EP1315855A1

EP1315855A1 - Method and device for the continuous, single-step production of a homogeneous solution of cellulose in hydrous tertiary aminoxides

Info

Publication number: EP1315855A1
Application number: EP00972575A
Authority: EP
Inventors: Christoph Michels; Andreas Diener
Original assignee: List AG; Thueringisches Institut fuer Textil und Kunststoff Forschung eV
Current assignee: List AG; Thueringisches Institut fuer Textil und Kunststoff Forschung eV
Priority date: 2000-09-05
Filing date: 2000-09-05
Publication date: 2003-06-04
Also published as: CN1454267A; CA2427478A1; WO2002020885A1; US6875756B1; CN1211508C

Abstract

The invention relates to a method and to a device for the continuous, single-step production of a homogeneous solution of cellulose in hydrous aminoxides on the basis of cellulose and aqueous aminoxides, preferably N-methylmorpholino-N-oxide (NMMO), at temperatures in the range of from 50 to 130 DEG C under a vacuum and water evaporation. The cellulose and the NMMO are dosed separately to the device, mixed while sheared, the water is evaporated until the mixture is dissolved, the solution is homogenized and directly fed to the consumer via screw conveyors, pumps and filters.

Description

[Godfather registration]

[Name of the invention:]

Process and device for the continuous, one-step production of a homogeneous solution of cellulose in water-containing tertiary amine oxides.

[Description]

The invention relates to a method and a device for the continuous, one-step production of a homogeneous solution of cellulose in water-containing amine oxides from cellulose and aqueous amine oxides, preferably N-methylmorpholine-N-oxide (NMMO), at temperatures in the range from 50 to 130 ° C. Vacuum and water evaporation.

[State of the art]

The dissolving of cellulose in amine oxides with a defined water content at temperatures above 70 ° C. is known (DRP 713 486; USP 3 447 939). The solving process is very slow. The dissolution is significantly accelerated if the cellulose is dispersed in aqueous NMMO and then the excess water is distilled off under vacuum and stirring at temperatures above 85 ° C. with simultaneous dissolution of the cellulose (GB 8 216 566). It is also known to mix comminuted cellulose in a ring layer mixer (WO 96/33221) or in a horizontal mixing chamber with a rotor and radial stirring elements (WO94 / 28217) with water-containing NMMO. The homogeneity of the suspension can be improved by high consistency grinding. The suspension is transferred into a solution by means of a thin-film evaporator (EP 356 419) or in the shear field of a horizontal screw remover (DE 4 441 468). It is also known to continuously produce cellulose solutions by first dispersing the cellulose and aqueous NMMO in a horizontal twin-shaft kneader, metering the suspension continuously into a horizontal single-shaft kneader via an intermediate container and converting it to a solution under vacuum and water evaporation (A. Diener and G Raouzeos Chemical Fibers International 49 [1999] 3 pp. 40-42; DE 19 837 210).

-15/3 All processes have in common that the production of the cellulose solution basically takes place in two spatially separate stages, namely on the one hand in suspending the comminuted cellulose in the strongly water-containing amine oxide, optionally with aftertreatment, and on the other hand in transferring the

Suspension under scissors and water evaporation in the actual solution.

[Object of the invention] The object of the invention is to create a method and a device for the continuous, one-step production of a homogeneous solution of cellulose in water-containing amine oxides. That Cellulose and water-containing amine oxide, preferably NMMO, are continuously converted into a homogeneous cellulose solution in a device without explicit transport and metering of a suspension in one step and are supplied to the potential consumer in the shortest possible way.

In the method mentioned at the outset, this object is achieved in that:

(a) promotes, homogenizes and temperature-regulates water-containing cellulose in the first section of a first shear zone of a mixing / kneading reactor under vacuum, (b) conveys preheated, water-containing amine oxide in the second section of the first shear zone of the mixing / kneading reactor mixes the water-containing cellulose under shear, homogenizes and heats up with the start of water evaporation, (c) removes water in the third section of the first shear zone of the mixing / kneading reactor with kneading, shearing and tempering the suspension until it is completely transferred to a cellulose gel, (d) in the second shear zone of the mixing / kneading reactor, the cellulose gel is converted into a homogeneous solution under vacuum, cooling, kneading and shearing,

(e) separates, transports and transports the homogeneous solution from the vacuum-carrying part of the mixing / kneading reactor by means of temperature-controlled screw conveyors, preferably in a double screw design

(f) feeds the homogeneous solution directly to the consumer via pumps and safety filters. The solution quality is characterized by the particle content determined by means of laser diffraction and the size distribution of the particles, as described in detail in the literature (Ch. Michels and F. Meister Das Papier 51 [1997] 4 pp. 161-165; B. Kosan and Ch. Michels Chemical Fibers International 49 [1999] 3 pp. 50-54). It is expedient to try to express the particle content and the particle distribution in only one size, the so-called filter value. It is defined as the quotient of the maximum particle diameter X _m and the logarithm of the number of particles N ₁₀ in the size class 10 μm.

Solutions with filter values <50 lead to very high and filter values <100 lead to high spinning safety.

The achieved solution state is described by the zero shear viscosity, the relaxation time and the relaxation time spectrum, which are easily accessible from rheological data. The methods are also described in detail in the literature (Ch. Michels, Das Papier 52 [1998] 1 pp. 3 -8)

In one embodiment of the process according to the invention, the cellulose or cellulose mixture is subjected to activation. This can be a hydrothermal (DD 298 789)

-13/3 or enzymatic (DE 4 439 149) pretreatment. Activating the cellulose increases the dissolving speed and improves the quality of the solution.

In a further embodiment of the method according to the invention, part of the water-containing NMMO is replaced by diluents, such as e.g. ε-aminocaprolactam, piperidone, pyrrolidone or polyvinylpyrrolidone methacrylate copolymer. The diluent lowers the melting point of the solvent NMMO and thus allows the selection of a lower working temperature.

In a further embodiment of the process according to the invention, additives are metered in simultaneously with the cellulose or the water-containing amine oxide. The additives, such as cellulose derivatives, starch, starch derivatives, titanium dioxide, silicates, kaolin, carbon black, chitosan, surfactants, polyethyleneimine, etc. can be solid, liquid and / or soluble in amine oxide. Insoluble, solid additives are advantageously mixed with the cellulose or dosed separately. The object is further achieved according to the invention in the device mentioned at the outset by providing a screw conveyor with a twin- or multi-shaft kneading / mixing reactor with at least two heating / cooling zones and a speed-controlled drive unit, a vacuum station, two or more vacuum-tight metering units assigned as a discharge unit, a safety filter, two feed pumps and a potential consumer. A kneading / mixing reactor is expediently used as a horizontal twin-shaft co-rotating processor (LIST AG Arisdorf Switzerland) with two heating / cooling zones and a freely selectable shaft speed for setting the required shear field. The kneading / mixing shafts of the reactor rotate in the same direction. The first heating / cooling zone is a control piston pump for dosing water-containing cellulose, a heated pump with a controllable control valve for dosing the water-containing NMMO and

-12/3 optionally assigned one or more units for metering one or more additives. A vacuum station, consisting of a vacuum pump (s) and a condensation unit, supplies the kneading / mixing reactor with the vacuum required to remove the water. At the outlet of the "Co Rotating Processor", a large-volume, vertical twin-screw unit separates the kneading / mixing reactor on the vacuum side, takes over the promotion of the solution and at the same time serves as a buffer to compensate for fluctuations in the potential consumer's consumption. The twin-screw unit is one between two pumps Pumps and safety filters are designed in such a way that a shear rate of 5 [1 / s] is not exceeded differ.

In another embodiment of the device according to the invention, an “opposing rotating processor” is used as the kneading / mixing reactor, ie the kneading / mixing shafts of the reactor rotate in opposite directions. The invention is explained in more detail with reference to drawings and examples Device according to the invention consisting of the kneading / mixing reactor 1 with the heating / cooling zones 1.1 and 1.2 and drive unit 1.3, the vacuum station 2, the metering units 3 4 5, the screw conveyor 6, the safety filter 7, the feed pumps 8 9 and the consumer 10th

[Examples]

example 1

A "Co-Rotating Processor Type LIST-CRP 63 Batch" with two heating / cooling zones served as the kneading / mixing reactor. In the first shear zone of the reactor, 364 g / min, which have been crushed, enzymatically pretreated and stabilized cellulose (Cuoxam

-11/3 DP 540; molecular non-uniformity U _η = 5.8; Water content 49.0%) and a control unit consisting of pump and control valve, 1405 g / min pre-heated to 85 ° C NMMO (water content 16.0%). Under strong shear and an applied vacuum of 150 mbar, intensive mixing and distillation of the excess water (approx. 222 g / min) takes place while the suspension is heated to a melt temperature of 115 ° C. After passing through the first shear zone (residence time 15-20 minutes) the mixture appears glassy, highly viscous and is present as a swollen gel. In the second shear zone of the reactor, with further shear and simultaneous cooling to a melt temperature of 85 ° C, the gel is converted into a solution, which is then taken up by the vertical twin-screw conveyor, further homogenized and fed to the precision gear pump. At a constant melt temperature of 85 ° C, this conveys 1334 ml / min solution through a safety filter with a mesh size of 15 μm to the second pump, which feeds the same amount of solution to the consumer in a fiber test spinning system. The pressure difference in the safety filter was zero even after many hours of operation. The solution had a composition of 12.0 mass% cellulose, 76.3 mass% NMMO and 11.7 mass% water. The zero shear viscosity at 85 ° C was 5360 Pas, the relaxation time λ _m at the maximum frequency 5.4 seconds and the inconsistency U _η = 5.8.

The non-uniformity U _η is obtained from the quotient of zero shear viscosity η ₀ and the "viscosity component η ^# " at the crossing point of the dynamically recorded deformation curves [G ';G''= f (ω)], ie if the storage G' and loss module G ''are the same size.

U = ^ -1 ^η η *

-10/3 The index η is intended to indicate that the non-uniformity results from rheological data and not from the determination of the number and mass average of the molar mass.

The solution has a relaxation time spectrum as shown in FIG. 2 and a particle distribution determined by laser diffraction as shown in FIG. 3. The particle content is 4.7 μl / kg solution, the particle diameter at the maximum frequency is 6.6 μm, the maximum particle diameter is 16.5 μm and the filter value was calculated to be 28.

Example 2

In example 2, the procedure is essentially the same as in example 1, except that the mixing / kneading reactor used is an approximately the same size "Opposite Rotating Processor type LIST-ORP Conti" and the residence time in the reactor is 1.5 times higher Solution state largely corresponds to that of the solution in Example 1.

Example 3 The kneading / mixing reactor differs from that in Example 1 in that 3 components can be metered in separately in the first shear zone.

344 g / min of crushed, hydrothermally pretreated and stabilized cellulose with a water content of 46% by mass, consisting of a mixture of 95 parts of spruce sulfite pulp (Cuoxam DP 490; U _η = 5.9) and 5 parts of cotton, are shredded via the control piston pump. Linter cellulose (Cuoxam DP 1900; U _η = 3.4) and via two separate control units, consisting of a pump and control valve, 1328 g / min NMMO (water content 20% by mass) preheated to 90 ° C and 119 g / min

Polyvinyl pyrrolidone (PVP product VP-MA91 W from BASF Ludwigshafen), which also contains 0.5 mass% titanium dioxide. With shear and an applied vacuum of 140 mbar, intensive mixing and distillation of approx. 260 are carried out

-9/3 g / min water with simultaneous heating of the suspension to 110 ° C. After the gel state has been reached, the further dissolution process takes place with simultaneous cooling in the second shear zone to 75 ° C. 1530 g / min spinning solution with a melt temperature of 75 ° C was fed to the consumer, a filament spinning machine for coarse titre filament yarns, via screw conveyors, safety filters and pumps. The solution consisted of 12.2 mass% cellulose, 69.5 mass% NMMO, 7.7 mass% PVP and 10.6 mass% water. The zero shear viscosity at 85 ° C was 3600 Pas, the relaxation time λ _m = 6.5 seconds and the non-uniformity U _η = 6.8. The particle analysis resulted in a particle content of 8.7 μl / kg solution, a particle diameter at the maximum frequency of 10.5 μm and a filter value of 56.

Example 4

In Example 4, the procedure is analogous to Example 3, with the difference that a single-shaft, horizontal "List Discotherm B-Conti" is used as the mixing / kneading reactor. Instead of the polyvinyl-pyrrolidone copolymer, the same amount of preheated ε-aminocaprolactam is added. The residence time is double and the solution quality largely corresponds to the solution in Example 3.

Example 5

In a mixing / kneading reactor according to Example 3, 272 g / min of crushed cellulose (Cuoxam DP 430, water content 35% by mass, non-uniformity 6.8) are crushed via a control piston pump, and 71 g / min of polyethyleneimine (“Polymin” commercial product) via a precision gear pump BASF Ludwigshafen, molar mass> 750

000, water content 50 mass%) and metered and mixed via a pump and control valve 1232 g / min NMMO (water content 23 mass%), heated to 120 ° C. under a vacuum of 160 mbar and distilled off approx. 275 g / min water. The in the

-8/3 The bright yellow solution that forms in the second shear zone is simultaneously cooled to 80 ° C, taken over by the screw conveyor and fed to the consumer, a fiber spinning system, in an amount of 1300 g / min via pumps and safety filters. The solution consists of 13.6 mass% cellulose, 2.7 mass% polyethyleneimine, 73.0 mass% NMMO and 10.7 mass% water. The zero shear viscosity at 85 ° C is 5100 Pas, the relaxation time at the maximum frequency 1.7 seconds, the particle content 5.2 μl / kg solution, the particle diameter at the maximum frequency 9.5 μm and the filter value 45.

Example 6

A "co-rotating processor type" serves as the kneading / mixing reactor

LIST-CRP 250 Conti "with a drive unit for the speed range of 80-120 rpm, 2 heating / cooling zones, and 2 metering nozzles. Analogously to Example 1, 924 g / min crushed and enzymatically pretreated cellulose ( Eucalyptus pulp Cuoxam DP 580, non-uniformity 5.9, water content 45 mass%) and 3673 g / min NMMO (water content 45 mass%) metered into the second nozzle, in the first shear zone under vacuum of 160 mbar, intensive mixing and kneading heating the suspension to 120 ° C with simultaneous evaporation of 533 g / min of water until the transition to the gel state In the second shear zone, with simultaneous cooling to 82 ° C, a homogeneous solution is created, which is taken over by a vertical twin-screw conveyor and via two pumps and a safety filter is supplied to the consumer in an amount of 3474 ml / min. The solution consisted of 12.5 mass% cellulose, 75.9 mass% NMMO and 11.6 mass% water, their zero shear The viscosity was 6760 Pas, the relaxation time at the maximum of 6.3 seconds, the particle content 8.4 μl / kg of solution, the particle diameter at the maximum of 8.1 μm and the filter value 32.

-7/3 [REFERENCE LIST]

Figure 1

1 kneading / mixing reactor

1.1 Heating / cooling zone

1.2 Heating / cooling zone

1.3. drive unit

2 vacuum station

3, 4, 5 dosing units

6 screw conveyors

7 safety filters

8, 9 feed pumps

10 consumers

-6/3 [Attached drawings]

Number of attached drawings: [3]

-5/3

Claims

[Claims]

1. Process for the continuous, one-step preparation of a homogeneous solution of cellulose and, if appropriate, additives in water-containing tertiary amine oxides at temperatures in the range between 50 and 130 ° C. under vacuum and water evaporation, characterized in that

(a) conveying, homogenizing and tempering cellulose containing water into the first section of a first shear zone of a mixing / kneading reactor which is under vacuum,

(b) promotes preheated, water-containing amine oxide in the second section of the first shear zone of the mixing / kneading reactor, mixes it with the water-containing cellulose under shear, homogenizes it and heats it up with the beginning of water evaporation

(c) in the third section of the first shear zone of the mixing / kneading reactor, with kneading, shearing and tempering the suspension, until water has completely passed into a cellulose gel, (d) in the second shear zone of the mixing / kneading reactor, the cellulose gel under vacuum, cooling , Kneading and shearing into a homogeneous solution,

(e) the homogeneous solution is separated, transported and transported from the vacuum-carrying part of the mixing / kneading reactor by means of a temperature-controlled screw conveyor, preferably in a vertical twin-screw design

(f) feeds the homogeneous solution directly to the consumer via pumps and safety filters.

2. The method according to claim 1, characterized in that the cellulose from wood, cotton linters or other annual plants has been isolated and contains 0.5-80% by mass, preferably 30-60% by mass of water.

-4/3

3. The method according to claim 1, characterized in that the cellulose alone or in a mixture is homogenized or mixed by whipping in water and then pressed.

4. The method according to claim 1, characterized in that the cellulose is activated by hydrothermal pretreatment.

5. The method according to claim 1, characterized in that the cellulose is activated by enzymatic pretreatment.

6. The method according to claim 1, characterized in that the water-containing amine oxide is an N-methylmorpholine-N-oxide and contains at least 7% by mass of water.

7. The method according to claim 1, characterized in that the water-containing amine oxide contains diluent, preferably ε-aminocaprolactam or polyvinylpyrrolidone methacrylate copolymer.

8. The method according to claim 1-7, characterized in that additives are entered depending on their properties in step (a) or (b) parallel to the water-containing cellulose or to the water-containing amine oxide.

9. The method according to claim 1-7, characterized in that the additives are mixed with the water-containing cellulose or suspended or dissolved in the water-containing amine oxide and entered together with the main components in step (a) or (b).

10. The method according to claim 1-7, characterized in that in steps (a) to (c) an increasing temperature

-3/3 profile in the range 50 - 130 ° C, in stage (d) a falling temperature profile in the range 130 - 60 ° C and in stage (e) to (f) largely maintains the end temperature of stage (d).

11. The method according to claims 1-7, characterized in that the composition of the mixture or solution in stages (b) to (d) is controlled by the speed of the kneader shafts, the vacuum and the melt temperature and the solution quality via the Pressure difference in the safety filter checked.

12. The method according to claim 1-7, characterized in that the temperature-controlled screw conveyor is used as a buffer between the mixing / kneading reactor and the consumer.

13. The method according to claims 1-7, characterized in that the shear rate in the safety filter is low, preferably less than 5 [1 / sec.].

14. The method according to claims 1-7, characterized in that the shear rate in the feed pumps to the safety filter and consumer is low, preferably less than 5 [1 / sec.].

15. The method according to claim 1-14, characterized in that the solution quality is characterized by measuring the particle content and particle distribution by means of laser diffraction.

16. The method according to claim 1-14, characterized in that the solution state is characterized by the zero shear viscosity, relaxation time / relaxation time spectrum and the molecular non-uniformity, determined from rheological data.

-2/3

17. Device for the continuous, single-stage production of a homogeneous solution of cellulose in water-containing amine oxide consisting of metering devices, a kneading / mixing reactor, safety filter and feed pumps, characterized in that a horizontal single or multi-shaft kneading / mixing reactor (1), with heating - / Cooling zones (1.1) and (1.2) and drive unit (1.3), a vacuum station (2), two or more vacuum-tight metering units (3), (4), (5), a screw conveyor (6), a safety filter ( 7), two feed pumps (8), (9) and the potential consumer (10) according to FIG. 1.

18. The apparatus according to claim 17, characterized in that a horizontal twin-shaft co-rotating processor running in the same direction is used as the kneading / mixing reactor (1).

19.Device according to claim 17, characterized in that the kneading / mixing reactor (1) is a horizontal double-shaft, oppositely running "opposing rotating processor".

20. The apparatus according to claim 17, characterized in that a horizontal single-shaft "Discotherm B-Conti processor" is used as the mixing / kneading reactor (1).

21. The apparatus according to claim 17, characterized in that "control piston pumps" is used for metering water-containing cellulose (3).

22. The apparatus according to claim 17, characterized in that "double-piston metering device" is used for metering solid additives (5).

-1/3

23. The device according to claim 17, characterized in that a combination of heatable feed pump and controllable control valve is used for metering water-containing amine oxides (4) and low-viscosity additives (5).

24. The device according to claim 17, characterized in that precision gear pumps are used for metering highly viscous additives (5).

25. The device according to claim 17, characterized in that a large-volume, preferably vertically arranged, twin-screw device is used as the screw conveyor (6).

0/3