Bleaching and dyeing; fluid treatment and chemical modification – Treatment of hides – skins – feathers and animal tissues – Depilating
Patent
1982-10-29
1984-07-03
Tungol, Maria Parrish
Bleaching and dyeing; fluid treatment and chemical modification
Treatment of hides, skins, feathers and animal tissues
Depilating
8 9417, C14C 106, C14C 104
Patent
active
044577591
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a new, environment-protecting method for the liming and unhairing of raw hides. According to the method of the invention the environmental pollution caused by the various ingredients of technological sewage can be eliminated or at least reduced considerably.
The increase in the production of leather industry involves a similar increase in the amount of chemicals utilized. This results in a significant increase in both the amount and the contamination degree of sewages, leading to serious problems of environmental protection.
It is also known that about 70% of the contaminations arising in the sewages from hide processing originate from the liming-soaking step. Of these contaminating substances, sulfide ions, originating from sodium sulfide utilized to decompose hair keratin, cause the greatest problems. Sulfide ions are poisonous, inhibiting the functions of the bacterium flora of biological sewage treatment plants, and even more, beyond a critical concentration, destroying the bacterium flora completely.
A major part of calcium hydroxide, which is also added to the liming bath, separates as an insoluble substance, which further increases the problems appearing at sewage purification.
Apart from the above substances, dissolution or decomposition products (such as proteins, fats, etc.) originating from the raw hide also contaminate the sewages of the liming procedure.
Thus, some of the contaminating substances which appear in the sewages of liming procedure originate from the processed hides themselves, whereas others arise from the chemicals introduced into the bath in accordance with the technology applied.
The amount and quality of contaminating components originating from the hides themselves are not to be changed, since one of the purposes of hide processing technologies is just the removal of the undesired or superfluous components of the hide. The degree of protein destruction depends on the required quality of the finished leather.
Several attempts have been made to eliminate or reduce the above phenomena detrimental to environment. The presently known so-called environment protecting steeping-liming technologies can be classified into two groups. In the methods belonging to the first group it is suggested to replace sodium sulfide and/or sodium sulfide hydrate as well as calcium hydroxide, utilized in the conventional technologies, partly or completely by other substances less hazardous to the environment [see H. Fritz: The Leather Manufacturer 1979, p. 322 (1979 Oct.)].
In the methods belonging to the second group the once-used baths are replenished and then recycled for repeated use, decreasing thereby the amount of sewage and thus its detrimental effects, too [see B. Schubert: Leder and Hautemarkt, Gerbereiwissenschaft und Praxis 1975, 318 (1975)].
The majority of the methods belonging to the first group aim at the elimination of the use of poisonous sulfide ions or at least at the reduction of their amount. Examples for these methods are the hair-loosening technique based on the use of dimethyl amine, a method developed by American authors a long time ago but utilized in practice scarcely and as a secondary treatment only; the technologies based on the use of enzymes produced by the firm Rohm G [see Grimm, Trabitsch: Revue Technique 1964, 134 (1964); German patent specifications Nos. 2,307,603, 2,404,789 and 2,301,603], furthermore the methods based on the use of organic mercaptans manufactured by the firm BASF, such as Melescal SF [see H. Fritz: The Leather Manufacturer, 1979, 32 (1979 Oct.)].
A common disadvantage of these known methods is that they are either too expensive or they still require the use of a certain amount of sodium sulfide in order to attain a safe unhairing effect or to ensure the required quality of finished leather.
Methods for sewage purification aiming at the partial or total destruction of the sulfide content of sewage have also been described in the literature. Of these methods those based on catalytic oxidation or precipitation with iron sulf
REFERENCES:
patent: 2157969 (1939-05-01), Rohm
patent: 2179899 (1939-11-01), Rohm
patent: 3574516 (1971-04-01), Heidmann et al.
patent: 4278432 (1981-07-01), Monsheimer et al.
Fekete Kalman
Karnischer Tamas
Lukasics Bela
Makk nee Petranyi Magdolna
Malovecz Istvan
Bor- Mubor- es Cipoipari Kutato Intezet
Tungol Maria Parrish
LandOfFree
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