FI85894C - FISHERY FISHING VALUE FOR THE PURPOSE OF THE PURPOSE AND THE PURPOSE OF THE PURPOSE. - Google Patents

Description

85894 J Calendering method, associated roll and its use

Kalandreringsförfarande, Vals för användning i samband med detta samt användningen av detta 5

The invention relates to a method for calendering with one or more nips through which the track to be calendered passes, one of the rolls formed by each IQ nip being a heated roll.

The invention also relates to a roll used in the method and to the use of the method.

1g The paper coming from the paper machine has a rough surface in the raw space, which needs post-treatment for most applications, which leads to leveling and compaction of the surface. For finishing, smoothing devices (e.g. machine calenders) and flexible nip calenders (e.g. soft or supercalenders) are known. The smoothing devices comprise only hard rollers (rolls) and smooth the paper interfaces so that the parts forming the paper surfaces are substantially in one plane. The roll spacings of a flexible nip calender are so-called soft roll spacings, i.e. those in which the hard roll is resiliently paired with a flexible roll. In the flexible nip calender, the resiliently flexible Vals-25 sit are nowadays quite predominantly paper rolls, i.e. rolls consisting of paper strips layered on top of each other. The calender also has a certain effect on the smoothing, but primarily on the gloss, i.e. the surface of the paper web condenses and closes.

30 The terms super- and soft-calendering in the application are not official names, some talk about matte-calendering instead of soft-calendering. A supercalender is an off-machine device, while a soft calender is already an on-machine (1 or 2 nips) or off-machine (up to 4 nips) device. In soft calenders, the flexible rolls are not paper-35 rolls, as in supercalenders, but different types of polymer or vast rolls, which have a lower internal heat generation than paper rolls and a lower sensitivity to marking. At its purest, soft calendering would be calendering performed as an on-line function utilizing high temperatures (clearly higher than supercalender temperatures) with as few nips as possible. Today, soft calenders are widely used instead of machine calenders with matte grades and coated papers in connection with a paper or coating machine when either the running speeds are low and / or the machines are narrow and / or the line pressures and / or temperatures used are not the highest. In general, high gloss papers are still calendered with a supercalender.

10 A modular calender is traditionally a calender consisting of one or more nips (i.e., modules) formed by a steel and a soft roll.

Most flexible nip calenders are so-called supercalenders, which consist of a number of superimposed rollers that are alternately soft and hard. In this way, the paper web passes successively through several nips. The hard rolls used in a typical supercalender are metal, usually steel and / or cast iron, and the soft rolls are paper or fabric filled.

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The metal rolls of the pairs of rollers are usually heated to obtain good results. The main problem with paper calendering has been the poor ability of flexible rolls to withstand high temperatures. Previous attempts to extend the life of flexible rollers have been e.g. cooling the steel core by filling it with asbestos and cellulose and using so-called heat-resistant fibers.

In the above-mentioned supercalenders, on the flexible roll side, the properties of the paper develop less than on the steel roll side.

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One reason is due to the different surface properties of the rolls and another is that the surface temperatures of the steel rolls are higher than those of the flexible rolls. When moving to sofal calendering, the aim is to use ever higher temperatures, which further increases the difference between the parties. In order to minimize one-sidedness, an even number of nips must be used in soft calendering, so that both sides of the paper receive the same number of steel roll treatments, because without a flexible counter roll it is not possible to calender the paper to a high quality.

The different calendering result given by the steel and flexible roll and the one-sidedness of the use of high temperatures (only on the steel roll side) is a problem in both super- and soft calendering. In the past, to solve this problem, i.e. in soft calenders, an even number of nips has often been used, whereby each side of the paper receives the same number of (hot steel roll) treatments. Since the heat could not be put to good use on one side of the paper per nip, it means extra nips and loss of soot. FI application 885231 provides a solution to this problem. According to the method presented in FI application 885231, the resiliently coated roll of each pair is also heated to a high temperature. This patent application also discloses materials and heating methods that also allow heating of the resiliently coated roll.

The purpose of the present patent application is to further develop the idea according to FI patent application 885231.

To achieve this object, the method according to the invention is mainly characterized in that in the method both rolls of one or more pairs of rollers are elastically coated rolls, one or both of which are heated to a high temperature.

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The roll used in the method according to the invention, in turn, is mainly characterized in that its flexible roll coating is thermally conductive or has a thermally conductive material which can be heated to a high temperature.

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Preferred embodiments of the invention have the features of the subclaims.

In the solution presented in the above-mentioned FI application 885231, one of the rolls of a pair of rollers was always a hard roll and only the second flexible roll. In the solution presented by the present invention, spring-coated rolls can now be used as both rolls of a pair of rollers.

The materials used in the flexible rolls used in the invention can be the same as those presented in patent application FI 885231. The solution according to the invention can be used in both a soft calender and a supercalender. Other possible applications are, for example, the press section of a paper machine.

10 The rollers can be heated either traditionally from the inside or from both the inside and the outside or only from the outside. If the heating takes place on the surface of the roll only from the outside, the surface or coating to be heated must be insulated from the inside because thermal energy is not transferred as waste heat to the inside of the roll. If internal heating-15 is also used, no insulation layer is required.

The heating can be performed e.g. externally by induction or some other method which causes the coating or coating or the thermally conductive material 20 in the coating or coating to be heated, e.g. by radiation or conduction. Such methods may, in addition to induction, be e.g. a separate heated steel roll in contact with the surface of the coating or coating or infrared, shortwave or laser radiation, etc. or conventional conventional oil or circulating water heating within the roll depending on the nature of the material to be heated. Heating systems can operate either alone or in various combinations and are dependent on how the direct heat-power calendering process requires.

The roll coating consists of a binder coating and a thermally conductive material and any insulators. The binder coating may contain, for example, a high temperature resistant polymer such as polyimide, polyamide-imide, polyether (ether) ketone, etc. or some other material, e.g. a cermet composite, to which the optimized elastic and hardness properties as well as the mechanical and technical properties can be modified. properties and which withstands high temperatures and is suitable for the calendering process. The thermally conductive material may be, for example, carbon or metal in the form of particles, fibers or films, or some other material, e.g. a composite mixture, which has good thermal conductivity properties and which can be combined with a binder. The insulating material can be, for example, of the foam type or some other material with a high insulation density, e.g. of the ceramic composite type, or when using the filling roll technology, the filling material itself is an insulator.

The rollers are manufactured by methods known in the art.

In a heated roll, the thermally conductive coating can be heated internally and externally as disclosed in patent application FI 885231 to temperatures above 110 ° C, generally to about 200 ° C, but can be heated even above 300 ° C if necessary. According to one alternative, the coating to be heated is metallized and the heating takes place only ul-10 koa, in which case there is a flexible non-thermally conductive insulation under the coating. Other alternatives are a flexible coating made with filling roller technology (previously known method), the surface of which is metallized and the heating takes place from the outside. Another option is a jacket made entirely of high-strength composite, in which case the layer to be heated is optimized for its elastic properties and the heating takes place from the outside. The prior art solution uses a flexible coating or coating and a coating from a sheet matrix compressed in the direction of the steel axis. The most preferred embodiment of the invention is single nip (e.g. modular calender) and in the best solution the rolls are flexible rolls with a heated coating with optimized spring-to-properties, a high strength composite which is both an insulator and a roll shell and is heated by induction or other external heat source.

In a single-nip calender, in which the surface of the flexible roll is e.g. externally heated and its jacket is a high-strength ceramic metal or plastic composite with an insulator inside, preferably a composite insulator, and the layer to be heated has optimized elastic properties. The solution can also be used in an on-line process with two nips in a row to obtain high quality polished paper.

35 6 85894 ^ Popular embodiments may also be other than a single nip ka-lanteri, e.g. in the on-line process one or more nips in a row (modules) when high quality polished paper is desired.

® The heating and coating material options described above can be combined in any way according to the application of the desired properties.

The following are examples of preferred embodiments to which the invention is not intended to be limited.

Example 1

Figure 1 shows a sectional view of a flexible roll, 1S according to the invention

wherein the heating (L) takes place both internally and externally, and wherein the coating (1) consists of metal particles dispersed in the binder. This is a homogeneous metal polymer blend, with the coating being thermally conductive throughout. Because heating takes place both inside and out, no insulation is needed.

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Example 2

Figure 2 shows a section of a flexible roll according to the invention, which is heated only from the outside by a second roll with a metal coating (1a), an insulating material (2a) and a steel sheath (3a). In Fig. 2, the heated flexible roll according to the invention has a metal coating (1) with a filling material acting as an insulator (2) and in which the steel shaft (3) of the roll is also shown.

Example 3 30

Figure 2 shows a section of a flexible roll according to the invention, which is heated only from the outside. The roll then has a thermally conductive coating (1), an insulating layer under it (2), under which there is a steel sheath (3).

i 35 7 Θ5894

Example 4

Figure 3 shows a section of a flexible roll according to the invention with a thermally conductive coating (1) and under it also a high-strength composite jacket (2) acting as an insulator 5. Heating is performed from the outside.

In the following, we present the claims, within the scope of which the inventive idea is defined, the various details of the invention may vary.

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Claims (14)

8 85894 ^ Claims A method for calendering with one or more pairs of rollers through which the track to be calendered passes, characterized in that in method 5, both rolls of one or more pairs of rollers are flexible-coated rolls, one or both of which are heated to a high temperature of 100-300 ° C . Method according to Claim 1, characterized in that the heating of the rolls takes place in a different manner or in the same way. Method according to Claim 1 or 2, characterized in that the heating of the rolls of each pair of rollers is carried out by a single device or by a combination of different devices. 15 Method according to Claim 1 or 2, characterized in that the heating of the rolls of each pair of rollers can be carried out only from the inside, both externally and internally or only from the outside. Method according to one of Claims 1 to 4, characterized in that when the heating is carried out only from the outside, the distance between the roll body and its surface is insulated. Method according to one of Claims 1 to 5, characterized in that the external heat sources can be a separate heated steel roll, infrared radiation, short-wave radiation, laser radiation depending on the nature of the material to be heated. Roll for use in the calendering method 30 according to any one of claims 1 to 6, characterized in that its flexible roll coating is thermally conductive or has a thermally conductive material which can be heated to a high temperature. Roll according to Claim 7, characterized in that the flexible roll coating 35 has optimized elastic or hardness properties as well as mechanical and technical properties. 9 85894 Roll according to Claim 7 or 8, characterized in that the flexible roll coating of the flexible roll consists of a combined binder coating and a thermally conductive material. 5 Roll according to one of Claims 7 to 9 and for use in the method according to Claim 5, characterized in that the roll has an insulating layer between the blade body and the surface. Roll according to one of Claims 7 to 9 or 10, characterized in that the binder coating comprises a high-temperature-resistant polymer, such as polyimide, polyamide, imide or polyether (ether) ketone, or another material required by Claim 8, e.g. a cermet. - the plastic composite and the thermally conductive material are carbon or metal in the form of particulate fibers or films or a composite mixture or other material with good thermal conductivity which can be combined with a binder and the possible insulating material may be foam or ceramic composite. Use of a method according to claim 1 or 2 in a 1-nip calender. Use according to Claim 12, characterized in that the surface of the roll or rolls is heated externally and its casing is made of a high-strength ceramic metal composite or plastic composite with an insulator, preferably a composite insulator, inside and the layer to be heated has optimized elastic properties. 30 Use of a roll according to any one of claims 1 or 2, characterized in that in an on-line process with two or more nips in succession to obtain high-quality polished paper. 35 ίο 85894 ^ Patentkrav