FI81404C - Method for tip drawing a paper web and apparatus for use in the method - Google Patents

Description

81 404 1 Method The device used in the head and flight of the paper web

The invention relates to a method for using a paper web head and a device used in the method.

10 Paper web breaks most often originate in the edge areas of the web because they are subjected to greater stresses in the paper machine, especially in multi-cylinder dryers, and especially in its free web pulls due to flutter, than in the central areas of the web. Difficulties in exporting the head of the web and the problems caused by the breaks in the web are particularly pronounced on paper machines which produce relatively thin grades. Especially as paper machine speeds increase, these problems become more pronounced.

Prior art solutions aim to increase the edge strength of the paper web by increasing the basis weight or increasing the proportion of long fiber in the pulp. This is a very expensive method and therefore is not usually used. The strength of the paper web has also been improved by adding various chemicals to the short cycle of the paper machine. This so-called pulp gluing takes place over the entire width of the paper web. However, this does not apply to all paper grades and is also a cost-increasing method.

It is an object of the present invention to provide a new method and apparatus which has been able to increase the speed of paper web head export and to facilitate paper web head export.

30

According to the invention, it has been realized to build a liquid or powder chemical applicator on the press or at the beginning of the drying section, which spreads the chemical drying the web from the width of the headband. In the method according to the invention, the dry matter content of the paper web is thus increased by the width of the headband. As the dry matter content increases, the paper web is more resistant to head tapping and at the same time increasing the dry matter content reduces the adhesion of the head tension tape to the cylindrical surfaces. The drier track can also be passed more easily without separate cord outlets and guiding blow jets.

The method according to the invention is mainly characterized in that in the method 5 an additive chemical is applied to the surface of the paper web, which is adapted to dry the paper web. fiber bonds and thus improve the durability of the web.

The device according to the invention is mainly characterized in that the device comprises a container containing an additive chemical applied to the edge region of the paper web, adapted to absorb water from the paper web, thereby increasing the dry matter content of the paper web and thus increasing the edge strip strength.

The invention will now be described with reference to some preferred embodiments of the invention shown in the figures of the accompanying drawings 20, to which, however, the invention is not intended to be exclusively limited.

Figure 1 schematically shows an additive 25 applicator according to the invention.

Figure 2A shows the additive applicator used in the method according to the invention in connection with the central roll of the press part.

Figure 2B shows the scraper structure used to apply the additive material.

Figure 3 schematically shows another position of the additive applicator.

Figure 4 shows a third additive applicator according to the invention

II

35 3 81404 1 embodiment. In the embodiment of the figure, a special application roller is used as the additive applicator.

As shown in Fig. 1, the paper web W is reinforced from the region 5 of the edge strip so that an additive 11 is introduced from the container 10 onto the upper surface of the paper web W, which removes water from the paper web W. The import of the additive also reduces the adhesion of the paper web W to the surfaces of the cylinders. The method according to the invention uses an additive which increases the dry matter content of this part of the paper web and improves the bond strength of the fibers. Examples of such substances may be calcium carbonate, glauber's salt, starch glue or the like. The additive chemical has a substantially different composition than the paper web W. These substances can be applied either in liquid or powder form. The reinforcement of the strip is based not only on the water-binding effect of the dry powder but also on the effect of the fiber bonds due to the additive. The drier track W also adheres less weakly to the cylinder surfaces. The chemical can be applied with a wire section or a press section or at the beginning of the drying section. In Fig. 1, the direction of travel of the paper web is indicated by an arrow L 1 and the additive chemical layer introduced into the edge area of the paper web, i.e. the additive film, is marked with a ll.

Figure 2A shows a preferred embodiment of an additive applicator according to the invention. The apparatus comprises a nozzle 12 which applies the additive 11 to the central roll 13 on its side. Excess additive 11 is removed 25 by one or more scrapers 14. The additive applied by the nozzle 12 travels forward in the edge region of the roll 13 and further to the press nip between the rollers 13 and 15, where it adheres to the paper web W. The additive 11 is thus applied via the central roll 13.

As shown in Figure 2B, the scraper 14 may be shaped to scrape off the additive 11 from the surface of the roll 13 elsewhere, but leave it at the desired location on the roll surface 13a. The scraper 14 may also be displaceable with respect to the roll width and thus the desired coating area may be selected by changing the position of the scraper 14. The clearance S of the scraper 14 and the roll surface 35 13a may also be adjustable to apply the desired amount of additive chemical to the paper web W. The clearance S leaves the additive chemical film 11a on the roll 13 surface 13a and the film 11a is further impregnated This gives an edge band area coated with the contaminant chemical 11.

Figure 3 shows the spraying of additive chemicals 11 directly onto the top roll 16 of the press-5 tin nip. Thus, the top 11 of the top roll 16 is introduced into the position above the roll by spraying it from the nozzle 12. The scraper 14 forms a film 11a of desired thickness on the roll surface 16a. The roll 16 further transfers the chemical 11 in connection with the paper web W to the nip N 1 between the upper roll 16 and the lower roll 17, where the Kemi-10 cabbage 11 is absorbed into the paper web W at its edge region. The absorption is facilitated by the pressure prevailing in the nip N ^.

The import of the chemical 11 can take place continuously or only in a certain driving situation, in which case an embodiment of the invention is also possible in which an additive chemical is introduced into a certain area of the paper web and the substance is further removed from the paper web for later use. In that procedure, the chemical costs do not increase.

Figure 4 shows the use of an application roller 18 as a chemical 11 applicator. The applicator roll 18 is preferably the width of the desired chemical-potassium film. The applicator roll 18 is located partially immersed in the container 19 where the additive chemical 11 is located. The application roll 16 is pressed onto the center roll 13 as shown in the figure. The center roll 13 thus rotates the application roll 17, whereby the additive 11 moves from the container 19 attached to the application roll 18 surface 18a and on the application roll 18 surface 18a to the nip N 1 between the application roll 18 In said nip N 1, it is attached to the central roll 13 and passes further with the central roll 13 to the press nip N 1 between the central roll 13 and the counter roll 15. In the nip, the chemical 11 adheres to the paper web W 30 at its edge area.

There is also a possible embodiment of the invention in which the powdered additive is applied by sprinkling on the edge area above the paper web from the container 10. The sprinkled material 11 is transferred to the press nip on the upper surface 35 of the paper web W and finally adheres to the paper web W in the nip.

Claims (11)

A method for securing a paper web head to a paper web head, characterized in that an additive chemical (11) is applied to the surface of the paper web (W) adapted to dry the paper web (W) over the width of the headband, whereby the dry and at the same time, as the dry matter content increases, the adhesion sensitivity of the headband to the cylinder surfaces is reduced and fiber bonds are added in the region of the headband 10 and thus the durability of the web (W) is improved. 1 Claims Process according to Claim 1, characterized in that a liquid or powdery substance is used as the additive chemical. 15 Process according to Claim 1 or 2, characterized in that calcium carbonate or starch glue or glauber's salt is used as the additive chemical. Method according to one of the preceding claims, characterized in that the additive chemical (11) is applied to the surface of the roll (13; 16) and conveyed on said roll surface (13a, 16a) to a press nip (N 1; 6) between the roll and the counter roll, where the additive chemical ( 11) adheres to the surface of the paper web (W) at its edge region. 25 Method according to one of the preceding claims, characterized in that a scraper (14) is used on the surface (13a, 16a) of the roll (13; 16) by means of which the additive chemical (11) is conveyed to the press nip (Ν ^, Ν ^). so adjustable as to leave an additive film (11a) of suitable thickness and width on the roll surface (13a; 16a). 5 81404 Method according to one of the preceding claims, characterized in that the additive (11) is applied from the container (19) by means of an application roller (18) partially placed in the container as the additive adheres to the surface (18a) of the application roller (18) and moves from the application roller (18) to the application roller ) engaging a central roll (13), on the surface (13a) of the central roll (13) the additive (11) is further transferred to a press nip (N 1) between the central roll (13) and the counter roll (15), where the additive (11) adheres to the paper web (W) surface to its periphery. 6 81404 Ί A method according to claim 1, characterized in that the additive chemical (11) is sprayed or sprayed or drained directly on the upper surface of the paper web (W) in the region of its edge band and that the additive chemical (11) is then attached to the paper web (W) 5 by passing it. with the additive chemical sprinkled on top of the press nip of the paper machine press. Device for securing a paper web head according to one of the preceding claims, characterized in that the device comprises a container (10) containing an additive chemical (11) applied to the edge region of the paper web (W) and adapted to absorb water from the paper web ( W), thereby increasing the dry matter content of the paper web (W) and thus increasing the strength of the edge tape. 15 Device according to the preceding claim, characterized in that the device comprises a nozzle (12) by means of which the substance (11) is sprayed from the container (10) directly into the region of the edge strip or roll surface (13a; 16a) of the paper web (W). 20 Device according to one of the preceding claims, characterized in that the device comprises additive chemical import arrangements, e.g. a nozzle (12) arranged in a position close to the center roll (13), the additive chemical (11) being applied from the nozzle (12) to the center roll (13) the additive chemical is conveyed to the edge area and via the central roll to the press nip (N 1) between the central roll (13) and the counter roll (15), where the additive chemical (11) adheres to the paper web (W). Device according to one of the preceding claims, characterized in that the device comprises a container (19) with an additive chemical (11) and an applicator roll (18) extending at least partially into the container (19), which roll (18) is a pressed central roll ( 13), wherein the additive chemical travels on the surface (18a) of the applicator roll (18) 35 to the nip (N 1) between the applicator roll (18) and the central roll (13) and adheres to the surface (13a) of the central roll (13) in said button (N 1), the additive chemical (11) further travels on the surface (13a) of the central roll (13) to the press nip (N 1) between the central roll (13) and the counter roll (15), where the additive chemical (11) adheres to the paper web (K) at its edge region . 5 10 15 20 25 30 35 81404 8