EP1357225A1 - Method of treating a web of material and calender - Google Patents

Abstract

In a paper-making finishing process a paper web (27) is treated in a calender at high temperature and pressure and then wound onto a spool. Prior to leaving the calender the paper is esp. cooled, then moistened, then further cooled. Following emergence from the calender the paper is again cooled, before being treated (62, 64) on one side from steam and then moistened on the other by an elastic roller (25). A cooling unit (37) is located prior to the last nip (25) point.

Description

The invention relates to a method for treating a Material web in a calender, in which the material web in the calender with pressure and elevated temperature acted upon and after passing through the calender winds. The invention further relates to a Calender with at least one nip that is heated by a Roller is limited, and with a winder behind the last nip.

The invention is particularly for the treatment of a Suitable for paper or cardboard. The invention is in following using a paper web as an example of a Material web described.

Paper webs are made through in the course of their manufacture passed a calender and there with increased pressure and elevated temperature. Treatment in one Calenders, the so-called calendering, have several effects. On the one hand, it leads to a compression of the Paper web, on the other hand it improves surface properties, like gloss or smoothness. The elevated temperature in simple terms, in the calender that the fibers are on the surface of the paper web plasticize, which facilitates the smoothing process. There is also a certain requirement for good smoothness Moisture of the paper web is an advantage.

However, it has been found that the paper web partially when passing through the calender suffers significant loss of moisture. This Loss of moisture is basically inevitable. He can be partially offset by the fact that the paper web additionally exposed to moisture in the calender becomes.

Nevertheless, it can always be stated that the paper web is too dry when winding, i.e. one too low moisture. This can happen with subsequent Processing operations, for example when printing problems in a print shop. There a certain amount of moisture is essential, for example for a registration between successive To ensure printing processes.

An attempt has therefore been made to increase the moisture in the Ensure the winding roll by making sure that the paper web with increased moisture in the calender runs in or reinforced in the calender Provides moisture. This brings the desired one Moisture in the winding roll of the wound paper web. However, the higher humidity results in the Treatment of the paper web to a serious disadvantage: black satin appears more often. this in turn leads to a considerable reduction in quality the paper web. The printability of the paper web will significantly affected by this black satin.

The invention is based, the risk to keep the black satin finish of the material web small.

This task is carried out in a method of the type mentioned at the beginning Art solved in that the material web cools before leaving the calender.

It has been observed that in addition to the loss of moisture, that occurs in the calender itself, another, not more negligible loss of moisture on the Distance between the calender and the winding occurs. This can be explained by the fact that the material web an increased one when leaving the calender Has temperature of, for example, 80 to 90 ° C. at this elevated temperature becomes part of that in the material web contained moisture evaporate, resulting in leads to undesirable moisture reduction. If the material web before leaving the calender cools, for example from 85 ° C to 65 ° C, then the loss of moisture due to the evaporation of liquid on the route between the calender and the rewinder significantly reduced. If you have 1% less Loses moisture, then you can with a 2% reduce the moisture in the calender, which significantly increases the risk of black satin reduced. The material web is then also when winding up something cooler, which helps reduce tension in the Avoid winding roll. The winding roll is due easier to handle at their lower temperature. Especially but can the material web be calendered with a improved surface provided without one has to accept increased risk of black satin.

Preferably, the material web is moistened after Cool. This has the consequence that the material web can give additional moisture. So you can even part of the loss of moisture in the calender compensate. Applying moisture after Cooling has the advantage that the material web in one cooler state is much better able Absorb moisture. This is especially true when when the material web is steamed. The steam condenses the colder it gets, the better on the material web Material web is. By moistening after cooling So the efficiency of the humidification can be considerably increase. This will result in an undesirable release of moisture diminished into the environment. The procedure this makes it more economical.

The material web is preferably cooled after moistening again. Especially when using Steam for humidification will not only dampen the Material web entered. The web of material also gets a slightly higher temperature. This slightly higher temperature may well be desired, for example around the treatment effects in the last nip with one to be able to exploit good effectiveness. The increased However, temperature harbors the risk that too much Moisture on the way between the calender and the Winder is lost. If you look now the material web cools again after moistening, then reduces this risk. The cooling is preferably carried out after the last nip, i.e. the material web can also with an elevated temperature in the last nip be treated. Nevertheless, this is increased The temperature in the last nip is usually much lower than the temperature of a web of material without having occurred previously Cooling.

The material web is preferably covered after the Leaving the calender, especially vapor impermeable. If you cover the material web, then has steam even at an elevated web temperature basically no way to escape. This applies particularly if the cover is actually is impermeable to steam. Such a cover can by many plastic materials or Realize metal bands. In this case, the in moisture contained in the material web kept and not released to the environment. It is not even requiring that the cover be on the longitudinal edges of the material web is closed. There may lose some moisture in the form of steam go. However, this plays for the total moisture of the In principle, rail does not matter.

The material web is preferably moistened a side that rests on an elastic roller. In particular, the material web before the last nip only moistened on this side. Humidifying one Material web side that does not touch a hard roller basically makes for the improvement of surface properties no sense. For this purpose you would have to to moisten the side of the web of material that is on a very smooth surface, i.e. on the hard roller, is applied. However, if you apply the moisture to the other side of the material web, i.e. the page, which lies on the soft roller, then you take in Basically no longer any influence on the surface properties. But you increase the moisture content of the Train. Moisture can build up on the elastic Penetrate roller much better into the material web.

The task is carried out by a calender of the type mentioned Art solved in that before the last nip a Cooling device is arranged.

As stated above in connection with the process, this cooling device is used to control the temperature of the Material web so that between the calender and the winder less moisture loss by evaporating the contained in the material web Moisture. You can therefore use the material web with a lower overall moisture in retract the calender so that a black satin can be effectively avoided by excessive moisture can.

The cooling of a material web in a calender itself is known from DE 35 42 342 A1. Used there you add a cooling device in front of a nip, to effect temperature gradient calendering, i.e. you want a temperature gradient in the material web can generate over the thickness of a paper web to achieve different compression behavior.

Is preferably between the cooling device and the last nip arranged a humidifier. The humidifier is used for additional Apply moisture to the web so that the material web when winding a higher overall Has moisture. This moisture is reached without that the material web as a whole with a higher Moisture must enter the calender. About that also has the humidification after the cooling device the advantage that you get the moisture with a apply much better efficiency to the material web can. This shapes the operation of the calender and the treatment of the material web economically.

The last nip is preferably an elastic one Roller limited and the humidifier is on arranged on the side of a web of material on the rests on the elastic roller. In a super calender the web of material passed through nips through a hard and an elastic roller are formed. The elastic Roller is also referred to as a "soft" roller, because their surface is more flexible than the surface the hard roller. In contrast, the material web guided in a smoothing work by nips that are limited by two hard rollers. With a super calender with the "soft" nips through a hard one and an elastic roller are limited, the Smoothing of the material web basically only on the side, which lies against the hard roller. The soft roller forms just an abutment for the one taking place in the nip Forming. So basically it doesn't Sinn, the side of the elastic roller Moisten the material web. But if you only have this Side moistened, then you increase the moisture the material web without losing its surface properties affect.

The moistening device preferably brings about a rise in temperature of the material web after the cooling device. Especially when you have the treatment effect with a good effect in the last nip want to take advantage of is a slightly increased Temperature is an advantage. One can therefore with the help of Cooling device a relatively strong cooling of the web effect and then by moistening raise the temperature of the material web again.

It is particularly preferred that the moistening device is designed as a steam humidifier. On Steam humidifier carries water vapor onto the material web on. The water vapor condenses on the material web and thereby contributes to an increase in moisture the material web at. At the same time the temperature the material web increased. This leads to an advantageous one Effect in treatment in the following last nip.

An after-cooling device is preferably located behind the last nip arranged. The after-cooling device ensures making sure that a temperature increase that the web of material experienced in the last nip or before, not too an increased evaporation of moisture on the Path between the calender and the take-up device leads. For example, the material web on a Temperature in the range of 50 to 65 ° C are cooled, what the evaporation of moisture from the web of material in the area significantly reduced. At a Appropriate cooling can reduce moisture loss on the way between the calender and the Practically halve the take-up device.

There is preferably a material web cover behind the last nip provided that in particular impermeable to steam is trained. A web cover inhibits the escape of steam from the material web. If the web cover is vapor impermeable, then the moisture leakage becomes even more or less completely prevented. Moisture coming from the web emerges, can at most up to the cover arrive and condense there. But it becomes automatic returned to the material web. you can now cover the material web until it has reached a temperature at which the evaporation problem no longer plays a decisive role.

It is particularly preferred that the material web cover up to a rewinder or post-cooling device extends. If the web cover extends to the rewinder, then goes between the calender and the winder only a very small amount of moisture is lost. The material web can then with an elevated temperature, but also wound up with increased moisture become. Alternatively, you can cover the web of material covered material web up to the after-cooling device lead where the web of material has cooled so far is that the negative phenomena of evaporation also no longer play a major role.

It is preferred that the material web cover is designed as a cooling device. You use the Material web cover then no longer just one To prevent the escape of moisture in the form of steam but you take care of it with the material web cover at the same time that the temperature of the material web is lowered so far that even after Leaving the web cover the risk of Evaporation and the associated loss of moisture has been significantly reduced.

The cooling device is preferably designed as a cooling roller. This is a particularly simple embodiment for cooling the web of material, which is also inside of the calender can be used. For example you can use one of the ones you need in the calender anyway Design deflection rollers as cooling rollers. Such Cooling roller can be before the last and / or penultimate nip be arranged.

Fig. 1

eine erste Ausführungsform eines Kalanders mit Aufwicklung und

Fig. 2

eine zweite Ausführungsform eines Kalanders.

The invention is described below with reference to preferred embodiments in conjunction with the drawing. Show here:

Fig. 1

a first embodiment of a calender with winding and

Fig. 2

a second embodiment of a calender.

1 shows a calender 1 with a roll stack 2, which has a series of rollers 3-14, each adjacent rollers 3, 4; 5, 6 etc. Nips 15-25 between educate yourself. The nips 15-19 are so-called "soft" nips formed, i.e. they are between a hard roller 3, 5, 7 and an elastic Roll 4, 6, 8 formed. The elastic rollers 4, 6, 8 have a surface cover 26, the surface softer and more flexible than the surface a hard roller 3, 5, 7.

Similarly, the nips 21-25 are soft nips trained, i.e. they are each by a soft Roller 9, 11, 13 and a hard roller 10, 12, 14 limited. The middle nip 20 is designed as an interchangeable nip, which is formed by two soft rollers 8, 9. The change nip ensures that a material web 27, in the present case a paper web, first with one side on the hard rollers 3, 5, 7 and then with the other side on the hard rollers 10, 12, 14 can concern.

The hard rolls 5, 7, 10, 12 are heated rolls formed what through schematically illustrated heating channels 28 should be identified. Through the heating channels 28 a heat transfer medium can be conducted, for example a hot liquid or steam the heated rollers 5, 7, 10, 12 with an increased Surface temperature. The increased Surface temperature is passed on to the material web 27, if the web of material is the appropriate Goes through nips. This gives the material web one high temperature.

The two end rollers 3, 14 and the two middle ones Rollers 8, 9, which limit the change nip 20, are as Deflection adjusting rollers, the two middle rollers 8, 9 in both directions with pressure are acted upon. This is due to support shoes 29 shown schematically.

The material web 27 is between the nips 15-25 Deflection rollers 30 passed. Before the first nip 15 is the Material web passed over a guide roller 31. After this Leaving the last nip 25, the material web is over another guide roller 32 passed.

The roll stack 2 is on the top of a stand 33 arranged, this upper side by about 45 ° opposite the vertical is inclined.

Following the calender 1 there is a winding device 34, in which the material web 27 to a Winding roll 35 is wound. Between the calenders 1 and the winding device 34 are still different, not individually provided with reference numerals Guide rollers provided.

The material web passes as it travels through the calender 27 a range of humidifiers 36, which are designed as steam humidifiers. The humidifiers 36 have the task of the material web 27 to moisten and especially the moisture profile in the transverse direction of the material web 27 to keep as even as possible.

A cooling roller 37 is arranged in front of the last nip 25, which is slightly larger than the other deflection rollers 30. With the cooling roller, the material web 27 before Chilled through the last nip. Between the Cooling roller 37 and the last nip is another Steam humidifier 38 arranged as a humidifier. This steam humidifier 38 acts on the side of the Material web 27 in the last nip 25 on the soft Roller 13 abuts. The guide roller 32 behind the last one Nip 25 is also designed as a cooling roller.

This arrangement has the advantage that the material web 27 is cooled before leaving the calender 1. Accordingly can be between the last nip 25 and the Rewinder 34 no longer has as much moisture get lost like an uncooled material web 27. Evaporation losses are reduced considerably. If you assume that with a material web 27, which leaves the calender 1 uncooled and until the winding device 34 runs, a loss of moisture occurs in the order of 2 to 3%, then this loss of moisture becomes now reduced to about 1%. This has the beneficial effect that the material web 27 with a by about 2% lower humidity can be run into the calender 1 can and still with the desired moisture from about 4 to 5% wound on the winding roll 35 can be.

In addition, the steam humidifier 38 can still more Apply moisture to the material web 27. The Steam humidifier 38 carries the moisture to the Side of the material web 27 with the elastic Roller 13 comes into contact. The moisture that comes through the steam humidifier 38 is therefore not used to the smoothness of the web 27 on the side increase that with the hard and smooth roller 14 in Contact comes. It is used only for the Moisture of the web 27 to increase.

Since the steam humidifier 38 following the cooling roller 37 is inserted, the one emitted by the steam humidifier 38 comes Steam onto a much colder material web 27 and can therefore condense better. This The procedure improves the moisture penetration in the material web 27.

The increase in temperature associated with steam humidification is by the guide roller designed as a cooling roller 32 after passing through the last nip 25 undone again so that the material web 27 after the guide roller 32 only a temperature in the range from 50 to about 65 ° C.

In that the material web 27 with a significant less moisture in the calender 1 can be and also through the humidifiers 36 additionally applied humidity kept lower is the risk of black satin or a mottling has become much smaller. Nevertheless, there is a loss of quality in the surface properties not observed.

Fig. 2 shows another calender 51, the only has a single nip 52 that is between one hard and heated roller 53 and a shoe roller 54 is formed. The shoe roller has a rotating one Coat 55, which is correspondingly compliant and by a support shoe assembly 56 against the hard 53 is pressed. Furthermore, the calender 51 can also be other Have rollers like this, dashed with a Roller 57 is shown.

The web of material 58, the nip 52, the Breitnip is formed, passes through, is in front of the wide nip 52 passed over a cooling roller 59, but also omitted can be if one described below Material web cover is used. Behind the Breitnip 52 is, as in the embodiment of FIG. 1 also, a winder 60 with a winding roll 61 arranged.

In addition to the material web 58, there is a first transfer belt 62 passed through the nip 52. The first transfer belt 62 is made of a vapor impermeable plastic educated. It covers the web of material 58 on her Bottom, i.e. the side facing the shoe roller 54, over a predetermined distance long until the material web 58 on a cooling roller 63 comes free from the first transfer belt 62.

The opposite side of the material web 58 is from a second transfer belt 64 covered that also is designed as a plastic band and is impermeable to steam is. Instead of plastic, you can for the first and of course the second transfer belt 62, 64 also Use metal tape.

Between the second transfer belt 64 and the roller 53 a sealing arrangement 65 is provided, specifically expediently where the second transfer belt 64 is deflected via a deflection roller 66. This creates a closed room 67, in which over briefly or long builds up a steam atmosphere in which the Steam has the same pressure as in the material web 58th

The material web 58 is in the area of a cooling roller 68 lifted off the first transfer belt 62, the second Transfer belt 62 is passed over a deflection roller 69. The second transfer belt is in the area of the deflection roller 69 62 opposite the cooling roller 68 by a sealing arrangement 70 sealed. This creates a Room 71, in which there is also a steam atmosphere in which the steam forms the same pressure as within the material web 58 has. The covering device therefore also acts as a cooling device here.

In addition, a moistening device can be placed in front of the nip 52 72 may be arranged on the side of Material web 58 acts on the shoe roll 54 or abuts the first transfer belt 62.

The material web 58 is thus immediately after leaving of the nip 52 on one side of the first Transfer belt 62 covered so that no steam escapes there can. On the opposite side Do not let steam escape either. First of all there is the Vapor pressure in room 67 counter. Later the other one Side covered by the second transfer belt 64.

The cover of the shoe roller 54 is indeed opposite Side of the material web 58 in the area of Cooling roller 68 canceled. There is also a steam outlet here in room 71 but not possible because one Such steam outlet opposes the steam pressure in room 71. The material web 58 is through the chill roll 68 chilled on one side and later after the first transfer belt 64 is lifted off the material web 58 has, from the first-mentioned cooling roll 63 on the other side. When lifting the second transfer belt 64 of the material web 58 is not a seal more required because the material web 58 is already on such a low temperature has been brought that a notable leakage of steam in the relative short area between the lifting of the second transfer belt 64 and the laying on of the material web 58 the cooling roller 63 is no longer possible.

Of course you can use such a cover also use with a calender as shown in Fig. 1 is shown.

Claims (16)

Method for treating a material web in a calender, in which pressure and elevated temperature are applied to the material web in the calender and wound up after passing through the calender, characterized in that the material web (27) is cooled before it leaves the calender (1) , A method according to claim 1, characterized in that the material web (27) is moistened after cooling. A method according to claim 2, characterized in that the material web (27) is cooled again after moistening. Method according to claim 3, characterized in that the material web (27) is cooled after leaving the calender (1). Method according to one of claims 1 to 4, characterized in that the material web (27) is covered in particular vapor-impermeably after leaving the calender. Method according to one of claims 1 to 5, characterized in that the material web (27) is moistened on one side which rests on an elastic roller (25). Calender with at least one nip, which is delimited by a heated roller, and with a winding device behind the last nip, characterized in that a cooling device (37) is arranged in front of the last nip (25). Calender according to claim 7, characterized in that a moistening device (38) is arranged between the cooling device (37) and the last nip (25). Calender according to claim 8, characterized in that the last nip (25) is delimited by an elastic roller (13) and the moistening device (38) is arranged on the side of a material web (27) which bears against the elastic roller (13) , Calender according to claim 8 or 9, characterized in that the moistening device (38) causes an increase in the temperature of the material web (27) after the cooling device (37). Calender according to claim 10, characterized in that the moistening device (38) is designed as a steam moistener. Calender according to one of claims 7 to 11, characterized in that an after-cooling device (32) is arranged behind the last nip (25). Calender according to one of claims 7 to 12, characterized in that a material web cover (62, 64) is provided behind the last nip (52), which is in particular made impermeable to steam. Calender according to claim 13, characterized in that the material web cover (62, 64) extends up to a winding (60) or the after-cooling device (63). Calender according to claim 13 or 14, characterized in that the material web cover (62, 64) is designed as a cooling device (68). Calender according to one of claims 7 to 15, characterized in that the cooling device (37, 32; 63, 68) is designed as a cooling roll.

Images