JP2002028262A - Golf ball - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a golf ball which hardly gives rise to fliers in a shot from the rough, has high repulsion and has excellent flying performance. SOLUTION: The cover of the golf ball consisting of a core having a single layer or multilayered structure and the cover for covering and forming the core has complex modulus of elasticity of 20 to 150 MPa and tanδ>=0.05 at -10 deg.C at a temperature distribution curve of the complex modulus of elasticity and loss tangent tanδobtained by the measurement of the dynamic viscoelasticity under the conditions of a frequency 10 Hz, a dynamic distortion 5% and temperature raising rate 4 deg.C/min.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a golf ball which hardly flies even when shot from a rough, has a high rebound, and has excellent flight performance.

[0002]

2. Description of the Related Art Conventionally, solid golf balls such as two-piece golf balls and three-piece golf balls and thread-wound golf balls have been used as round golf balls. A solid golf ball is a core in which a rubber composition mainly composed of polybutadiene is integrally molded and covered with a cover made of a thermoplastic resin such as an ionomer resin, and a thread-wound golf ball is provided on a central solid or liquid core. Then, a thread rubber is wound under a high stretching force to form a wound core, which is then covered with a cover made of an ionomer resin, balata, or the like.

[0003] During round play, the ball often enters the rough or deep grass. It has been pointed out that a miss shot called a flyer easily occurs in a shot from such a place. The flyer is a phenomenon in which a weed or lawn bites between the club and the ball in such a shot, so that the backspin amount decreases and the ball rises higher. When a flyer is generated, it is difficult to control the trajectory and spin amount of the golf ball, and this is one of the causes of poor controllability particularly on approach shots, which has been a serious problem. This phenomenon occurs in any golf ball irrespective of whether the golf ball is a solid golf ball or a thread-wound golf ball.
Was one.

When this flyer is examined by cover type,
It has been found that a golf ball using an ionomer resin-based cover is more likely to occur than a golf ball using a balata-based cover. In addition, golf balls using a balata cover are less likely to cause flyer and have excellent spin control, but the resilience of the cover material itself is low,
There was a disadvantage that the cut resistance was poor. On the contrary,
The ionomer resin-based cover has a high elastic modulus and excellent resilience performance, but also has a disadvantage that spin is hardly applied and controllability is poor.

[0005] To solve the above flyer problem,
In order to provide golf balls with excellent resilience performance,
The present inventors have found that the complex elastic modulus at −10 ° C. based on the dynamic viscoelasticity measurement of a golf ball cover is 50 to 1500 kgf / cm ² (5 to 150 kgf).
MPa) and the rebound resilience by a trypsometer is 50%
It was proposed to select the above materials (Japanese Unexamined Patent Publication No.
No. 305115). However, recent demands for round golf balls are high, and even if such conditions are satisfied, it cannot be said that flyer resistance is still sufficient.

[0006]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems of the conventional golf ball, and has a high resilience and is unlikely to cause flyer even when shot from a rough. An object is to provide a golf ball having excellent flight performance.

[0007]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, by defining the values of the complex elastic modulus and tan δ of the cover within specific ranges, the present inventors have found that The present inventors have found that a golf ball which hardly causes a flyer even with a shot, has high resilience and is excellent in flight performance can be obtained, and has completed the present invention.

That is, the present invention relates to a golf ball comprising a core having a single-layer or multi-layer structure and a cover formed by covering the core, wherein the cover has a frequency of 10 Hz, a dynamic strain of 5% and a heating rate. It has a complex elastic modulus of 20 to 150 MPa at -10 ° C and a tan δ value of 0.05 or more in a temperature dispersion curve of a complex elastic modulus and a loss tangent tanδ obtained by dynamic viscoelasticity measurement at 4 ° C / min. And a golf ball.

As described above, the cover material previously proposed by the present inventors (JP-A-10-305115) has a specific temperature, frequency and dynamic strain as factors representing dynamic hardness. The measured complex elastic modulus is defined within a specific range. This is a condition in which the spin is most likely to be applied in the approach shot by selecting the condition in the approach shot, that is, the dynamic hardness at normal temperature, high frequency and large deformation.

However, a more detailed examination of the cover material reveals that even if this condition is satisfied,
It was found that some fryer resistances were sufficient and others were not. This is because flyers occur under special conditions. In other words, simply by the dynamic hardness based on the deformation condition at the time of the approach shot, it is possible to show the behavior of the golf ball when a weed or a lawn is struck between the golf club face and the golf ball. It was not possible. Therefore, it is necessary to reconsider how to prevent the flyer from occurring, and in particular, what characteristics of the golf ball in the special state as described above should be focused on.

In order for a golf ball to have excellent flyer resistance, backspin must not be applied even when weeds and grass are sandwiched between the face of the golf club and the surface of the golf ball. That is, even if weeds and the like are sandwiched between the golf ball and the golf ball surface, no spin can be given to the golf ball unless frictional force acts between the golf ball face and the golf ball surface. In other words, if the frictional force can be maintained at the time of hitting even when weeds and the like are sandwiched, fryer resistance can be improved. Therefore, attention was paid to characteristics related to the frictional force.

A polymer material used as a cover material of a golf ball generally has viscoelasticity, and properties such as elastic modulus, bending strength, and hardness of such a material mainly depend on elasticity, Properties such as strength and frictional force (friction coefficient) mainly depend on viscosity.

The present inventors have made various studies on the above points, and as a result, in addition to the complex elastic modulus as a factor representing the dynamic hardness of the cover material, the same can be obtained by dynamic viscoelasticity measurement. We focused on the loss tangent “tanδ” that represents mechanical damping as a characteristic. Here, the complex elastic modulus and tan δ will be described. In general, the complex elastic modulus E ^* and tan δ are represented by the following two formulas: E ^* = (E ′ ² + E ″ ² ) ^1/2 tan δ = E ″ / E ′ (where, E ′ is a storage elastic modulus, and E ″ is a loss elastic modulus.) An angle representing a time delay between applied stress and strain is δ, and a loss tangent tan δ is a loss coefficient. It also refers to the ability to dissipate stress applied to a material as thermal energy, ie, energy loss, ie, tan.
When the value of δ is large, the characteristic value depending on the viscosity, such as the impact strength and frictional force, becomes large.

The frictional force is generally represented by the following formula: frictional force = (adhesive frictional force) + (deformation loss frictional force) + (grinding frictional force). The adhesive friction force is a force required to shear-break the bond, assuming that a bond at a molecular level occurs at the interface between the face of the golf club and the surface of the golf ball. This adhesive frictional force is affected by the contact surface, and increases as the contact area increases.

When the golf ball is hit, the cover on the surface of the golf ball repeats the compression deformation and the recovery behavior according to the unevenness of the face of the golf club which is the contact surface, but energy loss occurs inside the cover, which is caused by external stress. Deformation loss frictional force occurs when supplementing with work. This deformation loss friction force is a friction force generated by deformation. The grinding friction force is not a control factor from the ball side, and should not be considered here because the cover of the golf ball surface has little grinding force to the golf club due to the relationship between the golf ball surface and the face of the golf club. Is also good.

The influence of the adhesive frictional force increases in a normal shot without the influence of weeds and lawn, and the effect of the deformation loss frictional force increases in a shot with weeds and lawn sandwiched. Generally, the deformation loss frictional force tends to increase as the hardness decreases, and when the hardness decreases to some extent, the deformation coefficient increases as the loss coefficient tanδ increases. Conversely, when the hardness is high, tan δ becomes small, and the effect becomes small. That is, the smaller the complex elastic modulus indicating the hardness and the larger the tan δ, the better the flyer resistance.

Therefore, in the golf ball of the present invention, the cover has a complex elastic modulus and a loss tangent tan δ obtained by dynamic viscoelasticity measurement under the conditions of a frequency of 10 Hz, a dynamic strain of 5%, and a heating rate of 4 ° C./min. It is necessary to have a complex elastic modulus at −10 ° C. of 20 to 150 MPa and a tan δ value of 0.05 or more in a temperature dispersion curve, and the complex elastic modulus is preferably 100 MPa.
Or less, more preferably 50 MPa or less, and tan δ is preferably 0.07 or more. However, if the complex elastic modulus is too small or tan δ is too large, the coefficient of restitution, which is a major factor in flight performance, decreases. Therefore, the complex elastic modulus is preferably 30 MPa or more, tan
δ is preferably 0.3 or less, more preferably 0.11 or less.

According to the temperature-frequency conversion rule, the present inventors consider the case where the frequency becomes high at room temperature when the golf ball is hit and the case where the complex is obtained by dynamic viscoelasticity measurement at a frequency of 10 Hz at a low temperature (−10 ° C.). It was clarified that the elastic modulus had a correlation. In addition, by making the dynamic strain amount 5%, which is a deformation amount close to the time of an actual approach shot, it was clarified that the complex elastic modulus at −10 ° C. measured at the dynamic strain 5% is correlated with the occurrence of the flyer ( JP-A-10-305115).

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. The golf ball of the present invention comprises a core and a cover formed on the core. The golf ball of the present invention may be a solid golf ball such as a two-piece golf ball or a thread-wound golf ball. The core (solid core) used in the solid golf ball may be a conventionally used one. For example, for 100 parts by weight of a base rubber such as polybutadiene rubber, α, such as acrylic acid and methacrylic acid, 10 to 60 parts by weight of vulcanizing agent (crosslinking agent) consisting of β-unsaturated carboxylic acid or its metal salt or functional monomer such as trimethylolpropane trimethacrylate alone or co-crosslinked with organic peroxide A rubber composition containing 0.5 to 5 parts by weight of an initiator, 10 to 30 parts by weight of a filler such as zinc oxide and barium sulfate, and, if necessary, an antioxidant and the like is kneaded using an appropriate kneading machine such as a normal roll. Then, it can be obtained by subjecting it to heat and pressure molding in a predetermined mold at, for example, 140 to 170 ° C. for 10 to 40 minutes. In this case, the core may have a single layer structure or a multilayer structure.

Further, the core (thread-wound core) used in the thread-wound golf ball may be a conventionally used core, and is formed by winding a thread rubber around the center and around the center in a stretched state. And a rubber layer. Liquid center as a center (liquid center)
Alternatively, any of rubber type (solid center) may be used. The thread rubber wound on the center may be the same as that conventionally used for the wound layer of the thread-wound golf ball. For example, sulfur, vulcanization of natural rubber or natural rubber and synthetic polyisoprene may be used. A rubber composition obtained by vulcanizing a rubber composition containing an auxiliary, a vulcanization accelerator, an antioxidant and the like may be used. The rubber thread is stretched and wound about 10 times on the center to produce a wound core. However, these solid cores and thread-wound cores are merely examples, and the present invention is not limited thereto.

The core has a diameter of 40.0 to 42.5 mm, preferably 40.3 to 42.0 mm. If it is less than 40.0 mm, the volume fraction of the core with respect to the entire ball becomes smaller and the resilience decreases, and if it is more than 42.5 mm, the cover becomes thinner, or the effect of improving the fryer resistance of the present invention becomes insufficient, The durability decreases.

Next, a cover is coated on the core. The cover of the present invention can be used at a temperature of −10 ° C. in a temperature dispersion curve of a complex elastic modulus and a loss tangent tan δ obtained by dynamic viscoelasticity measurement under the conditions of a frequency of 10 Hz, a dynamic strain of 5%, and a heating rate of 4 ° C./min. Complex elastic modulus of 20 to 150 MPa and tan δ
It is required to have a value of 0.05 or more.

This cover is not limited to a single-layer structure, but may have a multilayer structure of two or more layers. The material used for the cover of the present invention is not particularly limited as long as it satisfies the above complex elastic modulus and tan δ, but it is not suitable to use an ionomer resin alone as a general cover material. Especially high
In order to achieve tan δ, it is effective to use a thermoplastic elastomer, an ethylene-methacrylic acid copolymer, or a mixture thereof with an ionomer resin.

The thermoplastic elastomer has a soft segment exhibiting rubber elasticity in the molecule and a frozen phase or a crystal phase as a molecular constraint component (hard segment) for suppressing plastic deformation, such as a styrene thermoplastic elastomer. An amide-based thermoplastic elastomer, an ester-based thermoplastic elastomer, an olefin-based thermoplastic elastomer, a urethane-based thermoplastic elastomer, an ester-based thermoplastic elastomer, or the like can be used. Thermoplastic elastomers not only have a low complex modulus, but also allow a high tan δ by selecting the soft segment configuration as described above. Styrene-based thermoplastic elastomers are particularly preferable. For example, SBS resin comprising a polystyrene phase (S) and a polybutadiene phase (B), SIS resin containing a polyisoprene phase (I) instead of the B phase, B
SEPS resins having an ethylene / propylene phase (EP) instead of the phase, SEBS resins having an ethylene / butylene phase (EB) instead of the B phase, and the like can be given.

As specific examples of these, for example, JSR Corporation
From the product name "TR" series (for example, "TR278
7 ") and" SIS "series (for example," SIS500
0 "), commercially available from Asahi Kasei Kogyo Co., Ltd. under the trade name" Tuftec "series (for example," Tuftec Z514 "), and commercially available from Kuraray Co., Ltd. under the trade name" Septon "series. What is being done (for example,
"Septon 2002"), and those marketed by Aronkasei Co., Ltd. under the trade name "AR790".

Specific examples of the ethylene-methacrylic acid copolymer include those commercially available under the trade name “Nucrel” series (for example, “Nucrel AN421”).
1 "," Nucrel AN4213 ", etc.).

The polymer component for the cover composition can be used as a mixture with another cover material having high resilience, for example, an ionomer resin. The polymer component for the cover composition contains at least 30% by weight of the thermoplastic elastomer. It is desirable to include the above.

As the above-mentioned ionomer resin, a resin obtained by neutralizing at least a part of carboxyl groups in a copolymer of ethylene and α, β-unsaturated carboxylic acid with a metal ion,
Alternatively, at least a part of carboxyl groups in a terpolymer of ethylene, α, β-unsaturated carboxylic acid and α, β-unsaturated carboxylic acid ester is neutralized with a metal ion. As the above α, β-unsaturated carboxylic acid, for example, acrylic acid, methacrylic acid, fumaric acid, maleic acid,
Crotonic acid and the like are mentioned, and acrylic acid and methacrylic acid are particularly preferable. Further, as the α, β-unsaturated carboxylic acid ester metal salt, for example, acrylic acid, methacrylic acid,
Methyl, ethyl, propyl such as fumaric acid and maleic acid,
N-butyl, isobutyl ester and the like are used, and acrylate and methacrylate are particularly preferred.
Carboxyl groups in the above-mentioned copolymers of ethylene and α, β-unsaturated carboxylic acid or in terpolymers of ethylene, α, β-unsaturated carboxylic acid and α, β-unsaturated carboxylic acid ester As the metal ion that neutralizes at least a part of, sodium, potassium, lithium, magnesium,
Calcium, zinc, barium, aluminum, tin, zirconium, cadmium ions and the like can be mentioned, and sodium, zinc and magnesium ions are particularly preferred because of their good repulsion and durability.

Specific examples of the ionomer resin include:
Without limitation, Haimilan 1555, 1557, 16
05, 1652, 1702, 1705, 1706, 1707, 1855, 1856 (manufactured by Mitsui DuPont Polychemicals), Surlyn (SURLYN) 8945,
9945, 6320, AD8511, AD8512, AD8542 (manufactured by DuPont), Iotek (IOTEK) 7010, 8000 (Exxon (Exxo
n), etc.).

In the present invention, in addition to the polymer component as a main component, a filler such as barium sulfate, a coloring agent such as titanium dioxide, and other additives may be added to the cover composition, if necessary. Agents such as a dispersant, a plasticizer, an antioxidant, an ultraviolet absorber, a light stabilizer, a fluorescent material or an optical brightener, and the like, as long as the desired properties of the golf ball cover are not impaired. .

The cover of the golf ball of the present invention has a thickness of 0.5 mm.
It is desirable to have 3 to 3.5 mm, preferably 0.8 to 2.5 mm. If the cover thickness is less than 0.3 mm, the effect of improving the fryer resistance of the present invention will be insufficient, or the durability of the cover will be reduced due to insufficient strength. And the resilience decreases.

The method for covering the above cover is not particularly limited, and it can be performed by a usual method for covering a cover. The cover composition is preliminarily formed into a hemispherical shell-shaped half shell, and the core is wrapped using two of the half shells.
Press molding at 130 to 170 ° C. for 1 to 5 minutes, or injection molding of the cover composition directly onto the core to wrap the core is used. Then, when forming the cover, dimples may be formed on the ball surface as necessary, and after the cover is formed, paint finishing, stamping, and the like may be performed as necessary.

In the injection molding method, when a thermoplastic elastomer is used, the material in a fluidized state is heated and poured, then cooled, and then taken out in a solidified state. Also, in the press molding method, when molding a half shell of a hemispherical shell shape, similarly to the above-mentioned injection molding method, when using a thermoplastic elastomer, the material in a flowing state was cooled after injection, and solidified. Remove in state.

When forming the cover, a large number of depressions called dimples are formed on the surface as necessary. The golf ball of the present invention enhances aesthetics and enhances commercial value.
It is usually put on the market after being painted, marked, etc. As described above, the factors that affect the shape and surface of the cover affect the frictional force and spin when directly contacting the face of the golf club,
It has little effect on fryer resistance in which weeds are interposed. In addition, the golf ball of the present invention is formed to have a diameter of not less than 42.67 mm (preferably 42.70 to 43.20 mm) and a weight of not more than 45.93 g based on the golf ball rules.

The golf ball covered with the cover is compressed (from an initial load of 98N to a final load of 12N).
Deformation amount when 75N is loaded) It is desirable that the deformation amount is 2.2 to 4.5 mm, preferably 2.5 to 3.3 mm, and more preferably 2.9 to 3.2 mm. If it is smaller than 2.2 mm, the ball becomes too hard and the shot feeling is deteriorated, and if it is larger than 4.5 mm, it becomes too soft and the resilience deteriorates and the flight distance decreases.

According to the present invention, there is provided a golf ball which hardly causes flyer even when shot from a rough, has high resilience, and is excellent in flight performance.

[0037]

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

(Preparation of Core) A rubber composition for a core having the composition shown in Table 1 below was mixed, kneaded, and cured under a vulcanization condition of 155.
Heat pressing was performed at 18 ° C. for 18 minutes to produce a spherical solid core having a diameter of 38.5 mm.

[0039]

[Table 1]

(Note 1) Trade name “BR0” from JSR Corporation
1) commercially available under the trade name "Yoshinox 425" from Yoshitomi Pharmaceutical Co., Ltd.

(Preparation of cover composition) The materials having the composition shown in Table 2 below were mixed at 160 to 180 ° C by a twin-screw kneading extruder.
To prepare a pellet-shaped cover composition. Extrusion conditions were: screw diameter 45 mm, screw rotation speed 200 rpm, screw L / D = 35 and cylinder temperature
210 ° C. The dynamic viscoelasticity of the obtained cover composition was measured, and the complex elastic modulus and tan δ at −10 ° C. are shown in Tables 3 and 4.

[0042]

[Table 2]

(Note 3) SEBS (styrene-ethylene-butadiene-styrene copolymer) manufactured by Aronkasei Co., Ltd. (Note 4) Ethylene-methacrylic acid copolymer manufactured by Mitsui-DuPont Polychemicals (Note 5) ) Ethylene-methacrylic acid copolymer manufactured by Mitsui Dupont Polychemical Co., Ltd. (Note 6) Polyester thermoplastic elastomer manufactured by Toray Dupont Co., Ltd. (Note 7) Polyurethane thermoplastic manufactured by Takeda Birdish Urethane Co., Ltd. Elastomer (Note 8) Sodium ion-neutralized ethylene-methacrylic acid copolymer ionomer resin (manufactured by Mitsui DuPont Polychemicals, Inc.) (Note 9) SEPS (styrene-ethylene-manufactured by Kuraray Co., Ltd.)
Propylene-styrene copolymer)

(Examples 1 and 2 and Comparative Examples 1 to 7) The above cover compositions were directly injection molded on the cores obtained as described above. Next, deburring, paint pretreatment,
The same treatment as that of a normal golf ball such as paint was performed and finished to obtain a two-piece solid golf ball having a diameter of 42.7 mm. The flying distance, the amount of compressive deformation and the fryer resistance of the obtained golf ball were measured or evaluated, and the results are shown in Tables 3 and 4. The test method was as follows.

(Test Method) Dynamic Viscoelasticity Measurement A piece of 4 mm wide × 30 mm long × 0.5 mm thick prepared from the cover composition was viscoelastic spectrometer DVA200.
Using a mold (manufactured by Shimadzu Corporation), it was forcibly vibrated at a frequency of 10 Hz and a dynamic strain of 5% in a tensile mode (simple elongation in the length direction), and the temperature was raised from -50 to 50 ° C at 4 ° C / min. The complex elastic modulus and tanδ of each cover at −10 ° C. in the temperature dispersion curve of the complex elastic modulus and tanδ obtained from the amplitude ratio and the phase difference between the drive unit and the response unit are shown below.
And

Flying distance A No. 1 wood club (driver) was attached to a swing robot manufactured by True Temper, and a golf ball was hit at a head speed of 45 m / sec. Carry (flying distance to the drop point)
Was measured. The measurement was performed for each of eight golf balls, and the average value was used as the result of each golf ball.

Ball Compression A final load from a state in which an initial load of 98 N is applied to a golf ball.
It was determined by measuring the amount of deformation up to the time of loading 1275N.

Flyer resistance In the approach shot by the pitching wedge, the spin amount P ₁ immediately after hitting when the ball is hit on the tee and the spin amount P immediately after hitting when hitting the ball from a rough with a depth of 4 cm. ₂ and is determined by the ratio P ₂ / P ₁ × 100 of the _two . The smaller the value, the easier the flyer is caused, and the larger the value, the less likely the flyer is caused. The result is a senior golfer 10
It was represented by the average value when actually hit by a person.

(Test results)

[Table 3]

[0050]

[Table 4]

From the above results, the first embodiment of the present invention in which the values of the complex elastic modulus and tan δ of the cover are defined within specific ranges.
It was found that the golf balls of Nos. 1 to 2 had excellent flyer resistance and a long flight distance as compared with the golf balls of Comparative Examples 1 to 7.

On the other hand, the golf balls of Comparative Examples 1 to 3 and 7 have excellent flyer resistance due to the large tan δ of the cover, but have short flight distance due to small complex elastic modulus. In the golf ball of Comparative Example 4, the flight distance is short because the complex elastic modulus of the cover is small, and the flyer resistance is poor because the value of tan δ is small. The golf ball of Comparative Example 5 has good flyer resistance because the cover has a large tan δ, but has a short flight distance due to a small complex elastic modulus. In the golf ball of Comparative Example 6, although the flight distance was long because the complex elastic modulus of the cover was large,
The fryer resistance is poor because nδ is small.

[0053]

According to the golf ball of the present invention, by defining the values of the complex elastic modulus and tan δ of the cover within specific ranges, a flyer is unlikely to occur even when shot from a rough, and excellent flight performance is obtained. It could have.

Claims (2)

[Claims] 1. A golf ball comprising a core having a single-layer or multilayer structure and a cover formed by coating the core, wherein the cover has a frequency of 10 Hz, a dynamic strain of 5%, and a temperature rising rate of 4 ° C./min. The complex elastic modulus at −10 ° C. in the temperature dispersion curve of the complex elastic modulus and loss tangent tan δ obtained by dynamic viscoelasticity measurement under the conditions of 20 to 150 MPa and tan δ value of 0.0
A golf ball having 5 or more. 2. The golf ball according to claim 1, wherein the cover contains 30% by weight or more of the thermoplastic elastomer in the base polymer.