Coating processes – With post-treatment of coating or coating material – Heating or drying
Reexamination Certificate
2001-04-10
2002-11-26
Cameron, Erma (Department: 1762)
Coating processes
With post-treatment of coating or coating material
Heating or drying
Reexamination Certificate
active
06485786
ABSTRACT:
This invention relates to an aqueous composition suitable for use as a stain-blocking coating and a method for blocking stains, particularly marker stains, by coating a substrate with the aqueous stain-blocking coating composition. More particularly this invention relates to an aqueous composition suitable for use as a stain-blocking coating including an aqueous emulsion copolymer, the copolymer having a glass transition temperature (Tg) from −20° C. to 60° C., and the copolymer including as polymerized units at least one ethylenically unsaturated nonionic monomer and 1.5-6%, by weight based on the dry weight of the copolymer, ethylenically unsaturated strong acid monomer, or salts thereof.
The present invention serves to provide an aqueous composition suitable for use, when dry, as a stain-blocking coating. By stain-blocking coating herein is meant a coating disposed between a stain-bearing substrate and a later-applied aqueous coating which minimizes or eliminates the tendency of stains on a substrate such as, for example, markings made by pens or marking devices on a wall to migrate through a later-applied aqueous coating and appear on the surface of the dry later-applied coating as discolored area or markings.
U.S. Pat. No. 4,812,510 discloses colloid-free vinyl acetate latexes which include up to 15 weight parts of an ionic comonomer such as sodium styrene sulfonate, sodium vinyl sulfonate, and mono- and di-phosphated hydroxyethyl methacrylate and are prepared with up to 20 weight parts of certain anionic surfactants including phosphates and sulfonates for use in a variety of adhesives and coatings. But the use of the latexes in stain-blocking coating compositions is not disclosed.
U.S. Pat. No. 5,922,410 discloses in clear (unpigmented) wood coating compositions including a copolymer containing 0.1 to 50 wt. % of a copolymerized monomer containing a conjugate base of an acid, the acid having a pKa of less than 4 for use in clear coatings to enhance the yellowness (warmth) of the wood to which it is applied. But the use of the copolymers in stain-blocking coating compositions is not disclosed.
The problem faced by the inventors is the provision of an aqueous composition suitable for use as a stain-blocking coating and a method for blocking stains, particularly marker stains, by coating a substrate with the aqueous stain-blocking coating composition before the application of an additional coating. Unexpectedly, the inventors found that the aqueous compositions of this invention containing a selected amount of copolymerized strong acid monomers, or the salts thereof, were highly effective in blocking stains, particularly marker stains.
In a first aspect of the present invention there is provided an aqueous stain-blocking coating composition including an aqueous emulsion copolymer, the copolymer having a glass transition temperature (Tg) from −20° C. to 60° C., the copolymer including as polymerized units at least one ethylenically unsaturated nonionic monomer and 1.5-6%, by weight based on the dry weight of the copolymer, ethylenically unsaturated strong acid monomer, or salts thereof
In a second aspect of the present invention there is provided a method for blocking stains including forming an aqueous coating composition including an aqueous emulsion copolymer, the copolymer having a glass transition temperature (Tg) from −20° C. to 60° C., and the copolymer including, as polymerized units, at least one ethylenically unsaturated nonionic monomer and 1.5-6%, by weight based on the dry weight of the copolymer, ethylenically unsaturated strong acid monomer, or salts thereof; applying the aqueous composition to a substrate bearing a stain; and drying, or allowing to dry, the aqueous composition.
This invention relates to an aqueous composition suitable for use as a stain-blocking coating. As a stain-blocking coating, when dry, it is intended to prevent the migration of stains so that a later-applied aqueous coating, when dry, will provide an aesthetically pleasing appearance with minor visible or no stains on the surface of the later-applied coating. Alternatively, one skilled in the art might describe the stain-blocking coating as a stain-blocking primer or a stain-locking primer.
The aqueous stain-blocking coating composition contains an aqueous emulsion copolymer, the copolymer having a glass transition temperature (Tg) from −20° C. to 60° C., and the copolymer including as copolymerized units at least one ethylenically unsaturated nonionic monomer and 1.5-6%, by weight based on the dry weight of the polymer, ethylenically unsaturated strong acid monomer, or salts thereof.
The aqueous emulsion copolymer includes at least one copolymerized ethylenically unsaturated nonionic monomer. By “nonionic monomer” herein is meant that the copolymerized monomer residue does not bear an ionic charge between pH=1-14. The ethylenically unsaturated nonionic monomers include, for example, (meth)acrylic ester monomers including methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, decyl acrylate, lauryl acrylate, methyl methacrylate, butyl methacrylate, isodecyl methacrylate, lauryl methacrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate; (meth)acrylonitrile; (meth)acrylamide; amino-functional and ureido-functional monomers; monomers bearing acetoacetate-functional groups; styrene and substituted styrenes; butadiene; ethylene, propylene, &agr;-olefins such as 1-decene; vinyl acetate, vinyl butyrate and other vinyl esters; and vinyl monomers such as vinyl chloride, vinylidene chloride. Preferred are all-acrylic, predominantly acrylic, styrene/acrylic, and vinyl acetate/acrylic copolymers.
The emulsion copolymer contains 1.5-6%, by weight based on the dry weight of the copolymer, copolymerized ethylenically unsaturated strong acid monomer, or salts thereof. By “ethylenically unsaturated strong acid monomer” herein is meant a monomer bearing a pendant acid group having a pKa (in water at 20 C.) less than 4, or a salt thereof. Strong acid monomers include, for example, 2-acrylamido-2-methylpropane sulfonic acid, vinyl sulfonic acid, styrene sulfonic acid, 1-allyloxy-2-hydroxypropane sulfonic acid, alkyl allyl sulfosuccinic acid, sulfoethyl (meth)acrylate, phosphoalkyl (meth)acrylates such as phosphoethyl (meth)acrylate, phosphopropyl (meth)acrylate, and phosphobutyl (meth)acrylate, phosphoalkyl crotonates, phosphoalkyl maleates, phosphoalkyl fumarates, phosphodialkyl (meth)acrylates, phosphodialkyl crotonates, and allyl phosphate. Preferred are Phosphorous-containing strong acid monomers. It is also contemplated that the copolymerized ethylenically unsaturated strong acid monomer may be formed after the polymerization of at least one ethylenically unsaturated nonionic monomer and a strong acid precursor monomer by effecting the reaction of the copolymerized strong acid precursor monomer so as to convert it to a copolymerized strong acid monomer; for example a polymer containing, as a polymerized unit, hydroxyethyl methacrylate which may then be reacted, as is well known in the art, to form, for example, sulfoethyl methacrylate or phosphoethyl methacrylate.
The emulsion copolymer may contain from 0 to 5%, by weight based on the dry weight of the copolymer, copolymerized ethylenically unsaturated carboxylic acid monomer, based on the weight of the polymer, such as, for example, acrylic acid, methacrylic acid, crotonic acid, itaconic acid, fumaric acid, maleic acid, monomethyl itaconate, monomethyl fumarate, monobutyl fumarate, and maleic anhydride. Preferred is 0-1% copolymerized ethylenically unsaturated carboxylic acid monomer.
The emulsion copolymer may contain from 0% to 5%, by weight based on the dry weight of the copolymer, copolymerized multi-ethylenically unsaturated monomers such as, for example, allyl methacrylate, diallyl phthalate, 1,4-butylene glycol dimethacrylate, 1,2-ethylene glycol dimethacrylate, 1,6-hexanediol diacrylate, and divinyl benzene. Preferred is the use of no copolymerized multi-ethylenically unsaturated mo
de la Cuesta Sheppard Aurelia
Deng Hai
Deshmukh Kirti
Winkle Mark Robert
Bakule Ronald D.
Cameron Erma
Rohm and Haas Company
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