FI64210C - PROCEDURE FOR THE PURPOSE OF THE PROCESSING OF FOLLMEDELS- OCH / ELLER FINANCIAL REQUIREMENTS AND PAPERS FOR SAMT PAPER FRAMSTAELLT MED FOERFARANDET OCH / ELL ERNORDNING - Google Patents

Description

64210

Method and apparatus for controlling the thickness and / or fines distribution of the paper web in the direction of thickness and for paper produced by the method and / or apparatus

The invention relates to a method for controlling the thickness-like filler and / or fines distribution of a paper web, which method is applied in a two-wire former in which dewatering takes place through both wires, in which an aqueous filler and / or fines slurry is fed at or shortly before with feeders arranged inside and / or outside the loop.

The invention furthermore relates to devices for carrying out the method according to the invention.

The invention furthermore relates to paper produced by the method and / or devices according to the invention.

15 Fillers, which are usually minerals, are added to paper mainly because of their effect in improving their printing properties. As is known, the addition of filler takes place in two ways, either by bulk filling or by coating. In the previous procedure, the filler is added as a slurry to the pulp stock before the stock reaches the paper machine, so that the filler is mixed with all of the fibrous material in the finished paper. In the latter procedure, a suitable adhesive, e.g. starch or casein, is mixed with the filler in the aqueous phase, after which the surface of the paper is brushed with this mixture.

Fillers are usually added to the pulp as an aqueous slurry.

The addition is carried out, for example, to a pulper, grinders or close to the headbox of the machine to a suitable pulp tank or circulating water to the suction side of the pump. More commonly, fillers are used in printing papers. The addition of filler improves their opacity, brightness, ink absorption and surface smoothness. Particularly preferably, the fillers affect the quality of the paper to be polished.

Fillers adhere poorly to the fiber network, which is one important reason for poor retention of fillers. Therefore, the filtration effect of the fiber mesh-5 ton filler particles becomes an important factor influencing the retention. The filtration effect, in turn, is determined by the thickness of the pulp web passing through the wire, the density of the fiber network, the density of the wire, and the dewatering effects on the web. Grinding, which fibrillates the fibers, improves the retention of the filler by promoting the formation of a fiber network and the adhesion of the filler to the fiber.

The physical properties of the filler particles, such as their size, shape, and density, affect retention. Large particles leach better than small ones, which easily pass through the filtration layer. Heavy particles leach worse than light ones.

Like paper fines such as blanks and dyes, fillers also tend to be unevenly distributed in the thickness direction of the paper, causing the paper to be one-sided. The one-sidedness of the paper-made paper is due to the fact that the fillers are flushed with the water to be removed from the lower part of the pulp web to the filtrate water, whereby they become enriched to the upper part of the web. Retention problems have been known to be reduced not only by retention enhancing additives but also by gentle dewatering in the initial filtration step, which requires a longer dewatering distance, lengthening the wire section or reducing the speed of the paper machine.

The fines distribution on the wire section affects the smoothness of the paper smoothness and the pore structure. Unilateralism is also affected by e.g.

30 the structure and dewatering direction of the presses, so that a uniform distribution of fines on the wire section does not always guarantee that the one-sidedness of the finished paper can be avoided. A uniform fines distribution can be considered an advantage in terms of paper printability.

35 With flat wire machines, fines and filler distribution difficulties occur when making papers for offset printing. The high content of filler and fines on the top surface of the paper causes dusting, which is a serious drawback in the offset process. In contrast, papers made on a double wire machine are considered to be well suited for offset printing. This is due to the symmetrical shape of the fines distribution and the leaching of both surfaces of the web due to double-sided dewatering. It is generally considered that, due to a more even fines distribution, offset printing of paper made on a double wire machine is more successful than printing of paper made on a double wire machine. Offset printing is therefore of increasing importance, as offset printing is increasingly displacing the letterpress method.

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On the other hand, the filler content of the surfaces of the paper web is not always brought to the desired level by the two-wire former, and even with flat wires only the upper side of the web (opposite side of the wire) is satisfactory in terms of filler content. Particularly problematic is the low filler content of the web surfaces. SC gravure papers. An attempt can be made to increase the filler content of the paper surfaces by increasing the filler content of the headbox pulp, but even this solution does not achieve a satisfactory situation due to the above-mentioned poor retention and enrichment of the paper interior. In addition, when you have to increase the filler content of the headbox, the consistency of the headbox easily increases too much, weakening the paper formation.

It is an object of the present invention to reduce the retention problems described above. In addition, it is an object to provide a method and apparatus for controlling the filler or fines distribution which requires even less fillers or fines to be fed from the headbox.

This can reduce the consumption of pumping energy and keep the consistency of the headbox at a reasonable level.

It is a further object of the invention to provide a method and apparatus by which the quality properties of paper with respect to fines and fillers can be optimized in a controlled manner.

In order to achieve the above and later objects, the method according to the invention is mainly characterized in that said filler and / or slow-fed slurry is fed to the eyes of one or both wires and thereby further to the surface or surfaces of the web, taking into account said feeders in the direction of web using the dewatering elements of this dewatering step and the compressive force caused by them 5 as an aid in introducing the fine and / or filler into the web.

The supply of filler through the wire is provided by the poor fine / filler retention effect of the wires (more than 90% throughput is common) and the fact that the properties of the wires include unmarked infiltration ability (fines spread evenly as they pass through the wire).

On the other hand, the supply of filler according to the present invention is provided by the fact that the consistency of the filler slurry can be raised quite high without the risk of focusing inherent in the fibers. Therefore, the late supply of filler slurry does not necessarily imply the need for additional dewatering capacity.

Consideration of the dewatering direction when selecting the sludge feed direction and side 20, on the other hand, is crucial because the retention of the feed filler / fines is remarkably good when the dewatering effects of the next dewatering step (dewatering pressure) penetrate and adhere the If the slurry were fed to the side of the web from which the water was next removed, most of the slurry and solids therein would be washed away.

The first device according to the invention, in turn, is mainly characterized in that the device comprises a filler and / or fines slurry feed pipe supported transversely to the feel of the wire and that said supply pipe is connected to an applicator lip structure extending over the entire width of the web and having an orifice opens on the surface of the wire.

35 Said supply pipe is designed as a flow spreader so that • y 6421 0 5 the filler / fines slurry can be spread evenly over the width of the machine. In principle, such flow diffusers are, for example, the manifold of the headbox of a paper machine and the spray pipes of a paper machine. The applicator lip forms a transverse slot of the narrow machine opening into the surface of the wire, the walls of the walls of which may be of equal or different dimensions.

The second device according to the invention is mainly characterized in that the device comprises a filler and / or fines application pattern-10, the application blade of which is against the surface of the wire loop and which has a feed scraper or other slurry feed source from which the filler and / or fines fed to the spreading blade.

In a third embodiment of the invention, the device comprises a feeder containing a filler / fines slurry, from which the slurry is fed by a wire and / or roll surface to a closing groove between the wire and the roll or wire and some other element such as a curved shoe. attached to the paper web 20.

It is characteristic of said three supply devices that they are arranged to operate in connection with or in the vicinity of a dewatering element.

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For example, for the operation of the first two devices, it is advantageous to place them on the opposite side of the suction box, whereby the vacuum (suction) can be controlled by the vacuum of the suction box without pressure in the supply device. It is not necessary to proceed in this way, but pressure can be applied in the feeder 30 or the feeder can, for example, drain a flat layer of sludge above the wire shortly before the effect of the dewatering pressure begins. However, in order to increase the efficiency of the first two feeding devices, the gut formed by the wire and the roll or wire and some other element 35 can be used in connection with the third device, whereby the slurry is fed to the wire and paper web by the first or second device, after which feeding step further enhances the slurry penetration. perirainaan. Likewise, the adhesion and penetration of the sludge into the paper web can be enhanced by the ultrasonic vibration generated between the wire and an element in contact with the wire, e.g. a curved shoe. For ultrasonic applications, reference is made to Applicant's FI-Pat. No. 5 802180.

The paper according to the invention is mainly characterized in that in the thickness direction of the paper its filler and / or fines content in the vicinity of the paper surfaces is higher than said concentration 10 in the paper thickness direction on average.

In the following, the invention will be described in detail with reference to some embodiments of the invention shown in the figures of the accompanying drawing, the details of which are in no way limited to the invention.

Figure 1 schematically shows a side view of a two-wire former in which a first embodiment of the invention has been applied.

Figure 2 shows another twin wire former in which a second embodiment of the invention has been applied.

Figure 3 shows a two-wire former with a curved forming shoe in which a third embodiment of the invention is applied.

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Figure A shows a fourth embodiment of the invention.

Figure 5 shows graphically the normal filler and fines distribution obtained with the two-wire former and the effect of the addition according to the invention on this distribution.

According to Fig. 1, the forming part of the paper machine comprises a supporting wire 10, in which there is a single-wire forming part 10a after the lip opening of the headbox (not shown). The forming part includes a covering wire 11 which runs under the guidance of guide rollers 18. The carrier wire 10 and the covering wire 18 form a two-wire section known per se, in which dewatering from the web W takes place due to the turning a sector 11 of the large-diameter forming roll 12 under the effect of centrifugal forces through the covering wire 11 (arrows F). The forming roll 12 is preferably solid-coated and has a smooth surface, but a hollow-roll roll 13 can also be used. The two-wire portion 5 between the forming roll 12 and the suction roll 13 has planar boxes 19 or the like inside the loop of the support wire 10, as a result of which dewatering takes place through the support wire 10. The web W is detached between the suction roll 13 and the traction roll 14 of the wire 10 by running a wire 10 on a pickup roller 15 provided with a suction zone 15a on a pick-up felt 16 and guided forward as is known per se.

Fig. 2 shows a two-wire infiltration device in which the flow between the rollers 12 and 13 has a bend at the roll 18a, in connection with which there is a special multi-part suction box 20 with two parts 20a and 20b inside the loop of the wire 10, the cover parts 21a and 21b 10 against the inner surface. The structure and operation of the forming shoe 20 are described in more detail in the applicant's FI patent application No. 800808 (filed March 11, 1980). Due to the guiding effect of the roll 18a, the web W and the wires 10,11 change their direction at an angle 8, due to which the dewatering takes place through the supporting wire 10.

Figure 5 shows, with a broken line, the normal fines distribution obtained with a two-wire former. In Figure 5, the coordinate H shows the thickness direction of the web and Q the filler and fines content. The wire side of the web base is marked with A and the covering wire side with B.

As shown in Fig. 5 (full line), the fine filler content on the web surfaces A and B is normally, without the effect of the invention, lower than the corresponding average content. According to the invention, fines and filler additions Afi and Α ^ are obtained on both surfaces of the web, so that fines and filler concentrations Q. and Q „are obtained on the web surfaces, which are greater than said concentration Q_, in the web thickness direction on average.

According to the invention (Fig. 1), after the forming roll 12, an aqueous slurry of one or more fillers and / or fines is fed from the distribution tube 31 through the distribution lip 31 in a uniform layer over the entire width of the web W to the wire 11 covering 64210 8le. Under the influence of the dewatering direction and pressure of the flat boxes 19 or other similar dewatering means, the filler suspension fed through the lip 35 is absorbed from the mesh of the wire 11 into the web W at least in the upper area so as to give a cross-hatched increase A in Fig. 5.

According to Figure 1, before the forming roll 12, filler-slurry supply devices are arranged, which comprise a distribution tube 30 and an application lip 36 or an application pad which opens in connection with the lower surface 10 of the support wire 10. When drainage of the forming roll sector a is the centrifugal force, assisted by the wire with respect to 10 outwards and the covering of the wire 11 through the water discharge direction due to causes the filler material slurry to pass the web W, the fabric 10 side surface of the box so as to provide the web W wire 10 Side A filler addition, 15 which in Fig. 5 is indicated by a crossed-out area A.

SL

According to Fig. 2, the roll 18a is preceded by a filler or fines feed trough 32 according to the invention with a feed pond S and a spreading scraper 37. The spreading scraper 37 is opposite a suction box 20 in the direction of the wire 11 covering the dewatering scraper 37. a filler and / or fines material increases the wire 10 side of a filler content.

According to Figure 3, a curved forming shoe 22 is used, the guide surface of which against the carrying wire 10 is preferably smooth. Formation on the curved surface of the shoe 22 is optionally ultrasonic sensors 23, the "shaking effect" of which promotes the penetration of the filler and / or fines slurry added through the trough 34 preceding the shoe 22 onto the web side A. For the effect and operation of ultrasonic sensors 07.07.1980). The lower edge of the applicator lip 34 of the applicator trough 34 is formed by the curved front portion 22a of the shoe 22. Pressed by the groove of the wire 10 and the front part 22 of the shoe, efficient penetration of the filler slurry is achieved. After the forming shoe 22, there are normal leveling boxes 24, 35 which provide some dewatering, but whose main purpose is to ensure that the web W follows the support wire 10 from which it is detached to the pick-up felt, as is known per se.

6421 O

9 16 pick-up roll 15 in the suction zone 15a. Above the boxes 24, the feeding devices 31, 35 shown in Fig. 1 can be used, if necessary.

According to Fig. 4, after the forming roll 12, a two-wire portion 5a is followed by a suction roll 40 inside the loop of the wire 11. Against the suction zone 40a of the suction roll 40, a feed trough 41 with a filler and / or fines feed pond S is provided on the side of the wire 10, from which the feed scraper 42 applies sludge to the eyes of the wire 10, where it is absorbed by the web W By adjusting the vacuum in zone 10 40a, the absorption event, i.e. the intrusion, can be controlled.

Many variations are possible within the scope of the inventive idea.

For example, in Fig. 2, a roll 18 or other similar rolls can be used as an applicator roll 15 with a slurry feed trough. In Fig. 3, the curved shoe 22 can be provided with an application lip, from which the slurry is fed with an overpressure, which has the advantage of e.g. the fact that the overpressure supply does not cause a change in the shape of the web to the wires tensioned on the arc 10,11, such as to a straight-running wire, so that the pulse 20 which is detrimental to the web due to the sudden change of direction is omitted.

The invention also relates to paper produced by the method or device according to the invention, the filler and / or fines distribution of which is referred to in Figure 5, which shows that the thickness fines distribution in the paper according to the invention is such that the fines concentrations on or in the vicinity of the paper are substantially higher. than the average filler and / or fines content Q ^. As shown in Figure 5, the minimum concentration Q 1 is located substantially at the center of the thickness W of the web. Maximum web filler-30 and / or fines concentrations are obtained on either one or both surfaces A, B or in the immediate vicinity of these surfaces. In this way, the quality properties of the paper, in particular its printing properties, can be substantially improved and it can be made possible to produce paper suitable for many uses with kake wire.

35 This allows the surfaces of the web to be rinsed or high-ash (ash = filler) paper to be made. Thus, the scope of application of the double wire former is expanded.

6421 0 10

The following are claims within the scope of which the various details of the invention may vary within the scope of the inventive idea.

Claims (10)

6421 O A method for controlling the thickness-oriented filler and / or fines distribution of a paper web, which method is applied in a two-wire former in which dewatering takes place through both wires (10, 11), in which the filler and / or fines aqueous slurry 5 is fed with two or few previously provided with feeding devices (30,31,32,34,35,36,37; 41,42) arranged inside and / or outside the loop of one or both wires (10,11), characterized in that said filling and / or the fines slurry is fed to the eyes of one or both wires (10,11) and thereby further to the surface or surfaces (A, B) of the web (W) taking into account said feeders in the direction of the next dewatering event in the direction of web (W) and using dewatering elements for this dewatering step and the compressive force they cause to assist in introducing the fines and / or filler into the web (W). 15 Method according to Claim 1, characterized in that the filling and / or fines feeders are arranged both inside the loop of the supporting wire (10) and inside the loop of the covering wire (11), so that both feeders are followed by a dewatering zone ($) after the web (W). ) or dewatering devices (19; 20; 24; 33,35) for providing a dewatering effect on the surface of the web (W). A method according to claim 1 or 2, applied to a twin wire former comprising an initial portion (10a) of a single wire infiltration zone formed by a running, preferably horizontal, run following the headbox of the carrier wire (10), followed by a loop of carrier wire ( 10) an internal forming roll (12) or forming shoe (22), in the region of which the roll (12) or the shoe (22) is dewatered by a centrifugal force through a covering wire (11) and after which the roll (12) or shoe (22) followed by a two-wire portion by which dewatering takes place by means of special dewatering means (19; 20; 24) through the supporting wire (10), characterized in that said forming roll (12) or forming shoe (22) is in front of and / or or thereafter, filling and / or 6421 0 fines feed devices (30,36; 32,37; 34; 41,42) are arranged inside the loop of the supporting wire (10) so that the filling and / or grinding noainetta imeyte on the surface of the web (W) bearing the wire (10) by the suction effect caused by dewatering provided by special suction devices (33; 40a) and / or through the covering wire (11) when the wires (10, 11) change direction of said forming roll ( 12) or guided by a forming shoe (22). Method according to Claim 3, characterized in that filling and / or fines supply devices (31, 35) are arranged inside the loop of the covering wire (11), by means of which filling material is fed to the surface (11) on the covering side of the web (W). and / or fines addition utilizing the dewatering means (19) for providing dewatering through the supporting wire (10). 15 Method according to Claim 1, 2, 3 or 4, characterized in that said addition of filler and / or fines is effected by a special scraper device (37; 42) which feeds the filler and / or fines into a feed trough (32; 41). ) from the pond (S) to the meshes of the wire (10,11) 20 and thereby by the action of dewatering and / or a special suction device (33; 40a) further to one or both surfaces (A, B) of the web (W). Apparatus for carrying out the method according to claim 1, 2, 4, 4 or 5, characterized in that the apparatus comprises a filler and / or fines slurry supply pipe (30) supported in the transverse direction of the wire (10,11) and that a supply lip structure (35,36) is connected to said supply pipe, which extends over the entire width of the web (W) and the mouth of which opens onto the pin-30 of the wire (10,11). Device for carrying out the method according to claim 1, 2, 4, 4 or 5, characterized in that the device comprises a filler and / or fines application scraper (37; 42), the application blade 35 of which is against the surface of the wire loop (10, 11) and in connection with the spreading scraper device, there are feeding devices or a feeding pond (S) with which the filler and / or fines are fed in connection with the spreading blade of the scraper. 6421 O Device according to claim 6 or 7, characterized in that special suction devices (33; 40a) are arranged inside said loop of the wire (11) opposite to said spreading lip (35, 36) or spreading scraper (37; 42), the main or additional purpose of which is to absorb the addition of filler and / or fines introduced by said feeders into the fibrous network of the web (U). Device for carrying out the method according to Claims 1 to 5, characterized in that the device comprises a feed pond containing filler and / or fines slurry, from which the slurry is fed by the wire and / or roll surface by means of wire and roll or wire (11) and some other element such as a closing shoe between a curved shoe (22), where the resulting pressure penetrates the filler / fines slurry into the paper web (W). 15 Paper produced by the method according to Claims 1 to 5 and / or by the device according to Claims 6 to 9, characterized in that in the thickness direction of the paper its filler and / or fines content (Q iqg) in the vicinity of the paper surfaces (A, B) is greater than said concentration (Qg) in the paper thickness direction on average (Figure 5). 6421 0