CA2251191A1

CA2251191A1 - Paper pulp drainage aid

Info

Publication number: CA2251191A1
Application number: CA002251191A
Authority: CA
Inventors: Edmond Lascaris
Original assignee: Individual
Current assignee: PARTICIPANT PROJECT IP Ltd
Priority date: 1996-04-03
Filing date: 1997-04-02
Publication date: 1997-10-16
Also published as: NZ331961A; AUPN909696A0; EP0891442A4; WO1997038164A1; EP0891442A1

Abstract

To improve the drainage and consequently the machine speed in making paper or paperboard from recycled paper, a starch hydrolysing enzyme [alpha-amylase] is added prior to the forming section. The enzyme must be active in the temperature range of 40 to 90 ~C and in the pH range of 6 to 9. Amounts as low as 0.05 % by weight of the oven dried paper forming the pulp can allow increases in machine speeds of about 5 % or more.

Description

WO 97/38164 PCTIAU97nO182 I

PAPER PULP DRAINAGE AID
Field of the Invention - This invention relates to improvements in treating pulp and process water in paper mills and in particular to a drainage aid for use in recycled paper mills Background to the Invention The use of recycled paper to produce paper pulp creates problems in the free drainage of the paper pulp and the treatment and recycling of the process water Because of the wide range of source material ,a large range of components are present in the bacl~water. These include the organic components fibres, fibrils,pitch, starch derivatives. lignin, synthetic polymers and inorganic components to include clay, titanium dioxide, gypsum, talc, chalk, zinc oxide, aluminium sulfate, ferrous sulphate, and calcium carbonate. Much of this material is present as finesl i.e. below 120 micrometresl. It is preferable to retain some of the fines, which may comprise up to 5% of the paper sheet on the filter mat, without reducing drainage rates and paper properties and consequently affecting process times.
Enzyme treatment of paper pulps has been proposed to improve the freeness and physical properties of paper pulps with some ~l?.iming success with recycled fibre as well as virgin fibre . The enzymes that have been proposed arexyl~n~ces. cellulases, and other hemicellulases. These are commercially available as crude mixtures characterised by the dominant presence of the named enzyme. One defect of these treatments is that careful regulation of the addition and treatment conditions is required, because excessive treatment can ~ lead to a decline in drainage. Another ~liffic~llty is that paper pulps are usually neutral and many cellulases are active in the acidic pH range.

WO 9'7/38164 rCl~/AU97100182 U S A patent 4923565 proposed the use of a cellulase (having cel~ulase and xylanase activity), as a drainage aid for recycled paper pulp. One shortcoming of this proposal is that the pH must be adjusted to within the range 3 to 7.
An improvement to this patent is U S A patent 5116474 which utilises cellulases active in the pH range of 7 to 9.
U S A patents 51~9497 and 5423946 suggest using the drainage aid of the '565 patent with cationic polymers such as acryl~mi-l~s Patent specification WO 91/17243 discloses that a cellulase having an endo -gluc~n~.~e component active between pH 6 and 10 can be used as a drainage aid for paper pulps including waste paper pulp. The purpose of the enzyme is to reduce h~rshness or clarify colour in cellulose containing fabrics Brief description of the invention It is an object of this invention to improve the drainage of recycled paper pulpusing a more effective enzymatic treatment. The term "recycled paper" is intended to cover paper pulp, which includes a major portion of paper or paperboard that has been recycled.
To this end the present invention provides, as a drainage aid for improving the free drainage of recycled paper pulp slurries, a preparation cont~ining a major portion of a starch hydrolysing enzyme, preferably an amylase and more 2() preferably an alpha-amylase.
The invention also includes a method of improving drainage of recycled paper pulp which includes the step of adding to the pulp a drainage aid cont~ining a major portion of a starcb hydrolysing enzyme, preferably amylase, prior to the separation of the water from the pulp. The drainage aid is added in an amount 2j of at least 0.05% by weight of oven dried paper forming the pulp, ~or a time and at a temperature sllffi-,ient to produce an improved drainage rate and at a pH at which the enzymes are active. At the lower coneent~ ation the addition of enzyrne WO 97/38164 PCr/AU97/00182 will improve drainage to the extent that the p.aper m~rhine speed and production can be increased by about 5% or more.
In part this invention is predicated on the discovery that drainage of recycled paper pulps is hampered by co~ti-lgs on solid components in the pulp, particularly by the fine particles in the pulp. A .qiFnific~nt proportion of recycled paper contains starch or starch based materials and in part this invention is based on the realisation that that enzymatic treatment may remove this coating.
This invention is also founded on the discovery that amylase is able to act on the coatings of particles in the pulp regardless of its inner composition which is not the case with previously proposed enzymes such as cellulase. It is thought that the coatings are starch based and cellulases have little effect on the starch, but are more likely to act on the particles which are pri-n~rily cellulose. This further discovery also inrlic~tes that amylase is specific in its action on the starch components. This has the consequence that careful regulation of the tre~t~ent iS not nece.ss~ry and PYcessive treatment does not decrease the drainage improvement. The improved effectiveness of a drainage aid having a major amylase component may be due to the coatings on the fines being largely composed of starch and thus more susceptible to amylase or other starch hydrolysing enzyme treatment. Because the amylase has little action on the 2~1 cellulose component of the fibres, excess treatment is unlikely to cause any deleterious effect. This contrasts with the prior art enzymes which are prim~rily cellulases which are usually recommended for papers made with a high content of virgin fibre.
Although amylase is a major component of the drainage aid, other enzymes, 2j particularly cellulases active in the neutral- ~lk~ e pH range, particularly pH
6 to 9 may be present. Some cellulases do improve drainage which is inhibited by cellulose based materials in the pulp and part of drainage inhibition in recycled pulps may be reduced with cellulases. For many recycled pulps or mixed virgin and recycled fibres a mixture of amylase and cellulase may provide ;~) the optimum improvement.

W O 97t38164 PCT/AU97~82 Detailed description of the invention Process conditions for dewatering paper pulp using the drainage aid of this invention are typically:
temperature 40 to 90 oC
pH 6to9 enzyme dosage 2.5x106 to 15X106 IU of activity per tonne of pulp which for an alpha amylase such as BAN 240L is equivalent to 0.5 to 3 Kg per oven dried tonne of recycled paper.
contact times 15 to 120 minutes o The International Unit [I U~ of enzyme activity is the amount of enzyme necess~ry to produce 1 micromole of reducing sugar product per minute.
The enzymes used in the drainage aid can comprise an amvlase alone preferably a crude amylase or an amylase in comhi~tion with a cellulase such as endogluc~n~se. xyl~qn~ce, or other hemi cellulases such as m~nn~n~qe, all of which are preferably active in the neutral to ~Ik~line pH range of 6 to 9. A
preferred crude alpha- amylase is that derived from Bacillus subtilis. Starch hydrolysing enzymes from other microbial species may also be used inrll~ling B.licheniformis and Aspergillus oryzae In addition to the amylase drainage aid the convPntion~l polymeric flocc..l~nts~such as cationic polyacrylamide, which also aid in drainage can be used. The amylase presence will allow a reduction in the amount of the floccl~lz.ntc required.
Laboratory scale drainage tests were carried out on backwater samples from a recycled paper plant. A crude and a purified alpha- amylase was used to treat 2~ the backwater s~mrles. The pl~tific~on was achieved by chrom~toEraphic foc~c~inE. Drainage pPrfo m~nce was measured using a modified Schopper-egler drainage jar. A brass woven screen with 50 micron gaps captured the fines to form a filter cake. This filter cake sllfficiently impeded the backwater to permit accurate drainage readings to be taken by continuously collecting and weighing the filtrate. Drainage improvement was evaluated by comparing the difference between control and enzyme treated samples over 30 minutes.
Example 1 Experiments were conducted using both crude and purified alpha amylase as identified in table 1. The backwater characteristics and fines size dist~ibutionare set out in tables 2 and 3.

Table 1 alpha-amylas~characteri.~ tion alpha- CMC Xylan oat Xylan Starch Amylo-amylase IU/mg spelts birchwood IU/mg pectin IU/mg IU/mg IU/mg crude 0.006 0.649 0.3g5 243.750 291.667 purified 0 19.875 0 175.624 182.500 Table 2 Backwater char~cter-s~tion Batch pH Conductance micro S/cm Drymass glL Ash %

7.23 8~0 6.31 18.19 2 , .12 980 6.53 20.55 3 7.34 860 7.08 19.04 , Table 3 Particle ~ ize analvsis Number density parameters (microns) Batch 1 Batch 2 Batch 3 Median 1.20 0.89 0.96 Mean 1.80 1.35 1.55 SD 2.13 1.56 2.00 Mode 1.25 0.75 0.75 W 097~8164 PCT/AU97~182 G

The results of the experiments are set out in.table 4.
Because the fines in the backwater samples are in a higher concentration than in the pulp the dosage rates are higher because the surface area to volume ratios for the fines is 20 to 30 times the ratio for pulp. Thus the dosage requirement for treating pulps will be .si~ific~ntly less than the table suggests.

Table 4 Drair age analysis Batch amylase amylase amylase Drainage vol. Drainage purity dosage mg/Ldosage After 30 mins improvement units/K~ mL %
1 control 0 0 768.57 na 1 pure 0.15 4,171 791.07 2.93 1 crude 0.15 5789 804.56 4.68 1 crude 1.5 57,890 874.g 13.83 1 crude 15.0 578,900 932.71 21.36 2 control 0 0 764.19 na 2 pure 0.15 4032 774.59 1.36 2 crude 0.15 5597 793.86 3.88 2 crude 1.5 55,970 822.92 7.69 2 crude 15.0 559,700 902.34 18.08 3 control 0 0 707.93 na 3 pure 0.15 3720 725.6 2.50 3 crude 0.15 5163 733.87 3.66 3 crude 1.5 51,630 794.06 12.17 3 crude 15.0 516,300 861.49 21.69 These results show that amylase acts on the surface of all the components in thebackwater regardless of inner composition, by removing starch coatings on both W O 97/38164 PCT/AU97~182 fines and fibres. F.~rces.~ive treatment with cellulases tends to increase the fines leading to a decline in drainage performance and paper strength.
The large surface area and particulate nature of the fines is regarded as the major contributor to poor drainage perform~nce of recycled pulps. By selectivelyhydrolysing the surface m~teri5~1 on fines and fibres, the interaction between particle surface, retention and drainage aids and water is thought to be enhanced. This consequently encourages better drainage in the forming section of the paper plant.
Example 2 o A mill trial was conducted on a twin wire fourdrinier m~(~hine producing liners and medium for corrugated boxes. The m~(~hine is capable of producing between 12 and 15 tons of paper per hour from furnish consisting of mixed waste paper, newsprint and OCC.
The enzyme selected for the mill trial was BAN 240L which is an alpha amylase preparation produced by Novo Nordisk. It is a clear brown watery liquid obtained from a purified culture of Bacillus subtilis variety amyloliquefaciens.
The enzyme a~ ition comm~nced from 9am on day 1 and ceased 12pm on day 3[appro~cim~tely 48hoursl. The enzyme was dosed at 30 llhr [as received basisl in at two points in the stock preparation area.
2~) Table 5 shows the mill perform~nce over 7 days with the enzyme a-l-litio~
oc~rring on days 1 to 3. During the period of enzyme atlflition the machine speed increased by 4.49% compared to the operation without enzyme a-lAitinn In the table production rates have been extrapolated to remove lost time.
Product output increased 6.5% but when adjusted for trim the increase was 4.48%.

WO 97/381~ PCTtAU97~182 Trial Days 1 2 3 4 5 6 7 Av. Dry end speed 516.21 523.4 507.34 4g3.05 490.12 493.28 497.31 mlmin Production Tlday 314.~1 318.87 319.91 300.38 298.65 296.27 298.43 T~m mm 2788.60 2843.00 2800.46 2717.26 2806.65 2775.48 2729.96 An improvement in the freeness of the pulp as measured by the Schopper-Reigler [SR~ drainage values in the headbox and m~chine chests, and for both top and bottom lines was observed.

Schopper-Reigler Freeness values of pulp Headbox lleadbox Machine chest Machine chest top bottom -top - bottom Dunng trial 35 40 31 40 After tri~ 57 59 51 63 o This shows that the enzyme decreases the SR freeness values by 32% to 39%
depending on the sample origin.
This compares favourably with the performance of the cellulases with recycled paper pulp disclosed in USA patent 5116474 which obtained decreases in SR
values of between 5% and 23%
This mill trial showed that a cost ~ ;live enzyme treatment produced an additional 19.4 tonnes of paper per day, increased m~hine speed by 22.14 mJmin and improved the S R values.

Example 3- Comparative The enzymes as described in tables 7a 7b and 7c were tested for comparison purposes.
"na" means the data is not available TABLE 7a Name AMG 300L BAN 240L Celluclast D~nim~Y L
1.5 L
Enzyme Amylo- Alpha Cellulase Endo-glucosidase amylase gll~e~n~ce Organism ofAspergillus R~cil11~s Trichoderma Non patho-origin niger subtilis reesei genic mould Density g/mL 1.2 1.2 1.2 na p~I optima 4.5 5-7 4.5-6.0 4.5-5.5 Temp.oC 60 50-70 50-60 45-55 React~on time na na na na Dosage na na na na TABLE 7b Name Fungamyl Irgazyme 40 Novozyme Pergalase Enzyme Alpha- Xylanase Cellulase,glu Cellula~e amylase lno cellulase canase and Pretlnmin~nt activity] hemir~llulase Organism ofAspergillus Trichoderma na Trichoderma ongin oryzae lo-~gibrachiat longibrachiat um um Density glmL 1.25 1.01-1.15 na 1.01-1.15 pH optima 4.5-6.0 7.0-8.5 7.5-8.5 5-7 Temp. oC 55-60 50-70 ~0 35-55 Reac~ion time na 0.5-3 hrs lnr 0.5-2 hrs Dosage na 0.2-0.7 l/t 4~t 0.5-1.811t I() TABLE 7c NamePromozyme 200L Pulpzyme HB San Super 240L
Enzyme p~ n~se Xylanase Amylogluco~ida~e Pullan6-glucano- Endo-1,4-beta-D- [and alpha amylase hydrolase xylanase Organism ofBacillus B~cteri~l na origin acidopull~llytics Density g/mL 1.25 na 1.25 pH optima 4.0-6.0 7-8 5.5 Temp. oC 50-60 5~ 55 RP~ction time na 2-3 na Dosage na lkg/t na These enzymes were tested in the laboratory to assess the drainage improvement with pulp backwater in cimil~r f~chion to example 1. The results are shown in table 8. The reducing sugar increase is an indication that the enzyme was active. These results show that the alpha amylases BAN 240L and FUNGAMYL out p~rformed the other enzyme types with the exception of the cellulase CELLUCLAST.

W O 97~8164 PCT/AU97~182 ll Trea~ent of backwater con~sinin~ fines wi~h enzymes listed in tables 7a, 7b and 7c - Enzyme ! Drainage Reducing sugar I improvement(%) increase (mM) AMG 300L 0.7 9.2 BAN 240L 4.0 ~ 0.77 CELLUCLAST 1.5L 2.8 1 0.28 DENIMAX L 1.7 ~ 0.94 FUNGAMYL 800L 2.5 2.75 IRGAZYME 40 0.9 0.78 NOVAZYME 342 1.3 0.78 PERGALASE A40 0.4 O.o PROMOZYME 200L 0.0 1.35 PULPZYME HB 1.0 1 0.31 SANSUPER240L 0.9 1 4.81 Example 4- Flocc~ nts Backwater samples having a consistency at 0.631%, were treated with alpha amylase obtained from Bacillus licheniformis, incubations were performed at O
and 300 IU/ml at 500C for 3 hours. High molecular weight cationic polyacrylamide {CATPAMl was added at a set dosage of 0.3 micrograms per o lOOOmL of backwater. The backwater cont~ining the polymer was inverted 30 times in a glass measuring cylinder. Particle size analysis was performed in therange 0.2 to 60 micrometres.

W O 97~8164 PCT/~U97100182 alpha-~mylase and polymer treated backwater ParticleMeasurement Volume Volume No polymer ~llflition polymer addition ¦ CONTROL - Median 19.3 1 23.46 - Mean 20.91 ~ 23.91 - SD 14.30 14.75 alpha-Amylase-Median 17.21 25.63 - Mean 19.68 '25.31 -SD 14.32 !~5.67 Control particle count decreased from 212056 to 144617 while the a-Amylase particle count decreased from 178404 to 128787.
In the ~hsence of polymer the particle count of the enzyme treated backwater decreased by 15% relative to the control. The particle count decreased further with the ~d~itio~ of polymer to the backwater. The control decreased by 32%.
whereas the enzyme treated backwater decreased by 40% relative to the control o without polymer. The mean par~cle mass for the enzyme treated backwater, with polymer, increased by 6% relative to the control with polymer. These results imply that the enzyme treated fines are more receptive to polymer inter~rtior ~ as ~monstrated by the greater ~oc size and lower particle count.
These results compare favourably with the data in USA patent 5169497 which 5 show an improvement in freeness when a cationic polyacryl~mid~ is added to a cellulase treated recycled paper pulp.

W O97/38l64 PCTIAU97/OOlX2 S~lmmnry of benefits From the above results it can be seen that the present invention by improving drainage allows the speed of the paper section to improve, increasing the outputof paper from the recycled paper stock.
In addition the following i~n~ill5/ry benefits can also be recognised Avoids degradation of cellulose Overdosing does not degrade paper Iodine can be used to monitor the reaction The alpha-Amylase ls inactivated in the drying section . alpha-Amylase is a food grade enzyme and is safe for use in making food p~k:~ging alpha-Amylase is commonly available

Claims

The claims defining the invention are as follows:

1) In a method of forming paper from recycled paper stock the improvement comprising the addition of a drainage improving amount of a starch hydrolysing enzyme, preferably amylase to the pulp suspension prior to the forming section of the paper making plant.

2) The improvement as claimed in claim 1 wherein the enzyme is an amylase active within the temperature range of 40 to 90°C and the pH
range 6 to 9.

3) The improvement of claim 1 wherein the enzyme is added to the pulp suspension at least 15 minutes prior to entering the paper forming section.

4) The improvement of claim 1 wherein the enzyme is added in an amount of at least 0.05% by weight of the oven dried paper forming the pulp.

5) The improvement of claim 3 in which at least one cellulase is also added to the pulp with the starch hydrolysing enzyme.

6) A paper pulp drainage aid consisting of a major portion of a starch hydrolysing enzyme, preferably an amylase, active in the pH range 6 to 9 and the temperature range of 40 to 90°C.

7) A drainage aid as claimed in claim 3 which also contains a cellulase active in the pH range 6 to 9.