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
2000-01-14
2001-05-29
Niland, Patrick D. (Department: 1714)
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...
C524S507000, C524S839000, C524S840000, C524S504000, C525S123000, C525S455000
Reexamination Certificate
active
06239214
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a graft copolymer emulsion and a waterborne polymer composition containing the graft copolymer emulsion, the emulsion comprising a polymer backbone and a macromonomer compound. This composition is stabilized anionically and contains 0.5 to 30 weight percent of an amine-functional monomer copolymerized in the backbone and/or the macromonomer. The copolymer emulsions of this invention can be cured with a polyisocyanate.
Coating compositions generally comprise a carrier liquid, a film-forming polymer and a curing (crosslinking) agent. For waterborne coatings, the carrier liquid is primarily water. The combination of the film-forming polymer and the crosslinking agent is commonly referred to as a binder. It is desirable that the binder have a low viscosity such that the binder is readily sprayable using automated spraying equipment and a high solids content such that an adequate paint film thickness is yielded with one to two cross-passes of a spray gun.
In a one-package system, the binder is contained within a single package, and curing is typically accomplished by baking the coating after application. In a two-package (2K) system, the binder is contained in two separate packages: a first package contains the film-forming polymer and a second package contains the curing agent. Shortly prior to application, the contents of the two packages are combined, and curing occurs through chemical crosslinking reactions. Once the two packages are combined, the crosslinking reaction is irreversible, and thus two-package systems have a relatively short pot life.
Film-forming polymers most commonly employed are linear addition-type copolymers containing functional groups such as hydroxyl groups, and these copolymers are cured by reaction with crosslinking agents. In two-package urethane technology, curing agents based on isocyanate functional polymers are used that, upon mixing with a hydroxy-functional copolymer, react to form a crosslinked network.
The most relevant art appears to be WO95/32229. This publication, however, does not disclose the particular graft copolymer emulsion (of this invention) or the coating composition (of this invention) characterized as they are by the combination of excellent dry-film build, Persoz hardness, and solvent-resistance described herein (see Table 11).
SUMMARY OF THE INVENTION
This invention relates to graft copolymer emulsions which are anionically stabilized by an acid functional macromonomer and in which either macromonomer and/or backbone contain an amine functional monomer, preferably t-butylamino ethyl methacrylate (TBAEMA). We have found that such macromonomers are able to stabilize an overall waterborne polymer composition which has amino functional groups.
This invention concerns a graft copolymer emulsion which is anionically stabilized and which contains an amine functional monomer. The graft copolymer has a weight average molecular weight of at least 3,000 and further comprises 20 to 95 weight percent of a polymer backbone of 5 to 80 weight percent of a macromonomer. Preferably, the graft copolymer comprises 60 to 95 weight percent of a polymer backbone and 5 to 40 weight percent of a macromonomer. The polymer backbone and/or macromonomer further comprises 0.5 to 30 weight percent of a secondary amino-functional monomer, preferably t-butylaminoethyl methacrylate. The macromonomer further comprises at least about 5 weight percent of an unsaturated acid-functional monomer, preferably methacrylic acid. The macromonomer is prepared using a cobalt-based catalytic chain transfer agent and has a weight average molecular weight of about 1,000 to 30,000.
The graft copolymer emulsion can be used in a waterborne coating composition of this invention which comprises 20 to 95 weight percent solids, based on binder solids, of a graft copolymer and 5 to 80 weight percent solids of a polyisocyanate curing agent and 0 to 75% of other film-forming polymers.
Preferred embodiments of this invention are the following.
A. A graft copolymer emulsion having a weight average molecular weight of at least 3.000 which is anionically stabilized and which comprises
i) 20 to 95 weight percent of a polymer backbone of polymerized unsaturated compounds;
ii) 5 to 80 weight percent of a macromonomer comprising at least about 5 weight percent of an unsaturated acid functional monomer, said macromonomer prepared using a cobalt-based catalytic chain transfer agent and said macromonomer having a weight average molecular weight of about 1,000 to 30,000;
so that the backbone comprises 0.5 to 30 weight percent of the total polymerizable unsaturated compounds of an amino-functional polymerizable component.
B. A waterborne coating composition comprising as binder components:
a) 20 to 95 weight percent solids of graft copolymer emulsion A;
b) 5 to 80 weight percent solids of a polyisocyanate curing agent; and
c) 0 to 75 weight percent of other film-forming polymers.
C. The waterborne coating composition of B wherein said secondary amino functional monomer is t-butylaminoethyl methacrylate.
D. The waterborne coating composition of B wherein said catalytic chain transfer agent is selected from the group consisting of borondifluoro-stabilized chelates of a dialkyl- or diaryl-glyoxime of CoII or CoIII.
E. The waterborne coating composition of B wherein said graft copolymer comprises 60-95 weight percent of said polymer backbone and 5 to 40 weight percent of said macromonomer.
F. The waterborne coating composition of B wherein said polymer backbone comprises 5 to 50 weight percent of a vinyl aromatic. 10 to 70 weight percent of a compound selected from the group consisting of alkyl acrylate, cycloalkyl acrylate, and mixtures thereof, 5 to 40 weight percent of a compound selected from the group consisting of a hydroxy-functional polymerizable acrylate, hydroxy functional polymerizable methacrylate, and the mixtures thereof. 1 to 8 weight percent of a secondary amino functional monomer.
G. The waterborne coating composition of B wherein the said macromonomer comprises 10 to 90 weight percent of a compound selected from the group consisting of alkyl methacrylate, cycloalkyl methacrylate, and mixtures thereof, 0 to 40 weight percent of a hydroxy functional methacrylate, 0 to 20 weight percent of a secondary amino functional methacrylate, and 5 to 80 weight percent of an unsaturated acid functional monomer, wherein said macromonomer has a weight average molecular weight of 1,500 to 10,000.
H. The waterborne coating composition of B wherein said unsaturated acid functional monomer is methacrylic acid.
I. The waterborne coating composition of B wherein said graft copolymer is neutralized with an amine.
J. The waterborne coating composition of B further comprising an oligomeric methacrylate having a degree of polymerization for 2 to 10, wherein said oligomeric methacrylate is added in an amount to control the weight average molecular weight of the graft copolymer to about 3,000 to 80,000.
K. The waterborne coating composition of B wherein said polyisocyanate curing agent is selected from the group consisting of derivatives of hexamethylene diisocyanate, derivatives of isophorone diisocyanate, derivatives of m-xylylene diisocyanate, and mixtures thereof.
L. The waterborne coating composition of B further comprising 0-75 weight percent solids of a compound selected from the group consisting of auxiliary binder and crosslinker, additives, pigments, and extenders.
M. The waterborne coating composition of B wherein said polyisocyanate curing agent further comprises 0 to 75 weight percent hydrophobic polyisocyanate and about 25 to 100 weight percent hydrophilic polyisocyanate.
N. The waterborne coating composition of M wherein said hydrophobic polyisocyanate curing agent is selected from the group consisting of biurets or cyclotrimers of hexamethylene diisocyanate and/or isophorone diisocyanate.
O. The waterborne coating composition of M wherein said polyisocyanate curing agent is selected from polyisocyanates such as hexamethylene diisocyanate and iso
Bruylants Peter Paul
De Marre Anne
Huybrechts Josef
Costello James A.
Deshmukh Sudhir G.
E. I. Du Pont de Nemours and Company
Niland Patrick D.
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