EP1593778A1 - Process and apparatus for treating a web of paper or board - Google Patents

Abstract

The functional coating is applied contactlessly, followed by satining (a glossing process) of the coated web. Satining is effected in a wide nip shoe-calender (9). (A wide nip (18) is a nip prolonged by pronounced indentation under pressure). The calender has a rotary shoe roller (10) with outer covering (11) around it, operating against a counter-roller (14). The nip temperature is held below 60[deg]C. With a wide nip length of at least 40 mm, the stretching load is set to 600 N/mm at most. The casing of the shoe roller is held fixed and the counter-roller is pressed into it. A curtain coater (4) applies the functional coating, which is thermo-sensitive. Web speed through the nip is 900-1300 m/min. Pressure applied in the nip compresses web thickness by 2.5% at most. An independent claim is included for corresponding equipment.

Description

The invention relates to a method for treating a Web of paper or cardboard, in which a functional line applied to the web and then the web is satined. Furthermore, the invention relates to a Apparatus for treating a web of paper or Carton with a coater and a calender.

Paper or board webs, which in the following also briefly are called "train", are often with a Stroke on at least one surface provided. This Dash, so a coating, can be different Have purposes. You can smooth the train. You can do that Stroke but also assign another function. For example you can with the help of the line the train make thermosensitive. A thermosensitive web can for example, in fax machines or other printers be used, which the web with the help of locally applied Describe heat.

Function bars are relatively expensive. Accordingly increase the cost of railways that with a functional line are provided.

The invention is based on the object, webs with Functional line cost-effective to produce.

• der Funktionsstrich wird berührungslos aufgetragen,
• die Bahn wird online mit dem Strichauftrag satiniert und
• die Satinage erfolgt in einem Breitnip eines Schuhkalanders, der eine Schuhwalze mit einem umlaufenden Mantel und eine Gegenwalze aufweist.

This object is achieved by a combination of the following features:

• the functional bar is applied without contact,
• the web is satin and online with the stroke order
• the calendering takes place in a wide nip of a shoe calender, which has a shoe roll with a circumferential jacket and a counter roll.

By this combination can be surprisingly the amount of functional stroke required to meet certain Requirements is necessary, significantly reduce. When the functional bar applied without contact , you can change the layer thickness of the function bar to a minimum. The training Layer then follows the contour of the surface of the Web, i. it is not necessary the roughness of the Balance the track and fill in "valleys". This kind Painting a line thus saves considerable costs because you need less coating color. After application the dash are all areas of the track in sufficient Measurements evenly covered with the functional line. The fact that the train is not then in a "normal" Calender is calendered, in which two rollers interact, but in a shoe calender, in Running direction of the web has a relatively long nip, done a calendering, in which the train a certain Scuff resistance. It is not necessary, that the web satin on smoothness or shine is, although here are some beneficial effects to adjust. It is believed that by using a Wide nips the compressive stresses acting on the web act, can be kept so small that the "Tips", which exist due to the roughness of the web not by those formed by the functional line Press layer through. Also in use a very thin layer of the functional bar the web remains over its full area with coating color covered, so that the calendering the previously achieved advantage the non-contact coating order not again destroys. The combination of non-contact Line application and calendering in the nip thus leads to a significant reduction in the need for material for the function bar, in other words, the Coating color. Now if you have the satinage online with the Stroke order makes, then one reaches not only Savings in handling. The railway will also be in satined in a stage where the functional bar has not yet received its final strength. It is therefore still possible within certain limits, a transformation at least on the surface of the functional bar make, without the thickness of the functional line Significantly reduce the layer formed.

Preferably, one keeps a temperature in the nip below 60 ° C. The shoe calender is therefore driven "cold". This is unusual because shoe calender basically always be operated at relatively high temperatures. It has but it has been shown that at the relatively low temperatures, which can even be far below 60 ° C, for example, at 40 ° C or even 30 ° C, the calendering the web is sufficient to the desired properties achieve. In particular, the train gets a sufficient Rub resistance.

It is preferable to set at a length of the wide nip of at least 40 mm a maximum line load 600 N / mm. This is enough to reduce the roughness of the Lane to a desired value. on the other hand becomes at this low value of the line load the volume is not appreciably reduced.

Preferably, the coat of the shoe roll of the Shoe calender stationary and dips the counter roll in the coat. This has the advantage that no Mantle stretching results and thus no flexing. Accordingly, results in the areas of the lateral Edge zones also no overheating. The coat is less stressed. Accordingly decline the costs.

Preferably, a curtain coater is used to apply the coating. For example, a curtain coater is offered by Voith Paper, 89522 Heidenheim, Germany. With a curtain coater, the line can be applied without contact and with a relatively small thickness.
Preferably, the web is passed through the nip at a speed in the range of 900 to 1,300 m / min. This speed shows the best calendering result.

It is also advantageous if you have a compressive stress in the nip selects where the thickness of the web by a maximum 2.5% decreases. This can be a volume-saving Achieve satiny.

• die Streicheinrichtung ist als berührungslos arbeitende Streicheinrichtung ausgebildet,
• der Kalander ist online mit der Streicheinrichtung angeordnet und
• der Kalander ist als Schuhkalander mit einer einen umlaufenden Mantel aufweisenden Schuhwalze und einer mit der Schuhwalze zusammenwirkenden Gegenwalze ausgebildet.

The object is achieved in a device of the type mentioned by the following combination:

• the coating device is designed as a contactless coating device,
• The calender is placed online with the coater and
• the calender is designed as a shoe calender with a shoe roller having a circumferential jacket and a counter-roller cooperating with the shoe roller.

As stated above in connection with the method, can be achieved with this combination of advantage that the coating order kept extremely thin can be, without the line through the following Satinage is locally destroyed again. At the exit of the Wide nips you get a track that evenly with the Function bar is covered without, for example the "peaks" of the roughness of the "raw" orbit through the Layer of the function bar has been pushed are.

Preferably, the counter roll has a surface temperature of a maximum of 60 ° C. The shoe calender will So cold. Up to now, this has basically been the case not promised a particularly good effect. in the Connection with a function bar results however a sufficient calendering effect, in particular a excellent rub resistance.

The shoe calender preferably has a broad nip with a length of at least 40 mm, in which a Line load of a maximum of 600 N / mm prevails. With that result Although only low compressive stresses. These compressive stresses but sufficient to the railway the necessary To give scuff resistance.

It is also advantageous if the shoe roll has a stationary one Shoe has and the counter roll in the coat is sinkable. In this case you avoid edge strains on the front sides of the shell of the shoe roll. The flexing work that develops in the sheath of the shoe roll stays lower. This avoids problems with overheating at the edge zones. The stress of the coat is kept small. Overall, it can be increase the life of the jacket. The costs will be lowered.

Preferably, the coating device is a curtain coater educated. With a curtain coater can be achieve a particularly thin coating order.

The invention will be described below with reference to a preferred Embodiment in conjunction with the drawing described. Herein shows the single figure a device for treating a Train.

The drawing shows a device 1 for treatment a web 2 of paper or cardboard. The train is coming out a paper or board machine shown only schematically 3. You can also choose from one Roll, such as a jumbo roll, unwound become.

The web 2 passes through a coating device 4, in the a functional rule 5 applied to a surface becomes. The coating device 4 is here as "Curtain Coater "trained, the coating color in the form of a Curtain 6 (symbolized by an arrow) on the Run lane 2. By a vote of the issued Quantity on the speed of the lane 2 leaves an extremely thin line on the surface create the web 2. For the sake of representability the stroke 5 in the drawing is exaggeratedly thick shown.

The function bar 5 may be, for example to act on a thermosensitive bar, so that the Lane 2 ultimately a thermosensitive paper or becomes a thermosensitive cardboard. The dash 5 contains usually except a binder and some Minor constituents two dye precursors by Melt reacted with each other a mostly produce black color. The main application areas are fax papers, printer, plotter and label papers. The thermoreactive stroke can by a not shown heat-insulating primer supported, also with a curtain Coater can be applied.

The coating device has an output device 7 on, which is the stroke 5, also called "coating color" can be applied to the web 2, and a Drip tray 8, in the laterally excessive coating color can be included. In not shown Way, the coating color from the drip tray 8 returned to the output device 7 again become.

Online to the coating device 4 is a shoe calender 9 arranged, which is a shoe roll 10 with a circumferential Sheath 11 and a support shoe 12 has. Of the Support shoe 12 has a pressure surface 13 which with Not shown devices for introducing is provided by lubricants, such as hydraulic oil. With the jacket 11 of the shoe roll 10 acts a Counter roller 14 together, which has a variety of peripheral Holes 15, the temperature at the surface to adjust the counter roll 14 can. As indicated by a double arrow 16, the counter-roller 14 with respect to the shoe roll 10 displaced. Of the Support shoe 12 of the shoe roll 10 is arranged stationary. The counter-roller 14 is thus in the shell 11 of Shoe roll 10 immersed. This has the advantage that the jacket 11 is not stretched at its axial ends must become. There he is usually with front discs provided, which rotate about an axis 17.

The shoe roll 10 forms with the counter roll 14 a broad nip 18, in which the web 2 with the applied Function bar 5 is satined. One puts now the temperature in the extended nip 18 to a relatively low Value. The maximum surface temperature of the Counter roller 14 is 60 ° C. To achieve this, can it will be necessary to have the peripheral holes 15 of one to flow through something colder medium, the Counter roll 14 so cool. This depends on how hot the web 2 is and what temperature increase by applying the web 2 in the nip 18 results. Preferably, the temperature of the counter roll 14 even lower, namely at 40 ° C or only 30 ° C.

The broad nip 18 has a length of at least 40 mm in the running direction of the web 2. A longer length is preferred. The length can be up to 400 mm. In the broad nip one generates a line load of, for example, 600 N / mm, so that a compressive stress of about 15 N / mm ² results at a Nipänge of 40 mm. The compressive stress should be chosen so that the volume of the web 2 does not substantially decrease in the extended nip 18, that is, for example, only reduced by 2.5%.

The web 2 passes through the broad nip 18 at a speed in the range of 900 to 1,300 m / min. Together with the low temperature and the relatively low Compressive stress is achieved with the functional line 5 is sufficiently solidified, so that the web 2 receives a good rub resistance. The Smoothness and gloss values of the web 2 also rise something on. However, this is not the focus here.

With the illustrated device to reach an extraordinary thin layer thickness of the bar 5, so that one with a relatively small amount of expensive ones Coating color gets along. Despite this thin layer thickness the two-dimensional coverage of the web 2 is retained even then when the web 2 is satined in the nip 18 and the coated side on the counter roll 14, the one hard and smooth surface, is applied. Of the Sheath 11, however, is made softer, i. he is plastically deformable.

It is advantageous if the pressure surface 13 is formed is that considering the thickness the shell 11 of the contour of the peripheral surface of the counter roll 14 follows. But this is not mandatory.

Claims (13)

Process for treating a web of paper or board, in which a functional coating is applied to the web and the web is subsequently satin, characterized by the combination of the following features: the functional bar is applied without contact, the web is satin and online with the stroke order the calendering takes place in a wide nip of a shoe calender, which has a shoe roll with a circumferential jacket and a counter roll. Process according to Claim 1, characterized in that a temperature in the extended nip is kept below 60 ° C. A method according to claim 1 or 2, characterized in that sets a line load of a maximum of 600 N / mm at a length of the broad nip of at least 40 mm. Method according to one of claims 1 to 3, characterized in that the casing of the shoe roll of the shoe calender is held stationary and the counter roll can be immersed in the casing. Process according to one of Claims 1 to 4, characterized in that a curtain coater is used to apply the coating. Process according to one of Claims 1 to 5, characterized in that a thermosensitive coating is applied. Process according to one of Claims 1 to 6, characterized in that the web is passed through the nip at a speed in the range from 900 to 1,300 m / min. Method according to one of claims 1 to 7, characterized in that one chooses a compressive stress in the extended nip, wherein the thickness of the web decreases by a maximum of 2.5%. Apparatus for treating a web of paper or board with a coater and a calender, characterized by the following combination: the coating device (4) is designed as a contactless coating device, the calender is arranged online with the coater (4) and the calender is designed as a shoe calender (9) with a shoe roll (10) having a circumferential jacket (11) and a counter-roller (14) cooperating with the shoe roll (10). Apparatus according to claim 9, characterized in that the counter-roller (14) has a surface temperature of at most 60 ° C. Apparatus according to claim 9 or 10, characterized in that the shoe calender (9) has a broad nip (18) with a length of at least 40 mm, in which a line load of a maximum of 600 N / mm prevails. Device according to one of claims 9 to 11, characterized in that the shoe roll (10) has a stationary shoe (12) and the counter-roller (14) in the jacket (11) is einenkbar. Device according to one of claims 9 to 12, characterized in that the coating device (4) is designed as a curtain coater.

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