JPH09215778A - Two-piece solid golf ball - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a golf ball which is good in carry, controllability and the rolling and rectilinear advancing properties at the time of putting and hardly burrs in an iron shot. SOLUTION: The solid core of the two-piece solid golf ball constituted by coating the solid core with a cover and forming many dimples on the cover surface is formed of a rubber base material having a sp. gr. of >=1.00. The sp. gr. of the cover is larger than the sp. gr. of the solid core and the ball surface occupying rate of dimples 1 is >=60%. The value V0 obtd. by dividing the dimple space volume under the planes enclosed by the edges 7 of the individual dimples by the circular volume having the planes described above as the base and the max. depth of the dimples 1 from the base as a height is 0.40 to 0.65. The inertia moment (M) of the golf ball is MDL<=M<=MUL (where, MUL=0.08D+84.8, MDL=0.08D+77.8 and D denotes the Shore D hardness of the outermost cover).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-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.

According to the present invention, by optimizing the moment of inertia of the ball according to the hardness of the cover, and optimizing the dimple form, the flight distance, controllability, straightness on the green and rolling performance are excellent. An object of the present invention is to provide a two-piece solid golf ball having a cover with 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 object, the present inventor has found that the core of a two-piece solid golf ball has a specific gravity of 1.00 using a rubber base material. In addition to the above formation, the cover specific gravity is made 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, where D is the Shore D hardness of the cover. ), That is, the moment of inertia is selected according to the cover hardness, and the ball surface occupancy of the dimples is set to 60% or more, and the dimple space volume under the plane surrounded by the edges of the individual dimples. Is divided by the cylindrical volume whose height is the maximum depth of dimples from the bottom with the above plane as the bottom, and V ₀ is 0.40 to 0.40.
The range of 0.65, more preferably the core hardness,
By optimizing the Dst value and the cover hardness expressed by the following formula, and in this case, by advantageously forming the cover with a thermoplastic polyurethane elastomer, the flight distance, the controllability, and the launching time with a putter on the green can be achieved. The present invention has been completed on the basis of the finding that the rolling property and the straight running property are excellent, and the resilience and the durability of the cover due to the impact of the iron are good.

That is, according to the present invention, (1) in a two-piece solid golf ball in which a solid core is covered with a cover and a large number of dimples are formed on the surface of the cover, the solid core is made of a rubber base material and has a specific gravity of 1. 00 or more, the specific gravity of the cover is larger than that of the solid core, the ball surface occupation ratio of the dimples is 60% or more, and the dimple space volume under the plane surrounded by the edges of the individual dimples is A value V ₀ divided by a cylindrical volume having the plane as the bottom surface and the maximum depth of the dimples from the bottom surface as the height is 0.40 to 0.65, and the moment of inertia (M) of the solid golf ball is M _DL. ≦ M ≦ M _UL (in the formula, M _UL = 0.08D + 84.8, M _DL = 0.08)
D + 77.8, where D is the Shore D hardness of the cover. (2) a two-piece solid golf ball, (2) a two-piece solid golf ball according to (1), wherein the deflection amount of the solid core under a load of 100 kg is 2.0 to 4.5 mm; The dimples have various dimple diameters Dmk and depth Dp.
When k and the number is Nk (however, k = 1, 2, 3, ...
n), the dimple total surface area index (Ds shown by the following formula
The two-piece solid golf ball according to (1) or (2), wherein t) is 4.0 or more, and (4) the cover hardness is 40 to 68 in Shore D hardness, and (1) to (3). Any one of (1) to (4), which has the two-piece solid golf ball described in (1) and (5) a cover whose main component is a thermoplastic polyurethane elastomer.
A two-piece solid golf ball according to the above item is provided.

[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 two-piece solid golf ball of the present invention comprises a solid core made of a rubber base material and a cover. The solid core has a specific gravity of 1.00 or more. Preferably 1.02 to 1.18, more preferably 1.06 to 1.
Use the one of 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 to 40 parts by weight, preferably 20 to 0 parts by weight
30 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.
The amount is 0 parts by weight, more preferably 8 to 15 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 4.5 m
m, more preferably 2.5 to 4.3 mm, still more preferably 2.6 to 4.0 mm, and by setting the deflection amount within the above range, it has sufficient resilience, It is possible to obtain a good feel at impact and an excellent swelling durability.

The solid core has a diameter of 3
It is preferably from 7 to 41 mm, especially from 38 to 40 mm, and has a weight of from 30 to 37 g, especially from 31 to 36.5 g.

Next, the cover for covering the solid core has a larger specific gravity than that of the core, and thereby a high moment of inertia can be obtained, and flight stability and straight running stability with a putter are good. A good golf ball can be obtained. On the other hand, if the cover specific gravity is smaller than the core specific gravity, the object of the present invention cannot be achieved. The cover specific gravity is appropriately selected according to the specific gravity of the core, but is usually 1.10 to 1.2.
It is preferable to form so that the difference in specific gravity is 0.01 to 0.15.

The hardness of the cover is also not particularly limited, but it is preferable that the cover has a Shore D hardness of 40 to 68, more preferably 43 to 65, and still more preferably 45 to 60. If the D hardness is less than 40, the resilience may decrease, and if it exceeds 68, the feel may be poor.

The cover material used in the present invention is not particularly limited as long as it is formed so as to have a specific gravity larger than that of the above solid core, and can be formed by a normal cover material. It can be preferably used. Examples of the thermoplastic resin include thermoplastic urethane elastomer, ionomer resin, polyester elastomer, polyamide elastomer, propylene-butadiene copolymer, 1,2-polybutadiene, styrene-butadiene copolymer, 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, PANDEXT-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.

The golf ball can be manufactured by a conventional method, and a solid golf ball can be obtained by coating the cover material with the solid core by an injection molding method, a compression molding method or the like.

Further, the golf ball of the present invention has a moment of inertia (M) within the range represented by the following formula in accordance with the 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 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 providing 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.

[0025]

(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%. The dimples are provided so as to be 80%. 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 460. 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.

Further, 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.

[0029]

(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 is circular with this maximum diameter (maximum length). Then, V ₀ is calculated in the same manner as described above.

In the golf ball of the present invention, 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), 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.

[0032]

(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.

[0033]

INDUSTRIAL APPLICABILITY The two-piece solid golf ball of the present invention has good flight distance, controllability, rolling during putting, and straightness, and is unlikely to cause flapping on iron shots.

[0034]

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 3, Comparative Examples 1 and 2] The core materials shown in Table 1 were kneaded and vulcanized in a mold at 160 ° C. for about 18 minutes to give the outer diameters shown in Table 4. A solid core having a weight, a specific gravity and a deflection amount under a load of 100 kg was obtained.

Next, the cover materials shown in Table 2 were kneaded and injection-molded to coat the solid core, and
Two-piece solid golf balls were obtained by forming the dimples shown in Table 3 on the cover surface. The weight and outer diameter of the obtained golf ball are shown in Table 4.

In Table 4, 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.

[0038]

(Equation 6)

Flying distance Using a striking machine manufactured by True Temper, the drop distance (carry) and the 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 △: Normal ×: Poor

[0040]

[Table 1]

[0041]

[Table 2]

[0042]

[Table 3]

[0043]

[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 two-piece solid golf ball comprising a solid core covered with a cover and a large number of dimples formed on the surface of the cover, wherein the solid core is made of a rubber base material and has a specific gravity of 1.00 or more. The specific gravity of the cover is larger than that of the solid core, the ball surface occupancy of the dimples is 60% or more, and the dimple space volume under the plane surrounded by the edges of the individual dimples is the bottom surface with the plane as the bottom surface. The value V _{0 obtained} by dividing the maximum depth of dimples from
0 to 0.65, and the moment of inertia (M) of the solid golf ball is M _DL ≦ M ≦ M _UL (wherein M _UL = 0.08D + 84.8, M _DL = 0.08).
D + 77.8, where D is the Shore D hardness of the cover. ) Is a two-piece solid golf ball. 2. A two-piece solid golf ball according to claim 1, wherein the amount of deflection of the solid core under a load of 100 kg is 2.0 to 4.5 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. The two-piece solid golf ball described in 2. 4. The cover hardness is 40 to 6 in Shore D hardness.
The two-piece solid golf ball of claim 1, wherein the two-piece solid golf ball is 8. 5. The two-piece solid golf ball according to claim 1, which has a cover mainly composed of a thermoplastic polyurethane elastomer.