Method and device for producing nano films

Abstract

A method for producing films or more precisely stated, mats and plates out of nanofibers, in particular films or mats and plates out of cellulose nanofibers, wherein nanofiber material is dispersed in solvent; the solids content is between 1 and 4% by volume and the resulting slurry is applied by means of an application device to a conveyor belt that is moving in the conveying direction and then the poured-on slurry is pre-dried and the pre-dried slurry, after the pre-drying, is subjected to the main drying and after the achievement of a predetermined moisture content, is removed from the conveyor belt.

1 . A method for producing films or mats and plates out of cellulose nanofibers, comprising:
 dispersing nanofiber material in solvent, resulting in a slurry having a solids content between 1 and 4% by volume;   pouring the resulting slurry onto a conveyor belt that is moving in a conveying direction;   pre-drying the slurry that has been poured on the conveyor belt using infrared heating elements that are arranged longitudinally and/or transversely or diagonally to the conveying direction of the conveyor belt;   after the pre-drying, subjecting the pre-dried slurry to a main drying performed with middle-wave and/or short-wave infrared heating elements with a high power density, wherein the infrared heating elements are controlled individually or in groups, and selectively removing solvent vapor and removing moisture in the main drying by supplying air and/or other gases that are diffusely directed into a region of the main drying; and   after achieving a predetermined moisture content, removing the slurry from the conveyor belt.   
     
     
         2 . The method according to  claim 1 , wherein the nanofiber material is dispersed in a solvent selected from at least one of the group consisting of: water an organic solvent, and alcohol. 
     
     
         3 . The method according to  claim 1 , wherein the slurry is poured onto the conveyor belt and applied using a doctor blade, a profiled doctor blade, a bar with an indentation ground into it, a blade-shaped nozzle, a slot nozzle, a slide-die nozzle, or a volume-controlled application nozzle. 
     
     
         4 . The method according to  claim 1 , wherein the slurry is poured onto a smooth conveyor belt. 
     
     
         5 . The method according to  claim 1 , comprising heating the conveyor belt to 40 to 95° C. 
     
     
         6 . The method according to  claim 1 , comprising carrying out the pre-drying in a housing with a controlled gas supply or air supply. 
     
     
         7 . The method according to  claim 1 , wherein the infrared heating elements are individually controllable. 
     
     
         8 . The method according to  claim 1 , comprising adjusting a gas flow or air flow during the main drying with regard to a relative humidity and/or flow speed of the slurry. 
     
     
         9 . The method according to  claim 1 , wherein after the main drying, the dried slurry material is remoistened to a desired moisture content. 
     
     
         10 . A device for performing a method for producing films from cellulose nanofibers, comprising:
 a conveyor belt;   a plurality of rollers for conveying the conveyor belt along a longitudinal direction in a loop in the form of an upper and lower run;   an application device for applying a film slurry onto a region of the conveyor belt;   a pre-drying unit, following the application device in a conveying direction of the conveyor belt, wherein the pre-drying unit comprises infrared heating elements that act on the poured-on slurry; and   following the pre-drying unit in the conveying direction of the conveyor belt, a main drying unit with infrared heating elements; wherein in the region of the conveyor belt in which the conveyor belt supports the slurry, the conveyor belt is held by rollers, at least some of the rollers are heatable.   
     
     
         11 . The device according to  claim 10 , wherein the main drying unit is followed in the conveying direction by a remoistening unit. 
     
     
         12 . The device according to  claim 10 , further comprising a dispersing device, which comprises a receptacle and an agitating device; wherein the agitating device can agitate at more than 1,000 revolutions per minute.