HK1097290B - Aqueous adhesive dispersions - Google Patents

Description

Aqueous adhesive dispersions

The invention relates to aqueous polyurethane-based polymer dispersions, to a method for the production thereof and to the use thereof.

Polyurethane-based adhesives are primarily solvent-containing adhesives which are applied to two substrates to be bonded and dried. By subsequently bonding the two substrates at Room Temperature (RT) and pressure or after thermal activation, a bonded structure with high initial strength is obtained immediately after the bonding operation.

For ecological reasons, there is an increasing need for suitable aqueous binder dispersions which can be processed into corresponding aqueous binder formulations. Such systems have the disadvantages that: even if the dried adhesive film is heat-activated beforehand, the initial heat resistance immediately after the bonding operation after moisture evaporation is significantly lower as compared with the solvent-containing adhesive.

The use of silica products for various applications is known in the art. Simultaneous solid SiO₂The products are usually used as fillers or as adsorbents for controlling the rheology, silica sols being used mainly as binders for various inorganic materials, polishing agents for semiconductors or as flocculation compatibilizers in colloidal chemistry. For example, EP-A0332928 discloses the use of polychloroprene latexes as impregnation layers in the production of fire-resistant elements in the presence of silica sols. FR-A2341537 and FR-A2210699 describeFumed silica is combined with polychloroprene latex to produce fire resistant foam finishes or asphalt coatings and JP-A06256738 describes their combination with chloroprene/acrylic copolymers.

The object of the present invention is to provide aqueous adhesive compositions which, after application to the substrates to be glued and bonding, have a high initial heat resistance, especially after heat activation.

It has surprisingly been found that adhesives showing a higher initial heat resistance after bonding can be prepared by suitable combination of polyurethane dispersions and aqueous silica dispersions.

The invention relates to aqueous polymer dispersions, comprising

a) At least one polyurethane dispersion having an average particle diameter of from 60 to 350nm, preferably from 20 to 80 nm, and

b) at least one of having SiO₂Aqueous silicon dioxide dispersions having a particle diameter of 20 to 400 nm, preferably 30 to 100 nm, particularly preferably 40 to 80 nm.

The polyurethane dispersion (a) to be used according to the invention comprises a polyurethane (a) which is the reaction product of:

A1) a polyisocyanate,

A2) a polymer polyol and/or polyamine having an average molar weight of 400 to 8000,

A3) optionally a mono-or poly-polyol or mono-or poly-amine or amino alcohol having a molar weight of at most 400,

and at least one compound selected from

A4) Compounds containing at least one ionic or potentially ionic group and/or

A5) A non-ionic hydrophilic compound.

In the context of the present invention, a latent ionic group is a group capable of forming an ionic group.

The polyurethanes (a) are preferably prepared using from 7 to 45% by weight of a1), from 50 to 91% by weight of a2), from 0 to 15% by weight of a5), from 0 to 12% by weight of ionic or potentially ionic compounds a4) and optionally from 0 to 30% by weight of compounds A3), where the sum of a4) and a5) is from 0.1 to 27% by weight and the sum of the individual components is 100% by weight.

It is particularly preferred that the polyurethane (a) is formed from 10 to 30% by weight of a1), 65 to 90% by weight of a2), 0 to 10% by weight of a5), 3 to 9% by weight of the ionic or potentially ionic compound a4) and optionally 0 to 10% by weight of the compound A3), wherein the sum of a4) and a5) is 0.1 to 19% by weight and the sum of the individual components is 100% by weight.

Very particularly preferably, the polyurethanes (a) are prepared from 8 to 27% by weight of a1), 65 to 85% by weight of a2), 0 to 8% by weight of a5), 3 to 8% by weight of the ionic or potentially ionic compound a4) and optionally 0 to 8% by weight of the compound A3), where the sum of a4) and a5) is 0.1 to 16% by weight and the sum of the individual components is 100% by weight.

Suitable polyisocyanates (A1) are aromatic, araliphatic, aliphatic or cycloaliphatic polyisocyanates. It is also possible to use mixtures of these polyisocyanates. Examples of suitable polyisocyanates are butylidene diisocyanate, Hexamethylene Diisocyanate (HDI), isophorone diisocyanate (IPDI), 2, 4-and/or 2, 4, 4-trimethylhexamethylene diisocyanate, isomerized bis (4, 4 '-isocyanatocyclohexyl) methane or mixtures thereof in any isomer content, isocyanatomethyl-1, 8-octane diisocyanate, 1, 4-cyclohexylene diisocyanate, 1, 4-phenylene diisocyanate, 2, 4-and/or 2, 6-benzylidene (Toluylen) diisocyanate, 1, 5-naphthylene diisocyanate, 2, 4' -or 4, 4 '-diphenylmethane diisocyanate, triphenylmethane 4, 4' -triisocyanate or mixtures thereof having the urethane structure, Derivatives of isocyanurate structures, allophanate structures, biuret structures, uretdione structures, iminooxadiazinedione structures, and mixtures thereof. Preference is given to hexamethylene diisocyanate, isophorone diisocyanate and the isomeric bis (4, 4' -isocyanatocyclohexyl) methanes and mixtures thereof.

The polyisocyanate is preferably a polyisocyanate or a mixture of polyisocyanates of the type described having exclusively aliphatically and/or cycloaliphatically bonded isocyanate groups. Very particularly preferred starting components (A1) are polyisocyanates or polyisocyanate mixtures based on HDI, IPDI and/or 4, 4' -diisocyanatodicyclohexylmethane.

Further suitable polyisocyanates as polyisocyanates (A1) are any polyisocyanates having a uretdione, isocyanurate, urethane, allophanate, biuret, iminooxadiazinedione and/or oxadiazinetrione structure, formed from at least two diisocyanates and prepared by modification of simple aliphatic, cycloaliphatic, araliphatic and/or aromatic diisocyanates, for example those described in J.Prakt.chem.336(1994) page 185-200.

Suitable polymer polyols or polyamines (A2) have an OH functionality of at least 1.5 to 4, such as polyacrylates, polyesters, polylactones, polyethers, polycarbonates, polyestercarbonates, polyacetals, polyolefins and polysiloxanes. Polyols having an OH functionality of 2 to 3 in the molar weight range of 600 to 2500 are preferred.

Suitable polycarbonates containing hydroxyl groups are obtained by reacting carbonic acid derivatives, such as diphenyl carbonate, dimethyl carbonate or phosgene, with diols. Suitable such diols are, for example, ethylene glycol, 1, 2-and 1, 3-propanediol, 1, 3-and 1, 4-butanediol, 1, 6-hexanediol, 1, 8-octanediol, neopentyl glycol, 1, 4-bishydroxymethylcyclohexane, 2-methyl-1, 3-propanediol, 2, 4-trimethyl-1, 3-pentanediol, dipropylene glycol, polypropylene glycol, dibutylene glycol, polybutylene glycol, bisphenol A, tetrabromobisphenol A and lactone-modified diols. The diol component preferably comprises from 40 to 100% by weight of hexanediol, preferably 1, 6-hexanediol and/or hexanediol derivatives, preferably those which comprise, in addition to terminal OH groups, ether or ester groups, for example products obtained by reaction of 1 mol of hexanediol with at least 1 mol, preferably 1 to 2 mol, of caprolactone according to DE-A1770245 or di-or trihexylene by self-etherification of hexanediol. The preparation of these derivatives is known, for example, from DE-A1570540. The polyether-polycarbonate diols described in DE-A3717060 can also be used.

The hydroxy polycarbonate is preferably linear. However, they may optionally be lightly branched by the incorporation of polyfunctional components, especially low molecular weight polyols. For example, glycerol, trimethylolpropane, 1, 2, 6-hexanetriol, 1, 2, 4-butanetriol, trimethylolpropane, pentaerythritol, p-cyclohexanediol (Chinit), mannitol and sorbitol, methylglucoside, 1, 3, 4, 6-dianhydrohexitol (Dianhydrohexite) are suitable for this purpose.

Suitable polyether polyols are the polytetramethylene glycol polyethers known per se from polyurethane chemistry, which can be prepared, for example, by cationic ring-opening polymerization of tetrahydrofuran.

Further suitable polyether polyols are polyethers, for example polyols prepared from styrene oxide, propylene oxide, butylene oxide or epichlorohydrin using starter molecules, especially polyols of propylene oxide.

Suitable polyester polyols are, for example, the reaction products of polyhydric, preferably dihydric and optionally additionally trihydric alcohols with polybasic, preferably dibasic, carboxylic acids. It is also possible to use the corresponding polycarboxylic anhydrides or corresponding polycarboxylic esters of lower alcohols or mixtures thereof in place of the free polycarboxylic acids in the preparation of the polyesters. The polycarboxylic acids may be aliphatic, cycloaliphatic, aromatic and/or heterocyclic in nature and may optionally be substituted, for example by halogen atoms, and/or unsaturated.

Component (A3) is suitable for end-capping polyurethane prepolymers. For this purpose, monofunctional alcohols and monoamines are suitable. Preferred monoalcohols are aliphatic monoalcohols having 1 to 18 carbon atoms, such as ethanol, n-butanol, ethylene glycol monobutyl ether, 2-ethylhexanol1-octanol, 1-dodecanol or 1-hexadecanol. Preferred monoamines are aliphatic monoamines, such as diethylamine, dibutylamine, ethanolamine, N-methylethanolamine or N, N-diethanolamine andamines of the M series (Huntsman corp. europe, Belgium) or amino-functionalized polyethylene oxides and polypropylene oxides.

Polyols, aminopolyols or polyamines having a molecular weight below 400 are also suitable as component (A3), which are described in large numbers in the corresponding literature.

Preferred components (a3) are, for example:

a) alkane-diols and-triols, such as ethylene glycol, 1, 2-and 1, 3-propanediol, 1, 4-and 2, 3-butanediol, 1, 5-pentanediol, 1, 3-dimethylpropanediol, 1, 6-hexanediol, neopentyl glycol, 1, 4-cyclohexanedimethanol, 2-methyl-1, 3-propanediol, 2-ethyl-2-butylpropanediol, trimethylpentanediol, positionally isomeric diethyloctanediols, 1, 2-and 1, 4-cyclohexanediols, hydrogenated bisphenol A [2, 2-bis (4-hydroxycyclohexyl) propane ], 2-dimethyl-3-hydroxypropionic acid- (2, 2-dimethyl-3-hydroxypropyl ester), trimethylolethane, glycerol, A trimethylolpropane or a glycerol, and a mixture of the trimethylolpropane and the glycerol,

b) ether glycols, such as diethylene glycol (diethylene glycol), triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, 1, 3-butanediol or hydroquinone dihydroxyethyl ether,

c) ester diols of the general formulae (I) and (II)

HO-(CH₂)_x-CO-O-(CH₂)_y-OH (I)，

HO-(CH₂)_x-O-CO-R-CO-O(CH₂)_x-OH (II)，

Wherein

R is an alkylene or arylene group having 1 to 10 carbon atoms, preferably 2 to 6 carbon atoms,

x is 2 to 6 and

y is a number of from 3 to 5,

such as delta-hydroxybutyl-epsilon-hydroxyhexanoate, omega-hydroxyhexyl-gamma-hydroxybutyrate, beta-hydroxyethyl adipate and bis (beta-hydroxyethyl) terephthalate, and

d) di-and poly-amines, such as 1, 2-diaminoethane, 1, 3-diaminopropane, 1, 6-diaminohexane, 1, 3-and 1, 4-phenylenediamine, 4, 4 ' -diphenyl-methanediamine, isophoronediamine, isomer mixtures of 2, 2, 4-and 2, 4, 4-trimethylhexamethylenediamine, 2-methyl-pentamethylenediamine, diethylenetriamine, 1, 3-and 1, 4-xylylenediamine, α, α, α ', α ' -tetramethyl-1, 3-and-1, 4-xylylenediamine, 4, 4-diaminodicyclohexylmethane, amino-functionalized polyethylene oxides or polypropylene oxides, which may be referred to by the namesObtained under the D series (Huntsman corp. europe, Belgium), diethylenetriamine and triethylenetetramine. Suitable diamines within the scope of the invention are also hydrazine, hydrazine hydrate and substituted hydrazines, such as N-methylhydrazine, N' -dimethylhydrazine and their homologues as well as dihydrazide, adipic acid, beta-methyladipic acid, sebacic acid, hydroxypropionic acid and terephthalic acid, ureidoamino-alkylene hydrazides, such as beta-ureidoaminopropionic acid hydrazide (described, for example, in DE-A1770591), ureidoalkylene-carbazepine esters, such as 2-ureidoaminoethyl carbazepine ester (described, for example, in DE-A1918504) or semicarbazide compounds, such as beta-aminoethyl-ureidoamino-carbonate (described, for example, in DE-A1902931).

Component (a4) contains ionic groups which may be cationic or anionic in nature. Compounds having a cationic, anionic dispersing action are those which contain, for example, sulfonium, ammonium, phosphonium, carboxylate, sulfonate, phosphonate groups or groups which are converted into the abovementioned groups by salt formation (potentially ionic groups) and which can be introduced into the macromolecules via the isocyanate-reactive groups present. Preferred suitable isocyanate-reactive groups are hydroxyl and amine groups.

Suitable ionic or potentially ionic compounds (A4) are, for example, mono-and di-hydroxycarboxylic acids, mono-and di-aminocarboxylic acids, mono-and di-hydroxysulfonic acids, mono-and di-sulfamic acids and mono-and di-hydroxyphosphonic acids or mono-and di-aminophosphonic acids and their salts, such as dimethylolpropionic acid, dimethylolbutyric acid, hydroxypivalic acid, N- (2-aminoethyl) -beta-alanine, 2- (2-amino-ethylamino) -ethanesulfonic acid, 1, 2-or 1, 3-propylenediamine-beta-ethanesulfonic acid, ethylenediamine-propyl-or-butyl-sulfonic acid, malic acid, citric acid, glycolic acid, lactic acid, glycine, alanine, taurine, salts of maleic acid, salts of maleic acid, maleic, Adducts of lysine, 3, 5-diaminobenzoic acid, IPDI and acrylic acid (EP-A0916647, example 1) and their salts and/or ammonium salts with alkali metals; adducts of sodium bisulfite with 2-butene-1, 4-diol, polyether sulfonates, 2-butanediol, and NaHSO₃Propoxylated adducts of (A) as described, for example, in DE-A2446440 (pages 5 to 9, formulae I to III) and units which can be converted into cationic groups, such as N-methyl-diethanolamine, as hydrophilic structural component. Preferred ionic or potentially ionic compounds are those having carboxyl or carboxylate and/or sulfonate groups and/or ammonium groups. Particularly preferred ionic compounds are those which contain carboxyl and/or sulfonate groups as ionic or potentially ionic groups, such as N- (2-aminoethyl) - β -alanine, 2- (2-amino-ethylamino) ethanesulfonic acid or the adduct of IPDI and acrylic acid (EP-A0916647, example 1) and the salt of dimethylolpropionic acid.

Suitable compounds (A5) having a nonionic hydrophilic action are, for example, polyoxyalkylene ethers which contain at least one hydroxyl or amino group. These polyethers comprise from 30% to 100% by weight of components derived from ethylene oxide. Polyethers of linear structure having a functionality of 1 to 3 and also compounds of the formula (III) are also suitable,

wherein

R¹And R²In each case independently of one another, each represent an aliphatic, cycloaliphatic or aromatic radical having from 1 to 18 carbon atoms which may be interrupted by oxygen and/or nitrogen atoms, and

R³represents an alkoxy-terminated polyethylene oxide group.

Compounds having a nonionic hydrophilicizing action are, for example, also monopolyoxyalkylene polyether alcohols which have a statistical average of from 5 to 70, preferably from 7 to 55, oxyethylene units per molecule and are obtainable in a manner known per se by alkoxylation of suitable starter molecules (for example in Ullmanns)der technischen Chemie, 4 th edition, volume 19, VerlaggChemie, Weinheim, pages 31-38).

Suitable starter molecules are, for example, saturated monoalcohols, such as methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, sec-butanol, the isomeric pentanols, hexanols, octanols and nonanols, n-decanol, n-dodecanol, n-tetradecanol, n-hexadecanol, n-octadecanol, cyclohexanol, the isomeric methylcyclohexanols or hydroxymethylcyclohexane, 3-ethyl-3-hydroxymethyloxetane or tetrahydrofurfuryl alcohol; diethylene glycol monoalkyl ethers such as diethylene glycol monobutyl ether; unsaturated alcohols, such as allyl alcohol, 1-dimethylallyl alcohol or oleyl alcohol; aromatic alcohols such as phenol, cresol and methoxyphenol isomers; araliphatic alcohols, such as benzyl alcohol, anisyl alcohol or cinnamyl alcohol; secondary monoamines, such as dimethylamine, diethylamine, dipropylamine, diisopropylamine, dibutylamine, bis (2-ethylhexyl) -amine, N-methyl-and N-ethyl-cyclohexylamine or dicyclohexylamine, and heterocyclic secondary amines, such as morpholine, pyrrolidine, piperidine or 1H-pyrazole. Preferred starter molecules are saturated monoalcohols. Particular preference is given to using diethylene glycol monobutyl ether as starter molecule.

Alkylene oxides suitable for the alkoxylation reaction are, in particular, ethylene oxide and propylene oxide, which can be used in any desired sequence or in a mixture for the alkoxylation reaction.

The polyoxyalkylene polyether alcohol is either a pure polyoxyethylene polyether or a mixed polyoxyalkylene polyether whose alkylene oxide units consist of at least 30 mol.%, preferably at least 40 mol.%, of ethylene oxide units. Preferred nonionic compounds are monofunctional mixed polyoxyalkylene polyethers which comprise at least 40 mol.% of ethylene oxide units and not more than 60 mol.% of propylene oxide units.

A combination of nonionic (A4) and ionic (A5) hydrophilicizing agents is preferably used for the preparation of the polyurethanes (A). Combinations of non-ionic and anionic hydrophilizing agents are particularly preferred.

The preparation of the aqueous polyurethanes (A) can be carried out in one or more stages in a homogeneous phase or, in the case of a multi-stage reaction, partly in a disperse phase. After complete or partial polyaddition, a dispersing, emulsifying or dissolving step is carried out. Then optionally further polyaddition or modification in the disperse phase is carried out.

The polyurethane (A) can be prepared by all methods known in the art, such as the emulsifier shear method, the acetone method, the prepolymer mixing method, the melt emulsification method, the ketimine method and the solid spontaneous dispersion method or their derivatization methods. For an overview of these processes, see Methoden der organischen Chemie (Houben-Weyl, supplement volume 4, volume E20, H.Bartland J.Falbe, Stuttgart, New York, Thieme 1987, page 1671-. The melt emulsification method, the prepolymer mixing method and the acetone method are preferred. The acetone process is particularly preferred.

To prepare the polyurethane prepolymers, the components (A2) to (A5) which do not contain primary or secondary amino groups and the polyisocyanate (A1) are generally initially placed in a reactor, in whole or in part, and optionally diluted with a water-miscible, but isocyanate-group-inert solvent (but preferably without solvent) and heated to a relatively high temperature, preferably in the range from 50 to 120 ℃.

Suitable solvents are, for example, acetone, butanone, tetrahydrofuran, dioxane, acetonitrile, dipropylene glycol dimethyl ether and 1-methyl-2-pyrrolidone, which can be added not only at the beginning of the preparation but also at a later time, optionally in portions. Acetone and butanone are preferred. The reaction can be carried out at atmospheric pressure or at elevated pressure, for example above the atmospheric-boiling temperature of the solvent (e.g., acetone).

It is also possible to initially charge simultaneously or to meter in later the known catalysts which accelerate the isocyanate addition reaction, such as triethylamine, 1, 4-dioxabicyclo- [2, 2, 2] -octane, dibutyltin oxide, tin dioctoate or dibutyltin dilaurate, tin bis (2-ethylhexanoate) or other organometallic compounds. Dibutyltin dilaurate is preferred.

The components (A1), (A2), optionally (A3) and (A4) and/or (A5) which have not been added at the beginning of the reaction are then metered in. In the preparation of the polyurethane prepolymers, the mass ratio of isocyanate groups to isocyanate-reactive groups is from 0.90 to 3, preferably from 0.95 to 2.5, particularly preferably from 1.05 to 2.0. The reaction of components (a1) to (a5) is carried out partially or completely, preferably completely, according to the total amount of isocyanate-reactive groups of (a2) to (a5) which do not contain a portion of primary or secondary amino groups. The degree of conversion is usually monitored by tracking the NCO content of the reaction mixture. For this purpose, both spectroscopic measurements (for example infrared or near-infrared spectroscopy, determination of the refractive index) and chemical analyses (for example titration) of the samples taken can be carried out. The polyurethane prepolymers containing free isocyanate groups are obtained as a substance or in the form of a solution.

After or during the preparation of the polyurethane prepolymers from (A1) and (A2) to (A5), a partial or complete salt formation of the groups having an anionic and/or cationic dispersing action takes place if this is not done in the starting molecules. As anionic groups, bases are used for this purpose, such as ammonia, ammonium carbonate or ammonium bicarbonate, trimethylamine, triethylamine, tributylamine, diisopropylethylamine, dimethylethanolamine, diethylethanolamine, triethanolamine, potassium hydroxide or sodium carbonate, preferably triethylamine, triethanolamine, dimethylethanolamine or diisopropylethylamine. The amount of base used is 50 to 100%, preferably 60 to 90% of the amount of anionic groups used. As cationic groups, dimethyl sulfate or succinic acid are used. If only the nonionic hydrophilic compound (A5) having an ether group is used, the neutralization step can be omitted. Neutralization may also be carried out simultaneously with dispersion by dispersing water already comprising the neutralizing agent.

Possible amine components are (A2), (A3) and (A4), which can be used to convert the optionally remaining isocyanate groups. This chain extension can be carried out in a solvent before, during or in water after dispersion. If an amine component is used as (A4), the chain extension is preferably carried out before the dispersion.

The amine component (a2), (A3) or (a4) can be added to the reaction mixture diluted with an organic solvent and/or water. Preferably 70 to 95 wt% of solvent and/or water are used. If multiple amine components are present, the conversion can be carried out sequentially in any desired order or simultaneously by adding mixtures.

To prepare the polyurethane dispersion (A), the polyurethane prepolymer is optionally introduced into the dispersed water using vigorous shear forces (e.g.vigorous stirring) or using a jet disperser or, conversely, the water used for dispersion is stirred into the prepolymer. Then, if not in homogeneous phase, the increase in molar mass can be achieved by reacting the optionally present isocyanate groups with components (A2), (A3). The amount of polyamine (A2), (A3) used depends on the unreacted isocyanate groups still present. Preferably from 50 to 100%, particularly preferably from 75 to 95%, of the amount of isocyanate groups used are converted with the polyamines (A2), (A3).

The organic solvent may optionally be distilled off. The dispersions have a solids content of from 10 to 70% by weight, preferably from 25 to 65% by weight, particularly preferably from 30 to 60% by weight.

The polyurethane dispersions according to the invention can be used alone or together with the following known substances: binders, auxiliary substances and additives, in particular light stabilizers such as UV absorbers and sterically Hindered Amines (HALS), and also antioxidants, fillers and coating auxiliaries such as antisettling agents, defoamers and/or wetting agents, flow aids, reactive diluents, plasticizers, catalysts, auxiliary solvents and/or thickeners and additives such as dispersions, pigments, dyes or matting agents. In particular in combination with polyurethane dispersions or polyacrylate dispersions (which optionally can also be hydroxyl-functionalized) are of course possible. Additives can be added to the PUR dispersions according to the invention immediately before processing. However, it is also possible to add at least a portion of the additive before or during the dispersion of the binder or binder/crosslinker mixture. The selection and metering of these substances which can be added to the individual components and/or to the entire mixture is known to the person skilled in the art.

Aqueous dispersions of silica have long been known. They exist in various structural forms depending on the preparation method.

Suitable silicon dioxide dispersions b) according to the invention can be obtained on the basis of silica sols, silica gels, pyrogenic silica or precipitated silica or mixtures thereof.

Silicic acid sols are colloidal solutions of amorphous silica in water, which are also referred to as silica sols but are often referred to simply as silica sols. The silica is present in the form of nearly spherical particles whose surface has been hydroxylated. The particle size of the colloidal particles is generally from 1 to 200 nm, and the BET specific surface area (determined by the method of G.N. Sears, Analytical Chemistry Vol.28, N.12, 1981-1983, December 1956) corresponds to a particle size of from 15 to 2000 square meters per gram. The SiO₂The surface of the particles has a charge balanced by the corresponding counter-ions, resulting in stabilization of the colloidal solution. The alkali-stabilized silica sol is meant to have a pH of 7 to 11.5 and to include, for example, small amounts of Na₂O、K₂O、Li₂O, ammonia, organic nitrogen bases, tetraalkylammonium hydroxides or alkali metal aluminates or ammonium aluminates as alkalizing agents. Silica sols can also be present in the weakly acidic form as semi-stable colloidal solutions. It is also possible to use Al₂(OH)₅Cl coats the surface to produce a cation-modified silica sol. Solid concentration of the silica solDegree of 5 to 60% by weight SiO₂。

The preparation method of the silica sol basically comprises the following production steps: dealkalization of water glass by ion exchange, regulation and stabilization of SiO₂The desired particle size (distribution) of the particles, respectively, is adjusted₂In concentration and optionally using, for example, Al₂(OH)₅Cl to SiO₂The particles are surface modified. In any of these steps the SiO₂The particles do not leave the state of being dissolved in colloidal form. This indicates the presence of discrete primary particles with particularly high binder efficiency.

Silica gel is understood to be a colloidal, either tangible or intangible silica having an elastic to solid consistency of a loose to dense porous structure. The silica is present in the form of highly condensed polysilica. The siloxane and/or silanol groups are located on the surface. The silica gel is prepared by reacting water glass with a mineral acid.

In addition, a distinction is made between pyrogenic silica and precipitated silica. In the precipitation method, water is first added and then water glass and acid (such as H) are added simultaneously₂SO₄). This step produces colloidal primary particles which aggregate and grow as the reaction proceeds to form agglomerates. These primary particles of silica in the solid state are intimately cross-linked into secondary agglomerates.

Fumed silica can be prepared by flame hydrolysis or by means of an electric arc process. The main synthesis method of fumed silica is flame hydrolysis, in which tetrachlorosilane is decomposed in an oxyhydrogen flame. The silica thus formed is amorphous (according to X-ray). Fumed silicas have significantly fewer OH groups on their nearly nonporous surfaces than precipitated silicas. Pyrogenic silicas produced by flame hydrolysis have a specific surface area (DIN 66131) of from 50 to 600 square meters per gram and a primary particle size of from 5 to 50 nm; the silicas produced by the arc process have a specific surface area (DIN 66131) of from 25 to 300 square meters per gram and a primary particle size of from 5 to 500 nm.

Further data on the synthesis and properties of solid silicic acids can be found, for example, in K.H.Buhel, H. -H.Moretto, P.Woditsch "Industrial ville Anorganische Chemie", WileyVCH Verlag 1999, chapter 5.8.

SiO if present as a separate solid₂The starting material (e.g. pyrogenic or precipitated silica) is used in the polymer dispersion according to the invention, and this is converted by dispersion into aqueous SiO₂A dispersion.

The silica dispersion is produced using a prior art disperser, preferably a disperser suitable for producing high shear rates, such as an ultrarorrax or dissolver plate (dispolerscheib).

It is preferable to use SiO thereof₂Aqueous silicon dioxide dispersions having particles with a primary particle size of 20 to 400 nm, preferably 30 to 100 nm, particularly preferably 40 to 80 nm. When precipitated silicas are used, they are ground to reduce the particle size.

Preferred polymer dispersions according to the invention are those in which the SiO of the silicon dioxide dispersion b)₂Those in which the particles are present as discrete, uncrosslinked primary particles.

SiO is also preferred₂The particles have hydroxyl groups on the surface of the particles.

It is particularly preferred to use an aqueous silicic acid sol as the aqueous silica dispersion.

To prepare the polymer dispersions according to the invention, the proportions of the components used are chosen such that the resulting dispersions have a content of dispersed polymer of from 30 to 60% by weight, where the content of polyurethane dispersion (a) is from 55 to 99% by weight and the content of silicon dioxide dispersion (b) is from 1 to 45% by weight, the percentages being based on the weight of the nonvolatile components and summing to 100% by weight.

The polymer dispersions according to the invention preferably comprise a mixture of a polyurethane dispersion (a) in an amount of from 70 to 98% by weight and a silica sol dispersion (b) in an amount of from 2 to 30% by weight, particularly preferably from 80 to 93% by weight and from 20 to 7% by weight, based on the weight of the nonvolatile constituents and adding up to 100% by weight, of dispersion (a).

The polyurethane dispersion may also optionally include other dispersions, such as polyacrylate, polyvinylidene chloride, polybutadiene, polyvinyl acetate, polychloroprene or styrene-butadiene dispersions, in amounts of up to 30% by weight.

The polymer dispersions according to the invention optionally also comprise binder auxiliary substances and additives. For example, fillers such as quartz flour, quartz sand, barite, calcium carbonate, chalk, dolomite or talc, optionally together with wetting agents such as polyphosphates, for example sodium hexametaphosphate, naphthalenesulfonic acid, ammonium polyacrylate or sodium polyacrylate, can be added in amounts of from 10 to 60% by weight, preferably from 20 to 50% by weight, and from 0.2 to 0.6% by weight, based in each case on nonvolatile constituents.

Further suitable auxiliary substances are, for example, organic thickeners, such as cellulose derivatives, alginates, starches, starch derivatives, polyurethane thickeners or polyacrylic acids, in amounts of from 0.01 to 1% by weight, based on the nonvolatile constituents, or inorganic thickeners, such as bentonites, in amounts of from 0.05 to 5% by weight, based on the nonvolatile constituents.

For preservation, fungicides may also be added to the adhesive composition according to the invention. These are used in amounts of from 0.02 to 1% by weight, based on nonvolatile constituents. Suitable fungicides are, for example, phenol and cresol derivatives or organotin compounds.

Optionally, tackifying resins, such as unmodified or modified natural resins, for example rosin esters, hydrocarbon resins, or synthetic resins, for example phthalate resins (see, for example, "Klebharze" R.Jordan, R.Hinterwaldner, pages 75-115, Hinterwaldner Verlag Munich 1994) may be added in dispersed form to the polymer dispersion according to the invention. Alkylphenol resins and terpene phenol resin dispersions having softening points of more than 70 ℃ are preferred, particularly preferably more than 110 ℃.

Organic solvents such as toluene, acetone, xylene, butyl acetate, methyl ethyl ketone, ethyl acetate, dioxane or mixtures thereof; or plasticizers such as those based on adipates, phthalates or phosphates, in amounts of from 0.5 to 10 parts by weight, based on nonvolatile constituents.

The invention further relates to a process for preparing the polymer dispersions according to the invention, which is characterized in that the polyurethane dispersions (a) are mixed with the silicon dioxide dispersions (b) and, optionally, conventional binder auxiliary substances and additives are added.

A preferred process for the preparation of the polymer dispersions according to the invention is characterized in that the polyurethane dispersion (a) is first mixed with the binder auxiliary substances and the additives and the silica sol (b) is added during or after the mixing.

The adhesive formulation can be applied according to known methods, for example by brushing, pouring, knife coating, spraying, rolling or dipping. Drying of the adhesive film can be carried out at room temperature or at elevated temperatures up to 220 ℃.

The adhesive formulations can be used in one-component form or in a known manner with the aid of crosslinking agents.

The polymer dispersions according to the invention can be used as adhesives, for example for gluing any substrate of the same type or of a different type, such as wood, paper, plastic, textiles, leather, rubber or inorganic materials, such as ceramics, porcelain, glass fibres or cement.

Examples

1.1 substances used

Table 1: polyurethane dispersions

Table 2: silicon dioxide

Table 3: crosslinking agent

^＊)90.77 wt.% of polymer-hydrophilized HDI trimer (HDI)N3600), 4.78% by weight of an internal emulsifier having EO/PO starting from a monofunctional alcohol and an OH number of 40

1.2 measurement method

1.2.1 determination of the Peel Strength on Soft polyvinyl chloride after impact activation

The test was performed according to EN 1392. On two soft PVC test specimens (30% dioctyl phthalate, DOP) of size 100x30 mm roughened with sandpaper (particle size 80), the dispersion was coated with a brush on both roughened faces and dried at room temperature for 60 minutes. The test sample was then shock-activated: the adhesive surface was irradiated with an IR lamp from Funk corporation (impact activator 2000) for 10 seconds. During this operation, the adhesive film is heated to a surface temperature of 90 ± 2 ℃. After heat activation of the adhesive-coated test specimens, gluing takes place immediately by placing the activated adhesive layers against one another and pressing them in a press (60 seconds; operating pressure of 4 bar). Tear tests were performed at room temperature on a commercial tensile tester. The strength values were determined immediately and three days after gluing. The test samples were stored at 23 ℃ and 50% relative humidity.

1.2.2 determination of Initial Heat Resistance (IHR) on beech/rigid PVC

Materials:

beech test specimens 50x150x4mm

PVC membranes (Renolit 32052096 Strukton; Renolit works, Co., DE)DN

Coating of the adhesive:

coating of the one-component adhesive with a spatula, 200. mu.m

Air evaporation time:

at least 3 hours at room temperature after application of the adhesive

Pressing conditions are as follows:

-a pressing pressure of 4 bar at a bonding temperature of 77 ℃ for 10 seconds

Test conditions in the dry box:

circulating air drying cabinet at-80 ℃ and load of 2.5 kg

The procedure is as follows:

the one-component adhesive was applied to a wooden test specimen (200 microns) with a spatula. The film was cut so that the total length after folding the edges three times was 12 cm. After 3 hours of application of the adhesive, the wooden test specimen was bonded to the film by pressing on a film press at a bonding temperature of 77 ℃ for 10 seconds at an effective pressure of 4 bar.

Immediately thereafter, the composite (without the load) was placed in a heat stable oven for 3 minutes and then loaded with 2.5 kg for 5 minutes. For this purpose, the wooden test specimen is suspended in the hot box and a holding device with a weight is clamped on the film, which has been folded three times in order to reinforce the film. At the end of this time, the weight was immediately removed and the composite was removed. The peeled area was measured and recorded [ mm/min ].

1.3 preparation of the adhesive composition

To prepare the formulations, the polyurethane dispersions were first introduced into a glass beaker. Silica was added while stirring. For two-component glues, 100 parts by weight of the dispersion are homogenized with 3 parts by weight of an emulsifiable crosslinker isocyanate for at least 2 minutes. This mixture can be used for about 2 hours.

Table 4: preparation of

1.4 results

1.4.1 determination of the Peel Strength on Soft PVC

Table 5: peel strength soft PVC

Example No. 2	Preparation No. 2	Desmodur DN[Tl.]	Immediate peel strength [ N/mm ]]	Peel Strength [ N/mm ] after 3 days]
					1	1	-	5.0	10.2
2	1	3	3.5	10.1
					3	2	-	6.1	9.5
4	2	3	5.2	9.5
					5	3	-	1.0	1.0
6	3	3	0.9	2.3
					7	4	-	6.1	8.9
8	4	3	5.5	8.7
					9	5	-	5.5	5.4
10	5	3	5.4	7.0
					11	6	-	1.4	0.2
12	6	3	1.6	0.8

^＊: comparative examples

As can be seen from table 5: adding5005 has the effect of the same high strength level as the unformulated PU dispersion. Has the advantages of3030 the formulation has the effect of significantly impairing the peel strength on soft PVC.

1.4.2 determination of the initial Heat resistance on beech/rigid PVC

Table 6: initial heat resistance

Example No. 2	Preparation No. 2	AWF [ mm/min ]]
			13	4	9.8
14	5	1.9
			15	6	Peeling off

^＊: comparative examples

As can be seen from table 6: addition in comparison with the unformulated PU dispersions5005 has an effect of significantly improving the initial heat resistance. Has the advantages of3030 the formulation resulted in complete peeling of the test sample.

Claims (10)

1. An aqueous dispersion comprising

a) A polyurethane dispersion having an average particle size of 60 to 350nm which is the reaction product of:

A1) a polyisocyanate, and

A2) a polymer polyol or polyamine having an average molar weight of 400 to 8000,

A3) optionally a mono-or poly-polyol or a mono-, poly-amine or an amino alcohol having a molar weight of at most 400,

and at least one compound selected from

A4) A compound containing at least one ionic or potentially ionic group, or

A5) (ii) a non-ionic hydrophilic compound,

with the proviso that if a monoamine is present, said monoamine is selected from the group consisting of diethylamine, dibutylamine, amino-functionalized polyethylene oxide and polypropylene oxide, and

b) with SiO₂An aqueous silica dispersion having a particle size of 20 to 400 nm.

2. Aqueous polymer dispersion according to claim 1, characterised in that the SiO is₂The particles have a particle size of 30 to 100 nanometers.

3. Aqueous polymer dispersion according to claim 1, characterised in that the SiO is₂The particles have a particle size of 40 to 80 nanometers.

4. Aqueous polymer dispersion according to any one of claims 1 to 3, characterized in that the SiO is₂The particles are present as discrete, uncrosslinked primary particles.

5. Aqueous polymer dispersion according to any one of claims 1 to 3, characterized in that the SiO is₂The particles have hydroxyl groups on the surface of the particles.

6. Aqueous polymer dispersion according to any of claims 1 to 3, characterized in that the aqueous silica dispersion b) is an aqueous silica sol.

7. Process for the preparation of polymer dispersions according to claim 1, characterized in that the polyurethane dispersion (a) is mixed with the silicon dioxide dispersion (b) and optionally conventional binder auxiliary substances are added.

8. Use of the polymer dispersion according to claim 1 as an adhesive.

9. Substrates glued by the polymer dispersion according to claim 1.

10. Substrates according to claim 9, characterized in that they are structural components of footwear or are footwear.