Wet cellulose fiber sheet and method for producing cellulose fiber molded body
A wet sheet which is hard to be fractured during production into a molded body, stable in shape, and easy to handle in processing, and a method for producing a molded body from the wet sheet. The wet sheet includes fine cellulose fibers having an average fiber diameter of 10000 nm or smaller, and pulp, wherein the wet sheet has a water content of 60 mass % or higher, and a thickness of 0.5 mm or more and 10 mm or less. A method for producing a molded body includes applying heat and pressure to a wet sheet to obtain a molded body, wherein the wet sheet includes fine cellulose fibers having an average fiber diameter of 10000 nm or smaller, and pulp, and has a water content of 60 mass % or higher, and a thickness of 0.5 mm or more and 10 mm or less.
1 . A method for producing a molded body, comprising:
preparing a slurry by mixing cellulosic pulp having an average fiber diameter of over 10 μm and 100 μm or smaller, and fine cellulose fibers having an average fiber diameter of 10 μm or smaller,
shaping the slurry into a wet sheet by holding the slurry between two facing net sheets and applying pressure to the slurry to dewater, and
applying heat and pressure to the wet sheet to obtain a molded body,
wherein the wet sheet has a water content of 60 mass % or higher and a thickness of 0.5 mm or more and 10 mm or less,
wherein a content of the fine cellulose fibers in the wet sheet (solid concentration) is 10 to 38 mass %, and
wherein a rate of thickness change of the wet sheet determined by formula 1 is 0.4 or lower:
Rate of thickness change=((Thickness of wet sheet after application of pressure at 100 kPa in thickness direction for 1 second)−(Thickness of wet sheet after application of pressure at 100 kPa in thickness direction for 5 seconds))/(Thickness of wet sheet after application of pressure at 100 kPa in thickness direction for 1 second) Formula 1.
2 . The method for producing a molded body according to claim 1 ,
wherein the shaping in the wet sheet is carried out substantially without heating.
3 . The method for producing a molded body according to claim 1 ,
wherein the fine cellulose fibers are at least either of cellulose nanofibers and microfibrillated cellulose having a larger average fiber diameter than that of the cellulose nanofibers.