Multi-piece solid golf balls

Abstract

To provide a multi-piece solid golf ball which is a distance-type golf ball, focusing on extending the distance, and can achieve a superior distance on full shots with a driver (W#1) and with irons.SOLUTION: In a multi-piece solid golf ball having a core, an envelope layer, an intermediate layer and a cover, the core is formed of a rubber composition, the envelope layer, intermediate layer and cover are each formed of a resin material; the hardness relationship of the layers satisfies the following two conditions: material hardness of cover>material hardness of intermediate layer, and material hardness of envelope layer≥surface hardness of core (the hardness in the conditions denote Shore C hardness) and the thickness relationship of the layers satisfies the following condition: (cover thickness+intermediate layer thickness)<envelope layer thickness.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a multi-piece solid golf ball having four or more layers including a core, an envelope layer, a mid layer, and a cover. [Background technology]

[0002] Many efforts have been made to design balls with multi-layer structures, and many balls have been developed that satisfy not only professional golfers but also ordinary amateur golfers from beginners to advanced players. For example, functional multi-piece solid golf balls have become popular, in which the material hardness and surface hardness of each layer, i.e., the core, surrounding layer, intermediate layer, and cover (outermost layer), are optimized. Furthermore, several technologies have been proposed that focus on the hardness distribution of the core, which accounts for the majority of the ball's volume, and design various modes of internal core hardness to provide high-performance golf balls.

[0003] Examples of such technical documents include the following Patent Documents 1 to 13. These golf balls have a multi-layer structure of four or more layers, and relate to distance-oriented (distance-type) golf balls in which the cover (outermost layer) is designed to be harder than the intermediate layer.

[0004] However, the proposed golf ball still has room for improvement in terms of optimizing the core hardness distribution and the thickness relationship between each layer. In other words, the proposed golf ball makes it difficult for amateur users, especially those with low head speeds, to achieve a satisfactory distance. While the proposed golf ball provides satisfactory distance when shot with a driver, it does not provide superior distance performance when shot with an iron. Therefore, the proposed distance-oriented (distance-oriented) golf ball still has room for improvement in terms of achieving a longer distance when shot with a driver (W#1) and an iron. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-061002 [Patent Document 2] Japanese Patent Application Laid-Open No. 2000-061000 [Patent Document 3] Japanese Patent Application Laid-Open No. 2001-218872 [Patent Document 4] Japanese Patent Application Laid-Open No. 2005-218859 [Patent Document 5] Japanese Patent Application Laid-Open No. 2010-253268 [Patent Document 6] Japanese Patent Application Laid-Open No. 2014-132955 [Patent Document 7] Japanese Patent Application Laid-Open No. 2016-016117 [Patent Document 8] Japanese Patent Application Laid-Open No. 2016-179052 [Patent Document 9] Japanese Patent Application Publication No. 2019-198467 [Patent Document 10] Patent Publication No. 2021-087743 [Patent Document 11] Japanese Patent Application Publication No. 10-295852 [Patent Document 12] Japanese Patent Application Laid-Open No. 2000-140160 [Patent Document 13] Japanese Patent Application Laid-Open No. 2013-244129 Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention has been made in consideration of the above circumstances, and aims to provide a multi-piece solid golf ball that is designed to provide an advantageous distance when hit with a driver (W#1) or an iron for full shots, in a distance-oriented golf ball. [Means for solving the problem]

[0007] As a result of extensive research into achieving the above object, the present inventors have found that a multi-piece solid golf ball having a core, an envelope layer, a mid layer, and a cover can be produced by forming the core from a rubber composition, and forming the envelope layer, the mid layer, and the cover from resin materials, and satisfying the following two equations regarding the relationship between the Shore C hardness of each layer: Hardness of the cover material > hardness of the mid layer material, and Material hardness of the envelope layer ≧ surface hardness of the core The inventors discovered that by constructing a golf ball so that the above ratio satisfies the above and the thickness of each layer satisfies the following relationship: (cover thickness + intermediate layer thickness) < surrounding layer thickness, not only can advantageous distance be obtained on full shots with a driver (W#1), but also on full shots with an iron, leading to the invention of the present invention.

[0008] That is, the golf ball of the present invention has a ball structure in which the three cover layers (surrounding layer, intermediate layer, and cover) surrounding the core are all formed of a resin material, with the cover being harder than the intermediate layer. This golf ball has excellent distance performance on full shots with a driver (W#1) and also on full shots with an iron, satisfying the performance requirements of average amateur golfers. Furthermore, the golf ball of the present invention has a soft, satisfactory feel and excellent crack resistance on repeated impacts.

[0009] Accordingly, the present invention provides the following multi-piece solid golf ball. 1. A multi-piece solid golf ball having a core, an envelope layer, a mid layer, and a cover, wherein the core is formed of a single layer or multiple layers of a rubber composition. The envelope layer, the intermediate layer, and the cover are each formed of a single layer of resin material, and the resin material for one or both of the envelope layer and the intermediate layer contains the following components (A) to (D): (a-1) an olefin-unsaturated carboxylic acid binary random copolymer and / or a metal ion-neutralized product of an olefin-unsaturated carboxylic acid binary random copolymer; (a-2) an olefin-unsaturated carboxylic acid-unsaturated carboxylic acid ester ternary random copolymer and / or a metal ion-neutralized product of an olefin-unsaturated carboxylic acid-unsaturated carboxylic acid ester ternary random copolymer, (A) a base resin blended in a mass ratio of 100:0 to 0:100; (B) a non-ionomer thermoplastic elastomer in a mass ratio of 100:0 to 50:50, (C) 5 to 120 parts by mass of a fatty acid and / or a derivative thereof having a molecular weight of 228 to 1500; (D) 0.1 to 17 parts by mass of a basic inorganic metal compound capable of neutralizing unneutralized acid groups in the components (A) and (C) and a highly neutralized resin material containing the above as essential components,The hardness relationship between each layer is given by the following two equations: Hardness of the cover material > hardness of the mid layer material, and Material hardness of the envelope layer ≧ surface hardness of the core (However, the hardness in the above formula means Shore C hardness.) Meet And, The thickness relationship of each layer is as follows: (Cover thickness + Mid layer thickness) < Surrounding layer thickness A multi-piece solid golf ball characterized by satisfying the above. 2.The hardness relationship between each layer is as follows: Cover material hardness > Intermediate layer material hardness > Surrounding layer material hardness ≥ Core surface hardness 2. A multi-piece solid golf ball according to 1 above, which satisfies the above formula (wherein the hardness is Shore C hardness). 3 The above resin materials of both the envelope layer and the intermediate layer are different types of highly neutralized resin materials containing components (A) to (D) as essential components. 1 1. The multi-piece solid golf ball as described above. 4 The thickness relationship of each layer is as follows: Thickness of envelope layer / (thickness of cover + thickness of intermediate layer)≧1.2 Satisfy the above 1~ 3 1. A multi-piece solid golf ball according to any one of claims 1 to 9. 5 The relationship between the core diameter and the ball diameter is given by the following formula: 0.65≦(core diameter) / (ball diameter)≦0.78 Satisfy the above 1~ 4 1. A multi-piece solid golf ball according to any one of claims 1 to 9. [Effects of the Invention]

[0010] The multi-piece solid golf ball of the present invention has excellent distance performance when hit with a driver (W#1) or an iron for full shots, provides a soft and pleasant feel when hit, and is highly resistant to cracking when hit repeatedly. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic cross-sectional view of a multi-piece solid golf ball (four-layer structure) of the present invention. [Figure 2] FIG. 2 is a plan view showing the dimple pattern common to each example and each comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0012] The present invention will be described in more detail below. As shown in Figure 1, the multi-piece solid golf ball of the present invention is a golf ball G having four or more layers, including a core 1, an envelope layer 2 enclosing the core, an intermediate layer 3 enclosing the envelope layer, and a cover 4 enclosing the intermediate layer. Numerous dimples D are typically formed on the surface of the cover 4. Although not specifically shown, a paint layer is typically formed on the surface of the cover 4. The cover 4 is the outermost layer of the golf ball's layer structure, excluding the paint layer. The core 1 is not limited to a single layer and can be formed of two or more layers, but the envelope layer 2, intermediate layer 3, or cover 4 is typically formed of a single layer.

[0013] The core is obtained by vulcanizing a rubber composition mainly made of a rubber material, which is usually composed of a base rubber as the main component, and is compounded with a co-crosslinking agent, a crosslinking initiator, an inert filler, an organic sulfur compound, etc. to obtain the rubber composition.

[0014] Polybutadiene is preferably used as the base rubber. Commercially available polybutadiene products can be used, such as BR01, BR51, and BR730 (manufactured by JSR Corporation). The proportion of polybutadiene in the base rubber is preferably 60% by mass or more, and more preferably 80% by mass or more. Rubber components other than the polybutadiene may be blended into the base rubber within a range that does not impair the effects of the present invention. Examples of rubber components other than polybutadiene include polybutadienes other than the polybutadienes mentioned above, and other diene rubbers, such as styrene-butadiene rubber, natural rubber, isoprene rubber, and ethylene-propylene-diene rubber.

[0015] The co-crosslinking agent is an α,β-unsaturated carboxylic acid and / or a metal salt thereof. Specific examples of unsaturated carboxylic acids include acrylic acid, methacrylic acid, maleic acid, and fumaric acid, with acrylic acid and methacrylic acid being particularly preferred. Metal salts of unsaturated carboxylic acids are not particularly limited, but examples include those obtained by neutralizing the above-mentioned unsaturated carboxylic acids with desired metal ions. Specific examples include zinc salts and magnesium salts of methacrylic acid, acrylic acid, and the like, with zinc acrylate being particularly preferred.

[0016] The unsaturated carboxylic acid and / or metal salt thereof is blended in an amount of typically 5 parts by weight or more, preferably 9 parts by weight or more, and more preferably 13 parts by weight or more, per 100 parts by weight of the base rubber, with the upper limit typically being 60 parts by weight or less, preferably 50 parts by weight or less, and more preferably 40 parts by weight or less. If the blended amount is too high, the ball may become too hard, resulting in an unbearable feel at impact, while if the blended amount is too low, the resilience may decrease.

[0017] An organic peroxide is preferably used as the crosslinking initiator. Specifically, commercially available organic peroxides can be used, such as Percumyl D (manufactured by Nippon Oil & Fats Co., Ltd.), Perhexa C-40, Perhexa 3M (manufactured by Nippon Oil & Fats Co., Ltd.), and Luperco 231XL (manufactured by Atochem). These may be used alone or in combination of two or more. The amount of organic peroxide added is preferably 0.1 parts by weight or more, more preferably 0.3 parts by weight or more, and even more preferably 0.5 parts by weight or more, per 100 parts by weight of the base rubber. The upper limit is preferably 5 parts by weight or less, more preferably 4 parts by weight or less, even more preferably 3 parts by weight or less, and most preferably 2.5 parts by weight or less. If the amount added is too high or too low, it may be difficult to achieve a favorable feel, durability, and resilience.

[0018] Suitable fillers include, for example, zinc oxide, barium sulfate, and calcium carbonate. These may be used alone or in combination. The amount of filler is preferably at least 1 part by weight, and more preferably at least 3 parts by weight, per 100 parts by weight of the base rubber. The upper limit of the amount is preferably no more than 200 parts by weight, more preferably no more than 150 parts by weight, and even more preferably no more than 100 parts by weight, per 100 parts by weight of the base rubber. If the amount is too high or too low, it may be difficult to obtain the appropriate mass and appropriate resilience.

[0019] As the antioxidant, for example, commercially available products such as Nocrac NS-6, Nocrac NS-30, Nocrac 200, Nocrac MB (manufactured by Ouchi Shinko Chemical Industry Co., Ltd.) can be used. These may be used alone or in combination of two or more.

[0020] The amount of antioxidant blended is not particularly limited, but is preferably at least 0.05 part by weight, more preferably at least 0.1 part by weight, and preferably not more than 1.0 part by weight, more preferably not more than 0.7 part by weight, and even more preferably not more than 0.5 part by weight, per 100 parts by weight of base rubber. If the blended amount is too high or too low, the appropriate core hardness gradient may not be obtained, and favorable resilience, durability, and spin reduction effect on full shots may not be achieved.

[0021] Furthermore, the rubber composition can be blended with an organic sulfur compound to impart excellent resilience. Specifically, it is recommended to blend thiophenol, thionaphthol, halogenated thiophenol, or a metal salt thereof. More specifically, zinc salts of pentachlorothiophenol, pentafluorothiophenol, pentabromothiophenol, parachlorothiophenol, pentachlorothiophenol, and the like, and diphenyl polysulfide, dibenzyl polysulfide, dibenzoyl polysulfide, dibenzothiazoyl polysulfide, dithiobenzoyl polysulfide, and the like having 2 to 4 sulfur atoms can be mentioned. In particular, the zinc salt of pentachlorothiophenol and diphenyl disulfide can be preferably used.

[0022] The organic sulfur compound is blended in an amount of no more than 5 parts by weight, preferably no more than 4 parts by weight, more preferably no more than 3 parts by weight, and most preferably no more than 2 parts by weight per 100 parts by weight of the base rubber. If the blended amount is too high, the hardness may become too low, while if the blended amount is too low, improvement in resilience may not be expected.

[0023] The core can be produced by vulcanizing and curing a rubber composition containing the above components. For example, the core can be produced by kneading the rubber composition using a kneader such as a Banbury mixer or a roll, compression molding or injection molding using a core mold, and curing the molded product by appropriately heating the molded product at a temperature sufficient for the organic peroxide and co-crosslinking agent to act, 100 to 200°C, preferably 140 to 180°C, for 10 to 40 minutes.

[0024] In the present invention, the core is formed of a single layer or multiple layers. If a multiple-layer rubber core is formed, peeling may occur at the interface between the rubber layers when hit repeatedly if there is a large difference in hardness at the interface, which may result in a loss of initial velocity of the ball on full shots.

[0025] The core diameter is preferably 27.5 mm or more, more preferably 28.5 mm or more, and even more preferably 29.5 mm or more. The upper limit of this diameter is preferably 33.5 mm or less, more preferably 32.5 mm or less, and even more preferably 32.0 mm or less. If the diameter deviates from the above range, it becomes difficult to achieve both low spin and high initial velocity on full shots, and the desired distance may not be achieved.

[0026] The deflection (mm) of the core when subjected to an initial load of 98 N (10 kgf) to a final load of 1,275 N (130 kgf) is not particularly limited, but is preferably at least 3.3 mm, more preferably at least 3.5 mm, and even more preferably at least 3.7 mm, with the upper limit being preferably no more than 6.0 mm, more preferably no more than 5.0 mm, and even more preferably no more than 4.5 mm. If the deflection of the core is too small, i.e., if the core is too hard, the ball may have too much spin, resulting in poor flight distance or a hard feel on impact. On the other hand, if the deflection of the core is too large, i.e., if the core is too soft, the ball may have too little resilience, resulting in poor flight distance, a soft feel on impact, or poor durability to cracking on repeated impact.

[0027] Next, the hardness distribution of the core will be described. Note that the hardness of the core described below refers to Shore C hardness. This Shore C hardness is a hardness value measured using a Shore C hardness tester conforming to ASTM D2240 standard.

[0028] The center hardness (Cc) of the core is preferably 50 or more, more preferably 55 or more, and even more preferably 60 or more, with the upper limit being preferably 66 or less, more preferably 65 or less, and even more preferably 64 or less. If this value is too high, the feel on impact may be too hard, or the spin rate on full shots may increase, preventing the desired flight distance from being achieved. On the other hand, if this value is too low, the resilience may be reduced, resulting in a loss of flight distance, or the durability to cracking when hit repeatedly may be reduced.

[0029] The surface hardness (Cs) of the core is preferably at least 68, more preferably at least 70, and even more preferably at least 72, with the upper limit being preferably not more than 83, more preferably not more than 80, and even more preferably not more than 78. Any deviation from these hardness limits may result in the same adverse effects as those described for the center hardness (Cc) of the core.

[0030] The difference between the surface hardness (Cs) and center hardness (Cc) of the core is preferably at least 8, more preferably at least 10, and even more preferably at least 12, with the upper limit being preferably at most 25, more preferably at most 20, and even more preferably at most 16. If this difference is too small, the low spin effect on full shots may be insufficient, resulting in a loss of distance. On the other hand, if the difference is too large, the initial velocity on actual impact may be low, resulting in a loss of distance, or the durability to cracking from repeated impacts may be reduced.

[0031] Next, the envelope layer will be described. The material hardness of the envelope layer is not particularly limited, but is preferably 36 or more, more preferably 41 or more, and even more preferably 46 or more in Shore D hardness, and the upper limit is preferably 58 or less, more preferably 56 or less, and even more preferably 54 or less.

[0032] The envelope layer material hardness, expressed in Shore C hardness, is preferably 58 or more, more preferably 64 or more, and even more preferably 71 or more, with the upper limit being preferably 87 or less, more preferably 84 or less, and even more preferably 82 or less. If the envelope layer material hardness is too softer than the above range, the spin rate on full shots may be increased or the initial velocity may be low, resulting in an inability to achieve the desired distance. On the other hand, if the material hardness is too hard, the spin rate on full shots may be increased, resulting in an inability to achieve the desired distance, or the feel may be too hard.

[0033] The thickness of the envelope layer is preferably 2.1 mm or more, more preferably 2.5 mm or more, and even more preferably 2.8 mm or more. On the other hand, the upper limit of the envelope layer thickness is preferably 4.8 mm or less, more preferably 4.4 mm or less, and even more preferably 4.2 mm or less. If the envelope layer is too thick or too thin, it becomes difficult to achieve both low spin and high initial velocity on full shots, and the desired flight distance may not be achieved.

[0034] In the present invention, the thickness relationship of each layer is expressed by the following formula: (Cover thickness + Mid layer thickness) < Surrounding layer thickness It is necessary to satisfy the following.

[0035] The envelope layer is made of a resin material, and in particular, various thermoplastic resin materials can be suitably used. Examples of the resin material for the envelope layer include ionomer resins and the following components (A) to (D): (a-1) an olefin-unsaturated carboxylic acid binary random copolymer and / or a metal ion-neutralized product of an olefin-unsaturated carboxylic acid binary random copolymer; (a-2) an olefin-unsaturated carboxylic acid-unsaturated carboxylic acid ester ternary random copolymer and / or a metal ion-neutralized product of an olefin-unsaturated carboxylic acid-unsaturated carboxylic acid ester ternary random copolymer, (A) a base resin blended in a mass ratio of 100:0 to 0:100; (B) a non-ionomer thermoplastic elastomer in a mass ratio of 100:0 to 50:50, (C) 5 to 120 parts by mass of a fatty acid and / or a derivative thereof having a molecular weight of 228 to 1500, and (D) 0.1 to 17 parts by mass of a basic inorganic metal compound capable of neutralizing unneutralized acid groups in the components (A) and (C). It is preferable to use a resin composition containing the above as essential components.

[0036] As for the components (A) to (D), for example, the resin materials (A) to (D) for the intermediate layer described in JP-A No. 2010-253268 can be suitably used.

[0037] Examples of the non-ionomeric thermoplastic elastomer include polyolefin elastomers (including polyolefins and metallocene polyolefins), polystyrene elastomers, diene polymers, polyacrylate polymers, polyamide elastomers, polyurethane elastomers, polyester elastomers, and polyacetals, and in particular thermoplastic polyether ester elastomers such as thermoplastic polyether ester elastomers.

[0038] The resin material may contain any additives depending on the intended use, such as pigments, dispersants, antioxidants, ultraviolet absorbers, and light stabilizers.

[0039] Next, the intermediate layer will be described. The material hardness of the intermediate layer is not particularly limited, but is preferably 40 or more, more preferably 45 or more, and even more preferably 50 or more in Shore D hardness, with the upper limit being preferably 62 or less, more preferably 60 or less, and even more preferably 58 or less. The Shore C hardness is preferably 63 or more, more preferably 70 or more, and even more preferably 76 or more, with the upper limit being preferably 92 or less, more preferably 89 or less, and even more preferably 87 or less. If the material hardness of the intermediate layer is too softer than the above range, the spin rate on full shots may increase too much, resulting in a loss of distance, and crack resistance due to repeated impacts may be reduced. On the other hand, if the material hardness of the intermediate layer is too hard, crack resistance due to repeated impacts may be reduced and the feel may be poor.

[0040] The thickness of the intermediate layer is preferably 0.7 mm or more, more preferably 0.9 mm or more, and even more preferably 1.1 mm or more. The upper limit of the thickness of the intermediate layer is preferably 1.5 mm or less, more preferably 1.4 mm or less, and even more preferably 1.3 mm or less. If the thickness of the intermediate layer is too thin, the durability to cracking due to repeated impacts may be poor, or the feel may be poor. Furthermore, if the thickness of the intermediate layer is too thick, the spin rate on full shots may increase, resulting in a loss of distance.

[0041] For the intermediate layer, it is preferable to use various thermoplastic resins used as golf ball materials, especially ionomer resins and highly neutralized resin materials containing components (A) to (D) described above for the envelope layer material, in order to achieve superior distance by reducing spin on full shots. However, when highly neutralized resin materials are used for both the envelope layer and the intermediate layer, it is preferable to use different types of highly neutralized resin materials.

[0042] Any additives can be added to the intermediate layer material depending on the application. For example, various additives such as pigments, dispersants, antioxidants, UV absorbers, and light stabilizers can be added. When these additives are added, the amount of the additives added is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, and preferably 10 parts by mass or less, more preferably 4 parts by mass or less, per 100 parts by mass of the base resin.

[0043] Next, the cover (outermost layer) will be described. The cover material hardness is not particularly limited, but is preferably 55 or higher, more preferably 59 or higher, and even more preferably 61 or higher in Shore D hardness, with the upper limit being preferably 70 or lower, more preferably 68 or lower, and even more preferably 65 or lower. The Shore C hardness is preferably 83 or higher, more preferably 88 or higher, and even more preferably 91 or higher, with the upper limit being preferably 100 or lower, more preferably 98 or lower, and even more preferably 96 or lower. If the cover material hardness is too softer than the above range, the spin rate upon driver (W#1) shots will increase and the initial velocity of the ball will decrease, resulting in a loss of distance. On the other hand, if the cover material hardness is too hard, the crack resistance upon repeated shots will be poor.

[0044] The cover thickness is preferably 0.6 mm or more, more preferably 0.8 mm or more, and even more preferably 1.1 mm or more. The upper limit of the cover thickness is 1.7 mm or less, preferably 1.5 mm or less, and even more preferably 1.3 mm or less. If the cover thickness is too thin, the durability to cracking during repeated impacts may be poor. On the other hand, if the cover thickness is too thick, the spin rate upon driver (W#1) impacts may be too high, resulting in a loss of distance and an excessively hard feel in short games and when hitting with a putter.

[0045] As the material for the cover, various thermoplastic resins used as golf ball materials are preferably used, and in particular, ionomer resins are preferred because they achieve superior distance by reducing the spin rate on full shots.

[0046] The cover material can contain any additives appropriate for the application. For example, various additives such as pigments, dispersants, antioxidants, UV absorbers, and light stabilizers can be added. When these additives are added, the amount of the additives added is preferably at least 0.1 parts by weight, more preferably at least 0.5 parts by weight, per 100 parts by weight of the base resin, and preferably no more than 10 parts by weight, more preferably no more than 4 parts by weight.

[0047] The multi-piece solid golf ball formed by laminating the above-mentioned core, envelope, intermediate layer, and cover (outermost layer) can be manufactured by a conventional method such as a known injection molding method. For example, the envelope and intermediate layer materials are sequentially injected into respective injection molds around the core to obtain each covered sphere, and finally, the cover material, which is the outermost layer, is injection molded to obtain a multi-piece golf ball. Alternatively, each covered layer can be formed by encasing the covered sphere in two half-cups previously molded into a spherical half-shell and molding the covered sphere under heat and pressure.

[0048] The golf ball preferably deflects at least 2.5 mm, more preferably at least 2.6 mm, and even more preferably at least 2.7 mm, when subjected to an initial load of 98 N (10 kgf) and a final load of 1,275 N (130 kgf). The upper limit of the deflection is preferably 3.5 mm or less, more preferably 3.3 mm or less, and even more preferably 3.1 mm or less. If the golf ball deflects too little, i.e., is too hard, the spin rate may increase too much, resulting in poor flight distance, or the feel on impact may be too hard. On the other hand, if the deflection is too large, i.e., the ball is too soft, the resilience of the ball may be too low, resulting in poor flight distance, the feel may be too soft, or the durability to cracking during repeated impact may be poor.

[0049] If C (mm) is the deflection of the core when an initial load of 98 N (10 kgf) is applied to a final load of 1,275 N (130 kgf), and B (mm) is the deflection of the ball when an initial load of 98 N (10 kgf) is applied to a final load of 1,275 N (130 kgf), the value of CB is preferably 0.90 mm or more, more preferably 1.00 mm or more, and even more preferably 1.10 mm or more, with the upper limit being preferably 1.60 mm or less, more preferably 1.50 mm or less, and even more preferably 1.40 mm or less. If this value is too small, the amount of spin on a full shot may increase, and the desired distance may not be achieved. On the other hand, if this value is too large, the initial velocity on a full shot may decrease, and the desired distance may not be achieved.

[0050] [ Hardness relationship of each layer 〕 In the present invention, the hardness relationship between the layers is expressed by the following formula: Hardness of the cover material > hardness of the mid layer material, and Material hardness of the envelope layer ≧ surface hardness of the core (However, the hardness in the above formula means Shore C hardness.) It is necessary to satisfy the following formula, and preferably, Cover material hardness > Intermediate layer material hardness > Surrounding layer material hardness ≥ Core surface hardness The purpose is to satisfy the following.

[0051] The value obtained by subtracting the material hardness of the intermediate layer from the material hardness of the cover is greater than 0, preferably greater than 3, more preferably greater than 7, in Shore C hardness, with the upper limit being preferably 25 or less, more preferably 18 or less, and even more preferably 12 or less. If this value is too small, the amount of spin on a full shot may increase, resulting in a failure to achieve the desired distance. On the other hand, if this value is too large, the initial velocity on a full shot may decrease, resulting in a failure to achieve the desired distance and a poor resistance to cracking when hit repeatedly.

[0052] The value obtained by subtracting the material hardness of the envelope layer from the material hardness of the intermediate layer is greater than 0, preferably greater than 2, more preferably greater than 5, in Shore C hardness, with the upper limit being preferably equal to or less than 20, more preferably equal to or less than 15, and even more preferably equal to or less than 10. If this value is too small, the amount of spin on a full shot may increase, resulting in a failure to achieve the desired distance. On the other hand, if this value is too large, the initial velocity on a full shot may decrease, resulting in a failure to achieve the desired distance and a deterioration in crack resistance when hit repeatedly.

[0053] The value obtained by subtracting the surface hardness of the core from the material hardness of the envelope layer is 0 or greater, preferably 1 or greater, more preferably 2 or greater, in Shore C hardness, with the upper limit being preferably 17 or less, more preferably 12 or less, and even more preferably 7 or less. If this value is too small, the amount of spin on a full shot may increase, and the desired distance may not be achieved. On the other hand, if this value is too large, the initial velocity on a full shot may decrease, and the desired distance may not be achieved, or the durability to cracking may decrease when hit repeatedly.

[0054] [ Layer thickness relationships 〕 In the present invention, the thickness relationship of each layer is expressed by the following formula: (Cover thickness + Mid layer thickness) < Surrounding layer thickness The above formula is satisfied. That is, the value of the envelope layer thickness / (cover thickness + intermediate layer thickness) is greater than 1.0, preferably 1.1 or greater, more preferably 1.2 or greater, with an upper limit of 2.0 or less, more preferably 1.8 or less, and even more preferably 1.6 or less. Furthermore, the value obtained by subtracting the total thickness of the cover and intermediate layer from the envelope layer thickness is greater than 0, preferably 0.2 or greater, more preferably 0.4 or greater, with an upper limit of 2.1 or less, more preferably 1.8 or less, and even more preferably 1.5 or less. Furthermore, if the above range is not met, it becomes difficult to achieve both low spin and high initial velocity on full shots, and the desired distance may not be achieved.

[0055] The value obtained by subtracting the intermediate layer thickness from the envelope layer thickness is preferably 1.00 mm or more, more preferably 1.30 mm or more, and even more preferably 1.60 mm or more, with the upper limit being preferably 3.20 mm or less, more preferably 3.00 mm or less, and even more preferably 2.80 mm or less. If the above value deviates from the above range, it becomes difficult to achieve both low spin and high initial velocity on full shots, and the desired flight distance may not be achieved.

[0056] [ Relationship between volume and hardness of each layer 〕 [Core volume (mm 3 ) × (Shore C hardness of core surface + Shore C hardness of core center) / 2) is Core·vh, and the volume of the surrounding layer material (mm 3 ) × Shore C hardness of the surrounding layer material] is E·vh, and [volume of the intermediate layer material (mm 3 ) × Shore C hardness of intermediate layer material) is expressed as I·vh, 0.80≦(E·vh + I·vh) / Core·vh ≦2.00 It is preferable that the following be satisfied. Specifically, the value of (E·vh + I·vh) / Core·vh is preferably 0.80 or more, more preferably 1.00 or more, and even more preferably 1.10 or more, with the upper limit being preferably 2.00 or less, more preferably 1.90 or less, and even more preferably 1.80 or less. If the value deviates from the above range, it becomes difficult to achieve both low spin and high initial velocity on full shots, and the desired flight distance may not be achieved.

[0057] The Core·vh value is preferably 700 or greater, more preferably 800 or greater, and even more preferably 900 or greater, with the upper limit being preferably 1600 or less, more preferably 1400 or less, and even more preferably 1200 or less. If this value is too large, the spin rate may increase, resulting in reduced flight distance, or the feel on impact may be too hard. On the other hand, if this value is too small, the resilience may be too low, resulting in reduced flight distance, the feel on impact may be too soft, or durability to cracking upon repeated impact may be poor.

[0058] The value of E·vh is preferably at least 650, more preferably at least 750, and even more preferably at least 850, with the upper limit being preferably at most 1600, more preferably at most 1400, and even more preferably at most 1200. If the value is outside the above range, the amount of spin on a full shot will increase, and the desired flight distance may not be achieved.

[0059] The value of I·vh is preferably at least 260, more preferably at least 360, and even more preferably at least 460, with the upper limit being preferably at most 850, more preferably at most 700, and even more preferably at most 560. If the value is outside the above range, the amount of spin on a full shot will increase, and the desired flight distance may not be achieved.

[0060] A large number of dimples can be formed on the outer surface of the cover. There are no particular limitations on the number of dimples that can be arranged on the cover surface, but the number is preferably 250 or more, more preferably 300 or more, and even more preferably 320 or more, with the upper limit being preferably 440 or less, more preferably 400 or less, and even more preferably 360 or less. If the number of dimples exceeds the above range, the ball's trajectory may be lower, resulting in a shorter flight distance. Conversely, if the number of dimples is lower, the ball's trajectory may be higher, resulting in a shorter flight distance. The dimples may be arranged in a tetrahedral, octahedral, icosahedral, or other multifaceted polygonal symmetry, or in a rotational symmetry about an axis connecting the poles.

[0061] It is preferable to form two or more types of dimples with different diameters and / or depths, and more preferably three or more types. The planar shape of the dimples can be any one or a combination of two or more types, such as circular, various polygonal, dewdrop, or other elliptical shapes. For example, when using circular dimples, the diameter can be approximately 2.5 mm to 6.5 mm, and the depth can be 0.07 mm to 0.30 mm. The cross-sectional shape of the dimples can be defined by one or a combination of two or more types, such as an arc, a cone, a pan bottom, or a curve expressed by various functions, and may have multiple inflection points other than near the edges.

[0062] The dimple surface coverage (SR value) (%), which is the percentage of the total area of ​​the imaginary sphere enclosed by the edges of each dimple, is desirably 70% to 90% in order to fully demonstrate aerodynamic characteristics. Furthermore, the cylindrical volume ratio (V0), which is the value obtained by dividing the spatial volume of the dimple below the plane enclosed by the edges of each dimple by the volume of a cylinder whose base is the plane and whose height is the maximum depth of the dimple from this base, is preferably 0.35 to 0.80 in order to optimize the trajectory of the ball. Furthermore, the VR value, which is the ratio of the total volume of dimples formed below the plane enclosed by the edges of the dimples to the volume of the ball as if no dimples were present, is preferably 0.6% to 1.0%. Any deviation from the above-mentioned ranges may result in a poor trajectory and an insufficient distance. Furthermore, in order to satisfy the rule for symmetry in ball flight distance, the volume of dimples near the poles may be made smaller and the volume of dimples near the equator may be made larger than the volume of dimples near the poles and equator.

[0063] A paint film layer (coating layer) can be formed on the surface of the cover. This paint film layer can be applied using various paints, and as the paint, a paint composition containing a urethane paint composed of a polyol and a polyisocyanate as the main component is preferably used, since the paint must be able to withstand the harsh conditions of use of the golf ball.

[0064] Examples of the polyol component include acrylic polyols, polyester polyols, etc. These polyols include modified polyols, and other polyols may be added to further improve workability.

[0065] As the polyol component, it is preferable to use two types of polyester polyols in combination. In this case, if the two types of polyester polyols are component (a) and component (b), the polyester polyol of component (a) can be a polyester polyol having a cyclic structure introduced into the resin skeleton, such as a polyester polyol obtained by polycondensation of a polyol having an alicyclic structure such as cyclohexanedimethanol with a polybasic acid, or a polyol having an alicyclic structure with a diol or triol with a polybasic acid. On the other hand, the polyester polyol of component (b) can be a polyester polyol having a multi-branched structure, such as a polyester polyol having a branched structure such as "NIPPOLAN 800" manufactured by Tosoh Corporation.

[0066] On the other hand, the polyisocyanate is not particularly limited and may be a commonly used aromatic, aliphatic, alicyclic, or other polyisocyanate, such as tolylene diisocyanate, diphenylmethane diisocyanate, xylylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, lysine diisocyanate, isophorone diisocyanate, 1,4-cyclohexylene diisocyanate, naphthalene diisocyanate, trimethylhexamethylene diisocyanate, dicyclohexylmethane diisocyanate, 1-isocyanato-3,3,5-trimethyl-4-isocyanatomethylcyclohexane, etc. These may be used alone or in combination.

[0067] Various organic solvents can be mixed into the coating composition depending on the coating conditions. Examples of such organic solvents include aromatic solvents such as toluene, xylene, and ethylbenzene, ester solvents such as ethyl acetate, butyl acetate, propylene glycol methyl ether acetate, and propylene glycol methyl ether propionate, ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone, ether solvents such as diethylene glycol dimethyl ether, diethylene glycol diethyl ether, and dipropylene glycol dimethyl ether, alicyclic hydrocarbon solvents such as cyclohexane, methylcyclohexane, and ethylcyclohexane, and petroleum hydrocarbon solvents such as mineral spirits.

[0068] The thickness of the coating layer made of the above coating composition is not particularly limited, but is usually 5 to 40 μm, preferably 10 to 20 μm. The coating layer thickness here refers to the average thickness of the coating measured at three locations: the center of the dimple and two locations between the center of the dimple and the edge of the dimple.

[0069] In the present invention, the elastic work recovery rate of the coating layer made of the above-mentioned coating composition must be 60% or more, and preferably 80% or more. If the elastic work recovery rate of this coating layer is within the above range, the coating layer will have high elasticity, therefore a high self-repair function and excellent abrasion resistance. Furthermore, the various performance properties of golf balls coated with the above-mentioned coating composition can be improved. The above-mentioned elastic work recovery rate can be measured as follows.

[0070] The elastic work recovery is a parameter of the nanoindentation method, which evaluates the physical properties of a coating layer. Conventional methods can only measure the size of the deformation mark (plastic deformation mark) corresponding to the maximum load. However, the nanoindentation method automatically and continuously measures the relationship between the indentation load and the indentation depth. This allows for highly accurate evaluation of the physical properties of a coating layer without the individual variability that occurs when visually measuring deformation marks with an optical microscope. Because the coating layer on a golf ball's surface is significantly affected by impacts from drivers and various clubs, and the coating layer's influence on the physical properties of a golf ball is significant, measuring the coating layer with the ultramicrohardness test method, which can be performed with higher precision than conventional methods, is a highly effective evaluation method.

[0071] The hardness of the coating layer is preferably 40 or more, more preferably 60 or more, in Shore M hardness, with an upper limit of preferably 95 or less, more preferably 85 or less. This Shore M hardness conforms to ASTM D2240. The hardness of the coating layer is preferably 40 or more, more preferably 50 or more, in Shore C hardness. The upper limit is preferably 80 or less, more preferably 70 or less. This Shore C hardness conforms to ASTM D2240. If the coating layer has a hardness that is too high above the above range, the coating may become brittle upon repeated impacts, potentially making it unable to protect the cover layer. If the coating layer has a hardness that is too low below the above range, the ball surface may be easily scratched when hit against a hard object, which is undesirable.

[0072] When using the above coating composition, the coating composition of the present invention can be prepared at the time of coating a golf ball manufactured by a known method, applied to the surface using a conventional coating process, and then dried to form a coating layer on the surface of the ball. In this case, the coating method can be suitably spray coating, electrostatic coating, dipping, or the like, and is not particularly limited.

[0073] The multi-piece solid golf ball of the present invention can be made to conform to the Rules of Golf for competitive use, with an outer diameter that does not pass through a ring with an inner diameter of 42.672 mm, and a mass preferably ranging from 45.0 to 45.93 g. [Example]

[0074] EXAMPLES The present invention will be specifically explained below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0075] [Examples 1 to 4, Comparative Examples 1 to 8] Core formation The rubber compositions of Examples 1 to 4 and Comparative Examples 1 to 7 shown in Table 1 were prepared, and then vulcanized and molded under the vulcanization conditions of each example shown in Table 1 to produce solid cores.

[0076] However, for Comparative Example 8, a core was prepared based on the formulation in Table 1 in the same manner as above.

[0077] [Table 1]

[0078] The details of each component listed in Table 1 are as follows: Polybutadiene A: JSR Corporation, product name "BR01" Polybutadiene B: JSR Corporation, product name "BR51" Zinc acrylate: "ZN-DA85S" (Nippon Shokubai Co., Ltd.) Organic peroxide (1): Dicumyl peroxide, trade name "Percumyl D" (manufactured by NOF Corporation) Organic peroxide (2): a mixture of 1,1-di(t-butylperoxy)cyclohexane and silica, trade name "Perhexa C-40" (manufactured by NOF Corporation) Antioxidant: 2,2-methylenebis(4-methyl-6-butylphenol), product name "Nocrac NS-6" (manufactured by Ouchi Shinko Chemical Industry Co., Ltd.) Zinc oxide: Product name "Triple Zinc Oxide" (manufactured by Sakai Chemical Industry Co., Ltd.)

[0079] Enveloping layer formation Next, for Examples 1 to 4 and Comparative Examples 1 and 2, an envelope layer was formed around the core by injection molding using envelope layer material with the No. 1 formulation shown in Table 2. For Comparative Example 8, an envelope layer was prepared in the same manner as above, based on the formulation in Table 2. Note that no envelope layer was formed in Comparative Examples 3 to 7.

[0080] Formation of the intermediate layer Next, for Examples 1 to 4 and Comparative Examples 1 and 2, an intermediate layer was formed around the envelope-layer-coated sphere obtained above by injection molding using an intermediate layer material of No. 2 formulation shown in Table 2. For Comparative Examples 3 to 7, an intermediate layer was formed around the core obtained above by injection molding using an intermediate layer material of No. 1 or No. 2 formulation shown in Table 2. For Comparative Example 8, an envelope layer was prepared based on the formulation in Table 2, as in Examples 1 to 4 and Comparative Examples 1 and 2 above.

[0081] Formation of the cover (outermost layer) Next, a cover (outermost layer) was formed around each of the intermediate layer-covered balls by injection molding using cover material No. 3 of the formulations shown in Table 2. A number of predetermined dimples common to all Examples and Comparative Examples were formed on the cover surface. For Comparative Example 8, a cover with a number of dimples formed on the outer surface was prepared in the same manner as above.

[0082] [Table 2]

[0083] The trade names of the main materials listed in the table are as follows: "HPF1000" and "HPF2000" are trademarks of The Dow Chemical Company. "Himilan 1605", "Himilan 1706", and "AM7329" are ionomers manufactured by Mitsui Dow Polychemicals "Surlyn 7930" and "Surlyn 6320" are ionomers manufactured by The Dow Chemical Company. "Nucrel 9-1" (trademark) manufactured by DuPont "Nucrel" "Low molecular weight polyolefin" Sanwax 161-P manufactured by Sanyo Chemical Industries, Ltd. "Magnesium stearate" NOF Corporation's "Zinc Stearate G" "Titanium oxide" "A-190" manufactured by Sakai Chemical Industry Co., Ltd.

[0084] The dimples common to all examples and comparative examples were eight types of circular dimples, the details of which are shown in Table 3 below, and their arrangement as shown in Figure 2. Figure 2(A) shows a plan view of the dimples as seen from directly above with the ball's pole at the center, and Figure 2(B) shows a plan view of the dimples as seen from diagonally above with the ball's pole shifted upward in Figure 2(A). Note that in Figure 2, the symbol D indicates a dimple, and the symbol P indicates the pole of golf ball G.

[0085] [Table 3]

[0086] Dimple definition Edge: The highest point on the cross section passing through the center of the dimple Diameter: The diameter of the plane enclosed by the dimple edge Depth: The maximum depth of the dimple from the plane bounded by the dimple edge SR: The ratio of the total dimple area, defined as the plane surrounded by the edges of the dimples, to the area of ​​the ball as if no dimples existed. Dimple volume: The volume of the dimple below the plane surrounded by the dimple edge Cylinder volume ratio V0: The ratio of the dimple volume to the volume of a cylinder with the same diameter and depth as the dimple VR: The total volume of the dimples formed below the plane surrounded by the edges of the dimples is the volume of the ball as if no dimples existed.

[0087] The physical properties of each of the resulting golf balls, such as the surface and center hardness of the core, the outer diameter of the core and each coated sphere, the thickness of each layer and the material hardness, were evaluated by the methods described below and are shown in Table 4.

[0088] The outer diameter of each of the core, the envelope layer-coated sphere, and the intermediate layer-coated sphere The temperature was adjusted in a thermostatic chamber at 23.9±1°C for at least 3 hours, and then measurements were taken at five random points on the surface in a room at 23.9±2°C. The average value was used as the measurement value for one sphere, and the average value for 10 measurements was calculated.

[0089] Ball diameter The ball was placed in a thermostatic chamber at 23.9±1°C for at least three hours, and then 15 randomly selected dimple-free locations were measured in a room at 23.9±2°C. The average value was used as the measurement value for one ball, and the average value for 10 balls was calculated.

[0090] Deflection of the core and ball The core or the target covered sphere of the ball is placed on a hard plate and the amount of deflection is measured when an initial load of 98 N (10 kgf) is applied and a final load of 1275 N (130 kgf) is applied. The above deflection amount is measured in a room at 23.9 ± 2°C after being regulated at a temperature of 23.9 ± 1°C for at least three hours. The pressure speed of the head compressing the core, each layer of covered sphere, or the ball is 10 mm / s.

[0091] Core center and surface hardness The core's surface is spherical, and the needle of the hardness tester was set nearly perpendicular to the spherical surface, and the core's surface hardness, Cs, was measured in Shore C hardness in accordance with ASTM D2240. Hardness was measured using an automatic rubber hardness tester "P2" manufactured by Kobunshi Keiki Co., Ltd., equipped with a Shore C hardness tester. The maximum hardness value was read. All measurements were performed in an environment of 23±2°C. The core's center hardness, Cc, was measured by cutting the core into a hemisphere, flattening the cross section, and pressing the needle of the hardness tester perpendicular to the measurement area. It is expressed as a Shore C hardness value.

[0092] Material hardness of the envelope layer, mid layer, and cover (Shore C hardness, Shore D hardness) The resin material for each layer was molded into a 2 mm thick sheet and left to stand at a temperature of 23 ± 2°C for two weeks. Three sheets were stacked together during measurement. The Shore C hardness and Shore D hardness were measured using a Shore C hardness tester and a Shore D hardness tester, respectively, in accordance with the ASTM D2240 standard. To measure the hardness, an automatic rubber hardness tester "P2" manufactured by Kobunshi Keiki Co., Ltd., equipped with a Shore C or Shore D hardness tester, was used. The hardness value was read as the maximum value.

[0093] [Table 4]

[0094] The flight performance (1) to (3) of each golf ball was evaluated as follows. The results are shown in Table 5.

[0095] (1) Distance performance (W#1) A driver (W#1) was attached to a golf hitting robot, and the distance traveled when hitting the ball at a head speed of 45 m / s was measured and judged according to the following criteria. The club used was the Bridgestone Sports TourStage X-Drive 410 (2007 model) (loft angle: 9.5°). The spin rate was also measured immediately after hitting the ball using an initial condition measuring device. <Judgment criteria> ◎ Total flying distance of 235.0m or more 〇 Total distance: 234.0m or more and less than 235.0m × Total flying distance less than 234.0m

[0096] (2) Distance performance (W#1) A driver (W#1) was attached to the golf hitting robot, and the distance was measured when hitting the ball at a head speed of 40 m / s, and judged according to the following criteria. The club used was the Bridgestone Sports "TourStage X-Drive 410 (2007 model)" (loft angle: 9.5°), as above. The spin rate was also measured using an initial condition measuring device on the ball immediately after hitting. <Judgment criteria> ◎ Total distance of 208.0m or more 〇 Total distance: 207.0m or more and less than 208.0m × Total flying distance less than 207.0m

[0097] (3) Distance performance (I#6) An iron (I#6) was attached to the golf hitting robot, and the ball was hit at a head speed of 40 m / s, and the flight distance was measured and judged according to the following criteria. The club used was the "J's Classical Edition" (I#6) manufactured by Bridgestone Sports Co., Ltd. The spin rate was also measured using an initial condition measuring device on the ball immediately after impact. <Judgment criteria> ◎ Total flying distance of 160.0m or more 〇 Total distance: 158.5m or more and less than 160.0m × Total flying distance less than 158.5m

[0098] [Table 5]

[0099] As shown in the results in Table 5, the golf balls of Comparative Examples 1 to 8 are inferior to the products of the present invention (Examples) in the following respects. In Comparative Example 1, the envelope layer is thinner than the combined thickness of the cover and the intermediate layer, and the envelope layer material is softer than the core surface hardness. As a result, the balance between the spin rate and the initial velocity on full shots is poor, resulting in a failure to achieve the desired distance. In Comparative Example 2, the thickness of the envelope layer is thinner than the combined thickness of the cover and the intermediate layer. As a result, the balance between the spin rate and the initial velocity on full shots is poor in terms of distance (1) and distance (3), and the desired distance is not achieved. Comparative Example 3 has a three-piece ball structure without an envelope layer, which results in a poor balance between the amount of spin and the initial velocity on full shots, preventing the desired distance from being achieved. Comparative Example 4 has a three-piece ball structure without an envelope layer. As a result, in terms of distance (1) and distance (2), the balance between the spin rate and the initial velocity on full shots is poor, and the desired distance is not achieved. Comparative Example 5 has a three-piece ball structure without an envelope layer, and as a result, in terms of flight (2), the balance between the spin rate and the initial velocity on full shots is poor, resulting in a failure to achieve the desired flight distance. Comparative Example 6 has a three-piece ball structure without an envelope layer. As a result, in terms of distance (1) and distance (2), the balance between the spin rate and the initial velocity on full shots is poor, and the desired distance is not achieved. Comparative Example 7 has a three-piece ball structure without an envelope layer. As a result, in terms of distance (2) and distance (3), the balance between the spin rate and the initial velocity on full shots is poor, and the desired distance is not achieved. In Comparative Example 8, the cover material hardness is softer than the intermediate layer material hardness, resulting in a large amount of spin on full shots with a driver (W#1), which does not achieve the desired distance.

Claims

1. A multi-piece solid golf ball having a core, an envelope layer, a mid layer, and a cover, wherein the core is formed from a single layer or multiple layers of a rubber composition, and the envelope layer, the mid layer, and the cover are each formed from a single layer of a resin material, and the resin material of one or both of the envelope layer and the mid layer is selected from the group consisting of the following components (A) to (D): (a-1) an olefin-unsaturated carboxylic acid binary random copolymer and / or a metal ion-neutralized product of an olefin-unsaturated carboxylic acid binary random copolymer; (a-2) a metal ion-neutralized product of an olefin-unsaturated carboxylic acid-unsaturated carboxylic acid ester terpolymer and / or an olefin-unsaturated carboxylic acid-unsaturated carboxylic acid ester terpolymer, (A) a base resin blended in a mass ratio of 100:0 to 0:100; (B) a non-ionomer thermoplastic elastomer in a mass ratio of 100:0 to 50:50, (C) 5 to 120 parts by mass of a fatty acid and / or a derivative thereof having a molecular weight of 228 to 1500; (D) 0.1 to 17 parts by mass of a basic inorganic metal compound capable of neutralizing unneutralized acid groups in the components (A) and (C) The hardness relationship of each layer is expressed by the following two formulas: Hardness of the cover material > hardness of the intermediate layer material, and Material hardness of the envelope layer ≧ surface hardness of the core (However, the hardness in the above formula means Shore C hardness.) and the thickness relationship of each layer satisfies the following formula: (Cover thickness + intermediate layer thickness) < Surrounding layer thickness A multi-piece solid golf ball characterized by satisfying the above.

2. The hardness relationship between each layer is as follows: Cover material hardness > Intermediate layer material hardness > Surrounding layer material hardness ≥ Core surface hardness (However, the hardness in the above formula means Shore C hardness.) 2. The multi-piece solid golf ball of claim 1, wherein the above formula satisfies the above formula.

3. 2. The multi-piece solid golf ball according to claim 1, wherein the resin materials of both the envelope layer and the intermediate layer are different types of highly neutralized resin materials containing components (A) to (D) as essential components.

4. The thickness relationship of each layer is as follows: envelope layer thickness / (cover thickness+intermediate layer thickness)≧1.2 4. The multi-piece solid golf ball according to claim 1, wherein the above formula (1) is satisfied.

5. The relationship between the core diameter and the ball diameter is given by the following formula: 0.65≦(core diameter) / (ball diameter)≦0.78 5. The multi-piece solid golf ball according to claim 1, wherein the above formula (1) is satisfied.

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