EP1852529A1

EP1852529A1 - Process for extracting collagen fibres from animal skin tissues and machine for carrying out the process

Info

Publication number: EP1852529A1
Application number: EP06009246A
Authority: EP
Inventors: Alessandro Fratini
Original assignee: Individual
Current assignee: Individual
Priority date: 2006-05-04
Filing date: 2006-05-04
Publication date: 2007-11-07

Abstract

A process for extracting collagen fibres from tissue obtained from animal skin that allows to obtain collagen fibres with high physical and mechanical characteristics necessary for causing its transformation into yarn and fabric by using common plants of the textile industry. The process provides the steps ofpretreating a skin tissue, unravelling the pretreated skin tissue obtaining a mass of loose fibres; tanning the fibres obtained from the unravelling step; treating the tanned fibres and sending the treated fibres to a spinning step. In particular, the unravelling step provides the steps of: introducing in an aqueous solution pieces of said pretreated skin tissue; circulating the aqueous solution the pieces against at least one unravelling roller, frictioning the pieces against said roller, whereby fibres in suspension are gradually formed in said solution, up to forming a product in a bath made completely of loose fibres, i.e. a mass of loose fibres.

Description

Field of the invention

The present invention relates to a process for extracting collagen fibres for use in the textile industry from some products and by-products of the tanning industry, such as pieces of "pelt split" and "fleshings", and in general from other tissue obtained from animal skin.
Furthermore, the invention relates to a machine that carries out this process.

Description of the prior art

As well known, the tanning step a tissue obtained from animal skin, which is carried out with heavy metal salts, with tannin or other tanning products, changes this tissue into leather or hide, causing it to be manageable in working processes.
If it were not tanned, the skin tissue would maintain the features of a soft biological tissue, that could be easily damaged by temperature, bacteria and chemical compounds and would not be useable by the industry.
In order to exploit at best the waste of the tanning industry, many processes have been tested transforming products and by-products and scrap tissue of already tanned animal skin.
A first process provides "milling" the tanned products into small fibre-like particles, generally very short, adapted to covering other textile supports by means of gluing, or mixed with resins and then pressed into "non woven fabric".
However, the products of this process are not adapted to the traditional spinning and weaving operations since very short or irregular in the separation of fibres.
A second type of process provides "Cutting" of the tanned skin into thin strips, then glued in turn with one another, in order to form a continuous thread. This method has, however, the drawback of making thick and heavy threads, not adapted to make light fabrics.
A further process provides "recycling" collagen by means of chemical treatment of materials coming from the slaughtering animals (skins, bones, tendons), or from by-products of the tanning industry (pieces of pelt split and fleshings). The long chains of fibres of collagen are broken into molecules of only collagen by means of breaking of the peptidic links with alkali or enzymes. The elementary collagen is then treated with aldehydes and/or salt metal such as chromium, aluminum, zirconium etc., and/or epoxy compounds, and then extruded. However, also in this case the product that is obtained has a low quality and should be considered as an artificial fibre, in particular, of synthetic fibre.
Some products and by-products of the tanning industry, such as pieces of "pelt split" and "fleshings", but also in general other waste of tissue obtained from animal skin, are rich of collagen, and then are used to make fibres for textile use.
In the textile industry it is common to recycle textile waste such as waste of spinning or weaving processes or already worn garments. For this step the technique is adopted of "unravelling". The machines commonly used for unravelling are not in any case capable of transforming the products of the tanning industry into spinnable fibres.
In fact, using the textile technique of unravelling to obtain a yarn and starting from scraps of leather tanned with chromium, also called "wet-blue pelt", have traditional unravelling machines been used substantially comprising a drum coated outside of steel pins. This drum is caused to rotate near two squeezing cylinders that hold the material being unravelled. The pins of the drum graze this material and tear its fibres. However, the tests made with these machines, using the wet-blue pelt as unravelling material, have given poor results. The material from these product essentially consisting small particles still very compact and several single fibres very very short, impossible to use in spinning.
A particular carding-unravelling machine has been used so-called "garnet", which also comprises a drum coated outside with steel pins that rotates carrying the material to unravel against toothed cylinders located on the circumference of the same. The material, hooked by the pins of the drum, is torn at each passage near the toothed cylinders. Even this solution has given poor results, in particular, very short fibres and small inextricable clots have been produced.
Better results have been obtained using a drum used for tanning leather, suitably coated inside with pins of metal resistant to the chemical corrosion. This drum has been partially filled with an abrasive material and a solution of water, acid and salt of different nature with softening and swelling function, sulphonated oils with the function of lubricants for a better extraction of the fibres from the felt of the skin. When rotating, like a washing machine, the wet-blue pelt is slowly unravelled by the steel pins. The fibres obtained with this drum are of good length and resistance, however the process requires very long time owing to the low unravelling pressure of the steel pins.
In IT2002P000006 , granted as IT1332476 , in the name of the same applicant, already tanned leather is used so-called "wet blue pelt", treated with an acid, in particular, oxalic acid, and then organic salts and inorganic salts used in the tanning industry are added for swelling and relaxing the skin structure. Then, the material is rinsed and a solution is added based on lubricants, such as sulphonate or sulphated oils. Then, the treated skin is passed between carding cylinders. The material thus unravelled is separated from the liquid and rinsed, and then dried. A further carding step is eventually carried out.
In GB 1466058 scrap leather is carded after liming and tanning, and then mixed with dissolved particles and textile fibres or asbestos and eventually spinning. The leather waste comprises pelt, i.e. the softer layer of the skin that is normally discarded.
In GB 1134668 fibres are prepared from collagen coming from tanning residues. It provides the removal of fleshings (subcutaneous connective tissue, fleshing machine offal) from the skin, and a treatment with lime (liming), a possible treatment with acid (pickling) or removing the lime (deliming), possible to use of enzymes, and then the tanning step, with removal of grease before or after tanning. A mechanical disintegration follows in a surplus of water and then unravelling into fibres, partial drying, carding and complete drying, for then proceeding to a spinning into textile fibres with conventional techniques.
However, during the tanning process, which is effected before disintegration, the skin tissue tends to shrink and to compact, complicating the fibres extraction step, the shrinked and tightened fibres, tied to one another, tend to tear than to shrink further. Therefore, the fibres extracted from already tanned skin tissue, leather or hide, as described in the last cited three documents, even if are faster of the technique that gives the better qualitative results that uses drums, are of less quality for a use in the textile industry.

Summary of the invention

It is then a feature of the present invention to provide a process for extracting collagen fibres from tissue obtained from animal skin overcoming the drawbacks of the prior art.
It is another feature of the present invention to provide a process for extracting collagen fibres from tissue obtained from animal skin that allows to obtain collagen fibres with high physical mechanical characteristics and suitable for transformation into yarn and fabric by using common plants of the textile industry, like already possible with other natural, artificial and synthetic fibres.
It is a further feature of the present invention to provide such a process for extracting fibres that is adapted to industrial production processes.
These and other objects are accomplished by the process for extracting collagen fibres from tissue obtained from animal skin comprising the following steps:

pretreating a skin tissue;
unravelling the pretreated skin tissue and preparing a mass of loose fibres;
tanning the fibres obtained from the unravelling step;
treating the tanned fibres and sending the treated fibres to a spinning step.

Advantageously, said unravelling step provides the further steps of:

introducing pieces of said pretreated skin tissue in an aqueous solution;
circulating said aqueous solution and said pieces against at least one unravelling roller, frictioning said pieces against said roller, whereby fibres in suspension are gradually formed in said solution, up to forming a product in a bath made completely of loose fibres.

Preferably, said aqueous solution is slightly acidified water, in particular, with formic acid.
Preferably, said tanning step comprises

adding to said product made of loose fibres an acid solution up to bringing said bath to a pH set between 2,5-3,5;
adding in the solution of said bath a tanning agent, in particular, selected from the group comprised of: heavy metal salts, tannin, unsaturated oils, sulphochlorides, glutaraldehyde.

Preferably, said tanning step comprises furthermore:

circulating the bath for a time set between 1 and 12 hours;
resting the bath for a time set between 12 and 24 hours at a temperature kept between 25 and 40°.

Preferably, said tissue obtained from animal skin is selected from the group comprised of:

pieces of pelt split;
fleshings,
limed skin;
pelt;
pickled skin.

The method as above described gives surprising effects for the fact of extracting the collagen fibres from the skin not yet tanned, i.e. in a status of soft biological and putrescible tissue commonly called "pelt" or "limed pelt" or "pickled pelt" or "fleshings". The skin tissue not yet tanned is like whitish wet and viscid felt of collagen fibres and this typical viscidity has the merit to decrease the sliding friction of the fibres that then can be "carded" without "tearing" them. The tanning step, indispensable for giving physical and mechanical characteristics necessary to the textile industry, is carried out after the extraction of the fibres (unravelling step).
Advantageously, said step of pretreating a skin tissue provides at least one of the following steps:

washing with water for removing soluble salts and the organic impurities,
treating with solvents in close loop for removing grease, which is recycled with a separate process,
treating with diluted acid, in particular, formic, hydrochloric or sulphuric acid, for removing residues of lime deriving from the process of liming executed upstream before the separation from the skin.

Advantageously, said step of treating the carded skin tissue provides at least one of the following steps:

dyeing, dripping and drying the fibres obtained.

According to another aspect of the invention, a fibres extracting apparatus for carrying out the process according to at least one of the above mentioned steps, comprises a unravelling roller having a plurality of pins and an adjustable element adapted to cause said pieces to pass in a forced way against said roller.
Such adjustable element can pass gradually from a first position, where a maximum gap for said pieces is left with respect to said roller, to a second position, where a minimum gap for said pieces is left with respect to said roller.
Advantageously, said circulation is obtained making a closed loop channel along which at least one of said rollers is arranged, the rotation of said or each roller causing a flow that drags the solution, the pieces and the fibres in suspension along said channel.
The apparatus now described, owing to its structure and owing to the fact of working with the method according to the invention, carries out a plastic and progressive of the skin in order to decrease at most the number of torn fibres.

Brief description of the drawings

The invention will be made clearer with the following description of an exemplary embodiment thereof, exemplifying but not limitative, with reference to the attached drawings wherein:

Figure 1 shows diagrammatically a machine that carries out the process for extracting collagen fibres from tissue obtained from animal skin, according to the present invention.
Figure 2 shows diagrammatically in a partial view a possible configuration that can be associated to the machine of figure 1 for unravelling the processed material;
Figure 3 shows diagrammatically in a partial view another configuration that can be associated to the machine of figure 1.

Description of preferred exemplary embodiments.

With reference to figure 1, a machine 150 for extracting collagen fibres from the subcutaneous layer of animal skin comprises a tank 200 in which there are arranged a roller 10a, wheeled about its own axis 11 by a motor 90, and a roller 10b wheeled by means of gears 40a and 40b coaxial to cylinders 10a and 10b, in order to generate a flow 100.
In particular, as shown in detail in figures 2 and 3, each roller 10 is coated outside with metal pins 15 and is immersed for half of its circumference in a housing 30 arranged perpendicularly to the bath flowing path 40.
During the rotation of the roller 10, the pins 15 are to locate alternatively, immersed in the housing 30 or contacting any objects present in the bath flowing path, running for the immersion 31 and emersion 32 edges.
In emersion step the pins 15 hook the material 50 present in the bath and bring it towards the immersion line 31. Near this line a comb 35 is arranged, inclined with respect to the tangential envelope of roller 10. The comb 35 has teeth 36 that penetrate partially the pins 15 of the roller 10 for blocking the material 50 hooked to them.
The rotation of the roller 10 causes this way a movement of material 50 from the emersion edge 32 towards immersion edge 31, generating a circulation 100 of the bath in the tank.
By the circulation of the bath the material 50 encounters an inclined grid 60 that with the bath flowing path creates a funnel in a direction of roller 10. The grid 60 comprises distanced parallel rods in order to leave the liquid to pass along small fractions of material already cut into fibres, and causes larger pieces 50 to flow towards roller 10.
On roller 10 two bars are arranged, one fixed bar 65 and a movable bar 66, which cross all the width of the channel. The rods 65 and 66 with the top part of roller 10, define a bottleneck 80 through which the material 50 is forced to pass. In this bottleneck a compression of the material 50 is created, i.e. a high sliding viscous friction.
This viscous friction causes the material 50 to be kept hooked and dragged by roller 10, causing it to be plastically and progressively divided into fibres.
The occlusion of funnel 80 and then the intensity of friction generated is adjusted by movable rod 66. More in detail, rod 66 has an end 67 hinged to fixed rod 65 and the other end 68 movable and provided with a comb with thick and sharp teeth.
Movable part 66 can then pass, by means of an operating rod 70, from a first position to which a passage gap S1 corresponds (figure 2), when the material 50 to be unravelled is still of large size, to a second position in which the movable part is very close to the pins 15 of roller 10 to which a gap S₂<S₁ corresponds for refining progressively the unravelling step (figure 3).
The invention will now be described in a way not limitative, through the following example.

EXAMPLE

A mass of fibres adapted to the spinning is obtained with the following process.
200 kg of pelt split coming from splitting after liming have been washed in a solution of ammonium sulphate for eliminating part of the residue lime and lowering the pH to up to 7-7.5 and then is cut into pieces with size on average less than 100-200 cm2.
The pieces thus obtained has been immersed in the tank of the machine above described containing a same weight of slightly acidified water with formic acid.
After a few hours of circulation in the tank all the pieces was practically loosened into fibres, in a suspension of separate fibres.
By keeping a gentle circulation to the bath a solution of water, sodium chloride and formic acid has been progressively added up to bringing the bath contained in the tank to a pH 2,8-3.
Then a concentrated solution of a tanning product is added: in this case an acid chromium salt, frequently used by the tanning industry, at a 6% weight ratio of the skin originally loaded in the tank.
A gentle circulating is kept in the bath for on hour and then it is left still to rest for a night at a temperature kept between 30 and 35 degrees.
The next day a large part of the liquid of the bath is discharged, keeping all the solid part with the aid of suitable filters.
To this solid part remained in the tank water has been added in a 70% weight ratio of the originally loaded skin and a gentle circulation is re-established.
Progressively, at 15 minutes intervals, a solution of water and ammonium bicarbonate is added, rising the pH, up to reaching pH 5, considered optimal in the tanning practice, and then grease is added, in this case made with a further addition of a commercial product called Likersol (a sulphonated oil) at a 18% weight ratio of the skin originally loaded.
A gentle circulation is kept for about one hour and finally discharged in a carriage having a thick grid, located on the bottom, dripping the liquid surplus and keeping the fibres.
After dripping the fibres are put in a centrifugal extractor for spin drying them and then brought on a conveyor belt to be dried in warm air without coming to a complete dried condition.
The drying step is then completed maintaining the fibres in a chamber with gently circulating warm air for about 24 hours.
The mass of fibres is then carded, spinned, woven, dyed and refined with very good results, using common plants of the textile industry.
The foregoing description of a specific embodiment will so fully reveal the invention according to the conceptual point of view, so that others, by applying current knowledge, will be able to modify and/or adapt for various applications such an embodiment without further research and without parting from the invention, and it is therefore to be understood that such adaptations and modifications will have to be considered as equivalent to the specific embodiment. The means and the materials to realise the different functions described herein could have a different nature without, for this reason, departing from the field of the invention. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation.

Claims

A process for extracting collagen fibres from tissue obtained from animal skin comprising the following steps:
- pretreating a skin tissue;

- unravelling the pretreated skin tissue and preparing a mass of loose fibres;

- tanning said loose fibres obtained after said unravelling step;

- treating the tanned fibres and sending the treated fibres to a spinning step.
Process for extracting fibres according to claim 1, wherein said unravelling step provides the steps of:
- introducing pieces of said pretreated skin tissue in an aqueous solution;

- circulating said aqueous solution and said pieces against at least one unravelling roller, frictioning said pieces against said roller, whereby fibres in suspension are gradually formed in said solution, up to forming a product in a bath made completely of loose fibres.
Process for extracting fibres according to claim 1, wherein said aqueous solution is slightly acidified water, in particular, with formic acid.
Process for extracting fibres according to claim 1, wherein said tanning step comprises:
- adding to said product made of loose fibres an acid solution up to bringing said bath to a pH set between 2,5-3,5;

- adding in the solution a tanning agent, in particular, selected from the group comprised of: heavy metal salts, tannin, unsaturated oils, sulphochlorides, glutaraldehyde.
Process for extracting fibres according to claim 1, wherein said tissue obtained from animal skin is selected from the group comprised of:
- pieces of pelt split;

- fleshings,

- limed skin;

- pelt;

- pickled skin.
Process for extracting fibres according to claim 1, wherein said step of pretreating a skin tissue provides at least one of the following steps:
- washing with water for removing soluble salts and the organic impurities,

- treating with solvents in close loop for removing grease, which is recycled with a separate process,

- treating with diluted acid, in particular, formic, hydrochloric or sulphuric acid, for removing residues of lime deriving from the process of liming executed upstream before the separation from the skin;
Process for extracting fibres according to claim 1, wherein said step of treating the carded skin tissue provides at least one of the following steps:
- dyeing, dripping and drying the fibres obtained.
Fibres extracting apparatus for carrying out the process according to the previous claims, comprising a unravelling roller having a plurality of pins and an adjustable element adapted to cause said pieces to pass in a forced way against said roller.
Fibres extracting apparatus according to claim 9, wherein said adjustable element can pass gradually from a first position, where a maximum gap for said pieces is left with respect to said roller, to a second position, where a minimum gap for said pieces is left with respect to said roller.
Fibres extracting apparatus according to claim 9, wherein said circulation is obtained making a closed loop channel along which at least one unravelling roller is arranged, the rotation of said or each roller causing a flow that drags said solution, said pieces and fibres in suspension along said closed loop channel.