DE3113200A1 - Process and device for the continuous preparation of solutions or dispersions and emulsions or spreadable pastes with a high solids concentration - Google Patents

Abstract

Polymer as powder, for example polyacrylonitrile (PAN), is charged via a metering balance (12) in free fall into a multi-stage mixing unit (13) which is equipped with a floatingly mounted shaft (14) bearing a plurality of rotors (15) at its lower end. The powder is sprayed in free fall at room temperature with solvent, for example dimethylformamide (DMF), via nozzles (9) connected to a circular pipe (8), the mixture is swirled by the rotors (15) and sheared in a turbulent manner. The solution flows via an edge distributor (18) into a gravity pipe (17), is degassed under vacuum and discharged as a final spinning solution (27) by means of a screw pump (25, 26). The process and the device can also be advantageously used for producing dispersions or emulsions and spreadable pastes. <IMAGE>

Description

PROCEDURES AND DIRECTIONS FOR CONTINUOUS

PREPARATION OF LESINGS OR DISPERSIONS AND EMULSIONS OR PAINTABLE HIGH SOLID CONCENTRATION PASTS In the production of Spinning solutions for the production of synthetic fibers are solutions with the highest possible Concentration desired in order to give the fibers special properties and the Reduce the amount of solvent, reducing the cost of raw materials, specicll Solvent, for its recovery and the associated energy requirement can be minimized.

Powdered solids tend during the preparation of solutions, Dispersions and the like when wetting with solvents at an instantaneous Agglomerate formation, since mostly powder particles due to surface tension effects swell, cover themselves with a sticky gelatinous skin and clump together. The skin formed around the agglomerates or lumps also inhibits further penetration of the solvent.

In order to overcome the phenomena, high-speed, multi-stage mixing rates are used used, but so far have not been able to experience difficulties in an advantageous manner to overcome that in the production of spinning solutions with high solids concentration occur because the viscosity of the solution increases with increasing solids concentration increases exponentially.

For example, solutions with 20-25% PAN in DMF have an initial viscosity of only approx. 25,000 m Pas while the initial viscosities of solutions are 29 - 35 % PAN are already at 600,000 m Pas and during post-ripening to approx. 1 million m Pas rise. The consequence is then that the spinning solution is already in the brackets a multi-stage mixing unit produces a highly viscous stable film as it flows out forms, which leads to rapid bonding. To get around these difficulties, So far, one has helped by letting the solvent run at lower temperatures was cooled.

The dissolving speed could be reduced to the extent that the product flowed out of the mixing unit as a low-viscosity suspension. So far the DMF has been for example cooled down to +50 to -50 C, which with a corresponding quite an energy expenditure of about 42 kJ / kg net. Then had to this suspension is heated up to approx. 800C by supplying energy and at steady Stir slowly to completion, observing special precautionary measures Solution and maturity are brought.

The purpose of the invention is a method and a device for continuous To propose preparation of polymer solutions or dispersions in which the mentioned disadvantages no longer occur, in particular the continuous Production of a spinning solution at room temperature is made possible without the additional Energy used to cool the raw material components and reheat the solution must become.

The proposed method uses a continuous one multi-stage mixing unit in which first the dry polymer and then the reading medium are fed in sequentially. The procedure is that the components collapsed without prior cooling at room temperature, with little energy input turbulent sheared and dispersed or dissolved, whereupon a Venting takes place. Appropriately, the components are only about 0.001 kWh / kg Energy supplied, whereupon these are dispersed or dissolved in 2-5 seconds. This short dwell time can only be achieved with a very compact design. to this is the purpose of the flow path between the individual stages of the mixing unit and the outlet and the flow resistance when the product flows out is reduced reduced from the mixing unit. The nature of a spinning solution produced in this way meets the requirements of the fiber industry. To remove some vesicles it would be possible, as before, to bring the spinning solution to 800C with gentle stirrers heat so that the solution becomes low-viscous. In this state there is a degassing both continuously and discontinuously possible, but both in terms of apparatus as well as energetically complex.

As a further development of the proposed method is therefore a Appropriate procedure, according to which the outflowing product immediately after discharge is vented from the mixing unit by vacuum.

The device for carrying out the procedure consists of one multi-stage mixing and dissolving unit in a vertical arrangement, preferably with direct The following venting device according to the invention is not at the lower end Bearing shaft of the mixing and dissolving unit with at least two close together arranged rotors provided, which by a smooth housing wall without stators are surrounded.

On the accompanying drawing is an embodiment of the inventive Device shown, on the basis of which the method is also explained. Included let's stick with the example already chosen, according to which spinning solutions made from PAN and DMF can be prepared and vented at room temperature.

The figures show: FIG. 1 an overall device for continuous production a spinning solution in a schematic representation, FIG. 2 shows a mixing apparatus comprising Detail of the device in vertical section, Fig. 3 is a plan view of the housing of the mixing apparatus, FIG. 4 shows an enlarged representation of a rotor in part in vertical section, and FIG. 5 is a view of the rotor from above.

The creation of a spinning solution with a high concentration at room temperature in a mixer is associated with considerable difficulties, since the spinning solution as soon as it drains, a film immediately forms which is very stable, and itself gradually builds up.

Therefore, when using a conventional mixer turbine Form material approaches on the stators, which lead to gluing and then to Blocking the machine lead. An increase in the rotor speed brought no significant improvement. This sticking is due to bad drainage attributed to the spinning solution, which is primarily due to a strong film formation the stators. The dwell time is increased by reducing the path significantly shortened between the mixing stages and the outlet. Furthermore, through Omission of the stators and the lower shaft bearings reduce the flow resistance Outflow de: Product reduced from the mixer. Through these measures It is possible, for example, to still have a relatively good flowing solution with a high solids content to produce a so-called dry spinning solution at room temperature without any problems.

According to FIG. 1, the overall structure of such a device comprises two Container 2 for receiving DM1, which containers alternate via a pipe 3 are connected to a vertical mixing and dissolving unit 13, which is a cylindrical Housing 5 has. The housing Algc corresponds to about twice the diameter of the Housing. A metering pump 6 and a flow meter 7 are installed in the line 3. Said line 3 is connected to a ring line 8 with injection nozzles 9 is provided, through which DMF is injected into the mixing and dissolving unit 13.

A weighing bunker 10 in the floor of the latter serves to accommodate PAN Discharge screw 11 is present, the outlet of which is slightly above the ring line 8 opens into the housing 5. Bunker 10 with discharge screw 11 are on a weighbridge 12 arranged. The discharge screw 11 is driven by the control motor M 1. Central in the housing 5 is a multi-stage mixer 13 with a shaft 14 vertical built-in, equipped with two rotors 15. A top is used to drive the shaft 14 arranged motor M 2.

The more detailed training of the mixer 13 will be explained later on the basis of Figures 2-5 described in more detail.

The continuation of the housing 5 forms a vertical degassing shaft 16, in which a central downpipe 17 is provided, which with its upper end is located directly below the mixer 13 and coaxial to this runs. In the downpipe 17, a conical insert 18 is arranged as an edge distributor. A connection 19 of the degassing shaft 16 leads to a condenser 20 with a cooling coil 21, which is connected to a vacuum pump 22. The exhaust air leaves through a line 23 the vacuum pump 22.

A transition pipe forms the lower end of the degassing shaft 16 24, which is connected to the input side of the housing 25 of a screw pump 26, which is driven by a control motor M 3. The finished spinning solution 27 leaves through the outlet 25 'the screw pump.

The more detailed design of the mixer 13 can be seen in FIGS. 2-5. In the housing 5 there are bearings 28 at the top, in which the shaft 14 is cantilevered is. The upper end of the shaft 14 protruding from the housing 5 carries a belt pulley 29, which is connected via a drive belt 30 to the motor M 2 in FIG Connection. The lower end 31 of the shaft is tapered and carries two rotors 15 arranged closely one above the other. In the area of the rotors 15, the Housing wall 39 is smooth and above the upper rotor 15 is an annular constriction 32 vorgeccllcn, under which three injection nozzles 9 for the DMF are arranged are. The entire cylindrical housing 5 is tilted and hinged, it hangs on one triangular support plate 33 and is held together by means of clamping screws. The support plate 33 rests on support buffers 33 'and the housing 5 is supported by two Pillars 34 and supported by a pivot shaft 35. On the connector 36 of the housing 5 the discharge screw 11 for the supply of PAN powder is connected.

The shape of the rotor disks 15 can be seen from FIGS. 4 and 5.

These are provided with radially distributed wings 38. But it can other suitable rotor shapes can also be used, with a tangential velocity from 3-31 m / sec. is adjustable. The machine is expediently in operation started with little PAN, whereupon the PAN concentration is increased. Through the described simple arrangement of the rotors and the smooth housing could make a significant difference preferably 2-5 seconds shortened dwell time of the product between the rotors or between the lowest rotor and the outlet, so that sticking the parts of the mixing unit that come into contact with the product are prevented. The high shaft speed of preferably 2000 - 7000 rpm. and the constructive The design of the mixing unit enables smooth, continuous operation Production of high quality solutions with minimal energy consumption, the is only about 0.001 kWh / kg. The axial length of the mixing and dissolving zone corresponds to approximately the diameter of the housing 5 of the device. For the solids feed and the dry solids disintegration is required an equal length, from which a total constraint of the process part in the housing results, which the twofold Diameter corresponds. The shaft can be cantilevered due to the upper bearing described are carried out, which means that there is no need for storage at the end of the shaft. From it this results in the free, unhindered drainage of the solution from the mixing unit. The product becomes immediate after leaving the mixer using vacuum in the downpipe without supply of heat degassed, which is an economical solution. By installing the downpipe 17 the surface of the PAN solution, which is still flowing well, is enlarged. The degassing is further improved by the conical insert 18, which only leaves a narrow annular gap open as a passage and thus an effective closure forms between the mixer and the vacuum.

The described preparation of spinning solutions with a high concentration of solids at room temperature has the further great advantage that during the subsequent venting no solvent vapors in and of themselves in continuous production get carried away. To include those that occur briefly when starting up the facility The built-in vacuum line is used to securely remove solvent deposits Capacitor 20 with sensor coil 21.

Application example: In a mixer as described above, with a housing diameter of 100 mn, fed by a metering piston pump for DMF and a weighfeeder for PAN were at one speed of the shaft of the mixing unit from 7,000 rpm. in continuous operation at a room temperature of approx. 240 C. continually 200 kg / h spinning solution produced and then immediately deaerated under vacuum. There were three injection nozzles and two rotor disks on the lower part of the Arranged shaft. The downpipe had a length of 750 mn with a diameter of 140 mm, the edge distributor left a 20 mm wide annular gap free. It showed that the degree of degassing is well controlled by using the edge distributor can be. No sticking occurred in the apparatus, and the product was free of nodules and gas bubbles and had an initial viscosity at 29% PAN content in the solution from 600,000 to 610,000 m Pas, determined with a rotary viscometer. Through the The very short residence time resulted in the rate of dissolution being considerably increased at room temperature Taken into account and allows an unimpeded flow of the spinning solution, The The described method and the device are in principle also suitable for production of dispersions or emulsions and spreadable pastes with or without ventilation.

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Claims (10)

PATENT CLAIMS Process for the continuous production of polymer solutions and / or polymer dispersions and emulsions or spreadable pastes with high Concentration of solids in solvents by means of a multi-stage mixing unit in which first the dry polymer and then the solvent successively are fed, characterized in that the components without prior Cooling combined at room temperature and sheared turbulently with the addition of energy and dispersed or dissolved, followed by deaeration. 2) Method according to claim 1, characterized in that the components about 0.001 ktSh / kg of energy is supplied, whereupon it disperses in 2-5 seconds or be resolved. 3) Method according to claim 1, characterized in that for shortening the residence time of the components in the mixing unit the flow path between the individual components Stages of the mixing unit and the outlet are reduced and the flow resistance is reduced when the product flows out of the mixing unit. 4) Method according to claim 1, characterized in that the outflowing The product is vented in a vacuum immediately after exiting the mixing unit. 5) device for performing the method according to claim 1, consisting from a multi-stage mixing and Iijseaggregat in a vertical arrangement, preferably with a directly following ventilation device, characterized in that the preferably at the lower end (31) not mounted shaft (14) of the mixing and ibse unit (13) is provided with at least two rotors (15) arranged closely one above the other, which are surrounded by a smooth housing wall (39) without stators. 6) Device according to claim 5, characterized in that the length of the housing (5) of the mixing and dissolving unit, preferably twice the housing diameter is, with a part of the housing is designed as a Mts; ch and Wsezone, their Length roughly corresponds to the housing diameter. 7) device according to claims 5 and 6, characterized in that that A degassing shaft (16) is provided below the mixing unit (13), in which In the middle there is a central downpipe (17). 8) Device according to claims 5-7, d a d u r c h g e k e n n z E i c h e t that a vacuum pump (22) is connected to the degassing shaft (16) is. 9) Device according to claims 5-8, characterized in that an insert (18) is arranged in the downpipe (17) as a film-forming edge distributor. 10) Device according to claims 5-9, characterized in that the vacuum pump (22) is preceded by a condenser (20).