EP0183863B2 - Format paper with a low dust content, process for its manufacture and its use - Google Patents

Abstract

1. Format paper with 2 to 7 wt. % water, 10 to 20 wt. % ash and, as the remainder, paper fibrous materials with a woody fibre fraction of more than 10 wt. %, referred to the paper fibrous materials, a brightness within the range from 65 to 91, characterised by dust adhesion Mv at least one longitudinal edge corresponding to a luminous reflectance value by the adhesive tape method within the range from 2 to 6, and dust adhesion at least one transverse edge corresponding to a luminous reflectance value by the adhesive tape method below 1.5, in each case measured on a ream of paper.

Description

The invention relates to format paper with 2 to 7% by weight of water, 10 to 20% by weight of ash and, as the remainder, paper fibers with a proportion of more than 10% by weight, based on the paper fibers, woody fibers, a brightness in the range from 65 to 91, and processes for its production and use.

Low-dust format papers are increasingly required. These are particularly important for use when copying. In the production of copy papers, it is possible to start exclusively with cellulose, which fillers and conventional paper chemicals, e.g. B. glues, are added during manufacture on the paper machine.

High demands are placed on copy papers with regard to the properties that can influence the copying process. Good smoothness and rigidity of the paper suitable for copying are just as important as controlled moisture and sufficient picking resistance, dimensional stability and properties that allow good toner fixation, legibility and resolving power. Other criteria of importance for copy papers are format accuracy, right-angled cut as well as low dust and burr-free format paper.

The increasing awareness of the need to protect the environment and the scarcity of valuable raw materials has favored the production of so-called recycled paper in the area of the production of paper.These are made from possibly pre-sorted waste paper, such as waste paper from magazines, people who refuse to print, household items, etc., whereby efforts are made are becoming more and more important properties of wood-free paper in important properties due to procedural improvements. This applies in particular with regard to the production of copy papers which are essentially made from waste paper components.

The present invention has for its object to novel paper formats based on recycling, ie. H. at least partially starting from waste paper, which have particularly favorable properties with regard to their use for copying. The papers should have a particularly low level of dust and burr-free cuts. The invention is also directed to methods for producing such low-dust format papers and to their use as copy papers.

This task is accomplished by creating a format paper with 2 to 7% by weight of water, 12 to 20% by weight & ash and the remainder of paper pulps with a share of more than 10% by weight, based on the pulps, woody fibers and a brightness in the range from 65 to 91, which is characterized by dust adherence Mv on at least one longitudinal edge corresponding to a light reflectance value according to the adhesive tape method in the range from 2 to 6, and dust adherence on at least one transverse edge corresponding to a light reflectance value according to adhesive tape method below 1.5, measured in each case on the paper giant, and solved by methods for its production

The term "longitudinal edge" used in the context of the invention denotes the edge of the format paper which was cut with the longitudinal knife, while the term "transverse edge" stiffens the cut through the transverse knife. For narrow web cuts, this means that with A4 and A3 formats, the longer edge is the "longitudinal edge" (and the "transverse edge" is the shorter). In the case of wide web cuts, the "longitudinal edge" becomes the shorter edge (and the "Querilcante" the longer edge) for the formats A4 and A3.

The proportion of lignified fibers, based on the fiber materials, can be very high, and it is even possible that the lignified fibers form almost the entire proportion of fibers. In the context of the invention, woody fibers are understood to mean either wood sanding itself, or refiner sanding or TMP (thermo-mechanical pulp) or TCMP etc. fibers or mixtures thereof. According to one embodiment of the paper according to the invention, the woody fibers are represented with 58 to 82% by weight of the (paper) fiber fraction, and particularly preferably with 65 to 80% by weight of the fiber fraction, the remaining fiber fraction being formed by cellulose fiber.

The paper according to the invention is particularly controlled with regard to its ash content, which is preferably between 14 and 17% by weight, based on the paper. The water content or the moisture of the paper according to the invention is also controlled within narrow limits and is particularly preferably between 4 and 5.5% by weight, based on the total paper.

Accordingly, in a particularly preferred embodiment, the low-dust paper according to the invention has (4 to 5.5) ± 0.5% by weight of water, 14 to 17% by weight of ash and the remainder paper pulp, with respect to the pulp , the proportion of woody fibers makes up 65 to 80% by weight. It is also preferred that the paper according to the invention has a brightness in the range between 73 to 80.

The paper according to the invention is characterized in particular by a very low level of dust, the dust adhesion on at least one longitudinal edge being in the range from 2.5 to 6 and preferably 2.5 to 5.5. High-quality papers which are particularly suitable for copying purposes have a medium one Dust adhesion in the range from 2.5 to 5 min at least one longitudinal edge. In the context of the invention, but in particular the use of the papers according to the invention for copying, those specifications are preferred which have the specified values for dust adhesion on at least one longitudinal edge, but particularly advantageously on both longitudinal edges present. Due to the high level of dust of the papers according to the invention, those are particularly well suited for use in copying which have the above-mentioned dust adhesion areas and in particular those specified here for one longitudinal edge, while the other longitudinal edge has dust adhesion values which are around 10 to 40% and can preferably be 12 to 30% higher.

The papers according to the invention can have a bulk density in the range of 0.65-0.90 gsm ³ (according to DIN 53105), the range of 0.7-0.8 being particularly advantageous.

The format paper according to the invention also has a small proportion of cross-edge dust, which is generally less than 1.5 and preferably in the range from 0.5 to 1 for at least one cross-edge, but advantageously both cross-edges.

The above-mentioned values for dust adhesion on the longitudinal and transverse edges (n) each relate to the adhesive tape methodology explained in more detail below, measured on the paper giant.

The surface dust of the format papers according to the invention is also low, with a dust number of less than 3 for one, but preferably both, paper surfaces (i.e. both the top and the bottom of the paper). The values for the dust number relate to the determination by means of a Lorentzen & Wettres dust tester of the code no. 56 of the Swedish manufacturer mentioned, the methodology being explained in more detail below.

As previously mentioned, the paper according to the invention is produced from at least partially waste paper. It is preferred that the paper is obtained from at least 60% pulp, preferably 70 to 100% and particularly preferably completely from pulp that was produced from waste paper. If only partial use of pulp from waste paper is used, a corresponding share of native materials used for paper production is added.

In principle, the papers according to the invention can be produced by methods such as are the subject of German patent applications P 3 148 749 and 3 148 750 (applicant Steinbeis Papier GmbH, Gemmrigheim), although additional, complex measures are provided to achieve a low dust level of the papers according to the invention .

The invention is particularly advantageously directed to low-dust form paper, which is preferably in A4 and A3 format, with 4 to 5% by weight of water, 14 to 17% by weight of ash, and the remainder paper pulp with a proportion of 65 to 80% by weight, based on the fiber materials, woody fibers, a brightness in the range from 73 to 80, with dust adherence on at least one longitudinal edge corresponding to a light reflectance value according to the adhesive tape method in the range from 2 to 5.5, and dust adherence according to adhesive tape methodology on at least one transverse edge corresponding to a light reflectance value below 1.1, measured in each case on the paper giant, producible using possibly sorted, processed waste paper using a dissolving, deinking, sorting and optionally dispersing and bleaching stage ( n), as well as paper production from 60 to 100% of the pulp obtained in this way on the paper machine, the optionally using crushing bars with Integrated dust extraction at a speed of 100 to 400 m / min. Blown guided paper webs in the longitudinal cut in the cut and the resulting dust is suctioned off, after which the longitudinally cut paper web is guided over an elongated-hole suction table in such a way that the longitudinal edges of the paper web lie exactly over the elongated holes, from which dust is again drawn off and then on the transverse measuring and dust is blown off or drawn off again during the subsequent reaming application, the vacuum applied for dust extraction being kept in the range of advantageously 250 to 80 mbar.

The process according to the invention for producing format papers with a proportion of woody fibers of more than 10% by weight, as mentioned above, sees the use of optionally pre-sorted, processed waste paper using dissolving, deinking, sorting and optionally dispersing and Bleaching stage (s), which is then followed by paper production on the paper machine, dust being drawn off during the cutting process, both during longitudinal cutting and during transport for cross cutting as well as during cross cutting of the paper produced.

According to an advantageous embodiment of the method according to the invention, a dust extraction is also provided after the cross cutting during transport and sorting.

It is also of particular advantage in the context of the method if the glue liquor circulated is filtered.

The composition of the sizing can also influence the low dust level, which is why it is preferred not only to add resin glue but also cationic starch in addition to the usual auxiliaries.

In the method according to the invention, air is blown into the cut edge of the paper web, which is optionally guided over break bars with integrated dust extraction, and the resulting dust is suctioned off, after which the longitudinally cut one The paper web is guided over a suction table having elongated holes in such a way that the longitudinal edges of the paper web lie exactly above the elongated holes from which dust is again drawn off and then dust is blown off or drawn off again at the transverse knives.

According to the cross-section, it can also be advantageous to blow off or remove dust again from the building giants in the transverse channel.

The counter-rotating upper and lower knives of the slitter or cross cutter preferably have a hard metal or WIDIAO alloy coating on at least one knife. It can also be preferred within the scope of the method according to the invention to arrange the upper and lower knives without angles to one another in order to achieve an optimal cutting-time behavior.

After the longitudinal cut has been made, the paper web is guided, as mentioned above, over a suction table having elongated holes, dust being drawn off from the region of the longitudinal edges by a vacuum. This is additionally facilitated by the fact that the elongated holes are preferably arched transversely to the direction of transport of the paper webs, so that the giant ^R conveyed thereon "blows up and also releases the dust from the inner regions of the paper webs. In addition, the dust can also be extracted through the elongated holes acting brushes can be improved, for example they can be designed as rotary brushes which are arranged directly above the elongated holes.

According to a further embodiment of the method according to the invention, dust can additionally be suctioned off in the area of the lower knives of the longitudinal knife section, and, as mentioned above, air blowing from below can also be present in the area of the upper knives for extracting dust.

The vacuum in the dust extraction in the area of the lower knives of the longitudinal knife and / or cross knife section and / or the suction table can be at cutting speeds between 100 to 400 mlmin. advantageously be kept in the range of about 250 to 40 mbar. The best results are achieved in this area, although it is also possible to set the vacuum values specified above the limit values.

Regarding the details of the pretreatment of the waste paper, the type of the waste paper and its conversion into pulp, which can be used proportionately, but also completely for the production of the paper according to the invention (preferred proportions 60 or 70 to 100%), is referred to the aforementioned German Patent applications P 3 148 749 and P 3 148 750 (Applicant Steinbeis Papier GmbH, Gemmrigheim). However, it is also possible to modify these previously known methods for producing suitable papers or to use other methodologies, but the measures mentioned above are used to achieve a particularly low level of dust. These measures are explained in more detail below with the aid of the respective device shown in the figures, these also being intended to represent a preferred part of the invention claimed here.

The method according to the invention ( ^R adhesive tape method ") for determining the cut edge dust is now described below: It is based on the principle that a clear or transparent adhesive tape is applied to the edge to be measured on a clamped paper giant and then removed again. The clear adhesive tape the adhering dust is applied to a black adhesive tape and the brightness of the black adhesive tape stuck with the clear adhesive tape is measured, the standard value being the black adhesive tape with the applied clear adhesive tape which was not applied to a paper giant, the deviation of the brightness from the initial value represents represents a measured value that allows conclusions to be drawn about the amount of dust used. In particular, the measurement method according to the invention, on which the above-mentioned values of the edge dust are based, is used:

A transparent adhesive tape with the following specification: PVC film 19 mm wide with a tensile strength of 100 N / 25 mm, elongation 50%, adhesive strength 7 N / 25 mm with an adhesive made of acrylic resin. "Tesa®-Film" clear, No. 4206 (Beiersdorf, Hamburg) was used as a representative of such a clear adhesive tape.

A 30 mm wide specification is suitable as black adhesive tape. As such, "Tesa® film" No. 104 black (manufacturer Beiersdorf, Hamburg) was used with advantage.

Furthermore, the following are required or useful: carton 250 glm ² , a tensioning device for the ream, a suitable design being shown in FIG. 1. Furthermore, a load roller for the adhesive tape with a weight of the roller of approx. 6 kg, the roller being held in such a way that the axis remains freely movable and no additional force is exerted on the press gap during the loading process. The roll is covered with a rubber layer with a hardness of 40 ° Shore A. Finally, a so-called Hunterlab device is used (D 25 D 2MIL color and color difference measuring device from Hunter Associates Laboratory, Inc., 9529 Lee Highway, Fairfax, Virg. 22030, USA). The measuring opening is reduced to a value of 15 x 49 mm (according to FIG. 3).

The Hunter D 25 D2 MIL device also measures the brightness of the referenced papers. All measurements are based on the LAB system as nominal conditions (measuring conditions 115 V, 50 to 60 Hz, 45 ° Lighting, 0 ° view). The standard was C2-3598 with L = 94.55 and A = 0.7 and B = + 0.4.

The individual procedure is as follows: The cardboard is cut to approx. 35 - 50 cm and glued parallel to the long edge at a distance of approx. 2 cm with black adhesive tape (Tesa film No. 104)

A ream is pushed open to the side and clamped with the pushed edge down into the tensioning device (according to FIG. 1). The pressure on the pressure gauge is adjusted so that a weight of 1 kg / cm ^{2 is} exerted on the ream according to the area in the piston becomes.

With regard to the longitudinal edge to be checked, the rip cut there is cut approx. 10 mm below the longitudinal edge with a carpet knife. This prevents any cutting dust from getting through the cut of the wrapping paper on the surface to be tested.

The clear adhesive tape (Tesa® film No. 4206) is now applied to the cut edge over the entire length and pressed five times with the load roller. The feed speed for the roll is selected so that a loading process for the longitudinal edge takes approx. 1 second for A4 format and proportionally shorter for the transverse edge. The roll is also guided in such a way that only its own weight is loaded.

Approx. 5 to 10 seconds after loading, the clear adhesive tape is peeled off in approx. 2 seconds (with A4 format) with a force between 0.75 and 1.25 N, preferably approx. 1 N, and onto the black adhesive tape ( Tesa®-Film No. 104) applied over the entire length in the middle in such a way that the adhering dust is enclosed between the two adhesive tapes. The tape is then pressed on evenly without bubbles using a cloth

Brightness measurements are then carried out on the Hunterlab device with the reduced measuring aperture (FIG. 3). B. three measurements per edge are sufficient.

The brightness of the black adhesive tape (Tesa® film No. 4206) stuck with the dust-free clear adhesive tape (Tesa® film No. 4206) is entered as a starting value in the Hunterlab device. The deviation from the initial value is then used as the measured value for the dust intensity.

A different paper cut surface is recorded across the width of the measurement opening in accordance with the sheet thickness or the basis weight. In order to essentially rule out this influence and to obtain comparable values, the measured value M found is converted to a unit bulk density of 1 g / cm ³ , ie multiplied by the ratio of the bulk density.

• Mv = Vergleichsmesswert
• M = Messwert
• p1 = Rohdichte 1,0 glcm³
• p = Rohdichte des zu messenden Papiers,
• L_w = Helligkeit 90 %
• L = Helligkeit des zu messenden Papieres.

In order to rule out the influence of different reflection of different fiber materials, the measurement result M is additionally converted to a uniform brightness of 90%. This gives the comparison measurement value Mv, which enables the comparison of different papers in the range of the indicated brightnesses, regardless of the basis weight and thickness.

• Mv = comparison measured value
• M = measured value
• p1 = bulk density 1.0 glcm ³
• p = bulk density of the paper to be measured,
• L _w = brightness 90%
• L = brightness of the paper to be measured.

With this method, based on the comparative measurement of reflectance values, conclusions can be drawn about the dust adherence on the longitudinal and transverse edges.

The surface dust values were determined using a code 56 dust tester from AB Lorentzen & Wettre, Sweden. The determination of the dusting number is based on the fact that a number of sheets of paper are brought into contact with water via rollers, and the dust picked up here is retained on black filter paper and compared visually. In particular, a type according to drawing A 3178-4375 of the manufacturer's announcement dated January 21, 1983 and the measurement method described herein are used as the dust tester of code 56.

• Fig. 1 zeigt eine Spannvorrichtung zur Ermittlung des Kantenstaubes;
• Fig. 2 zeigt eine Ansicht der Auflagerolle, eingesetzt zur Ermittlung des Kantenstaubes;
• Fig. 3 zeigt die verkleinerte Messöffnung des Hunterlab-Gerätes;
• Fig. 4 stellt grafisch die ermittelten Helligkeitsdifferenzen in nicht korrigierter und korrigierter Form dar, die bei der Messung an den Längskanten bei erfindungsgemässen Papieren und drei Handelsprodukten festgestellt werden konnten;
• Fig. 5 zeigt schematisch die Aufeinanderfolge der einzelnen Entstaubungsmassnahmen vor, beim und nach dem Längs- und Querschneiden der auf der Papiermaschine erzeugten Papiere;
• Fig. 6 zeigt eine Brechleiste mit integrierter Staubabsaugung;
• Fig. 7 zeigt einen Längsschnitt der Staubabsaugung über Luftverblasung im Bereich der Längsmesser sowie eine Staubabsaugung im Bereich der Untermesser der Längsmesserpartie;
• Fig. 8 zeigt einen Schnitt über einen Saugtisch mit Langlöchem, über den das Papier nach dem Längsschnitt geführt wird;
• Fig. 9 zeigt die Staubabsaugung im Bereich der Quermesser, während
• Fig. 10 die Staubabsaugung im Quertransport seitlich an den Transportgurten im Schnitt darstellt.

The invention is illustrated below in the figures, which represent preferred embodiments of the invention individually and in combination.

• Fig. 1 shows a clamping device for determining the edge dust;
• Fig. 2 shows a view of the support roller, used to determine the edge dust;
• 3 shows the reduced measurement opening of the Hunterlab device;
• 4 graphically shows the determined brightness differences in uncorrected and corrected form, which could be determined during the measurement on the longitudinal edges with papers according to the invention and three commercial products;
• 5 shows schematically the sequence of the individual dedusting measures before, during and after the longitudinal and transverse cutting of the papers produced on the paper machine;
• Fig. 6 shows a break bar with integrated dust extraction;
• 7 shows a longitudinal section of the dust extraction via air blowing in the area of the longitudinal knife and a dust extraction in the area of the lower knife of the longitudinal knife section;
• Fig. 8 shows a section over a suction table with slots, over which the paper is guided after the longitudinal cut;
• Fig. 9 shows the dust extraction in the area of the cross knife, during
• Fig. 10 shows the dust extraction in lateral transport on the side of the conveyor belts in section.

The tensioning device shown in FIG. 1 for determining the amount of edge dust on a paper giant according to the adhesive tape method comprises a base plate 10, on which a hydraulic pump unit 12 is attached in the right half in FIG. 1. This pump unit is actuated by an electrical switching device 14, on the top of which switching buttons 16 are arranged. The space on the right above the base plate 10 with the pump assembly 12 and the switching device 14 is delimited by a separating plate 18 welded on at right angles above the base plate 10. On the side of this separating plate 18 facing away from the pump assembly 12 there is a hydraulic drive 20 which is hydraulically connected to the pump unit 12 via hydraulic lines 22 and a manometer 24. On the side facing away from the separating plate 18, the hydraulic drive 20 is connected to a movable clamping plate 26. At a distance from this movable clamping plate 26 there is a fixed clamping plate 28 on the side facing away from the separating plate 18, which is welded onto the base plate 10 in parallel relationship to the movable clamping plate 26. On the two end faces of the clamping plates 26 and 28 there are cutouts 30 which serve to facilitate manual grasping of a ream which is to be clamped between the clamping plates.

The paper to be examined is inserted between the clamping plates before the examination, after which the movable clamping plate 26 is moved by means of the hydraulic drive 20 onto the fixed clamping plate 28 until the desired pressure is displayed on the manometer 24, which corresponds to the defined pressure with which the paper giant is to be pressed together by the clamping plates.

The support roller shown in FIG. 2 for pressing the adhesive tape onto the edge surface of the ream to be examined with regard to the dust accumulation consists of a steel core 32, on the circumference of which a rubber jacket 34 is applied. Since this support roller should only exert a defined pressure on the adhesive tape, which corresponds to the weight of the roller, a special connection between the roller and the handle 36 is provided. This connection is designed such that pins 38 are arranged on the axial end faces of the steel core 32, each of which engages in a guided but movable manner in an elongated hole 40 of a holding bracket 42, which holding bracket 42 is provided with a push rod 44 and a handle 46 attached to it. in the illustrated embodiment, the push rod 44 is welded at right angles to the center of the bracket 42.

This constructive structure of the support roller prevents the drive force applied when moving the roller from having a component in the direction of the support surface of the support roller, so that a defined pressure always acts on the adhesive tape when the roller is moved.

FIG. 3 of the drawings shows a section according to FIG. 3a and a plan view according to FIG. 3b for dust measurement by means of the so-called “Hunterlab” device. As a basic element, this diaphragm consists of a solid ring 46 with a height H. The ring is conically tapered on the inner circumference and on the outer circumference in the same sense, so that a large upper ring opening 48 and a lower, smaller ring opening 50 are provided in the interior of the ring 46 is. This lower, smaller ring opening 50 has a rectangular shape with a width b and a length I, which is greater than the diameter D of the upper ring opening 48. The actual diaphragm opening is thus formed by the lower ring opening 50

4a and 4b each show a diagram. The difference in brightness is plotted on the ordinate of the diagrams. The abscissa indicates whether it is the paper according to the invention or a commercial type I, II or 111 paper. The boxes indicated in the diagrams indicate the brightness difference ranges for the respective paper quality, the reference size being the black one Is the surface of the reference surface, which practically results in a reflection of 0, i. H. a minimal remission sanctity If the dust removed from the edge of the paper giant is on the black reference surface due to the adhesive tape, the reflectance brightness varies depending on the amount of dust, i. H. bigger the more dust there is. The diagrams clearly show that the brightness difference values for the paper according to the invention are substantially lower than for the known paper types specified, i.e. H. the paper according to the invention has in the region of the edges or edges a significantly lower accumulation of dust which has arisen from the cutting action on the paper.

Fig. 5 shows schematically a part of a system which shows, in succession, processing stations in which the paper web is acted on in different ways. In particular, various dedusting measures are taken.

5 shows, from left to right, a station A in which the paper web is guided past a break bar. This is followed by a station B, in which, if desired, the paper web is perforated through a rotary hole. This is followed by the longitudinal process in a station C. cutting the paper web. The paper web is cross-cut in a subsequent station D, which is followed by a sorting switch E and a collecting station F, where the cut paper sheets are sorted or stacked. In the last station G, the stacked sheets of paper are transversely transported.

The individual stations are now described below on the basis of FIGS. 6 to 10:

6 shows the crushing bar 52 located in station A with integrated dust extraction. As can be seen in FIG. 6, the paper web P runs from a roller 54 to the break bar 52, where the paper web is guided with a deflection (a) around an edge 56 of the break bar 52

The crushing bar consists of a hollow box 58, in which a suction nozzle 60 is fastened on the side facing away from the breaking edge 56, to which suction nozzle 60 a hose 62 is fastened

The breaking edge 56 is located on a block 64 which is fastened on the side of the hollow box 58 facing away from the suction nozzle 60. In the immediate area of the breaking edge 56 and in the running direction of the paper web P in front of the breaking edge 56, there is a suction channel 66 in block 64, which is aligned with a suction opening 68 in hollow box 58. Two suction channels 66, 67 are provided in a symmetrical arrangement, so that block 64 The position can be changed such that after the breaking edge 56 has worn, the breaking edge 57 arranged symmetrically thereto can be used.

According to the double arrow 69, the entire crushing bar 52 can be pivoted back and forth about the central axis M of the roller 54 to a specific deflection angle (a).

When suction is carried out through the hose 62, an air flow results according to the arrows shown from the area immediately in front of the breaking edge 56, through the suction channel 66, the suction opening 68, the hollow box 58 into the suction nozzle 60, so that more accumulates in the area of the breaking edge Dust is entrained with the air flow and discharged.

7 shows station C in more detail. An upper knife 72 and a lower knife 74 are rotatably mounted in a frame 70 of this station, these knives being designed as circular knives which are arranged parallel to one another in the direction of their axis of rotation, one in each case circular cutting edge 75 of the lower knife 74 and an annular cutting edge 73 of the upper knife 72 cooperate and overlap one another in a longitudinal cutting area a. The axes of the circular knives 72, 74 are aligned parallel and one above the other perpendicular to the direction of movement of the paper web. There is a guide plate 76 in the direction of movement of the paper web in front of the rotary knives and behind the rotary knives there is a guide table designed as a suction table 78. The paper web runs continuously over the guide plate 76 and the suction table 78, with the aforementioned knife cutting the paper web lengthways. With this slitting, paper dust develops, which should be removed as completely as possible. In the large area of longitudinal cutting, this is done in three ways, namely by means of a first suction device 80 located directly below the lower knife 74, a second suction device 82 adjoining it, located above the suction table 78 and behind the upper knife 72, and one below the suction table 78 in the direction of movement third suction device 84 located on the paper web behind the second suction device 82.

For the first suction device 80 there are a row of suction openings 88 in an L-shaped lower knife bar 86 directly below the lower knife 74, below which a suction box 9 is connected to the lower knife bar 86 and is connected to a hose 94 via a connecting piece 92.

The above-mentioned guide plate 76 is fastened to the vertical leg of the lower knife bar 86 above a bar 96. A cladding plate 98 is fastened in the inner angular region of the lower knife bar 86 in order to prevent dust nests from forming there. At the free end of the horizontal leg of the lower cutter bar 86, an end plate 100 is attached, which extends to the lower cutter 74 and thus forms a suction space 102 in the lower region of the lower cutter together with the lower cutter 74, the strip 96, the guide plate 76 and the suction table 78.

If air is sucked out through the hose 94, air is sucked in in the cutting area of the two knives, which air enters the suction box 90 via the suction opening 88 and from there into the hose 94. This air flow entrains a large part of the dust that occurs in the immediate area of the knives when slitting.

The second suction device 82 has a blow pipe 104, which is located below the suction table 78. In the radiation area of this blow pipe 104 there are slots 77 in the suction table 78, through which the interfaces of the paper web extend after the longitudinal cutting, so that dust still at the interfaces is blown off and directed into the mouth opening 106 of an upper suction pipe 108.

The third suction device 84 is located behind the second suction device 82 with respect to the direction of movement of the paper web and essentially consists of a suction box 110 located below the suction table 78, to which a hose 112 is fastened. The suction box 110 is provided with elongated holes 114 in the suction table 78 Connection over which the previously mentioned interfaces of the paper web run after the longitudinal cutting. In the direction of movement of the paper web behind this third suction device 84 there is a further guide plate 116, to which a pair of pulling rollers 118 is connected.

A more detailed illustration of this third suction device can be seen in FIG. 8, in which FIG. 8b shows a section through an elongated hole 114 along the line b - b in FIG. 8a.

The upper knife 72 and the lower knife 74 can be seen schematically on the left in FIG. H. in the running direction of the paper web adjoining suction table 78 with the suction box 110 underneath. On the right side of the suction table is the already mentioned pair of pull rollers 118, which are pull rollers with which the paper web is pulled over the suction table.

As can be seen from FIG. 8b, the edges 79 of the longitudinal slots 114, which extend transversely to the longitudinal direction of the longitudinal slots 114, are arched downward. The radius of this arching is about 3 mm when new and changes with increasing wear. The width of the longitudinal slots depends on the paper quality and is selected in exact coordination with the length of the longitudinal slots, whereby the opening cross-section of the longitudinal slots depends on the suction power and the available space in the machine.The slots are located directly behind the longitudinal cutter, but must be more uniform in the area Tension must be arranged in front of the cross knife.

A single, inherently rigid suction box or suction table does not necessarily have to be used. With a corresponding design, possibly with nested suction boxes, the slits can be changed in the width direction in order to adapt them to the respective sheet form.

As has already been described, the convex edges 79 serve to fan out the interface of one or more superimposed paper webs when the paper web with the interface is continuously moved over the longitudinal slot 114 and air is sucked through the longitudinal slots into the suction box, which air is not only a deforming action on the paper sheets in the longitudinal section area, but also has an effect in that residual dust still present, favored by the fanning out, is drawn off into the suction box.

Even when cutting the paper web cross-wise, dust removal must be carried out, although to a lesser extent. A corresponding suction device results from FIG. 9, where two identical knife drums 122 lying one above the other are rotatably mounted in a frame 120 in such a way that the knives 124 located therein come into contact with one another at a very specific point, so that at this point a cross cutting of the Paper web takes place Below the lower knife drum 122 there is a U-shaped bar 125 which surrounds at least the lower half of the lower knife drum 122 and thus forms a suction space 126. In the bar 125 below the suction chamber 126 suction openings 128 are formed, to which a suction device, not shown, is connected. In the direction of movement of the paper web from left to right in front of the two knife drums 122 there is also a guide plate 130 for the paper web, which in the rest enlarges the suction space 126 up to the top of the lower knife drum.

The running into the area of the cross cutters is stabilized by guiding the paper web over the suction table 78 already mentioned and described, so that a perfect cross cutting can take place.

Finally, during the removal, and in particular when the paper giant is transported transversely, a last edge dove extraction is carried out to remove residual dust. The relevant suction device is shown in FIG. 10. In FIG. 10, a cross conveyor belt 132 is shown, on which the paper giant R rests. The paper giant R is laterally delimited by support belts 134 deflected about vertical axes, with a small space remaining between the paper giant and the support belts. Below the conveyor belt 132 there is a suction box 136 with a suction nozzle 138 and a hose 140 adjoining it. Laterally, the suction box 136 there are suction openings 142, which are in communication with the gap between paper rolls R and the support belts 134. Thus, when a suction is performed through the hose 140, it is according to the Pfe illustrated ^g en air from the surroundings into the said gap between the ream R and support bands 134 and from there into the suction box 136 drawn through the resulting air stream is at the edges of the Existing residual dust is suctioned off and removed.

The invention is further illustrated in an example below:

example

Mixed, sorted waste paper, which mainly consisted of household collections and magazine waste, was fed into a high-density pulper (Lamort company). The dissolution is achieved in the course of 25 minutes without specks and with high fiber friction at a temperature of approx. 45 ° C. The material density with dissolution was approx. 14%. After sorting out rough and Heavy parts in a sorting drum as well as a downstream thick material spinner, the fiber suspension was treated in a sorting stage with fine slotted sieves with a material density of approx. 3%, which was followed by a fine sorting with the same material density. Then the printing ink was removed at a consistency of approx. 1% using a conventional deinking system with two flotation towers. After pressure sorting using a perforated screen with a hole diameter of 1.6 mm, the rejects obtained were re-sorted using a slotted basket. The acceptor of the sorter was first thickened to a solids content of 14% by means of disk filtration, then diluted to a solids content of 3.5% and then brought to a solids content of 28%. After-treatment was carried out in the disperser at temperatures up to 95 ° C, if necessary using peroxide or bleach Sodium dithionite (at approx. 6% and 50 to 60 ° C). The pulp obtained was placed on a conventional paper machine. The papers produced for this were then cut as follows or subjected to the following conditions:

• Längskante (korrigierte Helligkeitsdifferenz) = 2,8 bis 4;
• Querkante = 0,6 bis 0,9,
• Staubungszahl für Oberflächenstaub (Siebseite sowie Oberflächenseite) = 2,2 bis 2,5.

The upper and lower knives of the rip and cross cutter sections were arranged essentially without an angle to one another, and the efficiency of the lower knives covered with WIDIA alloy was continuously checked. The dedusting was carried out by means of the devices which are shown in detail in FIGS. 5 to 10. The papers obtained had a low level of dust on the longitudinal edges as well as a very low level of dust adherence to the surface or the transverse edges. This was confirmed by means of the adhesive tape methodology described above and the methodology for determining the surface dust. The value of the dust adhesion on the longitudinal edges and the transverse edges and the transverse dust edges determined for 10 A4 paper giant (500 sheets; 3 measurements each) were as follows:

• Longitudinal edge (corrected difference in brightness) = 2.8 to 4;
• Transverse edge = 0.6 to 0.9,
• Dust number for surface dust (sieve side and surface side) = 2.2 to 2.5.

• 4 % Feuchte,
• 16 % Asche,

The paper had the following composition:

• 4% moisture,
• 16% ash,

Rest of paper fibers, whereby the proportion of woody fibers (wood pulp) was approx. 80% (remaining paper fibers: cellulose fibers).

The paper war yellow colored and had a brightness value of 80%.

Claims (27)

1. Format paper with 2 to 7 wt.% water 10 to 20 wt.% ash and, as the remainder, paper fibrous materials with a woody fibre fraction of more than 10 wL% referred to the paper fibrous materials, a brightness within the range from 65 to 91, characterised by dust adhesion Mv at at least one longitudinal edge corresponding to a luminous reflectance value by the adhesive tape method within the range from 2 to 6, and dust adhesion at at least one transverse edge corresponding to a luminous reflectance value by the adhesive tape method below 1.5, in each case measured on a ream of paper.

2. Low-dust paper according to claim 1, characterised in that the woody fibres comprise 50 to 82 wt.% of the fibre fraction.

3. Low-dust paper according to claim 1, characterised in that the woody fibres comprise 65 to 80 wt.% of the fibre fraction.

4. Low-dust paper according to claim 1, characterised in that the remaiming fibre fraction is cellulose fibre.

5. Low-dust paper according to claim 1, characterised in that the ash content comprises 14 to 17 wt.%.

6. Low-dust paper according to claim 1, characterised in that the water content comprises 4 to 5.5 wt.%.

7. Low-dust paper according to claim 1 with (4 to 4.5) ± 0.5 wt.% water, 14 to 17 wt.% ash and, as the remainder, paper fibrous materials, the woody fibre fraction herein comprising 65 to 80 wt.%.

8. Low-dust paper according to one or more of the preceding claims, but in particular claim 7, characterised in that the brightness is within the range from 70 to 80.

9. Low-dust paper according to one or more of the preceding claims, characterised in that the dust adhesion at at least one longitudinal edge is within the range 25 to 6.

10. Low-dust paper according to claim 1 or 9, characterised in that the mean dust adhesion at at least one longitudinal edge is within the range from 2.5 to 5.5.

11. Low-dust paper according to claim 1 or 10, characterised in that the mean dust adhesion at at least one longitudinal edge is within the range from 2.5 to 4.5.

12. Low-dust paper according to claim 1, characterised in that the dust adhesion at at least one transverse edge is within the range from 0.5 to 1.

13. Low-dust paper according to claim 1, characterised in that the surface dust for at least one side corresponds to a dust count of less than 3, measured by the filtration method (instrument as per code 56 of AB Lorentzen & Wettre, Sweden).

14. Low-dust paper according to claim 13, characterised in that the surface dust corresponds to a dust count within the range from 1.5 to 2.6.

15. Low-dust paper according to one or more of the preceding claims, characterised in that it is formed from 60 to 100 wt.% half stuff which has been prepared from waste paper.

16. Format paper according to claim 1 in DIN A4 format.

17. Use of the low-dust paper according to one or more of the preceding claims as copy paper.

18. Method for the manufacture of format paper with a woody fibre fraction of more than 10 wt%, according to one or more of claims 1-16, in particular using treated waste paper, screened if necessary, employing dissolving, de-inking, screening and if necessary dispersing and bleaching stages, as well as paper manufacture on the paper making-machine, dust being extracted during the cutting process, characterized in that dust extraction is performed:

a) during longitudinal cutting;

b) during transport for transverse cutting; and

c) during transverse cutting of the manufactured paper.

19. Method according to claim 18, characterised in that dust extraction is performed in addition after transverse cutting during transport and screening.

20. Method according to claim 18 or 19, characterised in that filtration of the circulating size liquor is performed.

21. Method according to one or more of claims 18 to 20, characterised in that the paper webs, which are if necessary guided over breaker strips with built-in dust extraction means are blown at the cut during longitudinal cutting and the accumulating dust is extracted, then the longitudinally cut paper web is guided over a suction table comprising slots in such a way that the longitudinal edges of the paper web lie precisely over the slots from which dust is again extracted, and then at the transverse cutters dust is again blown off or extracted.

22. Method according to claim 21, characterised in that with the accumulating reams in the transverse channel, dust is again blown off or extracted.

23. Method according to claim 22, characterised in that the longitudinally cut paper web is guided over slots which are curved inwards perpendicularly to the direction of transport of the paper webs.

24. Method according to claim 22 or 23, characterised in that dust extraction is improved by brushes operating over the slots.

25. Method according to one or more of claims 21 to 24, characterised in that dust is extracted in addition in the region of the lower blades of the longitudinal cutter section.

26. Method according to one or more of the preceding claims 18-25, characterized in that pres- creened waste paper, selected from among household collection material, shredded magazines, printed returns, newspapers and periodicals, is used for preparation of the half stuff.

27. Method according to one or more of the preceding claims 18-26, characterized in that the vacuum during dust extraction in the region of the lower blades and/or the suction table at cutting speeds between 100 and 400 m/min the vacuum is maintained within the range from about 250-40 mbar.

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