U.S. patent application number 12/855352 was filed with the patent office on 2010-12-02 for multi-layer golf balls having moisture barrier layers based on polyalkenamer compositions.
Invention is credited to Mark L. Binnette, Robert Blink, David A. Bulpett, Brian Comeau, Douglas S. Goguen, Michael J. Sullivan.
Application Number | 20100304895 12/855352 |
Document ID | / |
Family ID | 43220891 |
Filed Date | 2010-12-02 |
United States Patent
Application |
20100304895 |
Kind Code |
A1 |
Comeau; Brian ; et
al. |
December 2, 2010 |
MULTI-LAYER GOLF BALLS HAVING MOISTURE BARRIER LAYERS BASED ON
POLYALKENAMER COMPOSITIONS
Abstract
Golf balls having a dual-core comprising an inner core and outer
moisture barrier core layer are provided. The outer core help
prevent moisture from penetrating into the inner core. A cover
layer, preferably made of a polyurethane or polyurea material, is
disposed about the outer core layer. The inner and outer cores are
formed of a rubber composition, preferably a polyalkenamer rubber.
The polyalkenamer rubber composition may further include other
rubbers such as polybutadiene, polyisoprene, ethylene propylene
rubber, ethylene propylene diene rubber, and styrene-butadiene
rubber. The outer core has a moisture vapor transmission rate
(MVTR) lower than that of the cover. In one version, the outer core
has a MVTR of 1 gramsmm/m.sup.2day or less, preferably in the range
of 0.45 to 0.95 gramsmm/m.sup.2day.
Inventors: |
Comeau; Brian; (Berkley,
MA) ; Bulpett; David A.; (Boston, MA) ;
Sullivan; Michael J.; (Barrington, RI) ; Blink;
Robert; (Newport, RI) ; Goguen; Douglas S.;
(New Bedford, MA) ; Binnette; Mark L.;
(Mattapoisett, MA) |
Correspondence
Address: |
ACUSHNET COMPANY
333 BRIDGE STREET, P. O. BOX 965
FAIRHAVEN
MA
02719
US
|
Family ID: |
43220891 |
Appl. No.: |
12/855352 |
Filed: |
August 12, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12358358 |
Jan 23, 2009 |
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12855352 |
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11767070 |
Jun 22, 2007 |
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12358358 |
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10773906 |
Feb 6, 2004 |
7255656 |
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11767070 |
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10341574 |
Jan 13, 2003 |
6852044 |
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10773906 |
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10002641 |
Nov 28, 2001 |
6547677 |
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10341574 |
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11833601 |
Aug 3, 2007 |
7503855 |
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12358358 |
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11537830 |
Oct 2, 2006 |
7267621 |
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11833601 |
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10665176 |
Sep 19, 2003 |
7115049 |
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11537830 |
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Current U.S.
Class: |
473/376 ;
473/374; 473/378 |
Current CPC
Class: |
A63B 37/0062 20130101;
A63B 37/12 20130101; A63B 37/0043 20130101; A63B 37/0064 20130101;
A63B 37/0003 20130101; A63B 37/0066 20130101; A63B 37/0051
20130101; A63B 37/0031 20130101; A63B 37/0045 20130101 |
Class at
Publication: |
473/376 ;
473/374; 473/378 |
International
Class: |
A63B 37/02 20060101
A63B037/02; A63B 37/12 20060101 A63B037/12; A63B 37/06 20060101
A63B037/06 |
Claims
1. A golf ball, comprising: a dual-core comprising an inner core
and outer moisture barrier core layer, wherein the outer core layer
surrounds the inner core, the inner core having a diameter of about
1.30 inches to about 1.58 inches and a compression of about 100 or
less, the inner core being formed from a first rubber composition
and the outer core layer being formed from a second rubber
composition, the second rubber composition comprising a
polyalkenamer in an amount of at least 50 weight percent; the outer
core layer having a thickness of about 0.01 inches to about 0.20
inches and outer surface hardness of about 80 Shore C or greater,
wherein the outer core has a moisture vapor transmission rate lower
than that of the cover; and a cover layer surrounding the outer
core layer, the cover layer having a material hardness of about 30
to about 65 Shore D.
2. The golf ball of claim 1, wherein the outer core has a moisture
vapor transmission rate of 1 gramsmm/m.sup.2day or less.
3. The golf ball of claim 2, wherein the outer core has a moisture
vapor transmission rate of 0.45 to 0.95 gramsmm/m.sup.2day.
4. The golf ball of claim 1, wherein the inner core has a
compression of 70 to 90.
5. The golf ball of claim 1, wherein the inner core has a surface
hardness of 75 to 90 Shore C.
6. The golf ball of claim 1, wherein the inner core has a surface
hardness of 78 to 87 Shore C.
7. The golf ball of claim 1, wherein the outer core layer has a
surface hardness of 83 to 97 Shore C.
8. The golf ball of claim 1, wherein the outer core layer has a
surface hardness of 85 to 93 Shore C.
9. The golf ball of claim 1, wherein the inner core has as diameter
of 1.45 to 1.57 inches.
10. The golf ball of claim 1, wherein the outer core layer has a
thickness of 0.025 to 0.060 inches.
11. The golf ball of claim 1, wherein the cover layer comprises an
inner cover layer and outer cover layer.
12. The golf ball of claim 11, wherein the inner cover has a
material hardness greater than the material hardness of the outer
cover.
13. A golf ball, comprising: a dual-core comprising an inner core
and outer moisture barrier core layer, wherein the outer core layer
surrounds the inner core, the inner core having a diameter of about
1.51 inches to about 1.58 inches and a compression of about 100 or
less, the inner core being formed from a first rubber composition
and the outer core layer being formed from a second rubber
composition, the second rubber composition comprising a
polyalkenamer in an amount of at least 50 weight percent; the outer
core layer having a thickness of about 0.01 inches to about 0.06
inches and outer surface hardness of about 80 Shore C or greater,
wherein the outer core has a moisture vapor transmission rate lower
than that of the cover; and a cover layer surrounding the outer
core layer, the cover layer being formed from a composition
comprising polyurethane; polyurea; or a hybrid, copolymer or blend
of polyurethane and polyurea and having a material hardness of
about 30 to about 65 Shore D.
14. The golf ball of claim 13, wherein the outer core has a
moisture vapor transmission rate of 1 gramsmm/m.sup.2day or
less.
15. The golf ball of claim 14, wherein the outer core has a
moisture vapor transmission rate of 0.45 to 0.95
gramsmm/m.sup.2day.
16. The golf ball of claim 13, wherein the cover layer has a
thickness of 0.010 to 0.055 inches.
17. The golf ball of claim 13, wherein the cover layer has a
thickness of 0.020 to 0.040 inches.
18. The golf ball of claim 13, wherein the cover layer has a
material hardness of 40 to 63 Shore D.
19. The golf ball of claim 13, wherein the cover layer comprises an
inner cover layer and outer cover layer, the inner cover layer
being formed from an olefin-based ionomer copolymer and the outer
cover layer being formed from a composition comprising
polyurethane; polyurea; or a hybrid, copolymer, or blend of
polyurethane and polyurea.
20. The golf ball of claim 19, wherein the inner cover has a
material hardness of 60 Shore D or greater and the outer cover has
a material hardness of 30 to 65 Shore D.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation-in-part of co-pending,
co-assigned U.S. patent application Ser. No. 12/358,358 filed Jan.
23, 2009, 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 aforementioned U.S. patent application Ser. No.
12/358,358 is also a continuation-in-part of U.S. application Ser.
No. 11/833,601, filed Aug. 3, 2007, now U.S. Pat. No. 7,503,855
which is a continuation of U.S. patent application Ser. No.
11/537,830, filed Oct. 2, 2006, now U.S. Pat. No. 7,267,621, which
is a continuation of U.S. patent application Ser. No. 10/665,176,
filed Sep. 19, 2003, now U.S. Pat. No. 7,115,049. The entire
disclosure of each of these references is 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 containing dual-layer cores having
a large, relatively soft inner core layer surrounded by a thin,
relatively hard outer core layer. In one embodiment, the outer core
is a moisture barrier layer made of a rubber composition comprising
polyalkenamer rubber and preferably polyoctenamer. The moisture
barrier layer is disposed about the inner core to prevent moisture
from penetrating into the core.
[0004] 2. Brief Review of the Related Art
[0005] Dual- and multi-layer cover golf balls having desirable
performance properties, such as spin profile, have been constructed
using an ionomeric inner cover layer and a polyurethane outer cover
layer. However, there remains a need in the industry for a golf
ball construction which provides similar performance properties
without requiring more than one cover layer. The present invention
provides such golf ball construction, which includes the use of a
large, relatively soft inner core layer surrounded by a thin,
relatively hard outer core layer, and a cover layer. By eliminating
the need for more than one cover layer, while maintaining desirable
performance characteristics, golf balls of the present invention
provide a viable, cost efficient alternative to current dual- and
multi-layer cover golf balls.
[0006] Multi-piece golf balls having solid inner cores made from a
polybutadiene rubber material cross-linked with peroxide and/or
zinc diacrylate are common in the industry. The core acts as an
"engine" for the golf ball and is the primary source of resiliency.
One problem with such multi-piece golf balls is that moisture can
penetrate into the core and harmfully affect the core's properties.
As the core absorbs water, it tends to lose its resiliency. The
compression and coefficient of restitution (COR) of the ball can be
reduced significantly if a substantial amount of water enters the
core. The golf ball industry has looked to address the problem of
moisture-penetration by applying a barrier layer over the inner
core. The moisture barrier layer surrounds and encapsulates the
core to protect it from the negative effects of moisture. Some
materials for making moisture barrier layers are described in the
patent literature. For example, Cavallaro et al., U.S. Pat. No.
6,632,147 and Hogge et al., U.S. Pat. No. 6,838,028 disclose golf
balls having an intermediate moisture vapor barrier layer that may
be made from: (i) multi-layer thermoplastic films including
polypropylene films that have been metalized or coated with
polyvinylidene chloride (PVDC), (ii) blends of ionomers polyvinyl
alcohol copolymer and polyamides, and (iii) dispersions of acid
salts of polyetheramines, among others.
[0007] Hogge et al., U.S. Pat. No. 6,932,720 discloses golf balls
having moisture vapor barrier layers made of butyl rubber. The
butyl rubber may be a halogenated butyl rubber such as bromobutyl
rubber or chlorobutyl rubber. Also, the butyl rubber may be a
sulfonated butyl rubber. The butyl rubber may be blended with other
polymers such as double bond-vulcanizable rubber, ethylene
propylene diene monomer rubber and vinylidene chloride.
[0008] Hogge et al., U.S. Pat. No. 7,004,854 discloses a golf ball
having a core, intermediate barrier layer, and cover. The barrier
layer is made of a thermoplastic or thermoset composition
comprising microparticles such as fibers, whiskers, metal flakes,
micaceous particles, nanoparticles, or combinations thereof. The
microparticles are dispersed in a binder such as rubber,
polyolefins, styrene polymers, single-site catalyzed polymers, and
combinations thereof.
[0009] Hogge et al., U.S. Pat. No. 7,182,702 discloses a golf ball
having a moisture vapor barrier layer formed from a composition
comprising an elastomer (for example, halogenated butyl rubber) and
a double-bond vulcanizable rubber that is cured by infrared or
ultraviolet radiation.
[0010] Other materials that can be used in multi-piece golf balls
are known in the industry. 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 natural and synthetic
rubbers such as 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 outer core is a moisture barrier layer that
prevents moistures from penetrating into the inner core layer, and
the inner core and/or outer core is made of a polyalkenamer rubber
composition.
[0011] Although some moisture barrier layers are generally
effective at preventing moisture penetration, there is a need for
an improved golf ball having a relatively thin moisture barrier
layer. The composition needs to be effective at blocking moisture
from penetrating into the core, but it also must not degrade the
playing performance of the ball. The present invention provides
golf balls having such features as well as other advantageous
properties and benefits.
SUMMARY OF THE INVENTION
[0012] In one embodiment, the present invention provides a golf
ball comprising an inner core layer, an outer core layer, and a
cover layer. The inner core layer has a diameter of from 1.51
inches to 1.58 inches and a compression of 100 or less. The outer
core layer has a thickness of from 0.01 inches to 0.06 inches and
an outer surface hardness of 80 Shore C or greater. The cover layer
has a material hardness of from 30 to 65 Shore D.
[0013] In another embodiment, the present invention provides a golf
ball consisting essentially of an inner core layer, an outer core
layer, and a cover layer. The inner core layer has a diameter of
from 1.51 inches to 1.58 inches and a compression of 100 or less.
The outer core layer has a thickness of from 0.01 inches to 0.06
inches and an outer surface hardness of 80 Shore C or greater. The
cover layer is formed from a polyurethane- or polyurea-based
composition having a material hardness of from 30 to 65 Shore
D.
[0014] In another embodiment, the present invention provides a golf
ball comprising an inner core layer, an outer core layer, and a
cover layer. The inner core layer has a diameter of from 1.51
inches to 1.58 inches and a compression of 100 or less. The outer
core layer has a thickness of from 0.01 inches to 0.06 inches and
an outer surface hardness of 80 Shore C or greater. The cover layer
has a material hardness of from 30 to 65 Shore D. The golf ball
does not include a layer formed from an ionomer-based
composition.
[0015] In a particularly preferred embodiment, the golf ball
contains a dual-core comprising an inner core and outer moisture
barrier core layer. The inner core has a diameter of about 1.30 to
about 1.58 inches and a compression of about 100 or less,
preferably about 70 to about 90. The inner core is made of a first
rubber composition and the outer core is made of a second rubber
composition comprising a polyalkenamer rubber in an amount of at
least 50 weight percent. For example, a polyalkenamer rubber having
a trans-content of 55% or greater and a melting point of 30.degree.
C. or greater can be used to form the outer core. Polyoctenamer
rubbers are particularly preferred. The concentration of
polyalkenamer rubber is preferably in the range of about 60 to
about 100 weight percent based on weight of polymer in the
composition. The polyalkenamer rubber helps block moisture from
penetrating into the inner core without degrading the playing
performance of the ball. The polylalkenamer 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 polylalkenamer rubber
composition also may be used to make the inner core. The outer core
layer helps prevent moisture from penetrating into the inner core
and has a thickness of about 0.01 to about 0.20 inches and outer
surface hardness of about 80 Shore C or greater. The outer core has
a moisture vapor transmission rate (MVTR) lower than that of the
cover. In one version, the outer core has a MVTR of 1
gramsmm/m.sup.2day or less, preferably in the range of 0.45 to 0.95
gramsmm/m.sup.2 day, more preferably 0.6 gramsmm/m.sup.2day or
less, and most preferably 0.4 gramsmm/m.sup.2day or less. A cover
layer is disposed about the outer core layer and has a material
hardness of about 30 to about 65 Shore D in one preferred
embodiment. The cover layer may comprise inner and outer cover
layers. Preferably, the outer cover layer is formed of a
composition comprising a polyurethane; polyurea; or hybrid, blend,
or copolymer of polyurethane and polyurea.
[0016] The inner core preferably has a surface hardness of about 75
to about 90, more preferably about 78 to about 87. While the outer
core layer preferably has a surface hardness of about 83 to about
97 Shore C and more preferably about 85 to about 93 Shore C. In one
version, the inner core has a diameter of about 1.45 to about 1.57
inches and the outer core has a thickness of about 0.025 to about
0.060 inches. In one version, the polyurethane, polyurea, or hybrid
polyurethane-polyurea cover layer has a thickness of about 0.010 to
about 0.055 inches and preferably 0.020 to 0.040 inches. The
polyurethane, polyurea, or polyurethane-polyurea hybrid cover layer
has a material hardness of about 40 to about 63 Shore D in one
preferred embodiment. In another version, the cover layer comprises
inner and outer cover layers, wherein the inner cover has a surface
hardness of about 60 Shore D or greater and the outer cover has a
surface hardness of about 30 to about 65 Shore D gradient.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] 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:
[0018] FIG. 1 is a front view of a dimpled golf ball made in
accordance with the present invention;
[0019] FIG. 2 is a cross-sectional view of a three-piece golf ball
having an inner core, outer moisture barrier core layer comprising
a polyalkenamer rubber, and cover made in accordance with the
present invention;
[0020] FIG. 3 is a cross-sectional view of a four-piece golf ball
having an inner core, outer moisture barrier core layer comprising
a polyalkenamer rubber, and inner and outer cover layers made in
accordance with the present invention; and
[0021] FIG. 4 is a cross-sectional view of a five-piece golf ball
having an inner core, outer moisture barrier core layer comprising
the polyalkenamer rubber, intermediate layer, and inner and outer
cover layers made in accordance with the present invention.
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 polyalkenamer, preferably a
polyoctenamer. For example, a polyalkenamer rubber having a
trans-content of 55% or greater and a melting point of 30.degree.
C. or greater can be used to form the outer core. Golf balls having
various constructions may be made in accordance with this
invention. For example, golf balls having three-piece, four-piece,
and five-piece constructions with dual-cores and single or
multi-layered cover materials may be made The term, "layer" as used
herein means generally any spherical portion of the golf ball. More
particularly, in one version, a three-piece golf ball comprising a
dual-core having a solid center (otherwise referred to as an inner
core) and a surrounding outer core layer and a single-layered cover
is made. The outer core layer has moisture barrier properties to
protect the inner core and prevent moisture from penetrating
therein. In another version, a four-piece ball having a dual-core
and multi-layered cover (having an inner cover layer and outer
cover layer) 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
[0023] In one preferred embodiment, the golf ball contains a large,
relatively soft inner core layer surrounded by a thin, relatively
hard outer core layer. The large, relatively soft inner core layer
has an outer diameter within a range having a lower limit of 1.50
or 1.51 or 1.52 or 1.53 or 1.54 or 1.55 inches and an upper limit
of 1.55 or 1.56 or 1.57 or 1.58 inches. The volume of the inner
core layer is preferably at least 70%, or at least 75%, or at least
80% of the total volume of the combined inner and outer core
layers. The inner core layer has a compression of 100 or less, or
less than 100, or 90 or less, or less than 90, or 70 or less, or
less than 70, or a compression within a range having a lower limit
of 70 or 75 or 80 or 85 and an upper limit of 90 or 95 or 100 or
110. The inner core layer has an outer surface hardness within a
range having a lower limit of 50 or 55 or 60 or 65 or 70 or 75 or
78 or 80 Shore C and an upper limit of 80 or 85 or 90 or 95 Shore
C, and a center hardness within a range having a lower limit of 40
or 45 or 50 or 55 Shore C and an upper limit of 60 or 65 or 70
Shore C. The inner core layer has a negative hardness gradient,
zero hardness gradient, or a positive hardness gradient of up to 45
Shore C.
[0024] The thin, relatively hard outer core layer has a thickness
within a range having a lower limit of from 0.005 or 0.01 or 0.02
or 0.03 or 0.035 inches and an upper limit of 0.035 or 0.04 or
0.045 or 0.05 or 0.055 or 0.06 inches. The thickness of the outer
core layer is preferably such that the dual-layer core has an outer
diameter within a range having a lower limit of 1.60 or 1.61 or
1.62 inches and an upper limit of 1.62 or 1.63 or 1.64 inches. The
outer core layer has an outer surface Shore C hardness greater than
the Shore C hardness of the inner core layer's outer surface. In
one embodiment, the outer core layer has an outer surface hardness
of 80 Shore C or greater or 82 Shore C or greater. In another
embodiment, the outer core layer has an outer surface hardness
within a range having a lower limit of 80 or 82 or 85 Shore C and
an upper limit of 90 or 92 or 93 or 95 Shore C. In another
embodiment, the outer core layer has an outer surface hardness
within a range having a lower limit of 50 or 53 or 55 or 58 Shore D
and an upper limit of 60 or 62 or 64 or 70 Shore D. In an
alternative embodiment, the thin, relatively hard outer core layer
is replaced with a thin, relatively soft and flexible outer core
layer having an outer surface hardness of from 50 to 80 Shore
C.
[0025] For purposes of the present disclosure, a hardness gradient
of a golf ball layer is defined by hardness measurements made at
the outer surface of the layer and the inner surface of the layer.
"Negative" and "positive" refer to the result of subtracting the
hardness value at the innermost surface of the golf ball component
from the hardness value at the outermost surface of the component.
For example, if the outer surface of a solid core has a lower
hardness value than the center (i.e., the surface is softer than
the center), the hardness gradient will be deemed a "negative"
gradient.
[0026] In one embodiment, the golf ball contains a dual-core having
an inner core and a surrounding outer moisture barrier 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 team, "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 teiin, "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 steep 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. Hardness gradients are disclosed
more fully, for example, in U.S. Pat. Nos. 7,429,221; 7,427,242;
7,410,429; and 7,255,656, the entire disclosures of which are
hereby incorporated herein by reference.
[0027] The inner and outer core layers are preferably formed from
rubber-based compositions. Suitable rubber core compositions
include natural and synthetic rubbers including, but not limited
to, polybutadiene, polyisoprene, ethylene propylene rubber ("EPR"),
styrene-butadiene rubber, styrenic block copolymer rubbers (such as
SI, SIS, SB, SBS, SIBS, and the like, where "S" is styrene, "I" is
isobutylene, and "B" is butadiene), 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. Diene rubbers are preferred, particularly polybutadiene,
styrene-butadiene, and mixtures of polybutadiene with other
elastomers wherein the amount of polybutadiene present is at least
40 wt % based on the total polymeric weight of the mixture.
Suitable polybutadiene-based and styrene-butadiene-based rubber
core compositions preferably comprise the base rubber, an initiator
agent, and a coagent. Suitable examples of commercially available
polybutadienes include, but are not limited to, Buna CB neodymium
catalyzed polybutadiene rubbers, such as Buna CB 23, and
Taktene.RTM. cobalt catalyzed polybutadiene rubbers, such as
Taktene.RTM. 220 and 221, commercially available from LANXESS.RTM.
Corporation; SE BR-1220, commercially available from The Dow
Chemical Company; Europrene.RTM. NEOCIS.RTM. BR 40 and BR 60,
commercially available from Polimeri Europa.RTM.; UBEPOL-BR.RTM.
rubbers, commercially available from UBE Industries, Inc.; BR 01,
commercially available from Japan Synthetic Rubber Co., Ltd.; and
Neodene neodymium catalyzed high cis polybutadiene rubbers, such as
Neodene BR 40, commercially available from Karbochem.
[0028] Suitable initiator agents include organic peroxides, high
energy radiation sources capable of generating free radicals, and
combinations thereof. High energy radiation sources capable of
generating free radicals include, but are not limited to, electron
beams, ultra-violet radiation, gamma radiation, X-ray radiation,
infrared radiation, heat, and combinations thereof. 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; lauryl peroxide; benzoyl peroxide;
and combinations thereof. In a particular embodiment, the initiator
agent is dicumyl peroxide, including, but not limited to
Perkadox.RTM. BC, commercially available from Akzo Nobel. Peroxide
initiator agents 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 by
weight per 100 parts of the base rubber, 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.
[0029] Co-agents are commonly used with peroxides to increase the
state of cure. Suitable coagents include, but are not limited to,
metal salts of unsaturated carboxylic acids; 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, nickel, and
sodium. In a particular embodiment, the co-agent is selected from
zinc salts of acrylates, diacrylates, methacrylates,
dimethacrylates, and mixtures thereof. In another particular
embodiment, the co-agent is zinc diacrylate. 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 base rubber, and an upper
limit of 24 or 25 or 30 or 35 or 40 or 45 or 50 or 60 parts by
weight per 100 parts of the base rubber. When one or more less
active co-agents are used, such as zinc monomethacrylate and
various liquid acrylates and methacrylates, the amount of less
active co-agent used may be the same as or higher than for zinc
diacrylate and zinc dimethacrylate co-agents. 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 co-agent.
[0030] The rubber composition optionally includes a curing agent.
Suitable curing agents include, but are not limited to, sulfur;
N-oxydiethylene 2-benzothiazole sulfenamide;
N,N-di-ortho-tolylguanidine; bismuth dimethyldithiocarbamate;
N-cyclohexyl 2-benzothiazole sulfenamide; N,N-diphenylguanidine;
4-morpholinyl-2-benzothiazole disulfide; dipentamethylenethiuram
hexasulfide; thiuram disulfides; mercaptobenzothiazoles;
sulfenamides; dithiocarbamates; thiuram sulfides; guanidines;
thioureas; xanthates; dithiophosphates; aldehyde-amines;
dibenzothiazyl disulfide; tetraethylthiuram disulfide;
tetrabutylthiuram disulfide; and combinations 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 contain one or more fillers to
adjust the density and/or specific gravity of the core. 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).
[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 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 within a range having a lower limit of 0.05 or
0.1 or 0.2 or 0.5 phr and an upper limit of 1.0 or 2.0 or 3.0 or
5.0 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 and metal-containing organosulfur compounds;
organic sulfur compounds, including mono, di, and polysulfides,
thiol, and mercapto compounds; inorganic sulfide compounds; blends
of an organosulfur compound and an inorganic sulfide compound;
Group VIA compounds; substituted and unsubstituted aromatic organic
compounds that do not contain sulfur or metal; aromatic
organometallic compounds; hydroquinones; benzoquinones;
quinhydrones; catechols; resorcinols; and combinations thereof.
[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.
Suitable organosulfur compounds are further disclosed, for example,
in U.S. Pat. Nos. 6,635,716, 6,919,393, 7,005,479 and 7,148,279,
the entire disclosures of which are hereby incorporated herein by
reference. In a particular embodiment, the soft and fast agent is
selected from zinc pentachlorothiophenol, pentachlorothiophenol,
ditolyl disulfide, diphenyl disulfide, dixylyl disulfide,
2-nitroresorcinol, and combinations thereof.
[0037] Suitable types and amounts of base rubber, initiator agent,
co-agent, filler, and additives are more fully described in, for
example, U.S. Pat. Nos. 6,566,483, 6,695,718, and 6,939,907,
7,041,721 and 7,138,460, the entire disclosures of which are hereby
incorporated herein by reference. In a particular embodiment, the
inner and/or outer core layer composition includes from 1 to 100
phr of a stiffening agent. Preferably, a stiffening agent is
present in the outer core layer composition and not the inner core
layer composition. Suitable stiffening agents include, but are not
limited to, ionomers, acid copolymers and terpolymers, polyamides,
and polyesters. Stiffening agents are further disclosed, for
example, in U.S. Pat. Nos. 6,120,390 and 6,284,840, the entire
disclosures of which are hereby incorporated herein by reference. A
transpolyisoprene (e.g., TP-301 transpolyisoprene, commercially
available from Kuraray Co., Ltd.) or transbutadiene rubber may also
be added to increase stiffness to a core layer and/or improve
cold-forming properties, which may improve processability by making
it easier to mold outer core layer half-shells during the golf ball
manufacturing process. When included in a core layer composition,
the stiffening agent is preferably present in an amount of from 5
to 10 pph.
[0038] The specific gravity of the outer core layer is preferably
the same as, substantially the same as, or greater than the
specific gravity of the inner core layer. In a particular
embodiment, the specific gravity of the outer core layer is greater
than that of the inner core layer, and the outer core layer is
formed from a thin dense layer composition. Thin dense layer
compositions include those disclosed, for example, in U.S. Pat. No.
6,494,795, the entire disclosure of which is hereby incorporated
herein by reference. Also suitable for use as thin dense layer
compositions are the thermoplastic materials disclosed in U.S. Pat.
Nos. 6,149,535 and 6,152,834, the entire disclosure of which is
hereby incorporated herein by reference. In a particular
embodiment, the outer core layer is a thin dense layer, preferably
having a specific gravity of 1.2 or greater, or 1.5 or greater, or
1.8 or greater, or 2 or greater, and a thickness within the range
having a lower limit of 0.001 inches or 0.005 inches or 0.01 inches
and an upper limit of 0.02 inches or 0.03 inches or 0.05 inches or
0.06 inches. The thin dense layer is preferably applied to the core
as a liquid solution, dispersion, lacquer, paste, gel, melt, etc.,
such as a loaded or filled natural or non-natural rubber latex,
polyurethane, polyurea, epoxy, polyester, any reactive or
non-reactive coating or casting material; and then cured, dried or
evaporated down to the equilibrium solids level. The thin dense
layer may also be formed by compression or injection molding, RIM,
casting, spraying, dipping, powder coating, or any means of
depositing materials onto the inner core. The thin dense layer may
also be a thermoplastic polymer loaded with a specific gravity
increasing filler, fiber, flake or particulate, such that it can be
applied as a thin coating and meets the preferred specific gravity
levels discussed above. One particular example of a thin dense
layer, which was made from a soft polybutadiene with tungsten
powder using the compression molded method, has a thickness of from
0.021 inches to 0.025 inches, a specific gravity of 1.31, and a
Shore C hardness of about 72. For reactive liquid systems, the
suitable materials include any material which reacts to form a
solid such as epoxies, styrenated polyesters, polyurethanes or
polyureas, liquid polybutadienes, silicones, silicate gels, agar
gels, etc. Casting, RIM, dipping and spraying are the preferred
methods of applying a reactive thin dense layer. Non-reactive
materials include any combination of a polymer either in melt or
flowable form, powder, dissolved or dispersed in a volatile
solvent.
[0039] The dual-layer core is surrounded by a cover having one or
more layers. Suitable cover materials include, but are not limited
to, ionomer resins and blends thereof (e.g., Surlyn.RTM. ionomer
resins and DuPont.RTM. HPF 1000 and HPF 2000, commercially
available from E. I. du Pont de Nemours and Company; Iotek.RTM.
ionomers, commercially available from ExxonMobil Chemical Company;
Amplify.RTM. JO ionomers of ethylene acrylic acid copolymers,
commercially available from The Dow Chemical Company; and
Clarix.RTM. ionomer resins, commercially available from A. Schulman
Inc.); polyurethanes; polyureas; copolymers, blends, and hybrids of
polyurethane and polyurea; polyethylene, including, for example,
low density polyethylene, linear low density polyethylene, and high
density polyethylene; polypropylene; rubber-toughened olefin
polymers; acid copolymers, e.g., (meth)acrylic acid, which do not
become part of an ionomeric copolymer; plastomers; flexomers;
styrene/butadiene/styrene block copolymers;
styrene/ethylene-butylene/styrene block copolymers; dynamically
vulcanized elastomers; ethylene vinyl acetates; ethylene methyl
acrylates; polyvinyl chloride resins; polyamides, amide-ester
elastomers, and graft copolymers of ionomer and polyamide,
including, for example, Pebax.RTM. thermoplastic polyether block
amides, commercially available from Arkema Inc; crosslinked
trans-polyisoprene and blends thereof; polyester-based
thermoplastic elastomers, such as Hytrel.RTM., commercially
available from E. I. du Pont de Nemours and Company;
polyurethane-based thermoplastic elastomers, such as
Elastollan.RTM., commercially available from BASF; synthetic or
natural vulcanized rubber; and combinations thereof. Suitable cover
materials and constructions also include, but are not limited to,
those disclosed in U.S. Pat. Nos. 6,117,025, 6,767,940, and
6,960,630, the entire disclosures of which are hereby incorporated
herein by reference.
[0040] Ionomer-based compositions, particularly olefin-based
ionomers, are known to be useful as a golf ball cover material, and
particularly as a golf ball inner cover layer material.
Olefin-based ionomers are acid copolymers that normally include
.alpha.-olefin, such as ethylene and an
.alpha.,.beta.-ethylenically unsaturated carboxylic acid, such as
methacrylic acid, acrylic acid, or maleic 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%.
[0041] However, by the present invention, a novel golf ball
construction has been discovered having desirable performance
characteristics without the need for more than one cover layer, and
particularly without the need for an ionomer-based inner cover
layer. Thus, in one embodiment, the present invention provides golf
balls which do not include a layer formed from an ionomer-based
composition. In embodiments of the present invention wherein the
golf ball does include a layer formed from an ionomer-based
composition, preferred ionomeric compositions include: [0042] (a) a
composition comprising a "high acid ionomer" (i.e., having an acid
content of greater than 16 wt %), such as Surlyn 8150.RTM.; [0043]
(b) a composition comprising a high acid ionomer and a maleic
anhydride-grafted non-ionomeric polymer (e.g., Fusabond.RTM. maleic
anhydride-grafted metallocene-catalyzed ethylene-butene
copolymers). 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.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;
[0044] (c) a composition comprising a 50/45/5 blend of Surlyn.RTM.
8940/Surlyn.RTM. 9650/Nucrel.RTM. 960, preferably having a material
hardness of from 80 to 85 Shore C; [0045] (d) 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; [0046] (e) a composition comprising a 50/50 blend
of Surlyn.RTM. 8940/Surlyn.RTM. 9650, preferably having a material
hardness of about 86 Shore C; [0047] (f) a composition comprising a
blend of Surlyn.RTM. 7940/Surlyn.RTM. 8940, optionally including a
melt flow modifier; [0048] (g) a composition comprising a blend of
a first high acid ionomer and a second high acid ionomer, wherein
the first high acid ionomer is neutralized with a different cation
than the second high acid ionomer (e.g., 50/50 blend of Surlyn.RTM.
8150 and Surlyn.RTM. 9150), optionally including one or more melt
flow modifiers such as an ionomer, ethylene-acid copolymer or ester
terpolymer; and [0049] (h) a composition comprising a blend of a
first high acid ionomer and a second high acid ionomer, wherein the
first high acid ionomer is neutralized with a different cation than
the second high acid ionomer, and from 0 to 10 wt % of an
ethylene/acid/ester ionomer wherein the ethylene/acid/ester ionomer
is neutralized with the same cation as either the first high acid
ionomer or the second high acid ionomer or a different cation than
the first and second high acid ionomers (e.g., a blend of 40-50 wt
% Surlyn.RTM. 8140, 40-50 wt % Surlyn.RTM. 9120, and 0-10 wt %
Surlyn.RTM. 6320).
[0050] Surlyn 8150.RTM., Surlyn.RTM. 8940, and Surlyn.RTM. 8140 are
different grades of E/MAA copolymer in which the acid groups have
been partially neutralized with sodium ions. Surlyn.RTM. 9650,
Surlyn.RTM. 9910, Surlyn.RTM. 9150, and Surlyn.RTM. 9120 are
different grades of E/MAA copolymer in which the acid groups have
been partially neutralized with zinc ions. Surlyn.RTM. 7940 is an
E/MAA copolymer in which the acid groups have been partially
neutralized with lithium ions. Surlyn.RTM. 6320 is a very low
modulus magnesium ionomer with a medium acid content.
Nucrel.RTM.960 is an E/MAA copolymer resin nominally made with 15
wt % methacrylic acid. Surlyn.RTM. ionomers, Fusabond.RTM.
copolymers, and Nucrel.RTM. copolymers are commercially available
from E. I. du Pont de Nemours and Company.
[0051] Ionomeric cover compositions 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, thermoplastic polyether block
amides (e.g., Pebax.RTM. block copolymers, 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, polyethylene-(meth)acrylate,
plyethylene-(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.,
ethylene propylene diene monomer rubber, metallocene-catalyzed
polyolefin) and ground powders of thermoset 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.
[0052] Polyurethanes, polyureas, and blends, copolymers, and
hybrids of polyurethane/polyurea are particularly suitable for
forming cover layers of golf balls of the present invention. When
used as cover layer materials, polyurethanes and polyureas can be
thermoset or thermoplastic. Thermoset materials can be formed into
golf ball layers by conventional casting or reaction injection
molding techniques. Thermoplastic materials can be formed into golf
ball layers by conventional compression or injection molding
techniques.
[0053] Polyurethane cover compositions of the present invention
include those formed from the reaction product of at least one
polyisocyanate and at least one curing agent. The curing agent can
include, for example, one or more diamines, one or more polyols, or
a combination thereof. The polyisocyanate can be combined with one
or more polyols to form a prepolymer, which is then combined with
the at least one curing agent. Suitable polyurethane cover
compositions of the present invention also include those formed
from the reaction product of at least one isocyanate and at least
one curing agent or the reaction produce of at least one
isocyanate, at least one polyol, and at least one curing agent.
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.
[0054] Any method known to one of ordinary skill in the art may be
used to combine the polyisocyanate, polyol, and curing agent of the
present invention. One commonly employed method, known in the art
as a one-shot method, involves concurrent mixing of the
polyisocyanate, polyol, and curing agent. This method results in a
mixture that is inhomogeneous (more random) and affords the
manufacturer less control over the molecular structure of the
resultant composition. A preferred method of mixing is known as a
prepolymer method. In this method, the polyisocyanate and the
polyol are mixed separately prior to addition of the curing agent.
This method affords a more homogeneous mixture resulting in a more
consistent polymer composition.
[0055] Suitable polyurethanes and polyureas are are further
disclosed, for example, in U.S. Pat. Nos. 5,334,673; 5,484,870;
6,476,176; 6,506,851; 6,835,794; 6,867,279; 6,958,379; 6,960,630;
6,964,621; 7,041,769; 7,105,623; 7,131,915; and 7,186,777, the
entire disclosures of which are hereby incorporated herein by
reference. The cover compositions 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 cover compositions may also include one or more filler(s), such
as the fillers given above for rubber compositions of the present
invention (e.g., titanium dioxide, barium sulfate, etc.), and/or
additive(s), such as coloring agents, fluorescent agents, whitening
agents, antioxidants, dispersants, UV absorbers, light stabilizers,
plasticizers, surfactants, compatibility agents, foaming agents,
reinforcing agents, release agents, and the like.
[0056] In a particular embodiment, the cover is a single-layer
cover, having an overall thickness of 0.02 inches or greater or
0.03 inches or greater or 0.04 inches or greater or a thickness
within a range having a lower limit of 0.02 or 0.03 or 0.04 inches
and an upper limit of 0.15 inches. In a particular aspect of the
embodiment, the single-layer cover is formed from a polyurethane-
or polyurea-based composition. In another particular aspect of this
embodiment, the cover composition has a material hardness within a
range having a lower limit of 30 or 40 or 45 Shore D and an upper
limit of 55 or 60 or 65 Shore D. In another particular aspect of
this embodiment, the golf ball does not include a layer formed from
an ionomeric composition.
[0057] In another particular embodiment, the cover is a dual- or
multi-layer cover including an inner or intermediate cover layer
formed from an ionomeric composition and an outer cover layer
formed from a polyurethane- or polyurea-based composition. In a
particular aspect of this embodiment, the ionomeric layer
preferably has a Shore D hardness of 65 or less, or a Shore D
hardness of less than 65, or a Shore D hardness of from 50 to 65,
or a Shore D hardness of from 57 to 60, or a Shore D hardness of
58, and has a thickness of from about 0.015 inches to about 0.100
inches or from about 0.20 inches to about 0.50 inches, and more
preferably has a thickness of about 0.035 inches. Preferred
ionomers include, but are not limited to, those selected from
copolymers of a C.sub.3 to C.sub.8 .alpha.,.beta.-ethylenically
unsaturated mono- or dicarboxylic acid and ethylene or a C.sub.3 to
C.sub.6 .alpha.-olefin, optionally including a softening monomer.
The ionomer is optionally highly neutralized (i.e., at least 70%,
or at least 90%, or at least 100%, of the acid moieties thereof are
neutralized). Commercially available ionomeric materials suitable
for use cover layers of the present invention 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. Also suitable are blends of ionomers
with thermoplastic elastomers. In another particular aspect of this
embodiment, the outer cover layer has a thickness of from about
0.015 to about 0.040 inches, or a thickness of from about 0.030
inches to about 0.040 inches, or a thickness of from about 0.20
inches to about 0.35 inches.
[0058] The moisture vapor transmission rate (MVTR) of the outer
core layer is important, because this layer is disposed immediately
about the inner core. That is, the moisture barrier layer
encapsulates and envelopes the inner core. The moisture barrier
layer protects the inner core and prevents moisture from
penetrating therein. The moisture barrier layer has a moisture
vapor transmission rate that is lower than the transmission rate of
both the cover and inner core. This means that moisture will
penetrate through the cover layer, but the interceding moisture
barrier layer will minimize the level of moisture penetrating into
the inner core. Preferably, the moisture barrier layer (made up of
the polyalkenamer rubber composition) has a MVTR of 1
gramsmm/m.sup.2day or less; and preferably it is in the range of
0.45 to 0.95 gramsmm/m.sup.2 day or less, which is typically the
MVTR of an ionomer resin such as SURLYN. More preferably, the MVTR
of the moisture barrier layer is 0.6 gramsmm/m.sup.2day or less,
and most preferably 0.4 gramsmm/m.sup.2day or less. The moisture
vapor transmission rate is defined as the mass of moisture vapor
that diffuses into a material of a given thickness per unit area
per unit time. The test methods for measuring MVTR are described in
further detail below.
[0059] In the present invention, it has been found that no
substantial amount of moisture will pass through the interface
between the moisture barrier layer and inner core as compared to a
core that does not have the dual layer construction of this
invention, when exposed to similar conditions. By encapsulating the
core in the moisture barrier layer of this invention, the inner
core is protected substantially from liquid and vapor penetration.
As a result, the optimum properties of such golf balls (for
example, high COR) are not substantially reduced when the balls are
stored in humid conditions as opposed to golf balls that do not
contain the inventive moisture barrier layer. Under standard
humidity conditions for testing, the temperature would be in the
range of about 100.degree. to 120.degree. F. and the relative
humidity would be in the range of about 70% to about 90% for six
weeks.
[0060] In accordance with the present invention, it now has been
found that rubber compositions comprising "cycloalkene rubber" can
be used to provide an effective moisture barrier core layer.
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##
[0061] 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.
[0062] 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).
[0063] 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.
[0064] 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.
[0065] 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 layer that effectively protects the inner core from moisture
penetrating therein. As a result, the COR and other optimum
properties of such golf balls are not substantially reduced when
the balls are stored in humid conditions as opposed to golf balls
that do not contain the inventive moisture barrier layer. 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. Furthermore, the ball has a soft feel
that 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.
[0066] 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%.
[0067] 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%.
[0068] 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.
[0069] 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).
[0070] 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.
[0071] 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.
[0072] 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.
[0073] 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.
[0074] 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.)
[0075] 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 layers 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 cover layer(s) as discussed further below.
[0076] Coefficient of restitution ("COR") and Compression are
important properties of the golf balls of this invention. 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. The compression can affect
the ball's spin rate off the driver and the feel of the ball. The
golf balls of the present invention preferably have a COR of at
least 0.750 and more preferably at least 0.800 and compression of
from about 70 to about 110, preferably from 90 to 100. The test
methods for measuring COR and compression are described in further
detail below.
[0077] In addition to the material 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 inomer, 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.
[0078] 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.
[0079] In one embodiment, the outer cover layer comprises a
partially- or fully-neutralized ionomer, a polyurethane, polyurea,
or copolymer, blend or hybrid polyurethane-polyurea. 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. The inner cover
layer material may be a partially-neutralized ionomer-based
composition containing zinc, sodium or lithium such as SURLYN.
8940, 8945, 9910, 7930, 7940, or blend thereof having a Shore D
hardness of about 63 to about 68. In another embodiment of the
multi-layer cover, 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.
[0080] As discussed above, ionomer-based compositions, particularly
olefin-based ionomers, are known to be useful as golf ball cover
materials, 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] As also discussed above, the golf balls of this invention
may be constructed so they do not include a layer formed from an
ionomer-based composition. In such instances, a variety of
thermoplastic or thermosetting non-ionomeric-based compositions
could be used in the cover or intermediate layers. These
compositions include, for example, polyesters; polyamides;
polyamide-ethers, and polyamide-esters; polyurethanes, polyureas,
and polyurethane-polyurea hybrids; fluoropolymers; non-ionomeric
acid polymers, such as E/Y- and E/X/Y-type copolymers, wherein E is
an olefin (e.g., ethylene), Y is a carboxylic acid, and X is a
softening comonomer such as vinyl esters of aliphatic carboxylic
acids, and alkyl alkylacrylates; metallocene-catalyzed polymers;
polystyrenes; polypropylenes and polyethylenes; polyvinyl chlorides
and grafted polyvinyl chlorides; polyvinyl acetates; polycarbonates
including polycarbonate/acrylonitrile-butadiene-styrene blends,
polycarbonate/polyurethane blends, and polycarbonate/polyester
blends; polyvinyl alcohols; polyethers; polyimides,
polyetherketones, polyamideimides; and mixtures of any two or more
of the above thermoplastic polymers. Compositions disclosed herein
can be either foamed or filled with density adjusting materials to
provide desirable golf ball performance characteristics. The
intermediate layer may have moisture barrier properties as
described in U.S. Pat. Nos. 6,632,147, 6,838,028, 6,932,720,
7,004,854, and 7,182,702, the disclosures of which are hereby
incorporated by reference.
[0082] 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.
[0083] When injection molding is used, the composition is typically
in a pelletized or granulated form that can be easily fed into the
throat of an injection molding machine wherein it is melted and
conveyed via a screw in a heated barrel at temperatures of from
150.degree. F. to 600.degree. F., preferably from 200.degree. F. to
500.degree. F. The molten composition is ultimately injected into a
closed mold cavity, which may be cooled, at ambient or at an
elevated temperature, but typically the mold is cooled to a
temperature of from 50.degree. F. to 70.degree. F. After residing
in the closed mold for a time of from 1 second to 300 seconds,
preferably from 20 seconds to 120 seconds, the core and/or core
plus one or more additional core or cover layers is removed from
the mold and either allowed to cool at ambient or reduced
temperatures or is placed in a cooling fluid such as water, ice
water, dry ice in a solvent, or the like.
[0084] When compression molding is used to form a core, the
composition is first formed into a preform or slug of material,
typically in a cylindrical or roughly spherical shape at a weight
slightly greater than the desired weight of the molded core. Prior
to this step, the composition may be first extruded or otherwise
melted and forced through a die after which it is cut into a
cylindrical preform. The preform is then placed into a compression
mold cavity and compressed at a mold temperature of from
150.degree. F. to 400.degree. F., preferably from 250.degree. F. to
400.degree. F., and more preferably from 300.degree. F. to
400.degree. F. When compression molding a cover layer, half-shells
of the cover layer material are first formed via injection molding.
A core is then enclosed within two half-shells, which is then
placed into a compression mold cavity and compressed.
[0085] Reaction injection molding processes are further disclosed,
for example, in U.S. Pat. Nos. 6,083,119, 7,208,562, 7,281,997,
7,282,169, 7,338,391, the entire disclosures of which are hereby
incorporated herein by reference.
[0086] Thermoplastic layers herein may be treated in such a manner
as to create a positive or negative hardness gradient. In golf ball
layers of the present invention wherein a thermosetting rubber is
used, gradient-producing processes and/or gradient-producing rubber
formulation may be employed.
[0087] Golf balls of the present invention will typically have
dimple coverage of 60% or greater, preferably 65% or greater, and
more preferably 75% or greater. 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.
[0088] 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,
three-piece, four-piece, and five-piece designs. 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 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 three-piece golf ball (12)
that can be made in accordance with this invention is illustrated.
In this version, the ball (12) includes a dual-core (14) comprising
an inner core (14a) and outer moisture barrier core layer (14b)
along with a polyurethane cover (16). In FIG. 3, a four-piece golf
ball (20) containing a dual-core (22) having inner core (22a) and
outer moisture barrier core layer (22b), and multi-layer cover (26)
comprising inner cover (26a) and outer cover (26b) is shown. In
another embodiment, as shown in FIG. 4, the five-piece golf ball
(30) contains a dual-core (32) made up of inner core (32a) and
outer moisture barrier core layer (32b). The golf ball (40) further
includes an intermediate layer (34) and a multi-layered cover (36)
comprising inner cover layer (36a) and outer cover layer (36b).
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. 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.
[0089] 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.
[0090] Test Methods
[0091] Hardness. 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.
[0092] The outer surface hardness of a golf ball layer 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
insure 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. Hardness points should only be
measured once at any particular geometric location.
[0093] 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.
[0094] 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.
[0095] 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 is measured according to
the test methods D-2240 as described above.
[0096] Moment of Inertia. Golf balls of the present invention
preferably have a Moment of Inertia ("MOI") of 70-95 gcm.sup.2,
preferably 75-93 gcm.sup.2, and more preferably 76-90 gcm.sup.2.
For low MOI embodiments, the golf ball preferably has an MOI of 85
gcm.sup.2 or less, or 83 gcm.sup.2 or less. For high MOI
embodiments, the golf ball preferably has an MOI of 86 gcm.sup.2 or
greater, or 87 gcm.sup.2 or greater. 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.
[0097] Compression. 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.
[0098] Coefficient of Restitutuion ("COR"). 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).
[0099] Moisture Vapor Transmission Rate ("MVTR"). The preferred
standards of measuring the moisture vapor transmission rate include
ASTM F1249-90 entitled "Standard Test Method for Water Vapor
Transmission Rate Through Plastic Film and Sheeting Using a
Modulated Infrared Sensor;" ASTM F372-94 entitled "Standard Test
Method for Water Vapor Transmission Rate of Flexible Barrier
Materials Using an Infrared Detection Technique;" ASTM D-96
entitled "Water Vapor Transmission Rate;" and ASTM D1653-03 (2008)
"Standard Test Methods for Water Vapor Transmission of Organic
Coating Films" among others.
EXAMPLE
[0100] The following Example is for illustrative purposes only and
is not meant to limit the scope of the invention.
Example 1
[0101] In this Example, a slug of a rubber composition having the
formulation described in Table 1 was cured at about 330.degree. F.
for about 11 minutes to make a core material. The resulting core
had a center hardness of about 68 Shore C and a surface hardness of
about 70.5 Shore C. In addition, the core had a compression of
about 70 and a COR of about 0.775@125 f/s (1.550 inch diameter
solid sphere). When the core was cured at about 350.degree. F. for
about 11 minutes, the compression increased to about 90 and the COR
increased to about 0.790@125 f/s (1.550 inch diameter solid
sphere).
TABLE-US-00001 TABLE 1 Concentration Core Composition (parts per
hundred) Vestenamer .RTM. 8012 - polyoctenamer rubber 100 available
from Evonik Degussa GmbH. Zinc diacrylate (ZDA) co-agent 50 Zinc
oxide (ZnO) filler 6 Trigonox 145 free-radical initiator 1.5 *
peroxide free-radical initiator available from Akzo Nobel. Zinc
pentachlorothiophenol (ZnPCTP) 1
[0102] As used herein, the term "about," used in connection with
one or more numbers or numerical ranges, should be understood to
refer to all such numbers, including all numbers in a range. When
numerical lower limits and numerical upper limits are set forth
herein, it is contemplated that any combination of these values may
be used.
[0103] 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.
[0104] 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.
* * * * *