JPH08322962A - Solid golf ball - Google Patents

Abstract

(57) [Summary] [Purpose] High repulsion performance, excellent flight performance, and durability,
A solid golf ball having excellent controllability and shot feeling. In a solid golf ball having a core and a cover, the core has an inner diameter of 32.7 to 38.4 mm.
And the amount of deformation from when the initial load of 10 kg is applied to the core to when the final load of 130 kg is 3.5 to
The cover is composed of ionomer resin as a main component and has a bending elastic modulus of 3500 to 60 mm.
Thickness of the resin composition of 00 kgf / cm ² is 1.1 to
2.5mm inner layer cover and flexural modulus 2300-5
In 500 kgf / cm ^2, and the flexural modulus than the cover inner layer is composed of two layers of the outer cover thickness 1.1~2.5mm consisting 500 kgf / cm ² or more low resin composition.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid golf ball, and more particularly to a solid golf ball having high resilience performance, excellent flight performance, durability, controllability and shot feeling.

[0002]

BACKGROUND ART Golf balls are roughly classified into solid golf balls having high resilience performance, excellent flight performance, and durability, and wound golf balls having excellent controllability and shot feeling (feeling at the time of hitting). There is a ball.

Among the above solid golf balls, a two-piece solid golf ball consisting of a core and a cover occupies the mainstream because it is particularly excellent in flight performance and durability. It has the drawback of poor controllability and shot feeling compared to a thread-wound golf ball.

Therefore, in order to improve the controllability of the two-piece solid golf ball, it has been proposed that the cover has two layers (for example, Japanese Patent Publication No. 5-411).
No. 0).

[0005]

However, the two-layer cover solid golf ball having the improved controllability is adopted in the conventional two-piece solid golf ball in order to improve both the resilience performance and the shot feeling. That is, the elastic modulus of the outer layer cover, inner layer cover, and core was set according to the so-called outer rigid inner softness, which makes the cover relatively hard and the core relatively soft. There was a drawback in that the durability was lowered due to concentration, and the durability was poorer than that of a normal two-piece solid golf ball.

Therefore, the present invention solves the above problems in the conventional solid golf ball, and provides a solid golf ball having high resilience performance, excellent flight performance, and excellent durability, controllability and shot feeling. The purpose is to provide.

[0007]

SUMMARY OF THE INVENTION The present invention provides a solid golf ball cover having a flexural modulus of 3500 to 6000.
2 of the inner cover made of the resin composition kgf / cm ^2, bending modulus 2300~5500kgf / cm ^2, and an outer layer covering the flexural modulus than the inner cover is made of 500 kgf / cm ² or more low resin composition Consists of layers,
The above object is achieved by defining the thickness of the inner layer cover, the thickness of the outer layer cover, the diameter of the core, and the amount of deformation of the core in specific ranges.

That is, durability is improved by making the cover into two layers and making the outer layer cover softer than the inner layer cover, and the bending elastic modulus of the outer layer cover is lower than the bending elastic modulus of the inner layer cover by 500 kgf / cm ² or more. By doing so, the controllability was improved.

In the present invention, the bending elastic modulus of the inner layer cover is specified to be 3500 to 6000 kgf / cm ² and the bending elastic modulus of the outer layer cover is specified to be 2300 to 5500 kgf / cm ² , and the bending of the outer layer cover is specified. The elastic modulus is 500 kgf / cm ² from the bending elastic modulus of the inner layer cover.
Although it has been lowered above, this is due to the following reasons.

The bending elastic modulus of the inner cover is 3500 kgf
If it is lower than / cm ² , the entire cover becomes too soft, resulting in poor durability. If the flexural modulus of the inner cover is higher than 6000 kgf / cm ² , the feel at the time of hitting becomes hard and the feel at impact is high. Deteriorate. Further, when the flexural modulus of the outer cover is lower than 2300 kgf / cm ² , the resilience performance is lowered and the flight performance is lowered, and when the flexural modulus of the outer cover is higher than 5500 kgf / cm ² , the feel at the time of hitting the ball is improved. Becomes hard and the feel at impact becomes poor. When the difference between the bending elastic modulus of the inner layer cover and the bending elastic modulus of the outer layer cover is smaller than 500 kgf / cm ² , the deformation stress at the time of hitting the ball is concentrated on the outer layer cover, and the durability is lowered.

In the solid golf ball of the present invention, the core is made of a crosslinked molded product of a rubber composition. The core has a diameter of 32.7 to 38.4 mm and the inner cover has a thickness of 1. The thickness of the outer layer cover is 1.1 to 2.5 mm.

When the core diameter is smaller than 32.7 mm, the resilience performance is deteriorated and the flight performance is deteriorated.
When the feel at impact becomes poor and the diameter of the core becomes larger than 38.4 mm, the resilience performance is lowered, the flight performance is lowered, and the durability is lowered.

When the thickness of the inner layer cover is less than 1.1 mm, the resilience performance is lowered and the flight performance is lowered, and when the thickness of the inner layer cover is more than 2.5 mm, the shot feeling is deteriorated. And when the thickness of the outer cover is less than 1.1 mm, the durability is reduced and the thickness of the outer cover is 2.5 mm.
The thicker the ball, the worse the shot feeling.

Further, in the solid golf ball of the present invention, the deformation amount of the core is from when the initial load of 10 kg is applied to when the final load of 130 kg is applied to the core.
It is required to be 5 to 6.5 mm. If the amount of deformation from the initial load of 10 kg to the final load of 130 kg is less than 3.5 mm, the core is hard and the feel at impact becomes poor, and the initial load of 10 k is applied to the core.
If the amount of deformation from when g is applied to when the final load is 130 kg is greater than 6.5 mm, the core is soft and the resilience performance and durability deteriorate.

In the solid golf ball of the present invention, the internal hardness of the core is a hardness measured by a JIS-C type hardness meter, and the difference between the hardness of the central portion and the hardness of the portion other than the center is 5% or less. Preferably there is. That is, when the core has a small internal hardness, the difference between the hardness of the central portion and the hardness of the portion other than the central portion is as small as 5% or less, and the core has a small hardness difference.
High resilience performance and excellent durability are obtained, but if the difference between the internal hardness of the core and the hardness of the parts other than the center is greater than 5%, the resilience performance and durability tend to decrease. There is.

The core comprises a base rubber containing cis-1,4-polybutadiene or cis-1,4-polybutadiene as a main component, a metal salt of α, β-unsaturated carboxylic acid, and an organic peroxide as an initiator. It is composed of a cross-linked molded article of a rubber composition containing an oxide, a filler and the like, and if necessary, an antioxidant and a stabilizer.

As the cis-1,4-polybutadiene, so-called high cis polybutadiene having a cis-1,4 structure of at least 40% or more, preferably 80% or more is preferable. The base rubber is composed of cis-1,4-polybutadiene or contains cis-1,4-polybutadiene as a main component.
The main component of 4-polybutadiene is, for example, cis-1,4-polyisoprene, styrene-butadiene rubber,
This refers to a case where ethylene propylene rubber, ethylene propylene diene rubber, chloroprene rubber, etc. are mixed with the above cis-1,4-polybutadiene to form a base rubber. However, the rubber other than the cis-1,4-polybutadiene is preferably 10% by weight or less in the whole base rubber.

Examples of the metal salt of α, β-unsaturated carboxylic acid include metal salts of acrylic acid such as zinc acrylate and magnesium acrylate and metal salts of methacrylic acid such as zinc methacrylate and magnesium methacrylate. One kind or two or more kinds are selected and used from the inside. The amount of the metal salt of the α, β-unsaturated carboxylic acid to be blended is 10 to 25 parts by weight, and particularly 15 to 100 parts by weight of the base rubber.
-20 parts by weight is preferred. If the amount of the metal salt of unsaturated carboxylic acid is less than the above range, the core becomes soft and the amount of deformation of the core becomes larger than 6.5 mm.
The resilience performance tends to decrease and the flight performance tends to decrease. Also, when the amount of the unsaturated carboxylic acid metal salt compounded exceeds the above range, the amount of deformation of the core becomes less than 3.5 mm and the impact at the time of hitting the ball is reduced. The strength tends to increase and the shot feeling tends to deteriorate.

Examples of the initiator include dicumyl peroxide and 1,1-bis (t-butylperoxy)-
3,3,5-trimethylcyclohexane, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane,
Organic peroxides such as di-t-butyl peroxide are used, but dicumyl peroxide is particularly preferable.
The amount of the initiator compounded is preferably 0.1 to 5 parts by weight, and more preferably 0.3 to 3 parts by weight, based on 100 parts by weight of the base rubber. When the amount of the initiator compounded is less than the above range, crosslinking does not proceed sufficiently, and therefore, there is a tendency that sufficient repulsion performance cannot be obtained. Further, when the amount of the initiator compounded is more than the above range, crosslinking does not occur. If the ball moves too far, the core becomes hard and the shot feeling tends to deteriorate.

As the filler, for example, zinc oxide, barium sulfate, calcium carbonate, hydrated silicate, etc. may be mentioned. The amount of the filler compounded is 1 to 40 parts by weight per 100 parts by weight of the base rubber. Particularly, 5 to 25 parts by weight is preferable. If the blending amount of this filler is less than the above range,
The hardness of the core tends to be insufficient, and when the amount of the filler to be blended is more than the above range, the specific gravity of the core tends to be too large, and the resilience performance tends to decrease.

The core can be obtained by filling the above-mentioned rubber composition in a core mold and crosslinking and molding. The kneading conditions for preparing the rubber composition for the core and the crosslinking conditions for the core composition are known to those skilled in the art, but crosslinking molding is usually performed under pressure.
It is carried out by heating at a temperature of 0 to 180 ° C. for 15 to 55 minutes.

The cover includes both the inner layer cover and the outer layer cover.
It is formed from a resin composition containing an ionomer resin as a main component. Examples of the ionomer resin include high milan 1605 (Na) and high milan 1706 (Z
n), Himilan 1707 (Na), Himilan AM7
315 (Zn), Himilan AM7316 (Zn), Himilan AM7317 (Zn), Himilan AM731
8 (Na), Himilan MK7320 (K), Himilan 1555 (Na), Himilan 1557 (Zn) (all are trade names, manufactured by Mitsui DuPont Polychemical Co., Ltd.), Surlyn 8920 (Na), Surlyn 8940 (Na), Surlyn AD8512. (Na), Surlyn 7930 (L
i), Surlyn 7940 (Li), Surlyn 9910
(Zn), Surlyn AD8511 (Zn), Surlyn 9
650 (Zn) (both are trade names, manufactured by DuPont, USA), Iotech 7010 (Zn), Iotech 8
000 (Na) (both are trade names, manufactured by Exxon Chemical Co., Ltd.)
Etc., and these ionomer resins are used alone or as a mixture of two or more kinds. N described in parentheses after the trade name of the ionomer resin
a, Zn, K, Li and the like represent those neutralizing metal ion species. Then, both the resin composition for the inner layer cover and the resin composition for the outer layer cover, the above ionomer resin is appropriately blended with a pigment such as titanium dioxide or barium sulfate, and if necessary, further an antioxidant, a fluorescent bleaching agent, etc. It is prepared by appropriately mixing additives. Also,
Polyolefin such as polyethylene and polypropylene, polyamide or the like may be appropriately added as long as the characteristics of the ionomer resin are not impaired. However, it is preferable that the amount of the added resin is 10% by weight or less based on the entire resin components.

The method of coating the inner layer cover and the outer layer cover on the core is not particularly limited, and it can be carried out by a method adopted for ordinary cover coating. For example, when the core is covered with the inner cover, the resin composition for the inner cover is formed into a half-shell-shaped half shell in advance, and the core is wrapped with two pieces of the shell, and the temperature is set to 100 to 170 ° C.
And the like, or a method of wrapping the core by directly molding the resin composition for the inner layer cover onto the core by injection molding for 1 to 15 minutes. And, when the outer layer cover is coated on the inner layer cover, the same method as in the case of coating the inner layer cover on the core can be performed.

Next, an example of the structure of the solid golf ball of the present invention will be described with reference to the drawings. FIG. 1 is a sectional view schematically showing an example of the solid golf ball of the present invention. In the figure, 1 is a core, 2 is a cover for covering the core, and this cover 2 is an inner cover 2a and an outer cover. 2b, and a dimple 3 is provided on the outer layer cover 2b.

The core 1 is made of a cross-linked molded body of a rubber composition, which is a so-called solid core. The core 1 has a diameter of 32.7 to 38.4 mm, and an initial load of 10 kg is applied to the core. The final load from when applied 130
The deformation amount by the time of multiplying kg is 3.5 to 6.5 mm. The core 1 has an internal hardness of JI.
It is preferable that the difference between the hardness of the central portion and the hardness of the portion other than the center is 5% or less, which is the hardness measured by an S-C hardness meter.

The inner layer cover 2a has a bending elastic modulus of 3500.
And made of a resin composition ~6000kgf / cm ^2, the inner cover 2a is made of a resin composition mainly composed of an ionomer resin, its thickness 1.1 to 2.5
mm.

[0027] Then, the outer layer cover 2b is bent elastic modulus 2300~5500kgf / cm ^2, and the flexural modulus than the inner cover 2a consists 500 kgf / cm ² or more low resin composition, the outer layer cover 2b ionomer resin Of a resin composition containing as a main component, and the thickness thereof is 1.1 to 2.5 mm.

The above-mentioned dimples 3 are provided in an appropriate number and form so as to obtain desired or desired characteristics, and the surface of the ball is painted or marked as necessary. It

[0029]

BEST MODE FOR CARRYING OUT THE INVENTION Next, the present invention will be described more specifically with reference to Examples. However, the present invention is not limited to only those examples.

Examples 1 to 6 and Comparative Examples 1 to 5 Rubber core compositions were prepared with the compounding compositions shown in Tables 1 and 2,
The obtained rubber composition for cores was filled in a mold for cores, and 1
A core was prepared by crosslinking molding at 65 ° C. for 25 minutes. The diameter, deformation amount and hardness of the obtained core were measured.
The results are shown in Tables 1-2. The blending amount of each component in the table is based on parts by weight, and this is the same in the tables showing the blending composition hereinafter. The amount of deformation of the core is measured by applying an initial load of 10 kg to a final load of 130 kg on the core, and measuring the core hardness according to JIS-
C type hardness tester, 5m from the center of the core to the surface
The measurement was performed at the position of m, the position of 10 mm from the center to the surface, the position of 15 mm from the center to the surface, and the surface. The hardness inside the core was measured at predetermined positions after cutting the core into two equal parts.

Table 1 shows the composition of the cores of Examples 1 to 6, the diameter of the core, the amount of deformation of the core and the hardness of the core, and Table 2 shows those of Comparative Examples 1 to 5. In addition, about what was represented by the brand name in the table, the detail is shown after Table 2.

[0032]

[Table 1]

[0033]

[Table 2]

* 1: BR-11 (trade name) High cis polybutadiene manufactured by Japan Synthetic Rubber Co., Ltd. having 96% cis-1,4 structure

Next, a resin composition for the inner layer cover and a resin composition for the outer layer cover were prepared with the compounding compositions shown in Tables 3 to 4. Table 3 shows the formulations of the inner cover and the outer cover of Examples 1 to 6, and Table 4 shows that of Comparative Examples 1 to 5. In the table, the ionomer resin is shown by the trade name, and the details are shown after Table 4. In addition, the formulations shown in Tables 3 to 4 show only the resin component, and both the resin composition for the inner layer cover and the resin composition for the outer layer cover are respectively mixed with 100 parts by weight of the resin component shown in Tables 3 to 4. It contains 2 parts by weight of titanium.

[0036]

[Table 3]

[0037]

[Table 4]

* 2: Himilan 1706 (trade name) This is a zinc ion neutralized ionomer resin of ethylene-methacrylic acid copolymer system manufactured by Mitsui DuPont Polychemical Co., Ltd. Bending elastic modulus = about 2600 kgf / cm ² * 3: Himilan 1707 (Product name) Mitsui DuPont Polychemical Co., Ltd. is an ethylene-methacrylic acid copolymer-based sodium ion-neutralized ionomer resin, flexural modulus = approximately 3800 kgf / cm ² * 4: High Milan 1605 (Product name) Mitsui DuPont Polychemical It is a sodium ion neutralized ionomer resin of ethylene-methacrylic acid copolymer system manufactured by K.K. and has a bending elastic modulus of about 3100 kgf / cm ^2.

* 5: Iotech 8000 (trade name) A sodium ion neutralized ionomer resin of ethylene-acrylic acid copolymer system manufactured by Exxon Chemical Co., which has a flexural modulus of about 4000 kgf / cm ² * 6: High Milan AM7315 (commodity) Name) Mitsui DuPont Polychemical Co., Ltd. is an ethylene-methacrylic acid copolymer type zinc ion neutralized ionomer resin, flexural modulus = about 4500 kgf / cm ² * 7: High Milan 1557 (trade name) Mitsui DuPont Polychemical Co., Ltd. Is a zinc ion neutralized ionomer resin of ethylene-methacrylic acid copolymer system, and has a flexural modulus of elasticity of about 2190 kgf / cm ² * 8: Hymiran 1855 (trade name) Mitsui DuPont Polychemical Co., Ltd. ethylene-methacrylic acid-acrylic acid Zinc ion neutralization of ester terpolymer system Ionomer resin, flexural modulus = about 950 kgf / c
m ²

The bending elastic moduli of the resin composition for the inner layer cover and the resin composition for the outer layer cover prepared as described above are shown in Tables 5 to 7. In addition, these bending elastic moduli use Stiffness tester made by Toyo Seiki Co., Ltd., and ASTM D-7
47 was measured at 23 ° C. in accordance with No. 47, and the bending elastic modulus measurement sample was formed by subjecting the resin composition for the inner layer cover and the resin composition for the outer layer cover to hot press molding to form flat plates each having a thickness of about 2 mm. It was used for measurement after being left for 2 weeks at 23 ° C. and 50% relative humidity.

Next, the resin composition for an inner layer cover prepared as described above is injection-molded on the core to form an inner layer cover, and the resin composition for an outer layer cover is injection-molded on the inner layer cover. An outer layer cover is formed to have an outer diameter of 42.7.
mm, a solid golf ball having a ball weight of 45.4 g was produced.

The amount of ball deformation, the coefficient of restitution, the flight distance (carry), the amount of spin, the durability, and the feel at impact of the obtained golf ball were examined.

The methods for measuring or evaluating the above-mentioned ball deformation amount, repulsion coefficient, flight distance, spin amount, durability and shot feeling are as follows.

Amount of ball deformation: Initial load of 10 kg on the ball
The amount of deformation from the time of applying the load to the time of applying the final load of 130 kg is measured.

Coefficient of Repulsion: Using a R & A (British Golf Association) initial velocity measuring machine, 198.4 g of a metal cylinder was used for the ball to measure 4 times.
The ball velocity when colliding at a velocity of 5 m / s is measured and calculated from the ball velocity.

Flying distance: A No. 1 wood club is attached to a swing robot manufactured by Trutemper Co., a ball is hit at a head speed of 45 m / s, and a distance to a falling point is measured as a carry distance (carry).

Spin amount: A swing robot manufactured by Trutemper Co. was equipped with a pitching wedge, the ball was hit with a head speed of 20 m / s, and the hit ball was continuously photographed and examined.

Durability: 4 balls on a metal plate with an air gun
The number of times until the ball was cracked by colliding at a ball speed of 5 m / s was examined, and the impact resistance number of Example 1 (the number of times before the crack was generated) was taken as 100 and shown as an index.

Hit feeling: 10 top professionals actually hit the ball with a No. 1 wood club and evaluate it. The evaluation criteria are as follows. When the evaluation results are displayed in the table, the same symbols are used, but in this case, 8 or more out of 10 people who were evaluated have the same evaluation.

Evaluation criteria: ◯: Good. △: Normal ×: Bad. XX: Very bad.

Tables 5 to 7 show the above measurement and evaluation results together with the bending elastic modulus and thickness of the inner layer cover and the bending elastic modulus and thickness of the outer layer cover. In addition, Table 5 shows those regarding Examples 1-3, Table 6 shows those regarding Examples 4-6, and Table 7 shows those regarding Comparative Examples 1-5.

[0052]

[Table 5]

[0053]

[Table 6]

[0054]

[Table 7]

As is clear from the comparison between the ball characteristics of Examples 1 to 6 shown in Tables 5 to 6 and the ball characteristics of Comparative Examples 1 to 5 shown in Table 7, Examples 1 to 6 have a large coefficient of restitution. It had high repulsion performance, long flight distance and excellent flight performance, a large durability index and excellent durability, high spin rate, excellent controllability, and excellent shot feeling.

That is, these Examples 1 to 6 and Comparative Example 1
Nos. 5 to 5 have the same composition of the core, and except for Examples 4 and 5, the core has the same diameter and the same amount of deformation, but Examples 1 to 6 have bending elastic moduli of the inner cover and the outer cover. As a result, the high repulsion performance, the excellent flight performance, the durability, the controllability, and the shot feeling were excellent.

On the other hand, in Comparative Example 1, both the inner layer cover and the outer layer cover had a bending elastic modulus lower than the range specified by the present invention, so that the repulsion performance was low, the flight distance was short, and the durability was poor. In Comparative Example 2, the bending elastic modulus of the inner layer cover was higher than the range specified in the present invention, and therefore the shot feeling was particularly poor.

In Comparative Example 3, since the bending elastic modulus of the outer cover was lower than the range specified in the present invention, the resilience performance was low, the flight distance was short, and the durability was poor. In Comparative Example 4, both the inner layer cover and the outer layer cover had bending elastic moduli higher than the range specified in the present invention, and therefore the shot feeling was particularly poor. Comparative Example 5 was particularly poor in durability because there was no difference between the flexural modulus of the inner cover and the flexural modulus of the outer cover.

Comparative Examples 6 to 11 Core compositions were prepared with the compounding compositions shown in Table 8, the obtained core compositions were filled in core molds, and crosslinked at 165 ° C. for 25 minutes to form cores. Was produced.

With respect to the obtained core, its diameter, the amount of deformation and the hardness measured by a JIS-C type hardness meter were measured in the same manner as in Example 1. Table 8 shows the results. The materials used for blending the core are the same as those used in Example 1, and are indicated by trade names.

[0061]

[Table 8]

Next, an inner cover composition and an outer cover composition were prepared with the composition shown in Table 9, and the core was coated with the inner cover composition in the same manner as in Example 1. An inner layer cover is formed, and further, the inner layer cover is coated with the outer layer cover composition to form an outer layer cover,
A solid golf ball having an outer diameter of 42.7 mm and a ball weight of 45.4 g was produced. The ionomer resin used for the cover is the same as that used in Examples 1 to 6 and Comparative Examples 1 to 5, and is indicated by the trade name.

With respect to the obtained golf ball, the amount of deformation of the ball, the coefficient of restitution, the flight distance (yard), the amount of spin, the durability and the feel at impact were examined in the same manner as in Example 1. The results are shown in Tables 10-11. Tables 10 to 11 also show the bending elastic moduli and thicknesses of the inner layer cover and the outer layer cover, which were measured by the same method as in Example 1 above.

[0064]

[Table 9]

[0065]

[Table 10]

[0066]

[Table 11]

As is clear from the results shown in Tables 10 to 11, in Comparative Examples 6 to 11, any one or more of flight distance, durability, controllability, and shot feeling, such as a short flight distance, are provided. The characteristics were inferior. That is,
In Comparative Example 6, the deformation amount of the core is smaller than the range specified by the present invention, in Comparative Example 7 the deformation amount of the core is larger than the range specified by the present invention, and in Comparative Example 8, the diameter of the core is the range specified by the present invention. It is smaller and the thickness of the inner layer cover and the thickness of the outer layer cover are thicker than the ranges specified by the present invention, Comparative Example 9 has a thickness of the inner layer cover smaller than the range specified by the present invention, and Comparative Example 10 has a thickness of the outer layer cover. Since the diameter of the core is larger than the range specified in the present invention, and the thickness of the inner layer cover and the outer layer cover are smaller than the ranges specified in the present invention, the thickness is smaller than the range specified in the present invention. ,
Any one of flight distance, durability, controllability and shot feeling
One or two or more had poor properties.

[0068]

As described above, according to the present invention, it is possible to provide a solid golf ball having high resilience performance, excellent flight performance, durability, controllability and shot feeling.

[Brief description of drawings]

FIG. 1 is a sectional view schematically showing an example of a solid golf ball of the present invention.

[Explanation of symbols]

 1 core 2 cover 2a inner layer cover 2b outer layer cover

Claims (2)

[Claims] 1. A solid golf ball having a core and a cover, wherein the core has a diameter of 32.7 to 38.4.
mm, and the amount of deformation from an initial load of 10 kg to a final load of 130 kg is 3.5 to 6.5 mm, and the cover has a bending elastic modulus of 3500 to 6000 kgf / and the inner cover made of the resin composition cm ^2, a flexural modulus of 2300~5500k
gf / cm ² , and the flexural modulus is 50 than that of the inner cover.
0 kgf / cm ² or more made from a low two layers of an outer layer cover made of a resin composition, the thickness of the inner layer cover is 1.1 to 2.
A solid golf ball having a thickness of 5 mm, a thickness of the outer cover of 1.1 to 2.5 mm, and both of the inner cover and the outer cover made of a resin composition containing an ionomer resin as a main component. 2. The internal hardness of the core is a hardness measured by a JIS-C type hardness meter, and the difference between the hardness of the central portion and the hardness of the portion other than the central portion is 5% or less. 1
The solid golf ball described.