FI93230B - Method for reducing resin difficulties in mechanical pulp - Google Patents

Abstract

The invention relates to a method for reducing the pitch trouble of mechanical pulp and/or papermaking pulp containing mechanical pulp by treating the pulp or white water with a cellulase/hemicellulase enzyme preparation.

Description

93230

Method for reducing resin difficulties in mechanical pulp

The invention relates to a process for reducing the resin difficulties of mechanical pulp 5 and / or pulp containing mechanical pulp using cellulase / hemicellulase enzyme treatment.

Mechanical masses include grind, grit, pressure grind, thermomechanical mass and CTMP or core thermomechanical mass. In the production of mechanical pulp, the fibers are separated from the wood mainly mechanically with the help of heat. In this case, the fiber is stressed in such a way that the lignin which binds the fibers together softens and the fibers detach from each other when the elasticity of the lignin fails.

15 Wood contains about 1 to 10% resin and extracts soluble in organic solvents in addition to its main components (cellulose, hemicellulose and lignin). Resin is composed of fatty acids, rosin acids, glycerides, etc. It is well known that the main raw material in the mechanical pulp, i.e. coniferous wood, has high resin concentrations compared to, for example, hardwood. During the pulping process, the resin components are released from the pulp into a free space, e.g. circulating water. The resin suspended in the circulating water is in the form of particles with a diameter of 0.2 to 2 μm, also known as "colloid resin".

In papermaking, resin can accumulate in tubes, tanks, wire, or presses, causing resin problems in the form of paper quality defects (e.g., holes and spots) and paper breaks. It can also clog blankets and 30 wires, making it difficult to remove water from the paper web. Resin problems can lead to long production downtime. Resin problems are particularly common when using a pulp rich in mechanical pulp as a raw material.

Resin problems have traditionally been avoided by storing wood outdoors for long periods of time (3-6 months 2,93230 or more), whereby resin materials are decomposed mainly due to the oxidizing effect of air. Inorganic substances such as talc and anionic surfactants which disperse the resin particles have also been used to control resin problems.

FI patent application 870072 discloses a resin control method using certain water-soluble polyquaternary amines. These compounds are added to a pulp or papermaking system to avoid resin problems.

FI patent application 900679, on the other hand, describes a method for reducing the resin content of wood by means of fungi which decompose wood resin and resin materials.

FI patent application 895901 discloses a method for avoiding resin problems associated with mechanical pulp by adding an acyl glycerol lipase enzyme to paper pulp or circulating water. This enzyme breaks down the triglycerides in resin.

The use of enzymes, including cellulases and hemic-20 lulases, to improve pulp properties is known per se. For example, FR patent publication 2557894 discloses a method for treating pulp with the enzyme xylanase in order to shorten the grinding time. CA Patent Publication 758488 relates to a method for improving the grinding properties of pulp by cellulase / pectinase / lipase enzyme treatment. FR patent publication 2571738 relates to a process in which cellulase treatment gives the pulp the properties of a special pulp.

FI patent application 874113 (= FR patent application 30 8613208) relates to a method for improving the properties of e.g. recycled pulp (in this case pulp rich in chemical pulp) by cellulase / hemicellulase treatment. FI publication 81394, on the other hand, concerns the improvement of the permeability of a mechanical pulp by hemicellulase treatment (not cellulase).

Il 3 93230

In addition, FI patent application 890214 describes the treatment of the circulating water of a papermaking system with enzymes to decompose substances dissolved or dispersed in the pulp, such as hemicellulose.

The object of the invention was to develop a method by which resin problems associated with the production of mechanical pulp, in particular pulp containing mechanical pulp, could be reduced. The methods known so far have been used with varying degrees of success, and problems have not been completely avoided.

It was now surprisingly found that the cellulase / hemicellulase treatment substantially reduced the resin problems associated with the production of mechanical pulp. The resin content was indicated by the extractant contents of the pulp filtrate water, in particular the fatty acid, resin acid and sterol contents, decreased sharply and the turbidity of the filtrate water decreased.

According to the invention, the resin problem associated with the production of mechanical pulp and / or pulp containing mechanical pulp was solved by treating the mechanical pulp, pulp containing mechanical pulp and / or circulating water with an enzyme preparation containing cellulase / hemicellulase enzyme activity.

It was completely unexpected that the cellulase and hemi-25 cellulase enzymes, which are known to cleave cellulose and hemicellulose, also affected the main components of the resin, i.e. fatty acid, rosin acid and sterol type substances.

In practice, the reduction in resin problems was seen e.g.

30 in that the runnability of the paper machine improved, the wires and blankets remained clean, and the number of holes and spots in the paper decreased.

Other beneficial effects were also achieved by enzyme treatment. Thus, for example, the infiltration properties of the pulp were improved. The enzyme treatment also did not impair the optical or printing properties of the pulp, but improved the brightness, light scattering coefficient, compressibility and smoothness of the pulp.

The enzyme treatment according to the invention can be carried out at any stage of the pulping process after mechanical separation of the fibers. The enzyme can be added, for example, to a pulp storage tank, storage tower or dosing tank. The enzyme treatment may be performed before the pulp bleaching, during any of the pulp bleaching processes 10, or after the pulp bleaching. The enzyme can also be added to the circulating water.

The cellulase / hemi-cellulase enzymes used according to the invention can be prepared from known e.g. by fungi, bacteria and fungi.

Commercial cellulase / hemicellulase preparations can also be used, eg Liftase A40 enzyme preparation (manufactured by Genencor International Europe Ltd.) produced by the fungus Trichoderma longibrachiatum and having a CMCase activity (carboxymethylcellulose-20 activity) of 2500 U / ml, filter paper activity (FPU activity) 110 U / ml and xylanase activity 500 U / ml. Of these, carboxymethylcellulase activity and filter paper activity describe cellulolytic activity and xylanase activity hemicellulolytic activity. The determination of filter paper activity is described in Ghose, T.K., Patnak, A.N., Bisaria, V.S., Symposium of Enzymatic Hydrolysis of Cellulose, Bailey, M., Enari, T.M., Linko, M., Eds. (SITRA, Aulanko, Finland, 1975), 111-136; Determination of CMCase Activity 30 in Mandels, M., Weber, J., Adv. Chem. Ser. 95 (1969) 391-413; and the determination of xylanase activity in Khan, A.W., Tremblay, D., LeDuy, A., Enzyme Microb. Technol., 8 (1986) 373-377.

Other cellulase / hemicellulose preparations from the same manufacturer (Ge-35 nencor International Europe Ltd) can also be used, e.g. Multifect L250 and Cytolase 123, as well as cellulase / hemicellulase preparations from other manufacturers.

Suitable enzyme dosages, expressed as enzyme activities per kg dry matter of the pulp, are within the following limits (U = unit of activity):

Cellulases: filter paper activity 1-20,000 U / kg pulp CMCase activity 10-500,000 U / kg pulp

Hemicellulases: 10 xylanase 0-2 000 000 U / kg mass.

Preferred enzyme dosages are: filter paper act. about 20 to 600 U / kg of mass CMCase act. about 500 to 10,000 U / kg pulp, and 15 xylanase acts. about 500 to 100,000 U / kg mass.

The enzyme treatment is generally carried out at a pH in the range of about 2 to 10, preferably in the range of about 4 to 8. The temperature of the enzyme treatment may be in the range of about 10 to 90 ° C, most preferably in the range of about 25 to 70 ° C.

The invention is described in more detail below by means of the following examples based on laboratory tests and factory-scale test runs, which are intended only to illustrate but not to limit the invention. Measurements were performed according to SCAN standards unless otherwise noted.

Example 1

A thermomechanical mass (TMP) of spruce (Picea abies) taken from the factory process with a consistency of 30 4%, pH 4.9, a freeness value of 69 ml CSF and a brightness of 66% ISO was treated with an enzyme preparation called Liftase A40. Liftase A40 (manufactured by Genencor International Europe Ltd.) is produced by the microorganism Trichoderma longibrachiatum and contains the following main activities: 6 93230 CMCase activity 2,500 U / ml FPU activity 110 U / ml xylanase activity 500 U / ml 5 Liftase A40 was carefully added to the pulp at 55 ° C in an amount corresponding to 2.5 liters / ton of pulp dry matter.

The dosages of the added enzyme preparation, expressed as cellulase / hemicellulase activities per kg of pulp as 10 wt, were as follows: CMCase activity 6,250 U / kg FPU activity 275 U / kg xylanase activity 1,250 U / kg 15

The enzyme was allowed to react with the pulp at 55 ° C and pH 4.9, stirring the pulp at 150 rpm for a total of 1 hour. The pulp was sampled at regular intervals to determine turbidity and also the extractant contents from the remaining 20 samples. Turbidity agents in the solution part of the TMP pulp are extractants (resin), suspended carbohydrates and other small constituents detached from the pulp. Thus, turbidity gives a rough estimate of the changes to all of the above components. A separate analysis of the extractants refines the result specifically for resin. For turbidity measurement, 250 g of the pulp mixture was centrifuged (1800 rpm, 20 min). The supernatant (solution portion) was collected and immediately measured for turbidity with a Novasine Analite NTM-150 turbidimeter-30. The extracts were measured from the supernatant by gas chromatography.

The control sample was treated similarly to the enzyme-treated sample except without enzyme.

The measurement results are shown in Table 1.

il, 7 93230

table 1

Effect of enzyme treatment on turbidity and extractant contents of TMP pulp solution 5 COMPARISON OF ENZYME

WROUGHT

SAMEUS, NTU

- 0 min 320 320 10 - 10 min 300 190 - 30 min 310 100 - 60 min 330 25 EXTRACTORS, mg / l 15 60 min - fatty acids 65 6.2 - rosin acids 21 2.5 - sterols 13 1.2 20 According to the results the turbidity of the solution part of the pulp decreases considerably even after a reaction time of 10 minutes. The solution part is almost clear, i.e. turbidity of 25 NTU after a reaction time of 60 minutes, in which case the concentration of extractants in the solution part has decreased to 1/10 of the original. This indicates that the extract-25 substances precipitate or adhere to the surface of the fiber due to the enzyme treatment.

Example 2.

It was also decided to find out the significance of the reduction of the resin content of the mechanical pulp filtrate-water in practice 30, i.e. to carry out a factory-scale test run. The test run was performed on an LWC machine with on-machine coating.

The machine used peroxide-bleached TMP as the mechanical pulp, and since the experiments of Example 1 had been performed with 35 unbleached TMPs, it was decided to perform a set of 8,93230 confirmatory tests in the laboratory before the test run. Peroxide bleached TMP was taken directly from the process at a consistency of 3.2%. The pH of the pulp was 5.5 and the temperature was 45 ° C. Ko. under the conditions the pulp was subjected to enzyme treatment using Liftase A40 enzyme 5 2 1 / t. Resin content was assessed by turbidity measurement. For background, the pulp was filtered through Macherey-Nagel MN 640 w filter paper, and turbidity was measured with the meter mentioned in Example 1. The results at different reaction times are shown in the table below.

10 Reaction time Turbidity (min) (NTU) 0 323 40 110 120 28 15 As can be seen, the enzyme has performed excellently and thus a factory test run was started.

The duration of the test run was chosen to be 6 days and the enzyme Liftase A40 at a dose of 2 1 / t TMP was chosen. The enzyme was metered into peroxide bleached TMP from a storage tower at 20 ns. to the suction side of the pump pumping the tread type. The enzyme treatment conditions in the trowel type were as follows: - pH 5.5 - temperature, ° C 45 - consistency,% 3.5 25 - reaction time, min 42

After the mill vat, the peroxide bleached TMP was mixed with the chemical pulp and wreck in a mixing vessel. The pulp mixture was then pumped into the machine pan and from there on to the paper machine headbox after further dilution with wire water. During the test run, the resin content was evaluated by measuring the turbidity of the TMP pulp from the filtrate water and in addition the freeness of the TMP pulp was measured. The results are in the table below.

li 9 93230

COMPARISON ENZYME

Filtration turbidity, NTU

before the trowel type 370 370 5 - after the trowel type 420 250

Freeness, ml - before rubbing type 62 62 - after rubbing type 59 65 10

The results show that the enzyme has also functioned under factory conditions and the resulting turbidity reduction is 170 units, indicating a clear reduction in the resin content in the filtrate, i.e. the adhesion or precipitation of the resin to the fiber. In addition, it is observed that the freeness of TMP has increased by 6 units, which means easier drainage.

During the test run, the following observations were made on the machine, which support the elimination / reduction of resin problems: - The runnability of the machine during the whole enzyme cycle was 20 exceptionally good.

- The wires and blankets and the whole wire section remained very clean.

- The number of holes and spots in the base paper was clearly lower than normal.

25 The results of the test run were verified by a re-test run lasting 10 days. In terms of resin and runnability, the results were similar to those of the first test run. In addition, it was found that the enzyme treatment has a positive effect on the performance of the conventional retention aid, since the target retention level of 30 was achieved with a 20-30% lower dose of the retention aid.

Example 3.

The increase in the mechanical mass of freenek observed in the factory test run raised the question of how it affects the The optical and printing properties of the pulp are driven by the use of mainly enzymatically treated pulp in uncoated paper grades such as SC paper and newsprint. For this purpose, a sample of a typical mechanical pulp of SC paper was obtained. Ko.

5 pulps were subjected to enzyme treatment under the conditions shown in Table 2 with different doses of Liftase A40. After the enzyme treatment, laboratory sheets were made from the pulp, and the properties measured on the sheets, both directly and after calendering, are also shown in Table 2. 10 As the results show, the enzyme treatment did not impair the optical or printing properties of the pulp, even up to 25 units. on the contrary, because - the light absorption coefficient has decreased, indicating an improvement in brightness, - the light scattering coefficient has improved, - the compressibility has increased (density after calendering), and - the smoothness has improved (roughness decreases).

Thus, there are no barriers to the use of enzyme-treated pulp in uncoated grades as well, but on the contrary, in addition to reducing resin problems, quality improvement can be expected either directly or at least through the possibility of increasing the fineness of mechanical pulp and compensating for poorer dewatering.

Example 4.

To verify the results obtained, it was decided to perform experiments with both unbleached TMP and dithionite-30 bleached TMP and to measure not only the resin but also the effect on freeness and water retention (WRV) and sheet properties. This time the sheets were made using the so-called kiertovesiarkkimuottia. The enzyme treatment conditions and the results obtained are shown in Table 3. As can be seen, the enzyme treatment with respect to resin 11 93230 (turbidity) also works with these pulps. In addition, the following positive aspects are observed: - Dewatering properties improve (freeness increases and WRV decreases) 5 - Optical properties improve (light scattering coefficient and brightness increase) - Printing properties improve (roughness decreases and compressibility increases, i.e. density increases after calendering).

10 Example 5.

When it was found that the enzyme treatment has a positive effect on the brightness of the mechanical pulp, it was decided to check what is the case if the enzyme treatment is carried out before bleaching. To this end, the pulps of Example 1 (reference pulp and enzyme-treated pulp) were peroxide bleached with different amounts of peroxide using standard peroxide bleaching conditions (consistency 16%, temperature 60 ° C, reaction time 90 min, DTPA 0.2%, MgSO 4 .7H 2 O 0.5% and Na silicate 5% by weight). After bleaching, the pulps were brightened both immediately and after aging. The results are shown in Figure 1. It is observed that the brightness has improved and the improvement is also visible after aging. Thus, it can be stated that the enzyme treatment also has a positive effect on the bleachability of the mechanical pulp. 25 Example 6.

It was decided to verify the positive effect of the enzyme on the function of the conventional retention agent observed in a factory test run by a laboratory experiment. Unbleached TMP taken from the mechanical pulp intermediate tank was treated with 30 Liftase A40 under the following conditions: pH 5.0

- temperature 50 ° C

- reaction time 1 hour - mass consistency 3.7% 35 - enzyme dosage 0, 1, 2 and 4 1 / t TMP.

95230 12

The corresponding enzyme doses, expressed as cellulase / hemicellulase activities per kg dry matter of the pulp, were as follows: 5 1 1 / h 2 1 / h 4 1 / h CMCase act. 2,500 U / kg 5,000 U / kg 10,000 U / kg FPU act. 110 U / kg 220 U / kg 440 U / kg

Ksylanaasiakt. 500 U / kg 1,000 U / kg 2,000 U / kg 10

After enzyme treatment, TMP was blended with chemical pulp and kaolin in the following proportions: TMP 42% 15 - chemical pulp 24% - kaolin 33%.

The pulp mixture was diluted to a concentration of about 10 g / l. The dry matter content and fines content as well as the total, fines and ash retention of the pulp mixture were determined with a Dynamic Drainage Jar according to the method TAPPI T261 pm-80. The retention measurement was performed on the pulp mixture as such and after the addition of the retention aid.

The results obtained are summarized in Table 4. It is found that the enzyme treatment actually improves the retention, i.e. in practice the operation of the conventional retention aid is enhanced and in the pursuit of a constant retention it is possible to reduce the amount of the conventional retention aid.

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Claims (12)

A process for reducing resin problems of mechanical pulp and / or pulp containing mechanical pulp, characterized in that mechanical pulp, paper pulp containing mechanical pulp and / or backwater is treated with an enzyme preparation containing cellulase / hemicellulase enzyme activity. , for depositing the resin on the surface of the fibers. 10 2. A method according to claim 1, characterized in that the pulp consists of abrasive pulp, refiner pulp, press grinding pulp, thermomechanical pulp or chemiteromechanical pulp. 3. A method according to claim 1 or 2, characterized in that the pulp is unbleached pulp. Method according to claim 1 or 2, characterized in that the pulp is bleached pulp. 20 5. A process according to claim 4, characterized in that the enzyme treatment is carried out before the bleaching of the pulp. Method according to claim 4, characterized in that the enzyme treatment is carried out after the bleaching of the pulp. Process according to any of the preceding claims, characterized in that the enzyme preparation is added in an amount corresponding to 1-20,000 units of cellulolytic activity expressed as filter paper activity, 10-500,000 units of cellulolytic activity expressed as CMCas activity and 0-2,000,000 units of hemicellulolytic activity expressed as xylanase activity, per kg of dry matter of the pulp. 8. A process according to claim 7, characterized in that the enzyme preparation is added in an amount corresponding to about 20 to 600 units of cellulolytic activity expressed as filter paper activity, about 500 to 10,000 units of cellulolytic activity expressed as CMCas activity and about 500 - 100,000 units of hemicellululytic activity expressed as xylanase activity. Method according to any of the preceding claims, characterized in that the enzyme treatment is carried out within a pH range of about 2-10. 10. A process according to claim 9, characterized in that the enzyme treatment is carried out within a pH range of about 4-8. Process according to any of the preceding claims, characterized in that the enzyme treatment is carried out at a temperature of about 10 - 90 ° C. 15 12. A process according to claim 11, characterized in that the enzyme treatment is carried out at a temperature of about 25 - 70 ° C. TL