JP2023001555A - Golf ball - Google Patents

Abstract

To provide a golf ball which, although the golf ball includes a silicone-based additive in an outer surface (a coating layer) of the golf ball, has a good spin performance on approach shots not only in a wet situation but also in a (normally) dry situation, and can exhibit both good water-repelling performance and good friction performance.SOLUTION: In a golf ball having a core, a cover, and a coating layer, the coating layer is formed of an urethane coating that includes an organic solvent having a boiling point of 80°C or less and a silicone-based additive, and the urethane coating includes a polyisocyanate as a curing agent. The polyisocyanate contains an adduct and an isocyanurate of hexamethylene diisocyanate (HMDI).SELECTED DRAWING: None

Description

The present invention relates to a golf ball comprising a core, a cover and a paint layer, and more particularly to a golf ball in which the cover is made of a polyurethane resin composition and the paint layer is made of a urethane paint composition.

For the purpose of protecting the surface of a golf ball or maintaining a good aesthetic appearance, the surface of the golf ball is often coated with a coating composition. As such a coating composition for golf balls, a two-component curable polyurethane coating is preferably used by mixing a polyol and a polyisocyanate immediately before use because it can withstand large deformation, impact and friction. ing.

Japanese Patent Application Publication No. 2014-524335 (Patent Document 1) describes a golf ball incorporating a "low energy" composition in the soft surface coating, the low energy composition lowering the coefficient of friction, This is done for purposes such as facilitating handling during manufacturing and reducing the tendency of mud to stick to the ball. Low energy compositions are described using silicone additives.

Japanese Patent Application Laid-Open No. 2019-10190 (Patent Document 2) discloses that the surface of a golf ball is made water-repellent so that the coefficient of friction of the surface of the golf ball is lowered, and the flight of the driver during play in the rain is prevented. It is stated to prevent the distance from falling. Examples of water-repellent additives include silicone-based additives such as silicone resins, silicone oils, and silicone rubbers.

Further, Japanese Patent Application Laid-Open No. 2021-53367 (Patent Document 3) discloses that forming the outer surface layer of a material having a contact angle of 90° or more makes the surface of the golf ball water-repellent, and the coefficient of friction of the surface of the golf ball is is reduced, and it is possible to prevent the driver's flight distance from decreasing when playing in the rain. Examples of water-repellent additives include silicone-based additives such as silicone resins, silicone oils, and silicone rubbers.

However, in the golf ball proposed above, the use of the silicone additive provides water repellency and improves spin performance in wet conditions, but tends to reduce approach spin performance in dry conditions (normal conditions). there were.

Therefore, in Patent Document 3 mentioned above, the outer surface layer of a golf ball is formed of a material containing a water-repellent additive and hexamethylene diisocyanate (HMDI), and the HMDI is an adduct and an isocyanurate. It is also proposed to include However, even the proposed golf ball is not sufficiently satisfactory in spin performance on approach.

Japanese Patent Publication No. 2014-524335 JP 2019-10190 A Japanese Patent Application Laid-Open No. 2021-53367

The present invention has been devised in view of the above circumstances. Even if a silicone additive is contained in the outer surface (paint layer) of a golf ball, the approach spin performance is good not only in the wet but also in the dry (normal). Therefore, it is an object of the present invention to provide a golf ball that achieves both water repellency and friction performance.

The inventors of the present invention have made intensive studies to achieve the above object, and have found that a urethane coating composition, which normally forms a coating layer corresponding to the outer surface of a golf ball, contains a polyisocyanate as a curing agent. The polyisocyanate contains an adduct of hexamethylene diisocyanate (HMDI) and an isocyanurate, and by selecting an organic solvent with a relatively low boiling point for the main agent or curing agent, the silicone component is reduced during coating. By preparing the coating so that the organic solvent on the surface of the coating film evaporates before floating on the outer surface and the coating composition is cured, it is possible to achieve both water repellency and friction performance, not only when wet The inventors have found that the approach spin performance is improved when the ball is dry (normal time), and have completed the present invention. In particular, by using a low resilience urethane resin composition as a cover material for a golf ball, the controllability during the approach is further improved, and the effects of the present invention can be fully exhibited. .

Accordingly, the present invention provides the following golf balls.
1. A golf ball comprising a core, a cover, and a paint layer, wherein the paint layer is formed of a urethane paint containing an organic solvent having a boiling point of 80° C. or less and a silicone additive, and the urethane paint contains a curing agent. A golf ball comprising a polyisocyanate, wherein the polyisocyanate contains an adduct of hexamethylene diisocyanate (HMDI) and an isocyanurate.
2. 2. The golf ball of claim 1, wherein the proportion of the organic solvent having a boiling point of 80° C. or less in the total coating composition is 20% by mass or more.
3. 3. The golf ball of 1 or 2, wherein the mixing ratio (A)/(B) of the isocyanurate (A) and the adduct (B) of hexamethylene diisocyanate is 85/15 to 15/85 by mass. .
4. At least one layer of the cover is formed of a resin composition containing the following components (I) and (II) (I) polyurethane or polyurea (II) an aromatic vinyl elastomer, and 4. The golf ball of any one of 1 to 3, wherein the group vinyl elastomer has a Shore D hardness of 30 or less and a rebound resilience of 30% or less.
5. 5. The golf ball of any one of items 1 to 4, wherein component (II) is contained in an amount of 5 to 20 parts by mass per 100 parts by mass of component (I).
6. The resin composition further contains (III) a thermoplastic polyester elastomer, and the thermoplastic polyester elastomer as component (III) has a Shore D hardness of 45 or less and a rebound resilience of 74% or less. 6. The golf ball according to 4 or 5 above, which has a melt viscosity of 1.5×10 ⁴ (dPa·s) or less at 200° C. and a shear rate of 243 (1/sec).
7. When a golf ball is free-falled from a height position 3 m above the impact surface inclined at 58 degrees to the horizontal direction, the golf ball starts to slide on the impact surface and then stops. When the amount of displacement in the vertical direction of the golf ball up to is defined as the amount of slippage (Ds) of the golf ball, Ds is 2.0 mm or less, and the distance from the impact surface after the golf ball stops sliding on the impact surface 7. The golf ball according to any one of 1 to 6 above, wherein Tc is 400 μs or more, where the time until the slip contact time (Tc) is defined.

According to the golf ball of the present invention, even if the outer surface (paint layer) of the golf ball contains a silicone-based additive, the approach spin performance is improved not only when wet but also when dry (normal time), and water repellency is improved. Performance and friction performance can be fully compatible.

The present invention will be described in more detail below.
The golf ball of the present invention is a golf ball comprising a core, a cover and a paint layer.

The core can be formed using a known rubber material as a base material. As the base rubber, known base rubbers such as natural rubber or synthetic rubber can be used. recommended to be used for Further, in the base rubber, natural rubber, polyisoprene rubber, styrene-butadiene rubber, etc. can be used in combination with the polybutadiene described above, if desired.

Moreover, polybutadiene can be synthesized using a metal catalyst such as a rare earth element-based catalyst such as an Nd catalyst, a cobalt catalyst, or a nickel catalyst.

Co-crosslinking agents such as unsaturated carboxylic acids and metal salts thereof, inorganic fillers such as zinc oxide, barium sulfate and calcium carbonate, dicumyl peroxide and 1,1-bis(t-butyl Organic peroxides such as peroxy)cyclohexane and the like can be blended. In addition, if necessary, a commercially available anti-aging agent or the like can be added as appropriate.

The core can be produced by vulcanizing and curing a rubber composition containing the above components. For example, it is kneaded using a kneader such as a Banbury mixer or a roll, compression molded or injection molded using a core mold, and the temperature is 100 to 100 as a temperature sufficient for the organic peroxide or co-crosslinking agent to act. By appropriately heating the molded article under conditions of 200° C., preferably 140 to 180° C., for 10 to 40 minutes, the molded article can be cured and produced.

In the golf ball of the present invention, the core is covered with a single-layer or multiple-layer cover. Examples of such golf balls include a golf ball having a core with a single-layer cover, and a golf ball having a core, an intermediate layer covering the core, and an outermost layer covering the intermediate layer. be done.

In the present invention, the resin material for at least one layer of the cover includes the following components (I) and (II),
(I) Polyurethane or polyurea (II) It is preferably formed from a resin composition containing an aromatic vinyl elastomer.

(I) Polyurethane or Polyurea Polyurethane or polyurea can be the main material or base resin of the cover material (resin composition). The details of this component, polyurethane (Ia) or polyurea (Ib), are as follows.

(Ia) Polyurethane The structure of polyurethane is composed 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 constituting 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. These may be used individually by 1 type, and may use 2 or more types together.

As the polymer polyol, it is preferable to use a polyether-based polyol.

The number average molecular weight of the long-chain polyol is preferably within the range of 1,000 to 5,000. By using a long-chain polyol having such a number-average molecular weight, it is possible to reliably obtain a golf ball made of a polyurethane composition that is excellent in various properties such as resilience and productivity. The number average molecular weight of the long-chain polyol is more preferably in the range of 1,500 to 4,000, even more preferably in the range of 1,700 to 3,500.

The number average molecular weight 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. However, with some isocyanate species, it is difficult to control the cross-linking reaction during injection molding.

In addition, 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 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.

A thermoplastic polyurethane material is preferably used as the polyurethane described above, and an ether-based thermoplastic polyurethane material is particularly preferable. As the thermoplastic polyurethane material, commercially available products can be suitably used. be able to.

(Ib) 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 are no particular restrictions, 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, without limitation. 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.

Regarding the material hardness of component (I), the Shore D hardness is preferably 52 or less, more preferably 50 or less, and even more preferably 50 or less in Shore D hardness, from the viewpoint of the spin characteristics and scratch resistance of the golf ball. is 48 or less. The lower limit thereof is preferably 38 or more in Shore D hardness, more preferably 40 or more in Shore D hardness, from the standpoint of moldability.

The impact resilience of component (I) is preferably 55% or more, more preferably 57% or more, and still more preferably 59% or more, from the viewpoint of improving the spin rate on approach. The rebound resilience is measured according to JIS-K 6255:2013 standard.

The above component (I) is the main component of the resin composition, and from the viewpoint of sufficiently imparting the scratch resistance of the urethane resin, it is 50% by mass or more, preferably 60% by mass or more, more preferably 70% by mass of the resin composition. % by mass or more, more preferably 80% by mass or more, and most preferably 90% by mass or more.

(II) Aromatic Vinyl Elastomer Next, the (II) aromatic vinyl elastomer will be described.
(II) The aromatic vinyl-based elastomer, as described later, has good compatibility with component (I), which is the base resin, when blended in a small amount below a certain level. It has good compatibility with the elastomer, and can maintain good scratch resistance and moldability in the golf ball and its manufacturing method.

An aromatic vinyl-based elastomer is a polymer (elastomer) composed of a polymer block mainly composed of an aromatic vinyl compound and a random copolymer block of an aromatic vinyl compound and a conjugated diene compound. That is, aromatic vinyl-based elastomers generally have blocks composed of aromatic vinyl compound components as hard segments at both ends, and blocks composed of conjugated diene compound components as soft segments, as typified by SEBS. have in the middle. Recent studies have also reported a polymer in which, in addition to a conjugated diene compound component, an aromatic vinyl-based component is randomly incorporated in the midblock. In general, the hardness of aromatic vinyl elastomers decreases as the content of the aromatic vinyl that forms the hard segment decreases, and the impact resilience increases due to the increase in the soft segment component. On the other hand, when the aromatic vinyl component is randomly incorporated into the soft component of the mid-block, the impact resilience is lowered without significantly increasing the hardness. A similar effect can also be obtained by using a conjugated diene compound exhibiting a high Tg instead of the aromatic vinyl compound randomly incorporated in the intermediate block. In particular, in the present invention, it is preferable to use a hydrogenated polymer (elastomer) as the component (III) in order to sufficiently exhibit the above-described effects.

Examples of aromatic vinyl compounds in the polymer include styrene, α-methylstyrene, p-methylstyrene, divinylbenzene, 1,1-diphenylethylene, N,N-dimethyl-p-aminoethylstyrene, N, Examples include N-diethyl-p-aminoethylstyrene. These may be used alone or in combination of two or more. Among these groups, styrene is preferred.

Examples of the conjugated diene compound in the polymer include butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 2-methyl-1,3-pentadiene, and 1,3-hexadiene. etc. These may be used alone or in combination of two or more. Among these groups, butadiene and isoprene are preferred, and butadiene is more preferred.

Units derived from the conjugated diene compound, for example, units derived from butadiene, become ethylene units or butylene units by hydrogenation. For example, a styrene-butadiene-styrene block copolymer (SBS) is hydrogenated to give a styrene-ethylene-butylene-styrene block copolymer (SEBS).

As the aromatic vinyl elastomer as the component (II), as described above, it is preferable to employ a hydrogenated aromatic vinyl elastomer, that is, a hydrogenated aromatic vinyl elastomer. The hydrogenated aromatic vinyl elastomer is obtained by hydrogenating a polymer block composed mainly of an aromatic vinyl compound and a random copolymer block of an aromatic vinyl compound and a conjugated diene compound. Elastomers are preferred, and elastomers obtained by hydrogenating a polymer consisting of a polymer block mainly composed of styrene and a random copolymer block of styrene and butadiene are more preferred. A polymer consisting of a random copolymer block with butadiene, in particular, a polymer block mainly composed of styrene at both ends (especially a polymer block consisting only of styrene at both ends) and a random copolymer block in the middle Elastomers obtained by addition are preferred. By using a copolymer having this structure, it has both low hardness and low resilience, and because it has a fast solidification speed after molding, it has little tack, and is compatible with (I) polyurethane or polyurea, which is the main component. It is thought that deterioration of physical properties due to blending can be minimized due to excellent compatibility.

Specific examples of the hydrogenated aromatic vinyl elastomer include styrene-ethylene/butylene-styrene block copolymer (SEBS), styrene-isobutylene-styrene block copolymer (SIBS), and styrene-isoprene-styrene block. copolymer (SIS), styrene-isobutylene block copolymer (SIB), styrene-ethylene/propylene-styrene block copolymer (SEPS), styrene-ethylene/ethylene/propylene-styrene block copolymer (SEEPS), Styrene-butadiene/butylene-styrene block copolymer (SBBS), styrene-ethylene-propylene block copolymer (SEP), and the like.

In the aromatic vinyl-based elastomer, the ratio of units derived from the aromatic vinyl compound in the copolymer (that is, the content of the aromatic vinyl compound, preferably the content of styrene) is 30% by mass or more. is preferred, more preferably 40% by mass or more, still more preferably 50% by mass or more, and most preferably 60% by mass or more. Thus, by setting the aromatic vinyl compound content, preferably the styrene content, to a large amount, the compatibility with polyurethane or polyurea, which is the component (I), is improved, and the desired hardness and moldability are deteriorated. can be prevented. The content of units derived from the aromatic vinyl compound (preferably the styrene content) can be calculated by H ¹ -NMR measurement.

In addition, in the aromatic vinyl elastomer, the glass transition temperature (Tg) indicated by the tan δ peak temperature obtained by dynamic viscoelasticity measurement (DMA) is preferably -20 to 50°C, more preferably 0°C. 5° C. or higher, more preferably 5° C. or higher. That is, by having the tan δ peak temperature near the temperature at which golf balls are normally used, the impact resilience of the entire resin composition is kept low in the temperature range at which golf balls are normally used, and the desired effect of the present invention can be achieved. can be increased.

Commercially available products can be used as the aromatic vinyl-based elastomer that is the component (II). For example, commercially available products include “S.O.E. "Dick Styrene" manufactured by DIC Corporation can be mentioned.

Regarding the material hardness of component (II), the Shore D hardness is 30 or less, more preferably 28 or less, and still more preferably 26 or less, from the viewpoint of improving the spin rate on approach. The lower limit thereof is preferably 18 or more in Shore D hardness, more preferably 20 or more in Shore D hardness.

The modulus of rebound resilience of component (II) is preferably 30% or less, more preferably 25% or less, still more preferably 25% or less, in order to maintain the approach spin rate and keep the rebound on approach low to obtain controllability. is 22% or less. By keeping the modulus of rebound resilience very low in this way, it is possible to reduce the initial velocity of the ball on approach shots without adversely affecting the physical properties of the golf ball with a small addition amount. However, the lower limit of the modulus of rebound resilience is preferably 15% or more, more preferably 20% or more, in order to minimize the effect of reducing rebound on driver shots and shortening flight distance. The rebound resilience is measured according to JIS-K 6255:2013 standard.

The blending amount of component (II) is 30 parts by mass or less, preferably 20 parts by mass or less, more preferably 15 parts by mass or less per 100 parts by mass of component (I). In addition, the lower limit of the blending amount is preferably 5 parts by mass or more, more preferably 10 parts by mass or more. If the blending amount of component (II) is too large, the scratch resistance and moldability may deteriorate. On the other hand, if the blending amount of component (II) is too small, the cover resin material may not have low hardness and desired rebound resilience, and the effect of lowering the ball's initial velocity on approach shots may be reduced.

The resin composition containing the components (I) and (II) may further contain (III) a thermoplastic polyester elastomer. (III) Component is explained below.

(III) Thermoplastic Polyester Elastomer The thermoplastic polyester elastomer of component (III) imparts a certain level of resilience to the resin composition, and in combination with this resilience, can maintain a spin rate above a certain level on approach. is. In addition, the thermoplastic polyester elastomer of component (III) has good compatibility with component (I), which is the base resin, and in particular, has better compatibility than conventionally used thermoplastic polyester elastomers. Good scratch resistance can be imparted. Furthermore, by blending the thermoplastic polyester elastomer as an essential component in the resin composition, it has a melt viscosity of a certain level or more, thereby imparting solidification property after molding of the resin composition. The softness of the component (I) suppresses a decrease in the viscosity of the entire resin composition, prevents a decrease in moldability (productivity) and an increase in appearance defects of golf balls after molding, and increases production costs due to an increase in cooling time. can be suppressed.

The thermoplastic polyester elastomer of component (III) is
A resin composition comprising (b-1) a polyester block copolymer and (b-2) a hard resin. Further, the component (b-1) is composed of (b-1-1) a high melting point crystalline polymer segment and (b-1-2) a low melting point polymer segment.

The (b-1-1) high melting point crystalline polymer segment constituting the polyester block copolymer of the component (b-1) is an aromatic dicarboxylic acid or an ester-forming derivative thereof, a diol or an ester-forming derivative thereof. It is a polyester formed of one or more selected from the group consisting of:

Specific examples of aromatic dicarboxylic acids include terephthalic acid, isophthalic acid, phthalic acid, naphthalene-2,6-dicarboxylic acid, naphthalene-2,7-dicarboxylic acid, anthracenedicarboxylic acid, diphenyl-4,4′- Dicarboxylic acids, diphenoxyethanedicarboxylic acid, 4,4′-diphenyletherdicarboxylic acid, 5-sulfoisophthalic acid, 3-sodium sulfoisophthalate and the like. In the present invention, aromatic dicarboxylic acids are mainly used, and if necessary, some of these aromatic dicarboxylic acids may be 1,4-cyclohexanedicarboxylic acid, cyclopentanedicarboxylic acid, and 4,4′-dicyclohexyldicarboxylic acid. Aliphatic dicarboxylic acids such as acids and aliphatic dicarboxylic acids such as adipic acid, succinic acid, oxalic acid, sebacic acid, dodecanedioic acid, and dimer acid may be substituted. Specific examples of ester-forming derivatives of dicarboxylic acids include lower alkyl esters, aryl esters, carbonic acid esters and acid halides of the dicarboxylic acids described above.

As the diol, a diol having a molecular weight of 400 or less can be preferably used. Specifically, aliphatic diols such as 1,4-butanediol, ethylene glycol, trimethylene glycol, pentamethylene glycol, hexamethylene glycol, neopentyl glycol, and decamethylene glycol, 1,1-cyclohexanedimethanol, 1 , 4-dicyclohexanedimethanol and tricyclodecanedimethanol, xylylene glycol, bis(p-hydroxy)diphenyl, bis(p-hydroxy)diphenylpropane, 2,2′-bis[4 -(2-hydroxyethoxy)phenyl]propane, bis[4-(2-hydroxyethoxy)phenyl]sulfone, 1,1-bis[4-(2-hydroxyethoxy)phenyl]cyclohexane, 4,4'-dihydroxy- Aromatic diols such as p-terphenyl and 4,4'-dihydroxy-p-quarterphenyl can be exemplified. Further, specific examples of ester-forming derivatives of diols include the above-described acetyl derivatives of diols and alkali metal salts.

The above aromatic dicarboxylic acids, diols, and derivatives thereof may be used singly or in combination of two or more.

Examples of the component (b-1-1) include those composed of polybutylene terephthalate units derived from terephthalic acid and/or dimethyl terephthalate and 1,4-butadiol, isophthalic acid and/or dimethyl isophthalate and 1, A polybutylene terephthalate unit derived from 4-butanediol and a copolymer of both can be preferably used.

The (b-1-2) low melting point polymer segment is an aliphatic polyether and/or an aliphatic polyester.

Aliphatic polyethers include poly(ethylene oxide) glycol, poly(propylene oxide) glycol, poly(tetramethylene oxide) glycol, poly(hexamethylene oxide) glycol, copolymers of ethylene oxide and propylene oxide, poly(propylene oxide) Examples thereof include ethylene oxide addition polymers of glycols, copolymer glycols of ethylene oxide and tetrahydrofuran, and the like. Aliphatic polyesters include poly(ε-caprolactone), polyenantholactone, polycaprolactone, polybutylene adipate, polyethylene adipate and the like. In the present invention, from the viewpoint of elastic properties, poly(tetramethylene oxide) glycol, ethylene oxide adduct of poly(propylene oxide) glycol, copolymer glycol of ethylene oxide and tetrahydrofuran, poly(ε-caprolactone), polybutylene adipate, and Polyethylene adipate and the like can be preferably used. Furthermore, among these, it is particularly recommended to use poly(tetramethylene oxide) glycol, ethylene oxide adduct of poly(propylene oxide) glycol, and copolymer glycol of ethylene oxide and tetrahydrofuran. The number average molecular weight of these segments is preferably about 300 to 6000 in the copolymerized state.

The above component (b-1) can be produced by a known method. Specifically, a method of subjecting a lower alcohol diester of a dicarboxylic acid, an excessive amount of a low-molecular-weight glycol, and a low-melting-point polymer segment component to a transesterification reaction in the presence of a catalyst, and polycondensing the resulting reaction product; and an excess amount of glycol and the low-melting-point polymer segment component in the presence of a catalyst, and polycondensing the resulting reaction product.

The proportion of component (b-1-2) in component (b-1) is 30 to 60% by mass. In this case, the preferable lower limit can be 35% by mass or more, and the preferable upper limit can be 55% by mass or less. If the proportion of component (b-1-2) is too small, the impact resistance and compatibility may be insufficient (especially at low temperatures). On the other hand, if the proportion of the component (b-1-2) is too high, the resin composition (and molded article) may lack rigidity.

The hard resin of component (b-2) is not particularly limited, but examples include polycarbonate, acrylic resin, ABS resin, styrene resin such as polystyrene, polyester resin, polyamide resin, polyvinyl chloride, and modified One or more selected from the group consisting of polyphenylene ethers can be used. In the present invention, a polyester resin can be preferably used from the viewpoint of compatibility, and more preferably, it is recommended to use polybutylene terephthalate and/or polybutylene naphthalate.

The blending ratio [(b-1):(b-2)] of the above components (b-1) and (b-2) is not particularly limited, but the mass ratio is 50:50 to 90. :10, more preferably 55:45 to 80:20. If the proportion of component (b-1) is too small, the impact resistance (at low temperatures) may be insufficient. On the other hand, if the proportion of the component (b-1) is too high, the composition (and molded article) may be insufficient in rigidity and moldability.

Commercially available products can be used as the (III) thermoplastic polyester-based elastomer, and a specific example thereof is "Hytrel" manufactured by DuPont-Toray.

Regarding the material hardness of the component (III), the Shore D hardness is 45 or less, more preferably 43 or less, and still more preferably 41 or less, from the viewpoint of improving the approach spin rate. The lower limit thereof is preferably 36 or more in Shore D hardness, more preferably 38 or more in Shore D hardness.

The rebound resilience of component (III) is preferably 74% or less, more preferably 73% or less, and even more preferably 72% or less, from the viewpoint of lowering the initial approach velocity. The lower limit of the rebound resilience is preferably 50% or higher, more preferably 52% or higher, and even more preferably 60% or higher. The rebound resilience is measured according to JIS-K 6255:2013 standard.

The melt viscosity of the thermoplastic polyester elastomer of component (III) is 1.5×10 ⁴ (dPa·s) or less, preferably 1.45×10 ⁴ (dPa·s) or less, more preferably 1.0. × 104 (dPa s) or less, more preferably 0.8 × 10 ⁴ (dPa s) or less, and the lower limit is preferably 0.4 × 10 ⁴ (dPa s) or more, more preferably It is preferably 0.5×10 ⁴ (dPa·s) or more. By having this melt viscosity, solidification property can be imparted after molding of the resin composition, and good moldability (productivity) can be maintained. This melt viscosity indicates the melt viscosity at a shear rate of 243 (1/sec) when measured with a capillograph at a temperature condition of 200° C. according to ISO 11443:1995.

The amount of component (III) is 20 parts by mass or less, preferably 15 parts by mass or less per 100 parts by mass of component (I). There is The lower limit of the above compounding amount is preferably 3 parts by mass or more, more preferably 5 parts by mass or more, per 100 parts by mass of component (I).

The resin composition containing the above (I) to (III) may contain other resin materials in addition to the resin components described above. The purpose is to further improve the fluidity of the resin composition for golf balls and improve various physical properties such as resilience and resistance to cracking.

Specific examples of other resin materials include polyamide elastomers, ionomer resins, ethylene-ethylene/butylene-ethylene block copolymers or modified products thereof, polyacetal, polyethylene, nylon resins, methacrylic resins, polyvinyl chloride, polycarbonate, It is selected from polyphenylene ether, polyarylate, polysulfone, polyethersulfone, polyetherimide and polyamideimide, and one or more of them can be used.

In addition, the resin composition can further contain an active isocyanate compound. This active isocyanate compound reacts with polyurethane or polyurea, which is the main component, to further improve the scratch resistance of the entire resin composition. can be improved.

As the above isocyanate compound, any isocyanate compound that is commonly used in polyurethane can be used without particular limitation. Mixtures of these two, 4,4-diphenylmethane diisocyanate, m-phenylene diisocyanate, 4,4'-biphenyl diisocyanate, etc., and hydrogenated products of these aromatic isocyanate compounds, such as dicyclohexylmethane diisocyanate, can also be used. Aliphatic diisocyanates such as tetramethylene diisocyanate, hexamethylene diisocyanate (HDI) and octamethylene diisocyanate, and alicyclic diisocyanates such as xylene diisocyanate are also included. Furthermore, a blocked isocyanate compound obtained by reacting an isocyanate group of a compound having two or more isocyanate groups at its end with a compound having an active hydrogen, and a uretidione compound obtained by dimerization of isocyanate may be mentioned.

The amount of the above isocyanate compound is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, relative to 100 parts by mass of the polyurethane or polyurea resin as component (I). The value is preferably 30 parts by mass or less, more preferably 20 parts by mass or less. If this amount is too small, a sufficient cross-linking reaction may not be obtained, and no improvement in physical properties may be observed. On the other hand, if the blending amount is too large, problems such as discoloration due to heat or ultraviolet rays over time, loss of thermoplasticity, and a decrease in resilience may occur.

Furthermore, any additive can be appropriately added to the resin composition according to the application. Examples of optional additives include fillers (inorganic fillers), organic short fibers, reinforcing agents, cross-linking agents, pigments, dispersants, anti-aging agents, ultraviolet absorbers, and light stabilizers. 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 rebound resilience of the resin composition is required to be 50% or more, preferably 52% or more, more preferably 52% or more, as measured according to JIS-K 6255:2013 standard, in order to improve the spin rate on approach. It is 54% or more, and the upper limit is 72% or less, preferably 70% or less, more preferably 68% or less.

Regarding the material hardness of the resin composition, it is required that the Shore D hardness is 49 or less, preferably 48 or less, and more preferably 47 or less in Shore D hardness, from the viewpoint of improving the spin rate on approach. be. The lower limit thereof is preferably 30 or more in Shore D hardness, more preferably 35 or more in Shore D hardness, from the standpoint of moldability.

Regarding the method of preparing each component of the resin composition, for example, it is possible to mix using various kneaders such as a kneading type (single-screw or) twin-screw extruder, Banbury, kneader, labo plastomill, or Each component may be mixed by dry blending during injection molding of the resin composition. Furthermore, when using the above-mentioned active isocyanate compound, it may be contained at the time of resin mixing using various kneaders, or a master batch containing the active isocyanate compound and other components is prepared separately in advance, and the resin composition The components may be mixed by dry blending during injection molding of the article.

For example, as a method of molding the cover with the above resin composition, for example, the above resin composition may be supplied to an injection molding machine, and the cover may be molded by injecting the melted resin composition around the core. can. In this case, the molding temperature is usually in the range of 150 to 270° C., depending on the type of the main component (I) polyurethane or polyurea.

The thickness of the cover is preferably 0.4 mm or more, more preferably 0.5 mm or more, still more preferably 0.6 mm or more, and the upper limit is preferably 3.0 mm or less, more preferably 2.0 mm or less. .

When at least one intermediate layer is interposed between the core and the above, the material of the intermediate layer is preferably selected from various thermoplastic resins used in golf ball cover materials, particularly ionomer resins. and a commercial product can be used as the ionomer resin. In this case, the thickness of the intermediate layer can be set within the same range as the thickness of the cover.

In terms of aerodynamic performance, the golf ball of the present invention is provided with a large number of dimples on the surface of the outermost layer. The number of dimples formed on the surface of the outermost layer is not particularly limited, but is preferably 250 or more, more preferably 270 or more, still more preferably 270 or more, from the viewpoint of enhancing aerodynamic performance and increasing flight distance. The number is 290 or more, most preferably 300 or more, and the upper limit is preferably 400 or less, more preferably 380 or less, still more preferably 360 or less.

In the present invention, a paint layer is formed on the surface of the cover. This paint layer is formed of a urethane paint containing an organic solvent having a boiling point of 80° C. or less and a silicone additive. As the urethane coating, it is preferable to adopt a two-liquid curing type urethane coating. Specifically, it contains a main component mainly composed of polyol resin and a curing agent mainly composed of polyisocyanate.

Although the polyol is not particularly limited, it is preferable to use one or two or more polyester polyols. For example, two types of polyester polyols, polyester polyol (A) and polyester polyol (B), can be used as main ingredients. These two types of polyester polyols have different weight average molecular weights (Mw), the weight average molecular weight (Mw) of component (A) is 20,000 to 30,000, and A weight average molecular weight (Mw) of 800 to 1,500 is preferred. The weight average molecular weight (Mw) of component (A) is more preferably 22,000 to 29,000, and still more preferably 23,000 to 28,000. On the other hand, the weight average molecular weight (Mw) of component (B) is more preferably 900 to 1,200, more preferably 1,000 to 1,100.

The above two types of polyester polyols are obtained by polycondensation of polyols and polybasic acids. Examples of this polyol include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol and diethylene glycol. , dipropylene glycol, hexylene glycol, dimethylolheptane, polyethylene glycol, polypropylene glycol, triols, tetraols, and polyols having an alicyclic structure. Examples of polybasic acids include aliphatic dicarboxylic acids such as succinic acid, adipic acid, sebacic acid, azelaic acid and dimer acid; aliphatic unsaturated dicarboxylic acids such as fumaric acid, maleic acid, itaconic acid and citraconic acid; acids, aromatic polycarboxylic acids such as isophthalic acid, terephthalic acid, trimellitic acid and pyromellitic acid, tetrahydrophthalic acid, hexahydrophthalic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, endo Dicarboxylic acids having an alicyclic structure, such as methylenetetrahydrophthalic acid, and tris-2-carboxyethyl isocyanurate. In particular, as the polyester polyol of the component (A), a polyester polyol having a cyclic structure introduced into the resin skeleton can be employed. Condensation, or polyester polyol obtained by polycondensation of a polyol having an alicyclic structure and diols or a triol and a polybasic acid. On the other hand, as the polyester polyol of component (B), a polyester polyol having a multi-branched structure can be employed, and examples thereof include polyester polyols having a branched structure such as "NIPPOLAN 800" manufactured by Tosoh Corporation.

In addition, the overall weight average molecular weight (Mw) of the main agent comprising the above two polyester polyols is preferably 13,000 to 23,000, more preferably 15,000 to 22,000. In addition, the total number average molecular weight (Mw) of the main agent comprising the above two types of polyester polyols is preferably 1,100 to 2,000, more preferably 1,300 to 1,850. If these average molecular weights (Mw and Mn) deviate from the above range, the abrasion resistance of the coating film may be lowered. The weight-average molecular weight (Mw) and number-average molecular weight (Mn) are measured values (polystyrene conversion values) obtained by gel permeation chromatography (hereinafter abbreviated as GPC) by differential refractometer detection.

The blending amount of the two types of polyester polyols (A) and (B) is not particularly limited, but the blending amount of the component (A) is 20 to 30% by mass with respect to the total amount of the main agent, and (B) It is preferable that the blending amount of the components is 2 to 18% by mass based on the total amount of the main agent.

Moreover, when using only 1 type as said polyol, it is suitable to employ|adopt the polyester polyol (A) of the said description.

On the other hand, polyisocyanate includes two kinds of isocyanurate and adduct of hexamethylene diisocyanate. Isocyanate prepolymers are generally divided into three structures (adduct, burette, and isocyanurate). Adduct refers to an adduct of diisocyanate and trimethylolpropane. Isocyanurate refers to a trimer of diisocyanate.

The hexamethylene diisocyanate also includes its modified form. Examples of modified hexamethylene diisocyanate include polyester-modified hexamethylene diisocyanate and urethane-modified hexamethylene diisocyanate.

The mixing ratio (A)/(B) of the isocyanurate body (A) and the adduct body (B) of hexamethylene diisocyanate is 85/15 to 15 in terms of mass ratio from the viewpoint of improving the spin rate on approach. /85, more preferably 80/20 to 20/80, and still more preferably 75/25 to 25/75.

Nurate forms of hexamethylene diisocyanate (HMDI) include, for example, trade names "Coronate 2357" (manufactured by Tosoh Corporation), "Sumidule N3300" (manufactured by Sumika Covestro Urethane Co., Ltd.), and "Duranate TPA-100" (Asahi Kasei Co., Ltd.). (manufactured by Mitsui Chemicals), "Takenate D170N", "Takenate D177N" (all manufactured by Mitsui Chemicals), and "Barnock DN-980" (manufactured by DIC). One of these can be used alone, or two or more of them can be used in combination.

Examples of adducts of hexamethylene diisocyanate (HMDI) include trade names "Coronate HL" (manufactured by Tosoh Corporation), "Takenate D160N" (manufactured by Mitsui Chemicals, Inc.), "Duranate E402-80B" and "Duranate E405- 70B" (both manufactured by Asahi Kasei Corporation), "Barnock DN-955" and "Barnock DN-955S" (both manufactured by DIC). One of these can be used alone, or two or more of them can be used in combination.

The molar ratio (NCO group/OH group) between the hydroxyl group (OH group) of the polyester polyol and the isocyanate group (NCO group) of the polyisocyanate is preferably 0.6 or more, more preferably 0.65 or more. , the upper limit is preferably 1.5 or less, more preferably 1.0 or less, and still more preferably 0.9 or less. If this molar ratio is less than 0.6, unreacted hydroxyl groups may remain, resulting in poor performance and water resistance as a golf ball coating film. On the other hand, if it exceeds 1.5, the isocyanate groups become excessive, and urea groups (brittle) are formed by reaction with moisture, and as a result, the performance of the golf ball coating may deteriorate.

As the curing catalyst (organometallic compound), an amine-based catalyst or an organometallic catalyst can be used. Those blended as curing agents for type urethane paints can be preferably used.

In the present invention, the coating composition contains silicone additives such as silicone resins, silicone oils and silicone rubbers in order to lower the coefficient of friction of the surface of the golf ball and impart water repellency. A silicone-modified acrylate can be used as the silicone resin. A silicone-modified acrylate is a surface control agent in which an acrylic structure and a silicone structure are incorporated in one molecule. By attaching a polysiloxane chain to the acrylic skeleton, unlike ordinary polyrotaxane-based silicone resins, it becomes difficult to slip even if the amount of silicone-based additive added is increased, and water repellency can be improved. Examples of silicone-modified acrylates include trade names “BYK3550” and “BYK3700” (both manufactured by BYK-Chemie). Examples of silicone oil include methyl hydrogen silicone oil and dimethyl silicone oil.

The ratio of the silicone additive to the total amount of the coating composition is preferably 0.01% by mass or more, more preferably 0, in order to lower the coefficient of friction of the surface of the golf ball and provide sufficient water repellency. 0.02% by mass or more, more preferably 0.03% by mass or more. Moreover, as an upper limit, it is 0.5 mass % or less. If this upper limit is exceeded, the desired control performance may not be obtained during approach.

In addition, you may add a well-known coating compounding component to a coating composition as needed. Specifically, an appropriate amount of a thickener, an ultraviolet absorber, a fluorescent whitening agent, a slipping agent, a pigment, or the like can be added.

When a coating composition is used, the coating composition can be prepared at the time of coating, applied to the ball surface using a conventional coating process, and dried to form a coating layer on the ball surface. In this case, as a coating method, a spray coating method, an electrostatic coating method, a dipping method, or the like can be suitably employed, and there is no particular limitation.

The coating composition can be mixed with various organic solvents. Examples of such organic solvents include aromatic solvents such as toluene, xylene, and ethylbenzene, ester solvents such as ethyl acetate, butyl acetate, propylene glycol methyl ether acetate, and propylene glycol methyl ether propionate, acetone, and methyl ethyl ketone. , methyl isobutyl ketone, ketone solvents such as cyclohexanone, ether solvents such as diethylene glycol dimethyl ether, diethylene glycol diethyl ether, dipropylene glycol dimethyl ether, alicyclic hydrocarbon solvents such as cyclohexane, methylcyclohexane, ethylcyclohexane, mineral spirits, etc. A petroleum hydrocarbon solvent or the like can be used.

In the present invention, an organic solvent having a boiling point of 80°C or less is included. This is to reduce as much as possible the silicone component that floats to the surface during coating. Examples of organic solvents having a boiling point of 80°C or less include hydrocarbon solvents such as normal hexane (68°C), cyclohexane (80°C), and benzene (80°C), methyl acetate (57°C), ethyl acetate (77°C), and the like. Ester-based solvents, ketone-based solvents such as acetone (56° C.) and methyl ethyl ketone (79° C.) can be used. The numbers in parentheses indicate boiling points. Among the above organic solvents having a boiling point of 80° C. or lower, ester solvents and ketone solvents can be preferably used in consideration of the effects on the human body and the environment.

The proportion of the organic solvent having a boiling point of 80° C. or less in the total amount of the coating composition is preferably 20% by mass or more, more preferably 20% by mass or more, in order to sufficiently reduce the amount of the silicone component that floats to the surface during coating. is 30% by mass or more, more preferably 40% by mass or more. Moreover, as an upper limit, it is 80 mass % or less. If this upper limit is exceeded, the leveling property of the surface of the coating layer will not be high, and the gloss of the coating surface may decrease.

The above drying process may be performed in the same manner as for a known two-liquid curing urethane paint, with a drying temperature of about 40° C. or higher, particularly 40 to 60° C., and a drying time of 20 to 90 minutes, particularly 40 to 50 minutes. can be

Although the thickness of the paint layer is not particularly limited, it is preferably 3 to 50 μm, more preferably 5 to 20 μm.

In the golf ball of the present invention having the paint layer, the amount of deflection when the ball is loaded with an initial load of 98 N (10 kgf) to a final load of 1,275 N (130 kgf) is preferably 2.0 mm or more, more preferably It is 2.3 mm or more, more preferably 2.5 mm or more, and the upper limit is preferably 3.3 mm or less, more preferably 3.0 mm or less. If this value is too low, the spin on the driver will increase and the flight distance may decrease. On the other hand, if the above value is too large, approach spin may decrease and controllability may deteriorate.

Further, in the golf ball of the present invention having the above paint layer, when the golf ball is free-falled from a height position 3 m above the impact surface inclined at 58 degrees with respect to the horizontal direction, When the amount of displacement in the vertical direction of the golf ball from when the golf ball starts to slide to when it stops slipping is defined as the amount of slippage (Ds) of the golf ball, Ds is preferably 2.0 mm or less. , preferably 1.5 mm or less, more preferably 1.2 mm or less. Within this numerical range, the golf ball has a sufficient "feel of biting" to the face, and the golf ball has a good hitting feel. The "bite feeling" of the golf ball on the face is defined as a phenomenon in which the golf ball does not slide very much on the face surface of the golf club when the face of the golf club collides with the golf ball when the golfer hits the ball. presumed to point to This sensory evaluation uses the numerical value of the slip amount Ds as an evaluation index. Specifically, it is described in [0043] and FIG. 3 of JP-A-2019-217078, which is the prior art of the applicant.

Further, with respect to the above golf ball, when the contact time after sliding (Tc) is defined as the time from when the golf ball stops sliding on the impact surface until it separates from the impact surface, Tc must be 400 μs or more. is suitable, preferably 500 μs or more, more preferably 540 μs or more. Within this numerical range, the golf ball has a sufficient "glue feel" to the face, and the hitting feel of the golf ball is good. The "glue feeling" of the golf ball to the face is defined as the phenomenon in which the golf ball is in contact with the face of the golf club for a long time when the face of the golf club collides with the golf ball when the golfer hits the ball. presumed to point to In this sensory evaluation, the numerical value of the contact time after sliding (Tc) is used as an evaluation index. Specifically, it is described in [0048] of Japanese Patent Application Laid-Open No. 2019-217078 and FIGS. The post-slip contact time (Tc) corresponds to the “second contact time” described in JP-A-2019-217078.

The golf ball of the present invention may conform to the Rules of Golf for use in competitions, and has an outer diameter of 42.672 mm or less, which does not pass through a ring with an inner diameter of 42.672 mm, and a weight of 45.0 mm or less. ˜45.93 g.

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 8, Comparative Examples 1 to 6]
A core with a diameter of 38.6 mm is produced. The formulation of the core was common to all the examples and comparative examples. As the base rubber, polybutadiene A (trade name “BR51” manufactured by JSR) 20 parts by weight, polybutadiene B (trade name “BR730” manufactured by JSR) 80 parts by weight, zinc acrylate (manufactured by Wako Pure Chemical Industries, Ltd.) 29.5 parts by weight, 0.6 parts by weight of dicumyl peroxide (trade name "Percumyl D" manufactured by NOF Corporation) as an organic peroxide, 2,2-methylenebis(4-methyl-6- Butylphenol) (trade name "Nocrac NS-6" manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.) 0.1 parts by weight, zinc oxide (trade name "three-kind zinc oxide" manufactured by Sakai Chemical Industry Co., Ltd.) 19.3 parts by weight, organic 0.3 parts by weight of pentachlorothiophenol zinc salt (manufactured by Wako Pure Chemical Industries, Ltd.) is blended as a sulfur compound. Vulcanization of the rubber composition is performed under conditions of a temperature of 155° C. and a time of 15 minutes. The compounding specific gravity is 1.138.

Formation of Intermediate Layer Next, a resin material for an intermediate layer is injection molded around a core having a diameter of 38.6 mm to produce an intermediate layer-covered sphere having an intermediate layer having a thickness of 1.25 mm. The resin material for the intermediate layer is the same in all of the examples and comparative examples, and the product names are "Himilan 1605", "Himilan 1557" and "Himilan 1706" (all ionomers manufactured by Mitsui Dow Polychemicals Co., Ltd.). resin) are blended at a ratio of 50:12:38 (mass ratio), respectively, and 1.1 parts by mass of trimethylolpropane (manufactured by Tokyo Chemical Industry Co., Ltd.) is blended with respect to a total of 100 parts by mass of this ionomer resin. .

Formation of cover (outermost layer) Next, using another injection molding die, the resin material for the cover (outermost layer) shown in Table 1 below was injection-molded around the intermediate layer-covered sphere. A three-piece golf ball with a diameter of 42.7 mm having an outermost layer of thickness 0.8 mm is produced.

The details of the components contained in the cover material in Table 1 are as follows.
・"TPU 1" trade name "Pandex" manufactured by DIC Covestro Polymer Co., Ltd., ether-type thermoplastic polyurethane (Shore D hardness "43" and rebound resilience modulus "61%")
・"TPU 2" trade name "Pandex" manufactured by DIC Covestro Polymer, ether-type thermoplastic polyurethane (Shore D hardness "47" and impact resilience modulus "54%")
・ "S.O.E. S1611": Hydrogenated aromatic vinyl elastomer manufactured by Asahi Kasei Corporation (styrene content: 60 wt%, Shore D hardness "23", and rebound resilience modulus "20%")
・"Hytrel 2401" Thermoplastic polyether ester elastomer manufactured by Toray DuPont (Shore D hardness "40", impact resilience "67%", melt viscosity "5700 dPa s")

Material hardness of the cover: A resin material having a thickness of 2 mm is molded into a sheet and left at a temperature of 23±2° C. for two weeks. Three sheets are superimposed during the measurement. Shore D hardness is measured with a Shore D hardness tester conforming to ASTM D2240 standard. For hardness measurement, an automatic rubber hardness tester "P2" manufactured by Kobunshi Keiki Co., Ltd. equipped with a Shore D type hardness tester is used. Read the maximum hardness value.

Formation of Coating Layer (Coating Film) Next, in the coating composition shown in Table 1 below, the surface of the outermost layer on which many dimples were formed was coated with the following coating composition consisting of a main agent and a curing agent using an air spray gun. , and a coating layer (coating film) having a thickness of 15 μm is formed on the golf ball of each example.

<Main agent>
A polyester polyol synthesized by the following method is used as the main polyol.
140 parts by mass of trimethylolpropane, 95 parts by mass of ethylene glycol, 157 parts by mass of adipic acid, and 58 parts by mass of 1,4-cyclohexanedimethanol were placed in a reactor equipped with a reflux condenser, a dropping funnel, a gas inlet tube and a thermometer. After charging, the temperature was raised to 200 to 240° C. while stirring, and the mixture was heated (reacted) for 5 hours. Thereafter, a polyester polyol having an acid value of 4, a hydroxyl value of 170 and a weight average molecular weight (Mw) of 28,000 was obtained.

As the organic solvent used for the main agent, ethyl acetate (boiling point: 77°C) was used in a predetermined amount shown in Table 1 except for Comparative Examples 3, 5, and 6. Comparative Examples 3, 5, and 6 used butyl acetate (boiling point: 126°C). is used in the amounts shown in Table 1. In Examples 1 to 8 and Comparative Examples 3, 5, and 6, the main agent contained a silicone-modified acrylate (trade name “BYK3700” manufactured by BYK-Chemie) in a predetermined amount shown in Table 1 as a silicone additive.

<Curing agent>
The isocyanate of curing agent A is hexamethylene diisocyanate (HMDI) nurate (isocyanurate), trade name "Duranate TPA-100" manufactured by Asahi Kasei Corporation (NCO content 23.1%, nonvolatile content 100%). was used. As the isocyanate of the curing agent B, an adduct of hexamethylene diisocyanate (HMDI), trade name “Duranate E402-80B” (NCO content: 7.6%, non-volatile content: 80%) manufactured by Asahi Kasei Corporation is used.

As the organic solvent used for the curing agent, butyl acetate (boiling point: 126° C.) is used in a predetermined amount shown in Table 1 in all examples.

The resulting golf balls of each example are evaluated for ball deformation, static friction coefficient, hitting feel, and approach controllability. Table 1 shows the results.

Amount of ball deformation A ball, which is a target spherical object, is placed on a hard plate, and the amount of deflection is measured from an initial load of 98 N (10 kgf) to a final load of 1275 N (130 kgf). In addition, the amount of deflection described above is a measured value after the temperature is adjusted to 23.9°C.

Coefficient of Static Friction A golf ball is attached to a jig and pulled under the following conditions.
<Measurement conditions>
Vertical force: 3.5N
Face plate: Stainless steel Tensile speed: 50mm/min
Temperature: 23 degrees

Evaluation of hit feeling A sand wedge (trade name "X-WEDGE H8101" manufactured by Bridgestone Sports Co., Ltd., 58 degrees) was attached to a golf hitting robot, and the golf ball slippage Ds when hitting the golf ball at a head speed of 20 m/s. (mm) and post-slip contact time Tc (μs) as indices.
<Test method>
An evaluation system similar to that in FIG. 1 of JP-A-2019-217078 is prepared. That is, as shown in FIG. 1 of the publication, the evaluation system has a high-speed camera, an evaluation device, and a collision member.
・Procedure 1: A golf ball is allowed to fall freely from a height of 3 m.
• Procedure 2: A golf ball is made to collide with a collision surface inclined at 58 degrees with respect to the horizontal direction.
• Procedure 3: Observe the state of the golf ball on the impact surface with a high-speed camera, and analyze and calculate the amount of slippage Ds (mm) of the golf ball and the contact time after slippage Tc (μs).

<Evaluation of bite feeling>
[criterion]
◎ ・・・ Slip amount (Ds) 1.30 mm or less ○ ・・・ Slip amount (Ds) within the range of 1.31 to 2.00 mm × ・・・ Slip amount (Ds) 2.01 mm or more

<Evaluation of stickiness>
[criterion]
◎ ・・・ Contact time after sliding (Tc) 540 μs or more ○ ・・・ Contact time after sliding (Tc) within the range of 500 to 539 μs × ・・・ Contact time after sliding (Tc) 499 μs or less

Approach controllability (DRY: normal)
Initial velocity (m/s) and backspin amount when a sand wedge (trade name “X-WEDGE H8101” manufactured by Bridgestone Sports Co., Ltd., 58 degrees) is attached to the golf hitting robot and a golf ball is hit at a head speed of 20 m/s. (rpm) is measured. Controllability was determined by sensory evaluation. The clubs used are sand wedges (SW) of each golfer, and when the golfers actually hit the balls, they are evaluated according to the following criteria.
[criterion]
(double-circle) ... Very excellent in operability.
O: Excellent operability.
x: Inferior in operability.
It should be noted that the determination of whether or not the operability is excellent depends not only on the amount of spin of the ball, but also on the length of contact time between the ball and the club face due to the initial velocity of the ball.

Approach controllability (under wet conditions)
Furthermore, in order to confirm the effect of water repellency, the evaluation of the approach spin rate in wet conditions is also carried out under the following conditions.
A golf ball is submerged in a bucket of water, and the amount of backspin (rpm) when hit with water drops is measured and judged according to the following criteria.
[criterion]
◎ ・・・ 5750 rpm or more ○ ・・・ 5000 to 5749 rpm
× ・・・ 4999 rpm or less

As shown in Table 1, in Examples 1 to 4, the paint contains a silicone additive and the curing agent contains an HMDI adduct, and the controllability during approach (both normal and wet) is good. results. Moreover, in Examples 5 to 7, the cover further contains urethane, polyester, and aromatic vinyl elastomer, and as compared with Example 2, controllability is better.

On the other hand, in Comparative Example 1, the paint does not contain a silicone additive and the curing agent does not contain an HMDI adduct, so the wet spin rate is small.
In Comparative Example 2, since the paint does not contain a silicone-based additive, the wet spin rate is small.
In Comparative Example 3, since the paint does not contain an organic solvent having a boiling point of 80° C. or less, the coefficient of static friction is small and the amount of spin is also small.
In Comparative Example 4, since the paint does not contain a silicone-based additive, the wet spin rate is small.
In Comparative Example 5, since the paint does not contain an organic solvent having a boiling point of 80° C. or less, the coefficient of static friction is small and the amount of spin is also small.
In Comparative Example 6, since the paint does not contain an organic solvent having a boiling point of 80° C. or less, the coefficient of static friction is small and the amount of spin is also small.

Claims (7)

A golf ball comprising a core, a cover, and a paint layer, wherein the paint layer is formed of a urethane paint containing an organic solvent having a boiling point of 80° C. or less and a silicone additive, and the urethane paint contains a curing agent. A golf ball comprising a polyisocyanate, wherein the polyisocyanate contains an adduct of hexamethylene diisocyanate (HMDI) and an isocyanurate. 2. The golf ball of claim 1, wherein the organic solvent having a boiling point of 80[deg.] C. or less is contained in an amount of 20% by mass or more of the total coating composition. The golf according to claim 1 or 2, wherein the mixing ratio (A)/(B) of the isocyanurate (A) and the adduct (B) of hexamethylene diisocyanate is 85/15 to 15/85 in mass ratio. ball. At least one layer of the cover is formed of a resin composition containing the following components (I) and (II) (I) polyurethane or polyurea (II) an aromatic vinyl elastomer, and 4. The golf ball of claim 1, wherein the group vinyl elastomer has a Shore D hardness of 30 or less and a rebound resilience of 30% or less. The golf ball of any one of claims 1 to 4, wherein component (II) is added in an amount of 5 to 20 parts by mass per 100 parts by mass of component (I). The resin composition further contains (III) a thermoplastic polyester elastomer, and the thermoplastic polyester elastomer as component (III) has a Shore D hardness of 45 or less and a rebound resilience of 74% or less. 6. The golf ball of claim 4 or 5, which has a melt viscosity of 1.5×10 ⁴ (dPa·s) or less at 200° C. and a shear rate of 243 (1/sec). When a golf ball is free-falled from a height position 3 m above the impact surface inclined at 58 degrees to the horizontal direction, the golf ball starts to slide on the impact surface and then stops. When the amount of displacement in the vertical direction of the golf ball up to is defined as the amount of slippage (Ds) of the golf ball, Ds is 2.0 mm or less, and the distance from the impact surface after the golf ball stops sliding on the impact surface The golf ball of any one of claims 1 to 6, wherein the contact time after sliding (Tc) is 400 µs or more.