JP2003000757A - Solid golf ball - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a golf ball that gives a good feeling of hitting. SOLUTION: The solid golf ball is made from a solid core and a cover. The solid core has a multilayer structure having an inner core and an outer core. The principal material of the inner core is an ionomer, of 3 to 20 mm in a diameter, and 0.9 to 1.5 in a specific gravity. The diameter and the specific gravity satisfy G>=0.014×a+0.929 (G is the specific gravity of the inner core, and a is the diameter of the inner core) and the Shore D hardness of the inner core is 40 to 95, and 10 or more higher than the Shore D hardness of the outer core. The principal material the outer layer core is a thermoplastic resin, and the outer layer core is made of a 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 having improved feeling and hitting sound.

[0002]

2. Description of the Related Art In recent years,
In order to improve the performance of golf balls, various multi-piece type golf balls such as three-piece and four-piece golf balls have been proposed.

In order to maintain the resilience of the golf ball itself, these golf balls use a rubber base material for the innermost core, and the diameter thereof is about 30 mm. Therefore, when hit, the innermost core made of rubber greatly affects the ball performance, and the ball generally intended for high head speed players has a hard feeling, while The ball, which is said to be intended for low head speed players, would be too soft and could be improved.

That is, from a player of a general level to an advanced player and a professional golfer, the ball having the softest inner core is soft, and the ball having the hardest inner core is hard.

Further, regarding the hitting sound which is an important element of the golf ball, the contribution of the innermost core is large, and a ball having a softest innermost core has a dull sound, and a hard ball has a high sound.

The present invention has been made in view of the above circumstances.
An object of the present invention is to provide a solid golf ball having a good feeling and giving a comfortable hitting sound.

[0007]

Means for Solving the Problems and Embodiments of the Invention In order to achieve the above object, the present invention provides the following solid golf ball. Claim 1: A solid golf ball comprising a solid core covered with a cover, the solid core having a multilayer structure having an innermost core and an outer core covering the innermost core. Is mainly made of resin and has a diameter of
mm, the specific gravity is 0.9 to 1.5, and the diameter and the specific gravity are the following formula G ≧ 0.014 × a + 0.929 (wherein G is the specific gravity of the innermost core, and a is the innermost core). Diameter (mm)
Indicates. ), The surface shore D hardness of the innermost core is 40
~ 95 and Shore D of the innermost layer of the outer core
The hardness is 10 or more greater than the hardness, and the innermost layer of the outer core is mainly composed of a thermoplastic resin, and the outer layer of the outer core is formed with a rubber composition covering the thermoplastic resin as a main material. A solid golf ball. Claim 2: The solid golf ball according to claim 1, wherein the amount of deflection of the solid core under a load of 100 kg is 2.2 to 4.3 mm.

That is, as a result of various studies in view of the above-mentioned object, the present inventor divides the solid core into an innermost core and an outer layer core and optimizes them to change the feel when hit. It was found that the tapping sound can be improved.
More specifically, in the present invention, the innermost core having a size of 3 to 20 mm, which is smaller than the usual innermost core, is used. By making it small like this, it does not adversely affect the resilience of the ball itself,
It has been found that especially when it undergoes a large deformation, it produces an unprecedented sound and feeling. Also, for the innermost core, a material mainly made of rubber is usually used to maintain its resilience, but the rubber material has a limit of hardness, and if it is formed with a small diameter, the productivity decreases. Therefore, a resin-based material is used. By using resin balls, the resilience of itself is inferior to that of ordinary rubber materials, but the diameter of the innermost core is 3 to
By setting the thickness to 20 mm, the reduction in the resilience of the ball itself becomes very small. In this case, this effect depends on the diameter of the innermost core. The larger the diameter, the greater the degree of reduction in resilience, so make sure to satisfy the relationship of G ≧ 0.014 × a + 0.929 (G is the specific gravity of the innermost core, and a is the diameter (mm) of the innermost core). The innermost core with a larger diameter has a higher specific gravity. In a commonly used material, if a filler is added to increase the specific gravity, the resilience of the material decreases. That is, by forming the innermost core having a larger diameter with a higher specific gravity, the specific gravity of the outer layer core covering the innermost core can be reduced, the resilience can be compensated, the diameter of the innermost core can be reduced, and By optimizing the specific gravity according to the size, even if the resin core is used, the performance of the ball itself is not deteriorated.

Further, the Shore D hardness of the innermost core is 40 to 95.
By setting the inner core layer of the outer layer core to be 10 or more softer than the innermost core, a structure with a hard and small core at the center of the soft core will give a soft but corey feeling. It gives a moderately high sound.

Further, the hardness of the ball itself can be optimized by setting the amount of deflection of the solid core under a load of 100 kg within the range of 2.2 to 4.3 mm.

As described above, by having a small and hard resin core inside, a feeling that has never been obtained is obtained, and the sound when hit is not too low, and a comfortable sound is obtained.

The present invention will be described in more detail below. The solid golf ball of the present invention comprises a solid core 1 and a cover 2 for covering the solid core 1, as shown in FIG. The core 1 is formed to have a structure including an innermost core 3 and an outer layer core 4 that covers the innermost core 3 on the surface thereof, and a cover is formed around the inner core 3. In FIG. 1, the solid core 1 has two layers,
Although the covers 2 are each formed in a single layer, the outer core layer 4 can be formed in a multi-layer structure of two or more layers if necessary, and the cover can be formed in a two-layer, three-layer structure or the like.

Here, the innermost core 3 constituting the solid core 1 is made of a resin as a main material, not formed by using a rubber composition like a conventional golf ball.

Examples of the resin that can be used for the innermost core include known thermoplastic resins and thermoplastic elastomers. Specifically, nylon, polyarylate, ionomer resins, polypropylene resins, polyurethane thermoplastic elastomers, etc. , Polyester-based thermoplastic elastomers, etc., and commercially available Surlyn AD
8512 (Ionomer resin manufactured by DuPont), Himilan 1706, 1707 (Ionomer resin manufactured by Mitsui DuPont), Rilsan BMNO (Nylon resin manufactured by Toray), U Polymer U-8000 (polyarylate resin manufactured by Unitika), etc. are preferably used. Can be used.

Furthermore, in the above resin material, if desired,
Inorganic fillers such as barium sulfate, titanium dioxide and zinc oxide can be added as a weight adjusting agent, and the weight of the innermost core can be increased by adding a large amount of such a filler. By increasing the ratio of the rubber component of the outer core, the resilience of the golf ball can be dramatically improved. In addition, when a high specific gravity filler is used, the degree of eccentricity of the innermost core can be easily confirmed by X-ray inspection, which is preferable in production. In this case, the blending amount of the weight adjusting agent is 0 to 11 relative to 100 parts by weight of the resin.
It can be 5 parts by weight, especially 5 to 100 parts by weight.

The innermost core formed of the above resin as a main material has a diameter of 3 to 20 mm, preferably 5 to 18 m.
m, more preferably 8 to 15 mm. If it is too small, the effect is not exhibited, and if it is too large, the resilience may be affected.

The specific gravity of the innermost core is 0.9 to 1.5, particularly 1.0 to 1.45, and the following formula G ≧ 0.014 × a + 0.929 (wherein G is Specific gravity of innermost core, a is diameter of innermost core (mm)
Indicates. ) Is satisfied.

The surface hardness of the innermost core is 40 to 95, preferably 43 to 90, and more preferably 4 in Shore D hardness.
5 to 87. If the hardness is too small, it is too soft,
Feeling and tapping cannot be improved.

The innermost core can be obtained by injection molding the innermost core material containing the above resin as a main material.

Next, the outer layer core 4 surrounding the innermost core
Can have a multi-layer structure of two or more layers, but the Shore D hardness of the innermost core is made higher than the Shore D hardness of the innermost layer (layer covering the innermost core). Therefore, it is necessary that the Shore D hardness of the innermost core is 10 or more, preferably 12 or more, more preferably 15 or more higher than the Shore D hardness of the innermost layer of the outer layer core. If this difference is less than 10, sufficient improvement in tapping sound and feeling cannot be obtained. When the innermost layer of the outer layer core is made of a rubber material or the like and has a hardness distribution, the innermost core is required to have a Shore D of 10 or more higher than all the portions (that is, higher than the highest hardness portion). Is.

As described above, the outer layer core has the hardness difference from the innermost core as described above. However, from the viewpoint of the adhesiveness between the innermost core and the outer layer core, the innermost core is made of a thermoplastic resin. An outer layer core structure of two or more layers is formed by covering the core and further covering the core to provide a core outer layer formed of a rubber composition.

As the thermoplastic resin forming the outer layer core, an ionomer resin, a polyurethane-based thermoplastic elastomer, a polyester-based thermoplastic elastomer, or the like can be used as in the case of the innermost core.

On the other hand, the rubber composition preferably uses polybutadiene as the base material. Suitable examples of the polybutadiene include 1,4-cis polybutadiene having a cis structure of at least 40%. If desired, natural rubber, polyisoprene rubber, styrene-butadiene rubber, etc. may be added to the polybutadiene in the base rubber. By increasing the rubber component, the resilience of the golf ball can be improved. It should be noted that it is preferable to add 10 parts by weight or less of these components to 100 parts by weight of polybutadiene.

Further, the above rubber composition may contain, as a crosslinking agent, a zinc salt of an unsaturated fatty acid such as zinc methacrylate and zinc acrylate, an ester compound such as a magnesium salt or trimethylpropane methacrylate, but it is particularly repellent. Because of its high height, zinc acrylate can be preferably used. The compounding amount of these cross-linking agents is 1 with respect to 100 parts by weight of the base rubber.
It is preferably 0 to 30 parts by weight.

In the present invention, the rubber composition for the outer core usually contains a vulcanizing agent, and the temperature at which the half-life is reached in 1 minute is 155 ° C. or less in this vulcanizing agent. It is recommended that peroxide is contained, and the blending amount thereof is preferably 30% by weight or more, particularly 40 to 70% by weight based on the entire vulcanizing agent. Examples of such peroxides include commercially available products, and examples thereof include Perhexa 3M (manufactured by NOF Corporation). The compounding amount thereof may be 0.6 to 2 parts by weight with respect to 100 parts by weight of the base rubber.

If necessary, zinc oxide, barium sulfate, or the like can be added to the rubber composition as an antioxidant or a filler for adjusting the specific gravity. The content of the specific gravity adjusting agent is 1 to 30 parts by weight with respect to 100 parts by weight of the base rubber.

The solid core formed by coating the innermost core with the outer layer core preferably has an outer diameter of 36 to 41.5 mm. Further, in this case, as described above, when the outer core is formed of the resin or the mixture of the resin and the rubber on the inner side and the rubber composition on the outer side, the thickness of the core inner layer is 0.5. ~ 5.0 mm, especially 1.0-4.0 mm, core outer layer thickness is 4-17 mm, especially 6-15 m
It is preferably m.

The specific gravity of the outer layer core is not particularly limited, but is 0.90 in a layer containing a resin as a main material.
1.30, preferably 0.95 to 1.25, and 1.00 to 1.30, preferably 1.05 to 1.25 in the rubber-based layer.

The amount of deflection of the solid core under a load of 100 kg is 2.2 to 4.3 mm, more preferably 2.4 to 4.1 mm, and further preferably 2.5 to 4.0.
It is preferably mm. If it is less than 2.2 mm, the feeling may be too hard, and if it is more than 4.3 mm, it may be too soft and the performance as a ball may be deteriorated.

In the production of a solid core, the rubber composition can be produced by vulcanizing and curing by a known method. First, primary vulcanization (semi-vulcanization) is performed to form a pair of hemispherical cup bodies. Then, the vulcanization step is carried out in which the innermost core prepared in advance is placed on one hemispherical cup body and the other hemispherical cup body is covered with the secondary vulcanization (total vulcanization). A method divided into two stages can be suitably adopted, and a method of producing a solid core simultaneously with the formation of the outer layer core can be suitably adopted. A vulcanization step is required to mold the outer layer core, and the innermost core is exposed to high temperatures. Therefore, the melting point of the innermost core is preferably 150 ° C. or higher. Further, in the case of a resin or a mixture of resin and rubber, it can be manufactured by injection molding.

In this case, the innermost core placed in the hemispherical cup body can be coated with an adhesive in advance before the placement, and the interface between the innermost core and the outer layer core is firmly bonded with the adhesive. It is possible to further improve the durability of the golf ball and obtain high resilience. Further, it is recommended to roughen the surface of the innermost core with a barrel grinder or the like to form fine irregularities on the surface so as to improve the adhesion between the innermost core and the outer layer core.

The golf ball of the present invention comprises the above-mentioned solid core 1 and a cover 2 formed thereon, and can be formed by using a known cover material.
It is preferably 3.5 mm, particularly preferably 1 to 2.5 mm. The Shore D hardness is 40 to 75, more preferably 45 to 70, and further preferably 50 to 65. If the hardness is low, the ball rebound may be low, and if it is high, the durability may be poor. Its specific gravity is recommended to be 0.95-1.25. As described above, the cover may have a multi-layer structure.

Here, as the cover material, known cover materials may be used, and examples thereof include ionomer resins, balata rubber, thermoplastic elastomers such as polyurethane, polyamide, and polyester. Ordinary injection molding can be suitably used for forming the cover.

The solid golf ball formed as described above has a deformation amount of 2.2 to 3 when a load of 100 kg is applied.
It is recommended to be 8 mm, especially 2.4-3.5 mm.

Further, the golf ball of the present invention forms a large number of dimples on the cover surface in the same manner as a normal golf ball, but the total number of dimples is 350 to 500,
Preferably 370 to 480, more preferably 390 to
450 pieces, or, as its geometrical arrangement, an octahedron,
The icosahedron and the like are not limited to circular dimple patterns, and any square type, hexagon type, pentagon type, triangle type or the like may be used.

Further, the dimple diameter, dimple depth, and dimple cross-sectional shape can be optimized for the purpose of improving flight distance. Dimple surface occupation rate [(total dimple surface area /
Ball surface area) × 100] is 65% or more, preferably 7
The dimples can be provided so as to be 0 to 80%. If the dimple surface occupancy rate is less than 65%, it may not be possible to increase the flight distance. The dimple volume ratio [(total dimple volume / ball volume) × 100] is 0.
It can be set to 76 to 1.0%, preferably 0.78 to 0.94%. If the dimple volume ratio is less than 0.76%, the trajectory may be too high, and if it is more than 1.0%, the trajectory may be too low to reduce the flight distance.

The golf ball of the present invention can be formed to have a diameter and a weight of 42.67 mm or more and a weight of 45.93 g or less in accordance with the golf rules.

[0038]

The golf ball of the present invention is excellent in feel and feel.

[0039]

EXAMPLES The present invention will be specifically described below by showing Examples and Comparative Examples, but the present invention is not limited to the following Examples.

[Examples and Comparative Examples] Resin components having the compositions shown in Table 1 were injected into an injection molding die to produce innermost cores having the properties shown in Table 1. On the other hand, a resin composition having the composition shown in Table 1 was injection-molded on the innermost core, and this, or for the innermost core,
The rubber composition is kneaded using a kneading roll, and primary vulcanization (semi-vulcanization) is performed at 130 ° C. for 6 minutes to produce a pair of hemispherical cup bodies. Within 15
The outer layer core was subjected to secondary vulcanization (total vulcanization) under conditions of 5 ° C. and 15 minutes to produce a solid core having a two-layer or three-layer structure.

With respect to each of the obtained solid cores, the cover material shown in Table 1 was injection-molded to have a thickness of 2.1 m.
m, number of dimples 392 (dimple surface occupancy rate 78
%, And a volume ratio of 0.88%) to form a solid golf ball having the properties shown in Table 1.

Next, regarding the obtained golf ball,
Each property was evaluated as follows. The results are shown in Table 1. Flying Performance A carry robot and a total flying distance were measured by hitting with a driver (# W1) at a head speed of 40 m / s using a swing robot. Hitting and Hitting Sound Three professional golfers evaluated hitting feeling and hitting sound when hitting with # W1. Hitting ◯: 3 persons judged to have a moderate softness and firmness ×: 3 persons judged to be too soft Hitting sound ○: 3 persons judged to be moderate sound Δ: 2 persons judged to be dull sound ×: 3 people judged to be dull sound

[0043]

[Table 1] * 1 XER91P: Resin modifier made by Japan Synthetic Rubber Co., Ltd.
Functional rubbery copolymer with crosslinked nitrile-butadiene rubber with carboxyl groups

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of a solid golf ball of the present invention.

[Explanation of symbols]

1 solid core 2 cover 3 innermost core 4 Outer layer core

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Takashi Maruko             Bridgestone, 20 Onohara, Chichibu City, Saitama Prefecture             Within Sports Co., Ltd. (72) Inventor Hiroshi Masutani             Bridgestone, 20 Onohara, Chichibu City, Saitama Prefecture             Within Sports Co., Ltd.

Claims (2)

[Claims] 1. A solid core covered with a cover,
A solid golf ball having a multi-layer structure in which the solid core has an innermost core and an outer layer core that covers the innermost core.
20 mm and a specific gravity of 0.9 to 1.5,
The diameter and the specific gravity are the following formula G ≧ 0.014 × a + 0.929 (In the formula, G is the specific gravity of the innermost core, and a is the diameter (mm) of the innermost core.
Indicates. ), The surface shore D hardness of the innermost core is 40
~ 95 and Shore D of the innermost layer of the outer core
The hardness is 10 or more greater than the hardness, and the innermost layer of the outer layer core is mainly composed of a thermoplastic resin, and the outer layer of the outer layer core is formed with a rubber composition covering the thermoplastic resin as a main material. A solid golf ball. 2. The solid golf ball of claim 1, wherein the amount of deflection of the solid core under a load of 100 kg is 2.2 to 4.3 mm.