JP2012245352A - Golf ball - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a golf ball having soft feel on an impact and providing an excellent flight performance even to a golfer having a low head speed.SOLUTION: In the golf ball composed of a core and a cover for covering the core, a cover thickness is not smaller than 1.3 mm and not larger than 1.8 mm, material hardness is not higher than a Shore D hardness of 58, a deflection amount from a state that an initial load 98N (10 kgf) is applied to the core to a state that a final load 1275 N (130 kgf) is applied to the core is not smaller than 4.1 mm, a deflection amount from a state that the initial load 98N (10 kgf) is applied to a ball to a state that the final load 1275 N (130 kgf) is applied to the golf ball is not smaller than 3.8 mm, and a ratio (core/ball) of the deflection amount of the core to the deflection amount of the golf ball is not smaller than 0.8 and not larger than 1.2. The golf ball can be sufficiently deformed when being hit by a driver even by the golfer having a low head speed. Not only a carry is increased by sufficiently utilizing the rebounding of the ball but also comfortable feel on the impact and sufficient durability are achieved.

Description

  The present invention relates to a golf ball for a female golfer or a junior golfer who has a soft feel and can obtain excellent flying performance even under hitting conditions at a low head speed.

  Conventionally, in order to meet the demands of professional golfers and amateur advanced players, many balls have been developed that can provide excellent flying performance, spin characteristics, and a comfortable feel when hit at high head speeds. However, such balls are usually designed to obtain the optimal amount of deformation when struck at high head speeds, so female golfers and junior golfers with slow head speeds should deform the ball sufficiently. There are many cases that cannot be done. For this reason, golfers with a slow head speed may not be able to exhibit the original performance of the above-mentioned ball, and the flight distance may not be sufficiently extended or the feel of hitting may be poor.

  Therefore, it is important to develop a golf ball that allows a golfer with a slow head speed to sufficiently deform the ball and that provides excellent flying performance and a comfortable feel to the golfer. It is.

  As prior art of the present invention, Japanese Patent No. 2822926 (US Pat. No. 5,695,413), US Pat. No. 6,142,886, Japanese Patent No. 2,576,787 (US Pat. No. 5,454,898), US Pat. No. 5,743,817, US Pat. No. 5,831,924, and the like.

Japanese Patent No. 2822926 US Pat. No. 5,695,413 US Pat. No. 6,142,886 Japanese Patent No. 2576787 US Pat. No. 5,454,898 US Pat. No. 5,743,817 US Pat. No. 5,831,924

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a golf ball that has a soft feel and provides excellent flying performance even with a golfer with a low head speed.

  As a result of intensive studies to achieve the above object, the present inventors have formed a soft and thin cover around a soft core having a large amount of deflection, thereby providing a comfortable feel and sufficient durability. It is possible to apply sufficient deformation to the ball at the time of hitting with a driver even under low head speed hitting conditions, making use of the repulsion of the ball and suppressing excessive spin rate, leading to increased flight distance. The headline and the present invention were made.

Accordingly, the present invention provides the following golf balls.
[1] In a golf ball comprising a core and a cover covering the core, the cover has a thickness of 1.3 mm to 1.8 mm and a material hardness of Shore D hardness of 58 or less, and an initial load of 98 N against the core. The amount of deflection from when the load (10 kgf) is applied to when the final load 1275N (130 kgf) is applied is 4.1 mm or more, and when the initial load 98N (10 kgf) is applied to the ball, the final load 1275N (130 kgf) is applied. The amount of deflection until loaded is 3.8 mm or more, and the ratio of the amount of deflection of the core and the amount of deflection of the ball (core / ball) is 0.8 or more and 1.2 or less. Golf ball to play.
[2] The golf ball according to [1], wherein the cover is formed of a resin composition containing ionomer as a main material, and the melt flow rate (MFR) of the resin composition is 4 or more.
[3] The golf ball according to [2], wherein the proportion of the ethylene-methacrylic acid-methacrylic acid ester copolymer resin in the polymer component contained in the ionomer composition is 10 to 80% by mass.
[4] The golf ball of [1], wherein the cover is formed of a resin composition mainly composed of polyurethane, and the MFR of the resin composition is 16 or more.

  The golf ball of the present invention can be sufficiently deformed when hit by a driver even if it is a female golfer or a junior golfer with a low head speed. In addition, it has both a comfortable feel and sufficient durability.

1 is a schematic cross-sectional view of a golf ball according to an embodiment of the present invention.

Hereinafter, the present invention will be described in more detail.
The structure of the 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. Note that a large number of dimples D are usually formed on the surface of the cover 2. In addition, although the said core 1 and the cover 2 are each made into the single layer here, it is arbitrary to make a core into a multilayer structure of 2-6 layers, or to make a cover into two or more layers.

  The core is obtained by vulcanizing a rubber composition mainly composed of a rubber material. Specifically, a rubber composition containing a base rubber, a crosslinking initiator, a co-crosslinking agent, an antiaging agent, a filler and the like can be used.

  The base rubber of the rubber composition is not particularly limited, but polybutadiene is preferably used. As this polybutadiene, 1,4-cis polybutadiene having a cis structure of at least 40% or more can be preferably used. In the base rubber, natural rubber, polyisoprene rubber, styrene butadiene rubber, or the like can be appropriately blended with the polybutadiene as desired. By increasing the rubber component, the resilience of the golf ball can be improved.

  As the crosslinking initiator, an organic peroxide can be suitably used in the present invention. As the organic peroxide, dicumyl peroxide, 1,1-bis (tert-butylperoxy) cyclohexane and the like can be suitably used. As the organic peroxide, commercially available products can be used, and examples thereof include Perhexa 3M, Perhexa C40, Park Mill D (manufactured by NOF Corporation), Luperco 231XL, Luperco 101XL (manufactured by Atchem). These can be used individually by 1 type or in mixture of 2 or more types.

  The blending amount of the crosslinking initiator is not particularly limited, but is preferably 0.2 parts by mass or more, more preferably 0.4 parts by mass or more, and still more preferably 0.8 parts by mass with respect to 100 parts by mass of the base rubber. It can be 6 parts by mass or more. Further, the upper limit of the amount is not particularly limited, but can be preferably 2.0 parts by mass or less, more preferably 1.5 parts by mass or less, still more preferably 1.2 parts by mass or less, and most preferably 0. .9 parts by mass or less. If the amount is too large, scorching may occur during rubber kneading and heat molding, and a golf ball core and golf ball having sufficient durability cannot be obtained. If the blending amount is too small, workability at the time of heat-molding the rubber composition is lowered, or sufficient hardness of the golf ball core cannot be obtained. Further, although not particularly limited, in the present invention, sulfur can be blended with the rubber composition, and examples thereof include powdered sulfur. Specifically, the trade name “sulfur Z (Zet)” (dispersibility) Sulfur) “Tsurumi Chemical Co., Ltd.” is exemplified. The compounding amount of sulfur is 0.01 to 0.5 parts by mass, preferably 0.01 to 0.4 parts by mass, more preferably 0.01 to 0.1 parts by mass with respect to 100 parts by mass of the base rubber. Part. If the amount of sulfur is too small, the hardness distribution of the solid core cannot be increased beyond a certain level, resulting in low rebound resilience and a decrease in flight distance. Moreover, when there is too much compounding quantity of sulfur, there exists a possibility that inconveniences, such as an explosion of a rubber composition, may arise at the time of thermoforming.

  In the present invention, an α, β-unsaturated carboxylic acid such as zinc methacrylate and zinc acrylate can be blended as the co-crosslinking agent, and zinc acrylate can be particularly preferably used. The compounding amount of the co-crosslinking agent is not particularly limited, but can be 10 parts by mass or more, preferably 15 parts by mass or more with respect to 100 parts by mass of the base rubber. The upper limit of the amount is not particularly limited, but can be 50 parts by mass or less, preferably 39 parts by mass or less. If the amount is too large, the core will be too hard and the ball will become hard as a result. May not appear. If the amount is too small, sufficient durability may not be obtained.

  In the present invention, an anti-aging agent can be added to the rubber composition. For example, Nocrack NS-6, NS-30, SP-N (Ouchi Shinsei Chemical Co., Ltd.), Yoshinox 425 (Yoshitomi) Commercial products such as those manufactured by Pharmaceutical Co., Ltd. can be used. 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 0.02 mass part or more with respect to 100 mass parts of base rubber, More preferably, it is 0.05 mass part or more, Preferably it is 1 as an upper limit. It is not more than part by mass, more preferably not more than 0.8 part by mass, still more preferably not more than 0.6 part by mass. If the amount is too large, a sufficient initial velocity of the golf ball may not be obtained. If the blending amount is too small, scorching may occur during rubber kneading and thermoforming, and a golf ball core and golf ball having sufficient durability may not be secured.

  There is no restriction | limiting in particular as a filler, Zinc oxide, barium sulfate, titanium dioxide, calcium carbonate, etc. can be mix | blended. These compounding amounts are not particularly limited, but can be 3 parts by mass or more, preferably 5 parts by mass or more with respect to 100 parts by mass of the base rubber. The upper limit of the amount is not particularly limited, but can be 60 parts by mass or less, preferably 50 parts by mass or less.

  The core can be produced by vulcanizing a rubber composition containing the above components by a known method. For example, the above components are kneaded using a kneader such as a Banbury mixer or roll to obtain a rubber composition, and then compression molding or injection molding is performed using a core mold to obtain a spherical molded body. Next, the obtained molded body is appropriately heated and cured under conditions sufficient for the crosslinking initiator or co-crosslinking agent to act, thereby obtaining a core having a predetermined hardness. In addition, the heating conditions of the said molded object are about 130-170 degreeC normally, when dicumyl peroxide is used as a crosslinking initiator and zinc acrylate is used as a co-crosslinking agent, for example, it is 10-degree at 150-160 degreeC normally. It can be 40 minutes, in particular 12-20 minutes.

  The diameter of the core is not particularly limited, but is preferably 24 mm or more, more preferably 26 mm or more, still more preferably 28 mm or more, and the upper limit is preferably 42 mm or less, more preferably 41.5 mm or less, More preferably, it is 41 mm or less. When the diameter of the core is out of this range, sufficient resilience performance may not be obtained, excessive spin may be caused, and good feeling may not be obtained.

  The amount of deflection from when the initial load of 98 N (10 kgf) is applied to when the final load of 1275 N (130 kgf) is applied to the core is required to be 4.1 mm or more, preferably 4.2 mm or more. More preferably, it is 4.3 mm or more. The upper limit of the amount of deflection is not particularly limited, but is preferably 8.0 mm or less, more preferably 7.0 mm or less, particularly preferably 6.0 mm or less, and even more preferably 5.5 mm or less. If the core is softer than the above values, the resilience of the core may be poor. Conversely, if the core is harder than the above value, the ball feel may be worsened.

  In the present invention, the cover formed around the core can be formed of a known material and is not particularly limited. For example, a thermoplastic resin such as an ionomer or various thermoplastic elastomers can be used. Can be mentioned. Specific examples of the thermoplastic elastomer include polyester-based thermoplastic elastomers, polyamide-based thermoplastic elastomers, polyurethane-based thermoplastic elastomers, olefin-based thermoplastic elastomers, and styrene-based thermoplastic elastomers.

  In the present invention, such a cover material is not particularly limited, but a resin composition mainly composed of the following ionomer or polyurethane can be suitably used. Hereinafter, these materials will be described in order.

  First, in the present invention, the resin composition mainly comprising an ionomer is a metal salt of an olefin-unsaturated carboxylic acid-unsaturated carboxylic acid ester random copolymer and / or an olefin-unsaturated carboxylic acid random copolymer. It is a resin composition mainly composed of a metal salt.

  The above olefin usually has 2 or more carbon atoms and preferably has an upper limit of 8 or less, particularly 6 or less. Specific examples include ethylene, propylene, butene, pentene, hexene, heptene, octene, etc. Preferably there is.

  Moreover, as unsaturated carboxylic acid, acrylic acid, methacrylic acid, maleic acid, fumaric acid etc. can be mentioned, for example. In the present invention, among these, acrylic acid and methacrylic acid are preferable, and methacrylic acid is particularly preferable.

  And as unsaturated carboxylic acid ester, the lower alkyl ester of unsaturated carboxylic acid mentioned above etc. are suitable, for example, specifically, methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, acrylic acid Examples thereof include methyl, ethyl acrylate, propyl acrylate, butyl acrylate and the like, and butyl acrylate (n-butyl acrylate, i-butyl acrylate) is particularly preferable.

  The random copolymer can be obtained by random copolymerizing the above components according to a known method. Here, the content (acid content) of the unsaturated carboxylic acid contained in the random copolymer is not particularly limited, but is usually 2% by mass or more, preferably 6% by mass or more, and more preferably 8% by mass. % Or more. Also, the upper limit of the unsaturated carboxylic acid content (acid content) is not particularly limited, but it is usually recommended to be 25% by mass or less, preferably 20% by mass or less, and more preferably 15% by mass or less. If the acid content is low, the resilience may be reduced, and if it is high, the processability of the material may be reduced.

The acid groups in the random copolymer described above are partially or completely neutralized with metal ions. In this case, the degree of neutralization is not particularly limited, but 20 mol% or more of acid groups are preferably neutralized, more preferably 30 mol% or more, still more preferably 40 mol% or more. can do. The upper limit is not particularly limited, but can be 100 mol% or less, preferably 90 mol% or less, more preferably 80 mol% or less. If the degree of neutralization is less than 20 mol%, the resilience may be lowered. Here, examples of metal ions that neutralize acid groups include Na ⁺ , K ⁺ , Li ⁺ , Zn ⁺⁺ , Cu ⁺⁺ , Mg ⁺⁺ , Ca ⁺⁺ , Co ⁺⁺ , Ni ⁺⁺ , and Pb. ⁺⁺ etc. are mentioned. Of these, Na ⁺ , Li ⁺ , Zn ⁺⁺ , Mg ⁺⁺ , Ca ^{++ and the} like are particularly preferable in the present invention.

  Although content in particular of the metal salt (ionomer resin) of the said random copolymer is not restrict | limited, It is preferable to contain 100-20 mass% with respect to the whole resin composition. In this case, a more preferable lower limit is 40% by mass or more, and further preferably 50% by mass or more. Moreover, a more preferable upper limit is 90 mass% or less, More preferably, it is 85 mass% or less.

  Although not particularly limited, ethylene-methacrylic acid-methacrylic acid, which is a polymer component other than the ionomer contained in the ionomer composition, from the viewpoint of improving fluidity and molding processability during injection molding. The ratio of the acid ester copolymer is preferably 10 to 80% by mass. Specifically, the product name “Nucleel AN4319” (manufactured by Mitsui DuPont Polychemical Co., Ltd.) and the like can be exemplified. The preferable lower limit of this ratio is 15% by mass or more, more preferably 20% by mass or more, and the preferable upper limit is 70% by mass or less, more preferably 60% by mass, and still more preferably 50% by mass. If the fluidity is too low, it may be difficult to form a thin cover around the core by an injection molding method, which may be inefficient in production.

  In the present invention, as the above ionomer, known ones can be used. Specifically, trade names “HIMILAN 1557”, “HIMIRAN 1601” (manufactured by Mitsui DuPont Polychemical Co., Ltd.), trade names “HPF1000”, Examples of the resin composition described in “HPF2000” (manufactured by DuPont) and US Patent Application No. 12 / 340,790 (or US Patent Application No. 12 / 706,175) Can do. These can be used individually by 1 type or in mixture of 2 or more types.

  Various additives can be further added to the resin composition as necessary. For example, pigments, dispersants, anti-aging agents, ultraviolet absorbers, light stabilizers, and the like can be appropriately blended. .

  Furthermore, the melt flow rate (MFR) of the resin composition mainly composed of the above ionomer is not particularly limited, but from the viewpoint of improving fluidity during injection molding and molding processability. When measured under conditions of a test temperature of 190 ° C. and a test load of 21.18 N (2.16 kgf) in accordance with JIS K-7210, it is preferably 4 g / 10 min or more, more preferably 5 g / 10 min or more, still more preferably It can be set to 6 g / 10 min or more. Also, the upper limit is not particularly limited, but it is recommended that it is preferably 14 g / 10 min or less, more preferably 13 g / 10 min or less. If the fluidity is too low, it may be difficult to form a thin cover around the core by an injection molding method, which may be inefficient in production.

  Next, when a cover is formed using a resin composition mainly composed of polyurethane, in the present invention, a thermoplastic polyurethane elastomer or a thermosetting polyurethane resin can be used, and a thermoplastic polyurethane elastomer is particularly suitable. Can be used for

  The structure of the thermoplastic polyurethane elastomer is composed of a soft segment composed of a polymer polyol (polymeric glycol), a chain extender constituting a 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 suitably used. For example, aromatics such as 4,4′-diphenylmethane diisocyanate, 2,4-toluene diisocyanate, and 2,6-toluene diisocyanate can be 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.

  As the thermoplastic polyurethane material composed of the above-mentioned materials, commercially available products can be suitably used. For example, trade names “Pandex T8180”, “Pandex T8195”, “Pandex T8290”, “Pandex T8295” “Pandex T8260” (manufactured by DIC Bayer Polymer Co., Ltd.), trade names “Rezamin 2593”, “Rezamin 2597” (manufactured by Dainichi Seika Kogyo Co., Ltd.) and the like.

  Various additives can be further added to the thermoplastic polyurethane material as necessary. For example, pigments, dispersants, anti-aging agents, ultraviolet absorbers, light stabilizers, and the like can be appropriately blended. it can.

  In the present invention, the MFR of the resin composition mainly composed of polyurethane is not particularly limited. However, from the viewpoint of improving fluidity and molding processability at the time of injection molding, JIS K-7210 is used. Accordingly, when measured under the conditions of a test temperature of 210 ° C. and a test load of 21.18 N (2.16 kgf), it is preferably 16 g / 10 min or more, more preferably 17 g / 10 min or more, still more preferably 18 g / 10 min or more, It can be. The upper limit is not particularly limited, but is preferably 40 g / 10 min or less, more preferably 35 g / 10 min or less. If the fluidity is too low, it may be difficult to form a thin cover around the core by an injection molding method, which may be inefficient in production.

  The cover thickness needs to be 1.3 mm or more. Moreover, the upper limit is 1.8 mm or less, Preferably it is 1.7 mm or less. When the thickness of the cover deviates from the above range, a good feel may not be obtained. Moreover, sufficient durability may not be obtained.

  The material hardness of the cover is required to be 58 or less in Shore D hardness, preferably 57 or less, more preferably 56 or less. Further, the lower limit is not particularly limited, but preferably it can be 30 or more in JIS-A hardness, more preferably 35 or more, particularly preferably 40 or more, still more preferably 45 or more, and most preferably. May be 50 or more in Shore D hardness. If the cover material hardness is too high, it will be difficult for the cover to follow the deformation of the core at the time of hitting, which may lead to repeated hitting durability deterioration. Often it will be sufficient. Here, regarding the above material hardness, the Shore D hardness is a hardness measured using a type D durometer in accordance with ASTM D2240 for a sheet obtained by press-molding a cover material to a thickness of about 2 mm. Hardness shows the hardness measured according to JIS K-6301 about the sheet.

  The above cover can be formed by a known method, and injection molding, compression molding, or the like can be employed. For example, when a cover is formed by injection molding, a solid core prepared using the above rubber composition in advance is set in a mold for forming a cover, and the cover material described above is placed in the mold according to a conventional method. Can be introduced by injection. As another method, a pair of half cups is molded in advance using the cover material described above, and the core is wrapped with the half cups, and compression-molded, for example, at 120 to 170 ° C. for 1 to 5 minutes. Can also be used.

  The golf ball of the present invention needs to have a deflection amount of 3.8 mm or more from a state in which an initial load of 98 N (10 kgf) is applied to a final load of 1275 N (130 kgf). The thickness is preferably 3.9 mm or more, more preferably 4.0 mm or more. The upper limit of the deflection is not particularly limited, but is preferably 8.0 mm or less, more preferably 7.0 mm or less, particularly preferably 6.0 mm or less, still more preferably 5.0 mm or less, and most preferably 4. 7 mm or less. If the ball is too soft, an appropriate launch angle may not be obtained. If it is too hard, the ball may not fly under the hitting condition of a low head speed golfer, or the hit feeling may be deteriorated.

  Further, the deflection amount from when the initial load 98N (10 kgf) is applied to the core to when the final load 1275N (130 kgf) is applied, and from the state where the initial load 98N (10 kgf) is applied to the ball. The ratio (core / ball) to the amount of deflection until 1275N (130 kgf) is loaded is 0.8 or more, preferably 0.82 or more, more preferably 0.84 or more, and further preferably 0.86. That's it. Moreover, the upper limit is 1.2 or less, Preferably it is 1.19 or less, More preferably, it is 1.18 or less. When the above ratio is out of the range, the thickness and hardness of the cover do not match the deflection amount of the core, and a good feeling cannot be obtained at the time of impact.

  In the golf ball of the present invention, although not particularly limited, in order to further improve the aerodynamic characteristics and improve the flight distance, it is possible to form a large number of dimples on the cover surface as in the case of a normal golf ball. it can. By optimizing the kind and total number of the dimples, the trajectory is more stable and the flight performance is excellent. In addition, in order to improve the design and durability of the golf ball, the cover surface can be coated, and at that time, various treatments such as ground treatment and stamping are optional.

  Hereinafter, preferred embodiments of dimples in the golf ball of the present invention will be described in detail.

  The number of dimples on the entire surface of the golf ball is preferably about 200 or more, more preferably about 220 or more, still more preferably about 260 or more, and still more preferably about 300 or more. The upper limit of the number of dimples is preferably about 450 or less, more preferably about 430 or less, and further preferably about 410 or less. By setting the number of dimples within this range, the golf ball can be easily lifted, and the flying distance of the driver can be increased.

  A plurality of types of dimples having different diameters and / or depths can be formed. The number of types of dimples is preferably 4 or more, more preferably 5 or more, and still more preferably 6 or more. The upper limit of the type of dimple is preferably about 20 or less, more preferably about 15 or less, and still more preferably about 12 or less. By setting the type of dimple within this range, the surface occupancy rate of the dimple can be easily increased and the flight distance can be improved.

  The shape of the dimple is preferably a planar circular shape. The average diameter is preferably about 2.8 mm or more, more preferably about 3.5 mm or more, and further preferably about 3.8 mm or more. The upper limit of the average diameter is preferably about 5.0 mm or less, preferably about 4.6 mm or less, and more preferably about 4.3 mm or less. From the viewpoint of obtaining an appropriate trajectory, the average dimple depth is preferably about 0.120 mm or more, more preferably about 0.130 mm or more, and further preferably about 0.140 mm or more. The upper limit of the average depth is preferably about 0.185 mm or less, more preferably about 0.180 mm or less, and further preferably about 0.174 mm or less.

  The average diameter is an average value of the diameters of all the dimples, and the average depth is an average value of the depths of all the dimples. In many cases, golf balls are painted, and the dimple diameter and depth are measured with the dimples coated with paint. The dimple diameter is measured by measuring the width of the gap between the land portion, which is the surface of the golf ball on which no dimples are formed, and the surface where the dimples are depressed. The depth of the dimple is measured by measuring the vertical distance from the center position to the bottom surface of the dimple when a virtual plane circle is drawn connecting the points where the dimple contacts the land.

Regarding the dimple occupancy rate, specifically, the ratio (SR value) of the total dimple area defined by the plane surrounded by the dimple edges to the surface area of the phantom sphere assuming no dimples exist on the ball surface. From the viewpoint of sufficiently exhibiting aerodynamic characteristics, it is preferably about 60% or more, more preferably about 65% or more, and further preferably about 68% or more. The upper limit of the dimple occupancy is not particularly limited, but is preferably about 90% or less, more preferably about 85% or less, and still more preferably about 80% or less in the present invention. Further, a value V _{0 obtained} by dividing the space volume of the dimple below the plane surrounded by the edge of each dimple by the volume of the cylinder having the plane as the bottom and the maximum depth of the dimple from the bottom as a height is: From the viewpoint of optimizing the ball trajectory, it is preferably about 0.35 or more. The upper limit of V ₀ is not particularly limited, but is preferably about 0.80 or less. Furthermore, the ratio (VR value) of the total volume of dimples formed below the plane surrounded by the edges of the dimples to the volume of the phantom sphere on the assumption that no dimples are present on the ball surface is about 0.00. 6% or more is preferable, about 0.7% or more is more preferable, and about 0.8% or more is more preferable. The upper limit of the VR value is preferably about 1.0% or less, and more preferably about 0.9% or less.

  The golf ball of the present invention can be used in competition and comply with the golf rules. It is preferable that the ball outer diameter is 42.67 mm or more and the weight is 45.93 g or less.

  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 1-8]
After preparing a rubber composition having a composition shown in Table 1 (Example) or Table 2 (Comparative Example), a solid core was produced by vulcanization molding at 155 ° C. for 10 minutes. Next, a cover having the composition shown in Table 1 or 2 was molded around the core obtained above by an injection molding method, and two-piece solid golf balls of Examples and Comparative Examples were obtained.

The details of the above-mentioned core composition are as follows.
・ Zinc oxide: manufactured by Sakai Chemical Co., Ltd. ・ polybutadiene: trade name “BR730”, manufactured by JSR ・ dicumyl peroxide: trade name “Park Mill D”, manufactured by NOF Corporation ・ 1,1-bis (tert-butylperoxy) cyclohexane 40 % Diluted product: trade name “Perhexa C40”, manufactured by NOF Corporation, 2,2′-methylenebis (4-methyl-6-tert-butylphenol): trade name “NOCRACK NS-6”, manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.・ Zinc acrylate: manufactured by Nippon Distillation Co., Ltd. ・ Zinc stearate: manufactured by NOF Corporation ・ Titanium dioxide: trade name “Taipeke R550”, manufactured by Ishihara Sangyo Co., Ltd. ・ Zinc salt of pentachlorothiophenol: manufactured by Tokyo Chemical Industry Co., Ltd.

The details of the cover composition are as follows.
High Milan 1557: Mitsui DuPont Polychemical Co., Binary Copolymer Zinc Ionomer Himiran 1601: Mitsui DuPont Poly Chemical Co., Binary Copolymer Sodium Ionomer Nuclerel AN4319: Mitsui DuPont Poly Chemical Co., Ltd. 3, Original Copolymer / Titanium Dioxide: Trade name “Taipeke R550”, Ishihara Sangyo Co., Ltd./Pandex: DIC Bayer Polymer Co., Ltd. MDI-PTMG type thermoplastic polyurethane / polyethylene wax: Trade name “Sun Wax 161P”, Sanyo Chemical Made by company

  The following physical properties of the obtained golf ball were examined. In addition, a flying test was performed by the following method to evaluate crack durability and feel. The results are shown in Tables 1 and 2.

Cover material hardness Shore D hardness measured in accordance with ASTM D-2240 for a cover material (resin composition) melted by heating and molded into a 2 mm thick sheet.

Deflection amount of core and ball (mm)
The amount of deformation (mm) from when the initial load of 98 N (10 kgf) was applied to the test object to when the final load of 1275 N (130 kgf) was applied was measured.

Flying Performance A flying distance when a golf hitting robot was hit with a driver at a head speed of 35 m / s was measured. The club used a driver “Tour Stage ViQ HT 460” (loft 9.5 °) manufactured by Bridgestone Sports. The table shows the difference between the measured values when Example 5 was set to the reference value “0”.

Ball spin rate (rpm)
The spin rate was measured under the same conditions as above. The table shows the difference between the measured values when Comparative Example 2 was set to the reference value “0”.

Crack Durability Durability of a golf ball was evaluated 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. For each ball, the number of times when the speed ratio (reflection speed / incidence speed) was 97% or less was measured. The table shows the difference between the measured values when Example 5 was set to the reference value “0”.

Hit feeling at the time of driver shot Five golfers with a head speed of about 35 m / s hit the target ball, and the hit feeling at that time was evaluated according to the following criteria. The club used is a driver “Tour Stage ViQ HT 460” (loft 9.5 °) manufactured by Bridgestone Sports.
○: Good △: Bad

  Comparative Examples 1, 2, 3, 5, and 6 have inferior cracking durability but are inferior in terms of driver flight distance. In Comparative Examples 4 and 7, although the driver flight distance can be secured, the crack durability is inferior. Comparative Example 8 is inferior to the other in terms of both driver flight distance and crack durability. Moreover, both the comparative example 1 and the comparative examples 3-8 have bad hit feeling. In contrast to these comparative examples, Examples 1 to 8 ensure both driver flight distance and crack durability, and have a good hit feeling.

1 Core 2 Cover G Golf ball D Dimple

Claims (4)

  A golf ball comprising a core and a cover covering the core has a cover thickness of 1.3 mm to 1.8 mm, a material hardness of Shore D hardness of 58 or less, and an initial load of 98 N (10 kgf) on the core. When the final load of 1275 N (130 kgf) is applied to the ball when the initial load of 98 N (10 kgf) is applied to the ball and the final load of 1275 N (130 kgf) is applied. A golf ball characterized in that the deflection amount up to 3.8 mm and the ratio of the core deflection amount to the ball deflection amount (core / ball) is from 0.8 to 1.2 .   The golf ball according to claim 1, wherein the cover is formed of a resin composition containing ionomer as a main material, and the melt flow rate (MFR) of the resin composition is 4 or more.   The golf ball according to claim 2, wherein the proportion of the ethylene-methacrylic acid-methacrylic acid ester copolymer resin in the polymer component contained in the ionomer composition is 10 to 80% by mass.   The golf ball according to claim 1, wherein the cover is formed of a resin composition mainly composed of polyurethane, and the MFR of the resin composition is 16 or more.

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