Coating processes – With post-treatment of coating or coating material – Heating or drying
Reexamination Certificate
1999-04-20
2001-02-13
Cameron, Erma (Department: 1762)
Coating processes
With post-treatment of coating or coating material
Heating or drying
Reexamination Certificate
active
06187385
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is directed to waterborne coating compositions containing an aqueous polymer dispersion and a non-polymeric material containing an acetoacetyl group which serves as a coalescing agent and promotes adhesion of the film formed from the coating composition to a substrate.
2. Background of the Invention
Waterborne coatings comprise particles of polymeric materials dispersed in an aqueous medium. When applied to a substrate and dried, the particles coalesce to form films which protect the substrate. Certain additives such as coalescing agents or plasticizers are frequently used to promote coalescence of the latex particles in the coating during film formation so that the resulting film has a smooth glossy appearance and completely covers and protects the substrate. Other additives are used to improve adhesion of the coating film especially on metal substrates.
U.S. Pat. Nos. 4,296,226 and 4,421,889 teach that polymers having acetoacetyl pendant groups have improved adhesion to smooth non-absorbent surfaces. Further, U.S. Pat. Nos. 5,055,511 and 5,120,607 describe the use of acetoacetylated acrylic polymers in mastic caulking compositions. Other patents, such as U.S. Pat. No. 5,002,998, EP 390,370, EP 262,720 and EP 326,723, and Japanese Kokai Hei 4 (1992)-164873 describe the use of polymers containing acetoacetoxy groups bound to the polymeric structure. U.S. Pat. No. 5,349,026 describes the use of a polymer containing an acetoacetate group in a coating or impregnating composition. The polymer functions to coalesce and crosslink an emulsion polymer. U.S. Pat. No. 5,494,975 describes preparation of polymers containing functional acetoacetate groups which are then reacted with a functional amine to form an enamine.
In all of the above references, the acetoacetoxy group is chemically bound to the polymer which forms the coating. This severely limits the chemical nature of the polymeric coating, since the polymer must either be based upon an acetoacetylated copolymerizable monomer or it must contain pendant groups, such as hydroxy or amine, which are capable of reacting with an acetoacetylating agent.
Japanese Patent 3,290,486 describes a process for promoting adhesion to a tin-lead alloy plated steel sheet which involves immersing the sheet in an aqueous acetoacetic acid ester prior to painting.
SUMMARY OF THE INVENTION
The present invention provides waterborne coating compositions comprising an aqueous polymer dispersion, an acetoacetate ester, and optional conventional additives. The waterborne composition has improved adhesion to substrates, particularly to corroded, oxidized and galvanized metal surfaces.
Another embodiment of this invention includes a method for improving the adhesion of waterborne coating compositions to various substrates, especially to rusty, corroded or galvanized metal.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Applicants have unexpectedly found that when a non-polymeric acetoacetate ester is added to waterborne coating compositions, the film resulting from the waterborne coating composition containing the acetoacetate exhibits improved adhesion to a substrate, especially corroded metal substrates. The acetoacetate ester may be added to the waterborne coating composition during formulation of the aqueous dispersion polymer or just prior to application of the formulation onto the substrate. The acetoacetate ester may be added either neat (pure) or as a solution together with other conventional paint additives, such as coalescing aids, plasticizers, etc. The resulting waterborne coating composition has the desirable properties of the latex composition, and in addition, exhibits greatly improved adhesion, especially to corroded metal and oxidized substrates.
Thus, the present invention provides waterborne coating compositions comprising: (A) an aqueous dispersion polymer, (B) an acetoacetate compound of Formula (I):
(R
1
C(═O)CH
2
COO)
x
R
2
(I)
wherein R
1
is a C
1
-C
6
alkyl group, R
2
is a C
1
-C
6
alkyl group or the residue of a polyol and x is an integer of from 1 to 3; and (C) optional, conventional additives.
Component (A)—Aqueous Dispersion Polymer
Useful aqueous dispersion polymers may be selected from the group consisting of acrylic latex polymers, vinyl latex polymers and waterborne alkyds.
Preferably, the aqueous dispersion polymer of the present invention is an acrylic latex polymer or vinyl latex polymer formed by polymerization of known monoethylenically unsaturated monomers. The term “latex” is used in the conventional meaning to denote stable dispersions of resin particles in a water system. Further, the term “polymer” is used to denote a homopolymer or a copolymer.
Suitable polymerizable or copolymerizable monoethylenically unsaturated monomers for the preparation of a latex polymer include, but are not limited to, a monoethylenically unsaturated monomer which may be represented by the general Formula (II):
CH
2
═C(R
3
)COOR
4
(II)
where R
3
is hydrogen or a C
1
-C
3
alkyl group, and R
4
is a C
1
-C
20
alkyl group, phenyl, benzyl, hydroxy-(C
1
-C
4
)-alkyl, alkoxy-(C
1
-C
4
)-alkyl, cyclopentyl, cyclohexyl, C
1
-C
4
-alkylfuryl, tetrahydrofuryl, C
1
-C
4
alkyltetrahydrofuryl and combinations of these monomers thereof. Combinations of monomers where R
3
is hydrogen and monomers where R
3
is an alkyl group are used to modify the glass transition temperature of the latex polymer.
Preferred examples of comonomers are, but are not limited to, methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, hexyl (meth)acrylate, isooctyl (meth)acrylate, isodecyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, phenoxyethyl (meth)acrylate, methoxyethyl (meth)acrylate, benzyl (meth)acrylate, ethoxyethyl (meth)acrylate, 2-ethylhexyl (meth)-acrylate, cyclopentyl (meth)acrylate, and isobornyl (meth)acrylate, as well as combinations of those monomers thereof. The term “(meth)acrylate” is used to denote an acrylate or methacrylate. The term “alkyl” is used to denote straight chain or branched alkyl groups.
Additional suitable polymerizable monoethylenically unsaturated monomers include styrenic monomers. Styrenic monomers denote styrene, or substituted styrenes, such as C
1
-C
6
alkyl ring-substituted styrene, C
1
-C
3
alkyl-substituted styrene or a combination of ring and -alkyl substituted styrene. Preferred styrenic copolymerizable monomers include styrene, p-methyl styrene, o-methyl styrene, -methyl styrene and combinations thereof.
In addition, vinyl ester monomers may be used as polymerizable monoethylenically unsaturated monomers. Such vinyl esters include vinyl acetate, di-n-butylmaleate, and compounds of the general Formula (III):
CH
2
═CH—OC(═O)—(C—(R
5
)
2
)
n
(III)
where R
5
is a hydrogen or a C
1
-C
12
alkyl group and where n is an integer of 1 to 20; preferably at least one R
5
is methyl.
Olefin monomers, such as ethylene or propylene, and diolefin monomers, such as butadiene may also be included.
The latex polymers referred to herein are known polymers. Latex polymers can be prepared by conventional free radical emulsion polymerization processes known in the art. Conventional catalysts used in emulsion polymerization include hydrogen peroxide, potassium or ammonium peroxidisulfate, dibenzoyl peroxide, lauryl peroxide, ditertiarybutyl peroxide, 2,2′-azobisisobutyronitrile, t-butyl peroxide, t-butyl hydroperoxide, benzoyl peroxide, sodium formaldehyde sulfoxylate and the like.
Suitable surfactants for the preparation of latex polymers include anionic or nonionic surfactants, such as alkylpolyglycol ethers including ethoxylation products of lauryl, oleyl, and stearyl alcohols; alkylphenol-polyglycol ethers, such as ethoxylation products of octyl- or nonylphenol, diisopropylphenol, triisopropylphenol; alkali metal ammonium salts or alkyl, aryl or alkylaryl sulfonates, sulfates, phosphates, and the like, in
Allen Rose M.
Cameron Erma
Eastman Chemical Company
Gwinnell Harry J.
LandOfFree
Non-polymeric acetoacetates as adhesion promoting coalescing... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Non-polymeric acetoacetates as adhesion promoting coalescing..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Non-polymeric acetoacetates as adhesion promoting coalescing... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2587359