Patent Application
20150240077
This invention relates to a Waterborne Polyurethane Dispersions (WPU) derived from the reaction products of tertiary alkyl glycidyl esters based hydroxyl terminal polyester polyols with polyisocyanates and chain extended with polyfunctional amines and water that have shown surprising characteristics for self-coalescence.
The shift from organic solvents to water for dispersing and applying resins in various systems solved many of the environmental and cost problems associated with the use of organic solvents. Water-borne systems, however, have resulted in other problems.
Polyurethane coatings are well known in the coatings market as high performance, protective coatings. These products are well established and known in the industry as highly versatile products that may be tailored for specific and diverse applications to deliver exceptional performance properties such as adhesion, abrasion resistance, mar/scuff resistance, resiliency, flexibility, hardness or softness, weather ability and substrate protection. Water based polyurethane products have made significant impact in the same diverse application areas primarily due to their ability to deliver the high performance characteristics associated with polyurethane polymers while reducing the total volatile organic compound emissions in application. The manufacture of such polyurethane polymers is well known in the art and generally involves the reaction of multifunctional isocyanate compounds with multifunctional hydroxyl compounds and multifunctional amine compounds. One limiting factor in universal acceptance of polyurethane products, and in particular water base polyurethane products, has been the relatively high cost associated with these polymers. A major factor in creating the relatively higher cost of polyurethane products is the high cost of the multifunctional polyisocyanate starting material necessary for the manufacture. Although water based polyurethane products yield a significant reduction in volatile organic emissions there is an on-going drive to further reduce volatile organic emissions beyond the levels achieved with standard water based polyurethane polymers currently available in the market but maintain the desired high performance characteristics. Co-solvent free and even VOC free polyurethane products are known and available in the market today in an attempt to meet this need but all are insufficient in one or more areas like room temperature film formation and hardness. Multi-component water base polyurethane products are available but are comprised of low molecular weight entities that require careful premixing prior to application, create short limitations in pot-life after mixing, and require in-situ reaction to gain sufficient molecular weight to achieve desired performance properties. Water base polyurethanes utilizing linear and branched polyester hydroxyl compounds are available but yield low film hardness and/or insufficient film formation at room temperature and generally yield less than desired abrasion resistance properties.
Water base polyurethane products utilizing linear, dihydroxy polyesters, polycaprolactones, polyethers and polycarbonates as the multifunctional hydroxyl component either yield low film hardness, or require high levels of co-solvent to effect film formation at room temperature. Water base polyurethanes utilizing the di-isocyanate (TMXDI) are available but either yield low film hardness and/or require high levels of post added co-solvent to effect film formation at room temperature and are cost prohibitive due to the high relative cost of the TMXDI polyisocyanate entity. Numerous water based systems exist utilizing water base polyurethane chemistry in conjunction with alternate polymer technology but these systems are not wholly water base polyurethane technology and in many cases tend to dilute the expected resulting water base polyurethane properties.
Aqueous polyurethane dispersions are used in a large variety of applications due to a well balanced performance profile such as good flexibility and durability, good resistance to abrasion, good chemical resistance as well as good adhesion to various substrates. They can be found in adhesives, paints and coatings such as those for kitchen cabinets, wood and vinyl flooring, plastics, leather coatings, glass fiber sizing, glass coatings, automotive/transportation coatings, textile coatings etc.
The production process for WPU entails the incorporation of water soluble entities of either a nonionic, cationic or ionic nature. The most popular method for waterborne polyurethane manufacture, well established in the art, entails the incorporation of polar species like dimethylol propionic acid (DMPA) into the pre-polymer backbone to ensure subsequent water dispersibility and solubility via ion formation through neutralization of the acid with basic compounds like triethylamine. The incorporation of the solid DMPA entity generally results in significant increases in the pre-polymer viscosity and necessitates the addition of cosolvents to keep the viscosity at a level sufficient for processing at the required temperatures. The common cosolvent used for WPU manufacture is n-methyl pyrrolidone (NMP). The NMP serves multiple functions in the WPU process. First, the NMP acts as a diluent to help lower viscosity of the pre-polymer to manageable levels for processing. Second, the NMP assists to dissolve the solid DMPA entity thereby decreasing cycle times for pre-polymer processing. Third, and generally regarded as the critical determining factor in establishing required cosolvent levels, the residual NMP in the final fully reacted WPU system serves as a coalescent for the WPU film. Total levels of required cosolvents may vary greatly but are generally determined by the amounts necessary to allow fully coalesced final WPU films at room temperature. In general, this level is in excess of what is required for viscosity control process purposes. Once the pre-polymer is diluted with cosolvent to suitable processing viscosity levels and made suitably hydrophilic via the salt formation at the ionic groups attached the low molecular weight pre-polymer is than dispersed in water and chain extended to high molecular weight WPU chains via reaction with various multifunctional amines such as hydrazine.
Changes in legislation on the labeling of products containing N-methylpyrolidone (NMP; toxicity and reprotoxicity R phrases added) have resulted in increased efforts of the coating industry to replace NMP with alternative co-solvents or reduce or avoid the use of co-solvents altogether.
In the present invention it has been surprisingly found that hydroxyl terminal telechelic polyesters polyols derived from the reaction products of tertiary alkyl glycidyl esters based hydroxyl terminal polyester polyols with polyisocyanates, suitable hydrophilic entity, chain extended with polyfunctional amine and dispersed in water have shown surprising improved coalescence ability resulting in decreased co-solvent demand for room temperature coalescence.
WO 2006/002864 patent describes a polyurethane dispersion containing ≦5 wt-% NMP by weight of polyurethane and where the polyurethane is derived from either aliphatic or aromatic isocyanate and isocyanate-reactive polyol bearing ionic and/or potentially ionic water dispersing groups and non-ionic isocyanate-reactive polyols. The pre-polymerization is performed in the presence of reactive diluents such as vinyl monomers, e.g. methyl methacrylate, ethyl methacrylate and styrene and in consequence a hybrid polyurethane vinyl polymer is obtained which requires a reduced amount of NMP as co-solvent due to the diluting effect of the vinyl monomers during the pre-polymerization process. The reactive diluent is polymerized with suitable peroxide or persulfate catalysts after the polyurethane pre-polymer has been reacted with at least one active hydrogen chain-extending compound to form the PU polymer.
“Preparation and properties of waterborne polyurethanes with natural dimmer fatty acids based polyester polyol as soft segment” by Xin Liu et al., published in Progress in Organic Coatings 72 (2011), 612-620 describes the advantages of the incorporation of dimer fatty acids based polyester polyols such as C36 dimer Priplast polyols from Croda. Improvements in surface hydrophobicity (increase in water contact angle >90 degree), hydrolytic resistance, water resistance and thermal resistance are reported although physico-mechanical properties, notably elongation at break were reduced by introduction of dimer fatty acid polyesters.
It is concluded that the observed improvements are effected by the incorporation of long hydrophobic branched chains and the high degree of phase separation which the PU polymer exhibited.
U.S. Pat. No. 6,482,474 by D. R. Fenn et al. describes the use of a hydroxyl functional polymer which is preferably derived from a polyfunctional carboxylic acid and a monoepoxide such as Cardura E10. To that purpose low molecular weight polyols (Mw 66-150) such as ethylene glycol, propylene glycol, trimethylol propane or neopentylglycol are reacted with dicarboxylic acid anhydrides such as maleic anhydride, succinic anhydride, phtalic anhydride and hexahydrophtalic anhydride. The resulting polyfunctional acid compound has substantially the same number of acid groups as the polyol had hydroxyl groups. The ensuing reaction of the polyfunctional acid compound with the monoepoxide yields a OH-functional polyester polyol which can be further reacted with additional moles of polyfunctional acid and monoepoxide. The final hydroxyl functional polyol is then reacted with the polyisocyanate mixture in the presence of an organic solvent. The coating is used as a chip resistant sandable primer in the spot repair of automotive paints producing high quality results.
An anonymous research disclosure No. 505 033 in May 2006 in Research Disclosure titled “Glycidyl ester based telechelic polyesters” describes the step growth polymerization of hydroxyl terminated telechelic polyesters from dicarboxylic acids, dicarboxylic acid anhydrides and glycidyl esters. 1 mole of diacid is first reacted with 2 moles of glycidyl ester until at least 85 mole % conversion is achieved. The resulting diol is then reacted sequentially with n times 2 moles of dicarboxylic anhydride and then 2 moles of glycidyl ester until the desired molecular weight is achieved (n can vary from 0 to 10). The resulting polyester polyols have been found suitable to make polyurethane dispersions.
U.S. Pat. No. 3,607,900 by Kazy Sekmakas describes water-dispersible polyurethane resins that are provided by reacting a resinous polyol with a stoichiometric deficiency of polyisocyanate to provide hydroxyl-functional polyurethane in which carboxyl functionality is generated with a portion of the carboxyl functionality being preferably consumed by reaction with monoepoxide to generate hydroxyl ester groups remote from the backbone of said polyurethane resin. The aqueous polyurethane resins are employed in electro coating processes in which a unidirectional electrical current is passed through the aqueous bath containing the dispersed resin to deposit at the anode of the system.
The U.S. Pat. No. 6,087,444 by Shanti Swarup at al. is about aqueous dispersions of polyurethane/acrylic polymers can be made that provide water-based coating compositions with good humidity resistance as well as a combination of performance properties required for commercial coating uses, without requiring the use of costly special types of polyisocyanates. The authors are not telling the reader on the way that it could be achieved a low viscosity composition and high hardness of the cured film.
EP0682049 is about hydrophilic polyurethane-polyureas which are useful as dispersants for synthetic resins obtained by reacting: a polyisocyanate component comprising at least one organic polyisocyanate and at least one isocyanate reactive fatty acid derivative. These resins are specially designed for water base composition for air-drying coatings.
In WO 2000/56827 an aqueous cross linkable coating composition comprising i) an autoxidisably cross linkable polymer containing unsaturated fatty acids residue, ii) a not autoxidisably cross linkable vinyl polymer bearing carbonyl groups and iii) carbonyl-reactive groups to crosslink the vinyl polymer.
Waterborne polyurethane dispersions (WPU)of this invention, derived from the reaction products of tertiary alkyl glycidyl esters based hydroxyl terminal polyester polyols with aliphatic isocyanates and chain extended with hydrazine and dispersed in water have shown surprising inherent, characteristics for self-coalescence.
The observed phenomena resulted in a decreased demand for external co-solvent like n-methyl-pyrolidone (NMP) for room temperature film formation or allowed for the elimination of NMP altogether. The resulting polymer films have shown a higher degree of hardness compared to stoichiometrically equivalent industry benchmarks which would allow for a reduction of the necessary isocyanate content. Furthermore the cured films have shown improved hardness and abrasion resistance over these benchmarks.
The benefits of the invention are:
The polyurethane aqueous dispersion composition of the invention and comprising (i) a hydroxyl terminal oligomer derived from an alkyl glycidyl ester and carboxylic di-acids and anhydride, hemi-ester wherein the di-acids, the anhydride the or the hemi-ester are not derived from unsaturated fatty acids, (ii) a poly-isocyanate and (iii) suitable hydrophilic entity know in the art wherein the oligomer is characterized in that the molecular weight is between 600 and 5000, preferably between 800 and 3500, and most to preferably between 1200 and 2800, lead to the above listed properties, and free of meth(acrylic) derivatives.
An embodiment of this invention is wherein the alkyl glycidyl ester is a linear or branched alkyl glycidyl ester with the alkyl group containing from 4 to 12 carbon atoms.
A preferred embodiment of this invention is wherein the branched alkyl chain is a tertiary alkyl chain with 4 to 12 carbon atoms, preferably from 8 to 10 carbon atoms and most preferably with 9 carbon atoms.
The above composition are formulated for use with the level of co-solvent being lower than 8.6 weight % on total composition and possibly the composition is free of N-methylpyrolidone.
The compositions of this invention are formulated with a level of isocyanate between 7.5 and 17.5 weight % on total composition.
Another embodiment of this invention is that the hydroxyl terminal oligomer is a diol derived from an alkyl glycidyl ester and carboxylic di-acids and anhydride, hemi-ester and a poly-isocyanate, wherein the oligomer is characterized in that the molecular weight is between 600 and 5000, preferably between 800 and 3500, and most preferably between 1200 and 2800.
The alkyl glycidyl ester can be with a linear alkyl chain such as glycidyl esters of C-6 to C-20 fatty Acids. or with a branched alkyl chain such as glycidyl neodecanoate.
The most preferred glycidyl ester monomers are commercially available from Hexion Inc. (previously Momentive Specialty Chemicals Inc.) as Cardura 10, Cardura 9 and Cardura 5 (glycidyl pivalate).
Cardura polyols are prepared as taught in the anonymous research disclosure and Hexion Inc. brochure “Cardura E10P—Low Viscosity Diol and Triol Polyesters”, 2006, flexion Inc.
Polyurethane dispersions were prepared as detailed in the next section. As industry benchmark Sancure 815 was chosen, this product currently has 8.5% NMP and while it does help in processing, it is also needed for film formation. These products utilize a hexane diol/neopentyl glycol/adipic acid diol. In addition to the diol, these products utilize Desmodur W (H12MDI) as the isocyanate, DMPA to introduce the acid functionality and are chain extended with hydrazine.
Wet dispersions and cured film of Cardura polyester based experimental PUDs and industry benchmark were subjected to below mentioned test regimen. The primary application purpose of experimental coatings was in clear wood coatings, but the invention also has uses in adhesives, paints and coatings such as those for kitchen cabinets, wood and vinyl flooring, plastics, leather coatings, glass fiber sizing, glass coatings, automotive/transportation coatings, textile coatings etc.
Manufacture of water base polyurethane utilizing Cardura polyol as the di-hydroxyl component in place of polyester polyols such as hexanediol adipate polyester polyols, butandiol adipate polyester polyols, hexane/neopentyl adipate polyester polyols or butanediol initiated polycaprolactone polyols and maintaining all other reactants at equivalent weight levels comparatively yields:
Manufacture of water base polyurethane utilizing Cardura polyol as the di-hydroxyl component in place of CHDM initiated polycarbonate polyol and maintaining all other reactants at equivalent weight levels comparatively yields:
Use of Cardura polyols addresses the need for reduced co-solvent demand for room temperature film formation while supplying increased surface hardness at equal isocyanate content and/or decreased isocyanate demand for equal surface hardness resulting in reduced cost, and, maintaining equal or improved abrasion resistance properties.
The composition of the invention wherein the weight % level of cosolvent required for film formation at 25° C. of the resulting polyurethane polymer is 35 to 60% lower than stochiometrically equivalent polyurethane systems utilizing hexane-neopentyl adipate polyester or BDO initiated polycaprolactone or CHDM initiated polycarbonate as the polyol component.
The composition according to the invention and wherein the Koenig Hardness of the resulting polyurethane polymer is 83 to 124% higher than stochiometrically equivalent polyurethane systems utilizing hexane-neopentyl adipate polyester or BDO initiated polycaprolactone as the polyol component.
The composition according to the invention and wherein the Koenig Hardness of the resulting polyurethane polymer is 2 to 3% higher, and, the weight % level of cosolvent required for film formation at 25° C. of the resulting polyurethane polymer is 55 to 60% lower than stochiometrically equivalent polyurethane systems utilizing CHDM initiated polycarbonate as the polyol component.
The composition according to the invention and wherein the Taber Abrasion resistance measured as mg loss/1000 cycles yields between 49 to 84% reduction in mg loss comparative to stochiometrically equivalent polyurethane systems utilizing hexane-neopentyl adipate polyester or BDO initiated polycaprolactone as the polyol component.
The composition according to the invention and wherein the Taber abrasion resistance measured as mg loss/1000 cycles yields between 10 to 15% reduction in mg loss comparative to stochiometrically equivalent polyurethane systems utilizing CHDM initiated polycarbonate as the polyol component.
The composition according to the invention and wherein the resulting polyurethane film may yield approximately equivalent Koenig Hardness and 40-46% reduction in cosolvent required for film formation at 25° C. and 20-22% reduction in polyisocyanate required as compared to a system utilizing hexanediol-neopentyl glycol polyester polyol component.
To a clean, dry reactor vessel add 138.51 grams of dicyclohexylmethane diisocyanate (H12MDI) and 199.29 grams of 1258 molecular weight hydroxyl terminal polyester diol derived from the reaction products of tertiary alkyl glycidyl esters. Start mixing and heat the mixture to 77° C. (170° F.). Start a nitrogen bleed into the head space of the reactor vessel. With heating on low charge 0.017 grams stannous octoate catalyst. Allow the reaction mixture to exotherm resulting in increased internal batch temperature to 110-121° C. (230-250° F.) with heating off. Allow reaction mixture to begin cooling while removing and testing an aliquot for complete reaction of the polyisocyanate with the polyester to yield a maximum amount of residual polyisocyanate content of 9.19%. Upon confirmation of completeness of reaction charge 48.00 grams of dipropylene glycol dimethyl ether cosolvent. Adjust the internal batch temperature to 93° C. (200° F.). Charge 14.17 grams of dimethylol propionic acid. Hold the internal batch temperature at 88-96° C. (190-205° F.). Approximately 20 minutes after charging the dimethylol propionic Acid test an aliquot of the reaction mixture for complete reaction of the residual polyisocyanate with the dimethylol propionic Acid to yield a maximum amount of residual polyisocyanate content of 5.54%. Upon confirmation of completeness of reaction cool the reaction mixture to 175 F.
To the reaction mixture at 79.5° C. (175° F.) add 10.6 grams of triethylamine neutralizing agent. To a separate vessel add 520.63 grams of water at 35-40.5° C. (95-105° F.) and 0.09 grams of DeeFo PI40 defoamer (supplied by Munzing). Start agitation in the water containing vessel. Slowly add 359.36 grams of the reaction mixture to the water allowing incorporation and dispersion of the reaction mixture into the water over a 3-7 minute period. Mix the dispersion for 10-20 minutes after complete addition of the reaction mixture. To the dispersion add 10.23 grams of 64% hydrazine hydrate diluted with water to 35% solids content. Mix for 10-15 minutes after addition of the hydrazine hydrate and test a small aliquot for residual isocyanate content via FTIR analysis (2250−cm peak). Mix to complete elimination of the residual isocyanate peak as determined by FTIR. The resulting dispersion has a polyurethane solids content of 35% by weight and a polyurethane solids composition of 38.53% polyisocyanate, 55.43% polyester polyol, 3.94% dimethylol propionic acid, 2.08% hydrazine. As produced the dispersion contains 13.35% dipropylene glycol monomethyl ether cosolvent based upon polyurethane solids content.
Upon complete elimination of the residual isocyanate peak as determined by FTIR analysis allow the liquid dispersion to equilibrate to 21.1° C. (70° F.) temperature. Test the liquid dispersion for film formation at 21.1° C. (70° F.) and 50% Relative Humidity by applying a 10 wet mil film of the dispersion to clean glass at 21.1° C. (70° F.) temperature and allowing the film to air dry. Determination of coalescence is made by visual observation of the elimination of film ‘cracks’ and fractures upon air dry of a 254 microns wet (10 wet mils) film on glass at 50% relative humidity and 21.1° C. (70° F.) temperature. Post add stepwise additions of dipropylene glycol dimethyl ether and record the total amount of additional dipropylene glycol dimethyl ether required to create film formation as described at 21.1° C. (70° F.) and 50% relative humidity.
Upon establishment of dipropylene glycol dimethyl ether content required for coalescence use wet solutions with added cosolvent at determined levels to test resulting films for the following:
Processing and test results for Example 1 and versions A, B and C are as follows:
Test results indicate that the use of hydroxyl terminal polyester diol derived from the reaction products of tertiary alkyl glycidyl esters in the preparation of a water based polyurethane can yield the unique resulting property attributes of reduced cosolvent coalescent demand required for film formation at room temperature, increased film penetration hardness, improved abrasion resistance as compared to stochiometrically equivalent polyurethane systems utilizing polyester diols that are currently commercially available in the industry and well known to the art.
| Number | Date | Country | Kind |
|---|---|---|---|
| 12075105.2 | Sep 2012 | EP | regional |
| 13000586.1 | Feb 2013 | EP | regional |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2013/002648 | 9/3/2013 | WO | 00 |
