JP2005261667A - Method of manufacturing golf ball - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a golf ball with a uniform inner structure and the improved sphericity. <P>SOLUTION: The method of manufacturing the golf ball comprises a process of inserting an uncrosslinked polymeric composition into a half-shell forming mold 17 to form a half shell, a process of covering a center of a pair of half shells with a preform forming die 21 to form a preform, and a process of crosslinkng the preform by a core crosslinking die to form a core. The ratio of the volume V2 of the preform to the volume V1 of the core (V2/V1) × 100 is at least 100% and not more than 102.5%; or preferably, the ratio (V2/V1) × 100 is at least 100.5%, and preferably, the ratio (V2/V1) × 100 is not more than 102.0%. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing a golf ball. Specifically, the present invention relates to a method for manufacturing a golf ball including a center, an intermediate layer, and a cover.

  A multi-layer golf ball called a multi-piece ball, which is a kind of solid ball, is used. The multi-piece ball includes a core, a cover, and paint. A center which is a polymer sphere is used for the inner core of the core. An intermediate layer of a polymer layer composed of one layer or a plurality of layers is formed on the center.

  A half shell method may be used for the manufacturing method of this core. In the half shell method, the polymer composition used for the intermediate layer is molded with an arm-shaped mold. This shaped uncrosslinked polymer composition is called a half shell. A spherical preform is formed from the pair of half shells and the center by a mold. Since the preform is made of an uncrosslinked polymer, the preform is handled at a temperature higher than room temperature or a temperature that does not reach the crosslinking temperature.

  The preform is heated and pressed with a core crosslinking mold to produce a crosslinked core. When this preform is cross-linked by the core cross-linking mold, it is heated to a high temperature. During this heating, the volume of the preform increases due to thermal expansion. On the other hand, the material used for the core has great resilience and high durability. A material that retains these performances has viscoelastic properties that combine plasticity and elasticity in an uncrosslinked state. For these reasons, in the production of golf balls, there are many elements that make the core structure difficult to be uniform.

JP-A-2000-5347 and JP-A-2002-248180 disclose a method of manufacturing a multi-piece golf ball manufactured by a half shell method. The relationship between the volume of the preform and the volume of the crosslinked core has a great influence on the flow of the polymer serving as the intermediate layer. In the above prior art, an attempt is made to optimize the ratio between the volume of the preform mold cavity and the volume of the core bridge mold cavity.
JP 2000-5347 A JP 2002-248180 A

  However, since the preform is coated with the uncrosslinked polymer composition as described above, the volume of the preform does not easily match the volume of the preforming mold. If the volume of the preform is too small, it becomes a defect with a bear or bubbles. If the volume is too large, the flow of uncrosslinked polymer in the mold becomes large, and the thickness of the intermediate layer tends to be uneven. According to the setting of the volume of the mold, the volume of the preform is controlled to 3% or slightly larger than the core volume. Burrs may occur in the preform during the production process. This burr is undesirable for the uniformity of the crosslinked core.

  It is known that the golf ball flight distance, flight direction, and other performances depend on the uniformity of the golf ball structure. For this reason, the internal structure of the golf ball is not biased and is required to have higher uniformity. In particular, the uniformity of the core occupying most of this internal structure is important. There is still room for improvement in the way in which highly uniform cores are efficiently produced. The present invention has been made in view of such a current situation, and an object thereof is to provide a golf ball manufacturing method having a uniform internal structure and improved sphericity.

  The method for manufacturing a golf ball according to the present invention includes a step in which an uncrosslinked polymer composition is inserted into a half shell molding die to form a half shell, and the center is a preforming die by this half shell pair. It includes a step of forming a preform by coating and a step of forming the core by crosslinking the preform with a core crosslinking mold. The ratio (V2 / V1) × 100 of the volume V2 of the preform to the volume V1 of the core is 100% or more and 102.5% or less.

  Preferably, the ratio (V2 / V1) × 100 is 100.5% or more.

  The ratio (V2 / V1) × 100 is preferably 102.0% or less.

  Furthermore, it is preferable that the preform is kept at a temperature of 10 ° C. or more and 60 ° C. or less before being put into the core crosslinking mold.

  According to this golf ball manufacturing method, a stable cross-linked core having a very high sphericity can be obtained. In addition, the occurrence of defects in production, which is an index of uniformity, is extremely small. For this reason, the productivity of golf ball production is improved along with the performance of the golf ball.

  Hereinafter, the present invention will be described in detail based on preferred embodiments with appropriate reference to the drawings.

  FIG. 1 is a cross-sectional view illustrating a golf ball 1 obtained by a manufacturing method according to an embodiment of the present invention. This golf ball 1 is a three-piece golf ball including a core 7 composed of a center 3 and an intermediate layer 5 and a cover 9. The center 3 and the intermediate layer 5 are formed by cross-linking the polymer composition. The cover 9 is formed from a polymer composition that is harder than the core 3. Dimples 11 are formed on the surface of the cover 9. The surface portion of the cover 9 other than the dimple 11 is a smooth portion. The golf ball 1 includes a paint layer and a mark portion (not shown) on the surface of the cover 9.

  FIG. 2 is a partial perspective view showing the molding apparatus 15 used in the manufacturing method of the present invention. By this molding device 15, an uncrosslinked half shell 19 formed in a saddle shape to be the intermediate layer 5 is molded. The molding device 15 can also mold the preformed body 23 by covering the center 3 with the half shell 19. The molding device 15 is a combined device for half shell molding and preliminary molding. The half shell molding die 17 includes a concave die 25 and a convex die 27. The concave mold 25 is fixed to the plate 29.

  The plate 29 includes a pair of plates 31 and 33. The plates 31 and 33 are connected by a support shaft 35. The support shaft 35 is driven by, for example, a pinion and a rack, and can be moved in the left-right direction in FIG. Therefore, the concave mold 25 of the plate 29 can be moved to a position where it is combined with the convex mold 27. The number of convex molds 27 is provided corresponding to the concave mold 25. The number of pairs of concave molds 25 to be overlaid is not particularly limited as long as the accuracy required for superposition is maintained. Further, the support shaft 35 is provided with a hinge mechanism 37. This hinge mechanism 37 is used for preforming described later, and the support shaft 35 is driven to rotate so that the plate 33 can be superimposed on the plate 31. Thereby, the concave molds 25 are overlapped.

  FIG. 3 is a cross-sectional view showing a state in which the half shell 19 is molded by the half shell molding die 17 of the molding apparatus 15 of FIG. FIG. 3A is a cross-sectional view showing a state where a polymer composition for a half shell is put into a concave mold 25 which is a lower mold. FIG. 3B is a cross-sectional view showing a state where the convex mold 27 is engaged with the concave mold 25.

  As the base polymer of the polymer composition for the half shell, polybutadiene is mainly used. In view of physical properties, high-cis polybutadiene is particularly preferably used. Examples of the polymer blended therewith include polyisoprene, styrene-butadiene copolymer, ethylene-propylene-diene copolymer, thermoplastic elastomer and natural rubber. As the co-crosslinking agent, a metal salt of α, β-unsaturated carboxylic acid, particularly a zinc salt of acrylic acid or methacrylic acid is preferably used from the viewpoint of obtaining high resilience. As the crosslinking agent, organic peroxides such as dicumyl peroxide and di-t-butyl peroxide are preferably used. As the filler, zinc oxide, barium sulfate, calcium carbonate and the like are mainly used.

  This base polymer is kneaded in an open mill at a temperature of about 50 ° C. for 3 to 10 minutes, and then added with additives such as a co-crosslinking agent, a crosslinking agent and a filler, and kneaded in a closed kneader or the like. The kneaded polymer composition for a half shell is formed into a lump called a plug 41 having a predetermined shape by an extruder. The volume of the polymer composition is controlled by the plug 41. The shape of the plug 41 is not particularly limited, but a certain shape such as a disk shape or a column shape is preferable. This material is maintained at a temperature that does not reach room temperature or the crosslinking temperature and promotes plastic flow, and is preferably maintained at 10 ° C to 60 ° C.

  The plug 41 inserted into the concave mold 25 is moved to a position where it is engaged with the convex mold 27 as described above. When the convex mold 27 is moved up and down, the half shell molding mold 17 is opened and closed. As shown in FIGS. 3A and 3B, the convex mold 27 is lowered and the plug 41 is pressurized. By pressing, the polymer composition of the plug 41 is plastically flowed, and the half shell 19 is formed into the shape of the cavity 43. In addition, the movement of the plate 29 may be configured such that the convex mold 27 moves in the opposite direction.

  The concave mold 25 includes an inclined portion 45 and a circumferential groove 47 for preventing air from being caught in the half shell 19 and preventing the molded half shell 19 from falling off the concave mold. The pressing time by the convex mold 27 is about 5 seconds. The half shell 19 remains in the concave mold 25 after the convex mold 27 is raised. The volume P2 of the plug 41 is controlled so that the ratio (P2 / P1) × 100 of the volume P2 of the plug 41 to the volume P1 of the cavity 43 of the half shell molding die 17 is 90% or more and 100% or less. Yes.

  FIG. 4 is a cross-sectional view showing how the preform 23 is formed from the half shell 19 and the center 3 by the preforming mold 21 of FIG. In the molding apparatus 15 of FIG. 2, the concave mold 25 with the molded half shell 19 is moved from a position below the convex mold 27 to a center supply apparatus (not shown). Here, the center 3 is put on the half shell 19 only on the plate 31 side. The center 3 is separately cross-linked by a center molding die and kept under predetermined conditions. As shown in FIG. 4, the concave mold 25 having only the half shell 19 on the plate 33 is engaged with the concave mold 25 on the plate 31 on the side where the center 3 is inserted. By this step, the preform 23 in which the center 3 is coated with the polymer composition of the half shell 19 is molded.

  FIG. 5 is a cross-sectional view showing how the core 7 is formed by the core cross-linking device 53 including the core cross-linking mold 51. The core cross-linking mold 51 includes an upper mold 55 and a lower mold 57 that are combined to form a finished cavity of the core 7. First, the preform 23 is put into the lower mold 57. Next, the preform 23 is pressurized in the cavity and heated to about 160 ° C. The preformed body 23 is cross-linked in this cross-linking step, and the core 7 is formed. A coating layer 59 having an appropriate thickness and volume is formed on the core 7. The polymer composition used for the center 3 is also basically the same as the polymer composition for the intermediate layer in terms of the types of base polymer, co-crosslinking agent, cross-linking agent and the like used. However, the amount of the material and additives are different from those in the intermediate layer so as to conform to the specific gravity and other physical properties required for the center 3.

  Since the core 7 is formed by being cross-linked at a high temperature of about 160 ° C., the size and the accuracy of the volume are good. On the other hand, the volume of the preform 23 is relatively inaccurate as described above. Therefore, the relationship between the core volume, the actual volume of the preform and the core uniformity was investigated in detail. As a result, when the volume of the core is V1 and the volume of the preform is V2, the ratio of V2 to V1 (V2 / V1) × 100 is found to be 100% or more and 102.5% or less. It was. Preferably, the ratio (V2 / V1) × 100 is 100.5% or more. Further, this ratio (V2 / V1) × 100 is preferably 102.0% or less.

  In order to obtain this ratio, the cavities of the molds of the half shell 19 and the preform 23 are set so as to match each other. The smoothness of the composition flow depends on the processing history and storage environment. The uncrosslinked polymer composition needs to be provided with an appropriate plastic fluidity that flows along the mold during molding. For this reason, the base polymer is sufficiently masticated by an open mill or the like to impart appropriate fluid plasticity. If the plastic fluidity is insufficient, the polymer composition is difficult to conform to the shape of the mold, and thus the target volume is difficult to obtain. On the other hand, if the plastic fluidity is too high, pressure is not applied and it is difficult to discharge bubbles and the desired volume is difficult to obtain. In production, as described above, the degree of mastication of the base polymer, the storage temperature of the half shell 19 and the preform 23, and the like are managed.

  A cover 9 is coated on the surface of the molded core 7. The cover 9 is formed by an injection molding method, a compression molding method, or the like. Next, a paint layer is formed on the surface of the cover 9. The paint layer is marked and the golf ball 1 is finished.

  Hereinafter, although the effect of the present invention will be clarified based on examples, the present invention should not be construed limitedly based on the description of the examples.

[Example 1]
High-cis polybutadiene (“JR01” manufactured by JSR) was used as the base polymer for the half shell, and kneaded by kneading method A (kneading for 8 minutes in an open mill at a surface temperature of 50 ° C.). This high-cis polybutadiene 100 parts by mass, zinc acrylate 25 parts by mass, zinc white 14.5 parts by mass and dicumyl peroxide 1 part by mass were kneaded in a closed kneader. As the polymer composition, plugs having plug weights and volumes described in Table 1 were used. A half shell was formed from this plug by a forming apparatus. Next, a preform was molded using the center and the half shell. This preform was subjected to cross-linking molding at 160 ° C. for 25 minutes using a core cross-linking mold to obtain a core. The mold of the molding apparatus and the core crosslinking mold used were set so as to correspond to the preformed body volume and the volume after core crosslinking described in Table 1.

[Example 2]
A core was obtained in the same manner as in Example 1 except that the mold for the half shell and the preform was changed and the plug weight and the like were adjusted as shown in Table 1.

[Example 3, Comparative Example 1, Comparative Example 2, and Comparative Example 3]
The high cis polybutadiene is kneaded by kneading method B (kneading for 1 minute with an open mill at a surface temperature of 25 ° C.), the mold for the half shell and the preform is changed, and the plug weight and the like are listed in Table 1. A core was obtained in the same manner as in Example 1 except that it was adapted as described above.
[Evaluation]
The presence or absence of a bear was inspected by 100 appearances for each type of molded core. The bear is a defect of a dent generated on the core surface. The shoulder of the core, that is, the so-called shoulder bear, occurs when the burrs of the preform are large or the like, and the polymer flow in the intermediate layer becomes uneven. Bears other than the shoulder often result from a lack of material. Table 1 shows the ratio of the number of bare defects to the number of inspections of the produced crosslinked core. The degree of sphericity indicates the difference between the maximum value and the minimum value of the thickness of the intermediate layer at a plurality of cut points when the core is cut in different directions, and the smaller the better. The sphericity is preferably 0.10 mm or less. More preferably, it is 0.07 mm or less, More preferably, it is 0.05 mm or less. The results are shown in Table 1.

  From this result, it is clear that the manufacturing method of the example is superior to the manufacturing method of the comparative example.

  The present invention can be applied to a method for producing a multi-piece solid golf ball.

FIG. 1 is a cross-sectional view illustrating a golf ball obtained by a manufacturing method according to an embodiment of the present invention. FIG. 2 is a partial perspective view showing a preforming device used in the manufacturing method of the present invention. FIG. 3 is a cross-sectional view showing how the half shell is molded by the half shell molding die of the molding apparatus of FIG. FIG. 4 is a cross-sectional view showing a state where a preform is formed from the half shell and the center by the preforming mold shown in FIG. FIG. 5 is a cross-sectional view showing a state in which a core is formed by a core cross-linking apparatus provided with a core cross-linking mold.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Golf ball 3 ... Center 5 ... Middle layer 7 ... Core 9 ... Cover 11 ... Dimple
DESCRIPTION OF SYMBOLS 15 ... Molding device 17 ... Half shell molding die 19 ... Half shell 21 ... Preliminary molding die 23 ... Preliminary molded body 25 ... Concave die 27 ... Convex Molds 29, 31, 33 ... Plate 35 ... Support shaft 37 ... Hinge mechanism 41 ... Plug 43 ... Cavity 51 ... Core cross-linking die 53 ... Core cross-linking device 59 ... Coating layers

Claims (4)

A process in which an uncrosslinked polymer composition is inserted into a half shell molding die to form a half shell;
The center is covered with a preforming mold by the half shell pair, and a preform is formed,
The preform is cross-linked with a core cross-linking mold and a core is formed,
A method for producing a golf ball, wherein the ratio (V2 / V1) × 100 of the volume V2 of the preform to the volume V1 of the core is 100% or more and 102.5% or less.   The method for manufacturing a golf ball according to claim 1, wherein the ratio (V2 / V1) × 100 is 100.5% or more.   The method for manufacturing a golf ball according to claim 1, wherein the ratio (V2 / V1) × 100 is 102.0% or less. The golf ball manufacturing method according to claim 1, wherein the preform is maintained at a temperature of 10 ° C. or more and 60 ° C. or less before being put into the core cross-linking mold.

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