EP3298193B1 - Method and device for producing highly filled papers - Google Patents

Description

The invention relates to a process for producing highly filled decorative papers for application to a carrier material, from an aqueous suspension, the suspension being applied by means of a headbox to a circulating drainage screen which comprises a turbulence generator with a plurality of turbulence channels arranged next to one another and forming a line, and the like Turbulence generator is immediately downstream of a nozzle, and the suspension is passed through the turbulence channels and through the nozzle to form a suspension jet.

The invention also relates to an apparatus for performing the method.

Methods of this type are known. So the document reveals DE 10 2009 028 385 A1 a method for operating a sheet formation unit for a machine for producing fibrous webs. The reflocculation of the fibers of the fiber suspension in the headbox and beyond should be avoided, so that a fiber suspension jet with high uniformity is created. Fiber webs with good formation can thus be produced. This is achieved in that, on the one hand, a pressure loss of more than 50 mbar is generated in the last fluidization area of a turbulence-generating duct of the turbulence generator for deflocculating the fibers. On the other hand, the residence time of the fiber suspension between the fluidization area and the point of impact of the jet on the screen of the sheet-forming unit should be as short as possible and below the reflocculation time. A nozzle length of less than 500 mm is suggested. This process is suitable for fiber suspensions with increased consistency (fibers and fillers).

Highly filled papers contain a high proportion of fillers, which is higher than that of writing and printing papers or of cardboard and packaging papers. This leads to special challenges in the production of the papers to achieve the desired quality with regard to their further processing and processing in terms of usage properties. Decorative papers also count among the highly filled papers. Decorative papers are special papers for the surface finishing of wood materials for the production of kitchen worktops, laminate floors, furniture and other end products. The decor papers are laminated to carrier materials. The surface of the decorative paper is printed with patterns, such as wood reproductions or with other single or multi-colored designs. To achieve the desired printing result, the decorative paper must have a very uniform formation, dimensional stability and smoothness in order to ensure the required optical properties of the finished products. A certain strength of the decorative papers is also necessary for the further processing of the end products. To achieve this, the decor papers are impregnated with resin. Uniform properties of the decorative papers are also necessary for this step in order to ensure a uniform penetration of the resin.

Due to the increasing demands on quality, the smallest disturbances in the uniformity of the quality of the high-filled papers, especially the decorative papers, can lead to impairments or to a limitation of the quality of the end products.

It is an object of the invention to improve the quality of highly filled papers, in particular decorative papers, with regard to the consistency of the properties in order to meet the increasing demands on the quality of the end products.

The object is achieved by the method according to claim 1. A process for the production of highly filled papers, in particular decorative papers for application to a carrier material, from an aqueous suspension is proposed, the suspension being applied by means of a headbox to a circulating dewatering screen, which has a turbulence generator with a plurality of turbulence channels arranged side by side, which form a line form, includes, and the turbulence generator is immediately followed by a nozzle, and the suspension is passed through the turbulence channels and through the nozzle to form a suspension jet. According to the invention, the papers are produced from an aqueous suspension with a total consistency of more than 1.5%, a pulp density of less than 1.2% and an ash mass fraction of more than 30%, and at least 3 rows are arranged one above the other and the Suspension is passed through the turbulence channels with a maximum hydraulic diameter of less than 25 mm, in particular less than 20 mm and then through a nozzle with a length of more than 500 mm, in particular more than 700 mm. In the nozzle between the adjacent lines of the turbulence generator, lamellae are inserted which, starting at the turbulence generator, extend over at least part of the length of the nozzle.

• die Gesamtstoffdichte aus der Gesamtmasse der Feststoffe, also der Faser- und der Aschemasse dividiert durch die Gesamtmasse der Feststoffe und der Masse der Flüssigkeit
• die Faserstoffdichte aus der Masse der Fasern dividiert durch die Gesamtmasse der Feststoffe und der Masse der Flüssigkeit
• Asche-Masseanteil aus der Masse der Asche dividiert durch die Gesamtmasse der Feststoffe

It is calculated

• the total density of the total mass of solids, i.e. the fiber and ash mass divided by the total mass of solids and the mass of the liquid
• fiber density divided by the mass of the fibers divided by the total mass of solids and the mass of the liquid
• Ash mass fraction from the mass of the ash divided by the total mass of the solids

Despite the very high ash mass fraction and the very low fiber density, the solution according to the invention enables adequate mixing of the components of the suspension on the one hand and a hydraulically very uniform material jet as a prerequisite for uniform dewatering and sheet formation. In contrast to known methods, the hydraulic instabilities in the suspension jet are reduced to such an extent that the flatness of the decorative paper is significantly improved. Inter alia, faults and defects in the lamination process could be eliminated by the invention.

The invention has a particularly advantageous effect particularly at higher throughputs of the suspension of more than 4000 l / (min ^∗ m _working width) and at speeds of the suspension jet of more than 400 m / min, since sufficient uniformity is achieved especially with increasing throughputs and speeds the nature of the highly filled papers, especially decorative papers, is becoming increasingly difficult.

It can also be advantageous if at least 4 lines, in particular at least 5 lines, are arranged one above the other. This reduces the hydraulic instabilities in the suspension jet.

The total density of the suspension can be up to 3% and more and the ash mass fraction can be up to 90%, preferably 50% to 80%. The fiber density can be reduced to 0.8% and less, in particular to 0.6% and less, without impairing the quality of the decorative paper web. The invention therefore enables a wide range of decorative paper types to be produced with good quality.

In a practical example, the suspension is dewatered through the dewatering screen and then pressed, thermally dried and the paper web thus formed is wound up.

The highly filled paper web, in particular the decorative paper web, can be impregnated, preferably with synthetic resin. This improves the processability.

The highly filled paper web produced, in particular the decorative paper web, is provided for application to a carrier material by laminating. It is bonded to the carrier material under pressure and elevated temperature. As a result, end products such as kitchen worktops, laminate floors, furniture and others can be manufactured.

It is also conceivable that the paper web is glued to the carrier material.

In a practical and advantageous embodiment, the turbulence channels, viewed in the flow direction, comprise a first section and a second section and an end section with an outlet cross section. These sections have a hydraulic diameter which is calculated from the four-fold cross-sectional area divided by the circumference of the respective section of the turbulence channel. The ratio between the hydraulic diameter of the second section and the hydraulic diameter of the first section is greater than or equal to 1.25. This cross-sectional expansion, which can be carried out as a step change, generates sufficiently high shear forces and turbulence for sufficient mixing of the components of the suspension.

In a further embodiment of the invention, the sum of the lengths of the second section and of the end section is 4 to 10 times the root of the exit surface, where the exit area is given in mm ² and the length in mm. The second section can, for example, pass into the end section via a non-detachable diffuser. This helps to avoid or reduce hydraulic instabilities in the suspension jet and thus to improve the flatness of the highly filled paper, in particular the decorative paper, and to reduce faults and defects in the lamination process.

Furthermore, it is also conceivable that the second section contains the end section. In this case, the second section also forms the outlet cross section with an outlet cross-sectional area. The turbulence channel therefore has only two sections. The length of the second section is thus 4 to 10 times the root of the area of the outlet cross section, the area being given in the unit mm ² and the length in the unit mm.

In an advantageous further development, the length of the slats is the same or different.

The length of the fins is between 0.3 and 1.2 times, in particular between 0.5 and 0.8 times the length of the nozzle.

In an advantageous embodiment, the nozzle has an inlet cross-section assigned to a line and the ratio between the area of the inlet cross-section and the sum of the outlet cross-sections of the turbulence channels of a line is less than 1.75, the inlet cross-section of the nozzle being the cross-section through which flow can pass. This avoids gross hydraulic instabilities in the suspension jet.

The area of the outlet cross section is advantageously less than 600 mm ² , preferably less than 350 mm ² .

The outlet cross section of the individual turbulence channels can be rectangular, square or hexagonal.

In a practical embodiment, the suspension is passed through the nozzle with a gap width of the outlet gap in the range from 7 to 14 mm, in particular from 8 to 11 mm.

It has also proven to be advantageous if the suspension is guided in a straight line through the turbulence generator and the nozzle. The channels of the turbulence generator are therefore essentially aligned with the nozzle, so that no flow deflection is necessary.

The object is also achieved by the features of the device claim 8. A headbox for carrying out the method according to claim 1 for the production of highly filled papers, in particular decorative papers for application to a carrier material, is proposed. The headbox comprises a turbulence generator with a plurality of turbulence channels arranged side by side, which form a row, the turbulence generator being immediately followed by a nozzle, and an aqueous suspension being able to be passed through the turbulence channels and through the nozzle to form a suspension jet. According to the invention, it is provided that an aqueous suspension with a total density of more than 1.5%, a fiber density of less than 1.2% and an ash mass fraction of greater than 30% can be passed through the headbox, and that at least 3 rows one above the other are arranged and that the turbulence channels have a maximum hydraulic diameter of less than 25 mm, in particular less than 20 mm and that the nozzle has a length of more than 500 mm, in particular more than 700 mm and in the nozzle between the adjacent lines of the turbulence generator, fins are used which, starting at the turbulence generator, extend over at least part of the length of the nozzle.

It can also be advantageous if at least 4 lines, in particular at least 5 lines, are arranged one above the other. This reduces the hydraulic instabilities in the suspension jet.

In a practical case, lamella holders for fastening the lamellae are arranged between the rows of turbulence channels.

Furthermore, the headbox can be followed by a forming area, a press area, a drying area, a winding area and an impregnation device and / or a laminating device.

In a practical and advantageous embodiment, the turbulence channels, viewed in the flow direction, comprise a first section and a second section and an end section with an outlet cross section. These sections have a hydraulic diameter which is calculated from the four-fold cross-sectional area divided by the circumference of the respective section of the turbulence channel. The ratio between the hydraulic diameter of the second section and the hydraulic diameter of the first section is greater than or equal to 1.25. This cross-sectional expansion, which can be carried out as a step change, generates sufficiently high shear forces and turbulence for sufficient mixing of the components of the suspension.

In a further embodiment of the invention, the sum of the lengths of the second section and the end section is 4 to 10 times the root of the exit area, the exit area being given in the unit mm ² and the length in the unit mm. The second section can, for example, pass into the end section via a non-detachable diffuser. This helps to avoid or reduce hydraulic instabilities in the suspension jet and thus to improve the flatness of the highly filled paper, in particular the decorative paper, and to reduce faults and defects in the lamination process.

Furthermore, it is also conceivable that the second section contains the end section. In this case, the second section also forms the outlet cross section with an outlet cross-sectional area. The turbulence channel therefore has only two sections. The The length of the second section is thus 4 to 10 times the root of the area of the outlet cross section, the area being given in the unit mm ² and the length in the unit mm.

In an advantageous further development, the length of the slats is the same or different.

The length of the fins is between 0.3 and 1.2 times, in particular between 0.5 and 0.8 times the length of the nozzle.

In an advantageous embodiment, the nozzle has an inlet cross-section assigned to a line and the ratio between the area of the inlet cross-section and the sum of the outlet cross-sections of the turbulence channels of a line is less than 1.75, the inlet cross-section of the nozzle being the cross-section through which flow can pass. This avoids gross hydraulic instabilities in the suspension jet.

The outlet cross section is advantageously less than 600 mm ² , preferably less than 350 mm ² .

The outlet cross section of the individual turbulence channels can be rectangular, square or hexagonal.

In a practical embodiment, the suspension is passed through the nozzle with a gap width of the outlet gap in the range from 7 to 14 mm, in particular from 8 to 11 mm.

It has also proven to be advantageous if the suspension is guided in a straight line through the turbulence generator and the nozzle. The channels of the turbulence generator are therefore essentially aligned with the nozzle, so that no flow deflection is necessary.

Further features and advantages of the invention result from the following description of preferred exemplary embodiments with reference to the drawing.

Figur 1

eine Ausführungsform eines erfindungsgemäßen Stoffauflaufs in schematischer und stark vereinfachter Darstellung;

Figur 2

eine Ansicht entgegen der Durchströmrichtung des erfindungsgemäßen Stoffauflaufs nach Figur 1 in schematischer und stark vereinfachter Darstellung;

Show it

Figure 1

an embodiment of a headbox according to the invention in a schematic and highly simplified representation;

Figure 2

a view against the flow direction of the headbox according to the invention Figure 1 in a schematic and highly simplified representation;

The embodiment of a headbox according to the invention Figure 1 shows in a section along the flow direction D a turbulence generator 2 and a nozzle 3 with fins 4. The turbulence generator 2 comprises a plurality of turbulence channels 7.1n, 7.2n, 7.3n, 7.4n. Part of the plurality of turbulence channels 7.1n, 7.2n, 7.3n, 7.4n are arranged next to one another across the width of the headbox (1) and each form a line 7.1, 7.2, 7.3, 7.4 of turbulence channels. In total, the headbox in this example comprises four lines 7.1, 7.2, 7.3, 7.4 lying one above the other. Each turbulence channel 7.1n, 7.2n, 7.3n, 7.4n has a first section 8, into which the suspension is fed, a second section 9 and an end section 10. The hydraulic diameters of the individual sections become larger in the flow direction D. The first section 8 consists of a tubular cross section, which in a step-like extension merges into the second section 9, which is also formed from a tubular cross section. The ratio between the hydraulic diameter of the second section 9 and the hydraulic diameter of the first section 8 is greater than or equal to 1.25. This sudden expansion ensures that the solids contained in the aqueous suspension are thoroughly mixed. The end section 10 following the second section forms a transition from the round cross section of the second section 9 to a square cross section of the outlet cross section 10.1n, 10.2n, 10.3n, 10.4n of the turbulence channel 7.1n, 7.2n, 7.3n, 7.4n. into the nozzle 3. However, it is also possible for the second section 9 to include the end section 10. In this case, the cross section of the second section 9 also forms the outlet cross section 10.1n, 10.2n, 10.3n, 10.4n with an outlet cross-sectional area of the turbulence channel 7.1n, 7.2n, 7.3n, 7.4n. The step change between the first and the second section 9 then takes place from a round to a square cross section.

The sum of the lengths 9L of the second section 9 and of the end section 10 is 4 to 10 times the value from the root of the exit area of the exit cross section 10.1n, 10.2n, 10.3n, 10.4n, the exit area being in the unit mm ² and Length is given in mm. In this example, the second section 9 merges into the end section 10 via a non-detachable diffuser. The exit surface of the exit cross section 10.1n, 10.2n, 10.3n, 10.4n is less than 600 mm ² , preferably less than 350 mm ² . The outlet cross-section of the individual turbulence channels 7.1n, 7.2n, 7.3n, 7.4n is square in this example. Slat holders 14 for fastening the slats 4 are arranged between all adjacent rows 7.1, 7.2, 7.3, 7.4. The lamellae 4 are thinner than the lamella holder 14 and extend until shortly before the end of the nozzle in the area of the outlet gap with the gap width 15. In this example the lamella length 5 is 0.8 times the nozzle length 6 and the gap width lies in Range from 7 mm to 14 mm. All slats 4 have essentially the same length 5. The turbulence channels 7.1n, 7.2n, 7.3n, 7.4n are arranged in relation to the nozzle 3 such that an essentially rectilinear flow pattern is created. The suspension flow is therefore not significantly deflected by this arrangement. The formation of disruptive instabilities by deflections is thus avoided.

The Figure 2 shows a detail in the view against the flow direction D of the headbox 1 according to the invention Figure 1 in a schematic and highly simplified representation. For the sake of simplicity, only three turbulence channels 7.1n, 7.2n, 7.3n, 7.4n arranged next to one another in the direction of the width of the headbox are shown per line 7.1, 7.2, 7.3, 7.4. The number of one of the turbulence channels transverse to the flow direction D in a line is designated by "n", where "n" can take values from 1 to the number of turbulence channels in a line. The four lines 7.1, 7.2, 7.3, 7.4 are separated by lamella holders 14. The slats 4 are indicated by dashed lines. The outlet cross sections 10.1n, 10.2n, 10.3n, 10.4n has a square shape. The hydraulic diameter 12 of the end section 10 corresponds to the edge length of the respective turbulence channel 7.1n, 7.2n, 7.3n, 7.4n. As can be seen in this illustration, the sum of the areas of the outlet cross sections 10.1n, 10.2n, 10.3n, 10.4n of the turbulence channels 7.1n, 7.2n, 7.3n, 7.4n is smaller by the land area 13 than that of the respective line 7.1 , 7.2, 7.3, 7.4 assigned area of the inlet cross-section of the nozzle 3. The inlet cross-section of the nozzle 3 is thus the cross-section through which flow can pass. This cross-sectional expansion must be as small as possible in order to limit hydraulic instabilities in the suspension jet. The ratio between the area of the inlet cross section of the nozzle 3 assigned to a line and the sum of the areas of the outlet cross sections 10.1n, 10.2n, 10.3n, 10.4n of the turbulence channels 7.1n, 7.2n, 7.3n, 7.4n of this line is less than 1 , 75th This avoids gross hydraulic instabilities in the suspension jet. The area of the inlet cross section results from the height 11 of the inlet cross section multiplied by the flow-through width of the nozzle.

LIST OF REFERENCE NUMBERS

1

headbox

2

turbulence generator

3

jet

4

slats

5

lamellar length

6

nozzle length

7.1

first line

7.2

second line

7.3

third line

7.4

fourth line

7.1N

Turbulence channels on the first line

7.2N

Turbulence channels on the second line

7.3n

Turbulence channels on the third line

7.4n

Turbulence channels on the fourth line

8th

first section

8L

Length of the first section

9

second part

9L

Sum of the lengths of the first section and the end section

10

end

10.1N

Exit cross section of a turbulence channel of the first line

10.2n

Exit cross section of a turbulence channel of the second line

10.3n

Exit cross section of a turbulence channel of the third line

10.4n

Exit cross section of a turbulence channel of the fourth line

11

Height of the inlet cross-section

12

Hydraulic diameter of the end section

13

land area

14

Blade support

15

gap width

D

flow direction

Claims (14)

1. Method for producing highly filled decorative papers for application to a carrier material, from an aqueous suspension, wherein the suspension is applied to a circulating dewatering fabric by means of a headbox (1), which a turbulence generator (2) having a plurality of rows arranged one above another, which each comprise turbulence channels (7.1n, 7.2n, 7.3n, 7.4n) arranged beside one another, wherein a nozzle (3) is arranged immediately following the turbulence generator (2) downstream, and the suspension is led through the turbulence channels (7.1n, 7.2n, 7.3n, 7.4n) and through the nozzle (3) to form a suspension jet, and wherein at least 3 rows (7.1, 7.2, 7.3, 7.4) are arranged above one another, and the suspension is led through the turbulence channels (7.1n, 7.2n, 7.3n, 7.4n) with a maximum hydraulic diameter (12) of less than 25 mm, in particular of less than 20 mm, and lamellae (4) which, beginning at the turbulence generator (2), extend over at least part of the length (6) of the nozzle, are inserted into the nozzle (3) between the adjacent rows of the turbulence generator (2),
   characterized in that
   the decorative paper is produced from an aqueous suspension having a total stock consistency of more than 1.5%, a fibre stock consistency of less than 1.2% and an ash mass fraction of greater than 30% and after that, is led through a nozzle (3) having a length (6) of more than 500 mm, in particular of more than 700 mm.
2. Method according to Claim 1,
   characterized in that
   the suspension is dewatered through the dewatering fabric and then pressed, dried thermally, and the paper web produced as a result is wound up.
3. Method according to Claim 1 or 2,
   characterized in that
   the paper web is impregnated, preferably with synthetic resin, and/or laminated onto a carrier material.
4. Method according to one of the preceding claims,
   characterized in that
   the turbulence channels (7.1n, 7.2n, 7.3n, 7.4n), seen in the flow direction (D), comprise a first section (8) and a second section (9) and an end section (10) with an outlet cross section (10.1n, 10.2n, 10.3n, 10.4n), and in that the ratio between the hydraulic diameter of the second section (9) and the hydraulic diameter of the first section (8) is greater than or equal to 1.25.
5. Method according to Claim 4,
   characterized in that
   the sum of the lengths (9L) of the second section (9) and the end section (10) is 4 to 10 times the square root of the area of the outlet cross section (10.1n, 10.2n, 10.3n, 10.4n), wherein the area is specified in mm² and the length in mm.
6. Method according to one of the preceding claims,
   characterized in that
   the length (5) of the lamellae (4) is between 0.3 and 1.2, in particular between 0.5 and 0.8, of the length (6) of the nozzle (3).
7. Method according to one of the preceding claims,
   characterized in that
   the nozzle (3) has an inlet cross section assigned to a row (7.1, 7.2, 7.3, 7.4), and the ratio between the area of the inlet cross section and the sum of the outlet cross sections (10.1n, 10.2n, 10.3n, 10.4n) of the turbulence channels (7.1n, 7.2n, 7.3n, 7.4n) of a row is less than 1.75.
8. Headbox (1) for carrying out the method according to Claim 1, comprising a turbulence generator (2) having a plurality of rows arranged one above another, which each comprise turbulence channels (7.1n, 7.2n, 7.3n, 7.4n) arranged beside one another, wherein a nozzle (3) is arranged immediately following the turbulence generator (2) downstream, and wherein an aqueous suspension having a total stock consistency of more than 1.5%, a fibre stock consistency of less than 1.2% and an ash mass fraction of greater than 30% can be led through the turbulence channels (7.1n, 7.2n, 7.3n, 7.4n) and through the nozzle to form a suspension jet, and in that at least 3 rows are arranged above one another, and in that the turbulence channels (7.1n, 7.2n, 7.3n, 7.4n) have a maximum hydraulic diameter (12) of less than 25 mm, in particular of less than 20 mm, and lamellae (4) which, beginning at the turbulence generator (2), extend over at least part of the length (6) of the nozzle (3), are inserted into the nozzle (3) between the adjacent rows (7.1, 7.2, 7.3, 7.4) of the turbulence generator (2),
   characterized in that
   the aqueous suspension has a total stock consistency of more than 1.5%, a fibre stock consistency of less than 1.2% and an ash mass fraction of greater than 30%, and in that the nozzle (3) has a length (6) of more than 500 mm, in particular of more than 700 mm.
9. Headbox (1) according to Claim 8,
   characterized in that
   the turbulence channels (7.1n, 7.2n, 7.3n, 7.4n), seen in the flow direction (D), comprise a first section (8) and a second section (9) and an end section (10) with an outlet cross section (10.1n, 10.2n, 10.3n, 10.4n), and in that the ratio between the hydraulic diameter of the second section (9) and the hydraulic diameter of the first section (8) is greater than or equal to 1.25.
10. Headbox (1) according to Claim 9,
    characterized in that
    the sum of the lengths (9L) of the second section (9) and the end section (10) is 4 to 10 times the square root of the area of the outlet cross section (10.1n, 10.2n, 10.3n, 10.4n), wherein the area is specified in mm² and the length in mm.
11. Headbox (1) according to Claim 9 or 10,
    characterized in that
    the second section (9) includes the end section (10) .
12. Headbox (1) according to one of Claims 8 to 11,
    characterized in that
    the length (5) of the lamellae (4) is between 0.3 and 1.2, in particular between 0.5 and 0.8, of the length (6) of the nozzle (3).
13. Headbox (1) according to one of the preceding Claims 8 to 12,
    characterized in that
    the nozzle (3) has an inlet cross section assigned to a row, and the ratio between the area of the inlet cross section and the sum of the outlet cross sections (10.1n, 10.2n, 10.3n, 10.4n) of the turbulence channels (7.1n, 7.2n, 7.3n, 7.4n) of a row is less than 1.75.
14. Headbox (1) according to one of the preceding Claims 8 to 13,
    characterized in that
    the turbulence generator (2) and the nozzle (3) are arranged in such a way that the suspension is led rectilinearly through the turbulence generator (2) and the nozzle (3).

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