U.S. patent application number 14/495925 was filed with the patent office on 2015-01-08 for golf ball cores based on polyalkenamer rubber having positive hardness gradients.
This patent application is currently assigned to ACUSHNET COMPANY. The applicant listed for this patent is Acushnet Company. Invention is credited to Mark L. Binette, Robert Blink, David A. Bulpett, Brian Comeau, Douglas S. Goguen, Michael J. Sullivan.
Application Number | 20150011337 14/495925 |
Document ID | / |
Family ID | 43354833 |
Filed Date | 2015-01-08 |
United States Patent
Application |
20150011337 |
Kind Code |
A1 |
Comeau; Brian ; et
al. |
January 8, 2015 |
GOLF BALL CORES BASED ON POLYALKENAMER RUBBER HAVING POSITIVE
HARDNESS GRADIENTS
Abstract
Golf balls having a core comprising a polyalkenamer rubber
composition are provided. The rubber composition may further
include other rubbers such as, for example, polybutadiene,
polyisoprene, ethylene propylene rubber, ethylene propylene diene
rubber, and styrene-butadiene rubber. The rubber composition helps
improve resiliency of the core and provides the ball with a
comfortable and soft feel. In one version, a solid, single core
having an outer surface and geometric center is provided, wherein
the outer surface has a hardness greater than the hardness of the
geometric center to define a positive hardness gradient of at least
10 Shore C. In a second version, a dual-core having an inner core
and surrounding outer core layer is provided. The inner core has a
positive hardness gradient, while the outer core has a zero;
negative; or positive hardness gradient.
Inventors: |
Comeau; Brian; (Berkley,
MA) ; Bulpett; David A.; (Boston, MA) ;
Sullivan; Michael J.; (Old Lyme, CT) ; Blink;
Robert; (Newport, RI) ; Goguen; Douglas S.;
(New Bedford, MA) ; Binette; Mark L.;
(Mattapoisett, MA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Acushnet Company |
Fairhaven |
MA |
US |
|
|
Assignee: |
ACUSHNET COMPANY
Fairhaven
MA
|
Family ID: |
43354833 |
Appl. No.: |
14/495925 |
Filed: |
September 25, 2014 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
12855319 |
Aug 12, 2010 |
8845457 |
|
|
14495925 |
|
|
|
|
12047982 |
Mar 13, 2008 |
|
|
|
12855319 |
|
|
|
|
11767070 |
Jun 22, 2007 |
|
|
|
12047982 |
|
|
|
|
10773906 |
Feb 6, 2004 |
7255656 |
|
|
11767070 |
|
|
|
|
10341574 |
Jan 13, 2003 |
6852044 |
|
|
10773906 |
|
|
|
|
10002641 |
Nov 28, 2001 |
6547677 |
|
|
10341574 |
|
|
|
|
Current U.S.
Class: |
473/376 |
Current CPC
Class: |
A63B 37/0064 20130101;
A63B 37/0062 20130101; A63B 37/02 20130101; C08K 5/14 20130101;
A63B 37/0066 20130101; C08K 5/0025 20130101; A63B 37/0051 20130101;
A63B 37/06 20130101; A63B 37/0075 20130101; C08K 5/098 20130101;
A63B 37/0003 20130101; A63B 37/0063 20130101 |
Class at
Publication: |
473/376 |
International
Class: |
A63B 37/00 20060101
A63B037/00 |
Claims
1. A golf ball, comprising: a dual-core comprising an inner core
and outer core layer, wherein the outer core layer surrounds the
inner core, the inner core having a first outer surface and a
geometric center, the inner core being formed from a first rubber
composition, the first rubber composition comprising a cycloalkene
rubber having a trans-content of 55% or greater and a melting point
of 30.degree. C. or greater in an amount of at least 50 weight
percent, wherein the first outer surface and geometric center each
has a hardness, the hardness of the first outer surface being
greater than the hardness of the geometric center to define a
positive hardness gradient of at least 10 Shore C units; the outer
core layer having a second outer surface and an inner surface, the
outer core layer being formed from a second rubber composition,
wherein the second outer surface and inner surface each has a
hardness, the hardness of the second outer surface being in the
range of 50 to 85 Shore C units and the hardness of the inner
surface being in the range of 51 to 86 Shore C units, the hardness
of the second outer surface being the same or less than the
hardness of the inner surface to define a zero or negative hardness
gradient; and a cover layer surrounding the outer core layer.
2. The golf ball of claim 1, wherein the cycloalkene rubber has a
trans-content of 75% or greater and a melting point of 50.degree.
C. or greater.
3. The golf ball of claim 1, wherein the rubber composition
comprises the cycloalkene rubber in an amount in the range of about
60 to about 100 weight percent based on weight of polymer.
4. The golf ball of claim 1, wherein the rubber composition
comprises peroxide in an amount of 2.5 phr or greater based on
weight of the cycloalkene rubber.
5. The golf ball of claim 1, wherein the overall diameter of the
dual-core is from 1.51 to 1.59 inches.
6. The golf ball of claim 1, wherein the hardness of the second
outer surface is 65 to 76 Shore C units and the hardness of the
inner surface is 67 to 82 Shore C units.
7. The golf ball of claim 1, wherein the outer core layer has a
zero hardness gradient.
8. The golf ball of claim 1, wherein the outer core layer has a
negative hardness gradient in the range of -1 to -20 Shore C
units.
9. The golf ball of claim 8, wherein the negative hardness gradient
is in the range of -6 to -15 Shore C units.
10. The golf ball of claim 8, wherein the negative hardness
gradient is in the range of -8 to -12 Shore C units.
11. The golf ball of claim 1, wherein the cover layer comprises an
inner cover layer and an outer cover layer.
12. The golf ball of claim 11, wherein the outer cover layer has a
material hardness less than the inner cover layer.
13. A golf ball, comprising: a dual-core comprising an inner core
and outer core layer, wherein the outer core layer surrounds the
inner core, the inner core having a first outer surface and a
geometric center, the inner core being formed from a first rubber
composition, the first rubber composition comprising a cycloalkene
rubber having a trans-content of 55% or greater and a melting point
of 30.degree. C. or greater in an amount of at least 50 weight
percent, wherein the first outer surface and geometric center each
has a hardness, the hardness of the first outer surface being
greater than the hardness of the geometric center to define a
positive hardness gradient of at least 10 Shore C units; the outer
core layer having a second outer surface and an inner surface, the
outer core layer being formed from a second rubber composition,
wherein the outer core layer and inner surface each has a hardness,
the hardness of the second outer surface being in the range of 51
to 86 Shore C units and the hardness of the inner surface being in
the range of 50 to 85 Shore C units, the hardness of the second
outer surface being greater than the hardness of the inner surface
to define a second positive hardness gradient; and a cover layer
surrounding the outer core layer.
14. The golf ball of claim 13, wherein the cycloalkene rubber has a
trans-content of 75% or greater and a melting point of 50.degree.
C. or greater.
15. The golf ball of claim 13, wherein the rubber composition
comprises the cycloalkene rubber in an amount in the range of about
60 to about 100 weight percent based on weight of polymer.
16. The golf ball of claim 13, wherein the rubber composition
comprises peroxide in an amount of 2.5 phr or greater based on
weight of the cycloalkene rubber.
17. The golf ball of claim 13, wherein the cover layer comprises an
inner cover layer and an outer cover layer.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional of co-pending, co-assigned
U.S. patent application Ser. No. 12/855,319, filed Aug. 12, 2010,
now allowed, which is a continuation-in-part of co-pending,
co-assigned U.S. patent application Ser. No. 12/047,982, filed Mar.
13, 2008, which is a continuation-in-part of U.S. patent
application Ser. No. 11/767,070, filed Jun. 22, 2007, now
abandoned, which is a continuation-in-part of U.S. patent
application Ser. No. 10/773,906, filed Feb. 6, 2004, now U.S. Pat.
No. 7,255,656, which is a continuation-in-part of U.S. patent
application Ser. No. 10/341,574, filed Jan. 13, 2003, now U.S. Pat.
No. 6,852,044, which is a continuation-in-part of U.S. patent
application Ser. No. 10/002,641, filed Nov. 28, 2001, now U.S. Pat.
No. 6,547,677, the entire disclosures of which are hereby
incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention generally relates to golf balls and
more particularly to golf balls having single-layer and dual-layer
cores. The golf ball includes a cover that may be single or
multi-layered. In one version, the single-layer core has a positive
hardness gradient. In another version, the dual-layer core has an
inner core with a positive hardness gradient and a surrounding
outer core layer with a zero, positive, or negative gradient.
Preferably, the cores are made of a rubber composition comprising
cylcoalkene (polyalkenamer) rubber and more preferably
polyoctenamer rubber.
[0004] 2. Brief Review of the Related Art
[0005] Numerous golf balls having a multi-layer construction,
wherein the core hardness and cover hardness have been variously
improved, are disclosed in the prior art. For example, U.S. Pat.
No. 6,987,159 to Iwami discloses a solid golf ball with a solid
core and a polyurethane cover, wherein the difference in Shore D
hardness between a center portion and a surface portion of the
solid core is at least 15, the polyurethane cover has a thickness
(t) of not more than 1.0 mm and is formed from a cured urethane
composition having a Shore D hardness (D) of from 35 to 60, and a
product of t and D ranges from 10 to 45.
[0006] U.S. Pat. No. 7,175,542 to Watanabe et al. discloses a
multi-piece solid golf ball composed of a multilayer core having at
least an inner core layer and an outer core layer, one or more
cover layers which enclose the core, and numerous dimples formed on
a surface of the cover layer. The golf ball is characterized in
that the following hardness conditions are satisfied: (1) (JIS-C
hardness of cover)-(JIS-C hardness at center of core).gtoreq.27,
(2) 23.ltoreq.(JIS-C hardness at surface of core)-(JIS-C hardness
at center of core).ltoreq.40, and (3) 0.50.ltoreq.[(deflection
amount of entire core)/(deflection amount of inner core
layer)].ltoreq.0.75.
[0007] U.S. Pat. No. 6,679,791 to Watanabe discloses a multi-piece
golf ball which includes a rubbery elastic core, a cover having a
plurality of dimples on the surface thereof, and at least one
intermediate layer between the core and the cover. The intermediate
layer is composed of a resin material which is harder than the
cover. The elastic core has a hardness which gradually increases
radially outward from the center to the surface thereof. The center
and surface of the elastic core have a hardness difference of at
least 18 JIS-C hardness units.
[0008] U.S. Pat. No. 5,782,707 to Yamagishi et al. discloses a
three-piece solid golf ball consisting of a solid core, an
intermediate layer, and a cover, wherein the hardness is measured
by a JIS-C scale hardness meter, the core center hardness is up to
75 degrees, the core surface hardness is up to 85 degrees, the core
surface hardness is higher than the core center hardness by 8 to 20
degrees, the intermediate layer hardness is higher than the core
surface hardness by at least 5 degrees, and the cover hardness is
lower than the intermediate layer hardness by at least 5 degrees.
Additional examples can be found, for example, in U.S. Pat. No.
6,686,436 to Iwami, U.S. Pat. No. 6,786,836 to Higuchi et al., U.S.
Pat. No. 7,153,224 to Higuchi et al., and U.S. Pat. No. 7,226,367
to Higuchi et al.
[0009] The golf ball industry is constantly looking to develop
compositions that can be used in multi-piece golf balls. For
example, Kim et al., U.S. Pat. No. 7,528,196 and U.S. Patent
Application Publication US 2009/0191981 disclose a golf ball
comprising a core, cover layer, and optionally one or more inner
cover layers, wherein at least one portion of the ball comprises a
blend of a polyalkenamer and polyamide. The polyalkenamer/polyamide
composition contains about 2 to about 90 weight % of a
polyalkenamer polymer and about 10 to about 98 weight % of a
polyamide. The '196 Patent and '981 Published Application further
disclose that the polyalkenamer/polyamide composition may be
blended with other polymers including polybutadiene, polyisoprene,
polychloroprene, polybutylene, and styrene-butadiene rubber prior
to molding. However, neither the '196 Patent nor '981 Published
Application discloses a dual-core having an inner core and
surrounding outer core layer, wherein the inner core has a positive
hardness gradient, and the outer core layer has a zero; negative;
or positive hardness gradient and the inner core and/or outer core
is made of a polyalkenamer rubber composition.
[0010] In Voorheis et al., U.S. Pat. No. 6,767,940, a golf ball
having a core, an intermediate layer, and a cover is disclosed. The
core is formed from a composition containing an elastomeric
polymer, free-radical initiator, and at least one stable
free-radical. The stable free-radical increases the scorch time
(time between start of reaction and onset of cross-linking) of the
elastomeric polymer. The '940 Patent discloses numerous materials
that can be used to form the intermediate layer, which is
distinguishable from the core, including natural rubbers; balata;
gutta-percha; cis-polybutadienes; trans-polybutadienes; synthetic
polyisoprenes; polyoctenamers; polypropylene resins; ionomer
resins; polyamides; polyesters; urethanes; polyureas; chlorinated
polyethylenes; polysulfide rubbers; and fluorocarbons.
[0011] In Sullivan et al., U.S. Pat. Nos. 6,783,468, 7,041,009,
7,044,864, 7,118,495, and 7,125,345, a golf ball having a low
compression and high coefficient of restitution (COR) layer
supported and reinforced by a low deformation layer is disclosed.
The preferred polymeric composition for the high COR layer is a
base rubber compound, a co-reaction agent, a halogenated
organosulfur compound, and a co-cross-linking or initiator agent.
The low deformation layer may be made of rigid plastics or polymers
reinforced with high strength organic or inorganic fillers or
fibers. In one embodiment, the golf ball comprises an innermost
core, an outer core, and a cover. The inner core comprises a low
deformation material and the outer core comprises a rubber
composition. The patents disclose that natural rubbers, including
cis-polyisoprene, trans-polyisoprene or balata, synthetic rubbers
including 1,2-polybutadiene, cis-polybutadiene,
trans-polybutadiene, polychloroprene, poly(norbornene),
polyoctenamer and polypentenamer may be used for the outer core.
However, there is no disclosure of forming a dual-core, wherein the
inner core has a positive hardness gradient and the outer core
layer has a zero; negative; or positive hardness gradient, and the
inner core and/or outer core is made of a polyalkenamer rubber
composition.
[0012] In addition, Llort, U.S. Pat. No. 4,792,141 describes a
balata-covered golf ball, where up to 40% of the balata used to
form the cover has been replaced with polyoctenylene rubber. The
golf ball contains a core and a cover wherein the cover is formed
from a composition comprising about 97 to about 60 parts balata and
about 3 to about 40 parts by weight polyoctenylene rubber based on
100 parts by weight polymer in the composition. The '141 Patent
discloses that using more than about 40 parts by weight of
polyoctenylene produces deleterious effects.
[0013] One objective of the present invention is to develop
compositions that can be used to make a core for a golf ball,
wherein the core provides the ball with high resiliency along with
a comfortable and soft "feel." The present invention provides golf
ball core compositions having such properties as well as other
advantageous characteristics, features, and benefits.
SUMMARY OF THE INVENTION
[0014] In a particularly preferred embodiment, the core is made of
a rubber composition comprising a cycloalkene (polyalkenamer)
rubber, for example, a polyoctenamer, having a trans-content of 55%
or greater and a melting point of 30.degree. C. or greater in an
amount of at least 50 weight percent. The concentration of
cycloalkene rubber is preferably in the range of about 60 to about
100 weight percent based on weight of polymer in the composition.
The rubber composition may further include other rubbers such as,
for example, polybutadiene, polyisoprene, ethylene propylene
rubber, ethylene propylene diene rubber, and styrene-butadiene
rubber. The rubber composition helps improve core resiliency and
provides the ball with a comfortable and soft feel. The core may
have different constructions. In one version, a solid, single core
having an outer surface and geometric center is provided, wherein
the hardness of the outer surface is greater than the hardness of
the geometric center to define a positive hardness gradient of at
least 10 Shore C. In a second version, a dual-core having an inner
core and surrounding outer core layer is provided. The inner core
may be made of a polyalkenamer rubber composition and have a
positive hardness gradient. The outer core layer has a second outer
surface and an inner surface and also may be made of a
polyalkenamer rubber composition. In one example, the hardness of
the second outer surface is the same or less than the hardness of
the inner surface to define a zero or negative hardness gradient.
In another example, the hardness of the second outer surface is
greater than the hardness of the inner surface to define a second
positive hardness gradient.
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 front view of a dimpled golf ball made in
accordance with the present invention;
[0017] FIG. 2 is a cross-sectional view of a two-piece golf ball
having an inner core made of a polyalkenamer rubber composition and
a cover layer made of a polyurethane composition in accordance with
the present invention;
[0018] FIG. 3 is a cross-sectional view of a three-piece golf ball
having a dual-core comprising an inner core and outer core made of
polyalkenamer rubber compositions and a cover layer made of a
polyurethane composition in accordance with the present
invention;
[0019] FIG. 4 is a cross-sectional view of a four-piece golf ball
having a dual-core comprising an inner core and outer core made of
polyalkenamer rubber compositions; an inner cover layer made of an
ethylene-based acid ionomer; and an outer cover layer made of a
polyurethane composition in accordance with the present
invention;
[0020] FIG. 5 is a cross-sectional view of a five-piece golf ball
having a dual-core comprising an inner core and outer core made of
polyalkenamer rubber compositions made in accordance with the
present invention; and
[0021] FIG. 6 is a graph of the hardness values of different core
samples as measured at different points extending radially from the
center of the core.
DETAILED DESCRIPTION OF THE INVENTION
[0022] The present invention relates generally to golf balls
containing a core made from a rubber composition, wherein the
rubber composition comprises a cycloalkene (polyalkenamer) rubber,
preferably a polyoctenamer, having a trans-content of 55% or
greater and a melting point of 30.degree. C. or greater in an
amount of at least 50 weight percent. Golf balls having various
constructions may be made in accordance with this invention. For
example, golf balls having two-piece, three-piece, four-piece, and
five-piece constructions with single or multi-layered cores and
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
solid center (otherwise referred to as an inner core) and a
multi-layered cover (having an inner cover layer and outer cover
layer) is made. In another version, a four-piece golf ball
comprising a dual-core having an inner core and a surrounding outer
core layer and a multi-layered cover is made. In yet another
construction, a five-piece golf ball having a dual-core,
intermediate layer, and multi-layered cover is made. 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. The
core may contain sections having substantially the same hardness or
different hardness levels. That is, there can be substantially
uniform hardness throughout the different sections or there can be
hardness gradients as discussed in further detail below.
[0023] In one preferred golf ball, the core is a single-core
constituting a solid core having a "positive" hardness gradient
(that is, the outer surface of the core is harder than its
geometric center.) In a second preferred embodiment, the core is a
dual-core comprising an inner core and a surrounding outer core
layer. The inner core has a "positive" hardness gradient and the
outer core layer has 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.) Other embodiments of golf balls
having various combinations of positive, negative, and zero
hardness gradients may be made in accordance with this invention.
For example, the inner core may have a positive hardness gradient
and the outer core layer also may have a positive hardness
gradient. In another example, the inner core may have a positive
hardness gradient and 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.) Particularly, the term,
"zero hardness gradient" as used herein, means a surface to center
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 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 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 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 step positive hardness gradient of 35, 40, or 45
Shore C or greater. Methods for measuring the hardness of the inner
core and surrounding layers and determining the hardness gradients
are discussed in further detail below.
[0024] As mentioned above, in one embodiment, the golf ball has a
solid, single-core and a two-layered cover. When a single-layered
core is used, the core preferably has a diameter within a range
having a lower limit of 1.40 or 1.45 or 1.50 or 1.51 or 1.53 inches
and an upper limit of 1.55 or 1.59 or 1.60 or 1.62 or 1.66 inches,
and more preferably has a diameter within a range having a lower
limit of 1.51 or 1.53 inches and an upper range of 1.55 or 1.59
inches. In a particularly preferred embodiment, the core has a
diameter of about 1.53 inches. In a second embodiment, the golf
ball has a dual-core (that is, two-layer core) and a two-layered
(dual) cover enclosing the core. The dual-core constitutes an inner
core (center) and an outer core layer. The inner core has a
diameter within a range having a lower limit of 0.75 or 0.85 or
0.875 inches and an upper limit of 1.125 or 1.15 or 1.39 inches.
The outer core layer encloses the inner core such that the
two-layer core has an overall diameter within a range having a
lower limit of 1.40 or 1.50 or 1.51 or 1.52 or 1.525 inches and an
upper limit of 1.54 or 1.55 or 1.555 or 1.56 or 1.59 inches
[0025] When a single-layered core is used, the core preferably has
a center hardness of 70 Shore C or less, or 65 Shore C or less; or
a center hardness within a range having a lower limit of 30 or 40
or 45 Shore C and an upper limit of 70 or 75 or 80 Shore C; or a
center hardness of about 60 Shore C. The surface hardness of the
core is preferably greater than 70 Shore C, or 75 Shore C or
greater, or 80 Shore C or greater, or greater than 80 Shore C, or
85 Shore C or greater, or greater than 85 Shore C, or 87 Shore C or
greater, or 90 Shore C or greater. In a particular embodiment, the
surface hardness of the core is greater than the center hardness of
the core to define a positive hardness gradient and more preferably
the surface hardness of the core is at least 10 Shore C units
greater than the center hardness of the core. In a particularly
preferred embodiment, the core has a steep positive hardness
gradient wherein the surface hardness of the core is at least 20
Shore C units greater than the center hardness of the core.
[0026] When a dual-layered core is used, the inner core (center)
preferably has a geometric center hardness of 50 Shore C or
greater, or 55 Shore C or greater, or 60 Shore C or greater, or
within a range having a lower limit of 50 or 55 or 60 Shore C and
an upper limit of 65 or 70 or 80 Shore C. The inner core preferably
has a surface hardness of 65 Shore C or greater, or 70 Shore C or
greater, or within a range having a lower limit of 55 or 60 or 65
or 70 Shore C or 75 Shore C and an upper limit of 80 or 85 Shore C.
Meanwhile, the outer core layer preferably has an outer surface
hardness of 75 Shore C or greater, or 80 Shore C or greater, or 85
Shore C or greater, or 87 Shore C or greater, or 89 Shore C or
greater, or 90 Shore C or greater, or within a range having a lower
limit of 75 or 80 or 85 Shore C and an upper limit of 90 or 95
Shore C. And, the inner surface of the outer core preferably has a
surface hardness of 65 Shore C or greater, or 70 Shore C or
greater, or within a range having a lower limit of 55 or 60 or 65
or 70 Shore C or 75 Shore C and an upper limit of 80 or 85 Shore
C.
[0027] The cores have positive, negative, or zero hardness
gradients defined by hardness measurements made at the surface of
the inner core (or outer core layer) and radially inward towards
the center of the inner core. These measurements are made typically
at 2-mm increments as described in the test methods below. In
general, the hardness gradient is determined by subtracting the
hardness value at the innermost portion of the component being
measured (for example, the center of a single core; the center of
an inner core in a dual-core construction; the inner surface of the
outer core layer in a dual-core construction; and the like) from
the hardness value at the outer surface of the component being
measured (for example, the outer surface of a single core; the
outer surface of an inner core in a dual-core; the outer surface of
an outer core layer in a dual-core; and the like.) For example, if
the outer surface of a single core has a greater hardness value
than its geometric center (that is, the surface is harder than the
center), the hardness gradient will be deemed "positive" (a larger
number minus a smaller number equals a positive number.) On the
other hand, if the outer surface of a single core has a lower
hardness value than its geometric center (that is, the center is
harder than the surface), the hardness gradient will be deemed
"negative" (a smaller number minus a larger number equals a
negative number.)
[0028] In general, the cores of the golf balls may be formed from a
rubber composition or a highly resilient thermoplastic polymer such
as a highly neutralized polymer ("HNP") composition. Particularly
suitable thermoplastic polymers include Surlyn.RTM. ionomers,
Hytrel.RTM. thermoplastic polyester elastomers, and ionomeric
materials sold under the trade names DuPont.RTM. HPF 1000 and
DuPont.RTM. HPF 2000, all of which are commercially available from
E. I. du Pont de Nemours and Company; Iotek.RTM. ionomers,
commercially available from ExxonMobil Chemical Company; and
Pebax.RTM. thermoplastic polyether block amides, commercially
available from Arkema, Inc.
[0029] Suitable HNP compositions for use in forming the core
comprise an HNP and optionally additives, fillers, and/or melt flow
modifiers. Suitable HNPs are salts of homopolymers and copolymers
of .alpha.,.beta.-ethylenically unsaturated mono- or dicarboxylic
acids, and combinations thereof, optionally including a softening
monomer. The acid polymer is neutralized to 70% or higher,
including up to 100%, with a suitable cation source. Suitable
additives and fillers include, for example, blowing and foaming
agents, optical brighteners, coloring agents, fluorescent agents,
whitening agents, UV absorbers, light stabilizers, defoaming
agents, processing aids, mica, talc, nanofillers, antioxidants,
stabilizers, softening agents, fragrance components, plasticizers,
impact modifiers, acid copolymer wax, surfactants; inorganic
fillers, such as zinc oxide, titanium dioxide, tin oxide, calcium
oxide, magnesium oxide, barium sulfate, zinc sulfate, calcium
carbonate, zinc carbonate, barium carbonate, mica, talc, clay,
silica, lead silicate, and the like; high specific gravity metal
powder fillers, such as tungsten powder, molybdenum powder, and the
like; regrind, i.e., core material that is ground and recycled; and
nano-fillers. Suitable melt flow modifiers include, for example,
fatty acids and salts thereof, polyamides, polyesters,
polyacrylates, polyurethanes, polyethers, polyureas, polyhydric
alcohols, and combinations thereof. Suitable HNP compositions also
include blends of HNPs with partially neutralized ionomers as
disclosed, for example, in U.S. Patent Application Publication No.
2006/0128904, the entire disclosure of which is hereby incorporated
herein by reference, and blends of HNPs with additional
thermoplastic and thermoset materials, including, but not limited
to, ionomers, acid copolymers, engineering thermoplastics, fatty
acid/salt-based highly neutralized polymers, polybutadienes,
polyurethanes, polyesters, thermoplastic elastomers, and other
conventional polymeric materials. Particularly suitable as a core
layer material is DuPont.RTM. HPF 1000, commercially available from
E. I. du Pont de Nemours and Company. Suitable HNP compositions are
further disclosed, for example, in U.S. Pat. Nos. 6,653,382,
6,756,436, 6,777,472, 6,894,098, 6,919,393, and 6,953,820, the
entire disclosures of which are hereby incorporated herein by
reference.
[0030] Suitable rubber compositions for use in forming the core
comprise a base rubber, a cross-linking agent, a filler, and a
co-cross-linking or initiator agent. Typical base rubber materials
include natural and synthetic rubbers, and combinations of two or
more thereof. The base rubber is preferably polybutadiene or a
mixture of polybutadiene with other elastomers. Particularly
preferred is 1,4-polybutadiene having a cis-structure of at least
40%. More preferably, the base rubber is a high-Mooney-viscosity
rubber. Lesser amounts of other thermoset materials may be
incorporated into the base rubber. Such materials include, for
example, cis-polyisoprene, trans-polyisoprene, balata,
polychloroprene, polynorbornene, polyoctenamer, polypentenamer,
butyl rubber, EPR, EPDM, styrene-butadiene, and similar thermoset
materials. The cross-linking agent typically includes a metal salt,
such as a zinc-, aluminum-, sodium-, lithium-, nickel-, calcium-,
or magnesium-salt, of an unsaturated fatty acid or monocarboxylic
acid, such as (meth)acrylic acid. Preferred cross-linking agents
include zinc acrylate, zinc diacrylate (ZDA), zinc methacrylate,
and zinc dimethacrylate (ZDMA), and mixtures thereof. The
cross-linking agent must be present in an amount sufficient to
crosslink a portion of the chains of the polymers in the resilient
polymer component. The cross-linking agent is generally present in
the rubber composition in an amount of from 15 to 30 phr, or from
19 to 25 phr, or from 20 to 24 phr. The desired compression may be
obtained by adjusting the amount of cross-linking, which can be
achieved, for example, by altering the type and amount of
cross-linking agent. The initiator agent can be any known
polymerization initiator which decomposes during the cure cycle,
including, but not limited to, dicumyl peroxide,
1,1-di-(t-butylperoxy) 3,3,5-trimethyl cyclohexane, a-a
bis-(t-butylperoxy)diisopropylbenzene,
2,5-di-(t-butylperoxy)-2,5-dimethyl hexane, di-t-butyl peroxide,
n-butyl-4,4-bis(t-butylperoxy)valerate, lauryl peroxide, benzoyl
peroxide, t-butyl hydroperoxide, and mixtures thereof.
[0031] The rubber composition optionally contains one or more
antioxidants. Antioxidants are compounds that can inhibit or
prevent the oxidative degradation of the rubber. Some antioxidants
also act as free radical scavengers; thus, when antioxidants are
included in the rubber composition, the amount of initiator agent
used may be as high or higher than the amounts disclosed herein.
Suitable antioxidants include, for example, dihydroquinoline
antioxidants, amine type antioxidants, and phenolic type
antioxidants.
[0032] The rubber composition may also contain one or more fillers
to adjust the density and/or specific gravity of the core or cover.
Fillers are typically polymeric or mineral particles. Exemplary
fillers include precipitated hydrated silica, clay, talc, asbestos,
glass fibers, aramid fibers, mica, calcium metasilicate, zinc
sulfate, barium sulfate, zinc sulfide, lithopone, silicates,
silicon carbide, diatomaceous earth, polyvinyl chloride, carbonates
(e.g., calcium carbonate, zinc carbonate, barium carbonate, and
magnesium carbonate), metals (e.g., titanium, tungsten, aluminum,
bismuth, nickel, molybdenum, iron, lead, copper, boron, cobalt,
beryllium, zinc, and tin), metal alloys (e.g., steel, brass,
bronze, boron carbide whiskers, and tungsten carbide whiskers),
oxides (e.g., zinc oxide, tin oxide, iron oxide, calcium oxide,
aluminum oxide, titanium dioxide, magnesium oxide, and zirconium
oxide), particulate carbonaceous materials (e.g., graphite, carbon
black, cotton flock, natural bitumen, cellulose flock, and leather
fiber), microballoons (e.g., glass and ceramic), fly ash, regrind
(i.e., core material that is ground and recycled), nanofillers and
combinations thereof. The amount of particulate material(s) present
in the rubber composition is typically within a range having a
lower limit of 5 parts or 10 parts by weight per 100 parts of the
base rubber, and an upper limit of 30 parts or 50 parts or 100
parts by weight per 100 parts of the base rubber. Filler materials
may be dual-functional fillers, such as zinc oxide (which may be
used as a filler/acid scavenger) and titanium dioxide (which may be
used as a filler/brightener material). Further examples of suitable
fillers and additives include, but are not limited to, those
disclosed in U.S. Pat. No. 7,041,721, the entire disclosure of
which is hereby incorporated herein by reference.
[0033] The rubber composition may also contain one or more
additives selected from processing aids, processing oils,
plasticizers, coloring agents, fluorescent agents, chemical blowing
and foaming agents, defoaming agents, stabilizers, softening
agents, impact modifiers, free radical scavengers, accelerators,
scorch retarders, and the like. The amount of additive(s) typically
present in the rubber composition is typically within a range
having a lower limit of 0 parts by weight per 100 parts of the base
rubber, and an upper limit of 20 parts or 50 parts or 100 parts or
150 parts by weight per 100 parts of the base rubber.
[0034] The rubber composition optionally includes a soft and fast
agent. As used herein, "soft and fast agent" means any compound or
a blend thereof that is capable of making a core 1) softer (have a
lower compression) at a constant "coefficient of restitution" (COR)
and/or 2) faster (have a higher COR at equal compression), when
compared to a core equivalently prepared without a soft and fast
agent. Preferably, the rubber composition contains from 0.05 phr to
10.0 phr of a soft and fast agent. In one embodiment, the soft and
fast agent is present in an amount of from 0.05 phr to 3.0 phr, or
from 0.05 phr to 2.0 phr, or from 0.05 phr to 1.0 phr. In another
embodiment, the soft and fast agent is present in an amount of from
2.0 phr to 5.0 phr, or from 2.35 phr to 4.0 phr, or from 2.35 phr
to 3.0 phr. In an alternative high concentration embodiment, the
soft and fast agent is present in an amount of from 5.0 phr to 10.0
phr, or from 6.0 phr to 9.0 phr, or from 7.0 phr to 8.0 phr. In
another embodiment, the soft and fast agent is present in an amount
of 2.6 phr.
[0035] Suitable soft and fast agents include, but are not limited
to, organosulfur or metal-containing organosulfur compounds, an
organic sulfur compound, including mono, di, and polysulfides, a
thiol, or mercapto compound, an inorganic sulfide compound, a Group
VIA compound, a substituted or unsubstituted aromatic organic
compound that does not contain sulfur or metal, an aromatic
organometallic compound, or mixtures thereof. The soft and fast
agent component may also be a blend of an organosulfur compound and
an inorganic sulfide compound. Other suitable soft and fast agents
include, but are not limited to, hydroquinones, benzoquinones,
quinhydrones, catechols, and resorcinols.
[0036] Preferably, the halogenated thiophenol compound is
pentachlorothiophenol, which is commercially available in neat form
or under the tradename STRUKTOL.RTM., a clay-based carrier
containing the sulfur compound pentachlorothiophenol loaded at 45
percent (correlating to 2.4 parts PCTP). STRUKTOL.RTM. is
commercially available from Struktol Company of America of Stow,
Ohio. PCTP is commercially available in neat form from eChinachem
of San Francisco, Calif. and in the salt form from eChinachem of
San Francisco, Calif. Most preferably, the halogenated thiophenol
compound is the zinc salt of pentachlorothiophenol, which is
commercially available from eChinachem of San Francisco, Calif.
Additional examples are disclosed in U.S. Pat. No. 7,148,279, the
entire disclosure of which is hereby incorporated herein by
reference.
[0037] Examples of commercially available polybutadienes suitable
for use in forming the core include, but are not limited to, BUNA
CB 23, commercially available from Lanxess Corp; SE BR-1220,
commercially available from The Dow Chemical Company;
Europrene.RTM. NEOCIS.RTM. BR 40 and BR 60, commercially available
from Polimeri Europa; UBEPOL-BR.RTM. rubbers, commercially
available from UBE Industries, Ltd.; and BR 01 commercially
available from Japan Synthetic Rubber Co., Ltd.
[0038] Suitable types and amounts of base rubber, cross-linking
agent, filler, co-cross-linking agent, initiator agent and
additives are more fully described in, for example, U.S. Pat. Nos.
7,138,460; 7,041,721; 6,939,907; 6,695,718; 6,566,483; and
6,939,907, the entire disclosures of which are hereby incorporated
herein by reference.
[0039] The core may also comprise thermosetting or thermoplastic
materials such as polyurethane, polyurea, partially or fully
neutralized ionomers, thermosetting polydiene rubber such as
polybutadiene, polyisoprene, ethylene propylene diene monomer
rubber, ethylene propylene rubber, natural rubber, balata, butyl
rubber, halobutyl rubber, styrene butadiene rubber or any styrenic
block copolymer such as styrene ethylene butadiene styrene rubber,
etc., metallocene or other single site catalyzed polyolefin,
polyurethane copolymers, e.g., with silicone, as long as the
material meets the desired coefficient of restitution ("COR").
[0040] Additional materials suitable for forming the core include
the core compositions disclosed in U.S. Pat. No. 7,300,364, the
entire disclosure of which is hereby incorporated herein by
reference. For example, suitable core materials include HNPs
neutralized with organic fatty acids and salts thereof, metal
cations, or a combination of both. In addition to HNPs neutralized
with organic fatty acids and salts thereof, core compositions may
comprise at least one rubber material having a resilience index of
at least about 40. Preferably the resilience index is at least
about 50. Polymers that produce resilient golf balls and,
therefore, are suitable for the present invention, include but are
not limited to CB23, CB22, commercially available from of Bayer
Corp. of Orange, Tex., BR60, commercially available from Enichem of
Italy, and 1207G, commercially available from Goodyear Corp. of
Akron, Ohio Additionally, the unvulcanized rubber, such as
polybutadiene, in golf balls prepared according to the invention
typically has a Mooney viscosity of between about 40 and about 80,
more preferably, between about 45 and about 65, and most
preferably, between about 45 and about 55. Mooney viscosity is
typically measured according to ASTM-1646.
[0041] In one embodiment, the core is enclosed with a cover
comprising an inner cover layer and an outer cover layer and the
surface hardness of the core is greater than the material hardness
of the inner cover layer. In a particular embodiment, the surface
hardness of the core is greater than both the inner cover layer and
the outer cover layer.
[0042] The cured polybutadiene-based compositions typically have a
hardness of 15 Shore A or greater, and preferably have a hardness
of from 30 Shore A to 80 Shore D, more preferably from 50 Shore A
to 60 Shore D. The inner cover layer preferably has a material
hardness of 90 Shore C or less, or 85 Shore C or less, or a
material hardness of from 80 Shore C to 90 Shore C, or a material
hardness within a range having a lower limit of 70 or 75 or 80 or
82 Shore C and an upper limit of 85 or 86 or 90 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. Methods for measuring hardness of the layers in the golf
ball are described in further detail below.
[0043] Suitable materials for forming the inner and outer cover
layer include ionomer resins and blends thereof (particularly
Surlyn.RTM. ionomer resins), polyurethanes, polyureas,
(meth)acrylic acid, thermoplastic rubber polymers, polyethylene,
and synthetic or natural vulcanized rubber, such as balata.
Suitable commercially available ionomeric cover materials include,
but are not limited to, Surlyn.RTM. ionomer resins and DuPont.RTM.
HPF 1000 and HPF 2000, commercially available from E. I. du Pont de
Nemours and Company; and Iotek.RTM. ionomers, commercially
available from ExxonMobil Chemical Company.
[0044] Also suitable for forming cover layers are blends of
ionomers with thermoplastic elastomers. Suitable ionomeric cover
materials are further disclosed, for example, in U.S. Pat. Nos.
6,653,382, 6,756,436, 6,894,098, 6,919,393, and 6,953,820, the
entire disclosures of which are hereby incorporated by reference.
Suitable polyurethane cover materials are further disclosed in U.S.
Pat. Nos. 5,334,673, 6,506,851, and 6,756,436, the entire
disclosures of which are hereby incorporated herein by reference.
Suitable polyurea cover materials are further disclosed in U.S.
Pat. Nos. 5,484,870 and 6,835,794, the entire disclosures of which
are hereby incorporated herein by reference. Suitable
polyurethanes, polyureas, and polyurethane-urea hybrids, which are
blends or copolymers comprising urethane and urea segments, as
disclosed in U.S. Pat. Nos. 6,476,176; 6,958,379; 6,960,630;
6,964,621; 7,041,769; 7,105,623; 7,131,915; and 7,186,777, the
entire disclosure of which is hereby incorporated herein by
reference, also may be used. Additional suitable cover materials
are disclosed, for example, in U.S. Pat. Nos. 7,182,702 and
5,919,100, the entire disclosures of which are hereby incorporated
herein by reference.
[0045] The inner cover layer is preferably formed from a
composition comprising an ionomer or a blend of two or more
ionomers. In a particular embodiment, the inner cover layer is
formed from a composition comprising a high acid ionomer. For
purposes of the present disclosure, "high acid ionomer" includes
ionomers having an acid content of greater than 16 wt %. A
particularly suitable high acid ionomer is Surlyn 8150.RTM.,
commercially available from E. I. du Pont de Nemours and Company.
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
formed 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 572D.RTM.,
commercially available from E. I. du Pont de Nemours and Company.
Fusabond 572D.RTM. 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
572D.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.
[0046] In another particular embodiment, the inner cover layer is
preferably 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 preferably 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 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 E/MAA 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 E/MAA copolymer in which the MAA acid groups have been
partially neutralized with zinc ions. Nucrel.RTM. 960 is an E/MAA
copolymer resin nominally made with 15 wt % methacrylic acid.
Surlyn.RTM. 8940, Surlyn.RTM. 9650, Surlyn.RTM. 9910, and
Nucrel.RTM. 960 are commercially available from E. I. du Pont de
Nemours and Company. Non-limiting examples of preferred inner cover
layer materials are shown in the Examples below.
[0047] Ionomeric compositions of the present invention can be
blended with non-ionic thermoplastic resins, particularly to
manipulate product properties. Examples of suitable non-ionic
thermoplastic resins include, but are not limited to, polyurethane,
poly-ether-ester, poly-amide-ether, polyether-urea, Pebax.RTM.
thermoplastic polyether block amides commercially available from
Arkema Inc., styrene-butadiene-styrene block copolymers,
styrene(ethylene-butylene)-styrene block copolymers, polyamides,
polyesters, polyolefins (e.g., polyethylene, polypropylene,
ethylene-propylene copolymers, ethylene-(meth)acrylate,
ethylene-(meth)acrylic acid, functionalized polymers with maleic
anhydride grafting, Fusabond.RTM. functionalized olefins
commercially available from E. I. du Pont de Nemours and Company,
functionalized polymers with epoxidation, elastomers (e.g., EPDM,
metallocene-catalyzed polyethylene) and ground powders of the
thermoset elastomers. The inner cover layer material may include a
flow modifier, such as, but not limited to, Nucrel.RTM. acid
copolymer resins, and particularly Nucrel.RTM. 960. Nucrel.RTM.
acid copolymer resins are commercially available from E. I. du Pont
de Nemours and Company. The outer cover layer is preferably formed
from a composition comprising polyurethane; polyurea; or a blend,
copolymer, or hybrid of polyurethane/polyurea. The outer cover
layer material may be thermoplastic or thermoset. Basically,
polyurethane compositions contain urethane linkages formed by
reacting an isocyanate group (--N.dbd.C.dbd.O) with a hydroxyl
group (OH). Polyurethanes are produced by the reaction of a
multi-functional isocyanate with a polyol in the presence of a
catalyst and other additives. The chain length of the polyurethane
prepolymer is extended by reacting it with a hydroxyl-terminated
curing agent. Polyurea compositions, which are distinct from the
above-described polyurethanes, also can be formed. In general,
polyurea compositions contain urea linkages formed by reacting an
isocyanate group (--N.dbd.C.dbd.O) with an amine group (NH or
NH.sub.2). The chain length of the polyurea prepolymer is extended
by reacting the prepolymer with an amine curing agent. Hybrid
compositions containing urethane and urea linkages also may be
produced. For example, a polyurethane/urea hybrid composition may
be produced when a polyurethane prepolymer is reacted with an
amine-terminated curing agent. The term, "hybrid
polyurethane-polyureas" is also meant to encompass blends and
copolymers of polyurethanes and polyureas.
[0048] In a particularly preferred embodiment, the present
invention provides a golf ball consisting of: a single-layer core,
an inner cover layer, and an outer cover layer. The core is
preferably formed from a rubber composition and, in a particularly
preferred embodiment, has one or more of the following properties:
a diameter of about 1.53 inches, a compression of about 70, a
center hardness of about 60 Shore C, and a surface hardness of
about 85 Shore C. The rubber composition preferably has the
following formulation: 100 parts high-cis butadiene rubber, 30 phr
zinc diacrylate, 5 phr zinc oxide, BaSO.sub.4 in amount necessary
to achieve the desired specific gravity, 0.5 phr zinc
pentachlorothiophenol, 1.2 phr Perkadox BC, and from 10 to 20 phr
regrind material. The inner cover layer is preferably formed from a
composition comprising a 84 wt %/16 wt % blend of Surlyn 8150.RTM.
and Fusabond 572D.RTM.. The outer cover layer is preferably formed
from a polyurethane or polyurea composition.
[0049] A moisture vapor barrier layer is optionally employed
between the core and the cover. Moisture vapor barrier layers are
further disclosed, for example, in U.S. Pat. Nos. 6,632,147,
6,932,720, 7,004,854, and 7,182,702, the entire disclosures of
which are hereby incorporated herein by reference.
[0050] In addition to the materials disclosed above, any of the
core or cover layers may comprise one or more of the following
materials: thermoplastic elastomer, thermoset elastomer, synthetic
rubber, thermoplastic vulcanizate, copolymeric ionomer,
terpolymeric ionomer, polycarbonate, polyolefin, polyamide,
copolymeric polyamide, polyesters, polyester-amides,
polyether-amides, polyvinyl alcohols,
acrylonitrile-butadiene-styrene copolymers, polyarylate,
polyacrylate, polyphenylene ether, impact-modified polyphenylene
ether, high impact polystyrene, diallyl phthalate polymer,
metallocene-catalyzed polymers, styrene-acrylonitrile (SAN),
olefin-modified SAN, acrylonitrile-styrene-acrylonitrile,
styrene-maleic anhydride (S/MA) polymer, styrenic copolymer,
functionalized styrenic copolymer, functionalized styrenic
terpolymer, styrenic terpolymer, cellulose polymer, liquid crystal
polymer (LCP), ethylene-propylene-diene rubber (EPDM),
ethylene-vinyl acetate copolymer (EVA), ethylene propylene rubber
(EPR), ethylene vinyl acetate, polyurea, and polysiloxane. Suitable
polyamides for use as an additional material in compositions
disclosed herein also include resins obtained by: (1)
polycondensation of (a) a dicarboxylic acid, such as oxalic acid,
adipic acid, sebacic acid, terephthalic acid, isophthalic acid or
1,4-cyclohexanedicarboxylic acid, with (b) a diamine, such as
ethylenediamine, tetramethylenediamine, pentamethylenediamine,
hexamethylenediamine, or decamethylenediamine,
1,4-cyclohexyldiamine or m-xylylenediamine; (2) a ring-opening
polymerization of cyclic lactam, such as .epsilon.-caprolactam or
.omega.-laurolactam; (3) polycondensation of an aminocarboxylic
acid, such as 6-aminocaproic acid, 9-aminononanoic acid,
11-aminoundecanoic acid or 12-aminododecanoic acid; or (4)
copolymerzation of a cyclic lactam with a dicarboxylic acid and a
diamine. Specific examples of suitable polyamides include Nylon 6,
Nylon 66, Nylon 610, Nylon 11, Nylon 12, copolymerized Nylon, Nylon
MXD6, and Nylon 46.
[0051] Other preferred materials suitable for use as an additional
material in golf ball compositions disclosed herein include Skypel
polyester elastomers, commercially available from SK Chemicals of
South Korea; Septon.RTM. diblock and triblock copolymers,
commercially available from Kuraray Corporation of Kurashiki,
Japan; and Kraton.RTM. diblock and triblock copolymers,
commercially available from Kraton Polymers LLC of Houston,
Tex.
[0052] Ionomers are also well suited for blending with compositions
disclosed herein. Suitable ionomeric polymers include
.alpha.-olefin/unsaturated carboxylic acid copolymer- or
terpolymer-type ionomeric resins. Copolymeric ionomers are obtained
by neutralizing at least a portion of the carboxylic groups in a
copolymer of an .alpha.-olefin and an .alpha.,.beta.-unsaturated
carboxylic acid having from 3 to 8 carbon atoms, with a metal ion.
Terpolymeric ionomers are obtained by neutralizing at least a
portion of the carboxylic groups in a terpolymer of an
.alpha.-olefin, an .alpha.,.beta.-unsaturated carboxylic acid
having from 3 to 8 carbon atoms, and an .alpha.,.beta.-unsaturated
carboxylate having from 2 to 22 carbon atoms, with a metal ion.
Examples of suitable .alpha.-olefins for copolymeric and
terpolymeric ionomers include ethylene, propylene, 1-butene, and
1-hexene. Examples of suitable unsaturated carboxylic acids for
copolymeric and terpolymeric ionomers include acrylic, methacrylic,
ethacrylic, .alpha.-chloroacrylic, crotonic, maleic, fumaric, and
itaconic acid. Copolymeric and terpolymeric ionomers include
ionomers having varied acid contents and degrees of acid
neutralization, neutralized by monovalent or bivalent cations as
disclosed herein. Examples of commercially available ionomers
suitable for blending with compositions disclosed herein include
Surlyn.RTM. ionomer resins, commercially available from E. I. du
Pont de Nemours and Company, and Iotek.RTM. ionomers, commercially
available from ExxonMobil Chemical Company.
[0053] Silicone materials are also well suited for blending with
compositions disclosed herein. Suitable silicone materials include
monomers, oligomers, prepolymers, and polymers, with or without
adding reinforcing filler. One type of silicone material that is
suitable can incorporate at least 1 alkenyl group having at least 2
carbon atoms in their molecules. Examples of these alkenyl groups
include, but are not limited to, vinyl, allyl, butenyl, pentenyl,
hexenyl, and decenyl. The alkenyl functionality can be located at
any location of the silicone structure, including one or both
terminals of the structure. The remaining (i.e., non-alkenyl)
silicon-bonded organic groups in this component are independently
selected from hydrocarbon or halogenated hydrocarbon groups that
contain no aliphatic unsaturation. Non-limiting examples of these
include: alkyl groups, such as methyl, ethyl, propyl, butyl,
pentyl, and hexyl; cycloalkyl groups, such as cyclohexyl and
cycloheptyl; aryl groups, such as phenyl, tolyl, and xylyl; aralkyl
groups, such as benzyl and phenethyl; and halogenated alkyl groups,
such as 3,3,3-trifluoropropyl and chloromethyl. Another type of
suitable silicone material is one having hydrocarbon groups that
lack aliphatic unsaturation. Specific examples include:
trimethylsiloxy-endblocked dimethylsiloxane-methylhexenylsiloxane
copolymers; dimethylhexenylsiloxy-endblocked
dimethylsiloxane-methylhexenylsiloxane copolymers;
trimethylsiloxy-endblocked dimethylsiloxane-methylvinylsiloxane
copolymers; trimethylsiloxyl-endblocked
methylphenylsiloxane-dimethylsiloxane-methylvinysiloxane
copolymers; dimethylvinylsiloxy-endblocked dimethylpolysiloxanes;
dimethylvinylsiloxy-endblocked dimethylsiloxane-methylvinylsiloxane
copolymers; dimethylvinylsiloxy-endblocked
methylphenylpolysiloxanes; dimethylvinylsiloxy-endblocked
methylphenylsiloxane-dimethylsiloxane-methylvinylsiloxane
copolymers; and the copolymers listed above wherein at least one
group is dimethylhydroxysiloxy. Examples of commercially available
silicones suitable for blending with compositions disclosed herein
include Silastic.RTM. silicone rubber, commercially available from
Dow Corning Corporation of Midland, Mich.; Blensil.RTM. silicone
rubber, commercially available from General Electric Company of
Waterford, New York; and Elastosil.RTM. silicones, commercially
available from Wacker Chemie AG of Germany.
[0054] Other types of copolymers can also be added to the golf ball
compositions disclosed herein. For example, suitable copolymers
comprising epoxy monomers include styrene-butadiene-styrene block
copolymers in which the polybutadiene block contains an epoxy
group, and styrene-isoprene-styrene block copolymers in which the
polyisoprene block contains epoxy. Examples of commercially
available epoxy functionalized copolymers include ESBS A1005, ESBS
A1010, ESBS A1020, ESBS AT018, and ESBS AT019 epoxidized
styrene-butadiene-styrene block copolymers, commercially available
from Daicel Chemical Industries, Ltd. of Japan.
[0055] The present invention is not limited by any particular
process for forming the golf ball layer(s). It should be understood
that the layer(s) can be formed by any suitable technique,
including injection molding, compression molding, casting, and
reaction injection molding. Coefficient of Restitution ("COR") and
Compression are important properties of the golf balls of this
invention as discussed further below. The golf balls typically have
a COR of 0.70 or greater, preferably 0.75 or greater, and more
preferably 0.78 or greater and a Compression of 40 or greater, or a
Compression within a range having a lower limit of 50 or 60 and an
upper limit of 100 or 120, preferably 90 to 100. Methods for
measuring COR and Compression are described in the test methods
below.
[0056] In one embodiment of a dual-core golf ball, the inner core
layer preferably has a compression of 20 or less. The cores of the
present invention preferably have an overall compression within a
range having a lower limit of 40 or 50 or 60 or 65 or 70 or 75 and
an upper limit of 80 or 85 or 90 or 100 or 110 or 120, or an
overall compression of about 90. In addition, the golf balls
typically will have dimple coverage of 60% or greater, preferably
65% or greater, and more preferably 75% or greater. Furthermore,
the golf balls preferably have a Moment of Inertia ("MOT") of 70-95
gcm.sup.2, preferably 75-93 gcm.sup.2, and more preferably 76-90
gcm.sup.2. For low MOT embodiments, the golf ball preferably has an
MOT of 85 gcm.sup.2 or less, or 83 gcm.sup.2 or less. For high MOT
embodiments, the golf ball preferably has an MOT of 86 gcm.sup.2 or
greater, or 87 gcm.sup.2 or greater. Methods for measuring MOT are
described in further detail below.
[0057] The United States Golf Association specifications limit the
minimum size of a competition golf ball to 1.680 inches. There is
no specification as to the maximum diameter, and golf balls of any
size can be used for recreational play. Golf balls of the present
invention can have an overall diameter of any size. The preferred
diameter of the present golf balls is from 1.680 inches to 1.800
inches. More preferably, the present golf balls have an overall
diameter of from 1.680 inches to 1.760 inches, and even more
preferably from 1.680 inches to 1.740 inches.
[0058] The resiliency and rebounding performance of the golf ball
is based primarily on the core of the ball. The core acts as the
"engine" for the ball. In general, the rebounding performance of
the ball is based on its initial velocity after being struck by the
face of the golf club and its outgoing velocity after making impact
with a hard surface. More particularly, the "coefficient of
restitution" or "COR" of a golf ball refers to 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 vertical 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
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
harder core imparts a higher initial velocity to the ball and
results in the golf ball traveling a greater distance. These harder
balls, however, tend to provide the player with a rougher and less
natural "feel" when he/she strikes the ball with the club face. The
player senses less control over the hard ball as the club face
makes impact with the ball. The sensation experienced when hitting
such hard balls tends to be harsh and the playability of such hard
balls can be difficult. Developing a rubber composition that can be
used to improve the resiliency of the core while at the same time
providing the ball with a comfortable and soft "feel" is desirable
for the golf ball industry and the present invention provides such
compositions.
[0059] In accordance with the present invention, it now has been
found that rubber compositions comprising "cycloalkene rubber" can
be used to provide a golf ball having improved resiliency and
rebounding properties along with a soft feel. Cycloalkene rubbers
are rubbery polymers made from one or more cycloalkenes having from
5 to 20, preferably 5 to 15, ring carbon atoms. The cycloalkene
rubbers (also referred to as polyalkenylene or polyalkenamer
rubbers) may be prepared by ring opening metathesis polymerization
of one or more cycloalkenes in the presence of organometallic
catalysts as is known in the art. Such polymerization methods are
disclosed, for example, in U.S. Pat. Nos. 3,492,245 and 3,804,803,
the disclosures of which are hereby incorporated by reference. By
the term, "cycloalkene rubber" as used herein, it is meant a
compound having at least 20 weight % macrocycles (cyclic content).
The cyclic and linear portions of the cycloalkene rubber have the
following general chemical structures:
##STR00001##
[0060] Suitable cyclic olefins that can be used to make the
cycloalkene rubber include unsaturated hydrocarbons with 4 to 12
ring carbon atoms in one or more rings e.g., 1-3 rings, which
exhibit in at least one ring an unsubstituted double bond which is
not in conjugation to a second double bond which may be present and
which may have any degree of substitution; the substituents must
not interfere with the metathesis catalysts and are preferably
alkyl groups of 1 to 4 carbon atoms or a part of a cyclic structure
of 4 to 8 carbon atoms. Examples are cyclobutene, cyclopentene,
cycloheptene, cis- and trans-cyclooctene, cyclononene, cyclodecene,
cycloundecene, cis- and trans-cyclododecene, cis,
cis-cyclooctadiene, 1-methyl-1,5-cyclooctadiene,
3-methyl-1,5-cyclooctadiene, and
3,7-dimethyl-1,5-cyclooctadiene.
[0061] Examples of suitable polyalkenamer rubbers are
polypentenamer rubber, polyheptenamer rubber, polyoctenamer rubber,
polydecenamer rubber and polydodecenamer rubber. Polyoctenamer
rubbers are commercially available from Evonik Degussa GmbH of
Marl, Germany and sold under the VESTENAMER tradename. The
polyalkenamer rubber used in the present invention preferably has a
trans-bond content of about 55% or greater and a second heat
melting point of about 30.degree. C. or greater. More preferably,
the cycloalkene rubber has a trans-bond content of 75% or greater
and a second heat melting point of 50.degree. C. or greater.
Furthermore, the polyalkenamer rubber material preferably has a
molecular weight of about 80,000 or greater (measured according to
GPC); a glass transition temperature (Tg) of about 55.degree. C. or
less (measured according to ISO 6721 or 4663); a cis-to-trans ratio
of double bonds of about 40:60 or preferably about 20:80 (measured
according to IR); a Mooney viscosity ML (1+4) 100.degree. C. of
less than about 10 (measured according to DIN 53 523 or ASTM-D
1646); a viscosity number J/23.degree. C. of about 130 or
preferably about 120 ml/g (measured according to ISO 1628-1); and a
density of about 0.9 g/cm.sup.3 or greater (measured according to
DIN 53 479 A or ISO 1183).
[0062] The polyalkenamer rubber compound, of and by itself, has
relatively high crystallinity. For example, a specific grade of
polyalkenamer rubber (VESTENAMER 8012) has a crystallinity of
approximately 30% (measured by DSC, second melting.) The ratio of
cis double bonds to trans double bonds (cis/trans ratio) in the
polymer is significant in determining the degree of crystallinity
in the polymer. In general, if the trans-bond content of the
polymer is relatively high, the crystallinity and melting point of
the polymer is relatively high. That is, as the trans-bond content
increases, the crystallinity of the polymer increases. The
polyalkenamer rubber, VESTENAMER 8012 has a trans-bond content of
about 80%. In accordance with the present invention, it has been
found the compression of polyalkenamer rubber cores is reduced and
the Coefficient of Restitution ("COR") of the cores is increased
when the rubber composition is cross-linked to a relatively high
degree and the composition does not contain a reactive
cross-linking co-agent such as zinc diacrylate (ZDA). The
polyalkenamer rubber composition may be cured using a conventional
curing process such as peroxide-curing, sulfur-curing, and
high-energy radiation, and combinations thereof. For example, the
composition may be peroxide-cured. When peroxide is added at
relatively high amounts (particularly, at least 2.5 and preferably
5.0 phr) and the composition (which if it does not contain a
reactive cross-linking co-agent such as ZDA) is cured to cross-link
the rubber chains, then the compression of the polyalkenamer rubber
cores is reduced and the COR of the cores is increased. It is
believed this phenomenon is due, at least in part, to disrupting
the crystalline structure of the polymer by curing and
cross-linking the composition in accordance with this invention.
While not wishing to be bound by any theory, it is believed the
cross-linking causes the tightly packed structures within the mass
of polyalkenamer polymer to spread out, thus disrupting the
crystallinity of the material. It appears the crystllinity may be
partially disrupted and the polymer remains in a partially
crystalline state. As a result, the polyalkenamer rubber (which if
it does not contain a reactive cross-linking agent such as ZDA)
becomes softer and more rubbery and the compression of core samples
made from the composition decreases.
[0063] One example of a commercially-available material that can be
used in accordance with this invention is VESTENAMER 8012
(trans-bond content of about 80% and a melting point of about
54.degree. C.). The material, VESTENAMER 6213 (trans-bond content
of about 60% and a melting point of about 30.degree.) also may be
effective.
[0064] In the present invention, it has been found that rubber
compositions comprising polyoctenamer rubber are particularly
effective. Polyoctenamer rubber compositions can be used to make a
core that provides the golf ball with good rebounding properties
(distance) without sacrificing a nice feel to the ball. The
resulting ball has a relatively high COR allowing it to reach a
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. Meanwhile, the soft feel of the ball
provides the player with a more pleasant sensation when he/she
strikes the ball with the club. The player senses more control over
the ball as the club face makes impact. Furthermore, the soft feel
of the ball's cover allows players to place a spin on the ball and
better control its flight pattern which is particularly important
for approach shots near the green.
[0065] The polyalkenamer rubber is used in an amount of at least
50% by weight based on total amount of polymer in the rubber
composition used to make the core. Preferably, the polyalkenamer
rubber is present in an amount of 65 to 100% by weight and more
preferably 75 to 100% by weight based on total polymer weight. It
is believed that when the concentration of the polyalkenamer rubber
is less than 50% by weight, the resiliency of the rubber
composition is not significantly improved. In particular versions,
the blend may contain a lower concentration of polylakenamer rubber
in the amount of 50%, 55%, 60%, 65%, or 70% and an upper
concentration of polyalkenamer in the amount of 75%, 80%, 85%, 90%,
or 95%.
[0066] The polyalkenamer rubber may be blended with other rubber
and polymeric materials. As described above, these rubber materials
include, but are not limited to, polybutadiene, polyisoprene,
ethylene propylene rubber ("EPR"), ethylene propylene diene rubber
("EPDM"), styrene-butadiene rubber, styrenic block copolymer
rubbers (such as SI, SIS, SB, SBS, SIBS, SEBS, and the like, where
"S" is styrene, "I" is isobutylene, "B" is butadiene, and "E" is
ethylene), butyl rubber, halobutyl rubber, polystyrene elastomers,
polyethylene elastomers, polyurethane elastomers, polyurea
elastomers, metallocene-catalyzed elastomers and plastomers,
copolymers of isobutylene and para-alkylstyrene, halogenated
copolymers of isobutylene and para-alkylstyrene, copolymers of
butadiene with acrylonitrile, polychloroprene, alkyl acrylate
rubber, chlorinated isoprene rubber, acrylonitrile chlorinated
isoprene rubber, and combinations of two or more thereof. A
preferred base rubber is 1, 4-polybutadiene having a cis-bond
structure of at least 40%, preferably greater than 80%, and more
preferably greater than 90%.
[0067] Examples of commercially available polybutadiene rubbers
that can be used in accordance with this invention include, but are
not limited to, BUNA.RTM. CB22 and BUNA.RTM. CB23, commercially
available from Lanxess Corp.; UBEPOL.RTM. 360L and UBEPOL.RTM. 150L
and UBEPOL-BR rubbers, commercially available from UBE Industries,
Ltd. of Tokyo, Japan; KINEX.RTM. 7245 and KINEX.RTM. 7265,
commercially available from Goodyear of Akron, Ohio; SE BR-1220,
and BUNA.RTM. CB1203G1, CB1220, and CB1221, commercially available
from Lanxess Corp.; EUROPRENE.RTM. NEOCIS.RTM. BR 40 and BR 60,
commercially available from Polimeri Europa; and BR 01, BR 730, BR
735, BR 11, and BR 51, commercially available from Japan Synthetic
Rubber Co., Ltd; and Afdene 45, Afdene 50, Neodene 40, and Neodene
45, commercially available from Karbochem (PTY) Ltd. of Bruma,
South Africa.
[0068] As discussed above, the polyalkenamer rubber composition may
be cured using a conventional curing process. 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 base
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 base rubber. In
one preferred version, the peroxide free-radical initiator is
present in an amount of at least 2.5 and more preferably 5 parts
per hundred (phr). As further discussed in the Examples below, it
is believed the high crystallinity of the polyalkenamer rubber is
reduced by adding the peroxide at relatively high amounts to the
rubber composition and curing the composition so it is
cross-linked.
[0069] The polyalkenamer rubber composition 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 total rubber.
[0070] Radical scavengers such as a halogenated organosulfur,
organic disulfide, or inorganic disulfide compounds may be added to
the polyalkenamer rubber composition to increase the COR at a given
compression. 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.
[0071] The polyalkenamer compositions of the present invention also
may include "fillers," which are added to adjust the density and/or
specific gravity of the material. As used herein, the term
"fillers" includes any compound or composition that can be used to
adjust the density and/or other properties of the subject golf
ball. Suitable fillers include, but are not limited to, polymeric
or mineral fillers, metal fillers, metal alloy fillers, metal oxide
fillers and carbonaceous fillers. Fillers can be in the form of
flakes, fibers, fibrils, or powders. Regrind, which is ground,
recycled core material (for example, ground to about 30 mesh
particle size), can also be used. The amount and type of fillers
utilized are governed by the amount and weight of other ingredients
in the golf ball, since a maximum golf ball weight of 45.93 g (1.62
ounces) has been established by the United States Golf Association
(USGA). Suitable fillers generally have a specific gravity from
about 2 to 20. In one preferred embodiment, the specific gravity
can be about 2 to 6.
[0072] Suitable polymeric or mineral fillers include, for example,
precipitated hydrated silica, clay, talc, asbestos, glass fibers,
aramid fibers, mica, calcium metasilicate, barium sulfate, zinc
sulfide, lithopone, silicates, silicon carbide, diatomaceous earth,
polyvinyl chloride, carbonates such as calcium carbonate and
magnesium carbonate. Suitable metal fillers include titanium,
tungsten, aluminum, bismuth, nickel, molybdenum, iron, lead,
copper, boron, cobalt, beryllium, zinc, and tin. Suitable metal
alloys include steel, brass, bronze, boron carbide whiskers, and
tungsten carbide whiskers. Suitable metal oxide fillers include
zinc oxide, iron oxide, aluminum oxide, titanium oxide, magnesium
oxide, and zirconium oxide. Suitable particulate carbonaceous
fillers include graphite, carbon black, 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.
[0073] As discussed above, the rubber compositions may include
antioxidants to prevent the breakdown of the elastomers. In
addition, the polyalkenamer rubber compositions may optionally
include processing aids such as high molecular weight organic acids
and salts thereof. 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, 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.)
[0074] 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. The core may be formed by mixing and molding the
rubber composition using conventional techniques. These cores can
be used to make finished golf balls by surrounding the core with
outer core layer(s), intermediate layer(s), and/or cover materials
as discussed further below.
[0075] In one embodiment, the polyalkenamer rubber composition may
be used to make a solid, single core having a hard-to-soft gradient
from the surface of the core to the center of the core, otherwise
known as a "positive hardness gradient." In a second embodiment,
the polyalkenamer rubber composition may be used to make a
dual-core comprising a solid inner core and solid outer core layer
that surrounds the inner core. The inner core has a positive
hardness gradient, while the outer core layer, which surrounds the
inner core, has a soft-to-hard gradient from the outer surface of
the outer core layer to its inner surface, otherwise known as a
"negative hardness gradient." In a third embodiment, the outer core
layer has a zero hardness gradient.
[0076] As discussed above, the polyalkenamer rubber composition of
this invention may be used in a wide variety of golf ball
constructions, particularly single core and dual-core products.
More particularly, in one version of the golf ball of this
invention, the polyalkenamer rubber composition may be used to make
a solid, single core having a positive hardness gradient. That is,
the hardness of the outer surface of the core is greater than the
hardness of the geometric center of the core. The positive hardness
gradient preferably has a magnitude of at least 10 Shore C units
and more preferably at least 20 Shore C units.
[0077] For example, the hardness of the outer surface of the core
may be 70 Shore C or greater, or 75 Shore C or greater, or 80 Shore
C or greater, or 85 Shore C or greater, or 87 Shore C or greater,
or 90 Shore C or greater. Meanwhile, the geometric center of the
core may have a hardness of 70 Shore C or less, or 65 Shore C or
less; or 60 Shore C or less; or within a range having a lower limit
of 30 or 40 or 45 Shore C and an upper limit of 70 or 75 or 80
Shore C; or a center hardness of about 60 Shore C. In other
instances, the hardness gradient may have a magnitude of less than
8 Shore C units to define a zero hardness gradient. For example,
the hardness of the outer surface of the core may range from 52
Shore C to 68 Shore C and the hardness of the center of the core
may range from 49 Shore C to 63 Shore C to define a zero hardness
gradient.
[0078] The single-layered core of this invention may be enclosed
with one or two cover layers. In one 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 60 or less, more
preferably 55 or less, and most preferably about 52 or less. The
inner cover layer is harder than the outer cover layer in this
version.
[0079] 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. A
preferred inner cover layer material is a partially-neutralized
ionomer comprising zinc, sodium or lithium neutralized ionomer such
as SURLYN 8940, 8945, 9910, 7930, 7940, or blend thereof having a
Shore D hardness of about 63 to about 68. In another multi-layer
cover, single 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.
[0080] As discussed above, ionomer-based compositions, particularly
olefin-based ionomers, are known to be useful as a golf ball cover
material, particularly as an inner cover layer, because they can
impart desirable hardness to the ball. Olefin-based ionomers are
acid copolymers that normally include .alpha.-olefin, such as
ethylene and an .alpha.,.beta.-ethylenically unsaturated carboxylic
acid having 3 to 8 carbons, such as methacrylic acid or acrylic
acid. Other possible carboxylic acid groups include, for example,
crotonic, maleic, fumaric, and itaconic acid. The acid copolymers
may optionally contain a softening monomer such as alkyl acrylate
and alkyl methacrylate, wherein the alkyl groups have from 1 to 8
acarbon atoms. "Low acid" and "high acid" olefin-based ionomers, 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
carboxylic acid, whereas high acid ionomers are considered to be
those containing greater than 16 wt. % of carboxylic acid. The
acidic group in the olefin-based ionic copolymer is partially or
totally neutralized with metal ions such as zinc, sodium, lithium,
magnesium, potassium, calcium, manganese, nickel, chromium, copper,
or a combination thereof. For example, ionomeric resins having
carboxylic acid groups that are neutralized from about 10 percent
to about 100 percent may be used. In one embodiment, the acid
groups are partially neutralized. That is, the neutralization level
is from 10 to 80%, more preferably 20 to 70%, and most preferably
30 to 50%. In another embodiment, the acid groups are highly or
fully neutralized. That is, the neutralization level is from 80 to
100%, more preferably 90 to 100%, and most preferably 95 to
100%.
[0081] In another version, the polyalkenamer rubber composition may
be used to may a dual-core comprising a solid inner core and solid
outer core layer that surrounds the inner core. In one preferred
version, the polyalkenamer rubber composition is used to make an
inner core having a positive hardness gradient as described above.
The positive hardness gradient preferably has a magnitude of at
least 10 Shore C units and more preferably at least 20 Shore C
units.
[0082] Meanwhile, the outer core layer, which surrounds the inner
core, may have an outer surface hardness substantially the same or
less than its inner surface hardness to define a zero or negative
hardness gradient. The outer core layer may be made of the
polyalkenamer rubber composition or a traditional rubber
composition used for golf ball cores such as, for example,
polybutadiene, as described above. In still another version, the
inner core may have a positive hardness gradient as described above
and the hardness gradient from outer surface of the outer core
layer to the inner surface of the outer core layer also may be
positive. For dual-core and other multi-layered core constructions,
the polyalkenamer rubber composition is used in at least one of the
core layers.
[0083] The positive and negative hardness gradients, particularly
in the above embodiments, can have any slope (i.e., steep, shallow,
or substantially flat). In a preferred version, the golf ball
contains a dual-core, wherein the inner core has a steep positive
hardness gradient and the outer core layer has a zero or negative
hardness gradient of varying slope. For example, in one embodiment,
the golf ball has a dual-core, wherein the inner core has a steep
positive hardness gradient of 20 Shore C or greater, more
preferably 25 Shore C or greater, most preferably 30 Shore C or
greater, and the outer core layer has a gradual zero or negative
gradient of -1 to -5 Shore C, more preferably -2 to -5 Shore C,
most preferably -2 to -4 Shore C. More particularly, in one
embodiment, the hardness of the outer surface of the outer core
layer may range from 42 Shore C to 60 Shore C and the hardness of
the inner surface of the outer core layer may range from 52 Shore C
to 65 Shore C to define a zero or negative hardness gradient.
[0084] As discussed above, the polyalkenamer rubber materials of
this invention may be used with any type of ball construction known
in the art. Such golf ball designs include, for example, two-piece,
three-piece, four-piece, and five-piece designs. The core,
intermediate casing, and cover material can be single or
multi-layered. Referring to FIG. 1, one version of a golf ball that
can be made in accordance with this invention is generally
indicated at (10). Various patterns and geometric shapes of dimples
(11) can be used to modify the aerodynamic properties of the golf
ball (10). The dimples (11) can be arranged on the surface of the
ball (10) using any suitable method known in the art. Referring to
FIG. 2, a two-piece golf ball (20) that can be made in accordance
with this invention is illustrated. In this version, the ball (20)
includes a solid, single inner core (22) made of a polyalkenamer
rubber composition and polyurethane cover (24). In FIG. 3, a
three-piece golf ball (30) having a dual-core (32) comprising an
inner core (32a) and outer core layer (32b) made of polyalkenamer
rubber compositions and polyurethane cover (36) is shown. In
another embodiment, as shown in FIG. 4, the four-piece golf ball
(40) contains a dual-core (42) comprising an inner core (42a) and
outer core layer (42b) made of polyalkenamer rubber compositions.
The golf ball (40) further includes a multi-layer cover (46)
comprising inner cover (46a) and outer cover (46b) layers.
Conventional thermoplastic or thermoset resins such as olefin-based
ionomeric copolymers, polyamides, polyesters, polycarbonates,
polyolefins, polyurethanes, and polyureas as described above can be
used to make the inner and outer cover layers. Turning to FIG. 5 in
yet another version, a five-piece golf ball (50) containing a
dual-core (52) comprising an inner core (52a) and outer core layer
(52b) can be made. This ball includes an intermediate layer (54)
and a multi-layered cover (55) comprising an inner cover layer
(55a) and outer cover layer (55b). As used herein, the term,
"intermediate layer" means a layer of the ball disposed between the
core and cover. The intermediate layer may be considered an outer
core layer or inner cover layer or any other layer disposed between
the inner core and outer cover of the ball. The intermediate layer
also may be referred to as a casing or mantle layer. The
intermediate layer may be made of any suitable material known in
the art including thermoplastic and thermosetting materials,
particularly ionomeric or non-ionomeric materials.
[0085] In one version, the intermediate layer comprises
highly-neutralized polymers and blends thereof ("HNP"). The acid
moieties of the HNP'S, typically ethylene-based ionomers, are
preferably neutralized greater than about 70%, more preferably
greater than about 90%, and most preferably at least about 100%.
The HNP's can be also be blended with a second polymer component,
which, if containing an acid group, may be neutralized in a
conventional manner. The second polymer component, which may be
partially or fully neutralized, preferably comprises ionomeric
copolymers and terpolymers, ionomer precursors, thermoplastics,
polyamides, polycarbonates, polyesters, polyurethanes, polyureas,
thermoplastic elastomers, polybutadiene rubber, balata,
metallocene-catalyzed polymers (grafted and non-grafted),
single-site polymers, high-crystalline acid polymers, cationic
ionomers, and the like. HNP polymers typically have a material
hardness of between about 20 and about 80 Shore D.
Test Methods
[0086] Hardness.
[0087] 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 arms 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.
[0088] 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 indentor 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 conform to ASTM D-2240.
[0089] 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.
[0090] 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.
[0091] 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 C hardness was measured according to
the test methods D-2240.
[0092] Moment of Inertia.
[0093] Moment of Inertia (MOI) is measured on a model MOI-005-104
Moment of Inertia Instrument manufactured by Inertia Dynamics of
Collinsville, Conn. The instrument is connected to a PC for
communication via a COMM port and is driven by MOI Instrument
Software Version #1.2
[0094] Compression.
[0095] 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.
[0096] Coefficient of Restitutuion ("COR").
[0097] 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 calculates 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).
Examples
[0098] It should be understood that the examples below are for
illustrative purposes only. In no manner is the present invention
limited to the specific disclosures therein.
Example 1
[0099] Twelve ionomeric inner cover layer compositions according to
the present invention were prepared by melt blending Surlyn.RTM.
8150 and Fusabond.RTM. 572D in a twin screw extruder, at a
temperature of at least 450.degree. F. (230.degree. C.). The
relative amounts of each component used are indicated in Table 1.
Flex bars of each blend composition were formed and evaluated for
hardness according to ASTM D2240 following 10 days of aging at 50%
relative humidity and 23.degree. C. The results are reported below
in Table 1.
TABLE-US-00001 TABLE 1 (Inner Cover Layer Compositions) Shore C
Surlyn .RTM. Fusabond .RTM. Hardness at Example 8150, wt % 572D, wt
% 10 Days 1 89 11 91.2 2 84 16 89.8 3 84 16 90.4 4 84 16 89.6 5 81
19 88.9 6 80 20 89.1 7 78 22 88.1 8 76 24 87.6 9 76 24 87.2 10 73
27 86.6 11 71 29 86.7 12 67 33 84.0
Example 2
[0100] In this Example, a slug of a rubber composition having the
formulation described in Table 2 was cured at about 350.degree. F.
for about 11 minutes to make a solid, single-layered core. The
resulting core had a center hardness of about 57 Shore C and a
surface hardness of about 89 Shore C providing a positive hardness
gradient. In addition, the core had a compression of about 90 and a
COR of about 0.790 @125 f/s (1.550 inch diameter solid sphere.)
TABLE-US-00002 TABLE 2 (Core Compositions) Concentration Core
Composition (parts per hundred) Vestenamer .RTM. 8012 -
polyoctenamer rubber 90 available from Evonik Degussa GmbH. Buna
.RTM. CB 23 - polybutadiene rubber 10 Available from Lanxess Corp.
Zinc diacrylate (ZDA) co-agent 50 Zinc oxide (ZnO) filler 13
Perkadox .RTM. BC free-radical initiator 5 * peroxide free-radical
initiator available from Akzo Nobel. Zinc pentachlorothiophenol
(ZnPCTP) 1
Example 3
[0101] In this Example, slugs of different polyalkenamer rubber
compositions having the formulations described in Table 3 were
cured at different temperature/time cycles as described in Table 4
to make solid, single-layered core samples. Concentrations are in
parts per hundred (phr) unless otherwise indicated. As used herein,
the term "parts per hundred," also known as "phr," 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 base rubber
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.
TABLE-US-00003 TABLE 3 (Core Compositions Containing 100%
Polyalkenamer as Base Rubber) Peroxide Zinc ZDA Co- Free-Radical
Oxide Soft and Base agent Initiator Filler Fast Agent Sample Rubber
(phr) (phr) (phr) (phr) A Vestenamer* 0 0 0 0 8012 B Vestenamer 0
2.50 parts 0 0 8012 Varox* 231- XL C Vestenamer 0 5.00 parts 0 0
8012 Varox 231- XL D Vestenamer 33.5 parts 0.85 parts 19.9 parts 0
8012 SR-526* Perkadox* ZnO* BC E Vestenamer 33.5 parts 1.75 parts
19.9 parts 0 8012 SR-526 Perkadox BC ZnO F Vestenamer 33.5 parts
3.00 parts 19.9 parts 0 8012 SR-526 Perkadox BC ZnO G Vestenamer
33.5 parts 5.00 parts 19.9 parts 0 8012 SR-526 Perkadox BC ZnO H
Vestenamer 33.5 parts 5.00 parts 19.9 parts 1.0 parts 8012 SR-526
Perkadox BC ZnO ZnPCTP* I Vestenamer 50 parts 1.00 parts 13.0 parts
1.0 parts 8012 SR-526 Perkadox BC ZnO ZnPCTP J Vestenamer 50 parts
1.00 parts 13.0 parts 1.0 parts 8012 SR-526 Perkadox BC ZnO ZnPCTP
K Vestenamer 50 parts 2.00 parts 13.0 parts 1.0 parts 8012 SR-526
Perkadox BC ZnO ZnPCTP L Vestenamer 50 parts 2.00 parts 13.0 parts
1.0 parts 8012 SR-526 Perkadox BC ZnO ZnPCTP
TABLE-US-00004 TABLE 4 (Curing Cycle and Properties for Core
Samples) Cure Temp Cure Time DCM Shore C Sample (.degree. F.)
(Minutes) (Compression) COR Hardness A No Heat- No Heat- 102 0.568
75 Curing Curing B 350.degree. F. 12 Min. 47 0.617 41 C 350.degree.
F. 12 Min. -62 0.687 -- D 350.degree. F. 11 Min. 60 0.767 80.4 E
350.degree. F. 11 Min. 68 0.778 82.9 F 350.degree. F. 11 Min. 79 --
85.9 G 350.degree. F. 11 Min. 75 0.780 87.6 H 350.degree. F. 11
Min. 56 0.788 83.8 I 330.degree. F. 11 Min. 91 0.794 85.9 J
350.degree. F. 11 Min. 94 0.795 89 K 330.degree. F. 11 Min. 98
0.792 90.7 L 350.degree. F. 11 Min. 99 0.796 90.7 * Vestenamer
.RTM. 8012--polyoctenamer rubber having a trans-content of
approximately 80% and a melting point of approximately 54.degree.
C., available from Evonik Degussa GmbH. * SR-526--zinc diacrylate
available from Akzo Nobel NV. * Varox .RTM.
231--XL-1,1-di(t-butylperoxy)-3,3,5-trimethylcyclohexane available
from Atofina. * Perkadox .RTM. BC--dicumyl peroxide granules
available from Akzo Nobel NV. * ZnO--zinc oxide * ZnPCTP--zinc
pentachlorothiophenol, available from Strukol Company and
Echina.
Example 4
[0102] In this Example, slugs of different polyalkenamer rubber
compositions having the formulations described in Table 5 were
cured at different temperature/time cycles as described in Table 6
to make solid, single-layered core samples.
TABLE-US-00005 TABLE 5 (Core Compositions Containing Blends of
Polyalkenamer and Polybutadiene Rubber) Peroxide Soft ZDA Free-
Zinc and Co- Radical Oxide Fast Base Secondary agent Initiator
Filler Agent Sample Rubber Rubber (phr) (phr) (phr) (phr) M 80
parts 20 parts 40 parts 1 part 23.5 1 part Vestenamer Buna CB
SR-526 Perkadox parts ZnPCTP 8012 23 BC ZnO N 80 parts 20 parts 40
parts 1 part 23.5 1 part Vestenamer Buna CB SR-526 Perkadox parts
ZnPCTP 8012 23 BC ZnO O 80 parts 20 parts 40 parts 3 parts 23.5 1
part Vestenamer Buna CB SR-526 Perkadox parts ZnPCTP 8012 23 BC ZnO
P 80 parts 20 parts 40 parts 3 parts 23.5 1 part Vestenamer Buna CB
SR-526 Perkadox parts ZnPCTP 8012 23 BC ZnO Q 80 parts 20 parts 30
parts 1 part 26 parts 2 parts Vestenamer Buna CB SR-526 Perkadox
ZnO ZnPCTP 8012 23 BC R 80 parts 20 parts 30 parts 1 part 26 parts
2 parts Vestenamer Buna CB SR-526 Perkadox ZnO ZnPCTP 8012 23 BC S
80 parts 20 parts 30 parts 2 parts 26 parts 2 parts Vestenamer Buna
CB SR-526 Perkadox ZnO ZnPCTP 8012 23 BC T 80 parts 20 parts 30
parts 2 parts 26 parts 2 parts Vestenamer Buna CB SR-526 Perkadox
ZnO ZnPCTP 8012 23 BC * Buna .RTM. CB-23--polybutadiene rubber
available from Lanxess Corp.
TABLE-US-00006 TABLE 6 (Curing Cycle and Properties for Core
Samples) Cure Temp Cure Time DCM Shore C Sample (.degree. F.)
(Minutes) (Compression) COR Hardness M 350.degree. F. 11 Min. 89
0.789 51.4 N 330.degree. F. 11 Min. 89 0.788 51.7 O 350.degree. F.
11 Min. 99 58.9 P 330.degree. F. 11 Min. 96 58.6 Q 350.degree. F.
11 Min. 51 0.778 43.2 R 330.degree. F. 15 Min. 54 0.780 44.5 S
350.degree. F. 11 Min. 57 0.780 46.9 T 330.degree. F. 15 Min. 59
0.780 48.6
[0103] In above Tables 3 and 4, the sample cores are made of rubber
compositions containing 100% Vestenamer.RTM. 8012--polyoctenamer
rubber (Samples A-L), while in Tables 5 and 6, the sample cores
(M-T) are made of rubber compositions containing 80% Vestenamer
8012 and 20% Buna CB 23--polybutadiene rubber (Samples M-T).
[0104] In each of the samples, when the peroxide free-radical
initiator is added to the rubber composition and heat and pressure
are applied, a complex curing reaction occurs. In general, the
resulting cross-linked core compositions have higher COR values.
Cores with higher COR values have higher rebound velocities. These
high COR cores (and golf balls made with such cores) generally
rebound faster, retain more total energy when struck with a club,
and have longer flight distance. The relatively high resiliency of
the core means that it will reach a higher velocity when struck by
a golf club and travel longer distances.
[0105] Surprisingly, however, the compression of the polyalkenamer
rubber core composition in the above inventive samples does not
increase substantially as the COR increases, as would be expected
with conventional polybutadiene rubber cores. Rather, the
compression of the polyalkenamer rubber core remains substantially
the same or is reduced as the COR increases. While not wishing to
be bound by any theory, it is believed the high crystallinity of
the polyalkenamer rubber is reduced by adding the peroxide,
particularly at relatively high amounts, as shown in Samples C and
H (5 phr peroxide), and curing the composition so the rubber chains
are cross-linked. This may cause the compression or stiffness of
the polyalkenamer rubber composition to be reduced. Adding the
peroxide at these high levels and curing and cross-linking the
composition may disrupt the crystallinity of polyalkenamer. The
material becomes softer and more rubbery, and the compression of
the core sample is reduced. The compression of the core affects the
"feel" of the ball as the club face makes impact with the ball. In
general, cores with relatively low compression values have a softer
feel. Golf balls made with such cores tend to have better
playability and the sensation of hitting such balls is generally
more pleasant. Furthermore, in general, when the ball contains a
relatively soft core, the resulting spin rate of the ball is
relatively low. The compressive force acting on the ball is less
when the cover is compressed by the club face against a relatively
soft core.
[0106] Hardness Gradients
[0107] Referring to the graph in FIG. 6, the hardness values of
different core samples from Tables 5 and 6, as measured at
different points extending radially from the center of the core,
are plotted. Each of the sample cores in FIG. 6 has a positive
hardness gradient.
[0108] 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. At the very least, and not as an
attempt to limit the application of the doctrine of equivalents to
the scope of the claims, each numerical parameter should at least
be construed in light of the number of reported significant digits
and by applying ordinary techniques.
[0109] 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.
[0110] While the illustrative embodiments of the invention have
been described with particularity, it will be understood that
various other modifications will be apparent to and can be readily
made by those of ordinary skill in the art without departing from
the spirit and scope of the invention. Accordingly, it is not
intended that the scope of the claims appended hereto be limited to
the examples and descriptions set forth herein, but rather that the
claims be construed as encompassing all of the features of
patentable novelty which reside in the present invention, including
all features which would be treated as equivalents thereof by those
of ordinary skill in the art to which the invention pertains.
* * * * *