DE665959C - Process for the production of pulp from beech wood - Google Patents

Description

Process for the production of pulp from beech wood The digestion from beech wood, especially red beech, to pulp that can be bleached, such as that used for the Purposes of the paper and cardboard industry required, is so far technically and economically unsatisfactory. In particular, it turned out that always the red-brown colored parts of the beech wood are not accessible to the digestion.

Numerous proposals have already been made to process beech wood into bleachable pulp using the bisulfite process. So was z. B. proposed to cook beech wood with calcium bisulfite solution in three to five times the amount, based on the weight of the wood; but it turned out that this method, which is known for softwoods, cannot be used with success on beech wood. Even the special dosage of the calcium bisulfite solution with a lime content of around 0.9 % and an SO @ content of up to 5% could not change this. It has also been proposed to soak the beech wood to be cooked with calcium bisulphite solution in caustic soda at about zoo ° before cooking, but the inefficiency of such a process is obvious. A proposed combined treatment of non-conifers wood with alkaline liquids, subsequent defibration, post-treatment with chlorine and again alkali is fiber-damaging, furthermore so time-consuming and complex that it could not be implemented. For a long time, attempts have therefore been made to make beech wood more accessible for digestion by comminuting it to a particle size that is greater than that of the z. B. coniferous wood went beyond the usual level. Up to now i1-lan has shredded rather haphazardly on any machines, whereby no value was placed on fiber protection and either the particles were not made small enough or too small, so that either no satisfactory digestion was obtained or. but there was a good that was largely made up of short or damaged fibers. Even where you z. B. Hammer mills or cross beater mills were used, so far only emphasis was placed on the greatest possible size reduction, but not on fiber protection. Apart from that, it has hitherto been the case that either unsuitable cooking liquors or cooking conditions were used when comminuting to an essentially correct pulp size, or unsuitable comminution methods when using per se suitable cooking conditions. Only through the combination of comminution measures with cooking processes and aftertreatment according to the present invention was it possible to achieve complete success. - ",..

The present invention relates to a drive for the production of Zellstoff` ia beech wood by pretreating the ze nerten wood with lye and boiling with bisulfite solution, in which the beech wood after comminution using a beater or hammer mill to 10 to 15 mm long and 5 to 10 mm wide Schnitzel at a temperature of less than 100 °, in particular at 80 °, with lime up to 5 % of its weight in the presence of water, preferably in three to four times the amount (based on the weight of the wood), q. Pre-treated for up to 8 hours, then brought to a lime content of 2.5% by washing and then boiled with the bisulfite solution. The S 02 and the lime content of the bisulfite solution is expediently adjusted so that, after mixing with the aqueous lime-containing semi-cellulose, it contains, as usual, 3 to 5% total S02 and 0.8 to 1.2% Ca0.

The schnitzels can be contaminated by the dust they contain and coarser splinters are freed before they undergo the treatment given above expediently subject to movement. The amount of water is measured so that one works at about three to five times the dilution, i.e. three to five times the dilution Amount of water of the weight of the wood is used. The quick lime can be added to the food added in solid form or mixed beforehand with the dilution water as Milk of lime can be used.

A convenient type of treatment is e.g. B. is that the reaction mass is subjected to several hours of mechanical work at 8o to 9o °, where the heating can be done by direct or indirect steam heating. For this treatment are suitable for. B. very good the common kettle stoves; man but can also use reaction vessels with stirrers and the like. as well The caustic circulation process commonly used in the pulp industry can also be used Find. The time of treatment depends on the condition of the wood and will in most cases between about 4 to 8 hours. When the treatment is over, so it is washed out to such an extent that the lime content of the substance is, if possible, down to 2.5% Ca0 or less has decreased. Depending on how much the pulp is washed out it contains 5% or less Ca O.

This semi-pulp is subjected to the customary bisulfite boiling, with only the water and lime content of the pretreated semi-pulp having to be taken into account during the production of the cooking liquors. Experience has shown that the digestion is good if the cooking liquid in the digester after mixing with the semi-cellulose contains 3 to 5 % total SO and about 0.8 to 1.2% Ca. If the semi-pulp already. B. 2.5% Ca contains 0 and about 5o to 6o% water, so can z. B. a cooking liquor can be added, which has a higher concentration, but less CaO than usual. This lye must therefore be adjusted so that, after mixing with the semi-pulp, it has a total content of 0.8 to 1.2 Ca 0 (i.e. including the lime in the semi-pulp) and 3 to 5% SO (i.e. despite the dilution by the water of the semi-pulp).

The bisulfite cooking is done in the usual way with or without Caustic circulation carried out. With normal cooking, depending on the condition of the wood and the desired degree of digestion requires a cooking time of 8 to 12 hours It is advisable to carefully add the cooking liquor towards the end of the boil monitor to prevent the cooking from turning over.

The yield of cooked material which can be easily bleached (with about 5 to 6 % chlorine consumption) is about 48 to 50% of the semi-pulp. Higher yields can only be achieved at the expense of a lower bleaching capacity, that is to say an increased use of chlorine.

The cooked fabric can be washed in the usual way, by one Opener dissolved and through drainage channels (sand trap) on good sorting facilities carefully cleaned. Then you get a pure white, splinter- and speck-free, first-class pulp, which is primarily used for absorbent papers and fine printing papers, but can also be used as an additive to writing paper and fine cardboard boxes.

In order to obtain a completely pure pulp, it is advisable to already after mechanical pre-shredding through suitable measures dust and Separate impurities and coarse wood splinters.

Although it is known to use other raw materials, e.g. B. straw or conifer wood, by comminuting in a special way to prepare it so that it is already can be digested into a semi-pulp with low-percentage lime liquors; but it must be noted that pine wood itself is easier to open and the Straw fiber is very thin and the pieces of straw in the above-mentioned pre-shredding method split lengthways be while following the procedure pieces of beech wood produced according to the present invention are generally coarser Character are as the corresponding, straw parts. So it wasn't at first before =: `.; it can be seen that beech wood under AnwArif # -dung of z. B. for straw known principles can be transformed into a pulp, and furthermore not that one such pulp can be converted into such an excellent beech wood pulp leaves, with the so far not or only with the usual sulfite process Insufficiently digestible red-brown colored parts surprisingly unlocked will.

Claims (2)

PATENT CLAIMS: i. Process for the production of pulp from beech wood by pretreating the shredded wood with lye and cooking with bisulfite solution, characterized in that the beech wood after. Comminution using a cross beater or hammer mill to 10 g to 15 mm long and 5 to 10 mm wide chips at a temperature of less than 100 °, in particular at 80 °, with lime up to 5 % of its weight in the presence of water, preferably . in three to four times the amount (based on the weight of the wood),, pretreated for 4 to 8 hours, then brought to a lime content of 2.5% by washing and then boiled with the bisulfite solution. 2. The method according to claim i, characterized in that the SO.- and lime content of the bisulfite solution is adjusted so that this after mixing with the aqueous calcareous semi-pulp, as usual, 3 to 5% total SO. and o.8 contains up to 1.2 % Ca 0.