MXPA99011890A - Polyurethane resin, method for the production and use thereof in an aqueous dual component clear varnish - Google Patents

Abstract

La presente invención proporciona una resina de poliuretano que puede obtenerse (A) haciendo reaccionar en una primera etapa de reacción (A), (a) uno o varios diisocianatos y/o poliisocianatos, (b) uno o varios compuestos (b) que tienen por lo menos un grupo que asegura la dispersabilidad en agua y más de un grupo que es reactivo con grupos isocianato, y (c) si asíse desea, uno o varios compuestos que tienen por lo menos 2 y no más de 3 grupos OH, para dar un agente intermedio (A) que tiene grupos libres de isocianato y que cuenta con grupos uretano, (B) agregar en una segunda etapa de reacción (B), (d) uno o varios monoisocianatos al agente intermedio (A) obtenido en la etapa (A), y (C) hacer reaccionar subsiguientemente la mezcla resultante (B) con uno o varios polímeros que contienen hidroxilo (D) para dar la resina de poliuretano (P), con el uso de menos de 20%en peso, basado en el peso de la resina de poliuretano (contenido sólido) de dioles deóxido de polialquileno y/o de polioles deóxido de polialquileno a fin de preparar la resina de poliuretano.

Description

POLYURETHANE RESIN, PROCEDURE FOR ITS PREPARATION AND ITS USE IN AQUEOUS CLEAR COATINGS OF TWO COMPONENTS _ The present invention relates to a polyurethane resin, suitable as a rheological control additive for aqueous coating compositions. The present description also relates to processes that serve to prepare this polyurethane resin and to coating compositions based on polyurethane, of an aqueous type and of a bicomponent character comprising this polyurethane resin, it also refers to the use of such coating compositions and use of the polyurethane resin as an additive to control the rheology of the coating compositions. In the field of coating plastics there is a well-defined desire to have aqueous systems, both as primary layers and as top coatings. In these applications, the coating materials used have to meet a large number of different requirements. Thus, for example, particularly in the field of coating plastics there is a requirement that the resulting coatings exhibit a good "appearance", ie, for example, a high degree of brightness and low levels of haze or turbidity. In addition, for example, in the wet-on-wet process to produce a basecoat / clearcoat system, the transparentcoats applied to the basiccoat not yet cured should not give rise to an incipient dissolution of the basecoat film or nor should it interrupt the film in any other way, otherwise finishes with a defective appearance would be achieved. The above is particularly applicable to finishes produced with the use of basic coatings containing effect producing pigments (for example, metc pigments, especi aluminum flakes or also pearlescent pigments). Furthermore, it can be said that the coating compositions must show a very low tendency towards sliding (formation of curtains, development of tears, sagging) on vertical faces, on the edges, as well as on the slats after application, and especi during the baking operation or in the course of drying at temperatures gener ranging from room temperature to about 80 ° C. It is known that this tendency to shift can be influenced by controlling the rheology of the coating compositions. However, as the viscosity of the known coating materials increases, the improvement that can be obtained in the tendency to shift is inadequate. In fact it is known that polyurea compounds act to stabilize the shift. A serious drawback of the known polyureas is on the other hand the turbidity in the baked coating film especi when the polyureas are used in the transparent coatings. In order to overcome this problem, German specification DE-A-42 36 901 proposed the use of acrylated polyurethane resins prepared by reacting a hydroxyl-containing acrylate copolymer, a hydroxy-functional microdispersion, a diisocyanate and a monoamine as additive for control the rheology of traditional coating compositions. The polyurethane resins described in German specification DE-A-42 36 901, on the other hand, have the disadvantage that their preparation requires a complex process consisting of a plurality of synthesis steps and that are unsuitable for use in materials of aqueous coating.

Furthermore, German specification DE-C-31 50 174 discloses also certain hydrophobic polyurethane resins containing urea groups, these resins being based on a polyalkylene oxide diol having a molecular weight of 2000 to 20,000 and their use as thickeners for control the rheology of aqueous coating compositions. Due to the high level of ether groupsIt must be said, on the other hand, that the polyurethane resins described in the German specification DE-C-31 50 174 have the disadvantage that the films become sensitive to condensation. It is further noted that the thickeners described there become manageable only at the high levels of dilution. Nor can these thickening agents be used as film formers. Since the polyether segments of the thickening agent enter into stable interactions with water, there may be instances of instability when the material is stored at levels above 40 ° C. In addition the German Memory, Patent Application P 196 11 646.5, without publishing the priority date of the present description, discloses a bicomponent, aqueous polyurethane coating composition suitable for coating plastics. The use of polyurethane resins modified as monoisocyanate as rheology control additives, on the other hand, is not described in said document. It also discloses German Patent Application P 196 06 783.9, without publishing on the priority date of the present description, polyurethane resins and its use as an additive for aqueous coating materials in order to increase the stability of the rheology. On the other hand, polyurethane resins, modified with monoisocyanate, are not described in said document. Accordingly, it is the object of the present invention to provide suitable polyurethane resins as an additive, especially in aqueous coating compositions, in which they can be used to control viscosity. As far as possible, such polyurethane resins should also function as a binder component in such compositions. Particularly these polyurethane resins and especially when used in aqueous bicomponent polyurethane coating compositions and with particular preference when used in the transparent coatings, should lead to coatings having a good appearance (for example a high degree of gloss and a glossiness). or low turbidity). At the same time, the resulting coating compositions should exhibit a minimal tendency to run or bleed, after application. Above, coating compositions prepared with the use of these polyurethane resins should show good wetting of the base coat when they are used as a clear coat to produce a multiple coat paint system. In addition, in the case of the two component coating compositions, the binder component (I) of the coating composition must have a very long stability during storage. Finally, in the area of plastic coatings, there is an additional requirement that the coating compositions employed be curable at low temperatures (generally below 100 ° C) and even when cured at these low temperatures, leading to films possessing the desired properties. This object is surprisingly achieved by a polyurethane resin (P) which can be obtained by the following (A) in a first reaction step (A) reacting (a) one or more diisocyanates and / or polyisocyanates, (b) one or several compounds (b) having at least one group that ensures dispersibility in water and more than one group that is reactive towards the isocyanate groups, and (c) if desired, one or more compounds that have at least one 2 and not more than 3 OH groups, to generate an intermediate product (A) having free isocyanate groups and urethane groups, (B) in a second reaction step (B) add (d) one or more monoisocyanates to the intermediate product (A) obtained in step (A), and (C) subsequently reacting the resulting mixture (B) with one or more polymers and / or oligomers (D) containing hydroxyl to render the polyurethane resin (P), using less than 20% by weight, based on the weight of the polyurethane resin (solid content), of polyalkylene oxide diols and / or polyalkylene oxide polyols in order to prepare the polyurethane resin. The invention further provides processes for preparing these polyurethane resins and coating compositions, especially aqueous, bicomponent polyurethane compositions, comprising the polyurethane resin, to make possible the use of these coating compositions and the use of the polyurethane resin as a additive for the control of rheology. It is surprising and it could not be foreseen that the polyurethane resins act as a binder component and that they possess at the same time controlling properties of the rheology, thus promoting the formation of transparent coating films with a high degree of homogeneity. Another advantage is that polyurethane resins, especially used in aqueous, bicomponent polyurethane coating compositions, preferably when used in transparent coatings, lead to coatings having a good appearance (for example a high degree of gloss and a low gloss). turbidity level) in combination with a minimal tendency to shift. In addition, the compositions prepared with the use of these polyurethane resins exhibit a good degree of wetting of the base layer when used as a transparent coating in order to produce a multiple coating paint system. In addition, the binder component (I) of the coating composition - in the case of bicomponent coating compositions - possesses stability over long storage times. Finally, it is also advantageous that the coating compositions used can be cured at low temperatures (generally at less than 100 ° C) and that even when cured at these low temperatures, they lead to films having the desired properties. The preparation of the polyurethane resin (P) of the invention involves the following (A) in a first reaction step (A) reacting (a) one or more diisocyanates and / or polyisocyanates, (b) one or more compounds (b) having at least one group that ensures dispersibility in water and more than one group that is reactive towards the isocyanate groups, and (c) if desired, one or more compounds which they have at least 2 and not more than 3 OH groups, to generate an intermediate product (A) that has free isocyanate groups and urethane groups. As suitable multifunctional isocyanates (A) for preparing the polyurethane (P) resins, mention may be made of aliphatic, cycloaliphatic and / or aromatic polyisocyanates having at least two isocyanate groups per molecule, preference being given to the use of isocyanates whose urethanes they are capable of forming allophanates. The isomers or mixtures of isomers of the organic diisocyanates deserve the preference. On the basis of their good stability to ultraviolet light, (cyclo) aliphatic diisocyanates give rise to products that have a low tendency towards yellowing. The polyisocyanate component used to form the polyurethane resin can also include a polyisocyanate fraction of a higher functionality, as long as no gelation is caused thereby. The products, which have been found to be suitable as triisocyanates, are those formed by trimerization or oligomerization of the diisocyanates or by reaction of the diisocyanates with the polyfunctional compounds containing OH or NH groups. The average functionality can be reduced, if desired, by the addition of monoisocyanates. Examples of the polyisocyanates that can be used are phenyl diisocyanate, toluene diisocyanate, xylylene diisocyanate, bisphenylene diisocyanate, naphthylene diisocyanate, diphenylmethane diisocyanate, isophorone diisocyanate, propylenecyclohexyl isocyanate, cyclobutane diisocyanate, cyclopentene diisocyanate. diisocyanate, cyclohexylene diisocyanate, methylcyclohexylene diisocyanate, dicyclohexylmethane diisocyanate, ethylene diisocyanate, trimethylene diisocyanate ylene tetrame diisocyanate ylene pentamet diisocyanate, hexamethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, propylene diisocyanate, ethylethylene , as well as the trimethylhexane diisocyanate and derivatives thereof. Preference is given to the use of hexamethylene diisocyanate, isophorone diisocyanate, isocyanatopropylcyclohexyl diisocyanate, and the 4,4'-dicyclohexylmethanediyl diisocyanate. Generally speaking, polyurethanes are not compatible with water unless certain specific components are incorporated and / or certain preparation steps are carried out during their synthesis. Thus, for preparing the polyurethane (P) resins according to the present invention, compounds (b) containing more than one isocyanate-reactive group as well as at least one group that ensures dispersibility in water are used. Suitable groups of this class are nonionic groups "(for example polyethers), groups capable of forming anions, mixtures of these two groups or also those groups capable of forming cations, preferably groups capable of forming anions.

On the other hand, within this context it is equally important not to incorporate too large a number of ether groups in the polyurethane resin. Therefore, the polyurethane resin is prepared using less than 20% by weight, based on * the weight of the polyurethane resin (solid content) of polyalkylene oxide dyes and / or polyalkylene oxide polyols. Further preference is given to the use of the polyalkylene oxide diols and polyols having an average number-average molecular weight of less than 2000. Particular preference is given to the fact that basically polyalkylene oxide diols or polyalkylene oxide polyols are not used. to prepare the polyurethane resins (P). Therefore it is It is possible in a preferred embodiment to incorporate such an acid number in the polyurethane resin that the neutralized product can be dispersed in a stable form in the water. This is done using compounds that contain more than one isocyanate-reactive group and at least one group capable of forming anions. Particularly suitable isocyanate-reactive groups are the hydroxyl groups and also. the primary and / or secondary amino groups. The groups capable of forming anions are in particular the carboxyl groups sulfonic acid and / or phosphonic acid. Preference is given to the use of alkanoic acids having two substituents on the alpha carbon atom. The substituent can be a hydroxyl group, an alkyl group or an alkylol group. These polyols possess at least one group and generally from 1 to 3 carboxyl groups in the molecule. They have from 2 to 25 approximately and preferably from 3 to 10 carbon atoms. It is preferable to use dihydroxyalkanoic and / or polyhydroxyalkanoic acids and very particularly preference is given to the use of dimethylolpropanoic acid and dimethylolbutanoic acid. Compound (b) can -constitute from 1 to 25% by weight, preferably from 1 to 20% by weight, of the total polyol constituent (i.e., including component (D)) in the polyurethane resin (P) . The amount of ionizable carboxyl groups, which are available in salt form as a result of the neutralization of the carboxyl groups, is generally at least 0.4% by weight, preferably at least 0.7% by weight, based on the solids. The upper limit is of the order of 12% by weight. The amount of dihydroxyalkanoic acids in the non-neutralized pre-polymer produces an acidity of at least 5 mg KOH / g, preferably a minimum level of 10 mg KOH / g. At very low acid levels, it is generally necessary to take additional measures in order to achieve dispersibility in water. The upper limit with respect to the acid number is 150 mg KOH / g, preferably 40 mg KOH / g, based on the solids. The acidity is preferably in the range of 20 to 40 mg KOH / g. All compounds which are commonly used and which possess at least 2 and not more than 3 OH groups are suitable as the alcohol component (c) ~ preference is given to the use, as component (c) of compounds with a low molecular mass, although it is also conceivable to use holigomeric and / or polymeric compounds, only in combination with compounds of a low molecular mass. Therefore preference is given as component (c) to the use of compounds having an average numerical molecular weight of from 60 to 600 and preferably up to 400 at maximum and / or with a hydroxyl number from 10 to 1800 and from preference between 50 and 1200 mg KOH / g. As examples of suitable compounds (c) mention may be made of trimethylolethane, trimethylolpropane, glycerol, trisydroxyethyl isocyanurate, 1,2,4-butanetriol, the propanes triols and the hexanotriols. The polyols (c) can be used alone or as a mixture. The preference is given to the use of trimethylolpropane. Intermediates (A) containing isocyanate and urethane can be prepared by reacting the polyols (C) and the compounds (b) with an excess of polyisocyanates (A) at temperatures up to 150 ° C, preferably between 50 and 130 ° C, in organic solvents that can not react with isocyanates. As solvents in this first stage of the process it is thus possible to use, for example, ketones, ethers or ethers having terminal ester groups such as for example ethylexypropionate, or also N-methylpyrrolidone and the like. For the preparation of intermediate (A) the proportion of the equivalents of the NCO groups of the compound (a) with respect to the OH groups of the compounds (b) and (c) is usually between 4.0 and 1.0 and >; 1.0: 1.0 and preferably between 3.0: 1 and 1.8: 1. In a second reaction step (B), the intermediate product (A) obtained in the first stage and containing isocyanate and urethane groups is mixed with 1 or more monoisocyanates (d) to form the mixture (B). All monoisocyanates commonly used are - suitable as the monoisocyanate (d) although it is preferable to use the monoisocyanates which are not highly volatile at room temperature, namely having a boiling point of preferably more than 50 ° C. As examples of suitable monoisocyanates, mention may be made of cycloaliphatic monoisocyanates, such as, for example, cyclohexyl isocyanate and cyclopenylisocyanate, and also aliphatic monoisocyanates, such as, for example, dodecylisocyanate, isodecylisocyanate, lauryl isocyanate and stearyl isocyanate. Stearyl isocyanate is used preferentially. The reaction with the monoisocyanate usually takes place at temperatures up to 150 ° C, preferably between 50 and 130 ° C, in organic solvents that can not react with the isocyanates. The catalysts, such as dibutyltin diraulate, zinc stearate, tin oxide, etc. They can be used equally for this reaction. Examples of solvents that can be used in this first stage of the process are again ketones, ethers or those ethers having terminal ester groups, such as for example ethyl ethoxypropionate, or N-methylpyrrolidone and the like. In order to prepare the mixture (B), the ratio of the NCO group equivalents of the monoisocyanates (d) to the urethane groups of the intermediate group (A) is preferably between 1: 1 and 0.5: 1. In the high stage of the reaction (C), the mixture (B) is subsequently reacted with one or more oligomers and / or polymers (D) containing hydroxyl in order to form the polyurethane resin (P). In this context it is preferred to use the hydroxyl-containing polymers (D) having an OH number from 100 to 1800 mg KOH / g, with particular preference for the amount of 120 to 1200 mg KOH / g, and with very high preference. in particular towards the levels of 180 to 800 mg of KOH / g, and with numerical molecular weight on average located between 500 and 3000, with particular preference for the level of 750 to more than 2000 and / or with a degree of branching from 2 As polymer and / or oligomer (D) it is possible to use in particular those polyesters containing hydroxyl, alkyd resins, polyethers, polyacrylate resins, polyurea resins, polyurethane resins and / or polycarbonate resins. In order to obtain a polyurethane resin with high flexibility it is necessary to use as polymer (D) a high proportion of a linear polyol predominantly having a preferred OH number of 30 to 150 mg KOH / g. Up to 97% by weight of the total polyol used to prepare the polyurethane (P) (ie the components (b), (c) and (D)) can consist of polyesters and / or polyethers of saturated or unsaturated type which have an average numerical molecular weight of Mn equivalent to 400 to 5000 dalton. The selected polyether diols should not introduce excessive amounts of ether groups any time the formed polyols otherwise swell in the water. The polyester diols are prepared by esterifying the organic dicarboxylic acids or their anhydrides with organic diols or deriving from a hydroxycarboxylic acid or a lactone. In order to prepare the branched polyester polyols it is possible to use polyols or polycarboxylic acids having a higher functionality to a lesser degree. The proportions of components (a) to (d) and (D) can be chosen within broad limits and as a function of the reaction components. However, such proportions are selected in such a way that the polyurethane resin (P) has the desired characteristic numbers. In the context of these numbers, preferably the polyurethane resin (P) will have an acidity of from 20 to 40 mg KOH / g, preferably between 25 and 35 mg KOH / g, and / or OH number from 60 to 60. 300 mg of KOH / g, preferably between 1500 and 5000. If the polyurethane resin contains hydrophilic groups (such as for example ether groups) also the polyurethane resin can have an acidity of minus 20 mg KOH / g, down to a level of 1 mg KOH / g. As the component (D) in step (C) for preparing the polyurethane (P) resins of the invention, a very particular preference is given to the use of a polycondensation product formed from (kl) from 10 to 45 mol% of at least one diol, (k2) from 5 to 50 mol% of at least one polyol having at least 3 OH groups per molecule, (k3) from 35 to 47 mol% of at least one dicarboxylic acid and / or polycarboxylic, alone or in combination COELU? monocarboxylic acid, and (k4) from 0 to 20 mol% of at least monool, the sum of the molar percentage of the components (kl) up to (k4) being in each case equivalent to 100 mol%, while the product of preferably condensation can be obtained in this case by subjecting the components (kl) to (k4) to a condensation reaction until the reaction product (D) has an acidity of 1 to 10 mg KOH / g. The polymers (D) used with particular preference are obtained when the components are used (kl), (k2), (k3) and (k4) are used in molar ratios such that the sum of the building blocks of OH (kl), (k2) and (k4) in general terms and the sum of the blocks of construction of COOH (k3) are within the ratio of_ 0.8: 1 to 1.6: 1. As examples of the psychoboxylic acids which can be used as the component (k3), mention may be made of aliphatic and cycloaliphatic aromatic polycarboxylic acids. It is preferred to use aromatic and / or aliphatic polycarboxylic acids as component (k3). Examples of suitable polycarboxylic acids include are italic acid, isophthalic acid, terephthalic acid, alphtalic acids such as tetrachlorophthalic acid and tetrabromophthalic acid, adipic acid, glutaric acid, azelaic acid, cebasic acid, fumaric acid, maleic acid, trimellitic acid, pyromellitic acid, iodine tetrahydrof acid, hexahydrofonic acid, 1,2-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 4-methexydhexahydrophthalic acid, endomethylenetetrahydrophthalic acid, tricyclodecanedicarboxylic acid, endoethylenehexahydrofonic acid , camphoric acid, cyclohexanetetracarboxylic acid, cyclobutanetetracarboxylic acid, etc. The cycloaliphatic polycarboxylic acids can be used either in their cis form or in their trans form and as a mixture of both forms. Also suitable are the esterifiable derivatives of the polycarboxylic acids mentioned above, such as, for example, their monoesters or polyesters with aliphatic alcohols having 1 to 4 carbon atoms or hydroxy alcohols having 1 to 4 carbon atoms. It is also possible to use the anhydrides of the acids mentioned above, as long as they exist. Examples of suitable diols (kl) for preparing the polyester (D) are ethylene glycol, propanediols, butanediols, hexanediols, neopentyl glycol-hydroxypivalates, neopentyl glycol, diethylene glycol, cyclohexanediol, cyclohexanedimethanol, trimethylpentanediol and ethylbutylpropanediol. Also suitable are aliphatic polyether diols, such as linear or branched poly (oxyethylene) glycols, poly (oxypropylene) glycols and / or poly (oxybutylene glycols) glycols., as well as mixed polyether diols such as, for example, poly (oxyethyleneoxypropylene) glycols. The polyether diols usually have a molar mass Mn from 400 to 3000. The diols used can also include, above, aromatic or alkylaromatic diols such as, for example, 2-alkyl-2-phenyl-1,3-propanediol, the biphenol derivatives with ether functionality, etc. Other suitable diols also include the esters of the hydroxycarboxylic acids with diols in which case the diol used can be any of the diols mentioned above. Examples of hydroxycarboxylic acids are hydroxypivalic acid or dimethylolpropanoic acid or dimethylolbutanoic acid. The diols can be used alone or also as a mixture of different diols. Examples of suitable polyols as a component (k2) are: ditrimethylolpropane, trimethylolethane, trimethylolpropane, glycerol, pentaerythritol, homopentaerythritol, dipentaerythritol, trishydroxyethyl-isocyanate, 1,2,4-butanetriol, the triols of propane and of hexane, as well as trihydroxycarboxylic acids, such as trihydroxymethyl (ethyl) ethanoic acids. The polyols having at least 3 OH groups can be used alone or in the form of a mixture. If desired, the triols can be used together with the monohydric alcohols (k4), for example butanol, octanol, lauryl alcohol, cyclohexanol, tertiary butyl cyclohexanol as the ethoxylated and / or propoxylated phenols.

The polyesters (D) are prepared with the known esterification methods as described for example in German specification DE-A-40 24 204, page 4, lines 50 to 65. This reaction usually occurs at temperatures between 180 and 280 ° C. in the presence or absence of a suitable esterification catalyst such as, for example, lithium octoate, dibutyltin oxide, dibutyltin dilaurate, para-toluenesulfonic acid and the like The preparation of polyesters (D) is carried out usually in the presence of small amounts of a suitable solvent as entraining agent Examples of entraining agents used are aromatic hydrocarbons, especially xylene and (cyclo) aliphatic hydrocarbons, such as cyclohexane. polyesters without solvent (mass reaction) The condensing reaction is carried out preferably to a degree of conversion such that the reaction mixture n has an acidity of from 1 to 10 and preferably between 1 and 5. Before its further reaction with the mixture (B) it is diluted to the resulting polyester (D) at a solid content of 50 to 90% with a solvent which advantageously does not participate in the reaction. Suitable solvents include glycol ethers such as ethylene glycol dimethyl ether, glycol ether esters, such as ethyl glycol acetate, butyl glycol acetate, 3-methoxy-n-butyl acetate, butyl diglycol acetate, methoxypropyl acetate, esters, butyl acetate, isobutyl acetate, amyl acetate, ketones such as methyl ethyl ketone, methyl isobutyl ketone, diisobutyl ketone, cyclohexanone and isophorone. There is also the possibility of using aromatic hydrocarbons, such as xylene and aliphatic hydrocarbons. In the reaction step (C) the polyester (D) and if appropriate, the other polymers (D) are reacted or reacted in a manner known per se with the mixture (B) containing isocyanate groups, i.e. Uretaniza (D). The urethanization reaction is preferably carried out to a high degree of conversion; the isocyanate content of the reaction product obtained is preferably below 0.5 and in particular below 0.1%. The polyurethane (P) obtained in this way can be used in the form of the organic solution or otherwise as an aqueous dispersion. To prepare the aqueous dispersion, the reaction mixture is neutralized with a base afterwards. { s give the reaction (C). For neutralization it is possible to use ammonia and / or amines (especially alkylamines), amino alcohols and cyclic amines, diethylamine and triethylamine, dimethylaminoethanolamine, diisopropanolamine, morpholine, or an N-alkyl-morpholine. Highly volatile amines are preferred for neutralization. After the reaction, the reaction product thus obtained can be further processed and formulated in a known manner. Preferably, after the reaction, the reaction mixture is first diluted with water and the organic solvent is removed under reduced pressure. The solid content of the mixture can be adjusted with water. It is preferably adjusted to a solid content from 35% to 65%. The pH of the resulting dispersion is between 6.4 and 7.5. The resulting polyurethane resin (P) according to the invention is eminently suitable for serving simultaneously as a binder., and as a rheology control additive for coating compositions, especially as an additive for aqueous coating compositions, such as coating materials, held in water of type 1K (ie monocomponent), the coating materials held in the water of type 2K (bicomponents) and those coating materials, held in the water, which are physically dried. With particular preference, the polyurethane resin of the invention is used as an additive for aqueous polyurethane coating compositions (1K, 2K, and physical drying). On a preferential basis, polyurethane resin is used as an additive for transparent coatings and top coatings, especially for the coating of plastics. The polyurethane resin (P) according to the present invention is used with particular preference in aqueous bicomponent polyurethane coating compositions comprising a component (I) and a component (II) and in which the component (I) comprises (1-1) one or more polyurethane resins (P) according to the invention, (1-2) one or more water-soluble or water-dispersible copolymers of acrylate, which contain hydroxyl groups and acid groups that can be converted in the groups of corresponding acid anions and / or acrylated polyesters and / or acrylated polyurethanes which "have an OH number from 40 to 200 mg KOH / g, and an acidity from 5 to 150 mg KOH / g, and (1-3) if desired, one or more additional polymers and component (II) comprises a polyisocyanate component as a crosslinking agent, the mentioned components (1-1) to (1-3) and the crosslinking agent being used. in amounts such that the ratio of equivalents of the hydroxyl groups of the components (1-1) to (1-3) to the isocyanate groups of the crosslinking agent is between 1: 2 and 2: 1, preferably between 1: 1.2 and 1: 1.5. " Aqueous, bicomponent polyurethane coating compositions of this kind are described, for example, in German Patent Application P 196 11 646.5, which has not been published on the priority date of the present disclosure. As the acrylate copolymer, (1-2) containing hydroxyl groups and acid groups, all acrylate copolymers having OH numbers of from 40 to 200 mg KOH / g, acid from 5 to 150 mg KOH are suitable. g and preferably with numerical molecular weights on average from 1,000 to 30,000 and with particular preference from 1,000 to 15,000. As the component (1-2) it is preferred to use the acrylate copolymers obtainable by polymerizing in an organic solvent or a mixture of solvents and in the presence of at least one polymerization initiator: a) a (meth) acrylic ester which is different from, but which can be copolymerized with (a2), (a3), (a4), (a5) and (aß) and which remains essentially free of acid groups or a mixture of such monomers, a2) an ethylenically unsaturated monomer which is different from (a5) and which can be copolymerized with (a), (a3), (a4), (a5) and (a6), which carries at least one hydroxyl group per molecule and which remains essentially free of acid groups or a mixture of such monomers, a3) an ethylenically unsaturated monomer which is copolymerizable with (a), (a2), (a4), (a5) and (a6) and which carries per molecule at least one acid group which can be converted into the corresponding acid anion group, or a mixture of such monomers, and a4) if so desired, one or more vinyl esters of the alpha-branched monocarboxylic acids possessing from 5 to 18 carbon atoms per molecule and / or a5) if desired, at least one reaction product of acrylic acid and / or acid methacrylic with the glycidyl ester of an alpha-branched monocarboxylic acid having from 5 to 18 carbon atoms per molecule or, in place of the reaction product, an equivalent amount of acrylic acid and / or methacrylic acid which is then reacted during or after of the polymerization reaction with the glycidyl ester of an alpha-branched monocarboxylic acid having from 5 to 18 carbon atoms per molecule, a6) if desired, an ethylenically unsaturated monomer which is different from (al), (a2) , (a4) and (a5) and which is copolymerizable with (al), (a2), (a3), (a4) and (a5) and which remains essentially free of acid groups or a mixture of such monomers, the character being selected and the amount of (al), (a2 ), (a3), (a4), (a5) and (a6) in such a way that the polyacrylate resin has the desired OH number, the appropriate acid number and the desired molecular weight. In order to prepare the polyacrylate resins used according to the invention it is possible to use as component (a) any ester of (meth) acrylic acid which is copolymerizable with (a2), (a3), (a4), (a5) and (a6) and which remains essentially free of acid groups, either the ethoxylated or propoxylated derivatives of such ester, or a mixture of such monomers. As component (a2) it is possible to use ethylenically unsaturated monomers which are different from (a5) and which are copolymerizable with (a), (a3), (a4), (a5) and (a6), which carry at least one hydroxyl group per molecule and which remain essentially free of acid groups or a mixture of such monomers. Examples are the hydroxyalkyl esters of acrylic acid, methacrylic acid or another ethylenically unsaturated carboxylic acid of the alpha, beta type. These esters can be derived from an alkylene glycol, which has been esterified with the acid, or can also be obtained by zreacting the acid with an alkylene oxide. As component (a2) it is preferred to use the hydroxyalkyl esters of acrylic acid or methacrylic acid in which the hydroxyalkyl group contains up to 20 carbon atoms, the reaction products of the cyclic esters, such as epsilon-caprolactone, for example, with these hydroxyalkyl esters , or the mixtures of these hydroxyalkyl esters and / or the hydroxyalkyl esters modified with epsilon-caprolactone In addition, it is possible to use as the component (a2) the olefinically unsaturated polyols and / or the trimethylolpropane monoallyl ether. the possibility of using any ethylenically unsaturated monomer carrying at least one acid group, preferably a carboxyl group per molecule and which can be copolymerizable with (a), (a2), (a4), (a5) and (a6), or a mixture of such monomers The particular preference is given to the use as component (a3) of acrylic acid and / or methacrylic acid. It is possible to use, for example, sulphonic or phosphonic, ethylenically unsaturated acids and / or their partial esters as component (a3). As the component (a4), one or several vinyl esters of the alpha-branched monocarboxylic acids having 5 to 18 carbon atoms in the molecule are used. Due to its immediate availability a particular preference is given to the use of vinyl esters of saturated aliphatic monocarboxylic acids having 9 to 11 carbon atoms and which are branched on the alpha-carbon atom. The reaction product of acrylic acid and / or methacrylic acid with the glycidyl ester of an alpha-branched monocarboxylic acid having 5 to 18 carbon atoms per molecule is used as component (a5). The glycidyl esters of the highly branched monocarboxylic acids are commercially available under the tradename "Cardura". The reaction of the acrylic acid or methacrylic acid with the glycidyl ester of a carboxylic acid having a tertiary alpha-carbon atom can take place before, during or after the polymerization reaction. As component (a6) it is possible to use all ethylenically unsaturated monomers, or mixtures of such monomers which are copolymerizable with (a), (a2), (a3), (a4) and (a5) and which are different from (a), (a2), (a3) and (a4) and that are essentially free of acid groups. As component (a6) it is preferred to use vinylaromatic hydrocarbons, such as styrene, alpha-alkylstyrenes and vinyltoluene. The polysiloxane macromonomers can also be used as the (aß) component, in combination with other monomers specified as being suitable for use, the (aß) component. Suitable polysiloxane macromonomers are, for example, those having an average numerical molecular weight, Mn, from 1000 to 40,000 daltons, preferably from 2,000 to 10,000 daltons, and which on average have from 0.5 to 2.5, preferably from 0.5 to 1.5. ethylenically unsaturated double bonds per molecule. Suitable examples are the polysiloxane macromonomers described in German specification DE-A 38 07 571 on pages 5 to 7, in the German report DE-A 37 06 095 in columns 3 to 7, in European patent EP-B 358 153 on pages 3 to 6, as well as in the Patent US-A 4,754,014 in columns 5 to 9. The amounts of the polysiloxane macromonomers (aβ) which are used to modify the acrylate copolymers are less than 5% by weight, and are preferably between 0.05% and 2.5% by weight, with particular preference for the range of 0.05 to 0.8% by weight, based in each case on the overall weight of the monomers used to prepare the copolymer. The acrylate resins used with particular preference are obtained by polymerizing (al) from 20% to 60% by weight, preferably from 30% by weight. 50% by weight of component (a), (a2) from 10% to 40% by weight, preferably from 15% to 35% by weight of component (a2), (a3) from 1% to 15% by weight, preferably from 2% to 8% by weight of component (a3), (a4) from 0% to 25% by weight, preferably 5% by weight % by weight of component (a4), (a5) from 0% to 25% by weight, preferably from 5% to 15% by weight of component (a5), and (aß) from 5% to 30% by weight , preferably from 10% to 20% by weight of the component (aß), the sum of the fractions by weight of the components (a) to (aβ) in each case being 100% by weight.

The polyacrylate resins (1-2) used according to the invention are prepared in an organic solvent or in a mixture of solvents and in the presence of at least one polymerization initiator. In this context it is also possible to first prepare the polyacrylate resins in a solvent which can not be diluted in water and, if desired, to partially replace this solvent with a solvent soluble in water after the polymerization. The initiators are preferably used in an amount of 2% to 25% by weight, particularly preferably in the range of 4 to 10% by weight based on the overall weight of the monomers. The polymerization is carried out with intelligent criteria, at a temperature of 80 to 160 ° C, and preferably in the range of 110 to 160 ° C. Preferably, the polyacrylate resin is prepared in a process consisting of two steps, since in this way the resultant aqueous coating compositions have a better processability. It is therefore preferred to use the polyacrylate resins that can be obtained by 1. polymerising a mixture of (a), (a2), (a4), (a5) and (aß), or a mixture of the component portions (a), (a2), (a4), (a5) and (aß) in an organic solvent, 2. then at a minimum of 60% by weight of the mixture consisting of (a), (a2), ( a4), (a5) and if present (aß), adding after the previous addition (a3) and then any remaining components (al), (a2), (a4), (a5) and (aß) ) to continue the polymerization and 3. after completion of the polymerization, subject the resulting polyacrylate resin, if desired, to at least partial neutralization, ie, converting the acid groups to the corresponding acid anion groups. But additionally, it is also possible to introduce the components (a4) and / or (a5) together with at least a portion of the solvent, as an initial charge and to be dosed in the other components. The components (a4) and / or (a5) can also be included only partly in the initial charge, together with at least a portion of the solvent, and the rest of these components can be added in the manner described above. Preferably, for example, at least 20% by weight of a solvent and about 10% by weight of the components (a4) and numerical molecular averages, Mn, between 1000 and 50000 dalton, more preferably between 1000 and 15000 dalton , values measured in each case compared to a polystyrene standard. The acrylated polyurethanes used as the component (1-2) are also known. Suitable acrylated polyurethanes are described, for example, in DE-A-41 22 2ß5, page 2, row 15 to page 5, row 44; DE-A-40 10 176, page 2, row 41 to page 6, row 64; EP-A-308 115, page 2, line 29 to page 5, line 21; EP-A-510 572, page 3, line 21 to page 5, line 42; and US -A-4, 496, 708, column 4, row 5 to column 12, line 46. Suitable components such as component (1-3) for preparing the coating compositions according to the invention are for example all the water-soluble or water-dispersible polyester resins containing hydroxyl groups and acid group which can be converted to the corresponding acid anion groups, preferably those polyester resins having an OH number from 30 to 250 mg KOH / g, preferably particular to the range of 60 to 200 mg of KOH / g and an acidity of 5 to 150 mg of KOH / g with particular preference to the range of 15 to 75 mg of KOH / g and with a very particular preference to the range of 20 to 50 mg of 39 KOH / g. These polyester resins preferably have numerical molecular weights on average, Mn, from 500 to 30,000 daltons, with particular preference for the range of 1000 to 10,000 dalton and very particularly preferably for the range of 1000 to 5000 dalton, which in each case is measured compared to a standard or polystyrene standard. It is preferred to use the branched polyesters. Preference is given to the use of the polyesters obtainable by reacting the dicarboxylic and / or polycarboxylic acids or their esterifiable derivatives, alone or in combination with the monocarboxylic acids, p2) the diols p3) the polyols, alone or in combination with the monooles and p4) in each desired, other modifying components. A particular preference is given within this context to the use of polyesters that have been prepared without the use of monooles or monocarboxylic acids. Similarly and with particular preference it is pointed out that the polyesters are free of unsaturated fatty acids. With reference to the compounds (pl) to (p3) suitable for preparing the polyesters, it can be 40 (a5) and if desired, portions of the components (al) and (a6) are included in the initial charge. Equally deserving is the preparation of the polyacrylate resins by a two-stage process in which stage (I) lasts from 1 to 8 hours, preferably from 1.5 to 4 hours, while the addition of the mixture of (a3) and any remaining components (al), (a2), (a4), (a5) and (a6) are effected in the course of 20 to 120 minutes, preferably in a time of 30 to 90 minutes. At the end of the addition of the mixture of (a3) and any other components (a), (a2), (a4), (a5) and (aß), the polymerization is continued until all the monomers used have undergone a fundamentally complete reaction. The amount and rate of addition of the initiator is preferably chosen so as to give a polyacrylate resin having the desired numerical molecular weight on average. It is preferred to start feeding the initiator at a certain time, generally about 15 minutes before feeding the monomers. In addition, preference is given to a process in which addition of the initiator is started at the same time as addition of the monomers and ending approximately half an hour after completion 36 the addition of the monomers. The initiator is preferably added in a constant amount per unit of time. After the addition of the initiator, the reaction mixture is maintained at the polymerization temperature (generally 1.5 hours) until all the monomers used have undergone a virtually complete reaction. The term "virtually complete reaction" should mean that preferably 100% by weight of the monomers employed have gone into reaction but that it is also possible that a small residual monomer content of not more than 0.5% by weight, based on in the weight of the reaction mixture, which has remained unreacted. Preferably, the monomers for preparing the polyacrylate resins are polymerized with a not too high polymerization solid content, preferably with a solid polymerization content of 80% to 50% by weight and then the solvents are partially removed by distillation so that the resulting solutions of the polyacrylate resin have a solid content of preferably 80% to 60% by weight. Also suitable as component (1-2) are acrylated polyesters having an OH number from 40 to 200 mg KOH / g, with particular preference 37 to the range of 60 to 160 mg of KOH / g, and with an acidity of 5 to 150 mg of KOH / g, preferably a range of 15 to 75 mg of KOH / g and particularly preferably an amount of 20 to 50 mg of KOH / g. Preferably, acrylate polyesters have numerical molecular weights in-average Mn, of between 1000 and 50,000 daltons, more preferably between 1000 and 15,000 dalton, amounts that in each case are measured against a norm or polystyrene standard. The polyesters used as component (I-2) are known. Suitable acrylate polyesters can be prepared using various methods known to those skilled in the art: for example by incorporation of the triraethylol monoallyl ether. propane or maleic anhydride or other maleic anhydride or other reactive anhydrides which can be polymerized with styrene and / or (meth) acrylates, followed by acrylation (organic or aqueous). Also suitable, component (1-2) are acrylated polyurethanes having an OH number of 40 to 200 mg KOH / g, with particular preference for the range of 60 to 160 mg KOH / g, and an acidity of 5 to 10 mg. to 150 mg of KOH / g, preferably between 15 and 75 mg of KOH / g and with particular preference of 20 to 50 mg of KOH / g. Preferably the acrylated polyurethanes have weights refer to the description of the polymers (D). Particularly suitable compounds as the component (p4) for preparing the polyesters are those which possess a group which is reactive with the functional groups of the polyester. As a modifying component (p4) it is possible to use, for example, the diepoxide compounds, also the monoepoxide compounds, if desired. Suitable components (p4) are described, for example, in DE-A-40 24 204 on page 4 of row 4 to 9. Equally suitable as the component (p4) for preparing polyesters are the compounds which, in addition to having a The group reactive with the functional groups of the polyester has an aminotercial group, examples being monoisocyanates having at least one aminotercial group or mercapto compounds possessing at least one aminotercial group. For further details, the reader is referred to the German report DE-A-40 24 204, page 4, lines 10 to 49. Particular preference is given to the use of polyesters that have been prepared by a two-stage process in which A hydroxyl-containing polyester having an OH number of 100 to 400 mg KOH / g, preferably between 150 and 350 mg KOH / g, an acidity of less than 10 mg KOH / g and a weight is prepared. Molecular number average, Mn, from 500 to 2000 dalton, and then this material is reacted in a second stage with carboxylic anhydrides to give the desired polyester. The amount of carboxylic anhydrides in this case is chosen in such a way that the resulting polyester has the desired acidity. All acid anhydrides commonly used are suitable for this reaction. In addition to this reaction of the carboxylic anhydrides, acidic groups can also be introduced into the polyester by the use of dimethylolpropionic acid and the like. The component (I) of the coating composition can comprise as another constituent (IB) all the usual coating pigments in proportions of 0 to 60% by weight, based on component I. The pigments can consist of organic or inorganic compounds and can be of effect type and / or of type producer of color. As another constituent (I-C), the component (I) and if appropriate, also the binder, can comprise at least one organic solvent, totally or partially soluble in water. Such solvents can also participate in the reaction with the crosslinking component (II) to act as well as the reactive diluent. The solvents (I-C) can also consist, in whole or in part, of oligomeric compounds of low molecular mass, which can be reactive or, if desired, not reactive towards the interlacing component (II). Solvents (I-C) are usually used in an amount from 0% to 20% by weight, preferably in an amount less than 15% by weight, based on the general weight of component (I). Component (I) normally includes as constituent (I-D) at least one neutralizing agent. A particularly preferred neutralizing agent used is dimethylethanolamine. The amount of neutralizing agent used in general terms in the coating composition according to the present invention is chosen such that from 1 to 100 equivalents, preferably from 50 to 90 equivalents, of the acidic groups of the binder (I-A) are neutralized. Component (I), if desired, may comprise as constituent (I-E) at least one additional rheology control additive. Examples of such rheology control additives are entangled polymeric microparticles, inorganic type sheet silicates as well as synthetic polymers possessing ionic and / or associative groups or else urethanes or polyacrylates, ethoxylated, hydrophobically modified. ) preferably includes from 0% to 2% by weight of these additional rheology control additives, based on the overall weight of component (I). Component (I) can further comprise, if desired, at least one usual additive for coatings, of an additional type Examples of such additives are defoamers, dispersion aids, emulsifiers and auxiliaries for leveling Finally, component (I) also includes water The coating component (II) comprises as a crosslinking agent at least one diisocyanate and / or polyisocyanate (Fl), preferably not blocked, which, if desired, is dissolved or dispersed in _1 or several organic solvents, possibly dilutable in water. The polyisocyanate component (Fl) comprises any desired organic polyisocyanate having free isocyanate groups attached to the aliphatic, cycloaliphatic, araliphatic and / or aromatic moieties. Preference is given to the use of polyisocyanates having 2 to 5 isocyanate groups per molecule and viscosities of 100 to 2000 mPas (at 23 ° C). If desired, the polyisocyanates can also be mixed with small amounts of an organic solvent, preferably between 1% and 25% by weight, based on the pure polyisocyanate, in order to thereby improve the ease of incorporation of the isocyanate, and if thus it is desired to reduce the viscosity of the polyisocyanate to a value that falls within the ranges mentioned above. Suitable solvents, additives for the polyisocyanates are, for example, ethoxyethyl propionate, butyl acetate and the like. Examples of suitable diisocyanates are described, for example, in "Methoden der organischen Chemie" Houben-eyl, volume 14/2, 4th edition, Georg Thieme Editorial, Stuttgart 1963, page 61 to 70 and by. Siefken, Liebigs Ann. Chem 562, 75 to 136. Examples of those suitable are the isocyanates (a) mentioned in relation to the description of the polyurethane (P) resins and / or the isocyanato-functional polyurethane prepolymers, which can be prepared by reacting the polyols with an excess of polyisocyanates and that preferably have a low viscosity. It is also possible to use polyisocyanates having isocyanurate and / or biuret groups or allophanate groups and / or urethane and / or urea groups and / or uretadione groups. Polyisocyanates having urethane groups, for example, they are obtained by reacting some of the isocyanate groups with polyols such as trimethylolpropane and glycerol, to mention only two examples. It is preferred to use aliphatic or cycloaliphatic polyisocyanates, especially hexamethylene diisocyanate, dimerized and trimerized hexamethylene diisocyanate, isophorone diisocyanate, 2-isocyanatopropylcyclohexyl-isocyanate, dicyclohexylmethane-2,4'-diisocyanate or dicyclohexylmethane-4, 4 '-diisocyanate or mixtures of these polyisocyanates. A very particular preference is given to the use of the polyisocyanate mixtures which are based on hexamethylene diisocyanates and containing uretadione and / or isocyanurate and / or allophanate groups, as formed by the catalytic oligomerization of hexamethylene diisocyanate with the use of suitable catalysts. The polyisocyanate component (Fl) could also consist of any desired mixture of the exemplified polyisocyanates. In the coating compositions according to the present invention, the polyisocyanate component (Fl) is advantageously used in an amount such that the ratio of the hydroxyl groups of the binder (A) to the isocyanate groups of the interlayer (Fl) is between 1 and 2. : 2 and 2: 1, with particular preference to the range from 1: 1 to 1: 1.5. The two components (I) and (II) of the coating composition according to the present invention are prepared by the usual methods of the individual constituents with stirring. The preparation of the coating composition comprising these two components (I) and (II) takes place similarly by stirring or dispersing with the use of apparatuses that are employed as a rule, for example, by means of dissolvents or the like or by means of the dosing units and bicomponent mixers, commonly employed or by means of the process intended to prepare aqueous, 2K type polyurethane coating materials, which is described in the German specification DE-A-195 10 651, page 2 , line 62 to page 4, line 5. Aqueous coating materials -prepared with the use of the polyurethane resin (P) according to the present invention generally contain in their ready-to-apply condition, from 5% to 14% by weight of the polyurethane resin (P), from 25 to 75%, preferably from 35 to 70% by weight of water, ~ from 0 to 50%, and preferably between 0 and 20% by weight of organic solvents, from 6% to 70% by weight and d and preferably between 15 and 60% by weight of the binders (1-1) to (1-3), preferably between 0 and 25% by weight of pigments and / or fillers and from 0% to 10% by weight of other additives such as, for example, catalysts, thickeners, leveling agents and the like, the percentages by weight in the formulation generally being based on the coating materials in their ready-to-apply state (ie with a viscosity suitable for spraying) and on the solid content of the crosslinking binders and the polyurethane resin (P). Aqueous coating materials according to the present invention can be used to "coat plastics with primary layer or without primary layer such as for example: ABS, AMMA, ASA, CA, CAB, EP, UF, CF, MF, MPF, PF, PAN, P, PC, PE, HDPE, LD ?, ZLLDFE, UHM PE, PET, PMMA, PP, PS, SB, PUR, PVC, RF, SAN PBT, PPE, POM, PUR-RIM, SMC, BMC, PP -EPDM and UP (the abbreviations are in accordance with DIN 7728P1) The plastics that must be coated can be polymer blends, modified plastics or "fiber reinforced" plastics. The coating compositions according to the present invention are preferably used to coat mixtures of PPE / PA, polycarbonate blends (eg PC / ASA, PC / PBT) and polypropylene blends. The coating compositions of the invention are used in particular for those plastics that are commonly used in the construction of vehicles, especially in the construction of automotive vehicles. In the case of the surface of non-functionalized and / or non-polar substrates, this surface must be subjected to a preliminary treatment, such as a plasma or flame treatment, before coating is carried out. Suitable primary layers in this context are all the usual primary layers, both conventional and aqueous. Of course it is also possible to use radiation curable primary coatings and water-curable primary coatings. The coating compositions according to the present invention are used to produce a coating system of a single coating or of multiple coatings, and preferably as clear coatings or as top coatings, in particular as the clear coat of a coat painting system. manifolds that are produced using the wet / on / wet technique. Plastics or other types of substrates can of course also be coated directly with the transparent layer or with the upper layer. Finally, the coating compositions can also be applied to other substrates such as metal, wood or paper or also mineral substrates. They can also be used for coatings of cargo containers - and for packing materials or the like. The application is made with the help of the usual methods, and the examples are spraying, knife coating, dipping, brushing or the roll coating process. The coating compositions of the present invention are usually cured at temperatures below 120 ° C, preferably at temperatures not higher than 100 ° C and very particularly preferably at levels not exceeding 80 ° C. In the specific embodiments of the coating compositions of the invention it is also possible to use higher curing temperatures. The coating compositions of the invention are preferably used to produce the top coatings. The coating compositions of the invention can be used both in the OEM finish as well as in the refinishing of automobile bodies. However, they are preferably used in the re-finishing sector and with particular preference to the sector for coating plastic parts. Finally, the present invention also provides the use of the polyurethane resin described above (P) as a rheology control additive for coating compositions and provides for the use of the resulting coating compositions. In the following text the invention is explained in greater detail with reference to some working examples. In these examples, all parts are by weight unless expressly stated otherwise. 1, Preparation of a dispersion of a polyurethane resin (PI) 1.1 Preparation of a polyester containing hydroxyl (DI) For 1 kilogram of polyester, 128.9 grams of neopentyl glycol, 318.9 grams of neopentyl glycol hydroxipivalate, 166.0 grams of trimethylolpropane, 205.5 grams of isophthalic acid, 40 grams of xylene and 254.3 grams of hexahydrophthalic were weighed, introducing these materials in a steel apparatus suitable for carrying out the polycondensation reactions, the mixture then being heated in a continuous manner to also continuously remove the condensation water. With an acidity of the product of 3 mg KOH / g, the reaction was terminated and the mixture was cooled to 100 ° C and diluted to 80% solids with methyl ethyl ketone (MEK) (viscosity with 50% strength or intensity). in MEK, 0.2 dPa.s). The condensation product obtained in this way had an OH number of 202 mg KOH / g and an acidity of 3.5 mg KOH / g, in each case based on the solid resin. 1. - repair of a polyurethane resin (P) An amount of 444.4 grams of isophorone diisocyanate, 133.9 grams of dimethylolpropionic acid and 568.0 grams of methyl ethyl ketone were metered and loaded into a suitable steel reactor to effect polyaddition reactions and heated the material to 80 ° C. With a constant isocyanate content of 7.4% based on the mixture used, the mixture was cooled to 50 ° C, 294.7 grams of stearyl isocyanate were added and this mixture was again heated to 82 ° C. Heating is continued at this temperature until a constant value of NCO is obtained. The mixture was then cooled to 50 ° C then 2110 grams of the solution described above of polyester (D1) were added. The mixture was then heated to 8 ° C. With an isocyanate content of less than 0.1% and a viscosity of 3.6 dPas (10: 3 in N-methylpyrrolidone) the mixture was neutralized with 71.2 grams of N, N-dimethylethanolamine. Then it was diluted with water and the organic solvent was removed under reduced pressure Finally a solid content of 49.2% was established with the use of deionized water The pH of a dispersion was 6.8 The dispersion was free of gel spots it was homogeneous and stable during storage at 50 ° C for at least 4 weeks.The DMEA content was 13% and the solvent content was 0%. "Polyurethane resin had an OH number of 99 mg KOH / g, an acidity of 23.4 mg KOH / g and an average numerical molecular weight of 1934 (molecular weight with average weight of 5566), measured against a polystyrene standard and based on solid resin. 2. Preparation of a solution of the polyurethane resin (Pl) This preparation was initially carried out in the same way as for the preparation of the polyurethane resin dispersion but with the difference that the MEK was replaced by isopropoxypropanol by vacuum distillation . A solid content of the 64.9% solution was established using isopropoxypropanol. The product had a pH of 7.4 and a viscosity at 23 ° C of 3.9 dPas (10: 3 in N-methylpyrrolidone). 3. Preparation of a dispersion? Lg a polyurethane resin (PV1) unmodified with monoisocyanate 488.4 grams of meta-tetramethylxylylene-diisocyanate, 134.1 grams of dimethylolpropionic acid and 568.0 grams of methyl ethyl ketone were dosed, loading the materials into a suitable steel reactor to make Polyaddition reactions and the material was heated to 80 ° C. With a constant isocyanate content of 7.4%, based on the mixture used, the mixture was cooled to 50 ° C and 2110 grams of the above-described solution of polyester (D1) were added. Then the mixture was heated to 80 ° C. With an isocyanate content of less than 0.1% and a viscosity of 3.6 dPas (10: 3 in N-met ilpyrrolidone), the mixture was neutralized with 71.2 grams of N, N-dimethylethanolamine. It was then diluted with water and the organic solvent was removed under reduced pressure. Finally, a solid content of 43% was established using deionized water. The pH of the dispersion was 6.8. the dispersion was free of gel spots, was homogeneous and stable during storage at 50 ° C for at least 8 weeks. The content in DMEA was 1.42% and the solvent content was 0.5%. the polyurethane resin had an OH number of 98 mg KOH / g, an acidity of 26 mg KOH / g and an average numerical molecular weight of 1713, measured against a polystyrene standard and based on solid resin. 4. Preparation of a dispersion of - an "acrylate resin A steel vessel with a capacity of 4 liters, equipped with two feeding gates for monomeric material, an initiator feeder gate, stirrer and reflux condenser is charged with 470 parts in weight of n-butanol as solvent component (B2) (solubility in water S: 9.0, evaporation index EVN: 33, boiling point BP: 118 ° C) and heated to 110 ° C. Then a solution of 36 is added parts by weight of tertiary butyl peroxyethylhexanoate in 92.4 parts by weight of n-butanol (B2) at a rate such that the addition lasts more than 5.5 hours The start of the addition of the tertiary butyl peroxyethylhexanoate solution is accompanied by the beginning of the addition of the mixture of (al) to (aß): (al): 240 parts by weight of n-butyl methacrylate, 209 parts by weight of methyl methacrylate, 120 parts by weight of lauryl methacrylate (Methacryl ester 13 from Rohm GMBH), (a2): 270 parts by weight of hydroxyethyl methacrylate, and (aβ): 180 parts by weight of styrene. The mixture of (al), (a2) and (aß) is added at a rate such that the addition is more than 5 hours. A second monomer feed is started, 3.5 hours after starting the first monomer feed, and this last feed is terminated in conjunction with the first monomer feed and consists of a mixture of the monomer components (a2) and (a5): (a2) ): 120 parts by weight of hydroxyethyl methacrylate and (a5): 61 parts by weight of acrylic acid. After the addition of the tertiary butyl peroxyethylhexanoate solution, the reaction mixture is stored at 120 ° C for a further 2 hours. The solution of the resin is then cooled to 80 ° C and neutralized to a degree of neutralization of 85% over the course of about 30 minutes with 63 parts by weight of dimethylethanolamine in 1379 parts by weight of water. The solvent (B) n-butanol is then removed by azeotropic distillation until it can no longer be detected by gas chromatography more than 1% by weight (B), based on the dispersion. After distillation, the dispersion is adjusted to the following final parameters by the addition of deionized water: Acidity of the total solids: 37.2 mg KOH / g, Solid content (1 hour, 130 ° C): 38.3%, PH: 7.40. Dimethylethanolamine content: 2.11%. Solvent content: 0.52%. The acrylate resin prepared in this way had an average numerical molecular weight of 7772 dalton and a molecular weight by weight, on average of 26,651, measured against a polystyrene standard, an OH number in the order of 140 mg KOH / g. an acidity of 37.2 mg KOH / g, based in each case on the solid resin. 5. Preparation of the coating compositions of Examples 1 and 2 and of Comparative Example 1 From the components indicated in Table 1, the coating compositions are prepared by premixing first the polyurethane dispersion described above (Pl) and the dispersion of Acrylate described above by means of stirring for 10 minutes with a laboratory stirrer (500 revolutions per minute). In addition, a solution of additives is prepared from the additives mentioned in Table 1, stirring with a laboratory stirrer. This solution of additives is incorporated into the premix of the polyurethane and acrylate dispersions by means of a stirring for 10 minutes with a laboratory stirrer (500 revolutions per minute), then deionized water is incorporated by stirring for 10 minutes with a laboratory stirrer. (500 revolutions per minute). The existence, that is, the depositing material of the aqueous type, obtained in the manner indicated, has a solid content of 33%. To prepare the transparent coating, the isocyanate solution is incorporated into the aqueous tank coating material, stirring for 5 minutes with a laboratory stirrer (500 revolutions per minute). Finally, the transparent coating is adjusted, that is to say the clear layer, with deionized water until achieving the viscosity indicated in Table 1. 6. Application of the coating compositions and the results of the tests of the resulting coatings The coating compositions prepared from this In this way they are pneumatically applied to PP-type panels (thin film thickness of 30 to 35 micrometers). The panels coated in this manner are suddenly cooled to room temperature for 10 minutes and then baked at 90 ° C for 45 minutes. Then "they are aged for 8 days at 22 ° C and under a relative atmospheric humidity of 50%." Then the free-layer clear films are subjected to different tests.The results of the coatings tests have been summarized in the Table 2. In addition, the coating compositions prepared in this manner are pneumatically applied (thickness of the thin film layer from 30 to 35 microns) to steel panels that were first coated with a commercial surface-coating agent based on polyurethane (Füller FC 60- 7415 from BASF Lacke + Farben AG, Münster) and then with an aqueous based coating based on commercial type polyurethane (FV 95-9416 from BASF Lacke + Farben AG, Münster). The panels coated in this manner are suddenly cooled to a temperature for 10 minutes and then baked at 90 ° C for 45 minutes. They are then aged for 8 days at 22 ° C and under a relative atmospheric humidity of 50%. The clear coating films, free, then undergo different tests. The results of the coatings tests have been summarized in Table 2. Summary of the Test Results Example 1 shows that, by using a polyurethane resin modified with monoisocyanate as another binder, if they obtain transparent coatings that have good appearance (turbidity values) and good wetting on the aqueous base coat (contact angle), and that the resulting coatings also show good gloss. Furthermore, it can be said that the binder components (I) of the example exhibit good stability when stored for at least six months at 23 ° C or at least for 8 weeks at 40 ° C.

Table 1: Composition of the coating compositions of Example 1 and Comparative Example 1 Legend for Table 1: 1): Polyurethane (Pl) dispersion described in section 1. 2): Polyurethane solution (Pl) described in the section 2. 3): polyurethane dispersion (VPl) described in section 3. 4): polyacrylate dispersion described in section 4. 5): 1 (2) - isopropoxy -2 (1) -propanol. ß): 1 (2) -butoxy -2 (1) -propanol. 7): 2-butoxyethyl-acetate. 8): commercial emulsifier based on the polyglycol ether of octylphenol 9) dimethyloligo-siloxane modified by polyether, commercial 10 dimethylpolysiloxane modified with commercial polyether 11): commercial wetting agent based on a heptamethyl-trisiloxane 12): light stabilizer, commercial, based in benzotriazole 13): light stabilizer, commercial, based on a stereo-hindered mine (HALS) 14): aqueous solution with 10% concentration of a commercial thickener based on dialkyl polyglycol-ether 15): water added to adjust the viscosity of the deposit coating material 16): solid content of all binders 17): commercial polyisocyanate (concentration of 80% in ethylexypropionate) based on hexamethylene diisocyanate having an NCO content of 20% 18): ethoxyethyl-propionate 19): water added to adjust the viscosity Table 2: Test Results Legend for Table 2: 1): viscosity of the clear coat at 23 ° C "in mPas s after adjusting to a 30-second effluent time from the cup according to DIN 4, measured with a rate of sizing of 10 s'1 2): measured with the aid of a measuring instrument of the commercial contact angle of Krüs on the steel panels described above under 7, the panels being coated with the surface coating agent, the aqueous base coat and the layers clear 3): brightness at 20 °, measured with the use of the instrument Haze-Gloss by Byk-Gardner on steel panels, as described above in section 7 4): turbidity at 20 °, measured with the use of Byk-Gardner's Haze-Gloss instrument on steel panels, as per described above in section 7 5): appearance of a drop on glass of the coating material in deposit, visually evaluated 6): appearance of a low on glass of the Al component, visually evaluated.

Claims (5)

1. CLAIMS: A polyurethane resin (P) obtainable by (A) reacting in a first reaction stage (A) (a) one or more diisocyanates and / or polyisocyanates, (b) one or more compounds (b) having at least one group that ensure dispersibility in water and more than one group that is reactive towards the isocyanate groups, and (c) if desired, one or more compounds containing at least 2 and not more than 3 OH groups , to produce intermediate agent (A) having isocyanate-free groups and having urethane groups, (B) to add in a second reaction stage (B) (d) one or more monoisocyanates to intermediate (A) obtained in step (A), and (C) then reacting the resulting mixture (B) with one or more polymers containing hydroxyl (D) to provide the resin of polyurethane (P), by using less than 20% by weight, based on the weight of the polyurethane resin (solid content), of polyalkylene oxide diols and / or polyalkylene oxide polyols in order to prepare the resin of polyurethane. A polyurethane resin as claimed in claim 1, which can be obtained by using in the reaction step (C) polymers having hydroxyl (D) having an OH number from 100 to 1800 mg KOH / g and / or oque_ have a number-average molecular weight from 500 to 3000 and / or a degree of branching from 2 to 4. A polyurethane resin as defined in claim 1 or 2, obtainable by use in the reaction step (C) as hydroxyl-containing polymers (D) hydroxyl-containing polyesters, alkyd resins, polyethers, polyacrylate resins, polyurea resins, polyurethane resins and / or polycarbonate resins. 4. A proliurethane resin as defined in any one of claims 1 to 3, obtainable by using in the reaction step (C) as polymers containing hydroxyl (D) the polycondensation products formed from (k) from 10 to 45 mol% of at least one diol, (k2) from 5 to 50 mol% of at least one polyol having at least 3 OH groups, (k3) from 35 to 47 mol% of less a dicarboxylic acid and (k4) from 0 to 20 mol% of at least monool, the sum of the molar percentage of the components (kl) to (k4) in each case being 100 mol% and the condensation product can be obtained "preferably by subjecting the components (kl) to (k4) to a polycondensation reaction until the reaction product (D) has an acidity of from 1 to 10 mg KOH / g 5. A polyurethane resin as defined in US Pat. any of claims 1 to 4, wherein component (a) comprises aliphatic diisocyanates and polyisocyanates and / or cycloaliphatics, isocyanates based on hexamethylene diisocyanate isophorone diisocyanate, isocyanate propylcyclohexyl isocyanate and / or 4,4'-dicyclohexylmethanediyl and / or component (b) comprises dihydroxycarboxylic acids and / or polyhydroxycarboxylic acids and / or the component ( d) comprises aliphatic and / or cycloaliphatic monoisocyanates in preference to stearyl isocyanate. A polyurethane resin as claimed in any of claims 1 to 5, wherein the proportions of the components (a) (b) and (c) in the first reaction step (A) are chosen in such a way that the proportion of the equivalents of the NCO groups of the component (a) with respect to the OH groups of the compounds (b) and (c) is between 4.0: 1.0 and > 1.0: 1.0 and / or the proportions of the components (A) and (d) in the second reaction stage (B) choose in such a way that the proportion of the isocyanate groups of the monoisocyanate (d) with respect to the urethane groups of the component (A) is between 1: 1 and 0.5: 1 and / or in that in the third reaction stage (C) the proportions of the components (B) and (d) are chosen in such a way that the polyurethane resin ( P) essentially no longer contains free isocyanate groups. A polyurethane resin as defined in any of claims 1 to 6, wherein the polyurethane resin (P) has an acidity of from 20 to 40 mg KOH / g, preferably between 25 and 35 mg KOH / g and / or an OH number from 60 to 300 mg KOH / g, preferably between 80 and 200 mg KOH / g and / or a number average molecular weight from 1000 to 10,000 and preferably between 1500 and 5000. A process for preparing a polyurethane resin as defined in any of claims 1 to 7 , which comprises reacting in a first reaction step (A) (a) one or more diisocyanates and / or polyisocyanates, (b) having at least one group that ensures dispersibility in water and more than one group that is reactive with isocyanate groups, and (c) if so desired one or more compounds having at least 2 and not more than 3 OH groups, to give an intermediate agent (A) having free isocyanate free groups and having urethane groups , (B) add in a second reaction stage (B) (d) one or more monoisocyanates to intermediate (A) obtained in step (A), and then reacting the resulting mixture (B) with one or more polymers containing hydroxyl (D) to give the polyurethane resin (P) ). 9. An aqueous coater composition comprising a polyurethane (P) resin as defined in any of claims 1 to 7. 10. An aqueous coater composition as defined in claim 9, containing from 5 to 14% by weight of the polyurethane resin (P) based on the overall weight of the coating composition based on the solid content of the polyurethane resin 11. A coating composition as defined in claim 9 or 10, which is a coating composition of bicomponent polyurethane and comprising a component (I) and a component (II), "" (I) comprising the component (I) (1-1) one or more polyurethane resins (P) as defined in any of the claims 1 to 7, (1-2) one or more water-soluble or water-dispersible acrylate copolymers containing hydroxyl groups and acid groups which can be converted into the corresponding groups of acid anion and / or acrylated polyesters s and / or acrylated polyurethanes having an OH number from 40 to 200 mg KOH / g, and an acidity from 5 to 150 mg of KOH / g, and (1-3) if desired, one or more additional polymers, and II) component (II) comprises a polyisocyanate component as a cross-linking agent, the components (1-1) being used (1-3) and the mentioned crosslinking agent in amounts such that the ratio of the equivalents of the hydroxyl groups of the components (1-1) to (1-3) to the isocyanate groups of the crosslinking agent is between 1: 2 and 2: 1, preferably between 1: 1.2 and 1: 1.5. The use of a polyurethane resin as defined in any of claims 1 to 7 in a coating composition, especially an aqueous, bicomponent polyurethane coating composition, to control rheology and, if appropriate, optical properties. The use of a coating composition as defined in any of claims 9 to 11 as a topcoat or as a clearcoat, in particular for coating plastics. Polyurethane resin, process for its preparation and its use in clear aqueous coatings of two components SUMMARY OF THE INVENTION The present invention provides a polyurethane resin which can be obtained by (A) reacting in a first reaction step (A) (a) one or more diisocyanates and / or polyisocyanates, (b) one or more compounds (b) having at least one group that ensures dispersibility in water and more than one group that is reactive with isocyanate groups, and (c) if desired, one or more compounds having at least 2 and not more than 3 OH groups, "" to give an intermediate agent (A) having isocyanate-free groups and having urethane groups, (B) adding in a second reaction step (B) (d) one or more monoisocyanates to the intermediate agent (A) obtained in step (A), and (C) subsequently reacting the resulting mixture (B) with one or more polymers containing hydroxyl (D) to give the polyurethane resin (P), with the use of less than 20% by weight, based on the weight of the polyurethane resin (solid content) of polyalkylene oxide diols and / or polyalkylene oxide polyols in order to prepare the polyurethane resin.