Golf ball

According to the present invention, in a golf ball having a soft feeling, the head speed (HS) of the driver (W # 1) is as low as 35 m / s or less, which is excellent in flying performance even for a golf player, and the durability and molding of repeated hits are excellent. It relates to a golf ball with improved sex.

In order to obtain a soft feel on a golf ball, it is necessary to make the core relatively soft. Various developments have been made for golf balls not only for high head speeds but also for low head speeds, but golf balls for low head speeds have a longer flight distance than before, even if a soft feel is obtained. It was difficult to achieve both a flight distance and a feel of hitting because the ball had dropped.

That is, a golf player with a low head speed tends to use a driver (W # 1) having a larger loft angle than a golf player with a high head speed in an attempt to increase the launch angle in order to increase the flight distance. In this case, when the ball is hit, the launch angle becomes high and the spin amount of the ball increases, resulting in a decrease in the flight distance. Therefore, it has been proposed to reduce the spin amount of the ball as much as possible and increase the flight distance by designing a ball structure in which a soft core is covered with a thin cover. For example, Japanese Patent Application Laid-Open No. 9-313643 (Patent Document 1) and Japanese Patent Application Laid-Open No. 10-305114 (Patent Document 2) describe a golf ball having a three-layer structure including a core, an intermediate layer, and a cover. There is. However, in these golf balls, the moldability is not improved from the viewpoint of the fluidity of the cover, and the flight distance characteristic cannot be sufficiently obtained even when hit at a low head speed.

Further, Japanese Patent Application Laid-Open No. 2003-175128 (Patent Document 3) discloses a golf ball having a cover in which a ternary composite of a rubber component, a polyolefin component, and a nylon component is mixed with an olefin resin. However, in this golf ball, the improvement of the repeated hitting durability of the cover is insufficient.

<patcit num="1"><text>Japanese Unexamined Patent Publication No. 9-313643</text></patcit><patcit num="2"><text>Japanese Unexamined Patent Publication No. 10-305114</text></patcit><patcit num="3"><text>Japanese Unexamined Patent Publication No. 2003-175128</text></patcit>

<p> The present invention has been made in view of the above circumstances, and is superior to a golf player having a low head speed (HS) of 35 m / s or less of the driver (W # 1) in a golf ball having a soft feeling. It is an object of the present invention to provide a golf ball having improved flying performance and improved repeatability and moldability.</p>

<p> As a result of diligent studies to achieve the above object, the present inventors have conducted injection molding of a thin cover in a multi-piece solid golf ball having a multi-layer cover having a soft core and a thin outermost layer cover. In order to solve the problem of molding defects that occur in the outermost layer cover, to increase the fluidity of the resin composition of the outermost layer cover, and to prevent the deterioration of the repeated impact durability due to the thin cover, the core hardness and the outermost layer cover hardness and As a result of focusing on the melt flow rate of the outermost layer cover resin composition, the hardness of the core is 3.5 mm or more in the amount of compression deflection when an initial load of 10 kgf is applied to a final load of 130 kgf, and the outer layer cover is organically short. It consists of a resin composition containing fibers, and the melt flow rate of the resin composition is JIS. According to the measurement according to K7210 (1999 version), it is 3 or more, the shore D hardness of the outer layer cover is 55 or more, it is harder than the inner layer cover, and the thickness of the outer layer cover is 1.4 mm or less. The characteristic golf ball has a soft feel, is excellent in flying performance even for golf players with a low head speed of 35 m / s or less, and has improved repeated hitting durability and moldability. This is what led to the discovery and the present invention. In particular, by adding a binary copolymer composed of a polyolefin component and a polyamide component to the resin base material of the cover, the repeated impact durability is significantly improved even for a thin cover of 1.4 mm or less. The inventors have found out and completed the present invention.</p><p> Therefore, the present invention provides the following golf balls. [1] In a golf ball composed of a core and a multi-layer cover having at least an inner layer cover and an outer layer cover, the hardness of the core is 3.5 mm or more in terms of the amount of compression deflection when an initial load of 10 kgf is applied to a final load of 130 kgf. At the same time, the outer layer cover is made of a resin composition containing organic short fibers, and the melt flow rate of the resin composition is JIS. A golf ball characterized in that it is 3 or more as measured according to K7210, the shore D hardness of the outer layer cover is 55 or more, is harder than the inner layer cover, and the thickness of the outer layer cover is 1.4 mm or less. ball. [2] The resin component of the resin composition of the outer layer cover is (a) an olefin-unsaturated carboxylic acid copolymer, an olefin-unsaturated carboxylic acid-unsaturated carboxylic acid ester copolymer, and a metal of these copolymers. The golf ball according to [1], which is obtained by mixing at least one component selected from an ion neutralized product and (b) a binary copolymer composed of a polyolefin component and a polyamide component. [3] The golf ball according to [2], wherein the polyamide of the component (b) is fibrous. [4] The golf ball according to [2], wherein the mass ratio of (a) / (b) is 100 / 0.1 to 100/50. [5] The golf ball according to [2], wherein the mass ratio of the polyolefin component / polyamide component among the components (b) above is 25/75 to 95/5. In the present invention, the cover has a plurality of layers because, when the ball structure has a two-layer structure of a core and a single-layer cover, a support pin is used to hold the core during injection molding. Since an interface that reaches the core is formed at the mark, the durability against repeated impacts will deteriorate, but if a ball is formed with two or more cover layers, the interface will stay with one cover. , It is based on the improvement of repeated hitting durability because it does not reach the core. In particular, from the viewpoint of improving the feel of hitting in a short game or putter and further improving the durability of repeated hits, it is also considered in the present invention that the inner layer cover needs to be softer than the outer layer cover. It was done.</p>

<p> The golf ball of the present invention has a soft feeling, can obtain superior flying performance even for golf players with a low head speed of 35 m / s or less, and has improved repeated hitting durability and moldability. Is.</p>

Hereinafter, the present invention will be described in more detail. The golf ball of the present invention comprises a multi-layer cover having at least an inner layer cover and an outer layer cover, and exemplifies, for example, a three-piece ball structure including a single layer core 1 and an inner layer cover 2 and an outer layer cover 3 shown in FIG. be able to.

The solid core can be formed by using, for example, a rubber composition containing a co-crosslinking agent, an organic peroxide, an inert filler, an organic sulfur compound and the like. It is preferable to use polybutadiene as the base rubber of the rubber composition.

The rubber component polybutadiene has a cis-1,4-bond of 60% by mass or more, preferably 80% by mass or more, more preferably 90% by mass or more, and most preferably 95% by mass or more in the polymer chain. Is preferable. Too few cis-1,4-bonds in the molecule can reduce resilience.

The content of the 1,2-vinyl bond contained in the polybutadiene is usually 2% or less, preferably 1.7% or less, and more preferably 1.5% or less in the polymer chain. If the content of 1,2-vinyl bond is too high, the resilience may decrease.

The polybutadiene used in the present invention is preferably synthesized with a rare earth element catalyst or a group VIII metal compound catalyst from the viewpoint of obtaining a vulcanized molded product of a rubber composition having good resilience. In particular, it is preferably synthesized with a rare earth element-based catalyst.

Such a rare earth element-based catalyst is not particularly limited, but for example, a catalyst formed by combining a lanthanum series rare earth element compound, an organoaluminum compound, an armoxane, a halogen-containing compound, and if necessary, a Lewis base. Can be mentioned.

Examples of the lanthanum-series rare earth element compound include metal halides having atomic numbers 57 to 71, carboxylates, alcoholates, thioalcolates, and amides.

In the present invention, in particular, the use of a neodymium-based catalyst using a neodymium compound as a lanthanum-series rare earth element compound produces a polybutadiene rubber having a high content of 1,4-cis bond and a low content of 1,2-vinyl bond. It is preferable because it can be obtained with excellent polymerization activity, and specific examples of these rare earth element-based catalysts are described in JP-A-11-35633, JP-A-11-164912, and JP-A-2002-293996. Can be preferably mentioned.

Polybutadiene synthesized using a lanthanum series rare earth element compound catalyst is preferably contained in the rubber component in an amount of 10% by mass or more, preferably 20% by mass or more, particularly 40% by mass or more in order to improve resilience. ..

In addition to the polybutadiene, other rubber components may be added to the rubber base material as long as the effects of the present invention are not impaired. Examples of the rubber component other than the polybutadiene include polybutadiene other than the polybutadiene and other diene rubbers such as styrene butadiene rubber, natural rubber, isoprene rubber, and ethylene propylene diene rubber.

Examples of the co-crosslinking agent include unsaturated carboxylic acids and metal salts of unsaturated carboxylic acids.

Specific examples of the unsaturated carboxylic acid include acrylic acid, methacrylic acid, maleic acid, fumaric acid and the like, and acrylic acid and methacrylic acid are particularly preferably used.

The metal salt of the unsaturated carboxylic acid is not particularly limited, and examples thereof include those obtained by neutralizing the unsaturated carboxylic acid with a desired metal ion. Specific examples thereof include zinc salts such as methacrylic acid and acrylic acid, magnesium salts and the like, and zinc acrylate is particularly preferably used.

The unsaturated carboxylic acid and / or the metal salt thereof is usually 10 parts by mass or more, preferably 15 parts by mass or more, more preferably 20 parts by mass or more, and usually 60 parts by mass as an upper limit with respect to 100 parts by mass of the base material rubber. Hereinafter, it is preferably blended in an amount of 50 parts by mass or less, more preferably 45 parts by mass or less, and most preferably 40 parts by mass or less. If the blending amount is too large, the feel may become too hard and the feel may be unbearable, and if the blending amount is too small, the resilience may decrease.

Commercially available products can be used as the organic peroxide, and for example, Park Mill D (manufactured by NOF Corporation), Perhexa 3M (manufactured by NOF Corporation), Luperco 231XL (manufactured by Atchem Co., Ltd.) and the like are preferably used. Can be used. These may be used alone or in combination of two or more.

The organic peroxide is usually 0.1 part by mass or more, preferably 0.3 part by mass or more, more preferably 0.5 part by mass or more, most preferably 0.7 part by mass or more, and usually 5 by mass with respect to 100 parts by mass of the base material rubber. It is blended by mass or less, preferably 4 parts by mass or less, more preferably 3 parts by mass or less, and most preferably 2 parts by mass or less. If the amount is too large or too small, it may not be possible to obtain a suitable feel, durability and resilience.

As the inert filler, for example, zinc oxide, barium sulfate, calcium carbonate and the like can be preferably used. These may be used alone or in combination of two or more.

The blending amount of the inert filler is usually 1 part by mass or more, preferably 5 parts by mass or more, and the upper limit is usually 50 parts by mass or less, preferably 40 parts by mass or less, more preferably 40 parts by mass or more, based on 100 parts by mass of the base rubber. It is 30 parts by mass or less, most preferably 20 parts by mass or less. If the blending amount is too large or too small, it may not be possible to obtain an appropriate mass and suitable resilience.

Furthermore, anti-aging agents can be added as needed. For example, commercially available products include Nocrack NS-6, NS-30 (manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.), and Yoshinox 425 (Yoshitomi Pharmaceutical Industries, Ltd.). ), Etc. These may be used alone or in combination of two or more.

The blending amount of the anti-aging agent is usually 0 parts by mass or more, preferably 0.05 parts by mass or more, more preferably 0.1 parts by mass or more, most preferably 0.2 parts by mass or more, and usually as an upper limit, with respect to 100 parts by mass of the base rubber. It is 3 parts by mass or less, preferably 2 parts by mass or less, more preferably 1 part by mass or less, and most preferably 0.5 part by mass or less. If the blending amount is too large or too small, it may not be possible to obtain suitable resilience and durability.

It is preferable to add an organic sulfur compound to the core in order to improve the resilience of the golf ball and increase the initial velocity of the golf ball.

The organic sulfur compound is not particularly limited as long as it can improve the resilience of the golf ball, and examples thereof include thiophenols, thionaphthols, halogenated thiophenols, and metal salts thereof. More specifically, pentachlorothiophenol, pentafluorothiophenol, pentabromothiophenol, parachlorothiophenol, zinc salt of pentachlorothiophenol, zinc salt of pentafluorothiophenol, zinc salt of pentabromothiophenol, Zinc salts of parachlorothiophenols, diphenyl polysulfides having 2 to 4 sulfur numbers, dibenzyl polysulfides, dibenzoyl polysulfides, dibenzothiazoyl polysulfides, dithiobenzoyl polysulfides and the like, and in particular, zinc salts of pentachlorothiophenols and diphenyls. Disulfide is preferably used.

The blending amount of such an organic sulfur compound is usually 0.05 parts by mass or more, preferably 0.1 parts by mass or more, and the upper limit is usually 5 parts by mass or less, preferably 4 parts by mass or less, and further, with respect to 100 parts by mass of the base rubber. It is recommended that the amount is preferably 3 parts by mass or less, most preferably 2.5 parts by mass or less. If the blending amount is too large, the effect may reach a plateau and no further effect may be seen, and if the blending amount is too small, the blending effect may not be sufficiently achieved.

The diameter of the core is usually 36.7 mm or more, particularly preferably 37.0 mm or more, while the upper limit is usually 40.5 mm or less, particularly preferably 38.5 mm or less. The weight is usually 30 to 36 g, particularly preferably 31 to 34 g.

In this case, the core of the present invention has a compression deflection (hardness 10-130 kgf) of 3.5 mm or more, preferably 4.0 mm or more, particularly 4.3 mm or more when an initial load of 10 kgf is applied to a final load of 130 kgf in the above diameter range. The range is 6.0 mm or less, preferably 5.5 mm or less, and particularly preferably 4.7 mm or less. If the amount of deformation is too small, the feel of hitting will be hard. In addition, the amount of spin increases, and the flight distance may decrease when hit with a driver (W # 1) at a low head speed or when hit with an iron. On the other hand, if the amount of deformation is too large, the durability against cracking due to repeated striking deteriorates, and the repulsion becomes too low, so that a sufficient flight distance cannot be obtained.

As the resin composition of the inner layer cover, a known synthetic resin can be used without particular limitation, and in particular, (a-1) olefin-unsaturated carboxylic acid binary random copolymer and / or olefin-non-free. Metal ion neutralized product of saturated carboxylic acid binary random copolymer and (a-2) olefin-unsaturated carboxylic acid-unsaturated carboxylic acid ester ternary random copolymer and / or olefin-unsaturated carboxylic acid- It contains a metal ion neutralized product of an unsaturated carboxylic acid ester ternary random copolymer at a ratio of (a-1) / (a-2) = 100/0 to 0/100 (mass ratio) (A). It is preferable that the ionomer resin and (B) a non-ionomer-based thermoplastic elastomer are contained in a ratio of (A) / (B) = 100/0 to 50/50 (mass ratio), and further, the above (A). (C) Molecular weight with respect to 100 parts by mass of the resin component containing the ionomer resin and the (B) non-ionomer-based thermoplastic elastomer at a ratio of (A) / (B) = 100/0 to 50/50 (mass ratio) A basic inorganic metal compound 0.1 capable of neutralizing 5 to 80 parts by mass of an organic fatty acid and / or a derivative thereof of 280 to 1500, and (D) the unneutralized acid group in the resin component and the (C) component. It is more preferable that the mixture is a mixture of ~ 10 parts by mass.

As the olefin in the component (a-1) and the component (a-2), an olefin having 2 or more carbon atoms and an upper limit of 8 or less, particularly 6 or less, is preferably used. More specific examples of such olefins include ethylene, propylene, butene, pentene, hexene, heptene, octene and the like, and ethylene is particularly preferably used.

Examples of unsaturated carboxylic acids include acrylic acid, methacrylic acid, maleic acid, fumaric acid and the like, and acrylic acid and methacrylic acid are particularly preferably used.

Examples of the unsaturated carboxylic acid ester in the component (a-2) include the above-mentioned lower alkyl ester of the unsaturated carboxylic acid, and more specifically, methyl methacrylate, ethyl methacrylate, and propyl methacrylate. , Butyl acrylate, methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate and the like, and butyl acrylate (butyl n-butyl acrylate, butyl i-butyl acrylate) is particularly preferably used.

The olefin-unsaturated carboxylic acid binary random copolymer of the component (a-1) and the olefin-unsaturated carboxylic acid-unsaturated carboxylic acid ester ternary random copolymer of the component (a-2) (hereinafter, these) (Sometimes abbreviated as "random copolymer") are obtained by randomly copolymerizing the above-mentioned olefin, unsaturated carboxylic acid, and if necessary, unsaturated carboxylic acid ester by a known method. be able to.

The random copolymer preferably has an unsaturated carboxylic acid content (acid content) adjusted. In this case, the content of the unsaturated carboxylic acid contained in the component (a-1) is usually 4% by mass or more, preferably 6% by mass or more, more preferably 8% by mass or more, still more preferably 10% by mass or more, and the upper limit. It is usually 30% by mass or less, preferably 20% by mass or less, more preferably 18% by mass or less, still more preferably 15% by mass or less. The content of the unsaturated carboxylic acid contained in the component (a-2) is usually 4% by mass or more, preferably 6% by mass or more, more preferably 8% by mass or more, and the upper limit is usually 15% by mass or less, preferably. It is 12% by mass or less, more preferably 10% by mass or less.

If the content of the unsaturated carboxylic acid contained in the component (a-1) and / or the component (a-2) is too small, the resilience may decrease, and if it is too large, the processability may decrease.

The metal ion neutralized product of the olefin-unsaturated carboxylic acid binary random copolymer of the component (a-1) and the olefin-unsaturated carboxylic acid-unsaturated carboxylic acid ester ternary randomized component of the component (a-2). The metal ion neutralized product of the polymer (hereinafter, these may be collectively abbreviated as "metal ion neutralized product of the random copolymer") is a part of the acid group in the above random copolymer. Alternatively, it can be obtained by neutralizing the whole with metal ions.

Examples of the metal ion that neutralizes the acid group in the random copolymer include Na.⁺, K⁺, Li⁺, Zn⁺⁺, Cu⁺⁺, Mg⁺⁺, Ca⁺⁺, Co⁺⁺, Ni⁺⁺, Pb⁺⁺Etc., especially Na⁺, Li⁺, Zn⁺⁺, Mg⁺⁺Is preferable, and Na is particularly suitable from the viewpoint of improving resilience.⁺Is preferable to use.

As a method for obtaining a metal ion neutralized product of the random copolymer using such a metal ion, for example, a formate, an acetate, or a nitrate of the metal ion is used with respect to the random copolymer having an acid group. , Carbonates, bicarbonates, oxides, hydroxides, alkoxides and the like may be added to neutralize. The degree of neutralization of the acid groups by these metal ions is not particularly limited in the present invention.

Commercially available products can be used as the component (a-1) and the component (a-2). For example, as a random copolymer of the component (a-1), for example, Nucrel 1560, 1214, the same. 1035 (all manufactured by Mitsui and DuPont Polychemical), ESCOR5200, 5100, 5000 (all manufactured by EXXON MOBIL CHEMICAL), etc., were used as metal ion neutralized products of the random copolymer of the component (a-1). , For example, Hymilan 1554, 1557, 1601, 1605, 1706, AM7311 (all manufactured by Mitsui / DuPont Polymer), Sarlin 7930 (manufactured by DuPont, USA), Iotech 3110, 4200 (manufactured by EXXON MOBILCHEMICAL). Etc., as random copolymers of the component (a-2), for example, Nuclel AN4311, AN4318 (all manufactured by Mitsui / DuPont Polychemical), ESCOR ATX325, ATX320, ATX310 (all EXXON MOBIL). CHEMICAL) and the like as metal ion neutralized products of the random copolymer of the component (a-2), for example, Hymilan 1855, 1856, AM7316 (all manufactured by Mitsui / DuPont Polychemical), Sarlin 6320. , 8320, 9320, 8120 (all manufactured by DuPont, USA), Iotech 7510, 7520 (all manufactured by EXXON MOBIL CHEMICAL), etc. can be mentioned. These may be used alone or in combination of two or more as each component.

Examples of the zinc-neutralized ionomer resin suitable as the metal ion-neutralized product of the random copolymer include Hymilan 1706, 1557, and AM7316.

The ratio of the component (a-2) to the total amount of the component (a-1) and the component (a-2) is usually 0% by mass or more, preferably 50% by mass or more, and usually as an upper limit. It is 100% by mass or less.

The non-ionomer-based thermoplastic elastomer (B) is a component preferably blended from the viewpoint of further improving the feeling and resilience when hitting a golf ball. In the present invention, the (A) ionomer resin and (B) non-ionomer-based thermoplastic elastomer may be collectively abbreviated as "resin component". More specific examples of such (B) non-ionomer-based thermoplastic elastomers include olefin-based elastomers, styrene-based elastomers, polyester-based elastomers, urethane-based elastomers, and polyamide-based elastomers, which further enhance resilience. From the viewpoint of enhancing, an olefin-based elastomer and a polyester-based elastomer are particularly preferably used.

As such a component (B), a commercially available product may be used, and examples thereof include dynaron (manufactured by Nippon Synthetic Rubber Co., Ltd.) as an olefin-based elastomer and Hytrel (manufactured by Toray DuPont) as a polyester-based elastomer. These may be used alone or in combination of two or more.

The ratio of the component (B) to the resin component is usually 0% by mass or more, preferably 20% by mass or more, and the upper limit is usually 50% by mass or less, preferably 40% by mass or less. If the proportion of the component (B) in the resin component exceeds 50% by mass, the compatibility of each component may decrease, and the durability of the golf ball may be significantly reduced.

The component (C) in the present invention is an organic fatty acid having a molecular weight of 280 or more and 1500 or less and / or a derivative thereof, has an extremely small molecular weight as compared with the base resin, appropriately adjusts the melt viscosity of the mixture, and particularly flows. Since it is a component that contributes to the improvement of properties, it is preferably blended.

The molecular weight of the organic fatty acid of the component (C) is usually 280 or more, preferably 300 or more, more preferably 330 or more, further preferably 360 or more, and the upper limit is usually 1500 or less, preferably 1000 or less, more preferably 600 or less. , More preferably 500 or less. If the molecular weight is too small, the heat resistance may be inferior, and if it is too large, the fluidity may not be improved.

Examples of the organic fatty acid of the component (C) include unsaturated organic fatty acids containing double or triple bonds in the alkyl group, and saturated organic fatty acids in which the bonds in the alkyl group are composed of only a single bond. It can be preferably used.

The number of carbon atoms in one molecule of the organic fatty acid is usually 18 or more, preferably 20 or more, more preferably 22 or more, further preferably 24 or more, and the upper limit is usually 80 or less, preferably 60 or less, more preferably 40 or less. More preferably, it is 30 or less. If the number of carbon atoms is too small, not only the heat resistance may be inferior, but also the content of the acid group is too large and the interaction with the acid group contained in the base resin becomes excessive, resulting in fluidity. The improvement effect of is reduced. On the other hand, when the number of carbon atoms is too large, the molecular weight becomes large, so that the effect of fluidity modification may not be noticeable.

More specific examples of the organic fatty acid of the component (C) in the present invention include 12-hydroxystearic acid, behenic acid, oleic acid, linoleic acid, linolenic acid, arachidic acid, lignoceric acid, and the like. Arachidic acid, behenic acid, lignoceric acid, particularly behenic acid are preferably used.

As the derivative of the organic fatty acid of the component (C), a metal soap in which the proton contained in the acid group of the organic fatty acid described above is replaced with a metal ion can be exemplified. In this case, the metal ion is, for example, Na.⁺, Li⁺, Ca⁺⁺, Mg⁺⁺, Zn⁺⁺, Mn⁺⁺, Al⁺⁺⁺, Ni⁺⁺, Fe⁺⁺, Fe⁺⁺⁺, Cu⁺⁺, Sn⁺⁺, Pb⁺⁺, Co⁺⁺Etc., especially Ca⁺⁺, Mg⁺⁺, Zn⁺⁺Is preferable.

More specifically, as a derivative of the organic fatty acid of the component (C), for example, magnesium stearate, calcium stearate, zinc stearate, magnesium 12-hydroxystearate, calcium 12-hydroxystearate, zinc 12-hydroxystearate, arachidic acid. Magnesium, calcium arachidic acid, zinc arachidic acid, magnesium behenate, calcium behenate, zinc behenate, magnesium lignocerate, calcium lignocerate, zinc lignocerate, etc. can be mentioned, among which magnesium stearate, calcium stearate, stearic acid, etc. Zinc, magnesium arachidic acid, calcium arachidic acid, zinc arachidic acid, magnesium behenate, calcium behenate, zinc behenate, magnesium lignocerate, calcium lignocerate, zinc lignocerate can be preferably used. These may be used alone or in combination of two or more.

The amount of the component (C) to be blended is usually 5 parts by mass or more, preferably 10 parts by mass or more, more preferably 15 parts by mass or more, and further preferably 18 parts by mass with respect to 100 parts by mass of the resin component. The amount is usually 80 parts by mass or less, preferably 40 parts by mass or less, more preferably 25 parts by mass or less, and further preferably 22 parts by mass or less. If the amount of the component (C) is too small, the melt viscosity may be too low and the workability may be lowered, and if it is too large, the durability may be lowered.

In the present invention, it is also possible to use known metal soap-modified ionomers (USP5312857, USP5306760, WO98 / 46671, etc.) as a mixture of the (A) ionomer resin and the (C) component.

The component (D) in the present invention is a basic inorganic metal compound capable of neutralizing an unneutralized acid group in the resin component and the component (C). When the component (D) is not blended and, for example, the metal soap-modified ionomer resin is used alone, a large amount of metal soap undergoes an exchange reaction with the unneutral acid group contained in the ionomer resin during heating and mixing. Fatty acids are generated and vaporized, which may cause problems such as molding defects, deterioration of coating adhesion, and reduction of resilience of the obtained molded product. In view of these points, the component (D) is preferably blended in the present invention.

It is preferable that the component (D) has high reactivity with the resin component and does not contain an organic acid in the reaction by-product.

Examples of the metal ion in the component (D) include Li.⁺, Na⁺, K⁺, Ca⁺⁺, Mg⁺⁺, Zn⁺⁺, Al⁺⁺⁺, Ni⁺⁺, Fe⁺⁺, Fe⁺⁺⁺, Cu⁺⁺, Mn⁺⁺, Sn⁺⁺, Pb⁺⁺, Co⁺⁺Etc., and these may be used alone or in combination of two or more. As the component (D), a known basic inorganic filler containing these metal ions can be used, and more specifically, for example, magnesium oxide, magnesium hydroxide, magnesium carbonate, zinc oxide, sodium hydroxide, etc. Examples thereof include sodium carbonate, calcium oxide, calcium hydroxide, lithium hydroxide, lithium carbonate and the like. In particular, hydroxide or monooxide is recommended, and calcium hydroxide and magnesium oxide having high reactivity with the base resin are preferably used.

The blending amount of the component (D) with respect to 100 parts by mass of the resin component is usually 0.1 part by mass or more, preferably 0.5 part by mass or more, more preferably 1 part by mass or more, still more preferably 2 parts by mass or more, and usually as an upper limit. It is 10 parts by mass or less, preferably 8 parts by mass or less, more preferably 6 parts by mass or less, and further preferably 5 parts by mass or less. If the amount of the component (D) is too small, the thermal stability and resilience may not be improved, and if it is too large, the heat resistance of the golf ball material may be lowered due to the excessive basic inorganic metal compound. There is.

The degree of neutralization of the mixture obtained by mixing the above components (A) to (D) is usually 50 mol% or more, preferably 60 mol% or more, more preferably based on the total amount of acid groups in the mixture. Is 70 mol% or more, more preferably 80 mol% or more. Due to such high neutralization, even when a metal soap-modified ionomer resin is used, for example, the exchange reaction between the metal soap and the unneutralized acid group contained in the ionomer resin does not easily occur during heating and mixing, and the thermal mixture is thermally generated. The risk of impairing stability, moldability and resilience is reduced.

In the inner layer cover of the present invention, in addition to each of the components (A) to (D), additives such as a pigment, a dispersant, an antiaging agent, an ultraviolet absorber, and a light stabilizer are further added. Can be done. The blending amount is not particularly limited, but is usually 0.1 part by mass or more, preferably 0.5 part by mass or more, based on 100 parts by mass of the resin component composed of the component (A) and the component (B). It is more preferably 1 part by mass or more, and the upper limit is usually 10 parts by mass or less, preferably 6 parts by mass or less, and more preferably 4 parts by mass or less.

The inner layer cover can be obtained by heating and mixing each of the above-mentioned components. For example, under a heating temperature of 150 to 250 ° C., an internal mixer such as a kneading type twin-screw extruder, a Banbury, or a kneader is used. It can be obtained by kneading. On the other hand, as the resin composition of the outer layer cover in the present invention, known synthetic resins can be used without particular limitation, and in particular, (a) olefin-unsaturated carboxylic acid copolymer and olefin-unsaturated carboxylic acid. -By a component selected from an unsaturated carboxylic acid ester copolymer and a metal ion neutralized product of these copolymers, and (b) a resin composition containing a binary copolymer composed of a polyolefin component and a polyamide component as essential components. It is preferable to form.

The above component (a) is a metal ion neutralized product of an olefin-unsaturated carboxylic acid binary random copolymer, an olefin-unsaturated carboxylic acid binary random copolymer, and an olefin-unsaturated carboxylic acid-unsaturated carboxylic acid. It is selected from the metal ion neutralized product of the ester ternary random copolymer and the olefin-unsaturated carboxylic acid-unsaturated carboxylic acid ester ternary random copolymer. , Usually 2 or more, and the upper limit is 8 or less, particularly preferably 6 or less, and specific examples thereof include ethylene, propylene, butene, penten, hexene, heptene, and octene, and ethylene is particularly preferable. ..

Examples of the unsaturated carboxylic acid include acrylic acid, methacrylic acid, maleic acid, fumaric acid and the like, and acrylic acid and methacrylic acid are particularly preferable.

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

The olefin-unsaturated carboxylic acid binary random copolymer and the olefin-unsaturated carboxylic acid-unsaturated carboxylic acid ester ternary random copolymer of the component (a) of the present invention are prepared by preparing the above-mentioned materials, respectively. It can be obtained by random copolymerization by a known method.

It is recommended that the random copolymer has an adjusted unsaturated carboxylic acid content (acid content). Here, the content of the unsaturated carboxylic acid contained in the random copolymer of the component (a) is usually 4% by mass or more, preferably 6% by mass or more, more preferably 8% by mass or more, still more preferably 10% by mass. As described above, it is recommended that the upper limit is 30% by mass or less, preferably 20% by mass or less, more preferably 18% by mass or less, and further preferably 15% by mass or less.

Metal ion neutralization of olefin-unsaturated carboxylic acid binary random copolymer of component (a) of the present invention, metal ion neutralization of olefin-unsaturated carboxylic acid-unsaturated carboxylic acid ester ternary random copolymer In the product (hereinafter, the metal ion neutralized products of these copolymers are collectively referred to as the metal ion neutralized products of the random copolymer), the acid groups in the random copolymer are partially contained with metal ions. It can be obtained by summing.

Here, as the metal ion that neutralizes the acid group, for example, Na⁺, K⁺, Li⁺, Zn⁺⁺, Cu⁺⁺, Mg⁺⁺, Ca⁺⁺, Co⁺⁺, Ni⁺⁺, Pb⁺⁺Etc., preferably Na⁺, Li⁺, Zn⁺⁺, Mg⁺⁺Etc., more preferably Zn⁺⁺Is.

In order to obtain a metal ion neutralized product of the random copolymer of the present invention, the random copolymer may be neutralized with the metal ions. For example, the metal ion formates, acetates and nitrates of the metal ions may be used. , A method of neutralizing using a compound such as carbonate, bicarbonate, oxide, hydroxide and alkoxide can be adopted. The degree of neutralization of these metal ions with respect to the random copolymer is not particularly limited.

In the present invention, a zinc ion-neutralized ionomer resin can be preferably used as the metal ion-neutralized product of the random copolymer, the melt flow rate of the material is increased, and the melt flow rate is adjusted to the optimum melt flow rate described later. Is easy, and the moldability can be improved.

As the component (a) of the present invention, a commercially available product may be used. For example, as a binary random copolymer, Nuclel 1560, 1214, 1035 (all manufactured by Mitsui / DuPont Polychemical), ESCOR5200, 5100, 5000 (all manufactured by EXXON MOBIL CHEMICAL), etc. as ternary random copolymers, for example, Nuclel AN4311, AN4318 (both manufactured by Mitsui / DuPont Polychemical), ESCOR ATX325, ATX320, same ATX310 (both manufactured by EXXON MOBIL CHEMICAL) and the like can be mentioned.

In addition, as metal ion neutralized products of the binary random copolymer, for example, Hymilan 1554, 1557, 1601, 1605, 1706, AM7311 (all manufactured by Mitsui / DuPont Polychemical), Sarlin 7930 (all manufactured by Mitsui / DuPont Polychemical). DuPont, USA), Iotech 3110, 4200 (EXXON MOBIL CHEMICAL), etc. are used as metal ion neutralized products of ternary random copolymers, for example, Hymilan 1855, 1856, AM7316 (all by Mitsui and DuPont). (Polychemical), Sarlin 6320, 8320, 9320, 8120 (all made by DuPont in the US), Iotech 7510, 7520 (all made by EXXON MOBIL CHEMICAL), etc. can be mentioned. Examples of the zinc-neutralized ionomer resin suitable as the metal ion neutralized product of the random copolymer include Hymilan 1706, 1557, and AM7316.

On the other hand, as the polyolefin component of the component (b), low density polyethylene (LDPE), high density polyethylene (HDPE), polypropylene, polystyrene and the like can be used, and among them, polyethylene and low density polyethylene having high crystallinity are preferable.

Nylon 6, nylon 66, nylon 11, nylon 12, nylon 610, nylon 612, copolymerized nylon, nylon MXD6, nylon 46, aramid, polyamideimide, polyimide, etc. can be used as polyamide components, but due to the balance between physical properties and price. Nylon 6 is preferred. Further, as the form of the polyamide component, a fibrous form is preferable, and a nylon fiber is particularly preferable. In this case, the average diameter of the nylon fibers is 10 μm or less, more preferably 5 μm or less, still more preferably 1 μm or less, and 0.01 μm or more is preferable from the viewpoint of exhibiting effective reinforcing performance with respect to the blending amount. The average diameter here is a value measured by observing the cross section of the sample using a transmission electron microscope.

As the aspect of the component (b) in the present invention, it is particularly preferable that the crystalline polyolefin component is bonded to the surface of the nylon fiber. The term "bonding" here means that the polyamide component and the polyolefin component are graft-bonded by the addition of a binder. As the binder, a silane coupling agent, a titanate-based coupling agent, an unsaturated carboxylic acid, an unsaturated carboxylic acid derivative, an organic peroxide and the like are used.

In the above component (b), the ratio of the polyolefin component (b-1) and the polyamide component (b-2) is 25/75 to 95/5 for (b-1) / (b-2) as a mass ratio. , More preferably 30/70 to 90/10, still more preferably 40/60 to 75/25. If the amount of the polyamide component is too small, a sufficient reinforcing effect will not be exhibited. If it is too large, it will be difficult to mix with the component (a) when kneading with a twin-screw extruder or the like.

The ratio of the component (a) to the component (b) is 100 / 0.1 to 100/50, more preferably 100/1 to 100/40, and even more preferably 100/0.1 to 100/50 in terms of mass ratio of (a) / (b). It is preferably 100/2 to 100/30. If the blending amount is too small, a sufficient effect will not be exhibited. If the amount is too large, it becomes difficult to knead or mold the golf ball cover.

The kneading temperature of the components (a) and (b) is equal to or higher than the melting point of the polyolefin component, preferably 10 ° C or higher than the melting point, and lower than the melting point of the polyamide component in order to maintain the shape of the polyamide component as much as possible. The temperature is preferably 10 ° C or lower, which is the melting point of the polyamide component, but this is not always the case.

The resin temperature at the time of molding into a golf ball is preferably in the above temperature range, but may exceed this range if necessary.

In addition to the above resin components, various additives can be added to the resin composition containing the above components (a) and (b) as essential components, if necessary. Examples of such additives include pigments, dispersants, antioxidants, UV absorbers, UV stabilizers, mold release agents, plasticizers, inorganic fillers (zinc oxide, barium sulfate, titanium dioxide, etc.) and the like. be able to. It is preferable that the components (a) and (b) are contained in the resin composition in an amount of 30% by mass or more, particularly 60 to 100% by mass, from the viewpoint of exerting the effect of the present invention.

The shore D hardness of the outer layer cover formed by using this resin composition is 55 or more, preferably 57 or more, and more preferably 59 or more. If the Shore D hardness of the cover is too small, the repulsion will be poor and it will not fly. The shore D hardness of the outer layer cover is 65 or less, preferably 63 or less, and more preferably 61 or less. If the Shore D hardness of the cover is too high, the cracking durability due to repeated impacts may deteriorate. The shore D of the cover is a value measured by a Type D durometer based on ASTM D 2240.

The upper limit of the thickness of the outer layer cover is 1.4 mm, preferably 1.3 mm, and more preferably 1.2 mm. If the upper limit is exceeded, the driver (W # 1) spins the ball. The amount cannot be suppressed and a sufficient flight distance may not be obtained. The lower limit of the cover thickness is 0.5 mm, and the preferable lower limit is 0.9 mm, particularly 1.1 mm. If the lower limit is not met, the cracking durability due to repeated striking may deteriorate.

Further, in the present invention, the melt flow rate of the cover resin composition of the outer layer cover is 3 or more, preferably 4 or more, and more preferably 4.5 or more as measured according to JIS K7210 (1999 edition). is there. If the melt flow rate of the cover resin composition is less than the lower limit, it may be difficult for the molten resin to wrap around during injection molding, resulting in molding failure. The measurement according to JIS K7210 (1999 version) specifically means the melt flow rate of the cover resin composition measured according to the conditions of a test temperature of 190 ° C and a test load of 21.2 N (2.16 kgf). ..

The total thickness of the cover is usually within the range of 1.5 to 3.0 mm, preferably 2.0 to 2.8 mm, and more preferably 2.4 to 2.6 mm. If the total thickness of the cover is too thin, the cracking durability during repeated hits may deteriorate. If the total thickness of the cover is too thick, the amount of spin when hitting the driver (W # 1) will increase, and it may not be possible to obtain a sufficient flight distance.

In the present invention, the hardness of the outer layer cover is set higher than that of the inner layer cover. Regarding the hardness difference between the outer layer cover and the inner layer cover, the shore D hardness is preferably 1 or more, more preferably 3 or more, and even more preferably 5 or more. If the difference in hardness is too small, the feel of hitting will be poor, or the amount of spin will be too large when hitting the driver (W # 1), and the flight distance will decrease. The upper limit of hardness is preferably 25 or less, more preferably 20 or less, and even more preferably 15 or less. If the hardness difference is too large, the durability against repeated impacts may deteriorate.

In the present invention, the cover layer is composed of a plurality of layers having at least an inner layer cover and an outer layer cover, but if necessary, one or two or more other cover layers are provided between the inner layer cover layer and the outer layer cover layer. Can be provided. As the material of the other cover layer, a known thermoplastic resin such as ionomer resin or a thermoplastic elastomer can be used. The thickness and hardness of the other covers can be appropriately selected as long as the gist of the present invention is not changed.

The golf ball of the present invention can be made to comply with the Rules of Golf for competition, and its diameter can be usually 42.60 to 42.80 mm and its mass can be usually 45.0 to 45.93 g.

Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples.

[Examples, comparative examples]

Solid cores of each Example and Comparative Example were prepared by the core compounding and vulcanization methods shown in Table 1 below. In addition, the amount of compression deflection (hardness 10-130 kgf) when an initial load of 10 kgf was applied to a final load of 130 kgf was measured for each of the prepared solid cores.

<tables num="1"><img file="JP2005296655A_D0001.tif" /></tables>

Next, each solid core of each Example and Comparative Example was coated with an inner layer cover and an outer layer cover having a predetermined thickness made of the cover resin compositions of compositions A to F shown in Table 2 to obtain a three-piece solid golf ball. For these balls, moldability, flying performance, shot feeling and repeated hitting durability were measured according to the following methods. The results are shown in Table 3.

<tables num="2"><img file="JP2005296655A_D0002.tif" /></tables>

<u style="single">Moldability</u> In the step of covering the cover by injection molding, when the cover resin composition wraps around in the cavity, the easiness of wrapping around is investigated. Specifically, the moldability was judged by whether or not the weld line could be visually detected in the vicinity of the degassing position. The number of balls that the weld line could visually detect while molding 100 balls was 10 or less × The weld line could be visually detected while molding 100 balls. 16 or more balls<u style="single">Flying performance</u> A club was attached to the striking robot, and each ball was striked under the condition of a head speed of 30 m / s to measure the total flight distance. The total flight distance was calculated as the average value of 10 balls. Total flight distance is 120m or more × Total flight distance is less than 120m<u style="single">Hit feeling</u> Ten amateur golfers with a driver (W # 1) head speed of 30 to 35 m / s evaluated the feel when hit with W # 1 according to the following criteria. 7 out of 10 people perceived a soft and good feel × 7 out of 10 people perceived a hard feel<u style="single">Repeated impact durability</u> The hit to the ball was repeated at a head speed of 35 m / s, the number of times the ball began to crack was measured, and the index was obtained when the number of times in Example 3 was 100. : Index 100 or more ×: Index 90 or less

<tables num="3"><img file="JP2005296655A_D0003.tif" /></tables>

From the results in Table 3, the golf ball of this example has a soft feeling, and excellent flying performance can be obtained even for a golf player with a low head speed of 35 m / s or less, and repeated hitting durability. It can be seen that the formability is improved. On the other hand, in Comparative Example 1, since the cover does not contain organic short fibers, the durability against repeated impacts is poor. In Comparative Example 2, the outer layer cover is softer than the inner layer cover, the spin amount becomes too large, and the flight distance decreases. In Comparative Example 3, since the outer layer cover is too soft, the amount of spin becomes too large and the flight distance decreases. In Comparative Example 4, the fluidity of the outer layer cover is low, and injection molding cannot be performed satisfactorily. In Comparative Example 5, since the thickness of the outer layer cover is too large, the spin amount becomes too large and the flight distance decreases. In Comparative Example 6, the core hardness is too hard, the feel at impact is poor, the spin amount is too large, and the flight distance is reduced.

<figref num="1">It is the schematic sectional drawing of the golf ball which showed one Example of this invention.</figref>