FI60743B - FOERFARANDE FOER FRAMSTAELLNING AV WELLPAPP - Google Patents

Description

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Jgfo 11 UTLAGG NI NGSSKRI FT 6U / 4 0 C (45) Patent granted 10 03 1932 Patent meddelat (51) Kv.lk?/Int.CI.3 d 21 F 11/12 FINLAND — FI NLAND (21) Pu «nttlh * k * mut - Patantintfiknlnf 1507/73. . (22) HikemlipWvl - An * eknln | * dtf 10.05.73 '' (23) Alkuplivt - Glttlfhendif 10.05.73 (41) Tullut JulklMksI - Bllvlt effuntllj 09.12.73

Patent and Registration Office .... ....

. ". . . . . (44) Date of issue and date of issue. - "

Patent * och registerstyrelsen Antttkan utligd och utl.skrlftan publkerad 30.11.8l (32) (33) (31) Pyydetty etuoikeus — Begird prloritet 08.06.72

Federal Republic of Germany-Förbundsrepubliken Tyskland (DE) P 2227Ö11.1 (71) Elda AG, Spielhof 1, 8750 Glarus, Switzerland-Switzerland (CH) (72) Alfons Karl Herr, Karlsruhe, Saxony Federal Republic-Förbundsrepubliken Tyskland (DE) (7) The present invention relates to a process for the production of corrugated board, in which the pre-dried pulp at a moisture content of more than 50% is corrugated and dried in connection therewith.

According to a prior art method, such cardboard is produced by conveying the pulp on a porous substrate through a suction mold provided with corrugation parallel to the conveying direction of the pulp. As the pulp is transferred through this suction mold, deeper waves are gradually generated in the pulp and at the same time water is sucked from the pulp. From the point of view of water suction as well as the formation of cardboard, it is then advantageous to press the profile rolls on the gradually solidifying fibrous mass at the same time, as well as to post-shape the material, after leaving the suction mold, between the profile rollers. In addition, a method is known in which corrugating cylinders arranged transversely to the direction of travel are arranged between the long wire and the drying section of the long wire machine. Although this method gives very precisely corrugated cardboard, it is difficult to implement due to the precise control of the pulp required and is also quite expensive due to the high investment costs.

60743 The disadvantage of cardboard made according to these or similar methods is that the waves gradually straighten under the influence of moisture, even very quickly. However, the straightened cardboard thus no longer has the rigidity necessarily required in this product.

Indeed, studies have shown that a preform made of organic fibers is prestressed into the form in which it is first dried.

This means that flat cardboard from which water has been dehydrated in this form and which has been dried and subsequently shaped always tends to return to its original shape, i.e. as flat cardboard. Thus, when examining corrugated boards made according to known methods, it was found that the lack of dimensional stability of these boards was due to the fact that the shaped cellulosic fibers of the raw material tend to return to their initial positions. These corrugated boards do not take into account the most advantageous position of the individual cellulosic fibers, but rather form a completely disorganized network. Thus, the shaping device also shapes the fibers in all possible angular positions, according to which also always in their longitudinal direction, except in the case where the fibers are in the direction of corrugation. But it is precisely the longitudinally formed fiber that tends to return to its original state, thus also tends to restore the design of the material. Therefore, the material must be kept in this design until complete drying, i.e. until the binding of the private particles. Even then, under the influence of moisture, that is, when the bonding forces yield, it is still possible for the design to recover (back) at least in part.

It is therefore an object of the invention to guarantee the shape stability of corrugated board. This is achieved according to the invention by giving the fibers a clearly defined direction in the direction of travel of the resulting web and in that the longitudinal direction of the wave is parallel to this main direction of the fibers.

According to the invention, the cardboard material is shaped so that the longitudinal direction of the wave is parallel to the main fiber direction given to the cardboard. A certain fiber direction, i.e. the "main fiber direction", is obtained especially with rotary wire board machines, because the fibers are arranged parallel to the direction of rotation on the rotary wire when the material is fed. This can be further promoted by the use of circular wire board machines operating according to the countercurrent principle. This material thus obtained, namely a cardboard sheet in which the individual fibers forming the cardboard are parallel in a certain direction, is now corrugated so that the majority of the fibers are in the longitudinal direction of the weave, so that these fibers do not resist corrosion and naturally generate any restoring forces. The shaping is thus permanent and in the subsequent drying step it is no longer necessary to stabilize the material with the shaping means. Since the cardboard also does not resist shaping, it is also possible to dispense with the subsequent pressing of the cardboard, which is necessary in a shaping device to be connected to a long wire machine - thus it is also possible to actually process cardboard sheets from a rotary wire machine without post-processing.

As this both simplifies working conditions and significantly reduces investment costs, the production of such corrugated board is relatively inexpensive.