DE2448009A1 - LEATHER IMPREEGNATION WITH POLYISOCYANATE - Google Patents

Description

Bayer Aktiengesellschaft 2448009

Central area of patents, trademarks and licenses

Sf "b-RM ⁵ ^ Leverkusen, Bayerwerk

l ^ö OKI

Impregnation of leather with polyisocyanates

The present invention relates to the impregnation of Flat structures based on protein, in particular leather, with isocyanate prepolymers containing plasticizers.

The tanning of leather with isocyanate compounds or the subsequent treatment of tanned or pretanned leathers with such products has long been state of the art. So Z describes ₀ B. British Patent No. _0,692,450 the treatment of chrome-tanned leather with an aqueous dispersion of low molecular weight diisocyanates, for example hexamethylene diisocyanate, with emulsifiers such as isododecyl-phenyl-polyethylene glycol ether co-used ,, A similar method is the subject of German patent 853 438 _β The German patent specification 857 425 teaches the impregnation of leather with solutions or vapors of polyisocyanates in order to improve the wet strength. Similarly, according to German Patent 923, leather is made waterproof by impregnation with a solution of monoisocyanates which contain an alkyl chain with more than 6 carbon atoms. British patent 521 116 describes the finishing of fabrics such as leather, textiles, etc _e with reactive mixtures of polyisocyanates

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and alcohols or amines containing more than 6 carbon atoms to make the fabrics waterproof. Here, too, the application takes place from solution. According to German patent specification 868 721, the pretreatment of leather, textiles, etc. with low molecular weight diisocyanates such as hexamethylene diisocyanate, diphenylmethane diisocyanate or toluylene diisocyanate facilitates the subsequent painting _{o The} subject of German patent specification 889 349 is the refinement of loose-grain leathers by impregnating the grain side with a solution Mixture of alkyd resins containing hydroxyl groups and crosslinking agents such as polyisocyanates. Similarly, according to DAS 1 056 090, leather can be dyed and impregnated in a single step if dyes and, at the same time or afterwards, solutions of isocyanate-modified polyesters which still contain free hydroxyl groups, together with polyisocyanates and catalysts in an organic solvent, are applied to the leather "DAS 1 669 349 describes the impregnation of the grain side of unfinished leather with reaction products of polyether polyols and polyisocyanates containing free NCO groups. These NCO prepolymers are also applied from organic solvents, preferably toluene or xylene. Further processes for treating leather with isocyanate compounds can be found, for example, in German patents 556 058, 857 425 and 889 349 and in DOS 1,469,012.

In a presentation by Dr. K. Eitel in Das Leder, 1953, pp. 234-240, the known processes of isocyanate tanning are extensive shown.

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In practice, isocyanates could be used for leather tanning and impregnation have not yet been implemented. On the one hand, all known processes require solvents or Emulsifiers to prevent the isocyanate compound from penetrating into the To enable leather, especially in the case of the use of higher molecular weight reaction products of polyols and a Excess of polyisocyanates. This not only leads to ecological problems because of the greater or lesser degree of toxicity the solvents but also to the inefficiency of the process because of the high prices for solvents »In addition In addition, tanneries are usually not equipped to process systems containing solvents. on the other hand low molecular weight isocyanates, which could possibly be processed solvent-free, because of their known toxic properties also only use under complex safety precautions.

As mentioned, toxicologically harmless high molecular weight polyisocyanates have the disadvantage that they are high because of their high According to previous knowledge, viscosity can only be applied from solution. Surprisingly, it has now been found that the viscosity of such higher molecular weight isocyanate compounds is increased by the addition of 1 to 80% by weight, preferably 3 to 40, particularly preferably 5-30% by weight Softeners can be reduced to such an extent that they are free of solvents or emulsifiers to strengthen the grain and, if necessary, without any problems coloring impregnation or priming of leather and other flat structures based on protein such as Eollagenvlies can be used. The procedure leaves can also be used, for example, to color crust leather.

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Low-viscosity, low-volatile organic compounds are used as plasticizers when processing polyvinyl chloride Great importance ,, These plasticizers all have the disadvantage that they migrate after a while. The polymer becomes brittle Consequently. In the case of the higher molecular weight polyisocyanates to be used according to the invention, however, such migration phenomena occur in the viscosity-reducing compounds generally not, especially not when an organic compound is used as a plasticizer that is capable of being absorbed onto leather or collagen.

The present invention thus relates to a method for impregnating flat structures based on protein with one isocyanate group, optionally emulsified in water containing compound, which is characterized in that the isocyanate group-containing compound is solvent-free in a mixture of 1 to 80% by weight, based on the total impregnating agent, of a non-volatile, mixable with it, the viscosity-lowering, migration-resistant, liquid organic compound is used as a plasticizer.

For the purposes of the present invention, flat structures based on protein include, for example, processes known per se to understand tanned leather or collagen fleece.

The compounds containing isocyanate groups to be used according to the invention should be of low volatility for toxicological reasons. Systems are preferably used which contain less than 1% by weight, particularly preferably less than 0.7% by weight, of ^{volatile substances which can be stripped off in a vacuum of 12 Torr at 20 °} C. in one hour. The isocyanates intend to do so the addition of plasticizers

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a viscosity of more than 500 cp, preferably more than 1500 cp at 20 ^° C. Its molecular weight is preferably between 300 and 20,000, particularly preferably between 500 and 10,000.

Compounds containing isocyanate groups include both unmodified and, preferably, modified polyisocyanates and / or reaction products of polyisocyanates with compounds in question that have at least 2 compared to isocyanates have reactive hydrogen atoms. These include amino groups, thiol groups or carboxyl groups Compounds, preferably water, and high and / or low molecular weight polyhydroxy compounds are to be understood. Suitable high molecular weight polyhydroxy compounds are for Example at least 2, but preferably 2-4, hydroxyl-containing polyesters, polyethers, polythioethers, polyacetals, Polycarbonates and polyester amides with a molecular weight between 50 and 5000, preferably 800-3000, as they are for the production of homogeneous and cellular polyurethanes are known per se «,

The possible polyesters containing hydroxyl groups are, for example, reaction products of polyvalent, preferably dihydric and optionally additionally trihydric alcohols with polybasic, preferably dibasic, carboxylic acids. Instead of the free polycarboxylic acids, the corresponding polycarboxylic acid anhydrides or corresponding Polycarboxylic acid esters of lower alcohols or mixtures thereof can be used to produce the polyesters. the Polycarboxylic acids can be aliphatic, cycloaliphatic ^ be aromatic and / or heterocyclic in nature and optionally, e.g. by halogen atoms, substituted and / or

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be unsaturated. Examples include: succinic acid, Adipic acid, suberic acid, azelaic acid, sebacic acid, phthalic acid, isophthalic acid, trimellitic acid, phthalic anhydride, Tetrahydrophthalic anhydride, hexahydrophthalic anhydride, Tetrachlorophthalic anhydride, endomethylenetetrahydrophthalic anhydride, Glutaric anhydride, maleic acid, maleic anhydride, fumaric acid, dimers and trimeric fatty acids such as oleic acid, optionally mixed with monomeric fatty acids, dimethyl terephthalate and Terephthalic acid bis-glycol ester. As polyhydric alcohols e.g. ethylene glycol, propylene glycol (1,2) and - (1,3), butylene glycol (1,4) and - (2,3), hexanediol (1,6), octanediol (i, 8), Neopentyl glycol, cyclohexanedimethanol (1,4-bis-hydroxymethylcyclohexane), 2-methyl-1,3-propanediol,

Glycerine, trimethylolpropane, hejcanetriol- (1,2,6), butanetriol- (1,2,4), Trimethylolethane, pentaerythritol, quinite, mannitol and sorbitol, methyl glycoside, also diethylene glycol, Triethylene glycol, tetraethylene glycol, polyethylene glycol Dipropylene glycol, polypropylene glycols, dibutylene glycol and Polybutylene glycols in question. The polyesters can be proportionate have terminal carboxyl groups. Also polyesters from lactones, e.g. ε-caprolactone or hydroxycarboxylic acids, e.g. ω-Hydroxycaproic acid can be used.

Also those that come into question, at least two, usually two to eight, but preferably two to three, Polyethers containing hydroxyl groups are those of the type known per se and are, for example, by polymerizing Epoxides such as ethylene oxide, propylene oxide, butylene oxide, tetrahydrofuran, Styrene oxide or epichlorohydrin with itself, e.g. in the presence of BF ^, or by increasing it Epoxides, optionally in a mixture or in succession, on starting components with reactive hydrogen atoms such as Alcohols or amines, e.g. water, ethylene glycol, propylene glycol- (1,3) or - (1,2), trimethylolpropane, 4,4'-dihydroxydiphenylpropane, Aniline, ammonia, ethanolamine, ethylenediamine are produced. Sucrose polyethers, such as those found in the German interpretation documents 1 176 358 and 1 064 938

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are possible. With vinyl polymers modified polyethers, such as those obtained by polymerizing styrene and acrylonitrile in the presence of polyethers arise (American patents 3,383,351, 3,304,273, 3,523,093, 3,110,695, German patent I.I52.536), are also suitable, as are OH groups comprising polybutadienes.

Among the polythioethers are in particular the condensation products of thiodiglycol with themselves and / or with others Glycols, dicarboxylic acids, formaldehyde, aminocarboxylic acids or amino alcohols are listed. Depending on the co-components acts the products are polythio mixed ethers, polythio ether esters, Polythioether ester amides.

As polyacetals come e.g. those from glycols, such as diethylene glycol, Triethylene glycol, 4,4'-dioxethoxy-diphenyldimethylmethane, Hexanediol and formaldehyde preparable compounds in question. Also let through the polymerization of cyclic acetals According to the invention, suitable polyacetals can be prepared.

Polycarbonates containing hydroxyl groups are those of per se known type into consideration, e.g. by reacting diols such as propanediol- (1,3), butanediol- (1,4) and / or hexanediol- (1.6), diethylene glycol, triethylene glycol, tetraethylene glycol can be produced with diaryl carbonates, e.g. diphenyl carbonate or phosgene.

The polyesteramides and polyamides include, for example , the predominantly linear condensates obtained from polyvalent saturated and unsaturated carboxylic acids or their anhydrides and polyvalent saturated and unsaturated amino alcohols, diamines, polyamines and their mixtures.

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It is also possible to use polyhydroxy compounds already containing urethane or urea groups and, if appropriate, modified natural poly oils, such as castor oil, carbohydrates, starch. Addition products of alkylene oxides with phenol-formaldehyde resins or with urea-formaldehyde resins can also be used.

Further examples of higher molecular weight polyhydroxyl compounds are, for example, in High Polymers, Vol. XVI, "Polyurethanes, Chemistry and Technology", written by Saunders-Frisch, Interscience Publishers, New York, London, Volume I, 1962, pages 32-42 and pages 44- 54 and Volume II, 1964, pages 5-6 and 198-199, and in the Kunststoff-Handbuch, Volume VII, Vieweg-Höchtlen, Carl-Hanser-Verlag, Munich, 1966, for example on pages 45 to 71, are described.

As low molecular weight polyhydroxy compounds (molecular weight 18 to 500), in addition to water, there are, for example, those mentioned above as starting components for polyester production Connections into consideration.

Suitable polyisocyanates which are used as such or preferably in the form of their reaction products with water and / or the aforementioned polyhydroxyl compounds and / or polyamines in the process according to the invention can be of an aliphatic, cycloaliphatic, araliphatic, aromatic and heterocyclic nature. A detailed description of these polyisocyanates can be found in W. Siefgen in Justus Liebigs Annalen der Chemie, 562, pages 75 to 136. Examples include ethylene diisocyanate, 1,4-tetramethylene diisocyanate, 1,6-hexamethylene diisocyanate, 1,12- Dodecane diisocyanate, cyclobutane-1,3-diisocyanate, cyclohexane-1,3- and 1,4-diisocyanate and

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any mixtures of these isomers, 1-isocyanato-3 * 3,5-trimethyl-S-isocyanato-methyl-cyclohexane (DAS 1 202 785), 2,4- and 2,6-hexahydrotoluylene diisocyanate and any mixtures of these isomers, hexahydro-1,3 - and / or A , 4-phenylene diisocyanate, perhydro-2,4'- and / or ^^ '- diphenylmethane diisocyanate, 1,3- and 1,4-phenylene diisocyanate, 2,4- and 2, G- tolylene diisocyanate and mixtures of these isomers, diphenylmethane-2,4'- and / or -4,4'-diisocyanate, naphthylene-1,5-diisocyanate, triphenylmethane-4,4 ^1, 4 "-triisocyanate, polymethylene polyisocyanates PoIyphenyl as they are obtained by aniline-formaldehyde condensation and subsequent phosgenation and are described, for example, in British patents 874 430 and 848 671, perchlorinated aryl polyisocyanates, such as those described, for example, in German Auslegeschrift 1,157

Polyisocyanates containing carbodiimide groups, as described in German Patent 1 092 007, the diisocyanates described in US Pat. No. 3,492,330, polyisocyanates containing allophanet groups, according to British patent specification 994 890, the Belgian Patent specification 761 626 and the published Dutch patent application 7 102 524, containing isocyanurate groups

Polyisocyanates, such as are described in German Patents 1,022,789, 1222 Q67 and 1,027,394 and in German Offenlegungsschriften 1,929,034 and 2,004,048, for example, i polyisocyanates containing urethane groups as described for example in Belgian Patent 752,261 or in American patent 3,394,164, polyisocyanates containing acylated urea groups according to German patent 1,230,778, polyisocyanates containing biuret groups, such as those described, for example, in German patent 1 101 394, in British patent 889 050 and in French patent 7 017 514 to be discribed,

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those described e.g. in Belgian patent specification 723 640 polyisocyanates prepared by telomerization reactions, polyisocyanates containing ester groups, such as those described, for example, in British Patents 956,474 and 1,072,956, American Patent 3,567,763 and US Pat German Patent 1,231,688 and reaction products of the above-mentioned isocyanates with acetals according to German patent specification 1,072,385.

According to the invention, preference is given to those having free isocyanate groups Reaction products of hexamethylene diisocyanate, tolylene diisocyanate and 1-isocyanato-3-isocyanatomethyl-3,5,5-trimethylcyclohexane with the compounds containing active hydrogen atoms described above. These reaction products are preferably used in the inventive Process e.g. by distilling excess volatile monomeric diisocyanates in a thin-film evaporator withdrawn.

The non-volatile compounds containing isocyanate groups and which are preferably to be used according to the invention include e.g. the reaction products from 1 mole of trimethylolpropane and 3 moles of tolylene diisocyanate or 1 mole of water and 2 moles of tolylene diisocyanate or that of 1 mole of water and 3 moles Hexamethylene diisocyanate produced polyisocyanates containing biuret groups

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According to the invention in an amount of 1 to 80 wt _o -9 <>, preferably 3-40 _'o wt -%, particularly preferably 5-30 GeWo-%, based on the total impregnating agent, to be used concomitantly low volatility and migration-resistant, liquid organic compound acts as a viscosity-reducing plasticizer for the highly viscous polyisocyanate _u

Plasticizers suitable in accordance with the invention must be miscible with the compound containing isocyanate groups and essentially inert towards isocyanates, that is to say have no free hydroxyl or amino groups. They preferably have a viscosity of 5 to 20,000 cp, particularly preferably 10 to 1000 cp (at 20 ° C.) _; and a volatility of less than 10%, preferably less than 5 % (expressed by the weight loss after 72 hours at 90 ^° C. in a drying cabinet, for example a Brabender rapid water meter).

Plasticizers particularly suitable according to the invention are those organic compounds which are capable of being absorbed onto leather (so-called leather fatliquors); see z _o B "Stather," Gerbereichemie und Gerbereitechnologie ", Akademieverlag Berlin, 1969 , Chapter 21" Such compounds preferably have at least one of the groups -COOH, -0-SOpOH or -SO ^ H. Chlorinated paraffinic hydrocarbons also have a certain affinity for leather fibers. Compounds which have an excessively hydrophilic effect are generally less suitable, but some of them can also be used in order to control the hydrophilicity or hydrophobicity of the leather in a targeted manner.

The plasticizers preferred according to the invention also include phenol esters of long-chain sulfonic acids and phthalic acid esters _o Phosphoric acid esters, monocarboxylic acid esters, dibenzyl ethers and chlorinated aromatic hydrocarbons,

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as they are known per se as plasticizers from the plastics processing industry, according to the invention can be used if they have the physical properties listed above.

The following compounds may be mentioned as examples of plasticizers to be used according to the invention:

Mixtures of fatty acids and sulfonated fatty acids, such as those produced in the technical sulfonation of triglycerides, Claw oil, turquoise red oil, chlorinated paraffinic hydrocarbons, Dibutyl phthalate, the phenyl esters of lauryl phosphate, triethylhexyl phosphate, diphenyl esters of lauryl sulfonic acid, Palmitin sulfonic acid and stearyl sulfonic acid as well as chlorinated diphenyl »

As already mentioned, these are preferred according to the invention Plasticizers are used, which have a greasy effect on leather. Since the connections throughout the tanning or “impregnation process are present, their greasy ones come Properties come into their own. The electrolyte sensitivity of the frequently occurring in conventional tanning processes Fatliquor which, when using tanning agents with ionic groups, interferes with or prevents penetration into the leather, does not need to be taken into account in the method according to the invention to become.

The solvent-free mixture of 20-99% by weight of the compound containing isocyanate groups and 1-80% by weight of the plasticizer to be used as an impregnating agent according to the invention should have a viscosity of less than 15,000 cP, preferably less than 5000 cP, particularly preferred have less than 1500 cP (at 20 ^° C.) so that perfect, uniform penetration into the substrate is guaranteed.

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The impregnating agents according to the invention can by any method, for example by pouring, spraying, printing or Plush can be applied to the substrate «, It is also possible to use the mixture of plasticizer and polyisocyanate With the help of conventional emulsifiers or dispersants to be converted into aqueous emulsions and that to be impregnated To treat substrate with such aqueous liquors, preferably however, the process is carried out without the addition of water or emulsifiers.

If the leather is to be impregnated and colored at the same time, then the impregnating agents to be used according to the invention are used Dyes, for example organic or inorganic pigments, are added. However, it is also possible to use the isocyanate groups containing compound prior to impregnation with a small amount (preferably 1 to 20 mol%, based to isocyanate) of an organic dye which has isocyanate-reactive groups. on In this way, the dye is incorporated into the polyisocyanate and chemically bonded to the leather during the impregnation.

The impregnation is generally carried out at room temperature, for example with the aid of commercially available spray devices; however, casting or printing machines are even more suitable. The latter are particularly material-saving.

After the impregnation agent has absorbed into the leather, what generally takes 10 seconds to about an hour (longer soaking times are usually for economic reasons not useful) the leather can e.g. by treating it with aqueous polymers as binders, optionally ironing and subsequent application of finishes or lacquers in are known to be finally trimmed. this applies

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for both grain leather and sanded upper leather.

A particular advantage of the method according to the invention lies in that the application of further finishing layers does not depend on the storage time of the impregnated leather, as which is the case with known processes for impregnating leather. The inventive method is in particular also for suitable for the impregnation of sheepskin and pigskin. These types of leather often have a spongy structure and are therefore unsuitable for many uses. With the help of the method according to the invention it is possible to make this spongy Eliminate structure. The inventive method even makes it possible to impregnate grain leather so that it can easily be provided with thick, firmly adhering layers of lacquer.

The following examples explain the process according to the invention. Unless otherwise noted, figures are given as parts by weight or percentages by weight.

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example 1

Reduction of the viscosity of NCO prepolymers through addition of plasticizers.

A) A polypropylene glycol ether molecular weight of 2000 is dewatered at 13 Torr and 110 ⁰ C. The dewatered polyether is added to a 6-fold excess of l _o 6-hexane diisocyanate ,. After stirring for 2 hours at 100 C, the product is in a thin film evaporator of excess 1,6-hexane diisocyanate freed The product contains 0.3% of free diisocyanates thereafter It has a NGO content of 3.14% and a viscosity of 1,860 cp at 25 ⁰ C .

Dibutyl phthalate is used as a plasticizer.

Table 1 (cP) in scars- in ground-
leather fenes upper
leather 35 min Prepolymer 2100 > 60 min 35 min (Parts) 1450 > 60 min 30 min 100 Penetration speed
Plasticizer viscosity 980 40 min 25 min 90 (Parts) 620 40 min 10 min 80 0 380 38 min 12 min 70 10 280 28 min 3 min 60 20th 220 10 min 120 see 50 30th 100 8 min 7? lake 40 40 80 6 min 65 see 30th 50 30th 3 min 15 see 20th 60 _ 2 min 10 70 0 80 90 100

Penetration speed is the time it takes a drop of 0.5 ml to soak into the leather that its surface no longer shines.

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B) The polyisocyanate used is the commercially available reaction product of 1 mole of water and 3 moles of 1,6-hexane diisocyanate, which has been freed from free monomeric diisocyanate by thin layers. It has an NCO content of 21% by weight and a viscosity of more than 15,000 cP at 20 ^° C.

A commercially available alkyl sulfonic acid ester of the formula is used as the plasticizer

R - SO ₂ - 0 -

in which R stands for a mixture of alkyl groups with 10 to C atoms _o The plasticizer is a light yellow liquid with a density of 1.05, it has a viscosity of 100 cP at 20 ⁰ C and a molecular weight of 390 «,

Table 2 viscosity Prepolymer Plasticizers (cP) (Parts) (Parts) > 15,000 100 0 3,200 80 20th 1,700 60 40 1,020 50 50 650 40 60 400 20th 80 100 0 100

In a 2 _O experiment, dibutyl phthalate is used as the plasticizer.

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Table 3 viscosity Prepolymer Plasticizers (cP) (Parts) (Parts) > 15,000 100 0 2 ο 600 80 20th 850 60 40 420 50 50 230 40 60 90 20th 80 0 100

Example 2

50 parts of the NCO prepolymer from Example 1 A are with 50 parts of the alkyl sulfonic acid ester from Example 1B are added.

A sanded upper leather is divided into two parts. One part is plushed with the mixture produced. The other part is treated with the help of a spray gun. After the primer has dried, both leathers are finished with an emulsion varnish based on nitrocellulose. Very smooth, grain-resistant, soft, finished upper leathers with the following properties are obtained: The adhesive strength according to SaTRA (for the measurement method, see the publication in the Journal of the Society of Leather Trades ¹ Chemists, Vol. 41, page 22; Jan. 1957) is between 1,100 and 1,200 g.

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Tensometer test according to IUP 13 (published in "Das Leder", No. 12, pages 304-306; 196l): after a linear expansion of 25 % , an expansion between 10 and 14 % remains; the necessary pressure is on

between 10 and 11 kp / cm.

Another part of the primed leather was provided with a commercially available polyurethane lacquer finish. "The lacquered leathers obtained showed no damage in the flexometer after 000 creases." The adhesion of the lacquer film to the leather was very good. In the thermosetting test (published in “Leder- und Häutemarkt ¹¹ , Issue 3 of January 18, 1997 in the supplement“ Tannery Science and Practice ”) the leather showed no damage.

Example 3

A) Manufacture of the impregnation agent:

8000 g (8950 mmol OH) of a polyester of adipic acid, hexamethylene-l _e 6 and 2.2 Dimetiiyl-propanediol lo3 were for 40 minutes at 110 ⁰ C with 1.560 g (17,900 mmol NCO) of a mixture of 80 parts by weight 96 2.4 -and 20 parts by weight 96 2 _e 6-tolylene diisocyanate reacted in 5150 g of dioctyl phthalate ,, There was a plasticizer-containing NCO-prepolymer having 3.48% NCO, based on prepolymer (theroret NCO content of the impregnant 2.56 96. found: 2.096), and a viscosity of 1100 cP at 20 ° C.

B) Method according to the invention:

Various sanded upper leathers, grain leathers and split leathers were impregnated with the NCO prepolymers, with 40 to 120 g of product being applied per m «,

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After the impregnation, the leathers were finished with various customary finishing systems. First pigment dispersions were applied as top paints, then the leather was bound with aqueous polymer dispersions based on acrylate or butadiene and finally coated with commercially available nitrocellulose emulsion paints. The finished battered leather showed the following properties: The adhesive strength of the finished layer by Satra was in all cases more than 1 000 g per cm, usually about 1 500 grams per cm _β All leather survived 10,000 kinks in the Bally Flexometers without damage. The leathers were grain-resistant and very soft. In the case of some leathers, the water absorption and the water penetration were determined in the Bally penetrometer. At a degree of compression of 15 % , the leathers treated according to the invention had absorbed half as much water as non-impregnated leathers. The water penetrated only after a 10-20% longer time than with the non-impregnated leather

An analog impregnated split leather was used in accordance with BeIg. Patent specification 769 812 (DOS 2 034 536), Example 7 "Provided with a reactive polyurethane finish" A obtained very soft coated split leather, the coating of which adhered very firmly and 200,000 kinks protrudes in the Bally flexometer without damage

The plasticized prepolymer could do the same Success by means of

a) Spray gun with air

b) Airless spray gun

c) Type LZF casting machine from Bürkle in Freudenstadt (FRG)

d) Type C 03 printing machine from Dornbusch in Krefeld (FRG) or a machine to Dubois.

be applied. The most economical method has been to use a printing machine or a casting machine; the losses in product were with these methods

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least. Spraying on the prepolymer also yielded perfect results, the products penetrated the materials very well and showed an excellent impregnation effect .

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Claims (7)

Patent claims: 1. Process for the impregnation of flat structures based on protein with a, optionally emulsified in water, Compound containing isocyanate groups, characterized in that the compound containing isocyanate groups Connection solvent-free in a mixture with 1 - 80% by weight, based on the total impregnation agent, a non-volatile, viscosity-reducing, migration-resistant, liquid that can be mixed with it organic compound is used as a plasticizer. 2. The method according to claim 1, characterized in that the compounds containing isocyanate groups are used which ^{contain less than 1% by weight of volatile substances which can be stripped off in a vacuum of 12 Torr at 20 °} C. in one hour, a viscosity of more comprise than 500 cP at 2O ⁰ C and a molecular weight between 300 and 20,000. 3. The method according to claim 1 and 2, characterized in that that the compound containing isocyanate groups is a reaction product of a polyisocyanate and Water and / or high and / or low molecular weight polyols is used. 4. The method according to claim 1 to 3, characterized in that such organic compounds as plasticizers can be used that are able to mount on leather. 5. The method according to claim 1 to 4, characterized in that that the mixture of isocyanate group-containing compound and plasticizer is colored before use. Le A 15 850 - 21 - 609817/0989 6. The method according to claim 5> characterized in that the compound containing isocyanate groups before the impregnation with 1 to 20 ΜοΙ, -%, based on the Isocyanate, an organic dye which has isocyanate-reactive groups. 7. The method according to claim 1-6, characterized in that the impregnating agent with the aid of a pressure or Casting machine is applied » Le A 15 850 - 22 - \
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