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
1996-10-04
2003-07-01
Reddick, Judy M. (Department: 1713)
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...
C427S385500, C427S393000, C428S463000, C428S484100, C428S485000, C428S514000, C524S477000, C524S522000, C524S523000, C524S558000
Reexamination Certificate
active
06586516
ABSTRACT:
The present invention relates to aqueous coating compositions. In particular, the aqueous coating compositions of the present invention have a low level of volatile organic compounds (“VOC”) and provide dry films having excellent resistance properties and durability. Aqueous coating compositions of the present invention are useful in polish and coating applications where durability and resistance properties are important.
Various methods have previously been employed to prepare durable, resistant aqueous coating compositions. One approach has been to prepare zinc-complexed polymers. Another approach uses polymers having a glass transition temperature (“Tg”) above ambient temperature in conjunction with volatile organic coalescents to aid in film formation. Higher Tg polymers provide better durability and resistance properties, but also require higher levels of VOC. Unfortunately, coating compositions having either zinc or high levels of VOC present regulatory and environmental concerns.
One attempt to overcome the problems associated in preparing a durable, environmentally friendly coating with good resistance properties is disclosed in U.S. Pat. No. 5,428,107. The disclosed coating composition contains a polymer having acetoacetate groups and acid-functional monomer. The polymer is post-treated with amino-functional silane. In one embodiment of U.S. Pat. No. 5,428,107, the acid-functionality on the polymer can be further reacted with divalent metal ions. While this composition can be used to produce durable, zinc-free coatings, it still contains relatively high levels of VOC. Additionally, coating compositions containing amino-functional silane are more expensive than conventional coatings.
The present invention has overcome the environmental problems associated with zinc and high VOC, in the absence of expensive amino-functional silanes. We have found that durable, resistant coatings can be formed from aqueous compositions having VOC levels below seven percent by formulating an acetoacetate-functional polymer with selected metal ions. The coating compositions of the present invention can be used to produce tough, resistant coatings on various substrates such as floors, walls, wood, metal, plastic, stone, paper, leather and concrete.
In a first aspect of the present invention, there is provided a coating composition comprising:
a) polymer comprising, as polymerized units, from 0.5 percent to 100 percent by weight acetoacetate-functional monomer; wherein the polymer has a glass transition temperature in the range of from −20° C. to 150° C.; and
b) divalent metal ion;
wherein the molar ratio of acetoacetate-functional monomer to divalent metal ion is in the range of from 20:1 to 2:1; wherein the composition is substantially free of sulfopolyester; and wherein the composition is substantially free of amino-functional silane.
In a second aspect of the present invention, there is provided a process comprising:
a) forming a coating composition by admixing:
1) polymer comprising, as polymerized units, from 0.5 to 100 percent acetoacetate-functional monomer; wherein the polymer has a glass transition temperature in the range of from −20° C. to 150° C.; and
2) divalent metal ion;
wherein the molar ratio of acetoacetate-functional monomer to divalent metal ion is in the range of from 20:1 to 2:1; wherein the composition is substantially free of sulfopolyester; and wherein the composition is substantially free of amino-functional silane;
b) applying said coating composition to a substrate to form a coated substrate; and
c) drying said coated substrate.
In a third aspect of the present invention, there is provided a coating composition comprising:
a) polymer comprising, as polymerized units, from 0.5 percent to 100 percent by weight acetoacetate-functional monomer; wherein said polymer has a glass transition temperature in the range of from −20° C. to 150° C.; and wherein said polymer comprises less than 5 percent by weight acid-functional monomer;
b) divalent metal ion; and
c) amino-functional silane;
wherein the molar ratio of acetoacetate-functional monomer to divalent metal ion is in the range of from 20:1 to 2:1; and wherein the molar ratio of acetoacetate functional monomer to amino-functional silane is in the range of from 20:1 to 2:1.
In a fourth aspect of the present invention, there is provided an article comprising a substrate coated with the aqueous coating composition of the present invention.
Polymers
Polymers useful in the present invention have, as polymerized units, acetoacetate-functional monomer. These polymers can be homopolymers, copolymers or mixtures of such polymers. Suitable acetoacetate-functional monomers include acetoacetoxyethyl acrylate, acetoacetoxypropyl methacrylate, acetoacetoxyethyl methacrylate, allyl acetoacetate, acetoacetoxybutyl methacrylate, and 2,3-di(acetoacetoxy)propyl methacrylate. A preferred monomer is acetoacetoxyethyl methacrylate (“AAEM”).
The acetoacetate-functional polymer may contain from 0.5 percent to 100 percent by weight of the acetoacetate-functional monomer. The amount of acetoacetate-functional monomer required will vary depending upon the end-use application. Generally, the acetoacetate-functional monomer level will be between 1 percent and 75 percent by weight. Conventional floor polish and coatings polymers will usually contain from 0.5 percent to 50 percent by weight acetoacetate-functional monomer. Polymers having a molecular weight of from 1,000 to over one million are useful in the present invention. In general, lower molecular weight polymers will have higher relative levels of acetoacetate-functional monomer. For example, a copolymer having a molecular weight under 10,000 would typically contain 30 percent or more of acetoacetate-functional monomer.
The polymers of this invention are most often copolymers of the acetoacetate-functional monomer and other monomers. As used herein, “(meth)acrylate” is used to mean either acrylate or methacrylate. Examples of useful comonomers include simple olefins such as ethylene, alkyl (meth)acrylates where the alkyl group has 1 to 20 carbon atoms (preferably 1 to 12 carbon atoms), vinyl acetate, acrylonitrile, styrene, isobornyl methacrylate, acrylamide, hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, N-vinyl pyrolidinone, butadiene, isoprene, vinyl halides such as vinyl chloride and vinylidene chloride, alkyl maleates, and alkyl fumarates.
In a preferred embodiment of the present invention, the polymer also contains, as polymerized units, acid-functional monomers or salts thereof Suitable acid-functional monomers include, for example, carboxylic acid monomers, sodium vinyl sulfonate, sodium methallyl sulfonate, phosphoethylmethacrylate, or 2-acrylamido-2-methylpropanesulfonic acid. Preferably, the acid-functional monomer is a carboxylic acid monomer such as, for example, acrylic acid, methacrylic acid, fumaric acid, maleic acid, and itaconic acid. Acid-functional monomers are incorporated at a level sufficient to provide removability of a dried film formed from the composition. The acid-functional monomer level is preferably greater than 3 percent and more preferably from 5 to 75 percent by weight of the polymer. Most preferably, the acid-functional monomer level is in the range of from 8 percent to 50 percent by weight of the polymer, to provide detergent resistance and water resistance to the dried coating. If too much acid-functional monomer is incorporated into the polymer, the resistance of the film to scrubbing with alkaline detergent solutions and resistance to aqueous solutions are greatly compromised.
Also, acetoacetate-functional polymers having no acid-functional monomer are useful in the present invention. When used in the composition of the present invention, such polymers produce durable, resistant coatings useful in applications that do not require film removal, such as those used to seal floors and furniture.
In another embodiment of the invention, where the level of acid-functional monomer in the acetoacetate-functional polymer is below f
Gebhard Matthew Stewart
Kesselmayer Mark Alan
Tysak Theodore
von Trentini Min-Chi Tsai
Bakule Ronald D.
Gironda Kevin F.
Johnson Stephen E.
Reddick Judy M.
Rohm and Haas Company
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