JPH10309331A - Multipiece solid golf ball - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a golf ball which is a multipiece solid golf ball having good productivity and is capable of assuring desired properties even without the execution of a drying treatment, etc., before molding and is capable of maintaining a ball hitting feel and flying performance in a winter time or cold season as well. SOLUTION: This multipiece solid golf ball is constituted by coating a solid core of the plural layer constitution obtd. by coating an inside layer core 1 with one or >=2 layers of outer layer cores, with a cover. In such a case, the outermost layer of the outer layer core 2 comprises a material contg. an aramid based elastomer. The material contg. the aramid based elastomer is preferably a material of which 10 to 100 wt.% of the polymer component is the aramid based elastomer and the other polymer component is ionomer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-piece solid golf ball represented by three pieces, which has excellent mass productivity by forming an outer layer core of a thermoplastic material, and further has a flying performance and a hit feeling. And a multi-piece solid golf ball having good durability.

[0002]

2. Description of the Related Art In recent years, a multi-piece solid golf ball formed by dividing a solid core portion into two or three or more layers and varying hardness, specific gravity, and diameter (thickness) of each layer has been proposed.

In a typical three-piece golf ball as a multi-piece solid golf ball, there is a ball in which an inner layer and an outer layer forming a core are formed of crosslinked polybutadiene rubber. In the case of such a ball, after forming the inner layer core, It must be coated with an outer core composition and crosslinked. For this reason, the number of man-hours for producing a core is increased as compared with a two-piece golf ball, and there is a problem that productivity is poor.

[0004] In order to solve the problem of productivity in a three-piece golf ball, there has been proposed a golf ball in which the outer layer core is made of a thermoplastic elastomer. Since the thermoplastic elastomer does not need to go through a crosslinking step, the outer layer core can be formed only by injection molding after forming the inner layer core.

A three-piece golf ball having an outer layer core made of a thermoplastic elastomer is disclosed in, for example,
No. 244,174 discloses a golf ball in which at least 10% of the composition constituting the outer layer is made of a thermoplastic material containing an amide block copolymer. The amide block copolymer used here is a polyether nylon-based elastomer in which the soft segment is a polyether and the hard segment is a nylon-based nylon such as nylon 6, nylon 66, or nylon 12.

JP-A-6-142228 discloses that the outer layer core is composed of 100 to 50% of a polyetherester type thermoplastic elastomer and 0 to 50% by weight of an ionomer of an ethylene- (meth) acrylic acid copolymer. A three-piece golf ball formed of a mixture-based material is disclosed. Here, in the polyetherester-based thermoplastic elastomer, the soft segment is a polyether such as polypropylene glycol or polytetramethylene glycol, and the hard segment is a polyester portion such as polybutylene terephthalate.

[0007]

However, polyester-based elastomers have high hygroscopicity, and when injection-molded pellets that have absorbed moisture, they are hydrolyzed to deteriorate physical properties and dimensional stability. In order to secure desired physical properties, it is necessary to dry the pellets before use in molding, which is troublesome.

[0008] In addition, in both the nylon and polyester elastomers, rubber elasticity decreases at low temperatures, so that the impact feeling in winter, that is, the shot feeling becomes hard,
Furthermore, the durability tends to be inferior due to a decrease in impact resistance at low temperatures.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a multi-piece solid golf ball having good productivity and performing a drying process or the like before molding. It is an object of the present invention to provide a golf ball that can secure desired physical properties without having to have the same, and can maintain shot feeling and flying performance even in winter.

[0010]

In other words, the multi-piece solid golf ball of the present invention is a multi-piece solid golf ball having a multi-layer solid core in which an inner core is covered with one or more outer cores. The piece solid golf ball is characterized in that the outermost layer of the outer layer core is made of a material containing an aramid elastomer.

In the above-mentioned material containing an aramid elastomer, it is preferable that 10 to 100% by weight of the polymer component is an aramid elastomer and the other polymer component is an ionomer.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the multi-solid golf ball of the present invention will be described. FIG. 1 shows a three-piece golf ball according to an embodiment of the present invention, in which a solid core in which an inner core 1 is covered with a single outer core 2 is covered with a cover 3.

The inner core 1 is formed by heating, pressing and molding a rubber composition containing a base rubber, a metal salt of an unsaturated carboxylic acid, an organic peroxide, a filler as a specific gravity adjuster, and the like. Is done. As the base rubber, natural rubber and / or synthetic rubber conventionally used for solid golf balls is used, and in particular, so-called high cis having at least 90% or more, preferably 95% or more cis-1,4-structure. Polybutadiene rubber is preferred, and if desired, natural rubber, polyisoprene rubber, styrene polybutadiene rubber, EPDM, and the like may be blended.

The metal salt of an unsaturated carboxylic acid is added as a co-crosslinking agent, and specifically, zinc of an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms such as acrylic acid or methacrylic acid; Monovalent or divalent metal salts such as magnesium salts are used, and among these, zinc acrylate which imparts high resilience is preferably used. The compounding amount of the unsaturated carboxylic acid metal salt is preferably 20 to 60 parts by weight, particularly preferably 20 to 50 parts by weight, based on 100 parts by weight of the base rubber. 6
If the amount is more than 0 parts by weight, it becomes too hard and the hit feeling becomes poor, and if it is less than 20 parts by weight, the resilience becomes poor and the flight distance decreases. The amount of the unsaturated carboxylic acid metal salt may be adjusted depending on the diameter of the inner layer core, the type of the cover material, and the like so as to impart a desired elastic modulus.

The organic peroxide is added as a crosslinking agent or a curing agent, and specifically, dicumyl peroxide,
1-bis (t-butylperoxy) -3,5-trimethylcyclohexane, 2,5-dimethyl-2,5-di (t
-Butylperoxy) hexane, di-t-butyl peroxide, etc., of which dicumyl peroxide is preferably used. The compounding amount of the organic peroxide is preferably from 0.1 to 3.0 parts by weight, particularly preferably from 0.3 to 2.5 parts by weight, based on 100 parts by weight of the base rubber.
If the amount is less than 0.1 part by weight, it becomes too soft, the rebound becomes worse, and the flight distance decreases. If the content exceeds 3.0 parts by weight, the composition becomes too hard, and the hit feeling becomes poor.

Among the specific gravity adjusters, the filler for lowering the specific gravity (low specific gravity filler) may be any one which is usually blended in the core of a golf ball. For example, an inorganic salt, specifically, Zinc oxide, barium sulfate, calcium carbonate and the like can be mentioned, and among these, zinc oxide is particularly preferable. The filler for increasing the specific gravity (high specific gravity filler) has a specific gravity of 8 to 20.
Metal powders, metal oxides, metal nitrides, and the like, or mixtures thereof.
3), tungsten carbide (specific gravity 15.8), molybdenum (specific gravity 10.2), lead (specific gravity 11.3), lead oxide (specific gravity 19.3), nickel (specific gravity 8.9) and copper (specific gravity 8) .9) or mixtures thereof. You may mix and use a low specific gravity filler and a high specific gravity metal powder. The compounding amount is 5-1 to 100 parts by weight of the base rubber.
It is preferably 10 parts by weight. If the amount is less than 5 parts by weight, it is difficult to adjust the weight. If the amount exceeds 110 parts by weight, the weight ratio of the rubber becomes small, and the rebound becomes too low.

The diameter of the inner layer core having such a configuration is as follows.
It is preferably from 25 to 37 mm. The outer core 2
It is composed of a thermoplastic material containing an aramid elastomer.

Here, the aramid elastomer is a copolymer elastomer comprising a hard segment and a soft segment, and the hard segment is formed of a wholly aromatic polyamide. As the wholly aromatic polyamide, poly (o-phenylenephthalamide), poly (m-
Phenylene isophthalamide), poly (p-phenylene terephthalamide) and the like.
Poly (p-phenylene terephthalamide), which is the most rigid and has excellent heat resistance, is preferred. The soft segment is generally made of polyether or polyester, but is preferably made of polyether which is hardly hydrolyzed when heated during injection molding or the like. Examples of the polyether diol component constituting the polyether include polyoxytetramethylene glycol, polyoxypropylene glycol, polyoxyethylene glycol, and polyoxyhexamethylene glycol.

Among such aramid elastomers, a thermoplastic elastomer represented by the following structural unit using polytetramethylene oxide as a soft segment and poly (p-phenylene terephthalamide) as a hard segment in a molecular chain is preferable. Used. In the formula, n is preferably from 10 to 60.

[0020]

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Such an aramid elastomer has a Shore A hardness of 65 to 95 and a tensile strength at break of 25.
It is preferably from 40 to 40. The aramid-based elastomer having the above-mentioned structure has a wide rubber elasticity region because the wholly aromatic polyamide constituting the hard segment is more rigid than polyester and nylon and has excellent heat resistance and low-temperature characteristics, and provides a shot feeling, resilience, and durability. Excellent in nature. Especially,
Even in winter, rubber elasticity can be exhibited, so that the same flight performance and shot feeling as in summer can be ensured in winter. Further, the aramid-based elastomer has excellent low-temperature impact resistance as compared with the polyester-based elastomer, and therefore has excellent low-temperature durability. The aramid elastomer is
One type or two or more types of aramid elastomers may be used as a mixture.

The outer layer core 2 may be composed of the aramid elastomer alone or may be used by mixing the aramid elastomer with another thermoplastic resin. However, if the mixing ratio of the aramid elastomer is too small, Since the intended improvement in durability, hit feeling in winter and hitting performance in winter cannot be sufficiently ensured, the mixing ratio of the aramid elastomer is preferably 10% by weight or more, more preferably 20% by weight.
% By weight or more, particularly preferably 40% by weight or more.

As the other thermoplastic resin, an ionomer having excellent durability and resilience is preferably used. As the ionomer, a metal ion neutralized product of a copolymer of an α-olefin and an α, β-unsaturated carboxylic acid is preferably used. Specifically, ionomers of ethylene- (meth) acrylic acid copolymer, such as "Surlyn" manufactured by DuPont, "Iotek" manufactured by Exxon Chemical, and "High Milan" manufactured by DuPont Mitsui Chemicals.

When an ionomer is contained, when the mixing ratio of the ionomer is increased, rubber elasticity is reduced and rigidity is increased, so that resilience is improved and durability is also improved. Preferably, it is more preferably mixed at 20% by weight or more. On the other hand, even if the mixing ratio is too large, little improvement in resilience is observed, but durability deteriorates due to a decrease in impact resistance, and the shot feeling deteriorates due to too high rigidity. Therefore, the mixing ratio of the ionomer is preferably 90% by weight or less of the polymer component, more preferably 80% by weight or less, and particularly preferably 60% by weight or less.

As a constituent material of the outer layer core, in addition to other polymer components such as an aramid elastomer and an ionomer, if necessary, a filler such as a weight adjusting agent and an antioxidant may be appropriately contained. As the weight adjusting agent, the filler for low specific gravity and the filler for high specific gravity used in the inner layer core can be used.

The outer layer core composed of the above materials is
Overall Shore D hardness 60 or less, JIS-A hardness 7
It is preferably 0 or more. If the Shore D hardness is more than 60, the rebound resilience will be low even if the durability is good due to being too rigid, resulting in a decrease in the resilience coefficient of the whole ball, and the impact feeling will be hard. On the other hand, JIS-
If the A hardness is less than 70, it is too soft and the amount of deformation when receiving an impact increases, resulting in poor durability.

Outer layer core 2 made of such a material
After the preparation of the inner core 1, the outer core composition was added to the inner core 1.
And then press molding, or coating and molding may be performed in one step by injection molding. Since the outer layer core is made of a thermoplastic material as described above, it can be formed by injection molding or extrusion molding, and can achieve higher productivity than a crosslinked rubber.

FIG. 1 shows the case of a three-piece golf having one outer layer core. In the case of two or more outer layer cores, if the outermost layer is made of a material containing the above-mentioned aramid elastomer, Good. And as a whole solid core,
What is necessary is just to comprise so that diameter may be 35-39 mm.

The solid core having a multilayer structure obtained as described above is covered with the cover 3. The cover 3 has a thickness of 1 to 3 mm, and is made of a material mainly containing an ionomer resin and a thermoplastic elastomer, and optionally containing an inorganic filler such as a white filler, a specific gravity adjuster, and a gloss imparting agent.
As a constituent material of the cover 3, a material containing an ionomer as a main component is preferable from the viewpoint of resilience. As the ionomer resin used for the cover 3, an ionomer that can be included in the constituent material of the outer layer core is preferably used.

The cover 3 is formed by forming a solid core composed of the inner core 1 and the outer core 2 and then coating the solid core. A method in which a cup is molded, a core is packed in the cup, and hot press molding is performed is used.

[0031]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to specific embodiments. Example 1 A rubber composition obtained by mixing a co-crosslinking agent and a filler with polybutadiene rubber was crosslinked to form an inner layer core having a diameter of 28 mm. The hardness was 58 ° according to JIS-C.

Next, an aramid elastomer (T8821J (trade name) manufactured by Tosoh Corporation, Shore A hardness: 88, tensile breaking strength: 31) having poly (p-phenylene terephthalamide) as a hard segment, and white filler ,
An elastomer composition prepared by adding a specific gravity adjuster and a gloss-imparting agent, and extruding and mixing each zone at a temperature of 200 to 230 ° C. using a twin-screw extruder (screw diameter: 43 mm, L / D = 35). Was injection molded so as to cover the inner layer core to form an outer layer core. The thickness of the outer layer core was 5.5 mm, and the hardness of the entire outer layer core was 90 ° according to JIS-A.

Further, a mixture of a zinc ion-neutralized ethylene-methacrylic acid copolymer ionomer and a sodium ion-neutralized ethylene-methacrylic acid copolymer ionomer was injection-molded so as to cover the outer layer core.
An 8-mm cover was formed to produce a three-piece golf ball.

Examples 2 to 5: In the same manner as in Example 1 except that the diameter of the inner layer core, the thickness of the outer layer core, the elastomer composition of the outer layer core, and the hardness of the outer layer core were changed as shown in Table 1, 3 A piece golf ball was created.

The ionomer used for the outer layer core composition was Surlyn 8511 (a zinc ion neutralized ethylene-methacrylic acid copolymer type ionomer resin) manufactured by DuPont.
It is.

Comparative Examples 1-3: As shown in Table 1, the outer layer core composition was as follows: ionomer alone, polyester elastomer ("Hytrel 404" manufactured by Du Pont-Toray Co., Ltd.)
7 ") and a nylon-based elastomer (" Pebax 4033 "manufactured by ATOCHEM Co., Ltd.).
In the same manner as in the above, a three-piece golf ball was prepared.

Reference Example 1 Example except that the outer layer core was formed of a crosslinked rubber (JIS-C hardness 75 °) obtained by vulcanizing a rubber composition obtained by blending a co-crosslinking agent and a filler with polybutadiene rubber. In the same manner as in 1, a three-piece golf ball was prepared.

REFERENCE EXAMPLE 2 A core having a diameter of 39 mm was made of a crosslinked polybutadiene rubber having a JIS-C hardness of 75 ° and the ionomer used in Example 1 was 1.8 m thick.
m was formed to produce a two-piece golf ball.

[Evaluation] The examples, comparative examples, and reference examples were evaluated for durability, resilience, and shot feeling by the following methods. Table 1 shows the results.

Durability The ball was hit with a metal plate at a speed of 45 m / sec with an air gun, and the number of times until the ball was broken was measured. The index was expressed as an index when the golf ball of Reference Example 2 was set to 100. The larger the index value, the better the ball durability.

The resilience R & A (British Golf Association) measures the ball speed when a cylinder of 198.4 g collides with a ball at a speed of 45 m / sec with an air gun of the same model as the air gun used for initial velocity measurement. The coefficient of restitution was calculated from the result and is shown as an index when the golf ball of Reference Example 2 was set to 100. The greater the value, the greater the rebound resilience of the ball and the greater the flight distance.

Hitting Feeling The hitting feel at the time of hitting a W # 1 club by ten top amateurs was averaged, and this hitting feeling was represented by a five-point scale. The higher the score, the softer the shot feeling, the smaller the impact and the better. The shot feeling is normal temperature (23 ° C) and 0
The test was performed on the ball left at 24 ° C. for 24 hours.

[0043]

[Table 1]

A, D, C in parentheses in the column of hardness in Table 1
Depends on the type of the spring type testing machine.
A, JIS-C and Shore D are shown. As can be seen from Table 1, with respect to durability, the three-piece ball whose outer layer core was a polyester elastomer or a crosslinked rubber was inferior (Comparative Example 2 and Reference Example 2), whereas the polyamide elastomer was a two-piece golf ball. (Example and Comparative Example 3). Further, the durability was improved as the outer layer core was composed of the ionomer-containing material, but the durability did not change when the mixing ratio of the ionomer was 60% by weight or more (Examples 2 to 5 and Comparative Example 1). Also, from Example 2 and Comparative Examples 2 and 3, it can be seen that the ball whose outer layer core was made of an aramid elastomer was more durable than the ball whose outer layer core was made of another thermoplastic elastomer.

Comparison between Comparative Examples 2 and 3 and Example 2 shows that the aramid elastomer is superior to the nylon elastomer or polyester elastomer in terms of resilience. In addition, as the mixing ratio of the ionomer increases, the rigidity increases and the resilience tends to be improved (Examples 2 to 5). However, even when the mixing ratio of the ionomer is 60% by weight or more, the improvement in the resilience is almost impossible. Not recognized (Examples 4, 5).

The shot feeling was soft because the ionomer having high plasticity was hard, whereas the elastomers all had rubber elasticity. However, the shot feeling at 0 ° C. showed that the aramid elastomer having a wide rubber elasticity region showed the same shot feeling at room temperature, whereas both the nylon elastomer and the polyester elastomer became harder than at room temperature. (Comparative Examples 2, 3). Also, in the case of the crosslinked rubber, the rubber elasticity decreased at 0 ° C. and the rubber became hard (Reference Example).

Further, from the comparison between Example 1 and Example 2, it can be seen that when the outer layer core is composed solely of aramid elastomer, the thinner the soft outer layer core, the better the durability and resilience. .

[0048]

As described above, the multi-piece solid golf ball of the present invention uses an aramid-based elastomer having a rigid hard segment and a wider rubber elasticity area than other elastomers as an elastomer component of the outer layer core. It is more durable and resilient than in the past, and can provide the same shot feeling at room temperature in winter.

Further, the multi-piece solid golf ball of the present invention can be used without drying treatment since the outer layer core is composed of a thermoplastic elastomer and the pellets have low hygroscopicity. Since the outer core can be formed in one step without any process, the productivity is excellent.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a configuration of a three-piece golf which is one embodiment of the present invention.

[Explanation of symbols]

 1 inner core 2 outer core 3 cover

Claims (2)

[Claims] 1. A multi-piece solid golf ball in which an inner core is covered with one or two or more outer cores and a multi-layer solid core is covered with a cover, wherein the outermost layer of the outer core is aramid-based. A multi-piece solid golf ball comprising a material containing an elastomer. 2. The multi-piece solid golf according to claim 1, wherein in the material containing the aramid elastomer, 10 to 100% by weight of the polymer component is an aramid elastomer, and 90 to 0% by weight of the polymer component is an ionomer. ball.