JP2002143348A - One piece solid golf ball - Google Patents

Abstract

(57) Abstract: According to the present invention, there is provided a one-piece solid golf ball having excellent resilience performance and good shot feeling without impairing workability and durability. The present invention provides (i) a Mooney viscosity of 50 to 85 ML.
_{1 + 4} has a ₍₁₀₀ ° C.), a weight average molecular weight (Mw) 70 × 10 ⁴
Polybutadiene (a) synthesized using a nickel-based catalyst having 120120 × 10 ⁴ , and (ii) Mooney viscosity of 30-50
ML _{1 + 4} (100 ℃), Mw 55 × 10 ⁴ or more 70 × 10 ⁴
Polybutadiene (b) synthesized using a cobalt catalyst having a weight ratio (a) / (b) of 95/5 to 70/30, comprising a base rubber comprising a polybutadiene mixture and a vulcanization stabilizer. The vulcanization stabilizer is hydroquinone or a derivative thereof, and the golf ball is JIS-C
It has a center hardness (minimum ball hardness) of 55 to 68 and a surface hardness of 75 to 90 depending on the hardness, and the difference between the maximum and minimum ball hardness is
It relates to a one-piece solid golf ball of 16 to 25.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a one-piece solid golf ball having excellent resilience performance and good shot feeling without impairing workability and durability.

[0002]

2. Description of the Related Art Generally, golf balls are roughly classified into two types, one for rounds and one for practice ranges. The performance required for these two types of golf balls is not necessarily the same. That is, the performance required for the round golf ball is a good shot feeling and excellent flight performance. However, when such a golf ball for a round is used as a golf ball for a driving range, although a good shot feeling and excellent flight performance are maintained, it is extremely durable as a golf ball for a driving range that is repeatedly hit. Will be bad. For this reason, in practice ranges, golf balls having higher durability than golf balls for rounds are used, with durability being prioritized over shot feeling and flight performance.

[0003] The golf balls for practice ranges also include low rebound, low trajectory, high trajectory, water practice balls and the like according to the size of the practice range in which the golf balls are used, the height of the net, and the like. Further, structurally, there are various golf balls such as a one-piece golf ball and a two-piece golf ball, and a one-piece solid golf ball mainly used as a driving range golf ball at present is used.

However, recently, golf balls for driving ranges have been required to have a performance such as a shot feeling that is closer to that of a round golf ball, and even a one-piece solid golf ball having excellent durability has a good shot feeling. And better flight performance. However, if the ball is softened in order to improve the feel at impact, the durability will be reduced, and if the flight performance is to be improved, the durability will be reduced, and the shot feeling and flight performance will be improved without lowering the durability. It was very difficult.

As a general one-piece golf ball composition, a rubber composition containing high-cis polybutadiene, methacrylic acid (or a metal salt of methacrylic acid) as a co-crosslinking agent, and an organic peroxide is widely used. .
When zinc acrylate, which is used as a co-crosslinking agent in a rubber composition for a core of a two-piece golf ball, is used in a one-piece golf ball, the resilience performance is good, but the durability is extremely poor, so that it is not usually used.

Therefore, in order to improve durability and resilience, a solid golf ball using a polybutadiene rubber having a high Mooney viscosity or having a flat hardness distribution has been proposed (for example, JP-A-2-1777973). Gazette,
Patent No. 2,644,226). JP-A-2-1777973 discloses that a rubber composition containing polybutadiene having a high Mooney viscosity (48 to 85 ML _{1 + 4} (100 ° C.)) is obtained by vulcanization molding, and the difference between the maximum value and the minimum value of the hardness is obtained. Is described as a one-piece solid golf ball having a hardness distribution of 15 or less. However, in the above-mentioned golf ball, since polybutadiene rubber having high Mooney viscosity is used, the molecular weight is high and the workability is poor, the resilience is good, but the durability is poor, and the hardness distribution is flattened. There was a problem that the feel at impact deteriorated.

Japanese Patent No. 2644226 discloses Mooney viscosity (45 to 90 ML _{1 + 4} (100 ° C.)), weight average molecular weight (Mw).
A solid golf ball using a rubber composition containing a polybutadiene having a ratio (Mw / Mn) of the rubber composition and a number average molecular weight (Mn) within a specific range is described. However, since polybutadiene having a high Mooney viscosity is used as in the above publication, there is a problem that the molecular weight is high and the processability is poor, and the resilience is good but the durability is poor.

[0008]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems of the conventional one-piece solid golf ball, and provides excellent resilience performance and good shot feeling without impairing workability and durability. It is an object of the present invention to provide a one-piece solid golf ball having:

[0009]

Means for Solving the Problems The present inventors have made intensive studies to achieve the above object, and as a result, have found that polybutadiene synthesized using a nickel catalyst and polybutadiene synthesized using a cobalt catalyst are used. Using a rubber composition containing a mixture and hydroquinone or a derivative thereof as a vulcanization stabilizer, the Mooney viscosity and weight ratio of two types of polybutadiene, the amount of the vulcanization stabilizer, the center hardness of the golf ball (golf ball hardness) By defining the difference between the maximum value and the minimum value of the surface hardness and the hardness of the golf ball within a specific range, excellent resilience performance and good shot feeling can be obtained without impairing workability and durability. It has been found that a one-piece solid golf ball having the same can be obtained, and the present invention has been completed.

That is, the present invention relates to (i) a cis-1,4 bond of 96%
Containing the above, Mooney viscosity 50-85ML _{1 + 4} (100 ℃)
And polybutadiene (a) synthesized using a nickel-based catalyst having a weight average molecular weight (Mw) of 70 × 10 ^{4 to} 120 × 10 ⁴ , and (ii) containing 96% or more of cis-1,4 bonds. And a weight ratio of polybutadiene (b) synthesized using a cobalt-based catalyst having a Mooney viscosity of 30 to 50 ML _{1 + 4} (100 ° C.) and a weight average molecular weight (Mw) of 55 × 10 ⁴ or more and less than 70 × 10 ⁴ (a) / (b) is a base rubber composed of a polybutadiene mixture having 95/5 to 70/30, an unsaturated carboxylic acid and / or a metal salt thereof, an organic peroxide, an inorganic filler, and a vulcanization stabilizer. A one-piece solid golf ball comprising a rubber composition comprising: the vulcanization stabilizer is hydroquinone or a derivative thereof in an amount of 0.05 to 2.0 parts by weight based on 100 parts by weight of a base rubber; It has a center hardness of 55 to 68 and a surface hardness of 75 to 90 depending on the hardness. The golf is the minimum value of the hardness of the ball, the difference between the maximum value and the minimum value of the hardness in the golf ball is on the one-piece solid golf ball is 16-25.

Further, in order to preferably carry out the present invention, the hydroquinone or a derivative thereof is 2,5-di-t-butylhydroquinone, and the polybutadiene (b) synthesized using the cobalt catalyst is Weight average molecular weight (M
It is preferable to have a ratio (Mw / Mn) of w) to the number average molecular weight (Mn) of 3.0 to 5.0.

The one-piece solid golf ball of the present invention comprises a base rubber, a co-crosslinking agent, an organic peroxide, an inorganic filler,
It comprises a vulcanized integral molded product of a rubber composition containing a vulcanization stabilizer and, if necessary, an antioxidant.

The base rubber used in the golf ball of the present invention includes (i) a cis-1,4 bond of 96% or more, a Mooney viscosity of 50 to 85 ML _{1 + 4} (100 ° C.), and a weight average molecular weight. (Mw) polybutadiene (a) synthesized using a nickel-based catalyst having 70 × 10 ^{4 to} 120 × 10 ⁴ , and (i)
i) Contains 96% or more of cis-1,4 bonds and has a Mooney viscosity of 30 to 5
0ML _{1 + 4} (100 ° C), weight average molecular weight (Mw) 55x
A polybutadiene (b) synthesized using a cobalt-based catalyst having 10 ⁴ or more and less than 70 × 10 ⁴ has a weight ratio (a) / (b) of 95/5 to
It is required to consist of a polybutadiene mixture that is 70/30.

The nickel-based catalyst used in the synthesis of polybutadiene (a) in the present invention includes, for example, a one-component system such as nickel diatomaceous earth in which nickel is applied on diatomaceous earth as a carrier, and Raney nickel / titanium tetrachloride. And a three-component catalyst such as a nickel compound / organic metal / boron trifluoride etherate. Examples of the nickel compound include reduced nickel with a carrier, Raney nickel, nickel oxide, nickel carboxylate, and organic nickel complex salt. Examples of the organic metal include trialkylaluminums such as triethylaluminum, tri-n-propylaluminum, triisobutylaluminum, tri-n-hexylaluminum and the like; alkyllithiums such as n-butyllithium, s-butyllithium, t-butyl lithium,
1,4-butanedilithium and the like; dialkyl zinc such as diethyl zinc, dibutyl zinc and the like.

The polymerization of butadiene in the presence of these nickel-based catalysts is generally carried out by adding a butadiene monomer to a reactor and a catalyst such as nickel octanoate or triethylaluminum together with a usual solvent so that desired properties can be obtained. The reaction is carried out at a temperature of 5 to 60 ° C. and a reaction pressure of 1 to about 70 atm.

The polybutadiene (a) used in the present invention
Contains 96% or more cis-1,4-bonds and has a Mooney viscosity of 5
0-85ML_{1 + 4}(100 ° C).
Preferably 50-70, more preferably 55-65 ML_{1 + 4}(100 ℃)
Having. The cis-1,4-bond of the polybutadiene (a) is
If it is less than 96%, sufficient resilience performance cannot be obtained. Above poly
Butadiene (a) has a Mooney viscosity of 50 ML_{1 + 4}(100 ° C)
If it is low, the workability will be good, but the resilience performance will decrease, and 85M
L_{1 + 4}If it is higher than (100 ° C), sufficient resilience performance can be obtained,
Workability is reduced, and productivity is reduced. Used in the present invention
Polybutadiene (a) has a weight average molecular weight (Mw) of 70 × 10
⁴~ 120 × 10⁴, But preferably
Is 80 × 10⁴~ 110 × 10⁴, More preferably 80 × 10⁴~ 100
× 10⁴Having. Mw of polybutadiene (a) is 70 × 10⁴
If it is smaller, the resilience performance will decrease, 120 × 10 ⁴Greater than
And workability falls, and productivity falls.

In the present invention, the polybutadiene (a) has a ratio (Mw / Mn) of the weight-average molecular weight (Mw) to the number-average molecular weight (Mn), which is an index of the molecular weight distribution, of 3.0 to 6.0, preferably 4.0.
It is desirable to have ~ 5.5. If Mw / Mn is less than 3.0, the molecular weight distribution becomes too narrow and polybutadiene
The compatibility with (b) deteriorates, and if it is larger than 6.0, a low molecular weight component is contained, so that the resilience performance decreases. The polybutadiene (a) of the present invention has a number average molecular weight (Mn) of 10 × 10 ⁴ to 30.
× 10 ⁴ , preferably 15 × 10 ^{4 to} 25 × 10 ⁴ . If the Mn of the polybutadiene (a) is smaller than 10 × 10 ⁴ , sufficient resilience cannot be obtained, and 30 × 10 ⁴
If it is larger, the workability is deteriorated.

A specific example of the above-mentioned polybutadiene (a) is given by a trade name, and BR-B commercially available from JSR Corporation is
18 and the like.

Here, "Mooney viscosity" is an index of industrial viscosity measured by a Mooney viscometer, which is a kind of rotary plasticity meter, and is often used in the rubber industry to measure the viscosity of compounded rubber. Can be When the compound rubber is hermetically filled in the cavity formed by the cylindrical die and the rotor at the center, and the rotor is rotated at a test temperature of 100 ° C., a preheating time of 1 minute, a rotation time of the rotor of 4 minutes, and a rotation speed of 2 rpm. Is obtained by the torque value generated in ML as unit symbol
_{1 + 4} (100 ° C.), where M is Mooney viscosity, L is the shape of the rotor and represents a large rotor (L type), (1 + 4) is 1 minute of preheating time, 4 minutes of rotating time of the rotor, 100 ° C.
Represents the test temperature, which is used (JIS K 6300).

In the present invention, the cobalt catalyst used for the synthesis of polybutadiene (b) includes elemental cobalt and Raney cobalt, cobalt chloride, cobalt bromide, cobalt iodide, cobalt oxide, cobalt sulfate, cobalt carbonate, cobalt phosphate. , Cobalt nontalate, cobalt carbonyl, cobalt acetylacetonate, cobalt diethyl dithiocarbamate, [(C ₂ H ₅ ) ₂ NCS ₂ ] ₂
Co, cobaltanilinium nitrite, [(C ₆ H ₅
NH ₃ ) ₃ .Co (NO ₂ )], cobalt dinitrosyl chloride, and the like. In particular, these cobalt compounds and dialkylaluminum monochlorides (eg, diethylaluminum monochloride and diisobutylaluminum monochloride), trialkylaluminums (eg, triethylaluminum, tri-n-propylaluminum, triisobutylaluminum and tri-n- A combination with hexyl aluminum) and aluminum chloride, or a combination with alkyl aluminum sesquichloride (Al ₂ R ₃ Cl ₃ ) (for example, ethyl aluminum sesquichloride) and aluminum chloride is preferable as the cobalt-based catalyst.

The polymerization of butadiene in the presence of these cobalt-based catalysts is generally carried out in the same manner as nickel-based catalysts.
A butadiene monomer is added to a reactor together with a cobalt-based catalyst, usually a solvent, and the reaction is performed at a temperature of 5 to 60 ° C. and a reaction pressure of 1 to about 70 atm so as to obtain desired characteristics.

The polybutadiene (b) used in the present invention
Contains 96% or more cis-1,4-bonds and has a Mooney viscosity of 3
It is required to have 0-50ML _{1 + 4} (100 ° C),
Preferably it has 33-43 ML _{1 + 4} (100 ° C.). If the cis-1,4-bond of the polybutadiene (b) is less than 96%, sufficient resilience cannot be obtained. If the Mooney viscosity of the above polybutadiene (b) is lower than 30 ML _{1 + 4} (100 ° C.), the workability will be good, but the resilience performance will decrease. If it is higher than 50 ML _{1 + 4} (100 ° C.), the durability will decrease. , Workability is significantly reduced. The polybutadiene (b) used in the present invention has a weight average molecular weight (M
w) It is required to have 55 × 10 ⁴ or more and less than 70 × 10 ^4, but preferably 58 × 10 ^{4 to} 65 × 10 ⁴ . If the Mw of the polybutadiene (b) is smaller than 55 × 10 ⁴ , the resilience performance will be reduced, and if it is 70 × 10 ⁴ or more, the durability will be reduced.

In the present invention, the polybutadiene (b) has a ratio (Mw / Mn) between the weight average molecular weight (Mw) and the number average molecular weight (Mn), which is an index of the molecular weight distribution, 3.0 to 5.0, preferably 2.5 to 2.5.
It is desirable to have ~ 4.5. If Mw / Mn is less than 3.0, the high molecular weight component is low and the low molecular weight component is also low, so that improvement in durability cannot be expected. If Mw / Mn is higher than 5.0, the molecular weight distribution becomes too wide and the high molecular weight component and the low molecular weight component are separated. , Compatibility is reduced, and processability is deteriorated.

Polybutadiene synthesized using a cobalt-based catalyst generally varies depending on polymerization conditions such as monomer concentration, catalyst concentration, polymerization temperature, type of solvent, etc. Tend to have a broad molecular weight distribution as compared to Therefore, in the present invention, by controlling the Mw / Mn of polybutadiene (b) synthesized using a cobalt-based catalyst having a broader molecular weight distribution within the above specific range, the high molecular weight component and low molecular weight The processability and durability are improved by controlling the ratio of the components.

The polybutadiene (b) of the present invention has a number average molecular weight (Mn) of 10 × 10 ⁴ to 30 × 10 ⁴ , preferably 10 × 10 4
⁴ it is desirable to have a to 25 × 10 ^4. If the Mn of the polybutadiene (b) is smaller than 10 × 10 ⁴ , sufficient resilience cannot be obtained, and if it is larger than 30 × 10 ⁴ , the processability becomes poor.

A specific example of the above-mentioned polybutadiene (b) is given by a trade name. BR23 commercially available from Ube Industries, Ltd.
0, BR230 and the like.

In the present invention, the weight ratio of polybutadiene (a) to polybutadiene (b) in the polybutadiene mixture (a) /
(b) is required to be 95/5 to 70/30, preferably 95/5 to 80/20. If the polybutadiene (a) is less than 70% by weight and the polybutadiene (b) exceeds 30% by weight based on the total weight of the polybutadiene mixture, the resilience performance is reduced, and the polybutadiene (b) is less than 5% by weight and the polybutadiene (a ) Exceeds 95% by weight, the durability is reduced.

In general, when Mw of polybutadiene rubber increases, resilience improves, but durability and processability tend to deteriorate. Conversely, when Mw decreases, processability improves, but resilience increases. Tends to decrease. The polybutadiene rubber (b) alone has good workability but has low resilience, and the polybutadiene rubber (a) alone has high resilience but poor workability and low productivity. By using the above polybutadiene rubbers (a) and (b) together within the above weight ratio range, a one-piece solid golf ball having improved resilience, good workability and excellent durability can be obtained.

As used herein, “workability” refers to
Wrapping around a roll during rubber compound kneading (biting)
The evaluation is based on the rough surface of the dough when extruding a plug (unvulcanized molded product) used during molding. If workability is poor,
Poor winding around the roll, severe roughening of the dough, poor dispersion of the composition, and variations in performance. In addition, the appearance of the plug deteriorates due to the roughened surface of the plug, and the release agent enters and the durability is reduced.

The base rubber used in the present invention may be only the above polybutadiene rubbers (a) and (b), but if desired, natural rubber, polyisoprene rubber, styrene polybutadiene rubber, ethylene-propylene-diene rubber may be used. (EPDM) may be blended.
The total amount of the polybutadiene rubbers (a) and (b) is at least 80% by weight, preferably 90% by weight, based on the total weight of the base rubber.
It is preferable that When the polybutadiene rubbers (a) and (b) are less than 80% by weight, the resilience decreases and the processability decreases.

Examples of the co-crosslinking agent include α, β-unsaturated carboxylic acids having 3 to 8 carbon atoms, such as acrylic acid and methacrylic acid, and monovalent or divalent metal salts thereof such as zinc and magnesium salts. Or a reaction of the above α, β-unsaturated carboxylic acid with a metal oxide such as zinc oxide during mixing of the rubber composition to form a metal salt of α, β-unsaturated carboxylic acid;
Examples include polyfunctional acrylates such as trimethylolpropane triacrylate and polyfunctional methacrylates such as trimethylpropane trimethacrylate. Methacrylic acid or a metal salt of methacrylic acid, which imparts excellent durability to the obtained golf ball, is preferred.
The compounding amount is 19 to 29 parts by weight, based on 100 parts by weight of the base rubber.
Preferably it is 22 to 26 parts by weight. If it is more than 29 parts by weight, it becomes too hard and the feel at impact deteriorates.If it is less than 19 parts by weight, it is necessary to increase the amount of the organic peroxide to obtain appropriate hardness, and high resilience is obtained. Absent.

Organic peroxides act as crosslinkers or hardeners, for example, dicumyl peroxide, 1,1-bis (t
-Butylperoxy) -3,3,5-trimethylcyclohexane, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, di-t-butylperoxide, 2,2-di (t -
Butylperoxy) butane, t-butyl perbenzoate, with dicumyl peroxide being preferred. The compounding amount is 0.1 to 3.0 parts by weight, based on 100 parts by weight of the base rubber,
Preferably it is 1.5 to 2.0 parts by weight. If it is less than 0.1 part by weight, it becomes too soft to obtain high resilience, and if it exceeds 3.0 parts by weight, it is necessary to reduce the amount of the co-crosslinking agent to obtain appropriate hardness, and high resilience is obtained. Absent. Such an organic peroxide is decomposed by heat to generate a radical, and increases the degree of crosslinking between the co-crosslinking agent and the base rubber, thereby improving resilience.

Examples of the inorganic filler include zinc oxide, silicon oxide, barium sulfate, calcium carbonate, aluminum silicate and a mixture thereof. These inorganic fillers are used as a reinforcing agent for improving hardness and strength, and as a specific gravity (weight) adjusting agent, and particularly preferred is zinc oxide which also functions as a vulcanization aid. The blending amount is 10
6060 parts by weight, preferably 12 to 50 parts by weight, and if it exceeds 60 parts by weight, the weight fraction of the rubber component is reduced and the resilience is reduced, and if it is less than 10 parts by weight, it becomes difficult to adjust the ball weight, The durability may deteriorate.

As the vulcanization stabilizer, hydroquinone or a derivative thereof, for example, 2,5-di-t-butylhydroquinone, 2,5-di-t-amylhydroquinone, 2,6-dimethylhydroquinone, bromohydroquinone, 3,5,6
-Tetrachlorohydroquinone and the like. 2,5-Di-t-butylhydroquinone is preferred because it has low toxicity, is a general-purpose product, and has appropriate radical stability.
The blending amount is required to be 0.05 to 2.0 parts by weight, preferably 0.1 to 1.0 part by weight, more preferably 0.1 to 1.0 part by weight.
0.5 parts by weight. If the amount is less than 0.05 part by weight, the effect as a vulcanization stabilizer cannot be sufficiently obtained, and the resilience decreases.If the amount exceeds 2.0 parts by weight, a large amount of a vulcanization initiator is used, so that the whole becomes brittle and has poor durability. Become.

Further, the one-piece solid golf ball of the present invention may be appropriately blended with a pigment such as titanium dioxide, an antioxidant or a peptizer, a softener, and other components which can be generally used in the production of one-piece solid golf balls. Good.

The one-piece solid golf ball of the present invention can be obtained by uniformly kneading the above rubber composition using an appropriate kneading machine such as a kneading roll, a kneader or the like, and vulcanizing and molding in a mold. . Conditions at this time are not particularly limited, but usually 130 to 240 ° C., pressure 2.9 to 11.8 MPa,
It takes 15-60 minutes. Also, multi-stage vulcanization using two or more stages of temperatures may be employed as needed.

In the above ball forming, usually, dimples are formed on the surface of the ball, and after the ball is formed, paint finishing is performed.
Stamps and the like can be applied as needed.

The center hardness of the one-piece solid golf ball of the present invention according to JIS-C hardness is required to be 55 to 68, preferably 58 to 63, more preferably 60 to 63.
It is. If it is less than 55, durability is poor, and it is too soft at the time of hitting, and the shot feeling is unreliable. If it is larger than 68, the core feels hard at the time of hitting, and the shot feeling is poor.

The one-piece solid golf ball of the present invention must have a surface hardness of 75 to 90 according to JIS-C hardness, preferably 80 to 90, more preferably 80 to 87.
It is. If it is smaller than 75, the shot feeling becomes heavy, and the resilience is reduced to reduce the flight distance. If it is larger than 90, it becomes too hard and the shot feeling becomes poor. The term “center hardness” used in the present specification means a hardness measured at a center position of a cut surface of a golf ball produced by vulcanization molding, usually cut into two equal parts. Further, the surface hardness means the hardness measured on the surface of the golf ball produced above.

Further, in the one-piece solid golf ball of the present invention, it is required that the center hardness is the minimum value of the hardness of the golf ball, and the difference between the maximum value and the minimum value of the hardness of the golf ball is 16 to 25. But preferably 20 to
25, more preferably 22-25. If the hardness difference is smaller than 16, the shot feeling is heavy and bad, and the flight performance is reduced,
If it is larger than 25, only the surface becomes too hard, and on the contrary, it becomes brittle, resulting in poor durability.

In general, polybutadiene rubber having a large Mw such as polybutadiene rubber (a) is often used in order to improve the resilience. Although improved, the durability is reduced only with the polybutadiene rubber (a). Therefore, by using the polybutadiene rubbers (a) and (b) together, a one-piece solid golf ball having excellent resilience (flying performance), durability and workability can be obtained. By controlling the difference from the minimum value to an appropriate range, the shot feeling is improved.

In general, the same compression
In a golf ball having (compression deformation), the smaller the difference between the maximum value and the minimum value of the hardness, that is, the flatter the hardness distribution, the higher the resilience. However, if the hardness distribution becomes flat, the shot feeling becomes poor, and the larger the difference in hardness, the better the shot feeling. The above-mentioned prior art (Japanese Unexamined Patent Publication No.
In Japanese Patent Application Laid-Open No. H11-209, a flat hardness distribution with a small difference in hardness is realized by adding a vulcanization stabilizer, and the golf ball obtained thereby has excellent resilience but a poor shot feeling. On the other hand, in the present invention, it is possible to obtain a golf ball having a high rebound and a large difference in hardness by controlling the reaction rate by adding vulcanization stabilizer hydroquinone or a derivative thereof and vulcanizing at a high temperature. And The golf ball of the present invention has the same compression
The surface hardness is higher than that of a golf ball having (compression deformation). Therefore, the surface of the golf ball is hardly damaged, and the durability against the damage is significantly improved.

The golf ball of the present invention has a compression (compression deformation) of 2.0 to 4.0 mm, preferably 2.0 to 4.0 mm, from a state of applying an initial load of 98 N to a state of applying a final load of 1275 N.
~ 3.0mm. If the compression is smaller than 2.0 mm, the ball is too hard and the shot feeling is deteriorated. If it is larger than 4.0 mm, the ball is too soft and the resilience performance is reduced.

At present, the weight of a large-sized ball is specified to be 45.92 g or less according to rules, but there is no standard for the lower limit. The one-piece solid golf ball of the present invention weighs 44.0 to 45.8 g, preferably 44.2 to 45.8 g.
Having. If the ball weighs less than 44.0 g, it loses inertia during the flight, stalls in the latter half of the flight, and reduces the flight distance.
If it is heavier than g, the shot feeling will be heavy and worse.

The diameter of the one-piece golf ball of the present invention can be 41.0 to 44.0 mm, but is preferably 42.67 mm or more, which is suitable for the specification of a large-sized ball, and is usually about 42.75 mm.

The present invention provides a one-piece solid golf ball having excellent resilience performance and good shot feeling without impairing workability and durability.

[0047]

Next, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to these examples.

(Examples 1 to 3 and Comparative Examples 1 to 6) The rubber compositions having the compositions shown in Tables 1 and 2 below were mixed and kneaded, and were mixed in the upper and lower molds having hemispherical cavities. A one-piece golf ball having a diameter of 42.75 mm was produced by hot pressing under the vulcanization conditions shown. Mooney viscosity, Mw and Mn, and cis of the polybutadiene rubber used
Table 1 shows the -1,4-butadiene content.

[0049]

[Table 1]

[0050]

[Table 2]

(Note 1) 2,5-Di-t-butylhydroquinone commercially available from Ouchi Shinko Chemical Industry Co., Ltd. under the trade name “Nocrack NS-7”

[0052]

[Table 3]

(Note 2) Measuring method: JIS K 6300 compliant (Note 3) Measuring method: NMR (nuclear magnetic resonance absorption method) (Note 4) Measuring method: Mw (weight average molecular weight) and Mn
(Number average molecular weight) is determined by gel permeation chromatography using tetrahydrofuran as the organic solvent used for the eluent.
It was measured using (GPC) and calculated from a calibration curve using standard polystyrene.

The compression, restitution coefficient, durability, hardness distribution including center hardness and surface hardness according to JIS-C hardness, and shot feeling of the obtained one-piece solid golf ball were measured or evaluated. The results were shown in Tables 4 and 5. It was shown to. The difference between the maximum value and the minimum value of the ball hardness was calculated, and the results are shown in the same table. The test method was performed as follows.

(Test Method) Compression (Compression Deformation) The amount of compression deformation from when an initial load of 98 N to a final load of 1275 N is applied to a golf ball was measured, and the reciprocal thereof was determined as Comparative Example 1.
Is represented by an index when the value is set to 100. The larger these indices are, the harder it is.

Coefficient of Restitution A stationary golf ball was loaded with a metal cylinder of 198.4 g at 40 m /
The collision was performed at a speed of 2 seconds, and the velocities of the cylinder and the golf ball before and after the collision were measured, and were calculated from the respective velocities and weights. The measurement was performed five times for each golf ball, and the average value was used as the coefficient of restitution of each golf ball, and was expressed as an index when Comparative Example 1 was set to 100. The larger these indices, the better the resilience performance.

Durability The same impact was continuously applied to the golf ball (the golf ball was hit against an iron flat plate at a speed of 45 m / sec), and the number of hits until the golf ball was broken was measured. To
It was expressed as an index when it was set to 100. The larger the value, the better the durability.

Durability (Scratch) Using a golf ball previously scratched in two places,
The durability is evaluated in the same manner as described above. The scratch is made at a depth of 2 mm on the parting line and at the top of the golf ball. The results were expressed as indices when Comparative Example 1 was set to 100 in the same manner as described above.

Hardness and Hardness Distribution A golf ball is cut into two equal parts, and at the center of the cut surface, at positions of 5 mm, 10 mm and 15 mm from the center and at the ball surface, a spring-type hardness tester JI specified in JIS K 6301 is used.
Determined by measuring the JIS-C hardness at 20 ° C using an SC type.

Hitting Feeling The hitting feel is evaluated on a scale of 10 out of 10 points by an actual hitting test with a metal head driver by 10 top amateurs. The higher the score, the better the shot feeling. The evaluation criteria are as follows. Judgment criteria ○: Total score of 80 points or more △: Total score of 60 points or more and less than 80 points ×: Total score of less than 60 points

[0061]

[Table 4]

[0062]

[Table 5]

From the above results, it was confirmed that the golf balls of Examples 1 to 3 of the present invention were superior to the golf balls of Comparative Examples 1 to 6 in resilience performance, durability and shot feeling. Was.

On the other hand, the golf balls of Comparative Examples 1 and 2 are the same as those of the prior art (JP-A-2-177973,
No. 644226), but the coefficient of restitution is equivalent to or slightly lower than that of the example, but the shot feeling deteriorates due to a small hardness difference between the maximum value and the minimum value of the ball hardness. ing. In addition, both have low surface hardness, so that the surface is easily scratched, and the durability of the scratch is very poor.
In the golf ball of Comparative Example 1, the durability was poor because polybutadiene (polybutadiene (a)) having a high Mooney viscosity was used alone. The golf ball of Comparative Example 2 has a low coefficient of restitution because of a large amount of polybutadiene (polybutadiene (b)) having a low Mooney viscosity.

Since the golf ball of Comparative Example 3 did not use a vulcanization stabilizer, the golf ball had a low coefficient of restitution. In the golf ball of Comparative Example 4, since the amount of the vulcanization stabilizer was large, it was necessary to mix a large amount of an organic peroxide to adjust the compression, and the golf ball became brittle as a whole and had extremely poor durability. Has become.

The golf ball of Comparative Example 5 had the same composition as that of Example 1 but had different vulcanization conditions. As a result, the difference in hardness was small and the shot feeling was poor. In addition, since the surface hardness is low, the surface is easily scratched, and the durability of the scratches is very poor. In the golf ball of Comparative Example 6, the hardness difference is within the range of the present invention, but the durability is poor because polybutadiene (polybutadiene (a)) having a high Mooney viscosity is used alone.

[0067]

The one-piece solid golf ball of the present invention comprises a mixture of polybutadiene synthesized using a nickel-based catalyst and polybutadiene synthesized using a cobalt-based catalyst, and hydroquinone or a derivative thereof as a vulcanization stabilizer. Using the rubber composition contained, Mooney viscosity and weight ratio of two kinds of polybutadiene, blending amount of vulcanization stabilizer, center hardness of golf ball (minimum value of golf ball hardness), surface hardness and hardness in golf ball By defining the difference between the maximum value and the minimum value in a specific range, the resilience performance and shot feeling can be improved without impairing workability and durability.

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Claims (3)

[Claims] (1) containing at least 96% of cis-1,4 bonds,
Polybutadiene (a) synthesized using a nickel-based catalyst having a Mooney viscosity of 50 to 85 ML _{1 + 4} (100 ° C.) and a weight average molecular weight (Mw) of 70 × 10 ^{4 to} 120 × 10 ⁴ , and
(ii) Contains 96% or more of cis-1,4 bonds and has a Mooney viscosity of 30
5050 ML _{1 + 4} (100 ° C.), weight average molecular weight (Mw) 5
The weight ratio (a) / (b) of polybutadiene (b) synthesized using a cobalt-based catalyst having 5 × 10 ⁴ or more and less than 70 × 10 ⁴ is 95
A one-piece solid golf ball comprising a rubber composition containing a base rubber comprising a polybutadiene mixture of / 5 to 70/30, a co-crosslinking agent, an organic peroxide, an inorganic filler, and a vulcanization stabilizer, The vulcanization stabilizer is hydroquinone or its derivative 0.05 to 2.0 parts by weight based on 100 parts by weight of the base rubber.
Parts by weight, the golf ball has a center hardness of 55 to 68 according to JIS-C hardness and a surface hardness of 75 to 90, and the center hardness is the minimum value of the hardness of the golf ball. A one-piece solid golf ball having a difference between a maximum value and a minimum value of 16 to 25. 2. The one-piece solid golf ball according to claim 1, wherein the hydroquinone or a derivative thereof is 2,5-di-t-butylhydroquinone. 3. The polybutadiene (b) synthesized using the cobalt-based catalyst has a weight average molecular weight (Mw) to number average molecular weight (Mn) ratio (Mw / Mn) of 3.0 to 5.0. Or a one-piece solid golf ball according to 2.