JP2006089698A - Rubber composition for pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber composition for pneumatic tire compounded with an inorganic filler such as silica, and a silane coupling agent, wherein the problem (short in scorch time) in use of mercaptosilane as the silane coupling agent is settled to impart excellent physical properties as a rubber for tire. <P>SOLUTION: The rubber composition for pneumatic tire comprises a rubber component containing diene-based rubber, an inorganic filler such as silica, and mercaptosilane as the silane coupling agent, and contains 0.5-8 pts. wt. isocyanate compound per 100 pts. wt. of the rubber component. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a rubber composition for a pneumatic tire.

  Conventionally, in a rubber composition for tires, an inorganic filler such as silica is blended alone or together with carbon black in order to provide reinforcing properties and reduce rolling resistance. And in order to disperse | distribute and couple this inorganic filler in the diene rubber which is a rubber component, the silane coupling agent is mix | blended.

  Examples of such silane coupling agents include sulfide silane and mercaptosilane. Conventionally, in rubber compositions for tires, sulfides such as bis- (3-triethoxysilylpropyl) tetrasulfide are generally blended. Silane. This is because, compared to sulfide silane, mercaptosilane is excellent in reinforcing properties and the effect of reducing rolling resistance, and should be able to give good physical properties originally, but the scorch time is short, so kneading, This is because there is a high possibility that burning due to the progress of vulcanization occurs during extrusion, and there is a high possibility that vulcanized rubber having good physical properties cannot be provided.

  In order to solve such a problem of mercaptosilane, that is, to prevent scorch, Patent Document 1 below proposes a protected mercaptosilane in which a mercapto moiety is protected with a blocking group. Although such a protected mercaptosilane has an excellent effect in terms of preventing scorch, it has a problem of high cost.

  Patent Document 2 below proposes that an amine compound and an isocyanate compound are used in combination as an anti-scorch agent mainly in a rubber compound for an anti-vibration product. However, this document does not disclose that the scorch prevention effect can be obtained by using an isocyanate compound alone in the presence of a specific silane coupling agent.

Further, in Patent Documents 3 to 7 below, a free radical-containing compound having a functional group such as an isocyanate group, amino group, or hydroxyl group in the molecule or a compound that generates a radical improves the exothermic property of the vulcanized rubber. It has been proposed as a rubber modifier. However, in these documents, the rubber modifier is added to reduce the free end of rubber by binding to a rubber terminal that is increased by radical trapping and reacting with a filler such as carbon black. Neither the combination with silane nor the technical idea of blending an isocyanate compound as a means for solving the short scorch time of mercaptosilane is disclosed at all.
Special table 2001-505225 gazette JP-A-6-306210 JP 2001-335661 A Japanese Patent Laid-Open No. 2002-3654 JP 2002-69238 A JP 2002-201312 A JP 2002-294000 A

  An object of the present invention is to solve a problem when a mercaptosilane is used as a silane coupling agent in a rubber composition for a pneumatic tire in which an inorganic filler such as silica and a silane coupling agent are blended. It is to provide excellent physical properties.

  As a result of diligent studies to solve the above problems, the present inventor, when blending mercaptosilane as a silane coupling agent, adds a specific amount of an isocyanate compound, thereby scorching time that was a conventional drawback of mercaptosilane. The present inventors have found that it is possible to improve the physical properties such as rolling resistance by demonstrating the original performance of mercaptosilane while eliminating the shortness.

  That is, the rubber composition for a pneumatic tire according to the present invention contains a rubber component containing a diene rubber, an inorganic filler, and a mercaptosilane, and further contains 0 isocyanate compound relative to 100 parts by weight of the rubber component. It is characterized by containing 5-8 parts by weight.

  According to the present invention, in a rubber composition containing an inorganic filler and a mercaptosilane, by blending an isocyanate compound, it is possible to eliminate the short scorch time that was a major drawback of a silane coupling agent composed of mercaptosilane. it can. Therefore, the original performance of mercaptosilane can be exhibited, and tire characteristics such as rolling resistance can be improved as compared with the case where sulfide silane is used.

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

  In the rubber composition of the present invention, as the diene rubber used as a rubber component, various diene rubbers generally used in tire rubber compositions can be used. For example, natural rubber (NR), polyisoprene rubber (IR), styrene-butadiene copolymer rubber (SBR), polybutadiene rubber (BR), butyl rubber (IIR), halogenated butyl rubber, acrylonitrile-butadiene copolymer rubber (NBR) ), Ethylene-propylene-diene terpolymer rubber (EPDM) and the like, and these may be used alone or in combination of two or more. Preferably, at least one selected from the group consisting of natural rubber, polyisoprene rubber, styrene-butadiene copolymer rubber and polybutadiene rubber is used.

  In the rubber composition of the present invention, examples of the inorganic filler include silica, titanium oxide, aluminum silicate, clay, and talc. Among them, it is particularly preferable to use silica which is a reinforcing filler. In that case, silica alone or a combination of silica and other inorganic fillers may be used. Silica is not particularly limited, and examples thereof include 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. It is preferable that the compounding quantity of an inorganic filler is 5-120 weight part with respect to 100 weight part of rubber components.

  You may mix | blend carbon black with the said inorganic filler with the rubber composition of this invention. That is, in the rubber composition of the present invention, the filler may be the above inorganic filler alone or a combination of the above inorganic filler and carbon black. When the inorganic filler and carbon black are used in combination, the total amount of both is preferably 20 to 150 parts by weight with respect to 100 parts by weight of the rubber component.

  In the rubber composition of the present invention, the mercaptosilane compounded as a silane coupling agent for dispersing and coupling an inorganic filler such as silica in the rubber component is not particularly limited. For example, 3-mercaptopropyltrimethoxy Examples include mercaptoalkyltrialkoxysilanes such as silane, 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, and 2-mercaptoethyltriethoxysilane. The mercaptosilane usable in the present invention also includes protected mercaptosilane in which the mercapto moiety is protected with a blocking group. The blending amount of mercaptosilane is preferably 1 to 20 parts by weight with respect to 100 parts by weight of the inorganic filler.

  The isocyanate compound blended in the rubber composition of the present invention is not particularly limited. For example, diisocyanates such as diphenylmethane diisocyanate (MDI), tolylene diisocyanate (TDI), hexamethylene diisocyanate (HDI), isophorone diisocyanate, And polyisocyanates such as (4-isocyanatophenyl) methane. In addition, a blocked isocyanate in which an isocyanate group is blocked with a protective group that can be separated under a predetermined condition can also be used.

  The amount of the isocyanate compound is preferably 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 the isocyanate compound is less than 0.5 parts by weight, the effect of the present invention such as elimination of the short scorch time cannot be obtained sufficiently. On the other hand, if it exceeds 8 parts by weight, the original properties of mercaptosilane are impaired, and rolling resistance and the like are deteriorated.

  In addition to the above-described components, the rubber composition of the present invention includes a rubber composition for pneumatic tires such as a vulcanizing agent such as sulfur, a vulcanization accelerator, an anti-aging agent, zinc white, stearic acid, wax and oil. Various additives generally used as products can be blended.

  The rubber composition of the present invention composed of the above can be used in various parts of a pneumatic tire, but is particularly preferably used as a rubber composition for a tread, and is resistant to rolling by vulcanization molding according to a conventional method. Thus, a tread having excellent characteristics can be formed.

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

  Using a Banbury mixer, tire rubber compositions for tire treads of Examples 1 to 4 and Comparative Examples 1 to 4 were prepared according to the composition shown in Table 1 below. The details of each formulation in Table 1 are as follows.

・ SSBR: "VSL5025-OHM" made by LANXESS
・ BR: “BR01” manufactured by JSR
・ Silica: “AQ” made by Tosoh Silica
Mercaptosilane (1): Nippon Unicar “A-189” (HS- (CH ₂ ) ₃ Si (OCH ₃ ) ₃ : 3-mercaptopropyltrimethoxysilane).

Mercaptosilane (2): “Si-263” manufactured by Degussa (HS- (CH ₂ ) ₃ Si (OC ₂ H ₅ ) ₃ : 3-mercaptopropyltriethoxysilane (MPTES)).

Sulfide silane: “Si-69” (bis- (3-triethoxysilylpropyl) tetrasulfide) manufactured by Degussa.

Isocyanate: “Sumijour 44V-20” (diphenylmethane diisocyanate (MDI)) manufactured by Sumitomo Bayer Urethane.

  In each rubber composition, as a common compounding agent, 40 parts by weight of aroma oil (“Process X140” manufactured by Japan Energy), 1 part by weight of wax (“paraffin wax 155” manufactured by Nippon Seiwa), an anti-aging agent 6PPD ( 1 part by weight of Ouchi Shinsei Chemical Co., Ltd. “NOCRACK 6C”), 2 parts by weight of zinc white (“Zinc Oxide 2” manufactured by Mitsui Mining & Mining), 2 parts by weight of stearic acid (“LUNAC S-25” manufactured by Kao) 2 parts by weight of sulfur accelerator DPG (“Noxeller D” manufactured by Ouchi Shinsei Chemical Industry), 1.8 parts by weight of vulcanization accelerator CZ (“Noxeller CZ” manufactured by Ouchi Shinsei Chemical Industry), sulfur (“Tsurumi Chemical Industries” 2 parts by weight of “5% oil-containing fine powder sulfur”) was blended.

  The scorch was measured for each rubber composition. Moreover, using each rubber composition as a tread rubber, a pneumatic radial tire having a tire size of 205 / 65R15 was produced by vulcanization molding according to a conventional method, and rolling resistance of each obtained tire was measured. Each measuring method is as follows.

Scorch: Measured according to JIS K 6300-1 and displayed as an index with the value of Comparative Example 1 being 100. The larger the index is, the longer the scorch time is. Therefore, it means that burning is less likely to occur during kneading and extrusion.

-Rolling resistance: Rolling resistance was calculated | required according to American Automobile Engineers Association standard, SAE J1269, and it showed with the index | exponent calculated by the following formula. The smaller the index, the better.
(Rolling resistance of each tire) × 100 / (Rolling resistance of the tire of Comparative Example 1)

  As shown in Table 1, in Comparative Example 2 in which sulfide silane was simply changed to mercaptosilane, compared to conventional Comparative Example 1 (using sulfide silane as a silane coupling agent) containing conventional general tread rubber, rolling resistance However, the scorch time was extremely short. On the other hand, when it is Examples 1-4 which concern on this invention, while using mercaptosilane as a silane coupling agent, and having mix | blended a predetermined amount of isocyanate compounds (MDI), the scorch time is extended significantly, Scorch could be delayed to the same extent as when sulfide silane was added. In addition, the rolling resistance is improved as compared with the case where sulfide silane is blended, and the fuel efficiency is excellent.

  The rubber composition for a pneumatic tire of the present invention can be used as a rubber composition for various parts of a tire such as a tread and a sidewall, and particularly preferably used as a rubber composition for a tread. it can.

Claims (1)

A pneumatic component comprising a rubber component including a diene rubber, an inorganic filler, and mercaptosilane, and further containing 0.5 to 8 parts by weight of an isocyanate compound with respect to 100 parts by weight of the rubber component Rubber composition for tires.