JP2002080636A - Rubber composition for tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rubber composition for a tire which has a high hardness, enables a low fuel consumption and is excellent in extensibility and heat resistance. SOLUTION: The rubber composition for a tire comprises 5-30 parts by weight of cis-1,4-polybutadiene containing 5-20% by weight of syndiotactic-1,2- polybutadiene staple fiber, 100 parts by weight of a rubber component containing 50-90 parts by weight of at least one conjugative diene rubber selected from the group consisting of a natural rubber(NR), a polyisoprene rubber(IR), a styrene-butadiene copolymer rubber (SBR) and a polybutadiene rubber (BR), and 3-10 parts by weight of a cresol resin containing a cresol component in which m-cresol has 50% by weight or more, wherein the composition has a JIS hardness (20 deg.C) of 68 or higher and a tensile elongation of 300% or higher as the vulcanization properties.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a rubber composition for a tire, and more particularly to a cis-1,4-polybutadiene containing syndiotactic-1,2-polybutadiene short fiber and a phenol component in the rubber composition for a tire. A hardness of 68 or more and a tensile elongation of 3 obtained by mixing a cresol resin in which 50% by weight or more of m-cresol is m-cresol.
The present invention relates to a rubber composition for tires having a vulcanization property of at least 00% and particularly suitable for undertread.

[0002]

2. Description of the Related Art JP-A-54-132645 discloses that
A rubber composition (VCR) containing butadiene rubber in which natural rubber or synthetic rubber is blended with short fibers of syndiotactic-1,2-polybutadiene having a maximum diameter of 10 μm or less and an average diameter of less than 1 μm is obtained by mixing fibers in rubber. It is described that orientation can improve the reinforcing properties, fracture resistance and fatigue resistance of rubber. Japanese Patent Application Laid-Open No. H11-222012 discloses that a rubber composition containing short fibers is used as a tire undertread. Is described. On the other hand, it is necessary to reduce the fuel consumption of the undertread in order to reduce the fuel consumption of automobiles. In high performance tires,
There is a strong need for higher hardness to improve ride comfort.

[0003]

Accordingly, in order to meet the needs of the tire industry, an object of the present invention is to provide a rubber composition for tires having high hardness, low fuel consumption, and excellent elongation and heat resistance. Is to do.

[0004]

According to the present invention, syndiotactic-1,2-polybutadiene short fibers 5 to 20 are provided.
5 to 30 parts by weight of cis-1,4-polybutadiene containing natural rubber (NR), polyisoprene rubber (I
R), 100 parts by weight of a rubber component containing 50 to 90 parts by weight of at least one conjugated diene rubber selected from the group consisting of a styrene-butadiene copolymer rubber (SBR) and a polybutadiene rubber (BR); Of 50
Cresol resin 3 to 3% by weight or more of m-cresol
A rubber composition for a tire, comprising 10 parts by weight and exhibiting vulcanization properties of JIS hardness (20 ° C.) of 68 or more and tensile elongation of 300% or more is provided.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The present inventors have found that by using syndiotactic-1,2-polybutadiene short fibers in combination, hardness and elongation are compatible, and cresol containing 50% by weight or more of m-cresol in a phenol component. Resin improves elongation and hardness. More preferably, a conventional sulfur is used as a vulcanization accelerator together with a metal salt of alkyl thiophosphate to obtain a JIS hardness (20 ° C.) of 68.
It has been found that a rubber composition having a vulcanization property of 300% or more and a tensile elongation of 300% or more can be obtained.

The rubber composition for a tire according to the present invention contains, as an essential component, cis-1,4 containing 5 to 20% by weight, preferably 10 to 15% by weight of short syndiotactic-1,2-polybutadiene fibers. -5 to 30 parts by weight of polybutadiene, preferably 10 to 20 parts by weight, and natural rubber (N
R), 50 to 90 parts by weight, preferably 60 parts by weight of at least one conjugated diene rubber selected from the group consisting of polyisoprene rubber (IR), styrene-butadiene copolymer rubber (SBR) and polybutadiene rubber (BR). ~ 80
Rubber parts including parts by weight are included.

The above syndiotactic-1,2-polybutadiene staple fiber is a known substance, and can be produced, for example, by the method described in the monthly journal of the Chemical Society of Japan, January 23, 1988, page 23. It is a crystalline polymer, and has no commercial value by itself. Achieves rubber reinforcement when used with rubber. In the present invention, cis-1,4-polybutadiene containing 5 to 20% by weight, preferably 10 to 15% by weight of the short fibers is blended with the conjugated diene rubber. If the blending amount of the short fibers is too small, the reinforcing property is small, so that it is not preferable. On the contrary, if it is too large, the reinforcing property is too strong and too hard, so that it is not preferable. The rubber containing the short fibers is blended in an amount of 5 to 30 parts by weight, preferably 10 to 20 parts by weight, based on 100 parts by weight of the total rubber. If the amount is too small, the effect cannot be exhibited. On the other hand, if the amount is too large, the butadiene component increases, and the heat resistance and physical properties decrease, which is not preferable.

The rubber composition for a tire according to the present invention comprises 3 to 10 parts by weight, preferably 3 to 10 parts by weight, of a cresol resin in which at least 50% by weight of the phenol component is m-cresol based on 100 parts by weight of the rubber component. JIS hardness (20 ° C.) of 68 or more, preferably 70 or more, and a tensile elongation of 300% or more, preferably 3 or more.
It shows vulcanization properties of 50% or more. If the m-cresol content in the phenolic component of the cresol resin used is low, the tensile elongation tends to be low, so that it is not preferable.

In the rubber composition for a tire according to the present invention, a general sulfur and a vulcanization accelerator are used as a vulcanization system, and in addition, a metal salt of alkylthiophosphate is used as a vulcanization accelerator. Is preferred. Such metal salts of alkyl thiophosphates (eg zinc dithiophosphat
e) can be, for example, Rhenocure ZDT (Rhein Chemie / BAYER). The amount of the alkyl thiophosphate is not particularly limited.
0.5 to 10 parts by weight per 0 parts by weight, more preferably 1 to 10 parts by weight
5 parts by weight. By blending the metal salt of alkylthiophosphate, the vulcanization rate is accelerated, and the effect of forming a crosslinked structure having high heat resistance is obtained.

The rubber composition according to the present invention contains, in addition to the above-mentioned essential components, reinforcing agents (fillers) such as carbon black and silica, various oils, anti-aging agents, plasticizers and other tires, and other general rubbers. Various additives generally blended for use in the composition can be blended, and such a blend can be kneaded, vulcanized to form a composition by a general method, and used for vulcanization. The compounding amounts of these additives can also be conventional general compounding amounts, as long as they do not contradict the object of the present invention.

[0011]

EXAMPLES Hereinafter, the present invention will be further described with reference to Examples, but it goes without saying that the scope of the present invention is not limited to these Examples.

[0012] In the formulations shown in preparation Table I of Comparative Examples 1-4 and Examples 1-3 samples, the components except for sulfur and a ZDT vulcanization accelerator in a 1.8 liter internal mixer 3-5
The mixture was kneaded for a minute and released when the temperature reached 165 ± 5 ° C. to obtain a master batch. The masterbatch was kneaded with an 8-inch open roll with a vulcanization accelerator, ZDT and sulfur to obtain a rubber composition. The obtained rubber composition is 15 × 15 ×
The target test piece (rubber sheet) was prepared by press vulcanization in a 0.2 cm mold at 160 ° C. for 20 minutes, and the vulcanization properties were evaluated. The results are shown in Table I.

The test methods for evaluating the physical properties of the compositions obtained in the respective examples are as follows. Physical property evaluation test method 1) Vulcanization time T90 (min): Measured at 160 ° C. based on JIS K 6300. 2) Hardness (20 ° C): Measured at 20 ° C according to JIS K 6253 3) 300% modulus M300 (MPa): JIS K
4) Breaking strength (MPa): Measured according to JIS K6251 5) Breaking elongation (%): Measured according to JIS K6251

[0014]

[Table 1]

Footnotes in Table I ^{* 1} : Natural rubber (TSR) ^{* 2} : Polyisoprene rubber IR 2200 manufactured by Zeon Corporation ^{* 3} Solution polymerization SBR Tufden 1000R manufactured by Asahi Kasei ^{* 4} : VCR 412 manufactured by Ube Industries ^{* 5} : Manufactured by Zeon Corporation Polybutadiene rubber Nipol BR
1220 ^{* 6} : Carbon black seast 7HT manufactured by Tokai Carbon ^{* 7} : m-cresol resin manufactured by Nippon Shokubai ^{* 8} : Desolex No. 3 manufactured by Showa Shell Sekiyu ^{* 9} : Zinc oxide manufactured by Shodo Chemical ^{* 10} : Industrial stearic acid manufactured by Nippon Yushi ^{* 11} : Antigen antiaging agent 6C (S13) manufactured by Sumitomo Chemical ^{* 12} : Vulcanization accelerator Santocure manufactured by Flexsys
CBS ^{* 13} : Rhenocure ZDT manufactured by Bayer ^{* 14} : Sulfur manufactured by Tsurumi Chemical

As is clear from the results in Table I, Example 1
In the VCR blended systems of Examples 1 and 2, and the BR blended systems of Comparative Examples 1 and 2, the hardness was significantly improved by the blending of VCR. From the comparison between Example 1 and Comparative Example 3, the use of ZDT significantly reduced T90. As a result, the workability was improved, and a comparison between Example 1 and Comparative Example 4 confirmed that the addition of the m-cresol resin significantly increased the elongation at break.

[0017]

As described above, according to the present invention, a rubber composition for tires having high hardness, low fuel consumption, and excellent elongation and heat resistance can be obtained.

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) C08L 9/00 C08L 9/00 9/06 9/06 // (C08L 7/00 (C08L 7/00 47:00 47 : 00 61:08) 61:08) F-term (reference) 4J002 AC011 AC031 AC061 AC081 BC051 BL012 BL013 CC054 DA046 EW168 FA043 FD146 FD157 FD158 GN01

Claims (2)

[Claims] 1. 5 to 30 parts by weight of cis-1,4-polybutadiene containing 5 to 20% by weight of syndiotactic-1,2-polybutadiene short fiber, natural rubber (NR), polyisoprene rubber (IR), 100 parts by weight of a rubber component containing 50 to 90 parts by weight of at least one conjugated diene rubber selected from the group consisting of styrene-butadiene copolymer rubber (SBR) and polybutadiene rubber (BR) and 50 parts by weight in a phenol component %. A rubber composition for a tire, comprising 3 to 10 parts by weight of a cresol resin having m-cresol in an amount of at least JIS hardness (20 ° C.) of at least 68 and a tensile elongation of at least 300%. 2. A vulcanization system containing a metal salt of alkylthiophosphate in addition to sulfur and a vulcanization accelerator.
The rubber composition for a tire according to the above.