Method for dewatering a web comprising microfibrillated celluose and a film produced from the dewatered web

Patent metadata

Field	Value
Publication number	US-12286752-B2
Application number	US-202118003187-A
Country	US
Kind code	B2
Filing date	Jun 24, 2021
Priority date	Jun 26, 2020
Publication date	Apr 29, 2025
Grant date	Apr 29, 2025

Abstract

The present invention relates to a method for dewatering a web comprising microfibrillated cellulose, wherein the method comprises the steps of: providing a suspension comprising between 50 wt-% to 100 wt-% of microfibrillated cellulose based on total dry weight, forming a fibrous web of said suspension on a support wherein said web has a dry content of 1-25% by weight, applying a dewatering felt into direct contact with the fibrous web, conducting said fibrous web, arranged between said dewatering felt and said support, through at least one shoe press equipment, drying the dewatered web to form a film which film has an Oxygen Transmission Rate (OTR) value (23° C., 50% RH) below 100 cc/m 2 /24 h according to ASTM D-3985.

First claim

The invention claimed is:

1. A method for dewatering a web comprising microfibrillated cellulose, wherein the method comprises the steps of:
providing a suspension comprising between 50 wt-% to 100 wt-% of microfibrillated cellulose based on a total dry weight,
forming a fibrous web of said suspension on a support wherein said fibrous web has a dry content of 1-25% by weight, wherein the fibrous web comprises more than one layer of microfibrillated cellulose,
applying a dewatering felt into direct contact with the fibrous web,
conducting said fibrous web, arranged between said dewatering felt and said support, through at least one shoe press equipment at a high speed of at least 150 m/min to dewater the fibrous web at the high speed to produce a dewatered web without deteriorating barrier properties, wherein a linear load in the at least one shoe press equipment is between 250-1500 kN/m and
drying the dewatered web to form a film which film has an Oxygen Transmission Rate (OTR) value (23° C., 50% RH) below 100 cc/m 2 /24 h according to ASTM D-3985.

2. The method as claimed in claim 1 , wherein the at least one shoe press equipment has a nip length of at least 150 mm.

3. The method according to claim 1 , wherein the linear load in the at least one shoe press equipment is changed during treatment of the fibrous web in the nip.

4. The method according to claim 1 , wherein the fibrous web arranged between said dewatering felt and said support is conducted through at least one press roll equipment before being conducted through the at least one shoe press equipment.

5. The method according to claim 1 , wherein at least two shoe press equipments are used, wherein the at least two shoe pressequipments are located one after the other.

6. The method according to claim 5 , wherein the at least two shoe press equipments are located at different sides of said fibrous web.

7. The method according to claim 5 , wherein a total nip length of the at least two shoe press equipments is at least 350 mm.

8. The method according to claim 1 , wherein the fibrous web is conducted through a smoothening roll equipment after being conducted through the shoe press equipment.

9. The method according to claim 1 , wherein the support is a metal support.

10. The method according to claim 1 , wherein the fibrous web is formed by cast coating.

11. The method according to claim 1 , wherein the support is a porous wire.

12. The method according to claim 1 , wherein the fibrous web has a dry content between 25-45 wt-% after being conducted through the at least one shoe press equipment.

Assignees

• Stora Enso Oyj

Inventors

• Heiskanen Isto
• Backfolk Kaj
• Kankkunen Jukka
• Kauppi Anna
• Hjerpe Mikael
• Korvenniemi Juha

Classifications

• D21H11/18 Primary

  Highly hydrated, swollen or fibrillatable fibres · CPC title

• D21F11/145

  including a through-drying process · CPC title

• D21C9/002

  by chemical means; preparation of dewatered pulp, e.g. in sheet or bulk form, containing special additives · CPC title

• C08J2301/02

  Cellulose; Modified cellulose · CPC title

• C08J5/18

  Manufacture of films or sheets · CPC title