Polymers containing partially neutralized silanols

Details Polymers containing partially neutralized silanols Polymers containing partially neutralized silanols

1999-01-25

2001-04-24

Dawson, Robert (Department: 1712)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Mixing of two or more solid polymers; mixing of solid...

C528S038000, C528S041000, C528S030000, C528S405000, C524S823000, C524S822000, C525S350000, C525S384000, C525S386000, C526S318400

Reexamination Certificate

active

06221976

ABSTRACT:

BACKGROUND OF THE INVENTION
The invention relates to polymers containing partially neutralized silanols. Crosslinked water-borne coatings having performance similar to that of solvent-borne coatings are useful for applications including high gloss architectural paint, industrial maintenance coatings, and wood coatings. Of particular interest are formaldehyde-free, single-container water-borne systems that have extended shelf-stability in a wet state, and undergo rapid crosslinking at ambient temperature in a dry coating. See John L. Gardon, “A Perspective on Resins for Aqueous Coatings,” Chapter 2
, Technology for Waterborne Coatings
, ACS Symposium Series, No. 663. American Chemical Society, Washington, D.C., pp. 27-43 (1997).
It would be an advantage to prepare a shelf stable aqueous-based dispersion or solutions that cure rapidly and preferably at low temperatures when coated onto a substrate.
SUMMARY OF THE INVENTION
The present invention addresses a need in the art by providing a latent crosslinking composition comprising a shelf-stable aqueous-based solution or dispersion of a polymer having a carbon-containing backbone attached to silanol groups which are sufficiently neutralized to inhibit silanol condensation.
In another aspect, the present invention is a latent crosslinking composition comprising a shelf-stable aqueous-based solution or dispersion of a polymer having a backbone that contains pendant silanol groups which are sufficiently neutralized to inhibit silanol condensation, which silanol groups are connected to the backbone through a secondary amine, an ether, or a sulfide group.
In a third aspect, the present invention is a latent curative comprising a stable aqueous dispersion of a polymer containing pendant partially neutralized silane triol groups prepared by reacting at a pH greater than 5 an alkali metal salt of 3-aminopropyl-silane triol or N-(2-aminoethyl)-3-aminopropyl-silanetriol and a polymer that contains pendant oxirane or enol groups formed from the polymerization of glycidyl methacrylate or acetoacetoxyethyl methacrylate and at least one non-interfering monomer.
The latent curative of the present invention solves a need by providing a shelf-stable, water-borne polymer that cures rapidly when applied as a coating to a substrate.
DETAILED DESCRIPTION OF THE INVENTION
The latent curative of the present invention can be prepared, for example, by reacting a partially neutralized silanol containing a nucleophile with a) an electrophilic polymer; or b) an electrophilic monomer followed by polymerization; or c) an electrophilic compound followed by grafting onto a polymer backbone.
The partially neutralized nucleophilic silanol is either a partially neutralized silanediol or silanetriol, preferably a silanetriol, that contains at least one nucleophile connected to the silanol through a first connecting group. As used herein, the term “partially neutralized” means that at least some of the silanol groups are in the form of mono-, di-, or tribasic alkali metal salts, more particularly lithium, sodium, or potassium salts. The extent of neutralization is that amount sufficient to inhibit condensation of the silanol. The partially neutralized nucleophilic silanol can be represented as follows:
where n is 1, 2, or 3; m is 0, 1, or 2; p is 0 or 1, preferably 0, with the proviso that m+n+p=3; X is the first connecting group; M
+
is the alkali metal salt; Nu is the nucleophile; and R is a linear, branched, or cyclic C
1
-C
8
-alkyl group, preferably methyl or ethyl, more preferably methyl.
The first connecting group X is preferably a linear, branched, or cyclic alkylene group, or arylene group, or a combination thereof, and may contain one or more heteroatoms, which may themselves be nucleophilic. More preferably, X is a C
2
-C
6
-alkylene group or a group of the type —R′—NH—R′—, where each R′ is independently a C
2
-C
4
-alkylene group.
Examples of suitable nucleophiles include amines, phenols, mercaptans, and carboxylates, with primary and secondary amines and mercaptans being preferred, primary and secondary amines being more preferred, and primary amine being most preferred. The most preferred partially neutralized aminosilanetriols are potassium or sodium salts of 3-aminopropyl-silane triol and N-(2-aminoethyl)-3-aminopropyl-silanetriol.
Though not bound by theory, it is believed that stability of the partially neutralized silanol is enhanced by the presence of a heteroatom that contains a hydrogen atom capable of hydrogen bonding with the partially neutralized silanol.
As used herein, the terms “electrophilic polymer” and “electrophilic monomer” refer to a polymer and a monomer (respectively) that contain electrophilic pendant groups that can react with the partially neutralized nucleophilic silanol to form a chemical bond. Examples of suitable electrophlic pendant groups include oxiranes, benzyl halide, allyl halides, alkyl halides, esters, ethers, and anhydrides. Examples of preferred electrophilic monomers include ethylenically unsaturated compounds such as glycidyl methacrylate, vinyl benzyl halides, and acetoacetoxyethyl methacrylate. In some instances it may be desirable to prepare the electrophilic polymer first, then react the polymer with the nucleophilic silanol. In other cases, it may be desirable to react the electrophilic monomer with the nucleophilic silanol, then polymerize or copolymerize the ethylenically unsaturated partially neutralized silanol. It may also be desirable to graft electrophilic substituents such as maleic anhydride onto a polymer backbone, or to graft a substituent that contains the partially neutralized silanol.
If the polymer containing the partially neutralized pendant silanol groups is prepared by way of an electrophilic polymer, it is preferred that the electrophilic polymer be prepared by copolymerization of an electrophilic monomer and a non-interfering monomer using emulsion polymerization methods well-known in the art. As used herein, the term “non-interfering monomer” is a monomer that does not interfere with the reaction between the electrophile and the nucleophile, and is non-reactive with either the nucleophile or the electrophile.
The preferred concentration of the electrophilic monomer with respect to the non-interfering monomer is generally a balance between an acceptable degree of crosslinking for the desired application and the cost that can be borne by that application. Preferably, the concentration of the electrophilic monomer is not less than 0.1. more preferably not less than 0.5. and most preferably not less than 1 mole percent, and preferably not greater than about 50. more preferably not greater than about 30. and most preferably not greater than about 20 mole percent of the total monomers used to prepare the electrophilic polymer.
Examples of suitable non-interfering monomers include acrylates such as methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, and allyl acrylate; methacrylates such as methyl methacrylate, ethyl methacrylate, butyl methacrylate, allyl methacrylate, 2-hydroxyethyl methacrylate, polypropylene glycol monomethacrylate, and 2-hydroxypropyl methacrylate; and styrene or C
1
-C
4
alkyl- or alkenyl-substituted styrenes, preferably styrene, &agr;-methylstyrene, vinyltoluene, and t-butylstyrene.
The non-interfering monomer may also be cationic or anionic. Examples of suitable cationic monomers include salts of ethylenically unsaturated compounds having quaternary ammonium, cyclic sulfonium, or phosphonium functionality. The salts may be, for example, chloride, bromide, nitrate, phosphate, carbonate, bicarbonate, acrylate, methacrylate, methylsulfate, or sulfate salts. Examples of suitable monomers having quaternary ammonium functionality include ethylenically unsaturated trialkylammonium salts such as vinylbenzyl tri-C
1
-C
4
-alkylammonium chloride or bromide; trialkylammoniumalkyl acrylates or methacrylates such as 2-[(methacryloyloxy)ethyl]trimethylammonium c

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