Coating processes – With post-treatment of coating or coating material – Heating or drying
Reexamination Certificate
2001-10-17
2003-02-25
Cameron, Erma (Department: 1762)
Coating processes
With post-treatment of coating or coating material
Heating or drying
Reexamination Certificate
active
06524656
ABSTRACT:
This invention relates to a method for providing a coated substrate. More particularly this invention relates to a method including applying an aqueous composition including an aqueous emulsion polymer, the polymer having a glass transition temperature (Tg) from −60° C. to 80° C., the polymer formed by the free radical polymerization of at least one ethylenically unsaturated nonionic acrylic monomer, 0.1-50%, by weight based on the total weight of the polymer, ethylenically unsaturated aldehyde reactive group-containing monomer, and 0-7.5%, by weight based on the total weight of the polymer, ethylenically unsaturated acid monomer, in the presence of 0.01-1.0%, by weight based on the total weight of the polymer, t-alkyl hydroperoxide, t-alkyl peroxide, or t-alkyl perester wherein the t-alkyl group includes at least 5 Carbon atoms. And a method for improving the scrub resistance of a coating, a method for lowering the minimum film formation temperature of an aqueous coating composition, and a method for improving the adhesion of a coating to a substrate are provided.
The present invention serves to provide a method for providing a coated substrate including applying and drying an improved coating, by which is meant that the coating, “coating” herein including, for example, paint, topcoat, primer, paper coating, and leather coating, exhibits improvement in at least one of scrub resistance, marker stain blocking, exterior durability as indicated, for example, by gloss retention or cracking resistance, adhesion to substrates, water vapor permeability, and water swelling, relative to a coating in which an emulsion polymer of the same composition not so formed is employed.
U.S. Pat. No. 5,540,987 discloses emulsion polymers including at least 50% vinyl acetate having low residual formaldehyde and providing saturated cellulosic webs having improved tensile strength. The polymers are formed by the use of an hydrophobic hydroperoxide and ascorbic acid initiator throughout the course of the reaction.
The problem faced by the inventors is the provision of a method for providing a coated substrate, for improving the scrub resistance of a coating, for lowering the minimum film formation temperature of an aqueous coating composition, and for improving the adhesion of a coating to a substrate. Unexpectedly, the inventors found that the use of certain levels of t-alkyl hydroperoxide, t-alkyl peroxide, or t-alkyl perester wherein the t-alkyl group includes at least 5 Carbon atoms during the polymerization of a monomer mixture including aldehyde reactive group-containing monomers or even only in the last stages of the polymerization was sufficient to provide emulsion polymers which led to improved dry coatings properties.
In a first aspect of the present invention there is provided a method for providing a coated substrate including forming an aqueous coating composition comprising an aqueous emulsion polymer, the polymer having a glass transition temperature (Tg) from −60° C. to 80° C., formed by the free radical polymerization of at least one ethylenically unsaturated nonionic acrylic monomer, 0.1-50%, by weight based on the total weight of the polymer, ethylenically unsaturated aldehyde reactive group-containing monomer, and 0-7.5%, by weight based on the total weight of the polymer, ethylenically unsaturated acid monomer in the presence of 0.01-1.0%, by weight based on the total weight of the polymer, t-alkyl hydroperoxide, t-alkyl peroxide, or t-alkyl perester wherein the t-alkyl group includes at least 5 Carbon atoms and, optionally, at least one other oxidant; applying the aqueous coating composition to the substrate; and drying, or allowing to dry, the aqueous composition.
In a second aspect of the present invention there is provided a method for improving the scrub resistance of a coating including forming an aqueous coating composition including an aqueous emulsion polymer, the polymer having a glass transition temperature (Tg) from −60° C. to 80° C., formed by the free radical polymerization of at least one ethylenically unsaturated nonionic acrylic monomer, 0.1-50%, by weight based on the total weight of the polymer, ethylenically unsaturated aldehyde reactive group-containing monomer, and 0-7.5%, by weight based on the total weight of the polymer, ethylenically unsaturated acid monomer in the presence of 0.01-1.0%, by weight based on the total weight of the polymer, t-alkyl hydroperoxide, t-alkyl peroxide, or t-alkyl perester wherein the t-alkyl group includes at least 5 Carbon atoms and, optionally, at least one other oxidant; applying the aqueous coating composition to the substrate; and drying, or allowing to dry, the aqueous composition.
In other aspects of the present invention there are provided a method for lowering the minimum film formation temperature of an aqueous coating composition, a method for improving the adhesion of a coating to a substrate, and a method for improving the adhesion of a coating to an alkyd substrate.
This invention relates to a method including applying an aqueous coating composition including an aqueous emulsion polymer, the polymer having a glass transition temperature (Tg) from −20° C. to 80° C., formed by the free radical polymerization of at least one ethylenically unsaturated nonionic acrylic monomer, 0.1-50%, by weight based on the total weight of the polymer, ethylenically unsaturated aldehyde reactive group-containing monomer, and 0-7.5%, by weight based on the total weight of the polymer, ethylenically unsaturated acid monomer in the presence of 0.01-1.0%, by weight based on the total weight of the polymer, t-alkyl hydroperoxide, t-alkyl peroxide, or t-alkyl perester wherein the t-alkyl group includes at least 5 Carbon atoms and, optionally, at least one other oxidant.
The aqueous emulsion polymer contains at least one copolymerized ethylenically unsaturated nonionic acrylic 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 acrylic 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. Other ethylenically unsaturated nonionic monomers which may be incorporated into the polymer include, for example, styrene and substituted styrenes; butadiene; vinyl acetate, vinyl butyrate and other vinyl esters; vinyl monomers such as vinyl chloride, vinyl toluene, and vinyl benzophenone; and vinylidene chloride. Preferred are all-acrylic, styrene/acrylic, and vinyl acetate/acrylic polymers. Preferred is a predominantly acrylic aqueous emulsion polymer. By “predominantly acrylic” herein is meant that the polymer contains greater than 50%, preferably greater than 60%, by weight, copolymerized units deriving from (meth)acrylic monomers such as, for example, (meth)acrylate esters, (meth)acrylamides, (meth)acrylonitrile, and (meth)acrylic acid. The use of the term “(meth)” followed by another term such as acrylate or acrylamide, as used throughout the disclosure, refers to both acrylates or acrylamides and methacrylates and methacrylamides, respectively.
The emulsion polymer contains from 0.1% to 50%, by weight based on total monomer weight, of a copolymerized ethylenically-unsaturated aldehyde reactive group-containing monomer, based on the weight of the polymer. By “aldehyde reactive group-containing monomer” is meant herein a monomer which, in a homogeneous solution containing 20% by weight of the monomer and an equimolar amount of formaldehyde at any pH from 1 to 14, will exhibit greater than 10% extent of reaction between the monomer and formaldehyde on a molar basis in one day at 25° C. Included as ethylenically-unsaturated aldehyde reactive group-containing monomers are, for example, vinyl acetoacetate, acetoacetoxyethyl (meth)acrylate, acetoaceto
Even Ralph Craig
Slone Robert Victor
Bakule Ronald D.
Cameron Erma
Rohm and Haas Company
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