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 at a low head speed, 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. 8-294549 (Patent Document 1) uses a core having a core hardness of 3.5 mm or more as a deformation amount under a load of 100 kg as a solid core, and uses Shore D as a cover for covering the core. A golf ball characterized by using a cover mainly made of ionomer resin having a hardness in the range of 50 to 63 and a 300% modulus in the range of 15 to 35 MPa is disclosed. However, in the above-mentioned golf ball, 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 2) 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. 8-294549</text></patcit><patcit num="2"><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 aimed to solve the problem of molding defects that occur when a thin cover is injection-molded in a golf ball having a soft core and a thin cover. As a result of paying attention to the core hardness and the melt flow rate of the cover resin composition in order to increase the fluidity of the cover resin composition and prevent the deterioration of the repeated impact durability due to the thin cover, the hardness of the core is increased. The amount of compression deflection when loaded from an initial load of 10 kgf to a final load of 130 kgf is 3.5 mm or more, and the melt flow rate of the cover resin composition is JIS. A golf ball characterized by a measurement according to K7210 of 3 or more and a cover thickness of 1.7 mm or less has a soft feeling and a low head speed golf of 35 m / s or less. It was found that the ball has excellent flying performance for the player, and the durability and moldability for repeated hitting are improved, and the present invention has been made. 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 1.7 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 cover formed by using a cover resin composition, 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 melt flow rate of the cover resin composition is JIS. A golf ball characterized in that it is 3 or more as measured according to K7210 and the thickness of the cover is 1.7 mm or less. [2] The hardness at the center of the core is 28 to 40 at the shore D hardness, the hardness at the surface of the core is 35 to 52 at the shore D hardness, and the hardness difference between the core surface and the core center is 3 to 20. A golf ball described in [1]. [3] The resin component of the cover resin composition is an olefin-unsaturated carboxylic acid copolymer, an olefin-unsaturated carboxylic acid-unsaturated carboxylic acid ester copolymer, and a metal ion neutralized product of these copolymers. The golf ball according to [1], which is at least one component selected from the group. [4] The golf ball according to [1], wherein short organic fibers are dispersed and blended in the cover resin composition. [5] The resin component of the cover resin composition is in (a) an olefin-unsaturated carboxylic acid copolymer, an olefin-unsaturated carboxylic acid-unsaturated carboxylic acid ester copolymer, and metal ions of these copolymers. The golf ball according to [1], which is obtained by mixing at least one component selected from Japanese products and (b) a binary copolymer composed of a polyolefin component and a polyamide component. [6] The golf ball according to [5], wherein the polyamide of the component (b) above is fibrous. [7] The golf ball according to [5], wherein the mass ratio of (a) / (b) is 100 / 0.1 to 100/50. [8] The golf ball according to [5], wherein the mass ratio of the polyolefin component / polyamide component among the components (b) above is 25/75 to 95/5.</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 has a core and a cover, and the ball structure G including the single-layer core 1 and the single-layer cover 2 shown in FIG. 1 can be exemplified.

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 39.3 mm or more, particularly preferably 39.5 mm or more, while the upper limit is usually 40.7 mm or less, particularly preferably 40.1 mm or less. The weight is usually 35 to 39 g, particularly preferably 37 to 38 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 5.0 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 poor, and conversely, if the amount of deformation is too large, the durability of cracking due to repeated hits will be poor, and the repulsion will be too low, making it impossible to obtain a sufficient flight distance.

The core surface hardness in the present invention is a shore D hardness of 35 to 52, preferably 37 to 50, and more preferably 40 to 48. The core center hardness is 28 to 40, preferably 30 to 39, and more preferably 32 to 38 in shore D hardness. The Shore D hardness is a value measured by a Type D durometer similar to ASTM D 2240. If the hardness is too high, the feel of hitting may become too hard. If the hardness is too low, the feel of hitting may be too soft.

Further, in the present invention, the value obtained by subtracting the core center hardness from the core surface hardness is 3 to 20, preferably 4 to 16, and more preferably 5 to 12 in shore D hardness. If the difference in hardness is too high, the durability against repeated impacts will be deteriorated, the repulsion will be low, and a sufficient flight distance may not be obtained. If the above hardness difference becomes small, the amount of spin increases when the driver (W # 1) hits, and as a result, a sufficient flight distance may not be obtained.

For the cover in the present invention, the melt flow rate of the cover resin composition is 3 or more and the cover thickness is 1.7 mm or less as measured according to JIS K7210.

As the cover resin composition, a known synthetic resin can be used without particular limitation, and in particular, (a) an olefin-unsaturated carboxylic acid copolymer and an olefin-unsaturated carboxylic acid-unsaturated carboxylic acid ester. It is preferably formed by a resin composition containing a copolymer and a component selected from the metal ion neutralized products of these copolymers, and (b) a binary copolymer composed of a polyolefin component and a polyamide component as essential components.

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 cover formed by using this resin composition is preferably 55 to 65, preferably 57 to 63, and particularly preferably 59 to 61. If the Shore D hardness of the cover is too small, the repulsion will be poor and it will not fly. Further, if the shore D hardness of the cover is too large, 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 cover thickness is 1.7 mm, preferably 1.6 mm, and more preferably 1.5 mm. If the upper limit is exceeded, the amount of spin of the ball by the driver (W # 1) It may not be possible to obtain a sufficient flight distance. The lower limit of the cover thickness is 0.5 mm, and the preferable lower limit is 1.0 mm, particularly 1.3 mm. If the lower limit is not met, the crack durability due to repeated striking may deteriorate.

Further, in the present invention, the melt flow rate of the cover resin composition is 3 or more, preferably 4 or more, and more preferably 4.5 or more as measured according to JIS K7210 (1999 edition). 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 melt flow rate of the cover resin composition is 20 or less, preferably 15 or less, and more preferably 10 or less as measured according to JIS K7210 (1999 edition). If the melt flow rate of the cover resin composition exceeds the upper limit, burrs tend to get around the support pin and the degassing pin, 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). ..

Further, 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 formed to be 42.60 to 42.80 mm and its mass can be formed to 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 when a load from an initial load of 10 kgf to a final load of 130 kgf was measured for each of the prepared solid cores.

<tables num="1"><img file="JP2005296654A_D0001.tif" /></tables>

Next, each solid core of each Example and Comparative Example was coated with a cover having a predetermined thickness made of the cover resin compositions of compositions A to C shown in Table 2 to obtain a two-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="JP2005296654A_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 Comparative Example 2 was 100. : Index 100 or more ×: Index 90 or less

<tables num="3"><img file="JP2005296654A_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 is thick, the spin amount of the ball after hitting with the driver (W # 1) becomes too large and the flight distance decreases. In Comparative Example 2, the fluidity of the cover resin composition is poor, and it is difficult to mold the cover. Further, the cover does not contain a binary copolymer composed of a polyolefin component and a polyamide component, which results in poor repeated impact durability. In Comparative Example 3, the core hardness is hard, the spin amount of the hit by the driver (W # 1) is too large, a sufficient flight distance cannot be obtained, and the hit feeling is also hard.

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