EP1382742A2 - Apparatus and process for impregnating a web of paper or board - Google Patents

Abstract

A process impregnates a carton or paper web having a specific weight of more than 40 g/m. The application process has a fluid or film press (4) which is esp. preceded by a wide-nip (17) calender (5). Also claimed is a commensurate assembly in which the rotating wide-nip (17) calender (5) has a mantle (18) which is presented to a counter-pressure drum (14). No further processing devices are located between the wide nip (17) and adhesive spreader (4) other than rollers (23, 24). The wide nip has a regulated heater (14) which raises the temperature to above the fibre plasticizing temperature of 200C or more. The film press (4) is followed by a drier which operates at a temperature below that of the wide nip heater. No smoothing assembly is located between the film press and roll-up winder.

Description

The invention relates to a device for impregnating a paper or cardboard web with a weight per unit area of more than 40 g / m ² , with a web path in which a device for applying an impregnating agent, such as a starch solution, so-called starch glue, or other application means commonly used in paper finishing is arranged is. The invention further relates to a method for impregnating a paper or cardboard web with an impregnating agent, such as a starch solution, so-called starch glue, or other application agents customary in paper finishing, the impregnating agent being pressed wholly or partially into the web.

Paper or cardboard webs are predominantly made of cellulose fiber educated. They therefore have a polar, strong hydrophilic in character, so are due to water easily wettable and swellable. About the uncontrolled Penetration of water or other polar liquids in the open pore fiber structure to prevent or limit some types of paper or cardboard "glued", ie by adding a liquid impregnating agent, like starch glue, also called "glue" for short, or other more common in paper finishing Application agent, at least partially hydrophobic. The Impregnation also has the advantage that the Strength of the web is increased.

When impregnating with glue or other means of application commonly used in paper finishing, one would like the glue to penetrate the web as completely as possible, so that the web is completely "filled". In the case of thinner papers with a basis weight of up to 80 g / m ^2, this is usually relatively easy to do by letting the web run through a so-called size press with a glue or starch liquor and compressing it after soaking in the press nip and thereby the Pushing glue into the web. Another possibility is to have the web run through a so-called film press. The glue then penetrates the web through the compressive stresses acting in the nip. In the case of thicker paper or cardboard webs with a basis weight of 90 g / m ² or more, this procedure results in otherwise unchanged conditions that the glue, in particular in the case of film pressing, is only pressed into certain surface areas, i.e. does not completely penetrate the web. Such a web, which is not completely penetrated, has, for example, reduced strength properties compared to a fully loaded web.

You could theoretically increase the pressure in the nip, to push the glue into deeper areas of the web. However, a higher pressure has the disadvantage that it is associated with a loss in volume of the web. This in turn leads to a smaller thickness of the web and with it a weakening or diminution of firmness. To compensate for this disadvantage, it would be necessary to use more material which in turn leads to a higher basis weight of the cardboard web leads. With cardboard webs you want on the one hand high strength and, on the other hand, the lowest possible Reach basis weight.

The invention has for its object the impregnation to improve the paper or cardboard web without have to accept a larger volume loss.

This task is at a device of the beginning mentioned type in that in front of the path the application device arranged a wide nip calender is one by a circumferential coat and one cooperating counter-pressure element formed Has Breitnip through which the web running path leads is.

It is assumed that the web compresses somewhat in the wide nip becomes. If the web is compressed and then is inserted into the application device, it "sucks" so to speak full of impregnating agent. You lead this is due to the fact that by squeezing the Fibers the capillary action is increased so that the Transport of the liquid applied impregnating agent is improved into the web. The wide nip calender has the advantage of elastic compression is reachable, i.e. one comes with relatively small ones Compressive stresses. Those entered in the Breitnip Forces are distributed over a relatively large area, so that there is a volume-saving effect. The coat the Breitnipkalander should have a certain flexibility have so that it conforms to the shape of the counter pressure element, for example, a counter roller can. This flexibility has another advantage. It leads to the fact that the web in the Breitnip is not squeezed. So none become local Structures destroyed. In the wide nip, the path becomes even condensed, i.e. also flake areas not overpressed, but similar to neighboring ones Areas where there are no such areas Have accumulated fibers. Because the train is everywhere is evenly compressed, also results everywhere the same capillary action, i.e. the impregnating agent is sucked up evenly over the entire surface of the web. This results in a higher rigidity of the Web, higher strength, e.g. Tensile strength, a improved burst pressure and a favorable glide angle for cardboard webs, i.e. the surface roughness is big enough that boxes standing on top of each other don't slide. Otherwise, these advantages only come with more Mass reached, i.e. a higher basis weight what again increases costs.

Preferably between the wide nip and the application device, apart from possibly existing ones Control devices, no further processing equipment arranged. So the web comes from the Breitnip out and runs directly into the order facility into it. In between, it can be redirected and may also be spread out. An editing in the sense of an impact on the train or her However, there is no structure. This approach has the advantage that compression, even if only is temporary, still exists when the web is in the order facility arrives. There can be Then soak the web with impregnating agent, the Order of course still by a certain External printing can be supported.

The wide nip preferably has a heating device on. The heater has two advantages. On the one hand the surface properties of the web are improved. On the other hand, the penetration of the liquid impregnating agent into the web by an elevated temperature the train supports. The capillary effect is improved.

The heating device is preferably provided by the counterpressure element educated. This is a relatively simple one Possibility of the required thermal energy in the Breitnip to be entered, more precisely, transferred to the web.

It is preferred that the heating device is a Has web surface path in the wide nip delimiting surface, whose temperature is adjustable to 200 ° C or more is. If the web in the Breitnip with such a high Temperature is heated, then it has in the following Application device still a temperature that is high enough to prevent the penetration of the waterproofing agent to support in the train. The temperature of the train in the order facility is usually under 100 ° C, so that there is no risk that the Impregnant liquid begins to boil.

The application device is preferably a film press educated. The use of a film press versus A size press has the advantage that you can get higher speeds can drive. The film press, too called "Speed Sizer" comes with a film of the liquid impregnating agent and transfers this film in a nip on the paper or cardboard web. The film press therefore effects a contour application of the liquid impregnating agent on the surface of the Paper or cardboard web. This results in a particularly advantageous one Interact with the wide nip, where a contour smoothing, So a similar processing takes place. The Breitnip has a uniform density of Path creates, whereas the generation of a uniform Thickness is of minor importance.

In a preferred embodiment it is provided that a drying area downstream of the application device is, the temperature in the wide nip is higher than the temperature in the drying area. In particular the temperature in the drying area should be lower than the plasticizing temperature of the fibers the train. The surface of the web is therefore in the drying area no longer significantly changed.

The temperature in the wide nip is preferably at least to the plasticizing temperature of the fibers of the Paper or cardboard web adjustable. This means that the surface of the web in the Breitnip can be closed can. Closing creates a smooth surface on the Web without the penetration of the impregnating liquid to prevent. The impregnating agent can due to the capillary effect still in the Advance inside the train. This is especially true if the impregnation agent application due to a pressure effect from the outside, for example through the film press or a size press is supported.

Due to the higher temperature in the wide nip, at which the The fibers of the web are plasticized at least on the surface is achieved, that the fibers after themselves can no longer set up after leaving the wide nip. So there is an overall smoother surface, accordingly the impregnating agent can be applied more evenly.

There is preferably between the application device and a downstream winding device from the reasons mentioned no smoothing device arranged. Under the smoothing device, both a smoothing unit should be used with two hard rollers as well as another two or Multi-roller machine can be understood in the at least one roller is elastic or resilient Surface. By using the wide nip calender gets the paper or cardboard web already such a smooth surface that subsequent smoothing is often no longer necessary.

Surprisingly, it has been shown that papers and Stone groundwood boxes, wood pulp (mechanical pulp) and TMP (thermomechanical pulp) in the device according to the invention (broad nips satin, Glue application, drying) during final drying "rise up". In other words, these papers or boxes gain while the surface smoothness once achieved is retained behind the order facility even in thickness and volume.

The task is in a method of the aforementioned Kind of solved in that the web before the order of the impregnating agent in a wide nip with pressure is acted upon by a circumferential jacket and a counter pressure element cooperating therewith is formed is.

In the Breitnip, the web is compressed a little, and that is compacted so that when applying the impregnating agent shows an excellent capillary action. The The web then soaks up with the impregnating agent, whereby the application and penetration of waterproofing agent are of course reinforced by external pressures can, as applied by cooperating rollers can be. However, such pressures can be far be kept lower so that the volume loss the web when applying the impregnating agent smaller can be held. By treatment in Breitnip takes a certain loss of volume in purchase. However, this loss of volume can be extraordinary be kept small. Due to the large exposure area the web in Breitnip it is possible to Adjust the compression of the web very precisely. The Compressive stresses that act on the web in the wide nip, can be kept relatively small.

The web is preferably heated in the wide nip. The heating has two advantages, as stated above. A warmer web has improved capillary action, i.e. the liquid impregnating agent can be absorbed more easily and penetrate into the interior of the web. To the others, the web in the Breitnip to a certain extent smoothed so that the impregnating agent on a smoother Surface can be applied, which in turn the Order uniformity improved.

The impregnating agent is preferably applied in the contour application applied. For example, a Use film press. Because in the wide nip a contour smoothing the contour application of the impregnating agent fits the previous treatment of the web in favorable way.

Fig. 1

eine schematische Darstellung einer Papiermaschine,

Fig. 2

einen vergrößerten Ausschnitt mit einem Breitnipkalander und einer Filmpresse und

Fig. 3

eine vergrößerte Darstellung eines Ausschnitts aus einer Kartonbahn.

The invention is described below with reference to a preferred embodiment in connection with the drawing. In it show:

Fig. 1

a schematic representation of a paper machine,

Fig. 2

an enlarged section with a wide nip calender and a film press and

Fig. 3

an enlarged view of a section of a cardboard web.

1 schematically shows a paper machine 100 a wire section 1, a press section 2, a dryer section 3, which is divided into two parts 3a, 3b and between the two parts 3a, 3b of the dryer section an application device 4 for an impregnating agent, like a starch solution, a so-called starch glue, or other means of order commonly used in paper finishing, e.g. an aqueous pigment dispersion, with an upstream wide nip calender 5. Behind the The second part of the dryer section 3b is a winding device 6 arranged in a paper or cardboard web 7 is wound into a winding roll 8. It is to note that between the application device 4 and the winding device 6 no longer arranged a smoothing device is, i.e. lane 7 is already in the Wide nip calender 5 and the subsequent application device provided with such a surface smoothness, that further smoothing is not necessary.

The operation of the paper machine is known per se and should therefore only be briefly explained. In the Sieve section 1 becomes liquid pulp with a solids content in the order of 1% applied to a sieve 9. The liquid flows through the sieve 9, so that the web with a solids content of about 20% in the press section 2 can break in. There are different ones Press nips formed that the paper or cardboard web passes together with a felt web 11. In The press nips 10 is further water from the web 7th pressed out and transferred into the felt webs 11. To passing through the press section 2 comes the web 7 in the dryer section 3a, where it has a variety of Drying cylinders 12 is guided. The drying cylinders 12 are heated, preferably with steam. So that will further moisture evaporated from the web 7. After this The first part 3a of the dryer section is through the web 7 the Breitnipkalander 5 and then by the order facility 4 headed. After that, it will be in the second section 3b the dryer section dried, where further Drying cylinders 13 are provided, which are also heated are to evaporate liquid from the web 7.

Fig. 2 now shows an enlarged section of the paper machine with the application device 4 and the Wide nip calender 5.

The wide nip calender 5 is formed by a heated one Counter roll 14, which is provided with heating channels 15, through which a hot liquid or other heating medium can be passed to the counter roller 14 heat. The counter roller 14 is heated so that its Surface 16 assumes a temperature of at least 200 ° C. The temperature of the surface 16 should be as high be that the web fibers at least in the area of their Surface plasticized.

The counter roller 14 forms a wide nip 17 together with a circumferential jacket 18 which, under the action of a Pressure shoe 19 on the surface 16 of the counter roller 14 rests and the counter roller 14 over part of its Circumferentially wraps. The jacket 18 is not in direct contact the surface 16 of the counter roller 14, but under Intermediate layer of the web 7. The pressure shoe 19 has a Contact surface 20, the curvature of the curvature of the Surface 16 of the counter roller 14 is adapted. In not is shown in more detail, but is known per se the contact surface 20 is lubricated, for example hydrostatically or hydrodynamic. The pressure shoe 19 can via a piston-cylinder device 21 with a Force are applied so that in the Breitnip 17 a certain compressive stress can be generated. The compressive stress in the Breitnip 17, however, is relatively small compared to a compressive stress that otherwise unchanged force relationships in a nip between two reels would prevail.

The jacket 18 can be relatively stiff, as shown and circulate like a roller shell. Here will he is supported by rollers 22. The jacket 18 can also be relatively thin, so that it is in accordance with Art of a band. In both cases, it should be a little compliant.

The wide nip 17 has one in the running direction of the web 7 relatively large length. This is preferably between 50 and 700 mm. One is therefore able to Set pressure tensions in the Breitnip 17 relatively sensitively.

The web 7 is over guide rollers 23, 24 of the application device 4 supplied, which in the present case as Film press or "Speed Sizer" is trained.

The application device 4 has two rollers 25, 26, which rotate in the direction of arrows 27, 28 and in the direction the arrows 29, 30 are pressed against each other and form a nip 31. The web 7 is guided through the nip. A certain amount of pressure is applied to it.

Each roller 25, 26 is with an impregnating agent dispenser 32, 33 provided, the impregnation film 34, 35 on the surface of the rollers 25, 26. The impregnation film 34, 35 is set so that Impregnating agent practically completely from the web 7 can be included.

The web 7 is somewhat compressed in the wide nip 17. This However, compression does not take place with the aim of the width of the web 7 to produce a uniform thickness. Rather, the pressurization of the web 7 in Breitnip 17 so that you create a uniform density. The pressurization is limited so far that flake areas are not crushed. Local thickening of web 7 is therefore retained. This can be seen in Fig. 3, where the web 7 in sections is shown in cross section. They are surveys 36 recognizable, which alternate with valleys 37. The smoothing in the wide nip 17 is therefore a contour smoothing.

The compression in the wide nip 17 is set so that the web 7 in the nip 31 of the application device 4 develops an increased capillary action. The impregnating agent from the impregnating agent films 34, 35 is therefore not only introduced into the web 7 by the pressure 29, 30. The impregnation agent entry is rather supported by the fact that the impregnation agent is absorbed by the capillary action of the web 7. As a result, it can penetrate or penetrate the web 7 much more quickly and deeply than would be possible simply by applying pressure. Due to the improved penetration of the web 7 with impregnating agent, thicker webs 7, i.e. webs with larger basis weights, for example 90 g / m ² or more, can be completely impregnated with impregnating agent without having to accept a greater loss of volume. A certain loss of volume in the Breitnip 17 is inevitable. However, this volume loss is relatively small due to the relatively low compressive stresses in the wide nip 17.

In addition, the capillary effect can also be caused by the heating the web 7 supported by the counter roller 14 become. It improves within certain limits Capillary action with increasing temperature. Indeed one will ensure that the temperature of the Lane 7 in the nip 31 of the application device 4 below 100 ° C. remains to boil the liquid waterproofing agent to prevent.

The temperature of the counter roll 14 is preferably so set that the fibers of the web 7 in the broad nip 17th be plasticized. So the fibers are shaped that they can’t line up anymore. This improves the ability of the web 7 in the nip 31 impregnating agent to record because the web is then "full-surface" can rest on the rollers 25, 26.

The application device 4 designed as a film press causes a contour application of the impregnating agent the surface of the web 7, which is also shown in FIG. 3 is recognizable. A layer 38 is shown schematically there, which symbolize the applied impregnating agent should. It can be seen that this layer 38 has essentially the same thickness everywhere.

Claims (12)

Device according to impregnate a paper or board web having a basis weight of about 40 g / m ^2, with a web running path, in which a device for applying an impregnating agent such as a starch solution, so-called starch glue, or any other customary in paper finishing applying means is arranged, characterized that in the web running path in front of the application device (4) a wide nip calender (5) is arranged, which has a wide nip (17) formed by a circumferential jacket (18) and a cooperating counter pressure element (14) through which the web running path is guided. Apparatus according to claim 1, characterized in that apart from any guide devices (23, 24) that may be present, no further processing device is arranged between the wide nip (17) and the application device (4). Apparatus according to claim 1 or 2, characterized in that the wide nip (17) has a heating device (14). Device according to claim 3, characterized in that the heating device is formed by the counter pressure element (14). Apparatus according to claim 3 or 4, characterized in that the heating device (14) has a surface delimiting the web path in the wide nip (17), the temperature of which can be set to 200 ° C or more. Device according to one of claims 1 to 5, characterized in that the application device (4) is designed as a film press. Device according to one of claims 1 to 6, characterized in that the application device (4) is followed by a drying area (36), the temperature in the wide nip (17) being higher than the temperature in the drying area. Device according to one of claims 1 to 7, characterized in that the temperature in the wide nip (17) is adjustable at least to the plasticizing temperature of the fibers of the paper or cardboard web (7). Device according to one of claims 1 to 8, characterized in that no smoothing device is arranged between the application device (4) and a subsequent winding device (6). A process for impregnating a paper or cardboard web with an impregnating agent, such as a starch solution, so-called starch glue, or other application means customary in paper finishing, the impregnating agent being pressed wholly or partially into the web, characterized in that the web is applied before the impregnating agent is applied is subjected to pressure in a wide nip, which is formed by a circumferential jacket and a counter pressure element cooperating therewith. A method according to claim 10, characterized in that the web is heated in the wide nip. A method according to claim 10 or 11, characterized in that the impregnating agent is applied in a contour application.

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