U.S. patent application number 10/138329 was filed with the patent office on 2003-04-03 for composition for improving the property of a golf ball cover.
This patent application is currently assigned to BRIDGESTONE SPORTS CO.,LTD.. Invention is credited to Ichikawa, Yasushi, Takesue, Rinya.
Application Number | 20030064833 10/138329 |
Document ID | / |
Family ID | 18993425 |
Filed Date | 2003-04-03 |
United States Patent
Application |
20030064833 |
Kind Code |
A1 |
Ichikawa, Yasushi ; et
al. |
April 3, 2003 |
Composition for improving the property of a golf ball cover
Abstract
Disclosed is a golf ball cover property improving composition to
be added to a thermoplastic polymer material such as a
thermoplastic polyurethane material when a golf ball cover is
formed from the thermoplastic polymer material, to thereby impart
high restitution and excellent scuff resistance to the golf ball
cover. The golf ball cover property improving composition contains
an isocyanate mixture in which an isocyanate compound (X) having at
least two isocyanate groups serving as functional groups in the
molecule is dispersed in a thermoplastic resin (Y) which is
substantially non-reactive with the isocyanate groups and which has
a restitution elastic modulus of at least 45%.
Inventors: |
Ichikawa, Yasushi; (Saitama,
JP) ; Takesue, Rinya; (Saitama, JP) |
Correspondence
Address: |
SUGHRUE MION, PLLC
2100 PENNSYLVANIA AVENUE, N.W.
WASHINGTON
DC
20037
US
|
Assignee: |
BRIDGESTONE SPORTS CO.,LTD.
|
Family ID: |
18993425 |
Appl. No.: |
10/138329 |
Filed: |
May 6, 2002 |
Current U.S.
Class: |
473/378 |
Current CPC
Class: |
A63B 37/008 20130101;
C08L 75/08 20130101; A63B 37/0003 20130101; C08L 27/06 20130101;
A63B 37/0095 20130101; C08L 25/06 20130101; A63B 37/0084 20130101;
A63B 37/0031 20130101; C08L 67/02 20130101; A63B 37/0074 20130101;
A63B 37/12 20130101; A63B 37/0024 20130101; C08K 5/29 20130101;
A63B 37/0083 20130101; C08L 75/08 20130101; C08L 2666/02
20130101 |
Class at
Publication: |
473/378 |
International
Class: |
A63B 037/12 |
Foreign Application Data
Date |
Code |
Application Number |
May 17, 2001 |
JP |
2001-148035 |
Claims
What is claimed is:
1. A golf ball cover property improving composition comprising an
isocyanate mixture in which an isocyanate compound (X) having at
least two isocyanate groups serving as functional groups in the
molecule is dispersed in a thermoplastic resin (Y) which is
substantially non-reactive with the isocyanate groups and which has
a restitution elastic modulus of at least 45%.
2. A golf ball cover property improving composition according to
claim 1, wherein the isocyanate compound (X) is
4,4'-diphenylmethane diisocyanate.
3. A golf ball cover property improving composition according to
claim 1, wherein the thermoplastic resin (Y) is a polyester
elastomer.
4. A golf ball cover property improving composition according to
claim 1, wherein the ratio by weight of the thermoplastic resin (Y)
to the isocyanate compound (X) is 100:5 to 100:100.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a composition for improving
the property of a golf ball cover (hereinafter the composition will
be referred to as a "golf ball cover property improving
composition"), which is employed when a golf ball cover is formed
from a thermoplastic polymer material; and more particularly to a
golf ball cover property improving composition for being added to a
thermoplastic polymer material when a golf ball cover is formed
predominantly from the polymer material, the polymer material being
virtually reactive with an isocyanate group contained in the
composition. The golf ball cover property improving composition
serves as a cross-linking agent for the polymer material.
[0003] 2. Description of the Related Art
[0004] In recent years, polyurethane materials have become of
interest as materials for forming a golf ball cover. Polyurethane
materials are classified into thermosetting polyurethane materials
and thermoplastic polyurethane materials, and a process for forming
a thermosetting polyurethane material into a product differs from a
process for forming a thermoplastic polyurethane material into a
product. A thermosetting polyurethane material can be formed into a
product through the following procedure: a urethane prepolymer
having an isocyanate end group and a curing agent such as polyol or
polyamine, which serve as liquid raw materials, are mixed under
heating; and the resultant mixture is fed directly to a mold and
then heated, to thereby allow urethane curing reaction to
proceed.
[0005] Many studies have heretofore focused on golf balls formed
from thermosetting polyurethane materials. For example, U.S. Pat.
Nos. 5,334,673, 6,117,024, and U.S. Pat. No. 6,190,268 disclose
such golf balls. Meanwhile, U.S. Pat. Nos. 5,006,297, 5,733,428,
5,888,437, 5,897,884, and U.S. Pat. No. 5,947,843 disclose forming
methods of thermosetting polyurethane materials.
[0006] Since a thermosetting polyurethane material exhibits no
thermoplasticity, the material and a product formed from the
material cannot be recycled. In addition, when a thermosetting
polyurethane material is employed for forming a specific product
such as a golf ball cover (i.e., a product which covers a core),
efficient production of the product is not attained, since the
heating-curing step and the cooling step of the material requires
long time, and high reactivity and instability of the material make
control of the molding time very difficult.
[0007] In the case where a thermoplastic polyurethane material is
formed into a molded product, the product is not directly obtained
through reaction of raw materials, but is formed from a linear
polyurethane material--an intermediate--which has been synthesized
by employment of raw materials and a synthesis method, the raw
materials and the method differing from those employed in the case
of the aforementioned thermosetting polyurethane material. Such a
linear polyurethane material exhibits thermoplasticity, and is
cured through cooling. Therefore, such a polyurethane material can
be molded by use of an injection molding machine. Injection molding
of a thermoplastic polyurethane material is a technique suitable
for forming a golf ball cover, since the molding time of a
thermoplastic polyurethane material is much shorter than that of a
thermosetting polyurethane material, and a thermoplastic
polyurethane material is suitable for precise molding. Meanwhile, a
thermoplastic polyurethane material can be recycled, and is thus
environmentally friendly. U.S. Pat. Nos. 3,395,109, 4,248,432, and
U.S. Pat. No. 4,442,282 disclose golf balls formed from
thermoplastic polyurethane materials.
[0008] However, when a golf ball cover is formed from a
conventional thermoplastic polyurethane material, the resultant
golf ball is not satisfactory in terms of feeling on impact,
controllability, restitution, and scuff resistance upon being hit
with an iron.
[0009] In order to solve such a problem, Japanese Patent
Application Laid-Open (kokai) No. 9-271538 discloses a golf ball
cover formed from a thermoplastic polyurethane material exhibiting
high restitution. However, the disclosed golf ball cover is not
satisfactory in terms of scuff resistance upon being hit with an
iron.
[0010] Japanese Patent Application Laid-Open (kokai) No. 11-178949
discloses a golf ball cover exhibiting relatively excellent scuff
resistance upon being hit with an iron, which predominantly
contains a reaction product formed from a thermoplastic
polyurethane material and an isocyanate compound. When the cover is
formed, an isocyanate compound such as a diisocyanate or a block
isocyanate dimer, serving as an additive, is added to a
thermoplastic polyurethane material in the course of heating,
melting, and mixing by use of an extruder, or in the course of
injection molding, to thereby allow reaction to proceed.
[0011] However, in the case of molding of the cover disclosed in
Japanese Patent Application Laid-Open (kokai) No. 11-178949, since
an isocyanate compound must be handled with great care due to its
inactivation by moisture, obtaining a stable reaction product is
difficult. Meanwhile, a block isocyanate exhibiting moisture
resistance is not suitable for forming the cover, since a blocking
agent issues a strong odor when the isocyanate is thermally
dissociated. When an isocyanate compound assumes the form of powder
or solution, control of the amount of the compound which is added
to a thermoplastic polyurethane material is difficult, and
therefore cover properties cannot be controlled adequately. In
addition, since the thermoplastic polyurethane material differs in
melting point and melt viscosity from the isocyanate compound,
thorough and satisfactory kneading thereof may fail to be attained
in a molding apparatus. Therefore, in the technique disclosed in
the above publication, the effect of moisture on a cover material
and the amount of an additive is not satisfactorily controlled,
resulting in failure to produce a golf ball cover which is
satisfactory in terms of improvement of scuff resistance.
[0012] Japanese Patent Application Laid-Open (kokai) No. 11-178949
discloses an aliphatic isocyanate-based thermoplastic polyurethane
material to be used as a desirable thermoplastic polyurethane
material. However, since the thermoplastic polyurethane material is
highly reactive with isocyanate and its reaction is difficult to
control, the polyurethane material involves the following problems:
gelation easily occurs before injection molding, and sufficient
plasticity cannot be maintained; gelation may occur during molding
of a cover; and the polyurethane material cannot be recycled, due
to gelation. Because of such problems, the thermoplastic
polyurethane material is difficult to use in practice.
[0013] Japanese Patent Publication (kokoku) No. 58-2063 (U.S. Pat.
No. 4,347,338) discloses a process for producing a thermosetting
polyurethane product, in which a compound having two or more
isocyanate groups is mixed with a thermoplastic resin which is
non-reactive with an isocyanate group, the resultant mixture is
incorporated into a thermoplastic polyurethane material, and the
resultant material is subjected to molding by use of a molding
machine. However, the purpose of the technique disclosed in the
above publication is to improve the polyurethane product only in
terms of solvent resistance and durability against continuous,
repeating friction, and the publication does not disclose use of
the aforementioned forming material as a material of a golf ball
cover. There still exists demand for golf ball cover materials
which can provide a golf ball with various necessary properties,
such as restitution, total distance, spin performance,
controllability, feeling on impact, scuff resistance, cut
resistance, and discoloration resistance. Moreover, there exists
demand for appropriate combination of such golf ball cover
materials.
SUMMARY OF THE INVENTION
[0014] In view of the foregoing, an object of the present invention
is to provide a golf ball cover property improving composition to
be added to a thermoplastic polymer material, such as a
thermoplastic polyurethane material, when a golf ball cover is
formed from the thermoplastic polymer material, the golf ball cover
property improving composition serving as a cross-linking agent for
the thermoplastic polymer material and realizing production of a
golf ball cover exhibiting high restitution and excellent scuff
resistance.
[0015] In order to achieve the above object, the present invention
provides the following golf ball cover property improving
compositions.
[0016] (1) A golf ball cover property improving composition
comprising an isocyanate mixture in which an isocyanate compound
(X) having at least two isocyanate groups serving as functional
groups in the molecule is dispersed in a thermoplastic resin (Y)
which is substantially non-reactive with the isocyanate groups and
which has a restitution elastic modulus of at least 45%.
[0017] (2) A golf ball cover property improving composition
according to (1), wherein the isocyanate compound (X) is
4,4'-diphenylmethane diisocyanate.
[0018] (3) A golf ball cover property improving composition
according to (1) or
[0019] (2), wherein the thermoplastic resin (Y) is a polyester
elastomer.
[0020] (4) A golf ball cover property improving composition
according to any one of (1) through (3), wherein the ratio by
weight of the thermoplastic resin (Y) to the isocyanate compound
(X) is 100:5 to 100:100.
DESCRIPTION OF THE INVENTION AND PREFERRED EMBODIMENTS
[0021] The present invention will next be described in more detail.
In the present invention, the isocyanate compound (X) having at
least two isocyanate groups serving as functional groups in the
molecule is preferably an isocyanate compound which is
conventionally employed in the technical field related to
thermoplastic polyurethane materials. Examples of the isocyanate
compound include, but are not limited to, aromatic diisocyanates
such as 4,4'-diphenylmethane diisocyanate, 2,4-toluene
diisocyanate, and 2,6-toluene diisocyanate; and aliphatic
diisocyanates such as hexamethylene diisocyanate. Of these,
4,4'-diphenylmethane diisocyanate is most preferred, in
consideration of reactivity and operational safety.
[0022] The thermoplastic resin (Y) which is substantially
non-reactive with isocyanate is preferably a resin exhibiting low
water-absorbability and excellent compatibility with a
thermoplastic polymer material (described below) to be
cross-linked. The thermoplastic resin (Y) must exhibit excellent
compatibility with a thermoplastic polymer material to be
cross-linked, high restitution elasticity, and high strength. The
restitution elastic modulus of the thermoplastic resin (Y) is
preferably at least 45%, more preferably at least 50%, much more
preferably at least 55%, as measured in accordance with JIS-K7311.
When the restitution elastic modulus is lower than 45%, the
resultant molded product exhibits considerably low restitution.
Therefore, the thermoplastic resin (Y) suitable for a thermoplastic
polymer material to be cross-linked can be selected in
consideration of the aforementioned properties of the resin. For
example, when a thermoplastic urethane material is employed as the
thermoplastic polymer material, in consideration of the
aforementioned properties, the thermoplastic resin (Y) is
preferably selected from among polyester elastomers such as
ether-ester block copolymers and ester-ester block copolymers.
[0023] In the composition of the present invention, the ratio by
weight of the thermoplastic resin (Y) to the isocyanate compound
(X) is preferably 100:5 to 100:100, more preferably 100:10 to
100:40. When the ratio of the isocyanate compound (X) to the
thermoplastic resin (Y) is excessively low, in the case where a
specific amount of the golf ball cover property improving
composition of the present invention is added to a thermoplastic
polymer material, the effect of the properties of the resin (Y)
becomes greater than the effect of the compound (X), resulting in
insufficient improvement of scuff resistance and cut resistance of
the resultant golf ball cover. In contrast, when the ratio of the
isocyanate compound (X) to the thermoplastic resin (Y) is
excessively high, in the case where a specific amount of the golf
ball cover property improving composition of the present invention
is added to a thermoplastic polymer material, the effect of the
properties of the resin (Y) becomes low and restitution of the
resultant golf ball cover may be improved only insufficiently.
[0024] The composition of the present invention can be obtained
through, for example, the following procedure: the isocyanate
compound (X) is incorporated into the thermoplastic resin (Y), and
the resultant mixture is completely kneaded by use of a mixing roll
or a banbury mixer at 130 to 250.degree. C., followed by
pelletization or pulverization after cooling. If moisture is
present during kneading, most of the isocyanate groups are
inactivated through reaction between moisture and isocyanate, and
thus the composition no longer functions as a cross-linking agent.
Therefore, entering of moisture must be prevented.
[0025] No particular limitation is imposed on the thermoplastic
polymer material to which the composition of the present invention
is added during molding of a golf ball cover; i.e., the
thermoplastic polymer material which is virtually reactive with
isocyanate and which may be employed in combination with the
composition of the present invention. However, the thermoplastic
polymer material preferably has a polar group such as an amino
group, a hydroxyl group, a urea group, or a urethane group. Any
thermoplastic polymer material may be employed, so long as the
polymer material can cross-link with isocyanate and can be used as
a golf ball cover material. Examples of such a thermoplastic
polymer material include a thermoplastic polyurethane material, a
polyamide elastomer, a modified polyester elastomer, and a resin or
elastomer having a polar group, such as ionomer resin. Of these, a
thermoplastic polyurethane material is particularly preferred, in
consideration of restitution, flexibility, and reactivity with
isocyanate.
[0026] The thermoplastic polyurethane material includes soft
segments formed of a polymeric polyol (polymeric glycol), a chain
extender constituting hard segments, and a diisocyanate. No
particular limitation is imposed on the polymeric polyol serving as
a raw material, and the polymeric polyol may be any one selected
from polymeric polyols which are conventionally employed in the
technical field related to thermoplastic polyurethane materials.
Examples of the polymeric polyol include polyester polyols and
polyether polyols. Of these, polyether polyols are more preferred
to polyester polyols, since a thermoplastic polyurethane material
having high restitution elastic modulus and exhibiting excellent
low-temperature properties can be synthesized. Examples of the
polyether polyols include polytetramethylene glycol and
polypropylene glycol. From the viewpoints of restitution elastic
modulus and low-temperature properties, polytetramethylene glycol
is particularly preferred. The average molecular weight of the
polymeric polyol is preferably 1,000 to 5,000. The average
molecular weight is more preferably 2,000 to 4,000, in order to
synthesize a thermoplastic polyurethane material having high
restitution elastic modulus.
[0027] Any chain extender which is conventionally employed in the
technical field related to thermoplastic polyurethane materials is
preferably used. Examples of the chain extender include, but are
not limited to, 1,4-butylene glycol, 1,2-ethylene glycol,
1,3-butanediol, 1,6-hexanediol, and 2,2-dimethyl-1,3-propanediol.
The average molecular weight of the chain extender is preferably 20
to 15,000.
[0028] Any diisocyanate which is conventionally employed in the
technical field related to thermoplastic polyurethane materials is
preferably used. Examples of the diisocyanate include, but are not
limited to, aromatic diisocyanates such as 4,4'-diphenylmethane
diisocyanate, 2,4-toluene diisocyanate, and 2,6-toluene
diisocyanate; and aliphatic diisocyanates such as hexamethylene
diisocyanate. Some diisocyanates involve difficulty in controlling
cross-linking reaction during injection molding. In the present
invention, 4,4'-diphenylmethane diisocyanate, which is an aromatic
diisocyanate, is most preferred, in consideration of stability in
reaction with the aforementioned composition of the present
invention.
[0029] Preferred examples of the thermoplastic polyurethane
material containing the aforementioned materials include
commercially available polyurethane materials, such as Pandex
T-8290, T-8295, and T-8260 (products of DIC Bayer Polymer Ltd.),
and Resamine 2593 and 2597 (products of Dainichiseika Color &
Chemicals Mfg. Co., Ltd.).
[0030] The ratio by weight of the thermoplastic polymer material
which is virtually reactive with isocyanate groups of a
thermoplastic polyurethane material, etc. to the composition of the
present invention is preferably 100:1 to 100:100, more preferably
100:5 to 100:50, much more preferably 100:10 to 100:30. When the
ratio of the composition of the present invention to the
thermoplastic polymer material is excessively low, the composition
exerts insufficient cross-linking effect, whereas when the ratio is
excessively high, unreacted isocyanate imparts a color to the
resultant cover-forming material. In the present invention, the
cover-forming material may contain other thermoplastic polymer
components in addition to the aforementioned components. Examples
of such "other thermoplastic polymer components" include polyester
elastomer, polyamide elastomer, ionomer resin, styrene block
elastomer, polyethylene, and nylon resin. In this case, the
incorporation amount of thermoplastic polymer materials other than
the aforementioned thermoplastic polymer material which is
virtually reactive with isocyanate groups of a thermoplastic
polyurethane material, etc. is 0 to 100 parts by weight, preferably
10 to 75 parts by weight, more preferably 10 to 50 parts by weight,
on the basis of 100 parts by weight of the thermoplastic polymer
material which is virtually reactive with isocyanate groups of a
thermoplastic polyurethane material, etc. and which serves as an
essential component. The incorporation amount is appropriately
determined in accordance with various purposes, including
regulation of the hardness of the cover-forming material and
improvement of the restitution, fluidity, and adhesion of the
cover-forming material. If desired, the cover-forming material may
further contain various additives, such as pigments, dispersants,
antioxidants, light-resistant stabilizers, UV absorbers, and
release agents.
[0031] In use of the composition of the present invention, for
example, the composition is added to a thermoplastic polymer
material which is virtually reactive with isocyanate groups of a
thermoplastic polyurethane material, etc. and then dry-mixed, and
the resultant mixture is subjected to injection molding, to thereby
form a cover around a core. The molding temperature varies with the
type of the thermoplastic polymer material to be employed, but is
typically 120 to 300.degree. C.
[0032] When the thermoplastic polymer material is a thermoplastic
polyurethane material, in the resultant golf ball cover, reaction
or cross-linking is thought to proceed as follows: an isocyanate
group is reacted with a residual OH group of the thermoplastic
polyurethane material, to thereby form a urethane bond; or an
isocyanate group is added to a urethane group of the thermoplastic
polyurethane material, to thereby form an allophanate or biuret
cross-linking structure. In this case, although cross-linking
proceeds insufficiently immediately after injection molding of the
cover-forming material, cross-linking proceeds through annealing
after injection molding, and the resultant golf ball cover is
endowed with useful properties. As used herein, the term
"annealing" refers to aging through heating at a certain
temperature for a predetermined period of time, or aging at room
temperature for a predetermined period of time.
[0033] In the golf ball containing the composition of the present
invention, the surface hardness of the cover-forming material is
preferably 40 to 80, more preferably 43 to 60, much more preferably
45 to 55, as measured by use of a D-type durometer in accordance
with JIS-K6253. When the surface hardness of the cover-forming
material is excessively low, the resultant golf ball tends to
produce excessive back-spin upon being hit with an iron; i.e.,
controllability of the golf ball is impaired. In contrast, when the
surface hardness of the cover-forming material is excessively high,
the resultant golf ball tends to produce insufficient back-spin
upon being hit with an iron; i.e., controllability of the golf ball
is lowered, and feeling on impact is impaired.
[0034] In the golf ball containing the composition of the present
invention, the restitution elastic modulus of the cover-forming
material is preferably at least 45%, more preferably 45 to 85%,
further preferably 50 to 80%, much more preferably 50 to 60%, as
specified by JIS-K7311. Since the thermoplastic polymer material
which is virtually reactive with isocyanate, such as a
thermoplastic polyurethane material, does not exhibit high
restitution, preferably, the restitution elastic modulus is
strictly selected. When the restitution elastic modulus of the
cover-forming material is excessively low, the total distance of
the golf ball is considerably lowered. In contrast, when the
restitution elastic modulus of the cover-forming material is
excessively high, the initial velocity of the golf ball becomes
excessively high when being shot or putted (i.e., when
controllability of the golf is required within the range of a total
distance of 100 yards or less), and the golf ball may fail to meet
a golfer's demand.
[0035] No particular limitation is imposed on the core employed in
the golf ball containing the composition of the present invention,
and any type of cores that are usually employed can be employed.
Examples of the core which may be employed include a solid core for
a two-piece ball, a solid core having a plurality of vulcanized
rubber layers, a solid core having a plurality of resin layers, and
a thread-wound core having a thread rubber layer. No particular
limitation is imposed on the outer diameter, weight, hardness, and
material of the core. The thickness of the golf ball cover of the
present invention preferably falls within a range of 0.1 to 5.0 mm.
The cover may have a multi-layer structure, so long as the overall
thickness of the cover falls within the above range.
[0036] The golf ball containing the composition of the present
invention is formed so as to have a diameter and a weight as
specified under the Rules of Golf approved by R&A. Typically,
the diameter is at least 42.67 mm, and the weight is 45.93 g or
less. The diameter is preferably 42.67 to 42.9 mm. The deformation
amount of the golf ball under application of a load of 980 N (100
kg) is preferably 2.0 to 4.0 mm, more preferably 2.2 to 3.8 mm.
EXAMPLES
[0037] The present invention will next be described in detail by
way of Examples, which should not be construed as limiting the
invention thereto.
Examples and Comparative Examples
[0038] Golf ball cover property improving compositions of the
present invention; i.e., compositions 1 through 3 were prepared
from components shown in Table 1 (unit: parts by weight).
4,4'-Diphenylmethane diisocyanate (Millionate MT-F, product of
Nippon Polyurethane Industry Co., Ltd.) was employed as isocyanate
compound (X). The following material was employed as a base resin:
an ether-ester block copolymer which had been dried in advance to
thereby remove moisture (thermoplastic resin (Y), restitution
elastic modulus: 70%), soft vinyl chloride resin pellets which had
been dried in advance to thereby remove moisture (plasticizer
DOP50PHR, restitution elastic modulus: 35%), or a polystyrene resin
which had been dried in advance to thereby remove moisture
(restitution elastic modulus: 35%). The above components were mixed
sufficiently by use of a tumbler, and the resultant mixture was
subjected to extrusion molding by use of a vent-type extruder at
120 to 200.degree. C., to thereby yield strands. After being
cooled, the resultant strands were formed into pellets.
1 TABLE 1 Composition 1 Composition 2 Composition 3 Ether-ester
block copolymer 70 Soft polyvinyl chloride resin 70 Polystyrene
resin 70 4,4'-diphenylmethane diisocyanate 30 30 30
[0039]
2 Core composition Polybutadiene rubber 100 parts by weight Zinc
acrylate 21.5 parts by weight Zinc oxide 12 parts by weight Dicumyl
peroxide 1 part by weight
[0040] The components of the aforementioned core composition were
kneaded, and then subjected to vulcanization and molding at
155.degree. C. for 20 minutes, to thereby obtain a solid core for a
two-piece solid golf ball (diameter: 38.5 mm). BRO1 (product of
Japan Synthetic Rubber Co., Ltd.) was employed as the polybutadiene
rubber. The specific gravity of the thus-obtained core was 1.07;
the deformation amount under application of a load of 980 N (100
kg) was 3.4 mm; and the initial velocity as measured by means of a
method specified by USGA (R&A) was 78.1 m/s.
[0041] Cover materials shown in Tables 2 and 3 (unit: part(s) by
weight) were kneaded by use of a twin-screw extruder at 190.degree.
C., to thereby obtain cover-forming materials. Components shown in
Tables 2 and 3 are described below.
[0042] Polyurethane 1 (Thermoplastic Polyurethane Material)
[0043] Pandex T8290: MDI-PTMG-type thermoplastic polyurethane
material (product of DIC Bayer Polymer Ltd.) (JIS A surface
hardness: 93, restitution elastic modulus: 52%)
[0044] Polyurethane 2 (Thermoplastic Polyurethane Material)
[0045] Pandex T8295: MDI-PTMG-type thermoplastic polyurethane
material (product of DIC Bayer Polymer Ltd.) (JIS A surface
hardness: 97, restitution elastic modulus: 44%)
[0046] Polyurethane 3 (Thermoplastic Polyurethane Material)
[0047] Pandex T8260: MDI-PTMG-type thermoplastic polyurethane
material (product of DIC Bayer Polymer Ltd.) (Surface hardness as
measured by use of a D-type durometer: 56, restitution elastic
modulus: 45%)
[0048] Subsequently, each of the aforementioned solid cores was
placed in a mold for injection molding, and a cover (thickness: 2.1
mm) was formed from each of the cover-forming materials--obtained
by dry-mixing the cover materials (1) and (2))--around the core by
means of injection molding, to thereby produce a two-piece solid
golf ball (Examples and Comparative Examples). The resultant golf
ball was allowed to stand at room temperature for one week, and
then properties of the golf ball were evaluated. The evaluation
methods are described below. A sheet (thickness: 2 mm) formed
through injection molding was allowed to stand at room temperature
for one week, and then subjected to measurement of cover
properties. The results are shown in Tables 2 and 3.
[0049] (Cover Properties)
[0050] Surface Hardness
[0051] The surface hardness of the cover was measured by use of a
D-type durometer in accordance with JIS-K6253.
[0052] Restitution Elastic Modulus
[0053] The restitution elastic modulus of the cover was measured in
accordance with JIS-K7311.
[0054] (Ball Properties)
[0055] Hardness
[0056] The deformation amount of the golf ball under application of
a load of 980 N (100 kg) was measured.
[0057] Initial Velocity
[0058] The initial velocity of the golf ball was measured by means
of a method specified by USGA (R&A).
[0059] Total Distance
[0060] The golf ball was hit at a head speed of 45 m/s by use of
No. 1 wood (a driver) mounted on a swing robot machine, to thereby
measure a total distance.
[0061] Scuff Resistance Upon Being Hit With an Iron
[0062] The golf ball was maintained at 23.degree. C., 13.degree.
C., or 0.degree. C., and then hit at a head speed of 33 m/s by use
of a pitching wedge mounted on a swing robot machine. Thereafter,
the scuff resistance of the resultant golf ball was visually
evaluated on the basis of the following criteria.
[0063] 5: No scuffing or substantially no scuffing is observed.
[0064] 4: Scuffing is observed, but is negligible.
[0065] 3: The surface of the ball is slightly scaly.
[0066] 2: The surface of the ball is scaly, and a portion between
dimples of the cover is lost to some extent.
[0067] 1: A portion between dimples of the cover is completely
exfoliated.
3 TABLE 2 Cover material Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 (1)
Polyurethane 1 50 Polyurethane 2 50 100 100 100 Polyurethane 3 100
Titanium oxide 3 3 3 3 3 Polyethylene wax 1 1 1 1 1 (2) Composition
1 20 5 10 20 20 Cover Surface hardness 47 47 49 53 58 properties
Restitution elastic modulus (%) 50 45 46 48 48 Ball Outer diameter
(mm) 42.7 42.7 42.7 42.7 42.7 properties Weight (g) 45.2 45.1 45.2
45.3 45.3 Hardness (mm) 3.3 3.2 3.1 2.8 2.6 Initial velocity (m/s)
77.1 76.9 77 77.2 77.3 Total distance (m) 226 226 227 227 228 Scuff
resistance at 23.degree. C. 5 5 5 5 5 at 13.degree. C. 5 5 5 5 5 at
0.degree. C. 4 3 4 4 4
[0068]
4 TABLE 3 Cover material Comp. Ex. 1 Comp. Ex. 2 Comp. Ex. 3 (1)
Polyurethane 2 100 100 100 Titanium oxide 3 3 3 Polyethylene wax 1
1 1 (2) Composition 2 20 Composition 3 20 Cover Surface hardness 47
47 47 properties Restitution elastic modulus (%) 35 38 45 Ball
Outer diameter (mm) 42.7 42.7 42.7 properties Weight (g) 45.2 45.3
45.1 Hardness (mm) 3.2 3.2 3.2 Initial velocity (m/s) 76 76.3 76.7
Total distance (m) 216 219 224 Scuff resistance at 23.degree. C. 5
5 3 at 13.degree. C. 5 5 2 at 0.degree. C. 4 3 1
[0069] As is clear from Tables 2 and 3, the golf balls of the
Examples exhibit high restitution and excellent flight performance,
since they contain the composition of the present invention. The
results show that the golf balls of the Examples exhibit excellent
scuff resistance upon being hit with an iron. In contrast, the golf
balls of the Comparative Examples exhibit poor restitution and are
not satisfactory in terms of scuff resistance upon being hit with
an iron, since they do not contain the composition of the present
invention.
[0070] As described above, when the golf ball cover property
improving composition of the present invention is added to a
thermoplastic polymer material such as a thermoplastic polyurethane
material upon molding of a golf ball cover from the thermoplastic
polymer material, the resultant golf ball cover exhibits high
restitution and excellent scuff resistance.
* * * * *