JP2023078501A - multi-piece solid golf ball - Google Patents

Abstract

To provide a golf ball that achieves a satisfactory distance on full shots with an iron, is superior in the short game, and has a good feel at impact and a good durability.SOLUTION: The golf ball comprises a core, an envelope layer, an intermediate layer, and a cover, wherein the core is formed of a rubber composition as one or more layer; the envelope layer is formed of a resin material as one or more layer; the intermediate layer is formed of a resin material as one layer; the cover is formed of a resin material as one layer having a thickness of not more than 1.0 mm; the Shore C hardness at a surface of the core, the Shore C hardness at a surface of the sphere obtained by encasing the core with the envelope layer (envelope layer-encased sphere), the Shore C hardness at a surface of the sphere obtained by encasing the envelope layer-encased sphere with the intermediate layer (intermediate layer-encased sphere) and the Shore C hardness at a surface of the ball together satisfy the conditions (Shore C hardness at surface of envelope layer-encased sphere)>Shore C hardness at surface of core) and (Shore C hardness at surface of intermediate layer-encased sphere)>(Shore C hardness at surface of ball); the golf ball also specifying the relationship between the amount of deflection when a predetermined load is applied to the core and ball, and further specifying the internal hardness distribution of the core.SELECTED DRAWING: Figure 1

Description

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

Conventionally, many attempts have been made to design balls having a multi-layered structure, and many balls have been developed that satisfy not only professional golfers but also advanced and intermediate golfers. For example, functional multi-piece solid golf balls in which the surface hardness of each of the core, envelope layer, intermediate layer and cover (outermost layer) are optimized are widespread. In addition, several techniques have been proposed to provide high-performance golf balls for professionals and middle-advanced golfers by focusing on the core hardness distribution, which occupies most of the volume of the ball, and designing various aspects of the core's internal hardness. It is

Examples of such technical documents include Patent Documents 1 to 17 below. These golf balls are multi-layered golf balls with four or more layers, and patents focusing on the surface hardness of each layer of the core, envelope layer, intermediate layer, and cover (outermost layer), thickness of each layer, core hardness distribution, etc. Literature.

However, the proposed golf ball still has room for improvement in optimizing the hardness distribution of the core and the thickness relationship with each layer. That is, many of the golf balls proposed above are insufficient in flight distance on iron shots, even if they can maintain a good flight distance when hit with a driver (W#1). Some of the golf balls proposed above exhibit sufficiently high spin performance when attempting to obtain superior flight distance performance not only when hit with a driver but also when shot with an iron. There are also golf balls that do not have high gameability, or do not have a good feel on full shots.

Also, for a certain user group of amateur users, it is possible that better golf game characteristics can be achieved by improving the flight distance performance when hit with an iron rather than the flight distance when hit with a driver. Accordingly, there is a demand among users for proposals and development of a golf ball that has excellent short-game performance while greatly improving flight distance performance when hit with an iron and improving other characteristics such as feel and durability. there is

JP-A-9-248351 Japanese Patent Application Laid-Open No. 2006-326301 JP 2007-319667 A JP 2012-071163 A Japanese Patent Application Laid-Open No. 2007-330789 JP 2008-068077 A JP 2009-034507 A JP 2009-095364 A JP 2016-101254 A JP 2016-116627 A JP 2009-095358 A JP 2016-101256 A JP-A-2008-149131 JP 2009-095365 A JP 2009-095369 A JP 2020-089633 A JP 2021-037157 A

The present invention has been devised in view of the above-mentioned circumstances, and provides an improved controllability in the short game, a softer feel, and resistance to cracking due to repeated hits, while ensuring an increase in flight distance when hit with an iron. To provide a multi-piece solid golf ball having good properties.

As a result of intensive studies in order to achieve the above object, the present inventor has developed a golf ball comprising a core, an envelope layer, an intermediate layer, and a cover, in which the cover is relatively soft and the intermediate layer is relatively hard, The present inventors have found that the problems of the present invention can be solved by focusing on forming the envelope layer adjacent to the inner side of the intermediate layer as a single layer or multiple layers so as to be softer than the intermediate layer and harder than the core surface. That is, the core is formed of a single layer or multiple layers from a rubber composition, the envelope layer is formed from a single layer or multiple layers from a resin material, the intermediate layer is formed from a single layer of a resin material, and the cover has a thickness of 1.5 mm. The surface hardness of the core, the surface hardness of the envelope-covered sphere, the surface hardness of the intermediate layer-covered sphere, and the surface hardness of the ball are determined by (the surface of the envelope-covered sphere Hardness)>(Surface hardness of the core) and (Surface hardness of the intermediate layer coated sphere)>(Ball surface hardness) are specified, and a predetermined load is applied to the core and the ball. A golf ball is designed so that B≧2.8 and 1.6≦C/B≦2.3, where C and B (mm) respectively denote the amount of deflection when the core is bent. , Cc is the Shore C hardness of the center of the core, Cs is the Shore C hardness of the surface of the core, C75 is the Shore C hardness of the position 75% of the length of the core radius from the core center toward the surface, When the Shore C hardness at a position 50% of the length of the core radius toward the cm ³ )×C50 as Core vh, the golf ball was designed to satisfy the condition of 630≦Core vh≦1000. The present inventors have found that the ball provides a very soft feel on impact, is excellent in durability to cracks on repeated impacts, and has good controllability around the green, and has thus completed the present invention.

In other words, the golf ball of the present invention is a spin-type golf ball having three or more cover layers, is specialized for flight distance on full iron shots, and is spin-intensive in the short game. Satisfies the needs of users who want controllability around them. In addition, the golf ball of the present invention provides a soft and good hitting feel on all shots. Normally, it is difficult to hit a golf ball well with a driver (W#1), and it depends on the time whether it flies well or not. On the other hand, the golf ball of the present invention is a golf ball that reliably provides a flight distance at least when hit with an iron, and is a golf ball that specializes in flight distance on full iron shots and is intended for such users. .

Accordingly, the present invention provides the following multi-piece solid golf ball.
1. A multi-piece solid golf ball comprising a core, a surrounding layer, an intermediate layer and a cover, wherein the core is made of a single layer or multiple layers and is made of a rubber composition, and the surrounding layer is made of a single layer or multiple layers and is made of a resin material. , the intermediate layer is a single layer formed of a resin material, and the cover is a single layer having a thickness of 1.0 mm or less and is formed of a resin material, and the Shore C hardness of the surface of the core and the core coated with the surrounding layer Shore C hardness of the surface of the sphere covered with the envelope layer (enveloping layer-covered sphere), Shore C hardness of the surface of the sphere obtained by covering the envelope-covered sphere with the intermediate layer (intermediate layer-covered sphere), and Shore C hardness of the surface of the ball However, the conditions of (Shore C hardness of the surface of the envelope-covered sphere)>(Shore C hardness of the surface of the core) and (Shore C hardness of the surface of the intermediate-layer-covered sphere)>(Shore C hardness of the ball surface) The amount of deflection is C (mm) when the core is loaded with an initial load of 98 N (10 kgf) to a final load of 1,275 N (130 kgf), and the ball is subjected to an initial load of 98 N (10 kgf) to a final load. When B (mm) is the amount of deflection when a load of 1,275 N (130 kgf) is applied, B≧2.8 and 1.6≦C/B≦2.3. , Cc is the Shore C hardness of the center of the core, Cs is the Shore C hardness of the surface of the core, C75 is the Shore C hardness of the position 75% of the length of the core radius from the core center toward the surface, From the core center to the surface When the Shore C hardness at the position 50% of the length of the core radius is C50, 1.0 ≤ (Cs - C75) / (C50 - Cc) ≤ 2.3 is satisfied, and the core volume V (cm ³ ) A multi-piece solid golf ball satisfying the condition 630≤Core vh≤1000, where Core vh is the value of xC50.
2. Regarding the internal hardness of the core, 3.0 ≤ (Cs - C50) / (C25 - Cc) ≤ 20, where C25 is the Shore C hardness at a position 25% of the length of the core radius from the center of the core toward the surface. 1. The multi-piece solid golf ball according to 1 above, which satisfies .0.
3. 3. The multi-piece solid golf ball of 1 or 2 above, wherein the core has an internal hardness that satisfies (Cs-C50)/(C50-Cc)≧1.1.
4. The relationship between the surface Shore C hardness of the envelope-covered sphere and the surface Shore C hardness of the intermediate layer-covered sphere is: (Surface Shore C hardness of intermediate-layer-covered sphere)>(Surface Shore C hardness of envelope-covered sphere) 4. A multi-piece solid golf ball according to any one of 1 to 3 above, which satisfies the conditions.
5. 5. The multi-piece solid golf ball of any one of 1 to 4 above, wherein the relationship between the thicknesses of the layers satisfies the following condition: (cover thickness)<(intermediate layer thickness)≦(total thickness of surrounding layers).
6. 6. The multi-piece solid golf according to any one of 1 to 5 above, wherein the thickness ratio of each layer satisfies the condition of (total thickness of surrounding layers)/(cover thickness+intermediate layer thickness)≧1.0. ball.
7. 7. The multi-piece solid golf ball of any one of 1 to 6 above, wherein the envelope layer comprises an inner envelope layer and an outer envelope layer and is formed of at least two layers.
8. The Shore C hardness of the surface hardness of each layer is expressed by the following formula (Shore C hardness of the surface of the ball)<(Shore C hardness of the surface of the intermediate layer-covered sphere)>(Shore C hardness of the surface of the outer envelope layer-covered sphere)≧ 8. The multi-piece solid golf ball according to 7 above, which satisfies the following condition: (Surface Shore C hardness of inner envelope layer-covered sphere)>(Core surface Shore C hardness).
9. 9. The multi-piece solid golf ball of any one of 1 to 8 above, wherein the relationship between the core diameter and the ball diameter satisfies the condition 0.65≦(core diameter)/(ball diameter)≦0.80.

According to the multi-piece solid golf ball of the present invention, when a full shot with an iron is made, a good flight distance can be obtained with a low spin rate, and a very soft feel can be obtained. Both the controllability in the surrounding area is good, and it is particularly useful for golf users who place importance on flight distance on full iron shots.

1 is a schematic cross-sectional view of a multi-piece solid golf ball (five-layer structure) of the present invention; FIG. FIG. 4 is a plan view showing a dimple mode (pattern) common to each example and each comparative example; 4 is a graph showing hardness distributions of cores of Examples 1 to 4. FIG. 5 is a graph showing hardness distributions of cores of Comparative Examples 1 to 5 and 7. FIG. 10 is a graph showing hardness distributions of cores of Comparative Examples 6 and 8. FIG.

The present invention will be described in more detail below.
The multi-piece solid golf ball of the present invention, as shown in FIG. A golf ball G having four or more layers with a cover 4 that In FIG. 1, the enveloping layer 2 is formed of two layers, an inner enveloping layer 2a and an outer enveloping layer 2b. A large number of dimples D are usually formed on the surface of the cover 4 . Moreover, although not shown, a coating film layer is usually formed on the surface of the cover 4 by painting. Except for the coating layer, the cover 4 is the outermost layer in the layered structure of the golf ball. The core 1 or the enveloping layer 2 is not limited to a single layer, but may be formed of two or more layers, while the intermediate layer 3 or the cover 4 is formed of a single layer.

The diameter of the core is preferably 24.7 mm or more, more preferably 25.7 mm or more, still more preferably 26.7 mm or more. The upper limit of this diameter is preferably 34.7 mm or less, more preferably 33.3 mm or less, still more preferably 31.7 mm or less.

The value of core diameter/ball diameter is preferably 0.65 or more, more preferably 0.67 or more, and still more preferably 0.70 or more, and the upper limit is preferably 0.80 or less, more preferably 0.70 or more. It is preferably 0.76 or less, more preferably 0.73 or less. If this value is too small, the initial velocity of the ball will be low, or the flexural hardness of the ball as a whole will be hard, resulting in an increase in the spin rate on a full shot, which may make it impossible to obtain the desired flight distance. If the above value is too large, the spin rate on full iron shots will increase, making it impossible to obtain the desired flight distance, and the durability to cracking on repeated hits will deteriorate.

The amount of deflection (mm) when the core is loaded with 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 5.0 mm or more, more preferably 5.0 mm or more. It is 5 mm or more, more preferably 6.0 mm or more, and the upper limit is preferably 9.0 mm or less, more preferably 8.5 mm or less, and even more preferably 8.0 mm or less. If the deflection amount of the core is too small, that is, if the core is too hard, the spin rate of the ball may increase too much, resulting in poor flight or an excessively hard hitting feel. On the other hand, if the deflection of the core is too large, i.e., if the core is too soft, the resilience of the ball will be too low and the ball will not fly, the feel on impact will be too soft, or the durability to cracking on repeated impact will be poor. Sometimes.

The core is obtained by vulcanizing a rubber composition mainly composed of a rubber material. The rubber composition is usually composed mainly of a base rubber, and is blended with a co-crosslinking agent, a cross-linking initiator, an inert filler, an organic sulfur compound, and the like to obtain a rubber composition.

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

Co-crosslinking agents are α,β-unsaturated carboxylic acids and/or metal salts 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. Although the metal salt of unsaturated carboxylic acid is not particularly limited, examples thereof include those obtained by neutralizing the above unsaturated carboxylic acid with a desired metal ion. Specific examples include zinc salts and magnesium salts of methacrylic acid and acrylic acid, and zinc acrylate is particularly preferably used.

The unsaturated carboxylic acid and/or metal salt thereof is usually 5 parts by mass or more, preferably 9 parts by mass or more, more preferably 13 parts by mass or more, and the upper limit is usually 60 parts by mass, per 100 parts by mass of the base rubber. Below, it is preferably 50 parts by mass or less, more preferably 40 parts by mass or less. If the amount is too large, the ball may become too hard, resulting in an unbearable feel on impact. If the amount is too small, the rebound may decrease.

As a cross-linking initiator, it is preferable to use an organic peroxide. Specifically, commercially available organic peroxides can be used. Co., Ltd.) and the like can be suitably used. These may be used singly or in combination of two or more. The amount of the organic peroxide compounded is preferably 0.1 parts by mass or more, more preferably 0.3 parts by mass or more, and still more preferably 0.5 parts by mass or more with respect to 100 parts by mass of the base rubber. The upper limit is preferably 5 parts by mass or less, more preferably 4 parts by mass or less, still more preferably 3 parts by mass or less, and most preferably 2.5 parts by mass or less. If the blending amount is too large or too small, it may not be possible to obtain a suitable feel on impact, durability and resilience.

As the filler, for example, zinc oxide, barium sulfate, calcium carbonate, etc. can be preferably used. These may be used individually by 1 type, and may use 2 or more types together. The amount of the filler compounded is preferably 1 part by mass or more, more preferably 3 parts by mass or more with respect to 100 parts by mass of the base rubber. Also, the upper limit of the amount to be compounded is preferably 200 parts by mass or less, more preferably 150 parts by mass or less, and even more preferably 100 parts by mass or less with respect to 100 parts by mass of the base rubber. If the blending amount is too large or too small, it may not be possible to obtain proper mass and suitable resilience.

As the anti-aging agent, commercially available products such as Nocrac NS-6, Nocrac NS-30, Nocrac 200 and Nocrac MB (manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.) can be used. These may be used individually by 1 type, and may use 2 or more types together.

The amount of the anti-aging agent to be blended is not particularly limited, but is preferably 0.05 parts by mass or more, more preferably 0.1 parts by mass or more, and preferably 1.0 as the upper limit, with respect to 100 parts by mass of the base rubber. It is no more than 0.7 parts by mass, more preferably no more than 0.5 parts by mass. If the blending amount is too large or too small, it may not be possible to obtain an appropriate core hardness gradient, resulting in failure to obtain suitable resilience, durability, and a low spin effect on full shots.

Furthermore, the rubber composition can be blended with an organic sulfur compound to impart excellent resilience. Specifically, thiophenol, thionaphthol, halogenated thiophenol, or metal salts thereof can be blended. More specifically, zinc salts such as pentachlorothiophenol, pentafluorothiophenol, pentabromothiophenol, parachlorothiophenol, and pentachlorothiophenol, diphenyl polysulfides with 2 to 4 sulfur atoms , dibenzylpolysulfide, dibenzoylpolysulfide, dibenzothiazolylpolysulfide, dithiobenzoylpolysulfide, and the like. Particularly, zinc salt of pentachlorothiophenol and diphenyldisulfide can be preferably used.

The amount of the organic sulfur compound is 0.05 parts by mass or more, preferably 0.07 parts by mass or more, more preferably 0.1 parts by mass or more, with an upper limit of 5 parts by mass or less, preferably 4 parts by mass or less, more preferably 3 parts by mass or less, and most preferably 2 parts by mass or less. If the amount is too large, the hardness becomes too soft, and if the amount is too small, no improvement in resilience can be expected.

The core can be produced by vulcanizing and curing a rubber composition containing the above components. For example, it is kneaded using a kneader such as a Banbury mixer or a roll, compression molded or injection molded using a core mold, and the temperature is 100 to 100 as a temperature sufficient for the organic peroxide or co-crosslinking agent to act. By appropriately heating the molded article under conditions of 200° C., preferably 140 to 180° C., for 10 to 40 minutes, the molded article can be cured and produced.

In addition, the core can be formed not only as a single layer but also as two layers of an inner core layer and an outer core layer. When the core is formed of two layers, an inner core layer and an outer core layer, the above-described rubber material can be used as the main material for both the inner layer core and the outer core layer. Further, the rubber material of the outer core layer covering the inner core layer may be the same as or different from the material of the inner core. Specifically, it is the same as explained for each component of the rubber material of the core.

Next, the hardness distribution of the core will be described. The hardness of the core described below means Shore C hardness. This Shore C hardness is a hardness value measured with a Shore C hardness tester conforming to the ASTM D2240 standard.

The center hardness (Cc) of the core is preferably 33 or more, more preferably 38 or more, and still more preferably 43 or more, and the upper limit thereof is preferably 62 or less, more preferably 59 or less, and still more preferably 54 or less. is. If this value is too large, the hitting feel may be hard, or the spin rate may increase on full shots, making it impossible to obtain the desired flight distance. On the other hand, if the above value is too small, the resilience will be low and the ball will not fly, or the durability to cracking when hit repeatedly will be poor.

The Shore C hardness (C25) at 25% of the length of the core radius from the center of the core toward the surface is preferably 35 or more, more preferably 40 or more, and still more preferably 45 or more, and the upper limit thereof is It is preferably 64 or less, more preferably 61 or less, and even more preferably 56 or less. Deviating from these hardnesses may lead to the same disadvantageous results as explained for the center hardness (Cc) of the core.

The Shore C hardness (C50) at 50% of the length of the core radius from the core center toward the surface is preferably 37 or more, more preferably 42 or more, and still more preferably 47 or more, and the upper limit thereof is It is preferably 66 or less, more preferably 63 or less, and even more preferably 58 or less. Deviating from these hardnesses may lead to the same disadvantageous results as explained for the center hardness (Cc) of the core. The above Shore C hardness (C50) corresponds to the hardness (Cm) at the midpoint between the core surface and the core center.

The Shore C hardness (C75) at 75% of the length of the core radius from the core center to the surface is preferably 40 or more, more preferably 45 or more, and still more preferably 49 or more, and the upper limit thereof is It is preferably 69 or less, more preferably 65 or less, still more preferably 61 or less. Deviating from these hardnesses may lead to the same disadvantageous results as explained for the center hardness (Cc) of the core.

The surface hardness (Cs) of the core is preferably 45 or more, more preferably 50 or more, and still more preferably 55 or more, and the upper limit thereof is preferably 74 or less, more preferably 70 or less, and further preferably 66 or less. is. Deviating from these hardnesses may lead to the same disadvantageous results as explained for the center hardness (Cc) of the core.

The difference between the surface hardness (Cs) of the core and the central hardness (Cc) of the core is preferably 5 or more, more preferably 7 or more, still more preferably 10 or more, and the upper limit is preferably 25 or less, more preferably is 20 or less, more preferably 15 or less. If this value is too small, the amount of spin on a full shot with a driver will increase, and the desired flight distance may not be obtained. If the above value is too large, the durability to cracking on repeated hits will be poor, or the initial velocity of actual hits will be low, making it impossible to obtain the desired flight distance.

Regarding the internal hardness of the core, the value of (Cs-C75)/(C50-Cc) must be 1.0 or more, preferably 1.2 or more, more preferably 1.3 or more. The value is 2.3 or less, preferably 2.0 or less, more preferably 1.8 or less. If this value is too large, the durability to cracking on repeated hits may deteriorate, or the initial speed of actual hits may become low, making it impossible to obtain the desired flight distance. On the other hand, if the above value is too small, the spin amount on a full shot will increase, and the target flight distance may not be obtained.

In addition, the value of (Cs-C50)/(C25-Cc) is preferably 3.0 or more, more preferably 3.3 or more, still more preferably 3.6 or more, and the upper limit is preferably is 20.0 or less, more preferably 13.0 or less, still more preferably 7.0 or less. If this value is too large, the durability to cracking on repeated hits may deteriorate, or the initial speed of actual hits may become low, making it impossible to obtain the desired flight distance. On the other hand, if the above value is too small, the spin amount on a full shot will increase, and the target flight distance may not be obtained.

Further, the value of (Cs-C50)/(C50-Cc) is preferably 1.1 or more, more preferably 1.3 or more, still more preferably 1.6 or more, and the upper limit is particularly Although there is no limitation, it is preferably 8.0 or less, more preferably 4.0 or less. If this value is too large, the durability to cracking on repeated hits may deteriorate, or the initial speed of actual hits may become low, making it impossible to obtain the desired flight distance. On the other hand, if the above value is too small, the spin amount on a full shot will increase, and the target flight distance may not be obtained.

Regarding the core used in the present invention, Core vh is required to be 630 or more, preferably 650 or more, more preferably 650 or more, where Core vh is the value of core volume V (cm ³ )×C50. It is 680 or more, and the upper limit is 1000 or less, preferably 950 or less, more preferably 900 or less. If this value is too large, the amount of spin on a full shot may become too large, making it impossible to obtain the desired flight distance. On the other hand, if the above value is too small, the actual hitting initial velocity will be low, and the target flight distance may not be obtained.

Next, the surrounding layer will be explained.
In the present invention, the envelope layer can be formed as a single layer or multiple layers of two or more layers. When two or more envelope layers are formed, the innermost layer is called the inner envelope layer, and the outermost layer is called the outer envelope layer. When the envelope layer is a plurality of layers, the material hardness and surface hardness of the envelope layer described below refer to the material hardness and surface hardness of the outer envelope layer.

The material hardness of the envelope layer is not particularly limited, but the Shore C hardness is preferably 67 or more, more preferably 70 or more, and still more preferably 72 or more, and the upper limit is preferably 90 or less, more preferably 89. 88 or less, more preferably 88 or less. The Shore D hardness is preferably 43 or more, more preferably 45 or more, still more preferably 47 or more, and the upper limit is preferably 60 or less, more preferably 56 or less, and still more preferably 54 or less.

The surface hardness of the sphere obtained by coating the core with the surrounding layer is preferably 75 or more, more preferably 78 or more, and still more preferably 80 or more in Shore C hardness, and the upper limit is preferably 95 or less, more preferably 93. 92 or less, more preferably 92 or less. The Shore D hardness is preferably 49 or more, more preferably 51 or more, still more preferably 53 or more, and the upper limit is preferably 66 or less, more preferably 62 or less, and still more preferably 60 or less.

If the material hardness and surface hardness of the envelope layer are too soft, the spin may be too high on a full shot, or the initial velocity may be low, resulting in a loss of flight distance. On the other hand, if the material hardness and surface hardness of the envelope layer are too hard beyond the above ranges, the feel on impact will be hard, the durability to cracking on repeated hits will be poor, and the spin rate on full shots will increase, resulting in increased flight distance. may not come out.

When the envelope layer has a plurality of layers, the surface hardness of the outer envelope layer is preferably higher than the surface hardness of the inner envelope layer, and one or more layers are interposed between the inner envelope layer and the outer envelope layer. In this case, it is preferable to design so that each layer gradually increases in height from the inner enveloping layer toward the outer enveloping layer. Otherwise, the amount of spin on a full shot may increase and the flight distance may not be achieved. Also, designing a multi-layered envelope in this way may result in an advantage over a single-layered envelope in flight distance due to the low spin effect on full shots.

The thickness of the envelope layer is preferably 2.0 mm or more, more preferably 2.7 mm or more, still more preferably 3.5 mm or more. On the other hand, the upper limit of the thickness of the envelope layer is preferably 7.0 mm or less, more preferably 6.5 mm or less, and even more preferably 6.0 mm or less. The thickness of the enveloping layer referred to here means the total thickness of the enveloping layer when the enveloping layer has a plurality of layers. If the enveloping layer is too thin, the effect of lowering the spin rate on full iron shots may not be sufficient, making it impossible to obtain the desired flight distance. If the enveloping layer is too thick, the initial velocity of the ball as a whole will be low, and the actual initial velocity at impact will be too low, making it impossible to obtain the desired flight distance.

In addition, the thickness of the envelope layer must meet the condition of (cover thickness)<(intermediate layer thickness)≦(total envelope layer thickness) in relation to the thicknesses of the intermediate layer and the cover, which will be described later. preferred. In addition, regarding the thickness ratio of each layer, the value of (total thickness of envelope layer thickness)/(cover thickness + intermediate layer thickness) is preferably 1.0 or more, more preferably 1.5 or more. , more preferably 1.8 or more, and the upper limit is preferably 3.5 or less, more preferably 3.0 or less, and still more preferably 2.6 or less. If the above value is too large, the initial velocity may be low, resulting in a loss of flight distance or poor durability to cracking due to repeated impacts. If the above value is too small, the spin-lowering effect may be insufficient, resulting in a lack of flight distance.

The material for the envelope layer is not particularly limited, but known resins can be used. Examples of particularly preferred materials include the following components (a) to (c),
(a) an olefin-unsaturated carboxylic acid binary random copolymer and/or a metal ion neutralized product of an olefin-unsaturated carboxylic acid binary random copolymer;
(b) 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 base resin blended in a mass ratio of 100:0 to 0:100;
(c) A resin composition blended with a non-ionomer thermoplastic elastomer at a mass ratio of 100:0 to 50:50 can be exemplified.

For the above components (a) to (c), for example, intermediate layer resin materials described in JP-A-2010-253268 can be suitably employed.

Arbitrary additives can be appropriately added to the above resin 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 these additives are blended, the blending amount is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, with respect to the total 100 parts by mass of the base resin, and the upper limit is preferably It is 10 parts by mass or less, more preferably 4 parts by mass or less.

Next, the intermediate layer will be explained.
The material hardness of the intermediate layer is not particularly limited, but the Shore D hardness is preferably 58 or more, more preferably 60 or more, and still more preferably 63 or more, and the upper limit is preferably 70 or less, more preferably 68. 65 or less, more preferably 65 or less. The Shore C hardness is preferably 87 or higher, more preferably 89 or higher, and still more preferably 93 or higher, and the upper limit is preferably 100 or lower, more preferably 98 or lower, and still more preferably 96 or lower.

Further, the surface hardness of the sphere obtained by coating the envelope layer-covered sphere with the intermediate layer (intermediate layer-covered sphere) is preferably 64 or higher, more preferably 66 or higher, further preferably 69 or higher in Shore D hardness. The value is preferably 76 or less, more preferably 74 or less, and even more preferably 71 or less. The Shore C hardness is preferably 90 or higher, more preferably 93 or higher, still more preferably 96 or higher, and the upper limit is preferably 100 or lower, more preferably 99 or lower, and still more preferably 98 or lower.

If the material hardness and surface hardness of the intermediate layer are too soft, the spin may be too high on a full shot, or the initial velocity may be low, resulting in a poor flight distance. On the other hand, if the material hardness and surface hardness of the intermediate layer are higher than the above ranges, the durability to cracking on repeated impacts may deteriorate, and the feel on impact may become too hard on putter or short approach shots.

In addition, the surface hardness of the intermediate layer-coated sphere is related to the ball surface hardness as follows:
(Surface hardness of intermediate layer-coated sphere) > (Ball surface hardness)
It is desirable to satisfy the conditions of Otherwise, the amount of spin on full shots increases, resulting in a loss of flight distance or poor controllability in short games.

The thickness of the intermediate layer is preferably 0.7 mm or more, more preferably 0.8 mm or more, still more preferably 1.0 mm or more. On the other hand, the upper limit of the thickness of the intermediate layer is preferably 1.8 mm or less, more preferably 1.4 mm or less, still more preferably 1.2 mm or less. The thickness of the intermediate layer is preferably thicker than the later-described cover (outermost layer). If the thickness of the intermediate layer deviates from the above range, or if it is formed thinner than the cover, the effect of reducing the spin rate when hit with a driver (W#1) may be insufficient, resulting in a loss of flight distance. On the other hand, if the intermediate layer is too thin, the durability to cracking during repeated impacts and the durability at low temperatures may deteriorate.

For the material of the intermediate layer, various thermoplastic resins used in golf ball materials, especially highly neutralized resin materials and ionomer resins containing the components (a) to (c) mentioned in the material of the envelope layer are used. It is preferable to

Specific examples of ionomer resin materials include sodium-neutralized ionomer resins, zinc-neutralized ionomer resins, and the like, and these may be used alone or in combination of two or more.

Particularly preferred is a mode in which a zinc-neutralized ionomer resin and a sodium-neutralized ionomer resin are mixed and used as the main material. The mixing ratio of zinc-neutralized/sodium-neutralized (mass ratio) is 25/75 to 75/25, preferably 35/65 to 65/35, more preferably 45/55 to 55/45. If the Zn-neutralized ionomer and the Na-neutralized ionomer are not included in this ratio, the rebound will be too low to obtain the desired flight, or the durability to cracking when repeatedly hit at room temperature will deteriorate, or even at low temperatures. The cracking durability at (below zero) may deteriorate.

Further, as the resin material for the intermediate layer, among commercially available ionomer resins, a high acid content ionomer resin having an acid content of 16% by mass or more can be blended with a normal ionomer resin. It is possible to obtain a good flight distance when hit with a driver (W#1) due to spin.

The content of unsaturated carboxylic acid contained in the high acid content ionomer resin (the acid content is usually 16% by mass or more, preferably 17% by mass or more, more preferably 18% by mass or more, and the upper limit is preferably It is 22% by mass or less, more preferably 21% by mass or less, and even more preferably 20% by mass or less If this value is too small, the spin rate increases on full shots, and the target flight distance may not be obtained. On the other hand, if the above value is too large, the feel on impact may become too hard, or the durability to cracking upon repeated impact may deteriorate.

The high acid content ionomer resin is preferably 10% by mass or more, more preferably 30% by mass or more, and still more preferably 60% by mass or more with respect to 100% by mass of the resin material. If the amount of the ionomer resin with a high acid content is too small, the spin rate increases when hit with a driver (W#1), and the flight distance may not be achieved.

Arbitrary additives can be appropriately added to 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 these additives are blended, 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 base resin, and the upper limit is preferably 10 parts by mass. parts or less, more preferably 4 parts by mass or less.

As for the material of the intermediate layer, it is preferable to polish the surface of the intermediate layer in order to increase the degree of adhesion with polyurethane, which is preferably used in the cover material described later. 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-enhancing agent to the material.

The specific gravity of the intermediate layer material is usually less than 1.1, preferably 0.90-1.05, more preferably 0.93-0.99. If it deviates from this range, the rebound of the ball as a whole will be low, resulting in a loss of flight distance, or the resistance to cracking due to repeated impacts will deteriorate.

Next, the cover (outermost layer) will be described.
The material hardness of the cover is not particularly limited, but the Shore D hardness is preferably 35 or more, more preferably 40 or more, and still more preferably 45 or more, and the upper limit is preferably 60 or less, more preferably 55 or less, more preferably 50 or less. The Shore C hardness is preferably 57 or more, more preferably 63 or more, still more preferably 70 or more, and the upper limit is preferably 89 or less, more preferably 83 or less, and even more preferably 76 or less.

The surface hardness of the sphere obtained by covering the intermediate layer-covered sphere with a cover (ball-covered sphere) is preferably 50 or more, more preferably 53 or more, and still more preferably 56 or more in Shore D hardness. , preferably 70 or less, more preferably 67 or less, still more preferably 64 or less. The Shore C hardness is preferably 75 or more, more preferably 80 or more, still more preferably 85 or more, and the upper limit is preferably 95 or less, more preferably 92 or less, and still more preferably 90 or less.

If the material hardness of the cover and the ball surface hardness are too softer than the above ranges, the spin rate may increase on full iron shots, resulting in a loss of distance. On the other hand, if the hardness of the material of the cover and the surface hardness of the ball are too hard beyond the above ranges, spin may not be applied on approach shots, and scuff resistance may deteriorate.

The thickness of the cover is preferably 0.3 mm or more, more preferably 0.45 mm or more, still more preferably 0.6 mm or more. On the other hand, the upper limit of the thickness of the cover is 1.0 mm or less, preferably 0.9 mm or less, and more preferably 0.85 mm or less. If the cover is too thick, the repulsion will be insufficient or the spin rate will increase on full shots with an iron, resulting in a loss of flight distance. On the other hand, if the cover is too thin, the scuff resistance may deteriorate, and the spin on the approach may not be applied, resulting in insufficient controllability.

Various thermoplastic resins and thermosetting resins used in golf ball cover materials can be used as the material for the cover, but urethane resin is preferably used from the viewpoint of controllability and scratch resistance. can do. In particular, from the viewpoint of mass-producibility of ball products, it is preferable to use thermoplastic polyurethane as the main component, and more preferably, (I) thermoplastic polyurethane and (II) polyisocyanate compound are the main components. It can be formed by a resin formulation.

The total mass of components (I) and (II) is recommended to be 60% or more, more preferably 70% or more, of the total amount of the resin composition for the cover. The components (I) and (II) are described in detail below.

Regarding the above (I) thermoplastic polyurethane, the structure of the thermoplastic polyurethane consists of a soft segment composed of a high-molecular polyol (polymeric glycol), which is a long-chain polyol, and a hard segment composed of a chain extender and a polyisocyanate compound. include. Here, as the long-chain polyol used as a raw material, any of those conventionally used in techniques related to thermoplastic polyurethanes can be used, and there is no particular limitation, but examples include polyester polyols, polyether polyols, and polycarbonate polyols. , polyester polycarbonate polyols, polyolefin polyols, conjugated diene polymer polyols, castor oil polyols, silicone polyols, vinyl polymer polyols, and the like. One type of these long-chain polyols may be used, or two or more types may be used in combination. Among these, polyether polyols are preferable in that a thermoplastic polyurethane having a high rebound resilience and excellent low-temperature properties can be synthesized.

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

As the polyisocyanate compound, those used in conventional techniques relating to thermoplastic polyurethanes can be suitably used, and there is no particular limitation. Specifically, 4,4′-diphenylmethane diisocyanate, 2,4-(or) 2,6-toluene diisocyanate, p-phenylene diisocyanate, xylylene diisocyanate, naphthylene 1,5-diisocyanate, tetramethylxylene diisocyanate, hydrogenation One or more selected from the group consisting of xylylene diisocyanate, dicyclohexylmethane diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, norbornene diisocyanate, trimethylhexamethylene diisocyanate, and dimer acid diisocyanate can be used. However, with some isocyanate species, it is difficult to control the cross-linking reaction during injection molding. In the present invention, 4,4'-diphenylmethane diisocyanate, which is an aromatic diisocyanate, is most preferred from the viewpoint of the balance between the stability during production and the physical properties that are exhibited.

Commercially available thermoplastic polyurethanes can be used as specific component (I), such as Pandex T8295, Pandex T8290 and Pandex T8260 (all manufactured by DIC Covestro Polymer).

Although not an essential component, a thermoplastic elastomer other than the thermoplastic polyurethane can be blended with the above components (I) and (II) as a separate component (III). By blending this component (III) into the resin composition, it is possible to further improve the fluidity of the resin composition, resilience, scratch resistance, and other physical properties required for golf ball cover materials. .

The composition ratio of the components (I), (II) and (III) is not particularly limited, but in order to fully and effectively exhibit the effects of the present invention, the mass ratio of (I):(II) : (III) = 100: 2 to 50: 0 to 50, more preferably (I): (II): (III) = 100: 2 to 30: 8 to 50 (mass ratio) It is to be.

Furthermore, various additives other than the components constituting the thermoplastic polyurethane can be blended into the above resin composition, if necessary, such as pigments, dispersants, antioxidants, and light stabilizers. , an ultraviolet absorber, a release agent, and the like can be appropriately added.

A multi-piece solid golf ball formed by stacking the layers of the core, envelope layer, intermediate layer and cover (outermost layer) described above can be manufactured by a conventional injection molding method or the like. For example, materials for the envelope layer and the intermediate layer are sequentially injected around the core using respective injection molding dies to obtain each covered sphere, and finally the material for the outermost layer, the cover, is injection molded. A multi-piece golf ball can be obtained. Alternatively, a golf ball can be produced by wrapping the coated sphere with two half-cups, which have been formed in advance into a semi-spherical shape, as the respective coating layers, and molding the coated sphere under heat and pressure.

The amount of deflection (mm) of the golf ball when an initial load of 98 N (10 kgf) to a final load of 1,275 N (130 kgf) is applied must be 2.8 mm or more, preferably 3.1 mm or more. , more preferably 3.4 mm or more. On the other hand, the upper limit of the amount of deflection is preferably 4.5 mm or less, more preferably 4.2 mm or less, and even more preferably 4.0 mm or less. If the amount of deflection of the golf ball is too small, that is, if it is too hard, the spin rate may be too high, resulting in poor flight or an excessively hard hitting feel. On the other hand, if the amount of deflection is too large, that is, if the sphere is too soft, the resilience of the ball will be too low and the ball will not fly, the feel on impact will be too soft, or the durability to cracking on repeated impact will be poor. Sometimes.

The amount of deflection is C (mm) when the core is loaded with an initial load of 98 N (10 kgf) to a final load of 1,275 N (130 kgf), and the ball is subjected to an initial load of 98 N (10 kgf) to a final load of 1,275 N. The value of C/B is required to be 1.6 or more, preferably 1.7 or more, where B (mm) is the amount of deflection when (130 kgf) is applied. On the other hand, the upper limit needs to be 2.3 or less, preferably 2.1 or less. If this value is too large, the initial speed at actual hit may be low, resulting in a loss of flight distance or poor durability to cracking due to repeated hits. On the other hand, if the above value is too small, the effect of lowering the spin rate of the ball may be insufficient, resulting in a lack of flight distance.

Further, the value of CB is preferably 2.5 mm or more, more preferably 2.6 mm or more, still more preferably 2.7 mm or more, and the upper limit is preferably 5.0 mm or less, more preferably 4 0.6 mm or less, more preferably 4.3 mm or less. If the above value is too large, the initial velocity at actual hit may be low, the flight distance may not be obtained, or the durability to cracking due to repeated hitting may be deteriorated. If the above value is too small, the spin-lowering effect may not be sufficient, and the flight distance may not be obtained.

[ Hardness relationship of each layer ]
In the present invention, the Shore C hardness of the surface of the core, the Shore C hardness of the surface of a sphere obtained by coating the core with an envelope layer (envelope-layer-covered sphere), and the sphere obtained by coating the envelope-layer-covered sphere with an intermediate layer (intermediate The Shore C hardness of the surface of the layer coated sphere) and the Shore C hardness of the surface of the ball are
(Shore C hardness of the surface of the envelope-covered sphere)>(Shore C hardness of the surface of the core) and (Shore C hardness of the surface of the intermediate-layer-covered sphere)>(Shore C hardness of the ball surface)
It is necessary to satisfy the conditions of

The value obtained by subtracting the surface hardness of the core from the surface hardness of the envelope-coated sphere is greater than 0, preferably 8 or more, more preferably 15 or more in Shore C hardness, and the upper limit is preferably 50 or less, more preferably 15 or more. It is preferably 43 or less, more preferably 36 or less. If the above value deviates from the above numerical range, the spin amount on a full shot will increase, and the target flight distance may not be obtained.

The value obtained by subtracting the surface hardness of the ball from the surface hardness of the ball coated with the intermediate layer is greater than 0, preferably 3 or more, more preferably 5 or more in Shore C hardness, and the upper limit is preferably 30 or less, more preferably 30 or less. is 22 or less, more preferably 15 or less. If the above value is too small, the controllability in the short game may deteriorate. On the other hand, if the above value is too large, the spin rate on full shots will increase, and the target flight distance may not be obtained.

The value obtained by subtracting the center hardness of the core from the surface hardness of the envelope-coated sphere is preferably 29 or more, more preferably 32 or more, and still more preferably 35 or more in Shore C hardness. , preferably 55 or less, more preferably 50 or less, still more preferably 45 or less. If the above value is too large, the durability to cracking on repeated hits may deteriorate, or the initial speed of actual hits may become low, making it impossible to obtain the desired flight distance. On the other hand, if the above value is too small, the spin amount on a full shot will increase, and the target flight distance may not be obtained.

The value obtained by subtracting the surface hardness of the envelope-covered sphere from the surface hardness of the intermediate-layer-covered sphere is preferably greater than 0 in Shore C hardness, more preferably 4 or more, and still more preferably 8 or more. , preferably 28 or less, more preferably 22 or less, still more preferably 16 or less. If the above value deviates from the above numerical range, the spin amount on a full shot will increase, and the target flight distance may not be obtained.

The value obtained by subtracting the center hardness of the core from the surface hardness of the intermediate layer-covered sphere is preferably 33 or more, more preferably 38 or more, and still more preferably 43 or more in Shore C hardness. is 65 or less, more preferably 60 or less, still more preferably 55 or less. If the above value is too large, the durability to cracking on repeated hits may deteriorate, or the initial speed of actual hits may become low, making it impossible to obtain the desired flight distance. On the other hand, if the above value is too small, the spin amount on a full shot will increase, and the target flight distance may not be obtained.

[Relationship Between Volume and Hardness of Core and Surrounding Layer]
Core volume (cm ³ )×Shore C hardness (Cm) at the midpoint between core surface and core center is Core vh, Volume of inner envelope (cm ³ )×Surface hardness of sphere covered with inner envelope (Shore C) is IE vh, and OE vh is the volume of the outer enveloping layer (cm ³ )×the surface hardness (Shore C) of the sphere covered with the outer enveloping layer, the value of (OE vh + IE vh)/Core vh is 1.0. or more, more preferably 1.2 or more, still more preferably 1.4 or more. 9 or less. If the above value is too large, the initial velocity at actual hit may be low, resulting in a loss of flight distance or poor durability to cracking due to repeated impacts. On the other hand, if the above value is too small, the spin-lowering effect may not be sufficient, and the flight distance may not be obtained.

A large number of dimples can be formed on the outer surface of the cover, which is the outermost layer. The number of dimples arranged on the surface of the cover is not particularly limited, but is preferably 250 or more, preferably 300 or more, more preferably 320 or more, and the upper limit is preferably 380 or less, more preferably 350. 1 or less, more preferably 340 or less. If the number of dimples exceeds the above range, the trajectory of the ball will be low and the flight distance will be reduced. Conversely, if the number of dimples is small, the trajectory of the ball becomes high, and the flight distance may not increase.

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

The dimple occupancy rate of the spherical surface of the golf ball, specifically, the total dimple area defined by the edge of the plane surrounded by the edges of the dimples occupies the spherical area of the ball assuming no dimples. The ratio (SR value) is desirably 70% or more and 90% or less from the viewpoint of being able to sufficiently exhibit the aerodynamic characteristics. Also, the value _V0 obtained by dividing the spatial volume of a dimple under a plane surrounded by the edges of each dimple by the volume of a cylinder whose bottom is the plane and whose height is the maximum depth of the dimple from this bottom is From the point of view of optimizing the trajectory of the ball, it is preferable to set it to 0.35 or more and 0.80 or less. Furthermore, the total dimple volume formed downward from the plane surrounded by the edges of the dimples occupies the ball volume assuming that no dimples exist, and the VR value should be 0.6% or more and 1.0% or less. is preferred. If the range of each numerical value is deviated from the range described above, the trajectory may not provide a good flight distance, and a sufficiently satisfactory flight distance may not be obtained.

A coating film layer (coating layer) can be formed on the surface of the cover. This coating layer can be coated with various types of paints. As the paint, it is necessary to withstand the harsh conditions of use of the golf ball. It is preferred to use a composition.

Examples of the polyol component include acrylic polyols and polyester polyols. These polyols include modified polyols, and other polyols can be added in order to further improve workability.

As the polyol component, it is preferable to use two kinds of polyester polyols together. In this case, when two types of polyester polyols are used as components (a) and (b), a polyester polyol having a cyclic structure introduced into the resin skeleton can be employed as the polyester polyol for component (a). , polycondensation of polyols having an alicyclic structure such as cyclohexanedimethanol and polybasic acids, or polyester polyols obtained by polycondensation of polyols having an alicyclic structure and diols or triols and polybasic acids. . On the other hand, as the polyester polyol of component (b), a polyester polyol having a multi-branched structure can be employed, and examples thereof include polyester polyols having a branched structure such as "NIPPOLAN 800" manufactured by Tosoh Corporation.

On the other hand, the polyisocyanate is not particularly limited, and is commonly used aromatic, aliphatic, alicyclic polyisocyanate, specifically, 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-isocyanate Natomethylcyclohexane and the like can be mentioned. These can be used singly or in combination.

Various organic solvents can be mixed in 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, acetone, and methyl ethyl ketone. , methyl isobutyl ketone, ketone solvents such as cyclohexanone, ether solvents such as diethylene glycol dimethyl ether, diethylene glycol diethyl ether, dipropylene glycol dimethyl ether, alicyclic hydrocarbon solvents such as cyclohexane, methylcyclohexane, ethylcyclohexane, mineral spirits, etc. A petroleum hydrocarbon solvent or the like can be used.

The thickness of the coating film layer composed of the coating composition is not particularly limited, but is usually 5 to 40 µm, preferably 10 to 20 µm. The thickness of the coating film layer referred to here means the average thickness of the coating film measured at a total of three locations, namely, the center of the dimple and two locations between the center of the dimple and the dimple edge.

In the present invention, the elastic work recovery rate of the coating layer composed of the above coating composition is required to be 60% or more, preferably 80% or more. When the elastic work recovery rate of the coating layer is within the above range, the coating layer has a high elastic force, so that the self-healing function is high and the wear resistance is extremely excellent. In addition, various performances of golf balls coated with the coating composition can be improved. The method for measuring the elastic work recovery rate is as follows.

The elastic work recovery rate is an ultra-micro hardness test method that controls the indentation load on the order of micro Newtons (μN) and tracks the indenter depth during indentation with nanometer (nm) accuracy. It is one of the parameters of the nanoindentation method for evaluating physical properties. Conventional methods could only measure the size of the deformation mark (plastic deformation mark) corresponding to the maximum load, but the nanoindentation method automatically and continuously measures the relationship between the indentation load and the indentation depth. can be obtained. Therefore, it is thought that the physical properties of the coating film layer can be evaluated with high accuracy without individual differences such as in the conventional visual measurement of deformation marks with an optical microscope. The coating layer on the surface of the ball is greatly affected by the impact of drivers and clubs, and the effect of the coating layer on the physical properties of the golf ball is not small. However, it will be a very effective evaluation method if it is performed with higher accuracy than before.

As for the hardness of the coating layer, the Shore M hardness is preferably 40 or more, more preferably 60 or more, and the upper limit is preferably 95 or less, more preferably 85 or less. The Shore M hardness conforms to ASTM D2240. Further, the hardness of the coating film 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. The Shore C hardness conforms to ASTM D2240. If the hardness of the coating layer is higher than the above range, the coating becomes brittle when repeatedly hit, and the cover layer may not be protected. If the coating layer has a hardness smaller than the above range, the surface of the ball tends to be scratched when it hits a hard object, which is undesirable.

When the above coating composition is used, the coating composition of the present invention is prepared at the time of coating on a golf ball manufactured by a known method, applied to the surface using a conventional coating process, and then dried. A coating film layer can be formed on the ball surface through In this case, as a coating method, a spray coating method, an electrostatic coating method, a dipping method, or the like can be suitably employed, and there is no particular limitation.

The multi-piece solid golf ball of the present invention may conform to the Rules of Golf for competition, and has an outer diameter of 42.672 mm so that it does not pass through a ring with an inner diameter of 42.672 mm. ˜45.93 g.

The initial velocity of a golf ball based on the R&A Golf Rules is usually 76.8 ms, preferably 77.0 m/s or more, more preferably 77.1 m/s or more, and the upper limit is 77.724 m/s. /s or less. If this initial speed value exceeds 77.724 m/s, it will be out of the official rules. On the other hand, if the above initial velocity value is too low, the flight distance on a full shot may not be obtained.

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

[Examples 1 to 4, Comparative Examples 1 to 8]
core formation
After preparing the rubber composition of each example and comparative example shown in Table 1, vulcanization molding was performed under the vulcanization conditions of each example shown in Table 1 to prepare a solid core.

However, for Examples 1 and 2 and Comparative Examples 7 and 8, the cores are produced based on the formulations shown in Table 1 in the same manner as described above.

In addition, the details of each component described in Table 1 are as follows.
・Polybutadiene: manufactured by JSR, trade name “BR730”
・ Zinc acrylate: “ZN-DA85S” (manufactured by Nippon Shokubai Co., Ltd.)
・Organic peroxide: a mixture of 1,1-di(t-butylperoxy)cyclohexane and silica, trade name “Perhexa C-40” (manufactured by NOF Corporation)
・Zinc stearate: Product name “Zinc stearate G” (manufactured by NOF Corporation)
· Anti-aging agent: 2,2-methylenebis (4-methyl-6-butylphenol), trade name "Nocrac NS-6" (manufactured by Ouchi Shinko Chemical Industry Co., Ltd.)
・ Zinc oxide: Product name “Three kinds of zinc oxide” (manufactured by Sakai Chemical Industry Co., Ltd.)
・Pentachlorothiophenol zinc salt: manufactured by Wako Pure Chemical Industries, Ltd.

Surrounding layer (inner/outer)
Next, for each example and each comparative example except for comparative examples 4 to 6, No. 2 shown in Table 2 was attached around the core. An inner envelope layer was formed by an injection molding method using the inner envelope layer material blended in No. 1, and then the No. 1 shown in the same table was formed. 1, No. 2 or No. The outer envelope layer was formed by an injection molding method using the outer envelope layer material of formulation No. 3. For Comparative Examples 4 to 6, No. in Table 2. 1 or No. A single-layer enveloping layer (details are given in the "outer enveloping layer" column in the table) was formed around the core by an injection molding method using the materials of formulation 3.

However, in Examples 1 and 2 and Comparative Examples 7 and 8, the envelope layers were produced based on the formulations in Table 2 in the same manner as described above.

Formation of Intermediate Layer and Cover (Outermost Layer) Next, for all of the examples and comparative examples, No. 2 of the composition shown in Table 2 was added around the envelope-coated spheres obtained above. 4 or No. 5 was used to form an intermediate layer by injection molding. Next, No. 1 of the formulation shown in Table 2 was placed around the intermediate layer-covered spheres of each of the above examples. 6 or No. A cover (outermost layer) was formed by an injection molding method using the cover material having the composition of No. 7. At this time, a predetermined number of dimples common to all the examples and comparative examples were formed on the cover surface.

However, for Examples 1 and 2 and Comparative Examples 7 and 8, the intermediate layer and the cover are produced based on the formulations shown in Table 2 in the same manner as described above.

The trade names of the main materials listed in the table are as follows.
"HPF1000""HPF2000" (trademark) "HPF" manufactured by THE DOW CHEMICAL COMPANY
"Himilan 1605", "Himilan 1557", "Himilan 1706" Ionomer "Surlyn 8120" manufactured by Mitsui Dow Polychemicals Co., Ltd. Ionomer "Dynaron 6100P" manufactured by THE DOW CHEMICAL COMPANY Hydrogenated polymer "Behenic acid" manufactured by JSR NOF "NAA222-S" manufactured by the company (bead designation)
"Calcium hydroxide""CLS-B" manufactured by Shiraishi Kogyo Co., Ltd.
"Trimethylolpropane""TPU(1)" and "TPU (2)" manufactured by Tokyo Chemical Industry Co., Ltd., trade name "Pandex" manufactured by DIC Covestro Polymer Co., Ltd., ether type thermoplastic polyurethane

Eight types of circular dimples were used as the dimples common to all examples and comparative examples, the details of which are shown in Table 3 below, and the arrangement of which is shown in FIG. FIG. 2(A) shows a plan view of the dimple, and FIG. 2(B) shows a side view thereof.

Definition of dimple Rim: Highest point in a cross section passing through the center of the dimple Diameter: Diameter of the plane surrounded by the edge of the dimple Depth: Maximum depth of the dimple from the plane surrounded by the edge of the dimple SR: The ratio of the total dimple area defined by the plane surrounded by the edges of the dimples to the spherical area of the ball assuming no dimples Dimple volume: Dimple volume under the plane surrounded by the edges of the dimples Cylindrical volume ratio: Ratio of dimple volume to the volume of a cylinder with the same depth as the dimple VR: The total volume of the dimples formed downward from the plane surrounded by the edges of the dimples is the sphere volume of the ball assuming that no dimples exist.

Formation of paint layer (coating layer) Next, a paint composition shown in Table 4 below was used as a paint composition common to all Examples and Comparative Examples. The above paint was applied by an air spray gun to prepare a golf ball having a paint layer with a thickness of 15 μm.
However, for Examples 1 and 2 and Comparative Examples 7 and 8, the above paint is applied in the same manner as described above to form a paint layer having a thickness of 15 μm to produce a golf ball.

[Synthesis example of polyester polyol (A)]
140 parts by mass of trimethylolpropane, 95 parts by mass of ethylene glycol, 157 parts by mass of adipic acid, and 58 parts by mass of 1,4-cyclohexanedimethanol were placed in a reactor equipped with a reflux condenser, a dropping funnel, a gas inlet tube and a thermometer. After charging, the temperature was raised to 200 to 240° C. while stirring, and the mixture was heated (reacted) for 5 hours. Thereafter, "polyester polyol (A)" having an acid value of 4, a hydroxyl value of 170 and a weight average molecular weight (Mw) of 28,000 was obtained.
Next, the synthesized polyester polyol (A) was dissolved in butyl acetate to prepare a varnish having a non-volatile content of 70% by mass.

Coating composition "C" in Table 4 is "polyester polyol (B)" (saturated aliphatic polyester polyol "NIPPOLAN 800" manufactured by Tosoh Corporation, weight average molecular weight ( Mw) of 1,000 and a solid content of 100%) was mixed with 15 parts by mass of an organic solvent to prepare a main agent. This mixture had a non-volatile content of 38.0 mass %.

Elastic Work Recovery Rate The elastic work recovery rate of the paint is measured using a coating film sheet having a thickness of 50 μm. As a measuring device, an ultra-micro hardness tester "ENT-2100" manufactured by Elionix Co., Ltd. is used, and the measuring conditions are as follows.
・Indenter: Berkovich indenter (material: diamond, angle α: 65.03°)
・Load F: 0.2mN
・Loading time: 10 seconds ・Holding time: 1 second ・_Unloading time: 10 _seconds The elastic work recovery rate is calculated by the following formula.
Elastic work recovery rate = W _elast / W _total x 100 (%)

Shore C hardness and Shore M hardness The Shore C hardness and Shore M hardness in Table 3 above were obtained by preparing a sheet with a thickness of 2 mm, stacking three sheets, and using a Shore C hardness tester and Shore M hardness in accordance with the ASTM D2240 standard as a test piece. Each was measured using a meter.

Each golf ball thus obtained was evaluated for various physical properties such as the internal hardness of the core, the outer diameter of the core and each coated sphere, the thickness and material hardness of each layer, and the surface hardness of each coated sphere. and Table 6.

At a temperature of 23.9 ± 1° C for the outer diameter of each of the core, (inner/outer) envelope-covered spheres, and intermediate-layer-covered spheres, five arbitrary surfaces were measured, and the average value was calculated for each sphere. , and the average value of 10 measurements was obtained.

At a temperature of 23.9±1° C., the diameter of the ball was measured at 15 locations without any dimples. .

Deflection of the core, covered spheres in each layer and ball Place the core, covered spheres in each layer or target covered spheres of the ball on a hard plate and apply an initial load of 98N (10kgf) to a final load of 1275N (130kgf). Measure the amount of deflection when In addition, the amount of deflection described above is a measured value after the temperature is adjusted to 23.9°C. The pressing speed of the head that compresses the core, the coated spheres of each layer, or the ball is 10 mm/s.

Core Hardness Distribution The surface of the core is spherical, and the needle of a hardness tester was set so as to be substantially perpendicular to the spherical surface, and the core surface hardness was measured in terms of Shore C hardness according to ASTM D2240. For hardness measurement, an automatic rubber hardness tester "P2" manufactured by Kobunshi Keiki Co., Ltd. equipped with a Shore C type hardness tester is used. Read the maximum hardness value. All measurements are made in an environment of 23±2°C. Core center hardness Cc, surface hardness Cs, position hardness C75 at 75% of core radius length from center to surface, position hardness C50 at 50% core radius length from center to surface, from center For the cross-sectional hardness at a predetermined position of each core with a position hardness C25 of 25% of the length of the core radius toward the surface, cut the core into a hemispherical shape, make the cross section flat, and place the needle of the hardness tester perpendicular to the measurement part. It was measured by pressing against It is indicated by the value of Shore C hardness.

The hardness distribution of the core of each example and each comparative example is shown in the graphs of FIG. 3 (Examples 1 to 4), FIG. 4 (Comparative Examples 1 to 5 and 7) and FIG. 5 (Comparative Examples 6 and 8) .

(Inside/Outside) Surrounding layer, intermediate layer and cover material hardness (Shore C hardness, Shore D hardness)
The resin material of each layer was formed into a sheet having a thickness of 2 mm and left at a temperature of 23±2° C. for 2 weeks. Three sheets are superimposed during the measurement. Shore C hardness and Shore D hardness were measured with a Shore C hardness tester and a Shore D hardness tester conforming to the ASTM D2240 standard, respectively. For hardness measurement, an automatic rubber hardness tester "P2" manufactured by Kobunshi Keiki Co., Ltd. equipped with a Shore C type hardness tester or a Shore D type hardness tester is used. Read the maximum hardness value.

(Inside/outside) Surface hardness (Shore C hardness, Shore D hardness) of envelope-covered spheres, intermediate-layer-covered spheres, and balls
Measurements were taken by pressing the needle perpendicular to the surface of each sphere. The surface hardness of the ball (cover) is the measured value of land portions on the surface of the ball where no dimples are formed. Shore C hardness and Shore D hardness were measured with a Shore C hardness tester and a Shore D hardness tester conforming to the ASTM D2240 standard, respectively. For hardness measurement, an automatic rubber hardness tester "P2" manufactured by Kobunshi Keiki Co., Ltd. equipped with a Shore C type hardness tester or a Shore D type hardness tester is used. Read the maximum hardness value.

The ball initial velocity was measured using an initial velocity measuring instrument of the same type as the USGA drum rotation type initial velocity instrument, which is an apparatus approved by the R&A. After the balls were temperature-controlled in an environment of 23.9±1° C. for more than 3 hours, they were tested in a room at room temperature of 23.9±2° C. 5. Strike the ball with a 250 lb (113.4 kg) head (striking mass) at a striking speed of 143.8 ft/s (43.83 m/s), striking each of the dozen balls four times6. The time to pass through 28ft (1.91m) was measured and the initial speed (m/s) was calculated. This cycle was performed for approximately 15 minutes.

Each golf ball was evaluated for flight performance (I#6), spin rate on approach, feel on impact, and durability against repeated impact by the following methods. Table 7 shows the results.

Flight performance (I#6)
An iron (I#6) was attached to the golf hitting robot, and the flight distance was measured when hitting at a head speed of 44 m/s, and judged according to the following criteria. The club used was "TourB X-CB"(I#6) manufactured by Bridgestone Sports. In addition, the spin amount was similarly measured by an initial condition measuring device immediately after hitting.
<criterion>
Total flight distance 179.0m or more ... ○
Total flight distance less than 179.0m ・・・ ×

Evaluation of Spin Amount During Approach A golf hitting robot was attached with a sand wedge (SW) and hit at a head speed (HS) of 20 m/s. Similarly, the spin amount was measured by an initial condition measuring device immediately after hitting the ball. As the sand wedge (SW), "TourB XW-1" (SW) manufactured by Bridgestone Sports was used.
<criterion>
A spin rate of 5900 rpm or more ・・・ ○
Spin amount less than 5900 rpm ・・・ ×

Hit feeling Amateur golfers with a handicap of 15 to 25 use irons (I#6
The hitting feeling when a full shot is made with is evaluated according to the following criteria.
<criterion>
More than 15 out of 20 people rated the ball as very soft and good hitting feeling ・・・ ○
More than 10 and less than 14 out of 20 people rated it as soft and good hitting feeling ・・・ △
Less than 9 out of 20 people rated the ball as soft and good hitting feeling ・・・ ×

Durability of Cracking by Repeated Strikes A driver (W#1) was attached to a golf hitting robot, and the head speed was 45 m/s.
<criterion>
Using 10 balls, the number of hits when each ball starts to crack is counted, 3 balls with the least number of hits are selected, and the average value of the number of cracks of the 3 balls is calculated as "cracking" of each example. number of times”. The number of cracks in Example 3 was set to 100 as an index.
Index 90 or more ・・・ 〇 Index less than 90 ・・・ ×

As shown in Table 7, the golf balls of Comparative Examples 1 to 8 are inferior to the products of the present invention (Examples) in the following points.
In Comparative Example 1, Core vh, which is the value of core volume V (cm ³ )×C50, is less than 630, and the value of (Cs−C75)/(C50−Cc) is greater than 2.3. , The crack durability due to repeated impact is not good.
In Comparative Example 2, Core vh, which is the value of core volume V (cm ³ )×C50, is smaller than 630, and the value of (Cs−C75)/(C50−Cc) is greater than 2.3. (ball deflection)/(ball deflection) is greater than 2.3. Hard to say.
In Comparative Example 3, Core vh, which is the value of core volume V (cm ³ )×C50, is smaller than 630, resulting in poor feel on impact.
In Comparative Example 4, the ball deflection amount is less than 2.8 mm, and the value of (ball deflection amount)/(core deflection amount) is smaller than 1.6. Furthermore, Core vh, which is the value of core volume V (cm ³ )×C50, is greater than 1000, and the value of (Cs-C75)/(C50-Cc) is less than 1.0. As a result, the flight distance of the iron is inferior and the hit feeling is not good.
In Comparative Example 5, the ball deflection amount is less than 2.8 mm, and the value of (ball deflection amount)/(core deflection amount) is smaller than 1.6. Furthermore, Core vh, which is the value of core volume V (cm ³ )×C50, is greater than 1000, and the value of (Cs-C75)/(C50-Cc) is less than 1.0. As a result, the flight distance of the iron is inferior and the hit feeling is not good.
In Comparative Example 6, the ball deflection amount is less than 2.8 mm, and the value of (ball deflection amount)/(core deflection amount) is smaller than 1.6. Furthermore, Core vh, which is the value of core volume V (cm ³ )×C50, is greater than 1000, and the value of (Cs-C75)/(C50-Cc) is less than 1.0. As a result, the flight distance of the iron is inferior and the hit feeling is not good.
In Comparative Example 7, the surface hardness of the ball is higher than the surface hardness of the intermediate layer. As a result, the spin rate increases when hit with an iron, resulting in poor flight distance and a low spin rate on approach shots.
In Comparative Example 8, the thickness of the cover (outermost layer) is greater than 1.0 mm. As a result, the spin rate when hit with an iron increases, the initial speed of actual hits decreases, and the flight distance is poor.

Claims (9)

A multi-piece solid golf ball comprising a core, a surrounding layer, an intermediate layer and a cover, wherein the core is made of a single layer or multiple layers and is made of a rubber composition, and the surrounding layer is made of a single layer or multiple layers and is made of a resin material. , the intermediate layer is a single layer formed of a resin material, and the cover is a single layer having a thickness of 1.0 mm or less and is formed of a resin material, and the Shore C hardness of the surface of the core and the core coated with the surrounding layer Shore C hardness of the surface of the sphere covered with the envelope layer (enveloping layer-covered sphere), Shore C hardness of the surface of the sphere obtained by covering the envelope-covered sphere with the intermediate layer (intermediate layer-covered sphere), and Shore C hardness of the surface of the ball However, the conditions of (Shore C hardness of the surface of the envelope-covered sphere)>(Shore C hardness of the surface of the core) and (Shore C hardness of the surface of the intermediate-layer-covered sphere)>(Shore C hardness of the ball surface) The amount of deflection is C (mm) when the core is loaded with an initial load of 98 N (10 kgf) to a final load of 1,275 N (130 kgf), and the ball is subjected to an initial load of 98 N (10 kgf) to a final load. When B (mm) is the amount of deflection when a load of 1,275 N (130 kgf) is applied, B≧2.8 and 1.6≦C/B≦2.3. , Cc is the Shore C hardness of the center of the core, Cs is the Shore C hardness of the surface of the core, C75 is the Shore C hardness of the position 75% of the length of the core radius from the core center toward the surface, From the core center to the surface When the Shore C hardness at the position 50% of the length of the core radius is C50, 1.0 ≤ (Cs - C75) / (C50 - Cc) ≤ 2.3 is satisfied, and the core volume V (cm ³ ) A multi-piece solid golf ball satisfying the condition 630≤Core vh≤1000, where Core vh is the value of xC50. Regarding the internal hardness of the core, 3.0 ≤ (Cs - C50) / (C25 - Cc) ≤ 20, where C25 is the Shore C hardness at a position 25% of the length of the core radius from the center of the core toward the surface. 2. The multi-piece solid golf ball of claim 1, which satisfies .0. 3. The multi-piece solid golf ball according to claim 1, wherein the internal hardness of the core satisfies (Cs-C50)/(C50-Cc)≧1.1. The relationship between the surface Shore C hardness of the envelope-covered sphere and the surface Shore C hardness of the intermediate layer-covered sphere is: (Surface Shore C hardness of intermediate-layer-covered sphere)>(Surface Shore C hardness of envelope-covered sphere) The multi-piece solid golf ball of any one of claims 1 to 3, which satisfies the conditions. 5. The multi-piece solid golf according to any one of claims 1 to 4, wherein the thickness relationship of each layer satisfies the condition of (cover thickness) < (intermediate layer thickness) ≤ (total thickness of surrounding layers). ball. The multi-piece according to any one of claims 1 to 5, wherein the thickness ratio of each layer satisfies the condition of (total thickness of surrounding layers)/(cover thickness + intermediate layer thickness) ≥ 1.0. solid golf ball. The multi-piece solid golf ball according to any one of claims 1 to 6, wherein the envelope layer comprises an inner envelope layer and an outer envelope layer and is formed of at least two layers. The Shore C hardness of the surface hardness of each layer is expressed by the following formula (Shore C hardness of the surface of the ball)<(Shore C hardness of the surface of the intermediate layer-covered sphere)>(Shore C hardness of the surface of the outer envelope layer-covered sphere)≧ 8. The multi-piece solid golf ball of claim 7, satisfying the condition of (Shore C hardness of surface of inner envelope layer-covered sphere)>(Shore C hardness of surface of core). The multi-piece solid golf ball according to any one of claims 1 to 8, wherein the relationship between the core diameter and the ball diameter satisfies the condition of 0.65≤(core diameter)/(ball diameter)≤0.80.

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