JPH10165542A - Multilayered structure golf ball - Google Patents

Abstract

(57) [Problem] To provide a golf ball having a multi-layered golf ball, particularly a golf ball having a good hit feeling characteristic of a conventional thread-wound golf ball, and having a large initial velocity in a low initial velocity region and a long flight distance. I will provide a. The present invention provides (a) a solid core 1 having an outer diameter of 23 to 37 mm, and (b) a thickness formed on the solid core.
An intermediate layer cover 2 made of a thermoplastic resin having a thickness of 0.5 to 5.0 mm, (c) a thickness of 1.0 to 5.
The present invention relates to a multi-layer golf ball comprising a thread rubber layer 3 having a thickness of 0 mm and (d) an outer layer cover 4 made of a thermoplastic resin formed on the thread rubber layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a golf ball having a multilayer structure. More specifically, the present invention relates to a golf ball that retains a good shot feeling characteristic of a conventional thread wound golf ball, has a large ball initial velocity in a low initial velocity region, and has a long flight distance.

[0002]

2. Description of the Related Art In the prior art, there are mainly two types of golf balls. One is a solid golf ball such as a solid two-piece ball or a three-piece ball, and includes a core made of an integrally molded rubber member and a thermoplastic resin cover such as an ionomer resin coated on the core. The other is a thread-wound golf ball in which a central solid or liquid core is wound with a rubber thread and then covered with a 1-2 mm thick cover made of an ionomer resin or balata. Among the solid golf balls, a two-piece solid golf ball consisting only of a core and a cover is mainly commercially available because of ease of production and the like. Two-piece solid golf balls are more durable than thread-wound golf balls.
Also, since the ball speed at the time of hitting is high, the flight distance is large and the flight characteristics are excellent. Particularly, it is used by many golfers, especially amateur golfers. On the other hand, a two-piece solid golf ball lacks controllability in approach because the shot feeling is hard and the spin rate is small.

In recent years, what is required of a golf ball is not only the flight distance but also the softness of the shot feeling has become a very important factor. He emphasized the softness and was inferior in flight distance.

[0004]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems of the conventional golf ball, retains the hit feeling of a conventional thread-wound golf ball, and has a soft impact when hit. In particular, it is an object of the present invention to provide a golf ball having a large initial velocity at a low speed and a long flight distance.

[0005]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to achieve the above object, and as a result, the cover layer on the solid core has been divided into three thick layers, and between the two thermoplastic resin layers. By providing a thread rubber cushion layer around which thread rubber is wound, the initial velocity of the ball, especially at low speeds, is large, and the highly resilient thread rubber layer at the time of impact becomes easy to deform as a cushion layer. It has been found that a golf ball having a soft feel at impact can be obtained, and the present invention has been completed.

That is, the present invention provides (a) a solid core 1 having an outer diameter of 23 to 37 mm, and (b) an intermediate layer cover formed on the solid core and made of a thermoplastic resin having a thickness of 0.5 to 5.0 mm. 2, (c) a thickness of 1.0 wound on the intermediate layer cover
The present invention relates to a multi-layer golf ball comprising a rubber thread layer 3 having a thickness of about 5.0 mm and (d) an outer cover 4 made of a thermoplastic resin formed on the rubber thread layer.

The structure of the golf ball of the present invention will be described with reference to FIG. 1. An intermediate layer cover 2 is formed on a solid core 1, a thread rubber layer 3 is wound on the intermediate layer cover 2, and Then, the outer cover 4 is formed. The solid core is a rubber composition containing 10 to 30 parts by weight of a metal (meth) acrylate, 0.3 to 3 parts by weight of a cross-linking agent, and a filler, if necessary, based on 100 parts by weight of the base rubber. By kneading using an internal mixer (Banbury or kneader) and a roll to produce a plug of a predetermined size, followed by heat compression vulcanization in a predetermined mold. As the base rubber, natural rubber and / or synthetic rubber conventionally used for solid golf balls are used.
A so-called high cis polybutadiene rubber having at least 40% or more, preferably 80% or more of 4-bonds is preferable, and natural rubber, polyisoprene rubber, styrene polybutadiene rubber, ethylene-propylene-diene rubber (EPDM) and the like may be blended as desired. Is also good.

[0008] Metal (meth) acrylates act as co-crosslinking agents, particularly zinc, magnesium salts of α, β-unsaturated carboxylic acids having 3 to 8 carbon atoms such as acrylic acid or methacrylic acid. And monovalent or divalent metal salts, but zinc acrylate which imparts high resilience is preferred. The compounding amount is preferably 10 to 30 parts by weight based on 100 parts by weight of the base rubber. If the amount is more than 30 parts by weight, the ball becomes too hard, and the shot feeling becomes poor.

[0009] Crosslinking agents include organic peroxides such as dicumyl peroxide or t-butyl peroxide, with dicumyl peroxide being preferred. The compounding amount is preferably from 0.3 to 3 parts by weight based on 100 parts by weight of the base rubber. If it is less than 0.3 parts by weight, it becomes too soft and rebound becomes worse, resulting in a shorter flight distance. If the amount exceeds 3 parts by weight, the ball becomes too hard and the shot feeling becomes poor.

[0010] The filler may be any one which is usually compounded in the core of a golf ball. For example, an inorganic salt (specifically,
Zinc oxide, barium sulfate, calcium carbonate), high specific gravity metal powder (for example, tungsten powder, molybdenum powder, etc.) and mixtures thereof. The amount is preferably 5 to 70 parts by weight based on 100 parts by weight of the base rubber. If the amount is less than 5 parts by weight, the weight of the core becomes light, and as a result, the weight of the ball becomes light, which is not preferable. If it exceeds 70 parts by weight, the weight of the core becomes heavy, and as a result, the weight of the ball becomes too heavy.

Further, the core of the golf ball of the present invention may be appropriately compounded with an antioxidant or a peptizer, and other components which can be generally used for producing a core of a solid golf ball.

The solid core has an outer diameter of 23 to 37 mm, preferably 25 to 35 mm. If it is smaller than 23 mm, the launch angle at impact is small, the spin amount increases, the flight distance decreases, and if it is larger than 37 mm, the thread rubber layer becomes too thin, and it ends up before the thread rubber tension is applied, As a result, the rebound of the ball is reduced. The surface hardness of the solid core is JIS-C hardness (same as Shore C hardness) of 30 to 85, preferably 40 to 80.
If it is less than 30, the rebound of the ball is small and the flight distance is difficult to come out. If it is more than 85, the spin amount is increased and the flight distance is hard to come out, and the shot feeling is also poor. In the case of the present invention, the solid core is changed from an initial load of 10 kg to a final load of 130 k.
The amount of distortion until g is applied is 2.5 to 10 mm, preferably 2.8
８8 mm. If it is smaller than 2.5 mm, not only does the spin amount increase and the flight distance becomes difficult to appear, but the shot feeling also worsens,
If it is larger, the ball becomes too soft and rebound of the ball is inferior.

The intermediate cover and the outer cover of the present invention are both formed of the same material, and will be described at once. Both covers are thermoplastic resins, especially ionomer resins in which some of the carboxylic acids in the copolymer of α-olefins and α, β-unsaturated carboxylic acids having 3 to 8 carbon atoms are neutralized with metal ions, or The mixture is used. As the α-olefin in the ionomer resin, ethylene,
Propylene is preferred, and acrylic acid, methacrylic acid and the like are preferred as α, β-unsaturated carboxylic acids. Further, as the metal ions to be neutralized, alkali metal ions such as Na ion, K ion and Li ion; divalent metal ions such as Zn ion, Ca ion and Mg ion; trivalent metal ions such as Al ion; Nd ions and the like; and mixtures thereof, including Na ions, Zn ions,
Li ions and the like are often used because of their resilience and durability.
Specific examples of the ionomer resin include, but are not limited to, Himilan 1557, 1605, 1652, 1705, 1706,
1707, 1855, 1856 (manufactured by Mitsui Dupont Polychemicals), IO
TEC 7010, 8000 (manufactured by Exxon) and the like.

Further, as an example of a preferable material of the intermediate layer cover and the outer layer cover, only the ionomer resin as described above may be used, but a combination of the ionomer resin and a special elastomer or resin is suitably used. Examples of such combinations include the following four types. (a) an ionomer resin and an acid-modified thermoplastic elastomer or a thermoplastic elastomer having an OH group added to a terminal,
With an SBS (styrene-butadiene-styrene) structure block copolymer having an epoxy group-containing polybutadiene block or an SIS (styrene-isoprene-styrene) structure block copolymer having an epoxy group-containing polyisoprene block Heated mixture (b) Heated mixture of ionomer resin and terpolymer composed of ethylene-unsaturated carboxylic acid ester-unsaturated carboxylic acid (c) Ionomer resin, maleic anhydride-modified thermoplastic elastomer, and glycidyl group-modified heat Heated mixture with plastic elastomer (d) Heated mixture of ionomer resin and polyamide elastomer. Further, a resin having a Shore D hardness of 40 to 80 is used for the two covers of the present invention. If the Shore D hardness is less than 40, the ball becomes too soft and it is difficult for the ball to rebound. If the Shore D hardness exceeds 80, on the contrary, the ball becomes too hard and the shot feeling becomes poor.

[0015] In the present invention, the cover composition may further include, if necessary, other than the resin as a main component.
Fillers such as barium sulfate and coloring agents such as titanium dioxide,
Other additives, such as dispersants, antioxidants, ultraviolet absorbers, light stabilizers and fluorescent materials or fluorescent brighteners,
Although it may be contained within a range that does not impair the desired properties of the golf ball cover, usually, the amount of the coloring agent is 2
~ 6 parts by weight are preferred. The intermediate layer cover often does not require the coloring agent or additive.

The cover layer of the present invention can be formed by using a generally known method used for forming a cover of a golf ball, and is not particularly limited. The composition for the intermediate layer cover is formed in advance into a hemispherical shell-like half shell,
Wrap the solid core with two pieces of it, and
Pressure molding may be performed for 5 minutes, or a method may be used in which the composition for the intermediate layer cover is directly injection-molded onto the solid core to wrap the solid core. The thickness of the middle layer cover is
It is 0.5 to 5.0 mm, preferably 0.5 to 3 mm. If it is less than 0.5 mm, the repulsive force of the intermediate layer will not be utilized, and the ball will not easily rebound. If it is more than 5.0 mm, the shot feeling will be poor. The diameter after covering the intermediate layer cover is desirably 30 to 38 mm.
If the diameter after covering the intermediate layer cover is less than 30 mm, the spin rate at impact will increase and the flight performance will be inferior, and if it exceeds 38 mm, the rubber thread layer will become thin and the resilience of the rubber thread and the impact mitigation at impact will be reduced Is not utilized and the flight distance is shortened.

The rubber thread wound on the intermediate layer cover may be the same as that conventionally used for the wound layer of a wound golf ball. For example, natural rubber or natural rubber and synthetic polyisoprene may be used. Those obtained by vulcanizing a rubber composition containing sulfur, a vulcanization aid, a vulcanization accelerator, an antioxidant and the like may be used. The rubber thread can be wound on the intermediate layer cover in a method of manufacturing a wound core of a wound golf ball. The thickness of the rubber thread layer is 1 to 5 mm, preferably 1 to 3 mm. 1mm
If the thickness is thinner, the impact relaxation at the time of hitting is not utilized, and the shot feeling is poor. If the thickness is more than 5 mm, the spin rate at the time of hitting is increased and the flight performance is poor.

Further, the method of covering the outer layer cover is the same as the method of covering the intermediate layer cover. When molding the outer layer cover, a large number of depressions called dimples are formed on the surface as necessary. The golf ball of the present invention is usually put on the market after being subjected to a paint finish, a marking stamp, or the like, in order to enhance aesthetic appearance and commercial value. The thickness of the outer cover is 0.5 to 3 mm, preferably 1 to 3 mm.
2.5 mm. If it is thinner than 0.5mm, the cover is too thin.
When repeatedly hit, there is a disadvantage that the cover is liable to crack, and when it is thicker than 3 mm, the hit feeling is deteriorated.

The total thickness of the cover (intermediate layer cover / fiber rubber layer /
The outer layer cover) is preferably 3 to 10 mm, more preferably 4 to 9.5 mm. If it is less than 3 mm, the overall hardness of the ball will be small and the coefficient of restitution will be small. If it exceeds 10 mm, the hardness of the entire ball will be large and controllability and shot feeling will be poor.

According to the present invention, there can be provided a golf ball having a high initial ball speed in a low initial velocity region and an improved flight distance without impairing a good shot feeling characteristic of a conventional thread wound golf ball.

[0021]

EXAMPLES The present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples. Preparation of Solid Core A rubber composition for solid core having the composition shown in Table 1 below was kneaded and heated and pressed at 165 ° C. for 20 minutes to obtain a solid core having a diameter of 2 mm.
A solid core of 2 to 34 mm was obtained. The core weight was adjusted with barium sulfate so that each final ball weight became an appropriate weight.

[Table 1] Table 1 Solid core compounding type Parts by weight BR11 (Note 1) 100 Zinc acrylate 20 Dicumyl peroxide 1.5 Zinc oxide 15 Antioxidant (Note 2) 0.5 Barium sulfate Suitable amount (Note 1) Nippon Synthetic Rubber Co., Ltd. ) High cis polybutadiene (1,4-cis-polybutadiene content: 96%) (Note 2) Nocrack NS-6 (2,5-di-t-butylhydroquinone manufactured by Ouchi Shinko Chemical Co., Ltd.)

Preparation of Intermediate Layer Cover Composition The cover compounding materials shown in Table 2 below were mixed by a twin-screw kneading extruder to obtain a pellet-like intermediate layer cover composition. The extrusion conditions were a screw diameter of 45 mm, a screw rotation speed of 200 rpm, and a screw L / D 35, and the blend was heated to 200 to 260 ° C. at the die position of the extruder. The flexural rigidity was measured based on ASTM D-747 after storing a hot-pressed sheet having a thickness of about 2 mm at 23 ° C for 2 weeks, and the Shore D hardness was measured by stacking three or more sheets. It was measured with a meter.

[0023]

[Table 2] Table 2 (parts by weight) Type ABCDE Himilan 1605 (Note 3)--50--Himilan 1706 (Note 4)--50-80 Himilan 1855 (Note 5) 20----Surlyn AD8511 (Note 6) 25 25---Surlyn AD8512 (Note 7) 25 25---Tuftec Z514 (Note 8) 20----Bondyne AX8390 (Note 9) 10----ESBS AT015 (Note 10)- 15 − − − HG-252 (Note 11) − 35 − − − Iotech 8000 (Note 12) − − − 60 − Iotech 7010 (Note 13) − − − 40 − Qu relax R-6500 (Note 14) − − − −20 Barium sulfate 4 4 4 4 4 Intermediate layer Cahershore D hardness 54 52 63 66 70 Flexural rigidity (MPa) 135 90 330 390 560 (Note 3) Sodium ion neutralized ethylene manufactured by Mitsui Dupont Polychemicals Co., Ltd. Methacrylic acid copolymerized ionomer resin, MI = 2.8, flexural rigidity = about 310 MPa (Note 4) Zinc ion neutralized ethylene manufactured by Mitsui DuPont Polychemicals -Methacrylic acid copolymer ionomer resin, MI = 0.8, flexural rigidity = about 260 MPa (Note 5) Zinc ion neutralized ethylene-butyl acrylate-methacrylic acid terpolymer ionomer resin manufactured by Du Pont-Mitsui Polychemicals Co., Ltd. , MI = 1.0, flexural rigidity = about 9
0MPa (Note 6) Zinc ion neutralized ethylene-methacrylic acid copolymer ionomer resin manufactured by DuPont, MI = 3.4, flexural rigidity = about 220MPa (Note 7) DuPont sodium ion neutralized ethylene-methacrylic acid copolymer Polymerized ionomer resin, MI = 4.4, flexural rigidity = about 280 MPa (Note 8) Glycidyl methacrylate adduct of styrene-butadiene-styrene block copolymer hydrogenated product manufactured by Asahi Kasei Corporation, JIS-A hardness = 65, styrene content = about 20 wt%, hydrogenated butadiene content = about 80 wt%, glycidyl methacrylate content about 1% (Note 9) Ethylene-ethyl acrylate-maleic anhydride ternary manufactured by Sumitomo Chemical Co., Ltd. Copolymer, MI = 7.0, Shore D
Hardness = 14, ethyl acrylate + maleic anhydride content =
32% (including 1 to 4% of maleic anhydride) (Note 10) Styrene-butadiene having a polybutadiene block containing an epoxy group manufactured by Daicel Chemical Industries, Ltd.
Styrene block polymer, butadiene / styrene = 60/40 (weight ratio), JIS-A hardness = 67, epoxy content = approx.
1.5 to 1.7% by weight (Note 11) Hydrogenated styrene with terminal OH group added by Kuraray Co., Ltd.
-Isoprene-styrene block copolymer, JIS-A hardness = 8
0, Styrene content = about 40% by weight (Note 12) Sodium ion neutralized ethylene-acrylic acid ionomer resin manufactured by Exxon Chemical Co., MI = 0.8, Flexural rigidity = about 370 MPa (Note 13) Zinc manufactured by Exxon Chemical Co. Ion neutralized ethylene
-Acrylic acid ionomer resin, MI = 0.8, flexural rigidity = about 160 MPa (Note 14) Polyamide elastomer manufactured by Dainippon Ink and Chemicals, Inc.

Formation of the wound layer The above-described composition for the intermediate layer cover is directly coated around the solid core by injection molding, and the base rubber is natural rubber / low cis-isoprene rubber (Shell IR-manufactured by Shell Chemical Co., Ltd.). 309) =
A 50/50 (weight ratio) blend rubber thread rubber was wound, and the outer diameter after thread winding was about 39.0 mm.

(Examples 1 to 4 and Comparative Examples 1 to 5) A half shell having a hemispherical shell shape was formed by using the composition for the outer layer cover shown in Table 3 below, and the above-mentioned composition was obtained by using two of the shells. The wound core was wrapped, press-compression molded in a mold, and painted on the surface to obtain a golf ball having an outer diameter of 42.8 mm. The initial performance, launch angle, carry and spin rate, and feel at impact were evaluated as the flight performance of the obtained golf ball, and the results are shown in Table 4 (Examples) and Table 5 (Comparative Examples) below. The test method was performed as described below.

[Table 3] Table 3 (parts by weight) Type a b c d Himilan 1605 (Note 3)--50-Himilan 1706 (Note 4)--50-Himilan 1855 (Note 5) 20---Surlyn AD8511 (Note 6) ) 25 25 − − Surlyn AD8512 (Note 7) 25 25 − − Tuftec Z514 (Note 8) 20 − − − Bondyne AX8390 (Note 9) 10 − − − ESBS AT015 (Note 10) − 15 − − HG-252 (Note) 11) − 35 − − Iotek 8000 (Note 12) − − − 60 Iotek 7010 (Note 13) − − − 40 Q-Relax R-6500 (Note 14) − − − − Barium sulfate 2 2 2 2 Titanium dioxide 2 2 2 2 Outer layer cover shore D hardness 54 52 63 66 Flexural rigidity (MPa) 135 90 330 390

(Test method) Flight performance Wood No. 1 (W
# 1) Attach a club and golf ball at head speed 4
Hit the ball at 5m / sec and 35m / sec, measure the ball's initial velocity, launch angle (ballistic height), and carry (flying distance to the drop point), and measure the amount of spin by taking continuous shots of the hit golf ball. I asked. Hitting feeling Evaluated by an actual hitting test by 10 top professionals. The criteria were as follows. Judgment Criteria …: Eight or more out of ten answered that the soft feeling was good. × Eight or more of ten answered that the shot feeling was hard and bad.

(Test results)

[Table 4] Table 4 Example Test items 1 2 3 4 Solid core diameter (mm) 24 29 30 34 Intermediate layer cover composition CDEB Intermediate layer cover thickness (mm) 4 2 2 1 Diameter after intermediate layer cover (mm) 32 33 34 36 Outer layer cover composition c b a d Outer layer cover thickness (mm) 1.9 1.9 1.9 1.5 Total cover thickness (mm) 9.4 6.9 6.4 4.4 Ball diameter (mm) 42.8 42.8 42.8 42.8 Flight performance (W # Ball speed (m / s) 64.9 64.7 64.8 64.7 Launch angle (degrees) 12.20 12.25 12.33 12.30 Spin rate (rpm) 2700 2650 2550 2580 Carry (Yat ゛) 226.5 226.2 227.3 227.0 Flight performance (W # 1, (35m / sec) Initial ball speed (m / sec) 51.3 51.1 51.3 51.2 Launch angle (degree) 13.25 13.30 13.45 13.40 Spin rate (rpm) 2450 2330 2280 2300 Carry (Yat 17) 170.5 170.0 171.8 171.0 Shot feeling 〇 〇 〇 〇

[0028]

[Table 5] Table 5 Comparative test items 1 2 3 4 5 6 * Solid core diameter (mm) 34 34 24 22 34 Intermediate layer cover composition- BDDD Intermediate layer cover thickness (mm) 0 0.4 5.5 3.0 2.25 Diameter after intermediate layer cover (mm) 34 34.8 35 28 38.5 Outer layer cover composition b d c c c Outer layer cover thickness (mm) 2.1 1.5 2.3 3.0 1.5 Total cover thickness (mm) 4.4 9.4 10.4 4.4 2.3 Ball diameter (mm) 42.8 42.8 42.8 42.8 42.8 42.8 Flight performance (W # 1, 45m / s) Initial ball speed (m / s) 64.3 64.4 64.7 64.8 64.1 64.6 Launch angle (degrees) 12.10 12.15 12.20 11.20 12.35 12.30 Spin amount (rpm) 2750 2700 2650 3300 2500 2400 Carry (Yat) 223.0 224.0 226.5 223.5 222.5 224.5 Flight performance (W # 1, 35m / s) Ball initial speed (m / s) 49.8 50.3 51.2 51.0 50.0 50.5 Launch angle (degrees) 13.05 12.95 13.10 12.25 13.42 13.35 Spin amount (rpm) 2600 2530 2480 3050 2300 2250 carry (Yato Bu) 163.5 164.2 169.5 161.0 160.3 167.0 shot feeling O O × 〇 × × * our conventional two-piece solid golf Lumpur

From the above results, all the golf balls of Examples 1 to 4 of the present invention have a flight distance equal to or greater than that of a conventional two-piece golf ball, and the hitting feeling by a top professional is soft and good. there were. On the other hand,
Since the golf ball of Comparative Example 1 had a conventional so-called thread wound golf ball structure and had no intermediate layer cover, the ball did not have an initial velocity and the flight distance was short. The golf ball of Comparative Example 2
Since the thickness of the intermediate layer cover was small, the effect of the intermediate layer cover was not obtained, and the flight distance was short. On the contrary, the golf ball of Comparative Example 3 had a long flight distance due to the large thickness of the intermediate layer cover, but had a hard and poor shot feeling. Since the diameter of the golf ball of Comparative Example 4 after covering the intermediate layer cover was too small at 28 mm, the spin amount was large, the trajectory was high, and the flight distance was short. In the golf ball of Comparative Example 5, the diameter after covering the intermediate layer cover was too large, 38.5 mm, so that the repulsive force of the rubber thread was not utilized, and the initial velocity of the ball was slow and the flight distance was short. Comparative Example 6, which is a conventional two-piece golf ball, had excellent flight performance, but had a poor hit feeling and was not popular. In addition, when the golf ball was hit at a low head speed, the difference between the initial ball speed of the golf ball of the example and the golf ball of the comparative example was larger, and the difference in the flight distance was larger.

[0030]

The present invention provides a solid core / intermediate layer cover /
By providing a thicker cover, which is a particularly high resilience material, having at least a four-layer structure consisting of a thread rubber cushion layer and an outer layer cover, and additionally providing a cushion rubber layer as a cushion layer between the cover layers, the conventional thread-wound golf ball can be used. Such a shot feeling is maintained, the impact at the time of hitting is soft, the initial velocity of the ball is particularly large at low speed, and the flight distance can be improved.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of a golf ball of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Core 2 ... Intermediate layer cover 3 ... Thread rubber layer 4 ... Outer layer cover

Claims (3)

[Claims] 1. A solid core 1 having an outer diameter of 23 to 37 mm, (b) an intermediate layer cover 2 formed of a thermoplastic resin having a thickness of 0.5 to 5.0 mm formed on the solid core, (c) ) A thickness of 1.0 to 5.0 mm wound on the intermediate layer cover
And (d) an outer layer cover 4 made of a thermoplastic resin formed on the thread rubber layer. 2. The solid core has a surface hardness of JIS-JIS.
2. The multi-layer golf ball according to claim 1, wherein the golf ball has a C hardness of 30 to 85 and a strain of 2.5 to 10 mm from a state of applying an initial load of 10 kg to a state of applying a final load of 130 kg. 3. The intermediate layer cover and the outer layer cover,
The multilayer golf ball according to claim 1, having a Shore D hardness of 40 to 80. 4.