Compositions: coating or plastic – Coating or plastic compositions – Aluminum compound containing
Reexamination Certificate
2001-08-29
2003-03-18
Green, Anthony (Department: 1755)
Compositions: coating or plastic
Coating or plastic compositions
Aluminum compound containing
C106S015050, C106S018320, C106S401000, C427S397000, C427S429000, C524S437000
Reexamination Certificate
active
06533856
ABSTRACT:
The present invention relates generally to tannin stain inhibitors, and in particular to an improved tannin stain inhibitor in the form of a paint or stain additive for blocking tannin leachate and migration inherent with conventional wood and wood composite substrates. More specifically, the present invention is a tannin stain inhibitor comprising an aluminate salt complexing agent resulting in improved inhibiting of tannin leachate.
BACKGROUND OF THE INVENTION
A common problem with the use of conventional paint and stain coating products on typical wood and wood composite substrates and surfaces is the leaching of tannins from the wood, resulting in unsightly tannin stains on the painted surface. Tannin is a soluble complex group of compounds that occurs naturally in all wood and plant materials. However, the tannin cannot be effectively or efficiently removed from the wood or wood composite substrate prior to paint or stain application. As such, to avoid unsightly tannin staining, tannin leachate must be blocked or inhibited. Cedar and redwood are examples of two common types of wood suffering from severe tannin leachate and subsequent migration problems, however every wood species contains some form of organic water soluble tannic acid compounds.
Tannins easily dissolve in liquids, such as conventional paints and stains, to form water-soluble tannate salts, which in turn form adversely colored water-soluble or water-dispersible complexes. With the use of conventional paint and stain coating systems, which includes a first primer coat followed by a plurality of surface coats, tannin has a natural tendency to leach through the paint or stain coatings during the drying phase while the coat still retains moisture. The tannin is subsequently solublized by the alkaline properties of the paint or stain and migrated to the surface coat. Prolonged effects of tannin migration occur when the previously painted or stained wood or wood composite substrate is exposed to moisture, such as rainwater, wherein wetness is reintroduced into the coating system and the encapsulated tannins are subsequently solublized. This occurs notwithstanding the quality of the paint or stain, the amount of coatings applied, or the thickness of each subsequent coating.
The leached tannin adversely discolors the surface coat, thereby leaving a permanently unfavorable stained impression. This is mainly due to the easy solubility of the tannin compound. However, the discoloration and staining effect the tannin has on the surface coat is reliant upon many factors. For example, such factors include time, humidity, pressure, temperature, and other environmental variables.
It is well known in the industry that with the introduction of certain complex chemical additives with active ions into paint and staining products prior to the application of paint or stain onto the wood or wood composite substrate, the tannic acids can be neutralized and subsequent tannin leaching and migration can be controlled.
This is either accomplished by ultimately minimizing the effect the tannin staining appears to have on the surface coat color or by controlling the amount of tannin that migrates through coating layers. However, attempts at producing a reliable, efficient, and environmentally safe tannin-inhibiting compound have proved to be extremely difficult. Either the inhibiting additive has detrimental effects upon the coating system itself, such as degradation of product viscosity, stability or longitivity, or the additive changes the properties of the paint or stain so much that it is not practical for commercial use.
U.S. Pat. No. 3,852,087 to Nordyke et al., issued on Dec. 3, 1974, discloses a composite compound paint pigment for blocking tannin stains. The composite pigment is added into a conventional paint and subsequently blocks the leaching and migration of tannate salts to the surface coat layer. The composite pigment is based upon an aluminum metal hydrate. However, a drawback to such an additive is that the aluminum metal hydrate is not highly soluble and thus not as effective or efficient as the present invention which does not use an aluminum metal hydrate, is in liquid form and uses a stabilizing agent to reduce precipitation.
U.S. Pat. No. 3,900,620 to Gilman et al., issued on Aug. 19, 1975, discloses the use of a basic aluminum halide tannin stain inhibitor paint additive. Once again, the '620 patent is somewhat effective in inhibiting tannin migration. However, the aluminum hydroxide reaction to create the basic aluminum halide is solublized in a strong acid, thus creating a lower pH soluble form of aluminum, and subsequently destabilizing a typical alkaline coating system. The present invention is not acidic and thus is more stable and safer to handle than the '620 patent. Furthermore, the '620 patent is intended to be used as a preparation coat within a conventional coating system with subsequent, additive-free paint coats, whereas the present invention incorporates the tannin stain inhibiting additive within the complete coating system, as well the ability to be used independently as a pre-treatment.
U.S. Pat. No. 4,792,357 to Bier, issued on Dec. 20, 1988, discloses the use of a water-soluble salt, along with several other ionic compounds, within a tannin stain blocking paint additive. The '357 patent works on the premise of removing one of the available ions in tannate salts, thus rendering the resultant tannate salt less soluble. However, the '357 patent is intended to be used on stained interior building surfaces, unlike the present invention which is intended for use on any painted or stained wood or wood composite substrate or surface, which receive more environmental contamination. Furthermore, the '357 patent does not address the destabilizing effect that aluminate salts has with conventional paint coating products, whereas the present invention uses a stabilizing agent to prevent precipitation and to enhance pH buffering.
U.S. Pat. No. 5,512,323 to Beane et al., issued on Apr. 30, 1996, discloses a wood pretreatment tannin stain inhibitor. The pretreatment is applied to a wood substrate prior to the application of a conventional water-based paint or stain product and is not intended to be a paint or stain additive, unlike the present invention. Furthermore, the '323 patent discloses the use of an acidic aluminum salt as the chemical stain blocking composition. However, the use of the aluminum-based salt causes the pretreatment to have an acidic quality with a pH of between 2.5 and 6.5, thus establishing the potential for subsequent coating failure. Furthermore, the '323 patent is not intended to be incorporated within a coating system, but rather is used as an independent coating and/or pre-treatment product prior to using a conventional coating system, unlike the present invention which incorporates the tannin stain inhibiting additive into a conventional coating product, thus negating the need for substrate pre-treatment.
U.S. Pat. No. 5,320,872 to McNeel et al., issued on Jun. 14, 1994, discloses a tannin blocking paint additive that uses a metal salt of phosphonic acid as its complexing agent. The phosphonic acid, such as aluminum phosphonate, is a different complexing agent than that disclosed within the present invention and is not as stable as the present invention.
U.S. Pat. No. 5,989,515 to Watanabe et al., issued on Nov. 23, 1999, discloses a stabilizing alumina sol in a stable acidic and aqueous form. However, the disclosed invention does not disclose, suggest or address the concerns of stabilizing a sodium aluminate salt in an aqueous form or using an aluminate salt complexing agent as a coating system additive to inhibit tannin migration as in the present invention.
U.S. Pat. No. 6,113,989 to Sinko, issued on Sep. 5, 2000, discloses the use of a zirconium zinc complex compound for inhibiting tannate salt production in conventional water-based latex paints. However, the disclosed invention does not teach the incorporation of an aluminate salt into
Hodges Steve A.
Novelli Wendy
Sapp Mary Ann
Thorn Andrew
Green Anthony
Hammond Group, Inc.
Patula & Associates P.C.
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