MXPA01007590A - Polymers containing partially neutralized silanols - Google Patents

Abstract

A shelf-stable water-borne dispersion or solution that cures rapidly and at low temperatures when coated onto a substrate can be prepared with an aqueous-based solution or stable aqueous dispersion of a polymer having a backbone containing pendant silanol groups which are sufficiently neutralized to inhibit silanol condensation.

Description

POLYMERS THAT CONTAIN PARTIALLY NEUTRALIZED SILANQLES The invention relates to polymers containing partially neutralized silanols. Cross-linked water-bearing coatings that perform similar to solvent-borne coatings are useful for applications that include high-gloss architectural paint, industrial maintenance coatings, and wood coatings. Of particular interest are systems that carry water from a single container, without formaldehyde, which have shelf stability in a wet state, and undergo rapid cross-linking at room 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, DC. , pages 27-43 (1997). It would be an advantage to prepare a dispersion based on stable water in the rack or solutions that cure quickly and preferably at low temperatures when superimposed on a substrate. The present invention solves a need in the art by providing a latent crosslinking composition comprising a solution or dispersion based on stable water in the rack of a polymer having a central structure having carbon attached to silanol groups which are sufficiently neutralized to inhibit the silanol condensation. In another aspect, the present invention is a latent crosslinking composition comprising a stable water-based solution or dispersion in the rack of a polymer having a core structure containing pendant silanol groups that are sufficiently neutralized to inhibit silanol condensation, these silanol groups are connected to a central structure 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 pendent partially neutralized silane triols groups prepared by reacting at a pH greater than 5 an alkali metal salt of the 3-aminopropylsilane triol. or N- (2-aminoethyl) -3-aminopropyl-silanotriol and a pendant oxirane-containing polymer or ene groups formed from the polymerization of glycidyl methacrylate or acetoacetoxyethyl methacrylate and at least one non-interfering monomer. In a fourth aspect, the present invention is a latent crosslinking composition comprising a solution or dispersion based on stable water in the rack of a polymer having a central structure containing carbon attached to silanol groups which are sufficiently neutralized to inhibit condensation of the silanol wherein the silanol is partially neutralized amino silanotriol which is attached to the central structure of the polymer by means of either (a) reacting in the presence of water an amino silanotriol with a solution or a dispersion of a polymer having a central structure containing an electrophile; or (b) reacting in the presence of water an amino silanotriol and an ethylenically unsaturated electrophilic monomer to form an ethylenically unsaturated silanol, then polymerizing or copolymerizing the silanol, wherein the electrophilic is a group of benzyl halides, an oxirane group, or a acetoacetoxyethyl group, wherein the amino silanotriol is sufficiently neutralized to inhibit condensation. In a fifth aspect, the present invention is the composition of the fourth aspect, wherein the polymer is a stable aqueous dispersion which is prepared by polymerizing, in the presence of water, glycidyl methacrylate and at least one non-interfering monomer to form an electrophilic polymer having units of glycidyl methacrylate, then reacting the electrophilic polymer with an alkali metal salt of the amino silanotriol. In a sixth aspect, the present invention is the composition of the fifth aspect, wherein the mole percent of the structural units of the glycidyl methacrylate is from 1 to 50 percent based on the total moles of the monomers used to prepare the electrophilic polymer. The latent curative of the present invention solves a need by providing a stable waterborne polymer in the rack that cures quickly when applied as a coating to a substrate. 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 central polymer structure. The partially neutralized nucleophilic silanol is either silanodiol or partially neutralized silanotriol, preferably silanotriol, which contains at least one nucleophile connected to the silanol via a first connection 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 degree of neutralization is sufficient to inhibit silanol condensation. Partially neutralized nucleophilic silanol can be represented as follows: Nu-X-SKOTvf)., where n is 1, 2, or 3; m is 0, 1, or 2; p is < > or 1, preferably 0, with the proviso that m + n + p - 3; < it is the first connection group; M is the alkali metal salt; Nu is the nucleophile; and R is the alkyl group Je 1 l < > to 8 carbon atoms straight, branched or c? ci? _), preferably methyl or ethyl, more preferably methyl. The first connection group X is preferably a linear, branched or cyclic alkylene group, or an apleno irupo, or a combination of the inisms, and may contain one or more heteroatoms, which by themselves may be nucleophilic. More preferably, X is an alkoxylene group with 2 to 6 carbon atoms or a dialkylenenoam group of the type -R'-NH-R'-, wherein each R 'is independently an alkylene group with 2 to 4 carbon atoms . Examples of suitable nucleophiles include amines, phenols, mercaptans, and carboxylates, with primary and secondary amines and mercaptans being preferred, with primary and secondary amines being more preferred, and primary amines being still more preferred. The most preferred partially neutralized aminosilanelets are potassium or sodium salts of 3-aminopropylsilane triol and N- (2-aminoethyl) -3-aminopropyl-silanotriol. Although not bound by theory, it is believed that the stability of the partially neutralized silanol is increased by the presence of a heteroatom containing 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) containing electrophilic pendant groups that can react with the partially neutralized nucleophilic silanol to form a chemical bond. Examples of suitable electrophilic 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 cases it may be desirable to first prepare the electrophilic polymer, 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 to polymerize or copolymerize the partially neutralized ethylenically unsaturated silanol. It may also be desirable to graft electrophilic substituents such as maleic anhydride onto a central polymer structure, or graft a substituent containing the partially neutralized silanol. If the polymer containing the partially neutralized pendent silanol groups is prepared by means 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 not 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 electrophilic monomer is not less than 0.1, more preferably is not less than 0.5, and more preferably not less than 1 molar percent, and preferably is not greater than about 50, more preferably is not greater than about 30, and still more preferably it is not more than about 20 mole percent of the total monomers used to prepare the electrophilic polymer. Examples of 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 styrenes substituted by alkyl or alkenyl having from 1 to 4 carbon atoms, preferably styrene, α-methylstyrene, vinyltoluene and t-butylstyrene. The non-interfering monomer can also be cationic or anionic. Examples of suitable cationic monomers include salts of ethylenically unsaturated compounds containing quaternary ammonium, cyclic sulfonium, or phosphonium functionality. The salts can 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) alkyl ammonium chloride or bromide; trialkylammonioalkyl acrylates or methacrylates such as 2- [(methacryloyloxy) ethyl] trimethylammonium chloride and N, N-diethyl-N-methyl-2- [(1-oxo-2-propenyl) oxy] ethanamminium methylsulfate (Chem. Abstracts Reg Number 45076-54-8); and trialkylammonioalkyl acrylamides such as N, N, N-trimethyl-3- [(2-methyl-l-oxo-2-propenyl) amino] -1-propanaminium chloride (Chem. Abstracts Reg. Number 51441-64-6) and N, N-dimethyl-N- [3- [(2-methyl-l-oxo-2-propenyl) amino] propyl] -benzenemetaminium chloride (Chem. Abstracts Reg. Number 122988-32-3). A preferred polymerizable quaternary ammonium salt is 2- [(methacryloyloxy) ethyl] trimethylammonium chloride. Examples of suitable anionic monomers are alkali metal or ammonium salts of ethylenically unsaturated compounds having strong acid functionality such as salts of sulfonic acid, sulfinic acid, phosphinilic acid, and phosphonic acid. Examples of polymerizable unsaturated sulfonium salts include dialkylsulfonium salts such as [4-ethoxy-3- (ethoxycarbonyl) -2-methylene-4-oxobutyl] dimethylsulfonium bromide (Chem. Abstracts Reg. Number 63810-34-4); and vinylbenzyl dialkylsulfonium salts such as vinylbenzyl dimethylsulfonium chloride. Examples of polymerizable cyclic sulfonium salts include l- [4- [(ethenylphenyl) methoxy] phenyl] tetrahydro-2H-thiopyranium chloride (Chem. Abstracts Reg. Number 93926-67-1); and vinylbenzyl tetrahydrothio-phenonium chloride, which can be prepared by the reaction of vinylbenzyl chloride with tetrahydrothiophene. Examples of polymerizable phosphonium salts include 2-methacryloxyethyltri- (alkyl, aryl, or aralkyl with 1 to 20 carbon atoms) phosphonium salts such as 2-methacryloxyethyltri-n-octadecyl-phosphonium halide (Chem. Abstracts Reg. Number 166740-88-1); tri- (alkyl, aralkyl, or aryl with 1 to 18 carbon atoms) -vinyl benzylphosphonium such as trioctyl-3-vinyl benzylphosphonium chloride, trioctyl-4-vinylbenzylphosphonium chloride (Chem. Abstracts Reg. Number 15138-12- 4), tributyl-3-vinylbenzylphosphonium chloride, tributyl-4-vinylbenzylphosphonium chloride (Chem. Abstracts Reg. Number 149186-03-8), triphenyl-3-vinylbenzylphosphonium chloride, and triphenyl-4-vinylbenzylphosphonium chloride (Chem. Abstracts Reg. Number 145425-78-1); salts of alkenyltrialkylphosphonium, aralkylphosphonium, or arylphosphonium with 3 to 18 carbon atoms such as 7-octenyltriphenyl-phosphonium bromide (Chem. Abstracts Reg. Number 82667-45-6); and salts of tris (hydroxymethyl) - (1-hydroxy-2-propenyl) phosphonium (Chem. Abstracts Reg. Number 73082-48-1). Examples of ethylenically unsaturated compounds having sulfate or phosphate functionalities include: p-styrene sulfonic acid, 2-acrylamido-2-methyl-l-propane sulfonic acid, 2-sulfoethyl methacrylate, 2-sulfoethyl acrylate, 3-sulfopropyl methacrylate, allylsulfonic acid , 2-methyl- (hydroxyphosphinyl) methyl ester, and vinylphosphonic acid. The non-interfering monomer may also be an ethylenically unsaturated monomer containing a weak acid group or the salt of the weak acid group, even when these groups can, under certain conditions, act as nucleophiles. The phase-separated latex polymerization provides a means for separating the carboxylic acid groups from the electrophilic groups, thereby minimizing their interaction. See John L. Gardon in "A Perspective on Resins for Aqueous Coatings," Chapter 2, Technology for Wa terborne Coa tings, ACS Symposium Series, No. 663, American Chemical Society, Washington, DC, pages 27-43, 1997, whose teachings they are incorporated herein by reference. Alternatively, partially neutralized nucleophilic silanol can be pre-reacted with the electrophilic monomer to form a partially neutralized silanol monomer, which is then reacted with the monomer containing the weak acid group or the salt thereof at a sufficient pH basic to inhibit the silanol condensation. Examples of suitable ethylenically unsaturated monomers containing a weak acid group that can be used as comonomers with the electrophilic monomer include acrylic acid, methacrylic acid, itaconic acid, β-carboxyethyl acrylate, and vinylbenzoic acid. Although the above description relates specifically to the preparation of electrophilic polymers from electrophilic monomers, followed by the reaction with partially neutralized nucleophilic silanol, the teaching also applies to the preparation of polymers from a monomer formed from the reaction of an electrophilic monomer and a partially neutralized nucleophilic silanol. In a preferred embodiment of the present invention, the partially neutralized silanol, more preferably the partially neutralized silanotriol, is attached to the core structure of the polymer through a remainder of the nucleophile, preferably a remnant of an amine or a mercaptan. As used herein, the term "remnant" of the nucleophile refers to what remains in the nucleophile after the reaction with the electrophile. Thus, the remainder of a primary amine is a secondary amine, the remnant of a secondary amine is a tertiary amine, and the remainder of a mercaptan is a sulfide. The remnants of other nucleophiles become easily apparent by these examples. As used herein, "attached to the polymer through a nucleophilic remnant" means that the silanol binds to the first connection group X, which binds to the remnant of the nucieophile, which binds to a second group of Y connection, which is attached to the central structure of the polymer, as illustrated: of the polymer wherein X, M +, m, n, and p are as defined above. In the preferred embodiment of the present invention, the second connection group Y is or contains a remnant of the electrophile. As used herein, the term "remnant of the electrophile" refers to the fact that they remain in the electrophile after the reaction with the nucleophile. Thus, if the electrophilic polymer contains pendant benzyl halide groups or the electrophilic monomer is a vinyl benzyl halide, Y is a benzylene group, as illustrated.

If the electrophilic polymer contains pendant oxirane groups (e.g., from the polymerization of glycidyl methacrylate) or the electrophilic monomer is glycidyl metacrate, a portion of the partially neutralized silanol-containing polymer can be represented as shown.

The pH of the stable aqueous solution or dispersion of the partially neutralized silanol-containing polymer is sufficient to inhibit silanol condensation, and preferably is not less than 5, more preferably is not less than 7, and more preferably is not less than 9. It has surprisingly been found that the preferred compositions of the present inventions are stable on the shelf for at least six months, and still cure rapidly at room temperature when applied to a substrate. The following example is for illustrative purposes only and is not intended to limit the scope of this invention. All percentages or parts are by weight unless otherwise specified. Example 1 - Curing at room temperature of a latex with the potassium salt of 3-Aminopropyl Silanotriol A latex polymer having pendant oxirane groups was prepared by an emulsion polymerization reaction, continuous addition, seeded with butyl acrylate (50 parts), methyl methacrylate (10 parts), styrene (10 parts), and glycidyl methacrylate (30 parts). Tri-methylolpropane tris (3-mercaptopropionate) (5 parts) was added as a chain transfer agent. The Mw and Mn were determined to be 13,200 and 8,500 respectively by gel permeation chromatography. The latex contained 45.8 T. By weight solids, a glass transition temperature Tg of -6 ° C (measured by differential scanning calorimetry), a pH of 8.8, and a mean particle size in volume of 152 nm (measured by hydrodynamic chromatography). An aqueous solution of a potassium salt of 3-aminopropyl-silanotriol (3-AS) was synthesized in a 1 liter round bottom flask equipped with stirrer. Aqueous KOH (100 milliliters, 271 mmol KOH) was added to the flask followed by stirring addition of an aqueous solution of 3-aminopropyltriethoxysilane (150.240 grams, Dow Corning Z-6011, 60 grams, 271 mmol of the silane). After the addition was complete, the mixture was stirred at room temperature for 24 hours, after which hydrolysis to 3-AS was found to be complete by high performance liquid chromatography analysis. The theoretical concentration of 3-AS was 11.9 weight percent. A portion of the 3-AS (0.78 grams, 11.9 weight percent in water) was added to one portion of latex (20.0 grams) and left on the shelf for 6 months. The latex was stable on the shelf, without the appearance of latex gelation. Size exclusion chromatography showed that this latex modified with silanol was completely soluble in THF, even after being stored for 6 months, indicating inadvertent cross-linking in a wet state over that period of 6 months. This observation was supplemented with nuclear magnetic resonance spectroscopy with Si, which did not detect silicone condensation. The latex was molded to produce a film that was allowed to cure overnight. The resulting cured film was not dissolved in THF in a 24 hour agitation test and showed a gel content of 32 weight percent. These results mean that latex was cross-linked with 3-AS.

Claims (11)

1. A latent crosslinking composition comprising a solution or dispersion based on stable water in the rack of a polymer having a carbon-containing central structure attached to silanol groups which are sufficiently neutralized to inhibit silanol condensation and where the central structure it binds to the silanol groups through a tertiary amine, a secondary amine, or a sulfide group. The composition of claim 1, wherein the silanol is a neutralized amino silanotriol which is attached to the central structure of the polymer by means of either (a) reacting in the presence of water an amino silanotriol with a solution or a dispersion of a polymer having a central structure containing an electrophile; or (b) reacting in the presence of water an amino silanotriol and an ethylenically unsaturated electrophilic monomer to form an ethylenically unsaturated silanol, then polymerizing or copolymerizing the silanol, wherein the electrophilic is a benzyl halide group, an oxirane group, or a acetoacetoxyethyl group, wherein the amino silanotriol is sufficiently neutralized to inhibit condensation. The composition of claim 2, wherein the polymer is a stable aqueous dispersion which is prepared by polymerizing, in the presence of water, glycidyl methacrylate and at least one non-interfering monomer to form an electrophilic polymer having glycidyl methacrylate structural units, then reacting the electrophilic polymer with an alkali metal salt of the amino silanotriol. The composition of claim 3, wherein the mole percent of the glycidyl methacrylate structural units is 1 to 50 based on the total moles of the monomers used to prepare the electrophilic polymer. The composition of any of claims 3 or 4, wherein the alkali metal salt of the aminosilanol is the potassium salt of 3-aminopropylsilanetriol, or N- (2-aminoethyl) -3-aminopropyl-silanotriol. The composition of any of claims 3 to 5 wherein the alkali metal salt of the aminosilanol is a potassium salt of 3-aminopropylsilanetriol. The composition of any of claims 1 to 6, which is a stable aqueous dispersion having a pH of not less than 7. The composition of any of claims 1 to 7, which is a stable aqueous dispersion having a pH not less than 9. 9. A latent curative comprising a stable aqueous dispersion of a partially neutralized silanotriol group-containing polymer prepared by reacting at a pH greater than 7, an alkali metal salt of 3-aminopropylsilanetriol or N- ( 2-aminoethyl) -3-aminopropyl-silanotriol and an electrophilic polymer containing pendant oxirane groups or pendant benzyl halide groups. The composition of claim 1, wherein the tertiary amine, the secondary amine, or the sulfide group is connected to the central structure of the polymer through a remnant of an electrophile wherein the electrophile is or is prepared from glycidyl methacrylate, a vinylbenzyl halide, or acetoacetoxyethyl methacrylate and silanol is a partially neutralized silanotriol. 11. A latent crosslinking composition comprising a stable water-based solution or dispersion in the rack of a polymer having a carbon-containing core structure attached to silanol groups that are sufficiently neutralized to inhibit silanol condensation, wherein the structure The central is attached to the silanol group through a secondary amine, the secondary amine being connected to the central structure of the polymer through the remainder of an electrophile; wherein the silanol groups are partially neutralized silanotrioles and the electrophilic is a benzylhalide, an oxirane, an allyl halide, and ester, an ether, or an anhydride.