Coating processes – With post-treatment of coating or coating material – Heating or drying
Reexamination Certificate
2003-01-23
2004-09-28
Reddick, Judy M. (Department: 1713)
Coating processes
With post-treatment of coating or coating material
Heating or drying
C427S258000, C427S261000, C427S269000, C427S287000, C427S288000, C427S323000, C427S325000, C427S326000, C427S327000, C427S385500, C427S388400, C427S389000, C427S389700, C427S389900
Reexamination Certificate
active
06797328
ABSTRACT:
This invention relates to an aqueous composition suitable for use when dry as an improved coating, a method for preparing an aqueous emulsion polymer suitable for use in an improved coating and methods for providing a coated substrate and for improving the scrub resistance of a coating. More particularly this invention relates to an aqueous composition including a aqueous emulsion polymer, the polymer having a glass transition temperature (Tg) from greater than 20° C. to 80° C., the polymer formed by the free radical polymerization of at least one ethylenically unsaturated nonionic acrylic 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, a method of preparing the emulsion polymer, a method for providing a coated substrate wherein the coating contains the emulsion polymer having a Tg from −20° C. to 80° C., and a method for improving the scrub resistance of a coating by including the emulsion polymer having a Tg from −20° C. to 80° C.
The present invention serves to provide an aqueous composition suitable for use when dry as an improved coating, by which is meant that the coating, “coating” herein including, for example, paint, clearcoat, topcoat, primer, paper coating, and leather coating, expressly excluding elastomeric coating, caulk, sealant, and pressure sensitive adhesive, exhibits improvement in at least one of scrub resistance, marker stain blocking, corrosion resistance over metal, flash rust resistance over metal, gloss (higher), 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 Tg 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 an aqueous composition suitable for use when dry as an improved coating. 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 or even only in the last stages of the polymerization was sufficient to provide emulsion polymers which led to improved coatings properties.
In a first aspect of the present invention there is provided an aqueous coating composition comprising an aqueous emulsion polymer, the polymer having a glass transition temperature (Tg) from greater than 20° C. to 80° C., formed by the free radical polymerization of at least one ethylenically unsaturated nonionic acrylic 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.
In a second aspect of the present invention there is provided a method for preparing an aqueous emulsion polymer suitable for use in a coating composition comprising forming an aqueous emulsion polymer, the polymer having a glass transition temperature (Tg) from greater than 20° C. to 80° C., formed by the free radical polymerization of at least one ethylenically unsaturated nonionic acrylic 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.
In a third aspect of the present invention there is provided a method for providing a coated substrate comprising forming an aqueous coating composition comprising 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 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; 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 improving the scrub resistance of a coating, a method for improving the outdoor durability of a coating, and a method for improving the pick strength of a paper or paperboard coating.
This invention relates to an aqueous composition suitable for use when dry as a coating including an aqueous emulsion polymer, the polymer having a glass transition temperature (Tg) from greater than 20° C. to 80° C., formed by the free radical polymerization of at least one ethylenically unsaturated nonionic acrylic 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%, 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% to 7.5%, by weight based on total monomer weight, of a copolymerized monoethylenically-unsaturated 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, maleic anhydride, 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, phosp
Brown Albert Benner
Even Ralph Craig
Lorah Dennis Paul
Maurice Alvin Michael
Slone Robert Victor
Bakule Ronald D.
Reddick Judy M.
Rohm and Haas Company
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