WO2013113739A1

WO2013113739A1 - Low-viscosity, cationically hydrophilised polyurethane dispersions

Info

Publication number: WO2013113739A1
Application number: PCT/EP2013/051757
Authority: WO
Inventors: Stefan Sommer; Jürgen Lippemeier
Original assignee: Bayer Intellectual Property Gmbh
Priority date: 2012-02-01
Filing date: 2013-01-30
Publication date: 2013-08-08

Abstract

The present invention describes a method for producing low-viscosity, radiation-hardenable aqueous dispersions on the basis of polyurethane acrylates (UV-PUDs), wherein the UV-PUDs hydrophilised cationically and/or with potentially cationic groups have a lower initial viscosity if a greater share of the urethanisation, in other words reaction of the NCO-functionalised compounds with the OH-functionalised compounds, first takes place in the absence of acid-bearing compounds and the integration of the acid-bearing compounds via hydroxyl function thereof takes place as late as possible.

Description

Low-viscosity, cationically hydrophilicized polyurethane dispersions

Aqueous, radiation-curable coatings based on polyurethane (meth) acrylate dispersions are gaining ever greater market share because their coatings on wood, plastics and other substrates have very good chemical and mechanical resistance. Further advantages are the low viscosity required for spray applications as well as the fast curing by actinic radiation.

As a rule, radiation-curable, aqueous polyurethane dispersions are hydrophilized via anionic groups or via anionic groups in the presence of hydrophilic polyether groups. Hydrophilization via cationic groups is known in principle in the literature, but there are few concrete examples. Most applications for aqueous, radiation-curable polyurethane dispersions are based on anionically hydrophilized types. In this case, aqueous binders with cationic hydrophilization can be outstandingly suitable when it comes to coatings for paper and leather as well as inks. In addition, in multilayer constructions on various substrates, such as plastics and wood, the combination of coatings based on anionically hydrophilicized binders with coatings based on cationically hydrophilicized binders leads to better adhesion between the layers and better resistances.

In DE-Al 2732955, cationically hydrophilicized urethane acrylate dispersions are described as binders for cathodic dip coating. The viscosity of the binders is not critical to this application because the binders are diluted to very low solids levels of 10% by weight. The incorporation of the potentially cationic groups occurs at the beginning of the synthesis of the polyurethane.

Radiation-curable, aqueous polyurethane (meth) acrylate dispersions for the production of coatings having special haptic properties are described in EP-AI 1489120. There are disclosed potentially anionic and cationic groups as structural components of polyurethane (meth) acrylate dispersions, with potential anionic groups being preferred for hydrophilization. The incorporation of the potentially ionic groups takes place in all examples at the beginning of the urethanization.

In GB-A 2270916 tertiary polyhydroxylamines are incorporated as potentially cationic groups in polyurethane (meth) acrylate dispersions. They are used as inks. The incorporation of the tertiary polyhydroxyamines occurs in all examples at the beginning of the synthesis of the polymer. The dispersions accumulate highly viscous immediately after the synthesis. - -

One reason for the low spread of cationically hydrophilicized, aqueous, radiation-curable polyurethane dispersions is the relatively high viscosity directly after dispersing the corresponding polyurethane (meth) acrylates. In principle, the user would like to receive a water-thin binder for a spray application, which he can adjust to the desired viscosity by means of thickener. However, if the viscosity is very high, z. B. more than 60 sec flow time (determined according to DIN EN ISO 2431 using the 4 mm DIN cup), the viscosity falls within weeks after production very strong. The formulation of the paint must therefore be adjusted daily in relation to the amount of thickener to adjust the desired spray viscosity. However, such an effort can rarely be made and interferes with the automated application process.

The object of the present invention was to provide a process for the synthesis of cationically hydrophilized, aqueous polyurethane (meth) acrylate dispersions in which the aqueous, radiation-curable polyurethane dispersion is obtained as a binder of lower viscosity directly after the synthesis than in previously known processes.

Surprisingly, it has been found that cationic and / or potentially cationic groups hydrophilized radiation-curable polyurethane dispersions have a lower initial viscosity, when a large part of the urethanization, d. H. Implementation of the NCO-functionalized compounds with the OH-functionalized compounds, first in the absence of cationic and / or potentially cationic compounds takes place and the incorporation of the cationic and / or potentially cationic compounds via their NCO-reactive functions takes place as late as possible. Such dispersions have a significantly lower viscosity after preparation than those in which the cationic and / or potentially cationic components were added at the beginning of the urethanization.

The invention relates to a process for preparing radiation-curable, aqueous dispersions based on polyurethane (meth) acrylates (i) as structural components A) one or more compounds having at least one isocyanate-reactive group and at least one free-radically polymerizable unsaturated group, preferably (meth) acrylate groups,

B) optionally one or more monomeric and / or polymeric compounds other than A),

C) one or more organic polyisocyanates, - -

D) one or more compounds having at least one isocyanate-reactive function and additionally at least one cationic and / or potentially cationic function,

E) optionally different from A) to D) compounds having at least one isocyanate-reactive group, characterized in that the components A) to C) are reacted in a first reaction step to a polyurethane (meth) acrylate, which is neither cationic nor potentially cationic Contains groups and after determination of the NCO content, an NCO value is achieved which by up to 1.5 wt .-% NCO (absolute), preferably by up to 1.0 wt .-% NCO (absolute), particularly preferably by up to 0.7 wt .-% NCO (absolute) may differ from the theoretical NCO value, and in a second reaction step with the component D) with still free NCO groups from the reaction product of components A) to C) is reacted and after re-determination of the NCO content, an NCO value is achieved which is up to 1.5 wt .-% NCO (absolute), more preferably by up to 1.0 wt .-% NCO (absolute) of the theoretical NCO Value can vary, and optionally in a third reaction step the Kom component E) is reacted with still free NCO groups.

To the obtained urethane acrylate from the components A) to D) is added a neutralizing agent for producing the cationic groups necessary for the dispersion before, during or after the preparation of the reaction product from the components A) to D), followed by a dispersing step by the addition of water to urethane acrylate or transfer of the urethane acrylate in an aqueous template, wherein optionally in a third reaction step before, during or after the dispersion chain extension by means of component E) can be carried out.

The invention also provides a process according to the above description, in which one or more reactive diluents containing at least one free-radically polymerizable group, component (ii), are admixed. "(Meth) acrylate" in the context of this invention refers to corresponding acrylate or (meth) acrylate functions or to a mixture of both. - -

The theoretical NCO value refers to the NCO content, which is reached after complete reaction of all OH-reactive compounds with all NCO-containing compounds, with an excess of NCO-containing compounds is used. For the control of the reaction, the NCO content is determined experimentally at regular intervals by titration, infrared or near-infrared spectroscopy. Thus, it is possible in a controlled manner, after each reaction step, to achieve an NCO content by adding NCO-reactive compounds which is within a defined range around the theoretical NCO value. The experimentally determined NCO content may differ from the theoretical NCO content by up to 1.5% by weight of NCO (absolute), i. z. At a theoretical NCO content of 1.7% by weight, the experimentally determined NCO content may be in the range of 3.2% to 0.2% by weight. The experimentally determined NCO content may be below the theory, if less reactive groups, such as. As urethane groups, react with free NCO. As a rule, this only happens when the more reactive OH, NH and / or SH group-carrying compounds have reacted. For the preparation of the dispersions by the process according to the invention, it is possible to use all processes known from the prior art, such as emulsifier shear force, acetone, prepolymer mixed, melt emulsified, ketimine and solid spontaneous dispersing processes or derivatives thereof become. These methods are known in the art, see, for. B. Methods of Organic Chemistry, Houben-Weyl, 4th Edition, Volume E20 / Part 2 on page 1659, Georg Thieme Verlag, Stuttgart, 1987. Preferred is the melt emulsification and the acetone method. Particularly preferred is the acetone process.

In order to produce a product by the process according to the invention, the components A) and B) are introduced into the reactor in a first reaction step and optionally diluted with acetone. Optionally, component (ii) may also be added to components A) and B). It is possible to add urethanization catalysts before the conversion with the polyisocyanate (s) C) takes place. The one or more polyisocyanates C) are then metered in and the mixture is heated to allow the reaction to start. As a rule, temperatures of 30 to 60 ° C are required. The reverse variant is also possible, in which case the polyisocyanates C) are initially charged and the isocyanate-reactive components A) and B) are added. The addition of components A) and B) can also be carried out in succession and in any order. Taken together, the components A) to C) until reaching the theoretical NCO value, by up to 1.5 wt .-% NCO, preferably by up to 1.0 wt .-% NCO, more preferably by up to 0 , 7 wt .-% NCO may differ, implemented in a first reaction step. The addition product thus obtained contains neither cationic nor potentially cationic groups. In a second reaction step, the addition of component D) follows, and the reaction is continued until the theoretical again - -

NCO value, by up to 1.5 wt .-% NCO, preferably by up to 1.0 wt .-% NCO. Subsequently, optionally component E) is reacted with still free NCO groups in a third reaction step. To accelerate the addition of isocyanate Isocyanatadditionsreaktion catalysts such. B triethylamine, 1,4-diazabicyclo [2,2,2] octane, tin dioctoate, dibutyltin dilaurate or bismuth octoate, and the mixture is heated to allow initiation of the reaction. As a rule, temperatures of 30 to 60 ° C are required. The molar ratios of isocyanate groups in C) to isocyanate-reactive groups in A) and B) are from 1.2: 1.0 to 4.0: 1.0, preferably 1.5: 1.0 to 3.0: 1.0.

The molar ratios of isocyanate groups in C) to isocyanate-reactive groups in A), B) and D) are from 1.05: 1.0 to 2.5: 1.0, preferably 1.2: 1.0 to 1 , 5: 1.0.

After the preparation of the aqueous, radiation-curable polyurethane (meth) acrylate (i) according to the inventive method from the components A) to D), if potentially cationic groups were used, the salt formation of the compounds D). These potentially cationic groups D) contain basic groups, so that preferably acids are used, such as. For example, inorganic acids such as hydrochloric acid, phosphoric acid and / or sulfuric acid, and / or organic acids such as formic acid, acetic acid, lactic acid, methane, ethane and / or p-toluenesulfonic acid to convert them into the corresponding salts. The degree of neutralization is preferably between 50 and 125%. The degree of neutralization in the case of base-functionalized polymers is defined as the quotient of acid and base. If the degree of neutralization is more than 100%, more acid is added to base-functionalized polymers than basic groups are present in the polymer.

Following this, optionally a reactive diluent (ii) or a mixture of reactive diluents (ii) can be added. The admixing of component (ii) is preferably carried out at 30 to 45 ° C. Once this has dissolved, optionally followed by the last reaction step, take place in the aqueous medium, a molecular weight increase by the component E) and the formation of the dispersions required for the coating system according to the invention. The polyurethane (meth) acrylate (i) synthesized from the components A) to D), and optionally the reactive diluent (ii) optionally dissolved in acetone are added with vigorous stirring either to the dispersing water containing the amine (s) E) , is added or stirred inversely the dispersing water-amine mixture to the polyurethane solution (i). In addition, the dispersions formed in the coating system of the invention are formed. The - - Amount of amine E) used depends on the remaining, unreacted isocyanate groups. The reaction of the still free isocyanate groups with the amine E) can be carried out to 35% to 150%. In the event that a deficiency of amine E) is used, free isocyanate groups react slowly with water. If an excess of amine E) is used, then there are no more free isocyanate groups and an amine-functional polyurethane (meth) acrylate (i) is obtained. Preferably, 80% to 110%, particularly preferably 90% to 100% of the still free isocyanate groups are reacted with the amine E).

In a further variant, it is possible to increase the molar mass by the amine E) already in acetonic solution, ie. H. prior to dispersion, and optionally before or after the addition of the reactant (s) (ii).

If desired, the organic solvent, if present, can be distilled off. The dispersions then have a solids content of from 20 to 60% by weight, in particular from 30 to 58% by weight.

It is also possible to carry out the dispersion and distillation step in parallel, that is to say simultaneously or at least partly simultaneously. Building components A) and optionally component (ii) are used in amounts such that the content of copolymerizable double bonds between 0.5 and 6.0 mol / kg, preferably between 1, 0 and 5.5 mol / kg, more preferably between 1.5 and 5.0 mol / kg of non-aqueous constituents of the dispersion. Component (ii) is used at 0 to 65 wt .-%, preferably 0 to 40 wt .-%, particularly preferably 0 to 35 wt .-%, wherein the components (i) and (ii) to 100 wt. Add%.

As component A) are, for example, polyester (meth) acrylates, polyether (meth) acrylates, polyether (meth) acrylates, unsaturated polyester with Allyletherstruktureinheiten and polyepoxy (meth) acrylates having an OH number in the range of 15 to 300 mg KOH / g Substance and monohydroxy-functional, (meth) acrylate-containing alcohols.

Of the polyester (meth) acrylates, the hydroxyl-containing polyester (meth) acrylates having an OH number in the range from 15 to 300 mg KOH / g substance, preferably from 60 to 200 mg KOH / g substance, are used as component A). In the preparation of the hydroxy-functional polyester (meth) acrylates as component A), a total of 7 groups of monomer constituents may be used: - -

The first group (a) contains alkanediols or diols or mixtures of these. The alkanediols have a molecular weight in the range of 62 to 286 g / mol. Preferably, the alkanediols are selected from the group of ethanediol, 1,2- and 1, 3-propanediol, 1,2-, 1,3- and 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, Neopentyl glycol, cyclohexane-l, 4-dimethanol, 1,2- and 1,4-cyclohexanediol, 2-ethyl-2-butylpropanediol. Preferred diols are ether oxygen-containing diols, such as diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, polyethylene, polypropylene or polybutylene glycols having a number average molecular weight Mn in the range from 200 to 4000, preferably 300 to 2000, particularly preferably 450 to 1200 g / mol. Reaction products of the aforementioned diols with ε-caprolactone or other lactones can also be used as diols.

The second group (b) contains trihydric and higher alcohols having a molecular weight in the range of 92 to 254 g / mol and / or polyethers started on these alcohols. Particularly preferred trihydric and higher alcohols are glycerol, trimethylolpropane, pentaerythritol, dipentaerythritol and sorbitol. A particularly preferred polyether is the reaction product of 1 mole of trimethylolpropane with 4 moles of ethylene oxide.

The third group (c) contains monoalcohols. Particularly preferred monoalcohols are selected from the group of ethanol, 1- and 2-propanol, 1- and 2-butanol, 1-hexanol, 2-ethylhexanol, cyclohexanol and benzyl alcohol.

The fourth group (d) contains dicarboxylic acids having a molecular weight in the range of 104 to 600 g / mol and / or their anhydrides. Preferred dicarboxylic acids and their anhydrides are selected from the group of phthalic acid, phthalic anhydride, isophthalic acid, tetrahydrophthalic acid, tetrahydrophthalic anhydride, hexahydrophthalic acid, hexahydrophthalic anhydride, cyclohexanedicarboxylic acid, maleic anhydride, fumaric acid, malonic acid, succinic acid, succinic anhydride, glutaric acid, adipic acid, pimelic acid, suberic acid, sebacic acid , Dodecanedioic acid, hydrogenated dimers of fatty acids as listed under the sixth group (f).

The fifth group (e) contains trimellitic acid or trimellitic anhydride.

The sixth group (f) contains monocarboxylic acids, such as. B. benzoic acid, cyclohexanecarboxylic acid, 2-ethylhexanoic acid, caproic acid, caprylic acid, capric acid, lauric acid, and natural and synthetic fatty acids, such as. Lauric, myristic, palmitic, margarine, stearic, beehive, cerotin, palmitoleic, oleic, icosenic, linoleic, linolenic and arachidonic acids. - -

The seventh group (g) contains acrylic acid, methacrylic acid and / or diniere acrylic acid.

Suitable hydroxyl-containing polyester (meth) acrylates A) comprise the reaction product of at least one constituent from group (a) or (b) with at least one constituent from group (d) or (e) and at least one constituent from group (g).

Particularly preferred constituents from group (a) are selected from the group consisting of ethanediol, 1,2- and 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, cyclohexane-l, 4-dimethanol , 1,2- and 1,4-cyclohexanediol, 2-ethyl-2-butylpropanediol, ether oxygen-containing diols selected from the group consisting of diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, and tripropylene glycol. Preferred constituents from group (b) are selected from the group of glycerol, trimethylolpropane, pentaerythritol or the reaction product of 1 mol of trimethylolpropane with 4 mol of ethylene oxide. Particularly preferred constituents from groups (d) and (e) are selected from the group of phthalic anhydride, isophthalic acid, tetrahydrophthalic anhydride, hexahydrophthalic acid, hexahydrophthalic anhydride, maleic anhydride, fumaric acid, succinic anhydride, glutaric acid, adipic acid, dodecanedioic acid, hydrogenated dimers of fatty acids, as described in US Pat of the 6th group (f) and trimellitic anhydride. Preferred ingredient from group (g) is acrylic acid.

Optionally, dispersing groups generally known from the prior art can also be incorporated into these polyester (meth) acrylates. For example, polyethylene glycols and / or methoxypolyethylene glycols may be proportionally used as the alcohol component. Alcohol-initiated polyethylene glycols, polypropylene glycols and their block copolymers and the monomethyl ethers of these polyglycols can be used as compounds. Particularly suitable is polyethylene glycol mono-methyl ether having a number average molecular weight Mn in the range from 500 to 1500 g mol. It is also possible, after esterification, to react some of the still free, non-esterified carboxyl groups, in particular those of (meth) acrylic acid, with mono-, di- or polyepoxides. Preferred as epoxides are the glycidyl ethers of monomeric, oligomeric or polymeric bisphenol A, bisphenol F, hexanediol and / or butanediol or their ethoxylated and / or propoxylated derivatives. This reaction can be used in particular to increase the OH number of the polyester (meth) acrylate, since in each case an OH group is formed in the epoxide-acid reaction. The acid number of the resulting product is between 0 and 20 mg KOH / g, preferably between 0 and 10 mg KOH / g and more preferably between 0 and 5 mg KOH / g - -

Substance. The reaction is preferably catalyzed by catalysts such as triphenylphosphine, thiodiglycol, ammonium and / or phosphonium halides and / or zirconium or tin compounds such as tin (II) ethylhexanoate. The preparation of polyester (meth) acrylates is on page 3, line 25 to page 6, line 24 of DE-A 4 040 290, on page 5, line 14 to page 11, line 30 of DE-A 3 316 592 and Page 123 to 135 of PKT Oldring (Ed.) In Chemistry & Technology of UV & EB Formulations For Coatings, Inks & Paints, Vol. 2, 1991, SITA Technology, London.

Also suitable as component A) are hydroxyl-containing polyether (meth) acrylates, which arise from the reaction of acrylic acid and / or methacrylic acid with polyethers, such. B. homo-, co- or block copolymers of ethylene oxide, propylene oxide and / or tetrahydrofuran on any hydroxy-functional starter molecules, such as. B. trimethylolpropane, ethylene glycol, propylene glycol, diethylene glycol, Dipropylengykol, glycerol, pentaerythritol, neopentyl glycol, butanediol and hexanediol.

Likewise suitable as component A) are the known hydroxyl-containing epoxy (meth) acrylates having an OH number in the range from 20 to 300 mg KOH / g, preferably from 100 to 280 mg KOH / g, more preferably from 150 to 250 mg KOH / g or hydroxyl-containing polyurethane (meth) acrylates having an OH number in the range of 20 to 300 mg KOH / g, preferably from 40 to 150 mg KOH / g, more preferably from 50 to 140 mg KOH / g. Such compounds are also described on page 37-56 in PKT Oldring (Ed.), Chemistry & Technology of UV & EB Formulations For Coatings, Inks & Paints, Vol. 2, 1991, SITA Technology, London. Hydroxyl-containing epoxy (meth) acrylates are based in particular on reaction products of acrylic acid and / or methacrylic acid with epoxides (glycidyl compounds) of monomeric, oligomeric or polymeric bisphenol A, bisphenol F, hexanediol and / or butanediol or their ethoxylated and / or propoxylated derivatives , Hydroxyl-containing epoxy (meth) acrylates also include the addition products of acrylic acid and / or methacrylic acid with epoxides of unsaturated fats (fatty acid triglycerides), such as. B. Photomer ^® 3005 F (Fa. Cognis, Dusseldorf, Germany).

Preferred unsaturated group-containing compounds as component A) are selected from the group of polyester (meth) acrylates, polyether (meth) acrylates, polyether (meth) acrylates and polyepoxy (meth) acrylates, which in addition to the unsaturated groups still have hydroxyl groups.

Also suitable as component A) are monohydroxy-functional, (meth) acrylate-containing alcohols. In such monohydroxyfunktionellen, (meth) acrylate groups-containing - -

Alcohols are, for example, 2-hydroxyethyl (meth) acrylate, caprolactone-lengthened modifications of 2-hydroxyethyl (meth) acrylate such as Pemcure ^® 12A (Cognis, DE), 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 3-hydroxy-2,2-dimethylpropyl (meth) acrylate, the average monohydroxyfünktionellen di-, tri- or penta (meth) acrylates of polyhydric alcohols such as trimethylolpropane, glycerol, pentaerythritol, ditrimethylolpropane, dipentaerythritol, ethoxylated, propoxylated or alkoxylated Trimethylolpropane, glycerol, pentaerythritol, ditrimethylolpropane, dipentaerythritol or their technical mixtures.

In addition, alcohols which can be obtained from the reaction of double-bond-containing acids with optionally double-bond-containing, monomeric epoxide compounds can also be used as monohydroxy-functional, (meth) acrylate-containing alcohols. Preferred reaction products are selected from the group of (meth) acrylic acid with glycidyl (meth) acrylate or the glycidyl ester tertiary, saturated monocarboxylic acid. Tertiary, saturated monocarboxylic acids are, for example, 2,2-dimethylbutyric acid, ethylmethylbutyric, ethylmethylpentane, ethylmethylhexane, ethylmethylheptane and / or ethylmethyloctanoic acid.

Particularly preferred as monohydroxy-functional, (meth) acrylate-containing alcohols as component A) are 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, pentaerythritol triacrylate, dipentaerythritol pentaacrylate and the addition product of Ethylmethylheptansäureglycidylester with (meth) acrylic acid and their technical mixtures , very particularly preferred is 2-hydroxyethyl (meth) acrylate.

The listed under component A) compounds can be used alone or as mixtures.

Component B) contains monomeric mono-, di- and / or triols each having a molecular weight of 32 to 240 g / mol, such as. Methanol, ethanol, 1-propanol, 1-butanol, 1-pentanol, 1-hexanol, 2-propanol, 2-butanol, 2-ethylhexanol, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, 1, 2 Propanediol, 1,3-propanediol, 1,4-butanediol, neopentyl glycol, 2-ethyl-2-butylpropanediol, trimethylpentanediol, 1,3-butylene glycol, 1,4-cyclohexanedimethanol, 1,6-hexanediol, 1,2- and 1 , 4-cyclohexanediol, hydrogenated bisphenol A (2,2-bis (4-hydroxycyclohexyl) propane), dimer fatty acid derived diols, 2,2-dimethyl-3-hydroxypropionic acid (2,2-dimethyl-3-hydroxypropyl ester), glycerol , Trimethylol- ethane, trimethylolpropane, trimethylolbutane and / or castor oil. Preference is given to neopentyl glycol, 1,4-butanediol, 1,4-cyclohexanedimethanol, 1,6-hexanediol and / or trimethylolpropane. - -

Furthermore, component B) contains oligomeric and / or polymeric, hydroxy-functional compounds. These oligomeric and / or polymeric, hydroxy-functional compounds are, for example, polyesters, polycarbonates, polyethercarbonate polyols, C2, C3 and / or C4 polyethers, polyetheresters, polycarbonate polyesters having a functionality of 1.0 to 3.0, each with a weight average of Molar mass Mw in the range of 300 to 4000, preferably 500 to 2500 g / mol.

Hydroxy-functional polyester alcohols are those based on mono-, di- and tricarboxylic acids with monomeric di- and triols, as have already been enumerated as component B), and lactone-based polyester alcohols. The carboxylic acids are, for example, phthalic acid, isophthalic acid, terephthalic acid, trimellitic acid, adipic acid, maleic acid, fumaric acid, tetrahydrophthalic acid, hexahydrophthalic acid, malonic acid, succinic acid, glutaric acid, pimelic acid, suberic acid, sebacic acid, dodecanedioic acid, hydrogenated dimers of fatty acids and saturated and unsaturated fatty acids , such as As palmitic acid, stearic acid, myristoleic acid, palmitoleic acid, oleic acid, linoleic acid, linolenic acid, ricinoleic acid and their technical mixtures. Of the di- and tricarboxylic acids, the analog anhydrides can also be used.

Hydroxy-functional polyetherols are obtainable, for example, by polymerization of cyclic ethers or by reacting alkylene oxides with a starter molecule.

Hydroxy-functional polycarbonates are hydroxyl-terminated polycarbonates prepared by reacting diols, lactone-modified diols or bisphenols, eg. As bisphenol A, with phosgene or carbonic diesters, such as diphenyl carbonate or dimethyl carbonate, accessible polycarbonates. Hydroxy-functional polyether carbonate polyols are those as described for the construction of polyurethane dispersions in DE 102008000478.

Component C) are polyisocyanates selected from the group of aromatic, araliphatic, aliphatic or cycloaliphatic polyisocyanates or mixtures of such polyisocyanates. Suitable polyisocyanates are, for. B. 1,3-cyclohexane diisocyanate, 1-methyl-2,4-diisocyanato-cyclohexane, l-methyl-2,6-diisocyanato-cyclohexane, tetramethylene diisocyanate, 4,4'-diisocyanatodiphenylmethane, 2,4'-diisocyanatodiphenylmethane, 2nd , 4-diisocyanatotoluene, 2,6-diisocyanatotoluene, α, α, α, 'α,' - tetra-methyl-m- or p-xylylene diisocyanate, 1,6-hexamethylene diisocyanate, 1-isocyanato-3,3 , 5-trimethyl-5-isocyanatomethylcyclohexane (isophorone diisocyanate or IPDI), 4,4-diisocyanato-dicyclohexylmethane, 4-isocyanatomethyl-l, 8-octane-diisocyanate (triiso-cyanatononane, TIN) (EP-A 928 799), homologs or Oligomers of these enumerated - -

Polyisocyanates with biuret, carbodiimide, isocyanurate, allophanate, iminooxadiazinedione and / or uretdione groups and mixtures thereof.

Likewise suitable as component C) are compounds having at least two free isocyanate groups, at least one allophanate group and at least one free-radically polymerizable C =C double bond bonded to the allophanate group, as described as component a) in WO 2006089935 A1.

Preferred as component C) are 1,6-hexamethylene diisocyanate, 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane (isophorone diisocyanate or IPDI) and 4,4'-diisocyanato-dicyclohexylmethane, homologues or oligomers of 1.6 Hexamethylene diisocyanate, 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane (isophorone diisocyanate or IPDI) and 4,4'-diisocyanato-dicyclohexylmethane with biuret, carbodiimide, isocyanurate, allophanate, iminooxadiazinedione and / or Uretdione groups and their mixtures. Very particular preference is given to 4,4'-diisocyanato-dicyclohexylmethane.

Component D) comprises compounds having at least one isocyanate-reactive group and additionally at least one cationic and / or potentially cationic group. The potentially cationic groups are converted, for example, by salt formation into the corresponding cationic groups. Suitable cationic groups are ammonium groups, potentially cationic groups are primary, secondary or tertiary amino groups, particularly preferred potentially cationic groups are tertiary amino groups. Preferably suitable isocyanate-reactive groups are hydroxyl, primary and / or secondary amino groups. As component D) suitable compounds with potentially cationic groups are, for example, ethanolamine, 3-hydroxy-1-methylpiperidine, 4- (2-hydroxyethyl) morpholine, 1- (2-hydroxyethyl) pyrrolidin-2-one, diethanolamine, triethanolamine, 2- Propanolamine, dipropanolamine, tripropanolamine, N-methylethanolamine, N-methyl-diethanolamine and N, N-dimethylethanolamine, preferably triethanolamine, tripropanolamine, N-methylethanolamine, N-methyl-diethanolamine and Ν, Ν-dimethylethanolamine, more preferably N-methyl-diethanolamine and N, N-dimethylethanolamine.

The potentially cationic groups are converted by reaction with neutralizing agents, such as. As inorganic acids such as hydrochloric acid, phosphoric acid and / or sulfuric acid, and / or organic acids such as formic acid, acetic acid, lactic acid, methane, ethane and / or p-toluenesulfonic acid, converted into the corresponding salts. The degree of neutralization is preferably between 50 and 125%. The degree of neutralization is at - -

Base-functionalized polymers defined as quotient of acid and base. If the degree of neutralization is more than 100%, more acid is added to base-functionalized polymers than base groups are present in the polymer. The compounds listed under component D) can also be used in mixtures.

The compounds listed under component D) are incorporated into the polyurethane (meth) acrylate (i) in amounts such that amine numbers (calculated theoretically or determined in accordance with DIN 53176) of preferably 8 to 25, particularly preferably 12 to 20, mg KOH / g of substance for the polyurethane (meth) acrylate (i).

If appropriate, to increase the molecular weight of the polyurethane (meth) acrylates according to the invention (i) mono- and diamines and / or mono- or difunctional amino alcohols are used as component E). Preferred diamines are those which are more reactive towards the isocyanate groups than water, since the extension of the polyester urethane (meth) acrylate optionally takes place in an aqueous medium. The diamines are particularly preferably selected from the group consisting of ethylenediamine, 1,6-hexamethylenediamine, isophoronediamine, 1,3-, 1,4-phenylenediamine, piperazine, 4,4'-diphenylmethanediamine, amino-functional polyethylene oxides, amino-functional polypropylene oxides (known by the name Jeffamin® D series [Huntsman Corp. Europe, Zavantem, Belgium]) and hydrazine. Very particular preference is given to ethylenediamine.

Preferred monoamines are selected from the group of butylamine, ethylamine and amines of the Jeffamin® M series (Huntsman Corp. Europe, Zavantem, Belgium), amino-functional polyethylene oxides, amino-functional polypropylene oxides and / or amino alcohols.

Component (ii) are reactive diluents, which are compounds which contain at least one free-radically polymerizable group, preferably acrylate and methacrylate groups, and preferably no groups reactive toward isocyanate or hydroxy groups. Preferred compounds (ii) have 2 to 6 (meth) acrylate groups, more preferably 4 to 6.

Particularly preferred compounds (ii) have a boiling point of more than 200 ° C at atmospheric pressure. - -

Reactive thinners are generally described in P.K. Oldring (eds.), Chemistry & Technology of UV & EB Formulations for Coatings, Inks & Paints, Vo. II, Chapter III: Reactive Diluents for UV & EB Curable Formulations, Wiley and SITA Technology, London 1997.

Reactive thinners are, for example, the alcohols completely esterified with (meth) acrylic acid, methanol, ethanol, 1-propanol, 1-butanol, 1-pentanol, 1-hexanol, 2-propanol, 2-butanol, 2-ethylhexanol, dihydrodicyclopentadienol, tetrahydrofurfuryl alcohol, 3 3,5-trimethylhexanol, octanol, decanol, dodecanol, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, neopentyl glycol, 2-ethyl 2-butylpropanediol, trimethylpentanediol, 1,3-butylene glycol, 1,4-cyclohexanedimethanol, 1,6-hexanediol, 1,2- and 1,4-cyclohexanediol, hydrogenated bisphenol A (2,2-bis (4-hydroxycyclohexyl) propane ), Glycerol, trimethylolethane, trimethylolpropane, trimethylolbutane, pentaerythritol, ditrimethylolpropane, dipentaerythritol, sorbitol and ethoxylated and / or propoxylated derivatives of the alcohols listed and the technical mixtures obtained in the (meth) acrylation of the abovementioned compounds.

Component (ii) is preferably selected from the group of (meth) acrylates of tetrols and hexols, such as (meth) acrylates of pentaerythritol, ditrimethylolpropane, dipentaerythritol, sorbitol, ethoxylated, propoxylated or alkoxylated pentaerythritol, ditrimethylolpropane, dipentaerythritol, sorbitol and ethoxylated and or propoxylated derivatives of the alcohols listed and the technical mixtures obtained in the (meth) acrylation of the abovementioned compounds.

The invention also provides the radiation-curable, aqueous dispersions based on polyurethane (meth) acrylates (i) prepared by the process according to the invention.

The invention also provides the use of the radiation-curable, aqueous dispersions prepared by the process according to the invention for the production of coatings, in particular of paints and adhesives.

The dispersions according to the invention give clear films after removal of the water by customary methods, such as heat, heat radiation, moving optionally dried air and / or microwaves. Subsequent radiation-chemically and / or free-radically induced crosslinking, the films cure to form high-quality and chemical-resistant lacquer coatings.

For radiation-chemically induced polymerization, electromagnetic radiation is suitable whose energy, optionally with the addition of suitable photoinitiators, is sufficient to effect a radical polymerization of (meth) acrylate double bonds. - -

The radiation-induced polymerization preferably takes place by means of radiation having a wavelength of less than 400 nm, such as UV, electron, X-ray or gamma rays. Particularly preferred is the UV radiation, wherein the curing is initiated with UV radiation in the presence of photoinitiators. In the case of the photoinitiators, a distinction is in principle made between two types, the unimolecular (type I) and the bimolecular (type II). Suitable (Type I) systems are aromatic ketone compounds, such as. As benzophenones in combination with tertiary amines, alkylbenzophenones, 4,4'-bis (dimethylamino) benzophenone (Michler's ketone), anthrone and halogenated benzophenones or mixtures of the types mentioned. Also suitable are (type II) initiators such as benzoin and its derivatives, benzil ketals, acylphosphine oxides, 2,4,6-trimethyl-benzoyl-diphenylphosphine oxide, bisacylphosphine oxides, phenylglyoxylic acid esters, camphorquinone, α-aminoalkylphenones, α, α-dialkoxyacetophenones and ct -Hydroxyalkylphenone. Preference is given to photoinitiators which are easy to incorporate into aqueous coating compositions. Such products are, for example, Irgacure ^® 500 (a mixture of benzophenone and (1-hydroxycyclohexyl) phenyl ketone, Fa. Ciba, Lampertheim, DE), Irgacure ^® 819 DW (Phenylbis- (2, 4, 6-trimethylbenzoyl) phosphine oxide, Fa. Ciba, Lampertheim, DE), Esacure ^® KIP EM (01igo- [2- hydroxy-2-methyl-l- [4- (l-methylvinyl) phenyl] -propanone], Fa. Lamberti, Aldizzate, Italy). It is also possible to use mixtures of these compounds.

For incorporation of the photoinitiators and polar solvents, such as. As acetone and isopropanol can be used.

Advantageously, the UV curing is carried out at 30 to 70 ° C, because at higher temperature, the degree of conversion of (meth) acrylate groups tends to increase. This can result in better resistance properties. However, in the case of UV curing, a possible temperature sensitivity of the substrate must be taken into consideration, so that optimum curing conditions for a particular coating agent / substrate combination are to be determined by the person skilled in the art in simple preliminary experiments.

The radiator (s) which initiate the radical polymerization can be stationary and the coated substrate is moved past the radiator by means of suitable conventional devices, or the radiators are movable by conventional means, so that the coated substrates are stationary during curing. It is also possible the irradiation z. B. in chambers, in which the coated substrate is introduced into the chamber, then the radiation is turned on for a certain period of time, and after the irradiation, the substrate is removed from the chamber again. - -

Optionally, under an inert gas atmosphere, i. H. oxygen-free, cured to prevent inhibition of free-radical cross-linking by oxygen.

If the curing takes place thermally-radically, water-soluble peroxides or aqueous emulsions of non-water-soluble initiators are suitable. These radical formers can be combined with accelerators in a known manner.

The radiation-curable polyurethane (meth) acrylate dispersions according to the invention can be applied by the usual techniques to a wide variety of substrates, preferably spraying, rolling, flooding, printing, knife coating, casting, brushing and dipping.

With the radiation-curable polyurethane (meth) acrylate dispersions according to the invention, basically all substrates can be coated or coated. Preferred substrates are selected from the group consisting of mineral substrates, wood, wood-based materials, furniture, parquet, doors, window frames, metallic objects, plastics, paper, cardboard, cork, mineral substrates, textiles or leather. They are suitable here as a primer and / or as a topcoat. In addition, the coating systems of the invention can also be used in or as adhesives, for. B. in contact adhesives, in thermally activated adhesives or in laminating adhesives.

However, the radiation-curable polyurethane (meth) acrylate dispersions according to the invention can also be used alone in binder mixtures with other dispersions. These may be dispersions which also contain unsaturated groups, such as. B. unsaturated, polymerizable group-containing dispersions on polyester, polyurethane, polyepoxy (meth) acrylate, polyether, polyamide, polysiloxane, polycarbonate, epoxyacrylate, polymer, polyester acrylate, polyurethane polyacrylate and / or polyacrylate.

It is also possible for such dispersions based on polyesters, polyurethanes, polyethers, polyamides, polyvinyl esters, polyvinyl ethers, polysiloxanes, polycarbonates, polymers and / or polyacrylates to be present in the coating systems according to the invention which contain functional groups, such as alkoxysilane groups, hydroxyl groups and / or optionally Blocked form present isocyanate groups. Thus, dual-cure systems can be produced, which can be cured by two different mechanisms. Likewise for dual-cure systems, it is possible to add to the radiation-curable polyurethane according to the invention (meth) acrylate dispersions, also known as crosslinkers. Preference is given to non-blocked and / or blocked polyisocyanates, polyaziridines, - -

Polycarbodiimides and melamine resins in question. Non-blocked and / or blocked, hydrophilized polyisocyanates for aqueous coating compositions are particularly preferred. Preferably, <20% by weight, particularly preferably <10% by weight, of solid crosslinker is added to the solids content of the coating composition.

It is also possible to use dispersions based on polyesters, polyurethanes, polyethers, polyamides, polysiloxanes, polyvinyl ethers, polybutadienes, polyisoprenes, chlorinated rubbers, polycarbonates, polyvinyl esters, polyvinyl chlorides, polymers, polyacrylates, polyurethane-polyacrylate, polyester acrylate, polyether acrylate, alkyd, Polycarbonate, polyepoxy, epoxy (meth) acrylate be included in the coating systems of the invention which have no functional groups. Thus, the degree of crosslinking density can be reduced, which influences physical drying, z. B. be accelerated, or an elastification or a liability adjustment are made. By virtue of the fact that the radiation-curable polyurethane according to the invention contains (meth) acrylate dispersions, it is also possible to use amino crosslinker resins based on melamine or urea and / or the polyisocyanates with free o and with cobalt Polyisocyanate groups, based on optionally hydrophilicizing groups containing polyisocyanates of hexamethylene diisocyanate, isophorone diisocyanate and / or toluylene diisocyanate with urethane, uretdione, Iminoxadiazindion-, isocyanurate, biuret and / or allophanate structures may be added in the coating compositions of the invention. Carbodiimides or polyaziridines are also possible as further crosslinkers.

The coating compositions according to the invention can with the known in paint technology binders, excipients and additives such. As pigments, dyes or matting agents are added or combined. These are leveling and wetting additives, slip additives, pigments including metallic effect pigments, fillers, nanoparticles, light protection particles, anti-yellowing additives, thickeners and surface tension reduction additives.

Coating compositions comprising the inventive radiation-curable aqueous dispersions based on polyurethane (meth) acrylate, as well as crosslinkers based on amino resins, blocked polyisocyanates, unblocked polyisocyanates, polyaziridines and / or polycarbodiimides, and / or one or more further dispersions are also provided by the present invention , Furthermore, substrates coated with the coating compositions of the invention are the subject of this invention. - -

Examples

methods

The NCO content was monitored in each case according to DIN EN ISO 11909 by titration.

The data for the amine number are calculated theoretically, but can also be determined according to DIN 53176.

The solids content was determined gravimetrically after evaporation of all volatile constituents in accordance with DIN EN ISO 3251.

The mean particle size was determined by laser correlation spectroscopy.

The flow time was determined in accordance with DIN EN ISO 2431 using the 4 mm DIN cup.

1) Preparation of radiation-curable aqueous polyurethane dispersion (comparison) 308 parts of the polyester acrylate Laromer ^® PE 44 F (BASF AG, Ludwigshafen, DE), component A), 10.4 parts of neopentyl glycol, component B), 293 parts of a linear, OH terminated aliphatic polycarbonate diol (OH number = 56 mg KOH / g substance), component B), 33.6 parts hexamethylene diisocyanate, component C), 113 parts isophorone diisocyanate, component C), 14.9 parts N-methyldiethanolamine, component D), and 0.2 part of dibutyltin dilaurate were dissolved in 213 parts of acetone and reacted to 60 ° C with stirring to an NCO content of 1.2 wt .-% (theory 1.01 wt .-%). The resulting polyurethane acrylate solution was dissolved in a further 375 parts of acetone, cooled to 40 ° C, and there was the addition of 6.9 parts of ethylenediamine, component E), in 35 parts of acetone. After stirring for 10 minutes, it was neutralized with 11.9 parts of D, L-lactic acid (85%, 15% by weight of water). 717 parts of water were added with stirring to the clear solution. Subsequently, the acetone was distilled off under slight vacuum from the dispersion. A radiation-curable, aqueous polyurethane dispersion 1) having a solids content of 40% by weight, an average particle size of 176 nm and a pH of 4.6 was obtained. The amine number of the polyurethane acrylate was 8.9 mg KOH / g substance. The viscosity was so high after the synthesis that the flow time in the 4 mm DIN cup was more than 120 seconds and was in fact not measurable. After two weeks of storage at 23 ° C, the flow time was 43 seconds. 2) Preparation of the invention, UV-curable, aqueous polyurethane dispersion, 308 parts of the polyester acrylate Laromer ^® PE 44 F (BASF AG, Ludwigshafen, DE), component A), 10.4 parts of neopentyl glycol, component B), 293 parts of a linear , OH-terminated aliphatic polycarbonate diols (OH number = 56 mg KOH / gm of substance), component B), 33.6 parts of hexamethylene diisocyanate, component C), 113 parts of isophorone diisocyanate, component C), and 0.2 part of dibutyltin dilaurate were added in 213 Dissolved acetone and reacted to an NCO content of 2.1 wt .-% (theory 2.07 wt .-%) at 60 ° C with stirring. The resulting polyurethane acrylate solution was dissolved in a further 375 parts of acetone, cooled to 50 ° C, and - - There was the addition of 14.9 parts of N-methyldiethanolamine, component D). The mixture was further stirred at 50 ° C until an NCO content of 1.1 wt .-% (theory 1.01 wt .-%) was reached, and then with stirring, 6.9 parts of ethylenediamine, component E. ), added in 35 parts of acetone. After stirring for 10 minutes, it was neutralized with 11.9 parts of D, L-lactic acid (85%, 15% by weight of water). 717 parts of water were added with stirring to the clear solution. Subsequently, the acetone was distilled off under slight vacuum from the dispersion. A radiation-curable, aqueous polyurethane dispersion 2) having a solids content of 40% by weight, an average particle size of 183 nm and a pH of 4.6 was obtained. The amine number of the polyurethane acrylate was 8.9 mg KOH / g substance. Viscosity was 14 seconds after synthesis in the 4 mm DIN cup and 13 seconds after storage for two weeks at 23 ° C.

3) Preparation of a Radiation-Curable Aqueous Polyurethane Dispersion (Comparison)

788 parts of the epoxyacrylate Ebecryl ^® 600 (Cytec, Drogenbos, BE), component A), 128 parts of 2-ethyl-l, 3-hexanediol, component B), 419 parts of a polyester diol based on adipic acid, neopentyl glycol and 1,6-hexanediol with an OH number of 66 mg KOH / g substance, component B), 277 parts hexamethylene diisocyanate, component C), 534 parts isophorone diisocyanate, component C), and 94.1 parts N-methyldiethanolamine, component D) were dissolved in 600 parts Dissolved acetone and up to an NCO content of 1.2 wt .-% (theory 1.12 wt .-%) at 60 ° C with stirring. The resulting polyurethane acrylate solution was dissolved in a further 1010 parts of acetone, cooled to 40 ° C, and there was the addition of 21.3 parts of ethylenediamine, component E), in 150 parts of acetone. After stirring for 10 minutes, it was neutralized with 81.7 parts of D, L-lactic acid (85%, 15% by weight of water). 3300 parts of water were added with stirring to the clear solution. Subsequently, the acetone was distilled off under slight vacuum from the dispersion. A radiation-curable, aqueous polyurethane dispersion 3) having a solids content of 36% by weight, an average particle size of 113 nm and a pH of 6.4 was obtained. The amine number of the polyurethane acrylate was 18.9 mg KOH / g substance. The viscosity was so high after the synthesis that the flow time in the 4 mm DIN cup was more than 120 seconds and was in fact not measurable. After two weeks of storage at 23 ° C, the flow time was 56 seconds.

4) Preparation of a radiation-curable, aqueous polyurethane dispersion

788 parts of the epoxyacrylate Ebecryl ^® 600 (Cytec, Drogenbos, BE), component A), 128 parts of 2-ethyl-l, 3-hexanediol, component B), 419 parts of a polyester diol based on adipic acid, neopentyl glycol and 1,6-hexanediol with an OH number of 66 mg KOH / g of the substance, component B), 277 parts of hexamethylene diisocyanate, component C) and 534 parts of isophorone diisocyanate, component C) were dissolved in 600 parts of acetone and up to an NCO content of 4.5 weight - -

% (Theory 4.58 wt .-%) at 60 ° C with stirring. The resulting polyurethane acrylate solution was dissolved in a further 1010 parts of acetone, cooled to 50 ° C, and there was the addition of 94.2 parts of N-methyldiethanolamine, component D). The mixture was further stirred at 50 ° C. until an NCO content of 1.1% by weight (theory 1.12% by weight) had been reached, followed by 6.9 parts of ethylenediamine, component E, with stirring ), added in 150 parts of acetone. After stirring for 10 minutes, it was neutralized with 81.7 parts of D, L-lactic acid (85%, 15% by weight of water). 3300 parts of water were added with stirring to the clear solution. Subsequently, the acetone was distilled off under slight vacuum from the dispersion. A radiation-curable, aqueous polyurethane dispersion 4) having a solids content of 36% by weight, an average particle size of 108 nm and a pH of 6.4 was obtained. The amine number of the polyurethane acrylate was 18.9 mg KOH / g substance. The viscosity was 17 seconds after synthesis in the 4 mm DIN cup and 14 seconds after storage for two weeks at 23 ° C. Table 1

Although the compositions of Examples 1 and 2 and Examples 3 and 4 are identical, Examples 2 and 4 in Table 1 produced by the process according to the invention show that the process according to the invention leads to significantly lower viscosities directly after the synthesis and also the viscosity decrease two weeks storage is much lower than in Comparative Examples 1 and 3.

Claims

Claims:

1. A process for the preparation of radiation-curable, aqueous dispersions based on polyurethane (meth) acrylates (i) comprising as structural components A) one or more compounds having at least one isocyanate-reactive group and at least one free-radically polymerizable unsaturated group,

B) optionally one or more monomeric and / or polymeric compounds other than A),

C) one or more organic polyisocyanates,

E) optionally different from A) to D) compounds having at least one isocyanate-reactive group, characterized in that the components A) to C) are reacted in a first reaction step to a polyurethane (meth) acrylate, which is neither cationic nor potentially cationic Contains groups and after determination of the NCO content, an NCO value is achieved which by up to 1.5 wt .-% NCO (absolute), preferably by up to 1.0 wt .-% NCO (absolute), particularly preferably by up to 0.7 wt .-% NCO (absolute) may differ from the theoretical NCO value, and in a second reaction step with the component D) with still free NCO groups from the reaction product of components A) to C) is reacted and after re-determination of the NCO content, an NCO value is achieved which is up to 1.5 wt .-% NCO (absolute), more preferably by up to 1.0 wt .-% NCO (absolute) of the theoretical NCO Value may vary,

Addition of a neutralizing agent to produce the cationic groups necessary for the dispersion before, during or after the preparation of the reaction product from the components A) to D).

2. A process for the preparation of radiation-curable, aqueous dispersions based on polyurethane (meth) acrylates (i) according to claim 1, characterized in that in a third reaction step, the component E) is reacted with still free NCO groups.

3. A process for the preparation of radiation-curable, aqueous dispersions based on polyurethane (meth) acrylates (i) according to claim 1 or 2, characterized in that one or more reactive diluents containing at least one radically polymerizable group, component (ii) are admixed.

4. A process for the preparation of radiation-curable, aqueous dispersions based on polyurethane (meth) acrylates (i) according to one of claims 1 to 3, characterized in that component D) is selected from the group consisting of ethanolamine, 3-hydroxy-l methylpiperidine, 4- (2-hydroxyethyl) morpholine, 1- (2-hydroxyethyl) pyrrolidin-2-one,

Diethanolamine, triethanolamine, 2-propanolamine, dipropanolamine, tripropanolamine, N-methyl ethanolamine, N-methyl-diethanol ^ amine and N, N-dimethylethanolamine.

5. A process for the preparation of radiation-curable, aqueous dispersions based on polyurethane (meth) acrylates (i) according to one of claims 1 to 4, characterized in that the molar ratios of isocyanate groups in D) to isocyanate-reactive groups in A) to C ) of 1.2: 1.0 to 4.0: 1.0.

6. A process for the preparation of radiation-curable, aqueous dispersions based on polyurethane (meth) acrylates (i) according to one of claims 1 to 5, characterized in that the molar ratios of isocyanate groups in D) to isocyanate-reactive groups in A), B ), C) and E) are from 1.05: 1.0 to 2.5: 1.0.

7. A process for the preparation of radiation-curable, aqueous dispersions based on polyurethane (meth) acrylates (i) according to one of claims 1 to 6, characterized in that after the first reaction step after determining the NCO content, an NCO value is achieved, the Up to 1.0 wt .-% NCO (absolute) may differ from the theoretical NCO value, and after the second reaction step after determining the NCO content, an NCO value is reached, which can be up to 1.0 wt. % NCO (absolute) may deviate from the theoretical NCO value.

8. Radiation-curable, aqueous dispersions based on polyurethane (meth) acrylates (i), prepared by the process according to one of claims 1 to 7.

9. Use of the radiation-curable aqueous dispersions based on polyurethane (meth) acrylates according to claim 8 for the preparation of coatings, paints and adhesives.