U.S. patent application number 15/296298 was filed with the patent office on 2017-02-09 for golf ball having medium positive gradient quotient.
This patent application is currently assigned to Acushnet Company. The applicant listed for this patent is Acushnet Company. Invention is credited to Mark L. Binette, Brian Comeau, Michael J. Sullivan.
Application Number | 20170036069 15/296298 |
Document ID | / |
Family ID | 58053916 |
Filed Date | 2017-02-09 |
United States Patent
Application |
20170036069 |
Kind Code |
A1 |
Sullivan; Michael J. ; et
al. |
February 9, 2017 |
GOLF BALL HAVING MEDIUM POSITIVE GRADIENT QUOTIENT
Abstract
A golf ball includes a core and a cover. The core has an outer
surface, a geometric center, and a soft transition region adjacent
to the outer surface. The soft transition region has a thickness of
4 mm or less, includes about 10 to 30% trans-polybutadiene isomer,
and has a positive hardness gradient of about 10 Shore C or less.
The cover layer has a hardness of about 50 Shore M or greater. The
core has a positive hardness gradient of about 10 to 42 Shore C. A
secondary gradient quotient, GQ', from about 2.2 to 9.5, GQ' being
defined by the equation: G ' + T 10 .times. COR ##EQU00001## where
G' is the core positive hardness gradient in Shore C, T is the
percent of trans-polybutadiene isomer at the core outer surface,
and COR is the coefficient of restitution of the core measured at
an incoming velocity of 125 ft/s.
Inventors: |
Sullivan; Michael J.; (Old
Lyme, CT) ; Comeau; Brian; (Berkley, MA) ;
Binette; Mark L.; (Mattapoisett, MA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Acushnet Company |
Fairhaven |
MA |
US |
|
|
Assignee: |
Acushnet Company
Fairhaven
MA
|
Family ID: |
58053916 |
Appl. No.: |
15/296298 |
Filed: |
October 18, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14943277 |
Nov 17, 2015 |
9468811 |
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15296298 |
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13945707 |
Jul 18, 2013 |
9186556 |
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14943277 |
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13945666 |
Jul 18, 2013 |
9259619 |
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13945707 |
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13549446 |
Jul 14, 2012 |
8672777 |
|
|
13945666 |
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12891250 |
Sep 27, 2010 |
8016696 |
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13549446 |
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12056361 |
Mar 27, 2008 |
7744490 |
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12891250 |
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12048665 |
Mar 14, 2008 |
7678312 |
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12056361 |
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11772903 |
Jul 3, 2007 |
7537529 |
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12048665 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A63B 37/006 20130101;
A63B 37/0075 20130101; A63B 37/0074 20130101; A63B 37/0039
20130101; A63B 37/0051 20130101; A63B 37/0022 20130101; A63B
37/0061 20130101; A63B 37/008 20130101; A63B 37/0043 20130101; A63B
37/0078 20130101; A63B 37/0083 20130101; A63B 37/0076 20130101;
A63B 37/0063 20130101; A63B 37/0087 20130101; A63B 37/0092
20130101 |
International
Class: |
A63B 37/00 20060101
A63B037/00 |
Claims
1. A golf ball comprising: a core having an outer surface, a
geometric center, and a soft transition region adjacent to the
outer surface, the soft transition region having a thickness of
about 4 mm or less, comprises about 10 to 30 percent of a
trans-polybutadiene isomer, and has a first positive hardness
gradient of about 10 Shore C or less; and an outer cover layer
having a hardness of about 50 Shore M or greater; wherein the core
has an outer surface hardness greater than a hardness at the
geometric center to define a second positive hardness gradient of
about 10 Shore C to 42 Shore C; and a secondary gradient quotient,
GQ', from about 2.2 to 9.5, GQ' being defined by the equation: G '
+ T 10 .times. COR ##EQU00009## where G' is the core positive
hardness gradient in Shore C, T is the percent of
trans-polybutadiene isomer at the core outer surface, and COR is
the coefficient of restitution of the core measured at an incoming
velocity of 125 ft/s.
2. The golf ball of claim 1, wherein the second positive hardness
gradient is about 12 Shore C to 35 Shore C.
3. The golf ball of claim 2, wherein the second positive hardness
gradient is about 13 Shore C to 24 Shore C.
4. The golf ball of claim 3, wherein the second positive hardness
gradient is about 14 Shore C to 21 Shore C.
5. The golf ball of claim 1, wherein the core has a COR of about
0.800 or greater.
6. The golf ball of claim 5, wherein the COR is about 0.810 or
greater.
7. The golf ball of claim 1, wherein the secondary gradient
quotient, GQ', is about 2.5 to 8.5 and the second positive hardness
gradient is about 12 Shore C to about 35 Shore C.
8. The golf ball of claim 7, wherein the secondary gradient
quotient, GQ', is about 2.7 to 6.9 and the second positive hardness
gradient is about 13 Shore C to about 24 Shore C.
9. The golf ball of claim 8, wherein the secondary gradient
quotient, GQ', is about 2.9 to 6.5 and the second positive hardness
gradient is about 14 Shore C to about 21 Shore C.
10. The golf ball of claim 1, wherein the golf ball comprises an
inner cover layer comprising an ionomer.
11. The golf ball of claim 10, wherein the ionomer comprises a
lithium ionomer or a sodium ionomer.
12. The golf ball of claim 1, wherein the golf ball comprises an
outer core layer disposed about the core.
13. The golf ball of claim 1, wherein the golf ball comprises at
least one coating layer disposed about the cover layer.
14. The golf ball of claim 13, wherein the coating layer has a
Shore M hardness of about 60 Shore M or less.
15. The golf ball of claim 13, wherein the coating layer has an
instrumented hardness of about 1 to 23 MPa.
16. The golf ball of claim 13, wherein the coating layer has a
thickness of about 0.001 inches to about 0.003 inches.
17. The golf ball of claim 1, wherein the soft transition region
comprises about 10 to 20 percent trans-polybutadiene isomer.
18. The golf ball of claim 1, wherein the soft transition region
comprises about 20 to 30 percent trans-polybutadiene isomer.
19. A golf ball comprising: a core having an outer surface, a
geometric center, and a soft transition region adjacent to the
outer surface, the soft transition region having a thickness of
about 4 mm or less, comprises about 10 to 30 percent of a
trans-polybutadiene isomer, and has a positive hardness gradient of
about 10 Shore C or less; and an outer cover layer having a
hardness of about 50 Shore M or greater; wherein the core has an
outer surface hardness greater than a hardness at the geometric
center to define a positive hardness gradient of about 12 Shore C
to 24 Shore C; and a secondary gradient quotient, GQ', from about
7.5 to 9.5, GQ' being defined by the equation: G ' + T 10 .times.
COR ##EQU00010## where G' is the core positive hardness gradient in
Shore C, T is the percent of trans-polybutadiene isomer at the core
outer surface, and COR is the coefficient of restitution of the
core measured at an incoming velocity of 125 ft/s.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation-in-part of co-pending
U.S. patent application Ser. No. 14/943,277, filed Nov. 17, 2015,
which is a continuation of U.S. patent application Ser. No.
13/945,707, filed Jul. 18, 2013 and now U.S. Pat. No. 9,186,556,
which is a continuation-in-part of U.S. patent application Ser. No.
13/945,666, filed Jul. 18, 2013 and now U.S. Pat. No. 9,259,619,
which is a continuation-in-part of U.S. patent application Ser. No.
13/549,446, filed Sep. 14, 2012 and now U.S. Pat. No. 8,672,777,
which is a continuation of U.S. patent application Ser. No.
12/891,250, filed Sep. 27, 2010 and now U.S. Pat. No. 8,016,696,
which is a continuation of U.S. patent application Ser. No.
12/056,361, filed Mar. 27, 2008 and now U.S. Pat. No. 7,744,490,
which is a continuation-in-part of U.S. patent application Ser. No.
12/048,665, filed Mar. 14, 2008 and now U.S. Pat. No. 7,678,312,
which is a continuation-in-part of U.S. patent application Ser. No.
11/772,903, filed Jul. 3, 2007 and now U.S. Pat. No. 7,537,529. The
above disclosures are incorporated herein by reference.
FIELD OF THE INVENTION
[0002] This invention relates generally to golf balls with cores,
more particularly single layer cores, having a surface hardness
equal to or less than the center hardness.
BACKGROUND OF THE INVENTION
[0003] Solid golf balls are typically made with a solid core
encased by a cover, both of which can have multiple layers, such as
a dual core having a solid center and an outer core layer, or a
multi-layer cover having an inner. Generally, golf ball cores
and/or centers are constructed with a thermoset rubber, typically a
polybutadiene-based composition. The cores are usually heated and
crosslinked to create certain characteristics, such as higher or
lower compression, which can impact the spin rate of the ball
and/or provide better "feel." These and other characteristics can
be tailored to the needs of golfers of different abilities. From
the perspective of a golf ball manufacturer, it is desirable to
have cores exhibiting a wide range of properties, such as
resilience, durability, spin, and "feel," because this enables the
manufacturer to make and sell many different types of golf balls
suited to differing levels of ability.
[0004] Heretofore, most single core golf ball cores have had a
conventional hard-to-soft hardness gradient from the surface of the
core to the center of the core. The patent literature contains a
number of references that discuss a hard surface to soft center
hardness gradient across a golf ball core.
[0005] U.S. Pat. No. 4,650,193 to Molitor et al. generally
discloses a hardness gradient in the surface layers of a core by
surface treating a slug of curable elastomer with a cure-altering
agent and subsequently molding the slug into a core. This treatment
allegedly creates a core with two zones of different compositions,
the first part being the hard, resilient, central portion of the
core, which was left untreated, and the second being the soft,
deformable, outer layer of the core, which was treated by the
cure-altering agent. The two "layers" or regions of the core are
integral with one another and, as a result, achieve the effect of a
gradient of soft surface to hard center.
[0006] U.S. Pat. No. 3,784,209 to Berman, et al. generally
discloses a soft-to-hard hardness gradient. The '209 patent
discloses a non-homogenous, molded golf ball with a core of "mixed"
elastomers. A center sphere of uncured elastomeric material is
surrounded by a compatible but different uncured elastomer. When
both layers of elastomer are concurrently exposed to a curing
agent, they become integral with one another, thereby forming a
mixed core. The center of this core, having a higher concentration
of the first elastomeric material, is harder than the outer layer.
One drawback to this method of manufacture is the time-consuming
process of creating first elastomer and then a second elastomer and
then molding the two together.
[0007] Other patents discuss cores that receive a surface treatment
to provide a soft `skin`. However, since the interior portions of
these cores are untreated, they have the similar hard surface to
soft center gradient as conventional cores. For example, U.S. Pat.
No. 6,113,831 to Nesbitt et al. generally discloses a conventional
core and a separate soft skin wrapped around the core. This soft
skin is created by exposing the preform slug to steam during the
molding process so that a maximum mold temperature exceeds a steam
set point, and by controlling exothermic molding temperatures
during molding. The skin comprises the radially-outermost 1/32 inch
to 1/4 inch of the spherical core. U.S. Pat. Nos. 5,976,443 and
5,733,206, both to Nesbitt et al., disclose the addition of water
mist to the outside surface of the slug before molding in order to
create a soft skin. The water allegedly softens the compression of
the core by retarding crosslinking on the core surface, thereby
creating an even softer soft skin around the hard central
portion.
[0008] Additionally, a number of patents disclose multilayer golf
ball cores, where each core layer has a different hardness thereby
creating a hardness gradient from core layer to core layer.
[0009] There remains a need, however, to achieve a single layer
core that has a soft-to-hard gradient (a "negative" gradient), from
the surface to the center, and to achieve a method of producing
such a core that is inexpensive and efficient. A core exhibiting
such characteristics would allow the golf ball designer to create
products with unique combinations of compression, "feel," and
spin.
SUMMARY OF THE INVENTION
[0010] The present invention is directed to a golf ball a golf ball
including a unitary core having an outer surface, a geometric
center, and a soft transition region adjacent to the outer surface.
The unitary core is formed from a substantially homogenous rubber
composition. At least one outer cover layer is formed over the
core. The soft transition region has a thickness of up to 4 mm and
includes about 8 to 20 percent trans-polybutadiene isomer. The soft
transition region also has a negative hardness gradient of up to 15
Shore C. The unitary core has an overall negative hardness gradient
of up to 20 Shore C and has a gradient quotient, GQ, defined by the
equation:
G + T 10 .times. COR .ltoreq. 7 ##EQU00002##
where G is the overall negative hardness gradient in Shore C, T is
the percent of trans-polybutadiene isomer at the core outer
surface, and COR is the coefficient of restitution measured at an
incoming velocity of 125 ft/s.
[0011] The transition region may include about 9 to about 15
percent trans-polybutadiene isomer. The core geometric center
includes about 5 to 15 percent trans-polybutadiene isomer. The core
outer surface includes about 10 to 30 percent trans-polybutadiene
isomer. Preferably, the core has a COR of about 0.800 or greater,
more preferably about 0.810 or greater, or even 0.813 or greater,
which is unusual for a core having such a soft outer portion and
comparable compression.
[0012] In one embodiment, the gradient quotient, GQ, is about 6 or
less, more preferably about 5 or less. The golf ball may include an
inner cover layer comprising an ionomer, which may be a blend of a
lithium ionomer and a sodium ionomer. The golf ball may include an
outer core layer disposed about the unitary core. In another
embodiment, the outer core layer has a negative hardness gradient.
The negative hardness gradient of the outer core layer is generally
about 1 to about 5 Shore C or, alternatively, the negative hardness
gradient is about 6 to about 20 Shore C. The outer core layer may
also have a positive hardness gradient. Preferably the positive
hardness gradient is about 1 to about 5 Shore C or, alternatively,
about 6 to about 20 Shore C.
[0013] The present invention is also directed to a one-piece golf
ball comprising a sphere having a dimpled outer surface, a
geometric center, and a soft transition region adjacent to the
dimpled outer surface, the sphere being formed from a substantially
homogenous rubber composition. The soft transition region has a
thickness of up to 4 mm, includes about 8 to 20 percent
trans-polybutadiene isomer, and has a negative hardness gradient of
up to 15 Shore C. The sphere has an overall negative hardness
gradient of up to 20 Shore C and has a gradient quotient, GQ,
defined by the equation:
G + T 10 .times. COR .ltoreq. 7 ##EQU00003##
where G is the overall negative hardness gradient in Shore C, T is
the percent of trans-polybutadiene isomer at the core outer
surface, and COR is the coefficient of restitution measured at an
incoming velocity of 125 ft/s.
[0014] The present invention is directed to a golf ball including a
single, solid center and at least one cover layer. The solid center
may include an outer core layer. The cover maybe formed from an
inner cover and an outer cover. An intermediate layer may be
included between the core and cover. In one embodiment, when the
golf ball is formed from a solid core and an outer cover, the an
outer cover layer preferably has a hardness of about 50 Shore M or
greater.
[0015] The core of this embodiment has an outer surface, a
geometric center, and a soft transition region located adjacent to
the outer surface. The soft transition region typically has a
thickness of about 4 mm or less. The soft transition region
includes about 10 to 30 percent of a trans-polybutadiene isomer. In
one embodiment, the soft transition region includes about 10 to 20
percent of a trans-polybutadiene isomer. In another embodiment, the
soft transition region includes about 20 to 30 percent of a
trans-polybutadiene isomer. The soft transition region includes
about 10 to 30 percent of a trans-polybutadiene isomer also has a
positive hardness gradient of about 10 Shore C or less.
[0016] The solid core preferably has an outer surface hardness
greater than the hardness at the geometric center to define a
positive hardness gradient (differing from the hardness gradient of
the soft transition region) of about 10 Shore C to 42 Shore C.
Preferably, the core has a positive hardness gradient of about 12
Shore C to 35 Shore C, more preferably about 13 Shore C to 24 Shore
C, and most preferably about 14 Shore C to 21 Shore C.
[0017] The core has a secondary gradient quotient (GQ') that ranges
from about 2.2 to 9.5. The secondary gradient quotient, GQ', is
defined by the equation:
G ' + T 10 .times. COR ##EQU00004##
where G' is the positive hardness gradient of the solid core in
Shore C; T is the percent of trans-polybutadiene isomer at the core
outer surface, and COR is the coefficient of restitution of the
core measured at an incoming velocity of 125 ft/s. In another
embodiment, the core has a secondary gradient quotient (GQ') that
ranges from about 7.5 to 9.5. Accordingly, the core typically has a
coefficient of restitution measured at an incoming velocity of 125
ft/s of about 0.800 or greater, preferably about 0.810 or
greater.
[0018] The secondary gradient quotient, GQ', is preferably about
2.5 to 8.5, more preferably the secondary gradient quotient, GQ',
is about 2.7 to 6.9, and most preferably the secondary gradient
quotient, GQ', is about 2.9 to 6.5. The second positive hardness
gradient is preferably about 12 Shore C to about 35 Shore C, more
preferably the second positive hardness gradient is about 13 Shore
C to about 24 Shore C, and most preferably the second positive
hardness gradient is about 14 Shore C to about 21 Shore C.
[0019] The golf ball may include one or more coating layers
disposed about the outer cover layer. The one or more coating
layers preferably have a thickness of about 0.003 inches or less.
In a preferred embodiment, the golf ball includes 3 coating layers,
each layer having a thickness of about 0.001 inches to about 0.003
inches. The one or more coating layers preferably have a Shore M
hardness of about 60 Shore M or less.
[0020] The one or more coating layers preferably have an
instrumented hardness of about 1 MPa to about 23 MPa.
[0021] The soft transition region of the golf ball may include
about 10 to about 20 percent trans-polybutadiene isomer or,
alternatively about 20 to about 30 percent trans-polybutadiene
isomer.
[0022] If the golf ball includes the optional inner cover layer it
is typically formed from an ionomer or ionomer blend. Preferably,
the ionomer comprises a lithium ionomer or a sodium ionomer, or
both.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] These and other aspects of the present invention may be more
fully understood with reference to, but not limited by, the
following drawings:
[0024] FIG. 1 is a representative cross section of a golf ball of
the invention;
[0025] FIG. 2 is a representative cross section of a golf ball of
the invention; and
[0026] FIG. 3 is a plot of hardness of a core as measured as a
function of distance away from the center of a representative
inventive core.
DETAILED DESCRIPTION OF THE INVENTION
[0027] The balls of the present invention may include a
single-layer (one-piece) golf ball, and multi-layer golf balls,
such as one having a core and a cover surrounding the core, but are
preferably formed from a core comprised of a solid center
(otherwise known as an inner core) and an outer core layer, an
inner cover layer and an outer cover layer. Of course, any of the
core and/or the cover layers may include more than one layer. In a
preferred embodiment, the core is formed of an inner core and an
outer core layer where both the inner core and the outer core layer
have a "soft-to-hard" hardness gradient (a "negative" hardness
gradient) radially inward from each component's outer surface
towards its innermost portion (i.e., the center of the inner core
or the inner surface of the outer core layer), although alternative
embodiments involving varying direction and combination of hardness
gradient amongst core components are also envisioned (e.g., a
"negative" gradient in the center coupled with a "positive"
gradient in the outer core layer, or vice versa).
[0028] The center of the core may also be a liquid-filled or hollow
sphere surrounded by one or more intermediate and/or cover layers,
or it may include a solid or liquid center around which tensioned
elastomeric material is wound. Any layers disposed around these
alternative centers may exhibit the inventive core hardness
gradient (i.e., "negative"). The cover layer may be a single layer
or, for example, formed of a plurality of layers, such as an inner
cover layer and an outer cover layer.
[0029] As briefly discussed above, the inventive cores may have a
hardness gradient defined by hardness measurements made at the
surface of the inner core (or outer core layer) and radially inward
towards the center of the inner core, typically at 2-mm increments.
As used herein, the terms "negative" and "positive" refer to the
result of subtracting the hardness value at the innermost portion
of the component being measured (e.g., the center of a solid core
or an inner core in a dual core construction; the inner surface of
a core layer; etc.) from the hardness value at the outer surface of
the component being measured (e.g., the outer surface of a solid
core; the outer surface of an inner core in a dual core; the outer
surface of an outer core layer in a dual core, etc.). 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 (a smaller
number-a larger number=a negative number). It is preferred that the
inventive cores have a zero or a negative hardness gradient, more
preferably between zero (0) and -10, most preferably between 0 and
-5.
[0030] The invention is more particularly directed to the creation
of a soft "skin" (or transition volume) on the outermost surface of
the core, such as the outer surface of a single core or the outer
surface of the outer core layer in a dual core construction. The
skin or transition volume is not a separate layer, but is a portion
of the unitary core having differing hardness properties from the
rest of the core, all of which are formed from the same
composition.
[0031] The "skin" is typically defined as the volume of the core
that is within about 0.001 inches to about 0.100 inches of the
surface, and more preferably about 0.010 inches to about 0.030
inches. In the most preferred embodiment, a single or multi-layer
core is treated as a perform (prior to molding) by coating the
surface of the perform with a cure-altering material. The
cure-altering material may be in a solid form, typically a powder,
prill, or small pellet, but alternatively may be in solution form,
such as a liquid, dispersion, or slurry in a solvent. Suitable
solvents include, but are not limited to, water, hydrocarbon
solvents, polar solvents, and plasticizers. If a liquid is used, it
is preferably water. In the most preferred embodiment, a
free-flowing, relatively small particle-size powder is used to
uniformly coat the perform. Preferably the layer is a core or core
layer, but also in an alternative embodiment a cover or cover layer
(inner or outer cover layer) comprising a diene rubber composition,
preferably polybutadiene rubber.
[0032] Cure-altering materials for treatment include, but are not
limited to, antioxidants, sulfur-bearing compounds such as
pentachlorothiophenol or metal salts thereof, ZDMA, softening
acrylate monomers or oligomers, and soft powdered thermoplastic
resins such as ethyl vinyl acetate, ethylene butyl acrylate,
ethylene methyl acrylate, and very-low-modulus ionomers. Preferred
cure-altering materials are phenol-comprising antioxidants,
hydroquinones, and "soft and fast" agents, such as organosulfur
compounds, inorganic sulfur compounds, and thiophenols,
particularly pentachlorothiophenol (PCTP) and metal salts of PCTP,
such as ZnPCTP, MgPCTP, DTDS, and those disclosed in U.S. Pat. Nos.
6,458,895; 6,417,278; and 6,635,716; and U.S. Patent Application
Publication Serial No. 2006/021586, the disclosure of which are
incorporated herein by reference. Alternatively, thermoplastic or
thermosetting powders, such as low molecular weight polyethylene,
ethyl vinyl acetate, ethylene copolymers and terpolymers (i.e.,
NUCREL.RTM.), ethylene butyl acrylate, ethylene methyl acrylate,
polyurethanes, polyureas, polyurethane-copolymers (i.e.,
silicone-urethanes), PEBAX.RTM., HYTREL.RTM., polyesters,
polyamides, epoxies, silicones, and Micromorph.RTM. materials, such
as those disclosed in U.S. patent application Publication Ser. Nos.
11/690,530 and 11/690,391, incorporated herein by reference.
[0033] In one particularly preferred embodiment, a polybutadiene
rubber preform is coated with an antioxidant-comprising powder and
then molded at 350-360.degree. F. for 11 minutes to form a single
core. The resultant core has an outer diameter of about 1.580
inches and a geometric center point hardness of about 60 Shore C to
about 80 Shore C, preferably about 65 Shore C to about 78 Shore C,
and most preferably about 70 Shore C to about 75 Shore C. The
hardness at a distance of about 8 mm from the center point is about
75 Shore C to about 77 Shore C; at 14 mm from the center point
about 73 Shore C to about 75 Shore C, at 18 mm from the center
point about 80 Shore C; at 25 mm from the center point about 85
Shore C; and at 30 mm from the center point about 90 Shore C. At a
point about 31 mm to about 40 mm from the center point of the core,
the soft "skin" has a hardness of about 60 Shore C to about 80
Shore C, preferably 65 Shore C to about 75 Shore C, and most
preferably about 68 Shore C to about 74 Shore C, resulting in an
overall gradient (as measured from center to surface) of zero, and
most preferably negative (i.e., about -30 to 0, more preferably
about -15 to 0, most preferably about -10 to 0). The core of this
example typically has an Atti compression of about 70 and a COR of
about 0.800, when measured at an incoming velocity of 125 ft/s.
Preferred Atti core compressions are 110 of less, preferably 100 or
less, more preferably 90 or less, and most preferably 80 or
less.
[0034] A second particularly preferred embodiment is a two-piece
core formed from an inner core and an outer core layer. The inner
core may or may not be "treated" as described herein, but
preferably the outer core layer is treated to create the soft outer
"skin." In one embodiment, a soft inner core is surrounded by a
relatively hard outer core layer. The inner core preferably has a
an outer diameter of about 1.0 inch, a center point hardness of
about 55 Shore C to about 60 Shore C, and an outer surface hardness
of about 75 Shore C to about 80 Shore C. The surface hardness of
the modified "skin" of the outer core layer is about 60 Shore C to
about 80 Shore C, more preferably about 65 Shore C to about 75
Shore C, and most preferably about 68 Shore C to about 74 Shore C.
A preferred overall gradient is negative to zero, most preferably
negative (i.e., about -30 to 0, more preferably about -15 to 0,
most preferably about -10 to 0).
[0035] Referring to FIG. 1, in one embodiment of the present
invention the golf ball 10 includes a low compression core 12,
having a geometric center 14 and a surface 16, and a cover layer
18. Geometric center 14 has a hardness that is greater than the
hardness at the core surface 16 so as to define a "negative
hardness gradient" across the core. Core 12 also includes a
transition volume 20.
[0036] Referring to FIG. 2, in one embodiment of the present
invention the golf ball 20 includes a low compression core 22,
having a geometric center 24, an outer core layer 26, a core
surface 28, an inner cover layer 30, and an outer cover layer 32.
Core 22 includes a transition volume 34.
[0037] Another preferred embodiment is a golf ball comprising a
unitary core having a volume, an outer surface, a geometric center,
and an outermost transition volume adjacent to the outer surface,
the core being formed from a substantially homogenous composition;
and a cover layer; wherein the outermost transition volume is
disposed between the core outer surface and the geometric center,
the transition volume has an outer portion congruent with the core
outer surface, and comprises the outermost 45% of the core volume
or less; and wherein both a hardness of the core outer surface and
a hardness within the outermost transition volume are less than the
hardness of the geometric center to define a negative hardness
gradient.
[0038] The transition volume comprises the outermost 5% to 40% of
the core volume, more preferably the outermost 10% to 30% of the
core volume, and most preferably the outermost 10% to 20% of the
core volume. The transition volume typically has a thickness of
0.65 mm to 2.5 mm, preferably 0.75 mm to 1.9 mm, and more
preferably 1 mm to 1.5 mm.
[0039] The hardness of the core outer surface is 1 Shore C to 10
Shore C lower than the hardness at the geometric center, more
preferably 1 Shore C to 5 Shore C lower than the hardness at the
geometric center. As can be seen in Table 1 below, the transition
volume has an inner portion and the hardness within the transition
volume decreases by at least 2 Shore C/mm, more preferably by at
least 3 Shore C/mm, and most preferably by at least 4 Shore C/mm,
in a direction away from the inner portion and towards the outer
portion. The cover layer is preferably formed from an ionomer, a
polyurethane, a polyurea, a polyurethane-urea, or a
polyurea-urethane.
TABLE-US-00001 TABLE 1 Distance from Center of Core (mm).sup.1
Control Treated Core Geometric Center 0 58 61.2 2 64.8 65.3 4 69.6
68.1 6 71.3 70.7 8 71.9 71 10 71.9 71 12 73.1 72.3 14 77.2 76.1 16
81.3 80.3 Surface 19.4 80.8 66.2 Compression 73 67 COR @ 125 ft/s
0.790 0.780 .sup.1for a core having an outer diameter of 1.57
inches
[0040] An alternative embodiment is a golf ball comprising a
unitary core having a volume, an outer surface, a geometric center,
and an outermost transition volume adjacent to the outer surface,
the core being formed from a substantially homogenous composition;
a cover layer; and an intermediate layer disposed between the
unitary core and the cover layer; wherein the outermost transition
volume is disposed between the core outer surface and the geometric
center, the transition volume has an outer portion congruent with
the core outer surface, and comprises the outermost 45% of the core
volume or less; and wherein both a hardness of the core outer
surface and a hardness within the outermost transition volume are
less than the hardness of the geometric center to define a negative
hardness gradient. The intermediate layer may be formed from an
ionomeric material. In another embodiment, the cover layer is
formed from a polyurethane, a polyurea, or a hybrid thereof.
[0041] A dual core embodiment includes a golf ball comprising a
unitary inner core having a volume, an outer surface, a geometric
center, and an outermost transition volume adjacent to the outer
surface, the core being formed from a substantially homogenous
composition; an outer core layer disposed about the unitary inner
core and having a negative hardness gradient or a positive hardness
gradient; an inner cover layer; and an outer cover layer comprising
a polyurethane, a polyurea, or a hybrid thereof; wherein the
outermost transition volume is disposed between the inner core
outer surface and the geometric center, the transition volume has
an outer portion congruent with the inner core outer surface, and
comprises the outermost 45% of the inner core volume or less; and
wherein both a hardness of the inner core outer surface and a
hardness within the outermost transition volume are less than the
hardness of the geometric center to define a negative hardness
gradient. Preferably, the inner cover layer is formed from an
ionomeric material.
[0042] The core formulations used in the invention are preferably
based upon high-cis polybutadiene rubber that is cobalt-, nickel-,
lithium-, or neodymium-catalyzed, most preferably Co- or
Nd-catalyzed, having a Mooney viscosity of about 25 to about 125,
more preferably about 30 to about 100, and most preferably about 40
to about 60. Lesser amounts of non-polybutadiene rubber, such as
styrene butadiene rubber, trans-polyisoprene, natural rubber, butyl
rubber, ethylene propylene rubber, ethylene propylene diene monomer
rubber, low-cis polybutadiene rubber, or trans polybutadiene
rubber, may also be blended with the polybutadiene rubber. A
coagent, such as zinc diacrylate or zinc dimethacrylate, is
typically present at a level of about 0 pph to about 60 pph, more
preferably about 10 pph to about 55 pph, and most preferably about
15 pph to about 40 pph. A peroxide or peroxide blend is also
typically present at about 0.1 pph to about 5.0 pph, more
preferably about 0.5 pph to about 3.0 pph. Zinc oxide may also be
present at about 5 pph to about 50 pph and the antioxidant is
preferably present at about 0 pph to about 0.1 pph to about 5.0
pph, preferably about 0.5 pph to about 3.0 pph.
[0043] Other embodiments include any number of core layers and
gradient combinations wherein at least one layer of the core has a
surface that is "treated" as described herein. Scrap automotive
tire regrind (in fine powder form) is also sufficient for creating
the inventive soft outer "skin," as well as other powdered rubbers
that are uncrosslinked or partially crosslinked and therefore able
to react with the polybutadiene. Fully crosslinked powdered rubber
may also still have enough affinity for the polybutadiene substrate
to adhere (even react minimally) enough to form a good bond.
[0044] Other potential surface-softening or cure-altering agents
include, but are not limited to, sulfated fats, sodium salts of
aklylated aromatic sulfonic acids, substituted benzoid alkyl
sulfonic acids, monoaryl and alkyl ethers of diethylene glycol and
dipropylene glycol, ammonium salts of alkyl phosphates, sodium
alkyl sulfates and monosodium salt of sulfated methyl oleate and
sodium salts of carboxylated eletrolytes. Other suitable materials
include dithiocarbamates, such as zinc dimethyl dithiocarbamate,
zinc diethyl dithiocarbamate, zinc di-n-butyl dithiocarbamate, zinc
diamyl dithiocarbamate, tellurium diethyl dithiocarbamate, selenium
dimethyl dithiocarbamate, selenium diethyl dithiocarbamate, lead
diamyl dithiocarbamate, bismuth dimethyl dithiocarbamate, cadmium
diethyl dithiocarbamate, and mixtures thereof.
[0045] The method for making the golf ball of the invention
includes a variety of steps and options. Typically, a Banbury-type
mixer or the like is used to mix the polybutadiene rubber
composition. The rubber composition is extruded as an extrudate and
cut to a predetermined shape, such as a cylinder, typically called
a "preform". The preform comprising the uncured polybutadiene
composition is then prepared for coating with at least one of the
cure-altering (inhibiting) materials, liquids, or solvents
described above. Preferred cure-altering materials include wherein
the cure-altering material comprises antioxidants, sulfur-bearing
compounds, zinc methacrylate, zinc dimethacrylate, softening
acrylate monomers or oligomers, soft powdered thermoplastic resins,
phenol-comprising antioxidants, or hydroquinones, most preferably
an antioxidant.
[0046] In one embodiment, more than one cure-altering material is
used, in succession. In this embodiment, a preferred combination
includes a first cure-altering material such as an antioxidant and
a second cure-altering material such as a different antioxidant or
a peroxide. A compatiblilizer and/or tie layer may be incorporated.
Additionally, a two-stage dip or roll (in the cure-altering
material) may be used to sequentially provide a first and second
antioxidant or an antioxidant and a peroxide.
[0047] Optionally, prior to coating the preform, the uncured
preform may be shaped or cold-formed into a rough sphere. The
coating may be performed in a variety of manners including, but not
limited to, rolling, spraying, dipping, or dusting. The coating may
be uniform or varied, but is preferably uniform.
[0048] The uncured, coated preform may optionally be heated to a
predetermined temperature for a predetermined time, the temperature
being substantially below the predetermined cure temperature, so
that the cure-altering material may diffuse, penetrate, migrate, or
otherwise work its way into the preform or, alternatively, any
solvent may evaporate or the preform may dry (if the coating was in
liquid form). If two cure-altering materials are employed, this
time is also preferred to allow any reaction that may occur to come
to completion.
[0049] The uncured coated preform is then cured or molded at a
predetermined temperature and time to form a crosslinked golf ball
core. As described in detail above, the core has an outer surface
having a first hardness and a geometric center having a second
hardness greater than the first to define a "negative" hardness
gradient. Any one of a number of cover layers may be formed around
the "negative" gradient core including, but not limited to, an
outer core layer, an inner cover layer, and an outer cover
layer.
[0050] The cured core is then typically centerless-grinded so that
the core is uniformly spherical and has a surface than is roughened
and textured to be better suited for adhesion with subsequent
layers. Prior to of after the centerless grinding the core may be
treated with plasma discharge, corona discharge, silanes, or
chlorination, for example, to aid in its adhesion properties.
[0051] A particularly preferred method includes the steps of
extruding a polybutadiene composition the form a cylindrical
extrudate; cutting the extrudate to form an uncured polybutadiene
preform; uniformly coating the preform with a cure-altering
material comprising a first antioxidant; curing the coated preform
to form a crosslinked core having an outer surface having a first
hardness and a geometric center having a second hardness greater
than the first to define a negative hardness gradient;
centerless-grinding the cured core to form a uniformly-spherical
core having increased surface roughness; forming an inner cover
layer about the uniformly-spherical core; and forming an outer
cover layer about the inner cover layer to form the golf ball.
[0052] Preferably, the core layers (inner core or outer core layer)
is made from a composition including at least one thermoset base
rubber, such as a polybutadiene rubber, cured with at least one
peroxide and at least one reactive co-agent, which can be a metal
salt of an unsaturated carboxylic acid, such as acrylic acid or
methacrylic acid, a non-metallic coagent, or mixtures thereof.
Preferably, a suitable antioxidant is included in the composition.
An optional soft and fast agent (and sometimes a cis-to-trans
catalyst), such as an organosulfur or metal-containing organosulfur
compound, can also be included in the core formulation
[0053] Other ingredients that are known to those skilled in the art
may be used, and are understood to include, but not be limited to,
density-adjusting fillers, process aides, plasticizers, blowing or
foaming agents, sulfur accelerators, and/or non-peroxide radical
sources. The base thermoset rubber, which can be blended with other
rubbers and polymers, typically includes a natural or synthetic
rubber. A preferred base rubber is 1,4-polybutadiene having a cis
structure of at least 40%, preferably greater than 80%, and more
preferably greater than 90%.
[0054] Examples of desirable polybutadiene rubbers include
BUNA.RTM. CB22 and BUNA.RTM. CB23, commercially available from
LANXESS Corporation; UBEPOL.RTM. 360 L and UBEPOL.RTM. 150 L 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
TAKTENE.RTM. 1203G1, 220, and 221, commercially available from Dow
Chemical Company; 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; PETROFLEX.RTM. BRNd-40; and KARBOCHEM.RTM. ND40,
ND45, and ND60, commercially available from Karbochem.
[0055] The base rubber may also comprise high or medium Mooney
viscosity rubber, or blends thereof. A "Mooney" unit is a unit used
to measure the plasticity of raw or unvulcanized rubber. The
plasticity in a "Mooney" unit is equal to the torque, measured on
an arbitrary scale, on a disk in a vessel that contains rubber at a
temperature of 100.degree. C. and rotates at two revolutions per
minute. The measurement of Mooney viscosity is defined according to
ASTM D-1646.
[0056] The Mooney viscosity range is preferably greater than about
40, more preferably in the range from about 40 to about 80 and more
preferably in the range from about 40 to about 60. Polybutadiene
rubber with higher Mooney viscosity may also be used, so long as
the viscosity of the polybutadiene does not reach a level where the
high viscosity polybutadiene clogs or otherwise adversely
interferes with the manufacturing machinery. It is contemplated
that polybutadiene with viscosity less than 65 Mooney can be used
with the present invention.
[0057] In one embodiment of the present invention, golf ball cores
made with mid- to high-Mooney viscosity polybutadiene material
exhibit increased resiliency (and, therefore, distance) without
increasing the hardness of the ball. Such cores are soft, i.e.,
compression less than about 60 and more specifically in the range
of about 50-55. Cores with compression in the range of from about
30 about 50 are also within the range of this preferred
embodiment.
[0058] Commercial sources of suitable mid- to high-Mooney viscosity
polybutadiene include Bayer AG CB23 (Nd-catalyzed), which has a
Mooney viscosity of around 50 and is a highly linear polybutadiene,
and Shell 1220 (Co-catalyzed). If desired, the polybutadiene can
also be mixed with other elastomers known in the art, such as other
polybutadiene rubbers, natural rubber, styrene butadiene rubber,
and/or isoprene rubber in order to further modify the properties of
the core. When a mixture of elastomers is used, the amounts of
other constituents in the core composition are typically based on
100 parts by weight of the total elastomer mixture.
[0059] In one preferred embodiment, the base rubber comprises a
Nd-catalyzed polybutadiene, a rare earth-catalyzed polybutadiene
rubber, or blends thereof. If desired, the polybutadiene can also
be mixed with other elastomers known in the art such as natural
rubber, polyisoprene rubber and/or styrene-butadiene rubber in
order to modify the properties of the core. Other suitable base
rubbers include thermosetting materials such as, ethylene propylene
diene monomer rubber, ethylene propylene rubber, butyl rubber,
halobutyl rubber, hydrogenated nitrile butadiene rubber, nitrile
rubber, and silicone rubber.
[0060] Thermoplastic elastomers (TPE) many also be used to modify
the properties of the core layers, or the uncured core layer stock
by blending with the base thermoset rubber. These TPEs include
natural or synthetic balata, or high trans-polyisoprene, high
trans-polybutadiene, or any styrenic block copolymer, such as
styrene ethylene butadiene styrene, styrene-isoprene-styrene, etc.,
a metallocene or other single-site catalyzed polyolefin such as
ethylene-octene, or ethylene-butene, or thermoplastic polyurethanes
(TPU), including copolymers, e.g. with silicone. Other suitable
TPEs for blending with the thermoset rubbers of the present
invention include PEBAX.RTM., which is believed to comprise
polyether amide copolymers, HYTREL.RTM., which is believed to
comprise polyether ester copolymers, thermoplastic urethane, and
KRATON.RTM., which is believed to comprise styrenic block
copolymers elastomers. Any of the TPEs or TPUs above may also
contain functionality suitable for grafting, including maleic acid
or maleic anhydride.
[0061] Additional polymers may also optionally be incorporated into
the base rubber. Examples include, but are not limited to,
thermoset elastomers such as core regrind, thermoplastic
vulcanizate, copolymeric ionomer, terpolymeric ionomer,
polycarbonate, polyamide, copolymeric polyamide, polyesters,
polyvinyl alcohols, acrylonitrile-butadiene-styrene copolymers,
polyarylate, polyacrylate, polyphenylene ether, impact-modified
polyphenylene ether, high impact polystyrene, diallyl phthalate
polymer, styrene-acrylonitrile polymer (SAN) (including
olefin-modified SAN and acrylonitrile-styrene-acrylonitrile
polymer), styrene-maleic anhydride copolymer, styrenic copolymer,
functionalized styrenic copolymer, functionalized styrenic
terpolymer, styrenic terpolymer, cellulose polymer, liquid crystal
polymer, ethylene-vinyl acetate copolymers, polyurea, and
polysiloxane or any metallocene-catalyzed polymers of these
species.
[0062] Suitable polyamides for use as an additional polymeric
material in compositions within the scope of the present invention
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-cyclohexanediamine, 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) copolymerization 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.
[0063] Suitable peroxide initiating agents include dicumyl
peroxide; 2,5-dimethyl-2,5-di(t-butylperoxy) hexane;
2,5-dimethyl-2,5-di(t-butylperoxy)hexyne;
2,5-dimethyl-2,5-di(benzoylperoxy)hexane;
2,2'-bis(t-butylperoxy)-di-iso-propylbenzene;
1,1-bis(t-butylperoxy)-3,3,5-trimethyl cyclohexane; n-butyl
4,4-bis(t-butyl-peroxy)valerate; t-butyl perbenzoate; benzoyl
peroxide; n-butyl 4,4'-bis(butylperoxy) valerate; di-t-butyl
peroxide; or 2,5-di-(t-butylperoxy)-2,5-dimethyl hexane, lauryl
peroxide, t-butyl hydroperoxide, .alpha.-.alpha. bis(t-butylperoxy)
diisopropylbenzene, di(2-t-butyl-peroxyisopropyl)benzene, di-t-amyl
peroxide, di-t-butyl peroxide. Preferably, the rubber composition
includes from about 0.25 to about 5.0 parts by weight peroxide per
100 parts by weight rubber (phr), more preferably 0.5 phr to 3 phr,
most preferably 0.5 phr to 1.5 phr. In a most preferred embodiment,
the peroxide is present in an amount of about 0.8 phr. These ranges
of peroxide are given assuming the peroxide is 100% active, without
accounting for any carrier that might be present. Because many
commercially available peroxides are sold along with a carrier
compound, the actual amount of active peroxide present must be
calculated. Commercially-available peroxide initiating agents
include DICUP.RTM. family of dicumyl peroxides (including
DICUP.RTM. R, DICUP.RTM. 40C and DICUP.RTM. 40KE) available from
Crompton (Geo Specialty Chemicals). Similar initiating agents are
available from AkroChem, Lanxess, Flexsys/Harwick and R. T.
Vanderbilt. Another commercially-available and preferred initiating
agent is TRIGONOX.RTM. 265-50B from Akzo Nobel, which is a mixture
of 1,1-di(t-butylperoxy)-3,3,5-trimethylcyclohexane and
di(2-t-butylperoxyisopropyl) benzene. TRIGONOX.RTM. peroxides are
generally sold on a carrier compound.
[0064] Suitable reactive co-agents include, but are not limited to,
metal salts of diacrylates, dimethacrylates, and monomethacrylates
suitable for use in this invention include those wherein the metal
is zinc, magnesium, calcium, barium, tin, aluminum, lithium,
sodium, potassium, iron, zirconium, and bismuth. Zinc diacrylate
(ZDA) is preferred, but the present invention is not limited
thereto. ZDA provides golf balls with a high initial velocity. The
ZDA can be of various grades of purity. For the purposes of this
invention, the lower the quantity of zinc stearate present in the
ZDA the higher the ZDA purity. ZDA containing less than about 10%
zinc stearate is preferable. More preferable is ZDA containing
about 4-8% zinc stearate. Suitable, commercially available zinc
diacrylates include those from Sartomer Co. The preferred
concentrations of ZDA that can be used are about 10 phr to about 40
phr, more preferably 20 phr to about 35 phr, most preferably 25 phr
to about 35 phr. In a particularly preferred embodiment, the
reactive co-agent is present in an amount of about 29 phr to about
31 phr.
[0065] Additional preferred co-agents that may be used alone or in
combination with those mentioned above include, but are not limited
to, trimethylolpropane trimethacrylate, trimethylolpropane
triacrylate, and the like. It is understood by those skilled in the
art, that in the case where these co-agents may be liquids at room
temperature, it may be advantageous to disperse these compounds on
a suitable carrier to promote ease of incorporation in the rubber
mixture.
[0066] Antioxidants are compounds that inhibit or prevent the
oxidative breakdown of elastomers, and/or inhibit or prevent
reactions that are promoted by oxygen radicals. Some exemplary
antioxidants that may be used in the present invention include, but
are not limited to, quinoline type antioxidants, amine type
antioxidants, and phenolic type antioxidants. A preferred
antioxidant is 2,2'-methylene-bis-(4-methyl-6-t-butylphenol)
available as VANOX.RTM. MBPC from R. T. Vanderbilt. Other
polyphenolic antioxidants include VANOX.RTM. T, VANOX.RTM. L,
VANOX.RTM. SKT, VANOX.RTM. SWP, VANOX.RTM. 13 and VANOX.RTM.
1290.
Suitable antioxidants include, but are not limited to,
alkylene-bis-alkyl substituted cresols, such as
4,4'-methylene-bis(2,5-xylenol);
4,4'-ethylidene-bis-(6-ethyl-m-cresol);
4,4'-butylidene-bis-(6-t-butyl-m-cresol);
4,4'-decylidene-bis-(6-methyl-m-cresol);
4,4'-methylene-bis-(2-amyl-m-cresol);
4,4'-propylidene-bis-(5-hexyl-m-cresol);
3,3'-decylidene-bis-(5-ethyl-p-cresol);
2,2'-butylidene-bis-(3-n-hexyl-p-cresol);
4,4'-(2-butylidene)-bis-(6-t-butyl-m-cresol);
3,3'-4(decylidene)-bis-(5-ethyl-p-cresol);
(2,5-dimethyl-4-hydroxyphenyl) (2-hydroxy-3,5-dimethylphenyl)
methane; (2-methyl-4-hydroxy-5-ethylphenyl)
(2-ethyl-3-hydroxy-5-methylphenyl) methane;
(3-methyl-5-hydroxy-6-t-butylphenyl)
(2-hydroxy-4-methyl-5-decylphenyl)-n-butyl methane;
(2-hydroxy-4-ethyl-5-methylphenyl)
(2-decyl-3-hydroxy-4-methylphenyl)butylamylmethane;
(3-ethyl-4-methyl-5-hydroxyphenyl)-(2,3-dimethyl-3-hydroxy-phenyl)nonylme-
thane;
(3-methyl-2-hydroxy-6-ethylphenyl)-(2-isopropyl-3-hydroxy-5-methyl--
phenyl)cyclohexylmethane; (2-methyl-4-hydroxy-5-methylphenyl)
(2-hydroxy-3-methyl-5-ethylphenyl)dicyclohexyl methane; and the
like.
[0067] Other suitable antioxidants include, but are not limited to,
substituted phenols, such as 2-tert-butyl-4-methoxyphenol;
3-tert-butyl-4-methoxyphenol; 3-tert-octyl-4-methoxyphenol;
2-methyl-4-methoxyphenol; 2-stearyl-4-n-butoxyphenol;
3-t-butyl-4-stearyloxyphenol; 3-lauryl-4-ethoxyphenol;
2,5-di-t-butyl-4-methoxyphenol; 2-methyl-4-methoxyphenol;
2-(1-methycyclohexyl)-4-methoxyphenol;
2-t-butyl-4-dodecyloxyphenol; 2-(1-methylbenzyl)-4-methoxyphenol;
2-t-octyl-4-methoxyphenol; methyl gallate; n-propyl gallate;
n-butyl gallate; lauryl gallate; myristyl gallate; stearyl gallate;
2,4,5-trihydroxyacetophenone; 2,4,5-trihydroxy-n-butyrophenone;
2,4,5-trihydroxystearophenone; 2,6-ditert-butyl-4-methylphenol;
2,6-ditert-octyl-4-methylphenol; 2,6-ditert-butyl-4-stearylphenol;
2-methyl-4-methyl-6-tert-butylphenol; 2,6-distearyl-4-methylphenol;
2,6-dilauryl-4-methylphenol; 2,6-di(n-octyl)-4-methylphenol;
2,6-di(n-hexadecyl)-4-methylphenol;
2,6-di(1-methylundecyl)-4-methylphenol;
2,6-di(1-methylheptadecyl)-4-methylphenol;
2,6-di(trimethylhexyl)-4-methylphenol;
2,6-di(1,1,3,3-tetramethyloctyl)-4-methylphenol; 2-n-dodecyl-6-tert
butyl-4-methylphenol;
2-n-dodecyl-6-(1-methylundecyl)-4-methylphenol;
2-n-dodecyl-6-(1,1,3,3-tetramethyloctyl)-4-methylphenol;
2-n-dodecyl-6-n-octadecyl-4-methylphenol;
2-n-dodecyl-6-n-octyl-4-methylphenol;
2-methyl-6-n-octadecyl-4-methylphenol;
2-n-dodecyl-6-(1-methylheptadecyl)-4-methylphenol;
2,6-di(1-methylbenzyl)-4-methylphenol;
2,6-di(1-methylcyclohexyl)-4-methylphenol;
2,6-(1-methylcyclohexyl)-4-methylphenol;
2-(1-methylbenzyl)-4-methylphenol; and related substituted
phenols.
[0068] More suitable antioxidants include, but are not limited to,
alkylene bisphenols, such as 4,4'-butylidene bis(3-methyl-6-t-butyl
phenol); 2,2-butylidene bis (4,6-dimethyl phenol); 2,2'-butylidene
bis(4-methyl-6-t-butyl phenol); 2,2'-butylidene
bis(4-t-butyl-6-methyl phenol); 2,2'-ethylidene
bis(4-methyl-6-t-butylphenol); 2,2'-methylene bis(4,6-dimethyl
phenol); 2,2'-methylene bis(4-methyl-6-t-butyl phenol);
2,2'-methylene bis(4-ethyl-6-t-butyl phenol); 4,4'-methylene
bis(2,6-di-t-butyl phenol); 4,4'-methylene bis(2-methyl-6-t-butyl
phenol); 4,4'-methylene bis(2,6-dimethyl phenol); 2,2'-methylene
bis(4-t-butyl-6-phenyl phenol);
2,2'-dihydroxy-3,3',5,5'-tetramethylstilbene; 2,2'-isopropylidene
bis(4-methyl-6-t-butyl phenol); ethylene bis (beta-naphthol);
1,5-dihydroxy naphthalene; 2,2'-ethylene bis (4-methyl-6-propyl
phenol); 4,4'-methylene bis(2-propyl-6-t-butyl phenol);
4,4'-ethylene bis (2-methyl-6-propyl phenol); 2,2'-methylene
bis(5-methyl-6-t-butyl phenol); and 4,4'-butylidene
bis(6-t-butyl-3-methyl phenol);
[0069] Suitable antioxidants further include, but are not limited
to, alkylene trisphenols, such as 2,6-bis
(2'-hydroxy-3'-t-butyl-5'-methyl benzyl)-4-methyl phenol; 2,6-bis
(2'-hydroxy-3'-t-ethyl-5'-butyl benzyl)-4-methyl phenol; and
2,6-bis(2'-hydroxy-3'-t-butyl-5'-propyl benzyl)-4-methyl
phenol.
[0070] The antioxidant is typically present in an amount of about
0.1 phr to about 5 phr, preferably from about 0.1 phr to about 2
phr, more preferably about 0.1 phr to about 1 phr. In a
particularly preferred embodiment, the antioxidant is present in an
amount of about 0.4 phr. In an alternative embodiment, the
antioxidant should be present in an amount to ensure that the
hardness gradient of the inventive cores is negative. Preferably,
about 0.2 phr to about 1 phr antioxidant is added to the core layer
(inner core or outer core layer) formulation, more preferably,
about 0.3 to about 0.8 phr, and most preferably 0.4 to about 0.7
phr. Preferably, about 0.25 phr to about 1.5 phr of peroxide as
calculated at 100% active can be added to the core formulation,
more preferably about 0.5 phr to about 1.2 phr, and most preferably
about 0.7 phr to about 1.0 phr. The ZDA amount can be varied to
suit the desired compression, spin and feel of the resulting golf
ball. The cure regime can have a temperature range between from
about 290.degree. F. to about 335.degree. F., more preferably about
300.degree. F. to about 325.degree. F., and the stock is held at
that temperature for at least about 10 minutes to about 30
minutes.
[0071] The thermoset rubber composition of the present invention
may also include an optional soft and fast agent. As used herein,
"soft and fast agent" means any compound or a blend thereof that
that is capable of making a core 1) be softer (lower compression)
at constant COR or 2) have a higher COR at equal compression, or
any combination thereof, when compared to a core equivalently
prepared without a soft and fast agent. Preferably, the composition
of the present invention contains from about 0.05 phr to about 10.0
phr soft and fast agent. In one embodiment, the soft and fast agent
is present in an amount of about 0.05 phr to about 3.0 phr,
preferably about 0.05 phr to about 2.0 phr, more preferably about
0.05 phr to about 1.0 phr. In another embodiment, the soft and fast
agent is present in an amount of about 2.0 phr to about 5.0 phr,
preferably about 2.35 phr to about 4.0 phr, and more preferably
about 2.35 phr to about 3.0 phr. In an alternative high
concentration embodiment, the soft and fast agent is present in an
amount of about 5.0 phr to about 10.0 phr, more preferably about
6.0 phr to about 9.0 phr, most preferably about 7.0 phr to about
8.0 phr. In a most preferred embodiment, the soft and fast agent is
present in an amount of about 2.6 phr.
[0072] Suitable soft and fast agents include, but are not limited
to, organosulfur or metal-containing organosulfur compounds, an
organic sulfur compound, including mono, di, and polysulfides, a
thiol, or mercapto compound, an inorganic sulfide compound, a Group
VIA compound, or mixtures thereof. The soft and fast agent
component may also be a blend of an organosulfur compound and an
inorganic sulfide compound.
[0073] Suitable soft and fast agents of the present invention
include, but are not limited to those having the following general
formula:
##STR00001##
where R.sub.1-R.sub.5 can be C.sub.1-C.sub.8 alkyl groups; halogen
groups; thiol groups (--SH), carboxylated groups; sulfonated
groups; and hydrogen; in any order; and also pentafluorothiophenol;
2-fluorothiophenol; 3-fluorothiophenol; 4-fluorothiophenol;
2,3-fluorothiophenol; 2,4-fluorothiophenol; 3,4-fluorothiophenol;
3,5-fluorothiophenol 2,3,4-fluorothiophenol;
3,4,5-fluorothiophenol; 2,3,4,5-tetrafluorothiophenol;
2,3,5,6-tetrafluorothiophenol; 4-chlorotetrafluorothiophenol;
pentachlorothiophenol; 2-chlorothiophenol; 3-chlorothiophenol;
4-chlorothiophenol; 2,3-chlorothiophenol; 2,4-chlorothiophenol;
3,4-chlorothiophenol; 3,5-chlorothiophenol; 2,3,4-chlorothiophenol;
3,4,5-chlorothiophenol; 2,3,4,5-tetrachlorothiophenol;
2,3,5,6-tetrachlorothiophenol; pentabromothiophenol;
2-bromothiophenol; 3-bromothiophenol; 4-bromothiophenol;
2,3-bromothiophenol; 2,4-bromothiophenol; 3,4-bromothiophenol;
3,5-bromothiophenol; 2,3,4-bromothiophenol; 3,4,5-bromothiophenol;
2,3,4,5-tetrabromothiophenol; 2,3,5,6-tetrabromothiophenol;
pentaiodothiophenol; 2-iodothiophenol; 3-iodothiophenol;
4-iodothiophenol; 2,3-iodothiophenol; 2,4-iodothiophenol;
3,4-iodothiophenol; 3,5-iodothiophenol; 2,3,4-iodothiophenol;
3,4,5-iodothiophenol; 2,3,4,5-tetraiodothiophenol;
2,3,5,6-tetraiodothiophenoland; and their zinc salts. 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.
[0074] As used herein when referring to the invention, the term
"organosulfur compound(s)" refers to any compound containing
carbon, hydrogen, and sulfur, where the sulfur is directly bonded
to at least 1 carbon. As used herein, the term "sulfur compound"
means a compound that is elemental sulfur, polymeric sulfur, or a
combination thereof. It should be further understood that the term
"elemental sulfur" refers to the ring structure of S.sub.8 and that
"polymeric sulfur" is a structure including at least one additional
sulfur relative to elemental sulfur.
[0075] Additional suitable examples of soft and fast agents (that
are also believed to be cis-to-trans catalysts) include, but are
not limited to, 4,4'-diphenyl disulfide; 4,4'-ditolyl disulfide;
2,2'-benzamido diphenyl disulfide; bis(2-aminophenyl) disulfide;
bis(4-aminophenyl) disulfide; bis(3-aminophenyl) disulfide;
2,2'-bis(4-aminonaphthyl) disulfide; 2,2'-bis(3-aminonaphthyl)
disulfide; 2,2'-bis(4-aminonaphthyl) disulfide;
2,2'-bis(5-aminonaphthyl) disulfide; 2,2'-bis(6-aminonaphthyl)
disulfide; 2,2'-bis(7-aminonaphthyl) disulfide;
2,2'-bis(8-aminonaphthyl) disulfide; 1,1'-bis(2-aminonaphthyl)
disulfide; 1,1'-bis(3-aminonaphthyl) disulfide;
1,1'-bis(3-aminonaphthyl) disulfide; 1,1'-bis(4-aminonaphthyl)
disulfide; 1,1'-bis(5-aminonaphthyl) disulfide;
1,1'-bis(6-aminonaphthyl) disulfide; 1,1'-bis(7-aminonaphthyl)
disulfide; 1,1'-bis(8-aminonaphthyl) disulfide;
1,2'-diamino-1,2'-dithiodinaphthalene;
2,3'-diamino-1,2'-dithiodinaphthalene; bis(4-chlorophenyl)
disulfide; bis(2-chlorophenyl) disulfide; bis(3-chlorophenyl)
disulfide; bis(4-bromophenyl) disulfide; bis(2-bromophenyl)
disulfide; bis(3-bromophenyl) disulfide; bis(4-fluorophenyl)
disulfide; bis(4-iodophenyl) disulfide; bis(2,5-dichlorophenyl)
disulfide; bis(3,5-dichlorophenyl) disulfide; bis
(2,4-dichlorophenyl) disulfide; bis(2,6-dichlorophenyl) disulfide;
bis(2,5-dibromophenyl) disulfide; bis(3,5-dibromophenyl) disulfide;
bis(2-chloro-5-bromophenyl) disulfide; bis(2,4,6-trichlorophenyl)
disulfide; bis(2,3,4,5,6-pentachlorophenyl) disulfide;
bis(4-cyanophenyl) disulfide; bis(2-cyanophenyl) disulfide;
bis(4-nitrophenyl) disulfide; bis(2-nitrophenyl) disulfide;
2,2'-dithiobenzoic acid ethylester; 2,2'-dithiobenzoic acid
methylester; 2,2'-dithiobenzoic acid; 4,4'-dithiobenzoic acid
ethylester; bis(4-acetylphenyl) disulfide; bis(2-acetylphenyl)
disulfide; bis(4-formylphenyl) disulfide; bis(4-carb amoylphenyl)
disulfide; 1,1'-dinaphthyl disulfide; 2,2'-dinaphthyl disulfide;
1,2'-dinaphthyl disulfide; 2,2'-bis(1-chlorodinaphthyl) disulfide;
2,2'-bis(1-bromonaphthyl) disulfide; 1,1'-bis(2-chloronaphthyl)
disulfide; 2,2'-bis(1-cyanonaphthyl) disulfide;
2,2'-bis(1-acetylnaphthyl) disulfide; and the like; or a mixture
thereof. Preferred organosulfur components include 4,4'-diphenyl
disulfide, 4,4'-ditolyl disulfide, or 2,2'-benzamido diphenyl
disulfide, or a mixture thereof. A more preferred organosulfur
component includes 4,4'-ditolyl disulfide. In another embodiment,
metal-containing organosulfur components can be used according to
the invention. Suitable metal-containing organosulfur components
include, but are not limited to, cadmium, copper, lead, and
tellurium analogs of diethyldithiocarbamate, diamyldithiocarbamate,
and dimethyldithiocarbamate, or mixtures thereof.
[0076] Suitable substituted or unsubstituted aromatic organic
components that do not include sulfur or a metal include, but are
not limited to, 4,4'-diphenyl acetylene, azobenzene, or a mixture
thereof. The aromatic organic group preferably ranges in size from
C.sub.6 to C.sub.20, and more preferably from C.sub.6 to C.sub.10.
Suitable inorganic sulfide components include, but are not limited
to titanium sulfide, manganese sulfide, and sulfide analogs of
iron, calcium, cobalt, molybdenum, tungsten, copper, selenium,
yttrium, zinc, tin, and bismuth.
[0077] A substituted or unsubstituted aromatic organic compound is
also suitable as a soft and fast agent. Suitable substituted or
unsubstituted aromatic organic components include, but are not
limited to, components having the formula
(R.sub.1).sub.X--R.sub.3-M-R.sub.4--(R.sub.2).sub.y, wherein
R.sub.1 and R.sub.2 are each hydrogen or a substituted or
unsubstituted C.sub.1-20 linear, branched, or cyclic alkyl, alkoxy,
or alkylthio group, or a single, multiple, or fused ring C.sub.6 to
C.sub.24 aromatic group; x and y are each an integer from 0 to 5;
R.sub.3 and R.sub.4 are each selected from a single, multiple, or
fused ring C.sub.6 to C.sub.24 aromatic group; and M includes an
azo group or a metal component. R.sub.3 and R.sub.4 are each
preferably selected from a C.sub.6 to C.sub.10 aromatic group, more
preferably selected from phenyl, benzyl, naphthyl, benzamido, and
benzothiazyl. R.sub.1 and R.sub.2 are each preferably selected from
a substituted or unsubstituted C.sub.1-10 linear, branched, or
cyclic alkyl, alkoxy, or alkylthio group or a C.sub.6 to C.sub.10
aromatic group. When R.sub.1, R.sub.2, R.sub.3, or R.sub.4, are
substituted, the substitution may include one or more of the
following substituent groups: hydroxy and metal salts thereof;
mercapto and metal salts thereof; halogen; amino, nitro, cyano, and
amido; carboxyl including esters, acids, and metal salts thereof;
silyl; acrylates and metal salts thereof; sulfonyl or sulfonamide;
and phosphates and phosphites. When M is a metal component, it may
be any suitable elemental metal available to those of ordinary
skill in the art. Typically, the metal will be a transition metal,
although preferably it is tellurium or selenium. In one embodiment,
the aromatic organic compound is substantially free of metal, while
in another embodiment the aromatic organic compound is completely
free of metal.
[0078] The soft and fast agent can also include a Group VIA
component. Elemental sulfur and polymeric sulfur are commercially
available from Elastochem, Inc. of Chardon, Ohio Exemplary sulfur
catalyst compounds include PB(RM-S)-80 elemental sulfur and
PB(CRST)-65 polymeric sulfur, each of which is available from
Elastochem, Inc. An exemplary tellurium catalyst under the
tradename TELLOY.RTM. and an exemplary selenium catalyst under the
tradename VANDEX.RTM. are each commercially available from RT
Vanderbilt.
[0079] Other suitable soft and fast agents include, but are not
limited to, hydroquinones, benzoquinones, quinhydrones, catechols,
and resorcinols.
[0080] Suitable hydroquinone compounds include compounds
represented by the following formula, and hydrates thereof:
##STR00002##
wherein each R.sub.1, R.sub.2, R.sub.3, and R.sub.4 are hydrogen;
halogen; alkyl; carboxyl; metal salts thereof, and esters thereof;
acetate and esters thereof; formyl; acyl; acetyl; halogenated
carbonyl; sulfo and esters thereof; halogenated sulfonyl; sulfino;
alkylsulfinyl; carbamoyl; halogenated alkyl; cyano; alkoxy; hydroxy
and metal salts thereof; amino; nitro; aryl; aryloxy; arylalkyl;
nitroso; acetamido; or vinyl.
[0081] Other suitable hydroquinone compounds include, but are not
limited to, hydroquionone; tetrachlorohydroquinone;
2-chlorohydroquionone; 2-bromohydroquinone;
2,5-dichlorohydroquinone; 2,5-dibromohydroquinone;
tetrabromohydroquinone; 2-methylhydroquinone;
2-t-butylhydroquinone; 2,5-di-t-amylhydroquinone; and
2-(2-chlorophenyl) hydroquinone hydrate.
[0082] More suitable hydroquinone compounds include compounds
represented by the following formula, and hydrates thereof:
##STR00003##
wherein each R.sub.1, R.sub.2, R.sub.3, and R.sub.4 are a metal
salt of a carboxyl; acetate and esters thereof; hydroxy; a metal
salt of a hydroxy; amino; nitro; aryl; aryloxy; arylalkyl; nitroso;
acetamido; or vinyl.
[0083] Suitable benzoquinone compounds include compounds
represented by the following formula, and hydrates thereof:
##STR00004##
wherein each R.sub.1, R.sub.2, R.sub.3, and R.sub.4 are hydrogen;
halogen; alkyl; carboxyl; metal salts thereof, and esters thereof;
acetate and esters thereof; formyl; acyl; acetyl; halogenated
carbonyl; sulfo and esters thereof; halogenated sulfonyl; sulfino;
alkylsulfinyl; carbamoyl; halogenated alkyl; cyano; alkoxy; hydroxy
and metal salts thereof; amino; nitro; aryl; aryloxy; arylalkyl;
nitroso; acetamido; or vinyl.
[0084] Other suitable benzoquinone compounds include one or more
compounds represented by the following formula, and hydrates
thereof:
##STR00005##
wherein each R.sub.1, R.sub.2, R.sub.3, and R.sub.4 are a metal
salt of a carboxyl; acetate and esters thereof; hydroxy; a metal
salt of a hydroxy; amino; nitro; aryl; aryloxy; arylalkyl; nitroso;
acetamido; or vinyl.
[0085] Suitable quinhydrones include one or more compounds
represented by the following formula, and hydrates thereof:
##STR00006##
wherein each R.sub.1, R.sub.2, R.sub.3, R.sub.4, R.sub.5, R.sub.6,
R.sub.7, and R.sub.8 are hydrogen; halogen; alkyl; carboxyl; metal
salts thereof, and esters thereof; acetate and esters thereof;
formyl; acyl; acetyl; halogenated carbonyl; sulfo and esters
thereof; halogenated sulfonyl; sulfino; alkylsulfinyl; carbamoyl;
halogenated alkyl; cyano; alkoxy; hydroxy and metal salts thereof;
amino; nitro; aryl; aryloxy; arylalkyl; nitroso; acetamido; or
vinyl.
[0086] Other suitable quinhydrones include those having the above
formula, wherein each R.sub.1, R.sub.2, R.sub.3, R.sub.4, R.sub.5,
R.sub.6, R.sub.7, and R.sub.8 are a metal salt of a carboxyl;
acetate and esters thereof; hydroxy; a metal salt of a hydroxy;
amino; nitro; aryl; aryloxy; arylalkyl; nitroso; acetamido; or
vinyl. Suitable catechols include one or more compounds represented
by the following formula, and hydrates thereof:
##STR00007##
wherein each R.sub.1, R.sub.2, R.sub.3, and R.sub.4 are hydrogen;
halogen; alkyl; carboxyl; metal salts thereof, and esters thereof;
acetate and esters thereof; formyl; acyl; acetyl; halogenated
carbonyl; sulfo and esters thereof; halogenated sulfonyl; sulfino;
alkylsulfinyl; carbamoyl; halogenated alkyl; cyano; alkoxy; hydroxy
and metal salts thereof; amino; nitro; aryl; aryloxy; arylalkyl;
nitroso; acetamido; or vinyl.
[0087] Suitable resorcinols include one or more compounds
represented by the following formula, and hydrates thereof:
##STR00008##
wherein each R.sub.1, R.sub.2, R.sub.3, and R.sub.4 are hydrogen;
halogen; alkyl; carboxyl; metal salts thereof, and esters thereof;
acetate and esters thereof; formyl; acyl; acetyl; halogenated
carbonyl; sulfo and esters thereof; halogenated sulfonyl; sulfino;
alkylsulfinyl; carbamoyl; halogenated alkyl; cyano; alkoxy; hydroxy
and metal salts thereof; amino; nitro; aryl; aryloxy; arylalkyl;
nitroso; acetamido; or vinyl.
[0088] Fillers may also be added to the thermoset rubber
composition of the core to adjust the density of the composition,
up or down. Typically, fillers include materials such as tungsten,
zinc oxide, barium sulfate, silica, calcium carbonate, zinc
carbonate, metals, metal oxides and salts, regrind (recycled core
material typically ground to about 30 mesh particle),
high-Mooney-viscosity rubber regrind, trans-regrind core material
(recycled core material containing high trans-isomer of
polybutadiene), and the like. When trans-regrind is present, the
amount of trans-isomer is preferably between about 10% and about
60%. In a preferred embodiment of the invention, the core comprises
polybutadiene having a cis-isomer content of greater than about 95%
and trans-regrind core material (already vulcanized) as a filler.
Any particle size trans-regrind core material is sufficient, but is
preferably less than about 125 .mu.m.
[0089] Fillers added to one or more portions of the golf ball
typically include processing aids or compounds to affect
rheological and mixing properties, density-modifying fillers, tear
strength, or reinforcement fillers, and the like. The fillers are
generally inorganic, and suitable fillers include numerous metals
or metal oxides, such as zinc oxide and tin oxide, as well as
barium sulfate, zinc sulfate, calcium carbonate, barium carbonate,
clay, tungsten, tungsten carbide, an array of silicas, and mixtures
thereof. Fillers may also include various foaming agents or blowing
agents which may be readily selected by one of ordinary skill in
the art. Fillers may include polymeric, ceramic, metal, and glass
microspheres may be solid or hollow, and filled or unfilled.
Fillers are typically also added to one or more portions of the
golf ball to modify the density thereof to conform to uniform golf
ball standards. Fillers may also be used to modify the weight of
the center or at least one additional layer for specialty balls,
e.g., a lower weight ball is preferred for a player having a low
swing speed.
[0090] Materials such as tungsten, zinc oxide, barium sulfate,
silica, calcium carbonate, zinc carbonate, metals, metal oxides and
salts, and regrind (recycled core material typically ground to
about 30 mesh particle) are also suitable fillers.
[0091] The polybutadiene and/or any other base rubber or elastomer
system may also be foamed, or filled with hollow microspheres or
with expandable microspheres which expand at a set temperature
during the curing process to any low specific gravity level. Other
ingredients such as sulfur accelerators, e.g., tetra methylthiuram
di, tri, or tetrasulfide, and/or metal-containing organosulfur
components may also be used according to the invention. Suitable
metal-containing organosulfur accelerators include, but are not
limited to, cadmium, copper, lead, and tellurium analogs of
diethyldithiocarbamate, diamyldithiocarbamate, and
dimethyldithiocarbamate, or mixtures thereof. Other ingredients
such as processing aids e.g., fatty acids and/or their metal salts,
processing oils, dyes and pigments, as well as other additives
known to one skilled in the art may also be used in the present
invention in amounts sufficient to achieve the purpose for which
they are typically used.
[0092] A number of cores were formed based on the formulation and
cure cycle described in TABLE 2 below and core hardness values are
reported in TABLE 3 below.
TABLE-US-00002 TABLE 2 Ex 1 Ex 2 Ex 3 Comp Ex 1 Comp Ex 2 Comp Ex 3
Formulation (phr) SR-526.sup.+ 34.0 34.0 31.2 29.0 29.0 29.0 ZnO 5
5 5 5 5 5 BaSO.sub.4 11.2 11.2 16.1 13.8 13.8 13.8 Vanox MBPC* 0.40
0.40 0.40 -- 0.50 -- Trigonox-265-50B** 1.4 1.4 1.6 -- -- 0.8
Perkadox BC-FF*** -- -- -- 1.0 1.6 -- polybutadiene 100 100 100 100
100 100 ZnPCTP 2.35 2.35 2.60 2.35 2.35 2.35 regrind -- -- 17 17 --
-- antioxidant/initiator 0.57 0.57 0.50 -- 0.31 -- ratio Cure Temp.
(.degree. F.) 305 315 320 350 335 335 Cure Time (min) 14 11 16 11
11 11 Properties diameter (in) 1.530 1.530 1.530 1.530 1.530 1.530
compression 69 63 70 69 47 -- COR @ 125 ft/s 0.808 0.806 0.804
0.804 -- -- *Vanox MBPC:
2,2'-methylene-bis-(4-methyl-6-t-butylphenol) available from R.T.
Vanderbilt Company Inc.; **Trigonox 265-50B: a mixture of
1,1-di(t-butylperoxy)-3,3,5-trimethycyclohexane and
di(2-t-butylperoxyisopropyl)benzene 50% active on an inert carrier
available from Akzo Nobel; ***Perkadox BC-FF: Dicumyl peroxide
(99%-100% active) available from Akzo Nobel; and .sup.+SR-526: ZDA
available from Sartomer
TABLE-US-00003 TABLE 3 Distance Shore C Hardness from Comp Center
Ex 1 Ex 2 Ex 3 Comp Ex 1 Comp Ex 2 Ex 3 Center 73 70 71 61 52 61 2
74 71 72 67 57 62 4 74 72 73 70 62 65 6 75 73 73 72 64 67 8 75 73
73 73 64 69 10 75 73 74 73 64 71 12 74 74 73 72 66 72 14 74 74 72
73 70 73 16 70 71 70 77 71 73 18 60 60 63 80 72 73 Surface 63 70 66
85 73 74 Surface - -10 0 -5 24 21 13 Center
[0093] The surface hardness of a core is obtained from the average
of a number of measurements taken from opposing hemispheres of a
core, 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 of a core, care must be taken to insure that the
core 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 all hardness
measurements and is set to take hardness readings at 1 second after
the maximum reading is obtained. The digital durometer must be
attached to, and its foot made parallel to, the base of an
automatic stand, such that the weight on the durometer and attack
rate conform to ASTM D-2240.
[0094] To prepare a core for hardness gradient measurements, 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, 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` core
surface is ground to a smooth, flat surface, revealing the
geometric center of the core, which can be verified by measuring
the height of 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.
[0095] 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. Hardness measurements at any distance
from the center of the core may be measured by drawing a line
radially outward from the center mark, and measuring and marking
the distance from the center, typically in 2-mm increments. All
hardness measurements performed on the 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.
The hardness difference from any predetermined location on the core
is calculated as the average surface hardness minus the hardness at
the appropriate reference point, e.g., at the center of the core
for single, solid core, such that a core surface softer than its
center will have a negative hardness gradient.
[0096] Referring to TABLES 1-2, in Example 1, the surface is 10
Shore C points lower than the center hardness and 12 Shore C points
lower than the hardest point in the core. In Example 3, the surface
is 5 Shore C points lower than the center hardness and 8 Shore C
points lower than the hardest point in the core. In Example 2, the
center and surface hardness values are equal and the softest point
in the core is 10 Shore C points lower than the surface.
[0097] In the examples of the invention presented in TABLE 1, the
cure temperatures are varied from 305.degree. F. to 320.degree. F.
and cure times are varied from 11 to 16 minutes. The core
compositions of examples 1 and 2 are identical, and only the cure
cycle is changed. In example 3 the amount of antioxidant is
identical to examples 1 and 2, but other ingredients are varied as
well the cure cycle. Additionally, the ratio of antioxidant to
initiator varies from 0.50 to 0.57 from example 1 and 2 to example
3.
[0098] The ratio of antioxidant to initiator is one factor to
control the surface hardness of the cores. The data shown in TABLE
2 shows that hardness gradient is at least, but not limited to, a
function of the amount of antioxidant and peroxide, their ratio,
and the cure cycle. It should be noted that higher antioxidant also
requires higher peroxide initiator to maintain the desired
compression.
[0099] The core of Comparative Example 1, whose composition is
shown in TABLE 2 was cured using a conventional cure cycle, with a
cure temperature of 350.degree. F. and a cure time of 11 minutes.
The inventive cores were produced using cure cycles of 305.degree.
F. for 14 minutes, 315.degree. F. for 11 minutes and 320.degree. F.
for 16 minutes. The hardness gradients of these cores were measured
and the following observations can be made. For the cores of the
Comparative Examples, as expected, a conventional hard surface to
soft center gradient can be clearly seen. The gradients for
inventive cores follow substantially the same shape as one
another.
[0100] In another alternative embodiment of the present invention,
a golf ball has a negative hardness gradient core, single or
multi-layer, where at least one of the single core or one of the
layers in a multi-layer embodiment has a very soft "skin" or
transition region. As used herein, the term "skin" or transition
region refers to a portion of a particular layer (i.e., a single
core, a core layer, etc.), is not a separate, discreet layer, and
is not formed by a surface treatment.
[0101] The soft skin (transition region) of the core preferably has
a hardness of about 70 Shore C or less, more preferably about 65
Shore C or less, and most preferably about 60 Shore C or less. The
hardness at the geometric center of the core is preferably greater
than the surface hardness such that the core has a "negative
hardness gradient" across the entire cross section of the core. The
negative hardness gradient of the inventive core is preferably
about 1 to 40 Shore C, more preferably about 5 to 35 Shore C, and
most preferably about 10 to 30 Shore C. In more preferred
embodiments, the negative hardness gradient is up to about 20 Shore
C, more preferably about 1 to 20 Shore C, 5 to 20 Shore C, 10 to 20
Shore C, or 10 to 15 Shore C.
[0102] In a dual core embodiment of the invention, which includes
an inner core and outer core layer, the soft skin may be part of
the inner core, the outer core, or both. In dual core embodiments,
because the dimensions of the components are smaller than for a
single, unitary core, the region or volume that the soft skin
occupies is much greater (a higher percentage of the volume of the
component). When the inner core includes the soft skin, the outer
core layer may have a negative hardness gradient, a positive
hardness gradient, or a zero hardness gradient.
[0103] The soft skin or transition region occupies a volume or
region that is close to the surface of the core (or core layer). In
a most preferred embodiment, the soft skin or transition region
does not includes the surface. The soft skin or transition
volume/region is created by using a specific rubber composition and
a specific cure process. Preferably, the composition includes at
least one polybutadiene rubber, such as CB23 and other suitable
rubbers disclosed herein, about 20 to 50 parts of ZDA, about 0.1 to
2 parts peroxide, about 0.1 to 2.5 parts of ZnPCTP, optionally 0 to
about 0.4 parts of an antioxidant, and about 5 to 25 parts of zinc
oxide. A wide range of hardness gradients can be achieved by
varying the selection of peroxide type and level and amount of
ZnPCTP.
[0104] In a preferred embodiment, a core having a narrow-banded,
very soft skin was formed with Luperox DI as the peroxide and
molded at 311.degree. F. for 20 minutes. The overall negative
hardness gradient of the 1.510-inch-diameter core is about 14 Shore
C (surface hardness of about 60 Shore C and geometric center
hardness of about 74 Shore C). The long, relatively low cure
temperature of the process, coupled with the formulation, generates
a core having unique physical properties, the narrow band of soft
skin, and a negative hardness gradient. In a preferred embodiment,
the soft skin has a thickness of about 4 mm or less, more
preferably about 3 mm or less and, in an alternative embodiment,
about 2 to 4 mm. In these embodiments, the hardness profile is
preferably a negative hardness gradient of about 5 Shore C or
greater, more preferably about 10 Shore C or greater, and most
preferably about 15 Shore C or greater. In an alternative
embodiment, the soft skin has a negative hardness gradient of up to
about 20 Shore C, about 5 to 20 Shore C, more preferably about 10
to 20 Shore C, or most preferably about 10 to 15 Shore C.
[0105] It is important that the cores have a high COR in addition
to the soft skin or transition region. Preferably the core having
the negative hardness gradient and soft skin transition region has
a COR measured at an incoming velocity of 125 ft/s of about 0.800
or greater, more preferably about 0.805 or greater, and most
preferably about 0.810 or greater. In a more preferred embodiment,
the above core has a compression of about 95 or less, more
preferably about 90 or less, and most preferably about 88 or less.
In one particularly preferred embodiment, the core has a COR of
about 0.813 or greater, a compression of 88 or less, and a negative
hardness gradient of at least about 10 Shore C.
[0106] Table 4 contains a variety of rubber compositions and
properties for golf ball cores formed from those compositions. A
number of 1.51-inch single cores were formed and molded at
311.degree. F. for 20 minutes. Example 3 depicts one of the
inventive cores having a soft skin transition region at the outer
surface of the core.
TABLE-US-00004 TABLE 4 Ex 1 Ex 2 Ex 3 Ex 4 Ex 5 Ex 6 Ex 7 CB23 100
100 100 100 100 100 100 ZDA 32 40 40 40 32 32 32 Perkadox BC 1.5
0.5 1.5 0.5 Luperox DI 1 2 Perkadox 14 1 ZnPCTP 0.2 2 2 2 0.2 2 2
ZnO 21 21 21 21 21 21 21 BHT 0.2 Varox MBPC 0.2 0.2 0.2 0.2 0.2 0.2
Compression 80 88 88 103 88 64 95 Surface Hardness 85.6 71.2 60.4
86.5 89.6 64.5 74.7 (Shore C) Center Hardness 62.8 66.8 74.0 65.7
67.2 64.8 65.3 (Shore C) Gradient 22.8 4.4 -13.6 20.8 22.4 -0.3 9.4
CoR @ 125 ft/s 0.802 0.817 0.813 0.809 0.803 0.810 0.811 % trans in
core 10.0 14.7 9.2 20.2 12.5 14.4 14.0
[0107] Referring to FIG. 3, as in Ex 3 above in Table 4, a core
having a negative hardness gradient and the soft skin of the
invention is depicted. Consider in FIG. 3, the hardness profile as
measured across a single core clearly shows, for a rubber
composition containing 1 part Luperox DI, that the outer 4 mm of
the core is the soft skin or the transition region--the overall
core has a negative hardness gradient of about 10 Shore C (e.g., 60
Shore C-70 Shore C) but the outer portion of the skin has a
hardness of about 60 Shore C that quickly increases to about 75
Shore C over a 4-mm region. Even though the hardness measurements
are being taken on a single, unitary core, the soft skin region
acts like another layer having a steep negative gradient over an
inner layer having a shallow positive hardness gradient (e.g., 75
Shore C at 16 mm from the center of the core -70 Shore C at the
center).
[0108] FIG. 3 also depicts an alternative embodiment of the present
invention. The single, unitary core containing 2 parts Luperox DI
has an overall positive hardness gradient of about 9 Shore C (e.g.,
74 Shore C at the surface -65 Shore C at the center) but the
outermost 2-3 mm soft skin has a negative hardness gradient of
about 8 Shore C (e.g., 74 Shore C at the core surface -82 Shore C
at a point about 2-3 mm towards the center of the core). Also see
Table 4, Ex 7. The amount and type of peroxide, along with the cure
process time and temperature determine the soft skin hardness, core
compression, and hardness gradient (both direction and
magnitude).
[0109] In another embodiment of the present invention, the golf
ball comprises a unitary core having an outer surface, a geometric
center, and a soft transition region adjacent to the outer surface.
The core can be formed of any material but is preferably a rubber
composition. The soft transition region in the outer portion of the
core preferably has a thickness of up to 4 mm. Preferably the
thickness of the soft transition region is about 1 mm to about 4
mm, more preferably about 1 mm to about 3 mm, and most preferably
about 1 mm to about 2 mm. The soft transition region comprises
about 8 to 20 percent trans-polybutadiene isomer. The
trans-polybutadiene isomer is preferably about 10 percent to about
20 percent, more preferably about 12 percent to about 19 percent,
and most preferably about 14 percent to about 18 percent. The soft
transition region also has a negative hardness gradient of up to 15
Shore C, preferably about 1 Shore C to about 15 Shore C, more
preferably about 5 Shore C to about 13 Shore C, and most preferably
about 7 Shore C to about 10 Shore C. The unitary core has an
overall negative hardness gradient of up to 20 Shore C, preferably
about 1 Shore C to about 20 Shore C, more preferably about 5 Shore
C to about 19 Shore C, and most preferably about 10 Shore C to
about 18 Shore C.
[0110] Because the inventive core is so unique in its properties,
very soft outer portion, negative hardness gradient, high COR (but
not high compression), it is defined by a gradient quotient, GQ.
The gradient quotient, GQ, is defined by the equation:
G + T 10 .times. COR .ltoreq. 7 ##EQU00005##
[0111] where G is the overall core (from geometric center to outer
surface) negative hardness gradient in Shore C, T is the percent of
trans-polybutadiene isomer at the core outer surface, and COR is
the coefficient of restitution measured at an incoming velocity of
125 ft/s. Because of the unique properties of the inventive core,
it is also suited to be a one-piece golf ball. A one-piece golf
ball comprises a sphere (effectively a single, unitary core) formed
from a substantially homogenous composition, preferably a
rubber-based composition. The sphere has a dimpled outer surface, a
geometric center, and a soft transition region adjacent to the
dimpled outer surface. The soft transition region has a thickness
of up to 4 mm, preferably about 0.5 mm to about 3 mm, more
preferably about 0.5 mm to about 2 mm, and most preferably about 1
mm to about 2 mm. In a preferred embodiment, the rubber sphere
comprises about 8 to 20 percent trans-polybutadiene isomer, and has
a negative hardness gradient of up to 15 Shore C, and wherein the
sphere has an overall negative hardness gradient of up to 20 Shore
C, but can also have the properties disclosed for the inventive
core. The sphere preferably has a gradient quotient, GQ, defined by
the equation:
G + T 10 .times. COR .ltoreq. 7 ##EQU00006##
where G is the overall negative hardness gradient in Shore C, T is
the percent of trans-polybutadiene isomer at the core outer
surface, and COR is the coefficient of restitution measured at an
incoming velocity of 125 ft/s.
[0112] Preferably, the core has a COR of about 0.800 or greater,
more preferably about 0.810 or greater, or even 0.813 or greater,
which is unusual for a core having such a soft outer portion and
comparable compression.
[0113] Optionally, the transition region may include about 9 to
about 15 percent trans-polybutadiene isomer. The core geometric
center includes about 5 to 15 percent trans-polybutadiene isomer.
The core outer surface includes about 10 to 30 percent
trans-polybutadiene isomer.
[0114] In an alternative embodiment, the golf ball includes a
single, solid center and at least one cover layer. The solid center
may include an outer core layer. The cover maybe formed from an
inner cover and an outer cover. An intermediate layer may be
included between the core and cover. In one embodiment, when the
golf ball is formed from a solid core and an outer cover, the an
outer cover layer preferably has a hardness of about 50 Shore M or
greater.
[0115] The core of this embodiment has an outer surface, a
geometric center, and a soft transition region located adjacent to
the outer surface. The soft transition region typically has a
thickness of about 4 mm or less, preferably about 3 mm or less,
more preferably about 2 mm or less, and most preferably about 1 mm
to about 2 mm. The soft transition region includes about 10 to 30
percent of a trans-polybutadiene isomer. In one embodiment, the
soft transition region includes about 10 to 20 percent of a
trans-polybutadiene isomer. In another embodiment, the soft
transition region includes about 20 to 30 percent of a
trans-polybutadiene isomer. The soft transition region includes
about 10 to 30 percent of a trans-polybutadiene isomer also has a
positive hardness gradient of about 10 Shore C or less, more
preferably about 8 Shore C or less, and most preferably about 5
Shore C or less.
[0116] The solid core preferably has an outer surface hardness
greater than the hardness at the geometric center to define a
positive hardness gradient (differing from the hardness gradient of
the soft transition region) of about 10 Shore C to 42 Shore C.
Preferably, the core has a positive hardness gradient of about 12
Shore C to 35 Shore C, more preferably the core has a positive
hardness gradient of about 13 Shore C to 24 Shore C, and most
preferably the core has a positive hardness gradient of about 14
Shore C to 21 Shore C.
[0117] The core has a secondary gradient quotient (GQ') that ranges
from about 2.2 to 9.5. The secondary gradient quotient, GQ', is
defined by the equation:
G ' + T 10 .times. COR ##EQU00007##
where G' is the positive hardness gradient of the solid core in
Shore C; T is the percent of trans-polybutadiene isomer at the core
outer surface, and COR is the coefficient of restitution of the
core measured at an incoming velocity of 125 ft/s. This
relationship may also be represented as:
2.2.ltoreq.(G '+T)/(10.times.COR).ltoreq.9.5
In another embodiment, the core has a secondary gradient quotient
(GQ') that ranges from about 7.5 to 9.5. This relationship may also
be represented as:
7.5.ltoreq.(G '+T)/(10.times.COR).ltoreq.9.5
Accordingly, the core typically has a coefficient of restitution
measured at an incoming velocity of 125 ft/s of about 0.800 or
greater, preferably about 0.810 or greater.
[0118] The secondary gradient quotient, GQ', is preferably about
2.5 to 8.5, more preferably the secondary gradient quotient, GQ',
is about 2.7 to 6.9, and most preferably the secondary gradient
quotient, GQ', is about 2.9 to 6.5. The second positive hardness
gradient is preferably about 12 Shore C to about 35 Shore C, more
preferably the second positive hardness gradient is about 13 Shore
C to about 24 Shore C, and most preferably the second positive
hardness gradient is about 14 Shore C to about 21 Shore C.
[0119] The golf ball may include one or more coating layers
disposed about the outer cover layer. The one or more coating
layers preferably have a thickness of about 0.003 inches or less,
more preferably about 0.002 inches of less, and most preferably
about 0.001 inches or less. In a preferred embodiment, the golf
ball includes 3 coating layers, each layer having a thickness of
about 0.001 inches to about 0.003 inches. The one or more coating
layers preferably have a Shore M hardness of about 60 Shore M or
less, more preferably about 55 Shore M or less, and most preferably
about 50 Shore M or less.
[0120] The one or more coating layers preferably have an
instrumented hardness of about 1 MPa to about 23 MPa, more
preferably the one or more coating layers have an instrumented
hardness of about 1 MPa to about 10 MPa, and most preferably the
one or more coating layers have an instrumented hardness of about 4
MPa to about 7 MPa. In one alternative embodiment, the one or more
coating layers have an instrumented hardness of about 25 MPa to
about 26 MPa.
[0121] The soft transition region of the golf ball may include
about 10 to about 20 percent trans-polybutadiene isomer or,
alternatively, the soft transition region may include about 20 to
about 30 percent trans-polybutadiene isomer.
[0122] If the golf ball includes the optional inner cover layer it
is typically formed from an ionomer or ionomer blend. Preferably,
the ionomer comprises a lithium ionomer or a sodium ionomer, or
both.
19. A golf ball comprising: [0123] a core having an outer surface,
a geometric center, and a soft transition region adjacent to the
outer surface, the soft transition region having a thickness of
about 4 mm or less, comprises about 10 to 30 percent of a
trans-polybutadiene isomer, and has a positive hardness gradient of
about 10 Shore C or less; and [0124] an outer cover layer having a
hardness of about 50 Shore M or greater; [0125] wherein the core
has an outer surface hardness greater than a hardness at the
geometric center to define a positive hardness gradient of about 12
Shore C to 24 Shore C; and a secondary gradient quotient, GQ', from
about 7.5 to 9.5, GQ' being defined by the equation:
[0125] G ' + T 10 .times. COR ##EQU00008##
where G' is the core positive hardness gradient in Shore C, T is
the percent of trans-polybutadiene isomer at the core outer
surface, and COR is the coefficient of restitution of the core
measured at an incoming velocity of 125 ft/s.
[0126] Shore M hardness measurements can be made on a Shore.RTM. 51
Micro Hardness Model 719 Digital Durometer, or the equivalent,
according to ASTM procedure D2240 as it relates to measuring Shore
M hardness.
[0127] The microhardness measurements were conducted with a
Modified Berkovich diamond indenter mounted on a TA
Instruments.RTM. Q800 DMA in force-controlled compression mode. The
measurement cycle used a 15-second load, 20-second hold, and a
15-second unload with a 100 mN maximum force. Instrumented Hardness
("HIT") was determined for each sample by a calculation using the
maximum force applied, the contact area, and depth of the indenter
at maximum deformation, and the slope of the unload curve as
described in ASTM procedure E2546-07, Standard Practice for
Instrumented Indentation Testing. Martens hardness was also
determined for each sample using the values obtained from the
force/indentation depth data at the end of the load cycle after
reaching maximum force in accordance with ISO 14577-1:2015(E) Annex
A.2.1. Samples for the analysis were prepared by gently pressing
the golf ball into a hemispherical holder and using a surface
grinding machine to remove any material above the equator of the
golf ball (leaving about half of the golf ball), exposing the
geometric center. The remaining golf ball hemisphere is removed
from the fixture, flipped, and ground with a surface grinder to
remove enough of the remaining half to form a 6-10 mm `puck` having
the center of the ball as one of the smooth, flat, and parallel
surfaces. Samples were held at 23.degree. C./50% relative humidity
("RH") for at least two days after preparation before hardness
measurements being taken at room temperature.
[0128] In many preferred embodiments of invention, the hardness of
the core at the surface is at most about the same as or
substantially less than the hardness of the core at the center.
Furthermore, the center hardness of the core may not be the hardest
point in the core, but in all cases, it is preferred that it is at
least equal to or harder than the surface. Additionally, the lowest
hardness anywhere in the core does not have to occur at the
surface. In some embodiments, the lowest hardness value occurs
within about the outer 6 mm of the core surface. However, the
lowest hardness value within the core can occur at any point from
the surface, up to, but not including the center, as long as the
surface hardness is still equal to, or less than the hardness of
the center. It should be noted that in the present invention the
formulation is the same throughout the core, or core layer, and no
surface treatment is applied to the core to obtain the preferred
surface hardness.
[0129] While the inventive golf ball may be formed from a variety
of differing and conventional cover materials (both intermediate
layer(s) and outer cover layer), preferred cover materials include,
but are not limited to: (1) polyurethanes, such as those prepared
from polyols or polyamines and diisocyanates or polyisocyanates
and/or their prepolymers, and those disclosed in U.S. Pat. Nos.
5,334,673 and 6,506,851; (2) polyureas, such as those disclosed in
U.S. Pat. Nos. 5,484,870 and 6,835,794; and (3) polyurethane-urea
hybrids, blends or copolymers comprising urethane or urea
segments.
[0130] Suitable polyurethane compositions comprise a reaction
product of at least one polyisocyanate and at least one curing
agent. The curing agent can include, for example, one or more
polyamines, 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. Thus, the polyols described herein are suitable for use in
one or both components of the polyurethane material, i.e., as part
of a prepolymer and in the curing agent. Suitable polyurethanes are
described in U.S. Patent Application Publication No. 2005/0176523,
which is incorporated by reference in its entirety.
[0131] Any polyisocyanate available to one of ordinary skill in the
art is suitable for use according to the invention. Exemplary
polyisocyanates include, but are not limited to,
4,4'-diphenylmethane diisocyanate (MDI); polymeric MDI;
carbodiimide-modified liquid MDI; 4,4'-dicyclohexylmethane
diisocyanate (H.sub.12MDI); p-phenylene diisocyanate (PPDI);
m-phenylene diisocyanate (MPDI); toluene diisocyanate (TDI);
3,3'-dimethyl-4,4'-biphenylene diisocyanate;
isophoronediisocyanate; 1,6-hexamethylene diisocyanate (HDI);
naphthalene diisocyanate; xylene diisocyanate; p-tetramethylxylene
diisocyanate; m-tetramethylxylene diisocyanate; ethylene
diisocyanate; propylene-1,2-diisocyanate;
tetramethylene-1,4-diisocyanate; cyclohexyl diisocyanate;
dodecane-1,12-diisocyanate; cyclobutane-1,3-diisocyanate;
cyclohexane-1,3-diisocyanate; cyclohexane-1,4-diisocyanate;
1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane; methyl
cyclohexylene diisocyanate; triisocyanate of HDI; triisocyanate of
2,4,4-trimethyl-1,6-hexane diisocyanate; tetracene diisocyanate;
napthalene diisocyanate; anthracene diisocyanate; isocyanurate of
toluene diisocyanate; uretdione of hexamethylene diisocyanate; and
mixtures thereof. Polyisocyanates are known to those of ordinary
skill in the art as having more than one isocyanate group, e.g.,
di-isocyanate, tri-isocyanate, and tetra-isocyanate. Preferably,
the polyisocyanate includes MDI, PPDI, TDI, or a mixture thereof,
and more preferably, the polyisocyanate includes MDI. It should be
understood that, as used herein, the term MDI includes
4,4'-diphenylmethane diisocyanate, polymeric MDI,
carbodiimide-modified liquid MDI, and mixtures thereof and,
additionally, that the diisocyanate employed may be "low free
monomer," understood by one of ordinary skill in the art to have
lower levels of "free" monomer isocyanate groups, typically less
than about 0.1% free monomer isocyanate groups. Examples of "low
free monomer" diisocyanates include, but are not limited to Low
Free Monomer MDI, Low Free Monomer TDI, and Low Free Monomer
PPDI.
[0132] The at least one polyisocyanate should have less than about
14% unreacted NCO groups. Preferably, the at least one
polyisocyanate has no greater than about 8.0% NCO, more preferably
no greater than about 7.8%, and most preferably no greater than
about 7.5% NCO with a level of NCO of about 7.2 or 7.0, or 6.5% NCO
commonly used.
[0133] Any polyol available to one of ordinary skill in the art is
suitable for use according to the invention. Exemplary polyols
include, but are not limited to, polyether polyols,
hydroxy-terminated polybutadiene (including partially/fully
hydrogenated derivatives), polyester polyols, polycaprolactone
polyols, and polycarbonate polyols. In one preferred embodiment,
the polyol includes polyether polyol. Examples include, but are not
limited to, polytetramethylene ether glycol (PTMEG), polyethylene
propylene glycol, polyoxypropylene glycol, and mixtures thereof.
The hydrocarbon chain can have saturated or unsaturated bonds and
substituted or unsubstituted aromatic and cyclic groups.
Preferably, the polyol of the present invention includes PTMEG.
[0134] In another embodiment, polyester polyols are included in the
polyurethane material. Suitable polyester polyols include, but are
not limited to, polyethylene adipate glycol; polybutylene adipate
glycol; polyethylene propylene adipate glycol;
o-phthalate-1,6-hexanediol; poly(hexamethylene adipate) glycol; and
mixtures thereof. The hydrocarbon chain can have saturated or
unsaturated bonds, or substituted or unsubstituted aromatic and
cyclic groups. In another embodiment, polycaprolactone polyols are
included in the materials of the invention. Suitable
polycaprolactone polyols include, but are not limited to,
1,6-hexanediol-initiated polycaprolactone, diethylene glycol
initiated polycaprolactone, trimethylol propane initiated
polycaprolactone, neopentyl glycol initiated polycaprolactone,
1,4-butanediol-initiated polycaprolactone, and mixtures thereof.
The hydrocarbon chain can have saturated or unsaturated bonds, or
substituted or unsubstituted aromatic and cyclic groups.
[0135] In yet another embodiment, polycarbonate polyols are
included in the polyurethane material of the invention. Suitable
polycarbonates include, but are not limited to, polyphthalate
carbonate and poly(hexamethylene carbonate) glycol. The hydrocarbon
chain can have saturated or unsaturated bonds, or substituted or
unsubstituted aromatic and cyclic groups. In one embodiment, the
molecular weight of the polyol is from about 200 to about 4000.
[0136] Polyamine curatives are also suitable for use in the
polyurethane composition of the invention and have been found to
improve cut, shear, and impact resistance of the resultant balls.
Preferred polyamine curatives include, but are not limited to,
3,5-dimethylthio-2,4-toluenediamine and isomers thereof;
3,5-diethyltoluene-2,4-diamine and isomers thereof, such as
3,5-diethyltoluene-2,6-diamine;
4,4'-bis-(sec-butylamino)-diphenylmethane;
1,4-bis-(sec-butylamino)-benzene,
4,4'-methylene-bis-(2-chloroaniline);
4,4'-methylene-bis-(3-chloro-2,6-diethylaniline);
polytetramethyleneoxide-di-p-aminobenzoate; N,N'-dialkyldiamino
diphenyl methane; p,p'-methylene dianiline; m-phenylenediamine;
4,4'-methylene-bis-(2-chloroaniline);
4,4'-methylene-bis-(2,6-diethylaniline);
4,4'-methylene-bis-(2,3-dichloroaniline);
4,4'-diamino-3,3'-diethyl-5,5'-dimethyl diphenylmethane;
2,2',3,3'-tetrachloro diamino diphenylmethane; trimethylene glycol
di-p-aminobenzoate; and mixtures thereof. Preferably, the curing
agent of the present invention includes
3,5-dimethylthio-2,4-toluenediamine and isomers thereof, such as
ETHACURE.RTM. 300, commercially available from Albermarle
Corporation of Baton Rouge, La.
[0137] Suitable polyamine curatives, which include both primary and
secondary amines, preferably have molecular weights ranging from
about 64 to about 2000.
[0138] At least one of a diol, triol, tetraol, or
hydroxy-terminated curatives may be added to the aforementioned
polyurethane composition. Suitable diol, triol, and tetraol groups
include ethylene glycol; diethylene glycol; polyethylene glycol;
propylene glycol; polypropylene glycol; lower molecular weight
polytetramethylene ether glycol; 1,3-bis(2-hydroxyethoxy) benzene;
1,3-bis-[2-(2-hydroxyethoxy) ethoxy] benzene;
1,3-bis-{2-[2-(2-hydroxyethoxy) ethoxy] ethoxy} benzene;
1,4-butanediol; 1,5-pentanediol; 1,6-hexanediol;
resorcinol-di-(.beta.-hydroxyethyl) ether;
hydroquinone-di-(.beta.-hydroxyethyl) ether; and mixtures thereof.
Preferred hydroxy-terminated curatives include
1,3-bis(2-hydroxyethoxy) benzene; 1,3-bis-[2-(2-hydroxyethoxy)
ethoxy] benzene; 1,3-bis-{2-[2-(2-hydroxyethoxy) ethoxy] ethoxy}
benzene; 1,4-butanediol, and mixtures thereof. Preferably, the
hydroxy-terminated curatives have molecular weights ranging from
about 48 to 2000. It should be understood that molecular weight, as
used herein, is the absolute weight average molecular weight and
would be understood as such by one of ordinary skill in the
art.
[0139] Both the hydroxy-terminated and amine curatives can include
one or more saturated, unsaturated, aromatic, and cyclic groups.
Additionally, the hydroxy-terminated and amine curatives can
include one or more halogen groups. The polyurethane composition
can be formed with a blend or mixture of curing agents. If desired,
however, the polyurethane composition may be formed with a single
curing agent.
[0140] In a preferred embodiment of the present invention,
saturated polyurethanes are used to form one or more of the cover
layers, preferably the outer cover layer, and may be selected from
among both castable thermoset and thermoplastic polyurethanes.
[0141] In this embodiment, the saturated polyurethanes of the
present invention are substantially free of aromatic groups or
moieties. Saturated polyurethanes suitable for use in the invention
are a product of a reaction between at least one polyurethane
prepolymer and at least one saturated curing agent. The
polyurethane prepolymer is a product formed by a reaction between
at least one saturated polyol and at least one saturated
diisocyanate. As is well known in the art, that a catalyst may be
employed to promote the reaction between the curing agent and the
isocyanate and polyol, or the curing agent and the prepolymer.
[0142] Saturated diisocyanates which can be used include, without
limitation, ethylene diisocyanate; propylene-1,2-diisocyanate;
tetramethylene-1,4-diisocyanate; 1,6-hexamethylene-diisocyanate
(HDI); 2,2,4-trimethylhexamethylene diisocyanate;
2,4,4-trimethylhexamethylene diisocyanate;
dodecane-1,12-diisocyanate; dicyclohexylmethane diisocyanate;
cyclobutane-1,3-diisocyanate; cyclohexane-1,3-diisocyanate;
cyclohexane-1,4-diisocyanate;
1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane;
isophorone diisocyanate; methyl cyclohexylene diisocyanate;
triisocyanate of HDI; triisocyanate of 2,2,4-trimethyl-1,6-hexane
diisocyanate. The most preferred saturated diisocyanates are
4,4'-dicyclohexylmethane diisocyanate and isophorone
diisocyanate.
[0143] Saturated polyols which are appropriate for use in this
invention include without limitation polyether polyols such as
polytetramethylene ether glycol and poly(oxypropylene) glycol.
Suitable saturated polyester polyols include polyethylene adipate
glycol, polyethylene propylene adipate glycol, polybutylene adipate
glycol, polycarbonate polyol and ethylene oxide-capped
polyoxypropylene diols. Saturated polycaprolactone polyols which
are useful in the invention include diethylene glycol-initiated
polycaprolactone, 1,4-butanediol-initiated polycaprolactone,
1,6-hexanediol-initiated polycaprolactone; trimethylol
propane-initiated polycaprolactone, neopentyl glycol initiated
polycaprolactone, and polytetramethylene ether glycol-initiated
polycaprolactone. The most preferred saturated polyols are
polytetramethylene ether glycol and PTMEG-initiated
polycaprolactone.
[0144] Suitable saturated curatives include 1,4-butanediol,
ethylene glycol, diethylene glycol, polytetramethylene ether
glycol, propylene glycol; trimethanolpropane;
tetra-(2-hydroxypropyl)-ethylenediamine; isomers and mixtures of
isomers of cyclohexyldimethylol, isomers and mixtures of isomers of
cyclohexane bis(methylamine); triisopropanolamine; ethylene
diamine; diethylene triamine; triethylene tetramine; tetraethylene
pentamine; 4,4'-dicyclohexylmethane diamine;
2,2,4-trimethyl-1,6-hexanediamine;
2,4,4-trimethyl-1,6-hexanediamine; diethyleneglycol
di-(aminopropyl)ether;
4,4'-bis-(sec-butylamino)-dicyclohexylmethane;
1,2-bis-(sec-butylamino)cyclohexane; 1,4-bis-(sec-butylamino)
cyclohexane; isophorone diamine; hexamethylene diamine; propylene
diamine; 1-methyl-2,4-cyclohexyl diamine; 1-methyl-2,6-cyclohexyl
diamine; 1,3-diaminopropane; dimethylamino propylamine;
diethylamino propylamine; imido-bis-propylamine; isomers and
mixtures of isomers of diaminocyclohexane; monoethanolamine;
diethanolamine; triethanolamine; monoisopropanolamine; and
diisopropanolamine. The most preferred saturated curatives are
1,4-butanediol, 1,4-cyclohexyldimethylol and
4,4'-bis-(sec-butylamino)-dicyclohexylmethane.
[0145] Alternatively, other suitable polymers include partially or
fully neutralized ionomer, metallocene, or other single-site
catalyzed polymer, polyester, polyamide, non-ionomeric
thermoplastic elastomer, copolyether-esters, copolyether-amides,
polycarbonate, polybutadiene, polyisoprene, polystryrene block
copolymers (such as styrene-butadiene-styrene),
styrene-ethylene-propylene-styrene,
styrene-ethylene-butylene-styrene, and the like, and blends
thereof. Thermosetting polyurethanes or polyureas are suitable for
the outer cover layers of the golf balls of the present
invention.
[0146] Additionally, polyurethane can be replaced with or blended
with a polyurea material. Polyureas are distinctly different from
polyurethane compositions, but also result in desirable aerodynamic
and aesthetic characteristics when used in golf ball components.
The polyurea-based compositions are preferably saturated in
nature.
[0147] Without being bound to any particular theory, it is now
believed that substitution of the long chain polyol segment in the
polyurethane prepolymer with a long chain polyamine oligomer soft
segment to form a polyurea prepolymer, improves shear, cut, and
resiliency, as well as adhesion to other components. Thus, the
polyurea compositions of this invention may be formed from the
reaction product of an isocyanate and polyamine prepolymer
crosslinked with a curing agent. For example, polyurea-based
compositions of the invention may be prepared from at least one
isocyanate, at least one polyether amine, and at least one diol
curing agent or at least one diamine curing agent.
[0148] Any polyamine available to one of ordinary skill in the art
is suitable for use in the polyurea prepolymer. Polyether amines
are particularly suitable for use in the prepolymer. As used
herein, "polyether amines" refer to at least polyoxyalkyleneamines
containing primary amino groups attached to the terminus of a
polyether backbone. Due to the rapid reaction of isocyanate and
amine, and the insolubility of many urea products, however, the
selection of diamines and polyether amines is limited to those
allowing the successful formation of the polyurea prepolymers. In
one embodiment, the polyether backbone is based on tetramethylene,
propylene, ethylene, trimethylolpropane, glycerin, and mixtures
thereof. Suitable polyether amines include, but are not limited to,
methyldiethanolamine; polyoxyalkylenediamines such as,
polytetramethylene ether diamines, polyoxypropylenetriamine, and
polyoxypropylene diamines; poly(ethylene oxide capped oxypropylene)
ether diamines; propylene oxide-based triamines;
triethyleneglycoldiamines; trimethylolpropane-based triamines;
glycerin-based triamines; and mixtures thereof. In one embodiment,
the polyether amine used to form the prepolymer is JEFFAMINE.RTM.
D2000 (manufactured by Huntsman Chemical Co. of Austin, Tex.).
[0149] The molecular weight of the polyether amine for use in the
polyurea prepolymer may range from about 100 to about 5000. In one
embodiment, the polyether amine molecular weight is about 200 or
greater, preferably about 230 or greater. In another embodiment,
the molecular weight of the polyether amine is about 4000 or less.
In yet another embodiment, the molecular weight of the polyether
amine is about 600 or greater. In still another embodiment, the
molecular weight of the polyether amine is about 3000 or less. In
yet another embodiment, the molecular weight of the polyether amine
is between about 1000 and about 3000, and more preferably is
between about 1500 to about 2500. Because lower molecular weight
polyether amines may be prone to forming solid polyureas, a higher
molecular weight oligomer, such as JEFFAMINE.RTM. D2000, is
preferred.
[0150] As briefly discussed above, some amines may be unsuitable
for reaction with the isocyanate because of the rapid reaction
between the two components. In particular, shorter chain amines are
fast reacting. In one embodiment, however, a hindered secondary
diamine may be suitable for use in the prepolymer. Without being
bound to any particular theory, it is believed that an amine with a
high level of stearic hindrance, e.g., a tertiary butyl group on
the nitrogen atom, has a slower reaction rate than an amine with no
hindrance or a low level of hindrance. For example,
4,4'-bis-(sec-butylamino)-dicyclohexylmethane (CLEARLINK.RTM. 1000)
may be suitable for use in combination with an isocyanate to form
the polyurea prepolymer.
[0151] Any isocyanate available to one of ordinary skill in the art
is suitable for use in the polyurea prepolymer. Isocyanates for use
with the present invention include aliphatic, cycloaliphatic,
araliphatic, aromatic, any derivatives thereof, and combinations of
these compounds having two or more isocyanate (NCO) groups per
molecule. The isocyanates may be organic polyisocyanate-terminated
prepolymers. The isocyanate-containing reactable component may also
include any isocyanate-functional monomer, dimer, trimer, or
multimeric adduct thereof, prepolymer, quasi-prepolymer, or
mixtures thereof. Isocyanate-functional compounds may include
monoisocyanates or polyisocyanates that include any isocyanate
functionality of two or more.
[0152] Suitable isocyanate-containing components include
diisocyanates having the generic structure:
O.dbd.C.dbd.N--R--N.dbd.C.dbd.O, where R is preferably a cyclic,
aromatic, or linear or branched hydrocarbon moiety containing from
about 1 to about 20 carbon atoms. The diisocyanate may also contain
one or more cyclic groups or one or more phenyl groups. When
multiple cyclic or aromatic groups are present, linear and/or
branched hydrocarbons containing from about 1 to about 10 carbon
atoms can be present as spacers between the cyclic or aromatic
groups. In some cases, the cyclic or aromatic group(s) may be
substituted at the 2-, 3-, and/or 4-positions, or at the ortho-,
meta-, and/or para-positions, respectively. Substituted groups may
include, but are not limited to, halogens, primary, secondary, or
tertiary hydrocarbon groups, or a mixture thereof.
[0153] Examples of diisocyanates that can be used with the present
invention include, but are not limited to, substituted and isomeric
mixtures including 2,2'-, 2,4'-, and 4,4'-diphenylmethane
diisocyanate; 3,3'-dimethyl-4,4'-biphenylene diisocyanate; toluene
diisocyanate; polymeric MDI; carbodiimide-modified liquid
4,4'-diphenylmethane diisocyanate; para-phenylene diisocyanate;
meta-phenylene diisocyanate; triphenyl methane-4,4'- and triphenyl
methane-4,4'-triisocyanate; naphthylene-1,5-diisocyanate; 2,4'-,
4,4'-, and 2,2-biphenyl diisocyanate; polyphenyl polymethylene
polyisocyanate; mixtures of MDI and PMDI; mixtures of PMDI and TDI;
ethylene diisocyanate; propylene-1,2-diisocyanate;
tetramethylene-1,2-diisocyanate; tetramethylene-1,3-diisocyanate;
tetramethylene-1,4-diisocyanate; 1,6-hexamethylene-diisocyanate;
octamethylene diisocyanate; decamethylene diisocyanate;
2,2,4-trimethylhexamethylene diisocyanate;
2,4,4-trimethylhexamethylene diisocyanate;
dodecane-1,12-diisocyanate; cyclobutane-1,3-diisocyanate;
cyclohexane-1,2-diisocyanate; cyclohexane-1,3-diisocyanate;
cyclohexane-1,4-diisocyanate; methyl-cyclohexylene diisocyanate;
2,4-methylcyclohexane diisocyanate; 2,6-methylcyclohexane
diisocyanate; 4,4'-dicyclohexyl diisocyanate; 2,4'-dicyclohexyl
diisocyanate; 1,3,5-cyclohexane triisocyanate;
isocyanatomethylcyclohexane isocyanate;
1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane;
isocyanatoethylcyclohexane isocyanate;
bis(isocyanatomethyl)-cyclohexane diisocyanate;
4,4'-bis(isocyanatomethyl) dicyclohexane;
2,4'-bis(isocyanatomethyl) dicyclohexane; isophorone diisocyanate;
triisocyanate of HDI; triisocyanate of 2,2,4-trimethyl-1,6-hexane
diisocyanate; 4,4'-dicyclohexylmethane diisocyanate;
2,4-hexahydrotoluene diisocyanate; 2,6-hexahydrotoluene
diisocyanate; 1,2-, 1,3-, and 1,4-phenylene diisocyanate; aromatic
aliphatic isocyanate, such as 1,2-, 1,3-, and 1,4-xylene
diisocyanate; meta-tetramethylxylene diisocyanate;
para-tetramethylxylene diisocyanate; trimerized isocyanurate of any
polyisocyanate, such as isocyanurate of toluene diisocyanate,
trimer of diphenylmethane diisocyanate, trimer of tetramethylxylene
diisocyanate, isocyanurate of hexamethylene diisocyanate,
isocyanurate of isophorone diisocyanate, and mixtures thereof;
dimerized uredione of any polyisocyanate, such as uretdione of
toluene diisocyanate, uretdione of hexamethylene diisocyanate, and
mixtures thereof; modified polyisocyanate derived from the above
isocyanates and polyisocyanates; and mixtures thereof.
[0154] Examples of saturated diisocyanates that can be used with
the present invention include, but are not limited to, ethylene
diisocyanate; propylene-1,2-diisocyanate; tetramethylene
diisocyanate; tetramethylene-1,4-diisocyanate;
1,6-hexamethylene-diisocyanate; octamethylene diisocyanate;
decamethylene diisocyanate; 2,2,4-trimethylhexamethylene
diisocyanate; 2,4,4-trimethylhexamethylene diisocyanate;
dodecane-1,12-diisocyanate; cyclobutane-1,3-diisocyanate;
cyclohexane-1,2-diisocyanate; cyclohexane-1,3-diisocyanate;
cyclohexane-1,4-diisocyanate; methyl-cyclohexylene diisocyanate;
2,4-methylcyclohexane diisocyanate; 2,6-methylcyclohexane
diisocyanate; 4,4'-dicyclohexyl diisocyanate; 2,4'-dicyclohexyl
diisocyanate; 1,3,5-cyclohexane triisocyanate;
isocyanatomethylcyclohexane isocyanate;
1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane;
isocyanatoethylcyclohexane isocyanate;
bis(isocyanatomethyl)-cyclohexane diisocyanate;
4,4'-bis(isocyanatomethyl) dicyclohexane;
2,4'-bis(isocyanatomethyl) dicyclohexane; isophorone diisocyanate;
triisocyanate of HDI; triisocyanate of 2,2,4-trimethyl-1,6-hexane
diisocyanate; 4,4'-dicyclohexylmethane diisocyanate;
2,4-hexahydrotoluene diisocyanate; 2,6-hexahydrotoluene
diisocyanate; and mixtures thereof. Aromatic aliphatic isocyanates
may also be used to form light stable materials.
[0155] Examples of such isocyanates include 1,2-, 1,3-, and
1,4-xylene diisocyanate; meta-tetramethylxylene diisocyanate;
para-tetramethylxylene diisocyanate; trimerized isocyanurate of any
polyisocyanate, such as isocyanurate of toluene diisocyanate,
trimer of diphenylmethane diisocyanate, trimer of tetramethylxylene
diisocyanate, isocyanurate of hexamethylene diisocyanate,
isocyanurate of isophorone diisocyanate, and mixtures thereof;
dimerized uredione of any polyisocyanate, such as uretdione of
toluene diisocyanate, uretdione of hexamethylene diisocyanate, and
mixtures thereof; modified polyisocyanate derived from the above
isocyanates and polyisocyanates; and mixtures thereof. In addition,
the aromatic aliphatic isocyanates may be mixed with any of the
saturated isocyanates listed above for the purposes of this
invention.
[0156] The number of unreacted NCO groups in the polyurea
prepolymer of isocyanate and polyether amine may be varied to
control such factors as the speed of the reaction, the resultant
hardness of the composition, and the like. For instance, the number
of unreacted NCO groups in the polyurea prepolymer of isocyanate
and polyether amine may be less than about 14 percent. In one
embodiment, the polyurea prepolymer has from about 5 percent to
about 11 percent unreacted NCO groups, and even more preferably has
from about 6 to about 9.5 percent unreacted NCO groups. In one
embodiment, the percentage of unreacted NCO groups is about 3
percent to about 9 percent. Alternatively, the percentage of
unreacted NCO groups in the polyurea prepolymer may be about 7.5
percent or less, and more preferably, about 7 percent or less. In
another embodiment, the unreacted NCO content is from about 2.5
percent to about 7.5 percent, and more preferably from about 4
percent to about 6.5 percent.
[0157] When formed, polyurea prepolymers may contain about 10
percent to about 20 percent by weight of the prepolymer of free
isocyanate monomer. Thus, in one embodiment, the polyurea
prepolymer may be stripped of the free isocyanate monomer. For
example, after stripping, the prepolymer may contain about 1
percent or less free isocyanate monomer. In another embodiment, the
prepolymer contains about 0.5 percent by weight or less of free
isocyanate monomer.
[0158] The polyether amine may be blended with additional polyols
to formulate copolymers that are reacted with excess isocyanate to
form the polyurea prepolymer. In one embodiment, less than about 30
percent polyol by weight of the copolymer is blended with the
saturated polyether amine. In another embodiment, less than about
20 percent polyol by weight of the copolymer, preferably less than
about 15 percent by weight of the copolymer, is blended with the
polyether amine. The polyols listed above with respect to the
polyurethane prepolymer, e.g., polyether polyols, polycaprolactone
polyols, polyester polyols, polycarbonate polyols, hydrocarbon
polyols, other polyols, and mixtures thereof, are also suitable for
blending with the polyether amine. The molecular weight of these
polymers may be from about 200 to about 4000, but also may be from
about 1000 to about 3000, and more preferably are from about 1500
to about 2500.
[0159] The polyurea composition can be formed by crosslinking the
polyurea prepolymer with a single curing agent or a blend of curing
agents. The curing agent of the invention is preferably an
amine-terminated curing agent, more preferably a secondary diamine
curing agent so that the composition contains only urea linkages.
In one embodiment, the amine-terminated curing agent may have a
molecular weight of about 64 or greater. In another embodiment, the
molecular weight of the amine-curing agent is about 2000 or less.
As discussed above, certain amine-terminated curing agents may be
modified with a compatible amine-terminated freezing point
depressing agent or mixture of compatible freezing point depressing
agents.
[0160] Suitable amine-terminated curing agents include, but are not
limited to, ethylene diamine; hexamethylene diamine;
1-methyl-2,6-cyclohexyl diamine; tetrahydroxypropylene ethylene
diamine; 2,2,4- and 2,4,4-trimethyl-1,6-hexanediamine;
4,4'-bis-(sec-butylamino)-dicyclohexylmethane;
1,4-bis-(sec-butylamino)-cyclohexane;
1,2-bis-(sec-butylamino)-cyclohexane; derivatives of
4,4'-bis-(sec-butylamino)-dicyclohexylmethane;
4,4'-dicyclohexylmethane diamine;
1,4-cyclohexane-bis-(methylamine);
1,3-cyclohexane-bis-(methylamine); diethylene glycol
di-(aminopropyl) ether; 2-methylpentamethylene-diamine;
diaminocyclohexane; diethylene triamine; triethylene tetramine;
tetraethylene pentamine; propylene diamine; 1,3-diaminopropane;
dimethylamino propylamine; diethylamino propylamine; dipropylene
triamine; imido-bis-propylamine; monoethanolamine, diethanolamine;
triethanolamine; monoisopropanolamine, diisopropanolamine;
isophoronediamine; 4,4'-methylenebis-(2-chloroaniline); 3,5;
dimethylthio-2,4-toluenediamine;
3,5-dimethylthio-2,6-toluenediamine;
3,5-diethylthio-2,4-toluenediamine; 3,5;
diethylthio-2,6-toluenediamine;
4,4'-bis-(sec-butylamino)-diphenylmethane and derivatives thereof;
1,4-bis-(sec-butylamino)-benzene; 1,2-bis-(sec-butylamino)-benzene;
N,N'-dialkylamino-diphenylmethane; N,N,N',N'-tetrakis
(2-hydroxypropyl) ethylene diamine;
trimethyleneglycol-di-p-aminobenzoate;
polytetramethyleneoxide-di-p-aminobenzoate;
4,4'-methylenebis-(3-chloro-2,6-diethyleneaniline);
4,4'-methylenebis-(2,6-diethylaniline); meta-phenylenediamine;
paraphenylenediamine; and mixtures thereof. In one embodiment, the
amine-terminated curing agent is
4,4'-bis-(sec-butylamino)-dicyclohexylmethane.
[0161] Suitable saturated amine-terminated curing agents include,
but are not limited to, ethylene diamine; hexamethylene diamine;
1-methyl-2,6-cyclohexyl diamine; tetrahydroxypropylene ethylene
diamine; 2,2,4- and 2,4,4-trimethyl-1,6-hexanediamine;
4,4'-bis-(sec-butylamino)-dicyclohexylmethane;
1,4-bis-(sec-butylamino)-cyclohexane;
1,2-bis-(sec-butylamino)-cyclohexane; derivatives of
4,4'-bis-(sec-butylamino)-dicyclohexylmethane;
4,4'-dicyclohexylmethane diamine;
4,4'-methylenebis-(2,6-diethylaminocyclohexane;
1,4-cyclohexane-bis-(methylamine);
1,3-cyclohexane-bis-(methylamine); diethylene glycol
di-(aminopropyl) ether; 2-methylpentamethylene-diamine;
diaminocyclohexane; diethylene triamine; triethylene tetramine;
tetraethylene pentamine; propylene diamine; 1,3-diaminopropane;
dimethylamino propylamine; diethylamino propylamine;
imido-bis-propylamine; monoethanolamine, diethanolamine;
triethanolamine; monoisopropanolamine, diisopropanolamine;
isophoronediamine; triisopropanolamine; and mixtures thereof. In
addition, any of the polyether amines listed above may be used as
curing agents to react with the polyurea prepolymers.
[0162] Cover layers of the inventive golf ball may also be formed
from ionomeric polymers, preferably highly-neutralized ionomers
(HNP). In a preferred embodiment, at least one intermediate layer
of the golf ball is formed from an HNP material or a blend of HNP
materials. 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, by the organic fatty acids of the present
invention, or both. 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, and a flexural
modulus of between about 3,000 psi and about 200,000 psi. In one
embodiment of the present invention the HNP's are ionomers and/or
their acid precursors that are preferably neutralized, either fully
or partially, with organic acid copolymers or the salts thereof.
The acid copolymers are preferably .alpha.-olefin, such as
ethylene, C.sub.3-8 .alpha.,.beta.-ethylenically unsaturated
carboxylic acid, such as acrylic and methacrylic acid, copolymers.
They may optionally contain a softening monomer, such as alkyl
acrylate and alkyl methacrylate, wherein the alkyl groups have from
1 to 8 carbon atoms.
[0163] The acid copolymers can be described as E/X/Y copolymers
where E is ethylene, X is an .alpha.,.beta.-ethylenically
unsaturated carboxylic acid, and Y is a softening comonomer. In a
preferred embodiment, X is acrylic or methacrylic acid and Y is a
C.sub.1-8 alkyl acrylate or methacrylate ester. X is preferably
present in an amount from about 1 to about 35 weight percent of the
polymer, more preferably from about 5 to about 30 weight percent of
the polymer, and most preferably from about 10 to about 20 weight
percent of the polymer. Y is preferably present in an amount from
about 0 to about 50 weight percent of the polymer, more preferably
from about 5 to about 25 weight percent of the polymer, and most
preferably from about 10 to about 20 weight percent of the
polymer.
[0164] Specific acid-containing ethylene copolymers include, but
are not limited to, ethylene/acrylic acid/n-butyl acrylate,
ethylene/methacrylic acid/n-butyl acrylate, ethylene/methacrylic
acid/iso-butyl acrylate, ethylene/acrylic acid/iso-butyl acrylate,
ethylene/methacrylic acid/n-butyl methacrylate, ethylene/acrylic
acid/methyl methacrylate, ethylene/acrylic acid/methyl acrylate,
ethylene/methacrylic acid/methyl acrylate, ethylene/methacrylic
acid/methyl methacrylate, and ethylene/acrylic acid/n-butyl
methacrylate. Preferred acid-containing ethylene copolymers
include, ethylene/methacrylic acid/n-butyl acrylate,
ethylene/acrylic acid/n-butyl acrylate, ethylene/methacrylic
acid/methyl acrylate, ethylene/acrylic acid/ethyl acrylate,
ethylene/methacrylic acid/ethyl acrylate, and ethylene/acrylic
acid/methyl acrylate copolymers. The most preferred acid-containing
ethylene copolymers are, ethylene/(meth) acrylic acid/n-butyl,
acrylate, ethylene/(meth)acrylic acid/ethyl acrylate, and
ethylene/(meth) acrylic acid/methyl acrylate copolymers.
[0165] Ionomers are typically neutralized with a metal cation, such
as Li, Na, Mg, K, Ca, or Zn. It has been found that by adding
sufficient organic acid or salt of organic acid, along with a
suitable base, to the acid copolymer or ionomer, however, the
ionomer can be neutralized, without losing processability, to a
level much greater than for a metal cation. Preferably, the acid
moieties are neutralized greater than about 80%, preferably from
90-100%, most preferably 100% without losing processability. This
accomplished by melt-blending an ethylene
.alpha.,.beta.-ethylenically unsaturated carboxylic acid copolymer,
for example, with an organic acid or a salt of organic acid, and
adding a sufficient amount of a cation source to increase the level
of neutralization of all the acid moieties (including those in the
acid copolymer and in the organic acid) to greater than 90%,
(preferably greater than 100%).
[0166] The organic acids of the present invention are aliphatic,
mono- or multi-functional (saturated, unsaturated, or
multi-unsaturated) organic acids. Salts of these organic acids may
also be employed. The salts of organic acids of the present
invention 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).
[0167] The ionomers of the invention may also be more conventional
ionomers, i.e., partially-neutralized with metal cations. The acid
moiety in the acid copolymer is neutralized about 1 to about 90%,
preferably at least about 20 to about 75%, and more preferably at
least about 40 to about 70%, to form an ionomer, by a cation such
as lithium, sodium, potassium, magnesium, calcium, barium, lead,
tin, zinc, aluminum, or a mixture thereof.
[0168] In a preferred embodiment, the inventive single-layer core
is enclosed with two cover layers, where the inner cover layer has
a thickness of about 0.01 inches to about 0.06 inches, more
preferably about 0.015 inches to about 0.040 inches, and most
preferably about 0.02 inches to about 0.035 inches, and the inner
cover layer is formed from a partially- or fully-neutralized
ionomer having a Shore D hardness of greater than about 55, more
preferably greater than about 60, and most preferably greater than
about 65. In this embodiment, the outer cover layer should have a
thickness of about 0.015 inches to about 0.055 inches, more
preferably about 0.02 inches to about 0.04 inches, and most
preferably about 0.025 inches to about 0.035 inches, and has a
hardness of about Shore D 60 or less, more preferably 55 or less,
and most preferably about 52 or less. The inner cover layer should
be harder than the outer cover layer. In this embodiment the outer
cover layer comprises a partially- or fully-neutralized iononomer,
a polyurethane, polyurea, or blend thereof. A most preferred outer
cover layer is a castable or reaction injection molded
polyurethane, polyurea or copolymer or hybrid thereof having a
Shore D hardness of about 40 to about 50. A most preferred inner
cover layer material is a partially-neutralized ionomer comprising
a zinc, sodium or lithium neutralized ionomer such as SURLYN.RTM.
8940, 8945, 9910, 7930, 7940, or blend thereof having a Shore D
hardness of about 63 to about 68.
[0169] In another multi-layer cover, single core embodiment, the
outer cover and inner cover layer materials and thickness are the
same but, the hardness range is reversed, that is, the outer cover
layer is harder than the inner cover layer.
[0170] In an alternative preferred embodiment, the golf ball is a
one-piece golf ball having a dimpled surface and having a surface
hardness equal to or less than the center hardness (i.e., a
negative hardness gradient). The one-piece ball preferably has a
diameter of about 1.680 inches to about 1.690 inches, a weight of
about 1.620 oz, an Atti compression of from about 40 to 120, and a
COR of about 0.750-0.825.
[0171] In a preferred two-piece ball embodiment, the single-layer
core having a negative hardness gradient is enclosed with a single
layer of cover material having a Shore D hardness of from about 20
to about 80, more preferably about 40 to about 75 and most
preferably about 45 to about 70, and comprises a thermoplastic or
thermosetting polyurethane, polyurea, polyamide, polyester,
polyester elastomer, polyether-amide or polyester-amide, partially
or fully neutralized ionomer, polyolefin such as polyethylene,
polypropylene, polyethylene copolymers such as ethylene-butyl
acrylate or ethylene-methyl acrylate, poly(ethylene methacrylic
acid) co- and terpolymers, metallocene-catalyzed polyolefins and
polar-group functionalized polyolefins and blends thereof. A
preferred cover material in the two-piece embodiment is an ionomer
(either conventional or HNP) having a hardness of about 50 to about
70 Shore D. Another preferred cover material in the two-piece
embodiment is a thermoplastic or thermosetting polyurethane or
polyurea. A preferred ionomer is a high acid ionomer comprising a
copolymer of ethylene and methacrylic or acrylic acid and having an
acid content of at least 16 to about 25 weight percent. In this
case the reduced spin contributed by the relatively rigid high acid
ionomer may be offset to some extent by the spin-increasing
negative gradient core. The core may have a diameter of about 1.0
inch to about 1.64 inches, preferably about 1.30 inches to about
1.620, and more preferably about 1.40 inches to about 1.60
inches.
[0172] Another preferred cover material comprises a castable or
reaction injection moldable polyurethane, polyurea, or copolymer or
hybrid of polyurethane/polyurea. Preferably, this cover is
thermosetting but may be a thermoplastic, having a Shore D hardness
of about 20 to about 70, more preferably about 30 to about 65 and
most preferably about 35 to about 60. A moisture vapor barrier
layer, such as disclosed in U.S. Pat. Nos. 6,632,147; 6,932,720;
7,004,854; and 7,182,702, all of which are incorporated by
reference herein in their entirety, are optionally employed between
the cover layer and the core.
[0173] While any of the embodiments herein may have any known
dimple number and pattern, a preferred number of dimples is 252 to
456, and more preferably is 330 to 392. The dimples may comprise
any width, depth, and edge angle disclosed in the prior art and the
patterns may comprises multitudes of dimples having different
widths, depths and edge angles. The parting line configuration of
said pattern may be either a straight line or a staggered wave
parting line (SWPL). Most preferably the dimple number is 330, 332,
or 392 and comprises 5 to 7 dimples sizes and the parting line is a
SWPL.
[0174] In any of these embodiments the single-layer core may be
replaced with a 2 or more layer core wherein at least one core
layer has a negative hardness gradient.
[0175] Other than in the operating examples, or unless otherwise
expressly specified, all of the numerical ranges, amounts, values
and percentages such as those for amounts of materials and others
in the specification may be read as if prefaced by the word "about"
even though the term "about" may not expressly appear with the
value, amount or range. Accordingly, unless indicated to the
contrary, the numerical parameters set forth in the specification
and attached claims are approximations that may vary depending upon
the desired properties sought to be obtained by the present
invention. At the very least, and not as an attempt to limit the
application of the doctrine of equivalents to the scope of the
claims, each numerical parameter should at least be construed in
light of the number of reported significant digits and by applying
ordinary rounding techniques.
[0176] Notwithstanding that the numerical ranges and parameters
setting forth the broad scope of the invention are approximations,
the numerical values set forth in the specific examples are
reported as precisely as possible. Any numerical value, however,
inherently contain certain errors necessarily resulting from the
standard deviation found in their respective testing measurements.
Furthermore, when numerical ranges of varying scope are set forth
herein, it is contemplated that any combination of these values
inclusive of the recited values may be used.
[0177] While it is apparent that the illustrative embodiments of
the invention disclosed herein fulfill the objective stated above,
it is appreciated that numerous modifications and other embodiments
may be devised by those skilled in the art. Therefore, it will be
understood that the appended claims are intended to cover all such
modifications and embodiments, which would come within the spirit
and scope of the present invention.
* * * * *