Enzymatic pre-treatment of market pulp to improve fiber drainage and physical properties

Abstract

Methods for reducing the effects of wetlapping, drying, and hornification of pulp fibers and consequently increasing the pulp drainage and strength properties in the final product (i.e., paper) are provided. The method which has been developed creates a “value-added” product by the wastepaper supplier or at the pulp and / or deinking (recycled paper) mill—a wastepaper load / bale, wet pulp stock or wet lap, or dried pulp treated with or impregnated with enzymes that enhance the quality of the pulp or paper product when it is repulped and processed at the paper mill.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application is a divisional of copending U.S. application Ser. No. 13 / 323,136, filed Dec. 12, 2011, which is incorporated herein by reference in its entirety.FIELD OF THE INVENTION[0002]The present invention is generally in the field of treating pulp, including wet lap or fully dried pulp, at virgin pulp and / or waste paper recycling mills and / or treatment or impregnation of dry furnish loads or bales with enzymes prior to wetting in a wastepaper processing plant for the purpose of combating the hornification / deterioration of pulp quality through the wet-lapping, drying and recycling processes and producing a greater value virgin or recycled pulp for the eventual user of the pulp product.BACKGROUND OF THE INVENTION[0003]Current methods of producing virgin pulp utilize large manufacturing facilities (pulp mills) that produce pulp for multiple end users. Pulp mills process pulp from softwood, hardwood logs or chips or non-wood sources i...

AI Technical Summary

Benefits of technology

[0014]Methods for reducing the effects of wetlapping, drying, and hornification of pulp fibers and consequently increasing the pulp drainage and strength properties in the final product (i.e., paper) are provided. The methods which have been developed creates a “value-added” product at the wastepaper dealer or processer or at the pulp and / or deinking mill, those being a wastepaper load or bale or wet lap or dried pulp treated with or impregnated with enzymes that will enhance the quality of the pulp product when it is rewetted and processed at the paper mill. The method of enhancing paper strength or pulp drainage in a virgin pulp mill or a recycled stock preparation plant includes the steps of administering an effective amount of enzyme formulation to either the wastepaper furnish at the wastepaper processing / baling facility or the wet pulp stock prior to dewatering and / or drying or directly to the dewatered or dried pulp prior to or after the wetlap machine or the pulp dryer, at the pulp plant, to treat the pulp prior to subsequent repulping for the manufacturing of paper products. The enzyme may be administered to:(1) wastepaper furnish at the furnish processing or baling site,(2) wet pulp stock prior to the wet lap machine or pulp dryer, or(3) wet lap pulp or dry lapped pulp after wet lapping or pulp drying while still in the deink plant or pulp plant

[0015]In one embodiment, the method includes the steps of (1) treating virgin or deinked pulp in the deinking or pulping plant with an effective amount of one or more enzymes and, (2) dewatering the virgin or deinked pulp to obtain wet lap or fully dried pulp having reduced hornification and damage of the pulp. In a second embodiment, the method includes (1) treatment of virgin or recycled pulp immediately or shortly after the wetlapping or fully-drying process with an effective amount of one or more enzymes to produce a wet lap or fully dried pulp having reduced hornification and damage of the pulp for the eventual papermaker using that pulp. In this embodiment, the pulp is impregnated at the deink plant or pulp mill with the enzymes which will modify the pulp later. In a third embodiment, the method includes the steps of treating the dry wastepaper furnish paper or bales at the wastepaper collecting or packaging facility with an effective amount of one or more enzymes for later use in a wastepaper processing plant.

[0016]Enzymes that can be applied to treat pulp at the pulp mill, before the pulp is dried and shipped to a paper mill, include cellulases, hemicellulases, xylanases, pectinases, pectin esterases and pectin and pectate lyases or combinations thereof. The enzyme treated pulp may be further treated at the paper mill with different methods to improve drainage and strength. Additional treatments to improve drainage and strength include, but are not limited to, mechanical refining and application of starch, dry strength or wet strength polymers. The enzyme treatment is performed at a temperature from about 10° C. to about 90° C. at ambient atmospheric pressure. More preferably, the enzyme treatment is performed at a temperature range between 15° C. and 60° C. Higher temperatures are possible depending on which enzyme formulations are used. Applications can be in pulp stocks with pH ranging from 3.5 to 9.5. A pH range of 4.5 to 8.0 is preferable for most enzymes. The enzyme treatment is effective to increase the strength and / or drainage of the pulp compared to untreated pulps and consequently to improve the strength of sheets made from the enzyme-treated pulp when compared to sheets made from untreated pulp. Increases in pulp drainage may be demonstrated using the Schopper-Riegler or Canadian Standard Freeness tests and various laboratory drainage tests.

[0017]The enzyme treated or impregnated wet lapped or fully-dried pulp with improved drainage and fiber strength sells as a value added-product, having increased strength and / or drainage of the pulp and improved strength of sheets made from enzyme-treated pulp compared to untreated pulps and sheets made from untreated pulp.

[0018]Wastepaper loads or bales treated or impregnated with enzyme formulation effective to enhance drainage, strength and other pulp and paper properties in the paper making process are also provided. These are produced using the method of enhancing paper strength or pulp drainage during the waste paper loading or baling process by administering an effective amount of enzyme formulation to wastepaper loads or bales that are later used to produce recycled papers.

Problems solved by technology

Normally, the thickening or wet-lapping process and drying process hornify and crush the fibers, and materially worsen the strength properties.

The drying process further impairs sheet bulk.

Micro fibrils created from refining can be damaged through time, especially in the pressing and drying process.

Charge chemistries are also weak and require a particular balance in application, so having too much time between chemical treatment and the actual formation of the sheet can be detrimental to strength development, drainage or retention.

With respect to the wet lap or fully dried pulp, strength treatments in or immediately prior to the paper machine may not adequately compensate for the hornification which has occurred during the wetlapping or drying process and the storage and transportation time.

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