AT520764B1 - Process for the production 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, whereby at least a portion of the keratin of the wool is dissolved; regenerating the keratin by adding an excess of water; Shaping the keratin into the desired shape.

Description

description

PROCESS FOR MANUFACTURING A LEATHER SUBSTITUTE

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 imitation leather are used in numerous areas such as clothing or for interior design. While genuine leather is a natural product that exhibits many excellent properties, there are ethical concerns associated with the raising and killing of animals for leather. Plastics such as PVC are used for artificial leather, which are also questionable for environmental reasons. Also, the properties in terms of moisture absorption, comfort and stability of such synthetic leather are not comparable to natural leather. Finally, there are reservations about wearing synthetic PVC-based imitation leather.

JP H06192433 A describes the production of keratin powder from wool and its use in the production of artificial 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 genuine leather and is ethically unobjectionable.

This object is achieved by a method for producing a leather substitute, comprising the steps:

* treatment of wool in a mixture comprising a swelling agent and a reducing agent and having a pH of between 6 and 8, whereby at least part of the keratin of the wool is dissolved, _

* Regenerating 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 and ethanol.

When wool is treated with a mixture of swelling agents, in particular a mixture of calcium chloride, water and ethanol, the keratin in the wool swells. Addition of the reducing agent results in 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 as a solid again. By appropriate shaping, the keratin can be brought into the desired shape.

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.

[0012] Suitable reducing agents are all reducing agents which can break up disulfide bridges. For example, the reducing agent can have an -SH group. It is preferably mercaptoacetic acid or a salt thereof (thiol glycolate).

[0013] 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 it is provided that only part of the wool is dissolved and that the non-dissolved 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 impart appropriate stability to the wool by suitably arranging the fibers, e.g. by crossing the fibers.

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

The matrix, whether it is pure wool, a non-wool matrix or a mixture thereof, can be, for example, a fleece, a cloth, a woven fabric, a knitted fabric or a flat structure. For example, a fiber blend may be present.

An oxidation step is preferably provided with or after the regeneration. This serves to form the free -SH groups in the regenerated keratin again -S-S-disulfide 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 method. The invention also relates to a leather substitute comprising regenerated keratin from wool, the leather substitute having a matrix made of wool, the matrix being embedded in the regenerated keratin.

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

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

The emollient may, for example, comprise glycerin and/or oils.

DETAILED DESCRIPTION OF THE INVENTION

Approximately 80 million tons of textile fibers such as polyester, cotton, polyamide are processed annually. Within this amount, wool fibers only account for a small proportion of a production volume of around 1.16 million tons of wool (2015). Wool's high moisture sorption capacity has led to a recent revival of 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 uses for coarse wool are known and waste that cannot be processed occurs in the processing of wool, a significant part of this natural material cannot be processed.

The present invention now also allows the recycling of coarse wool and wool waste, which were otherwise not recyclable.

It is known that wool can be dissolved in an aqueous medium at a pH of 12 in the presence of thioglycolate as a reducing agent, the precipitation can be initiated by the addition of acetic acid. Also known is the treatment of hair with alkaline reducing solutions, e.g. Ca(OH)2, Ca(HS)2 to remove hair from hides during leather production.

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 through regeneration and shaping. The dissolution of wool in the system CWE 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

To produce all-keratin composites, which were characterized by laser scanning microscopy, FTIR and in terms of mechanical properties, moisture sorption and water absorption.

EXPERIMENTAL PART

chemicals and reagents

The following chemicals were used: thioglycolic acid (= 98% wt, Merck Schuchhardt OHG, Hohenbrunn, Germany); CaCl2x2H,;0 (= 99% by weight), bromothymol blue and ethanol (= 99.9% by weight, Merck Darmstadt, Germany), Ca thioglycolate trihydrate (= 98% by weight) and ammonium thioglycolate (approx. 60% by weight Sigma-Aldrich, Steinheim, Germany); NH's; (>25 wt%), HCI (25 wt%, VWR International, Briare, France); Coomassie Blue G-250 (Fluka, Buchs, Switzerland). Wool fibers were used as scoured 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, regrinds and composites.

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

Solvent Potentiometric Titration (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 thioglycolic acid were added to a mixture of 37.3 g CaCl2 - 2H2:O, 27.4 g H2:O and 23.4 g ethanol. The pH and ORP electrodes were immersed in the solution and the jar sealed with plastic wrap. Titrations were performed at 60°C by direct addition of 0.25 mL portions of aqueous NH; (25% by weight). The pH was determined using a potentiometer (Zeller MP 225, Hohenems, Austria).

The redox potential was measured with a Pt electrode and an Ag/AgCl, 3M KCl reference electrode (Sen Tix ORP 3M KCl, WTW, Weilheim, Germany). A hexacyanoferrate redox buffer was prepared for calibration (0.528 g Kı[Fe(CN)el, 0.411 g K3[Fe(CN)e], 0.180 g KH2PO«, 0.390 g NazHPO«4 in 100 ml).

Stability of CWET

Stability of the solvent system in the presence of wool: 100 ml CWE thioglycolic acid solvent CWET (37.3 g CaCl2-2H2O, 27.4 g H2O, 23.4 g ethanol, 2 ml color indicator (bromothymol blue solution, 0 .1 g per 100 ml), 4 ml thioglycolic acid) were heated to 40 °C or 60 °C. The pH was adjusted by adding NH; adjusted to pH 7 + 0.3 and 0.5 g of wool was added to the solvent. The pH value 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 regeneration of the dissolved protein was initiated by the addition of 100 mL deionized water. The insoluble material in the filter and the regrind were collected, rinsed with deionized water and dried at 80°C. The mass of the insoluble matter and regrind were then determined by weighing.

Solving Capacity of CWET

First, a quantity of 22 g CWE solution, 9.31 g CaCl - 2H2.O, 6.85 g H.-O, 5.84 g ethanol, 0.5 ml color indicator (bromothymol blue, 0.1 g per 100 ml), then 1 ml thiogylcol-

acid and 1 ml NH 2 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 of wool per 109 g of solvent at 60 °C overnight.

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

Determination of the protein content in solution

[0036] Soluble protein was determined by photometry using Coomassie Blue G250 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 addition of 100 ml 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 deionized water and filtered to remove precipitated keratin. A 10 mL volume 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 prepared CWET solution was used to prepare a blank.

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

Composite preparation

Wool sliver (2.0-4.3 g) was placed in a PE plastic bag and a volume of 5-20 mL of CWET was added. The sample bag was then placed in another bag to avoid solvent release and reduce access of atmospheric oxygen. To help the solvent penetrate the wool sliver, the sample was squeezed three times with a laboratory fourlard (0.5 mm min”, 3 bar). The solvent/wool samples were compressed in a laboratory press (Serivtec, Polystat 200 T) for 10-20 min at 60° C. and 10 bar. After pressing, the samples were removed from the pouch and rinsed in excess water to coagulate dissolved keratin and remove solvent. The damp samples were then fixed between absorbent soft paper and allowed to dry 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 standard climate (20 °C, 65% RH), weighted (Wmoist), dried at 105 °C for 4 h, cooled in a desiccator and weighed again (wary ). Moisture content was calculated using Equation 1.

Kan * 100 (1) dry

To determine the water retention value, a 0.3 g sample was placed in deionized water and shaken overnight. The samples were then filtered and the capillary water was removed by centrifugation for 10 min at 4000 g (5580 rpm "wool fibers at 2000 g, 4000 rpm"). The samples were then weighed (Wwet) and dried at 105°C for 4 hours. After cooling in the desiccator, the weight of the dried samples was determined (wWary). The water retention value was calculated using Equation 2.

Wwet-Wary » 100 (2)

wary

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 performed at a speed of 1 cm min, without prestressing (tests were performed at least in duplicate). The thickness of the samples was measured using a caliper.

RESULTS AND DISCUSSION

Stability of the CWET solvent

The potentiometric titration of the CWET was carried out to study 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. 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 5.8 - 7.6, so green color was used to indicate near neutral solvent pH 6 - 7.

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

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

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

Figure 3 shows WRV and MC in composites as a function of the mass of CWET used per 1g 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 with laser scanning microscope.

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

Figure 7 shows a photomicrograph of a composite with oil as a plasticizer using a laser scanning microscope.

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

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, where a decrease in solution potential at higher pH was observed

2 HS-CH2-CO2H zZ (S-CH2-CO2H)2 + 2 € + 2 H* (1) 2 HS-CH2-CO» Z— (S-CH2-CO2-)2 + 2 e° +2 H * (2)

Based on these results, the stability of CWET in the presence of wool was examined in terms of 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 another experiment at 60 °C, a stable redox potential of -555 mV was also observed for 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 experimental conditions chosen, negative effects on the dissolution reaction due to air oxidation or pH changes are of minor importance.

The results show that in the presence of wool, a stable redox potential of 520 mV to -550 mV is established in solution, which is sufficient to reduce the disulfide bonds present in the wool. In particular, stable solution conditions were observed at a solution temperature of 60 °C, with a redox potential of less than -550 mV being reached within the first 10 min. Total solubility and regenerated keratin were both determined by gravimetric analysis of recovered keratin and 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. Insolubles were determined 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).

[0055] 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 regenerated wool and filtered undissolved matter remained almost constant, only the amount of dissolved non-regenerable proteins increased with the amount of wool.

The results show that only about a 40% proportion of wool keratin is soluble in CWET, while an almost constant proportion remains insoluble or as non-regenerable solution-state protein. The decrease in regeneration at 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 dissolution experiments with longer treatment times. An increase in soluble and non-regenerable keratin proteins should indicate hydrolytic degradation of the dissolved keratin. Results of dissolution tests of 0.5 g wool in 20 g CWET are shown in fig.

The amount of undissolved fiber components decreases to less than 20% with the treatment time, but no further increase in regenerated keratin is observed after 3-4 hours, with a maximum of dissolved and regenerated keratin accounting for 50-55% of the total mass of the wool is achieved. The amount of non-regenerable protein remains below 20% of the total mass of the wool fiber and starts to increase after 4 hours of treatment, indicating the tendency for hydrolytic degradation of keratin in CWET.

The protein staining test with Coomassie Blue G-250 was used to further analyze protein losses as soluble material during regeneration. In these experiments, the relative protein content was examined as a function of treatment time in CWET. For comparison, experiments with 3 hours previous 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 time of CWET treatment. Experiments with longer treatment times of 5 hours and 20 hours indicate a further increase in soluble proteins consistent with the

results.

The influence of the pH value of the CWET solution was investigated by dissolving experiments in CWET with different pH values (pH 6.3, pH 7.3 and pH 7.9). The redox potential measured in solution decreased with a pH value from -245 mV (pH 6.3) to -437 mV (pH 7.3) and 586 mV (pH 7.9). The mass of regenerated keratin isolated after 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. Coomassie staining also showed a significantly higher level of dissolved proteins for CWET at pH 7.9, while solutions at pH 6.3 and 7.3 showed lower levels of soluble protein.

[0062] FTIR analysis of the regenerates and the insoluble parts was performed to investigate possible changes in protein structure during the dissolution experiments and to identify differences between the regenerated keratin and the insoluble parts of the wool sample. The FTIR spectrum of the untreated wool is also shown for comparison (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 regenerated wool. Even after a 20-hour treatment in CWET, only slight differences between the wool fibers and the undissolved parts can be detected. The reasons for the observed incomplete dissolution of wool are still unclear. Saturation effects can be ruled out since the insoluble part of the wool fibers is independent of the wool to be dissolved and the dissolution time.

Preparation of all keratin composites

When 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 trials, the mass of CWET used relative to the wool fibers and the time of consolidation under compression were varied to identify the impact of each on the physical properties of the composite (Table 1). In addition to the composite formation with parallel orientation of the wool fibers, samples with 90° crossed fiber directions were also produced. The samples were characterized by laser scanning microscopy and for physical strength and elongation. FTIR spectra of the keratin composite, moisture sorption and water retention value were also recorded.

Due to the manufacturing process, the variation in the physical properties of the composite samples is considerably high, which is also indicated by thickness variations 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. When 2.6 - 3.2 g 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 CWET was used for 1 g wool.

A special property of keratin-based material is the ability to absorb significant amounts of moisture and to swell in water. In this way, possible changes in moisture sorption and water retention values were analyzed.

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

When WRV and MC are related to the amount of CWET used per 1g wool, a maximum of waterborne uptake is observed near 4.3g CWET per 1g wool, indicating that a high degree of fiber degradation and an open structure was obtained. At lower values the composite shape appears to be incomplete, while at higher levels of CWET per g of wool the compactness of the structure leads to a reduction in WRV and MC (Figure 3). Thus, for sample 3 with the highest ratio of CWET per g of wool, lower values of WRV and MC were already obtained.

FTIR-ATR spectra of the keratin composites were performed to identify possible changes in the chemical structure of the keratin (Figure 4). The FTIR ATR spectrum of the untreated wool is also shown for comparison. No significant difference in the spectra with regard to the occurrence of peaks or a significant shift in absorbance was observed.

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

[0071] The dissolution of wool fibers was achieved in a concentrated CaCl 2 /water/ethanol solution containing thioglycolic acid at neutral pH. Similar to the dissolution of fibroin in Ajisawa's reagent, the concentrated salt solution stabilizes the dissolved protein by forming an ion-rich hydration layer and interacting with charged and polar groups of keratin. The presence of thioglycic acid is required to cleave 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. Overall, 50% of the wool fibers are dissolved after 3 hours of treatment at 60°C, regardless of the amount of wool, with a proportion of 30% of the wool fibers remaining as an insoluble residue. Dilution of the keratin solution with water results in protein regeneration, however, 20% of the most likely lower molecular weight proteins 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 constructed as a combination of regenerated keratin and insoluble wool fibers.

[0073] While FTIR analysis indicates that no significant changes in the protein occurred, a significant increase in water retention value and moisture sorption was observed, which can be explained by the highly porous structure of the composite and the increased surface area of the regenerated keratin.

The technique indicates a new method for shaping 100% keratin-based material, which can be used both as a sustainable biodegradable material and as a material with potentially high biocompatibility for medical applications, e.g., scaffolds and implants.

Application example 1

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

A mixture of 30 g CaCl.x 2 H:O, 22 g H: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 KCI).

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

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

To determine the tear 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 Solution | Orientation |Press |HZK Elongation | Area top haul | medium ml min (N) % weight g g/cm? 20A_|3.88 15 X 20 33.4 18.0 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 .054 21A 15.28 15 IX 20 26 21.8 .0827 21B _|5.28 15 IX 20 11.5 [39.7 .1069 21C | 5.28 15 IX 20 22.2 18.0 0.0639 21D |5.28 15 IX 20 11.1 29.2 0.0762 22A 14.35 15 I 20 61 7.5 0.0503 22B |4, 35 15 I 20 20 51.2 0.0726 22C_ |4.35 15 I 20 12 32.7 0.0455 22D |4.35 15 I 20 21 6.0 0.0422 23A |4.6 15 U 20 8 .5 19.0 0.0712 23B |4.6 15U 20 20.2 62.5 0.0885 23C_|4.6 15U 20 17.8 |59.0 0.0789 23D |4.6 15U 20 27.4 16.5 0.0901

(HKZ = maximum tensile force)

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

The suffix letters denote the different post-treatments

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

B: Treatment of the wet samples with glycerol

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

D: Treatment of the dried samples with glycerine The post-treatment processes with glycerine when wet or with oil (WD 40) when dried allow the production of a leather-like condition.

Application example 2

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

Working instructions: 6 g of a sandwich made of woolen fabric (above) - top (middle) - woolen fabric below was placed in a plastic bag with 10 ml of standard solvent (30 g CaCl»×2H:O, 22 g H2-O, 29 g Ethanol, 8 g calcium thioglycolate and 12 ml hydrochloric acid 10% wt. (pH=6.75, redox potential=-464 mV, vs. Ag/AgCl, 3 M KCI)) impregnated for 20 min at 60° and 10 bar pressure in one hydraulic press, washed and dried.

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

Application example 3

A 10 g wool fleece is mixed with 20 ml standard solvent (30 g CaCl2 x 2 H.O, 22 g H2O, 29 g ethanol, 8 g calcium thioglycolate and 12 ml hydrochloric acid 10% wt. (pH=6.75, re-

dox potential = -464 mV, vs. Ag/AgCL, 3 M KCl)) impregnated and pressed for 20 min at 100° and 10 bar pressure in a hydraulic press.

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

Claims (9)

patent claims A leather substitute comprising regenerated keratin from wool, characterized by a matrix of wool, the matrix being embedded in the regenerated keratin. 2. Leather substitute according to claim 1, characterized by a non-wool matrix, wherein the non-wool matrix is embedded in the regenerated keratin. 3. Leather substitute according to claim 1 or claim 2, characterized by a plasticizer. 4. A method for producing a leather substitute according to any one of claims 1 to 3, comprising the steps: * treatment of wool in a mixture comprising calcium chloride, water, ethanol and a reducing agent and having a pH of between 6 to 8, whereby at least part of the keratin of the wool is dissolved, * Regenerating the keratin by adding an excess of water * Shaping the keratin into the desired shape. 5. The method according to claim 4, characterized in that the molar mixture between calcium chloride: water: ethanol is 1:5 to 7:1 to 3, preferably 1:6:2. 6. The method according to claim 4 or claim 5, characterized in that the reducing agent has a -SH group and preferably comprises mercaptoacetic acid or a salt thereof. 7. The method according to any one of claims 4 to 6, characterized in that only part of the wool is dissolved and that the undissolved part of the wool is integrated into the leather substitute during regeneration and shaping of the keratin into the desired shape. 8. The method according to any one of claims 4 to 7, characterized in that the leather substitute is then treated with a plasticizer. 9. Leather substitute obtainable according to one of claims 4 to 8. 4 sheets of drawings