CA2366428A1 - Paper making process with retention aid additives - Google Patents

Abstract

A pulp and paper additive comprising a selective protein recognition function that specifically links a component of a papermaking solution. The invention provides an improved process of paper manufacture and novel paper making additives of use therein.

Description

t PAPER MAKING PROCESS WITH RETENTION AID
ADDITIVES
FIELD OF THE INVENTION
This invention relates to paper making processes and additives of use therein.
BACKGROUND OF THE INVENTION
Modern papers are a sophisticated blend of fibers, fillers and polymers wherein during manufacture synthetic retention aids are required to enhance the I S deposition of fillers and fines onto the fibers before sheet formation.
Without retention aids, most of the fillers and some of the fines pass through the sheet and remain in the white water. Poor retention lowers product quality and paper-machine efficiency, and wastes raw material. Loss of fines is especially significant in thermomechanical and chemi-thermomechanical pulping processes, which produce a significant quantity of fines in suspension.
Typical retention aids include high molecular weight organic polymers, with either positive, negative or net neutral charges. Cationic polymers are frequently employed to bind with cellulosic fibres, which naturally possess a negative charge.
Unfortunately, conventional "effective" retention aids cause everything to stick to everything else. Fillers form large aggregates instead of uniformly depositing onto fibers and unwanted fiber-fiber flocculation gives poor sheet formation. A
fundamental problem is that retention aid adsorption is not selective in that fines, fillers and fibers compete for the retention additives.
Pulp and Paper Canada, 81, 54, 1980- R.H. Pelton, L.H. Allen, and H.M.
Nugent and TAPPI J, 68, 91, 1985 - R.H. Pelton describe the use of high molecular weight organic polymers as retention aids for pulp systems, and compare the effects of charge on retention aid effectiveness.

"Pulp and Paper: Chemistry and Chemical Technology, Vol 2", Chap 8, T.N.
Kershaw, ed., John Wiley and Sons, New York, 1981 - J.P. Casey describes the impact of the loss of cellulosic fines on paper properties, the justification for the need for retention aids for effective paper formation and the economic impact of fine fiber loss.
"Handbook for Pulp and Paper Technologies", Chap 15, CPPAlTAPPI joint textbook committee, 1982 - G.A. Smook describes, in a general way, the role of retention aids in papenmaking in that they facilitate the aggregation of fibers and fine materials of cellulosic fines or fillers, which are often less than about 5 microns.
J. Wood Chem. Technol., 9, 407, 1989 - S. Roy, M. Desrochers, and L.
Jurasek describes the use of proteins as potential retention aids, including lysozyme, trypsinogen, myoglobin, carbonic anhydrase and protease. Proteins were chosen based on their charge characteristics, without any consideration of their ability to bind chemically to the materials in a papermaking suspension, i.e., the expected mechanism of action for these proteins was essentially equivalent to that observed with high molecular weight polymers currently used in industry. However, the results suggested that, in addition to electrostatic interactions, some other form of binding was probably also occurring. The isoelectric point of the proteins had a significant effect on binding, suggesting that most of the binding was based on electrostatic interactions.
U.S. Patent 5,998,183, issued December 7, 1999 - G.N. Le Fevre and B.A.
Saville, describes the immobilization of enzymes, and means to ensure that enzyme activity is retained and maximized.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an improved process of paper manufacture and novel paper making additives of use therein.
Accordingly, in one aspect, the invention provides a process of preparing selective paper making additives by immobilizing cellulase/cellulose binding domain (CBD) onto a clay/kaolinite support, and by co-immobilizing cellulase/(CBD) and a amylase onto a clay/kaolinite support. The cellulase/CBD moiety selectively binds to cellulose in a papermaking suspension, while amylase will bind to starch. The product obtained is therefore highly selective, possessing specific recognition sites for starch and cellulose. Furthermore, the immobilization support (clay/kaolinite) is a commonly used filler within paper.
BRIEF DESCRIPTION OF THE DRAWINGS
In order that the invention may be better understood, prefer ed embodiments will now be described by way of example only with reference to the accompanying drawings, wherein Fig. 1 is a graph showing immobilized enzyme activity for different loadings of a clay; and Fig. 2 represents scanning election microscope images of clay onto cotton fibers.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
Use of the process of the invention for starch coatings is described herein.
Starch coatings ("sizes") are typically utilized to fill in gaps or voids on the surface of the sheet. These coatings may be administered on a size press, or by tub sizing. In the former operation, the rollers (or nip) are flooded with starch solution, which is then delivered and attached to the paper by absorption as it passes between the rollers. The process must be carefully controlled to avoid non-uniform distribution of the sizing agent onto the paper stock. In particular, the paper machine may need to run at relatively low or moderate speeds to ensure proper attachment of the solids in the sizing solution. In a tub sizing operation, the sheet passes through a shallow tub or bath that contains the starch solution; excess solution is subsequently removed by passing the sheet through a set of rollers.
In either type of process, the objective is to achieve a uniform coating of the sizing agent onto the paper. Selective or controlled deposition of starch onto the underlying cellulosic component of the paper will improve sheet formation and coating uniformity. The additives described herein, which promote selective binding between paper constituents and starch therefore improves deposition of starch coatings onto paper.
Enzymes were immobilized onto clay/kaolinite, through a cross-linking process, adapting an existing immobilization technology, in accordance with aforesaid USP 5,998,183, to a-amylase, cellulase, and the cellulose-binding domain (CBD) of cellulase. The effectiveness of the intelligent paper additive was established through adsorption studies, followed by examination of fibers using scanning electron microscopy. Measurements of the activity of the soluble and immobilized enzyme provided additional evidence regarding the effectiveness of the immobilization procedure.
Examples Example 1: Experiments with cellulase immobilized on kaolinite For a variety of different immobilization conditions, measurements of the activity of soluble cellulase before and after immobilization were conducted, based on the production of reducing sugars. The activity of the immobilized enzyme was affected by the duration of immobilization, and the relative concentration of cellulase to clay. For the support modification step, which takes place over 1.5 to 10 hours, the glutaraldehyde concentration typically ranged between 1 and 4% (v/v). For the immobilization step, the modified support was incubated in enzyme solution, comprised of raw enzyme solution diluted either 5, 10, or 20 fold, to establish the effect of protein concentration on the immobilization process. The activity of the immobilized enzyme for some different loadings of clay and immobilization conditions is shown in Figure 1. These data indicate that cellulase is attached to clay, and that this configuration recognizes the cellulose in the solution, establishing that cellulose and clay can be attached in this manner.
Adsorption studies with the immobilized cellulase were conducted by incubating the bioadditive in a solution containing cotton (cellulose) fibers.
As a control, fibers were also incubated in a suspension of clay alone. Figure 2 compares the SEM images of native cotton fibers, cotton fibers exposed to clay only, and cotton fibers incubated in cellulase immobilized onto clay, wherein (a) is untreated cotton fiber;
(b) is cotton fiber incubated in clay suspension;

(c) is cotton fiber incubated in clay-cellulase complex As shown in Fig. 2, much more clay is attached to the cotton when the clay is coupled to cellulase than if the cotton is incubated in clay alone. The selective interaction between cellulase and cellulose (cotton) thus facilitates greater deposition of clay.
Although this disclosure has described and illustrated certain preferred embodiments of the invention, it is to be understood that the invention is not restricted to those particular embodiments. Rather, the invention includes all embodiments which are functional or mechanical equivalents of the specific embodiments and features that have been described and illustrated.

Claims (4)

1. A pulp and paper additive comprising a selective protein recognition function that specifically links a component of a papermaking solution.

2. An additive as claimed in claim 1 wherein said component is selected from the group consisting of cellulose a filler and a binding agent.

3. An additive as claimed in claim 1 or claim 2 wherein said protein is selected from the group consisting of cellulase, a cellulose binding domain, xylanase and a amylase.

4. An additive as claimed in any one of claims 1 to 3, wherein said filler is selected from the group consisting of clay, kaolinite, titanium dioxide and calcium carbonate.