Method and equipment for two-sided coating of a printing paper w

Details Method and equipment for two-sided coating of a printing paper w Method and equipment for two-sided coating of a printing paper w

1996-03-19

1998-08-11

Dudash, Diana

Coating apparatus

Solid applicator contacting work

With work-handling or work-supporting

118220, 118226, 118227, 118261, 118407, 118413, 427211, 427356, 427359, 427382, B05C 104, B05D 504, B05D 302

Patent

active

057922608

DESCRIPTION:

BRIEF SUMMARY
FIELD OF THE INVENTION

The invention concerns a method for two-sided coating of a printing-paper web with a coating paste or equivalent, in which method the paper web is passed through the coating part of the paper machine, in which the first side of the web is coated in the first coating station of said coating part, and the coating-agent layer produced on the face of the web is dried at least partly by means of a first drying unit fitted after the first coating station, and in which method the second side of the web is coated after the first drying unit in the second coating station of the coating part, and the second coating-agent layer produced on the face of the web is dried at least partly by means of a second drying unit fitted after the second coating station.
Further, the invention concerns an equipment for two-sided coating of a printing-paper web with a coating paste or equivalent in a coating part of a paper machine, which equipment comprises a first coating station for the coating of the first side of the web and a first drying unit, fitted after the first coating station, for at least partial drying of the coating-agent layer produced in the first coating station, as well as a second coating station, fitted after the first drying unit, for the coating of the second side of the web and a second drying unit, fitted after said second coating station, for at least partial drying of the coating-agent layer produced in the second coating station.


BACKGROUND OF THE INVENTION

Traditionally, printing-paper webs are coated by means of various blade or bar coaters. A problem especially with thin printing-paper webs has been poor runnability. The quality of the coating in particular in respect of smoothness is good when blade or bar coaters are used.
In the Finnish Patent Application No. 924960, a method and an equipment are described for two-sided coating of a thin printing-paper web that contains mechanical pulp, which method and equipment were taken to production operation at the beginning of the year 1994. In said new method, the coating agent is first metered onto the face of the film roll of a film press and transferred further onto the paper in the nip between the rolls in the film press. The first side of the web is coated in a first coating station, after which the first coating layer that was formed is dried, and the second side of the web is coated in a second coating station. In respect of the runnability, the new method and equipment have fulfilled the expectations well.
In thin paper grades, with the method described above, the quality of the coating is highly competitive with corresponding blade-coated grades. With higher grammages of the web, in particular by means of a blade coating equipment provided with an applicator roll or equivalent, it is possible to run larger coating quantities than with a film press and, thus, also a printing paper of a clearly higher quality.
In the FI Laid-Open Publication No. 79,954, an equipment is described by whose means the paper web can be coated from both sides by alternatively using either the film press technique or coating applied directly onto the web. The aim of said publication is to utilize one film press unit, by whose means both sides of the web are coated. In the method in accordance with said publication, however, no attention has been paid to the coating of a thin web of low strength. Further, it is a drawback of this solution that, when the mode of coating is changed, the draw of the web becomes completely different, and, further, the construction has been accomplished so that, when film-press coating is used, the heaters that are used in order to dry the web on application of the coating directly onto the web are fully unnecessary.


OBJECTS AND SUMMARY OF THE INVENTION

The object of the present invention is to eliminate the deficiencies in the prior-art methods described above and to provide a novel and versatile method and equipment for two-sided coating of a printing-paper web.
In view of achieving the objectives of the invention,

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