AT520764A1 - Process for the preparation of a leather substitute - Google Patents

Abstract

A method of making a leather substitute, comprising the steps of: treating wool in a mixture comprising calcium chloride, water, ethanol and a reducing agent and having a pH of between 6 to 8, wherein at least a portion of the keratin of the wool is dissolved; Regenerating the keratin by adding an excess of water; Forms of keratin into the desired shape.

Description

SUMMARY

A process for producing a leather substitute comprising the steps of: treating wool in a mixture comprising calcium chloride, water, ethanol and a reducing agent and having a pH of between 6 and 8, at least part of the keratin of the wool being dissolved; Regenerate the keratin by adding an excess of water; Form the keratin into the desired shape.

1/24

22168-AT

METHOD FOR PRODUCING A LEATHER REPLACEMENT

The invention relates to a method for producing a leather substitute and a leather substitute produced by this method.

Background of the Invention

Products made of leather or synthetic leather come in numerous areas such as as clothing or for interior use. While genuine leather is a natural product that has numerous excellent properties, there are ethical concerns associated with rearing and killing animals to produce leather. For synthetic leather, plastics such as PVC are used, which are also of concern for environmental reasons. The properties with regard to moisture absorption, wearing comfort or stability of such synthetic leather are not comparable to natural leather. Finally, there are reservations about wearing synthetic PVC-based synthetic leather.

There is therefore an increasing need for leather substitutes which, on the one hand, have properties comparable to real leather, but which are ethically harmless.

Brief description of the invention

The object of the present invention is therefore to provide a leather substitute which has properties comparable to real leather and is ethically harmless.

This problem is solved by a method for producing a leather substitute, comprising the steps:

Treatment of wool in a mixture which comprises a swelling agent and a reducing agent and has a pH of between 6 and 8, at least part of the keratin of the wool being dissolved. Regeneration of the keratin, preferably by adding an excess of water. Shaping the keratin into the desired shape.

The swelling agent is preferably a mixture of calcium chloride, water, ethanol.

When wool is treated with a mixture of swelling agents, in particular a mixture of calcium chloride, water and ethanol, swelling of the

2.24

Keratins from the wool. The addition of the reducing agent leads to the breaking of the intra- and intermolecular disulfide bonds between the -SH groups of the cysteine residues of keratin. The keratin is preferably regenerated by adding water, so that the dissolved keratin protein forms again as a solid. The keratin can be brought into the desired shape by appropriate shaping.

The molar mixture between calcium chloride: water: ethanol (CWE) is preferably between 1 (CaCl ₂ ): 5 to 7 (water): 1 to 3 (ethanol), preferably about 1: 6: 2.

An alternative mixture as a swelling agent includes LiBr and urea.

All reducing agents that can break disulfide bridges are suitable as reducing agents. For example, the reducing agent can have an -SH group. It is preferably mercaptoacetic acid or a salt thereof (thiol glycolate).

Before the regeneration, a filtration step can also be provided in order to separate insoluble substances.

On the one hand, there is the possibility of completely dissolving the keratin and then regenerating it.

In one embodiment variant, it is provided that only part of the wool is dissolved and that the undissolved part of the wool is integrated into the desired shape in the leather substitute during regeneration and shaping of the keratin.

The undissolved part of the wool can then form a matrix for the leather substitute. The matrix can be made by suitably arranging the fibers of the wool, e.g. by crossing the fibers to give appropriate stability.

Alternatively, a non-wool matrix can of course also be used (e.g. a fabric or the like). In this case, the non-wool matrix is worked into the composite.

3.24

The matrix, regardless of whether it is pure wool, a non-wool matrix or a mixture thereof, e.g. a fleece, a cloth, a fabric, a knitted fabric or a flat structure. For example, a fiber mixture can be present.

An oxidation step with or after regeneration is preferably provided. This serves to re-form the free -SH groups in the regenerated keratin -S-SDisulfide bridges. The oxidation can be carried out by atmospheric oxygen or by adding an oxidizing agent.

The invention also relates to a leather substitute obtainable by the aforementioned process. The invention also relates to a leather substitute comprising regenerated keratin from wool.

The leather substitute can have a matrix of wool, the matrix being embedded in the regenerated keratin.

Alternatively or in combination, the leather substitute may have a non-wool matrix which is embedded in the regenerated keratin.

Since the leather substitute is hard like natural leather after production, a plasticizer is preferably added to make the leather substitute supple.

The plasticizer can e.g. Glycerin and / or oils include.

Detailed description of the invention

About 80 million tons of textile fibers, e.g. Polyester, cotton, polyamide processed. Within this amount, wool fibers only hold a small part of a production volume with approx.1.16 million tons of wool (2015). The high moisture sorption capacity of wool has recently revived wool clothing. The diameter of the wool fibers, which also determines the value and application, varies from superfine merino wool (<16 μm) to coarse hair / coarse wool (> 25 μm). Since only a few applications for coarse wool are known and waste that cannot be processed also occurs during the processing of wool, a considerable part of this natural material cannot be processed.

4.24

The present invention now also enables the recycling of coarse wool and wool waste that could not otherwise be used.

It is known that wool is dissolved in an aqueous medium at a pH of 12 in the presence of thioglycolate as a reducing agent, and the precipitation can be initiated by adding acetic acid. The treatment of hair with alkaline reducing solutions, for example Ca (OH) ₂ , Ca (HS) _2, for removing hair from hides during leather production is also known.

However, the inventors have found here for the first time that the use of a synergistic mixture of CWE and a reducing agent such as thioglycolic acid (CWET) is suitable for dissolving wool keratin and allows the production of an all-keratin composite by regeneration and shaping. The dissolution of wool in the CWE system and thioglycolic acid was characterized as a function of pH, temperature and time. Regenerated keratin was characterized by FTIR spectroscopy and water sorption properties. The process of dissolution and regeneration was then used in combination with wool fibers to produce all-keratin composites, which were characterized by laser scanning microscopy, FTIR and in terms of mechanical properties, moisture absorption and water absorption.

Experimental part

Chemicals and reagents

The following chemicals were used: thioglycolic acid (> 98% wt, Merck Schuchhardt OHG, Hohenbrunn, Germany); CaCl2x2H ₂ 0 (> 99% by weight), bromothymol blue and ethanol (> 99.9% by weight, Merck Darmstadt, Germany), CaThioglykolat trihydrate (> 98% by weight) and ammonium thioglycolate (approx. 60% by weight). -% Sigma-Aldrich, Steinheim, Germany); NH ₃ ; (> 25% by weight), HCl (25% by weight, VWR International, Briare, France); Coomassie Blue G-250 (Fluka, Buchs, Switzerland). Wool fibers were used as pre-washed, untreated wool from Schoeller Textil (Hard, Austria).

Microscopy and FTIR spectroscopy

A light microscope (CX41, Olympus, Tokyo, Japan) and a 3D laser scanning confocal microscope (VK-X200 Keyence, Osaka, Japan) were used to monitor fibers, regenerates and composites.

24.5

Infrared spectra were recorded by means of attenuated total reflection (ATR) with an FTIR spectrometer (Bruker Vector 22 FTIR spectrometer, spectral range 4000 to 400 cm ^-1 ), which was equipped with a diamond crystal unit.

Potentiometric titration of the solvent (CWET)

To determine the redox potential as a function of the pH of the solutions, 100 ml of CWE solvent were prepared with the addition of thioglycolic acid (CWET). A color indicator (2 ml bromothymol blue, 0.1 g per 100 ml) and 4 ml thiogylcolic acid were added to a mixture of 37.3 g CaCl ₂ 2 H ₂ O, 27.4 g H ₂ O and 23.4 g ethanol. The pH and redox electrodes were immersed in the solution and the vessel sealed with plastic wrap. Titrations were carried out at 60 ^° C. by the direct addition of 0.25 ml portions of aqueous NH ₃ (25% by weight). The pH was determined using a potentiometer (Zeller MP 225, Hohenems, Austria).

The redox potential was measured using a Pt electrode and an Ag / AgCI, 3 M KCI reference electrode (Sen Tix ORP 3M KCl, WTW, Weilheim, Germany). A hexacyanoferrate redox buffer was prepared for calibration (0.528 g K ₄ [Fe (CN) ₆ ], 0.411 g K ₃ [Fe (CN) ₆ ], 0.180 g KH ₂ PO ₄ , 0.390 g Na ₂ HPO ₄ in 100 ml) ,

Stability of CWET

Stability of the solvent system in the presence of wool: 100 ml CWEThioglycolic acid solvent CWET (37.3 g CaCl ₂ -2H ₂ O, 27.4 g H ₂ O, 23.4 g ethanol, 2 ml color indicator (bromothymol blue solution, 0.1 g per 100 ml), 4 ml thiogylcolic acid) were heated to 40 ° C or 60 ° C. The pH was adjusted to pH 7 ± 0.3 by adding NH ₃ and 0.5 g of wool was added to the solvent. The pH and the redox potential were measured at regular intervals for a period of 90 min. At the end of the experiment, the solutions were filtered through a paper filter and the regeneration of the dissolved protein was initiated by adding 100 ml of deionized water. The insoluble material in the filter and the regenerate were collected, rinsed with deionized water and dried at 80 ° C. The mass of the insoluble matter and the regrind were then determined by weighing.

6.24

Solution capacity from CWET

First, an amount of 22 g of CWE solution was added to 9.31 g of CaCl ₂ 2H ₂ O, 6.85 g of H ₂ O, 5.84 g of ethanol, 0.5 ml of color indicator (bromothymol blue, 0.1 g per 100 ml) , then 1 ml of thiogylcolic acid and 1 ml of NH ₃ were added, and then the pH was adjusted to pH 6-7 by dropwise addition of NH ₃ . The dissolution tests were carried out with 0.2 to 0.8 g wool per 10 g solvent at 60 ° C. overnight.

In a similar approach, the effect of dissolution time was examined by treating 0.5 g wool in 20 g CWET at pH 7. The treatment was carried out at 60 ° C for 1 to 6 hours and overnight. Insoluble parts were then removed by filtration through a PES screen (open width approx. 0.6 mm) and precipitated in 100 ml with water. The regenerate was then oven dried at 80 ° C for 1 h.

Determination of the protein content in solution

The soluble protein was determined by photometry using Coomassie Blue G-250 staining. The Coomassie Blue G-250 reagent solution was prepared by dissolving 100 mg of dye in 50 ml of ethanol (95% by weight). After adding 100 ml of H3PO4 (85 w / v%), the solution was filtered through a Whatman # 1 paper filter. To analyze the protein content remaining in solution, 0.5 g of a CWET wool blend was diluted with 50 ml of deionized water and filtered to remove precipitated keratin. A volume of 10 ml of filtrate was then diluted to 50 ml with water and 1 ml of this solution was mixed with 1 ml of the Coomassie reagent. The absorbance was measured at 595 nm. Freshly made CWET solution was used to make a blank.

A mass of 0.5 g wool was treated in 20 ml CWET and samples were taken at a defined time up to a maximum of 3 hours. Comparative experiments were carried out in which the addition of thiogylcolic acid was carried out after a pre-swelling in CWE for 3 hours and in a second batch the amount of thioglycolic acid in CWET was doubled. The results are given as the mean for a double determination.

Compound preparation

Wool fiber tape (2.0 to 4.3 g) was placed in a PE plastic bag and a volume of 5 to 20 ml of CWET was added. The sample bag was then placed in another bag to avoid the release of solvent

7/24 and to reduce the access of atmospheric oxygen. In order to support the penetration of the solvent into the wool fiber ribbon, the sample was squeezed three times with a laboratory sponge (0.5 m min ^-1 , 3 bar). The solvent / wool samples were compressed in a laboratory press (Serivtec, Polystat 200 T) for 10-20 minutes at 60 ° C and 10 bar. After pressing, the samples were removed from the bag and rinsed in excess water to coagulate dissolved keratin and remove the solvent. The wet samples were then fixed between absorbent soft paper and dried at room temperature overnight.

Moisture recovery and water retention value

To determine the moisture recovery of the samples, wool or composite materials were ground and stored in a normal climate (20 ° C, 65% rh), weighted (Wmoist), dried at 105 ° C for 4 h, cooled in a desiccator and weighed again (Wdry). The moisture content was calculated according to equation 1.

w _moist -w _dry * _10Q w dry

To determine the water retention value, 0.3 g of sample was placed in deionized water and shaken overnight. The samples were then filtered, and the capillary was removed by centrifugation for 10 min at 4000 g (5580 U min ^-1, wool fibers at 2000 g, 4000 U min ^-1) removed. The samples were then weighed ( _wet ) and dried at 105 ° C for 4 h. After cooling in the desiccator, the weight of the dried samples was determined (Wd _ry ). The water retention value was calculated according to equation 2.

w _wet -w _dry * ₁₀₀

WDRY

The tensile strength and the elongation at break were determined using a universal testing machine (Instron Universal Tester, Instron, Norwood, USA). Samples measuring 4 cm in length and 1 cm in width were produced from the composite materials. Tensile strength experiments were carried out at a speed of 1 cm min ^-1 , without pre-tensioning (tests were carried out at least as a double determination). The thickness of the samples was measured using a caliper.

8.24

Results and discussion

Stability of the CWET solvent

Potentiometric titration of the CWET was performed to investigate the interaction between the pH of the solutions and the reduction potential of thioglycolic acid and to analyze the sensitivity of the solvent to oxidation. As a result of the presence of disulfide group reducing conditions in the CWET system, reductive cleavage of the disulfide groups of keratin is initiated. In order to avoid alkaline conditions with possible hydrolysis of the keratin, a solution of bromothymol blue was added to the CWET solvent as a color indicator. The color of bromothymol blue changes from yellow to blue in the pH interval of 5.8-7.6, so green color was used to indicate an almost neutral solvent pH of 6-7.

The concept of pH is actually limited to rather dilute solutions, but the use of the glass electrode still allows an indication of the [H ⁺ ] activity and is therefore useful for the definition and analysis of the experimental conditions prevailing in the CWET system.

Fig. 1 shows the regeneration of keratin as a function of the dissolution time. Proportion of regenerated () keratin, (·) insoluble parts and (A) non-regenerable dissolved protein as a function of the treatment time in CWET.

2 shows FITR spectra of untreated wool, keratin regenerated from CWET after 1 h and 3 h of the dissolution treatment and corresponding insoluble parts after 20 h of treatment in CWET.

Fig. 3 shows WRV and MC in composite materials as a function of the mass of the CWET used per 1 g of wool.

4 shows FTIR-ATR spectra of keratin composites and wool in the wavelength range from 4000 cm-1 to 500 cm-1.

Figure 5 shows photomicrograph of untreated wool using a laser scanning microscope.

6 shows a microphotograph of a composite with glycerol as a plasticizer using a laser scanning microscope.

Fig. 7 shows a microphotograph of a composite with oil as a plasticizer using a laser scanning microscope.

8 shows a microphotograph of a composite with oil as a plasticizer using a laser scanning microscope.

9.24

Correlation coefficients of 0.986-0.994 were obtained from the titration curves, which corresponds to a redox reaction according to equations 1 and 2. Thus the reduction reaction of thioglycolic acid and ammonium thioglycolate in CWE is similar to the behavior in dilute aqueous solution, in which a decrease in the solution potential at higher pH was observed

HS-CH ₂ -CO ₂ H j --- ► (S-CH ₂ -CO ₂ H) ₂ + 2 e- + 2 H ⁺ (1)

HS-CH ₂ -CO ₂ - --- ► (S-CH ₂ -CO ₂ ) ₂ + 2 e- + 2 H ⁺ (2)

Based on these results, the stability of CWET in the presence of wool was investigated with regard to redox potential and pH for a period of 90 min at 40 ° C and 60 ° C. This resulted in a stable redox potential for at least 90 min at 60 ° C. In a further experiment at 60 ° C, a stable redox potential of -555 mV was observed even after a duration of 180 min. Changes in solution pH during an experiment remained stable within a range of ± 0.1 pH units. This indicates that under the chosen experimental conditions, negative effects on the dissolution reaction due to air oxidation or pH change are of minor importance.

The results show that a stable redox potential of -520 mV to -550 mV is produced in solution in the presence of wool, which is sufficient to reduce the disulfide bonds present in the wool. Stable solution conditions were observed in particular at a solution temperature of 60 ° C, a redox potential of less than -550 mV being reached within the first 10 minutes. Overall solubility and regenerated keratin were both determined by gravimetric analysis of the keratin obtained and the insoluble material. Depending on the temperature between 46.2 ± 5.9% (40 ° C) and 42.6 ± 6.9% (60 ° C), a total mass of 0.5 g wool could be obtained from a volume of 100 ml CWET solution be regenerated. Insoluble parts were found to be 34.4 ± 4.5% (40 ° C) and 23.9 ± 6.7% (60 ° C). Part of the dissolved keratin could not be precipitated during the dilution of the CWET and remained in the dissolved state (19.4 ± 1.4% (40 ° C) and 33.5 ± 10.2% (60 ° C)) (Fig 3).

To study the solubility of wool in CWET, the amount of wool present in CWET and the time of dissolution were varied. In the concentration range of 0.2 - 0.8 g wool per 22 g CWET the proportion of the regenerated wool and the

10/24 filtered undissolved matter almost constant, only the amount of dissolved non-regenerable proteins increased with the amount of wool.

The results show that only about 40% of the wool keratin is soluble in CWET, while an almost constant part remains insoluble or as a non-regenerable protein in the solution state. The decrease in regeneration with a higher wool mass is also due to the formation of gel-like components that are difficult to filter and contribute to the undissolved parts.

A possible decomposition of the protein by hydrolysis was investigated in a series of solution attempts with a longer treatment time. An increase in the soluble and non-regenerable keratin proteins should indicate a hydrolytic breakdown of the dissolved keratin. Results of attempts to dissolve 0.5 g wool in 20 g CWET are shown in FIG. 1.

The amount of undissolved fiber components decreases to less than 20% with the treatment time, but no further increase in the regenerated keratin is observed after 3-4 hours, with a maximum of dissolved and regenerated keratin reaching 50-55% of the total mass of the wool becomes. The amount of non-regenerable protein remains below 20% of the total mass of the wool fiber and begins to increase after 4 hours of treatment, which indicates the tendency to hydrolytically break down keratin in CWET.

The protein staining test with Coomassie Blue G-250 was used for further analysis of protein loss as a soluble material during regeneration. In these experiments, the relative protein content as a function of the treatment time in CWET was examined. For comparison, experiments with 3 hours prior swelling in CWE and experiment with double amount of thioglycolic acid are also shown.

The Coomassie tests showed a continuous increase in soluble proteins with the time of the CWET treatment. Experiments with a longer treatment time of 5 hours and 20 hours indicate a further increase in the soluble proteins, which corresponds to the results shown in FIG. 1.

The influence of the pH value of the CWET solution was investigated by dissolution experiments in CWET with different pH values (pH 6.3, pH 7.3 and pH 7.9). This in

11/24

The redox potential measured in solution decreased with a pH of -245 mV (pH 6.3) to -437 mV (pH 7.3) and -586 mV (pH 7.9). The mass of the regenerated keratin isolated after the treatment for about 20 hours decreased accordingly from 59.8% (pH 6.3) to 59.4% (pH 7.3) and 21.8% at pH 7.9. The Coomassie staining also showed a significantly higher level of dissolved proteins for CWET with a pH of 7.9, while solutions with pH 6.3 and 7.3 showed a lower level of soluble protein.

FTIR analysis of the regenerates and the insoluble parts was carried out to examine possible changes in the protein structure during the dissolution experiments and to identify differences between the regenerated keratin and the insoluble parts of the wool sample. For comparison, the FTIR spectrum of the untreated wool is also shown (Fig. 2). For a better comparison of the spectra, an offset in the direction of the y-axis was carried out.

The FTIR spectra show no significant changes between the untreated wool and the regenerates. Even after a 20-hour treatment in CWET, there are only slight differences between the wool fibers and the undissolved parts. The reasons for the observed incomplete dissolution of wool are still unclear. Saturation effects can be excluded because the insoluble part of the wool fibers is independent of the wool to be dissolved and the dissolution time.

Preparation of all keratin composites

If the keratin dissolution and regeneration is carried out in the presence of an excess of wool fibers, the coagulated keratin serves as a binder between the wool fibers and an all-keratin composite is obtained. In a series of composite preparation experiments, the mass of the CWET used in relation to the wool fibers and the time of solidification under pressure were varied in order to identify the respective influence on the physical properties of the composite (Table 1). In addition to the formation of a bond with parallel orientation of the wool fibers, samples with 90 ^° crossed fiber direction were also produced. The samples were characterized by laser scanning microscopy and in terms of physical strength and elongation. FTIR spectra of the keratin composite, moisture absorption and water retention value were also recorded.

12/24

Due to the manufacturing process, the variation in the physical properties of the composite samples is considerably high, which is also indicated by fluctuations in the thickness between 0.40 and 0.65 mm. The sample showed that a mass of 1.6 g CWET per 1 g wool is not sufficient to form an entire composite structure. If 2.6-3.2 g of CWET was used, a composite structure is formed and TS increases to 60 N. Highest values of TS were observed when more than 4 g of CWET were used for 1 g of wool.

A special property of keratin-based material is the ability to absorb significant amounts of moisture and to swell in water. Possible changes in moisture sorption and water retention were analyzed.

The WRV is primarily an indicator of liquid water that is stored in heavily swollen parts of the material. The results show a significant increase in water retention value (WRV) despite the fact that the untreated wool fibers were centrifuged with less centrifugal force. A value of approximately 37.9 ± 1.1% was determined for the wool reference fibers, which increases to 54-70% after treatment in CWET. This can be explained by a higher amount of small pores that can collect liquid water and a higher swelling of the more accessible keratin structure. The higher accessibility of the structure also leads to increased moisture absorption under conditions of the standard climate (20 ^° C. 65% rh).

When WRV and MC are related to the amount of CWET used per 1 g of wool, a maximum of water absorption is observed in the vicinity of 4.3 g of CWET per 1 g of wool, indicating that there is a high degree of fiber degradation and an open structure The composite form appears to be incomplete at lower values, while at higher levels of CWET per gram of wool the compactness of the structure leads to a reduction in WRV and MC (Fig. 3). For example, lower values of WRV and MC were already obtained for sample 3 with the highest ratio of CWET per g wool.

FTIR-ATR spectra of the keratin composites were carried out to identify possible changes in the chemical structure of the keratin (FIG. 4). The FTIR-ATR spectrum of the untreated wool is also shown for comparison. It

No significant difference in the spectra with respect to the appearance of peaks or a significant shift in the absorbance was observed in 13/24.

In the microphotographs obtained with the laser scanning microscope, the composite structure formed by regenerated keratins and insoluble wool fibers can be recognized. Depending on the amount of CWET used, the composite structure becomes more compact. A high number of pores are detected in all microphotographs, which explain the considerable increase in the water retention volume.

The dissolution of wool fibers was achieved in a concentrated CaCl ₂ / water / ethanol solution, which contained thioglycolic acid, at neutral pH. Similar to the dissolution of fibroin in Ajisawas reagent, the concentrated saline solution stabilizes the dissolved protein by forming an ion-rich hydration layer and interacting with charged and polar groups of keratin. The presence of thioglykylic acid is required to break the disulfide bonds present in wool. Redox potential measurements showed sufficient stability of the solvent against oxidative effects for the duration of the dissolution experiment. A total of 50% of the wool fibers are dissolved after 3 hours of treatment at 60 ° C., regardless of the amount of wool, with a portion of 30% of the wool fibers remaining as an insoluble residue. Dilution of the keratin solution with water leads to protein regeneration, but 20% most likely proteins with lower molecular weight have remained in solution.

If the dissolution and regeneration experiments are carried out in the presence of an excess of wool, an all-keratin composite can be obtained by consolidation under pressure. The composite materials are built up as a combination of regenerated keratin and insoluble wool fibers.

While FTIR analysis indicated that there were no significant changes in protein, a significant increase in water retention and moisture absorption was observed, which can be explained by the highly porous structure of the composite and the increased surface area of the regenerated keratin.

14/24

The technique indicates a new process for shaping 100% keratin-based material, which is both a sustainable biodegradable material and a material with potentially high biocompatibility for medical applications, e.g. Frameworks and implants.

Application example 1

To produce artificial leather from wool, nonwovens or fabrics are compressed with a solvent or swelling agent at 60 ° C under 10 bar pressure in a heatable press.

A mixture of 30 g CaCl ₂ x 2 H ₂ O, 22 g H ₂ O, 29 g ethanol, 8 g calcium thioglycolate and 12 ml hydrochloric acid 10% by weight (pH = 6.75, redox potential = - 464 mV, vs. Ag / AgCL, 3 M KCl) was used

The mixture is pressed into the goods by a roller crusher, then compacted for 20 min at 60 ° C and 10 bar pressure. The parts are washed out with water and treated in various ways with softening substances.

As exemplary plasticizers, glycerin or oils (e.g. WD-40) can be used. It can be applied after drying or when wet.

To determine the tensile strength, the samples were cut into 1 cm strips and air-conditioned in a normal climate (20 ° C, 65% relative humidity). The clamping length was 20mm. The results of the tensile tests are summarized in the following table.

No Wool roving g Solvent ml orientation Press min HZK (N) Strain % Weight g / cm ² 20A 3.88 15 X 20 33.4 8.0 .0671 20B 3.88 15 X 20 4.7 27.0 0.0751 20C 3.88 15 X 20 5.87 23.3 0.0533 20D 3.88 15 X 20 10 15.5 0.054 21A 5.28 15 IIX 20 26 21.8 0.0827 21B 5.28 15 IIX 20 11.5 39.7 .1069 21C 5.28 15 HX 20 22.2 18.0 0.0639 21D 5.28 15 HX 20 11.1 29.2 0.0762 22A 4.35 15 II 20 61 7.5 0.0503 22B 4.35 15 II 20 20 51.2 0.0726 22C 4.35 15 II 20 12 32.7 0.0455 22D 4.35 15 II 20 21 6.0 0.0422

15/24

23A 4.6 15 Illi 20 8.5 19.0 0.0712 23B 4.6 15 Illi 20 20.2 62.5 0.0885 23C 4.6 15 Illi 20 17.8 59.0 0.0789 23D 4.6 15 Illi 20 27.4 16.5 .0901

(HKZ = maximum tensile force)

The indication of the orientation relates to the orientation of the wool fibers during the production of the composite (X = crossed, II = parallel)

The letters below indicate the different post-treatments

A: Treatment of wet samples with oil (WD-40)

B: Treatment of the wet samples with glycerin

C: Treatment of dry samples with oil (WD-40)

D: Treatment of the dried samples with glycerin

The aftertreatment processes with glycerin in the wet state or with oil (WD 40) in the dried state allow the production of a leather-like state.

Example of use 2

In an analogous manner, leather-like composites can also be produced by compressing roving material with woolen fabrics.

Working instructions: 6 g of a sandwich made of wool fabric (top) - crest (middle) of wool fabric bottom, was placed in a plastic bag with 10 ml standard solvent (30 g CaCl ₂ x 2 H ₂ O, 22 g H ₂ O, 29 g ethanol, 8 g Calcium thioglycolate and 12 ml hydrochloric acid 10% by weight (pH = 6.75, redox potential = -464 mV, vs. Ag / AgCL, 3 M KCl)) impregnated, pressed for 20 min at 60 ° and 10 bar pressure in a hydraulic press, washed out and dried.

When dry, the samples were divided into four parts and treated with leather oil, coil oil and WD 40. This made all samples less brittle, more flexible. The maximum tensile force ZK varies from 50 N (leather oil, coil oil), over 60 N (shoe polish) to 65 N with WD40.

Example of use 3

A 10 g of a wool fleece is mixed with 20 ml of standard solvent (30 g CaCl ₂ x 2 H ₂ O, 22 g H ₂ O, 29 g ethanol, 8 g calcium thioglycolate and 12 ml hydrochloric acid 10% by weight (pH = 6.75, redox potential = -464 mV, vs. Ag / AgCL, 3 M KCl)) impregnated and pressed in a hydraulic press for 20 min at 100 ° and 10 bar pressure.

16/24

The sample is then washed out with a mixture of dilute citric acid (5 g / l) and hydrogen peroxide 30% (5 ml / l).

The pattern is then divided and treated with the softening substances as in Application Example 1, a leather-like character is achieved.

Without treatment with softening substances, the composite material has a brittle and hard character.

17/24

Claims (10)

EXPECTATIONS 1. A method for producing a leather substitute, comprising the steps: Treatment of wool in a mixture which comprises calcium chloride, water, ethanol and a reducing agent and has a pH of between 6 and 8, at least part of the keratin of the wool being dissolved. Regeneration of the keratin by adding an excess of water. Form the keratin into the desired shape. 2. The method according to claim 1, characterized in that the molar mixture between calcium chloride: water: ethanol is 1: 5 to 7: 1 to 3, preferably 1: 6: 2. 3. The method according to claim 1 or claim 2, characterized in that the reducing agent has an -SH group and preferably comprises mercaptoacetic acid or a salt thereof. 4. The method according to any one of claims 1 to 3, characterized in that only a part of the wool is dissolved and that the undissolved part of the wool is integrated into the desired shape in the leather substitute during regeneration and shaping of the keratin. 5. The method according to any one of claims 1 to 4, characterized in that the leather substitute is then treated with a plasticizer. 6. Leather substitute available according to one of claims 1 to 5. 7. Leather substitute, including regenerated keratin from wool. 8. Leather substitute according to claim 7, characterized by a matrix of wool, the matrix being embedded in the regenerated keratin. 9. Leather substitute according to claim 7 or claim 8, characterized by a non-wool matrix, the non-wool matrix being embedded in the regenerated keratin. 10. Leather substitute according to one of claims 6 to 9, characterized by a plasticizer. 18/24