Patent ID: 6426200
Filing Date: 2002-07-30
Classification: D21C,Y02W

Abstract:
A method for deinking toner from noncontact printed wastepaper and mixtures of noncontact and contact-printed wastepaper, said method comprising the steps of:(a) pulping wastepaper comprising noncontact printed wastepaper or wastepaper comprising noncontact printed paper and contact printed paper to produce a pulp slurry, wherein the pulp slurry has a concentration of from about 5 percent to about 15 percent, wherein said percent is on a weight dry pulp/weight pulp suspension basis; (b) adjusting the pH of said pulp slurry to between about 4 and about 6 with an acidifying agent selected from the group consisting of sulfuric acid, nitric acid, acetic acid, hydrochloric acid, chloric acid and citric acid; (c) adding a surfactant to a concentration of from about 0.02 percent to about 1.50 percent, wherein said percent is on a weight of surfactant/weight dry pulp basis to the pulp slurry; (d) adding a cation selected from the group consisting of calcium, magnesium, manganese, sodium and lithium to the pulp slurry to a final concentration of from about 20 ppm to about 800 ppm; (e) adding deinking enzymes to said pulp slurry, wherein said deinking enzymes have a &bgr;-glucosidase activity to filter paper units activity ratio of at least 30:1, wherein said &bgr;-glucosidase and filter paper units activities are measured in international units per ml, wherein said deinking enzymes comprise exo-glucanase, &bgr;-glucosidase, xylanase and filter paper units activities, and wherein said deinking enzymes are added at a concentration of from about 0.01 percent to about 0.50 percent, wherein said percents are on a weight of enzymes/weight dry pulp basis; (f) continuing pulping for at least about 10 to about 30 minutes to produce a treated pulp slurry comprising toner particles and pulp; (g) terminating the activity of said deinking enzymes, wherein the step of terminating is adjusting the pH of the treated pulp slurry to above 8 with an alkalinizing agent selected from the group consisting of sodium hydroxide, potassium hydroxide, calcium hydroxide and sodium carbonate; or heating the treated pulp slurry to a temperature above 70Â° C.; or adding a chemical deactivator to the treated pulp slurry; and (h) separating the toner particles from the pulp by flotation, washing, cleaning or screening or a combination thereof.