JP2024012831A - multi-piece solid golf ball - Google Patents

Abstract

To provide a golf ball that achieves superior distance when hit with a utility club or during full shots with irons, and exhibits good durability to repeated impact and good controllability in the short game.SOLUTION: In a golf ball having a core, an intermediate layer and a cover, the core is formed of a rubber composition, and the intermediate layer and the cover are each formed of a resin composition. The core, a sphere formed by encasing the core in the intermediate layer (the intermediate layer-encased sphere), and a sphere formed by encasing intermediate layer-encased sphere in the cover (the ball) have respective initial velocities which satisfy the following two conditions: (initial velocity of ball)<(initial velocity of intermediate layer-encased sphere) and 0.65≤(initial velocity of intermediate layer-encased sphere)-(initial velocity of core)≤1.15(m/s). When a predetermined load is applied to each sphere of the core and the ball, the deflection amounts (mm) are defined as C(mm) and B(mm), respectively, with the value of C-B being 1.20 mm or more.SELECTED DRAWING: Figure 1

Description

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

Conventionally, many efforts have been made to design balls with multilayer structures, and many balls have been developed that satisfy not only professional golfers but also general amateur golfers from beginners to advanced players. Among these, the most common type of golf ball is the development of a three-piece solid golf ball consisting of a core, an intermediate layer, and a cover (outermost layer). Specifically, there are many proposals for functional three-piece solid golf balls that optimize the material hardness of each layer of the intermediate layer and cover, the core surface hardness, and the surface hardness of the intermediate layer coating sphere. Several techniques have been proposed for providing high-performance golf balls by focusing on the core hardness distribution that accounts for the core hardness and designing various aspects of the internal hardness of the core.

Examples of such technical documents include three-piece solid golf balls disclosed in Patent Documents 1 to 6 below.

However, among the golf balls proposed above, there are some concerns regarding the relationship between the initial velocity of the intermediate layer coated sphere and each coated sphere of the ball, or the amount of deflection when a specific load is applied to the core and the amount of deflection when a specific load is applied to the ball. Although there are some disclosures regarding the relationship with the amount of deflection, it provides superior flight distance when hitting utility shots or irons, as well as controllability on approach, good feel, and excellent impact durability. Nothing was invented to improve golf balls. In particular, for advanced amateur golfers with small handicaps who do not have very high head speeds, there is a need for golf balls that can provide superior flight distance on utility and full iron shots.

Japanese Patent Application Publication No. 2011-120898 Japanese Patent Application Publication No. 2016-112308 JP 2017-183 Publication Unexamined Japanese Patent Publication No. 2017-470 Japanese Patent Application Publication No. 2018-183247 Japanese Patent Application Publication No. 2020-175021

The present invention has been developed in view of the above circumstances, and when used by advanced amateur users, the distance when hitting utility and iron shots is superior, the controllability during approach is good, and the present invention is good. The purpose of the present invention is to provide a golf ball that provides a comfortable hitting feel and excellent durability against repeated hits.

As a result of intensive studies to achieve the above object, the present inventor has determined that, in a multi-piece solid golf ball comprising a core, an intermediate layer, and a cover, the initial velocity of the core, the spherical body with the intermediate layer coated on the core (intermediate layer The relationship between the initial velocity of the sphere (sphere) and the initial velocity of the sphere (ball), which is an intermediate layer coated sphere covered with a cover, is expressed by the following two formulas: (Initial velocity of the ball) < (Initial velocity of the intermediate layer coated sphere)
0.65≦(initial velocity of intermediate layer coated sphere) - (initial velocity of core)≦1.15 (m/s)
In addition, the amount of deflection (mm) when an initial load of 98 N (10 kgf) to a final load of 1,275 N (130 kgf) is applied to each sphere of the core and ball is C (mm) and B (mm), respectively. By setting the C-B value to 1.20 mm or more, it provides utility when used by advanced amateur users, superior flight when hitting with an iron, and good controllability when approaching. The inventors have discovered that a good hitting feel and excellent durability against repeated impact can be obtained, and have thus come up with the present invention.

Note that the above-mentioned "advanced amateur user" is an amateur golfer with a small handicap, although his club head speed is not as fast as that of a professional golfer. The head speed of this golfer when hitting the driver (W#1) is approximately in the range of 35 to 44 m/s.

Accordingly, the present invention provides the following multi-piece solid golf ball.
1. A multi-piece solid golf ball comprising a core, an intermediate layer, and a cover, wherein the core is made of a rubber composition, the intermediate layer and the cover are both made of a resin composition, and the initial velocity of the core, The relationship between the initial velocity of a sphere whose core is coated with an intermediate layer (intermediate layer coated sphere) and the initial velocity of a sphere (ball) whose core is coated with an intermediate layer is expressed by the following two equations (initial velocity of ball) < (intermediate layer coated sphere). (initial velocity of layer-covered sphere)
0.65≦(initial velocity of intermediate layer coated sphere) - (initial velocity of core)≦1.15 (m/s)
In addition, the amount of deflection (mm) when an initial load of 98 N (10 kgf) to a final load of 1,275 N (130 kgf) is applied to each sphere of the core and ball is C (mm) and B (mm), respectively. A multi-piece solid golf ball characterized in that the value of CB is 1.20 mm or more.
2. The formula below,
Ball surface hardness <Surface hardness of intermediate layer coated sphere> Core surface hardness (However, the surface hardness of each sphere above means Shore C hardness.)
The multi-piece solid golf ball according to item 1 above.
3. 3. The multi-piece solid golf ball according to 1 or 2 above, wherein the resin composition of the intermediate layer contains a high acid ionomer resin having an acid content of 16% by mass or more.
4. 3. The multi-piece solid golf ball according to 1 or 2 above, wherein the intermediate layer has a specific gravity of 1.05 or more.
5. 3. The multi-piece solid golf ball according to 1 or 2 above, wherein the intermediate layer contains an inorganic particulate filler.
6. 3. The multi-piece solid golf ball according to 1 or 2 above, wherein the difference between the specific gravity of the cover and the specific gravity of the intermediate layer is within 0.15.
7. The formula below,
The multi-piece solid golf ball according to 1 or 2 above, wherein the thickness of the cover <thickness of the intermediate layer is satisfied.
8. 3. The multi-piece solid golf ball according to 1 or 2 above, wherein the core has a diameter of 36.7 to 40.1 mm.
9. In the hardness distribution of the core, the Shore C hardness at the center of the core is Cc, the Shore C hardness at the midpoint M between the center and the surface of the core _{is Cm} , and the Shore C hardness at positions 2 mm, 4 mm, and 6 mm inward from the midpoint M is The hardness is Cm-2, Cm-4, Cm-6, respectively.The Shore C hardness at the positions 2mm, 4mm, and 6mm outward from the center M is Cm+2, Cm+4, and Cm+6, respectively.The Shore of the surface of the core is When C hardness is Cs, the following areas A to F
・Area A: 1/2×2×(Cm-4-Cm-6)
・Area B: 1/2×2×(Cm-2-Cm-4)
・Area C: 1/2×2×(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)
For, the following formula (Area E + Area F) - (Area A + Area B) ≧1.0
The multi-piece solid golf ball according to item 1 or 2 above.
10. The formula below,
(Area D + Area E) - (Area B + Area C) ≧1.0
9. The multi-piece solid golf ball as described in 9 above.

According to the golf ball of the present invention, advantageous flight distance can be obtained on full shots with utility and irons, and advantageous distance can be obtained on full shots with utility and irons, mainly for advanced amateur golfers who do not have a very high head speed but have a small handicap. The spin rate is high and the shot game is also excellent. Moreover, the golf ball of the present invention provides a soft and good feel on all shots, and has good durability against repeated hits.

1 is a schematic cross-sectional view of a golf ball that is an embodiment of the present invention. 2 is a schematic diagram illustrating areas A to F of core hardness distribution using core hardness distribution data of Example 1. FIG. 3 is a graph showing the core hardness distribution of Examples 1 to 3. 3 is a graph showing the core hardness distribution of Comparative Examples 1 to 7.

The present invention will be explained in more detail below.
The multi-piece solid golf ball of the present invention has a core, an intermediate layer, and a cover, an example of which is shown in FIG. 1, for example. The golf ball G shown in FIG. 1 has a single-layer core 1, a single-layer intermediate layer 2 covering the core 1, and a single-layer cover 3 covering the intermediate layer. This cover 3 is located at the outermost layer in the layered structure of the golf ball, excluding the paint layer. Each layer of the core, intermediate layer, and cover can be formed into a single layer as shown in FIG. 1, or a plurality of layers. Note that a large number of dimples D are usually formed on the surface of the cover (outermost layer) 3 in order to improve aerodynamic characteristics. Further, although not particularly illustrated, a paint layer is usually formed on the surface of the cover 3. Each of the above layers will be explained in detail below.

The above-mentioned core is obtained by vulcanizing a rubber composition containing a rubber material as a main material. If the core material is not a rubber composition, the repulsion of the core will be low, and as a result, the ball may not fly. This rubber composition usually has a base rubber as its main component, and a co-crosslinking agent, a crosslinking initiator, an inert filler, an organic sulfur compound, etc. are blended therein to obtain a rubber composition.

It is preferable to use polybutadiene as the base rubber. As the type of polybutadiene, commercially available products can be used, and examples thereof include BR01, BR51, and BR730 (manufactured by JSR Corporation). Further, 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 blended into the base rubber to the extent that the effects of the present invention are not impaired. Examples of rubber components other than the above-mentioned polybutadiene include polybutadiene other than the above-mentioned polybutadiene, and other diene rubbers such as styrene-butadiene rubber, natural rubber, isoprene rubber, and ethylene-propylene diene rubber.

The co-crosslinking agent is an α,β-unsaturated carboxylic acid and/or a metal salt thereof. Specific examples of the unsaturated carboxylic acid include acrylic acid, methacrylic acid, maleic acid, and fumaric acid, with acrylic acid and methacrylic acid being particularly preferred. The metal salt of an unsaturated carboxylic acid is not particularly limited, but includes, for example, those obtained by neutralizing the above-mentioned unsaturated carboxylic acid with a desired metal ion. Specific examples include zinc salts and magnesium salts of methacrylic acid, acrylic acid, etc., and zinc acrylate is particularly preferably used.

The unsaturated carboxylic acid and/or its metal salt 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, based on 100 parts by mass of the base rubber. The amount 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 and give an unbearable feel on impact, while if the amount is too small, the repulsion may be reduced.

As a crosslinking initiator, it is preferable to use an organic peroxide. Specifically, commercially available organic peroxides can be used, such as Percmil D (manufactured by NOF Corporation), Perhexa C-40, Perhexa 3M (manufactured by NOF Corporation), and Luperco 231XL (manufactured by Atochem). (manufactured by Co., Ltd.) etc. can be suitably used. These may be used alone or in combination of two or more. The blending amount of the organic peroxide is preferably 0.1 parts by mass or more, more preferably 0.3 parts by mass or more, and even more preferably 0.5 parts by mass or more, based on 100 parts by mass of the base rubber. 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 amount is too large or too small, it may not be possible to obtain suitable feel, durability and resilience.

As the filler, for example, zinc oxide, barium sulfate, calcium carbonate, etc. can be suitably used. These may be used alone or in combination of two or more. The blending amount of the filler is preferably 1 part by mass or more, more preferably 3 parts by mass or more, based on 100 parts by mass of the base rubber. Further, the upper limit of the blending amount can be preferably 50 parts by mass or less, more preferably 40 parts by mass or less, still more preferably 30 parts by mass or less, based on 100 parts by mass of the base rubber. If the amount is too large or too small, it may not be possible to obtain an appropriate mass and suitable resilience.

As the anti-aging agent, commercially available products such as Nocrack NS-6, Nocrack NS-30, Nocrack NS-200, and Nocrack MB (manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.) can be used. These may be used alone or in combination of two or more.

There is no particular restriction on the amount of the anti-aging agent, but it is preferably 0.05 parts by mass or more, more preferably 0.1 parts by mass or more, and the upper limit is preferably 1.0 parts by mass, based on 100 parts by mass of the base rubber. The amount is not more than 0.7 parts by mass, more preferably not more than 0.5 parts by mass. If the blending amount is too large or too small, an appropriate core hardness gradient may not be obtained, and suitable resilience, durability, and low spin effect on full shots may not be obtained.

Furthermore, an organic sulfur compound can be blended into the above rubber composition in order to impart excellent resilience, and specifically, thiophenol, thionaphthol, halogenated thiophenol, or a metal salt thereof may be blended. More specifically, zinc salts such as pentachlorothiophenol, pentafluorothiophenol, pentabromothiophenol, parachlorothiophenol, and pentachlorothiophenol, and diphenyl polysulfide having 2 to 4 sulfur atoms are recommended. , dibenzyl polysulfide, dibenzoyl polysulfide, dibenzothiazoyl polysulfide, dithiobenzoyl polysulfide, etc., but zinc salt of pentachlorothiophenol and diphenyl disulfide can be particularly preferably used.

The organic sulfur compound is blended in an amount of 5 parts by mass or less, preferably 4 parts by mass or less, more preferably 3 parts by mass or less, most preferably 2 parts by mass or less, based on 100 parts by mass of the base rubber. Further, the lower limit of this blending amount is preferably 0.1 parts by mass or more, more preferably 0.2 parts by mass or more, and still more preferably 0.3 parts by mass or more. If this amount is too large, the hardness will become too soft, and if it is too small, no improvement in resilience may be expected.

Water can be added to the above rubber composition. This water is not particularly limited and may be distilled water or tap water, but it is particularly preferable to use distilled water that does not contain impurities. The amount of water blended is preferably 0.1 parts by mass or more, more preferably 0.2 parts by mass or more, and the upper limit is preferably 2 parts by mass or less with respect to 100 parts by mass of the base rubber. and more preferably 1.5 parts by mass or less.

By directly blending water or a material containing water with the core material, it is possible to promote the decomposition of the organic peroxide in the core blend. 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 becomes higher than a certain temperature. If the temperature is too high, the amount of decomposed radicals will be too large, leading to recombination and inactivation of the radicals. As a result, the number of radicals that effectively act on crosslinking is reduced. Here, when the organic peroxide decomposes during core vulcanization and generates decomposition heat, the temperature near the core surface is maintained at approximately the same level as the vulcanization mold, but the temperature near the center of the core is on the outside. Since the heat of decomposition of the organic peroxide decomposed from the mold is accumulated, the temperature becomes considerably higher than the mold temperature. When water or a material containing water is directly blended into the core, water has the effect of promoting the decomposition of organic peroxides, so the radical reaction described above can be changed at the core center and core surface. . In other words, the decomposition of the organic peroxide is further promoted near the core center, and the inactivation of radicals is further promoted, resulting in a further decrease in the amount of effective radicals, resulting in a core with a large difference in crosslinking density between the core center and the core surface. can be obtained.

The core can be manufactured by vulcanizing and curing a rubber composition containing the components described above. For example, it is kneaded using a kneading machine such as a Banbury mixer or a roll, and compression molded or injection molded using a core mold, and the temperature is set at 100 to 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.

In the present invention, the core is formed in a single layer or in multiple layers, but is preferably formed in a single layer. When a rubber core is made of multiple layers, if there is a large difference in hardness at the interface between these rubber layers, peeling may occur from the interface when repeatedly hit, and the ball may lose initial velocity when making a full shot.

The diameter of the core is preferably 36.7 mm or more, more preferably 37.2 mm or more, still more preferably 37.6 mm or more. The upper limit of this diameter is preferably 40.1 mm or less, more preferably 39.0 mm or less, even more preferably 38.0 mm or less. If the diameter of the core is too small, the initial velocity of the ball will be low, or the amount of deflection of the ball as a whole will be small, which will increase the amount of spin of the ball during a full shot, making it impossible to achieve the desired flight distance. On the other hand, if the diameter of the core is too large, the amount of spin during a full shot will increase, making it impossible to obtain the desired flight distance, or the durability of cracking when repeatedly hit may deteriorate.

The amount of deflection (mm) when an initial load of 98 N (10 kgf) to a final load of 1,275 N (130 kgf) is applied to the core is not particularly limited, but is preferably 3.8 mm or more, more preferably 4. It is 0 mm or more, more preferably 4.2 mm or more, and the upper limit is preferably 6.0 mm or less, more preferably 5.4 mm or less, and still more preferably 5.0 mm or less. If the amount of deflection of the core is too small, that is, if the core is too hard, the spin rate of the ball may increase too much and the ball may not fly far or the feel of the ball 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 ball's resilience will be too low and it will not fly, the feel will be too soft, or the durability of cracking during repeated hits will be poor. Sometimes.

Next, the hardness distribution of the core will be explained. Note that the hardness of the core described below means Shore C hardness. This Shore C hardness is a hardness value measured using a Shore C hardness meter based on the ASTM D2240 standard.

The center hardness (Cc) of the core is preferably 47 or more, more preferably 49 or more, even more preferably 51 or more, and the upper limit thereof is preferably 58 or less, more preferably 56 or less, and even more preferably 54 or less. It is. If this value is too large, the feel at impact may become hard, or the amount of spin may increase on full shots, making it impossible to achieve the desired flight distance. On the other hand, if the above-mentioned value is too small, the repulsion properties may be low and the ball may not fly, or the durability against cracking when repeatedly hit may deteriorate.

The hardness (Cm-6) at a position 6 mm inward from the intermediate 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 47 or more, More preferably, it is 49 or more, still more preferably 51 or more, and the upper limit is also not particularly limited, and is preferably 58 or less, more preferably 56 or less, and still more preferably 54 or less. If the hardness deviates from these values, there is a risk that the same disadvantageous results as explained with respect to the central hardness (Cc) of the core may occur.

The hardness (Cm-4) at a position 4 mm inward from the intermediate 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 47 or more, More preferably, it is 49 or more, still more preferably 51 or more, and the upper limit is also not particularly limited, and is preferably 58 or less, more preferably 56 or less, and still more preferably 54 or less. If the hardness deviates from these values, there is a risk that the same disadvantageous results as explained in connection with the central hardness (Cc) of the core may occur.

The positional hardness (Cm-2) at 2 mm inward from the intermediate position M of the core is not particularly limited, but may preferably be 49 or higher, more preferably 51 or higher, and still more preferably 53 or higher. The upper limit is also not particularly limited, and is preferably 59 or less, more preferably 57 or less, still more preferably 55 or less. If the hardness deviates from these values, there is a risk that the same disadvantageous results as explained with respect to the central hardness (Cc) of the core may occur. If the hardness deviates from these values, there is a risk that the same disadvantageous results as explained with respect to the central hardness (Cc) of the core may occur.

The cross-sectional hardness (Cm) of the intermediate position M of the core is not particularly limited, but is preferably 53 or more, more preferably 55 or more, and even more preferably 57 or more. The upper limit is also not particularly limited, but is preferably 63 or less, more preferably 61 or less, and still more preferably 59 or less. If the hardness deviates from these values, there is a risk that the same disadvantageous results as explained with respect to the central hardness (Cc) of the core may occur.

The surface hardness (Cs) of the core is preferably 71 or more, more preferably 73 or more, even more preferably 75 or more, and the upper limit thereof is preferably 84 or less, more preferably 82 or less, and even more preferably 80 or less. It is. If this value is too large, the durability against cracking upon repeated impact may deteriorate, or the feel on impact may become too hard. On the other hand, if the above-mentioned value is too small, the repulsion becomes low and the ball does not fly well, or the ball spins on a full shot so much that the desired flight distance may not be obtained.

The positional hardness (Cm+2) of 2 mm from the intermediate position M of the core to the outside toward the core surface (hereinafter simply referred to as "outside") is not particularly limited, but is preferably 57 or more, or more. It is preferably 59 or more, more preferably 61 or more, and the upper limit is also not particularly limited, and is preferably 68 or less, more preferably 66 or less, and still more preferably 64 or less. If the hardness deviates from these values, there is a risk that the same disadvantageous results as explained in relation to the surface hardness (Cs) of the core may occur.

The positional hardness (Cm+4) at 4 mm outward from the intermediate position M of the core is not particularly limited, but may preferably be 61 or higher, more preferably 63 or higher, and still more preferably 65 or higher. The upper limit is also not particularly limited, and is preferably 73 or less, more preferably 71 or less, and even more preferably 69 or less. If the hardness deviates from these values, there is a risk that the same disadvantageous results as explained in relation to the surface hardness (Cs) of the core may occur.

The positional hardness (Cm+6) at 6 mm outward from the intermediate position M of the core is not particularly limited, but may preferably be 64 or higher, more preferably 66 or higher, and still more preferably 68 or higher. Moreover, there is no particular restriction on the upper limit, and it is preferably 77 or less, more preferably 75 or less, and even more preferably 73 or less. If the hardness deviates from these values, there is a risk that the same disadvantageous results as explained in relation to the surface hardness (Cs) of the core may occur.

In the above core hardness distribution, the following areas A to F
・Area A: 1/2×2×(Cm-4-Cm-6)
・Area B: 1/2×2×(Cm-2-Cm-4)
・Area C: 1/2×2×(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 preferably 1.0 or more, more preferably 2.5 or more, even more preferably 4.0 or more, and the upper limit is , preferably 20.0 or less, more preferably 16.0 or less, even more preferably 10.0 or less. If this value is too large, the durability against cracking when repeatedly struck may deteriorate. On the other hand, if this value becomes too small, the amount of spin of the ball increases when a full shot is made, and the desired flight distance may not be achieved.

Further, the value of (area D + area E) - (area B + area C) is preferably 1.0 or more, more preferably 2.0 or more, even more preferably 3.0 or more, and the upper limit is , preferably 20.0 or less, more preferably 16.0 or less, even more preferably 10.0 or less. If this value is too large, the durability against cracking when repeatedly struck may deteriorate. On the other hand, if this value becomes too small, the amount of spin of the ball increases when a full shot is made, and the desired flight distance may not be achieved.

For the areas A to F above, use the following formula: Area A<Area C<(Area E+Area F), and Area B<Area C<(Area E+Area F)
It is preferable to satisfy, and more preferably, the following formula: Area A<Area C<Area D<(Area E+Area F), and Area B<Area C<Area D<(Area E+Area F)
It is to satisfy the following. If these relationships are not satisfied, the amount of spin of the ball increases when a full shot is made, and the desired flight distance may not be achieved.

Note that FIG. 2 is a schematic diagram illustrating the areas A to F using the core hardness distribution data of Example 1. In this way, the areas A to F are the areas of triangles whose bases are the differences in specific distances and whose heights are the differences in positional hardness.

The initial velocity of the core is preferably 75.3 m/s or more, more preferably 75.8 m/s or more, even more preferably 76.3 m/s or more, and the upper limit is preferably 77.5 m/s or less, More preferably, it is 77.0 m/s or less, and even more preferably 76.7 m/s. If this initial velocity value is too high, the initial velocity of the ball will become too high and may violate the rules. On the other hand, if the initial velocity of the core is too low, the repulsion of the ball will be low during a full shot, or the amount of spin will be high, making it impossible to achieve the desired flight distance. The above initial velocity value in this case is a value measured with a COR type initial velocity meter of the same type as R&A. Specifically, a COR type initial velocity device manufactured by Hye Precision in the United States is used. The conditions are to measure by changing the air pressure in four stages, constructing a relational expression between the incident velocity and COR, and from this relational expression, calculate the initial velocity at an incident velocity of 43.83 m/s. It is something to seek. Regarding the measurement environment of the above COR type initial velocity device, use a ball that has been temperature-controlled for at least 3 hours in a constant temperature bath adjusted to 23.9 ± 1 °C. Measured at room temperature.

Next, the middle layer will be explained.
The material hardness of the intermediate layer is not particularly limited, but it is preferably 90 or more, more preferably 92 or more, even more preferably 93 or more in terms of Shore C hardness, and the upper limit is preferably 100 or less, more preferably 98. Below, it is more preferably 96 or below. The Shore D hardness is preferably 64 or higher, more preferably 66 or higher, even more preferably 68 or higher, and the upper limit is preferably 75 or lower, more preferably 72 or lower, and even more preferably 70 or lower.

The surface hardness of the sphere having a core covered with an intermediate layer (intermediate layer coated sphere) is preferably 95 or more, more preferably 96 or more, and even more preferably 97 or more in terms of Shore C hardness, and the upper limit is preferably 100. Below, it is more preferably 99 or less, still more preferably 98 or less. The Shore D hardness is preferably 68 or higher, more preferably 69 or higher, and still more preferably 70 or higher, and the upper limit is preferably 78 or lower, more preferably 75 or lower, and still more preferably 72 or lower.

If the material hardness and surface hardness of these intermediate layers are too soft than the above range, the amount of spin during a full shot may increase too much, resulting in no distance, or the initial velocity of the ball may decrease, resulting in no distance. . On the other hand, if the material hardness and surface hardness of the intermediate layer are harder than the above ranges, the durability against cracking due to repeated hits may be poor, or the feel when hitting with a putter or short approach may become too hard.

The thickness of the intermediate layer is preferably 1.00 mm or more, more preferably 1.25 mm or more, and even more preferably 1.45 mm or more. On the other hand, the upper limit of the thickness of the intermediate layer is preferably 1.80 mm or less, more preferably 1.65 mm or less, and still more preferably 1.55 mm or less. Further, it is preferable that the thickness of the intermediate layer is thicker than that of the cover described later. If the thickness of the intermediate layer is outside the above range or is thinner than the cover, the ball may not have sufficient low spin effect when hit with a driver (W#1), resulting in a lack of flight distance. Furthermore, if the intermediate layer is too thin, the durability against cracking due to repeated blows and the durability at low temperatures may deteriorate.

The value obtained by subtracting the cover thickness from the intermediate layer thickness is preferably larger than 0 mm, more preferably 0.3 mm or more, still more preferably 0.5 mm or more, and the upper limit is preferably 1.5 mm or less, More preferably, it is 1.0 mm or less, and further preferably 0.7 mm or less. If the above value deviates from the above range, the amount of spin of the ball on a full shot may increase, the actual initial velocity of the ball may become low, and the desired flight distance may not be obtained. If the above value is too small, the durability against cracking when repeatedly struck may deteriorate.

As for the material of the intermediate layer, it is preferable to use an ionomer resin as the main material.

The ionomer resin material preferably contains a high acid content ionomer resin having an unsaturated carboxylic acid content (also referred to as "acid content") of 16% by mass or more.

Further, the content of the high acid content ionomer resin is preferably 20% by mass or more, more preferably 50% by mass or more, and even more preferably 60% by mass or more, based on 100% by mass of the resin material. is 100% by mass or less, more preferably 90% by mass or less, even more preferably 85% by mass or less. If the amount of the high acid content ionomer resin blended is too small, the amount of spin of the ball during a full shot may increase, resulting in a lack of flight distance. 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.

Furthermore, when an ionomer resin is used as the main material, it is desirable to use a mixture of a zinc-neutralized ionomer resin and a sodium-neutralized ionomer resin as the main material. The blending ratio of the zinc-neutralized type/sodium-neutralized type (mass ratio) is 5/95 to 95/5, preferably 10/90 to 90/10, and more preferably 15/85 to 85/15. If the Zn-neutralized ionomer and the Na-neutralized ionomer are not included in this ratio, the repulsion will be too low and the desired flight will not be obtained, the cracking durability during repeated impact at room temperature will deteriorate, and even lower temperature (below zero) cracking durability may deteriorate.

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

Regarding 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 agent to the material.

The material of the intermediate layer may contain an inorganic particulate filler. This inorganic particulate filler is not particularly limited, but zinc oxide, barium sulfate, titanium dioxide, etc. can be used as appropriate. Preferably, barium sulfate, particularly precipitated barium sulfate, can be suitably used since it has excellent cracking resistance due to repeated blows.

The average particle diameter of the inorganic particulate filler is not particularly limited, but it is preferably 0.01 to 100 μm, more preferably 0.1 to 10 μm. If the average particle diameter of the inorganic particulate filler is too small or too large, the dispersibility during material preparation may deteriorate. In addition, the above-mentioned average particle diameter means the particle diameter which is dispersed in an aqueous solution together with a suitable dispersant and measured by a particle size distribution measuring device.

The amount of the inorganic particulate filler blended is not particularly limited, but is preferably 0 parts by mass or more, more preferably 10 parts by mass or more, even more preferably It can be 15 parts by mass or more. The upper limit is also not particularly limited, but is 50 parts by mass or less, preferably 40 parts by mass or less, and more preferably 30 parts by mass or less. If the amount of inorganic particulate filler blended is too small, the durability against cracking due to repeated impact may deteriorate. On the other hand, if the amount of the inorganic particulate filler is too large, the ball's repulsion will be lowered or the ball will spin more on a full shot, which may prevent it from achieving the desired flight distance.

The specific gravity of the intermediate layer is preferably 1.05 or more, more preferably 1.07 or more, even more preferably 1.09 or more, and the upper limit is preferably 1.25 or less, more preferably 1.20 or less, More preferably, it is 1.15 or less. If the specific gravity of the intermediate layer is too small, the durability against cracking due to repeated impact may deteriorate. On the other hand, if the specific gravity of the intermediate layer is too large, the repulsion of the ball will be low, or the amount of spin of the ball will increase during a full shot, which may prevent the ball from achieving the desired flight distance.

The initial velocity of the sphere whose core is coated with an intermediate layer (intermediate layer coated sphere) is preferably 77.0 m/s or more, more preferably 77.3 m/s or more, even more preferably 77.5 m/s or more, and the upper limit The value is preferably 78.5 m/s or less, more preferably 78.2 m/s or less, still more preferably 77.9 m/s. If this initial velocity value is too high, the initial velocity of the ball will become too high and may violate the rules. On the other hand, if this initial velocity is too low, the rebound of the ball will be low or the amount of spin will be high during a full shot, which may make it impossible to obtain the desired flight distance. The initial velocity in this case is the same as the apparatus and conditions used for measuring the initial velocity of the core described above.

Next, the cover will be explained.
The material hardness of the cover is not particularly limited, but in terms of Shore C hardness, it is preferably 50 or more, more preferably 57 or more, even more preferably 63 or more, and the upper limit is preferably 80 or less, more preferably 74 or less. , more preferably 70 or less. The Shore D hardness is preferably 30 or more, more preferably 35 or more, and even more preferably 40 or more, and the upper limit is preferably 53 or less, more preferably 50 or less, and still more preferably 47 or less.

The surface hardness of the sphere (ball) obtained by covering the intermediate layer coated sphere with the cover is preferably 73 or more, more preferably 78 or more, and still more preferably 83 or more, and the upper limit is preferably 95 or less in terms of Shore C hardness. , more preferably 92 or less, still more preferably 90 or less. The Shore D hardness is preferably 50 or more, more preferably 53 or more, and still more preferably 56 or more, and the upper limit is preferably 70 or less, more preferably 65 or less, and still more preferably 60 or less.

If the material hardness and surface hardness of these covers are softer than the above ranges, the amount of spin during a full shot may increase too much, resulting in a loss of flight distance. On the other hand, if the material hardness and surface hardness of the cover are harder than the above ranges, spin may not be applied during approach, or the scratch 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 0.9 mm or less, and still more preferably 0.8 mm or less. If the cover is too thick, the repulsion of the ball may be insufficient during a full shot, or the amount of spin may increase, resulting in a lack of distance. On the other hand, if the cover is too thin, the abrasion resistance may be poor, or the spin may not be applied on approach, resulting in insufficient controllability.

As the material for the above cover, various thermoplastic resins used in golf ball cover materials can be used, but from the viewpoint of spin control and scratch resistance in short games, thermoplastic polyurethane is mainly used. It is preferable to use a resin material made of That is, it is preferable to form it from a resin compound containing (I) a thermoplastic polyurethane and (II) a polyisocyanate compound as main components.

It is recommended that the total mass of the above components (I) and (II) be 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 the thermoplastic polyurethane (I) above, the structure of the thermoplastic polyurethane consists of a soft segment made of a polymeric 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 used as a raw material, any of those conventionally used in the technology related to thermoplastic polyurethane can be used, and is not particularly limited, but for example, polyester polyol, polyether polyol, polycarbonate polyol. , 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 preferred because they can synthesize thermoplastic polyurethanes that have a high impact modulus and excellent low-temperature properties.

As the chain extender, those used in conventional technology related to thermoplastic polyurethane can be suitably used. Preferably, it is a molecular compound. Examples of chain extenders include 1,4-butylene glycol, 1,2-ethylene glycol, 1,3-butanediol, 1,6-hexanediol, 2,2-dimethyl-1,3-propanediol, etc. However, it is not limited to these. Among these, aliphatic diols having 2 to 12 carbon atoms are preferred as chain extenders, and 1,4-butylene glycol is more preferred.

As the polyisocyanate compound, those used in conventional techniques related to thermoplastic polyurethane can be suitably used, and there are no particular limitations. 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, dicyclohexylmethane diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, norbornene diisocyanate, trimethylhexamethylene diisocyanate, and dimer acid diisocyanate can be used. However, depending on the type of isocyanate, 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 preferred from the viewpoint of the balance between stability during production and physical properties developed.

As the specific thermoplastic polyurethane of component (I), commercially available products may be used, such as Pandex T8295, Pandex T8290, and Pandex T8260 (all manufactured by ICC Covestro Polymer Co., Ltd.).

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

There is no particular restriction on the composition ratio of the above components (I), (II), and (III), but in order to fully exhibit the effects of the present invention, the mass ratio of (I):(II) :(III)=100:2-50:0-50, more preferably (I):(II):(III)=100:2-30:8-50 (mass ratio) It is to be.

Furthermore, various additives other than the components constituting the thermoplastic polyurethane can be added to the above resin compound as necessary, such as pigments, dispersants, antioxidants, and light stabilizers. , an ultraviolet absorber, a mold release agent, etc. may be appropriately added.

The specific gravity of the cover is not particularly limited, but is preferably 1.00 or more, more preferably 1.03 or more, even more preferably 1.06 or more, and the upper limit is preferably 1.20 or less. , more preferably 1.17 or less, still more preferably 1.14 or less. If the specific gravity of the cover is smaller than the above range, the proportion of a material with a small specific gravity such as an ionomer blended into the urethane cover, which is the main material, will be high, which may result in poor scratch resistance. On the other hand, if the specific gravity of the cover is too high, the amount of filler added will be large, and the repulsion will be too low, making it impossible to obtain the desired flight distance.

The multi-piece solid golf ball formed by laminating the core, intermediate layer, and cover (outermost layer) described above can be manufactured by a conventional method such as a known injection molding method. For example, an intermediate layer material is injected around the core using an injection mold to obtain an intermediate layer coated sphere, and finally, a multi-piece golf ball is obtained by injection molding the material for the outermost layer, the cover. Can be done. Alternatively, a golf ball can also be produced by preparing in advance two half-cups formed into a half-shell shape, and wrapping the core and the intermediate layer-coated sphere with the half cups and molding them under heat and pressure.

The amount of deflection (mm) when applying an initial load of 98 N (10 kgf) to a final load of 1,275 N (130 kgf) to the golf ball is preferably 2.7 mm or more, more preferably 2.9 mm or more. , more preferably 3.0 mm or more. On the other hand, the upper limit of the amount of deflection 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, if it is too hard, the amount of spin may increase too much and the ball may not fly far or the feel of the ball may become too hard. On the other hand, if the amount of deflection is too large, that is, if the ball is too soft, the ball's resilience will be too low and it will not fly, the feel will be too soft, or the durability of cracking during repeated hits will be poor. Sometimes.

The initial velocity of the sphere (ball) obtained by covering the intermediate layer coated sphere with the cover is preferably 76.8 m/s or more, more preferably 77.0 m/s or more, and still more preferably 77.2 m/s or more, and the upper limit The speed is preferably 77.724 m/s or less. If this initial velocity value is too high, the initial velocity of the ball will become too high and may violate the rules. On the other hand, if this initial velocity is too low, the ball may not travel as far as a full shot. The initial velocity in this case is the same as the apparatus and conditions used for measuring the initial velocity of the core and intermediate layer coated spheres described above.

[ About the relationship between the surface hardness of each sphere ]
The value obtained by subtracting the surface hardness of the core from the surface hardness of the intermediate layer coated sphere is preferably 5 or more, more preferably 10 or more, and still more preferably 16 or more in Shore C hardness, and the upper limit is preferably 32 Below, it is more preferably 28 or less, still more preferably 25 or less. If you deviate from the above range, the amount of spin of the ball will increase when you take a full shot, and you may not be able to achieve the desired flight distance.

The value obtained by subtracting the center hardness of the core from the surface hardness of the intermediate layer coated sphere is preferably 40 or more, more preferably 41 or more, and even more preferably 42 or more in terms of Shore C hardness, and the upper limit is preferably 53. Below, it is more preferably 50 or less, still more preferably 47 or less. If the above value is too small, the amount of spin of the ball will increase during a full shot, and the desired flight distance may not be achieved. On the other hand, if the above-mentioned value is too large, the durability against cracking upon repeated hitting may deteriorate, or the actual initial hitting speed may become low, making it impossible to obtain the desired flight distance.

The value obtained by subtracting the surface hardness of the ball from the surface hardness of the intermediate layer coated sphere is preferably 2 or more, more preferably 4 or more, and even more preferably 6 or more in Shore C hardness, and the upper limit is preferably 25. Below, it is more preferably 17 or less, still more preferably 14 or less. If the above value is too small, controllability in short games may deteriorate. On the other hand, if the above value is too large, the spin during a full shot may increase, making it impossible to obtain the desired flight distance.

[ About the initial velocity relationship of each sphere ]
The relationship between the initial velocity of the core, the initial velocity of a sphere whose core is coated with an intermediate layer (intermediate layer coated sphere), and the initial velocity of a sphere whose intermediate layer coated sphere is covered with a cover (ball) is expressed by the following two equations. initial velocity) < (initial velocity of intermediate layer coated sphere)
0.65≦(initial velocity of intermediate layer coated sphere) - (initial velocity of core)≦1.15 (m/s)
It is necessary to satisfy the following. By optimizing the initial velocity relationship between these layers, it is possible to suppress the amount of spin when making a full shot and obtain a desired flight distance, and to improve cracking durability when repeatedly hit.

The value obtained by subtracting the initial velocity of the ball from the initial velocity of the intermediate layer coated sphere is greater than 0 m/s, preferably 0.10 m/s or more, more preferably 0.30 m/s or more, and the upper limit is preferably 1 It is .00 m/s or less, more preferably 0.70 m/s or less, still more preferably 0.50 m/s or less. If this value is too large, the amount of spin of the ball will increase during a full shot, the actual initial velocity of the ball will decrease, and the desired flight distance may not be achieved. On the other hand, if this value is too small and the problem is caused by the cover, the cover will become hard and no spin will be applied during short games, or the durability to repeated hits will be poor. Furthermore, if this small value is caused by the intermediate layer, the amount of spin of the ball increases on a full shot, and the desired flight distance may not be achieved.

The value obtained by subtracting the initial velocity of the core from the initial velocity of the intermediate layer coated sphere is preferably 0.65 m/s or more, more preferably 0.75 m/s or more, even more preferably 0.90 m/s or more, and the upper limit is is preferably 1.15 m/s or less, more preferably 1.13 m/s or less, even more preferably 1.10 m/s or less. If this value is too large, the durability against cracking when repeatedly struck may deteriorate. On the other hand, if this value is too small, the amount of spin will increase when making a full shot, making it impossible to obtain the desired distance.

[ About the specific gravity relationship between the middle layer and the cover ]
It is recommended that the difference between the specific gravity of the intermediate layer and the specific gravity of each layer be within ±0.15, preferably within ±0.10, and more preferably within ±0.05. That is, the value of (cover specific gravity) - (specific gravity of intermediate layer material) is usually -0.15 or more, preferably -0.10 or more, more preferably -0.05 or more, and the upper limit is: Usually, it is 0.15 or less, preferably 0.10 or less, more preferably 0.05 or less. If the difference in specific gravity between these layers is too large, the ball may When you hit a ball with a putter, there may be a large amount of vibration to the left or right.

[ About the specific gravity relationship between the middle layer and the core ]
It is recommended that the difference between the specific gravity of the intermediate layer and the specific gravity of each layer be within ±0.15, preferably within ±0.10, and more preferably within ±0.05. That is, the value of (intermediate layer specific gravity) - (core specific gravity) is usually -0.15 or more, preferably -0.10 or more, more preferably -0.05 or more, and the upper limit is usually: It is 0.15 or less, preferably 0.10 or less, more preferably 0.05 or less. If the difference in specific gravity between these layers is too large, and the middle layer material cannot be molded completely concentrically with the core layer and becomes eccentric, when the ball is hit with a putter, there will be a large amount of left and right vibration. Sometimes it happens.

[ About core diameter and ball diameter ]
The relationship between the core diameter and the ball diameter, that is, the value of (core diameter)/(ball diameter) is preferably 0.860 or more, more preferably 0.870 or more, and still more preferably 0.880 or more. be. On the other hand, the upper limit is preferably 0.940 or less, more preferably 0.910 or less, and still more preferably 0.890 or less. If this value is too small, the initial velocity of the ball will be low, or the amount of deflection of the entire ball will be small, making the ball hard, which will increase the amount of spin of the ball during a full shot, making it impossible to achieve the desired flight distance. be. On the other hand, if the above value is too large, the amount of spin of the ball during a full shot may increase, making it impossible to obtain the desired flight distance, or the durability of the ball to cracking when repeatedly hit may deteriorate.

[ About the difference in the amount of deflection between the core and the ball ]
When the amount of deflection (mm) when an initial load of 98 N (10 kgf) to a final load of 1,275 N (130 kgf) is applied to each sphere of the core and ball is C (mm) and B (mm), respectively. The value of CB must be 1.20 mm or more. If the CB value is less than 1.20 mm, the amount of spin will increase when hitting with a utility ball or iron, and you may not be able to achieve the desired flight distance. The value of CB is preferably 1.25 mm or more, more preferably 1.30 mm or more, even more preferably 1.35 mm or more, and the upper limit is preferably 1.80 mm or less, more preferably 1.70 mm or less. , more preferably 1.60 mm or less. If this value is too large, the durability against cracking when repeatedly hit may deteriorate, or the initial velocity at full shot may become low, making it impossible to obtain the desired flight distance.

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. or less, more preferably 340 or less. If the number of dimples is greater than the above range, the trajectory of the ball may become lower and the flight distance may be reduced. On the other hand, when the number of dimples decreases, the trajectory of the ball increases, and the flight distance may not increase.

Regarding the shape of the dimples, one type or a combination of two or more types, such as a circle, various polygons, dewdrop shapes, and other elliptical shapes, can be used as appropriate. For example, when circular dimples are used, the diameter can be approximately 2.5 mm or more and 6.5 mm or less, and the depth can be approximately 0.08 mm or more and 0.30 mm or less.

The dimple occupancy rate that the dimples occupy on the spherical surface of the golf ball, specifically, the total area of the dimples defined by the edges of the plane surrounded by the edges of the dimples in the spherical area of the ball assuming that there are no dimples. The ratio (SR value) is desirably 70% or more and 90% or less in order to fully exhibit aerodynamic characteristics. Further, the value V 0 obtained by dividing the space volume of the dimple under the plane surrounded by the edges of each dimple by the volume of a cylinder whose base is the plane and whose height is the maximum depth of the dimple from the _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 VR value, which is the total volume of dimples formed below the plane surrounded by the edges of the dimples, should be 0.6% or more and 1.0% or less, assuming that there are no dimples. is preferred. If the above-mentioned numerical values are outside the range, the ball will have a trajectory that does not provide a good flight distance, and it may not be possible to achieve a sufficiently satisfactory flight distance.

The multi-piece solid golf ball of the present invention can be used for competitions in accordance with the Rules of Golf, has an outer diameter of 42.672 mm and is large enough not to pass through a ring with an inner diameter, and preferably has a mass of 45.0 mm. ~45.93g.

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

[Examples 1 to 3, Comparative Examples 1 to 7]
Formation of the core
For Examples 1 to 3 and Comparative Examples 1 to 5, after preparing the rubber compositions of each example shown in Table 1, solid cores were obtained by vulcanization molding under the vulcanization conditions of each example shown in Table 1. Created.

Regarding Comparative Examples 6 and 7, cores are produced based on the formulations in Table 1 in the same manner as above.

Details of the above formulation are as follows.
・Polybutadiene A: Product name "BR01" (manufactured by JSR)
・Polybutadiene B: Product name “BR730” (manufactured by JSR)
・Polybutadiene C: Product name “T0700” (manufactured by JSR)
・Zinc acrylate: Product name “ZN-DA85S” (manufactured by Nippon Shokubai Co., Ltd.)
・Organic peroxide A: dicumyl peroxide, trade name "Percmil D" (manufactured by NOF Corporation)
・Organic peroxide B: 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.)
・Antioxidant A: 2,2-methylenebis(4-methyl-6-butylphenol), trade name "Nocrac NS-6" (manufactured by Ouchi Shinko Chemical Industry Co., Ltd.)
・Anti-aging agent B: 2-mercaptobenzimidazole, trade name "Nocrack MB" (manufactured by Ouchi Shinko Chemical Industry Co., Ltd.)
・Zinc stearate: Product name “Zinc Stearate GP” (manufactured by NOF Corporation)
・Zinc oxide: Product name: “Third-class zinc oxide” (manufactured by Sakai Chemical Industry Co., Ltd.)
・Pentachlorothiophenol zinc salt: Manufactured by Wako Pure Chemical Industries, Ltd.

Formation of intermediate layer and cover (outermost layer) Next, for Examples 1 to 3 and Comparative Examples 1 to 5, the intermediate layer resin shown in Table 2 was applied around the core surface using an injection mold. Material No. 1~No. 5 to form an intermediate layer. Next, using another injection mold, resin material No. 1 of the cover (outermost layer) shown in Table 2 was placed around the intermediate layer covered sphere. 9 to form a cover. At this time, a predetermined number of dimples common to all Examples and Comparative Examples were formed on the cover surface.

For Comparative Examples 6 and 7, using an injection mold, resin material No. 1 of the intermediate layer shown in Table 2 was applied around the core surface. 5 or no. 6 to form an intermediate layer. Next, using another injection mold, resin material No. 1 of the cover (outermost layer) shown in Table 2 was placed around the intermediate layer covered sphere. 7 or no. 8 to form a cover by injection molding. At this time, a predetermined number of dimples common to all Examples and Comparative Examples are formed on the cover surface.

Details of the ingredients in the above table are as follows.
The trade names of the main materials listed in the table are as follows.
"Himilan 1605", "Himilan 1855", "Himilan 1557", "Himilan 1706", "AM7318", "AM7327" Ionomers manufactured by Mitsui Dow Polychemicals "AN4319""AN4221C" Nucleol "Magnesium oxide" manufactured by Mitsui Dow Polychemicals “Kyowa Mag MF150” manufactured by Kyowa Chemical Industry Co., Ltd.
"Barium sulfate""Precipitated barium sulfate 300" manufactured by Sakai Chemical Industry Co., Ltd.
"Trimethylolpropane" (TMP) "TPU" manufactured by Tokyo Chemical Industry Co., Ltd. "Pandex" manufactured by DIC Covestro Polymer Co., Ltd., ether type thermoplastic polyurethane, material hardness (Shore D) "46"

For each golf ball obtained, various physical properties such as the internal hardness at each position of the core, the outer diameter of the core and each covered sphere, the thickness and material hardness of each layer, the surface hardness of each covered sphere, and the initial velocity of each covered sphere were determined. It was evaluated by the following method and shown in Tables 3 and 4.

Core hardness distribution The surface of the core is a spherical surface, and the needle of a hardness meter is set to be substantially perpendicular to the spherical surface, and the surface hardness is measured by Shore C hardness according to ASTM D2240. To determine the center and predetermined positions of the core, cut the core into a hemispherical shape, make the cross section flat, and measure by pressing the needle of a hardness tester vertically against the center and the predetermined positions shown in Table 3. The hardness of the position is indicated by the Shore C hardness value. For hardness measurement, an automatic rubber hardness meter "P2" manufactured by Kobunshi Keiki Co., Ltd. equipped with a Shore C type hardness meter is used. Read the maximum hardness value. All measurements are made in an environment of 23±2°C. Note that the numerical values in the table are Shore C hardness values.
In addition, 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 hardness 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 center M, Shore C hardness Cs of the surface of the core is the area A to F below
・Area A: 1/2×2×(Cm-4-Cm-6)
・Area B: 1/2×2×(Cm-2-Cm-4)
・Area C: 1/2×2×(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)
Calculate and find the values of the following six formulas.
(1) Area: A+B
(2) Area: B+C
(3) Area: D+E
(4) Area: E+F
(5) (Area: E+F) - (Area: A+B)
(6) (Area: D+E) - (Area: B+C)

As an explanation of the areas A to F of the core hardness distribution, a schematic diagram showing the areas A to F using the core hardness distribution data of Example 1 is shown in FIG.
Further, graphs of core hardness distributions of Examples 1 to 3 and Comparative Examples 1 to 7 are shown in FIGS. 3 and 4.

The outer diameter of each of the core and intermediate layer coated spheres is controlled at a temperature of 23.9 ± 1°C for at least 3 hours in a constant temperature bath, and five arbitrary surfaces are heated in a room at 23.9 ± 2°C. The average value is taken as the measured value for each sphere, and the average value for the number of 10 spheres measured is determined.

The diameter of the ball was adjusted at a temperature of 23.9 ± 1°C for at least 3 hours in a constant temperature bath, and the average value was measured at 15 locations without any dimples in a room at 23.9 ± 2°C. is the measured value of one ball, and the average value of 10 measured balls is determined.

Deflection amount of core, intermediate layer coated sphere, and ball Place each covered sphere on a hard board and measure the amount of deflection when an initial load of 98 N (10 kgf) is applied to a final load of 1275 N (130 kgf). do. The above deflection amount is a measured value measured indoors at 23.9±2° C. after adjusting the temperature in a constant temperature bath at 23.9±1° C. for at least 3 hours. The pressing speed of the head that compresses the core and the coated spheres or balls of each layer is 10 mm/s.

Material hardness of intermediate layer and cover (Shore C hardness, Shore D hardness)
The resin material of each layer was formed into a sheet having a thickness of 2 mm, and was left for 2 weeks at a temperature of 23±2°C. During measurement, three sheets are superimposed. Shore C hardness and Shore D hardness are measured using a Shore C hardness meter and a Shore D hardness meter, respectively, based on the ASTM D2240 standard. For hardness measurement, an automatic rubber hardness meter "P2" manufactured by Kobunshi Keiki Co., Ltd. equipped with a Shore C type hardness meter or a Shore D type hardness meter is used. Read the maximum hardness value. The measurement method follows the ASTM D2240 standard.

The surface hardness of each sphere of the intermediate layer coated sphere and the ball is measured by pressing a needle perpendicularly to the surface of each sphere. Note that the surface hardness of the ball (cover) is a value measured at a land portion on the ball surface where no dimples are formed. Shore C hardness and Shore D hardness are measured using a Shore C hardness meter and a Shore D hardness meter, respectively, based on the ASTM D2240 standard. For hardness measurement, an automatic rubber hardness meter "P2" manufactured by Kobunshi Keiki Co., Ltd. equipped with a Shore C type hardness meter or a Shore D type hardness meter is used. Read the maximum hardness value. The measurement method follows the ASTM D2240 standard.

The measurement principle for measuring the initial velocity of each sphere using a COR type initial velocity meter made by Hye Precision Products, which is the same type as R&A, is shown below.
The air pressure was changed to 4 levels of 35.5, 36.5, 39.5, and 40.5 psi, and the ball was launched at 4 levels of incidence velocity depending on each air pressure and collided with the barrier. Measure its COR (coefficient of restitution). That is, a correlation equation between the incident velocity and COR is created by changing the air pressure in four stages. Similarly, create a correlation equation between incident velocity and contact time.
Then, from these correlation equations, the COR (coefficient of restitution) and contact time (μs) at an incident speed of 43.83 m/s are determined and substituted into the following initial speed conversion equation to calculate the initial speed of each sphere.
IV=136.8+136.3e+0.019tc
[Here, e is the coefficient of restitution, and tc is the contact time (μs) at a collision speed of 143.8 ft/s (43.83 m/s). ]
In measuring the initial velocity of each sphere, the inner diameter of the barrel used was 39.88 mm for the cores of Examples 1 to 3 and Comparative Examples 1 to 5, 38.23 mm for the cores of Comparative Examples 6 and 7, and 38.23 mm for the cores of Comparative Examples 6 and 7. The coated sphere is 41.53 mm, and the balls in all cases are 43.18 mm.

The flight (utility) (I#6) (I#8) of each golf ball, controllability during approach, and durability against repeated hitting are evaluated using the following methods. The results are shown in Table 5.

Flight evaluation (utility)
A utility club is attached to a golf batting robot and the amount of spin and flight distance (total) are measured when hitting at a head speed (HS) of 38 m/s. The club used is "JGR H2 (2016 model)" manufactured by Bridgestone Sports. The judgment criteria are as follows.
〔Judgment criteria〕
Total flight distance is 166.0m or more... ○
Total flight distance is less than 166.0m... ×

Flying evaluation (I#6)
A 6-iron (I#6) is attached to a golf batting robot, and the amount of spin and flight distance (total) when hitting at a head speed (HS) of 35 m/s are measured and judged according to the following criteria. The club used is "JGR Forged I#6 (2016 model)" manufactured by Bridgestone Sports.
〔Judgment criteria〕
Total flight distance is 148.5m or more... ○
Total flight distance is less than 148.5m... ×

Flight evaluation (I#8)
An 8-iron (I#8) is attached to a golf batting robot, and the amount of spin and flight distance (total) when hitting at a head speed (HS) of 35 m/s are measured and judged according to the following criteria. The club used is "JGR Forged I#8 (2016 model)" manufactured by Bridgestone Sports.
〔Judgment criteria〕
Total flight distance is 121.0m or more... ○
Total flight distance is less than 121.0m... ×

Evaluation of the amount of spin during approach The evaluation is based on the amount of spin when the ball is hit at a head speed (HS) of 15 m/s using a golf batting robot equipped with a sand wedge. Similarly, the amount of spin is measured using an initial condition measuring device on the ball immediately after being hit. The sand wedge used is "TourStage TW-03 (loft angle 57°) 2002 model" manufactured by Bridgestone Sports.
〔Judgment criteria〕
〇 ... Spin amount 4500 rpm or more × ... Spin amount less than 4500 rpm

Durability to Cracking Due to Repeated Hits The durability of the ball is evaluated using ADC Ball COR Durability Tester manufactured by Automated Design Corporation in the United States. After a golf ball was fired using air pressure, it was made to continuously collide with two metal plates placed in parallel, and the average number of shots required until the ball broke was defined as durability. In this case, the average value is a value obtained by preparing 10 balls of the same type, firing each ball, and averaging the number of shots required for each of the 10 balls to break. The type of testing machine was a horizontal COR, and the incident speed to the metal plate was 43 m/s.
〔Judgment criteria〕
○ ・・・ Average value 150 times or more × ・・・ Average value 149 times or less

As shown in the results in Table 5, the golf balls of Comparative Examples 1 to 7 are inferior to the products of the present invention (Examples) in the following points.
In Comparative Example 1, the value of (the amount of deflection of the core - the amount of deflection of the ball) is 1.20 mm or less, and the value of (initial velocity of the intermediate layer coated sphere - initial velocity of the core) is greater than 1.15 m/s. As a result, the flight distance when hitting with an iron (I#6) is inferior.
In Comparative Example 2, the value of (initial velocity of intermediate layer coated sphere - initial velocity of core) is greater than 1.15 m/s. As a result, the durability against cracking when repeatedly struck is poor.
In Comparative Example 3, the value of (deflection amount of core - amount of deflection of ball) is 1.20 mm or less, and the value of (initial velocity of intermediate layer coated sphere - initial velocity of core) is greater than 1.15 m/s. As a result, the flight distance when hit with a utility ball is inferior, and the durability against cracking when hit repeatedly is poor.
In Comparative Example 4, the value of (initial velocity of intermediate layer coated sphere - initial velocity of core) is greater than 1.15 m/s. As a result, the durability against cracking when repeatedly struck is poor.
In Comparative Example 5, the value of (core deflection amount−ball deflection amount) is 1.20 mm or less. As a result, the flight distance when hitting with a utility ball and when hitting with an iron (I#6) is inferior.
In Comparative Example 6, the value of (core deflection amount−ball deflection amount) is 1.20 mm or less. As a result, the flight distance when hitting with utility, iron (I#6), and iron (I#8) are all inferior, and the amount of spin during approach is reduced.
In Comparative Example 7, the value of (deflection amount of core - amount of deflection of ball) is 1.20 mm or less, the relationship is (initial velocity of ball ≧ initial velocity of intermediate layer covered sphere), and (initial velocity of intermediate layer covered sphere) - initial velocity of the core) is smaller than 0.65 m/s. As a result, the flight distance when hitting with an iron (I#6) and iron (I#8) is both inferior, and the amount of spin during approach is reduced.

G Golf ball 1 Core 2 Intermediate layer 3 Cover D Dimple

Claims (10)

A multi-piece solid golf ball comprising a core, an intermediate layer, and a cover, wherein the core is made of a rubber composition, the intermediate layer and the cover are both made of a resin composition, and the initial velocity of the core, The relationship between the initial velocity of a sphere whose core is coated with an intermediate layer (intermediate layer coated sphere) and the initial velocity of a sphere (ball) whose core is coated with an intermediate layer is expressed by the following two equations (initial velocity of ball) < (intermediate layer coated sphere). (initial velocity of layer-covered sphere)
0.65≦(initial velocity of intermediate layer coated sphere) - (initial velocity of core)≦1.15 (m/s)
In addition, the amount of deflection (mm) when an initial load of 98 N (10 kgf) to a final load of 1,275 N (130 kgf) is applied to each sphere of the core and ball is C (mm) and B (mm), respectively. A multi-piece solid golf ball characterized in that the value of CB is 1.20 mm or more. The formula below,
Ball surface hardness <Surface hardness of intermediate layer coated sphere> Core surface hardness (However, the surface hardness of each sphere above means Shore C hardness.)
The multi-piece solid golf ball according to claim 1, which satisfies the following. 3. The multi-piece solid golf ball according to claim 1, wherein the resin composition of the intermediate layer includes a high acid ionomer resin having an acid content of 16% by mass or more. The multi-piece solid golf ball according to claim 1 or 2, wherein the intermediate layer has a specific gravity of 1.05 or more. The multi-piece solid golf ball according to claim 1 or 2, wherein the intermediate layer contains an inorganic particulate filler. 3. The multi-piece solid golf ball according to claim 1, wherein the difference between the specific gravity of the cover and the specific gravity of the intermediate layer is within 0.15. The formula below,
3. The multi-piece solid golf ball according to claim 1, wherein the thickness of the cover <thickness of the intermediate layer. The multi-piece solid golf ball according to claim 1 or 2, wherein the core has a diameter of 36.7 to 40.1 mm. In the hardness distribution of the core, the Shore C hardness at the center of the core is Cc, the Shore C hardness at the midpoint M between the center and the surface of the core _{is Cm} , and the Shore C hardness at positions 2 mm, 4 mm, and 6 mm inward from the midpoint M is The hardness is Cm-2, Cm-4, Cm-6, respectively. The Shore C hardness at the positions 2mm, 4mm, and 6mm outward from the center M is Cm+2, Cm+4, and Cm+6, respectively. The Shore of the surface of the core is Cm+2, Cm+4, and Cm+6. When C hardness is Cs, the following areas A to F
・Area A: 1/2×2×(Cm-4-Cm-6)
・Area B: 1/2×2×(Cm-2-Cm-4)
・Area C: 1/2×2×(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)
For, the following formula (Area E + Area F) - (Area A + Area B) ≧1.0
The multi-piece solid golf ball according to claim 1 or 2, which satisfies the following. The formula below,
(Area D + Area E) - (Area B + Area C) ≧1.0
The multi-piece solid golf ball according to claim 9, which satisfies the following.

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