JP2016120133A - Golf ball - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a golf ball that provides a unique soft and good hitting feeling which can be fully grasped especially by a senior or professional golf player, and enables a golf play to be performed comfortably and dominantly.SOLUTION: The golf ball comprises a cover 4 of one layer or two or more layers covering a spherical core 10, the core being formed by two layers including an inner layer core 11 of a hollow spherical body the central part of which is formed to be hollow, and an outer layer core 12 that covers the inner layer core. The golf ball satisfies (A)≥10.5 and (C)≤3.7 where (A) represents a deformation amount (mm) of the golf ball when a load from an initial load 98 N (10 kgf) to a final load 5880 N (600 kgf) is applied thereto, and (C) represents the deformation amount (mm) when a load from the initial load 98 N (10 kgf) to the final load 1275 N (130 kgf) is applied.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a golf ball comprising a spherical core and a cover of one layer or two or more layers covering the core, and more specifically, a golf ball having a hit feeling that can be fully satisfied by an advanced player or a professional golfer. About.

  In recent years, as golf populations have increased, golfers' demands for golf balls have been diversified and individualized, and various studies on ball structures have been attempted to meet such demands. Ideally, a golf ball is excellent in terms of the three factors of softness of hit feeling, flight distance, and spin.

  When the driver (W # 1) hits, the hit feeling is good because the whole ball or a part of the ball is greatly bent and is strongly struck, or the sensory evaluation such as feeling the resilience is strong. is there. In addition, a hard ball gives an unpleasant feeling, but a good hit feeling often increases the reliability of the ball and club and often has a positive effect on subsequent play. Therefore, especially for professionals and advanced players, they feel that the softness and softness of the hitting are soft, and in order to obtain a good hitting feeling, a golf ball suitable for the individual sense may be selected.

  In addition, many distance-based golf balls that have been proposed in order to earn a flight distance by a driver have a hard cover to increase the initial velocity at the time of hitting and realize low spin. However, many distance-based golf balls are inferior in spin control and feel at the time of iron. For this reason, although the device which forms a cover material thinly and makes a hit feeling soft and favorable is also proposed, the crack durability after hitting becomes disadvantageous.

  Recently, in order to improve the overall ball performance, the four-layer, five-layer or more four-piece solid golf balls and five-piece golf are more multilayered than the two-piece solid golf balls and the three-piece solid golf balls. Various balls have been proposed. Examples thereof include Japanese Patent Application Laid-Open Nos. 2001-231887, Japanese Patent No. 3362857, and Japanese Patent Application Laid-Open No. 2005-103264. However, although these golf balls can increase the flight distance due to ball rebound (initial speed) and low spin, and can optimize the approach spin amount, the hit feeling is neglected, especially for advanced players and professionals, It was not sufficient in terms of providing a comfortable feel such as softness and playing.

Japanese Patent Laid-Open No. 2001-231887 Japanese Patent No. 3362857 JP 2005-103264 A

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a golf ball capable of obtaining a soft and comfortable hit feeling while maintaining a good flight distance performance.

  As a result of intensive studies to achieve the above object, the present inventor has found that the golf ball is composed of a spherical core and one or two or more layers covering the core, and the core is hollowed at the center. It is formed into two layers of an inner core of a hollow sphere and an outer core covering the core, and the deformation amount (mm) when an initial load of 98 N (10 kgf) to a final load of 5880 N (600 kgf) is applied (mm) A) and the amount of deformation (mm) when loaded from an initial load of 98N (10kgf) to a final load of 1275N (130kgf) is (C), the values of (A) and (C) are specified within a predetermined range. By doing so, it has been found that professionals and advanced players can surely obtain a soft and comfortable hit feeling and can maintain a high flight performance at a certain level, and have made the present invention. That.

Accordingly, the present invention provides the following golf balls.
[1] A golf ball comprising a spherical core and one or two or more covers covering the core, wherein the core comprises a hollow spherical inner layer core having a hollow central portion and the core. It is formed by two layers of the outer layer core to be coated, and the deformation amount (mm) when applied from the initial load 98N (10 kgf) to the final load 5880N (600 kgf) is calculated from (A) and the initial load 98N (10 kgf). A golf ball characterized in that (A) ≧ 10.5 and (C) ≦ 3.7 when the deformation (mm) when loaded to a final load of 1275 N (130 kgf) is (C).
[2] The golf according to [1], wherein the hollow portion of the inner core is filled with a substance selected from the group consisting of air, water, polyvinyl alcohol (PVA) gel, cellulose gel, oily liquid, solid paraffin, and agar. ball.
[3] The golf ball according to [1] or [2], wherein the hollow portion of the inner layer core is a spherical space portion having a diameter of 5 to 18 mm.
[4] The golf ball of [1], [2] or [3], wherein the inner core has an outer diameter of 15 to 25 mm.
[5] The golf ball according to any one of [1] to [4], wherein the core has a diameter of 34 to 40 mm.
[6] The golf ball according to any one of [1] to [5], wherein the inner layer core has a surface hardness (S) in the range of 30 to 90 in terms of JIS-A hardness.
[7] The golf ball according to any one of [1] to [6], wherein in the cover covering the core, two layers of an intermediate layer and an outermost layer are formed from the inside.
[8] The golf ball according to any one of [1] to [6], wherein in the cover covering the core, three layers of an envelope layer, an intermediate layer, and an outermost layer are formed from the inside.
[9] The golf ball according to any one of [1] to [8], wherein the material hardness (Shore D hardness) of the outermost layer is higher than the material hardness of the envelope layer.

  According to the golf ball of the present invention, a soft and comfortable hit feeling can be reliably obtained by professionals and advanced players, and the flight distance can be maintained well.

It is a schematic sectional drawing which shows the structure of the golf ball which concerns on one Example of this invention. It is explanatory drawing for demonstrating the core used by this invention.

Hereinafter, the present invention will be described in more detail.
The golf ball of the present invention has an internal structure of a spherical core and a cover of one or more layers covering the core. Furthermore, the spherical core is formed in a two-layer structure of an inner layer core of a hollow spherical body whose central portion is formed as a cavity and an outer layer core covering the core. Specifically, the golf ball 1 shown in FIG. 1 includes a spherical core 10 and a cover layer 2, an intermediate layer 3 and an outermost layer 4 in order from the inside as a cover covering the core. It has a three-layer cover. A large number of dimples D are formed on the outer surface of the outermost layer. And the spherical core 10 in this golf ball has the inner layer core 11 which has a hollow part, and the outer layer core 12 which coat | covers this inner layer core, as shown in FIG.

  As shown in FIG. 2, the inner layer core 11 has a hollow central portion and has an inner diameter D1 and an outer diameter D2. The diameter (outer diameter) D2 of the inner layer core is preferably 15 mm or more, more preferably 18 mm or more, and the upper limit is preferably 25 mm or less, more preferably 22 mm or less. If it deviates from this range, depending on the material used for the inner layer core, the ball characteristics, particularly the resilience, may be deteriorated.

  The inner diameter D1 of the inner layer core is preferably 5 mm or more, more preferably 8 mm, and the upper limit is preferably 18 mm or less, more preferably 15 mm or less. If it deviates from this range, the effect as a hollow portion may not be obtained, or the characteristics of the ball itself, particularly the durability, may be deteriorated.

  About the material of an inner layer core, a well-known rubber material can be formed as a base material. As the base rubber, a known base rubber such as natural rubber (NR) or synthetic rubber can be used. More specifically, polybutadiene, particularly cis-1,4-having at least 40% of cis structure is used. It is recommended to use mainly polybutadiene. In addition, in the base rubber, natural rubber (NR), polyisoprene rubber (IR), styrene butadiene rubber (SBR) and the like can be used in combination with the above-mentioned polybutadiene if desired.

  Polybutadiene can be synthesized by a metal catalyst such as a rare earth element-based catalyst of Nd catalyst, a cobalt catalyst, or a nickel catalyst.

  The polybutadiene is not particularly limited, but is preferably 60% by mass or more in the base rubber. If this amount is insufficient, it may be difficult to obtain a golf ball imparted with good resilience.

  In addition, rubbers other than the above polybutadiene can be used and blended together as long as the object of the present invention is not impaired. Specific examples include natural rubber (NR), nitrile rubber (NBR), styrene butadiene rubber (SBR), polyisoprene rubber (IR), ethylene propylene diene rubber (EPDM), and the like. These can be used individually by 1 type or in combination of 2 or more types.

  Examples of the base rubber include co-crosslinking agents such as unsaturated carboxylic acids and metal salts thereof, inorganic fillers such as zinc oxide, barium sulfate and calcium carbonate, dicumyl peroxide and 1,1-bis (t-butyl). An organic peroxide such as peroxy) cyclohexane can be blended. Moreover, commercially available anti-aging agent etc. can be added suitably as needed.

  Moreover, a thermoplastic resin can be employ | adopted as a material of an inner layer core. For example, thermoplastic resins such as nylon, polyarylate, ionomer resin, polypropylene resin, polyurethane-based thermoplastic elastomer, and polyester-based thermoplastic elastomer can be used.

  The hollow portion of the inner core may be hollow, but it is filled with contents such as a semi-liquid having a viscosity such as gas, liquid, gel, or a substance whose form changes depending on chemical or physical factors. be able to. Examples of such contents include air, water, polyvinyl alcohol (PVA) gel, polymer gel such as polyurethane gel and cellulose gel, oily liquid such as paraffin oil and oleic acid, solid paraffin, agar, etc. Is mentioned. In this way, by filling the above-mentioned contents into the hollow portion of the inner layer core, the ball feel when hit with a driver (W # 1) is given a soft and comfortable unique feeling. Can do.

  About the filling method to the above-mentioned hollow part, although it changes with kinds and properties of the contents to be filled, for example, various polymer gels are poured into the inner core half cup and sealed, oil / water, etc. Examples thereof include a method of injecting a liquid material into a cavity of an inner layer core prepared in advance with a syringe or the like.

  Here, as shown in FIG. 2, the surface hardness (S) of the inner layer core is not particularly limited, but is preferably in the range of 30 to 90 in terms of JIS-A hardness, and more preferably. Is 60-80. By adjusting the surface hardness of the inner layer core to the above range, it can be expected that a sufficient difference in hardness from the surface hardness of the outer layer core is provided and a desired low spin effect is achieved. Specifically, the hardness difference between the surface hardness (S) of the inner layer core and the surface hardness of the outer layer core is preferably JIS-C hardness (or JIS-A hardness) of 10 to 20, particularly 14 to 17 is preferred.

  On the other hand, the outer layer core is a coating layer that directly covers the inner layer core, and the thickness thereof can be preferably 1 to 25 mm, more preferably 5 to 20 mm.

  About the material of an outer-layer core, a well-known rubber material can be formed as a base material. As the base rubber, a known base rubber such as natural rubber or synthetic rubber can be used. More specifically, polybutadiene, particularly cis-1,4-polybutadiene having at least 40% of cis structure is mainly used. Recommended for use. In the base rubber, natural rubber, polyisoprene rubber, styrene butadiene rubber and the like can be used in combination with the above-mentioned polybutadiene as desired.

  As a vulcanization method and a manufacturing method of the inner layer core and the outer layer core, a known method adopted for a two-layer core (inner layer core / outer layer core) of a golf ball can be used. For example, the inner layer core can be formed by appropriately selecting a rubber composition and vulcanizing and curing the same in the same manner as a known golf ball rubber composition. As for the vulcanization conditions, for example, the vulcanization temperature can be 100 to 200 ° C. and the vulcanization time can be 10 to 40 minutes.

  On the other hand, the method of forming the outer layer core using the rubber composition can also employ a known method, and is not particularly limited, but the following method can be suitably employed. First, an outer layer core-forming material is put into a predetermined mold, and primary vulcanization (semi-vulcanization) is performed to produce a pair of hemispherical half cups. Next, secondary vulcanization (total vulcanization) is performed in a state where the spherical inner layer core prepared in advance is wrapped in the half cup prepared above. That is, a method in which the vulcanization process is divided into two stages can be suitably employed. Also, a method of injecting and molding an outer layer core forming material around the inner layer core can be suitably employed.

  The diameter of the entire core consisting of the inner layer core and the outer layer core (hereinafter simply referred to as “core”) (or corresponding to the outer diameter of the outer layer core) is preferably 30 mm or more, more preferably 34 mm or more. The value is preferably 40 mm or less. If it deviates from this range, it becomes difficult to form a further multilayer structure on the core, and optimal ball characteristics cannot be obtained.

  Deflection amount of the core (the total core including the inner layer core and the outer layer core), that is, the deformation amount from when the initial load of 98 N (10 kgf) is applied to when the final load of 1275 N (130 kgf) is applied to the core Is preferably 2.0 mm or more, more preferably 2.5 mm or more, and the upper limit is preferably 6.0 mm or less, more preferably 5.5 mm or less. If the amount of deformation is too small, the feel may become too hard. If the value of the deformation amount is too large, the feeling of hitting may become too soft, or the ball cracking durability due to peeling from the core upper layer may be deteriorated during repeated hitting.

  Next, the cover will be described in detail. The cover is a member that covers the core and has at least one layer, and examples thereof include a two-layer cover and a three-layer cover. In the case of a two-layer cover, each layer may be referred to as an intermediate layer on the inside and an outermost layer on the outside. In the case of a three-layer cover, each layer may be referred to as an envelope layer, an intermediate layer, and an outermost layer in order from the inside. For example, as shown in FIG. 1, a cover of three layers of an envelope layer 2 that covers the core 10, an intermediate layer 3 that covers the envelope layer 2, and an outermost layer 4 that covers the intermediate layer 3 is illustrated. . Note that a large number of dimples D are usually formed on the outer surface of the outermost layer 4 in order to improve aerodynamic characteristics.

  A known cover material can be used as a material of each layer forming the cover. Specific examples include known thermoplastic resins, ionomer resins, highly neutralized resin compositions, thermoplastic and thermosetting polyurethanes, and polyamide-based and polyester-based thermoplastic elastomers.

  When using an ionomer resin or a highly neutralized resin composition as the material of each cover layer, commercially available products can be used. Specifically, HiMilan 1605, HiMilan 1601, and AM7318 (all are Mitsui DuPont Polychemical Co., Ltd.). Made from sodium neutralization ionomer resins such as Surlyn 8120 (manufactured by Dupont), zinc neutralization ionomer resins such as Himiran 1557, Himiran 1706 and AM7317 (all manufactured by Mitsui DuPont Polychemical Co., Ltd.), and products manufactured by Dupont Names “HPF 1000”, “HPF 2000”, “HPF AD1027” “HPF SEP1264-3” for experiments and the like can be mentioned. These can be used alone or in combination of two or more.

  The above resin materials can be used singly or in combination of two or more, but from the viewpoint of improving resilience, in particular, a combination of Zn neutralized ionomer resin and Na neutralized ionomer resin It can also be used. In this case, the compounding ratio of the Zn neutralized ionomer resin and the Na neutralized ionomer resin is not particularly limited, but is usually 25:75 to 75:25, preferably 35:65 to 65: by mass ratio. 35, more preferably 45:55 to 55:45. If this blending ratio is out of the above range, the resilience becomes too low and the desired flight performance may not be obtained.

  The resin material for each cover layer may include pigments, dispersants, antioxidants, UV absorbers, UV stabilizers, mold release agents, plasticizers, inorganic fillers (zinc oxide, barium sulfate, Various additives such as titanium) can be blended.

  The method for forming each cover layer is not particularly limited, but a known method can be adopted. For example, a material for forming each of the envelope layer, the intermediate layer, and the outermost layer is sequentially formed around the core. A method of injection molding and a pair of hemispherical half cups made in advance with each layer forming material, and intermediate products (intermediate spheres in which an enveloping layer and an intermediate layer are formed around the core and the core) ) And pressurizing and heating at 140 to 200 ° C. for 2 to 15 minutes.

  When the envelope layer is coated on the core, the thickness of the envelope layer is preferably 0.5 mm or more, and the upper limit is preferably 2.0 mm or less. If it deviates from this range, depending on the material used, peeling occurs at the boundary with the core, which causes a decrease in ball durability.

The material hardness of the envelope layer is not particularly limited, but can be 15 or more, preferably 20 or more in Shore D hardness. Also, the upper limit is not particularly limited, but it is preferably 80 or less, more preferably 70 or less. If it deviates from this range, it will cause a decrease in the initial velocity of the ball, or an unpleasant feel such as over-playing or over-hardness.Material hardness is the hardness when the material is molded into a sheet with a predetermined thickness. The same applies to the material hardness of each layer described later.

  When the envelope layer-coated sphere is coated with an intermediate layer, the thickness of the intermediate layer is preferably 0.5 mm or more, and the upper limit is preferably 1.5 mm or less. If it deviates from this range, there is a risk that the initial velocity of the ball will be lowered and the feel at impact will be impaired.

  The material hardness of the intermediate layer is not particularly limited, but can be 40 or more, preferably 45 or more in Shore D hardness. Further, the upper limit is not particularly limited, but can be preferably 70 or less, more preferably 65 or less. If it deviates from this range, durability at the time of hitting a driver may be lowered.

  When the outermost layer is coated on the intermediate layer coated sphere, the diameter of the coated sphere (that is, the ball) is preferably 42.7 mm or less as an upper limit value in accordance with the golf rules. The thickness of the outermost layer is preferably 0.5 mm or more, more preferably 1.0 mm or more, and the upper limit is preferably 2.5 mm or less, more preferably 2.0 mm or less. Beyond this range, it may be difficult to form a multilayer structure between the core and the outermost layer, and it may be difficult to optimize ball characteristics.

  The material hardness of the outermost layer is not particularly limited, but the Shore D hardness can be 50 or more, preferably 55 or more. Moreover, the upper limit is not particularly limited, but it is preferably 80 or less, more preferably 75 or less. If it deviates from this range, the ball surface is likely to be damaged, and the flight distance may be reduced, or the feel at impact may be impaired.

  The material hardness (Shore D hardness) of the outermost layer is preferably higher than the material hardness of the envelope layer from the viewpoint of improving ball characteristics, particularly spin characteristics.

  The deflection amount when the ball is loaded with a specific load, that is, the deformation amount (A) when the initial load 98N (10 kgf) to the final load 5880N (600 kgf) is applied to the sphere is preferably 10.5 mm or more. It needs to be. The above load load substantially corresponds to the impact applied to the ball at the time of a shot with the driver (W # 1), and the entire ball is largely crushed and becomes an index for the hit feeling at the time of impact. When deviating from this range, hardness may be felt in the ball hitting feeling.

  Further, the deflection amount when the ball is loaded with a specific load, that is, the deformation amount (B) when the initial load 98N (10 kgf) to the final load 4410N (450 kgf) is applied to the sphere is preferably 7.5 mm. As mentioned above, More preferably, it is 8.4 mm or more, As an upper limit, Preferably it is 10 mm or less, More preferably, it is 9.5 mm or less.

  The deformation amount (C) when the ball is loaded from an initial load of 98 N (10 kgf) to a final load of 1275 N (130 kgf) is 3.7 mm or less, preferably 3.5 mm or less. Although there is no restriction | limiting in particular, Preferably it is 2.5 mm or more, More preferably, it is 2.7 mm or more.

  Note that one or more dimples can be formed on the surface of the cover. In addition, various paints can be further applied to the cover surface, and as this paint, it is necessary to withstand the severe use conditions of golf balls, two-component curable urethane paint, in particular, non-yellowing Preferable examples include urethane paints.

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated concretely, this invention is not restrict | limited to the following Example.

[Examples 1 to 6, Comparative Examples 1 and 2]
After preparing the rubber composition shown in Table 1 below, a spherical inner layer core is prepared. That is, a composition blend using the rubber material shown in Table 1 below is kneaded, and a primary vulcanized product (semi-vulcanized inner layer half cup) is prepared at 120 ° C. for 10 minutes. Next, the material to be filled in the hollow portion in the inner half cup is wrapped, and subjected to secondary vulcanization (total vulcanization) at 158 ° C. for 10 minutes in the mold. An inner layer core having the filler shown in FIG.

About each example of an Example and a comparative example, the preparation methods of a sample are as follows.
First, as a method common to the examples of Examples 1 to 6, a composition serving as an inner layer core is kneaded to prepare a half-vulcanized half cup. Next, as shown in Table 2 below, various kinds of fillers are filled in the hollow portion of the inner layer core. Specifically, it is as follows.
For Examples 1 and 5 (inner layer cores No. 1 and No. 5), two half cups were bonded together as a pair, and then water or oil was applied from a part of the bonded surface to the center using a syringe. Inject. Then, secondary vulcanization is performed to obtain an inner layer core.
About Examples 2-4 (inner layer core No.2-No.4), the gel A-C used as a center raw material is poured into a half cup, and two half cups are bonded together as a pair. Then, secondary vulcanization is performed to obtain an inner layer core.
For Example 6 (inner layer core No. 6), two half cups were bonded together as a pair, followed by secondary vulcanization to obtain an inner layer core.

Details of the above rubber material (rubber I) blending are as follows.
・ Polybutadiene rubber: Trade name “BR51” (manufactured by JSR) polymerized with Nd-based catalyst ・ Zinc oxide: Trade name “Three kinds of zinc oxide” (manufactured by Sakai Chemical)
・ Barium sulfate: Trade name “Varico # 100” (manufactured by Hakusui Tech Co., Ltd.)
・ Anti-aging agent: Trade name “NOCRACK NS-6” (manufactured by Ouchi Shinsei Chemical Co., Ltd.)
・ Pentachlorothiophenol zinc salt: Wako Pure Chemical Industries, Ltd. ・ Zinc acrylate: Nippon Shokubai Co., Ltd. ・ Organic peroxide: Dicumyl peroxide Product name “Park Mill D” (manufactured by NOF Corporation)
(The amount of barium sulfate was adjusted so that the mass (weight) of the completed golf ball was 45.4 g.)

The center material is as follows (1) to (5).
(1) Gel A: Polyvinyl alcohol (PVA) gel (2) Gel B: Cellulose gel (3) Gel C: Polyurethane gel (4) Oil: Paraffin oil (5) Water: Tap water

The composition of the common outer layer core is as follows.
About the outer layer core of Examples 1-6, the compounding using the polybutadiene rubber material (Rubber II) shown in the following Table 3 was kneaded, and the primary vulcanized product (half-cured outer layer half) at 120 ° C. for 10 minutes. Cup). Next, the fully vulcanized inner layer core is enclosed in the hollow portion of the outer layer half cup, and this is wrapped and subjected to secondary vulcanization (total vulcanization) in a mold at 158 ° C. for 10 minutes. The core is filled with a hollow or center material as described above.

As for Comparative Example 1 of Comparative Example 1, a single core was produced by using a polybutadiene rubber material (Rubber II) and employing a normal rubber core molding method.

For the inner layer core and the outer layer core comparative example 2 of Comparative Example 2, a solid inner layer core was formed by injection molding using the resin material III shown in Table 3 below. This resin III is a material of 100 parts by mass of a thermoplastic polyester elastomer (trade name “Hytrel 3046” manufactured by Toray DuPont) as in the case of the resin material IV below. And by the same material and manufacturing method as the outer-layer core used in said Examples 1-6, the outer-layer core was enclosed in the inner-layer core, and the core was produced.

  Next, for each core, a resin material (cover material) common to each example shown in Table 4 below is sequentially injection-molded, and the envelope layer 2, the intermediate layer 3 and the core layer 10 around the core 10 as shown in FIG. A multi-piece solid golf ball in which the outermost layer 4 was sequentially formed was obtained. At this time, a large number of dimples D were formed on the surface of the outermost layer 4.

Details of the materials listed in Table 4 are as follows.
"Hytrel 3046": thermoplastic polyester elastomer manufactured by Toray DuPont "HPF1000": ionomer manufactured by DuPont "Himiran 1605": ionomer manufactured by Mitsui DuPont Polychemical "AM7329": Mitsui DuPont Polychemical Made ionomer

  About the golf ball of each example produced by the above, flying performance, approach spin performance, and hit feeling were evaluated by the following method. The results are shown in Table 5 (Example, Comparative example).

According to JIS K6301-1975 standard, the inner layer core surface hardness (S) and the outer layer core surface hardness (C), the inner layer core surface hardness (C), and the outer layer core surface hardness according to JIS-C hardness, respectively. The surface hardness was measured. That is, in accordance with JIS-A (standard for measuring the hardness of general rubber), an indenter (called a push needle or indenter) is pushed and deformed on the surface of the inner layer core, and the amount of deformation (pushing depth) is measured. The surface hardness of the inner layer core is measured with a durometer (spring type rubber hardness meter). About JIS-C hardness, the surface hardness of an outer layer core is measured with the spring type hardness meter (JIS-C type) prescribed | regulated to JISK6301-1975 similarly to the said JIS-A.

Material hardness of each layer (Shore D hardness)
The material hardness is a value measured by a type D durometer based on ASTM-D2240 for a measurement sample in which a material to be measured is a sheet of 6 mm thickness.

Compression deformation (deflection)
The ball of each example was compressed using a 4204 type manufactured by Instron Corporation at a speed of 10 mm / min and bent from the initial load of 98 N (10 kgf) to the final load of 5880 N (600 kgf). The amount of deformation (A) was measured.
Further, the amount of deflection deformation (B) from when the initial load 98N (10 kgf) was applied to when the final load 4410N (450 kgf) was applied was measured by the measuring instrument. Furthermore, the amount of deflection (C) from when the initial load 98N (10 kgf) was applied to when the final load 1275N (130 kgf) was applied was measured.

Initial velocity of the ball The initial velocity of the ball was measured using an initial velocity measuring device of the same type as a USGA drum rotation type initial velocity meter approved by R & A. The balls were conditioned at a temperature of 23 ± 1 ° C. for more than 3 hours and tested in a room at room temperature 23 ± 2 ° C. Ten balls were struck twice, the time required to pass between 6.28 ft (1.91 m) was measured, and the initial velocity was calculated.

Flying performance club by driver ("TourStage X-Drive 709" manufactured by Bridgestone Sports Co., Ltd.) was mounted on the striking robot, and the total flight distance was measured when striking at a head speed (HS) of 45 m / s. The amount is a value obtained by measuring the ball immediately after hitting with an initial condition measuring device, and the launch angle is 10.5 °.

Flying performance with irons Iron (I # 6) and (Tour Stage X-Blade 709 MC, manufactured by Bridgestone Sports Co., Ltd.) on a golf striking robot with a head speed (HS) of 45 m / s, the total flight distance The following criteria were used for the evaluation, and the spin amount and launch angle were measured in the same manner as described above.

Approach spin performance A golf ball hitting robot equipped with a sand edge (SW) and measured the ball spin rate immediately after hitting at a head speed (HS) of 21 m / s, and the values are shown in the table below.

Feeling (feeling)
Three top amateur golfers evaluated the hit feeling when hitting the ball with a driver (W # 1) at a head speed (HS) of 42 to 50 m / s according to the following criteria.
◯: Good hit feeling x: Too hard or too soft Note that the above “good hit feeling” means a unique hit feeling that has an appropriate softness at the time of hitting and is comfortable.

  From the test data of Table 5 above, Comparative Examples 1 and 2 can maintain the distance performance and the approach spin performance, but cannot obtain a desired good hit feeling, and are satisfied with advanced players and professionals. It turns out that it is not a thing. On the other hand, it can be seen that Examples 1 to 6 maintain good flight distance performance and approach spin performance, and can obtain a soft and comfortable hit feeling for professionals and advanced players.

DESCRIPTION OF SYMBOLS 1 Golf ball 2 Enveloping layer 3 Middle layer 4 Outermost layer 10 Core 11 Inner layer core 12 Outer layer core 11a Cavity part

Claims (9)

  A golf ball comprising a spherical core and a cover of one layer or two or more layers covering the core, wherein the core is an inner core of a hollow spherical body having a central portion formed in a cavity and an outer layer covering the core It is formed by two layers of the core, and the deformation (mm) when it is loaded from the initial load 98N (10 kgf) to the final load 5880N (600 kgf) is (A), and the initial load 98N (10 kgf) to the final load 1275N. A golf ball characterized in that (A) ≧ 10.5 and (C) ≦ 3.7 when the deformation (mm) when loaded to (130 kgf) is (C).   The golf ball according to claim 1, wherein the hollow portion of the inner layer core is filled with a substance selected from the group consisting of air, water, polyvinyl alcohol (PVA) gel, cellulose gel, oily liquid, solid paraffin, and agar.   The golf ball according to claim 1, wherein the hollow portion of the inner layer core is a spherical space portion having a diameter of 5 to 18 mm.   4. The golf ball according to claim 1, wherein the inner layer core has an outer diameter of 15 to 25 mm.   The golf ball according to claim 1, wherein the core has a diameter of 34 to 40 mm.   The golf ball according to claim 1, wherein the inner layer core has a surface hardness (S) in the range of 30 to 90 in terms of JIS-A hardness.   The golf ball according to claim 1, wherein the cover covering the core is formed with two layers of an intermediate layer and an outermost layer from the inside.   The golf ball according to claim 1, wherein the cover covering the core is formed with a cover of three layers of an envelope layer, an intermediate layer, and an outermost layer from the inside.   The golf ball according to claim 1, wherein a material hardness (Shore D hardness) of the outermost layer is higher than a material hardness of the envelope layer.

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