US20120214614A1 - Golf ball - Google Patents

Golf ball Download PDF

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Publication number
US20120214614A1
US20120214614A1 US13/396,962 US201213396962A US2012214614A1 US 20120214614 A1 US20120214614 A1 US 20120214614A1 US 201213396962 A US201213396962 A US 201213396962A US 2012214614 A1 US2012214614 A1 US 2012214614A1
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United States
Prior art keywords
intermediate layer
golf ball
core
outer cover
inner cover
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Abandoned
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US13/396,962
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English (en)
Inventor
Yoshifumi Miyata
Yuri Naka
Norikazu Ninomiya
Yoshihiro Fujikawa
Masashi Uda
Junnosuke Wada
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Mizuno Corp
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Mizuno Corp
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Assigned to MIZUNO CORPORATION reassignment MIZUNO CORPORATION ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: MIYATA, YOSHIFUMI, UDA, MASASHI, FUJIKAWA, YOSHIHIRO, NAKA, YURI, NINOMIYA, NORIKAZU, WADA, JUNNOSUKE
Publication of US20120214614A1 publication Critical patent/US20120214614A1/en
Abandoned legal-status Critical Current

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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
    • 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
    • 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
    • A63B37/0012—Dimple profile, i.e. cross-sectional view
    • 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
    • A63B37/0023—Covers
    • A63B37/0024—Materials other than ionomers or polyurethane
    • 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
    • A63B37/007—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
    • A63B37/008—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
    • A63B37/0077—Physical properties
    • A63B37/0083—Weight; Mass
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G69/00—Macromolecular compounds obtained by reactions forming a carboxylic amide link in the main chain of the macromolecule
    • C08G69/40—Polyamides containing oxygen in the form of ether groups
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G69/00—Macromolecular compounds obtained by reactions forming a carboxylic amide link in the main chain of the macromolecule
    • C08G69/44—Polyester-amides
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L77/00—Compositions of polyamides obtained by reactions forming a carboxylic amide link in the main chain; Compositions of derivatives of such polymers
    • C08L77/06—Polyamides derived from polyamines and polycarboxylic acids
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L77/00—Compositions of polyamides obtained by reactions forming a carboxylic amide link in the main chain; Compositions of derivatives of such polymers
    • C08L77/12—Polyester-amides
    • 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
    • A63B37/0033—Thickness
    • 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
    • A63B37/0039—Intermediate layers, e.g. inner cover, outer core, mantle characterised by the material
    • 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
    • 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
    • A63B37/0045—Thickness

Definitions

  • the present invention relates to a golf ball.
  • Ionomer resin and polyurethane resin are generally used as main components of the material for the outer cover, i.e., the outermost layer, of a golf ball.
  • golf balls using polyurethane resin are often used by professional golfers and like upper-level players due to their excellent scuff resistance and spin performance (see, for example, Patent Literature 1).
  • the urethane golf balls described above have drawbacks in that they exhibit a lower rebound property and a slower initial speed than golf balls that use ionomer resin in the outer cover (ionomer golf balls).
  • ionomer golf balls In order to improve the rebound property, techniques such as thinly forming the outer cover have been developed.
  • the rebound property is still insufficient compared to ionomer golf balls.
  • urethane golf balls posed problems in the mass production and production cost thereof as they required a technique for thinly forming the outer cover. Therefore, the present invention aims to provide golf balls having excellent scuff resistance and spin performance, and, at the same time, a desirable rebound property.
  • the golf ball of the present invention comprises a core, an intermediate layer formed so as to cover the core, an inner cover formed so as to cover the intermediate layer, and an outer cover formed so as to cover the inner cover.
  • the outer cover comprises a neutralized product containing an ethylene-unsaturated carboxylic acid-alkyl(meth)acrylate ternary copolymer having a weight average molecular weight (Mw) of 80,000 to 500,000, and an ethylene-acrylic acid or ethylene-methacrylic acid copolymer having a weight average molecular weight (Mw) of 2,000 to 30,000.
  • the inner cover also comprises the neutralized product contained in the outer cover.
  • ionomer resin in the outer cover makes the rebound property of this golf ball superior to that of golf balls that use polyurethane resin. Furthermore, because the inner cover also contains the ionomer resin that is used in the outer cover, the adhesion between the outer cover and the inner cover can be improved. As a result, scuff resistance can be enhanced and, at the same time, the rebound property can be improved by reducing the loss of energy from the striking force when hit by a driver or the like. Furthermore, the excellent rebound property of the ionomer resin enables the hardness to be reduced while maintaining the rebound property, and this can also improve the spin performance.
  • the neutralized product may be one obtained by preparing a mixture of a copolymer and an ethylene-unsaturated carboxylic acid-alkyl(meth)acrylate ternary copolymer and neutralizing the mixture using a base, one obtained by neutralizing an ethylene-unsaturated carboxylic acid-alkyl(meth)acrylate ternary copolymer and mixing a copolymer therewith, or one obtained by neutralizing a copolymer and mixing an ethylene-unsaturated carboxylic acid-alkyl(meth)acrylate ternary copolymer therewith.
  • the weight average molecular weight (Mw) is measured by GPC to obtain the polystyrene equivalent molecular weight distribution.
  • the Shore D hardness of the inner cover is preferably about 62 to 72, and more preferably about 64 to 70. This enhances the ability of the inner cover to follow the deformation of the outer cover, further increasing the scuff resistance.
  • the Shore D hardness of the outer cover is preferably about 50 to 57.
  • the Shore D hardness of the inner cover and that of the outer cover are respectively measured for the surface of an inner cover that is formed on an intermediate layer, and for the surface of a ball in which an outer cover is formed on an inner cover.
  • the Shore D hardness of the outer cover is measured at a portion where no dimple is formed.
  • the Shore D hardness of a core and that of an intermediate layer are respectively measured for the surface of an as-formed core, and for the surface of an as-formed intermediate layer. More specifically, the Shore D hardness of a core is measured on the top end portion of a rib in the outward radial direction. However, if the flat surface portion is insufficient to measure the hardness, the measurement may be performed on a flat surface other than a rib on the core. This is because the same temperature and pressure are generally applied to the rib and portions other than the rib during the production of the core; therefore, the top end portion of the rib and other portions have substantially the same hardness. Regarding the intermediate layer, the measurement should be performed on a portion where a rib is not provided. The surface hardness measurement is conducted based on JIS K7215.
  • the thickness of the inner cover is preferably 0.9 to 1.2 mm, and the thickness of the outer cover is preferably 0.9 to 1.2 mm.
  • the core and intermediate layer can be enlarged. This suppresses spin when hit by a driver and improves the rebound property, thus achieving a longer carry distance.
  • the diameter of the spherical body composed of the above-described intermediate layer and core is preferably about 37.5 to 39.5 mm.
  • the core is provided with a spherical main part and a plurality of ribs formed on the surface of the main part.
  • the intermediate layer may have a structure in which it is inserted into depressions surrounded by the ribs.
  • the scuff resistance can be further improved by making the edge angle of the plurality of dimples formed in the surface of the outer cover 6.2 to 7.2°.
  • the present invention can provide a golf ball having excellent scuff resistance and spin performance and a desirable rebound property.
  • FIG. 1 is a cross-sectional view showing a golf ball according to an embodiment of the present invention.
  • FIG. 2 is a perspective view of the core of the golf ball of FIG. 1 .
  • FIG. 3 is a figure illustrating the edge angle of a dimple of the golf ball of the present embodiment.
  • FIG. 4 is a perspective view of another example of the core of the golf ball of FIG. 1 .
  • FIG. 5 is a side view of the core of FIG. 4 .
  • FIG. 6 is a side view of the principal parts of another example of the core of the golf ball of FIG. 1 .
  • FIG. 7 is a side view of another example of the core of the golf ball of FIG. 1 .
  • FIG. 8 is a side view of another example of the core of the golf ball of FIG. 1 .
  • FIG. 9 is a side view of another example of the core of the golf ball of FIG. 1 .
  • FIG. 10 is a figure showing an example of a manufacturing method using the core of FIG. 5 .
  • FIG. 11 is a figure showing another example of a manufacturing method using the core of FIG. 5 .
  • FIG. 12 is a cross-sectional view showing a golf ball according to another embodiment of the present invention.
  • FIG. 13 is a cross-sectional view showing the condition of the golf ball of the present invention when hit.
  • the golf ball 1 of the present embodiment is a multi-piece golf ball comprising a core 3 covered with an intermediate layer 5 , an inner cover 7 and an outer cover 15 .
  • the diameter of a golf ball must be not less than 42.67 mm.
  • the core 3 is composed of a rubber composition, and, as shown in FIG. 2 , comprises a spherical main part 9 and three ribs (protrusions) 11 molded as a unit on the surface of the spherical main part 9 .
  • Each rib 11 extends along one of the great circles drawn around the main part 9 so as to intersect each other at right angles. These ribs form eight depressions 13 in the surface of the main part 9 .
  • the diameter of the main part 9 is preferably 34.0 to 36.0 mm, and more preferably 34.5 to 35.5 mm.
  • the height of the ribs 11 is preferably 1.5 to 2.5 mm, and more preferably 1.75 to 2.25 mm.
  • the Shore D hardness of the surface of the core 3 is preferably 50 to 60, and more preferably 53 to 58.
  • each rib 11 is structured so as to have a trapezoidal cross section in such a manner that its width increases as it approaches the main part 9 .
  • the width of the top portion a of each rib in the outward radial direction is preferably 1.5 to 2.5 mm, and the width of the bottom portion b in the inward radial direction is preferably 3.0 to 6.0 mm.
  • the widths of the end portions of the rib 11 may be set outside this range; however, by setting a lower limit for the width of each end portion of the rib 11 , it is possible to prevent the rib 11 from being deformed due to the pressure of inserting the intermediate layer 5 that results from tightly closing the mold when the intermediate layer 5 is inserted during the manufacturing process. As a result, the core 9 can be accurately held in the center of the mold.
  • the intermediate layer 5 is made of a rubber composition or an elastomer, covers the surface of the core 3 , and has a substantially spherical outside shape. As shown in FIG. 1 , the intermediate layer 5 has almost the same thickness as the height of the ribs 11 , and is inserted into each of the eight depressions 13 surrounded by the ribs 11 . The top portions of the ribs 11 are exposed through the surface of the intermediate layer 5 . In order to obtain a soft feeling when hit and improve the spin performance in an approach shot, it is necessary to make the hardness of the intermediate layer 5 lower than that of the core 3 .
  • the Shore D hardness of the intermediate layer 5 is preferably 47 to 57, and more preferably 50 to 55. In this structure, the Shore D hardness of the intermediate layer 5 is lower than that of the core 3 preferably by a value of 1 to 6.
  • the inner cover 7 is composed of an elastomer, and covers the top portions of the ribs 11 and the intermediate layer 5 .
  • the thickness of the inner cover 7 is preferably 0.7 to 1.5 mm, and more preferably 0.9 to 1.2 mm.
  • the Shore D hardness of the surface of the inner cover 7 is preferably 62 to 72, and more preferably 64 to 70.
  • the elastic modulus of the material for the inner cover 7 is preferably 300 to 500 Mpa, and more preferably 350 to 450 Mpa. The elastic modulus is measured in accordance with JIS K7016.
  • the outer cover 15 is composed of an elastomer, and covers the inner cover 7 .
  • Predetermined dimples (not shown) are formed in the outer surface of the outer cover.
  • the thickness of the outer cover 15 is preferably 0.7 to 1.5 mm, and more preferably 0.9 to 1.2 mm.
  • the Shore D hardness of the outer cover 15 is preferably 50 to 57, and more preferably 51 to 56.
  • the thickness of the outer cover 15 is defined as the distance from an arbitrary point on the outermost part in the outward radial direction where no dimple is formed to an arbitrary point that comes into contact with the intermediate layer. Here, the measurement is performed along the normal line.
  • the total thickness of the inner cover 7 and the outer cover 15 is preferably 1.5 to 3.0 mm, and more preferably 1.7 to 2.4 mm.
  • the outer cover 15 preferably has a loss coefficient (tan ⁇ ) at ⁇ 20° C. of 0.4 or less measured using a viscoelasticity analyzer (viscoelastic spectrometer) at a frequency of 10 Hz, a dynamic strain of 5%, tensile mode, and a rate of temperature increase of 4° C./min.
  • the loss coefficient (tan ⁇ ) tends to increase as the dynamic strain increases; however, if the loss coefficient (tan ⁇ ) falls within the range of 0.1 to 0.4 even at a dynamic strain of 5%, a golf ball having an excellent rebound property and spin performance can be obtained.
  • the dimples formed in the outer cover 15 are explained below.
  • the dimples can be circular or any of various polygonal, oval, or like shapes, and one type or a combination of two or more types can be used.
  • the diameter may be 3.5 to 5.0 mm.
  • the number of dimples is preferably 250 to 450. If too many dimples are provided, the trajectory of the ball lowers, and this may reduce the carry distance. On the other hand, if the number of dimples is too small, the trajectory of the ball rises, and this may also reduce the carry distance.
  • the proportion of the area of the dimples relative to the total area of the spherical surface of the golf ball is preferably 70% or more, and more preferably 75% or more.
  • edge angle a of the dimple is preferably 6.0 to 7.5°, and more preferably 6.2 to 7.2°. By setting such a lower limit, an unduly large lift force can be prevented, and a desirable carry distance performance can be maintained. Setting the above upper limit can also maintain an excellent scuff resistance. As shown in FIG. 3 , edge angle a of the dimple is the angle between line L 1 , which connects the ends of dimple D, and line T. Line T extends toward the dimple edge from intersection R of dimple D and line L 2 , which is offset 0.015 mm downward from line L 1 , and is tangent to the dimple arc.
  • the core 3 can be manufactured using a known rubber composition comprising a base rubber, a cross-linking agent, an unsaturated carboxylic acid metal salt, a filler, etc.
  • a base rubber include natural rubber, polyisobutylene rubber, styrenebutadiene rubber, EPDM, etc.
  • preferably used is high-cis polybutadiene that contains 80% or more cis-1,4 bonds.
  • cross-linking agents include dicumyl peroxide, t-butylperoxide and like organic peroxides; however, it is particularly preferable to use dicumyl peroxide.
  • the compounding ratio of the cross-linking agent is generally 0.3 to 5 parts by mass, and preferably 0.5 to 2 parts by mass per 100 parts by mass of the base rubber.
  • metal salts of unsaturated carboxylic acids it is preferable to use monovalent or bivalent metal salts of acrylic acid, methacrylic acid and like C 3 to C 8 unsaturated carboxylic acids.
  • the use of zinc acrylate can improve the rebound property of the ball and is particularly preferable.
  • the compounding ratio of the unsaturated carboxylic acid metal salt is preferably 10 to 40 parts by mass per 100 parts by mass of the base rubber.
  • fillers include those generally added to cores. Specific examples thereof include zinc oxide, barium sulfate, calcium carbonate, etc.
  • the preferable compounding ratio of the filler is 2 to 50 parts by mass per 100 parts by mass of the base rubber. If necessary, an antioxidant, a peptizer and the like may be added.
  • the intermediate layer 5 is composed of a rubber composition or elastomer as described above. When a rubber composition is used, the same materials as used for the core 3 described above can be used.
  • the intermediate layer 5 is composed of an elastomer
  • a styrene/butadiene/styrene block copolymer SBS
  • SIS styrene/isoprene/styrene block copolymer
  • SEBS styrene/ethylene/butylene/styrene block copolymer
  • SEPS styrene/ethylene/propylene/styrene block copolymer
  • thermoplastic elastomer an olefin-based thermoplastic elastomer having polyethylene or polypropylene as a hard segment and butadiene rubber, acrylonitrile butadiene rubber or ethylene/propylene rubber as a soft segment
  • vinyl chloride-based plastic elastomer having crystallized poly(vinyl chloride) as a hard segment and amorphous poly(vinyl)
  • the outer cover 15 use an ionomer resin as its main component.
  • An example of such an ionomer resin is a neutralized product comprising an ethylene-unsaturated carboxylic acid-alkyl(meth)acrylate ternary copolymer having a weight average molecular weight (Mw) of 80,000 to 500,000, an ethylene-acrylic acid or ethylene-methacrylic acid copolymer having a weight average molecular weight (Mw) of 2,000 to 30,000, and a metal salt.
  • Mw weight average molecular weight
  • Mw weight average molecular weight
  • Mw weight average molecular weight
  • Mw weight average molecular weight
  • Mw weight average molecular weight
  • Mw weight average molecular weight
  • Mw weight average molecular weight
  • Mw weight average molecular weight
  • Mw weight average molecular weight
  • Mw weight average molecular weight
  • Mw weight average molecular weight
  • Mw weight average molecular weight
  • a copolymer having a high weight average molecular weight is excellent in physical properties, such as the rebound property and scuff resistance, but such a copolymer has poor moldability. Therefore, a copolymer having a low weight average molecular weight, which has good flowability, is used in combination. These materials have similar structures and high compatibility with each other. Therefore, their combination enables a material having excellent moldability, rebound property and scuff resistance to be obtained. Furthermore, by adding a metal salt, the degree of neutralization of carboxylic acid can be increased and the rebound property can be enhanced accordingly.
  • the weight average molecular weight (Mw) of the neutralized product is measured by GPC (gel permeation chromatography) and calculated as a polystyrene equivalent molecular weight.
  • Mw weight average molecular weight
  • the weight average molecular weights of binary copolymer and ternary copolymer are immeasurable as they are; therefore, a sample thereof is dissolved in a mixed solvent of xylene and butanol by adding hydrochloric acid and heating the mixture. The weight average molecular weight of the obtained substance is then measured by letting the resulting solution reprecipitate in methanol.
  • the neutralized product may be one obtained by neutralizing, using a metal salt, a mixture of a copolymer and an ethylene-unsaturated carboxylic acid-alkyl(meth)acrylate ternary copolymer; one obtained by neutralizing an ethylene-unsaturated carboxylic acid-alkyl(meth)acrylate ternary copolymer using a metal salt and mixing a copolymer therewith; or one obtained by neutralizing a copolymer using a metal salt and mixing an ethylene-unsaturated carboxylic acid-alkyl(meth)acrylate ternary copolymer therewith.
  • the main component of the outer cover 15 refers to a material that is contained in the largest amount of weight among the materials for the outer cover 15 .
  • the proportion of the main component of the outer cover 15 is preferably about 60 to 100% by weight when the total weight of the outer cover 15 is defined as 100%.
  • Specific examples of ionomer resins preferably used as the main component of the outer cover 15 include HPC AD1043 and HPC AD1022 both manufactured by Dupont.
  • the outer cover 15 may contain other ionomer resins such as Himilan 1706 and Himilan 1605, manufactured by Dupont Mitsui Chemical Co., Ltd.; and Surlyn 9910, Surlyn 8940, Surlyn 8150, Surlyn 8120, and Surlyn 8320, manufactured by Dupont.
  • Himilan 1706 and Himilan 1605 manufactured by Dupont Mitsui Chemical Co., Ltd.
  • the inner cover 7 preferably contains the aforementioned ionomer resin that serves as the main component of the outer cover 15 in an amount of about 10 to 50% by weight, and more preferably about 15 to 45% by weight.
  • the inner cover 7 may further contain other ionomer resins such as an ethylene-(meth)acrylic acid binary copolymer having an acid content of 10% or more. Specific examples thereof include Himilan 1706 and Himilan 1605, manufactured by Dupont Mitsui Chemical Co., Ltd.; and Surlyn 9910, Surlyn 8940, Surlyn 8150, HPF 1000, and HPF 2000, manufactured by Dupont.
  • the golf ball 1 of the present embodiment having the above structure uses an ionomer resin instead of a urethane resin as the main component of the outer cover 15 .
  • This allows the golf ball 1 to exhibit an excellent rebound property. Having an excellent rebound property makes it possible to achieve remarkable spin performance by reducing the hardness while maintaining the rebound property.
  • the material for the inner cover 7 contains the main component of the outer cover 15 , adhesion between the outer cover 15 and the inner cover 7 can be enhanced; therefore, the deformation of the inner cover 7 follows the deformation of the outer cover 15 when hit. As a result, the scuff resistance can be improved and the loss of energy in the striking force when hit by a driver or the like can be reduced, further improving the rebound property.
  • the material for the inner cover 7 includes the main component of the soft outer cover 15 , the hardness of the inner cover 7 can be reduced and the spin performance in an approach shot can be improved accordingly.
  • the diameter of the spherical body composed of the core 3 and the intermediate layer 7 larger, reduction of the rebound property can be prevented.
  • the spin amount tends to undesirably increase in a conventional golf ball. This often results in the reduction of carry distance even when hit by a driver.
  • the spin amount can be reduced by using the restoring force of the ribs 11 that were deformed due to the shot by a driver.
  • the ribs 11 are not simple protrusions but are structured so as to form walls surrounding the intermediate layer 5 . Therefore, the restoring force of the ribs 11 acts strongly from the perimeter of the intermediate layer 5 via the entire wall surface, and this increases the force F opposite to the backspin B. This reduces the amount of backspin and achieves a significantly longer carry distance. This effect is particularly remarkable when the ball is hit by a driver, etc., which is designed to obtain a long carry distance.
  • the current condition is shown by the solid lines and the condition immediately before the current condition is shown by the dashed lines. This makes it possible to obtain both excellent spin performance in an approach shot and a long carry distance when hit by a driver.
  • FIG. 4 is a perspective view of a core provided with notches.
  • FIG. 5 is a cross-sectional view of the core of FIG. 4 .
  • the notches 24 are structured so as to have a bottom surface 24 a extending along a tangent plane H that passes through the intersections P of the great circles.
  • the notch 24 is formed by excising the rib 11 at the tangent plane H.
  • the bottom surface 24 a of the notch 24 may be formed along a plane H 1 that extends away from the tangent plane H by being slanted toward the center of the rib 11 by 1 to 3°, i.e., a plane having an angle made between the normal line n of the main part 9 passing through the intersection P is 91 to 93° as viewed from the front.
  • This arrangement enables the angle to serve as a draft angle, and, for example, when a core is molded using two molds, such as an upper mold and a lower mold, the core 3 can be easily removed from the mold.
  • the length of the notchless top portion of each arc section S of the ribs 11 in the arc direction, which is divided at the intersection P as shown in FIG. 5 is preferably 10 mm or more.
  • a notch 24 so as to have a bottom surface 24 a extending along a plane H 2 that is perpendicular to the normal line n that passes through the mid point in the height direction of the rib 11 .
  • the distance D from the top portion of the virtual rib 11 without a notch 24 to the bottom surface 24 a is preferably 1.2 mm or greater.
  • the length L should preferably be 10 mm or more, as in the above-described case.
  • a draft angle can be formed by forming the bottom surface 24 a of the notch 24 along a plane that has an angle of 91 to 93° relative to the normal line n in the same manner as shown in FIG. 6 .
  • a notch can also be provided in the middle of the arc section S of the rib 11 in the arc direction. More specifically, as shown in FIG. 8( a ), the notch 25 may be formed so as to have two bottom surfaces 25 a each extending toward the intersection P from a point on the normal line m of the main body 9 that passes through the mid point Q of each arc section in the circumferential direction.
  • the angle formed between the bottom surface 25 a and the normal line m is preferably 45 to 48° as viewed from the front. This arrangement makes it easy to remove the core 3 from the mold as described above. If this angle exceeds 48°, the above-described length L of the rib in the circumferential direction becomes unduly short.
  • the depth D of the notch 25 is preferably 1.2 mm or more.
  • the depth D may be set outside of this range; however, by setting the depth D in this range, the intermediate layer material can be smoothly spread throughout the depressions 13 .
  • the depth D of the notch 25 is defined as the length from the top of the virtual rib 11 without a notch 25 to the deepest portion of the notch 25 .
  • the notch 25 can be structured so as to have two side surfaces 25 b each extending in the direction of the intersection P from a point Q on a normal line m of the main part 9 that passes through the mid point of each arc section S in the arc direction, and a bottom surface 25 c of an arc shape along the main part 9 connecting the two side surfaces 25 b.
  • the angle between the side surface 25 b and the normal line m is preferably 45 to 48° as viewed from the front.
  • the bottom surface 25 c can also be formed so as to pass through the mid point in the height direction of the rib 11 .
  • the depth D of the notch is preferably 1.2 mm or more. As long as the easy removal of the core is ensured, two or more notches 25 may be provided in the middle of the arc section S.
  • the arc section S may have a notch 24 as shown in FIG. 5 , 6 , or 7 , and a notch 25 as shown in FIG. 8 .
  • the thickness of the intermediate layer 5 and the height of the rib 11 are the same; however, they do not necessarily have to be the same.
  • the thickness of the intermediate layer 5 may be greater than the height of the rib 11 .
  • FIGS. 10 and 11 show the method for manufacturing a four-piece golf ball comprising the core of FIG. 5 .
  • a core is molded.
  • a predetermined amount of non-vulcanized rubber composition is placed in a mold.
  • this rubber composition comprises a base rubber, a cross-linking agent, a metal salt of unsaturated carboxylic acid, a filler and the like those mixed by a Banbury mixer, a roller or like mixing equipment.
  • the rubber composition is then press molded at 130 to 180° C. to obtain a core 3 as shown in FIG. 4 .
  • an intermediate layer 5 is then formed by press molding.
  • the mold for the intermediate layer comprises an upper mold 43 and a lower mold 45 , each having a hemispherical depression 41 .
  • the depressions 41 of the upper mold 43 and lower mold 45 have the same kind of roughly finished surfaces as those of the molds for the core.
  • a plurality of depressions 49 for holding excess flow are formed.
  • a non-vulcanized rubber composition 61 is inserted into the depression 41 of the lower mold 45 , a rubber composition 61 is placed on the above-obtained core 3 , and the core 3 is positioned between the upper mold 43 and the lower mold 45 . Subsequently, as shown in FIG. 10( b ), the upper mold 43 and the lower mold 45 are brought into contact. The rubber composition 61 is subjected to full vulcanization at 130 to 180° C. for 5 to 25 minutes and press molding, to obtain an intermediate layer 5 .
  • the rubber compositions 61 placed on the core 3 and in the depression 41 of the lower mold 45 fill the depressions 13 while being pressed against the surface of the core 3 .
  • adjacent depressions 13 communicate with each other through notches 24 , and therefore the rubber composition spreads throughout each depression and uniformly fills the space therein.
  • the intermediate layer 5 may also be molded by injection molding using, for example, a mold such as that shown in FIG. 11 . In this case, if no notches are provided, it is impossible to uniformly insert the rubber composition into each depression 13 without providing a gate for each depression 13 .
  • the rubber composition can be uniformly inserted into the depressions 13 via the notches 24 in the same manner as described above even when the rubber composition is inserted from a single gate 50 after placing the core 3 into the molds 47 and 48 .
  • the core 3 covered with the intermediate layer 5 is removed from the mold. Thereafter, an inner cover 7 is applied to the surface of the intermediate layer 5 by press molding or injection molding. Thereafter, an outer cover is applied to the surface of the inner cover by press molding or injection molding in such a manner that the cover has predetermined dimples, thus obtaining a golf ball of the present embodiment.
  • notches 24 are provided in the ribs 11 , and adjacent depressions 13 communicate with each other through the notches 24 . Therefore, the rubber composition 61 spreads throughout the depressions 13 and uniformly fills the space therein when pressed from any position on the surface of the core 3 .
  • The makes it possible to cover the core 3 with an intermediate layer in a single press molding step. As a result, the manufacturing time can be significantly reduced.
  • a method for manufacturing a golf ball comprising an intermediate layer with notches is explained above.
  • a golf ball without notches can also be manufactured by almost the same method.
  • the golf ball of the present invention is not limited to this embodiment, and various modifications can be made as long as they do not depart from the scope of the invention.
  • three ribs are formed along great circles drawn around the main part in the present embodiment.
  • the embodiment of the ribs is not limited to this and the shape, number and location thereof may be appropriately modified as long as depressions, to which an intermediate layer is inserted, can be formed by the ribs.
  • the core 3 is explained as being provided with ribs 11 .
  • the core 3 may be composed of the spherical main part 9 without forming any ribs as shown in FIG. 12 .
  • each of the golf balls of the Examples and Comparative Examples has a shape as shown in FIG. 1 .
  • the golf ball of Example 21 has a shape as shown in FIG. 12 .
  • Table 1 below shows the shape, material and the like for each golf ball. All the golf balls were manufactured to have a diameter of about 42.70 mm, a weight of about 45.50 g, and 366 dimples.
  • hardness difference means the difference in hardness between the core and the intermediate layer
  • total thickness means the total thickness of the inner cover and the outer cover.
  • the diameter of the intermediate layer means the diameter of the intermediate layer including the core.
  • HPC HPC AD 1022 (an ionomer manufactured by DuPont)
  • 8940 stands for Surlyn 8940 (manufactured by DuPont)
  • 8150 stands for Surlyn 8150 (manufactured by DuPont);
  • 8320 stands for Surlyn 8320 (manufactured by DuPont).
  • the unit for the proportions of the materials is % by weight.
  • Table 2 shows the composition (unit: parts by mass) of the materials for the core of each golf ball.
  • Table 3 shows the composition (unit: parts by mass) of the materials for the intermediate layer of each golf ball.
  • BR-01 product name, manufactured by Japan Synthetic Rubber Company
  • Calcined Zinc Oxide (product name, manufactured by HakusuiTech Co., Ltd.) was used as the zinc oxide; precipitated barium sulfate (product name, manufactured by Sakai Chemical Industry Co., Ltd.) was used as the barium sulfate; Antage W-400, 2,2′-methylene bis-(4-methyl-6-tert-butyl phenol) (product name, manufactured by Kawaguchi Chemical Industry Co., Ltd.) was used as the antioxidant; Actor ZA (product name, manufactured by Kawaguchi Chemical Industry Co., Ltd.) was used as the zinc acrylate; and PERCUMYL D (product name, manufactured by NOF Corporation) was used as the dicumyl peroxide. Molding was performed under the conditions of a mold temperature of 160° C. and a crosslinking time of 6 minutes.
  • Example 15 Cis-1,4- 100.00 100.00 100.00 100.00 polybutadiene Zinc oxide 3.00 3.00 3.00 3.00 Barium sulfate 22.50 21.40 23.10 23.40 Antioxidant 0.10 0.10 0.10 0.10 Zinc acrylate 24.70 27.40 22.90 22.00 Dicumyl 1.50 1.50 1.50 peroxide
  • Example 1 62.2 2500 198 5500 4 5 0.775
  • Example 2 62.3 2600 197 5600 4 4 0.776
  • Example 3 62.1 2400 197 5400 4 5 0.774
  • Example 4 62.3 2600 197 5500 3.5 4 0.776
  • Example 5 62.1 2700 196 5700 4 5 0.774
  • Example 6 62.4 2400 200 5200 3.5 4 0.777
  • Example 7 62.1 2700 196 5800 4.5 5 0.774
  • Example 8 62.2 2400 198 5500 4.2 4 0.775
  • Example 9 62.1 2700 196 5800 3.5 5 0.774
  • Example 10 62.2 2500 197 5500 4.5 5 0.775
  • Example 11 62.1 2600 196 5500 4 4.5 0.774
  • Example 11 62.1 2600 196 5500 4 4.5 0.774
  • Example 12 62.4 2300 200 5200 4 5 0.777
  • Example 13 62.4 2800 192 5700 4 3 0.777
  • Example 14 62.0 2400 192 5300 4 4.5
  • Table 4 above shows the results of a hitting test conducted using the golf balls of the Examples and Comparative Examples.
  • the golf balls were hit using a hitting robot (manufactured by Miyamae Co., Ltd.: product name “SHOT ROBO V”) with a number 1-wood (1W: manufactured by Mizuno
  • the surface condition of the ball after conducting the aforementioned sand wedge hitting test was visually checked by five people and evaluated using a 5-step rating (1: A dent remained in which the cover material was peeled off, 2: A large amount of fraying or scratching was obvious on the ball surface, 3: A small amount of fraying or scratching could be seen on the ball surface, 4: A slight amount of scratching could be seen on the ball surface (just enough to be visible to the naked eye), or 5: Almost no dent could be seen on the ball surface).
  • the average of these values was used as the scratch score for each Example and Comparative Example. The higher the scratch score, the more resistant the ball was to scratches, i.e., the greater the scuff resistance.

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US20180318657A1 (en) * 2016-04-06 2018-11-08 Acushnet Company Golf ball components made using three-dimensional additive manufacturing systems

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US20050255944A1 (en) * 2004-03-19 2005-11-17 Norikazu Ninomiya Multi-piece golf ball and manufacturing method thereof
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US20040138006A1 (en) * 2003-01-10 2004-07-15 Norikazu Ninomiya Multi-piece golf ball and manufacturing method thereof
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US20180318657A1 (en) * 2016-04-06 2018-11-08 Acushnet Company Golf ball components made using three-dimensional additive manufacturing systems
US10668334B2 (en) * 2016-04-06 2020-06-02 Acushnet Company Golf ball components made using three-dimensional additive manufacturing systems

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