MXPA96003158A - Method for waterproofing cu - Google Patents

Abstract

The present invention relates to a method for waterproofing tanned leather, by treating this leather with a composition comprising 0.5 to 20 weight percent solids, based on the weight of the leather, of an aqueous dispersion of oil. silicone emulsified with a water-insoluble amphiphilic copolymer, this copolymer is formed from 50 weight percent to 90 weight percent, based on the weight of the copolymer, of at least one hydrophobic, ethylenically unsaturated monomer, selected from the monomers which consist of the hydrophobic alkyl (meth) acrylate, primary alkenes, vinyl esters of alkyl carboxylic acids, vinyl alkyl ethers, dialkyl esters, alkyl esters-N-alkylamides, di-N-alkylamides, semi-esters of alkyl or semi-N-alkylamides of unsaturated dicarboxylic acids, and from 10 weight percent to 50 weight percent, based on the weight of the copolymer, of at least one hydrophilic comonomer, acid or basic, ethylenically unsaturated, water soluble, copolymerizable, where this copolymer has a weight average molecular weight of 2000 to 100.00 and in which the ratio of the silicone oil to the amphiphilic copolymer, by weight, is from 1: 5 to 8

Description

METHOD FOR WATERPROOFING LEATHER This invention relates to a method for waterproofing leather. The invention also relates to a composition suitable for use in waterproofing leather. More particularly, this invention relates to a method for waterproofing tanned leather, by treating it with an aqueous dispersion of a silicone oil emulsified with an amphiphilic copolymer. insoluble in water. The present invention is involved with the final wet leather processes, which take place after the tanning has been completed, usually the "chrome tanning". The method of this invention is practiced before, during or after leather retannage, in order to provide an increased waterproofing, relative to that provided by the same amount of a single amphiphilic polymer and, especially, increased waterproofing with similar firmness. to that obtained by treating the leather with the amphiphilic copolymer alone or in conjunction with waterproofing liquor liquors. U.S. Patent No. 4,701,269 discloses a process for waterproofing leather and skins with a silicone oil and a N- (C9-C2o) -amino acid salt as a non-polymeric emulsifier for the silicone oil, which is carried carried out in the aqueous phase, during or after retanning.

U.A. Patent No. 5,316,860 discloses a method for obtaining a water-resistant leather by treating the tanned leather with an aqueous dispersion of a water-insoluble, dispersed amphiphilic copolymer. The problem facing the inventors is the provision of a method for waterproofing the leather, using an aqueous dispersion of a silicone oil, emulsified with a water-insoluble amphiphilic copolymer. In a first aspect of the present invention, a method is provided for waterproofing the tanned leather, treating this leather with a composition comprising 0.5 to 20 weight percent solids, based on the weight of the leather, of an aqueous dispersion of a silicone oil emulsified with a water-insoluble amphiphilic copolymer, this copolymer is formed from 50 to 90 weight percent, based on the weight of the copolymer, of at least one hydrophobic, ethylenically unsaturated monomer, selected from the monomers which consist of the hydrophobic alkyl (meth) acrylates; primary alkenes; vinyl esters of alkyl carboxylic acids; vinyl alkyl ethers; dialkyl esters, alkyl esters-N-alkylamides, di-N-alkyl-amides, semi-alkyl esters or semi-N-alkylamides of unsaturated dicarboxylic acids; and from 10 to 50 weight percent, based on the weight of the copolymer, of at least one hydrophilic, acidic or basic, ethylenically unsaturated comonomer, soluble in water, copolymerizable; wherein the copolymer has a weight average molecular weight of 2000 to 100,000; and wherein the ratio of the silicone oil to the amphiphilic copolymer, by weight, is from 1: 5 to 8: 1. In a second aspect of the present invention, an aqueous composition is supplied for use in waterproofing leather. This invention relates to the use of an aqueous dispersion of silicone oil, dispersed with a selected amphiphilic copolymer, as a treatment for waterproofing the leather. The silicone oil is dispersed in an aqueous medium, this "aqueous medium" is defined herein as that which contains more than 50% water. The aqueous dispersion of the silicone oil of this invention is substantially free of non-polymeric surfactants and contains lower concentrations of the organic solvent than the silicone oil dissolved in a water-miscible solvent, as practiced in industry, or, when the copolymers in the amphiphilic solution dissolved in at least one water-miscible solvent are used alone, to achieve the same degree of waterproofing. "Silicone oils", as used herein, refer to polysiloxanes, substituted polysiloxanes, and their mixtures. Polysiloxanes are suitable in which the residual valences of silicon are met by hydrocarbon radicals, such as, for example, methyl, ethyl, propyl and phenyl or by functionalized hydrocarbon radicals, such as, for example, amino functional radicals. , thiol or carboxy. Silicone oils having a viscosity of 25 to 1000 cSt are preferred. Commercial silicone oils, identified as dimethylpolysiloxanes and silicone oils ("MQ" resins) formed by combining mono- and tetra-functional units of SiO, dissolved in dimethylpolysiloxanes are preferred. The amphiphilic copolymer must contain at least one hydrophobic group and at least one hydrophilic group. The copolymer is formed from 10 percent by weight to 50 percent by weight of at least one hydrophilic monomer and from 50 percent by weight to 90 percent by weight of at least one hydrophobic comonomer (all percentages by weight are based on the weight of the amphiphilic copolymer). It is preferred that the copolymer be formed from 15 to 45 weight percent of at least one hydrophilic monomer and from 55 to 85 weight percent of at least one hydrophobic comonomer, and even more preferred, this copolymer is formed from 20 to 40 percent by weight of at least one hydrophilic monomer and 60 to 80 weight percent of at least one hydrophobic comonomer. The hydrophilic monomer used to prepare the amphiphilic copolymer is at least one monomer selected from monomers, acids or basic, ethylenically unsaturated, preferably monoethylenically unsaturated, water soluble, or mixtures thereof. Examples of suitable hydrophilic monomers include acrylic acid, methacrylic acid, itaconic acid, fumaric acid, maleic acid; and the anhydrides of such acids; (meth) acrylates substituted with acid, such as, for example, phosphoethyl methacrylate and sulfoethyl methacrylate; (meth) acrylamides substituted with acid, such as, for example, 2-acrylamido-2-methylpropylsulfonic acid; and (meth) acrylates and base-substituted (meth) acrylamides, such as, for example, amine-substituted methacrylates, including dimethylaminoethyl methacrylate, tertiary butyl methacrylate-aminoethyl and dimethylaminopropyl methacrylamide, and the like. Preferred hydrophilic, water-soluble monomers used to prepare the amphiphilic copolymer are acrylic acid and methacrylic acid.

The selection of the hydrophilic monomer and its level is such as to enable the amphiphilic copolymer to function as a dispersant for the silicone oil in the continuous phase, such as, for example, in water, and to enable the aqueous dispersion of the silicone oil be prepared with a high solids content, such as, for example, 50% solids, with a viscosity that can be handled or cut, without adversely affecting the ability of the dispersion to penetrate the leather. The hydrophobic comonomers used to prepare the amphiphilic copolymer include at least one monomer selected from the hydrophobic alkyl (meth) acrylates; primary alkenes; vinyl esters of alkyl carboxylic acids; vinyl alkyl ethers; dialkyl esters, alkyl esters-N-alkylamides, di-N-alkylamides, semi-alkyl esters or semi-N-alkylamides of unsaturated dicarboxylic acids, and mixtures thereof. Suitable hydrophobic monomers include the C4 to C22 alkyl acrylates; C4 to C22 alkyl methacrylates / C4 to C24 alkenes; vinyl esters of C4 to C22 alkyl carboxylic acids; vinyl-C4 to C22 alkyl ethers and C4 to C22 dialkyl esters and C4 to C22 alkyl-N-alkyl (c4 to c22) -amides, di-N-alkyl (C to c22) -acids, semil-alkyl esters (C4 to C22) -esters or semi-N-alkyl (C4 to C22) -amides of unsaturated dicarboxylic acids. The preferred hydrophobic monomers that have been found provide the amphiphilic copolymer with the best performance characteristics are the C4 to C22 alkyl (meth) acrylates and mixtures thereof. The use of the term "(met)" followed by another term, such as acrylate or acrylamide, as used throughout the description, refers to both acrylates or acrylamides as well as methacrylates and methacrylamides, respectively. Minor amounts of other copolymerizable, ethylenically unsaturated hydrophobic monomers, with levels less than 50 weight percent of the concentration of hydrophobic comonomers, may be used in combination with a predominant amount (greater than 50 weight percent) of at least one of the hydrophobic comonomers listed above. These other hydrophobic comonomers have been found to be useful as diluents for other hydrophobic comonomers, without adversely affecting the retannage / fat liquor properties, obtained in the treatment with the treatment composition. Examples of such useful, copolymerizable, hydrophobic diluent comonomers include styrene, methylstyrenes, vinyl acetate (meth) acrylonitrile, N-alkyl (meth) acrylamides, and olefins.

The amphiphilic copolymer can be prepared by the polymerization of the hydrophilic and hydrophobic monomers by any conventional polymerization technique, such as, for example, solution polymerization, emulsion polymerization and volumetric fusion polymerization. Polymerization of amphiphilic copolymers, using conventional emulsion polymerization, is taught in U.S. Patent No. 5,348,807, using a free radical initiator, soluble in water, at a concentration of 0.1 to 3 weight percent, based on the total weight of the monomer. This polymerization is preferably carried out at a temperature of 40 to 100 ° C, preferably 50 to 70 ° C, using a chain transfer agent, such as, for example, a mercaptan, to control the molecular weight. Polymerization of amphiphilic copolymers with the use of solution polymerization in a water-miscible solvent is taught in U.S. Patent No. 5,316,860, which employs a water-insoluble, free-radical initiator, such as, for example, for example, the per-ester and azo compounds, at a concentration of 0.2 to 5 weight percent, based on the total weight of the monomer. The polymerization is preferably carried out at a temperature of 60 to 150 ° C, preferably 85 to 120 ° C, using a chain transfer agent, such as, for example, a mercaptan, to control the molecular weight.

The weight average molecular weight of the amphiphilic copolymer useful in the method of the invention can be as low as 2000 to as high as 100,000, preferably less than 50,000. This weight average molecular weight is here that determined by gel permeation chromatography. The polymerization can be carried out by polymerizing all the monomers together or by the gradual addition of the monomers until the polymerization is essentially complete. Unreacted residual monomers can be incorporated into the polymer by the addition of a subsequent initiator by techniques well known in the art. The polymerization produces a concentration of the amphiphilic polymer solids from 20 to 75%. The amphiphilic copolymers exemplified in the illustrative examples presented hereinafter, were obtained according to the procedures described in Example 1 of the US patent, No. 5,316,860 for the copolymers in solution or in Example 1 of the US patent, No. 5,348,807, for the emulsion copolymers, varying the selection and proportion of the monomers and the relative amount of the chain transfer agent, to obtain polymers of different molecular weights.

The emulsification of the silicone oil with the selected amphiphilic copolymer is achieved by mixing this silicone oil and the amphiphilic copolymer, under low shear conditions, such as manually shaking in a closed container containing the ingredients. The mixture can be carried out in ingredients that have been heated; Typically the ingredients are heated in a hot water bath at a temperature of 602C. When the amphiphilic copolymers are semi-solid or waxy materials, it is preferred to heat the components to ensure adequate fluidity for effective dispersion. Optionally, miscible solvents in water, such as, for example, the butyl ether of ethylene glycol and the butyl ether of propylene glycol, can be incorporated to improve the fluidity; The absence of organic solvents is preferred due to the restrictions of solvent emissions. The addition of non-polymeric surfactants is not required to perform the emulsification of the silicone oil. "Emulsification" is defined here as the achievement of a uniform appearance, which is retained for more than 30 minutes, that is, a stratification does not occur during that time. Preferred are compositions that retain a uniform appearance, that is, remain dispersed, for 10 days or more. More preferred are compositions that retain a uniform appearance, ie remain dispersed, for 10 days, at 60 ° C., an accelerated test that simulates the stability of the dispersion for 1-2 years. The treatment method of the invention involves the contact of the leather with the treatment composition containing the aqueous dispersion of the silicone oil. The composition used to treat the leather contains 0.5 to 20 weight percent solids (amphiphilic copolymer silicone oil) in the aqueous dispersion, based on the weight of the leather, preferably in the range of 1 to 5 percent by weight. weight and more preferably in the range of 1 to 2 weight percent. The ratio of the silicone oil to the amphiphilic copolymer by weight is from 1: 5 to 8: 1. A ratio of the silicone oil to the amphiphilic copolymer, by weight, from 1: 3 to 4: 1 is preferred.

The treatment composition may contain retanning agents, fatty liquors, amphiphilic copolymers and other conventional adjuvants, in addition to the aqueous dispersion of the silicone oil. In the case that the additional amphiphilic copolymer is used, typically for economic reasons, the total amount of the amphiphilic resin is in the range of 0.5 to 20 weight percent solids, based on the weight of the leather, preferably from 2 to 20% by weight. 15 percent by weight solids, based on the weight of the leather.

Experimental Methods Master Flex: A test used to determine the degree of waterproofing of leather is the dynamic test of resistance to salt water. This test used a Maeser tester for water penetration, in accordance with ASTM D-2099-70. The number of bends required to cause the water to penetrate the leather was recorded. A value of Maeser flex greater than 15,000 is the minimum criterion established by the army of E. U. A., to waterproof the leather of military boots.

Percent of Water Admission: A second test used to determine the degree of waterproofing of the leather was a water intake test. A leather sample of 5.1 x 5.1 cm was weighed. Then it was placed in a 1-liter container, with 10 times its weight of water and rotated for 30 minutes. Then the leather was removed and placed between two rigid plates of the same size as this leather, each of which had a square of blotting paper disposed between the plate and the leather. A weight of 1 kilogram was placed on top of the set for 5 minutes. Then the weight was removed and the set was turned over and the weight was applied to the upper part of the inverted set for 5 more minutes. The leather was then removed from the set and weighed again. The percentage by weight of the water intake was reported, based on the dry weight of the leather in the duplicate samples. The water intake percentage of 30% or less is acceptable as a standard in the industry.

Softness: Softness was determined by the measurements of its constitution. The readings were made using a softness tester BLC ST300 Softness Tester (British Leather Confederation, Northampton, United Kingdom). Leather preparation procedure: The leather was prepared using the following procedure. Note that some of the steps have treatments that are specific to each Example that follows. Unless otherwise mentioned, all leathers were prepared using chrome-tan leather leathers of 1.58-1.74 kg / m2 (approximately 2-2.5 mm thick). The method is applicable to other types of hides and skins, such as substrates of animals tanned with minerals (chromium, aluminum, zirconium, titanium, magnesium), such as pig skins, sheep and the like. All weights are based on the weight of the untreated material (100% means a weight equal to the weight of the material in the drum). 1) The untreated material was washed with water, with the drum door open, for 15 minutes at a temperature of 40SC. 2) The drum then emptied. 3) The untreated material, in 200% of a flotation substance, was neutralized with 2% sodium acetate and a certain amount of sodium bicarbonate, specific for each Example. See each Example for the specific amount of sodium bicarbonate that is used. This neutralization step was done at a temperature of 402C for 2.5 hours. 4) The drum was then emptied and its temperature was raised to 50SC.

) The neutralized material was then washed with water, with the drum door open, for 15 minutes at 50 seconds. 6) The drum was emptied immediately. 7) The untreated material was then treated with a standard retannage and / or an amphiphilic copolymer. See each Example for the details of the specific treatment used in this step.

) The material then treated with 0.5% of the dye Pyrazol Orange Dye powder and the treatment was continued in the drum for 20 minutes at 50ac. 9) The material was then treated with a composition of the amphiphilic silicone / copolymer. See each Example for specific details. The product was previously dispersed in 50% of the flotation substance at a temperature of 50 ° C and the treatment of the drum was continued for 30 to 60 minutes.

) The material was then treated with 1.5% 88% formic acid in 300 grams of water. The formic acid solution was added in 3 aliquots spaced every 5 minutes. The treatment of the drum was continued for a total of 30 minutes. 11) The drum emptied. 12) The material was subjected to a water wash, with the drum door open, for 15 minutes at 35 seconds. 13) A sample strip of the neck section of the material was then subjected to stresses. 14) To the material was added 5% Wayne Tan 150 (Chrome Tanning Agent) in 200% of the flotation substance.

The treatment of the drum was continued for 60 minutes at 358C. This stage is called the Remate stage.

) The drum was emptied and the flotation substance was collected for disposal purposes. 16) The material was washed with water, with the door open, for 15 minutes. 17) The drum then emptied. 18) The material was subjected to efforts during the night. It was fixed the next day (to squeeze water from it) and dried under vacuum at 70 seconds for 2 minutes. 19) The material was then hung in a vertical perforated frame to expel the air, during the night.

) The dried (layered) leather was stacked (mechanically smoothed) and placed at a constant temperature (22 AD) and in a damp room (60% RH) for several days, before testing for its impermeability.

The following examples are presented to illustrate the invention and the results obtained by the testing procedures.

EXAMPLE 1. Effect of the level of the aqueous dispersion of the silicone oil in the waterproofing.

Preparation of the Sample 1. An aqueous dispersion of dimethylpolysiloxane, Dow Corning 200® 100 cSt silicone oil (Dow Corning Corp.) was prepared using an amphiphilic copolymer emulsifier, composed of cetyl-icosyl methacrylate / acrylic acid, which it has a molecular weight MW = 8500, with a ratio of the silicone oil: amphiphilic copolymer = 2: 1 and was used to treat the untreated material at three different levels. In addition all samples of the untreated material were treated simultaneously with 12% of another amphiphilic polymer. The exceptions for the leather preparation procedure were here: Stage 3. 1.75% sodium bicarbonate was used. Step 7. 4.3% solids of the amphiphilic copolymer which was previously dispersed in 100% of the flotation substance were applied. It was treated in the drum for 60 minutes at 502C. Step 9: The emulsion of the silicone / amphiphilic copolymer was dispersed in 50% of the flotation substance. It was treated in the drum for 60 minutes.

Table l.l - Waterproofing leather with various levels of the aqueous dispersion of silicone oil Samples 1.1 and 1.2 of this invention exhibited a good waterproofing in relation to Comparative Example A, in which the treatment level was below 0.5% based on the weight of the leather.

EXAMPLE 2 Effect of the level of the aqueous dispersion of the silicone oil in the waterproofing. Preparation of the Sample 2. An aqueous dispersion of silicone oil (mQ resin) formed by combining the mono- and tetra-functional units of the SiO, dissolved in dimethylpolysiloxanes (Wacker, Chemie; VP 1481), was prepared using a copolymer emulsifier. amphiphilic, composed of 70% cetyl-icosyl methacrylate / 30% acrylic acid, having a molecular weight, MW = 8500, with a ratio of silicone oil: amphiphilic copolymer = 2: 1 and was used to treat the material without dealing with two different levels. In addition all samples of the untreated material were treated simultaneously with 12% of another amphiphilic polymer.

The exceptions to the leather preparation procedure here were: Stage 3. 1.75% sodium bicarbonate was used. Step 7. 4.3% solids of the amphiphilic copolymer were applied, which were previously dispersed in 100% of the flotation substance. The treatment in the drum was 60 minutes at 502C. Step 9. Dispersed in the silicone emulsion / amphiphilic copolymer in 50% of the flotation substance. It was treated in the drum for 30 minutes.

Table 2.1 - Leather softening with various levels of aqueous dispersion of silicone oil Sample 2-1 of this invention exhibited good waterproofing relative to Comparative Sample B, in which the treatment level was below 0.5% by weight based on the weight of the leather.

EXAMPLE 3. The waterproofing of the leather with an aqueous dispersion of a functional polyorganosiloxane.

Sample Preparation 3. An aqueous dispersion of an amino functional polyorganosiloxane, with MW = about 15,999 (Wacker Silicones Corp., Silicone Fluid 1424M) was prepared using an amphiphilic copolymer emulsifier, composed of 70% cetyl-icosyl methacrylate / 30% acrylic acid, which has a MW average molecular weight = 8500, with a ratio of silico-na / amphiphilic copolymer = 1: 3 and was used to treat the untreated material. The exceptions in the leather preparation procedure here were: Stage 3. 2.0% sodium bicarbonate was used.

Step 7. An amphiphilic copolymer with 2.2% solids was applied, which was previously dispersed in 100% of the flotation substance. It was treated in the drum for 60 minutes at 502C. Stage . The silicone / amphiphilic copolymer emulsion was dispersed in 100% of the flotation substance. It was treated in the drum for 60 minutes. Table 3.1 - Performance of Leather EXAMPLE 4. Leather waterproofing with an aqueous dispersion of silicone oils of various molecular weights (various viscosities).

Preparation of the Samples 4. An aqueous dispersion of silicone oil CD 200/100 CSt (Sample 4.1) or CD 200/500 CSt (Sample 4.2) (Dow Corning Corp.) was prepared using an amphiphilic emulsion emulsion copolymer, compound 80% of 2-ethylhexyl acrylate / 20% acrylic acid, having an average molecular weight, MW = 15,000, with a ratio of the silicone oil: amphiphilic copolymer = 1: 3, and was used to treat the material without try. The exceptions in the leather preparation procedure here were: Stage 3. 1.75% sodium bicarbonate was used.

Step 7. 0.84% solids was applied from a commercial polyacrylic acid retanning agent, which was dissolved in 100% of the flotation substance. It was treated in the drum for 30 minutes at 50SC. Step 9. The silicone / amphiphilic copolymer emulsion was dispersed in 100% of the flotation substance. It was treated in the drum for 60 minutes.

Table 4.1 Treated Leather Test Samples 4.1 and 4.2 of this invention provided a good waterproofing to the leather. EXAMPLE 5. Impermeabilization of the leather with an aqueous dispersion of silicone oil of various molecular weights (various viscosities) Preparation of the Sample 5. An aqueous dispersion of silicone oil from Dow Corning 200® / 500 CSt (Sample 5.1) or CD 200 100 CSt (Sample 5.2) (Dow Corning Corp.) was prepared using an amphiphilic copolymer emulsifier, composed of 70% cetyl-icosyl methacrylate / 30% acrylic acid, having a molecular weight MW = 8500, with a ratio of the silicone oil: amphiphilic copolymer = 4: 1, and was used to treat the untreated material. Comparative Sample C was prepared using the same amounts of all the ingredients, including the amphiphilic copolymer used to disperse the silicone oil, but without using the silicone oil in Samples 5.1 and 5.1. The exceptions in the leather preparation procedure here were: Stage 3. 1.75% sodium bicarbonate was used for 2 hours.

Step 7 0.84% solids was applied from a commercial polyacrylic acid retanning agent (LEUCKOTAN® 1084), which was dissolved in 100% of the flotation substance. It was treated in the drum for 30 minutes at 50 seconds. Next, 4.3% solids of the amphiphilic copolymer which was previously dispersed in 50% of the flotation substance was applied to the material. It was treated in the drum for 60 minutes at 50 seconds. Step 9. The silicone / amphiphilic copolymer product was dispersed in 100% of the flotation substance. It was treated in the drum for 60 minutes.

Table 5.1 Test of treated leather Samples 5.1 and 5.2 of this invention exhibited a waterproofing superior to that of Comparative Sample C in which the silicone oil was absent.

EXAMPLE 6. Impermeabilization of the leather with an aqueous dispersion of a polysiloxane. Sample Preparation 6. An aqueous dispersion of a polyorganosiloxane (Dow Corning 200® Fluid / 100 cSt) was prepared using an amphiphilic copolymer emulsifier DENSODRIN® BA, a product of BASF, which is believed, based on the analysis of the Applicants, is composed of a C2o ~ c24 alpha-olefin hydrophobic and maleic acid (molar ratio of 1: 1), which has an average weight MW = 20,000 (soluble components) in a ratio of silicone oil: amphiphilic copolymer = 2 : 1 and was used to treat the untreated material. A comparative sample was prepared in the same manner, without the silicone / amphiphilic copolymer emulsion. The exceptions to the leather preparation procedure here were: Stage 3. 1.75% sodium bicarbonate was used, for 2.5 hours.

Step 7. 0.84% solids was applied from a commercial polyacrylic acid retanning agent, which was dissolved in 150% of the flotation substance. It was treated in the drum for 30 minutes at 50 seconds. Next, 4% solids of the amphiphilic copolymer, which was previously dispersed in 100% of the flotation substance, was applied to the material. It was treated in the drum for 60 minutes at 502C. Stage 8. No dye was used.

Step 9. 2.4% silicone / amphiphilic copolymer was dispersed in 50% of the flotation substance. It was treated in the drum for 60 minutes.

Sample 6 of this invention provided a good waterproofing of the leather, without significant change in the softness of the leather.

Claims (10)

1. NOVELTY OF THE INVENTION Having described the present invention, it is considered as a novelty and, therefore, property is claimed as contained in the following: CLAIMS 1. A method for waterproofing tanned leather, by the treatment of this leather with a composition comprising from 0.5 to 20 weight percent solids, based on the weight of the leather, of an aqueous dispersion of silicone oil emulsified with a water-insoluble amphiphilic copolymer, this copolymer is formed from 50 weight percent to 90 weight. percent by weight, based on the weight of the copolymer, of at least one hydrophobic, ethylenically unsaturated monomer, selected from the monomers consisting of the hydrophobic alkyl (meth) acrylates; primary alkenes; vinyl esters of alkyl carboxylic acids; vinyl alkyl ethers; dialkyl esters, alkyl esters-N-alkylamides, di-N-alkylamides, alkyl half-esters or semi-N-alkylamides of unsaturated dicarboxylic acids; and from 10 weight percent to 50 weight percent, based on the weight of the copolymer, of at least one hydrophilic, acidic or basic comonomer, ethylenically unsaturated, water soluble, copolymerizable; wherein this copolymer has a weight average molecular weight of 2000 to 100.00 and in which the ratio of the silicone oil to the amphiphilic copolymer, by weight, is from 1: 5 to 8: 1. The method according to claim 1, wherein the hydrophobic monomer is selected from the group consisting of the alkyl (meth) acrylates with 2 to 22 carbon atoms, or mixtures thereof. 3. The method according to claim 1, wherein the hydrophobic comonomer further comprises less than 50 weight percent of one or more hydrophobic comonomers, selected from the group consisting of styrene, methylstyrenes, vinyl acetate, (meth) acrylonitrile, N-alkyl (meth) acrylamides, and olefins. 4. The method according to claim 1, wherein the hydrophobic monomer is selected from the group consisting of (meth) acrylic acids, and mixtures thereof. 5. The method according to claim 1, wherein the ratio of the silicone oil to the amphiphilic copolymer, by weight, is from 1: 3 to 4: 1. 6. An aqueous composition for use in the permeabilization of leather, which comprises an aqueous dispersion of a silicone oil emulsified with a water-insoluble amphiphilic copolymer, this copolymer is formed from 50 weight percent to 90 weight. percent by weight, based on the weight of the copolymer, of at least one hydrophobic, ethylenically unsaturated monomer, selected from the monomers consisting of the hydrophobic alkyl (meth) acrylates; primary alkanes; vinyl esters of alkyl carboxylic acids; vinyl alkyl ethers; dialkyl esters, alkyl esters-N-alkylamides, di-N-alkylamides, alkyl half-esters or semi-N-alkylamides of unsaturated dicarboxylic acids; and from 10 weight percent to 50 weight percent, based on the weight of the copolymer, of at least one hydrophilic, acidic or basic, ethylenically unsaturated, water soluble, copolymerizable comonomer, wherein the copolymer has a weight average molecular weight from 2000 to 100,000, and in which the ratio of the silicone oil to the amphiphilic copolymer, by weight, is from 1: 5 to 8: 1. 7. The composition according to claim 6, wherein the hydrophobic monomer is selected from the group consisting of the alkyl (meth) acrylates with 2 to 22 carbon atoms, and mixtures thereof. The composition according to claim 6, wherein the hydrophobic comonomer further comprises less than 50 weight percent of one or more hydrophobic comonomers, selected from the group consisting of styrene, ethyl-styrenes, vinyl acetate, (meth) acrylonitrile, N-alkyl (meth) acrylamides, and olefins. 9. The composition according to claim 6, wherein the hydrophilic monomer is selected from the group consisting of (meth) acrylic acid, and mixtures thereof. 10. The composition according to claim 6, wherein the ratio of the silicone oil to the amphiphilic copolymer, by weight, is from 1: 3 to 4: 1.