JP2005272622A - Rubber composition and pneumatic tire using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber composition with lowered heat generation and improved in run-flat running performance, and a pneumatic tire using it. <P>SOLUTION: The rubber composition comprises (A) a rubber component containing 40 pts.wt. or more of a polybutadiene rubber, (B) a rubber composition obtained by blending 20-120 pts.wt. of a metal salt of an ethylenically unsaturated carboxylic acid with 100 pts.wt. of an ethylenically unsaturated nitryl-conjugated diene-based copolymer containing 30 wt.% or less of the conjugated diene units, (C) silica, and (D) an alkoxysilane having ethylenically unsaturated bonds of 5-50 wt.% of the blended silica content, and is crosslinked by an organic peroxide of 0.5-10 pts.wt. per 100 pts.wt. of the sum of the components (A) and (B). <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a rubber composition and a pneumatic tire using the rubber composition, and more particularly, a rubber composition in which silica and an alkoxysilane having an ethylenically unsaturated bond are blended to reduce heat generation and run-flat running performance is improved. And a pneumatic tire using the same.

  We have previously proposed a high-hardness rubber composition excellent in adhesion to general-purpose rubber and a pneumatic tire using the same in Patent Document 1, and the rubber composition is used as a side reinforcing layer. Or, a pneumatic tire used as a bead filler, particularly a pneumatic tire having a run-flat performance, has been proposed, but since this rubber composition has high heat generation properties, a sufficient run-flat performance is always obtained. I can't say that. Patent Document 2 discloses a rubber-reactive polysiloxane and a rubber composition containing the same, and can improve the unvulcanized and vulcanized characteristics of the rubber, particularly the vulcanization time and wear resistance. Reactive polysiloxanes and rubber compositions containing them are described.

Application for Japanese Patent Application No. 2003-198484 JP 2002-201278 A

  An object of the present invention is to provide a rubber composition having reduced heat generation and improved run-flat running performance, and a pneumatic tire using the same.

  According to the present invention, (A) a rubber component containing 40 parts by weight or more of polybutadiene rubber, (B) 100 parts by weight of an ethylenically unsaturated nitrile-conjugated diene copolymer having a conjugated diene unit content of 30% by weight or less. A composition comprising 20 to 120 parts by weight of a metal salt of an ethylenically unsaturated carboxylic acid, (C) silica, and (D) an alkoxysilane having 5 to 50% by weight of the ethylenically unsaturated bond based on the amount of the silica. And a rubber composition crosslinked with 0.5 to 10 parts by weight of an organic peroxide per 100 parts by weight of the total of the components (A) and (B).

  In the present invention, by adding silica and an alkoxysilane having an ethylenically unsaturated bond, the exothermic property (tan δ) of the compound can be lowered while suppressing a decrease in modulus and hardness.

  The rubber composition described in Patent Document 1 can provide a pneumatic tire that has excellent adhesion to general-purpose rubber and has run-flat performance. When used in a pneumatic tire, sufficient run-flat performance cannot always be obtained, and further improvements are required. Accordingly, as a result of studies conducted by the present inventors to solve such problems, (A) a rubber component containing 40 parts by weight or more, preferably 50 parts by weight or more of polybutadiene rubber, and (B) a content of conjugated diene units is 30. A composition in which 20 to 120 parts by weight, preferably 30 to 100 parts by weight of a metal salt of an ethylenically unsaturated carboxylic acid is blended with 100 parts by weight of an ethylenically unsaturated nitrile-conjugated diene copolymer (HNBR) of not more than 1% by weight. A rubber composition comprising an alkoxysilane having an ethylenically unsaturated bond of 5 to 50% by weight, preferably 5 to 40% by weight, based on silica and (C) silica and (D) silica, as components (A) and (B) A rubber composition cross-linked with 0.5 to 10 parts by weight, preferably 1 to 7 parts by weight of an organic peroxide per 100 parts by weight of the total amount of was successfully found and succeeded in achieving the object.

  The rubber composition according to the present invention contains, as component (A), a rubber component containing 40 parts by weight or more, preferably 50 parts by weight or more of polybutadiene rubber. As the polybutadiene rubber (BR) that can be used as the component (A), any of various polybutadiene rubbers that can be used for tires can be used. If the blending amount is less than 40 parts by weight, the exothermic property is impaired, which is not preferable.

  The rubber composition according to the present invention contains, as component (B), an ethylenically unsaturated nitrile-conjugated diene copolymer (HNBR) having a conjugated diene unit content of 30% by weight or less, preferably 20% by weight or less. A composition in which 20 to 120 parts by weight, preferably 25 to 100 parts by weight of a metal salt of an ethylenically unsaturated carboxylic acid is added to 100 parts by weight. When the content of the conjugated diene unit of the component (B) exceeds 30% by weight, that is, when the partial hydrogenation rate is about 50% or less, the strength of the rubber composition becomes insufficient, which is not preferable. As the ethylenically unsaturated nitrile-conjugated diene copolymer (HNBR), for example, the hydrogenated NBR is already known, and ethylenically unsaturated nitriles such as acrylonitrile and methacrylonitrile and 1,3-butadiene are used. , Isoprene, copolymers with conjugated dienes such as 1,3-pentadiene, monomers copolymerizable with the above two monomers, such as vinyl aromatic compounds (meth) acrylic acid, alkyl (meta ) Acrylates, alkoxyalkyl (meth) acrylates, multi-component copolymers with cyanoalkyl (meth) acrylates, specifically, acrylonitrile-butadiene copolymer rubber, acrylonitrile-isoprene copolymer rubber, acrylonitrile-butadiene- Isoprene copolymer rubber, acrylonitrile-butadiene-a Relate copolymer rubber, an acrylonitrile - butadiene - acrylate - can be mentioned methacrylic acid copolymer rubber. These rubbers contain 30 to 60% by weight of ethylenically unsaturated nitrile units, and conjugated diene units are made 30% by weight or less, preferably 20% by weight or less by means such as partial hydrogenation of conjugated diene units. .

  In the component (B) blended in the rubber composition according to the present invention, a metal salt of an ethylenically unsaturated carboxylic acid for the HNBR (for example, zinc dimethacrylate, magnesium dimethacrylate, zinc diacrylate, magnesium diacrylate, etc.) If the blending amount is too small, it is not preferable because the strength of the rubber becomes insufficient. On the contrary, if the amount is too large, the rubber becomes hard and the workability deteriorates. Component (B) is commercially available, for example, as a complex from Nippon Zeon Co., Ltd. as the “ZSC” (trade name) series, for example, ZSC2295, ZSC2295N, ZSC2395, ZSC2298. it can.

  The silica blended as the component (C) in the rubber composition of the present invention can be any silica that can be blended in a rubber composition used for a pneumatic tire or the like, for example, dry silica, wet silica, or the like. . Although there is no limitation in the compounding quantity of the silica in the rubber composition of this invention, Preferably it is 10-100 weight part with respect to 100 weight part of total amounts of component (A) and (B), More preferably, it is 10-70 weight. Part mix. If the blending amount is too small, the strength of the rubber becomes insufficient, which is not preferable. Conversely, if the amount is too large, the rubber becomes hard and the workability deteriorates, which is not preferable.

  In the rubber composition of the present invention, as the component (D), 5 to 50% by weight, preferably 6 to 20% by weight of the alkoxysilane having an ethylenically unsaturated bond, is blended with the amount of the silica of the component (C). . If the blending amount is too small, the strength of the rubber becomes insufficient and the processability deteriorates, which is not preferable. On the other hand, if the amount is too large, bleeding occurs and the rubber becomes too hard.

  Examples of the alkoxysilane having an ethylenically unsaturated bond blended as the component (D) in the rubber composition of the present invention include vinyltrimethoxysilane, vinyltriethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, and 3-methacrylic. Examples include loxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, and 3-methacryloxypropyltrimethoxysilane.

In the rubber composition of the present invention, the following alkoxysilyl group (I) and acyloxysilyl group (II):
≡Si-OR ¹ (I)
≡Si-OCOR ² (II)
(In the formula, R ¹ is a substituted or unsubstituted monovalent hydrocarbon group or ether bond-containing organic group having 1 to 18 carbon atoms, and R ² is hydrogen or a hydrocarbon group having 1 to 21 carbon atoms) A polysiloxane having an average polymerization degree of 3 to 10,000 is mixed. The polysiloxane is described in detail in, for example, JP-A-1998-53707, and can be followed in the present invention.

  The rubber composition of the present invention is crosslinked using 0.5 to 10 parts by weight, preferably 1 to 8 parts by weight of an organic peroxide with respect to 100 parts by weight of the total amount of the components (A) and (B). . If the amount of the organic peroxide used is too small, the crosslinking does not proceed and sufficient rubber strength cannot be obtained, which is not preferable. On the other hand, if the amount is too large, the scorch time becomes short and the workability deteriorates. .

  The organic peroxide is not particularly limited, and any organic peroxide capable of crosslinking a rubber can be used. Specifically, benzoyl peroxide (BPO), t-butyl peroxybenzoate ( Z), dicumyl peroxide (DCP), t-butylcumyl peroxide (C), t-butyl peroxide (D), 2,5-dimethyl-2,5-di-t-butylperoxyhexane (2 , 5B), 2,5-dimethyl-2,5-di-t-butylperoxy-3-hexyne (Hexyne-3), 2,4-dichloro-benzoyl peroxide (DC-BPO), di-t- Butylperoxy-di-isopropylbenzene (P), 1,1-bis (t-butylperoxy) -3,3,5-trimethyl-cyclohexane (3M), n-butyl = 4,4-bis (t-butylperoxy) valerate, 2,2-bis (t-butylperoxy) butane and the like. The crosslinking conditions are not particularly limited as in the past, but the crosslinking can be preferably performed at 140 to 200 ° C.

  A rubber composition obtained by crosslinking a rubber composition containing the components (A) to (D) according to the present invention using an organic peroxide has a 50% modulus of 3 to 10 MPa and a tan δ at 60 ° C. of 0.1. The following are preferable, and it is more preferable that they are 4 to 9.5 MPa and 0.09 or less, respectively.

  In addition to the above-described essential components, the rubber composition according to the present invention includes other reinforcing agents (fillers) such as carbon black, vulcanization or crosslinking agents, vulcanization or crosslinking accelerators, various oils, anti-aging agents, Various additives that are generally blended for tires such as plasticizers and other general rubbers can be blended. These additives are kneaded and vulcanized by a general method to obtain a composition, and then vulcanized. Or it can be used to crosslink. 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.

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

Examples 1 to 4 and Comparative Example 1
Sample preparation In the formulation shown in Table I, the components excluding the organic peroxide were kneaded for 4 minutes with a 2 liter closed mixer and released when the temperature reached 160 ± 5 ° C to obtain a master batch. An organic peroxide was kneaded with this masterbatch with an open roll to obtain a rubber composition.

  Next, the resulting rubber composition was vulcanized in a 15 × 15 × 0.2 cm mold at 160 ° C. for 30 minutes to prepare a vulcanized rubber sheet. The physical properties of the vulcanized rubber were measured by the following test methods. It was measured. The results are shown in Table I.

Rubber physical property evaluation test method tan δ (60 ° C.): Measured at 20 Hz, initial elongation 10% dynamic strain 2% with a viscoelastic device Rheograph Solid manufactured by Toyo Seiki Seisakusho (sample width 5 mm, temperature 60 ° C.) This value is small It shows that exothermic property is so low.

  Run-flat endurance test (running performance): The formulations shown in Table I are mixed as described above and extruded into a crescent mold. A 225 / 60R15 tire was produced in which the extrudate was disposed as a reinforcing layer on the side inner portion of the tire. A test tire is attached to the front wheel of an FR passenger car with a displacement of 2500 cc, runs at a speed of 80 km / h with an air pressure of 0 kPa, and the distance traveled until the tire breaks is a number expressed as an index with the tire of Comparative Example 1 as 100 The larger the value, the better the run flat durability.

Table I footnote * 1 Nipol BR1220 (manufactured by Nippon Zeon)
* 2 RSS # 3
* 3 ZSC2395 (manufactured by Nippon Zeon)
* 4 HTC # 100 (manufactured by Nippon Nikkei Carbon)
* 5 ZEOSIL 115Gr (made by Rhodia)
* 6 KBE-503 (Shin-Etsu Chemical Co., Ltd.)
* 7 KI-90E (Nihon Unicar)
* 8 Bead stearic acid (manufactured by Kao)
* 9 Nowguard 445 (manufactured by Uniroyal Chemical)
* 10 Park Mill D-40 (Nippon Yushi)

  According to the present invention, tan δ (60 ° C.) can be reduced (that is, the exothermic property can be reduced), so that the side reinforcing rubber of a pneumatic tire, particularly a pneumatic tire, particularly a pneumatic tire having run-flat performance, Useful as a beet filler.

Claims (5)

  (A) A rubber component containing 40 parts by weight or more of polybutadiene rubber, and (B) 100 parts by weight of ethylenically unsaturated nitrile-conjugated diene copolymer having a conjugated diene unit content of 30% by weight or less. A rubber composition containing 20 to 120 parts by weight of an acid metal salt, (C) silica, and (D) an alkoxysilane having an ethylenically unsaturated bond in an amount of 5 to 50% by weight of the amount of the silica. A rubber composition crosslinked with 0.5 to 10 parts by weight of an organic peroxide per 100 parts by weight in total of the components (A) and (B). In the rubber composition, the following alkoxysilyl group (I) and acyloxysilyl group (II):
≡Si-OR ¹ (I)
≡Si-OCOR ² (II)
(In the formula, R ¹ is a substituted or unsubstituted monovalent hydrocarbon group or ether bond-containing organic group having 1 to 18 carbon atoms, and R ² is hydrogen or a hydrocarbon group having 1 to 21 carbon atoms) The rubber composition according to claim 1, wherein a polysiloxane having an average degree of polymerization of 3 to 10,000 is blended.   The rubber composition according to claim 1 or 2, wherein the rubber composition has a 50% modulus of 3 to 10 MPa and a tan δ at 60 ° C of 0.1 or less.   A pneumatic tire using the rubber composition according to claim 1.   The pneumatic tire which has the run flat performance using the rubber composition of any one of Claims 1-3 for a side reinforcement rubber and / or a bead filler.