NO173703B - POLYURETHANE BASIC ADHESIVE AND PROCEDURES FOR PREPARING THEREOF - Google Patents

Abstract

A general purpose household adhesive comprises an essentially clear and at least largely solvent-free polyurethane aqueous dispersion based on: a mixture of polyols composed wholly or partly of polytetrahydrofurane; a bi- or multi-functional isocyanate component having an OH:NCO ratio with respect to the mixture of polyols between 1:0.5 and 1:2.0, preferably between 1:1.0 and 1:1.7 and in particular between 1:1.05 and 1:1.6; a functional component capable of forming salts in an aqueous solution; and, if desired, a chain-lengthening agent.

Description

The present invention relates to a household adhesive based on an essentially clear, and at least mainly solvent-free, aqueous one-component polyurethane dispersion and a method for its production.

Household adhesives - also called universal adhesives - have the purpose of gluing a large number of substrates found in households (paper, cardboard, photos, textiles, leather, felt, bast, cork, foils, metals, such as aluminum and iron, porcelain, ceramic materials, glass , wood, various plastics, such as polystyrene foam). Thereby, it is expected that on this large number of substrates, which differ from each other chemically and physically in terms of surface structure, and which are not usually subjected to any special surface treatment before gluing, a sufficient adhesion effect is achieved.

Compared to the large number of adhesive classes and types used in industry and crafts, there are only a few substances that satisfy the high demands placed on the universal applicability of a household adhesive. Polyvinyl acetate and its copolymers have thus found wide application, these are usually added in solution or, for wood bonding, as a dispersion.

The demand for universal applicability constitutes a very strict selection criterion for an adhesive. Ultimately, this means that the adhesive molecules must similarly exhibit a high affinity to polar and non-polar interfaces. A statement that a certain substance is suitable as an adhesive therefore gives the expert no indication as to whether it can be used as a household adhesive.

Alongside the requirement for universal applicability, for household adhesives there is also the desire to achieve odor-neutral, solvent-free, physiologically acceptable, clear, aqueous formulations. However, these formulations should also lead to adhesives whose dried films again have a certain water resistance. Furthermore, these water-based adhesives must also be able to bind difficult-to-glue substrates, such as plaster.

This requirement profile has so far not been able to be met at all points, either on the basis of the binders polyvinyl acetate and vinyl acetate copolymers, which have been preferred for universal adhesives up to now, or with alternatives such as nitrocellulose. Admittedly, polyvinyl acetate can be prepared solvent-free in the form of aqueous dispersions, however, these dispersions are not transparent, but rather milky white. They show, for example, good application properties when used as wood glue. Nor are the acrylates and styrene acrylates widely used as dispersion adhesives known on the market in the form of transparent household adhesives with the aforementioned properties.

It has now surprisingly been found that specially selected embodiments of the aqueous polyurethane dispersions known for several decades are suitable as universal adhesives. Polyurethane dispersions consist of adducts of multifunctional isocyanates to multifunctional OH compounds, which contain condensed building blocks which in aqueous solution are capable of salt formation.

In the German specification no. 15 95 602 which goes back to the year 1966, a method for the production of cationically modified polyurethane dispersions, which, as dispersing components, contain quaternary ammonium groups in an amount of at least 0.21% is described in a comprehensive way. The specification mentions numerous polyols, numerous isocyanate compounds and numerous cationic salt-forming components as modifiers. Also mentioned are the common chain extenders here. With the method described there, it is possible to produce optically approximately clear colloidal solutions of associates, which give adhesive-free or adhesive films. The use of the products as adhesives is also mentioned in general, and without further details.

The comprehensive description in DE 15 95 602 includes both polyurethane dispersions, whereby polyesters are used as OH-functional components, and also those where polyethers or polyacetals are used. However, polyurethane dispersions based on polyurethanes, which are made up of OH-functional polyesters, are less suitable as household adhesives, as they undergo hydrolysis upon storage and thus do not exhibit the required storage stability. Polyurethane dispersions whose basic OH-functional components are polyethylene oxide and/or polypropylene oxide are also not suitable as universal adhesives, as they show poor adhesion to plastic surfaces and thus do not meet the requirements for universal applicability.

DE 15 95 602 does indeed mention polytetrahydrofuran as a possible polyol. However, there is no indication that this particular polyol constitutes a suitable basis for polyurethane dispersions for household adhesives.

From the widely available Japanese patent publication No. 62(1987)-112676, published on 23/05/1987, an aqueous polyurethane adhesive is known which comprises an aqueous polyurethane dispersion, obtained by reacting a polytetrahydrofuran diol with a multifunctional isocyanate. Specifically, the Japanese specification teaches to react polytetrahydrofurandiol (molecular weight 400 to 2000) with organic diisocyanates and a dimethylolalkanoic acid, subjecting this to a chain extension step with hydrazine and after neutralization with a tertiary amine and reacting with a water-soluble epoxide or a water-soluble aziridine. The bonding is achieved by cross-linking the polyurethane with its carboxyl groups at the polypeptide or polyaziridine. However, the Japanese publication gives no indication that such polyurethane dispersions in themselves can be advantageously used as household adhesives.

The task of the present invention is therefore to point out that special, aqueous, transparent polyurethane dispersions meet the complex and partly contradictory previously mentioned requirements for household adhesives.

The object of the present invention is a household adhesive, based on an essentially clear and at least essentially solvent-free, aqueous one-component polyurethane dispersion based on the reaction products of a polyol mixture, a bi- or multi-functional isocyanate component, a functional component capable of for salt formation in aqueous solution and, if desired, a chain-extending agent, characterized in that

the polyol mixture consists wholly or partly of polytetrahydrofuran,

The isocyanate component is used in an amount so that the ratio between OE groups from the polyol and isocyanate groups is 1:0.5 to 1:2.0, preferably 1:1.0 to

1 : 1.7 and especially 1 : 1.05 to 1 : 1.6, and that

the multifunctional component capable of salt formation in aqueous solution is selected from the group consisting of dimethylolpropionic acid and of dihydroxy or diamino compounds with an ionizable sulfonic acid or ammonium group.

The polyurethanes which form the basis of the polyurethane dispersions used according to the invention are based on a polyol mixture consisting wholly or partly of polytetrahydrofuran, whereby the content of polytetrahydrofuran, relative to the polyol mixture, shall not be less than 30 and preferably not less than 70 wt-#. Here, polytetrahydrofuran is understood to mean polyethers which can theoretically or actually be produced by ring-opening polymerization of tetrahydrofuran, and which have a hydroxyl group at both chain ends. Suitable products thereby have a degree of oligomerization of 1.5 to 150, preferably of 5 to 100.

Alongside, or instead of, the polytetrahydrofurandiols, analogous compounds can also be used, where the tetrahydrofuran units participating in the structure of the polyols up to 50# have been replaced with ethylene oxide or propylene oxide. Among these compounds, those which are made up of 25 to 30 mol-# ethylene oxide units and 75 to 70 mol-% tetrahydrofuranoxide units are preferred. Alongside the diols based on tetrahydrofuran, analogous diamines can also be used.

The polytetrahydrofuran polyols which form the basis of the polyurethane dispersions used according to the invention can further be replaced by up to 70% by weight of other polyols common in such preparations. In general, these other polyols must have at least two reactive hydrogen atoms and be essentially linear, whereby the molecular weight can lie between 300 and 20,000, preferably between 500 and 6,000. Preferred here are polyesters, polyacetals, polyethers, polythioethers, polyamides and/or polyesteramides, which in any case have an average of 2 to 4 hydroxyl groups.

As polyethers can be mentioned, for example, the polymerization products of ethylene oxide, propylene oxide, butylene oxide as well as their mixed or graft polymerization products, as well as the polyethers obtained by condensation of polyhydric alcohols or mixtures thereof and those obtained by alkylation of polyhydric alcohols, amines, polyamines and amino alcohols. Isotactic polypropylene glycol can also be used.

As polyacetals, for example, those of glycols such as diethylene glycol, triethylene glycol, hexanediol and formaldehyde-producible compounds are mentioned. Suitable polyacetals can also be produced by polymerization of cyclic acetals. Among the polythioethers, the condensation products of thiodiglycol with itself and/or with other glycols, dicarboxylic acids, formaldehyde, aminocarboxylic acids or aminoalcohols should be mentioned in particular. Depending on the co-components, the products are polythioethers, polythioblendethers, polythioetheresters, polythioetheresteramides. Such polyhydroxyl compounds can also be used in alkylated form, or in a mixture with alkylating agents.

The polyesters, polyesteramides and polyamides also include the predominantly linear condensates obtained from polyvalent saturated and unsaturated carboxylic acids, respectively their anhydrides and polyvalent saturated and unsaturated alcohols, amino alcohols, diamines, polyamines and their mixtures, as well as for example polyterephthalate or polycarbonate. Polyesters of lactones, for example caprolactone or of hydroxycarboxylic acids are also usable. The polyesters can have hydroxyl or carboxyl end groups. For their structure, higher molecular polymers or condensates, such as polyethers, polyacetals, polyoxymethylene, can also be used as alcohol components.

Polyhydroxyl compounds which already contain urethane or urea groups as well as possibly modified natural polyols such as castor oil can also be used. In principle, polyhydroxyl compounds, which exhibit basic nitrogen atoms, are also mentioned, for example polyalkylated primary amines or polyesters or polythioethers, which contain condensed alkyl-diethanolamine. Furthermore, polyols can be used which have been obtained by complete or partial ring opening of epoxidized triglycerides with primary or secondary hydroxyl compounds, for example the reaction product of epoxidized soybean oil with methanol.

As polyisocyanates in the polyurethane dispersion of the present invention, all aromatic and aliphatic diisocyanates are suitable, such as, for example, 1,5-naphthylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 4,4'-diphenyldimethylmethane diisocyanate, di- and tetraalkyldiphenylmethane diisocyanate, 4 ,4'-dibenzyl diisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, the isomers of toluene diisocyanate, possibly in a mixture, 1-methyl-2,4-diisocyanate-cyclohexane, 1,6-diisocyanate-2,2,4- trimethylhexane, 1,6-diisocyanate-2,4,4-trimethylhexane, 1-isocyanate-methyl-3-isocyanate-1,5,5-trimethyl-cyclohexane, chlorinated and brominated diisocyanates, phosphorus-containing diisocyanates, 4,4'-diisocyanatephenylperfluoro -ethane, tetramethoxy-butane-1,4-diisocyanate, butane-1,4-diisocyanate, hexane-1,6-diisocyanate, dicyclohexylmethane diisocyanate, cyclohexane-1,4-diisocyanate, ethylene diisocyanate, phthalic acid bis-isocyanate ethyl ester , further polyisocyanates with reactive halogen atoms, such as l-chloromethylphenyl-2,4-diisocyanate, l-bromomethylphenyl-2,6-diisocyanate at, 3,3-bis-chloromethyl ether-4,4'-diphenyl diisocyanate. Sulphur-containing polyisocyanates are obtained, for example, by reacting 2 mol of hexamethylene diisocyanate with 1 mol of thiodiglycol or dihydroxydihexyl sulphide. A preferred diisocyanate is isophorone diisocyanate. Further important diisocyanates are trimethylhexamethyl diisocyanate, meta- and/or para-tetramethylxylene diisocyanate, 1,4-diisocyanatobutane, 1,2-diisocyanatododecane and dimer fatty acid diisocyanate. The previously mentioned isocyanates can be used alone or in a mixture. Cyclic or branched aliphatic diisocyanates such as isophorone diisocyanate are preferred.

Partially end-capped polyisocyanates that deserve interest, which enable the formation of self-crosslinking polyurethanes, are, for example, dimerized toluene diisocyanate, or polyisocyanates partially reacted with, for example, phenols, tertiary butanol, phthalimide, caprolactam.

The chain extenders with reactive hydrogen atoms include: - the usual saturated and unsaturated glycols, such as ethylene glycol or condensates of ethylene glycol, butanediol-1,3, butanediol-1,4, butenediol, propanediol-1,2, propanediol-1,3, neopentylglycol, hexanediol, bis-hydroxymethyl-cyclo-hexane, dioxyethoxyhydroquinone, terephthalic acid bis-glucol ester, succinic acid-di-2-hydroxyethyl-amide, succinic acid-di-N-methyl-(2-hydroxy-ethyl)-amide, 1, 4-di(2-hydroxy-methyl-mercapto)-2,3,5,6-tetrachlorobenzene, 2-methylenepropanediol-(1,3), 2-methylpropanediol-(1,3); - aliphatic, cycloaliphatic and aromatic diamines such as ethylenediamine, hexamethylenediamine, 1,4-cyclohexylenediamine, piperazine, N-methylpropylenediamine, diaminodiphenylsulfone, diaminodiphenylether, diaminodiphenyldimethylmethane, 2,4-diamino-6-phenyltriazine;

Diamines with undesirable material properties that can affect health must be excluded, such as hydrazine, diamino-diphenylmethane or the isomers of phenylenediamine. Furthermore, also carbohydrazides or hydrazides of dicarboxylic acids. - Amino alcohols such as ethanolamine, propanolamine, butanolamine, N-methyl-ethanolamine, N-methyl-isopropanolamine; - aliphatic, cycloaliphatic, aromatic and heterocyclic mono- and diaminocarboxylic acids such as glycine, 1- and 2-alanine, 6-aminocaproic acid, 4-aminobutyric acid, the isomers mono- and diaminobenzoic acids, the isomers mono- and diaminonaphthoic acids;

- water.

It must be emphasized that, within the scope of the present invention, no strict distinction can be made between the compounds with reactive hydrogen atoms with a molecular weight of 300 to 20,000 and the so-called "chain extenders", as the transitions between the two compound classes are fluid. Compounds that are not made up of several monomer units, but have a molecular weight of over 300, such as 3,3'-dibromo-4,4'-diaminodiphenylmethane, are considered chain extenders, as is pentaethylene glycol, although the latter according to to its composition is actually a polyetherdiol.

Special chain extenders with at least one basic nitrogen atom are, for example, mono-, bis- or polyoxalylated aliphatic, cycloaliphatic, aromatic or heterocyclic primary amines, such as N-methyldiethanolamine, N-ethyl-diethanolamine, N-propyl-diethanolamine, N-isopropyl- diethanolamine, N-butyl-diethanolamine, N-isobutyl-diethanolamine, N-oleyl-diethanolamine, N-stearyl-diethanolamine, oxyethylated coconut fat amine, N-allyl-diethanolamine, N-methyl-diisopropanolamine, N-ethyl-diisopropanolamine, N-propyl -diisopropanolamine, N-butyl-diisopropanolamine, C-cyclohexyl-diisopropanolamine, N,N-dioxytylaniline, N,N-dioctyltoluidine, N,N-dioctyl-aminopyridine, N,N'-dioxyethyl-piperazine, dimethyl-bis-oxo- ethylhydrazine, N,N'-bis-(2-hydroxy-ethyl)-N,N'-diethyl-hexa-hydro-p-phenylenediamine, N-12-hydroxyethyl-piperazine, polyalkylated amines such as oxypropylated methyl-diethanolamine, further compounds as N-methyl-N,N'-bis-3-aminopropylamine, N-(3-aminopropyl)-N,N'-dimethylethylenediamine, N-(3-amino-propyl)-N-methyl-ethanolamine, N ,N'-bis-(3-aminopropyl)-N,N'-dimethylethylenediamine, N,N'-bis(3-aminopropyl)-piperazine, N-(2-aminoethyl)-piperazine, N,N'-bisoxyethyl- propylenediamine, 2,6-diaminopyridine, diethanolamino-acetamide, diethanolamido-propionamide, N,N-bis-oxyethyl-phenyl-thiosemicarbazide, N,N-bis-oxetyl-methyl-semicarbazide, p,p'-bis-aminomethyl-di -benzylmethylamine, 2,6-diaminopyridine, 2-dimethylaminomethyl-2-methyl-propanediol-1,3.

Chain extenders with halogen atoms capable of quaternization, respectively R-SOgO groups, are for example glycerol-l-chlorohydrin, glycerol monotosylate, pentaerythritol bis-benzenesulfonate, glycerol monomethanesulfonate, adducts of diethanolamine and chloromethylated aromatic isocyanates or aliphatic halogen isocyanates such as N, N-bis-hydroxyethyl-N'-m-chloromethylphenylurea, N-hydroxyethyl-N'-chlorohexylurea, glycerol-mono-chloroethyl-urethane, bromoacetyl-dipropylenetriamine, chloroacetic acid diethanolamide.

The polyurethanes which form the basis of the polyurethane dispersions used according to the invention also have as an important component a functional component which in aqueous solution is capable of salt formation. As such, dihydroxy or also diamino compounds can be used, which contain an ionizable carboxylic acid, sulfonic acid or ammonium group. These compounds can either be used as such or they can be prepared in-situ. In order to introduce compounds carrying ionizable carboxylic acid groups into the polyurethane, the person skilled in the art can add dihydroxy carboxylic acids to the polyols. A preferred dihydroxycarboxylic acid is, for example, dimethylolpropionic acid.

To introduce sulphonic acid groups which are capable of salt formation, a diaminosulphonic acid can be added to the polyols. An example is 2,4-diaminobenzenesulfonic acid, but also N-(w-amino-alkane)-w'-aminoalkanesulfonic acids as described in DE 20 35 732.

In order to introduce ammonium groups which are capable of salt formation into the polymer, according to the previously mentioned DE 15 95 602 the polyurethane prepolymer can also be modified by means of an aliphatic or aromatic diamine in such a way that primary amino groups are present on the chain ends, which are then transferred with common alkylating agents to quaternary ammonium compounds or to amine salts.

According to the invention, it is preferred to make the polyurethane prepolymers used water-soluble by means of carboxylic acid or sulfonic acid groups, as polyurethane dispersions containing such anionic modifiers can be dissolved again under alkaline conditions, that is to say such adhesives can be removed again under washing conditions from special substrates, for example from textiles.

In the polyurethane dispersions used according to the invention, the polymers are present in salt form. In the case of the preferred polymers which have been modified with carboxylic acids or sulphonic acids, alkali metal salts, ammonia or amines, i.e. primary, secondary or tertiary amines, are present as counterions. In the case of the cationic modified products, counterions are acid anions, for example chloride, sulphate or the anions of organic carboxylic acids. The groups capable of salt formation can therefore be partially or completely neutralized by the counterions. An excess of neutralizing agent is also possible.

As already stated in the discussion of the chain extenders which can be used according to the invention, compounds with health-damaging or - affecting properties are not desired. This applies all the more because the present invention concerns a universally applicable adhesive, which is presumably also used by people who are at risk from a health point of view, such as children, the elderly, the sick, pregnant women, etc. Therefore, in a particularly preferred embodiment, it is not only important to emphasize the chain extenders when it comes to avoiding physiologically questionable substances such as hydrazine, but also when it comes to the other components of the adhesive it is important to strive for physiological acceptability of the components to the greatest extent possible in the adhesive. This includes, for example, the partial, if possible complete, exclusion of organic solvents. The health hazard often discussed in connection with polyurethane adhesives caused by free isocyanates, respectively unreacted NCO groups of the polymers or prepolymers is not present in the present invention, as the polyurethanes are dispersed in water and isocyanate groups react immediately, as is known to the person skilled in the art with water, so that it can be considered assured that the polyurethane dispersions of the invention do not exhibit reactive NCO groups.

For the production of the polyurethanes particularly suitable for the purposes of the invention, the polyols and an excess of diisocyanate are reacted to form a polymer with terminal isocyanate groups, whereby suitable reaction conditions and reaction times as well as temperatures can be varied depending on the relevant isocyanate. The person skilled in the art knows that the reactivity of the components to be reacted necessitates a corresponding equilibrium between reaction rate and unwanted side reactions, which lead to discoloration and molecular weight reduction. Typically, the reaction is carried out with stirring at 50 to 120°C during 1 to 6 hours.

The preferred preparation method is the so-called acetone method (D. Dietrich, Angew. Makromol. Chem 98, 133

(1981)). Furthermore, the polyurethane dispersions used according to the invention can also be produced by the method according to DE 15 95 602. A more recent method for producing polyurethane dispersions is described in DE 36 03 996 as well as in the state of the art indicated there, namely: DE-PS 8 80 485, DE-AS 10 44 404, US-PS 30 36 998, DE-PS 11 78 586, DE-PS 11 84 946, DE-AS 12 37 306, DE-AS 14 95 745, DE-OS 15 95 602 , DE-OS 17 70 068, DE-OS 24 46 440, DE-OS 23 45 256, DE-OS 24 27 274, US-PS 34 79 310 and Angewandte Chemie 82,53 (1970) and Angew. Macromol. Chem. 26.85 ff. (1972).

Of the methods mentioned, the "acetone method" is particularly important, analogously to the teaching in DE-OS 14 95 745 (=US-PS 34 79 310) and DE-OS 14 95 847 (GB-PS 10 67 788). In this way, a prepolymer with -NCO end groups is generally produced first, which is then dissolved in an inert solvent, followed by chain extension in solution to higher molecular weight polyurethane. The incorporation of the hydrophilic groups required for the dispersion preferably takes place either by incorporation of diols carrying ionic and/or potentially ionic and non-ionic hydrophilic groups in the prepolymer or by using corresponding amines as chain extenders. Dispersion takes place discontinuously in stirring containers with stirrers and possibly circuit breakers. The solvent used is usually distilled off immediately after dispersion in water from the mixing container.

Further methods for the production of polyurethane prepolymers, in particular for the continuous production of polyurethane prepolymers, are described in German specification documents 22 60 870, 23 11 635 and 23 44 135.

In order to achieve essentially clear, i.e. opaque to water-clear polyurethane dispersions, the person skilled in the art must emphasize a certain ratio between the components that are capable of salt formation and the other substances that make up the polyurethane. Accordingly, it is appropriate to use the components which are capable of salt formation, calculated as dimethylol propionic acid, in amounts of 1 to 30, preferably of 2 to 20, and especially of 10 to 18 weight-#, calculated on the basis of polyol. Furthermore, the transparency depends on the degree of neutralisation. In this way, the person skilled in the art can, through small preliminary experiments, determine from which quantity of modifiers are capable of ion formation, respectively from which quantity of neutralizing agent a sufficient degree of transparency is achieved. In general, as little of these substances as possible is used, as the water resistance of the adhesive can be disturbed if too much is used.

The present invention further provides a method for producing a household adhesive as described above, which is characterized in that

a prepolymer with NCO end groups is first prepared from a polyol mixture consisting wholly or partly of polytetrahydrofuran,

a ratio OH : NCO such as 1 : 0.5 to 1 : 2.0, preferably 1 : 1.0 to 1 : 1.7 and especially 1 : 1.05

to 1:1.6 used bi- or multi-functional isocyanate component and

a dimethylolpropionic acid as a functional component which

is capable of salt formation in aqueous solution, the prepolymer is then dissolved in an inert solvent,

dispersing is then carried out discontinuously in stirring containers with stirrers and, if desired, circuit breakers and

finally distilling off the used solvent, if desired immediately after the dispersion in water from the mixing container.

The polyurethane dispersion according to the invention means two-phase water/polyurethane systems, which preferably comprise colloidal systems and sols with a particle diameter of 10 to 100 nm. These systems are preferably optically opaque to transparent. From here, optically clear "real" resolutions must be delineated.

The solids content of the adhesive solution can be varied within wide limits. In practice, the solids content between 20 and 70 wt-#, especially between 30 and 50 wt-5é has proven appropriate.

Examples

General manufacturing procedures

The polyols are diluted with acetone or dissolved or dispersed therein. During stirring, the components that are capable of ion formation are added. At temperatures between 50 and 70°C, diisocyanate is then added until the NCO content no longer decreases. It is then neutralized at 60°C, for example with N-methyl-morpholine. After a duration of approx. After 30 minutes, the addition of water takes place. After 30 minutes of dispersion, acetone is then distilled off, later under elevated vacuum at temperatures of 55 to 60°C. Adhesive force (tensile shear strengths) according to "DIN 53254"

60 um - Value on chrome paper

Application of a 60 >jm adhesive f film with a spiral squeegee on chrome paper. Instant bonding with similar paper.

- Slow scraping against each other until material failure in time unit:

Storage test

Polyurethane dispersions used according to the invention according to the examples and according to comparative examples 1 to 4 were subjected to a storage test at temperatures of 50°C. The following development of the viscosity was observed:

Claims (8)

1. Household adhesive, based on a substantially clear and at least substantially solvent-free, aqueous one-component polyurethane dispersion based on the reaction products of a polyol mixture, a bi- or multi-functional isocyanate component, a functional component capable of forming salts in aqueous solution and if desired, a chain extension agent, characterized by the polyol mixture consists wholly or partly of polytetra hydrofuran, The isocyanate component is used in an amount such that the ratio between OE groups from the polyol and isocyanate groups is 1:0.5 to 1:2.0, preferably 1:1.0 to 1:1.7 and especially 1:1.05 to 1:1.6, and that the multi-functional component capable of salt formation in aqueous solution is selected from the group consisting of dimethylolpropionic acid and of dihydroxy or diamino compounds with an ionizable sulfonic acid or ammonium group. 2. Non-stick adhesive according to claim 1, characterized in that the polyol mixture which forms the basis of the polyurethane dispersions in an amount of 30 to 100% by weight consists of polytetrahydrofuran and 0 to 70% by weight of a polyether polyol, polyacetal polyol and/or polyester polyol with an average of 2 to maximum 4 OE groups. 3. Non-stick adhesive according to one of claims 1 or 2, characterized in that the polyol mixtures which form the basis of the polyurethane dispersions in an amount of 70 to 100% by weight consist of polytetrahydrofuran. 4. Non-stick adhesive according to one of the preceding claims, characterized in that the polyurethanes which form the basis of the polyurethane dispersion are made up of bi- or multi-functional aliphatic and/or aromatic diisocyanates, preferably of branched or cyclic aliphatic diisocyanates. 5 . Non-stick adhesive according to one of the preceding claims, characterized in that the polyurethanes which form the basis of the polyurethane dispersions contain condensed dimethylolpropionic acid, which is present as an alkali salt, ammonium salt or as a salt of primary, secondary or tertiary amines. 6. Non-stick adhesive according to one of the preceding claims, characterized in that the amount of dimethylol propionic acid amounts to 1 to 70 wt-56, preferably 2 to 30 wt-# and especially 10 to 18 wt-#, calculated on the basis of polyol. 7. Process for producing a household adhesive according to one of the preceding claims, characterized in that a prepolymer with NCO end groups is first prepared a polyol mixture consisting wholly or partly of polytetrahydrofuran, a ratio OE : NCO such as 1 : 0.5 to 1 : 2.0, preferably 1 : 1.0 to 1 : 1.7 and especially 1 : 1.05 to 1 : 1.6 applied two- or multifunction isocyanate component and a dimethylolpropionic acid as a functional component capable of salt formation in aqueous solution, the prepolymer is then dissolved in an inert solvent mlddel, dispersing is then carried out discontinuously in stirring containers with stirrers and, if desired, circuit breakers and finally distillation of used solvent, if desired immediately after the dispersion in water from the mixing container. 8. Process according to claim 7 for the production of a household adhesive, characterized in that the polyol component is diluted with acetone or dissolved, respectively dispersed therein, the addition of the dimethylolpropionic acid takes place with stirring, diisocyanate is added at temperatures between 50 and 70"C until the NCO content no longer decreases, neutralization takes place at 60°C when the NCO content does not longer sinks, and after a duration of approx. After 30 minutes, water is added, and after 30 minutes of dispersion, the acetone is distilled off, later under higher vacuum at temperatures of 55 to 60°C.