FI68273B - FOERFARANDE FOER FRAMSTAELLNING AV BARRTRAEDSCELLULOSA FOER KEISK VIDAREBEHANDLING SAOSOM FOER FRAMSTAELLNING AV SPECIA LPPPER - Google Patents

Description

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C Patent patented 12 08 1985 (* 5) Patent oeddelat (51) Kv.lk. «/ LntCl. * D 21 C 9/10 FINLAND —FINLAND (21) Puenttll application [Patentanaeknlng 782869 (22) Application date - Ansökningsdag 20.09.78 ( 23) Starting date - Glltighetsdag 20.09.78 (41) Tullut iulklsekil - Blivlt offentllg 21 .03.79

National Board of Patents and Registration Date of publication. -, _

Patent- OCh registerstyrelsen '' Ansttkan utlagd och utl.skriften publicerad 30. OH .05 (32) (33) (31) Privilege claimed - Begärd priority 20.09.77

The Federal Republic of Germany, the Förbundsrepubliken Tyskland (DE) P 2742262.4 (71) Degussa AktiengeselIschaft, Weissfrauenstrasse 9, 6000 Frankfurt 1,

Schwäbische Zellstoff AG, 7930 Ehingen (Donau), Federal Republic of Germany Förbundsrepubliken Tyskland (DE) (72) Horst Kruger, Darmstadt, Werner Traser, Darmstadt-Arheiligen,

Johann-Peter Franzreb, Ehingen, Heinrich Klein, Ehingen,

German Federal Republic-Federal Republic of Germany (DE) (74) Oy Kolster Ab (54) Method for the production of softwood pulp for chemical further processing, such as the production of specialty papers

The invention relates to a process for the production of medium or high viscosity softwood sulphite pulp.

Medium or high viscosity, alkali-treated softwood sulphite pulp is used as a base material in the production of specialty papers, for example photographic papers. Another use for processed softwood sulphite pulp is its use as a base material in the manufacture of cellulose esters, cellulose ethers, plastic pulps and hygienic products such as baby diapers.

Coniferous sulphite pulp with a C-cellulose content of at least 91% (calculated on Atro-cellulose), a DP value of at least 1000, a good reactivity, a maximum extraction content of 0,2% (dichloromethane) and an ash content of at most 0 have proved to be particularly suitable for these purposes, 15 S (calculated from atrocellulose).

It is known to prepare such softwood sulphite pulps in such a way that the lignin removal after pre-cooking is carried out 2 68273 completely with elemental chlorine (cf. S.A. Rydholm, Pulping Processes, (1965), Interscience Publishers, Wiley & Sons Inc.,

New York, London, Sidney, page 1066).

However, this method has the disadvantage that during the lignin removal process, chlorine-lignin-containing wastewater, which is polluted by the environment, is formed and, if at all, can still only be treated with great difficulty.

The object of the present invention is to develop a method for producing pulps meeting the above requirements, whereby environmentally friendly wastewater is obtained.

The invention relates to a process for the production of medium or high-viscosity softwood sulphite pulps, which process is characterized in that the pulp obtained by the sulphite extraction process, if desired treated with chlorine in an amount of 0.01 to 20% by weight, is used in a conventional bleaching process and / or or which, if desired, has undergone an acid pretreatment and, as a result of this chlorine treatment, the pulp further purified from lignin is subjected to alkali treatment at elevated temperature in a manner known per se, then treated with peroxide in an alkaline aqueous solution to remove lignin and bleached in a manner known per se.

In a preferred embodiment of the invention, a magnesium salt may be added to the alkaline aqueous medium during the peroxide lignin removal treatment. The magnesium salt can then be used in an amount of 0.01 to 1% by weight, based on the pulp.

The magnesium salts used in this case may be magnesium halides, such as, for example, MgCl2, MgBr2 or MgJ2, magnesium carbonate, magnesium silicate, magnesium sulphate, magnesium acetate or magnesium oxide.

The amount of chlorine used in the process according to the invention in the first stage of the process chain corresponds to 0.01 to 20% by weight of the amount of chlorine used in the chlorination steps known to date. Known methods use 4-6% by weight chlorine (cf. Rydholm, Pulping, Processes, (1965) Intersciense Publishers, Wiley & Sons, Inc. New York, London, Sidney, page 1066). When it is necessary in the known processes to extend the reaction time of the chlorination step up to one hour, in the process according to the invention the reaction time of the chlorination step can be limited to a maximum of 0.80 hours, preferably between 0.01 and 0.75 hours.

In a preferred embodiment of the invention, the chlorination can be performed at a pH of 1-2. This value can be adjusted with known inorganic mineral acids such as hydrochloric acid or sulfuric acid.

The acid pretreatment can be carried out with inorganic mineral acids, such as sulfuric acid, hydrochloric acid or sulfuric acid, and / or with organic acids, such as formic acid or acetic acid, at a pH of 2-5, at a temperature of 0-50 ° C, with a density of 2-5 % and in at least one minute, preferably in 0.1-1 hours.

At the end of the cooking process, the alkali can be carried out at a temperature between 60 ° C and the boiling point of the pulp suspension with little or no pulp further purified from lignin. In this case, a density of at least 6%, preferably a density of 10-20% and an alkali content of 2-12% (based on 100% Atro pulp) are used for at least 0.1 hour, preferably 0.5-4 hours.

In the removal of lignin by means of peroxide, an inorganic peroxide such as hydrogen peroxide, sodium peroxide or an organic peroxide such as t-butyl peroxide or mixtures of said peroxides can be used as the peroxide. The peroxide used can be added in an amount of 0.2 to 10% by weight, preferably 0.6. -6% by weight, based on 100% Atro screening.

Furthermore, a density of at least 4%, preferably 6-16% by weight, can be used for the removal of lignin with peroxide.

For the formation of an alkaline aqueous medium for the removal of lignin by peroxide, it is possible to use allyl chloride, such as, for example, NaOH, KOH, NH 4 (OH), MgIO 4) and / or an alkaline earth hydroxide, such as calcium hydroxide, of 0.5 to 4% by weight, preferably An amount of 1-3% by weight based on 100% Atro cellulose. The temperature during lignin removal can be maintained between 35 ° C and the boiling point of the pulp suspension.

In addition, stabilizers such as ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid, nitriloacetic acid and / or polycarboxylic acids can be added in accordance with DT-OS 19 04 940, DT-OS 19 04 941 and / or DT-OS 19 42 556.

The essential advantage of the process according to the invention is based on the fact that wastewater is obtained which, due to its low content of chloride ions or organically bound chlorine, can not only be used for regenerative reprocessing but can also be reused in the lignin removal process.

A further advantage is that the use of water-doped water glass as a stabilizer during lignin removal can be dispensed with.

The method according to the invention is illustrated in more detail by means of the following examples.

Example 1 (preparation of high viscose pulp)

The six-sulphite pulp (commercial chapter 17) produced by the calcium bisulphite process is treated in a five-step process according to the following process sequence: 1. weak chlorination (partial chlorination) temperature 35 ° C time 0.75 h density 4% pH value about 2 2. alkaline processing 8 % NaOH temperature 85 ° C time 2 h density 16% 5 68273 3. lignin removal with peroxide

1.5% H 2 O 2 (as aqueous solution) temperature 40 ° C

2% NaOH time 4 h bulk density 12% 0.3% MgCl 2 pulp The properties of the pulp thus treated are as follows: «(.-Cellulose 93%

Cuoxam viscosity 2600 mp extract content 0.06% (dichloromethane) The pulp obtained in the lignin removal bleach is then treated as follows in a manner known per se.

4. Chlorine dioxide bleaching

According to Ullmann's "Ehzyklopädie der technischen Chemie", Volume 18, 3, edition, page 780 (1967).

5. Hypochlorite bleaching

According to Ullmann's "Enzyklopädie her techischen Chemie", Volume 18, 3, edition, page 799 (1967).

The pulp obtained in this way after 5 steps has the following characteristics: β-cellulose 92% wood rubber 2.9% DP value 1500 R 18: 93.6% ash content 0.11% extract content 0.04% (dichloromethane) whiteness 91% MgO Cuoxam viscosity 2300 mp.

The properties were determined by the following known methods: -cellulose: Meddalatt Zellcheming 11/39/67 or Siber, Chemisch-technische Untersuchungsmethoden der Zell-stoff- und Papierindustrie, Springer Verlag 1957, page 598.

68273 6 3. Removal of lignin with peroxide

1.5% H2 <Ι> 2 (in aqueous solution) temperature 40 ° C

1.5% NaOH time 4 h Density 12% 0.3% MgCl2

The properties of the substance thus treated are as follows: 92.5% ck-cellulose

Whiteness 0.05% (dichloromethane)

Extract content 0,05% (dichloromethane) The pulp obtained from the lignin-removing pre-bleaching is then further treated in the following manner, known per se: 4. Chlorine dioxide bleaching

According to Ullmann's "Enzyklopädie der technischen Chemie", Volume 18, 3rd Edition, page 780 (1967).

5. Hypochlorite bleaching

According to Ullmann's "Enzyklopädie der rechnischen Chemie", 18, part 3rd edition, page 779 (1967).

Thus, the pulp obtained after step 5 had the following characteristics:

PuukumirMerkblatt Zellcheming 1V / 9/67 DP value: Merblatt Zellcheming D LLL / l / t2 R 18: Merkblatt Zellcheming 1V / 39/67

Ash content: Merkblatt Zellcheming 1V / 40/67 Extract content: Merkblatt Zellcheming 1V / 43/67

Copper number: Merkblatt Zellcheming 1V / 8/70

Degree of whiteness: Merkblatt Zellcheming V / 10/63

Cuoxam Viscosity: Merkblatt Zellcheming 1V / 30/62 The percentages given in this example are percentages by weight per 100% Atro-cellulose, unless another dimension is stated.

7 68273

Example 2 (preparation of medium viscose pulp)

The six-sulphite pulp prepared according to the calcium bisulphite method (Chapter 15) was treated according to the five-step method according to the following process sequence: 1. Weak chlorination (partial chlorination) 0.8% chlorine gas (in aqueous solution)

temperature 45 ° C

time 0.75 h density 4% pH value approx. 2 2. Alkaline treatment 6% NaOH (in aqueous solution) temperature 85 ° C time 2 h density 16% cL-cellulose 93% DP value 1200 ash content 0.08% extract content 0, 1-0.2% (dichloromethane) whiteness 94% MgO Cuoxam viscosity 600 sec

The measured values were determined according to the known methods given in Example 1.

The percentages mentioned in this example are percentages by weight based on 100% Atro cellulose, unless other values are mentioned.

Claims (2)

8 68273 Process for the production of medium or high-viscosity softwood sulphite pulp, characterized in that the pulp obtained by the sulphite extraction process, if desired treated with chlorine in an amount of 0.01 to 20% by weight of the amount used in the conventional bleaching process and / or if desired, the acid pretreatment is carried out and, as a result of this chlorine treatment, the lignin-purified pulp is subjected to treatment with alkali at elevated temperature in a manner known per se, then treated with peroxide in an alkaline aqueous solution to remove lignin and bleached in a manner known per se. Process according to Claim 1, characterized in that, in the lignin removal treatment with peroxide, a magnesium salt is added to the alkaline aqueous medium.