JPH09215775A - Multi-piece solid golf ball - Google Patents

Abstract

(57) [Summary] (Modified) SOLUTION: Each layer of the cover is formed of a thermoplastic resin, and the solid core is formed of a rubber base material, and has a specific gravity of 1.00 or more. The dimple space volume that is larger than the specific gravity of the inner layer cover and the dimple ball surface occupancy rate is 60% or more, and the dimple space volume under the plane surrounded by the edges of the individual dimples is the bottom face, and the maximum depth of the dimples from the bottom face. The value V ₀ divided by the circular volume whose height is the height is 0.40 to 0.65, and the moment of inertia (M) of the golf ball is M _DL ≦ M ≦ M _UL (where M _UL = 0. 08D + 84.8, M _DL = 0.08
D + 77.8, where D is the Shore D hardness of the outermost cover). [Effect] This golf ball has good flight distance, controllability, rolling during putting, and straightness, and is unlikely to cause flapping on iron shots.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-piece solid golf ball which has good flight distance, controllability, rolling during putting, straightness, rebound, and durability.

[0002]

2. Description of the Related Art Conventionally, a golf ball cover is mainly made of an ionomer resin, and a cover having a specific gravity of about 0.960 is often used. On the other hand, in order to use this solid golf ball for competition, it is necessary to meet the standards defined by the Golf Rules (R & A), and it is necessary to manufacture the solid golf ball so that the weight is 45.92 g or less and the outer diameter is 42.67 mm or more. . Therefore, the golf ball obtained by using the cover material containing the ionomer resin as the main material has a moment of inertia within a certain range.

Here, the moment of inertia of the golf ball has a great influence on the trajectory, flight distance, controllability and the like of the golf ball during flight. Generally, by increasing the moment of inertia, the spin attenuation rate during flight of the golf ball is reduced, and the spin amount is maintained even when the golf ball descends above the maximum altitude, resulting in a stretchable trajectory. Also, when hitting a putter on the green, it has high straightness and rolls well. Therefore, from such a point, a proposal has been made for a golf ball that can obtain a large moment of inertia.

For example, Japanese Unexamined Patent Publication (Kokai) No. 6-277312 proposes a solid golf ball which has a high moment of inertia by using an ionomer resin as a main material and mixing titanium white and barium sulfate.

However, according to this proposal, since the formed cover contains a large amount of filler such as titanium white or barium sulfate, flake damage is likely to occur when hit with an iron, and a large amount of filler repels the cover. Therefore, there is a problem in that a sufficient flight distance cannot be obtained because the performance is deteriorated.

The present invention optimizes the moment of inertia of the ball in accordance with the hardness of the outermost layer cover, and optimizes the dimple mode, etc., to achieve flight distance, controllability,
It is an object of the present invention to provide a multi-piece solid golf ball having a cover excellent in straightness and rolling property on a green and having excellent durability.

[0007]

MEANS FOR SOLVING THE PROBLEMS AND BEST MODE FOR CARRYING OUT THE INVENTION As a result of intensive studies to achieve the above-mentioned object, the present inventor has found that a rubber-based core of a multi-piece solid golf ball having two or more layers of cover is used. The specific gravity of the outermost layer is 1.00 or more, the outermost cover cover specific gravity is larger than the core specific gravity, and the moment of inertia (M) of the golf ball is expressed by the following formula M _DL ≦ M ≦ M _UL (where M _UL = 0.08D + 84.8, M _DL = 0.08
D + 77.8, and D represents the Shore D hardness of the thermoplastic resin forming the outermost layer cover. ) Range, that is, the moment of inertia is selected according to the hardness of the outermost layer, and the ball surface occupation ratio of the dimples is 6
A value V ₀ which is not less than 0% and which is obtained by dividing the dimple space volume under the plane surrounded by the edges of the individual dimples by the cylindrical volume whose height is the maximum depth of the dimples with the plane as the bottom. It is preferably in the range of 0.40 to 0.65, more preferably, the core hardness, the Dst value represented by the following formula, and the hardness of the outermost layer cover are optimized, and in this case, the outermost layer cover is preferably thermoplastic. Formed from polyurethane elastomer, it has excellent flight distance, controllability, rolling performance when hitting with a putter on the green, straightness, etc., and also has good resilience and durability of the cover when hit by an iron. Based on the above findings, the present invention has been completed.

That is, according to the present invention, (1) the solid core has two
In a multi-piece solid golf ball, which is formed by coating a cover of more than one layer and forming a large number of dimples on the outermost layer surface of the cover, each layer of the cover is formed of a thermoplastic resin, and the solid core is made of a rubber base material. In addition, the outermost layer cover has a specific gravity of 1.00 or more, the specific gravity of the outermost layer cover is greater than the specific gravity of the solid core and the inner layer cover, and the ball surface occupancy rate of the dimples is 60% or more. The value V ₀ obtained by dividing the dimple space volume under the enclosed plane by the cylindrical volume having the plane as the bottom and the maximum depth of the dimples from this bottom as the height is 0.40 to 0.65, and the inertia of the golf ball is Moment (M) is M _DL ≦ M ≦ M _UL (in the formula, M _UL = 0.08D + 84.8, M _DL = 0.08)
D + 77.8, and D represents the Shore D hardness of the thermoplastic resin forming the outermost layer cover. ) Is a multi-piece solid golf ball, (2) 10
Deflection of solid core is 2.0 when 0 kg is loaded.
(1) The multi-piece solid golf ball according to (1), which has a dimple diameter of Dmk, a depth of Dpk, and a number of dimples of Nk. = 1, 2, 3, ... N), and the dimple total surface area index (Dst) represented by the following formula is 4.0 or more (1) or (2), the multi-piece solid golf ball, (4) outermost layer Cover hardness is Shore D hardness 4
The multi-piece solid golf ball according to any one of (1) to (3), which is 0 to 68, and (5) the outermost layer cover is mainly composed of a polyurethane elastomer. A multi-piece solid golf ball according to claim 1.

[0009]

[Equation 2] (However, in the formula, R is the ball radius, Nk is the number of dimples k, and V ₀ has the above-mentioned meaning.)

The present invention will be described in more detail below. The multi-piece solid golf ball of the present invention comprises a solid core made of a rubber base material and a cover having two or more layers. The solid core has a specific gravity. It is 1.00 or more, preferably 1.02 to 1.18, and more preferably 1.06 to 1.15.

Here, the solid core can be formed of a known material, and can be obtained by appropriately adjusting the vulcanization conditions, the compounding ratio and the like by a conventional method. In this case, the core is compounded with a base rubber, a crosslinking agent, a co-crosslinking agent, an inert filler and the like. As the base rubber, natural rubber and /
Alternatively, synthetic rubber can be used, but in the present invention, it is preferable to use 1,4-polybutadiene having a cis structure of at least 40% or more. In this case, if necessary, natural rubber, polyisoprene rubber, styrene-butadiene rubber, or the like may be appropriately blended with the polybutadiene.

As the cross-linking agent, organic peroxides such as dicumyl peroxide and di-t-butyl peroxide can be used, but dicumyl peroxide is particularly preferable. The compounding amount of the cross-linking agent is usually 0.5 to 1.8 parts by weight, particularly 0.8 to 100 parts by weight with respect to 100 parts by weight of the base rubber.
It is preferably 1.5 parts by weight.

The co-crosslinking agent is not particularly limited, but a metal salt of an unsaturated fatty acid, particularly a zinc salt or a magnesium salt of an unsaturated fatty acid having 3 to 8 carbon atoms (eg acrylic acid, methacrylic acid) is used. Illustrative, zinc acrylate is particularly preferred. The amount of this co-crosslinking agent is 10
10-40 parts by weight, preferably 15-
35 parts by weight.

Examples of the inert filler include zinc oxide, barium sulfate, silica, calcium carbonate, zinc carbonate, etc., but zinc oxide is generally used, and the compounding amount thereof is the specific gravity of the core and the cover and the weight standard of the ball. Etc., but is not particularly limited, but is usually 5 to 2 with respect to 100 parts by weight of the base rubber.
5 parts by weight, more preferably 7 to 20 parts by weight.

The core composition obtained by blending the above components is kneaded using a conventional kneading machine such as a Banbury mixer or a roll, and then compressed or injection-molded into a core mold to form a molded product with a crosslinking agent and Sufficient temperature for the co-crosslinking agent to work (for example, using dicumyl peroxide as the crosslinking agent,
When zinc acrylate is used as the co-crosslinking agent, about 13
(0-170 ° C.) to prepare a core.

Here, a core having a desired hardness (deflection amount under a load of 100 kg) can be obtained by appropriately selecting the types and amounts of the compounding materials, particularly the crosslinking agent and the co-crosslinking agent, and the vulcanization conditions. In this case, the solid core is 1
Deflection amount when loaded with 00 kg is 2.0 to 5.0 m
m, particularly 3.0 to 4.8 mm is preferable, and by setting the deflection amount within the above range, sufficient resilience, good hit feeling, and excellent flapping durability can be obtained. You can

The solid core has a diameter of 2
It is preferably 5 to 41 mm, especially 30 to 40 mm, and the weight is 20 to 40 g, especially 23 to 39.5 g.

Next, the cover for covering the solid core has two or more layers, preferably two layers.

Here, the outermost layer cover has a larger specific gravity than the core and inner layer covers, whereby a high moment of inertia can be obtained and flight stability,
A golf ball satisfying straight running stability in a putter can be obtained. On the other hand, if the outermost layer cover specific gravity is smaller than the core specific gravity and the inner layer cover, the object of the present invention cannot be achieved. The specific gravity of the outermost layer cover is appropriately selected according to the specific gravities of the core and the inner layer cover, but is usually 1.10 or more, particularly 1.
It is preferable to form it so as to be 10 to 1.25,
The difference in specific gravity from the core is preferably 0.01 to 0.15.

The hardness of the outermost cover is also not particularly limited, but it is preferable to form it so that the Shore D hardness is 40 to 68, particularly 43 to 65, and the Shore D hardness is less than 40. And the resilience decreases, and 6
When it exceeds 8, the feel on impact may become poor.

The outermost cover material used in the present invention is not particularly limited as long as it is formed so as to have a specific gravity higher than that of the solid core and the inner cover, and can be formed by a normal cover material. A thermoplastic resin can be preferably used. Examples of the thermoplastic resin include thermoplastic urethane elastomers, ionomer resins, polyester elastomers, polyamide elastomers, propylene-butadiene copolymers, 1,2-polybutadiene, styrene-butadiene copolymers, and the like. One kind or two or more kinds can be used, but in the present invention, it is preferable to use a thermoplastic urethane elastomer as a main material, and specifically, PAN
DEX T-7890, PANDEX T-1198
(Trade name: manufactured by Dainippon Ink and Chemicals, Inc.) and the like can be preferably used. Further, in order to satisfy the cover specific gravity, various fillers such as barium sulfate, titanium oxide, magnesium stearate and the like can be blended in addition to the thermoplastic resin.

Here, the specific gravity of the inner cover is 0.9-1.
2. As described above, the outer layer cover is preferably 1.10 or more. Further, it is preferable that the outer cover has the highest specific gravity among the core, the inner cover and the outer cover.

The thickness of the inner and outer layer covers is arbitrary, but the inner layer cover has a thickness of 0.3 to 2.5 mm, and the outer layer cover has a thickness of 0.3 to 2.5 mm.
It is preferable to form it to 2.5 mm.

The golf ball of the present invention can be manufactured by a conventional method, and a solid material is prepared by previously manufacturing a pair of single-layer or multi-layer half cups with a cover material and applying a compression molding method or the like. It can be obtained by a method of covering the core with a cover to form two or more layers. Furthermore, it can be obtained by an injection molding method.

Further, the golf ball of the present invention has a moment of inertia (M) within the range represented by the following formula, depending on the outermost layer cover hardness (Shore D hardness). M _DL ≤ M ≤ M _UL where M _UL is 0.08D + 84.8 and M _DL is 0.08D
+77.8, and D is the Shore D hardness of the outermost layer cover.

That is, according to the study by the present inventor, the moment of inertia has an appropriate range in correlation with the cover hardness. That is, the cover needs to be large if it is hard, and need not be as large as the cover that is hard if it is soft. This is because if the cover is soft, the frictional force at impact is large and spin is likely to occur, and on the other hand, if the cover is hard, the frictional force is small and spin is hard to occur. Will quickly decay if the moment of inertia is small, and will stall when it falls. On the other hand, a ball launched with a high spin rate using a soft cover has a small spin damping when the moment of inertia is too large. Will tend to decrease.

Therefore, from the viewpoint of giving excellent ball characteristics, it is necessary to set the moment of inertia of the ball within the above range. If it is smaller than the lower limit of the above range, the trajectory becomes stall, and if it is larger than the upper limit, the trajectory becomes swollen and the flight distance is reduced. The moment of inertia (M) in the above range is calculated by the following formula.

[0028]

(Equation 3)

The solid golf ball of the present invention has a large number of dimples formed on the surface like a normal golf ball. Here, the golf ball of the present invention is
When the golf ball is regarded as a spherical surface and is regarded as a virtual spherical surface, the surface area of the virtual spherical surface surrounded by the edges of the individual dimples is a ratio of the total surface area of the virtual spherical surface, that is, the dimple surface occupancy rate is 60% or more, preferably 60 to 60%. 80% of dimples are provided. When the dimple surface occupancy rate is small, the effect of the above-mentioned moment of inertia during flight becomes small. The number of dimples is 350
It is preferable to set the number to 500, particularly 360 to 450. The arrangement of the dimples may be similar to that of a normal golf ball, and the dimples have different diameters, depths, etc. 2
It may be of a variety of species or more,
Diameter is 2.5-4.3mm, depth is 0.14-0.25
mm.

Furthermore, the dimples have a dimple space volume under a plane surrounded by edges of the dimples,
The value V ₀ divided by the cylindrical volume having the plane as the bottom and the maximum depth of each dimple from the bottom as the height is 0.4.
It is formed so as to be 0 to 0.65, particularly 0.43 to 0.60. If V ₀ exceeds 0.65, the ball may be blown up and stall, and a sufficient flight distance may not be obtained, and if it is less than 0.40, the ball may drop.

Here, the dimple shape will be described in more detail. In the case where the dimple plane shape is circular, FIG.
As shown in FIG. 5, a virtual sphere 2 having a ball diameter is set on the dimple 1 and a sphere 3 having a diameter smaller than the ball diameter by 0.16 mm is set. An intersection 4 between the circumference of the sphere 3 and the dimple 1 is obtained. A series of intersections 6 between the tangent line 5 at the intersection 4 and the virtual spherical surface 2 is referred to as a dimple edge 7. In this case, the setting of the dimple edge 7 described above is because the edge of the dimple 1 is usually rounded, and without such a setting, the exact position of the dimple edge cannot be determined. Then, as shown in FIGS. 2 and 3, the volume V _p of the dimple space 9 below the plane (circle: diameter D _m ) 8 surrounded by the edge 7 is obtained. On the other hand, the plane 8
, And the maximum dimple depth D _p from this plane 8
Is calculated, the ratio V ₀ of the dimple space volume V _p to the volume V _Q of the cylinder 10 having the height as V is calculated.

[0032]

(Equation 4)

If the plane shape of the dimple is not circular, the maximum diameter (or maximum length of the plane) of this dimple is calculated, and it is assumed that the dimple plane has a circular shape having this maximum diameter (maximum length). Then, V ₀ is calculated in the same manner as described above.

Further, in the golf ball of the present invention, when the number of dimples formed on the surface of the ball is n, the diameter of each dimple is Dmk, the maximum depth is Dpk, and the number is Nk (where k = 1. , 2, 3, ... N), and the dimple total surface area index Dst represented by the following formula is preferably 4.0 or more, more preferably 4.0 to 7.0.

[0035]

(Equation 5) Here, in the formula, R is a ball radius, V ₀ is synonymous with the specified value V ₀ , and Nk is the number of dimples k. The dimple total surface area index can optimize various dimple parameters to give a further flight distance to the golf ball having the solid core and the cover of the present invention, and the dimple total surface area index is 4.0 or more. In this case, the flight characteristics (flying distance, wind strength) of the golf ball are further enhanced.

[0036]

INDUSTRIAL APPLICABILITY The multi-piece solid golf ball of the present invention has good flight distance, controllability, rolling at the time of putting, and straightness, and is resistant to flaking on iron shots.

[0037]

EXAMPLES Hereinafter, the present invention will be described in detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples.

[Examples 1 to 4 and Comparative Example 1] The core materials shown in Table 1 were kneaded and vulcanized in a mold at 160 ° C. for about 18 minutes to give the weight, outer diameter, and A solid core having a specific gravity and a deflection amount under a load of 100 kg was obtained.

Next, the outer cover material shown in Table 2 and the inner cover material shown in Table 4 were kneaded together to obtain a half cup, and the core surface was coated in order and compression molded. In this case, a golf ball was obtained by forming the dimples shown in Table 3 on the outermost layer surface. The properties and various performances of the obtained golf ball were examined, and the results are also shown in Table 4.

In Table 4, the various properties of the golf ball were evaluated as shown below. Moment of inertia The diameter of each member was the average of the values obtained by measuring arbitrary 5 points. The weight was obtained by measuring each member separately. The attached weight and volume were calculated from there, and the specific gravity of each member was calculated. These values were applied to the following formula to obtain the moment of inertia.

[0041]

(Equation 6)

Flying distance Using a striking machine manufactured by True Temper, a drop distance (carry) and a reach distance (total) when the ball was actually hit with a driver at a head speed (HS) of 45 m / s were obtained. The ball was struck with a sandwedge (SW) at a head speed of 38 m / s once in each of two arbitrary positions with a swing resistance swing robot, and these two hitting parts were observed and evaluated according to the following criteria. ◯: Good Δ: Normal ×: Inferior continuous durability Using a fly hole striking machine, head speed 38 m
The ball was repeatedly hit with / s and the number of times until the ball was destroyed was evaluated according to the following criteria. ◯: Good Δ: Normal ×: Poor Feeling Heads were actually hit by three professional golfers with a head speed of 45 to 50 m / s, and evaluated according to the following criteria. ○: Soft △: Normal ×: Hard

[0043]

[Table 1]

[0044]

[Table 2]

[0045]

[Table 3]

[0046]

[Table 4]

[Brief description of drawings]

FIG. 1 Dimple V ₀Explanatory diagram explaining the calculation method of
FIG.

FIG. 2 is a perspective view of the same.

FIG. 3 is a sectional view of the same.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Dimple 2 Virtual sphere 3 Sphere 4 Intersection 5 Tangent line 6 Intersection 7 Dimple edge 8 Plane 9 Dimple space

Claims (5)

[Claims] 1. A multi-piece solid golf ball comprising a solid core covered with two or more layers of cover and a large number of dimples formed on the outermost surface of the cover, wherein each layer of the cover is formed of a thermoplastic resin. The solid core is made of a rubber base material, has a specific gravity of 1.00 or more, the outermost cover has a specific gravity larger than that of the solid core and the inner cover, and the dimple has a ball surface occupation ratio of 60% or more. Then, the value V ₀ obtained by dividing the dimple space volume under the plane surrounded by the edges of the individual dimples by the cylindrical volume with the plane as the bottom and the maximum depth of the dimples as the height is 0.40 to ₀ . .65, and the moment of inertia (M) of the golf ball is M _DL ≦ M ≦ M _UL (wherein M _UL = 0.08D + 84.8, M _DL = 0.08).
D + 77.8, and D represents the Shore D hardness of the thermoplastic resin forming the outermost layer cover. ) Is a multi-piece solid golf ball. 2. The multi-piece solid golf ball of claim 1, wherein the amount of deflection of the solid core under a load of 100 kg is 2.0 to 5.0 mm. 3. When there are n kinds of dimples, the diameter of each dimple is Dmk, the depth is Dpk, and the number is Nk (where k = 1, 2, 3, ... N), the following formula 1] (Where R is a ball radius, Nk is the number of dimples k, and V ₀ has the above-mentioned meaning), and the dimple total surface area index (Dst) is 4.0 or more. 2. The multi-piece solid golf ball described in 2. 4. The outermost cover hardness is 40 Shore D hardness.
The multi-piece solid golf ball of claim 1, wherein the multi-piece solid golf ball has a particle size of ˜68. 5. The multi-piece solid golf ball according to claim 1, wherein the outermost layer cover is mainly made of polyurethane elastomer.