- NFC films prepared on support material
- Water removed by evaporation
- Shrinkage controlled via adhesion on support
- Porosity controlled by pressing
- Solution is superior since all unit operations can be up-scaled - a real route to roll-to-roll applications
- NFC film - manufactured on plastics with controlled porosity - is a strong and transparent starting material for nano - composites
- Medical bandages and wound treatments
- Substrates for functionalities e.g. printed intelligence
- Laminated nano-composite materials
- Food packing materials
Our invention describes a method to prepare smooth and even film of nanofibrillated cellulose (NFC) in large scale. Films are prepared on the plastic film supports and by controlling the adhesion spreading of the NFC on the support material. Either removable NFC films or films of double layer structure can be prepared. NFC suspension can be applied on the plastics by rod, blade or roll coating methods. A combination of suitable substrate, controlled drying and hot pressing enables controlling the porosity of the NFC films and thus transparent and strong films with the thickness of 50-150 μm with good oxygen barrier properties can be manufactured.
NFC films formed on the support materials are dried via controlled evaporation in mild temperatures. This allows the cellulose hydroxyl groups to interact through the self association and this leads to even film formation. Thus, the slow dewatering procedure via filtration is avoided. In addition, the sufficient adhesion within the support material prevents the shrinkage of the NFC film upon drying.
The NFC film is further hot pressed at mild temperature in order to achieve a dense structure with controlled porosity. This procedure to prepare even, dense and uniform films can be regarded as a route to large scale roll-to-roll production of NCF films and membranes since all the unit operations can be up-scaled and substituted by on-line solutions. The films can be used as barrier films for oxygen and grease, and they can act as a strong starting material for nanocomposites and thermosets.
FI 123630 (granted)
JP 6169089 (granted)
EP 12844188.8 (pending)
US 14/353775 (pending)
CA 2853200 (pending)
KR 10-2014-0084256 (pending)
Priority: October 23rd, 2012
Arto Salminen, Ulla Hippi, Tekla Tammelin
+358 50 3397534