GB2278608A - Water-borne urethane coating compositions - Google Patents

Description

1 k, 1- 2278608 WATER-BORNE URETHANE COATING COMPOSITIONS This invention

relates to water-borne wood finishes. In particular, the present invention relates to a water-borne coating composition comprising a polyurethane polymer and polyfunctional silane crosslinkers.

It is common to treat the surface of a wood substrate to protect the wood surface from the elements to which it is exposed. Several urethane compositions are commercially available for this purpose.

For example, solvent-based urethane compositions have been used as coating compositions for wood substrates. These compositions have proven to have several drawbacks such as toxicity, flammability and odor. Indeed, many of the solvents exhibit adverse effects upon the Earth's atmosphere.

To overcome many of these drawbacks, aqueous polyurethane systems have come increasingly into use.

Various patents disclose a variety of such systems.

U.S. Patent No. 4,197,219 ("Damicoll) discloses aqueous polyurethane dispersions which contain: a.) an aqueous polyurethane latex, b.) an aqueous casein co-condensed phenolic-formaldehyde resin emulsion and c.) a nonionic fluorocarbon surfactant.

U.S. Patent No. 4,576,987 ("Crockatt et al.11) teaches the use of a coating composition comprising: a.) an aqueous microcrystalline wax dispersion, b.) an aqueous emulsion of copolymerized monoethylenically unsaturated monomers and c.) N-methylol functional self-crosslinking polyurethane aqueous dispersion. The Crockatt et al. polyurethane is a N-methylol terminated polyurethane containing neutralized carboxyl groups.

U.S. Patent No. 4,622,360 ("Gomi et al.") discloses a water-borne urethane resin coating composition containing carboxyl and/or carboxylate groups and a polyvalent metal complex used as the crosslinking agent. The Gomi et al. water-borne polyurethane resins can also be copolymers with vinyl monomers such as acrylic acid, acrylates and 5 nethacrylates.

Although water-based urethanes have been utilized as coating compositions for wood, they have found utility in other applications as well. For instance, U.S. Patent No. 5,006,413 ("Den Hartog et al.") teaches the use of a film forming binder for clear coat finishes on automobiles comprising: a.) a Taethylol (neth)acrylamide acrylic polymer and b.) a polyurethane.

U.S. Patent No. 3,412,054 ("Milligan") discloses water-dilutable polyurethanes utilized for surface coatings and printing inks. The Milligan polyurethanes are the reaction products of isocyanates and polyols that contain carboxylic acid groups that are substantially unreactive towards isocyanates. The free carboxylic acid groups disclosed in Milligan comprise the formula:

CH20H R-C-COOH CH20H wherein R represents a hydroxymethyl group, a hydrogen or an alkyl group having up to 20 carbon atoms. This composition can be neutralized by ammonia or amines to impart water-dilutability to the polyurethane.

U.S. Patent No. 4,278,578 ("Carpenter") discloses a coating composition for plastic substrates comprising a carboxy functional urethane polymer, a carboxy-functional acrylic copolymer and an aqueous h 9 alkali soluble resin. The Carpenter composition is crosslinked by a polyfunctional aziridine.

U.S. Patent No. 4,271,229 ("Temple") discloses urethane compositions that can be utilized in producing glass fibers having improved stability to ultraviolet light. The Temple urethane comprises: a a polyurethane polymer dispersed in water, b.) a ureidofunctional silane, c.) an aminofunctional silane and d.) glass fiber lubricants. The polyurethane is the reaction product of an isocyanate and an organic polyhydroxylated compound, a hydroxyl terminated ether or a polyester compound.

U.S. Patent No. 4,289,672 (19Friederich et al.11) discloses sizing compositions for glass fibers which comprise an aqueous polyurethane ionomer dispersion. The polyurethane dispersion in Friederich can comprise a polyester diol and diisocyanate. The polyurethane ionomer can be cationic or anionic and the Friederich et al. bonding agent can be an epoxy alkyl alkoxysilane or an aminoalkyl alkoxy silane.

It has now been found that many of the adverse effects of solvent-borne urethanes can be reduced by utilizing a composition which can used to coat and protect wood which comprises: a.) a urethane polymer comprising a polyisocyanate, a polyol and an acid selected from the group consisting of an aminocarboxylic acid, a hydroxy carboxylic acid, an aliphatic sulfonic acid or an aminosulfonic acid; and b.) one or more polyfunctional silanes to crosslink the urethane polymer.

The present invention includes a water-borne coating composition comprising: a.) a urethane polymer comprising a reaction product of a polyisocyanate, a polyol and an acid selected from the group consisting of an aminocarboxylic acid, a hydroxy carboxylic acid, an aliphatic sulfonic acid or an aminosulfonic acid and b.) one or more polyfunctional silanes are added to crosslink the urethane polymer. The urethane polymer and the polyfunctional silane(s) are provided in an amount sufficient to provide a protective coating which substantially prevents solvent stain on a wood surface. "To substantially prevent solvent stain" means that the composition has at least a rating of seven (7) according to the Solvent Stain Test described below.

Preferably, the organic acid utilized in the present invention is represented by the following formula:

(R2) xQ (RO y wherein Q represents a straight or branched, hydrocarbon radical containing 1 to 12 carbon atoms, R2 is independently selected from the group consisting of -OH or -NH2 R3 is independently selected from the group consisting of -COOH or -S03H x is an integer of at least 1 y is an integer of at least 1.

In one embodiment of the present invention, the organic acid and polyisocyanate are reacted prior to being reacted with the polyol.

In addition, it is preferred that the polyfunctional silanes are either epoxy silanes and/or amino silanes.

In another embodiment of the present invention, the composition is dispersed in an aqueous solution.

In addition, the present invention comprises an article coated with the composition of the present 35 invention.

6 The present invention provides a one-part, waterborne, crosslinkable coating composition that comprises a water-dispersible urethane polymer or an 5 acrylic copolymer thereof, and at least one polyfunctional silane.

The water-dispersible urethanes polymers are selected from a group consisting of a reaction product of a polyisocyanate, a polyol and an organic acid. The term "water-dispersible urethane polymer" is also meant to include water- dispersible urethane prepolymers. Suitable polyisocyanates used for preparing the waterdispersible urethane may be monomeric in nature or adducts prepared from organic diisocyanates and containing biuret, allophanate or urethane groups or isocyanate rings. These polyisocyanates include ethylene diisocyanate, 1,4-tetramethylene diisocyanate, 1,6-hexamethylene diisocyanate, 2,4,4-trimethyl, 1, 6hexamethylene diisocyanate, 1,12-dodecane diisocyanate, cyclobutane 1,3-diisocyanate, cyclohexane-1,3- and 1,4diisocyanate isocyanatomethyl cyclopentene, 1isocyanato-3,3,5-trimethyl-5- isocyanatomethy1 cyclohexane, 2,4- and 5,6-hexahydro toluene diisocyanate and mixtures of these isomers. 2,4'- and 4,4'-dicyclo hexyl methane diisocyanate, 1,3- and 1,4- phenylene diisocyanate, 2,4- and 2,6-tolylene diisocyanate, diphenyl methane-2,4'and/or 4,4'diisocyanate, naphthalene-1,5-diisocyanate, triphenyl methane-4,4',4"-triisocyanate, polyphenyl polymethylene polyisocyanate. The preferred polyols include ethylene glycol, 1,2- and 1, 3-propylene glycol, 1,3- and 1,4-butane diol, 1,6-hexanediol, 2,2dimethyl-1,3-propylene glycol, glycerine, trimethylol propane. 35 In order to make the urethane polymer waterdispersible, it is necessary to chemically incorporate an organic acid into the polymer. This can be achieved in two ways. The first way is to react the polyisocyanate with the organic acid and then react the reaction product with a polyol. The second way is to react the isocyanate with the reaction product of the polyol and the organic acid. Suitable organic acids contain at least one isocyanate-reactive hydrogen and at least one hydrophilic group. Examples of useful organic acids include, but are not limited to, aliphatic hydroxy carboxylic7acids, aliphatic or aromatic aminocarboxylic acids with primary or secondary amino groups, aliphatic hydroxy sulfonic acids and aliphatic or aromatic aminosulfonic acids with primary or secondary amino groups. Preferably, the acids have molecular weights below about 300.

It is preferred that the organic acids comprise the general formula:

(R2) XQ (R3) y wherein Q represents a straight or branched, an aromatic or aliphatic hydrocarbon radical containing 1 to 12 carbon atoms, R2 is independently selected from the group consisting of -OH or -NH2 R3 is independently selected from the group consisting of -COOH or -SO3H x is an integer of at least, preferably, x is an integer of at least 1, and y is an integer of at least, preferably, y is an integer of at least 1 wherein x+y = 24.

Preferably, x is an integer of 1 to 3 and y is an integer of I to 3.

In a more preferred embodiment of the present invention, it is preferred that the organic acids are - 7 hydroxy carboxylic acids which comprise the general formula:

(H0)xQ(COOH)y wherein Q represents a straight or branched, hydrocarbon radical containing 1 to 12 carbon atoms, x is an integer of at least, preferably, x is an integer of 1 to 3, and y is an integer of at least, preferably, y is an integer of 1 to 3. Examples of suitable hydroxy-carboxylic acids include citric acid and tartaric acid.

More preferably, the hydroxy carboxylic acids are the dihydroxy alkanoic acids described in U.S. Patent No. 3,412,054 which is incorporated by reference. These dihydroxy alkanoic acids are represented by the structural formula:

CH20H I Q'-C-COOH 1 CH20H wherein Q' is a hydrogen or an alkyl group containing 1 to 8 carbon atoms. The most preferred dihydroxy acid is oc,(x-dinethylol propionic acid wherein Q' is methyl in the above formula.

The preferred polyfunctional silanes in the practice of this invention are compounds of general formulae:

A- (R) --S i (OR,) 3 A-(R).-SiCH3 (OR,) 2 wherein A represents a reactive functional group such as a vinyl group, a gamma- methacyloxy group, a gamma-mercapto group, an amino group such as an N-2- (aminoethyl)-3-amino group and a 3glycidyloxy group; R represents a methylene group; R, is independently selected from the group consisting of a hydrogen atom, a lower alkyl or an acyl group having 1 to 4 carboi atom; and n is an-integer from 0 to 12.

The most preferred polyfunctional silanes are epoxy, Tnethacrylo andlor amino functionalities.

Examples of such silanes are represented-by the following formulae:

H H 1 1 H--C--C---CH20'C3H6Si(OCI')3 0 H H 1 1 c c PC3 1(0 %3 CA)2 0 H2NC31'16Si(OC2H5)3 CH3 1 CH2=C--C---0--C3II6Si(OC2H5)3 When the water-dispersible urethane polymer is blended with the polyfunctional silanes, the first silane function, i.e., the epoxide, methacrylo radical or amino group, may slowly react with carboxylic group of the urethane to form an ester or amide linkage during the long term storage. The second silane function hydrolyzes partially thereby stabilizing the polymer in water. Once applied to a wood surface, the second silane function crosslinks to form a siloxane bond in drying stage of the coating formation.

A small amount of coalescent agent can also be used in the composition of the present invention to help stabilize dispersions as well as to facilitate film formation. A coalescent agent is defined as any organic solvent which is polar and also miscible with water. Examples of suitable coalescent agents include, but are not limited to, ketones, ethers, alcohols, esters, glycols, acids, aldehydes, amines, amides and heterocyclic adducts. The most preferred coalescent agents are N-methylpyrrolidone, butyl acetate, and propylene glycol methyl ether acetate.

Acrylic copolymers can also be utilized in order to reduce the raw material cost, and thus to make the composition of the present invention more economical.

The preferred acrylic copolymers contain carboxylic functionalities, and typically comprise from about 3 to about 40% by weight carboxylic acid or carboxylate monomers along with other neutral group-containing monomers. The carboxylic acid or carboxy groups in these copolymers are typically derived from monoethylenically unsaturated carboxylic acid monomers, such as acrylic acid, methacrylic acid, crotonic acid and the like. Pendent neutral groups of these copolymers are typically from non-functional monomers such as styrene, acrylonitrile, vinyl esters such as vinyl acetate, vinyl ethers such as methyl vinyl ether and preferably, Cj-C8 aliphatic esters of methacrylic acid and acrylic acid such as methyl methacrylate, butyl acrylate and the like.

In addition, ultraviolet absorbers (11UV absorbers") can be added to the compositions of the present invention. An example of a suitable UV absorber is Tinuvirf'm 1130, a substituted hydroxyphenyl benzoltriazole, commercially available from Ciba-Geigy, at Hawthorne, New York. The UV absorbers increase the weatherability of the composition.

The composition of the present invention can be tailored to the desired end use. The water-borne composition of the present invention typically comprises a solids content from about 50 grams/liter to about 600 grams/liter, preferably from 100 grams/liter to 300 grams/liter. The remainder is water. Either too low or too high of a solid content may result in poor stability and coatability.

Preferably, the urethane polymer is present in an amount of about 10 to about 350 grams/liter. More preferably, it is present in amount of about 50 grams/liter to about 250 grams/liter.

It is preferred that the polyfunctional silane be added to the composition in amount of about I gram/liter to about 40 grams/liter, more preferably from about 10 to about 20 grams/liter. If too little silane is added, there is little or no noticeable effect upon the coating properties of the composition. If too much silane is added, gelation will occur.

The coalescent agents may be used in an amount of up to about 100 grams/liter, more preferably in an amount less than about 30 grams/liter.

If acrylic copolymers are utilized, they can present in an amount up to 500 grams/liter. The acrylic copolymers can range from about 100 grams/liter to about 200 grams/liter.

The balance of components in the polymer is also very important with respect to coating performance. Preferably, the molar ratio of isocyanate to polyol is 1.0 to 1.5 and the amount of organic acid is preferably 0.5 to 10 percent solids, more preferably 0.5 to 5.0 percent solids.

4 a The compositions of the present invention are also suitable for other uses such as priming. In addition, the compositions can be blended in with fillers, pigments, and other additives to form color paints and 5 coating materials.

The compositions can be coated onto porous substrates such as concrete, vinyl tile, ceramic, fabrics, paper, to retain the original appearance of such substrates as well as providing protection to the surface of the substrates. TEST SAMPLES Test samples were prepared by coating wood samples with three coats of the composition of the present invention. The wood samples included oak, cherry, maple, and pine. The test samples were allowed to cure 30 days under ambient conditions prior to being tested in accordance with the test methods discussed below.

TEST METHODS SOLVENT STAIN TEST The solvent stain test utilized was a modification of an ASTM test listed as ASTM-2198-68. The test was modified in that the time period was varied from the ASTM test. Solvent mixtures including ethanol (ETOH), methyl ethyl ketone (MEK) and water were utilized to create 14 standard solvent stains each of which were applied to the test samples in the manner described below. A scale listing the individual solvent mixtures is listed below in Table 1.

Three layers of 1/411 x 1/411 in. Whatman No. 1 filter paper were placed on top of the test samples. Thereafter, three drops of solvent stain were applied to the filter paper. After aging the test samples for 18 hours, the filter paper was removed. The test samples were then inspected and rated according to the scale set forth in Table 2. If the filter paper was easily removed, the coating was considered to have - 12 provided good solvent resistance. If the paper would adhere onto the test sample as a result of solvent attack, it was considered to have performed poorly. Each test sample was evaluated with all fourteen solvent stains and a composite score was recorded. The maximum score was 28.

TABLE 1

Com;'Midon MH NEK H10 A so so B c 1 D E 90 so 1 10 1 101 Increasing Aggressiveness F 20 10 G 30 10 H so 1 S K 70 10 L so m N so 60 10 1 90 1 10 1 100 1 J1 TABLE 2

Rating System ge - paper adhere& onto coating slightly gained - pq)er can be removed, but a ring main is left no damage - r can he removed without fing stain HOUSEHOLD STAIN TEST The household stain test was utilized to determine the deleterious effects of common household chemicals upon clear finishes. The test samples were examined for the following surface alterations: discoloration.

change of gloss, blistering, softening, swelling and loss of adhesion.

The household stain test utilized was a modification of the ASTM-D1308-87 test. The test was 13 - modified by varying the proscribed time period of the test and the type of chemicals utilized. The procedure to determine the efficacy of the compositions of the present invention included the steps of placing the chemicals listed in Table 3_ onto the test samples and visually observing the test samples for the effects listed above. The test samples were then inspected and rated according to the scale set forth in Table 4. Each test sample was evaluated with all the household stains and a composite score wa recorded. The maximum score is 22..

TABLE 3

Household Stains Grape juice' 5% ammonW Cooking oil' coffee' Milk7 5% TSM L_Detergent shoe polish' mustard6 nail polls permanent marker" Minute Maid@ Grape Juice commercially available from Coca-Cola Foods, Houston, Texas.

2 0 2 Analytical Grade 5% Ammonia, commercially available from the Aldrich Chemical Co., Milwaukee, Wisconsin.

3 4 6 7 8 9 Brown Shoe Polish, Kiwi Brands Inc., Douglassville, PA.

CriscoO Vegetable Oil, commercially available from the Procter & Gamble company, Cincinnati, OH.

Maxwell HouseO Ground Coffee Filter Packs, General Foods Corp., White Plains, N.Y.

Best Yet@ Mustard commercially available from Scriver Inc., Oklahoma City, OK.

3% Fat Milk commercially available from the Land-0Lakes Company, Minneapolis, MN.

Reagent Grade trisodium phosphate, Aldrich Chemical Company, Milwaukee, Wisconsin.

Cover Girl Nailslicksc, Noxwell Corp., Hunt Valley, Maryland.

TABLE 4

Rating System 0 damage blistering and discoloration 1 slightly stained slight swelling, change of gloss and softening no damage - few changes in surface conditions 2 SHELF-LIFE STABILITY TEST Test samples were tested for their shelf-life stability. The Shelf-Life Stability Test was conducted by placing a test sample into a glass bottle and then sealing the glass bottle. Thereafter, the sealed bottle containing the test sample was placed into a hot air oven sold under Model V-29HD by the.Dispatch Oven Company located in Minneapolis, MN. The oven was heated to and kept at a temperature of 120 F 30F. The test samples were aged for periods of 1 week, 4 weeks, 8 weeks and 10 weeks. After being aged, each sample was tested for solvent stains and household stains according to the Solvent Stain Test and the Household Stain Test described above.

10 AlconoxO 5% commercially available from VWR Scientific Inc., San Francisco, CA.

3M Permanentd, commercially available from the Minnesota Mining and Manufacturing Company, St. Paul, MN.

c EXAMPLES

The method of preparation of the composition of the present invention is described below. The following components were utilized:

1. Urethane Dispersion A is commercially available from Mobay Corporation of Pittsburgh, Pennsylvania under the trade name Baybond@ 123. Baybond@ 123 is an anionic dispersion of an aliphatic polycarbonate urethane polymer and is 35% solids. It also contains 12% N-methyl-2-pyrrolidone which is utilized as a coalescent agent; 2. Urethane Dispersion B is commercially available from Mobay Corporation of Pittsburgh, Pennsylvania under the trade name BaybondO XW-110-2.

Baybonds XW-110-2 is an anionic dispersion of an aliphatic polyester urethane polymer having 35% solids. It also contains 15% N-methyl-2pyrrolidone which is utilized as a coalescent agent; 3. Acrylate A is commercially available under the trade name Roplex@ WL-96 from Rohm and Haas Company of Philadelphia, Pennsylvania. It is a acrylate/methacrylate/acrylonitrile terpolymer which is 42% solids; 4. Acrylate B is commercially available under the trade name Synthemul@ 40-422 from Reichhold Chemicals, Inc. of Dover, Delaware. It is a high molecular weight acrylic/styrene copolymer which is 49% solids; 5. 7-glycidyloxypropyl trimethoxysilane is commercially available from Shin-Etsu Chemical Company, Tokyo, Japan under the tradename KBM-403; 6. 3-glycidyloxypropyl methyl diethoxysilane is commercially available from Shin-Etsu Chemical Company, Tokyo, Japan under the tradename KBE-402; 7. 3-aminopropyl triethoxysilane is commercially available from Shin-Etsu Chemical Company, Tokyo, Japan under the tradename KBM-903; 8. 3-methacryloxypropyl trinethoxysilane is commercially available from Shin-Etsu Chemical Company, Tokyo, Japan under the tradename KBM-503.

EXAMPLE 1

Example 1 was prepared in the following manner:

Seventy-five (75) grams of Urethane Dispersion A, three (3) grams Nmethyl-2-pyrrolidone and twenty-one (21) grams water were added together in a 4 Fl. oz.

size glass bottle with metal cap and stirred with a variable speed Lab Dispenser, Model CM-100, manufactured by D.H. Melton Co., Fullerton, CA for 10 minutes. One (1) gram 7-glycidyloxypropyl trimethoxysilane was added dropwise to the mixture. The resulting product was homogenous and milky white in appearance. The components, the amount of component and the test results are reported in Tables 5 and 6. COMPARATIVE EXAMPLE C1 Comparative Example C1 was prepared in accordance with the procedures outlined in Example 1. The composition of Comparative Example 1 lacked a polyfunctional silane. The components, the amount of component and the test results are reported in Table 5. EXAMPLE 2 Example 2 was prepared in accordance with the procedures described in Example 1. The components, the amount of each component and the test results are reported in Tables 5 and 6. Comparative Example C2 30 Comparative Example C2 was prepared in accordance with the procedures outlined in Example 1. The composition of Comparative Example I comprised Urethane B, but lacked a polyfunctional silane. The components, the amount of each component and the test results are reported in Table 5.

j 17 - EXAMPLES 3 and 4 Examples 3 and 4 were prepared in accordance with the procedures described in Example 1. The components, the amount of each component and the test results are 5 reported in Table 5. Comparative ExamDle C3 Comparative Example C3 was prepared in accordance with the procedures outlined in Example 1. The composition of Comparative Example 3 comprised an acrylate without a polyfunctional silane. The components, the amount of each component and the test results are reported in Table 5. EXAMPLES 5-7 Examples 5-7 demonstrate the use of acrylic esters in combination with urethane polymers. These examples were prepared in accordance with the procedures described in Example 1. The acrylic esters, Acrylates A and B, were added concurrently with Urethane Dispersions A and B. The components, the amount of each component and the test results are reported in Table 5. Comparative ExamDle C4 Comparative Example C4 was prepared in accordance with the procedures outlined in Example 1. The composition of Comparative Example C4 comprised a urethane polymer and an acrylate, but lacked a polyfunctional silane. The components, the amount of each component and the test results are reported in Tables 5 and 6.

- 18 Table 5

Composition (grams) Example No. CI I C2 2 3 4 1 C 5 6 C4 3 Urethane 75 75 75 75 14.5 14.5 14.5 Dispersion A I I I Urethane 75 1 75 Dispersion B I I Acrylate A -- 1 55 47.5 47.5 Acrylate B 47.5 47.5 r- 1.5 glycidyloxy propy, trimethoxy silane 3- 1.5 glycidyloxy propy, methyl diethoxy silane 3-amino propyltri ethoxy-silane 3-methacryl oxypropyl trimethoxy silane N-methyl-2- 3 3 3 3 3 3 pyrrolidone Water 22 21 22 21 21 21 45 36.5 36.5 36.5 (deionized) Solvent Stain 16 28 9 28 21 24 18 28 28 11 Test I I I I 7 14.5 36.5 26 COMPARATIVE EXAMPLE C5 Comparative Example C5 was prepared by mixing 75 grams Urethane Dispersion B, 1 gram of trimethylol propane-tris-(B-(N-aziridinyl) propionate), a polyfunctional aziridine sold under the trade name XAMA7-Z by Hoechst Celanese in Portsmouth, Virginia and 24 grams deionized water. The test samples were tested according to the procedures described above and test results are reported in Table 6. Table 6 SHELF-LIFE STABILITY TEST Initial 1 week 4 wks 8 wks 10 wks Example 1 solvent stain 28 - 28 household stain 17 - - 17 Example 2 solvent stain 28 - - 28 household stain 19 - - 19 Example 7 solvent stain 26 - 25 24 24 household stain 15 - - - 15 Comparative Example C5 solvent stain 28 9 - household stain 18 16 L - -i--i In summary, novel coating compositions have been described. Although specific embodiments and examples have been disclosed herein, it should be borne in mind that these have been provided by way of explanation and illustration and the present invention is not limited thereby. Certainly, modifications which are within the ordinary skill in the art are considered to lie within the scope of this invention as defined by the following claims and all equivalents.

Claims (13)

WHAT WE CLAIM IS:

1. A water-borne coating composition comprising a.) a urethane polymer comprising the reaction product of at least one polyisocyanate, at least one polyol and at least one organic acid represented by the following formula:

(R2) XQ (R3) y wherein Q represents a straight or branched, hydrocarbon radical containing 1 to 12 carbon atoms, R2 is independently selected from the group consisting of -OH or -NH2 R3 is independently selected from the group consisting of -COOH or -S03H x is an integer of at least 1 y is an integer of at least 1; and b.) one or more polyfunctional silanes to crosslink said urethane polymer.

2. The composition of Claim 1 wherein said polyfunctional silane is selected from the group consisting of an epoxy silane, a methylacrylosilane, an amino silane or one or more of the foregoing.

3 5 wherein:

3. The composition of Claim 1 wherein said silane is represented by the following formula:

A- (R) -S i (ORJ 3 t, is A represents a vinyl group, an acylalkoxy group, a mercapto group, a methacrylo group, an amino group, or a glycidyloxy group; R represents a methylene group; R, is independently selected from the group consisting of a H atom, a lower alkyl group or an acyl group having from about 1 to about 4 carbon atoms; and n is an integer of 0 to 12.

4. The composition of Claim 1 wherein said silane is represented by the following formula:

A-(R)-SiCH3(ORI)2 wherein:

A represents a vinyl group, an acylalkoxy group, a mercapto group, a methacrylo group, an amino group, or a glycidyloxy group; R represents a methylene group; R, is independently selected from the group consisting of a H atom, a lower alkyl group or an acyl group having from about 1 to about 4 carbon atoms; and n is an integer of 0 to 12.

5. The composition of Claim 1 wherein said silanes are crosslinked.

6. The composition of Claim 1 wherein said organic acid is represented by the following formula:

(H0) Q (COOH) y wherein:

Q represents a straight or branched hydrocarbon radical having from about 1 to about 12 carbon atoms; x is an integer of at least 1; and y is an integer of at least 1.

7. The composition of Claim 6 wherein said organic acid is represented by the following formula:

CH20H 1 Q'-C-COOH 1 CH20H wherein Q' is represented by a hydrogen or an alkyl group having from about 1 to about

8 carbon atoms; 8. An article comprising a substrate bearing 20 layer of the composition of Claim 1.

9. A water-borne coating composition comprising: a. a urethane polymer comprising the reaction product of at least one polyisocyanate, at least one polyol and at least one organic acid selected from the group consisting of an amino carboxylic acid, a hydroxy carboxylic acid, an aliphatic sulfonic acid, an amino sulfonic acid or one or more of the foregoing, wherein said organic acid and said polyisocyanate are reacted prior to being reacted with said polyol; and b. one or more polyfunctional silanes to crosslink said urethane polymer.

L_

10. An aqueous dispersion comprising an aqueous solution and a composition comprising: a. a urethane polymer comprising the reaction product of at least one polyisocyanate, at least one polyol and at least one organic acid represented by the following formula:

(R2) XQ (R3) y wherein represents a straight or branched, hydrocarbon radical containing 1 to 12 carbon atoms, R2 is independently selected from the group consisting of -OH or -NH2 R3 is independently selected from the group consisting of -COOH or -S03H x is an integer of at least 1. y is an integer of at least 1; and b. one or more polyfunctional silanes to crosslink said polymer.

11. A method of protecting a wood substrate from stain comprising the following steps:

1. providing a water-borne coating composition comprising: a.) a urethane polymer comprising a polyisocyanate, a polyol and an organic acid selected from the group consisting of an amino carboxylic acid, a hydroxy carboxylic acid, an aliphatic sulfonic acid, an amino sulfonic acid or one or more of the foregoing; b.) one or more polyfunctional silanes to crosslink said polymer wherein said urethane polymer and said polyfunctional silane are provided in a sufficient amount to 1 v - 24 substantially prevent solvent stain on an exterior surface of a wood substrate and c.) water 2. applying said coating composition to said exterior surface; and 5 3. allowing said coating composition to cure on said exterior surface.

12. A water-borne coating composition as claimed in Claim 1 substantially as herein described with reference to any one of the Examples.

13. A method of protecting a wood substrate as claimed in Claim 11 substantially as herein described with reference to any one of the Examples.

I