WO2012020026A1

WO2012020026A1 - Process for the production of polyurethane-urea dispersions

Info

Publication number: WO2012020026A1
Application number: PCT/EP2011/063716
Authority: WO
Inventors: Hans Georg Grablowitz; Thomas Feller; Thomas Michaelis; Petra JANßEN
Original assignee: Bayer Materialscience Ag
Priority date: 2010-08-12
Filing date: 2011-08-09
Publication date: 2012-02-16

Abstract

The present invention provides a process for the production of non-ionically hydrophilised aqueous polyurethane dispersions which have a broad particle size distribution combined with a relatively large particle size, are readily redispersible and when used to produce polymer films lead to polymer films having a low degree of gloss. The present invention also provides the use of the dispersions produced by the process according to the invention in coatings.

Description

Process for the production of polvurethane-urea dispersions

Owing to their advantageous properties, such as for example low-temperature flexibility, abrasion resistance and ecological safety, aqueous polyurethane dispersions have an important role to play as film formers in coatings. These resins have been established on the market for many years now and can be applied to a very wide range of substrates in the form of one-component or two-component systems and optionally by mixing them with other water-based resins. Thus the products are suitable for coating soft substrates such as textiles, leather and fibres on the one hand, whilst on the other hand hard substrates such as wood, metal, plastics and mineral substrates can also be coated with them. An overview of the various types and production processes can be found for example in Houben-Weyl: "Methoden der Organischen Chemie, Vol. E20, p. 1659-1692 " or in "Ullmann's Encyclopaedia of Industrial Chemistry" (1992), Vol. A21, p. 667-682.

Apart from the properties already mentioned, the optical properties of a coating in particular are very important. One important optical quantity in coatings is the degree of gloss, which in general terms specifies how much light is reflected at a surface at a given angle. In addition to the material characteristics of the surface, the roughness of the surface plays an important part. Thus rough surfaces always have a lower degree of gloss, as some of the reflected light beams remain in the valleys of the surface. On the other hand, as matt as possible a surface is desired for certain applications, and this is correspondingly always associated with a low degree of gloss. In the case of paints a low degree of gloss is often achieved by additionally adding inorganically based matting agents of a defined particle size distribution, such as Si0₂ particles for example, to the formulation. The disadvantage of these, however, is that they do not form a film and because of their incompatibility with the other organic constituents of the coating they are not firmly anchored and can therefore be rubbed out of the coating relatively easily. As a result of this, the degree of gloss of the surface can increase over time and the matting effect is lost.

In addition to inorganic particles, organic polymer particles too can be added to achieve a matt surface. These have the advantage in principle that because they are less hard they lead to more scratch-proof surfaces and they have a greater compatibility in combination with other binders. Thus matt paints based on organic particles lead to longer-lasting surfaces. The polymer particles have to have a relatively large particle size in order to be present after film formation in a microstructure that absorbs a large part of the reflected light. The particle size in polyurethane-urea dispersions can generally be controlled by the proportion of adsorbed or bound hydrophilic groups and the molar mass of the polymer chains. The particle size decreases with the growing proportion of hydrophilic groups and rising molar mass.

There is therefore still a need for one-component water-dispersible coating agents which are easy to produce and do not require the addition of matting agents in order to establish a low degree of gloss. Such coating agents can be obtained if the polyurethane polymers they contain have a large particle size combined with a broad particle size distribution.

Surprisingly it has been found that non-ionically hydrophilised polyurethane-urea dispersions containing polyurethane-urea polymers having a large particle size combined with a broad particle size distribution can be produced if the following condition is met for the percentage by weight WCE of water that is added during chain extension:

W_CE = ^m^ r (^CE _> 0 4

m_vater (CE) + m_water{D) where m_water(CE) is the mass of water added during chain extension and m_water(D) is the mass of water used for dispersion.

The present invention therefore provides a process for the production of dispersions containing exclusively non-ionically hydrophilised polyurethane-urea polymers, wherein water is added during chain extension of a polyurethane prepolymer in an amount m_water(CE) such that the following condition is met: . .

W_CE = ^m^ r (^CE _> 0 4

m_vater (CE) + m_water {D) where m_water(CE) is the mass of water added during chain extension,

m_WATER(D) is the mass of water used for dispersion, and W_CE is the percentage by weig water that is added during chain extension.

The polyurethane-urea polymers in the dispersion are not ionically hydrophilised. WC_E is preferably greater than 0.45 and particularly preferably greater than 0.50.

The polyurethane prepolymer preferably has a molecular weight in the range from 2000 to 50,000 g/mol, particularly preferably in the range from 2500 to 20,000 g/mol, most particularly in the range from 3000 to 15,000 g/mol.

The non-ionically hydrophilised polyurethane dispersions contain polyurethane-urea polymers which are preferably synthesised from the following components: 1) at least one polyisocyanate having a functionality of≥ 2

2) one or more polyols having a functionality of≥ 2 and an average molecular weight M_n of 400 g/mol to 8000 g/mol

3) optionally one or more polyols having a functionality of≥ 2 and an average molecular weight M_n of 62 g/mol to 200 g/mol 4) at least one non-ionic, isocyanate-reactive hydrophilising agent having a functionality of≥ 1 and

5) one or more polyamines having a functionality of≥ 2.

Suitable polyisocyanates of component 1 ) are the aromatic, araliphatic, aliphatic or cycloaliphatic polyisocyanates known per se to the person skilled in the art. Suitable polyisocyanates are for example 1,4-butylene diisocyanate, 1,6-hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), 2,2,4- and/or 2,4,4-trimethylhexamethylene diisocyanate, the isomeric bis-(4,4'-isocyanatocyclohexyl)methanes or mixtures thereof with any isomer content, 1,4-cyclohexylene diisocyanate, 1,4-phenylene diisocyanate, 2,4- and/or 2,6-toluylene diisocyanate or the hydrogenated 2,4- and/or 2,6-toluylene diisocyanate, 1,5- naphthylene diisocyanate, 2,4'- or 4,4'-diphenylmethane diisocyanate, 1,3- and l,4-bis-(2- isocyanatoprop-2-yl)benzene (TMXDI), l,3-bis(isocyanatomethyl)benzene (XDI), (S)-alkyl- 2,6-diisocyanatohexanoates or (L)-alkyl-2,6-diisocyanatohexanoates. Small amounts of polyisocyanates having a functionality of ≥ 2 can also be used. These include modified diisocyanates having a uretdione, isocyanurate, urethane, allophanate, biuret, iminooxadiazinedione and/or oxadiazinetrione structure and non-modified polyisocyanates having more than 2 NCO groups per molecule, for example 4- isocyanatomethyl- 1,8 -octane diisocyanate (nonane triisocyanate) or triphenylmethane-4,4',4"- triisocyanate.

They are preferably polyisocyanates or polyisocyanate mixtures of the aforementioned type having exclusively aliphatically and/or cycloaliphatically bonded isocyanate groups with an average functionality of 2 to 4, preferably 2 to 2.6 and particularly preferably 2 to 2.4.

Polymeric polyols for use as compounds 2) preferably have a molecular weight M_n of 400 to 8000 g/mol, particularly preferably 400 to 6000 g/mol and most particularly preferably 400 to 3000 g/mol. Their hydroxyl value is preferably 22 to 400 mg KOH/g, particularly preferably 30 to 300 mg KOH/g and most particularly preferably 40 to 250 mg KOH/g, and they have an OH functionality of preferably 1.5 to 6, particularly preferably 1.8 to 3 and most particularly preferably 1.9 to 2.1. Preferred polyols within the meaning of the present invention are the organic polyhydroxyl compounds known in polyurethane paint technology, such as for example the conventional polyester polyols, polyacrylate polyols, polyurethane polyols, polycarbonate polyols, polyether polyols, polyester polyacrylate polyols and polyurethane polyacrylate polyols, polyurethane polyester polyols, polyurethane polyether polyols, polyurethane polycarbonate polyols, polyester polycarbonate polyols, phenol/formaldehyde resins, alone or in mixtures.

Polyester polyols, polyether polyols or polycarbonate polyols are particularly preferred, with polyester polyols being most particularly preferred.

Suitable polyether polyols are for example the polyaddition products of styrene oxides, ethylene oxide, propylene oxide, tetrahydrofuran, butylene oxide, epichlorohydrin, and the co- addition and graft products thereof, as well as the polyether polyols obtained by condensation of polyhydric alcohols or mixtures thereof and by alkoxylation of polyhydric alcohols, amines and amino alcohols.

Suitable hydroxy-functional polyethers have OH functionalities of preferably 1.5 to 6.0, particularly preferably 1.8 to 3.0, OH values of preferably 20 to 700, particularly preferably 40 to 600 mg KOH/g solid, and molecular weights M_n of preferably 106 to 4000 g/mol, particularly preferably 200 to 3500, such as for example alkoxylation products of hydroxy- functional starter molecules such as ethylene glycol, propylene glycol, butanediol, hexanediol, trimethylolpropane, glycerol, pentaerythritol, sorbitol or mixtures thereof and also other hydroxy-functional compounds with propylene oxide or butylene oxide. Polypropylene oxide polyols with a molecular weight of 300 to 4000 g/mol are preferred as the polyether component 2). With correspondingly high OH contents the particularly low-molecular-weight polyether polyols can be water-soluble. However, water-insoluble polypropylene oxide polyols and polytetramethylene oxide polyols and mixtures thereof are particularly preferred.

Very suitable examples of polyester polyols are the polycondensates of diols and optionally triols and tetraols and dicarboxylic and optionally tricarboxylic and tetracarboxylic acids or hydroxycarboxylic acids or lactones known per se. In place of the free polycarboxylic acids, the corresponding polycarboxylic anhydrides or corresponding polycarboxylic acid esters of low alcohols can also be used to produce the polyesters. Examples of suitable diols are ethylene glycol, butylene glycol, diethylene glycol, triethylene glycol, polyalkylene glycols such as polyethylene glycol, also 1 ,2-propanediol, 1,3-propanediol, butanediol(l,3), butanediol( l,4), hexanediol( l ,6) and isomers, neopentyl glycol or hydroxypivalic acid neopentyl glycol ester, the last three cited compounds being preferred. Examples of polyols which can optionally also be used include trimethylolpropane, glycerol, erythritol, pentaerythritol, trimethylolbenzene or trishydroxy ethyl isocyanurate. Suitable dicarboxylic acids are for example phthalic acid, isophthalic acid, terephthalic acid, tetrahydrophthalic acid, hexahydrophthalic acid, cyclohexane dicarboxylic acid, adipic acid, azelaic acid, sebacic acid, glutaric acid, tetrachlorophthalic acid, maleic acid, fumaric acid, itaconic acid, malonic acid, suberic acid, 2-methyl succinic acid, 3,3-diethyl glutaric acid, 2,2-dimethyl succinic acid. Anhydrides of these acids can likewise be used where they exist. For the needs of the present invention the anhydrides are accordingly encompassed by the expression "acid". Monocarboxylic acids, such as benzoic acid and hexane carboxylic acid, can also be used, provided that the average functionality of the polyol is≥ 2. Saturated - - aliphatic or aromatic acids are preferred, such as adipic acid or isophthalic acid. Trimellitic acid can be mentioned here as a polycarboxylic acid which can optionally be incorporated in smaller amounts.

Hydroxycarboxylic acids which can be incorporated as reactants in the production of a polyester polyol having terminal hydroxyl groups are for example hydroxycaproic acid, hydroxybutyric acid, hydroxy decanoic acid, hydroxystearic acid and the like. Possible lactones are inter alia caprolactone, butyrolactone and homologues.

Polyester polyols based on butanediol and/or neopentyl glycol and/or hexanediol and/or ethylene glycol and/or diethylene glycol with adipic acid and/or phthalic acid and/or isophthalic acid are preferred. Polyester polyols 2) based on butanediol and/or neopentyl glycol and/or hexanediol with adipic acid and/or phthalic acid are particularly preferred.

The suitable polycarbonate polyols are obtainable by reacting carbonic acid derivatives, for example diphenyl carbonate, dimethyl carbonate or phosgene, with diols. Examples of such diols are ethylene glycol, 1,2- and 1,3-propanediol, 1,3- and 1 ,4-butanediol, 1,6-hexanediol, 1,8-octanediol, neopentyl glycol, 1 ,4-bishydroxymethyl cyclohexane, 2-methyl-l,3- propanediol, 2,2,4-trimethylpentanediol-l ,3, dipropylene glycol, polypropylene glycols, dibutylene glycol, polybutylene glycols, bisphenol A, tetrabromobisphenol A but also lactone- modified diols. The diol component preferably contains 40 to 100 wt.% of 1,6-hexanediol and/or hexanediol derivatives, preferably those having ether or ester groups in addition to terminal OH groups, for example products obtained by reacting 1 mol of hexanediol with at least 1 mol, preferably 1 to 2 mol, of ε-caprolactone or by etherifying hexanediol with itself to form the dihexylene or trihexylene glycol. Polyether-polycarbonate polyols can also be used.

Polycarbonate polyols based on dimethyl carbonate and hexanediol and/or butanediol and/or caprolactone are preferred. Polycarbonate polyols based on dimethyl carbonate and hexanediol and/or caprolactone are most particularly preferred.

The low-molecular-weight polyols 3) which can optionally be used to synthesise the polyurethane resins generally bring about a stiffening and/or a branching of the polymer chain. The molecular weight is preferably between 62 and 200 g/mol. Suitable polyols can contain aliphatic, alicyclic or aromatic groups. The low-molecular-weight polyols having up to about 20 carbon atoms per molecule, such as for example ethylene glycol, diethylene - - glycol, triethylene glycol, 1,2-propanediol, 1,3 -propanediol, 1,4-butanediol, 1,3-butylene glycol, 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, can be cited here by way of example. Ester diols such as for example 6-hydroxybutyl-s-hydroxyhexanoic acid ester, Q-hydroxyhexyl-y-hydroxybutyric acid ester, adipic acid-( -hydroxyethyl) ester or terephthalic acid-bis( -hydroxyethyl) ester can also be used . Hexanediol and/or trimethylolpropane and/or butanediol are preferred. Trimethylolpropane and/or butanediol are particularly preferred.

Suitable compounds 4) having a non-ionically hydrophilising effect are for example polyoxyalkylene ethers containing at least one hydroxy or amino group. These polyethers contain a proportion of 30 wt.% to 100 wt.% of structural units derived from ethylene oxide. Linearly structured polyethers having a functionality of between 1 and 3 are suitable, as too are compounds of the general formula (I),

each denote independently of each other a divalent aliphatic, cycloaliphatic or aromatic radical having 1 to 18 C atoms, which can be interrupted by oxygen and/or nitrogen atoms, and denotes an alkoxy-terminated polyethylene oxide radical.

Compounds having a non-ionically hydrophilising effect are for example also monohydric polyalkylene oxide polyether alcohols having a statistical mean of preferably 5 to 70, particularly preferably 7 to 55 ethylene oxide units per molecule, such as can be obtained in a manner known per se by alkoxylation of suitable starter molecules (e.g. in Ullmanns Encyclopadie der technischen Chemie, 4th Edition, Volume 19, Verlag Chemie, Weinheim p. 31-38).

Suitable starter molecules are for example saturated monoalcohols such as methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, sec-butanol, the isomeric pentanols, hexanols, octanols and nonanols, n-decanol, n-dodecanol, n-tetradecanol, n-hexadecanol, n-octadecanol, cyclohexanol, the isomeric methylcyclohexanols or hydroxymethylcyclohexane, 3-ethyl-3- hydroxymethyloxetane or tetrahydrofurfuryl alcohol, diethylene glycol monoalkyl ethers such as for example diethylene glycol monobutyl ether, unsaturated alcohols such as allyl alcohol, 1, 1 -dimethyl allyl alcohol or oleic alcohol, aromatic alcohols such as phenol, the isomeric cresols or methoxyphenols, araliphatic alcohols such as benzyl alcohol, anisic alcohol or cinnamic alcohol, secondary monoamines such as dimethylamine, diethylamine, dipropylamine, diisopropylamine, dibutylamine, bis-(2-ethylhexyl)amine, N-methyl- and N- ethylcyclohexylamine or dicyclohexylamine and heterocyclic secondary amines such as morpholine, pyrrolidine, piperidine or IH-pyrazole. Particularly preferred starter molecules are saturated monoalcohols. Diethylene glycol monobutyl ether is most particularly preferably used as the starter molecule.

Suitable alkylene oxides for the alkoxylation reaction are in particular ethylene oxide and propylene oxide, which can be used in the alkoxylation reaction in any sequence or in a mixture.

The molecular weight M_n of these structural units is preferably 300 g/mol to 6000 g/mol, particularly preferably 500 g/mol to 4000 g/mol and most particularly preferably 750 g/mol to 3000 g/mol with a functionality of 1.

Suitable non-ionically hydrophilising, monofunctional compounds of this type are for example monofunctional alkoxypolyethylene glycol s such as for example methoxypolyethylene glycols (MPEG Carbowax^® 2000 or methoxy PEG-40, molecular weight range 1800 to 2200, The Dow Chemical Company), monofunctional polyether monoalkyl ethers such as for example LB 25 synthesised from butanol and ethylene oxide and propylene oxide, with an average molecular weight M_n of 2250 g/mol, from Bayer MaterialScience, monofunctional polyether amines (Jeffamine^® M 1000, PO/EO molar ratio 3/19 and M 2070, PO/EO molar ratio 10/31, Huntsman Corp.). - -

The polyamines 5) used for chain extension are diamines or polyamines and hydrazides, for example ethylene diamine, 1,2- and 1,3-diaminopropane, 1,4-diaminobutane, 1,6- diaminohexane, isophorone diamine, mixtures of isomers of 2,2,4- and 2,4,4-trimethyl hexamethylene diamine, 2-methyl pentamethylene diamine, diethylene triamine, 1,3- and 1,4- xylylene diamine, a,a,a',a'-tetramethyl-l,3- and -1,4-xylylene diamine and 4,4- diaminodicyclohexylmethane, dimethylethylene diamine, hydrazine or adipic acid dihydrazide.

Compounds containing active hydrogen with varying reactivity to NCO groups can also be used in principle as component 5), such as compounds which in addition to a primary amino group also have secondary amino groups or which in addition to an amino group (primary or secondary) also have OH groups. Examples thereof are primary/secondary amines such as 3- amino- 1-m e t h y l am i n o p r o p an e , 3 -amino- 1 -ethylaminopropane, 3 -amino- 1 - cyclohexylaminopropane, 3-amino-l-methylaminobutane, also alkanol amines such as N- aminoethyl ethanolamine, ethanolamine, 3-aminopropanol or neopentanolamine. Diethanolamine and/or hydrazine and/or isophorone diamine (IPDA) and/or ethylene diamine are preferred. Hydrazine and/or isophorone diamine and/or ethylene diamine are particularly preferred. A mixture of hydrazine hydrate and IPDA is most particularly preferred.

All methods known from the prior art can be used to produce the PU dispersions according to the invention, such as for example the prepolymer mixing method, acetone method or melt dispersion method. The PU dispersion is preferably produced by means of the acetone method.

To produce the PU dispersion by the acetone method, part or all of constituents 1), 2), 3) and 4) containing no primary or secondary amino groups and the polyisocyanate component 1) for producing an isocyanate-functional polyurethane prepolymer are conventionally prepared and optionally diluted with a solvent that is miscible with water but inert with regard to isocyanate groups and heated to temperatures in the range from 50 to 120°C. The catalysts known in polyurethane chemistry can be used to accelerate the isocyanate addition reaction. Dibutyl tin dilaurate is preferred.

Suitable solvents are the conventional aliphatic, keto-functional solvents such as for example acetone, butanone and ethyl acetate, which can be added not only at the start of production but also optionally in portions later. Acetone and butanone are preferred. - -

The constituents 1), 2), 3) and 4) optionally not yet added at the start of the reaction are then incorporated.

In the production of the polyurethane prepolymer the substance ratio of isocyanate groups to isocyanate-reactive groups in components 1, 2, optionally 3 and 4 is 1.0 to 3.5, preferably 1.1 to 3.0, particularly preferably 1. 1 to 2.5.

The reaction of components 1), 2), 3) and 4) to form the prepolymer takes place partially or completely, but preferably completely. In this way polyurethane prepolymers containing free isocyanate groups are obtained in bulk or in solution.

In a further process step, if not already done or only partially done, the prepolymer obtained can then be dissolved with the aid of aliphatic ketones such as acetone or butanone.

Then possible NH₂- and/or NH-functional components 5) are reacted with the remaining isocyanate groups. In the chain extension process according to the invention the amine components 5) are added dissolved in water, wherein the following condition is met:

W_CE = ^m^ r (^CE _> 0 4

m_WATER(D) is the mass of water used for dispersion, and W_CE is the percentage by weight of water that is added during chain extension.

WC_E is preferably greater than 0.45 and most particularly preferably greater than 0.50.

The chain extension of the polyurethane prepolymers with a mixture of component 5) and water preferably takes place at a temperature in the range from 20 to 80°C, particularly preferably in the range from 30 to 60°C.

A mixture of component 5) and water with a percentage by weight of component 5) in the mixture in the range from 10 to 1 wt.%, particularly preferably in the range from 7.5 to 2.5 wt.%, is preferably used for chain extension. - -

The degree of chain extension, in other words the equivalents ratio of NCO-reactive groups in the compounds used for chain extension to free NCO groups in the prepolymer, in percent is between 40 and 140%, preferably between 50 and 130%, particularly preferably between 60 and 120%.

Production of the PU dispersion takes place following chain extension. To this end the dissolved and chain-extended polyurethane-urea polymer is either introduced into the dispersing water, optionally with intensive shearing, such as for example vigorous stirring, or conversely the dispersing water is stirred into the prepolymer solutions. The water is preferably added to the dissolved polymer.

The solvent still contained in the dispersions after the dispersing step is conventionally then removed by distillation. Removal during the dispersion step itself is likewise possible.

The solids content of the polyurethane-polyurea dispersion according to the invention is preferably between 20 and 70 wt.%, particularly preferably between 30 and 65 wt.% and most particularly preferably between 35 and 55 wt.%.

The particle size distribution of the polyurethane-urea polymers in the dispersions according to the invention is preferably multimodal and the particle size fractions are preferably in the range from 20 nm to 15,000 nm, particularly preferably in the range from 30 to 12,000 nm, most particularly preferably in the range from 40 to 10,000 nm. The exact distribution can be determined by means of methods known to the person skilled in the art, such as transmission electron microscopy (TEM) or ultracentrifugation (UC).

The average particle size of the polyurethane-urea polymers in the dispersion according to the invention is preferably in the range between 400 and 6000 nm, particularly preferably in the range between 500 and 5000 nm, most particularly preferably between 600 and 4000 nm. The value of the particle sizes is determined by laser correlation spectroscopy.

The dispersions according to the invention have a tendency to settle but can be redispersed very effectively by stirring, which is explained by the multimodal distribution. It is also possible to increase the viscosity of the dispersions according to the invention by adding thickeners and thus to counteract too great a settling. - -

The films of the dispersions according to the invention formed after evaporation of the water have a low degree of gloss and optically are semitransparent to opaque. Provided that the particle size of the particles in the micrometre range is not too great, the films are still smooth and have an attractive surface. The invention also provides the use of the polyurethane-polyurea dispersions according to the invention for the production of coating agents which can be used on various substrates.

Suitable substrates are wood, plastic, metal, glass, textiles, leather, paper and fibres, such as for example glass fibres, plastic fibres and graphite fibres, preferably for the production of sizes for fibres, such as for example glass, plastic and graphite fibres. A further area of application is the use of the dispersions according to the invention in the production of non- glossy yet transparent surfaces (anti-glare surfaces), such as are important for optical displays or LCD screens.

The dispersions according to the invention are particularly advantageous for matt coatings and can be used alone or blended with other aqueous dispersions. Blending allows a specific adjustment of the overall paint properties and appearance to be made. It is also possible to add conventional inorganic matting agents to increase the matting effect, wherein the proportion of inorganic matting agents can be reduced.

The dispersions according to the invention can also be processed in combination with further water-soluble or water-dispersible crosslinkers, such as hydrophilic polyisocyanates, polyamines, polyepoxides and melamines.

The dispersions according to the invention can be used as a constituent in water-based paints for the coating of surfaces. The dispersions according to the invention are formulated with additional components for this purpose. The necessary components and processes are known to the person skilled in the art. Co-binders, thickeners, adhesion promoters, lubricants, wetting additives, dyes, light stabilisers, antioxidants, pigments, flow control agents, antistatics, UV absorbers, film-forming aids, defoamers and plasticisers, for example, are suitable as additional components.

The PU dispersions according to the invention are applied by the methods known to the person skilled in the art, such as spraying, knife application, dip coating, atomisation and printing. - -

Examples:

Raw materials and methods:

Desmophen C2200: C2200, polycarbonate diol produced from hexanediol, OH value = 56, M_n = 2000 g-mol^"1 (Bayer MaterialScience AG, Leverkusen).

PolyTHFlOOO: PTHF, polytetrahydrofuran diol, OH value = 112, M_n = 1000 g-mol^"1 (BASF AG, Ludwigshafen).

PolyTHF2000: PTHF, polytetrahydrofuran diol, OH value = 56, M_n = 2000 g-mol^"1 (BASF AG, Ludwigshafen). PE 170 HN. PE 170 HN, polyester diol produced from adipic acid, hexanediol and neopentyl glycol, OH value = 66, M_n = 1700 g-mol^"1 (Bayer AG, DE)

1,4-Butanediol: BDI (Aldrich, DE)

Polyether LB 25 : Monoiunctional polyether based on ethylene oxide/propylene oxide with an ethylene oxide content of 84%, OH value 25, M_n = 2250 g-mol^"1 (Bayer MaterialScience AG, DE).

Desmodur I: IPDI, isophorone diisocyanate (Bayer MaterialScience AG, DE). Desmodur H: HDI, 1,6-hexamethylene diisocyanate (Bayer MaterialScience AG, DE). Desmodur W: W, dicyclohexylmethane diisocyanate, (Bayer MaterialScience AG, DE) IPDA: Isophorone diamine (Bayer MaterialScience AG, DE) Hydrazine: HY, hydrazine hydrate, 64% solution in water (Lanxess AG, DE)

The solids contents were determined in accordance with DIN EN ISO 3251.

Unless expressly indicated otherwise, NCO contents were determined volumetrically in accordance with DIN EN ISO 11909. - -

Average particle size: The average particle size (APS) was determined by means of laser correlation spectroscopy (using a Malvern Zetasizer 1000, Malvern Instruments Ltd.); the z averages are given.

Film appearance: Polymer films were applied with a knife to glass plates in a film thickness (wet) of 150 μιη, dried at room temperature for at least 12 h and the films were then assessed on a scale from 1 to 5 (1 = almost transparent, 5 = high opacity).

Degree of gloss: The dispersions were applied with a knife to black polycarbonate sheets (wet film thickness 150 μιη), dried at room temperature for 12 h and the degree of gloss was then determined at 60° and 90° in accordance with DIN 67530 using a Byk Gardener gloss meter.

Production of PU dispersions according to the invention: Example 1 (counterexample)

145 g of the polyol C2200, 188 g of the polyol PTHF2000, 71.5 g of the polyol PTHF1000, 34.7 g of the non-ionic monofunctional hydrophilising agent LB25 and 5.4 g of BDI are dehydrated in a reaction vessel under vacuum for one hour at 105°C. The mixture is then cooled to 70°C and 60 g of IPDI with 45.3 g of HDI are added with stirring, whilst maintaining the temperature at approx. 110°C. After reaching the NCO value (3.30, theoretical 3.58) the prepolymer is cooled to approx. 60°C and dissolved in 978 g of acetone. 9.4 g of hydrazine hydrate and 13.9 g of IPDA in 131.8 g of water are added at 40°C within 10 min during chain extension and the solution is stirred for a further 5 min. 644 g water are added within 15 min whilst stirring to form a dispersion and the mixture is stirred for a further 5 min. Then the acetone is removed by distillation at 120 mbar. An aqueous polyurethane-urea dispersion having a solids content of 44.0 wt.% and a pH of 5.8 was obtained. The average particle size is 230 nm and the dispersion forms a transparent film.

Example 2 (counterexample)

The dispersion was produced in an analogous manner to Example 1, but only 19.6 g of LB25 were used. The prepolymer had an NCO value of 3.35 (theoretical 3.72) and is dissolved in 951 g of acetone. An aqueous polyurethane-urea dispersion having a solids content of 44.0 - - wt.% and a pH of 5.2 is obtained. The average particle size is 270 nm and the dispersion forms a transparent film.

Example 3 (counterexample) The dispersion was produced in an analogous manner to Example 1, but only 13.7 g of LB25 were used. The prepolymer had an NCO value of 3.45 (theoretical 3.77) and is dissolved in 940 g of acetone. After chain extension and addition of water to form a dispersion, no dispersion was obtained but rather two separate phases.

Example 4 (counterexample)

The dispersion was produced in an analogous manner to Example 1 , but only 11.0 g of LB25 were used. The prepolymer had an NCO value of 3.59 (theoretical 3.79) and is dissolved in 940 g of acetone. After chain extension and addition of water to form a dispersion, no dispersion was obtained but rather a curd-like mass.

Example 5 (according to the invention)

The dispersion was produced in an analogous manner to Example 2, but the polyamines were dissolved in 377 g of water during chain extension and 377 g of water were used to form a dispersion. The prepolymer had an NCO value of 3.69 (theoretical 3.72). An aqueous polyurethane-urea dispersion having a solids content of 43.0 wt.% and a pH of 5.5 was obtained. The average particle size is 480 nm and the dispersion forms a slightly opaque film. The dispersion forms a sediment after a period of time, but this can be redispersed again by simply stirring or shaking.

Example 6 (according to the invention)

The dispersion was produced in an analogous manner to Example 2, but the polyamines were dissolved in 491 g of water during chain extension and 264 g of water were used to form a dispersion. The prepolymer had an NCO value of 3.50 (theoretical 3.72). An aqueous - - polyurethane-urea dispersion having a solids content of 42.5 wt.% and a pH of 5.2 was obtained. The average particle size is 610 nm and the dispersion forms a moderately opaque film. The dispersion forms a sediment after a period of time, but this can be redispersed again by simply stirring or shaking. The particle size distribution was characterised by means of transmission electron microscopy. To this end the dispersion was diluted and contrasted with ruthenium tetroxide. Three particle size fractions were detected, the coarse fraction having particle sizes of between 1 and 9 μιη. In addition, a fraction with a medium particle size of between 200 and 530 nm and a fraction with a small particle size of between 35 and 150 nm were determined.

Example 7 (according to the invention)

The dispersion was produced in an analogous manner to Example 2, but the polyamines were dissolved in 566 g of water during chain extension and 189 g of water were used to form a dispersion. The prepolymer had an NCO value of 3.56 (theoretical 3.72). An aqueous polyurethane-urea dispersion having a solids content of 42.1 wt.% and a pH of 5.3 was obtained. The average particle size is 530 nm and the dispersion forms a highly opaque film. The dispersion forms a sediment after a period of time, but this can be redispersed again by simply stirring or shaking.

Example 8 (according to the invention)

145 g of the polyol C2200, 188 g of the polyol PTHF2000, 71.5 g of the polyol PTHF1000 and 19.6 g of the non-ionic monofunctional hydrophilising agent LB25 are dehydrated in a reaction vessel under vacuum for one hour at 105°C. The mixture is then cooled to 70°C and 60 g of IPDI with 45.3 g of HDI are added with stirring, whilst maintaining the temperature at approx. 110°C. After reaching the NCO value (4.20, theoretical 3.71) the prepolymer is cooled to approx. 60°C and dissolved in 941 g of acetone. 11.8 g of hydrazine hydrate and 10.4 g of IPDA in 485 g of water are added at 40°C within 10 min during chain extension and the solution is stirred for a further 5 min. 261 g water are added within 15 min whilst stirring to form a dispersion and the mixture is stirred for a further 5 min. Then the acetone is removed by distillation at 120 mbar. An aqueous polyurethane-urea dispersion having a solids content of 42.0 wt.% and a pH of 5.3 was obtained. The average particle size is 3300 - - nm and the dispersion forms a highly opaque film. The dispersion forms a sediment after a period of time, but this can be redispersed again by simply stirring or shaking.

Example 9 (according to the invention) 324 g of the polyol PE 170 HN, 4.3 g of BDI and 15.7 g of the non-ionic monoiunctional hydrophilising agent LB25 are dehydrated in a reaction vessel under vacuum for one hour at 105°C. The mixture is then cooled to 70°C and 47.9 g of IPDI with 36.2 g of HDI are added with stirring, whilst maintaining the temperature at approx. 110°C. After reaching the NCO value (3.39, theoretical 3.72) the prepolymer is cooled to approx. 60°C and dissolved in 760 g of acetone. 7.5 g of hydrazine hydrate and 6.6 g of IPDA in 385 g of water are added at 40°C within 10 min during chain extension and the solution is stirred for a further 5 min. 207 g water are added within 15 min whilst stirring to form a dispersion and the mixture is stirred for a further 5 min. Then the acetone is removed by distillation at 120 mbar. An aqueous polyurethane-urea dispersion having a solids content of 43.1 wt.% and a pH of 5.5 was obtained. The average particle size is 1700 nm and the dispersion forms a moderately opaque film. The dispersion forms a sediment after a period of time, but this can be redispersed again by simply stirring or shaking.

Example 10 (according to the invention) 1 16 g of the polyol C2200, 150.4 g of the polyol PTHF2000, 57.2 g of the polyol

PTHFIOOO, 15.7 g of the non-ionic monofunctional hydrophilising agent LB25 and 4.3 g of BDI are dehydrated in a reaction vessel under vacuum for one hour at 105°C. The mixture is then cooled to 70°C and 56.6 g of W with 36.2 g of HDI are added with stirring, whilst maintaining the temperature at approx. 110°C. After reaching the NCO value (3.32, theoretical 3.65) the prepolymer is cooled to approx. 60°C and dissolved in 776 g of acetone.

7.5 g of hydrazine hydrate and 6.6 g of IPDA in 392 g of water are added at 40°C within 10 min during chain extension and the solution is stirred for a further 5 min. 21 1 g water are added within 15 min whilst stirring to form a dispersion and the mixture is stirred for a further 5 min. Then the acetone is removed by distillation at 120 mbar, during which process portions of water have to be added to prevent the viscosity from becoming too high. An aqueous polyurethane-urea dispersion having a solids content of 31.9 wt.% and a pH of 5.2 - - was obtained. The average particle size is 2900 nm and the dispersion forms a highly opaque film. The dispersion forms a sediment after a period of time, but this can be redispersed again by simply stirring or shaking.

- -

It can be seen that simply reducing the non-ionic hydrophilic component LB25 does not lead to the desired result and that if WC_E is increased then the dispersions according to the invention lead to the desired result of an opaque film appearance combined with good redispersibility and low gloss.

Claims

1. Process for the production of dispersions containing exclusively non-ionically hydrophilised polyurethane-urea polymers, wherein water is added during chain extension of a polyurethane prepolymer in an amount m_water(CE) such that the following condition is met:

W_CE = ^m^ r (^CE _> 0 4

m_vater (CE) + m_water {D) where m_water(CE) is the mass of water added during chain extension, m_water(D) is the mass of water used for dispersion, and W_CE is the percentage by weight of water that i added during chain extension.

Process according to claim 1, wherein WC_E is greater than 0.45. 3. Process according to claim 1 , wherein the polyurethane prepolymer has a molecular weight in the range from 3000 to 15,000 g/mol.

Process according to claim 1, wherein the polyurethane-urea dispersion contains polyurethane-urea polymers having an average particle size in the range between 400 and 6000 nm.

Process according to claim 1, wherein the polyurethane-urea dispersion contains polyurethane-urea polymers having a particle size distribution in the range from 20 nm to 15,000 nm.

Process according to claim 1 , wherein the polyurethane-urea dispersion contains polyurethane-urea polymers synthesised from the following components:

1) at least one polyisocyanate having a functionality of≥ 2 2) one or more polyols having a functionality of≥ 2 and an average molecular M_n of 400 g/mol to 8000 g/mol

3) optionally one or more polyols having a functionality of≥ 2 and an average molecular weight M_n of 62 g/mol to 200 g/mol

4) at least one non-ionic, isocyanate-reactive hydrophilising agent having a functionality of≥ 1 and

5) one or more polyamines having a functionality of≥ 2.

Process according to claim 6, wherein a mixture of component 5) and water with a percentage by weight of component 5) in the mixture in the range from 1 to 10 wt.% is used for chain extension.

Non-ionically hydrophilised polyurethane-urea dispersion obtainable by a method according to one or more of claims 1 to 7.

Use of a non-ionically hydrophilised polyurethane-urea dispersion obtainable by a method according to one or more of claims 1 to 7 for the production of coating agents.

Coating agent containing at least one non-ionically hydrophilised polyurethane- dispersion obtainable by a method according to one or more of claims 1 to 7.