Method for calendering a board web
AssigneeMetso Paper, Inc.
InventorsMatti Lares, Mikko Tani
Life of this patent
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Abstract
In the method, a long nip (N) shoe calender formed of a shoe roll (10) and a thermo roll (20) is used. In calendering, a nip dwell time which is over 10 ms. advantageously over 20 ms. a nip pressure which is below 3 MPa. advantageously below 1 MPa. and a surface temperature of the thermo roll (20) which is over 200° C. advantageously over 250° C. are used. In addition, the board web (W) surface to be pressed against the thermo roll (20) is moisturized before the nip.
Claims2
A method for calendering a board web (W) in a long nip (N) shoe calender formed of a shoe roll (10) and a thermo roll (20), in which method a nip dwell time which is over 10 ms, advantageously over 20 ms, a nip pressure which is below 3 MPa, advantageously below 1 Mpa is used, characterized in that a surface temperature of the thermo roll (20) which is over 200° C., advantageously over 250° C., is used, and that the board web (W) surface to be pressed against the thermo roll (20) is moisturized before the nip (N) by spraying atomized water onto the board web (W) surface to be placed against the thermo roll (20) in an amount of 1-20 g/m2 such that the time of action of the water before the nip is about 0.1-2 s.
Dependencies are inferred from the claim text.