JP7263749B2 - multi-piece solid golf ball - Google Patents

Description

The present invention relates to a multi-piece solid golf ball comprising five or more layers including a core, an inner envelope layer, an outer envelope layer, an intermediate layer and a cover.

Various golf balls have been developed as golf balls for professionals and advanced players. Multi-piece solid golf balls having a function of optimizing the hardness relationship of each coating layer covering the core have become popular. In addition to flight performance, the feel at impact (hit feeling) and the spin rate of the ball after hitting the club greatly affect ball control. Optimizing the thickness and hardness of each layer of the golf ball is also one of the important themes. Furthermore, there is a demand for durability against repeated impacts, which is caused by repeatedly hitting a golf ball with various clubs, and for suppressing the occurrence of burrs observed on the surface of the ball (improved scuff resistance). The aspect of protecting against external factors is also one of the important themes in developing balls.

A golf ball with four layers in its structure, that is, three layers, i.e., an envelope layer, an intermediate layer, and a cover (outermost layer), is used to cover the core. For example, US Pat. No. 7,335,115, US Pat. No. 7,918,749, US Pat. No. 8,764,584, US Pat.

In addition, each layer in the ball structure is composed of five layers, that is, the coating layers covering the core are composed of four layers, namely, an inner enveloping layer, an outer enveloping layer, an intermediate layer and a cover (outermost layer). Hardness<inner enveloping layer hardness<outer enveloping layer hardness<intermediate layer hardness>cover hardness. Techniques for golf balls that internally change the ball structure into multiple layers include, for example, U.S. Pat. Nos. 7,749,108 and 7,445,567. Japanese Patent Nos. 7637826 and 8371960. Other golf balls having five or more layers are disclosed, for example, in US Pat. Nos. 8,357,060 and 8,979,677.

However, the proposed golf ball still has room for improvement in optimizing the hardness distribution of the core and the thickness relationship with each layer. In other words, as a golf ball product for professionals and advanced players, there is still room for improvement in terms of achieving further improved flight performance and good hitting feel.

U.S. Pat. No. 7,335,115 U.S. Pat. No. 7,918,749 U.S. Pat. No. 8,764,584 U.S. Pat. No. 9,174,093 U.S. Pat. No. 7,749,108 U.S. Pat. No. 7,445,567 U.S. Pat. No. 7,637,826 U.S. Pat. No. 8,371,960 U.S. Pat. No. 8,357,060 U.S. Pat. No. 8,979,677

The present invention has been devised in view of the above circumstances, and is intended to provide a golf ball that can satisfy the professional and advanced golfers, provides excellent controllability on approach, provides a good feel on impact, and is scratch resistant. To provide a multi-piece solid golf ball having excellent properties.

As a result of intensive studies to achieve the above object, the inventors of the present invention have found a golf ball comprising a core, an envelope layer, an intermediate layer and a cover. Each layer of the layer and the cover is formed of the same or different resin material, and the envelope layer is formed of two layers, an inner layer and an outer layer.
Core center hardness <core surface hardness <surface hardness of inner envelope-covered sphere> surface hardness of outer envelope-covered sphere <surface hardness of intermediate-layer-covered sphere> ball surface hardness A multi-piece solid golf ball was produced. However, by suppressing the amount of spin on driver (W#1) shots and achieving a high initial speed, it is possible to obtain a good flight distance, and control performance is achieved by optimizing the amount of spin on approach shots in the short game. The inventors have found that the above-described driver (W#1) shots have a good feel, not too hard, and have completed the present invention.

That is, the golf ball of the present invention can reduce the spin rate of the ball when hit with a driver (W#1), and achieves a good flight distance by producing a high actual hit initial velocity. . In designing a golf ball, there is a tendency for the shot feel to be too hard when the flight distance is favored. The ball has both good flight distance and feel on impact, and is particularly suitable as a ball for professionals and advanced players. In the present invention, in order to achieve both high controllability in the short game and excellent scratch resistance, it is preferable to use a flexible and highly durable urethane resin material as the material for the outermost layer. is.

Accordingly, the present invention provides the following multi-piece solid golf ball.
1. A multi-piece solid golf ball comprising a core, an enveloping layer, an intermediate layer and a cover, wherein the core is made mainly of base rubber, and the enveloping layer, the intermediate layer and the cover are each made of a resin material. The envelope layer is formed of two layers, an inner layer and an outer layer, and has center hardness and surface hardness of the core and surface hardness of a sphere covering the core with the inner envelope layer (inner envelope layer-covered sphere). and the surface hardness of a sphere obtained by covering the inner envelope-covered sphere with an outer envelope (outer envelope-covered sphere) and a sphere obtained by covering the outer envelope-layer-covered sphere with an intermediate layer (intermediate-layer-covered sphere), and the ball satisfies the following formula: core center hardness<core surface hardness<surface hardness of inner enveloping layer-covered sphere>surface hardness of outer enveloping layer-covered sphere<surface hardness of intermediate layer-covered sphere>ball surface hardness And, in the hardness distribution of the core, Cc is the Shore C hardness of the center of the core, Cs is the Shore C hardness of the surface of the core, C M is the Shore C hardness of the midpoint M between the center and the surface of the core, and _the midpoint The Shore C hardness at positions 2.5 mm, 5.0 mm and 7.5 mm from M to the core surface side are respectively C _{M +2.5} , C _{M +5.0} and C _{M +7.5} , and from the midpoint M to the core center side When the Shore C hardnesses at the positions of 2.5 mm, 5.0 mm and 7.5 mm are respectively C _M-2.5 , C _M-5.0 and C _M-7.5 , the following areas A to F
・Area A: 1/2 × 2.5 × (C _M-5.0 -C _M-7.5 ),
・Area B: 1/2 × 2.5 × (C _M-2.5 -C _M-5.0 ),
・Area C: 1/2 × 2.5 × (C _M -C _M-2.5 ),
・Area D: 1/2×2.5×(C _M+2.5 −C _M ),
- Area E: 1/2 x 2.5 x (C _M+5 -C _M+2.5 ), and
・Area F: 1/2×2.5×(C _M+7.5 -C _M+5 )
, (Area D + Area E + Area F) - (Area A + Area B + Area C) ≥ 3.
2. A multi-piece solid golf ball comprising a core, an enveloping layer, an intermediate layer and a cover, wherein the core is made mainly of base rubber, and the enveloping layer, the intermediate layer and the cover are each made of a resin material. The envelope layer is formed of two layers, an inner layer and an outer layer, and has center hardness and surface hardness of the core and surface hardness of a sphere covering the core with the inner envelope layer (inner envelope layer-covered sphere). and the surface hardness of a sphere obtained by covering the inner envelope-covered sphere with an outer envelope (outer envelope-covered sphere) and a sphere obtained by covering the outer envelope-layer-covered sphere with an intermediate layer (intermediate-layer-covered sphere), and the ball and the surface hardness of the following formula
Core Center Hardness <Core Surface Hardness <Surface Hardness of Inner Surrounding Layer Covered Sphere> Surface Hardness of Outer Surrounding Layer Covered Sphere <Surface Hardness of Intermediate Layer Covered Sphere> Ball Surface Hardness
and the thickness of each layer of the envelope layer, the intermediate layer and the cover, the following formula
[Total thickness of inner and outer envelope layers (mm)]−[Total thickness of intermediate layer and cover (mm)]≧0.1
A multi-piece solid golf ball characterized by satisfying:
3. 2. The multi-piece solid golf ball of claim 1 , wherein (Area D+Area E)−(Area A+Area B+Area C)≧0 is satisfied for Areas A to E of the core hardness distribution.
4. The above 1 or 3 satisfying 0.15 ≤ [(area D + area E + area F) - (area A + area B + area C)] / (Cs - Cc) ≤ 0.6 for the areas A to F of the core hardness distribution A multi-piece solid golf ball as described.
5. 5. The multi-piece solid golf ball of 1, 3 or 4, wherein the areas B to E of the core hardness distribution satisfy Area B<Area C≦Area D<Area E.
6. 6. The multi-piece solid golf ball of any one of 1 to 5 above, wherein the thickness of the enveloping layer satisfies the following condition: thickness of inner enveloping layer≧thickness of outer enveloping layer.
7. 7. The multi-piece solid golf ball of any one of 1 to 6 above, wherein the thickness of the outer envelope layer and the intermediate layer satisfies the following relation: thickness of intermediate layer≧thickness of outer envelope layer.
8 . 8. The multi-piece solid golf ball of any one of 1 to 7 , wherein a coating layer is formed on the cover surface, and the coating layer has a Shore C hardness of 40 to 80.
9 . When the Shore C hardness of the coating layer is Hc, the difference (C _M -Hc) between the Shore C hardness C _M at the midpoint M between the center and the surface of the core and Hc is -10 or more and 10 or less. 9. The multi-piece solid golf ball according to 8 above.
10 . A multi-piece solid golf ball comprising a core, an inner envelope layer, an outer envelope layer, an intermediate layer, and a cover, wherein the surface hardness of the core and a sphere coated with the inner envelope layer (inner envelope layer-covered sphere) surface hardness of the inner envelope-covered sphere covered with the outer envelope layer (outer envelope-covered sphere) and the outer envelope-layer-covered sphere covered with the intermediate layer (intermediate-layer-covered sphere) and the surface hardness of the ball is calculated by the following formula: Core surface hardness <Surface hardness of each sphere of the inner enveloping layer covering sphere, outer enveloping layer covering sphere and intermediate layer covering sphere > Ball surface hardness (However, the surface hardness of the outer enveloping layer covering sphere The surface hardness is 60 or less in Shore D hardness, and the surface hardness of the intermediate layer-covered sphere is 66 or more in Shore D hardness.)
In the hardness distribution of the core, Cc is the Shore C hardness of the center of the core, Cs is the Shore C hardness of the surface of the core, and C is _the Shore C hardness of the midpoint M between the center and the surface of the core. , the Shore C hardness at positions 2.5 mm, 5.0 mm and 7.5 mm from the midpoint M to the core surface side are respectively C _{M +2.5} , C _{M +5.0} and C _{M +7.5} , and from the midpoint M to the core When the Shore C hardnesses at positions of 2.5 mm, 5.0 mm and 7.5 mm on the center side are respectively C _M-2.5 , C _M-5.0 and C _M-7.5 , the following areas A to F
・Area A: 1/2 × 2.5 × (C _M-5.0 -C _M-7.5 ),
・Area B: 1/2 × 2.5 × (C _M-2.5 -C _M-5.0 ),
・Area C: 1/2 × 2.5 × (C _M -C _M-2.5 ),
・Area D: 1/2×2.5×(C _M+2.5 −C _M ),
area E: 1/2 x 2.5 x (C _M+5 - C _M+2.5 ), and area F: 1/2 x 2.5 x (C _M+7.5 - _{C M+5} )
(Area D+Area E+Area F)−(Area A+Area B+Area C)≧6.
11 . 11. The above 10 , wherein the areas A to F of the core hardness distribution satisfy 0.15≦[(Area D+Area E+Area F)−(Area A+Area B+Area C)]/(Cs−Cc)≦0.6. Multi-piece solid golf ball.
12 . A coating layer is formed on the cover surface, and when the Shore C hardness of the coating layer is Hc, the difference between the Shore C hardness C _M at the midpoint M between the center and the surface of the core and Hc (C 12. The multi-piece solid golf ball according to 10 or 11 above, wherein _M -Hc) is -10 or more and 10 or less.

According to the multi-piece solid golf ball of the present invention, the spin rate of the ball on a full shot with a driver is reduced, the flight distance of the ball is further increased, the ball has good controllability on approach, and the feel on impact is good. The multi-layered golf ball has excellent scratch resistance and is very useful as a golf ball for professionals and advanced golfers.

1 is a schematic cross-sectional view of a multi-piece solid golf ball (five-layer structure) of the present invention; FIG. FIG. 2 is a schematic diagram explained using the core hardness distribution data of Example 1 in order to explain the areas A to F of the core hardness distribution.

The present invention will be described in more detail below.
The multi-piece solid golf ball of the present invention, as shown in FIG. , and a cover 4 covering the intermediate layer. A large number of dimples D are usually formed on the surface of the cover 4 . Moreover, although not shown, a coating film layer is usually formed on the surface of the cover 4 by painting. Except for the coating layer, the cover 4 is positioned as the outermost layer in the layered structure of the golf ball. The core 1, the intermediate layer 3, and the cover 4 are not limited to a single layer, but may be formed in multiple layers of two or more layers.

The diameter of the core is preferably 30.0 mm or more, more preferably 31.0 mm or more, and still more preferably 31.5 mm or more, and the upper limit is preferably 35.0 mm or less, more preferably 34.0 mm or less, and more preferably 34.0 mm or less. Preferably, it is 33.5 mm or less. If the diameter of the core is too small, the spin rate increases when hit with a driver (W#1), and the target flight distance may not be obtained. On the other hand, if the diameter of the core is too large, the durability against repeated impacts may deteriorate, or the feel on impact may deteriorate.

The amount of deflection (mm) when the core is loaded with an initial load of 98 N (10 kgf) to a final load of 1,275 N (130 kgf) is not particularly limited, but is preferably 3.0 mm or more, more preferably 3.0 mm. 0.5 mm or more, more preferably 4.0 mm or more, and the upper limit is preferably 7.0 mm or less, more preferably 6.0 mm or less, still more preferably 5.0 mm or less. If the deflection amount of the core is too small, that is, if the core is too hard, the spin of the ball may increase too much, resulting in poor flight or an excessively hard hitting feel. On the other hand, if the deflection of the core is too large, i.e., if the core is too soft, the resilience of the ball will be too low and the ball will not fly, the feel on impact will be too soft, or the durability to cracking on repeated impact will be poor. Sometimes.

A rubber material is used as the main material for the core. Specifically, a rubber composition can be produced by mainly comprising a base rubber and blending a co-crosslinking agent, an organic peroxide, an inert filler, an organic sulfur compound, and the like. Polybutadiene is preferably used as the base rubber.

Commercially available polybutadiene can be used, and examples thereof include BR01, BR51, and BR730 (manufactured by JSR Corporation). Also, the proportion of polybutadiene 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 rubber components other than polybutadiene include polybutadiene other than polybutadiene, and other diene rubbers such as styrene-butadiene rubber, natural rubber, isoprene rubber, and ethylene-propylene-diene rubber.

Examples of co-crosslinking agents include unsaturated carboxylic acids and metal salts of unsaturated carboxylic acids. Specific examples of unsaturated carboxylic acids include acrylic acid, methacrylic acid, maleic acid and fumaric acid, with acrylic acid and methacrylic acid being particularly preferred. Although the metal salt of unsaturated carboxylic acid is not particularly limited, examples thereof include those obtained by neutralizing the above unsaturated carboxylic acid with a desired metal ion. Specific examples include zinc salts and magnesium salts of methacrylic acid and acrylic acid, and zinc acrylate is particularly preferably used.

The unsaturated carboxylic acid and/or 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 the upper limit is usually 60 parts by mass, per 100 parts by mass of the base rubber. Below, it is preferably 50 parts by mass or less, more preferably 40 parts by mass or less. If the amount is too large, the ball may become too hard, resulting in an unbearable feel on impact. If the amount is too small, the rebound may decrease.

Commercially available products can be used as the organic peroxide. For example, Permil D (manufactured by NOF Corporation), Perhexa C-40, Perhexa 3M (manufactured by NOF Corporation), Luperco 231XL (manufactured by Atochem) ) and the like can be suitably used. These may be used singly or in combination of two or more. The amount of the organic peroxide compounded is preferably 0.1 parts by mass or more, more preferably 0.3 parts by mass or more, still more preferably 0.5 parts by mass or more, most preferably 100 parts by mass of the base rubber. is 0.6 parts by mass or more, and the upper limit is 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 on impact, durability and resilience.

In addition, as a compounding agent to be compounded with the base rubber, an inert filler can be mentioned, and for example, zinc oxide, barium sulfate, calcium carbonate, etc. can be preferably used. These may be used individually by 1 type, and may use 2 or more types together. The amount of the inert filler compounded 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, relative to 100 parts by mass of the base rubber. and more preferably 36 parts by mass or less. If the blending amount is too large or too small, it may not be possible to obtain proper mass and suitable resilience.

Furthermore, an anti-aging agent can be blended as necessary. ) made) and the like. These may be used individually by 1 type, and may use 2 or more types together.

The amount of the antioxidant compounded 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 the upper limit is preferably 3 parts per 100 parts by mass of the base rubber. The amount is not more than 2 parts by mass, more preferably not more than 2 parts by mass, particularly preferably not more than 1 part by mass, and most preferably not more than 0.5 parts by mass. If the blending amount is too large or too small, it may not be possible to obtain suitable resilience and durability.

In addition, an organic sulfur compound may be blended into 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 salts of parachlorothiophenol, diphenylpolysulfides having 2 to 4 sulfur atoms, dibenzylpolysulfides, dibenzoylpolysulfides, dibenzothiazolylpolysulfides, dithiobenzoylpolysulfides, etc., and zinc salts of pentachlorothiophenol are particularly preferred. used for The amount of the organic sulfur compound compounded is preferably 0 parts by mass or more, more preferably 0.05 parts by mass or more, and still more preferably 0.1 parts by mass or more, with respect to 100 parts by mass of the base rubber. It is recommended that the amount is 5 parts by mass or less, more preferably 3 parts by mass or less, and even more preferably 2.5 parts by mass or less. If the amount is too large, the effect of improving the resilience (especially on W#1 hits) cannot be expected any more, and the core may become too soft or the feel on impact may be poor. On the other hand, if the blending amount is too small, the effect of improving the resilience cannot be expected.

More specifically, by blending water (a water-containing material) directly with the core material, decomposition of organic peroxides in the core formulation can be accelerated. Further, it is known that the decomposition efficiency of the organic peroxide in the core rubber composition changes depending on the temperature, and the decomposition efficiency increases as the temperature rises above a certain temperature. If the temperature is too high, the amount of decomposed radicals will be too large, and the radicals will recombine or be inactivated. As a result, the number of radicals that effectively work for cross-linking is reduced. Here, when decomposition heat is generated by decomposition of the organic peroxide during core vulcanization, the temperature near the core surface is maintained at approximately the same temperature as that of the vulcanization mold, but the temperature near the core center is maintained on the outside. Since the decomposition heat of the organic peroxide decomposed from the mold is accumulated, the temperature becomes considerably higher than the mold temperature. When water (a material containing water) is added directly to the core, water acts to promote the decomposition of the organic peroxide, so it is possible to change the above-mentioned radical reaction between the core center and the core surface. can. That is, in the vicinity of the core center, the decomposition of the organic peroxide is further promoted, and the inactivation of radicals is further promoted, resulting in a further decrease in the amount of effective radicals. and cores with different dynamic viscoelastic properties at the center of the core can be obtained.

The water to be mixed with the core material is not particularly limited, and may be distilled water or tap water. In particular, it is preferable to use distilled water containing no impurities. be. The amount of water to be blended is preferably 0.1 parts by mass or more, more preferably 0.3 parts by mass or more, with respect to 100 parts by mass of the base rubber, and the upper limit is preferably 5 parts by mass or less. and more preferably 4 parts by mass or less.

The core can be produced by vulcanizing and curing a rubber composition containing the above components. For example, it is kneaded using a kneader such as a Banbury mixer or a roll, compression molded or injection molded using a core mold, and the temperature is 100 to 100 as a temperature sufficient for the organic peroxide or co-crosslinking agent to act. By appropriately heating the molded article under conditions of 200° C., preferably 140 to 180° C., for 10 to 40 minutes, the molded article can be cured and produced.

Moreover, the core can be formed not only as a single layer but also as two layers, an inner core layer and an outer core layer. When the core is formed of two layers, an inner core layer and an outer core layer, the above-described rubber material can be used as the main material for both the inner layer core and the outer core layer. Further, the rubber material of the outer core layer covering the inner core layer may be the same as or different from the material of the inner core. Specifically, it is the same as explained for each component of the rubber material of the core.

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

The center hardness (Cc) of the core is preferably 50 or more, more preferably 52 or more, and still more preferably 54 or more, and the upper limit thereof is preferably 59 or less, more preferably 57 or less, and further preferably 55 or less. is. If this value is too large, the hit feeling may become hard, or the spin may increase on full shots, making it impossible to obtain the desired flight distance. On the other hand, if the above value is too small, the resilience will be low and the ball will not fly, or the durability to cracking upon repeated hitting will deteriorate.

The surface hardness (Cs) of the core is preferably 73 or higher, more preferably 75 or higher, and still more preferably 77 or higher, and the upper limit thereof is preferably 85 or lower, more preferably 83 or lower, and further preferably 81 or lower. is. Deviating from these hardnesses may lead to the same disadvantageous results as explained for the center hardness (Cc) of the core.

The difference between the surface hardness (Cs) of the core and the central hardness (Cc) of the core is preferably 20 or more, more preferably 22 or more, still more preferably 24 or more, and the upper limit is preferably 35 or less, more preferably is 32 or less, more preferably 28 or less. If this value is too small, the effect of lowering the spin rate of the ball on driver shots may not be sufficient, and the flight distance may not be obtained. If the above value is too large, the initial velocity of the ball when actually hit may be low, resulting in a loss of flight distance, or the durability to cracking when hit repeatedly may be poor.

In the above core hardness distribution in the present invention, Cc is the Shore C hardness of the center of the core, Cs is the Shore C hardness of the surface of the core, C _M is the Shore C hardness of the midpoint M between the center and the surface of the core, and the midpoint The Shore C hardness at positions 2.5 mm, 5.0 mm and 7.5 mm from M to the core surface side are respectively C _{M +2.5} , C _{M +5.0} and C _{M +7.5} , and from the midpoint M to the core center side When the Shore C hardness at positions of 2.5 mm, 5.0 mm and 7.5 mm are respectively C _M-2.5 , C _M-5.0 and C _M-7.5 , the areas A to F calculated from the following formula
・Area A: 1/2 × 2.5 × (C _M-5.0 -C _M-7.5 ),
・Area B: 1/2 × 2.5 × (C _M-2.5 -C _M-5.0 ),
・Area C: 1/2 × 2.5 × (C _M -C _M-2.5 ),
・Area D: 1/2×2.5×(C _M+2.5 −C _M ),
area E: 1/2 x 2.5 x (C _M+5 - C _M+2.5 ), and area F: 1/2 x 2.5 x (C _M+7.5 - _{C M+5} )
, (Area D + Area E + Area F) - (Area A + Area B + Area C) preferably satisfies a specific range described later. FIG. 2 shows a schematic diagram explaining the areas A to F using the core hardness distribution data of Example 1. As shown in FIG. Thus, the areas A to F are areas of triangles whose bases are the differences in the specific distances and whose heights are the differences in the position hardness.

The lower limit of (Area D + Area E + Area F) - (Area A + Area B + Area C) is preferably 3 or more, more preferably 4 or more, and still more preferably 6 or more. This upper limit is preferably 20 or less, more preferably 15 or less, and even more preferably 10 or less. If the above value is too small, the effect of lowering the spin rate when hit with a driver (W#1) is insufficient, and the flight distance may not be obtained. If the above value is too large, the initial velocity of actual hits will be low, resulting in a loss of flight distance, or the resistance to cracking on repeated hits will be poor.

Further, in the core hardness distribution, it is preferable to satisfy the following formula: 0.15≤[(Area D + Area E + Area F) - (Area A + Area B + Area C)]/(Cs - Cc)≤0.60. The lower limit of this value is more preferably 0.20 or more, more preferably 0.25 or more, and the upper limit is more preferably 0.50 or less, still more preferably 0.40 or less. If the above value is too small, the effect of lowering the spin rate when hit with a driver (W#1) is insufficient, and the flight distance may not be obtained. If the above value is too large, the actual initial velocity of the ball may become low, resulting in a loss of flight distance or poor durability to cracking upon repeated hitting.

Furthermore, in the above core hardness distribution, the following formula -2 ≤ (area D + area E) - (area A + area B + area C) ≤ 8
is preferably satisfied, and the lower limit of this value is more preferably 0 or more, and still more preferably 1 or more. The upper limit is more preferably 6 or less, still more preferably 4 or less. If the above value is too small, the effect of lowering the spin rate when hit with a driver (W#1) is insufficient, and the flight distance may not be obtained. If the above value is too large, the actual initial velocity of the ball may become low, resulting in a loss of flight distance or poor durability to cracking upon repeated hitting.

The areas B to E of the core hardness distribution preferably satisfy area B<area C≦area D<area E. Otherwise, the effect of reducing the spin rate when hit with a driver (W#1) may be insufficient, resulting in a loss of flight distance.

Next, the surrounding layer will be explained.
In the present invention, the envelope layer is formed of two layers, an inner layer and an outer layer. They are hereinafter referred to as an inner envelope layer and an outer envelope layer, respectively.

The material hardness of the inner envelope layer is not particularly limited, but the Shore D hardness is preferably 46 or more, more preferably 48 or more, and still more preferably 50 or more, and the upper limit is preferably 60 or less, more preferably 58 or less, more preferably 56 or less. In addition, the surface hardness of the sphere obtained by coating the core with the inner envelope layer (inner envelope layer-covered sphere) is preferably 52 or higher, more preferably 54 or higher, and still more preferably 56 or higher in Shore D hardness. is preferably 66 or less, more preferably 64 or less, still more preferably 62 or less. If the material hardness and surface hardness of these inner enveloping layers are too softer than the above ranges, the spin rate of the ball on full shots will increase, and the desired flight distance may not be obtained. On the other hand, if the above material hardness and surface hardness are too high, the feel on impact may become too hard, or the durability to cracking due to repeated impact may deteriorate.

The thickness of the inner envelope layer is preferably 0.8 mm or more, more preferably 1.0 mm or more, and even more preferably 1.2 mm or more. On the other hand, the upper limit of the thickness of the inner envelope layer is preferably 1.8 mm or less, more preferably 1.6 mm or less, still more preferably 1.4 mm or less. If the thickness of the inner enveloping layer is out of the above range, the effect of reducing the spin rate when hit with a driver (W#1) may be insufficient, resulting in a loss of flight distance.

On the other hand, the material hardness of the outer envelope layer is not particularly limited, but the Shore D hardness is preferably 43 or more, more preferably 45 or more, and still more preferably 47 or more. It is preferably 52 or less, more preferably 50 or less. The surface hardness of the sphere obtained by coating the inner envelope-covered sphere with the outer envelope (outer envelope-covered sphere) is preferably 49 or more, more preferably 51 or more, and even more preferably 53 or more in terms of Shore D hardness. The upper limit is preferably 60 or less, more preferably 58 or less, still more preferably 56 or less. If the material hardness and surface hardness of these outer envelope layers are too softer than the above range, the spin rate of the ball on full shots will increase, and the desired flight distance may not be obtained. On the other hand, if the above material hardness and surface hardness are too high, the feel on impact may become too hard, or the durability to cracking due to repeated impact may deteriorate.

The thickness of the outer envelope layer is preferably 0.8 mm or more, more preferably 1.0 mm or more, still more preferably 1.1 mm or more. On the other hand, the upper limit of the thickness of the outer envelope layer is preferably 1.7 mm or less, more preferably 1.5 mm or less, and even more preferably 1.3 mm or less. If the thickness of the outer enveloping layer is outside the above range, the effect of reducing the spin rate when hit with a driver (W#1) may be insufficient, resulting in a loss of flight distance.

Materials for the inner envelope layer and the outer envelope layer are not particularly limited, but known resins can be used. Examples of particularly preferred materials include the following components (A) to (D),
(a-1) an olefin-unsaturated carboxylic acid binary random copolymer and/or a metal ion neutralized product of an olefin-unsaturated carboxylic acid binary random copolymer;
(a-2) Metal ion-neutralized olefin-unsaturated carboxylic acid-unsaturated carboxylic acid ester ternary random copolymer and/or olefin-unsaturated carboxylic acid-unsaturated carboxylic acid ester ternary random copolymer (A) base resin blended so that the mass ratio is 100: 0 to 0: 100,
(B) With respect to 100 parts by mass of the resin component blended with a non-ionomer thermoplastic elastomer at a mass ratio of 100:0 to 50:50,
(C) 5 to 120 parts by mass of fatty acids and/or derivatives thereof having a molecular weight of 228 to 1500;
(D) A resin composition containing, as an essential component, 0.1 to 17 parts by mass of a basic inorganic metal compound capable of neutralizing unneutralized acid groups in components (A) and (C). can be exemplified.

For the above components (A) to (D), for example, intermediate layer resin materials (A) to (D) described in JP-A-2010-253268 can be suitably employed.

The resin materials forming the inner enveloping layer and the outer enveloping layer may be the same or different.

A non-ionomer thermoplastic elastomer can be blended into each material of the inner envelope layer and the outer envelope layer. The amount of the non-ionomer thermoplastic elastomer to be blended is preferably 0 to 50 parts by mass per 100 parts by mass of the base resin.

Examples of the non-ionomer thermoplastic elastomers include polyolefin elastomers (including polyolefins and metallocene polyolefins), polystyrene elastomers, diene polymers, polyacrylate polymers, polyamide elastomers, polyurethane elastomers, polyester elastomers, and polyacetals. etc. can be mentioned.

Arbitrary additives can be appropriately added to the above resin material depending on the application. For example, various additives such as pigments, dispersants, anti-aging agents, ultraviolet absorbers and light stabilizers can be added. When these additives are blended, the blending amount is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, with respect to the total 100 parts by mass of the base resin, and the upper limit is preferably It is 10 parts by mass or less, more preferably 4 parts by mass or less.

Next, the intermediate layer will be explained.
The material hardness of the intermediate layer is not particularly limited, but the Shore D hardness is preferably 60 or more, more preferably 63 or more, and still more preferably 65 or more, and the upper limit is preferably 72 or less, more preferably 70. 68 or less, more preferably 68 or less. Further, the surface hardness of the sphere (intermediate layer-covered sphere) obtained by coating the outer envelope layer-covered sphere with the intermediate layer is preferably 66 or more, more preferably 69 or more, further preferably 71 or more in terms of Shore D hardness, The upper limit is preferably 78 or less, more preferably 76 or less, and even more preferably 74 or less. If the material hardness and surface hardness of these intermediate layers are too soft, the resilience of the ball on a full shot may be insufficient or the spin rate may be too high, resulting in a loss of flight distance. If the above material hardness and surface hardness are too high, the durability to cracking due to repeated impact may deteriorate, or the feel on impact may become too hard.

The thickness of the intermediate layer is preferably 0.8 mm or more, more preferably 1.0 mm or more, still more preferably 1.1 mm or more. On the other hand, the upper limit of the thickness of the intermediate layer is preferably 1.7 mm or less, more preferably 1.5 mm or less, and still more preferably 1.3 mm or less. The thickness of the intermediate layer is preferably thicker than the later-described cover (outermost layer). If the thickness of the intermediate layer deviates from the above range, or if it is formed thinner than the cover, the effect of reducing the spin rate when hit with a driver (W#1) may be insufficient, resulting in a loss of flight distance.

As for the material of the intermediate layer, it is preferable to employ various thermoplastic resins used in golf ball materials, particularly ionomer resins, and commercially available ionomer resins can be used. Further, as the resin material for the intermediate layer, among commercially available ionomer resins, a high acid content ionomer resin having an acid content of 16% by mass or more can be blended with a normal ionomer resin. It is possible to obtain a good flight distance when hit with a driver (W#1) due to spin.

The unsaturated carboxylic acid content (acid content) 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 is preferably is 22% by mass or less, more preferably 21% by mass or less, and still more preferably 20% by mass or less. If this value is too small, spin increases on full shots, and the target flight distance may not be obtained. Conversely, if the above value is too large, the feel on impact may become too hard, or the durability to cracking upon repeated impact may deteriorate.

The high acid content ionomer resin is preferably 10% by mass or more, more preferably 30% by mass or more, and still more preferably 60% by mass or more with respect to 100% by mass of the resin material. If the amount of the ionomer resin with a high acid content is too small, the spin rate increases when hit with a driver (W#1), and the flight distance may not be achieved.

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

As for the material of the intermediate layer, 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. Furthermore, it is preferable to apply a primer (adhesive) to the surface of the intermediate layer after the polishing treatment, or add an adhesion-enhancing agent to the material.

The specific gravity of the intermediate layer material is usually less than 1.1, preferably 0.90-1.05, more preferably 0.93-0.99. If it deviates from this range, the rebound of the ball as a whole will be low, resulting in a loss of flight distance, or the resistance to cracking due to repeated impacts will 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 35 or more, more preferably 40 or more, and the upper limit is preferably 55 or less, more preferably 53 or less, and further preferably 50 or less. is. The surface hardness of the sphere obtained by covering the intermediate layer-covered sphere with a cover (ball-covered sphere) is preferably 50 or more, more preferably 55 or more, and still more preferably 58 or more in Shore D hardness. , preferably 66 or less, more preferably 64 or less, still more preferably 63 or less. If the material hardness of the cover and the ball surface hardness are too softer than the above range, the spin rate increases when hit with a driver (W#1), and the flight distance may not be achieved. If the above material hardness and surface hardness are too high, the controllability in the short game may deteriorate, or the scuff resistance may deteriorate.

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 1.0 mm or less, and even more preferably 0.8 mm or less. Moreover, it is preferable that the thickness of the cover is thinner than that of the intermediate layer. If the thickness of the cover deviates from the above range or is thicker than the intermediate layer, the effect of reducing the spin rate when hit with a driver (W#1) may be insufficient, resulting in a loss of flight distance.

Various thermoplastic resins used in golf ball cover materials can be used as the cover material, but urethane resins are preferred from the viewpoint of controllability and scratch resistance. In particular, from the viewpoint of mass-producibility of ball products, it is preferable to use thermoplastic polyurethane as the main component, and more preferably, (I) thermoplastic polyurethane and (II) polyisocyanate compound are the main components. It can be formed by a resin formulation.

The total mass of components (I) and (II) is recommended to be 60% or more, more preferably 70% or more, of the total amount of the resin composition for the cover. The components (I) and (II) are described in detail below.

Regarding the above (I) thermoplastic polyurethane, the structure of the thermoplastic polyurethane consists of a soft segment composed of a high-molecular polyol (polymeric glycol), which is a long-chain polyol, and a hard segment composed of a chain extender and a polyisocyanate compound. include. Here, as the long-chain polyol used as a raw material, any of those conventionally used in techniques related to thermoplastic polyurethanes can be used, and there is no particular limitation, but examples include polyester polyols, polyether polyols, and polycarbonate polyols. , polyester polycarbonate polyols, polyolefin polyols, conjugated diene polymer polyols, castor oil polyols, silicone polyols, vinyl polymer polyols, 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, polyether polyols are preferable in that a thermoplastic polyurethane having a high rebound resilience and excellent low-temperature properties can be synthesized.

As the chain extender, those used in the technology related to conventional thermoplastic polyurethanes can be suitably used. It is preferably a molecular compound. Chain extenders 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, aliphatic diols having 2 to 12 carbon atoms are preferable as the chain extender, and 1,4-butylene glycol is more preferable.

As the polyisocyanate compound, those used in conventional techniques relating to thermoplastic polyurethanes can be suitably 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, hydrogenation One or more selected from the group consisting of xylylene diisocyanate, dicyclohexylmethane diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, norbornene diisocyanate, trimethylhexamethylene diisocyanate, and dimer acid diisocyanate can be used. However, with some isocyanate species, it is difficult to control the cross-linking reaction during injection molding. In the present invention, 4,4'-diphenylmethane diisocyanate, which is an aromatic diisocyanate, is most preferred from the viewpoint of the balance between the stability during production and the physical properties that are exhibited.

Commercially available products can also be used as specific thermoplastic polyurethanes for component (I), and examples thereof include Pandex T8295, Pandex T8290 and Pandex T8260 (all manufactured by DIC Covestro Polymer).

Although not an essential component, a thermoplastic elastomer other than the thermoplastic polyurethane can be blended with the above components (I) and (II) as a separate component (III). By blending this component (III) into the resin composition, it is possible to further improve the fluidity of the resin composition, resilience, scratch resistance, and other physical properties required for golf ball cover materials. .

The composition ratio of the components (I), (II) and (III) is not particularly limited, but in order to fully and effectively exhibit the effects of the present invention, the mass ratio of (I):(II) : (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.

Furthermore, various additives other than the components constituting the thermoplastic polyurethane can be blended into the above resin composition, if necessary, such as pigments, dispersants, antioxidants, and light stabilizers. , an ultraviolet absorber, a release agent, and the like can be appropriately added.

A multi-piece solid golf ball formed by stacking the core, inner envelope layer, outer envelope layer, intermediate layer, and cover (outermost layer) described above can be manufactured by a conventional method such as injection molding. can do. For example, materials for an inner envelope layer, an outer envelope layer, and an intermediate layer are sequentially injected around the core using respective injection molding dies to obtain each covering sphere, and finally, the material for the outermost layer, the cover. A multi-piece golf ball can be obtained by injection molding. Alternatively, a golf ball can be produced by wrapping the coated sphere with two half-cups, which have been formed in advance into a semi-spherical shape, as the respective coating layers, and molding the coated sphere under heat and pressure.

[ Hardness relationship of each layer ]
In the present invention, the center hardness and surface hardness of the core, the surface hardness of a sphere obtained by covering the core with an inner envelope layer (inner envelope layer-covered sphere), and the sphere obtained by coating the inner envelope layer-covered sphere with an outer envelope layer. The surface hardness of (outer envelope-covered sphere), the surface hardness of a sphere obtained by coating the outer envelope-layer-covered sphere with an intermediate layer (intermediate-layer-covered sphere), and the surface hardness of the ball are calculated by the following formula: core center hardness<core surface hardness< It is preferable to satisfy the following conditions: surface hardness of inner envelope-covered sphere>surface hardness of outer envelope-covered sphere<surface hardness of intermediate-layer-covered sphere>ball surface hardness. If the above hardness relationship is not satisfied, sufficient flight performance on driver (W#1) shots may not be obtained, or the feel may be hard on shots, and spin rate on approach shots may increase. becomes smaller, and the control performance may deteriorate.

Regarding the hardness relationship above, it is preferable to satisfy (core surface hardness) < (surrounding layer outer surface hardness) from the viewpoint of suppressing spin on driver (W#1) shots and ensuring good flight distance. is.

[ Thickness relationship of each layer ]
In the present invention, the thickness of the (inner/outer) enveloping layer satisfies (thickness of inner enveloping layer)≧(thickness of outer enveloping layer) from the viewpoint of achieving both good flight and controllability in the short game. In particular, it is preferred that the inner envelope layer is thicker than the outer envelope layer, and more preferably the inner envelope layer is thicker than the intermediate layer.

The thicknesses of the outer envelope layer and the intermediate layer preferably satisfy (thickness of the intermediate layer)≧(thickness of the outer envelope layer), and in particular, the intermediate layer is thicker than the outer envelope layer. is preferred.

As described above, the intermediate layer is preferably formed thicker than the cover. In this case, the thickness difference between the intermediate layer and the cover should be 0.2 mm or more and 1.2 mm or less. is preferred. Outside the above range, it may not be possible to achieve both good flight and controllability in the short game.

Further, the thickness of each layer of the envelope layer, the intermediate layer and the cover is calculated by [total thickness of the inner envelope layer and the outer envelope layer (mm)] - [total thickness of the intermediate layer and the cover (mm)]. is preferably 0.1 mm or more, more preferably 0.3 mm or more, and even more preferably 0.4 mm or more. The upper limit is preferably 1.0 mm or less, more preferably 0.8 mm or less, and even more preferably 0.6 mm or less. Outside the above range, it may not be possible to achieve both good flight and controllability in the short game.

A large number of dimples can be formed on the outer surface of the cover, which is the outermost layer. The number of dimples arranged on the surface of the cover is not particularly limited, but is preferably 250 or more, more preferably 300 or more, still more preferably 320 or more, and the upper limit is preferably 380 or less, more preferably 350 or less, more preferably 340 or less can be provided. If the number of dimples exceeds the above range, the trajectory of the ball will be low and the flight distance will be reduced. Conversely, if the number of dimples is small, the trajectory of the ball becomes high, and the flight distance may not increase.

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

The dimple occupancy rate of the spherical surface of the golf ball, specifically, the total dimple area defined by the edge of the plane surrounded by the edges of the dimples occupies the spherical area of the ball assuming no dimples. The ratio (SR value) is desirably 70% or more and 90% or less from the viewpoint of being able to sufficiently exhibit the aerodynamic characteristics. Also, the value _V0 obtained by dividing the spatial volume of a dimple under a plane surrounded by the edges of each dimple by the volume of a cylinder whose bottom is the plane and whose height is the maximum depth of the dimple from this bottom is From the point of view of optimizing the trajectory of the ball, it is preferable to set it to 0.35 or more and 0.80 or less. Furthermore, the total dimple volume formed downward from the plane surrounded by the edges of the dimples occupies the ball volume assuming that no dimples exist, and the VR value should be 0.6% or more and 1.0% or less. is preferred. If the range of each numerical value is deviated from the above range, the trajectory will not provide a good flight distance, and a satisfactory flight distance may not be obtained.

A coating film layer (coating layer) can be formed on the surface of the cover. This coating layer can be coated with various types of paints. As the paint, it is necessary to withstand the harsh conditions of use of the golf ball. It is preferred to use a composition.

Examples of the polyol component include acrylic polyols and polyester polyols. These polyols include modified polyols, 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 together. In this case, when two types of polyester polyols are used as components (a) and (b), a polyester polyol having a cyclic structure introduced into the resin skeleton can be employed as the polyester polyol for component (a). , polycondensation of polyols having an alicyclic structure such as cyclohexanedimethanol and polybasic acids, or polyester polyols obtained by polycondensation of polyols having an alicyclic structure and diols or triols and polybasic acids. . On the other hand, as the polyester polyol of component (b), a polyester polyol having a multi-branched structure can be employed, and examples thereof include polyester polyols having a branched structure such as "NIPPOLAN 800" manufactured by Tosoh Corporation.

On the other hand, the polyisocyanate is not particularly limited, and is commonly used aromatic, aliphatic, alicyclic polyisocyanate, specifically, tolylene diisocyanate, diphenylmethane diisocyanate, xylylene diisocyanate. , tetramethylene diisocyanate, hexamethylene diisocyanate, lysine diisocyanate, isophorone diisocyanate, 1,4-cyclohexylene diisocyanate, naphthalene diisocyanate, trimethylhexamethylene diisocyanate, dicyclohexylmethane diisocyanate, 1-isocyanato-3,3,5-trimethyl-4-isocyanate Natomethylcyclohexane and the like can be mentioned. These can be used singly or in combination.

Various organic solvents can be mixed in the coating composition depending on the coating conditions. Examples of such organic solvents 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. , methyl isobutyl ketone, ketone solvents such as cyclohexanone, ether solvents such as diethylene glycol dimethyl ether, diethylene glycol diethyl ether, dipropylene glycol dimethyl ether, alicyclic hydrocarbon solvents such as cyclohexane, methylcyclohexane, ethylcyclohexane, mineral spirits, etc. A petroleum hydrocarbon solvent or the like can be used.

The thickness of the coating film layer composed of the coating composition is not particularly limited, but is usually 5 to 40 µm, preferably 10 to 20 µm. The thickness of the coating film layer referred to here means the average thickness of the coating film measured at three points in total, namely, the center of the dimple and 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 coating layer composed of the above coating composition is required to be 60% or more, preferably 80% or more. When the elastic work recovery rate of the coating layer is within the above range, the coating layer has a high elastic force, so that the self-healing function is high and the wear resistance is extremely excellent. In addition, various performances of golf balls coated with the coating composition can be improved. The method for measuring the elastic work recovery rate is as follows.

The elastic work recovery rate is an ultra-micro hardness test method that controls the indentation load on the order of micro Newtons (μN) and tracks the indenter depth during indentation with nanometer (nm) accuracy. It is one of the parameters of the nanoindentation method for evaluating physical properties. Conventional methods could only measure the size of the deformation mark (plastic deformation mark) corresponding to the maximum load, but the nanoindentation method automatically and continuously measures the relationship between the indentation load and the indentation depth. can be obtained. Therefore, it is thought that the physical properties of the coating film layer can be evaluated with high accuracy without individual differences such as in the conventional visual measurement of deformation marks with an optical microscope. The coating layer on the surface of the ball is greatly affected by the impact of drivers and clubs, and the effect of the coating layer on the physical properties of the golf ball is not small. However, it will be a very effective evaluation method if it is performed with higher accuracy than before.

As for the hardness of the coating layer, the Shore M hardness 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 conforms to ASTM D2240. The Shore C hardness of the coating film layer is preferably 40 or more, and preferably 80 or less as an upper limit. The Shore C hardness conforms to ASTM D2240. If the hardness of the coating layer is higher than the above range, the coating becomes brittle when repeatedly hit, and the cover layer may not be protected. If the coating layer has a hardness smaller than the above range, the surface of the ball tends to be scratched when it hits a hard object, which is undesirable.

When the Shore C hardness of the coating layer is Hc, the difference between the Shore C hardness C _M at the midpoint M between the center and surface of the core and Hc (C _M -Hc) is preferably -10 or more, more preferably -5 or more, and the upper limit is preferably 10 or less, more preferably 5 or less.

When the above coating composition is used, the coating composition of the present invention is prepared at the time of coating on a golf ball manufactured by a known method, applied to the surface using a conventional coating process, and then dried. A coating film layer can be formed on the ball surface through In this case, as a coating method, a spray coating method, an electrostatic coating method, a dipping method, or the like can be suitably employed, and there is no particular limitation.

The multi-piece solid golf ball of the present invention can comply with the Rules of Golf for competition use, and has an outer diameter of 42.672 mm or less, which does not pass through a ring with an inner diameter of 42.672 mm, and a mass of preferably 42.80 mm or less. It can be formed from 45.0 to 45.93 g.

EXAMPLES Hereinafter, the present invention will be specifically described by showing examples and comparative examples, but the present invention is not limited to the following examples.

[Examples 1 to 4, Comparative Examples 1 to 8]
core formation
After preparing the rubber compositions of Examples and Comparative Examples shown in Table 1, solid cores were produced by vulcanization molding under vulcanization conditions of 155° C. for 15 minutes.

In addition, the details of each component described in Table 1 are as follows.
・Polybutadiene A: manufactured by JSR, trade name “BR01”
・Polybutadiene B: manufactured by JSR, trade name “BR51”
・ Polybutadiene C: manufactured by JSR, trade name “BR730”
・ Zinc acrylate: “ZN-DA85S” (manufactured by Nippon Shokubai Co., Ltd.)
・Organic peroxide (1): dicumyl peroxide, trade name “Percumyl D” (manufactured by NOF Corporation)
-Organic peroxide (2): a mixture of 1,1-di(t-butylperoxy)cyclohexane and silica, trade name "Perhexa C-40" (manufactured by NOF Corporation)
・Water: Pure water (manufactured by Seiki Pharmaceutical Co., Ltd.)
· Anti-aging agent: 2,2-methylenebis (4-methyl-6-butylphenol), trade name Nocrack NS-6 (manufactured by Ouchi Shinko Chemical Industry Co., Ltd.)
・Barium sulfate: Arsenic barium sulfate Barico #100 (manufactured by Shiramizu Chemical Industry Co., Ltd.)
・ Zinc oxide: Product name “Three kinds of zinc oxide” (manufactured by Sakai Chemical Industry Co., Ltd.)
・Pentachlorothiophenol zinc salt: manufactured by Wako Pure Chemical Industries, Ltd.

Surrounding layer (inner/outer)
Next, for each example and each comparative example except for comparative example 6, No. 1 shown in Table 2 was attached around the core. 1 or No. An inner envelope layer was formed by an injection molding method using the inner envelope layer material of formulation No. 4, and then the inner envelope layer was formed using No. 4 shown in the same table. 2, No. 3, No. 5, No. 6 or No. The outer envelope layer was formed by an injection molding method using the outer envelope layer material of formulation No. 7. For Comparative Example 6, No. in Table 2. 2, a single-layer envelope layer (outer envelope layer) was formed around the core by injection molding.

Formation of Intermediate Layer and Cover (Outermost Layer) Next, for all of the examples and comparative examples, No. 2 of the composition shown in Table 2 was added around the envelope-coated spheres obtained above. 8, No. 9 or No. The intermediate layer was formed by an injection molding process using 10 formulations of the intermediate layer material. Next, No. 1 of the formulation shown in Table 2 was placed around the intermediate layer-covered spheres of each of the above examples. 11, No. 12 or No. A cover (outermost layer) was formed by an injection molding method using 13 formulations of the cover material. At this time, a predetermined number of dimples common to all the examples and comparative examples were formed on the cover surface.

The trade names of the main materials listed in the table are as follows.
"HPF1000" Dupont HPF(TM) 1000
"HPF2000" Dupont HPF(TM) 2000
“Himilan” ionomer manufactured by DuPont Mitsui Polychemicals “Surlyn” ionomer manufactured by DuPont “Hytrel” Thermoplastic polyether ester elastomer manufactured by DuPont Toray “Trimethylolpropane” (TMP) “Polytail H” manufactured by Tokyo Chemical Industry Co., Ltd. "Mitsubishi Kasei Co., Ltd., polyhydroxy hydrocarbon-based polymer "T-8295, T-8290, T-8283" DIC Covestro Polymer Co., Ltd., MDI-PTMG type thermoplastic polyurethane "Polyethylene wax" Sanyo Kasei Co., Ltd. Made by "Sunwax 161P"
"Isocyanate compound"4,4'-diphenylmethane diisocyanate
Formation of coating layer (coating layer)
Next, as a coating composition common to all Examples and Comparative Examples, coating composition I shown in Table 3 below was used, and the above coating was applied by an air spray gun to the surface of a large number of covers (outermost layers). A golf ball was prepared by coating to form a coating film layer having a thickness of 15 μm.

[Synthesis example of polyester polyol (A)]
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 were placed in a reactor equipped with a reflux condenser, a dropping funnel, a gas inlet tube and a thermometer. After charging, the temperature was raised to 200 to 240° C. while stirring, and the mixture was heated (reacted) for 5 hours. Thereafter, "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) was dissolved in butyl acetate to prepare a varnish having a non-volatile content of 70% by mass.

Coating composition I in Table 3 is, for 23 parts by mass of the polyester polyol solution, "polyester polyol (B)" (saturated aliphatic polyester polyol "NIPPOLAN 800" manufactured by Tosoh Corporation, weight average molecular weight (Mw) 1,000, solid content 100%) was mixed with an organic solvent to prepare a main agent. This mixture had a non-volatile content of 38.0 mass %.

Elastic Work Recovery Rate The elastic work recovery rate of the paint is measured using a coating film sheet having a thickness of 50 μm. As a measuring device, an ultra-micro hardness tester "ENT-2100" manufactured by Elionix Co., Ltd. is used, and the measuring conditions are as follows.
・Indenter: Berkovich indenter (material: diamond, angle α: 65.03°)
・Load F: 0.2mN
・Loading time: 10 seconds ・Holding time: 1 second ・Unloading time: 10 seconds The elastic work recovery rate is calculated by
Elastic work recovery rate = Welast / Wtotal × 100 (%)

Shore C hardness and Shore M hardness Shore C hardness and Shore M hardness in Table 3 above were obtained by preparing a sheet with a thickness of 2 mm, stacking three sheets, and using a test piece as a Shore C hardness tester and Shore M hardness according to ASTM D2240 standards. Each was measured using a meter.

For each golf ball obtained, 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 were evaluated by the following methods. , as shown in Table 4.

At a temperature of 23.9 ± 1° C for the outer diameter of each of the core, (inner/outer) envelope-covered spheres, and intermediate-layer-covered spheres, five arbitrary surfaces were measured, and the average value was calculated for each sphere. , and the average value of 10 measurements was obtained.

At a temperature of 23.9±1° C., the diameter of the ball was measured at 15 locations without any dimples. .

Amount of Deflection of Core A core (sphere) was placed on a hard plate, and the amount of deflection from an initial load of 98 N (10 kgf) to a final load of 1275 N (130 kgf) was measured. In addition, the amount of deflection described above is a measured value after the temperature is adjusted to 23.9°C.

Core Hardness Distribution The surface of the core is spherical, and the needle of a hardness tester was set so as to be substantially perpendicular to the spherical surface, and the core surface hardness was measured in terms of Shore C hardness according to ASTM D2240. The cross-sectional hardness at the center of the core and a predetermined position of each core was measured by cutting the core into a hemispherical shape, flattening the cross section, and vertically pressing a needle of a hardness tester against the measured portion. It is indicated by the value of Shore C hardness.
Also, the center hardness Cc of the core, the surface hardness of the core Cs, the midpoint hardness _Cm between the center and the surface of the core, the positions of 2.5 mm, 5.0 mm and 7.5 mm from the midpoint M to the core surface side Shore C hardness C _M+2.5 , C _M+5.0 and C _{M+7.5 , position hardness C M-2.5 , C M-} 5.0 and C _M -5.0 and 2.5 mm, 5.0 mm and 7.5 _mm from the midpoint M to the core center side For C _M-7.5 , the following areas A to F Area A: 1/2 x 2.5 x (C _M-5.0 - _{C M-7.5} ),
・Area B: 1/2 × 2.5 × (C _M-2.5 -C _M-5.0 ),
・Area C: 1/2 × 2.5 × (C _M -C _M-2.5 ),
・Area D: 1/2×2.5×(C _M+2.5 −C _M ),
area E: 1/2 x 2.5 x (C _M+5 - C _M+2.5 ), and area F: 1/2 x 2.5 x (C _M+7.5 - _{C M+5} )
was calculated, and the values of the following three formulas were obtained.
・(Area D + Area E + Area F) - (Area A + Area B + Area C)
・(Area D + Area E) - (Area A + Area B + Area C)
・[(Area D + Area E + Area F)-(Area A + Area B + Area C)]/(Cs-Cc)
As an explanation of the core hardness distribution areas A to F, FIG. 2 is a schematic diagram showing the areas A to F using the core hardness distribution data of Example 1. FIG.

(Inside/Outside) Surrounding layer, intermediate layer and cover material hardness (Shore D hardness)
The resin material for each layer was molded into a sheet having a thickness of 2 mm and left for two weeks or longer. After that, the Shore D hardness was measured according to the ASTM D2240 standard.

(Inside/outside) Surface hardness (Shore D hardness) of envelope-covered spheres, intermediate-layer-covered spheres, and balls
Measurements were taken by pressing the needle perpendicular to the surface of each sphere. The surface hardness of the ball (cover) is the measured value of land portions on the surface of the ball where no dimples are formed. Shore D hardness was measured by a type D durometer according to ASTM D2240 standard.

Each golf ball was evaluated for flight performance (W#1), spin rate on approach, feel on impact, and scratch resistance by the following methods. Table 5 shows the results.

Flight performance A driver (W#1) was attached to the golf hitting robot, and the flight distance was measured when hitting at a head speed of 45 m/s, and judged according to the following criteria. The club used was “TourStage X-Drive709 D430 Driver/2013 model” (loft angle 9.5°) manufactured by Bridgestone Sports. In addition, the spin amount was similarly measured by an initial condition measuring device immediately after hitting.
<criterion>
Total flight distance 230.0m or more … ○
Total flight distance less than 230.0m … ×

Evaluation of Spin Amount During Approach The golf hitting robot was attached with a sand wedge and hit at a head speed of 22 m/s. Similarly, the spin amount was measured by an initial condition measuring device immediately after hitting the ball. The sand wedge used was “TOUR B XW-1 2018 model” (loft angle 56°) manufactured by Bridgestone Sports.
<criterion>
Spin amount is 6200 rpm or more … ○
Spin amount less than 6200 rpm … ×

Sensory evaluation was carried out in actual hitting by an advanced user with a head speed of 40 to 50 m/s with a driver (W#1), and judgment was made according to the following criteria.
<criterion>
More than 8 out of 10 people have a good hitting feeling and evaluation … ○
5 to 7 out of 10 people who evaluated it as good hitting feeling … △
Less than 4 out of 10 people who evaluated it as good hitting feeling … ×

A scratch-resistant non-plated pitching sand wedge was set on a hitting robot and hit once at a head speed of 35 m/s. The state of the ball surface was visually observed and evaluated according to the following criteria.
○: Still usable ×: Cannot withstand use anymore

As shown in Table 5, the golf balls of Comparative Examples 1 to 8 are inferior to the products of the present invention (Examples) in the following points.
In Comparative Example 1, the surface hardness of the outer envelope layer is lower than the surface hardness of the core, and as a result, the spin rate with a driver (W#1) increases, resulting in poor flight distance.
In Comparative Example 2, the surface hardness of the inner enveloping layer was equal to or lower than the surface hardness of the core, and the surface hardness of the enveloping layer was lower than the surface hardness of the core. It increases, and the flight distance is inferior.
In Comparative Example 3, the surface hardness of the outer envelope layer is harder than the surface hardness of the inner envelope layer, and as a result, the feel on impact is too hard.
In Comparative Example 4, the surface hardness of the intermediate layer is lower than the surface hardness of the outer envelope layer, and as a result, the spin rate with the driver (W#1) increases, resulting in poor flight distance.
In Comparative Example 5, the surface hardness of the ball is higher than the surface hardness of the intermediate layer. As a result, the amount of spin in the approach shot is reduced, the controllability in the short game is inferior, and the scuff resistance is also inferior.
Comparative Example 6, which is a four-piece (4P) solid golf ball with a single envelope layer, has an increased spin rate with a driver (W#1) and is inferior in flight distance.
In Comparative Example 7, the hardness distribution of the core (Area: D + E + F) - (Area: A + B + C) is less than 3, resulting in an increased spin rate with a driver (W#1) and a flight distance. In addition, the surface hardness of the outer enveloping layer is harder than the surface hardness of the inner enveloping layer, resulting in too hard feel on impact.
In Comparative Example 8, the value of (Area: D+E+F)-(Area: A+B+C) in the hardness distribution of the core was less than 3, and as a result, the spin rate with the driver (W#1) increased, resulting in an increased flight distance. In addition, the surface hardness of the outer enveloping layer is harder than the surface hardness of the inner enveloping layer, resulting in too hard feel on impact.

Claims (12)

A multi-piece solid golf ball comprising a core, an enveloping layer, an intermediate layer and a cover, wherein the core is made mainly of base rubber, and the enveloping layer, the intermediate layer and the cover are each made of a resin material. The envelope layer is formed of two layers, an inner layer and an outer layer, and has center hardness and surface hardness of the core and surface hardness of a sphere covering the core with the inner envelope layer (inner envelope layer-covered sphere). and the surface hardness of a sphere obtained by covering the inner envelope-covered sphere with an outer envelope (outer envelope-covered sphere) and a sphere obtained by covering the outer envelope-layer-covered sphere with an intermediate layer (intermediate-layer-covered sphere), and the ball satisfies the following formula: core center hardness<core surface hardness<surface hardness of inner enveloping layer-covered sphere>surface hardness of outer enveloping layer-covered sphere<surface hardness of intermediate layer-covered sphere>ball surface hardness And, in the hardness distribution of the core, Cc is the Shore C hardness of the center of the core, Cs is the Shore C hardness of the surface of the core, C M is the Shore C hardness of the midpoint M between the center and the surface of the core, and _the midpoint The Shore C hardness at positions 2.5 mm, 5.0 mm and 7.5 mm from M to the core surface side are respectively C _{M +2.5} , C _{M +5.0} and C _{M +7.5} , and from the midpoint M to the core center side When the Shore C hardnesses at the positions of 2.5 mm, 5.0 mm and 7.5 mm are respectively C _M-2.5 , C _M-5.0 and C _M-7.5 , the following areas A to F
・Area A: 1/2 × 2.5 × (C _M-5.0 -C _M-7.5 ),
・Area B: 1/2 × 2.5 × (C _M-2.5 -C _M-5.0 ),
・Area C: 1/2 × 2.5 × (C _M -C _M-2.5 ),
・Area D: 1/2×2.5×(C _M+2.5 −C _M ),
- Area E: 1/2 x 2.5 x (C _M+5 -C _M+2.5 ), and
・Area F: 1/2×2.5×(C _M+7.5 -C _M+5 )
, (Area D + Area E + Area F) - (Area A + Area B + Area C) ≥ 3. A multi-piece solid golf ball comprising a core, an enveloping layer, an intermediate layer and a cover, wherein the core is made mainly of base rubber, and the enveloping layer, the intermediate layer and the cover are each made of a resin material. The envelope layer is formed of two layers, an inner layer and an outer layer, and has center hardness and surface hardness of the core and surface hardness of a sphere covering the core with the inner envelope layer (inner envelope layer-covered sphere). and the surface hardness of a sphere obtained by covering the inner envelope-covered sphere with an outer envelope (outer envelope-covered sphere) and a sphere obtained by covering the outer envelope-layer-covered sphere with an intermediate layer (intermediate-layer-covered sphere), and the ball and the surface hardness of the following formula
Core Center Hardness <Core Surface Hardness <Surface Hardness of Inner Surrounding Layer Covered Sphere> Surface Hardness of Outer Surrounding Layer Covered Sphere <Surface Hardness of Intermediate Layer Covered Sphere> Ball Surface Hardness
and the thickness of each layer of the envelope layer, the intermediate layer and the cover, the following formula
[Total thickness of inner and outer envelope layers (mm)]−[Total thickness of intermediate layer and cover (mm)]≧0.1
A multi-piece solid golf ball characterized by satisfying: 2. The multi-piece solid golf ball of claim 1 , wherein (Area D+Area E)−(Area A+Area B+Area C)≧0 is satisfied for the areas A to E of the core hardness distribution. 2. The area A to F of the core hardness distribution satisfies 0.15≦[(area D+area E+area F)−(area A+area B+area C)]/(Cs−Cc)≦0.6 or 4. A multi-piece solid golf ball according to claim 3. 5. The multi-piece solid golf ball of claim 1 , wherein the areas B to E of the core hardness distribution satisfy area B<area C≦area D<area E. 6. The multi-piece solid golf ball of claim 1, wherein the thickness of the enveloping layer satisfies the following condition: thickness of inner enveloping layer≧thickness of outer enveloping layer. 7. The multi-piece solid golf ball of claim 1, wherein the thickness of the outer envelope layer and the intermediate layer satisfies the following relationship: thickness of intermediate layer≧thickness of outer envelope layer. 8. The multi-piece solid golf ball of claim 1 , wherein a coating layer is formed on the surface of the cover, and the coating layer has a Shore C hardness of 40 to 80. When the Shore C hardness of the coating layer is Hc, the difference (C _M -Hc) between the Shore C hardness C _M at the midpoint M between the center and the surface of the core and Hc is -10 or more and 10 or less. 9. The multi-piece solid golf ball of claim 8 . A multi-piece solid golf ball comprising a core, an inner envelope layer, an outer envelope layer, an intermediate layer, and a cover, wherein the surface hardness of the core and a sphere coated with the inner envelope layer (inner envelope layer-covered sphere) surface hardness of the inner envelope-covered sphere covered with the outer envelope layer (outer envelope-covered sphere) and the outer envelope-layer-covered sphere covered with the intermediate layer (intermediate-layer-covered sphere) and the surface hardness of the ball is calculated by the following formula: Core surface hardness <Surface hardness of each sphere of the inner enveloping layer covering sphere, outer enveloping layer covering sphere and intermediate layer covering sphere > Ball surface hardness (However, the surface hardness of the outer enveloping layer covering sphere The surface hardness is 60 or less in Shore D hardness, and the surface hardness of the intermediate layer-covered sphere is 66 or more in Shore D hardness.)
In the hardness distribution of the core, Cc is the Shore C hardness of the center of the core, Cs is the Shore C hardness of the surface of the core, and C is _the Shore C hardness of the midpoint M between the center and the surface of the core. , the Shore C hardness at positions 2.5 mm, 5.0 mm and 7.5 mm from the midpoint M to the core surface side are respectively C _{M +2.5} , C _{M +5.0} and C _{M +7.5} , and from the midpoint M to the core When the Shore C hardness at positions of 2.5 mm, 5.0 mm and 7.5 mm on the center side is respectively C _M-2.5 , C _M-5.0 and C _M-7.5 , the following areas A to F
・Area A: 1/2 × 2.5 × (C _M-5.0 -C _M-7.5 ),
・Area B: 1/2 × 2.5 × (C _M-2.5 -C _M-5.0 ),
・Area C: 1/2 × 2.5 × (C _M -C _M-2.5 ),
・Area D: 1/2×2.5×(C _M+2.5 −C _M ),
Area E: 1/2 x 2.5 x (C _M+5 - C _M+2.5 ) and Area F: 1/2 x 2.5 x (C _M+7.5 - C _M+5 )
(Area D+Area E+Area F)−(Area A+Area B+Area C)≧6. 11. The invention according to claim 10 , wherein the areas A to F of the core hardness distribution satisfy 0.15≦[(Area D+Area E+Area F)−(Area A+Area B+Area C)]/(Cs−Cc)≦0.6. multi-piece solid golf ball. A coating layer is formed on the cover surface, and when the Shore C hardness of the coating layer is Hc, the difference between the Shore C hardness C _M at the midpoint M between the center and the surface of the core and Hc (C 12. The multi-piece solid golf ball of claim 10, wherein _M -Hc) is -10 or more and 10 or less.

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