steering stability of the tire, and is not intended to suppress the discoloration of the amine anti-aging agent. There is also no disclosure of blending the rubber component with the inhibitor and the bisphenol-based compound previously melt-mixed.
JP-A-6-145422 JP 2006-143889 A JP 2001-348463 A JP-A-5-194790 JP-A-6-25471 JP 2007-56069 A

  The present invention has been made in view of the above points, and can improve the appearance by suppressing discoloration of the rubber surface without deteriorating the ozone resistance improvement effect by the amine-based anti-aging agent. It aims at providing a rubber composition and its manufacturing method.

  The rubber composition according to the present invention comprises a rubber component composed of a diene rubber and a mixture obtained by melt-mixing an amine anti-aging agent and a bisphenol compound, and with respect to 100 parts by weight of the rubber component, It contains 0.5 to 8 parts by weight of the amine antioxidant and 0.5 to 8 parts by weight of the bisphenol compound. In addition, the method for producing a rubber composition according to the present invention includes melt-mixing an amine-based antioxidant and a bisphenol-based compound, and mixing the resulting mixture with 100 parts by weight of the rubber component composed of a diene rubber. The rubber component is mixed with 0.5 to 8 parts by weight of the anti-aging agent and 0.5 to 8 parts by weight of the bisphenol compound.

  According to the present invention, by mixing a rubber component with a mixture obtained by pre-melting an amine-based antioxidant and a bisphenol-based compound, the amine resistance can be reduced without deteriorating the ozone resistance exhibited by the amine-based antioxidant. Discoloration of the rubber surface due to the anti-aging agent can be suppressed, and the appearance can be improved.

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

  The rubber composition according to the present invention contains a rubber component composed of a diene rubber, an amine antiaging agent, and a bisphenol compound.

  Examples of the diene rubber include natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber (NBR), chloroprene rubber (CR), and styrene. -Isoprene copolymer rubber, butadiene-isoprene copolymer and the like. These can be used alone or in combination of two or more. Preferred are natural rubber, butadiene rubber, styrene-butadiene rubber, or a blend of two or more thereof.

  As the amine-based antioxidant, an aromatic secondary amine is preferably used. Specifically, N- (1,3-dimethylbutyl) -N′-phenyl-p-phenylenediamine, N-isopropyl-N′-phenyl-p-phenylenediamine, N, N′-diphenyl-p-phenylene Diamine, N, N′-di-2-naphthyl-p-phenylenediamine, N- (3-methacryloyloxy-2-hydroxypropyl) -N′-phenyl-p-phenylenediamine, p- (p-toluenesulfonylamide) ) Diphenylamine, 4,4′-bis (α, α-dimethylbenzyl) diphenylamine, octylated diphenylamine, N-phenyl-1-naphthylamine and the like. These can be used alone or in combination of two or more.

  The compounding amount of the amine anti-aging agent is 0.5 to 8 parts by weight, more preferably 1 to 5 parts by weight with respect to 100 parts by weight of the rubber component. When there are too few compounding quantities of an amine type anti-aging agent, it will become difficult to ensure the ozone resistance of a rubber composition. On the other hand, when the compounding amount of the amine anti-aging agent is too large, it is difficult to suppress discoloration of the rubber surface even when a bisphenol compound is used in combination.

  The bisphenol-based compound can suppress discoloration of the rubber surface due to the amine-based anti-aging agent without deteriorating ozone resistance when used in combination with the amine-based anti-aging agent. Amine-based anti-aging agents are prone to change to highly colored substances due to oxidation, etc., but in combination with bisphenol-based compounds, oxidation of amine-based anti-aging agents can be prevented, thereby preventing discoloration it is conceivable that.

As the bisphenol compound, those generally marketed as bisphenol aging inhibitors can be used. In particular, those represented by the following general formula (1) are preferably used.

In the formula, A represents S or an alkylidene group having 1 to 3 carbon atoms, and R ₁ and R ₂ each independently represents an alkyl group having 1 to 4 carbon atoms.

  Specific examples of such bisphenol compounds include 2,2′-methylenebis (4-methyl-6-tert-butylphenol), 2,2′-methylenebis (4-ethyl-6-tert-butylphenol), 4,4 ′. -Butylidenebis (3-methyl-6-tert-butylphenol), 4,4'-thiobis (3-methyl-6-tert-butylphenol) and the like. These can be used alone or in combination of two or more.

  The compounding quantity of a bisphenol type compound is 0.5-8 weight part with respect to 100 weight part of said rubber components, More preferably, it is 0.5-5 weight part. If the amount of the bisphenol compound is too small, the effect of suppressing discoloration by the amine antioxidant is insufficient.

  The rubber composition according to the present invention can be prepared by melt-mixing the amine-based antioxidant and the bisphenol-based compound in advance, and adding and mixing the obtained mixture to the rubber component. By pre-melting in this way, the amine-based anti-aging agent and the bisphenol-based compound can be combined and integrated by the interaction between the two, making it difficult to bloom from the matrix rubber in a mixed state with the rubber component, The effect of improving the appearance can be further enhanced.

  It does not specifically limit about the method of making it melt-mix, It can implement by mixing an amine-type antioxidant and a bisphenol-type compound at the temperature more than those melting | fusing point. The pre-melted mixture may be added to the rubber component in a molten state, or may be added to the rubber component after being cooled. The mixing of the mixture with the rubber component can be carried out by kneading using a mixer such as a Banbury mixer or a kneader generally used for the preparation of the rubber composition, and the rubber composition according to the present invention is produced. Can do.

  Amine-based antioxidants and bisphenol-based compounds have the following relationship, where X (parts by weight) is the amount of amine-based antioxidants and 100 (parts by weight) of bisphenol-based compounds with respect to 100 parts by weight of the rubber component. It is preferable to blend in the rubber component so as to satisfy.

0.25 ≦ Y / X ≦ 2
If Y / X is less than 0.25, the amount of the bisphenol compound relative to the amine antioxidant is relatively small, and it is difficult to improve the appearance. Moreover, when Y / X exceeds 2, the compounding quantity of an amine type anti-aging agent will decrease, and it will become difficult to ensure ozone resistance. Y / X is more preferably 0.5 to 1.5.

  Various fillers such as carbon black, silica, clay, calcium carbonate and the like can be blended in the rubber composition according to the present invention. As the filler, carbon black, silica, or a combination of carbon black and silica is preferable. Although the compounding quantity of a filler is not specifically limited, It is preferable that it is 10-150 weight part with respect to 100 weight part of rubber components.

  In addition to the above-described components, the rubber composition according to the present invention contains various additives generally used in the rubber industry, such as zinc white, stearic acid, softener, sulfur, and vulcanization accelerator, as necessary. can do. The use of the rubber composition is not particularly limited, but can be used for various rubber compositions such as tires such as treads and sidewalls, conveyor belts, and vibration-proof rubbers.

  When the rubber composition is used for a tire, rubber portions (tread rubber, sidewall rubber, etc.) of various pneumatic tires can be formed by vulcanization molding at, for example, 140 to 180 ° C. according to a conventional method. In particular, it is preferably used for a sidewall portion of a pneumatic tire.

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

  The common compounding of the rubber composition in Examples is 50 parts by weight of natural rubber (RSS # 3), 50 parts by weight of butadiene rubber (“BR150” manufactured by Ube Industries), HAF grade carbon black (“Seast” manufactured by Tokai Carbon Co., Ltd.) 3 ") 60 parts by weight, zinc white (" No. 1 zinc white "manufactured by Mitsui Mining & Smelting Co., Ltd.) 3 parts by weight, stearic acid (" industrial stearic acid "manufactured by Kao Corporation), 2 parts by weight, sulfur (Tsurumi Chemical Industries) 2 parts by weight of “5% oil-treated powder sulfur” manufactured by Co., Ltd. and 1 part by weight of vulcanization accelerator NS (“Noxeller NS-P” manufactured by Ouchi Shinsei Chemical Co., Ltd.).

  The amine-based antioxidant and the bisphenol-based compound were blended as shown in Table 1 below with respect to 100 parts by weight of the rubber component composed of the natural rubber and butadiene rubber. The details of each component in Table 1 are as follows.

Amine-based anti-aging agent: N- (1,3-dimethylbutyl) -N′-phenyl-p-phenylenediamine, 6PPD, “NOCRACK 6C” manufactured by Ouchi Shinsei Chemical Co., Ltd.
Bisphenol compound 1: 2,2′-methylenebis (4-methyl-6-tert-butylphenol), “NOCRACK NS-6” manufactured by Ouchi Shinsei Chemical Co., Ltd.
Bisphenol compound 2: 2,2′-methylenebis (4-ethyl-6-tert-butylphenol), “NOCRACK NS-5” manufactured by Ouchi Shinsei Chemical Co., Ltd.
Bisphenol compound 3: 4,4′-thiobis (3-methyl-6-tert-butylphenol), “NOCRACK 300” manufactured by Ouchi Shinsei Chemical Co., Ltd.

  Here, in Examples 1 to 5 and Comparative Examples 4 and 5, the amine-based antioxidant and the bisphenol-based compound previously melted and mixed at 150 ° C. in an oil bath were used. The rubber composition was prepared by adding and mixing with the other compounding components with respect to the rubber component while the obtained molten mixture was in a molten state. A Banbury mixer was used for mixing the rubber composition. In Comparative Examples 1 to 3, the amine-based antioxidant and the bisphenol-based compound were added to the rubber component as they were together with other compounding components. Further, in Comparative Example 6, although an amine-based antioxidant and a bisphenol-based compound were used in combination, they were added to the rubber component together with other compounding components without being melted in advance.

  Each rubber composition thus obtained was vulcanized at 160 ° C. for 30 minutes to produce a test piece having a thickness of 2 mm, and the appearance and ozone resistance were evaluated using the obtained test piece. did. The evaluation method is as follows.

Appearance: The test piece is exposed to sunlight outdoors, and the surface of the test piece is visually observed before irradiation (0 day outdoor exposure), 20 days later (20 days outdoor exposure), and 40 days later (40 days outdoor exposure). The appearance was evaluated according to the following criteria.

A: Black surface, almost no discoloration,
○: Slightly brown or white
Δ: Discolored slightly brown or white,
X: Discolored to brown or white.

・ Ozone resistance: Place the above test piece in an ozone weather meter device under the condition of 25% elongation, leave it in an environment with an ozone concentration of 100 pphm and a temperature of 50 ° C. for 24 hours, and then visually check the occurrence of cracks. Observed and evaluated ozone resistance according to the following criteria.

◎: No cracking,
○: Cracks that cannot be confirmed with the naked eye but can be confirmed with a 10x magnifier have occurred.
Δ: Cracks of 1 mm or less have occurred,
X: Cracks exceeding 1 mm are generated.

  As shown in Table 1, Comparative Examples 1 and 3 using the amine type anti-aging agent alone were excellent in ozone resistance but poor in appearance. Moreover, although the comparative example 2 of single use of a bisphenol compound was excellent in the external appearance property, it was inferior in ozone resistance. On the other hand, when it is Examples 1-5 which concern on this invention, an external appearance property can be improved significantly, without impairing the ozone-resistant effect by an amine type antioxidant, and a bisphenol type compound is used together. It was excellent in the discoloration suppressing effect of the amine-based anti-aging agent.

  In Comparative Example 6, although the amine-based anti-aging agent and the bisphenol-based compound are used in combination, since these were added to the rubber component without being pre-melted, the effect of improving the appearance was clearly inferior to that of the example. It was.

Claims (5)

  A rubber component made of a diene rubber is blended with a mixture obtained by melt-mixing an amine antioxidant and a bisphenol compound, and the amine antioxidant is added to 100 parts by weight of the rubber component. A rubber composition containing 5 to 8 parts by weight and 0.5 to 8 parts by weight of the bisphenol compound.   The Y / X is 0.25 or more and 2 or less, where X is the compounding amount of the amine-based anti-aging agent with respect to 100 parts by weight of the rubber component, and Y is the compounding amount of the bisphenol compound. The rubber composition as described.   The amine-based anti-aging agent and the bisphenol-based compound are melt-mixed, and the resulting mixture is mixed with 100 to 10 parts by weight of the rubber component composed of a diene rubber. A method for producing a rubber composition, wherein the rubber component is mixed so that 0.5 to 8 parts by weight of a bisphenol compound is blended.   4. The Y / X is 0.25 or more and 2 or less, where X is the compounding amount of the amine-based anti-aging agent with respect to 100 parts by weight of the rubber component, and Y is the compounding amount of the bisphenol compound. The manufacturing method of the rubber composition of description.   A pneumatic tire using the rubber composition according to claim 1.