JPH09294830A - Thread wound golf ball - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high-performance and high-quality golf ball, by which the flying distance can be increased, and which is excellent in abrasion-resistance when it is hit by an iron club, discoloration and moldability. SOLUTION: In a thread wound gold ball formed by covering a thread wound core 3 comprising a solid center and a thread rubber layer 2 made by winding thread rubber round the center 1 with a cover 4, the cover 4 is mainly composed of non-yellowing thermoplastic polyurethane elastomer and a difference between the center specific gravity and the cover specific gravity is 0.2 or less.

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 comprising a thread-wound core in which a thread rubber layer is formed on the outer periphery of a solid center and a cover is covered with the thread-wound golf ball.
By using a non-yellowing thermoplastic polyurethane elastomer with high specific gravity as the cover material, the moment of inertia is increased, the flight distance is increased, the abrasion resistance on iron shot is improved, and the discoloration of the cover surface is improved. Low thread wound golf ball.

[0002]

2. Description of the Related Art
A thread-wound golf ball is formed by winding a high elongation thread rubber around a liquid center or solid center to form a thread rubber layer around the center, and covering the thread rubber layer with a cover made of balata rubber or ionomer resin. Being manufactured.

[0003] This thread-wound golf ball is preferred by professionals and advanced players because it has a softer hitting feel and is superior in spin performance (easy to apply spin) as compared with a two-piece solid golf ball. There is a disadvantage in that the ball is dandruffed by spinning and is inferior to a two-piece solid golf ball in flight distance.

For this reason, various developments of thread wound golf balls aiming at increasing the flight distance have been studied. One of them is an attempt to increase the moment of inertia of the golf ball.

That is, the moment of inertia of a golf ball is
It has a significant effect on the trajectory, flight distance, controllability, etc., when a golf ball flies, and in general,
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 a putter is hit on the green, the straightness is high and the rolling is good. Therefore, a proposal has been made for a golf ball that can obtain a large moment of inertia from such a point (Japanese Patent Publication No. 5-73427,
JP-A-59-129072 and JP-A-60-210272). Specifically, it has been proposed to blend an ionomer resin with a filler having a high specific gravity such as white barium sulfate and titanium oxide to increase the moment of inertia (Japanese Patent Laid-Open Publication No. 6-58242).
1-290969).

However, in the above proposal, the fluidity of the cover material is lowered, and in the thread-wound golf ball, the cover is less likely to penetrate into the thread rubber layer, the durability may be lowered, and the resilience is lowered. In addition to reducing the flight distance, there was a problem that the cover was raised or fluffed.

Further, attempts have been made to blend a high-weight filler such as tungsten having a specific gravity of 8 or more into the cover, but there is a limit in the blending with a weight regulator, and the whiteness of the cover cannot be satisfied. There was also a problem.

On the other hand, various studies have been conducted on cover resins, and many attempts have been made to use a thermosetting polyurethane elastomer having a good feeling and scuff resistance at a relatively low price as an alternative to balata rubber or ionomer resins. Proposed (US Pat. No. 4,123,061)
No. 3,985,568, No. 5,334,673).

However, although the above-mentioned thermosetting polyurethane elastomer is excellent in scratch resistance, which is a drawback of the softened blend of ionomer resin, it requires complicated operations such as curing reaction after the raw material is injected, and thus it is mass-produced. Needs a lot of hard work. In addition, the curing reaction rate of a thermosetting polyurethane elastomer using only an aliphatic isocyanate is slow, and it is preferable to partially use an aromatic isocyanate in order to increase the reaction rate. However, even if a white enamel paint is applied on the outside and concealed, the appearance color tone of the ball as well as the yellowing of the urethane cover changes.

On the other hand, various studies have been made on covers using thermoplastic polyurethane elastomers (US Pat. Nos. 3,395,109, 4,248,432, and 4).
No. 4,422,28), these thermoplastic polyurethane elastomers have improved scratch resistance and moldability upon hitting with an iron, but at present, an increase in flight distance due to an increase in moment of inertia can still be sufficiently satisfied. However, it is desired to develop a golf ball having higher performance and higher quality.

The present invention has been made in view of the above circumstances, and the flight distance is increased by the increase of the moment of inertia, and the abrasion resistance, discoloration, and moldability upon hitting with an iron are all excellent. To provide a high quality wound golf ball.

[0012]

Means for Solving the Problems and Modes for Carrying Out the Invention As a result of intensive studies to achieve the above object, the present inventors have found that a solid center and a rubber thread layer around which a rubber thread is wound are formed. In a thread-wound golf ball comprising a thread-wound core consisting of a cover, a non-yellowing thermoplastic polyurethane elastomer is used as a resin main component of the cover to obtain a cover material having a high specific gravity. By reducing the difference in specific gravity from the cover to 0.2 or less, the moment of inertia can be effectively increased, the moment of inertia can be optimized, flight stability can be improved, and flight distance can be dramatically increased. I found out that.
Moreover, since the cover material is a non-yellowing thermoplastic polyurethane elastomer, which is excellent in abrasion resistance when hit with an iron, it can effectively suppress fluffing and fuzzing of the ball surface and is thermoplastic. Therefore, in addition to having excellent moldability, it has an excellent property that the cover surface hardly turns yellow with the passage of time, and can effectively solve the conventional problems that have been pending. Found.

The hardness of the cover is 40 in Shore D hardness.
To 68, and by finding that the center is a solid center having a hardness of 1.6 to 4.4 mm with a deformation amount under a load of 30 kg, it is possible to more effectively achieve an increase in flight distance, The present invention has been completed.

Accordingly, the present invention provides (1) a thread-wound golf ball comprising a thread-wound core comprising a solid center and a thread-rubber layer formed by winding thread-rubber around the center and covering the cover with the cover having no yellow color. A thread-wound golf ball, characterized in that the difference between the center specific gravity and the cover specific gravity is 0.2 or less, and (2) the cover hardness is 40 to 40 as measured by a Shore D hardness meter. (1) The wound golf ball according to (1), and (3) the diameter of the solid center is 28 to.
36mm, hardness is 1.6 when the amount of deformation under load of 30kg
A thread-wound golf ball according to (1) or (2), which has a diameter of about 4.4 mm.

The present invention will be described in more detail below. In the thread-wound golf ball of the present invention, as shown in FIG. 1, a thread-wound core 3 having a thread rubber layer 2 formed on the outer periphery of a solid center 1 is covered with a cover 4. In the thread-wound golf ball formed as described above, a thermoplastic polyurethane elastomer having a high specific gravity is used as the main component of the cover resin, the difference between the center specific gravity and the cover specific gravity is reduced, and the moment of inertia is optimized.

As the thermoplastic polyurethane elastomer, which is the main component of the cover resin, a non-yellowing thermoplastic polyurethane elastomer is used in consideration of the yellowing resistance of the ball surface. In particular, the thermoplastic resin in which the diisocyanate is aliphatic is used. Polyurethane elastomer is preferable, and specifically, PANDEX T-R3080 and T-7890 (trade name: Dainippon Ink and Chemicals, Inc.)
Manufactured) and the like can be preferably used.

More specifically, the molecular structure of the thermoplastic polyurethane elastomer comprises a soft segment composed of a high molecular weight polyol compound, a monomolecular chain extender constituting a hard segment, and diisocyanate.

The high molecular weight polyol compound is not particularly limited, but polyester polyols,
Either a polycarbonate-based polyol or a polyether-based polyol may be used. Examples of the polyester-based polyol include polycaprolactone glycol, poly (ethylene-1,4-adipate) glycol, and poly (butylene-glycol).
Polycarbonate polyols such as (1,4-adipate) glycol and poly (diethylene glycol adipate) glycol include (hexanediol-1,6-
Examples of the polyether-based polyol such as carbonate) glycol include polyoxytetramethylene glycol. Their number average molecular weight is about 600-500
It is 0, preferably 1000 to 3000.

As the diisocyanate, an aliphatic diisocyanate is preferably used in consideration of the yellowing resistance of the cover. Specifically, hexamethylene diisocyanate (H
DI), 2,2,4 (2,4,4) -trimethylhexamethylene diisocyanate (TMDI), lysine diisocyanate (LDI), and the like, with hexamethylene diisocyanate (HDI) being particularly preferred.

The chain extender is not particularly limited, and ordinary polyhydric alcohols, amines and the like can be used,
Specifically, 1,4-butylene glycol, 1,2-ethylene glycol, 1,3-propylene glycol, 1,
6-hexyl glycol, 1,3-butylene glycol, dicyclohexylmethanediamine (hydrogenated MDA),
Isophoronediamine (IPDA) and the like.

Other thermoplastic resins may be appropriately blended with the above thermoplastic polyurethane elastomer. In this case, examples of the thermoplastic resin include polyamide elastomer, polyester elastomer, ionomer, styrene block elastomer, hydrogenated butadiene, ethylene-vinyl acetate copolymer (EVA) and the like.

If necessary, various additives such as pigments, dispersants, antioxidants, ultraviolet absorbers, release agents and the like can be added to the cover material in a usual amount in addition to the resin components.

Here, the specific gravity, hardness, thickness and the like of the cover 4 can be appropriately adjusted within the range in which the object of the present invention can be achieved, but the cover specific gravity is usually 1.0 to 1.3. Particularly, 1.1 to 1.25, the hardness is 40 to 68, particularly 4 as measured by a Shore D hardness meter (hereinafter referred to as Shore D hardness).
5-55, thickness 1.0-2.5 mm, especially 1.0-
It can be 1.8 mm.

Next, the solid center 1 is a system
It can be produced by a known method using a known material using an elastomer containing 1,4-polybutadiene as a main component.

It is necessary that the solid center specific gravity is larger than the cover specific gravity, and the difference between the center specific gravity and the cover specific gravity is 0.2 or less, more preferably 0.0 to 0.
Fifteen. If the specific gravity difference exceeds 0.2, the effect of increasing the moment of inertia cannot be sufficiently obtained, and the flight distance may not be increased.

The outer diameter and weight of the solid center 1,
And the hardness is not particularly limited, but the outer diameter of the solid center is usually 28 to 36 mm, particularly 30 to 3
4 mm, weight is 15 to 30 g, especially 17 to 28 g, hardness is 1.6 to 4.5 mm as a deformation amount under a load of 30 kg,
In particular, it can be 1.8 to 4.0 mm.

Next, the thread rubber layer 2 is attached to the center 1
It is formed by winding a rubber thread around the outer periphery of the rubber in a highly stretched state, and the weight of the rubber thread layer is usually 10 to 20.
g, especially 12-18 g, and the thickness can be 2.0-7.0 mm, especially 3.0-6.0 mm.

As the thread winding method, an ordinary method can be adopted, and the thread rubber to be used can also be a known material. Note that the specific gravity, size, thickness, etc. of the rubber thread are not particularly limited, and normally the specific gravity of the rubber thread is 0.93 to.
1.10, especially 0.93 to 1.0, the rubber thread has a width of 1.4 to 2.0 mm, especially 1.5 to 1.7 mm, and a thickness of 0.3 to 0.7 mm, especially 0.1. It can be 4 to 0.6 mm.

The diameter of the wound core 3 composed of the center 1 and the rubber rubber layer 2 is 37.5 to 40.8 mm, and particularly 3
It can be set to 9.0 to 40.6 mm.

The method of coating the above-mentioned cover 4 on the above-mentioned wound core 3 is usually the same as the conventional ionomer resin cover, for example, a method in which the cover material is directly injection-molded onto the wound core 3, or the cover material is preliminarily formed into a hemispherical shell shape. A method of forming two half cups, encapsulating the wound core 3 with these half cups, and pressurizing and molding at 140 to 180 ° C. for 2 to 10 minutes can be adopted.

The thread-wound golf ball of the present invention has a large number of dimples formed on the surface like a normal golf ball, and has a dimple index and arrangement for the purpose of improving flight characteristics by further increasing the moment of inertia. Rationalize.

First, the dimple surface occupancy rate, that is, when the golf ball is regarded as a spherical surface to be a virtual spherical surface, the surface area of the virtual spherical surface surrounded by the edges of the individual dimples is 65% or more of the total area of the virtual spherical surface. The dimples can be provided so as to be preferably 70 to 80%. If the dimple surface occupancy rate is less than 65%, it may not be possible to obtain the above-described excellent flight characteristics, particularly an increase in flight distance.

Next, (total dimple volume / ball volume)
The dimple volume ratio is calculated from × 100. here,
The ball volume is the volume of a true ball on the assumption that there are no dimples on the surface of the golf ball, and the total dimple volume indicates the total volume of each dimple. In this case, the dimple volume ratio is 0.76 to 0.9%, preferably 0.7.
It is 8 to 0.88%, more preferably 0.8 to 0.86%. If the dimple volume ratio is less than 0.76%, the trajectory may become too high and the flight distance may be reduced. On the other hand, 0.9
If it exceeds%, the trajectory will be too low and the flight distance may also be reduced.

The number of dimples is 350 to 500.
, Preferably 370 to 480, more preferably 39
It is 0 to 450. If the number of dimples is less than 350, the diameter of one dimple becomes large, and the sphericity of the ball decreases. On the other hand, if the number is more than 500, the diameter of one dimple becomes small, and the effect as a dimple may be lost. The dimple diameter, depth, etc. are not particularly limited, but the diameter is usually 1.4 to 2.2.
mm and the depth can be usually in the range of 0.15 to 0.25 mm, and two or more kinds or more kinds of dimples having different diameters, depths and the like can be formed. The arrangement of the dimples is not particularly limited, and known arrangements such as regular octahedron arrangement, regular dodecahedron arrangement and regular icosahedron arrangement can be adopted. The pattern formed on the can also be various patterns such as a square type, a hexagon type, a pentagon type and a triangle type.

The golf ball of the present invention has the above constitution, but the ball hardness is preferably 2.4 to 3.6 mm, particularly 2.6 to 3.4 mm in terms of the amount of deformation under a load of 100 kg.

It should be noted that the golf competition is conducted under the rules of golf common throughout the world, and the golf ball of the present invention is naturally premised on that the weight, diameter, symmetry, initial velocity, etc. comply with the golf rules. 45.93g or less, diameter 42.6
7 mm or more, initial velocity is 76.2 m / sec when measured with a device approved by R & A (the maximum allowable error is 2% (7
Up to 7.7 m / sec), the temperature of the ball during the test is 23 ±
(1 ° C.).

[0037]

EFFECTS OF THE INVENTION The thread-wound golf ball of the present invention uses a non-yellowing thermoplastic polyurethane elastomer as a cover material as a main component, so that a cover having a high specific gravity can be obtained, and the flight distance can be increased by increasing the moment of inertia. It is a high-performance, high-quality product that is excellent in scratch resistance, discoloration property, and moldability when hit with an iron.

[0038]

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] The solid center compositions shown in Table 1 were kneaded, and the mixture was placed in a mold at 150 ° C. for 15 hours.
Six types of solid centers A to F were molded by vulcanization molding for minutes.

The diameter, weight, specific gravity and hardness (deformation amount under a load of 30 kg) of each obtained center were measured. The results are also shown in Table 3. The solid center components are all parts by weight.

[0041]

[Table 1]

A thread rubber having the following composition was wound around the above solid center by an ordinary winding method to obtain a thread wound core. Thread rubber composition / conditions Polyisoprene rubber 70 parts by weight Natural rubber 30 〃 Zinc white 1.5 〃 Stearic acid 1 〃 Vulcanization accelerator 1.5 〃 Sulfur 1 〃 Specific gravity: 0.93 Thread rubber dimension: Width 1.55 mm, Thickness 0.55 mm Next, the cover components shown in Table 2 were kneaded to form two half shell spherical half cups from the cover compositions A to F, respectively.

[0043]

[Table 2]

On the other hand, the half cups of the covers A to F and the thread-wound cores A to F were superposed on each other in the combination shown in Table 3 and heat-press molded at 160 ° C. and 120 kg / cm ² for 5 minutes, and the results of Examples 1 to 1 were obtained. 4, thread-wound golf balls of Comparative Examples 1 to 3 were obtained. The number of dimples on the surface of each ball obtained was 396 (two types, large and small), and the dimple surface occupancy rate was 75.
%, And dimples having a dimple volume ratio of 0.85% are formed.

Various properties of each of the obtained golf balls were evaluated according to the following methods. The results are also shown in Table 3. Ball Hardness A load of 100 kg was applied to the ball, and the amount of change (mm) was measured. The larger the number, the softer the ball. Using a flying test swing robot machine, club No.1 wood (driver), head speed 45m / sec
Spin rate when actually hit with (HS45), initial speed (USGA
(Measured according to the measuring method of (R & A)), elevation angle, carry, and total distance were measured. The club has a sand wedge (S
W) was used to hit the ball once at two arbitrary positions at a head speed of 33 m / sec, and these two hitting sites were observed and evaluated according to the following criteria. ○: good ×: inferior discoloration test Mercury lamp (manufactured by Suga Test Instruments Co., Ltd.), using a Toshiba brown test mercury lamp H400-F, changes in Lab color on the ball surface before and after irradiation for 24 hours with multiple light sources. Spectral colorimeter MSC
-IS-2DH (made by Suga Test Instruments Co., Ltd.) was used for measurement. L
The ab color specification is based on JIS Z8701, L value, a value,
The b value was determined.

Of the Lab color specifications, L represents lightness,
The lightness refers to the lightness / darkness of a color, that is, the degree of lightness. The larger the L value, the brighter it is, and the L value is preferably 90 or more. Also, a and b represent colors,
a represents the red-green direction, and b represents the yellow-blue direction. Therefore, when the value a increases, the redness becomes stronger, when the value a decreases, the greenness becomes stronger, when the value a increases, the yellowness becomes stronger, and when the value a decreases, the blueness becomes stronger.

The color difference ΔE is calculated from the Lab color specification before and after irradiation of the ball with a mercury lamp. That is, the Lab color specification (L
1, a1, b1), the Lab color specification (L2, a2, after irradiation)
b2) is measured, and these differences ΔL = L1−L2, Δa =
a1-a2 and Δb = b1-b2 are calculated, and ΔE = (ΔL
The color difference ΔE before and after irradiation was determined from ² + Δa ² + Δb ² ) ^1/2 and evaluated according to the following criteria. ◯: Color difference ΔE is 3.5 or less ×: Color difference ΔE exceeds 3.5

[0048]

[Table 3]

From the results shown in Table 3, Comparative Examples 2 to 4 are not thermoplastic polyurethane elastomers whose covers are not yellowed, and Comparative Examples 2 and 4 have a specific gravity difference of 0.41 between the center and the cover.
Therefore, all of them have poor resistance to fraying, and the flight distance is not sufficient. Further, Comparative Example 1 is inferior in discoloring property because a normal thermoplastic polyurethane elastomer is used for the cover.

On the other hand, in Examples 1 to 4, since the non-yellowing thermoplastic polyurethane elastomer having a high specific gravity is used as the main component of the cover material, the difference in specific gravity from the center is 0.2 or less. , The flight distance is increased, the resistance to blistering,
The color change property is also good.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an example of a thread-wound golf ball of the present invention.

[Explanation of symbols]

 1 Center 2 Thread rubber layer 3 Thread winding core 4 Cover

Front page continued (72) Inventor Takashi Maruko 20 Onohara, Chichibu City, Saitama Prefecture, within Bridgestone Sports Co., Ltd. (72) Inventor Junji Umezawa 20 Onohara, Chichibu City, Saitama Prefecture, within Bridgestone Sports Co., Ltd. 3-6-503 Oichihara-cho, Izumiotsu-shi, Prefecture (72) Inventor Nobuhiko Matsumura 4-17-305 Jonan-cho, Izumiotsu-shi, Osaka Prefecture

Claims (3)

[Claims] 1. A thread-wound golf ball comprising a thread-wound core comprising a solid center and a thread-rubber layer having thread rubber wound around the center, and the cover being covered with a thermoplastic polyurethane elastomer which does not turn yellow. A thread-wound golf ball comprising a main component, wherein the difference between the center specific gravity and the cover specific gravity is 0.2 or less. 2. The thread wound golf ball according to claim 1, wherein the cover hardness is 40 to 68 as measured by a Shore D hardness meter. 3. The diameter of the solid center is 28 to 36 m.
m, hardness is a deformation amount under a load of 30 kg, and is 1.6 to 4.
The thread-wound golf ball according to claim 1, which has a length of 4 mm.