HK1081982B - Self cross-linking polyurethane-dispersions - Google Patents

Description

Self-crosslinking polyurethane dispersions

The present invention relates to aqueous self-crosslinking polyurethane dispersions, stoving enamels prepared therefrom and their use in clearcoats and pigmented coats, in particular in automotive topcoats.

With increasingly stringent emission standards governing the solvents released during paint application, the significance of aqueous paints and coatings has increased dramatically in recent years. Although aqueous coating systems are now available in many fields of application, these systems often do not achieve the high quality levels of conventional solvent-containing coatings in terms of solvent resistance and chemical resistance or elasticity and mechanical lifetime. In particular, no polyurethane-based coating has been disclosed so far which can be processed from an aqueous phase and which fully meets the stringent technical requirements of automotive topcoats.

This statement applies both to the systems of DE-A4001783 and DE-A2456469, DE-A2814815, EP-A0012348 and EP-A0424697 which relate to aliphatic polyisocyanates modified with special anions, and which describe aqueous stoving enamel binders based on blocked polyisocyanates and organic polyhydroxyl compounds. In addition, systems based on the carboxyl-containing polyurethane prepolymers of DE-A2708611 having blocked isocyanate groups or the blocked water-soluble polyurethane prepolymers of DE-A3234590 are largely unusable for this purpose, have a high functionality and are therefore not very suitable for the production of elastic coatings.

Further improvements have been made in recent years with respect to the one-component (1K) stoving enamels used, for example in EP-A0576952 which describes the combination of water-soluble or water-dispersible polyhydroxy compounds with water-soluble or water-dispersible blocked polyisocyanates, or in DE-A19930555 which discloses water-dispersible, hydroxyl-functional binder components containing urethane groups, binder components containing blocked isocyanate groups and prepared in a multistage process with more than two polymerization steps, the combination of amino resins and further components. A disadvantage of these one-component systems is that the components prepared beforehand are subsequently formulated into coatings, so that an additional mixing step is required.

However, the coatings described in the prior art do not meet all technical requirements and are not concerned with the solids content and stability of the paints and the surface quality, such as surface smoothness and gloss, of the coatings formed from them.

The object of the present invention is to provide improved 1K stoving systems, in which the paints should have a high solids content and the coatings should have a high gloss, in particular.

The invention provides a process for preparing self-crosslinking polyurethane polymers, characterized in that in one step an isocyanate component (A) having an isocyanate functionality of greater than or equal to 2 is reacted with an at least difunctional polyol component (B1) having an average molecular weight of 62 to 2500 comprising at least one acid-functional compound (C) to form a prepolymer containing isocyanate groups or containing hydroxyl groups, followed by the addition of one or more polyol components (B2) having an OH functionality of greater than or equal to 2 and optionally an isocyanate component (A'), which may be the same as or different from (A), the resulting NCO-functional product is mixed with a capping agent (D), and in another step the polyol component (B3) is added.

In a preferred embodiment of the present invention, the addition of the polyol component (B3) is followed by the addition in a final step of an acid-functional compound (C'), which may be the same as or different from (C), and an isocyanate component (a "), which may be the same as or different from (a) and (a").

In the process of the present invention, the ratio of isocyanate groups (including blocking groups) to all isocyanate-reactive groups is selected to be from 0.5 to 3.0: 1, preferably from 0.6 to 2.0: 1, more preferably from 0.8 to 1.5: 1.

The present invention likewise provides self-crosslinking polyurethane polymers obtainable by the process according to the invention.

Suitable isocyanate components (A), (A ') and (A') are aliphatic, cycloaliphatic, araliphatic and/or aromatic isocyanates having an average functionality of from 2 to 5, preferably 2, and an isocyanate content of from 0.5 to 60% by weight, preferably from 3 to 40% by weight, more preferably from 5 to 30% by weight, such as tetramethylene diisocyanate, cyclohexane 1, 3-and 1, 4-diisocyanate, 1, 6-Hexamethylene Diisocyanate (HDI), 1-isocyanato-3, 3, 5-trimethyl-5-isocyanatomethylcyclohexane (isophorone diisocyanate, IPDI), methylenebis (4-isocyanatocyclohexane), tetramethylxylylene diisocyanate (TMXDI), triisocyanatononane, Toluene Diisocyanate (TDI), diphenylmethane-2, 4 ' -and/or 4, 4 ' -diisocyanate (MDI), triphenylmethane-4, 4 ' -diisocyanate or naphthylene-1, 5-diisocyanate and any mixtures of these isocyanates. Preference is given to isophorone diisocyanate, bis (4, 4' -isocyanatocyclohexyl methane) and 1, 6-hexamethylene diisocyanate.

Preferred as components (A), (A ') and (A') are polyisocyanates containing heteroatoms in the radical containing isocyanate groups. Examples of these are polyisocyanates containing carbodiimide groups, allophanate groups, isocyanurate groups, urethane groups and biuret groups. Particularly preferred polyisocyanates are those which are used primarily for the preparation of paints, examples being the biuret-, isocyanurate-or uretdione-group-containing modified products of the abovementioned simple polyisocyanates, in particular 1, 6-hexamethylene diisocyanate or isophorone diisocyanate.

Also suitable are low molecular weight polyisocyanates containing urethane groups, such as those obtainable by reacting IPDI or TDI used in excess with simple polyols having a molecular weight in the range from 62 to 300, in particular with trimethylolpropane or glycerol.

Suitable polyisocyanates are furthermore known prepolymers containing terminal isocyanate groups, such as are obtainable in particular by reacting the abovementioned simple polyisocyanates, especially diisocyanates, with a substoichiometric amount of an organic compound containing at least two isocyanate-reactive functional groups. In these known prepolymers, the ratio of isocyanate groups to NCO-reactive hydrogen atoms, which are preferably derived from hydroxyl groups, is from 1.05: 1 to 10: 1, preferably from 1.5: 1 to 4: 1. The type and amount ratio of the starting materials used in the preparation of the NCO prepolymers are chosen such that the NCO prepolymers preferably have an average NCO functionality of 2 to 3 and a number average molecular weight of 500-10000, preferably 800-4000.

Also suitable as polyisocyanates according to the invention are those polyurethane-, polyester-and/or polyacrylate-based polymers containing free isocyanate groups, and optionally mixtures of these polymers, in which only a portion of the free isocyanate groups are blocked with blocking agents, while the remainder are reacted with an excess of hydroxyl-containing polyesters, polyurethanes and/or polyacrylates and optionally mixtures thereof, to give polymers which contain free hydroxyl groups and which crosslink without further addition of isocyanate-reactive groups when heated to suitable stoving temperatures (self-crosslinking one-component stoving systems).

The polyol component (B1) comprises a dihydroxy to hexahydroxy polyol component having a molecular weight of 62 to 2500, preferably 62 to 1000, more preferably 62 to 500, at least one of these components being an acid-functional compound (C). Preferred polyol components are, for example, 1, 4-and/or 1, 3-butanediol, 1, 6-hexanediol, 2, 2, 4-trimethyl-1, 3-pentanediol, trimethylolpropane and polyester polyols and/or polyether polyols having an average molecular weight of less than or equal to 1000.

The polyol component (B1) preferably comprises more than 50% by volume of the acid-functional compound (C); it is particularly preferred that component (B1) comprises only compound (C), more particularly preferably only dimethylolpropionic acid.

Suitable acid-functional compounds (C)/(C') are hydroxy-functional carboxylic and/or sulfonic acids, preferably mono-and dihydroxycarboxylic acids, such as 2-hydroxyacetic acid, 3-hydroxypropionic acid and 12-hydroxy-9-octadecanoic acid (ricinoleic acid). Particularly preferred carboxylic acids (C)/(C') are those in which the reactivity of the carboxyl group is retarded due to steric effects, such as lactic acid. More particularly preferred are 3-hydroxy-2, 2-dimethylpropionic acid (hydroxypivalic acid) and dimethylolpropionic acid.

The polyol component (B2) is selected from:

b1) dihydroxy to hexahydroxy alcohols having an average molecular weight of 62 to 300, preferably 62 to 182, more preferably 62 to 118,

b2) linear difunctional polyols having an average molecular weight of 300-,

b3) monofunctional linear polyethers having an average molecular weight of 300-.

Suitable polyol components (b1) include dihydroxy to hexahydroxy alcohols and/or mixtures thereof which do not contain ester groups. Typical examples are 1, 2-ethanediol, 1, 2-and 1, 3-propanediol, 1, 4-, 1, 2-or 2, 3-butanediol, 1, 6-hexanediol, 1, 4-dihydroxycyclohexane, glycerol, trimethylolethane, trimethylolpropane, pentaerythritol and sorbitol. Naturally, alcohols containing ionic groups or groups which can be converted into ionic groups can also be used as component b 1).

For example, preference is given to using 1, 4-or 1, 3-butanediol, 1, 6-hexanediol and/or trimethylolpropane.

Suitable linear difunctional polyols (b2) are selected from polyethers, polyesters and/or polycarbonates. The polyol component b2) preferably comprises at least one ester group-containing diol having a molecular weight in the range 350-4000, preferably 350-2000, more preferably 350-1000. The molecular weight is an average value that can be calculated from the hydroxyl number. Generally, the ester diol is a mixture which may also contain minor amounts of individual components having molecular weights below or above these limits. The compounds are polyester diols known per se, which are synthesized from diols and dicarboxylic acids. Suitable diols are, for example, 1, 4-dimethylolcyclohexane, 1, 4-or 1, 3-butanediol, 1, 6-hexanediol, neopentyl glycol, 2, 2, 4-trimethyl-1, 3-pentanediol, trimethylolpropane and pentaerythritol or mixtures of such diols. Suitable dicarboxylic acids are, for example, aromatic dicarboxylic acids such as phthalic acid, isophthalic acid and terephthalic acid, cycloaliphatic dicarboxylic acids such as hexahydrophthalic acid, tetrahydrophthalic acid, endomethylenetetrahydrophthalic acid and their anhydrides, and also aliphatic dicarboxylic acids, which are preferably used, such as succinic acid, glutaric acid, adipic acid, suberic acid, azelaic acid and sebacic acid or their anhydrides. Polyester diols based on adipic acid, phthalic acid, isophthalic acid and tetrahydrophthalic acid are preferably used as component (b 2).

It is particularly preferred to use polycaprolactone diols having an average molecular weight in the range from 350-400, preferably 350-2000, more preferably 350-1000 as component (b2), which can be prepared in a customary manner from the diols or mixtures of diols of the type listed above as starting compounds and epsilon-caprolactone. The preferred starter molecule in this respect is 1, 6-hexanediol. More particularly preferred are polycaprolactone diols prepared by polymerizing epsilon-caprolactone using 1, 6-hexanediol as the starting compound.

As linear polyol component (b2), it is also possible to use (co) polyethers from ethylene oxide, propylene oxide and/or tetrahydrofuran. Preferred are polyethers having an average molecular weight of 500-2000, such as polyethylene oxide or polytetrahydrofuran glycol.

Also suitable as (b2) are hydroxyl-containing polycarbonates, preferably having an average molecular weight of 400-2000, such as hexanediol polycarbonate.

Suitable monofunctional linear polyethers (b3) are, for example, (co) polyethers formed from ethylene oxide and/or propylene oxide. Preference is given to polyalkylene oxide polyethers prepared starting from monoalcohols, having an average molecular weight of 350-2500 and having at least 70% ethylene oxide units. Particularly preferred are polymers (copolymers) having more than 75% ethylene oxide units and a molecular weight of 300-. As starter molecules in the preparation of these polyethers, preference is given to using monofunctional alcohols having from 1 to 6 carbon atoms.

Suitable polyols (B3) are polyols having an OH functionality of greater than 2 and an average molecular weight of 300-.

Preferred polyols (B3) are, for example, polyethers having an average molecular weight of 300-2000 and an average functionality of 2.5-4OH groups/molecule. Also preferred are polyesters having an average OH functionality of from 2.5 to 4.0. Suitable diols and dicarboxylic acids for the polyesters are those specified under component (b2), but they additionally comprise short-chain polyols of 3-6 functions, such as trimethylolpropane, pentaerythritol or sorbitol. Preference is given to using polyester polyols based on adipic acid, phthalic acid, isophthalic acid and tetrahydrophthalic acid.

Also suitable as component (B3) are (co) polyethers of ethylene oxide, propylene oxide and/or tetrahydrofuran having an average functionality of more than 2, and also branched polycarbonates.

As blocking agents (D) it is possible to use all known monofunctional blocking agents, such as e-caprolactam, diethyl malonate, ethyl acetoacetate, oximes such as butanone oxime, diisopropylamine, dimethylpyrazole, triazole and mixtures thereof. Preference is given to, for example,. epsilon. -caprolactam, butanone oxime, diisopropylamine, 3, 5-dimethylpyrazole, triazole and/or mixtures thereof.

The reaction of components (A) with (B1) to form OH-or NCO-functional prepolymers is of particular importance for the process of the present invention. The reaction should be carried out before all other components are added. If necessary, further isocyanates (A ') and/or (A') to be used should likewise be added after the preparation of the prepolymer. The preparation of the prepolymer can be carried out in the same reactor as the reaction with the other components to form the dispersion of the invention.

The process of the invention is carried out such that in the reaction of components (A) and (B1) according to the theoretical stoichiometric equation, the amount of unreacted excess component (A) and/or (B1) is as minimal as possible.

Further reaction of the remaining components can be carried out according to methods known from the prior art.

Preference is, however, given to a process which is characterized in that in one step component (a) is reacted with component (B1) comprising at least one acid-functional compound (C) to form an NCO-functional prepolymer, then components (B1), (B2) and (B3) are added and, if desired, an isocyanate component (a'), which may be identical to or different from (a), is added, the resulting NCO-functional product being partially blocked with a blocking agent (D), and in a further step a polyol component (B3) is added. Then, it is particularly preferred that in the final step, an acid-functional compound (C '), which may be the same as or different from (C), and an isocyanate component (A "), which may be the same as or different from (A) and (A'), are added.

The next thing to do is to prepare an aqueous dispersion comprising the self-crosslinking polyurethane of the invention by the prior art process.

The carboxylic acid groups present in the polyurethane of the present invention are neutralized to a degree of at least 50%, preferably 80-120%, more preferably 95-105% with a suitable neutralizing agent, and then dispersed with deionized water. Neutralization may be carried out before, during or after the dispersing or dissolving step. However, it is preferred to perform neutralization prior to the addition of water.

Suitable neutralizing agents are, for example, triethylamine, dimethylaminoethanol, dimethylcyclohexylamine, triethanolamine, methyldiethanolamine, diisopropanolamine, diisopropylcyclohexylamine, N-methylmorpholine, 2-amino-2-methyl-1-propanol, ammonia or other common neutralizing agents or neutralizing mixtures thereof. Preference is given to using tertiary amines such as triethylamine, diisopropylhexylamine, particularly preferably dimethylethanolamine.

The invention likewise provides aqueous dispersions comprising the self-crosslinking polyurethanes of the invention. These aqueous dispersions are useful as aqueous one-component drying systems.

The aqueous dispersions of the invention contain from 5 to 60% by weight, preferably from 10 to 40% by weight, of OH-and/or NCO-functional prepolymers, from 0 to 50% by weight, preferably from 5 to 40% by weight, more preferably from 10 to 25% by weight, of components (A ') and/or (A "), from 1 to 10% by weight, preferably from 1 to 5% by weight, of component (B1), from 5 to 40% by weight, preferably from 10 to 25% by weight, of component (B2), from 1 to 10% by weight, preferably from 1 to 5% by weight, of component (B3), from 10 to 60% by weight, preferably from 20 to 50% by weight, of component (B3), from 1 to 10% by weight, preferably from 1 to 5% by weight, of component (C') and from 1 to 20% by weight, preferably from 1 to 10% by weight, of component (D), the sum of the components amounting to 100%.

To adjust the viscosity, a solvent may also be added to the reaction mixture if desired. Suitable solvents are all known solvents, such as N-methylpyrrolidone, methoxypropyl acetate or xylene. They are preferably used in an amount of 0 to 10% by weight, more preferably 0 to 5% by weight. The solvent is preferably added during the polymerization.

It is also possible to add a larger amount of (part of) a water-miscible solvent such as acetone or methyl ethyl ketone to the reaction mixture. After the reaction was completed, water was added to the reaction mixture and the solvent was distilled off. This is also known as the acetone or slurry process. The advantage of this procedure is the low proportion of solvent in the finished dispersion.

The catalyst may likewise be added to the reaction mixture. Preference is given to dibutyltin dilaurate and dibutyltin octoate.

The dispersions comprising the polyurethanes of the invention are used as one-component stoving systems containing free hydroxyl groups for the preparation of varnishes, paints and other formulations. It is likewise possible to add any auxiliaries and additives of the coating technology, such as pigments, flow-control agents, gas-barrier additives or catalysts, which are optionally used together, to the aqueous dispersion comprising the polyurethane of the invention.

The invention also provides for the use of dispersions comprising the polyurethanes of the invention for preparing paints, varnishes or adhesives.

The aqueous one-component coating compositions comprising the polyurethanes of the present invention can be applied to any desired heat-resistant substrate by any of the methods in coating technology, such as spraying, brushing, dipping, flow coating, or in one or more coats using a coating roll and doctor blade. The paint films generally have a dry film thickness of from 0.01 to 0.3 mm.

Examples of suitable substrates include metal, plastic, wood or glass. The paint film is cured at 80-220 ℃, preferably 130-180 ℃.

The aqueous one-component coating materials comprising the polyurethanes of the invention are preferably suitable for forming coatings and lacquers on steel sheets, for example for producing vehicle bodies, machines, housings, drums or freight containers. It is particularly preferred to use aqueous one-component coatings comprising the polyurethanes of the invention for the preparation of automotive surfacers and/or topcoat materials.

Examples

Example 1: preparation of NCO prepolymers

309.85g (2.31mol) of dimethylolpropionic acid and 822.36g of N-methyl-pyrrolidone were stirred in a stirred vessel at 50 ℃ until a clear solution formed (60 minutes) and then, at 50 ℃, 770.62g (3.47mol) of isophorone diisocyanate were added and the temperature was raised to 85 ℃. Stirring was continued for 3 hours at 85 ℃; at this time, the NCO content of the reaction mixture was 5.06% (calculated value: 5.10%). The reaction mixture was then used directly for further synthesis.

Example 2: preparation of NCO prepolymers

The procedure described in example 1 was repeated, but 1113.11g (5.00mol) of isophorone diisocyanate were added after the end of the reaction and the reaction mixture was cooled to room temperature with stirring. This gives a clear yellow liquid having a viscosity of 9000mPas (23 ℃).

Example 3: preparation of NCO prepolymers

The procedure described in examples 1 and 2 was repeated, but according to example 1 214.64g (1.6mol) of dimethylolpropionic acid, 427.2g of N-methyl-pyrrolidone and 711.68g (3.2mol) of isophorone diisocyanate were used, according to example 2 622.72g (2.8mol) of isophorone diisocyanate were used. The resulting yellow reaction mixture had a viscosity of 11000mPas (23 ℃ C.).

Example 4: (present invention)

123.90g (0.295mol) of a polyester of adipic acid and 1, 6-hexanediol having an average molecular weight of 840, 11.25g (0.005mol) of a polyethylene oxide-propylene oxide polyether (80: 20mol/mol) prepared starting from n-butanol and having an average molecular weight of 2250, 6.76g (0.15mol) of 1, 4-butanediol and 6.71g (0.1mol) of trimethylolpropane are heated to 85 ℃ in a stirred vessel and mixed homogeneously. After addition of 260.43g (1.1 equivalent NCO) of the compound of example 3, the mixture was stirred at 85 ℃ for 135 minutes. The resulting product contained 4.41% (calculated: 4.45%) of isocyanate groups. Subsequently, 26.54g (0.305mol) of butanone oxime were added over the course of 20 minutes at 85 ℃ and stirring was continued for 10 minutes thereafter. Then, 160g (0.5 equivalent OH) of a polyester formed from adipic acid, isophthalic acid, trimethylolpropane, neopentyl glycol and propylene glycol having a hydroxyl number of 189 were added and the reaction mixture was stirred at 85 ℃ overnight. Thereafter, it no longer contains any isocyanate groups (according to IR spectroscopy). At 85 ℃ a solution of 5.91g (0.05mol) hydroxypivalic acid in 9.45g of N-methyl-pyrrolidone was added, the mixture was stirred for 5 minutes, then 11.12g (0.1mol) isophorone diisocyanate was added, and the mixture was stirred for 200 minutes at 85 ℃. The reaction mixture then no longer contains any isocyanate groups. Subsequently, 22.29g (0.25mol) of N-dimethylethanolamine were added, after which stirring was continued for 10 minutes, after which the product was dispersed with 1390g of hot water at 50 ℃ under vigorous stirring, after which stirring was carried out for 3 hours at 50 ℃ and the product was allowed to cool, still under stirring. The resulting dispersion had the following properties:

solid content: 30 percent of

Viscosity (DIN cup No. 4): 14s

Particle size (laser correlation spectroscopy, LKS): 31nm

Example 5: (present invention)

The procedure described in example 4 was repeated, but instead of the prepolymer of example 3, first 6.76g (0.15mol) of 1, 4-butanediol, 26.83g (0.4mol) of dimethylolpropionic acid and 122.32g (1.1mol) of isophorone diisocyanate in 53.4g of N-methylpyrrolidone were reacted to a calculated NCO content of 10.97% (11.04%), after which 44.48g (0.4mol) of isophorone diisocyanate and the polyester, polyether, 1, 4-butanediol and trimethylolpropane according to example 4 were added. The resulting dispersion had the following properties:

solid content: 30 percent of

Viscosity (DIN cup No. 4): 16s

Particle size (LKS): 30nm

Example 6: (present invention)

The procedure described in example 4 is repeated, but in contrast to example 3, 123.9g (0.295mol) of a polyester formed from adipic acid and 1, 6-hexanediol, 26.83g (0.4mol) of dimethylolpropionic acid and 115.93g (1.0425mol) of isophorone diisocyanate in 62.85g of N-methylpyrrolidone are first reacted to an isocyanate content of 3.85%, after which 50.88g (0.458mol) of isophorone diisocyanate and the polyether according to example 4, 1, 4-butanediol and trimethylolpropane are added. The resulting dispersion had the following properties:

solid content: 30 percent of

Viscosity (DIN cup No. 4): 17s

Particle size (LKS): 26nm

Example 7: (present invention)

The procedure described in example 4 was repeated, but using 9.01g (0.2mol) of 1, 4-butanediol and 102.90g (0.245mol) of a polyester formed from adipic acid and 1, 6-hexanediol. The resulting dispersion had the following properties:

solid content: 30 percent of

Viscosity (DIN cup No. 4): 14s

Particle size (LKS): 28nm

Example 8: (present invention)

The procedure described in example 7 was repeated, but using 256.38g (1.1 equivalent of NCO) of the compound of example 2 instead of the compound of example 3 and 2.5g (0.005mol) of methanol ethoxylate instead of the polyether. The resulting dispersion had the following properties:

solid content: 30 percent of

Viscosity (DIN cup No. 4): 13s

Particle size (LKS): 48nm

Example 9: (present invention)

The procedure described in example 8 was repeated, but using, instead of the compound of example 2, a mixture of the reaction product of 59.49g (0.535mol) of isophorone diisocyanate and 26.83g (0.4mol) of dimethylolpropionic acid (solution in 53.40g N-methylpyrrolidone) having an NCO content of 4.02% (calculated: 4.06%) and 107.31g (0.97mol) of isophorone diisocyanate. The reaction mixture had 4.92% NCO groups before butanone oxime was added. The resulting dispersion had the following properties:

solid content: 30 percent of

Viscosity (DIN cup No. 4): 13s

Particle size (LKS): 61nm

Example 10: (present invention)

The procedure described in example 9 was repeated, but using the reaction product of isophorone diisocyanate and dimethylolpropionic acid with an isocyanate content of 4.00%. The reaction mixture had an NCO content of 4.40% before the butanone oxime was added. The dispersion had the following properties:

solid content: 30 percent of

Viscosity (DIN cup No. 4): 12s

Particle size (LKS): 82nm

Example 11: (present invention)

The procedure described in example 7 was repeated, but instead of the compound of example 3, a mixture of the reaction product of 20.12g (0.3mol) of dimethylolpropionic acid in 53.40g N-methylpyrrolidone with an isocyanate content of 5.08% (calculated: 5.10%) and 50.04g (0.45mol) of isophorone diisocyanate and 105.64g (0.95mol) of isophorone diisocyanate was used. The amount of water was 668.82 g. The resulting dispersion had the following properties:

solid content: 40 percent of

Viscosity (DIN cup No. 4): 12s

Particle size (LKS): 96nm

Example 12: (present invention)

The procedure described in example 8 was repeated, but using 11.25g (0.025mol) of the polyether according to example 4 and 767.75g of water. The dispersion had the following properties:

solid content: 40 percent of

Viscosity (DIN cup No. 4): 21s

Particle size (LKS): 63nm

Example 13: (present invention)

The procedure described in example 11 was repeated, but using 11.25g (0.025mol) of the polyether according to example 4 and 729.32g of water. The dispersion had the following properties:

solid content: 40 percent of

Viscosity (DIN cup No. 4): 18s

Particle size (LKS): 81nm

Example 14: (present invention)

309.85g (2.31mol) of dimethylolpropionic acid were dissolved in 822.4g of N-methylpyrrolidone at 80 ℃ with stirring and the solution was cooled to 50 ℃. After addition of 770.6g (3.456mol) of isophorone diisocyanate, the temperature was raised to 85 ℃ and the mixture was stirred for 4 hours. The NCO content reached 5.09% (calculated: 5.10%). 1113.1g (10.0mol) of isophorone diisocyanate were added to the mixture and stirred homogeneously (part I).

To 195.84g (0.8 equivalent NCO) of fraction I were added 33.36g (0.3mol) of isophorone diisocyanate, 102.90g (0.245mol) of a polyester formed from adipic acid and 1, 6-hexanediol, 2.50g (0.005mol) of monofunctional polyethylene oxide, 9.01g (0.2mol) of 1, 4-butanediol and 6.71g (0.1mol) of trimethylolpropane and stirred at 85 ℃ for 3.5 hours. Thereafter, 30.86g (0.305mol) of diisopropylamine are added over the course of 30 minutes at 80 ℃ and the mixture is stirred for 10 minutes thereafter. Subsequently, 159.09g (0.5 equivalent OH) of a polyester with an OH number of 189 formed from adipic acid, isophthalic acid, trimethylolpropane, neopentyl glycol and propylene glycol were added and the reaction mixture was stirred at 80 ℃ overnight. After this time, no NCO groups could be detected any more by IR spectroscopy. Subsequently, 5.53g of a solution of dimethylolpropionic acid in 9.45g N-methylpyrrolidone and 10.00g (0.09mol) of isophorone diisocyanate were added at 80 ℃ and the mixture was stirred at 80 ℃ for 3 hours (after which no free NCO groups were present anymore). Subsequently, 16.94g (0.19mol) of N-dimethylethanolamine were added and the mixture was stirred at 80 ℃ for 20 minutes. Then 1043g of deionized hot water at 80 ℃ were added, after which the mixture was stirred at 80 ℃ for 1 hour and cooled to room temperature over the course of 5 hours with stirring. The dispersion had the following properties:

solid content: 30 percent of

Viscosity (DIN cup No. 4): 15s

pH value: 9.04

Particle size (LKS): 50nm

Example 15: (present invention)

A solution of 26.80g (0.40mol) dimethylolpropionic acid in 77.84g of N-methylpyrrolidone is added at 80 ℃ to 104.8g (0.8mol) of bis (4, 4' -isocyanatocyclohexyl) methane (Desmodur ® W, Bayer AG, Lev.DE) and the mixture is stirred for 2 hours at 80 ℃. Thereafter, the temperature was raised to 90 ℃ and stirring was continued for a further 2 hours until an NCO content of 7.99% (calculated: 8.02%) was obtained. It was then cooled to 80 ℃ and 94.0g (0.72mol) of Desmodur ® W, 112.13g (0.345mol) of a linear polycaprolactone polyester, 11.25g (0.0225mol) of a monofunctional polyether having an average molecular weight of 500, 6.70g (0.1mol) of trimethylolpropane and 4.50g (0.1mol) of 1, 4-butanediol were added and stirring was continued for a further 5 hours until an isocyanate group content of 4.66% (calculated: 4.79%) was reached. The mixture was then cooled to 70 ℃ and, at this temperature, 40.48g (0.4mol) of diisopropylamine were added over the course of 60 minutes. Then stirring is continued for 30 minutes; the NCO content was 0.75% (calculated: 0.83%). Subsequently, 230.0g (0.575 equivalents OH) of a branched polyester (Desmophen ® 670, 4.25% by weight OH groups, Bayer AG, Lev.DE) were added and the mixture was stirred at 70 ℃ for a further 2 hours (until no free NCO groups were present). Then, 17.83g (0.20mol) of N-dimethylethanolamine was added and stirring was continued for 10 minutes. Thereafter, 932.14g of hot deionized water at 70 ℃ were added with vigorous stirring, after which the mixture was stirred at 70 ℃ for 1 hour and the product was then cooled to room temperature with stirring. The resulting dispersion had the following properties:

solid content: 30 percent of

Viscosity (23 ℃, rotational viscometer): 100mPas

Particle size (LKS): 71nm

Example 16: (present invention)

The procedure described in example 14 was repeated, but instead of the short-chain polyether, 11.25g of a monofunctional polyether having an average molecular weight of 2250, formed from ethylene oxide and propylene oxide (80: 20, w/w) and prepared starting from butanol, and 15.58g (0.175mol) of N-dimethylethanolamine and 788.3g of water were used. The dispersion had the following properties:

solid content: 45 percent of

Viscosity (23 ℃, rotational viscometer): 7000mPas

Particle size (LKS): 74nm

Example 17: (present invention)

The procedure described in example 14 was repeated, except that a solution of 5.90g (0.05mol) of hydroxypivalic acid in 9.45g N-methylpyrrolidone and 13.10g (0.1mol) of Desmodur ® W (Bayer AG, Lev., DE) were added at 70 ℃ before 15.58g (0.175mol) of N-dimethylethanolamine were added and the reaction mixture was stirred for 90 minutes until no NCO groups could be detected anymore in the IR spectrum. Thereafter, 947.8g of water were added. The resulting dispersion had the following properties:

solid content: 40 percent of

Viscosity (23 ℃, rotational viscometer): 30mPas

Particle size (LKS): 110nm

Comparative example 1:

the procedure described in example 4 was repeated except that no NCO-functionalized prepolymer was prepared; instead, all of the starting materials used in example 4 prior to the blocking step with butanone oxime were randomly reacted in the mixture. The resulting dispersion had the following properties:

solid content: 30 percent of

Viscosity (DIN cup No. 4): 19s

Particle size (LKS): 25nm

Comparative example 2:

the procedure described in example 17 was repeated except that no NCO-functionalized prepolymer was prepared; instead, all of the starting materials used in example 17 up to the end-capping step with butanone oxime were randomly reacted in the mixture. The resulting dispersion had the following properties:

solid content: 30 percent of

Viscosity (23 ℃, rotational viscometer): 100mPas

Particle size (LKS): 50nm

The advantages of the newly developed products are clearly the solids content and the higher gloss values at the same pH value.

The application example is as follows:

the following examples demonstrate the improvement in the properties of coatings by using the dispersions of the invention, in particular the highest solids content obtainable for the same run-off time and pH value, and also the gloss.

Comparative example 3:

30.93g of the pigment paste described in detail below were stirred with 68.26g of a 30% polyurethane dispersion according to comparative example 1 and 0.33g of a 10% aqueous dimethylethanolamine solution and 0.48g of a commercially available water-dilutable melamine resin in the form of 97% (Maprenal ® MF904, Solutia, Germany). The resulting spray viscosity was about 21s (5mm ISO cup).

Example 18: (present invention)

37.29g of the pigment grinding paste described in detail below were stirred with 61.73g of a 40% polyurethane dispersion according to example 12 and 0.40g of a 10% aqueous solution of dimethylethanolamine and 0.58g of a commercially available water-dilutable melamine resin in the form of 97% (Maprenal ® MF904, Solutia, Germany). The resulting spray viscosity was about 21s (5mm ISO cup).

Example 19: (present invention)

37.17g of the pigment grinding paste described in detail below were stirred with 61.53g of a 40% polyurethane dispersion as in example 13 and 0.72g of a 10% aqueous solution of dimethylethanolamine and 0.58g of a commercially available water-dilutable melamine resin in the form of 97% (Maprenal ® MF904, Solutia, Germany). The resulting spray viscosity was about 22s (5mm ISO cup).

Comparative example 4:

30.93g of the pigment paste described in detail below were stirred with 68.26g of a 30% polyurethane dispersion according to comparative example 2 and 0.33g of a 10% aqueous dimethylethanolamine solution and 0.48g of a commercially available water-dilutable melamine resin in the form of 97% (Maprenal ® MF904, Solutia, Germany). The resulting spray viscosity was about 27s (5mm ISO cup).

Example 20: (present invention)

35.39g of the pigment grinding paste described in detail below were stirred with 58.59g of a 40% polyurethane dispersion as in example 17 and 0.38g of a 10% aqueous solution of dimethylethanolamine and 0.55g of a commercially available water-dilutable melamine resin in the form of 97% (Maprenal ® MF904, Solutia, Germany) and diluted with distilled water to a spray viscosity of approximately 28s (5mm ISO cup).

Pigment grinding paste for paint examples

A predispersed slurry consisting of 11.0g of a 70% form of a water-dilutable polyester resin (Bayhydrol ® D270, 2.9% by weight OH groups, Bayer AG, Lev., DE), 20.9g of distilled water, 1.6g of a 10% aqueous dimethylethanolamine solution and 3.9g of a commercially available wetting agent, 3.6g of titanium dioxide (Tronox ® R-FD-I, Kerr McGee Pigments GmbH and Co.KG, Krefeld, DE), 1.7g of lamp black (Spezialschschez 4, Degussa-Hulst, Frankfurt, DE), 50.6g of barium sulfate (Blanc fixe Micro, Sachleben Chemie GmH, Duisburg, DE), 5.8g of Talc (TalcWert, Extra, Ex) was ground in a commercial bead mill for 30 minutes to an anti-settling agent (Tankfurt ®, Frankfurt).

This gives a paint system having a binder resin solids ratio of 10: 2: 88 parts by weight polyester resin/melamine resin/polyurethane dispersion and a binder-pigment/filler ratio of 1: 0.8 and showing the following properties (cf. examples):

examples comparative example 3 example 18 example 19

Solid content (% by weight) 42.551.151.0

pH value 8.38.38.3

Run-out time, 5mm ISO cup 22s 21s 22s

Stored at 40 ℃ for 30 days

After outflow time 15s 20s 21s

Examples comparative example 4 example 20

Solid content (% by weight) 42.548.5

pH value 8.38.3

Run-out time, 5mm ISO cup 27s 28s

Stored at 40 ℃ for 30 days

Later outflow time 19s 27s

These paints were applied to the following substrates at the resulting dry film thickness of 25-35 μm using a gravity-fed cup-type spray gun having a nozzle diameter of 1.5mm and an atomization pressure of 5 bar. The wet paint film was flash dried at 23 ℃ for 5 minutes and then dried in a forced air oven. The substrate in the case of the pendulum hardness and gloss test is a glass plate, and in the case of the cross-hatch adhesion and the Eschka-cupping test is a degreased steel plate.

The test results obtained are shown below:

drying conditions are as follows: 10 min RT and 20 min 165 deg.C

Examples comparative example 3 example 18 example 19

Pendulum impact hardness 115s 116s 94s

The gloss is 20 DEG/60 DEG 24E/69E 54E/83E 55E/84E

After 30 days of storage at 40 ℃

The gloss of the paint is 20 DEG/60 DEG 21E/66E 52E/82E 55E/84E

10mm 10mm 10mm in Eschen's Tuck test

Cross cut adhesion (0-5) 000

Examples comparative example 4 example 20

Pendulum impact hardness 52s 56s

The gloss is 20 DEG/60 DEG 22E/67E 49E/78E

Stored at 40 ℃ for 30 days

The gloss of the finished paint was 20 °/60 ° 19E/59E 45E/78E

10mm in Escherchia test

Adhesive force of cross-cut method (0-5) 00

The performance test was carried out according to the following method:

pendulum impact hardness: konig pendulum test to DIN 53157

Gloss measurement 20 °/60 °: according to DIN EN ISO 2813

The Ehrlich cupping test: according to DIN EN ISO 1520

Adhesive force of a grid cutting method: according to DIN EN ISO 2409

It is apparent that the inventive examples show higher solids and better gloss values than the comparative examples.

Claims (12)

1. Process for preparing a self-crosslinking polyurethane polymer, characterized in that in one step an isocyanate component (a) having an isocyanate functionality of greater than or equal to 2 is reacted with an at least difunctional polyol component (B1) having an average molecular weight of 62 to 2500 comprising at least one acid-functional compound (C) to form an isocyanate-containing or hydroxyl-containing prepolymer, followed by the addition of one or more polyol components having an OH functionality of greater than or equal to 2 (B2) selected from:

b1) dihydroxy to hexahydroxy alcohols having an average molecular weight of 62 to 300,

b2) a linear difunctional polyol having an average molecular weight of 300-4000,

b3) a monofunctional linear polyether having an average molecular weight of 300-3000,

the resulting NCO-functional product is partially blocked with a blocking agent (D) and in a further step a polyol component (B3) having an average molecular weight of 300-2000 and an average functionality of 2.5-4OH is added and in a final step an acid-functional compound (C '), which may be the same as or different from the acid-functional compound (C), and an isocyanate component (A ') which may be the same as or different from the isocyanate component (A) are added, wherein the acid-functional compounds (C) and (C ') are monohydroxycarboxylic acids or dihydroxycarboxylic acids.

2. A process according to claim 1, characterized in that in one step the isocyanate component (a) is reacted with a polyol component (B1) comprising at least one acid-functional compound (C) to form an NCO-functional prepolymer, said polyol components (B1), (B2) and (B3) are subsequently added, the resulting NCO-functional product is partially capped with a capping agent (D), and in another step the polyol component (B3) is added.

3. A process according to claim 1 or 2, characterized in that the isocyanate component (a'), which may be the same or different from the isocyanate component (a), is added after the reaction of the isocyanate component (a) with the polyol component (B1).

4. A process according to claim 3, characterized in that the isocyanate (a ") may be the same or different from the isocyanate component (a').

5. A process according to claim 3, characterized in that the isocyanate components (A)/(A')/(A ") are isophorone diisocyanate, bis (4, 4-isocyanatocyclohexyl-methane) and/or 1, 6-hexamethylene diisocyanate.

6. A process according to claim 1 or 2, characterized in that the polyol component (B1) comprises a dihydroxy to hexahydroxy polyol component having a molecular weight of 62 to 2500, at least one of these components being the acid-functionalized compound (C).

7. The process according to claim 1 or 2, characterized in that the acid-functional compound (C)/(C') is 3-hydroxy-2, 2-dimethylpropanoic acid (hydroxypivalic acid) or dimethylolpropionic acid.

8. A process as claimed in claim 1, characterized in that the polyol component (B3) is a polyether or polyester having an average functionality of 2.5 to 4OH groups per molecule.

9. A self-crosslinking polyurethane polymer obtainable by a process as claimed in claim 1.

10. An aqueous dispersion comprising a self-crosslinking polyurethane as claimed in claim 9.

11. Use of a self-crosslinking polyurethane polymer as claimed in claim 9 for preparing an aqueous dispersion.

12. Use of a self-crosslinking polyurethane polymer as claimed in claim 9 for the preparation of paints, varnishes or adhesives.