Method for treating a mixture

Abstract

A method for treating a mixture in a single-shaft or multi-shaft mixer (M), especially a kneader-mixer, especially for preparing a spinning solution. A solvent or solvent mixture is added to the product over the length of a product chamber in order to reduce a viscosity of the solvent or of the mixture and to increase an evaporative capacity. The viscosity of the solution or of the mixture is determined and/or modified in predetermined locations in the product chamber.

Claims

1. A method for treating a mixture in a single-shaft or multishaft mixer (M) for preparing a spinning solution, comprising metering a solvent or solvent mixture into a product over a length of a product chamber in order to reduce viscosity of the solvent or solvent mixture and to increase evaporative output, and determining the viscosity of the solution or mixture at predetermined locations along a shaft in the product chamber.

2. The method as claimed in claim 1, including modifying the viscosity of the solution or mixture at the predetermined locations in the product chamber.

3. The method as claimed in claim 1, wherein the determining step is carried out by measurement of a mechanical load on static and/or dynamic internals (2) in the product chamber.

4. The method as claimed in claim 3, including computing the viscosity of the solution or mixture by measurement of the product temperature and calculation back from a boiling point and a known viscosity for a different composition of the solution.

5. The method as claimed in claim 4, including controlling the temperature of the mixture or solution by controlling the quantity of solvent or solvent mixture which is metered.

6. The method as claimed in claim 1, wherein the viscosity is determined on the basis of a torque of the shaft (4) and/or of the static and/or dynamic internals (2).

7. The method as claimed in claim 1, wherein the viscosity is determined using deformation of the static and/or dynamic internals (2).

8. The method as claimed in claim 1, wherein the solvent mixture comprises at least one volatile and at least one nonvolatile solvent and a solid or liquid nonvolatile substrate, where the substrate dissolves in the solvent or solvent mixture as a result of at least partial evaporation of the at least one volatile solvent.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further advantages, features, and details of the invention will become apparent from the description below of preferred working examples, and also from the drawing, in which

(2) FIG. 1 shows a diagrammatically represented plan view of an apparatus of the invention for treating viscous-paste like compositions;

(3) FIG. 2 shows a perspective view of a kneading element of the invention with monitoring elements;

(4) FIG. 3 shows a block-diagram representation of a working example of a monitoring means.

DETAILED DESCRIPTION

(5) FIG. 1 shows a housing 1 of a kneader-mixer M, as shown more clearly in, for example, DE 43 03 852 A1 and in other specifications shown in the prior art. Located within this housing 1 are kneading elements 2, which have a C-shaped design and are directed radially inward. The kneading elements 2 cooperate with further kneading elements 3 in disk form, which are arranged on a shaft 4. Assigned to this shaft 4 is a drive 5.

(6) For a series of kneading elements 2 there is indicated, furthermore, one valve block 6 in each case, being connected via a line 7 to a monitoring means 8. As indicated by the arrow 9, this monitoring means 8 may be connected in turn to a central control means.

(7) The kneading element 2 according to FIG. 2 consists essentially of a kneading body 10 which is seated on a housing flange 11. The element is connected, furthermore, to a torque sensor 12, which is assigned a tensioning means 13.

(8) Located in the kneading body 10, indicated by dashed lines, is at least one channel 14, which is in operative connection with the valve block 6 downstream of the tensioning means 13. This channel 14 can be subjected to a pressure means through a pressure medium from a gas cylinder 15. The pressure in the channel 14 is monitored via a pressure meter 16, more particularly a manometer.

(9) The mode of function of the present invention is as follows:

(10) Located in the housing 1, preferably, are a plurality of kneading elements 2, as shown in FIG. 2. The kneading body 10 itself protrudes into the interior of the housing and is connected through the housing, by means of the housing flange 11, with the torque sensor 12 located outside the housing, the tensioning means 13, the valve block 6, and the gas cylinder or manometer. A pressure is maintained in the channel 14 by way of the gas cylinder 15. In the event of damage to the kneading body 10, the pressurized gas escapes through a possible crack into the interior of the housing, thereby reducing the pressure in the channel 14. This is determined by the manometer 16, which delivers a signal to the monitoring means 8. Here, of course, it is also possible to specify a particular limit, with the pressure switch responding only under said limit. Moreover, the filling volume selected, which is monitored, is to be extremely small, so as to ensure rapid sensitive monitoring.

(11) It is then possible, above the corresponding line 7, to identify the kneading element 2 which is possibly showing damage. The damaged kneading element can then be removed and neutralized, while the plant continues to be in operation. The kneader-mixer is operated further in an entirely normal way, specifically without shutdown.

(12) If there is also a temperature sensor connected to the kneading body, the temperature, particularly in the composition under treatment, can be ascertained. This temperature then serves for selective control of the treatment temperature regime.

(13) It is also possible for there to be unwanted deformation of the kneading element without cracking. Here, in accordance with the invention, provision is made for the deformation to be determined via corresponding strain gauges and/or else via the torque sensor 12, and for any damaged kneading element to be replaced.

(14) An essential advantage of the monitoring of the kneading elements for deformation by means of a torque sensor, for example, is that now it is also possible to monitor the viscosity of the product for treatment in the kneading apparatus, at a particular point in the product chamber, along the shaft. Before now, the overall viscosity in the kneading apparatus has been monitored by monitoring of the torque of the drive for the shaft. If, however, each individual kneading element or predetermined kneading elements along the length of the kneading apparatus are monitored, the viscosity can be determined in individual zones of the kneading apparatus between input and discharge. This is a significant advantage of the present invention.

(15) Another concept involves using the kneading elements designed in this way to feed, into the housing 1, agents which are supposed to be used for treating the viscous-paste-like composition.

(16) One working example of a monitoring means 8 of the invention is shown in more detail in FIG. 3. Here, the kneading elements 2 are connected to a common valve block 17. For this purpose there is a line 18 for a pressure means in each case. The valve block 17 is followed by a pressure means line 19, into which a flow sensor 20 and a pressure reducer 21 are connected, toward the pressure source 15. The flow sensor 20 is connected to a central control device 22, as is a pressure sensor 23, which determines whether there is a pressure means present between the pressure reducer 21 and the flow sensor 20 in the pressure means line 19.

(17) Not shown in any detail in the drawing is the fact that the control device, of course, is also connected to the pressure source connection 15 and to the valve block 17 and also to any control valves and/or sensors possibly present, in the case of the kneading elements 2.

(18) The mode of function of this monitoring means is as follows:

(19) The pressure source 15 is subject to a nitrogen gas at about 4 bar, at the pressure reducer 21, via the pressure means connection. As a result of the pressure reducer 21, the pressure is lowered tofor example1 bar. The nitrogen flows through the flow sensor 20 and the pressure means line 19 into the valve block 17, where it is distributed to the individual kneading elements 2.

(20) If there is a low flow, which shows no explosive increase, this may be attributable to normal leakage. In order to separate the two incidents and to avoid false alarm, a predetermined, preferably constant pressure is always maintained in the pressure means line 19, but the flow is monitored, especially in relation to the flow time. In the case of a normal leakage, there is a very low flow within a certain unit time. An alarm is only triggered when the flow experiences, for example, a sudden or sharp increase. This is a sign of a rupture or crack in the kneading element, and in that case an alarm is triggered.

(21) The corresponding control signal is in that case utilized, for example, to shut off the drive to the shaft of a kneader-mixer, or to shut down, engage or otherwise influence input and discharge members for reactant or product in or from a compartment of the kneading apparatus, or else in order to shut down or influence the heating of the kneading-apparatus compartment and/or of the kneading elements.