JP2003052853A - Thread winding golf ball - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a golf ball keeping a good ball hitting feeling peculiar to a thread winding golf ball and having a large carry. SOLUTION: This thread winding golf ball includes a solid center, a thread rubber layer formed by winding round the surface of the solid center, and a cover for covering the surface of the thread rubber layer, and the golf ball has dimples formed on the surface of the cover. When load of 9.8 N to 294 N is applied to the solid center, the deformation amount of the solid center is 1.0 to 1.5 m, the difference (A1-A2) between the diameter A1 of the solid center and the thickness A2 of the thread rubber layer is 34.5 to 36.5 mm, the Shore D hardness of the cover is 44 to 58, and the dimple volume rate Rv and the difference (A1-A2) between the diameter of the solid center and the thickness of the thread rubber layer satisfy the following expression: 2.45<=(A1-A2)×Rv<=29.0.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thread-wound golf ball, and more particularly, by setting the difference between the solid center diameter and the thickness of the thread rubber layer, and by setting the optimum dimple volume ratio, a good shot feeling is maintained, The present invention relates to a thread-wound golf ball with an improved flight distance.

[0002]

2. Description of the Related Art Proposals for improving the flight distance of thread-wound golf balls have conventionally specified the properties of the solid center of the thread-wound golf ball, such as the diameter, hardness, specific gravity or rebound of the solid center, and the hardness of the cover. It is done by.

For example, in Japanese Unexamined Patent Publication No. 60-72573, a highly elastic solid center having a diameter of 33 to 38 mm and a JIS-C hardness of 65 to 90 has a diameter of 1-2.
A thread-wound golf ball having a thread rubber wound around a thickness of 5 mm is disclosed.

Further, in JP-A-60-168471, in the case of a 1.62 inch size ball, the solid center has an outer diameter of 27 to 30 mm.
The hardness is 75 to 85, the mass is 20.5 to 23.5 g, and in the case of a 1.68 inch size ball, the solid center has an outer diameter of 28 to 32 mm, the JIS-A hardness is 70 to 80, and the mass is In addition to 17.5 to 21.0 g, the cover has a Shore D hardness of 65 or more and a softening point of 5
A thickness of 1.5 to 2.0 depending on the ionomer resin at 0 ° C or higher
A thread wound golf ball formed in mm is disclosed.

Recently, in addition to the above-mentioned properties of the solid center or the hardness of the cover to improve the flight distance, in addition to the properties of the solid center or the hardness of the cover, the dimple Proposals have been made in which properties such as the number of dimples or the dimple volume ratio are taken into consideration in a composite manner.

For example, in Japanese Patent No. 2886804, the outer diameter is 27 to 38 mm, the amount of deformation under a load of 30 kg is 1.5 to 3.5 mm, and the rebound when dropped from a height of 120 cm. Has a solid center of 96 cm or more and the number of dimples is 350 to 500
Disclosed is a thread-wound golf ball formed from individual dimples having a dimple volume ratio of 0.76 to 0.9%, an outer cover having a Shore D hardness of 40 to 55, and an inner cover having a Shore D hardness of 55 to 68. Has been done.

However, although the conventional proposal for improving the flight distance of the thread-wound golf ball considering only the properties of the solid center is a proposal for improving the flight distance by improving the initial flight conditions, the flight distance is improved. It does not consider the optimization of the trajectory that affects the.

Further, in the proposal considering the properties of the dimples in addition to the properties of the solid center, the initial flight condition and the optimization of the trajectory are individually considered, but the trajectory corresponding to the initial flight condition is considered. No further optimization is considered.

[0009]

The present invention considers the combination of the diameter of the solid center and the rubber thread layer to improve the initial flight conditions and to set the optimum dimple volume ratio corresponding to the initial flight conditions. The present invention aims to solve the above problems by further optimizing the trajectory to improve the flight distance while maintaining a good shot feeling.

[0010]

A thread-wound golf ball according to the present invention comprises a solid center and a thread rubber layer formed by winding the solid center on the surface of the solid center.
A thread-wound golf ball including a cover that covers the surface of the thread rubber layer, and having a dimple formed on the surface of the cover, wherein the solid center has a load of 9.8 N to 29.
The amount of deformation of the solid center when a 4N load is applied is 1.0 to 1.5 mm, which is the difference between the diameter A1 of the solid center and the thickness A2 of the thread rubber layer (A1-A2).
Is 34.5 to 36.5 mm, and the shore D of the cover is
The hardness is 44 to 58, and the dimple volume ratio Rv and the difference between the diameter of the solid center and the thickness of the rubber thread layer (A1−A2) are 24.5 ≦ (A1−A2) × Rv.
It is characterized in that the relationship of ≦ 29.0 is satisfied. Further, in the thread-wound golf ball according to the present invention, the surface hardness of the solid center measured by the JIS-C hardness tester is larger than the center hardness, and the hardness difference between the surface hardness and the center hardness is 15 to 35.
Is desirable.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in more detail below. The thread-wound golf ball of the present invention is produced by winding a thread rubber layer on a solid center and forming a cover on the thread rubber layer. .

The solid center of the present invention has a deformation amount of 1.0 to 1.5 mm from the load of 9.8 N to the load of 294 N. It is preferably 1.1 to 1.4 mm, more preferably 1.2 to
It is 1.4 mm. If the amount of deformation is less than 1.0 mm, the launch angle is low, the spin amount is increased, and the flight distance is reduced. If the amount of deformation is more than 1.5 mm, the solid center becomes too soft and the golf ball obtained has an appropriate hardness. This is because the repulsion property is reduced without

The solid center JIS of the present invention
The central hardness measured by the -C hardness meter is preferably 50 to 70. It is more preferably 52 to 68, and even more preferably 54 to 6.
It is 6. If the center hardness of the solid center is lower than 50, the obtained golf ball does not have proper hardness and the resilience is reduced, so that the flight distance is reduced and the center hardness is 70.
If it is higher than the above range, the obtained golf ball becomes too hard and the shot feeling becomes poor.

The solid center JIS of the present invention
The surface hardness measured by a -C hardness meter is preferably 70-90. It is more preferably 73 to 87, and further preferably 76 to 8
It is 5. If the surface hardness of the solid center is lower than 70, the obtained golf ball does not have proper hardness and the resilience is reduced, so that the flight distance is reduced and the surface hardness is 90.
If it is higher than the above range, the obtained golf ball becomes too hard and the shot feeling becomes poor.

Further, the solid center of the present invention is J
The surface hardness (Hs) measured by the IS-C hardness tester is the center hardness (H
The hardness difference (Hs-Hc) between the surface hardness and the center hardness of the solid center is preferably 15 to 35. It is more preferably 16 to 33, and further preferably 18 to 32. This is because if the difference is less than 15, the launch angle becomes low and the spin amount also increases to decrease the flight distance, and if the difference exceeds 35, the resilience decreases and the flight distance decreases.

The diameter of the solid center is A1.
When the thickness of the rubber thread layer is A2, the difference (A1-A2) between the diameter A1 of the solid center and the thickness A2 of the rubber thread layer is 34.5 to 36.5 mm. It is more preferably 34.8 to 36.3 mm, and further preferably 35.0 to 36.0 mm. (A1-A
If 2) is less than 34.5 mm, it means that the solid center diameter is small or the rubber thread layer is thick, so that the spin amount at the time of hitting increases and the flight distance decreases, and (A1-A2) When the value of () exceeds 36.5 mm, the thread rubber layer becomes thin, the resilience of the thread rubber is not exhibited, and the flight distance is reduced.

The cover of the present invention has a Shore D hardness of 44 to.
It is preferably 58. More preferably 45-57
And more preferably 46 to 55. If the Shore D hardness of the cover is less than 44, the spin amount at the time of hitting increases and the flight distance decreases, and if the Shore D hardness exceeds 58, the cover becomes too hard and the shot feeling of the obtained golf ball is high. This is because it gets worse.

During or after the molding of the cover, if necessary, a large number of dimples called dimples are formed on the surface.

Further, it is the difference between the dimple volume ratio Rv, the diameter of the solid center and the thickness of the rubber thread layer (A1-A).
2) and 24.5 ≦ (A1−A2) × Rv ≦ 29.
It is preferable to satisfy the relationship of 0. More preferably 2
5.0 ≦ (A1−A2) × Rv ≦ 28.7, and more preferably 25.3 ≦ (A1−A2) × Rv ≦ 28.
7

Here, the dimple volume ratio Rv (%) is a numerical value calculated by the following formula. In the formula below, V _T
(Mm ³ ) is the total volume of the dimples which is the total volume of the portion surrounded by the dimple concave portion and the surface connecting the dimple openings with a straight line, and V _G (mm ³ ) is a sphere having no dimples on the cover surface. It is the volume of the golf ball assuming that there is. That is, the dimple volume ratio Rv
(%) Is calculated by Rv (%) = 100 × V _T / V _G.

As described above, (A1-A2) is 34.5-
Within the range of 36.5 mm, the spin and repulsive force are optimized and the flight distance can be improved, but (A1-A2)
Is within the range of 34.5-36.5 mm, (A1
The smaller the value of -A2), the larger the spin amount, and the larger the value, the smaller the spin amount. In order to further improve the flight distance, the relationship between (A1-A2) and the property of the dimple should be considered. Considering this, the dimples can be designed according to (A1-A2).

That is, generally, when the dimple volume ratio Rv is large, the lift due to the dimples is small, and when the dimple volume ratio Rv is small, the lift due to the dimples is large. Therefore, (A1-A2) is 34.5 to 3
Within the range of 6.5 mm, (A1-A2) is 3
When the value is close to 4.5 mm and the spin amount is large, the flight distance can be further improved by increasing the dimple volume ratio Rv and decreasing the lift. Also, within the above range, (A1-A2) is 36.5 mm
When the amount of spin is small and the spin amount is small, the flight distance can be further improved by decreasing the dimple volume ratio Rv and increasing the lift.

Therefore, in order to further improve the flight distance, the optimized relationship between (A1-A2) and the dimple volume ratio Rv is the above-mentioned 24.5≤ (A1-A2).
It is possible to further improve the flight distance by forming the dimple volume ratio Rv on the surface of the cover, which is a relational expression of × Rv ≦ 29.0 and is adapted to the solid center diameter A1 and the thickness A2 of the rubber thread layer.

Further, the dimple volume ratio Rv in the present invention is preferably 0.600 to 0.950%. It is more preferably 0.620 to 0.930%, still more preferably 0.640 to 0.910%, and most preferably 0.
It is 700 to 0.810%. When the dimple volume ratio Rv is less than 0.600%, the trajectory of the obtained golf ball is easily blown up and the flight distance is reduced, and when the dimple volume ratio Rv is greater than 0.950%, the golf ball obtained is This is because the trajectory easily drops and the flight distance decreases.

The number of dimples in the present invention is 250.
~ 550 is good. The number is more preferably 300 to 500, and further preferably 320 to 480. When the number of dimples is less than 250, the diameter of each dimple formed on the cover surface is increased, and the sphericity of the obtained golf ball is lowered, and when the number of dimples is more than 550, the dimples are formed on the cover surface. This is because the diameter of each dimple becomes smaller and the effect of disturbing the air flow by the dimple becomes insufficient.

The solid center of the thread-wound golf ball of the present invention comprises a rubber composition containing a base rubber, a co-crosslinking agent, an organic peroxide, a filler and the like.

As the base rubber, natural rubber or synthetic rubber conventionally used for solid golf balls is used, and polybutadiene having a high resilience performance, particularly high cis polybutadiene is preferable. If desired, natural rubber, polyisoprene rubber, styrene polybutadiene rubber, ethylene-propylene-diene rubber (EPDM) and the like may be mixed with the polybutadiene rubber.

As the co-crosslinking agent, a metal salt of α, β-unsaturated carboxylic acid, in particular, an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms such as acrylic acid or methacrylic acid is added to zinc or magnesium. Examples thereof include salts neutralized with monovalent or divalent metal ions such as salts. Zinc acrylate is preferable because it imparts particularly high resilience. The compounding amount of the co-crosslinking agent is 10 to 40 parts by mass, preferably 15 to 35 parts by mass, relative to 100 parts by mass of the base rubber. Compounding amount is 40
This is because if the amount is more than 10 parts by mass, the ball becomes too hard and the shot feeling becomes poor, and if the amount is less than 10 parts by mass, the resilience becomes poor and the flight distance is reduced.

The organic peroxide acts as a cross-linking agent or a curing agent, and is, for example, dicumyl peroxide, 1,1.
-Bis (t-butylperoxy) -3,3,5-trimethylcyclohexane, 2,5-dimethyl-2,5-di (t-
Butyl peroxy) hexane or di-t-butyl peroxide are preferred. The compounding amount of the organic peroxide is 0.5 to 2.0 parts by mass, preferably 0.8 to 1.5 parts by mass, relative to 100 parts by mass of the base rubber. Compounding amount is 0.5
This is because if it is less than about 10 parts by mass, it becomes too soft and the rebound becomes worse and the flight distance decreases, and if it exceeds 2.0 parts by mass it becomes too hard and the shot feeling becomes poor.

The filler may be any filler that is usually blended with the core of a golf ball, such as an inorganic salt (specifically, zinc oxide, barium sulfate, calcium carbonate, etc.), a metal powder having a high specific gravity (eg, tungsten). Powder or molybdenum powder, etc.) and mixtures thereof. The compounding amount of the filler is 20 to 70 parts by mass, preferably 25 to 60 parts by mass, relative to 100 parts by mass of the base rubber. If the compounding amount is less than 20 parts by mass, the mass of the core becomes light, and as a result, the mass of the ball becomes light, which is not preferable, and if the compounding amount exceeds 70 parts by mass, the mass of the core becomes heavy, resulting in the mass of the ball. Is too heavy.

Further, in the solid center of the present invention,
An antiaging agent, a peptizing agent, or other components which can be usually used for producing a core of a solid golf ball may be appropriately blended. The antioxidant is preferably 0.2 to 0.5 parts by mass with respect to 100 parts by mass of the base rubber.

The solid center can be prepared by kneading the above-mentioned rubber composition and vulcanizing and molding it in a mold. The diameter of the solid center of the thread-wound golf ball of the present invention is larger than that of a normal one and is 35.0 to 38.
0 mm is good. More preferably 35.5-37.7 mm
And more preferably 36.0 to 37.5 mm. If the diameter of the solid center is smaller than 35.0 mm, the spin amount upon hitting will increase and the flight distance will decrease, and if the diameter of the solid center is larger than 38.0 mm, the rubber thread layer will be thin and the resilience of the rubber thread will be reduced. This is because the flight distance is reduced without being exhibited, or the cover becomes thin and the durability of the cover is reduced.

On the solid center obtained as described above, a rubber thread layer is then formed. The thread rubber wound on the solid center may be the same as that conventionally used for the thread rubber layer of the thread-wound golf ball. For example, natural rubber, natural rubber and synthetic polyisoprene rubber may be added with sulfur or sulfur. You may use what was obtained by vulcanizing the rubber composition which mix | blended a vulcanization | cure adjuvant, a vulcanization accelerator, an antioxidant, etc.

The thread rubber layer of the present invention can be wound around a solid center by a conventional method for producing a thread wound core of a thread wound golf ball. The thickness of the rubber thread layer is preferably 1.0 to 2.0 mm, more preferably 1.1.
~ 1.8 mm, most preferably 1.2-1.6 m
m. If the thickness of the rubber thread layer is less than 1.0 mm, the resilience of the rubber thread is not exerted, so the flight distance is reduced, and if the thickness of the rubber thread layer is more than 2.0 mm, the spin amount on impact increases. This is because the flight distance is reduced.

A cover is then formed on the obtained rubber thread layer. The base resin component of the cover of the present invention may be only an ionomer resin, but it is a heated mixture of an ionomer resin and an epoxy group-modified thermoplastic elastomer, an ionomer resin, a maleic anhydride modified thermoplastic elastomer, and a glycidyl group-modified thermoplastic elastomer. It may be a heated mixture with a plastic elastomer or a heated mixture of an ionomer resin and a terpolymer of ethylene-unsaturated carboxylic acid ester-unsaturated carboxylic acid. Further, the base resin component of the cover may be a heated mixture of an ionomer resin, a maleic anhydride-modified thermoplastic elastomer or a thermoplastic elastomer having a terminal --OH group, and an epoxy group-modified thermoplastic elastomer.

The above ionomer resin is obtained by neutralizing at least a part of the carboxyl groups in the copolymer of ethylene and (meth) acrylic acid with a metal ion, or ethylene, (meth) acrylic acid and α, β. At least part of the carboxyl groups in the terpolymer of unsaturated carboxylic acid ester is neutralized with metal ions. Further, the ionomer resin is preferably one in which 5 to 80% of the carboxyl groups are neutralized with metal ions.

Examples of ionomers obtained by neutralizing at least a part of the carboxyl groups in the copolymer of ethylene and (meth) acrylic acid with metal ions are commercially available from Mitsui DuPont Polychemical Co., Ltd. High Milan 1555 (Na) "," High Milan 1557 (Z
n) ”,“ HIMIRAN 1601 (Na) ”,“ HIMIRAN 1605 (Na) ”or“ HIMIRAN 1706 (Z
n) ”or the like, or“ Serlin AD8511 (Zn) ”or“ Sarrin AD85 ”commercially available from DuPont, USA
12 (Na) ”and the like.

As an example of a terpolymer ionomer resin obtained by neutralizing at least a part of carboxyl groups in a terpolymer of ethylene, (meth) acrylic acid and α, β unsaturated carboxylic acid ester with a metal ion. Are commercially available from, for example, Mitsui DuPont Polychemical Co., Ltd., “HIMIRAN 1856 (Na)” and “HIMIRAN 1855 (Z
n) ”or“ Himilan AM7316 (Zn) ”or the like, or“ Serlin AD8265 (N) as a terpolymer type ionomer resin commercially available from DuPont, USA.
a) ”or“ Surlyn AD8269 (Na) ”and the like. Incidentally, Na, Zn, etc. described in parentheses after the trade name of the above ionomer resin indicate the types of neutralizing metal ions thereof.

The epoxy group-modified thermoplastic elastomer is
Those having an epoxy group in the elastomer molecule, for example, "Epofriend A1" from Daicel Chemical Industries, Ltd.
Examples thereof include a styrene-butadiene-styrene (SBS) block copolymer having a polybutadiene block containing an epoxy group, which is commercially available under the trade name of "010", "Epofriend A1005" or "Epofriend A1020".

Examples of the maleic anhydride-modified thermoplastic elastomer include various maleic anhydride adducts of hydrogenated styrene-butadiene-styrene block copolymers under the trade name "Tuftec M series" from Asahi Kasei Kogyo Co., Ltd. It is commercially available in the following grades, and is also sold by Sumitomo Chemical Co., Ltd. under the trade name "Bondaine", ethylene-
Ethyl acrylate-maleic anhydride terpolymers are commercially available in various grades, and a graft modified product of ethylene-ethyl acrylate copolymer with maleic anhydride is available from Mitsui DuPont Polychemical Co., Ltd. under the trade name "AR series". They are commercially available and are preferably used in the present invention.

Examples of the glycidyl group-modified thermoplastic elastomer include ethylene-glycidyl methacrylate copolymer and ethylene-glycidyl methacrylate-methyl acrylate ternary copolymer commercially available from Sumitomo Chemical Co., Ltd. under the trade name "Bond First". There are polymers or ethylene-glycidyl methacrylate-vinyl acetate terpolymers, etc., and styrene-butadiene-styrene (SBS) block copolymers commercially available under the trade name "Tuftec Z514" or "Tuftec Z513" from Asahi Kasei Corporation. There are glycidyl methacrylate adducts of combined hydrogenation products. In addition, a terpolymer of ethylene-acrylic acid ester-glycidyl methacrylate, which is commercially available under the trade name "Elvaroy-AS" from DuPont, USA, and the like can be mentioned. The glycidyl group is broadly included in the epoxy group, but the term "epoxy group" is not used here to clarify that it is a glycidyl group.

As the terpolymer consisting of ethylene, unsaturated carboxylic acid ester and unsaturated carboxylic acid, for example, trade name "Neucrele AN4212C" or "Neucrele N0805J" available from DuPont Mitsui Polychemicals Co., Ltd. , An ethylene-isobutyl acrylate-methacrylic acid terpolymer, etc., which are commercially available.

The thermoplastic elastomer having a terminal --OH group has an OH group at the terminal of the elastomer molecule. For example, hydrogenated styrene-isoprene-styrene (SIS) block copolymer commercially available from Kuraray Co., Ltd. Is mentioned.

As described above, in order to achieve a desired hardness by compounding a cover other than the ionomer resin, the ionomer resin and the other resin or elastomer (epoxy group-modified thermoplastic elastomer or maleic anhydride-modified thermoplastic elastomer or The ratio with the terpolymer consisting of ethylene-unsaturated carboxylic acid ester-unsaturated carboxylic acid) is preferably 95: 5 to 20:80.

In addition to the above-mentioned base resin component, various additives such as pigments, dispersants, antioxidants, ultraviolet absorbers or light stabilizers are added to the cover used in the present invention, if necessary. You may.

When the ionomer resin and the other resin or elastomer are used, it is necessary to heat and mix both. Usually, heat mixing is performed by mixing for 1 to 20 minutes. Actually, the temperature is adjusted in the extruder.

In the present invention, in addition to the above-mentioned base resin component as a main component, the cover composition may further contain a filler such as barium sulfate or a coloring agent such as titanium dioxide, if necessary. Additives such as a dispersant, an antioxidant, an ultraviolet absorber, a light stabilizer and a fluorescent material or a fluorescent brightening agent may be contained within a range that does not impair the desired properties of the corfu ball cover. Usually, it is preferable that the blending amount of the colorant is 1.0 to 6.0 parts by mass.

The cover layer of the present invention can be produced by a generally known method used for forming a cover of a golf ball and is not particularly limited.
The cover composition is preliminarily molded into a half-shell-shaped half shell, and the wound core is wrapped by using two of the half shells.
You may use the method of pressure-molding at 170 degreeC for 1 to 5 minutes, or the method of encapsulating a solid core by injection-molding the said composition for covers directly on a wound core.

The cover of the present invention has a thickness of 1.0 to
2.0 mm is good. More preferably 1.1 to 1.9 mm
And more preferably 1.2 to 1.6 mm.
This is because if the thickness of the cover is thinner than 1.0 mm, the durability of the cover is lowered, and if the thickness of the cover is thicker than 1.9 mm, the spin amount upon hitting is increased and the flight distance is shortened.

Further, as the geometrical arrangement of the dimples in the present invention, any mode such as octahedron or icosahedron can be adopted, and as the model of the dimples, a square type, a hexagon type, a triangle type or the like can be adopted. Anything can be adopted.

The thread-wound golf ball of the present invention can be put on the market after being usually coated with paint, marking stamps or the like in order to enhance the appearance and the commercial value.

According to the present invention, it is possible to provide a golf ball having an improved flight distance without impairing the good shot feeling specific to the conventional thread wound golf ball.

[0053]

EXAMPLES The present invention will be described more specifically with reference to examples, but the invention is not limited to these examples.

(1) Preparation of solid center A spherical solid was prepared by kneading the core rubber composition having the composition shown in Tables 1 and 2 and heat-pressing in a mold at 165 ° C. for 23 minutes. Got the center. The blending amount of each component in Table 1 is based on parts by mass. Diameter, mass, center hardness, surface hardness of the obtained solid center,
The hardness difference and the amount of deformation when a load of 9.8 N to 294 N is applied are shown in the same table. The center hardness of the solid center is the center of the solid center divided into two hemispheres,
The cut cross section of the hemisphere was measured using a spring type hardness meter C type specified in JIS-K6301. The surface hardness of the solid center is divided into two parts by dividing the surface of the solid center into hemispheres.
It was measured using a spring type hardness meter C type specified in K6301. Further, the amount of deformation of the solid center was measured by measuring the amount of deformation from the state where an initial load of 9.8 N was applied to the solid center to when the final load of 294 N was applied.

[0055]

[Table 1]

[0056]

[Table 2]

(Note 1) High cis-polybutadiene rubber manufactured by JSR Co., Ltd. (2) Formation of wound layer A base rubber is a natural rubber / around the solid center.
Low cis-isoprene rubber (Shell IR manufactured by Shell Chemical Co.
A thread rubber made of a blend rubber of −309) = 50/50 (mass ratio) was wound to produce a thread wound core of 39.6 mm.

(3) Preparation of Cover Composition The cover ingredients shown in Table 3 were mixed by a twin-screw kneading extruder to obtain a pellet-shaped cover composition. Table 3
The blending amount of each component therein is based on parts by mass. The extrusion conditions were: screw diameter: 45 mm, screw rotation speed: 200 rpm, screw L / D: 35, and the blend was 200 to 260 at the die position of the extruder.
Heated to ° C.

The Shore D hardness of the obtained cover composition is shown in the same table. Shore D hardness is ASTM D-2240
A hot-press molded sheet having a thickness of about 2 mm, which was measured in accordance with the above, and was prepared from the composition for a cover, was stored at 23 ° C. for 2 weeks, and then three or more sheets were stacked using a spring type hardness meter Shore D type. Measured.

[0060]

[Table 3]

(Note 2) Sodium ion neutralized ethylene-methacrylic acid copolymer type ionomer resin manufactured by DuPont Co., Ltd. (Note 3) Zinc ion neutralized ethylene manufactured by DuPont Co., Ltd.
Methacrylic acid copolymer type ionomer resin (Note 4) Block copolymer of styrene-butadiene-styrene structure having epoxy group-containing polybutadiene block manufactured by Daicel Chemical Industries Ltd. (Note 5) Terminal manufactured by Kuraray Co., Ltd. Hydrogenated styrene-isoprene / butadiene-having hydroxyl groups (OH groups) added to
Block Copolymer of Styrene Structure (4) Preparation of Golf Balls of Examples and Comparative Examples Using the obtained cover compositions, hemispherical shell-shaped half shells were formed, and two sheets were used to obtain the above-mentioned products. The wound core was wrapped, press-heat-molded in a mold, and paint was applied on the surface to obtain golf balls of Examples and Comparative Examples having a diameter of 42.8 mm. The number of dimples in this golf ball is 410, and the dimple structure is
50 A dimples with a diameter of 4.3 mm, diameter 3.9 m
There are 210 B dimples of m, 110 C dimples of 3.6 mm in diameter, and 40 D dimples of 3.3 mm in diameter. Further, the dimple wall surface has a single radius in the cross-section. The dimple depth of each of such dimples was changed to obtain the dimple volume ratio Rv shown in the table.

The flight performance of the obtained golf ball was evaluated as to launch angle, spin rate, trajectory elevation angle, trajectory elevation angle-launch angle, flight distance and impact feeling upon impact, and the results are shown in Table 4 below. Examples 1 to 4) and Table 5 (Example 5)
~ 8) and Table 6 (Comparative Examples 1 to 4) and Table 7 (Comparative Examples 5 to 7). Here, the ballistic elevation angle is the angle between the launch point and the straight line connecting the highest peaks of the trajectory viewed from the launch point and the ground. The trajectory elevation angle-launch angle is the angle obtained by subtracting the launch angle from the trajectory elevation angle. A small trajectory results in a drop trajectory, and a large trajectory results in a blow up trajectory.

(5) Test method (i) Flight performance (launching angle, backspin amount, flight distance) A swing head robot manufactured by Trutemper Co., Ltd. was fitted with a wood head No. 1 club (driver) made of metal head, and a golf ball was loaded. The ball was hit at a head speed of 50 m / sec, and the launch angle immediately after launch, the amount of backspin immediately after launch, and the flight distance, which is the distance to the drop point, were measured.

(Ii) Impact Feeling at Hitting 10 golfers made actual hits with a wood No. 1 metal head club, and the impact strength at the time of hitting was evaluated according to the following criteria. It was a shock feeling.

Criteria ○: It is good that there is little impact.

Δ: Normal. ×: The impact is large and bad.

[0067]

[Table 4]

[0068]

[Table 5]

[0069]

[Table 6]

[0070]

[Table 7]

(6) Test Results In Comparative Example 1 and Comparative Example 2, the deformation amount of the solid center is in the range of 1.0 to 1.5 mm, and the Shore D hardness of the cover is in the range of 44 to 58. 24.5 ≦
Although the relational expression of (A1−A2) × Rv ≦ 29.0 is satisfied, the value of (A1−A2) needs to be within the range of 34.5 to 36.5 mm. Is (A
1-A2) has a value of 33.9 mm, and Comparative Example 2 has (A
Since the value of 1-A2) is 37.2 mm, the spin amount is increased in Comparative Example 1 and the resilience of the rubber thread is decreased in Comparative Example 2, so that the flight distance is inferior to that of the example. ing.

In Comparative Example 3, the value of (A1-A2) is 34.
It is in the range of 5 to 36.5 mm, the Shore D hardness of the cover is also in the range of 44 to 58, and 24.5 ≦ (A1-A
2) × Rv ≦ 29.0 is satisfied, but the deformation amount of the solid center is 0.84 mm and the deformation amount of the solid center is not within the range of 1.0 to 1.5 mm, Since the launch angle decreases and the spin amount increases,
The flight distance is inferior to that of the example.

In Comparative Example 4, the flight distance equivalent to that of the Example was measured, but since the Shore D hardness of the cover was 63, the golf ball became too hard, and the impact feeling at the time of impact was carried out. The result is inferior to the example.

In Comparative Example 5 and Comparative Example 6, the deformation amount of the solid center is in the range of 1.0 to 1.5 mm,
The value of (A1-A2) is in the range of 34.5 to 36.5 mm, and the Shore D hardness of the cover is also in the range of 44 to 58, but the value of (A1-A2) × Rv is 24.5. ≤ (A1
−A2) × Rv ≦ 29.0, it is necessary to satisfy the relational expression, Comparative Example 5 is 23.6, and Comparative Example 6 is 30.
6 and does not satisfy the above relational expression, the trajectory of the golf ball is easily blown up in Comparative Example 5, and the trajectory of the golf ball is easily dropped in Comparative Example 6, so the flight distance is inferior to that of the Example. It is the result.

In Comparative Example 7, the flight distance equivalent to that of the Example was measured, but since the Shore D hardness of the cover was 63, the golf ball became too hard, and therefore the impact feeling at the time of hitting was performed. The result is inferior to the example.

In the embodiment of the present invention, the deformation amount of the solid center is within the range of 1.0 to 1.5 mm, (A1
-A2) value is in the range of 34.5-36.5 mm, Shore D hardness of the cover is also in the range of 44-58, (A1-A2) x Rv value is 24.5 ≤ (A1
-A2) x Rv ≤ 29.0 Since all the requirements for satisfying the relational expression are satisfied, it is possible to improve the flight distance without impairing the shot feeling better than the comparative example. Is excellent at.

[0077]

EFFECTS OF THE INVENTION The golf ball of the present invention provides a good feel at impact peculiar to a thread-wound golf ball by defining the load deformation amount of the solid center, the diameter of the solid center, the rubber thread layer thickness and the cover hardness within the specified ranges. The flight initial conditions can be optimized without loss, and the trajectory can be optimized by setting the optimum dimple volume ratio for the flight initial conditions, and the flight distance can be further increased.

Continued front page    (72) Inventor Takahiro Sashima             3-6-9 Wakihama-cho, Chuo-ku, Kobe-shi, Hyogo               Sumitomo Rubber Industries, Ltd.

Claims (2)

[Claims] 1. A solid center, a rubber thread layer formed by winding the surface of the solid center, and a cover for covering the surface of the rubber thread layer, and having dimples formed on the surface of the cover. In the thread-wound golf ball, the amount of deformation of the solid center when a load of 9.8 N to 294 N is applied to the solid center is 1.0 to 1.5 mm, and the difference between the diameter A1 of the solid center and the thickness A2 of the thread rubber layer. (A1-A2) is 34.5 to 36.5 mm, the Shore D hardness of the cover is 44 to 58, and the dimple volume ratio Rv, the diameter of the solid center, and the thickness of the rubber thread layer are differences. (A1-
A thread-wound golf ball characterized by satisfying the following relationship with A2). 24.5 ≦ (A1−A2) × Rv ≦ 29.0 2. The thread-wound golf according to claim 1, wherein a surface hardness of the solid center measured by a JIS-C hardness meter is higher than a center hardness, and a hardness difference between the surface hardness and the center hardness is 15 to 35. ball.