JP2014069045A - Solid golf ball - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a golf ball having excellent crack durability, external appearance durability and abrasion resistance under low temperature as demand characteristics to be used for a long period of time, and capable of retaining stable shot feeling and flight performance for a long period of time.SOLUTION: The solid golf ball includes a core 1 and a cover 2. The core 1 is formed of a rubber composition containing a base rubber, a co-crosslinking agent, a crosslinking initiator and a metal oxide. The base rubber is a mixture of polybutadiene and a styrene-butadiene rubber, the styrene-butadiene rubber having a styrene bond content of not more than 35 mass%. The co-crosslinking agent is methacrylic acid. The core 1 has a deflection under specific loading of 2.5-7.0 mm. An occupancy ratio (VR) of a total volume of a dimple space formed downward a plane surrounded by edges of dimples D to a virtual ball volume assumed that there are no dimples D on the ball surface is 0.95-1.7.

Description

  The present invention relates to a golf ball that is used for a long period of time, and relates to a golf ball that is excellent in cracking durability and appearance durability, can maintain a stable hit feeling and flying performance for a long period of time, and has a controlled flight distance.

  In order to maintain durability in long-term use, it is necessary to improve the durability of each member of the golf ball and the wear resistance of the outer surface. In addition, it is necessary to maintain the performance of the golf ball depending on the season.

  By the way, a two-piece solid golf ball is composed of a core and a cover. The core is made of a base rubber mainly composed of cis-1,4-polybutadiene rubber and added with a co-crosslinking agent, a metal oxide, an organic peroxide, and the like. It is widely known that it is a desired rubber cross-linked structure obtained by using an agent. For example, in JP-A-59-49779, a predetermined amount of zinc methacrylate as a co-crosslinking agent is blended with cis-1,4-polybutadiene rubber as a rubber composition of a core of a two-piece solid golf ball. Proposed. However, when zinc methacrylate is used in the rubber composition for the core in this way, it becomes difficult to ensure the durability of the ball during long-term use.

  Japanese Patent Laid-Open No. 2003-70936 proposes blending a predetermined amount of zinc acrylate with cis-1,4-polybutadiene rubber as a rubber composition for the core of a two-piece solid golf ball. However, as described above, when zinc acrylate is used for the rubber composition for the core, it is difficult to ensure the durability of the ball over a long period of use.

  Furthermore, in JP 2004-180793 A and JP 2008-149190 A, a golf ball using zinc acrylate as a core compound and using thermoplastic polyurethane as a cover material has been proposed. The cover becomes hard, and the flying of the ball after the surface of the ball is worn is remarkably reduced, so that the mark durability is deteriorated.

JP 59-49779 JP 2003-70936 A JP 2004-180793 A JP 2008-149190 A

  The present invention has been made in view of the above circumstances, and is excellent in crack durability, appearance durability, ball surface chipping durability in long-term use, and maintains a long-term stable hit feeling and flying performance. An object of the present invention is to provide a controlled solid golf ball.

  As a result of intensive studies to achieve the above object, the present inventors have produced a solid golf ball having a core and a cover, used a mixture of polybutadiene and styrene butadiene rubber as a base rubber, and styrene. While optimizing the amount of styrene bonded to the butadiene rubber, using methacrylic acid as a co-crosslinking agent, blending a predetermined amount of a crosslinking initiator with respect to 100 parts by mass of the base rubber, and the amount of deflection at a specific load of the core By adopting a resin material having a breaking strength of 20 to 80 MPa and an elongation of 150 to 600% as a cover material, the initial velocity of the ball product and the dimple space occupation ratio VR are optimized. Because of the synergistic effect, it exceeds the prediction of golf ball designers and has excellent durability against cracking, chipping, and wear. In also the maintenance of good appearance, good feel, the flight distance was found that controlled golf ball is obtained, those obtained without the present invention.

  That is, in the present invention, methacrylic acid is blended as a co-crosslinking agent for the core rubber composition, and the cracking durability is higher than that of game balls by optimizing the blending amount of methacrylic acid and the blending amount of the crosslinking initiator. Can be very good. In addition, it is preferable to use a cover material made of polyurethane as a main material, and a golf ball excellent in crack durability and wear durability can be obtained. Moreover, it is preferable to optimize the internal hardness distribution of the core, and a solid golf ball having a good hit feeling can be obtained.

Accordingly, the present invention provides the following solid golf ball.
[1] A golf ball comprising a core and a cover, wherein the core is formed of a rubber composition containing a base rubber, a co-crosslinking agent, a cross-linking initiator, and a metal oxide. As described above, a mixture of polybutadiene and styrene butadiene rubber is used, the amount of styrene bonds in the styrene butadiene rubber is 35% by mass or less, methacrylic acid is used as a co-crosslinking agent, and the core has an initial load of 98 N (10 kgf) to a final load. The deflection amount (CH) when loaded on 1,275 N (130 kgf) is 2.5 to 7.0 mm, and the total dimple space volume formed downward from the plane surrounded by the dimple edges is The ratio (VR) of the volume of the phantom sphere assuming that no dimples exist on the ball surface is 0.95 to 1.7. Golf ball.
[2] The solid golf ball according to [1], wherein the metal oxide is zinc oxide.
[3] In the blending of each component of the rubber composition, the proportion of polybutadiene in the base rubber is 80% by mass or less, and the proportion of styrene butadiene rubber in the base rubber is 20 to 80% by mass. The proportion of the isoprene rubber in the base rubber is 60% by mass or less, and 6 to 40 parts by mass of methacrylic acid and 6 to 30 parts by mass of the metal oxide with respect to 100 parts by mass of the base rubber. The solid golf ball according to [1] or [2], comprising 0.3 to 5.0 parts by mass of a crosslinking initiator and 0.1 to 1.0 parts by mass of an antioxidant.
[4] The solid golf ball according to [1], [2] or [3], wherein the specific gravity of the core is 1.05 to 1.2.
[5] The solid golf ball according to any one of [1] to [4], wherein the resin material of the cover is mainly made of polyurethane.
[6] The solid golf ball according to [5], wherein the resin material of the cover is mainly composed of thermoplastic polyurethane.
[7] The solid golf ball according to any one of [1] to [6], wherein the cover has a Shore D hardness of 30 to 57.
[8] The solid golf ball according to any one of [1] to [7], wherein the resin material of the cover has a breaking strength of 20 to 80 MPa.
[9] The solid golf ball according to any one of [1] to [8], wherein an elongation of the resin material of the cover is 150 to 600%.
[10] The solid golf ball according to any one of [1] to [9], wherein the cover has a thickness of 0.3 to 2.5 mm.
[11] The solid golf ball according to any one of [1] to [10], wherein the initial velocity (BV) of the ball is 72 m / s or less.
[12] From the initial load 98N (10 kgf) when the initial load 98 N (10 kgf) to the final load 1,275 N (130 kgf) is applied to the core is CH (mm) and the ball is first measured. The amount of deflection of the ball up to when a final load of 1,275 N (130 kgf) is applied is BH1 (mm), and the initial velocity of the ball is BV1 (m / s). 350 days from the initial load of 98 N (10 kgf) to the final load of 1,275 N (130 kgf), the deflection of the ball is BH2 (mm), and the initial velocity of the ball is BV2 (m / S)
BH1 is 2.5 to 7.0 mm,
The value of CH / BH1 is 0.95 to 1.1,
The solid golf ball according to any one of [1] to [11], wherein a difference between BH2 and BH1 is within 0.2 mm, and a difference between BV2 and BV1 is within 0.3 m / s.
[13] The solid golf ball according to any one of [1] to [12], wherein dimples satisfying the following requirements (1) to (6) are formed on a surface.
(1) It has a dimple provided with a radius of curvature (R) of 0.5 to 2.5 mm at the peripheral edge.
(2) The ratio (ER) of the total number of dimples (RA) to the total number of dimples (N) in which the ratio (R / D ratio) of the radius of curvature (R) to the diameter (D) is 20% or more is 15 to 95. %.
(3) A dimple having a plurality of types of dimples having different diameters (D) and having a radius of curvature (R) of a dimple having a diameter (D) larger than its own diameter (D) equal to or less than its own radius of curvature (R) The ratio (DER) of the total number (DE) of the maximum diameter dimples having the maximum diameter (D) to the total number of dimples (N) is 80% or more.
(4) It has three or more types of dimples having different diameters (D).
(5) The total number of dimples (N) is 380 or less.
(6) The surface occupancy (SR), which is the ratio of the total dimple area defined by the plane surrounded by the dimple edges to the surface area of the phantom sphere assuming that no dimples exist on the ball surface, is 60 to 74 %.

  The solid golf ball of the present invention has excellent durability against cracking, appearance durability, and scratch resistance at low temperatures as required characteristics for a long period of time, and can maintain a stable feel and flying performance for a long period of time. Is.

1 is a schematic cross-sectional view of a solid golf ball showing an embodiment of the present invention. It is a schematic diagram of the core for demonstrating the site | part of (A)-(F) of the cross-sectional hardness of a core. It is the schematic which shows an example of the cross section of a dimple. An example of a dimple arrangement | sequence is shown, (A) is a top view, (B) is a front view. It is a top view which shows the mark attached | subjected to the golf ball produced in the Example and the comparative example.

Hereinafter, the present invention will be described in more detail.
The structure of the solid golf ball of the present invention is, for example, a two-piece solid golf ball G comprising a core 1 and a cover 2 covering the core, as shown in FIG. A large number of dimples D are usually formed on the surface of the cover 2. In addition, in this figure, although the core 1 and the cover 2 are each formed in the single layer, all can be made into multiple layers.

  The core is obtained by vulcanizing a rubber composition mainly composed of a rubber material. Specifically, as the rubber composition, for example, a rubber composition containing a base rubber, a co-crosslinking agent, a crosslinking initiator, a metal oxide, an anti-aging agent, and an inert filler as necessary is used. Can be formed. In the present invention, a mixture of polybutadiene and styrene butadiene rubber is used as the base rubber. In the present invention, as will be described later, there is a specific change in the core cross-section hardness from the core surface to the center, and it is desirable to adjust the hardness distribution of the core cross-section to a desired range. For this purpose, in the core formulation, it is necessary to appropriately adjust the blending amount, vulcanization temperature, vulcanization time, and the like of various additives described later.

  The polybutadiene as the rubber component has a cis-1,4-bond of 60% (mass%, the same shall apply hereinafter) or more, preferably 80% or more, more preferably 90% or more, and most preferably 95% or more. is necessary. If there are too few cis-1,4-bonds, the resilience will decrease. Further, the content of 1,2-vinyl bonds is preferably 2% or less, more preferably 1.7% or less, and still more preferably 1.5% or less.

The polybutadiene has a Mooney viscosity (ML _{1 + 4} (100 ° C.)) of preferably 30 or more, preferably 35 or more, more preferably 40 or more, and the upper limit is preferably 100 or less, more preferably 80 or less, still more preferably. 70 or less, most preferably 60 or less.

The Mooney viscosity referred to in the present invention is an industrial viscosity index (JIS K 6300) measured with a Mooney viscometer, which is a kind of rotational plasticity meter, and has ML _{1 + 4} as a unit symbol. (100 ° C.) is used. Further, M is Mooney viscosity, L is a large rotor (L type), 1 + 4 is a preheating time of 1 minute, and a rotor rotation time is 4 minutes, which is measured at 100 ° C.

  The polybutadiene is preferably synthesized with a rare earth element-based catalyst or a Group VIII metal compound catalyst from the viewpoint of obtaining a vulcanized molded product of a rubber composition having good resilience.

  The rare earth element-based catalyst is not particularly limited, but a catalyst using a lanthanum series rare earth element compound can be preferably used. Further, if necessary, a lanthanum series rare earth element compound can be used in combination with an organoaluminum compound, an alumoxane, a halogen-containing compound, and a Lewis base. As the various compounds exemplified above, those described in JP-A-11-35633, JP-A-11-164912, and JP-A-2002-293996 can be suitably used.

  Among the rare earth element-based catalysts described above, it is recommended to use a neodymium-based catalyst using a neodymium compound that is a lanthanum series rare earth element compound. In this case, a high content of 1,4-cis bonds, A polybutadiene rubber having a low vinyl bond content can be obtained with excellent polymerization activity.

  As the polybutadiene, the molecular weight distribution Mw / Mn (Mw: weight average molecular weight, Mn: number average molecular weight) is preferably 1.0 or more, more preferably 2.0 or more, still more preferably 2.2 or more, and most preferably. Is 2.4 or more, and the upper limit is preferably 6.0 or less, more preferably 5.0 or less, and even more preferably 4.5 or less. If Mw / Mn is too small, workability is improved. If it is too low, the resilience may decrease.

  The polybutadiene is used as the base rubber. In this case, the ratio of the polybutadiene to the whole base rubber is not particularly limited, but is preferably 80% by mass or less, more preferably 70% by mass. Hereinafter, it is more preferably 60% by mass or less, and most preferably 57% by mass or less. As a minimum, Preferably it is 30 mass% or more, More preferably, it is 35 mass% or more, Preferably it is 38 mass% or more.

  Specifically, as the cis-1,4-polybutadiene rubber, high cis BR01, BR11, BR02, BR02L, BR02LL, BR730, BR51 manufactured by Nippon Synthetic Rubber Co., Ltd. (manufactured by JSR) can be used.

  In the present invention, styrene butadiene rubber (SBR) is used as the base rubber together with the above polybutadiene (BR), which will be described below.

  As styrene butadiene rubber (SBR), solution polymerization styrene butadiene rubber and emulsion polymerization styrene butadiene rubber can be used. Specifically, solution polymerization SBR-SL552, SL555, SL563 manufactured by Nippon Synthetic Rubber Co., Ltd. (manufactured by JSR) as solution polymerized styrene butadiene rubber, etc. Emulsion polymerization SBR 1500, 1502, 1507, etc. can be used.

  The amount of styrene bonds in the styrene-butadiene rubber is preferably 5% by mass or more, more preferably 10% by mass or more, still more preferably 15% by mass or more, and most preferably 18% by mass or more. Moreover, the upper limit is 35 mass% or less in this invention, Preferably it is 30 mass% or less, More preferably, it is 25 mass% or less, More preferably, it is 22 mass% or less. If the amount of styrene bond is too large, the core becomes hard or the resilience changes greatly due to temperature changes due to seasonal differences. If the amount is too small, the workability during polishing of the core is greatly reduced. Moreover, when there is too much said styrene bond amount, the abrasion resistance in low temperature will worsen.

  The ratio of the styrene butadiene rubber to the whole base rubber is preferably 20% by mass or more, more preferably 25% by mass or more, still more preferably 30% by mass or more, and most preferably 35% by mass or more. The upper limit ratio is preferably 80% by mass or less, more preferably 70% by mass or less, still more preferably 60% by mass or less, and most preferably 57% by mass or less.

  In addition to the polybutadiene and styrene butadiene rubber (SBR), other rubber components can be blended with the base rubber as long as the effects of the present invention are not impaired. Examples of rubber components other than the above polybutadiene and styrene butadiene rubber (SBR) include polybutadiene other than the above polybutadiene and other diene rubbers such as natural rubber, isoprene rubber (IR), and ethylene propylene diene rubber.

The above isoprene rubber (IR) contains 60% or more, preferably 80% or more, more preferably 90% or more of cis-1,4-bond, and Mooney viscosity (ML _{1 + 4} (100 ° C.)). Is 60 or more, preferably 70 or more, more preferably 80 or more, and an upper limit of 90 or less, preferably 85 or less can be used. Specifically, IR2200 manufactured by Nippon Synthetic Rubber Co. (manufactured by JSR) or the like can be used. The proportion of the rubber component other than polybutadiene in the whole base rubber is preferably more than 0, more preferably 2% by mass or more, and most preferably 5% by mass or more. Moreover, as an upper limit, it is 60 mass% or less, More preferably, it is 40 mass% or less, More preferably, it is 20 mass% or less, Most preferably, it is 10 mass% or less.

  As the co-crosslinking agent, methacrylic acid is used as an essential component in the present invention. Methacrylic acid is preferably 6 parts by mass or more, more preferably 8 parts by mass or more, more preferably 10 parts by mass or more, and further preferably 11.5 parts by mass or more, with respect to 100 parts by mass of the base rubber. Preferably it is 40 mass parts or less, Preferably it is 35 mass parts or less, More preferably, it is 30 mass parts or less, More preferably, it is 25 mass parts or less. If the amount is too large, it may become too hard and unbearable feel may occur, and if the amount is too small, it may become too soft and unbearable feel.

  As the crosslinking initiator, an organic peroxide is preferably used. Specifically, Park Mill D (manufactured by NOF Corporation), Perhexa C40 (manufactured by NOF Corporation), Trigonox 29-40b Commercially available products such as (manufactured by Akzo Nobel) can be suitably used. These may be used alone or in combination of two or more.

  The crosslinking initiator is 0.3 parts by mass or more, preferably 0.5 parts by mass or more, more preferably 0.7 parts by mass or more, with respect to 100 parts by mass of the base rubber. Parts or less, preferably 4.0 parts by weight or less, more preferably 3.0 parts by weight or less, and most preferably 2.0 parts by weight or less. If the blending amount is too large, it will become too hard and an unbearable feel will be caused, and the cracking durability will be greatly reduced. On the other hand, if the blending amount is too small, the feel becomes too soft and unbearable, and the productivity may be greatly reduced.

  There is no restriction | limiting in particular as a metal oxide, Although it is suitable to use a zinc oxide in this invention, It is also possible to use metal oxides other than a zinc oxide unless the effect of this invention is impaired. About the compounding quantity of a metal oxide, Preferably it is 6 mass parts or more with respect to 100 mass parts of said base rubber, More preferably, it is 8 mass parts or more, More preferably, it is 10 mass parts or more, Most preferably, it is 12 mass parts or more. The upper limit is preferably 30 parts by mass or less, more preferably 28 parts by mass or less, still more preferably 26 parts by mass or less, and particularly preferably 24 parts by mass or less. If the amount is too large or too small, it may not be possible to obtain a proper mass and suitable hardness and resilience.

  Moreover, in this invention, it is suitable to mix | blend an anti-aging agent with a rubber composition, for example, commercially available, such as Nocrack NS-6, NS-30, and 200 (Ouchi Shinsei Chemical Co., Ltd. product). Product can be adopted. These may be used individually by 1 type and may use 2 or more types together.

  Although there is no restriction | limiting in particular about the compounding quantity of anti-aging agent, Preferably it is 0.1 mass part or more with respect to 100 mass parts of base rubber, More preferably, it is 0.15 mass part or more, Preferably it is 1.0 as an upper limit. It is 0.7 parts by mass or less, more preferably 0.4 parts by mass or less. If the amount is too large or too small, an appropriate core hardness gradient may not be obtained, and a suitable resilience, durability, and low spin effect during full shot may not be obtained.

  As the inert filler, for example, barium sulfate, calcium carbonate, silica and the like can be suitably used. These may be used individually by 1 type and may use 2 or more types together. The compounding amount of the inert filler is not particularly limited, but can be preferably more than 0, preferably 1 part by mass or more, more preferably 5 parts by mass or more with respect to 100 parts by mass of the base rubber. Moreover, the upper limit of the amount is preferably 50 parts by mass or less, more preferably 40 parts by mass or less, and still more preferably 30 parts by mass or less. If the blending amount of the inert filler is too much or too little, it may not be possible to obtain an appropriate weight, and suitable hardness and resilience.

  In the present invention, from the viewpoint of resource recycling, one or two powders selected from predetermined rubber powders (Ia), (Ib) and polyurethane resin powder (II) as the rubber component of the core are used. More than one species can be blended. In this case, the pulverized powder and the abrasive powder are more than 0, preferably 2% by mass or more, most preferably 5% by mass or more, and the upper limit is 40% by mass or less, more preferably 100% by mass of the base rubber. Can be blended in a small amount of 35% by mass or less, more preferably 30% by mass or less, and most preferably 25% by mass or less. The rubber powder (I) and polyurethane resin powder (II) used in the present invention can be obtained by the following method (i) or (ii).

Method (i) When a golf ball cover is formed of a polyurethane resin, when the golf ball cover is molded, the resin of the runner portion discharged as an unnecessary material, burrs generated at the time of molding, or defective molding are obtained. In addition, a golf ball and a finely pulverized abrasive powder obtained by polishing the core are used as a predetermined rubber powder (Ia), (Ib), and polyurethane resin powder (II). ) Can be preferably employed.

The method (ii) is a predetermined molding having a particle size of a certain size or less by pulverizing a poorly molded product or a used golf ball itself by a pulverizer and passing the pulverized product through a sieve. The rubber powders (Ia), (Ib) and the polyurethane resin powder (II) can be collected and used. Note that impurities such as paints and inks may be mixed when the golf ball is pulverized, but the pulverized product can be blended as it is unless it is blended in a large amount.

  The particle sizes of the rubber powders (Ia), (Ib) and the polyurethane resin powder (II) are required to be 3 mm or less, preferably 2 mm or less, more preferably as the size of the sieve mesh. Is 1.5 mm or less, more preferably 1 mm or less. When the particle size of the rubber powder (Ia), (Ib) and the polyurethane resin powder (II) exceeds the above size, the durability of the golf ball may be impaired. Adhesion due to the anchor effect may not be sufficiently secured.

  The polyurethane resin powder (II) may be either a thermoplastic polyurethane or a thermosetting polyurethane resin, but more preferably, a thermoplastic polyurethane is employed.

  In the present invention, as described above, one or more kinds of powders selected from two kinds of predetermined rubber powders (Ia) and (Ib) and polyurethane resin powder (II) are used as the core material. By mix | blending, suitable surface roughness is provided to a core, the adhesion surface area with an adjacent cover can be increased, and the adhesiveness by an anchor effect can be improved. In particular, by using thermoplastic polyurethane for the cover material, when the cover material is molded, the polyurethane resin blended in the cover material and the core material is melted, thereby further improving the adhesion between the core and the cover. it can.

Rubber powder (Ia)
In the present invention, the rubber powder (Ia) needs to contain methacrylic acid or a metal salt thereof as an essential component. By using rubber powder (Ia) containing methacrylic acid (MAA) or a metal salt thereof, the durability of the golf ball can be particularly improved. That is, as the rubber powder (Ia), a material obtained by pulverizing the core material described above can be preferably used. However, the rubber material to be pulverized includes an unsaturated carboxylic acid or a metal salt thereof as methacrylic acid. (MAA) or metal salts thereof are included. The content of the methacrylic acid or a metal salt thereof contained in the rubber powder (Ia) is preferably 5% by mass or more, more preferably 10% by mass or more, and further preferably 15% by mass or more. it can. On the other hand, the upper limit is preferably 60% by mass or less, more preferably 50% by mass or less, still more preferably 40% by mass or less, and most preferably 30% by mass or less. When this content is small, the durability is inferior, and when it is too large, the resilience may be lowered.

Rubber powder (Ib)
In the present invention, the rubber powder (Ib) needs to contain acrylic acid (AA) or a metal salt of acrylic acid as an essential component. By using rubber powder (Ib) containing acrylic acid (AA) or a metal salt of acrylic acid, the durability of the golf ball can be maintained well and the initial speed can be increased to improve the flight distance. Can do. That is, as the rubber powder (Ib), a material obtained by pulverizing the core material described above can be preferably used, but the rubber material to be pulverized includes an unsaturated carboxylic acid or a metal salt thereof as Acrylic acid (AA) or a metal salt thereof is included. Examples of the metal salt of acrylic acid include zinc acrylate (ZDA), magnesium acrylate, sodium acrylate, potassium acrylate, aluminum acrylate, calcium acrylate, and the like. The content of the acrylic acid or the metal salt thereof contained in the rubber powder (Ib) is preferably 3% by mass or more, more preferably 10% by mass or more, and further preferably 15% by mass or more. it can. On the other hand, the upper limit is preferably 60% by mass or less, more preferably 50% by mass or less, still more preferably 40% by mass or less, and most preferably 30% by mass or less. When this content is small, the durability is inferior, and when it is too large, the resilience may be lowered.

Polyurethane resin powder (II)
When the thermoplastic polyurethane powder is used, it is preferable to use a powder having a flow starting point of 150 ° C. or higher, more preferably 160 ° C. or higher, and still more preferably 170 ° C. or higher. . The upper limit is preferably 320 ° C. or lower, more preferably 300 ° C. or lower, and even more preferably 280 ° C. or lower. If the powder flow starting point is too low, the powder melts at the time of vulcanization of the core, and the durability and symmetry of the core may deteriorate. Conversely, if the powder flow starting point is too high, the surface polyurethane cannot be melted during cover molding, and therefore the effect of further improving durability by using thermoplastic polyurethane cannot be obtained. There is.

  The core can be produced by vulcanizing and curing a rubber composition containing the above components by a known method. For example, kneading using a kneader such as a Banbury mixer or roll, compression molding or injection molding using a core mold, and heat curing at a temperature sufficient for the organic peroxide or co-crosslinking agent to act. The core has a predetermined hardness distribution. In this case, the vulcanization conditions are not particularly limited, but the vulcanization temperature is usually about 100 to 200 ° C., and the lower limit is preferably 150 ° C. or higher, more preferably 155 ° C. or higher, and the upper limit. Is preferably 180 ° C. or lower, more preferably 175 ° C. or lower, and most preferably 170 ° C. or lower. The vulcanization time is usually about 10 to 40 minutes, and the lower limit is preferably 12 minutes or more, and the upper limit is preferably 30 minutes or less, more preferably 25 minutes or less, and most preferably 20 minutes or less. It is. The core hardness distribution of the present invention can be realized by a combination of vulcanization conditions and rubber compounding preparation.

  The diameter of the core is not particularly limited, but is 38.0 mm or more, preferably 38.9 mm or more, more preferably 39.3 mm or more, and the upper limit is preferably 42.1 mm or less, more preferably 41.1 mm. It is as follows. If the diameter of the core is out of this range, the cracking durability of the ball may be significantly reduced or the initial speed of the ball may be lowered.

  The specific gravity of the core is preferably 1.05 or more, more preferably 1.08 or more, further preferably 1.1 or more, and the upper limit is preferably 1.2 or less, more preferably 1.15 or less, still more preferably. 1.13 or less is recommended.

  The amount of deflection when the core is loaded, that is, the amount of deflection (mm) (CH) from when the initial load 98N (10 kgf) to the final load 1,275 N (130 kgf) is applied to the core is 2 It is 0.5 mm or more, preferably 2.6 mm or more, more preferably 2.7 mm or more. Moreover, as an upper limit, said deflection amount is 7.0 mm or less, Preferably it is 6.0 mm or less, More preferably, it is 5.5 mm or less, More preferably, it is 5.2 mm or less. If the deflection amount (CH) of the core is too small, the hit feeling becomes too hard and the hit feeling becomes unbearable, and conversely if it is too large, the feel becomes soft and unbearable hit feeling, and the productivity may be greatly reduced. .

  The core resilience (CV) is 60 m / s or more, preferably 63 m / s or more, more preferably 66 m / s or more, most preferably 67 m / s or more, and the upper limit is 73 m / s or less, more preferably It is 72.5 m / s or less, More preferably, it is 72 m / s or less. If the distance deviates from this range, the flight distance may be extremely reduced, or the flight distance may be excessive and sufficient control may not be possible. The resilience of the core is synonymous with the initial velocity of the core.

  In the present invention, as illustrated by the schematic diagram of the core of FIG. 2, the JIS-C hardness of the core surface is (A), the JIS-C hardness of 2 mm inside from the core surface is (B), and the core surface is The JIS-C hardness of the part 5 mm inside (C), the JIS-C hardness of the part 10 mm inside from the core surface (D), the JIS-C hardness of the part 15 mm inside from the core surface (E), and the core When the center JIS-C hardness is (F), it is not particularly limited, but each of (A) to (F) preferably has a specific range as described below. Thus, by setting the hardness distribution inside the core within a predetermined range, it is possible to obtain a comfortable feel close to a game ball and good cracking durability.

  When the JIS-C hardness of the core surface is (A), the value of (A) is preferably 60 or more, more preferably 63 or more, still more preferably 65 or more. It is preferable that it is 88 or less, More preferably, it is 86 or less, More preferably, it is 84 or less.

  When the JIS-C hardness of the portion 2 mm inside from the core surface is (B), the value of (B) is preferably 54 or more, more preferably 57 or more, still more preferably 59 or more. The upper limit is preferably 83 or less, more preferably 81 or less, and even more preferably 79 or less.

  When the JIS-C hardness of the portion 5 mm inside from the core surface is (C), the value of (C) is preferably 56 or more, more preferably 59 or more, still more preferably 61 or more. The upper limit is preferably 85 or less, more preferably 83 or less, and still more preferably 81 or less.

  When the JIS-C hardness of the portion 10 mm inside from the core surface is (D), the value of (D) is preferably 54 or more, more preferably 57 or more, and still more preferably 60 or more. The upper limit is preferably 80 or less, more preferably 78 or less, and still more preferably 76 or less.

  When the JIS-C hardness of the portion 15 mm inside from the core surface is (E), the value of (E) is preferably 51 or more, more preferably 54 or more, still more preferably 57 or more, The upper limit is preferably 75 or less, more preferably 73 or less, still more preferably 71 or less, and most preferably 70 or less.

  When the JIS-C hardness at the center of the core is (F), the value of (F) is preferably 48 or more, more preferably 51 or more, still more preferably 54 or more. It is suitable that it is 72 or less, More preferably, it is 70 or less, More preferably, it is 68 or less.

  Furthermore, in the hardness distribution of the core, the hardness relationship of (A)> (B) <(C) ≧ (D)> (E)> (F) is satisfied, and the value of (A) − (F) Is 19 or less, (A) to (F) are most hard to be formed, and it is preferable that the value of (A)-(C) is 0-8. If the above conditions are not satisfied, the hit feeling and crack durability may be reduced if the above conditions are not satisfied.

  About the value of (A)-(C), it is 0-8, Preferably it exceeds 0, More preferably, it is 1 or more, More preferably, it is 2 or more, As an upper limit, Preferably it is 8 or less, More preferably, it is 6 Hereinafter, it is more preferably 4 or less. About the value of (A)-(F), it is preferable that it is 2 or more as a lower limit, More preferably, it is 4 or more, More preferably, it is 6 or more, As an upper limit, Preferably it is 19 or less. More preferably, it is 18 or less, More preferably, it is 17 or less.

  In the present invention, the core may be surface-treated with a solution containing a halogenated isocyanuric acid and / or a metal salt thereof.

  Further, before the surface treatment is performed on the core with a solution containing a halogenated isocyanuric acid and / or a metal salt thereof shown below, the core surface is subjected to a polishing treatment, thereby adjoining the core surface. The adhesiveness with the material can be further improved.

  At this time, the polishing treatment removes the skin layer from the core surface after vulcanization, increases the permeability of the halogenated isocyanuric acid and / or its metal salt solution to the core surface, and the contact area with the adjacent cover material. Can be increased. Specific methods include buffing, barrel polishing, centerless polishing, and the like.

（ここで、Ｘは、水素原子、ハロゲン原子又はアルカリ金属原子を表す。Ｘの少なくとも１個はハロゲン原子である。ハロゲン原子としては、Ｆ、Ｃｌ、Ｂｒが好ましく、特にＣｌが好ましい。アルカリ金属原子としては、Ｌｉ、Ｎａ、Ｋが好ましい。） Said halogenated isocyanuric acid and its metal salt are compounds represented by the following formula (I).

(Here, X represents a hydrogen atom, a halogen atom or an alkali metal atom. At least one of X is a halogen atom. F, Cl and Br are preferable, and Cl is particularly preferable. Alkali metal. (As atoms, Li, Na, and K are preferable.)

  Specific examples of the halogenated isocyanuric acid and / or metal salts thereof include chloroisocyanuric acid, sodium chloroisocyanurate, potassium chloroisocyanurate, dichloroisocyanuric acid, sodium dichloroisocyanurate, sodium dichloroisocyanurate dihydrate, dichloroisocyanuric Examples thereof include salts of potassium acid, trichloroisocyanuric acid, isocyanuric tribromide, isocyanuric dibromide, isocyanuric bromide, sodium isocyanurate dibromide, hydrates thereof, difluoroisocyanuric acid and the like. Among these, chloroisocyanuric acid, sodium chloroisocyanurate, potassium chloroisocyanurate, dichloroisocyanuric acid, sodium dichloroisocyanurate, potassium dichloroisocyanurate, and trichloroisocyanuric acid are preferable. This is because they are easily hydrolyzed by moisture to generate an acid and chlorine and serve as an initiator for an addition reaction to a double bond in a diene rubber molecule. In particular, when trichloroisocyanuric acid is used, the effect of improving adhesiveness is remarkable.

  The halogenated isocyanuric acid and / or metal salt thereof is preferably used as a solution by dissolving in water or an organic solvent.

  When water is used as the solvent, the content of the halogenated isocyanuric acid and / or metal salt thereof in the treatment liquid is not particularly limited, but preferably 0.5 parts by mass or more with respect to 100 parts by mass of water. More preferably, it is 1 mass part or more, More preferably, it can be 3 mass parts or more. If the content of halogenated isocyanuric acid and / or metal salt thereof is too low, the effect of improving adhesiveness expected after the core surface treatment cannot be obtained, and the impact durability may be poor. Moreover, although the upper limit is a saturated solution density | concentration, when cost effectiveness is considered, it is preferable to make about 10 mass parts an upper limit with respect to 100 mass parts of water. Further, the immersion time of the core in the treatment liquid is not particularly limited, but is preferably 0.3 seconds or more, more preferably 3 seconds or more, and further preferably 10 seconds or more. Also, the upper limit is not particularly limited, but is preferably within 5 minutes, more preferably within 4 minutes. If it is too short, the treatment effect may not be obtained, and if it is too long, the productivity may be impaired.

  On the other hand, when using an organic solvent, a well-known thing can be used and especially the organic solvent soluble in water can be used conveniently. Specific examples thereof include ethyl acetate, acetone, methyl ethyl ketone and the like. Among these, acetone is particularly preferable from the viewpoint of permeability to the core surface. Solvents that are soluble in water are easy to incorporate moisture into the solvent, and the incorporated moisture is liable to hydrolyze with the halogenated isocyanuric acid and / or its metal salt adhering to the core surface, or to the next step. When washing is used, it is preferably used for the reason that the affinity to the core surface is improved and the hydrolysis reaction between water and a halogenated isocyanuric acid and / or a metal salt thereof easily occurs.

  When dissolved in an organic solvent, the content of the halogenated isocyanuric acid and / or metal salt thereof in the solution is preferably 0.3% by mass or more, more preferably 1% by mass or more, and further preferably 2.5% by mass. If it is above and it is less than 0.3 mass%, the adhesive improvement effect expected after core surface treatment cannot be obtained, and impact durability may be inferior. The upper limit can be up to a saturated solution concentration. However, in consideration of cost effectiveness, for example, when an acetone solution is used, it is preferable that the upper limit is about 10% by mass. Further, the immersion time of the core in the above solution is not particularly limited, but is preferably 0.3 seconds or more, more preferably 3 seconds or more, and further preferably 10 seconds or more. Also, the upper limit is not particularly limited, but is preferably within 5 minutes, more preferably within 4 minutes. If it is too short, the treatment effect may not be obtained, and if it is too long, the productivity may be impaired.

  As a method for treating the core surface with a halogenated isocyanuric acid and / or a metal salt thereof, a method of applying a halogenated isocyanuric acid and / or a metal salt solution thereof to the core surface by brushing or spraying, or the core is isocyanuric halide Although the method of immersing in an acid and / or its metal salt solution etc. is mentioned, the immersion method is used especially suitably from a viewpoint of productivity and the high permeability of the solution to the core surface.

  The core surface is preferably washed with water after the surface treatment is performed with a solution containing a halogenated isocyanuric acid and / or a metal salt thereof. Washing the core surface with water can be done by running water, spraying, soaking using a washing layer, etc., but it is not only for washing, but also for the purpose of starting and promoting the desired treatment reaction. A too rapid cleaning method is not suitable. Therefore, pickling and washing provided with a washing basket is preferably used. In this case, it is preferable to put it about 1 to 5 times in a washing bowl containing fresh water.

  By treating the core surface with a halogenated isocyanuric acid and / or a metal salt thereof, adhesion to the cover is greatly improved. The reason is not clear, but the following can be considered.

  First, the halogenated isocyanuric acid and / or its metal salt penetrates into the diene rubber forming the core together with the solvent, and approaches the double bond of the main chain. Thereafter, water enters the core surface, and the halogenated isocyanuric acid and / or its metal salt is hydrolyzed with water to release halogen. The halogen attacks the double bond of the nearby diene rubber main chain, and the addition reaction proceeds. In the course of the addition reaction, liberated isocyanuric acid is added to the diene rubber main chain together with halogen while maintaining the ring structure. The added isocyanuric acid has three —NHCO— structures in the molecule.

  Accordingly, the core surface treated with the halogenated isocyanuric acid and / or metal salt thereof is given a structure of -NHCO-, so that the adhesion to the cover material is further improved, so that the hitting durability as a golf ball is improved. It is thought that it is done. Further, when a polyurethane elastomer or a polyamide elastomer having the same —NHCO— structure in the polymer molecule is used as the cover material, it is considered that the impact durability is further increased because the affinity is further increased.

  The material of the surface portion of the solid core after the surface treatment does not show any exothermic or endothermic peak from room temperature to 300 ° C. by differential scanning calorimetry (DSC). This means that the introduced functional group is kept stable in this temperature range. In other words, the introduced functional group does not cause thermal decomposition in the molding process of the cover material, and maintains its effectiveness. Also, it does not cause melting like a hot-melt resin and begins to bleed into the parting line. This means that there is no concern about adverse effects on durability and appearance quality. In addition, as described above, the stability of the material of the surface portion of the solid core after the surface treatment is one of the evidence that isocyanuric acid having a melting point of 300 ° C. or higher was added while maintaining its molecular structure. It can be said that there is.

In addition, when addition of isocyanuric acid and chlorine to the diene rubber surface using an organic solvent, the state change of the bond before and after the addition is a C═O bond (stretching) at 1725 to 1705 cm ⁻¹ in the infrared absorption spectrum. absorption peak), broad absorption peak of N-H bond in 3450~3300cm ^-1 (stretching), it appears to increase the absorption peak of the C-Cl bond in 800~600cm ^-1. Therefore, by measuring the infrared absorption spectrum of the surface-treated core and confirming the increase of these absorption peaks, it was confirmed that the addition of isocyanuric acid and chlorine into the diene rubber molecule on the core surface occurred. Can be qualitatively supported.

Next, the cover material that is directly coated on the core will be described below.
In the present invention, a thermoplastic resin such as an ionomer resin or polyurethane can be used for the resin component of the cover. In particular, it is preferable to employ a resin material mainly composed of polyurethane. Specifically, a thermoplastic polyurethane elastomer or a thermosetting polyurethane resin can be used, and it is particularly preferable to employ a thermoplastic polyurethane elastomer.

  The thermoplastic polyurethane elastomer has a soft segment composed of a polymer polyol (polymeric glycol), a chain extender constituting the hard segment, and a diisocyanate. Here, as the raw material polymer polyol, any of those conventionally used in the technology relating to thermoplastic polyurethane materials can be used, and is not particularly limited. The polyether type is preferable to the polyester type in that a thermoplastic polyurethane material having a high elastic modulus and excellent low-temperature characteristics can be synthesized. Examples of the polyether polyol include polytetramethylene glycol and polypropylene glycol. Polytetramethylene glycol is particularly preferable from the viewpoint of the resilience modulus and low temperature characteristics. The average molecular weight of the polymer polyol is preferably 1000 to 5000, and particularly preferably 2000 to 4000 in order to synthesize a thermoplastic polyurethane material having high resilience.

  As the chain extender, those used in the conventional technology relating to thermoplastic polyurethane materials can be suitably used. For example, 1,4-butylene glycol, 1,2-ethylene glycol, 1,3-butanediol, 1 , 6-hexanediol, 2,2-dimethyl-1,3-propanediol and the like, but are not limited thereto. These chain extenders preferably have an average molecular weight of 20 to 15000.

  As the diisocyanate, those used in the conventional technology relating to thermoplastic polyurethane materials can be preferably used. Aliphatic diisocyanates, aliphatic diisocyanates such as hexamethylene diisocyanate, and the like, but are not limited thereto. However, some isocyanate species make it difficult to control the crosslinking reaction during injection molding. In the present invention, 4,4'-diphenylmethane diisocyanate which is an aromatic diisocyanate is most preferable.

  Commercially available products can be suitably used as the thermoplastic polyurethane material composed of the above-mentioned materials. For example, DIC Bayer Polymer Co., Ltd .: Pandex T8180, 8195, T8290, T8295, T8260, Dainichi Seika Kogyo ( Resamine 2593, 2597, etc.

  The polyurethane is not particularly limited, but is preferably a material that can be melt-bonded to the polyurethane resin powder (II), and is thermoplastic as the polyurethane resin powder (II). This resin is preferable because it can be expected to be melt-bonded. In particular, those having a high isocyanate content can be suitably used, and the adhesion to the core material can be improved.

  The thickness of the cover is preferably 0.3 mm or more, more preferably 0.5 mm or more, further preferably 0.7 mm or more, and the upper limit is preferably 2.5 mm or less, more preferably 2.1 mm or less. More preferably, it is 1.9 mm or less, and particularly preferably 1.7 mm or less. If the thickness of the cover is larger than the above range, the resilience is lowered and the flying performance may be deteriorated. When the thickness of the cover is smaller than the above range, the durability to cracking is lowered. In particular, the cover may tear when it is topped.

  The specific gravity of the cover is preferably 1.13 or more, more preferably 1.14 or more, still more preferably 1.15 or more, and the upper limit is preferably 1.30 or less, more preferably 1.20 or less, and further Preferably it is 1.17 or less.

  The material hardness of the cover is Shore D hardness, preferably 30 or more, more preferably 35 or more, and even more preferably 38 or more. The upper limit is preferably 57 or less, more preferably 54 or less, and still more preferably 51. Hereinafter, it is particularly preferably 50 or less. If the Shore D hardness of the cover is higher than the above range, the appearance performance (mark durability) during long-term use may be reduced, and the flying performance may be further reduced. If the Shore D hardness of the cover is softer than the above range, the cracking durability is greatly reduced, and the cover may be torn especially when it is topped. Also, the spin becomes very large, which may lead to a decrease in flight distance.

  In addition, in this invention, Shore D hardness means the measurement hardness (durometer D type hardness) by the type D durometer based on JISK7215.

  The breaking strength of the cover resin material is preferably 20 MPa or more, more preferably 25 MPa or more, further preferably 30 MPa or more, and most preferably 35 MPa or more. Further, the upper limit is preferably 80 MPa or less, more preferably 75 MPa or less, further preferably 70 MPa or less, and most preferably 65 MPa or less. The elongation of the cover resin material is preferably 150% or more, more preferably 200% or more, still more preferably 250% or more, and most preferably 300% or more. Moreover, as an upper limit, Preferably it is 600% or less, More preferably, it is 550% or less, More preferably, it is 520% or less, Most preferably, it can be 490% or less. In addition, said breaking strength and elongation (tensile test) mean the value measured based on the specification of JISK7311-1995. Thus, by adopting the cover resin material having a predetermined range of breaking strength and elongation, it is possible to improve the cracking durability, chipping durability, and wear durability required for long-term use.

  The present invention is usually provided with a large number of dimples on its surface. In the present invention, the ratio (VR) of the total volume of the dimple space formed below the plane surrounded by the edge of the dimple to the volume of the phantom sphere assuming that there is no dimple on the ball surface is 0. The preferred lower limit is 1.0 or more, more preferably 1.1 or more, still more preferably 1.2 or more, and the preferred upper limit is 1.6 or less, more preferably 1.5 or less, more preferably 1.45 or less.

  Further, although not particularly limited, it is preferable that the dimples formed on the solid golf ball of the present invention satisfy the following requirements (1) and (2). In addition, it is preferable that the following requirements (1) and (2) are satisfied at the same time, but it is also preferable that each of the following requirements is satisfied.

  First, as requirement (1), as shown in FIG. 3, it is preferable to have a dimple having a rounded portion with a radius of curvature (R) of 0.5 to 2.5 mm at the periphery. A more preferable lower limit value of the radius of curvature (R) is 0.55 mm or more, more preferably 0.6 mm or more, and a more preferable upper limit value is 1.8 mm or less, and further preferably 1.5 mm or less.

  Next, as requirement (2), the ratio (ER) of the total number of dimples (RA) to the total number of dimples (N) in which the ratio (R / D ratio) of the radius of curvature (R) to the diameter (D) is 20% or more. ) Is preferably 15 to 95%. In this case, the R / D ratio is represented by (R / D) × 100%, and the larger the ratio, the larger the ratio of the rounded portion to the size of the dimple, and the dimple having a smoother cross-sectional shape. It means that. The ER represents the ratio of the smooth dimples to all the dimples. By setting the ER to 15 to 95% as described above, damage to the coating film at the edge portion of the dimples can be effectively suppressed. It can be done. In addition, there is no restriction | limiting in particular in the upper limit of the said R / D ratio, However, Preferably it is 60% or less, More preferably, it is 40% or less. Further, the more preferable lower limit of the ER is 20% or more, further preferably 25% or more, and the more preferable upper limit is 90% or less, more preferably 85% or less, and most preferably 70% or less.

  Further, although not particularly limited, it is preferable to satisfy the following requirement (3). That is, as a requirement (3), when a plurality of types of dimples having different diameters (D) are provided, the radius of curvature (R) of the dimple having a diameter (D) larger than its own diameter (D) is set to the radius of curvature of its own ( R) The dimples are formed so that the ratio (DER) of the total number (DE) of the dimples with a maximum diameter (D) and the maximum diameter dimple (DE) to the total number of dimples (N) is 80% or more. Is preferred.

  Normally, if the depth of the dimple (see FIG. 3) is constant, the radius of curvature (R) of the roundness provided at the periphery decreases as the diameter decreases, but the requirement (3) adjusts the depth. By setting the radius R of the peripheral edge to be as large as possible even for dimples with a small diameter by means such as making a dimple having a smooth cross-sectional shape and setting the DER to 80% or more, the ratio of such a smooth dimple can be reduced. In many cases, damage to the coating film is more effectively suppressed. A more preferable value of this DER is 85% or more, more preferably 90% or more, and most preferably 93% or more. The upper limit value of DER is 100%.

  Furthermore, the dimple of the present invention is not limited, but preferably satisfies the following requirements (4) to (6). In addition, it is preferable that the following requirements (4) to (6) are all satisfied simultaneously, but it is also preferable that each of the following requirements (4) to (6) is satisfied individually.

  First, as requirement (4), it is preferable to provide three or more types of dimples having different diameters (D), and more preferably, five or more types of dimples are formed. In this case, the diameter (D) of the dimple is not particularly limited, but is preferably 1.5 to 7 mm. A more preferable lower limit is 1.8 mm or more, and a more preferable upper limit is 6.5 mm or less. It is. Further, the depth of the dimple is not particularly limited, but is preferably 0.05 to 0.35 mm, more preferably a lower limit is 0.1 mm or more, and further preferably 0.13 mm or more, A more preferable upper limit value is 0.32 mm or less, and further preferably 0.29 mm or less.

  Further, as the requirement (5), the total number (N) of dimples is preferably 380 or less, more preferably 350 or less, and more specifically 220 to 340.

  Further, as a requirement (6), the total dimple area defined by the plane surrounded by the dimple edge (the chain line in FIG. 3) occupies the surface area of the phantom sphere assuming that there is no dimple on the ball surface. It is preferable to form the dimples so that the surface occupancy ratio (SR) as a ratio is 60 to 74%. If SR exceeds 74%, the interval between adjacent dimples may become too narrow, and it may be difficult to provide the radius of curvature of the above requirement (1) at the periphery of the dimple, while SR is 60%. If it is less than the aerodynamic performance, the flight distance may decrease. A more preferable lower limit value of SR is 65% or more, still more preferably 68% or more, and a more preferable upper limit value is 73% or less.

  In general, a one-piece golf ball has a slightly yellow rubber color, so a white enamel paint is applied to the first layer, and then a clear paint is applied. From the viewpoint of securing the appearance, it is preferable to apply clear coating to the ball surface of the present invention. The film thickness of the clear coating is 10 μm or more for the dimple bank (Y), preferably 12 μm or more, most preferably 13 μm or more, and the upper limit is 30 μm or less, preferably 25 μm or less, most preferably 20 μm or less. ) Is 8 μm or more, preferably 10 μm or more, most preferably 11 μm or more, and the upper limit is 28 μm or less, preferably 23 μm or less, and most preferably 18 μm or less. Further, the ratio of the bank portion (Y) to the edge portion (Z), Z / Y × 100 is 60% or more, preferably 70% or more, most preferably 80% or more, and the upper limit is 100% or less, preferably 95%. It is as follows. When deviating from the above range, the mark durability at the dimple edge portion may be significantly deteriorated during long-term use.

  The diameter of the ball is 42 mm or more, preferably 42.3 mm or more, more preferably 42.67 mm or more, and the upper limit is 44 mm or less, preferably 43.8 mm or less, more preferably 43.5 mm or less, still more preferably 43 mm or less.

  The weight of the ball is preferably 44.5 g or more, more preferably 44.7 g or more, further preferably 45.1 g or more, and most preferably 45.2 g or more. The upper limit is preferably It is 47.0 g or less, more preferably 46.5 g or less, still more preferably 46.0 g or less.

  The deflection amount (BH1) when the ball is loaded from the initial load 98 N (10 kgf) to the final load 1,275 N (130 kgf) when measured for the first time is preferably 2.5 mm or more, more preferably 2.6 mm or more. More preferably, it is 2.65 mm or more, and the upper limit is preferably 7.0 mm or less, more preferably 6.0 mm or less, further preferably 5.5 mm or less, and most preferably 5.0 mm or less. When the initial load 98N (10 kgf) and the final load 1,275 N (130 kgf) are applied to the core and the ball, when the respective deflection amounts are (CH) and (BH1), (CH) / (BH1) The value is preferably 0.95 or more, more preferably 0.96 or more, further preferably 0.97 or more, and the upper limit value is preferably 1.1 or less, more preferably 1.09 or less, still more preferably 1.08 or less. When the value of (CH) / (BH1) is too large, the amount of deflection of the product is very small with respect to the amount of deflection of the core. That is, since the cover hardness is high, it may lead to a decrease in feel and a decrease in appearance after long-term use. On the other hand, if it is too small, the cover becomes very soft, so the cracking durability is greatly reduced, and the cover may break, especially when it is topped. Also, the spin becomes very large, which may lead to a decrease in flight distance. The above-mentioned “when the ball is measured for the first time” means that the measurement is made within approximately one month after the ball is manufactured.

  In the present invention, the upper limit of the resilience (BV) of the ball is preferably 72 m / s or less, more preferably 71.7 m / s or less, still more preferably 71.4 m / s or less, most preferably Preferably it is 71.2 m / s or less. Further, the lower limit is preferably 60 m / s or more, preferably 63 m / s or more, more preferably 66 m / s or more, and most preferably 67 m / s or more. The rebound of the ball is synonymous with the initial velocity of the ball.

  Further, in the present invention, from the viewpoint of ensuring durability over a long period of time, the deflection of the ball when it is loaded from the initial load 98N (10 kgf) to the final load 1,275 N (130 kgf) when the ball is first measured. The amount is BH1 (mm), the initial velocity of the ball is BV1 (m / s), the ball is first measured and left for 350 days, and then the initial load is 98 N (10 kgf) to the final load of 1 , 275 N (130 kgf) when the ball deflection is BH2 (mm) and the initial velocity of the ball is BV2 (m / s), the difference between BH2 and BH1 is within 0.2 mm It is suitable that it is within 0.15 mm, more preferably within 0.1 mm. The value of BV2-BV1 is preferably within 0.3 m / s, more preferably within 0.2 m / s, and even more preferably within 0.1 m / s. Thereby, the appearance quality and the flying performance are maintained even during long-term use. The above-mentioned “when the ball is measured for the first time” means that the measurement is made within approximately one month after the ball is manufactured.

  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 1-8, Comparative Examples 1-10]
When producing the solid golf balls in the examples and comparative examples, rubber materials having the composition shown in Table 1 below are prepared. This rubber composition is appropriately kneaded with a kneader or a roll, and then vulcanized according to the temperature and time conditions shown in Table 1 to prepare solid cores for each example. In addition, the number of each material in the following table | surface is represented by a mass part.

The material of the core composition in the above table has the following contents.
BR01: Ni catalyst butadiene rubber manufactured by JSR: Mooney viscosity ML “46”
IR2200: JSR isoprene rubber: Mooney viscosity ML “82”
BR730: Nd-catalyzed butadiene rubber manufactured by JSR: Mooney viscosity ML “55”
SL563: Solution-polymerized styrene butadiene rubber manufactured by JSR: Styrene bond amount “20%”
SBR0202: Emulsion-polymerized styrene butadiene rubber manufactured by JSR: Styrene bond amount “46%”
Perhexa C-40: an organic peroxide made from NOF, 1,1-bis (t-butylperoxy) cyclohexane. Since "Perhexa C-40" is a 40% diluted product, the actual addition amount is also shown in the above table.
-Park mill D: Organic peroxide made from Japanese fats and oils, dicumyl peroxide-Zinc oxide: Made by Sakai Chemical Industry Co., Ltd.-Anti-aging agent: "NOCRACK NS-6" made by Ouchi Shinsei Chemical Industry Co., Ltd.
・ Methacrylic acid: Kuraray ・ Zinc methacrylate: Asada Chemical Co., Ltd. ・ Zinc acrylate: Nippon Distillation Co., Ltd. ・ Titanium oxide: Ishihara Sangyo Co., Ltd.

  After the rubber composition was vulcanized and molded in accordance with the ingredients shown in Table 1, the core surface was polished to a desired outer diameter, and then the core surface was trichloroisocyanuric acid in acetone (concentration 3 wt. %) Is immersed for 30 seconds and then washed with water to carry out core surface treatment. Next, this core is set in a cover injection mold, and the cover composition shown in Table 2 below is injection molded around the solid core.

The explanation in the table is as follows.
Product name “High Milan”: Made by Mitsui DuPont Polychemical, ionomer resin Product name “Pandex”: DIC Bayer Polymer, thermoplastic polyurethane elastomer Product name “Surlin”: DuPont ionomer resin magnesium stearate: NOF Titanium dioxide made by the company: Trade name “Taipeku R550”, polyethylene wax by Ishihara Sangyo Co., Ltd .: trade name “Sun Wax 161P”, manufactured by Sanyo Chemical Industries

  The mold cavity has a number of convex protrusions corresponding to the dimple pattern so that a predetermined dimple pattern is formed on the cover surface. Is also typed. Details of the dimples are shown in Table 3 below. In addition, the mark shown in FIG. 5 is printed on the surface of the ball, and further, the base material: polyester resin (acid value 6, OH value 168) (solid content) / butyl acetate / PMA (propylene glycol) Adduct body of hexamethylene diisocyanate as a curing agent: non-yellowing polyisocyanate (Takeda Pharmaceutical Co., Ltd., Takenate D-) with respect to 100 parts by mass of the main agent, with 70/15/15 parts by mass of monomethyl ether acetate) 160N, NCO content of 8.5% by mass, solid content of 50% by mass) is 150 parts by mass and butyl acetate is 150 parts by mass. In Comparative Example 10, white enamel coating is applied to the first layer as a clear coating undercoat.

Details of each item in Table 3 are as follows.
R: radius of curvature R / D ratio of roundness provided at the peripheral portion: ratio of radius of curvature (R) to diameter (D) N: total number of dimples RA: total dimples with an (R / D ratio) of 20% or more Number ER: Ratio of (RA) to total number of dimples (N) DE: Dimple whose radius of curvature (R) is larger than its own diameter (D) and whose radius of curvature (R) is less than its own radius of curvature (R) The total number DER of the largest diameter dimples having the largest diameter (D): the ratio of (DE) to the total number of dimples (N) SR: the sum of the dimple areas defined by the plane surrounded by the edges of the dimples, Surface occupancy ratio VR, which is the ratio of the surface area of the phantom sphere assuming that no dimples exist on the ball surface VR: Total dimple space volume formed downward from the plane surrounded by the edges of the dimples Is the ratio of the volume of the phantom sphere assuming no dimples exist on the ball surface.

  The core and cover physical properties of the examples and comparative examples thus obtained and the physical properties, flight distance, durability and feel of the solid golf ball are evaluated according to the following criteria. The results are shown in Tables 4 and 5.

Deflection amount of core and ball products (mm)
The core and ball products, which are the target spheres, are compressed at a speed of 10 mm / min using “4204 type” manufactured by Instron Corporation, and an initial load of 98 N (10 kgf) to a final load of 1,275 N (130 kgf) is loaded. Measure the difference (mm) in the amount of deflection up to the time.

Cross section hardness of the core The core is cut with a fine cutter, and the portions B to F in the table below are adjusted to 23 ° C. ± 1 ° C. according to JIS-C (JIS K 6301-1975 standard), and the hardness Measurement was carried out (N = 5 at two locations).

Surface hardness of the core The core surface was temperature-controlled at 23 ° C. ± 1 ° C. according to JIS-C (JIS K 6301-1975 standard), and then the hardness was measured (N = 5 each for two locations).

Resilience of core and ball products (initial speed)
The initial speed is measured using an initial speed measuring device of the same type as the USGA drum rotation type initial speed meter approved by R & A. Sample cores and balls were temperature-controlled at 23 ± 1 ° C. for 3 hours or more and tested in a room at room temperature 23 ± 2 ° C. Each of 10 samples is hit twice, the time passing between 6.28 ft (1.91 m) is measured, and the initial speed is calculated.

Cover material hardness A cover sheet is prepared, and the hardness after temperature adjustment to 23 ± 1 ° C. is measured according to Shore D (ASTM D-2240).

Break strength and elongation of cover material (tensile test)
The material was formed into a sheet having a thickness of 2 mm and stored in an environment of 23 ± 1 ° C. for 2 weeks. This sample was processed into a dumbbell-shaped test piece in accordance with JIS K 7311-1995, measured in an environment of 23 ± 2 ° C. in accordance with JIS K 7311-1995, with a test speed of 5 mm / s, and a measurement number of 5 The average value of each sample was determined.

Film thickness measurement Bank portion (Y): The thickness of the clear coating of the bank portion at the center position between the dimples is measured.
Edge part (Z): The thickness of the clear coating of the dimple edge part is measured.
Two balls are measured at three locations, and the average value is calculated.

A ball immediately after hitting the ball at a head speed (HS) of 45 m / s with a TourStage X-DRIVE 701 (Loft angle: 9 °) manufactured by Bridgestone Sports as a flying distance driver (W # 1). Measure spin amount and total flight distance.
Further, the total flight distance of the ball after the mark endurance is measured.

Crack Durability A golf ball was evaluated for crack durability by ADC Ball COR Durability Tester manufactured by Automated Design Corporation. This test machine has a function of causing a golf ball to be blown with air pressure and then continuously colliding with two metal plates installed in parallel. The incident speed on the metal plate was 43 m / s. The number of firings required to break the golf ball was measured, and the average value of five golf balls was measured.

A low temperature scratch-resistant ball was prepared by adjusting the temperature at a temperature of 0 ± 1 ° C. for 3 hours or more. Bridgestone Sports TourStage X-Wedge 52 °, 2008 TourStage VIQ Pitching Sand 50 ° Titanium face, and attached to the striking robot, hitting the ball at a head speed (HS) of 33 m / s, The ball after hitting was examined visually. The ball appearance was evaluated according to the following criteria (average value of two types of clubs).
5 points: There are almost no scratches.
4 points: There are some scratches on the surface, but I do not care.
3 points: Although the surface is anxious, it can be used repeatedly.
2 points: Worried about scratches on the surface and fuzzy, but can be used somehow.
1 point: The surface is fuzzy and cannot be used repeatedly.

Abrasion test (mark durability)
Put 10 golf balls and 3 liters of sand for bunker in a magnetic ball mill with 8 liters of internal volume, mix for 144 hours, mark chipping due to sand abrasion, degree of surface damage, degree of gloss reduction, and The degree of sand adhesion was examined visually. The ball appearance was evaluated on the basis of good (◯), normal (Δ), and bad (×).

Ten hitting teaching professionals hit the target ball with a driver (W # 1), and the hit feeling at that time is evaluated on the basis of good (◯), slightly hard (Δ) and too hard (×).

From the results of Tables 4 and 5, it can be confirmed that the comparative examples are inferior to the examples as follows.
Since the golf ball of Comparative Example 1 uses styrene butadiene rubber (trade name: SBR0202) having a high styrene bond amount, the scratch resistance at low temperatures is poor.
Since the golf ball of Comparative Example 2 uses styrene butadiene rubber (trade name: SBR0202) having a high styrene bond amount, the scuff resistance at low temperatures is poor.
The golf ball of Comparative Example 3 has a low cover breaking strength and a low elongation, resulting in poor wear durability and a large decrease in flying performance. In addition, since the cover is hard, the driver feels bad.
The golf ball of Comparative Example 4 has a low cover breaking strength and a low elongation, resulting in poor wear durability and a large decrease in flying performance.
Since the golf ball of Comparative Example 5 uses a styrene butadiene rubber (trade name: SBR0202) having a high styrene bond amount, the scratch resistance at low temperatures is poor. Further, since the R of the dimple edge is small, the wear durability is poor and the flying performance is greatly reduced.
Since the golf ball of Comparative Example 6 uses styrene butadiene rubber (trade name: SBR0202) having a high styrene bond amount, the scratch resistance at low temperatures is poor. Moreover, since a cover is too thin, durability against cracking is reduced.
Since the golf ball of Comparative Example 7 has a very small core deflection, the driver feels very bad.
Since the golf ball of Comparative Example 8 is a core in which zinc methacrylate is blended, the deflection amount of the ball and the resilience change with time are large, and the crack durability is also poor.
Since the golf ball of Comparative Example 9 is a core blended with zinc acrylate, the change in the ball deflection and resilience with time is large, and the crack durability is poor.
The golf ball of Comparative Example 10 has a one-piece structure, and since the breaking strength and elongation of the surface rubber material are small, the cracking durability is poor, the wear durability is bad, and the flying performance is greatly reduced (the breaking strength of the rubber material). 15 MPa, elongation of 88%).

1 Core 2 Cover D Dimple G Golf ball

Claims (13)

  A golf ball comprising a core and a cover, wherein the core is formed of a rubber composition containing a base rubber, a co-crosslinking agent, a cross-linking initiator, and a metal oxide. And a styrene butadiene rubber mixture, the styrene bond content in the styrene butadiene rubber is 35% by mass or less, methacrylic acid is used as a co-crosslinking agent, and the core has an initial load of 98 N (10 kgf) to a final load of 1,275 N. The deflection amount (CH) when loaded on each of (130 kgf) is 2.5 to 7.0 mm, and the total dimple space volume formed downward from the plane surrounded by the edge of the dimple is the ball surface The solid golf ball characterized in that the ratio (VR) of the volume of the phantom sphere assuming that no dimples exist in the space is 0.95 to 1.7 Ball.   The solid golf ball according to claim 1, wherein the metal oxide is zinc oxide.   In the blending of each component of the rubber composition, the proportion of polybutadiene in the base rubber is 80% by mass or less, the proportion of styrene butadiene rubber in the base rubber is 20 to 80% by mass, and isoprene rubber Is 60% by mass or less in the base rubber, and 6 to 40 parts by weight of methacrylic acid, 6 to 30 parts by weight of metal oxide, and a crosslinking initiator with respect to 100 parts by weight of the base rubber. The solid golf ball according to claim 1 or 2, wherein 0.3 to 5.0 parts by mass and 0.1 to 1.0 parts by mass of an antioxidant are blended.   The solid golf ball according to claim 1, wherein the core has a specific gravity of 1.05 to 1.2.   The solid golf ball according to claim 1, wherein a resin material of the cover is mainly made of polyurethane.   6. The solid golf ball according to claim 5, wherein the resin material of the cover is mainly composed of thermoplastic polyurethane.   The solid golf ball according to claim 1, wherein the cover has a material hardness of 30 to 57 in Shore D hardness.   The solid golf ball according to claim 1, wherein the resin material of the cover has a breaking strength of 20 to 80 MPa.   The solid golf ball according to claim 1, wherein the resin material of the cover has an elongation of 150 to 600%.   The solid golf ball according to claim 1, wherein the cover has a thickness of 0.3 to 2.5 mm.   The solid golf ball according to claim 1, wherein the initial velocity (BV) of the ball is 72 m / s or less. The deflection from when the initial load 98N (10 kgf) to the final load 1,275 N (130 kgf) is applied to the core is CH (mm), and when the ball is first measured, the initial load 98N (10 kgf) to the final load 1 , 275 N (130 kgf) when the ball deflection is BH1 (mm), the initial velocity of the ball is BV1 (m / s), and 350 days after the ball was first measured After standing, the deflection amount of the ball from the initial load of 98 N (10 kgf) to the final load of 1,275 N (130 kgf) is BH2 (mm), and the initial velocity of the ball is BV2 (m / s) And when
BH1 is 2.5 to 7.0 mm,
The value of CH / BH1 is 0.95 to 1.1,
The solid golf ball according to claim 1, wherein a difference between BH2 and BH1 is within 0.2 mm, and a difference between BV2 and BV1 is within 0.3 m / s. The solid golf ball according to any one of claims 1 to 12, wherein dimples satisfying the following requirements (1) to (6) are formed on a surface.
(1) It has a dimple provided with a radius of curvature (R) of 0.5 to 2.5 mm at the peripheral edge.
(2) The ratio (ER) of the total number of dimples (RA) to the total number of dimples (N) in which the ratio (R / D ratio) of the radius of curvature (R) to the diameter (D) is 20% or more is 15 to 95. %.
(3) A dimple having a plurality of types of dimples having different diameters (D) and having a radius of curvature (R) of a dimple having a diameter (D) larger than its own diameter (D) equal to or less than its own radius of curvature (R) The ratio (DER) of the total number (DE) of the maximum diameter dimples having the maximum diameter (D) to the total number of dimples (N) is 80% or more.
(4) It has three or more types of dimples having different diameters (D).
(5) The total number of dimples (N) is 380 or less.
(6) The surface occupancy (SR), which is the ratio of the total dimple area defined by the plane surrounded by the dimple edges to the surface area of the phantom sphere assuming that no dimples exist on the ball surface, is 60 to 74 %.

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