JP2006036821A - Rubber composition and pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a rubber composition that raises hardness without deteriorating balance between rolling resistance and wet grip properties and a pneumatic tire using the same. <P>SOLUTION: The rubber composition comprises modified diene-based rubber into which an amino group and/or an epoxy group is introduced, silica, a silane coupling agent and an isocyanate compound. Preferably the amount of the isocyanate compound mixed is 0.5-8 parts wt. based on 100 parts wt. of the rubber component comprising the modified diene-based rubber. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

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

  Recently, as environmental and safety concerns increase, tires are also strongly required to improve fuel efficiency by reducing rolling resistance and improve road surface graspability, particularly wet road surface graspability (wet grip performance). It was. However, these characteristics are generally contradictory, and silica is blended as a filler in order to achieve both. Since such silica is generally difficult to disperse in the rubber component, the dispersibility is improved by adding a silane coupling agent, but the dispersibility is still insufficient and the characteristics are not fully exhibited. It's hard to say.

  Therefore, in such a silica formulation, in order to sufficiently disperse silica and reduce rolling resistance, the mixing energy (mixing time, mixing step, rotation speed, etc.) in preparing the rubber composition is increased, The structure and particle diameter of silica are changed, or a rubber polymer is modified with a hydroxyl group or an amino group (for example, see Patent Documents 1 and 2 below). By adopting such a method, the dispersibility of silica is improved, so that the effect of reducing rolling resistance is great and the balance with wet grip properties is greatly improved. However, in this case, the hardness of the rubber composition is lowered, and as a result, steering stability and cornering characteristics are deteriorated.

  In order to solve this problem, for example, when the amount of filler added is increased, the hardness is increased and the wet grip property is improved, but the effect of reducing rolling resistance is impaired. It is also possible to increase the hardness by increasing the amount of vulcanizing agents such as sulfur and vulcanization accelerators. In this case, although the rolling resistance is improved, the wet grip property is greatly reduced and high speed is also required. There is a problem that the tread rubber is chipped during running.

  The following Patent Document 3 discloses a rubber composition in which an amine compound and an isocyanate compound are used in combination, but it is not intended to increase the hardness in order to improve the steering stability and cornering characteristics of the tire, Moreover, the amine compound is used as a scorch inhibitor and is not introduced into the diene rubber.

  Further, Patent Document 4 below discloses a rubber composition in which a radical-containing compound having an isocyanate group is blended with a diene rubber in order to reduce rolling resistance, and this also provides steering stability and cornering characteristics of a tire. However, the isocyanate group is for reaction with silica and not for the reaction between the functional group of the rubber polymer and the isocyanate group.

Furthermore, the following Patent Document 5 aims to provide a rubber composition capable of producing a tire having improved wet skid property, low rolling resistance, high mechanical resistance, thermal resistance and improved wear resistance. It is disclosed that a diene rubber having a hydroxyl group and / or carboxyl group introduced therein and an isocyanate compound that reacts with the hydroxyl group and / or carboxyl group to crosslink the rubber. However, this document does not disclose an increase in hardness due to a reaction between an amino group and / or an epoxy group introduced into a diene rubber and an isocyanate compound.
WO96 / 23027 WO03 / 029299 JP-A-6-306210 Japanese Patent Laid-Open No. 2002-3654 JP 2001-187827 A

  An object of the present invention is to provide a rubber composition capable of increasing the hardness without deteriorating the balance between rolling resistance and wet grip property, and a pneumatic tire using the rubber composition.

  As a result of intensive studies to solve the above problems, the present inventor used an isocyanate compound together with a modified diene rubber having an amino group and / or an epoxy group as a functional group. It has been found that the hardness can be increased without impairing the balance between the rolling resistance and the wet grip property, and the present invention has been completed.

  That is, the rubber composition according to the present invention contains a modified diene rubber having an amino group and / or an epoxy group introduced therein, silica, a silane coupling agent, and an isocyanate compound.

  In the rubber composition of this invention, it is preferable to mix | blend the said isocyanate compound 0.5-8 weight part with respect to 100 weight part of rubber components containing the said modified diene rubber.

  The pneumatic tire according to the present invention is characterized by having a tread made of the rubber composition of the present invention described above.

  According to the present invention, in a rubber composition containing silica and a silane coupling agent, a modified rubber having an amino group and / or an epoxy group as a functional group is used as a diene rubber, and an isocyanate compound is added thereto. As a result, the hardness can be increased without impairing the balance between the rolling resistance and the wet grip property, and thus the steering stability and cornering characteristics can be improved.

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

  The diene rubber used as a rubber component in the rubber composition of the present invention is a modified diene rubber having these functional groups bonded to a polymer chain by being modified with an amino group and / or an epoxy group. In the present invention, the amino group may be any of a primary amino group, a secondary amino group, and a tertiary amino group. Preferred is a primary or tertiary amino group, and particularly preferred is a primary amino group.

  In the modified diene rubber, the base polymer is preferably a polymer of a conjugated diene monomer or a copolymer of a conjugated diene monomer and an aromatic vinyl monomer. Examples of the conjugated diene monomer include 1,3-butadiene, isoprene, 1,3-pentadiene, 2,3-dimethylbutadiene, and 1,3-butadiene and isoprene are particularly preferable. Examples of the aromatic vinyl monomer include styrene, o-, m- or p-methylstyrene, p-tert-butylstyrene, vinylnaphthalene and the like, and styrene is particularly preferable. Specifically, polybutadiene and styrene-butadiene copolymer are particularly suitable.

  The modification method of the modified diene rubber is not particularly limited, and by reacting a polymer having an active end with a compound having an amino group and / or an epoxy group as a modifier, these ends can be added to the end of the polymer. A functional group may be introduced. Moreover, you may introduce | transduce into a polymer chain by copolymerizing with the monomer of a base polymer using the polymerizable monomer which has these functional groups.

  Such modified diene rubber itself is known, and in the present invention, such known amino-modified diene rubber and epoxy-modified diene rubber can be used. Although not particularly limited, for example, with respect to amino-modified diene rubbers, a styrene-butadiene copolymer modified with a primary amino group and an alkoxysilyl group as disclosed in WO 03/029299, A styrene-butadiene copolymer modified with a tertiary amino group as disclosed in JP-A-9-71687 can be used. As for the epoxy-modified diene rubber, an epoxy group-containing styrene-butadiene obtained by modification with a tetrafunctional compound having two diglycidylamino groups in one molecule as disclosed in JP-A-9-136993. A copolymer or the like can be used.

  In the rubber composition of the present invention, the rubber component may be the above-mentioned modified diene rubber alone, but other diene rubber may be used in combination with the modified diene rubber. Examples of such other diene rubbers include natural rubber (NR), polyisoprene rubber (IR), styrene-butadiene copolymer rubber (SBR), polybutadiene rubber (BR), and the like. Or you may blend and use 2 or more types. When other diene rubbers are used in combination, it is preferable that 20 parts by weight or more of the modified diene rubber is contained in 100 parts by weight of the rubber component in order to sufficiently secure the effects of the present invention.

  Examples of the silica compounded in the rubber composition of the present invention include wet silica, dry silica, colloidal silica, precipitated silica and the like that are generally used as a reinforcing agent in rubber compounding. Particularly, hydrous silicic acid is the main component. It is preferable to use wet silica. It is preferable that the compounding quantity of a silica is 5-100 weight part with respect to 100 weight part of rubber components.

  The silane coupling agent blended in the rubber composition of the present invention promotes the bonding between silica and the polymer. For example, bis (3-triethoxysilylpropyl) tetrasulfide, bis (3-triethoxysilyl) Propyl) disulfide, bis (2-triethoxysilylethyl) tetrasulfide, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-nitropropyltrimethoxysilane, γ-aminopropyltriethoxysilane, etc. It is done. It is preferable that the compounding quantity of a silane coupling agent is 0.5-20 weight part with respect to 100 weight part of silica.

  Although it does not specifically limit as an isocyanate compound mix | blended with the rubber composition of this invention, For example, diphenylmethane diisocyanate (MDI), tolylene diisocyanate (TDI), hexamethylene diisocyanate (HDI), isophorone diisocyanate, tris (4-isocyanate) And polyisocyanates such as natophenyl) 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. If the isocyanate compound is less than 0.5 parts by weight, a sufficient increase in hardness cannot be expected. Moreover, when it exceeds 8 weight part, workability will worsen.

  In the rubber composition of the present invention, carbon black may be blended together with the above silica as a reinforcing filler. The carbon black is preferably blended in an amount of 1 to 100 parts by weight based on 100 parts by weight of the rubber component. In addition to silica, other inorganic fillers such as talc, clay, alumina, and calcium carbonate can be blended with the rubber composition of the present invention.

  The rubber composition of the present invention may further contain various additives such as a vulcanizing agent such as sulfur, a vulcanization accelerator, an anti-aging agent, zinc white, stearic acid, wax and oil.

  The rubber composition of the present invention can be used for various uses such as tires, automobile parts, and conveyor belts, and is particularly preferably used as a rubber composition for a tread of a pneumatic tire and vulcanized according to a conventional method. A tread can be formed by molding. The pneumatic tire produced in this way is excellent in fuel efficiency due to its low rolling resistance, is also excellent in wet grip properties, and has increased hardness, so that it has excellent steering stability and cornering characteristics. Will also be excellent.

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

  According to the composition shown in Table 1 below, rubber compositions of Examples 1 to 6 and Comparative Examples 1 to 7 were prepared. The details of each formulation in Table 1 are as follows.

SSBR1: “Nipol NS422” (solution-polymerized styrene-butadiene copolymer rubber not modified with an amino group or an epoxy group) manufactured by Nippon Zeon.

SSBR2: “Nipol NS116R” (solution-polymerized styrene-butadiene copolymer rubber modified with a tertiary amine) manufactured by Nippon Zeon.

SSBR3: Solution polymerized styrene-butadiene copolymer rubber having a primary amino group synthesized by the method described in WO03 / 029299 using N, N-bis (trimethylsilyl) aminopropylmethyldimethoxysilane as a modifier.

SSBR4: solution polymerized styrene-butadiene copolymer rubber having an epoxy group synthesized by a method described in JP-A-9-136993 using tetraglycidyl-1,3-bisaminomethylcyclohexane as a modifier.

・ BR1: JSR "BR01" (unmodified butadiene rubber)
BR2: “Nipol BR1250H” (butadiene rubber modified with a tertiary amine) manufactured by Zeon Corporation.

・ Silica: “AQ” made by Tosoh Silica
Silane coupling agent: Degussa “Si-69”
・ Isocyanate (1): “Sumijour 44V-20” (diphenylmethane diisocyanate (MDI)) manufactured by Sumitomo Bayer Urethane
Isocyanate (2): “Takenate PW-2400” (block isocyanate) manufactured by Mitsui Takeda Chemical.

  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 rubber composition was prepared by mixing the components excluding sulfur and the vulcanization accelerator with a 1.7 liter closed mixer into master batches, and sulfur and vulcanization accelerators in each master batch using an 8-inch open roll. This was done by kneading. Then, each rubber composition obtained was vulcanized at 160 ° C. for 20 minutes to prepare a test piece having a predetermined shape, and the hardness was measured using the obtained test piece.

  Further, pneumatic tires having a tire size of 205 / 65R15 were produced according to a conventional method using each rubber composition as a tire tread rubber, and rolling resistance and wet grip properties were evaluated. Each measurement / evaluation method is as follows.

Hardness: Measured according to JIS K6253 type A, and expressed as an index with the control value being 100 for each blending system. The larger the index, the higher the hardness, and thus the better the steering stability and cornering characteristics.

-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.
(Each prototype tire rolling resistance) x 100 / (Each control tire rolling resistance)

-Wet grip property: The traction coefficient was determined based on the traction test conditions on the wet asphalt road surface described in UTQGS of the United States. The traction coefficient was expressed as an index obtained by substituting it into the following formula. A larger index is preferable.
(Each prototype tire traction coefficient) x 100 / (Each control tire traction coefficient)

  The results are as shown in Table 1, and as shown in Comparative Examples 1 and 2, in SSBR in which the polymer does not have a specific functional group, the hardness increases by adding isocyanate, Rolling resistance was getting worse. In contrast, in Examples 1 to 6 in which a diene rubber having a specific functional group and an isocyanate compound are combined, the rolling resistance is not deteriorated even when the hardness is increased with respect to each control. The hardness could be increased without impairing the balance between resistance and wet grip. In the present invention, it is presumed that the amino group or epoxy group introduced into the polymer reacts with the isocyanate to cause cross-linking between the polymers, and this is considered to have led to the above preferable results.

  The rubber composition of the present invention can be used for various uses such as tires, automobile parts, and conveyor belts, and can be preferably used as a rubber composition for a tread of a pneumatic tire.

Claims (3)

  A rubber composition comprising a modified diene rubber having an amino group and / or an epoxy group introduced therein, silica, a silane coupling agent, and an isocyanate compound.   The rubber composition according to claim 1, wherein 0.5 to 8 parts by weight of the isocyanate compound is blended with 100 parts by weight of the rubber component containing the modified diene rubber. A pneumatic tire having a tread made of the rubber composition according to claim 1.