DE2059453C - Process for soaking hides or skins - Google Patents

Description

Among the numerous process steps involved in leather production, the operations in the water workshop are of decisive importance for the quality of the leather obtained. At the beginning of these ao operations there is the switch. Its task is to bring the raw hides and skins, which are in dried or salted form, into a state of swelling, as it was at the time of slaughter. In the simplest case, the switch consists of storing the pelts or hides in water. To accelerate the switch, however, mesh center ¹ or proteolytic enzymes are often added. But even with the use of such aids, the soak lasts so long - especially in the case of dried goods - that putrefactive bacteria can grow. The enzymes produced by these exert a damaging influence on the skin material, since the bacterial growth takes place unevenly and in an uncontrolled manner. Germicidal preservatives are therefore often added, but these in turn can impair the desired effect of the added enzymes. Preservatives that have this harmful side effect ■ light and are effective in low concentrations are relatively expensive and add to the process costs.

The unwanted bacterial growth can be avoided if one is in the strongly acidic or starl ' alkaline range works. However, this was previously not possible, as strong acids damage from hydrolytic Splitting of the main material and strong alkalis cause undesirable swelling. Too much swelling makes it difficult to loosen the hair and dissolve the cause in the skin Soft following operations. In German patents 288 095 and 369 587, Softening method using pancreatic enzymes described, using the soft liquor can also reach pH values above 10 according to the specified compositions. These procedures However, because of the swelling that occurs, they have no practical significance, especially the duration of the soak with 1 to 2 days is still relatively long. According to British patent specification 474 991, a papain-containing Soft liquor is used, which has a pH value of 9.5. The alkaline swelling is with this procedure a little less than the previous ones. A satisfactory ground loosening is however with all three mentioned procedure not achieved.

It has now been found that the strong swelling in the soft in the alkaline area by the Can avoid the addition of certain enzymes. At the same time, the soaking time is compared to the known Procedure reduced to a third to a quarter and a basic loosening enables the subject of the The invention is therefore a method for soaking pelts and hides, wherein the soaking in a pH between 10 and 12 in the presence of such a bacterial or fungal proteinase, their activity maxLjium against casein in one pH is between 10 and 12. Under these conditions the pelts or hides quickly absorb considerable amounts of water, but they do reach it not that state of plumpness, through which the basic loosening and depilation in the subsequent operations is made more difficult.

The majority of the proteolytic enzymes already used in the waterworks have the highest Activity in the neutral or weakly alkaline range and is practically ineffective at pH values above 10. For some years now, bacterial and fungal proteinases have become known that also operate in the pH range over 10 still have a strong effectiveness or even their maximum effect (compared to Casein) in this area. Enzymes of this type are suitable for the method of the invention. she are z. B. from cultures of Aspergillus niger, Aspergillus flavus, Penicillium cyanofulvum, Paecilomyces prosicinus, Streptomyces sp., Serratia sp. or Bacillus subtilis obtained.

From the German Offenlegungsschrift 1 800 508 (cf. in particular p. 50/51) it is already known that Enzymes of this type are used in the depilation of pelts or skins in the alkaline range be able. A swelling takes place, which, however, since a conventional switch is in the neutral range precedes, does not cause difficulties in depilation. In contrast to this well-known one Method, the method of the invention is limited to the softening process; i.e. it does not yet occur Hair loosening.

In the case of heavily soiled raw material, a dirt switch is expediently placed in front of the softening process of the invention. For the actual softening process a liquor of 100 to 1000%, based on the weight of the raw material, to a pH value im Range set from 10.0 to 12.0 and 23 to 25 ° C. Higher temperatures can also be used but in most cases this is not necessary. To adjust the pH is preferred Caustic soda is used, with the required amounts usually being 0.3 to 0.5%, based on on the salt weight, or 0.9 to 1.1%, based on the dry weight. In addition to or where appropriate Instead of caustic soda, you can also use sodium sulphide, soda, calcium formate, sodium sulphite or mixtures of which are used to produce the soft liquid. The soaking time for salted raw " it was 3 to 6 hours and for dried raw material 8 to 16 hours; during this time can be several times be moved briefly. As a result of the high pH value, there is no bacterial growth, so that the Soft process can be controlled very precisely.

The softening process according to the invention has a very advantageous effect on the subsequent operations out. A very uniform swelling is achieved in the liming over the entire surface of the leather and the formation of blood vessels and neck folds is suppressed. The basic relaxation, in particular with black-colored skins, is significantly improved.

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A fine grain of grain is also obtained, which has a high elasticity and a good connection to the underlying skin layers. The result is leather with a softer grip and improved tack.

example 1

100 kg of salted calfskins are mixed with four times the amount of water, based on the weight of the salt soaked by 28 ° C The soft

8.0 g of alkaline bacterial proteinase

with 125,000 LVE,
50 g sodium sulfite, calc,
200 g caustic soda, dandruff,

added.

It is treated 4 levels in the reel. At the beginning it is reeled for 10 minutes, then every full hour 2 to 4 minutes. Following this, liming is carried out in the same fleet.

Example 2

100 kg cattle hides in the weight class of 25

up to 29.5 kg are included in the barrel
250% water, 28 ° C,
0.012% a ^M '.alic bacterial proteinase

with 125,000 LVE ..
0.2% sodium carbonate, calc,
0.2%

softened.

At the beginning it will be 20 minutes, then
Hour moving 10 minutes. Soak duration:

Example 3

gives way:

800%
0.02%

0.03%

0.8%

1.5%
0.5%

every full 6 hours.

Water, 18 ° C,

alkaline bacterial proteinase with 125,000 LVE,
alkaline fungal proteinase with 150,000 LVE,
Sodium carbonate, cone., Caustic soda, flakes, of a polyglycol ether.

After a soaking time of 1 to 2 hours

started with the movement, which is increased as the soft effect increases. The soak duration is

12 to 15 hours. Before the switch is finished, it is reeled 2 to 3 times.

Example 4

100 kg of salted cattle hides are treated with 300% water, 20 to 22 ° C, based on the salt weight, soaked overnight. The water will be discarded next morning. A treatment is given in the fresh air With

300%
0.02%

0.2%
0.2%

Water, 30 ⁰ C,
alkaline fungal proteinase with 150,000 LVE,
Caustic soda, flakes, sodium carbonate, calc,

100 kg of goat skins are carried out in the reel as follows - based on the weight of the trek.

The intermediate treatment lasts 4 hours. At the beginning and every full hour there is 15 minutes of exercise.

The enzyme strength is determined against casein at pH 10 to 12 and is in each case in Löhlein-Volhard units (LVE) (see A. Küntzel, Gerbereichemisches Taschenbuch, Verlag Theodor Steinkopf, Dresden, 1955, 3. 86).

Claims (1)

Claim: Process for soaking pelts or hides by means of proteolytic enzymes in alkaline set fleets, characterized in that the switch is at carries out a pH value between 10 and 12 in the presence of such a bacterial or fungal proteinase, whose Ak * ivi.tätsmaximum compared to casein ίο at a pH between 10 and 12.