JP2002085589A - Multi-piece solid golf ball - Google Patents

Abstract

(57) [Summary] (With correction) [Solution] Solid core 294N (30 kgf)
The amount of deformation under load is 1.1 mm or more, the difference between the JIS-C hardness of the core surface and the JIS-C hardness of the core center (core surface-core center) is 15 or less, and the inner layer cover has the following component (a) To (c), (a) an olefin-unsaturated carboxylic acid random copolymer, an olefin-unsaturated carboxylic acid-unsaturated carboxylic acid ester random copolymer or a metal ion neutralized product of these copolymers, or A mixture of a copolymer and a neutralized product; (b) a fatty acid having a molecular weight of 280 or more or a derivative thereof; (c) a basic inorganic metal capable of neutralizing an acid group in the above components (a) and (b) It is formed of a resin composition containing a compound as an essential component. The multi-piece solid golf ball of the present invention has a long flight distance, and is particularly suitable for use by a player with a head speed of about 40 m / s.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a solid core,
More specifically, the present invention relates to a multi-piece solid golf ball that can suitably cope with the use of a player having a head speed of about 40 m / s, having a two-layer inner and outer cover covering the same.

[0002]

2. Description of the Related Art At present, golf balls having various structures have been proposed, and in particular, solid golf balls, in particular, a solid core is coated with a plurality of layers of covers in terms of flight distance, controllability (spin amount) and feeling. Many proposals have been made for multi-piece solid golf balls (JP-A-4-244174 and JP-A-6-1422).
No. 28, No. 7-24084, No. 7-2408
No. 5, No. 9-10358, No. 11-1042
No. 73).

[0003]

However, a multi-piece solid golf ball which is more excellent in flight performance, good in spin characteristics, excellent in feeling of wood, iron and putter shots, and excellent in rust resistance and durability. Is desired.

[0004]

Means for Solving the Problems and Embodiments of the Invention As a result of diligent studies to meet the above demand, the present inventor has found that a multi-piece solid having a solid core and an inner and outer two-layer cover for covering the solid core. In golf balls,
The amount of deformation of the solid core under a 294 N (30 kgf) load is 1.1 mm or more, and the JIS-
The difference between the C hardness and the JIS-C hardness of the core center (core surface-core center) is 15 or less, and the inner layer cover has the following component (a)
To (c), (a) an olefin-unsaturated carboxylic acid random copolymer, an olefin-unsaturated carboxylic acid-unsaturated carboxylic acid ester random copolymer or a metal ion neutralized product of these copolymers, or A mixture of a copolymer and a neutralized product; (b) a fatty acid having a molecular weight of 280 or more or a derivative thereof; (c) a basic inorganic metal capable of neutralizing the acid groups in the above components (a) and (b) The resin is formed from a resin composition containing a compound as an essential component in a specific amount, the inner layer cover has a Shore D hardness of 45 to 65, and the outer layer cover has a Shore D hardness of 35 to 55, The outer layer cover is formed softer than the inner layer cover, and the sum of the dimple trajectory volumes obtained by multiplying the dimple volume by the square root of the dimple diameter is 530 to 750. Bet is one that has been found that it is effective.

That is, the present invention provides the following multi-piece solid golf ball. [Claim 1] In a multi-piece solid golf ball having a solid core and two inner and outer cover layers covering the solid core, the solid core has a deformation of 1.1 mm or more under a 294 N (30 kgf) load, and The difference between the JIS-C hardness of the surface and the JIS-C hardness of the core center (core surface-core center) is 15 or less, and the inner layer cover is composed of the following components (a) to (c), (a) olefin-unsaturated carboxylic acid 100 parts by mass of a random copolymer, an olefin-unsaturated carboxylic acid-unsaturated carboxylic acid ester random copolymer or a metal ion neutralized product of these copolymers, or a mixture of these copolymers and neutralized products; (B) a fatty acid or a derivative thereof having a molecular weight of 280 or more, 5 to 80 parts by mass; (c) a basic inorganic substance capable of neutralizing the acid groups in the above components (a) and (b) It is formed of a resin composition containing 0.1 to 10 parts by mass of a metal compound as an essential component, and has a Shore D hardness of 45 to 6 of the inner cover.
5, and the Shore D hardness of the outer layer cover is 35 to 55.
A multi-piece solid golf ball, wherein the outer layer cover is formed softer than the inner layer cover, and the sum of the dimple trajectory volumes obtained by multiplying the dimple volume by the square root of the dimple diameter is 530 to 750. [2] The multi-piece solid golf ball according to [1], wherein the resin composition has a melt index of 0.5 dg / sec or more. [3] The multi-piece solid according to [1] or [2], wherein the outer layer cover is formed mainly of a thermoplastic or thermosetting polyurethane-based elastomer, polyester-based elastomer, ionomer resin, polyolefin-based elastomer or a mixture thereof. Golf ball. [4] The multi-piece solid golf ball according to [3], wherein the outer layer cover is formed mainly of a thermoplastic polyurethane-based elastomer obtained by using an aromatic or aliphatic diisocyanate. [5] The multi-piece solid golf ball according to [3], wherein the outer layer cover is formed mainly of a reaction product of a thermoplastic polyurethane elastomer and an isocyanate compound. [6] The multi-piece according to any one of [1] to [5], wherein the component (b) in the resin composition is a fatty acid having 18 to 80 carbon atoms in one molecule or a derivative thereof. Solid golf ball. [Claim 7] 5 of the acid groups in the essential components (a) and (b)
7. The multi-piece solid golf ball according to claim 1, wherein 0 mol% or more is neutralized with metal ions. [Claim 8] The inner layer cover is formed of a resin composition comprising 100 parts by mass or less of an olefin-based elastomer or a polyester-based elastomer with respect to 100 parts by mass of the essential components (a) to (c). A multi-piece solid golf ball according to any one of claims 1 to 7. [9] The golf ball according to any one of [1] to [8], wherein an adhesive layer is provided between the inner cover and the outer cover. [Claim 10] The adhesive layer is mainly composed of a urethane resin-based adhesive or a chlorinated polyolefin-based adhesive, and has a thickness of 0.1 to 0.1%.
10. The multi-piece solid golf ball according to claim 9, formed to have a thickness of 30 μm. [11] The specific gravity of the solid core is 1.0 to 1.3, the specific gravity of the inner layer cover is 0.8 to 1.5, and the specific gravity of the outer layer cover is 0.9 to 1.3. Items 1 to 10
The multi-piece solid golf ball according to any one of the above items. [Claim 12] When the area of the vertical cross-sectional shape at the center of the dimple is S ₁ , and the area obtained by multiplying the diameter of the dimple by the depth is S ₂ , the ratio of the dimple cross-sectional shape area ratio represented by S ₁ / S ₂ is obtained. Average value SA is 0.58 to 0.68,
The number of all dimples is 360-540.
2. The multi-piece solid golf ball according to claim 1.

The golf ball of the present invention has a relatively low trajectory, a long flight performance, a long flight distance, a high controllability in iron shots, and a golf ball of any wood, iron or putter. It has a good feeling even when it is performed, and is excellent in durability against danger when shot with a control shot with an iron.

In this case, the multi-piece solid golf ball of the present invention reduces the hardness distribution of the core,
A firm and comfortable hit feeling and good resilience can be obtained, which is particularly suitable for use by a player with a head speed of about 40 m / s. Also, at the same time,
The inner layer cover is formed of a resin composition which is excellent in heat stability, fluidity, moldability and is capable of imparting excellent resilience, and the hardness of the inner layer cover is adjusted, and the outer layer cover and the solid core are formed. With the synergistic effect of the above, a remarkably excellent resilience, durability and controllability can be improved.

Hereinafter, the present invention will be described in more detail.
The multi-piece solid golf ball of the present invention has a solid core and a cover having a two-layer structure of an inner cover and an outer cover that cover the solid core.

The solid core is preferably formed of a rubber composition. As the rubber composition, those using polybutadiene as a base material are preferable. The polybutadiene has a cis structure of at least 40.
% Or more of 1,4-cis polybutadiene. In the base rubber, a natural rubber, a polyisoprene rubber, a styrene-butadiene rubber, or the like can be appropriately compounded with the polybutadiene, if desired. By increasing the rubber component, the resilience of the golf ball can be improved.

The rubber composition may contain, as a crosslinking agent, a zinc salt of an unsaturated fatty acid such as zinc methacrylate or zinc acrylate, a magnesium salt, or an ester compound such as trimethylolpropane methacrylate. Zinc acid may be suitably used. The compounding amount of these crosslinking agents is 10 parts by mass or more, particularly 20 parts by mass or more, and 50 parts by mass or less as an upper limit, based on 100 parts by mass of the base rubber.
In particular, it is preferably at most 39 parts by mass.

The rubber composition generally contains a vulcanizing agent. The vulcanizing agent contains a peroxide whose temperature reaches a half-life of 155 ° C. or less in one minute. It is recommended that the compounding amount is 3
The content is 0% by mass or more, particularly 40% by mass or more, and the upper limit thereof is not particularly limited, but is preferably 70% by mass or less. Examples of such a peroxide include commercially available products, such as Perhexa 3M (manufactured by NOF Corporation), Parkmill D (manufactured by NOF Corporation), and Luperco.
231XL and Luperco 101XL (both manufactured by Atochem). The compounding amount is the base rubber 1
The amount may be 0.2 parts by mass or more, particularly 0.6 parts by mass or more, and 2.0 parts by mass or less, particularly 1.5 parts by mass or less, based on 00 parts by mass.

Further, if necessary, zinc oxide, barium sulfate and the like can be blended as an antioxidant and a filler for adjusting specific gravity.

The solid core composition obtained by blending the above components is kneaded using a conventional kneading machine, for example, a Banbury mixer or a roll, and is compressed or injection-molded into a core mold, and the molded product is crosslinked with a crosslinking agent. And a temperature sufficient for the co-crosslinking agent to act, for example, when dicumyl peroxide is used as the cross-linking agent and zinc acrylate is used as the co-crosslinking agent, it is usually about 130 to 170 ° C, particularly 150 to 160 ° C. Under the conditions of 10 to 40 minutes, particularly 12 to 20 minutes to produce a solid core having a predetermined hardness distribution.

The rubber composition can be vulcanized and cured by a known method to produce a solid core. The solid core has a diameter of 30 mm or more, preferably 33 mm or more, more preferably 35 mm or more. 40 mm or less, preferably 39 mm or less, more preferably 38 mm
It is preferable to set the following.

The solid core is 294N (3
The amount of deformation when a load of 0 kgf) is applied is 1.
1 mm or more, preferably 1.2 mm
mm or more, more preferably 1.4 mm or more, and still more preferably 1.5 mm or more.
f) If the amount of deformation under load is smaller than the above value, the feeling becomes hard, which is not preferable. Moreover, as an upper limit, 2.5 mm or less, More preferably, 2.3 mm or less,
More preferably, it is not more than 2.1 mm. If the amount of deformation is too large, the resilience and durability may be reduced.

The solid core according to the present invention has a J at the center of the core.
By optimizing the difference between the IS-C hardness and the surface JIS-C hardness of the core, a firm and comfortable hitting feel and good resilience are imparted.
The difference in hardness obtained by subtracting the JIS-C hardness at the center of the core from the hardness is J
It is required that the IS-C hardness is 15 or less, particularly 14 or less, preferably 13 or less, more preferably 12 or less, and the lower limit is 0 or more, particularly 1 or more, more preferably 2 or less.
That is all. By providing such a difference in hardness, it is possible to suitably cope particularly with the use of a player having a head speed of about 40 m / s, and the excellent performance as described above can be exhibited.

In the present invention, the JIS-C hardness of the core center and the core surface is not particularly limited, and the core JIS-C hardness of the core is usually 30 or more, particularly 35 or more, more preferably 40 or more. As described above, the upper limit is preferably 75 or less, particularly 70 or less, and more preferably 65 or less, and the surface JIS-C hardness of the core is usually 40 or more, particularly 45 or more, and more preferably 50 or more, and the upper limit is 90 or less, In particular, it is preferably 85 or less, more preferably 80 or less.

The specific gravity of the solid core is 1.0 or more, particularly preferably 1.05 or more, and further preferably 1.1.
As described above, the upper limit is 1.3 or less, more preferably 1.25.
Hereinafter, it is more preferable that it is 1.2 or less.

In the present invention, the inner layer cover needs to be formed of a resin composition containing the following components (a) to (c) as essential components. (A) an olefin-unsaturated carboxylic acid random copolymer, an olefin-unsaturated carboxylic acid-unsaturated carboxylic acid ester random copolymer, or a metal ion neutralized product of these copolymers, or a copolymer thereof; A mixture of a sum; (b) a fatty acid having a molecular weight of 280 or more or a derivative thereof; and (c) a basic inorganic metal compound capable of neutralizing an acid group in the components (a) and (b).

Here, the resin composition containing the above (a) to (c) as essential components has good thermal stability, fluidity and moldability, and can provide a golf ball excellent in resilience. It is. First, this material will be described.

The olefin of the component (a) is usually one having 2 or more carbon atoms and having an upper limit of 8 or less, particularly preferably 6 or less, and specifically, ethylene, propylene, butene, pentene, hexene, heptene. And octene, and ethylene is particularly preferable.

The unsaturated carboxylic acid includes, for example, acrylic acid, methacrylic acid, maleic acid, fumaric acid and the like, and particularly preferably acrylic acid and methacrylic acid.

Further, as the unsaturated carboxylic acid ester, a lower alkyl ester of the above-mentioned unsaturated carboxylic acid is preferable, and specifically, methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, acrylic acid Examples thereof include methyl, ethyl acrylate, propyl acrylate, and butyl acrylate, and particularly preferably butyl acrylate (n-butyl acrylate, i-butyl acrylate).

The random copolymer of the component (a) of the present invention can be obtained by random copolymerizing the above components according to a known method. Here, the content (acid content) of the unsaturated carboxylic acid contained in the random copolymer
Is usually 2% by mass or more, preferably 6% by mass or more, more preferably 8% by mass or more, and the upper limit is 25% by mass or less, preferably 20% by mass or less, more preferably 15% by mass or less. Is done. If the acid content is small, the resilience may decrease, and if it is large, the durability may decrease.

The neutralized product of the random copolymer (a) of the present invention can be obtained by partially neutralizing the acid groups in the random copolymer with metal ions. Here, as the metal ion for neutralizing the acid group, for example, N 2
a ⁺ , K ⁺ , Li ⁺ , Zn ⁺⁺ , Cu ⁺⁺ , Mg ⁺⁺ , Ca ⁺⁺ ,
Co ⁺⁺ , Ni ⁺⁺ , Pb ^{++ and the} like can be mentioned, preferably Na ⁺ , Li ⁺ , Zn ⁺⁺ , Mg ⁺⁺ , and more preferably Zn ⁺⁺ . The degree of neutralization of the random copolymer of these metal ions is not particularly limited. Such a neutralized product can be obtained by a known method,
For example, the random copolymer can be introduced by using a compound such as a formate, an acetate, a nitrate, a carbonate, a hydrogen carbonate, an oxide, a hydroxide, and an alkoxide of the metal ion. .

The component (a) of the present invention includes, for example, Nucrel AN4311, AN4318, and 1560.
(All manufactured by DuPont-Mitsui Polychemicals), Himilan 1554, 1557, 1601, 1605,
1706, 1855, 1856, AM7316
(All manufactured by Du Pont-Mitsui Polychemical Co., Ltd.), Surlyn 6320, 7930, 8120, 8940, 9910, 9945, 8945 (all manufactured by DuPont, USA), and the like. A Japanese ionomer resin (Himilan AM7316 or the like) can be preferably used.

The component (b) of the present invention is a fatty acid having a molecular weight of 280 or more or a fatty acid derivative thereof. The component (b) has an extremely small molecular weight as compared with the component (a) and contributes to improving the fluidity of the resin composition. , Which contribute to a significant increase in the melt viscosity of the mixture. The fatty acid (derivative) of the present invention has a molecular weight of 280 or more and a high content of acid group (derivative).
Therefore, loss of resilience can be suppressed.

The fatty acid or the fatty acid derivative thereof as the component (b) used in the present invention has a single bond in the alkyl group even if it is an unsaturated fatty acid (derivative) containing a double bond or a triple bond in the alkyl group. Although it may be a saturated fatty acid (derivative) composed of only one, the number of carbon atoms in one molecule is usually 18 or more, particularly 20 or more, preferably 22 or more, and more preferably 24 or more. It is recommended that the upper limit be 80 or less, particularly 60 or less, preferably 40 or less, and more preferably 30 or less. If the number of carbon atoms is small, the heat resistance may not be improved, and the content of the acid group is too large to reduce the effect of improving the fluidity due to interaction with the acid group contained in the component (a). May be. On the other hand, when the number of carbon atoms is large, the molecular weight becomes large, so that the fluidity modifying effect may be reduced.

As the fatty acid of the component (b), specifically,
Stearic acid, 12-hydroxystearic acid, behenic acid, oleic acid, linoleic acid, linolenic acid, arachidic acid, lignoceric acid, and the like, and in particular, stearic acid, arachidic acid, behenic acid, and lignoceric acid are preferably used. be able to.

The fatty acid derivatives of the present invention include those in which the proton contained in the acid group of the fatty acid has been substituted. Examples of such fatty acid derivatives include metal soaps substituted with metal ions. Examples of metal ions used for metal soap include Li ⁺ , Ca ⁺⁺ , M
^{g ++, Zn ++, Mn ++} , Al +++, Ni ++, Fe ++, F
^{e +++, Cu ++, Sn ++} , Pb ++, Co ++ , and the like, in particular Ca ^++, Mg ^++, Zn ⁺⁺ is preferred.

Specific examples of the fatty acid derivative of the component (b) include magnesium stearate, calcium stearate, zinc stearate, magnesium 12-hydroxystearate, calcium 12-hydroxystearate, zinc 12-hydroxystearate, and arachidic acid. Magnesium, calcium arachidate, zinc arachidate, magnesium behenate, calcium behenate, zinc behenate, magnesium lignocerate, calcium lignocerate, zinc lignocerate, etc., in particular, magnesium stearate, calcium stearate, stearin Zincate, magnesium arachidate, calcium arachidate, zinc arachidate, magnesium behenate, calcium behenate, zinc behenate, lignoce Magnesium phosphate, calcium lignoceric acid, can be preferably used zinc lignocerate.

When the above-mentioned components (a) and (b) are used, known metal soap-modified ionomers (USP 531857, US Pat. No. 5,306,760, W
O98 / 46671) can be used as a combination of the component (a) and the component (b).

The component (c) of the present invention is a basic inorganic metal compound capable of neutralizing the acid groups in the components (a) and (b). The mixing of the component (c) is based on the following reasons. That is, when only the component (a) and the component (b), in particular, only the metal-modified ionomer resin (for example, only the metal-soap-modified ionomer resin described in the above-mentioned patent publication) are mixed under heating, the metal soap and the ionomer are mixed as shown below. A fatty acid is generated by an exchange reaction with an unneutralized acid group contained in the water. The generated fatty acid has low thermal stability and easily vaporizes during molding, which not only causes molding failure, but also significantly reduces the adhesion of the coating film when the generated fatty acid adheres to the surface of the molded product. Cause you to

[0034]

Embedded image Unneutralized acid group contained in ionomer resin Metallic soap Fatty acid X Metal atom

In order to solve such a problem, the inner layer cover material of the present invention comprises a basic inorganic metal compound which neutralizes the acid groups contained in the components (a) and (b) of the component (c). Is blended as an essential component. The combination of the component (c) neutralizes the acid groups in the components (a) and (b), and the synergistic effect of each of the components increases the thermal stability of the heated mixture and at the same time, provides good molding. In addition to the properties, the ball can be used as an inner layer cover material to provide an excellent property of improving the resilience of the ball.

The component (c) is not particularly limited as long as it is a basic inorganic metal compound capable of neutralizing the acid groups in the components (a) and (b). Since the reactivity is high and the reaction by-product does not contain organic matter, the hydroxide is particularly recommended because it can increase the degree of neutralization of the heated mixture without impairing the thermal stability. You.

Here, the basic inorganic metal compound is used.
As the metal ion, for example, Li ⁺, Na⁺, K⁺, C
a⁺⁺, Mg⁺⁺, Zn⁺⁺, Al⁺⁺⁺, Ni⁺⁺, Fe⁺⁺, F
e⁺⁺⁺, Cu⁺⁺, Mn⁺⁺, Sn⁺⁺, Pb⁺⁺, Co⁺⁺Etc.
And the inorganic metal compounds include these metal ions
Basic inorganic metal compounds containing, specifically, magnesium oxide
Cium, magnesium hydroxide, magnesium carbonate, oxidation
Zinc, sodium hydroxide, sodium carbonate, calcium oxide
, Calcium hydroxide, lithium hydroxide, lithium carbonate
But a hydroxide is preferable as described above.
High reactivity with the component (a), especially the ionomer resin.
Calcium hydroxide can be suitably used.

The inner layer cover material of the present invention comprises component (a), component (b) and component (c) as described above, and can improve thermal stability, moldability and resilience. However, the amount of these components is required to be 5 parts by mass or more, particularly 10 parts by mass or more, and more preferably 15 parts by mass or more with respect to 100 parts by mass of the component (a). It is necessary to add 80 parts by mass or less, preferably 40 parts by mass or less, more preferably 25 parts by mass or less as an upper limit. The amount of the component (c) is 0.1 parts by mass or more, particularly 1 part by mass or more, further 2 parts by mass or more, and the upper limit is 10 parts by mass.
It is necessary that the amount be not more than 8 parts by mass, especially not more than 8 parts by mass, and further not more than 6 parts by mass. If the amount of the component (b) is too small, the melt viscosity becomes low and the processability is reduced. If the amount is too large, the durability is lowered. Therefore, the desired properties cannot be obtained as the inner layer cover, and the performance of the golf ball deteriorates. Leads to.
On the other hand, if the amount of the component (c) is too small, heat stability,
If the resilience is not improved and the amount is too large, the heat resistance of the composition is rather lowered due to an excessive amount of the basic inorganic metal compound.

The inner layer cover material of the present invention may use the above-mentioned materials as they are, or may appropriately mix other materials with the above-mentioned mixture, but may further include a melt index (JIS-K6760 (test temperature) as a heated mixture). It is preferable to prepare and use at 190 ° C. and a test load of 21 N (2.16 kgf), and the melt index is 0.5 d.
g / sec or more, preferably 1.0 dg / sec or more, more preferably 1.5 dg / sec or more is recommended. In addition, it is recommended that the upper limit is usually 20 dg / sec or less, preferably 15 dg / sec or less. If the melt index of the heated mixture is too small, the processability may be significantly reduced.

The inner layer cover material further has a carboxylate stretching vibration of 1530 to 1630 cm ^-1 with respect to the absorbance of an absorption peak belonging to a carbonyl stretching vibration of 1690 to 1710 cm ^-1 normally detected in infrared absorption measurement. Is preferably specified as the relative absorbance at the absorption peak (absorbance at the absorption peak attributed to the carboxylate stretching vibration / absorbance at the absorption peak attributable to the carbonyl stretching vibration).

Here, the carboxylate stretching vibration indicates a carboxyl group that has dissociated a proton (a carboxyl group neutralized by a metal ion), and the carbonyl stretching vibration indicates the vibration of an undissociated carboxyl group. Depends on the degree of neutralization. In the case of a commonly used ionomer resin having a degree of neutralization of about 50 mol%, the absorbance ratio of each peak is about 1: 1.

In order to improve the thermal stability, moldability, and resilience of the material, the absorbance of the peak attributed to the carboxylate stretching vibration is determined by comparing the absorbance of the peak due to the carbonyl stretching vibration with that of the carbonyl stretching vibration. At least 1.
It is recommended that the ratio be 5 times or more, preferably 2 times or more, and more preferably that there is no peak attributed to carbonyl stretching vibration.

The thermal stability of the inner layer cover material of the present invention can be measured by thermogravimetry. In the thermogravimetric measurement, 250 ° C based on the weight at 25 ° C is used.
Is usually 2% by mass or less, preferably 1.
It is recommended that the content be 5% by mass or less, more preferably 1% by mass or less.

The inner layer cover material of the present invention is obtained by using the above (a)
Although the component, the component (b) and the component (c) are essential components, the component (a) and the component (b) usually have an acid group in the component of at least 50 mol%, preferably at least 55 mol%, preferably at least 55 mol%. It is recommended that 60 mol% or more, more preferably 70 mol% or more, most preferably 80 mol% or more is neutralized, and the above-mentioned (a) is obtained by achieving high neutralization. ) The exchange reaction, which is a problem when only the component (b) and the fatty acid (derivative) of the component (b) are used, can be more reliably suppressed, the generation of fatty acids can be prevented, and the thermal stability can be significantly increased. A material having good resilience and having remarkably increased resilience as compared with a conventional inner layer cover material, particularly an ionomer resin. In this case, the neutralization of the material is performed in such a manner that the acid group of the essential component is made of a transition metal ion, an alkali metal ion and / or an alkaline earth metal ion in order to more reliably achieve a high degree of neutralization and fluidity. It is recommended that the transition metal ion has a weaker ion cohesion than the alkali (earth) metal ion. Significant improvements can be made.

In this case, the molar ratio of the transition metal ion to the alkali (earth) metal ion is appropriately adjusted, but is usually 10:90 to 90:10, particularly 20:80 to 80:20.
It is preferable that If the molar ratio of the transition metal ion is small, the effect of improving the fluidity may not be sufficiently obtained, and if the molar ratio is high, the resilience may be reduced.

Here, as the above-mentioned metal ions, specifically, as a transition metal ion, a zinc ion or the like, and as an alkali metal ion or an alkaline earth metal ion, a sodium ion, a lithium ion, a magnesium ion and a calcium ion are used. At least one selected ion or the like may be used.

The method for obtaining a heated mixture in which an acid group is neutralized with a transition metal ion and an alkali metal ion or an alkaline earth metal ion is not particularly limited.
For example, specific examples of the method of neutralizing with a transition metal ion (zinc ion) include a method of using zinc soap as a fatty acid, a method of including a zinc ion neutralized product as the component (a), and a basic method of the component (c). A method using zinc oxide as the inorganic metal compound is exemplified.

In order to improve the feel at impact and to further improve the resilience of the inner layer cover material of the present invention, various thermoplastic resins other than the component (a) may be optionally added in addition to the above essential components. A thermoplastic elastomer can be blended.Examples of such a thermoplastic elastomer include a polyolefin-based elastomer, a polyester-based elastomer, a polyurethane-based elastomer, a polyamide-based elastomer, and a polystyrene-based elastomer. The use of polyester elastomers is recommended.

More specifically, thermoplastic elastomers containing linear low-density polyethylene, low-density polyethylene, high-density polyethylene, polypropylene, rubber-reinforced olefin polymers, flexomers, plastomers, and acid-modified products (styrene-based block copolymers, hydrogenated Polybutadiene ethylene propylene rubber), dynamically vulcanized elastomer, ethylene acrylate, ethylene vinyl acetate and the like. As a commercial product, specifically,
“HPR” manufactured by Mitsui / Dupont Polychemicals Co., Ltd., and “Dynalon” manufactured by JSR Co., Ltd. are exemplified.

In the present invention, the optional components such as the above-mentioned polyolefin-based elastomer and polyester-based elastomer are usually added in an amount of 100 parts by mass or less, particularly 80 parts by mass, based on 100 parts by mass of the essential components (a) to (c). Less than,
60 parts by mass or less, more preferably 50 parts by mass or less,
More preferably, it is recommended to be added in an amount of 40 parts by mass or less, and as a lower limit, 0 part by mass or more, particularly 5 parts by mass or more, further 10 parts by mass or more, more preferably 15 parts by mass or more, further preferably 20 parts by mass or more It is recommended that

Various additives can be further prepared in the inner layer cover material as needed. Specific examples of such additives include pigments, dispersants, antioxidants, and ultraviolet absorbers. Agents, light stabilizers and the like can be added. More specifically, examples of such additives include inorganic fillers such as zinc oxide, barium sulfate, and titanium dioxide, and the amount of these inorganic fillers is usually 30% by mass or less, preferably May be compounded in an amount of 20% by mass or less, and 1% by mass or more as a lower limit.

The inner layer cover of the present invention has the above-mentioned (a) to
It is formed of a resin composition containing (c) as an essential component and having good thermal stability, fluidity and moldability, and capable of obtaining a golf ball having excellent resilience. Method can be adopted. For example, the above resin composition is kneaded by using a kneading type twin screw extruder, an internal mixer such as a Banbury or a kneader, etc. as a mixer at a heating temperature of 150 to 250 ° C. to prepare an inner layer cover material. The kneading conditions, kneading method, etc.,
It can be appropriately prepared.

Further, the specific gravity of the inner layer cover is 0.8 or more, more preferably 0.9 or more, still more preferably 0.92 or more, and most preferably 0.93 or more. In particular, 1.2 or less, more preferably 1.
It is preferably 16 or less, more preferably 1.1 or less, and most preferably 1.05 or less.

The thickness of the inner cover is 0.5 mm.
Above, more preferably 0.9 mm or more, still more preferably 1.1 mm or more, and as an upper limit 3.0 mm or less,
More preferably 2.5 mm or less, even more preferably 2.0 mm
mm or less is recommended.

The inner layer cover of the present invention has an optimized Shore D hardness. The Shore D hardness will be described later.

Next, the outer layer cover of the present invention is not particularly limited, but is preferably formed of a material mainly composed of a thermoplastic resin, a thermosetting resin or the like. As a main material of the outer layer cover, specifically, a thermoplastic or thermosetting polyurethane-based elastomer, a polyester-based elastomer,
Examples thereof include an ionomer resin, a polyolefin-based elastomer, and a mixture thereof. These are 1
The species can be used alone or as a mixture of two or more. Examples of such commercially available products include Surlyn 6320, Himilan 1855, Surlyn 8120 and the like, which will be described in detail later.

Further, for the main material of the outer layer cover,
Further, as an optional component, a polymer such as a thermoplastic elastomer other than the above can be blended. As the optional component polymer, specifically, a polyamide elastomer,
A styrene-based block elastomer, hydrogenated polybutadiene, ethylene-vinyl acetate (EVA) copolymer, or the like can be blended.

In the outer layer cover material of the present invention, only the main component of the above-mentioned component A may be used alone. Parts by mass, preferably 10 parts by mass or more, more preferably 15 parts by mass or more, while the upper limit is 100 parts by mass or less, preferably 75 parts by mass or less, more preferably 5 parts by mass or less.
0 parts by mass or less may be added. In the compounding, it can be appropriately adjusted according to the purpose of adjusting hardness, improving resilience, improving fluidity, improving adhesiveness, and the like.

In the present invention, it is preferable to use a thermoplastic polyurethane-based elastomer or an ionomer resin as the main material of the outer layer cover. Here, the molecular structure of the thermoplastic polyurethane-based elastomer is composed of a polymer polyol compound constituting a soft segment, a monomolecular chain extender constituting a hard segment, and diisocyanate.

The high molecular polyol compound is not particularly limited, but polyester polyols,
Polyether-based polyols, copolyester-based polyols, polycarbonate-based polyols and the like can be mentioned. Examples of polyester-based polyols include polycaprolactone glycol, poly (ethylene-1,4-adipate) glycol, and poly (butylene-1,4-adipate). Glycols such as poly (diethylene glycol adipate) glycol as copolyester-based polyols, polycarbonate-based polyols such as (hexanediol-1,6-carbonate) glycol, and polyether-based polyols such as polyoxytetramethylene glycol. Is mentioned. Their number average molecular weight is about 600-5000, preferably 1000-3000.

As the diisocyanate, an aliphatic diisocyanate is preferably used in consideration of yellowing resistance of the cover. Specific examples include hexamethylene diisocyanate (HDI), 2,2,4 (2,4,4) -trimethylhexamethylene diisocyanate (TMDI), and lysine diisocyanate (LDI).
DI is preferred from the viewpoint of compatibility when blended with another resin.

The monomolecular chain extender is not particularly limited, and ordinary polyhydric alcohols and amines can be used. Specifically, 1,4-butylene glycol, 1,2-
Ethylene glycol, 1,3-propylene glycol,
Examples include 1,6-hexylene glycol, 1,3-butylene glycol, dicyclohexylmethylmethanediamine (hydrogenated MDA), and isophoronediamine (IPDA).

The thermoplastic polyurethane-based elastomer having a tan δ peak temperature of -15 ° C or lower, particularly -16 ° C or lower, and a lower limit of -50 ° C or higher as measured by viscoelasticity is preferable from the viewpoint of softness and resilience.

As such a thermoplastic polyurethane elastomer, commercially available products can be used. For example, Pandex T7298 (−20 ° C.) and T7295 (−
26.degree. C.) and T7890 (-30.degree. C.) (manufactured by DIC Bayer Polymer Co., Ltd.) in which the diisocyanate is aliphatic. Note that the numbers in parentheses are all t
Shows an δ peak temperature.

As the outer layer cover material of the present invention, a reaction product of the above-mentioned thermoplastic polyurethane-based elastomer and an isocyanate compound described below can be used, whereby the surface durability upon impact with iron can be further improved. it can.

Here, as the isocyanate compound, any of the isocyanate compounds used in the conventional polyurethane-related technology can be used, and the present invention is not limited thereto. 2,4-toluene diisocyanate, 2,6-toluene diisocyanate and mixtures thereof, 4,4-diphenylmethane diisocyanate, m-phenylene diisocyanate,
4'-biphenyl diisocyanate and the like. Further, a hydrogenated product of the above aromatic isocyanate compound, for example, dicyclohexylmethane diisocyanate can also be used. Furthermore, aliphatic diisocyanates, such as tetramethylene diisocyanate, hexamethylene diisocyanate (HDI), and octamethylene diisocyanate, and alicyclic diisocyanates, such as xylene diisocyanate.

Examples of the isocyanate compound include a blocked isocyanate compound obtained by reacting an isocyanate group of a compound having two or more isocyanate groups with a compound having active hydrogen, and a uretidion compound obtained by dimerization of isocyanate. Can be

The amount of the isocyanate compound is usually 0.1 part by mass or more, preferably 0.2 part by mass or more, more preferably 0.3 part by mass or more based on 100 parts by mass of the thermoplastic polyurethane-based elastomer. The upper limit is 10 parts by mass or less, preferably 5 parts by mass or less, and more preferably 3 parts by mass or less. If the amount is too small, a sufficient crosslinking reaction cannot be obtained, no improvement in physical properties is observed, and the amount is too large. In such a case, discoloration due to aging, heat, and ultraviolet rays may increase, thermoplasticity may be lost, and rebound may be reduced.

Further, as described above, the outer layer cover of the present invention may be formed by using an ionomer resin as a main material, and may be formed by using an ionomer resin which is generally used as a cover material of a solid golf ball. can do. Specific examples of the ionomer resin include Himilan 1855 (manufactured by DuPont Mitsui Polychemicals),
Surlyn 8120, 8320, 6320 (manufactured by DuPont, USA) and the like, and two or more ionomer resins can be used in combination. Also, if necessary, a known additive such as a pigment, a dispersant, an antioxidant, an ultraviolet absorber, an ultraviolet stabilizer, and a plasticizer can be added to the ionomer resin.
1% by mass of inorganic filler such as barium sulfate and titanium dioxide
Above, especially 1.5% by mass or more, with an upper limit of 30% by mass
Hereinafter, it may be contained in an amount of 20% by mass or less.

The outer layer cover of the present invention is preferably adjusted in specific gravity regardless of the use of any of the above-mentioned materials, usually at least 0.9, preferably at least 0.95, more preferably at least 1. 2.0 or more, and 1.3 or less as an upper limit, preferably 1.25 or less, and more preferably 1.22 or less.
The following is preferred.

The thickness of the outer layer cover is 0.5 mm or more, preferably 0.9 mm or more, more preferably 1.1 mm or more.
mm or more and an upper limit of 2.5 mm or less, preferably 2.
It is preferably 3 mm or less, more preferably 2.0 mm or less.

In this case, the total thickness of the inner cover and the outer cover (the total thickness of the cover) is usually 1.0 mm or more, preferably 1.5 mm or more, more preferably 2.0 mm or more.
mm or more, and the upper limit is 5.5 mm or less, preferably 4.5 mm or less, and more preferably 3.5 mm or less.

In the present invention, it is required that the Shore D hardness of the inner layer cover and the outer layer cover be optimized. In the case of the inner layer cover, the Shore D hardness is 45 or more, particularly 47 or more, more preferably 49 or more, and preferably 49 or more. It is 50 or more, more preferably 52 or more, most preferably 54 or more, and the upper limit is 65 or less, especially 63 or less, preferably 61 or less, further preferably 60 or less, more preferably 59 or less, and even more preferably 58 or less. Below, most preferably 57
It is necessary to: If the inner layer cover is too soft, the resilience decreases, and if it is too hard, the hit feeling becomes hard.

On the other hand, the outer cover has a Shore D hardness of 35 or more, preferably 38 or more, more preferably 40 or more, and still more preferably 42 or more, and 55 or less, preferably 53 or less, more preferably 52 or less. Preferably, it is necessary to be 50 or less. If the outer layer cover is too soft, too much spin will be applied and the flight distance will be reduced. Conversely, if it is too hard, the feel on impact becomes hard, and the spin performance also decreases.

In the present invention, the outer layer cover is formed to be softer than the inner layer cover. In this case, the hardness of the outer layer cover is generally 2 or more, particularly 5 or more, preferably 7 or more, more preferably 9 or more, and the upper limit is 30 or less, especially 25 or less, more preferably 25 or less than the hardness of the inner layer cover. It is recommended to have a hardness difference of 20 or less. If the difference in hardness is too small, the spin distance tends to be too high and the flight distance tends to decrease. If the difference in hardness is too large, the durability may decrease.

Between the inner cover and the outer cover,
An adhesive layer can be provided for the purpose of improving the durability at the time of impact. In this case, examples of the adhesive include an epoxy resin-based adhesive, a vinyl resin-based adhesive, a rubber-based adhesive, and the like. Particularly, a urethane resin-based adhesive and a chlorinated polyolefin-based adhesive may be used. Preferably, as commercial products, Rezamin D6208 (made by Dainichi Seika Kogyo Co., Ltd .: urethane resin adhesive), RB182 primer (made by Nippon Bee Chemical Co., Ltd .: chlorinated polyolefin adhesive), and the like can be suitably used.

In this case, the formation of the adhesive layer can be carried out by dispersion coating, but the type of emulsion used for dispersion coating is not limited. As the resin powder for preparing the emulsion, either a thermoplastic resin powder or a thermosetting resin powder can be used. For example, vinyl acetate resin, vinyl acetate copolymer resin, EVA (ethylene-
(Vinyl acetate copolymer resin), acrylate (co) polymer resin, epoxy resin, thermosetting urethane resin, thermoplastic urethane resin and the like can be used. Of these, epoxy resins, thermosetting urethane resins, thermoplastic urethane resins, and acrylate (co) polymer resins are particularly preferred, with thermoplastic urethane resins being particularly preferred.

The thickness of the adhesive layer is 0.1 μm or more.
Especially 0.2 μm or more, especially 0.3 μm or more, 30 μm or less as an upper limit, especially 25 μm or less, especially 20 μm or less.
m or less.

In the present invention, dimples are formed on the outer layer cover. In this case, the sum of the dimple trajectory volumes obtained by multiplying the dimple volume by the square root of the dimple diameter needs to be 530 to 750. is there.

That is, the most required characteristic of a golf ball is that the flight distance is long. In this case, considering the run, a golf ball with a low trajectory is often advantageous in terms of the total flight distance, but the present inventor analyzed a large number of data and found that by multiplying the dimple volume by the square root of the dimple diameter. It has been found that the sum of the obtained dimple trajectory volumes (total dimple trajectory volume) controls the elevation angle. By setting the total dimple trajectory volume to an optimum value, it is possible to suppress the variation with respect to the ball's flight. Preferably, in addition to this, the dimple cross-sectional shape area ratio described below is set to an optimum value. With the same elevation angle, the carry could be extended more, and a low-ballistic dimple with growth was successfully developed.

More specifically, as described above, the golf ball of the present invention has a total dimple trajectory volume VT (total dimple trajectory volume TVT) of 53 obtained by multiplying the dimple volume by the square root of the dimple diameter.
0 to 750. In this case, the lower limit of TVT is 530 or more, preferably 550 or more, more preferably 580 or more, and still more preferably 600 or more, and the upper limit is 750 or less, preferably 730 or less, more preferably 7 or more.
00 or less, more preferably 670 or less.

Here, in the present invention, as shown in FIG. 1, when the vertical section at the center of the dimple 10 is viewed, the highest point in the case where the left and right highest points in FIG. dimple edge E, and E, the edge E, the inter-E and the diameter D _i of the dimples. Further, the distance dimple depth D _e of the edge E, the line connecting the E to dimple the deepest portion. Therefore, the dimple volume V is the dimple volume of the portion surrounded by the edge. Furthermore, the area S of the dimple longitudinal sectional shape
₁ is a hatched portion in FIG.

That is, TVT in the present invention is the sum of VT (= V × D _i ^0.5 ) of each dimple. This TVT
The value of gives an approximate trajectory height. Usually TV
When T is small, the elevation angle is large, and when TTV is large, the elevation angle is small. As described above, the present invention sets the TVT within the above-described range, and if the TVT is too small,
The trajectory is too high and runs are not enough, and the total flight distance decreases. On the other hand, if the TVT is too large, the trajectory will be too low and carry will be insufficient, and similarly, the flight distance will decrease.
Further, outside the range of the TVT of the present invention, the dispersion of the carry becomes large, and all of them lack the stability of the performance.

The golf ball of the present invention has a head speed of 40 m / h using a driver having a loft angle of 9.5 °.
The elevation angle when shot at s is 8.6 ° or more, especially 8.
It is preferably not less than 7 °, not more than 9.3 °, more preferably not more than 9.2 °, further preferably not more than 9.1 °, most preferably not more than 9.0 °.

[0085] When in the present invention, S ₁ the area of the vertical section of the dimple center and the area multiplied by the depth D _e in the diameter D _i of the dimple was set S _2, S ₁ /
Average value S of dimple cross-sectional shape area ratio S ₀ indicated by S ₂
A is 0.58 to 0.68, and in this case, at least 80% of all dimples have a dimple of 0.58 to 0.68.
Preferably it has a dimple cross section area ratio S ₀ of 0.68.

Here, S ₁ , D _i , and _De are as defined above. In addition, S ₂ is 1 in FIG.
This is the area of the rectangle enclosed by the dotted line. In addition, SA
It is a value obtained by dividing the sum of S ₀ of each dimple by the total number n of dimples.

In the present invention, the value of SA is preferably 0.58 or more, more preferably 0.60 or more, and still more preferably 0.62 or more.
Below, it is recommended that it is 0.67 or less, more preferably 0.66 or less. If the SA is too small, the trajectory tends to be difficult to run, and if the SA is too large, the trajectory may be difficult to carry.

[0088] In addition, 80% of all dimples, more preferably 88% or more, more preferably at least 94%, S ₀ is preferably in the range of 0.58 to 0.68. Even if SA is within the above range, 80 of all dimples
% Or more of S ₀ dimples Without the above range, the carry, the disadvantage of poor run both occur.

In the present invention, the dimple shape is usually a plane circle, and the diameter is 1.8 mm or more.
It is more preferably at least 2.4 mm, still more preferably 3.0 mm.
mm or more, and an upper limit of 4.6 mm or less, more preferably 4.4 mm or less, and still more preferably 4.2 mm.
The following is preferred. The depth is 0.08mm or more,
It is more preferably at least 0.10 mm, even more preferably at least 0.10 mm.
12 mm or more, and 0.22 mm or less as an upper limit, more preferably 0.20 mm or less, and still more preferably 0.1 mm or less.
It is preferably 9 mm or less.

The total number n of the dimples is usually 360 or more, preferably 370 or more, more preferably 380 or more, and the upper limit is 540 or less, preferably 5 or more.
It is 00 or less, more preferably 450 or less. In this case, the dimples are preferably multi-type dimples having a combination of two or more, more preferably three or more, different in diameter, and six or less, particularly five or less, different in diameter. Further, the depths may be different from each other. Therefore, it is preferable to use a combination of three or more types of dimples having different VTs from each other, and a combination of 10 or less types, particularly 8 or less types of dimples.

The arrangement method of the dimples may be a known method, and is not particularly limited as long as the dimples are arranged evenly. The octahedral arrangement, the icosahedral arrangement, and the hemisphere are equally divided into 2 to 6 parts. And the like, and a method of arranging dimples in the divided area can be adopted. It should be noted that a method of making fine corrections to these methods can be adopted. In this case, the dimple surface occupancy is 69
% Or more, preferably 70% or more, more preferably 72%
As described above, the upper limit is preferably 85% or less, particularly preferably 82% or less, and more preferably 77% or less.

The golf ball of the present invention is usually made into a product by further coating the above cover, and the golf ball of the present invention has a load of 980 N (100
kg), the amount of compressive deformation (hereinafter, 100 kgf)
Hardness) is usually 2.0 mm or more, preferably 2.2 mm.
mm or more, more preferably 2.5 mm or more, and the upper limit is 4.0 mm or less, preferably 3.7 mm or less, and more preferably 3.5 mm or less. 100
If the kgf hardness is too small, the hit feeling tends to be hard,
Conversely, if it is too large, durability and resilience may be reduced.

The diameter and weight of the golf ball of the present invention are in accordance with the Rules of Golf, but are not less than 42.67 mm and not more than 44 mm, more preferably not more than 43.5 mm.
More preferably, it is preferably formed in a range of 43 mm or less. The weight is 45.92 g or less, and the lower limit is 44.5 g or more, more preferably 44.8 g or more, still more preferably 45.0 g or more, and most preferably 45.1 g.
The above range is preferable.

[0094]

EXAMPLES The present invention will be described below in detail with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[Examples and Comparative Examples]
The inner layer cover shown in Table 3 on the solid core shown in
The outer layer covers shown in Tables 5 and 6 were sequentially formed, and the dimples shown in Tables 5 and 6 were formed uniformly to produce three-piece solid golf balls shown in Tables 7 and 8. In this case, for golf balls using an adhesive, the following adhesive was used according to a known method. Examples 1 and 2 and Comparative Examples 1 and 8: Resamine D6208 (made by Dainichi Seika Kogyo Co., Ltd .: urethane resin-based adhesive) Examples 3 and 4: RB182 primer (manufactured by Nippon Bee Chemical Co., Ltd .: chlorinated polyolefin-based adhesive)

The obtained golf balls were subjected to a flying test by the following method, and the spin amount, feeling, rust resistance, and continuous durability were evaluated. The results are shown in Tables 7 and 8.

Flying Test Using a swing robot manufactured by Miyama Co., Ltd., each ball was hit 20 times by a driver at a head speed (HS) of 40 m / s, and the carry and the total flying distance were measured. <Use club> Head: Bridgestone Sports, J's-MET
AL, loft angle 9.5 °, SUS630 stainless steel, lost wax method Shaft: Harmotec Pro, HM-70, LK (first tone), hardness X

For the spin amount # W1 and the sand wedge (#SW, head speed (HS) 20 m / s), the behavior of the ball immediately after impact was photographed and calculated by photographic resolution.

With respect to feeling # W1 and putter (#PT), the feel when actually hit by three professional golfers was evaluated according to the following criteria. ：: soft △: slightly hard ×: hard

By [0100] anti-hangnail of a swing robot, sand wedge (#SW, head speed of 38m / s) any to hit 2 places the ball, which was visually evaluated. ◎: Very good ○: Good △: Normal ×: Poor

Using a continuous durability flywheel hitting M / C, a head speed of 38
The golf ball was repeatedly hit at m / s and evaluated by the number of hits until the ball was broken. ○: good △: normal ×: bad

The main compositions described in Tables 1 to 8 are as follows. Dicumyl peroxide: Parkmill D manufactured by NOF Corporation Peroxide: Upperco 1 manufactured by Atochem
01XL Liquid monomer SR-351: Trimethylolpropane triacrylate (TMPTA) manufactured by Sartomer Dynalon: Polybutadiene hydrogenated product manufactured by JSR Hytrel: Thermoplastic polyester-based elastomer manufactured by Toray DuPont Nucrel: Ethylene manufactured by Mitsui / DuPont Polychemical Methacrylic acid-acrylic acid ester copolymer and ethylene-methacrylic acid copolymer PEBAX: Thermoplastic polyamide-based elastomer manufactured by Atochem Sirlin: Ionomer resin manufactured by DuPont, USA Himilan: Ionomer resin manufactured by DuPont Mitsui (Surlyn, Himilan) Polybutadiene: JSR BR11 antioxidant A: Ouchi Shinko Chemical Co., Ltd. Nocrack NS6 Antioxidant B: Yoshitomi Pharmaceutical Co. Yoshinox 425 Pandex: Thermoplastic polyurethane elastomer manufactured by DIC Bayer Polymer Co., Ltd. Diphenylmethane diisocyanate: Nippon Polyurethane Industry Co., Ltd. Dicyclohexylmethane diisocyanate: Sumitomo Bayer Urethane Industry Co., Ltd. Transpolyisoprene: Kuraray Co., Ltd. TP-301 Peroxide: Atochem Co., Ltd. Varox 230
XL

[0103]

[Table 1]

[0104]

[Table 2]

[0105]

[Table 3]

[0106]

[Table 4]

[0107]

[Table 5]

[0108]

[Table 6]

[0109]

[Table 7]

[0110]

[Table 8]

From the above results, all of the multi-piece solid golf balls of the present invention have excellent flight performance and spin performance, and can obtain a good feel when hit with a driver, iron or putter. In addition to being able to do so, it was excellent in rust resistance and durability.

On the other hand, none of the multi-piece solid golf balls of the comparative examples were formed of the inner layer cover material of the present invention, and had the following disadvantages. [Comparative Example 1] The difference in hardness between the cores is too large, the Shore D hardness of the inner layer cover is too soft, the inner layer cover is softer than the outer layer cover, the hit feeling with a driver is poor, and the trajectory is too low to drop. , The flight distance was reduced. [Comparative Example 2] The Shore D hardness of the inner layer cover was too soft,
The hardness of the outer cover was higher than that of the inner cover, the trajectory was relatively high, and the flying distance was reduced. [Comparative Example 3] The core hardness difference was too large, and the ionomer resin was used alone for the inner layer cover material.
Although the structure was close to the above, the flight distance was inferior. [Comparative Example 4] The trajectory was too high to blow up and the flight distance was poor. The outer layer cover was a balata cover, which caused crusting, reduced resilience, and reduced productivity. [Comparative Example 5] The Shore D hardness of the inner layer cover was too high, the rubber composition was used, the durability was poor, and the hit feeling at the time of putting was poor. [Comparative Example 6] The inner layer cover was too soft, the outer layer cover had a higher hardness than the inner layer cover, the spin was too large, the trajectory increased from a low level, and the flight distance was reduced. [Comparative Example 7] The inner layer cover material was an ionomer resin, and the trajectory was too low to drop and the flight distance was reduced. [Comparative Example 8] The inner layer cover was soft, the hardness of the outer layer cover was higher than that of the inner layer cover, the trajectory was too low to drop, and the flight distance was reduced. [Comparative Example 9] The inner layer cover material was an olefin-based elastomer and an ionomer resin.

[0113]

The multi-piece solid golf ball of the present invention has a long flight distance, is excellent in controllability, has a good feeling, and has excellent durability, and is particularly used by a player having a head speed of about 40 m / s. Can be suitably dealt with.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a dimple shape in the present invention.

[Explanation of symbols]

10 dimples D _i diameter D _e depth E Edge

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C08K 5/09 C08K 5/09 C08L 23/02 C08L 23/02 23/26 23/26 67/02 67 / 02 (72) Inventor Ichikawa Yasushi History 20 Onohara, Chichibu City, Saitama Prefecture Inside Bridgestone Sports Co., Ltd. (72) Inventor Tomoya Takenozu 20 Onohara, Chichibu City, Saitama Prefecture 20th Bridgestone Sports Co., Ltd. F term (reference) 4J002 BB04W BB04X BB07X BB08W BB14W BB14X BB17W BB17X BB23W BB23X DE057 DE077 DE087 DE107 DE227 DE237 EF056 EG026 EG036 EG046 FD010 GC01 GF00

Claims (12)

[Claims] 1. A solid core and inner and outer cores 2 covering the solid core.
In a multi-piece solid golf ball having a layer cover, the solid core is 294N (30 kgf).
The amount of deformation under load is 1.1 mm or more, the difference between the JIS-C hardness of the core surface and the JIS-C hardness of the core center (core surface-core center) is 15 or less, and the inner layer cover has the following component (a) ) To (c), (a) an olefin-unsaturated carboxylic acid random copolymer, an olefin-unsaturated carboxylic acid-unsaturated carboxylic acid ester random copolymer, or a metal ion neutralized product of these copolymers, or 100 parts by mass of a mixture of these copolymers and neutralized products; (b) 5 to 80 parts by mass of a fatty acid or a derivative thereof having a molecular weight of 280 or more; (c) acid groups in the above components (a) and (b); It is formed of a resin composition containing 0.1 to 10 parts by mass of a basic inorganic metal compound that can be neutralized as an essential component, and has a Shore D hardness of 45 to 6 for the inner layer cover.
5, and the Shore D hardness of the outer layer cover is 35 to 55.
A multi-piece solid golf ball, wherein the outer layer cover is formed softer than the inner layer cover, and the sum of the dimple trajectory volumes obtained by multiplying the dimple volume by the square root of the dimple diameter is 530 to 750. 2. The multi-piece solid golf ball according to claim 1, wherein the melt index of the resin composition is 0.5 dg / sec or more. 3. The multi-piece solid according to claim 1, wherein the outer layer cover is formed mainly of a thermoplastic or thermosetting polyurethane-based elastomer, polyester-based elastomer, ionomer resin, polyolefin-based elastomer or a mixture thereof. Golf ball. 4. The multi-piece solid golf ball according to claim 3, wherein the outer cover is formed mainly of a thermoplastic polyurethane elastomer obtained by using an aromatic or aliphatic diisocyanate. 5. The multi-piece solid golf ball according to claim 3, wherein the outer layer cover is formed mainly of a reaction product of a thermoplastic polyurethane elastomer and an isocyanate compound. 6. The multi-piece according to claim 1, wherein the component (b) in the resin composition is a fatty acid having 18 to 80 carbon atoms in one molecule or a derivative thereof. Solid golf ball. 7. The multi-piece solid according to claim 1, wherein 50 mol% or more of the acid groups in the essential components (a) and (b) are neutralized with metal ions. Golf ball. 8. The inner layer cover is formed of a resin composition obtained by mixing 100 parts by mass or less of the essential components (a) to (c) with 100 parts by mass or less of an olefin elastomer or a polyester elastomer. Claims 1 to 7
The multi-piece solid golf ball according to any one of the above items. 9. The golf ball according to claim 1, wherein an adhesive layer is provided between the inner cover and the outer cover. 10. An adhesive layer comprising a urethane resin-based adhesive or a chlorinated polyolefin-based adhesive as a main material and a film thickness of 0.1
The multi-piece solid golf ball according to claim 9, wherein the golf ball is formed to have a thickness of about 30 μm. 11. The specific gravity of the solid core is 1.0 to 1.3.
The specific gravity of the inner layer cover is 0.8 to 1.5, and the specific gravity of the outer layer cover is 0.9 to 1.3.
0. The multi-piece solid golf ball according to any one of 0. 12. When the area of the vertical cross-sectional shape at the center of the dimple is S ₁ , and the area obtained by multiplying the diameter of the dimple by the depth is S ₂ , the ratio of the dimple cross-sectional shape area ratio represented by S ₁ / S ₂ is obtained. The multi-piece solid golf ball according to any one of claims 1 to 11, wherein the average value SA is 0.58 to 0.68, and the total number of dimples is 360 to 540.