WO2019119009A1

WO2019119009A1 - Method for producing a leather substitute

Info

Publication number: WO2019119009A1
Application number: PCT/AT2018/060309
Authority: WO
Inventors: Thomas Bechtold; Christa Fitz-Binder; Markus Krüger
Original assignee: Universität Innsbruck; Schoeller Gmbh & Co Kg
Priority date: 2017-12-19
Filing date: 2018-12-19
Publication date: 2019-06-27
Also published as: AT520764B1; AT520764A1; EP3728724A1

Abstract

The invention relates to a method for producing a leather substitute, comprising the steps: treating wool in a mixture which comprises calcium chloride, water, ethanol and a reducing agent, and which has a pH of between 6 and 8, wherein at least one portion of the keratin of the wool is dissolved; regenerating the keratin by adding an excess of water; and shaping the keratin into the desired shape.

Description

METHOD FOR PRODUCING A LEATHER SUBSTANCE

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

BACKGROUND OF THE INVENTION

Leather or imitation leather products are used in many fields, such as used as clothing or for the interior. While genuine leather is a natural product that has many excellent properties, there are ethical concerns associated with the rearing and killing of animals to obtain leather. For artificial leather, plastics such as PVC are used, which are also of concern for environmental protection. Also, the properties in terms of moisture absorption, comfort or stability of such artificial leather are not comparable with natural leather. Finally, there are reservations about wearing synthetic, PVC-based artificial leather.

There is therefore an increasing demand for leather substitutes which on the one hand have comparable properties with genuine leather but are ethically harmless.

BRIEF DESCRIPTION OF THE INVENTION

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

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

Treating wool in a mixture comprising a swelling agent 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,

• Regenerate keratin, preferably by adding excess water

• Form the keratin into the desired shape.

Preferably, the swelling agent is a mixture of calcium chloride, water, ethanol.

In the treatment of wool with a mixture of swelling agents, in particular a mixture of calcium chloride, water and ethanol, the swelling of the Keratins from the wool. The addition of the reducing agent results in disruption of intra- and intermolecular disulfide bonds between the -SH groups of the cysteine residues of keratin. The regeneration of the keratin is preferably carried out by adding water so that the dissolved keratin protein forms again as a solid. 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): 5 to 7 (water): 1 to 3 (ethanol), preferably about 1: 6: 2.

An alternative mixture as swelling agent includes LiBr and urea.

Suitable reducing agents are all reducing agents in question, which disulfide bridges can break open. For example, the reducing agent may have an -SH group. Preferably, it is mercaptoacetic acid or a salt thereof (thiol glycolate).

Also, prior to regeneration, a filtration step may be provided to separate insoluble matter.

On the one hand, it is possible to completely dissolve the keratin and then regenerate it.

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

The undissolved part of the wool can then form a matrix for the leather substitute. The matrix may be obtained by suitable arrangement of the fibers of the wool, e.g. by crossing the fibers, give a corresponding stability.

Alternatively, of course, a non-wool matrix may also be used (eg, a fabric or the like). In this case, the non-wool matrix is incorporated into the composite. Regardless of whether it is pure wool, a non-wool matrix or a mixture thereof, the matrix may be a nonwoven, a cloth, a woven fabric, a knit or a sheet. For example, a fiber mixture may be present.

Preferably, an oxidation step is 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 the addition of an oxidizing agent.

The invention also relates to a leather substitute obtainable by the aforementioned method. In addition, the invention relates to a leather substitute comprising regenerated keratin of wool.

The leather substitute may comprise a matrix of wool, wherein the matrix is embedded in the regenerated keratin.

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

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

The plasticizer may e.g. Glycerol and / or oils.

DETAILED DESCRIPTION OF THE INVENTION

Every year, about 80 million tons of textile fibers, such as polyester, cotton, polyamide are processed. Within this quantity, wool fibers account for only a small proportion of a production volume of approximately 1.16 million tonnes of wool (2015). The high moisture sorptive capacity of wool has recently revived woolen clothing. The diameter of the wool fibers, which also determines the value and the application, varies from superfine merino wool (<16 pm) to coarse hair / coarse wool (> 25 pm). Since only a few applications for coarse wool are known and in the wool processing also occur waste that can not be processed, a significant portion of this natural material can not be processed. The subject invention now also allows the recovery of coarse wool and waste wool, which were otherwise unusable.

It is known that in an aqueous medium wool can be dissolved at pH 12 in the presence of thioglycolate as a reducing agent, the precipitate can be initiated by the addition of acetic acid. Also, the treatment of hair with alkaline reducing solutions, e.g. Ca (OH) 2, Ca (HS) 2 is known for removing hair from skins 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 the dissolution of wool keratin and allows regeneration and shaping the production of an all-keratin composite. 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 produce all-keratin composites characterized by laser scanning microscopy, FTIR and mechanical properties, moisture sorption and water uptake.

Experimental part

Chemicals and reagents

The following chemicals were used: thioglycolic acid (> 98% wt, Merck Schuchhardt OHG, Hohenbrunn, Germany); CaCl 2 × 2H 2 O (> 99% by weight), bromothymol blue and ethanol (> 99.9% by weight, Merck Darmstadt, Germany), calcium thioglycolate trihydrate (> 98% by weight) and ammonium thioglycolate (about 60% by weight). -% Sigma-Aldrich, Steinheim, Germany); NH3; (> 25 wt%), HCl (25 wt%, VWR International, Briare, France); Coomassie Blue G-250 (Fluka, Buchs, Switzerland). Wool fibers were used as prewashed untreated wool by Schoeller Textil (Hard, Austria).

Microscopy and FTIR spectroscopy

For monitoring fibers, regenerates and composites, a light microscope (CX41, Olympus, Tokyo, Japan) and a 3D laser scanning confocal microscope (VK-X200 Keyence, Osaka, Japan) were used. Infrared spectra were recorded by attenuated total reflection (ATR) with an FTIR spectrometer (Bruker Vector 22 FTIR spectrometer, Spectra I range 4000 to 400 cm ^-1 ) 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 CWE solvents were prepared with the addition of thioglycolic acid (CWET). To a mixture of 37.3 g of CaCl 2 H 2 O, 27.4 g of H 2 O and 23.4 g of ethanol was added a color indicator (2 ml of bromothymol blue, 0.1 g per 100 ml) and 4 ml of thiogylic acid. The pH and redox electrodes were immersed in the solution and the vessel sealed with plastic film. 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 with a potentiometer (Zeller MP 225, Hohenems, Austria).

The redox potential was measured with a Pt electrode and an Ag / AgCl, 3 M KCl reference electrode (Sen Tix ORP 3M KCl, WTW, Weilheim, Germany). For calibration, a ferrocyanide redox buffer was prepared (0.528 g K4 [Fe (CN) e], 0.411 g of K ₃ [Fe (CN) _6], 0.180 g KH ₂ P0 _4, 0.390 g Na ₂ hPoE ₄ in 100 ml).

Stability of CWET

Solvent system stability in the presence of wool: 100 ml of CWE thioglycolic acid solvent CWET (37.3 g CaCl ₂ -2H ₂ O, 27.4 g H2O, 23.4 g ethanol, 2 ml color indicator (bromothymol blue solution, 0.1 g per 100 ml), 4 ml of thiogylic acid) were heated to 40 ° C or 60 ° C. The pH was adjusted to pH 7 ± 0.3 by addition of NH ₃ and 0.5 g of wool was added to the solvent. The pH and redox potential were measured at regular intervals for a period of 90 minutes. At the end of the experiment, the solutions were filtered through a paper filter and the regeneration of the solubilized protein was initiated by the addition of 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 insoluble matter and regenerate were then determined by weighing. Solution capacity of CWET

First, an amount of 22 g of CWE solution, 9.31 g of CaCl 2 H 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 thiogylic 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 of wool per 10 g of solvent at 60 ° C overnight.

In a similar approach, the effect of dissolution time was examined by treating 0.5 g of wool in 20 g of 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 about 0.6 mm) and precipitated in 100 ml with water. The regenerate was then oven dried at 80 ° C for 1 h.

Determination of 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 H ₃ PO ₄ (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 Coomassie's reagent. The absorbance was measured at 595 nm. Freshly prepared 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 defined times up to a maximum duration of 3 hours. Comparative experiments were carried out in which the addition of thiogylciolic 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 an average for a double determination.

Compound preparation

Woolen 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 and to reduce the access of atmospheric oxygen. To aid penetration of the solvent into the wool fiber tape, the sample was squeezed three times with a laboratory float (0.5 m min ^-1 , 3 bar). The solvent / wool samples were compressed in a laboratory press (Serivtec, Polystat 200 T) for 10 to 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 composites were ground and stored in normal conditions (20 ° C, 65% RH), weighted (Wmoist), dried at 105 ° C for 4 hours, cooled in a desiccator and weighed again (W _dry ). The moisture content was calculated according to Equation 1. ^w moist ^w dry 1 r0 _\ r0 _\

- wdry (1)

To determine the water retention value, 0.3 g of sample in deionized water was added 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). The samples were then weighed (w _wet ) and dried at 105 ° C for 4 h. After cooling in the desiccator, the weight of the dried samples was determined (W _dry ). The water retention value was calculated according to Equation 2. L 1 r0 _\ r0 _\

(2)

Tensile strength and elongation at break were determined with a universal testing machine (Instron Universal Tester, Instron, Norwood, USA). The composite materials were used to produce samples measuring 4 cm in length and 1 cm in width. Tensile strength experiments were performed at a rate of 1 cm min ^-1 , with no bias (tests were performed at least as a duplicate). The thickness of the samples was measured by means of a sliding caliper. Results and discussion

Stability of the CWET solvent

The potentiometric titration of the CWET was performed to examine 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 as a color indicator was added to the CWET solvent. The color of bromothymol blue changes from yellow to blue at the pH interval of 5.8-7.6, so that green color was used to indicate a near neutral solvent pH of 6-7.

The concept of pH is in fact limited to rather dilute solutions, but the use of the glass electrode still allows an indication of the [H ⁺ ] activity and thus makes sense 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 dissolution time.

Proportion of regenerated ( _■ ) keratin, (·) insoluble parts and (▲) non-regenerable dissolved protein as a function of treatment time in CWET.

Figure 2 shows FITR spectra of untreated wool, CWET after 1 h and

3 h of dissolution treatment, regenerated keratin and corresponding insoluble parts separated after 20 h of treatment in CWET.

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

FIG. 4 shows FTIR-ATR spectra of keratin composites and wool in FIG

Wavelength range of 4000 cm-1 to 500 cm-1.

5 shows a microphotograph of untreated wool with laser scanning

Microscope.

Fig. 6 shows a microphotograph of a composite with glycerol as

Plasticizer with laser scanning microscope.

Fig. 7 shows a microphotograph of a composite with oil as a plasticizer

Laser scanning microscope.

Fig. 8 shows a microphotograph of a composite with oil as a plasticizer

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

Based on these results, the stability of CWET in the presence of wool was examined for redox potential and pH for a period of 90 minutes 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 over a period of 180 min. Changes in the 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 changes are of secondary importance.

The results show that in the presence of wool, a stable redox potential of -520 mV to -550 mV in solution is produced, which is sufficient to reduce the disulfide bonds present in the wool. Stable solution conditions were observed especially at a solution temperature of 60 ° C, within the first 10 min, a redox potential of less than -550 mV was reached. Total solubility and regenerated keratin were both determined by gravimetric analysis of the recovered keratin and the insoluble material. Depending on the temperature between 46.2 ± 5.9% (40 ° C) and 42.6 ± 6.9% (60 ° C), out of a volume of 100 ml of CWET solution, a total mass of 0.5 g of wool could be obtained 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 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 of wool per 22 g of CWET, the proportion of regenerated wool and filtered unresolved 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 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 solution attempts with a longer treatment time. An increase in soluble and non-regenerable keratin proteins should indicate hydrolytic degradation of the dissolved keratin. Results of dissolution experiments of 0.5 g of wool in 20 g of CWET are shown in FIG.

The amount of unresolved fiber components decreases with the treatment time to less than 20%, 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 weight 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, indicating the tendency for hydrolytic degradation of keratin in CWET.

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

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

The influence of the pH of the CWET solution was investigated by dissolution experiments in CWET with different pH (pH 6.3, pH 7.3 and pH 7.9). This in The measured redox potential dropped to -437 mV (pH 7.3) and -586 mV (pH 7.9) at a pH of -245 mV (pH 6.3). 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 content of dissolved proteins for CWET with a pH of 7.9, whereas solutions of pH 6.3 and 7.3 showed a lower content of soluble protein.

The FTIR analysis of the regenerates and insoluble parts was performed to examine 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. For comparison, the FTIR spectrum of the untreated wool is also shown (Figure 2). For a better comparison of the spectra, an offset in the direction of the y-axis was performed.

The FTIR spectra show no significant changes between the untreated wool and the regenerates. Even after a 20-hour treatment in CWET, only minor differences between the wool fibers and the undissolved parts are detectable. The reasons for the observed incomplete dissolution of wool are still unclear. Saturation effects can be excluded 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 experiments, the mass of the CWET used was varied with respect to the wool fibers and the time of solidification under pressure to identify the particular impact on the physical properties of the composite (Table 1). In addition to the composite formation with parallel orientation of the wool fibers, samples were also made with 90 ° crossed fiber direction. The samples were characterized by laser scanning microscopy and in terms of physical strength and elongation. Keratin composite FTIR spectra, 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 variations in thickness between 0.40 and 0.65 mm. The sample showed that a mass of 1.6 g of CWET per 1 g of wool is insufficient to form an entire composite structure. When 2.6-3.2 g of CWET were used, a composite structure is formed and TS increases to 60 N. Highest levels of TS were observed when more than 4 g of CWET was used for 1 g of wool.

A special feature of keratin-based material is the ability to absorb significant amounts of moisture and swell in water. Thus, possible changes in moisture sorption and water retention value were analyzed.

Above all, the WRV is 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 at lower centrifugal force. For the wool reference fibers a value of about 37.9 ± 1.1% was found, which after treatment in CWET increases to 54 - 70%. This can be explained by 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 results in increased moisture sorption under standard climate conditions (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 uptake is observed near 4.3 g CWET per 1 g of wool, indicating a high degree of fiber decomposition and an open structure At lower values, the composite form appears to be incomplete, while at higher levels of CWET per gram 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 already lower values of WRV and MC were obtained.

FTIR-ATR spectra of the keratin composites were performed to identify possible changes in the chemical structure of keratin (Figure 4). For comparison, the FTIR-ATR spectrum of the untreated wool is also shown. It No significant difference in spectra was observed with respect to the appearance of peaks or a significant shift in extinction.

In the photomicrographs obtained by 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. In all the photomicrographs a high number of pores is detected, which explain the considerable increase of the water retention volume.

The dissolution of wool fibers was achieved in a concentrated CaCl / water / ethanol solution containing thioglycolic acid at neutral pH. Similar to the dissolution of fibroin in Ajisawa's reagent, the concentrated saline solution stabilizes the solubilized 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 to 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 share of 30% of the wool fibers has remained as an insoluble residue. Dilution of the keratin solution with water results in protein regeneration, however, 20% most likely remained in solution with lower molecular weight proteins.

When the dissolution and regeneration experiments are performed 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 indicates that no significant changes in protein occurred, a significant increase in water retention and moisture sorption was observed, which can be explained by the highly porous structure of the composite and the increased surface area of regenerated keratin. The technique indicates a new method of shaping 100% keratin-based material, both as a sustainable biodegradable material and as a material with potentially high biocompatibility for medical applications, such as scaffolds and implants.

Application example 1

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

The source and solvent used is a mixture of 30 g CaClx 2 H 2 O, 22 g H 2 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, 3M KCl)

The mixture is pressed through a roller squeezing in the goods, then compressed for 20 min at 60 ° C and 10 bar pressure. The parts are washed out with water and treated in different ways with softening substances.

As exemplary plasticizers, glycerol or oils (e.g., WD-40) can be used. The application can take place after drying or already in the wet state.

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

(HKZ = maximum tensile strength)

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

The following letters indicate the different post-treatments A: Treatment of wet samples with oil (WD-40)

B: Treatment of 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 leathery state.

Application Example 2

In an analogous way, leather-like composites can be produced by compaction of worsted material with woolen fabrics.

Procedure: 6 g of a woolen sandwich (top) - worsted (center) - woolen fabric below, was packed in a plastic bag with 10 ml standard solvent (30 g CaChx2H2O, 22 g H2O, 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 KCl)), pressed for 20 min at 60 ° and 10 bar pressure in a hydraulic press, washed and dried.

When dry, the samples were divided into four parts and treated with leather oil, coil oil and WD 40. All samples became 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 WD 40.

Application example 3

A 10 g of a wool fleece are treated with 20 ml standard solvent (30 g CaCl x 2 H 2 O, 22 g H 2 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 KCl)) and pressed for 20 min at 100 ° and 10 bar pressure in a hydraulic press. 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 agents as in Application Example 1, a leathery character is achieved.

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

Claims

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,

• Regenerate keratin by adding excess 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 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

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 in the regeneration and shaping of the keratin in the desired shape in the leather substitute.

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 comprising regenerated keratin of wool.

7. leather substitute according to claim 6, characterized by a matrix of wool, wherein the matrix is embedded in the regenerated keratin.

8. leather substitute according to claim 6 or claim 7, characterized by a non-wool matrix, wherein the non-wool matrix is embedded in the regenerated keratin.

9. leather substitute according to any one of claims 6 to 8, characterized by a plasticizer.

10. leather substitute obtainable according to one of claims 1 to 5.