JP2000325500A - Golf ball and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a proper degree of hardness, and at the same time, provide a high repulsion property and a high spinning performance by forming the cover of a golf ball of a substance wherein a trans 1, 4-polyisoprene is made the major component, and also, an ultra accelerator comprising dithiocarbamic acid salts and/or zantate acid salts is contained. SOLUTION: When this golf ball comprising a core and a cover which covers the periphery of the core is manufactured, the cover is formed by using a composition for cover wherein trans 1,4-polyisoprene is made the major component, and also, an ultra accelerator for a low temperature valcanizaiton is contained. That is, the golf ball is manufactured through a process wherein the composition for cover is molded into a half shell, a process wherein the core is arranged in the half shell in a molding die, and a dimple pattern is formed on the cover surface, and a process wherein the cover composition is valcanized at a temperature which is at the melting point of the trans 1, 4-polyisoprene or lower. As the ultra accelerator, dithicarbamic acid salts and/or zantate acid salts are used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a golf ball having excellent spin performance and a method of manufacturing the same, and more particularly to a golf ball having a high rebound resilience that is unlikely to become a flyer even from a rough shot. The present invention relates to a ball and a method for manufacturing the ball.

[0002]

2. Description of the Related Art Conventionally, a solid golf ball in which a core made of butadiene rubber as a base material is covered with a cover resin, and a thread-wound golf ball in which a rubber material is wound around a core material and covered with a cover resin such as an ionomer, It is frequently used in round play. These golf balls often penetrate deep grass when playing. In shots from the lawn, the lawn often bites between the club and the ball, causing a phenomenon (flyer) in which the backspin amount decreases and the ball rises high, and especially the controllability of approach shots is poor. That was the problem. This phenomenon occurs regardless of whether the golf ball is a solid golf ball or a wound golf ball. In particular, the above-mentioned ionomer cover resin ball has a high elastic modulus and excellent repulsion performance, but has a drawback that spin is hardly applied and controllability is poor.

[0003] On the other hand, the ball of the balata cover is said to be less likely to fry and has excellent spin control properties, but because it has both a polymer crystal part and a crosslinked rubber part, it achieves moderate hardness and high spin performance. It depends. However, the crystal melting point of trans 1,4-polyisoprene (50-60 ° C .: by DSC measurement)
If the crosslinking is carried out at the above temperature, no crystal part is formed even when cooled after the crosslinking, and it becomes impossible to obtain an appropriate hardness. Therefore, as a conventional technique, it was necessary to perform vulcanization for a long time under a special atmosphere. For example, Japanese Patent Application Laid-Open No. 54-99177 discloses that a crosslinking reaction is carried out by immersing a golf ball in a xanthate-based super-vulcanization accelerator solution. There are many problems in the process. JP-A-6-54928 discloses a process for crosslinking balata with a metal salt of an unsaturated fatty acid and a crosslinking initiator. In this case, however, there is a drawback that the core wrapped in the cover is deteriorated due to heat generated during the reaction. In addition, since no crystal is formed, an appropriate hardness cannot be obtained. Further, when a usual accelerator for sulfur vulcanization is used, a vulcanization temperature of at least 120 ° C. is required and no crystal is formed, so that an appropriate hardness cannot be obtained.

[0004]

In order to solve the above problems, the present invention comprises a core and a cover surrounding the core,
The present invention provides a golf ball characterized in that the cover is mainly composed of trans 1,4-polyisoprene and contains a superpromoter composed of dithiocarbamates and / or xanthates. And the manufacturing method of the golf ball of the present invention, a core having a solid or wound structure,
A method of manufacturing a golf ball comprising a cover covering the periphery of the core, wherein (1) the cover is a transformer
A cover composition comprising polyisoprene as a main component and a super accelerator for low-temperature vulcanization, (2) forming the cover composition into a half shell, and (3) forming a half shell. Disposing the core in a mold and forming a dimple pattern on the cover surface;
A method for producing a golf ball, comprising a step of vulcanizing a cover composition at a temperature equal to or lower than the melting point of polyisoprene.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, a composition for a cover mainly comprises trans 1,4-polyisoprene. Here, trans 1,4-polyisoprene is defined as
It refers to one having a transformer structure of 60 or more. If the transformer structure is less than 60, the number of crystal parts is small, and thus the melting point is too low to satisfy the basic characteristics as a cover. The other polymer to be mixed and used as the cover material is preferably a resin, rubber, or a high repulsion material having a partial crystal structure, such as high styrene resin, high cis-polybutadiene, and ionomer resin.
These polymers are 5 to the polymer component of the cover material.
It can be blended in a range of 0% by weight or less, preferably 25% by weight or less. When the content of trans 1,4-polyisoprene is small, high spin performance and control performance are reduced.

Here, the thickness of the cover is 0.5 to 4.0 m.
m, particularly preferably in the range of 0.8 to 3.0 mm. 0.5
If it is less than 4.0 mm, the cover strength and durability are reduced, while 4.0
If it exceeds mm, the volume fraction of the cover component in the entire ball becomes large, and the repulsion performance of the ball decreases.

[0007] Next, in the present invention, 0.1 to 3.0 parts, particularly preferably 0.5 to 2.0 parts, of the super accelerator is added to 100 parts of the polymer component of the cover composition.

Here, the super-promoter means that the reaction initiation temperature is 7
An accelerator capable of initiating the reaction at a temperature of 0 ° C. or lower, preferably about 30 ° C.

For example, examples of the super-vulcanization accelerator include dithiocarbamates and xanthates, and the following substances are applicable.

As dithiocarbamates, for example,
Sodium dimethyl dithiocarbamate, diethyl
Sodium dithiocarbamate, sodium di-n-butylcarbamate, zinc dimethyldithiocarbamate, zinc zinc diethyldithiocarbamate, zinc di-n-butylcarbamate, zinc diamyldithiocarbamate, zinc dibenzyldithiocarbamate, N-pentamethylene -Zinc dithiocarbamate, pipecoline methylpentamethylene-dithiocarbamate, pipecoline salt of pipecolyl-dithiocarbamic acid, pentamethylene-dithiocarbamic acid, and the like.

Next, examples of the xanthate salts include sodium isopropyl xanthate, zinc isopropyl xanthate, and zinc butyl xanthate.

For example, when a resin and / or rubber other than trans 1,4-polyisoprene is used, 100 parts by weight of trans 1,4-polyisoprene may be used. 5-20 parts by weight of natural rubber, 5-20 parts by weight of high styrene resin,
It can be composed of 0 to 20 parts by weight of diene rubber, 1 to 10 parts by weight of zinc white, and 1 to 20 parts by weight of titanium oxide. In addition, a fiber reinforced rubber, a fiber reinforced resin, an inorganic single crystal component, a specific gravity adjuster, a metal powder, a metal oxide, and the like can be appropriately mixed. The amount of sulfur is 0.1 to 3 parts by weight, and the amount of super accelerator is 0.1 to 3 parts by weight.

If the amount of sulfur and the amount of super accelerator are less than the above ranges, the vulcanization does not proceed sufficiently, so that sufficient strength as a golf ball cover cannot be obtained. If the amount is larger than the above range, vulcanization occurs during material mixing with a roll or a kneader, and so-called rubber burn occurs. Therefore, both the sulfur content and the superpromoter content are preferably 0.1 to 3 parts by weight, and particularly preferably 0.2 to 2 parts by weight.

Next, the method for manufacturing a golf ball of the present invention includes the following steps. First, kneading of the cover composition can be performed by a roll or a kneader. The material temperature at this time is suitably from 50 ° C to 80 ° C. If the temperature is lower than 50 ° C., trans 1,4-polyisoprene does not melt, so that other materials cannot be mixed. At 80 ° C or higher,
The superpromoter initiates the reaction, causing rubber burn. The mixing time should be as short as possible. Specifically, the time is preferably 1 minute to 20 minutes, but is not limited to this because it varies depending on the blending amount of the super accelerator. If the mixing time is shorter than the above-mentioned time, dispersion of the compounding agent in the cover composition will be poor. On the other hand, if the time is longer than the above-mentioned time, rubber burning will occur.

Next, the above cover composition can be coated on either a solid core or a wound core. In order to coat the cover composition on the solid core or the wound core, a half shell having a half shell shape is prepared in advance, and the core is wrapped and pressed. During the production of the half-shell, it is carried out at 60 ° C. to 90 ° C. where the material flows and is as low as possible,
It is desirable to cool quickly.

Next, the core is wrapped in a half shell to form a dimple pattern on the ball surface.
It is preferable to mold at a temperature of and then rapidly cool.

At this point, the vulcanization reaction has not yet taken place, or even if it takes place, it does not impair the fluidity of the material.

After that, the cover composition is vulcanized, and the press temperature is set at 30 ° C. or more and 50 ° C. or less, and the crosslinking is completed in a mold for 2 to 72 hours, or after the press molding, it is cooled. Any method can be employed in which the product is removed from the mold and the crosslinking is completed at a similar temperature and time in an oven or the like. Here, the vulcanization temperature is preferably 30 ° C. to 50 ° C., which is lower than the crystal melting point of trans 1,4-polyisoprene. The vulcanization time is about 2 to 72 hours, depending on the amount and type of super accelerator. The cover material of the removed ball has been completely vulcanized.

The present invention can also be applied to a multi-piece core having one or more layers, or a wound core having a rubber wound around a solid center or a liquid center.

Example (1) Preparation of Core The following core composition was prepared and vulcanized at 155 ° C. for 30 minutes to obtain a core having a diameter of 38.4 mm. Further, the surface of the core was buffed to improve the adhesion to the cover material.

BROI (Note 1) 100 parts Zinc acrylate 25 parts Zinc flower 21 parts DCP 1 part (Note 1) BR01 is a polybutdiethane made by JSR Corporation and having a cis content of 98%. (2) Cover composition No. of cover composition shown in Table 1. 1 to No. A golf ball was manufactured by the following steps using the ninth golf balls. In each of the examples and comparative examples, the cover thickness was adjusted to 2.3 mm.

(3) Golf Ball Manufacturing Process The above composition is mixed at a roll temperature of 70 ° C. for 8 minutes to prepare a mixture, and the mixture is used to form a mixture in a half-shell forming mold.
After molding at 0 ° C. for 30 seconds, the mixture was cooled to 20 ° C. and shaped to form a half-shell half shell. The core is wrapped with the two half-shell half-shells, and again at 80 ° C. for 30 minutes in a mold with dimples.
After molding for 2 seconds, it was similarly cooled to obtain a ball with dimples.

Thereafter, the sample is placed in an oven set at 50 ° C. for 8 hours.
It was left for a time to complete the vulcanization reaction. The obtained golf ball has an outer diameter of 43.0 mm.

The physical properties of the golf ball were measured by the following methods. Crystallinity Heating rate 10 ° C / m by scanning calorimeter (DSC)
The measurement was performed in, and the crystallinity was determined from the size of the endothermic peak appearing at around 40 ° C. to 80 ° C. 1g sample
The unit for indicating the amount of heat per unit is J / g.

The amount of deflection of the ball when a load is applied to the compression ball from 10 kg to 130 kg, expressed in mm.

An aluminum cylinder having a coefficient of restitution of 200 g is collided at a speed of 35 m / s, the speeds of the cylinder and the golf ball before and after the collision are measured, and the coefficient of restitution of each golf ball is calculated from the respective speeds and weights. did. The measurement was performed twice for each golf ball, and the average of n = 8 balls was calculated to obtain the results for each golf ball.

Attach a SW crag to the fryer's test crane temper robot at speed 21
The spin rate at the time of launching at m / s was measured.

During the measurement, the ball and the club face were wetted by spraying in order to reproduce conditions that tend to cause fryer such as grass biting, and the measurement was performed under wet conditions. Further, the measurement was carried out even under a normal non-wetting dry condition, and the spin holding ratio was determined by the following equation.

Spin Retention (%) = (Spin Amount Under Wet Conditions / Spin Amount Under Dry Conditions) × 100 The spin retention was expressed as an index with the value of Example 1 being 100. The higher the value, the less likely it is to fly.

[0030]

[Table 1]

[0031]

[Table 2]

[0032]

[Table 3]

As shown in Tables 2 and 3, the examples of the present invention in which trans 1,4-polyisoprene was vulcanized by using a super-promoter maintain high crystallinity, high rebound index and low fryer resistance. I understand.

The embodiments disclosed this time are to be considered in all respects as illustrative and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

[0035]

According to the present invention, trans 1,4 is added to the cover composition.
-Since polyisoprene is used and vulcanized at a low temperature with a super accelerator, moderate hardness due to the material and crystal structure of trans 1,4-polyisoprene, and high repulsion and high spin performance are further improved.

Claims (4)

[Claims] 1. A cover comprising a core and a cover surrounding the core, the cover comprising a trans 1,4-polyisoprene as a main component, and a super-promoter comprising dithiocarbamates and / or xanthates. A golf ball vulcanized below the melting point of trans 1,4-polyisoprene. 2. A method for manufacturing a golf ball comprising a core having a solid or thread-wound structure and a cover covering the periphery of the core, wherein (1) the cover comprises trans-1,4-polyisoprene as a main component. And (2) a step of molding the cover composition into a half shell, and (3) disposing a core in the half shell in a mold. Forming a dimple pattern on the cover surface; and (4) vulcanizing the cover composition at a temperature equal to or lower than the melting point of trans 1,4-polyisoprene. 3. The method according to claim 2, wherein the superpromoter comprises a dithiocarbamate and / or a xanthate. 4. The method according to claim 2, wherein the vulcanization temperature is 30 ° C. to 50 ° C.