Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From hydrocarbon reactant
Reexamination Certificate
2002-03-25
2004-10-19
Buttner, David J. (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From hydrocarbon reactant
C528S397000, C473S354000, C473S374000, C473S376000
Reexamination Certificate
active
06806347
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to golf balls, more particularly to golf balls having thin water vapor barrier layers.
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. A known drawback of polybutadiene cores cross-linked with peroxide and/or zinc diacrylate is that this material is adversely affected by absorption of water vapor, which reduces the resiliency of the cores and degrades their properties. Thus, these cores must be covered quickly to maintain optimum ball properties. A cover that protects the core from the elements and repeated impacts from golf clubs is typically made from ionomer resins, balata, and urethane, among other materials. Ionomer covers, particularly hard ionomers, offer some protection against the absorption of water vapor. However, it is more difficult to control or impart spin to balls with hard covers. Conventional urethane covers provide better ball control but 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 38° C. and 90% humidity over 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 about 5 PGA to about 10 PGA or greater. The absorbed water vapor also reduces the golf ball coefficient of restitution (“COR”). When a golf ball is subjected to prolonged storage and/or use under ambient conditions such as 25-35% RH, as well as conditions of high temperature and high humidity, the COR of the golf ball tends to decrease over time due to water vapor absorption.
Several prior patents have addressed the water vapor absorption problem. U.S. Pat. No. 5,820,488 discloses a golf ball having a water vapor barrier (“WVB”) layer disposed between a core and a cover. The WVB layer preferably has a water vapor transmission (“WVT”) rate lower than that of the cover layer. The WVB layer may comprise polyvinylidene chloride (“PVDC”) or vermiculite. It can also be formed by an in situ reaction between a barrier-forming material and the outer surface of the core. The barrier properties of PVDC are best at or below ambient temperature, but degrade rapidly at elevated temperatures. U.S. Pat. Nos. 5,885,172 and 6,132,324 disclose, among other things, a golf ball with a polybutadiene or wound core having an ionomer inner cover and a relatively soft outer cover. The hard ionomer inner cover offers some resistance to water vapor absorption, while the soft outer cover provides desirable ball control. U.S. Pat. No. 6,232,389 discloses the application of a dispersed exfoliated layered filler in an elastomeric polymer based barrier coating mixture so as to reduce water vapor permeability in golf balls and other objects by at least 5-fold. Preferable fillers include layered silicates such as bentonite, vermiculite, montmorillonite, nontronite, beidellite, volkonskoite, hectorite, saponite, laponite, sauconite, magadiite, kenyaite, and ledikite. U.S. Pat. No. 6,287,216 discloses a wounded golf ball having a liquid center surrounded by a thermoplastic core layer formed of a hydrophobic material that has a water vapor permeation rate of less than about 170 g·mil/100 in
2
·24 h. Additionally, U.S. Pat. No. 5,875,891 discloses an impermeable packaging for golf balls to limit water absorption during storage.
As it becomes common practice to implement various materials of different properties to construct two-piece and multi-layer golf balls that are susceptible to water vapor absorption, there presents a need for a WVB layer within the golf balls. It is also desirable to minimize the WVB layer thickness such that characteristics and playability of the golf ball are unaffected.
SUMMARY OF THE INVENTION
The present invention is directed to a golf ball having a core, a cover, and a thin WVB layer having at least one layer that is formed from poly-para-xylylene and its derivatives (“parylenes”). The thin WVB layer has a WVT rate that is less than the WVT rate of the cover. Preferably, the WVT rate of the thin WVB layer is less than about 0.80 g·mil/100 in
2
·24 h at 38° C. and 90% relative humidity. Parylenes have a general structure:
where
A=a hydrogen or a group VIIA element;
B=a hydrogen or a group VIIA element;
X=a hydrogen or a group VIIA element;
Y=a hydrogen or a group VIIA element;
n=an integer between 1 and 100; and
A, B, X and Y may be the same or different from each other.
The parylenes are selected as materials of choice to form the thin WVB layer in part because they provide conformal, pinhole-free thin coatings that have superior WVB properties. Low WVT rates are typically exhibited by halogenated parylenes, in which at least one of the four moieties (A, B, X and Y) is a group VIIA element. Preferably, the group VIIA element is fluorine, chlorine, bromine, iodine, or astatine; more preferably, the element is chlorine. Among the commercially available halogenated parylenes suitable as the WVB materials, including poly-para-xylylene (“parylene N”), poly-chloro-para-xylylene (“parylene C”), and poly-dichloro-para-xylylene (“parylene D”), parylene C stands out as the most preferable to form the thin WVB layer in accordance with the present invention.
Because the WVB layer comprising parylenes is typically formed via vapor deposition polymerization at a steady rate, it is possible to produce a thin WVB layer of any thickness on golf ball cores or sub-assemblies in a controlled fashion. Preferably, the thin parylene-based WVB layer of the invention has a thickness of from about 0.025 &mgr;m to about 75 &mgr;m. More preferably, the thickness is from about 1 &mgr;m to about 25 &mgr;m; and most preferably, from about 3 &mgr;m to about 10 &mgr;m.
Optionally, the thin WVB layer comprising at least one parylene-based layer may further have an additional layer to enhance the overall WVB properties. This additional layer preferably has a thickness of less than 0.030 inches and a WVT rate of less than about about 0.80 g·mil/100 in
2
·24 h at 38° C. and 90% relative humidity. Materials suitable for this additional layer include, without limitation, poly-para-xylylene and its derivatives; polyvinylidene chloride; polyvinyl chloride; vermiculite; polyacrylonitrile; fluorohalocarbons including polychlorotrifluoroethylene copolymer, ethylene-tetrafluoroethylene copolymer; fluorinated ethylene propylene copolymer, polytetrafluoroethylene, polyvinylidene fluoride, polyvinyl fluoride, and perfluoroalkoxy resins; aluminum; silicon oxides; polyethylene terephthalate; polypropylene; high density polyethylene; multi-layer thermoplastic films; blends of ionomers; polyvinyl alcohol copolymers and polyamides; dispersions of acid salts of polyetheramines; and mixtures thereof.
In one embodiment of the present invention, the thin WVB layer is disposed immediately about the core. Alternatively, the WVB layer may be disposed anywhere between the core and the cover. The golf ball core is preferably a solid core having a diameter of at least about 1.00 inch. Preferably, the solid core has a diameter of at least about 1.550 inches. The golf ball cover preferably has a thickness of about 0.010 inches to about 0.080 inches.
In another embodiment of the invention, a golf ball comprises a core, a cover, at least one intermediate layer disposed between the core and the cover, and a first WVB layer comprising at least one layer formed from parylenes. The first WVB layer is also disposed between the core and the cover, preferably immediately about the core. Preferably, the first WVB layer has a thickness of less than 0.030 inches, and a WVT rate of less than about 0.80 g·mil/100 in
2
·24 h at 38° C. and 90% relative humidity. Optionally, a second WVB layer may be added between the cor
Harris Kevin M.
Hogge Matthew F.
Jones Douglas E.
Acushnet Company
Buttner David J.
Lacy William B.
LandOfFree
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