JPH0448473B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a solid golf ball, and particularly to a solid golf ball whose flight distance is improved by changing the structure of the golf ball's server. (Background of the Invention) High-grade solid golf balls for rounds include multilayer solid golf balls and two-piece solid golf balls, both of which are covered with a cover to protect the core. The core of this solid golf ball is usually manufactured by vulcanizing and molding polybutadiene, which is highly repellent, using a metal salt of an unsaturated fatty acid as a co-crosslinking agent. Covers are typically made from ionomer resin with a small amount of white filler added to increase the specific gravity.
It is adjusted to about 0.92 to 1.2 and coated onto the core. On the other hand, golf balls have a weight standard (45.91 g or less), but the weight is generally adjusted to around the maximum value of the weight standard in order to increase flight distance. Therefore, a large amount of filler (eg, zinc oxide, barium sulfate, etc.) is added to the core rubber composition as a weight regulator. However, the addition of such a large amount of weight modifier does not take advantage of the inherent repulsion performance of butadiene rubber, reducing the flight distance of the golf ball. Furthermore, as the specific gravity of the core increases, the moment of inertia decreases, spin is more likely to occur, the spin decays faster during flight, and flight distance becomes shorter. JP-A-60-53164 discloses that by increasing the specific gravity of the cover by adding high specific gravity materials (iron powder, metal oxides, etc.) to the cover, the rebound resilience of the core is increased and flight performance is improved. It is proposed that. However, the addition of high specific gravity materials to the entire cover, especially the addition of heavy metals or their salts (which usually have a blackish color), can result in coloring the cover, even if the cover is painted. It shows off its own appearance and is not suitable for practical use. Furthermore, in order to increase the specific gravity of the cover, a large amount of additives must be added, which tends to reduce the durability of the cover against impact from the club, which poses a practical problem. The present invention was made with the aim of developing a golf ball that does not have the above-mentioned drawbacks. (Structure of the Invention) That is, the present invention provides a solid golf ball consisting of a core and a cover covering the core, wherein the cover has two layers, an outer layer and an inner layer, and the outer layer and the inner layer have the following characteristics. :

Provided is a solid golf ball characterized by having the following: The present invention will be explained with reference to the drawings. Outer cover layer 1 of the solid golf ball of the present invention
is prepared in exactly the same way as conventionally used covers. Cover materials that can be used include various ionomer resins. Preferred ionomer resins include monoolefins and carbon atoms from 3 to 8.
at least one polymer selected from the group consisting of unsaturated mono- or dicarboxylic acids and their esters (containing 4 to 30% by weight of unsaturated mono- or dicarboxylic acids and/or their esters)
It is a thermoplastic resin with cross-metallic bonds added to it. Examples of such resins include various "Himilan" commercially available from Mitsui Polychemical Co., Ltd., for example,
1554, 1555, 1601, 1605, 1650, 1652, 1702,
1557, 1706, 1707, 1855, 1856 are listed. The material used for the outer layer of the cover is preferably one that is hard and has a high elastic modulus, making it difficult for the ball to spin when hit. For example, Shore D hardness 5
8-72, preferably 60-66, flexural modulus 280-
500MPa is preferable. Among the resins mentioned above, Himilan is an example of one having such characteristics.
Examples include 1605, 1706, 1707, and mixtures of these and other Himilan resins. The inner cover layer 2 is manufactured using substantially the same resin as the outer cover layer 1, but the specific gravity is adjusted to 1.2 or more, preferably 1.4 to 2.5. A high specific gravity filler is added to adjust the specific gravity. Examples of high specific gravity fillers (preferably specific gravity 10 to 20) include metal powders, metal oxides, metal nitrides, metal carbides, and the like. for example,
Tungsten (black, specific gravity: 19.3), tungsten carbide (blackish brown, specific gravity: 15.8), molybdenum (gray, specific gravity: 10.2), lead (gray, specific gravity: 11.3),
Lead oxide (dark gray, specific gravity: 9.3), nickel (silver gray, specific gravity: 8.9) and copper (reddish brown, specific gravity: 8.9)
Or a mixture thereof is exemplified. It is preferable to use the above-mentioned high specific gravity filler, but barium sulfate, titanium dioxide, or zinc white, which have a relatively low specific gravity, may also be used. In this case, in order to increase the specific gravity of the cover inner layer, the resin:filler weight ratio is 1:0.8~
Add about 1:1.5. Since the cover inner layer 2 is not directly subjected to force from the club when hit, it does not need to be particularly hard and have a high modulus of elasticity, and may be made of a material such as a conventionally used balata. In addition to the above ingredients, other additives may be added to both cover layers. Other additive amounts include, for example, white pigments and coloring agents such as titanium dioxide, anti-aging agents,
Lubricants, dispersants, stabilizers, ultraviolet absorbers, and the like are appropriately selected and used. In particular, when preparing a composition for a balata cover, sulfur, a vulcanization accelerator, and the like are used in addition to the above-mentioned amounts to be added to the cover. The preparation of the cover composition and the method for coating the core of the cover can be carried out by conventional means. For example, the preparation of the cover composition is carried out by uniformly mixing the cover main material, high specific gravity filler, if necessary, and desired cover ingredients using a roll, mixer, extruder, etc., and then coating the core. This is carried out by injection molding or compression molding. The thickness of both cover layers 1 and 2 is between 0.5 and 2 mm. The two cover layers must have a sufficient thickness as the cover of a solid golf ball, and the inner cover layer 2 must have a resin composition and thickness sufficient to mix the necessary amount of heavy metal filler. The weight of the core 3 in the solid golf ball is increased by adding the high specific gravity filler in the cover inner layer 2, so that the amount of filler that has been added to adjust the weight can be reduced. The components of the solid core include a base rubber, a crosslinking agent, a co-crosslinking agent, an inert filler, and the like. As the base rubber, 1,4-polybutadiene having at least 40% cis structure is particularly preferred, and if desired, natural rubber, natural rubber,
Polyisoprene rubber, styrene-butadiene rubber, etc. may be blended as appropriate. Dicumyl peroxide and t-
Examples include organic peroxides such as butyl peroxide and azo compounds such as azobisisobutylnitrile, but particularly preferred is dicumyl peroxide. The amount of the crosslinking agent blended is usually 0.5 to 3.0 parts by weight, preferably 1.0 to 2.5 parts by weight, based on 100 parts by weight of the base rubber. The co-crosslinking agent is not particularly limited, but metal salts of unsaturated resin acids, especially those having 3 carbon atoms, may be used.
Examples include zinc salts and magnesium salts of unsaturated fatty acids (for example, acrylic acid, methacrylic acid, etc.) of 8 to 8, but zinc acrylate (normal salt) is particularly suitable, and the amount to be blended is 100 parts by weight of the base rubber. 30 to 38 parts by weight, preferably 32 to 36 parts by weight. Although the addition of inert fillers to the core can be reduced as described above, they may also have the function of promoting rubber crosslinking, so it is preferable to add a small amount of zinc oxide or the like. Core 3 of the Solitz golf ball is prepared in the usual way,
For example, it can be obtained by kneading using a roll or kneader, compression molding in a mold, and crosslinking. Since the amount of filler added to adjust the weight has been reduced, the weight of Core 3 is usually 25 to 35 g for a small ball, and 25 to 35 g for a large ball.
Usually 30 to 35 g is preferred. (Effects of the Invention) According to the present invention, the addition of an inert filler to the core is reduced, and the inherent repellency of butadiene is fully exhibited.
Flight distance increases. In addition, the weight of the center of the solid golf ball has been reduced and the weight of the outer portion has increased, increasing the moment of inertia of the ball.
The initial spin when hitting the ball is reduced, the spin attenuation during flight is controlled, and flight distance is increased.
In particular, if a hard resin is used for the outer layer of the cover, the initial spin will be further reduced and the flight distance will be increased. Also,
The inner layer is made of a layer with a large amount of filler and poor durability, and the inner layer is covered with a layer with a small amount of filler and good durability as an outer layer, so the durability of the entire cover is high enough for practical use. (Example) Examples 1 to 5 and Comparative Examples 1 to 4 Core Preparation The rubber composition shown in Table 1 was vulcanized in a mold at 160°C for 25 minutes to produce a solid core with an outer diameter of 36.8 mm. In preparing the composition, the weight of the core was adjusted so that the total weight of the golf ball obtained was approximately 45.4 g. The blended parts of the compositions in Table 1 are based on parts by weight for both the cover and the core. Preparation of Cover Inner Layer The ionomers listed in Table 1 were melted and kneaded using a roll, and a predetermined amount of a high specific gravity filler was added thereto and mixed. After mixing, extrude into a sheet,
After storage at 150° C., a half shell for a ball was produced by a compression molding method and coated on the core. Next, a core coating was produced by heating at 155° C. for 2.5 minutes using a compression molding method. Preparation of outer cover layer and ball A pellet for the outer cover layer was prepared by extrusion molding using the formulation shown in Table 1, and this was coated on the core coating using the injection molding method to form a two-piece golf ball with a diameter of 41.2 mm. I got it. The physical properties of the obtained golf ball were measured and the results are shown in Table 2.

【table】

【table】

【table】 [Brief explanation of the drawing]

FIG. 1 is a sectional view of the solid golf ball of the present invention, in which 1: outer cover layer, 2: inner cover layer, and 3: core are shown.

Claims (1)

[Scope of Claims] 1. A solid golf ball consisting of a core and a cover covering the core, wherein the cover has two layers, an outer layer and an inner layer, and the outer layer and the inner layer have the following characteristics: ] A solid golf ball characterized by having the following. 2. The solid golf ball according to item 1, wherein the cover inner layer contains a high specific gravity filler. 3. The solid golf ball according to item 2, wherein the high specific gravity filler has a specific gravity of 10 to 20.