RU1781333C - Method of obtaining solution for moulding polyacrylonitril fibers - Google Patents

Abstract

Usage: production of synthetic fibers and threads used in the chemical and textile industries. SUMMARY OF THE INVENTION Acrylonitrile and vinyl derivatives are subjected to continuous copolymerization in the presence of an initiator and a molar mass regulator in several parallel reactors at 80-87 ° C for 1.5-2 hours. The reaction masses are mixed. It is then demonomerized at elevated temperature and cooled. 1 tab.

Description

The invention relates to the production of chemical fibers, in particular, to methods for producing a solution for forming polyacrylonitrile fibers and can be used in the manufacture of synthetic fibers and yarns.

A method is known for producing a dope solution of acrylonitrile copolymers in an aqueous solution of sodium rhodanide, which consists in copolymerizing acrylonitrile with methyl acrylate and itaconic acid in an aqueous solution of sodium rhodanide at a concentration of 50-52% in the presence of isopropyl alcohol-azobisisobutyronitrile initiator.

Obtained in this way the solution from different reactors after distillation of residual

monomers (demonomerization) are mixed in the averager at a low temperature for a long time. However, the fluctuations in the viscosities of solutions from different reactors usually reach significant values, which leads to a broadening of the molecular weight distribution (MMP) curve of the copolymer with an increase in the deviation of viscosity from the values of the average solution and a deterioration in fiber performance.

The aim of the invention is to increase the coefficient of variation in the strength characteristics of the fibers by improving the quality of the solution for forming the fibers.

The goal is achieved by carrying out the polymerization of the reaction mass

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in several reactors with subsequent bias - (averaging) in a continuous mixer at a polymerization temperature and subsequent demonomerization with the exception of the stage of averaging at a low temperature after demonomerization, I

In this case, the polymerization duration is 60-100 minutes, with a total process duration of 90-120 minutes, and the time for averaging after demonomerization is completely eliminated. The existing process has a polymerization time of 90-120 minutes. According to the invention, a solution is obtained with the same viscosity characteristics as in the existing process, but with a much narrower MMP curve. The fibers formed from the solution of the invention have improved performance.

The MIVlP width is estimated by the MMP curve, taken according to the generally accepted method for the qualitative determination of solution homogeneity by the molecular method of turbodimetric titration. The width of the MMP curve is determined at half the height of this curve in arbitrary units.

Example 1. The reaction mixture of the usual composition to obtain a solution in the production of nitron fiber, consisting of a mixture of monomers (%) 93 acrylonitrile, 5.7 methyl acrylate, 1.3 itaconic acid and 51.5 aqueous solution of sodium thiocyanate in mass ratio 18:82, which also contains an initiator (porphore ChKhZ-57) and a molecular weight regulator (isopropyl alcohol and thiourea dioxide), simultaneously fed into three parallel reactors of the same capacity and polymerized at 85 ° C for 70 min. the reaction product is fed to a homogenizer of the same capacity and stirred for 23 minutes. at 85 ° C. The averaged dope was demonomerized in a vacuum at 95 ° C to a residual monomer content of not more than 0.5%. Get a solution with

working viscosity 85c, g) sv 1.49 and a half-width curve MMP 12 units Fiber is formed from a solution in the usual way on a 50 / 0.08 mm die.

PRI me R 2 (comparative). The reaction mixture of Example 1 is simultaneously fed into three parallel reactors of equal volume and polymerized at 85 ° C for 93 minutes. Reaction products from

all three reactors are subjected to demonomerization to a residual monomer content of not more than 0.5%, then solutions with and working viscosity, respectively, from the first reactor 1.47 and 75 and with and from the second - 1.52

and 100 this third - 1,50 and 85 s are served in the averager, where they are mixed for 23 minutes. at 35 ° С obtaining a solution with averaged characteristics: St 1.49 and working viscosity 85 s, moreover, the half-width of the MMP curve

in this case is 16 units. A fiber is formed from the solution under the same conditions as in Example 1.

Examples 3-6. The solution is obtained analogously to example 1, however, change the number

reactors, reactor capacity and mixer.

The properties of the fibers according to examples 1-6 are shown in the table.

Claims (1)

SUMMARY OF THE INVENTION Method for preparing a solution for forming polyacrylonitrile fibers by continuous copolymerization of acrylonitrile with a vinyl derivative in a 50-52% aqueous solution of sodium rhodanide in the presence of an initiator and molecular weight regulator in several parallel reactors at 80-87 ° C within 1.5-2.0 hours using the subsequent stages of demonomerization at elevated temperature, cooling and mixing the reaction masses leaving the reactors, characterized in that, in order to increase the coefficient of variation in the strength characteristics of the fibers, the stage of mixing the reaction masses is carried out before demonomerization. Table continuation