Newsprint Deinking - A Low Cost Approach, 1992 Papermakers Conference Proceedings

Deinking of newsprint is of primary interest to mills producing book, magazine and newsprint stock. Many states are enacting legislation requiring publishers to include up to 50% recycled news in their newspapers or face tax penalties. Mills producing gypsum board and packaging are also interested in recycled news as a substitute for more expensive ledger grades and blank news. The expense and long wait for the purchase of mechanical deinking equipment is increasing mill demand for chemical products which will improve the deinking of newsprint or other groundwood furnishes with little mechanical treatment beyond the pulper.

Improved ink removal from newsprint during deinking is a function of the degree of wetting and dispersion of ink particles (predominately carbon black). The ability of raw materials to wet and disperse carbon black particles as expressed by contact angle, surface tension and zeta potential measurements was correlated to their ability to deink newsprint in the laboratory pulper. Brightness and reflectance measurements, as well as particle size analysis, was used to evaluate the cleanliness of treated stock.

A method for deinking newsprint at neutral pH with minimal temperature and washing was developed. In this method, a surfactant/dispersant blend is added to the pulper to disperse the ink particles, prevent their redeposition on the paper fibers and facilitate their removal in a washing stage. This program is currently being used successfully by a northeastern tissue mill.