JP6375707B2 - Multi-piece solid golf ball - Google Patents

Description

  The present invention relates to a multi-piece solid golf ball formed by laminating a core, an envelope layer, an intermediate layer, and a cover layer. More specifically, the present invention has a flying performance that can satisfy a professional golfer and an advanced amateur golfer. The present invention relates to a golf ball having both controllability and further pursuing low spin at the time of a full shot.

  Conventionally, in order to increase the flight distance and to improve the hit feeling, the golf ball has been devised to have a multilayer structure, and after that, low spin, high initial speed, and hit feeling are further improved. For the purpose of improvement and the like, various golf balls having a multilayer structure having three or more layers have been proposed.

  And now, among professional golfers and advanced amateur golfers, as a ball that combines excellent flight performance and controllability, a soft cover and an intermediate layer formed of an ionomer material that is relatively harder than the cover In addition, golf balls having a single-layer or two-layer solid core formed of a rubber material are widely used. Such a ball provides high control in a short game with a soft cover, combined with a layer of hard and highly repulsive ionomer material on the inside of the cover, which causes excessive spin during a full shot with a driver And has a high resilience.

  Various golf balls as described above have been proposed so far, for example, US Pat. No. 6,071,201 (Patent Document 1), US Pat. No. 6,254,495 (Patent Document 2), US US Pat. No. 6,271,296 (Patent Document 3), US Pat. No. 6,394,912 (Patent Document 4), US Pat. No. 6,431,1998 (Patent Document 5), US Pat. No. 6,605,009 (Patent Document 6) US Pat. No. 6,688,991 (Patent Document 7), US Pat. No. 6,756,436 (Patent Document 8), US Pat. No. 6,824,477 (Patent Document 9), US Pat. No. 6,894,098 (Patent Document). 10), US Pat. No. 6,939,907 (Patent Document 11), US Pat. No. 6,962,539 (Patent Document 12), US Pat. No. 69888962 (Patent Document 13), US Pat. No. 7,041,009 (Patent Document 14), US Pat. No. 7,125,348 (Patent Document 15), US Pat. No. 7,157,512 (Patent Document 16), US Patent No. 7230045 (Patent Document 17), US Pat. No. 7,285,059 (Patent Document 18), US Pat. No. 7,641,571 (Patent Document 19), US Pat. No. 7,652,866 (Patent Document 20) JP 2012-40376 (Patent Document 21), JP 2012-45382 A (Patent Document 22), US Pat. No. 7,648,427 (Patent Document 23), and the like.

  As described above, there is a great demand for golf balls capable of exhibiting performance corresponding to their technical level among professional golfers and advanced amateur golfers. Therefore, it is important to develop a golf ball having both flying performance and controllability that more golfers can satisfy in order to broaden the golfer's base.

US Pat. No. 6,071,201 US Pat. No. 6,254,495 US Pat. No. 6,271,296 US Pat. No. 6,394,912 US Pat. No. 6,433,1998 US Pat. No. 6,605,009 US Pat. No. 6,688,991 US Pat. No. 6,756,436 US Pat. No. 6,824,477 US Pat. No. 6,894,098 US Pat. No. 6,939,907 US Pat. No. 6,962,539 US Pat. No. 6,998,962 U.S. Pat. No. 7,041,009 US Pat. No. 7,125,348 US Pat. No. 7,157,512 US Pat. No. 7230045 Specification US Pat. No. 7,285,059 U.S. Pat. No. 7,641,571 US Pat. No. 7,652,086 JP 2012-40376 A JP2012-45382A US Pat. No. 7,648,427

  The present invention has been made in view of the above circumstances. As a golf ball for a professional golfer or an advanced amateur golfer, an increase in a flight distance at the time of a full shot with a driver (W # 1) and a controllability in a short game. An object of the present invention is to provide a multi-piece solid golf ball capable of improving the speed and further reducing the spin rate at the time of a full shot.

  As a result of intensive studies to achieve the above object, the inventors of the present invention used a soft thermoplastic elastomer for the solid core in a golf ball having a solid core, an envelope layer, an intermediate layer and a cover from the inside. By forming it, the spin at the time of full shot is suppressed and a good flight distance is obtained, and the envelope layer has a high resilience and is formed of a rubber material harder than the solid core, High actual hitting initial velocity at full shot and excessive spin can be suppressed, and by forming the intermediate layer using an ionomer resin harder than the envelope layer, spin at full shot can be suppressed, Furthermore, by using a soft urethane cover for the outermost layer cover, high approach spin performance and excellent scratch resistance in short games are achieved. And finding that it is possible to, the present invention has been accomplished.

Accordingly, the present invention provides the following multi-piece solid golf ball.
1. In a multi-piece solid golf ball comprising a core, an envelope layer that covers the core, an intermediate layer that covers the envelope layer, and a cover that covers the intermediate layer and has a plurality of dimples formed on the surface thereof,
The core is formed mainly of one or more thermoplastic elastomers selected from the group consisting of polyester, polyamide, polyurethane, olefin, and styrene, and the diameter is 10 to 30 mm and the specific gravity is 1.0 to less than 1.3 and the amount of deflection when loaded from an initial load of 98 N (10 kgf) to a final load of 1275 N (130 kgf) is 3.6 to 10 mm.
The envelope layer is formed of a rubber composition mainly composed of a rubber material, and the thickness thereof is 3 to 10 mm.
The intermediate layer is formed of a resin composition mainly composed of ionomer,
The cover is formed of a resin composition mainly composed of urethane, and the specific gravity difference between the core and the envelope layer (envelopment layer specific gravity-core specific gravity) is 0 to 0.2. The specific gravity of the layer and cover is
Enveloping layer specific gravity> Intermediate layer specific gravity <Cover specific gravity is satisfied, and surface hardness (Shore D hardness) of the core, envelope layer, intermediate layer and cover
Core surface hardness <enclosure layer surface hardness <intermediate layer surface hardness> A multi-piece solid golf ball that satisfies the relationship of cover surface hardness.
2. The multi-piece solid golf ball of the 1, wherein said core is formed of a polyether ester elastomer composed primarily.
3. The multi-piece solid golf ball of the 1 or 2, wherein the diameter of the core is 20 to 30 mm.
4). The multi-piece solid golf ball of the 3 wherein the diameter of the core is 22～28Mm.
5. The multi-piece solid golf ball according to any one of the above 1 to 4 the thickness of the envelope layer is 4 to 8 mm.
6). The surface hardness of the core, envelope layer, intermediate layer and cover (Shore D hardness)
1 ≦ enveloping layer surface hardness−core surface hardness ≦ 40
5 ≦ intermediate layer surface hardness−enveloping layer surface hardness ≦ 25
−25 ≦ Ball surface hardness−Intermediate layer surface hardness ≦ −1
The multi-piece solid golf ball according to any one of the above 1 to 5 satisfying the relationship.
7). The multi-piece solid golf ball according to any one of the above 1 to 6 specific gravity of the intermediate layer is less than 1.0.
8). The multi-piece solid golf ball according to any one of 1 to 7, wherein the envelope layer has a specific gravity of 1.1 to 1.5.
9. In a multi-piece solid golf ball comprising a core, an envelope layer that covers the core, an intermediate layer that covers the envelope layer, and a cover that covers the intermediate layer and has a plurality of dimples formed on the surface thereof,
The core is formed mainly of one or more thermoplastic elastomers selected from the group consisting of polyester, polyamide, polyurethane, olefin, and styrene, and the diameter is 10 to 30 mm and the specific gravity is 1.0 to less than 1.3 and the amount of deflection when loaded from an initial load of 98 N (10 kgf) to a final load of 1275 N (130 kgf) is 3.6 to 10 mm.
The envelope layer is formed of a rubber composition mainly composed of a rubber material, and the thickness thereof is 3 to 10 mm.
The intermediate layer is formed of a resin composition mainly composed of ionomer,
While the cover is formed of a resin composition mainly composed of urethane,
The specific gravity of the envelope layer, intermediate layer and cover is
Enclosure layer specific gravity> Intermediate layer specific gravity <Cover specific gravity
The surface hardness of the core, envelope layer, intermediate layer and cover (Shore D hardness)
Core surface hardness <enclosure layer surface hardness <intermediate layer surface hardness> cover surface hardness
Satisfying the relationship, and
20 ≦ enveloping layer surface hardness−core surface hardness ≦ 40
−25 ≦ cover surface hardness−intermediate layer surface hardness ≦ −10
A multi-piece solid golf ball that satisfies this relationship .
10. 10. The multi-piece solid golf ball according to 9, wherein the core is formed of a polyether ester elastomer as a main material .
11. The multi-piece solid golf ball according to 9 or 10, wherein the core has a diameter of 20 to 30 mm .
12 The multi-piece solid golf ball according to any one of 9 to 11, wherein the envelope layer has a thickness of 4 to 8 mm .
13. The multi-piece solid golf ball according to claim 9, wherein a specific gravity difference between the core and the envelope layer (envelope layer specific gravity−core specific gravity) is 0 to 0.2.

  According to the present invention, it is possible to increase the flight distance at the time of a full shot by the driver (W # 1) and to improve the controllability in a short game, and to further reduce the spin at the time of a full shot. A multi-piece solid golf ball can be provided.

1 is a schematic cross-sectional view of a multi-piece solid golf ball of the present invention. It is a top view showing the arrangement | sequence of the dimple formed in the ball | bowl surface of an Example.

  Hereinafter, the present invention will be described in more detail. First, FIG. 1 shows a cross-sectional structure of a multi-piece solid golf ball of the present invention. The golf ball G shown here has a four-layer structure including a core 1, an envelope layer 2 that covers the core, an intermediate layer 3 that covers the envelope layer, and a cover 4 that covers the intermediate layer. Have. A large number of dimples D are usually formed on the surface of the cover 4. Hereinafter, each of these layers will be described in detail.

First, a solid core (hereinafter sometimes simply referred to as a core) will be described.
The diameter of the core needs to be set to 10 to 30 mm. In this case, the more preferable lower limit of the diameter can be 20 mm or more, and more preferably 22 mm or more. On the other hand, the more preferable upper limit of the diameter is 28 mm or less, and more preferably 26 mm or less. If the diameter of the core is too small, the spin rate may become too large during a full shot, and the flight distance may not be achieved. On the other hand, if the diameter is too large, durability during repeated hitting may deteriorate, the hit feeling may become too hard, or the rebound of the ball as a whole may be insufficient, resulting in a loss of flight distance.

  The center hardness of the core is not particularly limited, but is preferably 10 or more, more preferably 20 or more, and further preferably 25 or more in Shore D hardness. Also, the upper limit is not particularly limited, but the Shore D hardness can be 55 or less, preferably 47 or less, more preferably 40 or less. If the center hardness is too low, the feel at impact may become too soft, and the cracking durability during repeated impacts may deteriorate. On the other hand, if the center hardness is too high, the spin amount may increase and the flight distance may not be extended, or the feel at impact may become too hard.

  The surface hardness of the core is not particularly limited, but the Shore D hardness is preferably 16 or more, more preferably 26 or more, and still more preferably 31 or more. The upper limit is not particularly limited, but it is preferably 61 or less, more preferably 53 or less, and still more preferably 46 or less in Shore D hardness. If the surface hardness is too low, the feeling of hitting may become too soft, and the cracking durability during repeated hitting may deteriorate. On the other hand, if the surface hardness is too high, the feeling of hitting may become too hard, and the cracking durability during repeated hitting may deteriorate.

  Here, the above-mentioned center hardness means the hardness measured at the center of a cross section obtained by cutting the core in half (through the center), and the surface hardness is measured on the surface (spherical surface) of the core. Means hardness. Moreover, Shore D hardness means the hardness measured by the type D durometer based on ASTM D2240-95 standard.

  The deflection amount when the core is loaded from the initial load 98N (10 kgf) to the final load 1275N (130 kgf) needs to be 3.6 to 10 mm. In this case, a preferable lower limit can be 4.0 mm or more, more preferably 5.0 mm or more. Moreover, a preferable upper limit can be 8.0 mm or less, More preferably, it can be 7.0 mm or less. If the amount of deflection is too large (too soft), the feel at impact may be too soft, or the durability to cracking at repeated impacts may deteriorate. On the other hand, if the above-described deflection amount is too small (too hard), the spin amount may increase so that it may not fly or the feel at impact may become too hard.

  The solid core is formed using a thermoplastic elastomer. In the present invention, one or more thermoplastic elastomers selected from the group consisting of polyester-based, polyamide-based, polyurethane-based, olefin-based, and styrene-based resins are particularly high in resilience and obtain excellent flight performance. Is used as the main material. Commercially available products can be used as the above-mentioned thermoplastic elastomers. Specifically, “Hytrel” (manufactured by Toray DuPont) as a polyester-based thermoplastic elastomer and “Pebax” (manufactured by Toray Industries, Ltd.) as a polyamide-based thermoplastic elastomer. ), "Pandex" (manufactured by Dainippon Ink & Chemicals, Inc.) as a polyurethane-based thermoplastic elastomer, "Santoprene" (manufactured by Monsanto) as an olefin-based thermoplastic elastomer, and "Tuftec" (Asahi Kasei Kogyo) as a styrene-based thermoplastic elastomer For example).

  In the present invention, a polyester-based thermoplastic elastomer is preferable from the viewpoints of moldability and resilience, and among these, a polyether ester elastomer can be particularly preferably used. Examples of commercially available products of the polyether ester elastomer include “Hytrel 3046”, “Hytrel 4047”, and “Hytrel 4767” manufactured by Toray DuPont.

  In addition, a filler can be added to the core from the viewpoint of adjusting specific gravity and increasing durability. Furthermore, various additives can be blended in the core forming material as necessary, for example, pigments, dispersants, antioxidants, light-resistant stabilizers, ultraviolet absorbers, release agents and the like. It can mix | blend suitably.

  The specific gravity of the core needs to be more than 1.0 and less than 1.3. In this case, a preferable lower limit can be 1.03 or more, and more preferably 1.05 or more. On the other hand, a preferable upper limit can be set to 1.25 or less, more preferably 1.20 or less. If the above specific gravity is too large, the resilience of the core will be low, and the flight distance may not be achieved. On the other hand, if the specific gravity is too small, the resilience may be lowered, and the durability during repeated hitting may be deteriorated.

  A method for obtaining the solid core is not particularly limited, but a known method such as an injection molding method can be used, and a method for injecting a core forming material into a cavity of a core molding die. It can be suitably employed.

Next, the envelope layer will be described.
The envelope layer is a layer covering the periphery of the core, and in the present invention, it is necessary to set the thickness to 3 to 10 mm. In this case, the more preferable lower limit of the thickness of the envelope layer is not particularly limited, but can be 4 mm or more, and more preferably 5 mm or more. On the other hand, the more preferable upper limit of the thickness is not particularly limited, but can be 9 mm or less, and more preferably 8.5 mm or less. If the envelope layer is too thin, the low spin effect at the time of a full shot may not be sufficient, and the flight distance may not be obtained, or the crack durability at the time of repeated hitting may be deteriorated. On the other hand, if the envelope layer is too thick, the low spin effect at the time of a full shot may not be sufficient and the flight distance may not be obtained, or the hit feeling at the time of a full shot may become too hard.

  The surface hardness of the envelope layer is not particularly limited, but is preferably 40 or more, more preferably 47 or more, and further preferably 55 or more in Shore D hardness. Further, the upper limit is not particularly limited, but the Shore D hardness is preferably 80 or less, more preferably 70 or less, and still more preferably 65 or less. If the surface hardness is too low, the resilience may be low, or the low spin effect at the time of a full shot may be insufficient, and the flight distance may not be obtained. On the other hand, if the surface hardness is too high, the feeling of hitting may become too hard, and the cracking durability during repeated hitting may deteriorate.

  Here, the surface hardness means a hardness measured on the surface of a sphere obtained by molding a material. Moreover, Shore D hardness means the hardness measured by the type D durometer based on ASTM D2240-95 standard. The same applies to the following description.

  The envelope layer is formed using a rubber composition. In the present invention, although not particularly limited, it is preferably formed using a rubber composition having polybutadiene as a base rubber described later from the viewpoint of high resilience and excellent flying performance.

  The polybutadiene is not particularly limited, but in the polymer chain, cis-1,4-bond is 60% by mass or more, preferably 80% by mass or more, more preferably 90% by mass or more, and most preferably It is recommended to have 95% by mass or more. If there are too few cis-1,4-bonds in the bonds in the molecule, the resilience may decrease.

  The content of 1,2-vinyl bond contained in the polybutadiene is not particularly limited, but is preferably 2% by mass or less, more preferably 1.7% by mass or less, in the polymer chain. It is recommended that the amount be 1.5% by mass or less. If the content of 1,2-vinyl bond is too large, the resilience may be lowered.

  The polybutadiene is preferably synthesized using a rare earth element-based catalyst or a Group VIII metal compound catalyst from the viewpoint of obtaining a vulcanized molded article having good resilience, and particularly using a rare earth element-based catalyst. It is preferably synthesized. Moreover, it is also optional to use these catalysts in combination with organoaluminum compounds, alumoxanes, halogen-containing compounds, Lewis bases, and the like as necessary. In the present invention, as the various compounds exemplified above, those described in JP-A No. 11-35633 can be preferably used.

  In the present invention, from the viewpoint of obtaining a polybutadiene rubber having a high content of cis-1,4-bonds and a low content of 1,2-vinyl bonds with excellent polymerization activity, among the rare earth element-based catalysts, in particular, lanthanum series rare earth elements. The use of a neodymium-based catalyst using a neodymium compound that is a compound is recommended. Specific examples of these rare earth element-based catalysts include those described in JP-A-11-35633, JP-A-11-164912, and JP-A-2002-293996.

  Examples of the lanthanum series rare earth element compounds include metal halides having an atomic number of 57 to 71, carboxylates, alcoholates, thioalcolates, and amides.

  The polybutadiene is not particularly limited, but is preferably contained in the base rubber in an amount of 10% by mass or more, more preferably 20% by mass or more, and still more preferably 40% by mass from the viewpoint of improving resilience. It is recommended to contain more.

  In the present invention, rubbers other than the polybutadiene can be blended within a range not impairing the effects of the present invention. Specific examples include polybutadiene rubber other than the above polybutadiene, styrene butadiene rubber, natural rubber, isoprene rubber, ethylene propylene diene rubber, and the like. These can be used individually by 1 type or in combination of 2 or more types.

  In the present invention, additives such as a later-described co-crosslinking agent, organic peroxide, anti-aging agent, inert filler and organic sulfur compound can be appropriately blended with the base rubber.

  Examples of the co-crosslinking agent include unsaturated carboxylic acids and metal salts of unsaturated carboxylic acids.

  Although it does not specifically limit as unsaturated carboxylic acid, For example, acrylic acid, methacrylic acid, maleic acid, fumaric acid, etc. can be mentioned, Especially acrylic acid and methacrylic acid can be used conveniently.

  Further, the metal salt of unsaturated carboxylic acid is not particularly limited, and examples thereof include those obtained by neutralizing the above unsaturated carboxylic acid with a desired metal ion. Specific examples include zinc salts such as methacrylic acid and acrylic acid, magnesium salts, and the like. In particular, zinc acrylate can be suitably used.

  The blending amount of the co-crosslinking agent is not particularly limited, but is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and still more preferably 15 parts with respect to 100 parts by mass of the base rubber. It can be more than mass parts. The upper limit of the amount is not particularly limited, but is preferably 60 parts by mass or less, more preferably 50 parts by mass or less, still more preferably 45 parts by mass or less, and most preferably 40 parts by mass with respect to 100 parts by mass of the base rubber. Part or less. If the blending amount is too large, it may become too hard and unbearable feel may occur, 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”, “Perhexa C-40”, “Perhexa 3M” (manufactured by NOF Corporation), “Luperco 231XL” (manufactured by Atchem), etc. It can be used suitably. These may be used alone or in combination of two or more.

  The amount of the organic peroxide is not particularly limited, but is preferably 0.1 parts by mass or more, more preferably 0.3 parts by mass or more, and still more preferably with respect to 100 parts by mass of the base rubber. Can be 0.5 parts by mass or more, and most preferably 0.7 parts by mass or more. The upper limit of the amount is not particularly limited, but 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 parts by mass with respect to 100 parts by mass of the base rubber. Part or less. If the blending amount is too large or too small, it may not be possible to obtain suitable feel, durability and resilience.

  Commercially available products can be used as the anti-aging agent. For example, “NOCRACK NS-6”, “NOCRACK NS-30” (manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.), “Yoshinox 425” (manufactured by Yoshitomi Pharmaceutical Co., Ltd.), etc. Can be mentioned. These may be used individually by 1 type and may use 2 or more types together.

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

  As the inert filler, for example, zinc oxide, barium sulfate, calcium carbonate and the like can be suitably used. These may be used individually by 1 type and may use 2 or more types together.

  Although the compounding quantity of the said inert filler is not restrict | limited in particular, Preferably it is 1 mass part or more with respect to 100 mass parts of said base rubber, More preferably, it can be 5 mass parts or more. The upper limit of the amount is not particularly limited, but is preferably 50 parts by mass or less, more preferably 40 parts by mass or less, still more preferably 30 parts by mass or less, and most preferably 25 parts by mass with respect to 100 parts by mass of the base rubber. Part or less. If the amount is too large or too small, the weight may not be appropriate or a suitable resilience may not be obtained.

  Furthermore, in order to improve the resilience of the golf ball, it is preferable to add an organic sulfur compound to the rubber composition. The organic sulfur compound is not particularly limited as long as it can improve the resilience of the golf ball. For example, thiophenols, thionaphthols, halogenated thiophenols, or metal salts thereof are preferably used. be able to. More specifically, pentachlorothiophenol, pentafluorothiophenol, pentabromothiophenol, parachlorothiophenol, zinc salt of pentachlorothiophenol, zinc salt of pentafluorothiophenol, zinc salt of pentabromothiophenol, Examples thereof include zinc salts of parachlorothiophenol, diphenyl polysulfide having 2 to 4 sulfur atoms, dibenzyl polysulfide, dibenzoyl polysulfide, dibenzothiazoyl polysulfide, dithiobenzoyl polysulfide and the like. In the present invention, among these, zinc salt of pentachlorothiophenol and diphenyl disulfide can be preferably used.

  The compounding amount of the organic sulfur compound is not particularly limited, but is preferably 0.05 parts by mass or more, more preferably 0.1 parts by mass or more, and still more preferably with respect to 100 parts by mass of the base rubber. It can be 0.2 parts by mass or more. The upper limit of the blending amount is not particularly limited, but is preferably 5 parts by mass or less, more preferably 3 parts by mass or less, and further preferably 2.5 parts by mass or less with respect to 100 parts by mass of the base rubber. it can. If the blending amount is too small, it may not be possible to obtain a sufficient resilience improvement effect. If the amount is too large, the effect of improving the resilience (especially when hit with W # 1) will reach its peak, and no further effect can be expected. Furthermore, the core becomes too soft and the feel of hitting It may get worse.

  The specific gravity of the envelope layer is not particularly limited, but is preferably 1.5 or less, more preferably 1.35 or less, and still more preferably 1.25 or less. On the other hand, the lower limit of the specific gravity is not particularly limited, but can be preferably 1.0 or more, more preferably 1.1 or more, and still more preferably 1.2 or more. If the specific gravity of the envelope layer deviates from the above range, good resilience cannot be obtained, the target hardness cannot be obtained, the flight distance cannot be obtained, and the cracking durability during repeated hitting is poor. May be.

  As a method for forming the envelope layer, a known method can be adopted, and it is not particularly limited, but the following method can be suitably adopted. First, a material for forming an envelope layer is put in a predetermined mold, and primary vulcanization (semi-vulcanization) is performed to produce a pair of hemispherical half cups. Next, secondary vulcanization (total vulcanization) is performed in a state where the solid core produced in advance is wrapped in the half cup produced above. That is, a method in which the vulcanization process is divided into two stages can be suitably employed. Further, a method of injecting and molding the envelope layer forming material around the solid core can be suitably employed.

Hereinafter, the intermediate layer will be described in detail.
The intermediate layer is a layer covering the periphery of the envelope layer. In the present invention, the thickness is not particularly limited, but it is recommended to form it thicker than the cover described later. More specifically, it is preferably 0.5 mm or more, more preferably 0.8 mm or more, and further preferably 1.0 mm or more. The upper limit is not particularly limited, but is preferably 2.5 mm or less, more preferably 2.0 mm or less, and still more preferably 1.5 mm or less. When the thickness of the intermediate layer is larger than the above range or thinner than the thickness of the outer layer cover described later, the flight distance is insufficient due to the low spin effect at the time of full shot with the driver (W # 1). It may not come out. On the other hand, if the thickness of the intermediate layer is too thin, the durability against cracking during repeated hitting and the durability at low temperatures may deteriorate.

  The surface hardness of the intermediate layer is not particularly limited, but the Shore D hardness is preferably 60 or more, more preferably 64 or more, and still more preferably 66 or more. Further, the upper limit of the surface hardness is preferably 80 or less, more preferably 76 or less, and still more preferably 73 or less in Shore D hardness. On the other hand, the material hardness of the intermediate layer is not particularly limited, but the Shore D hardness is preferably 53 or more, more preferably 58 or more, and still more preferably 60 or more. The upper limit of the material hardness is not particularly limited, but the Shore D hardness can be preferably 75 or less, more preferably 70 or less, and still more preferably 67 or less. If the hardness of the intermediate layer is too low, too much spin may occur during a full shot, and the flight distance may not be obtained. On the other hand, if the hardness is too high, the durability to cracking during repeated hitting may deteriorate, and the feel at the time of putting or short approach may become too hard.

  Here, the material hardness means the hardness measured for a sample obtained by molding the material into a sheet having a predetermined thickness, and the surface hardness is measured on the surface of a sphere obtained by molding the material. It means hardness. Moreover, Shore D hardness means the hardness measured by the type D durometer based on ASTM D2240-95 standard. The same applies to the following description.

  An ionomer resin is used as a material for forming the intermediate layer. As the ionomer resin, commercially available products can be used. Specifically, sodium neutralization such as HiMilan 1605, HiMilan 1601 and AM7318 (all manufactured by Mitsui DuPont Polychemical Co., Ltd.), Surlyn 8120 (manufactured by Dupont), etc. Zinc-neutralized ionomer resins, such as type ionomer resins and HiMilan 1557, HiMilan 1706 and AM7317 (all manufactured by Mitsui DuPont Polychemical Co., Ltd.). These can be used alone or in combination of two or more.

  Moreover, these ionomer resins can be used individually by 1 type or in combination of 2 or more types. In the present invention, from the viewpoint of improving resilience, it is particularly preferable to use a combination of a Zn neutralized ionomer resin and a Na neutralized ionomer resin. In this case, the compounding ratio of the Zn neutralized ionomer resin and the Na neutralized ionomer resin is not particularly limited, but is usually 25:75 to 75:25, preferably 35:65 to 65: by mass ratio. 35, more preferably 45:55 to 55:45. If this blending ratio is out of the above range, the resilience will be too low to obtain the desired flight performance, the cracking durability at the time of repeated impact at normal temperature will deteriorate, and the temperature will be lower (below zero). The durability against cracking may deteriorate.

  Furthermore, various additives can be blended in the material for forming the intermediate layer as necessary, for example, pigments, dispersants, antioxidants, light stabilizers, ultraviolet absorbers, release agents, etc. Can be appropriately blended.

  The specific gravity of the intermediate layer is not particularly limited, but is preferably less than 1.0, more preferably 0.98 or less, and even more preferably 0.96 or less. On the other hand, the lower limit of the specific gravity can be preferably 0.90 or more, and more preferably 0.94 or more. When the specific gravity of the intermediate layer deviates from the above range, the resilience is lowered, the flight distance may not be obtained, and the crack durability during repeated hitting may be deteriorated.

  The method for forming the intermediate layer is not particularly limited, and a known method may be adopted. For example, a method for injecting and molding an intermediate layer forming material around the envelope layer, A pair of hemispherical cup-shaped half cups are made of the layer forming material, and the intermediate product (here, the sphere in which the enveloping layer is formed around the solid core) is wrapped with these half cups. A method of pressurizing and heating for 10 minutes can be employed.

  Next, the cover will be described. In addition, the cover said to this invention means the outermost layer of a ball | bowl, and said intermediate | middle layer and envelope layer are excluded.

  The surface hardness of the cover (that is, the surface hardness of the ball) is not particularly limited, but the Shore D hardness can be preferably 45 or more, more preferably 50 or more, and still more preferably 55 or more. can do. Further, the upper limit of the surface hardness is preferably 70 or less, more preferably 65 or less, and still more preferably 60 or less in Shore D hardness. On the other hand, the material hardness of the cover is not particularly limited, but the Shore D hardness can be preferably 30 or more, more preferably 40 or more, and still more preferably 43 or more. Further, the upper limit of the material hardness is not particularly limited, but the Shore D hardness can be preferably 60 or less, more preferably 50 or less, and still more preferably 47 or less. If the cover hardness is too low, the spin may be applied too much during a full shot and the flight distance may not be achieved. On the other hand, if the hardness is too high, the golfer may not be able to spin on approach shots and lack controllability even for professional golfers and advanced amateur golfers.

  The thickness of the cover is not particularly limited, but is preferably 0.3 mm or more, more preferably 0.5 mm or more, and further preferably 0.7 mm or more. The upper limit is not particularly limited, but is preferably 1.5 mm or less, more preferably 1.2 mm or less, and still more preferably 1.0 mm or less. If the cover is thicker than the above range, the resilience may be insufficient when the driver (W # 1) is hit, or the spin amount may increase, resulting in an increase in flight distance. On the other hand, if the cover is thinner than the above range, the scratch resistance may deteriorate, and even a professional golfer or an advanced amateur golfer may lack control.

  The cover is formed using a resin composition mainly composed of urethane from the viewpoint of controllability and scratch resistance. In the present invention, among these, thermoplastic polyurethane can be preferably used from the viewpoint of mass productivity. More specifically, a resin composition containing (A) a thermoplastic polyurethane and (B) an isocyanate compound, which will be described later, can be suitably employed.

  In order to exhibit the effect of the present invention sufficiently effectively, a necessary and sufficient amount of unreacted isocyanate groups may be present in the cover resin material. Specifically, the above components (A) and (B) Is recommended to be 60% or more of the total mass of the cover layer, and more preferably 70% or more. The components (A) and (B) will be described in detail below.

  The structure of the thermoplastic polyurethane (A) includes a soft segment made of a polymer polyol (polymeric glycol) that is a long-chain polyol, and a hard segment made of a chain extender and an isocyanate compound. Here, as the long-chain polyol as a raw material, any of those conventionally used in the technology relating to thermoplastic polyurethane can be used, and is not particularly limited. For example, polyester polyol, polyether polyol, polycarbonate polyol , Polyester polycarbonate polyol, polyolefin polyol, conjugated diene polymer polyol, castor oil polyol, silicone polyol, vinyl polymer polyol and the like. These long chain polyols may be used individually by 1 type, and may use 2 or more types together. In the present invention, among these, polyether polyols are preferable in that a thermoplastic polyurethane having a high impact resilience and excellent low temperature characteristics can be synthesized.

  Examples of the polyether polyol include poly (ethylene glycol), poly (propylene glycol), poly (tetramethylene glycol), poly (methyltetramethylene glycol) and the like obtained by ring-opening polymerization of a cyclic ether. Can do. These polyether polyols may be used individually by 1 type, and may use 2 or more types together. In the present invention, among these, poly (tetramethylene glycol) and poly (methyltetramethylene glycol) can be preferably used.

  The number average molecular weight of these long-chain polyols is not particularly limited, but is preferably in the range of 1,500 to 5,000. By using a long-chain polyol having such a number average molecular weight, a golf ball made of a thermoplastic polyurethane composition excellent in various properties such as the resilience and productivity described above can be obtained with certainty. The number average molecular weight of the long-chain polyol is more preferably in the range of 1,700 to 4,000, and still more preferably in the range of 1,900 to 3,000.

  The number average molecular weight of the long-chain polyol is a number average molecular weight calculated based on a hydroxyl value measured according to JIS K1557.

  As a chain extender, what is used in the technique regarding the conventional thermoplastic polyurethane can be used suitably, and it does not restrict | limit in particular. In the present invention, a low molecular weight compound having a molecular weight of 400 or less having two or more active hydrogen atoms capable of reacting with an isocyanate group can be used, and among them, an aliphatic diol having 2 to 12 carbon atoms is preferably used. Can do. Specific examples include 1,4-butylene glycol, 1,2-ethylene glycol, 1,3-butanediol, 1,6-hexanediol, 2,2-dimethyl-1,3-propanediol, and the like. Among these, 1,4-butylene glycol can be particularly preferably used.

  As an isocyanate compound, what is used in the technique regarding the conventional thermoplastic polyurethane can be used suitably, and there is no restriction | limiting in particular. Specifically, 4,4′-diphenylmethane diisocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, p-phenylene diisocyanate, xylylene diisocyanate, naphthylene 1,5-diisocyanate, tetramethylxylene diisocyanate, hydrogenated One type or two or more types 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, some isocyanate species make it difficult to control the crosslinking reaction during injection molding. In the present invention, 4,4'-diphenylmethane diisocyanate, which is an aromatic diisocyanate, is most preferable from the viewpoint of the balance between the stability during production and the physical properties to be expressed.

  The most preferable thermoplastic polyurethane as the component (A) is a thermoplastic polyurethane synthesized using a polyether polyol as a long-chain polyol, an aliphatic diol as a chain extender, and an aromatic diisocyanate as an isocyanate compound, The polyether polyol is a polytetramethylene glycol having a number average molecular weight of 1,900 or more, the chain extender is 1,4-butylene glycol, and the aromatic diisocyanate is 4,4′-diphenylmethane diisocyanate. It is not limited to.

  In addition, the active hydrogen atom: isocyanate group blending ratio in the polyurethane forming reaction described above is a golf ball made of a thermoplastic polyurethane composition having various characteristics such as resilience, spin performance, scratch resistance and productivity. Can be adjusted within a preferable range. Specifically, in producing a thermoplastic polyurethane by reacting the above long-chain polyol, an isocyanate compound and a chain extender, the isocyanate compound is used with respect to 1 mole of active hydrogen atoms of the long-chain polyol and the chain extender. It is preferable to use each component in such a ratio that the isocyanate group contained in the mixture becomes 0.95 to 1.05 mol.

  The production method of the component (A) is not particularly limited, and it is produced by a prepolymer method or a one-shot method using a long-chain polyol, a chain extender and an isocyanate compound, using a known urethanization reaction. May be. Among them, it is preferable to perform melt polymerization in the substantial absence of a solvent, and it is particularly preferable to produce by continuous melt polymerization using a multi-screw extruder.

  A commercial item can also be used for the said (A) component, for example, Pandex T-8295, Pandex T-8290, Pandex T-8283, Pandex T-8260 (all are manufactured by DIC Bayer Polymer Ltd.). Etc.

  Next, the isocyanate compound as the component (B) needs to have two or more isocyanate groups. In the present invention, a necessary and sufficient amount of unreacted isocyanate groups may be present in the cover resin material in order to exhibit the effects of the present invention sufficiently effectively, and all the isocyanate groups in the compound are in an unreacted state. Things that have already been partially or wholly reacted may coexist.

  Although there is no restriction | limiting in particular as this isocyanate compound, Various isocyanate can be employ | adopted, Specifically, 4,4'- diphenylmethane diisocyanate, 2, 4- toluene diisocyanate, 2, 6-toluene diisocyanate, p -Phenylene diisocyanate, xylylene diisocyanate, naphthylene 1,5-diisocyanate, tetramethylxylene diisocyanate, hydrogenated xylylene diisocyanate, dicyclohexylmethane diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, norbornene diisocyanate, trimethylhexamethylene diisocyanate, dimer Use one or more selected from the group consisting of acid diisocyanates It can be. In the present invention, the use of 4,4′-diphenylmethane diisocyanate, dicyclohexylmethane diisocyanate and isophorone diisocyanate among the above-mentioned isocyanate groups is a molding due to an increase in viscosity associated with the reaction with the thermoplastic polyurethane as the component (A). This is preferable from the viewpoint of the balance between the influence on the properties and the physical properties of the obtained golf ball cover material.

  In the present invention, although not an essential component, a thermoplastic elastomer other than the thermoplastic polyurethane can be blended as the component (C) with the component (A) and the component (B). By blending the component (C) into the resin blend, various physical properties required for a golf ball cover material such as further improvement in fluidity, resilience, and abrasion resistance of the resin blend can be enhanced. .

  The mixing ratio of the above components (A) to (C) is not particularly limited, but in order to exhibit the effects of the present invention sufficiently effectively, (A) :( B) :( Preferably, C) = (100) :( 2-50) :( 0-50).

  In the present invention, the resin component is prepared by mixing the above components (A) and (B) and, if necessary, the component (C). At that time, at least a part of the polyisocyanate compound is prepared. It is preferable to select conditions such that there is a polyisocyanate compound in which all isocyanate groups remain in an unreacted state. For example, it is preferable to take measures such as purging with an inert gas such as nitrogen or vacuum treatment. This resin blend is then injection molded around the intermediate product (here, the sphere in which the envelope layer and the intermediate layer are formed around the solid core) placed in the mold. In order to make the handling smooth and easy, it is preferable to form the pellets having a length of 1 to 10 mm and a diameter of 0.5 to 5 mm. In the resin pellets, unreacted isocyanate groups remain, and the unreacted isocyanate groups are converted into the component (A) by post-treatment such as injection molding around the intermediate product and subsequent annealing. It reacts with component (C) to form a crosslinked product.

  In addition, the resin composition described above, that is, the cover forming material, includes a pigment, a dispersant, an antioxidant, an ultraviolet absorber, an ultraviolet stabilizer, a release agent, a plasticizer, an inorganic filler (if necessary). Various additives such as zinc oxide, barium sulfate, titanium dioxide, etc.) can be blended.

  The melt flow rate (MFR) at 210 ° C. of the cover forming material is not particularly limited, but is preferably 5 g / 10 min or more, more preferably 20 g / 10 min or more from the viewpoint of improving fluidity and productivity. More preferably, it is 50 g / 10 min or more. If the value of the melt flow rate of the material is small, the fluidity is lowered, which not only causes eccentricity during injection molding, but also may reduce the degree of freedom in designing the cover thickness. In addition, the measured value of said melt flow rate is a measured value based on JISK7210-1999.

  As a method of molding the cover, for example, a method of supplying the cover forming material to an injection molding machine and injecting a molten material around the intermediate layer can be employed. In this case, the molding temperature varies depending on the type of thermoplastic polyurethane and the like, but is usually in the range of 150 to 250 ° C.

  Although not particularly limited, when injection molding is performed, an inert gas such as nitrogen or a low-humidity gas such as low dew point dry air is used in part or all of the path from the resin supply unit to the mold. It is desirable to perform a treatment such as purging or vacuum treatment to make the inside of the path a low humidity environment. In addition, although not particularly limited, the above-described inert gas such as nitrogen and low-humidity gas such as low dew point dry air can be suitably used as a pressure-feed medium for resin transport. By carrying out the molding of the cover in a low humidity environment, the progress of the reaction of the isocyanate group until the resin compound is filled into the mold can be suppressed as much as possible, thereby the viscosity of the resin compound However, it is possible to improve the moldability and improve the substantial crosslinking efficiency.

  By forming the cover as described above, in addition to the effect of increasing the flight distance, the spin performance in the approach is also improved, and both controllability and flight distance can be achieved.

  Further, when forming the cover, there is no particular limitation, but in order to improve the adhesion with the intermediate layer, the surface of the intermediate layer (that is, the sphere after forming the intermediate layer) is previously polished. Is preferably applied. Furthermore, 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 cover forming material. Examples of the adhesion enhancer to be blended in the material include organic compounds such as 1,3-butanediol and trimethylolpropane, and oligomers such as polyethylene glycol and polyhydroxy polyolefin oligomer. In particular, trimethylolpropane and polyhydroxy polyolefin oligomer are preferably used. As these commercial products, for example, trimethylolpropane manufactured by Mitsubishi Gas Chemical Co., Ltd., polyhydroxypolyolefin oligomer manufactured by Mitsubishi Chemical Co., Ltd. (the main chain has 150 to 200 carbon atoms, and has a hydroxyl group at the end. Trade name Polytail H), etc. Can be mentioned.

  The details of the solid core, the envelope layer, the intermediate layer, and the cover have been individually described so far. The relationship between these layers will be described below.

The specific gravity of the envelope layer, intermediate layer and cover is as follows:
It is necessary to satisfy the relationship of envelope layer specific gravity> intermediate layer specific gravity <cover specific gravity. When the specific gravity of each of the above layers satisfies this relationship, good resilience can be ensured. If the specific gravity of the intermediate layer is too high, the resilience may be greatly reduced.

  Further, although not particularly limited, it is preferable to set the specific gravity of the core to be smaller than the specific gravity of the envelope layer from the viewpoint of ensuring good resilience. In this case, the specific gravity difference between the core and the envelope layer (envelope layer specific gravity-core specific gravity) can be within 0.2, preferably within 0.15, and more preferably within 0.1.

The surface hardness of the core, envelope layer, intermediate layer and cover (Shore D hardness) is:
Core surface hardness <enveloping layer surface hardness <intermediate layer surface hardness> It is necessary to satisfy the relationship of cover surface hardness. In the present invention, by increasing the surface hardness of the intermediate layer, the spin at the time of full shot is suppressed, and by making the core surface hardness lower than the above intermediate layer, a good feel that is not too hard at the time of full shot is obtained. At the same time, by setting the surface hardness of the envelope layer to an intermediate hardness between the intermediate layer and the solid core, good resilience and appropriate feel are imparted. Then, by making the surface hardness of the cover (ball) softer than the surface hardness of the intermediate layer, high control performance in a short game is given.
Furthermore, it is preferable that the surface hardness of each layer satisfies the following relationship.

  The difference between the surface hardness of the envelope layer and the surface hardness of the core (that is, the envelope layer surface hardness-the value of the core surface hardness) is not particularly limited, but can be preferably 1 or more in Shore D hardness. More preferably, it can be 10 or more, more preferably 20 or more. The upper limit is not particularly limited, but it can be preferably 40 or less, more preferably 35 or less, and still more preferably 30 or less in Shore D hardness. If the above-mentioned hardness difference is too large, the crack durability at the time of repeated hitting may deteriorate. On the other hand, if the hardness difference is too small, in particular, if the surface hardness of the envelope layer is lower than the surface hardness of the solid core, the spin rate may become too large during a full shot and the flight distance may not be achieved.

  The difference between the surface hardness of the intermediate layer and the surface hardness of the envelope layer (that is, the value of the intermediate layer surface hardness−the envelope layer surface hardness) is not particularly limited, but is preferably 5 or more in Shore D hardness. More preferably 7 or more, and still more preferably 9 or more. Further, the upper limit is not particularly limited, but the Shore D hardness can be preferably 25 or less, more preferably 20 or less, and still more preferably 12 or less. If the above-mentioned hardness difference is too large, the crack durability at the time of repeated hitting may deteriorate. On the other hand, if the hardness difference is too small, the amount of spin at the time of a full shot increases so that the flight distance may not be achieved.

  The difference between the surface hardness of the cover (ball) and the surface hardness of the intermediate layer (that is, the value of the cover surface hardness−the intermediate layer surface hardness) is not particularly limited, but the Shore D hardness is preferably −25 or more. More preferably, it can be −20 or more, more preferably −15 or more. Further, the upper limit is not particularly limited, but it can be preferably −1 or less, more preferably −5 or less, and still more preferably −10 or less in Shore D hardness. If the above hardness difference is too large (the above value is too large in the negative direction), the durability to cracking during repeated impacts may be deteriorated. On the other hand, if the hardness difference is too small, the spin rate may be too small in a short game.

  In the golf ball of the present invention, in order to further increase the aerodynamic characteristics and increase the flight distance, a large number of dimples can be formed on the surface of the cover in the same manner as a normal golf ball. In this case, the number of dimples formed on the ball surface is not particularly limited, but is preferably 280 or more, more preferably 300 or more, and further preferably 320 or more. The upper limit is not particularly limited, but it is preferably 360 or less, more preferably 350 or less, and still more preferably 340 or less. If the number of dimples exceeds the above range, the trajectory of the ball may be lowered and the flight distance may not be achieved. On the other hand, if the number of dimples is less than the above range, the trajectory of the ball may increase and the flight distance may not be extended.

  On the other hand, as the geometric arrangement of dimples, octahedrons, icosahedrons, etc. can be adopted. Furthermore, the shape of the dimples is not only circular but also various polygons such as square type, hexagon type, pentagon type, triangle type, etc. One type or two or more types can be appropriately selected from a drop shape, an elliptical shape, and the like. The diameter of the dimple (diagonal length in the case of a polygon) is not particularly limited, but is preferably 2.5 to 6.5 mm. Also, the depth of the dimple is not particularly limited, but is preferably 0.08 to 0.30 mm.

Further, a value V _{0 obtained} by dividing the space volume of the dimple below the plane surrounded by the edge of the dimple by the cylindrical volume having the plane as the bottom surface and the maximum depth of the dimple from the bottom surface as a height is particularly limited. However, in the present invention, it can be set to 0.35 to 0.80.

  The ratio SR of the total surface area of the phantom sphere assuming that the dimple area defined by the plane surrounded by the edge of the dimple does not exist on the ball surface is not particularly limited. From the viewpoint of reduction, it is preferably 60 to 90%. In addition to increasing the number of dimples to be formed, the SR is increased by mixing a plurality of types of dimples having different diameters or by forming a shape in which the distance between adjacent dimples (bank width) is substantially zero. be able to.

  The ratio VR of the total volume of the dimple space formed downward from the plane surrounded by the edge of the dimple to the volume of the phantom sphere assuming that no dimple exists on the ball surface is not particularly limited. In the present invention, the content may be 0.6 to 1%.

In the present invention, by setting the above V ₀ , SR, and VR within the above ranges, air resistance can be reduced, and a trajectory with a good flight distance can be easily obtained, and the flight performance can be improved.

  The diameter of the golf ball obtained by forming each layer described above is preferably 42.67 mm or more so as to correspond to the standard of the golf ball. The upper limit value is not particularly limited, but is preferably 44 mm or less, more preferably 43.8 mm or less, still more preferably 43.5 mm or less, and most preferably 43 mm or less. . On the other hand, the weight is not particularly limited, but is preferably in the range of 45.0 to 45.93 g for the same reason.

  In the present invention, in order to improve the design and durability of the golf ball, it is optional to perform various treatments such as ground treatment, stamping and painting on the cover surface.

  EXAMPLES Hereinafter, although an Example is shown and this invention is demonstrated concretely, this invention is not restrict | limited to the following Example.

Examples 1 and 2
First, Hytrel 3046 (manufactured by Toray DuPont) was injected into a core molding die to produce a solid core.
Next, a rubber composition having the composition shown in Table 1 was prepared using a kneading roll, and then primary vulcanization (semi-vulcanization) at 35 ° C. for 3 minutes to produce a pair of hemispherical half cups. did. Next, the above-described solid core was wrapped with the obtained half cup and subjected to secondary vulcanization (total vulcanization) in a mold at 155 ° C. for 14 minutes to form an envelope layer.

Details of the materials listed in Table 1 are as follows.
Polybutadiene rubber: “BR730” manufactured by JSR, polybutadiene rubber obtained using an Nd-based catalyst, cis-1,4-bond content of 96 mass%, Mooney viscosity “55”, molecular weight distribution “3”
Zinc acrylate: Nippon Distillation Kogyo Co., Ltd. Organic peroxide: NOF "Perhexa C-40", 1,1-bis (t-butylperoxy) cyclohexane diluted to 40% with inorganic filler, 155 ° C Half-life is about 50 seconds
Anti-aging agent: “NOCRACK 200” manufactured by Ouchi Shinsei Chemical Co., Ltd., 2,6-di-tert-butyl-4-methylphenol zinc oxide: Barium sulfate manufactured by Sakai Chemical Industry Co., Ltd. Barium 100 "

  Further, an intermediate layer was formed around the envelope layer formed above by an injection molding method using the resin material (No. 1) having the composition shown in Table 2. In Table 2, No. Each raw material shown in 2 (unit: part by mass) was kneaded under a nitrogen gas atmosphere by a twin screw extruder to obtain a resin material for forming a cover. This resin material was in the form of a pellet having a length of 3 mm and a diameter of 1 to 2 mm. Around the intermediate layer formed above, a cover is formed by an injection molding method using the pellet-shaped resin material (No. 2), and a solid core is covered with an envelope layer, an intermediate layer, and a cover. A multi-piece solid golf ball was obtained. At this time, dimples having the form shown in FIG. 2 were formed on the cover surfaces of the balls of all the examples. Details of the dimples are shown in Table 3. Details of the produced balls are shown in Table 4.

Details of the materials listed in Table 2 are as follows.
High Milan 1605, 1706, 1557: ionomer resin Pandex T-8290 manufactured by Mitsui DuPont Polychemical Co., Ltd. T-8283: MDI-PTMG type thermoplastic polyurethane titanium oxide manufactured by DIC Bayer Polymer Co., Ltd .: “Taipeke R680” manufactured by Ishihara Sangyo Co., Ltd.
Polyethylene wax: Sanyo Chemical Co., Ltd. “Sun Wax 161P”
Isocyanate compound: 4,4'-diphenylmethane diisocyanate

Dimple definition diameter: Diameter diameter of plane surrounded by dimple edges Depth: Maximum dimple depth from plane surrounded by dimple edges V ₀ : Spatial volume of dimple below plane surrounded by dimple edges Is divided by a cylindrical volume having the plane as the bottom and the maximum dimple depth from the bottom as the height SR: the sum of the dimple areas defined by the plane surrounded by the edges of the dimple is the ball surface The ratio of the surface area of the phantom sphere assuming that no dimple exists to the surface VR: The phantom sphere assuming that the total dimple space volume formed below the plane surrounded by the edge of the dimple does not have a dimple on the ball surface Ratio of volume to

  The following physical properties of the obtained golf ball were examined. Further, a flying test was conducted by the following method to evaluate the hit feeling. The results are shown in Table 4.

(1) Core deflection (mm)
The core was placed on a hard plate, and the amount of deflection from when an initial load of 98 N (10 kgf) was applied to when the final load of 1275 N (130 kgf) was applied was measured.
The above deflection amounts are all measured values after temperature adjustment to 23 ° C.
(2) Core hardness (Shore D hardness)
Measurement was performed by vertically pressing a Type D durometer needle conforming to the ASTM D2240-95 standard at the center of the cross section obtained by cutting the core in half (through the center).
The above hardness is a measured value after temperature control at 23 ° C. Table 4 also shows the JIS-C hardness (based on JIS K 6301) conversion value of the center hardness.
(3) Surface hardness of the core, envelope layer, intermediate layer and cover (Shore D hardness)
Measurement was performed by pressing a Type D durometer needle conforming to the ASTM D2240-95 standard so as to be perpendicular to the surface of the intermediate product or ball at the stage where the layer to be measured was formed. The surface hardness of the ball (cover) is a measured value in a land portion where no dimples are formed on the ball surface.
The above hardness is a measured value after temperature control at 23 ° C. Table 4 also shows the JIS-C hardness (based on JIS K 6301) conversion value of the surface hardness.
(4) Material hardness of the intermediate layer (Shore D hardness)
The intermediate layer forming material is formed into a sheet with a thickness of 2 mm, stored at 23 ° C. for 2 weeks, stacked to a thickness of 6 mm or more, and measured using a Type D durometer in accordance with the ASTM D2240-95 standard. did. Table 4 also shows the JIS-C hardness (based on JIS K 6301) conversion value of the material hardness.
(5) Material hardness of the cover (Shore D hardness)
A type D conforming to the ASTM D2240-95 standard after annealing treatment is performed on a sheet of 2 mm thickness obtained by injection molding of a cover forming material under conditions of 100 ° C. × 8 hours and left at room temperature for one week. Measurement was performed using a durometer. Table 4 also shows the JIS-C hardness (based on JIS K 6301) conversion value of the material hardness.
(6) Flying Performance A driver (W # 1) was attached to the golf striking robot, and the spin amount, carry, and total flying distance when striking at a head speed (HS) of 45 m / s were measured. The club used was “Tour Stage X-Drive 705 TYPE 415 (2011 model)” (loft 9.5 °) manufactured by Bridgestone Sports.
(7) Approach spin amount A sand wedge (SW) was attached to a golf striking robot, and the spin amount when striking at a head speed (HS) of 20 m / s was measured. The club used was “Tour Stage X-WEDGE” (Loft 56 °) manufactured by Bridgestone.

1 Core 2 Enveloping Layer 3 Intermediate Layer 4 Cover G Golf Ball D Dimple

Claims (13)

In a multi-piece solid golf ball comprising a core, an envelope layer that covers the core, an intermediate layer that covers the envelope layer, and a cover that covers the intermediate layer and has a plurality of dimples formed on the surface thereof,
The core is formed mainly of one or more thermoplastic elastomers selected from the group consisting of polyester, polyamide, polyurethane, olefin, and styrene, and the diameter is 10 to 30 mm and the specific gravity is 1.0 to less than 1.3 and the amount of deflection when loaded from an initial load of 98 N (10 kgf) to a final load of 1275 N (130 kgf) is 3.6 to 10 mm.
The envelope layer is formed of a rubber composition mainly composed of a rubber material, and the thickness thereof is 3 to 10 mm.
The intermediate layer is formed of a resin composition mainly composed of ionomer,
The cover is formed of a resin composition mainly composed of urethane, and the specific gravity difference between the core and the envelope layer (envelopment layer specific gravity-core specific gravity) is 0 to 0.2. The specific gravity of the layer and cover is
Enveloping layer specific gravity> Intermediate layer specific gravity <Cover specific gravity is satisfied, and surface hardness (Shore D hardness) of the core, envelope layer, intermediate layer and cover
Core surface hardness <enclosure layer surface hardness <intermediate layer surface hardness> A multi-piece solid golf ball that satisfies the relationship of cover surface hardness.   The multi-piece solid golf ball according to claim 1, wherein the core is formed of a polyether ester elastomer as a main material.   The multi-piece solid golf ball according to claim 1, wherein the core has a diameter of 20 to 30 mm.   The multi-piece solid golf ball according to claim 3, wherein the core has a diameter of 22 to 28 mm.   The multi-piece solid golf ball according to claim 1, wherein the envelope layer has a thickness of 4 to 8 mm. The surface hardness of the core, envelope layer, intermediate layer and cover (Shore D hardness)
1 ≦ enveloping layer surface hardness−core surface hardness ≦ 40
5 ≦ intermediate layer surface hardness−enveloping layer surface hardness ≦ 25
−25 ≦ Ball surface hardness−Intermediate layer surface hardness ≦ −1
The multi-piece solid golf ball according to claim 1, which satisfies the following relationship.   The multi-piece solid golf ball according to claim 1, wherein the intermediate layer has a specific gravity of less than 1.0. The multi-piece solid golf ball according to claim 1, wherein the envelope layer has a specific gravity of 1.1 to 1.5. In a multi-piece solid golf ball comprising a core, an envelope layer that covers the core, an intermediate layer that covers the envelope layer, and a cover that covers the intermediate layer and has a plurality of dimples formed on the surface thereof,
The core is formed mainly of one or more thermoplastic elastomers selected from the group consisting of polyester, polyamide, polyurethane, olefin, and styrene, and the diameter is 10 to 30 mm and the specific gravity is 1.0 to less than 1.3 and the amount of deflection when loaded from an initial load of 98 N (10 kgf) to a final load of 1275 N (130 kgf) is 3.6 to 10 mm.
The envelope layer is formed of a rubber composition mainly composed of a rubber material, and the thickness thereof is 3 to 10 mm.
The intermediate layer is formed of a resin composition mainly composed of ionomer,
While the cover is formed of a resin composition mainly composed of urethane,
The specific gravity of the envelope layer, intermediate layer and cover is
Enclosure layer specific gravity> Intermediate layer specific gravity <Cover specific gravity
The surface hardness of the core, envelope layer, intermediate layer and cover (Shore D hardness)
Core surface hardness <enclosure layer surface hardness <intermediate layer surface hardness> cover surface hardness
Satisfying the relationship, and
20 ≦ enveloping layer surface hardness−core surface hardness ≦ 40
−25 ≦ cover surface hardness−intermediate layer surface hardness ≦ −10
A multi-piece solid golf ball that satisfies this relationship . The multi-piece solid golf ball according to claim 9, wherein the core is formed of a polyether ester elastomer as a main material . The multi-piece solid golf ball according to claim 9 or 10, wherein the core has a diameter of 20 to 30 mm . The multi-piece solid golf ball according to claim 9, wherein the envelope layer has a thickness of 4 to 8 mm . The multi-piece solid golf ball according to any one of claims 9 to 12, wherein a difference in specific gravity between the core and the envelope layer (envelope layer specific gravity-core specific gravity) is 0 to 0.2.

Images