Method for the preparation of NFC films on supports

Abstract

The present invention concerns a method of preparing a film of nanofibrillated cellulose (NFC) on at least one surface of a support material, wherein the film is applied and spread directly onto a surface of the plastic support material in the form of a suspension of nanofibrillated cellulose, whereby the nanofibrillated cellulose forms a film. Further, the invention concerns a structure containing or consisting of a film of nanofibrillated cellulose prepared using said method.

1 . A method of preparing a detachable film of nanofibrillated cellulose (NFC) on at least one surface of a support material, or detached from the support, comprising applying and spreading a suspension of nanofibrillated cellulose directly onto a surface of a continuous plastic support material and a drying via controlled evaporation at a temperature maintained below 60° C., whereby the nanofibrillated cellulose forms a film on said support material in a continuous process. 
     
     
         2 . The method according to  claim 1 , wherein such a nanofibrillated cellulose is used, which can be dispersed into water or another compatible solvent, wherein it forms a gel. 
     
     
         3 . The method according to  claim 1 , wherein fine nanofibrillated cellulose is used. 
     
     
         4 . The method according to  claim 1 , wherein the suspension of nanofibrillated cellulose is formed using a solvent containing water. 
     
     
         5 . The method according to  claim 1 , wherein a suspension containing less than 2 wt-% nanofibrillated cellulose is used. 
     
     
         6 . The method according to  claim 1 , wherein the nanofibrillated cellulose is applied on a support made of a plastic material. 
     
     
         7 . The method according to  claim 1 , wherein the nanofibrillated cellulose or the support material, or both, is chemically modified, prior to formation of the film, by the addition of charged, hydrophobic or polar functional groups, preferably selected from functional groups containing one or more O, S or N atoms or one or more double bonds. 
     
     
         8 . The method according to  claim 1 , wherein the nanofibrillated cellulose is applied onto the support by a rod, blade or roll coating method. 
     
     
         9 . The method according to  claim 1 , wherein the nanofibrillated cellulose is applied onto the support to a thickness of 50 to 150 μm. 
     
     
         10 . The method according  claim 1 , wherein the film suspension is dried, after applying onto the support, via controlled evaporation at a temperature in the range of 25 to 60° C., whereby the film material solidifies in a controlled manner, forming an even film. 
     
     
         11 . The method according to  claim 1 , wherein the is detached from the support. 
     
     
         12 . The method according to  claim 1 , wherein the dried film is pressed, preferably by hot pressing, to obtain a thinner film structure, either after being detached from the support or while attached to the support. 
     
     
         13 .- 17 . (canceled) 
     
     
         18 . The method according to  claim 1 , wherein the NFC is an unmodified nanofibrillated cellulose. 
     
     
         19 . The method according to  claim 1 , wherein the NFC is a chemically modified nanofibrillated cellulose. 
     
     
         20 . The method according to  claim 1 , wherein the NFC is silylated nanofibrillated cellulose. 
     
     
         21 . The method according to  claim 3 , wherein the fine nanofibrillated cellulose has a fiber width from  5  nm to submicron values and a fiber length up to 30 μm. 
     
     
         22 . The method according to  claim 4 , wherein the solvent consists of water. 
     
     
         23 . The method according to  claim 1 , wherein a suspension containing less than 0.25 to 2 wt-% nanofibrillated cellulose is used. 
     
     
         24 . The method according to  claim 1 , wherein the nanofibrillated cellulose is applied on a support made of a plastic material selected from polyethylene, polystyrene and a cellulose ester.