CS212582B1 - Method of preparation of the highly refined celluloses - Google Patents

Abstract

The way of preparation is that chips after autohydrolysis or prehydrolysis are delignified in the soda brew solution in the presence of redox of the catalyst usually anthraquinone and its Derivatives. Spdsob can be done by continuous, discontinuous or combined procedure.

Description

The invention relates to a process for the preparation of highly refined pulps from any kind of wood for further chemical processing including the preparation of cellulose derivatives.

The prior art process for the preparation of high-boiled pulps for further chemical treatment consists in delignifying the pre-hydrolysed chips with a sulphate boiling solution. The disadvantages of this delignification process are the formation of enormous amounts of toxic fumes, the difficult bleachability of the pulp produced and the pollution of the environment with sulfur compounds.

The process for preparing high-boiled pulps according to the invention removes the drawbacks of the method used hitherto.

SUMMARY OF THE INVENTION The invention consists in that chips after autohydrolysis or prehydrolysis are further delignified in a soda boiling solution (sodium bottle) by application of 14 to 22% Na ₂ O, preferably 16 to 18% Na ₂ O, in the presence of an oxidation-reduction catalyst. , usually anthraquinone and its derivatives, in an amount of 0.01 to 2%, preferably 0.01 to 0.2%, based on the weight of the wood used. The application of said process can be carried out by a continuous, discontinuous or combined process.

By eliminating the use of sulfur (such as sodium sulfide) from the manufacturing process, as applied to the invention, it does not generate toxic pollutants and does not pollute the environment with sulfur compounds.

The removal of sulfur from the production process also simplifies the regeneration of chemicals in the incineration process of the concentrated liquor and significantly improves the working conditions. operating personnel. The high-harvest pulps prepared by the novel sulfur free process of the present invention exhibit better quality parameters than the pulps prepared by the prior art sulfate delignification process.

The pulps prepared according to the invention show, after delignification, a lower Kappa number (approx. 10%) and a higher whiteness of the original unbleached pulp (4 to 5% MgO), resulting in a substantially lighter whitening than the corresponding sulphate pulps prepared up to (see Table 1).

To achieve the same quality in terms of viscosity, average polymerization degree and whiteness, they need less bleaching agents (about 10-12 µl) than the corresponding equivalent kraft pulps.

The oxidation-reduction catalyst applied in the production of the high-purification pulps of the patent accelerates the alkaline delignification process to such an extent that it becomes equivalent to the sulfate delignification process.

In addition, the catalyst stabilizes the polysaccharide fraction of the pulp, making it less soluble in cold alkanes (e.g., 18% NaOH solution). The improved quality of the high-purity pulps prepared according to the sulfur-free process of the present invention consists in the higher content of alpha-cellulose and in particular in the substantially lower solubility of the pulp in 18% NaOH solution (about 30% compared to the method used to date). during mercerization and further processing of cellulose into derivatives (see Table 2).

Example

The wood chips are subjected to autohydrolysis (pre-hydrolysis), e.g. 80 min at 170 ° C in 1: 4 hydromodule water or in a vapor environment. After withdrawal of the prehydrolysate, the chips are boiled with NaOH solution of appropriate concentration so that the amount of Na 2 O applied to the wood is 17%.

0.1% anthraquinone catalyst is added to the alkaline caustic liquor (amount of catalyst calculated on the weight of the wood). The obtained unbleached pulp after washing has the characteristics as shown in Tab. 1. Pulp after bleaching with heel by a step bleaching process e.g. The CEDHH procedure (C = chlorination, E = hot alkaline extraction, D = chlorine dioxide stage, H = hypochlorite stage) shows the characteristics shown in Table 2.

For comparison in Tab. 1 and in Tab. 2, the characteristics of the pulp obtained by the hitherto used sulphate delignification technology are also presented.

From the results shown in Tab. 1 and in Tab. 2 shows that sulfur-free pulps with higher alpha-cellulose content, lower solubility values in NaOH solutions of the appropriate concentration, as well as better viscosity, average polymerization degree, whiteness and yield, as compared to the present invention, can be prepared are achieved by boiling the prehydrolyzed label with a sulfate process.

Table 1

Method of processing beech stickers and characteristics of unbleached pulp

Number prehydrolysis By the batch Alkaline grade samples Sprae Extract Contents yield Kappa PPS whiteness % lignin % % number CNP / g % MgO 2 Water 80 min r _{Q 7} at. ^the> '170 ° C 27.7 Sulfate 17% Na ₂ 0 35.4 6.7 608 81 1 34.1 3 soda 17% Na ₂ O + 35.6 6.1 596 795 38.3

+ 0.1% AQ

5 steam 80 min 70.0 29.7 Sulfate 17% Na ₂ 0 35.0 8.3 707 943 28.2 6 at _ 170 [deg.] C soda 17% Na-O + 35.3 7.4 674 898 33.8

+ 0.1% AQ

Table 2

Method of processing beech chips, consumption act. chlorine in the CEDHH bleaching process and the characteristics of the bleached pulp

Number Spraeovanie consumption whiteness CNP / g PPS Contents solubility in % samples Car- hydro- Dovárka act. Cl ₂ % % MgO alpha- celu-. i. ,, in 5% solution in 10% solution in 18% solution Lyza NaOH NaOH NaOH ^L 5 ^L 10 ^L 18 sulphate 1.7 88.2 475 633 97.0 1.44 3.6 2.4 3 water soda + 0.1% 1.5 88.5 462 616 97.1 1.45 4.1 1.7 Au 5 steam sulphate 2.1 88.5 532 709 97.1 1.09 4.0 1.7 soda 1.9 86.5 502 669 96.4 2.25 4.5 2.6

2.2582

Claims (1)

OBJECT OF THE INVENTION Process for the preparation of highly refined pulps intended for further chemical treatment by delignifying wood chips by prehydrolysis or autohydrolysis followed by alkaline boiling, characterized in that the chips after the prehydrolysis or autohydrolysis are further delignified in an NaOH solution up to 22 in alkaline, with a quantity of alkali up to 22 % Na ₂ O preferably, 6 to 18% Na ₂ O, calculated on the weight of wood, in the presence of an oxidation-reduction catalyst, usually anthraquinone and its derivatives, in an amount of 0.01 to 2%, preferably 0.01 to 0.2% calculated on the weight of wood.