EP0324345B1 - Method for water-proofing leather, furs and synthetic leathers - Google Patents

Description

The invention relates to a process for hydrophobizing leather, furs and leather substitutes with a carboxyl-containing polysiloxane, the carboxyl groups of which are present in neutralized form, in the aqueous phase in the absence of emulsifiers and without aftertreatment with mineral tanning agents.

Various processes for hydrophobizing are known for leather, furs and leather replacement materials. For example, processes in which high molecular weight, water-insoluble substances, such as paraffins, waxes, esters, polysiloxanes, natural and synthetic fatty substances or fatty acid condensation products, are converted into emulsion form with emulsifiers suitable for salt formation and incorporated into the leather in an aqueous medium. The emulsifiers used are then largely rendered ineffective by lowering the pH in the treatment liquor and subsequently treating the leather with mineral tannins, such as chromium III salts, aluminum salts or zirconium salts. This means a considerable additional expenditure of time, since the entire leather cross section must be penetrated by the fixing agent. In addition, undesirable residual amounts of the metal salts used occur in the waste water. It is also difficult in practice to precisely adjust color tones because the strongly cationic effect of the metal salts and their inherent color can lead to color changes.

Polysiloxanes, fluorocarbon resins, aluminum soaps or water-in-oil emulsifiers suitable for hydrophobicization are also suitable for the finishing stage of the hydrophobization of leather, furs and leather substitutes, which are always present in organic solvents, e.g. Petrol or chlorinated hydrocarbons, dissolved, are used. Disadvantages when working with these solvents are the harmful and environmentally harmful effects and the fire hazard when using gasoline. Incidentally, the leather treatment with products dissolved in organic solvents means a considerable amount of additional work.

In DE-OS 3 529 869 (EP-A- 0 213 480) a method for hydrophobicizing leather and furs with a silicone oil in the presence of a salt of an N- (C₉bisC₂₀-acyl) amino acid, for example oleic acid sarcoside or medialanic acid, as Emulsifier described in which the aqueous emulsion of a silicone oil in the presence of the above emulsifiers in an aqueous liquor lets the leather or fur to be treated act at pH values of 4.5 to 8.0, then sets them to a pH value of 3.0 to 5.0 and after-treatment with a 2-, 3- to maintain favorable results or 4-valent metal salt must be carried out. The silicone oils which can be used here are the commercially available silicone oils with viscosities of 30 to 1,000 mPas, preferably 80 to 500 mPas. Such silicone oils can be readily used by those skilled in the art, for example Römpps Chemie-Lexikon, 7th edition, Stuttgart, 1975, pp. 3223ff, or Ullmanns Enzyklopadie der techn. Chemie, 4th ed., 1982, volume 21, pp. 512ff. The viscosities given are a practical measure of the molecular weights, which can often only be determined with great effort.

Preferred silicone oils in this process are dimethylpolysiloxanes with a viscosity of 80 to 110 mPas, phenylmethyl polysiloxanes with a viscosity of 85 to 120 mPas, dimethylpolysiloxanes with amino groups as reactive groups, characterized by an amine number of about 0.8 to 1.1. 0 and a viscosity of 30 to 50 mPa · s, and dimethylpolysiloxanes with carboxyl groups as reactive groups, on average with 2 to 10 carboxyl groups per molecule. Dimethylpolysiloxanes, the methyl groups of which are partially replaced by mercaptopropyl or aminopropyl groups as reactive groups, are very particularly preferred.

The object of the present invention is to provide a process for waterproofing leather, furs and leather substitutes which can be carried out in an aqueous liquor and which involves the use of emulsifiers and aftertreatment with metal salts, in particular chromium III salts , can be dispensed with.

The solution to the problem consists in a process for hydrophobizing with a carboxyl-containing polysiloxane, the carboxyl groups of which are present in neutralized form. With the help of these special polysiloxanes, the salts of which have self-emulsifying properties in water or can be soluble, at least equivalent results to the prior art are achieved without the presence of emulsifiers and without aftertreatment with metal salts, since these can readily be incorporated into the leather in an unforeseeable manner have it incorporated. Organic solvents, especially hydrocarbons, can be dispensed with.

The method of the invention is characterized by its simple, time-saving, safe and environmentally friendly implementation. Usual auxiliaries for the preparation of the emulsions or solutions are not necessary. The invention relates to a process for the hydrophobization of leather, furs and leather substitutes with carboxyl-containing polysiloxane, which is characterized in that the carboxyl groups of the polysiloxane are in neutralized form and in that the neutralized polysiloxane is present in an amount of 0.1 to 15% by weight. , preferably 0.2 to 10% by weight, based on the shaved weight of the leather or wet weight of the furs, in an aqueous liquor at a pH of 4.0 to 8.0, preferably of 5.0 to 6.0 the leather or furs to be treated can act before, during or after retanning and then adjusts to a pH of 3.0 to 5.0, preferably 3.5 to 4.5.

The carboxyl-containing polysiloxanes used in the process according to the invention are known per se to the person skilled in the art. Particularly suitable are polysiloxanes in which the remaining valences of silicon are saturated by hydrocarbon radicals, in particular methyl, but also ethyl, propyl or phenyl, and which have carboxylic acid or preferably carboxylic acid anhydride groups at their ends and / or in the side chains in their production via these hydrocarbon radicals Molecule built in included.

Dimethylpolysiloxanes and methyl-propyl-polysiloxanes which have terminal carboxylic anhydride groups are particularly preferred. They can be characterized by their anhydride numbers from 0.2 to 1.7, preferably from 0.4 to 0.8. The molecular weights of the polysiloxanes with acid anhydride groups are expediently described by the viscosity ranges from 100 to 500 mPa · s, preferably 150 to 220 mPa · s (determined in each case in an Ubbelohde viscometer at 25 ° C.). The length of the siloxane chain, ie the number of (SiO) _n units, can be specified with n = 10 to 120, preferably n = 20 to 40.

To neutralize existing carboxylic acid groups or to hydrolyze and neutralize existing acid anhydride groups, the polysiloxanes are expediently brought to a pH of 7 in aqueous solution with the appropriate amount of alkali (for example sodium or valium hydroxide), ammonia, a saturated organic amine, alkanolamine or an aminocarboxylic acid to 10, preferably 7.5 to 8.5. The carboxylic anhydride groups can also first be reacted with alcohols to give the half ester, the free carboxyl group is then neutralized.

The salts are the alkali metal salts, in particular sodium or potassium, the ammonium salts, the amine salts, in particular those of mopoline, and the alkanolamine salts, in particular those of mono-, di- or trialkanolamines having 2 to 6 carbon atoms in the alkanol radical, such as mono-, di- or triethanolamine, in Consider. Furthermore, aminocarboxylic acids with a total of 2 to 6 carbon atoms, such as sarcosine, can also be used to neutralize the carboxyl groups. When the polysiloxanes containing anhydride groups are reacted, in particular the polysiloxanes which contain a maleic anhydride or succinic anhydride group as the end group, with amines, the corresponding half-amides are formed. Amines which are preferably used are morpholine or sarcosine. The polysiloxanes containing carboxylic anhydride groups can also with alcohols, for example monohydric C₁ to C₈ alcohols, such as methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, n-hexanol, n-octonal, isooctanol or 2-ethylhexanol the corresponding half-ester groups. Polyhydric alcohols, such as glycol or glycerol, can also react with the carboxylic anhydride end groups of the polysiloxanes to give the corresponding half-esters.

The hydrolysis of the acid anhydride groups with the bases required for complete neutralization takes place without difficulty in water.

For practical use in water repellent treatment, aqueous emulsions with a concentration of 5 to 90, preferably 20 to 50% by weight, as can be seen from the examples, are expediently prepared and added to the treatment liquor. The aqueous emulsions obtained are surprisingly stable, so that additional auxiliaries need not be used.

Under certain circumstances, solvent-water mixtures with a lower alcohol, such as isopropanol / water, ethanol / water or methoxypropanol / water, are useful, for example if dry leather is to be subsequently hydrophobized.

The invention also relates to the use of polysiloxanes containing carboxyl groups, the carboxyl groups of which are present in the neutralized form given above, for the hydrophobization of leather, furs and leather substitutes in an aqueous liquor before, during or after retanning without the use of emulsifiers.

The actual hydrophobization according to the invention takes place before, during or after retanning with drumming in a suitable device in a conventional manner: ie with liquor lengths of 10 to 2000%, preferably 50 to 200%, based on the fold weight of the leather or the wet weight of the furs , in the case of furs relatively long liquor lengths come into consideration, at temperatures of 20 to 60 ° C., preferably 30 to 50 ° C., the pH values between 4.0 and 8.0, preferably 5.0 to 6, initially 0, lie. The times required are between 20 and 180 minutes, preferably 30 to 90 minutes. At the end of the hydrophobization, the usual fixation of the tannins, dyes and any other tanning aids used is to a pH of 3.0 to 5.0, preferably 3.5 to 4.5, in particular 3.5 to 3, 9 set. The pH is preferably adjusted by adding formic acid.

It is also mentioned that the hydrophobization process according to the invention can advantageously be combined with conventional hydrophobizing agents for leather and furs, as are known to the person skilled in the art, for example, on the basis of a paraffin or wax emulsion.

The hydrophobization according to the invention can also take place in several stages, partly before, during and after the actual retanning, as can be seen from the application examples b and c. Starting leather is expediently mineral-tanned leather. Vegetable tanning agents and synthetic tanning agents based on phenolic and / or naphthalenesulfonic acid-formaldehyde condensates, polymeric tanning agents based on, for example, acrylates or methacrylates, aldehyde tanning agents or resin tanning agents based on e.g. Melamine-urea or dicyandiamide-formaldehyde condensates are used. The usual acidic, substantive or basic aniline dyes come into consideration as dyes.

Examples

Parts are parts by weight, percentages relate to the weight, unless stated otherwise. The viscosities were measured with an Ubbelohde viscometer at 25 ° C.

A. Preparation of polysiloxane emulsions to be used according to the invention example 1

100 parts of a dimethylpolysiloxane with carboxylic acid anhydride groups, an anhydride number of 0.65 and a viscosity of 190 mPa · s are mixed with 17.5 parts of morpholine (100%) with stirring and 400 parts of water are slowly stirred in at 30 ° C. and then homogenized. The resulting finely divided, stable, approximately 20% emulsion has a pH of 8.5.

Example 2

100 parts of a diomethylpolysiloxane with carboxylic acid anhydride groups, an anhydride number of 0.45 and a viscosity of 208 mPa · s are mixed with 50 parts of water at 20 ° C. and 85 parts of 10% strength aqueous ammonia are added with stirring. A further 265 parts of water at 30 ° C. are then stirred in and the resulting emulsion is homogenized. The emulsion has a pH of 8.35.

Example 3

100 parts of a methyl propyl polysiloxane with carboxylic acid anhydride groups, an anhydride number of 0.75 and a viscosity of 172 mPa · s are slowly mixed with 205 parts of 10% aqueous diethanolamine with stirring. A further 195 parts of water at 30 ° C. are then stirred in and the resulting emulsion is then homogenized. The finished emulsion has a pH of 8.6.

Example 4

100 parts of a dimethylpolysiloxane with carboxylic anhydride groups, an anhydride number of 0.6 and a viscosity of 160 mPa · s are mixed with 50 parts of water at 20 ° C. and 60 parts of n-sodium hydroxide solution are slowly added with stirring. The mixture is then diluted with a further 290 parts of water at 30 ° C. with stirring and the resulting emulsion is homogenized with a pH of 8.5.

B. Examples of use

In the following application examples, milling takes place at temperatures of 40 ° C.

Application example a:

Chrome-tanned cowhides (wet blues) with a fold thickness of 2 mm, which have been deacidified to a pH of 5, are based on the fold weight with 5% by weight of commercially available mimosa extract and 5% by weight of a commercially available synthetic tanning agent based on phenolsulfonic acid-formaldehyde -Condensation and 1% by weight of a commercially available aniline dye in the tanning drum for 60 minutes.

The mixture is then drummed for 60 minutes with 10% by weight of the polysiloxane emulsion given in Example 1 and the working liquor is acidified to a pH of 3.8 using 100% formic acid.

The leathers are then washed, mechanically stretched and dried. The leather obtained is soft and supple, has a pleasant feel and excellent dynamic water resistance.

Testing in a Bally penetrometer (according to JUP10, Das Leder, 1961, page 38 ff.) Showed the following values at 15% compression:

Example of use b:

Chrome-tanned cowhide with a fold thickness of 1.8 mm and deacidified according to Example a are based on the fold weight, with 4% by weight of a commercially available hydrophobicizing agent based on a paraffin emulsion and 2.5% by weight of the polysiloxane emulsion described in Example 4 for 30 minutes Tumbled in the tanning barrel. The mixture is retanned with 8% by weight of a synthetic tanning agent based on phenolsulfonic acid-formaldehyde condensate and dyed with 1% by weight of aniline dye and then acidified to a pH of 4.0 with 100% of the treatment liquor.

A further 2.5% by weight of the polysiloxane emulsion specified in Example 4 are then rolled in for 30 minutes in a fresh bath with 100% liquor. While walking for another 20 minutes, the mixture is acidified to a pH of 3.9, rinsed and the leather is finished in a customary manner.

The test in the Bally penetrometer at 15% compression showed the following values:

Application example c:

Chromium-tanned cowhide leather with a fold thickness of 1.1 mm and deacidified to a pH of 6.5 are dyed through with 4% by weight of aniline dye and with 8% by weight, a commercially available hydrophobizing agent based on a paraffin emulsion and with 2.5% by weight of the polysiloxane emulsion described in Example 1 pre-greased for 45 minutes. The retanning is carried out using 2% by weight of an acrylic-based polymer tanning agent and 4% by weight of a synthetic tanning agent based on phenolsulfonic acid-formaldehyde condensate. The mixture is then acidified to a pH of 3.8 using a further 6% by weight of a commercially available hydrophobicizing agent based on a paraffin emulsion and 2.5% by weight of the polysiloxane emulsion specified in Example 1, and the leather is acidified to a practical level, as indicated in Example a, completed.

The test in the Bally penetrometer at 15% compression showed the following values:

Claims (2)

1. A process for hydrophobizing leather, a pelt or a leather substitute material with a carboxyl-containing polysiloxane without the use of an emulsifier, wherein the carboxyl groups on the polysiloxane are present in neutralized form and the neutralized polysiloxane is applied to the leather or pelt before, during or after retanning in an amount of from 0.1 to 15% by weight, based on the shaved weight of the leather or the wet weight of the pelt, in an aqueous liquor at a pH of 4.0 to 8.0, and the pH is then adjusted to from 3.0 to 5.0.

2. Use of a carboxyl-containing polysiloxane whose carboxyl groups are present in neutralized form without the use of an emulsifier for hydrophobizing leather, pelts and leather substitute materials in an aqueous liquor before, during or after retanning.