Process and apparatus for treating a web of paper or board

摘要

The functional coating is applied contactlessly, followed by satining (a glossing process) of the coated web. Satining is effected in a wide nip shoe-calender (9). (A wide nip (18) is a nip prolonged by pronounced indentation under pressure). The calender has a rotary shoe roller (10) with outer covering (11) around it, operating against a counter-roller (14). The nip temperature is held below 60[deg]C. With a wide nip length of at least 40 mm, the stretching load is set to 600 N/mm at most. The casing of the shoe roller is held fixed and the counter-roller is pressed into it. A curtain coater (4) applies the functional coating, which is thermo-sensitive. Web speed through the nip is 900-1300 m/min. Pressure applied in the nip compresses web thickness by 2.5% at most. An independent claim is included for corresponding equipment.