DE19959653A1 - Preparation of aqueous polyurethane dispersions, used for leather preparations and as coating material, comprises reacting components to give a polyurethane, dispersing in water and completion of the polymerization reaction - Google Patents

Abstract

Preparation of an aqueous dispersion containing a dispersed polyurethane from (a) 4-30C diisocyanates, (b,c) diols, (d) multivalent compounds with reactive groups, (e) monovalent compounds with reactive groups comprises reacting components to give a polyurethane, dispersing ion water and completion of the reaction. An aqueous dispersion containing a dispersed polyurethane is prepared from: (a) 4-30C diisocyanates; (b) diols devoid of urethane and urea groups, of which (b1) 10-95 mole% on the total weight of diols have a molecular weight of 500-5000, and (b2) 5-90 mole% on the total weight of diols have a molecular weight of 60-500 g/mole, (i.e. an alkane diol (b2.1) or an alkane diol which also has a hydrophilic group or a potential hydrophilic group (b2.2)); (c) where the diols (b2.2) are not present or present only in sufficient amount to ensure water dispersibility, and of monomers (a) and (b) there are several monomers with at least one isocyanate group or at least one isocyanate reactive group, of which at least one is a hydrophilic group or a potential hydrophilic group, which ensure the water dispersibility of the polyurethane; (d) optionally further monomers (a) and (b), i.e. several multivalent compounds with a reactive group, i.e. alcoholic OH groups , primary or secondary amine or isocyanate groups; and (e) optionally further monomers (a) and (b), i.e. several monovalent compounds with a reactive group , i.e. alcoholic OH groups, primary or secondary amine or isocyanate groups, Preparation of the aqueous dispersion comprises (i) a macrodiol (b1) is reacted with enough diisocyanate to start the reaction, the ratio of isocyanate groups to alcohol groups is 0.1:1 to 0.9:1, and the reaction is continued until the maximum NCO content of the reaction mixture is 20% of the original value; (ii) the reaction product produced and the remaining components are reacted to give a polyurethane; (iii) this polyurethane, (or a prepolymer formed in an intermediate step) is dispersed in water; and (iv) the reaction is then continued until the polyurethane is formed. Independent claims are included for: (1) An aqueous dispersion containing the dispersed polyurethane obtained as above; (2) a composition containing the aqueous dispersion obtained as above, and pigments and other conventional leather additives; (3) an object glued or coated with the dispersion, e.g. textiles impregnated with the dispersion; (4) leather coated with the composition under (2) above.

Description

The present invention relates to a process for the preparation of aqueous dispersions comprising a polyurethane in dispersed form

• a) diisocyanates with 4 to 30 carbon atoms,
• b) diols, which are essentially free of urethane or urea groups, of which
  • 1. 10 to 95 mol%, based on the total amount of diols (b), have a molecular weight of 500 to 5000, and
  • 2. 5 to 90 mol%, based on the total amount of diols (b), have a molecular weight of 60 to 500 g / mol, which are alkanediols (b2.1) or alkanediols which additionally have a hydrophilic group or carry a potentially hydrophilic group (b2.2),
• c) if diols (b2.2) are not present or not in sufficient quantities are present to effect water dispersibility, monomers different from monomers (a) and (b) at least one isocyanate group or at least one against about isocyanate reactive group, moreover at least one hydrophilic group or one potentially hydro phile group, which makes the water dispersibility of the Polyurethane is caused
• d) optionally further ver of the monomers (a) to (c) different multivalent compounds with reactive groups, which are alcoholic hydroxyl groups, primary or secondary amino groups or isocyanate groups and
• e) optionally different from the monomers (a) to (d) monovalent compounds with a reactive group in which it is an alcoholic hydroxyl group, a primary one or secondary amino group or an isocyanate group,

being one

• a) in a first step, the macrodiols (b1) together with such amounts of diisocyanate (a) that at the beginning the reaction the ratio of the isocyanate groups to the  Alcohol groups is 0.1: 1 to 0.9: 1, and the reaction is continued until the NCO content of the reaction mix to a maximum of 20% of the original value wrestled
• b) the reaction product formed in step (i) with the rest Lichen components to a polyurethane, where one the finished polyurethane or one in an intermediate stage formed prepolymer dispersed in water and in the case of Dispersion of the prepolymer then the reaction to Polyurethane continues.

The invention further relates to dispersions according to this Processes are made, as well as be with these dispersions traded items, especially coated leather.

Aqueous polyurethane dispersions (also briefly as PUR dispersions ) and processes for their production are generally be knows. PUR dispersions have long been used to coat Substrates such as B. leather, textiles, wood, metal or art fabric used. Aqueous polyurethane dispersions that are special recommended as coating agents for leather are z. B. in DE-A-26 45 779 and EP-A-787751.

According to the manufacturing methods known from the prior art will be short chain and long chain polyols together with implemented the isocyanates. So z. B. in the "acetone ver drive ", the isocyanate and polyols such as macrodiols (e.g. poly ester or polyether polyols) and short-chain diols a prepolymer, which is then further processed Polyurethane is implemented.

The coated objects are in the course of the pro often subjected to thermal treatment. Leather and Textiles are used e.g. B. ironed; coated wood is i. A. at dried at elevated temperature. For undisturbed operation To ensure the process, it is essential that the coated Object has as little stickiness as possible.

In addition to the processing properties of the PUR dispersions, the use properties of the objects coated with them are of course also important. Poly urethane dispersions, the z. B. used as a coating agent for leather, the leather should lend the following properties ver

• - a slight tendency to stick even at elevated temperatures and pressure, e.g. B. when ironing and stacking
• - Insensitivity to water and moisture
• - high permanent flexural strength
• - good resistance to friction and abrasion and
• - a pleasant leather-typical "handle".

The desired property profile of the coatings can today mostly already through the PUR dispersions of the prior art Technology can be largely met. However, that is still critical Combination of the property "low tendency to stick to Er heating "with the property" high flexibility of coating high flexibility is particularly important when coating soft or flexible substrates such as textile or leather, e.g. B., as already stated above, the pleasant le the typical grip is retained.

The object of the invention was therefore to provide PUR dispersions places that are easy to process and can be used as a coating medium for different, especially flexible substrates own, it is particularly important that they are both high are flexible and do not stick even when heated.

Accordingly, the above-defined aqueous ones Dispersions found.

The monomers (a) which are usually used in polyurethane Chemistry used diisocyanates.

Particular mention should be made of diisocyanates X (NCO) ₂ , where X is an aliphatic hydrocarbon radical having 4 to 12 carbon atoms, a cycloaliphatic or aromatic carbon hydrogen radical having 6 to 15 carbon atoms or an araliphatic hydrocarbon radical having 7 to 15 carbon atoms. Examples of such diisocyanates are tetra methylene diisocyanate, hexamethylene diisocyanate, dodecamethylene diisocyanate, 1,4-diisocyanatocyclohexane, 1-isocyanato-3,5,5-tri methyl-5-isocyanatomethylcyclohexane (IPDI), 2,2-bis (4-iso cyanatocyclohexyl) propane, trimethylhexane diisocyanate, 1,4-diiso cyanatobenzene, 2,4-diisocyanatotoluene, 2,6-diisocyanatotoluene, 4,4'-diisocyanato-diphenylmethane, 2,4'-diisocyanato-diphenylmethane, p-xylylene diisocyanate, tetramethylxylylene diisocyanate (TMXDI ), the isomers of bis (4-isocyanatocyclohexyl) methane (HMDI) such as the trans / trans, the cis / cis and the cis / trans isomer and mixtures consisting of these compounds.

Mixtures of these are, in particular, mixtures of these isocyanates respective structural isomers of diisocyanatotoluene and diiso cyanato-diphenylmethane is important, in particular Mixture of 80 mol% 2.4 diisocyanatotoluene and 20 mol% 2,6-diisocyanatotoluene suitable. Furthermore, the mixtures of aromatic isocyanates such as 2,4 diisocyanatotoluene and / or 2,6-diisocyanatotoluene with aliphatic or cycloaliphatic Isocyanates such as hexamethylene diisocyanate or IPDI especially before partial, the preferred mixing ratio of the alipha tables to aromatic isocyanates 4: 1 to 1: 4.

As compounds (a) it is also possible to use isocyanates which in addition to the free isocyanate groups, further blocked isocyanate groups, e.g. B. wear uretdione or carbodiimide groups.

With regard to good film formation and elasticity come as diols (b) primarily higher molecular weight diols (b1), which a Molecular weight from about 500 to 5000, preferably from about Have 1000 to 3000 g / mol.

The diols (b1) are in particular polyester polyols which, for. B. from Ullmann's Encyclopedia of Industrial Chemistry, 4th Edition, Volume 19, pp 62 to 65 are known. Polyester polyols are preferably used which are obtained by reacting dihydric alcohols with dihydric carboxylic acids. Instead of the free polycarboxylic acids, the corresponding polycarboxylic anhydrides or corresponding polycarboxylic acid esters of lower alcohols or their mixtures can be used to prepare the polyester polyols. The polycarboxylic acids can be aliphatic, cycloaliphatic, araliphatic, aromatic or heterocyclic and optionally, e.g. B. by halogen atoms, substituted and / or unsaturated. Examples of these are suberic, azelaic acid, phthalic acid, isophthalic acid, phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride Tetrachlorphthal, endomethylenetetrahydrophthalic, glutaric anhydride, maleic anhydride, acid rock Alkenylbern, fumaric acid, dimer fatty acids. Preferred are dicarboxylic acids of the general formula HOOC- (CH ₂ ) _y -COOH, where y is a number from 1 to 20, preferably an even number from 2 to 20, e.g. B. succinic acid, adipic acid, dodecanedicarboxylic acid and sebacic acid.

As polyhydric alcohols such. B. ethylene glycol, propane-1,2-diol, propane-1,3-diol, butane-1,3-diol, butene-1,4-diol, butyne-1,4-diol, pentane-1,5- diol, neopentyl glycol, bis (hydroxy methyl) cyclohexanes such as 1,4-bis (hydroxymethyl) cyclohexane, 2-methyl propane-1,3-diol, methyl pentanediols and also diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, dipropylene glycol, polypropylene glycol , Dibutylene glycol and poly butylene glycols into consideration. Alcohols of the general formula HO- (CH ₂ ) _x -OH are preferred, where x is a number from 1 to 20, before being an even number from 2 to 20. Examples include ethylene glycol, butane-1,4-diol, hexane-1,6-diol, octane-1,8-diol and dodecane-1,12-diol. Neopentyl glycol and 1,5-pentanediol are further preferred.

Also come polycarbonate diols, such as z. B. by order Settlement of phosgene with an excess of that as build-up components for the low molecular weight polyester polyols Alcohols can be obtained.

Lactone-based polyester diols are also suitable, which are homopolymers or copolymers of lactones, preferably end products which have hydroxyl groups and which are end products of lactones with suitable difunctional starter molecules. Suitable lactones are preferably those which are derived from compounds of the general formula HO- (CH ₂ ) _z -COOH, where z is a number from 1 to 20 and an H atom of a methylene unit also by a C ₁ - to C ₄ -alkyl radical may be substituted. Examples are epsilon-caprolactone, β-propiolactone, γ-butyrolactone and / or methyl-epsilon-caprolactone and mixtures thereof. Ge suitable starter components are such. B. the above-mentioned as a building component for the polyester polyols low molecular weight dihydric alcohols. The corresponding polymers of epsilon caprolactone are particularly preferred. Lower polyester diols or polyether diols can also be used as starters for the preparation of the lactone polymers. Instead of the poly merisate of lactones, the corresponding chemically equivalent polycondensates of the hydroxycarboxylic acids corresponding to the lactones can also be used.

In addition, the monomers (b1) are polyether diols. They are in particular by polymerization of ethylene oxide, propylene oxide, butylene oxide, tetrahydrofuran, styrene oxide or epichlorohydrin with themselves, for. B. in the presence of BF ₃ or by storage of these compounds, optionally in a mixture or one after the other, on starting components with reactive hydrogen atoms, such as alcohols or amines, for. B. water, ethylene glycol, propane-1,2-diol, propane-1,3-diol, 1,2-bis (4-hydroxydi phenyl) propane or aniline available. Poly propylene glycol and polytetrahydrofuran with a molecular weight of 240 to 5000, and especially 500 to 4500, are particularly preferred.

Polyhydroxyolefins are also suitable, preferably those with 2 terminal hydroxyl groups, e.g. B. α-ω-dihydroxypolybutadiene, α-ω-Dihydroxypolymethacrylester or α-ω-Dihydroxypolyacrylester as monomers (c1). Such connections are made, for example known from EP-A-0622378. Other suitable polyols are poly acetals, polysiloxanes and alkyd resins.

The polyols can also be used as mixtures in a ratio of 0.1: 1 to 1: 9 can be used.

In addition to the diols (b1), the diols (b) are also of low molecular weight Diols (b2) with a molecular weight of about 62 to 500, preferably from 62 to 200 g / mol.

Suitable monomers (b2) are alkanediols (b2.1), i.e. H. those that have no other radio than their hydroxyl groups national groups. Above all, the construction Components of ge for the production of polyester polyols called short-chain alkanediols used, the unrelated branched diols with 2 to 12 carbon atoms and an even number number of carbon atoms and pentane-1,5-diol are preferred.

Other suitable diols (b2) are alkanediols which, except the hydroxyl groups hydrophilic groups or groups that are in Have hydrophilic groups transferred, wear. These are used for Improving the water dispersibility of the polyurethanes.

The term "hydrophilic groups or potentially hydrophilic Groups "is also referred to as" (potentially) hydrophilic groups " cuts.

The (potentially) hydrophilic groups react with isocyanates much slower than the functional groups of the monomers, which serve to build up the main polymer chain.

Ionic hydrophilic groups are mainly anionic groups such as the sulfonate, carboxylate and phosphate groups in the form their alkali metal or ammonium salts and cationic groups such as ammonium groups, especially protonated tertiary amino groups or quaternary ammonium groups.  

Potentially ionic hydrophilic groups are primarily those that through simple neutralization, hydrolysis or quaternization nization reactions in the above-mentioned ionic hydrophilic Have groups transferred, e.g. B. carboxylic acid groups, Anhydride groups or tertiary amino groups.

Diols (b2.2) are e.g. B. in Ullmann's Encyclopedia of Technical Chemie, 4th edition, volume 19, pp. 311-313 and for example in the DE-A 14 95 745 described in detail.

As (potentially) cationic diols (b2.2) are primarily monomers with tertiary amino groups of particular practical importance, for example, N, N'-bis (hydroxyalkyl) alkylamines, the Alkyl residues and alkanediyl units of these tertiary amines are independent dependent on each other consist of 1 to 6 carbon atoms.

There are also polyethers containing tertiary nitrogen atoms preferably with two terminal hydroxyl groups, as z. B. by alkoxylation of two water bound to amine nitrogen Amines containing substance atoms, e.g. B. methylamine, aniline or N, N'- Dimethylhydrazine, accessible in a conventional manner, in Consideration. Such polyethers generally have an intermediate 500 and 6000 g / mol molecular weight.

These tertiary amines are either with acids, preferably strong mineral acids such as phosphoric acid, sulfuric acid, halogenic acids or strong organic acids or by implementation with suitable quaternizing agents such as C ₁ - to C ₆ -alkyl halides or benzyl halides, for. B. bromides or chlorides in the ammonium salts.

Suitable diols (b2.2) with (potentially) anionic groups are usually aliphatic, cycloaliphatic, araliphatic or aromatic carboxylic acids and sulfonic acids which carry 2 alcoholic hydroxyl groups. Preferred are dihydroxy alkyl carboxylic acids, especially those with 3 to 10 carbon atoms, as are also described in US Pat. No. 3,412,054. In particular, compounds of the general formula

in which R ¹ and R ^{2 is} a C ₁ - to C ₄ -alkanediyl unit and R ^{3 is} a C ₁ - to C ₄ -alkyl unit and especially dimethylol propionic acid (DMPA) is preferred.

Corresponding dihydroxysulfonic acids and Dihydroxyphosphonic acids such as 2,3-dihydroxypropanephosphonic acid.

If diols (b2.2) with potentially ionic groups are used can be converted into the ionic form before, during, but preferably after the isocyanate polyaddition, because the ionic monomers in the reaction mixture often only difficult to solve. The carboxylate or are particularly preferably Sulphonate groups in the form of their salts with an alkali ion or an ammonium ion as a counter ion.

The proportion of the diols (b2), based on the total amount of the diols (b) is preferably at least 5 mol%.

In addition to the diols (b2.2) and components (a), (b), (d) and (e) can the polyurethanes to the water dispersibility of the poly To achieve or improve urethane, still from the compo nenten (a), (b), (d) and (e) different monomers (c) builds, the at least one isocyanate group or at least a group reactive toward isocyanate groups and beyond have at least one (potentially) hydrophilic groups.

The same applies in principle to these monomers (c) as for the diols (b2.2).

The proportion of components with (potentially) hydrophilic groups, d. H. of components (c) and (b2.2) on the total amount of other components (a), (b), (c), (d) and (e) are generally mean so that the molar amount of (potentially) hydrophilic Groups based on the amount by weight of all monomers (a) to (e), 30 to 1000, preferably 50 to 500 and particularly preferably 80 is up to 300 mmol / kg.

The (potentially) hydrophilic groups cannot be ionic or preferably around (potentially) ionic hydrophilic Trade groups.

The nonionic hydrophilic groups are polyalkylene oxide Residues, especially polyethylene glycol ethers, preferably from 5 to 100, preferably 10 to 80 repeating ethylene oxide units, in Consideration. The content of polyethylene oxide units is  general 0 to 10, preferably 0 to 6 wt .-%, based on the Weight amount of all monomers (a) to (e).

Preferred monomers with nonionic hydrophilic groups are Polyethylene oxide diols, polyethylene oxide monools and the reaction products from a polyethylene glycol and a diisocyanate, the carry a terminally etherified polyethylene glycol residue. The like diisocyanates and processes for their preparation are in the patents US 3 905 929 and US 3 920 598.

(Potentially) ionic monomers (c) are e.g. B. in Ullmanns Encyclopedia of Technical Chemistry, 4th Edition, Volume 19, Pp. 311-313 and for example in DE-A 14 95 745 in detail described.

As (potentially) cationic monomers (c) are primarily monomers with tertiary amino groups of particular practical importance, for example: tris (hydroxyalkyl) amines, N-hydroxyalkyl dialky lamines, tris (aminoalkyl) amines, N, N'-bis (aminoalkyl) alkylamines, N-aminoalkyl-dialkylamines, the alkyl radicals and alkanediyl Units of these tertiary amines independently of one another from 1 to 6 carbon atoms exist. The conversion to the ionic Form takes place in an analogous manner to that of the corresponding Diols with tertiary groups, which belong to the monomers (b2.2), is described.

Also come as monomers with (potentially) anionic groups aliphatic, cycloaliphatic, araliphatic or aromatic Carboxylic acids and sulfonic acids that are different from the diols (b2.2) and at least one alcoholic hydroxyl group or at least one primary or secondary amino group wear. As monomers (c) with isocyanate-reactive Amino groups come aminocarboxylic acids such as lysine, β-alanine, which in the adducts of aliphatic diprimaries mentioned in DE-A-20 34 479 Diamines on a, β-unsaturated carboxylic or sulfonic acids in Be dress.

Such compounds obey, for example, the formula (c1)

H ₂ NR ⁴ -NH-R ⁵ -X (c1)

in the
- R ⁴ and R ⁵ independently of one another for a C ₁ - to C ₆ -alkanediyl unit, preferably ethylene
and X represents COOH or SO ₃ H.

Particularly preferred compounds of formula (c1) are N- (2-aminoethyl) -2-aminoethane carboxylic acid and the as well as the N- (2-aminoethyl) -2-aminoethanesulfonic acid or the corresponding Alkali salts, Na being particularly preferred as the counter ion.

The adducts of the abovementioned are also particularly preferred aliphatic diprimary diamines on 2-acrylamido-2-methylpropane sulfonic acid as z. B. be in the German patent 19 54 090 are written.

If monomers with potentially ionic groups are used can be converted into the ionic form before, during, but preferably after the isocyanate polyaddition, because the ionic monomers in the reaction mixture often only difficult to solve. The carboxylate or are particularly preferably Sulphonate groups in the form of their salts with an alkali ion or an ammonium ion as a counter ion.

The monomers (d) differ from the monomers (a) to (c) are generally used for crosslinking or chains renewal. There are generally no more than two-valued ones phenolic alcohols, amines with 2 or more primary and / or secondary amino groups as well as compounds in addition to one or several alcoholic hydroxyl groups one or more primary and / or wear secondary amino groups.

Alcohols with a higher valence than 2, for adjustment a certain degree of branching or networking can, for. B. trimethylolpropane, glycerin or sugar.

Also suitable are monoalcohols which, in addition to the hydroxyl Group carry another isocyanate-reactive group such as monoalcohols with one or more primary and / or secondary amino groups, e.g. B. Monoethanolamine.

Polyamines with 2 or more primary and / or secondary amino Groups are mainly used when the chains extension or crosslinking take place in the presence of water Because amines are generally faster than alcohols or water react with isocyanates. This is often necessary when aqueous dispersions of cross-linked polyurethanes or polyures thanen with a high molecular weight are desired. In such cases the procedure is to prepare prepolymers with isocyanate groups provides, this dispersed quickly in water and then by  Addition of compounds with several isocyanates reactive amino groups chain-extended or cross-linked.

Suitable amines are generally polyfunctional amines of the molecular weight range from 32 to 500 g / mol, preferably from 60 to 300 g / mol, which selected at least two amino groups from the group of primary and secondary amino groups, ent hold. Examples include diamines such as diaminoethane and diamino propanes, diaminobutanes, diaminohexanes, piperazine, 2,5-dimethyl piperazine, amino-3-aminomethyl-3,5,5-trimethyl-cyclohexane (Iso phorondiamine, IPDA), 4,4'-diaminodicyclohexylmethane, 1,4-diamino cyclohexane, aminoethylethanolamine, hydrazine, hydrazine hydrate or Triamines such as diethylenetriamine or 1,8-diamino-4-aminomethyl octane.

The amines can also be in blocked form, e.g. B. in the form of ent speaking ketimines (see e.g. CA-1 129 128), ketazines (cf. e.g. B. US-A 4,269,748) or amine salts (see US-A 4,229,226) be set. Also oxazolidines, such as those in the US-A 4 192 937 are capped polyamines, for the production of the polyurethanes according to the invention Chain extension of the prepolymers can be used. At the use of such capped polyamines in generally ver with the prepolymers in the absence of water mixes and this mixture then with the dispersion water or part of the dispersion water mixed so that hydro the corresponding polyamines are lysed.

Mixtures of di- and triamines are preferably used, be mixtures of isophoronediamine and diethylene tri are particularly preferred amine.

The polyurethanes preferably contain no polyamine or 1 to 10, particularly preferably 4 to 8 mol%, based on the total amount of components (b) and (d) of a polyamine with at least 2 ge amino groups reactive with isocyanates as monomers (d).

Alcohols with a higher valence than 2, for adjustment a certain degree of branching or networking can, for. B. trimethylolpropane, glycerin or sugar.

For the same purpose, three and higher quality isocyanates are used. Commercial Compounds are, for example, isocyanurate or biuret of hexamethylene diisocyanate.  

Monomers (e) which may also be used are monoiso cyanates, monoalcohols and mono-primary and secondary amines. in the in general, their proportion is at most 10 mol%, based on the total molar amount of monomers. These monofunctional Compounds usually carry further functional groups such as olefinic groups or carbonyl groups and serve for Ein introduction of functional groups in the polyurethane that the Dispersion or crosslinking or other polymer-analogous order Allow setting of the polyurethane. Consider this Monomers such as isopropenyl-alpha, alpha-dimethylbenzyl isocyanate (TMI) and esters of acrylic or methacrylic acid such as hydroxyethyl acrylate or hydroxyethyl methacrylate.

In the field of polyurethane chemistry, it is well known how the molecular weight of the polyurethanes by choosing the proportions of the mutually reactive monomers and the arithmetic mean the number of reactive functional groups per molecule can be put.

Components (a) to (e) and their respective molar amounts are normally chosen so that the ratio A: B with

• A) the molar amount of isocyanate groups and
• B) the sum of the molar amount of the hydroxyl groups and the mol amount of functional groups with isocyanates in one Can react addition reaction

0.5: 1 to 2: 1, preferably 0.8: 1 to 1.5, particularly preferably 0.9: 1 to 1.2: 1. That is very particularly preferred Ratio A: B as close as possible to 1: 1.

The monomers (a) to (e) used are more common on average as 1.5 to 2.5, preferably 1.9 to 2.1, particularly preferably 2.0 Isocyanate groups or functional groups with isocyanates can react in an addition reaction.

The polyaddition of components (a) to (e) generally takes place mean at reaction temperatures of 20 to 180 ° C, preferably 50 up to 150 ° C under normal pressure or under autogenous pressure.

The required response times can vary over a few Extend minutes to a few hours. It is in the field of Polyurethane chemistry is known as the reaction time by a lot number of parameters such as temperature, concentration of the monomers, Reactivity of the monomers is influenced.  

To accelerate the reaction of the diisocyanates, the usual catalysts, such as dibutyltin dilaurate, stannous octoate or diazabicyclo- (2,2,2) octane.

Stirred kettles come into consideration as polymerization apparatus especially if by using solvents for low viscosity and good heat dissipation is ensured.

If the reaction is carried out in bulk, are suitable the usually high viscosities and the usually only short reaction times especially extruders, especially self-cleaning more screw extruder.

Preferred solvents are infinitely miscible with water, have a boiling point at normal pressure of 40 to 100 ° C and do not react or react only slowly with the monomers.

The aqueous dispersions according to the invention containing a polyurethane are prepared by

• a) in a first step, the macrodiols (b1) together with such amounts of diisocyanate (a) that at the beginning the reaction the ratio of the isocyanate groups to the Alcohol groups is 0.1: 1 to 0.9: 1, and the reaction is continued until the NCO content of the reaction Mixing to preferably a maximum of 10, but at least a maximum Has reduced 20% of the original value,
• b) the reaction product formed in step (i) (reaction product i) with the remaining components to form a poly reacting urethane, whereby the finished polyurethane or a prepolymer formed in an intermediate stage in water dispersed and in the case of dispersion of the prepolymer finally the reaction to the polyurethane continues.

Most often, the dispersions according to one of the following Ver drive manufactured:

After the "acetone process" is in a miscible with water and at normal pressure below 100 ° C boiling solvent from the Reaction product (i) the remaining components (a) to (c) ionic polyurethane manufactured. So much water is added until a dispersion forms, in which water the coherent Represents phase.  

The "prepolymer mixing process" differs from the acetonever drive in that not a fully reacted (potentially) ionic Polyurethane, but first from the reaction product (i) and the other components (a) to (e) a prepolymer that carries isocyanate groups. The components are here chosen so that the defined ratio A: B is greater than 1.0 to 3, preferably 1.05 to 1.5. The prepolymer comes first dispersed in water and then optionally by reak tion of the isocyanate groups with amines that are more than 2 opposite Wear isocyanate-reactive amino groups, crosslinked or with Amines which carry 2 amino groups reactive towards isocyanates, chain extended. A chain extension also takes place if no amine is added. In this case, isocyanate groups hydrolyzed to amino groups, with those still remaining Isocyanate groups of the prepolymers with chain extension react.

Usually, if in the manufacture of the polyurethane a solvent was used, most of the Solvent removed from the dispersion, for example by Distillation under reduced pressure. Preferably, the Dispersions have a solvent content of less than 10% by weight and are particularly preferably free of solvents.

The dispersions generally have a solids content of 10 to 75, preferably 20 to 65% by weight and a viscosity of 10 to 500 m Pas (measured at a temperature of 20 ° C. and a shear rate of 250 s ^-1 ).

Hydrophobic aids that can be difficult to homogenize to be distributed in the finished dispersion, for example Phenol condensation resins made from aldehydes and phenol or phenol derivatives or epoxy resins and other z. B. in DE-A-39 03 538, 43 09 079 and 40 24 567 polymers mentioned in polyurethane dispersions serve, for example, as adhesion improvers, can be according to the two writings mentioned above methods described be the polyurethane or the prepolymer are already added before the dispersion.

It is believed that because of that in an upstream First the reaction product (i) is produced instead of, as usual, all diols (b) together in be implemented in one step, a polyurethane with a ver changed fine structure, in which the macropolyols (b1) mainly in the form of blocks that can only be identified by the structural units derived from the monomers (a) are interrupted are, but not by other units that differ from the  other components derived for the construction of the polyurethane Derive (a) to (e). These blocks probably consist of statistical means from 2.5 to 10 units by the diols (b1) are derived.

The polyurethane dispersions can be commercially available auxiliaries and additives Substitutes such as blowing agents, defoamers, emulsifiers, Verdic agents and thixotropic agents, colorants such as dyes and Pigments included.

The aqueous polyurethane dispersions according to the invention are suitable itself as a coating agent for the un various substrates, e.g. B. leather, paper, textiles art fabric or metal, especially flexible for coating Substrates. You can use standard methods, e.g. B. by spraying, Squeegees or pouring can be applied to the substrates.

Experimental part Dispersion D 1 (comparison)

400 g (0.200 mol) of a polypropylene glycol (OHZ 56), 40.2 g (0.300 mol) DMPA, 0.1 g DBTL and 30 g NMP were stirred submitted boiler at 50 ° C. 164.5 g (0.74 mol) of IPDI were added given. After 120 min. Stirring at 95 ° C was mixed with 700 g of acetone thin and cooled to 50 ° C at the same time. The NCO content of the solution was 1.51% (calculated 1.52%). After adding 29.0 g (0.287 mol) TEA was reduced by adding 1000 g of water within 5 min. dispersed. After the end of the dispersion, a Solution of 8.2 g (0.080 mol) DETA and 20.4 g (0.120 mol) IPDA in 50 g of water added. After distillation of the acetone resulted a finely divided aqueous PU dispersion with a solids content of approx. 36%.

Dispersion D 2

400 g (0.200 mol) of a polypropylene glycol (OHZ 56), 20 g acetone and 0.1 g DBTL were placed in a stirred kettle at 50 ° C. To this was added 11.1 g (0.050 mol) of IPDI (I) (more original NCO content without acetone, calculated: 1.02%) after 90 min. Stir in 95 ° C the NCO content had dropped to <0.1%. Then 40.2 g (0.300 mol) DMPA, 30 g NMP and 153.4 g (0.690 mol) IPDI (II) given. After stirring for a further 90 minutes at 95 ° C., 680 g Diluted acetone and simultaneously cooled to 50 ° C. The NCO content the solution was 1.49% (calc. 1.52%). After adding 29.0 g (0.287 mol) TEA was added by adding 1000 g water dispersed from 5 min. After the end of the dispersion was a solution of 8.2 g (0.080 mol) DETA and 20.4 g (0.120 mol)  IPDA added in 50 g of water. After distilling the acetone resulted in a finely divided aqueous PU dispersion with approx. 36% Fixed salary.

Dispersion D 3

The procedure was as for dispersion D 2, but the was Amount of IPDI (I) 17.8 g (0.08 mol) and the amount of IPDI (II) 146.7 g (0.66 mol).

Dispersion D 4

The procedure was as for dispersion D 2, but the was Amount of IPDI (I) 22.2 g (0.10 mol) and the amount of IPDI (II) 142.3 g (0.64 mol).

Dispersion D 5

The procedure was as for dispersion D 2, but the was Amount of IPDI (I) 25.6 g (0.115 mol) and the amount of IPDI (II) 138.9 g (0.625 mol).

Dispersion D 6

The procedure was as for dispersion D 2, but the was Amount of IPDI (I) 27.8 g (0.125 mol) and the amount of IPDI (II) 136.7 g (0.615 mol).

Dispersion D 7

The procedure was as for dispersion D 2, but the was Amount of IPDI (I) 30.0 g (0.135 mol) and the amount of IPDI (II) 134.5 g (0.605 mol).

Dispersion D 8

The procedure was as for dispersion D 2, but the was Amount of IPDI (I) 32.2 g (0.145 mol) and the amount of IPDI (II) 132.3 g (0.595 mol).

Exam:
The dispersions were tested in an analogous manner as a primer for leather finishing. For this purpose, a mixture consisting of
100 g of a commercially available pigment preparation
330 g of one of the dispersions D1 to D8
570 g water

applied to cowhide leather. The application was carried out by spraying the mixture; spray 15 g / A4, dry, iron (80 ° C, 50 bar, 2 seconds), spray 10 g / A4, dry. The hot ironing fastness (HBE) of the coated leather was then checked. The test was carried out in the rubbing test with the rub fastness tester according to VESLIC (IUF450) and the heatable test stamp (stamp 10 × 10 mm) when the temperature of the test stamp rose in 10 ° C steps with 5 rubs each until the surface layer was damaged. The temperature at which the coating was still intact is indicated.

The examples clearly show that with the same gross composition of the dispersions by the process according to the invention tions are obtained that have a significantly improved hot iron have authenticity.

Abbreviations:
RT = room temperature
OHZ = hydroxyl number
ADS = adipic acid
DBTL = dibutyltin dilaurate
DMPA = dimethylol propionic acid
TEA = triethylamine
IPDA = isophoronediamine
FG = solids content
NMP = N-methylpyrrolidinone
DETA = diethylene triamine

Claims (7)

1. A process for the preparation of aqueous dispersions containing a polyurethane in dispersed form

• a) diisocyanates with 4 to 30 carbon atoms,
• b) diols which are essentially free of urethane or urea groups, of which
  • 1. 10 to 95 mol%, based on the total amount of diols (b), have a molecular weight of 500 to 5000, and
  • 2. 5 to 90 mol%, based on the total amount of diols (b), have a molecular weight of 60 to 500 g / mol, these being alkanediols (b2.1) or alkanediols, which additionally have a hydrophilic group or carry a potentially hydrophilic group (b2.2),
• c) if diols (b2.2) are not present or are not present in sufficient amounts to effect water dispersibility, monomers different from monomers (a) and (b) with at least one isocyanate group or at least one group which is reactive toward isocyanate groups, the furthermore carry at least one hydrophilic group or a potentially hydrophilic group, which causes the water dispersibility of the polyurethanes,
• d) optionally further from the monomers (a) to (c) different polyvalent compounds with reactive groups, which are alcoholic hydroxyl groups, primary or secondary amino groups or isocyanate groups and
• e) if appropriate, monomers different from the monomers (a) to (d) with a reactive group which is an alcoholic hydroxyl group, a primary or secondary amino group or an isocyanate group

being one

• a) in a first step the macrodiols (b1) are reacted together with such amounts of diisocyanate (a) that the ratio of the isocyanate groups to the alcohol groups is 0.1: 1 to 0.9: 1 at the start of the reaction, and the Reaction is continued until the NCO content of the reaction mixture has decreased to a maximum of 20% of the original value,
• b) the reaction product formed in step (i) is reacted with the remaining components to form a polyurethane, where the finished polyurethane or a prepolymer formed in an intermediate stage is dispersed in water and, if the prepolymer is dispersed, the reaction to the polyurethane then continues .

2. The method according to claim 1, wherein the monomer (b1) is a polyester or polyether diol. 3. The method of claim 1 or 2, wherein it is the diol (b2.2) is dimethylolpropionic acid. 4. Aqueous dispersions containing a polyurethane in disper form, obtainable by the method according to the claims Chen 1 to 3. 5. Preparations containing an aqueous dispersion according to An Proverb 4, pigments and other common leather trimmings aids included. 6. Articles ver with a dispersion according to claim 4 sticks or are coated, as well as textiles with this Dispersion are impregnated. 7. Leather coated with a preparation according to claim 5.