DE3034042A1 - METHOD FOR REDUCING THE RESIN CONTENT IN THE PRODUCTION OF CELLULOSE PULP FROM LIGNOCELLULOSE MATERIAL - Google Patents

Description

PATENTANWÄLTE, OUO H- j

mini, iniai P. WinTll · Dr. V. SCHMIED-KOWARZiK I

Dipl.-Ing. G. DANNENBERG Dr. P. WEINHOLD Dr. D. GUDEL

335024 SIEGFHIEDSTRASSE 8

TELEPHONE: CO ₈₈₃ ^ _{8000 MrJNCHEN 4Q}

Case 1410 Wd / Wd

Mo och Domsjö AB

Box 500

S-89101 Örnsköldsvik, Sweden

PROCESS FOR REDUCING THE RESIN CONTENT IN THE PRODUCTION OF CELLULOSE PULP FROM LIGNOCELLULOSE MATERIAL

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The present invention relates to a method for reducing the resin content of cellulose pulp during manufacture this pulp "^ wood pulp) made of lignocellulosic materials. As used in this specification, the term "cellulose pulp" preferably refers to chemical wood pulps, d. H. Wood pulps that are produced by chemical digestion processes. The invention finds Mainly used in the manufacture of sulphite pulp, but also in the manufacture of "Kraft" pulp from hardwood such as B. Birch is an important application of the present invention.

The starting material for the production of cellulose pulp is lignocellulose, for example in the form of wood, and this Always contains smaller or larger amounts of resin, It is expedient during the process of making the pulp to remove the resin as much as possible so that the fully treated pulp has a low resin content. High resin content in the finished pulp can cause problems when using the pulp (e.g. in papermaking) and can affect the quality of the end product. In addition, the resin actually does that Process of pulp production complicated.

.When producing the pulp using the sulphite process therefore the wood is always stored for a certain period of time before it is put into the stove and processed into cellulose pulp will. During storage, also called aging ("seasoning"), a change in the physical character occurs of the resin, which leads to a somewhat reduced amount of resin in the wood and also to changes in the resin itself, so that it becomes more soluble during the pulp making process. The storage of the wood can be on different ways. " For example, the wood in the form of unprocessed logs can first be stored in water are (floating and tied together), after which the logs are stored in the form of bundles in a wood storage area on land will. After a storage time of about 1 year, the

Pulp

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Trunks ground into chips in a pulp mill and further-j

j treated. According to a different method, the trunks j

already ground into schnitzel when they are at the mill come, and the schnitzels are then stored in a pile. With such a treatment, the storage time can be shortened to about 3 months. Apart from the location

treatment method is always associated with costs. j

In addition, there is the fact that at the same time there is a certain ver i

lust for wood occurs and considerable amounts of capital are j

are bound. j

Despite the storage, the wood still contains considerable j amounts of resin, although in a somewhat different form in comparison j to the resin in the fresh wood, - The greater part of the remaining Resin content is removed in several steps during the pulp making process. All of the resin is removed Removing the pulp is difficult and, moreover, costly. Therefore, finished pulp almost invariably contains it a certain amount of resin, during the actual breakdown of the wood, part of the resin is dissolved and removed by washing and sieving the pulp.

The final control of the resin content of the pulp takes place during bleaching. The resin becomes mainly during the alkaline Removed stage of bleach cycle. However, it is possible and also not uncommon for the final regulation in a chlorine dioxide level. The following bleaching cycle is common for sulphite mills: chlorine (C), alkali (E), 3Q hypochlorite (H) and chlorine dioxide (D), ie .. also: C-E-H-D. I. By changing the amount of alkali, usually sodium hydroxideJ In stage E smaller or larger amounts of resin ί can be extracted. Together with sodium hydroxide, in dispersants are often added to the Ε stage in order to keep the resin in dispersed form - (and not in agglomerate

restored condition), so that this is to the greatest possible extent can be washed out of the pulp at the washing step following step E. The final regulation of the resin content usually takes place in the D stage, i.e. through

1300H / 1 183

Varying the amount of chlorine dioxide added. The resin is separated from the pulp in the washing stage which follows the D stage. If there are problems with the resin in the grinder

(e.g. foaming and clumping) it may be necessary will be to reduce the amount of chlorine in the C stage and increase the amount of chlorine dioxide accordingly .. It's after known in the art that chlorination of resin means that it is more difficult to treat ". The great Disadvantage when using considerable amounts of chlorine dioxide, to solve resin problems is the high price of this chemical.

In the manufacture of pulp by the Kraft ^ process is the wood is not stored to any significant extent .. To resin problems to solve in the production of eg "B" birchwood pulp it is important that the trunks are carefully stripped of the bark because the bark and also the layer of cambium between the bark and wood contain large amounts of resin. As with sulphite digestion, a solution of the resin occurs in the Kraft digester around the resin during digestion to keep in dispersed form (to avoid clumping) tall oil is added to the digester. That during the Boil's extracted resin is separated from the pulp in the subsequent washing step and together with the black liquor evaporates, whereupon it is burned in the soda recovery cooker.

When producing fuel wood pulp, it is not possible to adjust the resin content by adding different amounts of alkali to regulate in the alkali stage of the bleach cycle. Rather, one has to rely entirely on the expensive bleach chemical chlorine dioxide limit for final regulation of the resin content.

In the manufacture of birch kraft pulp it is therefore necessary to to make expensive investments in high quality peeling equipment and / or large quantities of the expensive ones Adding chemical chlorine dioxide to bleaching to eliminate the resin problems. Even if these are costly Measures are taken, it is difficult to achieve as low a resin content as would be desirable.

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Pulp with low resin content is - as is known - on the Very popular in the market.

In addition to the above, it is possible to increase the resin content of the cellulose pulp to some extent by adding it various surface-active agents, so-called * wetting agents,

j at different points in the manufacturing process

reduce.
10

The procedures described above are the most commonly practiced procedures to resolve the resin problems during the To master making cellulose pulp.

Other methods have also been described in the literature. In the Swedish PS 150 651, for example, it was stated that when dealing with certain types of pulp, which are particularly difficult to de-resinate, it may be expedient to use the pulp in a known manner in connection with the to treat mechanically alkaline treatment. However, it has not been clearly stated what to do with mechanical treatment thinks, and it has not been described in detail how to proceed. Rather, it is suggested have been to carry out the alkali treatment in the presence of a nonionic surfactant to reduce the resin content to reduce the pulp.

In Finnish PS 28 621 there is a method of using unpeeled hardwood and sawmill waste for production of cellulose pulp has been described * The process consists of a combined mechanical-chemical Method of treating the cellulose pulp after cooking (digestion), washing and sieving, the method is thereby characterized in that the unbleached pulp at a temperature

rature of between 10-60 ⁰ C is mechanically treated in an alkaline suspension _; namely in known "Hollander" or grinding apparatus, whereupon the pulp is then treated with alkaline and oxidizing chemicals at a temperature between 10 and 80 ° C and then finally treated mechanically again in the manner described above,

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According to the example in the Finnish PS, the j

t Pulp treated in a "Hydrafiner" or similar "Hollander" grinder at a pH of about 8. This means that the mechanical grinding process takes place with a low pulp consistency (not more than 6%), since the "Hydrafiner" and similar grinding devices can only work with a low pulp concentration.

However, such treatment of the pulp has been found to be unsuccessful in solving the resin removal problem is, d. H. that the resin content of the pulp is not noticeably reduced. One of the reasons for this seems to be to be the one that the mechanical treatment, i.e. the grinding takes place at a relatively low pulp concentration. The minor one Pulp concentration is also accompanied by the disadvantage that the process consumes a lot of energy. It still persists the disadvantage that the Dutch treatment or grinding causes the fibers to be cut, which in many cases is not wanted.

It is also known from Swedish PS 341 323 to subject the cellulose pulp to a mechanical treatment after boiling, washing and, if necessary, sieving is subjected at a concentration of 10-50%, preferably 25-35%, the desired structural change of the fibers being obtained with a possible increase in the drainage resistance of at most k SR; the pulp treated in this way, which is subjected to bleaching or continued bleaching, is immediately diluted to a maximum concentration of 6%, whereupon the pulp is bleached and dried, preferably to a dry matter content of 90-95% the improvement of the paper-technical properties of the pulp. In this description it is not stated that the process creates a solution to the resin problem in the production of cellulose pulp. Tests have shown that this is also the case in practice.

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sen, which are discussed later in the present description.

b In order to obtain in the production of cellulose pulp, a final product of high quality, must be sought, which in the original lignocellulose (such, for example, wood) resin present to be removed to the maximum extent. The methods available to date for removing the resin are very expensive and in some cases unsatisfactory,

d. H. the resin content is not reduced to | the desirable, low level. j

j The present invention solves these problems and relates to {a process for reducing the resin content in the manufacture of bleached or unbleached cellulose pulp from lignocellulose substances. In this process, the lignocellulosic material is subjected to fiber separation, washing and sieving (if desired) and (if appropriate) delignification bleaching Is subjected to concentration devices to bring the pulp concentration to a value of 15-35%, preferably 19-29%; then the cellulose pulp is mixed with alkali in such an amount that the alkali - calculated as NaOH

/ the pulp in the pulp is up to 2-17g per kg of water, whereupon subjecting it to a mild mechanical treatment in a high-consistency treatment device.

This device is equipped with screws or screws, which rotate relative to each other, with an energy input of 8-100 kWh per ton of pulp, preferably from 10 - 75 kWh per ton of pulp. This method is further characterized in that the cellulose pulp after mild, mechanical treatment and with essentially unchanged pulp consistency with the added alkali React in a separate container over a period of 0.1-5 hours.

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The measures according to the invention are preferably carried out with unbleached cellulose pulp, i. E. h. after the lignocellulosic material was digested into cellulose pulp in a digester with digesting chemicals that was freed of spent digestion liquor in a washing zone. When the pulp has left the washing zone, it has they usually have a concentration of 4-6%. Usually the pulp is also sieved before it is subjected to the invention Measures is subjected, Before sieving, the pulp is diluted so that it has a concentration during sieving of 0.5-3%. In special cases it can be useful be the pulp of a mild delignification bleach with some bleach, e.g. chlorine and / or chlorine dioxide to undergo before it is treated according to the invention.

According to the invention, the starting pulp is dewatered in one or more steps so that a concentration of 15-35%, preferably 19-29%. Usually the pulp is concentrated in one stage. Appropriate drainage devices are drum washers, belt washers, press rolls and press screws, Whether concentrating the Pulp takes place in one or more steps (e.g. two) depends to a certain extent on whether the method according to the invention is applied in an already existing mill or whether the procedure is carried out in a new or remodeled device.

In existing mills, drum washers or settling tanks are usually installed after the screening zone, which increase the pulp concentration from a range of 0.5 to 3% - as is usual in the screening zone - to a range of 10 13%. However, it is not necessary that the drum washer have such a dewatering capacity; A very simple drum washer that raises the powder concentration to 4 % or more is sufficient.

After passing through the drum washer or thickener, the pulp is directed to a device in which the final dewatering to a pulp concentration of 15 35% takes place. A preferred device is one. Screw press. To facilitate the dewatering of the pulp,

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the pH of the incoming pulp can be adjusted to 7-9 by adding alkali.

After the dewatering step, alkali is added to the pulp in \ an amount such that the pH thereof exceeds about 11 J. In order to achieve this pH value, the addition of alkali must be 0.5 - 5%, based on absolutely dry pulp. The preferred alkali is sodium hydroxide, but it is! possible, other alkali compounds such as z _t . ®. Potassium hydroxide, \ oxidized white liquor, green liquor or sodium carbonate, to admit a mixture with sodium hydroxide .. The amount of alkali - calculated as NaOH in the invention is 2-17 g per kg of water of the pulp.

Thereafter, the pulp is subjected to a mild mechanical treatment in an apparatus suitable for high consistency treatment. This device is equipped with screws which rotate relative to one another under such conditions that the energy input is between about 8-100 kWh per ton of pulp. A device suitable for such a treatment is a screw defibrator ⁺ | screw refiner) from MoDoMekan AB with the trade name FROTAPULPER ^ This screw defibrator basically consists of two rotating screws that are mounted parallel to each other in a housing, one inlet and one outlet owns. The screws engage with each other for the purpose of kneading the Beschickungsinaterials and the threads ₃₀ are provided outer periphery of at least some threads with notches on J such that teeth are formed between the bay environments. Such a screw defibrator has been described in USP 3,064,908. The pulp mixed with chemicals is subjected to shear and kneading forces in the form of pulsating pressure surges in the screw defibrator. The result of this treatment is a very effective impregnation of the pulp with the added chemicals. For the pulp fibers this represents a mild treatment, since the fibers are not shortened (as is the case with the Hollander treatment or with grinding) and not in any other way either

+) also known as the screw defibrator.

130014/1163

were negatively influenced. The treatment in the screw defibrator is usually carried out at atmospheric pressure, but can also be carried out at above atmospheric pressure of up to 500 kPa. During the mechanical treatment, the temperature of the pulp is increased y · until at least 60% of the energy input has been converted into heat. The higher the energy input, the greater the temperature rise during the treatment. \

After the mild mechanical treatment, the pulp is removed by means of a suitable device, e.g. B, a pump, an I-screw conveyor or a conveyor belt in a tower} or like container for continuously% reaction with the chemicals added (mainly alkali)!

passed at the desired temperature. The dwell time! the pulp at this stage can vary from 6 minutes to 5 hours. J

The pulp is then washed in known washing apparatus so that the resin extracted from the pulp is removed therefrom will. Thereafter, no further treatment is required for the pulp, but this can be dried directly or the To be subjected to final treatment. In most cases, however, after the treatment according to the invention, the pulp is in passed a bleaching device for continued bleaching.

As far as the heat consumption in this process is concerned, economically favorable conditions can be created by the Unit of mechanical treatment., The transport device to the tower and the tower itself are insulated.

The heat can be used in a subsequent bleaching step so that the energy required for heating the pulp is reduced to a temperature suitable for bleaching. When the energy input in mechanical treatment is high or the mechanical treatment is carried out at superatmospheric pressure, the pulp can be emptied from this process step is carried out using a cyclone to separate the steam from the pulp ... the treatment made at superatmospheric pressure

+) ■ ^1l screw feeder ^ '

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also the possibility of carrying out the further treatment under above atmospheric pressure, d. H. the transport of the j Pulp to the dwelling tower, where this superatmospheric pressure

5 is maintained.

According to a preferred embodiment of the invention
becomes a short residence time between the dewatering step
and that of mild mechanical treatment. These

The short residence time is expediently achieved by the

Transport of the pulp by means of a screw conveyor j

j device * The dwell time should be between about 2-10 seconds. In addition to the use of a screw conveyor device, it is also possible to feed the pulp through a so-called. \

^ Direct Chemical Mixer, which is a device ^ for mixing chemicals into the pulp. As for the j addition of alkali, it is advantageous that at least a part j of the alkali to the pulp during the short residence time \ is added, z. B, in the screw conveyor. - j

In addition, alkali can also be added after the pulp has been dewatered, ie when it leaves the screw press. However, it is also possible to add the alkali all at once, either when the pulp is in the screw press
leaves or in the screw conveyor. Once in a while

₂₅ It is beneficial to use chemicals other than alkali in the pulp
to be added, such as, for example, B ₄ surface-active agents (so-called wetting agents) and complex-forming substances. The addition of this
Chemicals are carried out in a similar way to the addition of alkali »j When treating certain types of pulp it is necessary: j

_{3ü the reaction temperature of} the pulp as well as during the subsequent reaction with the alkali in the dwell tower above that temperature the temperature caused by the shearing and kneading treatment in order to achieve the desired removal of the
Resin .. In such cases the pulp becomes steam

₃₅ added. The steam should be added during the short dwell time.

The addition of steam and chemicals to the pulp is reduced
the pulp concentration. This concentration should however

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not less than about 15% during the mild mechanical treatment of the pulp.

When treating the cellulose pulp according to the invention and regulating the amount of alkali added, the temperature and the With the addition of energy it is possible to adjust the resin content of the finished pulp to the desired level »Raising the Amount of added alkali, increased temperature and increased energy input lead both individually and in particular in combination with an increased dissolution of the resin from the pulp, which means that the resin content the pulp is reduced accordingly.

The present invention can be used in various ways. be det. When using a sulfite mill it has been found that it is possible according to the invention to rely on the storage of the Do without wood and put fresh wood straight into the mill, i.e. to the factory to bring; As a result, the Manufacturing costs of sulfite pulp considerably lower, the same if one takes into account the cost of the equipment required for the inventive method.

Even if the wood storage in a sulphite mill is kept upright, the method according to the invention is of great use, since it creates the possibility of regulating the resin content of the finished pulp in a completely different and better way, than was previously possible. For example, the need for chlorine-containing bleaching agents is considerably less, which is dated from The point of view of keeping the environment clean is extremely desirable is.

In a power mill, for example, it is possible according to the invention to produce birch kraft pulp with a uniform and low resin content, which has not always been possible up to now. ₃₅ Furthermore, such pulp may, in the inventive manufacturing reduces the need of peeling of birch wood and the addition of expensive chlorine dioxide to be reduced, which is also advantageous from the standpoint of pollution of the environment.

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The advantages of the process according to the invention are also described in more detail in the following examples.

Fig. 1 shows a suitable device for a preferred embodiment of the method according to the invention.

A large number of experiments were carried out with the method according to the invention. The following examples show the implementation and the results of these tests.

Example 1 j

In this example, sieved spruce sulphite pulp \ which was manufactured for the production of cellulose derivatives \ and which had the following properties was used. \

Kappa number (according to SCAN-C 1:59) 7.5 y

R 18 value,% (»SCAN-C 2:61) 89.7

Viscosity, dm ³ / kg («SCAN-C 15:62) 700

Extract content dichloromethane,% ("SCAN-C 7:62) 1.70 Degree of milling, ⁰ SR (" SCAN-C 19:65) 13.0

The device according to FIG. 1 was used for this experiment according to the invention.

The screened pulp with a concentration of 10% and a temperature of 23 ^° C. was passed through line 1 to a screw press 2, in which it was dewatered to a concentration of 28%. The pressed water was removed through line 3. At the outlet of the screw press 2, alkali in the form of NaOH was added to the pulp in an amount of 3% (based on absolutely dry pulp) so that the pH of the pulp was 12.8. The alkali stored in the container 4 was sent to the screw press 2 through the pipes 5 and 6. From the screw press the pulp was passed through line 7 and screw conveyor 8. Steam was added through line 9 to the pulp in the screw conveyor 8 in such amounts that the temperature of the pulp rose to 85.degree. The steam supply corresponded to 260 kWh of heat

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energy per t of pulp, the pulp was fed into the screw defibrator 10 (type FROTAPULPER from MoDoMekan AB) by means of the screw transport device 8. This resulted in an increase in the temperature of the pulp to 90 ^° C. ... Then the pulp was passed through a vertical shaft and to the line 11, which leads to the tower 12, due to its gravity. The pulp was stored in this tower at 90 ^° C. for 2 hours. The complete reaction of sodium hydroxide and the pulp took place in the tower 12. After 2 hours, a pulp sample was taken, washed, dried and examined according to the above-mentioned measuring method.

For comparison, a test was carried out according to the method described in Swedish PS 341 323. With this one During the experiment, some parts of the device according to FIG. 1 were used. The screened pulp with a concentration of 10% and a temperature of 23 ° C was passed through line 1 to the screw press 2, in which the pulp on a concentration of 30% was dehydrated. Then the pulp was sent directly to the screw defibrator 10, where it was subjected to a shearing and kneading treatment according to an electric power consumption of 100 kWh per ton of pulp »The temperature of the pulp rose to 73 ° C. Then this was directed to tower 12, in which it was diluted to a concentration of 6% using water from the process, the Water temperature was 58 ° C., The temperature of the pulp suspension was then 61 ° C. A certain amount of pulp was removed from the tower and placed in a glass container, where it was heated to 90 ° C with steam. Then was sodium hydroxide in amounts of 3% - based on the pulp. The pulp sample was taken for 2 hours at 90 ° C in one Water bath held. The energy consumption for heating the sample from 61 ° to 90 ° C. with steam was calculated and corresponded 560 kWh per ton of pulp, .. After 2 hours, the treatment was interrupted by adding the pulp sample with pure water

1.3 00 U / 1 163

after invention Swedish PS according to 341 323 7.0 5.6 91.5 92.8 715 750 0.35 0.12 13.0 12.5

- 3Ö3Ä0Ä2

was washed. After drying, the pulp sample was examined according to the above measurement method.

The results are given in the table below.

Table 1
Properties of the pulp

Cap number

R 18 value, %

Viscosity, dm / kg extract dichloromethane,%

^1F degree of grinding, ° SR ° SR

Number of fiber bundles per j

100 g of sample 500. 100 j

Total energy consumption,

kWh per t pulp 660 283

As can be seen from Table 1, were in the invention Treatment of all the properties of the pulp in relation to the pulp, using the Swedish method PS 341 323 was treated, improved.

The most striking difference is the resin content, which is 0.12% in the treatment according to the invention compared to 0.35%

fraud.

The number of fiber bundles is also in accordance with the invention. j

The treated pulp was surprisingly lower than that of the other pulp. There is no generally applicable method for determining the last-mentioned pulp property; the number of bundles is according to the procedure according to the article in "Svensk Papperstidning JJ_, March 15, 1968 No. 5 pp 189-194"

35 has been determined, A comparison of the properties of the original Pulp with the properties of the pulp treated according to the tests shows that the treatments are too cleaning of the pulp. The kappa number, which indicates the lignin content of the pulp, has been reduced and the R 18 value has been increased. The finishing of the pulp occurs very much

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much stronger in the pulp treated according to the invention than in the process according to Swedish PS 341 323 emerged. The fact that the pulp viscosity increases after treatment seems surprising. She explains, However, from the fact that a certain amount of hemicellulose (which is made up of relatively short molecular chains) through the alkali is dissolved. The degree of grinding is essentially unchanged. This shows that the kneading and shearing treatment does not lead to a shortening of the pulp fibers.

Table 1 also shows that the properties of the inventive pulp are superior to those of the comparative pulp, although according to the invention, only half the energy was consumed that the comparison method requires.

At the moment no exact explanation can be given for the observed effect. “It is possible that one the reason for this is that the alkali, i.e. the sodium hydroxide is added to the pulp in such a way that the contact between the alkali and each individual pulp fiber is maximum. According to the invention, the alkali is mixed with the pulp before the kneading and shearing treatment. The penetration the alkali pulp could be lightened by the fact that steam is added to the screw conveyor which heats both the water in the pulp and the alkali solution, the viscosity of this liquid ' is reduced ... An important reason for the intense Contact between alkali and pulp fibers can also be the kneading and shearing treatments themselves, i.e. the pulsating ones Pressure surges to which the pulp is subjected.

Example 2

The experiments according to Example 1 were repeated, except that the sulphite pulp from spruce replaced the kraft pulp from birch was replaced. This pulp had a dichloromethane extract content of 0.44% and a viscosity of 900 dm / kg.

The pulp was made in the manner described in Example 1

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treated, partly according to the invention, partly according to the Swedish PS 341 323 «

The results of these tests are shown in Table 2.

Table 2

Properties of the pulp according to the invention

swed .. PS according to 341 323

Extract content dichloromethane,% 0.33 0.14 viscosity, dm ³ / kg 915 910

The table shows that the inventive method to

results in a pulp with a surprisingly low resin content, The resin content of the comparative pulp is two to three times as much.

Example 3

The experiment according to the invention according to Example 1 would be repeated with the difference that, in addition to the sodium hydroxide, there is also a surface-active agent and a complexing agent Means of sulfite pulp were added. In this experiment, 0.05% Na2P0 was added through lines 5 and 6, while from container 14 through line 15 3% sodium hydroxide and a surfactant (BEROCELL 25 from Berol Kemi AB) in an amount of 0.05% were admitted.

The results of the above tests and the test according to Example 1 are given in the following table.

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Table 3

Properties of the pulp

without addition of with addition of surface-active surface-active and complexing and complexing agent forming agents

Cap number

R 18 - Fourth, %

3 viscosity, dm / kg

Dichloromethane extract,%

5.6
92.8
750
0.12

5.3 92.7 710 0.08

This experiment shows that it is possible according to the invention by adding a surfactant and a complexing agent the resin content of the pulp in to a certain extent to be further reduced.

Example 4

The following experiment was carried out to show that the process according to the invention can, if successful, be coupled directly with an oxygen bleaching stage. The experiment was carried out with sieved birch kraft pulp. Certain parts of the device according to FIG. 1 were used. * A pulp suspension with a concentration of 3% and a temperature of 50 ° C. was thickened in the tendon press 2 to a concentration of 29% 6 0.2% MgSO ^ 7H ₂ O and 2% sodium hydroxide were added to the pulp, so that a pH of 11.2 was measured. Steam was added in the screw conveyor 8 so that the temperature rose to 95 ° C. The pulp was subjected to a kneading and shearing treatment with an energy input of 17 kWh per ton of pulp in the screw defibrator 10. This raised the temperature to 97 ° C. Thereafter, the device according to FIG passed to a tower in which oxygen was present at a superatmospheric pressure of 1.0 MPa. The pulp was further heated with steam to a temperature of 115 ° C and for 45 minutes with the alkali and the gas

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förraigen oxygen converted «Then the pulp was made withdrawn from the oxygen reactor, subjected to a washing stage and dried. Samples were taken for investigation that showed the following results.

Table 4 Properties of the pulp

Originally before pulp

Cap number

Viscosity, dm ³ / kg extract dichloromethane,% brightness ISO,%

21.0 998

0.43 32.0

Tulip treated according to the invention with the presence of oxygen in the last stage became

8.5 890

0.17 43.8

The brightness was determined to be 1'r: 75 according to SCAN-C. As As can be seen, the method according to the invention, modified in the last treatment stage with oxygen, leads to a considerable reduction in the lignin content of the pulp with a simultaneous increase in brightness * Also the resin content the pulp was considerably reduced «

130014/1163

Claims (12)

Godfather η t claims Process for reducing the resin content in the production of bleached or unbleached cellulose pulp from lignocellulose material, in which the lignocellulose material is subjected to a separation of the fibers (exposure), washing, optionally sieving and optionally delignification bleaching, characterized in that the lignocellulose is then subjected to -Material in the form of cellulose pulp in one or more dewatering devices is brought to a pulp concentration of 15-35%, preferably 19-29 % , the cellulose pulp alkali is added in such amounts that the alkali - calculated as NaOH - in the pulp up to 2-17 g per kg of water accompanying the pulp, whereupon the pulp is subjected to a mild, mechanical treatment with an energy input between 8 to 100 kWh per t of pulp, preferably 10 to 75 kWh per t of pulp, in a device for treatment at high consistency is, the device is equipped with screws that rela can rotate relative to one another, and after the mild mechanical treatment the cellulose pulp is reacted with the alkali for a period of 0.1-5 hours in a separate container with essentially unchanged pulp consistency. 2. The method according to claim 1, characterized in that between the dewatering stage and the mild one mechanical treatment a short dwell time is switched on, during which the alkali is added, namely after and in connection with the dewatering of the pulp and / or at least at a point in time during the short dwell time. 3. The method according to claim 2, characterized in that steam is supplied during the short residence time. 4. The method according to claim 2-3, characterized in that the short residence time after the dewatering stage 1300U / 1183 is created by conveying the cellulose pulp by means of a screw conveyor. 5. The method according to claim 2-4, characterized in that that the residence time is about 2-10 seconds. ! 6. The method according to claim 1-5, characterized in that that sodium hydroxide is used as the alkali. 7 »Method according to claim 1-6, characterized in that in addition to the alkali surface-active and Complexing agents can be added. 8. The method according to claim 1 - 7> characterized, that the pulp in addition to the reaction with alkali is reacted in a separate container with gaseous oxygen. 9. Apparatus for performing the method according to claims 1-8, characterized in that this a dewatering device (2) equipped with feed lines for chemicals (6), a screw defibrator (10), a container for the pulp (12), devices for conveying the pulp from the Dewatering device (2) for screw defibrator (10) and devices (11) for conveying the pulp from the screw defibrator (10) to the container (12). 10. The device according to claim 9, characterized in that that the device for conveying the pulp from the dewatering device (2) to the screw defibrator (10 a screw conveyor device (8), which is provided with feed lines (13, 15) for chemicals and a feed line (9) is equipped for steam. 11. The device according to claim 9-10, characterized in that the dewatering device (2) is a screw press is. 1300U / 1 163 12. The device according to claim 9-11, characterized in that the screw defibrator (10) has two rotating ones Includes screws which are arranged parallel to one another in a housing having an inlet and an outlet and which interlock to subject the material to a mechanical treatment, the Screws with threads with notches on their outer circumference on at least some threads ίο the snails are fitted, and between'den Notches form teeth. 1300U / 1st