SU907004A1 - Method for activating cellulose - Google Patents

Description

The invention relates to chemical technology, in particular to methods for increasing the chemical activity of cellulose, and can be used in the chemical processing of cellulose to obtain its esters, in the production of etrols, varnishes and other products. A known method of activating cellulose is by treating it with liquid ammonia. As a result of swelling of the original cellulose in liquid ammonia followed by its evaporation in air, the crystalline modification of natural cellulose (cellulose) due to redistribution and some weakening of the hydrogen bonds goes into a more chemically active crystalline modification cellulose III 1. The disadvantages of this method are large the consumption of liquid ammonia (. the processing of 1 ton of the original cellulose requires 2.0-2.5 tons of liquid ammonia) and the difficulty of its regeneration. In addition, in the cellulose treated with liquid ammonia, aets on average 1-3% cLtsellyulozy content, and after processing of the initial pulp with liquid ammonia is observed 4.56, 0 | -on shrinkage of cellulose fibers due to contraction of the cell walls, that further hinders access to the esterifying agent. The purpose of the invention is to reduce the consumption of the activating agent and increase the reactivity of cellulose. This goal is achieved by the fact that according to the method of cellulose activation by ammonia, the treatment is carried out with gaseous ammonia under a pressure of 0.5-0.7 MPa for 1-2 hours at room temperature. When cellulose is treated with ammonia gas under pressure, hydrogen bonds are weakened and the packing density of cellulose macromolecules decreases. This is due to the dip value of the ammonia molecule and

the polarity of the NH bonds, which lead to a change in the elementary crystalline cell of cellulose and the transition of the crystalline modification of natural cellulose (cellulose) to a more reactive crystalline modification — cellulose III. The reaction activity also increases due to the destruction of the primary cell walls caused by abrupt withdrawal pressure in the autoclave at the end of the treatment of cellulose with gaseous ammonia. The higher the pressure of ammonia gas in the autoclave. Topics (duration of processing is 5

ki material and vice versa. However, a decrease in the pressure of gaseous ammonia in the autoclave below 0.3 MPa does not give the desired effect of cellulose activation. In addition, at room temperature, a pressure of 0.5-0.7 MPa is provided by the saturated vapor pressure of liquid ammonia.

Example. An autoclave with a capacity of 3 l is loaded with initial sulfite cellulose in the form of sheets with dimensions of 0.20X0, m and total weight of 0.1 kg. After sealing, the autoclave is evacuated to -0.1 MPa. Then, ammonia gas is fed to the autoclave to an overpressure of 0.5 MPa. Treatment of cellulose with gaseous ammonia is carried out for 120 minutes at room temperature. After the treatment is completed, ammonia gas is sucked off from the autoclave for regeneration. Ammonia required;

for a treatment of 0.027 kg. The resulting activated pulp is ready for chemical processing. Example2. The autoclave with a capacity of 3 liters is loaded with the initial sulfite cellulose in the form of sheets with dimensions of 0.20 x 0.2 m and a total weight of 0.1 kg. After sealing, the autoclave is evacuated to -0.1 MPa. Then, ammonia gas is fed to the autoclave to an overpressure of 0.7 MPa. Treatment of cellulose with gaseous ammonia. Lead for 60 minutes at room temperature. After graduation

from the autoclave for regeneration. Amount of ammonia required for treatment is 0.025 kg. The resulting pulp is ready for chemical processing.

PRI me R 3 (comparative). Liquid ammonia is poured into an open vessel. Sulfite pulp in the form of sheets with dimensions of 0.20 x O, 2A m and a total mass of 0.1 kg is immersed in liquid ammonia for 5-10 seconds until the entire mass of cellulose is completely saturated with liquid ammonia. After that, cellulose is out; are drawn from liquid ammonia and dried in air until complete removal of the activating agent. Amount of ammonia required for treatment is 0.250 kg.

The table shows the main indicators and physico-chemical properties of activated sulfite pulp on the proposed and known methods. ammonia gas treatment

Amount of ammonia required per treatment t per 1 ton activated cellulose

Content of C1 cellulose,%

Capillary vmtyvaemost, mm

;Shrinkage,%

The nitrogen content of nitrocellulose after nitration for

t min

5 minutes

10 min

0.25-0.27 92.0

80-90 2.0-2.2

8.1

10.6

Claims (1)

12.7 5 907 From the table it follows that the proposed method for the activation of cellulose makes it possible to reduce the consumption of the activating agent by 8–10 times, as well as to increase the reactivity of cellulose by an average of 1.3 times. In addition, the proposed method provides for the treatment in an autoclave to the atmosphere of ammonia, which greatly simplifies the regeneration of the activating agent and improves the sanitary and hygienic conditions of production. Claims of Invention. A method of activating cellulose by treating it with ammonia, which is also distinguished by the fact that, in order to reduce j consumption of the activating agent and increase,. reaction of sph; cell pulp; the treatment is carried out with gaseous ammonia under a pressure of 0.50, 7 MPa for 1-2 hours at a temperature of 10 cm; Sources of information, pp attention for examination 1 Nikitin M. and others. M., Lesna industry, 1978, p.108 {prototype)