Title: Golf ball with vapor barrier layer
Abstract: A multi-layer golf ball comprising a core, a water vapor barrier layer and a cover is provided. The core may have any construction and may have multiple layers. The core may also have a solid or liquid center or wound layers, and may be constructed from a polybutadiene with mid to high Mooney viscosity. The water vapor barrier layer preferably comprises a terpolymer of ethylene, a softening acrylate class ester and methacrylic acid. th. Preferably, the water vapor barrier layer has an acid content of about 3% by weight to about 25% by weight.
Patent Number: 7,004,855 Issued on 02/28/2006 to Jordan
| Inventors:
|
Jordan; Michael D. (East Greenwich, RI)
|
| Assignee:
|
Acushnet Company (Fairhaven, MA)
|
| Appl. No.:
|
696475 |
| Filed:
|
October 29, 2003 |
| Current U.S. Class: |
473/374 |
| Current Intern'l Class: |
A63B 37/06 (20060101) |
| Field of Search: |
473/374,373,368,367,376
|
References Cited [Referenced By]
U.S. Patent Documents
| 3241834 | Mar., 1966 | Stingley.
| |
| 3313545 | Apr., 1967 | Bartsch.
| |
| 5779561 | Jul., 1998 | Sullivan et al.
| |
| 5820488 | Oct., 1998 | Sullivan et al.
| |
| 5830087 | Nov., 1998 | Sullivan et al.
| |
| 5875891 | Mar., 1999 | Snell.
| |
| 5885172 | Mar., 1999 | Hebert et al.
| |
| 5897884 | Apr., 1999 | Calabria et al.
| |
| 5919100 | Jul., 1999 | Boehm et al.
| |
| 6132324 | Oct., 2000 | Hebert et al.
| |
| 6306968 | Oct., 2001 | Bellinger et al.
| |
| Foreign Patent Documents |
| WO 00/2351/9 | Apr., 2000 | WO.
| |
| WO 01/2912/9 | Apr., 2001 | WO.
| |
Primary Examiner: Gorden; Raeann
Parent Case Text
STATEMENT OF RELATED PATENT APPLICATION
This utility patent application is a divisional application of co-pending application
Ser. No. 10/077,081, filed Feb. 15, 2002 which is a continuation-in-part of patent
application entitled "Low Spin Soft Compression Performance Golf Ball" filed on
Nov. 16, 2001 bearing Ser. No. 09/992,448, now abandoned. The parent applications
are hereby incorporated by reference in their entirety.
Claims
What is claimed is:
1. A golf ball comprising a core, a water vapor barrier layer and a cover, wherein
the water vapor barrier layer has a moisture vapor transmission rate that is lower
than that of the cover and the water vapor barrier layer comprises a non-ionomeric
terpolymer of ethylene, a softening acrylate class ester such as methyl acrylate,
n-butyl-acrylate or iso-butyl-acrylate, and a carboxylic acid such as acrylic acid
or methacrylic acid.
2. The golf ball set forth in claim 1, wherein the terpolymer is a terpolymer
of ethylene, methyl acrylate and acrylic acid.
3. The golf ball as set forth in claim 1, wherein the acid level by weight in
the terpolymer is in the range of about 3% to about 25%.
4. The golf ball as set forth in claim 3, wherein the acid level by weight in
the terpolymer is in the range of about 4% to about 15%.
5. The golf ball as set forth in claim 4, wherein the acid level by weight in
the terpolymer is in the range of about 7% to about 11%.
6. The golf ball set forth in claim 1, wherein the terpolymer has a melt flow
index in the range between about 1 gram/10 minutes to about 500 grams/10 minutes.
7. The golf ball set forth in claim 6, wherein the melt flow index of the terpolymer
is in the range of about 5 grams/10 minutes to about 20 grams/10 minutes.
8. A golf ball comprising a core, a water vapor barrier layer and a cover, wherein
the water vapor barrier layer has a moisture vapor transmission rate that is lower
than that of the cover and the water vapor barrier layer comprises a blend of a
terpolymer of ethylene, a softening acrylate class ester, and a carboxylic acid
having a melt flow index in the range of about 5-20 g/10 mm and a non-ionomeric
copolymer of ethylene and methacrylic acid.
9. The golf ball as set forth in claim 8, wherein the terpolymer is present in
an amount of about 25%, 50% or 75% and the non-ionomeric copolymer is present in
an amount of about 75%, 50% or 25%.
Description
FIELD OF THE INVENTION
The present invention relates to a novel structure for a golf ball, and more
particularly to a golf ball with a thin moisture vapor barrier layer.
BACKGROUND OF THE INVENTION
Solid core golf balls are well known in the art. Typically, the core is made
from polybutadiene rubber material, which provides the primary source of resiliency
for the golf ball. U.S. Pat. Nos. 3,241,834 and 3,313,545 disclose the early work
in polybutadiene chemistry. It is also known in the art that increasing the cross-link
density of polybutadiene can increase the resiliency of the core. The core is typically
protected by a cover from repeated impacts from golf clubs. The golf ball may comprise
additional layers, which can be an outer core or an inner cover layer. One or more
of these additional layers may be a wound layer of stretched elastic windings to
increase the ball's resiliency.
A known drawback of polybutadiene cores cross-linked with peroxide and/or zinc
diacrylate is that this material is adversely affected by moisture. Water moisture
vapor reduces the resiliency of the cores and degrades its properties. A polybutadiene
core will absorb water and loose its resilience. Thus, these cores must be covered
quickly to maintain optimum ball properties. The cover is typically made from ionomer
resins, balata, and urethane, among other materials. The ionomer covers, particularly
the harder ionomers, offer some protection against the penetration of water vapor.
However, it is more difficult to control or impart spin to balls with hard covers.
Conventional urethane covers, on the other hand, while providing better ball control,
offer less resistance to water vapor than ionomer covers.
Prolonged exposure to high humidity and elevated temperature may be sufficient
to allow water vapor to invade the cores of some commercially available golf balls.
For example at 110° F. and 90% humidity for a sixty day period, significant
amounts of moisture enter the cores and reduce the initial velocity of the balls
by 1.8 ft/s to 4.0 ft/s or greater. The change in compression may vary from 5 PGA
to about 10 PGA or greater. The absorbed water vapor also reduces the coefficient
of restitution (COR) of the ball.
Several prior patents have addressed the water vapor absorption problem.
U.S. Pat. No. 5,820,488 discloses a golf ball with a solid inner core, an outer
core and a water vapor barrier layer disposed therebetween. The water vapor barrier
layer preferably has a water vapor transmission rate lower than that of the cover
layer. The water vapor barrier layer can be a polyvinylidene chloride (PVDC) layer.
It can also be formed by an in situ reaction between a barrier-forming material
and the outer surface of the core. Alternatively, the water vapor barrier layer
can be a vermiculite layer. U.S. Pat. Nos. 5,885,172 and 6,132,324 disclose, among
other things, a golf ball with a polybutadiene or wound core with an ionomer resin
inner cover and a relatively soft outer cover. The hard ionomer inner cover offers
some resistance to water vapor penetration and the soft outer cover provides the
desirable ball control. Additionally, U.S. Pat. No. 5,875,891 discloses an impermeable
packaging for golf balls. The impermeable packaging acts as a moisture barrier
limiting moisture absorption by golf balls during storage but not during use.
It is also desirable to minimize the thickness of the water barrier layer such
that other properties of the ball are unaffected. None of these references, however,
discloses an efficient way to make a thin layer of water vapor barrier layer, that
otherwise would not alter the performance of the ball.
Hence, there remains a need for other golf balls with an improved water vapor
barrier layer and improved methods for applying a water vapor barrier layer on
to the core of the golf ball.
SUMMARY OF THE INVENTION
The present invention is directed to a golf ball comprising a core, a cover and
a thin film of moisture vapor barrier with a moisture vapor transmission rate preferably
lower than that of the cover to decrease the amount of moisture penetrating into
the core of the golf ball. The moisture vapor barrier layer preferably comprises
a non-ionomeric copolymer of ethylene and methacrylic acid. The moisture vapor
barrier layer may also comprise a non-ionomeric terpolymer of ethylene, a softening
acrylate class ester such as methyl acrylate, n-butyl-acrylate or iso-butyl-acrylate,
and a carboxylic acid such as acrylic acid or methacrylic acid. The moisture vapor
barrier layer may further comprise a non-ionomeric copolymer of ethylene and acrylic
acid. Alternatively, the moisture vapor barrier layer may comprise all three materials.
In accordance to another aspect of the invention, the preferred copolymer of ethylene
and methacrylic acid is polyethylene methacrylic acid resin.
In accordance to another aspect of the invention, the preferred moisture vapor
barrier materials have about 3% to about 25% of acid by weight, more preferably
in the range of about 4% to 15%, and most preferably about 7% to about 11% of acid
by weight. The preferred copolymers also have high melt flow index. High melt flow
index of the preferred materials helps to reduce the thickness of the moisture
vapor barrier layer. A readily apparent advantage of having a thin barrier layer
is that it does not significantly alter the predetermined and desired properties
of the designed golf ball. Preferably, the moisture vapor barrier has a thickness
of about 0.020 inch to about 0.005 inch. Preferably, the moisture vapor barrier
layer is made from two molded half shells that are compression-molded on to the core.
In accordance to another aspect of the invention, the moisture vapor barrier
can
be an intermediate layer, an inner cover layer, an outer core layer, a core coating
or an outer cover coating. The present invention is also directed to a golf ball
having a relatively large solid polybutadiene core, a thin moisture vapor barrier
layer with a thermoset urethane cover. Alternatively, the water vapor barrier layer
of the present invention can be used with any known core structures and covers.
BRIEF DESCRIPTION OF THE DRAWINGS
In the accompanying drawings, which form a part of the specification and are
to
be read in conjunction therewith and in which like reference numerals are used
to indicate like parts in the various views:
FIG. 1 is a front view of a dimpled golf ball in accordance to the present invention;
FIG. 2 is a cross-sectional view of the golf ball in FIG. 1 showing a solid
core surrounded by a thin moisture vapor barrier layer and a cover; and
FIG. 3 is a cross-sectional view of another golf ball in accordance to the present
invention showing a solid core with multiple wound layers surrounded by a thin
moisture vapor barrier layer.
DETAILED DESCRIPTION OF THE INVENTION
As shown generally in FIGS. 1 and 2, where like numbers designate like parts,
reference number
10 broadly designates a golf ball in accordance to the
present invention. Golf ball
10 preferably has a solid core
12, an
intermediate layer
14 and a cover
16.
Solid core
12 may comprise a single spherical element, or it may comprise
a core spherical element with one or more intermediate layers surrounding the spherical
element as shown in FIG. 3. Solid core
12 can be made from any suitable
core materials including thermoset plastics, such as natural rubber, polybutadiene
(PBD), polyisoprene, styrene-butadiene or styrene-propylene-diene rubber, and thermoplastics
such as ionomer resins, polyamides, polyesters, or a thermoplastic elastomer. Suitable
thermoplastic elastomers include Pebax®, Hytrel®, thermoplastic urethane,
and Kraton®, which are commercially available from Elf-Atochem, E. I. Du Pont
de Nemours and Company, various manufacturers, and Shell Chemical Company, respectively.
The core materials can also be formed from a castable material. Suitable castable
materials include those comprising a urethane, polyurea, epoxy, silicone, IPN'S, etc.
Additionally, suitable core materials may also include a reaction injection
molded polyurethane or polyurea, including those versions referred to as nucleated,
where a gas, typically nitrogen, is essentially whipped into at least one component
of the polyurethane, typically, the pre-polymer, prior to component injection into
a closed mold where essentially full reaction takes place resulting in a cured
polymer having reduced specific gravity. These materials are referred to as reaction
injection molded (RIM) materials. Alternatively, core
12 may include a liquid
center, such as center
12a shown in FIG. 3, and may have one or more
would layers, such as intermediate layers
12b and
12c.
Preferably, core
12 is made from a polybutadiene with a mid to
high range Mooney viscosity, which provides a soft but high velocity core. The
core may be blended with an organic sulfur plasticizer such as pentachlorolthiophenol
or a Zinc salt of pentachlorolthiophenol to further increase the softness and resiliency
of the core.
The core
12 of the golf ball of the present invention preferably has a
diameter in the range of about 1.53 inches to about 1.58 inches. In accordance
to one aspect of the present invention, the core is made from a polybutadiene rubber
that has a viscosity range from about 40 to about 60 Mooney. Polybutadiene rubber
with higher Mooney viscosity may also be used, so long as the viscosity of the
PBD does not reach a level where the high viscosity PBD clogs or otherwise adversely
interferes with the manufacturing machinery. It is contemplated that PBD with viscosity
less than 65 Mooney can be used with the present invention. A "Mooney" unit is
a unit used to measure the plasticity of raw or unvulcanized rubber. The plasticity
in a "Mooney" unit is equal to the torque, measured on an arbitrary scale, on a
disk in a vessel that contains rubber at a temperature of 100° C. and rotates
at two revolutions per minute. The measurement of Mooney viscosity is defined according
to ASTM D-1646.
Golf ball cores made with mid to high Mooney viscosity PBD material exhibit
increased resiliency, hence distance, without increasing the hardness of the ball.
Such cores are soft, i.e., compression of about 50-80, and when these soft cores
are incorporated into golf balls such cores generate very low spin and long distance
when struck by a driver. Cores with compression in the range of from about 30 to
about 50 are also within the range of the present invention.
In accordance to another aspect of the invention, the addition of an organic
sulfur
compound to the core further increases the resiliency and the coefficient of restitution
of the ball. Preferred organic sulfur compounds include, but not limited to, pentachlorothiophenol
(PCTP) and a salt of PCTP. A preferred salt of PCTP is ZnPCTP. The utilization
of PCTP and ZnPCTP in golf ball cores to produce soft and fast cores is disclosed
in co-pending U.S. application Ser. No. 09/951,963 filed on Sep. 13, 2001, and
is assigned to the same assignee as the present invention. This co-pending application
is incorporated by reference herein, in its entirety. A suitable PCTP is sold by
the Structol Company under the tradename A95. ZnPCTP is commercially available
from eChinaChem.
Commercial sources of suitable mid to high Mooney PBD sold by Bayer AG
include CB 23, which has a Mooney viscosity of about 51 and is a preferred PBD.
If desired, the polybutadiene can also be mixed with other elastomers known in
the art, such as natural rubber, styrene butadiene, and/or isoprene in order to
further modify the properties of the core. When a mixture of elastomers is used,
the amounts of other constituents in the core composition are based on 100 parts
by weight of the total elastomer mixture.
Metal salt diacrylates, dimethacrylates, and monomethacrylates suitable for
use in this invention include those where the metal is magnesium, calcium, zinc,
aluminum, sodium, lithium or nickel. Zinc diacrylate (ZDA) is preferred, but the
present invention is not limited thereto. ZDA provides golf balls with a high initial
velocity. Free radical initiators are also used to promote cross-linking of the
metal salt diacrylate, dimethacrylate, or monomethacrylate and the polybutadiene.
Free radical initiators are used to promote cross-linking of the metal salt diacrylate,
dimenthacrylate, or monomethacrylate and the polybutadiene rubber.
The core may also include fillers, added to the elastomeric composition to adjust
the density and/or specific gravity of the core. Fillers useful in the golf ball
core according to the present invention include, for example, metal (or metal alloy)
powders, metal oxide, metal searates, particulate, carbonaceous materials, and
the like or blends thereof.
Antioxidants may also be included in the elastomer centers produced
according to the present invention. Antioxidants are compounds, which prevent the
breakdown of the elastomer. Antioxidants useful in the present invention include,
but are not limited to, quinoline type antioxidants, amine type antioxidants, and
phenolic type antioxidants.
Other ingredients such as accelerators, processing aids, processing oils, dyes
and pigments, as well as other additives well known to the skilled artisan may
also be used in the present invention in amounts sufficient to achieve the purpose
for which they are typically used.
The core
12 may be formed by mixing and forming the base composition using
conventional techniques. Detailed disclosures concerning compositions of the core
to achieve desired properties in the ball are fully disclosed in co-pending patent
application Ser. No. 09/992,448. This patent application has been incorporated
by reference in its entirety.
Cover
16 is preferably tough, cut-resistant, and selected from conventional
materials used as golf ball covers based on the desired performance characteristics.
The cover may comprise one or more layers. Suitable cover materials include ionomer
resins, such as Surlyn® available from DuPont, blends of ionomer resins, thermoplastic
or thermoset urethane, acrylic acid, methacrylic acid, thermoplastic rubber polymers
consisting of block copolymers in which the elastomeric midblock of the molecule
is an unsaturated rubber or a saturated olefin rubber, e.g., Kraton® rubbers
available from Shell Chemical Co., polyethylene, and synthetic or natural vulcanized
rubber such as balata. Additionally, other suitable core and cover materials are
disclosed in U.S. Pat. No. 5,919,100 and international publications WO 00/23519
and WO 01/29129. These disclosures are incorporated by reference in their entirety.
Most preferably, core
12 is made from a CB-23 polybutadiene with ZnPCTP
additive and tungsten filler, and cover
16 is made from a composition comprising
a thermoset urethane.
To prevent or minimize the penetration of moisture, typically water vapor, into
core
12 of golf ball
10, intermediate layer
14 is a moisture
vapor barrier layer preferably disposed immediately around core
12. Preferably,
moisture vapor barrier layer
14 has a moisture vapor transmission rate that
is lower than that of the cover, and more preferably less than the moisture vapor
transmission rate of an ionomer resin such as Surlyn®, which is in the range
of about 0.45 to about 0.95 grams.mm/m
2.day. The moisture vapor transmission
rate is defined as the mass of moisture vapor that diffuses into a material of
a given thickness per unit area per unit time. The preferred standards of measuring
the moisture vapor transmission rate include ASTM F1249-90 entitled "Standard Test
Method for Water Vapor Transmission Rate Through Plastic Film and Sheeting Using
a Modulated Infrared Sensor," and ASTM F372-94 entitled "Standard Test Method for
Water Vapor Transmission Rate of Flexible Barrier Materials Using an Infrared Detection
Technique," among others.
In accordance to one aspect of the invention, preferred materials suitable for
the intermediate moisture vapor barrier layer
14 include copolymers of ethylene
and methacrylic acid, having an acid level from about 3% to about 25% by weight,
more preferably from about 4% to about 15%, and most preferably from about 7% to
about 11%, such as polyethylene methacrylic acid resins commercially available
under the tradename Nucrel® from DuPont. Copolymers of ethylene and methacrylic
acid have an advantage in that these compounds typically have high melt flow index.
The melt flow index, also known as the melt index, as used herein has its common
and ordinary meaning, which is the amount, in grams, of a thermoplastic resin which
can be forced through an extrusion rheometer orifice of 0.0825 inch diameter when
subjected to a force of 2.16 kg in 10 minutes at 190° C. The melt flow index
is typically measured in accordance to the ASTM D 1238 standard. The benefits of
higher melt flow index include easier extrusion, higher extrusion rate, higher
flow during heat sealing, and the ability to make thin films of moisture vapor
barrier layer. Without limiting the present invention to any particular theory,
materials with relatively high melt flow index have relatively low viscosity. Low
viscosity helps the materials spread evenly and thinly to produce a thin film.
Suitable polyethylene methacrylic acid resins include, for example, Nucrel®
599 resin, which contains 10% by weight of acid and a melt flow index of 500 g/10
min, and Nucrel® 2940 which contains 19% acid by weight and a melt flow index
of 395 g/10 min. These values, when compared to those of well-known ionomers such
as Surlyn®, which have melt flow index typically in the range of 1 g/10 min
to 14 g/10 min, show that polyethylene methacrylic acid resins have superior flow
characteristic under heat. Suitable polyethylene methacrylic acid resins exhibit
melt flow index in the range of about 1 g/10 min. to about 500 g/10 min., more
preferably in the range of about 3 g/10 min. to about 60 g/10 min., and even more
preferably less than about 35 g/10 min. or in the range of about 5 g/10 min. to
about 25 g/10 min.
The inventive use of copolymers of the ethylene and methacrylic acid allows the
production of very thin layers of moisture vapor barrier, which in turn allows
golf ball designers to add a barrier layer to a well designed golf ball without
significantly changing the designed properties of the ball. This simplifies the
golf ball design process by not introducing a new factor for consideration when
moisture vapor barrier capability is added to the ball.
The preferred materials, copolymers of ethylene and methacrylic acid, exhibit
water vapor barrier property of about 0.01 grams.mm/m
2.day to 0.90 grams.mm/m
2.day.
The thickness of intermediate layer
14 when made with the preferred materials
can be as thin as less than 0.030 inch, more preferably from about 0.020 inch to
about 0.005 inch. It can be readily appreciated that at this small thickness intermediate
layer
14 will not significantly alter the properties of golf ball
10.
More specifically, the specific gravity of copolymers of ethylene and methacrylic
acid is between about 0.93 and about 0.95. With the specific gravity in this range
and with the above thickness, the intermediate layer
14 would not have any
significant effect on the moment of inertia of ball
10. As used herein,
specific gravity is the ratio of the density of a substance to the density of water
at 4° C., which is 1.0 g/cm
3. Furthermore, the hardness of copolymers
of ethylene and methacrylic acid is available in the range of about 42 to 63 Shore
D. Hence, with the hardness in this range and with the above thickness, the intermediate
layer
14 would not have a significant impact on the hardness or compression
of ball
10.
In accordance to another aspect of the invention, other suitable materials for
the intermediate water vapor barrier layer include a blend of a copolymer of ethylene
and methacrylic acid and a suitable acid terpolymer of ethylene, a softening acrylate
class ester such as methyl acrylate, n-butyl-acrylate or iso-butyl-acrylate, and
a carboxylic acid such as acrylic acid or methacrylic acid. Suitable examples of
this acid terpolymer include terpolymers of ethylene, methyl acrylate and acrylic
acid (EMAAA), commercially available under the tradename Escor® Acid Terpolymers
from Exxon Mobile Chemical. Such acid terpolymers blend readily with copolymers
of ethylene and methacrylic acid, and have similar physical properties. For example,
these acid terpolymers have an acid content from about 6% to 6.5%, melt flow index
in the range of 5-20 g/10 min, specific gravity in the range of 0.94 to 0.95 and
hardness in the range of 23-41 Shore D. Hence, a thin layer of a blend comprising
a copolymer of ethylene and methacrylic acid and a terpolymer of ethylene, methyl
acrylate and acrylic acid would protect the golf ball core from water vapor invasion
while not significantly alter the other properties of the ball. Preferably, this
blend comprises 75% of a copolymer of ethylene and methacrylic acid and 25% of
a suitable acid terpolymer, e.g., EMAAA terpolymer, or 25% of a copolymer of ethylene
and methacrylic acid and 75% of acid terpolymer, or 50% of each component. Alternatively,
the water vapor barrier layer may comprise the acid terpolymer without a copolymer
of ethylene methacrylic acid.
In accordance to another aspect of the invention, another suitable material for
the intermediate water vapor barrier layer is a blend of a copolymer of ethylene
and methacrylic acid and a copolymer of ethylene and acrylic acid. Such copolymers
of ethylene and acrylic acid are commercially available as Primacor® copolymers
from Dow Plastics, and also have high acid content and high melt flow index. Typical
acrylic acid levels in commercial copolymers of ethylene and acrylic acid range
from about 3% and about 20.5% and the melt flow index can be in the range of 300
g/10 min or higher. Similarly, the hardness level of this materials is available
in the range of 50 on the Shore D scale, and the specific gravity is available
in the range of 0.96. Hence, a thin layer of a blend comprising a copolymer of
ethylene and methacrylic acid and a copolymer of ethylene and acrylic acid would
protect the golf ball core from water vapor invasion while not significantly alter
the other properties of the ball. Preferably, this blend comprises 25% of a copolymer
of ethylene and methacrylic acid and 75% of a copolymer of ethylene and acrylic
acid, or 75% of copolymer of ethylene and methacrylic acid and 25% of copolymer
of ethylene and acrylic acid, or 50% of each copolymer. Alternatively, the water
vapor barrier may comprise a copolymer of ethylene and acrylic acid, but not a
copolymer of ethylene and methacrylic acid.
In accordance to another aspect of the invention, the intermediate water vapor
barrier layer 14 can be made from a blend of (i) a copolymer of ethylene and methacrylic
acid, (ii) a terpolymer of ethylene, methyl acrylate and acrylic acid and (iii)
a copolymer of ethylene and acrylic acid. In accordance to another aspect of the
invention, the intermediate water vapor barrier may also include one or more of
the water vapor barrier materials disclosed in co-pending patent application Ser.
No. 09/973,342, which is assigned to the same assignee as the present invention
and which is incorporated herein by reference. The suitable materials discussed
above are all non-ionomeric compounds, which are compounds that are free of ions.
Other non-ionomeric compounds may also be suitable as a moisture vapor barrier layer.
Using CB-23 polybutadiene discussed above with the organic sulfur compound
ZnPCTP and tungsten fillers among other additives, prototype cores 12 having 1.58
inch diameter with core compression of
60,
65 and
75, respectively,
were made. Each core then has a thin layer of 0.020 inch of polyethylene methacrylic
acid resin (10.5% acid by weight) cased thereon. The subassembly then is covered
by a thermoset urethane cover. It has also been observed that resins having lower
levels of acid by weight generally achieve more desirable water vapor barrier property.
The physical properties of the three prototypes are compared to those of two
known commercial balls, Pinnacle Gold LS and Titleist Pro-V1, as shown below:
|
| |
Initial |
Ball |
|
Hardness |
|
| |
Velocity |
Com- |
Weight |
on Cover |
| Ball Type |
(ft/s) |
pression |
(oz.) |
(Shore D) |
CoR |
|
| Pinnacle Gold LS |
252.4 |
86 |
1.612 |
67 |
— |
| Titleist Pro-V1 |
253.6 |
90 |
1.611 |
58 |
— |
| Prototype A- |
252.9 |
63 |
1.602 |
49 |
0.803 |
| (60 core |
| compression) |
| Prototype B- |
253.4 |
71 |
1.606 |
51 |
0.809 |
| (65 core |
| compression) |
| Prototype C- |
254.1 |
80 |
1.610 |
52 |
0.814 |
| (75 core |
| compression) |
|
The flight characteristics of the prototypes when struck by various mechanical
clubs are shown below:
| |
|
| |
Pro 175 |
Standard Driver |
Average Driver |
|
|
| |
(175 ft/s) |
(160 ft/s) |
(140 ft/s) |
8 Iron |
Half Wedge |
| |
Spin |
Speed |
Spin |
Speed |
Spin |
Speed |
Spin |
Speed |
Spin |
Speed |
| Ball Type |
(rev/min) |
(ft/s) |
(rev/min) |
(ft/s) |
(rev/min) |
(ft/s) |
(rev/min) |
(ft/s) |
(rev/min) |
(ft/s) |
|
| Pinnacle |
2790 |
174.3 |
2962 |
159.4 |
3538 |
139.8 |
7641 |
114.9 |
4564 |
51.7 |
| Gold LS |
| Titleist |
3137 |
175.0 |
3356 |
160.6 |
3960 |
140.1 |
7935 |
115.1 |
7020 |
52.9 |
| Pro-V1 |
| Prototype A- |
2983 |
173.4 |
3076 |
159.5 |
3685 |
140.3 |
7245 |
115.0 |
6814 |
53.5 |
| (60 core |
| compression) |
| Prototype B- |
3100 |
174.1 |
3118 |
159.8 |
3787 |
140.9 |
7458 |
114.8 |
6866 |
53.4 |
| (65 core |
| compression) |
| Prototype C- |
3208 |
174.7 |
3340 |
160.2 |
4404 |
141.7 |
7845 |
115.3 |
7093 |
53.2 |
| (75 core |
| compression) |
|
Hence, the physical properties and flight characteristics of balls made in
accordance to the present invention are similar to and in some cases exceed those
of commercially successful balls.
In accordance to another aspect of the invention, the moisture vapor barrier
layer
14 may be made by a number of methods. A preferred method is the pre-formed
semi-cured shells method, where a quantity of mixed stock of the preferred moisture
vapor barrier material is placed into a compression mold and molded under sufficient
pressure, temperature and time to produce semi-cured, semi-rigid half-shells. The
half-shells are then place around a core (solid or wound) and the sub-assembly
is cured in another compression molding machine to complete the curing process
and to reach the desirable size. A cover is then formed on the core sub-assembly
by any known method to complete the fabrication of the ball.
As discussed above, the high melt flow index of the preferred materials allows
the construction of desirable thin half-shells of water vapor barrier material,
such that this layer do not significantly alter the properties of the ball.
Other suitable manufacturing techniques include sheet stock and vacuum, rubber
injection molding, spraying, dipping, casting, vacuum deposition, reaction injection
molding, among others. A two-pack casting method, such as the one disclosed in
U.S. Pat. No. 5,897,884, may also be used. A simplified casting method using a
single blocked material to produce the moisture vapor barrier layer
14 can
also be used. More particularly, this simplified method is usable to make any castable
components of the golf ball, including the moisture vapor barrier layer, any intermediate
layer, the innermost core or any portion of the cover. The suitable manufacturing
methods discussed herein are discussed in more details in co-pending patent application
Ser. No. 09/973,342, which has been incorporated by reference in its entirety.
While various descriptions of the present invention are described above, it
is understood that the various features of the present invention can be used singly
or in combination thereof. Therefore, this invention is not to be limited to the
specifically preferred embodiments depicted therein.
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