RU2807731C1 - Method for producing fibrous semi-finished product - Google Patents

Abstract

FIELD: wood processing.

SUBSTANCE: method for producing fibrous semi-finished products based on wood cellulose used in their production using continuous or combined technique. The method involves heating wood raw materials in the form of chips in a dimethyl sulfoxide environment in the presence of an acid catalyst - sulfuric acid. The resulting semi-finished product is washed from the rest of the delignifying solution with water and dried using conventional methods. The method makes it possible to produce semi-finished products based on coniferous and deciduous wood. The method allows the production of any grade of cellulose nitrates from any type of cellulose.

EFFECT: obtaining a semi-finished product with a yield of 52–56% with a Kappa number of 10–25 units.

3 cl, 1 tbl

Description

The invention relates to a technology for producing fibrous semi-finished products based on wood cellulose, and can be used in their production using continuous or combined technology.

There is a known method for producing cellulose (RU 2 490 384 C1 dated 08/20/2013), which consists of cooking wood chips at a temperature of 90-98°C, intensive stirring and an atmospheric pressure of 740-760 mm Hg. in a mixture containing 3.9-5.6 wt.% hydrogen peroxide, 25.2-26.7 wt.% acetic acid in the presence of 2.0% by weight of sulfuric acid catalyst chips, with a cooking duration of 2.5-3, 5 hours and hydromodule 5-10, followed by isolation of the target product. The method for producing cellulose is simplified, the yield of the target product is increased, the quality characteristics of the target product are improved by increasing the holocellulose content in it and reducing residual lignin.

The disadvantage of this method is the use of an oxidizing agent - hydrogen peroxide, which leads to the development of cellulose destruction during delignification. Another disadvantage is the high hydromodulus of the process - more than 5, which leads to the formation of a significant amount of waste solution.

There is a known method for producing a fibrous semi-finished product (RU 2,037,000 C1 dated 06/09/1995), which includes cooking plant raw materials with an organic solvent in a cooker, separating the waste solution and regenerating it by evaporating the organic solvent in a heat exchanger chamber with subsequent condensation of vapors formed in the upper part of the digester, and returning the regenerated solution for cooking, before returning the solution for cooking, organosolv lignin is removed from it by blowing it from the bottom of the heat exchanger chamber into a storage tank at a pressure of 0.1 - 1.0 MPa, while the degree of lignin removal is adjusted from the spent cooking solution according to the rate of supply of the spent cooking solution to the heat exchanger chamber. In this case, a solvent with a boiling point of 70 - 120°C is used as an organic solvent.

The disadvantage of this method is the use of a low-boiling organic solvent, which leads to an increase in pressure in the digester and a fire hazard in production.

The closest analogue of the proposed invention can be considered a method for producing cellulose pulp (RU 2 135 665 C1 dated 08/27/1999). A method for producing cellulose pulp from initial lignocellulose by cooking in an alkaline aqueous cooking solution containing one or more low-boiling organic solvents and one or more redox catalysts, characterized in that said alkaline cooking solution additionally contains an alkaline sulfite derivative. The method allows to achieve a cellulose yield of 50%.

The disadvantage of this method is the use of a low-boiling organic solvent, which leads to an increase in pressure in the digester and a fire hazard in production.

The problem to be solved by the invention is to develop a method for producing a fibrous semi-finished product without the use of low-boiling organic solvents while increasing the yield of cellulosic fibrous semi-finished product.

This is achieved by the fact that the delignification process of wood raw materials is carried out in a dimethyl sulfoxide environment containing water and an acid catalyst - sulfuric acid.

The method involves heating wood raw materials in the form of chips in a dimethyl sulfoxide environment in the presence of an acid catalyst - sulfuric acid. The resulting semi-finished product is washed from the rest of the delignifying solution with water and dried using conventional methods. The method makes it possible to produce semi-finished products based on coniferous and deciduous wood.

The method is carried out as follows. Wood raw materials in the form of chips are treated with a solution containing dimethyl sulfoxide, water and sulfuric acid at a temperature of 140 - 150 ° C (determined by the accuracy of maintaining temperature in the technological process) for 2 - 4 hours. Hydromodule 4. The water content in the solution used varies from 1 to 10 wt.%, and sulfuric acid from 1 to 5 wt.%. After the delignification process is completed, the mass is separated from the delignifying solution by filtration and the fibrous semi-finished product is broken up by washing with a stream of water and dried.

A fibrous semi-finished product is obtained with a yield of 52 - 56% with a residual lignin content characterized by a Kappa number of 10 - 25 units.

The specific conditions for implementing the method (mixture composition, temperature, time conditions) can vary and are determined based on the characteristics of the raw material.

The yield and kappa number for the resulting celluloses were determined using methods known and generally accepted in the art.

Examples confirming the possibility of obtaining fibrous semi-finished products using the proposed method in comparison with the prototype are given in Table 1.

To implement the proposed method, standard equipment can be used.

The inventive method is environmentally friendly, because Delignification does not produce toxic or difficult-to-dispose waste or by-products.

The inventive method can be used for fibrous semi-finished products both in laboratory practice and in industry, and is suitable for both periodic and continuous technological methods of nitration.

Table 1.
Examples confirming the possibility of implementing a method for producing a fibrous semi-finished product Example No. Water content, wt.% Sulfuric acid content, wt.% Duration, hour Yield of fibrous semi-finished product, % Kappa number, units 1 Prototype 4 50 32 2 1 5 2 52 10 3 5 2.5 3 54 20 4 10 1 4 56 25 5 1 1 2 56 23 6 5 2.5 3 53 12 7 10 5 2 53 eleven 8 1 2.5 2 54 18 9 10 2.5 4 52 10

The table shows average data for three experiments.

Claims (3)

1. A method for producing a fibrous semi-finished product, including heating wood raw materials in the form of chips in a delignifying solution, followed by washing the semi-finished product and drying, characterized in that a mixture of dimethyl sulfoxide, water and sulfuric acid is used as a delignifying solution, and the processing of wood raw materials is carried out at a temperature of 140 – 150 ^° C for 2 – 4 hours. 2. The method according to claim 1, characterized in that the water content in the delignifying solution is 1 – 10 wt.%. 3. The method according to claim 1, characterized in that the content of sulfuric acid in the delignifying solution is 1 - 5 wt.%.