JP2003159351A - Golf ball - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a golf ball showing excellent resilience property, abrasion resistance, discoloration resistance, and manufacturing efficiency and having excellent molding property. <P>SOLUTION: The golf ball made of a core and a cover formed by being coated over the core has a feature that the cover contains a thermoplastic polyurethane elastomer generated by using an alicyclic diisocyanate and polyol having crystallinity as a basic resin. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a golf ball having excellent resilience, scratch resistance, discoloration resistance and productivity, and good moldability.

[0002]

2. Description of the Related Art In recent years, ionomer resins have been widely used as cover materials for golf balls. This is because the ionomer resin is excellent in resilience, durability, workability and the like. However, since the ionomer resin has high rigidity and hardness, if only the ionomer resin is used as the cover material, the shot feeling becomes hard and bad, and there is a problem that the spin performance is not sufficient and the controllability is poor. there were.

Therefore, in order to solve the above problems, such a hard ionomer resin is blended with a soft ionomer resin of a terpolymer system (Japanese Patent Laid-Open No. 5-39).
No. 31, gazette of Japanese Patent No. 2709950, etc.), blending with a thermoplastic elastomer (JP-A-6-2990).
No. 52, JP-A-6-327794, etc.), various attempts have been proposed to soften the cover. However, in such a blend of a hard ionomer resin and a soft ionomer resin, when adjusted so that a good shot feeling and spin performance can be realized, the resilience performance is significantly reduced, and particularly due to the groove on the club face during an iron shot. The surface of the cover was easily scraped off, and the surface of the golf ball was fluffed or fluffed, resulting in poor scratch resistance. Further, in the blend of the hard ionomer resin and the thermoplastic elastomer, the resilience performance is superior to the blend of the soft ionomer resin, but there is a problem that the scratch resistance during iron shot is further deteriorated because the compatibility of the two is poor. It was

Further, a thermosetting polyurethane composition may be used as the cover material (Japanese Patent Laid-Open No. 51-74726,
Japanese Patent No. 2662909, US Pat. No. 4,123,
No. 061, etc.), using a thermoplastic polyurethane elastomer (US Pat. No. 3,395,109, US Pat. No. 4,248,432, JP-A-9-27138, JP-A-11-128401, JP-A-11-128401, Kaihei 11-1
28402, etc.), many attempts to solve the above problems have been proposed. However, when the thermosetting polyurethane composition is used for the cover material, the core is covered with the cover, although it is excellent in abrasion resistance, which is a drawback when the blend with the soft ionomer resin or the thermoplastic elastomer is used. Since the process is complicated, mass production is difficult and productivity is reduced.

Further, when a polyurethane thermoplastic elastomer is used for the cover material, productivity is improved as compared with a thermosetting polyurethane composition, but the shot feeling, controllability and rebound are not sufficiently obtained. Further, a general polyurethane thermoplastic elastomer using 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, a mixture thereof (TDI), 4,4′-diphenylmethane diisocyanate (MDI) as the diisocyanate is Although it has high strength and excellent abrasion resistance, it has a problem that it is easily yellowed and a white paint is required. Therefore, in order to improve such discoloration resistance, an attempt to use an aliphatic diisocyanate has been proposed (Japanese Patent Laid-Open No. 9-27138, etc.),
There is a problem that the strength is low and the scuff resistance is lowered as compared with the one using the aromatic diisocyanate as described above.

[0006]

SUMMARY OF THE INVENTION The present invention solves the problems of the conventional golf balls as described above, is excellent in resilience, scratch resistance, discoloration resistance and productivity, and has good moldability. An object of the present invention is to provide a golf ball having a golf ball.

[0007]

Means for Solving the Problems As a result of intensive studies to solve the above-mentioned object, the present inventors have found that an alicyclic diisocyanate and a crystalline polyol are used as a base resin for a cover. It was found that a golf ball having excellent resilience, abrasion resistance, discoloration resistance and productivity, and good moldability can be provided by using the produced polyurethane thermoplastic elastomer, and the present invention has been completed. Came to do.

That is, the present invention provides a golf ball comprising a core and a cover formed on the core, the polyurethane being produced by using an alicyclic diisocyanate and a crystalline polyol. The present invention relates to a golf ball comprising a thermoplastic resin as a base resin.

Further in order to preferably carry out the present invention, the alicyclic diisocyanate is 4,4'-dicyclohexylmethane diisocyanate, 1,3-bis (isocyanatomethyl) cyclohexane, isophorone diisocyanate and trans-1,4. -One or more selected from the group consisting of cyclohexanediisocyanate; the polyol having the above-mentioned crystallinity has a heat of crystal fusion of 0.1 to 0.7 mJ / ° C · mg by DSC measurement; and has the above-mentioned crystallinity The polyol is polycaprolactone diol (P
CL), polycarbonate diol (PC), polyethylene adipate (PEA), polybutylene adipate (PBA) and polyhexamethylene adipate (PH
MA) from the group consisting of one or more; the cover has a Shore D hardness of 30 to 55 and a thickness of 0.3 to.
Having 2.0 mm; preferably.

The present invention will be described in more detail below. The golf ball of the present invention has a cover coated on the core. The core may be one that has been conventionally used for solid golf balls. For example, 100 parts by weight of a base rubber such as cis-1,4-polybutadiene rubber may be used with respect to acrylic acid, methacrylic acid, or the like. Vulcanizing agent (crosslinking agent) consisting of α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms or its monovalent or divalent metal salt such as zinc or magnesium, or functional monomer such as trimethylolpropane trimethacrylate 10 to 60 parts by weight, alone or in total, 0.5 to 5 parts by weight of a co-crosslinking initiator such as an organic peroxide, 10 to 30 parts by weight of a filler such as zinc oxide or barium sulfate, and if necessary, an organic sulfur compound. The rubber composition containing an antioxidant and the like is uniformly kneaded using an appropriate kneading machine such as a normal kneading roll,
A spherical core can be obtained by vulcanization molding in a mold. The conditions at this time are not particularly limited, but usually 130 to 240 ° C., pressure 2.9 to 11.8 MPa, 15
~ 60 minutes. The surface of the obtained core is preferably buffed in order to improve the adhesion with the cover around it. However, the above cores are merely examples, and the present invention is not limited thereto.

Further, even if the core has a single layer structure,
You may have a multilayer structure more than a layer. In the case of a core having a multi-layer structure, the innermost layer is preferably made of a rubber composition containing cis-1,4-polybutadiene as a base rubber as described above, but the other layers are made of a resin such as a thermoplastic resin. May be used as the base material.

The core used in the golf ball of the present invention has a final load of 1275 from an initial load of 98N.
Deformation amount up to when N is loaded is 2.5 to 4.5 mm, preferably 2.6 to 4.2 mm, and more preferably 2.7 to.
It is desirable to have 4.0 mm. The amount of deformation is
If it is less than 2.5 mm or more than 4.5 mm, it becomes difficult to adjust the amount of deformation of the obtained golf ball to an appropriate range, and the shot feeling and flight distance may be impaired.

The core used in the golf ball of the present invention has a structure in which the center is the softest and the hardness distribution becomes high toward the outside. In terms of surface hardness, the hardness difference between the surface hardness and the central hardness due to Shore D hardness is 10 or more, preferably 15 to 45, and more preferably 1
It is desirable to be 8-40, most preferably 20-40.

The core used in the golf ball of the present invention desirably has a center hardness of 20 to 50, preferably 30 to 45, according to Shore D hardness. If it is less than 20, it becomes difficult to adjust the amount of deformation of the core within an appropriate range, and the repulsion also decreases. If it is larger than 45, the difference in hardness from the surface becomes small and the shot feeling and the flight distance may be impaired.

The core used in the golf ball of the present invention preferably has a surface hardness according to Shore D hardness of 45 to 72, preferably 50 to 70, more preferably 50 to 68. If it is less than 45, it becomes difficult to adjust the amount of deformation of the core within an appropriate range, and repulsion also decreases. When it is larger than 72, the shot feeling becomes too hard. In this specification,
The surface hardness of the core means the hardness measured on the surface of the outermost layer of the entire core, not only for the one-layer structure but also for the multi-layer structure, and the center hardness is usually cut into two equal parts and the cut surface thereof is cut. Means the hardness measured at the center point of the core.

As described above, when the core of the present invention has a multilayer structure composed of an inner core and one or more outer cores, the outer core is formed of the same rubber composition as the inner core as described above. Alternatively, it may be formed by using a thermoplastic resin, particularly an ionomer resin which is usually used for a cover of a golf ball as a base resin. As such an ionomer resin, particularly, an α-olefin and a carbon number of 3 to 8 are used.
An ionomer resin obtained by neutralizing part of the carboxylic acids in a copolymer of α, β-unsaturated carboxylic acids with metal ions, α
-At least a portion of the carboxylic acid in the terpolymer of an olefin, an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms and an α, β-unsaturated carboxylic acid ester was neutralized with metal ions One or a mixture thereof is used. As the α-olefin in the above ionomer resin, ethylene and propylene are preferable, and as the α, β-unsaturated carboxylic acid, for example, acrylic acid, methacrylic acid, fumaric acid, maleic acid, crotonic acid, etc., and particularly acrylic Acid, methacrylic acid and the like are preferable. Further, as the α, β-unsaturated carboxylic acid ester, for example, methyl, ethyl, propyl, n-butyl, isobutyl ester such as acrylic acid, methacrylic acid, fumaric acid, maleic acid or the like is used, and particularly acrylic acid ester Methacrylic acid esters are preferred. Further, as the metal ion to be neutralized, an alkali metal ion such as Na ion, K ion, Li ion and the like; 2
Examples thereof include valent metal ions such as Zn ions, Ca ions, Mg ions and the like; trivalent metal ions such as Al ions, Nd ions and the like; and mixtures thereof, but Na ions, Zn ions, Li ions and the like are repulsive, It is often used because of its durability.

Specific examples of ionomer resins include, but are not limited to, Hi-mila (Hi-mila).
n) 1555, Himilan 1557, Himilan 160
1, high milan 1605, high milan 1652, high milan 1702, high milan 1705, high milan 170
6, Himilan 1707, Himilan 1855, Himilan 1856, Himilan AM7316 (manufactured by Mitsui DuPont Polychemical Co., Ltd.), Surlyn 894
5, Surlyn 9945, Surlyn 6320, Surlyn 8
320, Surlyn AD8511, Surlyn AD851
2, AD8542 (manufactured by DuPont), Iotech (I
otek) 7010, Iotech 8000 (Exxon
(Manufactured by Exxon)) and the like. As these ionomers, those exemplified above may be used alone or as a mixture of two or more kinds.

Further, as a preferable example of the material of the outer core of the present invention, only the ionomer resin as described above may be used, but one or more kinds of the ionomer resin and the thermoplastic elastomer, the diene block copolymer or the like may be used. And may be used in combination. As a specific example of the thermoplastic elastomer, for example, a thermoplastic polyamide elastomer commercially available from Toray Industries, Inc. under the trade name "Pevax" (for example, "Pevax 2533"), a trade name of "Hytrel" from Toray DuPont Co., Ltd. (For example, "Hytrel 3548", "Hytrel 4047"), a thermoplastic polyester elastomer, marketed by Takeda Burdish Co., Ltd. under the trade name "Elastolan" (for example,
"Elastollan ET880") polyurethane-based thermoplastic elastomers and the like.

The above diene block copolymer has a double bond derived from the conjugated diene compound of the block copolymer or partially hydrogenated block copolymer. The block copolymer as the substrate is a block copolymer composed of a polymer block A containing at least one vinyl aromatic compound as a main component and a polymer block B containing at least one conjugated diene compound as a main component. Is. The partially hydrogenated block copolymer is obtained by hydrogenating the above block copolymer. Examples of vinyl aromatic compounds constituting the block copolymer include styrene,
One or more of α-methylstyrene, vinyltoluene, pt-butylstyrene, and 1,1-diphenylstyrene can be selected, and styrene is preferable. As the conjugated diene compound, for example, butadiene, isoprene, 1,3-pentadiene, 2,3-dimethyl-1,3-butadiene, etc. may be selected alone or in combination. And combinations thereof are preferred. Examples of preferred diene-based block copolymers include block copolymers having an SBS (styrene-butadiene-styrene) structure having a polybutadiene block containing an epoxy group or SIS having a polyisoprene block containing an epoxy group.
Examples thereof include a block copolymer having a (styrene-isoprene-styrene) structure. Specific examples of the diene-based block copolymer, for example those commercially available under the trade name "Epofriend" from Daicel Chemical Industries, Ltd. (for example,
"Epofriend A1010"), those marketed under the trade name "Septon" by Kuraray Co., Ltd. (for example, "Septon HG-252", etc.) and the like.

The blending amount of the above-mentioned thermoplastic elastomer, diene-based block copolymer and the like is such that the base resin 1 for the outer core is
1 to 60 parts by weight, preferably 1 to 100 parts by weight
35 parts by weight. If the amount is less than 1 part by weight, the effect of improving the shot feeling by blending them becomes insufficient,
If it is more than 60 parts by weight, the outer core becomes too soft and the resilience is lowered, or the compatibility with the ionomer resin is deteriorated and the durability is apt to be lowered.

When the core has a multi-layered structure and the outer core layer is formed of a rubber composition, the rubber composition is mixed and kneaded, and the inner core is concentrically coated, and then 160 is formed in a mold. A core obtained by coating the outer core layer on the inner core can be obtained by hot pressing at ˜180 ° C. for 10 to 20 minutes. When the core has a multi-layer structure, and the outer core layer is formed of a thermoplastic resin,
The core can be obtained by directly injection molding the resin composition onto the inner core. The surface of the obtained core is preferably buffed in order to improve the adhesion with the cover around it.

The core of the golf ball of the present invention has a diameter of 3
9.6 to 41.8 mm, preferably 39.8 to 41.4
It is preferred to have mm, more preferably 40.4 to 41.2 mm. If the diameter of the core is smaller than 39.6 mm, the cover becomes thicker and the resilience is reduced, resulting in 41.8 m.
If it is larger than m, the thickness of the cover becomes too thin, the effect of the cover cannot be sufficiently obtained, and molding becomes difficult.

The core of the golf ball of the present invention has a deformation amount of 2.50 to 3.20 mm, preferably 2.60 to 3.10 mm, from a state where an initial load of 98 N is applied to when a final load of 1275 N is applied. Preferably from 2.70
It is desirable to have 3.00 mm. If the amount of deformation is less than 2.50 mm, the shot feeling is hard and bad,
If it exceeds 3.20 mm, it becomes too soft and the shot feeling is heavy and bad.

A cover is then coated on the core. The cover used for the golf ball of the present invention is required to contain, as a base resin, a polyurethane-based thermoplastic elastomer produced by using an alicyclic diisocyanate and a crystalline polyol. The merit of using a polyurethane-based thermoplastic elastomer produced by using an alicyclic diisocyanate as the base resin of the cover composition is that it has good discoloration resistance (yellowing) and excellent scratch resistance. Is. Further, the merit of using the thermoplastic polyurethane-based elastomer produced by using the polyol having crystallinity as the base resin of the cover composition is that moldability is improved. When a polyurethane-based thermoplastic elastomer produced by using an alicyclic diisocyanate and a polyol having no crystallinity is used as the base resin of the cover composition, the cohesive force is very weak and solidification immediately after molding occurs. Tack (stickiness) that occurs immediately after molding (injection or pressing) due to slow speed
As a result, there is a disadvantage in molding such that the balls adhere to each other and the time required for mold opening (mold release) becomes long, and there is a problem that productivity is reduced. Therefore, the present inventors have solved the above problems by imparting crystallinity to the polyol used in the thermoplastic polyurethane elastomer.

The thermoplastic polyurethane elastomer is
Generally, a polyurethane structure is contained as a hard segment, and a polyol such as polyester polyol or polyether polyol is contained as a soft segment. The polyurethane structure generally contains a diisocyanate and a curing agent such as an amine type. In the polyurethane thermoplastic elastomer used for the cover of the present invention, the diisocyanate as a constituent component is an alicyclic diisocyanate, and the polyol is a crystalline polyol.

As an example of the above alicyclic diisocyanate, 4,4'-diphenylmethane diisocyanate (M
DI) hydrogenated product 4,4'-dicyclohexylmethane diisocyanate (H ₁₂ MDI), xylylene diisocyanate (XDI) hydrogenated product 1,3-
Bis (isocyanatomethyl) cyclohexane (H ₆ XD
I), one selected from the group consisting of isophorone diisocyanate (IPDI) and trans-1,4-cyclohexane diisocyanate (CHDI), or 2
A combination of two or more species may be mentioned, and H ₁₂ MDI is preferable in terms of versatility and processability. Specific examples of the polyurethane-based thermoplastic elastomer using the above H ₁₂ MDI include “Elastollan XNY90A (trade name)”, “Elastollan XNY97A (trade name)” and “Elastollan” commercially available from BASF Polyurethane Elastomers Co., Ltd. X
NY585 (trade name) "and the like.

From the viewpoint of discoloration resistance (yellowing), the above polyurethane-based thermoplastic elastomer uses a diisocyanate having no double bond in the skeleton structure in the molecule, that is, an aliphatic diisocyanate and an alicyclic diisocyanate. The polyurethane-based thermoplastic elastomer is preferable. Further, in consideration of scratch resistance and the like, a polyurethane-based thermoplastic elastomer using an alicyclic diisocyanate having a large mechanical strength and further an aromatic diisocyanate is preferable. As the polyurethane-based thermoplastic elastomer used for the cover of the golf ball of the present invention, a polyurethane-based thermoplastic elastomer using an alicyclic diisocyanate is used in consideration of both the discoloration resistance and the scratch resistance.

In the polyurethane-based thermoplastic elastomer used for the cover of the golf ball of the present invention, the above-mentioned crystalline polyol has a heat of crystal fusion of 0.1 to 0.7 mJ / ° C.mg, preferably 0. 1 to
0.6 mJ / ° C · mg, more preferably 0.1 to 0.4
mJ / ° C · mg, most preferably 0.14 to 0.33 m
It is desirable to have J / ° C · mg. If the heat of fusion of crystal is less than 0.1 mJ / ° C · mg, the effect of imparting crystallinity is small and it does not contribute to the improvement of moldability (solidification rate).
If it exceeds 7 mJ / ° C · mg, the fluidity will be poor. Here, the heat of crystal fusion of the polyol having crystallinity means the heat of fusion of the crystals of the polyol in the polyurethane-based thermoplastic elastomer measured by DSC (differential scanning calorimeter). Specifically, 15 mg of the above-mentioned thermoplastic elastomer as a sample is weighed, and (1) -70
C. to 230.degree. C. at a rate of 10.degree. C./min and held for 10 minutes, (2) 230.degree. C. to -70.degree. Up to ℃ 1
The temperature was raised again at 0 ° C / min. The heat of crystal fusion of the polyol having the above crystallinity was calculated from the area of the endothermic peak resulting from the melting of the crystals of the polyol in the polyurethane-based thermoplastic elastomer in (3) above. DSC measurement is TA
DS made by Instrument
C-2920 was used and the measurement was performed in the automatic measurement mode.

Examples of the above-mentioned crystalline polyols include polycaprolactone diol (PCL), polycarbonate diol (PC) and adipate type polyester polyols (polyethylene adipate (PEA),
Examples thereof include one selected from the group consisting of polybutylene adipate (PBA) and polyhexamethylene adipate (PHMA), or a combination of two or more thereof, with polycarbonate diol being preferred.

In the golf ball of the present invention, in the cover material, in addition to the above resin components, if necessary, a coloring agent such as titanium dioxide, a dispersant, an antiaging agent, an ultraviolet absorber and a light stabilizer. , A fluorescent material, an additive such as a fluorescent whitening agent, etc. may be contained within a range that does not impair the desired characteristics of the golf ball cover, but the amount of the coloring agent is usually 0.1.
-5 parts by weight is preferred.

The method of covering the cover is not particularly limited, and a usual method of covering the cover can be used. The cover composition is formed into a half-shell-shaped half shell in advance, two cores are used to wrap the core, and press molding is performed at 160 to 200 ° C. for 1 to 10 minutes, or the cover composition is directly placed on the core. The method of wrapping the core by injection molding is used. From the viewpoint of the uniformity of the cover thickness, the above press molding method is preferable.

The cover has a thickness of 0.3 to 2.0 mm,
Preferably 0.5-1.6 mm, more preferably 0.5
It is desirable to have ~ 1.2 mm. If it is smaller than 0.3 mm, it will be too thin and difficult to mold.
If it is larger than the above range, the thickness becomes too thick and the resilience is lowered to reduce the flight distance.

The cover of the golf ball of the present invention preferably has a Shore D hardness of 30 to 55, preferably 35 to 55, and more preferably 38 to 50. If the cover hardness is lower than 30, the resilience and scuff resistance will be reduced, and if it is higher than 55, a suitable spin amount will not be obtained, and the shot feeling will be hard and poor. In the present specification, the cover hardness means the hardness (slab hardness) measured using a hot press molded sheet produced from the cover composition.

In the golf ball of the present invention, dimples are formed on the surface of the ball, if necessary, at the time of molding the cover.
Further, after the cover is molded, paint finish, marking stamp, etc. may be applied as required.

The golf ball of the present invention has an initial load of 98 N.
2.50 to 3.10 mm of deformation amount from the state of being loaded to the state of applying a final load of 1275 N, preferably 2.6
0 to 3.00 mm, more preferably 2.65 to 2.90
It is desirable to have mm. If it is less than 2.50 mm, the shot feeling is hard and bad, and the spin rate at the time of hitting with a driver or an iron club becomes large.
If it exceeds mm, it becomes too soft and the resilience is low and the feel at impact is heavy and bad.

The golf ball of the present invention has a diameter of 42.67 mm or more (preferably 4 mm or more) based on the golf ball rules.
2.67 to 42.80 mm) and the weight is 45.93 g or less.

The standard diameter of the golf ball is 42.67.
Although it is limited to mm or more, the diameter of a normal golf ball is 42.67 to 42.80 mm because the air resistance during flight increases and the flight distance decreases when the diameter increases.
The present invention can be applied to a golf ball having this diameter. In addition, there are large-diameter golf balls, etc. that aim to improve the ease of hitting by increasing the diameter of the golf ball.
Furthermore, there are cases where golf balls that deviate from the above standards are required depending on the customer's wishes and purposes.
The diameter of the golf ball is 42-44 mm, and further 40-4
A range such as 5 mm is also conceivable, and the present invention is also applicable to golf balls having these diameter ranges.

In the present invention, the cover containing the thermoplastic polyurethane elastomer produced by using the alicyclic diisocyanate and the polyol having crystallinity as the base resin is excellent in moldability and flies well. Provided is a golf ball which has excellent abrasion resistance and discoloration resistance.

[0039]

EXAMPLES Next, the present invention will be described in more detail by way of examples. However, the present invention is not limited to these examples.

Preparation of Core (Core I) A rubber composition for a core having the composition shown in Table 1 below was mixed, kneaded, and hot-pressed at 170 ° C. for 15 minutes in a mold to have a diameter of 40.0 mm. A spherical core was obtained.

(Core II) (i) Preparation of Inner Core The core rubber composition having the composition shown in Table 1 below was mixed and kneaded, and heated and pressed in a mold at 170 ° C. for 15 minutes to give a diameter of 37. A spherical core having a diameter of 0.0 mm was obtained.

(Ii) Preparation of two-layer core (core formulation I) The composition for the outer core having the formulation shown in Table 1 below was directly injection-molded on the center produced in (i) above to obtain a diameter A spherical two-layer core having 40.0 mm was made.

(Core III) (i) Preparation of Inner Core The core rubber composition having the composition shown in the following Table 1 was mixed and kneaded, and heated and pressed at 170 ° C. for 15 minutes in a mold to have a diameter of 32. A spherical core having a diameter of 0.5 mm was obtained.

(Ii) Preparation of two-layer core The rubber composition for the outer core having the composition shown in Table 1 below was mixed and kneaded, and the inner core prepared in the above (i) was coated concentrically with gold, A spherical two-layer core having a diameter of 40.0 mm was produced by hot pressing in a mold at 170 ° C. for 15 minutes. The amount of compressive deformation, central hardness (a) and surface hardness (b) of the obtained one-layer core and two-layer core were measured, and the hardness difference (ba) was calculated from the results. The results are shown in the table.

[0045]

[Table 1]

(Note 1) Trade name "BR-1" from JSR Corporation
8 ”commercially available high-cis polybutadiene rubber (cis-1,
4-polybutadiene content = 96%) (Note 2) Diphenyl disulfide (Note 3) commercially available from Sumitomo Seika Chemicals Ltd. Dicumyl peroxide (Note 4) commercially available from NOF CORPORATION under the trade name "Park Mill D" Commercially available from Mitsui DuPont Polychemical Co., Ltd. under the trade name “HIMIRAN 1605” Sodium ion neutralized ethylene-methacrylic acid copolymer type ionomer resin (Note 5) Commercially available from Mitsui DuPont Polychemical Co., Ltd. under the trade name “HIMIRAN 1706” Zinc ion neutralized ethylene-
Methacrylic acid copolymer type ionomer resin

Preparation of Cover Composition The cover compounding materials shown in Table 2 below were mixed by a twin-screw kneading extruder to obtain a pellet-shaped cover composition. The extrusion conditions were: screw diameter 45 mm, screw rotation speed 200 rpm, screw L / D 35, and the blend was 200 to 260 at the die position of the extruder.
Heated to ° C. A 2 mm thick hot-pressed sheet prepared from the above cover composition was stored at 23 ° C. for 2 weeks,
Stack 3 or more of these sheets and follow ASTM-2240-6
The hardness measured by using a spring type hardness meter Shore D type specified in No. 8 is shown in Tables 2 to 4 as the cover hardness.

[0048]

[Table 2]

*: Endothermic peak is too small under these measurement conditions
Cannot be measured (Note 6) From BASF Polyurethane Elastomers Co., Ltd.
4,4 'sold under the trade name "Elastollan XNY90A"
-Dicyclohexylmethane diisocyanate (H ₁₂M
DI) -Polyoxytetramethylene glycol (PTM
G) type polyurethane thermoplastic elastomer, JIS-
A hardness = 90 (Note 7) From BASF Polyurethane Elastomers Co., Ltd.
Commercially available H under the product name "Elastollan XNY97A"₁₂M
DI-PTMG Polyurethane Thermoplastic Elastomer
ー 、 JIS-A hardness = 97 (Note 8) From BASF Polyurethane Elastomers Co., Ltd.
Commercially available under the product name "Elastollan ET890 (clear)"
4,4'-diphenylmethane diisocyanate (MDI)
Polyurethane polyurethane thermoplastic elastomer, JIS-A hard
Degree = 90 (Note 9) manufactured by BASF Polyurethane Elastomers Co., Ltd.
H₁₂MDI-polycaprolactone diol (PCL)
Polyurethane polyurethane thermoplastic elastomer, JIS-A hard
Degree = 97 (Note 10) Made by BASF Polyurethane Elastomers Co., Ltd.
H₁₂MDI-polycarbonate diol (PC) system
Polyurethane type thermoplastic elastomer, JIS-A hardness
= 94 (Note 11) Product name “Pan” from Dainippon Ink and Chemicals, Inc.
Hexamethylene diisocyanate commercially available as "DEX T7890"
Anate (HDI) type polyurethane thermoplastic elastomer
-

Examples 1 to 4 and Comparative Examples 1 to 4 The obtained cover compositions are directly injection-molded on the core obtained as described above to form a cover layer having a thickness of 1.4 mm. did. The mold releasability and tackiness as moldability were evaluated, and the results are shown in Table 3 (Examples) and Table 4 below.
(Comparative example). Then, clear paint was applied on the surface to obtain a golf ball having a diameter of 42.8 mm and a weight of 45.4 g. The amount of compressive deformation, coefficient of restitution, flight distance, scratch resistance and discoloration resistance (yellowing) of the obtained golf ball were measured or evaluated, and the results are shown in the same table. The test method was as follows.

(Test Method) (1) Compressive Deformation Amount of deformation was measured from a state where an initial load of 98 N was applied to a core or a golf ball to a final load of 1275 N.

(2) Cover Hardness (Slab Hardness) A hot press molded sheet having a thickness of 2 mm prepared from the composition for a cover was stored at 23 ° C. for 2 weeks, and then three or more sheets were piled up to ASTM-2240. The hardness was measured using a spring type hardness meter Shore D type specified at -68.

(3) Moldability (Releasability) After the golf ball was molded using an automatic handling machine, it was cooled for 30 seconds, and then the golf ball was picked up by the automatic picking device as one cycle. In this case, the above device is moved and taken up.
The releasability was evaluated by the number of times of inching required before this could be picked up. If you can pick up without jogging,
It shows that the releasability is good. Molding was performed for 10 cycles and evaluated by the total number of inching, and the evaluation criteria were as follows. Judgment Criteria 〇… Jogging times 0 △ △ Jogging times 1 to 4 ×… Jogging times 5 or more

(4) Moldability (Tackiness) After molding the golf ball for 30 seconds, the golf ball taken out of the mold is kept in contact with the golf ball for about 1 minute, and the tackiness (adhered state) of the golf ball is maintained. ) Was evaluated.
The criteria for judgment are as follows. Judgment criteria Yes ... No golf balls stick to each other ... No golf balls stick to each other

(5) Coefficient of Repulsion Each golf ball was loaded with 200 g of an aluminum cylinder.
The impact was made at a speed of 5 m / sec, the velocities of the cylinder and the golf ball after the impact were measured, and the coefficient of restitution of each golf ball was calculated from the velocity and weight before and after each impact. The measurement was performed 5 times for each golf ball, and the average value was used as the coefficient of restitution of each golf ball. Example 1
An index with the coefficient of restitution of 100 as 100 is shown as the result of each golf ball.

(6) Scratch resistance A swing robot manufactured by Trutemper Co., Ltd. was fitted with a commercially available pitching wedge (PW), and a head speed of 36 m /
Set to seconds, hit two points on each golf ball once each,
Two impact parts were visually observed. The criteria for judgment are as follows. Judgment Criteria: A slight scratch remains on the surface of the golf ball, but it is hardly noticeable. B: Scratches clearly remain on the surface of the golf ball, and some fluff is observed. × ... The surface of the golf ball was considerably scraped, and fluff was noticeable.

(7) Discoloration resistance (yellowing) Each golf ball was irradiated with 120 hours using a Sunshine Weather Meter of Suga Test Instruments Co., Ltd. The Lab color difference before and after that was measured by a colorimeter (commercially available from CR
-221) is used to measure (ΔL, Δa and Δ
b), represented by ΔE. ΔE is calculated using the following equation. The larger the color difference value, the easier the color change (yellowing). ΔE = [(ΔL) ² + (Δa) ² + (Δb) ² ] ^1/2

(Test result)

[Table 3]

[0059]

[Table 4]

From the above results, the golf balls of the present invention of Examples 1 to 4 are superior to the golf balls of Comparative Examples 1 to 4 in moldability, resilience, abrasion resistance and discoloration resistance. all right.

On the other hand, in the golf balls of Comparative Examples 1 and 2, since the crystallinity of the polyol component of the polyurethane-based thermoplastic elastomer used as the base resin for the cover is low, the coefficient of restitution is reduced and the mold release is improved. Moldability such as moldability and tackiness is poor.

In the golf ball of Comparative Example 3, since only the polyurethane thermoplastic elastomer using the aromatic diisocyanate is used as the base resin for the cover,
It is very easily yellowed, the coefficient of restitution is small, and the scratch resistance is also poor.

In the golf ball of Comparative Example 4, since only the polyurethane thermoplastic elastomer using the aliphatic diisocyanate is used as the base resin for the cover,
Although it does not easily turn yellow, the moldability is good, but the scratch resistance is poor.

[0064]

According to the present invention, by using a polyurethane-based thermoplastic elastomer produced by using an alicyclic diisocyanate and a polyol having crystallinity as the base resin for the cover, the resilience and resistance are improved. Abrading,
It is possible to provide a golf ball which is excellent in discoloration resistance and productivity and has good moldability.

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 4J034 AA01 AA06 DF02 DF12 DF16                       DF20 HA01 HA07 HC22 HC46                       HC53 HC54 HC71 QB16 QC03                       RA03

Claims (5)

[Claims] 1. A golf ball comprising a core and a cover formed on the core, the cover being a polyurethane-based thermoplastic elastomer produced by using an alicyclic diisocyanate and a crystalline polyol. A golf ball containing as a base resin. 2. The alicyclic diisocyanate is 4,
4'-dicyclohexylmethane diisocyanate, 1,
1 selected from the group consisting of 3-bis (isocyanatomethyl) cyclohexane, isophorone diisocyanate and trans-1,4-cyclohexane diisocyanate
The golf ball according to claim 1, which is one or more kinds. 3. The golf ball according to claim 1, wherein the polyol having crystallinity in the polyurethane-based thermoplastic elastomer has a heat of crystal fusion of 0.1 to 0.7 mJ / ° C. mg measured by DSC. 4. The crystalline polyol is polycaprolactone diol (PCL), polycarbonate diol (PC), polyethylene adipate (PE).
A), one or more selected from the group consisting of polybutylene adipate (PBA) and polyhexamethylene adipate (PHMA).
The golf ball according to the item. 5. The cover has a Shore D hardness of 30 to 55.
And a golf ball having a thickness of 0.3 to 2.0 mm.