JP2003250931A - Golf ball - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a golf ball 1 in which both an aerial performance and a sense of shot are improved. <P>SOLUTION: The golf ball 1 is provided with a spherical core 2, an intermediate layer 3 and a cover 4. The core 2 is composed of a bridged resin, and the intermediate layer 3 and the cover 4 are composed of thermoplastic resin compositions. A number of dimples 5 are formed on the surface of the cover 4. The ratio of surface hardness Hm of the intermediate layer 3 to surface hardness Hr of the core 2 (Hm/Hr) is 0.95 to 1.20. Specific gravity Dc of the cover 4 is ≥1.00. The ratio of specific gravity Dm of the intermediate layer 3 to the specific gravity Dc of the cover 4 (Dm/Dc) is 1.02 to 1.15. Total volume V of the dimples 5 is 420 to 580 mm<SP>3</SP>. The inertia moment of the golf ball 1 is ≥81. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a golf ball, and more particularly to a solid golf ball having a multi-piece structure including a core, an intermediate layer and a cover.

[0002]

2. Description of the Related Art When hit by a golf club, the golf ball flies with backspin. Due to this backspin, lift is applied to the golf ball. The lift force increases the trajectory of the golf ball. The elevation angle of the golf ball at the highest point of the trajectory is usually higher than the elevation angle of the golf ball immediately after hitting, because lift force acts on the golf ball during flight. The lift force increases the flight time of the golf ball and increases the flight distance.

The lift force exerted on the golf ball immediately after hitting to the highest point of the trajectory includes a negative horizontal component with respect to the direction from the hitting point to the falling point. The negative horizontal component reduces the flight distance of the golf ball. A golf ball whose ballistic highest point is close to the hit point is less susceptible to the negative horizontal component. By suppressing the backspin (hereinafter referred to as “initial spin”) immediately after hitting, the ballistic highest point approaches the hitting point. In the past, golf balls having a balata cover and a thread-wound core were the mainstream, but then a golf ball having an ionomer cover and a thread-wound core was developed,
Further, in recent years, golf balls having a solid core have become mainstream. The transition of such materials and structures is also the history of the challenge to suppress the initial spin.

One of the factors that influence the initial spin rate of a golf ball is the moment of inertia.
A golf ball having a larger moment of inertia tends to have a smaller initial spin. Golf balls having a solid core have also been improved in various ways from the viewpoint of increasing the moment of inertia. Japanese Unexamined Patent Publication No. 6-277312 discloses a golf ball having an increased moment of inertia by incorporating an inorganic filler in the cover.
Japanese Unexamined Patent Publication No. 2000-51397 discloses a golf ball having an increased moment of inertia by including an inorganic filler in the mid layer.

[0005]

The suppression of the initial spin is
Although it is preferable from the viewpoint that the maximum trajectory is close to the impact point, it causes a lack of lift in the overall trajectory. Insufficient lift causes a decrease in flight time and a resulting reduction in flight distance. In addition, the addition of the inorganic filler to the cover and the mid layer also causes a reduction in shot feeling of the golf ball.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a golf ball excellent in both flight performance and shot feeling.

[0007]

A golf ball according to the present invention comprises a spherical core made of solid rubber, an intermediate layer located outside the core, and a cover laminated on the intermediate layer. . The ratio (Hm / Hr) of the surface hardness Hm of the intermediate layer to the surface hardness Hr of the core is 0.95 or more and 1.20 or less. The specific gravity Dc of the cover is 1.00 or more. Specific gravity Dm of the intermediate layer to specific gravity Dc of the cover
(Dm / Dc) is 1.02 or more and 1.15 or less. A number of dimples are formed on the surface of the cover. The total volume V of these dimples is 420 mm ³ or more and 580 mm ³ or less. This golf ball is excellent in both flight performance and shot feeling.

Preferably, the cover is made of a thermoplastic resin composition containing titanium dioxide and barium sulfate. The compounding amount of titanium dioxide is 1 part by mass or more and 5 parts by mass or less based on 100 parts by mass of the base resin. The compounding amount of barium sulfate is 2 parts by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the base resin. This cover contributes to improving the moment of inertia of the golf ball. Moreover, this cover has high strength. From the viewpoint of improving the moment of inertia, the specific gravity Dc of the cover is preferably 1.05 or more.

Preferably, the intermediate layer comprises a thermoplastic resin composition containing titanium dioxide and barium sulfate. The compounding amount of titanium dioxide is 1 part by mass or more and 5 parts by mass or less based on 100 parts by mass of the base resin. The blending amount of barium sulfate is 5 parts by mass or more and 20 parts by mass or less based on 100 parts by mass of the base resin. This mid layer contributes to improving the moment of inertia of the golf ball. Moreover, this intermediate layer has high strength. From the viewpoint of improving the moment of inertia, the specific gravity Dm of the intermediate layer is preferably 1.03 or more.

Preferably, the golf ball has a moment of inertia of 81 or more, particularly 82 or more. This golf ball is further excellent in flight performance.

[0011] Preferably, the amount of compressive deformation of the core from a state where an initial load of 98 N is applied to a state where a final load of 1274 N is applied is 4.20 mm or more and 4.45 mm or less. This core contributes to improving the feel at impact of the golf ball.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, with reference to the drawings,
The present invention will be explained in detail based on the preferred embodiments.

FIG. 1 is a schematic sectional view showing a golf ball 1 according to one embodiment of the present invention. This golf ball 1 includes a spherical core 2, a mid layer 3, and a cover 4. The cover 4 is directly laminated on the outside of the mid layer 3. Many dimples 5 are formed on the surface of the cover 4. The golf ball 1 includes a paint layer and a mark layer on the outside of the cover 4, but these layers are not shown. This golf ball 1
The diameter is usually between 40mm and 45mm, especially 42m
It is from m to 44 mm. The diameter is preferably 42.67 mm or more and 42.80 mm or less from the viewpoint that the air resistance is reduced within the range where the standards of the American Golf Association (USGA) are satisfied. The golf ball 1 usually has a mass of 40.
It is g or more and 50 g or less, and particularly 44 g or more and 47 g or less. From the viewpoint that the inertia is increased within the range where the standards of the American Golf Association are satisfied, the mass is 45.00 g or more 4
It is preferably 5.93 g or less.

In this golf ball 1, the cover 4 and the mid layer 3 have high specific gravity, as will be described later in detail.
The cover 4 and the mid layer 3 increase the moment of inertia of the golf ball 1 and suppress the initial spin. The maximum trajectory when the golf ball 1 is hit is close to the hit point. Therefore, the negative horizontal component due to the lift has little influence on the trajectory. Moreover, in this golf ball 1, since the total volume of the dimples 5 is optimized, as will be described later in detail, a sufficient lift is exhibited as a whole trajectory. This golf ball 1 has excellent flight performance.

The core 2 is formed by crosslinking a rubber composition. As the base rubber of the rubber composition, polybutadiene, polyisoprene, styrene-butadiene copolymer,
Examples are ethylene-propylene-diene copolymer and natural rubber. Two or more of these rubbers may be used in combination. From the viewpoint of resilience performance, polybutadiene is preferable. Even when polybutadiene and other rubbers are used in combination, it is preferable that polybutadiene is the main component. Specifically, the proportion of polybutadiene in the total base rubber is preferably 50% by mass or more, and particularly preferably 80% by mass or more. Among polybutadiene, high cis polybutadiene having a cis-1,4 bond ratio of 40% or more, particularly 80% or more is preferable.

The cross-linking form of the core 2 is not particularly limited.
As the cross-linking agent, a co-cross-linking agent, organic peroxide, sulfur or the like can be used. The co-crosslinking agent and the organic peroxide are preferably used in combination because the resilience performance of the golf ball 1 is enhanced. The co-crosslinking agent preferable from the viewpoint of resilience performance is preferably a monovalent or divalent metal salt of an α, β-unsaturated carboxylic acid having 2 to 8 carbon atoms. Specific examples of preferable co-crosslinking agents include zinc acrylate, magnesium acrylate, zinc methacrylate and magnesium methacrylate. In particular, zinc acrylate, which can obtain high resilience performance, is preferable.

As the co-crosslinking agent, an α, β-unsaturated carboxylic acid having 2 to 8 carbon atoms and a metal oxide may be blended. Both react in the rubber composition to give a salt. Preferred α, β-unsaturated carboxylic acids include acrylic acid and methacrylic acid, with acrylic acid being particularly preferred. Examples of preferable metal oxides include zinc oxide and magnesium oxide, and zinc oxide is particularly preferable.

The blending amount of the co-crosslinking agent is preferably 10 parts by mass or more and 50 parts by mass or less with respect to 100 parts by mass of the base rubber.
If the amount is less than the above range, the resilience performance of the golf ball 1 may be insufficient. From this viewpoint, the blending amount is more preferably 12 parts by mass or more, and particularly preferably 15 parts by mass or more. If the blending amount exceeds the above range, the shot feeling of the golf ball 1 may become hard. From this viewpoint, the blending amount is particularly preferably 45 parts by mass or less.

The rubber composition used for the core 2 preferably contains an organic peroxide. The organic peroxide is
It functions as a crosslinking agent together with the aforementioned α, β-unsaturated carboxylic acid metal salt, and also as a curing agent. By blending the organic peroxide, the resilience performance of the golf ball 1 can be enhanced. Suitable organic peroxides include dicumyl peroxide, 1,1-bis (t-butylperoxy)-
Examples include 3,3,5-trimethylcyclohexane, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane and di-t-butylperoxide. A particularly versatile organic peroxide is dicumyl peroxide.

The amount of the organic peroxide compounded is 100
The amount is preferably 0.1 parts by mass or more and 3.0 parts by mass or less with respect to parts by mass. If the amount is less than the above range, the resilience performance of the golf ball 1 may be insufficient. From this viewpoint, the blending amount is more preferably 0.2 parts by mass or more, and is 0.4
The amount is more preferably at least 0.5 part by mass, and particularly preferably at least 0.5 part by mass. If the blending amount exceeds the above range, the shot feeling of the golf ball 1 may become hard. From this viewpoint, the blending amount is particularly preferably 2.5 parts by mass or less.

A filler may be added to the core 2 for the purpose of adjusting the specific gravity. Suitable fillers include zinc oxide,
Examples thereof include inorganic salts such as barium sulfate and calcium carbonate; powders made of high specific gravity metals such as tungsten and molybdenum. The blending amount of the filler is appropriately determined so that the intended specific gravity of the core 2 is achieved. The preferred filler is zinc oxide because it functions not only as a specific gravity control but also as a crosslinking aid. Various additives such as an antioxidant, a colorant, a plasticizer, and a dispersant may be added to the core 2 in an appropriate amount, if necessary. Cross-linked rubber powder or synthetic resin powder may be further blended in the core 2. The crosslinking temperature of the general core 2 is 140 ° C. or higher and 180 ° C. or lower, and the crosslinking time is 10 minutes or longer and 60 minutes or shorter.

The diameter of the core 2 is 25 mm or more and 41 mm or less, and particularly 27 mm or more and 40 mm or less.

The surface hardness Hr of the core 2 is preferably 65 or more and 82 or less. When the surface hardness Hr is less than the above range,
The resilience performance of the golf ball 1 may be insufficient.
From this viewpoint, the surface hardness Hr is more preferably 67 or more, further preferably 70 or more, and particularly preferably 73 or more. If the surface hardness Hr exceeds the above range, the shot feeling of the golf ball 1 may be insufficient. From this perspective,
The surface hardness Hr is more preferably 80 or less, further preferably 78 or less, and particularly preferably 75 or less. Surface hardness Hr
Is measured by a spring type hardness meter C type specified in "JIS K 6301". A hardness meter is pressed against the surface of the core 2 to measure the surface hardness Hr.

The specific gravity Dr of the core 2 is preferably 1.25 or less. If the specific gravity Dr exceeds the above range, the golf ball 1
The moment of inertia of may become low. From this viewpoint, the specific gravity Dr is more preferably 1.20 or less, and is 1.18.
The following are particularly preferred. The specific gravity Dr is usually set to 1.05 or more.

The amount of compressive deformation of the core 2 is preferably 4.20 mm or more and 4.45 mm or less. If the amount of compressive deformation is less than the above range, the shot feeling of the golf ball 1 may be insufficient. From this viewpoint, the amount of compressive deformation is more preferably 4.25 mm or more, and particularly preferably 4.30 mm or more.
If the amount of compressive deformation exceeds the above range, the resilience performance of the golf ball 1 may be insufficient. From this viewpoint, the amount of compressive deformation is particularly preferably 4.40 mm or less. In the measurement of the amount of compressive deformation, first, the core 2 is placed on a hard plate made of metal. Next, the metal cylinder gradually descends toward the core 2. The core 2 is sandwiched between the bottom of this cylinder and the rigid plate,
It gradually transforms. The moving distance of the cylinder from the state where the initial load of 98 N is applied to the core 2 to the state where the final load of 1274 N is applied is measured. This moving distance is the amount of compressive deformation.

The intermediate layer 3 may be composed of a thermoplastic resin composition or a crosslinked rubber. Preferably, the mid layer 3 is composed of a thermoplastic resin composition. Examples of preferable base resin include ionomer resin, polyester, polyurethane, polyolefin and various thermoplastic elastomers, and a mixture thereof may be used. From the viewpoint of contributing to the shot feeling and the resilience performance of the golf ball 1, the ionomer resin is particularly preferable.

Among the ionomer resins, one in which one part by mass of the carboxylic acid in the copolymer of α-olefin and α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms is neutralized with a metal ion. It is suitable. Ethylene and propylene are preferable as the α-olefin. Acrylic acid and methacrylic acid are preferable as the α, β-unsaturated carboxylic acid. Examples of metal ions for neutralization include alkali metal ions such as sodium ions, potassium ions and lithium ions; divalent metal ions such as zinc ions, calcium ions and magnesium ions; and trivalent metals such as aluminum ions and neodymium ions. Ions are mentioned. Neutralization may be done with more than one metal ion.
Particularly suitable metal ions from the viewpoint of resilience performance and durability of the golf ball 1 are sodium ion, zinc ion, lithium ion and magnesium ion.

Preferred thermoplastic elastomers include
Examples thereof include polyurethane-based thermoplastic elastomers, polyamide-based thermoplastic elastomers, polyester-based thermoplastic elastomers, and styrene-based thermoplastic elastomers. Two or more thermoplastic elastomers may be used in combination. From the viewpoint of resilience performance of the golf ball 1, polyester-based thermoplastic elastomers and styrene-based thermoplastic elastomers are particularly suitable.

The styrene-based thermoplastic elastomer (thermoplastic elastomer containing a styrene block) includes a styrene-butadiene-styrene block copolymer (SB
S), styrene-isoprene-styrene block copolymer (SIS), styrene-isoprene-butadiene-styrene block copolymer (SIBS), hydrogenated SBS, hydrogenated SIS and hydrogenated SIBS. Be done.
Examples of hydrogenated products of SBS include styrene-ethylene-butylene-styrene block copolymer (SEBS). Examples of hydrogenated products of SIS include styrene-ethylene-propylene-styrene block copolymer (SEPS). Examples of hydrogenated products of SIBS include styrene-ethylene-ethylene-propylene-styrene block copolymer (SEEPS).

The thermoplastic resin composition of the mid layer 3 preferably contains titanium dioxide and barium sulfate.
Titanium dioxide contributes to improving the whiteness of the golf ball 1,
At the same time, it contributes to the improvement of the specific gravity of the mid layer 3. However, if the content of titanium dioxide is excessive, the strength of the intermediate layer 3 may be insufficient. By using titanium dioxide and barium sulfate together, high strength and high specific gravity of the intermediate layer 3 are achieved.

The compounding amount of titanium dioxide is 100
It is preferably 1 part by mass or more and 5 parts by mass or less with respect to parts by mass.
When the blending amount is less than the above range, the whiteness of the golf ball 1 may be insufficient. From this viewpoint, the blending amount is particularly preferably 2 parts by mass or more. If the blending amount exceeds the above range, the strength of the mid layer 3 may be insufficient. From this point of view, the amount of compounding is particularly preferably 4 parts by mass or less.

The blending amount of barium sulfate is 100
The amount is preferably 5 parts by mass or more and 20 parts by mass or less with respect to parts by mass. If the blending amount is less than the above range, the specific gravity of the mid layer 3 may decrease. From this viewpoint, the blending amount is more preferably 7 parts by mass or more, and particularly preferably 10 parts by mass or more.
If the blending amount exceeds the above range, the shot feeling of the golf ball 1 may be insufficient. From this viewpoint, the compounding amount is 1
It is more preferably 9 parts by mass or less, and particularly preferably 17 parts by mass or less.

From the viewpoint of achieving both high strength and high specific gravity of the intermediate layer 3, it is preferable that the blending amount of barium sulfate is larger than that of titanium dioxide. When the compounding amount of titanium dioxide is 100 parts by mass of the base resin and the compounding amount of barium sulfate is Y parts by mass, the value of (Y−X) is preferably 1 part by mass or more and 20 parts by mass or less. 5 parts by mass or more 16
It is more preferably not more than 10 parts by mass, particularly preferably not less than 8 parts by mass and not more than 16 parts by mass.

The thickness of the intermediate layer 3 is 0.2 mm or more and 2.5.
mm or less is preferable. When the thickness is less than the above range, the shot feeling of the golf ball 1 may be insufficient. From this viewpoint, the thickness is more preferably 1.0 mm or more.
3 mm or more is particularly preferable. When the thickness exceeds the above range, the resilience performance of the golf ball 1 may be insufficient. From this viewpoint, the thickness is more preferably 2.0 mm or less, and particularly preferably 1.6 mm or less.

The surface hardness Hm of the mid layer 3 is 72 or more and 90 or more.
The following are preferred. If the surface hardness Hm is less than the above range, the resilience performance of the golf ball 1 may be insufficient. From this viewpoint, the surface hardness Hm is more preferably 75 or more, further preferably 78 or more, particularly preferably 80 or more. If the surface hardness Hm exceeds the above range, the shot feeling of the golf ball 1 may be insufficient. From this viewpoint, the surface hardness Hm is more preferably 88 or less, and particularly preferably 85 or less. The surface hardness Hm is “JIS K630
It is measured by a spring type hardness meter C type specified in 1 ". A hardness meter is pressed against the surface of the sphere consisting of the core 2 and the mid layer 3, and the surface hardness Hm is measured.

The specific gravity Dm of the intermediate layer 3 is preferably 1.03 or more. When the specific gravity Dm is less than the above range, the moment of inertia of the golf ball 1 becomes small, and the initial spin may not be suppressed. From this viewpoint, the specific gravity Dm is 1.0.
5 or more is more preferable, and 1.10 or more is particularly preferable.
If the specific gravity Dm is too large, the shot feeling of the golf ball 1 becomes insufficient, so the specific gravity Dm is usually set to 1.20 or less.

The cover 4 is located on the outermost side except the paint layer and the mark layer. It is composed of a thermoplastic resin composition. Preferable base resin is the same ionomer resin as in the case of the mid layer 3, polyester, polyurethane, polyolefin and various thermoplastic elastomers. From the viewpoint of contributing to the shot feeling and the resilience performance of the golf ball 1, the ionomer resin is particularly preferable.

The thermoplastic resin composition of the cover 4 preferably contains titanium dioxide and barium sulfate.
Titanium dioxide contributes to improving the whiteness of the golf ball 1,
At the same time, it contributes to the improvement of the specific gravity of the cover 4. However, if the content of titanium dioxide is excessive, the strength of the cover 4 may be insufficient. High strength and high specific gravity of the cover 4 are achieved by using titanium dioxide and barium sulfate together.

The compounding amount of titanium dioxide is 100% of the base resin.
It is preferably 1 part by mass or more and 5 parts by mass or less with respect to parts by mass.
When the blending amount is less than the above range, the whiteness of the golf ball 1 may be insufficient. From this viewpoint, the blending amount is particularly preferably 2 parts by mass or more. If the blending amount exceeds the above range, the strength of the cover 4 may be insufficient. From this viewpoint, it is particularly preferable that the blending amount is 3 parts by mass or less.

The barium sulphate content is 100% base resin.
The amount is preferably 2 parts by mass or more and 10 parts by mass or less with respect to parts by mass. If the amount is less than the above range, the cover 4 may have a low specific gravity. From this viewpoint, the blending amount is more preferably 3 parts by mass or more, and particularly preferably 5 parts by mass or more. If the blending amount exceeds the above range, the shot feeling of the golf ball 1 may be insufficient. From this viewpoint, the blending amount is more preferably 7 parts by mass or less, and particularly preferably 5 parts by mass or less.

From the viewpoint of achieving both high strength and high specific gravity of the cover 4, it is preferable that the content of barium sulfate is larger than the content of titanium dioxide. When the compounding amount of titanium dioxide is 100 parts by mass of the base resin and the compounding amount of barium sulfate is Y parts by mass, the value of (Y-X) is preferably 1 part by mass or more and 15 parts by mass or less. 1 part by mass or more 10
It is more preferably not more than 3 parts by mass, particularly preferably not less than 3 parts by mass and not more than 6 parts by mass.

If necessary, the cover 4 may be blended with an appropriate amount of a colorant, a dispersant, an antiaging agent, an ultraviolet absorber, a light stabilizer, a fluorescent agent, a fluorescent brightening agent and the like. For the purpose of adjusting the specific gravity, powder of high specific gravity metal such as tungsten or molybdenum may be blended in the cover 4.

The thickness of the cover 4 is 0.2 mm or more and 2.5.
mm or less is preferable. When the thickness is less than the above range, the durability of the golf ball 1 may be insufficient. From this viewpoint, the thickness is more preferably 1.0 mm or more.
3 mm or more is particularly preferable. When the thickness exceeds the above range, the shot feeling of the golf ball 1 may be insufficient. From this viewpoint, the thickness is more preferably 2.0 mm or less, and particularly preferably 1.6 mm or less.

The hardness Hc of the cover 4 is preferably 50 or more and 70 or less. When the hardness Hc is less than the above range, the resilience performance of the golf ball 1 may be insufficient. From this viewpoint, the hardness Hc is more preferably 53 or more, and particularly preferably 56 or more. If the hardness Hc exceeds the above range, the shot feeling of the golf ball 1 may be insufficient. From this viewpoint, the hardness Hc is more preferably 68 or less, and particularly preferably 65 or less. The hardness Hc is "ASTM-D 224
According to the regulations of "0-68", it is measured by a spring type hardness tester Shore D type. For the measurement, a slab made of the same thermoplastic resin composition as the cover 4 is used.

The specific gravity Dc of the cover 4 is 1.00 or more. When the specific gravity Dc is less than the above range, the moment of inertia of the golf ball 1 becomes small, and the initial spin may not be suppressed. From this viewpoint, the specific gravity Dc is 1.
A value of 05 or more is particularly preferable. If the specific gravity Dc is too large, the shot feeling of the golf ball 1 becomes insufficient, so the specific gravity Dc is usually set to 1.20 or less.

The ratio (Hm / Hr) of the surface hardness Hm of the intermediate layer 3 to the surface hardness Hr of the core 2 is 0.95 or more.
It is set to 20 or less. If the ratio (Hm / Hr) is less than the above range, the initial spin may not be sufficiently suppressed. From this viewpoint, the ratio (Hm / Hr) is more preferably 0.98 or more, and particularly preferably 1.00 or more. Ratio (H
When m / Hr) exceeds the above range, the shot feeling of the golf ball 1 may be insufficient. From this viewpoint, the ratio (H
m / Hr) is more preferably 1.18 or less and particularly preferably 1.15 or less.

The ratio (Dm / Dc) of the specific gravity Dm of the intermediate layer 3 to the specific gravity Dc of the cover 4 is 1.02 or more and 1.15 or less. In other words, the intermediate layer 3 has a higher specific gravity than the cover 4. As a result, the moment of inertia is increased while maintaining the shot feeling and durability of the golf ball 1. When the ratio (Dm / Dc) is less than the above range,
In some cases, the moment of inertia of the golf ball 1 becomes small and the initial spin is not sufficiently suppressed. From this viewpoint, the ratio (Dm / Dc) is more preferably 1.03 or more,
1.04 or more is particularly preferable. When the ratio (Dm / Dc) exceeds the above range, the resilience performance of the golf ball 1 may be insufficient. From this viewpoint, the ratio (Dm / Dc) is more preferably 1.12 or less, and particularly preferably 1.10 or less.

The moment of inertia of the golf ball 1 is 81
The above is preferable. If the moment of inertia is less than the above range, the initial spin may not be suppressed, and the ballistic highest point may move away from the hitting point, resulting in an insufficient flight distance. From this viewpoint, the moment of inertia is more preferably 82 or more,
4 or more is particularly preferable. Normally, the moment of inertia is 90
It is the following. The moment of inertia is "INERTIA D
YNAMICS 'product name "MOI-05-002"
Measured by

FIG. 2 is an enlarged plan view showing the golf ball 1 of FIG. 1, and FIG. 3 is a front view thereof. In Figure 2,
The type of dimple 5 is shown for one unit when the surface of the golf ball 1 is divided into ten equivalent units. The plane shape of all dimples 5 is
It is circular. This golf ball 1 has a diameter of 4.05 m.
A dimple having a volume of 1.555 mm ³ and a diameter of 3.60 mm and a volume of 1.087 mm ^3.
B dimples having a diameter of 3.40 mm and a C dimple having a volume of 0.938 mm ³ and a diameter of 3.
The D dimple having a volume of 20 mm and a volume of 0.782 mm ³ . The number of A dimples is 132, the number of B dimples is 180, the number of C dimples is 60, and the number of D dimples is 60.
It is an individual. The total number of dimples on this golf ball 1 is 4
There are 32.

FIG. 4 is a schematic sectional view showing a part of the golf ball 1 of FIG. In this figure, dimple 5
The neighborhood of is shown. What is indicated by a chain double-dashed line in this figure is a virtual spherical surface (the surface of the golf ball 1 when it is assumed that the dimples 5 do not exist). The volume of the space surrounded by the virtual spherical surface and the surface of the dimple 5 is the volume of the dimple 5. Double arrow d in FIG.
The diameter of the dimple 5 is shown by. The distance between both contact points when a common tangent line is drawn near the left and right edges of the dimple 5 is the diameter d. In FIG. 4, what is indicated by a double-headed arrow f is the depth of the dimple 5. The depth f is the distance between the virtual spherical surface and the deepest part of the dimple 5.

The total volume V of the dimples 5 is 420 m
It is set to m ³ or more and 580 mm ³ or less. Since the golf ball 1 has a large moment of inertia, the initial spin is suppressed, but when the total volume V is set to 580 mm ³ or less, a sufficient lift is exhibited for the entire trajectory.
From the viewpoint that sufficient lift can be obtained, the total volume V is 550.
mm ³ or less is preferable, 520 mm ³ or less is more preferable, and 500 mm ³ or less is particularly preferable. Total volume V is 42
If it is less than 0 mm ³ , the trajectory may hop. In this respect, the total volume V is preferably 450 mm ³ or more, 470 mm ³ or more is particularly preferable. 1 to 4
The total volume V of the golf ball 1 shown in, 504mm ³
Is.

The surface area occupation ratio Y of the dimples 5 is 0.7.
It is preferably 0 or more and 0.90 or less. If the surface area occupation ratio Y is less than the above range, the lift of the golf ball 1 during flight may be insufficient. From this viewpoint, the surface area occupation ratio Y is more preferably 0.72 or more, and particularly preferably 0.74 or more. If the surface area occupation ratio Y exceeds the above range, the trajectory of the golf ball 1 may be too high. From this viewpoint, the surface area occupation ratio Y is more preferably 0.88 or less,
0.86 or less is particularly preferable. The surface area occupation ratio Y of the golf ball 1 shown in FIGS. 1 to 4 is 0.80.

In the present specification, the term "surface area occupation ratio Y" means a value obtained by dividing the total area of all the dimples 5 by the surface area of the phantom sphere. Here, "Dimple 5
The area of the dimple 5 is the planar shape of the dimple 5 (the dimple 5 when the center of the golf ball 1 is seen from infinity).
(The shape of the contour of the). In the case of the circular dimple 5 having a diameter of d, the area s is calculated by the following mathematical formula. s = (d / 2) ² × π

The diameter of the dimple 5 is preferably 2.0 mm or more and 6.0 mm or less. When the diameter is less than the above range, the flight distance of the golf ball 1 may be insufficient. From this viewpoint, the diameter is more preferably 2.2 mm or more, further preferably 2.3 mm or more, and particularly preferably 2.5 mm or more. If the diameter exceeds the above range, the aerodynamic symmetry of the golf ball 1 may be insufficient. From this viewpoint, the diameter is more preferably 5.5 mm or less.
0 mm or less is more preferable, and 4.5 mm or less is particularly preferable. From the viewpoint of flight performance, it is preferable to provide a plurality of types of dimples 5 having different diameters. In this case, it is preferable that the diameters of all types are within the above range.

The depth f of the dimple 5 is 0.05 mm or more and 0.45 mm or less, and particularly 0.10 mm or more and 0.30 m.
It is set to m or less. From the viewpoint of flight performance, it is preferable to provide a plurality of types of dimples 5 having different depths. In this case, the depth is preferably within the above range for all types.

Instead of the circular dimples 5 or together with the circular dimples 5, non-circular dimples may be formed. Specific examples of non-circular dimples include polygonal dimples, elliptical dimples, and tear-shaped dimples. The area of the plane shape of the non-circular dimple is 3 mm ^3.
It is preferably 29 mm ³ or less.

The total number of dimples 5 is 250 or more and 50
0 or less is preferable. If the total number is less than the above range, there is a possibility that the original characteristic of the golf ball 1 that it is substantially spherical may not be maintained. From this viewpoint, the total number is more preferably 260 or more, further preferably 280 or more,
Particularly preferred is 300 or more. When the total number exceeds the above range, the drag coefficient (Cd) becomes large and the flight distance may be insufficient. From this viewpoint, the total number is more preferably 480 or less, and particularly preferably 460 or less.

The dimensions of the dimples 5 are the same as those of the golf ball 1.
It is required by actual measurement. Golf ball 1 on the surface
This pane typically has a paint layer.
It may be difficult to measure the dimensions accurately due to the
It In the present invention, for convenience, the golf ball before paint processing
1 may be measured, and after the paint layer is removed
The dimensions of the luff balls may be measured. No paint layer
The total dimple volume V in the open state is 435 mm^ThreeAbove is good
465mm^ThreeMore preferably, 485 mm
^ThreeThe above is particularly preferable. Display without paint layer
The total volume V of the sample is 595 mm^ThreeThe following is preferred, 56
5 mm^ThreeThe following is more preferable, 535 mm ^ThreeIn particular
preferable.

Although the core 2 of the golf ball 1 shown in FIG. 1 is composed of a single layer, a core 2 composed of two or more layers may be used. Another intermediate layer 3 may be provided between the core 2 and the intermediate layer 3.

[0060]

EXAMPLES The effects of the present invention will be clarified below based on Examples, but the present invention should not be construed in a limited way based on the description of the Examples.

[Example 1] 100 parts of polybutadiene (trade name "BR11" manufactured by JSR), 20 parts by mass of zinc acrylate, 10 parts by mass of zinc oxide, 0.8 parts by mass of dicumyl peroxide and an appropriate amount of barium sulfate were added. The mixture was kneaded with a closed kneader to obtain a rubber composition. The rubber composition was put into a mold having a spherical cavity and kept at 155 ° C. for 20 minutes to obtain a core having a diameter of 36.45 mm.
In addition, so that the mass of the golf ball becomes 45.4 g,
The compounding amount of barium sulfate was adjusted. The surface hardness Hr of this core was 72, the specific gravity Dr was 1.16, and the amount of compressive deformation was 4.46 mm.

Next, 70 parts by mass of an ionomer resin (trade name "HIMIRAN 1555" manufactured by Mitsui DuPont Polychemical Co., Ltd.), 30 parts by mass of another ionomer resin (trade name "HIMIRAN AM7316" manufactured by Mitsui DuPont Polychemical Co., Ltd.), titanium dioxide 2 parts by mass and 10 parts by mass of barium sulfate were kneaded to obtain a resin composition. On the other hand, the core is put into a molding die having a spherical cavity, and the resin composition melted by heating is injected around the core to have a thickness of 1.55.
A mm intermediate layer was molded. The surface hardness Hm of this intermediate layer was 80, and the specific gravity Dm was 1.05.

Next, an ionomer resin (Mitsui Dupont
Product name of Rechemical Co., Ltd. "HIMIRAN 1605") 60 quality
Parts, other ionomer resins (Mitsui DuPont Polychemica
Product name of Le company "Himilan 1557") 40 parts by mass, two
Kneading 2 parts by mass of titanium oxide and 5 parts by mass of barium sulfate
Then, a resin composition was obtained. On the other hand, with a spherical cavity
Insert a sphere consisting of a core and an intermediate layer into a mold and use this sphere.
Inject the molten resin composition around the body by heating
To form a cover having a thickness of 1.6 mm. Shape of cover
Simultaneously, the dimples were formed. Dimple pattern
The zones are as shown in FIGS. This hippo
Shore D hardness Hc is 61 and specific gravity Dc is 1.0
It was 1. Paint around this cover by known means
The golf ball of Example 1 was obtained. This golf bow
The total volume V of the dimples of the le is 504 mm ^ThreeMet.

[Examples 3 and 4 and Comparative Examples 4 and 5]
Examples 3 and 4 and Comparative Examples 4 and 5 were performed in the same manner as in Example 1 except that the mold for molding the cover was changed and the total volume D of the dimples was changed as shown in Tables 1 and 2 below. I got a golf ball. The change in the total dimple volume V was achieved by increasing the dimple depth. Therefore, Example 3
The dimple patterns and dimple diameters of the golf balls of Comparative Examples 4 and 5 and Comparative Examples 4 and 5 are the same as those of the golf ball of Example 1, respectively.

[Example 5 and Comparative Examples 3 and 6] The blending amounts of barium sulfate in the intermediate layer were as shown in Tables 1 and 2 below, and the specific gravity Dm and the ratio (Dm / D) of the intermediate layer were set.
Golf balls of Example 5 and Comparative Examples 3 and 6 were obtained in the same manner as in Example 1 except that c) was changed as shown in Tables 1 and 2 below.

[Examples 2 and 6 and Comparative Examples 2 and 7]
An example was performed in the same manner as in Example 1 except that the ratio of the ionomer resin in the intermediate layer was changed and the surface hardness Hm and the ratio (Hm / Hr) of the intermediate layer were as shown in Tables 1 and 2 below. Golf balls of 2 and 6 and Comparative Examples 2 and 7 were obtained.

[Example 7 and Comparative Example 1] The compounding amounts of barium sulfate in the cover were as shown in Tables 1 and 2 below, and the specific gravity Dc and the ratio (Dm / Dc) of the cover were shown in Tables 1 and 2 below. Golf balls of Example 7 and Comparative Example 1 were obtained in the same manner as in Example 1 except that the golf balls shown in Table 2 were used.

[Flying Distance Test] A swing machine (manufactured by Trutemper Co., Ltd.) was equipped with a driver (“XXIO W # 1” described above) equipped with a metal head. Then, the machine conditions were set so that the head speed was 45 m / sec, the golf ball was hit, and the initial spin speed and flight distance (distance from the launch point to the drop point) were measured. Two
The average values of 0 measurements are shown in Tables 1 and 2 below.

[Evaluation of shot feeling] Ten high-class golf players were provided with a driver equipped with a metal head to hit a golf ball. Then, the shot feeling was evaluated. 1
Among the 0 golfers, those who answered that they had a good shot feeling were 8 or more, "◎", those with 6 or more and 7 or less were "○", and those with 4 or more and 5 or less were " “A” was given, and three or less persons were given as “X”. The results are shown in Tables 1 and 2 below.

[0070]

[Table 1]

[0071]

[Table 2]

As is clear from Tables 1 and 2, the golf balls of the respective examples are excellent in both flight performance and shot feeling. From these evaluation results, the superiority of the present invention is clear.

[0073]

As described above, the golf ball of the present invention is excellent in both flight performance and shot feeling. This golf ball gives a golfer hitting the golf ball a refreshing feeling and contributes to an improvement in the score.

[Brief description of drawings]

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

FIG. 2 is an enlarged plan view showing the golf ball of FIG.

FIG. 3 is an enlarged front view showing the golf ball of FIG.

FIG. 4 is a schematic cross-sectional view showing a part of the golf ball of FIG.

[Explanation of symbols]

1 ... golf ball 2 ... core 3 ... Middle layer 4 ... Cover 5 ... Dimples A ... A dimple B ... B dimple C ... C dimple D ... D dimple

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Satoshi Iwami             3-6-9 Wakihama-cho, Chuo-ku, Kobe-shi, Hyogo               Sumitomo Rubber Industries, Ltd.

Claims (8)

[Claims] 1. A spherical core made of solid rubber, an intermediate layer positioned outside the core, and a cover laminated on the intermediate layer, wherein the surface hardness of the intermediate layer with respect to the surface hardness Hr of the core. The ratio of Hm (Hm / Hr) is 0.95 or more and 1.20 or less, the specific gravity Dc of the cover is 1.00 or more, and the ratio of the specific gravity Dm of the intermediate layer to the specific gravity Dc of the cover (Dm
/ Dc) is 1.02 or more and 1.15 or less, a large number of dimples are formed on the surface of the cover, and the total volume V of these dimples is 420 mm ³ or more and 58 or more.
A golf ball having a diameter of 0 mm ³ or less. 2. The cover is made of a thermoplastic resin composition, and the thermoplastic resin composition contains titanium dioxide and barium sulfate, and the content of titanium dioxide is 1 with respect to 100 parts by mass of the base resin. The golf ball according to claim 1, wherein the content of barium sulfate is 2 parts by mass or more and 5 parts by mass or less, and the compounding amount of barium sulfate is 2 parts by mass or more and 10 parts by mass or less based on 100 parts by mass of the base resin. 3. The golf ball according to claim 2, wherein the cover has a specific gravity Dc of 1.05 or more. 4. The intermediate layer is made of a thermoplastic resin composition, the thermoplastic resin composition contains titanium dioxide and barium sulfate, and the compounding amount of titanium dioxide is 100 parts by mass of the base resin. It is 1 mass part or more and 5 mass parts or less, and the compounding quantity of barium sulfate is 5 mass parts or more and 20 mass parts or less with respect to 100 mass parts of base resin. Golf ball. 5. The golf ball according to claim 4, wherein the intermediate layer has a specific gravity Dm of 1.03 or more. 6. The golf ball according to claim 1, which has a moment of inertia of 81 or more. 7. The golf ball according to claim 6, which has a moment of inertia of 82 or more. 8. From a state where an initial load of 98 N is applied, 12
The golf ball according to any one of claims 1 to 7, wherein the amount of compressive deformation of the core until a final load of 74 N is applied is 4.20 mm or more and 4.45 mm or less.