U.S. patent application number 13/191785 was filed with the patent office on 2013-01-31 for multi-layered cores having selective weight distribution for golf balls.
The applicant listed for this patent is Michael J. Sullivan. Invention is credited to Michael J. Sullivan.
Application Number | 20130029785 13/191785 |
Document ID | / |
Family ID | 47597660 |
Filed Date | 2013-01-31 |
United States Patent
Application |
20130029785 |
Kind Code |
A1 |
Sullivan; Michael J. |
January 31, 2013 |
MULTI-LAYERED CORES HAVING SELECTIVE WEIGHT DISTRIBUTION FOR GOLF
BALLS
Abstract
Multi-piece golf balls containing a multi-layered core or a
dual-core are provided. The cores have selective weighting
configurations (SWC). Particularly, the core layers are made of
different compositions having different specific gravity levels or
densities. Preferably, rubber and high neutralized ethylene acid
copolymer compositions are used to form at least one layer in the
core. The rubber and ionomer compositions may be loaded with
fillers to adjust the specific gravity levels. The moment of
inertia of the ball is adjusted and the resulting ball has good
resiliency and spin control properties.
Inventors: |
Sullivan; Michael J.;
(Barrington, RI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Sullivan; Michael J. |
Barrington |
RI |
US |
|
|
Family ID: |
47597660 |
Appl. No.: |
13/191785 |
Filed: |
July 27, 2011 |
Current U.S.
Class: |
473/373 ;
473/376 |
Current CPC
Class: |
A63B 37/0045 20130101;
A63B 37/0033 20130101; A63B 37/0047 20130101; A63B 37/0067
20130101; A63B 37/0092 20130101; A63B 37/0075 20130101; A63B
37/0051 20130101; A63B 37/0003 20130101; A63B 37/0043 20130101;
A63B 37/0062 20130101; A63B 37/0076 20130101; A63B 37/0066
20130101; A63B 37/0064 20130101; A63B 37/0083 20130101 |
Class at
Publication: |
473/373 ;
473/376 |
International
Class: |
A63B 37/06 20060101
A63B037/06; A63B 37/02 20060101 A63B037/02 |
Claims
1. A golf ball, comprising: a multi-layer core having i) an inner
core having a diameter in the range of about 0.015 to about 0.900
inches and specific gravity in the range of about 1.18 to about
5.00 g/cc (SG.sub.inner); ii) an intermediate core layer having a
thickness in the range of about 0.100 to about 0.600 inches and
specific gravity in the range of about 0.080 to about 1.20 g/cc
(SG.sub.intermediate); and iii) an outer core layer having a
thickness in the range of about 0.010 to about 0.200 inches and
specific gravity of about 1.18 to about 5.00 g/cc (SG.sub.outer);
so that SG.sub.inner is greater than SG.sub.intermediate and
SG.sub.intermediate is less than SG.sub.outer; and a cover having
at least one layer.
2. The golf ball of claim 1, wherein the weight of the multi-layer
core is in the range of about 28 to about 38 grams.
3. The golf ball of claim 1, wherein at least one of the core
layers is formed from a rubber composition comprising a rubber
material selected from the group consisting of polybutadiene,
ethylene-propylene rubber, ethylene-propylene-diene rubber,
polyisoprene, styrene-butadiene rubber, polyalkenamers, butyl
rubber, halobutyl rubber, polystyrene elastomers, copolymers of
isobutylene and p-alkylstyrene, halogenated copolymers of
isobutylene and p-alkylstyrene, copolymers of butadiene with
acrylonitrile, polychloroprene, alkyl acrylate rubber, chlorinated
isoprene rubber, acrylonitrile chlorinated isoprene rubber, and
mixtures thereof.
4. The golf ball of claim 3, wherein the rubber composition
comprises polybutadiene.
5. The golf ball of claim 4, wherein the polybutadiene rubber
composition is used to form the intermediate core layer, wherein
the layer has a specific gravity in the range of about 1.03 to
about 1.18 g/cc.
6. The golf ball of claim 1, wherein at least one of the core
layers is formed from an ionomer composition comprising an ethylene
acid copolymer containing acid groups such that greater than 70% of
the acid groups are neutralized.
7. The golf ball of claim 6, wherein the ionomer composition is
used to form the intermediate core layer, wherein the layer has a
specific gravity in the range of about 0.93 to about 0.97 g/cc.
8. The golf ball of claim 1, wherein at least one of the core
layers comprises high specific gravity filler selected from the
group consisting of metal powder, metal alloy powder, metal oxide,
metal stearates, particulates, carbonaceous material, and mixtures
thereof.
9. The golf ball of claim 8, wherein the high specific gravity
filler is selected from the group consisting of bismuth powder,
boron powder, brass powder, bronze powder, cobalt powder, copper
powder, inconel metal powder, iron metal powder, molybdenum powder,
nickel powder, stainless steel powder, titanium metal powder,
zirconium oxide powder, aluminum flakes, tungsten metal powder,
beryllium metal powder, zinc metal powder, tin metal powder, zinc
oxide, iron oxide, aluminum oxide, titanium dioxide, magnesium
oxide, zirconium oxide and tungsten trioxide.
10. The golf ball of claim 1, wherein the inner core has a diameter
in the range of about 0.025 to about 0.080 inches and specific
gravity in the range of about 1.20 to about 3.50 g/cc.
11. The golf ball of claim 1, wherein the inner core has a diameter
in the range of about 0.030 to about 0.075 inches and specific
gravity in the range of about 1.25 to about 3.25 g/cc.
12. The golf ball of claim 1, wherein the intermediate core layer
has a diameter in the range of about 0.025 to about 0.080 inches
and specific gravity in the range of about 0.090 to about 1.18
g/cc.
13. The golf ball of claim 1, wherein the outer core layer has a
thickness in the range of about 0.040 to about 0.170 inches and
specific gravity of about 1.10 to about 3.75 g/cc.
14. The golf ball of claim 1, wherein the center of the inner core
and surface of the intermediate core layer and surface of the outer
core layer each has a hardness, and the surface hardness of the
intermediate layer is greater than the center hardness of the inner
core and surface hardness of the outer core.
15. The golf ball of claim 1, wherein the center hardness of the
inner core is in the range of about 38 Shore D to about 62 Shore
D.
16. The golf ball of claim 1, wherein the surface hardness of the
intermediate core layer is in the range of about 46 Shore D to
about 68 Shore D.
17. The golf ball of claim 1, wherein the surface hardness of the
outer core layer is in the range of about 40 Shore D to about 64
Shore D.
18. The golf ball of claim 1, wherein the cover is a single layer
having a thickness of about 0.015 to about 0.090 inches and is
formed from a thermoplastic or thermoset material.
19. The golf ball of claim 1, wherein the cover comprises two or
more layers and has an overall thickness of about 0.020 to about
0.140 inches and wherein each cover layer is formed from a
thermoplastic or thermoset material.
20. The golf ball of claim 19, wherein the cover comprises an inner
cover layer and outer cover layer, the inner cover having a surface
hardness of 60 Shore D or greater and an outer cover layer having a
surface hardness in the range of about 20 to about 70 Shore D.
21. The golf ball of claim 20, wherein the inner and outer cover
layers are formed from a composition comprising a polymer selected
from the group consisting of ethylene acid copolymer ionomers;
polyesters; polyamides; polyamide-ethers, polyamide-esters;
polyurethanes, polyureas; fluoropolymers; polystyrenes;
polypropylenes and polyethylenes; polyvinyl chlorides; polyvinyl
acetates; polycarbonates; polyvinyl alcohols; polyethers;
polyimides, polyetherketones, polyamideimides; and mixtures
thereof.
22. A golf ball, comprising: a dual-core having i) an inner core
having a diameter in the range of about 0.015 to about 0.900 inches
and specific gravity in the range of about 1.18 to about 5.00 g/cc
(SG.sub.inner); and ii) an outer core layer having a thickness in
the range of about 0.100 to about 0.600 inches and specific gravity
in the range of about 0.080 to about 1.20 g/cc (SG.sub.outer) so
that SG.sub.inner is greater than SG.sub.outer; and a cover having
at least one layer.
23. The golf ball of claim 22, wherein the weight of the dual core
is in the range of about 28 to about 38 grams.
24. The golf ball of claim 22, wherein at least one of the core
layers is formed from a rubber composition comprising a rubber
material selected from the group consisting of polybutadiene,
ethylene-propylene rubber, ethylene-propylene-diene rubber,
polyisoprene, styrene-butadiene rubber, polyalkenamers, butyl
rubber, halobutyl rubber, polystyrene elastomers, copolymers of
isobutylene and p-alkylstyrene, halogenated copolymers of
isobutylene and p-alkylstyrene, copolymers of butadiene with
acrylonitrile, polychloroprene, alkyl acrylate rubber, chlorinated
isoprene rubber, acrylonitrile chlorinated isoprene rubber, and
mixtures thereof.
25. The golf ball of claim 22, wherein at least one of the core
layers is formed from an ionomer composition comprising an ethylene
acid copolymer containing acid groups such that greater than 70% of
the acid groups are neutralized.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention generally relates to multi-piece golf
balls having a solid core of at least two layers and cover of at
least one layer. Preferably, the ball contains a multi-layered core
having an inner core, intermediate core layer, and outer core
layer, or a dual-core having an inner core and surrounding outer
core layer. The cores have selective weighting configurations
(SWC), whereby the core layers have different densities. The cores
are used to provide finished balls having high resiliency and
spin-control properties.
[0003] 2. Brief Review of the Related Art
[0004] Multi-piece, solid golf balls having a solid inner core
protected by a cover are used today by recreational and
professional golfers. The golf balls may have single-layered or
multi-layered cores. Normally, the core layers are made of a highly
resilient natural or synthetic rubber material such as, for
example, styrene butadiene, polybutadiene, poly(cis-isoprene), or
poly(trans-isoprene) or highly neutralized ethylene acid copolymers
(HNPs). The covers may be single or multi-layered and made of a
durable material such as, for example, HNPs, polyamides,
polyesters, polyurethanes, or polyureas. Manufacturers of golf
balls use different constructions (for example, three-piece,
four-piece, and five-piece balls) to impart specific properties and
features.
[0005] The core is the primary source of resiliency for the golf
ball and is often referred to as the "engine" of the ball. The
resiliency or coefficient of restitution ("COR") of a golf ball (or
golf ball component such as a core) means the ratio of a ball's
rebound velocity to its initial incoming velocity when the ball is
fired out of an air cannon into a rigid plate. The COR for a golf
ball is written as a decimal value between zero and one. A golf
ball may have different COR values at different initial velocities.
The United States Golf Association (USGA) sets limits on the
initial velocity of the ball so one objective of golf ball
manufacturers is to maximize the COR under these conditions. Balls
(or cores) with a higher rebound velocity have a higher COR value.
Such golf balls rebound faster, retain more total energy when
struck with a club, and have longer flight distance. In general,
the COR of the ball will increase as the hardness of the ball is
increased. The test methods for measuring the COR are described in
further detail below. In some conventional golf balls, materials
are used to increase the hardness of the core so the resiliency of
the core is increased, and this, in turn, causes the compression of
the core to increase.
[0006] In general, compression refers to the deflection that a golf
ball (or golf ball component such as a core) undergoes when
subjected to a compressive load. Several different methods may be
used to measure compression of the golf ball and its components.
The compression is commonly measured using Atti or Riehle
compression gauges. In the Atti method, as described further below,
a piston is used to compress a ball against a spring. The travel
distance and load of the piston are fixed and the deflection of the
spring is measured. If the core is relatively soft, the spring will
deflect only by a minimal amount. On the other hand, if the core is
relatively hard, the spring will deflect a significant amount. The
test methods for measuring compression are described in further
detail below.
[0007] Cores having a higher compression are harder and tend to
have good durability and resiliency. Players may achieve greater
flight distance when using such golf balls, which is particularly
desirable when hitting the ball off the tee. However, some high
compression balls are relatively stiff and this may have a
detrimental effect. For example, such balls tend to have a low
initial spin rate and this makes the ball more difficult to
control. This can be particularly troubling when making approach
shots near the green. On the other hand, if the ball has a higher
spin rate, flight distance may be sacrificed. Some players may have
a more difficult time driving such balls a long distance off the
tee.
[0008] Golf ball manufacturers have looked at adjusting the density
or specific gravity among the multiple layers of the golf ball to
control its spin rate. In general, the total weight of a golf ball
has to conform to weight limits set by the United States Golf
Association ("USGA"). Although the total weight of the golf ball is
controlled, the distribution of weight within the ball can vary.
Redistributing the weight or mass of the golf ball either toward
the center of the ball or toward the outer surface of the ball
changes its flight and spin properties.
[0009] For example, the weight can be shifted towards the center of
the ball to increase the spin rate as described in Yamada, U.S.
Pat. No. 4,625,964, wherein the golf ball contains a core, an
intermediate layer, and a cover, and the core has a specific
gravity of at least 1.50 and a diameter of less than 32 mm, the
intermediate layer having a lower specific gravity than the core.
Chikaraishi et al., U.S. Pat. No. 5,048,838 discloses another
three-piece golf ball containing a two-piece solid core and a
cover. The dense inner core has a diameter in the range of 15-25 mm
with a specific gravity of 1.2 to 4.0 and the outer core layer has
a specific gravity of 0.1 to 3.0 less than the specific gravity of
the inner core. Gentiluomo, U.S. Pat. No. 5,104,126 discloses a
ball with a dense inner core made of steel, lead, brass, zinc,
copper, and a filled elastomer, wherein the core has a specific
gravity of at least 1.25. The inner core is encapsulated by a lower
density syntactic foam composition and this construction is
encapsulated by an ionomer cover. Yabuki et al., U.S. Pat. No.
5,482,285 discloses a three-piece golf ball having an inner core
and outer core encapsulated by an ionomer cover. The specific
gravity of the outer core is reduced so that it falls within the
range of 0.2 to 1.0. The specific gravity of the inner core is
adjusted so that the total weight of the inner/outer core falls
within a range of 32.0 to 39.0 g. In other instances, the weight
can be shifted to the outside portion of the ball and away from the
center. For example, Sullivan and Nesbitt, U.S. Pat. No. 6,120,393
discloses golf balls having a low spin rate. The balls comprise a
relatively soft, multi-piece core and a hard cover. The inner core
is hollow and may be filled with gases, while the outer core layer
is made of a soft, resilient material. Sullivan and Nesbitt, U.S.
Pat. No. 6,142,887 disclose a golf ball containing a core, a thin
spherical layer, and a polymeric outer cover. The thin spherical
layer comprises a metal, ceramic, or composite material such a
silicon carbide, glass, carbon, boron carbide, and aramid
materials.
[0010] Although some conventional multi-layered core constructions
are generally effective in providing high resiliency golf balls,
there is a continuing need for improved core constructions in golf
balls. Particularly, it would be desirable to have multi-layered
core constructions that would have selective weighting
configurations (SWC) to provide the ball with good flight distance
along with spin control. The present invention provides core
constructions and golf balls having such properties as well as
other advantageous features, and benefits.
SUMMARY OF THE INVENTION
[0011] The present invention provides a multi-piece golf ball
comprising a solid core having at least one layer and a cover
having at least one layer. The golf ball may have different
constructions. For instance, in one version, a golf ball having a
three-layered ("multi-layer") core is made; while in another
version, a golf ball having a two-layered ("dual") core is made. As
discussed further below, in the balls of this invention, the
overall density of the core is generally balanced. Some bits of
mass are positioned relatively close to the center of the ball,
while other bits of mass are positioned away from the center of the
ball. Thus, the ball does not have a relatively high or low moment
of inertia. Rather, the ball can be described as having a relative
"medium moment of inertia." Thus, the ball has generally good
flight distance and spin control.
[0012] In a first preferred embodiment, the golf ball comprises a
multi-layer core having an inner core, intermediate core layer, and
outer core layer; along with a cover disposed about the core. The
inner core preferably has a diameter in the range of about 0.015 to
about 0.900 inches and specific gravity in the range of about 1.18
to about 5.00 g/cc. The intermediate core layer preferably has a
thickness in the range of about 0.100 to about 0.600 inches and
specific gravity in the range of about 0.080 to about 1.20 g/cc.
The outer core layer preferably has a thickness in the range of
about 0.010 to about 0.200 inches and specific gravity of about
1.18 to about 5.00 g/cc. Preferably, the specific gravity of the
inner core (SG.sub.inner) is greater than the specific gravity of
the intermediate core (SG.sub.intermediate) and the
SG.sub.intermediate is less than the specific gravity of the outer
core (SG.sub.outer).
[0013] In one version, at least one of the core layers is formed of
a rubber material such as, for example, polybutadiene,
ethylene-propylene rubber, ethylene-propylene-diene rubber,
polyisoprene, styrene-butadiene rubber, polyalkenamers, butyl
rubber, halobutyl rubber, or polystyrene elastomers. And, at least
one of the core layers is formed from an ionomer composition
comprising an ethylene acid copolymer containing acid groups such
that greater than 70% of the acid groups are neutralized. More
particularly, a multi-layered core comprising an inner core formed
of a rubber composition; an intermediate core formed of the highly
neutralized ionomer composition; and outer core layer formed of a
rubber composition may be prepared. The rubber and ionomer
compositions may contain specific gravity fillers to adjust the
density of the respective layers. For example, these fillers may be
selected from the group consisting of metal powder, metal alloy
powder, metal oxide, metal stearates, particulates, carbonaceous
material, and mixtures thereof.
[0014] In a second preferred embodiment, the golf ball comprises a
dual-core having an inner core and outer core layer; along with a
cover disposed about the core. The inner core preferably has a
diameter in the range of about 0.015 to about 0.900 inches and
specific gravity in the range of about 1.18 to about 5.00 g/cc. The
outer core layer preferably has a thickness in the range of about
0.100 to about 0.600 inches and specific gravity in the range of
about 0.080 to about 1.20 g/cc so that the specific gravity of the
inner core (SG.sub.inner) is greater than the specific gravity of
the outer core (SG.sub.outer).
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] The novel features that are characteristic of the present
invention are set forth in the appended claims. However, the
preferred embodiments of the invention, together with further
objects and attendant advantages, are best understood by reference
to the following detailed description in connection with the
accompanying drawings in which:
[0016] FIG. 1 is a cross-sectional view of a four-piece golf ball
having a multi-layered core made in accordance with the present
invention; and
[0017] FIG. 2 is a cross-sectional view of a three-piece golf ball
having a dual-core made in accordance with the present
invention.
DETAILED DESCRIPTION OF THE INVENTION
[0018] Golf Ball Constructions
[0019] Golf balls having various constructions may be made in
accordance with this invention. For example, golf balls having
three-piece, four-piece, and five-piece constructions with single
or multi-layered cover materials may be made. The term, "layer" as
used herein means generally any spherical portion of the golf ball.
More particularly, in one version, a three-piece golf ball having a
dual-core and a cover is made. The dual-core includes an inner core
(center) and surrounding outer core layer. In another version, a
four-piece golf ball comprising a dual-core and dual-cover
comprising an inner cover and outer cover is made. In yet another
construction, a four-piece or five-piece golf ball having a
multi-layered core comprising an inner core (center), intermediate
core layer, and outer core layer, may be made. The golf balls of
this invention may further contain an intermediate layer(s). As
used herein, the term, "intermediate layer" means a layer of the
ball disposed between the core and cover. The intermediate layer
also may be referred to as a casing or mantle layer. The diameter
and thickness of the different layers along with properties such as
hardness and compression may vary depending upon the construction
and desired playing performance properties of the golf ball.
[0020] Referring to FIG. 1, one version of a golf ball that can be
made in accordance with this invention is generally indicated at
(12). The ball (12) contains a multi-layered core (14) having an
inner core (center) (14a); intermediate core layer (14b); and outer
core layer (14c) surrounded by a single-layered cover (16). The
inner core (14a) is relatively small in volume and generally has a
diameter within a range having a lower limit of about 0.15 or 0.25
or 0.35 or 0.45 or 0.55 inches and an upper limit of about 0.60 or
0.70 or 0.80 or 0.90 inches. In one preferred version, the inner
core has a diameter in the range of about 0.025 to about 0.080
inches, more preferably about 0.030 to about 0.075 inches. On the
other hand, the intermediate layer (14b) is relatively large in
volume and generally has a thickness in the range having a lower
limit of about 0.100 or 0.200 or 0.300 and an upper limit of about
0.400 or 0.500 or 0.600 inches. In one preferred version, the
intermediate core layer has a thickness in the range of about 0.150
to about 0.550 inches, more preferably about 0.250 to about 0.450
inches. The outer core layer (14c) generally has a thickness within
a range having a lower limit of 0.010 or 0.020 or 0.025 or 0.030
inches and an upper limit of 0.070 or 0.080 or 0.100 or 0.200
inches. In one preferred version, the outer core layer has a
thickness in the range of about 0.040 to about 0.170 inches, more
preferably about 0.060 to about 0.150 inches.
[0021] Golf balls made in accordance with this invention can be of
any size, although the USGA requires that golf balls used in
competition have a diameter of at least 1.68 inches. For play
outside of United States Golf Association (USGA) rules, the golf
balls can be of a smaller size. Normally, golf balls are
manufactured in accordance with USGA requirements and have a
diameter in the range of about 1.68 to about 1.80 inches. In
general, the multi-layer core (14) has an overall diameter within a
range having a lower limit of about 1.00 or 1.20 or 1.30 or 1.40
inches and an upper limit of about 1.58 or 1.60 or 1.62 or 1.64
inches. Referring to FIG. 2, in another version, the golf ball (18)
contains a dual-core (20) having an inner core (center) (20a) and
outer core layer (20b), and there is no intermediate core layer
present. The dual-core is surrounded by a single-layered cover
(22).
[0022] In the multi-layered core version, as shown in FIG. 1, the
inner core (14a) preferably has a relatively high specific gravity.
In general, the inner core (14a) has a specific gravity within a
range having a lower limit of about 1.18 or 1.50 or 2.00 or 2.50
g/cc and an upper limit of about 3.00 or 3.50 or 4.00 or 4.50 or
5.00 g/cc. In a preferred embodiment, the inner core has a specific
gravity of about 1.20 to about 3.50 g/cc, more preferably about
1.25 to about 3.00 g/cc. Meanwhile, the intermediate core layer
(14b) preferably has a relatively low specific gravity. The
intermediate core (14b) generally has a specific gravity within a
range having a lower limit of about 0.080 or 0.100 or 0.400 or
0.600 or 0.800 g/cc and an upper limit of about 1.00 or 1.10 or
1.20 g/cc. In a preferred embodiment, the intermediate core layer
has a specific gravity of about 0.090 to about 1.18 g/cc, more
preferably about 0.095 to about 1.15 g/cc. In a manner similar to
the inner core, the outer core (14c) has a specific gravity within
a range having a lower limit of about 1.18 or 1.50 or 2.00 or 2.50
g/cc and an upper limit of about 3.00 or 3.50 or 4.00 or 4.50 or
5.00 g/cc. In a particularly preferred embodiment, the specific
gravities of the center and outer core layer are equal or
substantially the same. For purposes of the present invention,
specific gravities are substantially the same if they are the same
or within 0.1 g/cc of each other. In the dual-layer core version,
as shown in FIG. 2, the inner core (20a) preferably has a specific
gravity within a range of about 1.18 to about 5.00 g/cc; and the
outer core layer (20b) has a specific gravity within a range of
about 0.080 to about 1.20 g/cc.
[0023] Preferably, the specific gravity of the inner core
(SG.sub.inner) is greater than the specific gravity of the
intermediate core layer (SG.sub.intermediate). And, the specific
gravity of the intermediate core layer (SG.sub.intermediate) is
less than the specific gravity of the outer core layer
(SG.sub.outer). The specific gravities of the inner core
(SG.sub.inner) and outer core layer (SG.sub.outer) may be
substantially the same.
[0024] As discussed further below, various polymeric compositions
may be used to make the multi-layered and dual-core structures of
the golf balls of this invention. The golf balls may contain
specific gravity fillers to adjust the weight of the core layers as
needed. The amount of fillers and other ingredients used in the
compositions is set so the weight of the golf ball does not exceed
limits set by the USGA. The USGA has established a maximum weight
of 45.93 g (1.62 ounces). For play outside of USGA rules, the golf
balls can be heavier. In one preferred embodiment, the weight of
the multi-layered core is in the range of about 28 to about 38
grams.
[0025] Core Structure
[0026] As discussed above, the core preferably has a multi-layered
or dual-layered structure. Preferably, the inner core has a center
hardness (CH) within a range having a lower limit of about 38 or 45
or 52 and an upper limit of about 55 or 60 or 62 Shore D.
Meanwhile, the intermediate core layer preferably has a surface
hardness (ICLSH) within a range having a lower limit of about 46 or
50 or 54 Shore D and an upper limit of about 60 or 64 or 68 Shore
D. The outer core layer preferably has a surface hardness (OCLSH)
within a range having a lower limit of about 40 or 44 or 48 or 52
Shore D and an upper limit of about 56 or 60 or 64 Shore D. In one
embodiment, the surface hardness of the intermediate core layer is
greater than the center hardness of the inner core and surface
hardness of the outer core layer. In an alternative embodiment, the
surface hardness of the intermediate core layer is less than the
center hardness of the inner core and surface hardness of the outer
core layer.
[0027] In one preferred golf ball, the inner core (center) has a
"positive" hardness gradient (that is, the outer surface of the
inner core is harder than its geometric center) and the outer core
layer has a "positive" hardness gradient (that is, the outer
surface of the outer core layer is harder than the inner surface of
the outer core layer.) In such cases where both the inner core and
outer core layer have "positive" hardness gradients, the outer
surface hardness of the outer core layer is preferably greater than
the material hardness of the inner core (center). In an alternative
version, the inner core may have a "negative" hardness gradient
(that is, the outer surface of the outer core layer is softer than
the inner surface of the outer core layer.) and the outer core may
have a positive hardness gradient. In another version, the inner
core (center) has a positive hardness gradient, while the outer
core layer has a negative hardness gradient In yet another version,
the outer core layer may have a "zero" hardness gradient. (That is,
the hardness values of the outer surface of the outer core layer
and the inner surface of the outer core layer are substantially the
same.) Such hardness gradients are further described in Bulpett et
al., U.S. Pat. Nos. 7,537,529 and 7,410,429 and Sullivan et al.,
U.S. Pat. Nos. 7,255,656 and 6,852,044, the disclosures of which
are hereby incorporated by reference.
[0028] Particularly, the term, "zero hardness gradient" as used
herein, means a surface to center (or second surface) Shore C
hardness gradient of less than 8, preferably less than 5 and most
preferably less than 3 and may have a value of zero or negative 1
to negative 25. The term, "negative hardness gradient" as used
herein, means a surface to center (or second surface) Shore C
hardness gradient of less than zero. The terms, "zero hardness
gradient" and "negative hardness gradient," may be used herein
interchangeably to refer to hardness gradients of negative 1 to
negative 25. The term, "positive hardness gradient" as used herein,
means a surface to center (or second surface) Shore C hardness
gradient of 8 or greater, preferably 10 or greater, and most
preferably 20 or greater. By the term, "steep positive hardness
gradient" as used herein, it is meant surface to center (or second
surface) Shore C hardness gradient of 20 or greater, more
preferably 25 or greater, and most preferably 30 or greater. For
example, the core may have a steep positive hardness gradient of
35, 40, or 45 Shore C or greater.
[0029] Preferably, the hardness gradient from geometric center of
the inner core to the surface of the outer core layer is a positive
hardness gradient. That is, the outer surface of the outer core
layer is harder than the center of the inner core. Methods for
measuring the hardness of the core and cover layers and determining
the hardness gradients are discussed in further detail below.
[0030] As discussed further below, in a multi-layered core, the
inner core and outer core layer, which have relatively high
specific gravity levels, may be formed from highly filled
thermoplastic or thermoset materials. Meanwhile, the intermediate
core layer may be formed of a thermoplastic or thermoset material,
which is substantially free of fillers. Preferably, at least one
core layer is formed of a rubber or ethylene acid copolymer ionomer
composition. The golf balls of this invention having the
above-described core constructions show good resiliency (distance)
while maintaining a nice feel. The resulting ball has a relatively
high COR allowing it to reach high velocity when struck by a golf
club. Thus, the ball tends to travel a greater distance which is
particularly important for driver shots off the tee. At the same
time, the ball has a soft feel and good spin control. In the
multi-layered core, a portion of the core's density is distributed
towards the center of the ball, that is, some bits of mass of the
ball are located relatively close to its axis of rotation. But, not
all of the core's density is distributed towards the center of the
ball. Rather, some bits of mass of the ball are located away from
its axis of rotation. In general, the Moment of Inertia of a ball
(or other object) about a given axis refers to how difficult it is
to change the ball's angular motion about that axis. If the ball's
mass is concentrated towards the center, less force is required to
change its rotational rate, and the ball has a relatively low
Moment of Inertia. Thereby, the initial spin rate of the ball is
increased. Conversely, if the ball's mass is concentrated towards
the outer surface, more force is required to change its rotational
rate, and the ball has a relatively low Moment of Inertia. The
initial spin rate of the ball is decreased.
[0031] In the golf balls of this invention, the overall density of
the core is generally balanced. Some bits of mass are positioned
relatively close to the center of the ball, while other bits of
mass are positioned away from the center of the ball. Thus, the
ball does not have a relatively high or low Moment of Inertia.
Rather, the ball can be described as having a relative "medium"
Moment of Inertia. Thus, the ball has generally good spin control.
With a medium spin rate, a professional (or highly skilled) golfer
can produce and control the spin of the ball. Such a golfer can
make nice approach shots with backspin so the ball stops quickly on
the green. At the same time, a recreational (or less skilled)
player can strike the ball with the club and still maintain control
so that it travels in a relatively straight line. Because of the
medium spin rate, the ball will have less side-spin and it is less
likely to drift completely off-course. A golfer can get
particularly frustrated with their play when they hook or slice the
ball, and the high side-spin rate of the ball causes it to land in
a neighboring fairway. The average golf player is able to hit the
golf balls of this invention with good distance and sense of
control.
[0032] More particularly, as described in Sullivan, U.S. Pat. No.
6,494,795 and Ladd et al., U.S. Pat. No. 7,651,415, the formula for
the Moment of Inertia for a sphere through any diameter is given in
the CRC Standard Mathematical Tables, 24th Edition, 1976 at 20
(hereinafter CRC reference). In accordance with the above
calculations, the Moment of Inertia for a 1.62 oz. golf ball having
a diameter of about 1.68 inches with evenly distributed weight
through any diameter is about 0.4572 oz./inch.sup.2 (83.6
g./cm.sup.2). Such golf balls with a Moment of Inertia
substantially higher than this value would be considered relatively
high Moment of Inertia golf balls; while golf balls with a
substantially lower value would be considered relatively low Moment
of Inertia golf balls. Meanwhile, golf balls with substantially the
same value would be considered "medium" Moment of Inertia golf
balls. In general, such golf balls having a medium Moment of
Inertia would have values in the range of about 0.3000
oz./inch.sup.2 to about 0.6000 oz./inch.sup.2
[0033] In addition, the cores of this invention typically have a
COR of about 0.75 or greater; and preferably about 0.80 or greater.
The compression of the core preferably is about 50 to about 130 and
more preferably in the range of about 70 to about 110.
[0034] Rubber Compositions
[0035] Preferably, at least one of the core layers is formed of a
rubber composition comprising a rubber material selected from the
group of: natural and synthetic rubbers including, but not limited
to, polybutadiene, polyisoprene, ethylene propylene rubber ("EPR"),
ethylene-propylene-diene ("EPDM") rubber, styrene-butadiene rubber,
styrenic block copolymer rubbers (such as "SI", "SIS", "SB", "SBS",
"SIBS", and the like, where "S" is styrene, "I" is isobutylene, and
"B" is butadiene), polyalkenamers such as, for example,
polyoctenamer, butyl rubber, halobutyl rubber, polystyrene
elastomers, polyethylene elastomers, polyurethane elastomers,
polyurea elastomers, metallocene-catalyzed elastomers and
plastomers, copolymers of isobutylene and p-alkylstyrene,
halogenated copolymers of isobutylene and p-alkylstyrene,
copolymers of butadiene with acrylonitrile, polychloroprene, alkyl
acrylate rubber, chlorinated isoprene rubber, acrylonitrile
chlorinated isoprene rubber, and combinations of two or more
thereof.
[0036] More preferably, the rubber composition comprises
polybutadiene. In general, polybutadiene is a homopolymer of
1,3-butadiene. The double bonds in the 1,3-butadiene monomer are
attacked by catalysts to grow the polymer chain and form a
polybutadiene polymer having a desired molecular weight. Any
suitable catalyst may be used to synthesize the polybutadiene
rubber depending upon the desired properties. Normally, a
transition metal complex (for example, neodymium, nickel, or
cobalt) or an alkyl metal such as alkyllithium is used as a
catalyst. Other catalysts include, but are not limited to,
aluminum, boron, lithium, titanium, and combinations thereof. The
catalysts produce polybutadiene rubbers having different chemical
structures. In a cis-bond configuration, the main internal polymer
chain of the polybutadiene appears on the same side of the
carbon-carbon double bond contained in the polybutadiene. In a
trans-bond configuration, the main internal polymer chain is on
opposite sides of the internal carbon-carbon double bond in the
polybutadiene. The polybutadiene rubber can have various
combinations of cis- and trans-bond structures. A preferred
polybutadiene rubber has a 1,4 cis-bond content of at least 40%,
preferably greater than 80%, and more preferably greater than 90%.
In general, polybutadiene rubbers having a high 1,4 cis-bond
content have high tensile strength. The polybutadiene rubber may
have a relatively high or low Mooney viscosity.
[0037] Examples of commercially available polybutadiene rubbers
that can be used in accordance with this invention, include, but
are not limited to, BR 01 and BR 1220, available from BST
Elastomers of Bangkok, Thailand; SE BR 1220LA and SE BR1203,
available from DOW Chemical Co of Midland, Mich.; BUDENE 1207,
1207s, 1208, and 1280 available from Goodyear, Inc of Akron, Ohio;
BR 01, 51 and 730, available from Japan Synthetic Rubber (JSR) of
Tokyo, Japan; BUNA CB 21, CB 22, CB 23, CB 24, CB 25, CB 29 MES, CB
60, CB Nd 60, CB 55 NF, CB 70 B, CB KA 8967, and CB 1221, available
from Lanxess Corp. of Pittsburgh. Pa.; BR1208, available from LG
Chemical of Seoul, South Korea; UBEPOL BR130B, BR150, BR150B,
BR150L, BR230, BR360L, BR710, and VCR617, available from UBE
Industries, Ltd. of Tokyo, Japan; EUROPRENE NEOCIS BR 60, INTENE 60
AF and P30AF, and EUROPRENE BR HV80, available from Polimeri Europa
of Rome, Italy; AFDENE 50 and NEODENE BR40, BR45, BR50 and BR60,
available from Karbochem (PTY) Ltd. of Bruma, South Africa; KBR 01,
NdBr 40, NdBR-45, NdBr 60, KBR 710S, KBR 710H, and KBR 750,
available from Kumho Petrochemical Co., Ltd. Of Seoul, South Korea;
DIENE 55NF, 70AC, and 320 AC, available from Firestone Polymers of
Akron, Ohio; and PBR-Nd Group II and Group III, available from
Nizhnekamskneftekhim, Inc. of Nizhnekamsk, Tartarstan Republic.
[0038] The polybutadiene rubber is used in an amount of at least
about 5% by weight based on total weight of composition and is
generally present in an amount of about 5% to about 100%, or an
amount within a range having a lower limit of 5% or 10% or 20% or
30% or 40% or 50% and an upper limit of 55% or 60% or 70% or 80% or
90% or 95% or 100%. Preferably, the concentration of polybutadiene
rubber is about 40 to about 95 weight percent. Lesser amounts of
other thermoset materials may be incorporated into the base rubber.
Such materials include the rubbers discussed above, for example,
cis-polyisoprene, trans-polyisoprene, balata, polychloroprene,
polynorbornene, polyoctenamer, polypentenamer, butyl rubber, EPR,
EPDM, styrene-butadiene, and the like.
[0039] The rubber compositions of this invention may be cured using
conventional curing processes. Suitable curing processes include,
for example, peroxide-curing, sulfur-curing, high-energy radiation,
and combinations thereof. Preferably, the rubber composition
contains a free-radical initiator selected from organic peroxides,
high energy radiation sources capable of generating free-radicals,
and combinations thereof. In one preferred version, the rubber
composition is peroxide-cured. Suitable organic peroxides include,
but are not limited to, dicumyl peroxide;
n-butyl-4,4-di(t-butylperoxy)valerate;
1,1-di(t-butylperoxy)3,3,5-trimethylcyclohexane;
2,5-dimethyl-2,5-di(t-butylperoxy)hexane; di-t-butyl peroxide;
di-t-amyl peroxide; t-butyl peroxide; t-butyl cumyl peroxide;
2,5-dimethyl-2,5-di(t-butylperoxy)hexyne-3;
di(2-t-butyl-peroxyisopropyl)benzene; dilauroyl peroxide; dibenzoyl
peroxide; t-butyl hydroperoxide; and combinations thereof. In a
particular embodiment, the free radical initiator is dicumyl
peroxide, including, but not limited to Perkadox.RTM. BC,
commercially available from Akzo Nobel. Peroxide free-radical
initiators are generally present in the rubber composition in an
amount of at least 0.05 parts by weight per 100 parts of the total
rubber, or an amount within the range having a lower limit of 0.05
parts or 0.1 parts or 1 part or 1.25 parts or 1.5 parts or 2.5
parts or 5 parts by weight per 100 parts of the total rubbers, and
an upper limit of 2.5 parts or 3 parts or 5 parts or 6 parts or 10
parts or 15 parts by weight per 100 parts of the total rubber.
Concentrations are in parts per hundred (phr) unless otherwise
indicated. As used herein, the term, "parts per hundred," also
known as "phr" or "pph" is defined as the number of parts by weight
of a particular component present in a mixture, relative to 100
parts by weight of the polymer component. Mathematically, this can
be expressed as the weight of an ingredient divided by the total
weight of the polymer, multiplied by a factor of 100.
[0040] The rubber compositions may further include a reactive
cross-linking co-agent. Suitable co-agents include, but are not
limited to, metal salts of unsaturated carboxylic acids having from
3 to 8 carbon atoms; unsaturated vinyl compounds and polyfunctional
monomers (e.g., trimethylolpropane trimethacrylate); phenylene
bismaleimide; and combinations thereof. Particular examples of
suitable metal salts include, but are not limited to, one or more
metal salts of acrylates, diacrylates, methacrylates, and
dimethacrylates, wherein the metal is selected from magnesium,
calcium, zinc, aluminum, lithium, and nickel. In a particular
embodiment, the co-agent is selected from zinc salts of acrylates,
diacrylates, methacrylates, and dimethacrylates. In another
particular embodiment, the agent is zinc diacrylate (ZDA). When the
co-agent is zinc diacrylate and/or zinc dimethacrylate, the
co-agent is typically included in the rubber composition in an
amount within the range having a lower limit of 1 or 5 or 10 or 15
or 19 or 20 parts by weight per 100 parts of the total rubber, and
an upper limit of 24 or 25 or 30 or 35 or 40 or 45 or 50 or 60
parts by weight per 100 parts of the base rubber.
[0041] Radical scavengers such as a halogenated organosulfur,
organic disulfide, or inorganic disulfide compounds may be added to
the rubber composition. These compounds also may function as "soft
and fast agents." As used herein, "soft and fast agent" means any
compound or a blend thereof that is capable of making a core: 1)
softer (having a lower compression) at a constant "coefficient of
restitution" (COR); and/or 2) faster (having a higher COR at equal
compression), when compared to a core equivalently prepared without
a soft and fast agent. Preferred halogenated organosulfur compounds
include, but are not limited to, pentachlorothiophenol (PCTP) and
salts of PCTP such as zinc pentachlorothiophenol (ZnPCTP). Using
PCTP and ZnPCTP in golf ball inner cores helps produce softer and
faster inner cores. The PCTP and ZnPCTP compounds help increase the
resiliency and the coefficient of restitution of the core. In a
particular embodiment, the soft and fast agent is selected from
ZnPCTP, PCTP, ditolyl disulfide, diphenyl disulfide, dixylyl
disulfide, 2-nitroresorcinol, and combinations thereof.
[0042] As discussed above, the compositions of this invention are
formulated to have specific gravity levels so that they can be used
to form certain core components of the golf ball. Particularly, the
compositions may contain "fillers" to adjust the specific gravity
as needed. As used herein the term "fillers" include any compound
or composition that can be used to vary the density or specific
gravity of selected portions of the golf ball. Fillers include
high-density and low-density fillers.
[0043] Suitable specific gravity fillers preferably have specific
gravity values in the range from about 2 to about 19, and include,
for example, metal (or metal alloy) powder, metal oxide, metal
stearates, particulates, carbonaceous materials, and the like or
blends thereof. Examples of useful metal (or metal alloy) powders
include, but are not limited to, bismuth powder, boron powder,
brass powder, bronze powder, cobalt powder, copper powder,
Inconel.TM. metal powder, iron metal powder, molybdenum powder,
nickel powder, stainless steel powder, titanium metal powder,
zirconium oxide powder, aluminum flakes, tungsten metal powder,
beryllium metal powder, zinc metal powder, or tin metal powder.
Examples of metal oxides include, but are not limited to, zinc
oxide, iron oxide, aluminum oxide, titanium dioxide, magnesium
oxide, zirconium oxide, and tungsten trioxide. Examples of
particulate carbonaceous materials include, but are not limited to,
graphite and carbon black. Examples of other useful fillers include
but are not limited to graphite fibers, precipitated hydrated
silica, clay, talc, glass fibers, aramid fibers, mica, calcium
metasilicate, barium sulfate, zinc sulfide, silicates, diatomaceous
earth, calcium carbonate, magnesium carbonate, regrind (which is
recycled uncured center material mixed and ground to 30 mesh
particle size), manganese powder, and magnesium powder, cotton
flock, natural bitumen, cellulose flock, and leather fiber. Micro
balloon fillers such as glass and ceramic, and fly ash fillers can
also be used.
[0044] In a particular aspect of this embodiment, the rubber
composition includes filler(s) selected from carbon black,
nanoclays (e.g., Cloisite.RTM. and Nanofil.RTM. nanoclays,
commercially available from Southern Clay Products, Inc., and
Nanomax.RTM. and Nanomer.RTM. nanoclays, commercially available
from Nanocor, Inc.), talc (e.g., Luzenac HAR.RTM. high aspect ratio
talcs, commercially available from Luzenac America, Inc.), glass
(e.g., glass flake, milled glass, and microglass), mica and
mica-based pigments (e.g., Iriodin.RTM. pearl luster pigments,
commercially available from The Merck Group), and combinations
thereof.
[0045] In addition, the rubber compositions may include
antioxidants to prevent the breakdown of the elastomers. Also,
processing aids such as high molecular weight organic acids and
salts thereof may be added to the composition. Suitable organic
acids are aliphatic organic acids, aromatic organic acids,
saturated mono-functional organic acids, unsaturated monofunctional
organic acids, multi-unsaturated mono-functional organic acids, and
dimerized derivatives thereof. Particular examples of suitable
organic acids include, but are not limited to, caproic acid,
caprylic acid, capric acid, lauric acid, stearic acid, behenic
acid, erucic acid, oleic acid, linoleic acid, myristic acid,
benzoic acid, palmitic acid, phenylacetic acid, naphthalenoic acid,
and dimerized derivatives thereof. The organic acids are aliphatic,
mono-functional (saturated, unsaturated, or multi-unsaturated)
organic acids. Salts of these organic acids may also be employed.
The salts of organic acids include the salts of barium, lithium,
sodium, zinc, bismuth, chromium, cobalt, copper, potassium,
strontium, titanium, tungsten, magnesium, cesium, iron, nickel,
silver, aluminum, tin, or calcium, salts of fatty acids,
particularly stearic, behenic, erucic, oleic, linoelic or dimerized
derivatives thereof. It is preferred that the organic acids and
salts of the present invention be relatively non-migratory (they do
not bloom to the surface of the polymer under ambient temperatures)
and non-volatile (they do not volatilize at temperatures required
for melt-blending.)
[0046] Other ingredients such as accelerators (for example, tetra
methylthiuram), processing aids, dyes and pigments, wetting agents,
surfactants, plasticizers, coloring agents, fluorescent agents,
chemical blowing and foaming agents, defoaming agents, stabilizers,
softening agents, impact modifiers, antioxidants, antiozonants, as
well as other additives known in the art may be added to the rubber
composition.
[0047] Other additives and fillers include, but are not limited to,
chemical blowing and foaming agents, optical brighteners, coloring
agents, fluorescent agents, whitening agents, UV absorbers, light
stabilizers, defoaming agents, processing aids, antioxidants,
stabilizers, softening agents, fragrance components, plasticizers,
impact modifiers, titanium dioxide pigment, acid copolymer wax,
surfactants, and fillers, such as zinc oxide, tin oxide, barium
sulfate, zinc sulfate, calcium oxide, calcium carbonate, zinc
carbonate, barium carbonate, tungsten, tungsten carbide, silica,
lead silicate, regrind (recycled material), clay, mica, talc,
nano-fillers, carbon black, glass flake, milled glass, and mixtures
thereof. Suitable additives are more fully described in, for
example, Rajagopalan et al., U.S. Patent Application Publication
No. 2003/0225197, the entire disclosure of which is hereby
incorporated herein by reference. In a particular embodiment, the
total amount of additive(s) and filler(s) present in the rubber
composition is 15 wt % or less, or 12 wt % or less, or 10 wt % or
less, or 9 wt % or less, or 6 wt % or less, or 5 wt % or less, or 4
wt % or less, or 3 wt % or less, based on the total weight of the
rubber composition.
[0048] Ethylene Acid Copolymers
[0049] Preferably, at least one of the core layers is formed from
an ionomer composition comprising an ethylene acid copolymer
containing acid groups that are at least partially neutralized. As
discussed further below, preferably, the neutralization level is
greater than 70%, more preferably at least 90% and even more
preferably at least 100%. Suitable ethylene acid copolymers that
may be used to form the compositions of this invention are
generally referred to as copolymers of ethylene; C.sub.3 to C.sub.8
.alpha., .beta.-ethylenically unsaturated mono- or dicarboxylic
acid; and optional softening monomer. Copolymers may include,
without limitation, ethylene acid copolymers, such as
ethylene/(meth)acrylic acid, ethylene/(meth)acrylic acid/maleic
anhydride, ethylene/(meth)acrylic acid/maleic acid mono-ester,
ethylene/maleic acid, ethylene/maleic acid mono-ester,
ethylene/(meth)acrylic acid/n-butyl (meth)acrylate,
ethylene/(meth)acrylic acid/iso-butyl (meth)acrylate,
ethylene/(meth)acrylic acid/methyl (meth)acrylate,
ethylene/(meth)acrylic acid/ethyl (meth)acrylate terpolymers, and
the like. The term, "copolymer," as used herein, includes polymers
having two types of monomers, those having three types of monomers,
and those having more than three types of monomers. Preferred
.alpha., .beta.-ethylenically unsaturated mono- or dicarboxylic
acids are (meth)acrylic acid, ethacrylic acid, maleic acid,
crotonic acid, fumaric acid, itaconic acid. (Meth)acrylic acid is
most preferred. As used herein, "(meth)acrylic acid" means
methacrylic acid and/or acrylic acid. Likewise, "(meth)acrylate"
means methacrylate and/or acrylate.
[0050] When a softening monomer is included, such copolymers are
referred to herein as E/X/Y-type copolymers, wherein E is ethylene;
X is a C.sub.3 to C.sub.8 .alpha., .beta.-ethylenically unsaturated
mono- or dicarboxylic acid; and Y is a softening monomer. The
softening monomer is typically an alkyl (meth)acrylate, wherein the
alkyl groups have from 1 to 8 carbon atoms. Preferred E/X/Y-type
copolymers are those wherein X is (meth)acrylic acid and/or Y is
selected from (meth)acrylate, n-butyl (meth)acrylate, isobutyl
(meth)acrylate, methyl (meth)acrylate, and ethyl (meth) acrylate.
More preferred E/X/Y-type copolymers are ethylene/(meth)acrylic
acid/n-butyl acrylate, ethylene/(meth)acrylic acid/methyl acrylate,
and ethylene/(meth)acrylic acid/ethyl acrylate.
[0051] The amount of ethylene in the acid copolymer is typically at
least 15 wt. %, preferably at least 25 wt. %, more preferably least
40 wt. %, and even more preferably at least 60 wt. %, based on
total weight of the copolymer. The amount of C.sub.3 to C.sub.8
.alpha., .beta.-ethylenically unsaturated mono- or dicarboxylic
acid in the acid copolymer is typically from 1 wt. % to 35 wt. %,
preferably from 5 wt. % to 30 wt. %, more preferably from 5 wt. %
to 25 wt. %, and even more preferably from 10 wt. % to 20 wt. %,
based on total weight of the copolymer. The amount of optional
softening comonomer in the acid copolymer is typically from 0 wt. %
to 50 wt. %, preferably from 5 wt. % to 40 wt. %, more preferably
from 10 wt. % to 35 wt. %, and even more preferably from 20 wt. %
to 30 wt. %, based on total weight of the copolymer. "Low acid" and
"high acid" ionomeric polymers, as well as blends of such ionomers,
may be used. In general, low acid ionomers are considered to be
those containing 16 wt. % or less of acid moieties, whereas high
acid ionomers are considered to be those containing greater than 16
wt. % of acid moieties.
[0052] The acidic groups in the copolymeric ionomers are partially
or totally neutralized with a cation source. Suitable cation
sources include metal cations and salts thereof, organic amine
compounds, ammonium, and combinations thereof. Preferred cation
sources are metal cations and salts thereof, wherein the metal is
preferably lithium, sodium, potassium, magnesium, calcium, barium,
lead, tin, zinc, aluminum, manganese, nickel, chromium, copper, or
a combination thereof. The metal cation salts provide the cations
capable of neutralizing (at varying levels) the carboxylic acids of
the ethylene acid copolymer and fatty acids, if present, as
discussed further below. These include, for example, the sulfate,
carbonate, acetate, oxide, or hydroxide salts of lithium, sodium,
potassium, magnesium, calcium, barium, lead, tin, zinc, aluminum,
manganese, nickel, chromium, copper, or a combination thereof.
Preferred metal cation salts are calcium and magnesium-based salts.
High surface area cation particles such as micro and nano-scale
cation particles are preferred. The amount of cation used in the
composition is readily determined based on desired level of
neutralization.
[0053] For example, ionomeric resins having acid groups that are
neutralized from about 10 percent to about 100 percent may be used.
In one ionomer composition, the acid groups are partially
neutralized. That is, the neutralization level is from about 10% to
about 70%, more preferably 20% to 60%, and most preferably 30 to
50%. These ionomer compositions, containing acid groups neutralized
to 70% or less, may be referred to ionomers having relatively low
neutralization levels.
[0054] On the other hand, the ionomer composition may contain acid
groups that are highly or fully-neutralized. These highly
neutralized polymers (HNPs) are preferred for forming at least one
core layer in the present invention. In these HNPs, the
neutralization level is greater than 70%, preferably at least 90%
and even more preferably at least 100%. In another embodiment, an
excess amount of neutralizing agent, that is, an amount greater
than the stoichiometric amount needed to neutralize the acid
groups, may be used. That is, the acid groups may be neutralized to
100% or greater, for example 110% or 120% or greater. In one
preferred embodiment, a high acid ethylene acid copolymer
containing about 19 to 20 wt. % methacrylic or acrylic acid is
neutralized with zinc and sodium cations to a 95% neutralization
level.
[0055] "Ionic plasticizers" such as organic acids or salts of
organic acids, particularly fatty acids, may be added to the
ionomer resin if needed. Such ionic plasticizers are used to make
conventional ionomer composition more processable as described in
Rajagopalan et al., U.S. Pat. No. 6,756,436, the disclosure of
which is hereby incorporated by reference. In one preferred
embodiment, the thermoplastic ionomer composition, containing acid
groups neutralized to 70% or less, does not include a fatty acid or
salt thereof, or any other ionic plasticizer. On the other hand,
the thermoplastic ionomer composition, containing acid groups
neutralized to greater than 70%, includes an ionic plasticizer,
particularly a fatty acid or salt thereof. For example, the ionic
plasticizer may be added in an amount of 0.5 to 10 pph, more
preferably 1 to 5 pph. The organic acids may be aliphatic, mono- or
multi-functional (saturated, unsaturated, or multi-unsaturated)
organic acids. Salts of these organic acids may also be employed.
Suitable fatty acid salts include, for example, metal stearates,
laureates, oleates, palmitates, pelargonates, and the like. For
example, fatty acid salts such as zinc stearate, calcium stearate,
magnesium stearate, barium stearate, and the like can be used. The
salts of fatty acids are generally fatty acids neutralized with
metal ions. The metal cation salts provide the cations capable of
neutralizing (at varying levels) the carboxylic acid groups of the
fatty acids. Examples include the sulfate, carbonate, acetate and
hydroxide salts of metals such as barium, lithium, sodium, zinc,
bismuth, chromium, cobalt, copper, potassium, strontium, titanium,
tungsten, magnesium, cesium, iron, nickel, silver, aluminum, tin,
or calcium, and blends thereof. It is preferred the organic acids
and salts be relatively non-migratory (they do not bloom to the
surface of the polymer under ambient temperatures) and non-volatile
(they do not volatilize at temperatures required for
melt-blending).
[0056] As noted above, the final ionomer compositions may contain
additional materials such as, for example, a small amount of ionic
plasticizer, which is particularly effective at improving the
processability of highly-neutralized ionomers. For example, the
ionic plasticizer may be added in an amount of 0.5 to 10 pph, more
preferably 1 to 5 pph. In addition to the fatty acids and salts of
fatty acids discussed above, other suitable ionic plasticizers
include, for example, polyethylene glycols, waxes, bis-stearamides,
minerals, and phthalates. In another embodiment, an amine or
pyridine compound is used, preferably in addition to a metal
cation. Suitable examples include, for example, ethylamine,
methylamine, diethylamine, tert-butylamine, dodecylamine, and the
like.
[0057] As discussed above, the ionomer compositions may contain a
wide variety of specific gravity fillers to adjust the specific
gravity of the composition as needed. High surface-area fillers
that have an affinity for the acid groups in ionomer may be used.
In particular, fillers such as particulate, fibers or flakes having
cationic nature such that they may also contribute to the
neutralization of the ionomer are suitable. For example, aluminum
oxide-containing fillers may be used. Also, silica, fumed silica,
or precipitated silica, such as those sold under the tradename
HISIL from PPG Industries, carbon black, and nano-scale materials
such as nanotubes, nanoflakes, nanofillers, or nanoclays may be
used.
[0058] Other additives and fillers include, but are not limited to,
chemical blowing and foaming agents, optical brighteners, coloring
agents, fluorescent agents, whitening agents, UV absorbers, light
stabilizers, defoaming agents, processing aids, antioxidants,
stabilizers, softening agents, fragrance components, plasticizers,
impact modifiers, TiO.sub.2, acid copolymer wax, surfactants, and
fillers, such as zinc oxide, tin oxide, barium sulfate, zinc
sulfate, calcium oxide, calcium carbonate, zinc carbonate, barium
carbonate, tungsten, tungsten carbide, silica, lead silicate,
regrind (recycled material), clay, mica, talc, nano-fillers, carbon
black, glass flake, milled glass, and mixtures thereof. Suitable
additives are more fully described in, for example, Rajagopalan et
al., U.S. Patent Application Publication No. 2003/0225197, the
entire disclosure of which is hereby incorporated herein by
reference. In a particular embodiment, the total amount of
additive(s) and filler(s) present in the final thermoplastic
ionomeric composition is 15 wt % or less, or 12 wt % or less, or 10
wt % or less, or 9 wt % or less, or 6 wt % or less, or 5 wt % or
less, or 4 wt % or less, or 3 wt % or less, based on the total
weight of the ionomeric composition.
[0059] In another version, the ionomer compositions may contain
carbon fibers or carbon fiber sheets comprising a weave of thin
carbon fibers held together in a resin. In yet another version, the
ionomer compositions may contain forged composite material composed
of bundles of microscopic carbon fibers held together in a resin.
These turbostratic carbon fibers are randomly dispersed in the
resin. The structure of the forged composite material differs over
traditional carbon fiber sheets. The forged composite material
contains discontinuous fibers intertwined in the resin; while
ordinary carbon fiber sheets are woven--they contain a weave of
fibers. As a result, the forged composite material is very
lightweight and has high mechanical strength.
[0060] Other suitable thermoplastic polymers that may be included
in the rubber or ethylene acid copolymer ionomer compositions of
this invention include, but are not limited to, the following
polymers (including homopolymers, copolymers, and derivatives
thereof.)
[0061] (a) polyesters, particularly those modified with a
compatibilizing group such as sulfonate or phosphonate, including
modified poly(ethylene terephthalate), modified poly(butylene
terephthalate), modified poly(propylene terephthalate), modified
poly(trimethylene terephthalate), modified poly(ethylene
naphthenate), and those disclosed in U.S. Pat. Nos. 6,353,050,
6,274,298, and 6,001,930, the entire disclosures of which are
hereby incorporated herein by reference, and blends of two or more
thereof;
[0062] (b) polyamides, polyamide-ethers, and polyamide-esters, and
those disclosed in U.S. Pat. Nos. 6,187,864, 6,001,930, and
5,981,654, the entire disclosures of which are hereby incorporated
herein by reference, and blends of two or more thereof;
[0063] (c) polyurethanes, polyureas, polyurethane-polyurea hybrids,
and blends of two or more thereof;
[0064] (d) fluoropolymers, such as those disclosed in U.S. Pat.
Nos. 5,691,066, 6,747,110 and 7,009,002, the entire disclosures of
which are hereby incorporated herein by reference, and blends of
two or more thereof;
[0065] (e) polystyrenes, such as poly(styrene-co-maleic anhydride),
acrylonitrile-butadiene-styrene, poly(styrene sulfonate),
polyethylene styrene, and blends of two or more thereof;
[0066] (f) polyvinyl chlorides and grafted polyvinyl chlorides, and
blends of two or more thereof;
[0067] (g) polycarbonates, blends of
polycarbonate/acrylonitrile-butadiene-styrene, blends of
polycarbonate/polyurethane, blends of polycarbonate/polyester, and
blends of two or more thereof;
[0068] (h) polyethers, such as polyarylene ethers, polyphenylene
oxides, block copolymers of alkenyl aromatics with vinyl aromatics
and polyamicesters, and blends of two or more thereof;
[0069] (i) polyimides, polyetherketones, polyamideimides, and
blends of two or more thereof; and
[0070] (j) polycarbonate/polyester copolymers and blends.
[0071] It also is recognized that the ionomer compositions may
contain a blend of two or more ionomers. For example, the
composition may contain a 50/50 wt. % blend of two different
highly-neutralized ethylene/methacrylic acid copolymers. In another
version, the composition may contain a blend of one or more
ionomers and a maleic anhydride-grafted non-ionomeric polymer. The
non-ionomeric polymer may be a metallocene-catalyzed polymer. In
another version, the composition contains a blend of a
highly-neutralized ethylene/methacrylic acid copolymer and a maleic
anhydride-grafted metallocene-catalyzed polyethylene. In yet
another version, the composition contains a material selected from
the group consisting of highly-neutralized ionomers optionally
blended with a maleic anhydride-grafted non-ionomeric polymer;
polyester elastomers; polyamide elastomers; and combinations of two
or more thereof.
[0072] Cover Structure
[0073] The golf ball cores of this invention may be enclosed with
one or more cover layers. A wide variety of materials may be used
for forming the outer cover including, for example, polyurethanes;
polyureas; copolymers, blends and hybrids of polyurethane and
polyurea; ethylene acid copolymer ionomer resins (for example,
Surlyn.RTM. ionomer resins and HPF.RTM. 1000 and HPF.RTM. 2000,
commercially available from DuPont; Iotek.RTM. ionomers,
commercially available from ExxonMobil Chemical Company;
Amplify.RTM. IO ionomers of ethylene acrylic acid copolymers,
commercially available from The Dow Chemical Company; and
Clarix.RTM. ionomer resins, commercially available from A. Schulman
Inc.); polyethylene, including, for example, low density
polyethylene, linear low density polyethylene, and high density
polyethylene; polypropylene; rubber-toughened olefin polymers; acid
copolymers, for example, poly(meth)acrylic acid, which do not
become part of an ionomeric copolymer; plastomers; flexomers;
styrene/butadiene/styrene block copolymers;
styrene/ethylene-butylene/styrene block copolymers; dynamically
vulcanized elastomers; copolymers of ethylene and vinyl acetates;
copolymers of ethylene and methyl acrylates; polyvinyl chloride
resins; polyamides, poly(amide-ester) elastomers, and graft
copolymers of ionomer and polyamide including, for example,
Pebax.RTM. thermoplastic polyether block amides, commercially
available from Arkema Inc; cross-linked trans-polyisoprene and
blends thereof; polyester-based thermoplastic elastomers, such as
Hytrel.RTM., commercially available from DuPont; polyurethane-based
thermoplastic elastomers, such as Elastollan.RTM., commercially
available from BASF; synthetic or natural vulcanized rubber; and
combinations thereof. Castable polyurethanes, polyureas, and
hybrids of polyurethanes-polyureas are particularly desirable
because these materials can be used to help make a golf ball having
high resiliency and a soft feel. By the term, "hybrids of
polyurethane and polyurea," it is meant to include copolymers and
blends thereof.
[0074] Polyurethanes, polyureas, and blends, copolymers, and
hybrids of polyurethane/polyurea are also particularly suitable for
forming cover layers. When used as cover layer materials,
polyurethanes and polyureas can be thermoset or thermoplastic.
Thermoset materials can be formed into golf ball layers by
conventional casting or reaction injection molding techniques.
Thermoplastic materials can be formed into golf ball layers by
conventional compression or injection molding techniques.
[0075] In one preferred embodiment, the ball includes a dual-cover
comprising inner and outer cover layers. The inner cover layer is
preferably formed from a composition comprising an ionomer or a
blend of two or more ionomers that helps impart hardness to the
ball. The inner cover layer preferably has a material hardness of
95 Shore C or less, or less than 95 Shore C, or 92 Shore C or less,
or 90 Shore C or less, or a material hardness within a range having
a lower limit of 60 or 65 or 70 or 75 or 80 or 84 or 85 Shore C and
an upper limit of 90 or 92 or 95 Shore C. The thickness of the
inner cover layer is preferably within a range having a lower limit
of 0.010 or 0.015 or 0.020 or 0.030 inches and an upper limit of
0.035 or 0.045 or 0.080 or 0.120 inches. The outer cover layer
preferably has a material hardness of 85 Shore C or less. The
thickness of the outer cover layer is preferably within a range
having a lower limit of 0.010 or 0.015 or 0.025 inches and an upper
limit of 0.035 or 0.040 or 0.055 or 0.080 inches.
[0076] In a particular embodiment, the inner cover layer is formed
from a composition comprising a high acid ionomer. A particularly
suitable high acid ionomer is Surlyn 8150.RTM. (DuPont). Surlyn
8150.RTM. is a copolymer of ethylene and methacrylic acid, having
an acid content of 19 wt %, which is 45% neutralized with sodium.
In another particular embodiment, the inner cover layer is framed
from a composition comprising a high acid ionomer and a maleic
anhydride-grafted non-ionomeric polymer. A particularly suitable
maleic anhydride-grafted polymer is Fusabond 525D.RTM. (DuPont),
which is a maleic anhydride-grafted, metallocene-catalyzed
ethylene-butene copolymer having about 0.9 wt % maleic anhydride
grafted onto the copolymer. A particularly preferred blend of high
acid ionomer and maleic anhydride-grafted polymer is a 84 wt %/16
wt % blend of Surlyn 8150.RTM. and Fusabond 525D.RTM.. Blends of
high acid ionomers with maleic anhydride-grafted polymers are
further disclosed, for example, in U.S. Pat. Nos. 6,992,135 and
6,677,401, the entire disclosures of which are hereby incorporated
herein by reference.
[0077] In one embodiment, the inner cover layer is formed from a
composition comprising a 50/45/5 blend of Surlyn.RTM.
8940/Surlyn.RTM. 9650/Nucrel.RTM. 960, and, in a particularly
preferred embodiment, has a material hardness of from 80 to 85
Shore C. In another particular embodiment, the inner cover layer is
formed from a composition comprising a 50/25/25 blend of
Surlyn.RTM. 8940/Surlyn.RTM. 9650/Surlyn.RTM. 9910, preferably
having a material hardness of about 90 Shore C. In another version,
a blend of 50% Surlyn.RTM. 7940 and 50% Surlyn.RTM. 8940 is used to
form the inner cover. In yet another particular embodiment, the
inner cover layer is preferably formed from a composition
comprising a 50/50 blend of Surlyn.RTM. 8940/Surlyn.RTM. 9650,
preferably having a material hardness of about 86 Shore C.
Surlyn.RTM. 8940 is an ethylene/methacrylic acid copolymer in which
the MAA acid groups have been partially neutralized with sodium
ions. Surlyn.RTM. 9650 and Surlyn.RTM. 9910 are two different
grades of ethylene/methacrylic acid copolymer in which the MAA acid
groups have been partially neutralized with zinc ions. Surlyn.RTM.
7940 is a copolymer of about 85% ethylene and 15% methacrylic acid
that has been neutralized with lithium ions. Nucrel.RTM. 960 is an
ethylene/methacrylic acid copolymer resin nominally made with 15 wt
% methacrylic acid, and available from DuPont.
[0078] As discussed above, the dual-core of the golf ball may be
enclosed with a single-layered or multi-layered covers. In one
embodiment, a single-layered cover having a thickness in the range
of about 0.020 to about 0.090 inches, more preferably about 0.030
to about 0.070 inches, is formed. The cover has a hardness of about
Shore D 80 or less, more preferably 70 or less, and most preferably
about 60 or less. In another embodiment, a multi-layered cover
comprising inner and outer cover layers is formed, where the inner
cover layer has a thickness of about 0.01 inches to about 0.06
inches, more preferably about 0.015 inches to about 0.040 inches,
and most preferably about 0.02 inches to about 0.035 inches. In
this version, the inner cover layer is formed from a partially- or
fully-neutralized ionomer having a Shore D hardness of greater than
about 55, more preferably greater than about 60, and most
preferably greater than about 65. The outer cover layer, in this
embodiment, preferably has a thickness of about 0.015 inches to
about 0.055 inches, more preferably about 0.02 inches to about 0.04
inches, and most preferably about 0.025 inches to about 0.035
inches, with a hardness of about Shore D 80 or less, more
preferably 70 or less, and most preferably about 60 or less. The
inner cover layer is harder than the outer cover layer in this
version. A preferred outer cover layer is a castable or reaction
injection molded polyurethane, polyurea or copolymer, blend, or
hybrid thereof having a Shore D hardness of about 40 to about 50.
In another multi-layer cover, dual-core embodiment, the outer cover
and inner cover layer materials and thickness are the same but, the
hardness range is reversed, that is, the outer cover layer is
harder than the inner cover layer.
[0079] Manufacturing Methods
[0080] As discussed above, the rubber and ionomer compositions of
this invention may be molded to form a multi-layered core that can
be used in a variety of ball constructions including, for example,
three-piece, four-piece, and five-piece ball designs. For instance,
a four-piece ball is shown in FIG. 1, wherein the ball (12)
contains a multi-layered core (14) having an inner core (center)
(14a); intermediate core layer (14b); and outer core layer (14c)
surrounded by a single-layered cover (16). In FIG. 2, the golf ball
(18) contains a dual-core (20) having an inner core (center) (20a)
and outer core layer (20b), and there is no intermediate core layer
present. The dual-core is surrounded by a single-layered cover
(22). As discussed above, it is preferred that at least one of the
core layers is formed from a rubber composition, and at least one
of the core layers is formed from a HNP composition comprising an
ethylene acid copolymer containing acid groups such that greater
than 70% of the acid groups are neutralized. In one particularly
preferred version, the inner core is formed from a rubber
composition; the intermediate core is formed from the HNP
composition; and the outer core is formed from a rubber
composition. In an alternative version, a rubber composition is
used to form each core layer.
[0081] The surfaces of the golf balls shown in FIGS. 1-2 may have
various dimple patterns to modify the aerodynamic properties of the
ball. It should be understood the golf balls shown in FIGS. 1-2 are
for illustrative purposes only and not meant to be restrictive.
Other golf ball constructions can be made in accordance with this
invention. For example, the golf ball may contain a multi-layered
cover, particularly a relatively hard inner cover surround by a
softer outer cover. The golf balls of this invention may further
contain an intermediate layer(s) that is formulated to have
specific properties such as layer that helps prevent moisture vapor
from penetrating into the core.
[0082] The core and cover compositions may be prepared using
conventional mixing techniques. The core composition can be formed
into an inner core structure by ordinary techniques such as, for
example, injection or compression molding. After molding, the core
structure is removed from the mold and its surface may be treated
using techniques such as corona discharge, sand blasting, or
grinding to improve adhesion of the surrounding core layers.
Injection molding or compression molding can be used to form
intermediate and outer core layers to produce an intermediate golf
ball. The cover layer(s) is subsequently molded over the core to
produce a final golf ball.
[0083] In compression molding, the outer core and/or inner cover
composition is formed into smooth surfaced hemispherical shells
which are then positioned around the inner core in a mold having
the desired inner cover thickness and subjected to compression
molding under heat followed by cooling. This process fuses the
shells together to form a unitary intermediate ball. Alternatively,
the intermediate balls may be produced by injection molding,
wherein the outer core and/or inner cover layer is injected
directly around the core placed at the center of an intermediate
ball mold under heat and pressure. After molding, the golf balls
produced may undergo various further processing steps such as
buffing, painting and marking using conventional techniques.
[0084] Test Methods
[0085] Hardness.
[0086] The center hardness of a core is obtained according to the
following procedure. The core is gently pressed into a
hemispherical holder having an internal diameter approximately
slightly smaller than the diameter of the core, such that the core
is held in place in the hemispherical portion of the holder while
concurrently leaving the geometric central plane of the core
exposed. The core is secured in the holder by friction, such that
it will not move during the cutting and grinding steps, but the
friction is not so excessive that distortion of the natural shape
of the core would result. The core is secured such that the parting
line of the core is roughly parallel to the top of the holder. The
diameter of the core is measured 90 degrees to this orientation
prior to securing. A measurement is also made from the bottom of
the holder to the top of the core to provide a reference point for
future calculations. A rough cut is made slightly above the exposed
geometric center of the core using a band saw or other appropriate
cutting tool, making sure that the core does not move in the holder
during this step. The remainder of the core, still in the holder,
is secured to the base plate of a surface grinding machine. The
exposed `rough` surface is ground to a smooth, flat surface,
revealing the geometric center of the core, which can be verified
by measuring the height from the bottom of the holder to the
exposed surface of the core, making sure that exactly half of the
original height of the core, as measured above, has been removed to
within 0.004 inches. Leaving the core in the holder, the center of
the core is found with a center square and carefully marked and the
hardness is measured at the center mark according to ASTM D-2240.
Additional hardness measurements at any distance from the center of
the core can then be made by drawing a line radially outward from
the center mark, and measuring the hardness at any given distance
along the line, typically in 2 mm increments from the center. The
hardness at a particular distance from the center should be
measured along at least two, preferably four, radial aims located
180.degree. apart, or 90.degree. apart, respectively, and then
averaged. All hardness measurements performed on a plane passing
through the geometric center are performed while the core is still
in the holder and without having disturbed its orientation, such
that the test surface is constantly parallel to the bottom of the
holder, and thus also parallel to the properly aligned foot of the
durometer.
[0087] The outer surface hardness of a golf ball layer is measured
on the actual outer surface of the layer and is obtained from the
average of a number of measurements taken from opposing
hemispheres, taking care to avoid making measurements on the
parting line of the core or on surface defects, such as holes or
protrusions. Hardness measurements are made pursuant to ASTM D-2240
"Indentation Hardness of Rubber and Plastic by Means of a
Durometer." Because of the curved surface, care must be taken to
ensure that the golf ball or golf ball subassembly is centered
under the durometer indenter before a surface hardness reading is
obtained. A calibrated, digital durometer, capable of reading to
0.1 hardness units is used for the hardness measurements. The
digital durometer must be attached to, and its foot made parallel
to, the base of an automatic stand. The weight on the durometer and
attack rate conforms to ASTM D-2240.
[0088] In certain embodiments, a point or plurality of points
measured along the "positive" or "negative" gradients may be above
or below a line fit through the gradient and its outermost and
innermost hardness values. In an alternative preferred embodiment,
the hardest point along a particular steep "positive" or "negative"
gradient may be higher than the value at the innermost portion of
the inner core (the geometric center) or outer core layer (the
inner surface)--as long as the outermost point (i.e., the outer
surface of the inner core) is greater than (for "positive") or
lower than (for "negative") the innermost point (i.e., the
geometric center of the inner core or the inner surface of the
outer core layer), such that the "positive" and "negative"
gradients remain intact.
[0089] As discussed above, the direction of the hardness gradient
of a golf ball layer is defined by the difference in hardness
measurements taken at the outer and inner surfaces of a particular
layer. The center hardness of an inner core and hardness of the
outer surface of an inner core in a single-core ball or outer core
layer are readily determined according to the test procedures
provided above. The outer surface of the inner core layer (or other
optional intermediate core layers) in a dual-core ball are also
readily determined according to the procedures given herein for
measuring the outer surface hardness of a golf ball layer, if the
measurement is made prior to surrounding the layer with an
additional core layer. Once an additional core layer surrounds a
layer of interest, the hardness of the inner and outer surfaces of
any inner or intermediate layers can be difficult to determine.
Therefore, for purposes of the present invention, when the hardness
of the inner or outer surface of a core layer is needed after the
inner layer has been surrounded with another core layer, the test
procedure described above for measuring a point located 1 mm from
an interface is used.
[0090] Also, it should be understood that there is a fundamental
difference between "material hardness" and "hardness as measured
directly on a golf ball." For purposes of the present invention,
material hardness is measured according to ASTM D2240 and generally
involves measuring the hardness of a flat "slab" or "button" formed
of the material. Surface hardness as measured directly on a golf
ball (or other spherical surface) typically results in a different
hardness value. The difference in "surface hardness" and "material
hardness" values is due to several factors including, but not
limited to, ball construction (that is, core type, number of cores
and/or cover layers, and the like); ball (or sphere) diameter; and
the material composition of adjacent layers. It also should be
understood that the two measurement techniques are not linearly
related and, therefore, one hardness value cannot easily be
correlated to the other. Shore hardness (for example, Shore C or
Shore D hardness) was measured according to the test method ASTM
D-2240.
[0091] Compression.
[0092] As disclosed in Jeff Dalton's Compression by Any Other Name,
Science and Golf IV, Proceedings of the World Scientific Congress
of Golf (Eric Thain ed., Routledge, 2002) ("J. Dalton"), several
different methods can be used to measure compression, including
Atti compression, Riehle compression, load/deflection measurements
at a variety of fixed loads and offsets, and effective modulus. For
purposes of the present invention, "compression" refers to Atti
compression and is measured according to a known procedure, using
an Atti compression test device, wherein a piston is used to
compress a ball against a spring. The travel of the piston is fixed
and the deflection of the spring is measured. The measurement of
the deflection of the spring does not begin with its contact with
the ball; rather, there is an offset of approximately the first
1.25 mm (0.05 inches) of the spring's deflection. Very low
stiffness cores will not cause the spring to deflect by more than
1.25 mm and therefore have a zero compression measurement. The Atti
compression tester is designed to measure objects having a diameter
of 42.7 mm (1.68 inches); thus, smaller objects, such as golf ball
cores, must be shimmed to a total height of 42.7 mm to obtain an
accurate reading. Conversion from Atti compression to Riehle
(cores), Riehle (balls), 100 kg deflection, 130-10 kg deflection or
effective modulus can be carried out according to the formulas
given in J. Dalton. Compression may be measured as described in
McNamara et al., U.S. Pat. No. 7,777,871, the disclosure of which
is hereby incorporated by reference.
[0093] Coefficient of Restitution ("COR").
[0094] The COR is determined according to a known procedure,
wherein a golf ball or golf ball subassembly (for example, a golf
ball core) is fired from an air cannon at two given velocities and
a velocity of 125 ft/s is used for the calculations. Ballistic
light screens are located between the air cannon and steel plate at
a fixed distance to measure ball velocity. As the ball travels
toward the steel plate, it activates each light screen and the
ball's time period at each light screen is measured. This provides
an incoming transit time period which is inversely proportional to
the ball's incoming velocity. The ball makes impact with the steel
plate and rebounds so it passes again through the light screens. As
the rebounding ball activates each light screen, the ball's time
period at each screen is measured. This provides an outgoing
transit time period which is inversely proportional to the ball's
outgoing velocity. The COR is then calculated as the ratio of the
ball's outgoing transit time period to the ball's incoming transit
time period (COR=V.sub.out/V.sub.in=T.sub.in/T.sub.out).
[0095] When numerical lower limits and numerical upper limits are
set forth herein, it is contemplated that any combination of these
values may be used. Other than in the operating examples, or unless
otherwise expressly specified, all of the numerical ranges,
amounts, values and percentages such as those for amounts of
materials and others in the specification may be read as if
prefaced by the word "about" even though the term "about" may not
expressly appear with the value, amount or range. Accordingly,
unless indicated to the contrary, the numerical parameters set
forth in the specification and attached claims are approximations
that may vary depending upon the desired properties sought to be
obtained by the present invention.
[0096] All patents, publications, test procedures, and other
references cited herein, including priority documents, are fully
incorporated by reference to the extent such disclosure is not
inconsistent with this invention and for all jurisdictions in which
such incorporation is permitted.
[0097] It is understood that the compositions and golf ball
products described and illustrated herein represent only some
embodiments of the invention. It is appreciated by those skilled in
the art that various changes and additions can be made to
compositions and products without departing from the spirit and
scope of this invention. It is intended that all such embodiments
be covered by the appended claims.
* * * * *