JPH11169485A - Solid golf ball - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solid golf ball having a good mold releasing property without impairing the excellent flying performance and durability intrinsic to the solid golf ball. SOLUTION: The core of the solid golf ball consisting of a core and a cover covering this core contains base material rubber and a metal salt of α,β- ethylenic unsatd. carboxylic acid as essential components and contains 0.1 to 20 pts.wt. polyethylene glycol per 100 pts.wt. base material rubber. The base material rubber is preferably a high cis-polybutadiene rubber having >=80% cis-1,4-bonds.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid golf ball having excellent mold release properties without impairing the excellent flight performance and durability inherent to a solid golf ball.

[0002]

2. Description of the Related Art Generally, golf balls include thread wound golf balls and solid golf balls. Solid golf balls consist of a core and a cover that covers it. The core may be composed of one or two or more layers, but basically comprises a rubbery component, and is usually composed of α, β- such as high cis polybutadiene, zinc acrylate or zinc methacrylate.
It is obtained by vulcanizing and molding a rubber composition containing a metal salt of an ethylenically unsaturated carboxylic acid, a peroxide crosslinking agent and other additives. The metal salt of α, β-ethylenically unsaturated carboxylic acid acts as a co-crosslinking agent. In addition to oxygen cross-linking of rubber molecules with a peroxide, the metal salt of α, β-ethylenically unsaturated carboxylic acid is separated between rubber molecules. Cross-linking increases the resilience performance and improves the feel when hitting.

However, when press molding or injection molding is carried out using a rubber composition containing the above-mentioned metal salt of α, β-ethylenically unsaturated carboxylic acid, the mold releasability of the molded product is extremely poor, and the fluororesin type There is a problem that a large amount of an external release agent such as a release agent or a silicone-based release agent must be used. Furthermore, when such a release agent is used, the release agent often exists on the surface of the molded product, and the remaining release agent reduces the adhesiveness between the core and the cover. The release agent must be removed by operation. Further, when the release agent remains in the concave portion, it is very difficult to remove the release agent.

Conventionally, to solve this problem, (a)
Methods such as applying a mold release treatment to the mold surface and (b) kneading an internal mold release agent into rubber have been studied.

As for (a), chromium nitride, titanium nitride, titanium aluminum nitride, diamond carbon and the like have been studied, but none of them has a poor repetitive durability and no satisfactory effect. Furthermore, the above-mentioned special release treatment is excellent because there is no adhesion of the release agent to the molded product, but at the same time, the special release treatment itself is a complicated operation, and the treatment is extremely difficult. It has the disadvantage of being expensive.

As for (b), an anionic surfactant containing a sulfur element or a phosphorus element (Japanese Patent Application Laid-Open No. 9-137000) and a metal salt of a higher fatty acid having 6 or more carbon atoms (Japanese Patent Application Laid-Open No. 4-298546) are used. Although it has been studied, although it has a certain effect, it results in deteriorating the performance as a golf ball.

[0007]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems of the conventional solid golf ball, has a good mold release property, and has excellent flight performance and hitting performance. An object of the present invention is to provide a solid golf ball having a feeling.

[0008]

Means for Solving the Problems The present inventors have conducted intensive studies to achieve the above object, and as a result, by adding a specific amount of polyethylene glycol to the core as an internal mold release agent, a good mold release was achieved. It has been found that a solid golf ball having a shape can be obtained, and the present invention has been completed.

That is, the present invention provides a solid golf ball comprising a core and a cover for covering the core, wherein the core comprises as a main component a base rubber and a metal salt of an α, β-ethylenically unsaturated carboxylic acid. The present invention relates to a solid golf ball containing 0.1 to 20 parts by weight of polyethylene glycol based on 100 parts by weight of a base rubber.

Hereinafter, the present invention will be described in more detail. In the golf ball of the present invention, a cover is formed on a core. The core used in the present invention is basically a base rubber, a crosslinking agent,
A rubber composition containing a metal salt of an α, β-ethylenically unsaturated carboxylic acid, polyethylene glycol, a filler, and an antioxidant, if necessary, is kneaded using an appropriate kneader such as a normal roll. 140-170 ° C, 90-120k in specified mold
It is obtained by heating and pressing at gf / cm ² for 10 to 40 minutes, and may have a multilayer structure of two or more layers.

As the base rubber used for the core of the present invention, natural rubber, synthetic rubber or a mixture thereof, which has been conventionally used for solid golf balls, is used.
Examples of the synthetic rubber include polybutadiene rubber, polyisoprene rubber, styrene polybutadiene rubber, and ethylene-propylene-diene rubber (EPDM). In particular, a so-called high cis polybutadiene rubber having at least 40% or more, preferably 80% or more of cis-1,4-bonds is preferable. Further, in the present invention, it is desirable that the polybutadiene rubber accounts for 80% by weight or more of the base rubber in view of the resilience performance of the obtained golf ball.

[0012] Crosslinking agents include organic peroxides such as dicumyl peroxide, 1,1-bis (t-butylperoxy) -3,
3,5-trimethylcyclohexane, 2,5-dimethyl-2,5-di
(t-butylperoxy) hexane, t-butyl peroxide, and the like, with dicumyl peroxide being preferred. The compounding amount is 0.5 to 5.0 parts by weight based on 100 parts by weight of the base rubber. If the amount is less than 0.5 parts by weight, it becomes too soft, the rebound becomes worse, and the flight distance decreases. If it exceeds 5.0 parts by weight, it will be too hard, and the feel when hitting will be poor.

The metal salt of an α, β-ethylenically unsaturated carboxylic acid acts as a co-crosslinking agent, and particularly, an α, β-ethylenically unsaturated carboxylic acid having 3 to 8 carbon atoms such as acrylic acid or methacrylic acid. And monovalent or divalent metal salts such as zinc and magnesium salts, but zinc acrylate which imparts high resilience is preferred. The amount is 15 to 50 parts by weight, preferably 20 to 35 parts by weight, based on 100 parts by weight of the base rubber. If it exceeds 50 parts by weight, it will be too hard and the feel at impact will be poor. If it is less than 15 parts by weight, rebound will be poor and the flight distance will be reduced.

The filler may be any one which is usually compounded in the core of a golf ball, and includes, for example, an inorganic salt (specifically,
Zinc oxide, barium sulfate, calcium carbonate), high specific gravity metal powder (for example, tungsten powder, molybdenum powder, etc.) and mixtures thereof. The compounding amount depends on the specific gravity and the size of the cover and the core and is not limited, but is 10 to 100 parts by weight, preferably 10 to 40 parts by weight based on 100 parts by weight of the base rubber. If the amount is less than 10 parts by weight, the core becomes too light and the ball becomes too light. If it exceeds 100 parts by weight, the core becomes too heavy and the ball becomes too heavy.

The rubber composition used for producing the core of the solid golf ball of the present invention contains polyethylene glycol in addition to the above. Polyethylene glycol is a polymer of ethylene glycol or a polymer of ethylene oxide and is a compound having a hydroxyl group at both terminals, and the polyethylene glycol used in the present invention has a molecular weight of 200 to 500,000, preferably 1,000 to 70,00.
Those having 0 are desirable in terms of mold release properties of the core. If the molecular weight of the polyethylene glycol is smaller than 200, excessive bleeding occurs and the vulcanization property of the surface is reduced, resulting in 500,00
If it exceeds 0, the kneadability deteriorates. Specific examples of the polyethylene glycol include PEG200 and PEG6000 commercially available from Lion Corporation and those commercially available as reagents from Wako Pure Chemical Industries, Ltd. The compounding amount is base rubber 10
0.1 to 20 parts by weight, preferably 0.5 to 10 parts by weight, based on 0 parts by weight
Parts by weight. If the amount is less than 0.1 part by weight, satisfactory mold release properties cannot be obtained. If the amount exceeds 20 parts by weight, the properties of the obtained golf ball deteriorate. By blending 0.1 to 20 parts by weight of the above polyethylene glycol into the rubber composition for the core, moderate bleeding occurs on the surface of the molded article during vulcanization, and good mold releasability is exhibited.

Further, the core of the golf ball of the present invention may appropriately contain an antioxidant or a peptizer, and other components which can be generally used for producing a center of a solid golf ball. The antioxidant is preferably used in an amount of 0.1 to 3.0 parts by weight based on 100 parts by weight of the base rubber.

In the present invention, the core is covered with a cover. The cover may have not only a single-layer structure but also a multi-layer structure having two or more layers. In this case, the cover material is a thermoplastic resin, especially α. -Olefin and α, β with 3-8 carbon atoms
-An ionomer resin, polyester, nylon, or the like in which a part of the carboxylic acid in the copolymer of unsaturated carboxylic acid is neutralized with metal ions, or a mixture thereof is used. As the α-olefin in the ionomer resin, ethylene and propylene are preferable, and as the α, β-unsaturated carboxylic acid, acrylic acid, methacrylic acid and the like are preferable. Further, the metal ions to be neutralized include alkali metal ions such as Na ion, K ion and Li ion; divalent metal ions such as Zn ion, Ca ion and Mg ion; and trivalent metal ions such as Al ion. And mixtures thereof, including Na ion, Zn ion, L
i-ions and the like are often used because of their resilience and durability. Specific examples of the ionomer resin include, but are not limited to, Surlyn AD8541, AD8542 (manufactured by DuPont), Himilan 1557, 1605, 1652, 1705, 1706, 1707, 1855,
1856 (manufactured by Mitsui DuPont Polychemicals), IOTEC 7010, 80
00 (manufactured by Exxon) and the like.

In the present invention, in addition to the above-mentioned resin as a main component, the above-mentioned cover composition may optionally contain
Fillers such as barium sulfate and coloring agents such as titanium dioxide,
Other additives, such as dispersants, antioxidants, ultraviolet absorbers, light stabilizers and fluorescent materials or fluorescent brighteners,
Although it may be contained within a range that does not impair the desired properties of the golf ball cover, usually, the compounding amount of the coloring agent is preferably 0.1 to 5.0 parts by weight based on 100 parts by weight of the resin for the cover.

The cover layer of the present invention can be formed by using a generally known method used for forming a cover of a golf ball, and is not particularly limited. The cover composition is preliminarily formed into a hemispherical shell half shell, and the two cores are used to wrap the core and pressure-molded at 130 to 170 ° C. for 1 to 15 minutes, or the cover composition is directly cored. A method of wrapping the core by injection molding may be used. The thickness of the cover is 0.5 to 5.0 mm, preferably 1.0 to 4.0 mm. 0.
If it is smaller than 5 mm, the overall hardness of the ball is reduced and the coefficient of restitution is reduced. If it is larger than 5.0 mm, the overall hardness of the ball is increased and controllability and feeling at impact are deteriorated.

In molding the cover, a large number of depressions called dimples are formed on the surface as necessary. The golf ball of the present invention is usually put on the market after being subjected to a paint finish, a marking stamp, or the like, in order to enhance aesthetic appearance and commercial value.

[0021]

EXAMPLES The present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

(Examples 1 to 6 and Comparative Examples 1 and 2) Preparation of core A rubber composition for a core having the composition shown in Table 1 below was kneaded.
A core having a diameter of 38.4 mm was obtained by hot pressing in a mold at 150 ° C. for 20 minutes. The releasability of the obtained core from the mold at the time of molding was evaluated, and the results are shown in Table 3. The test method was performed as described below.

Formation of Cover A cover composition having the composition shown in Table 2 below was mixed with a twin-screw kneading extruder to obtain a pellet-shaped cover composition. Extrusion conditions were: screw diameter 45 mm, screw rotation speed 200 rpm, screw L / D = 35,
The formulation was heated to 220-260C at the die. On the core obtained as described above, the cover composition prepared as described above was coated by injection molding to form a cover layer, and then painted, to give a solid golf ball having a diameter of 42.7 mm. Obtained. The flight distance and durability of the obtained golf ball were measured or evaluated, and the results are shown in Table 3. The test method was performed as described below.

[0024]

[Table 1] Core blending example Comparative example 1 2 3 4 5 6 12 2 BR01 (Note 1) 100 60 100 60 100 100 100 90 IR2200 (Note 2)-40-40----10 Zinc acrylate 30 30 30 30 30 30 30 30 Zinc oxide 10 10 10 10 10 10 10 10 Barium sulfate 10 10 10 10 10 10 10 10 10 Dicumyl peroxide 2 2 2 2 2 2 2 2 Polyethylene glycol Molecular weight 200 (Note 3) 5 − − − − − − − Molecular weight 6000 (Note 4) − 55 − − − − − − Molecular weight 20000 (Note 5) − − − 5 − − − − Molecular weight 70000 (Note 6) − − − − 5 − − − Molecular weight 500000 (Note) 7) − − − − − − 5 − − Dodecylbenzene sulfonic acid − − − − − − − 5 − Sodium stearate − − − − − − − − 5 (Note 1) High cis polybutadiene rubber manufactured by Nippon Synthetic Rubber Co., Ltd. (Note 2) High cis polyisoprene rubber manufactured by Nippon Synthetic Rubber Co., Ltd. (Note 3) Made by Lion Corporation Polyethylene glycol, trade name PEG200 (Note 4) Polyethylene glycol, trade name PEG6000 (Lion Co., Ltd.) (Note 5) Reagent from Wako Pure Chemical Co., Ltd. (Note 6) Reagent from Wako Pure Chemical Co., Ltd. (Note 7) Reagent manufactured by Wako Pure Chemical Industries, Ltd.

[0025]

[Table 2] Cover compounding type Parts by weight Himilan 1605 50 Himilan 1706 50 Titanium dioxide 2

(Test Method) Releasability After core molding, releasability from a mold was evaluated using the following evaluation criteria. The evaluation was performed using 2,000 samples (n =). Evaluation criteria ◎: Very good release, easy to remove by hand 〇: Good release, easy to remove ×: Poor release, core breaks inside Flying distance True swing temper manufactured by True Temper A wood No. 1 club (driver) was attached, a golf ball was hit at a head speed of 45 m / sec, and the distance to the drop point (carry) was measured as the flight distance. Durability A golf ball was hit against a metal plate at a speed of 45 m / sec.

(Test results)

[Table 3] Test item Example Comparative example 1 2 3 4 5 6 1 2 Releasability 〇 ◎ ◎ ◎ 〇 〇 × × Carry (yard) 235 229 235 230 235 234 234 200 200 Durability 100 95 100 105 95 100 66 70

From the above results, the golf balls of Examples 1 to 6 of the present invention in which polyethylene glycol was used for the core were compared with Comparative Example 1 in which polyethylene glycol was not used for the core.
It can be seen that the distance and durability are excellent and the mold releasability is good as compared with Nos.

On the other hand, in Comparative Examples 1 and 2, dodecylbenzenesulfonic acid and sodium stearate were used for the core, respectively, and polyethylene glycol was not used. It can be seen that the durability has also been reduced.

[0030]

As described above, the solid golf ball of the present invention has good mold release properties while maintaining excellent flight performance and durability by using polyethylene glycol for the core.

Claims (3)

[Claims] 1. A solid golf ball comprising a core and a cover covering the core, wherein the core contains a base rubber and a metal salt of an α, β-ethylenically unsaturated carboxylic acid as main components, and A solid golf ball comprising 0.1 to 20 parts by weight of polyethylene glycol based on 100 parts by weight of a base rubber. 2. The solid golf ball according to claim 1, wherein said base rubber contains at least 80% by weight of a polybutadiene rubber having at least 80% of cis-1,4-bonds. 3. The polyethylene glycol having a molecular weight of 20
The solid golf ball of claim 1 having a value of 0 to 500,000.