AU671005B2 - Use of an aqueous polyurethane dispersion as an adhesive - Google Patents

Description

VMIUUU I WWI'9 Regulation 3.2(2)

AUSTRALIA

Patents Act 1990

ORIGINAL

COMPLETE SPECIFICATION STANDARD PATENT .4 44** 44,4 4 9944 4449 44..

9* It 0 441.

Application Number: Lodged: C C

''IC

''CC

4'" 4 Cc Invention Title: USE OF AN AQUEOUS POLYURETHANE DISPERSION AS AN ADHESIVE The following statement is a full description of this invention, including the best mathod of performing it known to us

II

O.Z. 0050/44008 Use of an aqueous polvurethane dispersion as an adhesive The present invention relates to the use of an aqueous polyurethane dispersion as an adhesive. In order to avoid solvent wastes and solvent emissions, aqueous polymer dispersions, in particular polyurethane dispersions, are increasingly being used as adhesives. Polyurethane dispersions are described in, for example, DE-A- 39 03 538 and DE-A-14 95 745. Since the mechanical properties, in particular the heat distortion resistance, of adhesive bonds obtainable with such dispersions are often inadequate, they are crosslinked, for example by adding polyisocyanates, as described in, for example, EP-A-02 08 059 and US-A-47 62 880. However, this type of crosslinking has the disadvantage that the pot life, ie.

the time which remains for processing after the addition of the crosslinking agent, is very short.

The crosslinking of polyurethane dispersions by means of polyvalent metal complexes is disclosed in EP-A 228 481, which relates to removable floor coatings.

4 The unpublished German Patent Application P 4137556.4 discloses polyurethane dispersions which contain an adhesion-improving polymer and inorganic salts.

.4i.

It is an object of the present invention to S, improve the mechanical properties, in particular the heat distortion resistance, when polyurethane dispersions are used as an adhesive.

We have found that this object is achieved by the use of aqueous dispersions, containing a polyurethane which is essentially composed of a) organic polyisocyanates, b) polyhydroxy compounds having a molecular weight of from above 500 to 5,000 g/mol, c) compounds having at least one group reactive toward isocyanate and having at least one ionic group or group convertible into an ionic group and

'I

2 O.Z. 0050/44008 d) if required, compounds which differ from and have at least two functional groups reactive toward isocyanate and a molecular weight of from 60 to 500 g/mol, and at lease u/ chelate complex comprising a polyvalent metal as the central atom and a polydentate ligand, as an adhesive. We have also found aqueous dispersions which are suitable for use as an adhesive.

The polyurethane is essentially, preferably exclusively, composed of the components The functional groups reactive toward isocyanate are hydroxyl or primary or secondary amino groups.

Suitable polyisocyanates are in particular aliphatic, cycloaliphatic and aromatic diisocyanates.

S 15 Those of the general formula X(NCO) 2 where X is an aliphatic hydrocarbon radical of 4 to 12 carbon atoms or a cycloaliphatic or aromatic hydrocarbon radical of 6 to carbon atoms, are preferably used.

Examples of suitable aliphatic, cycloaliphatic and aromatic diisocyanates are butane 1,4-diisocyanate, hexane 1,6-diisocyanate, 2,2,4- and 2,4,4-trimethylhexamethylene diisocyanate, cyclohexane diisocyanate, methylcyclohexane diisocyanate, isophorone diisocyanate, 4,4'-diisocyanatodiphenylmethane, 4,4'-diisocyanatodicyclohexylmethane, toluylene 2,4- and 2,6-diisocyanate and tetramethylxylylene diisocyanate (TMXDI).

Mixtures of the diisocyanates may also be used.

Mixtures of aliphatic or cycloaliphatic diisocyanates with aromatic diisocyanates in a molar ratio of from 1 4 to 5 1 have proven particularly suitable.

In addition to the diisocyanates, it is also possible to use minor amounts of monoisocyanates for molecular weight regulation.

Compounds having more than 2 isocyanate groups, such as biurets or isocyanurates, for example those of isophorone diisocyanate or hexamethylene 1,6diisocyanate, may also be present.

RA4/

J

V

,t i L- -rr~L 3 O.Z. 0050/44008 Suitable polyhydroxy compounds, in particular dihydroxy compounds having a molecular weight of from above 500 to 5,000 are the known polyesters, polyethers, polythioethers, polylactones, polyacetals, polycarbonates and polyesteramides having 2 hydroxyl groups.

Preferred dihydroxy compounds are those whose molecular weight is from 750 to 3,000. Mixtures of these dihydroxy compounds can of course also be used.

If necessary, compounds with more than 2 hydroxyl groups, for example glycerol or trimethylolpropane alkoxylated with polypropylene oxide, may additionally be used.

Examples of suitable components which differ from are aliphatic, cycloaliphatic or aromatic monoor dihydroxycarboxylic acids. Dihydroxyalkanecarboxylic acids, in particular of 3 to 10 carbon atoms, as also described in US-A-3 412 054 are preferred. Compounds of the general formula

COOH

4

HO-R

2 C -R 3

-OH

1

R

where R' is hydrogen or alkyl of 1 to 4 carbon atoms and 20 R 2 and R 3 are each C,-C 4 -alkylene, are particularly preferred. An example is 2,2-dimethylolpropionic acid.

Tertiary ammonium salts containing one or two hydroxyl or amino groups and aminocarboxylic acids or S aminosulfonic acids, for example lysine, alanine, N-(2aminoethyl) -2-aminoethanesulfonic acid and the adducts of aliphatic diprimary diamines with a-olefinic carboxylic acids, disclosed in DE-A-20 34 479, for example the adduct of ethylenediamine with acrylic acid, are also noteworthy.

Component contains ionic groups or groups convertible into ionic groups, in order to ensure the S4 O.Z. 0050/44008 dispersibility of the polyurethane in water. Its content is usually from 0.03 to 0.5, preferably from 0.05 to 0.4, gram equivalent, based on 1 mol of isocyanate groups.

Inorganic and/or organic bases, such as sodium hydroxide, potassium hydroxide, potassium carbonate, sodium bicarbonate, ammonia or primary, secondary and in particular tertiary amines, eg. triethylamine or dimethylaminopropanol, can be used for converting potential anionic groups, for example carboxyl groups or sulfo groups, into ionic groups.

For the conversion of the potential cationic groups, for example the tertiary amino groups, into the corresponding cations, for example ammonium groups, inorganic or organic acids, for example hydrochloric acid, acetic acid, fumaric acid, maleic acid, lactic acid, tartaric acid, oxalic acid or phosphoric acid are suitable as neutralizing agents or, for example, methyl chloride, methyl iodide, dimethyl sulfate, benzyl chloride, ethyl chloroacetate or bromoacetamide are suitable as quaternizing agents. Further suitable neutralizing and quaternizing agents are described in, for example, U.S. Patent 3,479,310, column 6.

The neutralization or quaternization of the ionic t..c or of the potentially ionic groups can be carried out before, during and in particular after the isocyanate polyaddition reaction.

If necessary, nonionic emulsifiers, such as monohydric polyether alcohols having a molecular weight of from 500 to 10,000, preferably from 1,000 to 5,000, g/mol may also be present. However, the use of nonionic emulsifiers is generally not necessary, owing to the presence of compounds c).

Components d) are essentially compounds which contain two hydroxyl groups, two amino groups or one hydroxyl and one amino -group. For example, dihydroxy compounds, such as 1,3-propanediol or 1,4-butanediol, diamines, such as ethylenediamine, hexamethylenediamine, iL O.Z. 0050/44008 piperazine, 2,5-dimethylpiperazine, 1-amino-3-aminomethyl-3,5,5-trimethylcyclohexane (isophoronediamine), 4,4'-diaminodicyclohexylmethane, 2,4-diaminocyclohexane, 1,2-diaminopropane or hydrazine, or amino alcohols, such as ethanolamine, isopropanolamine, methylethanolamine or aminoethoxyethanol, are suitable.

Compounds having at least 3 groups reactive toward isocyanate may also be suitable, for example triols, such as trimethylolpropane or glycerol, or trihydroxy compounds having ether or ester groups, as well as pentaerythritol as a tetrahydroxy compound, triamine compounds, such as diethylenetriamine, 4-aminomethyloctanediamine or trisaminoethylamine, and compounds containing hydroxyl and amino groups, such as diethanolamine.

The total content of the components is preferably j ~chosen so that the sum of the hydroxyl and primary or secondary amino groups reactive toward isocyanate is from 0.9 to 1.3, particularly preferably from 0.95 to 1.1, based on 1 isocyanate group.

For the preparation of the polyurethane, the components a) to d) can be reacted in a known manner in a low-boiling, water-miscible, organic solvent or in the fi, l absence of solvents, as also described in DE-A-34 37 918.

All solvents which are unreactive toward isocyanate may be used as the solvent. Those which are infinitely miscible with water, for example tetrahydrofuran, methyl ethyl ketone, N-methylpyrrolidone and in particular acetone, are particularly preferred. Highboiling, water-miscible solvents, for example N-methylpyrrolidone or dimethylformamide, are less preferable.

Water-immiscible solvents, for example toluene or xylene, may also be present in minor amounts. The boiling point of the solvent is preferably below 100°C.

The reaction temperature is preferably from 50 to 120 0

C.

Conventional and known catalysts, such as 6 O.Z. 0050/44008 dibutyltin dilaurate, tin(II) octoate or 1,4-diazabicyclo [2.2.2]octane, may be present for accelerating the reaction of the diisocyanates.

The resulting polyurethane, which is essentially free of isocyanate groups, is then dispersed in water and the organic solvent is removed to the desired extent, in general completely, by distillation.

The polyitrthane may also be prepared by initially preparing a polyurethane prepolymer in an organic solvent. After the addition of the reaction product, the resulting polyurethane prepolymer, which still contains isocyanate groups, is dispersed in water.

The reaction with the further components can then be carried out. The organic solvent can then be removed, as described above.

The aqueous dispersion contains, in addition to the polyurethane, at least one chelate complex comprising a polyvalent metal as the central atom and a polydentate ligand.

The amount by weight of this complex is preferably from 0.01 to 10, particularly preferably from 0.01 to 5, very particularly preferably from 0.02 to 2.5, by weight, based on the polyurethane.

The polyvalent metal is preferably selected from the group consisting of the elements Mg, Ca, Sr, Ni, Ba, Al, Mn, Fe, Zn, Ti, Cu and Zr.

Mg, Ca, Zn, Al and Zr are particularly preferred.

At least one ligand of the central atom is polydentate, ie. has two or more coordinate bonds to the central atom, but preferably all such ligands are polydentate.

Such coordinate bonds are usually formed between groups such as primary, secondary or tertiary amino groups or ethylene oxide, carboxyl, carboxylate, keto, aldehyde, nitrile or mercapto groups or aromatic, ie.

phenolic hydroxyl groups and the central metal atom.

The formation constant K for the formation of a 7 O.Z. 0050/44008 complex of a central metal atom M and one of the polydentate ligands L is preferably calculated as log L, from K, a. a the values obtained being from 3 to 15 (a activity, cf.

also Anorganikum, Berlin 1977, 7th Edition, page 497).

Examples of polydentate ligands are dinitrilotetraacetic acid, pyrocatechol, acetylacetone, 2,2'bipyridyl, ethylenediamine, diethylenediamine, triethylenediamine and crown ethers.

Preferred chelate complexes are neutral complexes which carry no positive or negative charge.

J. The acetylacetonates, in particular tic'e of aluminum and of zirconium, are very particularly preferred.

V 4. The chelate complexes may be added to the polyurethane or to the polyurethane dispersion at any time before, during or after the preparation of the polyurethane. The chelate complexes are preferably added in the form of an organic solution, suitable solvents being, for example, the abovementioned solvents in the preparation of the polyurethane. The chelate complexes are preferably added to the polyurethane before dispersing in water.

The aqueous dispersion which is used according to the invention as an adhesive may furthermore contain an adhesion-improving polymer. The amount by weight of these polymers may be from 5 to 60, preferably from 5 to 30, by weight, based on the polyurethane.

The adhesion-improving polymer is likewise added to the polyurethane or to its prepolymer in water preferably before dispersing. In the case of the prepolymers, the further reaction to give the polyurethane is then carried out.

Suitable adhesion-improving polymers are a large i number of different polycondensates, free radical polymers or polyadducts.

8 O.Z. 0050/44008 The adhesion-improving polymers are preferably phenol/formaldehyde condensation resins or similar reaction products (in particular phenol resins) of a compound selected from the group consisting of aromatic compounds having one aromatic ring, two fused aromatic rings or two aromatic rings which are bonded by a Cl-C.-alkylene and are substituted on at least one ring by at least one hydroxyl grcap and are unsubstituted or substituted on the aromatic rings by from 1 to 3 Ci-C 12 alkyl or Ci-C 12 -alkoxy groups, and the mixtures of these aromatic compounds with a compound (II) selected from the group consisting of compounds having 1 to 20 carbon atoms and at least one keto or aldehyde group, a C 4 C diolefin, compounds having 2 to 10 carbon atoms and at 15 least one triple bond and mixtures thereof.

Preferred compounds are a- or S-naphthol, bisphenol A or phenol which is unsubstituted or substituted by from 1 to 3 C,-C,-alkyl or alkoxy groups. The substituents are preferably meta or para to the hydroxyl group on the aromatic rings. Unsubstituted phenol, aand S-naphthol and bisphenol A are particularly preferred.

I

Stl Preferred compounds are compounds which have one or two hydroxyl groups, particularly preferably one hydroxyl group.

Compounds (II) are preferably compounds having 1 to 14 carbon atoms and one or two keto or aldehyde groups, preferably one keto or aldehyde group. These compounds may be aliphatic or aromatic or may contain both aliphatic and aromatic groups. In addition to the keto or aldehyde group, the compounds preferably contain no further functional groups, ie. no further heteroatoms apart from the oxygen atom of the aldehyde or keto group.

Examples of compounds (II) are formaldehyde, acetaldehyde, n-propionaldehyde, glycolaldehyde, isopropionaldehyde, n-butyraldehyde, isobutyraldehyde, benzaldehyde, glyoxal, glutardialdehyde, oxaglutardialdehyde, il U 9 O.Z. 0050/44008 acetone, methyl ethyl ketone, benzophenone, butadiene, cyclopentadiene and bicyclopentadiene, acetylene, acrolein, methylacrolein or mixtures thereof.

Formaldehyde, acetaldehyde, propionaldehyde, n-butyraldehyde, isobutyraldehyde, acetone and mixtures thereof are particularly preferred.

Reaction products of the compounds and (II) are generally known. The reaction takes place similarly to the phenol/formaldehyde condensation, by addition of the keto or aldehyde group or of the double or triple bond predominantly ortho or para to the hydroxyl group on the aromatic ring.

The molar ratio of the compound to (II) in the condensation reaction is preferably from 1 0.1 to 1 2, particularly preferably from 1 0.7 to 1 1.

The reaction carried out in general by initially taking the compound with an acid as a catalyst, for example a hydrchalic acid, boron trifluoride, sulfuric acid, p-toluenesulfonic acid or dodecylbenzenesulfonic acid, and then metering in the compound (II) at 0 to 250 0 C, preferably from 20 .o 230 0

C.

After the end of the metering, postcondensation can be carried out, in particular at from 20 to 250 0

C,

preferably from 80 to 200 0 C. During the reaction, water can, if desired, be removed from the reaction mixture, if necessary with the use of an entraining agent.

The course of the reaction can be monitored by measuring the softening point of the resulting reaction product.

The reaction products preferably have a softening point (determined according to DIN 52,011) of from 50 to 200 0 C, particularly preferably from 80 to 140°C, very particularly preferably from 120 to 140 0

C.

Epoxy resins, preferably reaction products of epoxides, such as epichlorohydrin, with bisphenol A, are also suitable; those having weight average molecular weights of from 500 to 5,000 and softening points -i L .L -t s 10 O.Z. 0050/44008 of from 80 to 130 0 C are preferred.

Other suitable adhesion-improving polymers are polyvinyl acetate, polyvinyl chloride, polymethacrylates, styrene/acrylonitrile copolymers, polyamides, polyethers, polyesters, polyetherdiols, polyesterdiols, polyurethanes, in particular polyurethanes free of salt groups, and phenacrylate.

Preferred polyvinyl acetates are the homopolymers of vinyl acetate. Its copolymers which contain up to by weight of comonomers such as vinyl laurate, vinyl stearate or, preferably, (meth)acrylic acids, fumarates or maleates of Ci-C-alkanols, such as methanol, n-butanol or 2-ethylhexanol, may also be used. The polymers usually have a K value, measured at 25 0 C in cyclohexanone S 15 according to DIN 53,726, of from 45 to 60. Polyvinyl chloride is understood in general as meaning the homopolymers of vinyl chloride and its copolymers which contain up to 10% by weight of comonomers, such as ethylene or vinyl acetate. Their K value (25 0 C, cyclohexanone, DIN 53,726) should be from 45 to 55. The polymethacrylates used by the skilled worker are usu-l.ly It. I homopolymers of methyl acrylate or its copolymers with up to 10% by weight, based on the copolymer, of vinyl acetate, acrylates of C 1 -C,-alkanols or methacrylates of

C

2 -C.-alkanols. Their melt flow index MFI, deterni:ied according to DIN 53,735 (230 0 C/3.8 kg), is in geraatal from 0.1 to 3.0. These polymers are prepared in general by free radical mass, solution or emulsion polymerization of the ethylenically unsaturated monomers at from 30 to 150 0 C with subsequent drying. Such polymers are generally known, fc example from Houben-Weyl, Methoden der organischen Chemie, Volume E20, 1987, pages 1115- 1125, 1041-1062 and 1141-1174.

Suitable polyamides have a K value of from 65 to 80, measured in H 2

SO

4 at. 25 0 C according to DIN 53,727.

These are usually polymers which are derived from lactams having 7 to 13 ring members, such as €-caprolactam, it 11 O.Z. 0050/44008 e-capryllactam or w-laurolactam, fnr example polycaprolactam (PA6), and polyamides waich are obtained by reacting dicarboxylic acids with diamines. Examples of these are polyhexamethyleneadipamide (PA66), polyhexamethylenesebacamide (PA610) and polyhexamethylenedodecanamide (PA612). Examples of suitable dicarboxylic acids are alkanedicarboxylic acids of 4 to 12, in particular 6 to 10, carbon atoms and phthalic acid, terephthalic acid and isophthalic acid, as well as any mixtures of these acids. Examples of diamines are alkanediamines of 4 to 12, in particular 4 to 8, carbon atoms and m-xylylanediamine, p-xylylenediamine, hydrogenated derivatives thereof, bis(4-aminophenyl)methane, bis(4-aminocyclohexyl)methane or 2,2-bis (4-aminophenyl)propane or mixtures thereof. Owing to their good solubility, copoly- S.mers are preferred, for example a copolyanide of from to 40% by weight of adipic acid, from 15 to 20% by weight of hexamethylenediamine and from 30 to 35% by weight of E-caprolactam or from 15 to 20% by weight or e-aminocaproic acid. The preparation of these known polymers is general technical knowledge, cf. for example Rbmpp, Chemielexikon, 8th Edition, pages 2861, 3058 and 3267, or EP-A-129 195 and EP-A-129 196.

The polyetherdiols are known per se, for example from Kunststoff-Handbuch 7 (1983), 42-54. Examples are 4 polyethylene oxide, polypropylene oxide or polytetra- 4 hydrofuran or their copolymers having two terminal hydroxyl groups. They are prepared in a known manner by, in general, anionic polyaddition, cf. for example N.G.

Gaylord, High Polymers, Vol. 13, New York 1963, Part I.

Polyetherols, which are grafted with ethylene oxide to increase the reactivity, are of minor importance. The polyetherdiols generally have a molecular weight of from 300 to 3,000, corresponding to a K value of from 25 to in DMF at 25 0 C according to DIN 53,726. Preferred molecular weights are from 800 to 2,200.

The polyether used is, for example, polyethylene 4 -j R 12 O.Z. 0050/44008 oxide, polypropylene oxide or polytetrahydrofuran. The polyethers usually have a K value of from 20 to 50 in DMF at 25°C ccording to DIN 53,726. They are generally known, for example from Encyclopedia of Polymer Science and Technology, Volume 6, 1967, page 103 et seq., Volume 9, 1968, page 668 et seq., and Volume 13, 1970, page 670 et seq.

Preferred polyesters are monomer-free unsaturated polyester resins. These are known condensates of polybasic, in particular dibasic, carboxylic acids or the esterifiable derivatives thereof, in particular the anhydrides thereof which are esterified with polyhydric, in particular dihydric, alcohols and may contain additional radicals of monobasic carboxylic acids or mono- 15 hydric alcohols. Examples of starting materials are maleic acid, fumaric acid, phthalic acid, isophthalic acid, terephthalic acid, maleic anhydride, phthalic anhydride, isophthalic anhydride, ethylene glycol, propylene glycol, 1,4-butanediol and neopentylglycol.

Resins which are prepared by condensing bisphenol A, epichlorohydrin/bisphenol A condensates and methacrylic acid are of minor importance for the purposes of the present invention. In this context, monomer-free means the UP resins are insoluble in the monomers suitable for crosslinking, such as styrene. The products usually have a viscosity of from 1,000 to 6,000, in particular from 2,000 to 4 000, mPa.s at 150 0

C.

Sui-able polyesterdiols are condensates which have two terminal OH groups and are obtained from dicarboxylic acids, such as adipic acid or isophthalic acid, and diols, for example 1,4-butanediol, 1,6-hexanediol or neopentylglycol.

The molecular weight range of the polyesterdiols which can be used is in general from 300 to 5,000, preferably from 800 to 2,500, corresponding to a K value of from 30 to 55 in DMF at 25 0 C according to DIN 53,276.

These polymers and their preparation are generally known

A.

-13 O.Z. 0050/44008 from Kunststoff-Handbuch 7 (1983), 54-62, and DE 12 68 842.

Polyurethanes which are free of salt groups are known addition polymers based on polyetherdiols or polyesterdiols, isocyanates, such as hexamethylene diisocyanate, or 2,4-diisocyanatodiphenylmethane, and possibly bi- or trifunctional chain extenders which are prepared by conventional processes (Kunststoff-Handbuch, Karl-Hanser-Verlag, Volume 7 (1966)). Low molecular weight condensates (K value of from 25 to 60 in DMF at 0 C according to DIN 53,726) are preferably used.

Crosslinked polyurethanes are of minor importance.

Phenacrylates are preferably prepared by subjecting bisphenol A glycidyl ethers esterified with acrylic 15 acid or methacrylic acid to an addition reaction with terephthalic acid. Phenacrylates based on epoxidized novolaks may also be used. The K values of the polymers Sare in general from 30 to 55 (in cyclohexane at according to DIN 53,726).

The aqueous dispersions which, according to the invention, are used as adhesives and which contain a chelate complex and may contain an adhesion-improving polymer preferably have a solids content of from 10 to in particular from 20 to 50, by weight.

They can be used, for example, directly as contact adhesives for bonding a very wide range of substrates, for example wood, plastic, glass and metal.

In order to obtain special properties, further additives, such as plasticizers, film-forming assistants, fillers or polyacrylates, polyvinyl acetates, styrene/butadiene copolymers as components of the mixture, etc., may be added to the dispersions. Advantageously, adhesive coatings are applied to the surfaces of both substrates to be bonded.

The aqueous dispersions give adhesive bonds having high strength, in particular high heat distortion resistance.

2~.

14 O.Z. 0050/44008

EXAMPLES

The abbreviations used in the Examples below have the meanings given below: ADA =Adipic acid B14 =1,4-Eutanediol TDI =Toluylene diisocyanate HDI =Hexamethylene diisocyanate IPDI =Isophorone diisocyanate PUD =Sodium salt cf the Michael adduct of acrylic acid and ethylenediamine DBTL =Dibutyltin dilaurate DMPA Dimethylolpropionic acid TMP Trimethylolpropane *4 we., C *09* #814 we 0 O C St te t t 15 O.Z. 0050/44008 EXAMPLE 1A (Comparative Example) 20 Molar amount Parts by weight [mmol] [g] Polyesterdiol (OH number: 198 492 45.0) TDI 147 25.6 HDI 178 24.7 DBTL 0.1 Acetone I 133 Acetone II 532 PUD salt (40% strength) 94 42.0 Phenol/formaldehyde condensate resin, softening point (DIN 52,011) 128 0 C 240 Acetone III 240 Demineralized water 1200 The TDI was added to the mixture of dewatered polyesterdiol, prepared from adipic acid and 1,4-butanediol, acetone I and catalyst. After a reaction time of one hour at 65 0 C the HDI was added and the reaction was continued for a further 90 minutes. After acetone II had been added, the reaction mixture had an NCO content of 0.75%. At 50°C, chain extension was effected with PUD salt, which was present in the form of a 40% strength solution in water. After 5 minutes, the resin solution, prepared from acetone III and a condensate of phenol and formaldehyde, was added and stirring was carried out for 5 minutes at 50°C. Thereafter, dispersing was effected with water and the acetone was distilled off. The dispersion was brought to a solids content of 40% by redilution with demineralized water.

EXAMPLES 1B AND 1C The dispersion was prepared similarly to Example 16 O.Z. 0050/44008 1A (Comparative Example), except that, after the addition of the resin, 8.0 g of aluminum (or zirconium) acetylacetonate, dissolved in 100 ml of acetone, were added.

EXAMPLE 2A (Comparative Example) 20 2 Molar amount Parts by weight [mmol] [g] Polyesterdiol (OH number: 191 476 45.0) 1,4-Butanediol 176 14.1 Trimethylolpropane 17.4 2.3 IPDI 436 96.9 DBTL 0.2 Acetone I 133 Acetone II 532 PUD salt (40% strength) 94 35.0 Phenol/formaldehyde condensate resin, softening point (DIN 52,011) 128°C 240 30 Acetone III 240 4.4, Demineralized water 1200 ,4 11 The IPDI was added to the mixture of dewatered S 35 polyesterol, prepared from adipic acid and 1,4-butanel •diol, 1,4-butanediol, trimethylolpropane, acetone I and catalyst and the reaction was carried out for 130 J minutes. After acetone II had been added, the reaction mixture had an NCO content of 0.57%.

At 50 0 chain extension was carried out with PUD salt, which was present in the form of a 40% strength solution in water. After 5 minutes, the resin solution, prepared from acetone III and a condensate of phenol and formaldehyde, was added and stirring was carried out for 5 minutes at 50°C. Thereafter, dispersing was effected with water and the acetone was distilled off. The

J

i i'i:-"~uon~ 17 O.Z. 0050/44008 dispersion was then brought to a solids content of 40% by redilution with demineralized water.

EXAMPLES 2B AND 2C The dispersion was prepared similarly to Example 2A (Comparative Example), except that, after the addition of the resin, 8.0 g of aluminum (or zirconium) acetylacetonate, dissolved in 100 ml of acetone, were added.

EXAMPLE 3A (Comparative Example) t# 3 4.

C

I,

I

4It4

I)(

20 Molar amount Parts by weight [mmol] [g] Polypropylene oxide 298 597 (OH number: 56) Dimethylolpropionic acid 160 21.5 TDI 867 151 DBTL 0.3 Acetone 978 Demineralized water 1200 strength by weight 112 NaOH solution The TDI was added to the mixture of dewatered polypropylene oxide, dimethylolpropionic acid and catalyst and the reaction was carried out at a reaction temperature of 105 0 C for 3 hours. After acetone had been added, the reaction mixture had an NCO content of 0.45%.

The solution was cooled to 30 0 C, after which the NaOH solution was added and dispersing was effected with water in the course of 20 minutes and the acetone was distilled off. The dispersion was then brought to a solids content of 40% by redilution with demineralized water.

40 EXAMPLES 3B AND 3C The dispersion was prepared similarly to Example 3A (Comparative Example), except that, after the addition of NaOH, 8.0 g of aluminum (or zirconium) acetylacetonate, dissolved in 100 ml of acetone, were added.

i i Ei i; ii

II

i; i:i a z i ii z

B

~I

It, L .1 r i i ir 'i 18 O.Z. 0050/44008 EXAMPLE 4A (Comparative Example) The dispersion was prepared similarly to Comparative Example 1. Instead of the phenol/formaldehyde resin, however, a resin based on phenol and a mixture of n-butyraldehyde and isobutyraldehyde was used (molar ratio of n-butyraldehyde to isobutyraldehyde 1 1).

The softening point (DIN 52,011) was 153 0

C.

EXAMPLES 4B AND 4C The dispersion was prepared similarly to Example 4A (Comparative Example), except that, after the addition of the resin, 8.0 g of aluminum (or zirconium) acetylacetonate, dissolved in 100 ml of acetone, were added.

EXAMPLE 5A (Comparative Example) r r I -I I no 15 S L' *4tt i 30 I 35 Molar amount Parts by weight [mmol] [g] Polyesterdiol (OH number: 196 489 45.0) TDI 159 27.8 HDI 159 26.8 DBTL 0.1 Acetone I 133 Acetone II 532 PUD salt (40% strength) 94 42.0 Phenol/ isobutyraldehyde condensate resin, softening point (DIN 52,011) 132 0 C 240 Acetone III 240 Demineralized water 1200 The preparation was carried out similarly to Example 1, except that the reaction time with HDI was increased to 80 minutes.

19 O.Z. 0050/44008 EXAMPLES 5B AND The dispersion was prepared similarly to Example (Comparative Example), except that, after the addition of the resin, 8.0 g of aluminum (or zirconium) acetylacetonate, dissolved in 100 ml of acetone, were added.

EXAMPLE 6A (Comparative Example) 15 Is Stt <4C 30 Molar amount Parts by weight [mmol] [g] Polyetherol (OH number: 200 401 56) Dimethylolpropionic acid 161 21.6 TDI 670 117 DBTL 0.1 Acetone I 684 Phenol/isobutyraldehyde condensate resin, softening point (DIN 52,011) 128°C 240 Acetone II 240 Demineralized water 1200 30% strength by weight 112 NaOH solution 4 r The TDI was added to the mixture of dewatered polyetherol (polypropylene oxide having an OH functionality of 1.93 equivalent/mole), dimethylolpropionic acid and catalyst, and the reaction was carried out at a reaction temperature of 105 0 C for 3 hours. After acetone I had been added, the reaction mixture had an NCO content of 0.56%.

After neutralization with the NaOH solution, the resin solution, prepared from acetone II and a condensate of phenol and a mixture of n-butyraldehyde and isobutyraldehyde (molar ratio 1 was added. The solution was cooled to 30*C, after which dispersing was c. i -i: 20 O.Z. 0050/44008 effected with water in the course of 20 minutes and the acetone was distilled off. The dispersion was then brought to a solids content of 40% by redilution wtih demineralized water.

EXAMPLES 6B AND 6C The dispersion was prepared similarly to Example 6A (Comparative Example), except that, after the addition of the resin, 8.0 g of aluminum (or zirconium) acetylacetonate, dissolved in 100 ml of acetone, were added.

Contact adhesive bonding at room temperature Sample preparation: The dispersions were thickened with 5% by weight, based on its solid, of pyrogenic silica.

Shear strength: t 15 The particular dispersions were applied to beech wood panels over an area of 150 x 50 mm 2 with a knife coater having 1 mm teeth and were dried for 60 minutes at room temperature. These test specimens were then immediately adhesively bonded by pressing them for seconds at room temperature under a pressure of N/mm 2 The shear strength was measured immediately (instantaneous strength) and after storage for 7 days at room temperature (final strength), in N/mm 2 Heat distortion resistance: A hardboard was adhesively bonded with a PVC film over an area of 200 x 200 mm 2 (contact adhesive bonding at room temperature) The PVC film was subjected to a load of 300 g at a peeling angle of 1800. The temperature was increased by 10°C every 30 minutes. The maximum temperature at which the PVC film is still not completely detached from the hardboard is stated.

21 O.Z. 0050/44008 EXAMPLES 6B AND 6C The dispersion was prepared similarly to Example 6A (Comparative Example), except that, after the addition of the resin, 8.0 g of aluminum (or zirconium) acetylacetonate, dissolved in 100 ml of acetone, were added.

Contact adhesive bonding at room temperature Sample preparation: The dispersions were thickened with 5% by weight, based on its solid, of pyrogenic silica.

Shear strength: The particular dispersions were applied to beech wood panels over an area of 150 x 50 mm 2 with a knife coater having 1 mm teeth and were dried for 60 minutes at room temperature. These test specimens were then immediately adhesively bonded by pressing them for seconds at room temperature under a pressure of 0.5 N/mm 2 The shear strength was measured immediately (instantaneous strength) and after storage for 7 days at room temperature (final strength), in N/mm.

20 Heat distortion resistance: A hardboard was adhesively bonded with a PVC film over an area of 200 x 200 mm (contact adhesive bonding at room temperature). The PVC film was subjected to a load of 300 g at a peeling angle of 1800. The temperature was increased by 10 0 C every 30 minutes. The o maximum temperature at which the PVC film is still not 'completely detached from the hardboard is stated.

Ji t oo tmpraur) Te VCfim assujete t y 1 i I ill I I I e r r *rr -re r c r ne n r n r n rr rnh I'C a e r- r r I a n a I r r r lrr~ Adhesion values of the contact adhesive bond at room temperature Instantaneous strength Final strength [N/mm 2 Heat distortion resistance [N/anm 2

C]

A B C A B C A B C Example 1 1.2 1.1 1.0 3.0 3.0 2.9 Example 2 1.0 1.0 1.0 Example 3 0.5 0.5 0.5 Example 4 1.4 1.1 1.3 Example 5 1.5 1.4 1.3

T

2.7 2.5 2.6 1.5 1.7 1.4 4.2 4.0 4.1 5.0 4.8 4.9 80 110 100 70 80 60 80 60 80 Example 6 1.0 0.9 1.0 4.3 4.1 4.2 fl U U .4 U .1 A: Dispersion without B: Dispersion with 1% C: Dispersion with 1% chelate complexes (Comparative Example) by weight, based on polyurethane, of zirconium acetylacetonate by weight, based on polyurethane, of aluminum acetylacetonate -I i _i ii i~ 23 O.Z. 0050/44008 Testing of the contact adhesive bond after flash activation (heat activation) Sample preparation: The dispersions were thickened with 2% by weight, based on their solid, of polyvinylpyrrolidone.

Peel strength: The dispersions were applied with a brush (1 inch, fine bristles) uniformly to styrene/butadiene rubber (SBR1 rubber having a Shore A hardness of 90 (cf.

DIN 16,909)) over an area of 30 x 130 nm 2 and were dried for 45 minutes at room temperature. After the adhesive films had been heated once by IR radiation to 80 0 C in the course of about 5 secunds (flash activation), the samples were pressed for 10 seconds at 0.5 N/mm 2 The peel S 15 strength was measured immediately (instantaneous o* strength) and after storage for 5 days in a conditioned 00*° chamber (23 0 C/50% relative humidity) (final strength), according to DIN 52,273.

Heat distortion resistance: 20 The test specimens were produced as for testing S° of the peel strength. After being heated for 1 hour at 500C, they were loaded, at 500C, with 5, 10, 15, 20, and 30 N in ascending order, for 10 minutes in each case.

If the adhesive bond held, the load was removed from the sample and the sample was heated to 600C for 30 minutes and tested again up to 30 N in 10 minute steps. After each cycle, the test temperature was increased by 100C.

The temperature (OC) and the load at which breaking of the adhesive bond by more than 50 mm was detectable are stated in each case.

1 lil: I I I rlC t

C

t O I) r ~-rrl t O*--r r

I

Adhesion values of contact adhesive bond after heat activation Instatanaeous strength Final strength [N/mm 2 Heat distortion resistance [N/mm 2

C]

A B C A B C A B C Example 1 1.4 1.5 2.4 2.6 2.4 50/30 70/10 60/30 Example 2 3.3 3.2 3.2 3.5 3.7 3.4 60/20 80/5 70/30 Example 3 0.8 0.7 0.8 3.8 3.9 3.8 60/30 70/10 70/10 Example 4 2.5 2.6 2.5 4.5 4.3 4.4 50/30 60/30 70/05 Example 5 2.6 2.5 2.4 3.7 3.9 3.9 50/5 50/30 50/30 Example 6 1.0 0.9 1.0 4.3 4.1 4.2 60/20 70/30 70/25 A: Dispersion without B: Dispersion with 1% C: Dispersion with 1% chelate complexes (Comparative Example) by weight, based on polyurethane, of zirconium acetylacetonate by weight, based on polyurethane, of aluminum acetylacetonate ~Pa

Claims (4)

1. 2. Use as claimed in claim 1, wherein the content of the chelate complex in the dispersion is from 0.01 to by weight, based on the polyurethane. 20 3. An aqueous dispersion, containing a polyurethane and a chelate complex as claimed in claim 1, wherein the polydentate ligand is an acetylacetonate.
2. 4. An aqueous dispersion, containing a polyurethane and a chelate complex as claimed in claim 1 or 2 and in addition an adhesion-improving polymer. An aqueous dispersion as claimed in claim 4, wherein the adhesion-improving polymer is a phenol resin.
3. 6. An aqueous dispersion as claimed in claim 4 or wherein the adhesion-improving polymer is added to the polyurethane or to a polyurethane prepolymer prior to dispersing in water and, in the case of the polyurethane prepolymer, the further reaction to the polyurethane is carried out after dispersing.
4. 7. An adhesive bond obtainable by using an aqueous dispersion as claimed in'any of claims 1 to DATED this 28th day of April 1994. BASF AKTIENGESELLSCHAFT AL WATERMARK PATENT TRADEMARK ATTORNEYS "THE ATRIUM" 290 BURWOOD ROAD HAWTHORN. VIC. 3122. O.Z. 0050/44008 Abstract of the Disclosure: Aqueous dispersions contain- ing a polyurethane which is essentially composed of a) organic polyisocyanates, b) polyhydroxy compounds having a molecular weight of from above 500 to 5,000 g/mol, c) compounds having at least one group reactive toward isocyanate and having at least one ionic group or group convertible into an ionic group and d) if required, compounds which differ from and have at least two functional groups reactive toward isocyanate and a molecular weight of from 60 to 500 g/mol, and at least one chelate complex comprising a polyvalent metal as the central atom and a polydentate ligand are Soo used as an adhesive. oos