Method for manufacturing films comprising highly refined cellulose fibers

Patent metadata

Field	Value
Publication number	US-12467202-B2
Application number	US-202117998235-A
Country	US
Kind code	B2
Filing date	May 10, 2021
Priority date	May 11, 2020
Publication date	Nov 11, 2025
Grant date	Nov 11, 2025

Abstract

The present invention relates to a method for manufacturing a web or film comprising highly refined cellulose fibers in a paper machine, the method comprising the steps of: a) forming a wet web by applying an aqueous pulp suspension comprising highly refined cellulose fibers on a wire; and b) dewatering the wet web on the wire to obtain a dewatered web comprising highly refined cellulose fibers, wherein the dewatering comprises membrane assisted dewatering using a gas permeable membrane temporarily applied to the wet web, wherein the gas permeable membrane has a lower air permeability than the wire.

First claim

The invention claimed is:

1 . A method for manufacturing a film comprising highly refined cellulose fibers in a paper machine, the method comprising the steps of the following sequence:
a) forming a wet web by applying an aqueous pulp suspension comprising highly refined cellulose fibers having a Schopper-Riegler (SR) value of 65 or higher, on a wire; b) dewatering the wet web on the wire to obtain a dewatered web comprising highly refined cellulose fibers, wherein the dewatering comprises membrane assisted dewatering using a gas permeable membrane temporarily applied to the wet web, wherein the gas permeable membrane has an air permeability lower than an air permeability of the wire, wherein the air permeability of the gas permeable membrane is less than 75% of the air permeability of the wire, and wherein the wet web is pressed between the gas permeable membrane and the wire; and, c) drying the dewatered web to obtain a film comprising the highly refined cellulose fibers, the film having a grammage in a range of 20 to 100 g/m 2 and a density above 600 kg/m 3 , wherein the film is transparent or translucent to visible light, and wherein the film has a KIT value of at least 10, as measured according to standard ISO 16532-2.

2 . The method according to claim 1 , wherein the gas permeable membrane is selected from a group consisting of: a woven polymeric fabric, a non-woven polymeric fabric, and a porous polymer film.

3 . The method according to claim 1 , wherein a thickness of the gas permeable membrane is in a range of 0.01-4 mm.

4 . The method according to claim 1 , wherein the gas permeable membrane is permeable to air and steam, but substantially non-permeable to the liquid water and highly refined cellulose fibers of the wet web.

5 . The method according to claim 1 , wherein the gas permeable membrane is permeable to air, steam, and liquid water, but substantially non-permeable to the highly refined cellulose fibers of the wet web.

6 . The method according to claim 1 , wherein the air permeability of the gas permeable membrane is less than 50% of the air permeability of the wire.

7 . The method according to claim 1 , wherein the air permeability of the gas permeable membrane is below 3500 m 3 /m 2 /hour at 100 Pa.

8 . The method according to claim 1 , wherein the air permeability of the wire is above 5000 m 3 /m 2 /hour at 100 Pa.

9 . The method according to claim 1 , wherein the wet web is pressed between the wire and the gas permeable membrane by applying a negative gas pressure to the wire.

10 . The method according to claim 1 , wherein the wet web is pressed between the wire and the gas permeable membrane by applying a positive gas pressure to the gas permeable membrane.

11 . The method according to claim 1 , wherein the method is continuous.

12 . The method according to any claim 1 , wherein the wire and the gas permeable membrane are provided in the form of endless belts.

13 . The method according to claim 1 , wherein the wet web is pressed between the gas permeable membrane and the wire in a contact zone.

14 . The method according to claim 13 , further comprising:
moving both the wire and the gas permeable membrane, wherein the wire and the gas permeable membrane move in the same direction and at the same, or substantially the same, speed in the contact zone.

15 . The method according to claim 13 , wherein a length of the contact zone in the machine direction is in a range of 0.3-10 m.

16 . The method according to claim 13 , wherein the speed of the wire and the gas permeable membrane is above 250 m/min.

17 . The method according to claim 1 , wherein the dewatering step b) comprises partially dewatering the wet web without the use of a gas permeable membrane before the membrane assisted dewatering.

18 . The method according to claim 1 , wherein the dewatering step b) comprises further dewatering the wet web after the membrane assisted dewatering.

19 . The method according to claim 1 , wherein the pulp suspension comprises at least 50 wt % highly refined cellulose fibers, based on a total dry weight of the pulp suspension.

20 . The method according to claim 1 , wherein the pulp suspension is formed from a cellulose furnish having a Schopper-Riegler (SR) value in a range of 70-99.

21 . The method according to claim 1 , wherein the highly refined cellulose fibers comprises microfibrillated cellulose (MFC).

22 . The method according to claim 1 , wherein a basis weight of the wet web based on a total dry weight of the web is in a range of 10-100 g/m 2 .

23 . The method according to claim 1 , wherein a dry solids content of the wet web before the membrane assisted dewatering is above 0.5 wt %.

24 . The method according to claim 1 , wherein a dry solids content of the wet web after the membrane assisted dewatering is above 12 wt %.

25 . The method according to claim 1 , wherein the density of the film is above 900 kg/m 3 .

26 . The method according to claim 25 , wherein the film comprises less than 10 pinholes/m 2 , as measured according to standard EN13676:2001.

27 . The method according to claim 25 , wherein the film has a Gurley Hill value of at least 30,000 s/100 ml, as measured according to standard ISO 5636/6.

28 . The method according to claim 25 , wherein the film has an oxygen transfer rate (OTR) of less than 150 cc/m 2 /24 h/atm, as measured according to the standard ASTM D-3985 at 50% relative humidity and 23° C.

Assignees

• Stora Enso Oyj

Inventors

• Heiskanen Isto
• Backfolk Kaj

Classifications

• D21H11/18 Primary

  Highly hydrated, swollen or fibrillatable fibres · CPC title

• D21F11/02

  of the Fourdrinier type · CPC title

• B32B2307/7244

  Oxygen barrier · CPC title

• D21F3/0272

  in combination with suction or blowing devices · CPC title

• D21F1/00

  Wet end of machines for making continuous webs of paper · CPC title