Process for producing a smooth and glossy paper web, and calander therefor.

The invention relates to a method of the preamble of claims 1 and 2 corresponding type and a calender arrangement for implementing this method.

A generic method and a calender arrangement are known from DE-OS 36 00 033rd The known embodiment comprises two successively from the paper web passed through the roll pairs whose rollers are arranged vice versa, ie with the first pair of rollers engages the hard roll from one side of the paper web, the second pair of rollers of the other side. In this way, a same on both sides of treatment and surface formation of the paper web. The hard, that is, the steel roll is heated in the two pairs of rollers to a temperature at least equal to the temperature at which the fibers start of the paper web to deform. In the case of paper, this temperature is at about 175^O C. The high temperature results in a web having improved gloss without substantial loss of bulk, ie volume per gram pulp, which is the reciprocal of density.

A similar prior art is also described in US-PS 46 24 744th

The effect of calendering with highly heated steel rolls, this being referred to as Temperaturgradientenkalandrieren, 65 no. 10 (October 1982), p is 97 to 101 examined in the work of RH Crotogino in the journal "TAPPI" Journal Vol.. The contact of the paper web with a very hot roll during passage through the nip, the near-surface fibers are heated to a temperature at which they begin to be partly plastic. The fibers are known to be hollow and flattened permanently in the partially plastic state, thereby leveling the surface of the paper web enters, which is of course supported by the friction when working against a "soft" roll with paper or plastic covering. Since the heat conduction from the outer layers of the paper web is time dependent as the transport process in the interior, no significant heating takes place in the short time of passing the nip inside instead and the temperature remains low there, so that the fibers in the interior not be part plastically, rather retain their elasticity and return to their original shape after passing through the nip. The plasticizing is therefore limited to the surface layers.

This effect is desired. It is the presence on the surface of a good gloss as possible, without the paper web as a whole is compressed by a by a solid plasticizing into a compact mass with a low specific volume and poor opacity.

The invention is based on the object that is to increase this effect of brightening on the surface without lowering the "bulks", the specific volume in the interior, yet.

This object is achieved in a first method aspect, the reproduced in claim 1 invention.

The cooling is achieved that the temperature gradient between the hot surface of the hard roll and the interior of the paper web increases and the inner portions therefore remain away from the temperature region in which occurs the glanzerhöhende Teilplastifizierung of the fibers. This effect is rather very limited to the surface layers, so that the paper web in the interior retains its bulk and has a good opacity and printability.

The cooling with smoothness and gloss to provided paper webs is described per se in the US-PS 42 77 524th This is however not is an action on the fibers of the paper web. The paper web is rather painted with a synthetic resin emulsion which, after it has been plasticized by a first nip during the passage, before the passage to solidify by a second nip again, so that a particularly elevated gloss on the bottom line.

The withdrawal of heat in the cooling can be done on one side or from both sides. However, it must be so pervasive that even the inner regions of the paper web, heat is extracted noticeably.

The invention is carried out in another method aspect, which is reproduced in claim. 2

Here, the cooling of the material web takes place not before the entry into the nip, but in the nip itself from the side of the soft roll forth instead. Objective and effect are the same as in the method of Claim 1.

In both cases, it may be advisable to support the smoothing effect of the highly heated hard roll by an additional surface heating of the paper web on the side to be smoothed.

Thus, while serving to cool the preservation of bulks in the interior of the paper web, the surface heating increases the gloss effect of the hard roll by a already made increase the surface temperature. The additional surface heating should be of course done so that it is limited to the surface, thus not the effect of cooling is nullified. They especially at high operating speeds into consideration, where it may be difficult to bring the required heating in the short period of contact of the paper web in the highly heated hard roll about.

The invention also relates to the claims 1 and 2 corresponding Kalanderanordnungen which are given in claims 4 and 5. FIG.

In most cases it will be to treat the paper web from both sides to give her on both sides essentially the same properties.

In the preferred embodiment, therefore, two pairs of rollers are present, which form two of the paper web successively traversed roll nips, as is shown in the DE-OS 36 00 033rd

In this embodiment, according to claim 6, at least the second roll gap should be preceded by a cooling device for the continuous paper web to counteract the increase in temperature in the interior, which is caused by the treatment of the paper web in the first nip and the subsequent penetration of the heat into the paper web.

The most thorough effect takes place when the two nips, a cooling device is connected upstream (claim 7).

The cooling device can be designed in detail in accordance with claim 8 or 9th

As already mentioned, the smoothing effect of the highly heated hard roll may be supported by the web on the side to be smoothed before the inlet into the nip in question a certain amount of heat is applied (claim 10).

The appropriate heater may be formed in the individual according to claims 11 to 13th

The process requires, depending on the type, pretreatment and moisture content of the paper web and working speed and pressure in the nips in each of careful control of the transferred amounts of heat.

As far as this amount of heat is extracted by circulating rolling the paper web, or applied to, the change of the wrap according to claims 14 and 15 is a relatively easy to be realized method, the contact time of the web on the respective roller and thus adjust the passing over heat.

In the drawing an embodiment of the invention is shown schematically. It shows a side view of the calender according to the invention.

The whole reference 100 calender arrangement comprises two pairs of rollers 10 and 20, which are traversed by the paper web 1 in succession and each is a highly heated steel roller 2 with surface temperatures ranging from 150 to 250^O C and include a "soft", ie with a paper or plastic cover 4 provided roll. 3 When the roller pair 10, the highly heated steel roller 2 engages from below the paper web 1 to, wherein the roller pair 20, the corresponding high-heated steel roller 2 from above.

At least one of the cooperating rolls 2,3 of each pair of rollers 10,20 is deflection-controlled. For the protection of the coating 4 of the soft roll 3 can be provided that the paper web 1 is wider than the rim width, so that the lining 4 does not run against the heated roll up the second The protruding edges may be separated after completion of the treatment.

The paper web 1 runs with the usual moisture content of 5 to 15% initially in the drawing from the left by a cooling box 5, in which, for example, cold air blown onto the track surface, thereby lowering its temperature, for example, the ambient temperature, when the paper web 1 before had ambient temperature.

The cooled web of paper 1 is then deflected by a deflection pulley 6 vertically downward and passes through a heater 7 which can be formed for example as Strahlungssheizung and by means of which the paper web surface on the side facing the passage of the roller pair 10 of the highly heated hard roll 2 side temperature increase experienced. After covering a vertical portion in which the heater is 7, the paper web 1 is passed over a vertically movable deflecting roller eighth Thereafter, the paper web 1 runs into the nip 9 of the first roller pair 10th The vertical mobility of the guide roller 8 has the purpose to change the wrap angle α of the highly heated hard roll 2 to change by a correspondingly changed contact time the heat transfer from the roller 2 on the in the nip 9 to be smoothed lower side of the paper web 1 and customize to.

The effect of the treatment in the roller gap 9 on the to be smoothed lower side of the paper web 1 is detected by a Glättemeßeinrichtung 11, processes the signals in a control device 12 and are used α for controlling the position of the guide roller 8 and thus the angle of wrap.

The paper web 1 has, after leaving the roll gap 9 on the underside of which a considerable temperature which would normally propagate in the interior of the paper web first To prevent this, the paper web 1 is passed over a chill roller 13, which is connected upstream of the next pair of rollers 20th Thus, the previously highly heated side of the web 1 is cooled and removed from her total heat. The degree of cooling effect by changing the wrap angle β of the cooling roll 13 are controlled by the raised and lowered guide roller 14th

The guide roller 14 is followed in the web running direction, a raised and lowered guide roller 15 so that between the pulleys 14 and 15, a vertical track section is present, its location does not change with changes in the position of the pulleys 14,15 and in which the highly heated roll 2 the second pair of rollers 20 facing the upper side of the web 1, a heater 16 faces, which heats the web 1 superficial. With the superficial additional heat the web 1 enters the nip 19 of the second roller pair 20, wherein the angle of wrap γ of highly heated roll 2 and thus their effect on the paper web 1 by the position of the guide roller 15 is determined.

The effect of the treatment in the nip 19 is controlled by the measuring device 21 and a control device 22 is entered, which controls the position of the deflection roller 15th

Overheating of the linings to avoid 4 of rollers 3, temperature sensing means 17 are provided.

Instead of or in addition to the cooling means 5.13 can also be provided that the soft rolls are 3 cooled so that therefore the paper web 1 on one side at the highly heated hard roll 2, on the other side of the cooled roll 3 rests , The cooling effect of the soft roll 3 can be influenced by changing the angle of wrap. It is understood, that then simultaneously and the wrap angle can not be changed to the hard roller 2nd

All these features can be combined differently. Instead of cooling field 5 the cooling at this point can also be done through a cooled roll. can also, of course, instead of the cooled roll 13, a cooling box to be present, although the cooled roll 13 so far has advantages, as it specifically acts on the by the highly heated hard roll 2 of the roll gap 9 heated side of the web. 1 The heaters 7, 16 are only optional. It may also be only one or no additional heating means present.