JPH06287358A - Vulcanizable rubber composition - Google Patents

Abstract

PURPOSE:To obtain a rubber composition which can give a vulcanizate improved in strength properties and flexural fatigue resistance by mixing a high-cis 1,4- polyisoprene rubber with zinc methacrylate formed in the rubber and an organic peroxide. CONSTITUTION:The composition comprises 100 pts.wt. high-cis 1,4-polyisoprene rubber, 30-70 pts.wt. zinc methacrylate formed in the rubber by adding a zinc compound and methacrylic acid to this rubber and a necessary and effective amount of an organic peroxide. Examples of the high-cis polyisoprene rubbers used include a natural rubber and a synthetic polyisoprene rubber of a cis 1, 4 bond content of 90% or above. The synthetic polyisoprene rubber is obtained by polymerizing isoprene by using a polymerization catalyst which can give a cis 1, 4 bond content of 90% or above. The organic peroxide is used in an amount of usually 0.2-10 pts.wt. per 100 pts.wt. rubber, and the optimal amount can be suitably selected according to the required properties.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vulcanizable rubber composition, and more specifically, a vulcanizable rubber composition capable of giving a vulcanized rubber exhibiting excellent strength characteristics, bending fatigue resistance, abrasion resistance and the like. It relates to a rubber composition.

[0002]

2. Description of the Related Art A vulcanized rubber having improved strength characteristics and impact resilience can be obtained by mixing zinc dimethacrylate or basic zinc methacrylate with rubber and vulcanizing it with an organic peroxide. Are better known than ever before. For example, a golf ball whose surface is covered with the vulcanizate containing high-cis polybutadiene rubber as a main component (Japanese Patent Publication No. 61-18).
No. 465), a golf ball composed of an integrally molded product of the vulcanized product such as the polybutadiene (Japanese Patent Publication No. 63-39016).
(Japanese Patent Publication No. 4-59337, etc.) and the like in which natural rubber or the like is mixed with zinc dimethacrylate having a specific surface area to improve the strength characteristics.

[0003]

DISCLOSURE OF THE INVENTION The present inventors have obtained a crosslinked product having excellent strength properties by blending natural rubber or synthetic polyisoprene rubber with zinc methacrylic acid salt and crosslinking with an organic peroxide. Focusing on this, we examined the application to tire treads, carcasses, and sidewalls.
It was concluded that the fatigue resistance and abrasion resistance were not sufficient, and if this property was not improved, it would be difficult to use for the above applications.

The present inventors have conducted extensive studies to develop a composition using a zinc methacrylic acid salt having the above-mentioned properties improved, and as a result, instead of compounding the zinc methacrylic acid salt with a high cis polyisoprene rubber. It was found that the above characteristics are remarkably improved by using a rubber composition containing a zinc compound and methacrylic acid added to the rubber and producing zinc methacrylate in the rubber, thereby completing the present invention. .

[0005]

Thus, according to the present invention, a zinc compound and methacrylic acid were added to 100 parts by weight of a high cis 1,4-polyisoprene rubber to form the rubber in the rubber. A vulcanizable rubber composition comprising 30 to 70 parts by weight of zinc methacrylic acid salt and a necessary and effective amount of organic peroxide is provided.

The present invention will be described in detail below. The high cis polyisoprene rubber used in the present invention includes natural rubber and synthetic polyisoprene rubber having a cis 1,4 bond content of 90% or more. Synthetic polyisoprene rubber is obtained by polymerizing isoprene using a polymerization catalyst having a cis-1,4 bond content of 90% or more. As the polymerization catalyst, Ziegl using a transition metal such as Co or Ni is used.
er catalysts, alkali metal-based catalysts such as Li, etc. are usually used.

Examples of the zinc compound which reacts with methacrylic acid in situ in polyisoprene rubber to form a zinc methacrylic acid salt include zinc oxide, zinc carbonate and zinc hydroxide. When the reaction is carried out in the system, it is necessary to remove coarse particles having a particle size of 20 μm or more in advance by classification as a zinc compound, and to use the one in which the content ratio of the coarse particles is 5% by weight or less. It is preferable in improving strength characteristics such as strength.

The proportion of the zinc compound is adjusted together with the amount of methacrylic acid so that the amount of the zinc salt of methacrylic acid produced is 30 to 70 parts by weight based on 100 parts by weight of the polyisoprene rubber. For 10-60
Parts by weight. The mixing ratio of methacrylic acid is 10 to 60 parts by weight with respect to 100 parts by weight of polyisoprene rubber. The molar ratio of methacrylic acid and the zinc compound calculated based on the molecular weight of methacrylic acid and the formula weight of the zinc compound is usually 1: 0.5 to 1: 3.2, preferably 1 :.
The range is 0.5 to 1: 2.5.

To form a zinc methacrylic acid salt in the rubber, the rubber, the zinc compound, and methacrylic acid are
It is kneaded by a roll, Banbury, kneader, twin-screw extruder or the like. It is preferable to mix methacrylic acid after mixing the zinc compound with the rubber and sufficiently dispersing it. It is presumed that the zinc compound and methacrylic acid react in the rubber to produce zinc dimethacrylate and basic zinc methacrylate. The temperature at the time of mixing is not particularly limited, but usually 7
It is in the range of 0 to 150 ° C. If the amount of the produced zinc methacrylic acid salt is less than 30 parts by weight or more than 70 parts by weight, the strength properties are deteriorated. It is preferably 40 to 60 parts by weight.

Examples of the organic peroxide used in the present invention include dicumyl peroxide, di-t-butyl peroxide, t-butylcumyl peroxide, benzoyl peroxide, and 2,5-dimethyl-2, 5-
(T-butylperoxy) hexyne-3,2,5-dimethyl-2,5-di (benzoylperoxy) hexane,
2,5-dimethyl-2,5-mono (t-butylperoxy) hexane, α, α′-bis (t-butylperoxy-m-isopropyl) benzene and the like can be mentioned.

These organic peroxides are used in a required and effective amount by using one kind or two or more kinds. Usually, it is used in a ratio of 0.2 to 10 parts by weight, preferably 0.5 to 8 parts by weight, based on 100 parts by weight of the rubber, and an optimum amount is appropriately selected according to the required physical property values. be able to.

In the vulcanizable rubber composition of the present invention, if desired, reinforcing agents such as carbon black and silica, fillers such as calcium carbonate and talc, triallyl isocyanurate, trimethylolpropane tri (meth) acrylate, Various additives usually used in the rubber industry such as a crosslinking aid such as m-phenylene bismaleimide, a plasticizer, a stabilizer, a vulcanization aid, and a colorant can be added.

[0013]

EXAMPLES The present invention will be described in more detail below with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples. The parts and% in the examples and comparative examples are based on weight unless otherwise specified.

Examples 1 to 3 and Comparative Examples 1 to 4 Rubber compositions using polyisoprene rubber (Nipol IR2200, cis 1,4 bond content 98%) having the compounding formulation shown in Table 1 excluding organic peroxide. 12 with a kneader
Prepared at 0 ° C. Then, the organic peroxides shown in Table 1 were added to each kneaded product at a temperature at which the organic peroxide was not decomposed to prepare a vulcanizable rubber composition. The obtained vulcanizable rubber composition was press-vulcanized under vulcanizing conditions of 170 ° C. for 20 minutes to prepare test pieces for tensile strength, impact resilience, pico abrasion and demasher bending test. These characteristics are tested by JIS K-
It carried out according to 6301. Rebound resilience (at 60 ° C), pico wear and demasher flex test 30,000 flex cycles
The fatigue resistance indicated by the length of the cracks grown up to the time of vulcanization of the rubber composition was obtained by blending 100 parts by weight of the polyisoprene rubber with 50 parts of HAF carbon black and using 2.5 parts of sulfur. The corresponding characteristic value of the product was expressed as an index. The results are shown in Table 1.

[0015]

[Table 1]

As is clear from the results shown in Table 1,
It can be seen that the formation of zinc methacrylic acid salt in polyisoprene rubber improves the wear resistance and fatigue resistance, which are drawbacks of using the preformed salt.

[0017]

According to the present invention, a rubber composition containing a zinc salt of methacrylic acid obtained by reacting a zinc compound with methacrylic acid in a high cis polyisoprene rubber has excellent strength characteristics and abrasion resistance. Provided is a vulcanizable rubber composition which gives a vulcanizate having excellent properties and fatigue resistance. The rubber composition of the present invention is suitable for producing tire carcass and sidewalls.

Claims (1)

[Claims] 1. A high cis 1,4-polyisoprene rubber 10
Zinc methacrylic acid zinc salt formed in the rubber by adding a zinc compound and methacrylic acid to the rubber per 0 parts by weight 30
A vulcanizable rubber composition containing 70 to 70 parts by weight of a necessary and effective amount of organic peroxide.