Classifications

• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
  • D21F9/00—Complete machines for making continuous webs of paper
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
  • D21F11/00—Processes for making continuous lengths of paper, or of cardboard, or of wet web for fibre board production, on paper-making machines
  • D21F11/02—Processes for making continuous lengths of paper, or of cardboard, or of wet web for fibre board production, on paper-making machines of the Fourdrinier type
  • D21F11/04—Processes for making continuous lengths of paper, or of cardboard, or of wet web for fibre board production, on paper-making machines of the Fourdrinier type paper or board consisting on two or more layers
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
  • D21F3/00—Press section of machines for making continuous webs of paper
  • D21F3/02—Wet presses
  • D21F3/04—Arrangements thereof
  • D21F3/045—Arrangements thereof including at least one extended press nip

Definitions

• the invention relates to a device for producing white top kraftliner, in particular for producing white top kraftliner with a weight per unit area of at least 125 g / m 2
• White Top Kraftliner has a lighter top layer made of bleached and predominantly short-fiber kraft pulp, which is responsible for the name component “White Top”, and a darker back layer made of unbleached and predominantly long-fiber kraft pulp.
• the lighter top layer should be as white and smooth as possible in order to ensure good printability, while the darker back layer gives the paper web the necessary stability and strength.
• the object of the invention is to provide a particularly cost-effective concept for a device for producing white top kraftliner which at the same time makes it possible to produce high quality white top kraftliner.
• a device for the manufacture of white top kraftliner ie a multi-layer fibrous web at least one darker back layer and one lighter top layer
• the device comprising a wire section for forming the White Top Kraft liner, a press section for further dewatering of the White Top Kraftliner and a drying section for drying the White Top Kraftliner, the wire section for forming at least one first forming unit the darker back layer and at least one second forming unit for forming the lighter top layer of the White Top Kraftliner as well as a rubber zone, wherein the first forming unit and the second forming unit are arranged and designed such that the darker back layer to form the White Top Kraftliner in the rubber zone the lighter top layer is transferred so that the lighter top layer faces downwards when leaving the wire section
• the press section comprising at least three press nips, a first press nip from a shoe press roll and a vacuumed counter roll, a second press snip are formed by the vacuumed counter roll and a smooth central roll
• the White Top Kraftliner is produced in the so-called “top on bottle” arrangement, ie the lighter top layer points downwards when the wire section is left.
• This is actually disadvantageous, since after slumping the darker back layer drains through the lighter top layer, which results in the risk of the lighter top layer becoming gray.
• the inventor has recognized that this disadvantage can be accepted, since in this way a machine concept can be implemented in which the lighter top layer is in contact with the smooth surface of the central roll in a simple manner occurs, and even in two press nips, so that the lighter ceiling layer is effectively smoothed.
• the White Top Kraftliner can also be effectively dewatered in the press section, since the first press nip and the third press nip are formed as extended press nips by using a shoe press roll. Furthermore, the White Top Kraftliner in the first press nip is drained towards the darker back position due to the effect of the suction roll.
• the dewatering effect in the first press nip can be made more symmetrical in that a press felt is also arranged on the side of the White Top Kraftliner facing away from the suction roll. This also has the effect that the asymmetrical dewatering in a second and third press nip has less of an effect on the sheet symmetry in the press.
• a certain amount of drainage through the lighter top layer is actually desirable in the press section, since in this way more fillers remain in the lighter top layer, which in turn leads to a greater compression of the top layer, which is advantageous.
• a stronger compression of the top layer means that the fibers and the fillers are more firmly anchored and produce fewer defects, such as so-called linting or dusting, in a later printing process.
• a certain dewatering can also be achieved through the darker back layer, for example by the fact that a wire of the first forming unit and a wire of the second forming unit run parallel to one another over a predetermined distance immediately after the rubber zone and that in this At least one drainage unit, for example at least one suction box, is arranged at a predetermined distance on the side of the darker back layer.
• At least one drainage unit for example at least one suction box
• the White Top Kraftliner is deflected downwards by a guide roller after it has slumped. As a result of the downward deflection, centrifugal forces act on the water contained in the White Top Kraftliner, which drive the water out of the White Top Kraftliner through the darker supine position.
• a shoe press roll can also be arranged at the deflection point in order to reinforce the effect
• the invention also relates to the use of the device described above for the production of white top kraftliner.
• the advantages that can be achieved through this use reference should be made to the above description of the device according to the invention.
• FIG. 1 shows a schematic representation of a device according to the invention for producing white top kraftliner.
• a device according to the invention is designated quite generally by 100.
• the device 100 is used to produce a multi-layer fibrous web 102 of the paper type White Top Kraftliner.
• the device 100 comprises a wire section 104 for forming the fibrous web 102, a press section 106 for further dewatering of the fibrous web 102 and a first drying group 108a of a drying section 108 for drying the fibrous web 102 sake only a first part of the drying part 108 is shown.
• the White Top Kraftliner 102 has at least two layers.
• a first layer 110 forms the darker back or the supine position, and a second layer 112 forms the lighter ceiling or the ceiling layer of the White Top Kraft liner 102.
• the weight per unit area of the White Top Kraft liner 102 can be at least 125 g / m 2 , for example.
• the wire section 104 comprises a first forming unit 120 with a first headbox 122, via which pulp suspension is fed which contains, for example, unbleached long-fiber kraft pulp. Furthermore, the wire section 104 comprises a second forming unit 130 with a second headbox 132 to form the second layer 112 of the white top kraftliner 102, via which pulp suspension is fed which contains, for example, bleached short-fiber kraft pulp.
• stationary drainage elements 126 and 136 are arranged in the loop of the screen 124 of the first forming unit 120 and in the loop of the screen 134 of the second forming unit 130.
• the forming units 120, 130 for forming the white top kraftliner 102 are arranged and designed in relation to one another in such a way that the darker back layer 110 formed in the first forming unit 120 in a Gumming zone 140, ie at the couch roll 142, is transferred to the lighter top layer 112 of the white top kraftliner 102 formed in the second forming unit 130.
• the lighter top layer 112 therefore points downwards.
• the White Top Kraftliner 102 is arranged “top on bottom” when it leaves the wire section 104.
• This is actually disadvantageous because after the darker back layer 110 has slumped, drainage takes place through the lighter top layer 112, which results in the risk of the lighter top layer 112 becoming gray.
• the two screens 124, 134 after the couch roll 142 can still be guided over a predetermined distance parallel to one another, in which case they accommodate the rubberized layers 110 and 112 between them. This makes it possible to provide further drainage elements 128 and 138 not only below the sieve 134 but also above the sieve 124, which drain the White Top Kraftliner 102 not only through the lighter top layer 112 but also through the darker back layer 110.
• the stationary drainage elements 126, 128, 136, 138 can be formed by at least one blade and / or at least one foil which, if desired, can be arranged in at least one suction box.
• the White Top Kraft liner 102 formed in the wire section 104 is removed from the wire 134 by a water-absorbing, upper dewatering belt 160 and guided to the press section 106.
• This dewatering belt 160 then guides the fibrous web 102 together with a water-absorbing dewatering belt 162 running under the fibrous web 102 through a first press nip 164 of the press section 106.
• the first press nip 164 is elongated and for this purpose is formed by a lower shoe press roll 166 and an upper, vacuum press roll 168.
• Shoe press rolls usually have a flexible roll shell, which is pressed by a press shoe with a concave press surface to form an extended press nip against a cylindrical counter press roll. Because of the extended dwell time of the fibrous web 102 in the press nip, they enable intensive yet gentle dewatering.
• the fibrous web 102 in the first press nip 164 has a relatively high moisture content, it is sufficient to conserve the volume of the fibrous web 102 if the shoe length of the corresponding shoe press roll 166 is less than 270 mm, preferably less than 220 mm and in particular less than 140 mm.
• the line load in the first press nip 164 should be greater than 100 kN / m, preferably greater than 150 kN / m, and in particular greater than 175 kN / m.
• the shoe press roll 166 of the first press nip 164 has several, preferably three, separately controllable pressure zones arranged next to one another at right angles to the direction L of the web.
• the vacuumed press roll 168 has, like the suction guide rolls wrapped around by the air permeable dewatering belts 160 and 162, of which only one is provided with the reference numeral 170 for the sake of clarity, a perforated roll shell, the interior of which is at least partially connected to a vacuum source . It is also advantageous if at least one of the suction guide rollers 170 is coupled to a drive.
• the cylindrical, suctioned press roller 168 of the first extended press nip 164 has a jacket thickness of at least 40 mm.
• the evacuated press roller 168 can advantageously be coupled with a drive.
• the negative pressure prevailing in the vacuumed press roll 168 not only supports the removal of the water pressed from the fibrous web 102, but also the adhesion of the fibrous web 102 to the upper drainage belt 160, so that the lower drainage belt 162 can easily be removed from the first press nip 164 after the first press nip 164 Fibrous web 102 can be carried away.
• the fibrous web 102 runs together with the upper dewatering belt 160 through a second press nip 172 of the press section 106, which is gebil det from the vacuum press roll 168 and another cylindrical press roll 174 with a smooth outer surface.
• the fibrous web 102 is then guided to a third press nip 176 alone on the smooth outer surface of the press roll 174, which is also designed as an elongated press nip.
• the third press nip 176 is formed by the further, cylindrical press roll 174 and a further shoe press roll 180 arranged over the fibrous web 102 and wrapped around by a water-absorbing drainage belt 178.
• the moisture content in the first press nip 164 is significantly greater than in the third press nip 176, which are both extended press nips, it is sufficient to protect the web volume if the first press nip 164 is at most as long as the third press nip 176 and / or the line load in the first Press nip 164 is at most as large as in the third press nip 176.
• a line load between 100kN / m and 300kN / m, for example approx.
• the shoe used to form the third press nip is preferably longer than the shoe used to form the first press nip.
• the fibrous web 102 within the press section 106 can be acted upon with hot steam via one or more steam blow boxes (not shown in detail).
• the areas designated by 182 in FIG. 1 between the first press nip 164 and the second press nip 172 and between the second press nip 172 and the third press nip 176 are particularly suitable for this.
• the web guidance in the area of the extended press nips 164, 176 can be improved in that the fibrous web 102 wraps around the corresponding cylindrical press roll 168, 174 before and after each extended press nip on a path of at least 20 mm.
• the water-absorbing dewatering belts 160, 162, 178 can advantageously be designed as press felts.
• the upper dewatering belt 178 is removed from the fibrous web 102 after the third press nip 176 and the fibrous web 102 is only on the jacket of the smooth cylindrical press roll 174 until it is transferred to a drying wire 190 of a subsequent drying section 108 for drying the fibrous web 102 continued.
• the cylindrical press roller 174 with an endlessly rotating, semipermeable or impermeable To loop around the smooth transfer tape, which accordingly runs below and together with the fibrous web 102 through the second press nip 172 and the third press nip 176. After the third press nip 176 and a subsequent looping of the smooth central roll 174, the fibrous web 102 can then be transferred from the transfer belt to the dryer fabric 190 of the following dryer section 108 without free tension.
• the cylindrical press roll 174 according to FIG. 1 and the transfer belt mentioned above are so smooth that the fibrous web 102 is sufficiently flattened on the press roll 174 or the transfer belt and the dewatering belt 178 is guided away from the fibrous web 102 after the third press nip 176 can.
• This flattening can be reinforced by a short looping of the lower press roll 174 through the upper dewatering belt 178.
• the fibrous web 102 is supported by the dryer wire 190 and alternately guided in a meandering shape over heated drying cylinders 194 and suction guide rollers 196.
• the axes of the drying cylinders 194 and the axes of the suction guide rolls 196 are vertically offset from one another. In addition, these axes have a horizontal distance from one another which is greater than 80%, preferably greater than 90% and in particular greater than 95% of the sum of the radii of a drying cylinder 194 and a suction guide roll 196.

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Family Applications (1)

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• 2020
  • 2020-01-28 DE DE102020101913.0A patent/DE102020101913A1/de not_active Withdrawn
  • 2020-11-24 WO PCT/EP2020/083153 patent/WO2021151540A1/de unknown
  • 2020-11-24 EP EP20812264.8A patent/EP4097296A1/de active Pending
  • 2020-11-24 CN CN202080094890.0A patent/CN115023519A/zh active Pending

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