EP1045039B1 - Method for the preparation of leather from fish skin - Google Patents

Abstract

A process for the production of leather from fish skin uses undecomposed skin and involves (a) washing/degreasing with alcoh (b) descaling with enzymes, (c) alkaline digestion at not above 18 degrees C followed by decalcification and (d) tanning with sa solution plus organic acids and tanning agents, drying and lubricating with cationic agents.

Description

The invention relates to a method for producing leather from fish skin.

The purpose of the invention is the production of a fish leather, in which the natural Preserve structures, species-specific drawings and colors as far as possible stay.

A few years ago, leather made from reptile skin was very fashionable. The skins were mostly obtained from wild animals. This made some snake species almost eradicated, which has led to their protection status.

Due to the Washington Protection Convention, the import is numerous species of snakes or their skins are prohibited. Some types of snakes are propagated on farms. Nevertheless, there is interest in snakeskin declined.

The fish form the most diverse group of the animal kingdom. There is more than 24,000 species of fish, a large number of which are either commercial fish the waters, namely from the sea, from lakes and rivers, caught or in Ponds are created for consumption. All of these fish species are not legal protected so that no problems with the natural and Animal welfare laws can arise. In addition, the raw material is currently Fish skin is not used intensively. The skin of the fish is either at the Preparation of food with recycled or disposed of as a waste product.

The skin of the individual fish species is structured very differently. The Scale pattern, scale size, drawings and colors are species-specific. Even if you only get fish leather from all large, useful fish would be an almost inexhaustible, wide range for the fashion industry different leathers with different drawings, different structures and different color variations available. If you count less, but species not protected by law, exclusive leather products can also be found on the Market. Protected and endangered fish species can in relation to the wide variety of unprotected fish species be careful.

The exclusivity of fish leather is emphasized by the fact that Every product is an original because every single specimen of a fish species shows certain individual differences. The authenticity of the fish leather product can by means of the sideline organ, which no other family in the animal kingdom happens to be recognized with certainty.

That fish leather is currently neglected by the leather and fashion industry is due to the fact that the fish leather by previously known tanning methods is devalued. The scaly pockets are injured and the natural ones Structures such as coloring and species-specific drawings are destroyed. Moreover the fish-typical smell is not permanently removed.

The production of leather from fish skin is known from EP-B-0 285 738 and EP-A-0 575 632, as well as from US-A-4 379 708, 4 755 186 and 4 877 410. In the known methods of dried or salted skin, that is dead tissue, ran out, as is usual in the tannery. The Descaling is done mechanically. In addition, only with anionic fatliquors worked. In this leather production, the natural pigments destroyed and scaly pockets injured. The leather must then be colored with artificial colors when dressing, so that the species-specific Character of the fish leather as color and structure is destroyed.

The process according to the invention is intended to protect the natural structures of the Fish skin, especially the color and drawing, remain undamaged. The The method according to the invention is characterized in that fresh or frozen fish skin used in this state, in which after the death of the Fischs has not yet decomposed, and the fish skin with the help of Alcohol washes and degreases, descaled with the help of enzymes, so far present intermediate product with the help of alkaline substances at a temperature skin digestion of no more than 18 ° C and then descaling, it using saline and adding organic acids and tanned from tannins and then faded and mostly with cationic Means greasy.

The method according to the invention for the production of fish leather with natural coloring and structure based on a preferred implementation on the production from fresh fish skin or on the preservation of the fish skin in the fresh state with shock freezing process, removal of meat, fatty tissue and subcutaneous tissue (fleshing), washing and desquamation with the help of Enzymes and, if necessary, mechanical desquamation, digestion with alkaline substances and their removal by washing and so-called descaling, Acidification of the fish skin (pimples or conditioning), tanning and Greasing with a mixture of cationic and anionic greasing agents. It preferably also includes a new type of dressing with which the leather surface is treated so that the scales pockets when processing the Leather, e.g. B. when sewing products, do not solve, so can get up.

Below are examples of different variations of fish leather manufacturing and described the related processes.

In principle, only fresh fish skins are used for leather production. For later leather production, they are first used in the food industry frozen blast freeze. The skinned fish skins are packed in plastic bags and at a temperature of -30 ° C to -18 ° C frozen, the layer of fish skins intended for freezing should not exceed approx. 20 cm thick. The short-term storage of the Fish skin can then be done at a lower temperature (-3 ° C to -1 ° C).

Only the fish skins are suitable for further processing Process of autolysis, that is the natural process of self-digestion after Death of the organism, has not yet started. At this stage, when the Rigid to death, the tissue is still opposed by the body's enzymes Protects bacteria and fungi and is also more resistant than dead tissue against the attack of the enzymes that occur during desquamation Invention are used.

On the basis of the invention, it is possible to produce a fish leather in which the natural structures such as pigments and colors are largely preserved. Fresh or frozen and thawed fish skins are z. B. with the help of a Meat removal machine such as a meat removal cylinder with a working width of approx. 75 cm of muscle, fat and subcutaneous tissue. In the usual meat removal machines in the leather industry, consisting of a Pressure roller and a knife roller, the skins must be turned.

After fleshing, the fish skin is washed and degreased, thereby the smell of fish is eliminated. The wash solution is based on the weight of the fish skin from 200 to 300% water, 2 to 3% Supralan 80® (fatty alcohol ethoxylate) and / or 1 to 3% Supralan UF® (BASF AG) (fatty alcohol polyglycol ether) or 2 to 3% Baymol AN® (Bayer AG) (non-ionic emulsifier). The temperature should do not exceed 3 ° C. Duration about 30 minutes. With the above and The following percentages are based on the following scheme: 100 kg Fish skins correspond to 100%, 1% of the detergents, tannins, Salt, acids corresponds to 1 kg.

In the subsequent process, the fish skin is broken down with the help of the enzymes. For the enzymatic desquamation, 0.2 to 1.0% Oropon® (Röhm AG) (proteolytic enzymes based on pancreas) or the same amount Basozyme® (Bayer AG) (mixture of bacterial enzymes with descaling salts) used. The duration of the treatment is 20 to 90 minutes depending on the type of fish, z. B. Salmon 10 to 45 minutes, carp 20 to 75 minutes. The temperature of the Solution should be 33 ° C to 37 ° C and the pH between 7 and 9. The Fleet length 200 to 300%.

Some fish species have mechanical and enzymatic desquamation required. Before the actual tanning, the fish skins are removed with the help of open to alkaline substances. This is done with the help of a pre-washer (1 to 3% NaOH, liquor length 200% to 300%, duration 20 to 180 minutes) and one Nachaschers (4% CaOH, fleet length 200% to 300%, duration 24 to 120 hours). The temperature of the liquor must not exceed 18 ° C in both processes. The preferred temperature is 15 ° C.

Three methods are used for descaling. The first method: Extensive rinsing with water when the skins move continuously.

Second method: treatment with organic acids, such as vinegar or Formic acid, titration in small doses until a pH of 6.0 is stabilized. Fleet length 200 to 300%, duration 3 to 4 hours.

Third method: treatment with acidic salts of multivalent aromatic Acids, e.g. B. Decaltal N® (BASF AG). Add in small doses until the pH is stabilized at 6.0. Fleet length 200 to 300%, duration 12 hours, e.g. B. about Night.

The fish skins are pickled for optimal absorption of the tannins (Acidified). Before that, the fish skins are soaked in a solution for 15 to 60 minutes, consisting of 200 to 300% water and 60 to 100 g NaCl per liter, (equivalent of at least 6 B). After this time, the solution becomes organic Acids such as formic acid and acetic acid diluted 1:10 are added until a pH the solution from 3.0 to 4.0 is achieved. The pimple time depends on Fish species up to 48 hours.

After this time, the fish skins are ready for the actual one Tanning. It consists of the addition of mineral tannins such as chromoder Aluminum solutions, vegetable tanning solutions such as Mimosa, Valonea, Chestnut extracts etc., synthetic tanning agents, phenol, aldehyde, resin and Kombinationsgerbstoffen.

In the case of chrome tanning, the chemicals are preferably added in succession to the pickling liquor, the pH of which is 3.0 to 4.0: 1 to 2% aluminum tanning agent, namely Al ₂ O ₃ .3H ₂ O aluminum hydroxide, e.g. B. Novaltan AL® (Zschimmer & Schwarz GmbH) or Lutan BN® (BASF AG). This is followed by 7% chromium tanning agent, namely CrO ₂ , e.g. B. Chromitan B® (BASF AG) or a chromium sulfate known as Chromosal B® (Bayer AG) and / or 1 to 4% combination tanning agent chromium-syntan, e.g. B. Basyntan CN® (BASF AG). One hour before the end of the tanning, 1% Implenal AP® (BASF AG), a mixture of dicarboxylic acid salts, is added. The entire tanning process takes 24 hours.

Tanned leather is dulled with the help of 1 to 3% NaHCO ₃ (sodium hydrogen carbonate) or 2 to 3% NaHC00 (sodium formate), wilted and for approx. 12 to 48 hours, e.g. B. overnight on the goat. Afterwards, the leather is dulled again to a pH of 3.8 to 4.0, wilted and greased with the help of a hammer grease gun. A mixture of 15% Lipamin Licker SO® (BASF AG), a cationic fatliquor, and 5% Pelgrassol SF® (Zschimmer & Schwarz GmbH), an anionic fatliquor, is used for fatliquoring.

Dried leather is stollen, that is, softened, and can be used in it Condition can be used immediately. For certain purposes, it will be used after Stollen prepared. When dressing, there are several on the leather surface Lacquer coats applied. The first layer - the base layer - is applied that the paint, e.g. B. a mixture of 200 parts of Astacin-Grund UH® (BASF AG), an anionic polyurethane dispersion, + 780 parts water + 20 parts Astacin Finish PUM®, an anionic polyester-polyurethane dispersion, (BASF AG), in the shed pockets. The paint is brushed against the scale direction is applied, after which the scales pockets in reverse Direction to be smoothed again. After the base layer has dried, two Binding layers applied, the first in the same way as the base layer with Using a brush, and the second is done after repeated drying using a Spray device applied. The binding layers are e.g. B. a mixture of 100 Parts of Lepton Binder SD®, an acrylic-based copolymer, + 450 parts of water + Corial Grund OHN®, a polyacrylate dispersion + 100 parts of Astacin Finish PUM® (BASF AG), an aqueous anionic polyacrylate dispersion.

After each lacquer application, the leather is dried and then the dried leather is ironed at a temperature of 50 to 80 ° C. at a pressure of 20 · 10 ⁶ Pa (200 bar) for 3 to 10 seconds in an ironing press. The components of time, pressure and temperature are coordinated with one another depending on the desired leather quality, with less of one of the components being able to be compensated to a certain extent by more of another of the components. So you can z. B. increase two of these components and decrease one to achieve the same result. The optimal values of the components depend on the respective fish.

Two cover layers are then applied to the binding layers with the help applied to a sprayer and ironed again. For a matt surface z. B. a mixture of 500 parts of Astacin Mattierung MT®, an aqueous anionic dispersion of an acrylic polymer and polyester urethane, + 490 parts Water + 20 parts of Astacin Finish PUM® (BASF AF), an aqueous anionic Polyester-polyurethane dispersion, and for a shiny surface such. B. a Mixture with Astacin Top LB®, a dispersion of 500 parts of an aliphatic Polyurethane and the same amounts of other additives in matt painting used.

As described under the chrome tanning, the lacquered leather can - like described below - retanned:

200 to 300% water are added 20 g / l sodium chloride and 6 to 10 % white phenol containing phenol, e.g. B. Basyntan DLX® (BASF AG) in 3 to 4 servings, depending on the 30 minutes. The pH of the liquor is 3.8 and the tanning time is 8 to 12 hours. Then wilting and processing, as with the mineral Tanning described. This tanning method creates a white leather with light bluish tone. It corresponds to the natural color of the salmon and has that Quality of the gallantry leather.

In order to achieve the quality of a shoe upper leather, at a pH value from 3.6 to 3.8 gluten dialdehyde, e.g. B. Relugan GT 50® (BASF AG), directly into the Fleet of white tannins, e.g. B. from phenol-containing tannin added. The Leather gets a slightly yellowish tone, especially along the sideline is made clear. The leather becomes fuller, but loses speed.

Some people want leather on the market that is made with vegetable Tannins have been tanned. Below are two examples for completeness listed:

Leather that had previously been pickled is dulled to a pH of 4.3 to 4.5. The liquor length is 200 to 300%, there are 30 to 60 g / l sodium chloride and 2% phenol-containing tanning agent, e.g. B. Basyntan N® (BASF AG), in three doses each Added 30 minutes. This is followed by 7% vegetable tanning agent; z. B. gives Mimosa a leather dyed pink, quebracho a reddish tinge, sumac an ivory color, Tara a white color, Valonea a brown color. The herbal Tannin is added in four doses, two hours in a row. The tanning time is about 12 hours, e.g. B. overnight. The pH value of the leather is about 4.0 set to 4.5, then rinsed slightly, wilted and further processed, e.g. B. greased, dried, rolled and trimmed.

Alternatively, mineral-pretanned leather with vegetable substances be retanned. Leather dulled to a pH of 4.0 to 4.3 implemented in a new fleet, the pH of which is 4.3 to 4.5. The fleet length is 200 to 300%, 30 to 60 g / l sodium chloride are dissolved in this liquor and 7% vegetable tanning agent in four doses of two hours each. The tanning time is about 12 hours, e.g. B. overnight, whereupon the leather as described above is processed, e.g. B. greased, dried, rolled and trimmed becomes. This is how gallantry leather is produced. Becomes a shoe upper desired, after tanning with vegetable tanning agents, the leather can be used without Flushing after wilting in a new fleet can be tanned as follows:

Fleet length 200 to 300%, 20 to 60 g / l sodium chloride and 6% combination tanning agent chrome-sytan, e.g. B. Basyntan CD® (BASF AG) in four Cans in a row for 30 minutes. The tanning time is 8 to 12 hours, e.g. B. over night.

The tanning described above represents general parameters, ie Basic tanning, through special controls of the tanning process and the subsequent dressing can be more specific as needed and desired Types of leather are produced. With the present tanning process, e.g. B. Upholstery leather, gallantry leather (soft and fine leather), upper leather or clothing leather be generated.

Claims (13)

1. Process for making leather from fish skin, characterized in that fish skin is used in which no decomposition has begun after the death of the fish and

   a) the fish skin is washed and degreased with the help of alcohols,

   b) it is descaled with the help of enzymes,

   c) an opening up of the skin is carried out on the intermediate product so far obtained with the help of alkaline substances at a temperature of not more than 18°C and then it is delimed,

   d) it is tanned using a sodium chloride solution and adding organic acids and tannins and then sammed and greased predominantly with cationic agents.
2. Process according to claim 1, characterized in that the fresh, fleshed fish skins are preserved by shock-freezing methods in the stadium of rigor mortis thus avoiding the start of the autolytic process of the fish skin tissue and are stocked in their frozen state in order to later begin with step a) after defrosting them.
3. Process according to claim 1 or 2, characterized in that the washing and degreasing of the fish skin is carried out with a 1 to 3 % solution of the alcohols, thus removing the typical smell of fish skin.
4. Process according to any one of claims 1 to 3, characterized in that after the descaling of the fish skin with the help of the enzymes a mechanical descaling is carried out if necessary.
5. Process according to any one of claims 1 to 4, characterized in that the opening up of the skin is carried out with the help of pre-liming with a 1 to 3 % solution of NaOH during 20 to 180 minutes and with the help of post-liming with a 4 % solution of CaOH during 24 to 120 hours, wherein the quantity of float of both limings amounts to 200 to 300 % and the temperature of the solution preferably is between 14°C and 16°C, and the fish skin is washed with water and delimed to a pH value of 6.0 by means of titration with organic acids.
6. Process according to any one of claims 1 to 5, characterized in that for tanning the fish skin the sodium chloride solution is applied with a quantity of float of 200 to 300 %, adding 60 to 100 g of NaCl = equivalent of at least 6 B and the organic acids are added by titration to a pH value of 3.0 to 4.0, preferably 3.5.
7. Process according to claim 6, characterized in that for the tanning, mineral tannins, vegetable tannins, phenolic tannins, resin tannins, aldehyde tannins and combination tannins are used.
8. Process according to claim 6, characterized in that for the tanning, mineral solutions of chrome or aluminium tannins or of combination tannins as well as aldehyde tannins are added.
9. Process according to claim 8, characterized in that the pre-tanned leather is put into a new float consisting of phenolic white tannins, wherein aldehydes are added into the float if necessary.
10. Process according to any one of claims 1 to 9, characterized in that the sammed leather is greased with a mixture of cationic and anionic agents, i.e. preferably with a mixture of 15 % of cationic and 5 % of anionic agents, calculated on the basis of the weight of the sammed leather.
11. Process according to any one of claims 1 to 10, characterized in that the leather surface is dressed after the samming and greasing and after the drying and staking.
12. Process according to claim 11, characterized in that, in order to avoid that the scale pockets stand up during the subsequent processing, the leather surface is lacquered and then is coated with a base coating, two binder coatings and two top coatings, consisting of water-soluble lacquer emulsions, and that these coatings are welded together at a temperature of 50 to 80°C in an ironing press.
13. Process according to claim 12, characterized in that the coatings are applied to the leather surface as follows:

    a) as the base coating an aqueous solution of anionic polyurethane dispersion and anionic polyester polyurethane dispersion is applied;

    b) after the drying of the base coating the two binder coatings consisting of a mixture of a copolymer on acryl basis, a polyacrylate dispersion and an aqueous anionic polyester polyurethane dispersion are applied;

    c) after the drying of the two binder coatings the insofar obtained leather is ironed and coated with the two top coatings, wherein an aqueous solution of an anionic dispersion of an acryl polymer and polyester urethane with aqueous anionic polyester polyurethane dispersion is applied and is repeatedly welded together with the binder coating by means of ironing.