JP3304892B2 - Multi-piece 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 multi-piece solid golf ball having at least a four-layer structure including a solid core, a surrounding layer, an intermediate layer, and a cover, and optimizes the hardness, thickness, material, etc. of each layer. Accordingly, the present invention relates to a multi-piece solid golf ball which has excellent resilience, is very soft, has good hit feeling, and has excellent continuous hitting durability.

[0002]

2. Description of the Related Art Conventionally, solid golf balls such as two-piece golf balls, which have been proposed in many cases, have a trajectory called a so-called rod ball in both driver shots and iron shots as compared with thread-wound golf balls. In addition to this, there is an advantage that the total flight distance is increased due to a large number of runs due to the structural characteristics that are hardly applied to spin.

[0003] On the other hand, solid golf balls tend to be harder to stop on greens and less controllable than iron-wound golf balls because they are less likely to spin with irons than thread-wound golf balls.

[0004] On the other hand, a golf ball has an indispensable element of a hit feeling at the time of hitting as the flight distance increases, and without it, the commercial value is impaired. In general, thread-wound golf balls are structurally very soft and provide a good feel when hit, as compared to solid golf balls.

[0005] For this reason, in a two-piece solid golf ball composed of a core and a cover, it is generally practiced to soften the ball structure in order to achieve a soft feel when hitting. A number of three-piece solid golf balls have not been obtained and further provided with an intermediate layer between the core and the cover. It was extremely difficult to obtain a golf ball having a good feeling.

Recently, a multi-piece solid golf ball having a four-layer structure or more has been proposed (JP-A-9-266959, JP-A-10-127818, JP-A-10-127819, etc.).

[0007] These proposals are directed to a solid golf ball having a four-layer structure comprising a solid core having a three-layer structure of an inner layer, an intermediate layer, and a cover layer, and a cover covering the solid core. By providing the difference, the hit feeling and controllability are improved.

However, when the difference in hardness between the layers is large or when the thickness or material of each layer is not appropriate, the amount of deformation at the time of impact greatly differs between the layers, so that energy loss occurs at the interface between the layers and the resilience is reduced. In addition, there is a problem that the flight distance is reduced and the durability at the time of continuous impact is also deteriorated.

In particular, when the materials of the adjacent layers are different from each other and the adhesiveness thereof is low, the tendency is remarkable. When the hardness difference between the adjacent layers is reduced, the effect of improving the hit feeling is impaired. Problem.

[0010] The present invention has been made in view of the above circumstances, and has a solid core, at least one envelope layer covering the core, an intermediate layer covering the envelope layer, and at least one layer covering the intermediate layer. The object of the present invention is to provide a multi-piece solid golf ball having a soft feel and excellent continuous hit durability while maintaining the excellent flight performance of the solid golf ball in a multi-piece solid golf ball having a cover of And

[0011]

Means for Solving the Problems and Embodiments of the Invention In order to achieve the above object, the present inventor has proposed a multi-piece solid golf having at least a four-layer structure including a solid core, a surrounding layer, an intermediate layer and a cover. As a result of intensive studies on the hardness, thickness, material, etc. of each layer in the ball,
By using the same type of thermoplastic resin, especially ionomer resin, for the cover and the intermediate layer, the adhesion between them is increased, the durability is improved, the intermediate layer is softer than the cover, and the surrounding layer is softer than the intermediate layer. In other words, by forming a ball structure that becomes softer as it goes inward, energy loss due to deformation at impact can be minimized, preventing a decrease in resilience,
In addition to improving durability and having a soft feel, it is possible to use a thermoplastic resin excellent in resilience, particularly a thermoplastic polyester-based elastomer and a polyurethane-based elastomer, as a material for an envelope layer covering the periphery of the core. It has been found that the inorganic filler is effective, and that the durability is improved due to the reinforcing effect of the inorganic filler by adding the inorganic filler to at least one of the cover and the intermediate layer.

As a result of further intense studies by the present inventors based on the above findings, the solid core, at least one surrounding layer covering the core, an intermediate layer covering the surrounding layer, In a multi-piece solid golf ball having at least one cover that covers an intermediate layer, the solid core has a hardness of 2.5 to 7.0 mm in a deformation amount under a load of 100 kg, and the envelope layer is formed of a thermoplastic resin. A resin having a Shore D hardness of 15 to 47, the intermediate layer and the cover being formed of the same type of thermoplastic resin as a main material, and a Shore D hardness of the intermediate layer of 45 to 63. The cover has a Shore D hardness of 53 to 65, and the cover has a Shore D hardness higher than that of the intermediate layer. The hardness, thickness, material, etc. of each layer constituting the multi-piece solid golf ball by adding an inorganic filler to one layer, preferably by forming the Shore D hardness of the surrounding layer lower than the Shore D hardness of the intermediate layer. These layers act synergistically with each other to obtain a ball structure with extremely low energy loss, and have excellent flight performance and a very soft feel due to improved resilience. The present inventors have found that a multi-piece solid golf ball having significantly improved durability at the time of continuous impact can be obtained by the reinforcing effect of the inorganic filler added to any one of the layers, and the present invention has been completed.

Accordingly, the present invention provides: (1) a solid core, at least one surrounding layer covering the core, an intermediate layer covering the surrounding layer, and at least one cover covering the intermediate layer. In the multi-piece solid golf ball provided, the hardness of the solid core is 2.5 to
7.0 mm, wherein the surrounding layer is formed mainly of a thermoplastic resin, has a Shore D hardness of 15 to 47, which is lower than the Shore D hardness of the intermediate layer, and the intermediate layer and the cover are of the same type. The intermediate layer has a Shore D hardness of 45 to 63, the cover has a Shore D hardness of 53 to 65, and the cover has a Shore D hardness of the intermediate layer. A multi-piece solid golf ball having a hardness higher than that of the cover and an inorganic filler added to at least one of the cover and the intermediate layer; (2) a total thickness of the cover and the intermediate layer of 1.5; ~ 5.
0 mm, and the thickness of the surrounding layer is 1.0 to 5.0 m
(3) The multi-piece solid golf ball according to (1) or (2), wherein the cover and the intermediate layer are mainly composed of an ionomer resin, and (4) an inorganic filler. Is 1.0 to 1.5
The multi-piece solid golf ball according to any one of (1) to (3), (5) the multi-piece solid golf ball according to any one of (1) to (4), wherein the inorganic filler is barium sulfate. The multi-piece solid according to any one of claims 1 to 5, wherein the golf ball and (6) the inorganic filler are added in an amount of 10 to 45 parts by weight based on 100 parts by weight of the resin component forming the cover or the intermediate layer. Provide golf balls.

Hereinafter, the present invention will be described in more detail. As shown in FIG. 1, a multi-piece golf ball G of the present invention comprises a solid core 1, at least one envelope layer 2 covering the core 1, It has an intermediate layer 3 for covering the surrounding layer 2 and at least one cover 4 for covering the intermediate layer 3. Each layer has appropriate hardness, material and thickness as described later. , A cover and an intermediate layer to which at least one inorganic filler is added.

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
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 above-mentioned polybutadiene, but the resilience of the golf ball is improved by increasing the polybutadiene rubber component. 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 10 to 40 parts by weight based on 100 parts by weight of the base rubber.

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 0 to 50 parts by weight Zinc acrylate 10 to 40 parts by weight Barium sulfate 0 to 50 parts by weight Peroxide 0.1 to 5.0 parts by weight Antioxidant suitable amount Vulcanization conditions: preferably 5-20 at 150 ± 10 ° C
Vulcanize for a minute.

The above-mentioned rubber composition for the 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:
Its diameter is preferably 22.7-37.7 mm, more preferably 28-37 mm.

The amount of deformation of the core under a load of 100 kg is 2.5 to 7.0 mm, preferably 2.8 to 7.0 mm.
It is 6.8 mm, more preferably 3.0 to 6.5 mm. If the deformation amount is less than 2.5 mm, the hit feeling may be hard, while if it exceeds 7.0 mm, the resilience is reduced and good flight performance cannot be obtained.

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 materials.

In the present invention, at least one, preferably one or two surrounding layers are formed around the core. The surrounding layer 2 is formed mainly of a thermoplastic resin, and examples thereof include an ionomer resin, a polyester elastomer, a polyamide elastomer, a styrene elastomer, a polyurethane elastomer, an olefin elastomer, and a mixture thereof.
Particularly preferred are thermoplastic polyester elastomers and polyurethane elastomers having desired hardness and good resilience. Specifically, "Hytrel" (manufactured by Dupont Toray), "Pandex" (manufactured by Dainippon Ink and Chemicals, Inc.)
And other commercially available products.

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

The method for coating the surrounding layer around the core is not particularly limited, and ordinary injection molding or compression molding can be employed.

The thickness of the envelope layer formed in this manner is preferably 1.0 to 5.0 mm, more preferably 1.0 to 5.0 mm.
４4.0 mm and its Shore D hardness is 15１５47.

Next, an intermediate layer 3 is formed around the surrounding layer 2. The intermediate layer 3 can be formed by using a usual thermoplastic resin as a main material, and examples thereof include a polyester elastomer, an ionomer resin, a styrene elastomer, a polyurethane elastomer, a hydrogenated butadiene resin, and a mixture thereof. Ionomer resins are preferred. Specifically, "Himi Milan" (Mitsui
Commercial products such as Dupont Polychemical Co., Ltd.) and "Surlyn" (Dupont Co.) can be used. Note that a UV absorber, an antioxidant, a dispersant such as metal soap, or the like can be added to the intermediate layer material as needed.

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

The thickness of the thus formed intermediate layer is preferably 0.5 to 3.5 mm, more preferably 0.7 to 3.5 mm.
３3.0 mm, the Shore D hardness of which is 45-63,
The shore D hardness of the intermediate layer is preferably higher than the shore D hardness of the surrounding layer, and the difference in hardness is usually about 5 to 50 for the shore D.

The cover 4 is made of the same material as that of the intermediate layer 3, and is preferably formed mainly of an ionomer resin. By forming the cover and the intermediate layer from the same type of material in this manner, the adhesion between the two is increased, and the durability is improved. Note that a UV absorber, an antioxidant, a dispersant such as metal soap, or the like can be added to the cover material as needed.

This cover can be formed in at least one layer or more, preferably in one or two layers. The method of covering this cover is not particularly limited, and ordinary injection molding or compression molding can be employed. .

The thickness of the cover thus formed is preferably 0.5 to 3.5 mm, more preferably 0.7 to 3.5 mm.
To 3.0 mm, and the total thickness of the cover and the intermediate layer is 1.5 to 5.0 mm, preferably 2.0 to 4.5 mm.
mm.

The Shore D hardness of the cover is 53 to 65.
The Shore D hardness of this cover is the Shore D hardness of the middle layer.
It is necessary to be formed higher than the hardness, and the difference in hardness is 20 or less in Shore D, preferably 1 to 15.
If the Shore D hardness of the cover is lower than the Shore D hardness of the intermediate layer, a ball structure in which energy loss due to deformation at the time of impact is minimized cannot be obtained, and the object of the present invention cannot be achieved.

In the present invention, an appropriate amount of an inorganic filler is added to at least one of the cover and the intermediate layer, ie, only the cover, only the intermediate layer, or both the cover and the intermediate layer.

In this case, the inorganic filler is preferably added in an amount of 5 to 50 parts by weight, more preferably 10 to 45 parts by weight, based on 100 parts by weight of the resin component forming the cover or the intermediate layer. If the amount of the inorganic filler is less than 5 parts by weight, the reinforcing effect may not be obtained, while if it exceeds 50 parts by weight, the dispersibility and the resilience may be 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 preferably 4.8 or less. If the specific gravity exceeds 4.8, the cover or the intermediate layer itself becomes very heavy, and the total weight of the golf ball is specified by the golf rules. May not be realistic.

Examples of such an inorganic filler include barium sulfate, titanium dioxide, calcium carbonate, and the like. One of these can be used alone, or two or more can be used in combination. Is preferred.

When the inorganic filler is added to the intermediate layer and the cover, the specific gravity of the intermediate layer or the cover to which the inorganic filler is added is 1.0 to 1.5, preferably 1.05 to 1.5.
1.45.

The multi-piece solid golf ball of the present invention has the above-mentioned structure, and adjusts the material, hardness, thickness, etc. between the multilayers to an optimum value. In particular, the same type of thermoplastic resin is used for the cover and the intermediate layer. Using (ionomer resin), forming the intermediate layer softer than the cover, and further forming the surrounding layer softer than the intermediate layer, that is, forming a ball structure that becomes softer toward the inside.
Use of a soft and highly resilient thermoplastic resin (thermoplastic polyester-based elastomer, polyurethane-based elastomer) as the material of the envelope layer covering the periphery of the core, and adding an inorganic filler to at least one of the cover and the intermediate layer As a result, these act synergistically to provide a ball structure with unprecedented energy loss, and have improved flight performance due to the improved resilience. (Putter) has a very soft feel on impact and also has excellent continuous impact durability.

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 amount of deformation of the entire ball under a load of 100 kg is preferably 2.0 to 5.5 mm, more preferably 2.3 to 5.5 mm.
The ball diameter and the weight are 42.67 mm or more and the weight is 45.9 in accordance with R & A golf rules.
It can be formed to 3 g or less.

[0044]

According to the present invention, there can be obtained a multi-piece solid golf ball having excellent flight performance, very soft feel and excellent continuous hitting durability.

[0045]

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 Table 1 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. Solid cores 1 to 5 and Comparative Examples 1 to 3 were prepared.

The surrounding layer material, the intermediate layer material and the cover material shown in Table 1 were respectively formed around the obtained core by injection molding, and solids having a four-layer structure of Examples 1 to 5 and Comparative Example 3 were formed. A golf ball was created. Comparative Example 1 is a two-piece golf ball having a core and a cover without an envelope layer and an intermediate layer, and Comparative Example 2 is a three-piece golf ball without an envelope layer.

Next, regarding the obtained golf ball,
The core, ball hardness, flying performance, durability, and feel on impact were measured by the following methods. Table 2 shows the results. Core hardness, ball hardness The deformation amount (mm) when a load of 100 kg was applied to the core or the ball. Flying performance At a head speed of 45 m / sec (HS45), the club was carried by a swing robot manufactured by Miyamae using a driver ("PRO230 Titan loft 10 degrees" (Bridgestone Sports Co., Ltd.)) when the club was actually hit using a driver. The distance was measured. The club was used as a driver (“PRO230Tit”) by using a swing robot manufactured by Miyama Co., Ltd.
an loft 10 degrees "(manufactured by Bridgestone Sports Co., Ltd.) using a head speed of 45 m / sec (HS4
In 5), it was repeatedly hit 300 times and represented by the number of cracks. The feel when a golfer actually hits the golf club with a driver and a putter was evaluated by five professional golfers according to the following criteria. ◎: Very soft ： Soft × ： Hard

[0049]

[Table 1] * 1: "Hytrel" polyester elastomer manufactured by Toray DuPont * 2: "Pandex" polyurethane elastomer manufactured by Dainippon Ink & Chemicals, Inc. * 3: "Pebax" polyamide elastomer manufactured by Atochem * 4: "Himilan""Ionomer resin manufactured by Mitsui-Dupont Polychemicals * 5: Ionomer resin manufactured by" Surlyn "Dupont

[0050]

[Table 2]

As is clear from the results in Table 2, Comparative Example 1
Is a general two-piece solid golf ball, which has a good flight distance and durability, but is hard and inferior in both the driver and the putter feel.

Comparative Example 2 is a three-piece solid golf ball similar to that disclosed in Japanese Patent Application Laid-Open No. 9-313643, which has good durability, but has a slightly reduced flight distance, and has a hard hitting feel for both the driver and the putter. Inferior.

Comparative Example 3 is a four-piece solid golf ball similar to that disclosed in JP-A-10-127819. However, the hardness and thickness of each layer are not appropriate, and energy loss occurs at the interface between the layers. Both the flight distance and the durability are remarkably inferior, and the hardened cover is thick, so that the hit feeling particularly when hitting with a small deformation (putter) is hard.

On the other hand, in the balls of Examples 1 to 5, by optimizing the material, thickness and hardness of each layer formed in a multilayer structure, a ball structure with less energy loss can be obtained, and the resilience is improved. In addition to having excellent flight performance, it has a very soft feel on both drivers and putters and has excellent continuous hitting durability.

[Brief description of the drawings]

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Solid core 2 Surrounding layer 3 Intermediate layer 4 Cover G Golf ball

──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Yasumasa Shimizu 20 Onohara, Chichibu City, Saitama Pref. Inside Bridgestone Sports Co., Ltd. (56) References JP-A-9-56848 (JP, A) JP-A-9-271535 ( JP, A) JP-A-8-336618 (JP, A) JP-A-10-151226 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) A63B 37/00-37/14

Claims (6)

(57) [Claims] 1. A solid core, at least one surrounding layer covering the core, and an intermediate layer covering the surrounding layer.
In a multi-piece solid golf ball provided with at least one cover for covering the intermediate layer, the solid core has a diameter of 22.7 to 33.7 mm, and the solid core has a hardness of 2 kg under a load of 100 kg load. .5
The envelope layer is formed mainly of a thermoplastic resin, and has a Shore D hardness of 15 to 47, which is lower than the Shore D hardness of the intermediate layer. The same layer of thermoplastic resin is used as the main material, the intermediate layer has a Shore D hardness of 45 to 63, the cover has a Shore D hardness of 53 to 65, and the cover has a Shore D hardness of the intermediate layer. A multi-piece solid golf ball formed so as to have a hardness higher than D and having an inorganic filler added to at least one of the cover and the intermediate layer. 2. The combined thickness of the cover and the intermediate layer is 1.
5 to 5.0 mm, and the thickness of the surrounding layer is 1.0 to
2. The multi-piece solid golf ball according to claim 1, which is 5.0 mm. 3. The multi-piece solid golf ball according to claim 1, wherein the cover and the intermediate layer mainly comprise an ionomer resin. 4. The specific gravity of the layer to which the inorganic filler is added is 1.0.
The multi-piece solid golf ball according to any one of claims 1 to 3, wherein the number is 1.5 to 1.5. 5. The multi-piece solid golf ball according to claim 1, wherein the inorganic filler is barium sulfate. 6. The multi-piece solid golf ball according to claim 1, wherein the inorganic filler is added in an amount of 10 to 45 parts by weight based on 100 parts by weight of the resin component forming the cover or the intermediate layer. .