FI90573C - A way to improve the retention or treatment of pulp fiber suspensions or wastewater in the paper, pulp or board industry - Google Patents

Description

1 90573

The present invention relates to a method for improving the retention and / or purification of pulp fiber suspensions or effluents in the paper, pulp or paperboard industry by treating them by combining them. noliformaldehyde resin and high molecular weight polyethylene 10 oxide, as well as a cationic precision derivative or a cationic cellulose derivative.

Several ways are known in the paper, pulp and board industry to improve retention in the dewatering of pulp fiber suspensions by the addition of various polyelectrolytes such as cationic polyamine, cationic polyacrylamide and cationic cellulose derivative. Pulp fiber suspensions may contain, in addition to pulp fibers, various amounts of inorganic fillers, e.g. clay, dolomite lime and gypsum, epa-20 organic and organic binders, lignin and hemicellulose. The addition of polyelectrolytes facilitates the flocculation of the products contained in the pulp suspension and in turn promotes retention. West German Patent 2,549,089 also discloses the improvement of retention in the dewatering of pulp fiber suspensions by the use of a combination of high molecular weight polyethylene oxide, phenol-formaldehyde resin, alternatively phenol-sulfur resin, and polyamide.

After the water has been removed from the pulp fiber suspension, large MaSria effluents are obtained, which, even with good retention, contain smaller Maaria fine fibers, so-called zero fiber, fillers and binder residues, as well as dissolved ingredients from lignin and hemicellulose. In wastewater treatment, it is known to flocculate impurities by adding inorganic and / or organic polyelectrolytes 2 90B73 such as aluminum sulfate, ferric chloride, polyacrylamide, polyacrylate, polyethyleneimine and a cationic starch derivative.

Canadian patent CA 1 004 782 5 also discloses the use of phenol formaldehyde in combination with high molecular weight polyethylene oxide to improve retention in the dewatering of pulp fiber suspensions. In connection with the dewatering and waste water purification of SekS pulp fiber suspensions, the polyethylene oxide adduct facilitates the agglomeration of the Flocks formed with the phenol-formaldehyde resin, thereby facilitating retention and purification.

Although the combination of high molecular weight polyethylene oxide and phenol-liformaldehyde resin allows for good retention and purification, it has been found that some of the fine fibers and colloidal particles and solutes are not retained in the fibrous web or cannot be removed from the effluent by the proposed process. Thus, there is a need for procedures that further improve retention and purification. Such problems occur e.g. in the removal of water from fiber suspensions obtained from recycled pulp or mechanical pulp, or in the treatment of waste water from pulp or hulls. Thus, there is a need for procedures that further improve retention and purification.

It has now been found that retention and purification can be improved if a cationic starch derivative or a cationic cellulose derivative is added to the fiber suspension or water in addition to formaldehyde resin and high molecular weight polyethylene oxide. It has been shown that the presence of a cationic starch derivative improves the "traceability" of zero fibers and flocculated material present or formed during processing. When water is removed from the fiber suspension, zero fibers, binder particles, flocs, etc. increasingly bind to the web of pulp fibers, which means higher yields, faster dewatering, and cleaner wastewater. In wastewater treatment, it has been found that in the application of the invention, the zero fibers, binder particles, fillers, pigments, lignin and hemicellulose agglomerate to a much greater extent than before into flocs. The flocs are very stable and easy to remove after sedimentation, flotation or centrifugation.

In the process according to the invention, the molecular weight of the oral polyethylene oxide usable must be more than 500,000 and preferably more than 2,000,000. No critical upper limit has been observed and thus good results have been obtained with polyethylene oxide having a molecular weight of 12,000. 000. Achieving significantly higher molecular weights has proven difficult due to chain shortening in manufacturing. The polyethylene oxide according to the invention is mostly composed of oxyethylene groups, but there may be a small number of other groups / e.g. oxypropylene groups. The mSara of non-oxyethylene groups is limited by the condition that the polyethylene oxide must be water-soluble.

The phenol-formaldehyde resin of the invention is relatively water-soluble, although resins with limited solubility at neutral or mother-to-mother pH values may be used. The resin usually precipitates at acidic pH values.

The cationic observation derivative used according to the invention is preferably potato, corn or wheat starch substituted by quaternary amethio-3Q sodium groups. The degree of substitution is preferably 0.01 to 0.1.

The cationic cellulose derivative becomes water-soluble by modification. The cationic cellulose derivative must be water-soluble and may contain, in addition to the above-mentioned cationic groups, lower alkyl groups such as 35 methyl or ethyl groups as well as lower hydroxyalkyl groups 4,90573 such as hydroxyethyl, hydroxypropyl and hydroxybutyl groups. A suitable degree of substitution of the cationic groups of the cellulose derivative, preferably the quaternary ammonium groups, is 0.01 to 0.5 per anhydroglucose unit and the molecular weight is from about 10,000 to about 1,000,000.

The amounts of phenol formaldehyde resin, polyethylene oxide and cationic starch derivative or cationic cellulose derivative are not critical. LisaysmaSra is preferably adapted to the amount and type of zero fibers, fillers, binders, binders, lignin and hemicellulose. The amount of phenol formaldehyde resin is normally more than 1, preferably more than 5 ppm, the amount of polyethylene oxide is more than 0.1 ppm, preferably more than 1 ppm and the amount of cationic starch derivative is more than 1, preferably more than 5 ppm based on the effluent. Suitable yia limits are about 100, 20 and 200 ppm of effluent, respectively. Additional additives preferred for retention are 0.01-0.5% by weight of phenol-liformaldehyde resin, 0.001-0.1% by weight of polyethylene oxide and 0.01-1.0% by weight of cationic starch derivative 20 or cationic cellulose derivative in suspension. calculated on its own. The ratio of phenol formaldehyde to polyethylene oxide is preferably 1: 5 to 50: 1 and the ratio of cationic starch derivative or cationic cellulose derivative to polyethylene oxide is preferably 1: 5 to 25,100: 1, regardless of whether the components are used for water purification or retention.

The three components of the invention may be added in arbitrary order. The cationic starch derivative and the cationic cellulose derivative may be added, for example, first, and then the phenol formaldehyde resin and the polyethylene oxide in said order. It is also possible to act first by first adding a phenol formaldehyde resin and then a mixture of polyethylene oxide and a cationic starch derivative or a cationic cellulose derivative.

5,90573

The following embodiments illustrate the invention and are not intended to limit the scope of the invention.

Example 1

800 ml of effluent formed from a mixture of effluents from CTMP and board production was poured into a glass vessel. The pH of the wastewater was 6.5 and the dry matter content was 2.5 g per liter. The effluent was stirred at 500 rpm and polyelectrolyte was added. After stirring for one minute, pheno-10 liformaldehyde resin was added, and after one additional minute, a high molecular weight ethylene oxide adduct was added while stirring at 500 rpm. After 10 seconds from the last additional unit, the stirring speed was reduced to 100 rpm and after another 50 to 15 cycles, the stirring was stopped. The flocs formed in the wastewater were then allowed to settle and then nMytes were taken from the clear phase and turbidity was measured nephelometrically. The chemicals added, their amounts and the clarification achieved are shown in Table 1.

From the results, Kay shows that experiments 2 and 3 of the invention achieved significantly better clarification than Experiment 1, which is in accordance with Canadian Patent CA 1,004,782. Compared to Experiment 1, the addition of polyelectrolytes other than the cationic starch derivative 25 did not improve the results.

Example 2

The effluent obtained from the bleaching step of unbleached ceramic paper was purified at 25 ° C in the same manner as in Example 1. The dry matter content 30 of the effluent was 2.5 g / l and the pH value 7. The added chemicals, their amounts and results are apparent. from Table 1.

From the results, Kay shows that the addition of the cationic spray derivative or cationic cellulose derivative according to the invention provides a significantly better purification than the conventional combination of phenol formaldehyde resin and high molecular weight polyethylene oxide. No improvement occurred with combinations containing phenol-formaldehyde resin and high molecular weight polyethylene oxide and other polyelectrolytes.

Example 3 5 The effluent obtained from the bleaching step of bleached ceramic paper was purified at 25 ° C in the same manner as in Example 1. The effluent had a dry matter content of 4.4 g per liter and a pH of 8. The added chemicals, their mSarages and results are shown Table 3. It can be seen from the results that the experiments according to the invention achieved a significantly better purification than the use of phenol-formaldehyde resin alone or high molecular weight polyethylene oxide or a combination thereof.

Example 4 Retention tests were performed on a pulp suspension having a pulp fiber concentration of 0.55% by weight and a pH of 7 at 35 ° C. The composition of the pulp fiber was 60% washed detergent pulp, 30% sulphate pulp scrap and 10% bleached sulphate pulp. Retention experiments were performed according to Britt-20. See TAPPI 56 (10), 46 (1973). The added chemicals, their mSSrSt and results are shown in the table below. From the results, Kay showed that the results in the retention according to the invention were substantially better than in the comparative experiments.

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Claims (7)

11. O 5 7 3 • 1. A method for improving the retention and purification of pulp fiber suspensions or effluents in the paper, pulp and board industry by treating them with phenol-formaldehyde resin and high molecular weight polyethylene oxide, characterized in that Treatment with phenol-formaldehyde resin and high molecular weight polyethylene oxide resin is a combination with a cationic starch derivative or a cationic cellulose derivative. Process according to Claim 1, characterized in that the weight ratio of phenol formaldehyde resin to polyethylene oxide is 1: 5 to 50: 1 and the weight ratio of starch derivative or cellulose derivative to polyethylene oxide is 1: 5 to 100: 1. Process according to Claim 1 or 2, characterized in that the cationic groups of the starch derivative and the cellulose derivative are quaternary ammonium groups. Process according to one of the preceding claims, characterized in that the polyethylene oxide has a molecular weight of more than 500,000. Process according to Claims 1 to 4, characterized in that the degree of cationic substitution of the starch derivative is 0.01 to 0.1. Process according to one of the preceding claims 1 to 5, characterized in that the pulp fiber suspension is dewatered in the presence of 0.01 to 0.5% by weight of phenol formaldehyde resin, 0.001 to 0.1% by weight of polyethylene oxide and 0, 01 to 1.0% by weight of a cationic starch derivative or a cationic cellulose derivative. Process according to one of Claims 1 to 6, characterized in that the effluent is purified in the presence of more than 1 ppm of phenol formaldehyde resin, more than 0.1 12 90 573 ppm of polyethylene oxide and more than 1 ppm of cationic turkey derivative or cationic cellulose derivative, calculated from waste water . 13 90 573