DE4231034A1 - Polyurethane dispersions esp. for coating textiles and leather - based on di:isocyanato:di:cyclo:hexyl:methane - Google Patents

Abstract

Polyurethanes (I) are derived from polyisocyanates (II), NCO-reactive cpds. with OH gp(s). (III) and opt. cpds. with prim. or sec. amino gp(s). (IV). At least 40 mole% of (II) consists of di-isocyanato-dicyclohexyl-methane (DCHMDI), at least 30 wt% of which consists of the trans/trans isomer. The required DCHMDI mixt. is readily obtd. by sepn. of the solid trans/trans isomer from the cis/cis and cis/trans isomers at below deg. C followed by back-mixing as required. IPDI is preferred as a further isocyanate component. Pref. (III) are polyether-polyols or polyester-polyester-polyols, and (IV) are mixts. of IPDA and diethylenetriamine. USE/ADVANTAGE - Used as coating materials, esp. for textiles and leather (claimed). Polyurethanes (PU) with the above compsn. enable the prodn. of soft coatings with a low degree of stickiness, on leather, textiles etc. (contrast prior-art PU based on normal DCHMDI mixts., e.g. Desmodur W (RTM) with 20-25 wt% trans/trans isomer).

Description

The invention relates to a polyurethane composed of polyiso cyanates and compounds reactive towards polyisocyanates at least one hydroxyl group and optionally compounds with at least one primary or secondary amino group, since characterized in that it is at least 40 mol% of Polyisocyanate is diisocyanatodicyclohexylmethane and the Proportion of the trans / trans isomer of diisocyanatodicyclohexyl methane on the total amount of diisocyanatodicyclohexylmethane is at least 30% by weight.

The invention further relates to aqueous dispersions thereof Polyurethane and the use of the dispersions as coatings detergents, in particular for textiles and leather.

Binder based on aqueous polyurethane preparations Use of diisocyanatodicyclohexylmethane are e.g. B. in DE-A-14 95 745. You will u. a. also for coating softer substrates such. B. leather or textiles used. At Textile or leather coatings often depend on preservation the soft grip typical of the substrate. It is that Known in the art, the desired softness of the polyurethane z. B. by varying the urethane and urea content.

A disadvantage of the previously used polyurethane dispersions for Textile and leather coatings with high softness is that this softness also with a strong stickiness of the coating is connected.

This not only makes the handle uncomfortable for the end user of the coated leather or textile, but also skin fig hinder the coating process, e.g. B. by gluing the so treated leather.

The object of the present invention was therefore in the ready position aqueous polyurethane preparations, the manufacture enable softer, less adhesive coatings.  

Accordingly, the polyurethane defined above as well as aqueous Dispersions containing the polyurethane defined above were found. Furthermore, the use of the dispersion as a coating found especially for leather or textiles.

The polyurethane according to the invention is made of polyisocyanates (in further also called monomers I) and with respect to polyisocyanates reactive compounds with at least one hydroxyl group and optionally compounds with at least one primary or secondary amino group built.

At least 40 mol% of the polyisocyanates are Diisocyanatodicyclohexylmethane, which contains at least 30% by weight is present as a trans / trans isomer.

A distinction is made between diisocyanatodicyclohexylmethane and the following isomeric forms:

Commercially available diisocyanatodicyclohexylmethane, e.g. B. Desmodur® W from Mobay contains approx. 20-25% by weight of the trans / trans Isomers.  

The state of aggregation of the trans / trans isomer is in contrast to cis / cis or cis / trans isomers at 20 ° C solid. The trans / trans Therefore, isomer can be easily obtained by separating the solid component of still liquid isomer mixtures Temperatures below 20 ° C. Desired proportions of the trans / trans Isomers can then be backmixed by defined backfill parts of mixtures of isomers are adjusted.

It is preferably particularly at least 60 mol% preferably in 80 mol% of the polyisocyanates around diisocyanatodicyclo hexylmethane.

Preferably at least 40% by weight is particularly preferred at least 60 wt .-% of the diisocyanatodicyclohexylmethane in the trans / trans form.

As further polyisocyanates in addition to diisocyanatodicyclohexylmethane they are usually used in polyurethane chemistry consider polyisocyanates.

Particular mention should be made of diisocyanates X (NCO) ₂ , where X represents 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 ara lipatic hydrocarbon radical having 7 to 15 carbon atoms. Examples of such diisocyanates are tetramethylene diisocyanate, hexamethylene diisocyanate, dodecamethylene diisocyanate, 1,4-diisocyanatocyclohexane, 1-isocanato-3,5,5-trimethyl-5-iso cyanatomethylcyclohexane (IPDI), 4,4'-diisocyanato-dicyclohexyl propane-2,2 -, Trimethylhexane diisocyanate, 1.4 diisocyanatobenzene, 2.4 diisocyanatotoluene, 2,6-diisocyanatotoluene, 4,4'-diisocyanate, nato-diphenylmethane, p-xylylene diisocyanate and mixtures consisting of these compounds.

It is also possible to use those known in polyurethane chemistry higher functional polyisocyanates or modified polyiso cyanates, for example carbodiimide, allophanate, isocanurate, Polyisocyanates containing urethane and / or biuret groups to be used proportionately, in particular also according to the in US-A- 4,507,431.

Also preferred in terms of use as Coating agents for leather or textiles (cyclo) aliphatic Polyisocyanates are used, particularly preferably IPDI.  

The other structural components of the polyurethane are concerned are initially polyols with a molecular weight of 400 to 6000 g / mol, preferably 600 to 4000 g / mol (monomers II).

Polyether polyols or polyesters are particularly suitable polyols.

The polyester diols are in particular the known reaction products of dihydric alcohols with dibasic carboxylic acids. Instead of the free polycarboxylic acids can also the corresponding polycarboxylic anhydrides or ent speaking polycarboxylic acid esters of lower alcohols or their Mixtures can be used to produce the polyester polyols. The polycarboxylic acids can be aliphatic, cycloaliphatic, aroma be table or heterocyclic and optionally, e.g. B. by Halogen atoms, substituted and / or unsaturated. As with Games for this are mentioned: succinic acid, adipic acid, cork acid, azelaic acid, sebacic acid, phthalic acid, isophthalic acid, Phthalic anhydride, tetrahydrophthalic anhydride, hexahydroph thalic anhydride, tetrachlorophthalic anhydride, endomethylene tetrahydrophthalic anhydride, glutaric anhydride, maleic acid, Maleic anhydride, fumaric acid, dimeric fatty acids. As more term alcohols come e.g. B. ethylene glycol, propylene glycol (1,2) and - (1,3), butanediol- (1,4), - (1,3), butenediol- (1,4), butyne diol- (1.4), pentanediol- (1.5), hexanediol- (1.6), octanediol- (1.8), Neopentyl glycol, cyclohexanedimethanol (1,4-bis-hydroxymethylcy clohexane), 2-methyl-1,3-propanediol, pentanediol- (1,5), further Diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene lenglycol, dipropylene glycol, polypropylene glycol, dibutylene glycol and polybutylene glycols in question.

Lactone-based polyester diols are also suitable to homopolymers or copolymers of lactones, preferably to end permanent addition products from Lac with hydroxyl groups tone or lactone mixtures, such as. B. ε-caprolactone, β-propiolac clay, butyrolactone and / or methyl ε-caprolactone to suitable difunctional starter molecules, e.g. B. the above as a structure component for the low molecular weight polyester polyols, dihydric alcohols. The corresponding polymers ε-caprolactone are particularly preferred. Even lower poly Ester diols or polyether diols can be used as starters for the preparation the lactone polymers can be used. Instead of the polymerisa Te of lactones can also be the corresponding, chemically equivalent lenten polycondensates of the hydroxycar corresponding to the lactones bonic acids are used.  

The - optionally also in a mixture with polyester diols - a settable polyether diols, 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 addition of these compounds, optionally in a mixture or in succession, to starting components with reactive hydrogen atoms, such as alcohols or amines, for. B. water, ethylene glycol, propylene glycol (1,3) or - (1,2), 4,4'-dihydroxy diphenylpropane, aniline available.

The proportion of the monomer II described above is in generally 0.1 to 0.8 gram equivalent, preferably 0.2 to 0.7 Gram equivalent of the hydroxyl group of the monomer II based on 1 gram equivalent of isocyanate of the polyisocyanate.

Other structural components of the polyurethane are concerned compared to chain extenders or crosslinkers with at least two Isocyanate-reactive groups selected from hydroxyl groups, primary or secondary amino groups.

Polyols, in particular diols and triols with one, may be mentioned Molecular weight below 400 g / mol to 62 g / mol (monomers III).

In particular, those listed above are used to manufacture the Suitable polyester polyols diols and triols, as well as higher than trifunctional alcohols such as pentaerythritol or sorbitol in Consideration.

The proportion of the monomers III is generally 0-0.8 ins particular 0 to 0.7 gram equivalent based on 1 gram equivalent valent isocyanate.

The monomers IV which may be used are are at least difunctional amine chain extenders or crosslinker of the molecular weight range from 32 to 500 g / mol, before preferably from 60 to 300 g / mol, which have at least two primary, two secondary or one primary and one secondary amino group contain.

Examples include diamines, such as diaminoethane, diaminopropanes, Diaminobutanes, diaminohexanes, piperazine, 2,5-dimethylpiperazine, Amino-3-aminomethyl-3,5,5-trimethyl-cyclohexane (isophoronediamine, IPDA), 4,4'-diaminodicyclohexylmethane, 1,4-diaminocyclohexane, Aminoethylethanolamine, hydrazine, hydrazine hydrate or triamines such as Diethylenetriamine or 1,8-diamino-4-aminomethyloctane. The amino Group-containing chain extenders can also be blocked Shape, e.g. B. in the form of the corresponding ketimines (see e.g.  CA-1 129 128), ketazines (see e.g. US-A-4,269,748) or amine salts (see US-A-4,292,226). Even oxazolidines like them used, for example, in U.S. Patent No. 4,192,937 masked polyamines used for the preparation of the Invention appropriate polyurethanes for chain extension of the prepolymers can be placed. When using such capped Polyamines are generally used with the prepolymers in Absence of water mixed and then this mixture with the water of dispersion or part of the water of dispersion mixed, so that the corresponding hydrolytically Polyamines are released.

Mixtures of di- and triamines are preferably used, in particular other preferred mixtures of isophoronediamine and diethylenetriamine.

Where applicable, also as a chain extender setting monomers V are amino alcohols with a Hydroxyl and a primary or secondary amino group such as Ethanolamine, isopropanolamine, methylethanolamine or amino ethoxyethanol.

The proportion of the monomers IV or V is in each case preferably 0 to 0.4, particularly preferably 0 to 0.2 gram equivalent based to 1 gram equivalent of isocyanate of the polyisocyanate.

Connections can be used as a further structural component be at least one, preferably two versus Iso cyanate groups reactive groups, i.e. hydroxyl, primary or secondary amino groups, and also in contrast to the Monomers described above or by ionic groups a simple neutralization or quaternization reaction in ionic groups convertible, potentially ionic groups point. (Monomers VI). By introducing the monomers VI the polyurethanes themselves dispersible, d. H. when dispersing in In this case, water is not used as a dispersing agent Protective colloids or emulsifiers are required.

The introduction of the cationic or anionic groups can by using (potential) cationic or (poten tial) compounds having anionic groups with opposite Isocyanate-reactive hydrogen atoms take place. To this Groups of connections include e.g. B. tertiary nitrogen atoms comprising polyethers with preferably two terminal hydro xyl groups such as z. B. by alkoxylation of two amine Amines containing nitrogen-bound hydrogen atoms, e.g. B. Methylamine, aniline, or N, N'-dimethylhydrazine, in itself are accessible in the usual way. Such polyethers have  generally a molecular weight between 500 and 6000 g / mol on.

However, the ionic groups are preferably replaced by Mitver use of comparatively low molecular weight compounds (potential) ionic groups and towards isocyanate groups reactive groups introduced. Examples of this are in US-A 3,479,310 and 4,056,564 and GB-1,455,554 guided. Also dihydroxyphosphonates, such as the sodium salt of 2,3-Dihydroxypropane-phosphonic acid ethyl ester or the ent speaking sodium salt of the non-esterified phosphonic acid, can can also be used as an ionic structural component.

Preferred (potential) ionic monomers VI are N-Akyldi alkanolamines such as B. N-methyldiethanolamine, N-ethyldiethanol amine, diamino sulfonates, such as the Na salt of N- (2-amino ethyl) -2-aminoethanesulfonic acid, dihydroxysulfonates, dihydroxycar bonic acids such as dimethylolpropionic acid, diaminocarboxylic acids or carboxylates such as lysine or the Na salt of N- (2-amino ethyl) -2-aminoethane carboxylic acid and diamines with at least one additional tertiary amine nitrogen atom, e.g. B. N-methyl bis- (3-aminopropyl) amine.

Diamino- and dihydroxycarboxylic acids are particularly preferred, in particular the adduct of ethylenediamine with sodium acrylate or Dimethylol propionic acid.

The transfer of, if necessary, first to the polyaddition product built-in potential ionic groups at least partly in ionic groups happens in a conventional manner by neutralizing the potential anionic or cat ionic groups or by quaternization of tertiary amine Nitrogen atoms.

To neutralize potential anionic groups, e.g. B. Carboxyl groups, become inorganic and / or organic bases used like alkali hydroxides, carbonates or hydrogen carbonates, ammonia or primary, secondary and especially before adds tertiary amines such as triethylamine or dimethylaminopropanol.

To transfer the potential cationic groups, e.g. B. the tertiary amine groups in the corresponding cations, e.g. B. Ammo nium groups, are inorganic or as neutralizing agents organic acids, e.g. B. salt, phosphorus, ants, vinegar, Fumaric, maleic, lactic, tartaric or oxalic acid or as a quater Nierungsmittel, for. B. methyl chloride, methyl bromide, methyl iodide, Dimethyl sulfate, benzyl chloride, chloroacetic acid ester or bromine  suitable for acetamide. Further neutralization or quaternization means are z. Example, in US Pat. No. 3,479,310, column 6.

This neutralization or quaternization of the potential ions Groups can be before, during, but preferably after the isocanate Polyaddition reaction take place.

The amounts of the monomers VI in the case of potential ion groups containing components taking into account the neutralization or degree of quaternization, is suitably chosen so that the polyurethanes have a content of 0.05 to 2 meq / g polyurethane, preferably from 0.07 to 1.0 and particularly preferably from 0.1 to Have 0.7 meq / g of polyurethane on ionic groups.

Optionally, monofunctional amine or hydroxyl compounds used as structural components (monomers VII). It is preferably monohydric polyether alcohols Molecular weight range 500 to 10,000 g / mol, preferably from 800 up to 5000 g / mol. Monohydric polyether alcohols are e.g. B. by Alkoxylation of monovalent starter molecules, such as. B. methanol, Ethanol or n-butanol available, being used as an alkoxylating agent Ethylene oxide or mixtures of ethylene oxide with other alkylene oxides the, especially propylene oxide, are used. In the case of ver However, the use of alkylene oxide mixtures preferably contains them wise at least 40, particularly preferably at least 65 mol% Ethylene oxide.

Monomers VII can thus counteract in the polyurethanes possibly present in terminally arranged polyether chains Polyethylene oxide segments to be installed in addition to the polyurethane influence the hydrophilic character of the ionic groups and ensure or improve dispersibility in water.

The compounds of the type mentioned are preferred, according to uses them in such quantities that they from 0 to 10, preferably from 0 to 5% by weight of polyethylene oxide units into the polyurethane.

Further examples of in the manufacture of the invention Compounds usable as monomers I to VII of polyurethane are z. B. High Polymers, Vol. XVI, "Polyurethanes, Chemistry and Technology "by Saunders-Frisch, Interscience Publishers, New York, London, Volume I, 1962, pages 32 to 42 and pages 44 to 54 and Volume II, pages 5 to 6 and 198 to 199.  

As monomers VIII, which, in contrast to the above monomers, contain ethylenically unsaturated groups, z. B. esters of acrylic or methacrylic acid with polyols, at least one OH group of the polyol remains unesterified. Hydroxyalkyl (meth) acrylates HO (CH ₂ ) _n OOC (R ¹ ) C = CH ₂ (n = 2 to 8; R ¹ = H, CH ₃ ) and their positional isomers, mono (meth) acrylic acid esters of polyether diols are particularly suitable , such as B. listed in the monomers II, trimethylolpropane mono- and di (meth) acrylate, pentaerythritol and tri (meth) acrylate) or reaction products of epoxy compounds with (meth) acrylic acid, such as z. B. are mentioned in US-A-357 221. The adducts of (meth) acrylic acid with bisglycidyl ether of diols such as, for. B. bisphenol A or butanediol.

Adducts of (meth) acrylic acid with epoxidized can also be used Diolefins such as B. 3,4-epoxycyclohexylmethyl-3 ', 4'-epoxycyclo hexane carboxylate.

By incorporating the monomers VIII, the poly urethane thermally or photochemically, optionally in the presence an initiator, subsequently, d. H. after applying the coating tion, to be hardened.

In general, the proportion of ethylenically unsaturated is Groups under 0.2 mol per 100 g of polyurethane.

Overall, the proportion of the structural components is preferably so chosen that the sum of the isocyanate-reactive hydro xyl groups and primary or secondary amino groups 0.9 to 1.2, particularly preferably 0.95 to 1.1 based on 1 isocyanate group is.

The production of the polyurethane dispersions according to the invention can according to the usual methods such. B. in the above led writings are described.

Preference is given to an inert, water-miscible solution medium, such as acetone, tetrahydrofuran, methyl ethyl ketone or N-methylpyrrolidone from the monomers I and II and optionally III, V, VI, VII and VIII, if VI contains no amino groups, the polyurethane or, if a further reaction with amino functional monomers IV or VI is intended to be a poly urethane prepolymer with terminal isocyanate groups posed.  

The reaction temperature is generally between 20 and 160, preferably between 50 and 100 ° C.

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

The polyurethane prepolymer obtained can, if appropriate, after (further) dilution with solvents of the type mentioned above, preferably with solvents with boiling points below 100 ° C, at a temperature between 20 and 80 ° C with amino functional Compounds of the monomers VI and optionally IV further reversed be set.

The transfer of potential salt groups, e.g. B. carboxyl groups, or tertiary amino groups, which via the monomers VI in the Polyurethane has been introduced into the corresponding ions is carried out by neutralization with bases or acids or by Quaternization of the tertiary amino groups before or during the Disperse the polyurethane in water.

After dispersion, the organic solvent, if its boiling point is below that of the water, distilled off become. Optionally used solvents with a higher boiling points can remain in the dispersion.

The content of the polyurethane in the dispersions can in particular between 5 and 70 percent by weight, preferably between 20 and 50 % By weight, based on the dispersions.

The dispersions can be assisted, e.g. B. Thickener, Thixotro piercing agents, oxidation and UV stabilizers, release agents, Fillers or pigments can be added.

Hydrophobic aids that can be difficult to homogenize to be distributed in the finished dispersion can also be distributed the method described in USP 4,306,998, the polyurethane or be added to the prepolymer before the dispersion.

The polyurethanes and aqueous polyurethane containers according to the invention Rittungen are advantageously suitable as a coating medium, if for technical or aesthetic reasons soft loading layers with reduced stickiness are desired. Yeah Suitable substrates are in particular leather, textiles, plastic or paper. Of course, other sub strate such as metal, wood or glass.  

The polyurethane dispersions to be used according to the invention can stand alone or in a mixture with others, in the same direction charged dispersions of homo- or copolymers of e.g. B. acrylic or methacrylic acid esters, styrene or butadiene can be used. They can be applied by spraying, pouring or knife coating.

Examples Preparation of the polyurethane dispersion Dispersion A (for comparison)

600 g (0.3 mol) of a polyester diol from adipic acid, neopentyl glycol and 1,6-hexanediol (OH number 56), 27 g (0.3 mol) butane diol-1,4, 0.2 g dibutyltin dilaurate and 50 g acetone mixed, at 50 ° 185 g (0.7 mol) of commercially available Diisocya natodicyclohexylmethane (Desmodur® W from Bayer) added and at 70 ° C stirred. The content of this diisocyanatodicyclohexylmethane The individual isomers were determined by capillary gas chromatography determined more precisely and amounted to:

After 360 min, the mixture was diluted with 800 g of acetone and at 50 ° C chilled. Then 42 g (0.1 mol) of a 40% solution of the Adduct of ethylenediamine added to sodium acrylate and after 10 min stirring with 1300 g of water dispersed within 60 min. The acetone was then distilled off in vacuo.

A finely divided dispersion with about 38% solids was obtained salary.

Dispersion B (according to the invention)

The procedure was as described under A.

As the diisocyanatodicyclohexylmethane, however, one in the following Refurbished Desmodur® W used .:

1000 g of commercial Desmodur W were at 24 ° C for 24 hours stored, whereby a crystalline sediment formed.  

500 g of the supernatant liquid were then poured off The rest is homogenized again by melting and for the inventor dispersion used according to the invention.

The isomer distribution of the remaining diisocyanatodicyclo Hexylmethane was determined by gas chromatography as follows:

19.2 wt% cis
30.5% by weight cis / trans
46.7% by weight trans / trans.

Application test

The two dispersions were applied in an analogous manner as a primer Binder for leather finishing tested.

For this, a mixture consisting of

100 g of a commercially available pigment preparation,
315 g of dispersion and
585 g water

applied to cowhide leather.

The total amount applied was 30 g / m ² . The application was carried out by spraying twice, the leather being dried at 80 ° C. after each spray application and then ironed on a hydraulic ironing press at 70 ° C. and 50 bar.

The test for kink elasticity according to IUD 20 (method of physi Kalische Lederprüfung of the International Union of Leather Chemi ker associations) showed comparable good results in both cases nits. In both cases, there were 50,000 kinks (dry leather) or 20,000 kinks (wet leather) none Damage.

There were clear differences in the processing: While the leather with dispersion A from the comparative example in Iron strongly adhered to the ironing board, the leather showed with the Dispersion B had little adhesion and was easy on the hanger to release plate.

The handy properties are also different: the leather with dispersion A has a strong blocking, sticky handle, while the leather with dispersion B is a non-sticky, smooth surface.

Claims (5)

1. Polyurethane, composed of polyisocyanates and compounds reactive toward polyisocyanates with at least one hydroxyl group and optionally compounds with at least one primary or secondary amino group, characterized in that at least 40 mol% of the polyisocyanates are diisocyanatodicyclohexylmethane and the part of the trans / trans isomer of diisocyanatodicyclohexyl methane in the total amount of diisocyanatodicyclohexyl methane is at least 30% by weight. 2. Aqueous dispersion containing 5 to 70 wt .-% of the poly urethane according to claim 1. 3. Use of the aqueous dispersion according to claim 2 as Coating agent. 4. Use of the aqueous dispersion according to claim 2 as Coatings for textiles. 5. Use of the aqueous dispersion according to claim 2 as Coatings for leather.