JP2008501873A - Method for producing paper web and paper machine - Google Patents

Abstract

  A method for producing a glossy paper web in a paper machine, wherein the paper web is produced using a fiber material suspension comprising partially ash-filled fibers.

Description

  The present invention relates to a method for producing a glossy paper web on a paper machine.

  In paper produced by the prior art, it is confirmed that there is a relationship between black glow and paper roughness and gloss. Black glow is the local densification of a sheet of paper with a high gloss finish on uncoated wood-containing paper, or the local densification of a sheet of coated wood-containing paper. is there. This densification reduces the light scattering interface between the fiber and air. As a result, a transparent portion is generated in the single-wafer tissue during observation with transmitted light. In particular, transparent points occur at the fiber intersections, which are exposed to maximum compressive stress in the calendar as localized points of increased unit area mass. A transparent part in the transmitted light appears dark in the irradiated light. This is because light is transmitted and reflected only to a small part. The paper thus has a “gray” speckled appearance. Black glow is caused by fiber shrinkage in the gloss finish process. The fibers appear through due to the missing boundary layer between the fibers and air and the air and fibers in the lumen, i.e. the fiber void.

  An object of the present invention is to limit the black glow in the paper web.

  According to the present invention that solves this problem, a paper web is manufactured using a fiber material suspension containing fibers partially filled with ash.

  When supplying ash by a fiber filling process, for example, according to German Offenlegungsschrift 10 204 254, the ash settles directly into the fibers and binds to the fibers. As is apparent from microscopic photography, ash also accumulates in the fiber voids. Even in a shrinking fiber, there is a fiber-ash boundary layer and an ash-fiber boundary layer, so that black glow is prevented.

  That is, according to the invention, the black glow index is reduced by at least 10% at the same final roughness. Conversely, for the same black glow index, the final roughness of the paper is reduced by at least 12%.

  Advantageous configurations of the invention are evident from the dependent claims, the description and the drawings.

  In a particularly advantageous manner, the paper web is guided in a paper machine by a calendar having a plurality of nips. In this case, a linear load of 50 kN / m or more is applied to the paper web at the nip.

  In this case, linear loads of 100 kN / m or more or 350 kN / m or more are also particularly advantageous when applied to the paper web.

  It is also advantageous to over-dry the paper web to a moisture of 5% or less and subsequently rewet it to a moisture of 7% or more before the calendar.

  The invention also relates to a paper machine for producing a glossy paper web by the method described above.

  The paper machine has a device for filling the fiber material suspension with ash. The advantage of this device is that it is also effective in online production and offline production of paper webs. That is, even if the apparatus for filling the fiber material suspension and the machine for producing the paper web are not arranged in succession, the papermaking process is used to fill the fiber material suspension with ash. Even if it is performed immediately after, it is effective. By filling the fibers, the paper can be subjected to a higher linear load on the calendar, resulting in a higher smoothness of the paper web.

  Advantageously, this device comprises a static mixer, a preparation device for supplying calcium oxide or calcium hydroxide, a press or dewatering screw, a compensation reactor or leveling screw (Egalisierschneke), and a container used as a crystallization device. And a separate crystallizer and a carbon dioxide storage tank or additional device for recapturing carbon dioxide.

  In an advantageous configuration, the device comprises a high-concentration cleaner and / or a carbon dioxide heater and / or a storage tank for water removed in the press water or dewatering screw.

  It is advantageous if the filtrate of the fiber material suspension obtained in the dewatering screw can be returned via a conduit to a pre-vessel or another apparatus for preparing the fiber material suspension. But there is.

  In addition, it may be advantageous that an additional cleaning device is arranged behind the container used as the crystallization device for cleaning the fiber material suspension.

  More advantageously, the paper machine has a twin wire former. The press part located behind the twin wire former is preferably provided with at least one shoe press. Advantageously, the paper machine has a calendar with a plurality of nips, thereby reducing roughness and increasing smoothness.

  Advantageously, a device for rewetting the paper web is arranged in front of the calendar. Advantageously, rewetting is achieved by a steam spout box, which also increases the gloss of the paper.

  When producing LWC (light weight coated) paper and MWC (medium weight coated) paper, a coating device is preferably additionally used.

  When the fiber material suspension is handled by Fiber-Loading-Technology during papermaking, it results in a completely new product with new and improved properties compared to products known in the market. The process described below makes it possible to precipitate the filler (calcium carbonate) directly during material preparation in a paper mill. This filler is distributed and added exclusively to the fiber material and into the fiber material, in particular into the paper fiber and into the paper fiber.

  By producing a fiber material filled exclusively with precipitated calcium carbonate, in this case, calcium carbonate is added to or deposited in the fiber, and free precipitated calcium carbonate (PCC) formation is Be disturbed. By performing an additional washing step before the beating process and / or after the beating process and / or before the crystallization process in the crystallizer and / or before the headbox tank or before feeding to the paper machine, or press filtrate Is returned to the pre-vessel or another accumulator on the inlet side, so that the constant content of calcium hydroxide is adjusted or adjusted in the fiber filling device feed system. Calcium hydroxide can be fed directly to the fiber material dissolver. The press filtrate can be returned to the material dissolution system. Calcium hydroxide not added to or into the fiber is fed back into the pre-process.

  Only the filler not deposited in or within the fibers, i.e. only free precipitated calcium carbonate, is washed away. The fibers themselves with the filler on the inside and outside do not lose the filler due to the washing process and the return of the press filtrate, so that the advantageous effects of the fiber filling technology persist.

  In particular, according to the invention, the fiber material suspension is also fed into the pressing device for squeezing the filtrate. Subsequently, the filtrate is at least partially returned to the device for dissolving the fiber material suspension, i.e. to the storage container on the inlet side, for example the pre-vessel. Calcium hydroxide is added to the device for at least partially dissolving the fiber material. In a complete material dissolution system, i.e. an apparatus for dissolving fiber material, the pH value is maintained between 7-12, in particular 9-12.

  The aqueous or dry form of calcium hydroxide, or calcium oxide, is incorporated into the aqueous paper fiber material in a range between 0.01% and 60% of the solid fraction present. For the mixing process, a static mixer or pre-vessel or material melting system is used. In this case, the pH value is used in the range between 7 and 12, preferably between 9 and 12. The reactivity of calcium hydroxide is between 0.01 seconds and 10 minutes, preferably between 1 second and 3 minutes. Dilution water is mixed based on the reaction parameters described above.

  Carbon dioxide is incorporated according to the reaction parameters in the wet pulp dimension. In this case, calcium carbonate precipitates in a carbon dioxide atmosphere.

  At the same time, beating energy is supplied in the range between 0.1 kWh and 300 kWh per ton of dry pulp. Compared to a conventional process for producing a fiber material suspension, according to the present invention, a higher beating degree can be achieved in an energy efficient manner. According to the present invention, 50% of beating energy can be saved.

  The high mechanical strength achieved by the high beating degree of the final product works effectively in the production of all paper varieties. This is because the intermediate product produced by the mechanical load due to the process in the different sections of the paper machine, for example in the area where the press part, dry part or paper web is rolled up, and the final product to be produced, This is because the load is mechanically increased by using the take-up machine, the rewinding machine, and the processing machine. The energy supply in the beating process, ie the amount of heat and the heating resulting from the amount of heat, are controlled. Different forms of crystals can be produced depending on the control.

  The pretreatment according to the invention of the fiber material suspension also leads to conditions for better drying. This condition increases the efficiency in producing all types of paper. Advantageously, the residual moisture ranges between 1% and 20%.

  With the present invention, higher whiteness and / or higher optical values with improved brightness only up to 15 brightness points are also achieved in producing all types of paper.

  In particular, when the beating process is not performed, energy between 0.3 kWh / t and 8 kWh / t, in particular between 0.5 kWh / t and 4 kWh / t, is also consumed for the precipitation reaction. It's okay.

  Advantageously, the process temperature is between −15 ° C. and 120 ° C., in particular between 20 ° C. and 90 ° C. Advantageously, rhombohedral, declinated trihedral, spherical crystals are formed. In this case, the crystal has a size of 0.05 μm to 5 μm, in particular 0.3 μm to 2.5 μm.

  In order to produce a fiber material suspension filled with calcium carbonate, static mixer elements and / or movable, in particular rotary mixer elements are used.

  The process can be carried out in a pressure range between 0 bar and 15 bar, in particular between 0 bar and 6 bar. Likewise, the process is preferably carried out at pH values of 6 to 10, in particular 6.5 to 8.5. In this case, the reaction time is between 0.01 seconds and 1 minute, in particular between 0.05 seconds and 10 seconds.

  A further advantage of using the technique according to the invention for the above-mentioned paper varieties is that these paper varieties can be further processed in the calendar. When using fiber filling technology, blackening, i.e., black glow, is avoided by the fiber-filled particles being deposited in and around the fiber and on the fiber.

  The fiber material produced by the fiber-filled combination process technology according to the present invention has a higher dewatering capacity compared to the fiber material produced by the prior art. This dewatering capacity is between 5 ml and 100 ml CSF or up to 0.2 ° to 15 ° SR and depends on the required beating degree and filler content. This fiber material has a lower water holding capacity of about 2% to 25%, depending on the material used for papermaking. Compared to the prior art fiber material, water can be removed from the fiber material suspension more quickly, and the fiber material dries correspondingly more quickly. This fiber material has a positive effect on the printability of the paper varieties produced thereby, which is less rewet and in the papermaking process.

  Hereinafter, the present invention will be described in detail based on examples.

FIG. 1 is a schematic diagram showing the preparation process of a fiber material suspension in a machine for producing a fiber material web;
FIG. 2 shows a black glow as a function of paper web roughness;
FIG. 3 is a diagram showing the configuration of a paper machine for producing glossy paper.

  For the fiber material suspension, a conduit system 1 (FIG. 1) is provided in which control valves 2, 3 are provided. The control valve 2 is arranged in a pipe line 4, and the conduit system 1 is connected to the static mixer 5 via the pipe line 4. Dilution water is supplied to the mixer 5 via the valve 6. A tank 7 or a tank for storing the fiber material suspension is arranged behind the mixer 5 in the flow direction of the fiber material suspension. The fiber material suspension is pumped from the tank 7 to another static mixer 9 via the pump 8. Dilution water is also supplied to the mixer 9 via the valve 10. Similarly, the inflow of the calcium hydroxide suspension is controlled via the valve 11 attached in the pipe 12.

  The calcium hydroxide is provided from the preparation device 13, and solid calcium oxide or calcium hydroxide is supplied to the water in the preparation device 13. For this purpose, water is supplied to the preparation device 13 via a line 14 having a valve 15. The suspension formed in the preparation device 13 is introduced into the conduit 12 via the pump 16.

  Therefore, the fiber material suspension mixed with calcium hydroxide flows from the mixer 9 into the pipe line 17 having the valve 18 toward the dewatering screw 19. Water is removed from the fiber material suspension in the dewatering screw 19, and this water is returned as dilution water to the mixer 5 via, for example, the pipe line 20. As an alternative or in addition, the water removed with the dewatering screw 19 may be led to a storage tank 21 for the fiber material suspension or returned to the mixer 9. In all cases, in the device placed in front of the dehydration screw 19, the pH value can be increased and adjusted by returning water containing calcium hydroxide.

  The fiber material suspension reaches the leveling screw 23 from the dewatering screw 19 via the pipe line 22, thereby uniformizing the fiber material suspension. A container (crystallization apparatus) 25 is disposed behind the leveling screw 23 in the flow direction via a pipe line 24. The container 25 is connected to a carbon dioxide storage tank 30 through a conduit 29 for supplying carbon dioxide, which is provided with valves 26 and 27 and a pump 28. Carbon dioxide is introduced from this carbon dioxide storage tank 30 into the crystallizer 25, thereby forming the desired precipitation of calcium hydroxide and carbon dioxide to form calcium carbonate as a filler in the fiber of the fiber material. Cause a reaction.

  The carbon dioxide storage tank 30 is additionally connected to the leveling screw 23 via another line 31 that is branched from the line 29 and is provided with a valve 32. As a result, carbon dioxide can also be introduced into the leveling screw 23, whereby a precipitation reaction has already been carried out at least partially in the leveling screw 23.

  Similarly, the conduit 29 is connected to the static mixer 34 via another valve 33. This mixer 34 is used to add further carbon dioxide to the fiber material suspension flowing out of the crystallizer 25 via a line 36 provided with a valve 35.

  The fiber material suspension flows from the mixer 34 into the mixing tank 37. Between the mixer 34 and the mixing tank 37, a storage tank 38 which is additionally used as a filtering device may be arranged. From the storage tank 38, the calcium carbonate rich filtrate is returned to the pre-tank 7 or to another device that is pre-positioned to prepare dilution water or fiber material suspension. The mixing tank 37 is provided with a rotor 39 for mixing the fiber material suspension. The fiber material suspension flows directly from the mixer 34 to the paper machine headbox or is subjected to another mechanical treatment, for example in a refiner feed chest.

  The mixer 34 can likewise be fed from the conduit system 1 via the valve 3 and the conduit 40 to which the valve 3 is attached, to a fiber material suspension to which calcium hydroxide has not yet been added.

  Furthermore, from the machine for producing the paper web, in particular the paper machine, white water or process water re-recovered, for example in the screen area of the paper machine, is supplied to the tank 21 or, as already mentioned above, the fiber material suspension. The turbid liquid is supplied from the dewatering screw 19 to the tank 21. The tank 21 is supplied with dilution water, for example, via a pipe line 41 having a valve 42.

  Dilution water mixed with process water flows from the tank 21 into the crystallizer 25 via the pipe line 43, the pump 44, and the valve 45. Therefore, according to the structure shown in FIG. 1 of the device for filling the fiber material suspension with fillers, in particular calcium carbonate, the composition of the fiber material suspension to be formed has a number of influences at different production stages The possibility of

  Advantageously, a high concentration refiner 46 is arranged inside the conduit 4. A heating device 47 for carbon dioxide supplied from the storage tank 30 is also optional. The heating device 47 is operated with hot steam introduced via the inlet 48 and led out again via the outlet 49.

  When producing a web of SC (= supercalendered) paper (FIG. 2), depending on the quality of the paper or SC-A paper or SC-B paper, the roughness R measured in micrometers by the PPS measuring method. And a specified upper limit for the black glow S (blackening index) as a function of roughness. Only papers with values below the upper limit for roughness and darkness can be used.

  Glossy finished paper is particularly suitable for intaglio printing methods. In order to obtain the required smoothness of the paper surface, the paper is smoothed in the calendar nip. This is because otherwise there will be defects in the printed image. However, if a calendar with too few nips is used and too high a nip pressure is applied to the paper web, some of the fibers are crushed, which makes the fibers appear transparent. Due to the high paper quality, such obstacles should not exceed the limits shown in FIG. This limit is also defined for different paper varieties by the limit curve G shown in FIG. Even if the percentage of used paper (paper that has been deinked) is too high, the quality of the paper is made worse. The large roughness causes many print defect points ("netting"). On the other hand, if many nips are used in the printing process and operated at the same time with a small pressure or a small linear force, the production equipment is uneconomical. Thus, according to the present invention, the quality of the paper is improved by filling the voids in the fibers with ash. This allows for a significantly higher linear force at the calendar nip and the number of calendar nips can be reduced compared to the prior art. Therefore, the efficiency of the calendar can be increased at the same time as the black glow is reduced.

  A paper machine (FIG. 3) suitable for producing glossy paper has a twin wire former 50 and a press part 51 with two pairs of rollers arranged in series, In these roller pairs, each press roller is formed as a shoe press roller. The press part 51 is followed by a single-row dry part 52. In the calendar 53 having a large number of roller pairs, the paper web is smoothed. Subsequently, the paper web is wound up in the winding device 54.

FIG. 2 is a schematic diagram illustrating a preparation process of a fiber material suspension in a machine for producing a fiber material web. It is the figure which showed the black shine which is a function of the roughness of a paper web. It is the figure which showed the structure of the paper machine for manufacturing glossy paper.

Claims (17)

  A method for producing a glossy paper web on a paper machine, characterized in that the paper web is produced using a fiber material suspension comprising fibers partially filled with ash.   The method of claim 1, wherein the paper web is guided by a calendar having a plurality of nips.   The method according to claim 2, wherein a linear load of 50 kN / m or more is applied to the paper web at the nip.   The method according to claim 1 or 2, wherein a linear load of 100 kN / m or more is applied to the paper web.   The method according to claim 1 or 2, wherein a linear load of 350 kN / m or more is applied to the paper web.   The paper web according to any one of the preceding claims, wherein the paper web is over-dried to a moisture of 5% or less and subsequently rewetted to a moisture of 7% or more before the calendar (53). Method.   A glossy paper web according to any one of claims 1 to 6, characterized in that it has a device for filling the fiber material suspension with ash from the fiber material suspension. Paper machine for manufacturing.   The device for filling the fiber material suspension with ash comprises a static mixer (5, 9), a preparation device (13) for supplying calcium oxide or calcium hydroxide, and a press or dewatering screw (19). A compensation reactor or leveling screw (23), a vessel (25) used as a crystallizer, another static mixer (34), and a carbon dioxide storage tank (30) or to recapture carbon dioxide. The paper machine according to claim 7, further comprising:   9. A high-concentration cleaner (46) and / or a carbon dioxide heater (47) and / or a storage tank (21) for water removed in the press water or dewatering screw (19). The paper machine described.   The filtrate of the fiber material suspension obtained in the dewatering screw (19) is fed via the line (20) to the pre-tank (7) or to the other part for preparing the fiber material suspension. The paper machine according to claim 8 or 9, wherein the paper machine can be returned to the apparatus.   11. A paper machine according to any one of claims 8 to 10, wherein an additional washing device is arranged behind the container (25) used as a crystallization device for cleaning the fiber material suspension. .   12. A paper machine according to any one of claims 7 to 11, comprising a twin wire former (50).   13. A paper machine according to any one of claims 7 to 12, comprising a press part (51) with at least one shoe press.   14. A paper machine according to any one of claims 7 to 13, comprising a calendar (53) with a plurality of nips.   15. A paper machine according to claim 14, wherein a device for rewetting the paper web is arranged in front of the calendar (53).   16. A paper machine according to claim 15, wherein the device for rewetting the paper web is a steam spout box.   The paper machine according to any one of claims 7 to 16, comprising a coating device.

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