Composition of epoxysilane emulsion additives in water based reactive polymer dispersions and methods of preparation

Abstract

The present invention provides stable epoxy silane emulsions and methods for the preparation of a stable epoxy-silane emulsions comprising: (I) a water insoluble or slightly soluble epoxysilane; (II) an emulsifier; (III) water; and (IV) a water dispersible polymer containing a functional group with an active hydrogen. Also provided are two part systems such that an epoxysilane emulsion comprising components (I)-(III) are combined and the component (IV) may be added upon use of components (I) to (III). Moreover, additional components (V), such as catalysts and pH buffers may be added. Said compositions may be used for, among other things, coatings, adhesives and sealants.The water dispersible or slightly soluble epoxy functional silane for use herein are of the general structure R.sup.1.sub.a R.sup.2.sub.b Si(OR.sup.3).sub.4-a-b where R.sup.1 is an epoxy substituted alkyl or aralkyl group, where the alkyl may have from four to thirty carbon atoms, R.sup.3 is an alkyl or alkoxy-substituted alkyl, aryl or aralkyl group having from two to ten carbon atoms, R.sup.2 is an alkyl group or alkoxy substituted alkyl, aryl or aralkyl group having from one to ten carbon atoms, a is one to three, and b is zero to two, with the proviso that a+b is 1, 2, or 3. R.sup.1, R.sup.2, and R.sup.3 group may be cyclic, branched or linear.

Description

BACKGROUND OF THE INVENTION

Conventional organic solvent based polymer compositions have become disfavored due to problems associated with environmental pollution, conservation of resources and providing a safe working environment. Instead, aqueous solution or dispersion type coating compositions have been proposed as alternatives. In particular, much attention has been paid to reactive polymer emulsions and dispersions because of the ease with which they provide improved properties such as water and solvent resistance.

The use of combinations of polymers, aqueous emulsions and dispersions (latices) and epoxy resins or compounds is well known in the art. For example, U.S. Pat. No. 4,049,869 to Long taught a composition including a high acid acrylic latex (5 to 20% by weight), a crosslinking agent (1 to 10%) and an ultraviolet absorber for use in preserving porous inorganic substrates. The crosslinking agent can include an epoxy resin.

Water-soluble silanes as additives in latex systems have also been disclosed in the prior art. For example, U.S. Pat. No. 5,017,632 to Bredow disclosed coating compositions for Portland cement or metal. The coating composition thereof can be mixed from a pair of storage stable components; a dry mix including a fine particle size filler, an epoxy resin and optionally, a coarse aggregate, and a wet mix including a polymer latex, an amine-functional epoxy curing agent, and a water-soluble epoxy- or amino-silane.

U.S. Pat. No. 5,100,955 to Pons disclosed coating and adhesive compositions based on aqueous dispersions of addition polymers of one or more olefinically unsaturated monomers, emulsion stabilizers and/or emulsifiers and a water-soluble epoxysilane. The water-soluble epoxysilane is added preferably after the polymerization of the addition polymer. The shelf life, however, of such compositions is only from two to three days.

EP Patent No. 401,496 to Hahn disclosed aqueous silicon-modified plastic dispersions as adhesives by epoxysilane-treatment of a dispersion of emulsion copolymers containing carboxylic acid, amide and sulfonic acid groups. Water soluble epoxysilanes of the formula R.sub.1 R.sub.2 R.sub.3 R.sub.4 Si are disclosed with R.sub.1 =(cyclo)alkyl with reactive oxirane group; R.sub.2 =(cyclo)alkoxy, (cyclo)alkyl, aryl or aralkyl; R.sub.3, R.sub.4 =(cyclo)alkoxy, or OH. However, the composition of the synthetic latex is specific. Furthermore, the neat epoxysilane is added directly to the polymer.

In addition to these coating technologies, emulsions of trialkoxysilanes have been previously reported used as waterproofing agents. For example, buffered aqueous silane emulsions are disclosed in U.S. Pat. Nos. 4,877,654 and 5,393,330. Alkylalkoxysilanes are also emulsified with nonionic and anionic emulsifiers for water repellency properties in U.S. Pat. No. 5,226,954.

SUMMARY OF THE INVENTION

The present invention provides shelf stable compositions comprised of water-insoluble or slightly soluble epoxysilanes, emulsifier and a water dispersible or emulsifiable organic polymer which contains a functional group with an active hydrogen. The method of the present invention for the preparation of a shelf stable composition comprises: (a) dispersing a water insoluble or slightly soluble epoxysilane compound in an aqueous solution with emulsifier to yield an aqueous emulsion, and (b) adding the silane emulsion to a water dispersed or emulsified organic polymer which contains a functional group with an active hydrogen. Another aspect of the present invention is to provide an article coated and cured with the reactive, aqueous dispersion. The compositions of the present invention are stable for at least about six (6) months. Moreover, improved properties such as solvent resistance, adhesion, smoothness, hardness and mar resistance are achieved with compositions of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides stable epoxy silane containing compositions and methods for the preparation of stable epoxy-silane containing compositions comprising: (I) a water insoluble or slightly soluble epoxysilane; (II) emulsifier; (III) water; and (IV) water dispersible or emulsified polymer containing a functional group with an active hydrogen. Also provided are two part systems such that an epoxysilane emulsion comprising components (I)-(III) are combined and the component (IV) may be added upon use of components (I) to (III). Moreover, additional components, (V), such as catalysts and pH buffers may be added. Contemplated herein are also compositions for the preparation of the above compositons, namely the silane (I) and the emulsifier (II).

The present invention provides highly stable epoxysilane containing compositions that do not seed or gel during storage. Generally, they are stable for at least two to three weeks and more preferably two to three months. In fact, these compositions containing less than twenty weight percent epoxysilane last longer than six months of storage. This compares favorably with the prior art which taught silane/polymer compositions which would lose properties, such as adhesion, or even gel after two-three weeks.

(I) SILANES

The water insoluble or slightly soluble epoxy functional silane for use herein are of the general structure R.sup.1.sub.a R.sup.2.sub.b Si(OR.sup.3).sub.4-a-a where R.sup.1 is an epoxy substituted alkyl or aralkyl group, where the alkyl may have from four to thirty carbon atoms, R.sup.3 is an alkyl or alkoxy-substituted alkyl, aryl or aralkyl group having from two to ten carbon atoms, R.sup.2 is an alkyl group or alkoxy substituted alkyl, aryl or aralkyl group having from one to ten carbon atoms, a is one to three, and b is zero to two, with the proviso that a+b is 1, 2, or 3. Each R group may be cyclic, branched or linear. The term water insoluble or slightly soluble silanes includes silanes with solubilities between 0.1 and 8.0 weight percent in water. Water insoluble epoxy silanes are preferred. However, water soluble silanes are specifically excluded from these silanes because compositions made with such silanes are not stable for extended periods of time, i.e., more than two to three days at ambient conditions.

The preferred epoxy functional silanes include: ##STR1## where: R is (CH.sub.2).sub.m, where m has a value of zero to six;

R.sup.2 is an alkyl, alkoxy-substituted alkyl, aryl or aralkyl group, each of said groups having from one to ten carbon atoms; R.sup.3 is an alkyl, alkoxy-substituted alkyl, aryl or aralkyl group, each of said groups having from two to ten carbon atoms; R.sup.4, R.sup.5, R.sup.6 or R.sup.7 are each hydrogen or an alkyl group having from one to six carbon atoms; R.sup.8 is an alkyl group having from one to four carbon atoms or aralkyl or aryl group having six to ten carbon atoms; R.sup.9 is RSi.sub.R.spsb.2.sbsb.n (OR.sup.3).sub.3-n n has a value of zero, one or two; c, d and e each have a value of zero or one; and f has a value of zero, one or two.

More specifically, R.sup.2 denotes a substituted or unsubstituted monovalent hydrocarbon group exemplified by alkyl groups (e.g., methyl, ethyl, isobutyl, and octyl groups), alkenyl groups (e.g., vinyl and allyl groups), aryl groups (e.g., phenyl, tolyl and naphthyl groups), and aralkyl groups (e.g., benzyl and 2-phenylethyl groups), as well as those substituted groups obtained by the replacement of one or more of the carbon atoms in the above named hydrocarbon groups with various kinds of atoms and/or groups including sulfur and oxygen, and/or replacement of one or more of the hydrogen atoms in the above named hydrocarbon groups with various kinds of groups, including, but not limited to, halogen atoms, epoxy, methacryloxy, acryloxy, carboxyl, ester, cyano, and polyoxyalkylene groups.

R.sup.3 are alkyl, alkoxyalkyl, aryl or aralkyl radicals such as ethyl, n-propyl, n-butyl, n-hexyl, n-heptyl, n-octyl, n-nonyl, n-decyl, and cyclo radicals such as cyclopentyl, cyclohexyl, cycloheptyl, and cyclooctyl. Illustrative of suitable branched chain hydrocarbon radicals for R.sup.2 are alkyl radicals such as isopropyl, isobutyl, sec-butyl, isobutyl, sec-amyl, and 4-methyl-2-pentyl. Alkoxyalkyl groups may be exemplified by n-botoxy ethyl and methoxy propyl. Aryl groups may be exemplified by phenyl and aralkyl groups may be exemplified by benzyl or ethyl phenyl.

R.sup.4, R.sup.5, R.sup.6 or R.sup.7 are hydrogen atoms or monovalent hydrocarbon groups having 1 to 6 carbon atoms exemplified by alkyl groups (e.g., methyl, ethyl, propyl, isopropyl, n-butyl and isobutyl groups), alkenyl groups (e.g., vinyl and allyl groups), and aryl groups (e.g., phenyl group). These hydrocarbon groups may be substituted by halogen atoms and functional groups, including cyano and epoxy, for a part or all of the hydrogen atoms therein.

Examples of epoxy functional silanes used in accordance with the present invention include, but are not limited to, those silanes described by Brison and Lefort in French Patent No. 1,526,231. Specific examples are 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane, 4-(methyldiethoxysilyl)-1,2-epoxycyclohexane, 3-(3,4-epoxycyclohexyl)propyl tri(isobutoxy) silane, 3-(2,3-epoxybutoxy)propyltriethoxysilane, and �2.2.1!bicycloheptane 2,3-epoxy-5-(2-triethoxysilyl)ethyl.

The silane(s) is present at 0.1 to 30 percent by weight of the total composition �(I)-(IV)!. The preferred concentration is about 0.1 to 10 percent of the weight of the total composition. In preparing the precursor epoxy silane emulsion, as defined by components (I)-(III), the silane(s) is present at 0.1 to 60 weight percent.

(II) EMULSIFIER

The emulsifiers for use herein include nonionic, anionic and cationic surfactants or mixtures of nonionic with anionic or cationic surfactants. Examples of the nonionic surfactants include polyoxyethylene alkyl ethers, polyoxyethylene alkyl phenyl ethers, polyoxyethylene fatty acid esters, sorbitan fatty acid esters, and polyoxyethylene sorbitan fatty acid esters. Examples of the anionic surfactants include fatty acid salts, alkyl sulfate ester salts, alkyl benzene sulfonate, alkyl phosphate, alkylallyl sulfate ester salt, and polyoxyethylene alkylphosphate ester. Examples of the cationic surfactants include quaternary ammonium salts such as long chain alkyl trimethylammonium salts, long chain alkyl benzyl dimethyl ammonium salts, and di(long chain alkyl) dimethyl ammonium salts. A further listing of surfactants useful in the present invention may be those described in 1994 McCutcheon's Vol. 2: Functional Materials, North American Edition (The Manufacturing Confectioner Publishing Co., Glen Rock) 1994, which is incorporated herein by reference.

The emulsifier(s) should be present in the range of 0.05 to 30 weight percent based on weight of the total composition of (I)-(IV) and preferably 0.2 to 20 weight percent of the total composition. In the precursor epoxysilane emulsion, the emulsifier should be present at 0.1 to 50 weight percent of the epoxy silane (I).

The appropriate HLB (hydrophilic-lipophilic balance) of the surfactants is chosen to correspond to the HLB of the specific epoxy silane being emulsified. The method for selecting the optimum HLB for a substance is well known to one skilled in the art and described in "The HLB System" by ICI Americas Inc.

Because the reactive polymer emulsion, as defined by components (II)-(IV), may be prepared prior to the addition of the precursor epoxy silane emulsion, emulsifiers of the type described above can be used in preparing these precursor compositions. Again, the emulsifiers are chosen so that the appropriate HLB is chosen to correspond to the HLB of the specific reactive polymer being emulsified with the proviso that the emulsifier(s) chosen to emulsify the reactive polymer are compatible with the emulsifier(s) used to make the precursor epoxysilane emulsion. In the precursor reactive polymer emulsion, the emulsifier should be present at 1 to 50 weight percent of the reactive polymer.

(III) WATER

The water may be present in an amount ranging from 29.85 to 99.75 weight percent of the total composition (I)-(IV). When a precursor silane emulsion is made without the polymer, about 39 to 99.75% water should be present.

(IV) POLYMERS

The reactive polymers of the present invention are those which have an active hydrogen thereon, preferably in the form of a carboxylic group. Exemplary of such polymers are those which contain terminal or pendant carboxyl groups (--COOH), some of which may be in its neutralized salt form (e.g., --COOK). These reactive polymers have molecular weights between 500 and 10.sup.8 gms/mole. The preferred reactive polymer contains a carboxylic acid group in an amount sufficient to have an acid number, as determined by ASTM D669, between 1 and 780, and preferably, between, 10 and 280. The polymers may be added as dispersions, with no emulsifier, or as emulsions, with emulsifiers therein.

Examples of reactive polymers which can be used in the present invention include carboxylic acid modified polymers chosen from the following: polyethylene, polypropylene, polyethylene propylene copolymer, urethanes, epoxies, polystyrenes and urethane acrylic polymers. Also useful herein are acrylic homopolymers, vinyl acrylic polymers, methacrylic polymers, styrene acrylic copolymers, and polyesters. These reactive polymers may also contain other organic functional groups, including hydroxyl, amide, vinyl and halogens are contemplated as being within the scope of reactive polymers.

Specific examples of preferred reactive polymers which can be used in accordance with this invention include commercially available styrene acrylic emulsion polymers, such as JONCRYL.RTM.s 554, 540,77, and 95, and SCX 2500, all commercially available from SC Johnson Polymer of Racine, Wis. Other specific examples of commercially available preferred reactive polymers materials which can be used include NEOCRYL.RTM. acrylic emulsions, NEOREZ.RTM. water-borne urethane polymers and NEOPAC.RTM. water-borne urethane acrylic copolymers, available from ZENECA Resins of Wilmington, Mass., and UCAR.RTM. acrylic and vinyl acrylic latexes available from Union Carbide Corporation of Danbury, Conn.

Polymer dispersions, which contain no emulsifiers, may also be used herein.

The polymer should be present at 0.1 to 70 weight percent of the total composition.

(V) OPTIONAL INGREDIENTS

The composition of the present invention may additionally contain cross-linking agents, such as urea and melamine resins which are methylolated and/or alkoxylated, epoxy resins, aziridines and carbodiimides. Such agents may be present at 0.1 to 20 weight percent of the total composition, as long as they do not destabilize the composition during storage.

The compositions of the present invention optionally may comprise water soluble/emulsifiable/dispersible curing catalysts, which are hydrolytically stable, to modulate the curing conditions. Examples of such catalysts are organotitanate, organotin, chelated titanium, aluminum and zirconium compounds, and combinations thereof. Examples of chelated titanates are dihydroxy his �2-hydroxypropanato (2-)-O.sup.1,O.sup.2 !(2-) titanate, mixed titanium ortho ester complexes, acetylacetonate chelate, bis(ethyl-3-oxobutanolato-O.sup.1,O.sup.3 !bis(2-propanolato) titanium, isopropoxy(triethanolaminato) titanium and alkanolamine complex of titanium. Examples of organotin catalysts are FOMREZ.RTM. UL-1, UL-22, and UL-32 from Witco of Greenwich, Conn. and dibutyltin bis(1-thioglycerol).

The catalyst can be used in an amount of 0.01 to 20 percent, preferably 0.1 to 10 parts, based on reactive polymer component (IV).

The pH of the total composition may impact upon its hydrostability. High alkalinity or high acidity of the composition catalyzes the hydrolysis and condensation of the alkoxysilyl group of the epoxy silane. The closer the pH of the composition is to neutral (pH=7), the better the stability of the emulsion. Therefore, the preferred range of pH of the total composition is 5.5 to 8.5. Substances which can be used to adjust the pH are organic or inorganic buffers including sodium acetate, sodium citrate, sodium carbonate, sodium bicarbonate, sodium hydrogen phosphate, sodium dihydrogen phosphate, and the corresponding potassium salts.

Other optional ingredients for inclusion herein are fillers, thixotropes, pigments, plasticizers, coalescing agents, biocides and fungicides as are commonly known and used in the art.

METHOD OF PREPARATION AND USE

The precursor epoxysilane emulsions of the present invention are prepared by first mixing the emulsifier (II) with the epoxy functional silane (I). Water (III) is added and the mixture is stirred to provide a white, milky emulsion. The pH of the resulting emulsion is adjusted, if necessary, to pH 7.0.+-.1.5.

The precursor epoxysilane emulsion is added to the reactive polymer (IV) or to a reactive polymer emulsion �Components (II)-(IV)! to provide a stable composition. The method employed to mix these components is not critical and any commonly used low shear equipment, such as a blade or paddle mixer, is suitable. The optional ingredients (V) may be added at any time, although in some cases catalysts should be added last.

The emulsions may be used as two component systems, i.e., components (I)-(III) and component (IV), mixed in shortly before use, but have sufficient stability when mixed to be used as one-component systems. The composition of components (I)-(IV) form uniform aqueous dispersions or emulsions. Many uses of these compositions require drying under ambient conditions or at elevated temperatures (e.g., baking). The resulting dried material has excellent solvent resistance, chemical resistance, hardness, mar resistance, adhesion, water resistance, durability or weatherability.

The compositions made according to the present invention may be used as industrial and architectural coatings, sealants, wood coating, adhesives and in mastics, i.e., generally in any application where the polymer would be used. For example, in textile print paste applications, the composition of the present invention would provide crock resistant colorfast applications. In wood coating, the present compositions would provide stain resistance, mar resistance and block resistance between latex surfaces in storage. As to architectural coatings, the present composition would provide scrub resistance and other improved properties. In sealants, the present composition would provide adhesion to inorganic surfaces. As is clear to one of ordinary skill in the art, there is vast array of applications of the present invention in coating, sealant, adhesives, masonry sealers, fiberglass binders and sizes, inks and other water-borne polymer systems.

EXAMPLES

1. Preparation of a 40% 15 3,4-epoxycyclohexyl)ethyltriethoxysilane (Silane A) emulsion with 5% surfactants

Into a beaker were added 3.85 grams of SPAN.RTM. 60 surfactant (ICI Americas) and 3.65 grams of TWEEN.RTM. 40 surfactant (ICI Americas) which were heated together in a hot water bath to melt the solid materials. 60.0 grams of Silane A were added and the mixture was stirred with a mechanical stirrer. 82.5 grams of water were added and the mixture was stirred vigorously for approximately five minutes to provide a white, stable emulsion containing 40% by weight of Silane A.

2. Preparation of a 20% Silane A emulsion with 5% surfactants

Into a beaker were added 3.5 grams of SPAN.RTM. 60 and 1.5 grams of TWEEN.RTM. 40 which were mixed and heated together in a hot water bath to melt the solid materials. 20.0 grams of Silane A were added and the mixture was stirred with a mechanical stirrer. 75.0 grams of water were added and the mixture was stirred vigorously for approximately five minutes to provide a white, stable emulsion containing 20% by weight of Silane A.

3. Preparation of a 40% Silane A emulsion with 8% surfactants

Into a beaker was added 2.18 grams of SPAN.RTM. 80 surfactant (ICI America) and 2.22 grams of TWEEN.RTM. 40 which were mixed together. To the surfactant mixture was added 22.0 grams of Silane A and the mixture was stirred with a mechanical stirrer. 28.6 grams of water were added and the mixture was stirred vigorously for approximately five minutes to provide a white, stable emulsion containing 40% by weight of Silane A.

4. Preparation of a 40% Silane A emulsion with 10% surfactants

Into a beaker was added 2.73 grams of SPAN.RTM. 80 and 2.77 grams of TWEEN.RTM. 40 which were mixed together. To the surfactant mixture was added 22.0 grams of Silane A and the mixture was stirred with a mechanical stirrer. 27.5 grams of water were added and the mixture was stirred vigorously for approximately five minutes to provide a white emulsion containing 40% by weight of Silage A.

5. Preparation of a 40% .gamma.-glycidoxypropylmethyldiethoxysilane (Silane B) emulsion with 8% surfactants

1.93 grams of SPAN.RTM. 60 surfactant (ICI Americas) and 2.87 grams of Myrj.RTM. 52S surfactant (ICI Americas) were mixed together in a beaker and heated together in a hot water bath in order to melt the solid materials. 24.0 grams of Silane B were added and the mixture was stirred with a mechanical stirrer. 31.2 grams of water were added and the mixture was stirred for approximately thirty minutes to provide a white emulsion containing 40% by weight of Silane B. The epoxy silane emulsion was metastable and gelled within one month.

6. Preparation of 40% of .gamma.-glycidoxypropyltri-(isobutoxy) silane (Silane D) with 6 weight percent surfactants

2.72 grams of SPAN.RTM. 60 surfactant and 1.18 grams of TWEEN.RTM. 40 were mixed together in a beaker and heated together in a hot water bath to melt the solid materials. 26.0 grams of D were added and the mixture was stirred with a Barhart Mixer for 20 minutes. 35.1 grams of water were added and the mixture was stirred for approximately thirty minutes to provide a white, stable emulsion containing 40% by weight of Silane D.

7. Preparation of 40% .beta.-(3,4-epoxycyclohexyl)ethyl tri-(isobutoxy) silane (Silane E) emulsion with 6% surfactant

2.36 gms of SPAN.RTM. 60 and 1.04 grams of TWEEN.RTM. 40 were mixed together in a beaker and heated together in a hot water bath to melt the solid material. 26.0 grams of Silane E were added and the mixture was stirred with a mechanical stirrer for 10 minutes. 35.1 grams of water were added and the mixture was stirred for approximately ten minutes. Giv-Gard DXN (Givaudan-Roure), a preservative, was added.

8-33. Preparation of stable epoxy silane containing compositions

Stable epoxy silane containing compositions were prepared by adding various amounts of precursor epoxy silane emulsion (i.e., Components I-III), as prepared according to procedures described in Examples 1-7 to varying amounts of acid modified polymer dispersions (Components III-IV) or emulsions (Components II-IV). The mixtures of precursor epoxy silane emulsions and acid modified polymer dispersions or emulsions were stirred for approximately 10 minutes. The descriptions and amounts of each component of stable epoxy silane compositions are reported in Table I.

COMPARATIVE EXAMPLES I-XLIV

Comparative examples of epoxy silane acid modified polymer dispersions or emulsions were prepared by mixing various amounts of the epoxy silanes A-E and Z with varying amounts of commercially available acid modified polymer dispersions or emulsions. (see Table 1 for definition of silanes). The comparative example of alkylsilane U-W and diepoxy resin X were prepared by making an emulsion of the alkylsilanes or diepoxy resins according to procedures similar to those described in Examples 1-7, and then mixing various amounts of these alkyl silanes or diepoxy resin emulsions with varying amounts of commercially available acid modified polymer dispersions or emulsions. For example, the precursor diepoxy resin emulsion was prepared by charging into a beaker 2.44 grams of SPAN.RTM. 60 and 0.91 grams of MYRJ.RTM. 52S. The solids were melted by heating in a warm water bath with stirring. 18.2 grams of water were added to the mixture and stirred vigorously. 3.5 grams of 3,4 epoxycyclohexylmethyl 3,4 epoxycyclohexylcarboxylate (Union Carbide ERL-4221) were added and the mixture was stirred vigorously to yield a viscous paste. 28.7 grams of water were added and the stirring was continued for fifteen minutes to yield a white emulsion. The descriptions and amounts of each comparative example is reported in Table I.

TABLE I__________________________________________________________________________Compositions of present invention (precursor epoxy emulsions andcarboxylic acid modified polymers) and comparative examples.__________________________________________________________________________Example No. Silane % Surfactant.sup.1 % Polymer.sup.2 % Water %__________________________________________________________________________ 8 A 0.198 SPAN 60 0.035 JONCRYL 554 46.53 53.22 TWEEN40 0.015 (Acid No.54) 9 A 0.497 SPAN 60 0.087 JONCRYL 554 45.83 53.55 TWEEN 40 0.03710 A 0.998 SPAN 60 0.175 JONCRYL 554 44.66 54.09 TWEEN 40 0.07511 A 2.00 SPAN60 0.192 JONCRYL 554 44.65 52.97 TWEEN 40 0.18212 A 5.035 SPAN 60 0.485 JONCRYL 554 41.08 52.94 TWEEN 40 0.45913 A 0.497 SPAN 60 0.087 JONCRYL 540 42.91 56.47 TWEEN 40 0.037 (Acid No. 49)14 A 0.998 SPAN 60 0.175 JONCRYL 540 41.81 56.94 TWEEN 40 0.07515 A 5.035 SPAN 60 0.485 JONCRYL 540 38.46 55.56 TWEEN 40 0.45916 A 2.00 SPAN 60 0.192 JONCRYL 77 45.00 54.46 TWEEN 40 0.182 (Acid No. 55)17 B 2.00 SPAN 60 0.161 JONCRYL 77 43.70 53.90 MYRJ 52S 0.23918 A 2.00 SPAN 60 0.197 JONCRYL 95 28.50 69.12 TWEEN 40 0.18219 B 2.00 SPAN 60 0.161 JONCRYL 95 28.5 69.10 MYRJ 52S 0.23920 A 0.507 SPAN 60 0.089 SCX 2500 41.91 57.09 TWEEN 40 0.038 (Acid No. 19)21 A 1.013 SPAN 60 0.172 SCX 2500 40.82 57.92 TWEEN 40 0.07622 A 5.045 SPAN60 0.486 SCX 2500 37.58 56.43 TWEEN 40 0.46023 A 5.035 SPAN 60 0.485 JONCRYL 624 42.83 51.19 TWEEN 40 0.459 (Acid No.50)24 A 5.035 SPAN 60 0.485 NEOREZ R-972 29.72 64.30 TWEEN 40 0.459 (Acid No.13)25 A 5.035 SPAN 60 0.485 NEOREZ R-9679 32.34 61.68 TWEEN 40 0.459 (Acid No.23)26 A 5.035 SPAN 60 0.485 UCAR Latex 100 54.20 39.83 TWEEN 40 0.459 (Acid No.13)27 A 10.00 SPAN 60 1.203 UCAR Latex 100 47.24 40.42 TWEEN 40 1.14128 A 5.035 SPAN 60 0.485 UCAR Latex 154 52.45 41.57 TWEEN 40 0.459 (Acid No.16)29 A 10.00 SPAN 60 1.203 UCAR Latex 154 45.71 41.95 TWEEN 40 1.14130 A 5.035 SPAN 60 0.485 UCAR Latex 163 50.70 43.32 TWEEN 40 0.459 (Acid No.15)31 A 10.00 SPAN 60 1.203 UCAR Latex 163 44.19 43.47 TWEEN 40 1.14132 B 2.00 SPAN 60 0.160 JONCRYL 77 43.7 53.90 MYRJ 52S 0.23933 B 2.00 SPAN 60 0.160 JONCRYL 95 28.50 69.10 MYRJ 52S 0.239__________________________________________________________________________ComparativeExample Additive % Surfactant % Polymer % Water %__________________________________________________________________________I NONE NONE JONCRYL 554 47.00 53.00II NONE NONE SCX 2500 43.00 57.00III NONE NONE JONCRYL 77 46.00 54.00IV NONE NONE JONCRYL 540 44.00 56.00V NONE NONE JONCRYL 95 30.00 70.00VI X 2.00 SPAN 60 0.146 JONCRYL 540 43.12 54.63 MYRJ 52S 0.104VII X 2.00 NONE JONCRYL 77 44.83 53.17VIII A 2.00 NONE JONCRYL 77 44.83 53.17IX Y 2.00 NONE JONCRYL 77 44.83 53.17X C 2.00 NONE JONCRYL 77 44.83 53.17XI B 2.00 NONE JONCRYL 77 44.83 53.17XII Z 2.00 NONE JONCRYL 77 44.83 53.17XIII U 2.00 ARQUAD 2C75 0.100 JONCRYL 77 43.70 54.10 ARMEEN DMCD 0.100XIV V 2.00 SPAN 60 0.206 JONCRYL 77 43.70 53.90 TWEEN 40 0.194XV W 2.00 SPAN 60 0.206 JONCRYL 77 43.77 53.90 TWEEN 40 0.194XVI Y 2.00 NONE JONCRYL 95 29.40 68.60XVII C 2.00 NONE JONCRYL 95 29.40 68.60XVIII B 2.00 NONE JONCRYL 95 29.40 68.60XIX X 2.00 NONE JONCRYL 95 29.40 68.60XX Z 2.00 NONE JONCRYL 95 29.40 68.60XXI X 2.00 SPAN 60 0.136 JONCRYL 95 28.50 69.26 MYRJ 525 0.104XXII A 2.00 NONE JONCRYL 95 29.40 68.60XXIII U 2.00 ARQUAD 2C75 0.100 JONCRYL 95 28.50 69.20 ARMEEN DMCD 0.100XXIV V 2.00 SPAN 60 0.206 JONCRYL 95 28.50 69.10 TWEEN 40 0.194XXV W 2.00 SPAN 60 0.206 JONCRYL 95 28.50 69.10 TWEEN 40 0.194XXVI A 5.00 NONE JONCRYL 624 46.55 48.45XXVII Y 5.00 NONE JONCRYL 624 45.55 48.45XXVIII A 5.00 NONE NEOREZ R-972 32.30 62.70XXIX Y 5.00 NONE NEOREZ R-972 32.30 62.70XXX A 5.00 NONE NEOREZ R-9679 35.15 59.85XXXI Y 5.00 NONE NEOREZ R-9679 35.15 59.85XXXII A 5.00 NONE UCAR Latex 100 58.90 36.10XXXIII A 10.00 NONE UCAR Latex 100 55.80 34.20XXXIV Y 5.00 NONE UCAR Latex 100 58.90 36.10XXXV Y 10.00 NONE UCAR Latex 100 55.80 34.20XXXVI A 5.00 NONE UCAR Latex 154 57.00 38.00XXXVII A 10.00 NONE UCAR Latex 154 54.00 36.00XXXVIII Y 5.00 NONE UCAR Latex 154 51.00 38.00XXXIX Y 10.00 NONE UCAR Latex 154 54.00 36.00XL A 5.00 NONE UCAR Latex 163 55.10 39.90XLI A 10.00 NONE UCAR Latex 163 52.20 37.80XLII Y 5.00 NONE UCAR Latex 163 55.10 39.90XLIII Y 10.00 NONE UCAR Latex 163 52.20 37.80XLIV X 1.00 SPAN 60 0.073 JONCRYL 540 43.05 55.82 MYRJ 52S 0.051__________________________________________________________________________ A = (3,4epoxycyclohexyl)ethyltriethoxysilane B = 3glycidoxypropyldiethoxymethylsilane C = 3glycidoxypropyltriethoxysilane D = 3glycidoxypropyltri-(isobutoxy)silane E = (3,4epoxycyclohexyl)ethyltri-(isobutoxy)silane U = octyltriethoxysilane V = 1triethoxysilyl-2-methyldiethoxysilylethane W = amyltriethoxysilane X = (3,4epoxycyclohexylmethyl-3,4-epoxycyclohexylcarboxylate Z = 3glycidoxypropyltrimethoxysilane .sup.1 does not include the surfactants that may be in commercial acid modified polymer emulsion .sup.2 polymer weight is based upon solids in commercial products. 34-84. Shelf Life Stability

The shelf life stability oft he stable epoxy silane emulsions containing acid modified polymer dispersions or emulsions containing acid modified polymer dispersions or emulsions (Components I-IV) and the comparative examples were determined by measuring the viscosity of these compositions at various times after preparation. The viscosity was visually monitored for flow properties by titling a bottle containing the compositions back and forth or by measuring the viscosity of the compositions at 25.degree. C. using a Brookfield viscometer. The stabilities of the compositions are reported in Table II.

These examples show that the stable epoxy emulsions containing acid modified polymers (Components I-IV) are shelf stable for a period greater than 12 weeks provided that the pH of the composition is relatively neutral. For example, Example 27 has 10 weight percent Silane A and UCAR latex 100 and at a pH=6, had a viscosity of 1300cP after storing at room temperature for 12 weeks. The compositions of comparative examples XXXIII and XXXV, where 10 percent of the Silane A was simply mixed with UCAR latex 100 showed an increase in viscosity, as shown in Examples 38 and 39, respectively. Comparative example XXXIII had an increase in viscosity to 3000 cP after storing at room temperature for 12 weeks. Comparative example XXXV gelled within 12 weeks.

The shelf life of the stable epoxy emulsions is important to the end use properties. For example, compositions described in Example 24 were stable for a period of 12 weeks and form a film with a smooth surface upon drying as shown in Example 67. Comparative Example XXVIII, although it did not show a change in viscosity after 12 weeks, produced a poor quality film, as shown in Example 68. This film had a cracked surface and fish eyes. The source of the surface defects was attributed to the hydrolysis and condensation of the epoxy silane to form microgels and oils.

The pH of the compositions can have a pronounced effect on the stability of the compositions. For example, the viscosity of compositions set forth by Example 22 gradually increased and finally gelled after 24 weeks, as shown in Example 75. The increase in viscosity was attributed to the alkalinity of the composition. The pH of the composition was 8.6. These compositions may be useful as a two-component system where long pot time is required.

The stability of Example 32 was observed to be poor, as shown in Example 53. Silane B is slightly soluble in water and the water solubility of this silane makes the preparation of a stable precursor epoxy emulsion difficult. The precursor epoxy silane emulsion described in Example 3 gelled within one month. Lowering the water solubility of Silane B by changing the alkoxy groups attached to the silicon atom can significantly improve the stability of the precursor epoxy silane emulsion. For example, the precursor silane emulsion described in Example 6 was stable. Of note, Silane D is insoluble in water.

TABLE II__________________________________________________________________________Data showing that the compositions of present invention (I-IV) form morestable mixtures than simpleaddition of epoxy silane or additive to aqueous emulsion or dispersion ofan acid modified polymersand produce good film quality. The table also shows the effect of pH onthe stability of thecompositions of the present invention.__________________________________________________________________________ Viscosity of mixture (visual observation or measured viscosity in cP at 25.degree. C.) after storage at room temperature for various periods of time (weeks)Example No Cmpstn pH level 0 1 2 4 12 24 Film Quality__________________________________________________________________________34 26 6.0 Thin Thin35 XXXII 6.0 Thin Thick36 XXXIV 6.0 Thin Thick37 27 6.0 Thin 130038 XXXIII 6.0 Thin 300039 XXXV 6.0 Thin gel40 28 4.0 Thin Thin41 XXXVI 4.0 Thin Thick42 XXXVIII 4.0 Thin Thick43 29 4.0 Thin 110044 XXXVII 4.0 Thin 170045 XXXIX 4.0 Thin 200046 30 4.0 Thin Thin47 XL 4.0 Thin Thick48 XLII 4.0 Thin Thick49 31 4.0 Thin 100050 XLI 4.0 Thin 130051 XLII 4.0 Thin 150052 16 8.5 Thin Thin Smooth surface53 32 8.5 Thin Gel Smooth surface54 IX 8.5 Thin Thin Smooth surface55 X 8.5 Thin Gel Smooth surface56 XI 8.5 Thin Gel Smooth surface57 VI 8.5 Thin Gel Smooth surface58 18 8.5 Thin Thin Smooth surface59 33 8.5 Thin Separate into Smooth surface 2 layers60 XVI 8.5 Thin Thin Cratered Surface61 XVII 8.5 Thin Thin Smooth Surface62 XVIII 8.5 Thin Thin Cratered Surface63 XXI 8.5 Thin Separated into Smooth surface 2 layers64 23 8.0 Thin Thick Smooth surface65 XXVI 8.0 Thin Gel Gel particles & cratered66 XXVII 8.0 Thin Thick Rough, cratered surface67 24 8.0 Thin Thin Smooth Surface68 XXVIII 8.0 Thin Thin Fish eyes, cracked surface__________________________________________________________________________ Viscosity of mixture (visual observation or measured viscosity in cP at 25.degree. C.) after storage at room temperature pH level for various periods of time (weeks)Example No Composition (space) 0 1 2 4 12 24 weeks Film Quality__________________________________________________________________________69 XXIX 8.0 Thin Thin Cratered surface70 25 8.0 Thin Thin Smooth surface71 XXX 8.0 Thin Thin Fish eyes72 XXXI 8.0 Thin Thick Fish eyes73 20 8.5 50 49 50 6374 21 8.5 65 62 64 7575 22 8.6 148 146 107 gel76 II 8.5 28 30 29 4577 13 8.6 28 30 29 40078 14 8.6 135 154 192 44079 15 8.6 149 260 913 gel80 IV 8.6 228 206 208 24081 9 8.4 924 396 493 26082 10 8.5 234 378 500 93083 12 8.5 193 860 5675 gel84 I 8.5 4.13 397 423 520__________________________________________________________________________ 85-111. Solvent Resistance

The stable epoxy silane emulsions containing acid modified polymers are useful in improving the solvent resistance of films cast from them. The solvent resistance was determined by methyl ethyl ketone (MEK) double rubs. The tests were conducted according to ASTM D4752-87. Films were cured at 23.degree. C. and 50% relative humidity for seven days or cured at 121.degree. C. for 20 minutes and then 23.degree. C. at 50% relative humidity for 7 days. The results of solvent resistance is reported in Table III.

The solvent resistance of films cast from compositions of the present invention was significantly better than films cast from the acid modified polymers alone. For example, the number of MEK double rubs of a film cast from compositions described in Example 16 and shown in Example 90 and cured at 121.degree. C. for 20 minutes was 130 rubs. Comparative Example III, a film of JONCRYL 77 withstood only 11 MEK rubs, as shown in Example 91. Simple mixtures of Silane A and JONCRYL 77, Comparative Example VIII, withstood only 34 rubs. In some cases, simple blends of epoxy silanes and polymers, such as Comparative Example XI, yield solvent resistant films shown in Example 94, but the shelf life of these compositions is poor. For example, Comparative Example XI gelled in two weeks, as shown in Example 56/

TABLE III__________________________________________________________________________Data showing that the compositions of present invention have improvedsolvent resistance, as demonstrated by MEK double rubs MEK double rubs Cured at 23.degree. C. at 50% Cured at 121.degree. C. for 20 min. and thenExample No. Composition relative humidity for 7 days 23.degree. C. at 50% relative humidity for 7 days__________________________________________________________________________ 85 8 29 39 86 9 -- 40 87 10 26 -- 88 11 -- 50 89 I 14 9 90 16 41 130 91 III 14 11 92 IX 41 169 93 XII 110 171 94 XI 87 127 95 VI 8 9 96 VII 45 97 VIII 34 98 XIII -- 11 99 XIV -- 9100 XV -- 9101 18 19 182102 V 8 7103 XVI 2 22104 XX 57 241105 XVIII -- 22106 XXI 12 22107 XIX -- 46108 XXII -- 51109 XXIII -- 14110 XXIV -- 13111 XXV -- 8__________________________________________________________________________ 1. Film had craters. 112-115. Mar Resistance.

The compositions of the present invention have improved mar resistance when cast as films. The mar resistance was measured using an AATCC crockmeter, Atlas Electric Devices Company, model CM-5. Films were cast into Bonderite treated cold-rolled steel panels using a draw down bar and cured at 121.degree. C. for 20 minutes and 23.degree. C. and 50% relative humidity for seven days. The gloss values were determined according to ASTM D 523. The results of the mar resistance of these films are reported in Table IV. Films east from compositions of the present invention demonstrated an improvement in mar resistance for compositions freshly prepared and aged 6 months (Examples 112 and 113) as compared to compositions from Comparative Examples XLIV and IV (Examples 114 and 115).

TABLE IV__________________________________________________________________________Data showing that the mar resiatance of films cast from compositions ofpresentinventions are better than simple mixture of epoxy silaneand acid modified polymersExample No. Composition Initial Gloss (60.degree.) Gloss after 10 cycles % loss__________________________________________________________________________112 14.sup.1 96 32 67113 14.sup.2 100 50 50114 XLIV 98 26 73115 IV 103 24 77__________________________________________________________________________ .sup.1 film cast immediately after preparation of composition .sup.2 film cast 6 months after preparation of composition. 116 -125. Hardness

Films cast from the compositions of the present invention had an increase in hardness while maintaining other film properties, such as gloss, and adhesion, as indicated in Table V. Pencil hardness was measured according to ASTM D 3363-74. The gloss was measured according to ASTM-D 523. Crosscut tape adhesion was measured according to ASTM 3359-90. Wet adhesion of the film to E-coat steel panel was measured according to Method 6301 of US Federal Standard Test Method 141B. The films were prepared using a draw down bow. The dry film thickness was 2 mils. The films were cured at 121.degree. C. for 20 minutes and 23.degree. C. and 50% relative humidity for 7 days.

TABLE V______________________________________Data showing that composition of present invention give a goodbalance of film properties after curing at121.degree. C. for 2 minutes and 23.degree. for 7 days Gloss value Hardness Tape WetExample Composition 20.degree. 60.degree. Pencil Adhesion Adhesion______________________________________116 16 84 97 HB 5B 10117 17 78 99 H 5B 10118 XII 64 92 F 5B 10119 VI 80 99 B 5B 10120 III 89 105 B 5B 10121 18 80 94 2H 5B 10122 19 64 92 F 5B 10123 XX 80 99 HB 5B 10124 XXI 80 99 HB 5B 10125 V 96 107 B 5B 10______________________________________

A dramatic illustration of the usefulness of the composition of the present invention is presented for a filled latex sealant. The sealant formulations are set forth in Table VI. The sealants were prepared by charging UCAR latex polymer 105 and TRITON X-405 into a mixing vessel and stirring for five minutes. A solution of NUOCEPT 95 preservative, TRITON X-405 surfactant and water was added to the mixing vessel and stirred for five minutes. The ethylene glycol, TEMOL 850 dispersing agent, ASE 60 thickener, KTPP potassium tripolyphosphate, and SANTICISER 160 plasticizer were added and mixed using a high speed mixing propeller. Mineral spirits, precursor epoxy silane emulsion or silicone additive and ammonium hydroxide were added and mixed using a spatula. A MOLTINI PLANAMAX mixer was used to stir the mixture for 20 minutes under a nitrogen atmosphere. The TiO.sub.2 and DMDEE (2,2-dimorpholino diethyl ether) catalysts were added and mixed for five minutes. The mixture was degassed under reduced pressure for five minutes. The sealant was stored in a plastic sealant tube.

The sealants were cured at 23.degree. C. and 50% relative humidity for three weeks in an environmental chamber and 1 week at ambient conditions. The physical properties of the cured sealants were measured according to ASTM D 412C (percent elongation, tensile strength and modulus), ASTM 624 (tear strength), C-661 (shore A hardness) and C-794 (adhesion in peel).

The sealants were heat aged at 50.degree. C. for 4 weeks. The physical properties of the sealant are reported in Table VI. The compositions of the present invention, when fully formulated into a filled acrylic latex (Example 129), had excellent adhesion while maintaining high elongation and low modulus, especially after aging for 4 weeks at 50.degree. C. The comparative examples 126-28, 130-31 had either poor adhesion after heat aging or dramatic loss of percent elongation.

TABLE VI______________________________________Data showing that the compositions of the present invention givea good balance of properties in a filled latex selantLATEX SEALANT FORMULATIONS1. FILLED FORMULATIONComponents Parts Source______________________________________UCAR .RTM. Latex Polymer 105 200.0 Union CarbideTRITON .RTM. X -405 (70% Active Surfactant) 3.45 Union CarbideNUOSEPT .RTM. 95 (Preservative) 0.50 HulsTRITON .RTM. X - 405 0.50 Union CarbideDiltilled Water 0.50Ethylene Glycol 4.95 AldrichTEMOL .RTM. 850 (Dispersing Agent) 0.50 Rohm & HaasADE .RTM. 60 (Thickener) 4.00 Rohm & HaasKTPP (Potassium Tripolyphosphate) 0.50 FMCSANTICIXER .RTM. 160 (Plasticizer) 50.00 MonsantoMineral Spirits 4.00 AldrichOrganofunctional Silane or precursor 2.00 OSi Specialtiesepoxy emulsionAmmonium Hydroxide (28% Soln) 1.00 FisherDRIKALITE .RTM. (Treated Calcium Carbonate) 230.00 ECCTitanium Dioxide R-901 4.00 DuPontDMDEE (Catalyst) 0.50 Texaco______________________________________ __________________________________________________________________________PHYSICAL PROPERTIES.sup.a FOR FILLED ACRYLICLATEX SEALANT FORMULATION Adhesion to Anodized Cohesive Elongation Tensile Modulus Tear Hardness Aluminum FalureExample Silane % (psi) (Young's) (lbs/in) (Shore A) (lbs/in) Mode (%)__________________________________________________________________________126 None Initial 400 44.8 43.3 19.7 6 8.1 65% Aged.sup.b 347 41.2 29.0 20.1 15 9.5 10127 Z Initial 287 62.4 39.3 22.9 20 7.2 95% Aged 158 110.6 119.4 30.1 15 5.8 98%128 A Initial 300 72.6 36.2 26.6 23 4.4 100% Aged 70 116.3 313.8 16.4 16 3.4 100%129 Example 1 Initial 300 73.3 41 36.5 15 7.7 93% Aged 199 82.5 60.6 29.1 22 11.2 90%130 W Initial 567 27.4 9.3 9.3 15 5.1 20% Aged 200 125.3 25.5 25.5 24 7.5 7%131 T Initial 253 53.2 26.9 26.9 28 9.1 100% Aged 219 39.1 20.2 20.2 21 8.0 20%__________________________________________________________________________ .sup.a) Physical properties measurements obtained in accordance with accepted ASTM test specificatins; .sup.b) Samples were aged for four (4) weeks at 50.degree. C.; A = (3,4epoxycyclohexyl)ethyltriethoxysilane T = 3aminopropylsiloxanes in water Z = 3glycidoxypropyltrimethoxysilane Example 1. Precursor epoxy silane emulsion prepared in Example 1 W = amyltriethoxysilane. (The silane was added as an emulsion prepared by mixing 40 grams of amyltriethoxysilane, 4.11 grams of SPAN60 and 3.87 grams of TWEEN 40 and 52 grams of water.)

Claims

1. An emulsion comprising (a) a water insoluble or slightly soluble epoxy silane, (b) water (c) an organic polymer containing one or more terminal or pendant carboxylic groups and (d) an emulsifier, which is shelf stable for at least two months and wherein the epoxy silane is of the formula: ##STR2## where: R is (CH.sub.2).sub.m, where m has a value of zero to six;

R.sup.2 is an alkyl, alkoxy-substituted alkyl, aryl or aralkyl group, each of said groups having from one to ten carbon atoms;

R.sup.3 is an alkyl, alkoxy-substituted alkyl, aryl or aralkyl group, each of said groups having from two to ten carbon atoms; and

n has a value of zero, one or two.

2. The emulsion according to claim 1 wherein the emulsifier is selected from the group consisting of: polyoxyethylene alkyl ethers, polyoxyethylene alkyl phenyl ethers, polyoxyethylene fatty acid esters, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, fatty acid salts, alkyl sulfate ester salts, alkyl benzene sulfonate, alkyl phosphate, alkylallyl sulfate ester salt, polyoxyethylene alkylphosphate ester, quaternary ammonium salts, alkyl trimethylammonium salts, alkyl benzyl dimethyl ammonium salts, and dialkyl dimethyl ammonium salts.

3. A composition according to claim 1 wherein n=2.

4. An emulsion comprising: (I) 0.1 to 20 weight percent of a water insoluble or slightly soluble epoxysilane; (II) 0.1 to 25 weight percent of an emulsifier; (III) 10 to 80 weight percent of water; and (IV) 25 to 60 weight percent of an organic polymer containing one or more terminal or pendant carboxylic groups wherein the epoxy silane is of the formula ##STR3## wherein n has a value of zero, one or two, R is (CH.sub.2).sub.m, where m has a value of zero to Six; R.sup.2 is an alkyl, alkoxy-substituted alkyl, aryl or aralkyl group, each of said groups having from one to ten carbon atoms; and R.sup.3 is an alkyl, alkoxy-substituted alkyl, aryl or aralkyl group, each of said groups having from two to ten carbon atoms.

5. A coating made from the emulsion of claim 4.

6. An emulsion according to claim 4 additionally comprising a pH buffer.

7. An emulsion according to claim 4 additionally comprising a cure catalyst.

8. A method of preparing a coating or sealant comprising mixing together: (I)0.05 to 30 weight percent of a water insoluble or slightly soluble epoxysilane; (II) 0.05 to 30 weight percent of an emulsifier; (III) 29.85 to 99.75 weight percent of water; and (IV) 0.1 to 70 weight percent of an organic polymer containing one or more terminal or pendant carboxylic groups wherein the epoxy silane is of the formula ##STR4## wherein n has a value of zero, one or two, R is (CH.sub.2).sub.m, where m has a value of zero to six; R.sup.2 is an alkyl, alkoxy-substituted alkyl, aryl or aralkyl group, each of said groups having from one to ten carbon atoms; and R.sup.3 is an alkyl, alkoxy-substituted alkyl, aryl or aralkyl group, each of said groups having from two to ten carbon atoms.

9. The method according to claim 8 wherein n=2.