JP2006051148A - Manufacturing method of golf ball - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a golf ball, which has satisfactory manufacturing operability and excellent productivity. <P>SOLUTION: The manufacturing method of the golf ball consisting of a core and a cover which covers the core comprises: (a) a process of forming fluororesin thin film (30) in nearly the same form of a hemispherical cavity of a mold for core molding by using a cavity mold (10) having the hemispherical cavity and a core mold (20) having a hemispherical raised section; (b) (i) a process of fixing the fluororesin thin film (30) in a form along the hemispherical cavity (41) of the mold for core molding (40), (ii) a process of arranging a composition for core in the cavity, (iii) a process of press-molding the composition for core in the mold for core molding through the fluororesin thin film to form a spherical core, and (iv) a process of taking the core out of the mold; and (c) a process of covering the core with the cover. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing a golf ball, and more particularly to a method for manufacturing a golf ball having excellent manufacturing workability and excellent productivity.

  Generally, a golf ball includes a thread wound golf ball and a solid golf ball. A solid golf ball is composed of a core and a cover covering the core. The core may be composed of one layer or two or more layers, but is basically composed of a rubbery component and is usually an α, β-ethylenically unsaturated carboxylic acid metal salt such as high-cis polybutadiene, zinc acrylate or zinc methacrylate. It is obtained by vulcanizing and molding a rubber composition containing a peroxide crosslinking agent and other additives. However, when press molding or injection molding is performed using the rubber composition, there is a problem that the mold release property of the molded product is extremely poor.

Therefore, in order to improve mold releasability, a number of manufacturing methods have been proposed from both the following molds and molded products.
(1) A mold release agent is sprayed or baked on the cavity surface of the core molding die (Patent Document 1, etc.).
(2) A mold release agent is dipped in advance on the core preform (Patent Document 1, etc.).
(3) A mold release agent is kneaded in advance into the core preform (Patent Document 2, etc.).
(4) A mold release process is performed on the mold surface (Patent Document 3 etc.).
(5) It shape | molds through a polyester release sheet (patent document 4 grade | etc.,).

Patent Document 1 discloses a polyfluorocarbon group-containing phosphonic acid represented by the general formula RfCnH _2n PO (OH) ₂ [Rf is a polyfluorocarbon group having 4 to 20 carbon atoms, and n is 1 to 3] A release agent for golf balls is disclosed in which a salt and silicone oil or wax are dissolved or dispersed in an organic medium or an aqueous medium.

  Patent Document 2 discloses a rubber composition for a solid golf ball containing 10 to 60 parts by weight of a metal salt of an unsaturated carboxylic acid and 0.3 to 5.0 parts by weight of a white sub to 100 parts by weight of a base rubber. It is disclosed.

  Patent Document 3 is characterized in that a golf ball molding material is supplied into a cavity of a mold in which a solvent-soluble fluororesin film is formed on the surface of a cavity of a golf ball molding die body, and compression molding or injection molding is performed. A method for manufacturing a golf ball is disclosed.

Patent Document 4 discloses a method for producing a solid golf ball comprising a core and a cover covering the core, the method comprising (a) a step of preparing a core composition,
(B) a step of arranging a polyester film along the cavity shape in the cavity of the core molding die;
(C) including a step of vulcanizing the composition for a core in a mold through the polyester film to form a core, and (d) a step of forming a cover on the core. A method for producing a solid golf ball is disclosed.

  However, the method (1) is generally widely used. However, a mold release agent is mixed into a molded product to cause a defective product, or the mold release agent attached to the molded product is washed and removed. There have been problems such as periodic cleaning of the deposited release agent, and spraying the release agent every press or every several presses, resulting in poor productivity.

  In the methods (2) and (3), as in the above (1), the release agent is mixed into the molded product to generate defective products, or the mold release agent adhering to the molded product surface is removed by washing. There was a problem such as necessity. Further, this method alone has a problem that the releasability is not improved, and it is necessary to apply a release agent to the mold.

In the method (4), there is a method using, for example, a fluororesin coating as a mold release treatment on the mold surface, but there are the following problems.
(I) In order to improve the adhesion strength between the release layer and the mold surface, the surface of the mold is roughened by blasting using a shot material such as alumina, but repeated blasting for each coating of the release layer When the process is performed, the mold accuracy decreases.
(Ii) The durability of the release layer itself with respect to heat and pressure during core molding is low, and the release property can only be maintained for several weeks, resulting in an increase in manufacturing cost.
(Iii) Even when the release layer deteriorated as described above is removed and treated again, the fluororesin is insoluble in the solvent and cannot be removed by the solvent, so a physical method such as blasting is required. The removal process is very time consuming.
(Iv) In order to shorten the time required for the removal step, there is a method in which the mold is placed in a high-temperature furnace at 400 ° C. or higher, and the release layer is decomposed and carbonized, but corrosive fluorine gas is generated, Mold life due to high temperature treatment is reduced.
(V) Although there is a method (Patent Document 3) in which not only the above-mentioned fluororesin coating but also a solvent-soluble fluororesin film is applied, the durability is low and the production cost increases and the profitability is high although the material cost is high. bad.
(Vi) Since the baking process is performed at a temperature of 350 to 400 ° C. higher than the melting point of the fluororesin, the processing residual stress of the cavity is relaxed, and the cavity may be deformed.

In the method (5), the continuous use heat-resistant temperature of the polyester resin is low, so that there is a problem that the durability of the sheet is low.
JP-A-6-344353 JP-A-57-78875 JP-A-5-318491 Japanese Patent Laid-Open No. 11-169487

  An object of the present invention is to solve the problems of the conventional method for producing a golf ball as described above, and to provide a method for producing a golf ball having good production workability and excellent productivity. To do.

  As a result of intensive studies to achieve the above object, the present inventors have found that in a golf ball manufacturing method comprising a core and a cover coated on the core, the hemispherical cavity of the core molding die is substantially Form a fluororesin thin film in the same shape, fix the fluororesin thin film along the hemispherical cavity of the core molding die, and insert the core composition into the core molding die via the fluororesin thin film. It was found that a golf ball having good manufacturing workability and excellent productivity can be obtained by press molding under heating to form a spherical core, and the present invention has been completed.

That is, the present invention is a golf ball manufacturing method comprising a core and a cover coated on the core, the manufacturing method comprising:
(A) A fluororesin is molded using a cavity mold (10) having a hemispherical cavity and a core mold (20) having a hemispherical convex part (21) to form a hemispherical core mold Forming a fluororesin thin film (30) in substantially the same shape as the cavity;
(B) (i) a step of fixing the fluororesin thin film (30) so as to be along the hemispherical cavity (41) of the core mold (40);
(Ii) disposing a core composition in the cavity;
(Iii) forming the spherical core by press molding the core composition in the core molding die through the fluororesin thin film;
And (iv) a method of manufacturing a golf ball, comprising: removing the core from the mold; and (c) covering a cover on the core.

In order to more suitably implement the present invention,
The fluororesin is a polytetrafluoroethylene resin and / or a derivative thereof;
The fixing in the step (bi) is performed by a magnet or a combination of a holding plate and a countersunk screw;
The removal of the core in the step (b-iv) is performed together with the fluororesin thin film (30);
The fluororesin thin film has a thickness of 0.01 to 3.00 mm;
It is preferable.

The golf ball of the present invention forms a fluororesin thin film in substantially the same shape as the hemispherical cavity of the core molding die, and fixes the fluororesin thin film along the hemispherical cavity of the core molding die, By forming the core composition by press molding under heating in the core molding die through this fluororesin thin film,
There is no need to remove the mold during the coating, baking and removing process as in the case of using a fluororesin coating, and the productivity is greatly improved;
Since the release agent is not mixed in the molded product, the occurrence of defects due to the release agent can be greatly reduced;
Since there is no mold release agent on the core surface after molding, no washing and removing step is required;
The excellent mold releasability of the fluororesin thin film prevents the molded product from adhering to the upper mold when the mold is opened, and the cooling process for the purpose of assisting the mold release can be omitted, and the productivity is remarkably improved. Improved and energy loss due to heating and cooling can be greatly reduced;
Since the fluororesin thin film does not adhere to the cavity, the lower mold of the core mold does not need to be fixed by mechanical fixing means. It became possible to take out many cores at the same time together with the fluororesin thin film corresponding to the molds of the molds, and the productivity could be greatly improved;
Therefore, it has good manufacturing workability and can have excellent productivity.

  Hereinafter, the manufacturing method of the golf ball of the present invention will be specifically described with reference to FIGS. FIG. 1 is a schematic cross-sectional view of one embodiment of a cavity mold for forming a fluororesin thin film used in the golf ball manufacturing method of the present invention. FIG. 2 is a schematic cross-sectional view of one embodiment of a core molding die used in the golf ball manufacturing method of the present invention. FIG. 3 is a schematic cross-sectional view of another embodiment of a core mold used in the golf ball manufacturing method of the present invention. 1 shows a cavity mold (10) having two cavities, and FIGS. 2 and 3 show a core molding mold (40) having two cavities for the purpose of explanation, but the present invention is not limited thereto. It may be a multi-cavity mold that is actually used for manufacturing the core. 2 and 3 show only the lower mold, it is a core molding die (40) composed of an upper mold and a lower mold.

The method for manufacturing a golf ball of the present invention can be roughly divided into (a) a step of forming a fluororesin thin film, (b) a step of forming a core, and (c) a step of covering a cover on the core. The The golf ball manufacturing method of the present invention is particularly characterized by the steps (a) and (b). The step (b) is, as described above, (i) a step of fixing the fluororesin thin film (30) along the hemispherical cavity (41) of the core molding die (40),
(Ii) disposing a core composition in the cavity;
(Iii) a step of press-molding the core composition in the core molding die through the fluororesin thin film to form a spherical core; and (iv) removing the core from the die. Process,
It consists of the following four steps.

  In the step (a), as shown in FIG. 1, a fluororesin is molded using a cavity mold (10) having a hemispherical cavity and a core mold (20) having a hemispherical convex part (21). Then, the fluororesin thin film (30) is formed in substantially the same shape as the hemispherical cavity of the core molding die. The molding method is not particularly limited, and press molding, injection molding, or the like can be used.

  Examples of the fluororesin used in the fluororesin thin film (30) in the golf ball manufacturing method of the present invention include tetrafluoroethylene-perfluorovinyl ether copolymer (PFA), polytetrafluoroethylene resin (PTFE), tetra Examples thereof include fluoroethylene-hexafluoropropylene copolymer (FEP), polychlorotrifluoroethylene resin (PCTFE), and derivatives thereof. Specific examples of the fluororesin include fluororesins commercially available from Daikin Industries, Ltd. (for example, “Neoflon PFA (melting point: 310 ° C.)”, “Polyflon PTFE (melting point: 327 ° C.)”, “Neoflon FEP (melting point: 270 ° C.) ) "," Neoflon PCTFE (melting point 212 ° C) ") and the like.

  The fluororesin thin film (30) desirably has a thickness of 0.01 to 3.00 mm. Since the fluororesin has a low thermal conductivity (0.25 W / (m · K)), if the fluororesin thin film is thick, the molding time of the core becomes long, and the strength during heating is low. Since it is deformed by the expansion pressure, it is desirable to make it as thin as possible. Therefore, the upper limit of the thickness of the fluororesin thin film (30) is preferably 2.0 mm or less, more preferably 1.0 mm or less, from the viewpoint of thermal conductivity and deformation during heating. Further, since the molding becomes difficult when the thickness of the fluororesin thin film becomes too small, the lower limit is preferably 0.03 mm or more, more preferably 0.05 mm or more from the viewpoint of moldability.

  In the step (bi), as described above, the fluororesin thin film (30) obtained in the step (a) is placed along the hemispherical cavity (41) of the core molding die (40). Fix it. The fluororesin thin film (30) not only exhibits good releasability to the molded core, but also does not adhere to the hemispherical cavity (41) of the core molding die (40). In order to prevent the fluororesin thin film from being removed from the cavity when demolding, a fixing means such as a magnet as shown in FIG. 2 or a combination of a holding plate and a countersunk screw as shown in FIG. It is preferable to fix at a position other than the cavity of the core molding die. The magnet is not particularly limited as long as it can withstand the heating temperature during core molding and has a magnetic force that prevents the fluororesin thin film from being removed from the cavity during the core molding process. Even if the pressing plate and the countersunk screw are used, the material and the like are not particularly limited as long as they can withstand the heating temperature during core molding and the fluororesin thin film does not come off the cavity during the core molding process.

  Since the fluororesin thin film (30) is not in close contact with the cavity mold as described above, it can be easily removed by removing the fixing means when it deteriorates or deforms after long-term use. It can be easily replaced with a fluororesin thin film.

  The fluororesin used in the production method of the present invention having the above-described excellent mold release property and heat resistance is used as long as it does not cause deformation of the thin film after use when it is used as a fluororesin thin film. Is possible.

The fluororesin has a large coefficient of linear expansion (4.5 to 12 × 10 ⁻⁵ / ° C.), but in the practice of the present invention, even when performing a cooling step after molding for the purpose of assisting mold release, The fixing means as described above does not come off the surface of the cavity mold.

  The core composition used in the step (b-ii) basically comprises a rubber composition containing a base rubber, a crosslinking agent, a co-crosslinking agent, a filler, and an anti-aging agent if necessary. . As the base rubber used in the core of the present invention, natural rubber, synthetic rubber or a mixture thereof conventionally used for solid golf balls is used. Examples of the synthetic rubber include polybutadiene rubber, polyisoprene rubber, styrene polybutadiene rubber, and ethylene-propylene-diene rubber (EPDM). Particularly preferred are so-called high cis polybutadiene rubbers having a cis-1,4-structure of at least 40% or more, preferably 80% or more. Furthermore, in the present invention, it is desirable in view of the resilience performance of the obtained golf ball that the polybutadiene rubber accounts for 60% by weight or more of the base rubber.

  Crosslinkers used in the core include organic peroxides such as dicumyl peroxide, 1,1-bis (t-butylperoxy) -3,5-trimethylcyclohexane, 2,5-dimethyl-2,5- Examples thereof include di (t-butylperoxy) hexane and t-butyl peroxide, and dicumyl peroxide is preferable. A compounding quantity is 0.5-5.0 weight part with respect to 100 weight part of base rubbers. If the amount is less than 0.5 parts by weight, it becomes too soft and the rebound becomes worse and the flight distance decreases. If it exceeds 5.0 parts by weight, it becomes too hard and the feeling at the time of hitting becomes worse.

  As a metal salt of α, β-ethylenically unsaturated carboxylic acid used as a co-crosslinking agent, in particular, α, β-ethylenically unsaturated carboxylic acid having 3 to 8 carbon atoms such as acrylic acid or methacrylic acid, Monovalent or divalent metal salts such as zinc and magnesium salts can be mentioned, and zinc acrylate imparting high resilience is preferred. The amount is 15 to 50 parts by weight, preferably 20 to 35 parts by weight, based on 100 parts by weight of the base rubber. If it exceeds 50 parts by weight, it will be too hard and the feeling at impact will be poor, and if it is less than 15 parts by weight, the resilience will be poor and the flight distance will be reduced.

  The filler used for the core may be any compound that is usually blended in the core of the golf ball, such as inorganic salts (specifically, zinc oxide, barium sulfate, calcium carbonate), high specific gravity metal powder (for example, tungsten). Powder, molybdenum powder, etc.) and mixtures thereof. The blending amount depends on the specific gravity and size of the cover and the core and is not limited, but is 10 to 100 parts by weight, preferably 10 to 40 parts by weight with respect to 100 parts by weight of the base rubber. If it is less than 10 parts by weight, the core becomes too light and the ball becomes too light. If it exceeds 100 parts by weight, the core becomes too heavy and the ball becomes too heavy.

  Further, the golf ball core of the present invention may be appropriately blended with an anti-aging agent, a peptizer, and other components that can be normally used for the production of a solid golf ball center. The anti-aging agent is preferably 0.1 to 3.0 parts by weight with respect to 100 parts by weight of the base rubber.

  The core composition used in the production method of the present invention is obtained by kneading the above components using an appropriate kneader such as a normal roll.

In the above (b-iii) step, fluororesin thin film through, 140 to 170 ° C. the core composition in the core mold, and press-molded at 90~120kgf / cm ² 10~40 minutes To form a spherical core.

  As described above, since the fluororesin thin film (30) is not in close contact with the cavity mold, in addition to the low thermal conductivity of the fluororesin, it causes a decrease in the thermal conductivity. This is improved by pressing the fluororesin thin film against the cavity by charging and clamping the rubber composition (plug).

  The core preferably has a diameter of 10 to 42 mm, preferably 20 to 42 mm, more preferably 30 to 42 mm.

  In the step (b-iv), the obtained core is taken out from the core molding die (40). However, only the core may be taken out, or the core may be taken out together with the fluororesin thin film (30). Since the fluororesin thin film does not adhere to the cavity, it is necessary to fix the fluororesin thin film using the fixing means as described above in the upper mold of the core mold, but the lower mold of the core mold Then, there is no need to fix by mechanical fixing means, and if there is no problem in the rigidity of the release layer, together with the fluororesin thin film connected with a large number of cavity-shaped parts corresponding to a multi-cavity mold A large number of cores can be taken out at the same time, and productivity can be greatly improved.

  In the method for manufacturing a golf ball of the present invention, the cover is coated on the core (step (c)), but it may be a cover having a multilayer structure of two or more layers as well as a single layer structure. Materials include thermoplastic resins, in particular, ionomer resins, polyesters, in which a part of carboxylic acid in a copolymer of α-olefin and α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms is neutralized with metal ions, Nylon or the like or a mixture thereof is used. The α-olefin in the ionomer resin is preferably ethylene or propylene, and the α, β-unsaturated carboxylic acid is preferably acrylic acid or methacrylic acid. Further, the metal ions to be neutralized include alkali metal ions such as Na ions, K ions, Li ions, etc .; divalent metal ions such as Zn ions, Ca ions, Mg ions, etc .; trivalent metal ions such as Al ions, etc. And a mixture thereof, Na ions, Zn ions, Li ions and the like are often used from the viewpoint of resilience, durability, and the like. Specific examples of the ionomer resin include, but are not limited to, Surlyn AD8541, AD8542 (manufactured by DuPont), Hi-Milan 1557, 1605, 1652, 1705, 1706, 1707, 1855, 1856 (Mitsui Dupont) Polychemical Co., Ltd.), Iotek 7010, 8000 (Exxon Co., Ltd.) and the like can be exemplified.

  Further, in the present invention, in addition to the resin as a main component, the cover composition may include a filler such as barium sulfate, a colorant such as titanium dioxide, and other additives such as a dispersion, as necessary. Agents, anti-aging agents, ultraviolet absorbers, light stabilizers and fluorescent materials or fluorescent brightening agents, etc. may be contained within the range in which the desired properties of the golf ball cover are not impaired. The blending amount is preferably 0.1 to 5.0 parts by weight with respect to 100 parts by weight of the cover resin.

  The cover layer of the present invention can be formed by a generally known method used for forming a golf ball cover, and is not particularly limited. The cover composition is pre-molded into a half-shell half shell, and the two cores are used to wrap the core and pressure molded at 130-170 ° C. for 1-15 minutes, or the cover composition is directly cored A method of wrapping the core by injection molding may be used.

  The cover has a thickness of 0.5 to 5.0 mm, preferably 1.0 to 4.0 mm. If it is smaller than 0.5 mm, the hardness of the entire ball is reduced and the coefficient of restitution is reduced, and if it is larger than 5.0 mm, the hardness of the entire ball is increased and the controllability and feeling at impact are deteriorated.

  When forming the cover, if necessary, a number of dimples called dimples are formed on the surface. The golf ball of the present invention is usually put on the market with a paint finish, a marking stamp, etc. in order to enhance the beauty and increase the commercial value.

  Examples The present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

(Examples 1-8 and Comparative Examples 2-4)
(I) Formation of Release Resin Thin Film Using a cavity mold (10) having a hemispherical cavity and a core mold (20) having a hemispherical convex part (21) as shown in FIG. The thin film materials shown in Tables 3 and 4 below are press-molded at 350 ° C. for 30 minutes, and the release resin thin film having the same shape as the hemispherical cavity of the core molding die and the thickness shown in the same table ( 30) was formed. The continuous heat-resistant temperature of the used thin film material was measured, and the results are shown in the same table. The test method was performed as described later.

(Ii) Production of core Magnet (42) is formed in such a manner that the release resin thin film obtained in (i) is placed along hemispherical cavity (41) of core molding die (40) as shown in FIG. ), And knead the core rubber composition having the composition shown in Table 1 below to produce a core plug, put in the cavity, and heat-press in the mold at 150 ° C. for 20 minutes. As a result, a core having a diameter of 38.5 to 39.5 mm was obtained. This process was repeated to evaluate the release durability, and the results are shown in Tables 3-4. The test method was performed as described later.

(Comparative Example 1)
As a mold release treatment, Examples 1 to 3 were applied except that a fluorine mold release agent shown in Table 4 below was applied to the surface of a core mold having a hemispherical cavity and baked at 130 ° C. for 1 minute. 8 and Comparative Examples 2 to 4 were used to produce cores, and the mold release durability was evaluated. The results are shown in Table 4.

(Comparative Example 5)
A core was prepared in the same manner as in Examples 1 to 8 and Comparative Examples 2 to 4 except that the mold release treatment was not performed, and the mold release durability was evaluated. The results are shown in Table 4.

(Note 1) Product name, high cis polybutadiene rubber manufactured by JSR Co., Ltd. (Note 2) Zinc acrylate commercially available under the trade name “ZNDS-90S” from Nippon Distillation Co., Ltd. (Note 3) Toho Zinc Co., Ltd. Commercially available zinc oxide (Note 4) Dicumyl peroxide available from Nippon Oil & Fats Co., Ltd. under the trade name “Park Mill D” (Note 5) Commercially available diphenyl disulfide from Sumitomo Seika Co., Ltd.

Formation of Cover The cover composition having the formulation shown in Table 2 below was mixed with a twin-screw kneading extruder to obtain a pellet-shaped cover composition. The extrusion conditions were a screw diameter of 45 mm, a screw speed of 200 rpm, and a screw L / D = 35, and the blend was heated to 220-260 ° C. at the die position. A solid golf ball having a diameter of 42.7 mm is formed by coating the cover composition prepared as described above by injection molding on the core obtained as described above to form a cover layer, and applying paint. Got.

(Note 6) Sodium ion neutralized ethylene-methacrylic acid copolymer ionomer resin manufactured by Mitsui DuPont Polychemical Co., Ltd. (Note 7) Zinc ion neutralized ethylene-methacrylic acid copolymer system manufactured by Mitsui DuPont Polychemical Co., Ltd. Ionomer resin

(Test method)
(1) Heat-resistant temperature for continuous use Heating was performed at normal pressure, and the limit temperature at which the shape of the material did not change was measured.

(2) Releasing durability In the core molding die on which the release layer is formed, the process of press molding the core composition to form a spherical core is repeated, and the number of times until releasing is measured. The index was expressed by an index with the number of moldings of Example 8 taken as 100. The larger the index value, the better the release durability of the release layer.

PFA: Tetrafluoroethylene-perfluorovinyl ether copolymer commercially available from Daikin Industries, Ltd. under the trade name “Neofuron PFA” PTFE: Tetrafluoroethylene resin commercially available from Daikin Industries, Ltd. under the trade name “Polyflon PTFE” FEP: Tetrafluoroethylene-hexafluoropropylene copolymer marketed by Daikin Industries, Ltd. under the trade name “Neofuron FEP” FR: Fluorine mold release agent marketed by Neos Co., Ltd. under the trade name “Flease” PR: Toyobo Polyester resin available under the trade name "Toyobo Ester" from the company

  As is apparent from the results in Tables 1 and 2, the golf ball manufacturing method of Examples 1 to 8 is different from the golf ball manufacturing method of Comparative Examples 1 to 3 in that the mold for core molding is separated. It was found that the mold durability was very excellent, the manufacturing workability was good, and the productivity was excellent.

  On the other hand, in the golf ball manufacturing method of Comparative Example 1, the fluorine-based mold release agent was baked on the cavity surface of the core mold, but when the core molding was repeated, the mold release agent was applied to the core surface. Since it adhered and peeled off, the mold release durability was very inferior.

  In the golf ball manufacturing methods of Comparative Examples 2 to 4, the mold release durability is superior to that of Comparative Example 1 because the release resin thin film as in the example is fixed to the cavity surface of the core mold. Although the thickness of the release resin thin film is increasing in order, it is improving little by little, but since the polyester resin is used for the release resin thin film, the continuous use heat resistance temperature is very low, Compared with the examples, the mold release durability was very inferior.

  In the golf ball manufacturing method of Comparative Example 5, since the mold release treatment was not performed on the cavity of the core molding die, the mold could not be released once.

1 is a schematic cross-sectional view of one embodiment of a molding die for forming a fluororesin thin film used in the golf ball manufacturing method of the present invention. 1 is a schematic cross-sectional view of one embodiment of a core molding die used in the method for producing a golf ball of the present invention. It is the cross-sectional schematic of the other aspect of the metal mold | die for core formation used for the manufacturing method of the golf ball of this invention of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Cavity metal mold | die 20 ... Core metal mold | die 21 ... Hemispherical convex part 30 ... Fluorine resin thin film 40 ... Mold for core forming 41 ... Hemispherical cavity 42 ... Magnet 43 ... Countersunk screw 44 ... Holding plate

Claims (5)

A golf ball manufacturing method comprising a core and a cover coated on the core, the manufacturing method comprising:
(A) A fluororesin is molded using a cavity mold (10) having a hemispherical cavity and a core mold (20) having a hemispherical convex part (21) to form a hemispherical core mold Forming a fluororesin thin film (30) in substantially the same shape as the cavity;
(B) (i) a step of fixing the fluororesin thin film (30) so as to be along the hemispherical cavity (41) of the core mold (40);
(Ii) disposing a core composition in the cavity;
(Iii) forming the spherical core by press molding the core composition in the core molding die through the fluororesin thin film;
(Iv) A method for producing a golf ball, comprising: a step of removing the core from the mold; and (c) a step of covering a cover on the core.   The method according to claim 1, wherein the fluororesin is a polytetrafluoroethylene resin and / or a derivative thereof.   The method according to claim 1 or 2, wherein the fixing in the step (bi) is performed by a magnet or a combination of a holding plate and a countersunk screw.   The method according to any one of claims 1 to 3, wherein the removal of the core in the step (b-iv) is performed together with the fluororesin thin film (30). The method according to claim 1, wherein the fluororesin thin film has a thickness of 0.01 to 3.00 mm.

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