Coating processes – With post-treatment of coating or coating material – Gas jet or blast mechanically treats coating
Reexamination Certificate
1997-10-07
2001-01-23
Beck, Shrive (Department: 1762)
Coating processes
With post-treatment of coating or coating material
Gas jet or blast mechanically treats coating
C427S315000, C427S350000, C427S398400, C427S428010, C427S211000, C118S249000, C118S250000, C118S326000, C118S501000, C118S063000, C118S068000, C118S069000
Reexamination Certificate
active
06177137
ABSTRACT:
FIELD OF THE INVENTION
The invention concerns a method in film transfer coating, in which the coating agent is applied as a film onto the face of at least one of the rolls that form a film press nip, from which roll face the coating agent is transferred in the nip between the rolls onto the paper or board web running through the nip.
Further, the invention concerns an equipment intended for carrying out the method in film transfer coating in connection with a film transfer press, which film transfer press comprises a film press nip formed by a pair of rolls, through which nip the paper or board web is passed, and which film transfer press is provided with coating devices for spreading a coating agent as a film onto the face of at least one of the rolls that form the film press nip, from which roll face the coating agent is arranged to be transferred in the nip between the rolls onto the paper or board web.
BACKGROUND OF THE INVENTION
By means of the film transfer technique, in film size presses the application of a size or paste onto the paper is carried out so that, depending on whether one side or both sides of the paper are supposed to be coated, coating agent films of the desired thickness are spread onto the face or faces of one or both of the rolls in the film size press by means of applicator devices, in which connection these coating agent films are transferred onto the paper web in the nip formed by the size press rolls as the paper web runs through said nip. As a rule, the film rolls in the film size presses are provided with resilient coatings, and the application onto the roll face can be carried out by using some prior-art blade coater, a bar coater provided with a smooth or grooved coating bar, or an equivalent nozzle equipment. At present, in paper machines and, thus, also in the related film size presses, ever higher speeds are aimed at, in which connection in particular this increased speed in size film presses has provided a new problem, i.e., in particular when running takes place with large coating quantities, formation of mist of the coating agent occurs at the outlet side of the press nip. The formation of mist in itself would not be a major problem, but a problem arises when this mist gathers on the constructions of the machine and drips from there onto the paper web and spoils the paper quality, or when the mist spreads into the air in the room. Since the problem has been encountered with higher significance only with increased web speeds, in the prior art at least substantially significant solutions have not been suggested for elimination of this problem.
Indeed, there are some prior-art solutions, and of them can be mentioned, for example, the FI Patent No. 90,266, in whose solution attempts have been made to prevent formation of mist by using a particular hood construction. Similarly, in the FI Patent No. 93,243 a solution is suggested in which the formation of mist in itself is not prevented, but this mist is recovered, or at least attempts are made to recover the mist, by means of mechanical devices fitted at the outlet side of the nip, so that the mist should not have access to other constructions. Thus, this earlier publication does not provide a solution for the formation of mist itself either.
OBJECTS AND SUMMARY OF THE INVENTION
The object of the present invention is to provide a method by whose means, in the film size press, formation of mist of coating agent and problems arising from same are avoided. In view of achieving this object, the method in accordance with the invention is mainly characterized in that, in the coating process, formation of coating-agent mist is prevented at the outlet side of the film press nip so that steam jets are applied at least to the side of the web that is being coated.
The equipment in accordance with the invention is mainly characterized in that, in connection with the film transfer press, steam supply devices are provided so as to apply steam jets at least to the side of the web that is being coated in order to prevent formation of coating-agent mist at the outlet side of the film press nip in connection with the coating process.
It is the most important advantage of the present invention over the prior-art solutions that, in the invention, in itself, attempts are not made just to prevent spreading of mist, but instead, attempts are made to prevent formation of mist completely. When no mist is formed at all, it does, consequently, not constitute problems either. The formation of mist is prevented in the present invention by means of spraying of steam, which provides the additional advantage that, by means of said steam jets, the web is supported and, thus, fluttering of the web is prevented, and it has been noticed that said fluttering in itself causes formation of mist. Further advantages and characteristic features of the invention will come out from the following detailed description of the invention.
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patent: 90266 (1993-05-01), None
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J.M. Gess, “Measurement of Sizing”, Tappi Papermakers Conference (Chicago) Proceedings pp. 199-200. Apr. 11-13, 1988.
Barr Michael
Beck Shrive
Steinberg & Raskin, P.C.
Valmet Corporation
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