Paper making and fiber liberation – Processes of chemical liberation – recovery or purification... – Waste paper or textile waste
162 5, D21C 502
This invention relates to a process for deinking wastepaper and to the use of at least partly water soluble polymers containing amino and/or ammonium groups and having number average molecular weights in the range from 2,000 to 500,000 for the deinking of wastepaper printed with water-dilutable printing inks.
Today, wastepaper is used in large quantities for the production of, for example, newsprint and hygiene paper. Lightness and color are important quality features for papers of this type. To achieve this, the printing inks have to be removed from the printed wastepaper. This is normally done by deinking processes essentially comprising two steps, namely:
1. refining the wastepaper, i.e. fiberizing in water in the presence of the chemicals required for detachment of the printing ink particles and
2. removal of the detached printing ink particles from the fiber suspension.
The second step can be carried out by washing or flotation (Ullmanns Encyclopadie der technischen Chemie, 4th Edition, Vol. 17, pages 570-571 (1979)). In flotation, which utilizes the difference in wetability between printing inks and paper fibers, air is forced or dawn through the fiber suspension. Small air bubbles attach themselves to the printing ink particles and form a froth at the surface of the water which is removed by savers.
The deinking of wastepaper is normally carried out at alkaline pH values in the presence of alkali hydroxides, alkali silicates, oxidative bleaches and surfactants at temperatures in the range from 30 to 50.degree. C. Soaps and/or fatty alcohol polyglycol ethers are often used as surfactants which are responsible for the detachment and separation of the printing inks (Ullmanns Encyclopadie der technischen Chemie 4th Edition, Vol. 17, pages 571-572 (1979)). It is known from DE-OS 15 17 148 that printing inks based on petroleum oils can be removed from wastepaper in the presence of proteins having molecular weights of, for example, 10,000 or with polyvinyl pyrrolidones. DE-OSS 33 22 330 and 33 47 906 describe the use of alkylaminopolyethers for the removal of printing ink. In addition, ethyleneimine/ethylene oxide/propylene oxide copolymers are known as deinking chemicals from JP 84/137 587, abstracted in Chem. Abstr. 102, 80638b (1985) while ethylene oxide/propylene oxide/alkyl(alkenyl)amine adducts are known as deinking chemicals from JP 82/25 489, abstracted in Chem. Abstr. 97, 57393n (1982).
In recent years, conventional printing ink systems, for example based on nitrocellulose, maleate resins and/or shellac, which contain esters and/or ketones, for example ethyl acetate and/or methyl ethyl ketone, or alcohols as solvent, have been increasingly replaced by water-dilutable printing inks for reasons of pollution control. Another reason for the increasing use of water-dilutable printing inks lies in the non-inflammability of water which eliminates the need for the expensive safety systems which normally have to be installed in the printing factories where solvent-containing printing inks are used. Most water-dilutable printing inks contain as binder component anionic polymers, for example polymers containing carboxyl groups, of which the neutralization with bases makes the printing inks dilutable with water.
However, water-dilutable printing inks have the major disadvantage that they can only be removed completely inadequately, if at all, with the surfactants typically present in the deinking liquor (Wochenblatt fur Papierfabrikation 13, 537-538 (1988)). The result of this is that, hitherto, the wastepaper printed with water-dilutable printing inks, which is accumulating in ever-increasing quantities, is not recycled and, hence, is also not available as a wastepaper raw material for newsprint and hygiene papers.
Accordingly, the problem addressed by the present invention is to provide a deinking process by which it is possible to deink wastepaper containing constituents printed with water-dilutable printing inks.
It has now surprisingly been found that water-dilutable printing inks can be removed in wash
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Grandmaison Real J.
Hastings Karen M.
Henkel Kommanditgesellschaft auf Aktien
Jaeschke Wayne C.
Szoke Ernest G.
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