JP2000042140A - Multi-piece solid golf ball - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multi-piece solid golf ball excellent in all of bouncing performance, flying performance, hitting sensation and durability. SOLUTION: In a multi-piece solid golf ball comprising a core formed of an inner layer core and a center layer core, and a coating layer for coating the core, the diameter of the inner layer core is 20-35 mm, the thickness of the outer layer core is 2-11 mm, Shore D hardness (A) and (B) of the surface of the inner layer core and outer layer core satisfy relational expressions of 15<=(A)<=5.0, 35<=(B)<=70, A<=(B), and the coating layer is formed of resin composition containing 50-90 pts.wt. of ionomer resin and 50-10 pts.wt. of diene rubber.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-piece solid golf ball, and more particularly, to a multi-piece solid golf ball excellent in all of resilience performance, flying performance, hit feeling and durability.

[0002]

2. Description of the Related Art Multi-piece solid golf balls are:
A golf ball with two or more layers of cores and covers. It is developed to improve the feel of hitting, which is a disadvantage of a two-piece solid golf ball, and to maintain or improve the resilience performance and flight performance, which are its advantages. ing. For example, Japanese Patent Application Laid-Open No. 60-241264 proposes a structure in which the core has two layers and the inner core and the outer core have a specific gravity difference. However, as compared with a two-piece solid golf ball, a good hit feeling can be obtained, but the resilience performance is inferior. Japanese Patent Application Laid-Open No. 2-278978 proposes a structure in which the core has two layers and the inner layer core and the outer layer core have a difference in hardness. However, since the hardness difference between the inner layer core and the outer layer core is large, breakage is likely to occur at the interface, and the durability is poor. Many multi-piece solid golf balls have been proposed in addition to the above examples, but none of them satisfy the hit feeling, rebound performance, flying performance and durability.

[0003]

SUMMARY OF THE INVENTION The present invention provides a rebound performance,
It is an object of the present invention to provide a multi-piece solid golf ball excellent in all of flight performance, hit feeling and durability.

[0004]

That is, the present invention relates to a multi-piece solid golf ball comprising a core comprising an inner core and an outer core and a coating layer covering the core, wherein the inner core has a diameter of 20 to 35 mm, The outer layer core has a thickness of 2 to 11 mm, and the surfaces of the inner layer core and the outer layer core have Shore D hardnesses (A) and (B) of 1
5 ≦ (A) ≦ 50, 35 ≦ (B) ≦ 70, (A) ≦
Provided is a multi-piece solid golf ball that satisfies the relational expression (B) and is composed of a resin composition in which the coating layer contains 50 to 90 parts by weight of an ionomer resin and 50 to 10 parts by weight of a diene rubber.

Here, the specific gravity (C) of the inner core and the specific gravity (D) of the outer core are 1.0 ≦ (C) ≦ 1.
5, 1.0 ≦ (D) ≦ 1.5, | (C) − (D) | ≦
It is desirable to satisfy the relational expression of 0.1.

It is desirable that the diene rubber is dispersed in the ionomer resin and is thermally crosslinked.

The surface of the coating layer has a Shore D hardness of 40
It is preferably from 70 to 70, and more preferably from 40 to 65.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.

The present invention relates to a multi-piece solid golf ball comprising a core comprising an inner core and an outer core and a coating layer covering the core, wherein the inner core has a diameter of 20 to 35 mm and the outer core has a thickness of 2 to 35 mm. ~ 11mm
And the Shore D hardness (A) and (B) of the surface of the inner layer core and the outer layer core are 15 ≦ (A) ≦ 50, 35
≤ (B) ≤ 70, (A) ≤ (B), wherein the coating layer comprises a resin composition containing 50 to 90 parts by weight of an ionomer resin and 50 to 10 parts by weight of a diene rubber. It is a solid golf ball.

[0010] The coating layer of the multi-piece solid golf ball of the present invention comprises a resin composition containing 50 to 90 parts by weight of an ionomer resin and 50 to 10 parts by weight of a diene rubber. When the coating layer contains the diene rubber, the durability is greatly improved, and the resilience performance, the flying performance, and the impact feel are improved as compared with the case where the ionomer resin is used alone.

The ionomer resin has an ethylene-unsaturated carboxylic acid 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, ethylene and an unsaturated carboxylic acid having 3 to 6 carbon atoms, for example, acrylic acid,
It is a copolymer with methacrylic acid, maleic acid, fumaric acid, and vinyl benzoate. Metal compounds capable of supplying cations include, for example, alkali metals, alkaline earth metals, formate such as transition metals, acetates, nitrates, carbonates, bicarbonates,
Oxides, hydroxides, alkoxides and the like. Metals are sodium, zinc, lithium, magnesium, manganese,
Calcium, cobalt, potassium and the like can be mentioned.

The ionomer resin has a Shore D hardness of 5
It is preferably from 5 to 80. As described later, since the Shore D hardness of the surface of the coating layer is preferably 40 to 70, the Shore D hardness of the ionomer resin is 80.
This is because, if it exceeds, it is difficult to adjust the hardness of the coating layer. When the Shore D hardness of the ionomer resin is 55 or more, the resilience of the coating layer becomes good.

Specific examples of the ionomer resin include a metal salt of a copolymer of ethylene and methacrylic acid. Commercially available ones include Himilan 1605 and Himilan 17 manufactured by DuPont-Mitsui Polychemicals.
06, High Milan 1707, High Milan AM7315,
Himilan AM7317, Himilan AM7318, Surlyn 7930, Surlyn 7940 manufactured by DuPont, or the like can be used.

The diene rubber used for the coating layer includes natural rubber, butadiene rubber, isoprene rubber, styrene-butadiene copolymer rubber, ethylene-propylene-diene copolymer rubber, acrylonitrile-butadiene copolymer rubber, and the like. Can be Preferred is a butadiene rubber, particularly preferably a butadiene rubber having at least 40% of cis-1,4 bonds. As an example, Nippon Synthetic Rubber Co., Ltd. B
R-01, BR-11, BR-18, ZEON CORPORATION
Nipol 1220 manufactured by Ube Industries, Ltd., UBEP manufactured by Ube Industries, Ltd.
OL BR-210, 150L, 360L and the like. The particle diameter of the diene rubber is preferably 0.1 to 5 μm or less. This is because the resilience, durability, and appearance of the coating layer become favorable.

The weight ratio of the ionomer resin to the diene rubber in the resin composition is 50/50 to 10/90. If the ratio of the ionomer resin is larger than the above range, the hit feeling becomes too hard. If the ratio of the diene rubber is larger than the above range, the resilience performance and the flight performance deteriorate.

The diene rubber is preferably dispersed in the ionomer resin and is preferably thermally crosslinked. The thermal crosslinking makes the resilience, durability and appearance of the coating layer suitable. Here, "appropriate appearance" means that the coating layer has no fluff and looks good. When a crosslinking agent is used instead of thermal crosslinking, there are the following problems. For example, according to the organic peroxide crosslinking, the ionomer resin is also crosslinked at the same time, so that the fluidity of the coating layer is reduced and molding becomes difficult. According to the sulfur crosslinking, the resin composition is colored yellow.

The Shore D hardness of the surface of the coating layer is 40 to
70, more preferably 40 to 65, and particularly preferably 55 to 65. This is because durability is good in the above range. Further, if the Shore D hardness exceeds 70, the hit feeling becomes hard, and if the Shore D hardness is less than 40, the flight performance may deteriorate.

The resin composition has a tan δ at 0 ° C. of 0.01
It is preferably about 0.07. This is because the resilience is improved. The tan δ at 0 ° C. is set to 0.01 to 0.07 by using, for example, an ionomer resin having high hardness and a diene rubber having a low glass transition point.

The resin composition may contain other rubbers, elastomers, fillers, pigments, processing aids, stabilizers and the like, if necessary, in addition to the above components.

The method for producing the resin composition is not particularly limited, but the ionomer resin and the uncrosslinked diene-based rubber may be used in combination.
What is necessary is just to knead at a temperature of 0 to 260 [deg.] C. to thermally crosslink the diene rubber and disperse it in the ionomer resin.
The kneading in this case is preferably performed by stirring at a shear rate of 1000 / sec or more in a mixer. By this stirring, the diene rubber is in a state of being well dispersed in the ionomer resin, and the dispersed diene rubber can have a fine particle size of 5 μm or less. , Durability and appearance are good.

The multi-piece solid golf ball of the present invention has a diameter of the inner layer core of 20 to 35 mm, a thickness of the outer layer core of 2 to 11 mm, and a Shore D hardness (A) and (A) of the surface of the inner layer core and the outer layer core. B) is 15 ≦ (A)
≤50, 35≤ (B) ≤70, and (A) ≤ (B). Here, the diameter of the inner core is 20 to 30 m.
m is preferable. Also, 20 ≦ (A) ≦ 45,
It is preferable to satisfy the relational expression of 50 ≦ (B) ≦ 65. Further, as a specific example of the most preferable combination of the values of (A) and (B), 20 ≦ (A) ≦ 30 and 50 <
(B) ≦ 70, and 30 ≦ (A) ≦ 4
5 and 35 ≦ (B) <60.
In the case of, it is particularly preferable that 1.8 ≦ (B) / (A) ≦ 3.0, and in the case of 1.0 ≦ (B) /
It is particularly preferred that (A) ≦ 1.8.

When the diameter of the inner layer core is less than 20 mm, the hit feeling becomes too hard, and when the diameter of the inner layer core exceeds 35 mm, the hit feeling becomes too soft and the durability deteriorates. When the diameter of the inner core is 20 to 30 mm,
This is because the resilience performance is not impaired while maintaining an appropriate hit feeling. If the thickness of the outer layer core is less than 2 mm, the resilience performance and the flight performance are poor, and if it is 4 mm or more, the resilience performance and the flight performance are excellent. When the thickness of the outer layer core exceeds 11 mm, the diameter of the multi-piece solid golf ball becomes too large.

When (A) ≦ (B), the resilience performance and the flying performance are good. When (A)> (B), the resilience performance,
The flight performance is poor, and the ball has a hard feel with a core.
If (A) <15, when (B) is large, destruction is likely to occur from the interface, and when (B) is small, the impact feel becomes too soft. (A) If> 50,
The impact feel is too hard. (B) If <35, the hit feeling becomes too soft. (B) If> 70,
When (A) is large, the hit feeling becomes too hard,
When (A) is small, destruction is likely to occur from the interface. When 20 ≦ (A) ≦ 45 and 50 ≦ (B) ≦ 65, the balance between resilience performance, flying performance, impact feel and durability is suitable. More specifically, 20 ≦ (A) ≦ 3
In the case of 0, if (B) ≦ 50, the hit feeling becomes slightly soft, and if (B)> 70, the hit feeling becomes slightly hard. In the case of 30 ≦ (A) ≦ 45, if (B) <35, the hit feeling becomes slightly soft, and if (B) ≧ 60, the hit feeling becomes slightly hard. In the above case, if (B) / (A) <1.8, the hit feeling becomes slightly soft, and (B) / (A)
> 3.0, the hit feeling becomes slightly hard,
The durability is also slightly worse. In the above case, (B)
If /(A)<1.0, the feel of impact is somewhat cored and hard, and if (B) / (A)> 1.8, the feel of impact is slightly hard.

The specific gravity (C) of the inner core and the specific gravity (D) of the outer core are 1.0 ≦ (C) ≦ 1.5, 1.0 ≦ (D)
It is preferable to satisfy the relational expressions of ≦ 1.5 and | (C) − (D) | ≦ 0.1. 1.0 ≦ (C) ≦ 1.3, 1.
It is more preferable to satisfy the relational expressions of 0 ≦ (D) ≦ 1.3 and | (C) − (D) | ≦ 0.05. This is because the resilience performance, the flight performance, and the feel at impact become better. By providing the specific gravity difference, the strain at the interface when hit is increased, and breakage is likely to occur. Therefore, it is preferable to satisfy the above relational expression.

The core composition for forming the core of the multi-piece solid golf ball of the present invention is not particularly limited, and comprises a base rubber, a cross-linking agent, a co-cross-linking agent, a filler and the like usually used for forming a core.

The base rubber is not particularly limited, and natural rubber and / or synthetic rubber can be used. However, butadiene rubber is preferable because the flying performance is further improved. % Butadiene rubber is particularly preferred.

As the crosslinking agent, an organic peroxide, sulfur or the like can be used. The organic peroxide is not particularly limited as long as it is generally used for rubber crosslinking, but dicumyl peroxide, di-tert-butyl peroxide, 1,3-bis (t-butylperoxyisopropyl) benzene,
4′-di (t-butylperoxy) n-butyl valerate,
2,5-dimethyl-2,5-di (t-butylperoxy) hexane and the like.

The co-crosslinking agent is not particularly limited, and examples thereof include metal salts of unsaturated carboxylic acids. It is preferable to use zinc acrylate and / or zinc methacrylate. The unsaturated carboxylic acid metal salt used here may be used alone, but may be mixed with about 10% of a fatty acid such as stearic acid for improving dispersibility. Further, the average particle size of the unsaturated carboxylic acid metal salt is more preferably 5.0 μm or less. Here, the “average particle size” refers to a particle size measured by a normal sedimentation particle size distribution measuring method. 5.0 μm
If the content is less than or equal to the above, the dispersibility in the base rubber during kneading is improved, and the flight performance is further improved.

Examples of the crosslinking aid include zinc oxide. Examples of the inert filler include barium sulfate and the like.

The core composition for forming the core of the multi-piece solid golf ball of the present invention comprises, in addition to the above components,
If necessary, additives such as an antioxidant, a processing aid, a plasticizer, and a softener may be contained.

The method for producing the multi-piece solid golf ball of the present invention is not particularly limited. Coaxially on the inner layer core obtained by press-molding the inner layer core composition, the outer layer core composition is press-fit molded to provide the outer layer core, and the resin composition serving as the cover is injection molded to form the core. A wrapping method or the like can be suitably used.

[0032]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. <Preparation of Multi-Piece Solid Golf Ball> Raw materials for the inner layer core shown below were kneaded at a weight ratio shown in Table 1 with a kneader and a roll.
The molded body was heated and pressed at 60 ° C. for 20 minutes to obtain a spherical solid core (inner core). The raw materials for the outer layer core shown below are kneaded in a weight ratio shown in Table 1 with a kneader and a roll, and the obtained rubber composition is concentrically pressed on the inner layer core to form a two-layer molding. I got a body. The two-layered molded body is
It was heated and pressed at 20 ° C. for 20 minutes to obtain a two-piece solid core. The coating layer raw materials shown below were kneaded at a weight ratio shown in Table 1 with a kneader and a roll, and the two-piece solid core was coated with the obtained resin composition by an injection molding method. Created a ball. (1) Raw material for inner core and raw material for outer core Butadiene rubber: 97% cis-1,4 bond, BR-0
1. Zinc white zinc acrylate manufactured by Japan Synthetic Rubber Co .: Average particle size 2.5 μm (measured by a natural / centrifugal sedimentation type automatic particle size distribution analyzer CAPA-300 (manufactured by Horiba, Ltd.)), acrylic acid having an average particle size of 5.3 μm Antioxidant: Swanox BHT, manufactured by Seiko Chemical Co., Ltd. (2) Raw material for coating layer Ionomer resin 1: Sodium ionic ethylene-methacrylic acid copolymer, Shore D hardness 67, H160
5. Ionomer resin 2: manufactured by Du Pont-Mitsui Polychemical Co., Ltd .: zinc ionic ethylene-methacrylic acid copolymer, Shore D hardness 66, H1706, butadiene rubber manufactured by DuPont-Mitsui Polychemical Co .: 97% cis-1,4 bond , BR-0
1. Nippon Synthetic Rubber Co., Ltd. Titanium oxide: Taipa CR-60, Ishihara Sangyo Co., Ltd.

The following tests were performed on the multi-piece solid golf balls obtained as described above. As a standard of the ball physical properties, Comparative Example 17 was selected as a representative of a soft-piece / hard-cover type multi-piece solid golf ball close to a conventional ball. <Rebound performance test> A multi-piece solid golf ball was hit with a swing robot to measure the initial velocity. Using a screwdriver (wood # 1), head speed 43m
/ S. Assuming that the initial speed of Comparative Example 17 is 100,
The relative value of each initial speed was shown. <Flying performance test> Hit a multi-piece solid golf ball with a swing robot and carry it (flying distance).
Was measured. Using a driver (Wood # 1), head speed was 43 m / s. With the carry of Comparative Example 17 being 100, the relative value of each carry was represented. <Hit feeling test> A professional golfer hit a ball with a driver (Wood # 1) and tested the hit feeling. <Durability test> For each example and comparative example, five multi-piece solid golf balls were hit with a swing robot to test durability. Using a driver (Wood # 1), head speed was 43 m / s. Insufficient durability when one of five balls cracked after hitting 100 times (x). Durable when no crack occurred for all five balls hit 150 times. Good durability (△), good durability (○) when 200 hits and no cracks occurred for all five balls. Here, "breaking" refers to a state in which the cover is cracked and cannot be used as a ball. <Others> In addition to the above tests, the diameter of the inner core, the thickness of the outer core, and the Shore D hardness of the inner core and the outer core were measured.

The results are shown in Table 1. As is clear from Table 1, the multi-piece solid golf balls of the present invention (Examples 1 to 9) have good resilience performance, flying performance, impact feel and durability. Also,
It can be seen that the impact feeling can be finely adjusted by changing the Shore D hardness of the inner core and the outer core within the range of the present invention. On the other hand, when the Shore D hardness of the inner layer core or the outer layer core is out of the range of the present invention as in Comparative Examples 1 to 16, there is a problem in the shot feeling or durability. As in Comparative Example 17 or 18, when the weight ratio of the ionomer resin to the diene rubber in the resin composition forming the coating layer is out of the range of the present invention, there is a problem in the hit feeling, or the resilience performance and the flight performance. . The composition was the same as that of Example 3 except that the ionomer resin 1 was used in the coating layer.
, 40 parts by weight of the ionomer resin 2,
20 parts by weight of the butadiene rubber and 1 part of the titanium oxide
A multi-piece solid golf ball using 1.8 parts by weight of an organic peroxide (dicumyl peroxide, Parkmill D, manufactured by NOF CORPORATION) and crosslinked with a peroxide has a rebound performance of 101 and flying The performance was 100, the impact feeling was good, and the durability was good, but discoloration was observed in the coating layer.
In other Examples 1 to 9 and Comparative Examples 1 to 18, no discoloration was observed in the coating layer.

[0035]

[Table 1]

[0036]

[Table 2]

[0037]

[Table 3]

[0038]

[Table 4]

[0039]

[Table 5]

[0040]

[Table 6]

[0041]

The multi-piece solid golf ball of the present invention is extremely useful because it has excellent resilience performance, flying performance, impact feel and durability.

Claims (4)

[Claims] 1. A multi-piece solid golf ball comprising a core comprising an inner core and an outer core and a coating layer covering the core, wherein the diameter of the inner core is from 20 to
35 mm, the thickness of the outer layer core is 2 to 11 mm, and the Shore D hardness (A) and (B) of the surface of the inner layer core and the outer layer core are 15 ≦ (A) ≦ 50, 35 ≦
(B) ≦ 70, (A) ≦ (B)
A multi-piece solid golf ball comprising a resin composition in which the coating layer contains 50 to 90 parts by weight of an ionomer resin and 50 to 10 parts by weight of a diene rubber. 2. The specific gravity (C) of the inner core and the specific gravity (D) of the outer core are 1.0 ≦ (C) ≦ 1.5, 1.0
2. The multi-piece solid golf ball according to claim 1, wherein a relational expression of ≦ (D) ≦ 1.5 and | (C) − (D) | ≦ 0.1 is satisfied. 3. The multi-piece solid golf ball according to claim 1, wherein the diene rubber is dispersed in the ionomer resin and is thermally crosslinked. 4. The surface of the coating layer has a Shore D hardness of 40.
The multi-piece solid golf ball according to any one of claims 1 to 3, wherein