U.S. patent application number 13/737041 was filed with the patent office on 2014-07-10 for golf ball having a hollow center.
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 | 20140194225 13/737041 |
Document ID | / |
Family ID | 51061367 |
Filed Date | 2014-07-10 |
United States Patent
Application |
20140194225 |
Kind Code |
A1 |
Sullivan; Michael J. ; et
al. |
July 10, 2014 |
GOLF BALL HAVING A HOLLOW CENTER
Abstract
A golf ball includes a thermoset spherical inner core shell
layer having an outer surface, an inner surface, and an inner
diameter to define a hollow center; a thermoset outer core layer
formed about the shell layer; and an inner and outer cover layer
formed about the outer core layer. The inner cover includes an
ionomeric material and the outer cover layer includes a polyurea or
a polyurethane having a hardness less than the inner cover layer.
The hollow center has a diameter of about 0.51 to 1.1 inches, the
shell layer has a surface hardness greater than an inner surface
hardness by about 3 to 25 Shore C to define a first hardness
gradient, and the outer core layer has a second hardness gradient
different from the first.
Inventors: |
Sullivan; Michael J.;
(Barrington, RI) ; Binette; Mark L.;
(Mattapoisett, MA) ; Comeau; Brian; (Berkley,
MA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ACUSHNET COMPANY |
Fairhaven |
MA |
US |
|
|
Assignee: |
ACUSHNET COMPANY
Fairhaven
MA
|
Family ID: |
51061367 |
Appl. No.: |
13/737041 |
Filed: |
January 9, 2013 |
Current U.S.
Class: |
473/375 |
Current CPC
Class: |
A63B 37/0041 20130101;
A63B 37/008 20130101; A63B 37/0027 20130101; A63B 37/0064 20130101;
A63B 37/0039 20130101; A63B 37/0043 20130101; A63B 37/0056
20130101; A63B 37/0044 20130101; A63B 37/0076 20130101; A63B
37/0077 20130101; A63B 37/0092 20130101; A63B 37/006 20130101; A63B
37/0031 20130101 |
Class at
Publication: |
473/375 |
International
Class: |
A63B 37/00 20060101
A63B037/00 |
Claims
1. A golf ball comprising a hollow core, the golf ball comprising:
a spherical inner core shell layer comprising a first thermoset
rubber composition, the shell layer having an outer surface, an
inner surface, and an inner diameter to define a hollow center; an
outer core layer disposed about the shell layer, the outer core
layer comprising a second thermoset material; an inner cover layer
disposed about the outer core layer, the inner cover comprising an
ionomeric material and having a first hardness; and an outer cover
layer disposed about the inner cover layer, the outer cover
comprising a polyurea or a polyurethane and having a second
hardness less than the first; wherein the hollow center has a
diameter of about 0.51 to 1.1 inches, the shell layer has a surface
hardness greater than an inner surface hardness by about 3 to 25
Shore C to define a first hardness gradient, and the outer core
layer has a second hardness gradient different from the first.
2. The golf ball of claim 1, wherein the shell layer has a surface
hardness greater than about 55 Shore C.
3. The golf ball of claim 1, wherein the spherical inner core shell
layer has a coefficient of restitution less than about 0.700 when
measured at an incoming velocity of 125 ft/s.
4. The golf ball of claim 1, wherein the outer core layer has a
coefficient of restitution, measured at an incoming velocity of 125
ft/s, higher than the coefficient of restitution, measured at an
incoming velocity of 125 ft/s, of the inner core shell layer by
10-50%.
5. The golf ball of claim 1, wherein the second hardness gradient
is about 0 Shore C.
6. The golf ball of claim 1, wherein the second hardness gradient
is a negative hardness gradient of about 2 to 25 Shore C.
7. The golf ball of claim 1, wherein the second hardness gradient
is a positive hardness gradient of about 3 to 10 Shore C.
8. The golf ball of claim 1, wherein the inner cover has a hardness
of greater than about 60 Shore D and the outer cover layer has a
hardness of less than about 60 Shore D.
9. The golf ball of claim 1, wherein the golf ball has a first
volume and the hollow center has a second volume that is about 2%
to 30% of the first volume.
10. A golf ball comprising a hollow core, the golf ball comprising:
a spherical inner core shell layer formed from a first thermoset
rubber composition, the shell layer having an outer surface, an
inner surface, and an inner diameter to define a hollow center; an
outer core layer comprising a second thermoset material; a
thermoplastic intermediate core layer disposed between the shell
layer and the outer core layer; an inner cover layer disposed about
the outer core layer, the inner cover comprising an ionomeric
material and having a material hardness greater than about 60 Shore
D; and an outer cover layer disposed about the inner cover layer,
the outer cover comprising a polyurea or a polyurethane and having
a material hardness of less than about 60 Shore D; wherein the
hollow center has a diameter of about 0.15 to 1.1 inches, the shell
layer has a surface hardness greater than an inner surface hardness
by about 10 to 25 Shore C to define a first hardness gradient, and
the thermoset outer core layer has a second hardness gradient
different from the first.
11. The golf ball of claim 10, wherein the second hardness gradient
is about 0 Shore C.
12. The golf ball of claim 10, wherein the second hardness gradient
is a negative hardness gradient of about 2 to 25 Shore C.
13. The golf ball of claim 10, wherein the second hardness gradient
is a positive hardness gradient of about 3 to 10 Shore C.
14. A golf ball comprising a hollow core, the golf ball comprising:
a spherical inner core shell layer formed from a first thermoset
rubber composition, the shell layer having an outer surface, an
inner surface, and an inner diameter to define a hollow center; an
outer core layer comprising a second thermoset material; a
thermoset intermediate core layer disposed between the shell layer
and the outer core layer, the intermediate core layer comprising a
third thermoset rubber composition different from the first and the
second; an inner cover layer disposed about the outer core layer,
the inner cover comprising an ionomeric material and having a first
hardness; and an outer cover layer disposed about the inner cover
layer, the outer cover comprising a polyurea or a polyurethane and
having a second hardness less than the first; wherein the hollow
center has a diameter of about 0.15 to 1.1 inches, the shell layer
has a surface hardness greater than an inner surface hardness by
about 10 to 25 Shore C to define a first hardness gradient, and at
least one of the thermoset outer core layer or thermoset
intermediate core layer has a hardness gradient different from the
first.
15. The golf ball of claim 14, wherein the second hardness gradient
is about 0 Shore C.
16. The golf ball of claim 14, wherein the second hardness gradient
is a negative hardness gradient of about 2 to 25 Shore C.
17. The golf ball of claim 14, wherein the second hardness gradient
is a positive hardness gradient of about 3 to 10 Shore C.
Description
FIELD OF THE INVENTION
[0001] This invention relates generally to golf balls with a core
having a hollow center surrounded by one or more core layers and
one or more cover layers. Any of the core or cover layers may have
a `negative` or `positive` hardness gradient, depending on the
desired construction. More particularly, the golf ball includes a
core having a hollow center surrounded by a thermoset `shell layer`
and at least one additional core layer that is thermoset.
BACKGROUND OF THE INVENTION
[0002] In recent years, virtually all golf balls are of a solid
construction, typically including 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 and outer cover layer. Golf ball cores and/or
centers are formed from a thermoset rubber composition with
polybutadiene as the base rubber. The cores are usually heated and
crosslinked to create a core having certain pre-determined
characteristics, such as compression or hardness, which result in a
golf ball having the properties for a particular group of players,
whether it be professionals, low-handicap players, or mid-to-high
handicap golfers. 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 golf balls
suited to differing levels of ability.
[0003] There remains a need, however, for golf ball constructions
that allow differing properties to be achieved. One such novel
construction with no past commercial success is a golf ball having
a hollow core--meaning the innermost portion of the core is hollow
surrounded by a `shell layer` and one or more core and cover
layers. While, in the past, many commercially-available golf balls
have been constructed with non-solid centers, such as liquid
centers, very few golf balls having hollow centers have ever been
constructed.
[0004] While the patent literature references, mostly in a cursory
manner, a hollow core as a suitable general alternative
construction, very few are actually directed to a hollow core golf
ball. For example, U.S. Pat. No. 6,315,683 is generally directed to
an over-sized (greater than 1.70 inches) hollow solid golf ball
where the hollow core is contained in a thermoset rubber layer and
covered with a single ionomer cover. More recently, U.S. Pat. No.
8,262,508 generally describes a golf ball having a hollow center, a
mid-layer, an inner cover, and an outer cover. The hollow center
and mid-layer are both formed from a thermoset rubber composition,
and a conventional `positive hardness gradient` (layer hardness
gets softer in the direction of the interior of the layer). The
hollow `space` has a diameter of 0.08 to 0.5 inches and the core
layer has a low surface hardness of 25 to 55 Shore C. The golf ball
is covered by a harder ionomer outer cover and a softer ionomer
inner cover.
[0005] The inventive golf ball, however, has a hollow core
surrounded by a thermoset `shell layer`, a thermoset outer cover
layer, optionally, one or more thermoset or thermoplastic
intermediate core layers, and one or more cover layers. Combining
the hollow core construction with variations in the hardness
gradients of the adjoining thermoplastic and/or thermoset core
layers solves many of the problems associated with previous
attempts at hollow core constructions.
SUMMARY OF THE INVENTION
[0006] The present invention is directed to a golf ball including a
hollow core. The golf ball includes a spherical inner core shell
layer formed from a first thermoset rubber composition. The shell
layer has an outer surface, an inner surface, and an inner diameter
to define the hollow center. An outer core layer is formed around
the shell layer and includes a thermoset material, in one
embodiment different from the thermoset material used to form the
shell layer. An inner cover layer may be formed about the outer
core layer and in a preferred embodiment includes an ionomeric
material. An outer cover layer is typically formed about the
optional inner cover layer or directly over the core. The outer
cover is formed from a polyurea or a polyurethane material and
preferably has a second hardness less than that of the inner cover
layer, if present.
[0007] The hollow center has a diameter of about 0.51 to 1.1
inches. The thermoset shell layer has a surface hardness greater
than its inner surface hardness by about 3 to 25 Shore C to define
a first hardness gradient. The outer core layer has a second
hardness gradient different from the first.
[0008] Preferably, the shell layer has a surface hardness greater
than about 55 Shore C. In one embodiment, the spherical inner core
shell layer has a coefficient of restitution (COR) less than about
0.700 when measured at an incoming velocity of 125 ft/s.
Alternatively, the outer core layer has a coefficient of
restitution, measured at an incoming velocity of 125 ft/s, higher
than the coefficient of restitution, measured at an incoming
velocity of 125 ft/s, of the inner core shell layer by 10-50%.
[0009] In one embodiment, the second hardness gradient is about 0
Shore C. In an additional embodiment, the second hardness gradient
is a negative hardness gradient of about 2 to 25 Shore C. In still
another preferred embodiment, the second hardness gradient is a
positive hardness gradient of about 3 to 10 Shore C. The inner
cover may have a hardness greater than about 60 Shore D and the
outer cover layer may have a hardness of less than about 60 Shore
D. The golf ball typically has a first volume and the hollow center
typically has a second volume that is about 2% to 30% of the first
volume.
[0010] The invention is also directed to a golf ball comprising a
hollow core, the golf ball including a spherical inner core shell
layer formed from a first thermoset rubber composition, the shell
layer having an outer surface, an inner surface, and an inner
diameter to define a hollow center. In this preferred embodiment,
an outer core layer is formed from a second thermoset material and
a thermoplastic intermediate core layer is disposed between the
shell layer and the outer core layer. An optional inner cover layer
is formed about the outer core layer. The optional inner cover may
include an ionomeric material and having a material hardness
greater than about 60 Shore D. The golf ball also includes an outer
cover layer, which typically is formed from a polyurea or a
polyurethane material and has a material hardness of less than
about 60 Shore D.
[0011] The hollow center has a diameter of about 0.15 to 1.1
inches, the shell layer has a surface hardness greater than an
inner surface hardness by about 10 to 25 Shore C to define a first
hardness gradient, and the thermoset outer core layer has a second
hardness gradient different from the first.
[0012] In one embodiment, the second hardness gradient is about 0
Shore C. In an alternative embodiment, the second hardness gradient
is a negative hardness gradient of about 2 to 25 Shore C. In still
another embodiment, the second hardness gradient is a positive
hardness gradient of about 3 to 10 Shore C. In a preferred
alternative embodiment, a thermoset intermediate core layer is
disposed between the shell layer and the outer core layer, the
intermediate core layer comprising a third thermoset rubber
composition which may be the same or different than that of the
shell or outer core layers.
DETAILED DESCRIPTION OF THE INVENTION
[0013] The golf balls of the present invention may include
multi-layer golf balls, such as one having a core and a cover
surrounding the core, but are preferably formed from a core having
a hollow core and at least one outer core layer, an inner cover
layer, and an outer cover layer. Any of the core or cover layers
may include more than one layer. The cover layer of the golf ball
may be a single layer or formed of a plurality of layers, such as
an inner cover layer and an outer cover layer.
[0014] The hollow core is formed of a thermoset `shell layer` that
contains a spherical hollow portion in its interior. In a preferred
embodiment, the golf ball includes the thermoset hollow core and at
least two outer core layers, where the shell layer is formed from a
thermoset material, an outer core layer is formed from a thermoset
material, and an intermediate core layer, disposed between the
shell layer and the outer core layer, is formed from a
thermoplastic material. In an alternative preferred embodiment, the
golf ball includes the thermoset hollow core and at least two outer
core layers, where the shell layer is formed from a thermoset
material, an outer core layer is formed from a thermoset material,
and an intermediate core layer, disposed between the shell layer
and the outer core layer, is formed from a thermoset material.
[0015] The shell, outer core, or intermediate core layers may have
either a conventional "hard-to-soft" hardness gradient (i.e., the
outermost surface/portion of the layer is harder than the innermost
surface/portion), known as a "positive hardness gradient," or a
"soft-to-hard" hardness gradient (i.e., a "negative" hardness
gradient) as measured radially-inward from the outer surface or
portion of each component towards the innermost portion (i.e., from
the outer surface/portion towards the inner surface/portion of the
shell and/or core layers). As used herein, the terms "negative" and
"positive," with respect to hardness gradient, refer to the result
of subtracting the hardness value at the innermost portion of the
component being measured (e.g., the inner surface of a core layer)
from the hardness value at the outer surface of the component being
measured (e.g., the outer surface of an outer core layer). For
example, if the outer surface of a core layer has a lower hardness
value than at the inner surface, the hardness gradient will be
deemed a "negative" gradient (a smaller number-a larger number=a
negative number), although the magnitude may be disclosed in the
application as the absolute value of the subtraction result in
combination with the designation `negative`).
[0016] The thermoplastic shell, intermediate core layers, and outer
core layers of the invention may have `positive hardness gradients`
or `negative hardness gradients`, as described above.
Alternatively, the TP layers may have a `zero hardness gradient`,
defined herein to include a 0 Shore C hardness gradient .+-.2 Shore
C. The TP layer `positive hardness gradient` or `negative hardness
gradient` may be from about 0 Shore C to about 10 Shore C, more
preferably about 2 Shore C to about 8 Shore C, and most preferably
about 3 Shore C to about 5 Shore C.
[0017] The thermoset shell, intermediate core layers, and outer
core layers of the invention may have `positive hardness gradients`
or `negative hardness gradients`, as described above.
Alternatively, the TS layers may have a `zero hardness gradient`,
defined herein to include a 0 Shore C hardness gradient .+-.2 Shore
C. The TS layer `positive hardness gradient` or `negative hardness
gradient` may be from about 1 Shore C to about 30 Shore C,
preferably about 2 Shore C to about 27 Shore C, more preferably
about 5 Shore C to about 25 Shore C, and most preferably about 10
to 20 Shore C. Other suitable TS `positive hardness gradient` or
`negative hardness gradient` core layers can be found in U.S. Pat.
Nos. 7,537,529 and 7,537,530, the disclosures of which are
incorporated herein, in their entirety, by reference thereto.
[0018] A variety of the above TS and TP hardness gradient layers
are envisioned and both `positive hardness gradients` and/or
`negative hardness gradients` may be combined to form the hollow
cores of the invention having various layers of this nature.
[0019] The surface hardness of the shell or core layers is obtained
from the average of a number of measurements taken from opposing
hemispheres of the particular layer, taking care to avoid making
measurements on the parting line or any 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 the hollow core or
core layers, care must be taken to insure that they are 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 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.
[0020] To prepare the hollow core for hardness and hardness
gradient measurements, the core (shell layer or with one or two
core layers) 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.degree. 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 hollow
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.
[0021] 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 1- or 2-mm increments.
All hardness measurements performed on the plane passing through
the hollow 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.
[0022] One or more of the shell layer and/or core layers may be
formed 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` (sometimes called a cis-to-trans
catalyst), such as an organosulfur or metal-containing organosulfur
or thiol compound, can also be included in the core formulation.
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.
[0023] 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%.
[0024] Examples of desirable polybutadiene rubbers include
BUNA.RTM. CB22 and BUNA.RTM. CB23, CB1221, CB1220, CB24, and CB21,
commercially-available from LANXESS Corporation; UBEPOL.RTM. 360L
and UBEPOL.RTM. 150L and UBEPOL-BR rubbers, commercially available
from UBE Industries, Ltd. of Tokyo, Japan; KINEX.RTM. 7245,
KINEX.RTM. 7265, and BUDENE 1207 and 1208, commercially available
from Goodyear of Akron, Ohio; SE BR-1220; 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.
[0025] From the Lanxess Corporation, most preferred are the Nd- and
Co-catalyzed grades, but all of the following may be used: BUNA CB
21; BUNA CB 22; BUNA CB 23; BUNA CB 24; BUNA CB 25; BUNA CB 29 MES;
BUNA CB Nd 40; BUNA CB Nd 40 H; BUNA CB Nd 60; BUNA CB 55 NF; BUNA
CB 60; BUNA CB 45 B; BUNA CB 55 B; BUNA CB 55 H; BUNA CB 55 L; BUNA
CB 70 B; BUNA CB 1220; BUNA CB 1221; BUNA CB 1203; BUNA CB 45.
Additionally, numerous suitable rubbers are available from JSR
(Japan Synthetic Rubber), UBEPOL sold by Ube Industries Inc, Japan,
BST sold by BST Elastomers, Thailand; IPCL sold by Indian
Petrochemicals Ltd, India; NITSU sold by Karbochem or Karbochem Ltd
of South Africa; PETROFLEX of Brazil; LG of Korea; and Kuhmo
Petrochemical of Korea.
[0026] 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 and is
defined according to ASTM D-1646. The Mooney viscosity range is
preferably greater than about 40, more preferably in the range from
about 40 to 60 and most preferably in the range from about 40 to
52.
[0027] Commercial sources of suitable polybutadienes include Bayer
AG CB23 (Nd-catalyzed), which has a Mooney viscosity of around 50
and is a highly linear polybutadiene, and CB1221 (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.
[0028] 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.
[0029] 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.TM. family of dicumyl peroxides (including DICUP.TM.
R, DICUP.TM. 40C and DICUP.TM. 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.TM. 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.TM. peroxides are
generally sold on a carrier compound.
[0030] 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.
[0031] 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.
[0032] 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.
[0033] Suitable antioxidants include, but are not limited to,
alkylene-bis-alkyl substituted cresols; substituted phenols;
alkylene bisphenols; and alkylene trisphenols. The antioxidant is
typically present in an amount of about 0.1 phr to 5 phr,
preferably from about 0.1 phr to 2 phr, more preferably about 0.1
phr to 1 phr. In an alternative embodiment, the antioxidant should
be present in an amount to ensure that the hardness gradient of the
core layers is "negative." Preferably, about 0.2 phr to 1 phr
antioxidant is added to the core layer formulation, more
preferably, about 0.3 to 0.8 phr, and most preferably 0.4 to 0.7
phr. Preferably, about 0.25 phr to 1.5 phr of peroxide as
calculated at 100% active can be added to the core formulation,
more preferably about 0.5 phr to 1.2 phr, and most preferably about
0.7 phr to 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 from about 290.degree. F.
to 350.degree. F., more preferably about 300.degree. F. to
335.degree. F., and the stock is held at that temperature for about
10 minutes to 30 minutes.
[0034] The thermoset rubber compositions 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 thermoset core layer
compositions may contain about 0.05 phr to 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 3.0 phr, preferably about 0.05 phr to
2.0 phr, more preferably about 0.05 phr to 1.0 phr. In another
embodiment, the soft and fast agent is present in an amount of
about 2.0 phr to 5.0 phr, preferably about 2.35 phr to 4.0 phr, and
more preferably about 2.35 phr to 3.0 phr. 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.
[0035] Fillers may be added to the thermoset rubber layer
compositions typically include, but are not limited to, processing
aids and/or compounds to affect rheological and mixing properties,
density-modifying fillers, tear strength, or reinforcement fillers,
and the like. 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 size),
high-Mooney-viscosity rubber regrind, trans-rubber regrind
(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 60%. 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 may be added to one or more layers of the golf
ball to modify the density thereof.
[0036] The thermoset rubber shell and/or core layers may optionally
include at least one additive and/or filler. These materials are
also suitable for inclusion in the thermoplastic layers of the
present invention. Suitable additives and fillers include, but are
not limited to, chemical blowing and foaming agents, optical
brighteners, coloring agents, fluorescent agents, whitening agents,
UV absorbers, light stabilizers, defoaming agents, processing aids,
antioxidants, stabilizers, softening agents, fragrance components,
plasticizers, impact modifiers, TiO.sub.2, acid copolymer wax,
surfactants, performance additives (e.g., A-C performance
additives, particularly A-C low molecular weight ionomers and
copolymers, A-C oxidized polyethylenes, and A-C ethylene vinyl
acetate waxes, commercially available from Honeywell International
Inc.), fatty acid amides (e.g., ethylene bis-stearamide and
ethylene bis-oleamide), fatty acids and salts thereof (e.g.,
stearic acid, oleic acid, zinc stearate, magnesium stearate, zinc
oleate, and magnesium oleate), and fillers, such as zinc oxide, tin
oxide, barium sulfate, zinc sulfate, calcium oxide, calcium
carbonate, zinc carbonate, barium carbonate, tungsten, tungsten
carbide, silica, lead silicate, regrind, clay, mica, talc,
nano-fillers, carbon black, glass flake, milled glass, flock,
fibers, and mixtures thereof. Suitable additives are more fully
described in, U.S. Pat. No. 7,041,721 which issued on May 9, 2006,
the disclosure of which is hereby incorporated herein by reference.
In a particular embodiment, the total amount of additive(s) and
filler(s) present in the particle composition is 20 wt % or less,
or 15 wt % or less, or 12 wt % or less, or 10 wt % or less, or 9 wt
% or less, or 6 wt % or less, or 5 wt % or less, or 4 wt % or less,
or 3 wt % or less, or within a range having a lower limit of 0 or 2
or 3 or 5 wt %, based on the total weight of the particle
composition, and an upper limit of 9 or 10 or 12 or 15 or 20 wt %,
based on the total weight of the particle composition. In a
particular aspect of this embodiment, the particle composition
includes fillers selected from carbon black, micro- and nano-scale
clays and organoclays, including (e.g., CLOISITE and NANOFIL
nanoclays, commercially available from Southern Clay Products,
Inc.; NANOMAX and NANOMER nanoclays, commercially available from
Nanocor, Inc., and PERKALITE nanoclays, commercially available from
Akzo Nobel Polymer Chemicals), micro- and nano-scale talcs (e.g.,
LUZENAC HAR high aspect ratio talcs, commercially available from
Luzenac America, Inc.), glass (e.g., glass flake, milled glass,
microglass, and glass fibers), micro- and nano-scale mica and
mica-based pigments (e.g., IRIODIN pearl luster pigments,
commercially available from The Merck Group), and combinations
thereof. Particularly suitable combinations of fillers include, but
are not limited to, micro-scale fillers combined with nano-scale
fillers, and organic fillers with inorganic fillers.
[0037] For the thermoset rubber layers of the invention, the
fillers and/or additives are present in an amount of about 50 wt %
or less, preferably 30 wt % or less, more preferably 20 wt % or
less, and most preferably 15 wt % or less, based on the total
weight of the composition. Alternatively, for the thermoplastic
layers of the invention, the fillers and/or additives are present
in an amount of about 10 wt % or less, more preferably 6 wt % or
less, and most preferably 3 wt % or less, based on the total weight
of the composition.
[0038] The particle composition optionally includes one or more
melt flow modifiers. Suitable melt flow modifiers include materials
which increase the melt flow of the composition, as measured using
ASTM D-1238, condition E, at 190.degree. C., using a 2160-g weight.
Examples of suitable melt flow modifiers include, but are not
limited to, fatty acids and fatty acid salts, including, but not
limited to, those disclosed in U.S. Pat. No. 5,306,760, the
disclosure of which is hereby incorporated herein by reference;
fatty amides and salts thereof; polyhydric alcohols, including, but
not limited to, those disclosed in U.S. Pat. Nos. 7,365,128 and
8,163,823, the entire disclosures of which are hereby incorporated
herein by reference; polylactic acids, including, but not limited
to, those disclosed in U.S. Pat. No. 7,642,319, the disclosure of
which is hereby incorporated herein by reference; and the modifiers
disclosed in U.S. Pat. No. 8,163,823 and U.S. Patent Application
Publication No. 2009/0203469, the disclosures of which are hereby
incorporated herein by reference. Flow enhancing additives also
include, but are not limited to, montanic acids, esters of montanic
acids and salts thereof, bis-stearoylethylenediamine, mono- and
polyalcohol esters such as pentaerythritol tetrastearate,
zwitterionic compounds, and metallocene-catalyzed polyethylene and
polypropylene wax, including maleic anhydride modified versions
thereof, amide waxes and alkylene diamides such as bistearamides.
Particularly suitable fatty amides include, but are not limited to,
saturated fatty acid monoamides (e.g., lauramide, palmitamide,
arachidamide behenamide, stearamide, and 12-hydroxy stearamide);
unsaturated fatty acid monoamides (e.g., oleamide, erucamide, and
ricinoleamide); N-substituted fatty acid amides (e.g., N-stearyl
stearamide, N-behenyl behenamide, N-stearyl behenamide, N-behenyl
stearamide, N-oleyl oleamide, N-oleyl stearamide, N-stearyl
oleamide, N-stearyl erucamide, erucyl erucamide, and erucyl
stearamide, N-oleyl palmitamide, methylol amide (more preferably,
methylol stearamide, methylol behenamide); saturated fatty acid
bis-amides (e.g., methylene bis-stearamide, ethylene
bis-stearamide, ethylene bis-isostearamide, ethylene
bis-hydroxystearamide, ethylene bis-behenamide, hexamethylene
bis-stearamide, hexamethylene bis-behenamide, hexamethylene
bis-hydroxystearamide, N,N'-distearyl adipamide, and N,N'-distearyl
sebacamide); unsaturated fatty acid bis-amides (e.g., ethylene
bis-oleamide, hexamethylene bis-oleamide, N,N'-dioleyl adipamide,
N,N'-dioleyl sebacamide); and saturated and unsaturated fatty acid
tetra amides, stearyl erucamide, ethylene bis stearamide and
ethylene bis oleamide. Suitable examples of commercially available
fatty amides include, but are not limited to, KEMAMIDE fatty acids,
such as KEMAMIDE B (behenamide/arachidamide), KEMAMIDE W40
(N,N'-ethylenebisstearamide), KEMAMIDE P181 (oleyl palmitamide),
KEMAMIDE S (stearamide), KEMAMIDE U (oleamide), KEMAMIDE E
(erucamide), KEMAMIDE O (oleamide), KEMAMIDE W45
(N,N'-ethylenebisstearamide), KENAMIDE W20
(N,N'-ethylenebisoleamide), KEMAMIDE E180 (stearyl erucamide),
KEMAMIDE E221 (erucyl erucamide), KEMAMIDE S180 (stearyl
stearamide), KEMAMIDE 5221 (erucyl stearamide), commercially
available from Chemtura Corporation; and CRODAMIDE fatty amides,
such as CRODAMIDE OR (oleamide), CRODAMIDE ER (erucamide),
CRODAMIDE SR (stereamide), CRODAMIDE BR (behenamide), CRODAMIDE 203
(oleyl palmitamide), and CRODAMIDE 212 (stearyl erucamide),
commercially available from Croda Universal Ltd.
[0039] The shell layer, and intermediate and outer core layers of
the hollow golf ball may also be formed from thermoplastic
materials such as ionomeric polymers, and highly- and
fully-neutralized ionomers (HNP). Acid moieties of the HNP's,
typically ethylene-based ionomers, are preferably neutralized
greater than about 80%, more preferably greater than about 90%, and
most preferably 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.
[0040] Preferably, 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.
[0041] 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.
[0042] 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.
[0043] 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%).
[0044] The organic acids are typically 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).
[0045] 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.
[0046] Preferred thermoplastic materials are disclosed in U.S. Pat.
No. 7,591,742, the disclosure of which is incorporated herein in
its entirety by reference thereto.
[0047] Thermoplastic elastomers (TPE) many also be used for the
thermoplastic shell or core layers and/or to modify the properties
of the shell and/or core layers, or the uncured rubber 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.
[0048] Additional polymers may also optionally be incorporated into
the base rubber for the shell and core layers. 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.
[0049] 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.
[0050] The hollow interior of the shell layer has a diameter of
about 0.1 inches to about 1.1 inches, preferably about 0.2 inches
to about 0.9 inches, more preferably about 0.25 inches to about
0.75 inches, and most preferably about 0.3 inches to about 0.5
inches. In one preferred embodiment, the hollow interior of the
shell layer has a diameter of greater than 0.5 inches. The shell
layer has a thickness that ranges from 0.01 inches to about 0.4
inches. When the shell layer is desired to be relatively thick, the
shell layer thickness is about 0.125 inches to about 0.375 inches,
preferably about 0.2 inches to about 0.3125 inches, more preferably
about 0.25 inches to about 0.3 inches, and most preferably about
0.26 inches to about 0.275 inches. When the shell layer is desired
to be relatively thin, the shell layer thickness is about 0.01
inches to about 0.1 inches, preferably about 0.02 inches to about
0.075 inches, more preferably about 0.025 inches to about 0.04
inches, and most preferably about 0.03 inches to about 0.035
inches. When the shell layer is relatively thin and formed from a
thermoplastic material, the TP material is preferably selected to
be somewhat heat resistant (or blended with a heat resistant TP
material) to avoid melting of the layer by subsequent molding of
additional core and/or cover layers.
[0051] With the dimensions of the hollow interior in mind, the
hollow cores (shell layer, shell layer and outer core layer(s)) of
the invention preferably have an outer diameter of about 0.75
inches to about 1.58 inches, preferably about 1.0 inches to about
1.57 inches, more preferably about 1.3 inches to about 1.56 inches,
and most preferably about 1.4 inches to about 1.55 inches. In
preferred embodiments, the shell layer has an outer diameter of
about 0.75 inches, 1.0 inches, 1.20 inches, or 1.30 inches, with a
most preferred outer diameter being 0.75 inches or 1.0 inches. In
an alternative embodiment, the outer core layer should have an
outer diameter (the entire hollow core, shell layer plus outer core
layer) of about 1.30 inches to about 1.62 inches, preferably 1.4
inches to about 1.6 inches, and more preferably about 1.5 inches to
about 1.59 inches. In preferred embodiments, the outer core layer
has an outer diameter of about 1.51 inches, 1.53 inches, or most
preferably 1.550 inches.
[0052] The inner and outer cover layers preferably have a thickness
of about 0.010 to 0.080 inches, more preferably about 0.015 to
0.060 inches, and most preferably about 0.020 to 0.040 inches.
Alternatively, the inner and outer cover layers 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. The inner cover layer, if present,
preferably has a hardness of about 60 Shore D or greater, more
preferably about 65 Shore D or greater, and most preferably about
70 Shore D or greater. The inner cover layer is preferably harder
than the outer cover layer although in one embodiment the outer
cover layer is harder than the inner cover layer. The outer cover
layer preferably has a hardness of about 60 Shore D or less, more
preferably about 55 Shore D or less, and most preferably about 50
Shore D or less.
[0053] Formation of the shell and outer core layers of the
invention may be accomplished in a variety of ways, such as those
disclosed in U.S. Pat. Nos. 5,480,155; 6,315,683, and 8,262,508,
the disclosures of which are incorporated herein, in their
entirety, by reference thereto.
[0054] In a preferred embodiment, the golf ball of the present
invention includes a hollow core. The hollow core is formed from
spherical inner core shell layer that contains a spherical hollow
portion in its interior. The shell layer is formed from a thermoset
rubber composition and has an outer surface, an inner surface, and
an inner diameter to define the dimensions of the hollow center. In
this embodiment, a single outer core layer is formed around the
shell layer to create a hollow golf ball core. The outer core layer
is also formed from a thermoset material, which may be the same
rubber composition as the shell layer but is preferably a different
thermoset rubber composition. A single cover layer or multiple
cover layers are formed over the TS/TS hollow core. Preferably, an
inner cover layer and an outer cover layer are formed over the
outer core layer. In one embodiment, the inner cover includes an
ionomeric material and the outer cover layer includes a polyurea
or, preferably, a polyurethane. The outer cover layer is typically
softer than the inner cover layer, such as where the inner cover
has a hardness of greater than about 60 Shore D and the outer cover
layer has a hardness of less than about 60 Shore D.
[0055] In the above embodiment, the hollow center preferably has a
diameter of about 0.51 to 1.1 inches. The surface hardness of the
shell layer is preferably greater than the hardness of the inner
surface of the shell layer by about 3 to 25 Shore C to define a
first hardness gradient. In a preferred embodiment, the thermoset
outer core layer has a hardness gradient that is different from the
hardness gradient of the thermoset shell layer. Most preferably,
the shell layer has a surface hardness greater than about 55 Shore
C.
[0056] The thermoset inner core shell layer has a coefficient of
restitution (COR) less than about 0.750 when measured at an
incoming velocity of 125 ft/s. Preferably, the COR is less than
about 0.700, more preferably about 0.500 to 0.700, and most
preferably about 0.600 to 0.700. The overall hollow core (the
combination of the thermoset shell layer and the thermoset outer
core layer) has a COR, measured at an incoming velocity of 125
ft/s, higher than the COR of the inner core shell layer by greater
than about 5%, more preferably about 10 to 50%, and most preferably
about 15 to 30%.
[0057] In an alternative embodiment, the hardness gradient of the
thermoset outer core layer has a `zero hardness gradient`. The zero
hardness gradient is typically about 0 Shore C (defined herein as
.+-.2 Shore C). The hardness gradient of the thermoset outer core
layer may also have a `negative hardness gradient`, preferably
about 3 to 25 Shore C, more preferably about 5 to 20 Shore C, and
most preferably about 8 to 15 Shore C. The hardness gradient of the
thermoset outer core layer may also have a `positive hardness
gradient`, preferably about 3 to 25 Shore C, more preferably about
5 to 20 Shore C, and most preferably about 8 to 15 Shore C.
[0058] The golf ball has a first volume and the hollow center has a
second volume. The volume of the hollow center is about 2% to 30%
of the golf ball volume, more preferably about 5% to 25% of the
golf ball volume, and most preferably about 10% to 20% of the golf
ball volume.
[0059] In another embodiment of the invention, the hollow core
further includes a thermoplastic intermediate core layer disposed
between the thermoset shell layer and the thermoset outer core
layer. In still another embodiment, the hollow core further
includes a thermoset intermediate core layer disposed between the
thermoset shell layer and the thermoset outer core layer. The
intermediate core layer may formed from a thermoset rubber
composition which is the same or different from the thermoset
rubber compositions used to form the thermoset shell layer or the
thermoset outer core layer. In these embodiments, the hollow center
preferably has a diameter of about 0.15 to 1.1 inches, the shell
layer has a surface hardness greater than an inner surface hardness
by about 10 to 25 Shore C to define a hardness gradient, preferably
a `positive hardness gradient`. The thermoset outer core layer
preferably has a hardness gradient that is different from the
hardness gradient of the shell layer or the intermediate layer.
[0060] The hollow core of the present invention is covered by at
least one cover layer. An intermediate layer, such as an inner
cover layer, may optionally be disposed about the hollow core, with
the cover layer formed around the intermediate layer as an outer
cover layer. While any of the thermoplastic materials disclosed
herein may be suitable for the inner or outer cover layers of the
invention, in a preferred embodiment the outermost cover is formed
from a castable polyurea or a castable polyurethane; castable
hybrid poly(urethane/urea); and castable hybrid
poly(urea/urethane). Suitable polyurethanes include those disclosed
in U.S. Pat. Nos. 5,334,673 and 6,506,851. Suitable polyureas
include those disclosed in U.S. Pat. Nos. 5,484,870 and 6,835,794.
These patents are incorporated herein by reference thereto.
[0061] Other 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. More suitable
polyurethanes are described in U.S. Pat. No. 7,331,878, which is
incorporated by reference in its entirety.
[0062] 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, triisocyanate, 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.
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.
[0063] 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.
[0064] 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.
[0065] 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.
[0066] 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.
[0067] 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. Suitable polyamine curatives, which
include both primary and secondary amines, preferably have
molecular weights ranging from about 64 to about 2000.
[0068] 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.
[0069] 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.
[0070] 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
both castable thermoset and thermoplastic polyurethanes. 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.
[0071] Additionally, polyurethane can be replaced with or blended
with a polyurea material. Polyureas are distinctly different from
polyurethane compositions. The polyurea-based compositions are
preferably saturated in nature. The polyurea compositions 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.
[0072] 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.
[0073] 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. 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.
[0074] 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.
[0075] 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.
* * * * *