IE892588L - A polyurethane-based universal household adhesive - 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

h 1 ) i V —' v' ' -1 - A nolyureth&ne-based universal household adhesive This invention relates to the use of special, substantially clear, aqueous and at least largely solventless polyurethane dispersions as universal household adhesives.

Universal household adhesives, also known as multipurpose adhesives, are used for bonding a number of substrates encountered in the home (paper, cardboard, photographs, fabrics, leather, felt, bast, cork, films, metals, such as aluminium and iron, china, ceramics, glass, wood, various plastics, including for example polystyrene foams) . The adhesives in question are expected to produce an adequate adhesive effect on these various substrates which differ chemically and physically in their surface structure and which are normally subjected to a special surface treatment before bonding.

Compared with the large variety of classes and types of adhesive used in industry and workshops, there are only a few substances which are capable of meeting the stringent demands imposed on the universality (universality is used in the sense of "versatility) of a multipurpose household adhesive. Among those substances, only polyvinyl acetate and its copolymers are widely used - normally in solution or, for glueing wood, in the form of a dispersion.

The demand for universality represents a particularly difficult selection criterion for an adhesive. Ultimately, it means that the adhesive molecules must show equally high affinity for polar and apolair interfaces. Accordingly, the statement that a certain substance is suitable as an adhesive does not indicate to the expert whether it can also be used as a universal household adhesive.

In addition to the universality requirement, there has 5 also recently been a demand for eolventless, physiologically unobjectionable, clear, aqueous formulations of neutral odor in the field of universal household adhesives. However, these formulations are intended at the same time to lead to adhesives of which the dried films in-10 turn have a certain resistance to water. In addition, these water-based adhesives are also intended to be able to bond substrates that are difficult to bond, such as plastics.

This requirement profile could not be fully satisfied 15 either on the basis of the binders hitherto preferred for universal adhesives, namely polyvinyl acetate and vinyl acetate copolymers, or by such alternatives as nitrocellulose. Although polyvinyl acetate can be produced without solvents in the form of aqueous dispersions, the disper-20 sions obtained are not transparent, but milky white. They • show good performance properties when used, for example, as wood glue. The acrylates and styrene acrylates widely used as dispersion adhesives are also not known on the market in the form of transparent household adhesives with the 25 properties mentioned.

It has now surprisingly been found that specially selected embodiments of the aqueous polyurethane dispersions known for decades are suitable as universal adhesives. Polyurethane dispersions consist of adducts of poly-30 functional isocyanates with polyfunctional OH compounds which contain co-condensed units capable of salt formation in aqueous solution.

DE-OS 15 95 602, which goes back to the year 1966, broadly describes a process for the production of cati-35 onically modified polyurethane dispersions which contain 3 quaternary ammonium groups in a quantity of at least 0.21% as dispersing component. The specification names numerous polyols, numerous isocyanate compounds and numerous cati-onic salt-forming components as modifiers. The usual 5 chain-extending agents are also mentioned. It is possible by the process in question to produce optically almost clear colloidal solutions of aggregates which give tack free or tacky films. The use of the products as adhesives-is also generally mentioned without any particulars. 10 The broad disclosure of DE 15 95 602 encompasses both polyurethane dispersions, in which polyesters are used as the OH-functional component, and also those in which poly-ethers or polyacetals are used. However, polyurethane dispersions based on polyurethanes synthesized from OH-15 functional polyesters are not suitable as universal house hold adhesives because they undergo hydrolysis in storage and hence do not have the required stability in storage. Polyurethane dispersions based on polyethylene oxide and/or polypropylene oxide as OH-functional component are also not 20 suitable as multi-purpose adhesives because they show poor adhesion to plastics and thus do not satisfy the universality requirement.

Although DE 15 95 602 mentions polytetrahydrofuran as a possible polyol, there is no reference to the fact that 25 this particular polyol is a suitable basis for polyurethane dispersions for universal household adhesives.

Published Japanese patent application no. 62(1987)-112676 published on 23.05.1987 describes an aqueous polyurethane adhesive comprising an aqueous polyurethane dis-30 persion which has been obtained by reaction of a poly tetrahydrofuran diol with a polyfunctional isocyanate. More particularly, the published Japanese application teaches reacting polytetrahydrofuran diol (molecular weight 400 to 2,000) with organic diisocyanates and a dimethylol 35 alkanoic acid, subjecting the product of this reaction to - 4 - chain extension with hydrazine and, after neutralization with a tertiary amine, reacting the product with a water-soluble epoxide or a water-soluble aziridine. 5 Bonding is obtained by crosslinking of the carboxyl-terminated polyurethane with the polyepoxide or polyaziridine. There is no reference in the Japanese patent application to the fact that, basically, polyurethane dispersions of the type in question may 10 actually be used with advantage as universal household adhesives.

Accordingly, the problem addressed by the present invention is to show that special, aqueous, transparent polyurethane dispersions satisfy the complex and partly conflicting requirements mentioned 15 above in regard to universal household adhesives.

The present invention relates to the use of a substantially clear and at least largely solventless, aqueous, one-component polyurethane dispersion based on the reaction products of 20 a polyol mixture consisting completely or partly of polytetrahydrofuran, a difunctional or more than difunctional isocyanate component 25 used in an 0H:NC0 ratio of 1:0.5 to 1:2.0, preferably 1:1.0 to 1:1.7 and more preferably 1:1.05 to 1:1.6 thereto and dimethylol propionic acid as a functional component capable of salt formation in aqueous solution as a universal household adhesive. 30 The polyurethanes forming the basis of the polyurethane dispersions used in accordance with the invention are 35 based on a polyol mixture consisting completely or partly of polytetrahydrofuran, in which the polytetrahydrofuran content, based on polyol mixtures, should be no less than 30% by weight and, preferably, no less than 70% by weight. In the context of the invention, the term polytetrahydrofuran applies to polyethers which may be theoretically or actually prepared by ring-opening polymerization of tetrahydrofuran and have a hydroxyl group at either end of the chain. Suitable products have a degree of oligomerization of from approximately 1.5 to 150 and preferably from 5 to 100.

In addition to or instead of the polytetrahydrofuran diols, it is also possible to use the analogous compounds in which up to 50% of the tetrahydrofuran units involved in the synthesis of the polyols are replaced by ethylene oxide or propylene oxide. Among these compounds, preference is attributed to those which consist of 25 to 3 0 mol-% ethylene oxide units and 75 to 70 mol-% tetrahydrofuran oxide units.' In addition to the diols based on tetrahydrofuran, the analogous diamines may also be used.

In addition, up to 70% by weight of the polytetrahydrofuran polyols on which the polyurethane dispersions used in accordance with the invention are based may be replaced by other polyols typically used in preparations of the type in question. A general rule in this regard is that these other polyols must contain at least two reactive hydrogen atoms and should be substantially linear with a molecular weight in the range from 300 to 20,000 and preferably in the range from 500 to 6,000. Preferred other polyols are polyesters, polyacetals, polyethers, polythio-ethers, polyamides and/or polyester amides containing on average 2 to 4 hydroxyl groups.

Suitable polyethers are, for example, the polymerization products of ethylene oxide, propylene oxide, butylene oxide and copolymerization and graft polymerization prod- 6 ucts thereof and the polyetherB obtained by condensation of polyhydric alcohols or mixtures thereof and the polyethers obtained by alkoxylation of polyhydric alcohols, amines, polyamines and aminoalcohols. Isotactic polypropylene 5 glycol may also be used.

Suitable polyacetals are, for example, the compounds obtainable from glycols, such as diethylene glycol, tri-ethylene glycol, hexanediol amd formaldehyde. Suitable polyacetals may also 10 be prepared by polymerization of cyclic acetals.

Among the polythioethers, the condensates of thiodi-glycol on its own and/or with other glycols, dicarboxylic acids, formaldehyde, aminocarboxylic acids or aminoalcohols are mentioned in particular. Depending on the co-compon-15 ents, the products are polythioethers, polythio mixed ethers, polythioether esters, polythioether ester amides. Polyhydroxyl compounds such as these may also be used in alkylated form or in admixture with alkylating agents.

The polyesters, polyesteramides and polyamides include 20 the predominantly linear condensates obtained from poly- basic, saturated and unsaturated carboxylic acids or their anhydrides and polyhydric, saturated and unsaturated alcohols, aminoalcohols, diamines, polyamines and mixtures thereof and also, for example, polyterephthalates or 25 polycarbonates. Polyesters of lactones, for example caprolactone, or of hydroxycarboxylic acids may also be used. The polyesters may contain terminal hydroxyl or carboxyl groups. Relatively high molecular weight polymers or condensates such as, for example, polyethers, poly-30 acetals, polyoxymethylenes may also be (co-)used as alcohol component in their synthesis.

Polyhydroxyl compounds already containing urethane or urea groups and optionally Modified natural polyols, 6uch as castor oil, may also be used. Basically, polyhydroxyl 35 compounds containing basic nitrogen atoms such as, for example, polyalkoxylated primary amines or polyesters or polythioethers containing alkyl diethanolamine in co-condensed form may also be used. Polyols obtainable 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, are also suitable.

Suitable polyisocyanates in the PU dispersions according to the invention are any aromatic and aliphatic diisocyanates such as, for example, 1,5-naphthylene diiso-cyanate, 4,4'-diphenylmethane diisocyanate, 4,4'-diphenyl dimethyl methane diisocyanate, di- and tetraalkyl diphenyl methane diisocyanate, 4,4'-dibenzyl diisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, the isomers of tolylene diisocyanate, optionally in admixture, l-methyl-2,4-diisocyanatocyclohexane, 1,6-diisocyanato-2,2,4-trimethy1 hexane, l,6-diisocyanato-2,4,4-trimethyl hexane, i-isocyanatomethyl-3-isocyanato-l,5,5-trimethyl cyclohexane, chlorinated and brominated diisocyanates, phosphorus-containing diisocyanates, 4,4'-diisocyanato-phenyl perfluoroethane, tetramethoxy butane-1,4-diisocyanate, butane-l,4-diisocyanate, hexane-1,6-diisocyanate, dicyclohexyl methane diisocyanate, cyclohexane-l,4-diiso-cyanate, ethylene diisocyanate, phthalic acid-bis-isocyanatoethyl ester, also polyisocyanates containing reactive halogen atoms, such as i-chloromethylphenyl-2,4-diisocyanate, l-bromomethylphenyl-2,6-diisocyanate, 3,3-bis-chloromethylether-4,41-diphenyl diisocyanate. Sulfur-containing polyisocyanates are obtained, for example, by reaction of 2 mol hexamethylene diisocyanate with 1 mol thiodiglycol or dihydroxydihexyl sulfide. A preferred diisocyanate is isophorone diisocyanate. Other important diisocyanates are triznethyl htexamethylene diisocyanate, m-and/or p-tetramethyl xylene diisocyanate, 1,4-diisocyanato-butane, l,2-diisocyanatododecane and dimer fatty acid 8 diisocyanate. The isocyanates mentioned above may be used individually or even in admixture, cyclic or branch«d aliphatic diisocyanates, such as isophorone diisocyanate, are preferred.

Of interest are partly masked polyisocyanates which provide for the formation of self-crosslinking polyure-thanes, for example dimeric tolylene diisocyanate, or polyisocyanates partly reacted, for example, with phenols' tertiary butanol, phthalimide, caprolactam.

The chain extending agents containing reactive hydrogen atoms include the usual saturated and unsaturated glycols, such as ethylene glycol or condensates of ethylene glycol/ butane-l/3-diol, butane-l,4-diol, butenediol, propane-1,2-diol, propane-l,3-diol, neopentyl glycol, hexane-diol, bis-hydroxymethyl cyclohexane, dioxyethoxy hydroquinone, terephthalic acid-bis-glycol ester, succinic acid di-2-hydroxyethyl amide, succinic acid di-N-methyl-(2-hydroxyethyl)-amide, 1,4-di-(2-hydroxy-methylmercapto)-2,3,5,6-tetrachlorobenzene, 2 -methylene propane-l,3-diol, 2-methylpropane-l,3-diol; aliphatic, cycloaliphatic and aromatic diamines, such as ethylenediamine, hexamethylenediamine, l>4-cyclo-hexylenediamine, piperazine, N-methyl propylenedi-amine, diaminodiphenylsulfone, diaminodiphenyl ether, diaminodiphenyl dimethylmethane, 2,4-diamino-6-phenyl triazine; (not included are diamines having unwanted properties which could endanger health, such as for example hydrazine, diaminodiphenyl methane or the isomers of phenylenediamine; also carbohydraziaes or hydrazides of di.carboxylic acids) - aminoalcohols, such as ethanolamine, propanolamine, butanolamine, N-methyl ethanolamine, N-methyl 9 isopropanolamine; # aliphatic, cycloaliphatic, aromatic and heterocyclic mono- and diaminocarboxylic acids, such as glycine, l- i and 2-alanine, 6-aminocaproic acid, 4-aminobutyric 5 acid, the isomeric mono- and diaminobenzoic acids,, the isomeric mono- and diaminonaphthoic acids; water.

It is emphasized that it is not possible in the context of the invention strictly to distinguish between 10 compounds containing reactive hydrogen atoms with a molecular weight in the range from 3000 to 20,000 and the so-called "chain extending agents" because the boundaries between the two classes of compounds are not clearly defined. Compounds which do not consist of several monomer 15 units, but have a molecular weight above 300, such as for example 3,3'-dibromo-4,4'-diaminodiphenyl methane, are classed as chain-extending agents as is pentaethylene glycol although, on the basis of its composition, the latter is actually a polyether diol. 20 Special chain-extending agents containing at least one basic nitrogen atom are, for example, mono-, bis- or poly-alkoxylated aliphatic, cycloaliphatic, aromatic or heterocyclic primary amines, such as N-methyl diethanolamine, N-ethyl diethanolamine, N-propyl diethanolamine, N-isopropyl 25 diethanolamine, N-butyl diethanolamine, N-isobutyl dieth anolamine, N-oleyl diethanolamine, N-stearyl diethanolamine, ethoxylated coconut oil fatty amine, N-allyl diethanolamine, N-methyl diisopropanolamine, N-ethyl diisopro-panolamine, N-propyl diisopropanolamine, N-butyl diisopro-30 panolamine, N-cyclohexyl diisopropanolamine, N,N-diethoxyl- aniline, N,N-diethoxyl toluidine, N,N-diethoxyl-l-amino-pyridine, N,N'-diethoxyl piperazine, dimethyl-bis-ethoxyl hydrazine,N, N'-bis- (2-hydroxyethyl) -N,N' -diethylhexahydro-p-phenylenediamine, N-12-hydroxyethyl piperazine, polyal-35 koxylated amines, such as propoxylated methyl diethanol- 10 amine, also such compounds as N-methyl-N,N-bis-3-aminopro-pylanine, N-(3-aminopropyl)-N,N'-dimethyl ethylenediamine, N-(3-aminopropyl)-N-methyl ethanolamine, N,N'-bis-(3-aminopropyl)-N,N'-dimethyl ethylenediamine, N,N'-bis-(3-aminopropyl)-piperazine, N-(2-aminoethyl)-piperazine, N,N'-bisoxyethyl propylenediamine, 2,6-diaminopyridine, dieth-anolaminoacetamide, diethanolamidopropionamide, N,N-bis-oxyethylphenyl thiosemicarbazide, N,N-bis-oxyethylmethyI Bemicarbazide, p,p*-bis-aminomethyl dibenzyl methylamine, 2,6-diaminopyridine,2-dimethylaminomethyl-2-methylpropane-1,3-diol.

Suitable chain-extending agents containing P. S0?0 groups and/or halogen atoms capable of quaternization include for example, glycerol-i-chlorohydrin, glycerol monotosylate, penta- erythritol-bis-benzenesulfonate, glycerol monomethanesul- fonate, adducts of diethanolamine and chloromethylated aromatic isocyanates or aliphatic haloisocyanates, such as N,N-bis-hydroxyethyl-N'-m-chloromethyl phenylurea, N- hydroxyethyl-N'-chlorohexyl urea, glycerol monochloroethyl urethane, bromoacetyl dipropylene triamine, chloroactic acid diethanolamide.

The polyurethanes on which- the polyurethane dispersions used in accordance with the invention are based contain a functional component capable of salt formation in aqueous solution as another important constituent. This functional component may be a dihydroxy or even a diamino compound containing an ionizable carboxylic acid, sulfonic acid or ammonium group. These compounds may either be used as such or they may be prepared jjQ pitu. To introduce compounds bearing ionizable carboxylic acid groups into the polyurethane, the expert may add dihydroxycarboxylic acids to the polyols. A preferred dihydroxycarboxylic acid is, for example, dimethylolpropibnic acid.

To introduce sulfonic acid groups capable of salt formation, a diaminosulfonic acid may be added to the 11 polyols. Examples are 2,4-diaminobenzenesulfonic acid and also the N-(u-aminoalkane)-u-aninoalkanesulfonic acids described in DE 20 35 732.

To introduce ammonium groups capable of salt formation 5 into the polymer, it is also possible in accordance with DE 15 95 602 cited above to modify the polyurethane prepolymer with an aliphatic or aromatic diamine in such a way the chains are terminated by primary amino groups which may then be converted into quaternary ammonium compounds or 10 into amine salts with standard alkylating agents.

According to the invention, it is preferred to make the polyurethane prepolymers to be used soluble in water by means of carboxylic acid or sulfonic acid groups because polyurethane dispersions containing anionic modifiers such 15 as these can be removed under alkaline conditions, i.e. adhesives of the type in question can be removed from certain substrates, for example from fabrics, under washing conditions.

The polymers are present in salt form in the polyure-20 thane dispersions used in accordance with the invention.

In the case of the preferred polymers modified with carboxylic acids or sulfonic acids, alkali metal salts, ammonia or amines, i.e. primary, secondary or tertiary amines, are present as counterions. In the cationically 25 modified products, acid anions, for example chloride, sulfate or the anions of organic carboxylic acids, are present as counterions. The groups capable of salt formation may therefore be completely or partly neutralized by the counterions. An excess of neutralizing agent is also 30 possible.

As already mentioned in the discussion of the chain extending agents to be used according to the Invention, compounds which have properties which damage health or are detrimental are not desired. This is even more important 35 because the present invention relates to a universally 12 * applicable adhesive which may indeed be used by classes of people, such as children, old people, ill people, pregnant ) people etc., whose health is particularly at risk.

Therefore in a particularly preferred embodiment the chain 5 extending agents not only exclude those materials such as hydrazine which are physiologically objectionable .but al60 the remaining components of the adhesive are selected in as far as possible to be physiologically unobjectionable. In this connection for example, the partial or, if possible, 10 total absence of organic solvents is to be aimed at. In this connection the much discussed danger to health of polyurethane adhesives from free isocyanate or unreacted isocyanate groups of the polymers or prepolymers does not occur in the present invention because the polyurethanes 15 are dispersed in water and the isocyanate groups as is known to the expert react immediately with the water so it can be guaranteed that the polyurethane dispersions according to the invention contain no reactive NCO- groups.

To produce the polyurethanes particularly suitable for . 20 the purposes of the invention, the polyols and an excess of diisocyanate are reacted to form an isocyanate-terminated polymer, suitable reaction conditions and reaction times and also temperatures being variable according to the particular isocyanate. The expert knows that the reactivity 25 of the constituents to be reacted necessitates a corre sponding equilibrium between reaction velocity and unwanted secondary reactions which lead to discoloration and a reduction in molecular weight. The reaction is typically carried out with stirring over approximately 1 to 6 hours 3 0 at approximately 50*C to approximately 120*C.

The preferred production process is the so-called acetone process (D. Dietrich, Angew. Makrorool, Chem, 98, 133 (1981)). The polyurethane dispersions used in accordance with the invention may also be produced by the process 35 according to DE 15 95 602. A more recent process for the 13 production of polyurethane dispersions is described in DE 36 03 996 and in the prior art cited therein, namely: DE-PS 880 485, DE-AS 10 44 404, US-PS 3,036,998, DE-PS 11 78 586, DE-PS 1 184 946, DE-AS 12 37 306, DE-AS 14 95 745, DE-5 OS 15 95 602, DE-OS 17 70 068, DE-OS 20 19 324, DE-OS 20 35 732, DE-OS 24 46 440, DE-OS 23 45 256, DE-OS 24 27.274, USPS 3,479,310 and Angewandte Chemie 82, 53 (1970) and Angev. Makromol. Chem. 26, 85 et seq 1972) .

Of the processes mentioned, the "acetone process" 10 according to DE-OS 14 95 745 (« US-PS 3,479,310) and DE-OS 14 95 847 (GB-PS 1,067,788) is of particular importance. In this process, an NCO-terminated prepolymer is generally first prepared and then dissolved in an inert solvent, followed by chain extension in solution to form the high 15 molecular weight polyurethane. The hydrophilic groups required for dispersion are preferably introduced either by the incorporation of diols bearing ionic and/or potentially ionic and optionally nonionic hydrophilic groups into the prepolymer or by the use of corresponding amines as chain-extending agents. 2 0 Dispersion takes place continuously in stirred tanks equip ped with stirrers and, optionally, baffles. The solvent used is generally distilled of from the stirred tank immediately after dispersion in water.

Other processes for the production of polyurethane 25 prepolymers, more especially for the continuous production of polyurethane prepolymers, are described in DE-OSS 22 60 870, 23 11 635 and 23 44 135.

To obtain substantially clear, i.e. opaque to water-clear, polyurethane dispersions, it is important 3 0 to maintain a certain ratio between the component capable of salt formation and the other polyurethane-forming components. Thus, it is best to use the component capable of salt formation, expressed ag dimethylolpropionic acid, in quantities of from 1 to 3 0% by weight, preferably in quan-35 titles of from 2 to 20% by weight and more preferably in 14 quantities of from 10 to 18* by weight, based on polyol. In addition, the transparency depends on the degree of neutralization. The expert is able through a few preliminary tests to determine beyond what quantity of modifier 5 capable of ion formation or beyond what quantity of neutralizing agent an adequate degree of transparency is obtained. In general, as little of these components as possible will be used because they can adversely affect th€ water resistance of the adhesive film if used in excessive 10 quantities.

Under the polyurethane dispersions according to the invention are to be understood two-phase aqueous/ polyurethane systems which preferably comprise colloidal systems and sols with a particle size of 10 to 100 nm. 15 These systems are preferably optically opaque to transparent. Optically clear "true" solutions are to be distinguished therefrom.

The solids content of the adhesive solutions according to the invention may be varied within wide limits. Solids 20 contents of from 20 to 70% by weight and preferably from 30 to 50% by weight have proved effective in practice.

Examples 25 General production procedure The polyols are dissolved or dispersed in acetone.

The component capable of ion formation is then 30 added with stirring. Diisocyanate is then added at temper atures of 50 to 70*c until there is no further reduction in the NCO content. The reaction mixture is then neutralized at 60*c, for example with N-methyl morpholine. After about 30 minutes, water is added. After dispersion for 30 35 minutes, the acetone is distilled off, ultimately under a 15 relatively high vacuum at temperatures of 55 to 60*C.

Example Comparison Example 1 5 Polytetrahydrofuran 100 pbw Glycerol-started polyether - 100 pbw polyol, OH value 34 Oleochemical polyol - 82 pbw 10 acc. to DE 37 04 350, OH value 160 Dimethylolproplonic acid 15.58 pbw 21.50 pbw Acetone 50 pbw 50 pbw Isophorone diisocyanate 4 8.9 pbw 98.05 pbw 15 N-methyl morpholine 11.63 pbw 16.04 pbw Deionized water 23 3 pbw 4 50 pbw Adhesive strength (tensile shear strength) - DIN 53 254 20 25 Example Wood/PVC Nmm*2 Wood/wood Nmm"2 Wood/alu Nmm"2 Wood/ABS Nmm"2 6.0 8.5 6.0 5.0 Comparison Example 1 1.4 4.5 4.9 1.4 Universal adhesive, solvent-based n. d. 6-7 1.4 5.5 with swelling of the ABS PVAc dispersion 1.6 3.0 2.0 1.5 3 0 60 um value on chromo paper Application of a 60 Mm adhesive film to chromo paper using a Bpiral knife. Immediate glueing to paper of same type. Slow rubbing on one another until material tears in time units: 3 5 Example Comparison Universal adhesive PVAc disper- Example 1 solvent-based sion 15 sees. 20 sees. 70 sees. 25 sees.

* Polyester diol, molecnilar weight approx. 2000 OH value 60 Dimethylolpropionic acid (DWPA) Acetone Isophorone diisocyanate N-methy1-2-morpholine Deionized water Adhesive strength (DIN 53 254) Hood/plastic (PVC), Nmm'2 Wood/wood Wood/alu (F = failure) 16 Comparison Example 2 100 15.9 45 50.6 11.9 256 5.2 (F) 6.3 (F) 5.6 (P) Comparison Example 3 100 17.3 45.0 59.3 13.0 265 3.5 (F) 0.3 (F) 5.5 (F) Comparison Example 4 100 16.4 45.0 57.2 12.2 265 6.0 (F) 7.5 (F) 8.5 (F) 17 StorsCTC test Polyurethane dispersions to be used in accordance with the invention corresponding to the Example and polyurethane dispersions corresponding to Comparison Example 1 to A were subjected to a Btorage test at temperatures of 50*C. The following evolution of viscosity was observed: Initial viscosity (0m Pas) Viscosity after 3 months (in Pas) Example Comparison Example 1 Comparison Example 2 Comparison Example 3 Comparison Example 4 4000 4000 3700 3500 3600 4050 3700 180 120 410

Claims (9)

CLAIMS - 18 -

1. The use of a substantially clear and at least largely solventless, aqueous, one-component polyurethane dispersion based on the reaction 5 products of a polyol mixture consisting completely or partly of polytetrahydrofuran, 10 a difunctional or more than difunctional isocyanate component used in an 0H:NC0 ratio of 1:0.5 to 1:2.0, preferably 1:1.0 to 1:1.7 and more preferably 1:1.05 to 1:1.6 thereto and dimethylol propionic acid as a functional component capable of 15 salt formation in aqueous solution as a universal household adhesive.

2. The use claimed in Claim 1, characterized in that 30 to 100% by weight of the polyol mixtures on which the polyurethane dispersions are based consist of polytetrahydrofuran to 0 to 70% by weight of a 20 polyether polyol, polyacetal polyol and/or polyester polyol containing on average 2 to at most 4 OH groups.

3. The use claimed in Claim 1 or 2, characterized in that 70 to 100% by weight of the polyol mixtures on which the polyurethane dispersions 25 are based consist of polytetrahydrofuran.

4. The use claimed in any of the preceding claims, characterized in that the polyurethanes on which the polyurethane dispersions are based are synthesized from difunctional or more than difunctional aliphatic 30 and/or aromatic polyisocyanates, preferably from branched or cyclic aliphatic diisocyanates.

5. The use claimed in any of the preceding claims, characterized in that the polyurethanes on which the polyurethane dispersions are based 35 contain co-condensed dimethylol propionic acid which may be present as an alkali metal salt, ammonium salt or as a salt of primary, secondary or tertiary amines. - 19 -

6. The use claimed in any of the preceding claims, characterized in that the quantity of dimethylol propionic acid used is from 1 to 70% by weight, preferably from 2 to 30% by weight and more preferably from 10 to 18% by weight, based on polyol. 5

7. A process for the production of the universal household adhesive claimed in any of the preceding claims, characterized in that an NC0-terminated prepolymer is initially prepared from 10 a polyol mixture consisting completely or partly of polytetrahydrofuran, a difunctional or more than difunctional isocyanate component used 15 in an 0H:NC0 ratio of 1:0.5 to 1:2.0, preferably 1:1.0 to 1:1.7 and more preferably 1:1.05 to 1:1.6 thereto and dimethylol propionic acid as a functional component capable of salt formation in aqueous solution 20 and is then dissolved in an inert solvent, dispersion is then carried out discontinuously in stirred tanks comprising stirrers and, optionally baffles and 25 the solvent used is distilled off from the stirred tank, if desired immediately after dispersion in water.

8. A process for the production of the universal household adhesive 30 claimed in any of the preceding claims, characterized in that the polyol component is diluted with acetone or is dissolved or dispersed therein, 35 - the dimethylol propionic acid is added with stirring, diisocyanate is added at temperatures of 50 to 70°C until there is no further reduction in the NC0 content, - 20 - the product is neutralized at 60°C, water is added after about 30 minutes and 5 - after dispersion for 30 minutes, the acetone is distilled off, subsequently in a relatively high vacuum at temperatures of 55 to 60°C.

9. The use as claimed in any of the preceding claims substantially as 10 hereinbefore described by way of Example. TOMKINS & CO. 15 20 25 30 35