System for control of stickies in recovered and virgin paper processing

Abstract

Enhanced removal and / or control of adhesives or sticky materials, “stickies”, from recovered paper stock or virgin pulp fibers is achieved using a combination of enzyme treatment with adsorbents and / or absorbents. Pulp stock to be treated is typically obtained from old magazines, newspapers, household waste, but may include corrugated boxes and office waste. Virgin pulps may include mechanical, chemical, or semi-chemical pulps. Enzymes typically include hydrolases such as cellulases, hemicellulases, pectinases, amylases, and lipases such as esterases, lyases such as pectate lyases, and oxidoreductases. Adsorbents include activated bentonite, microparticles, talc, clay and modified silica. Absorbents typically include water soluble polymers, dispersants, coagulatants and agglomerants.

Description

BACKGROUND OF THE INVENTION [0001] The present invention relates to paper making processes and more particularly relates to enhanced removal and the control of adhesive contaminants and stickies in recovered paper processing. [0002] Conventional recycling of old paper products such as old newsprint, old corrugated containers, and mixed office waste is an important aspect of paper production today due to environmental demands that many paper grades have a portion of recycled fibers contained within the paper product. However, the recycling of the recovered paper generally requires additional processing steps in order to produce pulp, which is suitable for use in the final recycled paper product. [0003] Conventional recycling of recovered paper to produce pulp comparable to that used to originally make the virgin sheet is known in the art as “de-inking,” and typically involves pulping, soaking, screening, cleaning, washing, flotation, dispersion, thickening, and bleaching steps. Conve...

AI Technical Summary

Benefits of technology

[0014] Enhanced removal and/or control of adhesives materials, “stickies”, from recovered or recycled paper stock and virgin fiber processing is achieved using a combination of enzyme treatment with adsorbents and/or absorbents. Recovered paper stock to be treated is typically obtained from old magazines, newspapers, home waste or office waste, but may include corrugated cardboard boxes and other sources of recovered fiber. Enzymes typically include hydrolases such as cellulases, hemicellulases, amylases, proteases, β-glucosidase, lipases, esterases, and pectinases, lyases such as pectate lyase and oxidoreductases such as laccase, glucose oxidase, and peroxidases. Individual enzymes or any combinations of different varieties may be applied together with absorbents or adsorbents. Adsorbents include bentonite, both activated and non-activated, microparticles, talc, clay and modified silica gel. Absorbents typically include water soluble polymers, which can be either cationic or anionic. Dispersants may also be used.

[0015] Waste paper is initially treated in a pulper to make a slurry, which is screened mechanically and/or cleaned centrifugally and/or passed through a washer, flot

Problems solved by technology

Alkaline agents may cause yellowing of the fibers, which must then be bleached.

Recycled paper contains many components that, when repulped in recycled fiber plants, become stickies.

Stickies deposits on paper machine surfaces, fabrics, wires, felts, and rolls lead to problems such as wet end breaks, pressroom breaks, dryer section breaks, holes, sheet defects, high dirt counts, and difficulties in paper converting.

These deposits and associated problems lead to a significant amount of downtime and waste.

The cost of stickies is considerable, when factoring in the cost of downtime, chemical costs, production losses, scrap, rejected materials, and customer complaints.

These grades are becoming more difficult to find and are sold at much higher prices.

Flotation removes intermediate-size stickies (50-300 microns), which are troublesome because they are small enough to pass through screening and cleaning but too large to be removed by washing.

Unfortunately, even with the best of all of these methods, too many of the stickies are still present in the final product to avoid problems.

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