EP1152086A2 - Process and apparatus for making a multiply and /or multilayer fibrous web - Google Patents

Abstract

To form a multi-layer fiber web (34), especially of paper or cardboard, at least one of the two outer layers (34',34) is from a fiber material with at least one additive at the fiber surfaces. For a multi-layer paper/cardboard web, the additive is deposited on the surfaces of hollow fibers and, in addition, within the hollow fibers and at their walls. The additive includes a filling material, and the outer layers of the web have a higher filling material content than a center layer. Calcium carbonate is used as the additive or filling material at the wet fibers, or is used as a precipitate. To apply the calcium carbonate to wet fibers, a medium with calcium oxide and/or calcium hydroxide is used so that at least a portion associates with the water at the fibers. The treated fibers are exposed to carbon dioxide to give a chemical reaction with the calcium carbonate at the fiber surfaces. The calcium oxide and/or calcium hydroxide is used at a rate of 0.1-50.0 wt.% of the fiber dry weight. The fibers are treated with carbon dioxide in a closed vessel, as a gas under pressure, during a mixing phase where a high shear effect is applied to the fibers using an energy of at least 10-50 W/hr/kg based on the dry weight. The fiber material is derived in a pulper from cellulose or used paper materials, or it is a never-dried pulp. An Independent claim is included for a papermaking/cardboard production machine, to produce a multi-layer web, with stock inlet channels (36,40) charged with fiber materials where an additive is deposited on the fiber surfaces at least partially. Preferred Features: The multi-layer stock inlet assembly (28) is structured to form a web with two outer layers or a sandwich with an intermediate layer, where the pulp for the outer layers has fibers with an additive on their surfaces.

Description

The invention relates to a method for forming a multilayer and / or multi-layer fibrous web, in particular paper or cardboard web. It also relates to a device according to the preamble of the claim 17th

The one that is particularly necessary for economic and ecological reasons careful handling of raw material resources manifests itself in the Paper production in ever lower basis weights of the paper web as well as in the partial replacement of the fibrous material with fillers. This poses not only for the paper producer, but also for the same extent Paper machine manufacturers pose a challenge. Despite these measures the paper quality and productivity of those concerned Paper machine maintained or even further improved. there so-called multi-layer technology is increasingly used Use, in contrast to conventional multilayer sheet formation the web is constructed from individual layers with a very low basis weight becomes. The different that come out of the headbox Suspension jets in a sheet formation zone dewatered at the same time. Accordingly, different raw materials can be used for structuring of the sheet can be used. Become cheaper raw materials used, the quality should at least be maintained. With the same The use of raw materials is about improving this quality. Here play among others the strength, the optical properties and the processability of the end product plays a crucial role. For example in the case of graphic papers, it is economical and printing For reasons desirable, a higher filler content in the outer layers and to have a lower filler content in the middle class. The increased filler content in the outer layers results in an improved Printability and opacity. Even with the use of multi-layer technology using a multilayer headbox with very high filler content in the partial suspension streams forming the outer layers the results in this regard are still insufficient, which is due in particular to the low retention of the fillers is. For the partial suspension flows of the respective layers forming the outer layers Headbox therefore requires a greatly increased filler content. The poor retention results in a relatively high load of the white water cycle with fillers. As a result of the washout the outer layers due to the respective drainage conditions there is only a limited enrichment of the outer layers of the paper with ashes.

The aim of the invention is to provide an improved method and an improved To create device of the type mentioned, in which the previously mentioned disadvantages are eliminated and in a more economical manner in particular an increase in the enrichment of the outer layers of the Fibrous web with fillers possible beyond the previous limits is.

With regard to the method, this object is achieved according to the invention solved that at least one of the two outer layers and / or layers the fibrous web is produced using fiber material whose wetted fiber surfaces at least partially contain at least one additive, preferably filler, or its fibers at least partially with at least one additive, in particular filler, were loaded.

The term "wetted fiber surfaces" can mean all wetted surfaces of the individual fibers. This is especially the case Case recorded in which the fibers with the additive or filler both are loaded on their outer surface and inside (lumen).

Due to this special type of loading, the retention in the Outer layers or layers increased drastically, which can be attributed to this is that the additives, especially fillers, adhere well to the Fiber surface, partly are also bound to the inner surface of the fiber. This Binding of the fillers to the fiber surface is relatively strong. Thereby there is a high retention of the filler of the outer layers or -Layers of the paper with little white water pollution and relatively less Filler concentration of the suspension in the outer layers or layers in the headbox. If necessary, you can also use conventional Way to further increase the filler content of the layers or layers. The invention is not only in the formation of a fibrous web from in the z direction, i.e. Thickness direction, coated fiber suspensions with different additive or filler contents, but basically even when a fibrous web is formed from layers layered in the z direction Fibrous suspensions with the same filler content can be used. Moreover The invention can be used not only in the preferred multilayer sheet formation, but basically also in the conventional multi-layer sheet formation are used. It is essential that for the substances in a so-called "fiber loading" is used in the outer layers or layers described as such in US-A-5,223,090. When in this The process described in the publication will apply to the entire fabric accordingly treated. Otherwise, when storing additional or

Filler in the respective outer layer or layer, however, in particular in this way proceed as described in US-A-5,223,090. The The content of this document is hereby incorporated by reference into the present Registration included.

The additive is expediently on the outer surfaces of the Hollow fibers attached, wherein he preferably also both in the inner Cavities as well as embedded in the walls of the hollow fibers becomes. The additive is thus applied to the "wetted" fiber surface, So both on the outer surface and on the inside Cavities and also deposited in the walls of the hollow fibers.

In a particularly advantageous preferred embodiment of the invention Processes are used to form at least two and in particular at least three-layer or three-layer fibrous web both or only one of the outer layers or layers of the fibrous web produced using fiber material, on the wetted Fiber surfaces at least partially at least one additive has been. Both or only one outer layer or - location of the fibrous web are produced using fiber material, the hollow fibers at least partially with at least one additive were loaded, preferably again both on the outer surfaces the fibers as well as in the interior.

The additive can in particular comprise at least one filler.

It is advantageous to form at least two and in particular at least three-layer or layered fibrous web at least one of the two outer layers or layers with a higher additional or. Filler content generated as the at least one middle layer or layer.

In an expedient practical embodiment of the invention The process uses calcium carbonate as an additive or filler wetted fiber surfaces.

A preferred advantageous embodiment is characterized in that a calcium oxide and / or calcium hydroxide agent is added to a moist, disintegrated fiber material so that at least some of it is associated with the water present in the fiber material, and that the treated material is added to the moist, disintegrated fiber material Carbon dioxide is applied to the fiber material in such a way that the addition of calcium carbonate to the wetted fiber surfaces results from a corresponding chemical reaction. This does not mean that ₂ water of the fibrous suspension to be chemically reacted by addition of CaO and / or Ca (OH).

The agent containing calcium oxide and / or calcium hydroxide expediently in a proportion of approximately 0.1 to approximately 50% by weight based on the dry weight of the fiber material in question. The fiber material is advantageously closed Containers loaded with carbon dioxide containing the carbon dioxide gas in question is put under pressure accordingly.

It is advantageous if the fiber material during a mixing process to which it is exposed to a particularly high shear effect with Carbon dioxide is applied. The mixing process is expediently carried out with a shear effect that is at least so high that an energy input of at least about 10 to 50 watt-hours per kilogram Fiber on a dry weight basis.

In principle, it is also possible to form a two-layer or -layer fibrous web only one of the two layers or layers of To produce fibrous web using fiber material on the wetted fiber surfaces at least partially at least one additive was added in the manner described above.

Furthermore, it is advantageous if the fiber material is preferred on the one hand pulp dissolved in a pulper or waste paper dissolved with additives and on the other hand non-dried fiber ("never dried pulp ") is used. Both uses bring depending on the application both process engineering (including short process times), process engineering (including good controllability) as well as cost-effective (including cost saving potential) Benefits.

The device according to the invention is accordingly characterized in that that at least one to form an outer layer and / or The outer layer of the fibrous web provides the stock suspension feed can be loaded with fiber material, at least on the fiber surfaces partially at least one additive is deposited.

In an expedient practical embodiment, the device comprises at least one multilayer headbox, which is used to form two Layers or to form two outer layers and at least one interposed inner layer at least two or at least has three stock suspension feeders and in which only one or only the two stock suspension feeds used to form a respective outer layer are loaded with fiber material, at the Fiber surfaces at least partially at least one additive has been.

In principle, such an embodiment is also conceivable in the case of education two layers or to form two outer layers and at least an interposed inner layer at least two or at least three each having at least one stock suspension feed Headboxes include and that only one or only two of education a headbox serving with a respective outer layer with fiber material can be acted upon, at least partially on the fiber surfaces thereof an additive is attached.

The additive or filler can again be calcium carbonate, for example act.

Such an embodiment is also conceivable, for example, in which the device comprises at least one multilayer headbox which is used for Formation of two layers has two stock suspension feeders and in which only one of these two stock suspension feeds with fiber material can be acted on, on the fiber surfaces at least partially at least one additive is deposited in the manner described above has been.

According to a further expedient embodiment, the device comprises to form several layers at least two headboxes, from which can be loaded with at least one fiber material, at the wetted fiber surfaces at least partially at least one additive in the manner described above.

Furthermore, it is advantageous if the fiber material is preferred on the one hand pulp dissolved in a pulper or waste paper dissolved with additives and on the other hand non-dried fiber ("never dried pulp ") can be used.

In the subclaims are further advantageous refinements of the invention Method and the device according to the invention specified.

Figur 1

ein vereinfachtes Prozessdiagramm zur möglichen Behandlung von Faserstoff, der anschließend zur Bildung einer jeweiligen Außenschicht der betreffenden Faserstoffbahn verwendet wird,

Figur 2

eine vereinfachte schematische Darstellung der bei der Behandlung des Faserstoffes initiierten chemischen Reaktionen und

Figur 3

eine schematische Darstellung eines Ausführungsbeispiels eines Stoffauflaufs der betreffenden Papiermaschine.

The invention is described below with reference to exemplary embodiments with reference to the drawing; in this show:

Figure 1

a simplified process diagram for the possible treatment of fibrous material, which is then used to form a respective outer layer of the fibrous web in question,

Figure 2

a simplified schematic representation of the chemical reactions initiated in the treatment of the fiber and

Figure 3

is a schematic representation of an embodiment of a headbox of the paper machine in question.

Figure 1 shows a simplified process diagram for possible treatment of pulp, which is then used to form at least one of the two outer layers of a multilayer fibrous web used becomes. The fibrous web can in particular be a paper or Trade cardboard web.

The wetted fiber surfaces of the fiber material in question are used at least partially at least one additive, preferably a filler, attached. As such, in the present embodiment Additive or filler calcium carbonate, especially precipitated calcium carbonate, attached. The filler is deposited on the outer surfaces of the hollow fibers as well as an intercalation in the wetted internal cavities (lumens) and the walls of the Hollow fibers.

Molekulargewicht: 56 + 18 ⇒ 74 According to FIG. 1, the present fibrous stock material 10 is processed in a pulper 12 to a fibrous material 14 in which the fibers are then at least essentially already separated, that is to say separated from one another. The fiber material 14 at least partially contains water. This can be between the fibers as well as in the interior (lumens) and in the walls of the hollow fibers. The fiber material 14 can be provided, for example, in the form of a so-called "dewatered crumb pulp" (cf. US Pat. No. 5,223,090), which means that although water is stored in the hollow fibers of the fiber material 14, there is no free one in the fiber material Water is included. Furthermore, the pulp 12 can be used, on the one hand, preferably pulp 12 or pulp paper with additives, and on the other hand non-dried pulp ("never dried pulp"). The fiber material 14 is then fed to a collecting container 16 or the like, in which an agent 18 containing calcium oxide and / or calcium hydroxide (slaked lime) is added in such a way that at least a part thereof coincides with that in the fiber material, ie between the fibers, in the hollow fibers and associated in their walls, existing water. The following chemical reaction occurs (see also Figure 2):

Molecular weight: 56 + 18 ⇒ 74

Molekulargewicht: 74 + 44 ⇒ 100 + 18 Following the press 20, the fiber material 14 is fed to a "fiber loading" reactor 24. In this reactor 24, the fiber material 14 is then exposed to carbon dioxide (CO ₂ ) in such a way that calcium carbonate (CaCO ₃ ) is deposited on the wetted fiber surfaces. The following chemical reaction occurs:

Molecular weight: 74 + 44 ⇒ 100 + 18

For example, 560 kg CaO and 440 kg CO _{2 result in} 1 ton calcium carbonate.

This can be done, for example, via a valve 26 designed as a rotary valve suitably treated fiber material 14 then the respective one outer layer assigned stock suspension feed of the headbox 28 of the paper machine 30 in question.

The calcium oxide and / or calcium hydroxide can be in the collecting container 16 contained means 18, for example, in a proportion of about 0.1 up to about 50% by weight based on the dry weight of the fiber material in question be added.

The reactor 24 expediently comprises a closed container, pressurized with the relevant carbon dioxide gas becomes. Furthermore, the fiber material 14 in this reactor 24 can be one Be subjected to mixing process, in which there is a particularly higher Is exposed to shear. The exposure to carbon dioxide then takes place during the mixing process. This mixing process can for example with a shear effect, at least so It is high that there is an energy input of at least about 10 to about 50 Watt hours per kilogram of fiber on a dry weight basis.

FIG. 3 shows a possible embodiment of a headbox 28 in FIG paper machine 30 shown in FIG. 1.

The headbox 28 is in the z direction, i.e. in the thickness direction of the to be formed Fiber web 34, sectioned. In any resulting y in the transverse direction In the present case, sections are three arranged one above the other Stock suspension feeders 36, 38 and 40 are provided, respectively into a corresponding section of a section divided by slats 42 Chamber 44 of the headbox 28 open. Between these also in the transverse direction y has correspondingly divided chamber 44 and a nozzle 46 the headbox 28 has a turbulence generator 48. In the present case the fins 42 also extend into the turbulence generator 48, so that this is also sectioned accordingly. Even the interior of the Nozzle 46 can be sectioned accordingly, for which purpose in the present case for example, slats 50 can be provided. This results in a Multi-layer headbox to form a multi-layer, in the present Case of a three-layer fibrous web 34.

Each of the transversely y resultant section is respectively assigned to a mixer section 52 in which a portion of the suspension flow Q _H is a partial suspension stream Q _L admixed. These two partial suspension streams can have a different consistency, for example. The suspension partial flow Q _H fed to the headbox 28, for example via a transverse distributor line 54, is fed to the various section mixers 52 via branch lines 56. The suspension partial flow Q _L fed to the headbox 28 via a transverse distributor line 58 is fed to the various section mixers 52 via branch lines 60 and corresponding metering devices 62. The metering device 62 can comprise corresponding valves, for example.

The mixed flow Q _M obtained by a respective section mixer 52 is divided between the three stock suspension feeds 36, 38 and 40 of a respective section.

In the two outer stock suspension feeders 36 and 40, the Formation of the upper and lower layers 34 ', 34 "of the fibrous web 34 serve, each leads a feed line 64 of a metering device 66, via the respective stock suspension feed 36 or 40 each fiber material is supplied, in the hollow fibers, an additive, preferably a filler that is stored. The fiber material in question can a distributor line 68 running in the transverse direction is supplied, from that of a respective section resulting in the transverse direction branch the lines 64 assigned to the headbox 28.

The various supply lines 64 each open at an angle α a feed line 70, via which the fiber material, preferably filled with filler a further additive, preferably diluent or White water, can be mixed. This additive can also be used for example again via transverse distribution lines 72 are fed, of which the various, the individual are in Branch off the supply lines 70 assigned to the transverse direction of the sections.

A valve 74 is provided in each of the feed lines 70.

The angle α is expediently chosen so that the respective Dosing device 66 of the substance suspension feed 36 in question or 40 total current supplied remains constant regardless of the ratio, in which the dilution water is added.

Correspondingly, the various branch lines 60 can each open into the relevant section mixer 52 at such an angle that the mixed flow Q _M resulting at the outlet of the respective mixer 52 remains constant irrespective of the ratio in which the two partial substreams Q _H and Q _{L to} the headbox 28 are supplied. Instead, however, valves can also be provided, for example, between the cross line 54 and the section mixers 52, the mixed flow Q _M in the event of a change in the ratio between the two partial suspension flows Q _H and Q _L then being actuated accordingly by both these valves and the valves 62 is kept constant.

Reference list

10th

Source material

12th

Pulper

14

Fiber material

16

Collection container

18th

Agent containing calcium oxide and / or calcium hydroxide

20th

Press

22

Press water

24th

reactor

26

Valve

28

Headbox

30th

Paper machine

34

Fibrous web

34 '

Upper layer of the fibrous web

34 "

Lower layer of the fibrous web

36

Stock suspension feed

38

Stock suspension feed

40

Stock suspension feed

42

Slat

44

chamber

46

jet

48

Turbulence generator

50

Slat

52

Section mixer

54

Distribution line

56

Branch line

58

Distribution line

60

Branch line

62

Dosing device

64

Supply

66

Dosing device

68

Distribution line

70

Supply

72

Distribution line

74

Valve

Q _F

Fiber material

Q _H

Partial suspension stream

Q _L

Partial suspension stream

Q _M

Mixed flow

Claims (26)

Method for forming a multilayer and / or multilayer fibrous web (34), in particular paper or cardboard web,
characterized in that at least one of the two outer layers (34 ', 34 ") and / or layers of the fibrous web (34) is produced using fiber material (14), on the wetted fiber surfaces of which at least partially an additive has been attached. Method according to claim 1,
characterized in that the additive is attached to the outer surfaces of the hollow fibers. The method of claim 1 or 2,
characterized in that the additive is additionally incorporated both in the internal cavities and in the walls of the hollow fibers. Method according to one of the preceding claims,
characterized in that in order to form an at least two-layer and in particular at least three-layer or layered fibrous web (34) both or only one of the outer layers (34 ', 34 ") or layers of the fibrous web (34) using fiber material (14 ) are generated, on the wetted fiber surfaces of which at least partially at least an additive has been attached. Method according to one of the preceding claims,
characterized in that the additive comprises at least one filler. Method according to one of the preceding claims,
characterized in that at least one of the two outer layers (34 ', 34 ") or layers with a higher additive or filler content than the at least one to form an at least two-layer and in particular at least three-layer or layered fibrous web (34) Middle layer or layer is generated. Method according to one of the preceding claims,
characterized in that calcium carbonate is added to the wetted fiber surfaces as an additive or filler. Method according to one of the preceding claims,
characterized in that precipitated calcium carbonate is added to the fiber surfaces as an additive or filler. Method according to one of the preceding claims,
characterized in that for the addition of calcium carbonate to a moist fiber material (14) a calcium oxide and / or calcium hydroxide-containing agent (18) is added so that at least a part thereof associates with the water present in the fiber material (14), and that so treated fiber material (14) is subjected to carbon dioxide in such a way that the addition of calcium carbonate to the fiber surfaces results from a corresponding chemical reaction. Method according to claim 9,
characterized in that the agent containing calcium oxide and / or calcium hydroxide is added in a proportion of about 0.1 to about 50% by weight, based on the dry weight of the fiber material (14) in question. A method according to claim 9 or 10,
characterized in that the fiber material (14) is charged with carbon dioxide in a closed container (24) which is pressurized accordingly with the carbon dioxide gas in question. Method according to one of the preceding claims,
characterized in that the fiber material (14) is subjected to carbon dioxide during a mixing process in which it is exposed to a particularly high shear effect. Method according to claim 12,
characterized in that the mixing process takes place with a shear effect which is at least so high that there is an energy input of at least about 10 to about 50 watt-hours per kilogram of fiber on a dry weight basis. Method according to one of the preceding claims,
characterized in that only one of the two layers or layers of the fibrous web (34) is produced using fiber material (14) to form a two-layer or layered fibrous web (34), at least partially at least one additive corresponding to its wetted fiber surfaces was deposited. Method according to one of the preceding claims,
characterized in that pulp or waste paper with additives added to a pulper (12) is preferably used as the fiber material (14). Method according to one of the preceding claims,
characterized in that non-dried pulp ("never dried pulp") is used as the fiber material (14). Device (30) for producing a multilayer and / or multilayer fibrous web (34), in particular paper or cardboard web, with at least one headbox having at least one stock suspension feeder (36 - 40), in particular for carrying out the method according to one of the preceding claims,
characterized in that at least one material suspension feed (36, 40) provided for forming an outer layer (34 ', 34 ") and / or outer layer of the fibrous web (34) can be loaded with fibrous material (14), at least some of which has an additive attached to the fibrous surface thereof is. Device according to claim 17,
characterized in that the respective stock suspension feed (36, 40) can be acted upon with fiber material (14) in which the additive is attached to the outer surfaces of the hollow fibers. Device according to claim 17 or 18,
characterized in that the respective stock suspension feed (36, 40) can be acted upon with fiber material (14), in which the additive is additionally embedded both in the internal cavities and in the walls of the hollow fibers. Device according to one of claims 17 to 19,
characterized in that it comprises at least one multilayer headbox (28) which has at least two or at least three stock suspension feeds (36-40) to form two layers or to form two outer layers (34 ', 34 ") and at least one inner layer arranged between them, and in which only one or only the two suspension suspensions (36, 40) used to form a respective outer layer (34 ', 34 ") can be loaded with fiber material (14), at least some of which has an additive attached to its fiber surfaces. Device according to one of claims 17 to 20,
characterized in that it comprises at least two or at least three headboxes each having at least one stock suspension feeder to form two layers or to form two outer layers and at least one inner layer arranged therebetween, and that only one or only the two headboxes with fiber material used to form a respective outer layer (14) can be acted upon, on the fiber surfaces of which at least partially at least one additive is attached. Device according to one of claims 17 to 21,
characterized in that the respective stock suspension feed (36 - 40) or the respective headbox can be acted upon with an additive comprising at least one filler. Device according to one of claims 17 to 22,
characterized in that it comprises at least one multi-layer headbox (28) which has two stock suspension feeders to form two layers and in which only one of these two stock suspension feeders can be loaded with fiber material (14), on the fiber surfaces of which at least partially at least one additive has been appropriately attached. Device according to one of claims 17 to 23,
characterized in that it comprises at least two headboxes to form a plurality of layers, at least one of which can be loaded with fiber material (14), on the fiber surfaces of which at least partially at least one additive has been appropriately attached. Device according to one of claims 17 to 24,
characterized in that pulp or waste paper dissolved with additives can preferably be used as the fiber material (14) in a pulper (12). Device according to one of claims 17 to 25,
characterized in that non-dried pulp ("never dried pulp") can be used as the fiber material (14).

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