U.S. patent application number 15/099727 was filed with the patent office on 2017-10-19 for methods for making golf balls having heterogeneous layers and resulting balls.
This patent application is currently assigned to Acushnet Company. The applicant listed for this patent is Acushnet Company. Invention is credited to Edmund A. Hebert.
Application Number | 20170296881 15/099727 |
Document ID | / |
Family ID | 60039964 |
Filed Date | 2017-10-19 |
United States Patent
Application |
20170296881 |
Kind Code |
A1 |
Hebert; Edmund A. |
October 19, 2017 |
METHODS FOR MAKING GOLF BALLS HAVING HETEROGENEOUS LAYERS AND
RESULTING BALLS
Abstract
Methods for making multi-piece golf balls having an outer cover,
intermediate, or other layer comprising a heterogeneous composition
are provided. The heterogeneous composition comprises a mixture of
Compounds A and B. For example, the compounds can be different
polyurethanes, ethylene acid copolymer ionomers, polyesters,
polyamides, or any other suitable materials for making golf ball
layers. Compounds having different hardness levels can be used. For
example, the composition can comprise a mixture of hard and soft
materials. The invention also encompasses golf balls made from such
methods. The golf balls have good resiliency and impact durability
along with other optimum playing performance properties.
Inventors: |
Hebert; Edmund A.;
(Mattapoisett, MA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Acushnet Company |
Fairhaven |
MA |
US |
|
|
Assignee: |
Acushnet Company
Fairhaven
MA
|
Family ID: |
60039964 |
Appl. No.: |
15/099727 |
Filed: |
April 15, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A63B 37/0094 20130101;
A63B 37/0078 20130101; A63B 37/0074 20130101; A63B 37/0084
20130101; A63B 37/0032 20130101; A63B 37/0075 20130101; A63B 45/00
20130101 |
International
Class: |
A63B 45/00 20060101
A63B045/00; A63B 37/00 20060101 A63B037/00; A63B 37/00 20060101
A63B037/00; A63B 37/00 20060101 A63B037/00; A63B 37/00 20060101
A63B037/00; A63B 37/00 20060101 A63B037/00 |
Claims
1. A method for making a multi-piece golf ball, comprising the
steps of: a) introducing a first composition comprising Compound A
into upper and lower mold members, the upper and lower mold members
defining a mold cavity with a dimple pattern; b) introducing a
second composition comprising Compound B into the upper and lower
mold members so that the first and second compositions are mixed
together to form a heterogeneous composition comprising Compounds A
and B; c) placing a spherical core into the mold cavity; d)
applying heat and pressure to the mold members so the heterogeneous
composition encapsulates the core and forms an outer cover having a
dimpled pattern, and e) removing the multi-piece golf ball from the
mold.
2. The method of claim 1, wherein Compound A is an aliphatic
polyurethane and Compound B is an aromatic polyurethane.
3. The method of claim 1, wherein Compound A and Compound B are
O/X-type copolymers, wherein O is selected from the group
consisting of ethylene and propylene, and X is an acid group
selected from the group consisting of methacrylic acid, acrylic
acid, ethacrylic acid, crotonic acid, maleic acid, fumaric acid,
and itaconic acid, and wherein at least 70% of the acid groups in
Compound A are neutralized, and greater than 70% of the acid groups
in Compound B are neutralized.
4. The method of claim 3, wherein the O of the O/X-type acid
copolymer is ethylene and the X is methacrylic acid or acrylic
acid.
5. The method of claim 1, wherein Compound A and Compound B are
O/X/Y-type copolymers, wherein O is selected from the group
consisting of ethylene and propylene, and X is an acid group
selected from the group consisting of methacrylic acid, acrylic
acid, ethacrylic acid, crotonic acid, maleic acid, fumaric acid,
and itaconic acid, and Y is a (meth) acrylate or alkyl (meth)
acrylate wherein the alkyl groups have from 1 to 8 carbon atoms,
and wherein at least 70% of the acid groups in Compound A are
neutralized, and greater than 70% of the acid groups in Compound B
are neutralized.
6. The method of claim 1, wherein the outer cover layer formed from
the heterogeneous composition has a midpoint hardness and outer
hardness surface, the hardness of the outer surface being greater
than the hardness of the midpoint to define a positive hardness
gradient.
7. The method of claim 1, wherein the hardness of the outer surface
is in the range of about 35 to about 90 Shore D and the hardness of
the midpoint is in the range of about 30 to about 80 Shore D.
8. The golf ball of claim 1, wherein the outer cover layer formed
from the heterogeneous composition has a midpoint hardness and
outer hardness surface, the hardness of the outer surface being the
same or greater than the hardness of the midpoint to define a zero
or negative hardness gradient.
9. The method of claim 8, wherein the hardness of the midpoint is
in the range of about 40 to about 75 Shore D and the hardness of
the outer surface is in the range of about 35 to about 70 Shore
D.
10. The method of claim 1, wherein the core is single-layered, the
core being formed from a rubber composition.
11. The method of claim 1, wherein the core is dual-layered, the
core comprising an inner core and surrounding outer core layer, at
least one of the core layers being formed from a rubber
composition.
12. A method for making a multi-piece golf ball, comprising the
steps of: a) introducing a first composition comprising Compound A
into upper and lower mold members, the upper and lower mold members
defining a mold cavity; b) introducing a second composition
comprising Compound B into the upper and lower mold members so that
the first and second compositions are mixed together to form a
heterogeneous composition comprising Compounds A and B; c) placing
a spherical core into the mold cavity; d) applying heat and
pressure to the mold members so the heterogeneous composition
encapsulates the core and forms an intermediate layer the core and
surrounding intermediate layer comprising a ball subassembly; e)
removing the ball subassembly from the mold; and f) forming a cover
having at least one layer over the subassembly to form a
multi-piece golf ball.
Description
BACKGROUND OF THE INVENTION
Field of the Invention
[0001] The present invention relates generally to methods for
making multi-piece golf balls having an outer cover or other layer
comprising a heterogeneous composition. Particularly, in one
example, the ball may have a layer made from a heterogeneous
composition comprising a mixture of hard and soft ethylene acid
copolymer ionomers. In another example, the ball may have a layer
made from a heterogeneous composition comprising a mixture of
aliphatic and aromatic polyurethanes. The invention also
encompasses golf balls made from such methods.
Brief Review of the Related Art
[0002] Solid, multi-piece golf balls are commonly used by
professional and recreational golfers today. For example,
three-piece balls having an inner core, at least one intermediate
layer surrounding the core, and an outer cover are popular.
Different materials are used to make each of these layers. The
materials are designed to impart more desirable playing performance
properties to the golf ball.
[0003] For instance, a variety of materials may be used to make the
inner core of the ball, particularly natural and synthetic rubbers
such as styrene butadiene, polybutadiene, poly(cis-isoprene), and
poly(trans-isoprene) or thermoplastic materials such as ethylene
acid copolymer ionomers. The core is the primary source of
resiliency for the golf ball and is often referred to as the engine
of the ball. The ball may include one or more intermediate layers
made from thermoplastic or thermoset resins such as polyamides,
polyesters, ethylene acid copolymer ionomers, and the like.
[0004] The outer cover of the ball is designed to protect the core
and provides the ball with durability, toughness, and
cut/tear-resistance. The cover may comprise single or multiple
layers. Conventional cover materials include polyurethanes,
polyureas, and blends thereof, as well as highly neutralized
ethylene acid copolymer ionomers (HNPs). The combination of core,
intermediate layer(s), and cover provides the golf ball with its
targeted performance properties.
[0005] It is well known that hard golf balls having relatively
thick, hard outer covers can be made, and such balls generally have
good durability, toughness, and impact-resistance. For example,
hard ionomer resins can be used to make such covers. These
thick-covered, ionomeric golf balls generally are harder and more
resistant to wear and tear. The thick outer cover protects the core
and such balls have good impact durability and cut/tear-resistance.
However, these golf balls also can be overly stiff, and they tend
to have low spin. Players tend to experience a harder feel when
their club makes contact with such stiff balls. The player senses
less control. The player has generally a less natural and
comfortable sensation when striking such thick-covered, hard golf
balls versus thin-covered, soft balls.
[0006] Thus, the golf industry has looked to develop golf balls
having relatively thin cover layers. For example, golf balls having
covers made from relatively soft polyurethanes, polyureas, and
polyurethane/urea blends have been developed in recent years. For
example, Hebert et al., U.S. Pat. Nos. 6,132,324 and 5,885,172
disclose a method of forming a multi-layered golf ball comprising a
core, inner cover layer, and outer cover layer. A castable reactive
liquid polyurethane or polyurea material is introduced into mold
cavities and then a ball subassembly (core and inner cover layer)
is placed in one mold cavity. The upper and lower mold cavities are
joined together. The polyurethane or polyurea material in the
cavities encapsulates the ball subassembly and forms a thin cover
for the ball.
[0007] In Lutz et al., U.S. Pat. Nos. 6,783,808 and 6,706,332 a
method of coating a thin-layered over a golf ball component is
provided. The method involves providing a polymer material;
creating a polymer particulate from the polymer material;
fluidizing the polymer particulate; and coating the golf ball
component with a thin layer of the polymer material by placing the
golf ball component within the fluidized particulate. Suitable
polymers are described as including vinyl resins; polyolefins;
polyurethanes; polyureas; polyamides; acrylic resins; and other
thermoplastics and thermosets.
[0008] Conventional thin covers provide the ball with a softer
feel, and the player can place a spin on the ball and better
control its flight pattern. The softer cover feels more natural.
Players sense more control with such softer, relatively
thin-covered golf balls. There are drawbacks, however, with such
thin-covered golf balls, because the balls tend to have less
durability, toughness, and cut/tear-resistance. The ball may appear
excessively worn with scuff marks, cuts, and tears after continuous
play on the golf course. In addition, there can be drawbacks with
using conventional methods such as casting and reaction injection
molding ("RIM") to form thin cover layers. For example, casting
processes may produce undesirable waste, and RIM mold parts may be
difficult to position to achieve a uniform layer and leave pin
marks on the cores or golf ball subassemblies. Thin layers may also
be sprayed on the golf ball assemblies; however, spray applicators
or nozzles can be clogged and the liquid compositions to be sprayed
may also have undesirably high volatile organic components
(VOC).
[0009] It would be desirable to have new methods for making golf
balls having relatively thin cover layers. The present invention
provides such methods along with the resulting golf balls. The
balls have advantageous properties such as high impact durability,
toughness, and cut/tear-resistance along with other benefits. Such
covers, in combination with the cores, impart high resiliency to
the golf balls. This allows players to generate greater initial
ball velocity off the tee and achieve greater distance. At the same
time, the relatively thin cover layers would provide the ball with
a comfortable softness and natural feeling.
SUMMARY OF THE INVENTION
[0010] This invention relates to methods for making a multi-piece
golf ball. Golf balls having various constructions can be made in
accordance with this invention. In one preferred embodiment, the
method comprises the steps of: i) introducing a first composition
comprising Compound A into upper and lower mold members that define
a mold cavity with a dimple pattern; ii) introducing a second
composition comprising Compound B into the same upper and lower
mold members so the first and second compositions are mixed
together to form a heterogeneous composition comprising Compounds A
and B; iii) placing a spherical core into the mold cavity; iv)
applying heat and pressure to the mold members so the heterogeneous
composition encapsulates the core and forms an outer cover having a
dimpled pattern; and v) removing the multi-piece golf ball from the
mold.
[0011] In one preferred version, Compound A is an aliphatic
polyurethane and Compound B is an aromatic polyurethane. In another
preferred version, wherein Compound A and Compound B are O/X-type
copolymers, wherein O is selected from the group consisting of
ethylene and propylene, and X is an acid group selected from the
group consisting of methacrylic acid, acrylic acid, ethacrylic
acid, crotonic acid, maleic acid, fumaric acid, and itaconic acid,
and wherein at least 70% of the acid groups in Compound A are
neutralized, and greater than 70% of the acid groups in Compound B
are neutralized. For example, O can be ethylene and X can be
methacrylic acid or acrylic acid. The core can be a single piece or
multi-piece. For example, dual cores comprising an inner core and
surrounding outer core layer, wherein at least one of the layers is
formed from rubber, can be made.
[0012] The cover layers have different hardness levels. The outer
cover layer formed from the heterogeneous composition has a
midpoint hardness and outer hardness surface, and in one example,
the hardness of the outer surface (for example, 35 to 90 Shore D)
is greater than the hardness of the midpoint (for example, 30 to 80
Shore D) to define a positive hardness gradient. In another
version, the hardness of the outer surface is the same or less than
the hardness of the midpoint to define a zero or negative hardness
gradient. The heterogeneous composition comprising Compounds A and
B also can be used to form an intermediate layer in the ball. For
example, the heterogeneous composition can be applied over the core
so that is forms an intermediate layer. In this case, the core and
surrounding intermediate layer comprise a ball subassembly, and a
cover can be formed over the subassembly to form a multi-piece
ball. The resulting golf balls have good resiliency and impact
durability along with other optimum playing performance
properties
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] The novel features that are characteristic of the present
invention are set forth in the appended claims. However, the
preferred embodiments of the invention, together with further
objects and attendant advantages, are best understood by reference
to the following detailed description in connection with the
accompanying drawings in which:
[0014] FIG. 1 is a front view of a multi-layered dimpled golf ball
made in accordance with the present invention;
[0015] FIG. 2 is a cross-sectional view of a two-piece golf ball
having an outer cover made of a heterogeneous composition in
accordance with the present invention;
[0016] FIG. 3 is a cross-sectional view of a three-piece golf ball
having an outer cover made of a heterogeneous composition in
accordance with the present invention;
[0017] FIG. 4 is a cross-sectional view of a four-piece golf ball
having an outer cover made of a heterogeneous composition in
accordance with the present invention; and
[0018] FIG. 5 is a schematic diagram showing one embodiment for
making a molded golf ball in accordance with the present
invention.
DETAILED DESCRIPTION OF INVENTION
[0019] Golf balls having various constructions may be made in
accordance with this invention. For example, golf balls having
two-piece, three-piece, four-piece, and five-piece constructions
with single or multi-layered cover materials may be made.
Representative illustrations of such golf ball constructions are
provided and discussed further below. The term, "layer" as used
herein means generally any spherical portion of the golf ball. More
particularly, in one version, a two-piece ball containing a core
and surrounding cover also is made. In another version, a
three-piece golf ball containing a core, intermediate layer, and
cover layer is made. A four-piece golf ball containing a core, two
intermediate layers, and cover layer also can be made. In yet
another construction, a five-piece golf ball containing a core;
three intermediate layers, and a cover layer may be made. As used
herein, the term, "intermediate layer" means any layer of the ball
disposed between the core and cover.
[0020] Heterogeneous Compositions
[0021] In the present invention, a heterogeneous composition is
prepared and used to form an outer cover layer, intermediate layer,
or any other layer for a golf ball. The intermediate layer may be
considered an outer core layer or inner cover layer or any other
layer disposed between the inner core and outer cover of the ball
for purposes of this invention. The intermediate layer also may be
referred to as a casing or mantle layer. The diameter and thickness
of the different layers along with properties such as hardness and
compression may vary depending upon the construction and desired
playing performance properties of the golf ball.
[0022] In general, the method involves introducing a first
composition comprising "Compound A" into upper and lower mold
members. A second composition comprising "Compound B" is introduced
into the upper and lower mold members containing the first
composition. Thus, the first and second compositions are mixed
together to form a heterogeneous composition comprising Compounds A
and B. Although Compounds A and B are described primarily herein as
being polyurethane materials, it should be understood that
Compounds A and B can be any suitable material for making golf ball
cover layers or intermediate layers in accordance with this
invention.
[0023] For example, in producing an outer cover layer, a liquid
mixture of reactive polyurethane prepolymer and chain-extender
(curing agent) ("the first composition containing Compound A", for
example an aliphatic polyurethane as discussed further below") can
be poured into lower and upper mold members (half-shells), which
may be pre-heated (normally at a temperature of about 125.degree.
to about 300.degree. F.). The reactive polyurethane prepolymer and
chain extender form a thin coating (skin) over the interior
surfaces of the mold members.
[0024] Next, a liquid mixture of reactive polyurethane prepolymer
and chain-extender (curing agent) ("the second polyurethane
composition containing Compound B", for example an aromatic
polyurethane as discussed further below) is poured into the
skin-coated lower and upper mold members. After this second
polyurethane reactive mixture has resided in the lower mold member
for a sufficient time period (typically about 40 to about 100
seconds), the golf ball core structure is lowered at a controlled
speed into the reactive mixture. Ball suction cups can hold the
core structure in place via reduced pressure or partial vacuum.
After sufficient gelling of the reactive mixture (typically about 4
to about 12 seconds), the vacuum is removed and the core is
released into the mold cavity. Then, the upper mold member is mated
with the lower mold member under sufficient pressure and heat. An
exothermic reaction occurs when the polyurethane prepolymer and
chain extender are mixed and this continues until the cover
material encapsulates and solidifies around the core structure.
Finally, the molded balls are cooled in the mold and removed when
the molded cover is hard enough so that it can be handled without
deforming.
[0025] In one embodiment, the heterogeneous composition may contain
aromatic and aliphatic polyurethanes. In general, the aromatic
polyurethane has good mechanical strength and cut/shear-resistance.
However, one disadvantage with using aromatic isocyanates is the
polymeric reaction product tends to have poor light stability and
may discolor upon exposure to light, particularly ultraviolet (UV)
light. On the other hand, the aliphatic polyurethane has good light
stability but such polymers tend to have reduced mechanical
strength and cut/shear-resistance. In the present invention, the
heterogeneous composition may comprise both aromatic and aliphatic
polyurethanes.
[0026] Moreover, the cover or other layer can be tailored such that
there is a gradient of aromatic and aliphatic polyurethanes. For
example, the aliphatic polyurethane composition can be dispensed
into the mold cavity first and then the cavity may be gently
hand-rocked so this composition skin-coats the interior surface of
the cavity. Then, the aromatic polyurethane composition can be
dispensed into the mold cavity so that it lies over the aliphatic
polyurethane composition. The two separate and distinct
polyurethane compositions are co-mingled. The polyurethane
compositions are mixed to form a heterogeneous composition
comprising aliphatic and aromatic polyurethanes.
[0027] Hard and Soft Compositions
[0028] In another embodiment, the heterogeneous composition may
contain a mixture of relatively hard and soft materials. For
example, a very soft, but shear-resistant material (Compound A)
could be used. This material could be considered too soft or slow
when used, by and in itself, as a cover material. However, it could
be combined with a harder material (Compound B) that provides good
resilience but lacks good shear-resistance. In mixing these
materials, a relatively small shot of Compound A (softer material)
could be added to the mold cavity and then a relatively large shot
of Compound B (harder material) could be added over Compound A.
There would be some co-mingling or mixing of materials to form a
heterogeneous composition of Compounds A and B. In this example,
there would be a thin layer of soft material at the outer surface
of the cover, and a thicker layer of harder material below the
outer surface region. Thus, the heterogeneous composition contains
a hardness gradient, wherein the harder material is located in the
outer surface region of the cover layer (or intermediate or other
layer) and the softer material is located in the inner surface
regions of the cover layer ((or intermediate or other layer) or
vice versa.
[0029] As discussed above, in one embodiment, a heterogeneous
composition comprising distinct polyurethane compounds is prepared.
In another embodiment, the outer cover layer is made of a
heterogeneous composition comprising a first ethylene acid
copolymer ionomer and a second ethylene acid copolymer ionomer. In
one particular example, one of the ionomer compound may be a
relatively soft material and the other ionomer compound may be a
relatively hard material. For example, the first composition may
contain an ethylene acid copolymer ionomer having less than 70%
neutralization ("Compound A") and the second composition may
contain an ethylene acid copolymer ionomer having greater than 70%
neutralization ("Compound B").
[0030] In general, hardness gradients are described in Bulpett et
al., U.S. Pat. Nos. 7,537,529 and 7,410,429, the disclosures of
which are hereby incorporated by reference. Methods for measuring
the hardness of the core, intermediate, and cover layers in the
golf ball and determining the hardness gradients of the various
layers are described in further detail below. The layers have
positive, negative, or zero hardness gradients defined by hardness
measurements made at the outer surface of the layer, for example,
outer cover and radially inward towards the inner surface of the
layer. These measurements are made typically at 2-mm increments as
described in the test methods below. In general, the hardness
gradient is determined by subtracting the hardness value at the
innermost portion of the component being measured (for example, the
inner surface of the cover layer) from the hardness value at the
outer surface of the component being measured (for example, the
outer surface of the cover layer).
[0031] Positive Hardness Gradient.
[0032] For example, if the hardness value of the cover layer's
outer surface is greater than the hardness value of the cover
layer's inner surface, the hardness gradient will be deemed
"positive" (a larger number minus a smaller number equals a
positive number.) For example, if the outer surface of the cover
layer has a hardness of 67 Shore C and the inner surface of the
inner cover layer has a hardness of 60 Shore C, then the cover
layer has a positive hardness gradient of 7. Likewise, if the outer
surface of the outer core layer has a greater hardness value than
the inner surface of the outer core layer, the given outer core
layer will be considered to have a positive hardness gradient.
[0033] Negative Hardness Gradient.
[0034] On the other hand, if the hardness value of the outer
surface of the outer cover is less than the hardness value of the
outer cover's inner surface (that is, the cover has an outer
surface softer than its inner surface), the hardness gradient will
be deemed "negative." For example, if the outer surface of the
cover has a hardness of 68 Shore C and the inner surface of the
cover has a hardness of 70 Shore C, then the cover has a negative
hardness gradient of 2. Likewise, if the outer surface of the cover
layer has a lesser hardness value than the inner surface of the
outer core layer, the given outer core layer will be considered to
have a negative hardness gradient.
[0035] Zero Hardness Gradient.
[0036] In another example, if the hardness value of the outer
surface of the cover is substantially the same as the hardness
value of the inner surface of the cover (that is, the outer surface
and inner surface have about the same hardness), the hardness
gradient will be deemed "zero." For example, if the outer surface
of the cover and the inner surface of the cover each has a hardness
of 65 Shore C, then the cover has a zero hardness gradient.
Likewise, if the outer surface of the outer core layer has a
hardness value approximately the same as the inner surface of the
outer core layer, the outer core layer will be considered to have a
zero hardness gradient.
[0037] More particularly, the term, "positive hardness gradient" as
used herein means a hardness gradient of positive 3 Shore D or
greater, preferably 7 Shore D or greater, more preferably 10 Shore
D, and even more preferably 20 Shore D or greater. The term, "zero
hardness gradient" as used herein means a hardness gradient of less
than 3 Shore D, preferably less than 1 Shore D and may have a value
of zero or negative 1 to negative 10 Shore D. The term, "negative
hardness gradient" as used herein means a hardness value of less
than zero, for example, negative 3, negative 5, negative 7,
negative 10, negative 15, or negative 20 or negative 25. The terms,
"zero hardness gradient" and "negative hardness gradient" may be
used herein interchangeably to refer to hardness gradients of
negative 1 to negative 10.
[0038] In one example, the outer cover layer preferably has an
outer surface hardness (H.sub.outer surface of cover) of about 30
Shore D or greater, and more preferably within a range having a
lower limit of about 30 or 34 or 37 or 40 or 42 or 44 or 46 or 48
or 50 or 52 and an upper limit of about 54 or 56 or 58 or 60 or 62
or 64 or 70 or 74 or 78 or 80 or 82 or 85 or 87 or 88 or 90 Shore
D. The inner surface hardness of the cover layer (H.sub.inner
surface of cover) or midpoint hardness (H.sub.midpoint of cover) of
the cover layer, as measured in Shore D units, preferably has a
lower limit of about 30 or 34 or 37 or 42 or 44 or 45 or 47 or 50
or 52 or 54 or 55 or 58 or 60 or 63 or 65 or 67 or 70 or 73 or 75
Shore C, and an upper limit of about 78 or 80 or 85 or 88 or 89 or
90 Shore D. The midpoint of the outer core layer is taken at a
point equidistant from the inner surface and outer surface of the
layer to be measured. Once one or more core layers surround a layer
of interest, the exact midpoint may be difficult to determine,
therefore, for the purposes of the present invention, the
measurement of "midpoint" hardness of a layer is taken within plus
or minus 1 mm of the measured midpoint of the layer.
[0039] In one embodiment, the outer surface hardness of the outer
cover layer (H.sub.outer surface of cover), is less than the inner
surface hardness (H.sub.inner surface of cover) or midpoint
hardness (H.sub.midpoint of cover), of the outer cover by at least
3 Shore D units and more preferably by at least 5 Shore D to
provide a zero or negative hardness gradient.
[0040] In a second embodiment, the outer surface hardness of the
outer core layer (H.sub.outer surface of cover), is greater than
the inner surface hardness (H.sub.inner surface of hardness) or
midpoint hardness (H.sub.midpoint of cover), of the cover by at
least 3 Shore D units and more preferably by at least 5 Shore D to
provide a positive hardness gradient.
[0041] Other Components in Golf Ball Construction
[0042] The solid cores for the golf balls of this invention may be
made using any suitable conventional technique such as, for
example, compression or injection molding, Typically, the cores are
formed by compression molding a slug of uncured or lightly cured
rubber material into a spherical structure. Prior to forming the
cover layer, the core structure may be surface-treated to increase
the adhesion between its outer surface and adjacent layer. Such
surface-treatment may include mechanically or chemically-abrading
the outer surface of the core. For example, the core may be
subjected to corona-discharge, plasma-treatment, silane-dipping, or
other treatment methods known to those in the art.
[0043] The core sub-assembly may comprise an inner core and
surrounding outer core layer. That is, single-layered cores having
a single inner core and multi-layered cores having an inner core
and outer core layer may be made in accordance with this invention.
The ball sub-assembly may comprise the core structure (for example,
single-layered core or multi-layered core) and any overlying
intermediate layers. After the golf balls have been removed from
the mold, they may be subjected to finishing steps such as
flash-trimming, surface-treatment, marking, coating, and the like
using techniques known in the art. For example, in traditional
white-colored golf balls, the white-pigmented cover may be
surface-treated using a suitable method such as, for example,
corona, plasma, or ultraviolet (UV) light-treatment. Then, indicia
such as trademarks, symbols, logos, letters, and the like may be
printed on the ball's cover using pad-printing, ink-jet printing,
dye-sublimation, or other suitable printing methods. Clear surface
coatings (for example, primer and top-coats), which may contain a
fluorescent whitening agent, are applied to the cover. The
resulting golf ball has a glossy and durable surface finish.
[0044] In another finishing process, the golf balls are painted
with one or more paint coatings. For example, white primer paint
may be applied first to the surface of the ball and then a white
top-coat of paint may be applied over the primer. Of course, the
golf ball may be painted with other colors, for example, red, blue,
orange, and yellow. Markings such as trademarks and logos may be
applied to the painted cover of the golf ball. Finally, a clear
surface coating may be applied to the cover to provide a shiny
appearance and protect any logos and other markings printed on the
ball.
[0045] Referring to FIG. 1, one version of a golf ball that can be
made in accordance with this invention is generally indicated at
(6). Various patterns and geometric shapes of dimples (8) are used
to modify the aerodynamic properties of the golf ball (6). The
dimples (8) can be arranged on the outer surface of the ball (6) in
various patterns to modify the aerodynamic properties of the ball
as discussed in detail below.
[0046] As discussed above, the lower and upper mold cavities are
mated together to form the outer cover layer for the ball. The
outer cover material encapsulates the inner ball. The mold cavities
used to form the outer layer have interior dimple cavity details.
The cover material conforms to the interior geometry of the mold
cavities to form a dimple pattern on the surface of the ball. The
mold cavities may have any suitable dimple arrangement such as, for
example, icosahedral, octahedral, cube-octahedral, dipyramid, and
the like. In addition, the dimples may be circular, oval,
triangular, square, pentagonal, hexagonal, heptagonal, octagonal,
and the like. Possible cross-sectional shapes include, but are not
limited to, circular arc, truncated cone, flattened trapezoid, and
profiles defined by a parabolic curve, ellipse, semi-spherical
curve, saucer-shaped curve, sine or catenary curve, or conical
curve. Other possible dimple designs include dimples within
dimples, constant depth dimples, or multi-lobe dimples, as
disclosed in U.S. Pat. No. 6,749,525. It also should be understood
that more than one shape or type of dimple may be used on a single
ball, if desired.
[0047] The use of various dimple patterns and profiles provides a
relatively effective way to modify the aerodynamic characteristics
of a golf ball. Suitable dimple patterns include, for example,
icosahedron-based pattern, as described in U.S. Pat. No. 4,560,168;
octahedral-based dimple patterns as described in U.S. Pat. No.
4,960,281; and tetrahedron-based patterns as described in
co-assigned, co-pending, U.S. patent application Ser. No.
12/894,827, the disclosure of which is hereby incorporated by
reference. Other tetrahedron-based dimple designs are shown in
co-assigned, co-pending design applications D Ser. No. 29/362,123;
D Ser. No. 29/362,124; D Ser. No. 29/362,125; and D Ser. No.
29/362,126, the disclosures of which are hereby incorporated by
reference.
[0048] The total number of dimples on the ball, or dimple count,
may vary depending such factors as the sizes of the dimples and the
pattern selected. In general, the total number of dimples on the
ball preferably is between about 100 to about 1000 dimples,
although one skilled in the art would recognize that differing
dimple counts within this range can significantly alter the flight
performance of the ball. In one embodiment, the dimple count is
about 300-360 dimples. In one embodiment, the dimple count on the
ball is about 360-400 dimples.
[0049] Referring to FIG. 2, a cross-sectional view of a two-piece
golf ball (10) having a solid inner core (12) and outer cover (14)
made of the heterogeneous composition of this invention is shown.
The outer cover (14) contains numerous dimples as shown in FIG. 1.
To make the finished golf ball, the cover can be painted white or
another color. First, a primer coat can be applied to the cover and
then a pigmented paint can be applied over the primer. Typically, a
custom logo, symbol, or other mark is ink-printed onto the painted
surface and a clear, protective top coat is applied over the
printed mark to provide a glossy finish. In other instances, the
cover material may contain white pigment or a different colored
concentrate. In FIG. 3, a cross-sectional view of a three-piece
golf ball (16) having a solid core (18) and cover (20) made of the
heterogeneous composition of this invention is shown. An
intermediate layer (22) is disposed between the core (18) and cover
layer (20). Turning to FIG. 4, a golf ball (24) having a
multi-layered cover is shown. The golf ball (24) includes a solid
core (26) and intermediate layer (28). The inner cover layer (30)
is made of a conventional thermoplastic or thermoset polymer
composition, while the outer cover (32) is made of the
heterogeneous composition of this invention.
[0050] Turning to FIG. 5, one embodiment of the molding method of
this invention is shown, wherein the heterogeneous composition is
dispenses into the interior surfaces of an upper mold member (34)
and lower mold member (36) which define a mold cavity for holding a
golf ball subassembly (40). The heterogeneous composition (35),
which will be used to form the outer cover layer, is introduced
into the mold members. In FIG. 5, the golf ball subassembly (40)
includes a solid core (18) surrounded by a casing (22). The core
(18) can be made of a polybutadiene rubber and the casing (22) can
be made of an ionomer resin. The ball subassembly (40) is placed
into the mold cavity defined by the upper and lower mold halves
(34, 36). This step can be performed manually or automatically by
machine. Next, the mold members (34, 36) are joined and a
sufficient amount of heat and pressure is applied to the mold so
the heterogeneous composition (35) fuses and encapsulates the ball
subassembly (40). Thus, an outer cover (20) comprising a
heterogeneous outer cover layer is formed. The resulting molded
golf ball (42) is preferably cooled before it is removed from the
mold.
[0051] It should be understood that the golf balls shown in FIGS.
1-5 are for illustrative purposes only and not meant to be
restrictive. Other golf ball constructions can be made in
accordance with this invention.
[0052] In one embodiment, as discussed above, a cover layer
comprising a heterogeneous composition of aliphatic and aromatic
polyurethanes is made. The cover layer, in this embodiment, is a
single layer comprising Compounds A and B (aliphatic and aromatic
polyurethane) so it has the properties of two layers. The single
layer is essentially "split" as a heterogeneous composition,
wherein each compound contributes to the overall good physical and
playing properties of the ball. For example, the cover layer has
good durability and toughness. Furthermore, the cover layer has
good light stability. The cover layer has high ultraviolet light
(UV)-resistance and is less likely to discolor upon exposure to
sunlight. Thus, the golf balls of this invention have good light
stability without sacrificing important mechanical properties such
as durability and high cut/shear-resistance.
[0053] The method of this invention is particularly effective in
providing golf balls having a very thin outer cover layer. For
example, the thickness of this outer cover layer can be in the
range of about 0.004 to about 0.050 inches. In one preferred
embodiment, the thickness is about 0.006 to about 0.040 inches or
about 0.008 to about 0.030 inches and more preferably about 0.012
to about 0.018 inches.
[0054] When these methods are used to make the intermediate layer,
the thickness of that layer can be in the range of about 0.015
inches to about 0.100 inches. In one preferred embodiment, the
thickness is in the range of about 0.020 inches to about 0.080
inches, and more preferably about 0.030 inches to about 0.050
inches.
[0055] The United States Golf Association ("USGA") has set total
weight limits for golf balls. Particularly, the USGA has
established a maximum weight of 45.93 g (1.62 ounces) for golf
balls. There is no lower weight limit. In addition, the USGA
requires that golf balls used in competition have a diameter of at
least 1.68 inches. There is no upper limit so many golf balls have
an overall diameter falling within the range of about 1.68 to about
1.80 inches. The golf ball diameter is preferably about 1.68 to
1.74 inches, more preferably about 1.68 to 1.70 inches. In
accordance with the present invention, the weight, diameter, and
thickness of the core and cover layers may be adjusted, as needed,
so the ball meets USGA specifications of a maximum weight of 1.62
ounces and a minimum diameter of at least 1.68 inches. For play
outside of the USGA rules, the ball can have a greater weight than
1.62 ounces and can be of any diameter size.
[0056] A wide variety of materials may be used for forming the
outer cover and intermediate layers in accordance with this
invention including, for example, polyurethanes; polyureas;
copolymers, blends and hybrids of polyurethane and polyurea;
olefin-based copolymer ionomer resins (for example, Surlyn.RTM.
ethylene acid copolymer ionomer resins and DuPont HPF.RTM. 1000 and
HPF.RTM. 2000, commercially available from DuPont; Iotek.RTM.
ionomers, commercially available from ExxonMobil Chemical Company;
Amplify.RTM. IO ionomers of ethylene acrylic acid copolymers,
commercially available from The Dow Chemical Company; and
Clarix.RTM. ionomer resins, commercially available from A. Schulman
Inc.); polyethylene, including, for example, low density
polyethylene, linear low density polyethylene, and high density
polyethylene; polypropylene; rubber-toughened olefin polymers; acid
copolymers, for example, poly(meth)acrylic acid, which do not
become part of an ionomeric copolymer; plastomers; flexomers;
styrene/butadiene/styrene block copolymers;
styrene/ethylene-butylene/styrene block copolymers; dynamically
vulcanized elastomers; copolymers of ethylene and vinyl acetates;
copolymers of ethylene and methyl acrylates; polyvinyl chloride
resins; polyamides, poly(amide-ester) elastomers, and graft
copolymers of ionomer and polyamide including, for example,
Pebax.RTM. thermoplastic polyether block amides, commercially
available from Arkema Inc; cross-linked trans-polyisoprene and
blends thereof; polyester-based thermoplastic elastomers, such as
Hytrel.RTM., commercially available from DuPont or RiteFlex.RTM.,
commercially available from Ticona Engineering Polymers;
polyurethane-based thermoplastic elastomers, such as
Elastollan.RTM., commercially available from BASF;
polycarbonate/polyester blends such as Xylex.RTM., available from
SABIC Innovative Plastics; maleic anhydride-grafted polymers such
as Fusabond.RTM., available from DuPont; and mixtures of the
foregoing materials. Castable polyurethanes, polyureas, and hybrids
of polyurethanes-polyureas are particularly desirable because these
materials can be used to make a golf ball having high resiliency
and a soft feel. By the term, "hybrids of polyurethane and
polyurea," it is meant to include copolymers and blends
thereof.
[0057] The compositions used to make the cover layer may contain a
wide variety of fillers and additives to impart specific properties
to the ball. For example, relatively heavy-weight and light-weight
metal fillers such as, particulate; powders; flakes; and fibers of
copper, steel, brass, tungsten, titanium, aluminum, magnesium,
molybdenum, cobalt, nickel, iron, lead, tin, zinc, barium, bismuth,
bronze, silver, gold, and platinum, and alloys and combinations
thereof may be used to adjust the specific gravity of the ball.
Other additives and fillers include, but are not limited to,
optical brighteners, coloring agents, fluorescent agents, whitening
agents, UV absorbers, light stabilizers, surfactants, processing
aids, antioxidants, stabilizers, softening agents, fragrance
components, plasticizers, impact modifiers, titanium dioxide, clay,
mica, talc, glass flakes, milled glass, and mixtures thereof.
[0058] Polyurethanes
[0059] As discussed above, in one preferred embodiment, the outer
cover layer is made of a heterogeneous polyurethane composition
comprising a first polyurethane composition and a second compound
composition. The intermediate layer also may be made of a
heterogeneous polyurethane composition. For example, the first
polyurethane composition may contain aliphatic polyurethane
("Compound A") and the second polyurethane composition may contain
aromatic polyurethane ("Compound B").
[0060] In general, polyurethane compositions contain urethane
linkages formed by reacting an isocyanate group (--N.dbd.C.dbd.O)
with a hydroxyl group (OH). The polyurethanes are produced by the
reaction of a multi-functional isocyanate (NCO--R--NCO) with a
long-chain polyol having terminal hydroxyl groups (OH--OH) in the
presence of a catalyst and other additives. The chain length of the
polyurethane prepolymer is extended by reacting it with short-chain
diols (OH--R'--OH). The resulting polyurethane has elastomeric
properties because of its "hard" and "soft" segments, which are
covalently bonded together.
[0061] In one embodiment, the cover layer comprises aliphatic
polyurethane, which is preferably formed by reacting an aliphatic
diisocyanate with a polyol. Suitable aliphatic diisocyanates that
may be used in accordance with this invention include, for example,
isophorone diisocyanate (IPDI), 1,6-hexamethylene diisocyanate
(HDI), 4,4'-dicyclohexylmethane diisocyanate ("H.sub.12 MDI"),
meta-tetramethylxylyene diisocyanate (TMXDI), trans-cyclohexane
diisocyanate (CHDI), and homopolymers and copolymers and blends
thereof.
[0062] The cover layer also comprises aromatic polyurethane, which
is preferably formed by reacting an aromatic diisocyanate with a
polyol. Suitable aromatic diisocyanates that may be used in
accordance with this invention include, for example, toluene
2,4-diisocyanate (TDI), toluene 2,6-diisocyanate (TDI),
4,4'-methylene diphenyl diisocyanate (MDI), 2,4'-methylene diphenyl
diisocyanate (MDI), polymeric methylene diphenyl diisocyanate
(PMDI), p-phenylene diisocyanate (PPDI), m-phenylene diisocyanate
(PDI), naphthalene 1,5-diisocynate (NDI), naphthalene
2,4-diisocyanate (NDI), p-xylene diisocyanate (XDI), and
homopolymers and copolymers and blends thereof. The aromatic
isocyanates are able to react with the hydroxyl or amine compounds
and form a durable and tough polymer having a high melting
point.
[0063] Any suitable polyol may be reacted with the diisocyanate
compound. 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. One preferred polyol is PTMEG. In
another preferred embodiment, polyester polyols are sued including,
but 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. In still another embodiment, polycaprolactone
polyols are used.
[0064] There are two basic techniques that can be used to make the
polyurethane compositions of this invention: a) one-shot technique,
and b) prepolymer technique. In the one-shot technique, the
diisocyanate, polyol, and hydroxyl-terminated chain-extender
(curing agent) are reacted in one step. On the other hand, the
prepolymer technique involves a first reaction between the
diisocyanate and polyol compounds to produce a polyurethane
prepolymer, and a subsequent reaction between the prepolymer and
hydroxyl-terminated chain-extender. As a result of the reaction
between the isocyanate and polyol compounds, there will be some
unreacted NCO groups in the polyurethane prepolymer. The prepolymer
should have less than 14% unreacted NCO groups. Preferably, the
prepolymer has no greater than 8.5% unreacted NCO groups, more
preferably from 2.5% to 8%, and most preferably from 5.0% to 8.0%
unreacted NCO groups. As the weight percent of unreacted isocyanate
groups increases, the hardness of the composition also generally
increases.
[0065] Either the one-shot or prepolymer method may be employed to
produce the polyurethane compositions of the invention. In one
embodiment, the one-shot method is used, wherein the isocyanate
compound is added to a reaction vessel and then a curative mixture
comprising the polyol and curing agent is added to the reaction
vessel. The components are mixed together so that the molar ratio
of isocyanate groups to hydroxyl groups is in the range of about
1.01:1.00 to about 1.10:1.00. Preferably, the molar ratio is
greater than 1.05:1.00. For example, the molar ratio can be in the
range of 1.07:1.00 to 1.10:1.00. In a second embodiment, the
prepolymer method is used. In general, the prepolymer technique is
preferred because it provides better control of the chemical
reaction. The prepolymer method provides a more homogeneous mixture
resulting in a more consistent polymer composition. The one-shot
method results in a mixture that is inhomogeneous (more random) and
affords the manufacturer less control over the molecular structure
of the resultant composition.
[0066] The polyurethane compositions can be formed by
chain-extending the polyurethane prepolymer with a single
chain-extender or blend of chain-extenders as described further
below. Thermoset compositions, on the other hand, are cross-linked
polymers and are typically produced from the reaction of the
isocyanate blend and polyols at normally a 1.05:1 stoichiometric
ratio. In general, thermoset polyurethane compositions are easier
to prepare than thermoplastic polyurethanes.
[0067] As discussed above, the polyurethane prepolymer can be
chain-extended by reacting it with a single chain-extender or blend
of chain-extenders. In general, the prepolymer can be reacted with
hydroxyl-terminated curing agents, amine-terminated curing agents,
and mixtures thereof. The curing agents extend the chain length of
the prepolymer and build-up its molecular weight. Normally, the
prepolymer and curing agent are mixed so the isocyanate groups and
hydroxyl or amine groups are mixed at a 1.05:1.00 stoichiometric
ratio.
[0068] A catalyst may be employed to promote the reaction between
the isocyanate and polyol compounds for producing the prepolymer or
between prepolymer and chain-extender during the chain-extending
step. Preferably, the catalyst is added to the reactants before
producing the prepolymer. Suitable catalysts include, but are not
limited to, bismuth catalyst; zinc octoate; stannous octoate; tin
catalysts such as bis-butyltin dilaurate, bis-butyltin diacetate,
stannous octoate; tin (II) chloride, tin (IV) chloride,
bis-butyltin dimethoxide, dimethyl-bis[1-oxonedecyl)oxy]stannane,
di-n-octyltin bis-isooctyl mercaptoacetate; amine catalysts such as
triethylenediamine, triethylamine, and tributylamine; organic acids
such as oleic acid and acetic acid; delayed catalysts; and mixtures
thereof. The catalyst is preferably added in an amount sufficient
to catalyze the reaction of the components in the reactive mixture.
In one embodiment, the catalyst is present in an amount from about
0.001 percent to about 1 percent, and preferably 0.1 to 0.5
percent, by weight of the composition.
[0069] The hydroxyl chain-extending (curing) agents are preferably
selected from the group consisting of ethylene glycol; diethylene
glycol; polyethylene glycol; propylene glycol;
2-methyl-1,3-propanediol; 2-methyl-1,4-butanediol;
monoethanolamine; diethanolamine; triethanolamine;
monoisopropanolamine; diisopropanolamine; dipropylene glycol;
polypropylene glycol; 1,2-butanediol; 1,3-butanediol;
1,4-butanediol; 2,3-butanediol; 2,3-dimethyl-2,3-butanediol;
trimethylolpropane; cyclohexyldimethylol; triisopropanolamine;
N,N,N',N'-tetra-(2-hydroxypropyl)-ethylene diamine; diethylene
glycol bis-(aminopropyl) ether; 1,5-pentanediol; 1,6-hexanediol;
1,3-bis-(2-hydroxyethoxy) cyclohexane; 1,4-cyclohexyldimethylol;
1,3-bis-[2-(2-hydroxyethoxy) ethoxy]cyclohexane;
1,3-bis-{2-[2-(2-hydroxyethoxy) ethoxy]ethoxy}cyclohexane;
trimethylolpropane; polytetramethylene ether glycol (PTMEG),
preferably having a molecular weight from about 250 to about 3900;
and mixtures thereof.
[0070] Suitable amine chain-extending (curing) agents that can be
used in chain-extending the polyurethane prepolymer include, but
are not limited to, unsaturated diamines such as
4,4'-diamino-diphenylmethane (i.e., 4,4'-methylene-dianiline or
"MDA"), m-phenylenediamine, p-phenylenediamine, 1,2- or
1,4-bis(sec-butylamino)benzene, 3,5-diethyl-(2,4- or 2,6-)
toluenediamine or "DETDA", 3,5-dimethylthio-(2,4- or
2,6-)toluenediamine, 3,5-diethylthio-(2,4- or 2,6-)toluenediamine,
3,3'-dimethyl-4,4'-diamino-diphenylmethane,
3,3'-diethyl-5,5'-dimethyl 4,4'-diamino-diphenylmethane (i.e.,
4,4'-methylene-bis(2-ethyl-6-methyl-benezeneamine)),
3,3'-dichloro-4,4'-diamino-diphenylmethane (i.e.,
4,4'-methylene-bis(2-chloroaniline) or "MOCA"),
3,3',5,5'-tetraethyl-4,4'-diamino-diphenylmethane (i.e.,
4,4'-methylene-bis(2,6-diethylaniline),
2,2'-dichloro-3,3',5,5'-tetraethyl-4,4'-diamino-diphenylmethane
(i.e., 4,4'-methylene-bis(3-chloro-2,6-diethyleneaniline) or
"MCDEA"), 3,3T-diethyl-5,5'-dichloro-4,4'-diamino-diphenylmethane,
or "MDEA"),
3,3'-dichloro-2,2',6,6'-tetraethyl-4,4'-diamino-diphenylmethane,
3,3'-dichloro-4,4'-diamino-diphenylmethane,
4,4'-methylene-bis(2,3-dichloroaniline) (i.e.,
2,2',3,3'-tetrachloro-4,4'-diamino-diphenylmethane or "MDCA"),
4,4'-bis(sec-butylamino)-diphenylmethane,
N,N'-dialkylamino-diphenylmethane,
trimethyleneglycol-di(p-aminobenzoate),
polyethyleneglycol-di(p-aminobenzoate),
polytetramethyleneglycol-di(p-aminobenzoate); saturated diamines
such as ethylene diamine, 1,3-propylene diamine,
2-methyl-pentamethylene diamine, hexamethylene diamine, 2,2,4- and
2,4,4-trimethyl-1,6-hexane diamine, imino-bis(propylamine),
imido-bis(propylamine), methylimino-bis(propylamine) (i.e.,
N-(3-aminopropyl)-N-methyl-1,3-propanediamine),
1,4-bis(3-aminopropoxy)butane (i.e.,
3,3'-[1,4-butanediylbis-(oxy)bis]-1-propanamine),
diethyleneglycol-bis(propylamine) (i.e.,
diethyleneglycol-di(aminopropyl)ether),
4,7,10-trioxatridecane-1,13-diamine,
1-methyl-2,6-diamino-cyclohexane, 1,4-diamino-cyclohexane,
poly(oxyethylene-oxypropylene) diamines, 1,3- or
1,4-bis(methylamino)-cyclohexane, isophorone diamine, 1,2- or
1,4-bis(sec-butylamino)-cyclohexane, N,N'-diisopropyl-isophorone
diamine, 4,4'-diamino-dicyclohexylmethane,
3,3'-dimethyl-4,4'-diamino-dicyclohexylmethane,
3,3'-dichloro-4,4'-diamino-dicyclohexylmethane,
N,N'-dialkylamino-dicyclohexylmethane, polyoxyethylene diamines,
3,3'-diethyl-5,5'-dimethyl-4,4'-diamino-dicyclohexylmethane,
polyoxypropylene diamines,
3,3'-diethyl-5,5'-dichloro-4,4'-diamino-dicyclohexylmethane,
polytetramethylene ether diamines,
3,3',5,5'-tetraethyl-4,4'-diamino-dicyclohexylmethane (i.e.,
4,4'-methylene-bis(2,6-diethylaminocyclohexane)),
3,3'-dichloro-4,4'-diamino-dicyclohexylmethane,
2,2'-dichloro-3,3',5,5'-tetraethyl-4,4'-diamino-dicyclohexylmethane,
(ethylene oxide)-capped polyoxypropylene ether diamines,
2,2',3,3'-tetrachloro-4,4'-diamino-dicyclohexylmethane,
4,4'-bis(sec-butylamino)-dicyclohexylmethane; triamines such as
diethylene triamine, dipropylene triamine, (propylene oxide)-based
triamines (i.e., polyoxypropylene triamines),
N-(2-aminoethyl)-1,3-propylenediamine (i.e., N.sub.3-amine),
glycerin-based triamines, (all saturated); tetramines such as
N,N'-bis(3-aminopropyl)ethylene diamine (i.e., N.sub.4-amine) (both
saturated), triethylene tetramine; and other polyamines such as
tetraethylene pentamine (also saturated). One suitable
amine-terminated chain-extending agent is Ethacure 300.TM.
(dimethylthiotoluenediamine or a mixture of
2,6-diamino-3,5-dimethylthiotoluene and
2,4-diamino-3,5-dimethylthiotoluene.) The amine curing agents used
as chain extenders normally have a cyclic structure and a low
molecular weight (250 or less).
[0071] When the polyurethane prepolymer is reacted with
hydroxyl-terminated curing agents during the chain-extending step,
as described above, the resulting polyurethane composition contains
urethane linkages. On the other hand, when the polyurethane
prepolymer is reacted with amine-terminated curing agents during
the chain-extending step, any excess isocyanate groups in the
prepolymer will react with the amine groups in the curing agent.
The resulting polyurethane composition contains urethane and urea
linkages and may be referred to as a polyurethane/urea hybrid. The
concentration of urethane and urea linkages in the hybrid
composition may vary. In general, the hybrid composition may
contain a mixture of about 10 to 90% urethane and about 90 to 10%
urea linkages.
[0072] As discussed above, a heterogeneous polyurethane composition
comprising aromatic and aliphatic polyurethanes may be used in
accordance with this invention. For example, the aromatic
polyurethane may be used in an amount of at least about 10% by
weight based on total weight of composition and is generally
present in an amount of about 10% to about 100%, or an amount
within a range having a lower limit of 20% or 30% or 40% or 50% or
60% or 70% or 75% and an upper limit of 80% or 85% or 90% or 95% or
100%. Preferably, the concentration of aromatic polyurethane is at
least 40% and more preferably about 40% to about 100%, and even
more preferably at least 75% or about 75% to about 100%. Meanwhile,
the aliphatic polyurethane may be used in an amount of at least
about 10% by weight based on total weight of composition and is
generally present in an amount of about 10% to about 100%, or an
amount within a range having a lower limit of 20% or 30% or 40% or
50% or 60% or 70% or 75% and an upper limit of 80% or 85% or 90% or
95% or 100%. Preferably, the concentration of aliphatic
polyurethane is at least 40% and more preferably about 40% to about
100%, and even more preferably at least 75% or about 75% to about
100%.
[0073] In addition, the polyurethane compositions may contain
fillers, additives, and other ingredients that do not detract from
the properties of the final composition. These additional materials
include, but are not limited to, catalysts, wetting agents,
coloring agents, optical brighteners, cross-linking agents,
whitening agents such as titanium dioxide and zinc oxide,
ultraviolet (UV) light absorbers, hindered amine light stabilizers,
defoaming agents, processing aids, surfactants, and other
conventional additives. Other suitable additives include
antioxidants, stabilizers, softening agents, plasticizers,
including internal and external plasticizers, impact modifiers,
foaming agents, density-adjusting fillers, reinforcing materials,
compatibilizers, and the like. Some examples of useful fillers
include zinc oxide, zinc sulfate, barium carbonate, barium sulfate,
calcium oxide, calcium carbonate, clay, tungsten, tungsten carbide,
silica, and mixtures thereof. Rubber regrind (recycled core
material) and polymeric, ceramic, metal, and glass microspheres
also may be used. Generally, the additives will be present in the
composition in an amount between about 1 and about 70 weight
percent based on total weight of the composition depending upon the
desired properties.
[0074] Ethylene Acid Copolymers
[0075] As discussed above, in one preferred embodiment, a
heterogeneous polyurethane composition may be made. In another
preferred embodiment, the outer cover layer is made of a
heterogeneous composition comprising a first ethylene acid
copolymer ionomer and a second ethylene acid copolymer ionomer. The
intermediate layer also may be made of a heterogeneous ethylene
acid copolymer ionomer composition. For example, the first
composition may contain an ethylene acid copolymer ionomer having
less than 70% neutralization ("Compound A") and the second
composition may contain an ethylene acid copolymer ionomer having
greater than 70% neutralization ("Compound B").
[0076] Suitable ionomer compositions include partially-neutralized
ionomers and highly-neutralized ionomers (HNPs), including ionomers
formed from blends of two or more partially-neutralized ionomers,
blends of two or more highly-neutralized ionomers, and blends of
one or more partially-neutralized ionomers with one or more
highly-neutralized ionomers. For purposes of the present
disclosure, "HNP" refers to an acid copolymer after at least 70% of
all acid groups present in the composition are neutralized.
[0077] Preferred ionomers are salts of O/X- and O/X/Y-type acid
copolymers, wherein O is an .alpha.-olefin, X is a C.sub.3-C.sub.8
.alpha.,.beta.-ethylenically unsaturated carboxylic acid, and Y is
a softening monomer. O is preferably selected from ethylene and
propylene. X is preferably selected from methacrylic acid, acrylic
acid, ethacrylic acid, crotonic acid, and itaconic acid.
Methacrylic acid and acrylic acid are particularly preferred. Y is
preferably selected from (meth) acrylate and alkyl (meth) acrylates
wherein the alkyl groups have from 1 to 8 carbon atoms, including,
but not limited to, n-butyl (meth) acrylate, isobutyl (meth)
acrylate, methyl (meth) acrylate, and ethyl (meth) acrylate.
[0078] Preferred O/X and O/X/Y-type copolymers include, without
limitation, ethylene acid copolymers, such as
ethylene/(meth)acrylic acid, ethylene/(meth)acrylic acid/maleic
anhydride, ethylene/(meth)acrylic acid/maleic acid mono-ester,
ethylene/maleic acid, ethylene/maleic acid mono-ester,
ethylene/(meth)acrylic acid/n-butyl (meth)acrylate,
ethylene/(meth)acrylic acid/iso-butyl (meth)acrylate,
ethylene/(meth)acrylic acid/methyl (meth)acrylate,
ethylene/(meth)acrylic acid/ethyl (meth)acrylate terpolymers, and
the like. The term, "copolymer," as used herein, includes polymers
having two types of monomers, those having three types of monomers,
and those having more than three types of monomers. Preferred a,
.beta.-ethylenically unsaturated mono- or dicarboxylic acids are
(meth) acrylic acid, ethacrylic acid, maleic acid, crotonic acid,
fumaric acid, itaconic acid. (Meth) acrylic acid is most preferred.
As used herein, "(meth) acrylic acid" means methacrylic acid and/or
acrylic acid. Likewise, "(meth) acrylate" means methacrylate and/or
acrylate.
[0079] In a particularly preferred version, highly neutralized E/X-
and E/X/Y-type acid copolymers, wherein E is ethylene, X is a
C.sub.3-C.sub.8 .alpha.,.beta.-ethylenically unsaturated carboxylic
acid, and Y is a softening monomer are used. X is preferably
selected from methacrylic acid, acrylic acid, ethacrylic acid,
crotonic acid, and itaconic acid. Methacrylic acid and acrylic acid
are particularly preferred. Y is preferably an acrylate selected
from alkyl acrylates and aryl acrylates and preferably selected
from (meth) acrylate and alkyl (meth) acrylates wherein the alkyl
groups have from 1 to 8 carbon atoms, including, but not limited
to, n-butyl (meth) acrylate, isobutyl (meth) acrylate, methyl
(meth) acrylate, and ethyl (meth) acrylate. Preferred E/X/Y-type
copolymers are those wherein X is (meth) acrylic acid and/or Y is
selected from (meth) acrylate, n-butyl (meth) acrylate, isobutyl
(meth) acrylate, methyl (meth) acrylate, and ethyl (meth) acrylate.
More preferred E/X/Y-type copolymers are ethylene/(meth) acrylic
acid/n-butyl acrylate, ethylene/(meth) acrylic acid/methyl
acrylate, and ethylene/(meth) acrylic acid/ethyl acrylate.
[0080] The amount of ethylene in the acid copolymer is typically at
least 15 wt. %, preferably at least 25 wt. %, more preferably least
40 wt. %, and even more preferably at least 60 wt. %, based on
total weight of the copolymer. The amount of C.sub.3 to C.sub.8
.alpha.,.beta.-ethylenically unsaturated mono- or dicarboxylic acid
in the acid copolymer is typically from 1 wt. % to 35 wt. %,
preferably from 5 wt. % to 30 wt. %, more preferably from 5 wt. %
to 25 wt. %, and even more preferably from 10 wt. % to 20 wt. %,
based on total weight of the copolymer. The amount of optional
softening comonomer in the acid copolymer is typically from 0 wt. %
to 50 wt. %, preferably from 5 wt. % to 40 wt. %, more preferably
from 10 wt. % to 35 wt. %, and even more preferably from 20 wt. %
to 30 wt. %, based on total weight of the copolymer. "Low acid" and
"high acid" ionomeric polymers, as well as blends of such ionomers,
may be used. In general, low acid ionomers are considered to be
those containing 16 wt. % or less of acid moieties, whereas high
acid ionomers are considered to be those containing greater than 16
wt. % of acid moieties.
[0081] The various O/X, E/X, O/X/Y, and E/X/Y-type copolymers are
at least partially neutralized with a cation source, optionally in
the presence of a high molecular weight organic acid, such as those
disclosed in U.S. Pat. No. 6,756,436, the entire disclosure of
which is hereby incorporated herein by reference. The acid
copolymer can be reacted with the optional high molecular weight
organic acid and the cation source simultaneously, or prior to the
addition of the cation source. Suitable cation sources include, but
are not limited to, metal ion sources, such as compounds of alkali
metals, alkaline earth metals, transition metals, and rare earth
elements; ammonium salts and monoamine salts; and combinations
thereof. Preferred cation sources are compounds of magnesium,
sodium, potassium, cesium, calcium, barium, manganese, copper,
zinc, lead, tin, aluminum, nickel, chromium, lithium, and rare
earth metals. The amount of cation used in the composition is
readily determined based on desired level of neutralization. As
discussed above, for HNP compositions, the acid groups are
neutralized to 70% or greater, preferably 70 to 100%, more
preferably 90 to 100%. In one embodiment, an excess amount of
neutralizing agent, that is, an amount greater than the
stoichiometric amount needed to neutralize the acid groups, may be
used. That is, the acid groups may be neutralized to 100% or
greater, for example 110% or 120% or greater. In other embodiments,
partially-neutralized compositions are prepared, wherein 10% or
greater, normally 30% or greater of the acid groups are
neutralized. When aluminum is used as the cation source, it is
preferably used at low levels with another cation such as zinc,
sodium, or lithium, since aluminum has a dramatic effect on melt
flow reduction and cannot be used alone at high levels. For
example, aluminum is used to neutralize about 10% of the acid
groups and sodium is added to neutralize an additional 90% of the
acid groups.
[0082] In a particular embodiment, ionomer composition includes an
ionomer selected from DuPont.RTM. HPF ESX 367, HPF 1000, HPF 2000,
HPF AD1035, HPF AD1035 Soft, HPF AD1040, and AD1172 ionomers,
commercially available from E. I. du Pont de Nemours and Company.
The coefficient of restitution ("COR"), compression, and surface
hardness of each of these materials, as measured on 1.55''
injection molded spheres aged two weeks at 23.degree. C./50% RH,
are given in Table 1 below.
TABLE-US-00001 TABLE 1 Solid Sphere Solid Sphere Solid Sphere Shore
D Surface Example COR Compression Hardness HPF 1000 0.830 115 54
HPF 2000 0.860 90 47 HPF AD1035 0.820 63 42 HPF AD1035 Soft 0.780
33 35 HPF AD 1040 0.855 135 60 HPF AD1172 0.800 32 37
[0083] For example, the cover or intermediate layer can be formed
from a blend of two or more ionomers. In a particular aspect of
this embodiment, the blend is a 50 wt %/50 wt % blend of two
different partially-neutralized ethylene/methacrylic acid
copolymers.
[0084] In another particular embodiment, the cover or intermediate
layer can be formed from a blend of one or more ionomers and a
maleic anhydride-grafted non-ionomeric polymer. In a particular
aspect of this embodiment, the non-ionomeric polymer is a
metallocene-catalyzed polymer. In another particular aspect of this
embodiment, the blend includes a partially-neutralized
ethylene/methacrylic acid copolymer and a maleic anhydride-grafted
metallocene-catalyzed polyethylene.
[0085] In yet another particular embodiment, the cover or
intermediate layer can be formed from a composition selected from
the group consisting of partially- and fully-neutralized ionomers
optionally blended with a maleic anhydride-grafted non-ionomeric
polymer; polyester elastomers; polyamide elastomers; and
combinations of two or more thereof.
[0086] Ionic plasticizers such as organic acids or salts of organic
acids, particularly fatty acids, may be added to the ionomer resin.
Such ionic plasticizers are used to make conventional ionomer
composition more processable as described in Rajagopalan et al.,
U.S. Pat. No. 6,756,436, the disclosure of which is hereby
incorporated by reference. In the present invention such ionic
plasticizers are optional. In one preferred embodiment, a
thermoplastic ionomer composition is made by neutralizing about 70
wt % or more of the acid groups without the use of any ionic
plasticizer. On the other hand, in some instances, it may be
desirable to add a small amount of ionic plasticizer, provided that
it does not adversely affect the heat-resistance properties of the
composition. For example, the ionic plasticizer may be added in an
amount of about 10 to about 50 weight percent (wt. %) of the
composition, more preferably 30 to 55 wt. %.
[0087] The organic acids may be aliphatic, mono- or
multi-functional (saturated, unsaturated, or multi-unsaturated)
organic acids. Salts of these organic acids may also be employed.
Suitable fatty acid salts include, for example, metal stearates,
laureates, oleates, palmitates, pelargonates, and the like. For
example, fatty acid salts such as zinc stearate, calcium stearate,
magnesium stearate, barium stearate, and the like can be used. The
salts of fatty acids are generally fatty acids neutralized with
metal ions. The metal cation salts provide the cations capable of
neutralizing (at varying levels) the carboxylic acid groups of the
fatty acids. Examples include the sulfate, carbonate, acetate and
hydroxide salts of metals such as barium, lithium, sodium, zinc,
bismuth, chromium, cobalt, copper, potassium, strontium, titanium,
tungsten, magnesium, cesium, iron, nickel, silver, aluminum, tin,
or calcium, and blends thereof. It is preferred the organic acids
and salts be relatively non-migratory (they do not bloom to the
surface of the polymer under ambient temperatures) and non-volatile
(they do not volatilize at temperatures required for
melt-blending).
[0088] Other suitable thermoplastic polymers that may be used to
form the cover and intermediate layers include, but are not limited
to, the following polymers (including homopolymers, copolymers, and
derivatives thereof.): (a) polyesters, particularly those modified
with a compatibilizing group such as sulfonate or phosphonate,
including modified poly(ethylene terephthalate), modified
poly(butylene terephthalate), modified poly(propylene
terephthalate), modified poly(trimethylene terephthalate), modified
poly(ethylene naphthenate), and those disclosed in U.S. Pat. Nos.
6,353,050, 6,274,298, and 6,001,930, the entire disclosures of
which are hereby incorporated herein by reference, and blends of
two or more thereof; (b) polyamides, polyamide-ethers, and
polyamide-esters, and those disclosed in U.S. Pat. Nos. 6,187,864,
6,001,930, and 5,981,654, the entire disclosures of which are
hereby incorporated herein by reference, and blends of two or more
thereof; (c) polyurethanes, polyureas, polyurethane-polyurea
hybrids, and blends of two or more thereof; (d) fluoropolymers,
such as those disclosed in U.S. Pat. Nos. 5,691,066, 6,747,110 and
7,009,002, the entire disclosures of which are hereby incorporated
herein by reference, and blends of two or more thereof; (e)
polystyrenes, such as poly(styrene-co-maleic anhydride),
acrylonitrile-butadiene-styrene, poly(styrene sulfonate),
polyethylene styrene, and blends of two or more thereof; (f)
polyvinyl chlorides and grafted polyvinyl chlorides, and blends of
two or more thereof; (g) polycarbonates, blends of
polycarbonate/acrylonitrile-butadiene-styrene, blends of
polycarbonate/polyurethane, blends of polycarbonate/polyester, and
blends of two or more thereof; (h) polyethers, such as polyarylene
ethers, polyphenylene oxides, block copolymers of alkenyl aromatics
with vinyl aromatics and polyamicesters, and blends of two or more
thereof; (i) polyimides, polyetherketones, polyamideimides, and
blends of two or more thereof; and (j) polycarbonate/polyester
copolymers and blends.
[0089] Core Construction
[0090] As discussed above, the inner core is made preferably from a
thermoset rubber composition. In one embodiment, a two-layered or
dual-core is made, wherein the inner core is surrounded by an outer
core layer. Thermoplastic polymers such as highly-neutralized
polymers (HNPs), for example, ethylene acid copolymers containing
acid groups, wherein 90% or greater of the acid groups have been
neutralized, also can be used.
[0091] Suitable thermoset rubber materials that may be used to form
the outer core layer include, but are not limited to,
polybutadiene, polyisoprene, ethylene propylene rubber ("EPR"),
ethylene-propylene-diene ("EPDM") rubber, styrene-butadiene rubber,
styrenic block copolymer rubbers (such as "SI", "SIS", "SB", "SBS",
"SIBS", and the like, where "S" is styrene, "I" is isobutylene, and
"B" is butadiene), polyalkenamers such as, for example,
polyoctenamer, butyl rubber, halobutyl rubber, polystyrene
elastomers, polyethylene elastomers, polyurethane elastomers,
polyurea elastomers, metallocene-catalyzed elastomers and
plastomers, copolymers of isobutylene and p-alkylstyrene,
halogenated copolymers of isobutylene and p-alkylstyrene,
copolymers of butadiene with acrylonitrile, polychloroprene, alkyl
acrylate rubber, chlorinated isoprene rubber, acrylonitrile
chlorinated isoprene rubber, and blends of two or more thereof.
Preferably, the outer core layer is formed from a polybutadiene
rubber composition.
[0092] The thermoset rubber composition may be cured using
conventional curing processes. Suitable curing processes include,
for example, peroxide-curing, sulfur-curing, high-energy radiation,
and combinations thereof. Preferably, the rubber composition
contains a free-radical initiator selected from organic peroxides,
high energy radiation sources capable of generating free-radicals,
and combinations thereof. In one preferred version, the rubber
composition is peroxide-cured. Suitable organic peroxides include,
but are not limited to, dicumyl peroxide;
n-butyl-4,4-di(t-butylperoxy) valerate;
1,1-di(t-butylperoxy)3,3,5-trimethylcyclohexane;
2,5-dimethyl-2,5-di(t-butylperoxy) hexane; di-t-butyl peroxide;
di-t-amyl peroxide; t-butyl peroxide; t-butyl cumyl peroxide;
2,5-dimethyl-2,5-di(t-butylperoxy)hexyne-3;
di(2-t-butyl-peroxyisopropyl)benzene; dilauroyl peroxide; dibenzoyl
peroxide; t-butyl hydroperoxide; and combinations thereof. In a
particular embodiment, the free radical initiator is dicumyl
peroxide, including, but not limited to Perkadox.RTM. BC,
commercially available from Akzo Nobel. Peroxide free-radical
initiators are generally present in the rubber composition in an
amount of at least 0.05 parts by weight per 100 parts of the total
rubber, or an amount within the range having a lower limit of 0.05
parts or 0.1 parts or 1 part or 1.25 parts or 1.5 parts or 2.5
parts or 5 parts by weight per 100 parts of the total rubbers, and
an upper limit of 2.5 parts or 3 parts or 5 parts or 6 parts or 10
parts or 15 parts by weight per 100 parts of the total rubber.
Concentrations are in parts per hundred (phr) unless otherwise
indicated. As used herein, the term, "parts per hundred," also
known as "phr" or "pph" is defined as the number of parts by weight
of a particular component present in a mixture, relative to 100
parts by weight of the polymer component. Mathematically, this can
be expressed as the weight of an ingredient divided by the total
weight of the polymer, multiplied by a factor of 100.
[0093] The rubber compositions may further include a reactive
cross-linking co-agent. Suitable co-agents include, but are not
limited to, metal salts of unsaturated carboxylic acids having from
3 to 8 carbon atoms; unsaturated vinyl compounds and polyfunctional
monomers (e.g., trimethylolpropane trimethacrylate); phenylene
bismaleimide; and combinations thereof. Particular examples of
suitable metal salts include, but are not limited to, one or more
metal salts of acrylates, diacrylates, methacrylates, and
dimethacrylates, wherein the metal is selected from magnesium,
calcium, zinc, aluminum, lithium, and nickel. In a particular
embodiment, the co-agent is selected from zinc salts of acrylates,
diacrylates, methacrylates, and dimethacrylates. In another
particular embodiment, the agent is zinc diacrylate (ZDA). When the
co-agent is zinc diacrylate and/or zinc dimethacrylate, the
co-agent is typically included in the rubber composition in an
amount within the range having a lower limit of 1 or 5 or 10 or 15
or 19 or 20 parts by weight per 100 parts of the total rubber, and
an upper limit of 24 or 25 or 30 or 35 or 40 or 45 or 50 or 60
parts by weight per 100 parts of the base rubber.
[0094] Radical scavengers such as a halogenated organosulfur,
organic disulfide, or inorganic disulfide compounds may be added to
the rubber composition. These compounds also may function as "soft
and fast agents." As used herein, "soft and fast agent" means any
compound or a blend thereof that is capable of making a core: 1)
softer (having a lower compression) at a constant "coefficient of
restitution" (COR); and/or 2) faster (having a higher COR at equal
compression), when compared to a core equivalently prepared without
a soft and fast agent. Preferred halogenated organosulfur compounds
include, but are not limited to, pentachlorothiophenol (PCTP) and
salts of PCTP such as zinc pentachlorothiophenol (ZnPCTP). Using
PCTP and ZnPCTP in golf ball inner cores helps produce softer and
faster inner cores. The PCTP and ZnPCTP compounds help increase the
resiliency and the coefficient of restitution of the core. In a
particular embodiment, the soft and fast agent is selected from
ZnPCTP, PCTP, ditolyl disulfide, diphenyl disulfide, dixylyl
disulfide, 2-nitroresorcinol, and combinations thereof.
[0095] The rubber composition also may include filler(s) such as
materials selected from carbon black, clay and nanoclay particles
as discussed above, talc (e.g., Luzenac HAR.RTM. high aspect ratio
talcs, commercially available from Luzenac America, Inc.), glass
(e.g., glass flake, milled glass, and microglass), mica and
mica-based pigments (e.g., Iriodin.RTM. pearl luster pigments,
commercially available from The Merck Group), and combinations
thereof. Metal fillers such as, for example, particulate; powders;
flakes; and fibers of copper, steel, brass, tungsten, titanium,
aluminum, magnesium, molybdenum, cobalt, nickel, iron, lead, tin,
zinc, barium, bismuth, bronze, silver, gold, and platinum, and
alloys and combinations thereof also may be added to the rubber
composition to adjust the specific gravity of the composition as
needed. In addition, the rubber compositions may include
antioxidants. Also, processing aids such as high molecular weight
organic acids and salts thereof may be added to the composition.
Suitable organic acids are aliphatic organic acids, aromatic
organic acids, saturated mono-functional organic acids, unsaturated
monofunctional organic acids, multi-unsaturated mono-functional
organic acids, and dimerized derivatives thereof. Particular
examples of suitable organic acids include, but are not limited to,
caproic acid, caprylic acid, capric acid, lauric acid, stearic
acid, behenic acid, erucic acid, oleic acid, linoleic acid,
myristic acid, benzoic acid, palmitic acid, phenylacetic acid,
naphthalenoic acid, and dimerized derivatives thereof. The organic
acids are aliphatic, mono-functional (saturated, unsaturated, or
multi-unsaturated) organic acids. Salts of these organic acids may
also be employed. The salts of organic acids include the salts of
barium, lithium, sodium, zinc, bismuth, chromium, cobalt, copper,
potassium, strontium, titanium, tungsten, magnesium, cesium, iron,
nickel, silver, aluminum, tin, or calcium, salts of fatty acids,
particularly stearic, behenic, erucic, oleic, linoelic or dimerized
derivatives thereof. It is preferred that the organic acids and
salts of the present invention be relatively non-migratory (they do
not bloom to the surface of the polymer under ambient temperatures)
and non-volatile (they do not volatilize at temperatures required
for melt-blending.) Other ingredients such as accelerators (for
example, tetra methylthiuram), processing aids, dyes and pigments,
wetting agents, surfactants, plasticizers, coloring agents,
fluorescent agents, chemical blowing and foaming agents, defoaming
agents, stabilizers, softening agents, impact modifiers,
antiozonants, as well as other additives known in the art may be
added to the rubber composition.
[0096] Examples of commercially-available polybutadiene rubbers
that can be used in accordance with this invention, include, but
are not limited to, BR 01 and BR 1220, available from BST
Elastomers of Bangkok, Thailand; SE BR 1220LA and SE BR1203,
available from DOW Chemical Co of Midland, Mich.; BUDENE 1207,
1207s, 1208, and 1280 available from Goodyear, Inc of Akron, Ohio;
BR 01, 51 and 730, available from Japan Synthetic Rubber (JSR) of
Tokyo, Japan; BUNA CB 21, CB 22, CB 23, CB 24, CB 25, CB 29 MES, CB
60, CB Nd 60, CB 55 NF, CB 70 B, CB KA 8967, and CB 1221, available
from Lanxess Corp. of Pittsburgh. Pa.; BR1208, available from LG
Chemical of Seoul, South Korea; UBEPOL BR130B, BR150, BR150B,
BR150L, BR230, BR360L, BR710, and VCR617, available from UBE
Industries, Ltd. of Tokyo, Japan; EUROPRENE NEOCIS BR 60, INTENE 60
AF and P30AF, and EUROPRENE BR HV80, available from Polimeri Europa
of Rome, Italy; AFDENE 50 and NEODENE BR40, BR45, BR50 and BR60,
available from Karbochem (PTY) Ltd. of Bruma, South Africa; KBR 01,
NdBr 40, NdBR-45, NdBr 60, KBR 710S, KBR 710H, and KBR 750,
available from Kumho Petrochemical Co., Ltd. Of Seoul, South Korea;
and DIENE 55NF, 70AC, and 320 AC, available from Firestone Polymers
of Akron, Ohio.
[0097] In one embodiment, as discussed above, the core composition
comprises polybutadiene rubber, zinc diacrylate, zinc oxide,
stearic acid and/or zinc stearate, a filler such as barium sulfate,
a peroxide or other cross-linking initiator, and optionally an
organosulfur compound such as zinc pentachlorothiophenol (PCTP),
and optionally an antioxidant, and colorant pigment or dye. The
ingredients are mixed in an internal mixer such a Farrell Intermix
mixer, two-roll mill, or any other suitable mixer for mixing
rubber. The order of addition of ingredients and the time and
temperature of mixing are important. Generally, the rubber and all
ingredients (except peroxide) are mixed from about 1 to 30 minutes,
and more preferably about 2 to 10 minutes at a temperature of about
room temperature to about 200.degree. F. The heat-sensitive
peroxide initiator is added at a temperature of about 210.degree.
F. or less, preferably about 200.degree. F. or less and mixed for a
period of time that ensures good dispersion and uniform mixing of
all ingredients. The temperature of the batch should not rise above
the decomposition temperature of the peroxide, generally not
exceeding 220.degree. F., more preferably not above 210.degree. F.,
whereupon the batch is discharged from the mixer onto a two-roll
mill or a twin-screw sheeter or other device that allows the batch
to cool for storage and testing prior to subsequent processing into
preforms (generally, extrusion or barwell) and then molding.
Alternatively, the subsequent processing steps of extrusion and
molding may take place directly upon removal from the mixer, while
the batch is still warm.
Test Methods
[0098] Test Methods
[0099] Hardness.
[0100] The center hardness of a core is obtained according to the
following procedure. The core is gently pressed into a
hemispherical holder having an internal diameter approximately
slightly smaller than the diameter of the core, such that the core
is held in place in the hemispherical portion of the holder while
concurrently leaving the geometric central plane of the core
exposed. The core is secured in the holder by friction, such that
it will not move during the cutting and grinding steps, but the
friction is not so excessive that distortion of the natural shape
of the core would result. The core is secured such that the parting
line of the core is roughly parallel to the top of the holder. The
diameter of the core is measured 90 degrees to this orientation
prior to securing. A measurement is also made from the bottom of
the holder to the top of the core to provide a reference point for
future calculations. A rough cut is made slightly above the exposed
geometric center of the core using a band saw or other appropriate
cutting tool, making sure that the core does not move in the holder
during this step. The remainder of the core, still in the holder,
is secured to the base plate of a surface grinding machine. The
exposed `rough` surface is ground to a smooth, flat surface,
revealing the geometric center of the core, which can be verified
by measuring the height from the bottom of the holder to the
exposed surface of the core, making sure that exactly half of the
original height of the core, as measured above, has been removed to
within 0.004 inches. Leaving the core in the holder, the center of
the core is found with a center square and carefully marked and the
hardness is measured at the center mark according to ASTM D-2240.
Additional hardness measurements at any distance from the center of
the core can then be made by drawing a line radially outward from
the center mark, and measuring the hardness at any given distance
along the line, typically in 2 mm increments from the center. The
hardness at a particular distance from the center should be
measured along at least two, preferably four, radial arms located
180.degree. apart, or 90.degree. apart, respectively, and then
averaged. All hardness measurements performed on a plane passing
through the geometric center are performed while the core is still
in the holder and without having disturbed its orientation, such
that the test surface is constantly parallel to the bottom of the
holder, and thus also parallel to the properly aligned foot of the
durometer.
[0101] The outer surface hardness of a golf ball layer is measured
on the actual outer surface of the layer and is obtained from the
average of a number of measurements taken from opposing
hemispheres, taking care to avoid making measurements on the
parting line of the core or on surface defects, such as holes or
protrusions. Hardness measurements are made pursuant to ASTM D-2240
"Indentation Hardness of Rubber and Plastic by Means of a
Durometer." Because of the curved surface, care must be taken to
ensure that the golf ball or golf ball sub-assembly is centered
under the durometer indenter before a surface hardness reading is
obtained. A calibrated, digital durometer, capable of reading to
0.1 hardness units is used for the hardness measurements. The
digital durometer must be attached to, and its foot made parallel
to, the base of an automatic stand. The weight on the durometer and
attack rate conforms to ASTM D-2240.
[0102] In certain embodiments, a point or plurality of points
measured along the "positive" or "negative" gradients may be above
or below a line fit through the gradient and its outermost and
innermost hardness values. In an alternative preferred embodiment,
the hardest point along a particular steep "positive" or "negative"
gradient may be higher than the value at the innermost portion of
the inner core (the geometric center) or outer core layer (the
inner surface)--as long as the outermost point (i.e., the outer
surface of the inner core) is greater than (for "positive") or
lower than (for "negative") the innermost point (i.e., the
geometric center of the inner core or the inner surface of the
outer core layer), such that the "positive" and "negative"
gradients remain intact.
[0103] As discussed above, the direction of the hardness gradient
of a golf ball layer is defined by the difference in hardness
measurements taken at the outer and inner surfaces of a particular
layer. The center hardness of an inner core and hardness of the
outer surface of an inner core in a single-core ball or outer core
layer are readily determined according to the test procedures
provided above. The outer surface of the inner core layer (or other
optional intermediate core layers) in a dual-core ball are also
readily determined according to the procedures given herein for
measuring the outer surface hardness of a golf ball layer, if the
measurement is made prior to surrounding the layer with an
additional core layer. Once an additional core layer surrounds a
layer of interest, the hardness of the inner and outer surfaces of
any inner or intermediate layers can be difficult to determine.
Therefore, for purposes of the present invention, when the hardness
of the inner or outer surface of a core layer is needed after the
inner layer has been surrounded with another core layer, the test
procedure described above for measuring a point located 1 mm from
an interface is used. Likewise, the midpoint of a core layer is
taken at a point equidistant from the inner surface and outer
surface of the layer to be measured, most typically an outer core
layer. Once again, when one or more core layers surround a layer of
interest, the exact midpoint may be difficult to determine,
therefore, for the purposes of the present invention, the
measurement of "midpoint" hardness of a layer is taken within plus
or minus 1 mm of the measured midpoint of the layer.
[0104] Also, it should be understood that there is a fundamental
difference between "material hardness" and "hardness as measured
directly on a golf ball." For purposes of the present invention,
material hardness is measured according to ASTM D2240 and generally
involves measuring the hardness of a flat "slab" or "button" formed
of the material. Surface hardness as measured directly on a golf
ball (or other spherical surface) typically results in a different
hardness value. The difference in "surface hardness" and "material
hardness" values is due to several factors including, but not
limited to, ball construction (that is, core type, number of cores
and/or cover layers, and the like); ball (or sphere) diameter; and
the material composition of adjacent layers. It also should be
understood that the two measurement techniques are not linearly
related and, therefore, one hardness value cannot easily be
correlated to the other. Shore hardness (for example, Shore C or
Shore D hardness) was measured according to the test method ASTM
D-2240.
[0105] Compression.
[0106] As disclosed in Jeff Dalton's Compression by Any Other Name,
Science and Golf IV, Proceedings of the World Scientific Congress
of Golf (Eric Thain ed., Routledge, 2002) ("J. Dalton"), several
different methods can be used to measure compression, including
Atti compression, Riehle compression, load/deflection measurements
at a variety of fixed loads and offsets, and effective modulus. For
purposes of the present invention, compression refers to Soft
Center Deflection Index ("SCDI"). The SCDI is a program change for
the Dynamic Compression Machine ("DCM") that allows determination
of the pounds required to deflect a core 10% of its diameter. The
DCM is an apparatus that applies a load to a core or ball and
measures the number of inches the core or ball is deflected at
measured loads. A crude load/deflection curve is generated that is
fit to the Atti compression scale that results in a number being
generated that represents an Atti compression. The DCM does this
via a load cell attached to the bottom of a hydraulic cylinder that
is triggered pneumatically at a fixed rate (typically about 1.0
ft/s) towards a stationary core. Attached to the cylinder is an
LVDT that measures the distance the cylinder travels during the
testing timeframe. A software-based logarithmic algorithm ensures
that measurements are not taken until at least five successive
increases in load are detected during the initial phase of the
test. The SCDI is a slight variation of this set up. The hardware
is the same, but the software and output has changed. With the
SCDI, the interest is in the pounds of force required to deflect a
core x amount of inches. That amount of deflection is 10% percent
of the core diameter. The DCM is triggered, the cylinder deflects
the core by 10% of its diameter, and the DCM reports back the
pounds of force required (as measured from the attached load cell)
to deflect the core by that amount. The value displayed is a single
number in units of pounds.
[0107] Coefficient of Restitution ("COR").
[0108] The COR is determined according to a known procedure,
wherein a golf ball or golf ball sub-assembly (for example, a golf
ball core) is fired from an air cannon at two given velocities and
a velocity of 125 ft/s is used for the calculations. Ballistic
light screens are located between the air cannon and steel plate at
a fixed distance to measure ball velocity. As the ball travels
toward the steel plate, it activates each light screen and the
ball's time period at each light screen is measured. This provides
an incoming transit time period which is inversely proportional to
the ball's incoming velocity. The ball makes impact with the steel
plate and rebounds so it passes again through the light screens. As
the rebounding ball activates each light screen, the ball's time
period at each screen is measured. This provides an outgoing
transit time period which is inversely proportional to the ball's
outgoing velocity. The COR is then calculated as the ratio of the
ball's outgoing transit time period to the ball's incoming transit
time period (COR=V.sub.out/V.sub.in=T.sub.in/T.sub.out).
[0109] When numerical lower limits and numerical upper limits are
set forth herein, it is contemplated that any combination of these
values may be used. Other than in the operating examples, or unless
otherwise expressly specified, all of the numerical ranges,
amounts, values and percentages such as those for amounts of
materials and others in the specification may be read as if
prefaced by the word "about" even though the term "about" may not
expressly appear with the value, amount or range. Accordingly,
unless indicated to the contrary, the numerical parameters set
forth in the specification and attached claims are approximations
that may vary depending upon the desired properties sought to be
obtained by the present invention.
[0110] All patents, publications, test procedures, and other
references cited herein, including priority documents, are fully
incorporated by reference to the extent such disclosure is not
inconsistent with this invention and for all jurisdictions in which
such incorporation is permitted.
[0111] It is understood that the compositions and golf ball
products described and illustrated herein represent only some
embodiments of the invention. It is appreciated by those skilled in
the art that various changes and additions can be made to
compositions and products without departing from the spirit and
scope of this invention. It is intended that all such embodiments
be covered by the appended claims.
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