JP2003339912A - Golf ball and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a golf ball which has the excellent durability to repeated shots and has good spin characteristics, repulsiveness and feeling of shooting even after the repeated shots. <P>SOLUTION: The golf ball is formed by covering a core with cover layers including an inner layer and outer layer, in which the inner layer of the covers is formed of an ionomer resin as a main material and the outer layer of the covers is formed of a non-ionomer resin as a main material and the surface of the inner layer of the cover is subjected to an acid treatment. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a golf ball having excellent durability against repeated hits, good spin characteristics, resilience and feel, and a method for producing the same.

[0002]

2. Description of the Related Art Among multiple-piece golf balls, a golf ball having a polyurethane elastomer as an outer layer of a cover and an ionomer resin as an inner layer as a main material has become a recent trend in a multiple-piece golf ball (JP-A-9-215775). Japanese Patent Laid-Open No. 11-104271
No. 5,885,172, US Pat. No. 6,213,894, etc.). Usually, when manufacturing such a multiple-piece golf ball, a vulcanized rubber core mainly composed of polybutadiene rubber is coated with an ionomer resin for the inner layer to a thickness determined by injection molding or molding, and then it is used as a cover. The method of coating the polyurethane elastomer is selected.

However, in this case, there is a problem that the ionomer resin and the polyurethane elastomer of the inner layer are difficult to be directly bonded. Insufficient adhesion causes problems such as a reduction in resilience and flight distance, a reduction in durability of a golf ball upon repeated impacts, and unstable spin characteristics.
Therefore, in order to eliminate such adhesiveness, a specific thermoplastic resin in the cover inner layer or the cover outer layer is blended (JP-A-11-137726), or an adhesive / primer is applied on the inner layer in advance. (JP-A-10-1797
No. 95, JP 2001-585A) and a method of increasing the adhesive strength by performing plasma or corona discharge treatment on the inner layer surface (US Pat. No. 6,315,915) have been proposed.

However, there is room for improvement in any of these methods. For example, in a method of blending a specific thermoplastic resin or a method of applying an adhesive / primer, the resilience of the ball may decrease. Further, in the method of performing plasma treatment or corona discharge treatment, or the method of applying an adhesive / primer, there is a case where the adhesiveness is insufficient and the physical properties of the ball may not be improved, and moreover, the introduction of expensive new equipment is required. If necessary, the number of molding steps may increase and the production cost may increase. Therefore, there has been a demand for the development of a manufacturing method capable of more easily and effectively improving the adhesive force between the inner layer and the outer layer, and a golf ball in which the inner layer and the outer layer are well bonded.

The present invention has been made in view of the above circumstances.
An object of the present invention is to provide a golf ball having good adhesion between the inner layer and the outer layer of the cover, excellent durability against repeated hits, and good spin characteristics, resilience and feel, and a method for producing the same.

[0006]

Means for Solving the Problems and Modes for Carrying Out the Invention As a result of extensive studies to achieve the above object, the present inventor has found that the inner layer is an ionomer resin and the outer layer is a non-ionomer resin such as a polyurethane elastomer as a main material. In producing a golf ball having a cover formed as described above, acid-cleaning the surface of the inner layer markedly improves the adhesive strength between the inner layer and the outer layer. For example, 0.5N or more / 4 by the measurement method described later. The inventors have found that an adhesive strength of 0.5 mm can be obtained, and completed the present invention.

Accordingly, the present invention provides the following golf ball and method for manufacturing the same. [Claim 1] In a golf ball having a core covered with a cover layer including an inner layer and an outer layer, the inner cover layer is formed of an ionomer resin as a main material, and the outer cover layer is formed of a non-ionomer resin as a main material. And the surface of the inner layer of the cover is acid-treated. [Claim 2] The golf ball according to claim 1, wherein the cover inner layer surface is surface-polished, and the surface-polished cover inner layer surface is acid-treated. [Claim 3] The golf ball according to claim 1 or 2, wherein the outer layer of the cover is formed mainly of polyurethane elastomer. [Claim 4] The golf ball according to any one of claims 1 to 3, wherein the adhesive strength between the surface of the cover inner layer and the outer layer of the cover is 0.5 N or more / 4.5 mm. [Claim 5] In a method for producing a golf ball comprising a core covered with a cover layer including an inner layer and an outer layer, the core is coated to form an inner cover layer containing an ionomer resin as a main material, and the inner surface of the inner cover layer is formed. A method of manufacturing a golf ball, which comprises forming an outer cover layer, which is mainly composed of a non-ionomer resin, over the inner cover layer after acid treatment. [Claim 6] The method according to claim 5, wherein after forming the inner layer of the cover, the surface is polished and then the polished surface is acid-treated. [Claim 7] The method according to claim 5 or 6, wherein the outer layer of the cover is formed of a polyurethane elastomer as a main material.

The present invention will be described in more detail below.
The golf ball of the present invention, as shown in FIG.
A golf ball having a cover layer including an inner layer 2 and an outer layer 3 coated thereon, wherein the surface of the inner layer 2 is acid-treated 2a.

The core of the golf ball of the present invention may be either a solid core or a wound core, but the solid core is preferably used from the viewpoint of the effect of the present invention.

The above solid core can be formed using a rubber composition containing, for example, a co-crosslinking agent, an organic peroxide, an inert filler, an organic sulfur compound and the like. As a base rubber of the rubber composition, a rubber containing polybutadiene as a main material is preferably used. The polybutadiene is not particularly limited, and those conventionally used in solid cores for golf balls can be used. For example, 1,4-cis polybutadiene containing at least 40% by weight of cis structure is preferably used. Examples of the base rubber include polybutadiene, natural rubber, polyisoprene rubber,
You may use what mix | blended styrene butadiene rubber etc.

Examples of the co-crosslinking agent include unsaturated carboxylic acids and metal salts of unsaturated carboxylic acids. Specific examples of the unsaturated carboxylic acid include acrylic acid, methacrylic acid, maleic acid, fumaric acid and the like, and acrylic acid and methacrylic acid are particularly preferably used. The metal salt of unsaturated carboxylic acid is not particularly limited, and examples thereof include those obtained by neutralizing the above unsaturated carboxylic acid with a desired metal ion. Specific examples thereof include zinc salts and magnesium salts of methacrylic acid and acrylic acid, and zinc acrylate is particularly preferably used.

The unsaturated carboxylic acid and / or the metal salt thereof is usually 10 parts by weight or more, preferably 15 parts by weight or more, and more preferably 2 parts by weight with respect to 100 parts by weight of the base rubber.
0 parts by weight or more, usually 60 parts by weight or less as an upper limit, preferably 50 parts by weight or less, more preferably 45 parts by weight or less,
Most preferably, the amount is 40% or less. If the blending amount is too large, it may become too hard and have an unbearable feel.
If the blending amount is too small, the resilience may decrease.

Commercially available products can be used as the organic peroxide, for example, Park Mill D (manufactured by NOF CORPORATION),
Perhexa 3M (Nippon Yushi Co., Ltd.), Luperco
231XL (manufactured by Atochem Co., Ltd.) can be preferably used. These may be used alone or in combination of two or more.

The above-mentioned peroxide is usually 0.1 part by weight or more, preferably 0.3 part by weight or more, more preferably 0.5 part by weight or more, and most preferably 0, based on 100 parts by weight of the base rubber. 0.7 parts by weight or more, and the upper limit is usually 5 parts by weight or less, preferably 4 parts by weight or less, more preferably 3 parts by weight or less, and most preferably 2 parts by weight or less. If the blending amount is too large or too small, it may not be possible to obtain a suitable feel, durability and resilience.

Examples of the inert filler include zinc oxide,
Barium sulfate, calcium carbonate and the like can be preferably used, and one kind may be used alone, or two or more kinds may be used in combination. The compounding amount of the inert filler is 100% of the above base rubber.
5 parts by weight or more, preferably 7 parts by weight or more, and usually 50 parts by weight or less as an upper limit, preferably 40 parts by weight.
The amount is not more than 30 parts by weight, more preferably not more than 30 parts by weight, most preferably not more than 20 parts by weight. If the blending amount is too large or too small, it may not be possible to obtain a proper weight and a suitable resilience.

Further, an anti-aging agent may be blended if necessary. For example, as a commercial product, Nocrac NS-
6, NS-30 (manufactured by Ouchi Shinko Chemical Industry Co., Ltd.), Yoshinox 425 (manufactured by Yoshitomi Pharmaceutical Co., Ltd.) and the like.
These may be used alone or in combination of two or more. The compounding amount of the antioxidant is the base rubber 10 described above.
0 parts by weight or more, usually 0 parts by weight or more, preferably 0.0
5 parts by weight or more, more preferably 0.1 parts by weight or more, most preferably 0.2 parts by weight or more, and the upper limit is usually 3 parts by weight or less, preferably 2 parts by weight or less, more preferably 1 part by weight or less, most preferably Is 0.5 parts by weight or less. If the blending amount is too large or too small, suitable resilience and durability may not be obtained.

A sulfur compound may be added to the solid core in order to improve the resilience of the golf ball.
The sulfur compound is not particularly limited as long as it can improve the resilience of the golf ball, and examples thereof include thiophenol, thionaphthol, halogenated thiophenol and metal salts thereof. More specifically, pentachlorothiophenol, pentafluorothiophenol, pentabromothiophenol, parachlorothiophenol, zinc salt of pentachlorothiophenol, zinc salt of pentafluorothiophenol, zinc salt of pentabromothiophenol, Zinc salt of parachlorothiophenol, diphenyl polysulfide having a sulfur number of 2 to 4, dibenzyl polysulfide, dibenzoyl polysulfide,
Examples thereof include dibenzothiazoyl polysulfide and dithiobenzoyl polysulfide, and zinc salts of pentachlorothiophenol and diphenyl disulfide are particularly preferably used.

The compounding amount of such a sulfur compound is usually 0.05 parts by weight or more based on 100 parts by weight of the base rubber.
It is preferably 0.1 parts by weight or more, more preferably 0.2 parts by weight or more, and the upper limit is usually 5 parts by weight or less, preferably 4 parts by weight.
It is recommended that the amount is not more than 3 parts by weight, more preferably not more than 3 parts by weight, most preferably not more than 2.5 parts by weight. If the blending amount is too large, the effect may reach the ceiling and no further effect may be seen, and if the blending amount is too small, the blending effect may not be sufficiently achieved.

The solid core can be produced by vulcanizing and curing a rubber composition containing each of the above components by a known method. For example, a kneader such as a Banbury mixer or a roll is used. Kneading, compression molding or injection molding in a core mold, the molded body at a temperature sufficient for the peroxide or co-crosslinking agent to act, for example, dicumyl peroxide as the peroxide, and the co-crosslinking agent. When zinc acrylate is used as the material, it is usually about 130 to 170.
C., especially 150-160.degree. C. for 10-40 minutes, especially 12-.
By appropriately heating under the condition of 20 minutes, the molded body can be cured and manufactured.

The Shore D hardness of the surface of the solid core is preferably 45 or more, particularly 48 or more, and 58 or less, particularly 55 or less. In this case, it is possible to obtain the surface hardness (Shore D hardness) within the above range by appropriately selecting the compounding material of the solid core, the type and amount of the peroxide, the co-crosslinking agent, the vulcanization conditions, and the like. Become. If the hardness of the surface of the solid core is too low, the feel may be soft, or the resilience may be reduced and the flight distance may not be achieved.If the hardness is too high, the feel may be hard and the trajectory will blow up. There are cases.

The solid core structure described above can be formed in a single layer or a plurality of layers, and it is preferable to form a plurality of layers, particularly two layers in order to adjust the spin rate. When a solid core having a plurality of layers is used, the hardness of the solid core surface in the present invention means the surface hardness of the outermost layer of the core portion.

The diameter of the solid core is 25 mm.
Above, it is preferable to be 36 mm or more, on the other hand,
The upper limit is preferably 40 mm or less, and particularly preferably 24 mm or less. Also, the weight is 20 to 32 g, especially 27 to
It is preferably 30 g.

As the inner layer of the cover layer in the present invention, one formed by using an ionomer resin as a main material is used. The inner layer may be a single layer or a plurality of layers.

The above-mentioned ionomer resin is not particularly limited as long as it is a material capable of exhibiting performance as an inner layer of a golf ball, and known materials for golf balls are used. For example, olefin and unsaturated carboxylic acid are mainly used. A metal ion neutralized product of a copolymer as a monomer, a metal ion neutralized product of a copolymer having an olefin, an unsaturated carboxylic acid and an unsaturated carboxylic acid ester as a main monomer, or a mixture of these copolymers may be used. Can be mentioned.

Α-Olefin is preferably used as the olefin. Specific examples of the α-olefin include ethylene, propylene, 1-butene, and the like, and among these, ethylene is particularly preferable. Also,
You may use these olefins in combination of multiple types.

As the above-mentioned unsaturated carboxylic acid, α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms is preferably used. Specific examples of the α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms include acrylic acid, methacrylic acid, ethacrylic acid, itaconic acid, maleic acid and the like. Among these, acrylic acid and methacrylic acid are preferable. used. Further, a plurality of these unsaturated carboxylic acids may be used in combination.

As the above unsaturated carboxylic acid ester,
The lower alkyl esters of unsaturated carboxylic acids mentioned above are suitable, but are not limited thereto. Specific examples thereof include methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, methyl acrylate, ethyl acrylate, propyl acrylate, and butyl acrylate. Particularly, butyl acrylate (n- Butyl acrylate and i-butyl acrylate) are preferably used. These unsaturated carboxylic acid esters are
It is also possible to use a combination of plural kinds. These unsaturated carboxylic acid esters can contribute to improving the flexibility of the ionomer resin.

When producing the above-mentioned copolymer containing olefin and unsaturated carboxylic acid as a main monomer, or copolymer containing olefin, unsaturated carboxylic acid and unsaturated carboxylic acid ester as main monomers, Any monomer,
You may copolymerize in the range which does not impair the objective of this invention.
The content of unsaturated carboxylic acid in these copolymers is 0.2 mol% or more, particularly 5 mol% or more, and the upper limit is 25 mol% or less, and particularly 15 mol% or less in the copolymer. preferable. If the unsaturated carboxylic acid content is too low, the rigidity and rebound may be reduced, and the flight performance of the golf ball may be reduced. If the unsaturated carboxylic acid content is too high, the flexibility may be insufficient.

When a copolymer containing an olefin and an unsaturated carboxylic acid as a main monomer and a copolymer containing an olefin, an unsaturated carboxylic acid and an unsaturated carboxylic acid ester as a main monomer are blended and used, the blending amount thereof Is 10 by weight
It is preferably 0: 0 to 25:75. If the blending amount of the copolymer containing the olefin, the unsaturated carboxylic acid and the unsaturated carboxylic acid ester as a main monomer is too large, the resilience may be insufficient.

As the ionomer resin in the present invention, those obtained by neutralizing the above-mentioned copolymer with at least one kind of monovalent to trivalent metal ions are preferably used. Examples of 1 to 3 valent metal ions suitable for neutralization include sodium, potassium, lithium, magnesium, calcium,
Ions such as zinc, aluminum, ferrous iron and ferric iron can be mentioned.

The introduction of such metal ions can be carried out, for example, by using the above-mentioned copolymer with hydroxides, methoxides, ethoxides, carbonates, nitrates, formates, acetates and oxides of the above-mentioned monovalent to trivalent metals. It is achieved by reacting with.
The neutralization amount of the carboxylic acid contained in the copolymer is at least 10 mol% of the carboxylic acid groups in the copolymer.
As described above, it is preferable that 30 mol% or more and 100 mol% or less, particularly 90 mol% or less, are neutralized with metal ions. When the neutralization amount is small, the repulsion property may be low.

By appropriately blending ionomer resins containing different monovalent, divalent, or trivalent metal ion species, the balance between the resilience and durability of the layer formed mainly of the ionomer resin. It is well known that the above can be obtained, and it is preferable to blend in such a composition also in the present invention.

As the ionomer resin used in the present invention, a commercially available product may be used. For example, as a metal ion neutralized product of a binary random copolymer having an olefin and an unsaturated carboxylic acid as main monomers, for example, Himilan. 155
4, 1557, 1601, 1605, 170
6, AM7311 (all manufactured by Mitsui-DuPont Polychemical Co., Ltd.), Surlyn 7930 (manufactured by DuPont, USA),
Aiotech 3110 and 4200 (EXXONMOB
IL CHEMICAL) and the like, and as a metal ion neutralized product of a ternary random copolymer having olefins, unsaturated carboxylic acids and unsaturated carboxylic acid esters as main monomers, for example, Himilan 1855, 1856,
AM 7316 (all manufactured by Mitsui DuPont Polychemicals), Surlyn 6320, 8320, 9320,
8120 (both manufactured by DuPont, USA), Iotech 7510, 7520 (both EXXONMOBI
L CHEMICAL) and the like.

If desired, various additives may be added to the inner layer. Specific examples of such additives include pigments, dispersants, and anti-aging agents.
Ultraviolet absorbers, light stabilizers and the like can be added. More specifically, examples of such additives include inorganic fillers such as zinc oxide, barium sulfate, and titanium dioxide.

Next, as the outer layer of the cover layer in the present invention, a layer formed mainly of a non-ionomer resin is used. In this case, the outer layer may be a single layer or a plurality of layers.

The above-mentioned non-ionomer resin is not particularly limited as long as it is a material capable of exhibiting performance as the outer layer of the golf ball, and known materials for golf balls are used. Examples thereof include polyester elastomers and polyamide elastomers. Examples thereof include thermoplastic elastomers such as polyurethane elastomers, and polyurethane elastomers are particularly preferably used.

As the above polyurethane elastomer,
Although it is not particularly limited as long as it is an elastomer containing polyurethane as a main component, it may be composed of a polymer polyol compound forming a soft segment, and a diisocyanate and a monomolecular chain extender forming a hard segment. preferable.

The high molecular weight polyol compound is not particularly limited, but examples thereof include polyester type polyols and polyether type polyols. From the viewpoint of impact resilience and low temperature characteristics, polyether type is preferably used. To be Examples of the polyether-based polyol include polytetramethylene glycol, polypropylene glycol and the like, and polytetramethylene glycol is particularly preferably used. The number average molecular weight of these is preferably 1000 to 5000, more preferably 1500 to 3000.

The diisocyanate is not particularly limited, and examples thereof include aromatic diisocyanates such as 4,4'-diphenylmethane diisocyanate, 2,4-toluene diisocyanate and 2,6-toluene diisocyanate, and hexamethylene diisocyanate. The aliphatic diisocyanates of In the present invention, when the isocyanate mixture described below is blended,
From the viewpoint of reaction stability with an isocyanate mixture, 4,
4'-Diphenylmethane diisocyanate is preferably used.

The monomolecular chain extender is not particularly limited, but usual polyhydric alcohols and amines can be used, for example, 1,4-butylene glycol, 1,2-ethylene glycol and 1,3-propylene. Glycol,
1,3-butanediol, 1,6-hexylene glycol, 2,2-dimethyl-1,3-propanediol,
1,3-butylene glycol, dicyclohexylmethylmethanediamine (hydrogenated MDA), isophoronediamine (IPDA) and the like can be mentioned. The average molecular weight of these chain extenders is preferably 20 to 15,000.

As such a polyurethane elastomer, commercially available products can be used. For example, Pandex T7298, Pandex T3080, Pantone T8290 and Pandex T82.
95, T8260 (manufactured by DIC Bayer Polymer Co., Ltd.), Resamine 2593, and 2597 (manufactured by Dainichiseika Kogyo Co., Ltd.). These may be used alone or in combination of two or more.

For the outer layer of the present invention, the above polyurethane elastomer further mixed with a specific isocyanate mixture described below is preferably used. By blending the specific isocyanate mixture, compared with a golf ball using an outer cover formed by using a normal polyurethane elastomer alone as a main material, feeling,
It is possible to obtain a golf ball which is more excellent in controllability, cut resistance, abrasion resistance, and cracking durability when hit by repeated hits.

The above-mentioned specific isocyanate mixture is
(I) An isocyanate compound having two or more isocyanate groups as a functional group in one molecule, and (ii) a thermoplastic resin that does not substantially react with the isocyanate group. (I) is contained in (ii) It means a dispersed isocyanate mixture.

Here, as the isocyanate compound of (i) above, an isocyanate compound used in the conventional technique relating to polyurethane can be used, and examples thereof include aromatic isocyanate compounds, hydrogenated products of aromatic isocyanate compounds, and aliphatic diisocyanates. , And alicyclic diisocyanates, but are not limited thereto.

As the aromatic isocyanate compound, for example, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate and a mixture of these, 4,
4'-diphenylmethane diisocyanate, m-phenylene diisocyanate, 4,4'-biphenyl diisocyanate and the like can be mentioned. Examples of hydrogenated aromatic isocyanate compounds include dicyclohexylmethane diisocyanate. Examples of the aliphatic diisocyanate include tetramethylene diisocyanate, hexamethylene diisocyanate (HDI), octamethylene diisocyanate and the like. Examples of the alicyclic diisocyanate include isophorone diisocyanate (IPDI).

The thermoplastic resin (ii) is preferably a resin having low water absorption and excellent compatibility with the thermoplastic polyurethane material. Examples of such a resin include polystyrene resin, polyvinyl chloride resin, ABS resin, polycarbonate resin, polyester elastomer (polyether / ester block copolymer, polyester / ester block copolymer, etc.).
It is not limited to these. From the viewpoint of impact resilience and strength, polyether / ester block copolymers are particularly preferable.

In producing the isocyanate mixture, the compounding ratio of the above-mentioned components (ii) and (i) is 100: 5 to 5: 5.
100: 100 (weight ratio), especially 100: 10 to 10
It is preferably 0:40 (weight ratio). If the blending amount of the component (i) with respect to the component (ii) is too small, in order to obtain a sufficient amount for the crosslinking reaction with the polyurethane elastomer, a larger amount of the isocyanate mixture must be added, and (ii) The physical properties of the polyurethane elastomer after cross-linking may become insufficient due to the large influence of the component (a), and if the blending amount is too large, the component (i) causes a slip phenomenon during kneading, making it difficult to synthesize the mixture. May be.

Isocyanate mixtures are, for example, (ii)
Ingredient (i) is added to the ingredients, and these are heated to a temperature of 130 to 25
It can be obtained by sufficiently kneading with a mixing roll or Banbury mixer at 0 ° C., pelletizing or cooling and then pulverizing. A commercially available product can be used as the isocyanate mixture, and for example, Clonate EM30 manufactured by Dainichiseika Kogyo Co., Ltd. is preferably used, but the isocyanate mixture is not limited thereto.

The amount of the above isocyanate mixture is usually 1 part by weight or more, preferably 5 parts by weight or more, more preferably 10 parts by weight or more, and the upper limit is usually 100 parts by weight or less, based on 100 parts by weight of the polyurethane elastomer. It is preferably 50 parts by weight or less, more preferably 30 parts by weight or less. If the blending amount is too small, a sufficient cross-linking reaction cannot be obtained, and improvement in physical properties may not be observed.If the blending amount is too large, the discoloration due to heat, ultraviolet rays may become large, or the repulsion may decrease. Problems can occur.

As described above, the outer cover layer of the golf ball of the present invention is particularly preferably formed of a polyurethane elastomer as a main material, but if desired, other components such as a pigment, a dispersant, an antioxidant, and an ultraviolet absorber can be used. Agents, ultraviolet stabilizers, plasticizers, etc. and inorganic fillers (zinc oxide, barium sulfate, titanium dioxide, etc.) can also be added.

The surface Shore D hardness of the outer layer is preferably 40 or more and 65 or less, and more preferably 45 or more and 60 or less. If the hardness of the outer layer is too low, spin may be applied too much, resulting in insufficient flight distance.If the hardness of the outer layer is too high, the spin rate may be too low and ball control may be poor, or the ball may be hit repeatedly. The crack durability and scratch resistance may deteriorate.

The thickness of the cover inner layer of the present invention is 0.3 mm.
Or more, more preferably 1.0 mm or more, and the upper limit is 2.
It is preferably 0 mm or less, and more preferably 1.8 mm or less. If the thickness of the inner layer is too large, the resilience may decrease, and if the thickness of the inner layer is too small, the durability may decrease.

On the other hand, the thickness of the outer layer is preferably 0.3 mm or more, more preferably 1.0 mm or more, and the upper limit is 2.0 mm or less, more preferably 1.8 mm or less. If the thickness of the outer layer is too large, the resilience may decrease, and if the thickness of the outer layer is too small, the durability may decrease.

According to the present invention, the surface of the cover inner layer is treated with an acid when a golf ball having a core covered with a cover layer including an inner layer and an outer layer is prepared. A good golf ball can be obtained.

The acid used for the acid treatment is not particularly limited as long as it is an acid capable of desorbing the metal ion of the ionomer resin and protonating the carboxylic acid, and examples thereof include hydrochloric acid, sulfuric acid, nitric acid and the like. From the viewpoint of workability, hydrochloric acid is particularly preferably used. The acid concentration when used is also not particularly limited, but the acid concentration is 0.1% by weight or more, and particularly 0.1.
It is preferably 5 to 10% by weight or more. If the acid concentration is too low, the effect of improving the adhesiveness may not be seen.

The method of acid treatment is, for example, after forming the inner layer on the core, and then in an aqueous solution of the acid for 1 to 60 minutes.
Particularly, a method of immersing for 1 to 10 minutes can be mentioned.

The temperature of the acid treatment is 10 to 30 ° C.
In particular, the temperature may be 20 to 25 ° C., but usually room temperature to ambient temperature is sufficient. As described above, after the acid treatment (acid cleaning), it is washed sufficiently with water so that the acid does not remain on the surface. The washing method is not particularly limited, but for example, washing with a large amount of water can be used. In addition, it is preferable to polish the inner layer surface before the acid treatment. Examples of the polishing method include a method by random rotation in a diamond wheel, a method using diamond paper, and a sandblast method.

In the present invention, the cover inner layer is formed on the core as described above, preferably after surface polishing, acid treatment is carried out, and then the cover outer layer is formed on the acid treated cover inner layer. is there. As a method of forming the cover inner layer and the outer layer, a known method can be adopted, for example, an injection molding method, a pair of hemispherical half cups are formed in advance,
A method of pressure molding using this can be adopted. According to the present invention, as described above, after the acid treatment of the surface of the inner layer of the cover mainly composed of the ionomer resin, the outer layer of the cover mainly composed of the non-ionomer resin is formed on the inner layer, whereby the inner layer is treated with the primer. The outer layer can be directly bonded and formed directly on the inner layer with good adhesion without any need. For example, it should be 0.5 N or more / 4.5 mm, particularly 0.8 N or more / 4.5 mm in the method of measuring the adhesive strength described later. Is possible.

The golf ball of the present invention has a large number of dimples formed on the surface in the same manner as a normal golf ball, and the number of dimples is not particularly limited, but is usually 350 to 500, preferably Is 370-48
The number of dimples may be 0, more preferably 390 to 450, and the dimples may be of two or more kinds having different diameters, depths and the like. In this case,
Dimple diameter is usually 1.4-4.5 mm, especially 2.0
It is preferable to adjust the depth to be about 4.3 mm and the depth is usually 0.15 to 0.25 mm, especially 0.17 to 0.23 mm.

The golf ball of the present invention can be appropriately set in terms of ball properties in accordance with the golf rules unless it deviates from the above range, and can be formed to have a weight of 45.93 g or less and a diameter of 42.67 mm or more.

[0061]

EXAMPLES The present invention will be specifically described below by showing Examples and Comparative Examples, but the present invention is not limited to the following Examples.

[Examples and Comparative Examples] A cover inner layer having the composition shown in Table 1 was formed on the surface of the following solid core (A) by injection molding, and after treating the inner layer surface by the method of Table 1, The outer layer of the cover was formed by injection molding with dimples. afterwards,
A three-piece solid golf ball was produced by applying a coating treatment. The obtained golf ball was evaluated for its adhesive strength, resilience (initial velocity) and impact durability by the following methods. The results are shown in Table 2.

Solid core polybutadiene (product name BR11, manufactured by JSR)
00 parts by weight, zinc acrylate 34.1 parts by weight, dicumyl peroxide (product name Park Mill, manufactured by NOF CORPORATION) 0.6 parts by weight, 1,1-bis (t-butylperoxy) 3,3 , 5-trimethylsiloxane (product name: Perhexa 3M-40, manufactured by NOF CORPORATION), 0.6 parts by weight,
0.2 parts by weight of an anti-aging agent (product name Nocrac NS-6, manufactured by Ouchi Shinko Chemical Industry Co., Ltd.), 18.0 parts by weight of zinc oxide, 1 part by weight of pentachlorothiophenol zinc salt, and zinc stearate Using 5 parts by weight, vulcanization was performed with a core mold at a vulcanization temperature of 157 ° C. and a vulcanization time of 15 minutes to prepare solid cores (A) used in each of Examples and Comparative Examples. The obtained solid core (A) had an outer diameter of 36.40 mm and a surface hardness (Shore D) of 57.

Inner layer of cover

[Table 1]

[Inner Layer Surface Treatment] Spherical Polishing Using a diamond wheel, the inner layer injection molded product was subjected to buffing treatment for deburring. Acid treatment , washed in a 1 mol / L hydrochloric acid aqueous solution at room temperature for 1 minute,
Then, a treatment of washing with a large amount of water for 5 minutes was performed. Plasma treatment A low temperature plasma of argon gas was irradiated. Irradiation frequency 13.56MHz, power 80W, time 30 seconds,
Initial irradiation atmosphere 1 × 10 ⁻³ Torr, atmosphere during plasma processing (when gas is introduced) 0.1 Torr. Primer treatment RB-182 (a chlorinated polyethylene-based primer manufactured by Nippon Bee Chemical Co., Ltd.) was applied to a thickness of 5 μm or less. Outer cover thermoplastic elastomer (Product name: Pandex T829
5, manufactured by DC Bayer Polymer Co., Ltd.), 4 parts by weight of titanium dioxide, 1.5 parts by weight of polyethylene wax, 0.06 parts by weight of ultramarine, 0.4 parts by weight of amide wax, and silicone oil. Using 0.3 part by weight, the mixture was heated and kneaded with a twin-screw extruder to prepare a pandex compound. On the other hand, as the isocyanate mixture, the product name Clonate EM30: isocyanate masterbatch manufactured by Dainichiseika Kogyo Co., Ltd. was used [4, 4 '.
-Containing 30% by weight of diphenylmethane diisocyanate (concentration of amine back titration isocyanate measured by JIS K1556: 5 to 10% by weight), masterbatch base resin is polyester elastomer]. Pandex compound / isocyanate mixture = 10 immediately before molding the cover
Dry mixing was performed at 0/10 (weight ratio), and a cover resin was molded on the inner layer by an injection molding machine.

[Measurement of Physical Properties] Adhesive Strength In FIG. 2, the golf ball 10 was provided with two parallel cuts 11 and 12 penetrating the outer layer 3 and the inner layer 2 at intervals of 4.5 mm. At this time, two cut lines 11,1
Care was taken so that the center line of 2 coincided with the outermost circumference line of the golf ball, that is, the longest circumference line of the golf ball. Furthermore, the two cut lines 11,
After making a cut line 13 that crosses 12 at a right angle so as to penetrate the outer layer 3 and the inner layer 2, the laminate of the inner layer 2 and the outer layer 3 is peeled from the golf ball core 1 without separating the outer layer 3 and the inner layer 2. Thus, a strip-shaped test piece for measuring adhesive strength 14 was obtained. The measuring method uses an Instron tester,
Based on JIS K6256 "Adhesion test method for vulcanized rubber and thermoplastic rubber", the above-mentioned special test piece was used as the test piece, and the moving speed of the grip was 100 mm / min. Displacement of inner and outer layers of four test pieces when peeled off 20
The average of the tensile strengths up to 200 mm was taken as the adhesive strength (unit is N). Resilience (Initial Speed) The resilience of the golf ball was measured according to the USGA (R & A) measurement method. The higher the value, the better the resilience. Striking durability index driver (W # 1), repeatedly hit with an impact equivalent to HS = 50 m / s, and the time when the ball rebound is continuously reduced by 3% is determined as the number of times of adhesion reduction or ball destruction, and is carried out. The durability index in Example 1 is referred to as an index when the durability index is 100. The lower the value, the poorer the durability after repeated impact.

[0067]

[Table 2]

In Comparative Examples 1, 2, and 5, the inner layer ionomer resin was not treated except for spherical polishing, and the adhesive strength with the outermost layer polyurethane elastomer was low, and the resilience and durability against repeated impact were low. It was In addition, Comparative Example 3
Shows the case where plasma treatment is applied to the surface of the intermediate layer, and Comparative Example 4 shows the case where the primer is applied to the surface of the inner layer.
The durability against repeated impact was insufficient. On the other hand, in Examples 1 to 4, as shown in Table 1, the golf balls whose inner surface was washed with an acid had improved adhesive strength with the polyurethane elastomer of the outermost layer, resulting in repulsion and repeated impact. Durability has improved significantly.

[0069]

The golf ball obtained according to the present invention is
Excellent durability against repeated impacts, according to the present invention,
It is possible to provide a golf ball having good spin characteristics, resilience and feel after repeated hits.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a golf ball according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a method of collecting a test piece for measuring adhesive strength when measuring the adhesive strength between an inner layer and an outer layer of the cover.

[Explanation of symbols]

1 core 2 Cover inner layer 2a Acid treatment 3 outer layer of cover

─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] June 28, 2002 (2002.6.2)
8)

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0048

[Correction method] Change

[Correction content]

Isocyanate mixtures are, for example, (ii)
Ingredient (i) is added to the ingredients, and these are heated to a temperature of 130 to 25
It can be obtained by sufficiently kneading with a mixing roll or Banbury mixer at 0 ° C., pelletizing or cooling and then pulverizing. As the isocyanate mixture, a commercially available product can be used, and, for example, Crossnate EM30 manufactured by Dainichiseika Kogyo Co., Ltd. is preferably used, but the isocyanate mixture is not limited thereto.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0065

[Correction method] Change

[Correction content]

[Inner Layer Surface Treatment] Spherical Polishing Using a diamond wheel, the inner layer injection molded product was subjected to buffing treatment for deburring. Acid treatment , washed in a 1 mol / L hydrochloric acid aqueous solution at room temperature for 1 minute,
Then, a treatment of washing with a large amount of water for 5 minutes was performed. Plasma treatment A low temperature plasma of argon gas was irradiated. Irradiation frequency 13.56MHz, power 80W, time 30 seconds,
Initial irradiation atmosphere 1 × 10 ⁻³ Torr, atmosphere during plasma processing (when gas is introduced) 0.1 Torr. Primer treatment RB-182 (a chlorinated polyethylene-based primer manufactured by Nippon Bee Chemical Co., Ltd.) was applied to a thickness of 5 μm or less. Outer cover thermoplastic elastomer (Product name: Pandex T829
5, manufactured by DC Bayer Polymer Co., Ltd.), 4 parts by weight of titanium dioxide, 1.5 parts by weight of polyethylene wax, 0.06 parts by weight of ultramarine, 0.4 parts by weight of amide wax, and silicone oil. Using 0.3 part by weight, the mixture was heated and kneaded with a twin-screw extruder to prepare a pandex compound. On the other hand, as the isocyanate mixture, a trade name of Crosson EM30: isocyanate masterbatch manufactured by Dainichi Seika Kogyo Co., Ltd. was used [4
30% by weight of 4'-diphenylmethane diisocyanate
Included (amine back titration according to JIS K1556, concentration of isocyanate measured 5 to 10% by weight), masterbatch base resin is polyester elastomer]. Immediately before molding the cover, a pandex compound / isocyanate mixture = 100/10 (weight ratio) was dry-mixed, and a cover resin was molded on the inner layer by an injection molding machine.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Eiji Takehana             Bridgestone, 20 Onohara, Chichibu City, Saitama Prefecture             Within Sports Co., Ltd.

Claims (7)

[Claims] 1. A golf ball having a core covered with a cover layer including an inner layer and an outer layer, wherein the inner cover layer is formed of an ionomer resin as a main material, and the outer cover layer is formed of a non-ionomer resin as a main material. And the surface of the inner layer of the cover is acid-treated. 2. The golf ball according to claim 1, wherein the cover inner layer surface is surface-polished, and the surface-polished cover inner layer surface is acid-treated. 3. The golf ball according to claim 1, wherein the outer layer of the cover is formed mainly of polyurethane elastomer. 4. The golf ball according to claim 1, wherein the adhesive strength between the cover inner layer surface and the cover outer layer is 0.5 N or more / 4.5 mm. 5. A method of manufacturing a golf ball comprising a core covered with a cover layer including an inner layer and an outer layer, wherein the core is coated to form an inner cover layer containing an ionomer resin as a main material, and the inner surface of the inner cover layer is formed. A method of manufacturing a golf ball, which comprises forming an outer cover layer, which is mainly composed of a non-ionomer resin, over the inner cover layer after acid treatment. 6. The method according to claim 5, wherein after the inner layer of the cover is formed, the surface is polished and then the polished surface is acid-treated. 7. The method according to claim 5, wherein the outer cover layer is formed of a polyurethane elastomer as a main material.