JP2002355343A - Golf ball - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a golf ball having excellent durability against cracks and good feeling of striking a ball by combining a soft core and an interlayer composed of the layers wherein an appropriate quantity of inorganic filler is added at least to one layer. SOLUTION: The golf ball is provided with the core, the interlayer composed of two layers surrounding the core, and a cover containing a thermoplastic resin as a main material which covers the interlayer. The core contains a rubber base as a main material and has a diameter of 28-38 mm, and a deformation quantity of the core is 3.0 mm or greater when 100 kg of load is applied. At least one layer of the interlayer contains a resin component and 5-40 pts.wt. of the inorganic filler based on 100 pts.wt. of the resin component. A specific gravity of the cover is 0.93-1.15. An inside interlayer has a Shore D hardness of 45-70, an outside interlayer has a Shore D hardness of 55 or lower, and the cover has a Shore D hardness of 55-70. The hardness of the outside interlayer is lower than the hardness of the inside interlayer and the cover.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention comprises a core, an intermediate layer comprising one or two layers surrounding the core, and a cover mainly composed of a thermoplastic resin for covering the intermediate layer. The present invention relates to a golf ball having a good shot feeling and a significantly improved durability by adding an appropriate amount of an inorganic filler to an intermediate layer.

[0002]

2. Description of the Related Art Conventionally, many techniques for adding an inorganic filler to a cover material have been proposed (JP-B 5-73427, JP-A-6-27712, JP-A-57-25867 and JP-A-60-210272).

[0003] Above all, Japanese Patent Application Laid-Open No. Hei 6-27712 discloses that by adding an inorganic filler such as titanium white and barium sulfate to a cover material, the weight distribution in the ball is shifted from the center of the core to the cover side. By increasing the moment of inertia of the ball itself, suppressing the decay of spin during flight,
As a result, it becomes difficult to apply the initial spin at the time of impact, and the flight distance can be increased.

However, all of these proposals basically aim at increasing the moment of inertia of the ball by increasing the specific gravity of the cover and improving the flight distance performance. If too much is added, the resilience and cracking durability of the ball are impaired.

[0005] On the other hand, a golf ball is required to have a comfortable feel at the time of hitting, and without it, the commercial value is impaired.

For this reason, various proposals have been made to improve the feel at impact, but in the category of the prior art, if a soft feel at impact is obtained, on the other hand, durability in continuous hitting is reduced. It has been extremely difficult to simultaneously achieve a good feel at impact and an improvement in durability with continuous hitting.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a good hit ball by forming a single or two-layered intermediate layer around a soft core with an appropriate amount of an inorganic filler added. It is an object of the present invention to provide a golf ball capable of improving the feel and durability at the time of continuous hitting.

[0008]

Means for Solving the Problems and Embodiments of the Invention As a result of intensive studies to achieve the above object, the present inventor has found that a core and an intermediate layer comprising one or two layers surrounding the core are provided. In a golf ball provided with a layer and a cover mainly composed of a thermoplastic resin covering the intermediate layer, by forming at least one of the intermediate layers with a resin component to which an appropriate amount of an inorganic filler is added, It has been found that a golf ball having a soft feel at impact and excellent continuous hitting durability can be obtained.

That is, a golf ball comprising a core, an intermediate layer comprising one or two layers surrounding the core, and a cover mainly composed of a thermoplastic resin for covering the intermediate layer, Has a rubber base material as the main component, the core has a diameter of 28 to 38 mm, the deformation of the core under a load of 100 kg is 3.0 mm or more, and the specific gravity of the cover is 0.93 to
1.15, preferably 0.95 to 1.1,
At least one of the intermediate layers contains a resin component and 5 to 40 parts by weight of an inorganic filler based on 100 parts by weight of the resin component, and preferably has a specific gravity of 1.0 to 1%. 0.3, having a thickness of 0.5 to 6.0 mm, a single intermediate layer having a Shore D hardness of 45 to 70, more preferably 55 to 70, In the case of a layer, the Shore D hardness of the layer is 45
By setting the Shore D hardness of at least one layer to 55 or less, or by setting the specific gravity of the inorganic filler to 6.5 or less, the softly formed core and the intermediate layer to which an appropriate amount of the inorganic filler is added can be used. But surprisingly they act synergistically,
It has been found that a golf ball excellent in durability and appearance at the time of continuous hitting can be obtained, while the hitting feeling at the time of hitting, which has been a conventional problem, can be made soft and comfortable,
The present invention has been completed.

It is an object of the present invention to increase the moment of inertia of a ball by adding an inorganic filler to a cover material and increasing the specific gravity of the cover, as in the prior art, to improve flight performance. Rather than by combining a soft core and an intermediate layer consisting of one or two layers in which an inorganic filler is uniformly dispersed in an appropriate amount in an appropriate amount.
These compounds act synergistically to obtain a golf ball having an unprecedented hit feeling and excellent durability in continuous hitting.

Accordingly, the present invention provides (1) a golf ball having a core, an intermediate layer comprising a single layer surrounding the core, and a cover mainly composed of a thermoplastic resin covering the intermediate layer. In the above, the core is mainly composed of a rubber substrate,
The core has a diameter of 28 to 38 mm, the amount of deformation of the core under a load of 100 kg is 3.0 mm or more, and the intermediate layer is composed of a resin component and 100 parts by weight of an inorganic filler based on 100 parts by weight of the resin component. And the specific gravity of the cover is 0.93 to 1.15,
A golf ball, wherein the intermediate layer has a Shore D hardness of 45 to 70, the cover has a Shore D hardness of 55 to 70, and the intermediate layer hardness is lower than the cover hardness.
(2) A golf ball comprising a core, an intermediate layer comprising two layers surrounding the core, and a cover mainly composed of a thermoplastic resin covering the intermediate layer, wherein the core is a rubber base material. The main component, the diameter of the core is 28 to 38 mm,
The amount of deformation of the core under a load of 100 kg is 3.0 mm or more, and at least one of the intermediate layers includes a resin component and 5 to 40 parts by weight of an inorganic filler with respect to 100 parts by weight of the resin component. The cover has a specific gravity of 0.93 to 1.15, the inner middle layer has a Shore D hardness of 45 to 70, and the outer middle layer has a Shore D hardness of 55 or less, The Shore D hardness of the cover is 55
To 70, wherein the hardness of the outer intermediate layer is lower than the hardness of the inner intermediate layer and the cover.

Hereinafter, the present invention will be described in more detail. As shown in FIG.
A solid core 1, an intermediate layer 2 surrounding the solid core 1 (single layer) or a multilayered two-layer structure (FIG. 1 shows a case where the intermediate layer is a single layer); And a multi-layer structure having a cover 3 having an intermediate layer, and as described later, one or more intermediate layers are formed from a resin composition obtained by adding a suitable amount of a resin component and an inorganic filler thereto. is there.

The solid core 1 can be formed from a rubber composition mainly composed of a base rubber mainly composed of polybutadiene rubber, polyisoprene rubber, natural rubber, and silicone rubber. For this purpose, polybutadiene rubber is preferred. As the polybutadiene rubber, a cis-structure having at least 40% or more of a cis structure can be used.
1,4-polybutadiene is preferred. In the base rubber, natural rubber, polyisoprene rubber, styrene-butadiene rubber, and the like can be appropriately blended with the polybutadiene, if desired. Therefore, the rubber component other than polybutadiene is preferably not more than 10 parts by weight based on 100 parts by weight of polybutadiene.

The rubber composition may contain, in addition to the rubber component, a crosslinking agent such as zinc salts of unsaturated fatty acids such as zinc methacrylate and zinc acrylate, magnesium salts, and ester compounds such as trimethylpropane methacrylate. Particularly, zinc acrylate can be suitably used because of its high resilience. The amount of these crosslinking agents is preferably 15 to 40 parts by weight based on 100 parts by weight of the base rubber.

[0015] The rubber composition usually contains a vulcanizing agent such as dicumyl peroxide. The amount of the vulcanizing agent is 0.1 to 5 parts by weight based on 100 parts by weight of the base rubber. It can be by weight.

The rubber composition may further include, if necessary,
Zinc oxide, barium sulfate or the like can be blended as an antioxidant or a filler for adjusting specific gravity. The blending amount of these fillers is 0 to 130 parts by weight based on 100 parts by weight of the base rubber.

Preferred embodiments of the rubber composition for a core according to the present invention are as follows. Cis-1,4-polybutadiene 100 parts by weight Zinc oxide 5 to 40 parts by weight Zinc acrylate 15 to 40 parts by weight Barium sulfate 0 to 40 parts by weight Peroxide 0.1 to 5.0 parts by weight Antioxidant Suitable amount Vulcanization conditions : Preferably 5 to 20 at 150 ± 10 ° C.
Vulcanize for a minute.

The above-mentioned rubber composition for a core is kneaded using a usual kneader (for example, a Banbury mixer, a kneader and a roll), and the obtained compound is subjected to injection molding or compression molding using a core mold. Is formed.

The solid core thus obtained is
The diameter is preferably 28 to 38 mm, more preferably 30 to 37 mm, and the specific gravity is preferably 1.05 to
1.25, more preferably 1.07 to 1.23.

The amount of deformation of the core under a load of 100 kg must be 3.0 mm or more, preferably 3.0 to 8 mm, more preferably 3.3 to 7.0 mm.
It is. If the amount of deformation of the core is less than 3.0 mm, the core becomes too hard, the shot feeling at the time of hitting becomes hard, and the object of the present invention cannot be achieved. On the other hand, if it exceeds 8 mm, the core becomes too soft, and the resilience may be significantly reduced. The core may have a single-layer structure made of one kind of material, or may have a multi-layer structure made up of two or more layers made of different kinds of materials.

The intermediate layer 2 can be formed as a single layer around the core, or can be formed as two layers around the core.

This intermediate layer mainly contains a thermoplastic resin,
For example, polyester elastomer, ionomer resin,
Examples thereof include styrene-based elastomers, urethane-based resins, hydrogenated butadiene resins, and mixtures thereof. Specific examples include “Himilan” (manufactured by DuPont Mitsui Polychemicals), “Surlyn” (manufactured by DuPont), and “ Commercial products such as "Hytrel" (manufactured by Dupont Toray) and "Pandex" (manufactured by Dainippon Ink and Chemicals, Inc.) can be used.

When the intermediate layer is formed as a single layer (single layer) around the core, it is particularly preferable to use an ionomer resin as a main material, and two intermediate layers (first intermediate layer) are formed around the core. When the second intermediate layer is coated around the layer), a relatively high hardness ionomer resin is used for the first intermediate layer as a main component, and the second intermediate layer is formed more than the first intermediate layer. It is preferable to use a soft polyester-based elastomer, a polyurethane-based elastomer, or the like.

In the present invention, when the intermediate layer has a single-layer structure, an inorganic filler is added to the intermediate layer. Also,
When the intermediate layer has a two-layer structure, an inorganic filler is added to only one or both intermediate layers.

In this case, the inorganic filler is used in an amount of 5 to 40 parts by weight, preferably 10 to 38 parts by weight, more preferably 1 to 40 parts by weight, based on 100 parts by weight of the resin component forming the layer to which the inorganic filler is added.
Add 3 to 36 parts by weight. If the amount of the inorganic filler is less than 5 parts by weight, the reinforcing effect is not produced. On the other hand, if it exceeds 40 parts by weight, dispersibility and resilience are adversely affected.

The average particle size of the inorganic filler is usually 0.1.
It is from 0.1 to 100 µm, preferably from 0.1 to 10 µm, more preferably from 0.1 to 1.0 µm. If the average particle size is too small or too large, the dispersibility at the time of filling will be deteriorated, and the effect of the present invention may not be achieved.

The specific gravity of the inorganic filler is usually 6.5 or less, preferably 2.0 to 6.0. As such an inorganic filler, for example, barium sulfate (specific gravity of about 4.4
7), rutile type titanium white (specific gravity of about 4.17), calcium carbonate (specific gravity of about 2.6), and the like.
The species can be used alone or in combination of two or more.

Incidentally, an antioxidant, a dispersant such as metal soap and the like can be added to the intermediate layer composition, if necessary.

The method of coating the above-mentioned intermediate layer around the core is not particularly limited, and ordinary injection molding or compression molding can be employed.

The specific gravity of the intermediate layer thus formed is 1.0 to 1.3 as a whole, preferably 1.02 to 1.2.
8, more preferably 1.05 to 1.26.

The total thickness of the intermediate layer is preferably 0.5 to 6.0 mm, more preferably 1.0 to 5.0 m.
m, and when the number of the intermediate layers is two, the thickness of the layer to which the inorganic filler is added is preferably 0.7 to 4.0 mm, more preferably 0.8 to 3.5 mm.

The Shore D hardness in the case of one intermediate layer is 45.
To 70, preferably 55 to 70. When the intermediate layer has a two-layer structure, the outer intermediate layer has a Shore D hardness of 55 or less, and the inner intermediate layer has a Shore D hardness of 45 to 70, preferably 55 to 70.

The cover 3 is formed of a cover material mainly composed of a thermoplastic resin, and examples thereof include polyester elastomers, ionomer resins, styrene elastomers, urethane resins, hydrogenated butadiene resins, and mixtures thereof. Particularly, an ionomer resin is preferable, and specific examples thereof include “Himilan” (manufactured by DuPont-Mitsui Polychemicals) and “Surlyn” (manufactured by DuPont).

In the present invention, it is possible to add an inorganic filler to the cover, but if a large amount of the inorganic filler is added, appearance defects such as welds are likely to occur during injection molding. It is preferable that the filling amount of the cover is as small as possible.
It is 0 parts by weight, and it is desirable that titanium white for increasing whiteness, ultramarine for adjusting blueness, and the like be added to the above-mentioned minimum necessary amounts.

It is to be noted that a UV absorber, an antioxidant, a dispersant such as metal soap and the like can be added to the cover material as required.

The method for coating the cover on the intermediate layer is not particularly limited, and ordinary injection molding or compression molding can be employed.

The specific gravity of the cover thus formed is 0.93 to 1.15, preferably 0.95 to 1.1, and the thickness of the cover is 0.5 to 2.5 mm, preferably 0.1 to 2.5. The cover has a Shore D hardness of 55 to 70, preferably 58 to 68 mm. The cover may be formed in a plurality of layers selected from different materials.

The golf ball of the present invention has a soft and comfortable shot feeling and good appearance as well as a remarkably improved durability in repeated hits by having the above configuration.

Incidentally, the golf ball of the present invention has a large number of dimples formed on the surface thereof, and the surface can be subjected to a finishing treatment such as painting and stamping if necessary. The hardness of the entire ball is preferably 2.6 to 6.0 m, which is a deformation amount generated when a load of 100 kg is applied.
m, more preferably 3.0 to 5.8 mm, and the ball diameter and weight are in accordance with R &A's golf rules.
It can be formed in a size of 67 mm or more and a weight of 45.93 g or less.

[0040]

According to the present invention, a combination of a soft core and an intermediate layer consisting of one or two layers in which an inorganic filler is added to at least one layer in an appropriate amount provides an unprecedented excellent crack durability. A golf ball having a good shot feeling can be obtained.

[0041]

EXAMPLES The present invention will be described below in detail with reference to examples and comparative examples, but the present invention is not limited to the following examples. The amounts in Tables 1 and 2 are all parts by weight.

[Examples and Comparative Examples] The rubber compositions for cores having the composition shown in Table 1 were kneaded in a kneader and vulcanized in a core mold at a temperature of 155 ° C for about 15 minutes. A solid core of a comparative example was prepared.

Solid golf balls of Examples 1 to 4 and Comparative Examples 1 and 2 were formed by coating the intermediate layer material and the cover material shown in Table 2 around the obtained core by injection molding in combination with those shown in Table 3. It was created. Comparative Example 2 is a two-piece golf ball having a core and a cover without an intermediate layer.

Next, regarding the obtained golf ball,
Core hardness, continuous impact durability, shot feeling, and appearance were measured by the following methods. The results are also shown in Table 3. Core Hardness Deformation (mm) when a 100 kg load was applied to the core. Use a continuous impact durability swing robot to drive the ball (J's
World Stage With a loft angle of 11 degrees (Bridgestone Sports Co., Ltd.), a head speed of 4
After repeatedly hitting at a condition of 5 m / sec, the state of occurrence of cracks on the ball surface was relatively compared by the number of hits. ：: No problem at all ○: Cracks generated Δ: Relatively early destruction ×: Premature destruction hitting feeling Feel when actually hit by four professional golfers was evaluated according to the following criteria. ：: soft and comfortable ○: good △: slightly hard ×: hard appearance The state of the ball surface after molding was visually observed and evaluated according to the following criteria. ：: extremely good ○: good △: slightly bad ×: bad

[0045]

[Table 1]

[0046]

[Table 2]

[0047]

[Table 3]

From the results in Table 3, it can be seen that in Comparative Example 1, only 2 parts by weight of the inorganic filler was added to the first intermediate layer, and no inorganic filler was added to the second intermediate layer. It has poor durability.

Comparative Example 2 is a conventional two-piece ball composed of a core and a cover. Since a large amount of an inorganic filler was added to the cover, the durability against continuous impact and the appearance were inferior, and the shot feeling was extremely poor. .

On the other hand, the balls of Examples 1 to 4
By forming one or two intermediate layers in which an appropriate amount of an inorganic filler is added around the soft core, continuous hitting durability, shot feeling, and appearance are all excellent.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a golf ball according to one embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Solid core 2 Intermediate layer 3 Cover G Golf ball

Continued on the front page (72) Inventor Junji Hayashi Inside Bridgestone Sports Co., Ltd. 20, Onohara, Chichibu City, Saitama Prefecture

Claims (6)

[Claims] 1. A golf ball comprising a core, an intermediate layer comprising a single layer surrounding the core, and a cover mainly composed of a thermoplastic resin covering the intermediate layer, wherein the core is a rubber-based material. Material having a core diameter of 28 to 3
8 mm, the deformation of the core under a load of 100 kg is 3.
0 mm or more, the intermediate layer is a resin component,
The inorganic filler is 5 to 40 based on 100 parts by weight of the resin component.
Parts by weight, and the specific gravity of the cover is 0.9.
3 to 1.15, and the Shore D hardness of the intermediate layer is 4
A golf ball having a hardness of 5 to 70, a Shore D hardness of the cover of 55 to 70, and an intermediate layer hardness lower than the cover hardness. 2. A golf ball comprising a core, an intermediate layer comprising two layers surrounding the core, and a cover mainly composed of a thermoplastic resin for covering the intermediate layer, wherein the core is made of rubber. The base material is a main component, and the diameter of the core is 28 to 3
8 mm, the deformation of the core under a load of 100 kg is 3.
0 mm or more, and at least one of the intermediate layers contains a resin component and 5 to 40 parts by weight of an inorganic filler with respect to 100 parts by weight of the resin component. , The Shore D hardness of the inner middle layer is 45 to 70, the Shore D hardness of the outer middle layer is 55 or less, the Shore D hardness of the cover is 55 to 70, and the outer middle layer is Wherein the hardness of the intermediate layer is lower than the hardness of the inner intermediate layer and the cover. 3. The golf ball according to claim 1, wherein the cover has a specific gravity of 0.95 to 1.1. 4. The golf ball according to claim 1, wherein the specific gravity of the intermediate layer is 1.0 to 1.3. 5. The thickness of the intermediate layer is 0.5 to 6.0 mm.
The golf ball according to any one of claims 1 to 4, wherein 6. The golf ball according to claim 1, wherein the specific gravity of the inorganic filler is 6.5 or less.