JP2001070477A - Rubber thread-winding golf ball - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a hitting feel and durability and to improve a carry by optimizing the spin performance with respect to the impact with various kinds of clubs. SOLUTION: This rubber-thread winding golf ball includes a solid center, a thread rubber layer formed of rubber threads wound on the solid center and a cover formed to cover the surface of the thread rubber layer. In such a case, the solid center has a diameter of 29 to 37 mm, has a hardness distribution lower in the hardness of the outer surface than the central part. The hardness difference between the maximum value and minimum value of the solid center hardness is >=6 in JIS-C hardness, the JIS-C hardness of the outer surface is 50 to 85 and the deformation quantity of the solid center when load from an initial load of 1 kg to a final load of 50 kg is applied thereto is 2 to 4.5 mm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thread-wound golf ball which is excellent in spin performance, hit feeling and durability in response to various club hits, and which can increase the flight distance.

[0002]

2. Description of the Related Art As a thread wound golf ball, a thread wound core in which thread rubber is wound around a solid center and a solid center of a type formed by covering a cover with an ionomer resin, balata rubber or the like is used. is there. As a method for improving such a thread-wound golf ball, enlargement of the diameter of a solid center, reduction of hardness, and the like have been proposed. 1959-129
Nos. 072, 60-168471, 60-
No. 72573, JP-A-5-337217, JP-A-6-54930, JP-A-7-313630, JP-A-8-224323, JP-A-9-271737,
Japanese Patent Application Laid-Open No. 10-108922 discloses a technique relating to a solid center having a narrow hardness distribution.
No. 238013, No. 9-271538, No. 1
Japanese Patent Application Publication No. 0-201881 is known.

[0003] However, these proposals for golf balls have the following problems. Problems with larger diameter and lower hardness of center i. By increasing the diameter and lowering the hardness of the solid center, the spin rate at impact is reduced and the flight distance can be improved, but the spin rate of all shots is reduced, so the ball on the green on approach shots Stops and the controllability decreases. ii. The center is easily deformed at the time of thread winding, and it is difficult to ensure the quality. iii. The thread rubber layer must be reduced inevitably,
It becomes difficult to ensure resilience. Problem with Solid Center with Narrow Hardness Distribution When the hardness distribution from the center of the solid center to the surface is narrow, the entire solid center is deformed in response to a short iron hit from a driver. For this reason,
If the hardness of the solid center is softened uniformly and the flight distance is improved by lowering the spin rate on driver shots, the amount of spin on a short iron will also decrease, and control performance will decrease. Conversely, if the solid center is hardened to improve the controllability, the spin increases even on a driver shot, resulting in a reduction in flight distance.

On the other hand, when the head speed is low and the amount of deformation of the golf ball is small, as in an approach shot,
In order to increase the spin amount and improve the stopping on the green, the contribution of the cover becomes larger than the deformation amount of the ball, so it is necessary to soften the cover, but as described above, with the improved solid center, In combination,
Even when hit with another club, the spin amount increases, so it is difficult to obtain satisfactory spin performance for all club shots such as drivers, short irons, etc., such as blowing up in a head wind or decreasing the flight distance. .

The present invention has been made in view of the above circumstances, and is a thread-wound golf ball having excellent spin performance corresponding to various club shots, excellent hit feeling and durability, and capable of increasing the flight distance. The purpose is to provide.

[0006]

Means for Solving the Problems and Embodiments of the Invention The present inventors have made intensive studies to achieve the above object, and as a result, the spin performance of a golf ball is determined by the amount of deformation of the ball when hit, It was determined by the frictional force between the ball and the club face that the larger the deformation of the ball at the time of impact, the smaller the spin rate, and the harder the cover and the smaller the deformation, the smaller the spin rate.

Further, in order to improve the controllability with iron shots, it is necessary to form the cover softly and increase the spin rate. However, if the cover is simply softened to increase the spin rate, the driver is required to increase the spin rate. In shots and iron shots, the trajectory became too high when headwinds were encountered and the flight distance was reduced, so optimization of the amount of deformation of the ball with respect to cover hardness was studied.

Accordingly, in a thread-wound golf ball comprising a solid center, a thread rubber layer formed by winding thread rubber around the solid center, and a cover formed by covering the thread rubber layer, the diameter of the solid center is When,
By adjusting the hardness distribution and the difference between the maximum value and the minimum value of the hardness of the center itself, the JIS-C hardness of the surface of the solid center and the amount of deformation under a predetermined range of load, the club and the head speed are all changed. It has been found that an excellent spin performance that can respond to each scene can be obtained, and that a golf ball that has good hit feeling and durability and can improve the flight distance can be obtained.

In this case, the diameter of the solid center is A
(Mm), and when the amount of deformation of the solid center under a specific range of load is B (mm), the specific amount of deformation in this region, and further, the cover forming material and the Shore D hardness are specified. By doing so, when hitting with a high head speed and a large impact force like a driver shot, the amount of deformation of the center is larger than the conventional solid center, but it does not deform too much, a stable spin amount is obtained, and short Even when the head speed is low and the impact force is small, such as when shot with an iron, the solid center is easily deformed, and it has excellent hit feeling and durability, and it is possible to further increase the flight distance. The present invention has been accomplished.

Accordingly, the present invention provides the following golf ball. Claim 1: A thread-wound golf ball comprising a solid center, a thread rubber layer formed of thread rubber wound on the solid center, and a cover formed on the surface of the thread rubber layer. Center is diameter 2
9 to 37 mm, and has a hardness distribution in which the hardness of the outer surface is lower than that of the center portion, and the hardness difference between the maximum value and the minimum value of the solid center hardness is JIS-C hardness 6 or more, and the JIS- A thread-wound golf ball having a C hardness of 50 to 85 and a deformation amount of a solid center of 2 to 4.5 mm when a load from an initial load of 1 kg to a final load of 50 kg is applied. Claim 2: A diameter of the solid center is A (mm), and an initial load of 1 kg to a final load of 50 kg is applied to the solid center.
The amount of deformation of the solid center when a load of up to
The thread-wound golf ball according to claim 1, wherein the following relational expression is satisfied when (mm). −0.1 × A + 5 ≦ B ≦ −0.3 × A + 14 3. The thread-wound golf ball according to claim 1 or 2, wherein the cover is mainly composed of an ionomer resin and has a Shore D hardness of 40 to 60.

Hereinafter, the present invention will be described in more detail. The thread wound golf ball of the present invention has a cover wound around a thread core formed by winding thread rubber around a solid center.

Here, the solid center will be described in detail. The solid center of the present invention is a known rubber composition comprising a base rubber mixed with a co-crosslinking agent, an organic peroxide, an inert filler, an antioxidant, and the like. Can be obtained by heating, pressing and molding.

First, as the base rubber, specifically, polybutadiene or a mixture of polybutadiene and polyisoprene rubber which has been conventionally used for a solid center can be used. In order to obtain cis-1,4-polybutadiene having a cis structure of 40% or more, it is preferable to use cis-1,4-polybutadiene.

As the co-crosslinking agent, for example, zinc salts of unsaturated fatty acids such as methacrylic acid and acrylic acid, magnesium salts and ester compounds such as trimethylpropane trimethacrylate can be used. Zinc acrylate can be suitably used. The amount of the co-crosslinking agent is not particularly limited, but is not less than 10 parts by weight, especially not less than 15 parts by weight, and not more than 40 parts by weight, especially 35 parts by weight, based on 100 parts by weight of the base rubber. It can be:

As the peroxide, for example, commercially available peroxides such as perhexin 2,5B or a mixture of perhexin 2,5B with Parkmill D and Perhexa 3M (all manufactured by NOF Corporation) are preferably used. The compounding amount is 0.5% by weight or more, especially 0.5% by weight, in the case of a product containing 40% peroxide, based on 100% by weight of the base rubber.
It is preferably at least 8 parts by weight, more preferably at most 4.0 parts by weight, particularly preferably at most 3.5 parts by weight.

As the anti-aging agent, a bisphenol-based anti-aging agent is suitable, and Nocrack NS-
6 (manufactured by Ouchi Shinko Chemical Co., Ltd.) in an amount of usually 0.2 parts by weight or more, particularly 0.4 parts by weight or more, and 1.2 parts by weight or less, particularly 1.0 part by weight, based on 100 parts by weight of the base rubber. Less than parts by weight can be used.

Examples of the inert filler include zinc white, barium sulfate, silica, calcium carbonate and zinc carbonate. In general, it is preferable to use zinc white and barium sulfate. Is adjusted accordingly,
In particular, in order to improve the resilience of the solid center,
It is recommended to add zinc white to 30% by weight or more, especially 50% by weight or more of the total filler. Also, in order to prevent deformation of the center when the rubber thread is wound around the solid center, the center is frozen with dry ice. 2% by weight or more, especially 5% by weight or more,
% By weight, especially 15% by weight or less.

In order to obtain a solid center from the above materials, the solid center can be manufactured according to a known method. After kneading using a kneading machine such as a Banbury mixer or a roll,
The material can be placed in a center mold, heated to a temperature sufficient for the co-crosslinking agent and peroxide to act, and vulcanized and cured.

In order to obtain an appropriate hardness distribution of the solid center described later, the vulcanization temperature is usually set to 140 ° C. or higher, particularly 145 ° C. or higher, and preferably 180 ° C. or lower, particularly 175 ° C. or lower. .

The solid center of the present invention has a diameter of 29.
mm or more, especially 32 mm or more, at most 37 mm or less, especially 34 mm or less, if the diameter of the solid center is too small, low spin is not achieved by hitting the driver, which may lead to a reduction in flight distance. If it is too large, it will not be possible to wind a sufficient amount of thread rubber, and it will not be possible to ensure sufficient resilience, and it will also cause a decrease in initial speed, resulting in excessive deformation when hitting, In some cases, the spin rate at the time may decrease or controllability may be impaired.

The hardness of the solid center of the present invention requires that the hardness of the outer surface be lower than that of the center portion, but the JIS-C hardness of the outer surface is 50 or more, preferably 54 or more, more preferably 56 or more. And the upper limit is 85
In the following, it is particularly required to be 80 or less. J on outer surface
If the IS-C hardness is too soft, the center is likely to be deformed at the time of winding the yarn, and if the JIS-C hardness is too hard, the spin at the time of impact becomes so large that the flight distance is reduced.

Further, according to the solid center of the present invention, the hardness difference between the maximum value and the minimum value of the hardness of the entire center is JIS-
C hardness of 6 or more, preferably JIS-C
Hardness 7 or more, more preferably 8 or more, with an upper limit of 12
In the following, it can be made especially 10 or less.

In this case, the maximum value and the minimum value of the hardness can be specified by measuring the hardness at arbitrary positions from the center of the center to the outside, and calculating the difference between the maximum value and the minimum value. In the solid center of
After cutting the center in half and polishing the cut surface smoothly,
The hardness of the center of the solid center, 5 mm from the center, 10 mm from the center, 12 mm from the center, and the hardness at any point on the outer surface may be measured, and the minimum value may be subtracted from the maximum value of the hardness at these five points. As the center, a position within 70% of the center diameter is appropriate.
It is not preferable to measure the hardness of the cross section at the position of 3 mm.

Further, the solid center of the present invention has a diameter of A (mm) when the solid center is subjected to a load from an initial load of 1 kg to a final load of 50 kg (hereinafter referred to as a load of 1 to 50 kg). When it is assumed that the deformation amount is B (mm), it is desirable that the following relationship is satisfied: −0.1 × A + 5 ≦ B ≦ −0.3 × A + 14.

In this case, the solid center of the present invention is formed so that the deformation amount is 2.0 mm or more, preferably 2.1 mm or more, and is 4.5 mm or less, preferably 4.0 mm or less. If the amount of deformation is small, the spin at the time of hitting becomes too large, and if the amount of deformation is large, the center will be deformed even if the center is frozen during winding of the rubber thread as described later.

In the present invention, the weight and resilience of the solid center are not particularly limited.
g or more, especially 17 g or more, and preferably 30 g or less, particularly 29 g or less. In addition, the solid center is raised from a height of 120 cm to a diameter of 1.0 cm and a height of 10 cm.
It is preferable that the rebound height when dropped on an iron cylindrical column of cm is 96 cm or more, particularly 97 cm or more.

Next, in order to obtain a wound core by winding a rubber thread around the solid center, a known method can be adopted.
The solid center may be wound as it is or frozen to prevent deformation, and the thread rubber may be wound in a highly stretched state. In this case, a known rubber thread can be used, and examples thereof include a rubber thread formed of a rubber composition mainly composed of polyisoprene rubber. Its properties are not particularly limited, but usually have a specific gravity of 0.93.
As described above, the upper limit is 1.1 or less, particularly 1.0 or less, and the width is 1.4.
mm or more, especially 1.5 mm or more, the upper limit is 2.0 mm or less, particularly 1.7 mm or less, the thickness is 0.3 mm or more, especially 0.4 mm or more, and the upper limit is 0.7 mm or less, especially 0.6 mm or less.
mm or less, and the ratio of the width to the thickness of the rubber thread (thickness / width) is 0.3 or more, especially 0.35 or more, and 0.7 or less, especially 0.5 or less. Is preferred.

The method of winding the rubber thread is not particularly limited, and may be, for example, random winding (basket winding), great circle winding, or the like. Also, the degree of elongation of the rubber thread at the time of winding is required to be as high as possible in order to secure an appropriate amount of deformation.However, if the degree of elongation of the rubber is too high, cuts frequently occur during thread winding, Since the productivity may decrease and the durability and feel of the ball may deteriorate, it is usually 7 to 10 times, particularly 8 times.
It is preferable to wind at up to 9 times. In this case, in order to optimize the density of the thread rubber layer, it is recommended that the voids formed by overlapping the thread rubbers be uniformly distributed throughout the thread rubber layer. 4
Preferably it is 5 degrees.

The rubber thread layer of the golf ball of the present invention has a filling ratio (total weight of rubber thread / volume of rubber thread layer / specific gravity of rubber thread) of 0.65 in order to optimize deformation of the ball when hit.
g / cm ³ or more, especially 0.70 g / cm ³ or more,
It is preferably 0.90 g / cm ³ or less, and particularly preferably 0.85 g / cm ³ or less. If it is small, the amount of deformation of the ball may increase, and even if the surface hardness of the ball is relatively soft, the spin amount is low. It may decrease or the controllability may be impaired.If it is large, the amount of deformation of the ball is too small,
In some cases, the hit feeling is deteriorated, the spin rate on a driver shot becomes too large, and the flight distance is reduced.

The thread-wound golf ball of the present invention is formed by covering a wound core wound with the above thread rubber with a cover. In this case, the cover may have a single layer or a multilayer structure of two or more layers.

Here, when the cover of the present invention is formed into a single-layer cover or a multilayer structure, a known cover material can be used as the material of the outer layer cover. Specifically, the use of an ionomer resin alone, A combination of an ionomer resin with an ethylene-methacrylic acid copolymer or an ethylene-methacrylic acid-acrylate copolymer may be used.

As the above-mentioned ionomer resin, known ones can be blended, for example, Himilan 185
5, 1856, 1652 (manufactured by DuPont-Mitsui Polychemicals), Surlyn 8120, 7930, AM7
311 and AM8542 (manufactured by Dupont) can be used, and these can be used alone or as a mixture of two or more. Particularly, an ionomer resin having two or more kinds of neutralized metal ions can be used. It is preferable to use, and it is recommended to use two or more ionomer resins having different neutralizing metal ions in combination.
Examples include combinations of Na, Mg / Li, Mg / Na, and the like.

Examples of the ethylene-methacrylic acid copolymer include Nuclel N1560 (manufactured by DuPont-Mitsui Polychemicals) and the like. Examples of the ethylene-methacrylic acid-acrylic acid ester copolymer include: For example, Nuclell AN4311, AN42
13C and N035C (manufactured by DuPont-Mitsui Polychemicals).

In the present invention, the use of an ionomer resin alone as the cover material is recommended, but the ionomer resin is mixed with an ethylene-methacrylic acid copolymer or an ethylene-methacrylic acid-acrylate copolymer in combination. In this case, the content of the ethylene-methacrylic acid copolymer or the ethylene-methacrylic acid-acrylic acid ester copolymer relative to the entire cover material is usually less than 50% by weight, preferably 45% by weight or less, and the lower limit was 5% by weight
As described above, it is particularly preferable to adjust the content to 10% by weight or more. If the content is too large, scorching tends to occur at the time of impact, and a problem may occur in durability. If the amount is too small, the cover becomes hard, and the controllability with an iron may decrease.

The cover hardness formed by the cover material is not particularly limited, but when the cover is formed using only the ionomer resin, the Shore D hardness is usually 40 or more, preferably 44 or more. And it is recommended to be 60 or less, especially 56 or less. If the Shore D hardness is soft, too much spin is applied, which may cause a decrease in flight distance. If the Shore D hardness is too hard, controllability may be reduced. is there.

The specific gravity of the cover material is usually 0.95 or more, particularly 0.97 or more, and the upper limit is 1.3 or less, particularly 1.2.
It is preferable to set the following.

When a cover is formed using the above-mentioned cover material, the thickness of the single-layer cover is usually 1 mm or more, particularly 1.5 mm or more, and the upper limit is 3.2 mm or less, particularly 2.5 mm or less. When the outermost cover is a cover having a two-layer structure or more, the thickness is 0.4 mm or more, particularly 0.6 mm.
As described above, the upper limit can be set to 1.6 mm or less, particularly 1.4 mm or less. When a cover other than the outermost layer is formed, the total thickness is the same as the single-layer cover and the Shore D hardness is set. Can be adjusted. If the cover thickness is too thin in the above range, the spin rate on approach shots cannot be increased, and the durability of the ball deteriorates. If the cover thickness is too thick, the resilience decreases and the flight distance may decrease.

A known method can be used to cover the wound core with the cover material using the cover material. For example, a pair of hemispherical shell-shaped half cups are respectively prepared in advance using the inner and outer layer cover materials. These inner and outer half cups are stacked and bonded together to form a pair of two-layer half cups.
Compression molding for 10 to 10 minutes, encasing the wound core with only the inner layer half cup,
After compression molding at 0 ° C. for 2 to 10 minutes, a method of disposing the compression molding in an injection mold and injecting the outer layer cover can be used.

Dimples are formed on the surface of the cover according to a known method. Usually, the number of dimples is 350 or more, preferably 370 or more, more preferably 390 or more, and the upper limit is 500 or less. Is 4
The number is 80 or less, more preferably 450 or less. If the number of dimples is small, the diameter of each dimple needs to be increased, and the roundness of the ball decreases.If the number of dimples is large, the diameter of each dimple needs to be reduced, and the effect as a dimple is lost. There is.

The dimple diameter, depth, cross-sectional shape and the like are not particularly limited.
4 mm or more and 2.2 mm or less, and the depth can be 0.15 mm or more and 0.25 mm or less, and two or more kinds of dimples having different diameters and depths can be formed. .

When the dimple surface occupation ratio, that is, when the golf ball is regarded as a virtual sphere without dimples, the surface area of the virtual sphere surrounded by the edge of each dimple is 65% or more of the total area of the virtual sphere, preferably. Can be 70% or more, and the dimple can be provided so that the upper limit is 80% or less, particularly 78% or less. If the dimple surface occupation ratio is small, the above-mentioned excellent flight characteristics, particularly, an increase in the flight distance may not be obtained. If the occupancy is too high, the edges of the dimples may be narrowed and may be easily shaved when hit with an iron.

The dimple volume ratio [(dimple total volume / ball volume) × 100] is 0.76% or more, preferably 0.78% or more, and the upper limit is 1.1% or less, preferably 1.04%. (Here, the ball volume refers to the volume of a true spherical golf ball assuming that there are no dimples on the surface of the golf ball, and the total dimple volume is the sum of the volumes of the respective dimples. If the dimple volume ratio is small, the trajectory may be too high and the flight distance may be reduced. If the volume ratio is large, the trajectory may be too low and the flight distance may be reduced.

Further, the product of the dimple volume (mm ³ ) and the half power of the average dimple diameter (mm) is preferably 500 or more, more preferably 550 or more, and the upper limit is 800 or less, particularly 750 or less.

The geometric arrangement of the dimples includes an octahedral arrangement and an icosahedral arrangement. 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. Anything can be adopted.

The golf ball of the present invention can be formed to have a diameter and a weight of not less than 42.67 mm and a weight of not more than 45.93 g in accordance with the Rules of Golf.

[0046]

The golf ball of the present invention has a proper spin performance against various club hits, has good hit feeling and durability, and can improve the flight distance.

[0047]

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] Using the rubber compositions shown in Table 1, vulcanization pressure molding was performed under the conditions shown in Table 1 to produce a solid center. The ingredients shown in Table 1 are as follows.

Solid center compound BR01: High-cis polybutadiene antioxidant manufactured by Nippon Synthetic Rubber Co., Ltd .: Nocrack NS- manufactured by Ouchi Shinko Chemical Industry Co., Ltd.
6 Perhexin 2, 5B: Peroxide 40% manufactured by NOF Corporation
Included products Perhexa 3M: Pure product manufactured by NOF Corporation Park Mill D: Pure product manufactured by NOF Corporation Shape and physical properties of the solid center Deformation amount of the center when a load of 1 to 50 kg is applied (m
m) Average value of solid center diameter, weight and deformation amount were measured at each position after cutting each of 12 average values of 5 Jls-C hardness solid centers into 5 halves and polishing the cut surface flat. The average value at each position is obtained, and the value obtained by subtracting the minimum value from the maximum value is calculated as JIS-
Calculated as C hardness difference.

Next, a thread rubber having the following composition and shape was wound around the obtained core to obtain a thread-wound core. Thread rubber-containing polyisoprene rubber 70 parts by weight Natural rubber 30 parts by weight Zinc white 1.5 parts by weight Stearic acid 1 part by weight Vulcanization accelerator 1.5 parts by weight Sulfur 1 part by weight Specific gravity: 0.93 500% modulus 15 kg / cm ² Thread rubber dimensions: width 1.55mm, thickness 0.55mm

After kneading the cover materials shown in Table 2 using a twin-screw extruder, a pair of hemispherical shell-shaped half cups were formed with each cover material. Next, the wound core is covered with a half cup and compression-molded at 145 ° C. for 5 minutes to obtain a dimple surface occupancy of 76%, a volume ratio of 0.88%, and a wound golf ball having 396 dimples in total. It was created.

The obtained golf ball is 100 k
The amount of deformation (mm) when a load of g was applied was measured. In addition, using a swing robot, driver (W #
1), Iron (I # 9), Sand Wedge (S / W)
, Using a head speed (HS) of 45 m / s in order,
The golf ball was hit at 36 m / s and 20 m / s, respectively, and the initial speed, elevation angle, carry, total, and spin amount were checked according to the items. Table 3 shows the results.

[0053]

[Table 1]

[0054]

[Table 2]

[0055]

[Table 3]

Claims (3)

[Claims] 1. A thread wound golf ball comprising a solid center, a thread rubber layer formed of thread rubber wound around the solid center, and a cover formed on the surface of the thread rubber layer. The solid center has a diameter of 29 to 37 mm, has a hardness distribution in which the hardness of the outer surface is lower than that of the center, and the hardness difference between the maximum value and the minimum value of the solid center hardness is JIS-C hardness 6 or more, JIS-C hardness of the surface is 50 to 85,
A thread-wound golf ball, wherein a deformation amount of a solid center when a load from an initial load of 1 kg to a final load of 50 kg is applied is 2 to 4.5 mm. 2. The solid center has a diameter of A (mm),
An initial load of 1 kg to a final load of 50 is applied to the solid center.
The following relational expression is satisfied when the amount of deformation of the solid center when a load up to kg is applied is B (mm).
The thread-wound golf ball according to the above. −0.1 × A + 5 ≦ B ≦ −0.3 × A + 14 3. The cover is mainly composed of an ionomer resin,
3. The thread wound golf ball according to claim 1, wherein the Shore D hardness is 40 to 60.