Role of polymers in deinking mixed paper

Discarded paper contains plastics, ink, fillers, and coatings. All of these contaminants must be separated from the fibers that are useful for papermaking. In the conventional process, the plastics are removed by hand before the discarded paper is reused. The procedure increases the cost of the raw material. New investigations show the benefit of keeping the plastics in the furnish and using them as attributes in deinking. In the process, the polymers are transformed into scavengers for ink and other colloids after exposure of the discarded paper to a pulping liquor containing mineral spirits and sodium silicate. Deinking occurs when the ink and colloid-loaded plastics are removed from the clean fibers by screening. This study reveals that the join action of mineral spirits and sodium silicate is paramount for the transformation of the surface properties of the polymers and for the attachment of colloids to the surface-modified plastics. The data indicate that ink removal is temperature dependent. Adhesion of particles does not significantly affect the glass transition temperature and the FTIR spectra of the plastics. Application : this work demonstrates that mixed paper can be used without initial segregation of plastics. These polymers can play an important role in deinking the furnish.