JPS5819344A - Production of rubber composition containing zinc di-alpha,beta- ethylenically unsaturated carboxylate - Google Patents

Abstract

PURPOSE:To obtain a compsn. useful for the production of solid golf ball and contg. a normal zinc salt of an unsaturated carboxylic acid which has a long- term stability, by reacting an ethylenically unsaturated carboxylic acid with a zinc compd. in the presence of Ca(OH)2 in a rubber compsn. CONSTITUTION:A zinc compd. (a) such as ZnO and Ca(OH)2 (b) are kneaded with a rubber compsn. (A) for golf ball, obtd. by blending appropriate additives such as a filler, a pigment, etc. with a rubber such as polybutadiene rubber. Then the kneaded material is kneaded with an alpha,beta-ethylenically unsaturated carboxylic acid (c) such as methacrylic acid to obtain a rubber compsn. (B) contg. a normal zinc salt of an di-alpha,beta-ethylenically unsaturated carboxylic acid. Component (b) is blended in an amont of 1-25pts.wt. per 100pts.wt. component (c). A free-radical initiator is added to saic rubber compsn. (B) and the mixture is placed in a mold, molded and cured to form a golf ball having a high resilience.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for preparing a Z-α,β-ethylenically unsaturated carboxylic acid by forming a Zα,β-ethylenically unsaturated carboxylic acid zinc salt, particularly zinc dimethacrylate, inside the rubber. The present invention relates to a method for producing a rubber composition containing an acid zinc salt.

Zinc salts of α,β-unsaturated carboxylic acids, particularly zinc methacrylates, are used as co-crosslinking agents in the cores of solid golf balls and two-piece golf balls. The zinc salt is a normal salt in which 1 mole of zinc compound is reacted with 2 moles of α,β-ethylenically unsaturated carboxylic acid (hereinafter simply referred to as acid) and 1 mole of zinc compound.
There are two types of basic salts in which 1 mole of acid reacts with 1 mole of zinc compound. Of these, positive salt gives golf balls a high coefficient of repulsion. This normal salt is a solid, and is generally made into a fine powder and kneaded into rubber. At this time, if an internal mixer such as a Ni-Goo is used, the salt will stick to the inner wall of the mixer, and if an open roll is used, problems such as sticking to the roll surface and generation of dust will occur. In either case, the agglomerates are kneaded into the rubber due to the formation of agglomerates in the cross-wire and the peeling off of the adhering material on the wall of the mixer, which significantly impairs the value of the product.

Another method for introducing zinc salts into rubber is the so-called direct mixing method, in which an acid and a zinc compound are reacted in the rubber. In this method, a zinc compound for neutralization is kneaded into rubber in advance, and the mixture is put into an internal mixer such as a kneader or a Banbury mixer together with an acid, and the neutralization reaction is carried out while kneading. Also, at this time, the rubber mixed with acid and a zinc compound for neutralization are added and kneaded, or the rubber mixed with acid and the rubber mixed with a zinc compound for neutralization are mixed and neutralized. Reactions can also be carried out. According to this method, the appearance of the rubber dough is good, and there is almost no formation of agglomerates or adhesion to the mixer. However, this method generally requires a large excess of acid relative to the zinc compound in order to obtain a positive salt, particularly zinc dimethacrylate, which imparts favorable properties to the physical properties of the golf ball, and as a result, unreacted acid remains and Basic salts are also produced in large amounts,
Moreover, the produced normal salt also tends to change into a basic salt over time.

The present invention provides a method for producing stable Z-α,β-ethylenically unsaturated zinc carboxylic acid without the above-mentioned drawbacks by the above-mentioned direct mixing method.

That is, the present invention requires that when reacting an α,β-ethylenically unsaturated carboxylic acid with a zinc compound in a rubber composition, 1 to 25 parts by weight of calcium hydroxide is present per 100 parts by weight of the carboxylic acid. The present invention relates to a method for producing a rubber composition containing Z α,β-ethylenically unsaturated carboxylic acid zinc salt.

Examples of the α,β-ethylenically unsaturated carboxylic acid used in the present invention include methacrylic acid, acrylic acid, itaconic acid, and crotonic acid, but methacrylic acid is typically used.

Examples of the zinc compound that forms a salt with the above-mentioned carboxylic acid include zinc oxide, zinc hydroxide, and zinc oxide, particularly zinc oxide.

The blending ratio of α, β-ethylenically unsaturated carboxylic acid and zinc compound is 100 parts by weight of the former to 5 parts by weight of the latter in terms of zinc oxide.
The amount is 0 to 300 parts by weight, preferably 50 to 200 parts by weight.

In the present invention, when a small amount of calcium hydroxide is present when an acid and a zinc compound are reacted in a rubber, a zinc positive salt that is stable over time can be produced in the rubber without forming agglomerates.

The amount of calcium hydroxide used is 1 to 100 parts by weight of acid.
25 parts by weight, preferably 5 to 15 parts by weight. Other metal compounds, such as magnesium hydroxide, do not have sufficient effects as described above.

The reaction of the acid and zinc compound of the present invention is carried out in a suitable solid golf ball rubber composition. A particularly preferred rubber is polybutadiene, particularly one containing about 90% by weight or more of c i s -1,4 type polybutadiene. If desired, SBR, natural rubber, etc. may be blended therein. The rubber composition may also contain conventional fillers, pigments, and the like.

Although the reaction between a zinc compound and an α,β-ethylenically unsaturated carboxylic acid is not limited, for example, a zinc compound and calcium hydroxide are kneaded with a specified rubber composition using an open roll or an internal mixer, is added to the carboxylic acid previously placed in an internal mixer such as a kneader and kneaded. The temperature of this mixture is lower than the decomposition temperature of the radical initiator blended. Thereafter, the temperature is lowered and the radical initiator is added and mixed for an appropriate period of time.

To obtain a solid golf ball using this composition, it is cut into sections slightly larger and heavier than the ball and inserted into a standard ball cup mold. The composition in the mold is about 130
Cure at a temperature of ~160°C for typically 10-40 minutes. This results in a solid golf ball with a high coefficient of restitution.

The present invention will be explained below with reference to Examples.

Examples 1 to 10 Predetermined amounts of zinc oxide, calci hydroxide, and rum were uniformly kneaded into 100 parts by weight of Polybutadiene BR-01 manufactured by Nippon Synthetic Rubber Co., Ltd., and this was kneaded with methacrylic acid for about 10 minutes. The temperature gradually increases to about 80-90°C. The reactant was taken out and the amount of zinc dimethacrylate in the rubber was determined using X-ray diffraction method (the diffraction pattern of zinc dimethacrylate has characteristic peaks around diffraction angles of 2θ = 10° and 11°; Zinc methacrylate (basic salt) has a peak at 2θ = 7.4°. Zinc dimethacrylate is manufactured by Ware Chemical Company (W
are Chemical Co.) R-2R/A,
Zinc methacrylate is manufactured by Ste.
ETLEG Inc.) was used as a standard substance, it was mixed with polybutadiene, and a calibration curve was prepared from its X-ray diffraction pattern for quantification).

Table 1 shows the compounding ratio and the amount of zinc dimethacrylate produced in Rubber 10 (l).

Procedural amendment (spontaneous) 1. Indication of the case Process for manufacturing a rubber composition containing Patent Application No. 117273 of 1982 3. Person making the amendment Relationship with the case Patent applicant 4, Agent 111 = 5. Order for amendment Date (voluntary) 7. Contents of additions (1) Insert the following statement on a new line after line 7 on page 7 of the specification: ``Comparative Example 1 Polybutadiene BR-Q1100 manufactured by Nippon Synthetic Rubber Co., Ltd.'' 40 parts by weight of zinc oxide were uniformly kneaded, and this was kneaded with 30 parts by weight of methacrylic acid for about 10 minutes.The reactant was taken out and the amount of zinc dimethacrylate in the rubber was adjusted to be the same as in Fujo Example 1-10. When quantified, no formation was observed7).The results are shown in Table 1 along with the blending ratio.'' (2) Table 1 on page 8 of the same page is corrected as follows: (3)
Insert the following paper and table after Table-1 on page 8 of Ming Bao: "Examples 11 to 20 Comparative Example 2 Dicumyl in the amount shown in Table-2 to the ingredients in Table-1 The poles were manufactured by adding peroxide and mixing on a roll to prepare a rubber composition, placing it in a standard pole cup mold, and curing it at -150°C for 15 minutes.

Table 2 shows the physical properties of the ball.

Claims (1)

[Claims] When reacting an α,β-ethylenically unsaturated carboxylic acid with a zinc compound in a 1° rubber composition, the carboxylic acid 10
1. A method for producing a rubber composition containing Z α,β-ethylenically unsaturated carboxylic acid zinc salt, characterized in that calcium hydroxide is present in an amount of 1 to 25 parts by weight based on 0 parts by weight. 2. The method according to item 1, wherein the α,β-ethylenically unsaturated carboxylic acid is methacrylic acid. 3. The method according to item 1, wherein the zinc compound is zinc oxide.