JP4064083B2 - Golf ball - Google Patents

Description

【００７５】
【表２】

【００７６】
【表３】

【００７７】
【表４】

【００７８】
表４に示されているように、各実施例のゴルフボールは打球感に優れ、比較例のゴルフボールに比べて飛距離も遜色ない。この評価結果から、本発明の優位性は明らかである。
【００７９】
【発明の効果】
以上説明されたように、本発明のゴルフボールは、ヘッド速度が低いゴルファーに打撃された場合に、比較的柔軟な中間層によってソフトな打球感が得られる。しかも、このゴルフボールでは、柔軟な中間層に起因する飛距離の低下がディンプルによって抑制される。
【図面の簡単な説明】
【図１】図１は、本発明の一実施形態にかかるゴルフボールが示された断面図である。
【図２】図２は、図１のゴルフボールが示された正面図である。
【図３】図３は、図１のゴルフボールが示された平面図である。
【図４】図４は、図１のゴルフボールの一部が示された拡大断面図である。
【符号の説明】
１・・・ゴルフボール
２・・・コア
３・・・中間層
４・・・カバー
５・・・ディンプル
Ａ・・・Ａディンプル
Ｂ・・・Ｂディンプル
Ｃ・・・Ｃディンプル
Ｄ・・・Ｄディンプル
Ｅ・・・Ｅディンプル
Ｌ・・・大円[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a golf ball, and more particularly to a solid golf ball having an intermediate layer made of a synthetic resin composition.
[0002]
[Prior art]
Golf balls used for playing on golf courses are roughly classified into a thread-wound golf ball having a core around which rubber thread is wound and a solid golf ball having a core made of solid rubber. Thread-wound golf balls have been used for a long time. In the past, almost all first-class golf balls were thread-wound golf balls. However, since solid golf balls developed thereafter are easy to manufacture and can be obtained at low cost, more solid golf balls are supplied to the market than thread wound golf balls. In general, solid golf balls have the disadvantage that they feel harder than a wound golf ball. On the other hand, general solid golf balls are superior to thread wound golf balls in terms of flight distance.
[0003]
A solid golf ball having an intermediate layer made of a synthetic resin composition between a core and a cover has been proposed in order to improve the feel at impact or further improve flight performance (Japanese Patent Laid-Open No. 11-114094). JP 2000-70412 A, JP 2000-296187 A, and JP 2001-95947 A).
[0004]
Incidentally, the golf ball has dimples on its surface. The role of the dimples is to promote the turbulent transition of the boundary layer by disturbing the air flow around the golf ball when flying, thereby causing turbulent separation (hereinafter also referred to as “dimple effect”). . By promoting the turbulent transition, the separation point of the air from the golf ball is lowered backward, and the pressure resistance is reduced. Further, by promoting the turbulent transition, the difference between the peeling points on the upper side and the lower side of the golf ball due to backspin is promoted, and the lift acting on the golf ball is enhanced. By reducing the pressure resistance and improving the lift, the flight distance of the golf ball increases. A dimple that easily promotes turbulent transition, that is, a dimple that can better disturb the air flow, is superior in terms of aerodynamics.
[0005]
Various attempts have been made to optimize the combination of the structure and material of the golf ball and the dimple specifications. Such techniques are disclosed in Japanese Patent Application Laid-Open Nos. 11-57067, 2000-70414 and 2000-225209.
[0006]
[Problems to be solved by the invention]
When a golf ball is hit with a golf club, deformation occurs. When the head speed is high, each of the cover, the intermediate layer, and the core is significantly deformed. When the head speed is low, the core does not deform much, and mainly the cover and the intermediate layer are deformed. The feel at impact for a golfer with a slow head speed greatly depends on the material of the intermediate layer. When a golf ball with a slow head speed hits a golf ball having an intermediate layer made of a synthetic resin composition, it tends to feel hard.
[0007]
If a flexible material is used for the intermediate layer, the feel at impact is improved. However, the flexible intermediate layer increases the backspin amount. If the backspin amount is large, it becomes a hopping trajectory and the flight distance decreases. Actually, a golf ball that satisfies both a shot feeling and a flight distance for a golfer with a slow head speed has not yet been obtained.
[0008]
The present invention has been made in view of such circumstances, and an object of the present invention is to provide a golf ball that has a good shot feeling when hit by a golfer with a slow head speed and can obtain a large flight distance. It is.
[0009]
[Means for Solving the Problems]
The invention made to achieve the above object is
A golf ball comprising a core, an intermediate layer made of a synthetic resin composition and positioned outside the core, and a cover positioned outside the intermediate layer, and a plurality of dimples formed on the surface of the cover Because
The amount of compressive deformation of the core is Dc,
The amount of compressive deformation of the sphere including the core and the intermediate layer is Ds,
The ratio of the total area of the area surrounded by the dimple edges in the phantom sphere to the surface area of the phantom sphere is X,
The total volume of the space surrounded by the plane including the edge of the dimple and the surface of the dimple is Vb,
The total volume of the space surrounded by the plane including the edge of the dimple and the virtual spherical surface is defined as Vt,
When the ratio of Vt to Vb (Vt / Vb) is Y,
A golf ball having a ratio (Ds / Dc) of 0.90 or more and 0.98 or less, and a value of (Y−0.5X) of 0.20 or more and 0.37 or less,
It is.
[0010]
In this golf ball, the ratio (Ds / Dc) is not less than 0.90 and not more than 0.98. In other words, since the intermediate layer is relatively flexible, the shot feeling for a golfer with a slow head speed is soft. Moreover, since the dimple specifications are determined so that the value of (Y−0.5X) is 0.20 or more and 0.37 or less, even if the backspin amount is large, the hop of the golf ball is suppressed, and the large flying The distance is obtained. In this golf ball, the mid layer contributes to a good feel at impact, and dimples complement the decrease in flight distance caused by the mid layer.
[0011]
Preferably, the amount of compressive deformation Dc of the core is 3.5 mm or more and 7.0 mm or less, and the amount of compressive deformation Ds of the sphere composed of the core and the intermediate layer is 3.0 mm or more and 6.5 mm or less. This golf ball exhibits a better feel at impact.
[0012]
Preferably, the Shore D hardness of the intermediate layer is greater than 35 and less than the Shore D hardness of the core surface. This golf ball exhibits a better feel at impact.
[0013]
Preferably, the intermediate layer has a thickness of 1.0 mm to 2.5 mm. This golf ball has a good shot feeling and excellent resilience performance.
[0014]
Preferably, the base polymer of the intermediate layer contains an ionomer resin as a main component, and particularly contains the ionomer resin and the thermoplastic elastomer in a mass ratio of 50/50 or more and 95/5 or less. This intermediate layer contributes to improvement in feel at impact, durability and resilience performance.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail based on preferred embodiments with appropriate reference to the drawings.
[0016]
FIG. 1 is a cross-sectional view showing a golf ball 1 according to an embodiment of the present invention. The golf ball 1 includes a core 2, an intermediate layer 3, and a cover 4. A large number of dimples 5 are formed on the surface of the cover 4. The golf ball 1 includes a paint layer and a mark layer on the outside of the cover 4, but these are not shown. The golf ball 1 has a diameter of 40 mm to 45 mm, particularly 42 mm to 44 mm. From the viewpoint of reducing air resistance within a range that satisfies the standards of the US Golf Association (USGA), the diameter is preferably set to 42.67 mm or more and 42.80 mm or less. The golf ball 1 has a mass of 44 g or greater and 46 g or less, and particularly 45.00 g or greater and 45.93 g or less.
[0017]
The core 2 is formed by crosslinking a rubber composition. As the base rubber of the rubber composition, polybutadiene, polyisoprene, styrene-butadiene copolymer, ethylene-propylene-diene copolymer (EPDM), natural rubber and the like are suitable. Two or more of these rubbers may be used in combination. From the viewpoint of resilience performance, polybutadiene is preferred. Even when polybutadiene and another rubber are used in combination, it is preferable that polybutadiene is a main component. Specifically, the proportion of polybutadiene in the total base rubber is preferably 50% by mass or more, particularly 80% by mass or more. Among the polybutadienes, high cis polybutadiene having a cis-1,4 bond ratio of 40% or more, particularly 80% or more is preferable.
[0018]
The form of crosslinking of the rubber composition is not particularly limited, but from the viewpoint of resilience performance, an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms or a metal salt thereof is used as a co-crosslinking agent. Monovalent or divalent metal salts are particularly preferable. Specific examples of preferred co-crosslinking agents include zinc acrylate, magnesium acrylate, zinc methacrylate and magnesium methacrylate. In particular, zinc acrylate capable of obtaining high resilience performance is preferable.
[0019]
The amount of the co-crosslinking agent is preferably 10 parts or more and 50 parts or less with respect to 100 parts of the base rubber. If the blending amount is less than the above range, the core 2 may be soft and the resilience performance may be insufficient. In this respect, the amount to be blended is more preferably 15 parts or greater and particularly preferably 20 parts or greater. If the blending amount exceeds the above range, the core 2 may become hard and the feel at impact may not be soft. In this respect, the amount to be blended is more preferably equal to or less than 45 parts, and particularly preferably equal to or less than 35 parts. As used herein, the term “part” means mass ratio (parts by weight).
[0020]
The rubber composition used for the core 2 is preferably blended with an organic peroxide. The organic peroxide functions as a crosslinking agent together with the aforementioned α, β-unsaturated carboxylic acid metal salt, and also functions as a curing agent. By blending the organic peroxide, the resilience performance of the core 2 is enhanced. Suitable organic peroxides include dicumyl peroxide, 1,1-bis (t-butylperoxy) -3,3,5-trimethylcyclohexane, 2,5-dimethyl-2,5-di (t- Butyl peroxy) hexane and di-t-butyl peroxide. A particularly versatile organic peroxide is dicumyl peroxide.
[0021]
The compounding amount of the organic peroxide is preferably 0.1 part or more and 3.0 part or less with respect to 100 parts of the base rubber. If the blending amount is less than the above range, the core 2 may be soft and the resilience performance may be insufficient. In this respect, the amount is more preferably equal to or greater than 0.2 part, and particularly preferably equal to or greater than 0.5 part. If the blending amount exceeds the above range, the core 2 may become hard and the feel at impact may not be soft. In this respect, the amount to be blended is more preferably 2.8 parts or less, and particularly preferably 2.5 parts or less.
[0022]
In the rubber composition, a filler may be blended for the purpose of adjusting specific gravity and the like. Suitable fillers include powders composed of inorganic salts such as zinc oxide, barium sulfate, calcium carbonate, and high specific gravity metals such as tungsten and molybdenum. The blending amount of the filler is appropriately determined so that the intended specific gravity of the core 2 is achieved. A preferred filler is zinc oxide because it functions not only as a specific gravity adjustment but also as a crosslinking aid.
[0023]
In the rubber composition, various additives such as an anti-aging agent, a colorant, a plasticizer, and a dispersant may be blended in an appropriate amount as necessary.
[0024]
For molding the core 2, known molding methods such as compression molding and injection molding can be applied. Usually, the rubber composition is put into a spherical cavity of a mold and heated while being pressed, whereby the core 2 is molded. A crosslinking reaction occurs by heating, and the rubber composition is cured. The general heating time is 10 minutes or more and 60 minutes or less, and the heating temperature is 140 ° C. or more and 180 ° C. or less. In particular, if the crosslinking temperature is 160 ° C. or higher, the hardness difference of the core 2 is increased, which is preferable. The hardness difference is a value obtained by subtracting the minimum value from the maximum value in the distribution of hardness (JIS-C hardness) from the center of the core 2 to the surface.
[0025]
The specific gravity of the general core 2 is 1.05 or more and 1.25 or less. The diameter of the core 2 is preferably 30 mm or greater and 41 mm or less. If the diameter is less than the above range, the resilience performance and feel at impact of the golf ball 1 may be insufficient. In this respect, the diameter is more preferably 32 mm or more, and particularly preferably 36 mm or more. When the diameter exceeds the above range, the durability of the golf ball 1 may be insufficient. In this respect, the diameter is particularly preferably equal to or less than 40 mm. The core 2 may be composed of two or more layers.
[0026]
The surface hardness (Shore D) of the core 2 is preferably 30 or greater and 60 or less. When the surface hardness is less than the above range, the resilience performance of the golf ball 1 may be insufficient. In this respect, the surface hardness is particularly preferably equal to or greater than 35. If the surface hardness exceeds the above range, the feel at impact of the golf ball 1 may be insufficient. In this respect, the surface hardness is more preferably 55 or less, and particularly preferably 50 or less.
[0027]
The center hardness (JIS-C) of the core 2 is preferably 45 or greater and 75 or less. If the central hardness is less than the above range, the resilience performance of the golf ball 1 may be insufficient. In this respect, the center hardness is particularly preferably equal to or greater than 50. When the center hardness exceeds the above range, the feel at impact of the golf ball 1 may be insufficient. In this respect, the central hardness is more preferably equal to or less than 70, and particularly preferably equal to or less than 65.
[0028]
The cover 4 is usually made of a synthetic resin composition. Examples of the base polymer of the synthetic resin composition include ionomer resins, polyesters, polyurethanes, polyethylenes, polypropylenes, and thermoplastic elastomers. From the viewpoint of feel at impact, durability, and resilience performance, ionomer resins, thermoplastic elastomers, and mixtures thereof are preferred.
[0029]
Among the ionomer resins, those in which a part of the carboxylic acid in the copolymer of the α-olefin and the α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms is neutralized with a metal ion are preferable. As the α-olefin, ethylene and propylene are preferable. As the α, β-unsaturated carboxylic acid, acrylic acid and methacrylic acid are preferable. As metal ions for neutralization, alkali metal ions such as sodium ion, potassium ion and lithium ion; divalent metal ions such as zinc ion, calcium ion and magnesium ion; trivalent metal ions such as aluminum ion and neodymium ion Etc. Neutralization may be performed with two or more metal ions. Particularly suitable metal ions from the viewpoint of the resilience performance and durability of the golf ball 1 are sodium ions, zinc ions, lithium ions and magnesium ions.
[0030]
Specific examples of suitable ionomer resins include Mitsui Dupont Polychemical's trade names “High Milan 1555”, “Hi Milan 1557”, “Hi Milan 1601”, “Hi Milan 1605”, “Hi Milan 1652”, “Hi Milan 1705”, and “High Milan 1705”. "1706", "High Milan 1707", "High Milan 1855", "High Milan 1856";DuPont's trade names "Surlin 9945", "Surlin 8945", "Surlin AD8511", "Surlin AD8512";Exxon's trade names "IOTEK7010" ”,“ IOTEK8000 ”and the like. Two or more ionomer resins may be used in combination.
[0031]
Preferred thermoplastic elastomers include polyurethane-based thermoplastic elastomers, polyamide-based thermoplastic elastomers, polyester-based thermoplastic elastomers, styrene-based thermoplastic elastomers, and thermoplastic elastomers having an OH group at the end. Two or more thermoplastic elastomers may be used in combination. From the viewpoint of the resilience performance of the golf ball 1, polyester-based thermoplastic elastomers and styrene-based thermoplastic elastomers are particularly suitable.
[0032]
Styrenic thermoplastic elastomers (thermoplastic elastomers containing styrene blocks) include styrene-butadiene-styrene block copolymers (SBS), styrene-isoprene-styrene block copolymers (SIS), styrene-isoprene-butadiene- Styrene block copolymers (SIBS), SBS hydrogenated, SIS hydrogenated and SIBS hydrogenated are included. Examples of the hydrogenated product of SBS include styrene-ethylene-butylene-styrene block copolymer (SEBS). As a hydrogenated product of SIS, styrene-ethylene-propylene-styrene block copolymer (SEPS) can be mentioned. Examples of the hydrogenated product of SIBS include styrene-ethylene-ethylene-propylene-styrene block copolymer (SEEPS).
[0033]
Specific examples of the polyurethane-based thermoplastic elastomer include “Elastollan”, a trade name of BASF Polyurethane Elastomers, and specifically “Elastollan ET880”. As a specific example of the polyamide-based thermoplastic elastomer, trade name “Pebax” manufactured by Toray Industries, Inc. may be mentioned, and “Pebax 2533” may be mentioned in detail. Specific examples of the polyester-based thermoplastic elastomer include “Hytrel” trade name of Toray DuPont, and “Hytrel 3548” and “Hytrel 4047” are specifically mentioned. Specific examples of the styrene-based thermoplastic elastomer include “Lavalon”, trade name of Mitsubishi Chemical Corporation, and details are “Lavalon SR04”, “Lavalon SJ4400N”, “Lavalon SJ5400N”, “Lavalon SJ6400N”, “Lavalon SJ7400N”. "," Lavalon SJ8400N "," Lavalon SJ9400N ".
[0034]
A diene block copolymer may be blended in the cover 4. The diene block copolymer has a polymer block mainly composed of at least one vinyl aromatic compound and a polymer block mainly composed of at least one conjugated diene compound. The diene block copolymer has a double bond derived from a conjugated diene compound. A diene block copolymer in which hydrogen is added to a part of the polymer block can also be suitably used.
[0035]
Examples of the vinyl aromatic compound constituting the diene block copolymer include styrene, α-methylstyrene, vinyltoluene, pt-butylstyrene, and 1,1-diphenylstyrene. Two or more are selected. Styrene is particularly preferred. Examples of the conjugated diene compound include butadiene, isoprene, 1,3-pentadiene, and 2,3-dimethyl-1,3-butadiene, and one or more of these are selected. In particular, butadiene and isoprene and combinations thereof are preferred.
[0036]
Preferred diene block copolymers include those having an SBS (styrene-butadiene-styrene) structure having a polybutadiene block containing an epoxy group, and SIS (styrene-isoprene-styrene) having a polyisoprene block containing an epoxy group. Examples include structures. Specific examples of the diene block copolymer include Daicel Chemical's trade name “Epofriend” (specifically “Epofriend A1010”) and Kuraray's trade name “Septon” (for details, “Septon HG- 252).
[0037]
The cover 4 may be mixed with a filler as necessary. Suitable fillers include inorganic salts such as zinc oxide, barium sulfate and calcium carbonate, and powders of high specific gravity metals such as tungsten and molybdenum. Two or more fillers may be used in combination. If necessary, the cover 4 may be blended with an appropriate amount of a colorant such as titanium dioxide, a dispersant, an anti-aging agent, an ultraviolet absorber, a light stabilizer, a fluorescent agent, a fluorescent brightening agent, and the like.
[0038]
Usually, the cover 4 is formed by an injection molding method. In the injection molding method, a synthetic resin composition is injected into a cavity in which a sphere composed of a core 2 and an intermediate layer 3 is held at the center. The synthetic resin composition filled in the gap between the sphere and the cavity surface solidifies and becomes a cover. A half shell made of a synthetic resin composition may be used, and the cover 4 may be molded by a compression molding method. The specific gravity of the cover 4 is usually 0.9 or more and 1.4 or less.
[0039]
The thickness of the cover 4 is preferably 1.0 mm or greater and 2.5 mm or less. The cover 4 having a thickness less than the above range is difficult to mold, and there is a risk that the durability and resilience performance of the golf ball 1 will be reduced. In this respect, the thickness is more preferably equal to or greater than 1.3 mm, and particularly preferably equal to or greater than 1.5 mm. When the thickness exceeds the above range, the feel at impact may be deteriorated. In this respect, the thickness is more preferably equal to or less than 2.3 mm, and particularly preferably equal to or less than 2.0 mm. The cover 4 may be composed of two or more layers.
[0040]
The cover 4 has a hardness (Shore D) of preferably 55 or greater and 70 or less. If the hardness is less than the above range, the feel at impact may be heavy. In this respect, the hardness is more preferably 57 or greater, and particularly preferably 59 or greater. If the hardness exceeds the above range, the feel at impact may become hard. In this respect, the hardness is particularly preferably equal to or less than 67. The hardness is measured by a spring type hardness meter (Shore D type). For convenience, a sheet having a thickness of 2.0 mm formed by hot pressing from the same resin composition as the cover 4 is used for measurement. This sheet is kept in an environment of 23 ° C. for 2 weeks, and three sheets are stacked, and the hardness is measured.
[0041]
The intermediate layer 3 is made of a synthetic resin composition. As the base polymer of the intermediate layer 3, the same base polymer as that of the cover 4 described above can be used. In particular, an ionomer resin is preferably used as a main component. The proportion of the ionomer resin in the total amount of the base polymer is preferably 50% by mass or more, particularly preferably 55% by mass or more.
[0042]
It is particularly preferred that a thermoplastic elastomer is used with the ionomer resin. In this case, the mass ratio between the ionomer resin and the thermoplastic elastomer is preferably 50/50 or more and 95/5 or less. If the mass ratio is less than the above range, the resilience performance of the golf ball 1 may be insufficient. In this respect, the mass ratio is particularly preferably equal to or greater than 55/45. If the mass ratio exceeds the above range, the feel at impact may be insufficient. In this respect, the mass ratio is more preferably equal to or less than 90/10, and particularly preferably equal to or less than 80/20.
[0043]
A filler may be blended in the mid layer 3 as necessary. Suitable fillers include inorganic salts such as zinc oxide, barium sulfate and calcium carbonate, and powders of high specific gravity metals such as tungsten and molybdenum. Two or more fillers may be used in combination.
[0044]
The intermediate layer 3 is usually formed by an injection molding method. In the injection molding method, the synthetic resin composition is injected into a cavity in which the core 2 is held at the center. The synthetic resin composition filled in the gap between the core 2 and the cavity surface is solidified to form the intermediate layer 3. A half shell made of a synthetic resin composition may be used, and the intermediate layer 3 may be molded by a compression molding method.
[0045]
The specific gravity of the intermediate layer 3 is usually 0.9 or more and 1.4 or less. The thickness of the mid layer 3 is preferably 1.3 mm or greater and 2.5 mm or less. If the thickness is less than the above range, the feel at impact may be insufficient. In this respect, the thickness is more preferably equal to or greater than 1.3 mm, and particularly preferably equal to or greater than 1.5 mm. When the thickness exceeds the above range, the resilience performance of the golf ball 1 may be insufficient. In this respect, the thickness is more preferably equal to or less than 2.3 mm, and particularly preferably equal to or less than 2.0 mm. The intermediate layer 3 may be composed of two or more layers.
[0046]
The hardness (Shore D) of the mid layer 3 is preferably 35 or more. If the hardness is less than the above range, the resilience performance of the golf ball 1 may be insufficient. In this respect, the hardness is more preferably 37 or greater and particularly preferably 38 or greater. From the viewpoint of feel at impact, the mid layer 3 preferably has a lower hardness than the surface hardness of the core 2. Specifically, the hardness is preferably 50 or less, more preferably 45 or less, and particularly preferably 42 or less.
[0047]
The amount of compressive deformation Dc of the core 2 is preferably 3.5 mm or greater and 7.0 mm or less. When the amount of compressive deformation Dc is less than the above range, the feel at impact may be deteriorated. In this respect, the amount of compressive deformation Dc is more preferably equal to or greater than 3.7 mm, and particularly preferably equal to or greater than 4.0 mm. When the amount of compressive deformation Dc exceeds the above range, the resilience performance may be insufficient. In this respect, the amount of compressive deformation Dc is more preferably equal to or less than 6.5 mm, and particularly preferably equal to or less than 5.5 mm. The amount of compressive deformation in this specification means the amount of deformation of the sphere from the state in which the initial load of 98 N is applied to the sphere to be measured to the state in which the final load of 1274 N is applied.
[0048]
The amount of compressive deformation Ds of the sphere composed of the core 2 and the intermediate layer 3 (in other words, the sphere from which the cover 4 is removed from the golf ball 1) is preferably 3.0 mm or greater and 6.5 mm or less. When the amount of compressive deformation Ds is less than the above range, the feel at impact may be deteriorated. In this respect, the amount of compressive deformation Ds is more preferably equal to or greater than 3.2 mm, and particularly preferably equal to or greater than 3.7 mm. When the amount of compressive deformation Ds exceeds the above range, the resilience performance may be insufficient. In this respect, the amount of compressive deformation Ds is more preferably equal to or less than 6.0 mm, and particularly preferably equal to or less than 5.5 mm.
[0049]
The ratio (Ds / Dc) of the compression deformation amount Ds of the sphere composed of the core 2 and the intermediate layer 3 to the compression deformation amount Dc of the core 2 is 0.90 or more and 0.98 or less. When the ratio (Ds / Dc) is less than the above range, the deformation amount of the intermediate layer 3 becomes smaller than the deformation amount of the core 2 at the time of hitting, and the shot feeling may be insufficient. In this respect, the ratio (Ds / Dc) is particularly preferably equal to or greater than 0.91. When the ratio (Ds / Dc) exceeds the above range, the backspin amount is large and the flight distance may be insufficient. In this respect, the ratio (Ds / Dc) is more preferably equal to or less than 0.96, and particularly preferably equal to or less than 0.95.
[0050]
The compression deformation amount Db of the golf ball 1 is preferably 2.8 mm or greater and 4.5 mm or less. If the amount of compressive deformation Db is less than the above range, the feel at impact may be insufficient. In this respect, the amount of compressive deformation Db is more preferably equal to or greater than 2.9, and particularly preferably equal to or greater than 3.0. When the amount of compressive deformation Db exceeds the above range, the resilience performance may be insufficient. In this respect, the amount of compressive deformation Db is more preferably equal to or less than 4.2 mm, and particularly preferably equal to or less than 4.0 mm.
[0051]
The total (Db + Dc) of the compression deformation amount Db of the golf ball 1 and the compression deformation amount Dc of the core 2 is preferably 7.0 mm or greater and 10.0 mm or less. When (Db + Dc) is less than the above range, the feel at impact may be insufficient. In this respect, (Db + Dc) is more preferably equal to or greater than 7.1 mm, and particularly preferably equal to or greater than 7.2 mm. When (Db + Dc) exceeds the above range, the resilience performance may be insufficient. In this respect, (Db + Dc) is more preferably 9.5 mm or less, and particularly preferably 9.0 mm or less.
[0052]
2 is a front view showing the golf ball 1 shown in FIG. 1, and FIG. 3 is a plan view showing the golf ball 1 shown in FIG. As is apparent from these drawings, the golf ball 1 has four types of dimples 5 including A dimple, B dimple, C dimple and D dimple. All the dimples 5 are circular dimples. The diameter of the A dimple is 4.085 mm, the diameter of the B dimple is 3.815 mm, the diameter of the C dimple is 3.450 mm, and the diameter of the D dimple is 2.600 mm. 2 and 3 indicate a great circle that divides the surface of the golf ball 1 into eight spherical triangles. 2 and 3, the types of dimples 5 are shown for one spherical triangle. The other seven spherical triangles are provided with the same dimple 5 pattern as this dimple 5 pattern.
[0053]
FIG. 4 is an enlarged cross-sectional view showing a part of the golf ball 1 of FIG. In this figure, the vicinity of the dimple 5 is shown. The dimple surface Sd is recessed from the phantom spherical surface Sp (the surface of the golf ball 1 when it is assumed that the dimple 5 does not exist). 4 is a straight line drawn so as to contact both sides of the dimple 5. The contact P is a point on the dimple edge (the outline of the dimple 5). The distance between the two contacts P, P is the diameter Di of the dimple 5. In FIG. 4, a plane that is perpendicular to the paper surface and includes the straight line T is a plane that includes the edge of the dimple 5.
[0054]
The distance between the deepest part of the dimple surface Sd and the plane including the edge of the dimple 5 is the depth d1. The maximum distance between the virtual spherical surface Sp and the plane including the edge of the dimple 5 is the depth d2. The sum of the depth d1 and the depth d2 is the total depth de. The volume of the space surrounded by the plane including the edge of the dimple 5 and the dimple surface Sd is a volume vb. The volume of the space surrounded by the plane including the edge of the dimple 5 and the virtual spherical surface Sp is a volume vt. The sum total of the volumes vb of all the dimples 5 is Vb. The total sum of the volumes vt of all the dimples 5 is Vt. The ratio of Vt to Vb (Vt / Vb) is Y.
[0055]
The ratio of the total area of the area surrounded by the edge of the dimple 5 in the virtual spherical surface to the surface area of the virtual spherical surface is X. As shown in FIG. 4, when the edge of the dimple 5 does not exist on the phantom spherical surface, the sum of the areas of the regions surrounded by the portion immediately above the edge of the dimple 5 (the portion including the point P ′) in the phantom spherical surface is , X.
[0056]
The value of (Y−0.5X) is 0.20 or more and 0.37 or less. Thereby, although the mid layer 3 is relatively soft, the trajectory of the golf ball 1 is optimized, and a decrease in flight distance is suppressed. If the value of (Y−0.5X) is less than the above range, the trajectory may be too low and the flight distance may be insufficient. In this respect, the value of (Y−0.5X) is more preferably equal to or greater than 0.21, and particularly preferably equal to or greater than 0.23. If the value of (Y−0.5X) exceeds the above range, the trajectory may blow up and the flight distance may be insufficient. In this respect, the value of (Y−0.5X) is more preferably equal to or less than 0.35, and particularly preferably equal to or less than 0.33.
[0057]
The diameter Di of the dimple 5 is normally set in a range of 2.0 mm or more and 6.0 mm or less. If the diameter Di is less than the above range, the dimple effect may be insufficient. In this respect, the diameter Di is more preferably equal to or greater than 2.2 mm, and particularly preferably equal to or greater than 2.3 mm. When the diameter Di exceeds the above range, not only the appearance of the golf ball 1 is deteriorated but also there is a possibility that it is difficult to roll straight. In this respect, the diameter Di is more preferably equal to or less than 5.5 mm, and particularly preferably equal to or less than 5.0 mm. The total depth de of the dimples 5 is set to 0.10 mm to 0.40 mm, further 0.12 mm to 0.35 mm, and particularly 0.13 mm to 0.33 mm.
[0058]
From the viewpoint of improving the flight distance by promoting turbulent transition, it is preferable to provide two or more dimples 5 having different diameters Di or depths de. Here, “the diameters are different” means a state where the difference in diameter is 0.15 mm or more. “Different total depth” means a state where the difference in total depth is 0.005 mm or more. The number of types of dimples 5 is usually 10 or less.
[0059]
The depth d1 of the dimple type having the smallest diameter (D dimple in the embodiment of FIG. 2) is the depth d1 of other dimple types (A dimple, B dimple, or C dimple in the embodiment of FIG. 2). Is preferably larger. This promotes turbulent transition.
[0060]
A non-circular dimple may be formed instead of or together with the circular dimple. Since the edge of the non-circular dimple does not exist on the plane, the volume vb and the volume vt cannot be calculated strictly. In a non-circular dimple, a circle having the same area as the planar shape (contour shape when the dimple is viewed from the normal direction) is assumed, and a circular dimple having this circle as a planar shape is assumed. For convenience, the volume of the region surrounded by the plane including the edge and the phantom spherical surface is the volume vt of the non-circular dimple. For convenience, the volume vb is a value obtained by subtracting the volume vt from the volume of the region surrounded by the phantom spherical surface and the surface of the dimple.
[0061]
The total value of the volume Vb and the volume Vt is 480 mm ³ More than 620mm ³ The following is preferred. When the total value is less than the above range, the trajectory of the golf ball 1 becomes too high, and the flight distance may be insufficient. From this point of view, the total value is 490mm ³ More preferably, 500mm ³ The above is particularly preferable. If the total value exceeds the above range, the trajectory of the golf ball 1 may become too low and the flight distance may be insufficient. From this point of view, the total value is 610 mm ³ The following is more preferable, 600 mm ³ The following are particularly preferred:
[0062]
X is preferably 0.70 or more and 0.90 or less. When X is less than the above range, the effect of the dimple 5 that disturbs the air flow is small, and the flight performance of the golf ball 1 may be insufficient. In this respect, X is more preferably equal to or greater than 0.72 and particularly preferably equal to or greater than 0.75. When X exceeds the above range, it tends to be a trajectory that blows up. In this respect, X is more preferably equal to or less than 0.86, and particularly preferably equal to or less than 0.83.
[0063]
The total number of dimples 5 is preferably 300 or more and 500 or less. When the total number is less than the above range, it is difficult to make the golf ball 1 substantially spherical while maintaining the value of X in a desired range (that is, the smoothness of the surface of the golf ball 1 is impaired). There is a fear. In this respect, the total number is more preferably 320 or more, and particularly preferably 360 or more. If the total number exceeds the above range, the individual dimples 5 may become small and the effect of disturbing the air flow may be insufficient. In this respect, the total number is more preferably equal to or less than 450, and particularly preferably equal to or less than 440.
[0064]
【Example】
Hereinafter, although the effect of the present invention will be clarified based on examples, the present invention should not be construed limitedly based on the description of the examples.
[0065]
[Example 1]
100 parts of polybutadiene, 26 parts of zinc acrylate, 20 parts of zinc oxide, appropriate amounts of barium sulfate, 0.5 part of diphenyl disulfide and 0.8 part of dicumyl peroxide were kneaded in a closed kneader to obtain a rubber composition. . This rubber composition was put into a mold having a spherical cavity, heated to 160 ° C. and held for 25 minutes, to obtain a core having a diameter of 36.3 mm. The compounding amount of barium sulfate was adjusted so that the mass of the golf ball was 45.4 g.
[0066]
Next, 27.5 parts of ionomer resin (Himiran 1605), 27.5 parts of other ionomer resin (Himiran 1706), and 45 parts of styrene thermoplastic elastomer (Lavalon SR04) were kneaded to obtain a resin composition. On the other hand, a core was put into a mold having a spherical cavity, and a resin composition melted by heating was injected around the core to mold an intermediate layer having a thickness of 1.6 mm.
[0067]
Next, 47.5 parts of ionomer resin (Himiran 1605), 47.5 parts of other ionomer resin (Himiran 1706), 5 parts of styrene-based thermoplastic elastomer (Lavalon SR04) and 3 parts of titanium oxide were kneaded to obtain a resin composition. Got. On the other hand, a sphere composed of a core and an intermediate layer is placed in a mold having a spherical cavity and a large number of convex portions on the cavity surface, and a resin composition melted by heating is injected around the sphere to obtain a thickness. A 1.6 mm cover was molded. Simultaneously with the cover molding, a dimple having a shape in which the shape of the convex portion was inverted was formed. The specification of the dimple is I shown in Table 3. The dimple pattern of the specification I is shown in FIGS. The cover has a Shore D hardness of 61. A coating was applied around the cover to obtain a golf ball of Example 1.
[0068]
[Examples 2 to 5 and Comparative Examples 1 to 6]
As shown in Tables 1 to 4 below, Examples 2 to 5 and Comparative Examples 1 to 6 were performed in the same manner as Example 1 except that the core formulation, vulcanization conditions, intermediate layer formulation, and dimple specifications were changed. A golf ball was obtained. The dimple pattern of specifications II to V and the dimple pattern of specification I have different dimple dimensions, but the dimple positions are the same.
[0069]
[Core hardness measurement]
The surface hardness of the core was measured using a spring hardness tester (Shore D type). Moreover, the surface hardness and internal hardness of the core were measured using a spring type hardness meter (JIS-C type), and the hardness difference was calculated. These results are shown in Table 4 below.
[0070]
[Measurement of intermediate layer hardness]
A sheet having a thickness of 2.0 mm was formed by hot pressing from the same resin composition as that used for the intermediate layer. This sheet was kept in an environment of 23 ° C. for 2 weeks. Three sheets were stacked and the hardness was measured using a spring type hardness tester (Shore D type).
[0071]
[Measurement of coefficient of restitution]
An aluminum hollow cylinder having a mass of 200 g was caused to collide with the golf ball at a speed of 40 m / s. Then, the velocity of the hollow cylinder before and after the collision and the velocity of the golf ball after the collision were measured, and the restitution coefficient of the golf ball was obtained according to the law of conservation of momentum. Table 4 below shows the indices when the coefficient of restitution of the golf ball of Comparative Example 1 is 1.00.
[0072]
[Flight distance test]
A driver (W1) equipped with a metal head was attached to a swing machine (manufactured by Tsurutemper), and the machine condition was adjusted so that the head speed was 40 m / s, and a golf ball was hit. Then, the total flight distance (the distance from the hitting point to the point where the golf ball stopped) was measured. The average value of the total flight distance measured for five golf balls is shown in Table 4 below.
[0073]
[Evaluation of feel at impact]
Ten female golfers held drivers with metal heads and hit golf balls. And the quality was evaluated about the hit feeling (degree of impact at the time of hitting). When the number of golfers evaluated as good is 8 or more, “◎”, when 6 or more and 7 or less, “○”, when 4 or more and 5 or less, “△”, and when 3 or less Was marked “x”. The results are shown in Table 4 below.
[0074]
[Table 1]

[0075]
[Table 2]

[0076]
[Table 3]

[0077]
[Table 4]

[0078]
As shown in Table 4, the golf balls of the examples are excellent in feel at impact, and the flight distance is comparable to the golf balls of the comparative examples. From this evaluation result, the superiority of the present invention is clear.
[0079]
【The invention's effect】
As described above, when the golf ball of the present invention is hit by a golfer with a low head speed, a soft feel at impact can be obtained by a relatively soft intermediate layer. In addition, in this golf ball, the decrease in the flight distance due to the flexible intermediate layer is suppressed by the dimples.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a golf ball according to an embodiment of the present invention.
FIG. 2 is a front view showing the golf ball of FIG. 1;
FIG. 3 is a plan view showing the golf ball of FIG. 1;
4 is an enlarged cross-sectional view showing a part of the golf ball in FIG. 1. FIG.
[Explanation of symbols]
1 Golf ball
2 ... Core
3 ... Intermediate layer
4 ... Cover
5 ... Dimple
A ... A dimple
B ... B dimple
C ... C dimple
D ... D dimple
E ... E dimple
L ... great circle

Claims (7)

A golf ball comprising a core, an intermediate layer made of a synthetic resin composition and positioned outside the core, and a cover positioned outside the intermediate layer, and a plurality of dimples formed on the surface of the cover Because
The amount of compressive deformation of the core from the state where the initial load of 98 N is applied to the state where the final load of 1274 N is applied is Dc,
The amount of compressive deformation of the sphere including the core and the intermediate layer from the state where the initial load of 98 N is applied to the state where the final load of 1274 N is applied is defined as Ds,
The ratio of the total area of the area surrounded by the dimple edges in the phantom sphere to the surface area of the phantom sphere is X,
The total volume of the space surrounded by the plane including the edge of the dimple and the surface of the dimple is Vb,
The total volume of the space surrounded by the plane including the edge of the dimple and the virtual spherical surface is defined as Vt,
When the ratio of Vt to Vb (Vt / Vb) is Y,
The ratio (Ds / Dc) is 0.90 or more and 0.98 or less, and the value of (Y-0.5X) is 0.20 or more and 0.37 or less,
A golf ball characterized in that the intermediate layer has a Shore D hardness of 35 or more and 42 or less.   2. The golf according to claim 1, wherein a compression deformation amount Dc of the core is 3.5 mm or more and 7.0 mm or less, and a compression deformation amount Ds of a sphere composed of the core and the intermediate layer is 3.0 mm or more and 6.5 mm or less. ball.   The golf ball according to claim 1, wherein a shore D hardness of the intermediate layer is smaller than a shore D hardness of the core surface.   The golf ball according to claim 1, wherein the intermediate layer has a thickness of 1.0 mm to 2.5 mm.   5. The golf ball according to claim 1, wherein the base layer polymer of the intermediate layer contains an ionomer resin as a main component.   6. The golf ball according to claim 5, wherein the base polymer of the intermediate layer includes an ionomer resin and a thermoplastic elastomer, and a mass ratio of the ionomer resin to the thermoplastic elastomer is 50/50 or more and 95/5 or less. .   The golf ball according to claim 1, wherein the intermediate layer has a Shore D hardness of 38 or more and 42 or less.

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