Patent Grant
10507361
This application claims priority on Patent Application Nos. 2016-166388 and 2016-166389 filed in JAPAN on Aug. 29, 2016. The entire contents of these Japanese Patent Applications are hereby incorporated by reference.
The present invention relates to golf balls. Specifically, the present invention relates to golf balls having dimples on the surfaces thereof.
Golf balls have a large number of dimples on the surfaces thereof. The dimples enhance the aerodynamic characteristics of the golf balls.
A golf ball having minute projections and minute recesses together with dimples has been proposed. The projections and the recesses can contribute to aerodynamic characteristic, spin performance, appearance, ease of production, and the like.
JP2015-142599 (US2015/0182805) discloses a golf ball including a paint layer having large roughness. The roughness can be formed by blasting or the like. The paint layer enhances the aerodynamic characteristic of the golf ball.
A golf ball that is hit with a golf club flies in the air. The golf ball falls and rolls on the ground. At the time of falling and at the time of rolling, the golf ball comes into contact with the ground. As a result of the contact, soil or mud may adhere to the surface of the golf ball to soil the surface. When a golf ball is on a fairway or rough, a golf player cannot touch the golf ball. Therefore, the golf player cannot remove dirt on the golf ball. On a green, a golf player can remove dirt on a golf ball. However, the work for the removal takes time and effort. In some cases, the dirt cannot be sufficiently removed even through the work. In some cases, the dirt is not removed even by washing the golf ball with water. The golf ball having the dirt remaining thereon is replaced. The replacement imposes an economic burden on the golf player.
Soil and mud easily adhere to the golf ball disclosed in JP2015-142599, since the roughness of the paint layer is great. The anti-soiling property of the golf ball is not sufficient. Even when the golf ball is washed with water, it is difficult to remove soil and mud from the golf ball. The cleanability of the golf ball is not sufficient.
An object of the present invention is to provide a golf ball having an excellent anti-soiling property and cleanability.
A golf ball according to the present invention has a plurality of dimples and a land. The golf ball further has a large number of minute projections formed on surfaces of the dimples and/or the land. An average pitch Pav of the minute projections is less than 100 μm.
Preferably, an average height Hav of the minute projections is not less than 0.5 μm and not greater than 50 μm.
Preferably, the golf ball satisfies the following mathematical formula:
Lav<3*Tav,
wherein Lav represents an average value of distances L between the minute projections and other minute projections adjacent to the minute projections, and Tav represents an average value of widths T of the minute projections.
The golf ball can have a plurality of rows. Preferably, in each of the rows, a plurality of minute projections are aligned at equal pitches.
The golf ball can include a main body and a paint layer positioned outside the main body. Preferably, the minute projections each have a shape in which a surface shape of the main body is reflected.
According to another aspect, a golf ball according to the present invention has a plurality of dimples and a land. The golf ball further has a large number of minute projections formed on surfaces of the dimples and/or the land. An average pitch Pav of the minute projections is not less than 100 μm.
Preferably, an average height Hav of the minute projections is not less than 0.5 μm and not greater than 50 μm.
Preferably, the golf ball satisfies the following mathematical formula:
Lav>0.5*Tav,
wherein Lav represents an average value of distances L between the minute projections and other minute projections adjacent to the minute projections, and Tav represents an average value of widths T of the minute projections.
The golf ball can have a plurality of rows. Preferably, in each of the rows, a plurality of minute projections are aligned at equal pitches.
The golf ball can include a main body and a paint layer positioned outside the main body. Preferably, the minute projections each have a shape in which a surface shape of the main body is reflected.
The following will describe in detail the present invention based on preferred embodiments with appropriate reference to the drawings.
A golf ball 2 shown in
The golf ball 2 preferably has a diameter of not less than 40 mm and not greater than 45 mm. From the standpoint of conformity to the rules established by the United States Golf Association (USGA), the diameter is particularly preferably not less than 42.67 mm. In light of suppression of air resistance, the diameter is more preferably not greater than 44 mm and particularly preferably not greater than 42.80 mm. The diameter of the golf ball 2 according to the present embodiment is 42.7 mm.
The golf ball 2 preferably has a weight of not less than 40 g and not greater than 50 g. In light of attainment of great inertia, the weight is more preferably not less than 44 g and particularly preferably not less than 45.00 g. From the standpoint of conformity to the rules established by the USGA, the weight is particularly preferably not greater than 45.93 g.
The core 4 is formed by crosslinking a rubber composition. Examples of the base rubber of the rubber composition include polybutadienes, polyisoprenes, styrene-butadiene copolymers, ethylene-propylene-diene copolymers, and natural rubbers. Two or more rubbers may be used in combination. In light of resilience performance, polybutadienes are preferable, and high-cis polybutadienes are particularly preferable.
The rubber composition of the core 4 includes a co-crosslinking agent. Examples of preferable co-crosslinking agents in light of resilience performance include zinc acrylate, magnesium acrylate, zinc methacrylate, and magnesium methacrylate. The rubber composition preferably includes an organic peroxide together with a co-crosslinking agent. Examples of preferable organic peroxides include dicumyl peroxide, 1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, and di-t-butyl peroxide.
The rubber composition of the core 4 may include additives such as a filler, sulfur, a vulcanization accelerator, a sulfur compound, an anti-aging agent, a coloring agent, a plasticizer, and a dispersant. The rubber composition may include a carboxylic acid or a carboxylate. The rubber composition may include synthetic resin powder or crosslinked rubber powder.
The core 4 has a diameter of preferably not less than 30.0 mm and particularly preferably not less than 38.0 mm. The diameter of the core 4 is preferably not greater than 42.0 mm and particularly preferably not greater than 41.5 mm. The core 4 may have two or more layers. The core 4 may have a rib on the surface thereof. The core 4 may be hollow.
The mid layer 6 is formed from a resin composition. A preferable base polymer of the resin composition is an ionomer resin. Examples of preferable ionomer resins include binary copolymers formed with an α-olefin and an α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms. Examples of other preferable ionomer resins include ternary copolymers formed with: an α-olefin; an α,β-unsaturated carboxylic acid having 3 to 8 carbon atoms; and an α,β-unsaturated carboxylate ester having 2 to 22 carbon atoms. For the binary copolymer and the ternary copolymer, preferable α-olefins are ethylene and propylene, while preferable α,β-unsaturated carboxylic acids are acrylic acid and methacrylic acid. In the binary copolymer and the ternary copolymer, some of the carboxyl groups are neutralized with metal ions. Examples of metal ions for use in neutralization include sodium ion, potassium ion, lithium ion, zinc ion, calcium ion, magnesium ion, aluminum ion, and neodymium ion.
Instead of an ionomer resin, the resin composition of the mid layer 6 may include another polymer. Examples of the other polymer include polystyrenes, polyamides, polyesters, polyolefins, and polyurethanes. The resin composition may include two or more polymers.
The resin composition of the mid layer 6 may include a coloring agent such as titanium dioxide, a filler such as barium sulfate, a dispersant, an antioxidant, an ultraviolet absorber, a light stabilizer, a fluorescent material, a fluorescent brightener, and the like. For the purpose of adjusting specific gravity, the resin composition may include powder of a metal with a high specific gravity such as tungsten, molybdenum, and the like.
The mid layer 6 has a thickness of preferably not less than 0.2 mm and particularly preferably not less than 0.3 mm. The thickness of the mid layer 6 is preferably not greater than 2.5 mm and particularly preferably not greater than 2.2 mm. The mid layer 6 has a specific gravity of preferably not less than 0.90 and particularly preferably not less than 0.95. The specific gravity of the mid layer 6 is preferably not greater than 1.10 and particularly preferably not greater than 1.05. The mid layer 6 may have two or more layers.
The cover 8 is formed from a resin composition. A preferable base polymer of the resin composition is an ionomer resin. The golf ball 2 that includes the cover 8 including the ionomer resin has excellent resilience performance. The ionomer resins described above for the mid layer 6 can be used for the cover 8.
Instead of an ionomer resin, the resin composition of the cover 8 may include another polymer. Examples of the other polymer include polystyrenes, polyamides, polyesters, polyolefins, and polyurethanes. The resin composition may include two or more polymers.
The resin composition of the cover 8 may include a coloring agent, a filler, a dispersant, an antioxidant, an ultraviolet absorber, a light stabilizer, a fluorescent material, a fluorescent brightener, and the like in an adequate amount. When the hue of the golf ball 2 is white, a typical coloring agent is titanium dioxide.
The cover 8 has a thickness of preferably not less than 0.2 mm, more preferably not less than 0.4 mm, and particularly preferably not less than 0.6 mm. The thickness of the cover 8 is preferably not greater than 2.5 mm and particularly preferably not greater than 2.2 mm. The cover 8 has a specific gravity of preferably not less than 0.90 and particularly preferably not less than 0.95. The specific gravity of the cover 8 is preferably not greater than 1.10 and particularly preferably not greater than 1.05.
In
The area S of the dimple 12 is the area of a region surrounded by the contour line of the dimple 12 when the central point of the golf ball 2 is viewed at infinity. In the case of a circular dimple 12, the area S is calculated by the following mathematical formula.
S=(Dm/2)2*π
In the present invention, the ratio of the sum of the areas S of all the dimples 12 relative to the surface area of the phantom sphere 16 is referred to as an occupation ratio. From the standpoint that sufficient turbulization is achieved, the occupation ratio So is preferably not less than 75%. The occupation ratio So is preferably not greater than 95%.
From the standpoint that a sufficient occupation ratio is achieved, the total number N of the dimples 12 is preferably not less than 250. From the standpoint that each dimple 12 can contribute to turbulization, the total number N of the dimples 10 is preferably not greater than 450.
In the present invention, the “volume of the dimple” means the volume of a portion surrounded by the surface of the phantom sphere 16 and the surface of the dimple 12. In light of suppression of rising of the golf ball 2 during flight, the total volume of all the dimples 12 is preferably not less than 450 mm3. In light of suppression of dropping of the golf ball 2 during flight, the total volume is preferably not greater than 750 mm3.
The minute projections 18a, which belong to the first row I, and the minute projections 18b, which belong to the second row II, may be arranged zigzag. In other words, the positions of the minute projections 18a, which belong to the first row I, may be displaced relative to the positions of the minute projections 18b, which belong to the second row II, in the extending direction A.
In
For each minute projection 18, one pitch P is determined. An average pitch Pav is calculated by summing the pitches P of all the minute projections 18 and dividing the sum of the pitches P by the number of the minute projections 18. The average pitch Pav is preferably less than 100 μm. Particles of soil are less likely to adhere to the golf ball 2 in which the average pitch Pav is less than 100 μm. The golf ball 2 has an excellent anti-soiling property. On the golf ball 2 in which the average pitch Pav is less than 100 μm, water drops are less likely to enter between each minute projection 18 and the minute projection 18 adjacent thereto. Therefore, even when the surface of the minute projection 18 is soiled, if the minute projection 18 is washed with water, the water flows while taking in the dirt. The golf ball 2 has excellent cleanability. In light of anti-soiling property and cleanability, the average pitch Pav is more preferably not greater than 95 μm and particularly preferably not greater than 80 μm. From the standpoint that foreign matter is less likely to adhere to each minute projection 18, the average pitch Pav is preferably not less than 10 μm, more preferably not less than 15 μm, and particularly preferably not less than 20 μm.
In
For each minute projection 18, one distance L is determined. An average distance Lav is calculated by summing the distances L of all the minute projections 18 and dividing the sum of the distances L by the number of the minute projections 18. From the standpoint that particles of soil are less likely to adhere, the average distance Lav is preferably not less than 10 μm, more preferably not less than 15 μm, and particularly preferably not less than 20 μm. In light of cleanability, the average distance Lav is preferably not greater than 80 μm, more preferably not greater than 75 μm, and particularly preferably not greater than 70 μm.
The distance between the first minute projection 18c and the second minute projection 18d shown in
For each minute projection 18, one width T is determined. An average width Tav is calculated by summing the widths T of all the minute projections 18 and dividing the sum of the widths T by the number of the minute projections 18. From the standpoint that particles of soil are less likely to adhere, the average width Tav is preferably not less than 10 μm, more preferably not less than 15 μm, and particularly preferably not less than 20 μm. From the standpoint that the top surfaces of the minute projections 18 are less likely to be soiled, the average width Tav is preferably not greater than 60 μm, more preferably not greater than 50 μm, and particularly preferably not greater than 40 μm.
The golf ball 2 satisfies the following mathematical formula.
Lav<3*Tav
In the golf ball 2, the density of the minute projections 18 is high. Particles of soil are less likely to adhere to the golf ball 2. Therefore, the golf ball 2 has an excellent anti-soiling property and cleanability. In light of anti-soiling property and cleanability, the golf ball 2 preferably satisfies the following mathematical formula.
Lav≤2*Tav
The golf ball 2 preferably satisfies the following mathematical formula.
Lav>Tav
In
From the standpoint that particles of soil are less likely to adhere, the average area of the bottom surfaces 24 is preferably not less than 100 μm2, more preferably not less than 225 μm2, and particularly preferably not less than 400 μm2. From the standpoint that the top surfaces of the minute projections 18 are less likely to be soiled, the average area is preferably not greater than 3600 μm2, more preferably not greater than 2500 μm2, and particularly preferably not greater than 1600 μm2.
From the standpoint that particles of soil are less likely to adhere, the ratio of the total area of the bottom surfaces 24 of all the minute projections 18 relative to the surface area of the phantom sphere 16 is preferably not less than 5%, more preferably not less than 15%, and particularly preferably not less than 20%. From the standpoint that the top surfaces of the minute projections 18 are less likely to be soiled, the ratio is preferably not greater than 80%, more preferably not greater than 60%, and particularly preferably not greater than 50%.
In light of anti-soiling property and cleanability, the total number of the minute projections 18 is preferably not less than 500, more preferably not less than 1000, and particularly preferably not less than 2000. In light of anti-soiling property, the total number is preferably not greater than 500000, more preferably not greater than 300000, and particularly preferably not greater than 100000.
As described above, each minute projection 18 includes the projection portion 22 of the main body 10 and the paint layer 20 (see
Soiling of the golf ball 2 is prevented by a physical effect of the minute projections 18. Therefore, it is not necessary to use a cover 8 and a paint layer 20 that have special chemical properties for the purpose of preventing soiling.
The projection portions 22 of the main body 10 are formed simultaneously with formation of the main body 10. For the formation, a mold is used. The cavity face of the mold has a large number of minute recesses. Each recess has a shape that is substantially the inverted shape of the projection portion 22. The mold can be obtained from a master mold. One example of a method for producing the master mold is etching. During etching, a large number of minute maskings are used. By the maskings, projection portions are formed on the master mold. By the projection portions of the master mold, recesses are formed on the mold. The positions of the maskings correspond to the positions of the projection portions of the master mold, correspond to the positions of the recesses of the mold, and correspond to the positions of the minute projections 18 of the golf ball 2. The master mold can be produced by various methods other than etching. Examples of a method other than etching include laser radiation processing.
As described above, the minute projections 18 are formed on the surfaces of the dimples 12 and also on the surface of the land 14 (see
The shape of each minute projection 18 shown in
As is obvious from
The minute projections 118a, which belong to the first row I, and the minute projections 118b, which belong to the second row II, may be arranged zigzag. In other words, the positions of the minute projections 118a, which belong to the first row I, may be displaced relative to the positions of the minute projections 118b, which belong to the second row II, in the extending direction A.
In
For each minute projection 118, one pitch P is determined. An average pitch Pav is calculated by summing the pitches P of all the minute projections 118 and dividing the sum of the pitches P by the number of the minute projections 118. The average pitch Pav is preferably not less than 100 μm. Even when mud is brought into contact with the golf ball in which the average pitch Pav is not less than 100 μm, the mud flows between the minute projections 118 and the minute projections 118 adjacent thereto as a passage. Mud is less likely to adhere to the golf ball. The golf ball has an excellent anti-soiling property. On the golf ball in which the average pitch Pav is not less than 100 μm, water also flows between the minute projections 118 and the minute projections 118 adjacent thereto as a passage. Therefore, even when the surface of the golf ball is soiled, if the golf ball is washed with water, the water flows, while taking in mud. The golf ball has excellent cleanability. In light of anti-soiling property and cleanability, the average pitch Pav is more preferably not less than 110 μm and particularly preferably not less than 120 μm. From the standpoint that a passage is easily formed, the average pitch Pav is preferably not greater than 2 mm.
In
For each minute projection 118, one distance L is determined. An average distance Lav is calculated by summing the distances L of all the minute projections 118 and dividing the sum of the distances L by the number of the minute projections 118. From the standpoint that a passage is easily formed, the average distance Lav is preferably not less than 40 μm, more preferably not less than 60 μm, and particularly preferably not less than 75 μm. The average distance Lav is preferably not greater than 400 μm.
The distance between the first minute projection 118c and the second minute projection 118d shown in
For each minute projection 118, one width T is determined. An average width Tav is calculated by summing the widths T of all the minute projections 118 and dividing the sum of the widths T by the number of the minute projections 118. In light of anti-soiling property, the average width Tav is preferably not less than 40 μm, more preferably not less than 50 μm, and particularly preferably not less than 75 μm. From the standpoint that a passage is easily formed, the average width Tav is preferably not greater than 400 μm.
The golf ball satisfies the following mathematical formula.
Lav>0.5*Tav
On the golf ball, a passage is easily formed between the minute projections 118 and the minute projections 118 adjacent thereto. When the golf ball is washed with water, the water flows while taking in mud. Therefore, the golf ball has an excellent anti-soiling property and cleanability. In light of anti-soiling property and cleanability, the golf ball preferably satisfies the following mathematical formula.
Lav≥Tav
The golf ball preferably satisfies the following mathematical formula.
Lav<1.5*Tav
In
In light of anti-soiling property and cleanability, the average area of the bottom surfaces 124 is preferably not less than 100 μm2, more preferably not less than 225 μm2, and particularly preferably not less than 400 μm2. In light of anti-soiling property, the average area is preferably not greater than 3600 μm2, more preferably not greater than 2500 μm2, and particularly preferably not greater than 1600 μm2.
In light of anti-soiling property and cleanability, the ratio of the total area of the bottom surfaces 124 of all the minute projections 118 relative to the surface area of a phantom sphere is preferably not less than 5%, more preferably not less than 15%, and particularly preferably not less than 20%. In light of anti-soiling property, the ratio is preferably not greater than 80%, more preferably not greater than 60%, and particularly preferably not greater than 50%.
In light of anti-soiling property and cleanability, the total number of the minute projections 118 is preferably not less than 500, more preferably not less than 1000, and particularly preferably not less than 2000. In light of anti-soiling property, the total number is preferably not greater than 500000, more preferably not greater than 300000, and particularly preferably not greater than 100000.
As described above, each minute projection 118 includes the projection portion 122 of the main body and the paint layer 120 (see
Soiling of the golf ball is prevented by a physical effect of the minute projections 118. Therefore, it is not necessary to use a cover 108 and a paint layer 120 that have special chemical properties for the purpose of preventing soiling.
The projection portions 122 of the main body are formed simultaneously with formation of the main body. For the formation, a mold is used. The cavity face of the mold has a large number of minute recesses. Each recess has a shape that is substantially the inverted shape of the projection portion 122. The mold can be obtained from a master mold. One example of a method for producing the master mold is etching. During etching, a large number of minute maskings are used. By the maskings, projection portions are formed on the master mold. By the projection portions of the master mold, recesses are formed on the mold. The positions of the maskings correspond to the positions of the projection portions of the master mold, correspond to the positions of the recesses of the mold, and correspond to the positions of the minute projections 118 of the golf ball. The master mold can be produced by various methods other than etching. Examples of a method other than etching include laser radiation processing.
As described above, the minute projections 118 are formed on the surfaces of the dimples and also on the surface of the land. The minute projections 118 prevent soiling of the dimples and also prevent soiling of the land.
The shape of each minute projection 118 shown in
A rubber composition was obtained by kneading 100 parts by weight of a high-cis polybutadiene (trade name “BR-730”, manufactured by JSR Corporation), 25.5 parts by weight of zinc diacrylate, 12 parts by weight of zinc oxide, an appropriate amount of barium sulfate, 0.5 parts by weight of diphenyl disulfide, 0.9 parts by weight of dicumyl peroxide, 0.1 parts by weight of 2-naphthalenethiol, and 2 parts by weight of benzoic acid. This rubber composition was placed into a mold including upper and lower mold halves each having a hemispherical cavity, and heated at 160° C. for 20 minutes to obtain a core with a diameter of 38.7 mm. The amount of barium sulfate was adjusted such that a core having a predetermined weight was obtained.
A resin composition was obtained by kneading 26 parts by weight of an ionomer resin (trade name “Himilan AM7337”, manufactured by Du Pont-MITSUI POLYCHEMICALS Co., Ltd.), 26 parts by weight of another ionomer resin (trade name “Himilan AM7329”, manufactured by Du Pont-MITSUI POLYCHEMICALS Co., Ltd.), 48 parts by weight of a styrene block-containing thermoplastic elastomer (trade name “RABALON T3221C”, manufactured by Mitsubishi Chemical Corporation), 4 parts by weight of titanium dioxide, and 0.2 parts by weight of a light stabilizer (trade name “JF-90”, manufactured by Johoku Chemical Co., Ltd.) with a twin-screw kneading extruder. The core was covered with this resin composition by injection molding to form a mid layer with a thickness of 1.0 mm.
A resin composition was obtained by kneading 55 parts by weight of an ionomer resin (trade name “Himilan AM7329”, manufactured by Du Pont-MITSUI POLYCHEMICALS Co., Ltd.), 45 parts by weight of another ionomer resin (trade name “Himilan 1555”, manufactured by Du Pont-MITSUI POLYCHEMICALS Co., Ltd.), 4 parts by weight of titanium dioxide, and 0.2 parts by weight of a light stabilizer (trade name “JF-90”, manufactured by Johoku Chemical Co., Ltd.) with a twin-screw kneading extruder. The sphere consisting of the core and the mid layer was placed into a final mold that includes upper and lower mold halves each having a hemispherical cavity and having a large number of pimples and minute recesses on its cavity face. The mid layer was covered with this resin composition by injection molding to form a cover with a thickness of 1.0 mm. Dimples having a shape that is the inverted shape of the pimples were formed on the cover. Furthermore, minute projection portions having a shape that is the inverted shape of the minute recesses were formed on the cover.
A clear paint including a two-component curing type polyurethane as a base material was applied to this cover to obtain a golf ball of Example 1 with a diameter of about 42.7 mm and a weight of about 45.6 g. The golf ball has a large number of minute projections on the surface thereof. The specifications of these minute projections are shown in Table 1 below.
Golf balls of Examples 2 and 6 to 8 and Comparative Example 1 were obtained in the same manner as Example 1, except the final mold was changed and minute projections having an average pitch Pav, an average distance Lav, and an average width Tav shown in Tables 1 and 2 below were formed.
Golf balls of Examples 3 to 5 were obtained in the same manner as Example 1, except the final mold was changed and minute projections having an average height Hav shown in Table 1 below were formed.
A golf ball of Comparative Example 2 was obtained in the same manner as Example 1, except the final mold was changed and no minute projection was formed.
[Anti-Soiling Property]
The golf balls according to each Example and each Comparative Example were put into a bucket together with soil, and the soil was stirred. Thereafter, the degree of soiling of each golf ball was categorized on the basis of the following criteria.
A: There was very little dirt.
B: There was little dirt.
C: There was much dirt.
D: There was very much dirt.
The results are shown in Tables 1 and 2 below.
[Cleanability]
The golf balls subjected to the above anti-soiling property evaluation were put into a bucket together with water, and the water was stirred. Thereafter, the degree of soiling of each golf ball was categorized on the basis of the following criteria.
A: There was very little dirt.
B: There was little dirt.
C: There was much dirt.
D: There was very much dirt.
The results are shown in Tables 1 and 2 below.
As shown in Tables 1 and 2, the golf ball of each Example has an excellent anti-soiling property and cleanability. From the results of evaluation, advantages of the present invention are clear.
A rubber composition was obtained by kneading 100 parts by weight of a high-cis polybutadiene (trade name “BR-730”, manufactured by JSR Corporation), 25.5 parts by weight of zinc diacrylate, 12 parts by weight of zinc oxide, an appropriate amount of barium sulfate, 0.5 parts by weight of diphenyl disulfide, 0.9 parts by weight of dicumyl peroxide, 0.1 parts by weight of 2-naphthalenethiol, and 2 parts by weight of benzoic acid. This rubber composition was placed into a mold including upper and lower mold halves each having a hemispherical cavity, and heated at 160° C. for 20 minutes to obtain a core with a diameter of 38.7 mm. The amount of barium sulfate was adjusted such that a core having a predetermined weight was obtained.
A resin composition was obtained by kneading 26 parts by weight of an ionomer resin (trade name “Himilan AM7337”, manufactured by Du Pont-MITSUI POLYCHEMICALS Co., Ltd.), 26 parts by weight of another ionomer resin (trade name “Himilan AM7329”, manufactured by Du Pont-MITSUI POLYCHEMICALS Co., Ltd.), 48 parts by weight of a styrene block-containing thermoplastic elastomer (trade name “RABALON T3221C”, manufactured by Mitsubishi Chemical Corporation), 4 parts by weight of titanium dioxide, and 0.2 parts by weight of a light stabilizer (trade name “JF-90”, manufactured by Johoku Chemical Co., Ltd.) with a twin-screw kneading extruder. The core was covered with this resin composition by injection molding to form a mid layer with a thickness of 1.0 mm
A resin composition was obtained by kneading 55 parts by weight of an ionomer resin (trade name “Himilan AM7329”, manufactured by Du Pont-MITSUI POLYCHEMICALS Co., Ltd.), 45 parts by weight of another ionomer resin (trade name “Himilan 1555”, manufactured by Du Pont-MITSUI POLYCHEMICALS Co., Ltd.), 4 parts by weight of titanium dioxide, and 0.2 parts by weight of a light stabilizer (trade name “JF-90”, manufactured by Johoku Chemical Co., Ltd.) with a twin-screw kneading extruder. The sphere consisting of the core and the mid layer was placed into a final mold that includes upper and lower mold halves each having a hemispherical cavity and having a large number of pimples and minute recesses on its cavity face. The mid layer was covered with this resin composition by injection molding to form a cover with a thickness of 1.0 mm.
Dimples having a shape that is the inverted shape of the pimples were formed on the cover. Furthermore, minute projection portions having a shape that is the inverted shape of the minute recesses were formed on the cover.
A clear paint including a two-component curing type polyurethane as a base material was applied to this cover to obtain a golf ball of Example 9 with a diameter of about 42.7 mm and a weight of about 45.6 g. The golf ball has a large number of minute projections on the surface thereof. The specifications of these minute projections are shown in Table 3 below.
Golf balls of Examples 10 to 12 and 16 and Comparative Example 3 were obtained in the same manner as Example 9, except the final mold was changed and minute projections having an average pitch Pav, an average distance Lav, and an average width Tav shown in Tables 3 and 4 below were formed.
Golf balls of Examples 13 to 15 were obtained in the same manner as Example 9, except the final mold was changed and minute projections having an average height Hav shown in Tables 3 and 4 below were formed.
A golf ball of Comparative Example 4 was obtained in the same manner as Example 9, except the final mold was changed and no minute projection was formed.
[Anti-Soiling Property]
Soil and water were mixed to obtain mud. The golf balls according to each Example and each Comparative Example were put into a bucket together with the mud, and the mud was stirred. Thereafter, the degree of soiling of each golf ball was categorized on the basis of the following criteria.
A: There was very little dirt.
B: There was little dirt.
C: There was much dirt.
D: There was very much dirt.
The results are shown in Tables 3 and 4 below.
[Cleanability]
The golf balls subjected to the above anti-soiling property evaluation were put into a bucket together with water, and the water was stirred. Thereafter, the degree of soiling of each golf ball was categorized on the basis of the following criteria.
A: There was very little dirt.
B: There was little dirt.
C: There was much dirt.
D: There was very much dirt.
The results are shown in Tables 3 and 4 below.
As shown in Tables 3 and 4, the golf ball of each Example has an excellent anti-soiling property and cleanability. From the results of evaluation, advantages of the present invention are clear.
The aforementioned minute projections are applicable to golf balls having various structures such as a one-piece golf ball, a two-piece golf ball, a four-piece golf ball, a five-piece golf ball, a six-piece golf ball, a thread-wound golf ball, and the like in addition to a three-piece golf ball. The above descriptions are merely illustrative examples, and various modifications can be made without departing from the principles of the present invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2016-166388 | Aug 2016 | JP | national |
| 2016-166389 | Aug 2016 | JP | national |
| Number | Name | Date | Kind |
|---|---|---|---|
| 4438924 | Carr | Mar 1984 | A |
| 20150182805 | Sajima | Jul 2015 | A1 |
| 20160067552 | Hixenbaugh | Mar 2016 | A1 |
| 20160339302 | Nardacci | Nov 2016 | A1 |
| Number | Date | Country | |
|---|---|---|---|
| 20180056138 A1 | Mar 2018 | US |
