JP7047591B2 - Multi-piece solid golf ball - Google Patents

Description

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

Many ideas have been made to design the ball into a multi-layer structure, and many balls have been developed that satisfy not only professional golfers and advanced golfers but also amateur golfers with medium and low head speeds. For example, a functional multi-piece solid golf ball in which the surface hardness of each layer of the core, the surrounding layer, the intermediate layer, and the cover (outermost layer) is optimized is widespread.

Examples of such technical documents include the multi-piece solid golf balls described in JP-A-2014-132955, JP-A-2015-173860, JP-A-2016-16117, and JP-A-2016-179552. Can be mentioned. The golf balls described in these publications satisfy the relationship of ball surface hardness> intermediate layer surface hardness> surrounding layer surface hardness <core surface hardness hardness, and are excellent in flying even for amateur golfers whose head speed is not fast. It gives performance.

However, the golf ball proposed above has not been optimized for the hardness distribution of the core and the thickness relationship with each layer, and is further improved as a ball product for golfers with low head speeds. There is still room for improvement in terms of performance and good feel.

Japanese Unexamined Patent Publication No. 2014-132955 Japanese Unexamined Patent Publication No. 2015-173860 Japanese Unexamined Patent Publication No. 2016-16117 Japanese Unexamined Patent Publication No. 2016-179052

The present invention has been made in view of the above circumstances, and provides a multi-piece solid golf ball for amateur users who has excellent flight when hit by a golfer whose head speed is not so fast, and has a soft and good feel. The purpose is.

As a result of diligent studies to achieve the above object, the present inventors have determined the relationship between the thickness and the surface hardness of each layer in a multi-piece solid golf ball provided with a core, a surrounding layer, an intermediate layer and a cover. In addition to specifying, regarding the hardness distribution of the core, the position hardness of a specific distance from the midpoint M between the center and the surface of the core to the core surface side and the position hardness of a specific distance from the midpoint M to the core center side are determined and described below. As described in 1, the areas A to F consisting of the difference in hardness at each position and the difference in each specific distance are obtained, and the core hardness distribution is designed so that these areas A to F satisfy a specific formula. The present invention has been made by finding that a golfer whose head speed is not fast can obtain a good flight and a soft feel of flight.

Therefore, the present invention provides the following multi-piece solid golf balls.
1. 1. A multi-piece solid golf ball including a core, a surrounding layer, an intermediate layer and a cover, wherein the core is formed of a base material rubber as a main material, and the intermediate layer is formed thicker than the surrounding layer and the cover. The surface hardness of the core, the surface hardness of the sphere whose core is coated with the surrounding layer (the sphere coated with the surrounding layer), the surface hardness of the sphere whose sphere coated with the surrounding layer is coated with the intermediate layer (the sphere coated with the intermediate layer), and the ball. The surface hardness of
The surface hardness of the ball> the surface hardness of the intermediate layer-coated sphere> the surface hardness of the surrounding layer-coated sphere <the surface hardness of the core is satisfied, and 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 surface of the core is Cs, the Shore-C hardness at the midpoint _M between the center and the surface of the core is CM, and the middle point M is 2 toward the core surface side. The Shore-C hardnesses at the positions of 5.5 mm, 5.0 mm and 7.5 mm are CM _{+ 2.5} , CM _{+ 5.0} and CM _{+ 7.5} , respectively, and 2.5 mm from the midpoint M to the core center side. When the Shore-C hardness at the 0 mm and 7.5 mm positions is CM _-2.5 , _CM-5.0 and _CM-7.5 , respectively, the following areas A to F
-Area A: 1/2 x 2.5 x ( _CM-5.0 -CM _-7.5 ),
-Area B: 1/2 x 2.5 x ( _CM-2.5- CM _-5.0 ),
_-Area C: 1/2 x 2.5 x (CM _-CM-2.5 ),
_-Area D: 1/2 x 2.5 x ( _{CM + 2.5} -CM),
-Area E: 1/2 x 2.5 x ( _{CM + 5} -C _{M + 2.5} ) and-Area F: 1/2 x 2.5 x ( _{CM + 7.5} -C _{M + 5} )
, (Area D + Area E + Area F)-(Area A + Area B + Area C)> 0.
2. 2. The multi-piece solid golf ball according to 1 above, which satisfies (area D + area E)-(area A + area B + area C) ≧ 0 for the areas A to F of the core hardness distribution.
3. 3. The multi-piece solid golf ball according to 1 or 2 above, wherein the hardness difference (Cs-Cc) between the center and the surface of the core is 20 or more in Shore-C hardness.
4. Regarding the areas A to F of the core hardness distribution, the above 1 to 3 satisfying 0.15 ≦ [(area D + area E + area F)-(area A + area B + area C)] / (Cs-Cc) ≦ 0.6. Multi-piece solid golf ball described in any of.
5. The multi-piece solid golf ball according to any one of 1 to 4 above, wherein the thickness of the cover is 1.2 mm or less.
6. A large number of dimples are formed on the surface of the cover, and the dimples (specific cross-sectional shape) which are presented by a curved line or a combination of a straight line and a curved line and have a cross-sectional shape specified by the following procedures (i) to (iv). The multi-piece solid golf ball according to any one of 1 to 5 above, wherein at least one dimple) is arranged and the total number of dimples is 250 to 380.
(I) The foot (foot drop) of a perpendicular line drawn from the deepest point of the dimple to the virtual plane created at the periphery of the dimple is the dimple center, and the straight line passing through the dimple center and any one dimple edge is the reference line. do.
(Ii) Of the reference lines, the line segment from the dimple edge to the dimple center is divided into 100 points or more, and the distance between the points is 100% when the distance from the dimple edge to the dimple center is 100%. Calculate the ratio of.
(Iii) The ratio of the dimple depth in every 20% of 0 to 100% of the distance from the dimple edge to the dimple center is calculated.
(Iv) At the ratio of the depth in the dimple region of 20 to 100% of the distance from the dimple edge to the dimple center, the change amount ΔH of the depth every 20% of the distance is obtained, and this change amount ΔH is the above. The cross-sectional shape of the dimples is designed to be 6% or more and 24% or less in all the regions corresponding to the distance of 20 to 100%.
7. The multi-piece solid golf ball according to any one of 1 to 6 above, wherein a coating film layer is formed on the cover surface, and the hardness of the coating film layer is 40 to 80 in Shore-C hardness.

According to the multi-piece solid golf ball of the present invention, the golf ball has excellent flight performance when hit by a golfer whose head speed is not so fast, and has a soft and good feel, and is suitable as a golf ball for amateur users. Is.

It is a schematic sectional drawing of the multi-piece solid golf ball which is one Embodiment of this invention. In order to explain the area A to F of the core hardness distribution, it is the schematic which explained using the core hardness distribution data of Example 1. FIG. It is a schematic cross-sectional view of the dimples used in an Example and a comparative example, (A) is a dimple of a peculiar shape, and (B) is a cross-sectional view of a dimple having an arcuate cross section.

Hereinafter, the present invention will be described in more detail.
The multi-piece solid golf ball of the present invention has a core, a surrounding layer, an intermediate layer and a cover, and an example thereof is shown in FIG. The golf ball G shown in FIG. 1 has a core 1, a surrounding layer 2 covering the core 1, an intermediate layer 3 covering the surrounding layer, and a cover 4 covering the intermediate layer 3. .. The cover 4 is located at the outermost layer in the layer structure of the golf ball except for the coating film layer. In the present invention, the intermediate layer and the surrounding layer may be formed into two or more layers even if they are a single layer. A large number of dimples D are usually formed on the surface of the cover (outermost layer) 4 in order to improve the aerodynamic characteristics. Further, a coating film layer 5 is formed on the surface of the cover 4. Hereinafter, each of the above layers will be described in detail.

The diameter of the core is preferably 35.3 mm or more, more preferably 35.6 mm or more, further preferably 36.0 mm or more, and the upper limit is preferably 37.5 mm or less, more preferably 37.0 mm or less, and further. It is preferably 36.5 mm or less. If the diameter of the core is too small, the spin will increase when hitting the 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 be deteriorated or the feel at impact may be deteriorated.

The amount of deflection (mm) from the initial load of 98 N (10 kgf) to the final load of 1,275 N (130 kgf) is not particularly limited, but is preferably 3.0 mm or more, more preferably 3. It is 5.5 mm or more, more preferably 4.0 mm or more, and the upper limit value is preferably 7.0 mm or less, more preferably 6.0 mm or less, 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 of the ball may increase too much and the ball may not fly or the feel of hitting may become too hard. On the other hand, if the amount of deflection of the core is too large, that is, if the core is too soft, the repulsion of the ball becomes too low to fly, the feel of hitting becomes too soft, or the cracking durability at the time of repeated hitting deteriorates. Sometimes.

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

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

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

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

Commercially available products can be used as the organic peroxide, for example, Park Mill D (manufactured by NOF Corporation), Perhexa C-40, Perhexa 3M (manufactured by NOF Corporation), Luperco 231XL (manufactured by NOF CORPORATION). ) And the like can be preferably used. These may be used alone or in combination of two or more. The blending amount of the organic peroxide is preferably 0.1 part by mass or more, more preferably 0.3 part by mass or more, still more preferably 0.5 part by mass or more, most preferably, with respect to 100 parts by mass of the base material rubber. Is 0.6 parts by mass or more, and as an upper limit, preferably 5 parts by mass or less, more preferably 4 parts by mass or less, further preferably 3 parts by mass or less, and most preferably 2.5 parts by mass or less. If the blending amount is too large or too small, it may not be possible to obtain a suitable feel, durability and resilience.

In addition, examples of the compounding agent to be blended in the base rubber include an inert filler, and for example, zinc oxide, barium sulfate, calcium carbonate and the like can be preferably used. These may be used alone or in combination of two or more. The blending amount of the inert filler is preferably 1 part by mass or more, more preferably 5 parts by mass or more, and the upper limit is preferably 50 parts by mass or less, more preferably 40 parts by mass or less with respect to 100 parts by mass of the base rubber. More preferably, it is 35 parts by mass or less. If the blending amount is too large or too small, it may not be possible to obtain an appropriate mass and suitable resilience.

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

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

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

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

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

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

Further, the core can be formed not only in a single layer but also in two layers, an inner core and an outer core. When the core is formed into two layers, an inner layer core and an outer layer core, the above-mentioned rubber material can be used as the main material for both the inner layer and the outer layer core. Further, the rubber material of the outer layer core covering the inner layer core may be the same as or different from the material of the inner layer core. Specifically, it is the same as described 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 by a Shore-C hardness meter compliant with the ASTM D2240 standard, and the timing of reading the measured value is different from that of the JIS-C hardness method, but the measured value is JIS. -It is not so different from the value of C and is close to it.

The central hardness (Cc) of the core is preferably 50 or more, more preferably 52 or more, still more preferably 54 or more, and the upper limit thereof is preferably 59 or less, more preferably 57 or less, still more preferably 55 or less. Is. If this value is too large, the feel of hitting may become hard, or the spin may increase in a full shot and the target flight distance may not be obtained. On the other hand, if the above value is too small, the resilience may be low and the ball may not fly, or the cracking durability when repeatedly hit may be deteriorated.

The position hardness (C2.5) 2.5 mm away from the center of the core is preferably 51 or more, more preferably 53 or more, still more preferably 55 or more, and the upper limit is preferably 61 or less, more preferably 61 or less. It is 59 or less, more preferably 57 or less. Deviating from these hardnesses may lead to the same disadvantageous results as described in Core Hardness (Cc) above.

The position hardness (C5) 5 mm away from the center of the core is preferably 54 or more, more preferably 56 or more, still more preferably 58 or more, and the upper limit is preferably 63 or less, more preferably 61 or less, further. It is preferably 59 or less. Deviating from these hardnesses may lead to the same disadvantageous results as described in Core Hardness (Cc) above.

The position hardness (C7.5) 7.5 mm away from the center of the core is preferably 56 or more, more preferably 58 or more, still more preferably 60 or more, and the upper limit is preferably 65 or less, more preferably. It is 63 or less, more preferably 61 or less. Deviating from these hardnesses may lead to the same disadvantageous results as described in Core Hardness (Cc) above.

The position hardness (C10) 10 mm away from the center of the core is preferably 59 or more, more preferably 61 or more, still more preferably 63 or more, and the upper limit is preferably 68 or less, more preferably 66 or less, further. It is preferably 64 or less. Deviating from these hardnesses may lead to the same disadvantageous results as described in Core Hardness (Cc) above.

The position hardness (C12.5) 12.5 mm away from the center of the core is preferably 64 or more, more preferably 66 or more, still more preferably 68 or more, and the upper limit is preferably 75 or less, more preferably 75 or less. It is 73 or less, more preferably 71 or less. Deviating from these hardnesses may lead to the same disadvantageous results as described in Core Hardness (Cc) above.

The position hardness (C15) 15 mm away from the center of the core is preferably 69 or more, more preferably 71 or more, still more preferably 73 or more, and the upper limit is preferably 81 or less, more preferably 79 or less, further. It is preferably 77 or less. Deviating from these hardnesses may lead to the same disadvantageous results as described in Core Hardness (Cc) above.

The surface hardness (Cs) of the core is preferably 73 or more, more preferably 75 or more, still more preferably 77 or more, and the upper limit thereof is preferably 85 or less, more preferably 83 or less, still more preferably 81 or less. Is. Deviating from these hardnesses may lead to the same disadvantageous results as described in Core Hardness (Cc) above.

The difference between the surface hardness (Cs) of the core and the center 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 low spin effect of the ball at the time of a driver shot may be insufficient and the flight distance may not be obtained. If the above value is too large, the initial velocity of the ball at the time of actual hitting may be low and the flight distance may not be obtained, or the cracking durability at the time of repeated hitting may be deteriorated.

In the core hardness distribution in the present invention, the Shore-C hardness at the center of the core is Cc, the Shore-C hardness at the surface of the core is Cs, and the Shore-C hardness at the midpoint _M between the center and the surface of the core is CM. The Shore-C hardnesses at positions 2.5 mm, 5.0 mm and 7.5 mm from the midpoint M to the core surface side are set to CM _{+ 2.5} , _{CM + 5.0} and _{CM + 7.5} , respectively, from the midpoint M. Calculated from the following formula when the Shore _- C hardness at _2.5 mm, 5.0 mm and _7.5 mm on the core center side is CM-2.5, CM-5.0 and CM-7.5, respectively. Areas A to F
-Area A: 1/2 x 2.5 x ( _CM-5.0 -CM _-7.5 ),
-Area B: 1/2 x 2.5 x ( _CM-2.5- CM _-5.0 ),
_-Area C: 1/2 x 2.5 x (CM _-CM-2.5 ),
_-Area D: 1/2 x 2.5 x ( _{CM + 2.5} -CM),
-Area E: 1/2 x 2.5 x ( _{CM + 5} -C _{M + 2.5} ) and-Area F: 1/2 x 2.5 x ( _{CM + 7.5} -C _{M + 5} )
(Area D + Area E + Area F)-(Area A + Area B + Area C)> 0, that is, the value of (Area D + Area E + Area F) is higher than the value of (Area A + Area B + Area C). It is characterized by being large. Note that FIG. 2 shows a schematic diagram illustrating the areas A to F using the core hardness distribution data of Example 1. As described above, the areas A to F are the areas of each triangle having the difference in each specific distance as the base and the difference in hardness at each position as the height.

The lower limit of the above (area D + area E + area F)-(area A + area B + area C) is more than 0, preferably 3 or more, and preferably 6 or more. The upper limit is not particularly limited, but is preferably 20 or less, more preferably 15 or less, and further preferably 10 or less. If the above value is too small, the low spin effect at the time of hitting the driver (W # 1) may be insufficient and the flight distance may not be obtained. If the above value is too large, the initial velocity of the actual hit may be low and the flight distance may not be obtained, or the cracking durability at the time of repeated hits may be deteriorated.

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) ≦ 0.6. The lower limit of this value is preferably 0.20 or more, more preferably 0.25 or more. On the other hand, the upper limit of the above formula does not need to be set in particular, but is preferably 0.60 or less, more preferably 0.50 or less, and further preferably 0.40 or less. If the above value is too small, the low spin effect at the time of hitting the driver (W # 1) may be insufficient and the flight distance may not be obtained. If the above value is too large, the initial velocity of the actual hit may be low and the flight distance may not be obtained, or the cracking durability at the time of repeated hits may be deteriorated.

Further, in the core hardness distribution, the following formula (area D + area E)-(area A + area B + area C) ≧ 0
It is preferable that the condition is satisfied, and the lower limit of this value is preferably 0.5 or more, more preferably 1.0 or more. The upper limit value does not need to be set in particular, but is preferably 8.0 or less, more preferably 6.0 or less, and further preferably 4.0 or less. If the above value is too small, the low spin effect at the time of hitting the driver (W # 1) may be insufficient and the flight distance may not be obtained. If the above value is too large, the initial velocity of the actual hit may be low and the flight distance may not be obtained, or the cracking durability at the time of repeated hits may be deteriorated.

Next, the surrounding layer will be described.
The material hardness of the surrounding layer is not particularly limited, but the shore D hardness is preferably 15 or more, more preferably 20 or more, still more preferably 25 or more, and the upper limit is preferably 45 or less, more preferably 40. Below, it is more preferably 30 or less. The surface hardness of the sphere whose core is covered with the surrounding layer (the surrounding layer-covered sphere) is the shore D hardness, preferably 23 or more, more preferably 28 or more, still more preferably 33 or more, and the upper limit is set as an upper limit. It is preferably 53 or less, more preferably 48 or less, and even more preferably 38 or less. If the material hardness and surface hardness of these surrounding layers are too softer than the above range, the spin amount of the ball at the time of a full shot increases too much and the flight distance may not be obtained, or the cracking durability due to repeated hitting may deteriorate. .. If the above-mentioned material hardness and surface hardness are too hard, the cracking durability due to repeated hitting may be deteriorated, or the spin amount at the time of a full shot may be large, the flight distance may not be obtained especially at a low head speed, and the hit feeling may be deteriorated. be.

The thickness of the surrounding layer is preferably 0.5 mm or more, more preferably 0.7 mm or more, still more preferably 0.9 mm or more. On the other hand, the upper limit of the thickness of the surrounding layer is preferably 1.4 mm or less, more preferably 1.2 mm or less, and further preferably 1.0 mm or less. If this surrounding layer is too thin, the cracking durability due to repeated impacts may be deteriorated, or the feel of impact may be deteriorated. In addition, if the surrounding layer is too thick, the amount of spin of the ball at the time of a full shot may increase and the flight distance may not be obtained.

The material of the surrounding layer is not particularly limited, but various thermoplastic resin materials can be preferably adopted. Specifically, ionomer resin, urethane-based, amide-based, ester-based, olefin-based, and styrene-based materials can be used. Thermoplastic elastomers such as systems and mixtures thereof can be used, and in particular, thermoplastic polyether ester elastomers are suitable from the viewpoint of obtaining good repulsion within a desired hardness range.

There is no particular limitation on the amount of deflection (mm) from the initial load of 98 N (10 kgf) to the final load of 1,275 N (130 kgf) with respect to the sphere whose core is covered with the surrounding layer (the sphere covered with the surrounding layer). However, it is preferably 3.0 mm or more, more preferably 3.5 mm or more, still more preferably 4.0 mm or more, and the upper limit value is preferably 7.0 mm or less, more preferably 6.0 mm or less, still more preferably 5. It is 0.0 mm or less. If the amount of deflection of the sphere is too small, that is, if the sphere is too hard, the spin of the ball may increase too much and the ball may not fly or the feel of hitting may become too hard. On the other hand, if the amount of deflection of the sphere is too large, that is, if the sphere is too soft, the repulsion of the ball becomes too low to fly, the feel of hitting becomes too soft, or the cracking durability at the time of repeated hits is poor. May become.

Next, the intermediate layer will be described.
The material hardness of the intermediate layer is not particularly limited, but the shore D hardness is preferably 40 or more, more preferably 45 or more, still more preferably 47 or more, and the upper limit value is preferably 60 or less, more preferably 55. Below, it is more preferably 53 or less. The surface hardness of the sphere (intermediate layer-coated sphere) in which the surrounding layer-coated sphere is coated with the intermediate layer is the shore D hardness, preferably 46 or more, more preferably 51 or more, still more preferably 53 or more, and an upper limit value. It is preferably 66 or less, more preferably 61 or less, and further preferably 59 or less. If the material hardness and surface hardness of these intermediate layers are too softer than the above range, the spin amount at the time of a full shot increases too much and the flight distance may not be obtained, or the cracking durability due to repeated impacts may deteriorate. If the above-mentioned material hardness and surface hardness are too hard, the cracking durability due to repeated impacts will deteriorate, or the spin rate at full shot will increase, and the flight distance will not be obtained, especially at low head speeds, and the feel of hitting will deteriorate. There is.

The thickness of the intermediate layer is preferably 0.7 mm or more, more preferably 0.9 mm or more, still more preferably 1.1 mm or more. On the other hand, the upper limit of the thickness of the surrounding layer is preferably 1.5 mm or less, more preferably 1.3 mm or less, still more preferably 1.2 mm or less. If this intermediate layer is too thin, the cracking durability due to repeated impacts may deteriorate, or the feel of impact may deteriorate. Further, if the intermediate layer is too thick, the spin amount of the ball at the time of a full shot may increase and the flight distance may not be obtained.

A known resin can be used as the material for forming the intermediate layer, and the material is not particularly limited, but examples of preferable materials include the following components (A) to (D).
(A-1) A metal ion neutralized product of an olefin-unsaturated carboxylic acid binary random copolymer and / or an olefin-unsaturated carboxylic acid binary random copolymer.
(A-2) Metal ion neutralized product of olefin-unsaturated carboxylic acid-unsaturated carboxylic acid ester ternary random copolymer and / or olefin-unsaturated carboxylic acid-unsaturated carboxylic acid ester ternary random copolymer And (A) base resin blended so as to have a mass ratio of 100: 0 to 0: 100, and
(B) With respect to 100 parts by mass of the resin component blended with the non-ionomer thermoplastic elastomer so as to have a mass ratio of 100: 0 to 50:50.
(C) Fatty acid having a molecular weight of 228 to 1500 and / or a derivative thereof with 5 to 80 parts by mass.
(D) A resin composition comprising 0.1 to 17 parts by mass of a basic inorganic metal compound capable of neutralizing an unneutralized acid group in the component (A) and the component (C) as an essential component. It can be exemplified.

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

A non-ionomer thermoplastic elastomer can be added to the intermediate layer material. The amount of the non-ionomer thermoplastic elastomer to be blended is preferably 0 to 50 parts by mass with respect to 100 parts by mass of the total amount of the base resin.

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

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

The amount of deflection (mm) from the initial load of 98 N (10 kgf) to the final load of 1,275 N (130 kgf) with respect to the sphere (intermediate layer-coated sphere) in which the surrounding layer-coated sphere is coated with the intermediate layer is particularly large. Although there is no limitation, it is preferably 2.7 mm or more, more preferably 3.2 mm or more, still more preferably 3.7 mm or more, and the upper limit value is preferably 6.7 mm or less, more preferably 5.7 mm or less, and further. It is preferably 4.7 mm or less. If the amount of deflection of the sphere is too small, that is, if the sphere is too hard, the spin of the ball may increase too much and the ball may not fly or the feel of hitting may become too hard. On the other hand, if the amount of deflection of the sphere is too large, that is, if the sphere is too soft, the repulsiveness of the ball becomes too low to fly, the hit feeling becomes too soft, or the cracking durability at the time of repeated hits is poor. May become.

Next, the cover will be described.
The material hardness of the cover is not particularly limited, but the shore D hardness is preferably 55 or more, more preferably 59 or more, still more preferably 61 or more, and the upper limit is preferably 70 or less, more preferably 68 or less. , More preferably 65 or less. The surface hardness of the sphere (ball-coated sphere) in which the intermediate layer-coated sphere is covered with a cover is the shore D hardness, preferably 61 or more, more preferably 65 or more, still more preferably 67 or more, and the upper limit is set. It is preferably 76 or less, more preferably 74 or less, and even more preferably 71 or less. If the material hardness and the ball surface hardness of these covers are too softer than the above ranges, the spin increases when the driver (W # 1) hits, the initial velocity of the ball decreases, and the flight distance may not be obtained. If the above-mentioned material hardness and surface hardness are too hard, the cracking durability during repeated impact durability may deteriorate.

The thickness of the cover is preferably 0.6 mm or more, more preferably 0.8 mm or more, still more preferably 1.0 mm or more. On the other hand, the upper limit of the thickness of the cover is preferably 1.2 mm or less, more preferably 1.15 mm or less, and further preferably 1.1 mm or less. If this cover is too thin, it may have poor cracking durability due to repeated impacts. Further, if the cover is too thick, the spin when hitting the driver (W # 1) becomes too large and the flight distance may not be obtained, or the feel of the short game and the putter may become too hard.

As the cover material, it is preferable to use various thermoplastic resins used in the cover material of golf balls, particularly ionomer resin, and commercially available products can be used as the ionomer resin. Further, as the resin material of the cover, a high acid content ionomer resin having an acid content of 18% by mass or more among commercially available ionomer resins can be blended with a normal ionomer resin, and this blend has high resilience and low spin. It is possible to obtain a good flight distance when hitting the driver (W # 1) due to the change. Such a high acid content ionomer resin is preferably 10% by mass or more, more preferably 30% by mass or more, still more preferably 60% by mass or more, and usually 100% by mass as an upper limit value with respect to 100% by mass of the resin material. Hereinafter, it is preferably 90% by mass or less, more preferably 80% by mass or less. If the amount of the above-mentioned high acid content ionomer resin is too small, the spin may increase when the driver (W # 1) is hit, and the flight distance may not be obtained. On the other hand, if the amount of the above-mentioned high acid content ionomer resin is too large, the cracking durability during repeated impact durability may deteriorate.

The amount of deflection (mm) from the initial load of 98 N (10 kgf) to the final load of 1,275 N (130 kgf) with respect to the sphere (ball-coated sphere) in which the intermediate layer-coated sphere is covered with a cover is not particularly limited. However, it is preferably 2.4 mm or more, more preferably 2.9 mm or more, still more preferably 3.4 mm or more, and the upper limit value is preferably 5.0 mm or less, more preferably 4.5 mm or less, still more preferably. It is 4.0 mm or less. If the amount of deflection of the sphere is too small, that is, if the sphere is too hard, the spin of the ball may increase too much and the ball may not fly or the feel of hitting may become too hard. On the other hand, if the amount of deflection of the sphere is too large, that is, if the sphere is too soft, the repulsion of the ball becomes too low to fly, the feel of hitting becomes too soft, or the cracking durability at the time of repeated hits is poor. May become.

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

[ Hardness of each layer ]
In the present invention, it is necessary to satisfy the following mathematical formulas for the hardness relationship of each layer.
Surface hardness of ball> Surface hardness of intermediate layer coated sphere> Surface hardness of surrounding layer coated sphere <Surface hardness of core If the above hardness relationship is not satisfied, good flight and softness are achieved at both medium and low head speeds. It may not be possible to obtain a feel that has both a feel and a feel of flight.

As shown in the above formula, the surface hardness of the ball is larger than the surface hardness of the intermediate layer-coated sphere. The difference between the ball surface hardness and the intermediate layer surface hardness is the shore D hardness, preferably 4 to 20, more preferably 6 to 17, and even more preferably 8 to 13. If this difference is small, the low spin effect on a full shot may be insufficient and the flight distance may not be obtained. On the other hand, if this difference is too large, the cracking durability due to repeated impacts may deteriorate.

As described above, the surface hardness of the intermediate layer-coated sphere is larger than that of the surrounding layer-coated sphere. The difference between the surface hardness of the intermediate layer-coated sphere and the surrounding layer-coated sphere is the shore D hardness, preferably 4 to 40, more preferably 6 to 30, still more preferably 10 to 23. If this difference is small, it may not be possible to obtain a feel that has both a soft feel and a jump feel. On the other hand, if this difference is too large, the cracking durability due to repeated impacts may deteriorate.

As shown in the above formula, the surrounding layer-covered sphere is smaller than the core surface hardness. This difference in hardness is the shore D hardness, preferably -30 to -1, more preferably -25 to -3, and even more preferably -20 to -5. If this difference is too small, it may not be possible to obtain a feel that has both a soft feel and a jump feel. If this difference is too large, the spin may increase too much during a full shot and the flight distance may not be obtained.

Further, assuming that the amount of deflection (mm) from the initial load of 98 N (10 kgf) to the final load of 1,275 N (130 kgf) of each sphere of the core and the ball is P and Q, respectively, the value of PQ is It is preferably 0.2 to 1.3 mm, more preferably 0.4 to 1.1 mm, and even more preferably 0.6 to 0.9 mm. If this value is too large, the initial velocity of the actual hit will be low, and the flight distance may not be obtained. On the other hand, if the above value is too small, the low spin effect at the time of hitting the driver (W # 1) may be insufficient and the flight distance may not be obtained.

[ Thickness of each layer ]
In the present invention, there is no particular limitation, but it is desirable that the intermediate layer is formed thicker than the surrounding layer and the cover. In this case, the value obtained by subtracting the surrounding layer thickness from the intermediate layer thickness is preferably 0.05 to 0.5 mm, more preferably 0.1 to 0.4 mm, and further preferably 0.2 to 0. It is 3 mm. The value obtained by subtracting the cover thickness from the thickness of the intermediate layer is preferably 0.01 to 0.3 mm, more preferably 0.05 to 0.2 mm, and further preferably 0.1 to 0.15 mm. be. With a golf ball having a thickness of each layer that deviates from the above set range, the low spin effect at the time of hitting by the driver (W # 1) may be insufficient and the flight distance may not be obtained.

[ Mass relation of each layer ]
In the present invention, there is no particular limitation, but it is desired that the intermediate layer has a larger mass than the surrounding layer and the cover. That is, the value obtained by subtracting the mass of the surrounding layer from the mass of the intermediate layer is preferably 0.1 to 2.0 g, preferably 0.3 to 1.5 g, and more preferably 0.5 to 1.0 g. The value obtained by subtracting the cover mass from the intermediate layer mass is preferably 0.01 to 0.5 g, more preferably 0.02 to 0.2 g, and further preferably 0.03 to 0.04 g. With a golf ball having a mass of each layer that deviates from the above set range, the low spin effect at the time of hitting the driver (W # 1) may be insufficient and the flight distance may not be obtained.

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

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

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

Furthermore, by optimizing the cross-sectional shape of the dimples, it is possible to reduce the variation in flight and improve the aerodynamic performance. By keeping the rate of change in depth at a certain position in the dimple within a certain range, the effect of the dimple can be stabilized and the aerodynamic performance can be improved. At least one dimple having the cross-sectional shape shown below is arranged. Specific examples include having a peculiar dimple cross-sectional shape as shown in FIG. 3 (A). FIG. 3A is an enlarged cross-sectional view of a circular dimple in a plan view. In the figure, reference numeral D is a dimple, E and E are dimple edges, P is the deepest point of the dimple, a straight line L is a reference line passing through the dimple edge E and the dimple center O, and a broken line (dotted line) is a virtual spherical surface. The foot of the perpendicular line drawn from the deepest point P of the dimple D to the virtual plane formed at the periphery of the dimple D (hereinafter referred to as the foot drop) coincides with the center O of the dimple. The dimple edges E and E are boundaries between the dimple D and the region (land portion) where the dimple D is not formed on the ball surface, and correspond to the point where the virtual spherical surface is in contact with the ball surface (hereinafter, the same applies). .. Further, the dimple D shown in FIG. 3 is a circular dimple in a plan view, and the center O of the dimple and the deepest point P coincide with each other in the plan view.

The cross-sectional shape of the dimple D needs to satisfy the following conditions. The conditions will be described below.

First, as the condition (i), the foot (foot drop) of the perpendicular line drawn from the deepest point P of the dimple to the virtual plane created at the periphery of the dimple is set as the dimple center O, and the dimple center O and any one dimple. The straight line passing through the edge E is defined as the reference line L.

Next, as the condition of (ii), the line segment from the dimple edge E to the dimple center O in the reference line L is divided into 100 points or more. Then, when the distance from the dimple edge to the dimple center is 100%, the ratio of the distance of each point is calculated. The dimple edge E is a base point and is at a position of 0% on the reference line, and the dimple center O is at a position of 100% with respect to the line segment EO on the reference line.

Next, as the condition of (iii), the ratio of the dimple depth in 20% increments of 0 to 100% of the distance from the dimple edge E to the dimple center O is calculated. In this case, the dimple center O is the deepest part P of the dimple and has a depth H (mm). With this as 100% of the depth, the ratio of the dimple depth at each distance is calculated. The ratio of the dimple depth in the dimple edge E is 0%.

Then, as the condition of (iv), the amount of change ΔH of the depth in every 20% of the distance is obtained at the ratio of the depth in the dimple region of 20 to 100% of the distance from the dimple edge to the center of the dimple. The cross-sectional shape of the dimple is designed so that the amount of change ΔH is 6% or more and 24% or less in all the regions of the distance 20 to 100%.

In the present invention, by quantifying the cross-sectional shape of the dimples in this way, that is, by setting the value of the change amount ΔH of the dimple depth to 6% or more and 24% or less, the jump is performed by optimizing the cross-sectional shape of the dimples. The variation is reduced and the aerodynamic performance is improved. The above-mentioned change amount ΔH is preferably 8 to 22%, more preferably 10 to 20%.

Further, from the viewpoint of further enhancing the effect of the present invention, it is preferable that the change amount ΔH of the ratio of the dimple depth at a distance of 20% from the dimple edge is maximum in the dimple having the specific cross-sectional shape. Further, it is also preferably adopted that the curve showing the cross-sectional shape of the dimple having the specific cross-sectional shape includes two or more inflection points.

It is preferable to apply a clear coating on the cover surface from the viewpoint of ensuring the appearance. In the coating composition used for clear coating, it is preferable to use two kinds of polyester polyols as a main agent and polyisocyanate as a curing agent. In this case, various organic solvents can be mixed depending on the coating conditions. Examples of such an organic solvent include aromatic solvents such as toluene, xylene and ethylbenzene, ester solvents such as ethyl acetate, butyl acetate, propylene glycol methyl ether acetate and propylene glycol methyl ether propionate, acetone and methyl ethyl ketone. , Methylisobutylketone, ketone solvent such as cyclohexanone, ether solvent such as diethylene glycol dimethyl ether, diethylene glycol diethyl ether, dipropylene glycol dimethyl ether, alicyclic hydrocarbon solvent such as cyclohexane, methylcyclohexane, ethylcyclohexane, mineral spirit and the like. Petroleum hydrocarbon solvents etc. can be adopted.

The hardness of the coating layer by the clear coating is Shore-C hardness, preferably 40 to 80, more preferably 47 to 72, and further preferably 55 to 65. If this coating layer is too soft, mud may easily adhere to the surface of the ball when using golf. Further, if the coding layer is too hard, the coating layer may be easily peeled off when the ball is hit. The thickness of the coding layer is usually 9 to 22 μm, preferably 11 to 20 μm, and more preferably 13 to 18 μm.

The multi-piece solid golf ball of the present invention can be made to comply with the Rules of Golf for competition, and the outer diameter of the ball is 42.672 mm, the size does not pass through the inner diameter ring, and the mass is preferably 42.80 mm or less. It can be formed in the range of 45.0 to 45.93 g.

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

[Examples 1 to 4, Comparative Examples 1 to 7]
Core formation
After preparing the rubber compositions of each Example and Comparative Example shown in Table 1, a solid core was prepared by vulcanization molding under vulcanization conditions of 155 ° C. for 15 minutes.

The details of each component shown in Table 1 are as follows.
-Polybutadiene A: JSR, product name "BR01"
-Polybutadiene B: JSR, product name "BR51"
-Polybutadiene C: JSR, product name "BR730"
-Zinc acrylate: "ZN-DA85S" (manufactured by Nippon Shokubai)
-Organic peroxide (1): Dicumyl peroxide, trade name "Park Mill D" (manufactured by NOF CORPORATION)
-Organic peroxide (2): Mixture of 1,1-di (t-butylperoxy) cyclohexane and silica, trade name "Perhexa C-40" (manufactured by NOF CORPORATION)
・ Water: Pure water (manufactured by Shoki Yakuhin Kogyo Co., Ltd.)
-Anti-aging agent: 2,2-Methylenebis (4-methyl-6-butylphenol), trade name Nocrack NS-6 (manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.)
・ Barium sulfate: Barium arsenic Sulfate Varico # 100 (manufactured by Shiramizu Chemical Industry Co., Ltd.)
-Zinc oxide: Product name "Three types of zinc oxide" (manufactured by Sakai Chemical Industry Co., Ltd.)
・ Pentachlorothiophenol zinc salt: manufactured by Wako Pure Chemical Industries, Ltd.

Formation of Surrounding Layer and Intermediate Layer Next, for each example and each comparative example except Comparative Example 7, the surrounding layer was formed around the core by an injection molding method using the surrounding layer material having the formulation shown in Table 2. After that, an intermediate layer was formed by an injection molding method using the intermediate layer materials having the formulations shown in the same table, and a sphere covering the surrounding layer and the intermediate layer was obtained. In Comparative Example 7, an intermediate layer was formed around the core by an injection molding method using the intermediate layer materials having the formulations shown in Table 2, and a sphere coated with the intermediate layer was obtained.

Formation of Cover (Outermost Layer) Next, for all Examples and Comparative Examples, a cover (outermost layer) was covered by an injection molding method around the intermediate layer-coated spheres obtained above using the cover material having the composition shown in Table 2. The outermost layer) was formed. At this time, a large number of predetermined dimples common to all the examples and comparative examples were formed on the cover surface.

The product names of the main materials listed in the table are as follows.
"Hytrell": Toray DuPont polyester elastomer "Himilan, AM7318, AM7327": Mitsui-DuPont Polychemical Ionomer "Sarrin": US DuPont Ionomer "Nucrel": Mitsui-DuPont Polychemical Ionomer -(Meta) acrylic acid copolymer "Kyowamag MF-150": Magnesium oxide manufactured by Kyowa Chemical Industry Co., Ltd.

〔dimple〕
Two dimples, Type-A and Type-B, were used on the surface of the ball. Type-A used four types of dimples, the details of which are shown in Table 3. The cross-sectional shape is shown in FIG. 3 (A). Type-B used four types of dimples, the details of which are shown in Table 4. The cross-sectional shape is shown in FIG. 3 (B).

In the cross-sectional shape of FIG. 3, the depth of each dimple from the reference line L to the inner wall surface of each dimple is obtained at 100 points at equal intervals from the dimple edge E of the reference line L to the dimple center O, and Table 3 They are listed in Table 4 respectively.

Next, the amount of change ΔH in the ratio of the dimple depth at every 20% of the distance from the dimple edge E of the reference line L was obtained and shown in Tables 3 and 4, respectively.

Formation of coating layer (coating layer) Next, in the coating formulation shown in Table 5 below, the above coating was applied to the surface of the cover (outermost layer) on which a large number of dimples were formed with an air spray gun, and a coating film having a thickness of 15 μm was applied. A layered golf ball was produced.

As the polyol of the main agent, a polyester polyol synthesized by the following method was used.
140 parts by mass of trimethylol propane, 95 parts by mass of ethylene glycol, 157 parts by mass of adipic acid, 58 parts by mass of 1,4-cyclohexanedimethanol in a reactor equipped with a reflux condenser, a dropping funnel, a gas introduction tube and a thermometer. The temperature was raised to 200 to 240 ° C. with stirring, and the mixture was heated (reacted) for 5 hours. Then, a polyester polyol having an acid value of 4, a hydroxyl value of 170, and a weight average molecular weight (Mw) of 28,000 was obtained. Additives, that is, water-repellent additives, are commercially available products, which are silicone-based additives, stain-improving silicone additives, and fluorine-based polymers having an alkyl base chain length of 7 or less. Added.
As the isocyanate of the curing agent, Duranate TPA-100 (NCO content 23.1%, non-volatile content 100%) manufactured by Asahi Kasei Co., Ltd., which is a nurate form (isocyanurate form) of hexamethylene diisocyanate (HMDI), was used. ..
Butyl acetate was used as the solvent of the main agent, and ethyl acetate and butyl acetate were used as the solvent of the curing agent. The C hardness in the above table was measured by preparing a sheet having a thickness of 2 mm and measuring it with a Shore-C hardness tester compliant with the ASTM D2240 standard.

For each obtained golf ball, the internal hardness at each position of the core, the outer diameter of the core and each coated sphere, the thickness and material hardness of each layer, the surface hardness of each coated sphere, the predetermined load deformation amount (deflection amount), etc. Various physical properties are evaluated by the following methods and are shown in Table 6.

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

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

Deflection amount of each sphere of core, surrounding layer covering sphere, intermediate layer covering sphere and ball When each sphere is placed on a hard plate and the initial load of 98N (10kgf) is applied to the final load of 1275N (130kgf). The amount of deflection up to was measured. The above-mentioned deflection amounts are all measured values after the temperature is adjusted to 23.9 ° C.

Core hardness distribution The surface of the core is a spherical surface, but the needle of the hardness meter was set on the spherical surface so as to be substantially vertical, and the core surface hardness was measured by Shore-C hardness according to ASTM D2240. The cross-sectional hardness at the center of the core and at a predetermined position of each core was measured by cutting the core into a hemisphere, making the cross section flat, and pressing the needle of a hardness tester vertically against the measurement portion. It is indicated by the value of Shore-C hardness.
Further, the center hardness Cc of the core, the surface hardness of the core is Cs, the midpoint hardness CM between the center and the surface of the core, and the positions 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 of 2.5 mm, 5.0 mm and 7.5 mm from the midpoint M to the center of the core. For and _CM-7.5 , the following areas A to F and area A: 1/2 x 2.5 x ( _CM-5.0 -CM _-7.5 ),
-Area B: 1/2 x 2.5 x ( _CM-2.5- CM _-5.0 ),
_-Area C: 1/2 x 2.5 x (CM _-CM-2.5 ),
_-Area D: 1/2 x 2.5 x ( _{CM + 2.5} -CM),
-Area E: 1/2 x 2.5 x ( _{CM + 5} -C _{M + 2.5} ) and-Area F: 1/2 x 2.5 x ( _{CM + 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 areas A to F of the core hardness distribution, FIG. 2 shows a schematic view showing the areas A to F using the core hardness distribution data of Example 1.

Material hardness of surrounding layer, intermediate layer and cover (Shore D hardness)
The resin material of each layer was formed into a sheet having a thickness of 2 mm and left for 2 weeks or more. After that, the Shore D hardness was measured according to the ASTM D2240 standard.

Surface hardness (shore D hardness) of each sphere of the surrounding layer-coated sphere, the intermediate layer-coated sphere, and the ball
The measurement was performed by pressing the needle so that it was perpendicular to the surface of each sphere. The surface hardness of the ball (cover) is a measured value in the land area where dimples are not formed on the surface of the ball. Shore D hardness was measured by a Type D durometer according to the ASTM D2240 standard.

The flight performance (W # 1) and hit feeling of each golf ball were evaluated by the following methods. The results are shown in Table 7.

Flying performance A driver (W # 1) was attached to a golf hitting robot, and the flying distance when hitting at a head speed of 35 m / s was measured and judged according to the following criteria. The club used a "PHYZ driver" (loft angle 10.5 °) manufactured by Bridgestone Sports. Similarly, the spin amount was measured by the initial condition measuring device for the ball immediately after being hit.
<criterion>
Total flight distance 177.0m or more ・ ・ ・ ○
Total flight distance less than 177.0m ・ ・ ・ ×

A sensory evaluation was performed by an amateur user with a head speed of 30 to 40 m / s by a hitting feeling driver (W # 1) in actual hitting, and the judgment was made according to the following criteria.
<criterion>
8 or more out of 10 people have a good feel and evaluation ... ◎
6 to 7 out of 10 people who evaluated it as a good hit feeling ... △
5 out of 10 people who evaluated it as a good hit feeling ... ×

As shown in the results of Table 7, the golf balls of Comparative Examples 1 to 7 are inferior to the product of the present invention (Example) in the following points.
In Comparative Example 1, the hardness distribution of the core does not satisfy (area: D + E + F)-(area: A + B + C)> 0, and as a result, the spin amount of the ball increases and the flight distance does not come out.
In Comparative Example 2, the hardness distribution of the core does not satisfy (area: D + E + F)-(area: A + B + C)> 0, and as a result, the spin amount of the ball increases and the flight distance does not come out.
In Comparative Example 3, the cover is thicker than the intermediate layer, and as a result, the spin amount of the ball is increased and the flight distance is not obtained.
In Comparative Example 4, the ball has a thicker surrounding layer than the intermediate layer, and as a result, the spin amount of the ball increases and the flight distance does not increase.
Comparative Example 5 is a ball whose surface hardness is softer than the surface hardness of the intermediate layer-coated sphere, and as a result, the spin amount of the ball is increased, the actual hitting initial velocity is low, and the flight distance is not obtained.
In Comparative Example 6, the surface hardness of the surrounding layer-coated sphere is harder than the surface hardness of the intermediate layer-coated sphere, and as a result, the spin amount of the ball increases and the flight distance does not increase.
Comparative Example 7 is a three-piece ball without a soft surrounding layer, and as a result, the feel of hitting is not good.

Claims (7)

A multi-piece solid golf ball including a core, a surrounding layer, an intermediate layer and a cover, wherein the core is formed of a base material rubber as a main material, and the intermediate layer is formed thicker than the surrounding layer and the cover. The surface hardness of the core, the surface hardness of the sphere whose core is coated with the surrounding layer (the sphere coated with the surrounding layer), the surface hardness of the sphere whose sphere coated with the surrounding layer is coated with the intermediate layer (the sphere coated with the intermediate layer), and the ball. The surface hardness of
The surface hardness of the ball> the surface hardness of the intermediate layer-coated sphere> the surface hardness of the surrounding layer-coated sphere <the surface hardness of the core is satisfied, and 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 surface of the core is Cs, the Shore-C hardness at the midpoint _M between the center and the surface of the core is CM, and the middle point M is 2 toward the core surface side. The Shore-C hardnesses at the positions of 5.5 mm, 5.0 mm and 7.5 mm are CM _{+ 2.5} , CM _{+ 5.0} and CM _{+ 7.5} , respectively, and 2.5 mm from the midpoint M to the core center side. When the Shore-C hardness at the 0 mm and 7.5 mm positions is CM _-2.5 , _CM-5.0 and _CM-7.5 , respectively, the following areas A to F
-Area A: 1/2 x 2.5 x ( _CM-5.0 -CM _-7.5 ),
-Area B: 1/2 x 2.5 x ( _CM-2.5- CM _-5.0 ),
_-Area C: 1/2 x 2.5 x (CM _-CM-2.5 ),
_-Area D: 1/2 x 2.5 x ( _{CM + 2.5} -CM),
-Area E: 1/2 x 2.5 x ( _{CM + 5} -C _{M + 2.5} ) and-Area F: 1/2 x 2.5 x ( _{CM + 7.5} -C _{M + 5} )
, (Area D + Area E + Area F)-(Area A + Area B + Area C)> 0. The multi-piece solid golf ball according to claim 1, wherein the areas A to F of the core hardness distribution satisfy (area D + area E)-(area A + area B + area C) ≧ 0. The multi-piece solid golf ball according to claim 1 or 2, wherein the hardness difference (Cs-Cc) between the center and the surface of the core is 20 or more in Shore-C hardness. Claims 1 to Satisfy 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. The multi-piece solid golf ball according to any one of 3. The multi-piece solid golf ball according to any one of claims 1 to 4, wherein the thickness of the cover is 1.2 mm or less. A large number of dimples are formed on the surface of the cover, and the dimples (specific cross-sectional shape) which are presented by a curved line or a combination of a straight line and a curved line and have a cross-sectional shape specified by the following procedures (i) to (iv). The multi-piece solid golf ball according to any one of claims 1 to 5, wherein at least one dimple) is arranged and the total number of dimples is 250 to 380.
(I) The foot (foot drop) of a perpendicular line drawn from the deepest point of the dimple to the virtual plane created at the periphery of the dimple is the dimple center, and the straight line passing through the dimple center and any one dimple edge is the reference line. do.
(Ii) Of the reference lines, the line segment from the dimple edge to the dimple center is divided into 100 points or more, and the distance between the points is 100% when the distance from the dimple edge to the dimple center is 100%. Calculate the ratio of.
(Iii) The ratio of the dimple depth in every 20% of 0 to 100% of the distance from the dimple edge to the dimple center is calculated.
(Iv) At the ratio of the depth in the dimple region of 20 to 100% of the distance from the dimple edge to the dimple center, the change amount ΔH of the depth every 20% of the distance is obtained, and this change amount ΔH is the above. The cross-sectional shape of the dimples is designed to be 6% or more and 24% or less in all the regions corresponding to the distance of 20 to 100%. The multi-piece solid golf ball according to any one of claims 1 to 6, wherein a coating film layer is formed on the cover surface, and the hardness of the coating film layer is 40 to 80 in Shore-C hardness.

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