JP3401411B2 - Solid golf ball - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid golf ball having excellent flight performance, and excellent controllability and shot feeling. [0002] In the prior art, there are mainly two types of golf balls. One is a solid golf ball such as a solid two-piece ball, and is composed of a core made of an integrally molded rubber member and a thermoplastic resin cover such as an ionomer resin coated on the core. The other is a thread-wound golf ball, in which a solid or liquid core at the center is wound with a rubber thread winding,
It is covered with a cover of a 2 mm thick ionomer resin or balata. A solid golf ball has a longer flight distance and is superior in flight characteristics due to a higher durability and a higher ball speed at the time of hitting as compared with a thread-wound golf ball, and is used by many golfers, especially amateur golfers. On the other hand, solid golf balls have a low hitting feel, a high ball speed at the time of hitting, and a small spin due to a small contact area with the hitting surface of the golf club. There was a problem of lack of controllability. Therefore, solid golf balls
Professional golfers and advanced golfers who value the shot feeling and controllability tend to shy away. [0003] In order to solve this problem, attempts have been made to improve the controllability and shot feeling by softening the cover of a solid golf ball by using various means. However, when the cover is softened, rebound is reduced, and the launch angle is low when shot with a driver or a long iron, and the spin rate is increased. . SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems of the conventional solid golf ball, has excellent flight performance, and has excellent controllability and shot feeling. It is an object to provide a solid golf ball having the same. [0005] The present inventors have conducted intensive studies to achieve the above object, and as a result, softened the cover.
By reducing the rebound by reducing the thickness of the cover, reducing the difference between the surface hardness of the core and the hardness of the cover,
The inventor has found that controllability and shot feeling can be improved without impairing flight performance, and the present invention has been completed. That is, the present invention provides a solid golf ball comprising a core and a cover formed on the core, wherein the cover has a thickness of 1.0 to 2.1 mm and a JIS-C hardness of 75.
~ 95, and flexural rigidity of 800 ~ 1,800kgf /
has cm ^2, and the core is obtained from a rubber composition containing a metal salt 30-40 parts by weight of an unsaturated carboxylic acid based on cis-1,4-polybutadiene rubber 100 parts by weight,
The hardness of the core increases substantially linearly from the center to the surface, and the difference in hardness between the center and the surface is 15 or more in JIS-C hardness, and the core has an initial load of 10 kgf to a final load of 130 kg.
The amount of deformation when f is loaded is 2.3 to 3.2 mm,
And the difference between the surface hardness of the core and the hardness of the cover is JIS-
A solid golf ball having a C hardness of 10 or less. Hereinafter, the present invention will be described in more detail. In the solid golf ball of the present invention, a cover layer is formed on a core. The core is obtained by heating, pressing and molding a rubber composition containing cis-1,4-polybutadiene rubber as a base rubber, a metal salt of an unsaturated carboxylic acid, a crosslinking agent, an inert filler and the like. Can be In the present invention, the base rubber is cis-1,4-
Polybutadiene rubber is used. The cis-1,4-polybutadiene rubber has a high cis-1,4-structure having at least 40% or more, preferably at least 80% or more.
1,4-polybutadiene rubber is preferred, and if desired, natural rubber, polyisoprene rubber, styrene polybutadiene rubber, ethylene-propylene-diene rubber (EPDM) and the like may be blended. Examples of metal salts of unsaturated carboxylic acids acting as co-crosslinking agents include, in particular, zinc, magnesium, etc., of α, β-unsaturated carboxylic acids having 3 to 8 carbon atoms, such as acrylic acid or methacrylic acid. Examples thereof include monovalent or divalent metal salts such as salts, and zinc acrylate which imparts high repulsion is preferable. The compounding amount is cis-1,4-polybutadiene rubber 1
The amount is preferably 30 to 40 parts by weight with respect to 00 parts by weight. If the amount is more than 40 parts by weight, the ball becomes too hard and the shot feeling becomes poor. [0010] Crosslinking agents include organic peroxides such as dicumyl peroxide or t-butyl peroxide, with dicumyl peroxide being preferred. The amount is based on 100 parts by weight of cis-1,4-polybutadiene rubber.
It is preferably from 0.3 to 5.0 parts by weight. If the amount is less than 0.3 parts by weight, the ball becomes too soft and rebound is deteriorated, resulting in a reduced flight distance. If the amount exceeds 5.0 parts by weight, the ball becomes too hard and the shot feeling becomes poor. As the inert filler, zinc oxide, barium sulfate, calcium carbonate and the like may be used alone or in combination. The compounding amount depends on the size or specific gravity of the core or the cover and is not particularly limited, but is usually preferably 5 to 50 parts by weight based on 100 parts by weight of the cis-1,4-polybutadiene rubber. If it is less than 5 parts by weight, the core becomes too light,
If it exceeds 50 parts by weight, it becomes too heavy. The rubber composition of the core of the present invention may contain an antioxidant, a peptizer and the like other than the above components. Further, the core of the present invention may be a single layer or may be composed of two or more layers. In the present invention, it is desirable that the hardness of the core increases substantially linearly from the center to the surface, and that the hardness difference between the center and the surface is 15 or more in JIS-C hardness. If it is smaller than 15, the shot feeling will be too hard, and the ball will blow up when shot with a driver or long iron, and the flight distance will be reduced. The surface hardness of the core is JIS-C hardness, preferably 75 to 95, more preferably 80 to 92. In the present invention, the amount of deformation of the core when the initial load of 10 kgf is applied to the final load of 130 kgf is preferably 2.3 to 3.2 mm. If it is smaller than 2.3 mm, the ball becomes too hard and the shot feeling becomes poor, and if it exceeds 3.2 mm, it is too soft and rebound is poor and the flight distance is reduced. Next, a cover layer having a hardness such that the hardness difference from the surface hardness of the core is 10 or less in JIS-C hardness is coated on the core. If it is smaller than 10, the hardness difference between the core and the cover is small, so that an appropriate deformation can be obtained when hitting the ball, the shot feeling is improved, and the appropriate launch angle (11.3 to 12.8
°), spin (2,200-2,900 rpm). The cover can be formed of an ionomer resin commonly used as a cover material for a solid golf ball, and a small amount of another resin may be added. The above-mentioned cover composition may contain an additive such as titanium dioxide for coloring, and other additives such as an ultraviolet absorber, a light stabilizer, a fluorescent material or a fluorescent brightener, and the like. Although it may be contained within a range that does not impair the desired properties of the ball cover, usually, the amount of the coloring agent is preferably 0.1 to 0.5 part by weight based on 100 parts by weight of the cover resin. The cover layer of the present invention is formed by a generally known method used for forming a cover of a golf ball, for example, injection molding, press molding or the like. In the present invention, it is desirable that the cover has a thickness of 1.0 to 2.1 mm, preferably 1.2 to 1.9 mm and a JIS-C hardness of 75 to 95, preferably 80 to 92. Cover thickness is 1.0
If it is smaller, the effect of the cover is weakened, and if it exceeds 2.1 mm, the effect of the core does not appear. If the JIS-C hardness is less than 75, the ball is too soft and rebound is poor, and the flight distance is reduced. If it exceeds 95, the ball becomes too hard and controllability or shot feeling is deteriorated. The cover has a flexural rigidity of 800 to 1,800 kgf / cm ²
It is desirable that If it is less than 800 kgf / cm ² , the ball becomes too soft, resulting in a reduced flight distance and poor shot feeling. 1,80
If it exceeds 0 kgf / cm ² , controllability will be poor and the shot feeling will be too hard. The golf ball cover of the present invention has a JIS-C hardness of 75 to 95, which is smaller than the conventional ionomer resin cover having a JIS-C hardness of about 100. If the cover is soft, the rebound is reduced, so the cover thickness should be 1.0-2.1mm (conventionally about 2.0-2.3m
By reducing the thickness to m), the reduction in repulsion is suppressed, and the feeling is improved. The difference between the cover hardness and the core surface hardness was conventionally 15 or more (core surface hardness 70 to 85). In the present invention, by increasing the surface hardness of the core, making the cover thinner and softer, and reducing the hardness difference to 10 or less, the feeling becomes better, the initial flight conditions are improved, and high flight performance is achieved. When the core is covered with the cover, usually, many depressions called dimples are formed on the surface. This dimple is composed of multiple types, the number of dimples is 330 to 450
Preferably, the number is Outside of this range, good trajectory will not be obtained, and the flight distance will not be achieved. The golf ball of the present invention is usually coated with paint and put on the market in order to enhance aesthetic appearance and commercial value. In the present invention, without impairing flight performance,
A golf ball having excellent controllability and shot feeling is provided. The present invention will be described in more detail with reference to examples.
However, the present invention is not limited to these examples. Preparation of Core A spherical solid core was prepared by kneading the core components shown in Table 1 and then subjecting them to heat compression molding. The diameter, deformation and hardness of the obtained solid core were measured, and the results are shown in Table 1. The test method was performed as described below. Table 1 Example of core preparation (parts by weight) Type I II III IV V VI BR-18 (Note 1) 100 100 100 100 100 100 Zinc acrylate 34 34 34 34 25 34 Zinc white 18 16 14 16 20 9 Yoshinox 425 (Note 2) 0.5 0.5 0.5 0.5 0.5 0.5 Shikimyl peroxide 1.2 1.2 1.2 1.2 1.2 1.4 156 ° C 156 ° C 156 ° C 140 ° C 156 ° C 156 ° C × 20 minutes × 20 minutes × 20 minutes × 40 minutes × 20 minutes × 20 minutes Press conditions ＋ ＋ ＋＋＋ 170 ℃ 170 ℃ 170 ℃ 170 ℃ 170 ℃ × 8 minutes × 8 minutes × 8 minutes × 8 minutes × 8 minutes Core diameter (mm) 38.2 39.0 39.6 39.0 39.0 40.2 cores Deformation (mm) 2.4 2.6 2.8 2.2 3.5 2.7 Center 65 65 65 79 65 65 A 5 mm from center 75 75 74 79 73 70 Hard 10 mm from center 78 79 80 79 76 79 degrees 15 mm from center 84 86 85 79 80 86 Surface 88 88 90 70 78 91 Examples 1-4, Comparative Examples 1-5 Cover Layers Covers cores I-V obtained as described above were coated with a cover composition having the composition shown in Table 2 by injection molding. To form a cover layer Then, paint painting was performed to produce a solid golf ball. [Table 2] Table 2 Example of preparation of cover (parts by weight) Type A B C D Himilan 1605 (Note 3) 5 25 50 Himilan 1706 (Note 4) 25 50 Himilan 1555 (Note 5) 5 10 Himilan 1855 (Note 6) 95 85 50 Titanium dioxide 2 2 2 2 Hardness (JIS-C) 83 87 97-(Note 7) (Shore D) (56) (59) (66) (69) Flexural rigidity (kgf / cm ² ) 1000 1300
2500 3500 [0027] (Note 1) Japan Synthetic Rubber Co., Ltd. high cis-1,4
Polybutadiene (Note 2) Anti-aging agent manufactured by Yoshitomi Pharmaceutical Co., Ltd. (Note 3) Na ion-neutralized ethylene / methacrylic acid copolymer ionomer resin manufactured by Mitsui Dupont Polychemical Co., Ltd. (Note 4) Mitsui Dupont Polychemical Co., Ltd. Zn ion neutralized ethylene / methacrylic acid copolymer ionomer resin (Note 5) Mitsui Dupont Polychemical Co., Ltd. Na ion neutralized ethylene / methacrylic acid copolymer ionomer resin (Note) 6) Measuring not possible because the ionomer resin of Zn-neutralized ethylene / methacrylic acid / isobutyl acrylate terpolymer resin (manufactured by Mitsui DuPont Polychemicals Co., Ltd.) is 100 or more (Note 7). Type Hardness Flexural rigidity JIS C * Shore D ** (kgf / cm ² ) *** Himilan 1605 97 67 3,700 Himilan 1706 96 66 3,300 Himilan 1555 91 62 2,500 Himilan 1855 83 56 900 * JIS K 6301 ** ASTM D-2240 *** ASTM D-709A Each golf ball obtained was evaluated for flight performance, controllability, and feel at impact by a driver (Wood No. 1 club). The results are shown in Table 3. The test method was performed as follows. (Test method) Launch angle, spin amount and flight distance A driver was attached to a swing robot manufactured by True Temper, and the golf ball was hit at a head speed of 45 m / sec.
The launch angle (ballistic height) is measured, the distance to the drop point (carry) is measured as the flight distance, and the shot amount of the golf ball is continuously photographed to obtain the spin amount. Controllability and hitting feel Controllability is evaluated by using a sand wedge by 10 top professionals, and hitting feeling is evaluated by actually hitting with a driver. The evaluation criteria are as follows. Evaluation Criteria 1 ... 10 to 8 persons answered that they were good. Δ: 7 to 4 persons answered that they were good. ×: Three or less persons answered that it was good. (Test Results) Table 3 Example 3 Comparative Example 1 2 3 4 1 2 3 4 4 5 Cores Formula II II III VI I IV VII II Cover Formulation ABBBBBBBCD Ball Diameter (mm) 42.7 42.7 42.7 42.7 42.7 42.7 42.7 42.7 42.7 Ball weight (g) 45.4 45.4 45.4 45.4 45.4 45.4 45.4 45.4 45.4 Flight performance W # 1 Launch angle (°) 11.8 12.0 12.3 12.5 11.2 11.0 11.8 12.4 12.5 Spin amount (rpm) 2700 2600 2500 2400 3000 3100 2500 2300 1900 distance (yards) 254 255 256 257 250 251 248 255 255 40 Yato Bu control of Yes Yes Yes Yes Yes Yes Yes × × shot feeling Yes Yes Yes Yes Yes × △ × × [0030] From the above results, Examples 1-4 of the present invention
Indicates that the golf ball is excellent in flight distance with a driver, controllability on a 40-yard shot, and shot feeling. According to the solid golf ball of the present invention, the cover is softened, and the thickness of the cover is reduced so that the rebound is suppressed. The difference between the surface hardness of the core and the hardness of the cover is reduced. It has improved performance, controllability, and shot feeling.

Claims (1)

(57) Claims 1. A solid golf ball comprising a core and a cover formed on the core, wherein the cover has a thickness of 1.0 to 2.1 mm and a JIS-C hardness of 7
5 to 95, and flexural rigidity of 800 to 1,800 kgf
/ cm ² and the core is obtained from a rubber composition containing 30 to 40 parts by weight of a metal salt of an unsaturated carboxylic acid per 100 parts by weight of cis-1,4-polybutadiene rubber, the hardness of the core being Substantially increases linearly from the center to the surface, the difference in hardness between the center and the surface is 15 or more in JIS-C hardness, and the amount of deformation when an initial load of 10 kgf to a final load of 130 kgf is applied to the core is 2. A solid golf ball having a thickness of 3 to 3.2 mm and a difference between the surface hardness of the core and the hardness of the cover of 10 or less in JIS-C hardness.