EP0000171B1 - Carboxylate groups containing addition products of polyisocyanates and process for their preparation - Google Patents

Description

A number of processes for the production of polyurethanes which have carboxylate groups are known. For example, customary prepolymers with terminal isocyanate groups in an organic solvent can be reacted with aqueous solutions of aminocarboxylic acids or their salts to give corresponding polyurethane ureas containing carboxylate groups (cf., for example, DE-AS 1 495 745, British Pat. No. 1,076,688, US Pat. PS 3 539 483).

According to another method, dimethylofpropionic acid can be used as a chain extender for the construction of polyurethanes, the free carboxyl group being predominantly retained and then being able to be neutralized (see, for example, US Pat. No. 3,412,054, DE-OS 1,913,271).

According to a further known process, polyurethanes which contain free primary or secondary amino groups are reacted with β-propiolactone or the anhydride of a dicarboxylic acid, the polyurethane being modified with free carboxyl groups (cf. e.g. DE-AS 1 237 306).

It has also already been described to use polyethers or polyesters with terminal OH groups and pendant sulfonate or carboxylate groups for the construction of anionic polyurethane dispersions (cf. e.g. DE-AS 1 570615).

For the production of polyesters with pendant anionic groups, the concomitant use of diamines which contain sulfonate or carboxylate groups was considered (cf. e.g. DE-AS 1 570 615).

The disadvantages of the known methods are that they can either only be carried out in the presence of organic solvents or that specially constructed polyesters have to be used. The incorporation of dimethylolpropionic acid in isocyanate prepolymers is possible without solvent, but in a number of cases there is the problem of dissolving the dimethylolpropionic acid in the prepolymer at the required low reaction temperatures. Finally, it is disadvantageous that dimethylolpropionic acid can only be incorporated via an isocyanate reaction, which results in relatively high viscosities of the NCO prepolymer modified in this way.

Esters which contain both hydroxyl groups and free carboxyl groups are known from the chemistry of dispersible ester resins (cf., for example, DE-OS 2,323,546, US Pat. No. 4,029,617, BE-PS 803,346 or US Pat. No. 3,876 582), however, the reactive groups in such products are statistically distributed, so that the structure of structurally defined and in particular predominantly linear polyurethanes is not possible on the basis of these known products.

In contrast, a process has now been found which enables the preparation of polyisocyanate addition products containing carboxylate groups and in particular of aqueous dispersions thereof, in a simple manner both with and in particular without the use of organic solvents. In particular, the new process allows the production of low-viscosity anionic NCQ prepolymers using optimally low amounts of polyisocyanates, as a result of which solvent-free dispersion processes can be carried out in a particularly simple manner. The carboxyl component used is easily and inexpensively accessible and the entire manufacturing process is carried out under gentle conditions.

oder

in welcher

• m für 0 oder 1 steht,
• n für 1 oder 2 steht,
• R₁ für einen Rest steht, wie er durch Entfernung der Isocyanatgruppen aus einem organischen Di- . isocyanat erhalten wird,
• R₂ für einen Rest steht, wie er durch Entfernung der Hydroxylgruppen aus einem gegebenenfalls Äther- oder Estergruppen aufweisenden Glykol bzw. Glykol-Gemisch eines (mittleren) Molekulargewichts zwischen 62 und 10.000 erhalten wird,
• R₃ für einen Rest steht wie er durch Entfernung der Carboxylgruppen aus einer organischen Tri-oder Tetracarbonsäure erhalten wird und
• Kat⁽⁺⁾ für ein Alkali- oder ein sich aus einem tert. Amin ableitenden Kation steht.

The present invention relates predominantly to linear, carboxylate and amide groups containing polyisocyanate polyadducts identified by recurring structural units of the formulas

or

in which

• m represents 0 or 1,
• n represents 1 or 2,
• R _{1 represents} a radical as it is removed from an organic di- by removing the isocyanate groups. isocyanate is obtained
• R _{2 represents} a radical as obtained by removing the hydroxyl groups from a glycol or glycol mixture of (average) molecular weight between 62 and 10,000 which may have ether or ester groups,
• R _{3 represents} a radical as it is obtained by removing the carboxyl groups from an organic tri-or tetracarboxylic acid and
• Kat ⁽⁺⁾ for an alkali or a tert. Amine-derived cation.

• a) eine Polyhydroxylkomponente, welche entweder aus einem oder mehreren Glykolen des (mittleren) Molekulargewichts 62 bis 10 000 oder einem Alkoholgemisch einer mittleren OH-Funktionalität von 1,8 bis 3,0, welches einwertige Alkohole des Molekulargewichtsbereichs 32 bis 5000 und/oder zweiwertige Alkohole des Molekulargewichtsbereichs 62 bis 10 000 und/oder höherfunktionelle Alkohole des Molekulargewichtsbereichs 92 bis 10000 enthalten kann, besteht, mit intramolekularen Tricarbonsäuremonoanhydriden oder intramolekularen Tetracarbonsäuremonoanhydriden unter Ringöffnung der Anhydridgruppe in solchen Mengen umsetzt, daß pro Hydroxylgruppe der Polyhydroxylkomponente 0,05 bis 1 Anhydridgruppen vorliegen,
• b) die Carboxylgruppen des gemäß Reaktionsschritt a) erhaltenen Umsetzungsprodukte so mit einer anorganischen oder organischen Base teilneutralisiert, daß im statistischen Mittel pro Mol des Umsetzungsprodukts 0,1 bis 4 Mol Carboxylatgruppen und insgesamt 1,8 bis 3,8 Mol Carboxyl- und gegebenenfalls Hydroxylgruppen vorliegen,
• c) das gemäß Reaktionsschritt b) erhaltene Carboxylat-, Carboxyl- und gegebenenfalls Hydroxyl- gruppen aufweisende Reaktionsprodukt, sowie die gegebenenfalls im Gemisch vorliegende, nichtmodifizierte Polyhydroxylkomponente mit einer: Diisocyanatkomponente einer mittleren NCO-Funktionalität zwischen 1,8 und 3,0 zu einem Carboxylat-, Amid- und gegebenenfalls Urethan- gruppen aufweisenden Präpolymeren umsetzt, wobei (i) die Menge der Diisocyanatkomponente 1,2 bis 2 Äquivalenten an NCO-Gruppen pro Äquivalent an gegenüber Isocyanatgruppen reaktionsfähigen Gruppen entspricht, oder (ii) ein hoher Diisocyanatüberschuß eingesetzt wird, wobei nach Beendigung der Isocyanat-Additionsreaktion das überschüssige Diisocyanat durch Destillation entfernt wird, oder (iii) die Menge der Isocyanatkomponente 0,8 bis 1,2 Äquivalenten an NCO-Gruppen pro Äquivalent an gegenüber Isocyanatgruppen Reaktionsfähigen Gruppen entspricht, wobei gegebenenfalls durch einen vorzeitigen Abbruch der Isocyanat-Additionsreaktion durch eine sofortige Kettenverlängerungsreaktion gemäß d) sichergestellt wird, daß das Reaktionsprodukt noch freie Isocyanatgruppen aufweist, und
• d) schließlich das gemäß Reaktionsstufe c) erhaltene NCO-Präpolymere einer Kettenverlängerungsreaktion unterzieht.

The present invention also relates to a process for the preparation of predominantly linear carboxylate, amide and optionally urethane groups containing polyisocyanate polyadducts with recurring structural units of the formulas mentioned in claim 1 via the intermediate stage of prepolymers containing isocyanate groups, which by reaction of organic diisocyanates with carboxylate groups , free carboxyl groups and optionally hydroxyl-containing polyesters which have been obtained by reacting a polyhydroxyl component with an intramolecular carboxylic acid anhydride with subsequent partial neutralization of the reaction product, characterized in that

• a) a polyhydroxyl component, which consists either of one or more glycols of the (average) molecular weight 62 to 10,000 or an alcohol mixture with an average OH functionality of 1.8 to 3.0, the monohydric alcohols of the molecular weight range 32 to 5000 and / or dihydric Alcohols in the molecular weight range 62 to 10,000 and / or higher functional alcohols in the molecular weight range 92 to 10000, consists, with intramolecular tricarboxylic acid monoanhydrides or intramolecular tetracarboxylic acid monoanhydrides with ring opening of the anhydride group in such amounts that there are 0.05 to 1 hydroxyl group of the polyhydroxy component,
• b) the carboxyl groups of the reaction products obtained in reaction step a) are partially neutralized with an inorganic or organic base in such a way that, on average, 0.1 to 4 moles of carboxylate groups and a total of 1.8 to 3.8 moles of carboxyl and optionally hydroxyl groups per mole of the reaction product are present
• c) the carboxylate, carboxyl and optionally hydroxyl group-containing reaction product obtained according to reaction step b), as well as the optionally unmodified polyhydroxyl component with a: diisocyanate component having an average NCO functionality between 1.8 and 3.0 to give a carboxylate - prepolymers containing amide and optionally urethane groups, (i) the amount of the diisocyanate component corresponding to 1.2 to 2 equivalents of NCO groups per equivalent of groups which are reactive toward isocyanate groups, or (ii) a large excess of diisocyanate is used, wherein after the completion of the isocyanate addition reaction, the excess diisocyanate is removed by distillation, or (iii) the amount of the isocyanate component corresponds to 0.8 to 1.2 equivalents of NCO groups per equivalent of groups which are reactive toward isocyanate groups, if appropriate by premature termination the isocyanate addition freak tion is ensured by an immediate chain extension reaction according to d) that the reaction product still has free isocyanate groups, and
• d) finally subjecting the NCO prepolymer obtained in reaction step c) to a chain extension reaction.

The polyhydroxyl component used in the process according to the invention has a (mean) OH functionality of 1.8 to 3, preferably 1.8 to 2.2. These are either glycols or glycol mixtures with an (average) molecular weight of 62-10,000, preferably 200-50,000 and in particular 300-3,000, or alcohol mixtures which contain monohydric alcohols with a molecular weight of 32-5,000, preferably 500-4,000 and / or glycols mentioned molecular weight ranges and / or higher functional alcohols in the molecular weight range 92-10,000 preferably contain 92-300.

The glycols are preferably polyester diols or polyether diols.

In addition, however, simple alkane diols or also two hydroxyl-containing polythioethers, polyacetals, polyamides or polyurethanes can be used.

The higher functional polyhydroxyl compounds are preferably simple alkane polyols, but trifunctional or higher functional polyether polyols or polyester polyols are also suitable.

• 1. Alkandiole bzw. -polyole wie z.B. Äthylenglykol, 1,2-Propandiol, 1,3-Propandiol, Tetramethylenglykol, Hexamethylenglykol, Glycerin, Trimethyloläthan, Trimethylolpropan, Pentaerythrit, Sorbit, Bisphenol A, äthoxyliertes bzw. propoxyliertes Bisphenol A, 2,2-Bis-(4-hydroxycyclohexyl-)propan oder Dimethylol-tricyclodecan (5.2.1.0^2.6).
• 2. Modifizierte, d.h. insbesondere Äther oder Estergruppen aufwiesende Polyole oder aber auch Polyhydroxypolythioäther, Polyhydroxypolyacetale, Polyhydroxypolycarbonate und/oder Polyhydroxyplyesteramide.

The diols or polyols present in the polyhydroxyl component are thus

• 1. Alkanediols or polyols, such as, for example, ethylene glycol, 1,2-propanediol, 1,3-propanediol, tetramethylene glycol, hexamethylene glycol, glycerol, trimethylolethane, trimethylolpropane, pentaerythritol, sorbitol, bisphenol A, ethoxylated or propoxylated bisphenol A, 2.2 -Bis (4-hydroxycyclohexyl) propane or dimethylol-tricyclodecane (5.2.1.0 ^2.6 ).
• 2. Modified, ie in particular ethers or ester groups, polyols or else polyhydroxypolythioethers, polyhydroxypolyacetals, polyhydroxypolycarbonates and / or polyhydroxyplyesteramides.

The hydroxyl-containing polyesters in question are, for example, reaction products of polyhydric, preferably dihydric and optionally additionally trihydric alcohols with polyhydric, preferably dihydric, carboxylic acids. Instead of the free polycarboxylic acids, it is also possible to use the corresponding polycarboxylic anhydrides or corresponding polycarboxylic esters of lower alcohols or mixtures thereof for the preparation of the polyesters be used. The polycarboxylic acid can be aliphatic, cycloaliphatic, aromatic and / or heterocyclic in nature and optionally substituted, for example by halogen atoms, and / or unsaturated. Examples include: succinic acid, adipic acid, suberic acid, azelaic acid, Sebacic acid, phthalic acid, isophthalic acid, trimellitic acid, phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, tetrachlorophthalic anhydride, endomethylenetetrahydrophthalic anhydride, glutaric anhydride, maleic anhydride, fumaric acid, dimer of oleic acid and trimeric fatty acids, for example, optionally in admixture with monomeric fatty acids, terephthalic acid, terephthalic acid-bis-glykolester . Polyhydric alcohols include, for example, ethylene glycol, propylene glycol (1,2) and - (1,3), butylene glycol (1,4) and - (2,3), hexanediol (1,6), octanediol (1, 8), neopentyl glycol cyclohexanedimethanol (1,4-bis-hydroxymethylcyclohexane), 2-methyl-1,3-propanediol, glycerin, trimethylolpropane, hexanetriol- (1,2,6), butanetriol- (1,2,4), Trimethylolethane, pentaerythritol, quinite, mannitol and sorbitol, methylglycoside, also diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycols, dipropylene glycol, polypropylene glycols, dibutylene glycol and polybutylene glycols in question. The polyesters may have a proportion of terminal carboxyl groups. Polyesters of lactones, for example _E- caprolactone or hydroxycarboxylic acids, for example w-hydroxycaproic acid, can also be used.

The polyethers which are preferred according to the invention and preferably have two hydroxyl groups are those of the type known per se and are, for example, polymerized with themselves, for example in the presence of BF _a , by polymerization of epoxides such as ethylene glycol, propylene glycol, butylene glycol, tetrahydrofuran, styrene oxide or epichlorohydrin by adding these epoxides, optionally in a mixture or in succession, to starting components with reactive hydrogen atoms such as water or alcohols such as ethylene glycol, propylene glycol (1,3) or - (1,2), 4,4'-dihydroxy-diphenylpropane.

Polyethers modified by vinyl polymers, e.g. by polymerization of styrene or acrylonitrile in the presence of polyethers (American patents 3,383,351, 3,304,273, 3,523,093, 3,110,695, German patent 1,152,536) are also suitable. The proportionally higher-functionality polyethers to be used, if appropriate, are formed in an analogous manner by known alkoxylation of higher-functionality starter molecules, e.g. Ammonia, ethanolamine, ethylenediamine or sucrose.

Among the polythioethers, the condensation products of thiodiglycol with itself and / or with other glycols, dicarboxylic acids, formaldehyde, aminocarboxylic acids or amino alcohols should be mentioned in particular. Depending on the CO components, the products are polythio ether, polythio ether ester, polythio ether ester amide.

As polyacetals e.g. the compounds which can be prepared from glycols, such as diethylene glycol, triethylene glycol, 4,4'-diox-ethoxy-diphenyldimethylmethane, hexanediol and formaldehyde. Polyacetals suitable according to the invention can also be prepared by polymerizing cyclic acetals.

Suitable polycarbonates containing hydroxyl groups are those of the type known per se, which e.g. by reacting diols such as propanediol (1,3), butanediol (1,4) and / or hexanediol (1,6), diethylene glycol, triethylene glycol, tetraethylene glycol, with diaryl carbonates, e.g. Diphenyl carbonate or phosgene can be produced.

The polyester amides and polyamides include e.g. the predominantly linear condensates obtained from polyvalent saturated and unsaturated carboxylic acids or their anhydrides and polyvalent saturated and unsaturated amino alcohols, diamines, polyamines and their mixtures. Polyhydroxyl compounds already containing urethane or urea groups can also be used.

The polyhydroxyl component to be used according to the invention preferably consists exclusively of the glycols mentioned by way of example. Additional possible as already stated mixtures of such glycols with higher ^f unktionellen polyhydroxyl compounds into consideration, provided that the average hydroxyl functionality of the mixture within the above range. It is also possible to use monohydric alcohols in the polyhydroxyl component used according to the invention, although it is also conceivable that the polyhydroxyl component consists exclusively of a mixture of monohydric and higher than difunctional alcohols, provided the above-mentioned condition regarding the average OH functionality of the Mixture is satisfied. In general, however, when using monohydric or higher than dihydric alcohols, a glycol component will always be used in the polyhydroxyl mixture at the same time.

Suitable monohydric alcohols are e.g. simple aliphatic, cycloaliphatic or araliphatic monohydric alcohols such as methanol, ethanol, dodecanol, benzyl alcohol or cyclohexanol. However, the use of such simple monohydric alcohols is less preferred.

In order to increase the hydrophilicity of the prepolymers, it can often be advantageous to use hydrophilic nonionic structural components, i.e. especially monohydric or dihydric alcohols containing ethylene oxide units built into polyether chains. These hydrophilic structural components are either dihydroxy polyethers having polyethylene oxide segments and a molecular weight within the range mentioned above for the glycols, or polyether alcohols having monovalent ethylene oxide units and having a molecular weight within the range mentioned above for the monohydric alcohols. Such hydrophilic structural components are described, for example, in patent application P 26 37 690.9.

Mixtures of the polyhydroxy compounds mentioned are frequently used as the polyhydroxyl component, e.g. to adapt the hardness, elasticity and grip behavior of the coatings produced from the dispersions to the requirements.

The low molecular weight monohydric and polyhydric alcohols are used, if at all, preferably in amounts of up to a maximum of 50 hydroxyl equivalent percent based on the total polyhydroxyl component.

When carrying out the process according to the invention, the polyhydroxyl component is reacted with one or more intramolecular tricarboxylic acid monoanhydride (s) or tetracarboxylic acid monoanhydride (s). In this reaction, part or all of the hydroxyl groups of the polyhydroxyl component react with the anhydride with ring opening addition, i.e. with formation of ester groups.

• 1. Pyromellithsäuredianhydrid (1,2,4,5-Benzoi-tetracarbonsäuredianhydrid);
• 2. Bicyclo-(2,2,2)-octen-(7)-2,3,5,6-tetracarbonsäure-2,3:5,6-dianhydrid;
• 3. Perylen-3,4,9,10-tetracarbonsäuredianhydrid;
• 4. Naphthalintetracarbonsäuredianhydrid
• 5. Tetracarbonsäureanhydride folgender Konstitution
  
  
  wobei R für eine C₁―C₁₂-Alkylen, -CO-, -0-, -S-, -SO₂₌ -Brücke steht, wobei die Alkylenbrücke auch Heteroatome aufweisen kann, d.h. insbesondere, daß die Alkylengruppe an die Ringe über Estergruppen gebunden sein kann. Weitere erfindungsgemäß einsetzbare Carboxyanhydride oder als Vorstufen hierfür geeignete Dianhydride können der DOS 2 443 575, S. 6-7, entnommen werden.

The anhydrides are any intramolecular tricarboxylic acid monoanhydrides or tetracarboxylic acid monoanhydrides which have at least one free carboxyl group. It is therefore generally any monoanhydrides of aliphatic, cycloaliphatic, araliphatic or aromatic tri- or tetracarboxylic acids. Examples of particularly suitable monoanhydrides are trimellitic anhydride, meso-1,2,3,4-butanetetracarboxylic acid monoanhydride, 1,2,3,4-cyclopentane-tetracarboxylic acid monoanhydride, but less preferred are equimolar reaction products of tetracarboxylic acid dianhydrides with simple monoalcohols of those already mentioned above as examples Type, ie the ester anhydride monocarboxylic acids formed in this reaction. The following tetracarboxylic dianhydrides are suitable for this reaction:

• 1. pyromellitic dianhydride (1,2,4,5-benzoetetracarboxylic dianhydride);
• 2. Bicyclo- (2,2,2) -octen- (7) -2,3,5,6-tetracarboxylic acid 2,3: 5,6-dianhydride;
• 3. Perylene-3,4,9,10-tetracarboxylic acid dianhydride;
• 4. Naphthalene tetracarboxylic acid dianhydride
• 5. Tetracarboxylic anhydrides of the following constitution
  
  
  where R is a C ₁ ―C ₁₂ alkylene, -CO-, -0-, -S-, -SO _{2 =} bridge, wherein the alkylene bridge can also have heteroatoms, ie in particular that the alkylene group on the rings Ester groups can be bound. Further carboxy anhydrides which can be used according to the invention or dianhydrides which are suitable as precursors therefor can be found in DOS 2 443 575, pp. 6-7.

Any organic diisocyanates can be used in the process according to the invention. Diisocyanates R ₁ (NCO) ₂ are preferably used, where R _{1 has} the meaning already mentioned and preferably for an aliphatic hydrocarbon radical with 4 to 12 carbon atoms, a cycloaliphatic hydrocarbon radical with 6 to 15 carbon atoms, an aromatic hydrocarbon radical with 6 to 15 carbon atoms or one araliphatic hydrocarbon radical having 7 to 15 carbon atoms. Examples of such preferred diisocyanates are tetramethylene diisocyanate, hexamethylene diisocyanate, dodecamethylene diisocyanate, 1,4-diisocyanato-cyciohexane, 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane, 4,4'-diisocyanatodicyclohexylmethane, 4,4'-diisocyanato- dicyclohexylpropane- (2,2), 1,4-diisocyanatobenzene, 2,4-diisocyanatotoluene, 2,6-diisocyanatotoluene, 4,4'-diisocyanatodiphenylmethane, 4,4'-diisocyanato-diphenylpropane- (2,2), p- Xylylene diisocyanate or a, a, a ', a'-tetramethyl-m or p-xylylene diisocyanate, and mixtures consisting of these compounds.

It is of course also possible in the process according to the invention to use the polyfunctional polyisocyanates known per se in polyurethane chemistry, or else modified polyisocyanates containing, for example, carbodiimide groups, allophanate groups, isocyanurate groups, urethane groups and / or biuret groups. The use of monoisocyanates such as e.g. Phenyl isocyanate or dodecyl isocyanate or partially blocked polyisocyanates are possible in principle. However, care must always be taken to ensure that the average NCO functionality of the polyisocyanate component is between 1.8 and 3.0.

Any inorganic or organic bases are suitable for the partial neutralization of the reaction product between the polyhydroxyl component and anhydride having carboxyl groups. Before drawn neutralizing agents are tert. Amines of the molecular weight range 59-200 such as trimethylamine, triethylamine, triisopropylamine, tributylamine, N-methylpyrrolidine, N-methylpiperidine, dimethylaminoethanol, dimethylaminopropanol, dimethylaniline, pyridine. 2-methoxyethyl-dimethylamine, 2- (2-dimethylamino-ethoxy) ethanol, 5-diethylamino-2-pentanone. Also suitable are inorganic bases such as the hydroxides, oxides, carbonates, hydrogen carbonates of the alkali metals, in particular sodium hydroxide, potassium hydroxide, lithium hydroxide, potassium carbonate. These inorganic compounds can be added either as such in finely powdered form or as aqueous or alcoholic solutions. If a solvent which is reactive towards isocyanates, such as methanol or water, is also used, this must then be removed again by distillation.

The reactions of the first to third reaction stages can be carried out in the presence of organic solvents, in particular those of a polar type, such as acetone, methyl ethyl ketone, N-methylpyrrolidine, methylene chloride, the solvent being generally added to the extent that the increasing viscosity of the polymer melt requires it . The process is preferably carried out at elevated temperature and in the absence of solvents. If the presence of solvents is unavoidable for reasons of viscosity, preferably no more than about 10%, based on the reaction mixture, is used. If possible, those solvents are used which are also desirable from the point of view of later application and, for example, a reduction in the film. education temperature, improvement of flow, drying behavior, etc. cause. For the paint dispersions preferred according to the invention, paint solvents in particular are added, e.g. Methyl isobutyl acetate, glycol monomethyl ether acetate, glycol diethyl ether.

. For the first reaction stage, the reaction of the polyhydroxyl component with the carboxy-anhydride, the proportions of the reactants are chosen so that 0.05-1, preferably 0.1 to 0.5, anhydride groups are present in the reaction mixture for each hydroxyl group of the polyhydroxyl component. This reaction is preferably carried out at 40-170 ° C., in particular at 50-150 ° C., until the characteristic anhydride bands at 1780 cm- 'and 1860 cm-' have disappeared in the IR spectrum of a sample.

In the next reaction step, the carboxyl groups of the reaction product from the polyhydroxyl component and carboxy anhydride, which may be present in a mixture with excess, unmodified polyhydroxyl component, are partially neutralized with the bases mentioned by way of example so that 0.1-4 in one mole of the partially neutralized reaction product , preferably 0.2-1 mol of carboxylate groups, at least 0.1 mol of carboxyl groups and a total of 1.8-3.8, preferably 1.8-2.2 mol of carboxyl and optionally hydroxyl groups are present. Partial neutralization is easiest with tertiary amines, which are simply added to the reaction mixture in the required amount. Among the amines with isocyanate-reactive groups, preferred are those in which the reactivity of this group is poor, e.g. sec- or tert-hydroxy groups or amide or urethane groups, inorganic bases are preferably added in aqueous or alcoholic solution, the solvent then having to be removed by distillation.

The next reaction stage of the process according to the invention consists in the reaction of the carboxylate and free carboxyl groups as well as optionally partially neutralized reaction product containing hydroxyl groups, as well as the unmodified polyhydroxyl component optionally present in a mixture with the polyisocyanates mentioned as examples to give the corresponding NCO prepolymer. In this reaction, urethane groups are formed from hydroxyl groups and amide groups are formed from carboxyl groups with elimination of CO ₂ , so that an NCO prepolymer is formed which contains amide, carboxylate and optionally urethane groups. The proportions in this reaction are chosen so that each equivalent of groups that are reactive toward isocyanate groups (carboxyl and optionally hydroxyl groups) account for 1.2 to 2 and in particular 1.3 to 1.8 equivalents of NCO groups. It is also possible to use a large excess of polyisocyanate and, after the isocyanate addition reaction has ended, to remove the excess polyisocyanate, for example by distillation. The reaction is generally carried out at temperatures between 40 and 150 ° C, preferably 45 to 130 ° C. Particularly in the case of using branched reactants for the polyisocyanate component, ie of compounds which have a total of more than two carboxyl and hydroxyl groups on a statistical average, it can be expedient here not to complete the isocyanate addition reaction, ie until to calculate the predicted NCO content of the reaction products. For example, it is possible to terminate the reaction at a point in time in which free carboxyl and optionally hydroxyl groups are present in addition to free isocyanate groups in the reaction mixture. This reaction can be terminated, for example, by immediately subjecting the reaction mixture which has not fully reacted to the chain extension reaction according to the fourth reaction stage, for example by introducing the reaction mixture into an aqueous diamine solution.

In this procedure, in which not all carboxyl or. Hydroxyl groups are reacted with the polyisocyanate component is preferably in an equivalent ratio between isocyanate groups and groups reactive to isocyanate groups from 0.8: 1 to 1.2: 1 worked, ie it is also conceivable to use the polvisocvanate component in an amount which corresponds to an equivalent ratio of isocyanate groups to isocyanate-reactive groups of less than 1: 1, since the isocyanate addition reaction does not occur in the formation of the prepolymers is carried out to the end and this partial conversion of the isocyanate groups used ensures that the reaction product still has free isocyanate groups even with a deficient amount of polyisocyanate component. In this embodiment of the method according to the invention, an excessive increase in the viscosity of the NCO prepolymer and premature crosslinking can be avoided with certainty even when using compounds with more than two groups which are reactive toward isocyanate groups.

In a further variant of the process according to the invention, partially blocked polyisocyanates or mixtures of mono-, di- and / or polyfunctional isocyanates with partially blocked polyisocyanates can also be used as the polyisocyanate component in the third process stage. In this variant of the process according to the invention, too, a suitable choice of the functionality of the compounds with groups which are reactive toward isocyanate groups and / or the functionality of the polyisocyanate component (based on free isocyanate groups) can ensure that, on the one hand, there is no premature undesirable increase in viscosity or crosslinking and on the other hand Intermediates with terminal isocyanate groups and also blocked isocyanate groups, and in the case of incomplete reaction according to the statements made above with free carboxyl or. Hydroxyl groups can be obtained. Suitable partially blocked polyisocyanates are, in particular, partially blocked polyisocyanates which have a statistical average of 1.8-2.2 free isocyanate groups per molecule, i.e. for example triisocyanates with one blocked and two unblocked isocyanate groups. Suitable mixtures containing partially blocked polyisocyanates are, in particular, those which contain either the last-mentioned partially blocked polyisocyanates or else monoblocked diisocyanates in addition to mono-, di- and / or polyfunctional polyisocyanates, the individual components of these mixtures should be selected such that the average NCO Functionality (based on free isocyanate groups) is between 1.8 and 2.2. When using NCO prepolymers prepared according to this variant of the process according to the invention in the fourth reaction step described below, high molecular weight polyurethanes can be obtained which contain blocked isocyanate groups and optionally carboxyl or. Have hydroxyl groups and therefore represent self-crosslinking systems due to the influence of heat.

Suitable blocking agents are the monofunctional blocking agents known per se in polyurethane chemistry for organic polyisocyanates such as _E- caprolactam, phenols such as phenol or o-cresol, ketoximes such as methyl ethyl ketone ketoxime or CH-acidic compounds such as diethyl malonate. The partially blocked polyisocyanates are prepared using the organic polyisocyanates exemplified above by known methods of isocyanate chemistry.

The next step of the process according to the invention now consists in converting the above-described NCO prepolymers into the process products according to the invention by means of a chain extension or crosslinking reaction which is known per se. (In the context of the present invention, "chain extension" is understood to mean both a real chain extension without branching and also a branching or crosslinking of the prepolymers (use of higher than difunctional "chain extension agents"). According to a preferred embodiment of the process according to the invention, this chain extension reaction is combined with the simultaneous conversion of the process product into an aqueous dispersion. The simplest way to do this is to use water only as a chain extender. This means that the liquid prepolymer or honey-like consistency is stirred with a 0.2 to 10-fold amount by weight of water. Simple laboratory stirrers are sufficient for this mixing process, although it is of course also possible to use dispersing machines with high shear forces as well as the use of non-mechanical dispersing agents such as ultrasonic waves of extremely high frequency. The temperature during the mixing process is between 1 ° and 180 ° C, preferably between 20 ° C and 100 ° C. This process can also be carried out under pressure.

The chain extension reaction can, however, also be carried out using mixtures of water and water-soluble chain extenders, chain extenders preferably being used which have a higher reactivity towards isocyanate groups than water. It is also possible to disperse the NCO prepolymer in water and to add the chain extender mentioned after the dispersion has taken place. Such chain extenders are in particular exclusively hydrazines or polyamines having primary or secondary amino groups, preferably hydrazines or diamines having a molecular weight above 31, preferably between 32 and 600. Examples of such hydrazines or polyamines suitable as chain extenders are hydrazine, ethylenediamine, diethylenetriamine, 1,2-diaminopropane, 1,3-diaminopropane, 3,3,5-trimethyl-5-aminomethyl-cyclohexylamine or 1,4-diaminobutane. Further suitable bifunctional chain extenders are described in DT-OS 1 495 847 or in DT-AS 1 237 306. In this embodiment of the he According to the inventive method, the water is used in a 0.2 to 10 times the amount by weight, based on the NCO prepolymer.

In a particularly preferred embodiment of the process according to the invention, the chain extension reaction takes place using a mixture of water and polyamines of the type mentioned, which are additionally modified by chemically fixed ionic groups, preferably by chemically fixed sulfonate groups. Such an ionically modified chain extender is e.g. the N- (2-aminoethyl) -2-aminoethanesulfonic acid sodium.

The chain extension reaction which takes place in the fourth reaction stage can also be carried out using solvents in which the prepolymer is present in solution, although it is one of the essential advantages of the process according to the invention that such solvents can in principle be dispensed with. The solvents which may be used in the chain extension reaction correspond to the solvents which are also suitable for the preparation of the prepolymers.

A further possibility of chain extension of the NCO prepolymers obtained in the third process stage can also be carried out according to the principles of the process described in US Pat. No. 3,756,992 or in DE-OS 26 37 690, in such a way that the NCO Prepolymer first by reaction with vzw. Ammonia or primary amines such as e.g. Prepares methylamine or n-butylamine prepolymers with terminal urea groups and extends them via the intermediate stage of prepolymers containing methylol groups by reaction with formaldehyde or crosslinked with compounds of the type described in US Pat. No. 3,756,992 containing methylol groups. The reaction of the NCO prepolymers with compounds containing methylol groups of the type mentioned in US Pat. No. 3,756,992 without prior conversion of the terminal NCO groups into the corresponding urea groups to give prepolymers containing methylol groups and their subsequent thermal treatment according to US Pat. No. 3,756,992 represents a viable way of chain extension or crosslinking of the NCO prepolymers obtained in the third stage of the process according to the invention. The chain extension according to these latter variants also involves the construction of the high molecular weight polyadducts or the preparation of the intermediate products containing terminal methylol groups with their dispersion Water. Thus, the reaction of the NCO prepolymers with ammonia or the primary amines mentioned by way of example to give the corresponding prepolymers having terminal urea groups takes place in an aqueous medium, so that the prepolymers having urea groups are obtained in the form of aqueous dispersions or solutions. These prepolymers, which have terminal urea groups and are present as dispersions or solutions in water, are then either in the aqueous phase with formaldehyde or compounds which release formaldehyde, e.g. Paraformaldehyde or with compounds containing methylol groups in the aqueous phase to form terminal prepolymers containing methylol groups, the final extension or crosslinking thereof before and / or during and / or after the removal of the water, for example by evaporation or evaporation during the production of fabrics from the dispersions a heat treatment is carried out at 25 to 180 ° C. When the NCO prepolymers are reacted with compounds containing methylol groups without intermediate conversion of the NCO prepolymers into prepolymers containing urea groups, this reaction step is preferably carried out in the absence of water, followed by dispersion of the prepolymers containing methylol groups in water and their further treatment as described above.

A chain extension of the NCO prepolymers according to the principles of DE-OS 2 543 091 is also possible in principle.

• i) eine mittlere NCO-Funktionalität von 1,8 bis 2,2 vorzugsweise 2,
• ii) eine Viskosität von 5 000 bis 150000 cP bei 80°C,
• iii) einen Gehalt an Carboxylatgruppen von 0,1 bis 5, vorzugsweise 0,2 bis 2 Gew.-% und
• iv) ein mittleres Molekulargewicht von unter 25.000 vorzugsweise unter 10.000 aufweisen.

NCO prepolymers, which are particularly suitable for the various chain extension reactions

• i) an average NCO functionality of 1.8 to 2.2, preferably 2,
• ii) a viscosity of 5,000 to 150,000 cP at 80 ° C,
• iii) a carboxylate group content of 0.1 to 5, preferably 0.2 to 2 wt .-% and
• iv) have an average molecular weight of less than 25,000, preferably less than 10,000.

In the preparation of the NCO prepolymers in the reaction steps a) to c) according to the invention, the nature and proportions of the starting materials are therefore preferably chosen such that the NCO prepolymers obtained meet the criteria mentioned.

The production of aqueous dispersions of the process products according to the invention can of course also take place with the use of external emulsifiers, although one of the main advantages of the process according to the invention is that the use of such emulsifiers can be dispensed with.

The process according to the invention can of course also be carried out using the catalysts known per se which accelerate the NCO / OH reaction.

The new process according to the invention brings about a considerable increase in the space-time yield compared to the known solvent process, since on the one hand the solvent volume and on the other hand the energy and time-consuming distillation process are eliminated.

The preferred use of exclusively difunctional structural components in the process according to the invention results in the preferred ver according to the invention driving products of the general formulas mentioned at the beginning.

The dispersions produced by the process according to the invention have a wide variety of fields of application. They can e.g. use for leather finishing or can be used for coating a wide variety of materials, especially for textile coating. Here you can use it as an adhesive or cover rope. Textile foam coatings are also possible. Significant areas of application are also the use as an adhesive or as a lacquer.

The use of the solvent-free dispersions according to the invention for leather finishing and for the production of aqueous coating systems is very particularly preferred.

Example 1-8

These examples show the implementation of the process according to the invention with the use of acetone as auxiliary solvent.

• Polyester I (PE I): Polyester aus Adipinsäure, Hexamethylenglykol und 2,2-Dimethyl-1,3-propandiol des Molekulargewichts 2.000;
• Polyäther I (PÄ 1): Polytetramethylenglykol des Molekulargewichts 2.000;
• Hexamethylendiisocyanat (HDI);
• Trimellitsäureanhydrid (TMA);
• Äthylendiamin (ÄDA);
• Triäthylamin (TÄA).

Starting materials:

• Polyester I (PE I): polyester made from adipic acid, hexamethylene glycol and 2,2-dimethyl-1,3-propanediol with a molecular weight of 2,000;
• Polyether I (PÄ 1): polytetramethylene glycol with a molecular weight of 2,000;
• Hexamethylene diisocyanate (HDI);
• Trimellitic anhydride (TMA);
• Ethylenediamine (ÄDA);
• Triethylamine (TÄA).

• In einem Dreihalskolben mit Metallschliffrührer, Rückflußkühler mit CaCl₂₃-Rohr, Kontaktthermometer und Tropftrichter wurde entwässerter Polyester bzw. Polyäther bei 80°C unter Rühren mit gemörsertem TMA versetzt.

General description of the experiment:

• In a three-necked flask with a metal stirrer, a reflux condenser with a CaCl ₂₃ tube, a contact thermometer and a dropping funnel, dehydrated polyester or polyether was added at 80 ° C. while stirring with ground TMA.

After a reaction time of 2 hours at 120 ° C., a clear melt had formed which contained no undissolved TMA. After cooling to 60 ° C., TÄA was added first, and HDI was added quickly after 15 minutes. After heating to 110 ° C., the mixture was left to react at this temperature for 2 hours. The NCO prepolymer was dissolved in acetone and an acetone solution of ADA was added to form an emulsion. After stirring for 5 minutes at 56 ° C., deionized water was added with vigorous stirring. Dispersion was formed by reversing the phase, which occurred after the addition of approx. 40-70% of the water. Acetone was distilled off in vacuo until the gas phase warmed up more.

Test conditions and properties of the dispersions are given in Table 1.

Examples 9-39

These examples show the implementation of the process according to the invention without the use of an auxiliary solvent and with chain extension of the NCO prepolymers with water.

• Wie Beispiele 1-8, sowie
• Polyäther II (PÄ II): Polypropylenglykol des mittleren Molekulargewichts 1.025;

Starting materials:

• Like examples 1-8, as well
• Polyether II (PA II): polypropylene glycol with an average molecular weight of 1,025;

First, excess macroglycol with terminal OH groups is reacted with TMA for 30 minutes at 100 ° C. After neutralization of 50% of the calculated carboxyl groups of the reaction product obtained with TÄA, an NCO prepolymer is formed by reaction with excess HDI in the melt at 110 ° C .; the reaction time is 120 minutes.

When water is added to the NCO prepolymer with the excess NCO groups reacting with part of the water with chain extension, dispersion formation takes place.

• Polyester II (PE II): Phthalsäure-Äthylenglykol-Polyester des Molekulargewichts 2000 und der OH-Zahl 56;
• Polyester III (PE III): Phthalsäure-Adipinsäure-Äthylenglykol-Polyester des Molekulargewichts 1750 und der OH-Zahl 64;
• Polyester IV (PE IV): Adipinsäre-Butandiol(1,4)-Polyester des Molekulargewichts 2250 und der OH-Zahl 50;
• Polyester V (PE V): Adipinsäure-Hexamethylenglykol-Neopentylglykol-Polyester des Molekulargewichts 1700 und der OH-Zahl 66;
• Polyäther II (PÄlll): propoxyliertes Bisphenol A des Molekulargewichts 550;
• Polyäther IV (PÄIV): Monohydroxypolyäther des Molekulargewichts 2150 durch Alkoxylierung von n-Butanol, wobei zunächst eine Propoxylierung und anschließend eine Athoxylierung durchgeführt wird und wobei der Anteil des Propylenoxids 17 Gew.-% und der Anteil des Äthylenoxids 83 Gew.-% bezogen auf Gesamtmenge der Alkylenoxide ausmacht;
• Trimethylolpropan (TMP)
• Isophorondiisocyanat (IPDI).

In Examples 40-45 below, the following starting materials were used in addition to the starting materials already mentioned:

• Polyester II (PE II): phthalic acid-ethylene glycol polyester with a molecular weight of 2000 and an OH number of 56;
• Polyester III (PE III): phthalic-adipic acid-ethylene glycol polyester with a molecular weight of 1750 and an OH number of 64;
• Polyester IV (PE IV): adipic butanediol (1,4) polyester with a molecular weight of 2250 and an OH number of 50;
• Polyester V (PE V): adipic acid-hexamethylene glycol-neopentyl glycol polyester with a molecular weight of 1700 and an OH number of 66;
• Polyether II (PÄlll): propoxylated bisphenol A with a molecular weight of 550;
• Polyether IV (PAEIV): Monohydroxypolyether of molecular weight 2150 by alkoxylation of n-butanol, where first a propoxylation and then an ethoxylation is carried out and the proportion of propylene oxide is 17% by weight and the proportion of ethylene oxide is 83% by weight Makes up total amount of alkylene oxides;
• Trimethylolpropane (TMP)
• Isophorone diisocyanate (IPDI).

Example 40

• 0.3 mol PE 11
• 0.2 mol PE III
• 0.26 mol PA III
• 0.16 mol of TMP
• 0.6 mol TMA
• 0.6 mole TÄA
• 1.8 moles of HDI
• 1.6 mol NH ₃ (NH ₃ / NCO - molar ratio = 1: 1)

3780 g of deionized water (corresponding to a solids content of the dispersion obtained of 30% by weight)

The dewatered mixture of PE 11, PE III, PA III and TMP is mixed with the TMA and stirred at 120-130 ° C until a clear melt is formed. The mixture is then cooled to 80 ° C., the TÄA is added and stirring is continued for 15 minutes. Then add HDI and stir at 80-90 ° C until an NCO value of 4.2% is reached. A solution of the NH ₃ in half of the dispersing water is stirred into the prepolymer thus obtained at 70-80 ° C. and the remaining water is added as soon as the product is homogeneous. The result is a thin, colloidal dispersion that is stable in storage for more than 2 months. pH = 7.7. Expiry time (Ford D ₄ ) = 17 sec.

A sample of the dispersion was mixed with a melamine-formaldehyde resin of the hexamethoxymethylmelamine type (15% by weight, based on solids) and baked on a phosphated sheet at 160 ° C. The result was a clear, colorless, shiny, hard coating which is resistant to organic solvents such as xylene, ÄGA or acetone and is only superficially dissolved by DMF. After 24 hours of water storage, the film showed no haze.

Example 41

• 0,2 Mol PE 11
• 0,3 Mol PE III
• 0,26 Mol PÄ III
• 0,16 Mol TMP
• 0,45 Mol TMA (entsprechend 1,3 Gew.-% COO- im dispergierten Feststoff)
• 0,45 Mol TÄA
• 1,8 Mol HDI
• 1,4 Mol NH₃ (NH₃/NCO = 0,88)
• 1550 g entionisiertes Wasser (entsprechend einer 50 Gew.-%igen Dispersion) Herstellungsverfahren: wie Beispiel 40
• Dispersion: hochviskos (η = 6000 cP), weiß mit starkem Tyndall-Effekt kein NH₃-Geruch, pH = 6,3
• Film: (eingebrannt bei 160°C, mit 15% des Melamin-Formaldehyd-Harzes aus Beispiel 40): hart, klar, farblos, entspricht Beispiel 40.

Starting materials:

• 0.2 mol PE 11
• 0.3 mol PE III
• 0.26 mol PA III
• 0.16 mol of TMP
• 0.45 mol of TMA (corresponding to 1.3% by weight of COO in the dispersed solid)
• 0.45 mole TÄA
• 1.8 moles of HDI
• 1.4 mol NH ₃ (NH ₃ / NCO = 0.88)
• 1550 g of deionized water (corresponding to a 50% by weight dispersion) Production process: as example 40
• Dispersion: highly viscous (η = 6000 cP), white with strong Tyndall effect, no NH ₃ odor, pH = 6.3
• Film: (baked at 160 ° C, with 15% of the melamine-formaldehyde resin from Example 40): hard, clear, colorless, corresponds to Example 40.

Example 42

• 0.5 mol PE IV
• 0.5 mol PA III
• 0.6 mol TMA
• 0.6 mole TÄA
• 1.8 moles of HDI
• 1.6 moles of NH ₃
• 440 g deionized water (corresponding to a 30% dispersion)
• Procedure: as example 40
• Dispersion: thin, almost colloidal; 1 month shelf life;
• Film: (baked at 160 ° C., with 10% by weight of the melamine-formaldehyde resin from Example 40): colorless, lower hardness than in Examples 40 and 41.

Example 43

• 1 mole of PE V
• 0.6 mol TMA
• 0.6 mole TÄA
• 1.8 moles of HDI
• 1.6 moles of NH ₃
• 5140 g deionized water (corresponding to a 30% by weight concentration)
• Procedure: as example 40
• Dispersion: low viscosity, almost colloidal, stable in storage
• Film: corresponds to example 42.

_V Example ₄₄

• 1 mole of PE V
• 0.6 mol TMA
• 0.6 mole TÄA
• 1.8 moles of IPDI
• 1.6 mol NH,
• 5370 g deionized water (corresponding to a 30% dispersion)
• Procedure: as example 40
• Dispersion: low viscosity, almost colloidal, stable in storage
• Film: corresponds to example 42.

Example 45

• 0.97 mol PE V
• 0.06 mol PA IV (corresponding to 4.7% by weight ethylene oxide in the solid)
• 0.3 mol of TMA (corresponding to 0.6% by weight of COO in the solid)
• 0.3 mol TAA
• 1.8 moles of HDI
• 1.6 mol NH,
• 5120 g deionized water (corresponding to a 30% dispersion)
• Procedure: as example 40
• Dispersion: thin, white with Tyndall effect
• Film: corresponds to example 42.

Claims (7)

1. Polyisocyanate polyaddition products, characterized by recurrent structural units of the formulae

oder

in which

m represents 0 or 1,

n represents 1 or 2,

R, represents a group of the kind obtained by removal of the isocyanate groups from an organic diisocyanate

R₂ represents a group of the kind obtained by removal of the hydroxyl groups from a glycol or glycol mixture, which glycol or glycol mixture has a molecular weight or average molecular weight of between 62 and 10,000 and may contain ether or ester groups,

R₃ represents a group of the kind obtained by removal of the carboxyl groups from an organic tricarboxylic or tetracarboxylic acid, and

cat(+) represents an alkali metal cation or a cation derived from a tertiary amine.

2. Polyisocyanate polyaddition products according to claim 1, characterized by containing from 0.1 to 5% by weight of carboxylate groups.

3. Process for the preparation of predominantly linear polyisocyanate polyaddition products containing carboxylate and amide groups and optionally also urethane groups and having recurrent structural units of the formulae given in claim 1, via the intermediate stage of prepolymers containing isocyanate groups, which prepolymers have been obtained by the reaction of organic diisocyanates with polyesters which have carboxylate groups, free carboxyl groups and, optionally also hydroxyl groups, these polyesters having been obtained by reacting a polyhydroxyl component with an intramolecular carboxylic acid anhydride followed by partial neutralization of the reaction product, characterized in that

a) a polyhydroxyl component which consists either of one or more glycols having a molecular weight or average molecular weight of from 62 to 10,000 or of an alcohol mixture having an average OH functionality of 1.8 to 3.0, which alcohol mixture may contain monohydric alcohols with molecular weights in the range of 32-5,000 and/or dihydric alcohols within a molecular weight range of 62 to 10,000 and/or higher functional alcohols within a molecular weight range of 92 to 10,000 is reacted in such quantities with intramolecular tricarboxylic acid monoanhydrides or intramolecular tetracarboxylic acid monoanhydrides in a ring-opening reaction of the anhydride group that from 0.05 to 1 anhydride groups are present per hydroxyl group of the polyhydroxyl component;

b) the carboxyl groups of the reaction products obtained in reaction step a) are partly neutralized with an inorganic or organic base so that, on statistical average, from 0.1 to 4 mol of carboxylate groups and a total of from 1.8 to 3.8 mol of carboxyl groups and optionally hydroxyl groups are present per mol of reaction product;

c) the reaction product obtained in step b) containing carboxylate and carboxyl groups and may also contain hydroxyl groups, as well as the non-modified polyhydroxyl component which may also be present in the mixture, are reacted with a diisocyanate component having an average isocyanate functionality of between 1.8 and 3.0 to form a prepolymer which contains carboxylate and amide groups and may also contain urethane groups, wherein (i) the amount of the diisocyanate component corresponds to 1.2 to 2 equivalents of isocyanate groups per equivalent of isocyanate reactive groups, or (ii) a large excess of diisocyanate is used, the excess diisocyanate being removed by distillation after the isocyanate addition reaction, or (iii) the amount of the isocyanate component corresponds to 0.8 to 1.2 equivalents of isocyanate groups per equivalent of isocyanate reactive groups, if necessary prematurely stopping the isocyanate addition reaction by an immediate chain lengthening reaction according to d), to ensure that the reaction product still contains free isocyanate groups and

d) lastly, the isocyanate prepolymer obtained according to reaction step c) is subjected to a chain lengthening reaction.

4. Process according to claim 3, characterized in that chain lengthening according to reaction step d) is carried out by reacting the isocyanate prepolymer with water.

5. Process according to claim 3, characterized in that chain lengthening according to reaction step d) is carried out by reacting the isocyanate prepolymer with hydrazines or polyamines which have at least two primary and/or secondary amino groups.

6. Process according to claim 3, characterized in that chain lengthening according to reaction step d) is carried out by converting the isocyanate prepolymer into a prepolymer having urea end groups by reacting it with ammonia or a primary monoamine, and this prepolymer with urea end groups is then chain lengthened with formaldehyde or with formaldehyde derivatives.

7. Process according to claims 3 to 6, characterized in that the chain lengthening reaction is carried out in the presence of excess quantities of water with simultaneous formation of a dispersion of the polyisocyanate polyaddition product.