EP2668977B1 - Golf ball - Google Patents

Golf ball Download PDF

Info

Publication number
EP2668977B1
EP2668977B1 EP13168981.2A EP13168981A EP2668977B1 EP 2668977 B1 EP2668977 B1 EP 2668977B1 EP 13168981 A EP13168981 A EP 13168981A EP 2668977 B1 EP2668977 B1 EP 2668977B1
Authority
EP
European Patent Office
Prior art keywords
hardness
core
acid
jis
salt
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Active
Application number
EP13168981.2A
Other languages
German (de)
English (en)
French (fr)
Other versions
EP2668977A3 (en
EP2668977A2 (en
Inventor
Takahiro Sajima
Hirotaka Nakamura
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Dunlop Sports Co Ltd
Original Assignee
Dunlop Sports Co Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from JP2012126211A external-priority patent/JP5502146B2/ja
Priority claimed from JP2012126149A external-priority patent/JP5502145B2/ja
Application filed by Dunlop Sports Co Ltd filed Critical Dunlop Sports Co Ltd
Publication of EP2668977A2 publication Critical patent/EP2668977A2/en
Publication of EP2668977A3 publication Critical patent/EP2668977A3/en
Application granted granted Critical
Publication of EP2668977B1 publication Critical patent/EP2668977B1/en
Active legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Images

Classifications

    • A—HUMAN NECESSITIES
    • A63—SPORTS; GAMES; AMUSEMENTS
    • A63B—APPARATUS FOR PHYSICAL TRAINING, GYMNASTICS, SWIMMING, CLIMBING, OR FENCING; BALL GAMES; TRAINING EQUIPMENT
    • A63B37/00—Solid balls; Rigid hollow balls; Marbles
    • A63B37/0003—Golf balls
    • A63B37/005—Cores
    • A63B37/0051—Materials other than polybutadienes; Constructional details
    • A63B37/0054—Substantially rigid, e.g. metal
    • A—HUMAN NECESSITIES
    • A63—SPORTS; GAMES; AMUSEMENTS
    • A63B—APPARATUS FOR PHYSICAL TRAINING, GYMNASTICS, SWIMMING, CLIMBING, OR FENCING; BALL GAMES; TRAINING EQUIPMENT
    • A63B37/00—Solid balls; Rigid hollow balls; Marbles
    • A—HUMAN NECESSITIES
    • A63—SPORTS; GAMES; AMUSEMENTS
    • A63B—APPARATUS FOR PHYSICAL TRAINING, GYMNASTICS, SWIMMING, CLIMBING, OR FENCING; BALL GAMES; TRAINING EQUIPMENT
    • A63B37/00—Solid balls; Rigid hollow balls; Marbles
    • A63B37/0003—Golf balls
    • A—HUMAN NECESSITIES
    • A63—SPORTS; GAMES; AMUSEMENTS
    • A63B—APPARATUS FOR PHYSICAL TRAINING, GYMNASTICS, SWIMMING, CLIMBING, OR FENCING; BALL GAMES; TRAINING EQUIPMENT
    • A63B37/00—Solid balls; Rigid hollow balls; Marbles
    • A63B37/0003—Golf balls
    • A63B37/0023—Covers
    • A63B37/0029—Physical properties
    • A63B37/0031—Hardness
    • A—HUMAN NECESSITIES
    • A63—SPORTS; GAMES; AMUSEMENTS
    • A63B—APPARATUS FOR PHYSICAL TRAINING, GYMNASTICS, SWIMMING, CLIMBING, OR FENCING; BALL GAMES; TRAINING EQUIPMENT
    • A63B37/00—Solid balls; Rigid hollow balls; Marbles
    • A63B37/0003—Golf balls
    • A63B37/0023—Covers
    • A63B37/0029—Physical properties
    • A63B37/0031—Hardness
    • A63B37/0032—Hardness gradient
    • A—HUMAN NECESSITIES
    • A63—SPORTS; GAMES; AMUSEMENTS
    • A63B—APPARATUS FOR PHYSICAL TRAINING, GYMNASTICS, SWIMMING, CLIMBING, OR FENCING; BALL GAMES; TRAINING EQUIPMENT
    • A63B37/00—Solid balls; Rigid hollow balls; Marbles
    • A63B37/0003—Golf balls
    • A63B37/0038—Intermediate layers, e.g. inner cover, outer core, mantle
    • A—HUMAN NECESSITIES
    • A63—SPORTS; GAMES; AMUSEMENTS
    • A63B—APPARATUS FOR PHYSICAL TRAINING, GYMNASTICS, SWIMMING, CLIMBING, OR FENCING; BALL GAMES; TRAINING EQUIPMENT
    • A63B37/00—Solid balls; Rigid hollow balls; Marbles
    • A63B37/0003—Golf balls
    • A63B37/0038—Intermediate layers, e.g. inner cover, outer core, mantle
    • A63B37/004—Physical properties
    • A63B37/0043—Hardness
    • A63B37/0044—Hardness gradient
    • A—HUMAN NECESSITIES
    • A63—SPORTS; GAMES; AMUSEMENTS
    • A63B—APPARATUS FOR PHYSICAL TRAINING, GYMNASTICS, SWIMMING, CLIMBING, OR FENCING; BALL GAMES; TRAINING EQUIPMENT
    • A63B37/00—Solid balls; Rigid hollow balls; Marbles
    • A63B37/0003—Golf balls
    • A63B37/005—Cores
    • A63B37/0051—Materials other than polybutadienes; Constructional details
    • A—HUMAN NECESSITIES
    • A63—SPORTS; GAMES; AMUSEMENTS
    • A63B—APPARATUS FOR PHYSICAL TRAINING, GYMNASTICS, SWIMMING, CLIMBING, OR FENCING; BALL GAMES; TRAINING EQUIPMENT
    • A63B37/00—Solid balls; Rigid hollow balls; Marbles
    • A63B37/0003—Golf balls
    • A63B37/005—Cores
    • A63B37/006—Physical properties
    • A63B37/0062—Hardness
    • A63B37/00622—Surface hardness
    • A—HUMAN NECESSITIES
    • A63—SPORTS; GAMES; AMUSEMENTS
    • A63B—APPARATUS FOR PHYSICAL TRAINING, GYMNASTICS, SWIMMING, CLIMBING, OR FENCING; BALL GAMES; TRAINING EQUIPMENT
    • A63B37/00—Solid balls; Rigid hollow balls; Marbles
    • A63B37/0003—Golf balls
    • A63B37/005—Cores
    • A63B37/006—Physical properties
    • A63B37/0062—Hardness
    • A63B37/0063—Hardness gradient
    • A—HUMAN NECESSITIES
    • A63—SPORTS; GAMES; AMUSEMENTS
    • A63B—APPARATUS FOR PHYSICAL TRAINING, GYMNASTICS, SWIMMING, CLIMBING, OR FENCING; BALL GAMES; TRAINING EQUIPMENT
    • A63B37/00—Solid balls; Rigid hollow balls; Marbles
    • A63B37/0003—Golf balls
    • A63B37/007—Characteristics of the ball as a whole
    • A63B37/0072—Characteristics of the ball as a whole with a specified number of layers
    • A63B37/0076—Multi-piece balls, i.e. having two or more intermediate layers
    • A—HUMAN NECESSITIES
    • A63—SPORTS; GAMES; AMUSEMENTS
    • A63B—APPARATUS FOR PHYSICAL TRAINING, GYMNASTICS, SWIMMING, CLIMBING, OR FENCING; BALL GAMES; TRAINING EQUIPMENT
    • A63B37/00—Solid balls; Rigid hollow balls; Marbles
    • A63B37/0003—Golf balls
    • A63B37/007—Characteristics of the ball as a whole
    • A63B37/0077—Physical properties
    • A63B37/0092—Hardness distribution amongst different ball layers
    • A63B37/00922—Hardness distribution amongst different ball layers whereby hardness of the cover is lower than hardness of the intermediate layers
    • A—HUMAN NECESSITIES
    • A63—SPORTS; GAMES; AMUSEMENTS
    • A63B—APPARATUS FOR PHYSICAL TRAINING, GYMNASTICS, SWIMMING, CLIMBING, OR FENCING; BALL GAMES; TRAINING EQUIPMENT
    • A63B37/00—Solid balls; Rigid hollow balls; Marbles
    • A63B37/02—Special cores
    • A63B37/06—Elastic cores

Definitions

  • the present invention relates to golf balls. Specifically, the present invention relates to golf balls that include a solid core and a cover including two or more layers.
  • Flight performance In particular, golf players place importance on flight performance upon shots with a driver and a long iron. Flight performance correlates with the resilience performance of a golf ball. When a golf ball having excellent resilience performance is hit, the golf ball flies at a high speed, thereby achieving a large flight distance. Golf balls that include a core having excellent resilience performance are disclosed in JP61-37178 , JP2008-212681 ( US2008/0214324 ), JP2008-523952 ( US2006/0135287 and US2007/0173607 ), and JP2009-119256 ( US2009/0124757 ).
  • JP61-37178 is obtained from a rubber composition that includes a co-crosslinking agent and a crosslinking activator.
  • This publication discloses palmitic acid, stearic acid, and myristic acid as the crosslinking activator.
  • the core disclosed in JP2008-212681 is obtained from a rubber composition that includes an organic peroxide, a metal salt of an ⁇ , ⁇ -unsaturated carboxylic acid, and a copper salt of a fatty acid.
  • the core disclosed in JP2008-523952 is obtained from a rubber composition that includes a metal salt of an unsaturated monocarboxylic acid, a free radical initiator, and a non-conjugated diene monomer.
  • the core disclosed in JP2009-119256 is obtained from a rubber composition that includes a polybutadiene whose vinyl content is equal to or less than 2%, whose cis 1,4-blond content is equal to or greater than 80%, and which has an active end modified with an alkoxysilane compound.
  • An appropriate trajectory height is required in order to achieve a large flight distance.
  • a trajectory height depends on a spin rate and a launch angle. With a golf ball that achieves a high trajectory by a high spin rate, a flight distance is insufficient. With a golf ball that achieves a high trajectory by a high launch angle, a large flight distance is obtained.
  • Use of an outer-hard/inner-soft structure in a golf ball can achieve a low spin rate and a high launch angle.
  • JP6-154357 (USP 5,403,010 ), JP2008-194471 (USP 7,344,455 , US2008/0194358 , US2008/0194359 , and US2008/0214325 ), and JP2008-194473 ( US2008/0194357 and US2008/0312008 ).
  • a JIS-C hardness H1 at the central point of the core is 58 to 73
  • a JIS-C hardness H2 in a region that extends over a distance range from equal to or greater than 5 mm to equal to or less than 10 mm from the central point is equal to or greater than 65 but equal to or less than 75
  • a JIS-C hardness H3 at a point located at a distance of 15 mm from the central point is equal to or greater than 74 but equal to or less than 82
  • a JIS-C hardness H4 at the surface of the core is equal to or greater than 76 but equal to or less than 84.
  • the hardness H2 is greater than the hardness H1
  • the hardness H3 is greater than the hardness H2
  • the hardness H4 is equal to or greater than the hardness H3.
  • a Shore D hardness at the central point of the core is equal to or greater than 30 but equal to or less than 48, a Shore D hardness at a point located at a distance of 4 mm from the central point is equal to or greater than 34 but equal to or less than 52, a Shore D hardness at a point located at a distance of 8 mm from the central point is equal to or greater than 40 but equal to or less than 58, a Shore D hardness at a point located at a distance of 12 mm from the central point is equal to or greater than 43 but equal to or less than 61, a Shore D hardness in a region that extends over a distance range from equal to or greater than 2 mm to equal to or less than 3 mm from the surface of the core is equal to or greater than 36 but equal to or less than 54, and a Shore D hardness at the surface is equal to or greater than 41 but equal to or less than 59.
  • a Shore D hardness at the central point of the core is equal to or greater than 25 but equal to or less than 45
  • a Shore D hardness in a region that extends over a distance range from equal to or greater than 5 mm to equal to or less than 10 mm from the central point is equal to or greater than 39 but equal to or less than 58
  • a Shore D hardness at a point located at a distance of 15 mm from the central point is equal to or greater than 36 but equal to or less than 55
  • a Shore D hardness at the surface of the core is equal to or greater than 55 but equal to or less than 75.
  • JP2010-253268 ( US2010/0273575 ) discloses a golf ball that includes a core, an envelope layer, a mid layer, and a cover.
  • the hardness gradually increases from the central point of the core to the surface of the core.
  • the difference between a JIS-C hardness at the surface and a JIS-C hardness at the central point is equal to or greater than 15.
  • the hardness of the cover is greater than the hardness of the mid layer, and the hardness of the mid layer is greater than the hardness of the envelope layer.
  • US 2011/306443 A1 discloses a golf ball comprising a core, a mid layer positioned outside the core and a cover positioned outside the mid layer, wherein the core comprises a center and an envelope layer.
  • the core of the golf ball may be composed of a rubber composition including a base resin, a crosslinking initiator, a co-crosslinking agent, zinc oxide and barium sulfate.
  • US 2003/109332 A1 relates to a golf ball having a core, an inner cover and an outer cover, wherein the JIS-C hardness of the inner cover is higher than the JIS-C hardness at the surface of the core by less than 15.
  • the core of the golf ball may be composed of a rubber composition including a base resin, a crosslinking initiator, a co-crosslinking agent, zinc oxide and barium sulfate.
  • An object of the present invention is to provide a golf ball that exerts excellent flight performance upon a shot with a middle iron.
  • Another object of the present invention is to provide a golf ball that achieves a large flight distance and excellent feel at impact upon a shot with a driver.
  • the present invention relates to a golf ball, which consists of a spherical core and a cover covering the core and including two or more layers, wherein when distances (%) from a central point of the core to nine points and JIS-C hardnesses at the nine points, which nine points are obtained by dividing a region from the central point of the core to a surface of the core at intervals of 12.5% of a radius of the core, are plotted in a graph, R2 of a linear approximation curve obtained by a least-square method is equal to or greater than 0.95, wherein R2 is calculated by squaring a correlation coefficient R, wherein the correlation coefficient R is calculated by dividing the covariance of the distance (%) from the central point and the hardness (JIS-C) by the standard deviation of the distance (%) from the central point and the standard deviation of the hardness (JIS-C), the JIS-C hardness Hi of the innermost layer of the cover is greater than the JIS-C hardness Hs at the surface of
  • the JIS-C hardness Hi of an innermost layer of the cover is greater than a JIS-C hardness Hs at the surface of the core.
  • the hardness distribution of the golf ball is appropriate.
  • the energy loss is low when the golf ball is hit with a middle iron.
  • the spin rate is low. The low spin rate achieves a large flight distance.
  • the JIS-C hardness Hi of the innermost layer of the cover is equal to or less than the JIS-C hardness Hs at the surface of the core.
  • the hardness distribution is appropriate.
  • the energy loss is low when the golf ball is hit with a driver.
  • the spin rate is low.
  • the low spin rate achieves a large flight distance.
  • the innermost layer achieves soft feel at impact.
  • the golf ball of this embodiment has both excellent flight performance and excellent feel at impact.
  • a golf ball 2 shown in FIG. 1 includes a spherical core 4 and a cover 6 covering the core 4.
  • the cover 6 includes an inner cover 8 and an outer cover 10 positioned outside the inner cover 8.
  • the inner cover 8 is an innermost layer of the cover 6.
  • the outer cover 10 is an outermost layer of the cover 6.
  • the cover 6 may include another one or more layers between the inner cover 8 and the outer cover 10.
  • On the surface of the outer cover 10, a large number of dimples 12 are formed.
  • a part other than the dimples 12 is a land 14.
  • the golf ball 2 includes a paint layer and a mark layer on the external side of the outer cover 10, but these layers are not shown in the drawing.
  • the golf ball 2 has a diameter of 40 mm or greater but 45 mm or less. From the standpoint of conformity to the rules established by the United States Golf Association (USGA), the diameter is preferably equal to or greater than 42.67 mm. In light of suppression of air resistance, the diameter is preferably equal to or less than 44 mm and more preferably equal to or less than 42.80 mm.
  • the golf ball 2 has a weight of 40 g or greater but 50 g or less. In light of attainment of great inertia, the weight is preferably equal to or greater than 44 g and more preferably equal to or greater than 45.00 g. From the standpoint of conformity to the rules established by the USGA, the weight is preferably equal to or less than 45.93 g.
  • FIG. 2 is a line graph showing a hardness distribution of the core 4 of the golf ball 2 in FIG. 1 .
  • the horizontal axis of the graph indicates the ratio (%) of a distance from the central point of the core 4 to the radius of the core 4.
  • the vertical axis of the graph indicates a JIS-C hardness.
  • FIG. 2 also shows a linear approximation curve obtained by a least-square method on the basis of the distances and the hardnesses of the nine measuring points.
  • the broken line does not greatly deviate from the linear approximation curve.
  • the broken line has a shape close to the linear approximation curve.
  • the hardness linearly increases from its central point toward its surface.
  • R 2 of the linear approximation curve obtained by the least-square method is equal to or greater than 0.95.
  • R 2 is an index indicating the linearity of the broken line.
  • the shape of the broken line of the hardness distribution is close to a straight line.
  • the core 4 for which R 2 is equal to or greater than 0.95 has excellent resilience performance.
  • R 2 is more preferably equal to or greater than 0.96 and particularly preferably equal to or greater than 0.97.
  • R 2 is calculated by squaring a correlation coefficient R.
  • the correlation coefficient R is calculated by dividing the covariance of the distance (%) from the central point and the hardness (JIS-C) by the standard deviation of the distance (%) from the central point and the standard deviation of the hardness (JIS-C).
  • the core 4 is obtained by crosslinking a rubber composition.
  • the rubber composition includes:
  • the base rubber (a) is crosslinked by the co-crosslinking agent (b).
  • the heat of the crosslinking reaction remains near the central point of the core 4.
  • the temperature at the central portion is high.
  • the temperature gradually decreases from the central point toward the surface.
  • the acid reacts with a metal salt of the co-crosslinking agent (b) to bond to cation.
  • the salt reacts with the metal salt of the co-crosslinking agent (b) to exchange cation. By the bonding and the exchange, metallic bonding is broken.
  • Examples of the base rubber (a) of the core 4 include polybutadienes, polyisoprenes, styrene-butadiene copolymers, ethylene-propylene-diene copolymers, and natural rubbers. In light of resilience performance, polybutadienes are preferred. When a polybutadiene and another rubber are used in combination, it is preferred that the polybutadiene is included as a principal component. Specifically, the proportion of the polybutadiene to the entire base rubber is preferably equal to or greater than 50% by weight and more preferably equal to or greater than 80% by weight. The proportion of cis-1,4 bonds in the polybutadiene is preferably equal to or greater than 40% by weight and more preferably equal to or greater than 80% by weight.
  • a polybutadiene in which the proportion of 1,2-vinyl bonds is equal to or less than 2.0% by weight is preferred.
  • the polybutadiene can contribute to the resilience performance of the core 4.
  • the proportion of 1,2-vinyl bonds is preferably equal to or less than 1.7% by weight and particularly preferably equal to or less than 1.5% by weight.
  • a rare-earth-element-containing catalyst is preferably used for synthesis of a polybutadiene.
  • a polybutadiene synthesized with a catalyst containing neodymium, which is a lanthanum-series rare earth element compound, is preferred.
  • the polybutadiene has a Mooney viscosity (ML 1+4 (100°C)) of preferably 30 or greater, more preferably 32 or greater, and particularly preferably 35 or greater.
  • the Mooney viscosity (ML 1+4 (100°C)) is preferably equal to or less than 140, more preferably equal to or less than 120, even more preferably equal to or less than 100, and particularly preferably equal to or less than 80.
  • the Mooney viscosity (ML 1+4 (100°C)) is measured according to the standards of "JIS K6300". The measurement conditions are as follows.
  • the polybutadiene has a molecular weight distribution (Mw/Mn) of preferably 2.0 or greater, more preferably 2.2 or greater, even more preferably 2.4 or greater, and particularly preferably 2.6 or greater.
  • Mw/Mn molecular weight distribution
  • the molecular weight distribution (Mw/Mn) is preferably equal to or less than 6.0, more preferably equal to or less than 5.0, even more preferably equal to or less than 4.0, and particularly preferably equal to or less than 3.4.
  • the molecular weight distribution (Mw/Mn) is calculated by dividing the weight average molecular weight Mw by the number average molecular weight Mn.
  • the molecular weight distribution is measured by gel permeation chromatography ("HLC-8120GPC" manufactured by Tosoh Corporation).
  • the measurement conditions are as follows.
  • the co-crosslinking agent (b) is:
  • the rubber composition may include only the ⁇ , ⁇ -unsaturated carboxylic acid (b1) or only the metal salt (b2) of the ⁇ , ⁇ -unsaturated carboxylic acid as the co-crosslinking agent (b).
  • the rubber composition may include both the ⁇ , ⁇ -unsaturated carboxylic acid (b1) and the metal salt (b2) of the ⁇ , ⁇ -unsaturated carboxylic acid as the co-crosslinking agent (b).
  • the metal salt (b2) of the ⁇ , ⁇ -unsaturated carboxylic acid graft-polymerizes with the molecular chain of the base rubber, thereby crosslinking the rubber molecules.
  • the rubber composition preferably further includes a metal compound (f).
  • the metal compound (f) reacts with the ⁇ , ⁇ -unsaturated carboxylic acid (b1) in the rubber composition.
  • a salt obtained by this reaction graft-polymerizes with the molecular chain of the base rubber.
  • Examples of the metal compound (f) include metal hydroxides such as magnesium hydroxide, zinc hydroxide, calcium hydroxide, sodium hydroxide, lithium hydroxide, potassium hydroxide, and copper hydroxide; metal oxides such as magnesium oxide, calcium oxide, zinc oxide, and copper oxide; and metal carbonates such as magnesium carbonate, zinc carbonate, calcium carbonate, sodium carbonate, lithium carbonate, and potassium carbonate.
  • metal hydroxides such as magnesium hydroxide, zinc hydroxide, calcium hydroxide, sodium hydroxide, lithium hydroxide, potassium hydroxide, and copper hydroxide
  • metal oxides such as magnesium oxide, calcium oxide, zinc oxide, and copper oxide
  • metal carbonates such as magnesium carbonate, zinc carbonate, calcium carbonate, sodium carbonate, lithium carbonate, and potassium carbonate.
  • a compound that includes a bivalent metal is preferred.
  • the compound that includes the bivalent metal reacts with the co-crosslinking agent (b) to form metal crosslinks.
  • the metal compound (f) is particularly preferably a zinc compound
  • Examples of the ⁇ , ⁇ -unsaturated carboxylic acids include acrylic acid, methacrylic acid, fumaric acid, maleic acid, and crotonic acid.
  • Examples of the metal component in the metal salt (b2) of the ⁇ , ⁇ -unsaturated carboxylic acid include sodium ion, potassium ion, lithium ion, magnesium ion, calcium ion, zinc ion, barium ion, cadmium ion, aluminum ion, tin ion, and zirconium ion.
  • the metal salt (b2) of the ⁇ , ⁇ -unsaturated carboxylic acid may include two or more types of ions.
  • bivalent metal ions such as magnesium ion, calcium ion, zinc ion, barium ion, and cadmium ion are preferred.
  • the metal salt (b2) of the ⁇ , ⁇ -unsaturated carboxylic acid is particularly preferably zinc acrylate.
  • the amount of the co-crosslinking agent (b) is preferably equal to or greater than 15 parts by weight and particularly preferably equal to or greater than 20 parts by weight, per 100 parts by weight of the base rubber. In light of feel at impact, the amount is preferably equal to or less than 50 parts by weight, more preferably equal to or less than 45 parts by weight, and particularly preferably equal to or less than 40 parts by weight, per 100 parts by weight of the base rubber.
  • the crosslinking initiator (c) is preferably an organic peroxide.
  • the organic peroxide contributes to the resilience performance of the golf ball 2.
  • examples of preferable organic peroxides include dicumyl peroxide, 1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, and di-t-butyl peroxide. In light of versatility, dicumyl peroxide is preferred.
  • the amount of the crosslinking initiator (c) is preferably equal to or greater than 0.2 parts by weight and particularly preferably equal to or greater than 0.5 parts by weight, per 100 parts by weight of the base rubber. In light of feel at impact and durability of the golf ball 2, the amount is preferably equal to or less than 5.0 parts by weight and particularly preferably equal to or less than 2.5 parts by weight, per 100 parts by weight of the base rubber.
  • the co-crosslinking agent (b) is not included in the concept of the acid and/or the salt (d) . It is inferred that as described above, the acid and/or the salt (d) breaks the metal crosslinks by the co-crosslinking agent (b) in the central portion of the core 4 during heating and forming of the core 4.
  • the acid and/or the salt (d) is a carboxylic acid and/or a salt thereof (d1). Carboxylates are particularly preferred.
  • the carboxylic acid component of the carboxylic acid and/or the salt thereof (d1) has a carboxyl group.
  • the carbon number of the carboxylic acid component of the carboxylic acid and/or the salt thereof (d1) is preferably equal to or greater than 1 but equal to or less than 30, more preferably equal to or greater than 3 but equal to or less than 30, and even more preferably equal to or greater than 5 but equal to or less than 28.
  • Examples of the carboxylic acid include aliphatic carboxylic acids (fatty acids) and aromatic carboxylic acids. Fatty acids and salts thereof are preferred.
  • the rubber composition may include a saturated fatty acid or a salt thereof, or may include an unsaturated fatty acid or a salt thereof.
  • the saturated fatty acid and the salt thereof are preferred.
  • fatty acids examples include butyric acid (C4), valeric acid (C5), caproic acid (C6), enanthic acid (C7), caprylic acid (octanoic acid) (C8), pelargonic acid (C9), capric acid (C10), lauric acid (C12), myristic acid (C14), myristoleic acid (C14), pentadecylic acid (C15), palmitic acid (C16), palmitoleic acid (C16), margaric acid (C17), stearic acid (C18), elaidic acid (C18), vaccenic acid (C18), oleic acid (C18), linolic acid (C18), linolenic acid (C18), 12-hydroxystearic acid (C18), arachidic acid (C20), gadoleic acid (C20), arachidonic acid (C20), eicosenoic acid (C20), behenic acid (C22), erucic
  • aromatic carboxylic acid has an aromatic ring and a carboxyl group.
  • aromatic carboxylic acids include benzoic acid, phthalic acid, isophthalic acid, terephthalic acid, hemimellitic acid (benzene-1,2,3-tricarboxylic acid), trimellitic acid (benzene-1,2,4-tricarboxylic acid), trimesic acid (benzene-1,3,5-tricarboxylic acid), mellophanic acid (benzene-1,2,3,4-tetracarboxylic acid), prehnitic acid (benzene-1,2,3,5-tetracarboxylic acid), pyromellitic acid (benzene-1,2,4,5-tetracarboxylic acid), mellitic acid (benzene hexacarboxylic acid), diphenic acid (biphenyl-2,2'-dicarboxylic acid), toluic acid (methylbenzoic acid), xylic acid, prehnitylic acid (2,3,
  • the rubber composition may include a salt of an aromatic carboxylic acid substituted with a hydroxyl group, an alkoxy group, or an oxo group.
  • this carboxylic acid can include salicylic acid (2-hydroxybenzoic acid), anisic acid (methoxybenzoic acid), cresotinic acid (hydroxy(methyl) benzoic acid), o-homosalicylic acid (2-hydroxy-3-methylbenzoic acid), m-homosalicylic acid (2-hydroxy-4-methylbenzoic acid), p-homosalicylic acid (2-hydroxy-5-methylbenzoic acid), o-pyrocatechuic acid (2,3-dihydroxybenzoic acid), ⁇ -resorcylic acid (2,4-dihydroxybenzoic acid), ⁇ -resorcylic acid (2,6-dihydroxybenzoic acid), protocatechuic acid (3,4-dihydroxybenzoic acid), ⁇ -resorcylic acid (3,5-dihydroxybenzo
  • the cationic component of the carboxylate is a metal ion or an organic cation.
  • the metal ion include sodium ion, potassium ion, lithium ion, silver ion, magnesium ion, calcium ion, zinc ion, barium ion, cadmium ion, copper ion, cobalt ion, nickel ion, manganese ion, aluminum ion, iron ion, tin ion, zirconium ion, and titanium ion. Two or more types of ions may be used in combination.
  • the organic cation is a cation having a carbon chain.
  • Examples of the organic cation include organic ammonium ions.
  • Examples of organic ammonium ions include primary ammonium ions such as stearylammonium ion, hexylammonium ion, octylammonium ion, and 2-ethylhexylammonium ion; secondary ammonium ions such as dodecyl (lauryl) ammonium ion, and octadecyl (stearyl) ammonium ion; tertiary ammonium ions such as trioctylammonium ion; and quaternary ammonium ions such as dioctyldimethylammonium ion, and distearyldimethylammonium ion. Two or more types of organic cations may be used in combination.
  • preferable carboxylates include a potassium salt, a magnesium salt, an aluminum salt, a zinc salt, an iron salt, a copper salt, a nickel salt, or a cobalt salt of octanoic acid, lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, or behenic acid.
  • Zinc salts of carboxylic acids are particularly preferred.
  • Specific examples of preferable carboxylates include zinc octoate, zinc laurate, zinc myristate, and zinc stearate.
  • the amount of the carboxylic acid and/or the salt (d1) is preferably equal to or greater than 0.5 parts by weight, more preferably equal to or greater than 1.0 parts by weight, even more preferably equal to or greater than 1.5 parts by weight, and particularly preferably equal to or greater than 2.0 parts by weight, per 100 parts by weight of the base rubber.
  • the amount is preferably equal to or less than 40 parts by weight, more preferably less than 40 parts by weight, even more preferably equal to or less than 30 parts by weight, and particularly preferably equal to or less than 20 parts by weight, per 100 parts by weight of the base rubber.
  • the weight ratio of the co-crosslinking agent (b) and the carboxylic acid and/or the salt (d1) in the rubber composition is preferably equal to or greater than 3/7 but equal to or less than 9/1, and is particularly preferably equal to or greater than 4/6 but equal to or less than 8/2. From the rubber composition in which this weight ratio is within the above range, the core 4 whose hardness linearly increases from its central point toward its surface can be obtained.
  • zinc acrylate is preferably used as the co-crosslinking agent (b).
  • Zinc acrylate whose surface is coated with stearic acid or zinc stearate for the purpose of improving dispersibility to rubber is present.
  • this coating material is not included in the concept of the acid and/or the salt (d).
  • the rubber composition preferably further includes an organic sulfur compound (e).
  • the organic sulfur compound (e) can contribute to control of: the linearity of the hardness distribution of the core 4; and the degree of the outer-hard/inner-soft structure.
  • An example of the organic sulfur compound (e) is an organic compound having a thiol group or a polysulfide linkage having 2 to 4 sulfur atoms. A metal salt of this organic compound is also included in the organic sulfur compound (e).
  • organic sulfur compound (e) examples include aliphatic compounds such as aliphatic thiols, aliphatic thiocarboxylic acids, aliphatic dithiocarboxylic acids, and aliphatic polysulfides; heterocyclic compounds; alicyclic compounds such as alicyclic thiols, alicyclic thiocarboxylic acids, alicyclic dithiocarboxylic acids, and alicyclic polysulfides; and aromatic compounds.
  • aliphatic compounds such as aliphatic thiols, aliphatic thiocarboxylic acids, aliphatic dithiocarboxylic acids, and aliphatic polysulfides
  • heterocyclic compounds such as alicyclic thiols, alicyclic thiocarboxylic acids, alicyclic dithiocarboxylic acids, and alicyclic polysulfides
  • aromatic compounds such as aliphatic thiols, aliphatic
  • organic sulfur compound (e) examples include thiophenols, thionaphthols, polysulfides, thiocarboxylic acids, dithiocarboxylic acids, sulfenamides, thiurams, dithiocarbamates, and thiazoles.
  • Preferable organic sulfur compounds (e) are thiophenols, polysulfides having 2 to 4 sulfur atoms, thionaphthols, thiurams, and metal salts thereof.
  • organic sulfur compound (e) are represented by the following chemical formulas (1) to (4).
  • R1 to R5 each represent H or a substituent.
  • R1 to R10 each represent H or a substituent.
  • R1 to R5 each represent H or a substituent, and M1 represents a monovalent metal atom.
  • R1 to R10 each represent H or a substituent
  • M2 represents a bivalent metal atom.
  • each substituent is at least one group selected from the group consisting of a halogen group (F, Cl, Br, I), an alkyl group, a carboxyl group (-COOH), an ester (-COOR)of a carboxyl group, a formyl group (-CHO), an acyl group (-COR), a carbonyl halide group (-COX), a sulfo group (-SO 3 H), an ester (-SO 3 R) of a sulfo group, a sulfonyl halide group (-SO 2 X), a sulfino group (-SO 2 H), an alkylsulfinyl group (-SOR), a carbamoyl group (-CONH 2 ), an alkyl halide group, a cyano group (-CN), and an alkoxy group (-OR).
  • a halogen group F, Cl, Br, I
  • an alkyl group a carboxyl group (
  • Examples of the organic sulfur compound represented by the chemical formula (1) include thiophenol; thiophenols substituted with halogen groups, such as 4-fluorothiophenol, 2,5-difluorothiophenol, 2,4,5-trifluorothiophenol, 2,4,5,6-tetrafluorothiophenol, pentafluorothiophenol, 2-chlorothiophenol, 4-chlorothiophenol, 2,4-dichlorothiophenol, 2,5-dichlorothiophenol, 2,4,5-trichlorothiophenol, 2,4,5,6-tetrachlorothiophenol, pentachlorothiophenol, 4-bromothiophenol, 2,5-dibromothiophenol, 2,4,5-tribromothiophenol, 2,4,5,6-tetrabromothiophenol, pentabromothiophenol, 4-iodothiophenol, 2,5-diiodothiophenol, 2,4,5-triiodothiophenol, 2,4,5,6
  • organic sulfur compound represented by the chemical formula (1) is a compound substituted with at least one type of the above substituents and another substituent.
  • substituents include a nitro group (-NO 2 ), an amino group (-NH 2 ), a hydroxyl group (-OH), and a phenylthio group (-SPh).
  • the compound include 4-chloro-2-nitrothiophenol, 4-chloro-2-aminothiophenol, 4-chloro-2-hydroxythiophenol, 4-chloro-2-phenylthiothiophenol, 4-methyl-2-nitrothiophenol, 4-methyl-2-aminothiophenol, 4-methyl-2-hydroxythiophenol, 4-methyl-2-phenylthiothiophenol, 4-carboxy-2-nitrothiophenol, 4-carboxy-2-aminothiophenol, 4-carboxy-2-hydroxythiophenol, 4-carboxy-2-phenylthiothiophenol, 4-methoxycarbonyl-2-nitrothiophenol, 4-methoxycarbonyl-2-aminothiophenol, 4-methoxycarbonyl-2-hydroxythiophenol, 4-methoxycarbonyl-2-phenylthiothiophenol, 4-formyl-2-nitrothiophenol, 4-formyl-2-aminothiophenol, 4-formyl-2-hydroxythiophenol, 4-formyl-2-phenylthiophenol
  • Still another example of the organic sulfur compound represented by the chemical formula (1) is a compound substituted with two or more types of substituents.
  • the compound include 4-acetyl-2-chlorothiophenol, 4-acetyl-2-methylthiophenol, 4-acetyl-2-carboxythiophenol, 4-acetyl-2-methoxycarbonylthiophenol, 4-acetyl-2-formylthiophenol, 4-acetyl-2-chlorocarbonylthiophenol, 4-acetyl-2-sulfothiophenol, 4-acetyl-2-methoxysulfonylthiophenol, 4-acetyl-2-chlorosulfonylthiophenol, 4-acetyl-2-sulfinothiophenol, 4-acetyl-2-methylsulfinylthiophenol, 4-acetyl-2-carbamoylthiophenol, 4-acetyl-2-trichloromethylthiophenol, 4-acetyl-2-cyano
  • Examples of the organic sulfur compound represented by the chemical formula (2) include diphenyl disulfide; diphenyl disulfides substituted with halogen groups, such as bis(4-fluorophenyl)disulfide, bis(2,5-difluorophenyl)disulfide, bis(2,4,5-trifluorophenyl)disulfide, bis(2,4,5,6-tetrafluorophenyl)disulfide, bis(pentafluorophenyl)disulfide, bis(4-chlorophenyl)disulfide, bis(2,5-dichlorophenyl)disulfide, bis(2,4,5-trichlorophenyl)disulfide, bis(2,4,5,6-tetrachlorophenyl)disulfide, bis(pentachlorophenyl)disulfide, bis(4-bromophenyl)disulfide, bis(2,5-
  • organic sulfur compound represented by the chemical formula (2) is a compound substituted with at least one type of the above substituents and another substituent.
  • substituents include a nitro group (-NO 2 ), an amino group (-NH 2 ), a hydroxyl group (-OH), and a phenylthio group (-SPh).
  • the compound include bis(4-chloro-2-nitrophenyl)disulfide, bis(4-chloro-2-aminophenyl)disulfide, bis(4-chloro-2-hydroxyphenyl)disulfide, bis(4-chloro-2-phenylthiophenyl)disulfide, bis(4-methyl-2-nitrophenyl)disulfide, bis(4-methyl-2-aminophenyl)disulfide, bis(4-methyl-2-hydroxyphenyl)disulfide, bis(4-methyl-2-phenylthiophenyl)disulfide, bis(4-carboxy-2-nitrophenyl)disulfide, bis(4-carboxy-2-aminophenyl)disulfide, bis(4-carboxy-2-hydroxyphenyl)disulfide, bis(4-carboxy-2-phenylthiophenyl)disulfide, bis
  • Still another example of the organic sulfur compound represented by the chemical formula (2) is a compound substituted with two or more types of substituents.
  • the compound include bis(4-acetyl-2-chlorophenyl)disulfide, bis(4-acetyl-2-methylphenyl)disulfide, bis(4-acetyl-2-carboxyphenyl)disulfide, bis(4-acetyl-2-methoxycarbonylphenyl)disulfide, bis(4-acetyl-2-formylphenyl)disulfide, bis(4-acetyl-2-chlorocarbonylphenyl)disulfide, bis(4-acetyl-2-sulfophenyl)disulfide, bis(4-acetyl-2-methoxysulfonylphenyl)disulfide, bis(4-acetyl-2-chlorosulfonylphenyl)d
  • Examples of the organic sulfur compound represented by the chemical formula (3) include thiophenol sodium salt; thiophenol sodium salts substituted with halogen groups, such as 4-fluorothiophenol sodium salt, 2,5-difluorothiophenol sodium salt, 2,4,5-trifluorothiophenol sodium salt, 2,4,5,6-tetrafluorothiophenol sodium salt, pentafluorothiophenol sodium salt, 4-chlorothiophenol sodium salt, 2,5-dichlorothiophenol sodium salt, 2,4,5-trichlorothiophenol sodium salt, 2,4,5,6-tetrachlorothiophenol sodium salt, pentachlorothiophenol sodium salt, 4-bromothiophenol sodium salt, 2,5-dibromothiophenol sodium salt, 2,4,5-tribromothiophenol sodium salt, 2,4,5,6-tetrabromothiophenol sodium salt, pentabromothiophenol sodium salt, 4-iodothiophenol sodium salt, 2,5-diiodothiophenol
  • organic sulfur compound represented by the chemical formula (3) is a compound substituted with at least one type of the above substituents and another substituent.
  • substituents include a nitro group (-NO 2 ), an amino group (-NH 2 ), a hydroxyl group (-OH), and a phenylthio group (-SPh).
  • the compound include 4-chloro-2-nitrothiophenol sodium salt, 4-chloro-2-aminothiophenol sodium salt, 4-chloro-2-hydroxythiophenol sodium salt, 4-chloro-2-phenylthiothiophenol sodium salt, 4-methyl-2-nitrothiophenol sodium salt, 4-methyl-2-aminothiophenol sodium salt, 4-methyl-2-hydroxythiophenol sodium salt, 4-methyl-2-phenylthiothiophenol sodium salt, 4-carboxy-2-nitrothiophenol sodium salt, 4-carboxy-2-aminothiophenol sodium salt, 4-carboxy-2-hydroxythiophenol sodium salt, 4-carboxy-2-phenylthiothiophenol sodium salt, 4-methoxycarbonyl-2-nitrothiophenol sodium salt, 4-methoxycarbonyl-2-aminothiophenol sodium salt, 4-methoxycarbonyl-2-hydroxythiophenol sodium salt, 4-methoxycarbonyl-2-phenylthiothiophenol sodium salt, 4-formyl-2-nitrothiophenol sodium salt,
  • Still another example of the organic sulfur compound represented by the chemical formula (3) is a compound substituted with two or more types of substituents.
  • the compound include 4-acetyl-2-chlorothiophenol sodium salt, 4-acetyl-2-methylthiophenol sodium salt, 4-acetyl-2-carboxythiophenol sodium salt, 4-acetyl-2-methoxycarbonylthiophenol sodium salt, 4-acetyl-2-formylthiophenol sodium salt, 4-acetyl-2-chlorocarbonylthiophenol sodium salt, 4-acetyl-2-sulfothiophenol sodium salt, 4-acetyl-2-methoxysulfonylthiophenol sodium salt, 4-acetyl-2-chlorosulfonylthiophenol sodium salt, 4-acetyl-2-sulfinothiophenol sodium salt, 4-acetyl-2-methylsulfinylthiophenol sodium salt, 4-acetyl-2-carbamoylthiophenol sodium salt, 4-
  • Examples of the organic sulfur compound represented by the chemical formula (4) include thiophenol zinc salt; thiophenol zinc salts substituted with halogen groups, such as 4-fluorothiophenol zinc salt, 2,5-difluorothiophenol zinc salt, 2,4,5-trifluorothiophenol zinc salt, 2,4,5,6-tetrafluorothiophenol zinc salt, pentafluorothiophenolzinc salt, 4-chlorothiophenol zinc salt, 2,5-dichlorothiophenol zinc salt, 2,4,5-trichlorothiophenol zinc salt, 2,4,5,6-tetrachlorothiophenol zinc salt, pentachlorothiophenol zinc salt, 4-bromothiophenol zinc salt, 2,5-dibromothiophenol zinc salt, 2,4,5-tribromothiophenol zinc salt, 2,4,5,6-tetrabromothiophenol zinc salt, pentabromothiophenol zinc salt, 4-iodothiophenol zinc salt, 2,5-diiodothi
  • organic sulfur compound represented by the chemical formula (4) is a compound substituted with at least one type of the above substituents and another substituent.
  • substituents include a nitro group (-NO 2 ), an amino group (-NH 2 ), a hydroxyl group (-OH), and a phenylthio group (-SPh).
  • the compound include 4-chloro-2-nitrothiophenol zinc salt, 4-chloro-2-aminothiophenol zinc salt, 4-chloro-2-hydroxythiophenol zinc salt, 4-chloro-2-phenylthiothiophenol zinc salt, 4-methyl-2-nitrothiophenol zinc salt, 4-methyl-2-aminothiophenol zinc salt, 4-methyl-2-hydroxythiophenol zinc salt, 4-methyl-2-phenylthiothiophenol zinc salt, 4-carboxy-2-nitrothiophenol zinc salt, 4-carboxy-2-aminothiophenol zinc salt, 4-carboxy-2-hydroxythiophenol zinc salt, 4-carboxy-2-phenylthiothiophenol zinc salt, 4-methoxycarbonyl-2-nitrothiophenol zinc salt, 4-methoxycarbonyl-2-aminothiophenol zinc salt, 4-methoxycarbonyl-2-hydroxythiophenol zinc salt, 4-methoxycarbonyl-2-phenylthiothiophenol zinc salt, 4-formyl-2-nitrothiophenol zinc salt,
  • Still another example of the organic sulfur compound represented by the chemical formula (4) is a compound substituted with two or more types of substituents.
  • the compound include 4-acetyl-2-chlorothiophenol zinc salt, 4-acetyl-2-methylthiophenol zinc salt, 4-acetyl-2-carboxythiophenol zinc salt, 4-acetyl-2-methoxycarbonylthiophenol zinc salt, 4-acetyl-2-formylthiophenol zinc salt, 4-acetyl-2-chlorocarbonylthiophenol zinc salt, 4-acetyl-2-sulfothiophenol zinc salt, 4-acetyl-2-methoxysulfonylthiophenol zinc salt, 4-acetyl-2-chlorosulfonylthiophenol zinc salt, 4-acetyl-2-sulfinothiophenol zinc salt, 4-acetyl-2-methylsulfinylthiophenol zinc salt, 4-acetyl-2-carbamoylthiophenol zinc salt,
  • Examples of the bivalent metal represented by M2 in the chemical formula (4) include zinc, magnesium, calcium, strontium, barium, titanium (II), manganese (II), iron (II), cobalt (II), nickel (II), zirconium (II), and tin (II).
  • thionaphthols examples include 2-thionaphthol, 1-thionaphthol, 2-chloro-1-thionaphthol, 2-bromo-1-thionaphthol, 2-fluoro-1-thionaphthol, 2-cyano-1-thionaphthol, 2-acetyl-1-thionaphthol, 1-chloro-2-thionaphthol, 1-bromo-2-thionaphthol, 1-fluoro-2-thionaphthol, 1-cyano-2-thionaphthol, 1-acetyl-2-thionaphthol, and metal salts thereof.
  • 1-thionaphthol, 2-thionaphthol, and zinc salts thereof are preferred.
  • Examples of sulfenamide type organic sulfur compounds include N-cyclohexyl-2-benzothiazole sulfenamide, N-oxydiethylene-2-benzothiazole sulfenamide, and N-t-butyl-2-benzothiazole sulfenamide.
  • Examples of thiuram type organic sulfur compounds include tetramethylthiuram monosulfide, tetramethylthiuram disulfide, tetraethylthiuram disulfide, tetrabutylthiuram disulfide, and dipentamethylenethiuram tetrasulfide.
  • dithiocarbamates include zinc dimethyldithiocarbamate, zinc diethyldithiocarbamate, zinc dibutyldithiocarbamate, zinc ethylphenyldithiocarbamate, sodium dimethyldithiocarbamate, sodium diethyldithiocarbamate, copper (II) dimethyldithiocarbamate, iron (III) dimethyldithiocarbamate, selenium diethyldithiocarbamate, and tellurium diethyldithiocarbamate.
  • thiazole type organic sulfur compounds examples include 2-mercaptobenzothiazole (MBT); dibenzothiazyl disulfide (MBTS); a sodium salt, a zinc salt, a copper salt, or a cyclohexylamine salt of 2-mercaptobenzothiazole; 2-(2,4-dinitrophenyl)mercaptobenzothiazole; and 2-(2,6-diethyl-4-morpholinothio)benzothiazole.
  • MBT 2-mercaptobenzothiazole
  • MBTS dibenzothiazyl disulfide
  • sodium salt a zinc salt, a copper salt, or a cyclohexylamine salt of 2-mercaptobenzothiazole
  • 2-(2,4-dinitrophenyl)mercaptobenzothiazole 2-(2,6-diethyl-4-morpholinothio)benzothiazole.
  • the amount of the organic sulfur compound (e) is preferably equal to or greater than 0.05 parts by weight and particularly preferably equal to or greater than 0.1 parts by weight, per 100 parts by weight of the base rubber. In light of resilience performance, the amount is preferably equal to or less than 5.0 parts by weight and particularly preferably equal to or less than 2.0 parts by weight, per 100 parts by weight of the base rubber.
  • a filler may be included in the core 4.
  • suitable fillers include zinc oxide, barium sulfate, calcium carbonate, and magnesium carbonate.
  • the amount of the filler is determined as appropriate so that the intended specific gravity of the core 4 is accomplished.
  • a particularly preferable filler is zinc oxide. Zinc oxide serves not only as a specific gravity adjuster but also as a crosslinking activator.
  • an anti-aging agent a coloring agent, a plasticizer, a dispersant, sulfur, a vulcanization accelerator, and the like are added to the rubber composition of the core 4.
  • Crosslinked rubber powder or synthetic resin powder may also be dispersed in the rubber composition.
  • the difference (Hs-H(0)) between the surface hardness Hs and the central hardness H(0) is preferably equal to or greater than 15.
  • the difference is great.
  • the core 4 has an outer-hard/inner-soft structure.
  • the recoil (torsional return) is great, and thus spin is suppressed.
  • the core 4 contributes to the flight performance of the golf ball 2.
  • the difference (Hs-H(0)) is more preferably equal to or greater than 20 and particularly preferably equal to or greater than 25. From the standpoint that the core 4 can easily be formed, the difference (Hs-H(0)) is preferably equal to or less than 50.
  • the hardness H(0) at the central point of the core 4 is preferably equal to or greater than 40.0 but equal to or less than 70.0.
  • the golf ball 2 having a hardness H(0) of 40.0 or greater has excellent resilience performance.
  • the hardness H(0) is more preferably equal to or greater than 45.0 and particularly preferably equal to or greater than 50.0.
  • the core 4 having a hardness H(0) of 70.0 or less can achieve an outer-hard/inner-soft structure.
  • spin can be suppressed.
  • the hardness H(0) is more preferably equal to or less than 68.0 and particularly preferably equal to or less than 66.0.
  • the hardness Hs at the surface of the core 4 is preferably equal to or greater than 78.0 but equal to or less than 95.0.
  • the core 4 having a hardness Hs of 78.0 or greater an outer-hard/inner-soft structure can be achieved.
  • spin can be suppressed.
  • the hardness Hs is more preferably equal to or greater than 80.0 and particularly preferably equal to or greater than 82.0.
  • the golf ball 2 having a hardness Hs of 95.0 or less has excellent durability.
  • the hardness Hs is more preferably equal to or less than 93.0 and particularly preferably equal to or less than 90.0.
  • the core 4 preferably has a diameter of 38.0 mm or greater but 42.0 mm or less.
  • the core 4 having a diameter of 38.0 mm or greater can achieve excellent resilience performance of the golf ball 2.
  • the diameter is more preferably equal to or greater than 38.5 mm and particularly preferably equal to or greater than 39.0 mm.
  • the inner cover 8 and the outer cover 10 can have sufficient thicknesses.
  • the golf ball 2 that includes the inner cover 8 and the outer cover 10 which have large thicknesses has excellent durability.
  • the diameter is more preferably equal to or less than 41.0 mm and particularly preferably equal to or less than 40.0 mm.
  • the core 4 has an amount of compressive deformation Dc of preferably 3.0 mm or greater and particularly preferably 3.3 mm or greater.
  • the amount of compressive deformation Dc is preferably equal to or less than 4.6 mm and particularly preferably equal to or less than 4.3 mm.
  • a resin composition is suitably used.
  • the base polymer of the resin composition include ionomer resins, styrene block-containing thermoplastic elastomers, thermoplastic polyester elastomers, thermoplastic polyamide elastomers, and thermoplastic polyolefin elastomers.
  • Particularly preferable base polymers are ionomer resins.
  • the golf ball 2 that includes the inner cover 8 including an ionomer resin has excellent resilience performance.
  • An ionomer resin and another resin may be used in combination for the inner cover 8.
  • the principal component of the base polymer is preferably the ionomer resin.
  • the proportion of the ionomer resin to the entire base polymer is preferably equal to or greater than 50% by weight, more preferably equal to or greater than 60% by weight, and particularly preferably equal to or greater than 70% by weight.
  • preferable ionomer resins include binary copolymers formed with an ⁇ -olefin and an ⁇ , ⁇ -unsaturated carboxylic acid having 3 to 8 carbon atoms.
  • a preferable binary copolymer includes 80% by weight or greater but 90% by weight or less of an ⁇ -olefin, and 10% by weight or greater but 20% by weight or less of an ⁇ , ⁇ -unsaturated carboxylic acid.
  • the binary copolymer has excellent resilience performance.
  • Examples of other preferable ionomer resins include ternary copolymers formed with: an ⁇ -olefin; an ⁇ , ⁇ -unsaturated carboxylic acid having 3 to 8 carbon atoms; and an ⁇ , ⁇ -unsaturated carboxylate ester having 2 to 22 carbon atoms.
  • a preferable ternary copolymer includes 70% by weight or greater but 85% by weight or less of an ⁇ -olefin, 5% by weight or greater but 30% by weight or less of an ⁇ , ⁇ -unsaturated carboxylic acid, and 1% by weight or greater but 25% by weight or less of an ⁇ , ⁇ -unsaturated carboxylate ester.
  • the ternary copolymer has excellent resilience performance.
  • ⁇ -olefins are ethylene and propylene, while preferable ⁇ , ⁇ -unsaturated carboxylic acids are acrylic acid and methacrylic acid.
  • a particularly preferable ionomer resin is a copolymer formed with ethylene and acrylic acid or methacrylic acid.
  • some of the carboxyl groups are neutralized with metal ions.
  • metal ions for use in neutralization include sodium ion, potassium ion, lithium ion, zinc ion, calcium ion, magnesium ion, aluminum ion, and neodymium ion.
  • the neutralization may be carried out with two or more types of metal ions.
  • Particularly suitable metal ions in light of resilience performance and durability of the golf ball 2 are sodium ion, zinc ion, lithium ion, and magnesium ion.
  • ionomer resins include trade names "Himilan 1555”, “Himilan 1557”, “Himilan 1605", “Himilan 1706", “Himilan 1707”, “Himilan 1856", “Himilan 1855”, “Himilan AM7311”, “Himilan AM7315”, “Himilan AM7317”,”Himilan AM7318”, “Himilan AM7329”, “Himilan AM7337”, “Himilan MK7320”, and “Himilan MK7329”, manufactured by Du Pont-MITSUI POLYCHEMICALS Co., Ltd.; trade names “Surlyn 6120”, “Surlyn 6910", “Surlyn 7930”, “Surlyn 7940", “Surlyn 8140”, “Surlyn 8150”, “Surlyn 8940", “Surlyn 8945”, “Surlyn 9120”, “Surlyn 9150”, “Surlyn 9910", “Surlyn 9945”, "Surlyn
  • Two or more ionomer resins may be used in combination for the inner cover 8.
  • An ionomer resin neutralized with a monovalent metal ion, and an ionomer resin neutralized with a bivalent metal ion may be used in combination.
  • a preferable resin that can be used in combination with an ionomer resin is a styrene block-containing thermoplastic elastomer.
  • the styrene block-containing thermoplastic elastomer has excellent compatibility with ionomer resins.
  • a resin composition including the styrene block-containing thermoplastic elastomer has excellent fluidity.
  • the styrene block-containing thermoplastic elastomer includes a polystyrene block as a hard segment, and a soft segment.
  • a typical soft segment is a diene block.
  • Examples of compounds for the diene block include butadiene, isoprene, 1, 3-pentadiene, and 2,3-dimethyl-1,3-butadiene. Butadiene and isoprene are preferred. Two or more compounds may be used in combination.
  • styrene block-containing thermoplastic elastomers examples include styrene-butadiene-styrene block copolymers (SBS), styrene-isoprene-styrene block copolymers (SIS), styrene-isoprene-butadiene-styrene block copolymers (SIBS), hydrogenated SBS, hydrogenated SIS, and hydrogenated SIBS.
  • hydrogenated SBS include styrene-ethylene-butylene-styrene block copolymers (SEBS).
  • hydrogenated SIS examples include styrene-ethylene-propylene-styrene block copolymers (SEPS).
  • SIBS styrene-ethylene-ethylene-propylene-styrene block copolymers
  • the content of the styrene component in the styrene block-containing thermoplastic elastomer is preferably equal to or greater than 10% by weight, more preferably equal to or greater than 12% by weight, and particularly preferably equal to or greater than 15% by weight.
  • the content is preferably equal to or less than 50% by weight, more preferably equal to or less than 47% by weight, and particularly preferably equal to or less than 45% by weight.
  • styrene block-containing thermoplastic elastomers include an alloy of an olefin and one or more members selected from the group consisting of SBS, SIS, SIBS, SEBS, SEPS, SEEPS, and hydrogenated products thereof.
  • the olefin component in the alloy is presumed to contribute to improvement of compatibility with ionomer resins. Use of this alloy improves the resilience performance of the golf ball 2.
  • An olefin having 2 to 10 carbon atoms is preferably used. Examples of suitable olefins include ethylene, propylene, butene, and pentene. Ethylene and propylene are particularly preferred.
  • polymer alloys include trade names “Rabalon T3221C”, “Rabalon T3339C”, “Rabalon SJ4400N”, “Rabalon SJ5400N”, “Rabalon SJ6400N”, “Rabalon SJ7400N”, “Rabalon SJ8400N”, “Rabalon SJ9400N”, and “Rabalon SR04", manufactured by Mitsubishi Chemical Corporation.
  • Other specific examples of styrene block-containing thermoplastic elastomers include trade name “Epofriend A1010” manufactured by Daicel Chemical Industries, Ltd., and trade name “Septon HG-252" manufactured by Kuraray Co., Ltd.
  • a coloring agent such as titanium dioxide and a fluorescent pigment
  • a filler such as barium sulfate, a dispersant, an antioxidant, an ultraviolet absorber, a light stabilizer, a fluorescent material, a fluorescent brightener, and the like are included in the resin composition of the inner cover 8 in an adequate amount.
  • the inner cover 8 may include powder of a metal with a high specific gravity.
  • the inner cover 8 has a hardness Hi of preferably 80 or greater, more preferably 83 or greater, and particularlypreferably 85 or greater.
  • the hardness Hi is preferably equal to or less than 95 and particularly preferably equal to or less than 90.
  • the hardness Hi is measured with a JIS-C type hardness scale mounted to an automated rubber hardness measurement machine (trade name "P1", manufactured by Kobunshi Keiki Co., Ltd.). For the measurement, a slab that is formed by hot press and that has a thickness of about 2 mm is used. A slab kept at 23°C for two weeks is used for the measurement. At the measurement, three slabs are stacked. A slab formed from the same resin composition as the resin composition of the inner cover 8 is used.
  • the hardness Hi of the inner cover 8 is preferably greater than the surface hardness Hs of the core 4.
  • the difference (Hi-Hs) between the hardness Hi and the hardness Hs is preferably equal to or greater than 1 and particularly preferably equal to or greater than 2.
  • the difference (Hi-Hs) is preferably equal to or less than 5.
  • the hardness linearly increases from its central point toward its surface.
  • the energy loss is low when the golf ball 2 is hit with a middle iron.
  • the inner cover 8 preferably has a thickness of 0.2 mm or greater but 2.0 mm or less.
  • an outer-hard/inner-soft structure can be achieved.
  • the thickness is more preferably equal to or greater than 0.5 mm and particularly preferably equal to or greater than 0.8 mm.
  • the golf ball 2 that includes the inner cover 8 having a thickness of 2.0 mm or less has excellent resilience performance.
  • the thickness is more preferably equal to or less than 1.6 mm and particularly preferably equal to or less than 1.3 mm.
  • the sphere 16 consisting of the core 4 and the inner cover 8 has an amount of compressive deformation Di of preferably 3.2 mm or greater and particularly preferably 3.4 mm or greater.
  • the amount of compressive deformation Di is preferably equal to or less than 3.8 mm and particularly preferably equal to or less than 3.6 mm.
  • the inner cover 8 For forming the inner cover 8, known methods such as injection molding, compression molding, and the like can be used.
  • a resin composition is suitably used for the outer cover 10.
  • a preferable base polymer of the resin composition is an ionomer resin.
  • the golf ball 2 that includes the outer cover 10 including the ionomer resin has excellent resilience performance.
  • the ionomer resin described above for the inner cover 8 can be used for the outer cover 10.
  • an ionomer resin and another resin may be used in combination.
  • the ionomer resin is included as the principal component of the base polymer.
  • the proportion of the ionomer resin to the entire base polymer is preferably equal to or greater than 50% by weight, more preferably equal to or greater than 60% by weight, and particularly preferably equal to or greater than 70% by weight.
  • a preferable resin that can be used in combination with an ionomer resin is an ethylene-(meth)acrylic acid copolymer.
  • the copolymer is obtained by a copolymerization reaction of a monomer composition that contains ethylene and (meth)acrylic acid. In the copolymer, some of the carboxyl groups are neutralized with metal ions.
  • the copolymer includes 3% by weight or greater but 25% by weight or less of a (meth)acrylic acid component.
  • An ethylene-(meth)acrylic acid copolymer having a polar functional group is particularly preferred.
  • a specific example of ethylene- (meth) acrylic acid copolymers is trade name "NUCREL" manufactured by Du Pont-MITSUI POLYCHEMICALS Co., Ltd.
  • Another preferable resin that can be used in combination with an ionomer resin is a styrene block-containing thermoplastic elastomer.
  • the styrene block-containing thermoplastic elastomer described above for the inner cover 8 can be used for the outer cover 10.
  • a coloring agent such as titanium dioxide and a fluorescent pigment
  • a filler such as barium sulfate, a dispersant, an antioxidant, an ultraviolet absorber, a light stabilizer, a fluorescent material, a fluorescent brightener, and the like are included in the outer cover 10 in an adequate amount.
  • the outer cover 10 preferably has a JIS-C hardness Ho of 83 or greater but 96 or less.
  • a hardness Ho of 83 or greater an outer-hard/inner-soft structure can be achieved.
  • spin is suppressed.
  • the golf ball 2 has excellent flight performance.
  • the hardness Ho is more preferably equal to or greater than 84 and particularly preferably equal to or greater than 85.
  • the golf ball 2 that includes the outer cover 10 having a hardness Ho of 96 or less has excellent feel at impact.
  • the hardness Ho is more preferably equal to or less than 95 and particularly preferably equal to or less than 93.
  • the hardness Ho is measured by the same measurement method as that for the hardness Hi.
  • the outer cover 10 preferably has a thickness of 0.2 mm or greater but 1.5 mm or less.
  • the outer cover 10 having a thickness of 0.2 mm or greater can easily be formed.
  • the thickness is more preferably equal to or greater than 0.4 mm and particularly preferably equal to or greater than 0.6 mm.
  • spin is suppressed.
  • the thickness is more preferably equal to or less than 1.3 mm and particularly preferably equal to or less than 1.1 mm.
  • the outer cover 10 For forming the outer cover 10, known methods such as injection molding, compression molding, and the like can be used. When forming the outer cover 10, the dimples 12 are formed by pimples formed on the cavity face of a mold.
  • the cover 6 preferably has a total thickness of 2.5 mm or less.
  • the golf ball 2 that includes the cover 6 having a total thickness of 2.5 mm or less has excellent feel at impact.
  • the total thickness is more preferably equal to or less than 2.3 mm and particularly preferably equal to or less than 2.1 mm.
  • the total thickness is preferably equal to or greater than 0.3 mm, more preferably equal to or greater than 0.5 mm, and particularly preferably equal to or greater than 0.8 mm.
  • the JIS-C hardness Ho of the outer cover 10 is greater than the JIS-C hardness Hi of the inner cover 8.
  • the outer cover 10 can achieve an outer-hard/inner-soft structure of the golf ball 2.
  • the golf ball 2 has excellent flight performance and excellent feel at impact.
  • the difference (Ho-Hi) is preferably equal to or greater than 2, more preferably equal to or greater than 4, and particularly preferably equal to or greater than 6. In light of suppression of energy loss when the golf ball 2 is hit, the difference (Ho-Hi) is preferably equal to or less than 10.
  • the golf ball 2 has an amount of compressive deformation Db of preferably 2.8 mm or greater, more preferably 2.9 mm or greater, and particularly preferably 3.0 mm or greater.
  • the amount of compressive deformation Db is preferably equal to or less than 3.6 mm, more preferably equal to or less than 3.5 mm, and particularly preferably equal to or less than 3.4 mm.
  • a sphere such as the core 4, the golf ball 2, or the like is placed on a hard plate made of metal.
  • a cylinder made of metal gradually descends toward the sphere.
  • a migration distance of the cylinder starting from the state in which an initial load of 98 N is applied to the sphere up to the state in which a final load of 1274 N is applied thereto, is measured.
  • a golf ball 102 shown in FIG. 3 includes a spherical core 104 and a cover 106 covering the core 104.
  • the cover 106 includes an inner cover 108 and an outer cover 110 positioned outside the inner cover 108.
  • the inner cover 108 is an innermost layer of the cover 106.
  • the outer cover 110 is an outermost layer of the cover 106.
  • the cover 106 may include another one or more layers between the inner cover 108 and the outer cover 110.
  • On the surface of the outer cover 110 a large number of dimples 112 are formed. Of the surface of the golf ball 102, a part other than the dimples 112 is a land 114.
  • the golf ball 102 includes a paint layer and a mark layer on the external side of the outer cover 110, but these layers are not shown in the drawing.
  • the golf ball 102 has a diameter of 40 mm or greater but 45 mm or less. From the standpoint of conformity to the rules established by the United States Golf Association (USGA), the diameter is preferably equal to or greater than 42.67 mm. In light of suppression of air resistance, the diameter is preferably equal to or less than 44 mm and more preferably equal to or less than 42.80 mm.
  • the golf ball 102 has a weight of 40 g or greater but 50 g or less. In light of attainment of great inertia, the weight is preferably equal to or greater than 44 g and more preferably equal to or greater than 45.00 g. From the standpoint of conformity to the rules established by the USGA, the weight is preferably equal to or less than 45.93 g.
  • FIG. 4 is a line graph showing a hardness distribution of the core 104 of the golf ball 102 in FIG. 3 .
  • the horizontal axis of the graph indicates the ratio (%) of a distance from the central point of the core 104 to the radius of the core 104.
  • the vertical axis of the graph indicates a JIS-C hardness.
  • Nine measuring points obtained by dividing a region from the central point of the core 104 to the surface of the core 104 at intervals of 12.5% of the radius of the core 104 are plotted in the graph.
  • the ratio of the distance from the central point of the core 104 to each of these measuring points to the radius of the core 104 is as follows.
  • FIG. 4 also shows a linear approximation curve obtained by a least-square method on the basis of the distances and the hardnesses of the nine measuring points.
  • the broken line does not greatly deviate from the linear approximation curve.
  • the broken line has a shape close to the linear approximation curve.
  • the hardness linearly increases from its central point toward its surface.
  • the core 104 has excellent resilience performance.
  • Inthegolfball 102 that includes the core 104 spin is suppressed. When the golf ball 102 is hit with a driver, the flight distance is large.
  • R 2 of the linear approximation curve obtained by the least-square method is equal to or greater than 0.95.
  • R 2 is an index indicating the linearity of the broken line.
  • the shape of the broken line of the hardness distribution is close to a straight line.
  • the core 104 for which R 2 is equal to or greater than 0.95 has excellent resilience performance.
  • R 2 is more preferably equal to or greater than 0.96 and particularly preferably equal to or greater than 0.97.
  • R 2 is calculated by squaring a correlation coefficient R.
  • the correlation coefficient R is calculated by dividing the covariance of the distance (%) from the central point and the hardness (JIS-C) by the standard deviation of the distance (%) from the central point and the standard deviation of the hardness (JIS-C).
  • the core 104 is obtained by crosslinking a rubber composition.
  • the rubber composition includes:
  • the base rubber (a) is crosslinked by the co-crosslinking agent (b).
  • the heat of the crosslinking reaction remains near the central point of the core 104.
  • the temperature at the central portion is high.
  • the temperature gradually decreases from the central point toward the surface.
  • the acid reacts with a metal salt of the co-crosslinking agent (b) to bond to cation.
  • the salt reacts with the metal salt of the co-crosslinking agent (b) to exchange cation. By the bonding and the exchange, metallic bonding is broken.
  • This breaking is likely to occur in the central portion of the core 104 where the temperature is high, and is unlikely to occur near the surface of the core 104.
  • the crosslinking density of the core 104 increases from its central point toward its surface.
  • an outer-hard/inner-soft structure can be achieved.
  • the rubber composition includes an organic sulfur compound (e) together with the acid and/or the salt (d)
  • the gradient of the hardness distribution can be controlled, and the degree of the outer-hard/inner-soft structure of the core 104 can be increased.
  • the spin rate is low.
  • excellent flight performance is achieved upon a shot with a driver.
  • the rubber composition of the core 104 can include, as the base rubber (a), the base rubber (a) described above for the rubber composition of the core 4 according to the first embodiment.
  • the rubber composition of the core 104 can include, as the co-crosslinking agent (b), the co-crosslinking agent (b) described above for the rubber composition of the core 4 according to the first embodiment.
  • the co-crosslinking agent (b) is:
  • the rubber composition may include only the ⁇ , ⁇ -unsaturated carboxylic acid (b1) or only the metal salt (b2) of the ⁇ , ⁇ -unsaturated carboxylic acid as the co-crosslinking agent (b).
  • the rubber composition may include both the ⁇ , ⁇ -unsaturated carboxylic acid (b1) and the metal salt (b2) of the ⁇ , ⁇ -unsaturated carboxylic acid as the co-crosslinking agent (b).
  • the metal salt (b2) of the ⁇ , ⁇ -unsaturated carboxylic acid graft-polymerizes with the molecular chain of the base rubber, thereby crosslinking the rubber molecules.
  • the rubber composition preferably further includes a metal compound (f).
  • the metal compound (f) reacts with the ⁇ , ⁇ -unsaturated carboxylic acid (b1) in the rubber composition.
  • a salt obtained by this reaction graft-polymerizes with the molecular chain of the base rubber.
  • the rubber composition of the core 104 can include, as the metal compound (f), the metal compound (f) described above for the rubber composition of the core 4 according to the first embodiment.
  • the amount of the co-crosslinking agent (b) is preferably equal to or greater than 15 parts by weight and particularly preferably equal to or greater than 20 parts by weight, per 100 parts by weight of the base rubber. In light of feel at impact, the amount is preferably equal to or less than 50 parts by weight, more preferably equal to or less than 45 parts by weight, and particularly preferably equal to or less than 40 parts by weight, per 100 parts by weight of the base rubber.
  • the rubber composition of the core 104 can include, as the crosslinking initiator (c), the crosslinking initiator (c) described above for the rubber composition of the core 4 according to the first embodiment.
  • the amount of the crosslinking initiator (c) is preferably equal to or greater than 0.2 parts by weight and particularly preferably equal to or greater than 0.5 parts by weight, per 100 parts by weight of the base rubber. In light of feel at impact and durability of the golf ball 102, the amount is preferably equal to or less than 5. 0 parts by weight and particularly preferably equal to or less than 2.5 parts by weight, per 100 parts by weight of the base rubber.
  • the rubber composition of the core 104 includes, as the acid and/or the salt (d) the carboxylic acid and/or the salt (d1) described above for the rubber composition of the core 4 according to the first embodiment.
  • the co-crosslinking agent (b) is not included in the concept of the acid and/or the salt (d). It is inferred that as described above, the acid and/or the salt (d) breaks the metal crosslinks by the co-crosslinking agent (b) in the central portion of the core 104 during heating and forming of the core 104. Carboxylates are particularly preferred.
  • the carboxylic acid component of the carboxylic acid and/or the salt thereof (d1) has a carboxyl group.
  • the carbon number of the carboxylic acid component of the carboxylic acid and/or the salt thereof (d1) is preferably equal to or greater than 1 but equal to or less than 30, more preferably equal to or greater than 3 but equal to or less than 30, and even more preferably equal to or greater than 5 but equal to or less than 28.
  • Examples of the carboxylic acid include aliphatic carboxylic acids (fatty acids) and aromatic carboxylic acids. Fatty acids and salts thereof are preferred.
  • the rubber composition may include a saturated fatty acid or a salt thereof, or may include an unsaturated fatty acid or a salt thereof.
  • the saturated fatty acid and the salt thereof are preferred.
  • preferable carboxylates include a potassium salt, a magnesium salt, an aluminum salt, a zinc salt, an iron salt, a copper salt, a nickel salt, or a cobalt salt of octanoic acid, lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, or behenic acid.
  • Zinc salts of carboxylic acids are particularly preferred.
  • Specific examples of preferable carboxylates include zinc octoate, zinc laurate, zinc myristate, and zinc stearate.
  • the amount of the acid and/or the salt (d) is preferably equal to or greater than 0.5 parts by weight, more preferably equal to or greater than 1.0 parts by weight, even more preferably equal to or greater than 1.5 parts by weight, and particularly preferably equal to or greater than 2.0 parts by weight, per 100 parts by weight of the base rubber.
  • the amount is preferably equal to or less than 40 parts by weight, more preferably less than 40 parts by weight, even more preferably equal to or less than 30 parts by weight, and particularly preferably equal to or less than 20 parts by weight, per 100 parts by weight of the base rubber.
  • the weight ratio of the co-crosslinking agent (b) and the acid and/or the salt (d) in the rubber composition is preferably equal to or greater than 3/7 but equal to or less than 9/1, and is particularly preferably equal to or greater than 4/6 but equal to or less than 8/2. From the rubber composition in which this weight ratio is within the above range, the core 104 whose hardness linearly increases from its central point toward its surface can be obtained.
  • zinc acrylate is preferably used as the co-crosslinking agent (b).
  • Zinc acrylate whose surface is coated with stearic acid or zinc stearate for the purpose of improving dispersibility to rubber is present.
  • this coating material is not included in the concept of the acid and/or the salt (d).
  • the rubber composition preferably further includes an organic sulfur compound (e).
  • the organic sulfur compound (e) can contribute to control of: the linearity of the hardness distribution of the core 104; and the degree of the outer-hard/inner-soft structure.
  • An example of the organic sulfur compound (e) is an organic compound having a thiol group or a polysulfide linkage having 2 to 4 sulfur atoms.
  • a metal salt of this organic compound is also included in the organic sulfur compound (e).
  • the rubber composition of the core 104 can include, as the organic sulfur compound (e), the organic sulfur compound (e) described above for the rubber composition of the core 4 according to the first embodiment.
  • the amount of the organic sulfur compound (e) is preferably equal to or greater than 0.05 parts by weight and particularly preferably equal to or greater than 0.1 parts by weight, per 100 parts by weight of the base rubber. In light of resilience performance, the amount is preferably equal to or less than 5.0 parts by weight and particularly preferably equal to or less than 2.0 parts by weight, per 100 parts by weight of the base rubber.
  • a filler may be included in the core 104.
  • suitable fillers include zinc oxide, barium sulfate, calcium carbonate, and magnesium carbonate.
  • the amount of the filler is determined as appropriate so that the intended specific gravity of the core 104 is accomplished.
  • a particularly preferable filler is zinc oxide. Zinc oxide serves not only as a specific gravity adjuster but also as a crosslinking activator.
  • an anti-aging agent a coloring agent, a plasticizer, a dispersant, sulfur, a vulcanization accelerator, and the like are added to the rubber composition of the core 104.
  • Crosslinked rubber powder or synthetic resin powder may also be dispersed in the rubber composition.
  • the difference (Hs-H(0)) between the surface hardness Hs and the central hardness H (0) is preferably equal to or greater than 15.
  • the difference is great.
  • the core 104 has an outer-hard/inner-soft structure.
  • the recoil (torsional return) is great, and thus spin is suppressed.
  • the core 104 contributes to the flight performance of the golf ball 102.
  • the difference (Hs-H(0)) is more preferably equal to or greater than 20 and particularly preferably equal to or greater than 25. From the standpoint that the core 104 can easily be formed, the difference (Hs-H(0)) is preferably equal to or less than 50.
  • the hardness H(0) at the central point of the core 104 is preferably equal to or greater than 40.0 but equal to or less than 70.0.
  • the golf ball 102 having a hardness H(0) of 40.0 or greater has excellent resilience performance.
  • the hardness H (0) is more preferably equal to or greater than 45.0 and particularly preferably equal to or greater than 50.0.
  • the core 104 having a hardness H(0) of 70.0 or less can achieve an outer-hard/inner-soft structure. In the golf ball 102 that includes the core 104, spin can be suppressed.
  • the hardness H(0) is more preferably equal to or less than 68.0 and particularly preferably equal to or less than 66.0.
  • the hardness Hs at the surface of the core 104 is preferably equal to or greater than 78.0 but equal to or less than 95.0.
  • the core 104 having a hardness Hs of 78.0 or greater an outer-hard/inner-soft structure can be achieved.
  • the golf ball 102 that includes the core 104 spin can be suppressed.
  • the hardness Hs is more preferably equal to or greater than 80.0 and particularly preferably equal to or greater than 82.0.
  • the golf ball 102 having a hardness Hs of 95.0 or less has excellent durability.
  • the hardness Hs is more preferably equal to or less than 93.0 and particularly preferably equal to or less than 90.0.
  • the core 104 preferably has a diameter of 38.0 mm or greater but 42.0 mm or less.
  • the core 104 having a diameter of 38.0 mm or greater can achieve excellent resilience performance of the golf ball 102.
  • the diameter is more preferably equal to or greater than 38.5 mm and particularly preferably equal to or greater than 39.0 mm.
  • the inner cover 108 and the outer cover 110 can have sufficient thicknesses.
  • the golf ball 102 that includes the inner cover 108 and the outer cover 110 which have large thicknesses has excellent durability.
  • the diameter is more preferably equal to or less than 41.0 mm and particularly preferably equal to or less than 40.0 mm.
  • the core 104 has an amount of compressive deformation Dc of preferably 3.0 mm or greater and particularly preferably 3.3 mm or greater.
  • the amount of compressive deformation Dc is preferably equal to or less than 4.6 mm and particularly preferably equal to or less than 4.3 mm.
  • a resin composition is suitably used.
  • the base polymer of the resin composition include ionomer resins, styrene block-containing thermoplastic elastomers, thermoplastic polyester elastomers, thermoplastic polyamide elastomers, and thermoplastic polyolefin elastomers.
  • Particularly preferable base polymers are ionomer resins.
  • the golf ball 102 that includes the inner cover 108 including an ionomer resin has excellent resilience performance.
  • An ionomer resin and another resin may be used in combination for the inner cover 108.
  • the principal component of the base polymer is preferably the ionomer resin.
  • the proportion of the ionomer resin to the entire base polymer is preferably equal to or greater than 50% by weight, more preferably equal to or greater than 60% by weight, and particularly preferably equal to or greater than 70% by weight.
  • preferable ionomer resins include binary copolymers formed with an ⁇ -olefin and an ⁇ , ⁇ -unsaturated carboxylic acid having 3 to 8 carbon atoms.
  • a preferable binary copolymer includes 80% by weight or greater but 90% by weight or less of an ⁇ -olefin, and 10% by weight or greater but 20% by weight or less of an ⁇ , ⁇ -unsaturated carboxylic acid.
  • the binary copolymer has excellent resilience performance.
  • Examples of other preferable ionomer resins include ternary copolymers formed with: an ⁇ -olefin; an ⁇ , ⁇ -unsaturated carboxylic acid having 3 to 8 carbon atoms; and an ⁇ , ⁇ -unsaturated carboxylate ester having 2 to 22 carbon atoms.
  • Apreferable ternary copolymer includes 70% by weight or greater but 85% by weight or less of an ⁇ -olefin, 5% by weight or greater but 30% by weight or less of an ⁇ , ⁇ -unsaturated carboxylic acid, and 1% by weight or greater but 25% by weight or less of an ⁇ , ⁇ -unsaturated carboxylate ester.
  • the ternary copolymer has excellent resilience performance.
  • ⁇ -olefins are ethylene and propylene, while preferable ⁇ , ⁇ -unsaturated carboxylic acids are acrylic acid and methacrylic acid.
  • a particularly preferable ionomer resin is a copolymer formed with ethylene and acrylic acid or methacrylic acid.
  • some of the carboxyl groups are neutralized with metal ions.
  • metal ions for use in neutralization include sodium ion, potassium ion, lithium ion, zinc ion, calcium ion, magnesium ion, aluminum ion, and neodymium ion.
  • the neutralization may be carried out with two or more types of metal ions.
  • Particularly suitable metal ions in light of resilience performance and durability of the golf ball 2 are sodium ion, zinc ion, lithium ion, and magnesium ion.
  • ionomer resins include trade names "Himilan 1555”, “Himilan 1557”, “Himilan 1605", “Himilan 1706", “Himilan 1707”, “Himilan 1856", “Himilan 1855”, “Himilan AM7311”, “Himilan AM7315”, “Himilan AM7317”,”Himilan AM7318”, “Himilan AM7329”, “Himilan AM7337”, “Himilan MK7320”, and “Himilan MK7329”, manufactured by Du Pont-MITSUI POLYCHEMICALS Co., Ltd.; trade names “Surlyn 6120”, “Surlyn 6910", “Surlyn 7930”, “Surlyn 7940", “Surlyn 8140”, “Surlyn 8150”, “Surlyn 8940", “Surlyn 8945”, “Surlyn 9120”, “Surlyn 9150”, “Surlyn 9910", “Surlyn 9945”, "Surlyn
  • Two or more ionomer resins may be used in combination for the inner cover 108.
  • An ionomer resin neutralized with a monovalent metal ion, and an ionomer resin neutralized with a bivalent metal ion may be used in combination.
  • a preferable resin that can be used in combination with an ionomer resin is a styrene block-containing thermoplastic elastomer.
  • the styrene block-containing thermoplastic elastomer has excellent compatibility with ionomer resins.
  • a resin composition including the styrene block-containing thermoplastic elastomer has excellent fluidity.
  • the styrene block-containing thermoplastic elastomer includes a polystyrene block as a hard segment, and a soft segment.
  • a typical soft segment is a diene block.
  • Examples of compounds for the diene block include butadiene, isoprene, 1,3-pentadiene, and 2,3-dimethyl-1,3-butadiene. Butadiene and isoprene are preferred. Two or more compounds may be used in combination.
  • styrene block-containing thermoplastic elastomers examples include styrene-butadiene-styrene block copolymers (SBS), styrene-isoprene-styrene block copolymers (SIS), styrene-isoprene-butadiene-styrene block copolymers (SIBS), hydrogenated SBS, hydrogenated SIS, and hydrogenated SIBS.
  • hydrogenated SBS include styrene-ethylene-butylene-styrene block copolymers (SEBS).
  • hydrogenated SIS examples include styrene-ethylene-propylene-styrene block copolymers (SEPS).
  • SIBS styrene-ethylene-ethylene-propylene-styrene block copolymers
  • the content of the styrene component in the styrene block-containing thermoplastic elastomer is preferably equal to or greater than 10% by weight, more preferably equal to or greater than 12% by weight, and particularly preferably equal to or greater than 15% by weight.
  • the content is preferably equal to or less than 50% by weight, more preferably equal to or less than 47% by weight, and particularly preferably equal to or less than 45% by weight.
  • styrene block-containing thermoplastic elastomers include an alloy of an olefin and one or more members selected from the group consisting of SBS, SIS, SIBS, SEBS, SEPS, SEEPS, and hydrogenated products thereof.
  • the olefin component in the alloy is presumed to contribute to improvement of compatibility with ionomer resins. Use of this alloy improves the resilience performance of the golf ball 102.
  • An olefin having 2 to 10 carbon atoms is preferably used. Examples of suitable olefins include ethylene, propylene, butene, and pentene. Ethylene and propylene are particularly preferred.
  • polymer alloys include trade names “Rabalon T3221C”, “Rabalon T3339C”, “Rabalon SJ4400N”, “Rabalon SJ5400N”, “Rabalon SJ6400N”, “Rabalon SJ7400N”, “Rabalon SJ8400N”, “Rabalon SJ9400N”, and “Rabalon SR04", manufactured by Mitsubishi Chemical Corporation.
  • Other specific examples of styrene block-containing thermoplastic elastomers include trade name “Epofriend A1010” manufactured by Daicel Chemical Industries, Ltd., and trade name “Septon HG-252" manufactured by Kuraray Co., Ltd.
  • a coloring agent such as titanium dioxide and a fluorescent pigment
  • a filler such as barium sulfate, a dispersant, an antioxidant, an ultraviolet absorber, a light stabilizer, a fluorescent material, a fluorescent brightener, and the like are included in the resin composition of the inner cover 108 in an adequate amount.
  • the inner cover 108 may include powder of a metal with a high specific gravity.
  • the inner cover 108 has a hardness Hi which is equal to or less than the JIS-C hardness Hs at the surface of the core 104.
  • the inner cover 108 achieves soft feel at impact.
  • the difference (Hi-Hs) is preferably equal to or greater than 1, more preferably equal to or greater than 2, and particularly preferably equal to or greater than 7.
  • the difference (Hi-Hs) is preferably equal to or less than 20, more preferably equal to or less than 18, and particularly preferably equal to or less than 12.
  • the hardness Hi of the inner cover 108 is preferably equal to or less than 90, more preferably equal to or less than 85, and particularly preferably equal to or less than 83. In light of light feel at impact, the hardness Hi is preferably equal to or greater than 60, more preferably equal to or greater than 65, and particularly preferably equal to or greater than 71.
  • the hardness Hi is measured with a JIS-C type hardness scale mounted to an automated rubber hardness measurement machine (trade name "P1", manufactured by Kobunshi Keiki Co., Ltd.).
  • a slab that is formed by hot press and that has a thickness of about 2 mm is used.
  • a slab kept at 23°C for two weeks is used for the measurement.
  • three slabs are stacked.
  • a slab formed fromthe same resin composition as the resin composition of the inner cover 108 is used.
  • the inner cover 108 preferably has a thickness of 0.2 mm or greater but 2.0 mm or less.
  • the golf ball 102 that includes the inner cover 108 having a thickness of 0.2 mm or greater has excellent feel at impact.
  • the thickness of the inner cover 108 is more preferably equal to or greater than 0.5 mm and particularly preferably equal to or greater than 0. 8 mm.
  • the golf ball 102 that includes the inner cover 108 having a thickness of 2.0 mm or less has excellent resilience performance.
  • the thickness is more preferably equal to or less than 1.5 mm and particularly preferably equal to or less than 1.2 mm.
  • a sphere 116 consisting of the core 104 and the inner cover 108 has an amount of compressive deformation Di of preferably 3.2 mm or greater and particularly preferably 3.4 mm or greater.
  • the amount of compressive deformation Di is preferably equal to or less than 3.8 mm and particularly preferably equal to or less than 3.6 mm.
  • the inner cover 108 For forming the inner cover 108, known methods such as injection molding, compression molding, and the like can be used.
  • a resin composition is suitably used for the outer cover 110.
  • a preferable base polymer of the resin composition is an ionomer resin.
  • the golf ball 102 that includes the outer cover 110 including the ionomer resin has excellent resilience performance.
  • the ionomer resin described above for the inner cover 108 can be used for the outer cover 110.
  • an ionomer resin and another resin may be used in combination.
  • the ionomer resin is included as the principal component of the base polymer.
  • the proportion of the ionomer resin to the entire base polymer is preferably equal to or greater than 50% by weight, more preferably equal to or greater than 60% by weight, and particularly preferably equal to or greater than 70% by weight.
  • a preferable resin that can be used in combination with an ionomer resin is an ethylene-(meth)acrylic acid copolymer.
  • the copolymer is obtained by a copolymerization reaction of a monomer composition that contains ethylene and (meth)acrylic acid. In the copolymer, some of the carboxyl groups are neutralized with metal ions.
  • the copolymer includes 3% by weight or greater but 25% by weight or less of a (meth)acrylic acid component.
  • An ethylene-(meth)acrylic acid copolymer having a polar functional group is particularly preferred.
  • a specific example of ethylene- (meth) acrylic acid copolymers is trade name "NUCREL" manufactured by Du Pont-MITSUI POLYCHEMICALS Co., Ltd.
  • a coloring agent such as titanium dioxide and a fluorescent pigment
  • a filler such as barium sulfate, a dispersant, an antioxidant, an ultraviolet absorber, a light stabilizer, a fluorescent material, a fluorescent brightener, and the like are included in the outer cover 110 in an adequate amount.
  • the outer cover 110 preferably has a JIS-C hardness Ho of 83 or greater but 96 or less.
  • a hardness Ho of 83 or greater an outer-hard/inner-soft structure can be achieved.
  • spin is suppressed.
  • the golf ball 102 has excellent flight performance.
  • the hardness Ho is more preferably equal to or greater than 84 and particularly preferably equal to or greater than 85.
  • the golf ball 102 that includes the outer cover 110 having a hardness Ho of 96 or less has excellent feel at impact.
  • the hardness Ho is more preferably equal to or less than 95 and particularly preferably equal to or less than 93.
  • the hardness Ho is measured by the same measurement method as that for the hardness Hi.
  • the outer cover 110 preferably has a thickness of 0.2 mm or greater but 1.5 mm or less.
  • the outer cover 110 having a thickness of 0.2 mm or greater can easily be formed.
  • the thickness is more preferably equal to or greater than 0.4 mm and particularly preferably equal to or greater than 0.6 mm.
  • the golf ball 102 that includes the outer cover 110 having a thickness of 1. 5 mm or less has excellent feel at impact.
  • the thickness is more preferably equal to or less than 1.3 mm and particularly preferably equal to or less than 1.1 mm.
  • the outer cover 110 For forming the outer cover 110 , known methods such as injection molding, compression molding, and the like can be used. When forming the outer cover 110, the dimples 112 are formed by pimples formed on the cavity face of a mold.
  • the cover 106 preferably has a total thickness of 2.5 mm or less.
  • the golf ball 102 that includes the cover 106 having a total thickness of 2.5 mm or less has excellent feel at impact.
  • the total thickness is more preferably equal to or less than 2.3 mm and particularly preferably equal to or less than 2.1 mm.
  • the total thickness is preferably equal to or greater than 0.3 mm, more preferably equal to or greater than 0.5 mm, and particularly preferably equal to or greater than 0.8 mm.
  • the JIS-C hardness Ho of the outer cover 110 is greater than the JIS-C hardness Hi of the inner cover 108.
  • the outer cover 110 can achieve an outer-hard/inner-soft structure of the golf ball 102 .
  • the golf ball 102 has excellent flight performance and excellent feel at impact.
  • the difference (Ho-Hi) is preferably equal to or greater than 5, more preferably equal to or greater than 9, and particularly preferably equal to or greater than 16. In light of suppression of energy loss when the golf ball 102 is hit, the difference (Ho-Hi) is preferably equal to or less than 27 and particularly preferably equal to or less than 21.
  • the hardness of the outer cover 110 is the greatest. In the golf ball 102, spin is suppressed.
  • the golf ball 102 has an amount of compressive deformation Db of preferably 2.8 mm or greater, more preferably 2.9 mm or greater, and particularly preferably 3.0 mm or greater.
  • the amount of compressive deformation Db is preferably equal to or less than 3.6 mm, more preferably equal to or less than 3.5 mm, and particularly preferably equal to or less than 3.4 mm.
  • a sphere such as the core 104, the golf ball 102, or the like is placed on a hard plate made of metal.
  • a cylinder made of metal gradually descends toward the sphere.
  • the sphere squeezed between the bottom face of the cylinder and the hard plate, becomes deformed.
  • a migration distance of the cylinder starting from the state in which an initial load of 98 N is applied to the sphere up to the state in which a final load of 1274 N is applied thereto, is measured.
  • a rubber composition was obtained by kneading 100 parts by weight of a high-cis polybutadiene (trade name "BR-730", manufactured by JSR Corporation), 26 parts by weight of zinc diacrylate (trade name "Sanceler SR”, manufactured by SANSHIN CHEMICAL INDUSTRY CO., LTD.), 5 parts by weight of zinc oxide, an appropriate amount of barium sulfate, 0.2 parts by weight of 2-thionaphthol, 10 parts by weight of zinc stearate, and 0.75 parts by weight of dicumyl peroxide.
  • BR-730 high-cis polybutadiene
  • zinc diacrylate trade name "Sanceler SR” manufactured by SANSHIN CHEMICAL INDUSTRY CO., LTD.
  • This rubber composition was placed into a mold including upper and lower mold halves each having a hemispherical cavity, and heated at 170°C for 25 minutes to obtain a core with a diameter of 39.1 mm.
  • the amount of barium sulfate was adjusted such that the weight of a golf ball is 45.4 g.
  • a resin composition was obtained by kneading 40 parts by weight of an ionomer resin (the aforementioned "Himilan AM7337”), 40 parts by weight of another ionomer resin (the aforementioned "Himilan AM7329”), 20 parts by weight of a styrene block-containing thermoplastic elastomer (the aforementioned "Rabalon T3221C”), and 6 parts by weight of titanium dioxide with a twin-screw kneading extruder.
  • the core was placed into a mold.
  • the resin composition was injected around the core by injection molding to form an inner cover with a thickness of 1.0 mm.
  • a resin composition was obtained by kneading 5 parts by weight of an ionomer resin (the aforementioned "Himilan AM7337”), 10 parts by weight of another ionomer resin (the aforementioned "Himilan 1555"), 55 parts by weight of still another ionomer resin (the aforementioned "Himilan AM7329”), 30 parts by weight of an ethylene- (meth) acrylic acid copolymer (trade name "NUCREL N1050H", manufactured by Du Pont-MITSUI POLYCHEMICALS Co., Ltd.), 3 parts by weight of titanium dioxide, and 0.2 parts by weight of an ultraviolet absorber (trade name "TINUVIN 770", manufactured by Ciba Japan K.K.) with a twin-screw kneading extruder.
  • an ionomer resin the aforementioned "Himilan AM7337
  • 10 parts by weight of another ionomer resin the aforementioned "Himilan 1555"
  • the sphere consisting of the core and the inner cover was placed into a final mold having a large number of pimples on its cavity face.
  • the resin composition was injected around the sphere by injection molding to form an outer cover with a thickness of 0.8 mm. Dimples having a shape that is the inverted shape of the pimples were formed on the outer cover.
  • a clear paint including a two-component curing type polyurethane as a base material was applied to the outer cover to obtain a golf ball of Example I-1 with a diameter of 42.7 mm.
  • Example I-2 to I-14 and Comparative Examples I-1 to I-5 were obtained in the same manner as Example I-1, except the specifications of the core, the inner cover, and the outer cover were as shown in Tables I-7 to I-9 below.
  • the composition of the core is shown in detail in Tables I-1 and I-2 below.
  • the compositions of the inner cover and the outer cover are shown in detail in Table I-3 below.
  • a hardness distribution of the core is shown in Tables I-4 to I-6 below.
  • the golf ball according to Comparative Example I-3 does not have an inner cover.
  • a 5-iron (trade name "XXIO”, manufactured by SRI Sports Limited, shaft hardness: R, loft angle: 24°) was attached to a swing machine manufactured by Golf Laboratories, Inc.
  • a golf ball was hit under the condition of a head speed of 35 m/sec.
  • the spin rate was measured immediately after the hit.
  • the distance from the launch point to the stop point was measured.
  • the average value of data obtained by 12 measurements is shown in Tables I-7 to I-9 below.
  • Table I-1 Composition of Core (parts by weight) A C D E F M BR-730 100 100 100 100 100 100 100 100 Sanceler SR 27.0 26.0 27.5 29.5 31.5 25.0 Zinc oxide 5 5 5 5 5 5 Barium sulfate Appropriate amount 2-thionaphthol 0.2 0.2 0.2 0.2 0.2 0.2 Zinc stearate 0 10 20 30 40 - Aluminum stearate - - - - - 10 Dicumyl peroxide 0.75 0.75 0.75 0.75 0.75 0.75 0.75 0.75 0.75 0.75 0.75 Amount of compressive deformation Dc (mm) 3.86 3.85 3.86 3.85 3.86 3.83 Table I-2 Composition of Core (parts by weight) G H I J K L BR-730 100 100 100 100 100 100 100 100 100 100 100 100 Sanceler SR 26.5 25.5 25.0 25.5 26.0 25.5 Zinc oxide 5 5 5 5 5 5 Barium sulfate Appropriate amount 2-thionaphthol
  • the golf balls according to Examples have excellent flight performance upon a shot with a middle iron. From the results of evaluation, advantages of the present invention are clear.
  • a rubber composition was obtained by kneading 100 parts by weight of a high-cis polybutadiene (trade name "BR-730", manufactured by JSR Corporation), 26 parts by weight of zinc diacrylate (trade name "Sanceler SR”, manufactured by SANSHIN CHEMICAL INDUSTRY CO., LTD.), 5 parts by weight of zinc oxide, an appropriate amount of barium sulfate, 0.2 parts by weight of 2- thionaphthol, 10 parts by weight of zinc stearate, and 0.75 parts by weight of dicumyl peroxide.
  • BR-730 high-cis polybutadiene
  • zinc diacrylate trade name "Sanceler SR” manufactured by SANSHIN CHEMICAL INDUSTRY CO., LTD.
  • This rubber composition was placed into a mold including upper and lower mold halves each having a hemispherical cavity, and heated at 170°C for 25 minutes to obtain a core with a diameter of 39.1 mm.
  • the amount of barium sulfate was adjusted such that the weight of a golf ball is 45.4 g.
  • a resin composition was obtained by kneading 24 parts by weight of an ionomer resin (the aforementioned "Himilan AM7337”), 50 parts by weight of another ionomer resin (the aforementioned "Himilan AM7329”), 26 parts by weight of a styrene block-containing thermoplastic elastomer (the aforementioned "Rabalon T3221C”), and 6 parts by weight of titanium dioxide with a twin-screw kneading extruder.
  • the core was placed into a mold.
  • the resin composition was injected around the core by injection molding to form an inner cover with a thickness of 1.0 mm.
  • a resin composition was obtained by kneading 5 parts by weight of an ionomer resin (the aforementioned "Himilan AM7337”), 10 parts by weight of another ionomer resin (the aforementioned "Himilan 1555"), 55 parts by weight of still another ionomer resin (the aforementioned "Himilan AM7329”), 30 parts by weight of an ethylene- (meth) acrylic acid copolymer (trade name "NUCREL N1050H", manufactured by Du Pont-MITSUI POLYCHEMICALS Co., Ltd.), 3 parts by weight of titanium dioxide, and 0.2 parts by weight of an ultraviolet absorber (trade name "TINUVIN 770", manufactured by Ciba Japan K.K.) with a twin-screw kneading extruder.
  • an ionomer resin the aforementioned "Himilan AM7337
  • 10 parts by weight of another ionomer resin the aforementioned "Himilan 1555"
  • the sphere consisting of the core and the inner cover was placed into a final mold having a large number of pimples on its cavity face.
  • the resin composition was injected around the sphere by injection molding to form an outer cover with a thickness of 0.8 mm. Dimples having a shape that is the inverted shape of the pimples were formed on the outer cover.
  • a clear paint including a two-component curing type polyurethane as a base material was applied to the outer cover to obtain a golf ball of Example II-1 with a diameter of 42.7 mm.
  • Examples II-2 to II-14 and Comparative Examples II-1 to II-5 were obtained in the same manner as Example II-1, except the specifications of the core, the inner cover, and the outer cover were as shown in Tables II-7 to II-9 below.
  • the composition of the core is shown in detail in Tables II-1 and II-2 below.
  • the compositions of the inner cover and the outer cover are shown in detail in Table II-3 below.
  • a hardness distribution of the core is shown in Tables II-4 to II-6 below.
  • the golf ball according to Comparative Example II-2 does not have an inner cover.
  • a driver (trade name "XXIO”, manufactured by SRI Sports Limited, shaft hardness: R, loft angle: 10.5°) was attached to a swing machine manufactured by Golf Laboratories, Inc. A golf ball was hit under the condition of a head speed of 40 m/sec. The spin rate was measured immediately after the hit. Furthermore, the distance from the launch point to the stop point was measured. The average value of data obtained by 12 measurements is shown in Tables II-7 to II-9 below.
  • the golf balls according to Examples have excellent flight performance and excellent feel at impact upon a shot with a driver. From the results of evaluation, advantages of the present invention are clear.
  • the golf ball according to the present invention can be used for playing golf on golf courses and practicing at driving ranges.
  • the above descriptions are merely for illustrative examples, and various modifications can be made without departing from the principles of the present invention.

Landscapes

  • Health & Medical Sciences (AREA)
  • General Health & Medical Sciences (AREA)
  • Physical Education & Sports Medicine (AREA)
  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Compositions Of Macromolecular Compounds (AREA)
EP13168981.2A 2012-06-01 2013-05-23 Golf ball Active EP2668977B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP2012126211A JP5502146B2 (ja) 2012-06-01 2012-06-01 ゴルフボール
JP2012126149A JP5502145B2 (ja) 2012-06-01 2012-06-01 ゴルフボール

Publications (3)

Publication Number Publication Date
EP2668977A2 EP2668977A2 (en) 2013-12-04
EP2668977A3 EP2668977A3 (en) 2014-09-03
EP2668977B1 true EP2668977B1 (en) 2017-02-01

Family

ID=48470804

Family Applications (1)

Application Number Title Priority Date Filing Date
EP13168981.2A Active EP2668977B1 (en) 2012-06-01 2013-05-23 Golf ball

Country Status (4)

Country Link
US (1) US20130324321A1 (ko)
EP (1) EP2668977B1 (ko)
KR (1) KR101522086B1 (ko)
CN (1) CN103446721B (ko)

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20150196809A1 (en) * 2014-01-10 2015-07-16 Acushent Company Golf balls having particle-based foam center
US9839814B2 (en) * 2014-12-30 2017-12-12 Acushnet Company Multi-layer golf ball
USD823956S1 (en) * 2017-05-19 2018-07-24 Nexen Corporation Golf ball
JP7047591B2 (ja) * 2018-05-16 2022-04-05 ブリヂストンスポーツ株式会社 マルチピースソリッドゴルフボール

Family Cites Families (33)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS6137178A (ja) 1984-07-28 1986-02-22 住友ゴム工業株式会社 ソリツドゴルフボ−ル
JPS6154357A (ja) 1984-08-23 1986-03-18 株式会社東芝 列車過走防止装置
US4688801A (en) * 1985-09-23 1987-08-25 Pony Ind Inc Production of homogeneous molded golf balls
US5387637A (en) * 1992-08-20 1995-02-07 Lisco, Inc. Golf ball core compositions
JP3153362B2 (ja) 1992-11-26 2001-04-09 住友ゴム工業株式会社 ツーピースゴルフボール
AU667267B2 (en) * 1993-05-10 1996-03-14 Wilson Sporting Goods Company Golf ball with cover formed from hard and soft ionomer resins
JP3505922B2 (ja) * 1996-03-29 2004-03-15 ブリヂストンスポーツ株式会社 スリーピースソリッドゴルフボール
JP3772252B2 (ja) * 2000-02-10 2006-05-10 ブリヂストンスポーツ株式会社 マルチピースゴルフボールの製造方法
JP2002000764A (ja) * 2000-06-26 2002-01-08 Bridgestone Sports Co Ltd ゴルフボール
JP2003000762A (ja) * 2001-06-21 2003-01-07 Bridgestone Sports Co Ltd ゴルフボール
JP4708610B2 (ja) * 2001-07-06 2011-06-22 Ｓｒｉスポーツ株式会社 マルチピースソリッドゴルフボール
JP4092097B2 (ja) * 2001-10-31 2008-05-28 Ｓｒｉスポーツ株式会社 マルチピースソリッドゴルフボール
JP2003180872A (ja) * 2001-12-17 2003-07-02 Bridgestone Sports Co Ltd マルチピースゴルフボール
US7066836B2 (en) * 2004-02-04 2006-06-27 Bridgestone Sports Co., Ltd. Golf ball
US7199192B2 (en) 2004-12-21 2007-04-03 Callaway Golf Company Golf ball
US7850548B2 (en) * 2006-05-31 2010-12-14 Bridgestone Sports Co., Ltd. Multi-piece solid golf ball
US8764584B2 (en) * 2006-09-12 2014-07-01 Bridgestone Sports Co., Ltd. Multi-piece solid golf ball
US7510488B2 (en) 2007-02-13 2009-03-31 Bridgestone Sports Co., Ltd. Solid golf ball
US7344455B1 (en) 2007-02-13 2008-03-18 Bridgestone Sports Co., Ltd Solid golf ball
US7727085B2 (en) 2007-02-13 2010-06-01 Bridgestone Sports Co., Ltd. Solid golf ball
US7481722B2 (en) 2007-02-13 2009-01-27 Bridgestone Sports Co., Ltd. Solid golf ball
US7695379B2 (en) 2007-02-13 2010-04-13 Bridgestone Sports Co., Ltd. Solid golf ball
US7635311B2 (en) 2007-03-02 2009-12-22 Bridgestone Sports Co., Ltd. Golf ball
US7625301B2 (en) * 2007-03-02 2009-12-01 Bridgestone Sports Co., Ltd. Golf ball
US8039529B2 (en) 2007-11-09 2011-10-18 Bridgestone Sports Co., Ltd. Method of manufacturing a golf ball
US8133136B2 (en) * 2009-01-28 2012-03-13 Bridgestone Sports Co., Ltd. Multi-piece solid golf ball
US8545346B2 (en) * 2009-01-28 2013-10-01 Bridgestone Sports Co., Ltd. Multi-piece solid golf ball
US8123630B2 (en) 2009-04-27 2012-02-28 Bridgestone Sports Co., Ltd. Multi-piece solid golf ball
US8216090B2 (en) * 2009-05-21 2012-07-10 Bridgestone Sports Co., Ltd. Golf ball
US8393978B2 (en) * 2009-12-10 2013-03-12 Bridgestone Sports Co., Ltd. Multi-piece solid golf ball
JP5394327B2 (ja) * 2010-06-09 2014-01-22 ダンロップスポーツ株式会社 ゴルフボール
JP5331756B2 (ja) * 2010-06-29 2013-10-30 ダンロップスポーツ株式会社 ゴルフボール
US8764580B2 (en) * 2011-09-30 2014-07-01 Nike, Inc. Golf ball having relationships among the densities of various layers

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
None *

Also Published As

Publication number Publication date
EP2668977A3 (en) 2014-09-03
KR20130135754A (ko) 2013-12-11
EP2668977A2 (en) 2013-12-04
US20130324321A1 (en) 2013-12-05
KR101522086B1 (ko) 2015-05-20
CN103446721A (zh) 2013-12-18
CN103446721B (zh) 2016-02-17

Similar Documents

Publication Publication Date Title
US9345934B2 (en) Golf ball
EP2666521B1 (en) Golf ball
EP2666522B1 (en) Golf ball
US9283441B2 (en) Golf ball
JP6068002B2 (ja) ゴルフボール
JP5502146B2 (ja) ゴルフボール
EP2668977B1 (en) Golf ball
JP5499085B2 (ja) ゴルフボール
EP2669328B1 (en) Golf ball
EP2669326B1 (en) Golf ball
JP6068004B2 (ja) ゴルフボール
JP5499086B2 (ja) ゴルフボール
JP5502145B2 (ja) ゴルフボール
JP5499084B2 (ja) ゴルフボール
JP6068007B2 (ja) ゴルフボール
JP5499082B2 (ja) ゴルフボール
JP5499083B2 (ja) ゴルフボール

Legal Events

Date Code Title Description
PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

Free format text: ORIGINAL CODE: 0009012

AK Designated contracting states

Kind code of ref document: A2

Designated state(s): AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR

AX Request for extension of the european patent

Extension state: BA ME

PUAL Search report despatched

Free format text: ORIGINAL CODE: 0009013

AK Designated contracting states

Kind code of ref document: A3

Designated state(s): AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR

AX Request for extension of the european patent

Extension state: BA ME

RIC1 Information provided on ipc code assigned before grant

Ipc: A63B 37/00 20060101AFI20140728BHEP

17P Request for examination filed

Effective date: 20150227

RBV Designated contracting states (corrected)

Designated state(s): AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR

17Q First examination report despatched

Effective date: 20151002

GRAP Despatch of communication of intention to grant a patent

Free format text: ORIGINAL CODE: EPIDOSNIGR1

INTG Intention to grant announced

Effective date: 20160721

GRAJ Information related to disapproval of communication of intention to grant by the applicant or resumption of examination proceedings by the epo deleted

Free format text: ORIGINAL CODE: EPIDOSDIGR1

GRAR Information related to intention to grant a patent recorded

Free format text: ORIGINAL CODE: EPIDOSNIGR71

GRAS Grant fee paid

Free format text: ORIGINAL CODE: EPIDOSNIGR3

INTC Intention to grant announced (deleted)
GRAA (expected) grant

Free format text: ORIGINAL CODE: 0009210

INTG Intention to grant announced

Effective date: 20161222

AK Designated contracting states

Kind code of ref document: B1

Designated state(s): AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR

REG Reference to a national code

Ref country code: GB

Ref legal event code: FG4D

REG Reference to a national code

Ref country code: CH

Ref legal event code: EP

Ref country code: AT

Ref legal event code: REF

Ref document number: 865048

Country of ref document: AT

Kind code of ref document: T

Effective date: 20170215

REG Reference to a national code

Ref country code: IE

Ref legal event code: FG4D

REG Reference to a national code

Ref country code: DE

Ref legal event code: R096

Ref document number: 602013016918

Country of ref document: DE

REG Reference to a national code

Ref country code: FR

Ref legal event code: PLFP

Year of fee payment: 5

REG Reference to a national code

Ref country code: NL

Ref legal event code: MP

Effective date: 20170201

REG Reference to a national code

Ref country code: LT

Ref legal event code: MG4D

REG Reference to a national code

Ref country code: AT

Ref legal event code: MK05

Ref document number: 865048

Country of ref document: AT

Kind code of ref document: T

Effective date: 20170201

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: IS

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 20170601

Ref country code: GR

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 20170502

Ref country code: FI

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 20170201

Ref country code: LT

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 20170201

Ref country code: NO

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 20170501

Ref country code: HR

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 20170201

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: BG

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 20170501

Ref country code: PT

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 20170601

Ref country code: ES

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 20170201

Ref country code: LV

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 20170201

Ref country code: AT

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 20170201

Ref country code: RS

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 20170201

Ref country code: PL

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 20170201

Ref country code: SE

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 20170201

Ref country code: LU

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 20170531

Ref country code: NL

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 20170201

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: IT

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 20170201

Ref country code: SK

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 20170201

Ref country code: EE

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 20170201

Ref country code: CZ

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 20170201

Ref country code: RO

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 20170201

REG Reference to a national code

Ref country code: DE

Ref legal event code: R097

Ref document number: 602013016918

Country of ref document: DE

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: SM

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 20170201

Ref country code: DK

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 20170201

PLBE No opposition filed within time limit

Free format text: ORIGINAL CODE: 0009261

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: NO OPPOSITION FILED WITHIN TIME LIMIT

REG Reference to a national code

Ref country code: CH

Ref legal event code: PL

26N No opposition filed

Effective date: 20171103

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: MC

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 20170201

REG Reference to a national code

Ref country code: IE

Ref legal event code: MM4A

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: LI

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 20170531

Ref country code: SI

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 20170201

Ref country code: CH

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 20170531

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: LU

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 20170523

REG Reference to a national code

Ref country code: FR

Ref legal event code: PLFP

Year of fee payment: 6

REG Reference to a national code

Ref country code: BE

Ref legal event code: MM

Effective date: 20170531

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: IE

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 20170523

REG Reference to a national code

Ref country code: DE

Ref legal event code: R082

Ref document number: 602013016918

Country of ref document: DE

Representative=s name: MANITZ FINSTERWALD PATENT- UND RECHTSANWALTSPA, DE

Ref country code: DE

Ref legal event code: R082

Ref document number: 602013016918

Country of ref document: DE

Representative=s name: MANITZ FINSTERWALD PATENTANWAELTE PARTMBB, DE

Ref country code: DE

Ref legal event code: R081

Ref document number: 602013016918

Country of ref document: DE

Owner name: SUMITOMO RUBBER INDUSTRIES LTD., KOBE-SHI, JP

Free format text: FORMER OWNER: DUNLOP SPORTS CO., LTD., KOBE-SHI, HYOGO, JP

REG Reference to a national code

Ref country code: GB

Ref legal event code: 732E

Free format text: REGISTERED BETWEEN 20180607 AND 20180613

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: BE

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 20170531

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: MT

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 20170523

REG Reference to a national code

Ref country code: FR

Ref legal event code: TP

Owner name: SUMITOMO RUBBER INDUSTRIES, LTD., JP

Effective date: 20180914

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: HU

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT; INVALID AB INITIO

Effective date: 20130523

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: CY

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 20170201

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: MK

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 20170201

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: TR

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 20170201

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: AL

Free format text: LAPSE BECAUSE OF FAILURE TO SUBMIT A TRANSLATION OF THE DESCRIPTION OR TO PAY THE FEE WITHIN THE PRESCRIBED TIME-LIMIT

Effective date: 20170201

REG Reference to a national code

Ref country code: FR

Ref legal event code: PLFP

Year of fee payment: 11

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: GB

Payment date: 20230330

Year of fee payment: 11

P01 Opt-out of the competence of the unified patent court (upc) registered

Effective date: 20230510

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: FR

Payment date: 20230411

Year of fee payment: 11

Ref country code: DE

Payment date: 20230331

Year of fee payment: 11