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
1996-12-18
2003-01-28
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...
C427S361000, C427S368000, C427S371000, C427S385500, C427S388200, C427S388300, C427S389900, C427S391000, C427S393000, C427S393500, C427S393600, C524S543000, C524S555000, C524S556000
Reexamination Certificate
active
06512042
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to crosslinkable waterborne polymer compositions, especially emulsions or dispersions. In particular, the present crosslinkable waterborne polymer compositions are useful as coatings or binders in one-pack storage-stable coating compositions which have low moisture permeability.
It is well known that the durability and aesthetic value of a variety of substrates can be maintained or enhanced by application of a polymeric coating to the surface of such substrates, and that crosslinking after application improves coating performance (for example, by improving film hardness and strength, as well as chemical resistance properties). These improvements are particularly beneficial to substrates that require protection from environmental stresses, or substrates to which abrasives or organic solvents (cleaners) are frequently applied.
Where polymer particle dispersions contain amine nitrogen reactive carbonyl functional groups, maintaining dispersion stability in the presence of polyfunctional amines is difficult. One method of obtaining a stable polymer particle dispersion in an aqueous carrier is to incorporate carboxy acid functional groups into the polymer backbone. It is thought that, in an aqueous carrier at a pH equal to or greater than the pKa of the acid group, some of the carboxy acid groups located on the surface of the polymer particles ionize and form a dispersion-stabilizing electric double layer around the polymer particle. Sufficient carboxy acid groups must be present to block effectively the reaction between the amine nitrogen groups of the crosslinking agent and the carbonyl groups present on the dispersed polymer particles. Examples of such compositions are disclosed in EP 555 774 A1 (Kriessmann et al.) and WO 93/16133 (Esser). The main drawback to this method is that, although the carboxy acid groups on the polymer backbone stabilize the dispersion, these groups also increase moisture permeability of the resultant coating. That is, in the resulting polymeric coating, the presence of the carboxy acid groups increases the amount of water which is able to pass through the coating or which is absorbed by the coating itself, thus allowing more water to attack the substrate.
An alternate method of stabilizing a polymer particle dispersion is to incorporate certain hydrophilic compounds (such as amine-functional polyalkleneoxide compounds) into the dispersion. Examples of such compositions are disclosed in WO 95/09209 (Serelis et al.), which teaches that use of a polyoxyalkylene amine crosslinker increases storage-stability of the compositions. These compositions, however, have the same drawback as the previously described compositions, since the presence of such polyoxyalkylene amines is also known to increase the moisture permeability of such coatings.
The problem of storage-stability is addressed in the above-mentioned references, but at the expense of coating performance—through either the incorporation of high amounts of carboxy acid in the polymer backbone, or the use of hydrophilic, dispersion stabilizing crosslinkers such as polyoxyalkyldiamines. What is desired, then, is a one-pack storage-stable composition where coating performance (i.e., water resistance) is not sacrificed.
STATEMENT OF THE INVENTION
The coating compositions of the present invention comprise: (a) a polymeric component comprising an aqueous dispersion of latex polymer particles neutralized to a pH of not less than 6, the polymer having a Hansch value of 1.5 or greater, an acid number of 0-25, at least 5 percent by weight (“wt %”) of a carbonyl functional group capable of reacting with a nitrogen moiety, and at least 1 wt % of a non-acidic functional group having hydrogen-bondable moieties; and (b) a crosslinking agent comprising a nitrogen-containing compound having at least two nitrogen functional groups capable of reacting with a carbonyl functional moiety, wherein the mole equivalents ratio of such crosslinking agent to reactive carbonyl moieties is at least 0.25:1.
DETAILED DESCRIPTION OF THE INVENTION
As used in this specification, the following terms have the following definitions, unless the context clearly indicates otherwise. “Crosslinkable” and “crosslinking” refer to the formation of new chemical bonds between existing polymer chains, and “curing” refers to the crosslinking polymers after application to the substrate. “Storage-stable” refers to a coating composition wherein the reactive components do not substantially crosslink within the storage container itself, even upon prolonged storage. “Pot life” or “shelf life” refers to the period of time a composition is storage-stable. “Two-pack” or “two-component” refers to coating compositions (or systems) wherein the components are stored separately, then are mixed together just before use; on the other hand, “one-pack” or “one-component” refers to coating compositions wherein the components are stored in one container. Ranges specified are to be read as inclusive, unless specifically identified otherwise.
The multi-component one-pack storage-stable coating compositions of the present invention will include at least 5 wt % solids of the carbonyl functional group containing polymeric component, based on the total weight of the final composition. It is preferred that the compositions of the present invention will preferably include 5-70 wt % solids of the carbonyl functional group containing polymeric component, and most preferably 10-50 wt %.
The polymeric component of the present invention may be prepared by emulsion polymerization or (aqueous) dispersion polymerization techniques known to those skilled in the art. Ethylenically unsaturated monomers may be used to prepare the emulsion or dispersion polymers that constitute the polymeric component of this invention. Examples of suitable monomers include ethylenically unsaturated monomer, such as, for example, acrylic ester monomers including methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, decyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, lauryl (meth)acrylate, isobornyl (meth)acrylate, isodecyl (meth)crylate, oleyl (meth)acrylate, palmityl (meth)acrylate, stearyl (meth)acrylate, hydroxyethyl (meth)acrylate, and hydroxypropyl (meth)acrylate; acrylamide or substituted acrylamides; styrene or substituted styrenes; butadiene; ethylene; vinyl acetate; vinyl ester of “Versatic” acid (a tertiary monocarboxylic acid having C
9
, C
10
and C
11
chain length, the vinyl ester is also known as “vinyl versatate”), or other vinyl esters; vinyl monomers, such as, for example, vinyl chloride, vinylidene chloride, vinyl pyridine, N-vinyl pyrrolidone; non-reactive amino monomers, such as, for example, N,N′-dimethylamino (meth)acrylate, chloroprene, and acrylonitrile or methacrylonitrile. In addition, polyfunctional ethylenically unsaturated monomers may be incorporated, including allyl-, vinyl-, and crotyl- esters of acrylic, methacrylic, maleic, and fumaric acids, di- and tri-(meth)acrylate derivatives, divinylbenzene, diallylphthalate, triallylcyanurate, and polyvinyl ethers of glycols and glycerols. Suitable copolymerizable ethylenically-unsaturated acid monomers include, but are not limited to, acrylic acid, methacrylic acid, crotonic acid, itaconic acid, fumaric acid, maleic acid, monomethyl itaconate, monomethyl fumarate, monobutyl fumarate, maleic anhydride, 2-acrylamido-2-methyl-1-propanesulfonic acid, sodium vinyl sulfonate, and phosphoethyl methacrylate.
The polymeric component will have an Hansch value of 1.5 or greater, and an acid number of 0-25. The acid number of the polymer is preferably 1-20, and most preferably 5-15. The polymeric component will additionally contain at least 5 wt % (based on the weight of the monomer containing that group) of a carbonyl functional group capable of reacting with an amine nitrogen moiety, preferably at least 8 wt %, and most preferably at least 12 wt %; and at least 1 wt % (based on the weight of the monomer containing that group) o
Fioravanti, Jr. Louis Carl
Fischer Gordon Charles
Frazza Mark Stephen
Reddick Judy M.
Rohm and Haas Company
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