FI81394B - FOERFARANDE FOER BEHANDLING AV MASSA MED ENZYMER. - Google Patents

Abstract

The invention relates to a method for improving the drainability of mechanical pulp or pulp mainly containing mechanical pulp by means of enzyme treatment by adding to the pulp at least one hemicellulose-dissolving enzyme or an enzyme preparation containing at least one hemicellulose-dissolving enzyme and being substantially free from cellulose-dissolving enzymes. The enzyme treatment according to the invention not only improve the drainability of the pulp but also retains the strength properties of the pulp since no cellulose-dissolving enzymes are used.

Description

1 81394

Method for treating pulp with enzymes

The invention relates to a process for improving the infiltration of a mechanical pulp, such as a thermomechanical or deinked pulp, by treating the pulp with an hemicellulose hydrolysing enzyme.

The permeability of the pulp is usually characterized by the number "freeness". It is known that the mechanical treatment and the deinking process impair the permeability of the pulp.

10 In particular, the low permeability of deinking pulp limits the use of pulp. When processing the fiber mechanically, the fiber has to be stressed, resulting in a large amount of fine material. As a result, the dewatering properties of the finished pulp are not optimal, which is reflected in a reduced freeness value. Often, increasing the freeness value by 10 to 20 units would substantially facilitate the removal of water from the pulp, i.e., improve the use value of the pulp.

In the production of mechanical pulp, the fibers are mechanically separated from the wood without the addition of chemicals, using only 20 heat. In this case, the fiber is stressed in such a way that the lignin which binds the fibers together softens and, as the mechanical stress continues, the fibers become detached when the elasticity of the lignin fails.

Mechanical masses include grind, grit, pressure grind 25 and thermomechanical mass. In the production of mechanical pulps, the temperature increases in the above order, so that the temperature is the lowest in the production of groundwood and the highest in the production of thermomechanical pulp.

The higher the processing temperature, the more intact the fibers detach, but the surfaces of the fibers are increasingly covered with lignin. Mechanical pulping is characterized by the formation of a large amount of fines. This is not the case with chemical treatment of pulp, where lignin is chemically dissolved. The fines are to some extent advantageous in terms of strength, but disadvantageous in terms of the removal of water from the pulp, since it impairs the removal of water from the pulp.

With groundwood, the negative and positive properties of the fines are relatively balanced, but in particular the strength potential of the thermomechanical pulp is clearly better compared to the dewatering properties. However, the strength properties of the groundwood are relatively poor compared to the properties of the thermomechanical mass.

The so-called paper is currently also used as a raw material.

10 recycled masses. Recycled pulp is made from recycled paper, in which case the wood fiber served in the form of paper one or more times is reused. A key task in the recycled pulp process is to remove contaminants from the recovered paper. The methods used for this task can be divided into three groups: 1) mechanical methods 2) heat-based methods 3) chemical methods.

Recycled masses can be used deinked or untreated. The basic idea of deinking is to chemically and mechanically remove the ink from the fiber and place the detached ink in a fibrous-water stock in a hydrophilic state. The detached ink can be removed from the stock by foaming and / or washing.

The raw material for the deinking plant is mainly two grades of recovered paper: household waste paper and message-25 sheets. Of these, household waste paper is unsorted and its composition varies. It typically contains 60-70% newsprint, 20-30% magazine paper and less than 10% various types of cardboard and paperboard.

Based on the above, it can be calculated that a large part of the initial mass of the 30 recycled pulp is mechanical pulp (newsprint contains 85-100% and magazine paper 70-90% of the mechanical pulp). In addition, the production of recycled pulp is characterized in that when decomposing once-dried paper, mechanical energy always has to be used, whereby in addition to the desired effect, fines are formed. The detrimental effect of fines 3 81394 is particularly pronounced in certain applications of deinked pulp.

In every era. the pulps are rich in fines, but the poor dewatering properties compared to the 5 other application potentials are particularly pronounced with thermomechanical pulp and in certain applications of deinked pulp.

The properties of the pulp can be influenced by various enzyme treatments. However, the results of processing are usually difficult to predict. In most cases, combinations of different enzyme activities must be used while avoiding the presence of unwanted enzyme activities.

Examples of successful applications can be found in 15 literature:

French Patent Publication No. 2557894 relates to a process in which pulp is treated with the enzyme xylanase to reduce the grinding time. Canadian Patent Publication No. 758488 relates to a process in which the grinding properties of a pulp are improved by cellulase / pectinase / lipase enzyme treatment. French Patent Publication No. 2571738, on the other hand, relates to a process in which cellulase treatment gives the pulp special pulp properties. Japanese Patent Publication No. 25 60126395 relates to a method for improving the grinding process by the addition of an enzyme.

Japanese Patent Publication No. 59009299 relates to a method of adding alkaline cellulase together with a surfactant to the deinking process to enhance the removal of printing ink.

Japanese Application Publication No. 63059494 relates to a method for improving the whiteness of recycled pulp by means of an alkaline cellulase.

French Patent Application No. 8613208 relates to a process for improving the properties of a previously ground pulp, for example a recycled pulp with a Schopper-Riegler (SR) number of more than 25, by cellulase / hemicellulase treatment.

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According to the application, the SR number can be calculated without compromising the other properties of the pulp. The SR number describes the permeability of the pulp; the lower the SR number, the better the infiltration rate.

However, the FR patent application mainly describes the treatment of recycled pulps rich in chemical pulp. Applying the enzyme treatment according to that patent application to recycled pulps of mainly mechanical origin, it is found that the

1 Q

ly substantially with cellulase-containing enzyme mixtures reduces the strength properties of the pulps; this will be apparent from the examples to be given later. The strength values decrease even under the influence of even small amounts of cellulase, especially if the enzyme-containing pulp has to be stored for a long time, for example due to process disturbances. Therefore, it is preferred that the enzyme used in the treatment does not adversely affect the strength properties of the pulp, even over a long period of action (several hours).

It is an object of the present invention to improve the permeability of mechanical pulp, in particular thermomechanical pulp and / or deinked pulp, by enzyme treatment so that the strength properties of the pulp are maintained.

The invention is characterized in that a hemicellulose-degrading enzyme (s) or an enzyme preparation containing a hemicellulose-degrading enzyme / enzyme-free enzyme / enzyme-containing enzyme / enzyme The enzyme addition can be performed during or after the acidification of the pulp.

Hemicellulose degrading enzymes include e.g. xylanases, beta-xylosidase, acetyl esterase, alpha-arabinosidase, alpha-glucuronidase, arabinases and mannanases.

Particularly preferred enzymes are xylanases and mannanases.

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Enzymes useful in the practice of the invention include hemicellulases or hemicellulase preparations, especially xylanases and mannanases, which are substantially free of cellulases. By cellulases is meant herein enzymes capable of dissolving crystalline cellulose and releasing significant amounts of sugars or oligosaccharides therefrom. The enzymes referred to in the invention are known to be produced e.g. ray fungi (e.g. Streptomyces olivochromoqenes), bacteria (e.g. Bacillus 10 sp.) and fungi (e.g. Penicillium steckii).

A suitable enzyme dosage is about 30 to 200,000 units / kg dry matter of the pulp, preferably about 100 to 50,000 units / kg. The treatment can be performed in the pH range of about 2 to 10, preferably about 4 to 8, depending on e.g. the origin and properties of the 15 hemicellulase enzymes used. The treatment time depends on the enzyme dosage and treatment conditions, and ranges from 10 minutes to a day, preferably from 0.5 to 8 hours. The enzyme treatment temperature may range from about 10 to 90 ° C, preferably from about 25 to 70 ° C.

The xylanase activity of the enzyme preparations was determined as follows:

To one milliliter of xylan solution (1%, Sigma No: X-0376, made in 50 mM Na-citrate buffer, pH 5.3) was added 1 ml of appropriately diluted enzyme in the same buffer. The solution was incubated at + 50 ° C in a water bath for 30 minutes. The reaction was stopped by the addition of 3 ml of DNA reagent (3,5-dinitrosalicylate reagent), and the color was developed by boiling the sample for 5 min. The absorbance was measured at 30 540 nm. One unit of enzyme releases one micromole of reducing sugars, calculated as xylose, per minute under the assay conditions.

The mannanase activity of the enzyme preparations was determined as follows: To one ml of locust bean gum solution (0.5%, Sigma No: G-0753, made in 50 mM Na-citrate buffer 6,81394, pH 5.3) was added 1 ml of the same buffer as appropriate. diluted enzyme. The solution was incubated at + 50 ° C in a water bath for 10 minutes. The reaction was stopped by the addition of 3 ml of DNA reagent, and the color was developed by boiling for 5 to 5 min. The absorbance was measured at 540 nm. One enzyme unit releases one micromole of reducing sugars, calculated as mannose, per minute under assay conditions.

The cellulase activity of the enzyme preparations was determined as the filter paper activity (Ghose T.K. et al.,

Symposium of Enzymatic Hydrolysis of Cellulose, Bailey M., Enari T.M., Linko M., Eds. (SITRA, Aulanko, Finland, 1975), pp. III - 136): To 1 ml of acetate buffer (0.05 M NaAc, pH 4.8) was added a piece of filter paper (Whatman 1, 50 mg). 1 ml of appropriately diluted enzyme solution was added. The solution was incubated for 1 h at 50 ° C. The reaction was stopped by the addition of 3 ml of DNA reagent, and the color was developed and measured as in the xylanase assay. One unit of activity releases 20 μl of reducing sugars, calculated as glucose, in 1 minute.

The method according to the invention is illustrated by the following working examples. The following enzyme preparations were used in the working examples: 25 Enzyme preparation 1 MULTIFECT L 250 (commercial ready-made (cellulase preparation), „,.„ ......

you, Suomen Sokeri Oy, made

Trichoderma longibrachiatum by mold; activity; xylanase 250 units / g, cellulase about 100 units / g)

Enzyme preparation 2 MULTIFECT K (commercial preparation, (cellulase / hemicase- Suomen Sokeri Oy, manufactured Trilulase preparation) by means of choderma longibrachiatum mold: activity: xylanase 35,600 units / g, cellulase 30 units / g)

II

7 81394

Enzyme preparation 3 Xylanase preparation (prepared from hemicellulase

Streptomyces olivochromoqenes using the fungus Poutanen, K., Rättö, M., Puls, J.

5 and Viikari, L., Evaluation of differential microbial xylanolytic systems, Journal of Biotechnology, 6 (1987) 49-60). Of these enzyme preparations, Preparation 3 represents an enzyme preparation containing a hemicellulose-degrading enzyme (xylanase) useful in the method of the invention, which is substantially free of cellulose-degrading enzymes. Preparations 1 and 2 are comparative preparations which, in addition to hemicellulase activity, contain varying amounts of cellulose degrading enzyme activities.

Example 1 An aqueous slurry containing 10% dry matter was prepared from dried deinked pulp (Keräyskuitu Oy export quality) and allowed to stand at room temperature overnight. The slurry was then diluted with water to a dry matter content of 5% and decomposed in a laboratory mixer (3000 rpm, 25 min). The pH of the slurry was adjusted with 1-M sulfuric acid from an initial value of about 7 to 5.4.

The slurry was weighed for 3 kg for the experiment and heated to + 50 ° C. The temperature was maintained by keeping the vessel containing the slurry in a water bath. The test enzyme preparation was added to the slurry sample li-30 in the amounts shown in Table 1 and mixed well. 1 kg aliquots were taken from the sample after 1, 2 and 5 hours.

The enzyme-treated pulp was determined to have a freeness value and a circulating water kit was prepared for strength and color measurement. The sheets were made of so-called using a circulating water sheet mold in accordance with Central Laboratory standards 8 81394. All experiments were performed according to SCAN standard guidelines. The results are shown in Table 1. The control sample was treated in the same manner as the test samples, except that no enzyme was added. The amounts of enzyme added are expressed in enzyme units per kg of dry matter of the pulp.

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table 1

Results of Enzyme Treatment Sample Ents. 1 Ents. 2 Ents. 3 Control 5 Xylanase content (units / kg) 250 6000 5000

Cellulase content (units / kg) 100 30 -

Freeness (ml) 0 h 148 148 148 148 10 1 h 149 141 161 150 2 h 163 146 170 152 5 h 184 164 164 151

Tear index (mN m2 / g) 0 h 1 h 5.6 6.0 6.9 6.6 15 2 h 5.0 5.7 6.1 6.3 5 h 4.6 5.3 6.3 6 .8 ISO brightness (%) 0 h 1 h 54.1 54.1 54.2 54.0 2 h 54.1 54.1 54.3 54.3 5 h 54.1 54.3 54.4 54 3 20 Tensile index (Nm / g) 1 h 29.5 30.1 29.9 29.7 2 h 28.8 29.8 29.6 30.6 5 h 27.1 28.4 29.1 30.8

Light scattering coefficient (m2 / kg) 1 h 53.0 52.4 53.9 53.6 25 2 h 53.7 53.4 53.7 52.9 5 h 54.6 53.3 55.7 53.9

Air permeability resistance (s) 1 h 39 49 39 38 2 h 36 53 39 43 5 h 28 41 38 49 30 Density (kg / m2) 1 h 421 430 421 420 2 h 421 440 420 417 5 h 416 431 423 430

Ash content (%) 1 h 4.59 4.55 4.80 4.50 2 h 4.60 4.63 4.78 4.73 35 5 h 4.58 4.62 4.79 4.96 10 81 394

The use of hemicellulase clearly improved the properties of the pulp: both xylanase and cellulase improved the permeability, but at the same time the cellulase significantly reduced the tear index. The other properties of the pulp 5 were not impaired by the enzyme treatment.

Example 2

The experiments were performed as in Example 1. Only enzyme 3 (xylanase) was tested. The results are shown in Table 2.

10 Table 2

Results of Enzyme Treatment Sample Ents. 3 Comparison

Xylanase content (units / kg) 5000 15 Freeness (ml) 0 h 147 147 1 h 167 146 2 h 168 151 5 h 167 150 20 The hemicellulase treatment clearly improved the filtration of the pulp.

Example 3

The experiments were performed as in Examples 1 and 2. However, the amount of the added xylanase preparation (enzyme preparation 3) was smaller. Samples were taken after 1/2 hour as well as one hour and 4 hours. The results are shown in Table 3.

11 81394

Table 3

Results of Enzyme Treatment Sample Ents. 1 Ents. 3 Control 5 Xylanase content (units / kg) 250 1250

That Uula Sipi brought a mouth s (units / kg) 100

Freeness (ml) 0 h 160 160 160 10 0.5 h 158 - 156 1 h 165 170 155 4 h - 182 166

Tear index (mN nr / g) 0 h 6.5 6.5 6.5 0.5 h 6.1 - 6.5 15 1 h 5.8 6.5 6.6 4 h - 6.6 6.3 ISO brightness (%)

Oh 57.6 57.6 57.6 0.5 h 57.3 - 57.6 1 h 57.4 57.7 57.6 4 h - 58.0 57.9 2 0

The results are similar to Example 1. The xylanase treatment improved the properties of the pulp. Although the action time of the cellulase was shortened, it still deteriorated the strength properties of the pulp.

2 5 Example _4

Unbleached, non-acidified deinked pulp! ! (Keräyskuitu Oy) with a dry matter content of about 7.5% was soaked overnight, after which it was diluted to a concentration of 20 g / l and decomposed and ground with a Dutcher 30 until the freeness was 130. After grinding, the pH was adjusted to 5.5 IM H „SO.

'2 4

The xylanase enzyme preparation was added to the pulp: ((enzyme preparation 3) in the amounts shown in Table 4.

The mass was heated on a steam coil to 50 ° C and incubated at 50 ° C in a water bath. Freeness was determined after 1 h and 4 h of incubation. The results are shown in Table 4.

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Table 4

Results of Enzyme Treatment Sample Ents. 3 Ents. 3 Control 5 Xylanase content (units / kg) 500 1250

Cellulase content (units / kg) -

Freeness (ml) 0 h 142 142 142 10 1 h 154 158 140 4 h 153 163 141

It is found from the results that the xylanase enzyme preparation free of cellulase activity increases the freeness number of the unbleached, unacidified deinked pulp from 11 to 15 units depending on the dosage.

Example 5

The bleached, acidified (pH 7.7) normal mass (Kerääkuitu Oy) with a dry matter content of about 10% was soaked overnight, after which it was diluted to a concentration of 20 g / l and digested with a Dutcher. After decomposition, the pH was adjusted to 5.5 with 1M H 2 SO 4, followed by grinding. The freeness of the pulp before grinding was 199 and 5 min after grinding 131.

Xylanase enzyme preparation 25 (enzyme preparation 3) was added to the pulp in the amounts shown in Table 5. The mass was heated on a steam coil to 50 ° C and incubated at 50 ° C in a water bath. Freeness was determined after 1 h and 4 h of incubation. The results are shown in Table 5.

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Table 5

Results of Enzyme Treatment 13 81 394 Sample Ents. 3 Ents. 3 Control 5 Xylanase content (units / kg) 500 1250

Cellulase content (units / kg) -

Freeness (ml) 0 h 131 131 131 10 1 h 142 145 131 4 h 149 144 133

The results show that the xylanase enzyme preparation free of cellulase activity increases the freeness number of the bleached, acidified deinked pulp by about 10 to 15 units depending on the dosage.

Example 6 Additional Embodiments

When applying the enzyme to an integrated plant, in which either a mechanical pulp plant or a deinking plant is connected to a paper mill, the addition of the enzyme can be performed before the pulp is transferred to the paper machine. If the above deinking plant is not integrated with the paper mill, the enzymes can be added to the pulp slurry and allowed to act for a suitable time, after which the pulp is dried and post-treated as desired. Alternatively, the enzymes can be added to the pulp slurry at a paper mill and allowed to act if the pulp was purchased elsewhere.

30 The enzyme treatment is also suitable for chemimechanical pulp, where the main separation of the fibers takes place mechanically, but a mild chemical increase to soften the lignin is used as an aid. A typical example of such a pulp is CTMP pulp (chemical thermomechanical pulp-35 sa).

Claims (12)

A method of improving the drainage capacity of mechanical pulp or mainly mechanical pulp containing pulp by enzyme treatment, characterized in that an enzyme / enzymes which decompose hemicellulose or a enzyme preparation is added to the pulp. which contains an enzyme / enzymes which decompose hemicellulose, and which is substantially free of enzymes which decompose cellulose. 2. A method according to claim 1, characterized in that the mechanical pulp is thermomechanical pulp. 3. A method according to claim 1, characterized in that the mechanical pulp is degraded pulp. Process according to claim 1 or 3, characterized in that the enzyme (s) is added in conjunction with or after acidification of the pulp. Process according to any of the preceding patent claims, characterized in that the enzyme or enzyme preparation which decomposes hemicellulose is added in an amount of about 30 - 20000 enzyme units per kg of the dry matter of the pulp. 6. A process according to claim 5, characterized in that the enzyme or enzyme preparation which decomposes hemicellulose is added in an amount of about 100-50000 enzyme units per kg of the dry substance of the pulp. Process according to any of the preceding patent claims, characterized in that in the pulp is added xylanase or a xylanase preparation which is substantially free of enzymes which decompose cellulose. Process according to any of the preceding claims, characterized in that in the pulp is added mannanase or a mannanase preparation which is substantially free of enzymes which decompose cellulose. A 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. Method 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. 12. A process according to claim 11, characterized in that the enzyme treatment is carried out at a temperature of about 25 - 70 ° C.