JP2002126128A - One-piece golf ball - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a one-piece golf ball having a characteristic such as a multistructure while maintaining required durability. SOLUTION: In a golf ball composed of a single elastic body, this one-piece golf ball forms a part on the radial-directional inside of a position and a part softer than a ball surface part in the position in the close vicinity to a ball surface.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a one-piece golf ball having characteristics such as a plurality of structures made of different materials.

[0002]

2. Description of the Related Art Golf balls can be roughly classified into a course ball or a game ball used in a golf course and a practice ball used in a driving range depending on the application. For a course ball, usually the flying distance and the feel at impact are more important than the durability, so in the case of a solid structure that has been overwhelmingly popular in recent years, a rubber core with high rebound resilience and its A structure is known in which the periphery is covered with a plurality of resin covers having different physical properties, for example, a thickness of about 1.5 mm and a thickness of about 1.5 mm. Normally, the core portion is mainly used for the flight distance characteristics, and the outer hard cover is used for the trauma and abrasion resistance characteristics. In addition, an inner cover that is softer than the inner and outer adjacent layers is additionally arranged to obtain a good hit feeling. .

On the other hand, the structure of a practice ball is generally
The actual condition of use is that hits are repeated hundreds of times over a long period of time in a practice area set up on a relatively narrow site,
Therefore, there are many so-called one-piece balls formed of a single layer of rubber in connection with good durability, in which cracks, chipping, and the like, which are required for the ball, hardly occur.

[0004] In terms of hardness, such a one-piece ball is known to be formed to have almost the same hardness from the surface to the center of the ball as shown by a line Y in FIG. 182278) However, in this case, there are drawbacks such as a hard hit feeling at the time of hitting the ball and a heavy hit. On the other hand, in order to obtain a soft hit feeling, as shown by the line Z in FIG. There is known one in which hardness is gradually reduced toward a position (Japanese Patent Laid-Open No. 11-244418). But in this case too,
Although some softening of the feel is recognized, it has not been said that it has been solved yet.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide a one-piece golf ball having characteristics such as a multi-structure while maintaining necessary durability.

[0006]

SUMMARY OF THE INVENTION The present invention is directed to a golf ball made of a single elastic material, which is softer than the ball inner portion and the ball surface at a position close to the ball surface. A one-piece golf ball characterized by forming the above-mentioned portion.

It is preferable that the bottom position of the hardness in the soft portion is formed within a range of 0.2 to 3 mm in the radial direction from the ball surface. In that case, it is preferable that the JIS-C hardness at the bottom position of the above hardness is at least 2 points, more preferably 3 to 10 points smaller than the maximum value of the hardness of the inner part or the outer part in the radial direction. Further, the hardness difference at the hardness bottom position is:
It is more preferable to set the maximum hardness on both the inner side and the outer side in the radial direction.

The JIS-C hardness of the center of the ball and the surface of the ball are preferably in the range of 50 to 90 and 60 to 95, respectively.
In addition, the hardness distribution from the ball center to the radially outer side generally increases in the above hardness range, and forms a soft portion in which the hardness sharply decreases at a position close to the ball surface.
It is preferable that the portion having the highest hardness is formed on the ball surface or near the ball surface. However, the portion having the highest hardness may be provided at an intermediate portion between the ball center and the ball surface.

[0009]

An embodiment will be described below with reference to the drawings. FIG. 1 is a cross-sectional view of a one-piece golf ball, wherein reference numeral 1 denotes a golf ball, 2 denotes a ball body, 3 denotes a ball surface, 4 denotes a ball center, and 5 denotes a dimple. Usually on the ball surface
Although there is a layer of a coating film by painting, illustration is omitted.

The ball body 2 is formed of a single rubber layer. As the base rubber, natural rubber and / or synthetic rubber conventionally used for this type of ball can be used. Is preferably cis-1,4-polybutadiene having at least 40% by weight. If desired, natural rubber, polyisoprene, styrene-butadiene rubber and the like can be appropriately blended with the above-mentioned polybutadiene.

In order to increase the hardness, impact strength, durability and the like of the ball, zinc oxide, silicon oxide, calcium carbonate, aluminum silicate and the like can be blended as an inorganic filler.

Crosslinkable monomers for mainly exhibiting rebound resilience of the rubber composition include α, β-monoethylenically unsaturated carboxylic acids such as methacrylic acid and acrylic acid, or metal salts thereof, and trimethylpropane trimethacrylate. And polyfunctional methacrylates, trimethylolpropane triacrylate, and the like.

Examples of the crosslinking initiator include dicumyl peroxide, 2,2-di (tert-butylperoxy) butane,
For example, tert-butyl perbenzoate can be used.

[0014] In addition to the base rubber, inorganic filler, cross-linking monomer, and cross-linking initiator listed above as the rubber composition for the ball body 2, an anti-aging agent and other additives are appropriately compounded as necessary. can do.

FIG. 2 shows the hardness distributions of Examples 1, 2, 3 and 4 of the golf ball of the present invention, which have different compositions. The horizontal axis in FIG. 2 is the distance from the ball center 4 to the surface 3 (FIG. 1), the vertical axis is the JIS-C hardness, and the lines A, B, C and D are in Examples 1, 2, 3 and 4, respectively. Corresponding. Table 1 shows the compounding contents of these examples. Table 2 shows the blending contents of Comparative Examples described later.

[0016]

[Table 1]

[Table 2]

In measuring the hardness, as shown in FIG. 3 (cross-sectional view) and FIG. 4 (side view), each of the vertical and horizontal lengths a and b of the hemispherical portion of the ball 1 around the center line j is 10 mm. Was cut out, and a hardness tester was pressed against the prism 6 in parallel with the direction of the line j for measurement. And in that case, from the position of the ball surface 3 (height or radius r = 21.35 mm),
In the vicinity of surface 3 where the hardness changes rapidly (within a range of about 5 mm from surface 3), scraping is performed with a register of about 0.2 mm, and the measurement is repeated each time. FIG. 2 was obtained by shaving off, repeating the measurement in each case in the same manner, and graphing the results corresponding to the measurement positions.

In FIG. 2, curve A (Example 1) shows that the hardness is gradually increased from the center of the ball having a hardness of 54.5 to the radially outer side or to a position 62 at a hardness of about 17 mm away from the ball surface, and then the hardness is increased by 20 mm. Hardness sharply decreases to the bottom position of hardness 59 away, and from there the surface position (21.35 mm)
Has rapidly increased to a hardness of 67. The hardness at the center position is 67
Curve B (Example 2) starting with, and Curve C also starting with 68
(Example 3) and the curve D starting from 79 (Example 4) also have a hardness distribution to the surface position that is substantially similar to the curve A.
However, the highest point before the hardness begins to decrease is, in the case of curve B, similar to curve A, at about 17 mm from the center, while curves C and D are approximately 12 mm and 8 mm from the center, respectively.

On the other hand, the bottom position of the hardness is formed at a point of about 20 mm through the curves A to D or about 1.35 mm radially inward from the surface position. However, 0 .0 from the surface position.
It can be provided in an area 2 to 3.0 mm apart. The hardness difference of the hardness bottom position with respect to the maximum value inside and outside (surface position) in the ball radial direction is 3 and 8 in the case of the curve A, and the curve B in the case of the curve A.
Are 3.5 and 7.5, curve C is 7.5 and 9, curve D is 1
0 and 4.5.

In preparing the test ball, although not shown, it was molded using a mold having a spherical cavity formed therein. More specifically, a two-part mold having a large number of dimple-molding projections on the inner wall surface of the cavity and having a parting surface at a position corresponding to the equator of the cavity.

In Examples 1 to 4 of the present invention, a columnar slag was formed from the composition having the composition shown in Table 1, and the temperature was 30 ° C.
Into the mold set at a temperature of 5 ° C., and then gradually increase the mold temperature to approximately 160 ° C. in a straight line within 5 minutes.
Molding was carried out under vulcanization conditions of heating up to the maximum.

Comparative Examples 1 and 2 were added to these examples, and a comparative test of hit feeling and crack durability was performed and evaluated. Table 2 shows the formulations of Comparative Examples 1 and 2. Comparative Example 1
Is a slag molded at 173 ° C.
17 minutes and 20 seconds in a mold at a constant temperature set to
Was similarly molded in a mold at a constant temperature of 178 ° C. under vulcanization conditions of 12 minutes and 50 seconds.

Table 1 shows the test results of Examples 1 to 4, and Table 2 shows the test results of Comparative Examples 1 and 2. Table 1,
The display in the test result column of No. 2 is as follows. The feel of the impact is a driver ($ 1W) by amateur golfers
And a pitching wedge (PW) to apply an average sensory evaluation, respectively, to apply a soft feel to a circle, a slightly too hard or slightly too soft feel to a △ mark, and a too hard or too soft feel to ×. It is represented by a mark. The durability to cracking was evaluated by using a hitting machine, repeatedly hitting 10 balls at a head speed of 40 m / s, and comparing the number of hits of the ball that cracked the fastest as an evaluation target. However, all of them were of a very high standard, so all were marked with a circle.

[0024]

As described above, the golf ball according to the present invention has a single-structured elastic body, but has a radially inner portion and a softer portion than the ball surface at a position close to the ball surface. Therefore, in terms of characteristics, it has a soft feel similar to a three-piece structure in which a soft layer and hard layers are laminated on both sides thereof. Therefore, in addition to this good feel, even if you practice the ball for a longer time than usual, the feeling of fatigue is small, while the crack durability required for this kind of ball is sufficient as shown in the test results There is no need to worry about peeling failures that are likely to occur at the lamination interface which is inevitable in at least the three-piece structure.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a one-piece golf ball.

FIG. 2 is a hardness distribution diagram of an example in the present invention.

FIG. 3 is a cross-sectional view of a ball applied to the hardness measurement of the example.

FIG. 4 is a side view of a ball applied to the hardness measurement of the example.

FIG. 5 is a hardness distribution diagram of a conventional one-piece golf ball.

[Explanation of symbols]

 1 golf ball 2 ball body 3 ball surface 4 ball center 5 dimple

Claims (7)

[Claims] 1. A one-piece golf ball comprising a single elastic body, wherein a golf ball having a radially inner portion and a softer portion than the surface of the ball are formed at a position close to the ball surface. 2. The one-piece golf ball according to claim 1, wherein a bottom position of the hardness in the soft portion is formed within a range of 0.2 to 3 mm in a radial direction from the ball surface. 3. The one-piece golf ball according to claim 2, wherein the bottom position of the hardness is at least 2 points smaller in JIS-C hardness than the maximum value of the hardness of the radially inner or outer portion. 4. The JIS-C hardness of the ball center and the ball surface is 50 to 90 and 60 to 95, respectively.
A one-piece golf ball as described. 5. The one-piece golf ball according to claim 1, wherein a soft portion whose hardness generally increases radially outward from the center of the ball and whose hardness rapidly decreases near the surface of the ball is formed. 6. The one-piece golf ball according to claim 1, wherein a portion having the highest hardness is substantially formed on the surface of the bowl. 7. The one-piece golf ball according to claim 1, wherein the portion having the highest hardness is formed substantially at an intermediate position between the center of the ball and the surface.