SU794101A1 - Rayon pulp production method - Google Patents

Description

concentration after it is 5-8% and a temperature of 145-105 ° C.

The essence of the method is as follows. Cellulose-containing raw material - chips, mainly from hardwood, is treated with an aqueous solution of SOa with a concentration of 2-7%, at a temperature of LOO-120 ° C, for 30-90 minutes. The liquor obtained in this process has a high content of reducing substances and a 1M1INmal content of ligni and minerals. Depending on the selected temperature and duration of treatment, the content of reducing substances in the liquor is 3.0-5%, i.e. 55 -5% of the hemicelluloses contained in wood chips pass into the solution: 25-30% of the lignin dissolves initial content in wood. The liquor from the first stage is withdrawn and, after stripping off the excess SO2 sent to the regeneration, is used to process the dissolved carbohydrates into the corresponding polyhydric alcohols, for example, into xylitol.

Prehydrolyzed chips further, without intermediate washing, are treated with a sulphite-bisulphite solution with pH 5, 5 with a SOj content of 6-6.5% at a temperature for 3-5 hours.

These conditions are optimal for sulfonated condensed lignin. The spent liquor from the second stage of processing, after refining by SO2 and pH, can be used repeatedly. The obtained intermediate product is further treated with an aqueous solution of SO2, with a concentration of 5--8%, lie at a temperature C for 1-2 hours. When this occurs, the dissolution of condensed lignin.

The liquor after the third stage, released by stripping from excess SO2 sent for regeneration, can be thickened and used, for example, to obtain casting concentrates.

Example 1

45 g of air-dry birch chips are poured with an aqueous solution of SO2, concentration, 3.5%, with a modulus of 1: 5. Carry out pre-forced impregnation. Then raise the temperature to 120 ° C and maintain at this temperature of 0.6 4aica. At the same time, 25% of lignin and 78% of hemicelluloses from their initial content in wood dissolve. Spent liquor in the amount of 130 ml with SO2 content of 1.7% and reduction content of substances (PB) of 4.0% after stripping is transferred for utilization of the carbohydrate part. The solid residue, chips, is poured 130 ml of sulfite-bisulfite solution € pH 6.0 and the content of the sun. SO2 6.8%, in 2 hours, the temperature is raised to 155 ° C and maintained at this temperature for 4 hours, the third cooking step is carried out

SOa solution at a temperature of 145 ° C for 1 hour. The yield of unbleached pulp is 46%, the degree of delignification is 80 p. E., The viscosity is 100 MPa, there is no penetration. PRI me R 2.

130 g of air-dry chips are placed in an autoclave, filled with an aqueous solution of SO2 with a concentration of 3.8% at a 1: 5 module, forced pre-impregnated, the temperature rises to L20 ° iC in 90 minutes, maintained at this temperature for 30 minutes . Waste liquor is selected, containing SOa in which 1.8%, ooo, aee

reducing substances (PB) 4, i8% and transfer it to ut1ilizatsii carbohydrate part. At the same time, 28% of lignin and 88% of hemicelluloses from their initial content in wood were dissolved.

The solid residue - chips pour a sulfite-bisulfite solution containing 6.3% BC. SO2, pH 6.0 and 4 hours at a temperature of 155 ° C. This solution is drained and after the SO2 is saturated and the pH is adjusted to 6.2, it is used for the next cooking.

The third stage is carried out with an aqueous solution of SO2, with a concentration of 6.95%, at a temperature of 138 ° C for 1 hour.

The yield of unbleached pulp is 45.5%, the degree of delignification is 90 bp, the viscosity is 300 MPa, and the content of a-cellulose is 87.2%.

After bleaching with holding hot

refining at the consumption of alkali 5.7 and 9% and abs. dry Fiber samples of viscose pulp of different brands.

In tab. 1 compares the cooking conditions,

in tab. 2 - the composition of the liquor, in table. 3 - quality indicators of unbleached and bleached pulp.

Since the target product of the proposed method is viscose cellulose, the indicators of which should be lower than the derivative according to a known method of acetate cellulose, for comparison in Table. 3 shows the indicators GOST 5982-75 on the viscose .cellulose.

As follows from the table. 1-3 data, the yield obtained by the proposed method of the final product - viscose pulp does not decrease, its quality indicators are in accordance with

requirements of GOST 5939-7 5, and viscosity formation is higher; however, the liquor obtained after cooking by the proposed method have a significantly lower lignin content

n mineral substances, with a higher content of reducing substances (PB) than liquor, obtained after cooking by a known method. The low content of lignin and minerals makes it possible to use liquor from the first stage of the process. Before cooking, the initial cellulose-containing raw materials are subjected to pretreatment with an aqueous solution of SO2, with a concentration of 2-7% at a temperature of 100-120 ° C, and the boiling is carried out with a pH 5 , 0-6.5, temperature 150-170 ° С, and subsequent processing with an aqueous solution of SO2 is carried out at a concentration of the last 5-8% and temperature 145-165 ° С. 5 10 Sources of information taken into account during the examination: 1 Review "Cellulose for x chemical processing, M., “Forest industry, 1970, p. 22-25. 2. USSR author's certificate No. 253042, cl. D 21 C 3/26, 1967 (prototype).

Compiled by A. Monosov Tehred A. Kmzhnikova

Editor O. Ivanova

Order 1758 / 135iz. № 124 Circulation 430 Subscription

The NGO “Search for the USSR State Committee on Inventions and Discoveries

113035, Moscow, Zh-35, Raushsk nab. 4/5

Type of. Khark. Phil. before "Patent

Proof-reader I. Osinovska

Conditions of cooking known and proposed methods

The composition of liquor used for disposal

Comparison of quality indicators of unbleached pulp and quality indicators of finished products obtained by the known and proposed methods

Table 2 dissolved hemicelluloses

The composition of the liquor

Table,

Claims (1)

Claim The method of obtaining viscose pulp by sulphite pulping of cellulose-containing raw materials and subsequent treatment with an aqueous solution of 8O ₂ , characterized in that, in order to increase the effective