Wet adhesion monomer and derived copolymers for latex paints

Details Wet adhesion monomer and derived copolymers for latex paints Wet adhesion monomer and derived copolymers for latex paints

2000-06-26

2003-03-25

McKane, Joseph K. (Department: 1626)

Organic compounds -- part of the class 532-570 series

Organic compounds

Heterocyclic carbon compounds containing a hetero ring...

C548S316700, C526S263000

Reexamination Certificate

active

06538143

ABSTRACT:

BACKGROUND OF THE INVENTION
Coatings and paints represent an extremely large market for polymers. Particularly attractive from an application and safety perspective are so-called latex paints which are a water dispersion of polymer particles, usually prepared by emulsion polymerization. Although a significant reduction or elimination of volatile organic solvents is achieved by these products, the surfactants remaining after water evaporation, coupled with the relatively high molecular weight of the polymers, frequently prevent complete coalescence. Among other failure mechanisms, coatings may be composed of incompletely coalesced particles surrounded by surfactant. The latter represent buried hydrophiles running through the final coating which can readily absorb moisture. The result frequently is inadequate water resistance and, especially, poor wet adhesion, i.e., adhesion to a previously painted surface when wet.
A large number of polymerizable monomers have been proposed for enhancing wet adhesion of coatings and paints. Many of these materials are based on a polymerizable group attached to an imidazolidone (ethyleneurea), or another type of urea group. (Meth)acrylate and (meth)acrylamide units often have been employed to provide the polymerizable function for the monomer. Allylic functionality has also been used to provide a polymerizable function.
The following patents illustrate conventional wet adhesion monomers for use in preparing latex emulsions suited for paints:
British Patent 2 086 917 discloses wet adhesion promoters for aqueous film-forming surface coating compositions based upon acrylic functional ethylene ureas. In forming the wet adhesion monomer an ethylene urea or derivative is reacted with a hydroxy acrylate such as hydroxypropyl acrylate in the presence of a base.
U.S. Pat. No. 4,111,877 discloses wet adhesion monomers based on allyl esters of N-alkyl-omega-(alkylene ureido)carbamic acid in forming emulsion polymers suited for use in paints and coating compositions. The starting material for preparing the wet adhesion monomer is 2-aminoethylethyleneurea. It is formed by reacting diethylenetriamine with urea. The resulting ureido compound then is reacted with allyl.chloroformate to produce the allyl carbamate.
U.S. Pat. No. 3,369,008 discloses N-(cyclic ureido-alkyl) crotonamides for use as a wet adhesion monomers in coating and paint compositions. In the preparation of the wet adhesion monomer, a crotonic halide is reacted with an N-aminoalkyl-N,N′-alkylene urea or thiourea.
U.S. Pat. No. 4,632,957 discloses wet adhesion monomers based on ethylenically unsaturated ethylene and propylene ureas and their use in preparing latex coating compositions. The wet adhesion monomers are prepared by reacting a primary amine or primary alcohol with a monoisocyanate having ethylenic unsaturation. Representative primary amines are based upon imidazolidones. Monoisocyanates having ethylenic unsaturation include isocyanato-ethyl methacrylate and isocyanato propyl methacrylate.
U.S. Pat. No. 5,496,907 discloses a new class of wet adhesion monomers containing a ureido group and optionally nitrile functionality. The ureido compound is formed by cyanoethylating an amino alkylethylene urea or an amino alkylene oxyplkylene ethyl urea. Ethylenic unsaturation is imparted by reducing the nitrile and reacting the resulting amine with a monoisocyanate having acrylic functionality such as isocyanatoethyl methacrylate.
U.S. Pat. No. 4,429,095 discloses cyclic alkylene ureas having residual unsaturation for use as wet adhesion promoters in latex paints. In forming the wet adhesion monomers a mono-(alkylene ureido alkyl) urea or a bis-(alkylene ureido alkyl) urea is reacted with an unsaturated glycidyl ether.
U.S. Pat. No. 5,739,196 discloses latex compositions incorporating wet adhesion promoting monomers. Examples include those primarily having acrylic functionality as the polymerizable unit for the wet adhesion promoting moiety. Specifically, N-(2-methacryloxylethyl)ethylene urea, dimethylaminopropyl acrylate, 2-N-morpholinoethyl acrylate are shown.
BRIEF SUMMARY OF THE INVENTION
This invention relates to wet adhesion monomers having unique polymerizable functionality and to polymer emulsion prepared therefrom. The invention also relates to paint formulations incorporating the polymer having the polymerized wet adhesion monomer incorporated therein.
The wet adhesion monomer is formed by reaction of an unsaturated carbonate selected from the group consisting of vinyl ethylene carbonate and methacryloxypropylene carbonate or allyloxypropylene carbonate, with a wet adhesion promoting moiety, typically urea or a cyclic urea. The preferred polymerizable functionality based upon the reaction of vinyl ethylene carbonate coupled with a wet adhesion providing moiety is represented by the following structures:
wherein X is NH or O.
The resulting polymers incorporate polymerized units of the wet adhesion monomers and the resulting polymer emulsions are suited for use in producing improved latex paints and coatings.
Advantages of the wet adhesion monomer, the derived polymer emulsions and the latex paints incorporating the polymer emulsions include:
an ability to synthesize the wet adhesion monomers from readily available starting materials by simple mixing and, most conveniently, in water solution;
an ability to avoid the use of hazardous solvents, inert atmospheres and long reaction times at elevated temperatures as is common in forming many wet adhesion monomers;
an ability to use the crude reaction mixture, i.e., a solution of the monomer in water, in a subsequent polymerization without removal of unreacted ethylenically unsaturated starting material, by-products or co-products;
an ability to use the hydroxy group formed in the carbonate amine reaction as a crosslinking site;
an ability to react the wet adhesion monomers readily with comonomers, particularly vinyl acetate and acrylate monomers; and,
an ability to produce product emulsions that provide good coatings with improved wet adhesion using even small quantities of the wet adhesion monomer.
DETAILED DESCRIPTION OF THE INVENTION
The wet adhesion monomers of this invention are prepared by reacting an unsaturated carbonate with a wet adhesion promoting moiety. terminating in amine or hydroxy functionality, such as a hydroxy or amine terminated alkyl urea or cyclic urea, The unsaturated carbonate typically is vinyl ethylene carbonate (VEC) although methacryloxypropylene or allyloxypropylene carbonate may be used.
Conventionally, ureas and cyclic ureas such as imidazolidones have long been used as wet adhesion moieties for coupling with polymerizable functionality. The five membered cyclic urea, imidazolidone, is most preferred, but urea itself and substituted ureas or larger ring structures can also be used. N-aminoalkyl-N,N′-alkylene ureas or thioureas having a two carbon chain linkage are the two common amine substrates.
Representative structures of possible ureas and cyclic ureas for reaction with the vinyl ethylene carbonate for example are as follows:
wherein Z is A—R
0
, wherein A is NH, O and R
0
is C
1-10
alkylene or substituted akylene, and alkylene ether having from 1-6 carbon atoms and n is 1 or 2.
Examples of specific imidazolidones (ethylene ureas) and pyrimidones suited as wet adhesion promoting moieties are as follows:
1-(2-aminoethyl)-2-imidazolidone; 1-(2-aminoethyl)-2-imidazolidinethione; 1-(2-aminopropyl)-4-methyl-imidazolidone; N-methyl-N′-hydroxymethyl ethylene urea, and 1-(3-aminopropyl)-hexahydro-2-pyrimidone. Examples of ureas include N,N′-bis(hydroxymethyl)ethylene urea; N-(2-aminoethyl)urea, 3-aminopropyl urea, and 6-aminohexyl urea.
Other representative wet adhesion promoting urea moieties for synthesis of wet adhesion monomers by reaction with vinyl ethylene carbonate are described in U.S. Pat. Nos. 3,369,008, 4,783,539 and 5,496,907 and are incorporated by reference.
The wet adhesion monomers are preferably prepared at 0 to 100° C., typically 30 to 85° C. in water using near stoich

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