JP2616817B2 - Solid golf ball - Google Patents

Description

The present invention relates to a solid golf ball having a specific gravity of less than 1 and suitable for water practice.

[Conventional technology]

Generally, practice range golf balls have two uses depending on their use.
Are roughly divided into two. One is a ball generally used on land, and the other is a water practice ball used in a pond or lake. The performance required for these two types of practice golf balls is firstly durability, followed by a shot feeling equivalent to or close to that of a round ball.
However, for a water practice golf ball, the most important property is that it must float on water, ie, the specific gravity of the ball must be less than one.

Therefore, conventionally, the specific gravity has been reduced by blending cork.

However, a golf ball having a specific gravity of less than 1 by adding cork has a drawback that the shot feeling is significantly poorer than a round ball or a land practice ball.

In addition, water practice balls that have a hardness and shot feeling close to those of round balls and land practice balls by blending polyolefin and ABS resin etc. have been proposed, but these have very poor durability In addition, the flight distance was much smaller than the round ball, and was inferior to the regular land practice ball.

Therefore, the present inventor first, syndiotactic-
5 to 30% by weight of 1,2-polybutadiene, and cis-
A base rubber containing polybutadiene rubber containing at least 40% by weight of 1,4-polybutadiene as an essential component, and an average particle diameter of 50 μm.
We have developed and applied for a patent for a low specific gravity golf ball mainly composed of ultrafine high molecular weight polyolefin having a particle size of m or less. The details are disclosed in JP-A-62-142571.

[Problems to be solved by the invention]

The golf ball described in JP-A-62-142571 is significantly improved in shot feeling, durability and the like, and is close to a round ball and a land practice ball, as compared with the previous water practice golf ball. It has a shot feeling and durability.
However, it is the same in the field of golf balls that a better one is required when a good one emerges, and from the user, a water surface having a shot feeling, durability and flight distance closer to that of a round ball. There is a need for practice golf balls.

[Means for solving the problem]

The present inventor has conducted various improvement studies based on the rubber composition disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 62-142571 in order to respond to such a demand. While maintaining that the golf ball can be used as a water practice ball with a specific gravity of less than 1, the flight distance,
The inventor has found that the shot feeling and durability are further improved, and the ball is closer to a round ball, and the present invention has been completed.

That is, the present invention relates to a base rubber containing a polybutadiene rubber containing 5 to 30% by weight of syndiotactic-1,2-polybutadiene and 40% by weight or more of cis-1,4-polybutadiene as an essential component. A specific gravity of a crosslinked body of a rubber composition containing a particulate ultrahigh molecular weight polyolefin having a particle diameter of 50 μm or less, a crosslinkable monomer, a micro hollow sphere having a pressure resistance of 140 kg / cm ² or more, and an initiator as main component is 1
Less than a solid golf ball, that is, by cross-linking the rubber composition, into a so-called one-piece ball, or by coating the inner core obtained by cross-linking the rubber composition with an outer skin such as an ionomer, The present invention relates to a so-called two-piece solid golf ball having a specific gravity of less than 1.

In the present invention, the reason why the hollow microspheres having a pressure resistance of 140 kg / cm ² or more are blended is particularly as follows.

That is, the above-mentioned micro hollow spheres having a pressure resistance of 140 kg / cm ² or more have a very light average particle density of 0.37 g / cc to 0.63 g / cc. A large amount of a high specific gravity crosslinkable monomer or inorganic filler which contributes to improvement in hardness, durability, flight distance and the like can be compounded.

Further, since the pressure resistance is 140 kg / cm ² or more, the rubber composition can be kept in a hollow sphere without being broken at the time of kneading with an open roll or a kneader, so that the specific gravity of the rubber composition can be reduced. Furthermore, since it is a hollow sphere, the hitting sound can be improved.

Such a hollow microsphere having a pressure resistance of 140 kg / cm ² or more is made of various inorganic materials such as glass and ceramics. Examples of a material that can be preferably used in the present invention include, for example, Sumitomo 3M Limited. From Glass Bubbles
B37 / 2000, Glass Bubbles B38 / 4000, Glass Bubbles B4
Soda lime borosilicate glass commercially available under the trade names such as 6/4000 and Glass Bubbles S60 / 10000. Among them, Glass Bubbles B38 / 4000, Glass Bubbles B46 / 4000, Glass Bubbles S60 / 10000, etc. have large pressure resistance, and there is no risk of breaking during kneading,
It is particularly preferably used in the present invention.

The minute hollow spheres having a pressure resistance of 140 kg / cm ² or more are generally fine hollow spheres having a diameter in the range of 4 μm to 250 μm, and have good dispersibility in the rubber composition, as described above. The rubber composition is lightened in specific gravity, and it is possible to mix a large amount of a crosslinkable monomer or the like that improves shot feeling, hardness, durability, and flight distance.
The mixing amount of the fine hollow spheres of 0 kg / cm ² or more is preferably 2 to 50 parts by weight, particularly preferably 2 to 12 parts by weight based on 100 parts by weight of the base rubber. That is, the pressure resistance is 140 kg / cm ²
When the compounding amount of the above minute hollow spheres is smaller than the above range, the specific gravity is reduced as described above, and the shot feeling, hardness,
It is not possible to increase the amount of the crosslinkable monomer that improves durability, flight distance, etc., and the pressure resistance is 140 kg /
If the amount of the fine hollow spheres of cm ² or more is more than the above range, kneading, processability such as extrusion is deteriorated, and
The ball becomes too hard, and the shot feeling is adversely reduced.

In the present invention, polybutadiene rubber containing 5 to 30% by weight of syndiotactic-1,2-polybutadiene and 40% by weight or more of cis-1,4-polybutadiene is used as an essential component of the base rubber. Is a polybutadiene rubber containing 5 to 30% by weight of the syndiotactic-1,2-polybutadiene and 40% by weight or more of cis-1,4-polybutadiene (hereinafter, simply referred to as "syndiotactic-1, 2-polybutadiene-containing polybutadiene rubber)) has high crystallinity and high melting point syndiotactic-1,2-polybutadiene. Unlikely, it gives golf balls moderate hardness (ball compression) without adding a large amount of crosslinkable monomers and inorganic fillers that lead to an increase in specific gravity. Shot feel, as well as impart the hitting sound, it is possible to increase the durability.

The amount of syndiotactic-1,2-polybutadiene in the above-mentioned syndiotactic-1,2-polybutadiene-containing polybutadiene rubber is 5 to 30% by weight, which is the amount of syndiotactic-1,2-polybutadiene-containing polybutadiene rubber. If the amount of syndiotactic-1,2-polybutadiene in the mixture is less than the above range, the golf ball becomes soft and the durability is reduced, and a large amount of a crosslinkable monomer or an inorganic filler is used in order to improve hardness and durability. As a result, the specific gravity becomes large and it does not float on water, so that it cannot be used as a golf ball for water practice, and when the amount of syndiotactic-1,2-polybutadiene exceeds the above range. This is because the rebound resilience is reduced and a suitable shot feeling, flight distance and the like cannot be obtained.

Further, cis-1,4-polybutadiene in the above-mentioned syndiotactic-1,2-polybutadiene-containing polybutadiene rubber needs to be 40% by weight or more, and when this cis-1,4-polybutadiene is less than this, rebound resilience is required. Of the golf ball, and a good shot feeling and a suitable flight distance cannot be obtained.

Such a syndiotactic-1,2-polybutadiene-containing polybutadiene rubber can be obtained, for example, by performing normal cis polymerization of butadiene and then performing 1,2-syndiotactic polymerization in the same system. And, such syndiotactic-1,2-polybutadiene-containing polybutadiene rubber, that is, containing 5 to 30% by weight of syndiotactic-1,2-polybutadiene and 40% by weight or more of cis-1,4-polybutadiene. Specific examples of the polybutadiene rubber containing include, for example, Ube Industries, Ltd.
UBEPOL-VCR309 (trade name, composition: syndiotactic-1,2-polybutadiene 9% by weight, cis-1,4-polybutadiene 89% by weight, trans-1,4-polybutadiene 2)
% By weight), UBEPOL-VCR412 (trade name, composition: syndiotactic-1,2-polybutadiene 12% by weight, cis-1,4-)
There are commercially available products such as polybutadiene (86% by weight and trans-1,4-polybutadiene 2% by weight), which are suitably used in the present invention.

In the present invention, the syndiotactic-1,2-polybutadiene-containing polybutadiene rubber is an essential rubber component, and the syndiotactic-1,2-polybutadiene in the base rubber is used.
The more polybutadiene-containing polybutadiene rubber is contained, the better the physical properties of the golf ball are obtained. Therefore, only the syndiotactic-1,2-polybutadiene-containing polybutadiene rubber may be used as the base rubber, or the syndiotactic-1,2-polybutadiene-containing polybutadiene-containing rubber may be used in view of workability and cost. Natural rubber, cis-1,4-polybutadiene rubber, styrene butadiene rubber or the like may be blended with the above-mentioned polybutadiene rubber containing syndiotactic-1,2-polybutadiene, using polybutadiene rubber as an essential component. As described above, syndiotactic-1,2-polybutadiene-containing polybutadiene rubber and natural rubber and cis-1,4-polybutadiene rubber,
When styrene-butadiene rubber or the like is blended to form a base rubber, the content of the syndiotactic-1,2-polybutadiene-containing polybutadiene rubber is preferably at least 30% by weight in the base rubber. That is, in the present invention, it is preferable that the above-mentioned syndiotactic-1,2-polybutadiene-containing polybutadiene rubber accounts for 30 to 100% by weight of the base rubber.

The ultrafine high molecular weight polyolefin having an average particle size of 50 μm or less acts as a low-specific gravity reinforcing filler, increases the hardness of the golf ball, and increases the durability and flight distance.
Improves shot feeling and hitting sound. As such a particulate ultrahigh molecular weight polyolefin, for example, Miperon (trade name, a particulate ultrahigh molecular weight polyolefin having an average particle diameter of 20 μm and an average molecular weight of 2,000,000 or more) manufactured by Mitsui Petrochemical Industries, Ltd. is commercially available. It is suitably used in the present invention. When the average particle size is less than 50 μm or less in the amount of the ultrafine high molecular weight polyolefin, the hardness, durability, and flight distance of the golf ball are increased while maintaining a low specific gravity.
The effect of improving the feel at impact and hitting sound is not sufficiently exhibited, and when the blending amount of the ultrafine high molecular weight polyolefin having an average particle diameter of 50 μm or less is too large, the ball hardness becomes too high and the feel at impact is impaired. Usually, the compounding amount of such a particulate ultrahigh molecular weight polyolefin having an average particle diameter of 50 μm or less is preferably 10 to 40 parts by weight based on 100 parts by weight of the base rubber. In the present invention, the use of the particulate ultrahigh molecular weight polyolefin having an average particle diameter of 50 μm or less is because the average particle diameter of the particulate ultrahigh molecular weight polyolefin is
If it exceeds 50 μm, the dispersibility becomes poor, and as a result, the durability of the golf ball decreases. The smaller the particle size, the better the physical properties of the golf ball. However, considering workability and handling properties, it is appropriate to use those having an average particle size of about 2 μm or more as the particulate ultrahigh molecular weight polyolefin. .

The crosslinkable monomer is one that crosslinks the rubber composition to exhibit rebound resilience and the like, imparts hardness, durability, a suitable shot feeling, a shot sound to the golf ball, and increases the flight distance.
As such a crosslinkable monomer, for example, metal salts of α, β-monoethylenically unsaturated carboxylic acids such as methacrylic acid and acrylic acid are used. However, in preparing the rubber composition, the crosslinkable monomer is obtained by converting an α, β-monoethylenically unsaturated carboxylic acid such as methacrylic acid or acrylic acid and the α, β-monoethylenically unsaturated carboxylic acid into a metal. It may be blended with a metal oxide such as zinc oxide to form a salt, so as to be a metal salt of α, β-monoethylenically unsaturated carboxylic acid in the rubber composition. When the amount of the crosslinkable monomer is small, the rubber composition is crosslinked to exhibit rebound resilience and the like, and the hardness,
The effect of imparting durability, a suitable shot feeling and a shot sound and increasing the flight distance is not sufficiently exhibited, and if the amount of the crosslinking monomer is too large, the ball hardness becomes too high and the shot feeling is impaired. The amount of the crosslinkable monomer is usually 10 to 5 parts by weight based on 100 parts by weight of the base rubber.
It is preferably 0 parts by weight. When the crosslinkable monomer is blended with an α, β-monoethylenically unsaturated carboxylic acid such as methacrylic acid or acrylic acid and a metal salt such as zinc oxide, in order to obtain the preferred blending amount,
Α, β-monoethylenically unsaturated carboxylic acids such as methacrylic acid and acrylic acid are used in an amount of 5 to 2 parts per 100 parts by weight of the base rubber.
5 parts by weight, metal oxides such as zinc oxide
What is necessary is just to mix 5 to 25 weight part with respect to 00 weight part. However, metal oxides such as zinc oxide have α, β as described above.
-It reacts with monoethylenically unsaturated carboxylic acid and is used not only as a constituent material for forming a crosslinkable monomer, but also by itself, as an inorganic filler, increases the hardness and impact strength of a golf ball, Since the durability of the golf ball is increased, the shot feeling and the hitting sound are improved, and the flight distance is increased, the golf ball may be blended beyond the above range. However, since the specific gravity of the golf ball is large, the specific gravity of the golf ball becomes larger than 1 and the golf ball does not float on water when the compounding amount thereof is large. Therefore, when the compounded amount exceeds the above range, it is necessary to consider the specific gravity.

In addition, like the metal oxides such as the zinc oxide, inorganic fillers such as silicon oxide (SiO ₂ ), calcium carbonate, and aluminum silicate also increase the hardness and impact strength of the golf ball,
These inorganic fillers may be blended to increase the durability of the golf ball, improve the feel at impact and the sound of impact, and increase the flight distance. However, the specific gravity of these inorganic fillers is also large, and if the inorganic filler is added in a large amount, the specific gravity of the golf ball becomes larger than 1 and the golf ball does not float on water. Therefore, the compounding amount needs to be determined in consideration of the specific gravity. Generally, metal oxides such as zinc oxide as the inorganic filler (i.e., in excess of those used to convert the α, β-monoethylenically unsaturated carboxylic acid into a metal salt as described above) Metal oxides such as zinc oxide)
The amount of these inorganic fillers, including
It is appropriate that the content be 5 parts by weight or less based on 0 parts by weight.

The initiator is for initiating the polymerization of the crosslinkable monomer so as to crosslink the rubber composition,
As such an initiator, for example, a peroxide such as dicumyl peroxide, 2,2-di (tert-butylperoxy) butane, or tert-butyl perbenzoate is used. When the amount is too small, the polymerization of the crosslinkable monomer cannot be sufficiently started, and when the amount of the initiator is too large, the polymerization and the crosslinking speed become too fast to control and the appropriate physical properties It is generally preferred that the amount of the initiator be 0.5 to 5 parts by weight based on 100 parts by weight of the base rubber.

In the present invention, the crosslinked body of the specific rubber composition is mainly used, but this main body means that a golf ball is formed into a one-piece ball only by a crosslinked body of the specific rubber composition, or It means that a two-piece ball is formed by forming an inner core with a crosslinked body of the above specific rubber composition, and applying an outer skin made of an ionomer, trans polyisoprene or the like to the inner core.

In producing the one-piece ball or the inner core for a two-piece ball, the rubber composition is placed in a mold and heated under pressure to crosslink. Then, when the outer core is applied to the inner core obtained as described above, a pair of half shells is formed in advance with the outer skin composition, and the half shell is covered with the inner core and heated under pressure or is applied to the inner core. A method of applying a skin by injection molding is used.

In the present invention, a rubber composition for producing an inner core for a one-piece type golf ball or a two-piece ball includes a base rubber containing the above-mentioned syndiotactic-1,2-polybutadiene-containing polybutadiene rubber as an essential component,
Ultrafine high molecular weight polyolefin, crosslinkable monomer,
In addition to a micro hollow sphere having a pressure resistance of 140 kg / cm ² or more, an initiator, and the like, a high styrene resin or the like may be appropriately blended for the purpose of, for example, hardening the ball.

〔Example〕

Next, the present invention will be described in more detail with reference to examples.

Examples 1 to 4 and Comparative Examples 1 to 2 A rubber composition having the composition shown in Table 1 was prepared, and the obtained rubber composition was placed in a ball-molding mold and heated under pressure to crosslink. mm, a one-piece solid golf ball (Example 1, Examples 3 and 4, and Comparative Examples 1 and 2)
2). In preparing the rubber composition, the components except the initiator were kneaded with a kneader for about 10 minutes, and the initiator was kneaded with the kneaded product with an open roll for about 6 minutes.

The rubber composition was placed in a mold for molding an inner core, and heated under pressure to crosslink, thereby producing an inner core having a diameter of 38.3 mm. Then, titanium oxide (TiO ₂ ) was added to the inner core with respect to 100 parts by weight of an ionomer. The outer core was coated with 2 parts by weight of the composition for the outer skin by an injection molding machine to give an outer skin, and the diameter was 42.8 mm.
(Example 2).

The specific gravity, ball compression, durability, shot feeling, and flight distance of the obtained golf ball were examined. The results are shown in Table 1. In addition, the number of parts of each material shown in Table 1 is based on parts by weight. The method for measuring ball compression, durability, and flight distance, the method for determining the shot feeling, and the evaluation criteria are as follows.

Ball compression: The amount of deformation (unit: mm) of the golf ball from the time when the initial load of 3.8 kg is applied to the time when the final load of 130 kg is applied. The smaller the ball compression, the higher the hardness of the ball It is shown that.

Durability: Continuous impact on golf ball (ball at 45m / se
The number of impacts until the ball breaks is indicated by an index. The larger the value, the better the durability.

Shot feeling: Judged by the actual hitting of the first club in Wood by a total of five professional golfers and three amateur golfers (single players). The evaluation criteria are as follows.

Evaluation criteria: ◎: Very good ○: Good ×: Poor Flying distance: Head speed 45m / with the No. 1 wood club using a golf ball hitting tester (True Temper swing robot)
It is the carry value (unit is yard) when hit in sec.

As shown in Table 1, each of the golf balls of Examples 1 to 4 of the present invention has a specific gravity of less than 1 and can be used as a water practice golf ball, and has excellent durability and shot feeling, and The flight distance was great. The ball characteristics of Examples 1 to 4 will be described below in comparison with the balls of Comparative Examples 1 and 2 based on Table 1.

(1) Regarding the golf ball of Example 1 (1) -Comparison with Comparative Example 1 In Example 1, glass bubbles S60 / 10000, that is, micro hollow spheres having a pressure resistance of 140 kg / cm ² or more are compounded. On the other hand, Comparative Example 1 is a golf ball within the range disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 62-142571, in which the above-mentioned minute hollow spheres are not blended.

Comparing Example 1 with Comparative Example 1, Example 1 has smaller ball compression than Comparative Example 1, and
The durability and shot feeling are good and the flight distance is great, and the effect of blending the micro hollow sphere glass bubbles S60 / 10000 in these ball compression, durability, shot feeling and flight distance is apparent. Note that, in terms of composition, the amount of methacrylic acid and zinc oxide can be increased from that of Comparative Example 1 while maintaining a specific gravity of less than 1 in Example 1 by blending the micro hollow sphere glass bubbles S60 / 10000, as described above. This is considered to be a factor that produced good results in ball compression, durability, shot feeling, flight distance, and the like.

(1) -Comparison with Comparative Example 2 In Comparative Example 2, micro-hollow sphere Glass Bubbles B28 / 750 is blended, which has a compressive strength of 53 kg / cm ² and is broken during kneading to reduce the volume. Then, the specific gravity became 1 or more. Therefore, Comparative Example 2 was unsuitable as a water practice ball, and had poor durability, shot feeling, and poor flight distance as compared with Example 1.

(2) Regarding the Golf Ball of Example 2 Example 2 takes the form of a two-piece ball in which an inner core made of the same rubber composition as in Example 1 is provided with an outer skin. Although the durability of the second embodiment is slightly inferior to that of the first embodiment, the shot feeling and the flight distance are equal to or longer than those of the first embodiment, and are clear from the comparison between the second embodiment and the comparative examples 1 and 2. As described above, Example 2 had characteristics that could be sufficiently used as a golf ball for water practice.

(3) Regarding the Golf Ball of Example 3 In Example 3, the amount of zinc oxide and the initiator was increased in place of the high styrene resin in Example 1, and the durability of Example 3 was higher than that of Example 1. Although it was slightly inferior, the durability was superior to Comparative Examples 1 and 2, the ball compression was small, the shot feeling was good, and the flight distance was superior to Example 1. Naturally, Example 3 had a specific gravity of less than 1, and could be used as a water practice ball.

(4) Regarding the Golf Ball of Example 4 In Example 4, the base rubber was a blend of syndiotactic-1,2-polybutadiene-containing polybutadiene rubber and high-cis polybutadiene rubber.
Is the same as In Example 4, although the ball compression was slightly larger than Example 1, and the durability was slightly inferior, the durability was superior to Comparative Examples 1 and 2, the shot feeling was good, the flight distance was long, and It had a specific gravity of less than 1 and was sufficiently usable as a water practice ball.

〔The invention's effect〕

As described above, according to the present invention, there is provided a solid golf ball having a specific gravity of less than 1, having a good durability and a good shot feeling, and suitable for water practice with a long flight distance.

Claims (1)

(57) [Claims] 1. A base rubber comprising a polybutadiene rubber as an essential component containing 5 to 30% by weight of syndiotactic-1,2-polybutadiene and 40% by weight or more of cis-1,4-polybutadiene, and average particles The specific gravity of a crosslinked body of a rubber composition containing a particulate ultrahigh molecular weight polyolefin having a diameter of 50 μm or less, a crosslinkable monomer, a fine hollow sphere having a pressure resistance of 140 kg / cm ² or more, and an initiator is mainly 1. Less than a solid golf ball.