Method of producing a filament comprising a silica gel-fiber

A method of producing a filament comprising a silica gel fiber, comprising:

• pressing a spinning composition containing the silica gel fiber through a nozzle plate comprising a number of nozzles in a range from 1 to 1000, each of the number of nozzles having a nozzle opening,
• wherein the nozzle opening has a cross-sectional area of size A1,
• wherein a tear-off edge with an angle β in a range from 5° to 90° extends around the nozzle opening,
• wherein an area, which immediately adjoins the nozzle opening outside the nozzle and extends around the nozzle opening, has an area of the size A2,
• wherein a ratio A2/A1 is not more than 1,
• wherein the area of size A2 extends at an angle ω to the cross-sectional area of size A1,
• wherein the angle ω is greater than 0° and less than 80°,
• wherein each nozzle takes a form of a nozzle insert, which is inserted into a corresponding opening in the nozzle plate,
• wherein each of the number of nozzles comprises a channel, the channel comprising a first cylindrical section extending vertically in the direction of flow, a second conical section to form a conical region, and a third cylindrical section extending vertically from the second conical section and forming a nozzle opening at an end distal from the second conical section;
• wherein the conical region forms an angle γ with the third cylindrical section in the range of 10° to 80°
• wherein the third cylindrical section has a length L and a diameter D;
• wherein the following applies to a ratio L/D:
• 0.5≤L/D≤10;
• and,
• wherein the entire conical region is disposed outside the plate.