Paper making and fiber liberation – Processes and products – Running or indefinite length work forming and/or treating...
Patent
1988-04-28
1990-12-11
Simmons, David
Paper making and fiber liberation
Processes and products
Running or indefinite length work forming and/or treating...
162207, 162358, 162359, 162375, 100 93RP, D21F 300
Patent
active
049768204
ABSTRACT:
Method for pressing and dewatering a paper web, in which a hot-pressing stage is utilized where the wet paper web is pressed in direct contact with a cylinder face that has been heated to a temperature higher than about 100.degree. C. A relatively long pressing time and a relatively low compression pressure are applied in a pre-heating/pre-pressing stage. In this preliminary stage, a surface layer of the cylinder that heats the paper web is heated to a temperature higher than about 100.degree. C. In the immediately following stage, the compression pressure applied to the paper web is lowered so that vaporization of the water present in the paper web is intensified. Next, the web is passed substantially immediately into an intensive nip-pressing stage in which the web is pressed with a peak pressure, preferably higher by one order, so that water vapor is blown through the paper web, thereby causing some of the water present in intermediate spaces between fibers in the web to be blown out, and intensifying dewatering.
REFERENCES:
patent: 3880705 (1975-04-01), Tilburg
patent: 4576682 (1986-03-01), Laapotti
patent: 4586983 (1986-05-01), Laapotti
patent: 4738752 (1986-08-01), Busker et al.
"Impulse Drying", The Institute of Paper Chemistry.
Dang Thi
Simmons David
Valmet Paper Machinery Inc.
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