Resilient tires and wheels – Tires – resilient – Pneumatic tire or inner tube
Reexamination Certificate
1999-09-16
2002-09-03
Cain, Edward J. (Department: 1714)
Resilient tires and wheels
Tires, resilient
Pneumatic tire or inner tube
C152S530000, C524S501000, C524S503000, C524S506000
Reexamination Certificate
active
06443202
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a protective coating for tire sidewalls and method for protecting tire sidewalls.
BACKGROUND OF THE INVENTION
Tires having white sidewalls and/or raised white lettering, achieved by the addition of a white dye or pigment such as titanium dioxide, are popular in the United States and Canada. Colors other than white that contrast with the typical black-colored remainder of the tire can, of course, also be used on tire sidewalls for aesthetic purposes. The sidewalls of such tires are normally coated with protective paints or coatings after being manufactured to protect the colored sidewall and/or colored lettering on the tire while it is being shipped and stored prior to being mounted on a vehicle. The protective coating is removed from the sidewall of the tire after it is mounted on the vehicle.
The general purpose of such a protective coating is to inhibit or prevent migration of chemicals to the tire rubber composition from the surface of an adjacent black-colored tire during transportation and storage which would otherwise tend to stain and, thus, discolor the rubber. Staining caused by migration of chemicals upon contact from an adjacent tire usually becomes evident after exposure of the contacted rubber surface to ultraviolet light such as sunlight. Such contact staining phenomenon. is well known.
Rubber tires are typically black in color due to the carbon black reinforcement contained therein. If a contrasting or other color is desired for a part of the tire, a coloring pigment is used rather than carbon black. Many compounding ingredients typically used in rubber formulations are of the staining type; namely, amine-based antidegradants and aromatic rubber processing oils. These chemicals tend to migrate to the surface of the rubber and may stain or discolor the rubber surface of another article which contacts it for a period of time, particularly after the contacted rubber is exposed to ultraviolet light.
Often, a polyvinyl alcohol (PVA) based coating is used to protect the contrastingly colored rubber surfaces from other rubber surfaces of the staining type because the polyvinyl alcohol itself tends to be a barrier for the migration of such staining material. Moreover, the PVA can normally be easily removed from the coated rubber surface, when and if desired, by simple water-washing, usually with a soap solution, since the PVA itself normally has a relatively high degree of water solubility, particularly when the water contains a surfactant. Thus, the PVA coat is typically used for storage and shipping conditions and is usually removed by water-washing by the user. The PVA coating is normally used in conjunction with (mixed with) a plasticizer so that the resulting PVA-based coating has a degree of flexibility.
Tires are often stored under varying circumstances for various purposes so that they may be in contact with each other for a period of time such as, for example, storage during their shipping or transportation to various locations and warehouse storing. The storage conditions can vary considerably and sometimes the tires are stored under relatively high humidity conditions and sometimes at elevated temperatures.
Under such circumstances, where the tire surface has a PVA-based coating thereon, it has been observed that, under relatively high humidity conditions, the PVA-based coatings soften and easily scuff or abrade away, particularly as one tire may rub against another during shipment, thereby leaving a portion of the contrastingly colored sidewall unprotected and susceptible to chemical contact migration staining from other adjacent and contacting rubber products, including tires. At elevated temperatures, the aforesaid staining ingredients have a greater tendency to migrate to the surface of its host cured rubber product and, consequently, contribute to the staining of an adjacent and contacting rubber surface which is contrastingly light colored—even through many conventional protective barrier coatings (including PVA-based coatings).
Attempts have been made to provide a coating composition and a resultant coated rubber product, particularly a coated tire sidewall rubber surface, which will retard, inhibit and/or prevent the migration of amine-based antidegradants and aromatic rubber processing oils onto the rubber sidewall surfaces, such as a white sidewall, from an adjacent and contacting black rubber surface. For example, U.S. Pat. Nos. 5,137,070 and 5,240,056 to Kansupada et al. describe protective coatings for the white sidewalls on tires based on polyvinyl alcohol, and including a monovalent water-soluble salt of methylvinylether/maleic acid copolymer and a plasticizer. U.S. Pat. No. 4,911,218 to Patitsas describes a coating prepared from polyvinyl alcohol and mica or glass, and U.S. Pat. No. 5,149,591to Patitsas et al. describes a coating prepared from a blend of polyvinyl alcohol and water-dispersed polyurethane.
U.S. patent application Ser. No. 08/933,453, filed on Sep. 18, 1997, discloses an aqueous polyvinyl alcohol/polyvinyl acetate-based composition comprising: (i) an aqueous mixture including polyvinyl alcohol and polyvinyl acetate, wherein the weight ratio of polyvinyl alcohol to polyvinyl acetate is provided between about 15:85 to about 40:60 and (ii) an anti-scuff agent, such as a silicon emulsion, in an amount sufficient to provide increased scuff resistance for a coating prepared from the composition.
While such compositions are generally effective for protecting the white sidewall and/or raised white lettering on a tire against chemical contact migrating staining, research continues for new cost effective compositions capable of providing satisfactory protection and ease of application.
SUMMARY OF THE INVENTION
A first aspect of the invention is an aqueous paint composition particularly useful for protecting the white sidewalls of tires. A first embodiment of the composition includes (i) an aqueous mixture of polyvinyl alcohol and an ethylene/vinyl acetate copolymer, and (ii) a silicon emulsion in an amount sufficient to provide increased scuff resistance to a coating prepared from the composition. A second embodiment of the composition includes (i) an aqueous mixture including polyvinyl alcohol and an ethylene/vinyl acetate copolymer, and (ii) a thickening agent of a type and in an amount effective to render the composition shear-thinning (i.e., plastic or pseudoplastic). A third embodiment of the composition combines the components of the first and second embodiments, and includes (i) an aqueous mixture including polyvinyl alcohol and an ethylene/vinyl acetate copolymer, (ii) a silicon emulsion in an amount sufficient to provide increased scuff resistance to a coating prepared from the composition, and (iii) a thickening agent of a type and in an amount effective to render the composition shear-thinning.
The paint compositions offer a number of advantages over other known compositions, including (i) a decreased tendency to clog paint spray heads, (ii) less of a tendency to smear under conditions of high humidity, and (iii) ability to withstand cracking under conditions of low humidity.
A second aspect of the invention is a pneumatic tire wherein the white sidewall or white lettering thereon is protectively coated with one of the aqueous paint compositions described above.
A third aspect of the invention is a method of protecting the white sidewall or white lettering on a pneumatic tire against staining by applying a coating of one of the aqueous paint compositions described above over the white sidewall or white lettering.
DETAILED DESCRIPTION OF THE INVENTION INCLUDING A BEST MODE
The present invention relates to an aqueous coating composition which can be applied to a cured rubber surface, such as the white sidewall, colored sidewall and/or raised white lettering of a tire, to provide a protective coating against staining and scuffing.
Definitions
The aqueous coating composition can be referred to as an aqueous composition or a paint, or more simply as “the composition.” Once it
Burton James J.
Duchaine James M.
Huber Mortimer J.
Kansupada Bharat K.
Magnus Fredrick L.
Cain Edward J.
Lee Katarzyna W.
Quality Manufacturing, Inc.
Sherrill Michael S.
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