Waterborne coating composition

• US 5,478,601 A
• Filed: 02/09/1995
• Issued: 12/26/1995
• Est. Priority Date: 04/08/1994
• Status: Expired due to Term

• Current Assignee: Rohm and Haas Company (Dow, Inc.)
• Original Assignee: Rohm and Haas Company (Dow, Inc.)
• Inventors: Larson, Gary R., Smith, Linda S., Wood, Kurt A., Puschak, Caren A.
• Primary Examiner(s): Szekely, Peter A.
• Application Number:
  US08/385,944
• Time in Patent Office: 320 Days
• Field of Search: 427/388.4
• US Class Current: 427/388.4
• CPC Class Codes: C08G 18/62 Polymers of compounds having carbon-to-carbon double bonds
• CPC Class Codes: C08G 18/6225 Polymers of esters of acrylic or methacrylic acid
• CPC Class Codes: C08G 18/706 the liquid medium being water
• CPC Class Codes: C08G 18/792 formed by oligomerisation of aliphatic and/or cycloaliphatic isocyanates or isothiocyanates

Abstract

A waterborne coating composition containing an aqueous dispersion of a polymer, the polymer being substantially free from hydroxyl, primary amino, and secondary amino groups and the polymer bearing at least two active methylene groups, and an aqueous dispersion of a polyisocyanate bearing at least two isocyanate groups is provided. Also provided is a method of improving the chemical resistance of a coating and a substrate coated with the waterborne coating composition.

Claims

1. A method of improving the chemical resistance of a coating comprising:

(a) forming a waterborne coating composition by admixing an aqueous dispersion of a polymer, said polymer being substantially free from hydroxyl, primary amino, and secondary amino groups and said polymer bearing at least two active methylene groups; and

an aqueous dispersion of a polyisocyanate bearing at least two isocyanate groups;

(b) applying said coating composition to a substrate; and

(c) curing said coating composition.

2. The method of claim 1 wherein said active methylene groups are selected from the group consisting of acetoacetates, acetoacetamides, cyanoacetates, and cyanoamides.

3. The method of claim 1 wherein said polymer is an addition polymer formed by an emulsion polymerization of at least two ethylenically unsaturated monomers, said monomers comprising from about 5% to about 25% by weight, based on the weight of said addition polymer, acetoacetoxyethyl methacrylate.

4. The method of claim 3 wherein said addition polymer has a glass transition temperature from about -30°

C. to about 45°

C.

5. The method of claim 1 wherein said polyisocyanate comprises isocyanate groups selected from the group consisting of aliphatically bound isocyanate groups, cycioaliphatically bound isocyanate groups, and mixtures thereof.

6. The composition of claim 1 wherein said polyisocyanate comprises isocyanurate groups, said polyisocyanate having been formed from 1,6-hexamethylene diisocyanate.