EP2255035B1 - Headbox for a paper or board machine - Google Patents

Description

The invention relates to a headbox for a paper or board machine according to the preamble of claim 1.

Furthermore, the invention relates to a paper or board machine with such a headbox.

Paper or cardboard is a flat material consisting of fibers predominantly of vegetable origin and of excipients. The production of this material takes place industrially mostly by means of a paper machine, such as a Fourdriniermaschine. In the wet end of the paper machine, the dewatering of water-dispersed fibers, mostly wood fibers. One speaks in this context of a Feststoffaufschwemmung or a pulp suspension, often short accepts, pulp or simply fabric, as long as undiluted and stock. The fabric is by means of a headbox on a sieve, which also as a double screen, for example, with a lower sieve and an upper sieve like in the WO 01/83882 A2 described, may be formed, applied. The fabric applied to the screen belt is also referred to as a paper web or in short as a web.

The main component of the introduced into the headbox pulp suspension and thus the finished paper or cardboard are vegetable fiber raw materials, also called pulp, serve as their main source of wood, but increasingly also recyclable waste paper or man-made fibers. On the other hand, the non-fibrous starting materials of papermaking or paperboard production are referred to as paper auxiliaries or simply as auxiliaries.

The excipients include in particular substances such as fillers or any kind of chemicals, it is also called paper chemicals. In connection with the latter, so-called retention agents are of importance, which contribute in particular to the retention of the fillers and fines in the paper web, that is to the binding of fillers and fines to the fibers.

The main task of a headbox on a paper machine is to locally, ie in width, short CD for "cross direction", the fiber and auxiliarieshaltige suspension, and temporally, ie in the direction of the paper machine, short MD for "Machine Direction", evenly distributed on the rotating screen belt. It is known to form multilayer webs by means of headboxes in which the dispensing head is divided into sections. During the dewatering process, a fibrous felt is formed from the pulp suspension during sheet formation, which is then compacted and dried in the dryer section of the paper machine.

Headboxes are known in different forms. In order to achieve a uniform flow of the paper stock on the forming screen or on the forming screens, the headbox according to the DE 696 13 689 T2 an inlet header or manifold, which typically has a tapered configuration. Between the inlet header and a stowage device, the latter is also referred to as a nozzle of the headbox, can a large number of distribution pipes, which are regularly arranged in a kind of tubular battery, are located.

A shaper and a headbox for such a shaper are for example from the WO 02/063097 A2 known. The headbox comprises at least one stock suspension feed, a multi-channel turbulence block, and / or a multichannel tubular generator, and a headbox nozzle whose suspension jet impinges on a free or exposed surface of a dewatering belt, with at least a portion of the channels and / or headbox nozzle associated with eddy forming means are to produce in the guided through the channels in question suspended partial streams or in the headbox vortex flows, and wherein the suspension jet is at least partially covered by a wall on its side facing away from the drainage tape side.

The DE 697 19 756 T2 describes a headbox having means for combining a dilution flow with the stock flow derived from the inlet head of the paper machine, wherein the dilution liquid, which is preferably dilution water, enters into connection with the stock flow preferably from the inlet head in conjunction with the head Tube manifold occurs, which is located after the inlet head. In this headbox construction, the basis weight of the web across the wire width can be regulated by passage regulating valves which allow the desired dilution flow to be passed to various locations across the width of the headbox.

The EP-A-0 745 721 describes a pulp feed system for a multi-layer casserole and method in operation of a multi-layer casserole in which a pulp composition is fed into each inlet manifold of the multi-layer casserole made from the same virgin stock by adding the necessary chemicals and fillers to separate sections of the virgin stock. In the substance delivery system of Multilayer headbox is passed at least one dilution water line.

Of the DE 697 15 900 T2 For example, a multi-layer casserole may be taken for a paper or board machine, where the multi-layer casserole has distribution valves for dilution water across the width.

From the DE 699 20 426 T2 discloses a method for applying a layer of admixture in the web former unit of a board machine, in which two partial flows are generated from a same Zwischenganzstoff. To the one partial flow from which the side is formed, which is arranged on the side of the layer to be combined, the admixtures are added at a point in front of the pump, at a point after the pump and / or at the point after the machine screen, to increase the fines content and the bond strength between the sides. Thereafter, the sub-streams enter a multi-layer headbox, conventionally inlet heads, a tube header connected to each inlet head, an intermediate chamber connected to the tube header, a turbulence generator and turbulence tubes, a bleed nozzle cone downstream of the turbulence generator, and wings forming the Separate layers in the outlet nozzle cone has.

As indicated in the introduction, the substance is conventionally admixed, in front of the headbox, with retention aids and flocculants, which, as is known, serve to control the drainage and to control the consistency of the pulp. In paper or board production, they fulfill the task of effecting the linking of fibers and fillers by transshipment or bridging and to influence the retention and the drainage behavior favorably in terms of product quality.

Used as retention agents are high molecular weight compounds such as polyamines, polyamidoamines, polyacrylamides, polyethyleneimines, cationic starch and guar derivatives. The drainage accelerators used are polyamines and polyethylenimines.

So far, in the papermaking process, as is apparent from the above-cited prior art, in particular the retention agent is usually added before and / or after the classifier, but before the headbox, in any case before or at the latest in the distributor. Classifiers or sorters, also called screens in paper language, can be designed, for example, as vertical classifiers or as machine screens. They are known to be used to clean the pulp suspensions before they are passed on to the headbox.

Attempts by the applicant for deflocculation of pulp suspensions by increasing the pressure loss in the headbox have shown that this measure greatly reduces the effect of the retention agent metered in before or shortly after the sifter.

Of the DE 696 13 689 T2 a similar finding can be taken. It is stated that polymers as adjuvants lose their effectiveness when exposed to the increasing thrust that is often present in the stock as it moves toward the headbox outlet. This is because the polymers have a high molecular weight and break apart their long chains under the action of the thrust of the pulp suspension. Other additives, such as fillers, would ideally not be evenly distributed across the thickness or in the z direction of the paper web, but would rather concentrate on the surfaces. The DE 696 13 689 T2 recommends, therefore, for a system for injecting additives into the headbox, to inject components for modifying the stock in the direction of the thickness of the paper web in a controlled manner, in particular to introduce plasticizers at a selected level in the direction of thickness into the formed paper web and over a large number of Discharge feed lines into the intake manifold of a headbox. Plasticizers are known to have the task, the To improve the suppleness, creasability, stretchability, absorbency and satinability of paper as well as to prevent dusting. Substances such as paraffins, quaternary ammonium compounds, polyethylene glycols or polyalcohols are used.

Quite in this sense also argues the DE 102 55 842 A1 in which a method and a device for introducing chemicals into a fiber suspension is to be taken. According to this document, efforts have been made to exploit turbulence inducing devices in paper and board making processes for this purpose by adding chemical components to these sorters and pumps. The rapid rotation of the sorter or pump rotor blades produces extremely strong shear fields which cause turbulence. In practice, the resulting shear fields may even prove too strong and then lead to fragmentation of polymer chains, which reduces the effect of the polymers as retention aids. Fiber suspensions typically tend to flocculate, which is a problem with regard to optimally mixing chemicals together. Dissolve the flake structure can be loud DE 102 55 842 A1 by creating sufficient turbulence in the flow. An advantageous method for fluidizing the fiber suspension consists in the generation of turbulence in a step-shaped extension part of the flow channel of the fiber suspension. The intensity of the shear field generated in the rotationally symmetric extension of the flow channel is sufficient to provide optimum conditions for mixing the chemicals, but the shear stresses remain considerably less than, for example, in the shear field generated by pump or sorter blades. The optimal method of mixing chemicals under the entire volume of the fiber suspension is to introduce the various components into the tube extension so that they are directed to the interface of the returning vortex forming behind the extension and thus into a sufficiently intense, but the Polymer Molecules Chains advised unbreaked shear field. The dosage of chemicals can be either at one single or at several consecutive tube expansion stages.

All the above states of the art have, according to the findings described above, the disadvantage that the paper chemicals, in particular the retention agent, are added in the headbox in such a way that they are destroyed by a strong pressure drop or a turbulence field with strong shear fields. As a result, the effect of, in particular, the high molecular weight or polymeric paper chemicals, for example the retention agents, such as starch, is reduced or can be reduced.

In the WO 03/048452 For example, a method and method of making a multilayer fibrous web is described. It is a supply of at least two different pulp suspensions comprises by a headbox. The headbox separates by means of partitions the fiber streams from each other and leads them to a sheet forming device. Furthermore, the headbox forms a water layer with a transversally uniform flow at an outlet at the end of a lamella. The water layer is shaped such that it forms a continuation or extension of the lamella, whereby a mixing of the flow layers of the pulp suspensions is prevented. The sipe is freely movable in a substantially vertical direction to allow pressure equalization between the layers of pulp suspensions which are separated by the sipe, thereby reducing wake vortex flow effects downstream of the end edge of the sipes.

From the DE 101 59 412 A1 is a headbox, in particular multi-layer casserole, a paper machine out. This comprises a nozzle whose interior is at least partially subdivided by at least one partition wall or lamella.

From the WO 82/03413 , an international priority application of the DE 31 12 972 A1 , a layer separation by means of a multiple nozzle is already known.

The last three states of the art have the disadvantage that the Füllbeziehungsweise fines and optionally the paper chemicals, in particular the retention agents, are added to Zudosierstellen which seen in the flow direction, a strong pressure drop or a turbulence field with high shear fields, whereby the effect in particular the high molecular weight or polymeric paper chemicals, such as the retention agent, such as starch, is reduced or can be reduced.

There is a need in paper and board making paper properties and quality, in particular the tear behavior and the paper structure of the finished product to positively influence by the flow behavior of the pulp.

There is also a need in paper and board production on headboxes that solve the trilemma that, on the one hand, in certain areas of the headbox, such as the nozzle chamber, for the purpose of intimately mixing the components of the pulp doped pulp, turbulent flows, at least to some extent are desirable, but on the other hand, in certain other areas, such as in separating layers - be these solid or hydrodynamic lamellae - between the layers in a Mehrlagenstoffauflauf and especially at the interfaces between a hydrodynamic lamellar flow and a fiber layer no mixing and thus no turbulence or turbulence desired and that on the third side, the effect of certain high molecular weight or long chain ingredients of the pulp, in particular by turbulence and thereby caused shear fields, should not be reduced n.

The satisfaction of these needs succeeds with a headbox according to claim 1 or with a paper or board machine according to claim 10. Advantageous embodiments of the head box according to the invention are defined in claims 2 to 9.

According to the invention, it is provided that only in the region of the flowing first layer (12) is a turbulence generator (49) provided and no turbulence generator is introduced in the flow path of the second layer (8) and the at least one excipient is designed as a multicomponent system, wherein the metered addition of a Inlet (92) into a respective second supply means (16) distributed to an outlet (52) of the nozzle chamber (28) and thus takes place the metering in a location at the downstream no major pressure drop and / or no major turbulence in terms of Effect preservation of the excipient in the second layer (8) occurs or occur, and that the excipient is a paper chemical, in particular a retention agent.

In the following, the z direction refers to the vertical direction in accordance with the language usage of the field. The machine direction, MD for "machine direction", is the direction in which the paper web is transported, that is, the direction in which the screen belt moves on its side facing the paper web. The MD is also the direction in which the headbox causes the fabric, together with the added auxiliaries, to run onto the sieve belt. The transverse direction, CD for "Cross Direction", is the direction that is normal for both the MD and the z-direction. The CD is the direction in which the width of the screen belt extends while the MD is the direction in which the length of the screen belt extends.

Generically, the headbox is a multi-layer headbox with at least one metering device for at least one adjuvant, in particular retention agent. Such a headbox allows in a paper or board machine, the addition of at least one excipient in at least one flowing through the headbox Siebwasserstromschicht. In multi-layer drums several layers are present. It is at least a first layer, which carries a pulp suspension and a second layer, which leads essentially white water present. However, it is also possible for a plurality of white water layers and / or several fibrous material layers to be present be. The layers may also be composed of other flowing media. For example, a layer could also lead at least predominantly to fresh water. Conveniently, the different material transporting flow layers are arranged alternately in the z-direction of the headbox.

The headbox further generically comprises a second supply means for supplying substantially white water comprising the excipient. Furthermore, the headbox at least a first feeding the pulp suspension supplying means. First and second supply means are in turn connected to distribution pipes.

Furthermore, the headbox has a nozzle chamber tapering in the machine direction with a sieve-side outlet. Furthermore, a guide device is provided, to which the nozzle chamber connects. In the guide device Separiermittel, such as a partition exist. The separating means serves to separate or separate individual flowing layers in the headbox, in particular in the guide device. The separating means extends, at least in regions, towards the outlet of the nozzle chamber. In addition to the separating means, the headbox may also comprise movable louvers extending from the guide means into the nozzle chamber. In addition, at least one turbulence generator is provided between the guide device and the nozzle chamber. The turbulence generator is provided only in the region of the flowing first layer, that is to say the layer guiding the pulp suspension. Then, a metered addition of the excipient with the aid of the metering device to the white water of the second flowing layer can already take place in the region of the distributor tube or the supply line, without the mode of action of the excipient, in particular of the retention agent, being reduced. In the region of the second layer, which leads predominantly white water and the auxiliary material then no turbulence generator is provided. This results in little pressure drop, that is only a low pressure and only slight turbulence in this layer. Destroying the polymer chains of the excipient can thereby be prevented.

In the nozzle chamber, the individual layers can still be separated by lamellae.

As described above, the headbox has at least one metering device. The metering device feeds at least one flowing layer with the at least one adjuvant. The feed of the layer with the excipient through the metering device takes place at at least one metering location. The Zudosierort can also be in the guide device and even in the nozzle chamber. In principle, an arrangement of the metering location in the machine direction is possible in the entire range from an inlet for a feed means to the outlet of the nozzle chamber. When this is referred to as a low pressure, this is to be seen against the background that seen in the machine direction in the headbox in the presence of a turbulence generator, a strong pressure drop occurs. a low pressure is thus present, for example, if no turbulence generator is introduced in the flow path of the second layer. It depends on the application where metering points are the cheapest to choose. In any case, in terms of preserving the effect of the adjuvant, especially when the adjuvant has large fragile molecules, advantageously a location should be chosen where no major pressure drop and / or greater turbulence in the second layer occur downstream, thereby causing fragmentation of the molecular chains of the excipient, in particular a retention agent, no longer or no longer can occur in an effect-reducing manner. A most preferred location is as described above, the nozzle chamber, for example in the vicinity of the screen-side outlet. The metering device allows the metering of an excipient at the most effective metering location, which amounts to the correct amount in terms of correct wet chemistry. By chartering the flow layers with an additive at low pressure Zudosierorten, the effect of the excipient can be preserved, that is, it is avoided that the effect of the excipient, in particular a retention agent, is undesirably reduced by fragmentation of its molecules.

In a further embodiment of the invention, the metering device, which allows the metered addition of the excipient, is already arranged in the distributor tube or in the second delivery means. Preferably, the second supply means is operated with white water, that is, with the aid of the second supply means, white water is passed into the nozzle chamber. The white water can be known to act as a delamination agent. Above all, however, it is loaded with the excipient as a transport layer. Preferably, the addition of the excipient takes place over the entire machine width of the paper or board machine. For example, tubes or pipe rows are currently being used as the second supply means. The individual tubes open into a distributor tube which feeds the individual feed means.

The first supply means according to the invention are used to supply pulp suspension in the head box. They are usually connected to a separate distribution pipe.

Specifically, and in particular exclusively, pipes or lines intended for the metered addition of auxiliaries, in particular the metering device, can also advantageously be used. The dimensioning, that is properties such as cross-section, diameter, wall thickness, material selection, outer and inner surface finish, etc., of a pipe can be adapted to the substances to be transported or designed for this. By using conventional tubes as the second feed means, it is also possible advantageously to retrofit existing systems simply and inexpensively with the head box according to the invention.

The feed with excipient or with excipients can be made in the second feed means itself. Alternatively or additionally, the metered addition can also take place in the distributor tube for the second feed means. The distributor tube preferably extends in the transverse direction of the paper machine. In general, the metered addition of the at least one auxiliary substance can take place exclusively or in any combination, before, in or after the distributor tube. Preferably, a metered addition takes place shortly before entry into or in the nozzle chamber. By the possibility of selection or combination, the metering location or the plurality of metering locations, where or at which there is a specific, namely a selectable in the low pressure range, pressure, the respective excipient, in particular its molecule fragility, function in terms of paper chemistry, etc., be adjusted. Due to the favorable choice of metering sites and thus pressures and turbulence zones with regard to the desired effect of an adjuvant or an adjuvant combination or a multi-component system of one or more excipients, the amount of auxiliary consumed and the product quality can be positively influenced.

The dosing can be done discretely distributed. Conceivable and possible, however, is also a continuous metering along the described path. It is particularly advantageous if at least a first component of the excipient in the distributor tube, at least a second component of the excipient in the headbox, preferably in the nozzle chamber, can be added. Due to the different chemical modes of action of the different auxiliaries used in the production of paper or paperboard, in particular due to different reaction times, until a desired effect has been used in sufficient intensity, it is provided to form auxiliaries as multicomponent systems, wherein the addition of different Components for the aforementioned reasons can advantageously be done at different Zudosierorten.

It is particularly preferred if the at least one metering location, in particular for adaptation to a specific application, can be varied. The change in the position of a Zudosierorts, for example, by targeted training or, preferably dynamic, adjustment, preferably the length of the separating agent in the machine direction, take place. It is particularly favorable if the position of the metering location in the nozzle chamber, in particular from outside the nozzle chamber, and without disturbing the flow in the nozzle chamber, can be varied. By a, in particular finely variable, adjustability of Zudosierorts, especially from outside, for example by suitable actuator devices, such as telescoping or rotatable or movable systems, the product quality can be finely regulated in particularly narrow limits. The Justierbeziehungsweise adjustability from outside allows the integration of the fine control of the dosing of the excipient in a quality assurance system with particularly tight intervention limits.

In particular, for the formation of an asymmetric blade structure, it is advantageous if a first amount of the at least one adjuvant can be metered into at least one first flowing layer and one from the first different second amount into at least one second flowing layer. For better effect, the flowing layers can preferably be guided separately from one another by the at least one separating means. In asymmetric blade assembly, the required amount of excipient on the nature, such as dilution, thickness in the z-direction, pulp, etc., a flowing position dependent, this nature must be formed differently due to the desired asymmetry in different layers. The ability to drive different amounts of excipients in different layers thus supports the variety of manufacturable paper and board products. Depending on the application, the separating agent can improve the effect of the auxiliaries added in different amounts.

It is particularly advantageous if several metering locations are arranged along the machine width. The distribution of the metering locations along the machine width may, for example, be equidistant from that of the pulp suspension feeding first feed means and / or the white water supplying second feed means. However, the distribution may also be made smaller, that is, the number of metering locations along the machine width for an adjuvant per unit of machine width may be higher than the number of inlets for the pulp suspension. The distribution density affects the paper quality, in particular the uniformity of the paper quality, such as the basis weight or the tear behavior or more generally the paper structure in the transverse direction. With a dense distribution of metering sites, a reduction in the variance of paper or board properties, such as basis weight, across machine width can be achieved.

It is particularly preferred if, in order to enhance the action of the at least one adjuvant, in particular a retention agent, the pressure loss and thus the magnitude of the shear forces in the nozzle chamber can be adapted to occur in the first supply means supplying the adjuvant. Due to the adaptability of the pressure loss and thus the shear forces can, depending on the application, an optimal compromise between desired turbulence and thus mixing, for example, the dilution water with the excipient or the Hilfsstoffbefrachteten white water with a pulp suspension layer on the one hand and preservation or even enhancement of the effect of the excipient on the other hand achieved become.

Advantageously, the metering device is divided into at least a first and a second section. This allows profiling of the adjuvant feed over the machine width. Also, a delivery means may have a sectional division. Due to the fractionally different amounts of an excipient, it is possible to produce different product qualities side by side on a paper or board machine. The sectional subdivision can also be used for the most exact adaptation of the individual Sectors are used to desired profiles, for example in the case of a scheme for adapting an actual profile of a section to a predetermined nominal profile of the section. In particular, sectional nominal profiles may also be identical to one another, which in the control case results in that disturbing variables occurring in the headbox sectionally, that are sectionally, that is in the affected sections, can be corrected, without other, without departing, sections of be affected by a control intervention.

As indicated, it is particularly advantageous if the at least two sections of the metering device can be integrated into a control, in particular into a formation control, whereby the profiling of the auxiliary material charge can be regulated over the machine width by a different dosage of the auxiliary material, in particular of the retention agent. The ability to be integrated into a control system offers the possibility of adapting or adjusting sectional or sectoral actual profiles to sectional or sectoral nominal profiles.

The headbox according to the invention is advantageously used in a paper or board machine or is incorporated in such. With such a paper machine or board machine, papers and paperboard can be produced of particularly high and customer-specific tailor-made quality.

Fig. 1

eine schematische Seitenansicht der Nasspartie einer erfindungsgemäßen Papier- oder Kartonmaschine mit einer ersten Ausführungsform des erfindungsgemäßen Stoffauflaufs;

Fig. 2

einen Querschnitt in einer durch die z-Richtung und die Maschinenrichtung aufgespannten Ebene durch eine erste Ausführungsform des erfindungsgemäßen Stoffauflaufs;

Fig. 3

einen Querschnitt in einer durch die z-Richtung und die Maschinenrichtung aufgespannten Ebene durch eine zweite Ausführungsform des erfindungsgemäßen Stoffauflaufs;

Fig. 4

einen Querschnitt in einer durch die z-Richtung und die Maschinenrichtung aufgespannten Ebene durch eine dritte Ausführungsform des erfindungsgemäßen Stoffauflaufs;

Fig. 5

einen Querschnitt in einer durch die z-Richtung und die Maschinenrichtung aufgespannten Ebene durch eine vierte Ausführungsform des erfindungsgemäßen Stoffauflaufs;

Fig. 6

einen Querschnitt in einer durch die z-Richtung und die Maschinenrichtung aufgespannten Ebene durch eine fünfte Ausführungsform des erfindungsgemäßen Stoffauflaufs;

Fig. 7

eine kombinierte Schrägsicht von oben der Verteil- und Zuführmittel und einen Querschnitt in einer durch die z-Richtung und die Maschinenrichtung aufgespannten Ebene durch eine sechste Ausführungsform des erfindungsgemäßen Stoffauflaufs; und

Fig. 8

einen Querschnitt durch eine siebente Ausführungsform des erfindungsgemäßen Stoffauflaufs.

Further advantageous properties and embodiments of the invention will be described with reference to the drawings explained below, by or to which the scope of protection is in no way limited. In these drawings shows

Fig. 1

a schematic side view of the wet end of a paper or board machine according to the invention with a first embodiment of the head box according to the invention;

Fig. 2

a cross section in a plane spanned by the z-direction and the machine direction plane through a first embodiment of the head box according to the invention;

Fig. 3

a cross section in a plane defined by the z-direction and the machine direction plane through a second embodiment of the head box according to the invention;

Fig. 4

a cross-section in a plane spanned by the z-direction and the machine direction plane through a third embodiment of the head box according to the invention;

Fig. 5

a cross section in a plane spanned by the z-direction and the machine direction plane through a fourth embodiment of the head box according to the invention;

Fig. 6

a cross section in a plane spanned by the z-direction and the machine direction plane through a fifth embodiment of the head box according to the invention;

Fig. 7

a combined oblique view from above of the distribution and supply means and a cross section in a plane spanned by the z-direction and the machine direction plane through a sixth embodiment of the head box according to the invention; and

Fig. 8

a cross-section through a seventh embodiment of the head box according to the invention.

Hereinafter, an embodiment of the paper or board machine according to the invention and seven embodiments of the headbox 1 according to the invention will be described in more detail with reference to FIGS.

A paper machine 4 has, as is known to those skilled in the art, a wet end 7 with a dewatering device 105. It could also be a board machine. A substance 5 is applied to a wire 2 by means of a head box 1 according to the invention, which is designed here as a three-layer dilution hydrogen headbox. The headbox 1 has a screen-side outlet 52 along the transverse direction 88 of a panel 13. After leaving the nozzle chamber 28 of the headbox 1, the sheet formation begins on the wire 2, that is seen in the machine direction 76 after the outlet 52 are Blattbildungsorte 56. The wet end 7 may instead of the illustrated and a wire 2 having Langsiebformers also a Doppelsiebformer, such as a hybrid or gap former.

With the help of drainage elements 106, such as suction boxes, as is known, the dewatering of the fabric 5 guided in the material web 13 takes place on the wire 4. The paper machine 4 also comprises further parts, such as a Press section and a dryer section, as well as a winding machine, which are not shown for clarity sake.

In the machine direction 76 behind each dewatering element 106 and in front of the first dewatering element 106 in the machine direction 76, water weight sensors 107 for measuring the dewatering of the substance 5 are conventionally arranged. The machine direction 76 is indicated by an arrow.

The wire 2 is deflected material upstream side by means of a breast roll 6 and driven. The fabric web 13 rests on the upper side of the wire 2 and is continuously moved away from it in the machine direction 76 and thus from the headbox 1, wherein the fabric 5 is continuously dewatered via the dewatering elements 106. The white water is collected, for example in a white water tank, and pumped back to the headbox 1 as dilution water, where it is available for the formation or dilution of a flowing layer 12, 64, 68 (white water pan and return pump system are not in the drawing for clarity shown).

In Fig. 2 a first embodiment of a headbox 1 according to the invention is shown. According to the headbox 1 is designed as a multi-layer casserole. The multi-layer headbox comprises a first layer 12 which carries a pulp suspension and a second layer 8 which carries water, in the present case white water. The in Fig. 1 illustrated headbox 1 is formed as a multi-layer casserole with two outer layers 12, which carry a pulp suspension, and a second layer, a so-called. Middle layer 64, which leads substantially white water 80 is formed. Each layer of the multilayer headbox is fed with the pulp suspension or the white water with its own feed means. The first layer 12 is fed to the pulp suspension via first feed means 20, in the present case first feed lines. The first supply means 20 or supply lines, which lead the pulp suspension into the guide device 11 of the headbox 1, are fed by a common first distributor tube 84. The second layer 8, which is essentially Water, preferably white water, leads, the white water is supplied via second supply means 16. The second supply means are fed via a separate distribution pipe 24. In the illustrated embodiment, the additive or excipient, in particular the retention agent, is already added in the distributor tube 24 via the metering device 40. Advantageously, still follows the guide means 11 of the headbox 1 and in front of the nozzle 28, a turbulence generator 49, which is shown here only schematically. According to the invention, the turbulence generator 49 is formed only over the width of the first layer 12 which guides the fibrous material, whereas no turbulence generator is provided in the region of the second layer 8, which essentially carries white water and the auxiliary substance, in particular the retention agent. In the present case, the turbulence is generated in that the outlet opening is smaller than the width of the guide channel 13 itself. Also possible would be elongate turbulence generators with correspondingly shaped walls, for example projections on the walls. Since the turbulence on entry into the nozzle 28 is generated only in the first layer, but not in the second layer, breaking and thus destruction of the polymer chains of the excipient, in particular the retention agent is prevented. The aid comes after the turbulence generator 49 in the nozzle 28 in contact with the fibers of the pulp suspension and can act there

The second layer 8 loaded with the excipient is shown hatched for better distinctness from the first layer 12 comprising the pulp suspension. In the first embodiment, the middle layer 64 of the three flowing layers is the second layer 8 comprising the excipient.

The nozzle chamber 28 of the headbox 1 has a screen-side outlet 52 and tapers in the machine direction 76.

Furthermore, separating means 36, which here separate the two pulp suspension layers 12 from the middle layer 64, are present within the guide device. The separating means 36 are formed here as partitions. Thus is each individual layer within the guide device 11 associated with a separate channel, which is formed by partitions.

The second in Fig. 3 illustrated embodiment of the headbox 1 has three first layers, so-called pulp suspension layers 12, each extending between two second layers. The second layers essentially lead to white water wherein in the region of the distributor tube 24 or the auxiliaries are metered. Since the second embodiment is similar to the first embodiment, are for the same components in Fig. 2 the same reference numbers as in Fig. 1 used.

The third in Fig. 4 illustrated embodiment of the headbox 1 has two second layers 8, which is arranged in each case between two relative to one of the second layers 8 outer fibrous suspension layers 12. The guide device 11 is again formed with separating means 36. The separating means 36 are again partitions, so that in the guide device 11 individual, the respective layers associated channels are formed. A mixing of the layers in the guide device does not take place, but only where the separating ends, ie in the nozzle device. The layers can not only be separated in the z-direction, that is to say in the vertical direction, but also a separation along the machine width, that is to say in the CD direction, but this is not shown here. In the embodiment according to Fig. 3 the partitions are extended into the area of the nozzle chamber 28 with movable blades 32 which extend to close to the outlet 52. The excipient is thus mixed with the pulp suspension only at the nozzle outlet.

The fins 32 are movable, for example, suspended at a fulcrum 33. Preferably, the channel formed by the lamella tapers in the direction of the nozzle opening. Different slats can have both an equal length and different lengths. In this regard, for example, on Fig. 4 directed. If the slats vary in length formed, so in the machine direction, that is, in the MD direction for different z-locations a different location of the admixture of excipient, which is performed in the white water, are set. This makes it possible to specifically influence the sheet formation properties in the z direction.

• Leimungsmittel (sizing agents), die die Bedruckbarkeit der Papieroberfläche erhöhen;
• Trockenverfestigungsmittel (dry strength agents), die die mechanische Festigkeit erhöhen;
• Nassfestigkeitsmittel (wet strength agents), die eine Zerstörung der Faserbündel, wenn das Papier benetzt wird, verhindern;
• Farben (dyes), die dem Papier Farbe geben;
• optische Aufhellersubstanzen (optical brightener agents), die den Weißgrad erhöhen;
• Fixiersubstanzen (fixitatives), die anionische Substanzen an die Faser binden;
• Retentionshilfsstoffe (retention aid), die die Retention der Teilchen auf dem Sieb erhöhen;
• Deaeratoren (deaerators), die gelöste und freie Gase aus der Suspension lösen;
• Entschäumer (defoamer), die Schaum entfernen; und
• biozide Substanzen (Biocides), die gegen Mikroorganismen und ihre Ablagerungen wirken.

In the present case, excipients are understood as meaning fillers, any type of chemicals, but in particular retention aids. Functional chemicals, which are also referred to as auxiliaries and are used in the paper industry:

• Sizing agents that increase the printability of the paper surface;
• Dry strength agents that increase mechanical strength;
• Wet strength agents which prevent destruction of the fiber bundles when the paper is wetted;
• Colors (dyes) that give color to the paper;
• optical brightener agents that increase the whiteness;
• Fixatives (fixatives) that bind anionic substances to the fiber;
• Retention aids, which increase the retention of the particles on the screen;
• Deaerators that dissolve dissolved and free gases from the suspension;
• Defoamer (defoamer), remove the foam; and
• biocides (biocides) that act against microorganisms and their deposits.

Each of the layers that essentially guide the water, in particular the white water, may be charged with one or more of the abovementioned auxiliaries. It is also possible to transport different auxiliaries in different first layers.

Also at the in Fig. 3 illustrated embodiment, a turbulence generator 49 is provided. As in the embodiment according to Fig. 1 the turbulence insert in the areas in which the pulp suspension is guided, openings which define the channel, whereas by the turbulence generator, a channel boundary in the region of the second layer leading to the white water does not occur.

According to the invention, the excipient is metered into the first layer by at least one metering device 40. In the embodiments according to the FIGS. 1 to 3 the metered addition via the metering device is always in the distribution pipe 24, that is, in front of the guide means 11 of the headbox.

In contrast, the metering device 40 for the fourth embodiment, which is a Dreilichtenstoffauflauf 1 with two first layers 12, which carry pulp suspension 72, and a second layer, which leads substantially white water in Fig. 4 shown, the metering in the region of the guide device 11th

The metered addition or charging takes place at at least one metering location 44 in the guide device. Here, the feeding of the white water 80 leading middle layer 64 with the excipient through the metering device 40 by means of metering valves 41, which are installed in Zudosierleitungen 42 takes place. The feed takes place in the illustrated embodiment at four different Zudosierorten 44 along the machine direction 76. The metering 44 are arranged in the region of the guide means 11 of the headbox 1 in the machine direction 76. Preferably, the metering location 44 is located at a location of low pressure 48 in the headbox 1. Such prevails in the entire by separating walls as separating means of the fiber suspension layers 12 in the guide device separately guided second layer 8, in which the excipient is metered. The pressure here is so low, one could say, just just so high that a breakage of molecular chains of the excipient, which is preferably a retention agent, is avoided.

In the embodiment according to Fig. 4 are again provided in the nozzle chamber 28 fins 32. In contrast to the embodiment according to Fig. 3 the movable suspended slats 32 are formed differently long in the machine direction. In this way, the white water with the adjuvant is added to the different first layers 12 at different locations in the z direction in the nozzle chamber.

In Fig. 5 a further embodiment of the invention is shown. Again, the same components as in the embodiments according to FIGS. 1 to 4 marked with the same reference numerals. In contrast to the embodiment according to Fig. 4 the addition of the auxiliaries, in particular of the retention agent in the white water in the supply line 16 from the distribution pipe 24 to the guide means 11 of the headbox 1 is carried out, in turn, a blade 32 is provided in the nozzle means.

In Fig. 6 a fifth embodiment of the head box 1 according to the invention is shown. In this fifth embodiment, the first, with white water operated, second feed means 16 which is connected to the distribution pipe 24, the metering device 40, which the metering of the excipient, preferably over the entire machine width 60 of the paper or board machine 4, in various over distributed the machine width, the white water distributed with auxiliary leading channels of the guide device. In the embodiment according to Fig. 6 is provided for each of the first layers, which carry the pulp suspension a separate distribution pipe. Incidentally, the fifth embodiment has features such as partition walls 36, metering valves 41, metering lines 42, etc., which have already been described in the first four embodiments. It is therefore here in this regard only referred to these above statements.

The feeding of a supply means 16, 20 takes place, as in the FIGS. 2 to 5 is indicated, via at least one transversely extending manifold.

The metered addition of the at least one adjuvant can be carried out before, in or after the distributor tube 24, exclusively or in any desired combination.

The at least one adjuvant, in particular a retention agent, is designed as a multicomponent system. The addition of the excipient can take place at one or more locations from the distributor tube to the nozzle chamber 28.

For example, at least one first component or a first adjuvant in the distributor tube 24 and a second component or a second adjuvant may be metered into the second supply line 16.

In the embodiment in Fig. 6 two white water leading second layers 8 are shown with an excipient. Such an embodiment then allows in the z-direction an asymmetrical sheet structure.

In Fig. 7 a headbox 1 is shown in an oblique view with distribution and feeding means and a cross section of the headbox 1. The same components as in the preceding figures bear the same reference numerals. As in Fig. 6 a plurality of metering locations 44 for auxiliaries may be arranged along the machine width 60. Their distribution is here along the machine width 60 equidistant from that of the pulp suspension 72 supplying first feed means 20. However, it could also be smaller than this. A sectional division of the second supply means 16, in particular feed lines for white water with an auxiliary over the machine width allows the different addition of auxiliaries across the machine width and thus the adjustability of the paper quality across the machine width. For this purpose, each supply line 16 with its own Zudosiereinrichtung as in Fig. 6 equipped equipped.

To enhance the effect of the at least one adjuvant, in particular a retention agent, the pressure loss and thus the magnitude of the shear forces in the nozzle chamber 28 can be adjusted, which in the adjuvant supplying second Feed means 16 occur. This adaptation can be done for example by means of appropriate pump pressure settings.

The metering device 40 may be subdivided into at least a first and a second section 96, 100 to allow for profiling of the adjuvant feed over the machine width 60. The allocation of two metering valves 41 and two metering lines 42 to a section 96, 100 is in Fig. 7 indicated by two curved brackets.

The at least two sections 96, 100 of the metering device 40 in a paper or board machine 4 according to the invention in a regulation, in particular in a formation control, einbindbar, whereby the profiling of the auxiliary material feed over sectionally across the machine width 60 different dosage of the excipient, in particular the retention agent, is controllable.

The seventh embodiment of the headbox 1, which in Fig. 8 Finally, demonstrates the application of the invention in a three-layer casserole with two outer pulp suspension layers 12 and an arranged between these adjuvant leading middle layer 64, in which the pulp suspension layers 12 have different layer thickness in the z-direction.

With the invention, a headbox is specified for the first time, which allows a metered addition of auxiliaries, in particular retention agents, without these being destroyed and thus reduced in their effect. This is achieved in that the excipient is not supplied directly into the pulp suspension, but in a white water layer, the white water layer is guided separately through the guide means of the headbox and mixing takes place only in the area of the nozzle device of the headbox.

LIST OF REFERENCE NUMBERS

1

headbox

2

wire

4

Paper or board machine

5

Material; Fibrous suspension

6

breast roll

7

wet end

8th

Second shift

11

guide means

12

First shift

13

web

16

Second feeder

20

First delivery agent

24

distributor

28

nozzle chamber

32

lamella

33

pivot point

36

Separating agent, in particular partition

40

metering device

41

Zudosierventil

42

Zudosierleitung

44

Zudosierort

49

Swirling means, in particular turbulence generators

52

Sieve-side outlet

60

machine width

64

First flowing layer

67.1

opening

67.2

opening

76

machine direction

84

Distribution means, in particular distribution pipe

88

transversely

92

inlet

96

First section

100

Second section

105

dehydrator

106

dewatering element

107

Water weight sensor

Claims (10)

1. Headbox (1) for a paper or cardboard machine (4) having at least one first feed means (20) for fibrous stock suspension (5) into a guide device (11) which is connected to a nozzle chamber (28), from which the fibrous stock suspension (5) exits via an orifice, and having a metering apparatus (40) for metering in at least one additive, the headbox being a multilayer headbox (1) with at least one first (12) and one second layer (8), at least the first layer (12) of the headbox (1) comprising a fibrous stock suspension (5) and the second layer (8) of the headbox (1) comprising substantially white water, the white water being fed via a second feed means (16) to the guide device (11), the first and the second layer (8, 12) being guided separately at least in the guide device (11), the metering apparatus (40) being arranged and configured in such a way that the additive is fed substantially to the second layer (8), characterized in that a turbulence generator (49) is provided only in the region of the flowing first layer (12) and no turbulence generator being introduced into the flow path of the second layer (8) and the at least one additive being configured as a multiple-component system, the metering taking place by means of the metering apparatus (40) in a distributed manner from an inlet (92) into a respective second feed means (16) as far as an outlet (52) of the nozzle chamber (28), and the metering therefore taking place at a location, at which no greater pressure drop and/or no greater turbulence in the sense of the conservation of the effect of the additive occur/occurs in the second layer (8) downstream, and in that the additive is a paper chemical, in particular a retention agent.
2. Headbox (1) according to Claim 1, characterized in that the second feed means (16) have a metering apparatus (40) which makes the metering of the additive possible, preferably over the entire machine width (60) of the paper or cardboard machine (4).
3. Headbox (1) according to Claim 1 or 2, characterized in that the at least one additive comprises, as a multiple-component system, at least one first component of the additive and one second component of the additive, and the first component can be metered in the distributor pipe (24) and the second component can be metered in the second feed means (16) or into the guide device (11) or preferably into the nozzle chamber (28).
4. Headbox (1) according to one of the preceding claims, characterized in that the guide device (11) comprises separating means (36) in the machine direction (76), which separating means (36) form channels for guiding the first and the second layer (8).
5. Headbox (1) according to Claim 4, characterized in that, in particular in order to form an asymmetrical sheet structure, a first quantity of the at least one additive can be metered into at least a first flowing layer (64) and a second quantity which is different from the first can be metered into at least one second flowing layer, it being possible for the flowing layers (64) to be guided separately from one another in the guide device (11) by way of the at least one separating means (36).
6. Headbox (1) according to one of the preceding claims, characterized in that a plurality of metering locations (44) are arranged along the machine width (60), it being possible for their distribution along the machine width (60) to be configured to have the same spacing as or a smaller spacing than that of the first feed means (20) which feeds in the fibrous stock suspension (5).
7. Headbox (1) according to one of the preceding claims, characterized in that, in order to reinforce the effect of the at least one additive, in particular a retention agent, the pressure loss and therefore the magnitude of the shear forces can be adapted in the nozzle chamber (28), which shear forces occur in the second feed means (16) which feeds in the additive.
8. Headbox (1) according to one of the preceding claims, characterized in that the metering apparatus (40) is divided into at least one first and one second section (96, 100), in order to make profiling of the additive feeding over the machine width (60) possible.
9. Headbox (1) according to Claim 8, characterized in that the at least two sections (96, 100) of the metering apparatus (40) can be incorporated into a regulation, in particular into a formation regulation, it being possible for the profiling of the additive feeding to be regulated via metering of the additive (8), in particular of the retention agent, which metering is different sectionally over the machine width (60).
10. Paper or cardboard machine (4) having a headbox (1) according to one of Claims 1 to 9.

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