AU669273B2 - Polyurethane dispersion containing a free radical polymer having metal salt groups - Google Patents

Description

'/UUU 1 201511 Rogulaton 3.2(2)

AUSTRALIA

Patents Ac! 1990 R N r:

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ORIGINAL

COMPLETE SPECIFICATION STANDARD PATENT o o o o Application Number: Lodged: r r s a o r Invention Title: POLYURETHANE DISPERSION CONTAINING A FREE RADICAL POLYMER HAVING METAL SALT GROUPS The following statement is a full description of this invention, including the best method of performing it known to us O.Z. 0050/44009 Polyurethane dispersion containing a free radical polymer having metal salt groups The present invention relates to an aqueous dispersion containing A) a polyurethane 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 isocyanates and having at least one ionic group or group convertible into an ionic group d) if required, compounds which differ from c) and have at least two functional groups reactive toward isocyanate and a molecular weight of from 15 60 to 500 g/mol, and B) a free radical polymer containing metal salt groups, formed from at least divalent metals with acid "groups of the polymer, the content of salt groups 20 being from 5 to 1,000 mmol of salt groups per kg of the sum of A) and B).

Aqueous polymer dispersions, in particular polyurethane dispersions, are increasingly being used as adhesives, in order to avoid solvent wastes and solvent 25 emissions. 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 using 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 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. EP-A-228 481 relates to removable floor 2 O.Z. 0050/44009 coatings.

The unpublished German Patent Application P 4137556.4 discloses polyurethane dispersions which contain an adhesion-improving polymer and inorganic salts.

EP-A-373 918 and DE-A-4 004 915 0050/41405) disclose free radical polymers containing metal salt groups. They are used in particular as binders for coatings.

It is an object of the present invention to provide polyurethane dispersions which have improved heat distortion resistance when used as an adhesive.

We have found that this object is achieved by the aqueous dispersion defined above and its use as an 15 adhesive.

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

Particularly suitable polyisocyanates are aliphatic, cycloaliphatic and aromatic diisocyanates.

Those of the general formula X(NCO),, where X is an aliphatic hydrocarbon radical of 4 to 12 carbon atoms or a cycloaliphatic or aromatic hydrocarbon radical of 6 to 25 15 carbon atoms, are preferably used.

Suitable aliphatic, cycloaliphatic and aromatic diisocyanates are, for example, 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, 2,4- and 2,6-toluylene 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.

3 O.Z. 0050/44009 In addition to the diisocyanates, minor amounts of moncisocyanates for molecular weight regulation may also be used.

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

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 15 dihydroxy compounds may of course also be used.

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

Examples of suitable components which differ 20 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

HO-R

2 C -R 3

-OH

where R' is hydrogen or alkyl of 1 to 4 carbon atoms and

R

2 and R 3 are each Ci-C 4 -alkylene, are particularly preferred. 2,2-Dimethylolpropionic acid is an example.

Tertiary ammonium salts containing one or two hydroxyl groups or amino groups and aminocarboxylic acids or aminosulfonic acids, for example lysine, alanine and N-(2-aminoethyl)-2-aminoethanesulfonic acid and the adducts, stated in DE-A-20 34 479, of aliphatic diprimary 4 O.Z. 0050/44009 diamines with a-olefinic carboxylic acids, for example the adduct of ethylenediamine with acrylic acid, may also be mentioned.

Component contains ionic groups or groups convertible into ionic groups, in order to ensure the dispersibility of the polyurethane in water. The amount therefore 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 or, in particular, tertiary amines, eg. triethylamine or dimethylaminopropanol, may be used for converting potential 15 anionic groups, for example carboxyl or sulfo groups, into ionic groups.

For the conversion of the potential cationic groups, for example of the tertiary amino groups, into the corresponding cations, for example ammonium groups, 20 inorganic or organic acids, eg. hydrochloric acid, acetic acid, fumaric acid, maleic acid, lactic acid, tartaric acid, oxalic acid or phosphoric acid, are suitable as neutralizing agents and, for example, methyl chloride, methyl iodide, dimethyl sulfate, benzyl chloride, ethyl 25 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 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, owing to the presence of compounds the use of nonionic emulsifiers 5 O.Z. 0050/44009 is generally unnecessary.

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, piperazine, 2,5-dimethylpiperazine, l-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.

Other compounds which may be suitable are those having at least 3 groups reactive with isocyanate, for 15 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, trisaminoethylamine and compounds 20 containing hydroxyl and amino groups, such as diethanolamine.

Altogether, the amount of the components is preferably chosen so that the sum of the primary or secondary amino groups and the hydroxyl groups reactive 25 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 low-boiling, water-miscible organic solvent or in the absence of a solvent in a known manner, as also described in DE-A- 34 37 918.

All solvents which are unreactive toward isocyanates can be used as solvents. Those which are infinitely miscible with water, such as tetrahydrofuran, methyl ethyl ketone, N-methylpyrrolidone and in particular acetone, are particularly preferred. Highboiling water-miscible solvents, for example N-methyls 6 O.Z. 0050/44009 pyrrolidone or dimethylformamide, are less preferable.

Minor amounts of water-immiscible solvents, for example toluene or xylene, may also be present. The boiling point of the solvent is preferably below 100 0

C.

The reaction temperature is preferably from 50 to 120*C.

Conventional and known catalysts, such as 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 required extent, in general completely, by distillation.

15 The polyurethane can also be prepared by first 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 20 with the further components can then be carried out. The organic solvent can then be removed, as already described above.

The aqueous dispersion contains, in addition to the polyurethane, a polymer obtained by free radical polymerization and containing metal salt groups, formed from at least divalent, preferably divalent, metals with acid groups of the polymer.

The content of the salt groups is from 5 to 1,000 mmol, preferably from 10 to 500 mmol, particularly preferably from 10 to 150 mmol, per kg of the sum of A) and B).

The amount by weight of the polymer B) may be, for example, from 0.1 to 70, preferably from 0.2 to particularly preferably from 0.2 to 10, by weight, based on the polyurethane.

The polymer B) is preferably composed of a) from 3 to 60% by weight of an a,B-monoethylenically 7 O.Z. 0050/44009 unsaturated mono- or dicarboxylic acid of 3 to carbon atoms, b) from 97 to 40% by weight of at least one Ci-C 20 -alkyl (meth)acrylate, one vinyl ester of a carboxylic acid of 1 to 20 carbon atoms, one vinyl aromatic of up to carbon atoms, one ethylenically unsaturated nitrile of 3 to 6 carbon atoms, one vinyl halide or one nonaromatic hydrocarbon having 4 to 8 carbon atoms and at least 2 conjugated double bonds and c) from 0 to 50% by weight of at least one further ethylenically unsaturated monomer, from 5 to 100 mol of the acid groups from a) being converted into a metal salt group.

The amount by weight of the monomer a) is par- 15 ticularly preferably from 10 to 50% by weight, that of b) 'from 90 to 50% by weight and that of c) from 0 to 20% by weight.

Examples of suitable monomers a) are acrylic acid, methacrylic acid, maleic acid, fumaric acid, 20 crotonic acid, itaconic acid and maleic or fumaric halfesters, in particular of Ci-C,-alkanols.

Preferred monomers b) are Ci-C 20 -alkyl (meth)acrylates, in particular Ci-Co 1 -alkyl (meth)acrylates, such as methyl methacrylate, methyl acrylate, n-butyl 25 acrylate, ethyl acrylate and 2-ethylhexyl acrylate. A preferred vinyl aromatic compound of up to 20 carbon atoms is styrene. Vinyl esters of carboxylic acids of 1 to 20 carbon atoms are, for example, vinyl acetate and vinyl propionate. Compounds having two conjugated double bonds are, for example, butadiene, isoprene or chloroprene.

The further monomers c) may be, for example, C 1

C

10 -hydroxyalkyl acrylates, (meth)acrylonitrile, (meth)acrylamide or anhydrides, such as maleic anhydride.

The polymer is. prepared in general by free radical polymerization. Suitable polymerization methods, such as mass, solution, suspension or emulsion 8 O.Z. 0050/44009 polymerization, are known to the skilled worker.

For example, in the emulsion polymerization, the monomers can be polymerized in a conventional manner in the presence of a water-soluble initiator and of an emulsifier at, preferably, from 30 to 95 0 C. Examples of suitable initiators are sodium persulfate, potassium persulfate, ammonium persulfate, tert-butyl hydroperoxides, water-soluble azo compounds or redox initiators.

The emulsifiers used may be, for example, alkali metal salts of relatively long-chain fatty acids, alkylsulfates, alkylsulfonates, alkylated arylsulfonates or alkylated diphenyl ether sulfonates.

Other suitable emulsifiers are reaction products of alkylene oxides, in particular ethylene oxide or 15 propylene oxide, with fatty alcohols, fatty acids or phenol, or alkylphenols.

The acid groups in the polymer can be converted into salt groups, for example after the preparation of the polymer.

20 For example, basic salts, by means of which the acid groups can be converted into salt groups, may be added for this purpose.

.Oxides, hydroxides, carbonates and bicarbonates of metals, in particular divalent metals, such as Zn or 25 in particular Ca or Mg, are preferably added. In the case of these basic salts, free counter-ions no longer remain in the water after salt formation of the acid groups. Instead, the salt formation takes place with formation of H 2 0 or CO 2 The basic metal compounds are incorporated in the dispersion or solution of the polymer B) in general with stirring for several hours at a pH of, preferably, less than 7, in particular less than 3.

The metal compounds are preferably in finely divided form having a BET surface area of from 2 to 5 m 2 /g (determined by the method of Brunauer, Emmet and Teller, cf. P.W. Atkins, Physikalische Chemie, VCH- Verlag, D-6940 Weinheim, 1987, page 799 et seq.).

9 O.Z. 0050/44009 When incorporating the metal compounds, assistants, for example wetting agents, may also be present.

It should furthermore be mentioned that, when incorporating the metal compounds, it is also possible to start from polymers which, for example, initially contain only anhydride groups instead of acid groups. Depending on the conditions, the anhydride ring can be opened during the incorporation, so that a polymer B having the desired metal salt content is obtained.

The polymer B) having the desired content of salt groups may be added to the polyurethane at any time, even during the preparation of the polyurethane or of the aqueous polyurethane dispersion obtained after the preparation of the polyurethane.

1 The addition of the polymer B) to the resulting, queous polyurethane dispersion, ie. after dispersing of the polyurethane in water, is preferred.

The novel aqueous dispersion may furthermore contain an adhesion-improving polymer. The amount by 20 weight of this polymer may be from 5 to 60, preferably from 5 to 30, by weight, based on the polyurethane.

The adhesion-improving polymer is preferably added before the dispersing of the polyurethane or of its prepolymer in water. In the case of the prepolymer, the 25 further reaction to give the polyurethane is then carried .out.

Suitable adhesion-improving polymers are many different polycondensates, polymers obtained by free radical polymerization or polyadducts.

The adhesion-improving polymer is preferably phenol/formaldehyde condensation resin or a similar reaction product of a compound selected from aromatic compounds having one aromatic ring, two fused aromatic rings or two aromatic rings which are bonded by a Ci-C,alkylene group and are substituted by at least one hydroxyl group on at least one ring and unsubstituted or substituted by 1 to 3 CI-C 12 -alkyl or C,-C 12 -alkoxy groups L- I 10 O.Z. 0050/44009 on the aromatic rings, and the mixtures of these aromatic compounds with a compound (II) selected from 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 least one triple bond, or mixtures thereof.

Preferred compounds are a- or B-naphthol, bisphenol A or phenol which is unsubstituted or substituted by 1 to 3 Ci-C 8 -alkyl or alkoxy groups. The substituents are preferably meta or para to the hydroxyl groips on the aromatic rings.

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

15 Compound (II) is preferably a compound having 1 to 14 carbon atoms and one or two keto or aldehyde groups, preferably one ket, or aldehyde group. These compounds may be aliphatic or aromatic or may contain :i both aliphatic and aromatic groups. Apart from the keto 20 or aldehyde group, the compounds preferably contain no further functional groups, ie. no further hetero atoms apart from the oxygen atom of the aldehyde or keto group.

'Examples of compound (II) are formaldehyde, acetaldehyde, n-propionaldehyde, glycolaldehyde, isopropionaldehyde, n-butyraldehyde, isobutyraldehyde, benzaldehyde, glyoxal, glutardialdehyde, oxaglutardialdehyde, acetone, methyl ethyl ketone, benzophenone, butadiene, cyclopentadiene and bicyclopentadiene, acetylene, acrolein, methacrolein and mixtures thereof.

Formaldehyde, acetaldohyde, propionaldehyde, nbutyraldehyde, 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 II 11 O.Z. 0050/44009 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 is carried out in general by initially taking the compound with an acid as a catalyst, for example a hydrohalic acid, boron trifluoride, sulfuric acid, p-toluenesulfonic acid or dodecylbenzenesulfonic acid, and then metering in the compound (II) at from 0 to 250 0 C, preferably from 20 to 230 0

C.

After the end of the metering, postcondensation may also be carried out, in part.cular 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 using 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 0 C, very particularly preferably from 120 to 140 0

C.

Epoxy resins, preferably reaction products of epoxides, such as epichlorohydrin, with bisphenol A, are 25 also suitable; those having weight average molecul4 S" weights of from 500 to 5,000 and softening points ri from 80 to 130°C are preferred.

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

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)acrylates, fumarates or 12 O.Z. 0050/44009 maleates with C,-C.-alkanols, such as methanol, n-butanol or 2-ethylhexanol, may also be us, The polymers usually have a K value of from 45 to 6U, measured at 25 0

C

in cyclohexanone according to DIN 53,726. 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 polymethacrylate usually used by the skilled worker is a homopolymer of methyl acrylate or one of its copolymers with up to 10% by weight, based on the copolymer, of vinyl acetate, acrylates of C -C,-alkanols or methacrylates of C 2

-C

8 -alkanols. Its melt flow index MFI, 15 determined according to DIN 53,735 (230 0 C/3.8 kg) is in general from 0.1 to 3.0. These polymers are prepared in general by free radical polymerization of the ethylenically unsaturated monomers at from 30 to 150 0 C by mass, solution or emulsion polymerization and are 20 subsequently dried. Such polymers are generally known, for 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 25 80, measured in H2SO4 at 25 0 C according to DIN 53,727.

They are usually polymers which are derived from lactams having 7 to 13 ring members, such as e-caprolactam, ecapryllactam or u-laurolactam, for example polycaprolactam (PA6), and polyamides which are obtained by reacting dicarboxylic acids with diamines. Examples of these are polyhexamethyleneadipamide (PA66), polyhexamethylenesebacamide (PA610) or polyhexamethylenedodecanamide (PA612). Examples of suitable dicarboxylic acids are alkanedicarboxylic acids of 4 to 12, in particular 6 to 10, carbon atoms, as.well as phthalic acid, terephthalic acid and isophthalic acid and any mixtures of these acids. Examples of diamines are alkanediamines of 13 O.Z. 0050/44009 4 to 12, in particular 4 to 8, carbon atoms and mxylylenediamine, 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 the good solubility, copolymers are preferred, for example a copolyamide comprising from 30 to 40% by weight of adipic acid, from 15 to by weight of hexamethylenediamine and from 30 to 35% by weight of e-caprolactam or from 15 to 20% by weight of eaminocaproic acid. The preparation of these known polymers is part of general technical knowledge (cf. for example R6mpp, 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 Vol. 7 (1983), pages 42 to 54.

Examples are polyethylene oxide, polypropylene oxide or polytetrahydrofuran or copolymers thereof having two terminal hydroxyl groups. They are prepared in a known .:manner by, in general, anionic polyaddition (cf. for 20 example N.G. Gaylord, High Polymers, Vol. 13, New York 1963, Part Polyetherols, which are grafted with ethylene oxide to increase the reactivity, are of minor importance. The polyetherdiols have in general a molecular weight of from 300 to 3,000, which corresponds to a 25 K value of from 25 to 60 in DMF at 25°C according to DIN 53,726. Preferred molecular weights are from 800 to 2,200.

The polyether used is, for example, polyethylene oxide, polypropylene oxide or polytetrahydrofuran. The polyethers usually have a K value of from 20 to 50 in DMF at 25°C according 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

I

14 O.Z. 0050/44009 polybasic, in particular dibasic, carboxylic acids or esterifiable derivatives tnereof, in particular anhydrides thereof which are esterified with polyhydric, in particular dihydric, alcohols and may contain additional radicals of monobasic carboxylic acids or monohydric 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 of minor importance for the purpose of the present invention are those which are prepared by cocondensation of bisphenol A, epichlorohydrin/bisphenol A condensates and methacrylic acid. Monomer-free in this 15 context means that these UP resins are not dissolved 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 1500C.

Suitable polyesterdiols are condensates which 20 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-hexane- 'diol or neopentylglycol.

The molecular weight range of the polyesterdiols 25 used is in general from 300 to 5,000. A molecular weight of 800 to 2,500, corresponding to a K value of from 30 to in DMF at 25°C according to DIN 53,276, is preferred.

These polymers and their preparation are generally known from Kunststoff-Handbuch 7 (1983), 54 to 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 7 (1966), Karl-Hanser-Verlag). Low molecular weight s 15 O.Z. 0050/44009 condensates (K value of from 25 to 60 in DMF at 25 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 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 are in general from 30 to 55 (in cyclohexane at 25 0

C

according to DIN 53,726).

The novel aqueous dispersions preferably have a solids content of from 10 to 70, in particlar from 20 to 50, by weight.

They can be used, for example, as coating materi- 15 als for a very wide range of substrates or preferably as adhesives, in particular as contact adhesives for bonding a very wide range of substrates, for example wood, plastic, glass and metal. In order to achieve special properties, further additives, such as plasticizers, 20 film-forming assistants, fillers, etc., or polyacrylates, polyvinyl acetates or styrene/butadiene copolymers, as components of the mixture, may be added to the dispersions. Adhesive coatings are advantageously applied to the surfaces of both substrates to be adhesively bonded.

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

EXAMPLES

The abbreviations used in the Examples below have the meanings shown below: ADA Adipic acid B14 1,4-Bu.tanediol TDI Toluylene diisocyanate HDI Hexamethylene diisocyanate IPDI Isophorone diisocyanate PUD Na salt of the Michael adduct of acrylic acid and ethylenediamnine 16 O.Z. 0050/44009 *.e DBTL Dibutyltin dilaurate DMPA Dimethylolpropionic acid TMP Trimethylolpropane EXAMPLE 1A (Comparative Example) 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 Demineralised water 1200 The TDI was added to the mixture of dewatered polyesterdiol, prepared from ad.pic 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 the addition of acetone II, the reaction mixture had an NCO content of 0.75%. At 50 0 C, chain-extension was effected with PUD salt, which was present as 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 stirring was carried out for 5 minutes at 50 0 C. Thereafter, dispersing was effected with water and the acetone was distilled off.

17 O.Z. 0050/44009 The dispersion was brought to a solids content of 40% by redilution with demineralised water.

EXAMPLE 2A (Comparative Example) s a 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 Acetone III Demineralised water 240 1200 sc The IPDI was added to the mixture of dewatered polyesterol, prepared from adipic acid and 1,4-butanediol, 1,4-butanediol, trimethylolpropane, acetone I and catalyst and reacted for 130 minutes. After the addition of acetone II, the reaction mixture had an NCO content of 0.57%.

At 50 0 C, chain extension was effected with PUD salt, which was present as a 40% strength solution in water. After 5 minutes, the resin solution, prepared from acetone III and a condensate phenol and formaldehyde, was added and stirring was carried out for minutes at 50 0 C. Thereafter, dispersing was effected with water and the acetone was distilled off. The 18 O.Z. 0050/44009 o ro r dispersion was then brought to a solids content of 40% by redilution with demineralised water.

EXAMPLE 3A (Comparative Example) 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 30% strength by weight 112 NaOH solution Acetone 978 Demineralised water 1200 The TDI was added to the mixture of dewatered polypropylene oxide, dimethylolpropionic acid and catalyst and reacted at 105°C for 3 hours. After the addition of acetone, the reaction mixture had an NCO content of 0.45%.

After the solution had been cooled to 30 0 C, the NaOH solution was added and dispersing with water was effected 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 demineralised water.

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.

19 O.Z. 0050/44009 EXAMPLE 5A (Comparative Example) 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

I

o r Phenol/isobutyraldehyde condensate resin, softening point (DIN 52,011) 132°C 240 Acetone III Demineralised water 240 1200 The preparation was carried out similarly to Example 1, except that the reaction time with HDI was increased to 80 minutes.

20 O.Z. 0050/44009 EXAMPLE 6A (Comparative Example) o r 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) 1280C 240 Acetone II 240 Demineralised water 1200 30% strength by weight 112 NaOH solution The TDI was added to the mixture of dewatered polyetherol (polypropylene oxide having an OH functionality of 1.93 equivalents/mole), dimethylolpropionic acid and catalyst and reacted at 105°C for 3 hours. After the addition of acetone I, the reaction mixture had an NCO content of 0.56%.

Thereafter, the resin solution, prepared from acetone II and a condensate of phenol and a mixture of nbutyraldehyde and isobutyraldehyde (molar ratio 1 1), was added. After the solution was cooled to 300C, 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 demineralised water.

EXAMPLES 1B-6B by weight, based on the polyurethane, of a copolymer of 40% by weight of acrylic acid and 60% by o L I 21 O.Z. 0050/44009 weight of n-butyl acrylate was added to the polyurethane dispersions 1A-6A. 100 mol of the acid groups in the copolymer were present as Ca salt groups as a result of the addition of an equivalent amount of CaO.

EXAMPLES 1C-6C As for Examples 1B-6B, except that MgO was added instead of CaO, so that Mg salt groups were correspondingly present.

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 15 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 20 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 2 Heat distortion resistance: A hardboard was adhesively bonded with a PVC film 25 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 0 C every 30 minutes. The maximum temperature at which the PVC film is still not completely detached from the hardboard is stated.

0

O

Adhesion values of contact adhesive bond at room temperature Instantaneous strength Final strength [N/mm 2 Heat distortion resistance [N/mm 2 A B C A B C A B C Example 1 1.2 1.2 1.0 3.0 3.0 2.9 70 80 Example 2 1.0 1.0 1.0 2.7 2.5 2.5 80 110 110 Example 3 0.5 0.5 0.5 1.5 1.7 1.4 70 80 Example 4 1.4 1.4 1.2 4.2 4.0 3.8 60 80 Example 5 1.5 1.4 1.3 5.0 4.8 4.7 60 80 Example 6 1.0 0.9 0.8 4.3 4.1 4.0 70 90 90 _t 23 O.Z. 0050/4400L' Testing of the contact adhesive bond after flash activation (heat activation) Sample preparation: The dispersions were thickened with 20% 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 mm 2 and were dried for 45 minutes at room temperature. After the adhesive films had been heated once by IR radiaticn to 80 0 C in the cours- of about 5 seconds (flash act_-ation), the samples were pressed for 10 seconds at 0.5 N/mm 2 The peel 15 strength was measured immediately (instantaneous strength) and after storage for 5 days in a conditioned 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 of the peel strength. After being heated for 1 hour at 50 0 C, they were loaded, at 50 0 C, with 5, 10, 15, 20, and 30 N in ascending order, for 10 minules in each case.

If the adhesive bond held, the load was removed from the 25 sample and the sample was heated to 60°C for 30 minutes and tested again up to 30 N in 10 minute steps. After each cycle, the test temperature was increased by 10 0 C in the same way. The temperature and the load at which breaking of the adhesive bond by more than 50 mm was detectable are stated in each case.

Adhesion value,- of contact adhesive bond after flash activation Instantaneous strength [N /nn 2 Final strength [N /mm 2 Heat distortion 0

C]

resistance

C

Example 1 Example 2 Example 3

A

1.5 I -f 1.4 3.2 1.3 3.0 2.4 3.5 2.6 2.4 50/30 -t -I- 70/10 80/5 60/30 70/30 3.3 3.4 4 4 I I 60/20 60/30 0.8 0.8 0.8 3.8 3.9 3.8 70/10 70/10 Example 4] 2.5 12.5 2..3 4. 4.4 5/3 60/30 1 70/05 Example 5J Example 6 2.6 2 .6 2.4 4 I4 3.7 4.3 3.9 3.9 1.0 1.0 1.0 4.1 4.

50/5 60/20 50/30 70/30 50/30 70/25

Claims (10)

1. An aqueous dispersion containing A) a polyurethane 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 isocyanates and having at least one ionic group or group convertible into an ionic group d) if required, compounds which differ from c) and have at least two functional groups reactive toward isocyanate and a molecular weight of from 60 to 500 g/mol, 'and a d 15 B) a fr-g atI polymerycontaining metal salt groups, formed from at least divalent metals with acid groups of the polymer, the content of salt groups being from 5 to 1,000 mmol of salt groups per kg of the sum of A) and B). 20

2. An aqueous dispersion as claimed in claim 1, wherein the metals from the metal salts of B) are divalent metals.

3. An aqueous dispersion as claimed in claim 1, wherein the polymer B) is composed of 25 a) from 3 to 60% by weight of an a,B-monoethylenically unsaturated mono- or dicarboxylic acid of 3 to carbon atoms, b) from 97 to 40% by weight of at least one C 1 -C 20 -alkyl (meth)acrylate, one vinyl ester of a carboxylic acid of 1 to 20 carbon atoms, one vinyl aromatic of up to carbon atoms, one ethylenically unsaturated nitrile of 3 to 6 carbon atoms, one vinyl halide or one nonaromatic hydrocarbon having 4 to 8 carbon atoms and at least 2 conjugated double bonds and c) from 0 to 50% by weight of at least one further ethylenically unsaturated monomer and from 5 to 100 mol of the acid groups from a) are 4 26 O.Z. 0050/44009 converted into a metal salt group.

4. An aqueous dispersion as claimed in claim 1, wherein the polymer B) containing salt groups is obtain- able by reacting a polymer containing acid groups or anhydride groups with an oxide, hydroxide, carbonate or bicarbonate of a divalent metal.

An aqueous dispersion as claimed in claim 1, wherein the dispersion additionally contains 5 to 60% by weight, based on the polyurethane, of an adhesion- improving polymer which differs from A) and B).

6. An aqueous dispersion as claimed in claim wherein the adhesion-improving polymer is added to the polyurethane or to a polyurethane prepolymer before dispersing in water and, in the case of the polyurethane 15 prepolymer, the further reaction to give the polyurethane is then carried out.

7. A method of using an aqueous dispersion as claimed in claim 1 as an adhesive.

8. An adhesive bond obtainable using an aqueous 20 dispersion as claimed in claim 1.

9. A method of using an aqueous dispersion as claimed in claima 1 as a coating material.

10. A coated substrate obtainable using an aqueous dispersion as claimed in claim 1. DATED this 28th day of April 1994. BASF AKTIENGESELLSCHAFT WATERMARK PATENT TRADEMARK ATTORNEYS "THE ATRIUM" 290 BURWOOD ROAD HAWTHORN. VIC. 3122. O.Z. 0050/44009 Abstract of the Disclosure: An aqueous dispersion contains A) a polyurethane 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 isocyanates and having at least one ionic group or group convertible into an ionic group d) if required, compounds which differ from c) and have at least two functional groups reactive toward isocyanate and a molecular weight of from to 500 g/mol, and B) a free radical polymer containing metal salt groups, formed from at least divalent metals with acid groups of the polymer, the content of salt groups being from 5 to 1,000 mmol of salt groups per kg of the sum of A) and B). e