JP2949432B2 - Solid golf ball - Google Patents

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 excellent in resilience (flying performance), spin performance, and feel at impact.

[0002]

2. Description of the Related Art Solid golf balls include two-piece golf balls in which a core is covered with a cover, and golf balls having a multilayer structure of three or more layers in which an appropriate intermediate layer is provided between the core and the cover. A solid golf ball is formed by covering a core made of a rubber composition with a cover material such as an ionomer resin (ionic ethylene copolymer resin) having excellent impact resistance and resilience. In particular, two-piece golf balls are used by many golfers because of their long flight distance and excellent durability. However, compared to thread-wound golf balls, there is a problem that the feel at the time of hitting is hard, so that the hit feeling is inferior and the spin performance is poor.

Conventionally, in order to obtain the same spin performance and hitting feel as a thread-wound golf ball, a solid golf ball using a soft core and a soft cover, a difference in hardness between the core and the ball, a cover hardness and a cover thickness have been reduced. A defined solid golf ball has been proposed (JP-A-6-3198).
No. 30, etc.). However, these golf balls are excellent in spin performance and hit feeling, but insufficient in resilience.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a solid golf ball which is excellent in flight performance (rebound), and excellent in hit feeling and spin performance.

[0005]

According to the present invention, there is provided a golf ball having a core covered with a cover, wherein the ratio of the compression value of the golf ball to the compression value of the core is 1.2 or more and less than 1.5. The cover has a Shore D hardness of 62 or less. Since the compression value and the hardness of the cover are thus determined, the above object can be achieved. Here, the compression value of the golf ball is defined as 2.54 for the golf ball.
Refers to the compressive strength (kgf) when deformed by mm (1/10 inch). In addition, the compression value of the core is defined as 2.
Compressive strength when deformed 54mm (1/10 inch) (kgf)
Say.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, the ratio of the compression value of a golf ball to the compression value of a core is 1.
2 or more and less than 1.5. If it is less than 1.2, the resilience of the golf ball will be poor, while if it is more than 1.5, the golf ball will be too hard and the shot feeling will deteriorate.

The cover of the golf ball has a Shore D hardness of 62 or less, preferably a Shore D hardness of 45.
~ 62. If the Shore D hardness exceeds 62, the cover becomes too hard and the spin performance deteriorates. This cover is composed of 50 to 90 parts by weight of an ionomer resin having a Shore D hardness of 55 or more and less than 80 and 10 to 50 parts by weight of a diene rubber.
It is preferable that the composition be composed of a composition dispersed with a particle diameter of not more than m.

The ionomer resin has an ethylene-unsaturated carboxylic acid-based copolymer as a base resin,
For example, it can be obtained from an ethylene-unsaturated carboxylic acid copolymer and a metal compound capable of supplying a cation. Ethylene-
The unsaturated carboxylic acid-based copolymer is, for example, a copolymer of ethylene and an unsaturated carboxylic acid having 3 to 6 carbon atoms, such as acrylic acid, methacrylic acid, maleic acid, fumaric acid, or vinyl benzoate. .

Metal compounds capable of supplying cations include, for example, formate, acetate, nitrate, carbonate, bicarbonate, oxide, hydroxide of alkali metals, alkaline earth metals, transition metals and the like. Alkoxide and the like. Examples of the type of metal include Na, Zn, Li, Mg, Mn, Ca, Co, and K. This ionomer resin has a Shore D hardness of 55 or more and less than 80 (55 ≦ Shore D hardness <80). Shore D
The reason for setting the hardness to 55 or more is that the higher the hardness of the ionomer resin, the higher the rebound resilience. If the Shore D hardness is 80 or more, even if a diene rubber is mixed, the effect is not obtained, and the shot feeling of the obtained golf ball becomes too hard.

As the ionomer resin, for example,
A metal salt of a copolymer of ethylene and methacrylic acid is exemplified. This ionomer resin may be a commercially available one, for example, Himilan 1605, Himilan 1706, and Himilan 17 manufactured by Mitsui DuPont Polychemicals.
07, High Milan AM7315, High Milan AM731
7, Himilan AM7318, Surlyn 7930 and Surlyn 7940 manufactured by DuPont.

As the diene rubber, for example, butadiene rubber, natural rubber, isoprene rubber, ethylene-propylene-diene rubber, acrylonitrile-butadiene rubber, styrene-butadiene rubber and the like may be used. Of these, it is preferable to use butadiene rubber. A commercial product may be used as the butadiene rubber.
It is preferable to use one having a 1,4 structure of 40% or more.

The above-mentioned composition constituting the cover comprises 50 to 90 parts by weight of the ionomer resin and 10 parts of the diene rubber 10
-50 parts by weight. If the amount of the ionomer resin is less than 50 parts by weight, the hardness of the cover decreases and the shot feeling becomes too soft. On the other hand, if it exceeds 90 parts by weight, the softening by the diene rubber becomes insufficient and the shot feeling is too hard. I will.

In this composition, the diene rubber is dispersed in the ionomer resin with a particle diameter of 5 μm or less. The particle size is preferably from 0.1 μm to 5 μm
It is good. This is because by making the particle diameter as small as 5 μm or less, resilience, durability and appearance are improved.
In this composition, the diene rubber is preferably thermally crosslinked. Here, thermal crosslinking means that the uncrosslinked diene rubber is crosslinked only by heat without using a crosslinking agent (crosslinking is performed only by heating). If the diene rubber is not crosslinked, the resilience, durability and appearance of the cover deteriorate. Here, the deterioration of the appearance means that the cover is fluffed and the appearance is deteriorated.

When the diene rubber is cross-linked by using an organic peroxide as a cross-linking agent, the ionomer resin is also cross-linked at the same time. Therefore, the fluidity of the cover material composition comprising the ionomer resin and the diene rubber is significantly reduced, and Impossible. Further, when the crosslinking is carried out with a sulfur-based vulcanizing agent, there is a problem that the cover material composition is colored yellow and the commercial value is reduced. On the other hand, such a problem does not occur when crosslinking is performed only by heat without using a crosslinking agent. In particular, when cross-linking is performed only with heat, as compared with the case where cross-linking is performed with a sulfur-based vulcanizing agent, resilience is improved.

In order to produce the above-mentioned composition constituting the cover, the ratio of the viscosity of the ionomer resin at the melting temperature of the ionomer resin to the viscosity of the diene rubber at the same temperature (diene rubber / ionomer resin) is 1 / 1 to 5/1 ionomer resin and diene rubber at an ionomer resin melting temperature (130 ° C. to 260 ° C.).
It is advisable to mix the diene rubber in a ratio of 10 to 50 parts by weight to 90 to 90 parts by weight. Thereby, the diene rubber can be dispersed in the ionomer resin with a particle size of 5 μm or less.

If the ratio of the viscosities is greater than 5/1, the viscosity difference between the ionomer resin and the diene-based rubber increases, and no shearing force is applied during mixing, so that the diene-based rubber is not finely dispersed. On the other hand, when the viscosity ratio is smaller than 1/1, the viscosity of the ionomer resin becomes larger than that of the diene rubber, so that the ionomer resin has a structure in which the ionomer resin is finely dispersed in the diene rubber.
The mixing is preferably performed at a shear rate of 1000 / sec or more. If the shear rate is less than 1000 / sec, the diene rubber cannot have a particle size of 5 μm or less. As a mixer used for this mixing, it is preferable to use a twin-screw extruder.

[0017]

EXAMPLE A spherical solid core having a diameter of 38.3 mm was prepared using the core material shown in Table 4, and a cover having a thickness of 2.5 mm was put on the solid core using the cover material shown in Table 3. Thereby, the cover hardness shown in Table 1 and Table 2,
Two-layer golf balls having a two-layer structure having a compression ratio were manufactured (Examples 1 to 6, Comparative Examples 1 to 4).
The physical properties of these golf balls are shown in Tables 1 and 2 below.

[0018]

[Table 1]

[0019]

[Table 2]

[0020]

[Table 3]

[0021]

[Table 4] Note) * 1 A 2 mm thick injection-molded resin plate is 20 ° C at 23 ° C.
After curing for three days, three resin plates were stacked and measured at 23 ° C. using a Shore D hardness meter. * 2 Compressive strength (kgf) when the core is deformed by 2.54 mm (1/10 inch).

* 3 2.54 mm (1/10 inch) ball
Compressive strength when deformed (kgf). * 4 Ratio of ball compression value / core compression value. * 5 Driver (Wood #) using swing robot
Comparative Example 1 is the ratio of the initial speed of the golf ball to the head speed when hit at a head speed of 43 m / sec in 1).
Is a relative value when 100 is assumed. * 6 The backspin amount (rpm) when hit with a pitching wedge at a head speed of 33 m / sec.
Relative value assuming 00. * 7 The feel of a professional golfer hitting with a driver (wood club # 1). * 8 Mitsui DuPont Polychemical Co., Ltd., sodium ionic ethylene-methacrylic acid copolymer, Shore D
Hardness 67. * 9 Mitsui-Dupont Polychemical Co., Ltd., zinc ion ethylene-methacrylic acid copolymer, Shore D hardness 6
6. * 10 Mitsui DuPont Polychemical Co., Ltd., ethylene-ethyl acrylate copolymer sodium ion saponified resin,
Shore D hardness 28. * 11 Core-shell polymer (containing epoxy group) manufactured by Takeda Pharmaceutical Co., Ltd. * 12 Sodium ion ethylene-methacrylic acid-methacrylic acid ester copolymer, manufactured by DuPont, with a Shore D hardness of 47. * 13 Nippon Zeon, polybutadiene rubber, 1,4-cis structure 97%, Mooney viscosity 43. * 14 Polybutadiene rubber, 97% 1,4-cis structure, Mooney viscosity 42, manufactured by Nippon Synthetic Rubber Co., Ltd. * 15 Zinc diacrylate. * 16 Dicumyl peroxide. * 17 Irganox 1010.

As is clear from Tables 1 and 2, the golf balls of Examples 1 to 6 of the present invention have a better hit feeling compared to Comparative Examples 1 to 3 corresponding to conventional two-piece golf balls. Excellent resilience (flying performance) and spin performance. In Comparative Example 4, where the cover hardness was too high and the value (D / C) obtained by dividing the ball compression value by the core compression value was too large, the spin feeling was poor, although the hit feeling was good and the resilience was good.

[0024]

As described above, according to the present invention, in a golf ball having a core covered with a cover, the ratio of the compression value of the golf ball to the compression value of the core is 1.2 to less than 1.5. In addition, since the cover has a Shore D hardness of 62 or less, it is possible to provide a solid golf ball which is excellent in flight performance (repulsion), excellent in hit feeling, and excellent in spin performance. For example, driver shots are excellent in resilience, and iron shots are easy to apply back spin, and the hit feeling is good.

Claims (4)

(57) [Claims] 1. A golf ball having a core covered with a cover, wherein the ratio of the compression value of the golf ball to the compression value of the core is 1.2 or more and less than 1.5, and the hardness of the cover is Shore D hardness of 62. A solid golf ball that is: 2. The method according to claim 1, wherein the cover comprises 50 to 90 parts by weight of an ionomer resin having a Shore D hardness of 55 or more and less than 80 and 10 to 50 parts by weight of a diene rubber. 2. The solid golf ball according to claim 1, comprising a composition dispersed in the above. 3. The solid golf ball according to claim 1, wherein the diene rubber is thermally crosslinked without using a crosslinking agent. 4. The solid golf ball according to claim 1, wherein said diene rubber is butadiene rubber.