FI97407B - Device for coating paper or paperboard - Google Patents

Abstract

A roller which is provided for a coating device and which is provided with a flexible rubber cover which is applied to a metallic, cylindrical or hollow-cylindrical roller core, has a heating device for raising the temperature of the roller core beyond the temperature of the roller cover. <IMAGE>

Description

97407

Device for coating paper or paperboard

The invention relates to a coating device 5 according to the preamble of claim 1. The device consists of a roll, as is often used where the coating of paper or board takes place in a compression gap formed between two rolls. In this case, a small order quantity (special basis weight) is usually coated. The coating compositions usually contain considerable amounts of water as solvent.

Rollers coated with plastic, e.g. polyurethane or polyamide, run the risk of being damaged by hydrolysis, especially in the adhesive layer which forms the connection between the plastic sheath and the metal roll core. In addition, the plastic sheath softens, which leads to a change in its hardness and a decrease in its strength. Thus, of course, it also affects the life of such a roller and must be replaced in time. The roll according to the invention, the essential features of which are set out in the characterizing part of claim 1, limits this disadvantage, which takes place essentially in such a way that the core of the roll receives a higher temperature than the plastic jacket applied thereon. To this end,. for this purpose, the roll can be heated directly by a flowing heat transfer medium or heating rods or heating coils. In this case, indirect measures or; means for raising the core temperature of the roller, which is primarily and conventionally metal.

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'**:. :: 30 The measures according to the invention prevent the ingress of water from the surface of the roll shell and the coating mass i.: into the roll shell towards the core of the roll to an excessive extent.

This is, of course, only very slow, but still too fast, given the acceptable lifetime of the roll in its "35 production use. In this case, it is only particularly important that the core temperature of the roll is only slightly higher than the radial outer surface temperature of the roll shell.

2 97407

Generally, a temperature difference greater than 50 ° K (50 degrees Celsius) is not used.

Although heated rollers are known in a wide variety of constructions, these are purely metallic rollers which require a high surface temperature, e.g. for the applications prevailing in calenders.

The roller according to DE 37 41 232 A1, which has a rubber jacket on top of a metal core, is heated from the inside alone for the purpose of transferring the color which detaches hot from the carrier strip to the substrate, in particular as a letter or number. No water or other moisture or solvent is generated here. In this case, it is only a very small roll, 15 length about 15 cm, which is cheap and can often be renewed and at low cost.

The invention will now be described with reference to the figures in the drawing, in which Figure 1 shows in principle an axial section of a roll according to the invention and Figure 2 shows in cross-section another embodiment of a roller heating device according to the invention.

In Fig. 1, the core of the roll is indicated by reference numeral 1 and the casing of the roll by reference numeral 2, wherein the core of the roll is a hollow cylinder of metal, * primarily steel. The end faces of this hollow cylinder I «» *% · 'are closed and have shaft sections 3 and 4, * + * * · * ... · * which also have a through hole 5 in the middle. »· * V'30 natural heating or heating gas supply and discharge channels. The core temperature of the roller should only be kept above the ambient • temperature or the temperature of the coating mass ... ··· la if it needs to be heated and the roller jacket also heats up.

In many cases, however, the coating composition is not heated above ambient temperature. In this case, it is sufficient to heat the roll to approximately 30-50 ° C. This creates a natural "35 3 97407 temperature gradient between the core of the roll and the top surface of the roll shell.

A temperature difference of 0.1 ° K (0.1 ° C) is theoretically sufficient between the top surface of the jacket and the top surface 5 of the roll core, with a range of 1-20 ° K (1-20 ° C) being preferred.

If a particularly uniform heating of the roll is desired, the device may have special internal structures, as is known, for example, from DE-chips-10 of Musical Publications 32 29 471 and 38 02 477 and from U.S. Patent Nos. 43,518,386 and 42,518,184.

Another possibility is, of course, that there are 15 heating rods or heating coils on the inner surface of the core of the hollow, cylindrical roll. The electric heating power must then be transferred to the shaft section by means of a slip ring.

Another possibility is shown in Figure 2, where by means of inductive coupling eddy currents are generated from the electromagnet and from the core of the 20 rolls to the latter, which are converted into heating of the core. The electromagnet then consists of an iron core 8 with at least one coil 9. Figure 2 also shows the heating rods 6 and the heating coils 7 in the grooves 10.

. '.'. 25 / · '; ·, ·. One possible explanation for the effect is this: ·· ·: * · *: *. *. The adhesive layer of the roll coating (plastic sheath) can be penetrated by a few more water molecules, although not to such an extent that "moisture networks" are formed. Therefore, moisture cannot be affected by damaging structures.

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The roll can advantageously be used in a brush apparatus having • · · • · · · · · *: *:: two braiding rollers according to US publication 48 48 268, or; a counter-roller of the coating mass feeding device across the web, which guides through a certain bending angle, implemented e.g. according to U.S. Pat. No. 42,501,211.

Claims (7)

An apparatus for coating paper or cardboard with the base of a pigment or starch coating or coating composition comprising a coating roll or counter-roll comprising a core and a jacket, the core being metal, preferably steel, and coats of a rubber or rubber shaft elastic material, characterized in that the device is provided with heating elements for heating the metallic core (1) of the roller so that the core at least in the area of the rubber or rubber shaft elastic surface (2) adjacent the heat exchange to a temperature that is 0.1-50 ° K (0.1-50 ° C) higher than the temperature of men. Device according to claim 1, characterized in that it. the metallic core (1) at least in the region of the limiting heat exchange surface of the second rubber or rubber shaft elastic (2) can be brought to a temperature of 0.1-20 ° K f ♦ ·. · *. In (° C) higher than the temperature of men. • * · * ♦ ♦ / t • · ♦ // ♦ · « 3. Device according to claim 1 or 2, characterized in that heated gases, meadows or liquids can be introduced as heating medium into the interior of the roller. • · ·. · · * S · '· · Λ »' 5 ϊ ! 4. Device according to claim 1 or 2, characterized in that magnets (8, 9) are arranged radially at the outer circle of the drum for exposing the drum to magnetic fields which switch at a high frequency. Device according to any of the preceding claims, characterized in that the roller jacket consists of polyurethane. 97407 6. Apparatus according to any of the preceding claims, characterized in that, at least at the transition to the core, the roll jacket has a temperature not exceeding 20 ° K (° C) higher than the temperature of the applied coating mass or has a temperature of not more than 50. ° C. Use of a core and a shell resistant coating roll or counter roll for coating paper or cardboard with a pigment or starch formulated on the basis of a coating or coating composition, the core of the roll consisting of metal, preferably steel. , and the male member consists of a rubber or rubber shake elastic material, characterized in that the heating element has been connected to the heating element for increasing the temperature of its metallic core (1) at least in the region of the heat-exchangeable surface adjacent to the male (2). the temperature of menin by 0.1-50 ° K (° C). «· M t '• · 1» • · · · # • · · *. 1 • · · »·» * * # # · · · $ i • · · • · KP »• ·« 14 «• · · ·; : m i uti l.t.tja ... <· • · · «• ··% · • ·» «» •% 1 · • «» f