Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
2000-04-28
2003-06-03
Wu, David W. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S186000, C524S503000, C526S271000, C526S332000
Reexamination Certificate
active
06573325
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to aqueous surface treatment compositions, their preparation and their use.
BACKGROUND OF THE INVENTION
The concept of using aqueous compositions for coating purposes has been known for several years. Moreover, the drive towards more environmentally friendly coatings containing low to zero amounts of volatile organic components (also referred to as V.O.C.'s) has added momentum to the development of water based coatings over traditional solvent based coatings.
Technical advances in the field of emulsion formulations have formed a basis for the commercial development of the commercial aqueous coating field that includes, for example, paints, stains and topcoat coatings. A ubiquitous aqueous coating composition is acrylic latex paint. Aqueous coatings based upon water-borne or emulsion formulations, are those whereby a polymeric resin (also referred to as a binder), pigments, and other additives are added to water with stirring until phase inversion occurs. High shear speeds and elevated temperatures are sometimes employed in order to achieve aqueous emulsion-based coatings. As well, emulsion-based aqueous coatings can be prepared by addition of one or more water-miscible solvents followed by stripping to remove the solvent from the final coating composition.
Polymeric resins in coatings act as binders to bind the pigment particles into uniform coatings and make the coatings adhere to the surface to which they are applied. They may also act as water-soluble thickening agents to provide thickening effects to the coatings. Other conventional aqueous coatings composition additives include, for example, emulsifiers, thickeners, humectants, curing agents, biocides, germicides, plasticizers, fillers and extenders.
If a film-forming coating is desired, coalescents can be added to aqueous coating compositions to temporarily lower the minimum film forming temperature, commonly referred to as the “MFFT” of a polymeric resin, allowing the coating composition to form a continuous film at a lower temperature than its T
g
. The T
g
, or glass transition temperature, of a polymer is a measure of the hardness and melt flow of the polymer. The higher the T
g
, the less the melt flow and the harder the coating. T
g
generally defines the onset of long range molecular motion wherein the polymer preserves the outward appearance of a solid but becomes rubbery and then tacky with increasing temperature and undergoes plastic flow and elastic deformation.
If a film-forming coating is desired, a polymer having a glass transition temperature at or near room temperature can be utilizied in the coating composition. In other instances, non-film forming aqueous coating compositions are desirous. For example, U.S. Pat. No. 4,094,841 teaches the use of a non-film forming latex coating prepared by emulsion polymerization for use with paper coatings and opacifying agents.
Despite their acceptance, current emulsion-based technologies used for the preparation of aqueous coatings have several drawbacks. Stability of emulsion-based aqueous coatings can be problematic and emulsion processes typically require surface-active agents, referred to as surfactants, to help stabilize the emulsions over long periods of time and a wide range of temperatures. Surfactants are also employed to inhibit foaming and to help disperse the pigments, or combinations thereof Conventional types of surfactants include anionic surfactants, non-ionic surfactants, cationic surfactants, amphoteric surfactants, or combinations thereof.
In aqueous coatings compositions, the rheology of the coating must be controlled in order to obtain proper flow of the surface treatment with a minimum of dripping or spattering. There are many types of thickeners, including polymeric water-soluble thickening agents, that may be added to emulsion based coatings to obtain a desired rheology. Thickeners such as cellulose ethers, alkali soluble latex copolymers, copolymers of acrylic and methacrylic acids and esters which have a portion of the hydrogen ions of the copolymer carboxyl group replaced with ammonium or alkali metals ions have been used as thickeners. Examples of thickeners are described in the patent literature, including U.S. Pat. No. 4,384,096 which discloses a pH responsive thickener comprising an ethylenically unsaturated carboxylic acid, at least one ethylenically unsaturated monomer and an ethylenically unsaturated surfactant copolymerizable therewith. Similar systems are disclosed in U.S. Pat. Nos. 5,874,495 and 4,138,381.
Another drawback of the current emulsion-based aqueous coating compositions is the detrimental effects of aqueous coating compositions on substrates that are of a porous or cellulose nature such as wood fibres. Grain raising, lap marks, distension and distortion may result after an emulsion-based aqueous coating composition has been applied due to the water-borne nature of the coatings.
Finally, the appearance of emulsion-based aqueous surface treatments can be a drawback. Emulsion-based aqueous coating compositions often retain an aesthetically undesirable turbid characteristic.
In order to compete with more conventional solvent-based coating systems, the aesthetic and physical properties of aqueous based coatings must be comparable. Alternative coating systems and compositions, and methods and apparatus for creating such systems and compositions are desirable.
BRIEF SUMMARY OF THE INVENTION
In a first aspect of the present invention what is provided is an aqueous surface treatment composition comprising a polymeric water soluble thickening agent, water, and one or more than one basic neutralizing agents, wherein the percentages of components of said composition are selected in such a way that a viscous surface treatment composition is formed.
In accordance with a preferred embodiment of the invention, the aqueous surface treatment composition further comprises one or more than one colouring agent, or one or more than one polyol, or combinations thereof.
In accordance with yet another preferred embodiment of the invention, the polymeric water-soluble thickening agent has a T
g
greater than 30° C.
In accordance with yet another preferred embodiment of the invention the polymeric water soluble thickening agent comprises a crosslinked alkyl vinyl ether/maleic anhydride copolymer and the aqueous surface treatment composition is prepared, in part, by hydrolysis of the anhydride groups of the copolymer to the corresponding carboxylic acid groups, followed by neutralization using a basic neutralizing agent.
In accordance with yet another preferred embodiment of the invention, the aqueous surface treatment composition can be non-film forming upon application to a suitable substrate or film forming upon application to a suitable surface.
In accordance with yet another preferred embodiment of the invention, the aqueous surface treatment composition further comprises a polyol present at sufficient wt % such that, upon application of the surface treatment to a suitable surface, the surface treatment possesses a re-wettable edge.
In a second aspect of the present invention there is provided a method of providing a temporary surface treatment on a substrate comprising applying the surface treatment composition of the present invention to a substrate and allowing the composition to dry. As such, the surface treatment is subsequently removable upon application of water to the composition. Drying may take place under ambient temperatures or with the use of radiant heat.
In accordance with yet another preferred embodiment of the present invention, there is provided a method of providing a permanent surface treatment on a substrate by applying the surface treatment composition of the present invention to a substrate and allowing the composition to dry; followed by application of a sealant coating over the dried composition of the present invention. The sealant is allowed to dry to form a protective coating over the surface treatment composition. Drying may take place under ambient tempera
Currie Jack
Morton Ted
York David
Cheung William
Katten Muchin Zavis & Rosenman
Wu David W.
York David
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