US20220280840A1 - Multi-piece solid golf ball - Google Patents

Multi-piece solid golf ball Download PDF

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Publication number
US20220280840A1
US20220280840A1 US17/678,298 US202217678298A US2022280840A1 US 20220280840 A1 US20220280840 A1 US 20220280840A1 US 202217678298 A US202217678298 A US 202217678298A US 2022280840 A1 US2022280840 A1 US 2022280840A1
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Prior art keywords
hardness
core
layer
shore
envelope layer
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Inventor
Hideo Watanabe
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Bridgestone Sports Co Ltd
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Bridgestone Sports Co Ltd
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Assigned to BRIDGESTONE SPORTS CO. LTD. reassignment BRIDGESTONE SPORTS CO. LTD. ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: WATANABE, HIDEO
Publication of US20220280840A1 publication Critical patent/US20220280840A1/en
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    • 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
    • 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
    • A63B37/0004—Surface depressions or protrusions
    • A63B37/0018—Specified number of dimples
    • 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
    • A63B37/005—Cores
    • A63B37/006—Physical properties
    • A63B37/0064—Diameter
    • 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
    • A63B37/009—Coefficient of lift
    • 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
    • A63B37/0096—Spin rate

Definitions

  • the present invention relates to a multi-piece solid golf ball composed of five or more layers, including a core, an inner envelope layer, an outer envelope layer, an intermediate layer and a cover.
  • a variety of golf balls have hitherto been developed for professional golfers and skilled amateurs.
  • multi-piece solid golf balls having an optimized hardness relationship among the layers encasing the core are in widespread use because they provide both a superior distance performance in the high head-speed range and also a good controllability on iron shots and approach shots.
  • optimizing the thicknesses and hardnesses of the golf ball layers in order to achieve the best possible feel and spin rate is also an important topic in golf ball development.
  • Examples of such literature include JP-A 2008-149131, JP-A 2009-095358, JP-A 2009-095364, JP-A 2009-095365, JP-A 2009-095369, JP-A 2016-101254, JP-A 2016-101256, U.S. Published Patent Application No. 2009/0170634, U.S. Published Patent Application No. 2012/0129630, U.S. Published Patent Application No. 2013/0012338, U.S. Published Patent Application No. 2015/0251058, U.S. Published Patent Application No. 2015/0314169, U.S. Published Patent Application No. 2016/0317873, U.S. Published Patent Application No. 2017/0340925, U.S. Published Patent Application No.
  • some of the foregoing disclosures relate to golf balls which have a ball construction of five layers wherein the core is encased by four layers—an inner envelope layer, an outer envelope layer, an intermediate layer and a cover (outermost layer), and which have specifically defined hardness relationships and thickness relationships among these layers.
  • the core is formed primarily of a base rubber as one or more layer; the core as a whole has a diameter of at least 30 mm; the envelope layer is formed as two layers—an inner envelope layer and an outer envelope layer; the intermediate layer and the cover are both formed as single layers of a resin material; the core and the respective layer-encased spheres have surface hardnesses which together satisfy the following condition in which the hardnesses are Shore C hardness values:
  • the invention provides a multi-piece solid golf ball having a core, an envelope layer, an intermediate layer and a cover, the core being formed primarily of a base rubber as one or more layer, the core as a whole having a diameter of at least 30 mm, the envelope layer being formed as two layers—an inner envelope layer and an outer envelope layer, and the intermediate layer and the cover each being formed as single layers of a resin material.
  • the core has a surface hardness
  • the sphere obtained by encasing the core with the inner envelope layer has a surface hardness
  • the sphere obtained by encasing the inner envelope layer-encased sphere with the outer envelope layer has a surface hardness
  • the sphere obtained by encasing the outer envelope layer-encased sphere with the intermediate layer has a surface hardness
  • the ball has a surface hardness which together satisfy the following condition in which the hardnesses are Shore C hardness values:
  • the core center hardness (Cc), core surface hardness (Cs) and the hardness at a midpoint between the core surface and the core center (Cm) satisfy the condition:
  • the golf ball satisfies the condition:
  • Core vh is the volume (mm 3 ) of the core multiplied by the Shore C hardness at a midpoint between the core surface and the core center (Cm)
  • IE vh is the volume (mm 3 ) of the inner envelope layer multiplied by the Shore C hardness at the surface of the inner envelope layer-encased sphere
  • OE vh is the volume (mm 3 ) of the outer envelope layer multiplied by the Shore C hardness at the surface of the outer envelope layer-encased sphere.
  • the cover has a surface with from 323 to 380 dimples arranged thereon.
  • the multi-piece solid golf ball of the invention along with achieving a satisfactory distance on full shots not only with a driver (W#1) but also with various irons, is highly receptive to spin on approach shots and thus superior in the short game. Moreover, it has a good feel at impact and an excellent scuff resistance. Such qualities make this ball highly useful as a golf ball for professional golfers and skilled amateurs.
  • FIG. 1 is a schematic cross-sectional view of the multi-piece solid golf ball (5-layer structure) according to the invention.
  • FIGS. 2A and 2B are, respectively, a top view and a side view of the exterior of a golf ball showing the arrangement (pattern) of dimples common to all of the Examples and Comparative Examples described herein.
  • the multi-piece solid golf ball of the invention is a golf ball G having five or more layers, including a core 1 , an envelope layer 2 made of two layers (inner envelope layer 2 a and outer envelope layer 2 b ) that encases the core 1 , an intermediate layer 3 that encases the envelope layers, and a cover 4 that encases the intermediate layer 3 .
  • Numerous dimples D are generally formed on the surface of the cover 4 .
  • a coating layer is generally applied onto the surface of the cover 4 . Apart from the coating layer, the cover 4 is positioned as the outermost layer in the layered structure of the golf ball.
  • the core 1 is not limited to a single layer and may be formed of a plurality of two or more layers.
  • the core has a diameter of at least 30.0 mm.
  • the diameter is preferably at least 31.4 mm, and more preferably at least 32.0 mm.
  • the diameter upper limit is preferably not more than 35.0 mm, more preferably not more than 34.2 mm, and even more preferably not more than 33.5 mm.
  • the core has a deflection when compressed under a final load of 1,275 N (130 kgf) from an initial load of 98 N (10 kgf) which, although not particularly limited, is preferably at least 3.0 mm, more preferably at least 3.2 mm, and even more preferably at least 3.5 mm.
  • the core deflection upper limit is preferably 5.5 mm or less, more preferably 5.3 mm or less, and even more preferably 5.0 mm or less.
  • the core deflection is too large, i.e., when the core is too soft, the ball rebound may be too low, resulting in a poor distance, the feel at impact may be too soft, or the durability to cracking on repeated impact may worsen.
  • the core consists of one or more layer of a vulcanized rubber composition made up primarily of a rubber material, and is preferably formed of a single layer. If the core material is not a rubber material, the rebound may be too low and the ball may fail to travel a good distance. Also, when the core is composed of a plurality of layers, upon repeated impact, the ball may end up cracking early from the core interface.
  • the rubber composition of the core is typically obtained by using a base rubber as the primary ingredient and compounding with this a co-crosslinking agent, a crosslinking initiator, an inert filler, an organosulfur compound and the like.
  • a polybutadiene is preferable to use as the base rubber.
  • Commercial products may be used as the polybutadiene.
  • Illustrative examples include BR01, BR51 and BR730 (from JSR Corporation).
  • the proportion of polybutadiene within the base rubber is preferably at least 60 wt %, and more preferably at least 80 wt %. Rubber ingredients other than the above polybutadienes may be included in the base rubber, provided that doing so does not detract from the advantageous effects of the invention.
  • Examples of rubber ingredients other than the above polybutadienes include other polybutadienes and also other diene rubbers, such as styrene-butadiene rubbers, natural rubbers, isoprene rubbers and ethylene-propylene-diene rubbers.
  • the co-crosslinking agent is an ⁇ , ⁇ -unsaturated carboxylic acid and/or a metal salt thereof.
  • unsaturated carboxylic acids include acrylic acid, methacrylic acid, maleic acid and fumaric acid. The use of acrylic acid or methacrylic acid is especially preferred.
  • Metal salts of unsaturated carboxylic acids are exemplified by, without particular limitation, the above unsaturated carboxylic acids that have been neutralized with desired metal ions. Specific examples include the zinc salts and magnesium salts of methacrylic acid and acrylic acid. The use of zinc acrylate is especially preferred.
  • the unsaturated carboxylic acid and/or metal salt thereof is included in an amount, per 100 parts by weight of the base rubber, which is typically at least 15 parts by weight, preferably at least 20 parts by weight, and more preferably at least 25 parts by weight.
  • the amount included is typically not more than 50 parts by weight, preferably not more than 45 parts by weight, and more preferably not more than 40 parts by weight. Too much may make the core too hard, giving the ball an unpleasant feel at impact, whereas too little may lower the rebound.
  • an organic peroxide as the crosslinking initiator.
  • Commercial products may be used as the organic peroxide. Examples of such products that may be suitably used include Percumyl D, Perhexa C-40 and Perhexa 3M (all from NOF Corporation), and Luperco 231XL (from AtoChem Co.). One of these may be used alone, or two or more may be used together.
  • the amount of organic peroxide included per 100 parts by weight of the base rubber is preferably at least 0.1 part by weight, more preferably at least 0.3 part by weight, and even more preferably at least 0.5 part by weight.
  • the upper limit is preferably not more than 5 parts by weight, more preferably not more than 4 parts by weight, even more preferably not more than 3 parts by weight, and most preferably not more than 2.5 parts by weight. When too much or too little is included, it may not be possible to obtain a ball having a good feel, durability and rebound.
  • Fillers that may be suitably used include zinc oxide, barium sulfate and calcium carbonate. These may be used singly or two or more may be used in combination.
  • the amount of filler included per 100 parts by weight of the base rubber may be set to preferably at least 4 parts by weight, more preferably at least 5 parts by weight, and even more preferably at least 7 parts by weight.
  • the upper limit in the amount of filler included per 100 parts by weight of the base rubber may be set to preferably not more than 100 parts by weight, more preferably not more than 75 parts by weight, and even more preferably not more than 50 parts by weight. At a filler content which is too high or too low, a proper weight and a suitable rebound may be impossible to obtain.
  • Nocrac NS-6 Nocrac NS-30, Nocrac 200 and Nocrac MB (all products of Ouchi Shinko Chemical Industry Co., Ltd.) may be used as antioxidants. These may be used singly, or two or more may be used in combination.
  • the amount of antioxidant included per 100 parts by weight of the base rubber is preferably at least 0.05 part by weight, and more preferably at least 0.1 part by weight.
  • the upper limit is preferably not more than 1.0 part by weight, more preferably not more than 0.7 part by weight, and even more preferably not more than 0.5 part by weight.
  • an organosulfur compound may be included in the rubber composition so as to impart an excellent rebound.
  • Thiophenols, thionaphthols, halogenated thiophenols, and metal salts thereof are recommended for this purpose.
  • Illustrative examples include pentachlorothiophenol, pentafluorothiophenol, pentabromothiophenol, p-chlorothiophenol, and the zinc salt of pentachlorothiophenol; and also diphenylpolysulfides, dibenzylpolysulfides, dibenzoylpolysulfides, dibenzothiazoylpolysulfides and dithiobenzoylpolysulfides having 2 to 4 sulfurs.
  • the use of diphenyldisulfide or the zinc salt of pentachlorothiophenol is especially preferred.
  • the amount of the organosulfur compound included per 100 parts by weight of the base rubber is at least 0.05 part by weight, preferably at least 0.07 part by weight, and more preferably at least 0.1 part by weight.
  • the upper limit is not more than 5 parts by weight, preferably not more than 4 parts by weight, more preferably not more than 3 parts by weight, and most preferably not more than 2 parts by weight. Including too much organosulfur compound may excessively lower the hardness, whereas including too little is unlikely to improve the rebound.
  • the core can be produced by vulcanizing/curing the rubber composition containing the above respective ingredients.
  • production may be carried out by kneading the composition using a mixer such as a Banbury mixer or a roll mill, compression molding or injection molding the kneaded composition using a core mold, and curing the molded material by suitably heating it at a temperature sufficient for the organic peroxide or co-crosslinking agent to act, i.e., between 100° C. and 200° C., preferably between 140° C. and 180° C., for 10 to 40 minutes.
  • the hardness of the core refers hereinafter to the Shore C hardness.
  • This Shore C hardness is a hardness value measured with a Shore C durometer in accordance with ASTM D2240.
  • the core has a center hardness (Cc) which is preferably at least 54, more preferably at least 57, and even more preferably at least 60.
  • the upper limit is preferably not more than 69, more preferably not more than 67, and even more preferably not more than 65.
  • the core has a surface hardness (Cs) which is preferably at least 70, more preferably at least 74, and even more preferably at least 77.
  • the upper limit is preferably not more than 90, more preferably not more than 87, and even more preferably not more than 85.
  • a core surface hardness outside of this range may lead to undesirable results similar to those described above for the core center hardness (Cc).
  • the core has a hardness Cm at the midpoint between the core surface and core center which, although not particularly limited, may be set to preferably at least 58, more preferably at least 61, and even more preferably at least 64.
  • the upper limit value is preferably not more than 75, more preferably not more than 74, and even more preferably not more than 72. A hardness that deviates from these values may lead to undesirable results similar to those described above for the core center hardness (Cc).
  • the Shore C hardness value obtained by subtracting the core center hardness (Cc) from the core surface hardness (Cs) is 16 or more, preferably 17 or more, and more preferably 18 or more.
  • the upper limit value is preferably not more than 25, more preferably not more than 22, and even more preferably not more than 21.
  • this value is too small, the spin rate on full shots with a driver becomes high, as a result of which the desired distance may not be attainable.
  • this hardness difference is larger than the above range, the durability of the ball to cracking on repeated impact may worsen or the initial velocity on shots may decrease, as a result of which the intended distance may not be attainable.
  • the initial velocity of the ball on full shots with a driver is low, as a result of which the desired distance may not be attainable.
  • the value expressed as (Cs ⁇ Cm)/(Cm ⁇ Cc) is preferably at least 1.5, more preferably at least 1.7, and even more preferably at least 1.9.
  • the upper limit is preferably 10.0 or less, more preferably 8.0 or less, and even more preferably 5.0 or less.
  • the value of Core vh is preferably at least 800, more preferably at least 900, and even more preferably at least 1,000; the upper limit value is preferably 1,540 or less, more preferably 1,480 or less, and even more preferably 1,430 or less.
  • the Core vh value is too small, the ball initial velocity may decrease and a good distance may not be obtained.
  • the Core vh value is too large, the spin rate on full shots with an iron may rise and the intended distance may not be attainable.
  • the envelope layer is formed of two layers: an inner layer and an outer layer. These are referred to as, respectively, the inner envelope layer and the outer envelope layer.
  • the inner envelope layer has a material hardness on the Shore C hardness scale which, although not particularly limited, is preferably at least 67, more preferably at least 70, and even more preferably at least 72.
  • the upper limit is preferably not more than 90, more preferably not more than 89, and even more preferably not more than 88.
  • the material hardness of the inner envelope layer on the Shore D hardness scale is preferably at least 43, more preferably at least 45, and even more preferably at least 47.
  • the upper limit is preferably not more than 60, more preferably not more than 56, and even more preferably not more than 54.
  • the sphere obtained by encasing the core with the inner envelope layer has a surface hardness which, on the Shore C hardness scale, is preferably at least 75, more preferably at least 78, and even more preferably at least 80.
  • the upper limit is preferably not more than 94, more preferably not more than 92, and even more preferably not more than 90.
  • the surface hardness on the Shore D hardness scale is preferably at least 49, more preferably at least 51, and even more preferably at least 53.
  • the upper limit is preferably not more than 66, more preferably not more than 62, and even more preferably not more than 60.
  • the ball When the material hardness and the surface hardness of the inner envelope layer are lower than the above ranges, the ball may be too receptive to spin on full shots or the initial velocity may decline, as a result of which a good distance may not be achieved.
  • the material hardness and the surface hardness are too high, the feel at impact may become hard, the durability to cracking on repeated impact may worsen, or the spin rate on full shots may rise, as a result of which a good distance may not be achieved.
  • the surface hardness of the inner envelope layer-encased sphere is higher than the surface hardness of the core. When this is not the case, the spin rate on full shots rises and the intended distance cannot be attained.
  • the inner envelope layer has a thickness that is preferably at least 0.8 mm, more preferably at least 1.0 mm, and even more preferably at least 1.2 mm.
  • the upper limit in the thickness of the inner envelope layer is preferably 1.8 mm or less, more preferably 1.7 mm or less, and even more preferably 1.6 mm or less.
  • the spin rate lowering effect on full shots may be inadequate and a good distance may not be achieved.
  • the durability to cracking on repeated impact and the low-temperature durability may worsen.
  • IE vh be the inner envelope layer volume (mm 3 ) multiplied by the Shore C surface hardness of the inner envelope layer-encased sphere
  • the value of IE vh is preferably at least 380, more preferably at least 410, and even more preferably at least 440.
  • the upper limit value is preferably 520 or less, more preferably 500 or less, and even more preferably 480 or less.
  • the value of (OE vh+IE vh)/Core vh, where OE vh and Core vh are as defined below, is preferably at least 0.4, more preferably at least 0.5, and even more preferably at least 0.6.
  • the upper limit is preferably 1.1 or less, more preferably 1.0 or less, and even more preferably 0.9 or less.
  • the outer envelope layer has a material hardness on the Shore C hardness scale which is preferably at least 75, more preferably at least 78, and even more preferably at least 80.
  • the upper limit is preferably not more than 95, more preferably not more than 92, and even more preferably not more than 90.
  • the surface hardness of the outer envelope layer on the Shore D hardness scale is preferably at least 46, more preferably at least 48, and even more preferably at least 50.
  • the upper limit is preferably not more than 63, more preferably not more than 59, and even more preferably not more than 57.
  • the sphere obtained by encasing the inner envelope layer-encased sphere with the outer envelope layer (outer envelope layer-encased sphere) has a surface hardness on the Shore C hardness scale which is preferably at least 83, more preferably at least 86, and even more preferably at least 88.
  • the upper limit is preferably not more than 95, more preferably not more than 93, and even more preferably not more than 92.
  • the surface hardness on the Shore D hardness scale is preferably at least 52, more preferably at least 54, and even more preferably at least 56.
  • the upper limit is preferably not more than 69, more preferably not more than 65, and even more preferably not more than 63.
  • the ball When the material hardness and the surface hardness of the outer envelope layer are lower than the above ranges, the ball may take on too much spin on full shots or the initial velocity may decrease, as a result of which a good distance may not be achieved.
  • the material hardness and the surface hardness are too high, the feel at impact may become too hard, the durability to cracking on repeated impact may worsen, or the spin rate on full shots may rise, as a result of which a good distance may not be achieved.
  • the outer envelope layer has a thickness which is preferably at least 0.7 mm, more preferably at least 0.9 mm, and even more preferably at least 1.1 mm.
  • the upper limit in the thickness of the outer envelope layer is preferably 1.7 mm or less, more preferably 1.6 mm or less, and even more preferably 1.5 mm or less.
  • the spin rate-lowering effect on full shots may be inadequate and a good distance may not be achieved.
  • the durability to cracking on repeated impact and the low-temperature durability may worsen.
  • the outer envelope layer To lower the spin rate of the ball on full shots and increase the distance traveled by the ball, it is critical for the outer envelope layer to have a smaller thickness than the inner envelope layer.
  • the value obtained by subtracting the outer envelope layer thickness from the inner envelope layer thickness is larger than 0 mm, preferably at least 0.1 mm, and more preferably at least 0.2 mm.
  • the upper limit value is generally 0.5 mm or less, preferably 0.4 mm or less, and more preferably 0.3 mm or less. When this value falls outside of the above range, the spin rate on full shots may rise and a good distance may not be achieved.
  • the value of OE vh is preferably at least 380, more preferably at least 410, and even more preferably at least 440.
  • the upper limit value is preferably 600 or less, more preferably 540 or less, and even more preferably 480 or less.
  • the total thickness of the envelope layer is preferably at least 2.0 mm, more preferably at least 2.2 mm, and even more preferably at least 2.4 mm.
  • the upper limit value is preferably not more than 4.0 mm, more preferably not more than 3.5 mm, and even more preferably not more than 3.0 mm.
  • the materials making up the inner envelope layer and the outer envelope layer are not particularly limited; known resins may be used for this purpose.
  • preferred materials include resin compositions containing as the essential ingredients: 100 parts by weight of a resin component composed of, in admixture,
  • A a base resin of (a-1) an olefin-unsaturated carboxylic acid random copolymer and/or a metal ion neutralization product of an olefin-unsaturated carboxylic acid random copolymer mixed with (a-2) an olefin-unsaturated carboxylic acid-unsaturated carboxylic acid ester random terpolymer and/or a metal ion neutralization product of an olefin-unsaturated carboxylic acid-unsaturated carboxylic acid ester random terpolymer in a weight ratio between 100:0 and 0:100, and
  • thermoplastic elastomer in a weight ratio between 100:0 and 50:50;
  • Components A to D in the intermediate layer-forming resin material described in, for example, JP-A 2010-253268 may be advantageously used as above components A to D.
  • the resin materials that form the inner envelope layer and the outer envelope layer may be mutually like or unlike.
  • the outer envelope layer-encased sphere has a higher surface hardness than the inner envelope layer-encased sphere.
  • One way to have the resin material of the outer envelope layer be harder than the resin material of the inner envelope layer is to mix a suitable amount of a relatively hard ionomer resin together with the resin material composed of components (A) to (D) above, thereby forming a resin material for the outer envelope layer which differs from the resin material for the inner envelope layer.
  • a non-ionomeric thermoplastic elastomer may be included in the respective materials for the inner envelope layer and the outer envelope layer.
  • the non-ionomeric thermoplastic elastomer is preferably included in an amount of from 0 to 50 parts by weight per 100 parts by weight of the total amount of the base resin.
  • thermoplastic elastomers include polyolefin elastomers (including polyolefins and metallocene polyolefins), polystyrene elastomers, diene polymers, polyacrylate polymers, polyamide elastomers, polyurethane elastomers, polyester elastomers and polyacetals.
  • additives may be suitably included in the above resin materials.
  • pigments, dispersants, antioxidants, ultraviolet absorbers and light stabilizers may be added.
  • the amount added per 100 parts by weight of the overall base resin is preferably at least 0.1 part by weight, and more preferably at least 0.5 part by weight.
  • the upper limit is preferably not more than 10 parts by weight, and more preferably not more than 4 parts by weight.
  • the intermediate layer has a material hardness on the Shore D hardness scale which, although not particularly limited, is preferably at least 58, more preferably at least 60, and even more preferably at least 63.
  • the upper limit is preferably not more than 70, more preferably not more than 68, and even more preferably not more than 65.
  • the material hardness on the Shore C hardness scale is preferably at least 87, more preferably at least 89, and even more preferably at least 93.
  • the upper limit is preferably not more than 100, more preferably not more than 98, and even more preferably not more than 96.
  • the sphere obtained by encasing the outer envelope layer-encased sphere with the intermediate layer (intermediate layer-encased sphere) has a surface hardness on the Shore D hardness scale which is preferably at least 64, more preferably at least 66, and even more preferably at least 69.
  • the upper limit is preferably not more than 76, more preferably not more than 74, and even more preferably not more than 71.
  • the surface hardness on the Shore C hardness scale is preferably at least 90, more preferably at least 93, and even more preferably at least 96.
  • the upper limit is preferably not more than 100, more preferably not more than 99, and even more preferably not more than 98.
  • the ball When the material hardness and surface hardness of the intermediate layer are lower than the above respective ranges, the ball may take on too much spin on full shots, or the initial velocity may decrease, resulting in a poor distance. On the other hand, when the material hardness and surface hardness are too high, the durability of the ball to cracking on repeated impact may worsen or the feel at impact on shots with a putter and on short approaches may be too hard.
  • the surface hardness of the intermediate layer-encased sphere is set to a higher value than the surface hardness of the ball and the surface hardness of the outer envelope layer-encased sphere. When this is not the case, the spin rate on full shots will rise, preventing a good distance from being achieved, or the controllability of the ball in the short game will worsen.
  • the intermediate layer has a thickness of preferably at least 0.7 mm, more preferably at least 0.8 mm, and even more preferably at least 1.0 mm.
  • the upper limit in the intermediate layer thickness is preferably 1.8 mm or less, more preferably 1.4 mm or less, and even more preferably 1.2 mm or less.
  • the intermediate layer has a greater thickness than the subsequently described cover (outermost layer).
  • the value obtained by subtracting the cover thickness from the intermediate layer thickness is preferably at least 0.04 mm, and more preferably at least 0.08 mm.
  • the upper limit value is preferably 1.5 mm or less, more preferably 1.0 mm or less, and even more preferably 0.6 mm or less.
  • the intermediate layer material may be suitably selected from among various types of thermoplastic resins that are used as golf ball materials, with the use of the highly neutralized resin material containing components (a) to (c) described above in connection with the envelope layer materials or the use of an ionomer resin being preferred.
  • ionomer resin materials include high-acid ionomers having an acid content of at least 16 wt %, sodium-neutralized ionomer resins and zinc-neutralized ionomer resins. These may be used singly or two or more may be used together.
  • An embodiment that uses in admixture a zinc-neutralized ionomer resin and a sodium-neutralized ionomer resin as the chief materials is especially preferred.
  • the blending ratio therebetween expressed as the weight ratio (zinc-neutralized ionomer)/(sodium-neutralized ionomer), is from 25/75 to 75/25, preferably from 35/65 to 65/35, and more preferably from 45/55 to 55/45.
  • the rebound may become too low, as a result of which the desired distance may not be achieved, the durability to cracking on repeated impact at normal temperatures may worsen, or the durability to cracking at low temperatures (subzero Centigrade) may worsen.
  • additives may be suitably included in the intermediate layer material.
  • pigments, dispersants, antioxidants, ultraviolet absorbers and light stabilizers may be added.
  • the amount added per 100 parts by weight of the base resin is preferably at least 0.1 part by weight, and more preferably at least 0.5 part by weight.
  • the upper limit is preferably not more than 10 parts by weight, and more preferably not more than 4 parts by weight.
  • the intermediate layer material has a specific gravity which is typically less than 1.1, preferably between 0.90 and 1.05, and more preferably between 0.93 and 0.99. Outside of this range, the rebound of the overall ball may decrease and a good distance may not be obtained, or the durability of the ball to cracking on repeated impact may worsen.
  • the cover has a material hardness on the Shore D hardness scale which, although not particularly limited, is preferably at least 35, more preferably at least 40, and even more preferably at least 45.
  • the upper limit is preferably not more than 60, more preferably not more than 55, and even more preferably not more than 50.
  • the material hardness is preferably at least 57, more preferably at least 63, and even more preferably at least 70.
  • the upper limit is preferably not more than 89, more preferably not more than 83, and even more preferably not more than 76.
  • the surface hardness of the sphere obtained by encasing the intermediate layer-encased sphere with the cover (i.e., the ball), expressed on the Shore D hardness scale, is preferably at least 50, more preferably at least 53, and even more preferably at least 56.
  • the upper limit is preferably not more than 70, more preferably not more than 67, and even more preferably not more than 64.
  • the surface hardness is preferably at least 75, more preferably at least 80, and even more preferably at least 85.
  • the upper limit is preferably not more than 95, more preferably not more than 92, and even more preferably not more than 90.
  • the spin rate of the ball on full shots with an iron may rise and a good distance may not be achieved.
  • the material hardness of the cover and the surface hardness of the ball are too high, the ball may not be receptive to spin on approach shots or the scuff resistance may worsen.
  • the cover has a thickness of preferably at least 0.3 mm, more preferably at least 0.45 mm, and even more preferably at least 0.6 mm.
  • the upper limit in the cover thickness is preferably not more than 1.2 mm, more preferably not more than 1.15 mm, and even more preferably not more than 1.0 mm.
  • the cover thickness is preferably lower than the intermediate layer thickness. When the cover thickness falls outside of the above range or is greater than the intermediate layer thickness, the ball rebound on full shots with an iron may be inadequate or the spin rate may rise, as a result of which a good distance may not be achieved. On the other hand, when the cover is too thin, the scuff resistance may worsen, or the ball may not be receptive to spin on approach shots, resulting in an inadequate controllability.
  • thermoplastic resins and thermoset resins employed as cover stock in golf balls may be used as the cover material.
  • a urethane resin for reasons having to do with ball controllability and scuff resistance, preferred use can be made of a urethane resin.
  • a material that is composed primarily of a thermoplastic polyurethane and especially preferable to form the cover of a resin blend in which the main components are (I) a thermoplastic urethane and (II) a polyisocyanate compound.
  • the total weight of components (I) and (II) combined be at least 60%, and preferably at least 70%, of the overall amount of the cover-forming resin blend.
  • Components (I) and (II) are described below.
  • the thermoplastic polyurethane (I) has a structure which includes soft segments composed of a polymeric polyol (polymeric glycol) that is a long-chain polyol, and hard segments composed of a chain extender and a polyisocyanate compound.
  • the long-chain polyol serving as a starting material may be any that has hitherto been used in the art relating to thermoplastic polyurethanes, and is not particularly limited.
  • Illustrative examples include polyester polyols, polyether polyols, polycarbonate polyols, polyester polycarbonate polyols, polyolefin polyols, conjugated diene polymer-based polyols, castor oil-based polyols, silicone-based polyols and vinyl polymer-based polyols. These long-chain polyols may be used singly, or two or more may be used in combination. Of these, in terms of being able to synthesize a thermoplastic polyurethane having a high rebound resilience and excellent low-temperature properties, a polyether polyol is preferred.
  • chain extender that has hitherto been employed in the art relating to thermoplastic polyurethanes may be suitably used as the chain extender.
  • low-molecular-weight compounds with a molecular weight of 400 or less which have on the molecule two or more active hydrogen atoms capable of reacting with isocyanate groups are preferred.
  • the chain extender include 1,4-butylene glycol, 1,2-ethylene glycol, 1,3-butanediol, 1,6-hexanediol and 2,2-dimethyl-1,3-propanediol.
  • the chain extender is preferably an aliphatic diol having 2 to 12 carbon atoms, and more preferably 1,4-butylene glycol.
  • any polyisocyanate compound hitherto employed in the art relating to thermoplastic polyurethanes may be suitably used without particular limitation as the polyisocyanate compound.
  • use may be made of one or more selected from the group consisting of 4,4′-diphenylmethane diisocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, p-phenylene diisocyanate, xylylene diisocyanate, 1,5-naphthylene diisocyanate, tetramethylxylene diisocyanate, hydrogenated xylylene diisocyanate, dicyclohexylmethane diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, norbornene diisocyanate, trimethylhexamethylene diisocyanate and dimer acid diisocyanate.
  • thermoplastic polyurethane serving as component (I).
  • Illustrative examples include Pandex T-8295, Pandex T-8290 and Pandex T-8260 (all from DIC Covestro Polymer, Ltd.).
  • thermoplastic elastomer other than the above thermoplastic polyurethanes may also be optionally included as a separate component, i.e., component (III), together with above components (I) and (II).
  • component (III) By including this component (III) in the above resin blend, the flowability of the resin blend can be further improved and properties required of the golf ball cover material, such as resilience and scuff resistance, can be increased.
  • compositional ratio of above components (I), (II) and (III) is not particularly limited. However, to fully elicit the advantageous effects of the invention, the compositional ratio (I):(II):(III) is preferably in the weight ratio range of from 100:2:50 to 100:50:0, and more preferably from 100:2:50 to 100:30:8.
  • thermoplastic polyurethane various additives other than the ingredients making up the above thermoplastic polyurethane may be optionally included in this resin blend.
  • additives other than the ingredients making up the above thermoplastic polyurethane may be optionally included in this resin blend.
  • pigments, dispersants, antioxidants, light stabilizers, ultraviolet absorbers and internal mold lubricants may be suitably included.
  • multi-piece solid golf balls in which the above-described core, inner envelope layer, outer envelope layer, intermediate layer and cover (outermost layer) are formed as successive layers may be carried out by a customary method such as a known injection molding process.
  • a multi-piece golf ball can be produced by successively injection-molding the respective materials for the inner envelope layer, outer envelope layer and intermediate layer over the core in injection molds for each layer so as to obtain the respective layer-encased spheres and then, last of all, injection-molding the material for the cover serving as the outermost layer over the intermediate layer-encased sphere.
  • the encasing layers may each be formed by enclosing the sphere to be encased within two half-cups that have been pre-molded into hemispherical shapes and then molding under applied heat and pressure.
  • the golf ball has a deflection when compressed under a final load of 1,275 N (130 kgf) from an initial load of 98 N (10 kgf) which is preferably at least 1.8 mm, more preferably at least 2.0 mm, and even more preferably at least 2.2 mm.
  • the upper limit value is preferably not more than 3.0 mm, more preferably not more than 2.7 mm, and even more preferably not more than 2.5 mm.
  • the ball deflection is too large, i.e., when the ball is too soft, the ball rebound may become so low that the ball does not achieve a good distance, the feel at impact may be too soft, or the durability to cracking under repeated impact may worsen.
  • the surface hardness of the core it is critical for the surface hardness of the core, the surface hardness of the sphere obtained by encasing the core with the inner envelope layer (inner envelope layer-encased sphere), the surface hardness of the sphere obtained by encasing the inner envelope layer-encased sphere with the outer envelope layer (outer envelope layer-encased sphere), the surface hardness of the sphere obtained by encasing the outer envelope layer-encased sphere with the intermediate layer (intermediate layer-encased sphere) and the surface hardness of the ball to satisfy the following relationship in which the hardnesses are Shore C hardness values:
  • the Shore C hardness value obtained by subtracting the core surface hardness from the surface hardness of the inner envelope layer-encased sphere is more than 0, preferably 2 or more, and more preferably 4 or more.
  • the upper limit is preferably not more than 20, more preferably not more than 16, and even more preferably not more than 13. When this value is too small, the initial velocity of the ball is low and a good distance is not achieved. When this value is too large, the durability to cracking on repeated impact may worsen.
  • the Shore C hardness value obtained by subtracting the core center hardness from the surface hardness of the outer envelope layer-encased sphere is preferably 23 or more, more preferably 25 or more, and even more preferably 27 or more.
  • the upper limit is preferably not more than 40, more preferably not more than 35, and even more preferably not more than 32. When this value is too small, the spin rate on full shots may rise and a good distance may not be achieved. When this value is too large, the initial velocity on shots may decrease and a good distance may not be achieved, or the durability to cracking under repeated impact may worsen.
  • the Shore C hardness value obtained by subtracting the core surface hardness from the surface hardness of the outer envelope layer-encased sphere is preferably 5 or more, more preferably 6 or more, and even more preferably 7 or more.
  • the upper limit is preferably not more than 28, more preferably not more than 23, and even more preferably not more than 20. When this value is too small, the spin rate on full shots may rise and a good distance may not be achieved. When this value is too large, the initial velocity on shots may decrease and a good distance may not be achieved, or the durability to cracking under repeated impact may worsen.
  • the Shore C hardness value obtained by subtracting the surface hardness of the inner envelope layer-encased sphere from the surface hardness of the outer envelope layer-encased sphere is more than 0, preferably 2 or more, and more preferably 3 or more.
  • the upper limit is preferably not more than 16, more preferably not more than 14, and even more preferably not more than 12.
  • the Shore C hardness value obtained by subtracting the surface hardness of the outer envelope layer-encased sphere from the surface hardness of the intermediate layer-encased sphere is more than 0, preferably 2 or more, and more preferably 4 or more.
  • the upper limit is preferably not more than 18, more preferably not more than 15, and even more preferably not more than 12.
  • the Shore C hardness value obtained by subtracting the core center hardness from the surface hardness of the intermediate layer-encased sphere is preferably 30 or more, more preferably 32 or more, and even more preferably 34 or more.
  • the upper limit is preferably not more than 45, more preferably not more than 43, and even more preferably not more than 40.
  • the Shore C hardness value obtained by subtracting the ball surface hardness from the surface hardness of the intermediate layer-encased sphere is more than 0, preferably 2 or more, and more preferably 4 or more.
  • the upper limit is preferably not more than 20, more preferably not more than 17, and even more preferably not more than 14.
  • this value is too small, i.e., when the ball surface is harder than the intermediate layer surface, the ball is not sufficiently receptive to spin in the short game (this being the case especially when the cover is hard) or the spin rate on full shots rises, as a result of which a good distance is not achieved (this being the case especially when the intermediate layer is soft).
  • the value obtained by dividing the overall thickness of the envelope layer by the combined thickness of the cover and the intermediate layer which value is expressed as [(overall thickness of envelope layer)/(intermediate layer thickness+cover thickness)], is preferably at least 0.8, more preferably at least 0.9, and even more preferably at least 1.0.
  • the upper limit value is preferably 1.6 or less, more preferably 1.4 or less, and even more preferably 1.2 or less.
  • the core diameter/ball diameter value is preferably at least 0.702, more preferably at least 0.735, and even more preferably at least 0.749.
  • the upper limit value is preferably 0.821 or less, more preferably 0.802 or less, and even more preferably 0.785 or less.
  • this value is too small, the initial velocity of the ball may decrease, as a result of which a good distance may not be achieved.
  • this value is too large, the spin rate on full shots with an iron may rise, as a result of which the intended distance may not be achieved.
  • the value B ⁇ S is preferably at least 0.8 mm, more preferably at least 0.9 mm, and even more preferably at least 1.0 mm.
  • the upper limit value is preferably 3.3 mm or less, more preferably 2.7 mm or less, and even more preferably 2.2 mm or less.
  • the number of dimples arranged on the cover surface is preferably at least 323, more preferably at least 326, and even more preferably at least 330.
  • the upper limit is preferably not more than 380, more preferably not more than 360, and even more preferably not more than 350.
  • the dimple shapes used may be of one type or may be a combination of two or more types suitably selected from among, for example, circular shapes, various polygonal shapes, dewdrop shapes and oval shapes.
  • the dimple diameter may be set to at least about 2.5 mm and up to about 6.5 mm
  • the dimple depth may be set to at least 0.08 mm and up to 0.30 mm.
  • the dimple coverage ratio on the spherical surface of the golf ball i.e., the dimple surface coverage SR, which is the sum of the individual dimple surface areas, each defined by the flat plane circumscribed by the edge of a dimple, as a percentage of the spherical surface area of the ball were the ball to have no dimples thereon, to be set to at least 70% and not more than 90%.
  • the value V 0 defined as the spatial volume of the individual dimples below the flat plane circumscribed by the dimple edge, divided by the volume of the cylinder whose base is the flat plane and whose height is the maximum depth of the dimple from the base, to be set to at least 0.35 and not more than 0.80.
  • CL1 is the coefficient of lift at a Reynolds number of 80,000 and a spin rate of 2,000 rpm
  • CL2 is the coefficient of lift at a Reynolds number of 70,000 and a spin rate of 1,900 rpm
  • CL3 is the coefficient of lift at a Reynolds number of 200,000 and a spin rate of 2,500 rpm
  • CL4 is the coefficient of lift at a Reynolds number of 120,000 and a spin rate of 2,250 rpm.
  • the coefficients of lift (CL1, CL2, CL3 and CL4) are measured in conformity with the Indoor Test Range (ITR) method established by the United States Golf Association (USGA).
  • ITR Indoor Test Range
  • USGA United States Golf Association
  • the coefficient of lift can be adjusted by adjusting the golf ball dimple configuration (arrangement, diameter, depth, volume, number, shape, etc.).
  • the coefficient of lift does not depend on the internal construction of the golf ball.
  • the Reynolds number (Re) is a dimensionless number used in the field of fluid dynamics, and is computed using formula (I) below.
  • ⁇ represents the density of a fluid
  • v is the relative average velocity of an object relative to flow by the fluid
  • L is a characteristic length
  • ⁇ is the coefficient of viscosity of the fluid
  • the conditions under which the coefficient of lift CL1 is measured i.e., a Reynolds number of 80,000 and a spin rate of 2,000 rpm, generally correspond approximately to the state at the time that the coefficient of lift begins to decrease and, in turn, the golf ball begins to fall after having reached its highest point following launch.
  • the conditions under which the coefficient of lift CL2 is measured i.e., a Reynolds number of 70,000 and a spin rate of 1,900 rpm, generally correspond approximately to the state just before the golf ball falls to the ground after having reached its highest point following launch.
  • high-velocity conditions e.g., an initial velocity of 66 m/s, a spin rate of 2,600 rpm, and a launch angle of 11°.
  • These high-velocity conditions generally correspond to the launch conditions when the ball is hit with a driver by an amateur golfer.
  • the ratio CL2/CL1 has a value of preferably at least 0.900, more preferably at least 0.970, and even more preferably at least 0.990.
  • the decrease in lift as the golf ball falls can be suppressed, which in turn makes it easier for the flight distance (i.e., the carry) to be extended as the ball falls and for the run to be extended.
  • the total distance can be increased.
  • CL2/CL1 is too low, the golf ball tends to fall more abruptly, making it difficult to satisfactorily increase the carry and run.
  • a higher CL2/CL1 is better from the standpoint of increasing the total distance.
  • the carry is extended but the run decreases, as a result of which the total distance may not exceed the optimal value. Therefore, the upper limit value for CL2/CL1 is 1.100 or less, preferably 1.018 or less, more preferably 0.999 or less, and even more preferably 0.995 or less.
  • the conditions under which the coefficient of lift CL3 is measured i.e. a Reynolds number of 200,000 and a spin rate of 2,500 rpm, generally correspond approximately to the state just after the golf ball has been launched under high-velocity conditions (e.g., an initial velocity of 72 m/s, a spin rate of 2,500 rpm and a launch angle of 10°).
  • the conditions under which the coefficient of lift CL4 is measured i.e.
  • a Reynolds number of 120,000 and a spin rate of 2,250 rpm generally correspond approximately to the state when approximately 2 seconds have elapsed as the ball rises after being launched under high-velocity conditions (e.g., an initial velocity of 72 m/s, a spin rate of 2,500 rpm and a launch angle of 10°).
  • the ratio CL4/CL3 has a value of preferably at least 1.250, more preferably at least 1.252, and even more preferably at least 1.255.
  • the upper limit is preferably not more than 1.300, more preferably not more than 1.295, and even more preferably not more than 1.290.
  • the coefficient of lift CL1 is preferably at least 0.230. Also, CL1 is preferably not more than 0.240. From the same standpoint, the coefficient of lift CL2 is preferably at least 0.230. Also, CL2 is preferably not more than 0.240. From the same standpoint, the coefficient of lift CL3 is preferably at least 0.145. Also, CL3 is preferably not more than 0.155. From the same standpoint, the coefficient of lift CL4 is preferably at least 0.185. Also, CL4 is preferably not more than 0.195.
  • a coating layer may be formed on the surface of the cover.
  • This coating layer can be formed by applying various types of coating materials. Because the coating layer must be capable of enduring the harsh conditions of golf ball use, it is desirable to use a coating composition in which the chief component is a urethane coating material composed of a polyol and a polyisocyanate.
  • the polyol component is exemplified by acrylic polyols and polyester polyols. These polyols include modified polyols. To further increase workability, other polyols may also be added.
  • polyester polyol in which a cyclic structure has been introduced onto the resin skeleton may be used as the polyester polyol of component (a).
  • polyester polyols obtained by the polycondensation of a polyol having an alicyclic structure, such as cyclohexane dimethanol, with a polybasic acid; and polyester polyols obtained by the polycondensation of a polyol having an alicyclic structure with a diol or triol and a polybasic acid.
  • a polyester polyol having a branched structure may be used as the polyester polyol of component (b).
  • polyester polyols having a branched structure such as NIPPOLAN 800, from Tosoh Corporation.
  • the polyisocyanate is exemplified without particular limitation by commonly used aromatic, aliphatic, alicyclic and other polyisocyanates. Specific examples include tolylene diisocyanate, diphenylmethane diisocyanate, xylylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, lysine diisocyanate, isophorone diisocyanate, 1,4-cyclohexylene diisocyanate, naphthalene diisocyanate, trimethylhexamethylene diisocyanate, dicyclohexylmethane diisocyanate and 1-isocyanato-3,3,5-trimethyl-4-isocyanatomethylcyclohexane. These may be used singly or in admixture.
  • organic solvents may be mixed into the coating composition.
  • organic solvents include aromatic solvents such as toluene, xylene and ethylbenzene; ester solvents such as ethyl acetate, butyl acetate, propylene glycol methyl ether acetate and propylene glycol methyl ether propionate; ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone; ether solvents such as diethylene glycol dimethyl ether, diethylene glycol diethyl ether and dipropylene glycol dimethyl ether; alicyclic hydrocarbon solvents such as cyclohexane, methyl cyclohexane and ethyl cyclohexane; and petroleum hydrocarbon solvents such as mineral spirits.
  • the thickness of the coating layer made of the coating composition is typically from 5 to 40 ⁇ m, and preferably from 10 to 20 ⁇ m.
  • coating layer thickness refers to the coating thickness obtained by averaging the measurements taken at a total of three places: the center of a dimple and two places located at positions between the dimple center and the dimple edge.
  • the coating layer composed of the above coating composition has an elastic work recovery that is preferably at least 60%, and more preferably at least 80%.
  • the coating layer has a high elasticity and so the self-repairing ability is high, resulting in an outstanding abrasion resistance.
  • the performance attributes of golf balls coated with this coating composition can be improved. The method of measuring the elastic work recovery is described below.
  • the elastic work recovery is one parameter of the nanoindentation method for evaluating the physical properties of coating layers, this being a nanohardness test method that controls the indentation load on a micro-newton ( ⁇ N) order and tracks the indenter depth during indentation to a nanometer (nm) precision.
  • ⁇ N micro-newton
  • nm nanometer
  • prior methods only the size of the deformation (plastic deformation) mark corresponding to the maximum load could be measured.
  • the nanoindentation method the relationship between the indentation load and the indentation depth can be obtained by continuous automated measurement.
  • the hardness of the coating layer is preferably at least 40, and more preferably at least 60.
  • the upper limit is preferably not more than 95, and more preferably not more than 85. This Shore M hardness is obtained in accordance with ASTM D2240.
  • the hardness of the coating layer, as expressed on the Shore C hardness scale is preferably at least 40, and more preferably at least 50; the upper limit is preferably not more than 80, and more preferably not more than 70. This Shore C hardness is obtained in accordance with ASTM D2240.
  • coating layer hardnesses that are higher than these ranges the coating may become brittle when the ball is repeatedly struck, which may make it incapable of protecting the cover layer.
  • coating layer hardnesses that are lower than the above range are undesirable because the ball surface is more easily damaged when striking a hard object.
  • the formation of a coating layer on the surface of golf balls manufactured by a known method can be carried out via the steps of preparing the coating composition at the time of application, applying the composition onto the golf ball surface by a conventional coating operation, and drying the applied composition.
  • the coating technique is not particularly limited. For example, spray painting, electrostatic painting or dipping may be suitably used.
  • the multi-piece solid golf ball of the invention can be made to conform to the Rules of Golf for play.
  • the inventive ball may be formed to a diameter which is such that the ball does not pass through a ring having an inner diameter of 42.672 mm and is not more than 42.80 mm, and to a weight which is preferably between 45.0 and 45.93 g.
  • Comparative Examples 7 to 14 are predictive data that can be inferred from measured values obtained in the other Examples of the invention and Comparative Examples and are not Examples that were actually carried out. These Comparative Examples 7 to 14 are treated below in the same way as the other Examples and Comparative Examples.
  • Solid cores were produced by preparing rubber compositions for the respective Examples and Comparative Examples shown in Tables 1 and 2, and then vulcanizing the compositions for 15 minutes at 155° C.
  • an inner envelope layer was formed by injection-molding the inner envelope layer material shown in Table 3 over the core, following which an outer envelope layer was formed by injection-molding the outer envelope layer material shown in the same table over the inner envelope layer.
  • the material of formulation No. 2 in Table 3 was injection-molded over the core to form a single envelope layer (the details are provided in the “Outer envelope layer” section in the table). No envelope layer was formed in Comparative Example 18.
  • FIG. 2A is a top view of a golf ball on the surface of which the dimples D have been formed
  • FIG. 2B is a side view of the same.
  • ITR Indoor Test Range
  • Coating Composition C shown in Table 6 below As a coating composition common to all of the Examples and Comparative Examples, the coating was applied with an air spray gun onto the surface of the cover (outermost layer) having numerous dimples formed thereon, producing golf balls with a 15 ⁇ m-thick coating layer on top.
  • a reactor equipped with a reflux condenser, a dropping funnel, a gas inlet and a thermometer was charged with 140 parts by weight of trimethylolpropane, 95 parts by weight of ethylene glycol, 157 parts by weight of adipic acid and 58 parts by weight of 1,4-cyclohexanedimethanol, following which the reaction was effected by raising the temperature to between 200 and 240° C. under stirring and heating for 5 hours.
  • the Polyester Polyol (A) thus synthesized was then dissolved in butyl acetate, thereby preparing a varnish having a nonvolatiles content of 70 wt %.
  • the base resin for the coating composition in Table 6 was prepared by mixing together 23 parts by weight of the above polyester polyol solution, 15 parts by weight of Polyester Polyol (B) (the saturated aliphatic polyester polyol NIPPOLAN 800 from Tosoh Corporation; weight-average molecular weight (Mw), 1,000; 100% solids) and the organic solvent. This mixture had a nonvolatiles content of 38.0 wt %.
  • Polyester Polyol (B) the saturated aliphatic polyester polyol NIPPOLAN 800 from Tosoh Corporation; weight-average molecular weight (Mw), 1,000; 100% solids
  • the elastic work recovery of the coating material was measured using a coating sheet having a thickness of 50 ⁇ m.
  • the ENT-2100 nanohardness tester from Erionix Inc. was used as the measurement apparatus, and the measurement conditions were as follows.
  • the elastic work recovery was calculated as follows, based on the indentation work W elast (Nm) due to spring-back deformation of the coating and on the mechanical indentation work W total (Nm).
  • the Shore C hardness and Shore M hardness in Table 6 above were determined by forming the material being tested into 2 mm thick sheets and stacking three such sheets together to give test specimens. Measurements were taken using a Shore C durometer and a Shore M durometer in accordance with ASTM D2240.
  • the diameters at five random places on the surface were measured at a temperature of 23.9 ⁇ 1° C. and, using the average of these measurements as the measured value for a single core, envelope layer-encased sphere or intermediate layer-encased sphere, the average diameter for ten such spheres were determined.
  • the diameter at 15 random dimple-free areas was measured at a temperature of 23.9 ⁇ 1° C. and, using the average of these measurements as the measured value for a single ball, the average diameter for ten balls was determined.
  • the sphere to be measured (i.e., a core, inner envelope layer-encased sphere, outer envelope layer-encased sphere, intermediate layer-encased sphere or ball) was placed on a hard plate and the amount of deflection when compressed under a final load of 1,275 N (130 kgf) from an initial load of 98 N (10 kgf) was measured.
  • the amount of deflection refers in each case to the measured value obtained after holding the core isothermally at 23.9° C.
  • the indenter of a durometer was set substantially perpendicular to the spherical surface of the core, and the surface hardness on the Shore C hardness scale was measured in accordance with ASTM D2240.
  • the P2 Automatic Rubber Hardness Tester (Kobunshi Keiki Co., Ltd.) equipped with a Shore C durometer can be used for measuring the hardness. The maximum value is read off as the hardness value. Measurements were all carried out in a 23 ⁇ 2° C. environment.
  • the core center hardness Cc and the hardness Cm at the midpoint between the core center and core surface were measured by perpendicularly pressing the indenter of a durometer against the positions to be measured on the flat cross-section obtained by cutting the core into hemispheres. The results are indicated as Shore C hardness values.
  • the resin material for each layer was molded into a sheet having a thickness of 2 mm and left to stand for at least two weeks at a temperature of 23 ⁇ 2° C. Three sheets were stacked together at the time of measurement.
  • the Shore C hardness and Shore D hardness of each material were measured with a Shore C durometer and a Shore D durometer in accordance with ASTM D2240.
  • the P2 Automatic Rubber Hardness Tester (Kobunshi Keiki Co., Ltd.) having a Shore C durometer or Shoe D durometer mounted thereon can be used for measuring the hardness. The maximum value is read off as the hardness value.
  • the surface hardness of a ball is the value measured at a dimple-free area (land) on the surface of the ball.
  • the P2 Automatic Rubber Hardness Tester (Kobunshi Keiki Co., Ltd.) having a Shore C durometer or Shore D durometer mounted thereon can be used for measuring the hardness. The maximum value is read off as the hardness value.
  • a sand wedge (SW) was mounted on a golf swing robot and the amount of spin by the ball when struck at a head speed of 16 m/s was rated according to the criteria shown below. The spin rate was measured with a launch monitor immediately after the ball was struck.
  • the sand wedge used was the Tour B XW-1 manufactured by Bridgestone Sports Co., Ltd.
  • the golf balls of Comparative Examples 1 to 18 are inferior in the following respects to the golf balls according to the present invention that are obtained in Examples 1 to 4.
  • Comparative Example 1 the core diameter is smaller than 30 mm and the ball initial velocity is low. As a result, the distances traveled by the ball on full shots with a driver (W#1) and with an iron are both poor.
  • the core diameter is smaller than 30 mm and the ball initial velocity is low, in addition to which the Shore C hardness value obtained by subtracting the core center hardness from the core surface hardness is smaller than 16.
  • the distances traveled by the ball on full shots with a driver (W#1) and with an iron are both poor.
  • the core diameter is smaller than 30 mm and the ball initial velocity is low, in addition to which the Shore C hardness value obtained by subtracting the core center hardness from the core surface hardness is smaller than 16.
  • the distances traveled by the ball on full shots with a driver (W#1) and with an iron are both poor.
  • the ball in Comparative Example 15 is a four-piece ball (4-layer construction). As a result, the initial velocity when struck is low and the distance traveled by the ball on shots with a driver (W#1) is poor.
  • the ball in Comparative Example 16 is a four-piece ball (4-layer construction). As a result, the initial velocity when struck is low and the distance traveled by the ball on shots with a driver (W#1) is poor.
  • the ball in Comparative Example 17 is a four-piece ball (4-layer construction). As a result, the initial velocity when struck is low and the distance traveled by the ball on shots with a driver (W#1) is poor.
  • the ball in Comparative Example 18 is a three-piece ball (3-layer construction).
  • Japanese Patent Application No. 2021-035283 is incorporated herein by reference.

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US6416425B1 (en) * 1999-07-09 2002-07-09 Bridgestone Sports Co., Ltd. Solid golf ball
US6419595B1 (en) * 1999-07-09 2002-07-16 Bridgestone Sports Co., Ltd. Solid golf ball
US6527652B1 (en) * 1999-07-28 2003-03-04 Bridgestone Sports Co., Ltd. Solid golf ball
US20070060416A1 (en) * 2005-09-14 2007-03-15 Bridgestone Sports Co., Ltd. Solid golf ball
US20100048326A1 (en) * 2007-10-29 2010-02-25 Bridgestone Sports Co., Ltd. Multi-piece solid golf ball
US20100190581A1 (en) * 2009-01-23 2010-07-29 Bridgestone Sports Co., Ltd. Golf ball
US20100234138A1 (en) * 2007-10-29 2010-09-16 Bridgestone Sports Co., Ltd. Multi-piece solid golf ball
US20110143861A1 (en) * 2009-12-10 2011-06-16 Bridgestone Sports Co., Ltd. Multi-piece solid golf ball
US20110250987A1 (en) * 2010-04-09 2011-10-13 Bridgestone Sports Co., Ltd. Multi-piece solid golf ball
US20120100933A1 (en) * 2010-10-26 2012-04-26 Bridgestone Sports Co., Ltd. Multi-piece solid golf ball
US20120157235A1 (en) * 2010-12-21 2012-06-21 Bridgestone Sports Co., Ltd. Multi-piece solid golf ball
US20130090189A1 (en) * 2011-10-05 2013-04-11 Aero-X Golf, Inc. Kit for a driver and golf ball that provides optimum performance
US20130196790A1 (en) * 2010-04-09 2013-08-01 Bridgestone Sports Co., Ltd. Multi-piece solid golf ball
US20130225333A1 (en) * 2010-04-09 2013-08-29 Bridgestone Sports Co., Ltd. Multi-piece solid golf ball
US20150273278A1 (en) * 2014-03-28 2015-10-01 Dunlop Sports Co., Ltd. Golf ball
US20180256944A1 (en) * 2017-03-10 2018-09-13 Bridgestone Sports Co., Ltd. Multi-piece solid golf ball

Patent Citations (18)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5184828A (en) * 1990-06-01 1993-02-09 Ilya Co. Ltd. Solid three-piece golf ball
US5184828B1 (en) * 1990-06-01 1995-07-04 Ilya Co Ltd Solid three-piece golf ball
US6416425B1 (en) * 1999-07-09 2002-07-09 Bridgestone Sports Co., Ltd. Solid golf ball
US6419595B1 (en) * 1999-07-09 2002-07-16 Bridgestone Sports Co., Ltd. Solid golf ball
US6527652B1 (en) * 1999-07-28 2003-03-04 Bridgestone Sports Co., Ltd. Solid golf ball
US20070060416A1 (en) * 2005-09-14 2007-03-15 Bridgestone Sports Co., Ltd. Solid golf ball
US20100234138A1 (en) * 2007-10-29 2010-09-16 Bridgestone Sports Co., Ltd. Multi-piece solid golf ball
US20100048326A1 (en) * 2007-10-29 2010-02-25 Bridgestone Sports Co., Ltd. Multi-piece solid golf ball
US20100190581A1 (en) * 2009-01-23 2010-07-29 Bridgestone Sports Co., Ltd. Golf ball
US20110143861A1 (en) * 2009-12-10 2011-06-16 Bridgestone Sports Co., Ltd. Multi-piece solid golf ball
US20110250987A1 (en) * 2010-04-09 2011-10-13 Bridgestone Sports Co., Ltd. Multi-piece solid golf ball
US20130196790A1 (en) * 2010-04-09 2013-08-01 Bridgestone Sports Co., Ltd. Multi-piece solid golf ball
US20130225333A1 (en) * 2010-04-09 2013-08-29 Bridgestone Sports Co., Ltd. Multi-piece solid golf ball
US20120100933A1 (en) * 2010-10-26 2012-04-26 Bridgestone Sports Co., Ltd. Multi-piece solid golf ball
US20120157235A1 (en) * 2010-12-21 2012-06-21 Bridgestone Sports Co., Ltd. Multi-piece solid golf ball
US20130090189A1 (en) * 2011-10-05 2013-04-11 Aero-X Golf, Inc. Kit for a driver and golf ball that provides optimum performance
US20150273278A1 (en) * 2014-03-28 2015-10-01 Dunlop Sports Co., Ltd. Golf ball
US20180256944A1 (en) * 2017-03-10 2018-09-13 Bridgestone Sports Co., Ltd. Multi-piece solid golf ball

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