RU2787619C1 - Extrusion method for obtaining a spinning solution of cellulose in n-methylmorpholine-n-oxide for manufacturing a molded product - Google Patents

Abstract

FIELD: chemical technology.

SUBSTANCE: present invention relates to chemical technology, in particular to the process of processing cellulose by the method for direct dissolution of cellulose in N-methylmorpholine-N-oxide (MMO). An extrusion method for producing a spinning solution of cellulose in N-methylmorpholine-N-oxide (MMO) for the manufacture of molded products includes solid-phase activation in one twin-screw extruder, heating to transfer to a gel-like state and subsequent extrusion to obtain a homogeneous spinning solution. The extruder includes three functional zones, with temperature and mechanical conditions characteristic of each of them: solid-phase activation is carried out at a temperature of 10-15°C, the transition to a gel-like state of the solid activated mixture of components is carried out at a temperature of 70-80°C, obtaining a homogeneous spinning solution, suitable for molding is carried out at a temperature of 85-90°C, at a screw rotation speed of 60-120 rpm, and as a MMO containing water, a commercial product is used - MMO monohydrate with a content of 13.3 wt.% water.

EFFECT: increasing the intensity and manufacturability of the process.

3 cl, 3 dwg, 9 ex, 1 tbl

Description

The present invention relates to chemical technology, in particular to the process of processing cellulose by the method of direct dissolution of cellulose in N-methylmorpholine-N-oxide (MMO).

The process of obtaining hydrated cellulose fiber - "Lyocell" using MMO as a solvent today in world practice is an alternative to the environmentally unacceptable viscose process and provides high mechanical properties of the resulting fibers, due to which the range of their application is quite wide from a textile assortment to the manufacture of industrial reinforcing material for rubber products such as tires and belts, and carbon fiber precursors.

It is known from the prior art that the process of industrial processing of cellulose through solutions in MMO - "MMO-process", is carried out in several stages: the first stage, which provides the maximum possibility of penetration of the solvent into the ordered regions of cellulose, achieved, as a rule, by treating cellulose with an aqueous solution of a solvent ( water content 40-50%) until a uniform pulp is formed, followed by an energy-intensive stage of controlled distillation of excess water from the pulp under conditions of reduced pressure and elevated temperature to a water content in the system of 10-13.3%, the stage of system homogenization until a spinning solution is obtained, passing the solution through spinneret and molding by dry-wet method. These are the main, fundamental stages of the process, but each company that develops the MMO process, improving the technology, includes certain distinctive features in it.

Thus, US Pat. % water, until a suspension is formed, excess water is removed from the suspension using a thin film evaporator and a cellulose solution is obtained.

US Pat. % water, in a horizontal cylindrical mixer, additional swelling with stirring for several hours in a storage hopper, removal of water from a solution of high viscosity using a thin-film power-driven evaporator to obtain a cellulose spinning solution.

US Pat. No. 5,948,905 describes an industrial process for producing a cellulose solution by distilling off water from a mixture of cellulose and MMO containing 23 wt. % water. In this method, the mixture was subjected to distillation of excess water under reduced pressure during the passage of the mass through a reactor nozzle with a diameter of 1.5–6.0 mm. The installation consists of a number of chambers corresponding to several stages of distillation. The first stage chamber has a small number of relatively large diameter nozzles. As the chamber stage rises, the number of nozzles increases and the nozzle opening diameter decreases to increase the cross-sectional area to improve the efficiency of water evaporation. At the eighth, last stage, an extruder is used to transfer the system into solution.

US Pat. melting in the extruder.

WO 1997/47790 describes a process for preparing a cellulose solution by dissolving cellulose powder in liquid MMO directly in a twin screw extruder. A solution of cellulose is obtained by filing liquid MMO containing 12 wt. % water, in the first barrel of the extruder, which maintains a temperature of 100°C; supply of cellulose powder to the second barrel of the extruder, inside which the temperature is maintained at 75°C, then the system moves to the third cylinder, where, with stirring at a temperature of up to 120°C, a solution is obtained.

Korean Patent No. 2002-24689 describes an industrial process for producing highly homogeneous cellulose solution from a mixture of swollen cellulose powder and liquid MMO. It is proposed to dissolve a small amount of cellulose powder in molten N-methylmorpholine-N-oxide to reduce the crystallization temperature of MMO; subsequent supply of low-concentration liquid solution of MMO and cellulose powder in a mixing apparatus; obtaining a paste by mixing without reducing the pressure with the processes of swelling and partial dissolution of cellulose in the MMO solution, and then feeding the paste into the extruder for complete dissolution.

All the methods discussed above have a number of common disadvantages: the need to create original equipment for pulp production, increased dimensions of the apparatus for distillation of water under reduced pressure, a large amount of energy consumed, etc. In addition, the analogues proposed a method for obtaining a solution of cellulose by dissolving cellulose powder directly in liquid MMO containing about 13 wt. %, at temperatures above 85°C. However, this method has a disadvantage, which consists in the presence of under-dissolved cellulose particles in the resulting solutions.

In all the considered methods for obtaining solutions of cellulose in MMO, extrusion equipment is used to one degree or another, but most often at the final stage of obtaining solutions, the stage of homogenization.

US Pat. No. 5,584,919 describes a method for preparing a cellulose solution, comprising the use of a solid MMO containing from 5 to 17 wt. % water, feeding solid MMO and cellulose powder into a horizontal cylindrical high-speed mixer and mixing them to obtain a granular intermediate and further melting the intermediate in the extruder.

The disadvantage of this method lies in the wide variation in the properties of the resulting solution due to its heterogeneity and low yield. With an increase in the speed of the process, the variation in the characteristics of the resulting intermediate increases due to various cooking conditions. In a high-speed mixer, the crystalline solvent is melted, initiating partial dissolution of cellulose over the surface of the particles, which, upon subsequent cooling and crystallization of the solution shell of cellulose particles, leads to their “keratinization” with the formation of granules. Upon subsequent heating of these granules in the extruder, the surface of the granules melts, creating a solution film that hinders the access of solvent molecules to the cellulose particle, which leads to high heterogeneity of the resulting solution, and, accordingly, a wide spread of its properties.

As a result of studies protected by RF patent No. 2075560, IPC D01F 2/02, 03.20.1997), a method was developed for solid-phase dissolution of powdered cellulose in solid MMO, which proceeds under the influence of all-round compression and deformation of the solid-phase mixture. The obtained heterophase pre-solutions are converted into a viscous state by heating to a temperature above the melting point of the used MMO, forming highly concentrated highly homogeneous spinning solutions. However, the process under consideration is periodic; storage of solid-phase pre-solutions, due to their high hygroscopicity, does not allow stabilizing the temperature-time conditions for their processing into spinning solutions.

Closest to the claimed is an extrusion method for obtaining a spinning solution according to RF patent 2748551 C1, class. IPC B 1/00, publ. 05/26/2021), which includes mixing powders of cellulose and N-methylmorpholine-N-oxide containing water, solid-phase processing of the resulting mixture under shear stress and pressure conditions until complete homogenization with obtaining a solid pre-solution, transferring the solid pre-solution into a fluid state by heating at 110-125 ° C, in which flax pulp is used with a degree of polymerization equal to 800, an alpha cellulose content of 92 wt. % and a particle size of 201-250 μm, and used for dissolving N-methylmorpholine-N-oxide is characterized by a water content of 8-10 wt. % and melting point Tm. 110-125°C.

Solid-phase activation of powdered cellulose and MMO is carried out in one twin-screw extruder, cooled to 10-15°C, at a screw speed of 50 rpm until a homogeneous mixture is obtained. The output of the extruder for the resulting mixture is 1 kg/h, the electric power consumed for extrusion is 5.6 kW, the power consumed for cooling is 1 kW.

Then the activated mixture of cellulose and MMO (the so-called pre-solution) is transferred to the molding stand, where it is heated in another extruder to a melting point of 110-125 ° C and the liquid spinning solution is forced through the spinneret to obtain thin jets, from which, after coagulation in a spinning bath gel fibers are formed, which, after subsequent washing from the solvent and drying, are transformed into finished fibers taken on bobbins. The spinning dope output of the extruder is 0.4 kg/h, the electric power consumed for extrusion is 5 kW at a forming speed of 100 m/min, the power consumed for heating is 6 kW.

The main disadvantage of the described method is that the process is carried out in two stages and in two apparatuses, which is associated with the need to transfer a solid activated mixture of polymer and solvent from one apparatus to another, which, on the one hand, for such a hygroscopic solvent as MMO, leads to watering composition and deterioration of the subsequent dissolution and quality of the spinning solution, and on the other hand, it is inevitably accompanied by losses of the mixture.

In addition, the use of two devices increases energy and material costs, which reduces the economic efficiency of the process.

By the combination of essential features and the achieved technical result, this method is taken as a prototype.

The objective of the proposed technical solution is to develop an extrusion method for obtaining a homogeneous spinning solution of cellulose suitable for spinning, which would take place continuously and in one apparatus with lower energy and material costs.

The problem is solved by the fact that an extrusion method for obtaining a spinning solution of cellulose in N-methylmorpholine-N-oxide (MMO) for the manufacture of molded products is proposed, including solid-phase activation of a powdered initial mixture containing cellulose with MMO containing water, heating the solid-phase pre-solution before transferring to viscous state and subsequent extrusion, in which solid-state activation, heating until transfer to a viscous state and subsequent extrusion is carried out in one apparatus - a twin-screw extruder, which includes three functional zones, with temperature and mechanical conditions characteristic of each of them:

- solid-phase activation is carried out in zone A when the mixture is cooled to a temperature of 10-15°C;

- translation into a viscous state of the activated mixture of components is carried out in zone B when heated to a temperature of 70-80°C;

- obtaining a highly homogeneous spinning solution suitable for spinning is carried out in zone C with an increase in temperature to 85-90 ° C at a screw rotation speed of 60-120 rpm, and as a MMO containing water, a commercial product is used - MMO monohydrate with content of 13.3 wt. % water.

To improve the stability of the molding process by modifying the rheological properties of the composition, in particular, to increase elasticity, which makes it possible to stabilize the formation of liquid jets during molding, and to bring the viscosity to the required corridor value of 10 ³ -10 ⁴ Pa⋅s, at which the flow of the solution through the spinneret is facilitated, the initial mixture may additionally contain 2-3 wt. % polysaccharide other than cellulose or acrylonitrile terpolymer. As a polysaccharide other than cellulose, either starch, or pectin, or xanthan is used.

The technical results that can be obtained from the use of the proposed method are:

- in intensifying the process of obtaining a spinning solution of cellulose by combining two main stages of the process - the stage of solid-phase activation of a mixture of powdered cellulose and MMO, and the stage of melting a solid pre-solution with the formation of a highly homogeneous spinning solution - in one extrusion apparatus - a twin-screw extruder;

- in increasing the productivity of both the activated mixture and the finished solution due to the increased rotation speed of the screws common to the two stages;

- in optimizing the process of obtaining a spinning solution by eliminating a number of additional equipment required for the second stage, and, as a result, in increasing the overall economic efficiency of the process;

- in simplifying the process through the use of a commercial product - MMO monohydrate with a melting point of 76°C, which makes it possible to reduce the maximum molding temperature to 85-90°C compared to the prototype (125°C) and, as a result, reduce energy and material costs .

In addition, the use of MMO monohydrate in the process of obtaining a spinning solution by the proposed method does not require its special processing, as in the case of using high-melting MMO with a water content of 8-10% and a melting point of 110-125°C in the prototype, which must be conditioned by water content: either moisten or dry, which requires time, additional equipment and, as a result, increases the energy and material costs of the process.

To illustrate the proposed method in Fig. 1 is a photograph of an open housing of a twin screw extruder after a dope suitable for spinning has been obtained, where

in zone A, a stage of solid-phase activation of a mixture of cellulose and MMO powders is carried out when cooled to a temperature of 10-15°C;

in zone B, the activated mixture of cellulose and MMO (pre-solution) is transferred to a gel-like state when heated to 70-80°C;

in zone C, the gel-like pre-solution is melted when heated to 85-90°C and a transparent, highly homogeneous spinning solution of cellulose in MMO is obtained, suitable for molding;

These three zones comprise 12 sections, which in FIG. 1 marked:

pos. 1-12 show twelve extruder sections in which temperature control is carried out;

pos. 13 ⁿ (n=1-12) shows the heat exchangers by which the extruder sections are cooled or heated, where n is the section number;

pos. 14 shows two extruder screws that carry out the required mechanical action on the processed raw material;

while the movement of the processed raw materials occurs from right to left - from section 1 to section 12.

The intensity of the mechanical action applied in zone A of the extruder is estimated and maintained by the value of the torque of the motor shaft, equal to 20-40% of the maximum possible. At higher torque values, premature melting of the powdered pre-solution obtained in zone A is possible and, as a result, deterioration in the quality of the spinning dope.

The energy consumption for carrying out the proposed method is estimated as the total consumption of electrical power consumed by the extruder electric motor, heat exchangers for cooling in zone A and heating in zones B and C.

The following examples illustrate the proposed method for obtaining a spinning solution, but in no way limit it.

Example 1

The initial mixture containing 13 wt. % cellulose, prepared by mixing 141 g of crushed wood pulp with a degree of polymerization of 600, with an average content of α-cellulose 93%, moisture content of 8% and an average particle size of 225 microns, 870 g of MMO monohydrate with a melting point of 76 ° C and 0.43 g of n- propyl gallate as an antioxidant and loaded into the feeder of a multi-section twin-screw extruder with a screw diameter of 20 mm and a ratio of screw length to diameter of 48:1, equipped with a melt degassing system, as well as a spinning pump and spinneret at the exit.

In zone A of the extruder, where the temperatures in five sections correspond to the following series 10→10→10→15→15°C, the solid-phase activation of the mixture occurs to obtain a solid pre-solution; in zone B of the extruder, where the temperature in three sections corresponds to the series - 70→75→80°C, the solid pre-solution passes into a gel-like state; in zone C of the extruder, where the temperature in four sections corresponds to the series 85→87→90→90°C, complete dissolution occurs and a homogeneous spinning solution of cellulose in MMO suitable for spinning is obtained, while the rotation speed of the screws is 60 rpm, and the load of the extruder in terms of torque on the motor shaft is 20% of the maximum possible.

The viscosity of the spinning solution is 5⋅10 ³ Pa⋅s.

The spinning solution pressure at the spinneret inlet is 16 bar.

The productivity of the extruder for the finished solution is 0.6 kg/h.

The electric power consumed for extrusion is 4.5 kW, for cooling zone A - 0.8 kW, for heating zones B and C - 6 kW (total 11.3 kW).

The study of the resulting solution by polarization optical microscopy (Fig. 2) confirms its high homogeneity and the almost complete absence of undissolved cellulose fibers.

Compared with the prototype, it is possible to significantly reduce the total energy consumption (up to 36%), mainly due to the exclusion of the power consumed by the second extruder of the prototype. At the same time, the productivity of the solution increases.

Example 2

Preparation of a spinning solution containing 13 wt. % pulp is performed under the conditions of example 1, but the extrusion of raw materials through extruder zones A, B and C is performed at a screw speed of 100 rpm, while the load of the extruder in terms of torque on the motor shaft is 30% of the maximum possible.

The viscosity of the spinning solution is 5⋅10 ³ Pa⋅s.

The spinning solution pressure at the spinneret inlet is 21 bar.

The productivity of the extruder for the finished solution is 1.0 kg/h.

The electrical power consumed for extrusion is 5.0 kW, for cooling zone A - 0.8 kW, for heating zones B and C - 6 kW (total 11.8 kW).

The study of the resulting solution by polarization optical microscopy (Fig. 2) confirms its high homogeneity and the complete absence of undissolved cellulose fibers.

Compared to example 1, energy consumption for extrusion increased slightly due to the intensification of the process due to an increase in the speed of rotation of the screws. This significantly increases the productivity of the solution, as well as the pressure of the solution in front of the spinneret.

Example 3 (comparative)

The preparation of the spinning solution is performed under the conditions of example 1, but the initial mixture contains 20 wt. % wood pulp and high-melting MMO containing 10 wt. % water and having a melting point of 105°C, and melting in zone C of the extruder is carried out with a modified temperature series in four sections: 90→100→115→115°C, i.e. with an increase in maximum temperature.

At a screw speed of 60 rpm, the extruder torque load on the motor shaft is 40% of the maximum possible.

The viscosity of the spinning solution is 7⋅10 ³ Pa⋅s.

The spinning solution pressure at the spinneret inlet is 18 bar. The productivity of the extruder for the finished solution is 0.7 kg/h.

The electric power consumed for extrusion is 5 kW, for cooling zone A - 0.8 kW, for heating zones B and C - 7 kW (total 12.8 kW).

The study of the resulting solution by polarization optical microscopy (Fig. 3) confirms its homogeneity and the almost complete absence of undissolved cellulose fibers.

An increase in the concentration of cellulose in the solution compared to example 1 leads to a significant increase in the viscosity of the solution and, as a result, an increase in the pressure of the solution in front of the spinneret, an increase in the torque on the shaft of the extruder motor and an increase in energy consumption for extrusion. Also, the use of high-melting MMO forces the use of a higher melting temperature, which increases the energy consumption for heating.

Example 4 (comparative)

Preparation of a spinning solution containing 20 wt. % cellulose is performed under the conditions of example 3, but the extrusion of raw materials through extruder zones A, B and C is performed at a screw speed of 100 rpm, while the load of the extruder in terms of torque on the motor shaft is 45% of the maximum possible.

The viscosity of the spinning solution is 7⋅10 ³ Pa⋅s.

The spinning solution pressure at the spinneret inlet is 21 bar.

The productivity of the extruder for the finished solution is 1.2 kg/h.

The electric power consumed for extrusion is 5.5 kW, for cooling zone A - 0.8 kW, for heating zones B and C - 7 kW (total 13.3 kW).

The study of the resulting solution by polarizing optical microscopy (Fig. 3) confirms its homogeneity and the complete absence of undissolved cellulose fibers.

Compared to example 3, there was an increase in solution productivity, accompanied, however, by an increase in energy consumption for extrusion.

Example 5

Preparation of a spinning solution containing 13 wt. % cellulose, performed under the conditions of example 2, but instead of wood pulp, flax pulp with a polymerization degree of 900, an α-cellulose content of 97%, a moisture content of 8% and an average particle size of 230 μm is used. At a screw speed of 100 rpm, the extruder torque load on the motor shaft is 35% of the maximum possible.

The viscosity of the spinning solution is 1⋅10 ⁴ Pa⋅s.

The spinning solution pressure at the spinneret inlet is 24 bar.

The productivity of the extruder for the finished solution is 1.1 kg/h.

The electrical power consumed for extrusion is 5.0 kW, for cooling zone A - 0.8 kW, for heating zones B and C - 6 kW (total 11.8 kW).

Optical polarization microscopy data confirm the homogeneity of the spinning solution.

The energy parameters of the process remain similar to example 2, but due to the significantly higher viscosity of the flax pulp solution compared to wood pulp, an increase in the pressure of the solution in front of the spinneret by 12% was recorded.

Example 6

The preparation of the spinning solution is performed under the conditions of example 5, but using the initial mixture containing 12 wt. % flax pulp and 2 wt. % starch. At a screw speed of 100 rpm, the extruder torque load on the motor shaft is 30% of the maximum possible.

The viscosity of the spinning solution is 5⋅10 ³ Pa⋅s.

The spinning solution pressure at the spinneret inlet is 20 bar.

The productivity of the extruder for the finished solution is 1.0 kg/h.

The electrical power consumed for extrusion is 5.0 kW, for cooling zone A - 0.8 kW, for heating zones B and C - 6 kW (total 11.8 kW).

Optical polarization microscopy data confirm the homogeneity of the spinning solution.

Energy costs are similar to example 5, and the pressure of the solution in front of the spinneret is reduced to normal, due to a decrease in the viscosity of the cellulose solution in the presence of starch.

Example 7

The preparation of the spinning solution is performed under the conditions of example 6, but using the initial mixture containing 12 wt. % flax pulp and 2 wt. % pectin. At a screw speed of 100 rpm, the extruder torque load on the motor shaft is 30% of the maximum possible.

The viscosity of the spinning solution is 5⋅10 ³ Pa⋅s.

The spinning solution pressure at the spinneret inlet is 19 bar.

The productivity of the extruder for the finished solution is 1.0 kg/h.

The electrical power consumed for extrusion is 5.0 kW, for cooling zone A - 0.8 kW, for heating zones B and C - 6 kW (total 11.8 kW).

Optical polarization microscopy data confirm the homogeneity of the spinning solution.

All energy parameters of the process remain similar to example 6. The pressure of the solution in front of the spinneret is lower than in example 6, due to the higher concentration of the additive that reduces the viscosity of the cellulose solution.

Example 8

The preparation of the spinning solution is performed under the conditions of example 6, but using the original mixture containing 12 wt. % flax pulp and 2.5 wt. % xanthan. At a screw speed of 100 rpm, the extruder torque load on the motor shaft is 30% of the maximum possible.

The viscosity of the spinning solution is 4⋅10 ³ Pa⋅s.

The spinning solution pressure at the spinneret inlet is 17 bar.

The productivity of the extruder for the finished solution is 0.9 kg/h.

The electrical power consumed for extrusion is 5.0 kW, for cooling zone A - 0.8 kW, for heating zones B and C - 6 kW (total 11.8 kW).

Optical polarization microscopy data confirm the homogeneity of the spinning solution.

Due to the marked reduction in the viscosity of the cellulose solution compared to examples 5 and 6, the pressure of the solution in front of the spinneret and the productivity of the solution also turn out to be reduced. Energy parameters remain unchanged.

Example 9

The preparation of the spinning solution is performed under the conditions of example 6, but using the initial mixture containing 12 wt. % flax pulp and 3 wt. % acrylonitrile terpolymer.

At a screw rotation speed of 100 rpm, the extruder torque load on the motor shaft is 20% of the maximum possible.

The viscosity of the spinning solution is 1⋅10 ³ Pa⋅s.

The spinning solution pressure at the spinneret inlet is 15 bar.

The productivity of the extruder for the finished solution is 1.0 kg/h.

The electrical power consumed for extrusion is 4.0 kW, for cooling zone A - 0.8 kW, for heating zones B and C - 6 kW (total 10.8 kW).

Optical polarization microscopy data confirm that the dope is an emulsion.

In comparison with examples 6-8, the cellulose solution containing the acrylonitrile-based terpolymer has a significantly lower viscosity, which significantly reduces the energy consumption for extrusion (the lowest among all examples 1-9).

Table 1 summarizes the characteristics of the process for obtaining spinning solutions of cellulose in examples 1-9 and the prototype.

It can be noted that in comparison with the prototype in all examples 1-9, it is possible to significantly reduce the total energy consumption (up to 40%), mainly due to the exclusion of the power consumed by the second extruder of the prototype. The productivity of the solution in this case increases, especially when the process is intensified with an increase in the speed of rotation of the screws up to 100 rpm: up to 1.1 kg/h (example 5) compared to 0.4 kg/h (prototype).

The use of highly concentrated (up to 20 wt %) cellulose solutions and/or the use of cellulose with a high degree of polymerization (for example, linen) leads to an increase in energy consumption for additional heating and/or extrusion of solutions due to an increase in their viscosity.

Introduction to the composition of the initial mixture of 2-3 wt. % of another polysaccharide, or acrylonitrile terpolymer, can significantly reduce the viscosity of the cellulose solution and, as a result, facilitate the molding process and reduce energy costs for extrusion.

The homogeneity of the resulting spinning solutions is assessed by polarizing optical microscopy: when observing a sample of the molten solution through a microscope in the crossed polaroid mode, the number of unmelted cellulose fibers should not exceed 10% of the initial, unmelted state.

In FIG. 2 shows micrographs confirming the homogeneity of the cellulose solutions obtained according to examples 1-2, i.e. according to the proposed method, where:

a) a micrograph at 10°C of a powdered initial mixture that has passed only zone A of solid-phase activation, according to example 1;

b) micrograph at 80°C of the mixture, which has passed into a gel state, after passing through zones A and B according to example 1;

c) a micrograph at 90° C. of a solution that has passed into a homogeneous molten state after passing through zones A, B and C according to example 1;

d) micrograph at 90°C of a solution that has passed into a homogeneous molten state after passing through zones A, B and C according to example 2.

From FIG. 2 shows that as the zones A, B and C of the extruder pass, the state of aggregation and the homogeneity of the system change: from a powdery mixture of initial components to a transparent spinning solution. The use of higher screw speeds during the process improves the homogeneity of the obtained dope: comparison of photomicrographs (c) and (d) in FIG. 2, obtained under equal conditions, but according to examples 1 and 2, respectively, differing in the increase in the speed of rotation of the screws.

In FIG. 3 shows micrographs confirming the homogeneity of cellulose solutions obtained according to comparative examples 3-4, which differ from the proposed method in that high-melting MMO is used and the maximum temperature in the extruder is increased, where:

a) a micrograph at 10°C of a powdered initial mixture that has passed only zone A of solid-phase activation, according to example 3;

b) micrograph at 80°C of the mixture, which has passed into a gel state, after passing through zones A and B according to example 3;

c) a micrograph at 90° C. of a partially molten solution after passing through zones A, B and C according to example 3;

d) micrograph at 115° C. of a solution that has passed into a homogeneous molten state after passing through zones A, B and C according to example 3;

e) micrograph at 115°C of a solution that has passed into a homogeneous molten state after passing through zones A, B and C according to example 4.

Similarly to FIG. 2 from FIG. 3 shows that as the zones A, B and C of the extruder pass, the state of aggregation and the homogeneity of the system change: from a powdery mixture of initial components to a transparent spinning solution.

However, in contrast to the proposed method, complete melting occurs at a higher temperature, which is associated primarily with the use of high-melting MMO in examples 3-4, and not MMO monohydrate in examples 1-2 and 5-9: comparison of photomicrographs ( c) and (d) in Fig. 3 obtained for the solution according to example 3, but heated to different maximum temperatures.

In this case, the use of higher screw speeds also makes it possible to improve the homogeneity of the dope: comparison of photomicrographs (d) and (e) in Figs. 3, obtained under equal conditions, but according to examples 3 and 4, respectively, differing in the increase in the speed of rotation of the screws.

For cellulose solutions obtained according to examples 5-9, i.e. according to the proposed method and under temperature-mechanical conditions similar to example 2, the results of analysis by the method of polarizing optical microscopy coincide with the results shown in Fig. 2 and obtained for examples 1-2.

Thus, the proposed technical solution for obtaining spinning solutions of cellulose in N-methylmorpholine-N-oxide allows you to significantly increase the intensity and manufacturability of the process by carrying out all the main stages in one extrusion apparatus, as well as reduce material and energy costs in some cases up to 38% (example 9).

Claims (8)

1. An extrusion method for obtaining a spinning solution of cellulose in N-methylmorpholine-N-oxide (MMO) for the manufacture of molded products, including solid-phase activation of a powdered initial mixture consisting of cellulose and MMO containing water, heating the solid-phase pre-solution until it is transferred to a gel state and subsequent extrusion to obtain a homogeneous spinning solution suitable for spinning, characterized in that solid-phase activation, heating to transfer to a gel-like state and subsequent extrusion to obtain a homogeneous spinning solution is carried out in one twin-screw extruder, including three functional zones, with temperature characteristic for each of them and mechanical modes: - solid-phase activation is carried out at a temperature of 10-15°C; - translation into a gel-like state of the solid activated mixture of components is carried out at a temperature of 70-80°C; - obtaining a homogeneous spinning solution suitable for spinning is carried out at a temperature of 85-90°C; at a screw rotation speed of 60-120 rpm, and as MMO containing water, use a commercial product - MMO monohydrate with a content of 13.3 wt. % water. 2. The method according to p. 1, characterized in that the original components additionally contain 2-3 wt. % polysaccharide other than cellulose or acrylonitrile terpolymer. 3. The method according to p. 2, characterized in that either starch, or pectin, or xanthan is used as another polysaccharide.

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