JP2003093543A - Two-piece solid golf ball - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a two-piece solid golf ball excellent in carry, controllability, rolling at putting and straight-ahead movement, and hardly getting hangnails at iron shot. SOLUTION: The golf ball is made of a rubber base material at the solid core thereof, 1.02 to 1.18 in specific gravity, composed mainly of a thermoplastic polyurethane elastomer at the cover thereof, larger in specific gravity than the solid core, and 60 to 80% in the ball surface occupancy of dimples, wherein a value V0 obtained by dividing the volume of a dimple space under an area surrounded by the rim of the dimple by the volume of a cylinder having a bottom surface equal to the area and a height equal to the maximum depth of the dimple is 0.40 to 0.65, and MDL<=M<=MUL is established (wherein 'M' is the moment of inertia of the solid golf ball, MUL=0.08D+84.8, MDL=0.08D+77.8, and 'D' is the Shore D hardness).

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. In general, by increasing the moment of inertia, the spin attenuation rate during flight of the golf ball decreases, the spin amount is maintained even when the golf ball descends above the maximum altitude, and the trajectory becomes extended. 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 1.02 using a rubber substrate. To 1.18, the cover is formed of a thermoplastic polyurethane elastomer as a main material, and the cover specific gravity is formed to be larger than the core specific gravity. Further, the moment of inertia (M) of the golf ball is expressed by the following formula 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. ) Range, that is, the moment of inertia is selected according to the cover hardness, the ball surface occupancy of the dimples is set to 60 to 80%, and the dimple space under the plane surrounded by the edges of the individual dimples. A value V ₀ obtained by dividing a volume by a cylindrical volume whose bottom is the above-mentioned plane and whose height is the maximum depth of dimples from this bottom is 0.40.
To 0.65, more preferably by adjusting the core hardness, the Dst value represented by the following formula, and the cover hardness, the flight distance, the controllability, and the rolling property at the time of launching with a putter on the green. The present invention has been completed on the basis of the finding that it is excellent in straightness and the like, and that the resilience and the durability of the cover by hitting an iron are also 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. 02-1.1
8 and the cover is mainly made of a thermoplastic polyurethane elastomer, the specific gravity of which is larger than that of the solid core, and the dimple ball surface occupancy is 60 to 60%.
The value V ₀ is 80% and is obtained by dividing the dimple space volume under the plane surrounded by the edges of the individual dimples by the cylindrical volume having the plane as the bottom and the maximum depth of the dimples from this bottom as the height. .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. ) Is a two-piece solid golf ball, (2) the diameter of the solid core is 37 to 41 mm
The two-piece solid golf ball according to (1), wherein the solid core has a deflection amount of 2.0 to 4.5 mm under a load of 100 kg, and (3) has n kinds of dimples, and the diameter of each dimple is Dmk, When the depth is Dpk and the number is Nk (k = 1, 2, 3, ... N), the dimple total surface area index (Dst) represented by the following formula is 4.0 to 7.0 (1 ) Or the two-piece solid golf ball according to (2). (4) The two-piece solid golf ball according to any one of (1) to (3), wherein the cover hardness is 40 to 68 in Shore D hardness.
(5) The two-piece solid golf according to any one of (1) to (4), wherein the cover has a specific gravity of 1.10 to 1.25 and a specific gravity difference from the core is 0.01 to 0.15. Serve the ball.

[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 desired, natural rubber, polyisoprene rubber, styrene-butadiene rubber or the like may be appropriately mixed 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, it is about 13
A core is prepared by heat curing at 0 to 170 ° C.

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.

A thermoplastic resin can be preferably used for the cover material used in the present invention. Examples of the thermoplastic resin include a thermoplastic urethane elastomer, an ionomer resin, a polyester elastomer, a polyamide elastomer, a propylene-butadiene copolymer, 1,2-polybutadiene, and a styrene-butadiene copolymer. One kind or two or more kinds can be used, but in the present invention, a thermoplastic urethane elastomer is used as a main material. Specifically, PANDEX
T-7890, PANDEX T-1198 (trade name:
Dainippon Ink and Chemicals, Inc. etc. can be used conveniently. Further, in order to satisfy the cover specific gravity, in addition to the thermoplastic resin, barium sulfate, titanium oxide,
Various fillers such as magnesium stearate can also be blended.

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, while on the other hand, if the cover is hard, the frictional force is small and spin is less likely to occur, so a ball hit with a low spin amount using a hard cover. Will quickly decay if the moment of inertia is small, and will stall when it falls. On the other hand, a ball hit with a high spin rate using a soft cover has a small spin attenuation 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
It is preferably in the range of 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.
To explain, if the dimple plane shape is circular, FIG.
As shown in, the phantom spherical surface with the ball diameter on the dimple 1
2 and 0.16mm smaller than the ball diameter
Set the spherical surface 3 of the diameter, and the dimple and the circumference of this spherical surface 3.
1 is obtained, and the tangent 5 at the intersection 4 and the temporary
The dimple edge 7 is defined as a series of intersections 6 with the imaginary spherical surface 2.
It In this case, the setting of the dimple edge portion 7 described above is not necessary.
Since the edge of the normal dimple 1 is rounded,
Without such settings, you will not know the exact position of the dimple edge.
Because there is no. Then, as shown in FIGS.
A plane surrounded by the edge 7 (circle: diameter D _m) 8 lower de
Volume V of the sample space 9_pAsk for. On the other hand, the plane 8
As the bottom surface, and the maximum dimple depth D from this plane 8_p
Volume V of cylinder 10 with height as_QAgainst dimple sky
Volume V_pRatio V of₀To calculate.

[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 The present invention will be specifically described below by showing 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. Blistering resistance A ball was hit by a swing robot at a sand wedge (SW) at a head speed of 38 m / s once at arbitrary two points, and the two hitting points 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 is an explanatory diagram (cross-sectional view) illustrating a method of calculating dimples V ₀ .

FIG. 2 is a perspective view of the same.

FIG. 3 is a sectional view of the same.

[Explanation of symbols]

1 dimple 2 virtual sphere 3 spherical surface 4 intersections 5 tangent 6 intersections 7 Dimple edge 8 plane 9 dimple space

Continued front page    (72) Inventor Atsushi Nakamura             Bridgestone, 20 Onohara, Chichibu City, Saitama Prefecture             Within Sports Co., Ltd.

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 1.02 to 1.18. And the cover is mainly made of thermoplastic polyurethane elastomer,
Its specific gravity is larger than that of the solid core, the ball surface occupancy of the dimples is 60 to 80%, and the dimple space volume under the plane surrounded by the edges of the individual dimples is defined by the plane as the bottom surface. The value V ₀ obtained by dividing the maximum depth of the dimples by the cylindrical volume having 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 (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 solid core has a diameter of 37 to 41 mm and the solid core has a deflection amount of 2.0 to 4.5 mm under a load of 100 kg. 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 the ball radius, Nk is the number of dimples k, and V ₀ has the above-mentioned meaning), and the total dimple surface area index (Dst) is 4.0 to 7.0. Item 2. A two-piece solid golf ball according to item 1 or 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 according to claim 1, wherein the cover has a specific gravity of 1.10 to 1.25 and a difference in specific gravity from the core is 0.01 to 0.15. ball.