Recycled board consists totally or partially of recycled fibers and is used e. g. for packages of dry foods, as well as packages for other than foodstuffs.

WLC board is typically a quadruple or four-layer system, comprising, for example, a base layer (recycled pulp), a filler layer (recycled pulp), a chemical pulp layer, and a coating. Manufacturing amounts of WLC increase all the time, focusing primarily on Asia. While the quality of raw material deteriorates, the quality requirements for a finished product keep increasing and, thus, for example the coating process is commonly performed three times for a sufficient coverage. According to state of the art, the best grade WLC is obtained by pretreating the board surface prior to a coating process with a Yankee cylinder and a profiling machine calender.

It is an object of the present invention to provide an improved finishing method for producing grades of board, especially WLC boards, distinctly smoother and lighter than those available at present. In order to achieve this objective, a method of the invention is characterized in that the method comprises first subjecting a board web to machine calendering, followed by subjecting the web to a pre-coating process, then by running the web through a long-nip calender and further to an actual coating station/stations for applying one or more coating layers to the web surface, and finally subjecting the web to calender finishing. Downstream of the actual coating station, upstream of calender finishing, the web can be further subjected to additional coating by blade coating for improving the web even further in terms of its smoothness and gloss.

The invention will now be described in more detail with reference to the accompanying drawing, in which: Fig. 1 shows schematically the composition of a typical WLC board, and Fig. 2 shows schematically one arrangement for implementing a method of the invention.

Fig. 1 depicts schematically a multi-layer structure for one WLC board, which in the illustrated embodiment comprises a base layer 1 of recycled pulp, a filler layer 2, likewise of recycled pulp, a pulp layer 3, and a coating 4 which may consist of several coating layers.

The exemplary embodiment of fig. 2 depicts one finishing method of the invention, wherein a board web W is first passed through a machine calender 10 for profiling its thickness. This is followed by passing the web to a blade coating station 11 for pre-coating in order to improve the web smoothness. Then the web is driven through a long-nip calender, for example a shoe calender 12, as shown in fig. 2, or a belt calender, for improving the topography of web surface. The long-nip calender is followed by passing the web to an actual coating station, which can be for example a spray coating station 13, a curtain coating station, or an Opticoat Duo coating station. In this coating station, the web surface is provided with one or more coating layers for achieving a desired coverage. After the coating process, the web is still subjected to calender finishing, for example with a soft calender 14 or a multi-roll calender for improving the web smoothness and gloss. According to the invention, downstream of the actual coating station and upstream of calender finishing, it is further possible to optionally employ a blade coating for still improving the web smoothness and gloss.