Method for spinning a spinning solution and spinning head

Abstract

The present invention relates to a spinning head ( 8 ) for spinning a spinning dope, which is provided with a tubular, thin-walled spinning capillary ( 7 ) having a discharge opening ( 94 ). The spinning dope used is e.g. a mixture of cellulose, tertiary amine oxide and water. In order to reduce the fibrillation tendency of the fibres spun by means of the spinning head and in order to increase the non-looping property, the present invention is so conceived that the spinning capillary ( 7 ) is heated directly close to the discharge cross-section ( 94 ). By means of this simple measure, it is possible to reduce the fibrillation tendency and to increase the non-looping property.

1 . A method of spinning a spinning dope comprising a mixture of cellulose, water and tertiary amine oxide, said method comprising the steps of supplying the spinning dope to at least one spinning head and conducting it in said spinning head through at least one spinning capillary provided at its downstream end with a spinning-dope discharge opening through which the spinning dope is discharged from the spinning head, characterized in that, close to said spinning-dope discharge opening ( 94 ), the wall of the spinning capillary ( 7 ) is heated, at least sectionwise, to a temperature which is higher than the core temperature of the spinning dope in the spinning capillary.  
     
     
         2 . A method according to  claim 1 , characterized in that the wall of the spinning capillary is heated directly by a heating device ( 70 ,  72 ).  
     
     
         3 . A method according to  claim 1  or  2 , characterized in that the wall temperature of the spinning capillary ( 7 ) is controlled to an adjustable value by means of a temperature controller.  
     
     
         4 . A method according to one of the above-mentioned claims, characterized in that the wall temperature of the spinning capillary ( 7 ) is controlled in dependence upon the mass flow rate of the spinning dope through the spinning capillary ( 7 ).  
     
     
         5 . A method according to one of the above-mentioned claims, characterized in that the wall temperature of the spinning capillary ( 7 ) is controlled in dependence upon the spinning pressure in the spinning dope, preferably in dependence upon the spinning pressure of the spinning dope in the spinning capillary ( 7 ).  
     
     
         6 . A method according to one of the above-mentioned claims, characterized in that, a predetermined temperature profile across the flow cross-section of the spinning capillary ( 7 ) is adjusted by heating the spinning-capillary wall when the spinning capillary is in operation.  
     
     
         7 . A method according to one of the above-mentioned claims, characterized in that, a predetermined temperature profile of the spinning-capillary wall is adjusted in the direction rection of flow of the spinning dope by heating the spinning-capillary wall when the spinning capilary is in operations.  
     
     
         8 . A method according to one of the above-mentioned claims, characterized in that the spinning-capillary wall is heated by a heating fluid which flows around the wall of the spinning capillary on the outside thereof.  
     
     
         9 . A spinning head for spinning a spinning dope which consists of a mixture of cellulose, water and tertiary amine oxide and which flows through the spinning head, comprising at least one spinning capillary having a spinning-dope discharge opening at its downstream end, the spinning dope being discharged from the spinning head through said spinning-dope discharge opening, and further comprising a temperature-controlled heating device which acts on said spinning dope, characterized in that, in an area close to the spinning-dope discharge opening ( 94 ), the wall temperature of the spinning capillary ( 7 ) produced by the heating device ( 70 ,  72 ) is higher than the core temperature of the spinning dope, when the spinning head ( 8 ) is in operation.  
     
     
         10 . A spinning head according to  claim 9 , characterized in that the area of the spinning-capillary wall which is heated by said heating device ( 70 ,  72 ) and the temperature of which is higher than the core temperature of the spinning dope extends essentially up to the spinning-dope discharge opening ( 94 ).  
     
     
         11 . A spinning head according to  claim 9  or  10 , characterized in that the area of the spinning-capillary wall which is heated by said heating device ( 70 ,  72 ) and the temperature of which is higher than the core temperature of the spinning dope extends essentially over the whole length of the spinning capillary ( 7 ).  
     
     
         12 . A spinning head according to one of the  claims 9  to  11 , characterized in that the spinning capillary ( 7 ) is implemented as a spinning-capillary tube in the form of a substantially thin-walled tube, and that the heating device ( 70 ,  72 ) acts directly on the wall area of said spinning-capillary tube close to the spinning-dope discharge opening ( 94 ).  
     
     
         13 . A spinning head according to one of the  claims 9  to  12 , characterized in that a control unit is provided, which acts on the heating device ( 70 ,  72 ) and by means of which the temperature of the directly heated wall area of the spinning-capillary tube ( 7 ) is adapted to be controlled, at least sectionwise.  
     
     
         14 . A spinning head according to one of the  claims 9  to  13 , characterized in that the heating device ( 70 ,  72 ) comprises a heating fluid which surrounds the spinning-capillary tube ( 7 ), at least sectionwise.  
     
     
         15 . A spinning head according to  claim 14 , characterized in that the heating fluid of the heating device ( 70 ,  72 ) surrounds the spinning-capillary tube ( 7 ), at least sectionwise.  
     
     
         16 . A spinning head according to one of the  claims 9  to  15 , characterized in that the spinning-dope discharge opening ( 94 ) of the spinning-capillary tube ( 7 ) is surrounded, at least sectionwise, by a gap opening ( 74 ), a transport fluid flowing out of said gap opening ( 74 ) essentially in the direction of the spinning dope discharged from the spinning-dope discharge opening ( 94 ) when the spinning head is in operation.  
     
     
         17 . A spinning head according to  claim 16 , characterized in that the velocity of the transport fluid flowing out of said gap opening ( 74 ) when the spinning head is in operation corresponds substantially at least to the velocity of the spinning dope discharged from the spinning-dope discharge opening ( 94 ).  
     
     
         18 . A spinning head according to one of the  claims 9  to  17 , characterized in that, close to the spinning-dope discharge opening, the spinning-capillary tube ( 7 ) is surrounded by a heating chamber ( 70 ,  72 ) containing a heating fluid.  
     
     
         19 . A spinning head according to one of the  claims 16  to  18 , characterized in that the heating chamber ( 72 ) communicates with the gap opening ( 74 ).  
     
     
         20 . A spinning head according to one of the  claims 16  to  19 , characterized in that the heating fluid serves as a transport fluid and is conducted from the heating chamber ( 72 ) through the gap opening ( 74 ).  
     
     
         21 . A spinning head according to one of the  claims 16  to  20 , characterized in that an annular space ( 102 ) extends between said heating chamber ( 70 ) and said gap opening  
     
     
         14 . A spinning head according to one of the  claims 9  to  13 , characterized in that the heating device ( 70 ,  72 ) comprises a heating fluid which surrounds the spinning-capillary tube ( 7 ), at least sectionwise.  
     
     
         15 . A spinning head according to  claim 14 , characterized in that the heating fluid of the heating device ( 70 ,  72 ) surrounds the spinning-capillary tube ( 7 ), at least sectionwise.  
     
     
         16 . A spinning head according to one of the  claims 9  to  15 , characterized in that the spinning-dope discharge opening ( 94 ) of the spinning-capillary tube ( 7 ) is surrounded, at least sectionwise, by a gap opening ( 74 ), a transport fluid flowing out of said gap opening ( 74 ) essentially in the direction of the spinning dope discharged from the spinning-dope discharge opening ( 94 ) when the spinning head is in operation.  
     
     
         17 . A spinning head according to  claim 16 , characterized in that the velocity of the transport fluid flowing out of said gap opening ( 74 ) when the spinning head is in operation corresponds substantially to at least the velocity of the spinning dope discharged from the spinning-dope discharge opening ( 94 ).  
     
     
         18 . A spinning head according to one of the  claims 9  to  17 , characterized in that, close to the spinning-dope discharge opening, the spinning-capillary tube ( 7 ) is surrounded by a heating chamber ( 70 ,  72 ) containing a heating fluid.  
     
     
         19 . A spinning head according to one of the  claims 16  to  18 , characterized in that the heating chamber ( 72 ) communicates with the gap opening ( 74 ).  
     
     
         20 . A spinning head according to one of the  claims 16  to  19 , characterized in that the heating fluid serves as a transport fluid and is conducted from the heating chamber ( 72 ) through the gap opening ( 74 ).  
     
     
         21 . A spinning head according to one of the  claims 16  to  20 , characterized in that an annular space ( 102 ) extends between said heating chamber ( 70 ) and said gap opening ( 74 ), said annular space ( 102 ) surrounding the capillary tube ( 7 ) from outside essentially along the whole length of said tube.  
     
     
         22 . A spinning head according to  claim 20 , characterized in that the annular space ( 102 ) has a substantially oval cross-section.  
     
     
         23 . A spinning head according to one of the  claims 9  to  21 , characterized in that the length of the spinning capillary ( 7 ) is 20 to 150 times as long as the diameter of said spinning capillary.  
     
     
         24 . A spinning head according to  claim 23 , characterized in that said length is the length through which the spinning dope flows and/or that said diameter is the internal diameter of the spinning capillary ( 7 ).  
     
     
         25 . A spinning head according to one of the  claims 9  to  24 , characterized in that the discharge cross-section ( 94 ) is circular.  
     
     
         26 . A spinning head according to  claim 25 , characterized in that the discharge cross-section ( 94 ) has a diameter of less than 500 μm, preferably less than 250 μm.  
     
     
         27 . A spinning head according to one of the  claims 9  to  26 , characterized in that the wall thickness of the spinning-capillary tube ( 7 ) is less than 200 μm, preferably less than 150 μm.  
     
     
         28 . A spinning head according to one of the  claims 9  to  27 , characterized in that the temperature of the heating fluid in the heating chamber ( 70 ,  72 ) is at least 100° C., preferably approximately 150° C.  
     
     
         29 . A spinning head according to one of the  claims 9  to  27 , characterized in that the temperature of the heating fluid in the heating chamber ( 70 ,  72 ) ranges from 50° C. to 150° C.  
     
     
         30 . A spinning head according to one of the  claims 9  to  27 , characterized in that the temperature of the heating fluid in the heating chamber ( 70 ,  72 ) ranges from 80° C. to 150° C.  
     
     
         31 . A spinning head according to one of the  claims 9  to  27 , characterized in that the temperature of the heating fluid in the heating chamber ( 70 ,  72 ) ranges from 100° C. to 150° C.  
     
     
         32 . A spinning head according to one of the  claims 9  to  27 , characterized in that the temperature of the heating fluid in the heating chamber ( 70 ,  72 ) ranges from 50° C. to 180° C.  
     
     
         33 . A spinning head according to one of the  claims 9  to  32 , characterized in that at least one temperature sensor is provided for detecting the temperature of the capillary wall and/or the temperature of the spinning dope in the area of said capillary wall, the capillary-wall temperature being adapted to be outputted to the control device in the form of an electric signal by means of said temperature sensor.  
     
     
         34 . A spinning head according to  claim 33 , characterized in that the temperature sensor is implemented as an electric resistance element.  
     
     
         35 . A spinning head according to one of the  claims 9  to  34 , characterized in that at least one temperature sensor is provided for detecting the temperature of the heating fluid, the temperature of the heating fluid being adapted to be outputted to the control device in the form of an electric signal by means of said temperature sensor.  
     
     
         36 . A spinning head according to one of the  claims 9  to  35 , characterized in that the gap ( 74 ) is defined by a housing ( 100 ;  104   a,    104   b ) which is movable transversely to the longitudinal axis of the spinning capillary, at least sectionwise, and that the flow cross-section of said gap ( 74 ) is variable.  
     
     
         37 . A spinning head according to one of the  claims 9  to  36 , characterized in that the spinning capillary is surrounded by at least one electric heating element.  
     
     
         38 . A spinning system with a pressure equalizing container containing a spinning dope composed of cellulose, water and a tertiary amine oxide and of one or a plurality of stabilizing agents, said spinning system comprising a spinning head or a plurality of spinning heads by means of which the spinning dope can be spun so as to obtain formed bodies, and a spinning-dope conduit by means of which the spinning dope is conducted from said pressure equalizing container to said spinning head or said spinning heads, characterized in that the, spinning head ( 8 ) is implemented according to one of the  claims 9  to  37  and/or that the spinning system ( 1 ) is implemented for carrying out the method according to one of the  claims 1  to  8 .  
     
     
         39 . A spinning system according to  claim 38 , characterized in that said spinning system includes an air gap ( 10 ) after said spinning head ( 8 ) or said spinning heads ( 8 ), the spinning dope flowing into and being drawn in said air gap ( 10 ) after having left the spinning-dope discharge opening ( 94 ).  
     
     
         40 . A spinning system according to  claim 38  or  39 , characterized in that said spinning system ( 1 ) comprises a precipitation bath ( 11 ) downstream of said air gap ( 10 ), the spinning dope discharged from the spinning head ( 8 ) being immersed into said precipitation bath after having passed through the air gap ( 10 ) and after having been drawn so as to obtain a formed body.  
     
     
         41 . A spinning system according to one of the  claims 38  to  40 , characterized in that a drawing-off device ( 12 ) is provided by means of which the spinning dope can be drawn off from the precipitation bath in the form of a precipitated thread or formed body.