JP2004255013A - Method for producing golf ball - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a golf ball producing method capable of enhancing uniformity. <P>SOLUTION: An uncrosslinked polymer composition 45 is inserted into a half shell molding die 17 having a half shell shape cavity 33, so as to mold the half shell 47. Then a center part is covered by a pair of half shells 47, so as to mold a preliminary molded body. The preliminary molded body is crosslinked and molded by a core molding die, then the core is produced. When the capacity of the cavity 33 is defined as V1, and the volume of the polymer composition 45 is defined as V2, the ratio V2/V1 is ≥ 90% and ≤ 100%. When the half shells 47 are used, a polymer flowability is improved in the case of molding the preliminary molded body and crosslinking/ molding the core. Consequently, the core uniform in the cover layer being the intermediate layer of the golf ball is obtained. The golf ball using the core is excellent in the uniformity of performance. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【００３８】
表１において、比較例１から４の製造方法では、コア被覆層の偏肉が大きい。これに対して、実施例１から４の製造方法は偏肉が小さい、すなわち、真球度のよいコアが得られる。
【００３９】
【発明の効果】
以上説明したように、本発明に係るゴルフボールの製造方法によれば、均一度の高いコアが効率良く得られる。このコアを用いたゴルフボールは、飛び、方向性その他の性能にバラツキは少なく、優れている。
【図面の簡単な説明】
【図１】図１は、本発明の一実施形態に係る製造方法により得られたゴルフボールが示された模式的断面図である。
【図２】図２は、図１のゴルフボールのコアの予備成形体成形装置の一部が示された斜視図である。
【図３】図３は、図２のゴルフボールコアの製造方法で使用される金型が示された断面図である。
【図４】図４は、図３の金型を使用するコア製造方法の工程の一部が示された断面図である。
【図５】図５は、図２の予備成形体成形方法の工程の一部が示された断面図である。
【図６】図６は、図１のゴルフボールコアの製造方法の工程の一部が示された断面図である。
【図７】図７は、従来のゴルフボールのコアを製造する方法の一部が示された断面図である。
【符号の説明】
１・・・ゴルフボール
３・・・コア
５、８７・・・センター
７・・・中間層（コア被覆層）
１１・・・カバー
１７、７１・・・ハーフシェル成形用金型
２１、７５・・・ハーフシェル成形用凸型金型
１９、７７・・・ハーフシェル成形用凹型金型
３３、７９・・・ハーフシェル成形用キャビティ
３５・・・ハーフシェル成形用凹型金型傾斜面
３７・・・ハーフシェル成形用凹型金型溝
４５、７３・・・ポリマー組成物
４７、７４・・・ハーフシェル
１５・・・予備成形体成形装置
８１・・・バリ
５１、９１・・・コア成形用金型
５３、８５・・・予備成形体[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for manufacturing a golf ball. More specifically, the present invention relates to a method for manufacturing a golf ball including a core including a center and an intermediate layer.
[0002]
[Prior art]
A core having an intermediate layer is used in a golf ball having a multilayer structure called a multi-piece ball. These golf balls include a core including a center and an intermediate layer, a cover, and paint. Some intermediate layers are composed of a plurality of layers. It is known that the uniformity of the structure of a golf ball affects the performance of the golf ball, such as flight and directionality. In a golf ball having a multilayer structure, it is preferable that the thickness of each layer is uniform. The core is manufactured as a sphere having a polymer sphere as a center (inner core), which is coated with another polymer layer. A half shell method may be used as a method for manufacturing a core.
[0003]
In the half shell method, first, an uncrosslinked polymer composition is formed into a half shell by a mold having a bowl-shaped cavity. Next, the pair of half shells and the center are pressed with a mold to form a preform. The preform is pressure-crosslinked with a core molding die to produce a core. Since the half-shell polymer composition has viscoelasticity, it includes factors that tend to be non-uniform due to plastic flow and stickiness of the polymer.
[0004]
A method of manufacturing a golf ball by the half shell method is described in JP-A-10-24124. Among them, a mold is devised so that the half shell does not reach the convex mold. However, even if the mold and the manufacturing apparatus disclosed herein are used, the core uniformity is not sufficient.
[0005]
[Patent Document 1]
JP-A-10-24124
[Problems to be solved by the invention]
FIG. 7 is a cross-sectional view illustrating some steps of a conventional golf ball manufacturing method. FIGS. 7A to 7C schematically show how the half shell 74, the preform 85, and the core are formed. FIG. 7A shows a state in which the polymer composition 73 is charged into a half-shell molding die 71 and is press-molded. If the volume of the composition 73 to be charged is small, the molding pressure is not evenly applied to the half shell 74. For this reason, the flow of the polymer composition becomes uneven. This causes the coating layer 89 of the preform 85 to be biased as shown in FIG. 7B in the preforming step of covering the center 87.
[0007]
7A, when the volume of the polymer composition 73 is large, the composition 73 flows out of the half-shell molding cavity 79 to form burrs 81. As shown in FIG. When the half shell with the burr 81 is used, air is easily trapped in the coating layer in the preforming. Further, as shown in FIG. 7C, when the preform 85 is molded by the core molding device 91, the flow of the polymer composition in the portion of the burr 81 becomes uneven.
[0008]
On the other hand, from recent demands for performance and yield improvement, it is desired to further improve the uniformity of the golf ball. The present invention has been made in view of such circumstances, and has as its object to improve the uniformity of a golf ball.
[0009]
[Means for Solving the Problems]
The method of manufacturing a golf ball according to the present invention includes a step of forming a half shell by inserting an uncrosslinked polymer composition into a half shell forming mold. The center is covered with the pair of half shells to form a preform. The preform is cross-linked to form a core. In this step, when the volume of the cavity of the half shell is V1 and the volume of the polymer composition is V2, the ratio V2 / V1 is 90% or more and 100% or less. According to this manufacturing method, there is no uneven thickness of the preformed body, and the vulcanized core becomes uniform.
[0010]
The half-shell molding die includes a first die having a hemispherical convex portion and a second die having a hemispherical concave portion. The radius of the convex portion is r1, and the center is Is r2, the relationship between r1 and r2 is 0.10 ≧ (r2−r1) / r2 ≧ 0. According to this half shell molding die, it is easy to produce a preformed body having good adhesion to the center and good rubber flow during vulcanization of the core.
[0011]
It is preferable that the second mold has at least one groove parallel to the circumferential direction. In this manufacturing method using a mold, the half shell is not taken in the convex mold, so that the center can be directly inserted, and the productivity is good.
[0012]
More preferably, the ratio V2 / V1 is 94% or more and 100% or less. With such control, the uniformity of the core is further improved. This core allows the golf ball to be more uniform.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail based on preferred embodiments with reference to the drawings as appropriate.
[0014]
FIG. 1 is a cross-sectional view showing 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 3, a center 5, a mid layer 7, and a cover 11 that constitute the core 3. The center 5 and the intermediate layer 7 are formed by crosslinking the polymer composition. The cover 11 is formed from a polymer composition of a material harder than the core 3. Dimples 13 are formed on the surface of the cover 11. The surface portion of the cover 11 other than the dimples 13 is a flat portion. The golf ball 1 has a paint layer and a mark portion (not shown) on the surface of the cover.
[0015]
FIG. 2 is a perspective view showing a part of the preform forming apparatus 15. The forming device 15 is a device that combines the formation of a half shell and the formation of a preform. The half-shell forming mold 17 includes a concave mold 19 and a convex mold 21. This concave mold 19 is fixed to the plate 23. The plate 23 includes a pair of plates 25 and 27. As described later, the concave mold 19 is used by overlapping the molds. The set of the concave molds 19 to be superimposed may be a pair or a plurality of pairs. The number of pairs of the concave molds 19 is not particularly limited as long as the accuracy required for the superposition is maintained.
[0016]
The molding device 15 includes a support shaft 29 that connects the plates 25 and 27. The support shafts 29 are driven by, for example, a pinion and a rack, so that the plates 23 can move in the left-right direction in FIG. The support shaft 29 includes a hinge mechanism 31, and the plate 25 can be superimposed on the plate 27 by rotating the support shaft 29. In this step, the above-mentioned concave molds 19 are overlapped with each other, and a preform described later is manufactured.
[0017]
FIG. 3 is a cross-sectional view showing a mold 17 for forming a half shell. The half shell is a material for forming the mid layer 7 of the golf ball 1. In FIG. 2 described above, the plate 23 is moved so that the concave mold 19 is placed at a position where the concave mold 19 is overlapped with the convex mold 21. Conversely, the convex mold 21 may be configured to move. The cavity 33 is formed by closing the concave mold 19 and the convex mold 21. When the convex mold 21 moves up and down, the mold 17 is opened and closed. Therefore, the number of the convex molds 21 is provided corresponding to the concave mold 19. The concave mold 19 has an inclined portion 35 near the edge of the opening. In addition, one or more peripheral grooves 37 are provided on a side wall close to the opening.
[0018]
FIG. 4 is a cross-sectional view showing a state in which the uncrosslinked polymer composition 45 is molded into the half shell 47 by the molding die 17. The uncrosslinked polymer composition 45 is charged into the concave mold 19 in the form of a plug. The convex mold 21 is pressed against this plug. Then, the polymer composition 45 is plastically flowed and formed into the shape of the cavity 33. At this time, the inclined portion 23 makes it difficult for air to enter, and improves the flow of the polymer composition 31. The slope 23 may be a flat taper or a curved surface. The taper angle α is preferably 30 ° or more and 60 ° or less. When the inclined surface is a curved surface, this angle depends on the angle of a tangent to the curved surface center point.
[0019]
Suitable base polymers for the half shell 47 include polybutadiene, polyisoprene, styrene-butadiene copolymer, ethylene-propylene-diene copolymer, thermoplastic elastomer and natural rubber. In terms of physical properties, polybutadiene is particularly preferred.
[0020]
The polymer composition 45 is controlled to a predetermined volume. The shape of this material is not particularly limited, but is preferably a fixed shape of a disk or a column. The material is maintained at room temperature or at a temperature that does not reach the crosslinking temperature and promotes composition flow. The pressing time by the convex mold 21 is about 5 seconds. After the pressing, when the convex mold 21 rises, the half shell 47 is formed in the concave mold 19.
[0021]
The peripheral groove 37 acts so that the half shell molded body 47 remains on the concave mold 19 side when the convex mold 21 rises and the cavity 33 opens. It is important that the half shell 47 is attached to the concave mold 19 side because the manufacturing apparatus is automatically operated. This is because when the half shell 47 is attached to the convex mold 21, the half shell becomes a defective product, and it is necessary to stop the operation, remove the defective product, and the like. Therefore, it is preferable to provide at least one groove 37 parallel to the circumferential direction. More preferably, the width or depth is 0.2 mm or more and 2 mm or less. More preferably, a combination of a shallow wide groove 39 and a narrow groove 41 is used.
[0022]
The peripheral groove 37 includes a groove 39 having a gentle angle with respect to the curved surface of the inner wall of the concave mold 19 and a groove 41 having a small acute angle. The circumferential groove 37 may be a gutter shape having a curved surface. If the circumferential groove 37 is too large, the outer shape of the half shell 47 will be damaged, and the outer shape of the preformed body will be non-uniform. Non-uniformity of the preform may impair the uniformity of the core. If the circumferential groove 37 is too small, the half shell 47 may be attached to the convex mold 21. If the circumferential groove is small, a plurality of grooves may be provided. Thereby, the half shell 47 can be more reliably attached to the concave mold 19 while maintaining the half shell shape.
[0023]
Assuming that the volume of the cavity 33 is V1 and the volume of the uncrosslinked polymer composition 45 charged therein is V2, if V2 is larger than V1, excess polymer composition 45 flows out of the cavity 33. That is, when V2 / V1 exceeds 100%, the vehicle goes out of the cavity 33 by that much. This half shell 47 is accompanied by extra burrs that have flowed out. It was found that when a preformed body having large burrs was used when the core 3 was formed into a core 3, the core coating layer was likely to be uneven in thickness due to uneven flow of the composition in the burrs. Therefore, it is necessary that the volume V2 of the polymer composition forming the half shell 47 is not too large with respect to the cavity V1. In the method for manufacturing a half shell according to the present invention, the ratio V2 / V1 of V2 to V1 is 100% or less.
[0024]
Conversely, if V2 is too small with respect to V1, the polymer composition 45 cannot be sufficiently plastically deformed by the mold 17. It was found that the flow of the polymer composition 45 in the preforming was not uniform due to insufficient so-called habituation. When the preform is used to crosslink the core, the flow of the polymer in the core molding tends to be uneven. The condition under which a stable and uniform core 3 can be manufactured is that the ratio V2 / V1 is 90% or more. Therefore, the ratio V2 / V1 needs to be 90% or more and 100% or less. More preferably, the ratio V2 / V1 is 94% or more and 100% or less. By controlling the amount of the polymer composition in this manner, a half shell 47 having a uniform thickness can be obtained.
[0025]
At this time, the half shell 47 is attached to the concave mold 19 of the plate 23 (FIG. 2). The concave mold 19 on the plate 23 is moved from a position below the convex mold 21 and arranged at a position of a center supply device (not shown). Here, the center 5 is put on the half shell 47 only on the plate 25 side, and the plate 23 is returned to the original position by the support shaft 29. Note that, instead of the above-described movement of the plate 23, a configuration may be adopted in which the convex mold and the center supply device move. In addition, the center 5 may be inserted by a center supply device or manually.
[0026]
FIG. 5 is a cross-sectional view showing the positional relationship between the center 5 and the pair of half shells 47 and 47 ′ in the preforming. As described above, after the center is inserted, the hinge portion 31 is rotated, and the plate 27 is folded back to the plate 25. The half shell 47 'on the plate 27 side is pushed over the center 5 from above. The state of this pressing is shown in FIG. By this step, a preform is formed.
[0027]
In FIG. 5, the shapes of the half shell molding cavity 33 and the half shell 47 are indicated by phantom lines. R1 shown in the figure is a convex portion radius of the convex mold 21 for half shell molding. r2 is the radius of the center 5. The final position is shown where the center 5 is settled when it is preformed and covered by the upper and lower half shells 47 and 47 '. The shapes of the upper and lower half shells 47 and 47 'are the same. As can be seen from this figure, r1 is smaller than r2. That is, the thickness of the half shell 47 is larger than the thickness of the coating layer formed by the preliminary molding. Therefore, the half shells 47 and 47 'are pressed against the center by the preforming, are brought into close contact with the center, and are habitually attached.
[0028]
The relationship between r1 and r2 is preferably 0.10 ≧ (r2-r1) / r2 ≧ 0. When the value of (r2−r1) / r2 is greater than 0.10, burrs are generated at the time of forming and crosslinking the core of the half shell. In proportion to the size of this burr, the flow of the polymer composition 45 tends to be uneven. On the other hand, if the value is smaller than 0, the adhesion of the preform tends to be insufficient. According to the mold 17 for forming a half shell, a preform having good adhesion to the center and good flow of the polymer composition 45 at the time of crosslinking of the core can be formed. The preform molded by the molding device 15 is taken out of the device for core molding.
[0029]
FIG. 6 is a cross-sectional view showing a state where the preform 53 is molded into a core using the mold 51 of the core molding apparatus 50. The core molding die 51 includes an upper die 55 and a lower die 57 which form a cavity having a finished shape of the core. On the preform 53, a precoat layer 59 having a uniform thickness is formed. The preform 53 is put into the lower mold 57. The preform 53 is heated and pressurized in a cavity formed by the upper mold 55 and the lower mold 57 and crosslinked to form the core 3. In the core 3 using the preformed body 53 managed as described above, the thickness of the outer layer 7 (the intermediate layer of the golf ball 1) of the core 3 is uniform, and the uniformity is high.
[0030]
The surface of the molded core 3 is covered with a cover 11. The cover 11 is formed by an injection molding method, a compression molding method, or the like. Next, the paint layer 13 is formed on the surface of the cover. The paint layer is marked and the golf ball is finished.
[0031]
【Example】
Hereinafter, the effects of the present invention will be clarified based on examples, but the present invention should not be construed as being limited based on the description of the examples.
[0032]
[Example 1]
The steps from the half shell molding to the molding of the preform were performed by the molding apparatus 15 shown in FIG. The half shell was formed using a cavity 33 in which the radius of curvature r1 of the convex mold 21 (see FIG. 3) shown in FIG. 5 was 15.5 mm. Unvulcanized rubber obtained by kneading 100 parts by mass of high cis polybutadiene (BR01 from JSR), 20 parts by mass of zinc white, 30 parts by mass of zinc acrylate and 3 parts by mass of dicumyl peroxide as a material of the half shell. The composition was used. This rubber composition was made into a plug shape, and its volume V2 was adjusted so as to be 90% of the volume V1 of the half shell molding cavity 21. A preform 53 was formed using a pair of half shells 47 formed at this ratio and a center 5 mainly composed of high cis polybutadiene having a radius r2 of 15.75 mm. The preformed body 53 thus obtained was vulcanized at 160 ° C. for 25 minutes in a core forming die 51 shown in FIG. 6 to obtain a core.
[0033]
[Example 2, Comparative Example 1, and Comparative Example 4]
A core was obtained in the same manner as in Example 1, except that the volume ratio V2 / V1 of the uncrosslinked polymer was 92%, 85%, and 105%, respectively.
[0034]
[Example 3 and Comparative Example 2]
The radius of curvature r1 of the convex mold was 16 mm, and the radius r2 of the center was 16.75. Then, a core was obtained in the same manner as in Example 1 except that the volume ratio V2 / V1 of the rubber composition was 94% and 88%, respectively.
[0035]
[Example 4 and Comparative Example 3]
The radius of curvature r1 of the convex mold was set to 16.5 mm, and the radius r2 of the center was set to 16.75. Then, a core was obtained in the same manner as in Example 1 except that the volume ratio V2 / V1 of the rubber composition was set to 99% and 88%, respectively.
[0036]
[Evaluation of uniformity]
These cores were cut in two directions, a zenith direction and an equator direction, and the thickness deviation of the core coating layer was measured. The vertex direction is the vertical direction when the core is vulcanized, and the equator direction is the joint direction of the mold. The uneven thickness was determined by taking the difference between the maximum value and the minimum value of the thickness of the core coating layer. Table 1 shows the maximum value of the uneven thickness values of the 100 samples measured.
[0037]
[Table 1]

[0038]
In Table 1, in the manufacturing methods of Comparative Examples 1 to 4, the thickness of the core coating layer was large. On the other hand, in the manufacturing methods of Examples 1 to 4, a core having a small unevenness, that is, a core having good sphericity can be obtained.
[0039]
【The invention's effect】
As described above, according to the golf ball manufacturing method of the present invention, a core with high uniformity can be obtained efficiently. A golf ball using this core is excellent in flying, directionality and other characteristics with little variation.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view showing a golf ball obtained by a manufacturing method according to an embodiment of the present invention.
FIG. 2 is a perspective view showing a part of an apparatus for forming a preform of the core of the golf ball of FIG. 1;
FIG. 3 is a cross-sectional view illustrating a mold used in the method of manufacturing the golf ball core of FIG. 2;
FIG. 4 is a cross-sectional view showing a part of steps of a core manufacturing method using the mold of FIG. 3;
FIG. 5 is a cross-sectional view showing a part of the steps of the method of forming a preform in FIG. 2;
FIG. 6 is a cross-sectional view showing a part of the steps of the method for manufacturing the golf ball core of FIG. 1;
FIG. 7 is a cross-sectional view illustrating a part of a method of manufacturing a conventional golf ball core.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Golf ball 3 ... Core 5, 87 ... Center 7 ... Intermediate layer (core coating layer)
11: Cover 17, 71: Half shell molding mold 21, 75: Half shell molding convex mold 19, 77 ... Half shell molding concave mold 33, 79 ... Half-shell molding cavity 35 Half-shell molding concave mold inclined surface 37 Half-shell molding concave mold groove 45, 73 Polymer composition 47, 74 Half shell 15・ Preformed body forming device 81 ・ ・ ・ Burrs 51, 91 ・ ・ ・ Core forming dies 53, 85 ・ ・ ・ Preformed bodies

Claims (4)

A half-shell molding mold having a half-shell-shaped cavity, a step in which a half-shell is molded by inserting an uncrosslinked polymer composition,
A step of forming a pre-formed body by covering the center with the pair of half shells,
When the volume of the cavity is V1 and the volume of the polymer composition is V2, the ratio V2 / V1 is 90% or more and 100% or less. Golf ball manufacturing method. The half-shell molding die includes a first die having a hemispherical convex portion and a second die having a hemispherical concave portion. The radius of the convex portion is r1, and the radius of the center is The golf ball manufacturing method according to claim 1, wherein when the radius is r2, the relationship between r1 and r2 is 0.10≥ (r2-r1) / r2≥0. The method of manufacturing a golf ball core according to claim 2, wherein the second mold has at least one groove parallel to a circumferential direction. 4. The method of manufacturing a golf ball according to claim 1, wherein the ratio V2 / V1 is 94% or more and 100% or less. 5.

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