DD284695A5 - ENVIRONMENTALLY FRIENDLY PROCESS FOR SHEETING RAW ANIMAL SKIN AND SKIN - Google Patents

Abstract

The invention relates to an environmentally friendly method for AEschern of raw animal Haeuten and skins. The invention relates to a gerbvorbereitendes sub-area of leather production. It is based on the task and technical effect, without alkali sulfides, so sulfide-free, from the raw animal flax and hides the epidermis and hair in a few hours and in the fascia to remove, so that can be made from the resulting blooming high quality grain leather. The invention provides a two-stage AEscherverfahren. The first stage is carried out with hydrogen peroxide in an alkaline medium. It loosens or removes the keratin without damaging the collagen fibers of the scar surface as well as complete skin degeneration and is therefore interrupted at the earliest possible time by deflating and rinsing (washing) the skin material. The second stage, a white calcareous, finishes its scar cleansing and skin digestion. Their duration depends on the cleanliness of the scar surface achieved in the first stage and the desired skin disruption. Environment; animal skin and fur; liming; sulphide-free; fasz; hydrogen peroxide; alkaline medium; Weiszkalkaescher; Grain leather}

Description

Field of application of the invention

The invention relates to the field of leather production and has an environmentally friendly process for liming all crude animal hides and skins customary for the manufacture of leather.

It can be used in all plants that prepare raw animal skins and skins by depilating, debarking or unwilling to tan.

Characteristic of the known state of the art

The liming of raw animal hides and skins has to ensure that after its implementation, the then present pelts are thoroughly depilated without damaging their scar surface and have one of the respective leather to be produced sufficient skin digestion and thereby high quality leather and high yield can be produced from them ,

It relies largely on the cost-effective and proven exposure of certain chemicals to their two most important proteins, the highly resistant Keration and the collagen, in the strongly alkaline medium (Dr. Pauligk et al., Lederherstellung, I.Auflage, VEB Fachbuchverlag Leipzig, 1979, p. 87 and 88).

Particularly reaction-safe, cheap, simple and in the barrel act sodium sulfide and / or sodium hydrogen sulfide in the presence of calcium hydroxide. Therefore, despite the ecological disadvantage of sodium sulfide and / or sodium hydrosulfide, which has recently become more evident, and repeated attempts at their replacement, they have found widest application in the tanneries for decades, especially as lime-sulphide limerack (Prof. Dr. Stather, Gerbereichemie und Gerbereitechnologie, 4th edition, Akademie-Verlag Berlin, 1967, p 173, The Leather, Darmstadt 1967 8, p 184, ibid, 1987 3, p48, ibid, 1987 7, p 143). However, this can not mean to overlook that the vast majority of the highly toxic and oxygen-consuming sodium sulfide and / or sodium hydrosulfide used for the liming of the raw animal hides and skins pass unchanged into the tannery wastewater and thereby burdened it considerably. The installation and maintenance of complex sulphide recovery and desulphurisation plants are necessary if the characteristics of the tannery wastewater are or have to comply with the legal requirements. In addition, protective measures are indicated because, when handling sodium sulphide and / or sodium hydrosulphide, hydrogen sulphide may be produced before, during and after the liming of the raw animal hides and skins and may endanger the health of the workforce. Usually this is done by sucking the hydrogen sulfide from the production rooms to the atmosphere. This damages them and, as in the case of tannery waste, ultimately forces them to use expensive disposal facilities.

It is therefore no coincidence that the growing interest in technical solutions for the sulphide-free or low-sulphide liming of the raw animal hides and skins used for the production of leather is an urgent economic need. In addition, they should not swell and walk unduly in order to keep their scar surface smooth and firm (Das Leder, Darmstadt 1987 3, p. 48).

Sulfide-free technologies, which in a few hours lead to complete keratin degradation, but have not been able to prevail. Lack of efficiency, no or only inadequate use of the barrel and excessive scar drive are for the most part cited as causes and defects (ibid., Pp. 48-56, ibid., 1987 7, p. 143). According to the prevailing expert opinion, they should not be expected in the foreseeable future (LSL, Leipzig 1984 6, p. 265). The still continuing search for this more suitable options also detected hydrogen peroxide, a strong oxidizing agent with ecologically favorable decomposition products, which has long been advantageous use for the bleaching of various fibers.

alkaline medium has been described.

Firstly, skin material was treated at pH values between 11.5 and 13.5 with 1 to 3% hydrogen peroxide, based on skin mass, and characterized after 4 to 12 hours for skin disruption (Kozevenno-obuvnaja promyslennost, Moscow 1985 5, p. 40, 41 and 42).

On the other hand, it was found that the reaction of the hydrogen peroxide with the melanin and the disulfide compounds of keratin takes place at 25 to 30 ⁰ C and after 3.5 to 4 hours is completed (IVUZ, Kiev 1985 6, pp. 50, 51 and S2 ). For reworking these two experiments, it lacks essential parameters, such as the ratio of skin mass to liquor volume, which could, among other things, answer the important question of the effective hydrogen peroxide concentrations. Above all, the lack of statements on the quality of the scar surface is critical. It represents a defect insofar

because a completely cleaned of epidermis and all hair scar surface without nubuck effect is the basic requirement for the production of high-quality grain leather. The nubuck effect, usually recognizable only after drying of the leather, can be defined at this point as the effect of the already existing destruction of fine collagen fibers on the surface of the scar.

Obviously, it was not the stated goal of these experiments to convert the skin material treated with hydrogen peroxide in the alkaline medium into leather.

In addition, the problems of the manufacturers of grain leather from raw animal hides and skins after exposure to hydrogen peroxide in an alkaline medium are clarified by a present invention application (SU 1086014). It suggests the rapid and intense destruction of the collagen fibers of the scar surface of skin material by this same chemical.

Thus, the known state of the art does not yet provide sufficient information as to whether and how the raw animal skins and skins intended for the production of leather can be cremated with hydrogen peroxide in an alkaline medium.

Object of the invention

It is the object of the invention to develop an environmentally friendly process for liming the raw animal hides and skins intended for the production of leather with significantly lower contamination of the tannery waste water compared to the known state of the art.

As a result, the effort for the disposal of tannery waste water and the exhaust air to be reduced and the working conditions can be improved.

The quality and the surface yield of the leather produced by this process must at least meet the current requirements.

Explanation of the essence of the invention

The lack of the known state of the art for producing grain leather by treating the raw animal skins and skins provided with hydrogen peroxide in the alkaline medium in the absence of a proposal for complete Keratinentfernung without damaging the collagen fibers of their scar surface. As a rule, such work leads to their nubucking or total destruction.

The technical problem is therefore to develop a method with which it is possible, using hydrogen peroxide in an alkaline medium and calcium hydroxide and sodium sulfide and / or sodium hydrogen sulfide within a few hours, the epidermis and hair of the intended for the production of leather raw animal Remove hides and skins so that high quality grain leather can be made from the resulting pelts. According to the invention, this object can be achieved by a two-stage liming process.

In the first stage, the raw animal hides or skins are treated after being soaked with hydrogen peroxide in an alkaline medium. The technological parameters found for this effect the substantial or complete removal of the keratin. Adequate skin disruption is not sought in this first stage. Rather, it is important to stop them in time to protect the collagen fibers of the scar surface from damage. These are 1 to 3 hours treatment time of the skin material in 2.5 to 10% sodium hydroxide solution containing up to 3 parts by mass (MT), preferably 2 MT, hydrogen peroxide (100%), at a liquor volume of 30 to 150MT and a temperature of 20 to 32 ⁰ C required. Thereafter, the first stage liquor is discarded and the skin material rinsed.

In the second stage, keratin removal and skin digestion are completed with 1 to 4 MT calcium hydroxide in 50 to 300 MT liquor and the skin material rendered slippery by the alkali treatment is blunted to better handle it in subsequent mechanical operations. Depending on the cleanliness of the scar surface achieved in the first stage and the desired skin disruption of the depilated animal hides or skins, the second stage may range from intensive rinsing to a whitewash raker lasting several days. Normally it lasts at 25 to 32 ° C to 6 hours. All stated parts by weight always refer to the skin mass. The same applies to the following embodiments.

embodiment

The invention will be explained in more detail below with reference to preferred embodiments

example 1

Type of leather: full grain cowhide, soft quality

Tools: Drum made of stainless steel, float temperature adjustable

Skin material: 300 kg black-colored, pre-stained, saline-layer-preserved bullskins of the mass class 25 to 29.5 kg

Vorweiche: 200 MT water of 30 ⁰ C

0,5MTTensid

30 minutes at 30 ⁰ C fleet temperature, then discard fleet Main switch: 130 MT water from 30 ⁰ C

0,5MTTensid

210 minutes at 30 ⁰ C fleet temperature, then discard fleet

1st limber: 70 MT of water at 24 ⁰ C

6 kg of hydrogen peroxide (100%) 9 kg of sodium hydroxide (100%) 150 minutes at 6 U / min

Thereafter, the epidermis and hair are destroyed and the liquor temperature to 31 ° C and the pH

increased to 11.2. The fleet is frothy and looks reddish brown. She is rejected.

The bullskins are very slippery. There is something else on her scar surface

Keratinschlamm. Its swelling state is similar to that after a mild lime-sulphide liming. 2. Cutter Level: Wash with

150 MT of water from 30 ⁰ C15 minutes

150MTWaterfrom30 ° C3MTCalziumhydroxide240 minutes at 6rpm and 15 minutes of exercise and 30 minutes rest, then discard liquor and drain skin material

Further work / The so-limed bullskins are as pelts in comparison to the conventional lime-sulphide limers of light finished leather: and cleaner and are therefore also better for trimming in light shades.

They are easily defiled, split and usually too soft full grain cowhide

to process.

Their area is 5% larger than the parallel with lime and sulfide limed bullskin. example Type of leather: Piggy bank leather Work equipment: Stainless steel barrel, float temperature adjustable Skin material: 250 kg white-bristled, well-seeded, fresh pigskin croupons Vorweiche: 200 MT water of 30 ⁰ C

0,5MTTensid

30 minutes at 30 ⁰ C fleet temperature, then discard fleet Main diverter: 130 MT of water at 30 ° C

0,5MTTensid

210 minutes at 30 ° C fleet temperature, then discard fleet

1st limber: 100 m of water at 20 ° C

5.5 kg of hydrogen peroxide (100%) 8 kg of sodium hydroxide (100%) for 120 minutes at 6 rpm

Thereafter, the epidermis and the bristles are destroyed and the float temperature to 29 ° C and the pH

rose to 11.1.

The fleet is frothy and looks whitish-cloudy. She is rejected.

2nd limber: wash with

160 MT of water from 32 ⁰ C15 minutes

200 m of water from 32 ⁰ C3,5 MT of calcium hydroxide for 30 minutes at 6 rpm, then discard the liquor and empty the skin material or continue in the same vessel until chrome is tanned

Further work / The so-limed Schweinshautcroupons are as pelts very bright and clean. They can be processed without finished leather: difficulties to piggy bank leather. Their area is 3% larger than the parallel

with lime and sulphide limed pigskin croupons.

Example 3 Type of leather: cowhide leather Working equipment: barrel made of polyester resin, float temperature adjustable Skin material: 100 kg black colored, uncut, wet-salted bull skins of the mass class 30 to 39.5 kg Vorweiche: 200 MT water of 30 ⁰ C

0,5MTTensid

30 minutes at 30 ° C liquor temperature, then discard fleet Main switch: 130 MT of water from 30 ⁰ C

0,5MTTensid

Addition of an enzymatic softening agent (50 TE _cas / kg skin substance)

720 minutes at 30 ⁰ C fleet temperature and alternating 10 minutes of exercise and 50 minutes

Rest, then discard fleet 1st limber: 80 MT of water from 27 ⁰ C

1.8 M hydrogen peroxide (100%) 2.8 M potassium hydroxide (100%) 90 minutes at 10 rpm

Thereafter, the epidermis and hair are destroyed and the liquor temperature to 31 ° C and the pH

rose to 11.3. The fleet is frothy and looks reddish brown. She is rejected.

The bullskins are very slippery. There is some keratinous mud on her scar surface.

Fleshing / Dulling Washing with

Columns: 150 m of water at 30 ° C

10 minutes and 150 MT lime milk of 28 ° C

10 minutes, then discard liquor and empty main material as well as defile and split 2. Ashtray: 140 MT water of 32 ° C

3MTCalziumhydroxid

360 minutes at 10 rpm, then discard fleet and empty main material Continue working / The so corked bullskins as pelts are strikingly bright and clean. Finished leather: They can be easily processed into cowhide leather.

Their remarkable softness and tack suggests a better surface yield than the lime-sulphide limer.

Claims (2)

1. Environmentally friendly method for liming raw animal hides and skins in the fresh or wet state and in the barrel, characterized in that the skins or skins in a first stage with 30 to 150 parts by mass of the skin, based on the skin mass, the 2.5 to 10% sodium hydroxide solution and 1 to 3 parts by weight, preferably 2 parts by weight, of hydrogen peroxide (100%), based on the skin mass, treated at a temperature of 20 to 32 ° C for a period of 1 to 3 hours and after discarding the fleet in a second stage, a Weißkalkäscher, scar cleansing and skin digestion of the pelvic and finished the skin material are dulled. 2. Environmentally friendly method for liming according to claim!, Characterized in that potassium hydroxide is used as the alkali.