CN102526998B - Golf ball - Google Patents

Abstract

The invention aims to provide a golf ball having the largest flying distance. The golf ball comprises a ball-shaped core and at least one housing coating the ball-shaped core. The ball-shaped core is made from rubber composition having (a) base material rubber, (b) Alpha, Beta-unsaturated carboxylic acid having 3-8 carbon atoms served as co-crosslink agent and/or metallic salt thereof, (c) cross-linking initiator, (d) carboxylic acid having 1-13 carbon atoms. When (b) is Alpha, Beta-unsaturated carboxylic acid having 3-8 carbon atoms served as co-crosslink agent, the rubber composition further contains (e) metallic compound.

Description

golf

technical field

The present invention relates to a golf ball with a large flight distance on driving, and more specifically, to an improvement of a golf ball core.

Background technique

As a method of prolonging the flight distance of a golf ball at the time of a driver shot, there are, for example, a method of using a highly repulsive core, and a method of using a core having a hardness distribution whose hardness increases from the center of the core to the surface. The former has the effect of increasing the initial velocity of the golf ball, while the latter has the effect of increasing the angle of attack and reducing spin. A golf ball with a high launch angle and low spin will carry more distance.

As techniques for improving the resiliency of a core, there are Patent Documents 1 to 6, for example. Patent Documents 1 and 2 disclose a solid golf ball having an inner core mixed with zinc acrylate as a co-crosslinking agent, palmitic acid and stearin as a co-crosslinking auxiliary agent with respect to 100 parts by weight of rubber. acid or myristic acid, zinc oxide as co-crosslinking aid, reaction rate retarder.

Patent Document 3 discloses a solid golf ball obtained from a rubber composition containing 15 to 35 parts by weight of α,β-unsaturated carboxylic acid, 7 to 60 parts by weight of a metal compound that reacts with the α, β-unsaturated carboxylic acid to form a salt, and 1-10 parts by weight of a metal salt of a higher fatty acid.

Patent Document 4 discloses a golf ball characterized in that a base rubber contains a filler, an organic peroxide, an α,β-unsaturated carboxylic acid and/or a metal salt thereof as essential components, and is mixed with A cross-linked molded product of a rubber composition made of saturated or unsaturated fatty acid copper salt is used as a component.

Patent Document 5 discloses a golf ball and its composition, wherein a basic elastomer, an unsaturated mono A combination of at least one metal salt of a carboxylic acid, a free radical initiator, and a non-conjugated diene monomer.

Patent Document 6 discloses a method for producing a golf ball, which is characterized in that an unsaturated carboxylic acid and/or a metal salt thereof is mixed with a rubber material, and a masterbatch of the unsaturated carboxylic acid and/or a metal salt thereof is prepared in advance. The masterbatch is made into a rubber composition containing the rubber material, which is a golf ball manufacturing method in which the thermoformed product of the rubber composition is used as a golf ball component, and the unsaturated carboxylic acid and/or its metal salt masterbatch The following (A)-(C) are included.

(A) Modified polybutadiene 20 to 100% by mass, its ethylene content is 0 to 2%, and its cis-1,4-bonded content accounts for more than 80%, and it has active ends, and its active ends are covered by at least one type Modified by alkoxysilane compound

(B) 80 to 0% by mass of diene rubber other than the above (A) rubber component

[The above-mentioned figures represent mass % when the total amount of (A) and (B) is 100. ]

(C) unsaturated carboxylic acid and/or its metal salt

For example, Patent Documents 7 to 10 disclose a core having a hardness distribution. Patent Document 7 discloses a double-layer golf ball in which, in the double-layer golf ball composed of a core formed of a rubber composition containing a base rubber, a co-crosslinking agent, and an organic peroxide, and a cover, The core is represented by a JIS-C type hardness meter, and has a center hardness 1 of 58 to 73, a hardness 2 of 5 to 10 mm from the center of 65 to 75, a hardness of 15 mm from the center of 3 of 74 to 82, and a surface hardness of 4 of 76. For the hardness distribution of ~84, the hardness 2 is approximately constant within the hardness range, and the others satisfy the relationship of 1<2<3≤4.

Patent Document 8 discloses a golf ball in which, in a solid golf ball having a solid core and a cover layer covering it, the solid core is formed of a rubber composition containing 60-100 mass % of 100 mass parts of rubber substrates containing 60% or more cis-1,4-bonded polybutadiene rubber synthesized by rare earth element catalysts, and 0.1-5 mass parts of organic Sulfur compound, unsaturated carboxylic acid or its metal salt, inorganic filler and anti-aging agent. At the same time, the deformation of the solid core is 2.0 to 4.0mm when the load is from the initial load of 10kgf to the final load of 130kgf. Moreover, the solid core Has a hardness distribution as shown in the table below.

[Table 1]

Solid core hardness distribution Shore D Hardness center 30～48 4mm from the center 34～52 8mm from the center 40～58 Part 12mm from the center (Q) 43～61 Inner part (R) 2~3mm away from the surface 36～54 Surface (S) 41～59 Hardness difference [(Q)-(S)] 1～10 Hardness difference [(S)-(R)] 3～10

Patent Document 9 discloses a solid golf ball having a solid core and a cover layer covering it, wherein the solid core is formed of a rubber composition containing 60 ~100 parts by mass of 100 parts by mass of rubber substrates containing 60% or more cis-1,4-bonded polybutadiene rubber synthesized by rare earth element catalysts, and 0.1 to 5 parts by mass of organic sulfur compounds , unsaturated carboxylic acid or its metal salt, and inorganic fillers. At the same time, the deformation of the solid ball core from the initial load of 10kgf to the final load of 130kgf is 2.0-4.0mm, and the solid ball core has the following table hardness distribution.

[Table 2]

Solid core hardness distribution Shore D Hardness center 25～45 5~10mm from the center 39～58 15mm from the center 36～55 surface 55～75 Hardness difference between center and surface 20～50

Patent Document 10 discloses a multi-layer solid golf ball, which is characterized in that it has a core, an envelope layer covering the core, an intermediate layer covering the envelope layer, and a plurality of golf balls formed on the surface covering the intermediate layer. In the multi-layer solid golf ball with a dented shell, the core is made of rubber material as the main material, and the hardness gradually increases from the center of the core to the surface of the core. The difference in hardness between the center of the core and the surface of the core is measured in JIS -C hardness means 15 or more, and the average value of cross-sectional hardness at a position about 15 mm from the center of the core and the center of the core is set to (I), and the cross-sectional hardness at a position 7.5 mm from the center of the core is set to (II), The difference between the two hardnesses (I)-(II) is within ±2 in terms of JIS-C hardness, and the hardness of the surrounding layer, the middle layer and the shell meets the condition of shell hardness > middle layer hardness > surrounding layer hardness.

current technology

patent documents

Patent Document 1: Japanese Patent Application Laid-Open No. 61-37178

Patent Document 2: Japanese Patent Application Laid-Open No. 61-113475

Patent Document 3: Japanese Patent Laid-Open No. 61-253079

Patent Document 4: Japanese Patent Laid-Open No. 2008-212681

Patent Document 5: Japanese Patent Application Publication No. 2008-523952

Patent Document 6: Japanese Patent Laid-Open No. 2009-119256

Patent Document 7: Japanese Patent Laid-Open No. 6-154357

Patent Document 8: Japanese Patent Laid-Open No. 2008-194471

Patent Document 9: Japanese Patent Laid-Open No. 2008-194473

Patent Document 10: Japanese Patent Laid-Open No. 2010-253268

Contents of the invention

The problem to be solved by the invention

An object of the present invention is to provide a golf ball having a large flight distance on a driver shot.

In order to provide a novel golf ball with excellent flight performance, the present inventors proposed "a golf ball characterized in that it has a spherical core and at least one layer of shell covering the spherical core. The spherical core is formed of a rubber composition containing (a) a base rubber, (b) an α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms as a co-crosslinking agent, and /or its metal salt, (c) crosslinking initiator, (d) carboxylate and (e) organic sulfur compound; when (b) as a co-crosslinking agent only contains α with 3 to 8 carbon atoms, In the case of a β-unsaturated carboxylic acid, the rubber composition further contains (f) a metal compound; the content of the (d) carboxylate is 10 parts by mass or more with respect to 100 parts by mass of the (a) base rubber, less than 40 parts by mass" (Japanese Patent Application No. 2010-294589).

The gist of the invention related to Japanese Patent Application No. 2010-294589 is that the hardness distribution of the spherical core increases approximately linearly from the center of the core to the surface. Since the hardness distribution of the core increases approximately linearly from the center of the core to the surface, and the amplitude of the outer rigid and inner soft structure gradually increases, the amount of spin decreases and the performance of the flight distance is improved. The reason why the core hardness distribution increases substantially linearly from the core center to the surface is as follows. When the core is formed, the temperature inside the core is higher at the center of the core and lower near the surface of the core. This is because the reaction heat of the crosslinking reaction is accumulated in the center of the core. During core molding, the (d) carboxylate reacts with (b) metal salt of α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms to produce a metal salt of carboxylic acid. That is, the carboxylic acid salt of (d) exchanges cations with metal salts of α, β-unsaturated carboxylic acids having 3 to 8 carbon atoms, and cuts off α, β-unsaturated carboxylic acids having 3 to 8 carbon atoms. Metallic crosslinks produced by metal salts of carboxylic acids. This cation exchange reaction tends to occur at the center of the core where the temperature is relatively high inside the core, and becomes less likely to occur closer to the surface. In other words, severing of metal crosslinks occurs easily at the center of the core, and gradually becomes difficult near the surface. As a result, since the crosslink density inside the core increases from the center of the core to the surface, it is considered that the hardness of the core increases approximately linearly from the center of the core to the surface.

Moreover, the present inventors have further studied and found that by using (d) a carboxylate having 1 to 13 carbon atoms, the spherical core is stronger on the outside and softer on the inside than before, reducing the amount of spin on a tee shot. , thus completing the present invention.

means of solving problems

The golf ball of the present invention is characterized in that it has a core and at least one cover covering the spherical core, the spherical core is formed of a rubber composition containing (a) group material rubber, (b) α, β-unsaturated carboxylic acid with 3 to 8 carbon atoms and/or its metal salt as co-crosslinking agent, (c) crosslinking initiator, (d) carbon atom A carboxylate with a number of 1 to 13; when (b) only contains α, β-unsaturated carboxylic acids with 3 to 8 carbon atoms as a co-crosslinking agent, the rubber composition further contains (e ) metal compounds. According to the above-mentioned structure of the present invention, the width of the structure of the outer rigidity and inner softness of the spherical core is strengthened, the amount of spin on a driving shot is reduced, and the flight distance is increased. In addition, the spherical core used in the present invention sometimes has a partly reduced linearity of core hardness distribution. In this case, the degree of outer rigidity and inner softness is stronger than before, and the amount of spin on a driver shot is reduced.

The use of (d) a carboxylic acid having 1 to 13 carbon atoms makes the spherical core stronger on the outside and softer on the inside than before. The reason is as follows. As mentioned above, the metal salt of the carboxylic acid and the α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms is exchanged for cations, and the metal salt of the α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms is cut off. Metal crosslinking by metal salts. It is considered that the effect of cutting the metal crosslink is influenced by the number of moles of the added carboxylate having 1 to 13 carbon atoms. At the same time, the carboxylate having 1 to 13 carbon atoms also functions as a plasticizer for the spherical core. If the compounding amount (mass) of the added carboxylate having 1 to 13 carbon atoms is increased, the entire core will soften. This plasticizing effect is influenced by the compounding amount (mass) of the added carboxylic acid. Considering these effects, by using a carboxylic acid with a small number of carbon atoms (small molecular weight), compared with the case of using a carboxylic acid with a large number of carbon atoms (large molecular weight), in the case of the same mixing amount (mass), it is possible to add The number of moles increases. That is, while suppressing the overall softening of the spherical core due to the plasticizing effect, it is possible to enhance the effect of cutting metal crosslinks.

The effect of the invention

According to the present invention, it is possible to provide a golf ball having a large flight distance on driving.

Description of drawings

Fig. 1: A partially cut-away cross-sectional view showing a golf ball according to an embodiment of the present invention.

Figure 2: Graph showing core hardness distribution.

Figure 3: Graph showing core hardness distribution.

Figure 4: Graph showing core hardness distribution.

Figure 5: Graph showing core hardness distribution.

Figure 6: Graph showing core hardness distribution.

Figure 7: Graph showing core hardness distribution.

Figure 8: Graph showing core hardness distribution.

Figure 9: Graph showing core hardness distribution.

Figure 10: Graph showing core hardness distribution.

Figure 11: Graph showing core hardness distribution.

Figure 12: Graph showing core hardness distribution.

Detailed ways

The golf ball of the present invention is characterized in that it has a core and at least one cover covering the spherical core, the spherical core is formed of a rubber composition containing (a) a base material Rubber, (b) α,β-unsaturated carboxylic acid with 3 to 8 carbon atoms and/or its metal salt as co-crosslinking agent, (c) crosslinking initiator, (d) carbon number Carboxylate salts of 1 to 13; when (b) contains only α, β-unsaturated carboxylic acids with 3 to 8 carbon atoms as a co-crosslinking agent, the rubber composition further contains (e) metal compound.

First, the (a) base rubber used in the present invention will be described. As (a) base rubber, natural rubber and/or synthetic rubber can be used, for example, polybutadiene rubber, natural rubber, polyisoprene rubber, styrene polybutadiene rubber, ethylene-propylene- Diene rubber (EPDM), etc. These may be used alone or in combination of two or more. Among them, cis-1,4-bonded high-cis polybutadiene which is beneficial to rebound is particularly suitable, containing 40% by mass or more, preferably 80% by mass or more, more preferably 90% by mass.

The high cis polybutadiene preferably has a 1,2-vinyl bond content of 2% by mass or less, more preferably 1.7% by mass or less, further preferably 1.5% by mass or less. When the 1,2-vinyl bond content is too high, the repellency may decrease.

The high cis-polybutadiene is preferably synthesized with a rare earth element catalyst, and in particular, when a neodymium catalyst using a neodymium compound as a lanthanum series rare earth element compound is used, it can be obtained with excellent polymerization activity. Polybutadiene rubber having a high 1,4-cis bond content and a low 1,2-ethylene bond content is therefore preferred.

The high cis polybutadiene has a Mooney viscosity (ML ₁₊₄ (100°C)) of preferably 30 or more, more preferably 32 or more, further preferably 35 or more, preferably 140 or less, more preferably 120 or less, further preferably 100 or less , most preferably below 80. In addition, the Mooney viscosity (ML ₁₊₄ (100°C)) referred to in the present invention refers to JIS K6300, using an L rotor, preheating time of 1 minute, rotor rotation time of 4 minutes, and 100°C. The values measured under the conditions.

As the high cis polybutadiene, its molecular weight distribution Mw/Mn (Mw: weight average molecular weight, Mn: number average molecular weight) is preferably 2.0 or more, more preferably 2.2 or more, further preferably 2.4 or more, most preferably 2.6 or more, preferably 6.0 or less, more preferably 5.0 or less, further preferably 4.0 or less, most preferably 3.4 or less. If the molecular weight distribution (Mw/Mn) of high cis polybutadiene is too small, handleability may be reduced, and if it is too large, repellency may be reduced. In addition, the molecular weight distribution is determined by gel permeation chromatography (manufactured by Tosoh Corporation, "HLC-8120GPC"), using a differential refractometer as a detector, column: GMHHXL (manufactured by Tosoh Corporation), column temperature: 40 °C, mobile phase: measure under the condition of tetrahydrofuran, and the value is calculated based on standard polystyrene as conversion value.

Next, (b) α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms and/or its metal salt will be described. (b) α,β-unsaturated carboxylic acid with 3 to 8 carbon atoms and/or its metal salt, which is mixed in the rubber composition as a co-crosslinking agent, and is graft-polymerized to the molecule of the base rubber chain, which plays a role in cross-linking rubber molecules. When the rubber composition used in the present invention contains only an α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms as a co-crosslinking agent, the rubber composition further contains (e) a metal compound as an essential component. Because in the rubber composition, by neutralizing the α, β-unsaturated carboxylic acid with 3 to 8 carbon atoms with a metal compound, it can actually be obtained with the carbon number of 3 to 8 used as a co-crosslinking agent. α, β-unsaturated carboxylate metal salts have the same effect. In addition, when an α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms and a metal salt thereof are used together as a co-crosslinking agent, (e) a metal compound can also be used as an optional component.

Examples of the α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms include acrylic acid, methacrylic acid, fumaric acid, maleic acid, and crotonic acid.

As the metal constituting the metal salt of α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms, monovalent metal ions such as sodium, potassium, lithium, etc.; divalent metal ions such as magnesium, calcium, zinc, barium, cadmium, etc. Valence metal ions; Trivalent metal ions such as aluminum; Other ions such as tin and zirconium. These metal components may be used alone or as a mixture of two or more. Among these, divalent metals such as magnesium, calcium, zinc, barium, and cadmium are preferable as the metal component. This is because metal crosslinking is easily formed between rubber molecules by using a divalent metal salt of an α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms. In particular, zinc acrylate is preferable as the divalent metal salt in view of the high repulsion of the resulting golf ball. In addition, α,β-unsaturated carboxylic acids having 3 to 8 carbon atoms and/or metal salts thereof may be used alone or in combination of two or more.

(b) The content of α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms and/or its metal salt is preferably 15 parts by mass or more, more preferably 20 parts by mass, based on 100 parts by mass of (a) base rubber Part or more, preferably 50 parts by mass or less, more preferably 45 parts by mass or less, further preferably 35 parts by mass or less. (b) When the content of α,β-unsaturated carboxylic acid with 3 to 8 carbon atoms and/or its metal salt is less than 15 parts by mass, in order to make the parts formed from the rubber composition have appropriate hardness, it is necessary to Increasing the amount of the crosslinking initiator (c) described later tends to lower the repulsion of the golf ball. On the other hand, if the content of α, β-unsaturated carboxylic acid and/or its metal salt with 3 to 8 carbon atoms exceeds 50 parts by mass, the parts formed from the rubber composition will be too hard, which may cause golf balls Decline in hitting feel.

(c) The crosslinking initiator is mixed in order to crosslink (a) the base rubber component. As (c) crosslinking initiator, an organic peroxide is suitable. The organic peroxides can specifically include: dicumyl peroxide, 1,1-bis(tert-butyl peroxy)-3,3,5-trimethylcyclohexane, 2,5-di Methyl-2,5-bis(tert-butylperoxy)hexane, di-tert-butylperoxide, and the like. These organic peroxides may be used alone or in combination of two or more. Among these, dicumyl peroxide is preferably used.

The content of the (c) crosslinking initiator is preferably 0.2 parts by mass or more, more preferably 0.5 parts by mass or more, preferably 5.0 parts by mass or less, more preferably 2.5 parts by mass or less, based on 100 parts by mass of the (a) base rubber. When it is less than 0.2 parts by mass, the parts formed by the rubber composition are too soft, and the repulsion of the golf ball tends to decrease. If it exceeds 5.0 parts by mass, in order to ensure that the parts formed by the rubber composition have appropriate hardness, it is necessary to reduce the If the amount of the co-crosslinking agent used in (b) is too low, the repulsion of the golf ball will be insufficient and the durability may be deteriorated.

Next, (d) a carboxylate having 1 to 13 carbon atoms will be described. The (d) carboxylate having 1 to 13 carbon atoms used in the present invention is not particularly limited as long as it is a salt of a compound having a carboxyl group, but does not include (b) the carbon number used as a co-crosslinking agent. It is a salt of 3 to 8 α, β-unsaturated carboxylic acids. It is considered that (d) a carboxylate with 1 to 13 carbon atoms, when the nucleus is formed, in the center of the nucleus, there is a cut-off from (b) an α, β-unsaturated carboxylic acid with 3 to 8 carbon atoms The role of metal crosslinking produced by metal salts.

The (d) carboxylate having 1 to 13 carbon atoms is preferably an aliphatic carboxylate (in the present invention, it may be abbreviated as "fatty acid" salt). The carboxylate having 1 to 13 carbon atoms is preferably a carboxylate having 1 to 12 carbon atoms. The number of carbon atoms of the carboxylate is reduced, and there are problems such as toxicity and odor. In addition, the number of carbon atoms refers to the number of carbon atoms of the carboxylic acid component.

The fatty acid salt can be any one of saturated fatty acid salt and unsaturated fatty acid salt, preferably saturated fatty acid salt. Specific examples of the fatty acid component of the fatty acid salt include butyric acid (C4), pentanoic acid (C5), hexanoic acid (C6), heptanoic acid (C7), caprylic acid (caprylic acid) (C8), Nonanoic acid (C9), capric acid (capric acid) (C10), lauric acid (C12), etc. The said fatty acid component can be used individually or as a mixture of 2 or more types. As the fatty acid component, caprylic acid (caprylic acid) (C8), nonanoic acid (C9), capric acid (capric acid) (C10), lauric acid (C12) is preferable, and caprylic acid (caprylic acid) (C8 ), capric acid (capric acid) (C10) and lauric acid (C12).

As the cation component of the above-mentioned carboxylate, any one of metal ions and organic cations can be selected. Examples of metal ions include monovalent metal ions such as sodium, potassium, lithium, and silver; divalent metal ions such as magnesium, calcium, zinc, barium, cadmium, copper, cobalt, nickel, and manganese; and trivalent metal ions such as aluminum and iron. Metal ions; tin, zirconium, titanium and other ions. As the cationic component of the carboxylate, zinc ions are preferred. These cationic components may be used alone or as a mixture of two or more.

The aforementioned organic cations are cations having a carbon chain. It does not specifically limit as said organic cation, For example, an organic amine ion is mentioned. As above-mentioned organic amine ion, can enumerate such as: primary amine ion such as stearylamine ion, hexylamine ion, octylamine ion, 2-ethylhexylamine ion; ) base (stearyl) amine ions and other secondary amine ions; trioctyl amine ions and other tertiary amine ions; dioctyl dimethyl ammonium ions, distearyl dimethyl ammonium ions and other quaternary ammonium ions, etc. These organic cations may be used alone or in combination of two or more. In addition, the number of carbon atoms in the carboxylate having 1 to 13 carbon atoms is the number of carbon atoms in the carboxylic acid component, and does not include the number of carbon atoms in the organic cation.

As the (d) carboxylate having 1 to 13 carbon atoms, caprylic acid (caprylic acid) (C8), nonanoic acid (C9), capric acid (capric acid) (C10) or lauric acid (C12 ), more preferably the zinc salt of caprylic acid (caprylic acid) (C8), capric acid (capric acid) (C10) and lauric acid (C12).

The (d) content of the carboxylate having 1 to 13 carbon atoms is preferably 0.5 parts by mass or more, more preferably 1.0 parts by mass or more, and still more preferably 1.5 parts by mass or more, based on 100 parts by mass of the (a) base rubber, Preferably it is 30 parts by mass or less, more preferably 25 parts by mass or less, still more preferably 20 parts by mass or less. If the content is too small, the effect of adding (d) carboxylate having 1 to 13 carbon atoms will not be sufficient, and the range of rigidity on the outside and softness on the inside of the spherical core may become small. In addition, if the content is too high, the hardness of the obtained core may decrease as a whole, which may lower the repulsion properties. Furthermore, in order to improve the dispersibility of zinc acrylate used as a co-crosslinking agent in rubber, the surface of zinc acrylate may be treated with a carboxylate having 1 to 13 carbon atoms. When such a carboxylate with 1 to 13 carbon atoms is used for surface treatment of zinc acrylate, in the present invention, the amount of the carboxylate with 1 to 13 carbon atoms as a surface treatment agent is contained in (d) carbon Among the content of carboxylate with atomic number 1-13. For example, when using 25 parts by mass of zinc acrylate whose surface treatment amount is 10 mass % of carboxylate with 1 to 13 carbon atoms, the amount of carboxylate with 1 to 13 carbon atoms is 2.5 parts by mass, zinc acrylate 22.5 parts by mass, and 2.5 parts by mass as the content of (d) carboxylate having 1 to 13 carbon atoms.

When the rubber composition used in the present invention contains only an α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms as a co-crosslinking agent, it further contains (e) a metal compound as an essential component. The (e) metal compound is not particularly limited as long as it can neutralize (b) the α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms in the rubber composition. Examples of (e) the metal compound include metal hydroxides such as magnesium hydroxide, zinc hydroxide, calcium hydroxide, sodium hydroxide, lithium hydroxide, potassium hydroxide, and copper hydroxide; magnesium oxide, calcium oxide, and the like; , zinc oxide, copper oxide and other metal oxides; magnesium carbonate, zinc carbonate, calcium carbonate, sodium carbonate, lithium carbonate, potassium carbonate and other metal carbonates. (e) The metal compound is preferably a divalent metal compound, more preferably a zinc compound. Because the divalent metal compound reacts with α, β-unsaturated carboxylic acid with 3-8 carbon atoms to form metal cross-linking. In addition, by using a zinc compound, a highly resilient golf ball can be obtained. These (e) metal compounds may be used alone or in combination of two or more.

The rubber composition for a core used in the present invention preferably further contains (f) an organic sulfur compound. In addition to (d) a carboxylate having 1 to 13 carbon atoms, the rubber composition for a core is used together with (f) an organic sulfur compound, so that the substantially linear hardness distribution of the core can be maintained continuously, Controls the magnitude of the outer rigid inner soft structure of the core. (f) The organosulfur compound is not particularly limited as long as it is an organic compound containing a sulfur atom in the molecule, and examples thereof include polysulfides having a thiol group (-SH) or having 2 to 4 sulfur atoms bond (-S-S-, -S-S-S- or -S-S-S-S-), or their metal salts (-SM, -S-M-S-, -S-M-S-S-, -S-S-M-S-S-, -S-M-S-S-S-, etc., M is a metal atom). In addition, the organosulfur compound described in (f) can be used in aliphatic compounds (aliphatic mercaptans, aliphatic thiocarboxylic acids, aliphatic dithiocarboxylic acids, aliphatic polysulfides, etc.), heterocyclic compounds, aliphatic Optional one of formula compounds (alicyclic thiol, alicyclic thiocarboxylic acid, alicyclic dithiocarboxylic acid, alicyclic polysulfide, etc.) and aromatic compounds. Examples of (f) organosulfur compounds include thiophenols, naphthols, polysulfides, thiocarboxylic acids, dithiocarboxylic acids, sulfenamides, and thiurams. , dithiocarbamate, thiazoles, etc. From the viewpoint of increasing the hardness distribution of the spherical core, the organosulfur compound (f) is preferably an organosulfur compound having a thiol group (-SH) or a metal salt thereof, preferably thiophenols, naphthalenethiophenols, or the like. of metal salts. Examples of metal salts include monovalent metal salts such as sodium, lithium, potassium, copper (I), and silver (I); zinc, magnesium, calcium, strontium, barium, titanium (II), manganese (II), iron Divalent metal salts such as (II), cobalt (II), nickel (II), zirconium (II), and tin (II).

Examples of thiophenols include: thiophenol; 4-fluorothiophenol, 2,5-difluorothiophenol, 2,4,5-trifluorothiophenol, 2,4,5,6 -Tetrafluorothiophenol, pentafluorothiophenol and other thiophenols substituted by fluorine; 2-chlorothiophenol, 4-chlorothiophenol, 2,4-dichlorothiophenol, 2,5- Chlorine-substituted thiophenols such as dichlorothiophenol, 2,4,5-trichlorothiophenol, 2,4,5,6-tetrachlorothiophenol, pentachlorothiophenol; 4-bromothiophenol Thiophenol, 2,5-dibromothiophenol, 2,4,5-tribromothiophenol, 2,4,5,6-tetrabromothiophenol, pentabromothiophenol, etc. are substituted by bromine Thiophenols; 4-iodothiophenol, 2,5-diiodothiophenol, 2,4,5-triiodothiophenol, 2,4,5,6-tetraiodothiophenol, pentaiodo Thiophenols substituted with iodine, such as thiophenol, or their metal salts. As the metal salt, zinc salt is preferred.

Naphthalenethiols (naphthalenethiols) include, for example, 2-naphthalenethiol, 1-naphthalenethiol, 2-chloro-1-naphthalenethiol, 2-bromo-1-naphthalenethiol, 2- Fluoro-1-naphthylthiol, 2-cyano-1-naphthylthiol, 2-acetyl-1-naphthylthiol, 1-chloro-2-naphthalenethiol, 1-bromo-2-naphthalenethiol, 1-fluoro-2-naphthylthiol, 1-cyano-2-naphthylthiol, 1-acetyl-2-naphthalenethiol or their metal salts, preferably 1-naphthylthiol, 2-naphthalenethiol and their zinc salts.

Examples of sulfenamide-based organosulfur compounds include n-cyclohexyl-2-benzothiazole sulfenamide, n-hydroxydiethylene-2-benzothiazole sulfenamide, n-tert-butyl-2 -Benzothiazolesulfenamide. Examples of thiuram-based organic sulfur compounds include tetramethylthiuram monosulfide, tetramethylthiuram disulfide, tetraethylthiuram disulfide, tetrabutylthiuram disulfide, tetramethylthiuram disulfide, and tetramethylthiuram disulfide. Disulfide thiuram, etc. Examples of dithiocarbamate salts include zinc dimethyldithiocarbamate, zinc diethyldithiocarbamate, zinc dibutyldithiocarbamate, ethylphenyl dithiocarbamate Zinc carbamate, sodium dimethyldithiocarbamate, sodium diethyldithiocarbamate, copper(II) dimethyldithiocarbamate, iron(III) dimethyldithiocarbamate, diethyldithiocarbamate Selenium dithiocarbamate, tellurium diethyldithiocarbamate, etc. Examples of thiazole-based organic sulfur compounds include: 2-mercaptobenzothiazole (MBT), dibenzothiazole disulfide (MBTS), sodium salt, zinc salt, copper salt, or cyclohexylamine of 2-mercaptobenzothiazole salt, 2-(2,4-dinitrophenyl)mercaptobenzothiazole, 2-(2,6-diethyl-4-morpholinothio)benzothiazole, etc.

(f) The organosulfur compounds may be used alone or in combination of two or more.

(f) The content of the organic sulfur compound is preferably 0.05 parts by mass or more, more preferably 0.1 parts by mass or more, preferably 5.0 parts by mass or less, more preferably 2.0 parts by mass or less, based on 100 parts by mass of the (a) base rubber. If it is less than 0.05 parts by mass, the effect of adding (f) the organic sulfur compound cannot be obtained, and there is a possibility that the repulsion of the golf ball cannot be improved. In addition, if it exceeds 5.0 parts by mass, the amount of compression deformation of the resulting golf ball may increase, which may lower the repulsion.

The rubber composition used in the present invention may, if necessary, contain additives such as pigments, fillers for weight adjustment, antioxidants, peptizers, and softeners. In addition, as described above, when the rubber composition used in the present invention contains only an α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms as a co-crosslinking agent, it is preferable that the rubber composition further contains (e) metal compound.

Examples of pigments to be mixed in the rubber composition include white pigments, blue pigments, and purple pigments. As the white pigment, titanium oxide is preferably used. The type of titanium oxide is not particularly limited, but the rutile type is preferably used because of good hiding properties. The content of titanium oxide is preferably 0.5 parts by mass or more, more preferably 2 parts by mass or more, and preferably 8 parts by mass or less, more preferably 5 parts by mass or less, based on 100 parts by mass of the (a) base rubber.

It is also preferable that the rubber composition contains a white pigment and a blue pigment. Blue pigments are mixed to make white look more vivid, such as: ultramarine blue, cobalt blue, phthalocyanine blue, etc. Moreover, as said purple pigment, anthraquinone violet, dioxazine violet, methyl violet etc. are mentioned, for example.

The content of the blue pigment is preferably not less than 0.001 part by mass, more preferably not less than 0.05 part by mass, preferably not more than 0.2 part by mass, more preferably not more than 0.1 part by mass, based on 100 parts by mass of the (a) base rubber. If it is less than 0.001 parts by mass, the blue color will not be conspicuous, and it will appear slightly yellowed, and if it exceeds 0.2 parts by mass, it will be too blue and lose its bright white appearance.

The filler used in the rubber composition is mainly used to adjust the weight of the golf ball obtained as a final product, and the weight regulator may be mixed as needed. Examples of the filler include inorganic fillers such as zinc oxide, barium sulfate, calcium carbonate, magnesium oxide, tungsten powder, and molybdenum powder. The filler content is preferably not less than 0.5 parts by mass, more preferably not less than 1 part by mass, preferably not more than 30 parts by mass, more preferably not more than 25 parts by mass, and still more preferably not more than 20 parts by mass, based on 100 parts by mass of the base rubber. If the content of the filler is less than 0.5 parts by mass, it will be difficult to adjust the weight, and if it exceeds 30 parts by mass, the percentage by weight of the rubber component will decrease, which tends to lower the resiliency.

The content of the anti-aging agent is preferably not less than 0.1 part by mass and not more than 1 part by mass relative to 100 parts by mass of the (a) base rubber. In addition, the content of the peptizer is preferably not less than 0.1 parts by mass and not more than 5 parts by mass relative to 100 parts by mass of the (a) base rubber.

The rubber composition used in the present invention is mixed with (a) base rubber, (b) α, β-unsaturated carboxylic acid with 3 to 8 carbon atoms and/or its metal salt, (c) crosslinking initiator agent, (d) carboxylate having 1 to 13 carbon atoms, and other additives if necessary, obtained by kneading. The kneading method is not particularly limited, and for example, known kneading machines such as a kneading roll, a Banbury mixer, and a kneader can be used for kneading.

The spherical core of the golf ball of the present invention can be obtained by molding the kneaded rubber composition in a metal mold. The temperature for forming the spherical core is preferably 120°C or higher, more preferably 150°C or higher, still more preferably 160°C or higher, and preferably 170°C or lower. If the molding temperature exceeds 170°C, the surface hardness of the core tends to decrease. In addition, the pressure during molding is preferably 2.9 MPa to 11.8 MPa. The molding time is preferably 10 minutes to 60 minutes.

For the above-mentioned spherical core, divide the radius of the core equally at intervals of 12.5%, measure the hardness of the 9 equally divided points, and calculate the linear shape by the least square method when plotting these hardnesses and the distance from the center of the core. R ² of the approximate curve is preferably 0.95 or more. When ^R2 is 0.95 or more, the linearity of the hardness distribution of the core is high, the amount of spin on driver shots is reduced, and the flight distance performance is improved.

Regarding the hardness of the spherical core, an arbitrary radius of the spherical core was equally divided at intervals of 12.5%, and the JIS-C hardness of nine points of the average division was measured. That is, at 9 points at distances from the core center of 0% (core center), 12.5%, 25%, 37.5%, 50%, 62.5%, 75%, 87.5%, 100% (core surface) Measure JIS-C hardness. Next, the JIS-C hardness measured as above is taken as the axis of ordinate, and the distance (%) from the center of the core is taken as the axis of abscissa, and the measurement results are plotted into a graph. In the present invention, the linear approximation curve R ² obtained from this curve by the least square method is preferably 0.95 or more. ^R2 of the linear approximation curve obtained by the least square method is an index for judging the linearity of the obtained curve. In the present invention, when R ² is at least 0.95, it means that the hardness distribution of the spherical core is substantially linear. Using a golf ball with a roughly straight-line spherical core in the hardness distribution can reduce the amount of spin on tee shots. As a result, the flight distance of the driver shot increases. R ² of the linear approximation curve is more preferably 0.96 or more. By improving straightness, tee shots carry more distance.

The hardness difference (Hs-Ho) between the surface hardness Hs and the central hardness Ho of the spherical core is expressed in JIS-C hardness, preferably 27 or more, more preferably 28 or more, further preferably 30 or more, particularly preferably 31 or more, and most preferably 32 or more, preferably 80 or less, more preferably 70 or less, still more preferably 60 or less. If the difference in hardness between the surface of the core and the center of the core is large, a golf ball with a higher launch angle, lower spin, and greater flight distance can be obtained.

The center hardness Ho of the spherical core is preferably 30 or higher, more preferably 40 or higher, and still more preferably 45 or higher in terms of JIS-C hardness. When the central hardness Ho of the spherical core is less than 30 in terms of JIS-C hardness, the repulsion may be lowered due to being too soft. In addition, the center hardness Ho of the spherical core is preferably 70 or less, more preferably 65 or less, and still more preferably 60 or less in terms of JIS-C hardness. If the center hardness Ho exceeds 70 in terms of JIS-C hardness, it is too hard and tends to lower the impact feeling.

The surface hardness Hs of the spherical core is expressed in JIS-C hardness, preferably 76 or more, more preferably 78 or more, further preferably 80 or more, preferably 100 or less, more preferably 95 or less. In terms of JIS-C hardness, if the surface hardness of the spherical core is set to be 76 or higher, the spherical core will not become too soft and good resiliency can be obtained. In addition, when the surface hardness of the spherical core is set to be 100 or less in terms of JIS-C hardness, the spherical core will not be too hard and a good hitting feeling can be obtained.

The diameter of the spherical core is preferably 34.8 mm or more, more preferably 36.8 mm or more, further preferably 38.8 mm or more, preferably 42.2 mm or less, more preferably 41.8 mm or less, still more preferably 41.2 mm or less, most preferably 40.8 mm or less. If the diameter of the spherical core is more than 34.8mm, the thickness of the shell will not be too thick, and the resilience will be better. On the other hand, if the diameter of the spherical core is 42.2 mm or less, the shell will not be too thin, and the shell can function better.

When the spherical core has a diameter of 34.8 mm to 42.2 mm, the amount of compressive deformation (the amount of shrinkage toward the center in the compression direction) from the initial load of 98 N to the final load of 1275 N is preferably 2.0 mm or more, more preferably 2.0 mm or more. It is preferably 2.8 mm or more, preferably 6.0 mm or less, more preferably 5.0 mm or less. If the amount of compression deformation is greater than or equal to 2.0 mm, the hitting feeling will be better, and if the amount of compression deformation is less than or equal to 6.0 mm, the resiliency will be better.

The golf ball cover of the present invention is formed from a cover composition containing a resin component. Examples of the resin component include ionomer resins, thermoplastic polyurethane elastomers sold under the trade name "Elastoran (registered trademark)" by BASF Japan (Co., Ltd.), commercialized by Alkema (Co., Ltd.) Thermoplastic polyamide elastomers sold under the name "Pebakus (registered trademark)", thermoplastic polyester elastomers sold under the trade name "Hitorel (registered trademark)" by Toray Dupont Co., Ltd., and thermoplastic polyester elastomers sold under the trade name Thermoplastic styrene elastomers sold by "Laboron (registered trademark)" and the like.

As the ionomer resin, for example, the carboxyl groups in the binary copolymer of olefin and α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms are neutralized by metal ions, Substances in which the carboxyl groups of terpolymers of olefins and α, β-unsaturated carboxylic acids and α, β-unsaturated carboxylic acid esters with 3 to 8 carbon atoms are at least partly neutralized by metal ions, or mixtures thereof . The olefin is preferably an olefin having 2 to 8 carbon atoms, such as ethylene, propylene, butene, pentene, hexene, heptene, octene, etc., and ethylene is particularly preferable. Examples of the α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms include acrylic acid, methacrylic acid, fumaric acid, maleic acid, crotonic acid, etc., and acrylic acid or methacrylic acid is particularly preferable. In addition, as α, β-unsaturated carboxylic acid esters, methyl esters, ethyl esters, propyl esters, n-butyl esters, isobutyl esters, etc. of acrylic acid, methacrylic acid, fumaric acid, maleic acid, etc. can be used, Particular preference is given to acrylates and methacrylates. Among them, as the ionomer resin, metal ion neutralization products of ethylene-(meth)acrylic acid binary copolymers, metal ion neutralization products of ethylene-(meth)acrylic acid-(meth)acrylate terpolymers are preferable. ion neutralizer.

Specific examples of the ionomer resin include "Himilan (registered trademark)" sold by Mitsui DuPont Poly Chemical Co., Ltd. (for example: Himilan 1555 (Na), Himilan 1557 (Zn), HIMILAN 1605 (Na), HIMILAN 1706 (Zn), HIMILAN 1707 (Na), HIMILAN AM3711 (Mg), etc., HIMILAN 1856 (Na), HIMILAN 1855 (Zn) as the terpolymer ionomer resin wait".

Furthermore, as an ionomer resin sold by Dupont, "Surlyn (registered trademark)" (for example: Surlyn 8945 (Na), Surlyn 9945 (Zn), Surlyn 8140 (Na), Sa-Lin 8150 (Na), Sa-Lin 9120 (Zn), Sa-Lin 9150 (Zn), Sa-Lin 6910 (Mg), Sa-Lin 6120 (Mg), Sa-Lin 7930 (Li ), Sa-Lin 7940 (Li), Sa-Lin AD8546 (Li), etc., as the terpolymer ionomer resin, there are Sa-Lin 8120 (Na), Sa-Lin 8320 (Na), Sa-Lin 9320 ( Zn), Sa-Lin 6320 (Mg), HPF1000 (Mg), HPF2000 (Mg), etc.)".

In addition, examples of ionomer resins sold by ExonMobil Chemical Co., Ltd. include: "Aiotek (Iotek) (registered trademark) (for example: Aiotec 8000 (Na), Aiotek 8030 (Na), Aiotek 7010 (Zn), Aiotec 7030 (Zn), etc., as terpolymer ionomer resins, there are Aiotec 7510 (Zn), Aiotec 7520 (Zn), etc.)".

In addition, Na, Zn, Li, Mg, and the like described in parentheses after the trade name of the ionomer resin represent metal species that neutralize metal ions. These ionomer resins may be used alone or in combination of two or more.

The cover composition constituting the golf cover of the present invention preferably contains a thermoplastic polyurethane elastomer or an ionomer resin as a resin component. When an ionomer resin is used, it is preferably used in combination with a thermoplastic styrene elastomer. The content of the polyurethane or ionomer resin in the resin component of the composition for a casing is preferably 50% by mass or more, more preferably 60% by mass or more, and still more preferably 70% by mass or more.

The composition for the casing, in addition to the above-mentioned resin components, may also contain pigment components such as white pigments (such as titanium oxide), blue pigments, and red pigments, zinc oxide, calcium carbonate, and barium sulfate within the range that does not impair the casing performance. Equal weight regulator, dispersant, anti-aging agent, ultraviolet absorber, light stabilizer, fluorescent material or fluorescent whitening agent, etc.

The content of the white pigment (such as titanium oxide) is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, preferably 10 parts by mass or less, more preferably 8 parts by mass or less, based on 100 parts by mass of the resin component constituting the shell. When the content of the white pigment is at least 0.5 parts by mass, hiding properties can be imparted to the casing. In addition, when the content of the white pigment exceeds 10 parts by mass, the durability of the obtained casing may decrease.

The slab hardness of the cover composition is preferably appropriately set according to desired golf ball performance. For example, in the case of a distance golf ball in which flight distance is important, the slab hardness of the cover composition is preferably 50 or more, more preferably 55 or more, preferably 80 or less, and more preferably 70 or less in Shore D hardness. By setting the slab hardness of the cover composition to 50 or more, a golf ball with a high launch angle and low spin can be obtained at the time of driver shots and iron shots, thereby improving the flight distance. In addition, by setting the hardness of the cover composition to 80 or less, a golf ball excellent in durability can be obtained. In addition, in the case of a spin golf ball in which controllability is important, the slab hardness of the cover composition is preferably less than 50, preferably 20 or more, and more preferably 25 or more in Shore D hardness. The slab hardness of the cover composition is represented by Shore D hardness. If the hardness of the slab is less than 50, the resulting golf ball will pass through the core of the present invention. The amount of spin on the ball will increase, and it will be easier to stop on the green. In addition, by setting the hardness of the slab to 20 or more, scratch resistance performance can be improved. When there are a plurality of skin layers, the hardness of the slab constituting the composition for the skin of each layer may be the same or different as long as it is within the above range.

As a method of molding the golf ball cover of the present invention, for example, a method of molding a hollow shell-shaped cover from the cover composition, and then covering the core with a plurality of covers and compression molding (preferably molding the cover composition into a Hollow shell-shaped half shells, a method of covering the core with two half shells by compression molding), or a method of directly injection-molding the composition for the cover on the core.

When the shell is molded by compression molding, the half shell can be formed by either compression molding or injection molding, but compression molding is suitable. The conditions for compression-molding the casing composition into a half shell include, for example, a pressure of 1 MPa to 20 MPa, a molding temperature of -20°C or higher, 70°C relative to the temperature at which the casing composition begins to flow. the following. By setting the above forming conditions, it is possible to form a half shell having a uniform thickness. As a method of molding the shell using the half shells, for example, a compression molding method in which two half shells cover the core is mentioned. As the conditions for compression-molding the half-shell to form the shell, for example, at a molding pressure of 0.5 MPa or more and 25 MPa or less, the molding temperature is -20°C or more and 70°C or less relative to the temperature at which the composition for the shell begins to flow . By setting the molding conditions described above, it is possible to mold a golf cover having a uniform thickness.

When molding the case by injection molding the composition for the case, the composition for the case in the form of pellets obtained by extrusion may be used for injection molding, or the base resin component and the material for the case such as a pigment may be dry-mixed, Direct injection molding. As the upper and lower metal molds for molding the case, it is preferable to use hemispherical cavities, small protrusions, and a part of the small protrusions also serving as fixed pins that can move forward and backward. The molding of the casing by injection molding, after pushing out the fixing pin, putting in the ball core and fixing it, injecting the composition for the casing and cooling it, the casing can be formed, for example, the shape is fixed at a pressure of 9MPa to 15MPa The casing composition heated to 200° C. to 250° C. is injected into the metal mold within 0.5 seconds to 5 seconds, and then cooled within 10 seconds to 60 seconds to open the mold.

When the shell is formed, depressions called dimples are usually formed in the surface. The total number of dents is preferably not less than 200 and not more than 500. When the total number of dents is less than 200, it is difficult to obtain the effect of dents. Also, when the total number of dimples exceeds 500, the size of each dimple becomes small, making it difficult to obtain the effect of dimples. The shape of the dent formed (in plan view) is not particularly limited, and it can be used alone or in combination of two or more types. Polygons such as circles, roughly triangular, roughly square, roughly pentagonal, roughly hexagonal, and other indeterminate shapes can be used. .

The thickness of the casing is preferably 4.0 mm or less, more preferably 3.0 mm or less, and still more preferably 2.0 mm or less. If the thickness of the cover is less than 4.0 mm, the resulting golf ball will have better resiliency and hitting feeling. The thickness of the casing is preferably not less than 0.3 mm, more preferably not less than 0.5 mm, still more preferably not less than 0.8 mm, particularly preferably not less than 1.0 mm. When the thickness of the case is less than 0.3 mm, the durability and wear resistance of the case may be reduced. In the case of a plurality of outer shell layers, the total thickness of the plurality of outer shell layers is preferably within the above-mentioned range.

The golf ball body after the shell has been formed is taken out from the metal mold, and surface treatment such as deburring, cleaning, sandblasting, etc. may be preferably performed as necessary. In addition, a film or a mark may be formed as desired. The film thickness of the coating film is not particularly limited, but is preferably 5 μm or more, more preferably 7 μm or more, preferably 50 μm or less, more preferably 40 μm or less, still more preferably 30 μm or less. If the film thickness is less than 5 μm, the coating film is easy to wear and disappear due to continuous use. If the film thickness exceeds 50 μm, the effect of dents will be reduced, thereby reducing the flight performance of the golf ball.

In the golf ball of the present invention, when the diameter is 40 mm to 45 mm, the amount of compression deformation (shrinkage in the compression direction) from the state of loading the initial load of 98 N to the loading of the final load of 1275 N is preferably 2.0 mm or more, more preferably 2.4 mm or more , more preferably 2.5mm or more, most preferably 2.8mm or more, preferably 5.0mm or less, more preferably 4.5mm or less, still more preferably 3.6mm or less. A golf ball with a compressive deformation amount of 2.0 mm or more has an excellent hardness and a good hitting feeling. On the other hand, when the amount of compressive deformation is 5.0 mm or less, the resilience becomes high.

The structure of the golf ball of the present invention is not particularly limited as long as it has a spherical core and one or more layers of covers covering the spherical core. FIG. 1 is a model cross-sectional view showing a partially cutaway golf ball 2 according to an embodiment of the present invention. The golf ball 2 has a spherical core 4 and a cover 12 covering the spherical core 4 . A plurality of indentations 14 are formed on the surface of the housing. On the surface of the golf ball 2 , the portion other than the dimple 14 is a land 16 . In this golf ball 2, a paint layer and a marking layer are provided on the outside of the cover 12, but illustration of these layers is omitted.

The spherical core preferably has a single-layer structure. The spherical core of the single-layer structure has no energy loss when the interface of the multi-layer structure is hit, and can improve the resilience. In addition, the casing may have a structure of more than one layer, or may have a single-layer structure, or a multi-layer structure of at least two or more layers. As the golf ball of the present invention, for example: a double-layer golf ball composed of a spherical core and a single-layer cover arranged to cover the spherical core; A multi-layer golf ball (including a three-layer golf ball) with two or more shells; having a spherical core, a silk-containing rubber layer disposed around the core, and a shell disposed to cover the silk-containing rubber layer Rolled golf balls, etc. Golf balls of any structure described above are applicable to the present invention.

Example

The present invention will be described in detail according to the examples below, but the present invention is not limited to the following examples, as long as it is a change that does not exceed the gist of the present invention, any embodiment is included within the scope of the present invention.

[Evaluation method]

(1) Compression deformation (mm)

For the core or golf ball, the amount of deformation in the compression direction (the amount of contraction of the core or golf ball in the compression direction) from the initial load of 98N to the final load of 1275N was measured.

(2) rebound coefficient

Use each core or golf ball to impact a 198.4g metal cylinder at a speed of 40m/s, measure the speed of the cylinder and the core or golf ball before and after the impact, and calculate the core or golf ball from each speed and mass. The bounce coefficient of the ball. Each ball core or golf ball is respectively measured 12, gets its average value as the rebound coefficient of this ball core or golf ball. In addition, the rebound coefficient is shown as the difference in the rebound coefficient from the golf ball (core) No. 11 in Tables 3 to 4, and in the tables 5 to 6 as the rebound from the golf ball (core) No. 22. The difference in coefficients is displayed.

(3) Slab hardness (Shore D hardness)

A sheet having a thickness of about 2 mm was formed by injection molding using the composition for the casing, and stored at 23° C. for 2 weeks. In order not to be affected by the measurement substrate, etc., an automatic rubber hardness tester made by Polymer Meter Co., Ltd., equipped with a spring-type hardness tester Shore D type in accordance with ASTM-D2240, was used in a state where three or more sheets were stacked. Type P1, for the assay.

(4) Core hardness distribution (JIS-C hardness)

The JIS-C hardness of the core surface portion was measured as the core surface hardness using an automatic rubber hardness meter P1 manufactured by Polymer Meter Co., Ltd. with a spring-type hardness meter JIS-C type. In addition, the spherical core was cut into a hemispherical shape, and the hardness at the center of the cut surface and at a predetermined distance from the center was measured. In addition, the hardness at four points at a predetermined distance from the center was measured, and the average value thereof was used to calculate the core hardness.

(5) Kick-off flight distance (m) and spin amount (rpm)

Mount the metal head W#1 wood (manufactured by SRI Sports Co., Ltd., XXIO Sloft 11°) on the swing robot M/C manufactured by Golfura Boratori, and hit the golf ball at a head speed of 40 m/sec. The spin speed and flight distance (the distance from the launch start point to the rest point) of the golf ball immediately after impact were measured. Each golf ball was measured 12 times, and the average value was taken as the measured value of the golf ball. In addition, the spin speed of the golf ball immediately after impact is measured by continuously photographing the golf ball being hit. The flight distance and amount of spin on the driver's shot are shown as the difference from golf ball (core) No. 11 in Tables 3 to 4, and as the difference from golf ball (core) No. 22 difference display.

[making of golf ball]

(1) Production of the core

Knead the rubber compositions mixed as shown in Table 3 to Table 6 by means of a kneading roller, heat and press at 170°C for 20 minutes in an upper and lower metal mold with a hemispherical cavity, and obtain a spherical ball with a diameter of 39.8mm nuclear.

[table 3]

[Table 4]

[table 5]

[Table 6]

BR730: Made by JSR Corporation, high cis polybutadiene (cis-1,4-bonded content=96% by mass, 1,2-ethylene bonded content=1.3% by mass, Mooney viscosity (ML ₁₊₄ (100°C))=55, molecular weight distribution (Mw/Mn)=3)

Sanceler SR: Zinc acrylate manufactured by Sanshin Chemical Industry Co., Ltd. (10 mass% stearic acid surface coating product)

Zinc Oxide: "Silver Ridge R" manufactured by Toho Yaben Co., Ltd.

Barium sulfate: "Barium sulfate BD" manufactured by Sakai Chemical Co., Ltd. Adjust the weight of the final golf ball to 45.4g

2-Naphthalenethiol (2-Thio naphthol): manufactured by Tokyo Chemical Industry Co., Ltd.

Dicumyl peroxide: manufactured by NOF Corporation, "Pa-kumil (registered trademark) D (dicumyl peroxide)"

Zinc octoate: manufactured by Mitsuwa Chemical Co., Ltd. (purity: 99% or more)

Zinc laurate: manufactured by Mitsuwa Chemical Co., Ltd. (purity: 99% or more)

Zinc myristate: manufactured by NOF (purity 90% or more)

Zinc stearate: manufactured by Wako Pure Chemical Industries, Ltd. (purity 99% or more)

(2) Production of the shell

Next, the materials for shells mixed as shown in Table 7 were extruded with a twin-screw kneading type extruder to prepare a composition for shells in granular form. Extrusion was carried out under the conditions of a screw diameter of 45 mm, a screw rotation speed of 200 rpm, and screw L/D=35. The mixture is heated at 150-230°C at the die position of the extruder. The obtained cover composition was injection-molded on the spherical core obtained as described above to prepare a golf ball having a spherical core and a cover covering the core.

[Table 7]

Composition No. for casing A B Himilan 1605 50 - Himilan 1706 50 - Elastollan XNY97A - 100 Titanium oxide 4 4 Slab hardness (Shore D) 65 47

Mixing: parts by mass

Himilan 1605 (Himilan 1605): Sodium ion-neutralized ethylene-methacrylic acid copolymer-based ionomer resin manufactured by Mitsui DuPont Poly Chemical Co., Ltd.

Himilan 1706 (Himilan 1706): Zinc ion-neutralized ethylene-methacrylic acid copolymer-based ionomer resin manufactured by Mitsui DuPont Poly Chemical Co., Ltd.

エラストラン XNY97A (Elastollan XNY97A): thermoplastic polyurethane elastomer made by BASF Japan Co., Ltd.

From the results of Tables 3 to 6, it can be seen that golf balls having a core and at least one layer or more of a shell covering the spherical core have a long flight distance when hitting the tee shot, and the core of the golf ball is Containing (a) a base rubber, (b) an α,β-unsaturated carboxylic acid with 3 to 8 carbon atoms and/or a metal salt thereof as a co-crosslinking agent, (c) a crosslinking initiator, (d) A carboxylate having 1 to 13 carbon atoms. Any one of such golf balls,.

Industrial availability

The golf ball of the present invention has a large flight distance on a tee shot.

Claims (10)

1. a golf, is characterized in that, have the shell of spherical ball and at least coated described spherical ball of one deck, described spherical ball is formed by rubber composition,

Described rubber composition contains the α that (a) substrate rubber, (b) as the carbon number of co-crosslinker are 3 ~ 8, and beta-unsaturated carboxylic acid and/or its slaine, (c) cross-linked evocating agent, (d) carbon number are the carboxylate of 1 ~ 13;

When (b) only contains as co-crosslinker the α that carbon number is 3 ~ 8, during beta-unsaturated carboxylic acid, described rubber composition is further containing (e) metallic compound;

In described rubber composition, relative to (a) substrate rubber 100 mass parts, (b) carbon number containing 15 mass parts ~ 50 mass parts is the α of 3 ~ 8, beta-unsaturated carboxylic acid and/or its slaine, (c) cross-linked evocating agent of 0.2 mass parts ~ 5 mass parts, (d) carbon number of 0.5 mass parts ~ 30 mass parts is the carboxylate of 1 ~ 13.

2., as the golf that claim 1 is recorded, wherein, in described rubber composition, relative to (a) substrate rubber 100 mass parts, (d) carbon number containing 1.5 mass parts ~ 20 mass parts is the carboxylate of 1 ~ 13.

3., as the golf that claim 1 is recorded, wherein, the described case hardness of spherical ball and the difference of hardness of core rigidities are shown in more than 30 with JIS-C scale of hardness.

4., as the golf that claim 1 is recorded, wherein, in described rubber composition, be the α of 3 ~ 8 as the carbon number of co-crosslinker containing (b), the slaine of beta-unsaturated carboxylic acid.

5. as the golf that claim 1 is recorded, wherein, described (d) carbon number is the carboxylate of 1 ~ 13 is soap.

6., as the golf that claim 5 is recorded, wherein, described soap is fatty acid zinc salt.

7. as the golf that claim 1 is recorded, wherein, described rubber composition is further containing (f) organosulfur compound.

8., as the golf that claim 7 is recorded, wherein, described (f) organosulfur compound is benzenethiol class, diphenyl disulfide compound class, thionaphthol class, thiuram disulfides class or their slaine.

9. as the golf that claim 7 is recorded, wherein, in described rubber composition, relative to (a) substrate rubber 100 mass parts, (f) organosulfur compound containing 0.05 mass parts ~ 5 mass parts.

10. as the golf of claim 1 ~ 9 any one record, wherein, in described rubber composition, relative to (a) substrate rubber 100 mass parts, (b) carbon number containing 20 mass parts ~ 45 mass parts is the α of 3 ~ 8, beta-unsaturated carboxylic acid and/or its slaine.