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

Patent metadata

Field	Value
Publication number	US-11619004-B2
Application number	US-201917292191-A
Country	US
Kind code	B2
Filing date	Nov 8, 2019
Priority date	Nov 9, 2018
Publication date	Apr 4, 2023
Grant date	Apr 4, 2023

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 weight-% to 100 weight-% 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 substrate, through a pressing equipment. The invention further relates to a film produced from said method.

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 weight-% to 100 weight-% 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 and wherein said support is a metal support wherein said fibrous web is formed by cast coating on the metal support so that a surface on the metal support is smooth, wherein the metal support is heated to a temperature between 30-150° C. before said fibrous web is applied to the support,
applying a dewatering felt into direct contact with said fibrous web after said fibrous web has been formed,
conducting said fibrous web, arranged between said dewatering felt and said support, through a pressing equipment to provide a dewatered web, and
drying the dewatered web to form a film which has an Oxygen Transmission Rate (OTR) value (23° C., 50% RH) below 400 cc/m 2 /24 h according to ASTM D-3985.

2. The method as claimed in claim 1 , wherein the pressing equipment comprises an extended nip.

3. The method according to claim 1 , wherein the pressing equipment is a belt press.

4. The method according to claim 3 , wherein the fibrous web is treated in the belt press for a distance of at least 20% of a diameter of a roll of the belt press.

5. The method according to claim 1 , wherein the dewatering felt is applied to the fibrous web at least 20 cm before being conducted through the pressing equipment.

6. The method according to claim 1 , wherein a pressure used in the pressing equipment is between 1-100 bar.

7. The method according to claim 1 , wherein a pressure used in the pressing equipment is gradually increased.

8. The method according to claim 1 , wherein said fibrous web has a dry content of 15-50 weight-% after dewatering in the pressing equipment.

9. The method according to claim 1 , wherein the microfibrillated cellulose of the suspension has a Schopper-Riegler (SR) value above 90.

10. The method according to claim 1 , wherein said fibrous web is conducted through the pressing equipment at a speed of at least 50 m/min.

11. The method according to claim 1 , wherein said fibrous web is heated before the dewatering felt is applied into contact.

12. A film comprising:
microfibrillated cellulose and obtained by the method of claim 1 , wherein said film has a density above 700 kg/m 3 and an Oxygen Transmission Rate (OTR) value (23° C., 50% RH) below 400 cc/m 2 /24 h according to ASTM D-3985.

Assignees

• Stora Enso Oyj

Inventors

• Heiskanen Isto
• Kankkunen Jukka
• Pihko Riku
• Kunnari Vesa

Classifications

• C08J2301/02

  Cellulose; Modified cellulose · CPC title

• C08J2301/04

  Oxycellulose; Hydrocellulose · CPC title

• C08J5/18

  Manufacture of films or sheets · CPC title

• D21F3/0209 Primary

  with extended press nip · CPC title

• D21F3/08 Primary

  Pressure rolls · CPC title