JP2014213143A - Golf ball - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a golf ball whose carry performance is improved by achieving a low spin of the golf ball at a driver shot and whose durability, especially on a high head speed condition, is improved.SOLUTION: A golf ball includes: a core; at least one intermediate layer covering the core; and a cover which covers the intermediate layer. In the golf ball, at least one piece or one layer of the intermediate layers is formed of a material for an intermediate-layer, which contains thermoplastic polyurethane having slab hardness of 65-80 on Shore D hardness and upper yield stress (MPa)/lower yield stress (MPa) of 1.60 or less.

Description

The present invention relates to a golf ball.

Conventionally, golf balls have been required to improve the flight distance at the time of a driver shot, and in order to improve the performance, a multi-layer structure of golf balls and material development have been promoted. As a method of extending the flight distance, there is an outer-hard / inner-softening of the golf ball structure. For example, the intermediate layer has a higher rigidity / hardness to soften the entire golf ball, thereby reducing the spin on driver shots. Proposed.

Various ionomer resins are generally used as a material that imparts high rigidity to the intermediate layer of a golf ball and enables low spin, but there is a problem that durability decreases due to the increase in rigidity. is there.

Patent Document 1 also discloses a golf ball having a flight distance including an intermediate layer having a predetermined thickness and Shore D hardness, which is mainly composed of a thermoplastic resin other than an ionomer resin such as a polyurethane-based thermoplastic elastomer, Patent Documents 2 to 3 also disclose golf balls that use a polyurethane-based thermoplastic elastomer or the like and have an intermediate layer having a predetermined bending rigidity and the like that have improved flight distance.

However, the golf ball using the polyurethane-based thermoplastic elastomer used here as an intermediate layer does not have sufficient durability under high head speed conditions, and further improvement is desired.

Japanese Patent Application Laid-Open No. 2004-8404 JP 2004-187991 A JP 2004-242850 A

An object of the present invention is to solve the above-mentioned problems and to provide a golf ball that improves the flight distance performance by reducing the spin rate at the time of driver shot, and also improves the durability, particularly durability under high head speed conditions. .

The present invention is a golf ball having a core, one or more intermediate layers covering the core, and a cover covering the intermediate layer, wherein at least one piece or one layer of the intermediate layer has a slab hardness of Shore D hardness. 65 to 80, and relates to a golf ball formed from an intermediate layer material including thermoplastic polyurethane having an upper yield stress (MPa) / lower yield stress (MPa) of 1.60 or less.

The thermoplastic polyurethane preferably has an upper yield stress of 15 MPa or more and a lower yield stress of 10 MPa or more. Further, the thermoplastic polyurethane preferably has a breaking stress (MPa) of 25 MPa or more.
In the claims, delete the description of the upper limit.

The thermoplastic polyurethane preferably has a breaking stress (MPa) / slab hardness (Shore D hardness) of 0.70 or more. The thermoplastic polyurethane preferably has a flexural rigidity of 250 to 4000 MPa.

The intermediate layer preferably has a thickness of 0.5 to 2.0 mm.
The cover preferably includes a thermoplastic polyurethane having a slab hardness of Shore D hardness of 50 or less and a thickness of 0.3 to 1.5 mm.

According to the present invention, there is provided a golf ball having a core, one or more intermediate layers covering the core, and a cover covering the intermediate layer, wherein at least one piece or one layer of the intermediate layer has a slab hardness of Shore D. A golf ball formed from an intermediate layer material containing thermoplastic polyurethane having a hardness of 65 to 80 and an upper yield stress (MPa) / lower yield stress (MPa) of 1.60 or less. It is possible to improve flight distance performance and improve durability, particularly durability under high head speed conditions.

Stress-strain curve 1 of thermoplastic polyurethane (Elastolan 1164D). Stress-strain curve 2 of thermoplastic polyurethane.

The golf ball of the present invention has a core, one or more intermediate layers covering the core, and a cover covering the intermediate layer, and at least one piece or one layer of the intermediate layer has a slab hardness of Shore D. The intermediate layer material is made of a thermoplastic polyurethane having a hardness of 65 to 80 and an upper yield stress (MPa) / lower yield stress (MPa) of 1.60 or less.

By using thermoplastic polyurethane with a specific slab hardness and a ratio of upper yield stress and lower yield stress as the resin component of the intermediate layer, it is possible to reduce the driver shot and increase the flight distance, while at the same time durability. In particular, durability under high head speed conditions can be improved. Also, it is possible to secure a soft ball with a large amount of compressive deformation and to obtain a good shot feeling.

First, the intermediate layer material will be described.
The intermediate layer is formed of an intermediate layer material including a thermoplastic polyurethane (thermoplastic polyurethane elastomer) having a predetermined slab hardness and a ratio of upper yield stress to lower yield stress (upper yield stress / lower yield stress) as a resin component. Is done.

The thermoplastic polyurethane has a slab hardness of Shore D hardness of 65 or more, preferably 67 or more, more preferably 69 or more, and is 80 or less, preferably 78 or less, more preferably 76 or less. By using such a high-hardness thermoplastic polyurethane, it is possible to reduce the spin at the time of a driver shot and improve the flight distance performance. The slab hardness (Shore D hardness) can be measured by the method described later.

The thermoplastic polyurethane has an upper yield stress (MPa) / lower yield stress (MPa) of 1.60 or less, preferably 1.50 or less, more preferably 1.40 or less. If the difference between the upper and lower yield stress values at the yield point is large, a large strain is likely to occur when an impact exceeding the yield point is applied, and there is a tendency for further strain to occur due to deformation, resulting in a deterioration in durability. . Further, it is preferable that the difference between the values of the upper yield stress and the lower yield stress at the yield point is smaller. As the upper yield stress (MPa) / lower yield stress (MPa) is closer to 1.00, distortion due to impact hardly occurs and durability tends to be good.

The upper yield stress of the thermoplastic polyurethane is preferably 15 MPa or more, more preferably 18 MPa or more, and further preferably 21 MPa or more. If the upper yield stress is too small, the yield point tends to be exceeded with a small stress, and the deformation tends to progress and the impact resistance tends to deteriorate. The upper limit of the upper yield stress is not particularly limited, but is preferably 60 MPa or less, more preferably 55 MPa or less, and still more preferably 50 MPa or less.

The yield stress of the thermoplastic polyurethane is preferably 10 MPa or more, more preferably 13 MPa or more, and further preferably 16 MPa or more. If the lower yield stress is too small, when the deformation beyond the upper yield point occurs, a larger deformation tends to occur and the impact resistance tends to deteriorate. The upper limit of the yield stress is not particularly limited, but is preferably 50 MPa or less, more preferably 45 MPa or less, and still more preferably 40 MPa or less.

In the present invention, the upper yield stress and the lower yield stress are measured from a stress-strain curve shown in FIGS. 1 and 2 obtained by a tensile test measured according to ISO 527-1. Specifically, It can be measured by the method described later. When the stress-strain curve as shown in FIG. 2 in which the upper yield stress and the lower yield stress are not clearly expressed is obtained, the upper yield stress = the lower yield stress, and the upper yield stress / the lower yield stress is 1.00. It becomes.

The thermoplastic polyurethane preferably has a breaking stress (MPa) of 25 MPa or more, more preferably 28 MPa or more, and still more preferably 30 MPa or more. By being 25 MPa or more, excellent durability can be obtained. The upper limit of the breaking stress is not particularly limited, but is preferably 65 MPa or less, more preferably 60 MPa or less, and further preferably 55 MPa or less.

The thermoplastic polyurethane preferably has a breaking stress (MPa) / slab hardness (Shore D hardness) of 0.70 or more, more preferably 0.72 or more, and further preferably 0.74 or more. By being 0.70 or more, excellent durability can be obtained. Further, the upper limit of the breaking stress (MPa) / slab hardness (Shore D hardness) is not particularly limited, but high hardness is required for improving the flight distance performance, which is preferable from the viewpoint of both durability performance and flight distance performance. Is 0.88 or less, more preferably 0.86 or less, and still more preferably 0.84 or less. The breaking stress and slab hardness (Shore D hardness) can be measured by the methods described later.

The bending rigidity of the thermoplastic polyurethane is preferably 250 MPa or more, more preferably 280 MPa or more, and further preferably 300 MPa or more. The flexural rigidity is preferably 4000 MPa or less, more preferably 3600 MPa or less, and still more preferably 3200 MPa or less. By using such a high-rigidity thermoplastic polyurethane, it is possible to reduce the spin at the time of a driver shot and improve the flight distance performance. In the present invention, the flexural rigidity means a value measured according to ISO178.

The number average molecular weight of the thermoplastic polyurethane is preferably 20,000 or more, more preferably 30,000 or more, further preferably 40,000 or more, more preferably 200,000 or less, and more preferably 150,000 or less, More preferred is 100,000 or less. If the number average molecular weight is 20,000 or more, the scratch resistance of the resulting golf ball can be further improved. On the other hand, if the number average molecular weight is 200,000 or less, the fluidity is good and the moldability is good. In addition, a number average molecular weight (Mn) can be measured by standard polystyrene conversion based on the measured value by a gel permeation chromatograph (GPC).

The thermoplastic polyurethane having the predetermined slab hardness and the ratio of the upper yield stress and the lower yield stress and having a plurality of urethane bonds in the molecule and exhibiting thermoplasticity can be used. For example, a product in which a urethane bond is formed in a molecule by reacting a polyisocyanate and a polyol, a product obtained by a chain extension reaction with a lower molecular weight polyol or polyamine, if necessary, etc. Can be mentioned.

As the polyisocyanate component constituting the thermoplastic polyurethane, those having two or more isocyanate groups can be used. For example, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, a mixture of 2,4-toluene diisocyanate and 2,6-toluene diisocyanate (TDI), 4,4′-diphenylmethane diisocyanate (MDI), 1,5- Aromatics such as naphthylene diisocyanate (NDI), 3,3′-vitrylene-4,4′-diisocyanate (TODI), xylylene diisocyanate (XDI), tetramethylxylylene diisocyanate (TMXDI), paraphenylene diisocyanate (PPDI) polyisocyanates; 4,4'-dicyclohexylmethane diisocyanate _(H 12 MDI), hydrogenated xylylene diisocyanate _(H 6 XDI), hexamethylene diisocyanate (HDI), isophorone diisocyanate Over preparative (IPDI), an alicyclic polyisocyanate, or an aliphatic polyisocyanate such as norbornene diisocyanate (NBDI) and the like. These may be used alone or in combination of two or more. Among the polyisocyanate components, xylylene diisocyanate (XDI) and hexamethylene diisocyanate (HDI) are preferable, and 4,4′-diphenylmethane diisocyanate (MDI) is more preferable from the viewpoint of improving flight distance performance and durability.

As a polyol component which comprises the said thermoplastic polyurethane, what has multiple hydroxyl groups can be used, For example, a low molecular weight polyol, a high molecular weight polyol, etc. can be mentioned. Examples of the low molecular weight polyol include ethylene glycol, diethylene glycol, triethylene glycol, propanediol (eg, 1,2-propanediol, 1,3-propanediol, 2-methyl-1,3-propanediol, etc.), Dipropylene glycol, butanediol (eg, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 2,3-dimethyl-2,3-butanediol, etc. ), Diols such as neopentyl glycol, pentane diol, hexane diol, heptane diol, octane diol, 1,6-cyclohexane dimethylol, aniline diol, bisphenol A diol; glycerin, trimethylol propane, hexane triol, etc. G Ol; pentaerythritol, tetraol or a hexanol such as sorbitol. Examples of the high molecular weight polyol include polyether polyols such as polyoxyethylene glycol (PEG), polyoxypropylene glycol (PPG), and polyoxytetramethylene glycol (PTMG); polyethylene adipate (PEA), polybutylene adipate (PBA) ), A polycondensed polyester polyol such as polyhexamethylene adipate (PHMA); a lactone polyester polyol such as poly-ε-caprolactone (PCL); a polycarbonate polyol such as polyhexamethylene carbonate; and an acrylic polyol. These may be used alone or in combination of two or more.

The number average molecular weight of the high molecular weight polyol is not particularly limited, but is preferably 400 or more, more preferably 1,000 or more. If the number average molecular weight is too small, the resulting polyurethane will be hard and the feel at impact of the golf ball may be reduced. The upper limit is preferably 10,000 or less, more preferably 8,000 or less.

Moreover, what has at least 2 or more amino group can be used for the polyamine which comprises the said thermoplastic polyurethane as needed. Examples of the polyamine include aliphatic polyamines such as ethylenediamine, propylenediamine, butylenediamine, and hexamethylenediamine; alicyclic polyamines such as isophoronediamine and piperazine; and aromatic polyamines.

As the aromatic polyamine, one having at least two amino groups bonded directly or indirectly to an aromatic ring can be used. Here, being indirectly bonded means that the amino group is bonded to the aromatic ring via, for example, a lower alkylene group. The aromatic polyamine may be, for example, a monocyclic aromatic polyamine in which two or more amino groups are bonded to one aromatic ring, or an amino in which at least one amino group is bonded to one aromatic ring. It may be a polycyclic aromatic polyamine containing two or more phenyl groups.

Examples of the monocyclic aromatic polyamine include a type in which an amino group such as phenylenediamine, toluenediamine, diethyltoluenediamine, and dimethylthiotoluenediamine is directly bonded to an aromatic ring; and an amino group such as xylylenediamine. Examples include a type bonded to an aromatic ring via a lower alkylene group. The polycyclic aromatic polyamine may be poly (aminobenzene) in which at least two aminophenyl groups are directly bonded, or at least two aminophenyl groups intervene with a lower alkylene group or an alkylene oxide group. May be combined. Among the polyamines, 4,4′-methylene-bis- (3-chloro-2,6-diethylaniline) is preferable from the viewpoint of reactivity, and 4,4′-methylene-bis- (2,6- Diethylaniline) is more preferred.

Examples of constitutional aspects of the thermoplastic polyurethane include, for example, an aspect constituted by a polyisocyanate component and a high molecular weight polyol component; an aspect constituted by a polyisocyanate component, a high molecular weight polyol component, and a low molecular weight polyol component; And an embodiment composed of a high molecular weight polyol component, a low molecular weight polyol component and a polyamine component; an embodiment composed of a polyisocyanate component, a high molecular weight polyol component and a polyamine component.

Specific examples of the thermoplastic polyurethane include Elastollan (registered trademark) 1164D and 1174D manufactured by BASF Japan, and E568 and E574 manufactured by Nippon Milactone Co., Ltd.

The content of the thermoplastic polyurethane in the resin component constituting the intermediate layer is preferably 50% by mass or more, more preferably 65% by mass or more, still more preferably 80% by mass or more, and may be 100% by mass. When the content of the thermoplastic polyurethane in the resin component is 50% by mass or more, that is, when the thermoplastic polyurethane is used as a main component, the effect of reducing spin and improving durability is increased.

You may mix | blend resin components other than the said thermoplastic polyurethanes, such as various ionomer resin, with the grade which does not impair the effect of this invention to the said material for intermediate | middle layers. Also, pigment components such as white pigments (titanium oxide), blue pigments, red pigments, specific gravity adjusters such as calcium carbonate and barium sulfate, dispersants, anti-aging agents, UV absorbers, light stabilizers, fluorescent materials or fluorescent materials You may mix | blend a white agent etc. in the range which does not impair the effect of this invention.

Here, when a material other than the thermoplastic polyurethane is blended in the intermediate layer, the slab hardness (Shore D), upper yield stress / lower yield stress, upper yield stress of the intermediate layer material including all the materials constituting the intermediate layer The yield stress, the breaking stress (MPa), the breaking stress (MPa) / slab hardness (Shore D hardness), and the flexural rigidity are preferably in the same ranges as described for the thermoplastic polyurethane. Specifically, the thermoplastic polyurethane can be used as a main component and can be adjusted to a desired characteristic value by appropriately selecting other components within a range that does not significantly affect these characteristic values. Each characteristic can be measured by the same method as described above.

Next, the golf ball will be described.
The golf ball of the present invention has a core, one or more intermediate layers covering the core, and a cover covering the intermediate layer, and at least one piece or one layer of the intermediate layer includes the above-mentioned thermoplastic polyurethane. It is made of a layer material.

The core used in the present invention is not particularly limited, and examples thereof include a core composed of a center, and a multi-layer core (such as a two-layer core) composed of a center and one or more surrounding layers covering the center.

For the center, a conventionally known rubber composition (hereinafter sometimes simply referred to as “center rubber composition”) or a resin composition can be employed. For example, a rubber composition containing a base rubber, a crosslinking initiator, a co-crosslinking agent, and a filler can be molded by hot pressing. In addition, as the base resin of the resin composition, heat such as ionomer resin, thermoplastic olefin copolymer, thermoplastic polyurethane resin, thermoplastic polyamide resin, thermoplastic styrene resin, thermoplastic polyester resin, thermoplastic acrylic resin, etc. A plastic resin can be used.

As the base rubber, natural rubber and / or synthetic rubber can be used. For example, polybutadiene rubber, natural rubber, polyisoprene rubber, styrene polybutadiene rubber, ethylene-propylene-diene rubber (EPDM) and the like can be used. Among these, it is particularly preferable to use a high-cis polybutadiene having a cis bond advantageous for repulsion of 40% by mass or more, preferably 70% by mass or more, and more preferably 90% by mass or more.

The said crosslinking initiator is mix | blended in order to bridge | crosslink a base rubber component. As the crosslinking initiator, an organic peroxide is suitable. Specifically, dicumyl peroxide, 1,1-bis (t-butylperoxy) -3,5-trimethylcyclohexane, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, Examples include organic peroxides such as di-t-butyl peroxide. Among them, dicumyl peroxide is preferable. The amount of the crosslinking initiator is preferably 0.1 parts by mass or more, more preferably 0.3 parts by mass or more, and still more preferably 0.5 parts by mass or more with respect to 100 parts by mass of the base rubber. The amount is preferably 3 parts by mass or less, more preferably 2.8 parts by mass or less, and still more preferably 2.5 parts by mass or less. If the amount is less than 0.1 parts by mass, the core tends to be too soft and the resilience tends to decrease. If the amount exceeds 3 parts by mass, the amount of co-crosslinking agent used needs to be increased in order to obtain an appropriate hardness. There is a lack of resilience.

The co-crosslinking agent is not particularly limited as long as it has a function of crosslinking rubber molecules by graft polymerization to a base rubber molecular chain. For example, α, β- having 3 to 8 carbon atoms. Unsaturated carboxylic acid or its metal salt can be used, Preferably acrylic acid, methacrylic acid, or these metal salts can be mentioned. As a metal which comprises the said metal salt, zinc, magnesium, calcium, aluminum, sodium etc. can be mentioned, for example, Zinc is preferable from the resilience becoming high.

The amount of the co-crosslinking agent used is preferably 10 parts by mass or more, more preferably 15 parts by mass or more, and preferably 50 parts by mass or less, more preferably 45 parts by mass with respect to 100 parts by mass of the base rubber. Or less. If it is less than 10 parts by mass, the amount of the crosslinking initiator must be increased in order to obtain an appropriate hardness, and the resilience tends to decrease. On the other hand, if it exceeds 50 parts by mass, the center becomes too hard and the feel at impact may be reduced.

The filler contained in the center rubber composition is blended mainly as a specific gravity adjusting agent for adjusting the specific gravity of the golf ball obtained as a final product to a range of 1.0 to 1.5. What is necessary is just to mix | blend according to it. Examples of the filler include inorganic fillers such as zinc oxide, barium sulfate, calcium carbonate, magnesium oxide, tungsten powder, and molybdenum powder. The blending amount of the filler is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, and preferably 30 parts by mass or less, more preferably 20 parts per 100 parts by mass of the base rubber. It is below mass parts. If the amount is less than 0.5 parts by mass, it is difficult to adjust the weight. If the amount exceeds 30 parts by mass, the weight fraction of the rubber component tends to be small, and the resilience tends to decrease.

In addition to the base rubber, the crosslinking initiator, the co-crosslinking agent, and the filler, the center rubber composition may further contain an organic sulfur compound, an antioxidant, a peptizer, and the like as appropriate.

As the organic sulfur compound, diphenyl disulfides can be preferably used. Examples of the diphenyl disulfides include diphenyl disulfide; bis (4-chlorophenyl) disulfide, bis (3-chlorophenyl) disulfide, bis (4-bromophenyl) disulfide, bis (3-bromophenyl) disulfide, bis ( 4-fluorophenyl) disulfide, bis (4-iodophenyl) disulfide, bis (4-cyanophenyl) disulfide and other mono-substituted products; bis (2,5-dichlorophenyl) disulfide, bis (3,5-dichlorophenyl) disulfide, Bis (2,6-dichlorophenyl) disulfide, bis (2,5-dibromophenyl) disulfide, bis (3,5-dibromophenyl) disulfide, bis (2-chloro-5-bromophenyl) disulfide, bis (2- Shea Disubstituted products such as -5-bromophenyl) disulfide; trisubstituted products such as bis (2,4,6-trichlorophenyl) disulfide, bis (2-cyano-4-chloro-6-bromophenyl) disulfide; Tetra-substituted products such as 2,3,5,6-tetrachlorophenyl) disulfide; bis (2,3,4,5,6-pentachlorophenyl) disulfide, bis (2,3,4,5,6-pentabromophenyl) ) Penta-substituted compounds such as disulfide. These diphenyl disulfides have some influence on the vulcanized state of the rubber vulcanizate and can improve the resilience. Among these, diphenyl disulfide and bis (pentabromophenyl) disulfide are preferable from the viewpoint that a golf ball having high resilience can be obtained. The amount of the organic sulfur compound is preferably 0.1 parts by mass or more, more preferably 0.3 parts by mass or more, and preferably 5.0 parts by mass or less with respect to 100 parts by mass of the base rubber. More preferably, it is 3.0 parts by mass or less.

The amount of the anti-aging agent is preferably 0.1 to 1 part by mass with respect to 100 parts by mass of the base rubber. Moreover, the blending amount of the peptizer is preferably 0.1 to 5 parts by mass with respect to 100 parts by mass of the base rubber.

The center can be produced by mixing, kneading and molding the above rubber composition in a mold. The conditions at this time are not particularly limited. For example, the rubber composition is heated at 130 to 200 ° C. for 10 to 60 minutes, or heated at 130 to 150 ° C. for 20 to 40 minutes, and then 160 to 180 ° C. It is preferable to heat in two stages for 5 to 15 minutes.

Next, in the case of a multilayer core, an envelope layer constituting the core will be described.
The envelope layer composition forming the envelope layer includes, for example, trade names “Himiran (registered trademark)” (for example, Himiran 1605 and Himiran 1706) from Mitsui DuPont Polychemical Co., Ltd. Surlyn) (registered trademark) (for example, Surin 8140, Surlyn 9120) thermoplastic resin such as ionomer resin, trade name “Pebax (registered trademark)” (for example, “Pebax 2533”) from Arkema Co., Ltd. , A thermoplastic polyester elastomer commercially available under the trade name “Hytrel (registered trademark)” (for example, “Hytrel 3548” and “Hytrel 4047”) from Toray DuPont Co., Ltd., The product name “Elastollan (registered merchant) from BASF Japan (E.g., "Elastollan XNY97A") ", a thermoplastic polyurethane elastomer commercially available, and a thermoplastic polystyrene elastomer commercially available under the trade name" Lavalon (registered trademark) "from Mitsubishi Chemical Corporation. Examples thereof include elastomers and rubber compositions such as the center composition. The said thermoplastic resin and thermoplastic elastomer can be used individually or in mixture of 2 or more types.

As a method for forming the envelope layer, for example, the envelope layer is formed by covering the center with the envelope layer composition. The method for forming the envelope layer is not particularly limited. For example, the envelope layer composition is previously molded into a hemispherical half shell, and the two are used to wrap the center, and 1 to 5 at 130 to 170 ° C. For example, a method of pressure molding for a minute, or a method of wrapping the center by injection molding the composition for the envelope layer directly on the center is used.

The slab hardness of the envelope layer composition is preferably 40 or more in Shore D hardness, more preferably 42 or more, still more preferably 43 or more, and preferably 70 or less, more preferably 66 or less. Preferably it is 64 or less. By setting it to 40 or more, the resilience performance of the obtained golf ball becomes better, and by setting it to 70 or less, the shot feeling of the obtained golf ball becomes better. Here, the slab hardness of the envelope layer composition can be adjusted by appropriately selecting a combination of the above-described resin component or rubber composition.

The diameter of the center is preferably 5.0 mm or more, more preferably 10.0 mm or more, preferably 41.5 mm or less, more preferably 41.0 mm or less, and further preferably 40.5 mm or less. If it is 5.0 mm or more, the function of a relatively soft center will be more exhibited, and the spin rate will be further reduced, especially for shots with W # 1. On the other hand, if it is 41.5 mm or less, an envelope layer, an intermediate | middle layer, or a cover layer will not become thin too much, but the function of each layer will be exhibited more.

When the center has a diameter of 5.0 to 41.5 mm, the amount of compressive deformation (the amount by which the center contracts in the compression direction) from when the initial load 98N is applied to when the final load 1275N is applied is preferably 4. It is 0 mm or more, more preferably 4.5 mm or more, and preferably 10.0 mm or less, more preferably 8.0 mm or less. If the amount of compressive deformation is 4.0 mm or more, the feel at impact is better, and if it is 10.0 mm or less, the resilience is better.

The thickness of the envelope layer is preferably 3.0 mm or more, more preferably 5.0 mm or more, still more preferably 7.0 mm or more, and preferably 17.0 mm or less, more preferably 15.0 mm or less, even more preferably. Is 13.0 mm or less. If the thickness of the envelope layer is not less than the above range, the effect of the envelope layer is increased, and the spin suppression effect during driver shots and the like is further improved. On the other hand, if it is below the above range, the influence of the core becomes large and the resilience becomes better.

In the case of a multilayer core composed of the center and one or more surrounding layers covering the center, the diameter of the multilayer core is preferably 32.0 mm or more, more preferably 34.0 mm or more, and even more preferably 39. It is 0 mm or more, preferably 41.5 mm or less, more preferably 41.0 mm or less, and further preferably 40.5 mm or less. When the diameter of the core is within the above range, the effect of suppressing the spin at the time of driver shot is further improved.

When the core has a diameter of 32.0 to 41.5 mm, the amount of compressive deformation (the amount by which the core contracts in the compression direction) from when the initial load 98N is applied to when the final load 1275N is applied is preferably 2. It is 0 mm or more, more preferably 2.2 mm or more, further preferably 2.3 mm or more, preferably 4.5 mm or less, more preferably 4.0 mm or less, still more preferably 3.5 mm or less. If the amount of compressive deformation is 2.0 mm or more, the effect of suppressing spin and hit feeling at the time of a driver shot are further improved. On the other hand, if it is 4.5 mm or less, the resilience will be better.

The difference in hardness (Hs−Ho) between the surface hardness (Hs) and the center hardness (Ho) of the core is preferably 10 or more in Shore D hardness, more preferably 15 or more, and still more preferably 20 or more. By making the surface hardness of the core greater than the center hardness, the launch angle is increased, the spin rate is decreased, and the flight distance is improved. The Shore D hardness difference between the core surface hardness and the center hardness is preferably 55 or less, more preferably 50 or less, and still more preferably 40 or less. If the hardness difference becomes too large, the durability may be reduced.

Furthermore, the center hardness (Ho) of the core is preferably 20 or more in Shore D hardness, more preferably 27 or more, and further preferably 32 or more. By setting it to 20 or more, it is not too soft and good resilience is obtained. The central hardness (Ho) is preferably 70 or less in Shore D hardness, more preferably 65 or less, and still more preferably 62 or less. By setting it to 70 or less, it is not too hard and a good shot feeling can be obtained. In the present invention, the center hardness of the core means a hardness measured by a spring type hardness tester Shore D type at a center point of the cut surface by cutting the core into two equal parts.

The surface hardness (Hs) of the core of the golf ball of the present invention is preferably 45 or more in Shore D hardness, more preferably 47 or more, and further preferably 48 or more. By setting it to 45 or more, it is not too soft and good resilience is obtained. Further, the surface hardness (Hs) of the core is preferably 65 or less, more preferably 63 or less, still more preferably 60 or less in Shore D hardness. By setting it to 65 or less, the difference in hardness from the intermediate layer can be increased, so that the effect of reducing spin at the time of driver shot is further enhanced.

Next, one or more intermediate layers covering the core will be described.
The intermediate layer material containing the thermoplastic polyurethane described above is used for at least one piece or one layer of the intermediate layer.

As a method for forming the intermediate layer, for example, the intermediate layer is formed by covering the core with the intermediate layer material. The method for forming the intermediate layer is not particularly limited. For example, the intermediate layer material is previously formed into a hemispherical half-shell, and the two are used to wrap the core. For example, a method in which pressure molding is performed for 5 minutes to 5 minutes, or an intermediate layer material is directly injection molded on the core and the core is wrapped is used.

The thickness of the intermediate layer formed from the intermediate layer material is preferably 0.5 mm or more, more preferably 0.6 mm or more, still more preferably 0.7 mm or more, and preferably 2.0 mm or less, more preferably Is 1.8 mm or less, more preferably 1.6 mm or less. If the thickness is less than 0.5 mm, the intermediate layer is thin, and the durability may deteriorate. Moreover, when it exceeds 2.0 mm, a core diameter will become small and there exists a possibility of leading to low resilience.

The surface hardness (Hm) of the intermediate layer formed from the material for the intermediate layer is preferably 65 or more, more preferably 66 or more, still more preferably 67 or more, and more preferably 80 or less in Shore D hardness. Is 78 or less, more preferably 76 or less. If it is 65 or more, the hardness and rigidity of the intermediate layer are high, and the spin suppression effect during driver shots and the like is further improved. Moreover, if it is 80 or less, the hardness of an intermediate | middle layer will not become high too much and durability and the hit feeling of a golf ball will improve more.

The difference (Hm−Hs) between the surface hardness (Hm) of the intermediate layer formed from the material for the intermediate layer and the surface hardness (Hs) of the core is preferably 3 or more in Shore D hardness, more preferably It is 4 or more, more preferably 5 or more, and preferably 25 or less, more preferably 18 or less, and still more preferably 16 or less. By setting the difference in surface hardness (Hm−Hs) within the above range, the spin rate is further reduced and the flight distance is improved.

Examples of the form of the core and the intermediate layer include an aspect in which the core is covered with a single layer of the intermediate layer; and an aspect in which the core is covered with a plurality of pieces or a plurality of layers of the intermediate layer.

The shape after the core is covered with the intermediate layer is preferably spherical. When the shape of the intermediate layer is not spherical, the thickness of the cover is not uniform. As a result, a part in which the cover performance is partially reduced occurs. On the other hand, the shape of the core is generally spherical, but a ridge may be provided so as to divide the surface of the spherical core, for example, the ridge so as to divide the surface of the spherical core equally. May be provided. As an aspect which provides the said protrusion, the aspect which provides a protrusion integrally with an envelope layer on the surface of an envelope layer, the aspect which provides the envelope layer of an protrusion on the surface of a spherical center, etc. can be mentioned, for example.

For example, when the spherical core is regarded as the earth, the protrusions are preferably provided along the equator and an arbitrary meridian that equally divides the spherical core surface. For example, when the spherical core surface is divided into 8 parts, 90 degrees east longitude, 90 degrees west longitude, and east longitude (west longitude) with reference to the equator, an arbitrary meridian (longitude 0 degrees), and the meridian of such longitude 0 degrees It may be provided along the meridian of 180 degrees. When providing ridges on the core surface, the recesses partitioned by the ridges should be spherical with a plurality of intermediate layers or a single intermediate layer covering each of the recesses. Is preferred. The cross-sectional shape of the protrusion is not particularly limited, and examples thereof include an arc shape or a substantially arc shape (for example, a shape in which notched portions are provided at portions intersecting or orthogonal to each other).

And as said intermediate | middle layer, when the said core is coat | covered with the intermediate | middle layer of single layer or multiple layers, the recessed part which at least one layer of the intermediate | middle layer is partitioned off by the protrusion provided in the surface of the core Is filled with a plurality of intermediate layers, at least one of the plurality of intermediate layers is formed of the intermediate layer material. In the case where the core is covered with a plurality of intermediate layers or a plurality of intermediate layers, the core has an intermediate layer formed from an intermediate layer material other than the intermediate layer material as long as the effects of the present invention are not impaired. May be. In this case, it is preferable that the intermediate layer in contact with the cover is an intermediate layer formed from the intermediate layer material, and a plurality of pieces or a plurality of intermediate layers are all formed from the intermediate layer material. Preferably it is.

As the intermediate layer material other than the intermediate layer material, for example, the same material as the envelope layer composition described above can be used, and a specific gravity adjusting agent such as barium sulfate and tungsten, an antiaging agent, a pigment, and the like are blended. May be.

As a resin component of the cover composition forming the cover, in addition to a polyurethane resin and a conventionally known ionomer resin, a product name “Pebax (registered trademark)” (for example, “Pebax 2533”) is available from Arkema Co., Ltd. A thermoplastic polyester elastomer, commercially available from Toray DuPont Co., Ltd. under the trade name “Hytrel (registered trademark)” (for example, “Hytrel 3548”, “Hytrel 4047”), Mitsubishi Chemical ( The thermoplastic polystyrene elastomer etc. which are marketed by the brand name "Lavalon (trademark)" from the Co., Ltd. etc. are mentioned. These resin components may be used alone or in combination of two or more. Of these, polyurethane resins are preferred.

The cover composition constituting the cover of the golf ball of the present invention preferably contains 50% by mass or more of a polyurethane resin as a resin component, more preferably 60% by mass or more, and still more preferably 70% by mass or more. . It is most preferable to use only a polyurethane resin as the resin component in the cover composition.

The polyurethane resin is not particularly limited as long as it has a plurality of urethane bonds in the molecule. For example, a product in which urethane bonds are formed in the molecule by reacting a polyisocyanate component and a high molecular weight polyol component. Examples of the product obtained by a chain extension reaction with a lower molecular weight polyol or polyamine as required.

The slab hardness of the polyurethane resin is preferably 50 or less in Shore D hardness, more preferably 40 or less, and still more preferably 35 or less. Approach spin performance is improved by using low hardness polyurethane. The slab hardness is preferably 10 or more, more preferably 15 or more in Shore D hardness. If it is less than 10, the spin speed at the approach shot may be too high. Specific examples of the polyurethane resin include Elastollan (registered trademark) XNY75A, XNY80A, XNY83A, XNY85A, XNY97A, XNY90A, and ET880 manufactured by BASF Japan Ltd.

In the present invention, the cover includes, in addition to the resin component described above, pigment components such as titanium oxide, blue pigment, and red pigment, specific gravity adjusters such as zinc oxide, calcium carbonate, and barium sulfate, dispersants, anti-aging agents, and ultraviolet rays. You may contain an absorber, a light stabilizer, a fluorescent material, a fluorescent whitening agent, etc. in the range which does not impair the performance of a cover.

The content of the white pigment (titanium oxide) is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, and preferably 10 masses with respect to 100 parts by mass of the resin component constituting the cover. Part or less, more preferably 8 parts by weight or less. By setting it as 0.5 mass part or more, concealment property can be provided to a cover. Moreover, when it exceeds 10 mass parts, durability of the cover obtained may fall.

The slab hardness (Hc) of the cover is preferably 50 or less, more preferably 40 or less, and still more preferably 35 or less in Shore D hardness. By setting it to 50 or less, spin performance at the time of approach shots such as short irons is improved. As a result, a golf ball excellent in controllability at the approach shot can be obtained. Further, the slab hardness (Hc) of the cover is preferably 10 or more in Shore D hardness, more preferably 15 or more. If it is less than 10, the spin speed at the time of approach shots such as short irons may be too high. Here, the slab hardness of the cover is a hardness measured by molding the cover composition into a sheet shape, and is measured by a measurement method described later.

Although the aspect which shape | molds a cover using the composition for a cover is not specifically limited, The aspect which directly injection-molds the composition for a cover on a core, or shape | molds a hollow shell-like shell from a composition for a cover, and a core And a method of compression molding by coating with a plurality of shells (preferably a method of molding a hollow shell-shaped half shell from a cover composition and coating a core with two half shells) Can do. When forming a cover by injection molding the cover composition onto the core, the upper and lower molds for cover molding have hemispherical cavities, with pimples, which also serve as hold pins that allow part of the pimples to advance and retract. It is preferable to use what is. The cover can be molded by injection molding by protruding the hold pin, inserting the core and holding it, and then injecting the heat-melted composition for the cover and cooling, for example, The cover composition heated and melted at 150 to 230 ° C. is poured in a mold clamped at a pressure of 980 to 1,500 kPa in 0.1 to 1 second, and the mold is opened by cooling for 15 to 60 seconds. By doing.

When the cover is molded by the compression molding method, the half shell can be molded by either the compression molding method or the injection molding method, but the compression molding method is preferred. The conditions for compressing and molding the cover composition into a half shell include, for example, a pressure of 1 MPa or more and 20 MPa or less and a flow start temperature of the cover composition of −20 ° C. or more and + 70 ° C. or less. A molding temperature can be mentioned. By setting the molding conditions, a half shell having a uniform thickness can be molded. As a method for forming a cover using a half shell, for example, a method in which a core is covered with two half shells and compression-molded can be mentioned. As conditions for compression-molding the half shell into a cover, for example, at a molding pressure of 0.5 MPa or more and 25 MPa or less, a flow start temperature of the cover composition is −20 ° C. or more and + 70 ° C. or less. A molding temperature can be mentioned. By setting the molding conditions, a golf ball cover having a uniform cover thickness can be molded.

When a golf ball body is manufactured by covering a cover, a depression called dimple is usually formed on the surface. The total number of dimples formed on the cover is preferably 200 to 500. If it is less than 200, the dimple effect is difficult to obtain. On the other hand, if the number exceeds 500, the size of each dimple becomes small, and it is difficult to obtain the dimple effect. The shape (plan view shape) of the dimple formed is not particularly limited, and a circular shape; a polygon such as a substantially triangular shape, a substantially square shape, a substantially pentagonal shape, a substantially hexagonal shape; Alternatively, two or more kinds may be used in combination.

Further, it is preferable that the golf ball main body with the cover formed is taken out of the mold and subjected to surface treatment such as deburring, washing, and sand blasting as necessary. If desired, a coating film or a mark can be formed. The film thickness of the coating film is not particularly limited, but is preferably 5 μm or more, more preferably 7 μm or more, and preferably 25 μm or less, more preferably 23 μm or less. When the thickness is less than 5 μm, the coating film tends to be worn away by continuous use. When the thickness exceeds 25 μm, the dimple effect is lowered and the flight performance of the golf ball tends to be lowered.

The golf ball cover of the present invention preferably has a thickness of 0.3 mm or more, more preferably 0.4 mm or more. High initial speed can be achieved by thinning. The thickness of the cover is preferably 1.5 mm or less, and more preferably 1.0 mm or less. When the cover thickness is increased, the spin performance is improved, but the initial speed may be reduced. The cover thickness is an average value obtained by measuring at least four points of the thickness of the cover where the dimples are not formed, that is, directly under the land 12.

The golf ball of the present invention is not particularly limited as long as it has a core, one or more intermediate layers covering the core, and a cover covering the intermediate layer. Specific examples of the structure of the golf ball of the present invention include a three-piece golf ball having a core, an intermediate layer covering the core, and a cover covering the intermediate layer; a core comprising a center and an envelope layer covering the center; A four-piece golf ball having an intermediate layer covering the core and a cover covering the intermediate layer; a core comprising a center and an envelope layer covering the center; a plurality of pieces or a plurality of intermediate layers covering the core; And a multi-piece golf ball having a cover covering the intermediate layer.

When the golf ball of the present invention has a diameter of 40 to 45 mm, the amount of compressive deformation (the amount by which the golf ball shrinks in the compression direction) from when the initial load 98N is applied to when the final load 1275N is applied is preferably 2. It is 0 mm or more, more preferably 2.1 mm or more, further preferably 2.2 mm or more, preferably 3.0 mm or less, more preferably 2.9 mm or less, still more preferably 2.8 mm or less. When the amount of compressive deformation is 2.0 mm or more, a good feel at impact is obtained, and when it is 3.0 mm or less, good resilience is obtained.

The present invention will be specifically described based on examples, but the present invention is not limited to these examples.

(1) Center surface hardness, envelope layer surface hardness (Shore D hardness)
Using an automatic rubber hardness tester P1 type manufactured by Kobunshi Keiki Co., Ltd., equipped with a spring type hardness tester Shore D type as defined in ASTM-D2240, the Shore D hardness measured at the center or the surface portion of the envelope layer is measured at the center and the envelope layer. The surface hardness was taken.

(2) Slab hardness (Shore D hardness)
Using the intermediate layer material or the cover composition, a sheet having a thickness of about 2 mm was prepared and stored at 23 ° C. for 2 weeks. An automatic rubber hardness tester P1 type manufactured by Kobunshi Keiki Co., Ltd. equipped with a spring type hardness tester Shore D type as defined in ASTM-D2240 in a state where three or more sheets are stacked so as not to affect the measurement substrate. It measured using. The sheet was produced by injection molding.

(3) Upper yield stress, lower yield stress (MPa)
A sheet having a thickness of about 2 mm was produced by injection molding using the intermediate layer material, and stored at 23 ° C. for 2 weeks. A dumbbell-type test piece was prepared from this sheet, and a stress-strain curve at the time of a tensile test was obtained for the test piece according to ISO 527-1. In the obtained curve, the first stress where the stress decreased as the strain increased was the upper yield stress, and the first stress where the stress increased as the strain exceeded the upper yield stress was the lower yield stress.

(4) Breaking stress (MPa)
A sheet having a thickness of about 2 mm was produced by injection molding using the intermediate layer material, and stored at 23 ° C. for 2 weeks. A dumbbell-shaped test piece was prepared from this sheet, and the breaking stress of the test piece was measured according to ISO 527-1.

(5) Flexural rigidity (MPa)
A test piece having a length of 80.0 ± 2 mm, a width of 10.0 ± 0.2 mm, and a thickness of 4.0 ± 0.2 mm is produced by injection molding using the intermediate layer material, and stored at 23 ° C. for 2 weeks. did. The bending rigidity of this sheet was measured according to ISO178. The measurement was performed at a temperature of 23 ° C. and a humidity of 50% RH.

(6) Compression deformation (mm)
The amount of deformation in the compression direction (the amount by which the golf ball shrinks in the compression direction) from when the initial load 98N was applied to the golf ball to when the final load 1275N was applied was measured.

(7) Shot with a driver Mount a metal head W # 1 driver (Dunlop Sports, XXIO S Loft 11 °) on a swing robot M / C made by Golf Golf Laboratory, and play a golf ball at a head speed of 50 m / sec. The ball was hit and the flight distance (distance from the starting point to the resting point), the initial velocity of the ball, and the spin speed (ball spin amount) were measured. The measurement was performed 12 times for each golf ball, and the average value was taken as the measured value of the golf ball. In addition, the spin speed of the golf ball immediately after hitting was measured by taking continuous photographs of the hit golf ball.

(8) Durability A metal head # W1 driver was attached to a swing robot M / C manufactured by Golf Laboratories, and each golf ball was hit at a head speed of 50 m / sec to collide with a collision plate. This was repeated to measure the number of hits until the golf ball was broken. The durability of each golf ball is determined by golf ball No. The number of hits of 12 is assumed to be 100, and the number of hits for each golf ball is shown as an index value. The larger the indexed value, the better the durability of the golf ball under high head speed conditions.

[Production of golf balls]
(1) Production of Center A rubber composition having the composition shown in Table 1 was kneaded and heated and pressed at 170 ° C. for 30 minutes in an upper and lower mold having hemispherical cavities to obtain a center.

ポリブタジエンゴム：ＪＳＲ社製、「ＢＲ−７３０（ハイシスポリブタジエン）」
アクリル酸亜鉛：日本蒸溜工業社製、「ＺＮＤＡ−９０Ｓ」
酸化亜鉛：東邦亜鉛社製、「銀嶺（登録商標）Ｒ」
硫酸バリウム：堺化学社製、「硫酸バリウムＢＤ」
ジフェニルジスルフィド：住友精化社製
ジクミルパーオキサイド：日油社製、「パークミル（登録商標）Ｄ」

Polybutadiene rubber: “BR-730 (High cis polybutadiene)” manufactured by JSR Corporation
Zinc acrylate: “ZNDA-90S”, manufactured by Nippon Distillery Co., Ltd.
Zinc oxide: Toho Zinc Co., Ltd., “Ginseng (registered trademark) R”
Barium sulfate: Sakai Chemical Co., Ltd. “Barium sulfate BD”
Diphenyl disulfide: Dicumyl peroxide manufactured by Sumitomo Seika Co., Ltd .: NOF Corporation, “Park Mill (registered trademark) D”

An appropriate amount of barium sulfate was added so that the mass of the obtained golf ball was 45.4 g.

(2) Preparation of composition for envelope layer Using the compounding materials shown in Table 2, a composition for the envelope layer was prepared.

ポリブタジエンゴム：ＪＳＲ社製、「ＢＲ−７３０（ハイシスポリブタジエン）」
アクリル酸亜鉛：日本蒸溜工業社製、「ＺＮＤＡ−９０Ｓ」
酸化亜鉛：東邦亜鉛社製、「銀嶺（登録商標）Ｒ」
硫酸バリウム：堺化学社製、「硫酸バリウムＢＤ」
ジフェニルジスルフィド：住友精化社製
ジクミルパーオキサイド：日油社製、「パークミル（登録商標）Ｄ」

Polybutadiene rubber: “BR-730 (High cis polybutadiene)” manufactured by JSR Corporation
Zinc acrylate: “ZNDA-90S”, manufactured by Nippon Distillery Co., Ltd.
Zinc oxide: Toho Zinc Co., Ltd., “Ginseng (registered trademark) R”
Barium sulfate: Sakai Chemical Co., Ltd. “Barium sulfate BD”
Diphenyl disulfide: Dicumyl peroxide manufactured by Sumitomo Seika Co., Ltd .: NOF Corporation, “Park Mill (registered trademark) D”

(3) Preparation of cover layer composition and intermediate layer material Using the blended materials shown in Tables 3 and 4, the mixture was mixed with a twin-screw kneading extruder to form a pellet-shaped cover composition and intermediate layer Each material was prepared. The extrusion conditions were a screw diameter of 45 mm, a screw rotation speed of 200 rpm, and a screw L / D = 35, and the blend was heated to 160-230 ° C. at the die position of the extruder.

エラストランＸＮＹ７５Ａ：ＢＡＳＦ社製熱可塑性ポリウレタンエラストマー（ショアＤ硬度：２３）
エラストランＸＮＹ８３Ａ：ＢＡＳＦ社製熱可塑性ポリウレタンエラストマー（ショアＤ硬度：３０）
エラストランＸＮＹ８５Ａ：ＢＡＳＦ社製熱可塑性ポリウレタンエラストマー（ショアＤ硬度：３２）

Elastollan XNY75A: Thermoplastic polyurethane elastomer manufactured by BASF (Shore D hardness: 23)
Elastollan XNY83A: Thermoplastic polyurethane elastomer manufactured by BASF (Shore D hardness: 30)
Elastollan XNY85A: Thermoplastic polyurethane elastomer manufactured by BASF (Shore D hardness: 32)

プリマロイＣＸ３００：三菱化学社製ポリエステル系エラストマー（ショアＤ硬度：７２、曲げ剛性率：４００ＭＰａ、破断応力２９ＭＰａ、上降伏応力２３ＭＰａ、下降伏応力１４ＭＰａ）
エラストラン１１６４Ｄ：ＢＡＳＦ社製ポリエーテル系ポリウレタンエラストマー（ショアＤ硬度：６４、曲げ剛性率：３３０ＭＰａ、破断応力：５５ＭＰａ、上降伏応力：２３ＭＰａ、下降伏応力：２３ＭＰａ）
エラストラン１１７４Ｄ：ＢＡＳＦ社製ポリエーテル系ポリウレタンエラストマー（ショアＤ硬度：７４、曲げ剛性率：６６０ＭＰａ、破断応力：５５ＭＰａ、上降伏応力：３１ＭＰａ、下降伏応力：２２ＭＰａ）
エラストランＨＭ７６Ｄ：ＢＡＳＦ社製ポリエーテル系ポリウレタンエラストマー（ショアＤ硬度：７６、曲げ剛性率：７００ＭＰａ、破断応力：５０ＭＰａ、上降伏応力：３８ＭＰａ、下降伏応力２２ＭＰａ）
ミラクトンＥ５６８：日本ミラクトン社製ポリカプロラクトン系熱可塑性ポリウレタンエラストマー（ショアＤ硬度：６８、曲げ剛性率：３５０ＭＰａ、破断応力５５ＭＰａ、上降伏応力２８ＭＰａ、下降伏応力２５ＭＰａ）
ミラクトンＥ５７４：日本ミラクトン社製ポリカプロラクトン系熱可塑性ポリウレタンエラストマー（ショアＤ硬度：７４、曲げ剛性率：６４０ＭＰａ、破断応力：５６ＭＰａ、上降伏応力：３２ＭＰａ、下降伏応力：２４ＭＰａ）
サーリン８９４５：デュポン社製ナトリウムイオン中和エチレン−メタクリル酸共重合体アイオノマー樹脂（酸成分含有率１５質量％、ショアＤ硬度：６１、曲げ剛性率：２５４ＭＰａ、破断応力：２４ＭＰａ、上降伏応力：１５ＭＰａ、下降伏応力：１４ＭＰａ）
ハイミランＡＭ７３２９：三井・デュポンポリケミカル社製亜鉛イオン中和エチレン−メタクリル酸二元共重合体アイオノマー樹脂（酸成分含有率１５質量％、ショアＤ硬度：６１、曲げ剛性率：２５４ＭＰａ、破断応力：２４ＭＰａ、上降伏応力：１６ＭＰａ、下降伏応力：１４ＭＰａ）

Primalloy CX300: Polyester elastomer manufactured by Mitsubishi Chemical Corporation (Shore D hardness: 72, flexural rigidity: 400 MPa, breaking stress 29 MPa, upper yield stress 23 MPa, lower yield stress 14 MPa)
Elastollan 1164D: polyether polyurethane elastomer manufactured by BASF (Shore D hardness: 64, flexural rigidity: 330 MPa, breaking stress: 55 MPa, upper yield stress: 23 MPa, lower yield stress: 23 MPa)
Elastollan 1174D: polyether polyurethane elastomer manufactured by BASF (Shore D hardness: 74, flexural rigidity: 660 MPa, breaking stress: 55 MPa, upper yield stress: 31 MPa, lower yield stress: 22 MPa)
Elastollan HM76D: polyether polyurethane elastomer manufactured by BASF (Shore D hardness: 76, flexural rigidity: 700 MPa, breaking stress: 50 MPa, upper yield stress: 38 MPa, falling yield stress: 22 MPa)
Milactone E568: a polycaprolactone thermoplastic polyurethane elastomer manufactured by Nippon Milactone Co., Ltd. (Shore D hardness: 68, flexural rigidity: 350 MPa, breaking stress 55 MPa, upper yield stress 28 MPa, lower yield stress 25 MPa)
Milactone E574: Polycaprolactone thermoplastic polyurethane elastomer manufactured by Nippon Milactone Co., Ltd. (Shore D hardness: 74, flexural rigidity: 640 MPa, breaking stress: 56 MPa, upper yield stress: 32 MPa, lower yield stress: 24 MPa)
Surlyn 8945: DuPont sodium ion neutralized ethylene-methacrylic acid copolymer ionomer resin (acid component content 15 mass%, Shore D hardness: 61, flexural rigidity: 254 MPa, breaking stress: 24 MPa, upper yield stress: 15 MPa , Descent yield stress: 14 MPa)
High Milan AM7329: Zinc ion neutralized ethylene-methacrylic acid binary copolymer ionomer resin (acid component content 15 mass%, Shore D hardness: 61, flexural rigidity: 254 MPa, rupture stress: 24 MPa, manufactured by Mitsui DuPont Polychemical Co., Ltd. Upper yield stress: 16 MPa, Lower yield stress: 14 MPa)

(4) Production of Golf Ball Body An envelope layer was formed on the center obtained as described above using the envelope layer composition obtained above as necessary to produce a core. When the envelope layer composition is used, first, the envelope layer composition having the composition shown in Table 2 is kneaded, and the center upper mold in a state where the center is accommodated, and the necessary amount of the envelope layer composition. The core molding lower mold is clamped and pressed so that the composition is in contact with half of the center surface to produce an intermediate core molding having an envelope layer formed on half of the center surface. Next, a lower mold for core molding in which the envelope layer of the intermediate core molded product is accommodated, and an upper mold for core molding so that a required amount of the envelope layer composition contacts the remaining half of the center surface. The mold was clamped and pressed to form an envelope layer on the remaining portion of the center surface, and then heated and pressed at 170 ° C. for 30 minutes to form a core.

The intermediate layer material obtained above was injection-molded on the core obtained as described above to form an intermediate layer covering the core. Subsequently, a cover composition is injection-molded on the intermediate layer, or a half shell is produced by injection molding or compression molding using the cover composition so as to cover the core on which the intermediate layer is formed. After laminating two half shells, a cover was formed by heat pressing to produce a golf ball. The upper and lower molds for molding have hemispherical cavities, are provided with dimples, and also serve as hold pins in which a part of the dimples can advance and retreat. The hold pin is protruded, the core is inserted and then held, and a resin heated to 210 ° C. is injected into a mold clamped at a pressure of 80 tons in 0.3 seconds, cooled for 30 seconds, and the mold is opened to open a golf ball Was taken out.

The surface of the resulting golf ball body is sandblasted and marked, and then a clear paint is applied and heated in an oven at 40 ° C. for 4 hours to dry the paint. The diameter is 42.7 mm and the mass is 45.4 g. Got a golf ball.

Table 5 shows the results of evaluating the amount of compressive deformation of the obtained golf ball.

A golf ball No. 1 using a thermoplastic polyurethane elastomer having a specific slab hardness and upper / lower yield stress as an intermediate layer. Nos. 1 to 10 are golf ball Nos. 1 and 5 using a polyester elastomer or ionomer resin. As compared with 13, 14, 16-19, it was found that the spin amount is small, the flight distance can be extended, and the durability can be improved. In addition, golf ball Nos. With intermediate layer thicknesses of 0.3 mm and 2.5 mm. Even in 11-12, excellent flight distance and durability were ensured. Furthermore, the golf ball No. No. 15 was not durable and could not be evaluated.

The present invention is useful as a golf ball with improved flight distance performance and durability.

Claims (7)

A golf ball having a core, one or more intermediate layers covering the core, and a cover covering the intermediate layer,
An intermediate layer material comprising a thermoplastic polyurethane in which at least one piece or one layer of the intermediate layer has a slab hardness of 65 to 80 in Shore D hardness and an upper yield stress (MPa) / lower yield stress (MPa) of 1.60 or less. Golf ball formed from. The golf ball according to claim 1, wherein the thermoplastic polyurethane has an upper yield stress of 15 MPa or more and a lower yield stress of 10 MPa or more. The golf ball according to claim 1, wherein the thermoplastic polyurethane has a breaking stress (MPa) of 25 MPa or more. The golf ball according to claim 1, wherein the thermoplastic polyurethane has a breaking stress (MPa) / slab hardness (Shore D hardness) of 0.70 or more. The golf ball according to claim 1, wherein the thermoplastic polyurethane has a flexural modulus of 250 to 4000 MPa. The golf ball according to claim 1, wherein the intermediate layer has a thickness of 0.5 to 2.0 mm. The golf ball according to claim 1, wherein the cover includes a thermoplastic polyurethane having a slab hardness of Shore D hardness of 50 or less and a thickness of 0.3 to 1.5 mm.

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