CS244350B1 - Method of holocellulose preparation - Google Patents

Description

(54) Method for the preparation of holocellulose

2

The present invention relates to a process for the preparation of holocellulose. The principle is that it is impregnated on the plant material with an aqueous solution of chlorine dioxide at a concentration of 4 to 10 g / l in an amount equivalent to 15 to 100% by weight. of active chlorine relative to the plant material at a temperature of 30 to 60 ° C for 1 to 6 hours, and the delignified material is subsequently extracted with 0.1 to 1 wt. aqueous alkali solution. The alkali used is sodium hydroxide or potassium hydroxide or ammonium hydroxide. The solution is used in the chemical, pulp and paper and textile industries.

The invention relates to a process for the preparation of holocellulose.

Holocellulose, which is a cellulosic and hemicellulosic component of the plant matter, is obtained as a fibrous residue after removal of extractives, lignin and water-soluble components. With current plant material delignification technologies, the removal of lignin is accompanied by considerable degradation of hemicelluloses and their dissolution in the cooking liquor, while the remaining proportion of hemicelluloses in the fiber has varying chemical and molecular properties depending on the batch conditions. The most suitable methods for the preparation of holocellulose in which the native nature of hemicelluloses is essentially maintained are deignified with sodium chlorite in an acidic environment and peroxyacetic acid impregnation [T. E. Timell: Adv. Carbohydrate Chem. 19, 255 "(1964ΚΆ; M. pronka, W. Surewlcz: Cellulose Chem. Technol. 13, 511 (1979); M. Han, B. Swan: Svensk Papperstidn. 71, 552 (1968)]. non-economical and time-consuming applications). They are particularly demanding on the consumption of oxidizing agent.

The aforementioned disadvantages are substantially eliminated by the process for the preparation of holocellulose according to the invention, which comprises treating the plant material with an aqueous solution of 4-10 g / l of chlorine dioxide in an amount equivalent to 15-100% by weight. of active chlorine relative to the plant material at a temperature of 30 to 60 ° C for 1 to 6 hours, and the delignified material is subsequently extracted with 0.1 to 1 wt. aqueous alkali solution. The alkali used is sodium hydroxide, potassium hydroxide or ammonium hydroxide.

An advantage of the proposed process for the preparation of holocellulose over the prior art processes is that the present process is simpler and more economical because it requires a low consumption of the oxidizing agent commonly used in pulp bleaching. The process is also less demanding on the chemicals, energy and equipment used. It can be applied to various fiber wastes arising from the processing of annual and perennial plants.

Example 1

A suspension of 1.1 kg of air-dry beech fillings 27 1 of an aqueous solution of chlorine dioxide concentration of about 6 g / 1 was heated to 45 ^Q C and held at that>a> temperature with stirring for 2h. The delignified sawdust is then extracted with 0.5 wt. aqueous sodium hydroxide solution at 20 ° C for 1 h. After neutralization of the alkali with a dilute hydrochloric acid solution, the holocellulose is washed with water to a negative reaction to the chlorides and dried in the air. 78.6 wt. Holocellulose with a residual lignin content of 4,5% by weight.

Example 2

The procedure is as in Example 1, except that a shavings of sawdust are used as the starting material and to delignify twice 15 l of an aqueous 4 g / l chlorine dioxide solution for 1 hour at 40 ° C. 83.1 wt. % of holocellulose with a residual lignin content of 7.0 wt.

Example 3

The procedure is as in Example 1 except that wheat straw is used as the starting material and to delignify 13 liters of an aqueous chlorine dioxide solution at 60 ° C for 1 h. 0.1% by weight was used for the extraction. aqueous sodium hydroxide solution. 89.6 wt. Holocellulose containing residual lignin

3.8 wt.

Example 4

The procedure was as in Example 1 except that sawdust of a mixture of deciduous trees, 25 L of an aqueous solution of chlorine dioxide at a concentration of 10 g / l were used as the starting material, and the delignified sawdust was extracted with 1% by weight. aqueous ammonium hydroxide solution. 86.4 wt. Holocellulose containing residual lignin

3.4 wt.

Example 5

The procedure is as in Example 2 except that twice 25 l of an aqueous solution of 10 g / l of chlorine dioxide are used for 3 h at 30 ° C each time and for the extraction of delignified sawdust by 1% by weight. aqueous potassium hydroxide solution. 86.9 wt. % of holocellulose with a residual lignin content of 4.8 wt.

Holocelluloses, prepared according to Examples 1 to 5, are intermediates in the preparation of D-xylans, their sulfoalkyl derivatives, as well as other derivatives of the hemicellulose and cellulose components of plant materials. One can follow known procedures: Example 6 (Cs. AO 231 686); Example 7 (Cs. AO 197 914). Example 6

The procedure is as in Example 1 except that the delignified sawdust is extracted with 10 L of a 10% aqueous sodium hydroxide solution at 20 ° C for 2 hours before neutralizing the retained alkali. The extract was filtered off and the Holocellulose extract residue was washed with 5110% aqueous 24% sodium hydroxide solution. The combined extracts precipitated to 30% by volume. Ethanol, precipitate after repeated decantation of 75% v / v. neutralized with dilute acetic acid solution and washed with 75 to 96% by volume aqueous ethyl alcohol. aqueous ethyl alcohol. 87%. 4-O-methyl-D-glucuron-D-xylan, based on the hemicellulose component of beech sawdust.

Example 7

The procedure is as in Example 4 except that the delignified sawdust is mixed with an emulsion of 10 liters of isopropyl alcohol and 1 liters of 40% by weight before neutralizing the retained alkali. aqueous sodium hydroxide solution and stirred at 15 ° C for 1 hour. Then, 950 g of sodium β-chloroethylsulfonate was added to the reaction mixture, followed by 350

With vigorous stirring, the mixture is allowed to react at 65 ° C for 3 hours. The solid obtained by filtration was dissolved in 3 l of water and added 9 l of 96 vol. Ethyl alcohol precipitates sulfoethylated polysaccharides, which are lyophilized after dialysis. Water-soluble fraction with a sulfur content of 4.8% by weight. An alkali-soluble fraction with a sulfur content of 3.1% by weight is obtained in a yield of 56.1% by weight. in an extract of 26.5% by weight, based on starting sawdust.

The invention can find wide application in the production of hemicelluloses from deciduous and coniferous trees and various wastes in the processing of annual plants, in the preparation of various derivatives of hemicelluloses, as well as mixtures of hemicelluloses and cellulose. It is used in the chemical-pulp and paper industry, in the production of industrial auxiliaries, etc.

Claims (2)

SUBJECT Process for the preparation of holocellulose, characterized in that the plant material is treated with an aqueous solution of chlorine dioxide at a concentration of 4 to 10 g / l in an amount equivalent to 15 to 100% by weight. of active chlorine, relative to the plant material, at a temperature of 30 to 60 ° C for a period of from 1 to 60 ° C INVENTION 6 hours and the delignified material is subsequently extracted with 0.1-1% w / w. aqueous alkali solution. 2. The process according to claim 1, wherein the alkali is sodium hydroxide or potassium hydroxide or ammonium hydroxide.