HK1191358A - Aqueous resin composition comprising a polyester-polyurethane resin including a dendritic polyol - Google Patents

Description

Aqueous resin composition comprising polyester-polyurethane resin containing dendritic polyol

The present invention relates to aqueous resin compositions comprising polyester-polyurethane resins wherein a dendritic polyol is used as part of the reaction mixture. The invention also relates to a process for preparing the aqueous resin composition of the invention, an aqueous coating system comprising the aqueous resin composition of the invention and the use of the aqueous coating system of the invention for coating, painting and/or sealing substrates.

Aqueous adhesives based on polyurethane dispersions are known and are described, for example, in Houben-Weyl, Methoden der organischen Chemistry, 4 th edition, Vol.E 20, p.1659 (1987), J.W. Rosthauser, K. Nachtkamp, "Advances in Urethane Science and Technology", K.C. Frisch and D. Klempner, Vol.10, p.121-162 (1987) or D. Dietrrich, K. Uhlig, Ullmann's Encyclopedia of Industrial Chemistry, Vol.A 21, p.677 (1992).

When used as coatings, such binders can be used to enhance the appearance of the substrate or to protect the underlying substrate from adverse environmental conditions. Examples of prior disclosures include:

EP 0669352 a1 describes special aqueous polyester-polyurethane dispersions which, when combined with crosslinker resins and, if appropriate, linear hydroxyl-free polyurethane dispersions, can be cured to give coatings having good soft-feel effects, good mechanical properties and generally satisfactory solvent resistance. However, for certain applications, the resistance, in particular to sun protection liquids, still needs to be improved.

EP 0926172 a2 describes aqueous two-component (2K) polyurethane coatings in which the resistance to sun protection liquids (penetration of the sun protection liquid through the film, delamination and/or other damage) can be improved by using special ester-modified polyisocyanates. The binders used in this case are mixtures of carboxylate and/or sulfonate-hydrophilicized polyester polyol dispersions with physically drying carboxylate and/or sulfonate-hydrophilicized polyurethane dispersions.

EP 0578940 a1 describes water-dispersible polyurethane polyols based on polyester and polycarbonate polyols or block polyester carbonate polyols, which contain 25 to 100% of acid groups neutralized with a base, correspond to an acid number of 6 to 45 mg KOH/g, have a hydroxyl number of 20 to 250 mg KOH/g, a molecular weight Mw of 2000 to 150000, a content of urethane groups of 2 to 16% by weight and a carbonate content of 1 to 25% by weight. Also described is a process for making a water-dilutable binder combination from 30 to 90% by weight of such a polyol and 2 to 70% by weight of a crosslinker resin and the use of such a polyol as a binder component in a coating or sealing material.

EP 1418192 a1 relates to water-dilutable polyurethane resins having a carbonate content of from 5,8 to 20, 0% by weight and being present in a solvent which is inert towards isocyanate groups.

For coatings with good weathering stability, US 2010/0222448 a1 discloses aqueous polyurethane dispersions obtained by dispersing in water the reaction product obtained by reacting a reaction mixture comprising at least one organic, aliphatic, cycloaliphatic or aromatic di-, tri-or polyisocyanate, at least one isocyanate-reactive polycarbonate diol, triol or polyol, at least one compound comprising at least one isocyanate-reactive group and at least one free radically polymerizable unsaturated group, and at least one compound comprising at least one isocyanate-reactive group and at least one at least dispersing-active group and optionally at least one compound comprising at least two isocyanate-reactive groups and having a molecular weight of less than 1000 g/mol. Although not experimentally clarified, the general possibility that dendritic polyester and/or polyether polyols can be used to make polycarbonate diols, triols and polyols is mentioned in this patent application.

An example of a film-forming polymer dispersion comprising a dendritic polymer is given in US 6,284,233, which relates to an anti-wrinkle composition comprising, in a physiologically acceptable medium: containing at least one water-vapour-permeable film forming agent having a concentration of 108 to 1010N/m²And after application to water at a concentration of 7% and subsequent drying at a temperature of 30 ℃ and a relative humidity of 40% yields a dispersion of a film-forming polymeric system of greater than 1% isolated stratum corneum-contracting polymer and a dendritic polyester polymer having terminal hydroxyl functional groups.

There is a continuing need in the art for improved coatings that are not degraded by external conditions. This is particularly the case in coatings for objects in marine environments that are constantly exposed to moisture, direct and reflected sunlight and salt.

The object of the present invention is therefore to provide a composition for a coating for protecting objects in the above-mentioned environment for a longer period of time.

According to the present invention, this object is achieved by an aqueous resin composition comprising a polyester-polyurethane resin obtained by reacting a reaction mixture in a one-step or multi-step process, the reaction mixture comprising:

(A1) polyester polyol with the number average molecular weight Mn of more than or equal to 400 g/mol and less than or equal to 20000 g/mol,

(A2) at least one compound containing at least two isocyanate-reactive groups and at least one group capable of forming an anion,

(A3) a polyisocyanate, and

(B) a dendritic polyol obtainable from a central initiator molecule or initiator polymer having at least one reactive hydroxyl group (X) which, upon formation of an initial tree-like structure, is bonded to a reactive carboxyl group (Y) in a monomeric chain extender having two reactive groups (X) and (Y), and wherein said chain extender has at least one carboxyl group (Y) and at least two hydroxyl (X) or hydroxyalkyl substituted hydroxyl groups (X).

In combination with a binder, the aqueous resin composition of the present invention produces 1K or 2K coatings that exhibit excellent resistance to environmental conditions encountered in marine environments.

The molecular weight Mn (measured in accordance with DIN 55672/1 or DIN 55672/2) of the polyester polyols which can be used as component (A1) is ≥ 400 g/mol and ≤ 20000 g/mol, preferably ≥ 600 g/mol and ≤ 10000 g/mol, more preferably ≥ 600 g/mol and ≤ 6000 g/mol. Their hydroxyl number (DIN 53240 part 2) is generally from 22 to 400, preferably from 50 to 200 mg KOH/g. The OH functionality may be from 1.5 to 6, preferably from 1.8 to 3, more preferably from 1.9 to 2.5.

Very suitable compounds are the customary polycondensates of diols and, where appropriate, of polyols (triols, tetraols) and dicarboxylic acids and, where appropriate, of polycarboxylic acids (tricarboxylic acids, tetracarboxylic acids) or hydroxycarboxylic acids or lactones. Instead of the free polycarboxylic acids, it is also possible to use the corresponding polycarboxylic anhydrides or corresponding polycarboxylic esters of lower alcohols to prepare the polyesters. Examples of suitable diols are ethylene glycol, butanediol, diethylene glycol, triethylene glycol, polyalkylene glycols, such as polyethylene glycol, and also propylene glycol or 1, 4-butanediol, preference being given to 1, 6-hexanediol, neopentyl glycol or neopentyl glycol hydroxypivalate. If desired, polyols such as trimethylolpropane, glycerol, erythritol, pentaerythritol, trimethylolbenzene or trihydroxyethyl isocyanurate may also be used.

Examples of suitable dicarboxylic acids are phthalic acid, isophthalic acid, terephthalic acid, tetrahydrophthalic acid, hexahydrophthalic acid, cyclohexanedicarboxylic acid, adipic acid, azelaic acid, sebacic acid, glutaric acid, tetrachlorophthalic acid, maleic acid, fumaric acid, itaconic acid, malonic acid, suberic acid, 2-methylsuccinic acid, 3-diethylglutaric acid, 2-dimethylsuccinic acid. Possible anhydrides of these acids are likewise suitable. In the context of the present invention, "acid" always includes anhydrides.

Monocarboxylic acids such as benzoic acid and hexanecarboxylic acid may also be used, provided that the average functionality of the polyol is greater than 2. Saturated aliphatic or aromatic acids are preferred, such as adipic acid or isophthalic acid. Relatively small amounts of polycarboxylic acids, such as trimellitic acid, can also be used if desired.

Hydroxycarboxylic acids which can be used as reaction partners in the preparation of the polyester polyols having terminal hydroxyl groups are, for example, hydroxycaproic acid, hydroxybutyric acid, hydroxydecanoic acid, hydroxystearic acid and the like. Suitable lactones are, for example, caprolactone or butyrolactone.

The compounds of component (a1) may also contain at least proportionally primary or secondary amino groups as isocyanate-reactive groups.

Ionic compounds or potentially ionic compounds suitable as component (a2) include, for example, mono-and dihydroxycarboxylic acids, mono-and diaminocarboxylic acids, mono-and dihydroxysulfonic acids, mono-and diaminosulfonic acids and salts thereof, such as dihydroxycarboxylic acid, hydroxypivalic acid, N- (2-aminoethyl) - β -alanine, 2- (2-aminoethylamino) ethanesulfonic acid, ethylenediamine-propyl-or butylsulfonic acid, 1, 2-or 1, 3-propylenediamine- β -ethanesulfonic acid, lysine, 3, 5-diaminobenzoic acid, hydrophilicizing agents according to example 1 of EP 0916647 a2 and alkali metal salts and/or ammonium salts thereof; adducts of sodium bisulfite with poly (ether sulfonate) of but-2-ene-1, 4-diol, or 2-butenediol and NaHSO₃Propoxylated adducts of (e.g. in DE 2446440 a1, pages 5 to 9, formulae I to III). Preferred ionic compounds or potentially ionic compounds (a2) are those having carboxyl and/or carboxylate groups. Particularly preferred ionic compounds (A2) are dihydroxycarboxylic acids, especially α, α -dimethylolalkanoic acids, such as 2, 2-dimethylolacetic acid, 2-dimethylolpropionic acid, 2-dimethylolbutyric acid, 2-dimethylolpentanoic acid or dihydroxysuccinic acid.

The amount of component (A2) is preferably quite high, for example ≥ 2% by weight and ≤ 10% by weight, based on the total weight of components (A1), (A2), (A3) and (B). Particularly preferred is an amount of not less than 3% by weight and not more than 5% by weight. For example, 2-dimethylolpropionic acid as the only component (A2) may be present in an amount of ≥ 2% by weight and ≤ 10% by weight, particularly preferably in an amount of ≥ 3% by weight and ≤ 5% by weight, based on the total weight of components (A1), (A2), (A3) and (B).

The acid groups incorporated into the resin by component (a2) can be neutralized at least proportionally. An example thereof is dimethylethanolamine, which preferably acts as neutralizing agent.

In the context of the present invention, a dendritic polymer is generally a class of polymers in the form of highly branched spherical macromolecules. Dendrimers are traditionally classified into 2 classes: dendrimers and hyperbranched polymers. Dendrimers are characterized by a perfectly symmetrical spherical shape, which results from a stepwise controlled process that produces a monodisperse molecular weight distribution. The second class, hyperbranched polymers, is attractive in that they resemble dendrimers (they differ in their polydispersity and less perfect spherical shape), but they can be more easily produced on a larger scale.

Suitable dendritic polyols (B) are described in US 5,418,301.

Useful polyisocyanates (A3) include aromatic and aliphatic polyisocyanates, with aliphatic polyisocyanates being preferred.

For example, the polyester-polyurethane resin may be obtained by reacting a reaction mixture in a one-step or multi-step process, said reaction mixture comprising:

(A1) in an amount of not less than 40% by weight and not more than 60% by weight,

not less than 2% by weight and not more than 10% by weight of (A2) and

not less than 10% by weight and not more than 20% by weight (A3), and

not less than 25% by weight and not more than 40% by weight of (B), (A1), (A2), (A3) and (B), the total weight percentage being not more than 100% by weight.

Preferred embodiments and other aspects of the invention are described below. They may be freely combined unless the context clearly indicates otherwise.

In one embodiment of the aqueous resin composition of the present invention, in the dendritic polyol (B), the dendritic structure is further extended by the addition of further monomer chain extender molecules, extended and further branched from the initiator molecule or initiator polymer by means of bonding with its reactive groups (X) and (Y), and/or by reaction with a chain terminator.

In another embodiment of the aqueous resin composition of the present invention, in the dendritic polyol (B) the central initiator molecule or initiator polymer is selected from the group consisting of aliphatic diols, cycloaliphatic diols, aromatic diols, triols, tetrols, sugar alcohols, anhydroheptanol, dipentaerythritol, alpha-alkylglycosides, monofunctional alcohols and alkoxylated polymers (alkoxylate polymers) having a molecular weight of at most 8000 g/mol and being generated by reaction between an alkylene oxide and one or more hydroxyl groups originating from one of the above mentioned compounds.

Preferably, in the dendritic polyol (B), the central initiator molecule is selected from the group consisting of ditrimethylolpropane, ditrimethylolethane, dipentaerythritol, pentaerythritol, alkoxylated pentaerythritol, trimethylolethane, trimethylolpropane, alkoxylated trimethylolpropane, glycerol, neopentyl glycol, dimethylolpropane, 1, 3-dioxane-5, 5-dimethanol, sorbitol, mannitol and alpha-methyl glycoside.

In another embodiment of the aqueous resin composition of the present invention, in the dendritic polyol (B), the chain extender is selected from the group consisting of monofunctional carboxylic acids having at least two hydroxyl groups and monofunctional carboxylic acids having at least two hydroxyl groups wherein one or more of the hydroxyl groups are substituted by hydroxyalkyl groups.

Preferably, in the dendritic polyol (B), the chain extender is selected from dimethylolpropionic acid, α, α -bis (hydroxymethyl) butyric acid, α, α, α -tris (hydroxymethyl) -acetic acid, α, α -bis- (hydroxymethyl) pentanoic acid, α, α -bis (hydroxy) propionic acid and 3, 5-dihydroxybenzoic acid.

A particularly preferred combination is a dendritic polyol as outlined above wherein the central initiator molecule is trimethylolpropane and the chain extender is dimethylolpropionic acid.

In another embodiment of the aqueous resin composition of the present invention, the reaction mixture for obtaining the polyester-polyurethane further comprises

(A4) And polycarbonate polyols with number average molecular weight of more than or equal to 400 g/mol and less than or equal to 6000 g/mol, which are different from the polyester polyol (A1).

Component (A4) suitably comprises a hydroxyl-containing polycarbonate having a molecular weight M_n400 g/mol and 6000 g/mol (DIN 55672/1), preferably 600 g/mol and 3000 g/mol, and can be obtained, for example, by reacting carbonic acid derivatives, such as diphenyl carbonate, dimethyl carbonate or phosgene, with polyols, in some cases diols. Examples of suitable such diols include ethylene glycol, 1, 2-and 1, 3-propanediol, 1, 3-and 1, 4-butanediol, 1, 6-hexanediol, 1, 8-octanediol, neopentyl glycol, 1, 4-bis-hydroxymethylcyclohexane, 2-methyl-1, 3-propanediol, 2, 4-trimethyl-1, 3-pentanediol, dipropylene glycol, polypropylene glycol, dibutylene glycol, polybutylene glycol, bisphenol A, tetrabromobisphenol A, and lactone-modified diols. The diol component preferably contains from 40 to 100% by weight of hexanediol, preferably 1, 6-hexanediol and/or hexanediol derivatives, preferably those which contain ether groups or ester groups in addition to OH end groups, examples being products obtained by reacting 1 mol of hexanediol with at least 1 mol, in some cases 1 to 2 mol, of caprolactone or by etherifying itself with hexanediol to give dihexylene or trihexylene glycol. In addition, polyether-polycarbonate diols as described in DE 3717060A 1 can be used.

The hydroxypolycarbonate (A4) is preferably linear. If appropriate, however, they can be made slightly branched by incorporating polyfunctional components, in particular low molecular weight polyols. Compounds suitable for this purpose include, for example, glycerol, trimethylolpropane, 1,2, 6-hexanetriol, 1,2, 4-butanetriol, trimethylolethane, pentaerythritol, p-cyclohexanediol, mannitol and sorbitol, methyl glycosides or 1,3,4, 6-dianhydrohexitols.

In another embodiment of the aqueous resin composition of the present invention, the reaction mixture for obtaining the polyester-polyurethane further comprises

(A5) A low molecular weight compound having a molecular weight of 60 g/mol or more and 400 g/mol or less and containing two or more hydroxyl groups and/or amino groups.

Low molecular weight polyols (a5) are commonly used for the purpose of hardening and/or branching polymer chains. The molecular weight is in the range of 60 g/mol or more and 400 g/mol or less, preferably 62 g/mol or more and 200 g/mol or less. They may contain aliphatic, cycloaliphatic or aromatic groups. Suitable polyols (A5) are compounds having up to about 20 carbons per molecule, such as ethylene glycol, diethylene glycol, triethylene glycol, 1, 2-propanediol, 1, 3-propanediol, 1, 4-butanediol, 1, 3-butanediol, cyclohexanediol, 1, 4-cyclohexanedimethanol, 1, 6-hexanediol, hydroquinone dihydroxyethyl ether, bisphenol A (2, 2-bis (4-hydroxyphenyl) propane), hydrogenated bisphenol A (2, 2-bis (4-hydroxycyclohexyl) propane) and mixtures thereof, and trimethylolpropane, glycerol or pentaerythritol. It is also possible to use, for example, ester diols such as delta-hydroxybutyl-epsilon-hydroxyhexanoate, omega-hydroxyhexyl-gamma-hydroxybutyrate, beta-hydroxyethyl adipate or bis (beta-hydroxyethyl) terephthalate.

Diamines or polyamines and hydrazides are likewise usable as (A5), examples being ethylenediamine, 1, 2-and 1, 3-diaminopropane, 1, 4-diaminobutane, 1, 6-diaminohexane, isophoronediamine, isomer mixtures of 2,2, 4-and 2,4, 4-trimethylhexamethylenediamine, 2-methylpentamethylenediamine, diethylenetriamine, 1, 3-and 1, 4-xylylenediamine (xylyleneenediamine), α, α, α ', α' -tetramethyl-1, 3-and-1, 4-xylylenediamine and 4, 4-diaminodicyclohexylmethane, dimethylethylenediamine, hydrazine or adipic dihydrazide. Component (a5) preferably contains at least 2% by weight of at least one compound having a functionality of three or more in terms of reaction with NCO groups.

In another embodiment of the aqueous resin composition of the present invention, the reaction mixture for obtaining the polyester-polyurethane further comprises

(A6) Are monofunctional with regard to the reaction with NCO groups or compounds containing active hydrogen atoms of different reactivity, these units being located in each case at the chain end of the polymers containing urethane groups.

If appropriate, the resin may also comprise units (A6) which are each located at the chain ends and terminate them. These units are derived on the one hand from monofunctional isocyanate-reactive compounds, such as monoamines, in particular mono-secondary amines, or monoalcohols. Mention may be made herein, by way of example, of methylamine, ethylamine, propylamine, butylamine, octylamine, laurylamine, stearylamine, isononyloxypropylamine, dimethylamine, diethylamine, dipropylamine, dibutylamine, N-methylaminopropylamine, diethyl (methyl) aminopropylamine, morpholine, piperidine or substituted derivatives thereof, amidoamines made from diprimary amines and monocarboxylic acids, monoketimines of diprimary amines (monoketimines), primary/tertiary amines, such as N, N-dimethylaminopropylamine.

Also suitable as component (A6) are compounds containing active hydrogen atoms which differ in their reactivity towards isocyanate groups, such as compounds which contain secondary amino groups in addition to primary amino groups or COOH groups in addition to OH groups or OH groups in addition to amino groups (primary or secondary). Preference is given to compounds (A6) which contain OH groups in addition to amino groups (primary or secondary). Examples thereof are primary/secondary amines, such as 3-amino-1-methylaminopropane, 3-amino-1-ethylaminopropane, 3-amino-1-cyclohexylaminopropane, 3-amino-1-methylaminobutane; monohydroxycarboxylic acids, such as glycolic acid, lactic acid or malic acid, and alkanolamines, such as N-aminoethylethanolamine, ethanolamine, 3-aminopropanol, neopentanolamine, and, particularly preferably, diethanolamine. Whereby functional groups can additionally be introduced into the polymer end product.

In another embodiment of the aqueous resin composition of the present invention, the polyisocyanate component (A3) is selected from the group consisting of isophorone diisocyanate, hexamethylene diisocyanate, bis- (4-isocyanatocyclohexyl) -methane, omega' -diisocyanate-1, 3-dimethylcyclohexane, triisocyanatononane and 1, 3-bis (isocyanatomethyl) benzene.

Another aspect of the present invention is a process for preparing an aqueous resin composition according to claim 1, comprising the steps of:

reacting a reaction mixture in a one-step or multi-step process, said reaction mixture comprising

(A1) Number average molecular weight M_nPolyester polyol of not less than 400 g/mol and not more than 2000 g/mol

(A2) At least one compound containing at least two isocyanate-reactive groups and at least one group capable of forming an anion,

(A3) a polyisocyanate, and

(B) a dendritic polyol obtainable from a central initiator molecule or initiator polymer having at least one reactive hydroxyl group (X) which, upon formation of an initial tree-like structure, is bonded to a reactive carboxyl group (Y) in a monomeric chain extender having two reactive groups (X) and (Y), and wherein the chain extender has at least one carboxyl group (Y) and at least two hydroxyl (X) or hydroxyalkyl-substituted hydroxyl groups (X), and

adding a neutralizing agent.

For the components mentioned above, reference is made to the above description of the aqueous resin composition for the sake of brevity.

The urethanization reaction is generally carried out at temperatures of from 0 ℃ to 140 ℃ depending on the reactivity of the isocyanate used. To accelerate the urethanization reaction, suitable catalysts, such as those known to those skilled in the art for accelerating the NCO — OH reaction, may be used. Examples are tertiary amines, such as triethylamine, organotin compounds, such as dibutyltin oxide, dibutyltin dilaurate or tin bis (2-ethylhexanoate), or other organometallic compounds.

The urethanization reaction is preferably carried out in the presence of a solvent which is inert to isocyanate groups. Particularly suitable for this purpose are those solvents which are compatible with water, such as ethers, ketones and esters, and also N-methylpyrrolidone. The amount of such solvents suitably does not exceed 30% by weight and in some cases is from 10 to 25% by weight, in each case based on the total amount of polyurethane resin and solvent. The polyisocyanate (a3) can be added rapidly to the solution of the other components.

The acid groups incorporated into the resin by component (a2) can be neutralized at least proportionally. Particularly suitable for this neutralization are tertiary amines, such as trialkylamines having from 1 to 12, and in some cases from 1 to 6, carbon atoms in each alkyl group. Examples thereof are trimethylamine, triethylamine, methyldiethylamine, tripropylamine and diisopropylethylamine. The alkyl groups may also, for example, carry hydroxyl groups, as is the case with dialkylmonoalkanolamines, alkyldialkanolamines and trialkanolamines. An example of this is dimethylethanolamine, which preferably acts as neutralizing agent. As neutralizing agents, it is also possible, if appropriate, to use inorganic bases, such as ammonia or sodium or potassium hydroxide. The neutralizing agent is used in a molar ratio of 0.3:1 to 1.3:1, and in some cases 0.4:1 to 1:1, to the acid groups of the prepolymer.

The free COOH groups of the resin of the invention may be neutralized before, during or after the carbamation reaction. The neutralization step is preferably carried out after the carbamation reaction, generally at room temperature (23 ℃ C.) to 80 ℃ C., in some cases at 40 to 80 ℃ C.

In another embodiment, the reaction mixture further comprises a triol (C) selected from glycerol, trimethylolethane and trimethylolpropane.

The present invention also relates to an aqueous coating system comprising the aqueous resin composition of the present invention and at least one crosslinker compound.

One-component (1K) and two-component (2K) coatings can be prepared by combining with a crosslinker, depending on the reactivity of the crosslinker or, where appropriate, blocking the crosslinker. The 1K coating materials for the purposes of the present invention are coatings in which the binder component and the crosslinker component can be stored together without any crosslinking reaction occurring to a significant extent or to an extent detrimental to subsequent applications. Only at the time of application does the crosslinking reaction take place after the crosslinking agent has been activated. Such activation may be achieved, for example, by increasing the temperature. The 2K coatings used for the purposes of the present invention are coatings in which the binder component and the crosslinker component have to be stored in separate containers on account of their high reactivity. The two components are not mixed until shortly before application, at which point they typically react without additional activation. However, in order to accelerate the crosslinking reaction, it is also possible to use catalysts or to use higher temperatures.

Examples of suitable crosslinkers are polyisocyanate crosslinkers, amide-and amine-formaldehyde resins, phenol resins, aldehyde resins and ketone resins, such as phenol-formaldehyde resins, resol-phenolic resins, furan resins, urea-formaldehyde resins (urea resins), urethane resins, triazine resins, melamine resins, benzoguanamine resins, cyanamide resins, aniline resins, described in "Lackkunsharze", H.Wagner, H.F. Sarx, Carl Hanser Verlag Munich, 1971. Preferably the cross-linking agent is a polyisocyanate.

Polyisocyanates having free and/or blocked isocyanate groups may be used. Suitable such crosslinker resins include blocked polyisocyanates based on, for example, isophorone diisocyanate, hexamethylene diisocyanate, 1, 4-diisocyanatocyclohexane, bis- (4-isocyanatocyclohexane) methane or 1, 3-diisocyanatobenzene or based on lacquer polyisocyanates, such as polyisocyanates containing biuret or isocyanurate groups and derived from 1, 6-diisocyanatohexane, isophorone diisocyanate or bis- (4-isocyanatocyclohexane) methane, or contain urethane groups and are based on 2, 4-and/or 2, 6-diisocyanatotoluene or isophorone diisocyanate on the one hand and low molecular weight polyhydroxyl compounds on the other hand, such as trimethylolpropane, various isomers of propylene glycol or butanediol, or any desired mixtures of such polyhydroxy compounds.

Blocking agents suitable for the polyisocyanates are, for example, monoalcohols, such as methanol, ethanol, butanol, hexanol, cyclohexanol, benzyl alcohol, oximes, such as acetoxime, methylethylketoxime, cyclohexanone oxime, lactams, such as epsilon-caprolactam, phenols, amines, such as diisopropylamine or dibutylamine, dimethylpyrazole or triazole, and also dimethyl malonate, diethyl malonate or dibutyl malonate.

Preference is given to using low-viscosity, hydrophobic or hydrophilicized polyisocyanates having free isocyanate groups based on aliphatic, cycloaliphatic, araliphatic and/or aromatic isocyanates, more preferably on aliphatic or cycloaliphatic isocyanates, since in this way a particularly high level of resistance can be achieved in the coating film. In combination with these crosslinking agents, the advantages of the adhesive dispersions of the invention are most clearly demonstrated. These polyisocyanates generally have a viscosity of from 10 to 3500 mPas at 23 ℃. If necessary, the polyisocyanate may be used as a blend with a small amount of an inert solvent to reduce the viscosity to a level within the range. Nonane triisocyanate may also be used as a crosslinker component, alone or in mixtures.

The resins and dispersions described herein are generally sufficiently hydrophilic to ensure dispersibility of the crosslinker resin in any instance where the material in question is not soluble or dispersible in water. Water-soluble or gap dispersible polyisocyanates can be obtained by modification, for example, with carboxylate, sulfonate and/or polyoxyethylene groups and/or polyoxyethylene/polyoxypropylene groups.

Hydrophilization of polyisocyanates can be achieved, for example, by reaction with substoichiometric amounts of monohydric hydrophilic polyether alcohols. The preparation of hydrophilized polyisocyanates of this type is described, for example, in EP 0540985A 1 (page 3, line 55 to page 4, line 5). Also very suitable are the polyisocyanates containing allophanate groups described in EP 0959087A 1 (page 3, lines 39-51), which can be prepared by reacting polyisocyanates of low monomer content with polyoxyethylene polyether alcohols under allophanatization conditions. Also suitable are water-dispersible polyisocyanate mixtures based on triisocyanatononane as described in DE 10007821A 1 (page 2, line 66 to page 3, line 5), polyisocyanates hydrophilicized with ionic groups (sulfonate, phosphonate) as described, for example, in DE 10024624A 1 (page 3, lines 13 to 33). Another possibility is hydrophilization by addition of commercially customary emulsifiers.

It is naturally also possible in principle to use mixtures of different crosslinker resins.

Preferred crosslinker components are hydrophobic or hydrophilicized polyisocyanates containing free isocyanate groups based on aliphatic, cycloaliphatic, araliphatic and/or aromatic isocyanates.

The aqueous coating systems comprising the resins of the invention may, if appropriate, also contain other binders or dispersions, for example based on polyesters, polyurethanes, polyethers, polyepoxides or polyacrylates, and also, if appropriate, pigments and other auxiliaries and additives known in the coating industry.

Conventional coating auxiliaries and additives can be added to the aqueous coating systems before, during or after their preparation, or also to the binder or crosslinker components present in the systems. Examples include defoamers, thickeners, pigments, dispersing aids, matting agents, catalysts, antiskinning agents, antisettling agents or emulsifiers.

The coating system of the present invention exhibits excellent resistance to environmental conditions. The invention therefore also comprises the use of such a coating system for coating, painting and/or sealing a substrate, wherein the substrate is selected from the group consisting of wood, board, metal, stone, concrete, glass, cloth, leather, paper, and foam. Preferably, the metal substrate is selected from the group consisting of steel, cold rolled steel, hot rolled steel, stainless steel, aluminum, galvanized metal steel, zinc alloy plated steel, and mixtures thereof.

The coating system can be applied by various spraying methods, such as air pressure spraying, airless spraying or electrostatic spraying, for example using one-component or, if appropriate, two-component spraying equipment. However, the coating system can also be applied by other methods, for example by brushing, rolling or knife coating.

The invention is further illustrated by the following examples, without wishing to be limited thereto.

Examples 1 : polyester - Synthesis of polyurethane resin Dispersion

A polyester-polyurethane resin dispersion was prepared from the following components:

。

the polyester polyols used have an acid number (DIN 3682) of from 2.8 to 2.9 mg KOH/g, an OH number of from 200 mg KOH/g (theoretical value) and from 180 mg KOH/g to 205 mg KOH/g (experimental value) (DIN 53240 part 2). The dispersion had a solids content of 44.2 weight-% (solids content determined in the drying oven and calculated as follows: final weight [ g ]. times.100/initial weight [ g ] = wt% solids).

The polyester polyols used have an acid number (DIN 3682) of from 2.8 to 2.9 mg KOH/g, an OH number of from 200 mg KOH/g (theoretical value) and from 180 mg KOH/g to 205 mg KOH/g (experimental value) (DIN 53240 part 2). The dispersion had a solids content of 55.35 weight-% (solids content determined in the drying oven and calculated as follows: final weight [ g ]. times.100/initial weight [ g ] = wt% solids).

Dendritic polyol 1 is a dendritic polyol having OH end groups formed by the polymerization of trimethylolpropane as the central initiator molecule and 2, 2-dimethylolpropionic acid as the monomeric chain extender. OH number 560-. Available as Boltorn P500 from Perstorp.

The polyester polyol, dendritic polyol 1, dimethylol propionic acid, stannous ethyl hexanoate and acetone were charged to a reaction vessel and heated to 55 ℃ for 2 hours. Isophorone diisocyanate was added and the reaction temperature was maintained (approximately 58 ℃) until an NCO content of < 0.05% was reached. N, N-dimethylethanolamine was then added, the mixture was stirred for 15 minutes, and the mixture was dispersed in water. Finally, acetone was removed by vacuum distillation. After cooling, the viscosity was set to about 1000 mPas (measured with a Brookfield rotational viscometer at 23 ℃).

Examples 2 : polyester - Synthesis of polyurethane resin Dispersion

A polyester-polyurethane resin dispersion was prepared from the following components:

。

the polyester polyol was the same as used in example 1. The dispersion had a solids content of 42.8 weight-% (solids content determined in the drying oven and calculated as final weight [ g ] 100/initial weight [ g ] = wt% solids).

The polyester polyol was the same as used in example 1. The dispersion had a solids content of 54.8 weight-% (solids content determined in the drying oven and calculated as follows: final weight [ g ]. times.100/initial weight [ g ] = wt% solids).

Dendritic polyol 2 is a dendritic polyol with OH end groups formed by polymerization of trimethylolpropane as the central initiator molecule and 2, 2-dimethylolpropionic acid as the monomeric chain extender. OH number 430-590 mg KOH/g (DIN 53240 part 2), bimodal molecular weight distribution, and a nominal number average molecular weight (GPC) of 1500 g/mol. Available as Boltorn P500 from Perstorp.

The polyester polyol, dendritic polyol 2, dimethylol propionic acid, trimethylolpropane, stannous ethyl hexanoate and acetone were charged to a reaction vessel and heated to 55 ℃ for 2 hours. Isophorone diisocyanate was added and the reaction temperature was maintained (approximately 58 ℃) until an NCO content of < 0.05% was reached. N, N-dimethylethanolamine was then added, the mixture was stirred for 15 minutes, and the mixture was dispersed in water. Finally, acetone was removed by vacuum distillation. After cooling, the viscosity was set to about 1000 mPas (measured with a Brookfield rotational viscometer at 23 ℃).

Examples 3 : polyester - Synthesis of polyurethane resin

A polyester-polyurethane resin was prepared from the following components:

resin 3.1	Amount [ g ]]	Weight percent (a)
			Polyester polyols	2229	73.3
Dimethylolpropionic acid	180	6
			Stannous ethyl hexanoate	3.8	0.125
Acetone (II)	1615	For 65% by weight solids
			Isophorone diisocyanate	591	19.7

The polyester polyols used have an acid number (DIN 3682) of from 2.8 to 2.9 mg KOH/g, an OH number of from 200 mg KOH/g (theoretical value) and from 180 mg KOH/g to 205 mg KOH/g (experimental value) (DIN 53240 part 2).

The reaction vessel was charged with all components except isophorone diisocyanate and the mixture was heated to 55 ℃ for 2 hours. Isophorone diisocyanate was then added (exothermic reaction) and the reaction temperature was maintained at about 58 ℃ until an NCO content of < 0.05% was reached. The product was cooled to 35 ℃ and stored in containers.

Synthesis of prior art polyester-polyurethane resins	Amount [ g ]]	Weight percent (a)
			Resin of example 3.1 (65 wt-% solids)	6000	66.67
N, N-dimethylethanolamine	126
			Deionized water	5441	For 43% by weight of solids

The reaction vessel was charged with the resin of example 1 and acetone and heated to 55 ℃ for 2 hours. After cooling to 50 ℃, N-dimethylethanolamine was added, the mixture was stirred at this temperature for 1 hour, and the mixture was dispersed in water. Finally, the acetone was removed by vacuum distillation. After cooling, the viscosity was set to about 1000 mPas (measured with a Brookfield rotational viscometer at 23 ℃). The dispersion had a solids content of 47 wt% (measured in the drying oven and calculated as solids content: final weight [ g ] + 100/initial weight [ g ] = wt% solids).

Application test:

the crosslinked dispersions of examples 1.1 and 2.1 were tested in a pendulum absorption (pendulum absorption) experiment according to Koenig (DIN EN ISO 1522) and crosslinked with typical polyisocyanates of the prior art. Comparing the PU coating obtained on the glass substrate with the system of the prior art based on example 3, also on the glass substrate, shows a pendulum impact absorption of 125 seconds (example 1.1) and 96 seconds (example 2.1) after 16 hours at 60 ℃.

Table 1.

Properties of	Example 3	Example 1.1
			16h 30 min at 60 DEG CRear pendulum impact absorption	73 s	125 s

Properties of	Example 3	Example 2.1
			Swing impact absorption after 16h 30 min at 60 DEG C	73 s	96 s

Claims (15)

1. An aqueous resin composition comprising a polyester-polyurethane resin obtained by reacting in a one-step or multi-step process a reaction mixture comprising:

(A1) number average molecular weight M_nPolyester polyol of not less than 400 g/mol and not more than 20000 g/mol,

(A2) at least one compound containing at least two isocyanate-reactive groups and at least one group capable of forming an anion,

(A3) a polyisocyanate, and

(B) a dendritic polyol obtainable from a central initiator molecule or initiator polymer having at least one reactive hydroxyl group (X) which, upon formation of an initial tree-like structure, is bonded to a reactive carboxyl group (Y) in a monomeric chain extender having two reactive groups (X) and (Y), and wherein said chain extender has at least one carboxyl group (Y) and at least two hydroxyl (X) or hydroxyalkyl substituted hydroxyl groups (X).

2. An aqueous resin composition according to claim 1, wherein in said dendritic polyol (B) said dendritic structure is further extended by addition of further monomer chain extender molecules, by means of bonding with its reactive groups (X) and (Y) from an initiator molecule or initiator polymer and further branching, and/or by reaction with a chain terminator.

3. Aqueous resin composition according to claim 1, wherein in the dendritic polyol (B) the central initiator molecule or initiator polymer is selected from the group consisting of aliphatic diols, cycloaliphatic diols, aromatic diols, triols, tetrols, sugar alcohols, anhydrononane heptaols, dipentaerythritol, alpha-alkyl glycosides, monofunctional alcohols and alkoxylated polymers having a molecular weight of up to 8000 g/mol and produced by reaction between an alkylene oxide and one or more hydroxyl groups originating from one of the above mentioned compounds.

4. An aqueous resin composition according to claim 3, wherein in said dendritic polyol (B) said central initiator molecule is selected from the group consisting of ditrimethylolpropane, ditrimethylolethane, dipentaerythritol, pentaerythritol, alkoxylated pentaerythritol, trimethylolethane, trimethylolpropane, alkoxylated trimethylolpropane, glycerol, neopentyl glycol, dimethylolpropane, 1, 3-dioxane-5, 5-dimethanol, sorbitol, mannitol and alpha-methyl glycoside.

5. An aqueous resin composition according to claim 1, wherein in said dendritic polyol (B) said chain extender is selected from the group consisting of monofunctional carboxylic acids having at least two hydroxyl groups and monofunctional carboxylic acids having at least two hydroxyl groups wherein one or more hydroxyl groups are substituted by hydroxyalkyl groups.

6. An aqueous resin composition according to claim 5, wherein in said dendritic polyol (B) said chain extender is selected from the group consisting of dimethylolpropionic acid, α, α -bis (hydroxymethyl) butyric acid, α, α, α -tris (hydroxymethyl) -acetic acid, α, α -bis- (hydroxymethyl) pentanoic acid, α, α -bis (hydroxy) propionic acid and 3, 5-dihydroxybenzoic acid.

7. The aqueous resin composition according to claim 1, wherein said reaction mixture for obtaining a polyester-polyurethane further comprises

(A4) Number-average molecular weight M different from polyester polyol A1)_nPolycarbonate polyol with the weight ratio of more than or equal to 400 g/mol and less than or equal to 6000 g/mol.

8. The aqueous resin composition according to claim 1, wherein said reaction mixture for obtaining a polyester-polyurethane further comprises

(A5) A low molecular weight compound having a molecular weight of 60 g/mol or more and 400 g/mol or less and containing two or more hydroxyl groups and/or amino groups.

9. The aqueous resin composition according to claim 1, wherein said reaction mixture for obtaining a polyester-polyurethane further comprises

(A6) Are monofunctional with regard to the reaction with NCO groups or compounds containing active hydrogen atoms of different reactivity, these units being located in each case at the chain end of the polymers containing urethane groups.

10. The aqueous resin composition according to claim 1, wherein the polyisocyanate component (a3) is selected from the group consisting of isophorone diisocyanate, hexamethylene diisocyanate, bis- (4-isocyanatocyclohexyl) -methane, ω' -diisocyanate-1, 3-dimethylcyclohexane, triisocyanatononane and 1, 3-bis (isocyanatomethyl) benzene.

11. The aqueous resin composition according to claim 1, wherein the reaction mixture further comprises a triol (C) selected from the group consisting of glycerol, trimethylolethane and trimethylolpropane.

12. A process for preparing an aqueous resin composition according to claim 1, comprising the steps of:

reacting a reaction mixture in a one-step or multi-step process, said reaction mixture comprising

(A1) Number average molecular weight M_nPolyester polyol of not less than 400 g/mol and not more than 2000 g/mol,

(A2) at least one compound containing at least two isocyanate-reactive groups and at least one group capable of forming an anion,

(A3) a polyisocyanate, and

(B) a dendritic polyol obtainable from a central initiator molecule or initiator polymer having at least one reactive hydroxyl group (X) which, upon formation of an initial tree-like structure, is bonded to a reactive carboxyl group (Y) in a monomeric chain extender having two reactive groups (X) and (Y), and wherein the chain extender has at least one carboxyl group (Y) and at least two hydroxyl (X) or hydroxyalkyl-substituted hydroxyl groups (X), and

adding a neutralizing agent.

13. An aqueous coating system comprising the aqueous resin composition according to claim 1 and at least one crosslinker compound.

14. Use of an aqueous coating system according to claim 13 for coating, painting and/or sealing a substrate, wherein the substrate is selected from the group consisting of wood, board, metal, stone, concrete, glass, cloth, leather, paper and foam.

15. Use according to claim 13, wherein the metal substrate is selected from the group consisting of steel, cold rolled steel, hot rolled steel, stainless steel, aluminium, galvanized metal steel and galvanized alloy steel and mixtures thereof.