JP2000350795A - Solid golf ball - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solid golf ball for improving the initial velocity whether the head speed is high or low, and especially for improving the carry even when the head speed is low. SOLUTION: This golf ball has a multi-layered structure consisting of a solid core 1 with the innermost core 3 and at least one middle layer 4 to cover the innermost core 3 and a cover 2 to cover the solid core 1. The innermost core 3 rebounds less than 95 cm when it drops down naturally from the height of 120 cm, and the diameter of the innermost core 3 is 18 mm or smaller.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a golf ball capable of obtaining a high initial ball speed even when hit with a relatively low head speed and improving the flight distance.

[0002]

2. Description of the Related Art In the development of golf balls, one of the most required performances is to improve the flight distance.

[0003] In the golf rules stipulating golf games, the initial speed and the standard total distance are specified in the item d and the item e of the attached rule 3 in relation to the flight distance of the ball. Usually developed according to these rules.

For example, various multi-piece golf balls, such as three-piece and four-piece golf balls, have been proposed. However, since these golf balls are often developed in accordance with the above-mentioned rules, they mainly have a high head speed. It is developed for players, and when a low head speed player hits it, he cannot always obtain a satisfactory flying distance.

[0005] The present invention has been made in view of the above circumstances,
The initial speed can be improved regardless of the high / low head speed,
In particular, it is an object of the present invention to provide a solid golf ball that is excellent in resilience to a low head speed hit.

[0006]

SUMMARY OF THE INVENTION The present invention provides the following solid golf ball to achieve the above object. Claim 1: A solid golf ball formed by covering a solid core with a cover, and wherein the solid core has a multilayer structure having an innermost core and at least one intermediate layer covering the innermost core. The innermost core is 120cm high
A solid golf ball having a rebound of less than 95 cm when dropped naturally from a golf ball and having an innermost core diameter of 18 mm or less. Claim 2: The diameter of the innermost core is 2 to 18 mm.
The golf ball as described. In a preferred embodiment, the innermost core is mainly composed of a thermoplastic elastomer or a rubber composition as a main material.
3. The golf ball according to claim 1, wherein the amount of the inorganic filler is not more than 40 parts by weight based on 00 parts by weight.

According to the present invention, the initial speed can be set lower than a specified value in a specified relatively fast head speed region in accordance with a rule of an initial speed specification, and a relatively fast initial ball speed can be obtained in other ranges. Thus, a golf ball with good rebound efficiency can be provided. In other words, taking into account the deformation in a region having a relatively large amount of deformation as defined in the Rules of Golf, only that region is made to have low rebound,
By increasing the resilience in the low head speed region where many general players are distributed, a golf ball having more superior resilience to the general players is provided. Therefore, according to the present invention, golf players include not only players having so-called high head speeds, such as professionals and advanced players, but also many players having relatively low head speeds. A golf ball having a speed of about 42 m / s or less, particularly about 40 m / s or less, can be obtained.

Hereinafter, the present invention will be described in more detail. As shown in FIG. 1, the golf ball of the present invention comprises a solid core 1 and a cover 2 covering the solid core 1. Reference numeral 1 denotes a structure including an innermost core 3 and an intermediate layer 4 that covers the innermost core 3, and a cover is formed around the innermost core 3. In FIG. 1, the solid core 1 is formed in two layers and the cover 2 is formed in a single layer.
Can have a multi-layer structure of two or more layers, and the cover can be formed in a plurality of layers such as a two-layer structure and a three-layer structure.

Here, the material of the innermost core 3 constituting the solid core 1 is not particularly limited as long as it has a rebound to be described later, and a thermoplastic elastomer, a rubber composition or the like is preferably used. Can be used.

Examples of the thermoplastic elastomer include polyurethane-based thermoplastic elastomers and polyester-based thermoplastic elastomers. Commercial products include polyurethane-based thermoplastic elastomers such as T-8190 manufactured by Dainippon Ink Co., Ltd. Examples of polyester-based thermoplastic elastomers include Hytrel manufactured by Du Pont-Toray Co., Ltd.

On the other hand, the rubber composition preferably uses polybutadiene as a base material. Preferred examples of the polybutadiene include 1,4-cis polybutadiene having a cis structure of at least 40%. In the base rubber, a natural rubber, a polyisoprene rubber, a styrene-butadiene rubber, or the like can be appropriately compounded with the polybutadiene, if desired. By increasing the rubber component, the resilience of the golf ball can be improved.

In particular, when 1,4-cis polybutadiene having high resilience is used, styrene butadiene rubber may be blended with 1,4-cis polybutadiene in order to obtain the innermost core rebound performance described later. It is suitable.

The rubber composition may contain, as a crosslinking agent, a zinc salt of an unsaturated fatty acid such as zinc methacrylate or zinc acrylate, a magnesium salt, or an ester compound such as trimethylpropane methacrylate. Zinc may be suitably used. It is preferable that the compounding amount of these crosslinking agents is 10 parts by weight or more and 30 parts by weight or less based on 100 parts by weight of the base rubber.

The above rubber composition usually contains a vulcanizing agent. The vulcanizing agent contains a peroxide whose half-life reaches 155 ° C. or less in one minute. It is recommended that the compounding amount is 3
The content is 0% by weight or more, particularly 40% by weight or more, and the upper limit thereof is not particularly limited, but is preferably 70% by weight or less. Examples of such a peroxide include commercially available products, for example, Perhexa 3M (manufactured by NOF CORPORATION) and the like. The compounding amount can be 0.6 parts by weight or more and 2 parts by weight or less based on 100 parts by weight of the base rubber.

Further, if necessary, zinc oxide, barium sulfate or the like can be blended as an antioxidant or a filler for adjusting specific gravity.

In the present invention, an inorganic filler can be blended regardless of whether the material forming the innermost core is a thermoplastic elastomer or a rubber composition. Is preferably 40 parts by weight or less, particularly preferably 38 parts by weight or less, in order to improve workability in the kneading step and the like. If the amounts of these components are too large, the workability during kneading may decrease.

The innermost core of the present invention can be produced by injection molding in the case of the above-mentioned thermoplastic elastomer, and can be produced by pressure vulcanization molding of the above-mentioned rubber composition. In this case, the above-mentioned rubber composition can be manufactured by vulcanizing and curing by a known method.

In the present invention, the diameter of the innermost core is 18 mm
Hereinafter, it is preferably 17 mm or less, and more preferably 2 mm or more, preferably 5 mm or more. If the diameter is large, the resilience of the ball itself is reduced.

The innermost core of the present invention is a single core that is naturally dropped from a height of 120 cm to a sufficiently thick iron plate and has a rebound height of less than 95 cm, preferably 90 cm or less, more preferably 90 cm or less. It is 88 cm or less, and the lower limit is preferably 30 cm or more, particularly preferably 40 cm or more. In this case, if the rebound height is too high,
In particular, the resilience in a high head speed region is too high to achieve the object of the present invention.

It is recommended that the specific gravity of the innermost core be 1.1 or more, especially 1.11 or more, and the upper limit be 1.5 or less, especially 1.45 or less.

Next, the intermediate layer 4 surrounding the innermost core is
One or two or more layers can be used.
The material may be a rubber-based material, a material mainly composed of a thermoplastic resin, or a mixture of rubber and a thermoplastic resin. In this case, the above-mentioned material that can be used for the innermost core can be used for the rubber composition.

Examples of the thermoplastic resin that can be used in the intermediate layer include, for example, known thermoplastic resins and thermoplastic elastomers.
Polyarylate, ionomer resin, polypropylene resin, polyurethane-based thermoplastic elastomer, polyester-based thermoplastic elastomer, and the like can be given. Made ionomer resin), Rilsan BMNO
(Toray's nylon resin), U-Polymer U-8000
(Polyarylate resin manufactured by Unitika Ltd.) and the like can be suitably used. Further, a rubber composition can also be used, and a rubber composition composed of the components exemplified as the innermost core can be used.

Further, a mixture of these resins and rubber can be used. Specifically, as shown in JP-A-10-113406, a diene rubber such as butadiene rubber is dispersed in an ionomer resin. It may be a crosslinked one, or as shown in JP-A-10-314341, a compound obtained by blending a functional rubbery copolymer in which a carboxyl group is added to a crosslinked rubber in an ionomer resin. .

When a resin material is used, a known injection molding method can be employed as a method for obtaining the intermediate layer. When the material to be used is a rubber composition, a primary vulcanization (semi-vulcanization) is performed to produce a pair of hemispherical cups, and then the innermost core manufactured in advance is put into one hemispherical cup. A method in which the vulcanizing step of performing the secondary vulcanization (full vulcanization) with the other hemispherical cup body placed thereon and further covered with the other hemispherical cup body can be suitably adopted.

When a vulcanization step is required to form the intermediate layer with the rubber composition, the innermost core is exposed to a high temperature. Therefore, it is preferable to adjust the vulcanization temperature according to the melting point of the innermost core. However, it is desirable that the inner core used has a relatively high melting point. In this case, the innermost core placed in the hemispherical cup body is
An adhesive can be applied before placement, and the interface between the innermost core and the intermediate layer is firmly bonded with the adhesive, thereby further improving the durability of the golf ball and obtaining high resilience. Can be. It is also recommended to roughen the surface of the innermost core with a barrel polishing machine or the like to form fine irregularities on the surface and to arrange the innermost core in order to enhance the adhesion between the innermost core and the intermediate layer.

In the present invention, the thickness of the intermediate layer is not particularly limited, but is usually 0.3 mm or more, particularly 0.5 mm or more, and the upper limit is 20.0 mm or less, particularly 19.0 mm. It is recommended to be formed as follows. When the intermediate layer has a multilayer structure, the first layer directly covering the innermost core surface can be interposed as an envelope layer (inner intermediate layer). Is 0.3 mm or more, especially 0.5 mm or more, and it is recommended that the upper limit be 20.0 mm or less, especially 19.0 mm or less.

[0027] The solid core obtained by coating the innermost core with an intermediate layer, that is, before forming the cover, has an outer diameter of 36 mm or more, particularly 36.5 mm or more, and 41.5 mm or less, particularly 41.0 mm or less. Is preferred.

The amount of deflection of the solid core under a load of 100 kg is 2.0 mm or more, preferably 2.3 mm.
As described above, the thickness is more preferably 2.5 mm or more, and the upper limit is usually 6.0 mm or less, preferably 5.8 mm or less, more preferably 5.5 mm or less. If the amount of deflection is small, the feeling may be too hard, and if it is large, the ball may be too soft and the performance as a ball may be inferior.

The golf ball of the present invention is formed by covering the solid core 1 with the cover 2 and can be formed by using a known cover material.
As described above, it is particularly preferably 1 mm or more, and more preferably 4 mm or less. The Shore D hardness is 40 or more, preferably 45 or more, more preferably 50 or more, and the upper limit is 75 or less, preferably 70 or less, more preferably 65 or less. Is low, and when it is large, the durability may be poor. It is recommended that the specific gravity be 0.95 or more and 1.25 or less. As described above, the cover may have a multi-layer structure, but in this case, the total properties of the respective layers need only be within the above range.

Here, known cover materials can be used as the cover material, and examples thereof include ionomer resins, balata rubber, and thermoplastic elastomers such as polyurethane-based, polyamide-based, and polyester-based materials. Further, for forming the cover, a normal molding method can be adopted depending on the type.

The solid golf ball formed as described above has a deformation amount under a load of 100 kg of 2.2 mm or more, particularly 2.4 mm or more, and an upper limit of 4.5 mm or less, particularly 4.3 mm or less. It is recommended that

In the golf ball of the present invention, a large number of dimples are formed on the cover surface in the same manner as a normal golf ball, but the total number of dimples is 350 or more, preferably 370 or more, more preferably 390 or more. The number is 500 or less, preferably 480 or less, and more preferably 450 or less. The geometrical arrangement may be an octahedral or icosahedral arrangement, and the dimple pattern is not limited to a circle, but may be a square type, a hexagon type, a pentagon type, a triangle type, or the like. .

Further, for the purpose of improving the flight distance, the dimple diameter, dimple depth, and dimple cross-sectional shape can be optimized. The dimple surface occupancy [(dimple total surface area / ball surface area) × 100] is 65% or more, preferably 70% or more, and the dimples can be provided so that the upper limit is 80% or less. If the dimple surface occupancy is small, it may not be possible to increase the flight distance. Dimple volume ratio [(dimple total volume / ball volume) × 1
00] is 0.76% or more, preferably 0.78% or more, and can be set to 1.0% or less, preferably 0.94% or less. If the dimple volume ratio is too small, the trajectory becomes too high, and if it is too large, the trajectory becomes too low and the flight distance may decrease.

The golf ball of the present invention can be formed to have a diameter and a weight of 42.65 mm or more, particularly 42.67 mm or more and 42.75 mm or less in accordance with the Rules of Golf, and a weight of 45.93 g or less. Especially 45.90g
Below, it can be formed to 45.10 g or more.

[0035]

According to the golf ball of the present invention, the initial speed can be improved irrespective of the high / low head speed, and the flying distance can be improved even when the head speed is low. .

[0036]

EXAMPLES The present invention will be described below in detail with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[Examples and Comparative Examples] A resin component or a rubber component having the composition shown in Table 1 was used, and the innermost core, the intermediate layer (enclosure layer, the outer intermediate layer), and the cover were formed in this order according to the description in Table 2. Then, a golf ball having the same dimple on the surface was manufactured. In addition, the workability of the innermost core was evaluated as follows for the easiness of the operation at the time of kneading the innermost core material. Table 2 shows the results
Shown in Inner core workability ○: Kneading work could be performed smoothly. X: The workability of kneading decreased. Flying performance and initial speed Using a swing robot, the driver (# W1) was hit at a head speed of 50 m / s and 40 m / s, and the initial speed, carry and total flight distance were measured, respectively. Rebound measurement method A sufficiently thick iron plate (diameter 20 cm, thickness 20)
cm from a cylindrical iron plate) and a height of 1
The innermost core was freely dropped from a position of 20 cm, and the rebound height at that time was measured. For the measurement, the innermost core formed with the same composition was repeatedly dropped by n = 10 / seed, and the average value was used.

[0038]

[Table 1]

[0039]

[Table 2]

From the results shown in Table 2, it can be seen that the golf balls of the present invention of Examples 1 to 4 have high initial speeds and high flight distances at both high head speed and low head speed as compared with the comparative example. Met.

On the other hand, in Comparative Example 1, although the inner core having a relatively large rebound was used, the resilience of the ball was low because the size (outer diameter) was too large. . It can be seen from the HS 50 m / s initial speed measurement result that there is still room for the initial speed (rebound) at a high head speed. Comparative Example 2 is a golf ball having an innermost core having a rebound that is too large. Compared with the golf ball of the present invention, the initial speed and the flight distance are inferior, and the filler content of the innermost core is large. When the inner core was manufactured, the workability was poor. Comparative Example 3 is a golf ball having a double rubber structure core according to the prior art, in which the innermost core rebound is too high. This golf ball has an HS of 50 m /
Although the initial speed at the time of s is close to that of the embodiment, since the initial speed is regulated, the initial speed at a high head speed close to the specified region is almost the same as that of the embodiment as a result of adjusting to the specified value. On the other hand, at low head speeds, the values are lower than those of the embodiment.

[Brief description of the drawings]

FIG. 1 is a sectional view showing one embodiment of a solid golf ball of the present invention.

[Explanation of symbols]

 1 solid core 2 cover 3 innermost core 4 middle layer

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Takashi Maruko, Inventor Bridgestone Sports Co., Ltd., 20-20 Onohara, Chichibu City, Saitama Prefecture (72) Inventor Hiroshi Masutani 20th, Onohara, Chichibu City, Saitama Prefecture

Claims (3)

[Claims] 1. A solid core covered with a cover,
And a solid golf ball in which the solid core is formed in a multilayer structure having an innermost core and at least one intermediate layer covering the innermost core.
A solid golf ball having a rebound of less than 95 cm when dropped naturally from a cm and an innermost core diameter of 18 mm or less. 2. The golf ball according to claim 1, wherein the inner core has a diameter of 2 to 18 mm. 3. The method according to claim 1, wherein the innermost core comprises a thermoplastic elastomer or a rubber composition as a main material, and the amount of the inorganic filler is not more than 40 parts by weight based on 100 parts by weight of the main material. 3. The golf ball according to 1 or 2.