JPH1057526A - Golf ball - Google Patents

Abstract

(57) [Problem] To provide a golf ball excellent in durability and resilience performance and having a good feel (hit feeling) when hitting a ball. SOLUTION: In a golf ball having a core and a cover covering the core, a base polymer of the cover is composed of a polyolefin having a molecular weight distribution Mw / Mn of 1 to 3 and another polymer, and Contains at least an ionomer resin, and the base polymer 1 of the cover
2.5 to 50 parts by weight of a polyolefin having a molecular weight distribution Mw / Mn of 1 to 3 is contained in 00 parts by weight. In the molecular weight distribution Mw / Mn, Mw is a weight average molecular weight, Mn is a number average molecular weight, and the other polymer is preferably an ionomer resin or a mixture of an ionomer resin and a diene rubber.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a golf ball, and more particularly, to a golf ball having excellent durability and resilience performance and having a good feel when hitting a ball.

[0002]

2. Description of the Related Art Conventionally, ionomer resins have been frequently used as resins for cover of golf balls. This is because the ionomer resin has excellent resilience performance and cut resistance.

[0003] However, since the ionomer resin has high rigidity, there is a drawback that the feel when hitting the ball is hard.
Therefore, attempts have been made to improve the feel at the time of hitting a ball by blending (mixing) a rubber with an ionomer resin.

[0004] The present inventors have also proposed blending a diene rubber with an ionomer resin and dynamically vulcanizing the diene rubber in the ionomer resin to provide high resilience performance based on the ionomer resin and flexibility based on the diene rubber. A golf ball that has a long flight distance and a soft feel when hitting a ball has been developed.

[0005]

However, as described above, a golf ball in which a core is coated with a cover composition obtained by blending a rubber with an ionomer resin has excellent flight performance and feeling when hit, If the injection molding is performed at an extremely high injection speed in the injection molding when covering the cover, the strength of the weld line (fused portion) becomes weak due to the orientation of the rubber component and the durability against repeated impacts. There was a problem that became worse.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a golf ball which solves the above-mentioned problems of the prior art, has excellent durability and resilience performance, and has a good feel when hitting a ball.

[0007]

SUMMARY OF THE INVENTION The present invention provides a molecular weight distribution M
By blending a polyolefin having a narrow molecular weight distribution of w / Mn of 1 to 3 with another polymer, particularly an ionomer resin or a mixture of an ionomer resin and a diene rubber, at a specific ratio, durability and flight performance are excellent, and A golf ball having a good feeling at the time of hitting is obtained, and the above object has been achieved.

That is, the present invention relates to a golf ball having a core and a cover for covering the core, wherein the base polymer of the cover is another polymer containing a polyolefin having a molecular weight distribution Mw / Mn of 1 to 3 and at least an ionomer resin. Wherein the polyolefin having a molecular weight distribution Mw / Mn of 1 to 3 is contained in 2.5 to 50 parts by weight in 100 parts by weight of the base polymer of the cover. In the molecular weight distribution Mw / Mn, Mw is a weight average molecular weight, and Mn is a number average molecular weight.

The molecular weight distribution Mw / M used in the present invention
The polyolefin having n of 1 to 3 is a polyolefin polymerized using a single-site catalyst centered on a metallocene compound called a metallocene catalyst, and this polyolefin has a long-chain branch introduced into the main chain and a molecular weight distribution. Is controlled and the molecular weight distribution Mw / Mn is 3
The molecular weight distribution is narrow as follows, heat sealability, low temperature characteristics,
It has excellent impact resistance and flexibility.

[0010] By utilizing the excellent heat sealing property of the polyolefin, the strength of the weld line of the cover can be increased to improve the durability against repeated impact of the ball, and the flexibility of the polyolefin. This can improve the feel at the time of hitting the ball.

Further, the molecular weight distribution Mw / Mn is 1 to 3
Polyolefin having a narrow molecular weight distribution has a rebound resilience of 60% or more (however, the rebound resilience measured at 23 ° C. with a Dunlop trypsometer, and the same applies to the rebound resilience shown below). %, High resilience, and when blended with other polymers such as ionomer resin, does not decrease the high resilience performance of the ionomer resin, but rather improves the resilience performance. Golf balls can be obtained.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION As described above, the polyolefin used in the present invention has a molecular weight distribution Mw / Mn of 1 to 1.
3, preferably 1.5 to 2.5, having a narrow molecular weight distribution. Incidentally, a general polyolefin has a molecular weight distribution Mw / Mn of about 4 to 5.

When the molecular weight distribution Mw / Mn is 1 to
The other polymer to be blended with the polyolefin of No. 3 needs to contain at least an ionomer resin, and specifically, an ionomer resin or a mixture of an ionomer resin and a diene rubber is preferable.

In the present invention, the molecular weight distribution Mw / Mn of the polyolefin needs to be 1 to 3 for the following reasons. That is, when the molecular weight distribution Mw / Mn of the polyolefin is larger than 3, heat sealability, impact resistance and the like are reduced, and a golf ball excellent in durability and the like cannot be obtained. It is not possible that the molecular weight distribution Mw / Mn of the polyolefin is smaller than 1.

The polyolefin is not particularly limited as long as the molecular weight distribution Mw / Mn is in the range of 1 to 3, and various types can be used. Those having a unit are preferred, and polyethylene-based ones are particularly preferred because of good compatibility with the ionomer resin.
This is because many ionomer resins have polyethylene as a main chain.

A typical example of such a polyolefin is one having a basic structure of an ethylene copolymer. Examples of commercially available products include "Engage" manufactured by DuPont Dow Elastomer Co., Ltd. "Affinity" (all trade names) and the like. In addition, ethylene polymers such as "EXACT" (trade name) manufactured by Exxon Chemical Co., Ltd. and "Kernel" (trade name) manufactured by Mitsubishi Chemical Corporation )and so on.

On the other hand, when the molecular weight distribution Mw / Mn is 1 to 3
As another polymer to be blended with the polyolefin, it is necessary to contain at least an ionomer resin as described above, and other than the ionomer resin, for example, diene rubber, polyamide, polycarbonate, polyacetal, A polyester resin is exemplified. However, the other polymer is preferably an ionomer resin or a mixture of an ionomer resin and a diene rubber.
As a specific example, a case where the other polymer is an ionomer resin or a mixture of an ionomer resin and a diene rubber will be described.

As the above-mentioned ionomer resin, any of those conventionally used as a base resin for a cover of a golf ball can be used. Specific examples of such an ionomer resin can be exemplified by a trade name. Himilan 1605 manufactured by Mitsui Dupont Polychemical Co., Ltd.
(Trade name, sodium ion neutralized ethylene-methacrylic acid copolymer ionomer resin), Himilan 1707
(Trade name, sodium ion neutralized ethylene-methacrylic acid copolymer ionomer resin), Himilan 1706
(Trade name, zinc ion neutralized ethylene-methacrylic acid copolymer ionomer resin), Himilan AM7315
(Trade name, zinc ion neutralized ethylene-methacrylic acid copolymer ionomer resin), Himilan AM7317
(Trade name, zinc ion neutralized ethylene-methacrylic acid copolymer ionomer resin), Himilan 1555 (trade name, sodium ion neutralized ethylene-methacrylic acid copolymer ionomer resin), Himilan 1557 (trade name, sodium ion neutralized) Ethylene-methacrylic acid copolymer-based ionomer resin), Iotech 7010 (trade name, zinc ion-neutralized ethylene-acrylic acid copolymer-based ionomer resin) manufactured by Exxon Chemical Co., Ltd., Iotech 8000 (trade name, sodium-ion-neutralized ethylene-acrylic) Acid copolymer type ionomer resin), Surlyn 7930 (trade name, lithium ion neutralized ethylene-methacrylic acid copolymer type ionomer resin), Surlyn 8511 (trade name, zinc ion neutralized ethylene-methacrylic acid copolymer) manufactured by DuPont. Synthetic ionomer resin), Surlyn 8512 (trade name, sodium ion-neutralized ethylene-methacrylic acid copolymer ionomer resin), etc., each of which can be used alone or in combination of two or more. You can also. Of course, the ionomer resin is not limited to those exemplified above.

The molecular weight distribution Mw / Mn is 1 to
In the case where the polyolefin of No. 3 constitutes the base polymer of the cover with this ionomer resin, the base polymer 1
It is necessary to be 2.5 to 50 parts by weight in 00 parts by weight, and it is particularly preferable to be 2.5 to 35 parts by weight. That is, the ionomer resin is 50 to 97.5 parts by weight, particularly preferably 65 to 97.5 parts by weight, based on 100 parts by weight of the base polymer.

If the polyolefin having a molecular weight distribution Mw / Mn of 1 to 3 is less than 2.5 parts by weight in 100 parts by weight of the base polymer composed of the ionomer resin, the durability is not improved sufficiently. , The molecular weight distribution M
The polyolefin having a w / Mn of 1 to 3 is 50 in 100 parts by weight of a base polymer composed of an ionomer resin.
When the amount is more than the weight part, the high resilience performance of the ionomer resin decreases, and a golf ball with high resilience cannot be obtained.

When the base polymer of the cover is composed of a polyolefin having an molecular weight distribution Mw / Mn of 1 to 3, an ionomer resin and a diene rubber, the molecular weight distribution Mw / Mn is 1 to 3. Examples of the polyolefin and the ionomer resin include those described above. Examples of the diene rubber include ethylene propylene diene rubber (EPDM) and butadiene rubber (B
R), isoprene rubber (IR), styrene butadiene rubber (SBR), acrylonitrile butadiene rubber (NB
One or two of R) and the like can be used.

As described above, when the base polymer of the cover is composed of the three components of the polyolefin having the molecular weight distribution Mw / Mn of 1 to 3, the ionomer resin, and the diene rubber, the molecular weight distribution Mw / Mn is 1 to 3. The polyolefin is preferably 3 to 100 parts by weight, particularly 3 to 50 parts by weight, based on 100 parts by weight of the total amount of the ionomer resin and the diene rubber. Then, the ionomer resin and the diene rubber are such that, in a total amount of 100 parts by weight thereof, the ionomer resin is 40 to 95 parts by weight and the diene rubber is 5 parts by weight.
Preferably, it is 60 parts by weight. The polyolefin having a molecular weight distribution Mw / Mn of 1 to 3 was added in an amount of 3 to 100 parts by weight of the total amount of the ionomer resin and the diene rubber.
The blending amount of １００100 parts by weight is based on the molecular weight distribution Mw / Mn.
Is equivalent to the case where 2.9 to 50 parts by weight of a polyolefin having a molecular weight distribution Mw / Mn of 1 to 3 in 100 parts by weight of a base polymer composed of a polyolefin having 1 to 3 and an ionomer resin and a diene rubber. I do.

When the polyolefin having a molecular weight distribution Mw / Mn of 1 to 3 is less than 3 parts by weight based on 100 parts by weight of the total amount of the ionomer resin and the diene rubber, the heat sealability of the polyolefin makes it possible to form a weld line with a weldability. The effect of improving the resilience of the golf ball is low, and therefore, it is difficult to obtain a golf ball having excellent durability. Conversely, when the content is more than 100 parts by weight, the high resilience performance of the ionomer resin is reduced, and the golf ball having excellent resilience performance is obtained. Is difficult to obtain. The total amount of the ionomer resin and the diene rubber is 1
When the amount of the ionomer resin is less than 40 parts by weight in 00 parts by weight, the resilience performance of the ball is reduced. On the other hand, when the amount of the ionomer resin is more than 95 parts by weight, the feeling at the time of hitting is reduced due to the decrease in the diene rubber. May not be sufficiently improved.

When the base polymer of the cover is composed of a polyolefin having a molecular weight distribution Mw / Mn of 1 to 3, an ionomer resin, and a diene rubber, these three components may be merely mixed. To further improve the weldability of the weld line between the ring and the cover,
It is preferable that the diene rubber is dynamically vulcanized in the mixture thereof, and the average particle diameter of the vulcanized rubber particles is particularly 10 μm.
m or less.

As the vulcanizing agent used for the dynamic vulcanization, one of sulfur, vulcanizing agent, vulcanization accelerator, resin vulcanizing agent and the like used as a vulcanizing agent in a usual rubber compounding is used. Alternatively, two or more kinds can be used.

As such a vulcanizing agent, for example, p
-Benzoylquinone dioxime, p, p'-dibenzoylquinone dioxime, 4,4'-dithio-bis-dimorpholine, alkylphenol-formaldehyde,
Brominated alkylphenol-formaldehyde, phenolic resin, cumarone resin, dibenzothiazyl disulfide, N, N'-dicyclohexyl-2-benzothiazylsulfenamide, hexamethylenetetramine, mercaptobenzothiazole, tetramethylthiuram disulfide, tetraethylthiuram disulfide , Tetrabutylthiuram disulfide and the like, but are not limited thereto.

In preparing the cover composition for forming the cover, the molecular weight distribution Mw / Mn should be 1 to 3
To a base polymer composed of a polyolefin and an ionomer resin or another polymer such as an ionomer resin and a diene rubber, pigments, fillers, and other additives that are generally blended in preparing a golf ball cover composition are appropriately added. You may mix.

In preparing the cover composition, the mixing apparatus is not particularly limited. For example, a closed mixer such as a kneader, an open mixer such as a roll, and an extruder in a continuous apparatus. Is used. Also,
As the mixing method, for example, the same substance may be mixed by several or more kinds of kneading methods, and the order of mixing is not particularly limited.

For example, if the molecular weight distribution Mw / Mn is 1
When mixing the polyolefin, the ionomer resin, and the diene rubber with each other, the three types of materials may be added and mixed at once, or after mixing other than the polyolefin having a molecular weight distribution Mw / Mn of 1 to 3, The above polyolefins may be mixed. As described above, it is not always necessary to mix the ionomer resin and the diene rubber before mixing with the polyolefin having a molecular weight distribution Mw / Mn of 1 to 3.

In the case of performing dynamic vulcanization, when mixing the polyolefin having the molecular weight distribution Mw / Mn of 1 to 3, the ionomer resin, the diene rubber and the vulcanizing agent, four kinds of materials are added at once. Alternatively, the above-mentioned polyolefin may be mixed after mixing other than the above-mentioned polyolefin.

The dynamic vulcanization is performed, for example, by adjusting the temperature at the time of preparing the cover composition to a temperature suitable for dynamic vulcanization. Generally, the temperature of the dynamic vulcanization is suitably in the range of from 20 ° C. lower than the activation temperature of the vulcanizing agent to 260 ° C. That is, the temperature of the dynamic vulcanization depends on the activation temperature of the vulcanizing agent and varies depending on the activation temperature. Generally, the activation temperature of the vulcanizing agent is about 150 to 180 ° C. A temperature of about 130 to 260 ° C. is suitable as the temperature of the sulfur. And the time for dynamic vulcanization is generally 2 to
About 60 minutes is suitable.

The cover composition prepared as described above can be applied to the coating of any of a solid core and a wound core, and has a heat sealing property of a polyolefin having a molecular weight distribution Mw / Mn of 1 to 3. Improves the weldability of the weld line, improves the durability against repeated impact of the ball, shows resilience performance that is equal to or better than conventional resilience performance, and is based on the above-mentioned reolefin or polyolefin and diene-based The feel at the time of hitting can be softened by the flexibility of rubber.

The solid core and the thread wound core are not particularly limited to specific ones, and for example, conventional ones can be used.

The solid core may have not only a single-layer structure but also a multilayer structure having two or more layers.
For example, as a solid core for two-piece balls,
With respect to 100 parts by weight of butadiene rubber, a vulcanizing agent comprising an α, β-monoethylenically unsaturated carboxylic acid such as acrylic acid or methacrylic acid or a metal salt thereof, or a functional monomer such as trimethylolpropane trimethacrylate ( 10 to 60 parts by weight of a crosslinking agent) alone or in total, 10 to 30 parts by weight of a filler such as zinc oxide or barium sulfate, and 0.5 to 0.5 parts by weight of a peroxide such as dicumyl peroxide.
5 parts by weight, and if necessary, 0.1 g of an antioxidant.
By press vulcanization (cross-linking), the rubber composition blended with 1 to 1 part by weight is heated at a temperature of, for example, 140 to 170 ° C. to 10 to 40 parts by weight.
A material obtained by heating and compressing for a minute to form a spherical vulcanizate can be used.

The wound core is composed of a center and a rubber thread layer formed by winding a thread rubber around the center in a stretched state. The center is made of a vulcanized molded product of a rubber composition. A solid center may be used, or a liquid center in which liquid such as water or paste is sealed in a center cover made of vulcanized rubber may be used.

The method of covering the core with the cover is not particularly limited, and can be performed by a usual method.
For example, the cover composition is preliminarily formed into a hemispherical shell half shell, and two cores are used to wrap the core and then heat-press molding, or the cover composition is directly injection molded onto the core to form the core. Is adopted. The thickness of the cover is usually about 1 to 4 mm. Then, at the time of molding the cover, dimples are formed on the ball surface as necessary, and at the time of molding the cover, paint finishing, stamping, and the like are performed as necessary. When the cover is covered with the polyolefin having a molecular weight distribution Mw / Mn of 1 to 3 having an excellent molecular weight distribution, the weldability of the weld line is improved, and the durability against repeated impact is improved.

FIG. 1 is a sectional view schematically showing an example of the golf ball of the present invention. The golf ball shown in FIG. 1 has a core 1 made of a vulcanized molded product of a rubber composition and a cover for covering the core. 2 is a two-piece solid golf ball. The core 1 is not particularly limited to a specific one. For example, a solid core made of a vulcanized molded body of a rubber composition containing butadiene rubber as a main material as described above is used, and a cover 2 covering the core is used. It is formed from a cover composition containing the specific polyolefin as one component of the base polymer. Reference numeral 2a denotes a dimple provided on the cover 2. In the solid golf ball shown in FIG. 1, the core 1 is made of a vulcanized molded article of a rubber composition having a one-layer structure. Instead, for example, a vulcanized molded article of a rubber composition mainly containing butadiene rubber is used. A solid core having a two-layer structure in which an outer core made of a vulcanized molded product of a rubber composition mainly containing butadiene rubber is further formed around an inner core made of butadiene rubber.

FIG. 2 is a cross-sectional view schematically showing another example of the golf ball of the present invention. In FIG.
Is formed of a center 1a and a thread rubber layer 1b and is called a thread wound core, 2 is a cover for covering the core 1, and 2a is a dimple. The center 1a may be a solid type or a liquid type, and the cover 2 covering the core 1 is formed from a cover composition containing the specific polyolefin as one component of the base polymer. It is.

The dimples 2a are provided on the cover 2 in an appropriate number and in an appropriate form so that required or desired characteristics can be obtained. Is applied.

[0040]

Next, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to only these examples.

Examples 1 to 5 and Comparative Examples 1 and 2 The golf balls of Examples 1 to 5 and Comparative Examples 1 and 2 were produced through the following steps.

Preparation of Solid Core: A rubber composition having the composition shown in Table 1 was prepared, filled in a mold and vulcanized to obtain a spherical solid core having a diameter of 39.0 mm. The vulcanization conditions are performed in two stages as shown in Table 1,
After vulcanizing at 142 ° C for 20 minutes, it was further vulcanized at 165 ° C for 8 minutes. The butadiene rubber used was BR-11 (trade name) manufactured by Japan Synthetic Rubber Co., Ltd., and the anti-aging agent was Yoshinox 425 (trade name) manufactured by Yoshitomi Pharmaceutical Co., Ltd.

[0043]

[Table 1]

Preparation of cover composition: The compounding materials having the compositions shown in Table 2 were mixed by a twin-screw kneading extruder.
A pellet-shaped cover composition was prepared. The compounding amounts in the table are based on parts by weight, and the extrusion conditions are as follows:
3 mm, screw L / D = 35 and the formulation was heated to 220-260 ° C. at the extruder die.

[0045]

[Table 2]

* 1: Himilan 1706 (trade name) Zinc ion-neutralized ethylene-methacrylic acid copolymer ionomer resin manufactured by Mitsui Dupont Polychemical Co., Ltd. * 2: Engage 8100 (trade name) Dupont Dow Elastomer Co., Ltd. Ethylene-octene copolymer, molecular weight distribution Mw / Mn = 2.4

Preparation of golf ball: The above-described core composition was injection-molded on the core, the core was covered with a cover, and the surface was painted with paint to obtain an outer diameter of 42.7 m.
m golf balls.

The durability, resilience performance and feeling of the obtained golf ball were examined. Table 3 shows the results.
Table 3 also shows the composition of the base polymer of the cover of each Example and Comparative Example so that these physical properties and the composition of the base polymer of the cover can be easily compared. However,
In Table 3, the names of the polymers are indicated by generic names, and the ionomer resin is referred to as "ionomer" due to space limitations.
And a polyolefin having a molecular weight distribution Mw / Mn of 1 to 3 is simply shown as “olefin”. Table 3
The amount of the polymer contained therein is also parts by weight, and the details of the composition of the base polymer are as shown in Table 2. The measuring methods and evaluation methods of durability, resilience performance, feeling, etc. are as follows.

Durability: A ball is hit at an initial velocity of 45 m / s and hits a metal flat plate, and the number of times until the cover is broken is measured. The results are indicated by an index with the number of times until the destruction of Comparative Example 1 using only the ionomer resin as the base polymer of the cover taken as 100.

Repulsion performance: A stainless steel cylinder weighing 198 g was struck out by an air gun at an initial velocity of 35 m / s, and collided with a ball in front of the cylinder. The velocities of the cylinder and the ball before and after the collision were measured by two photoelectric tubes, respectively.
The coefficient of restitution was calculated from the respective speeds and weights, and the rate of increase / decrease from the coefficient of restitution of Comparative Example 1 using only the ionomer resin as the base polymer of the cover is indicated by an index expressed as a percentage. “+” Indicates an increase and “−” indicates a decrease.

Feeling: Ten top professionals hit the ball with the No. 1 wood club for evaluation. When the evaluation results are displayed in the table, the same symbols are used. In this case, eight or more out of the ten persons who made the evaluation gave the same evaluation.

Evaluation criteria: A : Soft and good. : Some lack of softness, but good. ○ H: Some hardness, but good. ○ S: A little too soft, but good. × H: Hard and bad. × S: too soft and bad.

[0053]

[Table 3]

As is clear from the results shown in Table 3, Examples 1 to 5 were excellent in durability and resilience performance, and had a good feeling when hitting a ball.

To explain this in detail, Comparative Example 1 uses only the ionomer resin as the base polymer of the cover and is a reference for comparison. Examples 1 to 5 of the present invention The index showing the durability is larger than that of Example 1, the durability is excellent, and the resilience performance is equal to or more than that of Comparative Example 1, the resilience performance is excellent, and the feeling at the time of hitting is different between Examples. Although there is a slight difference,
It was good.

On the other hand, in Comparative Example 1, since only the ionomer resin was used as the base polymer of the cover,
Although it had high rebound performance, the feel when hitting the ball was hard and poor, and the durability was inferior to those of the examples. Also,
In Comparative Example 2, since the polyolefin content was large and the ionomer resin content was small, the resilience performance was reduced, the durability was also reduced, and the feel at the time of hitting the ball was too soft, which was rather poor.

Examples 6 to 20 and Comparative Examples 3 to 9 The golf balls of Examples 6 to 20 and Comparative Examples 3 to 9 were produced through the following steps (1) to (6).

Preparation of a wound core: A rubber composition having the composition shown in Table 4 was prepared, and filled in a mold.
By carrying out vulcanization molding for 0 minutes, a solid center having a diameter of 34.0 mm was produced. The butadiene rubber used was BR-11 (trade name) manufactured by Japan Synthetic Rubber Co., Ltd.
The anti-aging agent is Yoshinox 425 manufactured by Yoshitomi Pharmaceutical Co., Ltd.
(Product name).

[0059]

[Table 4]

Next, a yarn made of a blend rubber in which the base rubber is natural rubber / low cis-isoprene rubber [Shell IR-309 (trade name), manufactured by Shell Chemical Co.] = 30/70 (weight ratio) in each of the centers. By winding the rubber in a stretched state to form a thread rubber layer, a thread wound core having an outer diameter of about 39 mm was produced.

Preparation of cover composition: The compounding materials having the compositions shown in Tables 5 to 9 were mixed by a twin-screw kneading extruder to prepare a pellet-shaped cover composition. The blending amounts in the table are based on parts by weight and are indicated by trade names in the table. Details of the components that have not been described so far are shown after Table 9. The extrusion conditions were a screw diameter of 43 mm, a screw rotation speed of 200 rpm,
The screw L / D = 35 and the formulation was heated to 220-260 ° C. at the die position of the extruder.

[0062]

[Table 5]

[0063]

[Table 6]

[0064]

[Table 7]

[0065]

[Table 8]

[0066]

[Table 9]

* 3: Esprene 505A (trade name) Ethylene propylene diene rubber (EPDM) manufactured by Sumitomo Chemical Co., Ltd. * 4: Tackilol (trade name) Alkylphenol formaldehyde, vulcanizing agent manufactured by Taoka Chemical Industry Co., Ltd. * 5: Sumikasen G701 (trade name) Polyethylene manufactured by Sumitomo Chemical Co., Ltd., belonging to conventional polyolefins.

Example 7, Example 11, and Example 1
In Example 5, the diene rubber (Esprene 505A) is dynamically vulcanized. The average particle diameter of the vulcanized rubber particles is 0.85 μm in Example 7, 1.02 μm in Example 11, and 1.05 μm in Example 11. 15 was 1.15 μm. The method for measuring the particle size is as follows.

First, a measurement sample was prepared by pulverizing the above-mentioned cover composition into a size of 3 to 5 mm, and then heat-molding the composition at 160 ° C. for 3 minutes under pressure. Then, the measurement of the particle diameter was performed by taking a backscattered electron image photograph using a scanning electron microscope (T-220A manufactured by JEOL), measuring the vertical length of any 50 of the rubber particles,
The numerical value based on the number average was defined as the average particle diameter.

Production of golf ball: A half-shell having a hemispherical shell shape was formed from the above composition for a cover,
The above-mentioned wound core is wrapped in a single piece, pressed in a ball mold at 158 ° C. for 2 minutes, the wound core is covered with a cover, and the surface is painted with paint to obtain an outer diameter of 4 mm.
A 2.8 mm golf ball was produced.

With respect to the obtained golf balls, durability, resilience performance and feeling were examined in the same manner as in Example 1 and the like. The results are shown in Tables 10 to 14. However, when indicating the durability, the number of times until the destruction of Comparative Example 3 using only the ionomer resin as the base polymer of the cover was set to 100, and when indicating the resilience performance, the same was applied. The increase or decrease with respect to the coefficient of restitution of Comparative Example 3 is indicated by an index expressed as a percentage (indicated by “+” when increasing, and by “−” when decreasing). Tables 10 to 14 also show the composition of the base polymer of the cover of each of the examples and the comparative examples so that these properties can be easily compared with the composition of the base polymer of the cover. However, in Table 3, the names of the polymers are shown by generic names, and in view of space, the ionomer resin is simplified to “ionomer”, and the molecular weight distribution Mw
Polyolefins having a / Mn of 1 to 3 are abbreviated as “olefins”, and conventional polyolefins are abbreviated as “conventional olefins”. The amounts of the polymers in these tables are also parts by weight, and the details of the composition of the base polymer are as shown in Tables 5 to 9.

[0072]

[Table 10]

[0073]

[Table 11]

[0074]

[Table 12]

[0075]

[Table 13]

[0076]

[Table 14]

As is evident from the results shown in Tables 10 to 14, Examples 6 to 20 were excellent in durability and resilience performance, and had a good feel when hitting a ball.

To explain this in detail, Comparative Example 3 uses only an ionomer resin as the base polymer of the cover, and is used as a reference for comparison in a multi-layer golf ball having these wound cores. Examples 6 to 20 of the invention have larger indices indicating durability than Comparative Example 3, are excellent in durability, and have a rebound performance of Comparative Example 1.
The resilience performance was excellent and the feeling was good although there was a slight difference between the examples.

On the other hand, in Comparative Example 3, since only the ionomer resin was used as the base polymer of the cover,
Although it has high resilience performance based on ionomer resin,
The feeling at the time of hitting the ball was hard and poor, and the durability was inferior to those of the examples.

Further, Comparative Example 4 shown in Table 10 is similar to Example 6
Comparative Example 3 contains an ionomer resin and a diene rubber in the same ratio as that of Examples 6 to 9, but does not contain a polyolefin having a narrow molecular weight distribution as in Examples 6 to 9, and thus has lower durability than Examples 6 to 9. Was also inferior to. In addition, the dynamically vulcanized Example 7 was more excellent in durability and the resilience performance further than Example 6 in which the composition was not dynamically vulcanized.

Similarly, Comparative Example 5 shown in Table 11 contains an ionomer resin and a diene rubber in the same ratio as in Examples 10 to 13, but contains a polyolefin having a narrow molecular weight distribution as in Examples 10 to 13. Therefore, the durability was inferior to Examples 10 to 13 and inferior to Comparative Example 3. In addition, the dynamically vulcanized Example 11 was more excellent in durability and the resilience performance further than Example 5 in which the composition was not dynamically vulcanized.

Comparative Example 6 shown in Table 12 is the same as Example 1
Although it contains an ionomer resin and a diene rubber in the same ratio as 4 to 16, but does not contain a polyolefin having a narrow molecular weight distribution as in Examples 14 to 16, the durability is inferior to Examples 14 to 16, and It was inferior to Example 3. Further, the dynamically vulcanized Example 15 was more excellent in durability and the resilience performance further than Example 14 in which the composition was not dynamically vulcanized.

Further, Comparative Examples 7 and 8 shown in Table 13
Contains an ionomer resin and a diene-based rubber at the same ratio as in Examples 17 to 18. However, since it does not contain a polyolefin having a narrow molecular weight distribution as in Examples 17 to 18, the durability is higher than that of Examples 17 to 18. Inferior to Comparative Example 3. Comparative Example 8 uses a conventionally used polyolefin in place of the polyolefin having a narrow molecular weight distribution in Example 17, but is inferior in durability and resilience performance to Example 17. Was.

Comparative Example 9 shown in Table 14 is the same as Example 1
Although it contains an ionomer resin and a diene rubber in the same ratio as 9 to 20, but does not contain a polyolefin having a narrow molecular weight distribution as in Examples 19 to 20, the durability is inferior to Examples 19 to 20, and Comparative Examples Inferior to 3

[0085]

As described above, according to the present invention, it is possible to provide a golf ball having excellent durability and resilience performance and good feeling when hitting a ball.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically showing one example of a golf ball of the present invention.

FIG. 2 is a cross-sectional view schematically illustrating another example of the golf ball of the present invention.

[Explanation of symbols]

 1 core 2 cover

Claims (10)

[Claims] 1. A golf ball having a core and a cover covering the core, wherein the base polymer of the cover comprises a polyolefin having a molecular weight distribution Mw / Mn of 1 to 3 and another polymer, and the other polymer is The base polymer 100 for the cover, comprising at least an ionomer resin.
A golf ball comprising 2.5 to 50 parts by weight of a polyolefin having a molecular weight distribution Mw / Mn of 1 to 3 in parts by weight. Mw in the molecular weight distribution Mw / Mn is a weight average molecular weight, and Mn is a number average molecular weight. 2. The above-mentioned other polymer is only an ionomer resin, and a polyolefin having a molecular weight distribution Mw / Mn of 1 to 3 is used in an amount of 2.5 to 5 in 100 parts by weight of a base polymer of the cover.
2. The golf ball according to claim 1, comprising 0 parts by weight and 50 to 97.5 parts by weight of an ionomer resin. 3. The golf ball according to claim 2, wherein the polyolefin having a molecular weight distribution Mw / Mn of 1 to 3 is 2.5 to 35 parts by weight, and the ionomer resin is 65 to 97.5 parts by weight. 4. The golf ball according to claim 1, wherein the other polymer is an ionomer resin and a diene rubber. 5. A polyolefin having a molecular weight distribution Mw / Mn of 1 to 3 is a total amount of an ionomer resin and a diene rubber of 1
The amount of the ionomer resin is 40 to 95 parts by weight, and the amount of the diene rubber is 5 to 60 parts by weight, based on 100 parts by weight, and 100 parts by weight of the total amount of the ionomer resin and the diene rubber. The golf ball according to claim 4, wherein 6. The polyolefin having a molecular weight distribution Mw / Mn of 1 to 3 is 3 to 50 parts by weight based on 100 parts by weight of the total amount of the ionomer resin and the diene rubber.
The golf ball as described. 7. The molecular weight distribution Mw /
Mn is 1.5-2.5.
Or the golf ball of 6. 8. The golf ball according to claim 1, wherein the polyolefin is an ethylene-octene copolymer. 9. A mixture of a polyolefin having an molecular weight distribution Mw / Mn of 1 to 3, an ionomer resin and a diene rubber, wherein only the diene rubber is dynamically vulcanized.
7. The golf ball according to 5 or 6. 10. The golf ball according to claim 9, wherein the average particle size of the dynamically vulcanized rubber particles is 10 μm or less.