Paper Processing Applications

Applications & Methods:

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The principal process step consists of the treatment of printed newsprint paper in a slurry of from 1 to 6% solids, contains from 0.2 to 0.33% based on the weight of fibres, of HYDROC COLLOID CLEANER at a temperature of from 32-82oC and preferably 4SoC. In the preferred form, this treatment is carried on in standard pulp defibreing equipment or other agitating equipment for reducing the paper stock to substantially individual fibres. It is essential that the printed-paper have no substantial treatment, such as soaking, prior to being added to the solution containing HYDROC COLLOID CLEANER. Thus, in the preferred form, bales of newspapers will be merely untied and dumped, unshredded, into the solution. The de-inking by the above process has been found to be completed within whatever time is necessary to reduce the newsprint to substantially individual fibres, thus requiring no more time in the paper stock preparation than would be required if there were no de-inking required.

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It has further been found that the de-inking of the newsprint paper is in no way altered or deterred by simultaneous bleaching of the fibres, such as by the additional presence in the slurry of sufficient sodium peroxide to prove a pH of from 9 to 10. A further important advantage of the process is its susceptibility to use with either hard or soft water.

Aside from the above-defined limited use of a bleaching agent, the use of any caustics is particularly avoided, in comparison to many prior processes wherein excessive caustics were required and resulted in a degradation and yellowing discolouration of the fibres.

Following the above de-inking process, conventional pulp washing equipment is employed wherein the slurry is thickened and simultaneously washed with progressively fresher water or progressive washing screens. The flow should be directly into the defibreing equipment, having therein a 120% +/- water solution of preferably 0.33% HYDROC COLLOID CLEANER. This solution is kept replenished by the addition of half of the waste water of a first washing processing, discussed herein below, such additional fresh or white water as necessary and additional HYDROC COLLOID CLEANER to maintain approximately a 0.33% solution."

The defibred pulp, reduced in form substantially to individual fibres and with the ink separated there from, is then subjected to a first washing using waste water from a subsequent second washing process. Approximately half of the wastewater of the first washing process is used as above described and the other half is disposed of. A second washing process follows using clarified white water from a paper machine or fresh water. These washing processes are in accordance with prior pulp preparation practice.

Accordingly, improved de-inking of waste newsprint is provided by a composition and temperature condition of the slurry maintained in the otherwise standard pulp defibreing steps, followed by the usual pulp washing steps, a process thus readily adaptable to existing manufacturing facilities.

Paper, with the face plies manufactured from 100% waste newsprint, de-inked in accordance with the above process, has been found to have the characteristics of a manila lined chip board and, more specifically, to have purity and brightness sufficient to meet requirements for a gypsum wall board front liner, providing cost saving in the manufacture of paper and consequently gypsum wallboard made there from. A gypsum wallboard, made in accordance with the process, includes a set gypsum core enclosed at least on the two faces thereof with paper, one liner thereof, intended as the exposed or front face, consisting of substantially 100% de-inked paper fibres.


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