LEATHER PROCESSING UTILIZING SUPER-CRITICAL OR NEAR SUPER-CRITICAL CO2 VALUE

Abstract

A method for processing natural or synthetic leather by using super-critical CO.sub.2. The leather can be dried leather, low grade leathers, thin leather, crust leathers, finished leathers, wet blue leathers, and tanned leather, as well as synthetic leather. In a second aspect the invention relates to leather obtained by said method, and in a third aspect to a stand-alone apparatus for performing said method.

Claims

1. A method of processing leather, comprising providing to be processed leather, and processing said leather by subjecting the leather to super critical CO.sub.2 (scCO.sub.2) under increased pressure of >7.3 MPa , a temperature of >30° C., during a period of >1 minute, wherein processing comprises at least one of (a) drying leather, wherein the leather is selected from wet-blue leather, (c) dyeing tanned and dried leather, of dyeing fat-liquored leather, of dyeing finished leather, (d1) coating leather, and (d2) waterproofing leather.

2. The method according to claim 1, wherein the leather is selected from low grade leathers, thin leathers, crust leathers, dried leather, finished leathers, wet blue leathers, and tanned leather.

3. The method according to claim 1, wherein the method is performed in one apparatus.

4. The method according to claim 1, wherein drying comprises subjecting the leather to super critical CO.sub.2 under increased pressure of >7.3 MPa, a temperature of >30° C., during a period of >1 hour.

5. The method according to claim 1, wherein fat-liquoring is selected from (b1) solvent exchange, and (b2) directly, wherein in case of (b1) solvent exchange the wet blue leather is (b11) pre-soaked into a solvent bath, during 1-24 hours, wherein the solvent is selected among the organic solvents, miscible with CO.sub.2, at a T of >40° C. and at a pressure of >7.3 MPa, and (b12) wherein the pre-soaked leather is then placed into an autoclave where it is contacted with an amount of 10-400 gr fat-liquoring material/kg leather at high pressure of >0.1 MPa in the presence of a CO.sub.2 flow comprising 1-10 gr fat-liquoring material/liter flow during a period of time of 10-180 minutes at a temperature of 30-90° C., wherein in case of direct fat-liquoring (b2) the (WB)leather is (a21) is dried to >10 wt. % moisture by subjecting the leather to scCO.sub.2 removing water at a working pressure of 8-50 MPa and a temperature of 30-60° C. during 10-180 minutes under constant stirring and/or recirculating of scCO.sub.2, wherein water is removed over an absorbent, selected from a zeolite, an ionic liquid, a water absorbing salt, a clay, a silica gel, and (b22) subsequently.

6. The method according to claim 5, wherein the fat-liquoring material is selected from fats and oils, land animals oils and fats, vegetable oils and fats, waxes, synthetic fats/oils, and silicones.

7. The method according to claim 1, wherein (c) dyeing leather comprises (c1) providing leather, and (c2) contacting the leather under scCO.sub.2 at a pressure of 5-500 MPa (50-500 bar) at a temperature of 40-120° C. during 10-180 minutes with at least one dye.

8. The method according to claim 7, wherein the dye is selected from a polyester dye, a pigment, colorant, and paints.

9. The method according to claim 8, wherein the natural pigment is obtained by the means of supercritical carbon dioxide, in particular wherein the natural pigment is obtained from a natural source, more in particular from red rose, black carrot, red radish, beetroot, marigold, tomato, and algae, and wherein the natural pigment is one of a flavonoid, an isoprenoid, a protein, a porphyrin, a tyrosine-thereof. thereof.

10. The method according to claim 7, wherein the dye is provided on one of a support, glass beads, porous supports, and textile materials.

11. The method according to claim 1, comprising providing a coating layer and waterproofing and impregnation under scCO.sub.2 at a pressure of 5-50 MPa (50-500 bar) at a temperature of 40-120° C. during 10-180 minutes.

12. A leather obtained by the method according to claim 1, with a tensile strength of >1 MPa.

13. A stand-alone apparatus for performing the method according to any claim 1, comprising a quick-closure autoclave, at least one CO.sub.2 pump, a CO.sub.2 storage, an integrated cooling/heating system, at least one chemical supply system, wherein the chemical supply system comprises at least one dye, wherein the dye is selected from a polyester dye, pigment, and paints, a processor and software for operating the apparatus, and a control panel for selecting at least one process step.

14. A computer program comprising instructions for operating the stand-alone apparatus according to claim 13, the instructions causing the computer to carry out the following steps: processing leather by subjecting the leather to super critical CO.sub.2 under increased pressure of >7.3 MPa, a temperature of >30° C., during a period of >1 minute, wherein processing comprises (a) drying wet-blue leather,(c) dyeing tanned and dried leather, dying fat-liquored leather, dying-finished leather, (d1) coating leather, and (d2) waterproofing leather.

Description

FIGURES

[0056] The invention although described in detailed explanatory context may be best understood in conjunction with the accompanying figures.

[0057] FIG. 1 shows a schematic overview of the process of obtaining leather.

[0058] FIG. 2a,b shows an example of a fat-liquored leather sample (to the left grain side, to the right flesh side of the leather).

[0059] FIG. 3a,b shows an example of a fat-liquored leather sample (to the left grain side, to the right flesh side of the leather.

[0060] FIG. 4a,b shows an example of dyed CS sample (to the left grain side, to the right flesh side of the leather).

[0061] FIG. 5a,b shows an example of dyed finished leather sample (to the left grain side, to the right flesh side of the leather).

[0062] FIGS. 6a and b show schematic layouts of the present stand-alone apparatus.

[0063] FIGS. 7 and 8 show treated leather.

[0064] FIG. 9 shows leather samples coloured with natural colorants.

DETAILED DESCRIPTION OF THE FIGS.

[0065] In FIG. 1 schematics of leather processing are shown. First the raw product, typically a hide or skin, is pre-processed, amongst others by removing hair. This process is called tanning and does not form part of the present invention.

[0066] The tanned leather, also referred to as wet blue, can then be further processed by drying, forming crust leather, by softening, such as by fat-liquoring, by direct dyeing of the crust or by dyeing of the softened leather, forming a ready to use leather, which may be post-processed, such as by impregnating, coating, and waterproofing.

[0067] FIGS. 2-5a-b show examples of processes leather in various stages of the process.

[0068] FIGS. 6a,b shows an exemplary embodiment of the present apparatus.

[0069] FIG. 7 shows a print of text, whereas FIG. 8 shows an imprint of “flower-like” figures, such as within the oval.

[0070] FIG. 9 shows leather samples coloured with natural colorants. Colours from left to right are red radish, black carrot, lycopene, red rose, and phycocyanin.

Example 1. WB Soaked

[0071] Inventors used supercritical CO.sub.2 as drying media and soaked WB in it. The hide was placed in ethanol bath for 12 h. The soaked WB was hanged inside the autoclave. On the CO.sub.2 line a support, made of textile fibres and soaked in FL, was placed. As fat-liquor, rapeseed's cold pressed oil was used. The amount of oil used for this test was calculated as 10% wt of the soaked leather's weight. The autoclave was provided with a recirculation system.

Example 2. WB Fat-Liquored Without Soaking

[0072] Supercritical CO.sub.2 was used as drying media and non-treated WB was fat-liquored with it. The WB was placed into the autoclave. On the CO.sub.2 line a support, made of textile fibres and soaked in FL, was placed. As fat-liquor, rapeseed's cold pressed oil was used. The amount of oil used for this test was calculated as 10% wt of the soaked leather's weight. The autoclave was provided with a recirculation system.

Example 3.Crust and Dyes

[0073] Supercritical CO.sub.2 was used as dyeing media and CS was dyed with it. The CS was hanged inside the autoclave. On the CO.sub.2 line glass beads were placed, which were covered with dye. The amount of dye, which was used for this test, was calculated as 1% wt. of the leather's weight. The autoclave was provided with CO.sub.2 recirculation. The collected dry dyes can be further stored for later use or re-dispersed into a mixture of matrix materials used for coating or impregnation.

Example 4. Finished Leather

[0074] Supercritical CO.sub.2 was used as dyeing media and finished leather was dyed with it. The finished leather was hanged inside the autoclave. On the CO.sub.2 line glass beads were placed, which were covered with dye. The amount of dye, which was used for this test, was calculated as 1% wt. of the leather's weight. The autoclave was provided with CO.sub.2 recirculation. The collected dry dyes can be further stored for later use or re-dispersed into a mixture of matrix materials used for coating or impregnation.