JP2017079905A - Multi-piece solid golf ball - Google Patents

Abstract

SOLUTION: A multi-piece solid golf ball of the present invention is the golf ball having a core and a cover, and making an intermediate layer of at least one layer interpose therebetween. The golf ball is characterized as follows: a hardness value obtained by subtracting the surface hardness of an intermediate layer coating sphere from the ball surface hardness and the hardness value obtained by subtracting the core surface hardness from the surface hardness of the intermediate layer coating sphere is adjusted in a predetermined range; each hardness value of a core center, a 5 mm position from the core center, a 10 mm position from the core center, a 15 mm position from the core center and the core surface in the core hardness distribution is determined in the predetermined range; and the value of V/H is assumed in the predetermined range when a ball initial velocity (m/s) is V and a bending amount (mm) in the predetermined load is H to the ball.EFFECT: According to the golf ball of the present invention, a ball structure becoming low-spin is provided in full shot for a general amateur golfer, and a good flying distance can be obtained in hitting with the driver (W#1) and the good flying distance can be obtained even as for the hitting by iron, and thereby it can strike a balance of flipping feeling between soft feeling and flying feeling as for feeling of hitting.SELECTED DRAWING: None

Description

  The present invention relates to a multi-piece solid golf ball having at least one core and at least one cover, and having at least one intermediate layer interposed therebetween.

  In recent years, various golf balls have been designed to increase the flight distance by increasing the number of golf balls and by designing a cover with an inner / soft outer / hardness whose outermost layer is harder than the intermediate layer. Proposed. As such a golf ball, for example, Japanese Patent No. 3505922, Japanese Patent No. 35339953, Japanese Patent No. 3575524, Japanese Patent No. 3661831, Japanese Patent No. 3575525, Japanese Patent No. 3428454, and Japanese Patent No. 3468153 are disclosed. Examples described in Japanese Patent Publication Nos. 3,685,245, 3,685,248, 3,772,252, 4,092,532, 5,042,455, and 5,445,620. In addition to the above technique, the four-piece solid golf is formed by forming a ball structure on a cover of three layers, an envelope layer, an intermediate layer, and an outermost layer, and forming the intermediate layer harder than the envelope layer and the outermost layer harder than the intermediate layer. Balls have been proposed, and examples thereof include golf balls described in Japanese Patent No. 3304891 and Japanese Patent No. 3304892. Furthermore, spin-type golf balls have been proposed in which the outermost layer is made of urethane and the outermost layer is softer than the intermediate layer, and the inner and outer soft balls are, for example, Japanese Patent Application Laid-Open Nos. 2015-077405 and 2015. The golf ball described in Japanese Patent No. 0470502 is mentioned.

  However, in the above golf balls, the hardness distribution of the core is not adequately optimized, and there is still room for improvement in the flight distance increase due to the low spin at the time of full shot, especially for general players and amateur golfers. . In addition, the golf ball described above has an insufficient flight distance when hit with a middle iron, and further has room for improving the hit feeling and durability during repeated hits.

Japanese Patent No. 3505922 Japanese Patent No. 3304891 Japanese Patent No. 3304892 Japanese Patent No. 3533953 Japanese Patent No. 3575524 Japanese Patent No. 3661831 Japanese Patent No. 3575525 Japanese Patent No. 3428454 Japanese Patent No. 3468153 Japanese Patent No. 3658245 Japanese Patent No. 3685248 Japanese Patent No. 3772252 Japanese Patent No. 4092532 Japanese Patent No. 50442455 Japanese Patent No. 5445620 JP2015-077405 Japanese Patent Laying-Open No. 2015-0470502

  The present invention has been made in view of the above circumstances. For general and amateur golfers, not only the flight distance when hitting a driver (W # 1) but also the flight distance when hitting a middle iron can be obtained well, and the software An object of the present invention is to provide a multi-piece solid golf ball that provides a good feel that strikes a balance between feeling and playing, and that is excellent in cracking durability when repeatedly hit.

  As a result of intensive studies to achieve the above object, the present inventors have found that in a multi-piece solid golf ball having a core and a cover, and at least one intermediate layer interposed therebetween. A value obtained by subtracting the surface hardness of the intermediate layer-coated sphere from the surface hardness of the ball, a value obtained by subtracting the core surface hardness from the surface hardness of the intermediate layer-coated sphere, and the core hardness distribution, the core center, a position 5 mm from the core center, The hardness at each position on the core surface at a position 10 mm from the core center, 15 mm from the core center, and the core surface is adjusted to a specific range, and the value obtained by subtracting the core center hardness from the core surface hardness is adjusted to a specific range, m / s) is V, and when the deflection amount (mm) from the initial load 98N to the final load 1,275N applied to the ball is H, the value of V / H is a specific range. By adjusting to, especially for general and amateur golfers, not only the flight distance when hitting the driver (W # 1), but also the flight distance when hitting the middle iron can be obtained well, and the soft feeling and flying feeling It has been found that a good hitting feeling that achieves both playing feeling and a superior durability against cracking at the time of repeated hitting, and has led to the present invention.

Accordingly, the present invention provides the following multi-piece solid golf ball.
[1] In a multi-piece solid golf ball having a core and a cover and having at least one intermediate layer interposed therebetween, the surface hardness of the intermediate layer-covered sphere is subtracted from the surface hardness of the ball. The value is 7 to 15 in Shore D hardness, the value obtained by subtracting the core surface hardness from the surface hardness of the intermediate layer coated sphere is within ± 6 in Shore D hardness, and in the core hardness distribution, the JIS-C hardness at the center of the core Is 55 ± 5, the JIS-C hardness is 57 ± 5 at a position 5 mm from the core center, the JIS-C hardness is 57 ± 5 at a position 10 mm from the core center, and the JIS-C hardness 70 is 15 mm from the core center. The JIS-C hardness of the core surface is 79 ± 5, the value obtained by subtracting the core center hardness from the core surface hardness is 22 or more in JIS-C hardness, and the initial ball velocity (m / s) is V vs ball Te, when the deflection amount of the initial load 98N until a final load 1,275N (mm) of the H, that the value of V / H is ^{18~24 (m / s · mm -1} ) Characteristic multi-piece solid golf ball.
[2] The multi-piece solid golf ball according to [1], wherein a value obtained by subtracting the surface hardness of the intermediate layer covering sphere from the surface hardness of the ball is 8 to 13 in Shore D hardness.
[3] In the core hardness distribution, the JIS-C hardness at the core center is 55 ± 3, the JIS-C hardness at the position 5 mm from the core center is 57 ± 3, and the JIS-C hardness at the position 10 mm from the core center is 57 ±. 3. The multi-piece solid golf ball according to [1] or [2], wherein the JIS-C hardness at a position 15 mm from the center of the core is 70 ± 3, and the JIS-C hardness of the core surface is 79 ± 3.
[4] In the core hardness distribution, the JIS-C hardness at the core center is 55 ± 2, the JIS-C hardness at 5 mm from the core center is 57 ± 2, and the JIS-C hardness at 10 mm from the core center is 57 ± 2. 2. The multi-piece solid golf ball according to [1] or [2], wherein the JIS-C hardness at a position 15 mm from the center of the core is 70 ± 2 and the JIS-C hardness of the core surface is 79 ± 2.
[5] When the JIS-C hardness at the core center is (Cc), the JIS-C hardness at a position 10 mm from the core center is (C10), and the JIS-C hardness at the core surface is (Cs) in the core hardness distribution. The following formulas (1) to (3)
0 <(C10) − (Cc) ≦ 8 (1)
(C10)-(Cc) <(Cs)-(C10) (2)
15 <(Cs)-(C10) (3)
The multi-piece solid golf ball according to any one of [1] to [4], which satisfies the relationship:
[6] When a load of 6864 N is applied to the golf ball, the pressure area (mm ² ) that is the area of the golf ball in contact with the plane is PS ₇ , and the area of the circle in the cross section along the diameter of the golf ball is S is the virtual plane area (mm ² ) when there is no dimple on the surface of the golf ball, and H is the amount of deflection (mm) from the initial load 98N to the final load 1,275N applied to the golf ball. And when
PS ₇ /S/H×100≧6.20 (mm ⁻¹ ) (4)
The multi-piece solid golf ball according to any one of [1] to [5], wherein:
[7] When a load of 1961 N is applied to the golf ball, the pressure area (mm ² ) that is the area of the golf ball in contact with the plane is PS ₂ , and the area of the circle in the cross section along the diameter of the golf ball is S is the virtual plane area (mm ² ) when there is no dimple on the surface of the golf ball, and H is the amount of deflection (mm) from the initial load 98N to the final load 1,275N applied to the golf ball. And when
PS ₂ /S/H×100≧1.85 (mm ⁻¹ ) (5)
The multi-piece solid golf ball according to any one of [1] to [6], wherein:

  According to the multi-piece solid golf ball of the present invention, a general amateur golfer has a ball structure that achieves a low spin on a full shot. As a result, a good flight distance and an iron hit when hitting a driver (W # 1) But good flight distance can be obtained. In addition, the golf ball feels soft and has a feeling of flying. Furthermore, the golf ball of the present invention maintains a satisfactory level of cracking durability when repeatedly hit.

It is an expanded sectional view of one dimple of the golf ball used in Examples 1 and 2. 6 is an enlarged cross-sectional view of one dimple of a golf ball used in Example 3. FIG. It is a figure for demonstrating the method of calculating | requiring the pressurization area of a golf ball.

Hereinafter, the present invention will be described in more detail.
The multi-piece solid golf ball of the present invention has a ball structure having a core and a cover, and at least one intermediate layer interposed therebetween.

  The diameter of the core is not particularly limited, but is 36.7 to 38.7 mm, preferably 37.1 to 38.3 mm, more preferably 37.3 to 38.1 mm, and further preferably 37.5 to 37. .9 mm. If the diameter of the core is too small, the actual initial hit speed will be low when the driver (W # 1) is hit, and the target flight distance may not be obtained. On the other hand, if the diameter of the inner layer core is too large, the durability to cracking when hitting repeatedly may deteriorate, or the target spin distance may not be obtained due to insufficient low spin effect when full shots are taken.

  The amount of deflection (mm) from the initial load 98N to the final load 1,275N applied to the core is not particularly limited, but is preferably 4.1 to 5.5 mm, more preferably 4.3 to 3. The thickness is 5.0 mm, more preferably 4.5 to 4.8 mm. If this value is too small, that is, it is too hard, the spin may increase so that it does not fly, or the feel at impact may become too hard. On the other hand, if the above value is too large, that is, if it is too soft, the resilience will be too low to fly, or the feel will be too soft, and the cracking durability when repeatedly struck may deteriorate. is there.

  The core hardness (Cc) and the cross-sectional hardness at a predetermined position described below mean the hardness measured at the center and a predetermined position of a cross-section obtained by cutting the core in half (through the center). The surface hardness (Cs) means the hardness measured on the surface (spherical surface) of the core.

  The center hardness (Cc) of the core is JIS-C hardness, preferably 50 to 60, more preferably 52 to 58, and further preferably 53 to 57. The JIS-C hardness (C5) at a position 5 mm from the center of the core is preferably 52 to 62, more preferably 54 to 60, and still more preferably 55 to 59. Furthermore, the JIS-C hardness (C10) at a position 10 mm from the center of the core is preferably 52 to 62, more preferably 54 to 60, and further preferably 55 to 59. If these hardness values are too large, the spin will increase excessively and may not fly, or the feel of hitting may be felt hard. On the other hand, if the hardness value is too small, the durability to cracking when repeatedly hit may be deteriorated, or the feel of hitting may become too soft.

  The JIS-C hardness (C15) at a position 15 mm from the center of the core is preferably 65 to 75, more preferably 67 to 73, and still more preferably 68 to 72. Moreover, about the surface hardness (Cs) of a core, it is JIS-C hardness, Preferably it is 74-82, More preferably, it is 76-80, More preferably, it is 77-81. If these hardness values are too large, the feeling of hitting may become hard, or the crack durability when repeatedly hitting may deteriorate. On the other hand, if the hardness value is too small, the spin may increase excessively, or the resilience may be lowered and may not fly.

  Next, the value (Cs)-(Cc) obtained by subtracting the core center hardness from the core surface hardness is 22 or more in JIS-C hardness, preferably 23 to 30, and more preferably 24 to 26. If the hardness difference is too small, the spin may increase and the flight distance may not be achieved.

  The value of (C10)-(Cc) is preferably 0-8, more preferably 1-6, and even more preferably 2-4. That is, this value means that the hardness distribution is not so steep from the core center to about 10 mm. If it deviates from this value, the spin at the time of a full shot increases, and the target flight distance may not be obtained, or the crack durability when repeatedly hit may be deteriorated.

  The value of (Cs)-(C10) is preferably larger than the value of (C10)-(Cc). That is, in the core hardness distribution, it means that the external hardness gradient is larger in the hardness gradient between the inner portion within 10 mm from the core center and the outer hardness gradient exceeding 10 mm. If the value of (Cs)-(C10) is smaller than the value of (C10)-(Cc), the spin at the time of a full shot increases and the target flight distance may not be obtained.

  The value of (Cs)-(C10) is preferably 10-30, more preferably 13-25, and even more preferably 15-22. That is, this value means that the hardness part between the position of 10 mm from the core center and the core surface has a steep core hardness distribution as the JIS-C hardness exceeds 15. If this value deviates from the above range, the spin at the time of a full shot increases and the target flight distance may not be obtained.

  A rubber material can be used as a main material as a core material having the above hardness distribution and deflection. Specifically, a rubber composition can be prepared by using a base rubber as a main component and adding a co-crosslinking agent, an organic peroxide, an inert filler, an organic sulfur compound, and the like thereto.

  It is preferable to use polybutadiene as the base rubber. As for polybutadiene, it is preferable that the polymer chain has cis-1,4-bond of 60% by mass or more, preferably 80% by mass or more, more preferably 90% by mass or more, and most preferably 95% by mass or more. is there. If there are too few cis-1,4-bonds in the bonds in the molecule, the resilience may decrease.

  In addition to the polybutadiene, other rubber components can be blended with the base rubber within a range that does not impair the effects of the present invention. Examples of the rubber component other than the polybutadiene include polybutadiene other than the polybutadiene, and other diene rubbers such as styrene butadiene rubber, natural rubber, isoprene rubber, and ethylene propylene diene rubber.

  Although it does not restrict | limit especially as an organic peroxide, It is suitable to use the organic peroxide whose 1 minute half-life temperature is 110-185 degreeC, and 1 type, or 2 or more types of organic peroxide are used. Things can be used. The compounding amount of the organic peroxide is preferably 0.1 parts by mass or more, more preferably 0.3 parts by mass or more with respect to 100 parts by mass of the base rubber, and the upper limit is preferably 5 parts by mass. Part or less, more preferably 4 parts by weight or less, and still more preferably 3 parts by weight or less.

  Examples of the co-crosslinking agent include unsaturated carboxylic acids and unsaturated carboxylic acid metal salts. Specific examples of the unsaturated carboxylic acid include acrylic acid, methacrylic acid, maleic acid, and fumaric acid. Acrylic acid and methacrylic acid are particularly preferably used. Although it does not specifically limit as a metal salt of unsaturated carboxylic acid, For example, what neutralized the said unsaturated carboxylic acid with the desired metal ion is mentioned. Specific examples include zinc salts such as methacrylic acid and acrylic acid, magnesium salts, and the like. In particular, zinc acrylate is preferably used.

  The unsaturated carboxylic acid and / or metal salt thereof is usually 10 parts by mass or more, preferably 15 parts by mass or more, more preferably 20 parts by mass or more, and usually 60 parts by mass as an upper limit with respect to 100 parts by mass of the base rubber. Hereinafter, preferably 50 parts by mass or less, more preferably 45 parts by mass or less, and most preferably 40 parts by mass 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.

  Moreover, in order to implement | achieve the said core satisfy | filling desired hardness distribution mentioned above, when mix | blending each component of the rubber composition for cores, water or the material containing water can be mix | blended. By blending water (a material containing water) directly into the core material, decomposition of the organic peroxide in the core composition can be promoted. Moreover, it is known that the decomposition efficiency of the organic peroxide in the core rubber composition changes depending on the temperature, and the decomposition efficiency increases as the temperature rises higher than a certain temperature. If the temperature is too high, the amount of radicals decomposed will increase too much, resulting in recombination and inactivation between radicals. As a result, radicals that effectively work for crosslinking are reduced. Here, when decomposition heat is generated by the decomposition of the organic peroxide during core vulcanization, the temperature near the core surface is maintained at about the same level as the temperature of the vulcanization mold, but the area near the core center is outside. Since the heat of decomposition of the organic peroxide decomposed from is accumulated, it becomes considerably higher than the mold temperature. When water (a material containing water) is blended directly into the core, water has a function of promoting the decomposition of the organic peroxide, so that the radical reaction as described above can be changed at the core center and the core surface. it can. That is, the decomposition of the organic peroxide is further promoted in the vicinity of the core center, and the radical inactivation is further promoted to further reduce the amount of effective radicals. In addition, cores having different dynamic viscoelastic properties at the center of the core can be obtained. A golf ball having such a core can achieve low spin, has excellent durability, and can reduce a change in resilience with time. In addition, when it replaces with said water and a zinc monoacrylate is used, water generate | occur | produces from a zinc monoacrylate by the heat | fever during kneading | mixing of a compounding material. As a result, the same effect as when water is blended can be obtained.

  There is no restriction | limiting in particular about said water, Although distilled water or tap water may be sufficient, Especially using distilled water which does not contain an impurity is employ | adopted suitably. The amount of water is preferably 0.1 parts by mass or more, more preferably 0.3 parts by mass or more, and preferably 5 parts by mass or less, with respect to 100 parts by mass of the base rubber. More preferably, it is 4 parts by mass or less.

Moreover, a monocarboxylic acid metal salt can be employed in place of the water. The monocarboxylic acid metal salt is presumed to be coordinated to the metal, and is distinguished from a dicarboxylic acid metal salt such as zinc diacrylate represented by [CH ₂ ═CHCOO] ₂ Zn, for example. The Since the monocarboxylic acid metal salt brings water into the rubber composition by performing a dehydration condensation reaction, the same effect as the above water can be obtained. In addition, since the monocarboxylic acid metal salt can be blended in the rubber composition as a powder, the work process can be simplified and it can be easily dispersed uniformly in the rubber composition. In order to perform the above reaction effectively, it is necessary to be a mono salt. The compounding amount of the monocarboxylic acid metal salt is preferably 1 part by mass or more, and more preferably 3 parts by mass or more with respect to 100 parts by mass of the base rubber. As an upper limit, the compounding amount of the monocarboxylic acid metal salt is preferably 60 parts by mass or less, and more preferably 50 parts by mass or less. If the amount of the monocarboxylic acid metal salt is too small, it is difficult to obtain an appropriate crosslinking density and Tan δ, and the low spin effect of the golf ball may not be sufficiently obtained. Further, when the amount is too large, the core becomes too hard, and it may be difficult to maintain an appropriate feel.

  As the carboxylic acid, acrylic acid, methacrylic acid, maleic acid, fumaric acid, stearic acid and the like can be used. Examples of the substitution metal include Na, K, Li, Zn, Cu, Mg, Ca, Co, Ni, and Pb. Zn is preferably used. Specific examples include zinc monoacrylate and zinc monomethacrylate, and it is particularly preferable to use zinc monoacrylate.

  As a manufacturing method of the core, a spherical molded product (core) can be formed by heat-compressing under a vulcanization condition of 140 ° C. or higher and 180 ° C. or lower and 10 minutes or longer and 60 minutes or shorter according to a conventional method.

Next, the intermediate layer will be described.
Although there is no restriction | limiting in particular in the material hardness of an intermediate | middle layer, Preferably it is 42-52 by Shore D hardness, More preferably, it is 44-50, More preferably, it is 46-48. Moreover, the surface hardness of the sphere coated with the intermediate layer is preferably 48 to 58, more preferably 50 to 56, and still more preferably 52 to 54 in terms of Shore D hardness. If the intermediate layer is too soft, the spin rate at the time of a full shot increases so that the flight distance may not be obtained. On the other hand, if the intermediate layer is too hard, the durability to cracking due to repeated impacts may deteriorate, or the feel at impact may become too hard.

  The thickness of the intermediate layer is not particularly limited, but is preferably 1.0 to 1.5 mm, more preferably 1.1 to 1.4 mm, and still more preferably 1.2 to 1.3 mm. If the thickness of the intermediate layer deviates from the above range, the low spin effect at the time of hitting the driver (W # 1) may be insufficient, and the flight distance may not be obtained.

  Although there is no restriction | limiting in particular about the material of an intermediate | middle layer, Various thermoplastic resin materials can be employ | adopted suitably. In particular, from the point that the desired effect of the present invention can be sufficiently achieved, it is preferable to employ a highly repulsive resin material as the material of the intermediate layer, for example, an ionomer resin material or a highly neutralized resin described later. It is preferred to use materials.

  Specifically, as the highly neutralized resin material, a heat-molded product of the resin composition of components (I) to (IV) described below can be employed.

It is preferable to use the following two types (I) and (II) as the base resin.
Component (I): Olefin-unsaturated carboxylic acid-unsaturated carboxylic acid ester ternary having a weight average molecular weight (Mw) of 140,000 or more and an acid content of 10 to 15% by mass and an ester content of 15% by mass or more Copolymer or its metal neutralized product (II) component: olefin-acrylic acid binary random copolymer having a weight average molecular weight (Mw) of 140,000 or more and an acid content of 10 to 15% by mass, Or the metal neutralized product By increasing the molecular weight as described above, the resilience of the resin material can be sufficiently ensured.

  Since the above base resins (I) and (II) are different from each other in the acid component and ester content constituting the copolymer, the two types of base resins are intertwined in a complicated manner, resulting in a molecular synergistic effect. It is considered that the resilience and durability can be increased. That is, the base resin (I) is a terpolymer, and a relatively soft material is selected by defining the weight average molecular weight, acid content, and ester content as described above, and the base resin (II) By selecting a relatively hard material by defining the type of acid, weight average molecular weight and acid content as components, these polymer blends can sufficiently ensure resilience and durability as a golf ball material.

  As described above, the components (I) and (II) use a copolymer or ionomer in which the weight average molecular weight (Mw) is set in a specific range. Specifically, the “Nucleel” series (Mitsui・ Use commercially available products such as DuPont Polychemical, Escor series (ExxonMobil Chemical), Surlyn series (DuPont, USA), and High Milan series (Mitsui / DuPont Polychemical). be able to.

Furthermore, it is preferable to blend (III) a basic inorganic metal compound as a component for neutralizing an acid group in the components (I), (II) and (IV) described later. By further neutralizing the resin material in this manner, it is possible to sufficiently increase the flight distance by further reducing the spin at the time of full shot without impairing the hit feeling. Examples of the metal ion of the basic inorganic metal compound include Na ⁺ , K ⁺ , Li ⁺ , Zn ²⁺ , Ca ²⁺ , Mg ²⁺ , Cu ²⁺ , and Co ^2+. Is Na ⁺ , Zn ²⁺ , Ca ²⁺ , Mg ²⁺ , more preferably Mg ²⁺ . These metal salts can be introduced into the resin using formate, acetate, nitrate, carbonate, bicarbonate, oxide, hydroxide and the like.

  The (III) basic inorganic metal compound is used in an amount corresponding to 70 mol% or more of the acid group in the resin composition. In this case, about the basic inorganic metal compound which is (III) component, the compounding quantity can be selected suitably in order to obtain a desired degree of neutralization. The blending amount depends on the degree of neutralization of the base resins (I) and (II) used, but is preferably about 100 parts by mass of the total amount of the base resins of the components (I) and (II). It is 1.0-2.5 mass parts, More preferably, it is 1.1-2.3 mass parts, More preferably, it is 1.2-2.0. In addition, the neutralization degree of the acid group in said (I)-(IV) component needs to be 70 mol% or more, Preferably it is 90 mol% or more, More preferably, it is 100 mol% or more.

  Moreover, (IV) anionic surfactant can also be mix | blended. The reason for blending the anionic surfactant is to ensure good durability after the resin molding while ensuring good fluidity in the entire resin composition. Although it does not specifically limit as an anionic surfactant, It is suitable to employ | adopt a molecular weight 140-1500. Anionic surfactants are classified into carboxylic acid type, sulfonic acid type, sulfuric acid ester type, and phosphoric acid ester type, and specifically, various fatty acids of stearic acid, behenic acid, oleic acid, maleic acid or derivatives thereof. Or one or more selected from the group of these metal salts. In particular, it is preferably selected from the group of stearic acid, oleic acid and mixtures thereof. In addition, as the organic acid metal salt of the component (R), metal soap is used, and as the metal salt, 1 to 3 metal ions are used, lithium, sodium, magnesium, aluminum, potassium, calcium. And zinc, and a metal stearate is particularly preferably used. Specifically, it is preferable to use magnesium stearate, calcium stearate, zinc stearate, or sodium stearate.

  The blending amount of the component (IV) is 1 to 100 parts by weight, preferably 10 to 90 parts by weight, more preferably 20 to 80 parts by weight with respect to 100 parts by weight of the base resin of the components (I) and (II). Part. If the blending amount of the component (IV) is small, it becomes difficult to soften the hardness of the resin material. Conversely, if the blending amount is large, the resin material becomes difficult to be molded and the surface of the material increases, resulting in a molded product. Affects.

  In the present invention, the moldability and productivity of the material can be further improved by adjusting the blending ratio of the component (III) and the component (IV). When the blending amount of the basic inorganic metal compound as the component (III) is too large, gas such as organic acid due to generation during molding decreases, but fluidity decreases. Conversely, when the amount of component (III) is small, the amount of gas generated increases. On the other hand, if the amount of the anionic surfactant as the component (IV) is too large, the amount of organic acid gas such as fatty acid increases at the time of molding, which greatly affects molding defects and productivity. Conversely, if the amount of component (IV) is small, the amount of gas generated decreases, but the fluidity and durability decrease. Therefore, the blending balance of the (III) and (IV) components is also important, and the blending ratio of the (III) component to the (IV) component is (III) :( IV) = 4.0: 96.0-1. 0: 99.0 (mass ratio), particularly 3.0: 97.0 to 1.5: 98.5 (mass ratio) is preferable.

  The proportion of the resin composition of the components (I) to (IV) described above is 50% by mass or more, preferably 60% by mass or more, more preferably 70% by mass or more, based on the total amount of the intermediate layer material. Preferably it is 90 mass% or more.

  In addition, a non-ionomer thermoplastic elastomer can be mix | blended with the said intermediate | middle layer material. The blending amount of the non-ionomer thermoplastic elastomer is preferably 1 to 50 parts by mass with respect to 100 parts by mass of the total amount of the base resin.

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

  Specific examples of the highly neutralized resin material containing the components (I) to (IV) described above include trade names “HPF 1000”, “HPF 2000”, “HPF AD1027” manufactured by DuPont, and experimental HPF SEP1264. -3 and the like.

  Arbitrary additives can be appropriately blended in the intermediate layer material depending on the application. For example, various additives such as pigments, dispersants, anti-aging agents, ultraviolet absorbers, and light stabilizers can be added. When blending these additives, the blending amount is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, with respect to 100 parts by mass of the sum of (I) to (IV). As an upper limit, Preferably it is 10 mass parts or less, More preferably, it is 4 mass parts or less.

  As for the intermediate layer material, as will be described later, it is preferable to polish the surface of the intermediate layer in order to increase the degree of adhesion with polyurethane suitably used as a cover (outermost layer). 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 material in the material.

  The specific gravity of the intermediate layer material is usually less than 1.1, preferably 0.90 to 1.05, more preferably 0.93 to 0.99. If it deviates from the range, the resilience is lowered, the flight distance cannot be increased, and the durability against cracking due to repeated impacts may be deteriorated.

  The value obtained by subtracting the core surface hardness from the surface hardness of the intermediate layer-coated sphere is within ± 6, preferably within ± 4, more preferably within ± 2, as Shore D hardness. When this value is too large, the hit feeling becomes too hard, or the durability to cracking when repeatedly hitting may deteriorate. On the other hand, if the above value is too small, the spin at the time of a full shot increases too much, and the target flight distance may not be obtained.

Next, a cover corresponding to the outermost layer of the ball will be described.
The material hardness of the cover (outermost layer) is not particularly limited, but is Shore D hardness, preferably 51 to 61, more preferably 53 to 59, and still more preferably 55 to 57.

  The surface hardness of the sphere covered with the cover (outermost layer), that is, the ball, is Shore D hardness, preferably 57 to 67, more preferably 60 to 65, and still more preferably 61 to 63. If it is softer than the above range, too many spins may occur at the time of hitting the driver (W # 1) or an iron full shot, and the target flight distance may not be achieved. When it is harder than the above range, durability against cracking due to repeated impacts may deteriorate, or the feel of impact may become too hard.

  The thickness of the cover (outermost layer) is not particularly limited, but is preferably 1.0 to 1.5 mm, more preferably 1.1 to 1.4 mm, and still more preferably 1.2 to 1.3 mm. If the range of the cover thickness is deviated, the low spin effect at the time of hitting the driver (W # 1) is insufficient and the flight distance may not be obtained.

  The value obtained by subtracting the thickness of the cover from the thickness of the intermediate layer described above is preferably −1.0 to 1.0 mm, more preferably −0.6 to 0.5 mm, and still more preferably −0. The range is 3 to 0 mm. If this value is too large or too small, the spin at the time of a full shot increases too much, and the target flight distance may not be obtained.

  Although there is no restriction | limiting in particular as a cover material, It is suitable to use an ionomer resin material.

  The manufacturing method of the multi-piece solid golf ball formed by laminating the core, intermediate layer and cover (outermost layer) described above can be performed by a conventional method such as a known injection molding method. For example, the core is placed in a predetermined injection mold, the intermediate layer material is injected to obtain an intermediate sphere, and the sphere is then placed in another injection mold to cover (the top A multi-piece golf ball can be obtained by injection molding the material of the outer layer. In addition, the cover can be laminated by a method of covering the cover (outermost layer) with an intermediate spherical body. For example, the intermediate spherical body is wrapped in two half cups previously formed into a half-shell spherical shape, and heated and pressed. can do.

  The value obtained by subtracting the surface hardness of the core from the surface hardness of the ball is Shore D hardness, preferably 4 to 16, more preferably 6 to 14, and further preferably 8 to 12. If this value is too large, the durability to cracking when repeatedly hit may deteriorate. On the other hand, if the above value is too small, the spin at the time of a full shot increases too much and a target flight distance may not be obtained.

  The value obtained by subtracting the surface hardness of the intermediate layer-coated sphere from the surface hardness of the ball is 7 to 15, preferably 8 to 13, and more preferably 9 to 11 in Shore D hardness. If the above value is too large, the durability to cracking when repeatedly struck may deteriorate. On the other hand, if the above value is too small, the spin will increase too much in a full shot, and the target flight distance may not be obtained.

  A large number of dimples can be formed on the outer surface of the cover (outermost layer). The dimples arranged on the cover surface are not particularly limited, but preferably 250 or more, more preferably 300 or more, and the upper limit is preferably 500 or less, more preferably 450 or less. it can.

The dimple surface occupancy ratio SR (that is, the ratio of the total area of the dimples to the total surface area of the phantom spherical surface of the golf ball assumed to have no dimples) is preferably 70% or more, and more preferably Is 75% or more, more preferably 80% or more. The upper limit of the surface occupation ratio SR of the dimple is not particularly limited, but is preferably 99% or less. In particular, it is preferable to dispose at least three types of dimples having different sizes, so that the dimples can be uniformly disposed on the spherical surface of the golf ball without a gap.

The dimple volume occupation ratio VR (that is, the ratio of the sum of the dimple volumes formed below the plane surrounded by the dimple edges to the phantom sphere volume of the golf ball assumed to have no dimples) is 0. The content is preferably 75% or more, more preferably 0.80% or more, and still more preferably 1.1% or more. The upper limit of the volume occupation ratio VR of the dimple is preferably 1.5% or less, and more preferably 1.4% or less.

  There are no particular restrictions on the shape of the dimple, but for example, the dimple's original aerodynamic performance is achieved by making the bottom surface of the dimple curved in a convex shape toward the outside of the golf ball at the center of the dimple. It is possible to have a predetermined pressure area to be described later without impairing the above. In the above dimple shape, the convexly curved portion can be made flat in the central region. In this case, the outer edge portion of the flat region is configured such that the corner portion is chamfered, thereby effectively increasing the contact area at the time of hitting the ball.

  Further, it is preferable that the relationship between the pressure area, the virtual plane area, and the deflection amount of the golf ball be within the range of the formula described later.

When a load of 6864 N (700 kgf) is applied to the golf ball, the pressure area (mm ² ) that is the area of the golf ball in contact with the plane is PS ₇ , and the area of the circle of the cross section along the diameter of the golf ball is S is the virtual plane area (mm ² ) when there is no dimple on the surface of the golf ball, and H is the amount of deflection (mm) from the initial load 98N to the final load 1,275N applied to the golf ball. It is preferable that the following mathematical formula is satisfied.
PS ₇ /S/H×100≧5.70 (mm ⁻¹ )
And more preferably
PS ₇ /S/H×100≧6.20 (mm ⁻¹ )

  In other words, by adopting a configuration in which the pressure area of the golf ball under the load on a general golfer's driver shot satisfies the above formula, the contact area between the ball and the golf club increases and the friction with the club increases. As a result, the backspin amount on driver shots can be reduced and the flight distance can be improved.

Further, when a load of 1961 N (200 kgf) is applied to the golf ball, the pressure area (mm ² ) that is the area of the golf ball in contact with the plane is PS ₂ , and the area of the circle of the cross section along the diameter of the golf ball is When the golf ball surface has no dimples at all, the virtual plane area (mm ² ) is S, and the amount of deflection (mm) when the golf ball is loaded with an initial load of 98N to a final load of 1,275N. When H is H, it is preferable that the following mathematical formula is satisfied.
PS ₂ /S/H×100≧1.70 (mm ⁻¹ )
And more preferably
PS ₂ /S/H×100≧1.85 (mm ⁻¹ )

  In other words, by adopting a configuration in which the pressure area of the golf ball under the load in a general golfer's approach shot satisfies the above formula, the contact area between the ball and the golf club increases, and the friction with the club The power is improved and the backspin amount on the approach shot is increased, so that it can be stopped immediately near the falling point.

  The virtual plane area S of the golf ball is determined by the diameter of the golf ball. The diameter of the golf ball may be in accordance with golf regulations for competition purposes, and is 42.80 mm or less in size that does not pass through a ring with a 42.672 mm inner diameter.

The pressure areas PS _{7 and} PS _{2 with} a predetermined load of the golf ball represent the contact area of the golf ball with the golf club at the time of a predetermined shot. Can be wide. This pressurization area PS depends on the size of the golf ball, and becomes larger as the size of the golf ball becomes larger, and becomes smaller as the size of the golf ball becomes smaller. Thus, an increase in the contact area due to the dimple structure can be evaluated without being influenced by the size of the golf ball. Further, the pressure area PS depends on the deflection amount H of the golf ball. The larger the deflection amount H, the wider the width, and the smaller the deflection amount H, the narrower. Therefore, further divide by the deflection amount H. Thus, an increase in the contact area due to the dimple structure can be evaluated without being influenced by the deflection amount of the golf ball. As for the method of measuring the pressure area, for example, pressure sensitive paper is laid on a flat surface, the target golf ball is placed, each load of 6864N and 1961N is applied to the golf ball, The total area of the areas where the pressure sensitive paper is colored by contact is measured. FIG. 3A shows an example of a pressure-sensitive paper that is actually colored when a load of 6864 N is applied to the golf ball. FIG. 3B shows a load of 1961 N applied to the same golf ball as FIG. An example of pressure-sensitive paper that actually developed color when applied. In the figure, a round part shows a dimple, and a painted part shows a colored part. The area of the colored portion can be easily obtained by using a commercially available pressure image analysis system.

  Further, the deflection amount (mm) from when the initial load 98N is applied to the ball to when the final load 1,275N is applied is not particularly limited, but is preferably 3.0 to 4.5 mm, more preferably 3. It is 2 to 4.0 mm, more preferably 3.5 to 3.8 mm. If the above value is too large, the feeling of hitting may become too soft, or the durability to cracking when repeatedly hitting may deteriorate. On the other hand, if the above value is too small, the feeling of hitting becomes too hard, and the spin at the time of a full shot increases, and the target flight distance may not be obtained.

  The initial velocity of the ball is preferably 76.4 to 77.724 m / s, preferably 76.7 m / s or more, more preferably 77.0 m / s or more in order to comply with the R & A rule standard. If the initial ball speed exceeds 77.724 m / s, the golf rule is violated and the ball is no longer a certified ball. Conversely, if the initial ball speed is too low, the desired flight distance may not be obtained during a full shot. The initial velocity of the ball is measured using the measurement apparatus and measurement conditions shown in the description of the example (paragraph [0089]).

Further, according to the present invention, when the initial velocity (m / s) of the ball is V and the deflection amount (mm) from when the initial load 98N to the final load 1,275N is applied to the ball is H, V / H Is required to be 18 to 24 (m / s · mm ⁻¹ ). The preferable value of V / H is 19 to 23.5, more preferably 20 to 23. If this value is too low, the target flight distance by the driver (W # 1) may not be obtained. On the other hand, if the above value is too large, the feeling of hitting becomes hard and the durability to cracking when repeatedly hitting may deteriorate.

  In addition, the multi-piece solid golf ball of the present invention can be used in accordance with golf rules for competition purposes, and the weight can be preferably 45.0 to 45.93 g.

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

[Examples 1 to 3, Comparative Examples 1 to 6]
Formation of Core After preparing the rubber composition shown in Table 1, the solid core of each Example and Comparative Example was produced by vulcanization molding under the vulcanization conditions shown in the same table.

In addition, the detail of each component described in Table 1 is as follows.
・ Polybutadiene A: Product name “BR01” manufactured by JSR Corporation
・ Polybutadiene B: Product name “BR730” manufactured by JSR Corporation
・ Zinc acrylate: Nippon Shokubai Co., Ltd. ・ Organic peroxide (1): Dicumyl peroxide, NOF Corporation, trade name "Park Mill D"
Organic peroxide (2): 1,1 di (t-butylperoxy) cyclohexane and silica mixture, manufactured by NOF Corporation, trade name “Perhexa C-40”
Anti-aging agent: 2,2-methylenebis (4-methyl-6-butylphenol), manufactured by Ouchi Shinsei Chemical Industry Co., Ltd., trade name “NOCRACK NS-6”
Barium sulfate (1): Trade name “Barico # 300” (manufactured by Hakusui Tech Co., Ltd.)
Barium sulfate (2): Trade name “Precipitable barium sulfate # 100” (manufactured by Sakai Chemical Industry Co., Ltd.)
・ Zinc oxide: Trade name "Zinc oxide 3 types" (manufactured by Sakai Chemical Industry Co., Ltd.)
・ Pentachlorothiophenol zinc salt: manufactured by ZHEJIANG CHO & FU CHEMI ・ Water: distilled water, manufactured by Wako Pure Chemical Industries, Ltd.

Formation of Intermediate Layer and Cover Intermediate layer-coated spheres were obtained around the core obtained above by the injection molding method using the intermediate layer material having the composition shown in Table 2. Next, a cover (outermost layer) is formed around the intermediate layer-coated sphere obtained above by injection molding using the cover material having the composition shown in the table, and the intermediate layer and cover (outermost layer) are formed around the core. A golf ball having an outer layer was produced.

Details of the materials listed in Table 2 are as follows.
・ "HPF2000": "HPF2000" manufactured by DuPont
・ “Surlin”: Ionomer made by DuPont ・ “Nuclele”: Mitsui ・ Ethylene-methacrylic acid copolymer made by DuPont Polychemical ・ “Magnesium stearate”: “Magnesium stearate G” made by NOF Corporation
・ "Calcium hydroxide": "Calcium hydroxide CLS-B" manufactured by Shiraishi Calcium
・ "Magnesium oxide": "Kyowa Mag MF150" manufactured by Kyowa Chemical Industry Co., Ltd.
"Polytail H": Mitsubishi Chemical Corporation "Hytrel 4047": Toray DuPont polyester elastomer

At this time, dimples having the specifications shown in Table 3 below are formed on the cover surfaces of the examples and comparative examples. For any of the golf balls of Examples and Comparative Examples, as shown in Table 3, six types of dimples having different diameters were arranged to obtain the same surface occupation ratio SR (%).

Dimple definition diameter: Diameter of the plane surrounded by the edge of the dimple (mm)
SR: Ratio of the total area of the dimples to the total surface area of the phantom spherical surface of the golf ball assumed to have no dimples (unit:%)

As for the dimple shape, Examples 1 and 2 and Comparative Examples 1 to 6 used dimple A (FIG. 1) and Example 3 used dimple B (FIG. 2). Of the six types of dimples having different diameters in Table 3, a typical dimple structure having a diameter of 4.4 mm is as follows.
Dimple A
In the cross-sectional shape of FIG. 1, the depth L of the deepest point is 0.150 mm.
Dimple B
2 has a depth H of 0.097 mm at the central point C, a depth D of 0.131 mm at the deepest point, and a distance from the outer peripheral edge E to the central point C as 100, the deepest point from the outer peripheral edge. The position is 39, the radius of curvature R is 0.5 mm, and the edge angle A2 is 10.5 °.

  For each of the obtained golf balls, various physical properties such as core hardness distribution, thickness and material hardness of each layer, and surface hardness of each coated sphere were evaluated by the following methods and are shown in Table 4.

Core hardness distribution The surface of the core is spherical, but a hardness meter needle was set on the spherical surface so as to be substantially perpendicular, and the core surface hardness was measured with JIS-C hardness according to JIS K6301-1975 standard.
The cross-sectional hardness at the center of the core and at a predetermined position was measured by cutting the core into a hemispherical shape, making the cross-section flat, and pressing the needle of a hardness meter vertically on the measurement part. It is shown by the value of JIS-C hardness.
In addition, the Shore D hardness of the surface of the core was measured with a type D durometer based on the ASTM D2240-95 standard.

The outer diameter of the core or intermediate layer-covered spheres Measure 5 points on any surface at a temperature of 23.9 ± 1 ° C., and use the average value as the measured value of one core or intermediate layer-covered sphere. The average value of each sphere was determined.

The diameter of the ball was measured at 5 locations at a temperature of 23.9 ± 1 ° C., and any part without any dimples was measured, and the average value was taken as the measurement value of one ball. .

Deflection amount of core and ball The core or ball was placed on a hard plate, and the deflection amount from when the initial load 98N was applied to when the final load 1275N was applied was measured. The above deflection amounts are measured values after temperature adjustment to 23.9 ° C.

Initial velocity of the ball The measurement was performed using an initial velocity measuring device of the same type as the USGA drum rotation type initial velocity meter approved by the R & A. The ball was temperature-adjusted for 3 hours or more in a 23.9 ± 1 ° C. environment, and then tested in a room at room temperature of 23.9 ± 2 ° C. 5. Using a 250 pound (113.4 kg) head (striking mass), hit the ball at a hitting speed of 143.8 ft / s (43.83 m / s) and hit a dozen balls 4 times each. The time passing through 28 ft (1.91 m) was measured, and the initial speed (m / s) was calculated. This cycle was performed in about 15 minutes.

Intermediate layer and cover material hardness (Shore D hardness)
The resin material for the intermediate layer and the cover was formed into a sheet shape having a thickness of 2 mm and left for 2 weeks or longer. Then, Shore D hardness was measured according to ASTM D2240-95 standard.

Intermediate layer coated sphere, ball surface hardness (Shore D hardness)
Measurement was performed by pressing the needle so as to be perpendicular to the surface of the intermediate layer-covered sphere or ball (cover). The surface hardness of the ball (cover) is a measured value in a land portion where no dimples are formed on the ball surface. Shore D hardness was measured with a Type D durometer conforming to the ASTM D2240-95 standard.

Pressurization area The measurement method of the pressurization area PS of the golf ball was such that pressure sensitive paper (for pressure measurement film manufactured by Fuji Film Co., Ltd., for pre-scale medium pressure) was laid on a flat surface, and the golf balls of the examples and comparative examples were installed. . Then, using a 4204 type manufactured by Instron Corporation, these golf balls were loaded with 6864 N (700 kgf) and 1961 N (200 kgf), and the total area of the areas where the pressure sensitive paper was colored by contact with the golf balls was measured. did. The area of the colored portion was determined using a prescale pressure image analysis system FPD-9270 (Fuji Film). The pressure area is the result of measurement at an arbitrary position on the golf ball.

  And the flying performance (W # 1 and I # 6), approach spin performance, hit feeling, and durability of the golf balls of the examples and comparative examples were evaluated according to the following criteria. The results are shown in Table 5.

Flying performance (W # 1 hit)
The flying distance when a golf hitting robot was hit with a driver (W # 1) at a head speed (HS) of 45 m / s was measured and evaluated according to the following criteria. The club used was “Tour Stage X-Drive 709 D430 Driver (2013 model)” (Loft 9.5 °) manufactured by Bridgestone.
[Criteria]
Total distance over 230.0m ・ ・ ・ ・ ○
Total flight distance 229.0m or more and less than 230.0m ・ ・ ・ ・ △
Total flight distance less than 229.0m ・ ・ ・ ・ ×

Flying performance (I # 6 strike)
When a golf striking robot was hit with an iron (I # 6) and hit with a head speed (HS) of 40 m / s, the flight distance was measured and evaluated according to the following criteria. The club used was “Tour Stage X-Blade 707 (2012 model)” manufactured by Bridgestone.
[Criteria]
Total distance over 173.0m ・ ・ ・ ・ ○
Total flight distance 170.0m or more, less than 173.0m ・ ・ ・ ・ △
Total flight distance less than 170.0m ・ ・ ・ ・ ×

Approach spin performance The amount of spin was measured when a golf hitting robot was hit with a sand wedge at a head speed (HS) of 20 m / s.

Hitting Feel Sensory evaluation was performed on the feeling of hitting when an amateur user hit a driver (W # 1) and hit a head speed (HS) of 40 to 50 m / s.
[Criteria]
More than 6 out of 10 people evaluated it as a good hit feeling.・ ・ ・ ・ ○
Three to five out of ten people evaluated it as a good hit feeling.・ ・ ・ ・ △
Less than 2 out of 10 people evaluated it as a good hit feeling.・ ・ ・ ・ ×

Durability A driver (W # 1) was attached to a golf striking robot and repeatedly hit at a head speed of 45 m / s. The average value was measured for each ball N = 3. The number of times when the initial ball speed of Example 1 was 97% or less compared to the initial initial average of 10 times was set to 100, and the determination was made according to the following index.
Crack index 95 or higher
Crack index less than 95 ...

The following is considered from the test results of Table 5.
In Comparative Example 1, the cover becomes soft, and as a result, the spin increases with a full shot and the flight distance does not appear.
In Comparative Example 2, the cover becomes hard, and as a result, the durability against cracking due to repeated impacts is poor.
In Comparative Example 3, the intermediate layer becomes hard, and as a result, the hit feeling at the time of full shot is poor and feels hard.
In Comparative Example 4, the intermediate layer and the cover become hard, and as a result, the feel of hitting is felt hard and the durability to cracking by repeated hitting is poor.
In Comparative Example 5, the intermediate layer becomes soft, and as a result, the spin during full shot increases and the flight distance does not appear.
In Comparative Example 6, the hardness distribution of the core is not appropriate, and as a result, the spin during full shot increases and the flight distance does not appear.

Claims (7)

In a multi-piece solid golf ball having a core and a cover, and at least one intermediate layer interposed therebetween, the value obtained by subtracting the surface hardness of the intermediate layer-coated sphere from the surface hardness of the ball is the Shore The D hardness is 7 to 15, the value obtained by subtracting the core surface hardness from the surface hardness of the intermediate layer-coated sphere is within ± 6 in Shore D hardness, and the JIS-C hardness at the center of the core is 55 ± in the core hardness distribution. 5, JIS-C hardness 57 ± 5 at a position 5 mm from the core center, JIS-C hardness 57 ± 5 at a position 10 mm from the core center, JIS-C hardness 70 ± 5 at a position 15 mm from the core center, JIS-C hardness of the core surface is 79 ± 5, the value obtained by subtracting the core center hardness from the core surface hardness is 22 or more in JIS-C hardness, and the ball initial velocity (m / s) is V, the ball Against When the deflection amount of the period load 98N until a final load 1,275N (mm) of the H, which characterized in that the value of V / H is ^{18~24 (m / s · mm -1} ) Multi-piece solid golf ball.   The multi-piece solid golf ball according to claim 1, wherein a value obtained by subtracting the surface hardness of the intermediate layer-coated sphere from the surface hardness of the ball is 8 to 13 in Shore D hardness.   In the core hardness distribution, the JIS-C hardness at the core center is 55 ± 3, the JIS-C hardness at 5 mm from the core center is 57 ± 3, the JIS-C hardness at 10 mm from the core center is 57 ± 3, the core The multi-piece solid golf ball according to claim 1 or 2, wherein the JIS-C hardness at a position 15 mm from the center is 70 ± 3, and the JIS-C hardness of the core surface is 79 ± 3.   In the core hardness distribution, JIS-C hardness at the core center is 55 ± 2, JIS-C hardness at 5 mm from the core center is 57 ± 2, JIS-C hardness at 10 mm from the core center is 57 ± 2, core 3. The multi-piece solid golf ball according to claim 1, wherein the JIS-C hardness at a position 15 mm from the center is 70 ± 2 and the JIS-C hardness of the core surface is 79 ± 2. In the core hardness distribution, when the JIS-C hardness at the core center is (Cc), the JIS-C hardness at 10 mm from the core center is (C10), and the JIS-C hardness at the core surface is (Cs), (1)-(3)
0 <(C10) − (Cc) ≦ 8 (1)
(C10)-(Cc) <(Cs)-(C10) (2)
15 <(Cs)-(C10) (3)
The multi-piece solid golf ball according to claim 1, wherein the multi-piece solid golf ball satisfies the following relationship. When a load of 6864 N is applied to the golf ball, the pressure area (mm ² ) that is the area of the golf ball in contact with the plane is PS ₇ , and the area of the circle in the cross section along the diameter of the golf ball, When the virtual plane area (mm ² ) when there is no dimple on the surface is S, and when the deflection amount (mm) from the initial load 98N to the final load 1,275N is applied to the golf ball is H ,
PS ₇ /S/H×100≧6.20 (mm ⁻¹ ) (4)
The multi-piece solid golf ball according to claim 1, wherein the multi-piece solid golf ball is satisfied. When a load of 1961 N is applied to the golf ball, the pressure area (mm ² ) that is the area of the golf ball in contact with the plane is PS ₂ , and the area of the circle in the cross section along the diameter of the golf ball is When the virtual plane area (mm ² ) when there is no dimple on the surface is S, and when the deflection amount (mm) from the initial load 98N to the final load 1,275N is applied to the golf ball is H ,
PS ₂ /S/H×100≧1.85 (mm ⁻¹ ) (5)
The multi-piece solid golf ball according to claim 1, wherein:

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