JP2022041841A - Multi-piece solid golf ball - Google Patents

Abstract

To provide a golf ball which can obtain a good carry on shots with hybrid and iron clubs, is receptive to spin well in a short game, has a soft feel at impact on all shots, and is useful to amateur golfers.SOLUTION: A golf ball G having a core 1, an envelope layer 2, an intermediate layer 3, and a cover 4, has a specific hardness distribution. Resin materials of at least one of the envelope layer 2 and the intermediate layer 3 contain a high-acid ionomer. A hardness relationship (the Shore C hardness) between a surface hardness of central hardness of the core 1 and an envelope layer encasing sphere and surface hardness of an intermediate layer encasing sphere satisfy the following two formulas. Surface hardness of the envelope layer encasing sphere<surface hardness of the intermediate layer encasing sphere. Surface hardness of the intermediate layer encasing sphere-center hardness (the Shore C hardness) of the core≥40. The deflection quantity (mm) when a load up to a prescribed load is applied to the golf ball G is 2.7 or more.SELECTED DRAWING: Figure 1

Description

The present invention relates to a multi-piece solid golf ball consisting of four or more layers including a core, a surrounding layer, an intermediate layer and a cover.

Many ideas have been made to design the ball into a multi-layered structure, and many balls have been developed that satisfy not only professional golfers but also advanced and intermediate amateur golfers. For example, a functional multi-piece solid golf ball in which the surface hardness of each layer of the core, the surrounding layer, the intermediate layer, and the cover (outermost layer) is optimized is widespread. In addition, focusing on the core hardness distribution that occupies most of the volume of the ball, we have proposed several technologies to provide high-performance golf balls for professionals and intermediate-advanced players by designing various forms of core internal hardness. Has been done.

Examples of such technical documents include the following Patent Documents 1 to 14. These golf balls relate to a golf ball having a multi-layer structure of four or more layers, and the surface hardness of each layer of the core, the surrounding layer, the intermediate layer and the cover (outermost layer), the relationship between the ball diameter and the core diameter, and the core hardness distribution. It is a patent document focusing on such things.

However, the golf ball proposed above still has room for improvement in optimizing the hardness distribution of the core and the thickness relationship with each layer. That is, the golf ball proposed above did not provide a sufficiently satisfactory flight distance for an amateur user whose head speed is not high, especially for a flight at a full shot with a utility or an iron. In addition, among the golf balls proposed above, if an attempt is made to obtain superior flight distance performance even at the time of iron shot, it is not possible to exert sufficiently high spin performance in terms of spin performance when approaching, and the game Some golf balls are not highly sexual or have a poor feel on a full shot. Therefore, as a golf ball for amateur golfers, the flight at full shots is improved with utilities and irons, a soft and good feel is obtained at all full shots, and a golf ball with high short game characteristics is proposed and developed. Is desired.

Japanese Unexamined Patent Publication No. 2006-326301 Japanese Unexamined Patent Publication No. 2007-319667 Japanese Unexamined Patent Publication No. 2007-330789 Japanese Unexamined Patent Publication No. 2008-08077 Japanese Unexamined Patent Publication No. 2008-149131 Japanese Unexamined Patent Publication No. 2009-034507 Japanese Unexamined Patent Publication No. 2009-095358 Japanese Unexamined Patent Publication No. 2009-095364 Japanese Unexamined Patent Publication No. 2009-095365 Japanese Unexamined Patent Publication No. 2009-095369 Japanese Unexamined Patent Publication No. 2012-071163 Japanese Unexamined Patent Publication No. 2016-101254 Japanese Unexamined Patent Publication No. 2016-101256 Japanese Unexamined Patent Publication No. 2016-116627

The present invention has been made in view of the above circumstances, and as a golf ball for amateur golfers, a superior flight distance can be obtained in a full shot with a utility or an iron, and the spin performance at the time of approach is excellent, which is most suitable for a short game. Moreover, it is an object of the present invention to provide a golf ball that is soft and gives a good hit feeling on all shots.

As a result of diligent studies to achieve the above object, the present inventor has formed a golf ball provided with a core, a surrounding layer, an intermediate layer and a cover softly by using a urethane resin material as a cover material. The surrounding layer is softer than the intermediate layer, and each layer is formed so that the resin material of at least one of the surrounding layer and the intermediate layer contains a high acid content ionomer, and in the design of the core hardness distribution and the hardness gradient, the core radius By determining the hardness gradient between two points at positions 2 mm apart from the midpoint toward the inside and outside, and optimizing these hardness gradients for the entire core, the spin at the time of a full shot is higher than that of a conventional golf ball. The amount can be suppressed, the flight distance is improved, especially good flight distance can be obtained with utilities and iron full shots, spin is often applied in short games, and a soft feel can be given. Furthermore, it was found that the durability against repeated impacts was also good. For amateur golfers who do not have a high head speed, an excellent flight distance can be obtained even at full shots of utilities and irons, a high level of spin performance when approaching can be maintained, and a golf ball with high game characteristics is finished. This is what led to the present invention.

Therefore, the present invention provides the following multi-piece solid golf balls.
1. 1. It comprises a core, a surrounding layer, an intermediate layer and a cover, the core is formed into one layer by a rubber composition, the surrounding layer is formed into one layer or a plurality of layers by a resin material, and the intermediate layer and the cover are each made of resin. A multi-piece solid golf ball formed in one layer by a material, the core diameter is 35.1 to 41.3 mm, and in the hardness distribution of the core, the shore C hardness at the center of the core is Cc, and the center of the core. The shore C hardness of the midpoint M between the surface and the surface is Cm, and the shore C hardness at the positions of 2 mm, 4 mm, and 6 mm inward from the midpoint M is Cm-2, Cm-4, Cm-6, and outward from the center M, respectively. When the shore C hardness at the positions of 2 mm, 4 mm, and 6 mm is Cm + 2, Cm + 4, Cm + 6, respectively, and the shore C hardness on the surface of the core is Cs, the following areas A to F
・ Area A: 1/2 x 2 x (Cm-4-Cm-6)
・ Area B: 1/2 x 2 x (Cm-2-Cm-4)
・ Area C: 1/2 x 2 x (Cm-Cm-2)
・ Area D: 1/2 x 2 x (Cm + 2-Cm)
・ Area E: 1/2 x 2 x (Cm + 4-Cm + 2)
・ Area F: 1/2 x 2 x (Cm + 6-Cm + 4)
The value of (Area E + Area F)-(Area A + Area B) is 1.0 or more, and Area A <Area C <(Area E + Area F), and at least one of the surrounding layer and the intermediate layer. The resin material contains an ionomer having a high acid content, and the central hardness of the core, the surface hardness of the sphere (surrounding layer-coated sphere) in which the core is coated with the surrounding layer, and the surrounding layer-coated sphere are coated with the intermediate layer. The hardness relationship (surface hardness means shore C hardness) with the surface hardness of the formed sphere (intermediate layer coated sphere) is the following formulas (1) and (2).
Surface hardness of the surrounding layer-coated sphere <Surface hardness of the intermediate layer-coated sphere ... (1)
Surface hardness of intermediate layer coated sphere-Center hardness of core (Shore C hardness) ≧ 40 ・ ・ ・ (2)
The multi-piece solid golf is characterized in that the amount of deflection (mm) from the initial load of 98 N (10 kgf) to the final load of 1,275 N (130 kgf) is 2.7 mm or more. ball.
2. 2. Regarding the thickness relationship of each layer, the following formula (3)
Cover thickness <Intermediate layer thickness <Envelopment layer thickness ... (3)
The multi-piece solid golf ball according to 1 above.
3. 3. About the surface hardness of the core or each coated sphere
Core surface hardness <Surface hardness of surrounding layer-coated sphere <Surface hardness of intermediate layer-coated sphere> Ball surface hardness ・ ・ ・ (1')
The multi-piece solid golf ball according to 1 or 2 above.
4. The multi-piece solid golf ball according to any one of 1 to 3 above, wherein the material hardness of the intermediate layer is 64 or more in shore D hardness.
5. In the above formula (2), the multi-piece solid according to any one of 1 to 4 above, wherein the upper limit of the value of (surface hardness of intermediate layer coated sphere)-(center hardness of core) is 53 or less in shore C hardness. Golf ball.
6. The multi-piece solid golf ball according to any one of 1 to 5 above, wherein the surrounding layer is a single layer.
7. The multi-piece solid golf ball according to any one of 1 to 6 above, wherein the core surface hardness (Cs) -core center hardness (Cc) is 20 or more.
8. For the areas A to F of the core hardness distribution, the following formula (area D + area E)-(area B + area C) ≧ 1.0
The multi-piece solid golf ball according to any one of 1 to 7 above.
9. The multi-piece solid golf ball according to any one of 1 to 8 above, wherein the resin material of the intermediate layer contains an ionomer having a high acid content.
10. It comprises a core, a surrounding layer, an intermediate layer and a cover, the core is formed into one layer by a rubber composition, the surrounding layer is formed into one layer or a plurality of layers by a resin material, and the intermediate layer and the cover are each made of resin. A multi-piece solid golf ball formed in one layer by a material, the core diameter is 35.1 to 41.3 mm, and in the hardness distribution of the core, the shore C hardness at the center of the core is Cc, and the center of the core. The shore C hardness of the midpoint M between the surface and the surface is Cm, and the shore C hardness at the positions of 2 mm, 4 mm, and 6 mm inward from the midpoint M is Cm-2, Cm-4, Cm-6, and outward from the center M, respectively. When the shore C hardness at the positions of 2 mm, 4 mm, and 6 mm is Cm + 2, Cm + 4, Cm + 6, respectively, and the shore C hardness on the surface of the core is Cs, the following areas A to F
・ Area A: 1/2 x 2 x (Cm-4-Cm-6)
・ Area B: 1/2 x 2 x (Cm-2-Cm-4)
・ Area C: 1/2 x 2 x (Cm-Cm-2)
・ Area D: 1/2 x 2 x (Cm + 2-Cm)
・ Area E: 1/2 x 2 x (Cm + 4-Cm + 2)
・ Area F: 1/2 x 2 x (Cm + 6-Cm + 4)
The value of (area E + area F)-(area A + area B) is 1.0 or more, the area A <area C <(area E + area F), and the material hardness of the intermediate layer is the shore D hardness. 65 or more, the center hardness of the core, the surface hardness of the sphere whose core is coated with the surrounding layer (surrounding layer-coated sphere), and the sphere whose surrounding layer-coated sphere is coated with the intermediate layer (intermediate layer-coated sphere). The hardness relationship with the surface hardness (surface hardness means shore C hardness) is the following formulas (1) and (2).
Surface hardness of the surrounding layer-coated sphere <Surface hardness of the intermediate layer-coated sphere ... (1)
Surface hardness of intermediate layer coated sphere-Center hardness of core (Shore C hardness) ≧ 40 ・ ・ ・ (2)
The multi-piece solid golf is characterized in that the amount of deflection (mm) from the initial load of 98 N (10 kgf) to the final load of 1,275 N (130 kgf) is 2.7 mm or more. ball.

According to the multi-piece solid golf ball of the present invention, a good flight distance can be obtained with a utility and an iron full shot, a good spin is applied in a short game, and a soft feel can be obtained in all shots. Furthermore, it is also excellent in repeated impact durability. In particular, it is a multi-layered golf ball useful as a golf ball for amateur golfers.

It is a schematic sectional drawing of the multi-piece solid golf ball which is one Embodiment of this invention. In order to explain the area A to F of the core hardness distribution, it is the schematic which explained using the core hardness distribution data of Example 2. It is a graph which shows the core hardness distribution of Examples 1 to 4 and Comparative Examples 3 and 8. It is a graph which shows the core hardness distribution of Comparative Examples 1, 2 and 4-7. It is a top view which shows the mode (pattern) of the dimple common to each Example and each comparative example.

Hereinafter, the present invention will be described in more detail.
The multi-piece solid golf ball of the present invention has a core, a surrounding layer, an intermediate layer and a cover, and an example thereof is shown in FIG. The golf ball G shown in FIG. 1 has a core 1, a surrounding layer 2 covering the core 1, an intermediate layer 3 covering the surrounding layer, and a cover 4 covering the intermediate layer 3. .. The cover 4 is located at the outermost layer in the layer structure of the golf ball except for the paint layer. In the present invention, the surrounding layer may be a single layer or may be formed into two or more layers. A large number of dimples D are usually formed on the surface of the cover (outermost layer) 4 in order to improve the aerodynamic characteristics. Further, although not particularly shown, a paint layer 5 is usually formed on the surface of the cover 4. Hereinafter, each of the above layers will be described in detail.

As the core material, a rubber material is used as the main material. Specifically, a rubber composition can be prepared by using a base rubber as a main component and blending it with a cocrosslinking agent, an organic peroxide, an inert filler, an organic sulfur compound and the like. It is preferable to use polybutadiene as the base rubber.

As the type of polybutadiene, a commercially available product can be used, and examples thereof include BR01, BR51, and BR730 (manufactured by JSR Corporation). The proportion of polybudaziene in the base rubber is preferably 60% by mass or more, more preferably 80% by mass or more. In addition to the polybutadiene, other rubber components may be added to the base rubber as long as the effects of the present invention are not impaired. Examples of the rubber component other than the polybutadiene include polybutadiene other than the polybutadiene and other diene rubbers such as styrene butadiene rubber, natural rubber, isoprene rubber, and ethylene propylene diene rubber.

Examples of the co-crosslinking agent include unsaturated carboxylic acids and metal salts of unsaturated carboxylic acids. Specific examples of the unsaturated carboxylic acid include acrylic acid, methacrylic acid, maleic acid, fumaric acid and the like, and acrylic acid and methacrylic acid are particularly preferably used. The metal salt of the unsaturated carboxylic acid is not particularly limited, and examples thereof include those obtained by neutralizing the unsaturated carboxylic acid with a desired metal ion. Specific examples thereof include zinc salts such as methacrylic acid and acrylic acid, magnesium salts and the like, and zinc acrylate is particularly preferably used.

The unsaturated carboxylic acid and / or a metal salt thereof is usually 5 parts by mass or more, preferably 9 parts by mass or more, more preferably 13 parts by mass or more, and usually 60 parts by mass as an upper limit with respect to 100 parts by mass of the base material rubber. Hereinafter, it is preferably blended in an amount of 50 parts by mass or less, more preferably 40 parts by mass or less. If the blending amount is too large, it may become too hard and the feel of hitting may be unbearable, and if the blending amount is too small, the resilience may decrease.

Commercially available products can be used as the organic peroxide, for example, Park Mill D (manufactured by NOF Corporation), Perhexa C-40, Perhexa 3M (manufactured by NOF Corporation), Luperco 231XL (manufactured by NOF CORPORATION). ) And the like can be preferably used. These may be used alone or in combination of two or more. The blending amount of the organic peroxide is preferably 0.1 part by mass or more, more preferably 0.3 part by mass or more, and further preferably 0.5 part by mass or more with respect to 100 parts by mass of the base material rubber. As the upper limit, preferably 5 parts by mass or less, more preferably 4 parts by mass or less, still more preferably 3 parts by mass or less, and most preferably 2.5 parts by mass or less. If the blending amount is too large or too small, it may not be possible to obtain a suitable feel, durability and resilience.

In addition, examples of the compounding agent to be blended in the base rubber include an inert filler, and for example, zinc oxide, barium sulfate, calcium carbonate and the like can be preferably used. These may be used alone or in combination of two or more. The blending amount of the inert filler is preferably 1 part by mass or more, more preferably 5 parts by mass or more, and the upper limit is preferably 50 parts by mass or less, more preferably 40 parts by mass or less with respect to 100 parts by mass of the base rubber. More preferably, it is 36 parts by mass or less. If the blending amount is too large or too small, it may not be possible to obtain an appropriate mass and suitable resilience.

Further, an anti-aging agent can be added as needed. For example, commercially available products include Nocrack NS-6, NS-30 (manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.), and Yoshinox 425 (Yoshitomi Pharmaceutical Co., Ltd.). ) Made) etc. These may be used alone or in combination of two or more.

The blending amount of the anti-aging agent is preferably 0 parts by mass or more, more preferably 0.05 parts by mass or more, particularly preferably 0.1 parts by mass or more, and preferably 3 as an upper limit with respect to 100 parts by mass of the base material rubber. It is not more than parts by mass, more preferably 2 parts by mass or less, particularly preferably 1 part by mass or less, and most preferably 0.5 part by mass or less. If the blending amount is too large or too small, suitable resilience and durability may not be obtained.

In addition, an organic sulfur compound can be added to the core in order to impart good resilience. The organic sulfur compound is not particularly limited as long as it can improve the resilience of the golf ball, and examples thereof include thiophenols, thionaphthols, halogenated thiophenols, and metal salts thereof. More specifically, pentachlorothiophenol, pentafluorothiophenol, pentabromothiophenol, parachlorothiophenol, zinc salt of pentachlorothiophenol, zinc salt of pentafluorothiophenol, zinc salt of pentabromothiophenol, Zinc salt of parachlorothiophenol, diphenylpolysulfide having 2 to 4 sulfur numbers, dibenzylpolysulfide, dibenzoylpolysulfide, dibenzothiazoylpolysulfide, dithiobenzoylpolysulfide and the like can be mentioned, and the zinc salt of pentachlorothiophenol is particularly preferable. Used for. The blending amount of the organic sulfur compound is preferably 0 parts by mass or more, more preferably 0.05 parts by mass or more, still more preferably 0.1 parts by mass or more, and preferably an upper limit with respect to 100 parts by mass of the base material rubber. It is recommended that the amount is 5 parts by mass or less, more preferably 3 parts by mass or less, still more preferably 2.5 parts by mass or less. If the blending amount is too large, the effect of improving the resilience (particularly, the impact by W # 1) cannot be expected any more, and the core may become too soft or the feel of hitting may be deteriorated. On the other hand, if the blending amount is too small, the effect of improving the resilience cannot be expected.

More specifically, by directly blending water (a material containing water) with the above-mentioned core material, decomposition of organic peroxide in the core blend can be promoted. Further, it is known that the decomposition efficiency of an organic peroxide in a rubber composition for a core changes depending on the temperature, and the decomposition efficiency increases as the temperature becomes higher than a certain temperature. If the temperature is too high, the amount of decomposed radicals will be too large, and the radicals will be recombined or inactivated. As a result, the number of radicals that work effectively for cross-linking is reduced. Here, when decomposition heat is generated by the decomposition of organic peroxide during core vulcanization, the temperature near the core surface is maintained at about the same level as the temperature of the vulcanization mold, but the vicinity of the core center is outside. Since the heat of decomposition of the organic peroxide decomposed from the above is accumulated, the temperature becomes considerably higher than the mold temperature. When water (a material containing water) is directly mixed with the core, water has a function of promoting the decomposition of organic peroxides, so that the radical reaction as described above can be changed at the core center and the core surface. can. That is, in the vicinity of the core center, the decomposition of organic peroxide is further promoted, and the inactivation of radicals is further promoted, so that the amount of effective radicals is further reduced. And can obtain cores having different dynamic viscoelastic properties at the center of the core.

The water to be blended in the above core material is not particularly limited and may be distilled water or tap water, but in particular, it is preferably used distilled water containing no impurities. Ru. The amount of water to be blended is preferably 0.1 part by mass or more, more preferably 0.3 part by mass or more, and the upper limit is preferably 5 parts by mass or less with respect to 100 parts by mass of the base rubber. It is more preferably 4 parts by mass or less.

The core can be produced by vulcanizing and curing a rubber composition containing each of the above components. For example, kneading is performed using a kneading machine such as a Banbury mixer or a roll, and compression molding or injection molding is performed using a core mold. The molded product can be cured and produced by appropriately heating the molded product at 200 ° C., preferably 140 to 180 ° C. for 10 to 40 minutes.

Further, the core can be formed in a single layer.

The diameter of the core is usually 35.1 to 41.3 mm, preferably 35.3 mm or more, more preferably 35.4 mm or more, and the upper limit is preferably 39.2 mm or less, more preferably 38. It is 3 mm or less. If the diameter of the core is too small, the initial velocity of the ball may be low, the deflection hardness of the entire ball may be hard, and the spin at the time of a full shot may increase, making it impossible to obtain the desired flight distance. On the other hand, if the diameter of the core is too large, the spin at the time of a full shot may increase and the target flight distance may not be obtained, or the cracking durability when repeatedly hit may be deteriorated.

The amount of deflection (mm) from the initial load of 98 N (10 kgf) to the final load of 1,275 N (130 kgf) is not particularly limited, but is preferably 3.6 mm or more, more preferably 3. It is 8.8 mm or more, more preferably 4.0 mm or more, and the upper limit value is preferably 6.0 mm or less, more preferably 5.7 mm or less, still more preferably 5.4 mm or less. If the amount of deflection of the core is too small, that is, if the core is too hard, the spin of the ball may increase too much and the ball may not fly or the feel of hitting may become too hard. On the other hand, if the amount of deflection of the core is too large, that is, if the core is too soft, the repulsiveness of the ball becomes too low to fly, the feel of hitting becomes too soft, or the cracking durability at the time of repeated hitting deteriorates. Sometimes.

Next, the hardness distribution of the core will be described. The hardness of the core described below means the shore C hardness. This shore C hardness is a hardness value measured by a shore C hardness tester conforming to the ASTM D2240 standard.

The central hardness (Cc) of the core is not particularly limited, but can be preferably 45 or more, more preferably 47 or more, still more preferably 48 or more. Further, the upper limit thereof is not particularly limited, but may be preferably 61 or less, more preferably 59 or less, and further preferably 57 or less. If this value is too large, the spin may increase and the target flight distance may not be obtained, or the feel of hitting may become too hard. On the other hand, if the above value is too small, the repulsion may be low and the target flight distance may not be obtained, or the cracking durability when repeatedly hit may be deteriorated.

The position hardness (Cm-6) of 6 mm inward from the position M between the center and the surface of the core (hereinafter, also referred to as “intermediate position M”) is not particularly limited, but is preferably 45 or more. It can be more preferably 47 or more, further preferably 49 or more, and the upper limit thereof is not particularly limited, and can be preferably 61 or less, more preferably 59 or less, still more preferably 57 or less. Deviating from these hardnesses may lead to the same disadvantageous results as described in Core Hardness (Cc) above.

Inside from the middle position M of the core toward the center of the core (hereinafter, simply referred to as "inside")
The position hardness (Cm-4) of is not particularly limited, but may be preferably 48 or more, more preferably 50 or more, still more preferably 52 or more, and the upper limit thereof is not particularly limited. It can be preferably 62 or less, more preferably 60 or less, still more preferably 58 or less. Deviating from these hardnesses may lead to the same disadvantageous results as described in Core Hardness (Cc) above.

The position hardness (Cm-2) of 2 mm inward from the intermediate position M of the core is not particularly limited, but can be preferably 50 or more, more preferably 52 or more, still more preferably 54 or more. Further, the upper limit thereof is not particularly limited, and may be preferably 64 or less, more preferably 62 or less, and further preferably 60 or less. Deviating from these hardnesses may lead to the same disadvantageous results as described in Core Hardness (Cc) above.

The cross-sectional hardness (Cm) of the intermediate position M of the core is not particularly limited, but may be preferably 54 or more, more preferably 56 or more, still more preferably 58 or more. Further, the upper limit thereof is not particularly limited, but may be preferably 68 or less, more preferably 66 or less, and further preferably 64 or less. Deviating from these hardnesses may lead to the same disadvantageous results as described in Core Hardness (Cc) above.

The position hardness (Cm + 2) of 2 mm outward (hereinafter, simply referred to as “outside”) from the intermediate position M of the core toward the core surface is not particularly limited, but is preferably 57 or more. It is preferably 60 or more, more preferably 62 or more, and the upper limit thereof is not particularly limited, and is preferably 74 or less, more preferably 71 or less, still more preferably 69 or less. If this value is too large, the cracking durability when repeatedly hit may be deteriorated, or the hitting feeling may become too hard. On the other hand, if the above value is too small, the repulsion may be too low, or the spin at the time of a full shot may increase and the target flight distance may not be obtained.

The position hardness (Cm + 4) of 4 mm outward from the intermediate position M of the core is not particularly limited, but may be preferably 62 or more, more preferably 64 or more, still more preferably 66 or more. Further, the upper limit thereof is not particularly limited, and may be preferably 77 or less, more preferably 76 or less, and further preferably 74 or less. If these hardnesses are deviated, the same disadvantageous results as described for the position hardness (Cm + 2) 2 mm away from the intermediate position M of the core may occur.

The position hardness (Cm + 6) of 6 mm outward from the intermediate position M of the core is not particularly limited, but may be preferably 63 or more, more preferably 65 or more, still more preferably 67 or more. Further, the upper limit thereof is not particularly limited, and may be preferably 81 or less, more preferably 79 or less, and further preferably 77 or less. If these hardnesses are deviated, the same disadvantageous results as described for the position hardness (Cm + 2) 2 mm away from the intermediate position M of the core may occur.

The surface hardness (Cs) of the core is not particularly limited, but may be preferably 69 or more, more preferably 71 or more, and further preferably 73 or more. Further, the upper limit thereof is not particularly limited, but may be preferably 87 or less, more preferably 85 or less, and further preferably 83 or less. If this value is too large, the cracking durability when repeatedly hit may be deteriorated, or the hitting feeling may become too hard. On the other hand, if the above value is too small, the repulsion may be too low, or the spin at the time of a full shot may increase and the target flight distance may not be obtained.

In order to increase the hardness difference between the inside and outside of the core, the hardness difference between the center and the surface of the core is optimized. That is, the value of the core surface hardness (Cs) -core center C hardness (Cc) is preferably 20 or more, more preferably 22 or more, and further preferably 24 or more in terms of shore C hardness. Further, the upper limit thereof is not particularly limited, but may be preferably 35 or less, more preferably 30 or less, and further preferably 28 or less. If the difference in hardness is too small, the spin at the time of a full shot increases, and the target flight distance may not be obtained. On the other hand, if the above-mentioned hardness difference is too large, the cracking durability when repeatedly hit may be deteriorated, or the actual hitting initial velocity may be lowered and the target flight distance may not be obtained. The central hardness (Cc) means the hardness measured at the center of the cross section obtained by cutting the core in half (passing through the center), and the surface hardness (Cs) is the surface of the core. It means the hardness measured in (spherical surface).

In the core hardness distribution in the present invention, the following areas A to F
・ Area A: 1/2 x 2 x (Cm-4-Cm-6)
・ Area B: 1/2 x 2 x (Cm-2-Cm-4)
・ Area C: 1/2 x 2 x (Cm-Cm-2)
・ Area D: 1/2 x 2 x (Cm + 2-Cm)
・ Area E: 1/2 x 2 x (Cm + 4-Cm + 2)
・ Area F: 1/2 x 2 x (Cm + 6-Cm + 4)
The value of (Area E + Area F)-(Area A + Area B) is 1.0 or more. The value of (Area E + Area F)-(Area A + Area B) is preferably 2.0 or more, more preferably 4.0 or more, and the upper limit value is preferably 20.0 or less, more preferably 16. It is 0.0 or less, more preferably 12.0 or less. If this value is too large, the cracking durability when repeatedly hit may deteriorate. On the other hand, if the above value becomes too small, the spin at the time of a full shot increases, and the target flight distance may not be obtained. Note that FIG. 2 shows a schematic diagram illustrating the areas A to F using the core hardness distribution data of Example 2. As described above, the areas A to F are the areas of each triangle having the difference in each specific distance as the base and the difference in hardness at each position as the height.

Regarding the above areas B to E, the value of (area D + area E)-(area B + area C) is not particularly limited, but is preferably 1.0 or more, more preferably 2.0 or more, still more preferably 4.0. As described above, the upper limit value is preferably 20.0 or less, more preferably 16.0 or less, and further preferably 12.0 or less. If this value is too large, the cracking durability when repeatedly hit may deteriorate. On the other hand, if the above value becomes too small, the spin at the time of a full shot increases, and the target flight distance may not be obtained.

Regarding the areas A to F of the core hardness distribution, the following conditions area A <area C <(area E + area F)
It is a requirement that the condition is satisfied, and preferably, the following conditions area A <area B <area C <(area E + area F)
Satisfying, more preferably
Area A <Area B <Area C <Area D <(Area E + Area F)
To meet. If this relationship is not satisfied, the spin will increase when a full shot is made with a utility or iron, and the target flight distance may not be obtained.

The material hardness of the surrounding layer is not particularly limited, but the shore D hardness is preferably 47 or more, more preferably 49 or more, still more preferably 51 or more, and the upper limit value is preferably 62 or less, more preferably 60. Below, it is more preferably 57 or less. The surface hardness of the sphere whose core is covered with the surrounding layer (the surrounding layer-covered sphere) is the shore D hardness, preferably 53 or more, more preferably 55 or more, still more preferably 57 or more, and the upper limit is set as an upper limit. It is preferably 68 or less, more preferably 66 or less, and even more preferably 63 or less. If the material hardness and surface hardness of these surrounding layers are too softer than the above range, too much spin may be applied at the time of a full shot, or the initial velocity may be lowered and the flight distance may not be obtained. On the other hand, if the above-mentioned material hardness and surface hardness are too hard, the feel of hitting becomes hard, the cracking durability when repeatedly hit is deteriorated, and the spin at the time of a full shot with a utility or an iron increases and the flight distance increases. It may not come out.

The surface hardness of the surrounding layer-coated sphere is set lower than the surface hardness of the intermediate layer-coated sphere. If the surface hardness of the surrounding layer-coated sphere is higher than that of the intermediate layer-coated sphere, the spin at the time of a full shot increases, and the flight distance may not be obtained or the feel of hitting may be deteriorated.

The material hardness of the surrounding layer is preferably 72 or more, more preferably 75 or more, still more preferably 78 or more, and the upper limit is preferably 92 or less, more preferably 90 or less, in terms of shore C hardness. More preferably, it is 88 or less. The surface hardness of the surrounding layer-coated sphere is preferably 80 or more, more preferably 83 or more, still more preferably 86 or more, and the upper limit is preferably 97 or less, more preferably 97 or more, in terms of shore C hardness. It is 95 or less, more preferably 93 or less.

The thickness of the surrounding layer is preferably 0.8 mm or more, more preferably 1.0 mm or more, still more preferably 1.2 mm or more. On the other hand, the upper limit of the thickness of the surrounding layer is preferably 2.0 mm or less, more preferably 1.8 mm or less, and further preferably 1.7 mm or less. If the thickness of the siege layer is too thin, the low spin effect when a full shot with a utility or iron is not sufficient, and the target flight distance may not be obtained. On the other hand, if the surrounding layer is too thick, the initial velocity of the entire ball becomes low, the actual initial velocity becomes too low, and the target flight distance may not be obtained. Further, it is preferable that the surrounding layer is formed thicker than the intermediate layer described later, or both layers are preferably formed to have the same thickness, and more preferably, the surrounding layer is formed thicker than the intermediate layer.

The material of the surrounding layer is not particularly limited, but various thermoplastic resin materials can be preferably used, and examples of particularly preferable materials include
The following components (A) to (D),
(A-1) A metal ion neutralized product of an olefin-unsaturated carboxylic acid binary random copolymer and / or an olefin-unsaturated carboxylic acid binary random copolymer.
(A-2) Metal ion neutralized product of olefin-unsaturated carboxylic acid-unsaturated carboxylic acid ester ternary random copolymer and / or olefin-unsaturated carboxylic acid-unsaturated carboxylic acid ester ternary random copolymer And (A) base resin blended so as to have a mass ratio of 100: 0 to 0: 100, and
(B) With respect to 100 parts by mass of the resin component blended with the non-ionomer thermoplastic elastomer so as to have a mass ratio of 100: 0 to 50:50.
(C) Fatty acid having a molecular weight of 228 to 1500 and / or a derivative thereof 5 to 120 parts by mass.
(D) A resin composition comprising 0.1 to 17 parts by mass of a basic inorganic metal compound capable of neutralizing an unneutralized acid group in the component (A) and the component (C) as an essential component. It can be exemplified.

As for the components (A) to (D), for example, the resin material (A) to (D) components of the intermediate layer described in JP-A-2010-253268 can be preferably adopted.

Examples of the non-ionomer thermoplastic elastomer include polyolefin-based elastomers (including polyolefins and metallocene polyolefins), polystyrene-based elastomers, diene-based polymers, polyacrylate-based polymers, polyamide-based elastomers, polyurethane-based elastomers, polyester-based elastomers, and polyacetals. In particular, a thermoplastic polyether ester elastomer such as a thermoplastic polyether ester elastomer can be mentioned.

Further, as the resin material of the surrounding layer, ionomer having a high acid content can be contained. In the present invention, the ionomer having a high acid content means an ionomer resin having an unsaturated carboxylic acid content of 16% by mass or more. The same meaning applies to ionomers having a high acid content used as a resin material for an intermediate layer, which will be described later.

The content (acid content) of the unsaturated carboxylic acid contained in the high acid content ionomer resin is usually 16% by mass or more, preferably 17% by mass or more, more preferably 18% by mass or more, and the upper limit value is It is preferably 22% by mass or less, more preferably 21% by mass or less, and further preferably 20% by mass or less. If this value is too small, the spin will increase during a full shot with a utility or iron, and the target flight distance may not be obtained. On the contrary, if the above value is too large, the feel of hitting may become too hard, or the cracking durability at the time of repeated hitting may deteriorate.

Further, the high acid content ionomer resin is preferably 10% by mass or more, more preferably 30% by mass or more, still more preferably 60% by mass or more with respect to 100% by mass of the resin material. If the amount of the above-mentioned high acid content ionomer resin is too small, the spin may increase during a full shot with a utility or an iron, and the flight distance may not be obtained.

Any additive can be appropriately added to the above resin material depending on the intended use. For example, various additives such as pigments, dispersants, antiaging agents, ultraviolet absorbers, and light stabilizers can be added.

Next, the intermediate layer will be described.
The material hardness of the intermediate layer is not particularly limited, but the shore D hardness is preferably 64 or more, more preferably 65 or more, still more preferably 66 or more, and the upper limit value is preferably 75 or less, more preferably 70. Below, it is more preferably 68 or less. The surface hardness of the sphere (intermediate layer-coated sphere) in which the outer surrounding layer-coated sphere is coated with the intermediate layer is the shore D hardness, preferably 68 or more, more preferably 69 or more, still more preferably 70 or more. The upper limit is preferably 81 or less, more preferably 76 or less, still more preferably 74 or less. If the material hardness and surface hardness of these intermediate layers are too softer than the above range, too much spin may be applied at the time of a full shot, or the initial velocity may be lowered and the flight distance may not be obtained. On the other hand, if the above-mentioned material hardness and surface hardness are too hard, the cracking durability due to repeated impacts may be deteriorated, or the feel of hitting when a putter or a short approach is carried out may be too hard.

The material hardness of the intermediate layer is preferably 90 or more, more preferably 92 or more, still more preferably 93 or more, and the upper limit is preferably 100 or less, more preferably 98 or less, in terms of shore C hardness. More preferably, it is 96 or less. The surface hardness of the intermediate layer-coated sphere is preferably 95 or more, more preferably 96 or more, still more preferably 97 or more, and the upper limit is preferably 100 or less, more preferably 100 or less, in terms of shore C hardness. It is 99 or less, more preferably 98 or less.

The surface hardness of the intermediate layer-coated sphere is formed higher than the surface hardness of the ball. If the surface hardness of the ball is harder than that of the sphere coated with the intermediate layer, the cracking durability due to repeated impacts may be deteriorated, or the controllability during a short game may be deteriorated.

The thickness of the intermediate layer is preferably 0.7 mm or more, more preferably 0.8 mm or more, still more preferably 1.0 mm or more. On the other hand, the upper limit of the thickness of the intermediate layer is preferably 1.8 mm or less, more preferably 1.4 mm or less, and further preferably 1.2 mm or less. It is preferable that the thickness of the intermediate layer is thicker than that of the cover (outermost layer) described later. If the thickness of the intermediate layer deviates from the above range or is thinner than the cover, the low spin effect at the time of a full shot with a utility or an iron may be insufficient and the flight distance may not be obtained. Further, if the intermediate layer is thinner than the above range, the cracking durability at the time of repeated striking and the durability at a low temperature may deteriorate.

As the material of the intermediate layer, various thermoplastic resins used as golf ball materials, particularly high neutralization type resin materials and ionomer resins containing the components (A) to (D) described in the material of the surrounding layer are adopted. It is preferable to do so.

Specific examples of the ionomer resin material include sodium-neutralized ionomer resin and zinc-neutralized ionomer resin, and one of these can be used alone or in combination of two or more.

Particularly preferable is an embodiment in which a zinc-neutralized ionomer resin and a sodium-neutralized ionomer resin are mixed and used as a main material. The blending ratio is 5/95 to 95/5, preferably 10/90 to 90/10, and more preferably 15/85 to 85/15 in the zinc-neutralized / sodium-neutralized type (mass ratio). If Zn-neutralized ionomers and Na-neutralized ionomers are not included in this ratio, the repulsion will be too low to obtain the desired flight, the cracking durability during repeated impacts at room temperature will deteriorate, and the temperature will be even lower. Cracking durability at (below zero) may deteriorate.

Further, as the resin material of the intermediate layer, ionomer having a high acid content can be contained. For example, among commercially available ionomer resins, a high acid content ionomer resin having an acid content of 16% by mass or more is blended with a normal ionomer resin and used. With this blend, it is possible to obtain a good flight distance by reducing the spin at the time of a full shot with a utility or an iron.

The content (acid content) of the unsaturated carboxylic acid contained in the high acid content ionomer resin is usually 16% by mass or more, preferably 17% by mass or more, more preferably 18% by mass or more, and the upper limit value is It is preferably 22% by mass or less, more preferably 21% by mass or less, and further preferably 20% by mass or less. If this value is too small, the spin will increase during a full shot with a utility or iron, and the target flight distance may not be obtained. On the contrary, if the above value is too large, the feel of hitting may become too hard, or the cracking durability at the time of repeated hitting may deteriorate.

Further, the high acid content ionomer resin is preferably 20% by mass or more, more preferably 50% by mass or more, still more preferably 60% by mass or more, and the upper limit is 100% by mass with respect to 100% by mass of the resin material. It is less than or equal to, preferably 90% by mass or less, and more preferably 85% by mass or less. If the amount of the above-mentioned high acid content ionomer resin is too small, the spin amount at the time of a full shot may increase and the flight distance may not be obtained. On the other hand, if the amount of the above-mentioned high acid content ionomer resin is too large, the repeated impact durability may deteriorate.

Any additive can be appropriately added to the intermediate layer material depending on the intended use. For example, various additives such as pigments, dispersants, antiaging agents, ultraviolet absorbers, and light stabilizers can be added. When these additives are blended, the blending amount thereof is preferably 0.1 part by mass or more, more preferably 0.5 part by mass or more, and the upper limit is preferably 10 parts by mass with respect to 100 parts by mass of the base resin. Parts or less, more preferably 4 parts by mass or less.

As for the intermediate layer material, it is preferable to polish the surface of the intermediate layer in order to increase the degree of adhesion with polyurethane, which is preferably used in the cover material described later. Further, it is preferable to apply a primer (adhesive) to the surface of the intermediate layer after the polishing treatment, or to add an adhesion reinforcing material to the material.

The specific gravity of the intermediate layer material is usually less than 1.1, preferably 0.90 to 1.05, and more preferably 0.93 to 0.99. If the ball deviates from that range, the repulsion of the entire ball may become low and the flight distance may not be obtained, or the cracking durability due to repeated hits may deteriorate.

Next, the cover (outermost layer) will be described.
The material hardness of the cover is not particularly limited, but the shore D hardness is preferably 30 or more, more preferably 35 or more, still more preferably 40 or more, and the upper limit is preferably 53 or less, more preferably 50 or less. , More preferably 47 or less. The surface hardness (ball surface hardness) of the sphere covered with the intermediate layer covering sphere is the shore D hardness, preferably 50 or more, more preferably 53 or more, still more preferably 56 or more, and the upper limit value is It is preferably 70 or less, more preferably 65 or less, still more preferably 60 or less. If the material hardness and ball surface hardness of these covers are too softer than the above range, the amount of spin increases during a full shot with a utility or an iron, and the desired flight distance may not be obtained. If the above-mentioned material hardness and surface hardness are too hard, the desired spin amount may not be applied at the time of approach, or the repeated impact durability may deteriorate.

The material hardness of the cover is preferably 50 or more, more preferably 57 or more, still more preferably 63 or more, and the upper limit is preferably 80 or less, more preferably 74 or less, and further. It is preferably 70 or less. The surface hardness of the ball is preferably 73 or more, more preferably 78 or more, still more preferably 83 or more, and the upper limit is preferably 95 or less, more preferably 92 or less, in terms of shore C hardness. More preferably, it is 90 or less.

The thickness of the cover is preferably 0.3 mm or more, more preferably 0.45 mm or more, still more preferably 0.6 mm or more. On the other hand, the upper limit of the thickness of the cover is preferably 1.2 mm or less, more preferably 0.9 mm or less, and further preferably 0.8 mm or less. If the cover is too thick, the desired flight distance may not be obtained due to insufficient repulsion or increased spin during a full shot with a utility or iron. On the other hand, if the cover is too thin, the scratch resistance may be deteriorated, or the spin may not be sufficiently applied at the time of approach, resulting in poor controllability.

As the material of the cover, various thermoplastic resins used in the cover material of golf balls can be used, but urethane resin can be preferably used from the viewpoint of controllability and scratch resistance. In particular, from the viewpoint of mass productivity of ball products, it is preferable to use mainly thermoplastic polyurethane, and more preferably, (I) thermoplastic polyurethane and (II) polyisocyanate compound as main components. It can be formed from a resin compound.

It is recommended that the total mass of the above components (I) and (II) combined is 60% or more, more preferably 70% or more, based on the total amount of the resin composition of the cover. The above components (I) and (II) will be described in detail below.

Regarding (I) thermoplastic polyurethane, the structure of the thermoplastic polyurethane consists of a soft segment made of a polymer polyol (polymeric glycol) which is a long-chain polyol and a hard segment made of a chain extender and a polyisocyanate compound. include. Here, as the long-chain polyol as a raw material, any of those conventionally used in the techniques related to thermoplastic polyurethane can be used, and the present invention is not particularly limited, but for example, a polyester polyol, a polyether polyol, and a polycarbonate polyol. , Polyester polycarbonate polyol, polyolefin-based polyol, conjugated diene polymerization-based polyol, castor oil-based polyol, silicone-based polyol, vinyl polymerization-based polyol, and the like. One type of these long-chain polyols may be used, or two or more types may be used in combination. Among these, a polyether polyol is preferable because it can synthesize a thermoplastic polyurethane having a high rebound resilience and excellent low temperature characteristics.

As the chain extender, those used in the conventional techniques for thermoplastic polyurethane can be preferably used. For example, a low molecular weight of 400 or less having two or more active hydrogen atoms capable of reacting with an isocyanate group in the molecule. It is preferably a molecular compound. Examples of the chain extender include 1,4-butylene glycol, 1,2-ethylene glycol, 1,3-butanediol, 1,6-hexanediol, 2,2-dimethyl-1,3-propanediol and the like. However, it is not limited to these. Among these, as the chain extender, an aliphatic diol having 2 to 12 carbon atoms is preferable, and 1,4-butylene glycol is more preferable.

As the polyisocyanate compound, those used in the conventional techniques for thermoplastic polyurethane can be preferably used, and there is no particular limitation. Specifically, 4,4'-diphenylmethane diisocyanate, 2,4- (or) 2,6-toluene diisocyanate, p-phenylene diisocyanate, xylylene diisocyanate, naphthylene 1,5-diisocyanate, tetramethylxylene diisocyanate, hydrogenated One or more selected from the group consisting of xylylene diisocyanate, dicyclohexamethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, norbornene diisocyanate, trimethylhexamethylene diisocyanate, and dimerate diisocyanate can be used. However, depending on the isocyanate type, it may be difficult to control the crosslinking reaction during injection molding. In the present invention, 4,4'-diphenylmethane diisocyanate, which is an aromatic diisocyanate, is most preferable from the viewpoint of the balance between the stability at the time of production and the physical characteristics developed.

As the specific component (I) of the thermoplastic polyurethane, a commercially available product can be used, and examples thereof include Pandex T8295, T8290, and T8260 (all manufactured by DC Cobestropolymer).

Although it is not an essential component, a thermoplastic elastomer other than the above-mentioned thermoplastic polyurethane can be blended with the above-mentioned components (I) and (II) as another component (III). By blending this component (III) into the resin formulation, various physical properties required for a golf ball cover material, such as further improvement of fluidity, resilience, and scratch resistance of the resin formulation, can be enhanced. ..

The composition ratios of the components (I), (II) and (III) are not particularly limited, but in order to fully exert the effects of the present invention, the mass ratios (I): (II) are used. : (III) = 100: 2 to 50: 0 to 50, more preferably (I) :( II) :( III) = 100: 2 to 30: 8 to 50 (mass ratio). It is to be.

Further, various additives other than the components constituting the above-mentioned thermoplastic polyurethane can be added to the above-mentioned resin formulation, if necessary, such as pigments, dispersants, antioxidants, and light-resistant stabilizers. , Ultraviolet absorber, mold release agent and the like can be appropriately blended.

The method for manufacturing a multi-piece solid golf ball formed by laminating each layer of the core, the surrounding layer, the intermediate layer, and the cover (outermost layer) described above can be performed by a conventional method such as a known injection molding method. For example, around the core, each material of the surrounding layer and the intermediate layer is sequentially injected with each injection molding die to obtain each coated sphere, and finally, the material of the cover which is the outermost layer is injection-molded. Allows you to obtain a multi-piece golf ball. Further, as each coating layer, a golf ball can be produced by wrapping the coated sphere with two half cups previously formed into a hemi-shell spherical shape and heat-pressing molding.

The amount of deflection (mm) from the initial load of 98 N (10 kgf) to the final load of 1,275 N (130 kgf) on the golf ball needs to be 2.7 mm or more, preferably 2.9 mm. As described above, it is more preferably 3.0 mm or more, and the upper limit value is preferably 3.8 mm or less, more preferably 3.6 mm or less, still more preferably 3.4 mm or less. If the amount of deflection of the golf ball is too small, that is, it is too hard, the spin may increase too much and the ball may not fly or the feel of hitting may become too hard. On the other hand, if the amount of deflection is too large, that is, if the sphere is too soft, the repulsiveness of the ball becomes too low to fly, the feel of hitting becomes too soft, or the cracking durability at the time of repeated hitting deteriorates. Sometimes.

[ Hardness of each layer ]
In the present invention, the surface hardness of the core and the sphere (surrounding layer coating) in which the core is coated with the surrounding layer are obtained from the viewpoint of achieving both excellent flight distance performance and excellent short game performance when a full shot is performed with a utility or an iron. The hardness relationship between the surface hardness of the sphere), the surface hardness of the sphere whose surrounding layer-coated sphere is coated with the intermediate layer (intermediate layer-coated sphere), and the surface hardness of the ball whose intermediate layer-coated sphere is coated with the cover (surface hardness is Shore C hardness) is the following formula (1).
Surface hardness of surrounding layer-coated sphere <Surface hardness of intermediate layer-coated sphere ... (1)
Is satisfied, preferably the following formula (1 ″), and more preferably (1 ′) is satisfied.
Surface hardness of surrounding layer-coated sphere <Surface hardness of intermediate layer-coated sphere> Ball surface hardness
... (1'')
Core surface hardness <Surface hardness of surrounding layer-coated sphere <Surface hardness of intermediate layer-coated sphere> Ball surface hardness ・ ・ ・ (1')

The intermediate layer-coated sphere has a higher surface hardness than the surrounding layer-coated sphere, and the difference between these surface hardness is the shore C hardness, preferably 1 or more, more preferably 3 or more, still more preferably 5 or more, as an upper limit value. Is preferably 25 or less, more preferably 17 or less, still more preferably 14 or less. If the above value is out of the above range, the spin when a full shot with a utility or iron increases, and the target flight distance may not be obtained.

The intermediate layer-coated sphere has a higher surface hardness than the ball, and the difference between these surface hardnesses is the shore C hardness, preferably 2 or more, more preferably 4 or more, still more preferably 6 or more, and the upper limit is preferable. Is 25 or less, more preferably 17 or less, still more preferably 14 or less. If the above value is too small, controllability in a short game may deteriorate. If the above value is too large, the spin on a full shot will increase, and the target flight distance may not be obtained.

The surrounding layer-covered sphere has a higher surface hardness than the core, and the difference between these surface hardnesses is the shore C hardness, preferably 1 or more, more preferably 4 or more, still more preferably 8 or more, and the upper limit is preferable. Is 25 or less, more preferably 20 or less, still more preferably 18 or less. If the above value is out of the above range, the spin at the time of a full shot increases, and the target flight distance may not be obtained.

Further, regarding the relationship between the surrounding layer-coated sphere and the intermediate layer-coated sphere and the central hardness of the core, it is preferable that the surface hardness of the former is higher than the surface hardness of the latter.

The value of (surface hardness of the surrounding layer-coated sphere)-(center hardness of the core) is preferably 28 or more, more preferably 32 or more, still more preferably 35 or more in the shore C hardness, and the upper limit is preferable. Is 45 or less, more preferably 42 or less, still more preferably 40 or less. If the above value is too large, the cracking durability when repeatedly hit may be deteriorated, or the actual hitting initial velocity may be lowered and the target flight distance may not be obtained. Further, if the above value becomes too small, the spin at the time of a full shot increases, and the target flight distance may not be obtained.

The present invention has the following formula (2).
Surface hardness of intermediate layer coated sphere-Center hardness of core (Shore C hardness) ≧ 40 ・ ・ ・ (2)
It meets the requirements. That is, the value obtained by subtracting the (center hardness of the core) from the (surface hardness of the intermediate layer-coated sphere) is 40 or more, preferably 41 or more, more preferably 42 or more, as the upper limit value in the shore C hardness. Is preferably 53 or less, more preferably 50 or less, still more preferably 47 or less. If the above value is too large, the cracking durability when repeatedly hit may be deteriorated, or the actual hitting initial velocity may be lowered and the target flight distance may not be obtained. In addition, if the above value becomes too small, the spin when a full shot with a utility or iron increases, and the target flight distance may not be obtained.

[ Thickness of each layer ]
Further, in the present invention, from the viewpoint of obtaining superior flight distance performance not only with the driver (W # 1) but also with an iron at the time of a full shot, the thickness of the surrounding layer, the thickness of the intermediate layer and the thickness of the cover are described. The following equation (3) is satisfied.
Cover thickness <Intermediate layer thickness <Envelopment layer thickness ... (3)

[ Relationship between core diameter and ball diameter ]
In the present invention, the value of the core diameter / ball diameter is 0.820 or more, preferably 0. It is 824 or more, more preferably 0.828 or more, and the upper limit value is preferably 0.970 or less, more preferably 0.920 or less, still more preferably 0.900 or less. If the above value is too small, the initial velocity of the ball may be low, the deflection hardness of the entire ball may be hard, and the spin at the time of a full shot may increase, making it impossible to obtain the desired flight distance. If the above value is too large, the spin at the time of a full shot may increase and the target flight distance may not be obtained, or the crack durability when repeatedly hit may be deteriorated.

A large number of dimples can be formed on the outer surface of the cover. The number of dimples arranged on the cover surface is not particularly limited, but is preferably 250 or more, preferably 300 or more, more preferably 320 or more, and the upper limit is preferably 380 or less, more preferably 350. The number or less, more preferably 340 or less, can be provided. If the number of dimples exceeds the above range, the trajectory of the ball becomes low and the flight distance may decrease. On the contrary, when the number of dimples is small, the trajectory of the ball becomes high and the flight distance may not be extended.

As for the shape of the dimples, one type or a combination of two or more types such as a circular shape, various polygonal shapes, a dewdrop shape, and an elliptical shape can be appropriately used. For example, when a circular dimple is used, the diameter can be about 2.5 mm or more and 6.5 mm or less, and the depth can be 0.08 mm or more and 0.30 mm or less.

The dimple occupancy of the dimples on the sphere of the golf ball, specifically the total dimple area defined by the surface edge of the plane surrounded by the edges of the dimples, occupies the ball area assuming no dimples. The ratio (SR value) is preferably 70% or more and 90% or less from the viewpoint of sufficiently exhibiting aerodynamic characteristics. Further, the value V ₀ obtained by dividing the space volume of the dimples under the plane surrounded by the edges of each dimple by the volume of a cylinder having the plane as the bottom surface and the maximum depth of the dimples from the bottom surface as the height is From the viewpoint of optimizing the trajectory of the ball, it is preferably 0.35 or more and 0.80 or less. Furthermore, the VR value of the total volume of dimples formed downward from the plane surrounded by the edges of the dimples to the volume of the ball ball assuming that the dimples do not exist shall be 0.6% or more and 1.0% or less. Is preferable. If it deviates from the range of each of the above-mentioned numerical values, the trajectory may not be able to obtain a good flight distance, and a sufficiently satisfactory flight distance may not be obtained.

A paint layer (coating layer) can be formed on the cover surface. This paint layer can be painted with various paints, and since it is necessary for the paint to withstand the harsh usage conditions of golf balls, a paint composition containing a urethane paint composed of a polyol and a polyisocyanate as a main component. It is preferable to use a thing.

Examples of the polyol component include acrylic polyols and polyester polyols. It should be noted that these polyols contain a modified form of the polyol, and other polyols can be added in order to further improve workability.

As the polyol component, it is preferable to use two kinds of polyester polyols in combination. In this case, assuming that the two types of polyester polyols are the component (a) and the component (b), as the polyester polyol of the component (a), a polyester polyol having a cyclic structure introduced into the resin skeleton can be adopted, for example. , Cyclohexanedimethanol and the like, and examples thereof include polyester polyols obtained by polycondensation of a polyol having an alicyclic structure with polybasic acid, or polycondensation of a polyol having an alicyclic structure with diols or triol and polybasic acid. .. On the other hand, as the polyester polyol of the component (b), a polyester polyol having a multi-branched structure can be adopted, and examples thereof include a polyester polyol having a branched structure such as "NIPPOLAN 800" manufactured by Tosoh Corporation.

On the other hand, the polyisocyanate is not particularly limited and is a commonly used aromatic, aliphatic, alicyclic or the like polyisocyanate. Specifically, it is a tolylene diisocyanate, a diphenylmethane diisocyanate, or a xylylene diisocyanate. , Tetramethylene diisocyanate, hexamethylene diisocyanate, lysine diisocyanate, isophorone diisocyanate, 1,4-cyclohexylene diisocyanate, naphthalene diisocyanate, trimethylhexamethylene diisocyanate, dicyclohexammethane diisocyanate, 1-isocyanato-3,3,5-trimethyl-4-isosia Examples thereof include natomethylcyclohexane. These can be used alone or in combination.

Various organic solvents can be mixed with the coating composition depending on the coating conditions. Examples of such an organic solvent include aromatic solvents such as toluene, xylene and ethylbenzene, ester solvents such as ethyl acetate, butyl acetate, propylene glycol methyl ether acetate and propylene glycol methyl ether propionate, acetone and methyl ethyl ketone. , Methylisobutylketone, ketone solvent such as cyclohexanone, ether solvent such as diethylene glycol dimethyl ether, diethylene glycol diethyl ether, dipropylene glycol dimethyl ether, alicyclic hydrocarbon solvent such as cyclohexane, methylcyclohexane, ethylcyclohexane, mineral spirit and the like. Petroleum hydrocarbon solvents etc. can be used.

When using the above paint composition, the paint composition of the present invention is adjusted at the time of painting on a golf ball manufactured by a known method, applied to the surface by adopting a normal painting process, and dried. A paint layer can be formed on the surface of the ball. In this case, as the coating method, a spray coating method, an electrostatic coating method, a dipping method and the like can be preferably adopted, and there is no particular limitation.

The thickness of the paint layer made of the above paint composition is not particularly limited, but is usually 5 to 40 μm, preferably 10 to 20 μm. The thickness of the paint layer referred to here means the average thickness of the paint obtained by measuring a total of three points, that is, the center of the dimple and the two positions between the center of the dimple and the edge of the dimple.

In the present invention, the elastic work recovery rate of the paint layer made of the above paint composition needs to be 60% or more, preferably 80% or more. When the elastic work recovery rate of this paint layer is within the above range, the paint layer has a high elastic force, so that it has a high self-repairing function and is extremely excellent in wear resistance. In addition, various performances of the golf ball coated with the above-mentioned coating composition can be improved. The above-mentioned method for measuring the elastic work recovery rate is as follows.

Elastic work recovery rate is an ultra-fine hardness test method that controls the indentation load on the order of micronewton (μN) and tracks the indentation depth at the time of indentation with an accuracy of nanometer (nm). It is one of the parameters of the nanoindentation method to evaluate. With the conventional method, only the size of the deformation mark (plastic deformation mark) corresponding to the maximum load can be measured, but with the nanoindentation method, the relationship between the indentation load and the indentation depth is measured automatically and continuously. Can be obtained. Therefore, it is considered that the physical properties of the paint layer can be evaluated with high accuracy without individual differences as in the case of visually measuring the deformation marks with an optical microscope as in the conventional case. Since the paint layer on the surface of the ball is greatly affected by the impact of various clubs such as drivers, utilities and irons, and the influence of the paint layer on the physical characteristics of the golf ball is not small, the paint layer is tested for ultra-fine hardness. Measuring by a method and performing it with higher accuracy than before is a very effective evaluation method.

The hardness of the paint layer is preferably 40 or more, more preferably 60 or more, and the upper limit is preferably 95 or less, more preferably 85 or less. The Shore M hardness is based on ASTM D2240. The hardness of the paint layer is preferably 40 or more in terms of shore C hardness, and is preferably 80 or less as an upper limit. The shore C hardness is based on ASTM D2240. If the paint layer is too high above the hardness range, the paint becomes brittle when repeatedly hit, and the cover layer may not be protected. If the paint layer is too small than the above hardness range, the ball surface is easily scratched when it hits a hard object, which is not preferable.

Regarding the hardness relationship between the paint layer and the cover, the value obtained by subtracting the material hardness of the paint layer from the material hardness of the cover is preferably -20 or more, more preferably -15 or more, still more preferably -10 or more in shore C hardness. The upper limit is preferably 25 or less, more preferably 20 or less, and even more preferably 15 or less. If it is out of the above range, the coating may easily come off when hit.

Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples.

[Examples 1 to 6, Comparative Examples 1 to 8]
Core formation
After preparing the rubber compositions of Examples 1 to 3 and Comparative Examples 4 and 5 shown in Table 1, a solid core was prepared by vulcanization molding under vulcanization conditions at 152 ° C. for 19 minutes.
Further, in the same manner, the solid cores of Examples 4 to 6 and Comparative Examples 1 to 3, 6 to 8 are prepared according to the rubber composition and vulcanization conditions shown in Table 1.

The details of each component shown in Table 1 are as follows.
-Polybutadiene A: JSR, product name "BR51"
-Polybutadiene B: JSR, product name "BR730"
-Zinc acrylate: "ZN-DA85S" (manufactured by Nippon Shokubai)
-Organic peroxide (1): Dicumyl peroxide, trade name "Parkmill D" (manufactured by NOF CORPORATION)-Organic peroxide (2): 1,1-di (t-butylperoxy) cyclohexane and silica Mixture with, trade name "Perhexa C-40" (manufactured by NOF Corporation)
・ Water: Pure water (manufactured by Shoki Yakuhin Kogyo Co., Ltd.)
-Anti-aging agent: 2,2-methylenebis (4-methyl-6-butylphenol), trade name Nocrack NS-6 (manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.)
-Zinc oxide: Product name "Three types of zinc oxide" (manufactured by Sakai Chemical Industry Co., Ltd.)
・ Pentachlorothiophenol zinc salt: manufactured by Wako Pure Chemical Industries, Ltd.

Formation of Surrounding Layer, Intermediate Layer and Cover (Outermost Layer) Next, for Examples 1 to 3 and Comparative Examples 4 and 5, the surrounding layer and the intermediate layer having the formulations shown in Table 2 are surrounded around the core obtained above. The surrounding layer and the intermediate layer were sequentially formed by an injection molding method using the material, and each coated sphere was obtained. In Comparative Examples 4 and 5, there was no surrounding layer, and the intermediate layer was directly coated around the core by the same method as described above to obtain each coated sphere. Next, a cover (outermost layer) was formed around the intermediate layer-coated sphere obtained above by an injection molding method using the cover material having the composition shown in the same table to prepare a multi-piece solid golf ball. At this time, a large number of predetermined dimples common to all the examples and comparative examples were formed on the cover surface.

Similarly, for Examples 4 to 6 and Comparative Examples 1 to 3, 6 to 8, the surrounding layer and the intermediate layer are formed in the same manner as described above, and each coated sphere is obtained. Next, a cover (outermost layer) is formed around the intermediate layer-coated sphere by an injection molding method using the cover material having the composition shown in the same table to produce a multi-piece solid golf ball. A large number of predetermined dimples common to all the examples and comparative examples shall be formed on the cover surface.

The product names of the main materials listed in the table are as follows.
"HPF1000" HPF (trademark) 1000 manufactured by THE DOW CHEMICAL COMPANY
"Himilan" Ionomer "AM7318""AM7329" manufactured by Mitsui Dow Polychemical Co., Ltd. Ionomer "Trimethylolpropane" (TMP) manufactured by Mitsui Dow Polychemical Co., Ltd. "TPU" manufactured by Tokyo Chemical Industry Co., Ltd. Brand name "Pandex", ether type thermoplastic polyurethane

Six types of circular dimples are used as dimples common to all the examples and comparative examples, the details thereof are shown in Table 3 below, and the arrangement mode thereof is as shown in FIG. FIG. 5A shows a plan view of the dimples, and FIG. 5B shows a side view thereof.

Definition of dimples <br /> Edge: Highest point in the cross section passing through the center of the dimples Diameter: Diameter of the plane surrounded by the edges of the dimples Depth: Maximum depth of the dimples from the plane surrounded by the edges of the dimples SR: The ratio of the total dimple area defined in the plane surrounded by the edges of the dimples to the ball ball area assuming that the dimples do not exist. Ratio of dimple volume to the volume of a cylinder with the same diameter as the dimple VR: The total volume of dimples formed downward from the plane surrounded by the edges of the dimples is the ball ball volume assuming that the dimples are not present.

Formation of paint layer (coating layer) Next, for Examples 1 to 3 and Comparative Examples 4 and 5, the paint composition shown in Table 4 below is used as the paint composition common to all Examples and Comparative Examples. The above paint was applied to the surface of a large number of formed covers (outermost layer) with an air spray gun to produce a golf ball having a paint layer having a thickness of 15 μm.
Similarly, for Examples 4 to 6 and Comparative Examples 1 to 3, 6 to 8, the above paint is applied to produce a golf ball having a paint layer having a thickness of 15 μm. ..

[Synthesis example of polyester polyol (A)]
A reactor equipped with a reflux condenser, a dropping funnel, a gas introduction tube and a thermometer was provided with 140 parts by mass of trimethylolpropane, 95 parts by mass of ethylene glycol, 157 parts by mass of adipic acid, and 58 parts by mass of 1,4-cyclohexanedimethanol. The temperature was raised to 200 to 240 ° C. with stirring, and the mixture was heated (reacted) for 5 hours. Then, a "polyester polyol (A)" having an acid value of 4, a hydroxyl value of 170 and a weight average molecular weight (Mw) of 28,000 was obtained.
Next, the synthesized polyester polyol (A) described above was dissolved in butyl acetate to prepare a varnish having a non-volatile content of 70% by mass.

The coating composition in Table 4 contains "polyester polyol (B)" (saturated aliphatic polyester polyol "NIPPOLAN 800" manufactured by Toso Co., Ltd., weight average molecular weight (Mw) 1) with respect to 23 parts by mass of the polyester polyol solution. (000, 100% solid content) was mixed with 15 parts by mass and an organic solvent to prepare a main agent. This mixture had a non-volatile content of 38.0% by mass.

Elastic work recovery rate The elastic work recovery rate of the paint is measured using a paint sheet having a thickness of 50 μm. As the measuring device, an ultra-micro hardness tester "ENT-2100" manufactured by Elionix Inc. is used, and the measurement conditions are as follows.
・ Indenter: Berkovich indenter (Material: Diamond, Angle α: 65.03 °)
・ Load F: 0.2mN
・ Load time: 10 seconds ・ Holding time: 1 second ・ Unloading time: 10 seconds Based on the push-in work amount Elastic (Nm) and mechanical push-in work amount Wtotal (Nm) due to the return deformation of the paint, the following formula is used. The elastic work recovery rate is calculated.
Elastic work recovery rate = Welast / Wtotal x 100 (%)

Shore C hardness and Shore M hardness For the Shore C hardness and Shore M hardness in Table 4 above, prepare a sheet with a thickness of 2 mm, stack three sheets, and use an ASTM D2240 standard-compliant Shore C hardness tester and Shore M hardness as test pieces. Measure each using a meter.

For each obtained golf ball, various physical properties such as internal hardness at each position of the core, outer diameter of the core and each coated sphere, thickness and material hardness of each layer, and surface hardness of each coated sphere are evaluated by the following methods. , Table 5 and Table 6.

At a temperature of an outer diameter of 23.9 ± 1 ° C. of each sphere of the core, the surrounding layer-coated sphere, and the intermediate layer-coated sphere, five arbitrary surface points were measured, and the average value was taken as the measured value of one sphere. Obtain the average value when the number of measured pieces is 10.

At a temperature of 23.9 ± 1 ° C., the diameter of the balls is measured at 15 points without any dimples, the average value is taken as the measured value of one ball, and the average value of 10 balls is obtained.

Deflection amount of core and ball The target coated sphere of the core or ball is placed on a hard plate, and the amount of deflection from the state where the initial load 98N (10 kgf) is applied to the final load 1275N (130 kgf) is measured. The amount of deflection is a measured value after the temperature is adjusted to 23.9 ° C. The pressurizing speed of the head that compresses the ball was 10 mm / s.

Core hardness distribution The surface of the core is a spherical surface, but the needle of the hardness tester is set on the spherical surface so as to be substantially vertical, and the surface hardness is measured by Shore C hardness according to ASTM D2240. For the center and predetermined position of the core, cut the core into a hemisphere to make the cross section flat, and measure by pressing the needle of the hardness tester vertically against the central part and the predetermined position shown in Table 5, and measure the center and each. The hardness of the position is indicated by the value of Shore C hardness. An automatic rubber hardness tester "P2" manufactured by Polymer Meter Co., Ltd. equipped with a Shore C type hardness tester is used for measuring the hardness. Read the maximum hardness value. All measurements are made in an environment of 23 ± 2 ° C. The numerical values in Table 5 are the values of Shore C hardness.
Further, in the hardness distribution of the core, the shore C hardness Cc at the center of the core, the shore C hardness C _m at the midpoint M between the center and the surface of the core, and the shore C at positions 2 mm, 4 mm, and 6 mm inward from the midpoint M. Hardness Cm-2, Cm-4, Cm-6, Shore C hardness Cm + 2, Cm + 4, Cm + 6 at positions 2mm, 4mm, 6mm outward from the center M, Shore C hardness on the core surface is Cs For, the following areas A to F
・ Area A: 1/2 x 2 x (Cm-4-Cm-6)
・ Area B: 1/2 x 2 x (Cm-2-Cm-4)
・ Area C: 1/2 x 2 x (Cm-Cm-2)
・ Area D: 1/2 x 2 x (Cm + 2-Cm)
・ Area E: 1/2 x 2 x (Cm + 4-Cm + 2)
・ Area F: 1/2 x 2 x (Cm + 6-Cm + 4)
Was calculated, and the values of the following two mathematical formulas were obtained.
(1) (Area: E + F)-(Area: A + B)
(2) (Area: D + E)-(Area: B + C)

As an explanation of the areas A to F of the core hardness distribution, FIG. 2 shows a schematic diagram showing the areas A to F using the core hardness distribution data of Example 2.
Further, graphs of the core hardness distributions of Examples 1 to 4 and Comparative Examples 1 to 8 are shown in FIGS. 3 and 4.

Material hardness of surrounding layer, intermediate layer and cover (Shore D hardness and Shore C hardness)
The resin material of each layer is formed into a sheet having a thickness of 2 mm and left for 2 weeks. After that, the shore D hardness and the shore C hardness are measured according to the ASTM D2240 standard. An automatic rubber hardness tester "P2" manufactured by Polymer Meter Co., Ltd. is used for measuring the hardness. Attach the Shore D hardness and Shore C hardness attachments and measure the respective hardness. Read the maximum hardness value. All measurements are made in an environment of 23 ± 2 ° C.

Surface hardness (shore D hardness and shore C hardness) of each sphere of the surrounding layer-coated sphere, the intermediate layer-coated sphere, and the ball.
Measure by pressing the needle so that it is perpendicular to the surface of each sphere. The surface hardness of the ball (cover) is a measured value in the land area where dimples are not formed on the surface of the ball. Shore D hardness and Shore C hardness are measured in accordance with the ASTM D2240 standard. An automatic rubber hardness tester "P2" manufactured by Polymer Meter Co., Ltd. is used for measuring the hardness. Attach the Shore D hardness and Shore C hardness attachments and measure the respective hardness. Read the maximum hardness value. All measurements are made in an environment of 23 ± 2 ° C.

The flight (utility) (I # 6) (I # 8) of each golf ball, the amount of spin at the time of approach, the feel of hitting, and the durability of repeated hits are evaluated by the following methods. The results are shown in Table 7.

Jump evaluation (utility)
A utility club was attached to the golf hitting robot, and the flight distance when hitting at a head speed of 38 m / s was measured. The club used is "JGR H2 (2016 model)" manufactured by Bridgestone Sports. Similarly, the spin amount is measured by the initial condition measuring device for the ball immediately after being hit.
<criterion>
Total flight distance 165.0m or more ・ ・ ・ ○
Total flight distance less than 165.0m ・ ・ ・ ×

Jump evaluation (I # 6)
A 6-iron (I # 6) was attached to the golf hitting robot, and the flight distance when hitting at a head speed of 35 m / s was measured and judged according to the following criteria. The club used is "JGR Forged (2016 model) I # 6" manufactured by Bridgestone Sports. Similarly, the spin amount is measured by the initial condition measuring device for the ball immediately after being hit.
<criterion>
Total flight distance 154.0m or more ・ ・ ・ ○
Total flight distance less than 154.0m ・ ・ ・ ×

Jump evaluation (I # 8)
An 8-iron (I # 8) was attached to the golf hitting robot, and the flight distance when hitting at a head speed of 35 m / s was measured and judged according to the following criteria. The club used is "JGR Forged (2016 model) I # 8" manufactured by Bridgestone Sports. Similarly, the spin amount is measured by the initial condition measuring device for the ball immediately after being hit.
<criterion>
Total flight distance 137.0m or more ・ ・ ・ ○
Total flight distance less than 137.0m ・ ・ ・ ×

Evaluation of spin amount at the time of approach Judgment is made by the amount of spin when a golf hitting robot is hit with a sand wedge at a head speed of 15 m / s. Similarly, the spin amount was measured by the initial condition measuring device for the ball immediately after being hit. For the sand wedge, "TourStage TW-03 (loft 57 °) 2002 model" manufactured by Bridgestone Sports Co., Ltd. is used.
<criterion>
Spin amount is 4500 rpm or more ... ○
Spin amount is less than 4500 rpm ・ ・ ・ ×

A feeling of hitting An amateur golfer with a head speed of 30 to 40 m / s of a driver (W # 1) actually hits the ball, and the feeling of hitting at that time is evaluated according to the following criteria.
<criterion>
More than 10 out of 20 people evaluated it as soft and good hitting feeling ... ○
The number of people who evaluated it as soft and good hitting feeling is 9 out of 20 people ... ×

Repeated hitting durability A driver (W # 1) is attached to a golf hitting robot, and N = 8 balls are hit repeatedly at a head speed of 45 m / s, and the average number of hits when all the balls start to crack. Evaluated by value. The number of cracks in Example 2 was set to 100 as an index.
<criterion>
Index 90 or higher ・ ・ ・ ○
Index less than 90 ・ ・ ・ ×

As shown in the results of Table 7, the golf balls of Comparative Examples 1 to 8 are inferior to the product of the present invention (Example) in the following points.
In Comparative Example 1, the surface hardness-core center hardness of the intermediate layer-coated sphere is less than 40 in shore C hardness, and the deflection of the ball is smaller than 2.7 mm. As a result, the flight distance is inferior when hitting the utility and I # 6. In addition, the feel of hitting is felt hard.
In Comparative Example 2, the surface hardness-core center hardness of the intermediate layer-coated sphere is less than 40 in shore C hardness, and as a result, the flight distance is inferior when the utility and I # 6 are hit.
In Comparative Example 3, the resin materials of the intermediate layer and the surrounding layer do not contain ionomers having a high acid content, and as a result, the utility and the flight distance when hit by I # 8 are inferior.
Comparative Example 4 is a golf ball having a three-piece (3P) structure without a surrounding layer, and as a result, the repeated hitting durability is inferior.
Comparative Example 5 is a golf ball having a three-piece (3P) structure without a surrounding layer, and as a result, the repeated hitting durability is inferior.
In Comparative Example 6, the area A and the area C calculated from the hardness distribution of the core do not satisfy the relationship of the area A <the area C, and the surface hardness of the intermediate layer-coated sphere-the core center hardness is 40 in the shore C hardness. As a result, the flight distance is inferior when hitting a utility and an iron.
In Comparative Example 7, the value of (area E + area F)-(area A + area B) calculated from the hardness distribution of the core is smaller than 1.0, does not satisfy the relationship of area A <area C, and is an intermediate layer. The surface hardness-core center hardness of the coated sphere is less than 40 in shore C hardness, and as a result, the flight distance is inferior when hitting a utility or an iron.
In Comparative Example 8, the surface hardness of the surrounding layer-coated sphere is higher than the surface hardness of the intermediate layer-coated sphere, and the surface hardness-core center hardness of the intermediate layer-coated sphere is less than 40 in shore C hardness. -The flight distance is inferior when hitting Titi and I # 6.

Claims (10)

It comprises a core, a surrounding layer, an intermediate layer and a cover, the core is formed into one layer by a rubber composition, the surrounding layer is formed into one layer or a plurality of layers by a resin material, and the intermediate layer and the cover are each made of resin. A multi-piece solid golf ball formed in one layer by a material, the core diameter is 35.1 to 41.3 mm, and in the hardness distribution of the core, the shore C hardness at the center of the core is Cc, and the center of the core. The shore C hardness of the midpoint M between the surface and the surface is C _m , the shore C hardness at the positions 2 mm, 4 mm, and 6 mm inward from the midpoint M is Cm-2, Cm-4, Cm-6, and the outside from the center M, respectively. When the shore C hardness at the positions of 2 mm, 4 mm, and 6 mm is Cm + 2, Cm + 4, Cm + 6, respectively, and the shore C hardness on the surface of the core is Cs, the following areas A to F
・ Area A: 1/2 x 2 x (Cm-4-Cm-6)
・ Area B: 1/2 x 2 x (Cm-2-Cm-4)
・ Area C: 1/2 x 2 x (Cm-Cm-2)
・ Area D: 1/2 x 2 x (Cm + 2-Cm)
・ Area E: 1/2 x 2 x (Cm + 4-Cm + 2)
・ Area F: 1/2 x 2 x (Cm + 6-Cm + 4)
The value of (Area E + Area F)-(Area A + Area B) is 1.0 or more, and Area A <Area C <(Area E + Area F), and at least one of the surrounding layer and the intermediate layer. The resin material contains an ionomer having a high acid content, and the central hardness of the core, the surface hardness of the sphere (surrounding layer-coated sphere) in which the core is coated with the surrounding layer, and the surrounding layer-coated sphere are coated with the intermediate layer. The hardness relationship (surface hardness means shore C hardness) with the surface hardness of the formed sphere (intermediate layer coated sphere) is the following formulas (1) and (2).
Surface hardness of surrounding layer-coated sphere <Surface hardness of intermediate layer-coated sphere ... (1)
Surface hardness of intermediate layer coated sphere-Center hardness of core (Shore C hardness) ≧ 40 ・ ・ ・ (2)
The multi-piece solid golf is characterized in that the amount of deflection (mm) from the initial load of 98 N (10 kgf) to the final load of 1,275 N (130 kgf) is 2.7 mm or more. ball. Regarding the thickness relationship of each layer, the following formula (3)
Cover thickness <Intermediate layer thickness <Envelopment layer thickness ... (3)
The multi-piece solid golf ball according to claim 1. About the surface hardness of the core or each coated sphere
Core surface hardness <Surface hardness of surrounding layer-coated sphere <Surface hardness of intermediate layer-coated sphere> Ball surface hardness ・ ・ ・ (1')
The multi-piece solid golf ball according to claim 1 or 2. The multi-piece solid golf ball according to any one of claims 1 to 3, wherein the material hardness of the intermediate layer is 64 or more in shore D hardness. The multi according to any one of claims 1 to 4, wherein in the above formula (2), the upper limit of the value of (surface hardness of intermediate layer coated sphere)-(center hardness of core) is 53 or less in shore C hardness. Peace solid golf ball. The multi-piece solid golf ball according to any one of claims 1 to 5, wherein the surrounding layer is a single layer. The multi-piece solid golf ball according to any one of claims 1 to 6, wherein the value of core surface hardness (Cs) -core center hardness (Cc) is 20 or more. For the areas A to F of the core hardness distribution, the following formula (area D + area E)-(area B + area C) ≧ 1.0
The multi-piece solid golf ball according to any one of claims 1 to 7. The multi-piece solid golf ball according to any one of claims 1 to 8, wherein the resin material of the intermediate layer contains an ionomer having a high acid content. It comprises a core, a surrounding layer, an intermediate layer and a cover, the core is formed into one layer by a rubber composition, the surrounding layer is formed into one layer or a plurality of layers by a resin material, and the intermediate layer and the cover are each made of resin. A multi-piece solid golf ball formed in one layer by a material, the core diameter is 35.1 to 41.3 mm, and in the hardness distribution of the core, the shore C hardness at the center of the core is Cc, and the center of the core. The shore C hardness of the midpoint M between the surface and the surface is Cm, and the shore C hardness at the positions of 2 mm, 4 mm, and 6 mm inward from the midpoint M is Cm-2, Cm-4, Cm-6, and outward from the center M, respectively. When the shore C hardness at the positions of 2 mm, 4 mm, and 6 mm is Cm + 2, Cm + 4, Cm + 6, respectively, and the shore C hardness on the surface of the core is Cs, the following areas A to F
・ Area A: 1/2 x 2 x (Cm-4-Cm-6)
・ Area B: 1/2 x 2 x (Cm-2-Cm-4)
・ Area C: 1/2 x 2 x (Cm-Cm-2)
・ Area D: 1/2 x 2 x (Cm + 2-Cm)
・ Area E: 1/2 x 2 x (Cm + 4-Cm + 2)
・ Area F: 1/2 x 2 x (Cm + 6-Cm + 4)
The value of (Area E + Area F)-(Area A + Area B) is 1.0 or more, and (Area A) <(Area C) <(Area E + Area F), and the material hardness of the intermediate layer. The shore D hardness is 65 or more, the center hardness of the core, the surface hardness of the sphere (surrounding layer-coated sphere) in which the core is coated with the surrounding layer, and the sphere (intermediate layer) in which the surrounding layer-coated sphere is coated with the intermediate layer. The hardness relationship with the surface hardness of the coated sphere (surface hardness means shore C hardness) is the following formulas (1) and (2).
Surface hardness of surrounding layer-coated sphere <Surface hardness of intermediate layer-coated sphere ... (1)
Surface hardness of intermediate layer coated sphere-Center hardness of core (Shore C hardness) ≧ 40 ・ ・ ・ (2)
The multi-piece solid golf is characterized in that the amount of deflection (mm) from the initial load of 98 N (10 kgf) to the final load of 1,275 N (130 kgf) is 2.7 mm or more. ball.

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