JP2559318B2 - Solid golf ball - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the improvement of the elastic portion of solid golf balls such as one-piece golf balls, two-piece golf balls and three-piece golf balls.

[0002]

2. Description of the Related Art Conventionally, as an elastic portion of a solid golf ball (a generic name for golf balls that are not wound balls),
It has been used that a base rubber such as polybutadiene is blended with a monomer having an unsaturated bond such as unsaturated carboxylic acid metal salt as a co-crosslinking agent, and further a peroxide and a metal oxide are blended. The co-crosslinking agent grafts or crosslinks to the polybutadiene main chain by the action of a peroxide-based polymerization initiator, forms a three-dimensional crosslinked polymer of polybutadiene and a monomer, and imparts appropriate hardness and repulsion to the golf ball. There is.

Recently, various proposals have been made as described below in order to improve the strength, resilience and durability of solid golf balls.

For example, Japanese Patent Application Laid-Open No. 63-311971 filed by the present applicant discloses that a fibrous alkali metal titanate surface-treated with a surface-treating agent is contained in a core material and / or a coating. A golf ball is shown.

JP-A-63-275356 discloses a rubber composition containing a base rubber, a co-crosslinking agent and a peroxide, the base rubber having a Mooney viscosity of 45 to 90.
A solid golf ball using 40% by weight or more of polybutadiene rubber having 80% or more of cis-1,4 bonds is shown.

Similarly, in JP-A-3-151985, the above-mentioned base rubber has an ultrahigh molecular weight polybutadiene rubber having 80% or more of cis-1,4 bonds and a number average molecular weight of more than 40 × 10 ^4. 5 to 50% by weight, and cis-
80% or more of 1,4 bonds, number average molecular weight 40 × 10
Solid golf balls comprising solid polybutadiene obtained from a solution mixture with less than ⁴ polybutadiene rubber of about 95-50% by weight are shown.

JP-A-3-106380 discloses that the number average molecular weight (Mn) is in the range of 17.5 × 10 ^{4 to} 35 × 10 ⁴ , and the weight average molecular weight (Mw) and the number average molecular weight (M
n) the polybutadiene rubber (A) having a ratio Mw / Mn of less than 4.0 and having 40% by weight or more of cis-1,4 bonds is 1
Acrylic acid metal salt is added to 100 parts by weight of a base rubber containing 80 parts by weight or more of 0 parts by weight or more and a polybutadiene rubber (B) having 90% by weight or more of cis-1,4 bonds. 5 to 10 parts by weight, 5 to 30 parts by weight of urethane acrylate, 5 to 50 parts of metal oxide
There is shown a solid golf ball having a core composed of parts by weight, 0.5 to 3.0 parts by weight of organic peroxide, and 10 to 30 parts by weight of silicon dioxide.

[0008]

Problems to be Solved by the Invention JP-A-63-3119
The golf ball disclosed in Japanese Patent Publication No. 71 has a certain effect in terms of strength improvement due to the addition of a fibrous alkali metal titanate, but the resilience performance still needs to be improved.

JP-A-63-275356, JP-A-3-151985 and JP-A-3-106380.
In the publication, the molecular weight of the base rubber, the Mooney viscosity,
Although improvements have been made with a focus on adjusting the content of cis-1,4 bonds, there is still room for improvement in terms of compressive fracture strength and durability.

Under such circumstances, it is an object of the present invention to provide a solid golf ball satisfying all the points of repulsion force, compressive fracture strength and durability.

[0011]

The solid golf ball of the present invention is a solid golf ball having an elastic portion made of a rubber composition containing a base rubber, a co-crosslinking agent, a peroxide and a metal oxide. The base rubber is composed of a mixture of two or more kinds of polybutadiene having different weight average molecular weights (Mw), and the weight average molecular weight (Mw) of each polybutadiene is in the range of 50 × 10 ⁴ to 70 × 10 ⁴ , and The base rubber made of these mixtures is 1,
80 wt% or more of those having a 4-cis structure are contained, and the weight average molecular weight (Mw) and the number average molecular weight (M
n), the ratio Mw / Mn is 2 to 3, and further, 1 to 10 parts by weight of fine fibers having a fiber length of 1 to 300 μm and an aspect ratio of 10 or more are contained with respect to 100 parts by weight of the base rubber. It is a feature.

The present invention will be described in detail below.

As the base rubber, a weight average molecular weight (M
A mixture of two or more polybutadienes having different w) is used. The reason for using two or more kinds of polybutadiene is as follows. That is, the repulsion property of the crosslinked product becomes higher as the molecular weight distribution width of the base rubber becomes narrower, but when dry blending, further adding a filler, and kneading with a kneader or an open roll, heat or mechanical shearing force is generated. It acts on the rubber material and causes molecular breakage, broadening the molecular weight distribution. When the molecular weight distribution is widened in this way, the repulsive force is inevitably reduced, but when a mixture of two or more kinds of polybutadiene having different weight average molecular weights (Mw) is used, molecular breakage during kneading is suppressed.

The weight average molecular weight (Mw) of each polybutadiene is required to be within a very narrow range of 50 × 10 ⁴ to 70 × 10 ⁴ . When the weight average molecular weight (Mw) is less than 50 × 10 ⁴ , the resilience becomes low,
On the other hand, when it exceeds 70 × 10 ⁴ , roll kneading property and dispersibility of chemicals are deteriorated, productivity is lowered, and repulsion and strength are also disadvantageous.

The base rubber composed of a mixture of two or more of the above is required to contain 80% or more of 1,4-cis structure, and the ratio of 1,4-cis structure is 80.
If it is less than%, satisfactory strength and resilience cannot be obtained.

Further, the weight average molecular weight (M
The ratio Mw / Mn between w) and the number average molecular weight (Mn) is 2-3.
Required to be in. When Mw / Mn is less than 2, the roll kneading property and the dispersibility of chemicals are deteriorated, and the productivity is lowered.
On the other hand, when Mw / Mn exceeds 3, the repulsive force decreases.

Fine fibers having a fiber length and an aspect ratio, which will be described later, are blended with the base rubber. The fine fiber content is selected from the range of 1 to 10 parts by weight with respect to 100 parts by weight of the base rubber, and if the fine fiber content is less than 1 part by weight, the compressive fracture strength is insufficient, while 10 parts by weight is used. If it exceeds, the repulsive force will decrease.

Here, the fine fibers are alumina fibers,
Silicate fiber, titania fiber, magnesium silicate fiber,
Calcium silicate fiber, silicon carbide fiber, titanium carbide fiber, boron carbide fiber, boron nitride fiber, titanium nitride fiber, carbon nitride fiber, boride carbon fiber, silicon boride fiber, titanium boride fiber, sodium titanate fiber, titanium Examples thereof include inorganic whiskers such as potassium acid fiber, lithium titanate fiber, calcium titanate fiber, magnesium titanate fiber, barium titanate fiber, and aluminum borate fiber.

Among these, potassium titanate fibers which are excellent in reinforcing property, heat resistance, whiteness and homogeneity dispersibility are particularly important. Potassium titanate fiber is a general formula
K ₂ O ・ n TiO ₂ or K ₂ O ・ n TiO ₂・ m H ₂ O (n is 2 to
8, m is a single crystal fiber represented by 0 to 4), and specific examples thereof include potassium tetratitanate fiber, potassium hexatitanate fiber and potassium octatitanate fiber.

Besides, as the fine fibers, carbon fibers, graphite fibers and the like can be preferably used. Further, glass fibers, metal fibers, and organic fibers (nylon fibers, polyester fibers, vinylon fibers, aromatic polyamide fibers, polyimide fibers, aromatic polyetheramide fibers, etc.) can also be used.

The fine fibers have a fiber length of 1 to 300 μm.
(Especially 5 to 200 μm) and an aspect ratio of 10 or more (preferably 10 to 1000, especially 10 to 300). If the fiber length is out of this range,
If the aspect ratio is less than 10, it is impossible to obtain a solid golf ball satisfying all the points of repulsion, compressive fracture strength and durability even if other conditions are satisfied.

It is desirable that the fine fibers are surface-treated with a surface-treating agent. Typical examples of such a surface treatment agent are mercapto group-containing silane compounds and silyl group-containing sulfide compounds.
A detailed explanation is given in Japanese Patent Application Laid-Open No. 63-311971 relating to the applicant's application described in the section of the prior art.

The elastic portion of the solid golf ball of the present invention comprises a rubber composition in which the above-mentioned base rubber is further mixed with a co-crosslinking agent, a peroxide and a metal oxide.

As the co-crosslinking agent, unsaturated carboxylic acids or salts thereof, and other unsaturated vinyl compounds are used.
The compounding amount of the co-crosslinking agent is 5 to 100 parts by weight of the base rubber.
It is desirable to use 60 parts by weight, especially 10 to 40 parts by weight, and if the proportion is too small, the ball will be too soft, while if it is too large, the resulting ball will be too hard.

As the unsaturated carboxylic acid or its salt,
Examples thereof include acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid, itaconic acid, derivatives thereof, and salts thereof. Examples of other unsaturated vinyl compounds include vinyl compounds such as vinyl acetate, vinyl propionate, vinyl caproate, styrene, vinyltoluene, and divinylbenzene; alkyl acrylates, alkyl methacrylates; acrylonitrile, methacrylonitrile, acrylamide. , Methacrylamide, glycidyl acrylate, glycidyl methacrylate; triallyl isocyanurate; and the like.

These compounds may be used either individually or in combination of two or more. Among the above, acrylic acid, methacrylic acid, zinc acrylate, and zinc methacrylate are particularly preferable.

As the peroxide, for example, diacetyl peroxide, dibenzoyl peroxide, dicapryl peroxide, di (p-chlorobenzoyl) peroxide, didecanoyl peroxide, di (2,4).
-Dichlorobenzoyl) peroxide, diisobutyl peroxide, diisononanoyl peroxide, dilauroyl peroxide, diperagonyl peroxide, dipropynyl peroxide, di (β-carboxypropinoyl) peroxide, methyl ethyl ketone peroxide, cyclohexanone Peroxide, dihydroxy-dimethyl-dioxacyclopentane, t-
Butyl peroxide, t-butyl peroxy (2-ethylhexanoate), t-butyl peroxyisobutyrate, o, o-t-butyl-o-isopropyl monoperoxycarbonate, t-butyl peroxypyrone Barrate, dimethyl-di (benzoylperoxy) hexane,
t-butylperoxy (2-ethylbutyrate), di-
t-butyl peroxide, dicumyl peroxide,
Dimethyl-bis (t-butylperoxy) hexane, t
An organic peroxide such as -butyl hydroperoxide, cumyl hydroperoxide, bis (t-butylperoxy) trimethylcyclohexane, n-butylbis (tbutylperoxy) valerate can be used,
Further, not limited to these exemplified ones, those having a similar action are used.

Among these, particularly dicumyl peroxide, cumyl hydroperoxide, t-butyl peroxide, dibutyl peroxide, bis (t-butylperoxy) trimethylcyclohexane, n-butylbis (t-butylperoxy). ) Valylate is suitable in that vulcanization proceeds uniformly due to the relationship between vulcanization temperature and half-life.

These peroxides can be used alone or in combination of two or more. The amount of peroxide used is about 0.1 to 15% by weight, preferably 0.5.
Often used in the range of up to 5% by weight.

As the metal oxide, for example, magnesium oxide, lead oxide, zinc oxide or the like is used. The metal oxide is often used in an amount of 5 to 50% by weight, particularly 10 to 30% by weight based on the base rubber.

In addition to the above components, in some cases, an appropriate amount of a crosslinkable resin such as a phenol resin, a melamine formaldehyde resin, a urethane resin, a polyester resin, a polyamide resin, an epoxy resin, or a low molecular weight or modified product thereof is used. You can also

In the present invention, various known additives can be added as required. Examples of such additives include vulcanization accelerators, vulcanization retarders, antioxidants,
Examples thereof include plasticizers, peptizers, tackifiers, anti-tacking agents, foaming agents, dispersants, dusting agents, mold release agents, solvents and softening agents.

Further, in the present invention, carbon black, magnesium carbonate, zinc oxide,
Calcium carbonate, barium sulfate, aluminum hydroxide,
Various inorganic fillers such as aluminum oxide, silica powder, titanium oxide, mica, talc, clay, diatomaceous earth, and clay powders such as kaolin, and any pigment or dye as a colorant may be blended.

The above-mentioned base rubber, co-crosslinking agent, peroxide and metal oxide, and other additives are kneaded by using a roll or a kneader to obtain a rubber composition, which is vulcanized in a mold. The elastic portion of the solid golf ball is obtained by molding. The vulcanization temperature is 140 to 170 ° C, and the vulcanization time is 2
It is often 0-40 minutes.

The crosslinked product obtained can be used as it is as a one-piece ball. A two-piece golf ball can be obtained by coating the obtained crosslinked body with a hard elastic body such as an ionomer resin or a transisoprene resin.
It can be a golf ball of three-piece or more.

[0036]

In the present invention, as a base rubber, a mixture of two or more kinds having a weight average molecular weight in a specific range is used, and the weight average molecular weight (Mw) and the number average molecular weight (Mn) of the base rubber made of the mixture are used. Since the ratio Mw / Mn is set in a narrow range such as 2 to 3 and the 1,4-cis structure is contained at 80% or more, preferable repulsion force and durability can be obtained.

Since such a base rubber is blended with a specific amount of fine fibers having a specific fiber length and an aspect ratio, it is extremely preferable in terms of compressive fracture strength. Generally, when fibers are added to polybutadiene, the cutting of the fibers tends to promote the molecular cutting of the rubber in the kneading step and the repulsion force tends to decrease, but the cutting of the rubber molecules is effective when the above mixture is used. Is suppressed by
An unexpected effect of maintaining the compressive fracture strength without impairing the repulsive force is exhibited.

[0038]

EXAMPLES The present invention will be further described with reference to examples. Hereinafter, "parts" refers to parts by weight. The molecular weight is in terms of polystyrene.

Examples 1 to 5 and Comparative Examples 1 to 5 As the base rubber, the following were prepared.・ BR210 Polybutadiene manufactured by Ube Industries, Ltd. “BR
210 ”Mw = 60 × 10 ⁴ , Mw / Mn = 4.3, 1,4-cis structure: 98.1% ・ BR150L Polybutadiene“ BR manufactured by Ube Industries, Ltd.
150L "Mw = 57 × 10 ⁴ , Mw / Mn = 2.4, 1,4-cis structure: 98.2% ・ BR360L Polybutadiene“ BR manufactured by Ube Industries, Ltd.
360 L ”Mw = 61 × 10 ⁴ , Mw / Mn = 2.4, 1,4-cis structure: 98.2%

The following were prepared as fine fibers. -TISMO Otsuka Chemical Co., Ltd. "Tismo D" fiber length: 14 μm, aspect ratio: 28-CF Taiyo Kaken Co., Ltd. carbon fiber fiber length: 200 μm, aspect ratio: 17 fiber length: 350 μm, aspect ratio: 30 Fiber length: 150 μm, aspect ratio: 8.3, three types ・ GPW graphite whiskers Fiber length: 20 μm, aspect ratio: 40

As the co-crosslinking agent, 20 zinc acrylate was used.
Parts, 3 parts of dicumyl peroxide (manufactured by NOF CORPORATION) were used as peroxides, and 15 parts of zinc oxide were used as metal oxides. In addition, 2,6 as an anti-aging agent
0.5 part of -di-t-butyl-4-methylphenol was blended. However, in Tables 1 and 2 described later, these types and compounding amounts are common to all the comparative examples and all the examples, and therefore the description is omitted.

Table 1 (Comparative Examples 1 to 5) and Table 2 described later
In the formulation shown in (Examples 1 to 5), each component except metal oxide (zinc oxide) was supplied to a kneader, and the temperature was 60 to 100 ° C.
After kneading for 10 minutes, the content was cooled to 60 to 70 ° C., and then a metal oxide (zinc oxide) was supplied and kneaded. This kneaded product is heated at 150 ° C. for 30 minutes with a mold for golf ball core material.
It was vulcanized for a minute to obtain a core material.

A hard elastic coating was applied to this core material by injecting a resin composition obtained by mixing 100 parts of an ionomer resin with 2 parts of titanium oxide so that the total weight per ball was 45 g.

With respect to the two-piece golf ball thus obtained, the coefficient of restitution, the compressive fracture strength and the durability were measured by the following methods. The results are shown in Table 1 (Comparative Examples 1 to 5).
And Table 2 (Examples 1 to 5). ○ means pass, □ means equivalent, and △ means not pass.

Repulsion coefficient The coefficient of restitution was calculated from the bounce speed when the molded ball was hit on a rigid body at a speed of 30 m / sec. The larger the coefficient of restitution is, the better the repulsive force is.

Compressive fracture strength This is the compressive load (t) at the time of fracture when the ball is compressed.

Durability The number of times until the ball was destroyed when it was hit with a head speed of 40 m / sec using a swing robot was represented as an index with Comparative Example 1 as 100.

[0048]

[Table 1] Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Base rubber type BR210 BR150L BR150L BR150L BR150L + BR360L + BR360L + BR360L Compounding amount (part) 100 100 50 + 50 50 + 50 50 + 50 Mw 60 × 10 ⁴ 57 × 10 ⁴ 62 × 10 ⁴ 62 × 10 ⁴ 62 × 10 ⁴ Mw / Mn 4.3 2.4 2.2 2.2 2.2 1,4-cis structure 98.1% 98.2% 98.2% 98.2% 98.2% Fine fiber type --- CF CF compound Amount (part)---5 5 Fiber length (μm)---350 150 Aspect ratio --- 30 8.3 Evaluation coefficient of restitution ○ 0.825 ○ 0.830 ○ 0.833 △ 0.810 △ 0.815 Compressive fracture strength △ 1.8t △ 2.0t △ 2.0 t ○ 5.5t ○ 4.0t Durability △ 100 △ 102 △ 101 ○ 125 ○ 120

[0049]

[Table 2] Example 1 Example 2 Example 3 Example 4 Example 5 Example 5 Base rubber type BR150L BR150L BR150L BR210 BR150L + BR360L + BR360L + BR360L + BR150L + BR360L + BR360L Compounding amount (part) 50 + 50 50 + 50 50 + 50 33 + 33 + 33 70 + 30 Mw 62 × 10 ⁴ 62 × 10 ⁴ 62 × 10 ⁴ 62 × 10 ⁴ 59 × 10 ⁴ Mw / Mn 2.2 2.2 2.2 2.5 2.1 1,4-cis structure 98.2% 98.2% 98.2% 98.2 % 98.2% Fine fiber type TISMO CF GPW TISMO TISMO Compounding amount (part) 3 5 10 5 10 Fiber length (μm) 14 200 20 14 14 Aspect ratio 28 17 40 28 28 Evaluation coefficient of restitution ○ 0.828 ○ 0.825 ○ 0.827 ○ 0.830 ○ 0.829 Compressive fracture strength ○ 3.5t ○ 4.0t ○ 3.5t ○ 3.5t ○ 3.5t Durability ○ 118 ○ 120 ○ 120 ○ 118 ○ 118

[0050]

INDUSTRIAL APPLICABILITY The solid golf ball of the present invention gives satisfactory results in all points of resilience, compressive fracture strength and durability. It also has an appropriate compression (hardness).

Claims (1)

(57) [Claims] 1. A solid golf ball having an elastic portion made of a rubber composition containing a base rubber, a co-crosslinking agent, a peroxide and a metal oxide, wherein the base rubbers have different weight average molecular weights (Mw). A base rubber made of a mixture of two or more kinds of polybutadiene and having a weight average molecular weight (Mw) of each polybutadiene in the range of 50 × 10 ⁴ to 70 × 10 ⁴ , and a mixture of these is
80% or more of those having a 1,4-cis structure are contained, and the weight average molecular weight (Mw) and the number average molecular weight (M
n), the ratio Mw / Mn is 2 to 3, and further, 1 to 10 parts by weight of fine fibers having a fiber length of 1 to 300 μm and an aspect ratio of 10 or more are contained with respect to 100 parts by weight of the base rubber. The characteristic solid golf ball.