AQUEOUS POLYURETHANE DISPERSION ADHESIVE COMPOSITIONS WITH IMPROVED HEAT RESISTANCE

Abstract: Aqueous dispersion adhesives of anionic polyurethanes which have high heat resistance and low activation temperature, even when employed without addition of a crosslinker. The polyurethane is the reaction product of an isocyanate terminated polyurethane prepolymer, and a chain extender. The polyurethane prepolymer is the reaction product of a polyol component and a diisocyanate component, the polyol component including: a sulfonated polyester polyol, a hydroxy carboxylic acid of the formula: (HO)xR(COOH)y wherein R represents a straight or branched, hydrocarbon radical containing 1 to 12 carbon atoms, and x and y represent values from 1 to 3, and a low molecular weight aliphatic diol having a molecular weight of from 60 to 400.

Description: AQUEOUS POLYURETHANE DISPERSION ADHESIVE COMPOSITIONS WITH IMPROVED HEAT RESISTANCE Background of (he Invention 1. Field of the Invention This invention relates new aqueous polyurethane dispersion adhesive compositions which can be an one component or a two component for use in tlicrmoforming. More particularly, this invention relates to aqueous polyuretlianc dispersion adhesive compositions comprising carboxylic acid and/or its salt-containing sulfonated polyurethane dispersions, and with or without compatible crosslinking agents. These new adhesive compositions exhibit good stability at low pH values, long pot life, high green strength, good water resistance and improved heal resistance. 2. Description of the Prior Art Aqueous dispersions of polyurclhancs arc known and arc described in, for example, US 3,479,310; Angcw. Chain., 82, 53, (1972); and Λngcw. Makroinol. Chan., 98, (1981). US 3,479,310 to Diclcrich et al discloses dispersing in water a fully chain extended, NCO-frcc polyurethane having internal ionic salt groups. For anionic aqueous polyurethane dispersions, the ionic salt groups arc salts of carboxylic acid or sulfonic acid. Aqueous polyurcthancs having only internal carboxylatc groups as anionic moieties arc stable only at pH >7. Such polyurethane dispersions can form a two component adhesive composition with a compatible crosslinkcr, such as polyfunctional isocyanatcs, cpoxics or aziridincs. Hcnning, ct al., US 4,870,129, discloses use of the sodium salt of N-(2-aminocthyl)-2-aminocthanc sulfonatc acid (AAS salt) to prepare polyurethane dispersions. The aqueous polyuretlianc dispersions arc reported to have exhibited good stability at low pH values (5-7), high green strength and medium heat resistance. Usually, after blending the sulfonated polyurethane dispersions with a polyisocyanatc crosslinkcr, such as the dispersible polyisocyanatc in U.S. Pat. 4,663,377 to Hombach et al, their heat resistance will be improved. Leung, US 4,762,880, discloses water-based tlicrmoforming adhesives comprising aromatic polyuretliancs, cross-linking agents and others. These kind of adhesive compositions will need high temperature to activate due to the aromatic polyurethane component. US 4,870,129 to Hcnning ct al discloses an adhesive consisting of an aqueous polyurethane containing chemically incorporated carboxylatc or sulfonalc groups. The adhesive of this reference showed low activation temperature but only medium heat resistance. Duan et al in copending application serial No. 08/126,508, filed September 24, 1993, disclose aqueous polyurethane dispersions based on sulfonated polyester polyols, which have an unusually high crystallization rate, while also exhibiting good stability at low pH values, high green strength and medium heat resistance. Summary of the Invention The present invention is directed to novel aqueous sulfonated polyurethane dispersions having low activation temperatures, long pot-life and high heat resistance, even without addition of a crosslinkcr at the time of use. The aqueous polyurethane dispersion adhesive compositions of the invention have good compatibility with other water based polymers, such as other aqueous polyurethane dispersions either sulfonated or carboxylated polyurethane dispersions, vinyl acetate emulsions and acrylatc emulsions, and also have good compatibility with thickening agents and pigments. The compositions of the invention arc aqueous dispersions of an anionic polyurethane, the polyurethane comprising the reaction product of an isocyanatc terminated polyurethane prepolymer, and a chain extender, the polyurethane prepolymer comprising the reaction product of a polyol component and a diisocyanate component, the polyol component comprising: a sulfonated polyester polyol, a hydroxy carboxylic acid of the formula: (HO) x R ( COOH) v wherein (R) represents a straight or branched, hydrocarbon radical containing 1 to 12 carbon atoms, and x and y represent values from 1 to 3, and a low molecular weight aliphatic diol having a molecular weight of from 60 to 400. The dispersions of the invention may be utilized with or without a compatible crosslinkcr, such as polyfunctional aziridine, zinc ammonium carbonate or zirconium carbonate. In their preferred embodiments, even the uncrosslinkcd adhesives provide equivalent or better heat resistance than prior art dispersions to which a cross-linker has been added at the lime of use. Detailed Description of the Invention The isocyanatc terminated polyurethane prepolymer used in the dispersions of the invention arc reaction products of a polyol mixture and a polyisocyanatc. The polyol mixture comprises a sulfonated polyester polyol, a hydroxy carboxylic acid and a low molecular weight diol. The sulfonated polyester polyols used to form the isocyanatc terminated polyurethane prepolymer may be any polyester polyol which incorporates sulfonate groups via sulfonate functional dicarboxylic acid residues and/or sulfonate functional diol residues. The sulfonate functional groups may be in acid or salt form. Suitable salt forms arc alkali metal salts, or tertiary amine salts. Typically such sulfonate functional dicarboxylic acid residues and/or sulfonate functional diol residues are a minor portion of the diol and/diacid moieties of the polyester, preferably 1.0%- 10.0% by weight of the polyester. The non-sulfonatcd diacids and diols used in forming the sulfonated polyesters may be aromatic or aliphatic. Examples of the non-sulfonatcd diacids include adipic, azclaic, succinic, suberic and phthalic acids. Examples of the non-sulfonatcd diols include ethylenc glycol, condensates of ediylene glycols, butancdiol, butencdiol, propanediol, ncopentylglycol, hexanediol, 1 ,4-cyclohexane dimcthanol, 1 ,2-propylcne glycol and 2-mcthyl-l,3 propanediol. Examples of the sulfonate diacids include sulfoisophthalic acid, 1,3- dihydroxybutanc sulfonic acid and sulfosuccinic acid. Examples of the sulfonate diols include 1,4 dihydroxy butane sulfonic acid and succinaldchyde disodium bisulfite. The preferred sulfonated polyester polyols arc based on 5- sulfoisophthalic acid monosodium salt, 1 ,6-hcxanediol and adipic acid. Examples of preferred commercially available sulfonated polyester polyols are Rucoflex XS-5483- 55 and Rucoflex XS-5536-60, made by Ruco Polymer Corporation. These sulfonated polyester polyols are based on 5-sulfoisophthalic acid monosodium salt (4 wt.% in XS-5483-55, and 6 wt.% in XS-5536-60), 1 ,6-hcxancdiol and adipic acid. The sulfonated polyester polyols desirably will have a molecular weight in the range of about 500 to 10,000 and a melting temperature in the range of about 10 to 100°C. The preferred molecular weight range is about 1,000 to 4,000 and the preferred melting temperature is between 30°C and 80°C, more preferably between 40°C and 60°C. The hydroxy carboxylic acids used to form the isocyanatc terminated polyurethane prepolymer arc compounds of the formula: (HO) x R (COOH) y wherein R represents a straight or branched, hydrocarbon radical containing 1 to 12 carbon atoms, and x and y represent values from 1 to 3. Preferably, the hydroxy carboxylic acids are α,α-dimcthylol alkanoic acids represented by the formula: CH 2 OH I I R'- C- COOH I CH 2 OH where R l denotes hydrogen or an alkyl group with up to about 20 carbon atoms. Examples of such compounds arc 2,2-dimcthylolacctic acid, 2,2-dimethylolpropionic acid, 2,2-dimethylolbutyric acid and 2,2-dimcthylolpcntanic acid. The preferred dihydroxyalkanoic acid is 2,2-dimcthylolpropionic acid (DMPA). The low molecular weight diols used in forming the isocyanatc terminated polyurethane prepolymer arc aliphatic diols, particularly alkylcne diols. Their molecular weight range is from 60 to 400. Preferably, the low molecular weight diols arc alkylcne diols and most preferably C 3 -C 6 alkylenc diols examples of the diols are ethylenc glycol, 1,3-propylcnc glycol, 1 ,4-butancdiol (1,4-BD) and 1,6-hcxanediol. The diisocyanates which arc used in forming the isocyanatc terminated polyurethane prepolymer can be aliphatic or aromatic diisocyanates or their mixtures. Examples of suitable aliphatic diisocyanates arc isophorone diisocyanate (IPDI), cyclopentylenediisocyanate, cyclohexylcncdiisocyanate, methylcyclohexylenediisocyanatc, dicyclohexylmcthancdiisocyanate, hexamethylenediisocyanatc (HDI), dicyclohcxyJmcthancdiisocyanate (H12MDI), and tetrametliylxylyencdiisocyanatc (TMXDI). Examples of suitable aromatic diisocyanates are phenylenediisocyanatc, tolylcncdiisocyanate (TDI), xylylenediisocyanatc, biphcnylcncdiisocyanatc, naphthylcnediisocyanatc and diphenylmelhancdiisocyanatc (MDI). The polyuretlianc prepolymer is desirably formed in the presence of a water compatible solvent such as l-mcthyl-2-pyrrolidone (NMP), dipropylcne glycol methyl ether acetate (DPMA), or acetone. In the case where NMP or DPMA are used the amount of solvent used is suitably in the range of 3-15% of the final polyuretlianc dispersion. In the case where acetone is used, after dispersing and chain extending of the prepolymer, the acetone is then distilled off so that the final level of acetone may be as little as 1.0% or even less without disrupting the stability of the dispersion. After the prepolymer is formed, it is dispersed in water. To accomplish dispersion, the sulfonate groups, if not already in salt form, and at least a portion of the carboxylic acid groups of the prepolymer arc neutralized with a tertiary amine. The tertiary amine may be added with the water, but more preferably neutralization is accomplished before the water is added, suitably by direct addition to the prcpolymer/solvent mixture. In the aqueous dispersion the isocyanatc terminated prepolymer is chain extended and terminated by reaction with primary or secondary amine functional compounds. The chain extenders used arc preferably water soluble compounds as these increase the dispersibility of the polymer end product in water. Organic diamines are preferably used because they generally provide the maximum increase in molecular weight without causing gelling of the polyurethane dispersion. Useful chain extenders include aliphatic, cycloaliphatic, and aromatic diamines. Examples of suitable diamines are cthylcncdiaminc (EDA), propylcncdiaminc, 1 ,4-butylencdiamine, pipcrazinc, 1 ,4-cyclohexyldimcthyldiaminc, hexamethylenediaminc (HDI), N-methylpropylcncdiaminc, diaminophcnylsulfonc, diaminodiphenylcthcr, diaminodiphcnyldimcthyimcthanc, 2,4-diamino-6- phenyltriazine, isophoronediamine, dimer fatty acid diaminc, N-isodccycloxy propyl- 1 ,3-diaminopropanc and imidazolidinonc functional diamines. Examples of useful chain terminators include aminoalcohols, like cthanolaminc, propanolaminc, butanolaminc, N-mcthylethanolamine, N-methyl- isopropanolamine, taurinc and iscthionic acid. The compositions of the invention may be crosslinkcd by adding a crosslinkcr to the dispersion at, or shortly before, the time it is applied to a substrate and dried. Crosslinking may be accomplished with conventional dispcrsable polyisocyanate crosslinkcrs. However these arc not preferred as optimal crosslinking performance requires a relatively high level of terminal primary or secondary amine groups in the aqueous polyurethane dispersions of the invention and therefore a correspondingly high level of diaminc chain extender used in the chain extension/termination reaction. Generally, the more amine used, the more difficult it is to maintain a stable dispersion and reduce the pot-life of the dispersion after addition of the polyisocyanatc crosslinkcr. Therefore, in a preferred embodiment of this invention, the carboxylatc groups introduced into the sulfonated polyurethane polymer via the hydroxy carboxylic acid component of the polyol component are employed as crosslinking sites. The carboxylatc groups arc reacted with carboxylic acid reactive crosslinkers active at room temperature, such as polyfunctional aziridine compounds, zinc ammonium carbonate, zirconium carbonate or polyfunctional carbodiimide compounds. It has been found that the aqueous polyurethane dispersion adhesive compositions of the present invention when compounded with a compatible carboxylic acid reactive crosslinkcr have improved heat resistance, good water resistance, and longer pot-life than obtained with conventional dispcrsable isocyanatc crosslinkers. Typically crosslinkcrs are added at a level of 1-10% by weight. It has also been found in this invention that the heat resistance of the aqueous polyurethane dispersions is significantly improved by the employment of the low molecular weight diol in forming the polyurethane prepolymer. In fact the heat resistance of the polyurethane polymer is so greatly improved by the low molecular weight diol that one component adhesive compositions used without crosslinkcr, in preferred embodiments of the invention, give better high temperature resistance than commercial prior art dispersion adhesives employing crosslinkers. The high heat resistance benefits arc obtained with low activation temperature. In film bonding use, the dispersion adhesive, with or without crosslinkcr, is applied to a film web substrate and dried, after which it is heated and the second film web substrate applied. The temperature of heating, referred to in the art as the activation temperature, is selected to provide good tack so the adhesive bonds to the second web and to change the physical properties of the adhesive by increasing the physical or chemical crosslinks so that the adhesive after heating provides a higher heat resistance, and usually higher water and solvent resistance, than before heating. Higher temperatures arc frequently required to accomplish a desired change in adhesive heat resistance properties than to merely assure good adhesive wetting. Unexpectedly, it has been found that the preferred one component aqueous polyurethane dispersion adhcsivcs not only give high heat resistance, but also do so at low heal activation temperatures. Activation temperatures as low as 125°F have been shown to effectively implement the heat resistance properties of the inventive formulations, even without crosslinkcr. In accordance with the invention, the aqueous polyurethane dispersions of the invention also have small particle sizes and excellent stability over a large pH range (3-11). The high green strength and high heat resistance at low activation temperature makes the one-component or two-component compositions of the invention particularly useful in automotive, aerospace, shoe material bonding, woodworking, bookbinding, fiberglass sizing and film laminating applications. For instance, a one-component composition substantially as in Example 13 below, may be used in automobiles, bonding polypropylene foam to polyvinyl chloride at activation temperature of about 215°F; in aerospace, bonding of DuPont Tedlar® PVF to phenolic composite at activation temperatures in the range of from room temperature to 210°F; in shoemaking, bonding leather to SBR (activation temperature 150-170°F), and bonding highly plasticizcd PVC to itself or other substrates (activation temperature 150-170°F); in woodworking, bonding PVC to medium density fiberboard (activation temperature 150°F); in bookbinding, bonding paper to paper using activation temperatures from room temperature to 200°F; in house siding for bonding Tedlar® to PVC, wood, wood composite, recycled wood and/or paper products; and in laminating of films of polyethylene tcrcphthalate to films of polypropylene, polyethylene or aluminum or other metal foils (activation temperatures of 125-150°F). The formulations of the invention have good compatibility with other water based polymer dispersions even those having low pH (pH 4-7). This compatibility makes the formulations of the invention useful in blends with acrylic, epoxy and vinyl acetate or other vinyl polymer dispersions, as well as other polyurethane polymer dispersions. Blends with water based acrylic polymers can be used for shoe and fiberglass sizing applications. Blends with vinyl acetate or other vinyl polymer dispersions have use in automotive, woodworking, and bookbinding applications. The invention is further illustrated, by the following non-limiting examples in which all parts and percentages arc by weight unless otherwise specified. EXAMPLES Heat resistance Drawdown polyurethane dispersion with or without a crosslinkcr on a 10 mil clear PVC film (polyvinyl chloride film from Laird Plastics) with a #28 Mylar rod to prime a lxl inch area of 1 inch wide strips of the PVC films. Dry to touch and cut the primed PVC film into 1x2 inch strips. Heat seal the primed strip to another uncoated 1x2 inch PVC strip using a Scntinal Heat Sealer at 50 psi nip pressure with a 30 second dwell time. The scaling temperature (activation temperature) selected are 125, 150, 175 and 200°F. Allow the bonds to age 7 days and then measure the heat resistance temperature. A 100 g weight was attached to each PVC bond in a T-pecl configuration and then placed in the Tcnncy oven. The T-pcels had a 1 square inch bond area. The T-peels were subjected to a 25°C increase in temperature each hour until 125°C. The temperatures and the times were recorded by the Tcnney sensing unit upon bond failure. The following abbreviations arc used in the Examples: Rucoflex XS-5483-55 a sulfonated polyester polyol based on 5-suifoisophthalic acid monosodium salt, adipic acid and 1,6-hcxancdiol, OH number 49.0 DMPA dimelhylolpropionic acid 1,4-BD 1,4-butancdiol TMXDI tetramcthylxylyenediisocyanatc IPDI isophoronc diisocyanate HDI hcxamcthylcncdiisocyanatc EDA cthylcncdiaminc TEA triethylaminc NMP l-methyl-2-pyrrolidone DPMA dipropylcnc glycol methyl ether acetate Dcsmodur DA dispersible polyisocyanatc based on HDI trimcr (Bayer) CX-100 a 100% active polyfunctional aziridine liquid crosslinkcr (ICI) Example 1 Two component Starting materials: 213.8 g of Rucoflex XS-5483-55 13.4 g of DMPA 40.3 g of HDI 14.6 g of TMXDI 5.1 g of EDA 9.0 g of TEA 90 g of NMP 550.4 g of water Preparation method: The Rucoflex XS-5483-55 was dried in vacuo at 100°C and then dissolved into the NMP at 70-80°C. The DMPA, TMXDI and HDI were added, whereupon the temperature was maintained at about 80°F for 3 hours and then cooled to about 65-70°C. At this temperature, the TEA was added and stirred for 10-15 minutes. The temperature was further reduced to about 60°C, the prepolymer was dispersed by adding the water. A finely divided dispersion having a solids content of 32.0% and a pH of 8.5 was obtained. 100.0 g of the aqueous polyurethane dispersion prepared above was mixed with 4.0 g of Desmodur DA (DDA) at room temperature to make a two component adhesive composition. 100.0 g of the same aqueous polyurethane dispersion was mixed with 2.0 g of CX-100, a commercial polyaziridine crosslinkcr compound, at room temperature to make another two component adhesive composition. The heat resistance of the aqueous polyurethane dispersion, the two-component adhesive compositions were tested. The testing results are shown in Table 2. Example 2 Two component formulations Starting materials: 213.8 g of Rucoflex XS-5483-55 6.7 g of DMPA 9.0 g of 1,4-BD 18.3 g of TMXDI 50.4 g of HDI 6.4 g of EDA 4.5 g of TEA 90.0 g of NMP 598.7 g of water Preparation method: The metliod for preparing the dispersion of Example 2 was the same as the metliod for Example 1 except that the 1 ,4-BD was added at the same time as the DMPA. A finely divided dispersion having a solids content of 31.4% and a pH of 7.95 was obtained. Two different two-component adhesive compositions were prepared following the same method as in Example 1. The testing results for heat resistance arc shown in Table 2. Examples 3-5 Two-component formulations Compositions were prepared as shown in Table 1. Table 1. Starling materials for Examples 3-5 Starting materials (g) Example 3 Comparative Example 5 Example 4 5484-55 213.8 213.8 213.8 DMPA 6.7 13.4 13.4 1,4-BD 4.5 0.0 22.5 IPDI 22.2 22.2 49.95 HDI 33.6 33.6 75.6 EDA 5J 5J 11.5 TEA 4.5 9.0 9.0 NMP 90.0 90.0 90.0 Water 570.6 580.7 728.6 Dispersion Properties Solids 31.5 31.6 32.6 content PH 7.5 8.0 8.1 The preparation metliod for Examples 3-5 was the same as the method of Examples 1-2 except that IPDI was used instead of TMXDI. The testing results for heat resistance arc shown in Table 2, where PUD refers to the one component dispersion, PUD DDA to its mixture with Desmondur DA crosslinkcr and PUD/CXI 00 to its mixture with CX-100 polyfunctional aziridine crosslinkcr. Table 2 Heat Resistance Temperature (°F) of Exampl es 1-5 Activation Temp. (°F) 125 150 175 200 Example 1 PUD RT 191 196 199 PUD/DDA 129 236 240 242 PUD/CXI 00 237 NF, 1/2" NF, 1/2" NF, 1/2" peeled peeled peeled Example 2 PUD 229 228 223 225 PUD/DDA 231 235 238 243 PUD/CXI 00 NF, 7/8" NF, 15/16" NF, 7/8" 243 peeled peeled peeled Example 3 PUD . 226 222 227 230 PUD/DDA 238 238 241 243 PUD/CXI 00 NF, 3/4" NF, 3/4" NF, 7/8" NF, 15/16" peeled peeled peeled peeled Example 4 (comparative example) PUD 218 219 218 226 PUD/DDA 241 238 238 240 PUD/CX100 241 246 NF, 15/16" NF, 3/4" peeled peeled Example 5 PUD RT 75 84 211 PUD/DDA 229 242 245 NF, 15/16" peeled PUD/CXI 00 NF, 3/4" NF, 3/4" NF, 3/4" NF, 7/8" peeled peeled peeled peeled RT: room temperature NF: no failure until 260°F. Where bond had begun to peel at 260°F the extent of peeling is indicated. Example 6 One-component formulation Starting materials: 213.8 g of Rucoflex XS-5483-55 6.7 g of DMPA 13.5 g of 1,4-BD 21.96 g of TMXDI 60.48 g of HDI 7.65 g of EDA 4.5 g of TEA 90.0 g of NMP 627.9 g of water Preparation method: The Rucoflex XS-5483-55 was dried in vacuo at 100°C and then dissolved into the NMP at 70-80°C. The DMPA, 1,4-BD, TMXDI and HDI were added, whereupon the temperature was maintained at about 80°C for 3 hours and then cooled to 65-70°C. At this temperature, the TEA was added and stirred for 10-15 minutes. The temperature was further cooled to about 60°C, tl e prepolymer was dispersed by adding the water. A finely divided dispersion having a solids content of 31.4% and a pH of 7.3 was obtained. This dispersion had good water resistance and high heat resistance and could be used as a one-component adhesive. The test results for heat resistance of the dispersion arc shown in Table 4. Examples 7-14 One-component formulations Table 3. Starting materials for Examples 7-12 Starting Example Example Example Example Example Example Example Example materials 7 8 9 10 1 1 12 13 14 Rucoflex 213.8 213.8 213.8 213.8 213.8 213.8 213.8 213.8 XS-5483- 55 DMPA 13.4 13.4 13.4 13.4 6.7 6.7 6.7 6.1 1,4-BD 13.5 4.5 9.0 13.5 9.0 13.5 9.0 9.0 TMXDI 25.62 0 0 0 0 0 0 0 IPDI 0 27.75 33.3 38.85 27.75 33.3 27.75 27.75 HDI 70.56 42.0 50.4 58.8 42.0 50.4 42.0 42.0 EDA 8.93 6.38 7.65 8.93 6.38 7.65 6.38 5.63 TEA 9.0 9.0 9.0 9.0 4.5 4.5 4.0 4.0 Acetone 0 0 0 0 0 0 50.0 50.0 NMP 90.0 90.0 ' 90.0 90.0 90.0 90.0 0 0 Water 667.2 610.2 639.8 669.4 600.2 629.8 558.0 574.5 Preparation method: The dispersion preparation method Examples 7-14 was the same as the method of Example 6 except for the use of IPDI instead of TMXDI in Examples 8-14 and the use of acetone solvent in Examples 13-14 in place of NMP solvent. The testing results of the heat resistance are shown in Table 4. All of the dispersion prepared in Examples 7-14 have good water resistance and high heat resistance and can be used as one-component adhesives. Table 4 Heat resistance temperature (°F) of Examples 6-12 Activation temp. (°F) 125 150 175 200 Example 6 <100 206 NF, 3/4" NF, 1/2" peeled peeled Example 7 236 NF, 7/8" NF, 3/4" NF, 3/4" peeled peeled peeled Example 8 NF, 15/16" NF, 15/16" 225 NF, 15/16" peeled peeled peeled Example 9 NF, 1/2" NF, 1/4" NF, 1/16" NF, 1/16" peeled peeled peeled peeled Example 10 NF, 1/4" NF, 1/4" NF, 1/32" NF, 1/32" peeled peeled peeled peeled Example 11 NF, 1/8" NF, 1/8" NF, 3/16" NF, 1/4" peeled peeled peeled peeled Example 12 NF, 1/16" NF, 1/16" NF, 1/8" NF, 1/16" peeled peeled peeled peeled Example 13 NF NF NF NF Example 14 NF NF NF NF NF: no failure until 260°F Example 15 (Comparative Example) In this example, formulations of Dispcrccoll KA 8464, an aqueous polyurethane dispersion product of Bayer Corporation, based on HDI and IPDI (Formulation B), and of an embodiment of the sulfonated polyester containing polyurethane dispersion invention of copending application serial No. 08/126,508, filed September 24, 1993 (Formulation A), were prepared and tested for heat resistance in one component and two-component compositions, the second component being a commercial polyisocyanatc crosslinkcr. The crosslinkcr employed was Desmodur DA (Bayer, a dispersible polyisocyanatc based on trimer of hcxamcthylencdiisocyanatc). The sulfonated polyester containing polyurethane dispersion, Formulation A, was prepared from the following ingredients: 35.0% Rucoflex XS-5483-55(sulfonatcd polyester polyol based on 5 sulfoisophthalic acid monosodium salt, adipic acid and 1,6-hexanediol, OH number 49.0) 3.4% hexamethylene diisocyanate (HDI) 1.2% tetramcthylxylylcnc diisocyanate (TMXDI) 0.4% cthylcncdiaminc (EDA) 60.0% water Heat resistance was determined as in the previous examples. Table 5. Heat resistance (°F) Activation temp. (°F) Formulation 125 150 175 200 A 221 227 225 233 A + 5% 219 236 244 238 Desmodur DA B 199 220 221 223 B + 5% 247 NF to 260 1/2" NF to 260 NF to 260 Desmodur DA peeled * PVC as substrate NF = No failure until 260°F Comparison of tl e results shown in Tables 4 and 5 demonstrate that the use of tlie compositions of the invention as one-component adhcsivcs provides adhesive bonds which are comparable in strength to prior art two-component crosslinked PUD formulations. Example 16 Films made from the one-component aqueous polyurethane dispersions of Examples 8-14 were immersed in water for 7 days, after which they had not changed. Films made from KA-8464 in Example 15 (uncrosslinkcd), by contrast, had totally lost their strength after immersing in water for only 1 day. Examples 17-18 Starting materials: Example 17 Exampl Rucoflex XS-5483-55 213.8 g 213.8 g DMPA 6.7 g 13.4 g 1,4-BD 4.5 g 22.5 g IPDI 66.6 g 149.9 g Dibutyltin dilauratc 2 drops 3 drops EDA 3.83 g 11.5 g TEA 4.0 g 9.0 g NMP 88.3 g 123.3 g water 588.3 g 821.5 g Preparation method: The Rucoflex XS-5483-55 was dried in vacuo at 100°C and then dissolved into the NMP at 70-80°C. The DMPA, 1,4-BD, and IPDI were added, whereupon the temperature was maintained at about 85°C for 3 hours and then cooled to 65-70°C. At this temperature, the TEA was added and stirred for 10-13 minutes. The temperature was further cooled to about 60°C, the prepolymer was dispersed by adding the water. Properties: Example 17 Example 18 Solids (%) 31.1 30.9 pH 9.5 9.8 Particle size (nm) 126 101 Viscosity (cps) 250 400 Crosslinkers used were 5% by weight Desmondur DA and 2% by weight CX-100. Heat resistance was determined as in the previous examples. Results arc shown in Table 6. Table 6. Heat Resistance Temperature (°F) of Examples 17-18 Activation Temp. (°F) 125 150 175 200 Example 17 PUD 137 189 193 194 PUD/DDA NF, 1/3" NF, 2/3" NF, 1/2" NF, 1/4" peeled peeled peeled peeled PUD/CXI 00 NF, 1/3" 248 NF, 7/8" NF, 3/4" peeled peeled peeled Example 18 PUD RT RT RT 90 PUD/DDA 232 236 243 243 PUD/CXI 00 NF, 2/3" NF, 2/3" NF, 1/2" NF, 1/2" peeled peeled peeled peeled

Claims: Claims What is claimed is: 1. An aqueous dispersion of an anionic polyurethane, the polyurethane comprising the reaction product of an isocyanatc terminated polyurethane prepolymer, and a chain extender, the polyurethane prepolymer comprising the reaction product of a polyol component and a diisocyanate component, the polyol component comprising: a sulfonated polyester polyol, a hydroxy carboxylic acid of the formula: (HO) x R (COOH) y wherein (R) represents a straight or branched, hydrocarbon radical containing 1 to 12 carbon atoms, and x and y represent values from 1 to 3, and a low molecular weight aliphatic diol having a molecular weight of from 60 to 400. 2. A dispersion as in claim 1 wherein the low molecular weight aliphatic diol is a C 2 -C„ alkylenc diol. 3. A dispersion as in claim 2 wherein the low molecular weight aliphatic diol is ethylene glycol, 1 ,3-propylenc glycol, 1 ,4-butanediol or 1 ,6-hcxancdiol. 4. A dispersion as in Claim 1 wherein the sulfonated polyester polyol is a hydroxy terminated polyester formed of residues from at least one carboxylic diacid, at least one diol and at least one sulfonate diacid or sulfonate diol. 5. A dispersion as in Claim 4 wherein the carboxylic diacid residue of tl e sulfonated polyester polyol comprises the residue of a diacid selected from the group consisting of adipic, azelaic, succinic, suberic and phthalic acids. 6. A dispersion as in Claim 4 wherein the diol residue of tl e sulfonated polyester polyol comprises the residue of a diol selected from the group consisting of ethylene glycol, condensates of ethylene glycols, butancdiol, butenediol, propanediol, neopentyl glycol, hexancdiol, 1 ,4-cyclohcxanc dimcthanol, 1 ,2-propylene glycol and 2-methyl-l ,3-propancdiol. 7. A dispersion as in Claim 4 wherein the sulfonate diacid or sulfonate diol residue comprises the residue of at least one member of the group consisting of sulfoisophthalic acid, sulfosuccinic acid, 1 ,4-dihydroxybutanc sulfonic acid and succinaldchyde disodium bisulfite. 8. A dispersion as in claim 1 wherein the sulfonated polyester polyol is based on 5-sulfoisophthalic acid monosodium salt, 1 ,6-hcxancdiol and adipic acid. 9. A dispersion as in Claim 1 wherein the sulfonated polyester polyol has a molecular weight in the range of about 500 to 10,000 and a melting temperature in the range of about 10 to 100°C. 10. A dispersion as in Claim 9 wherein the molecular weight range is about 1 ,000 to 4,000 and the elting temperature is about 40 to 60° C. 11. A dispersion as in claim 1 wherein the hydroxy carboxylic acid is a α,α-dimethylol alkanoic acid represented by the formula: CH 2 OH I I R l -C-COOH I I CH 2 OH where R 1 denotes hydrogen or an alkyl group with up to about 20 carbon atoms. 12. A dispersion as in claim 11 wherein the α,α-dimcthylol alkanoic acid is selected from the group consisting of 2,2-dimcthylolacctic acid, 2,2-dimethylolpropionic acid, 2,2-dimethylolbutyric acid, 2,2-dimethylolpentanic acid and mixtures thereof. 13. A dispersion as in claim 12 wherein the α,α-dimcthylol alkanoic acid is 2,2-dimethylolpropionic acid. 14. An adhesive formulation prepared by blending a dispersion as in claim 1 with a compatible acid reactive crosslinking agent. 15. An adhesive formulation as in claim 14 wherein the crosslinking agent is selected from the group consisting of polyfunctional aziridincs, zinc ammonium carbonate and zirconium carbonate. 16. An adhesive formulation prepared by blending a dispersion as in claim 1 with a polyisocyanatc crosslinking agent. 17. A bonded assembly of a pair of substrates, the assembly bonded with an adhesive comprising a dried dispersion of claim 1. 18. A bonded assembly as in claim 17 wherein, the substrate pairs include a member made of a material selected from the group consisting of polypropylene, polyvinyl chloride, phenolic composite, leather, slyrcnc-butadicnc rubber, medium density fiberboard, paper, polyvinyl fluoride, wood, wood composite, recycled wood, polyethylene tercphthalatc, polyethylene, and metal. 19. A bonded assembly as in claim 17 wherein said dispersion consists essentially of said polyurethane. 20. A bonded assembly as in claim 17 wherein said dispersion further comprises at least one of an acrylic, an cpoxy, a vinyl, or a second polyurethane polymer. 21. A bonded assembly as in claim 17 wherein said adhesive further comprises a compatible polyisocyanatc or acid reactive crosslinkcr. 22. A bonded assembly as in claim 17 wherein said substrate pair is selected from the group consisting of polypropylene foam /polyvinyl chloride; polyvinyl fluoride/phenolic composite; lcathcr/styrcnc-butadicnc rubber; PVC/medium density fiberboard; paper/paper; polyvinyl fluoride/polyvinyl chloride; polyvinyl fluoride/wood; polyvinyl fluoride/wood composite; polyvinyl fluoride/recycled wood; polyvinyl fluoride/paper products; polyethylene tercphtlialate/polypropylcnc; polyethylene tcrcphlhalatc/polyclhylcnc; polyetliylenc terephthalate/metal and plasticizcd polyvinyl chloridc/plasticizcd polyvinyl chloride. 23. An adhesive formulation prepared by blending a dispersion as in claim 1 with at least one of an acrylic, an cpoxy, a vinyl, or a second polyurethane polymer.

Inventors: DUAN YOULU, STAMMLER SONJA, DUAN, YOULU, STAMMLER, SONJA
Applicants: FULLER H B LICENSING FINANC, H.B. FULLER LICENSING AND FINANCING, INC.
Application year: 1995
Main classification: B32B15
IPC codes: B32B27, C08G18, C08L75, C09J175