JP2023075062A - Golf ball - Google Patents

Abstract

SOLUTION: To provide a golf ball which is constituted by providing an intermediate layer between a core and a cover layer, in which the cover layer is formed of a resin material having polyurethane or polyurea as a main component, a value of lightness (Li) of a surface of a sphere (an intermediate layer covering sphere) where the core is covered with the intermediate layer is 25 or more according to an L*a*b* color system of JIS Z8781, and visible area light transmittance of the cover layer is 0.6% or more.EFFECT: A golf ball has a characteristic aesthetic appearance on a ball surface, maintains excellent spin performance and scuff resistance, and is useful for a professional player and an advanced level player.SELECTED DRAWING: Figure 1

Description

The present invention relates to a golf ball provided with a cover layer made of polyurethane and having a surface lightness (Li) of 25 or more for a sphere in which the core is covered with an intermediate layer (intermediate layer-covered sphere). The present invention relates to a golf ball having an aesthetic appearance and capable of maintaining good spin performance and scratch resistance.

A golf ball is required to have properties such as the ability to fly and stop, and the ability to be scratch resistant. Balls that fly well when hit with a driver and have good backspin on approach shots have been developed. Until now, cover materials with high resilience and good scratch resistance have been developed. Recently, golf balls made of a polyurethane material, which is excellent in backspin on approach shots, are preferred as a cover material by professionals and advanced golfers. In addition to the usual white golf balls, colored balls are also becoming popular among golfers.

Polyurethane resin is generally translucent or cloudy in its uncolored state due to its molecular structure. Heat during kneading and a chemical reaction of the components contained in the polyurethane resin itself occur, resulting in poor color development and a dull color. Also, if a resin material colored with a dye is used, the dye may migrate into the resin transport path used during the golf ball manufacturing process, causing problems such as contamination of the manufacturing equipment.

As color golf balls whose cover material is made of polyurethane, yellow and orange golf balls already exist on the market. Although these colored golf balls meet the demand for colors other than white, they are colored balls for advanced golfers aiming at various performances such as visibility and spin performance.

As a method of coloring the cover material of a golf ball, a method of mixing a pigment or a dye into a cover resin material and a method of dyeing the surface of the cover have already been proposed. For example, Patent Documents 1 to 8 below have been proposed.

Japanese Patent Publication No. 2016-513488 Japanese Patent Publication No. 2016-513489 US Patent Application Publication No. 2014-256468 US Patent Application Publication No. 2014-250609 US Patent Application Publication No. 2018-080172 JP 2004-180921 A JP-A-58-143769 JP-A-58-112567

The present invention has been made in view of the above circumstances, and provides a golf ball whose cover material is mainly made of polyurethane resin. It is an object of the present invention to provide a golf ball having a high aesthetic appearance.

The inventors of the present invention have made intensive studies to achieve the above object, and have found that, in a golf ball having an intermediate layer interposed between the core and the cover layer, the cover layer is made of a resin material containing polyurethane or polyurea as a main component. and adjusting the lightness (Li) of the surface of the sphere (intermediate layer-covered sphere) in which the core is coated with the intermediate layer to 25 or more, and further, the visible region light transmittance of the cover layer is 0.6. % or more, the ball surface has a unique aesthetic appearance, spin performance and scratch resistance can be maintained well, and the golf ball is useful as a golf ball for professionals and advanced golfers. This is what has led to the present invention.

Accordingly, the present invention provides the following golf balls.
1. A sphere having an intermediate layer interposed between a core and a cover layer, the cover layer being formed of a resin material containing polyurethane or polyurea as a main component, and the core being coated with the intermediate layer (intermediate layer-coated sphere) The lightness (Li) of the surface of the cover layer is 25 or more based on the L*a*b* color system of JIS Z8781, and the visible region light transmittance of the cover layer is 0.6% or more. A golf ball.
2. 2. The golf ball according to 1 above, wherein the golf ball has a lightness (Lo value) of 25 or more based on the L*a*b* color system of JIS Z8781.
3. 3. The golf ball according to 2 above, wherein the ratio (Lo/Li) of the lightness (Lo value) of the golf ball to the lightness (Li) of the intermediate layer-covered sphere is 0.3 to 1.5.
4. 2. The golf ball of claim 1, wherein the resin material of the cover layer has a Shore D hardness of 65 or less.
5. 2. The golf ball of claim 1, wherein the cover layer is made of a resin material containing polyurethane as a main component, and the polyol component of the polyurethane contains polytetramethylene glycol (PTMG) having a number average molecular weight (Mn) of 3500 or less.

The golf ball of the present invention has a unique aesthetic appearance on the surface of the ball, can maintain good spin performance and scratch resistance, and is particularly useful as a golf ball for professionals and advanced golfers.

1 is a schematic cross-sectional view of a golf ball including a cover layer according to one embodiment of the invention; FIG.

The present invention will be described in more detail below.
The golf ball of the present invention comprises a core, at least one intermediate layer, and at least one cover layer, and the cover layer is made of a resin material containing polyurethane or polyurea as a main component. be.

The golf ball of the present invention, for example, as shown in FIG. 1, has a core 1, an intermediate layer 2 and a cover layer (outermost layer) 3, and a large number of dimples D are formed on the surface of the cover layer. Further, in FIG. 1, reference numeral 4 denotes a paint layer covering the surface of the cover layer, and reference numeral 2a denotes a coloring agent contained in the intermediate layer 2. As shown in FIG. This will be discussed later.

The core is usually obtained by vulcanizing a rubber composition containing a base rubber as a main component. Examples of this rubber composition include forming using a rubber composition containing a base rubber, a co-crosslinking agent, a crosslinking initiator, a metal oxide and an anti-aging agent. Polybutadiene is preferably used as the base rubber of the rubber composition.

Next, the intermediate layer will be explained.
In the present invention, the surface lightness (Li) of the sphere in which the core is coated with the intermediate layer (intermediate layer-coated sphere) is 25 or more, preferably 30 or more, more preferably 35 or more, still more preferably 40 or more, most preferably 40 or more. is greater than or equal to 45. This lightness (Li value) means the L* value (lightness) based on the L*a*b* color system of "JIS Z8781". If it is low, the middle layer will be dull.

As a means for producing the intermediate layer-covered spheres having the desired lightness, various additives such as known resin materials and pigments are used, and the blending amounts thereof are appropriately adjusted to form the intermediate layer. Although it can be adopted as a product, it is not limited to this method. At least one intermediate layer is preferably formed of a resin composition containing (A) and (B) below.
(A) Thermoplastic resin (B) Colorant composed of fluorescent dye or fluorescent pigment Components (A) and (B) are described below.

(A) Thermoplastic resin The thermoplastic resin is not particularly limited, but includes resins conventionally used as materials for golf balls, such as ionomer resins, polyester resins, polyurethane resins, polyamide resins, and polyolefins. Examples include resins, olefinic thermoplastic elastomers, styrene thermoplastic elastomers, and the like. In particular, ionomer resins are suitable, and specifically, (a) ethylene-α,β unsaturated carboxylic acid copolymer and/or metal salt thereof, or (b) ethylene-α,β unsaturated carboxylic acid It is preferable to contain any of the components (a) and (b) of -α,β unsaturated carboxylic acid ester copolymer and/or metal salt thereof.

Examples of α,β-unsaturated carboxylic acids of components (a) and (b) include acrylic acid, methacrylic acid, maleic acid, fumaric acid and the like, and particularly acrylic acid and methacrylic acid. is preferred. As the α,β unsaturated carboxylic acid ester of the component (b), lower alkyl esters of the above unsaturated carboxylic acids are suitable. Specifically, methyl methacrylate, ethyl methacrylate, propyl methacrylate , butyl methacrylate, methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, etc., and butyl acrylate (n-butyl acrylate, i-butyl acrylate) is particularly preferred.

The metal ion-neutralized copolymer of the components (a) and (b) partially replaces the acid groups of the olefin-unsaturated carboxylic acid (-unsaturated carboxylic acid ester) copolymer with metal ions. It can be obtained by neutralization. Examples of metal ions that neutralize acid groups include Na+, K+, Li+, Zn++, Cu++, Mg++, Ca++, Co++, Ni++, Pb++, etc. and particularly Na+, Li+, Zn++, Mg++, Ca++ and the like are preferably used. Such neutralized products can be obtained by known methods. Neutralized products can be obtained using compounds such as compounds and alkoxides.

Known components can be used as the components (a) and (b). Examples of commercially available acid copolymers include Nucrel N1560, N1214, N1035, AN4221C, AN4311, AN4318, and AN4319 (all manufactured by DuPont Mitsui Polychemicals). . In addition, as metal ion neutralized products of acid copolymers, for example, Himilan 1554, Himilan 1557, Himilan 1601, Himilan 1605, Himilan 1706, Himilan AM7311, Himilan 1855, Himilan 1856, Himilan AM7316 (all of which are Mitsui DuPont Polychemicals) (manufactured by DuPont), Surlyn 7930, 6320, 8320, 9320, 8120 (manufactured by DuPont).

The total amount of the thermoplastic resin of component (A) is not particularly limited, and should be blended in the total amount of the resin composition at 70% by mass or more, preferably 80% by mass or more, and more preferably 90% by mass or more. is recommended. If the above blending amount is insufficient, the desired effects of the present invention may not be obtained.

(B) A colorant comprising a fluorescent dye or fluorescent pigment The present invention provides a golf ball with a unique aesthetic appearance to impart a transparent and soft impression to the surface of the ball. A coloring agent comprising a fluorescent dye or a fluorescent pigment can be blended in the resin material of the layer as the component (B). As the colorant, a known fluorescent dye or fluorescent pigment is appropriately blended to color the intermediate layer. Here, for example, solvent yellow (dye), solvent orange (dye), anthraquinone (dye), phthalocyanine (dye), yellow fluorescent pigment, pink fluorescent pigment, orange fluorescent pigment and the like can be mentioned. These can use a well-known commercial item.

In the present invention, among the fluorescent colorants, it is preferable to use those having light-collecting properties. Here, the light-collecting fluorescent colorant is a material that has the function of concentrating sunlight and converting the wavelength to the long wavelength side as a fluorescent color, and while totally reflecting inside the colored material , is guided to the dimple edge, condenses, and is emitted in a concentrated state at the dimple edge, resulting in strong color development.

The light-collecting fluorescent colorants include orange, pink, red, yellow, blue, purple, and the like, and commercially available products can be used for any of the coloring systems. For example, trade names "Lumogen F Yellow 083", "Lumogen F Orange 240", "Lumogen F Red 305", "Lumogen F Blue 650" (all manufactured by BASF), "Lumicolor Red", "Smart Color LP Green ”, “Smart Color LP Yellow”, and “Smart Color LP Orange” (all manufactured by Kashinomoto Technology Co., Ltd.).

The blending amount of component (B) is 0.001 to 0.2 parts by mass, preferably 0.005 to 0.1 parts by mass, per 100 parts by mass of component (A). If the blending amount is too small, the fluorescence may become weak and the desired design may not be obtained. Conversely, if the amount is too high, the colorant, particularly the dye, may migrate and stain objects that come into contact with the golf ball.

(C) Inorganic filler or organic filler The resin composition of components (A) and (B) may further contain an inorganic filler or organic filler as component (C). The purpose of blending the inorganic and organic fillers is to appropriately prepare the resin composition so as to obtain a desired transmittance in the visible light region, as will be described later. However, in the present invention, component (C) is not an essential component.

When the component (C) is an inorganic filler, it is not particularly limited, but examples thereof include zinc oxide, barium sulfate, calcium carbonate, titanium dioxide, silica and the like. Further, by adding an inorganic filler, it becomes possible to impart translucency and adjust the color.

When the component (C) is an organic filler, it is not particularly limited, but examples include crosslinked polymethyl methacrylate (crosslinked PMMA), crosslinked polybutyl methacrylate, crosslinked polyacrylate, crosslinked acrylic-styrene copolymer Fine particles of coalesced, melamine resin, polyurethane and the like can be mentioned.

The amount of component (C) to be blended is 0.01 to 4.0 parts by mass, preferably 0.02 to 3.0 parts by mass, more preferably 0.02 to 3.0 parts by mass per 100 parts by mass of component (A). 03 to 2.0 parts by mass. If the blending amount is too large, the opacity may become too high, which may impair the high-class ball design, or the color may change significantly when exposed to sunlight.

The resin composition can be obtained, for example, by mixing the components described above using various kneaders such as a kneading type (single-screw or twin-screw) extruder, Banbury, kneader, and the like.

Various additives can be blended into the resin composition as necessary. For example, pigments, dispersants, antioxidants, light stabilizers, ultraviolet absorbers, lubricants, etc. can be blended as appropriate. can.

The thickness of the intermediate layer is not particularly limited, but is preferably 0.5 mm or more, more preferably 0.7 mm or more, and the upper limit is preferably 1.7 mm or less, more preferably 1.4 mm or less. is.

The hardness of the intermediate layer is not particularly limited, but the Shore D hardness is preferably 30 or more, more preferably 40 or more, and the upper limit is preferably 75 or less, more preferably 70. Below, more preferably 65 or less.

In the present invention, the cover layer is formed of a resin composition containing polyurethane or polyurea as a main component. Details of these resin materials are as follows.

Polyurethane The structure of polyurethane consists of a soft segment composed of a high-molecular-weight polyol (polymeric glycol), which is a long-chain polyol, and a chain extender and polyisocyanate that constitute a hard segment. Here, as the polymer polyol used as a raw material, any of those conventionally used in techniques related to polyurethane materials can be used, and there is no particular limitation. Examples include polyester polyols, polyether polyols, polycarbonate polyols, polyester polycarbonate polyols, polyolefin polyols, conjugated diene polymer polyols, castor oil polyols, silicone polyols, and vinyl polymer polyols. Specific examples of polyester-based polyols that can be used include adipate-based polyols such as polyethylene adipate glycol, polypropylene adipate glycol, polybutadiene adipate glycol, and polyhexamethylene adipate glycol, and lactone-based polyols such as polycaprolactone polyol. Polyether polyols include poly(ethylene glycol), poly(propylene glycol) and poly(tetramethylene glycol), poly(methyltetramethylene glycol) and the like.

In the present invention, the long-chain polyol preferably contains polytetramethylene glycol (PTMG) having a number average molecular weight (Mn) of 3500 or less from the viewpoint of workability, scratch resistance, and resilience during golf ball molding. be. Furthermore, the number average molecular weight (Mn) of this polytetramethylene glycol (PTMG) is preferably 3000 or less, more preferably 2500 or less, most preferably 2000 or less, and the lower limit is preferably 800 or more, more preferably It is preferably 900 or more, most preferably 1000 or more.

The number average molecular weight (Mn) mentioned above is the number average molecular weight calculated based on the hydroxyl value measured according to JIS-K1557 (hereinafter the same).

As the chain extender, those used in conventional polyurethane technology can be suitably used, and are not particularly limited. In the present invention, a low-molecular-weight compound having two or more active hydrogen atoms capable of reacting with an isocyanate group in the molecule and having a molecular weight of 2,000 or less can be used. Group diols can be preferably used. Specific examples include 1,4-butylene glycol, 1,2-ethylene glycol, 1,3-butanediol, 1,6-hexanediol, 2,2-dimethyl-1,3-propanediol, and the like. Among them, 1,4-butylene glycol can be preferably used.

As the polyisocyanate, those used in conventional polyurethane technology can be suitably used, and there is no particular limitation. Specifically, 4,4′-diphenylmethane diisocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, p-phenylene diisocyanate, xylylene diisocyanate, naphthylene 1,5-diisocyanate, tetramethylxylene diisocyanate, hydrogenation 1 selected from the group consisting of xylylene diisocyanate, dicyclohexylmethane diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, norbornene diisocyanate, trimethylhexamethylene diisocyanate, 1,4-bis(isocyanatomethyl)cyclohexane, dimer acid diisocyanate A species or two or more species can be used.

Also, the compounding ratio of active hydrogen atoms to isocyanate groups in the polyurethane-forming reaction can be appropriately adjusted within a preferred range. Specifically, in producing a polyurethane by reacting the long-chain polyol, the polyisocyanate compound and the chain extender, the polyisocyanate compound is It is preferable to use each component in such a proportion that the isocyanate group contained in is 0.95 to 1.05 mol.

The method for producing polyurethane is not particularly limited, and a long-chain polyol, a chain extender, and a polyisocyanate compound can be used, and a known urethanization reaction can be used to produce the polyurethane by either the prepolymer method or the one-shot method. good. Among them, it is preferable to carry out melt polymerization in the absence of a solvent, and it is particularly preferable to carry out continuous melt polymerization using a multi-screw extruder.

As the polyurethane mentioned above, it is preferable to use a thermoplastic polyurethane material. As the thermoplastic polyurethane material, commercially available products can be suitably used. be able to.

Polyurea Polyurea is a resin composition mainly composed of urea bonds produced by the reaction of (i) isocyanate and (ii) amine-terminated compounds. This resin composition will be described in detail below.

(i) Isocyanate As the isocyanate, those used in the conventional techniques related to polyurethane can be suitably used, and there is no particular limitation, and the same isocyanate as explained for the polyurethane material can be used.

(ii) Amine-terminated compound The amine-terminated compound is a compound having an amino group at the end of the molecular chain, and in the present invention, the following long-chain polyamines and/or amine-based curing agents can be used.

A long-chain polyamine is an amine compound having two or more amino groups capable of reacting with an isocyanate group in its molecule and having a number average molecular weight of 1,000 to 5,000. In the present invention, the number average molecular weight is more preferably 1,500-4,000, more preferably 1,900-3,000. Specific examples of the long-chain polyamine include amine-terminated hydrocarbons, amine-terminated polyethers, amine-terminated polyesters, amine-terminated polycarbonates, amine-terminated polycaprolactones, and mixtures thereof. can be, but are not limited to: One of these long-chain polyamines may be used alone, or two or more thereof may be used in combination.

On the other hand, an amine-based curing agent is an amine compound having two or more amino groups capable of reacting with an isocyanate group in its molecule and having a number average molecular weight of less than 1,000. In the present invention, the number average molecular weight is more preferably less than 800, more preferably less than 600. Specific examples of the amine curing agent include ethylenediamine, hexamethylenediamine, 1-methyl-2,6-cyclohexyldiamine, tetrahydroxypropyleneethylenediamine, 2,2,4- and 2,4,4-trimethyl-1, 6-hexanediamine, 4,4'-bis-(sec-butylamino)-dicyclohexylmethane, 1,4-bis-(sec-butylamino)-cyclohexane, 1,2-bis-(sec-butylamino)- Cyclohexane, derivatives of 4,4′-bis-(sec-butylamino)-dicyclohexylmethane, 4,4′-dicyclohexylmethanediamine, 1,4-cyclohexane-bis-(methylamine), 1,3-cyclohexane-bis -(methylamine), diethylene glycol di-(aminopropyl) ether, 2-methylpentamethylenediamine, diaminocyclohexane, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, propylenediamine, 1,3-diaminopropane, dimethylaminopropylamine , diethylaminopropylamine, dipropylenetriamine, imido-bis-propylamine, monoethanolamine, diethanolamine, triethanolamine, monoisopropanolamine, diisopropanolamine, isophoronediamine, 4,4'-methylenebis-(2-chloroaniline) , 3,5-dimethylthio-2,4-toluenediamine, 3,5-dimethylthio-2,6-toluenediamine, 3,5-diethylthio-2,4-toluenediamine, 3,5-diethylthio-2,6- toluenediamine, 4,4'-bis-(sec-butylamino)-diphenylmethane and its derivatives, 1,4-bis-(sec-butylamino)-benzene, 1,2-bis-(sec-butylamino)- Benzene, N,N'-dialkylamino-diphenylmethane, N,N,N',N'-tetrakis(2-hydroxypropyl)ethylenediamine, trimethylene glycol-di-p-aminobenzoate, polytetramethylene oxide-di-p -aminobenzoate, 4,4'-methylenebis-(3-chloro-2,6-diethyleneaniline), 4,4'-methylenebis-(2,6-diethylaniline), m-phenylenediamine, p-phenylenediamine, and mixtures thereof, but are not limited to these. These amine-based curing agents may be used singly or in combination of two or more.

(iii) Polyol Polyurea may contain a polyol in addition to the above components (i) and (ii), although it is not an essential component. As this polyol, those used in conventional polyurethane technology can be suitably used, and there is no particular limitation. Specific examples include the following long-chain polyols and/or polyol-based curing agents. can.

As the long-chain polyol, any one conventionally used in polyurethane technology can be used, and there is no particular limitation. Examples include polyester polyol, polyether polyol, polycarbonate polyol, polyester polycarbonate polyol, and polyolefin polyol. , conjugated diene polymer-based polyols, castor oil-based polyols, silicone-based polyols, vinyl polymer-based polyols, and the like. One of these long-chain polyols may be used alone, or two or more thereof may be used in combination.

The number average molecular weight of the long-chain polyol is preferably 1,000 to 5,000, more preferably 1,700 to 3,500. Within this number-average molecular weight range, the resilience, productivity and the like are further improved.

As the polyol-based curing agent, those used in conventional polyurethane technology can be suitably used, and are not particularly limited. In the present invention, a low-molecular-weight compound having two or more active hydrogen atoms capable of reacting with an isocyanate group in the molecule and having a molecular weight of less than 1000 can be used. can be preferably used. Specific examples include 1,4-butylene glycol, 1,2-ethylene glycol, 1,3-butanediol, 1,6-hexanediol, 2,2-dimethyl-1,3-propanediol, and the like. Among them, 1,4-butylene glycol can be preferably used. The number average molecular weight of the polyol-based curing agent is preferably less than 800, more preferably less than 600.

As for the method for producing the polyurea, a known method can be adopted, and a known method such as a prepolymer method or a one-shot method can be appropriately selected.

The blending amount of the polyurethane or polyurea is appropriately selected according to the required properties of the desired product. More preferably 60% by mass or more, still more preferably 80% by mass or more. Resin materials other than polyurethane or polyurea may be added to the resin composition for forming the cover layer as long as they do not impair the unique aesthetic appearance with good visibility. This is because the fluidity of the composition is further improved, and various physical properties such as resilience and scratch resistance are enhanced.

Furthermore, the cover resin composition can be appropriately blended with optional additives depending on the application. Various additives such as dispersants, anti-aging agents, UV absorbers and light stabilizers can be added. When these additives are blended, the blending amount is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, with respect to 100 parts by mass of the base resin, and the upper limit is preferably 10 parts by mass. parts or less, more preferably 4 parts by mass or less.

The method for molding the cover layer is not particularly limited, and injection molding, compression molding, cast molding, RIM molding, and other known molding methods can be used. For example, the cover layer can be formed by supplying the resin composition described above to an injection molding machine and injecting the melted resin composition for the cover layer around the intermediate layer-covered spheres. In this case, the molding temperature is usually in the range of 150 to 270° C., depending on the type of polyurethane or polyurea used as the main component.

The thickness of the cover layer is appropriately selected according to the intended structure of the golf ball, such as a three-piece golf ball. The upper limit of the thickness of the cover layer is usually 3.0 mm or less, preferably 2.0 mm or less, more preferably 1.5 mm or less. As for the lower limit of the thickness, the thinner the cover layer, the better the spin performance when hit with a driver, but the thinner the cover layer, the worse the scuff resistance. 0.4 mm or more, more preferably 0.5 mm or more, and still more preferably 0.6 mm or more.

The material hardness of the resin composition of the cover layer is appropriately selected from the viewpoint of the spin characteristics and scratch resistance of the golf ball. has a Shore D hardness of 60 or less, most preferably 55 or less. This is because a relatively low hardness results in higher transparency of the resin material and higher spin performance. The lower limit thereof is preferably 25 or more in Shore D hardness, more preferably 30 or more in Shore D hardness, from the standpoint of moldability.

The surface of the cover layer, which is the outermost layer, is usually provided with a large number of dimples from the viewpoint of aerodynamic performance. Although the number of dimples formed on the surface of the cover is not particularly limited, it is usually 250 to 400 from the viewpoint of enhancing aerodynamic performance and increasing flight distance.

The visible region light transmittance of the cover layer is required to be 0.6% or more, preferably 0.8% or more, more preferably 0.8% or more, in order to exhibit the desired unique aesthetic appearance of the present invention. The value is 1.0% or more, more preferably 1.5% or more. The upper limit of the visible region light transmittance is such that traces of melting of the cover resin material and the surface of the intermediate layer, which are generated in the process of covering and molding the cover layer, can be seen through, and the desired aesthetic appearance as the ball surface color cannot be obtained. Since there is a possibility that it may not be obtained, it is preferably 80% or less, more preferably 50% or less, and most preferably 20% or less. The visible region light transmittance can be measured using a commercially available spectrophotometer or the like based on the JIS K 0115 standard. In the present invention, since the transmittance of the cover layer in the visible region is measured, the target cover layer is peeled from the golf ball, cut into strips according to the shape of the measurement sample installed in the measuring instrument to be used, and attached to the measuring instrument. By installing it, the visible region light transmittance of the cover layer itself can be measured.

The lightness (Lo value) of the golf ball having the cover layer of the present invention is preferably 25 or higher, more preferably 30 or higher, still more preferably 35 or higher, and most preferably 40 or higher. The Lo value means the L* value (brightness) based on the L*a*b* color system of "JIS Z8781". The cover layer becomes dull in color.

The ratio Lo/Li between the lightness (Lo value) of the golf ball and the lightness (Li) of the surface of the intermediate layer-covered sphere should be 0.3 or more in order to further enhance the above-described desired effect of the present invention. is preferably 0.5 or more, more preferably 0.7 or more, most preferably 0.9 or more, and the upper limit is preferably 1.5 or less, more preferably 1.3 or less , more preferably 1.2 or less, and most preferably 1.1 or less.

In the present invention, the surface of the cover layer can be painted. As the paint for coating the surface of the cover layer, it is preferable to employ a two-liquid curable urethane paint. Specifically, in this case, the two-liquid curing type urethane paint contains a main component having a polyol resin as a main component and a curing agent having a polyisocyanate as a main component. Such coating is also called clear coating.

In the case of a two-component curing type urethane coating, various polyols such as saturated polyester polyols, acrylic polyols and polycarbonate polyols are used as the main agent, and non-yellowing polyisocyanates such as hexamethylene diisocyanate, isophorone diisocyanate, Adducts such as hydrogenated xylylene diisocyanate, burettes, isocyanurates, or mixtures thereof are preferably used.

The above-mentioned paint is made by adding various solvents and additives to the above-mentioned resin as a base, and may further contain a luster material. When a glittering material is used, it is preferable to use 1.0 to 10.0 parts by mass of the glittering material with respect to 100 parts by mass of the base resin. If the blending amount is too large, for example, the jetting property of the spray gun may deteriorate during spray coating, resulting in poor coating workability.

Luminescent materials are roughly classified into metal oxide-coated mica, basic lead carbonate, bismuth oxide chloride, and natural fish phosphorus foil. It is preferred to choose oxide-coated mica. Titanium dioxide and iron oxide are generally used as the metal oxide, and various colors and interference effects can be obtained by changing the coating ratio (thickness of the coating layer). The larger the particle size of these pigments, the more luster is obtained. However, the larger the particle size of the pigment, the easier it is to sediment brightly, so it is desirable to select a pigment having an appropriate particle size.

A golf ball coated with a paint containing the luster material as described above can reflect light at various angles, thereby increasing the quality of the golf ball. In addition, since the sunlight is sufficiently reflected, the golf ball can be found more easily.

Also, matting particles can be blended into the coating composition to give a so-called matte golf ball without gloss. In this case, the matte particles to be used include, for example, silica-based, melamine-based, acrylic-based, and the like. Specific examples include silica, polymethyl methacrylate, polybutyl methacrylate, polystyrene, and polybutyl acrylate, and may be organic or inorganic. Silica is particularly preferably used. .

The amount of the matte particles to be blended is preferably 5 to 10 parts by mass with respect to 100 parts by mass of the main component (total amount of resin component and solvent) of the coating composition. If the amount is too large, the viscosity of the coating composition tends to increase and the coating workability tends to be poor.

The method of applying the coating material to the surface of the cover layer is not particularly limited, and any known method can be used, such as an air gun coating method or an electrostatic coating method.

The thickness of the coating layer applied to the cover layer is not particularly limited, but is usually 8-22 μm, preferably 10-20 μm.

Ball specifications such as mass and diameter of the golf ball of the present invention can be appropriately set according to the Rules of Golf.

EXAMPLES Hereinafter, the present invention will be specifically described by showing examples and comparative examples, but the present invention is not limited to the following examples.

[Examples 1 to 17, Comparative Examples 1 to 6]
A core having a diameter of 38.6 mm was produced by preparing and vulcanizing a core rubber composition common to all examples according to the formulation shown in Table 1.

Details of the core material are as follows.
・"cis-1,4-polybutadiene" manufactured by JSR, trade name "BR01"
・"Zinc acrylate" manufactured by Nippon Shokubai Co., Ltd. ・"Zinc oxide" manufactured by Sakai Chemical Industry Co., Ltd. ・"Barium sulfate" manufactured by Sakai Chemical Industry Co., Ltd. )
・ “Organic peroxide (1)” dicumyl peroxide, trade name “Percumyl D” (manufactured by NOF Corporation)
・ “Organic peroxide (2)” 1,1-di(tert-butylperoxy)cyclohexane and silica mixture, trade name “Perhexa C-40” (manufactured by NOF Corporation)
・"Zinc stearate" manufactured by NOF Corporation

Next, resin materials for the intermediate layer of each example shown in Table 2 below were used. This resin material was injection molded around the 38.6 mm diameter core obtained above to produce intermediate-layer-covered spheres of each example having an intermediate layer with a thickness of 1.25 mm.

The above resin materials are as follows.
"Himilan 1605", "Himilan 1557" and "Himilan 1706": ionomer resin manufactured by Mitsui-Dow Polychemicals "Pigment 1": Pigment Yellow 53
"Pigment 2": Pigment Blue 29
"Dye 1": Solvent Green 5
“Dye 2”: Fluorescent dye manufactured by Kashinomoto Technology Co., Ltd., trade name “Smart Color LP Green 2”
“Dye 3”: Fluorescent dye manufactured by Kashinomoto Technology, trade name “Lumicolor (Red)”
“Lubricant”: Lubricant manufactured by Sanyo Kasei Co., Ltd., trade name “Sanwax 161-P”

Next, around the above intermediate layer-covered spheres, resin materials for the cover layer of each example shown below were injection-molded in the compounding amounts shown in Table 3 to form a cover layer (outermost layer) having a thickness of 0.8 mm. An unpainted golf ball (diameter 42.7 mm) having At this time, common dimples were formed on the cover surface of each example and comparative example, although not shown.

Next, for the golf balls of each example and each comparative example, four types of paint ("clear paint," "pearl paint," A coating layer (coating layer) was formed by coating the surface of the cover layer so as to have a thickness of 15 µm using "matte coating" and "matte pearl coating").

Details of each component in the above table are as follows.
- "Polyol" saturated polyester polyol, weight average molecular weight (Mw) 28,000, acid value 4, hydroxyl value 170
・ “Bright material” Natural mica (“Iriodin 7205” manufactured by Sano Paint Co., Ltd.)
・ “Matte particles” silica (Maruo Calcium Co., Ltd. “Finesil X-35” average primary particle diameter 2.4 μm, BET specific surface area 262 m ² /g)
・ “HDI Nurate” Asahi Kasei Co., Ltd. “Duranate TPA-100” NCO content 23.1% by mass, non-volatile content 100% by mass
- "Solvent" Ethyl acetate was used as the solvent for the main agent, and ethyl acetate and butyl acetate were used as the solvents for the curing agent.

The details of the polyurethane resin used as the resin material for the cover layer are as follows.
TPU (1)
DIC Covestro Polymer Co., Ltd. trade name "Pandex", thermoplastic polyurethane, polyol component: number average molecular weight "1000", Shore D hardness 40, uncolored product
TPU (2)
DIC Covestro Polymer Co., Ltd. trade name "Pandex", thermoplastic polyurethane, polyol component: number average molecular weight "1000", Shore D hardness 65, uncolored product
TPU (3)
DIC Covestro Polymer Co., Ltd. trade name "Pandex", thermoplastic polyurethane, polyol component: number average molecular weight "2000", Shore D hardness 40, uncolored product
TPU (4)
DIC Covestro Polymer Co., Ltd. trade name "Pandex", thermoplastic polyurethane, polyol component: number average molecular weight "2000", Shore D hardness 47, uncolored product
TPU (5)
DIC Covestro Polymer Co., Ltd. trade name "Pandex", thermoplastic polyurethane, polyol component: number average molecular weight "2000", Shore D hardness 53, uncolored product
TPU (6)
DIC Covestro Polymer Co., Ltd. trade name "Pandex", thermoplastic polyurethane, polyol component: number average molecular weight "2000", Shore D hardness 40, white colored product
TPU (7)
DIC Covestro Polymer Co., Ltd. trade name "Pandex", thermoplastic polyurethane, polyol component: number average molecular weight "2000", Shore D hardness 40, yellow colored product
TPU (8)
DIC Covestro Polymer Co., Ltd. trade name "Pandex", thermoplastic polyurethane, polyol component: number average molecular weight "2000", Shore D hardness 40, black colored product

In Comparative Example 5, a thermoplastic polyester elastomer (trade name "Hytrel 4001" manufactured by DuPont-Toray) was used as the resin material of the cover layer.

The light transmittance of the cover layer, the lightness of the ball (Lo value) and the lightness of the intermediate layer (Li value), the visibility of the golf ball, and the unique aesthetic appearance evaluation (kawaii degree) of the obtained examples and comparative examples. , spin performance on approach, and scratch resistance were evaluated according to the following criteria.

Light transmittance of the cover layer in the visible region The light transmittance (T%) was measured using an ultraviolet-visible spectrophotometer "UV-1800" (manufactured by Shimadzu Corporation). The cover layer was peeled off from the coated ball thus produced, and the cover layer was cut into strips, which were measured as samples to be measured. The optical path at the time of measurement was measured from the surface side of the cover layer, the slit width was set to 0.1 nm, and the average value was obtained by sampling the data in the range of 380 to 780 nm at a pitch of 1 nm.

L value (brightness)
It was measured using a color difference meter (model SC-P, manufactured by Suga Test Instruments Co., Ltd.), and the lightness (L value) was obtained based on the L ^* a ^* b ^* color specification of JIS Z8781. A larger value indicates a brighter color tone. Further, in the present invention, the ball (painted) is placed in a measuring instrument and measured, and the appearance of the ball itself is measured. In addition, for the brightness (Li value) of the intermediate layer, in order to measure the color tone of the surface of the intermediate layer in which the core is covered with the intermediate layer, the sphere covered with the intermediate layer is set in the measuring instrument and measured. do.

Appearance of the ball (Kawaii frequency)
Ten golfers sensory evaluated the golf balls of each example with the following 5-point scale (1 to 5), and the average value was used for evaluation.
[Rating]
1 point: It is perceived as not cute/ordinary in appearance.
2 points: Slightly cute/It is felt that it may be used.
3 points: Slightly cute/I feel like I want to use it because it looks good.
4 points: very cute/excellent appearance makes me want to use it.
5 points: Very cute/The appearance is particularly good, and I feel that I definitely want to use it.

Visibility of the Ball Ten advanced golfers sensory evaluated the visibility of the trajectory when hit with a driver (W#1) in fine weather on the golf balls of each example.
Sensory evaluation was carried out according to the following criteria by 10 advanced golf players.
⊚: 8 or more out of 10 felt that "the trajectory at the time of hitting is easy to see".
◯: 5 to 7 out of 10 felt that "the trajectory at hitting is easy to see".
△: 3 to 4 out of 10 felt that "the trajectory at the time of hitting is easy to see".
x: 2 or less out of 10 felt that "the trajectory at the time of hitting is easy to see".

The surface hardness of the ball was measured with a JIS-C hardness tester by pressing a needle perpendicular to the surface of each ball. The surface hardness of the ball (cover) is the measured value at the bank portion where no dimples are formed on the ball surface.

Spin Performance During Approach A sand wedge (SW) was attached to a golf hitting robot, and the backspin amount of the ball immediately after hitting at a head speed (HS) of 11 m/s was measured with an initial condition measuring device.

A scratch-resistant ball was heated to 23°C, and a swing robot machine was used to hit each ball with a club using a pitching wedge at a head speed of 33 m/s. evaluated.
⊚: No scratches or hardly noticeable scratches.
◯: Scratches are slightly observed, but are almost unnoticeable.
Δ: The surface is fuzzy and the dimples are missing, but it can be used.
x: Dimples were completely scraped off and not worthy of use.

The following points are considered based on the evaluation results of each example in Tables 3 and 4 above.
When the hardness of the urethane resin material used for the cover layer is different, the use of a relatively soft resin material gives the ball a clear appearance with high transparency and a strong appearance (impression), as well as good spin characteristics. The use of polyurethane resin also improves the scratch resistance of the ball. Furthermore, as a raw material for polyurethane resin, polytetramethylene glycol (PTMG) with a small number average molecular weight (Mn) is used as a long-chain polyol. It can be seen that the more methylene glycol (PTMG) is used, the better the scratch resistance is.

Claims (5)

A sphere having an intermediate layer interposed between a core and a cover layer, the cover layer being formed of a resin material containing polyurethane or polyurea as a main component, and the core being coated with the intermediate layer (intermediate layer-coated sphere) The lightness (Li) of the surface of the cover layer is 25 or more based on the L*a*b* color system of JIS Z8781, and the visible region light transmittance of the cover layer is 0.6% or more. A golf ball. 2. The golf ball of claim 1, wherein the golf ball has a lightness (Lo value) of 25 or more based on the L*a*b* color system of JIS Z8781. 3. The golf ball of claim 2, wherein the ratio (Lo/Li) of the lightness (Lo value) of the golf ball to the lightness (Li) of the intermediate layer-covered sphere is 0.3 to 1.5. 2. The golf ball of claim 1, wherein the resin material of the cover layer has a Shore D hardness of 65 or less. 2. The golf ball of claim 1, wherein the cover layer is made of a resin material containing polyurethane as a main component, and the polyol component of the polyurethane contains polytetramethylene glycol (PTMG) having a number average molecular weight (Mn) of 3,500 or less.

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