Press arrangement and method for pressing a fibrous blanket.

Description

1 / 12 “PRESS ARRANGEMENT AND METHOD FOR PRESSING A FIBROUS BLANKET”

[0001] The present invention relates to a press arrangement for pressing a fibrous blanket, in particular a continuous roll of packaging paper, comprising at least two presses arranged one behind the other in the direction of advance of the fibrous blanket, namely, a first press with a first pressing contact line and a second subsequent press with a second pressing contact line, which is an extended pressing contact line, wherein the second press is designed to be operated with a linear load of at least 500 kN / m. Furthermore, the invention relates to a method for pressing a fibrous blanket, preferably using such a press arrangement.

[0002] This press arrangement is described, for example, in the two publications WO8808051A1 and WO2017207475A1, the disclosure of which is incorporated here by reference.

[0003] Machines for producing a fibrous mat typically feature a press arrangement in which the fibrous mat is dewatered or dehumidified by mechanical pressure. The press arrangement is usually located between the forming and drying sections. A particularly efficient type of mechanical dewatering can be achieved by means of the so-called extended press contact line. The benefits of an extended press contact line are well known: the press contact line is flat and not essentially linear as in conventional roller presses. This means that the pressure to be exerted on the fibrous mat to be dewatered on the press contact line in the direction of operation does not start suddenly, but can be continuously increased from a low to a high value. This reduces the risk of the fibrous mat being crushed on the press contact line.This allows the fibrous mat to be dehydrated very efficiently in an extended pressing contact line, preserving its volume. Petition 870250087501, dated 09 / 26 / 2025, page 13 / 44 2 / 12

[0004] For example, the fibrous web can be guided through the extended press contact line together with a felt or between two felts, so that the extended press contact line can be formed in a so-called shoe press between a shoe press roll and a counter roll. In contrast to the production of continuous paper rolls, thickness or so-called volume is less important in the production of continuous paper rolls, especially continuous paper rolls for packaging. For this reason and due to the considerably higher basis weight of continuous paper rolls, especially continuous paper rolls for packaging, significantly higher line loads are used in the second press contact line, i.e., line loads of at least 500 kN / m.

[0005] The issues of “energy costs” and “CO2 footprint” play an increasingly important role in the production of fibrous webs.Energy consumption in the drying section, which is still mostly heated by gas, is a key influencing factor. To save energy and gas, it would be very advantageous if the fibrous slab from the upstream press arrangement already had the highest possible dry matter content. An obvious idea would be to simply increase the line load in the press arrangement to achieve a higher dry matter content. However, this approach has limited practical use, as there is a risk that the fibrous slab to be dehydrated will be crushed in the pressing contact line. Furthermore, energy consumption in the press arrangement also increases with increased line load at the same machine speed, and with increased line load, investment costs increase because a considerably more massive structure is required.

[0006] It is an objective of the present invention to reduce the energy costs and / or the CO2 footprint for the production of a fibrous blanket, in particular a continuous paper roll for packaging.

[0007] This objective is achieved by independent claims. Dependent claims refer to advantageous developments of Petition 870250087501, dated 09 / 26 / 2025, page 14 / 44 3 / 12 present invention.

[0008] Specifically, the objective is achieved by a generic press arrangement as described above, which is particularly characterized by the fact that the second press is designed in such a way that a ratio of average pressure to peak pressure on the second pressing contact line is less than 0.5.

[0009] The average pressure can be easily determined by dividing the line load by the length of the pressing zone of the press arrangement. The line load is the total force applied by the press arrangement divided by the machine width or the width of the pressing zone over which the total force is distributed in the pressing contact line of the press arrangement. The length of the pressing zone is the length in the pressing contact line, measured in the direction of the machine, over which an increased pressure is exerted on the fibrous web. A very low limit can be set for the pressure increase, such as 0.1 MPa above normal pressure. The length of the pressing zone is generally a well-known parameter of the press arrangement. It can be easily measured, for example, by means of a printing film that is inserted into the extended pressing contact line before pressure is applied to it by the press arrangement.The printing film then measures where pressure is applied on the press contact line. This also facilitates the determination of the peak pressure on the press contact line of the press arrangement. These printing films with different resolutions are offered commercially, for example, by Fujifilm under the brand name “Prescale”.

[0010] Interestingly, the ratio between the average pressure and the peak pressure depends only on the geometric design of the pressing elements that form the extended pressing contact line between them, in particular on the geometric design of any press shoe, but not on the peak pressure. In other words, for a given geometric design, the Petition 870250087501, dated 09 / 26 / 2025, page 15 / 44 The ratio between the average pressure and the peak pressure remains essentially constant, even when the peak pressure is increased, since an increase in peak pressure leads to an essentially proportional increase in average pressure. The ratio between average pressure and peak pressure indirectly describes the geometric design of the pressing elements, in particular of any press shoe. Since there is an uncontrollable number of different geometric designs, all leading to a ratio of average pressure to peak pressure that is less than 0.5, the choice of this ratio seems appropriate to describe the inventive solution. It is important that, for a press arrangement with a fixed design of the pressing elements, the value of the ratio between average pressure and peak pressure can be determined simply and unambiguously.

[0011] The inventors discovered that, with regard to the efficient dewatering of the fibrous mat, it is particularly advantageous if the geometric design of the pressing elements of the second press, which is operated with a line load of at least 500 kN / m, is selected so that the ratio between the average pressure and the peak pressure is less than 0.5. Thus, the geometric design of the pressing elements of the second press of the press arrangement according to the invention differs from known press assemblies, where this ratio is always greater than 0.5. To achieve a ratio of less than 0.5 with a line load of at least 500 kN / m, the product of the pressing zone length and the peak pressure must be relatively large. Thus, the present invention preferably describes geometric designs that result both in a relatively large pressing zone length and, at the same time, in a relatively large peak pressure.

[0012] The first press upstream of the second press serves to pre-compact and dehumidify the fibrous mat to such an extent that the fibrous mat is not crushed despite a high peak pressure at the contact line of the second press. The press arrangement according to the invention does not Petition 870250087501, dated 09 / 26 / 2025, p. 16 / 44 5 / 12 is limited to the first and second presses, but may also include one or more additional presses if necessary. In particular, another press may be installed upstream of the first press. Preferably, however, no other press is installed between the first and second presses.

[0013] In particular, the ratio between the average pressure and the peak pressure can be less than 0.46 and / or greater than 0.3. A geometric design of the pressing elements, in particular the press shoe of the second press, which results in a ratio between 0.3 and 0.46, has proven particularly advantageous in efficient drainage tests.

[0014] Regarding the line load with which the second press can be operated, this can also be significantly greater than 500 kN / m, i.e., at least 1,000 kN / m, or even at least 1,300 kN / m. As mentioned above, however, there are practical limits to increasing the line load due to the increased risk of crushing the fibrous blanket, due to the increased drive energy and the increasing investment costs, especially for the design of a more robust structure. The higher the line load selected, the greater the product of the pressing zone length and the peak pressure, which must be chosen according to the present invention, in order to achieve a value less than 0.5 for the quotient of the average pressure and the peak pressure.

[0015] Good results with respect to increasing the dry matter content of the fibrous mat in the press arrangement according to the invention can be obtained if the second press is designed to apply a peak pressure of at least 9 MPa, preferably at least 10 MPa, more preferably at least 12 MPa to the fibrous mat. These are noticeably higher peak pressures than those of known press arrangements of this type.

[0016] The first press, which has the specific task of pre-consolidating or dehumidifying the fibrous mat so that it can pass through the second press without being damaged, must be fundamentally designed in such a way that Petition 870250087501, dated 09 / 26 / 2025, p. 17 / 44 6 / 12 different from the second press, even though the first pressing contact line may also be an extended pressing contact line. In particular, the first press must be designed so that at least one of the following statements applies:

[0017] a) a ratio of average pressure to peak pressure on the first line of pressing contact is greater than 0.5;

[0018] b) the maximum line load with which the first press can be operated is less than the maximum line load with which the second press can be operated;

[0019] c) the peak pressure that can be applied to the fibrous blanket on the first line of pressing contact is less than the peak pressure that can be applied to the fibrous blanket on the second line of pressing contact.

[0020] A preferred embodiment of the invention provides that the second press is a shoe press, comprising a press shoe with a concave curved surface and a shoe press sleeve rotatably mounted around the press shoe.

[0021] It has been found to be advantageous if the shoe presser foot sleeve consists at least partially of polyurethane, which is formed by the reaction of a prepolymer and a crosslinking component, wherein the prepolymer is a reaction product of 1,4-phenylene diisocyanate (PPDI) and a polyol component containing at least one polyol polyether and / or at least one polyol polycarbonate, and wherein the crosslinking component contains a C2-14diol. It is further preferred that the polyol component of the prepolymer comprises polytetramethylene ether glycol (PTMEG) and at least one polyol polycarbonate.

[0022] Alternatively or additionally, the crosslinking component may comprise polytetramethylene ether glycol (PTMEG) and / or at least one polycarbonate. A press jacket with such a polyurethane layer has proven to be surprisingly durable even at high peak pressures. At the same time, this polyurethane mixture is able to maintain Petition 870250087501, dated 09 / 26 / 2025, p. 18 / 44 7 / 12 good adhesion to the reinforcing wires embedded in it, even after many alternating load cycles under high peak pressures.

[0023] According to a further aspect, the present invention relates to a machine for producing a fibrous blanket, preferably a Packaging Testliner, comprising a press arrangement previously described according to the invention.

[0024] Furthermore, the invention relates to a method for pressing a fibrous blanket, in particular a continuous roll of packaging paper, preferably using a press arrangement previously described according to the invention, wherein the fibrous blanket is successively passed through at least two presses, namely a first press with a first pressing contact line and a subsequent second press with a second pressing contact line, wherein the second pressing contact line is an extended pressing contact line and wherein the fibrous blanket is pressed in the second press with a line load of at least 500 kN / m, wherein the fibrous blanket is pressed in the second press such that the quotient between the average pressure and the peak pressure in the second pressing contact line is less than 0.5.

[0025] The effects and advantages mentioned above in relation to the press arrangement according to the invention also apply analogously to the pressing method according to the invention and vice versa.

[0026] Thus, in the method according to the invention, the ratio between the average pressure and the peak pressure can be less than 0.46 and / or greater than 0.3.

[0027] In addition, the fibrous blanket can be pressed in the second press with a line load of at least 1,000 kN / m, preferably at least 1,300 kN / m.

[0028] Preferably, the fibrous mat is pressed in the second press with a peak pressure of at least 9 MPa, more preferably at least 10 MPa, even more preferably at least 12 Petition 870250087501, dated 09 / 26 / 2025, p. 19 / 44 8 / 12 MPa over the fibrous blanket.

[0029] Also in the method according to the invention, the first press can be operated in such a way that at least one of the following statements applies:

[0030] a) a ratio of average pressure to peak pressure on the first line of pressing contact is greater than 0.5;

[0031] b) the maximum load of the line with which the first press is operated is less than the maximum load of the line with which the second press is operated;

[0032] c) the peak pressure applied to the fibrous blanket on the first line of pressing contact is less than the peak pressure applied to the fibrous blanket on the second line of pressing contact.

[0033] The method according to the invention can be used particularly efficiently if the fibrous mat consists of at least 20% by weight, preferably at least 50% by weight, of OCC fibers. OCC is an abbreviation known in the art and stands for old corrugated containers. In other words, the press arrangement according to the invention and the pressing method according to the invention are particularly suitable for efficiently pressing fibrous mats that have a considerable or even significant proportion of used fibers, i.e., no new fibers. This is due to the high strength of OCC fibers at high pressures. The remaining fibers of the fibrous mat to be pressed can be selected from wood pulp or cellulose, such as TMP, CTMP and / or PGW.

[0034] The invention will be explained in more detail below with reference to an embodiment described with the aid of schematic figures:

[0035] Figure 1: a press arrangement according to the invention, comprising a first press and a second press;

[0036] Figure 2: an enlarged and detailed view of the second press of Petition 870250087501, dated 09 / 26 / 2025, page 20 / 44 9 / 12 press arrangement shown in Figure 1.

[0037] Figure 1 shows a very schematic representation of a press arrangement according to the invention, comprising a first press 11 and a second press 1 disposed directly behind it in the direction of movement BR of a fibrous blanket 8. In this embodiment, both the first press 11 and the second press 1 are designed as shoe presses and therefore each has an extended pressing contact line. Alternatively, however, the first press 11 could not have an extended pressing contact line and / or the first press 11 and the second press 1 could share a common central roller. The central roller would then be a pressing element through which both the first pressing contact line of the first press 11 and the second pressing contact line of the second press 1 would be formed.

[0038] Figure 2 shows an enlarged and detailed view of the second press 1, which is of particular importance according to the invention. This press is designed to operate with a line load of at least 500 kN / m. The second pressing contact line 7 is provided by two pressing elements, namely, a press shoe roll 2 and a counter-roller 3. The press shoe roll 2 comprises a press shoe 5, which is supported on a stationary fork 4, and a press shoe sleeve 6, which is rotatably arranged around the press shoe 5. Preferably, the fibrous blanket 8 is guided in a sandwich-like manner between two pressing felts 9 through the extended second pressing contact line 7. The press shoe 5 has a substantially concave surface over which the press shoe sleeve 6 runs, while the press shoe 5 presses it with a high pressing force F in the direction of the counter-roller 3.The geometric design of the pressing elements, in particular the press shoe 5, is selected so that the ratio between the average pressure and the peak pressure on the second pressing contact line 7 is less than 0.5, according to the invention. Petition 870250087501, dated 09 / 26 / 2025, page 21 / 44 The 10 / 12 quotient can preferably be between 0.3 and 0.46.

[0039] The pressing force F is preferably selected to be so large that the peak pressure acting on the fibrous mat 8 in the second extended pressing contact line 7 is at least 9 MPa, more preferably at least 10 MPa, even more preferably at least 12 MPa. To achieve a ratio of average pressure to peak pressure in the second pressing contact line 7 that is less than 0.5, according to the invention, with such a high peak pressure and a line load of at least 500 kN / m, the pressing shoe 5 must be relatively long to provide a correspondingly large pressing zone length for the fibrous mat 8 in the second pressing contact line 7.

[0040] It has proven to be particularly advantageous at such high peak pressures if the shoe press jacket 6 consists at least partially of polyurethane, which is formed by the reaction of a prepolymer and a crosslinking component, wherein the prepolymer is a reaction product of 1,4-phenylene diisocyanate (PPDI) and a polyol component containing at least one polyether polyol and / or at least one polycarbonate polyol, and wherein the crosslinking component contains a C2-14-diol.For example, the shoe press cover 6 may have a reinforcing structure made of wires embedded in the polyurethane layer, wherein the polyurethane layer prepolymer consists of 50% by weight of a mixture of 1,4-phenylene diisocyanate (PPDI) and C5-6-polycarbonate diol and consists of 50% by weight of a mixture of 1,4-phenylene diisocyanate (PPDI) and polytetramethylene ether glycol (PTMEG), and wherein the crosslinker comprises polytetramethylene ether glycol (PTMEG) and 1,6-hexanediol or is preferably formed substantially from the same.

[0041] The first press 11 shown schematically in Figure 1 can and preferably is designed differently from the second press 1. In particular, unlike the second press 1, it can be designed Petition 870250087501, dated 09 / 26 / 2025, page 22 / 44 11 / 12 so that the ratio of average pressure to peak pressure on the first pressing contact line is greater than 0.5; and / or that the maximum load of the line with which the first press can be operated is less than the maximum load of the line with which the second press can be operated; and / or that the peak pressure that can be applied to the fibrous mat on the first pressing contact line is less than the peak pressure that can be applied to the fibrous mat on the second pressing contact line. Preferably, all three statements apply. In the press arrangement according to the invention, the first press 11 serves, in particular, to sufficiently pre-consolidate the fibrous mat 8 for passage through the second press 1, so that it is not excessively compressed, despite a high peak pressure on the second press 1.

[0042] The fibrous mat 8 is preferably used to produce a continuous roll of packaging paper or is such a continuous roll of packaging paper. In addition, the fibrous mat consists of at least 20% by weight, preferably at least 50% by weight, of OCC fibers, which are characterized by particularly high strength, even at high peak pressures.

[0043] The press arrangement 1 according to the invention could theoretically also have more presses than just the first press 11 and the second press 1. However, the second press 1 is preferably the last press in the press arrangement, i.e., the last press before the fibrous blanket 8 is transferred to a drying section downstream of the press arrangement. Only in exceptional cases may there be a smoothing press after the first press 1 and a drying section downstream, which, however, does not have an extended pressing contact line.

[0044] List of Reference Numbers second press roller shoe press Petition 870250087501, dated 09 / 26 / 2025, page 23 / 44 12 / 12 counterroller stationary fork press shoe press shoe sleeve second pressing contact line (extended) fibrous blanket press felt press arrangement first press direction of movement pressing force Petition 870250087501, dated 09 / 26 / 2025, page 24 / 44

Claims

1 / 4 CLAIMS 1. Press arrangement (10) for pressing a fibrous blanket (8), in particular a continuous roll of packaging paper, comprising at least two presses (11, 1) arranged one behind the other in the direction of advance of the fibrous blanket (8), namely, a first press (11) with a first pressing contact line and a subsequent second press (1) with a second pressing contact line, which is an extended contact line, wherein the second press (1) is designed to be operated with a line load of at least 500 kN / m, characterized in that the second press (1) is designed such that the quotient between the average pressure and the peak pressure on the pressing contact line is less than 0.5, and wherein the second press (1) is designed to apply a peak pressure of at least 12 MPa to the fibrous blanket (8).

2. Press arrangement (10), according to claim 1, characterized in that the ratio between the average pressure and the peak pressure is less than 0.46 and / or greater than 0.

3.

3. Press arrangement (10), according to claim 1 or 2, characterized in that the second press (1) is designed to be operated with a line load of at least 1,000 kN / m, preferably at least 1,300 kN / m.

4. Press arrangement (10), according to any of the preceding claims, characterized in that the first press (11) is designed in such a way that at least one of the following statements applies: a) a ratio between the average pressure and the peak pressure on the first pressing contact line is greater than 0.5; b) the maximum line load with which the first press (11) can be operated is less than the maximum line load with which the second press (1) can be operated; Petition 870250087501, dated 26 / 09 / 2025, p. 31 / 44 2 / 4 c) the peak pressure that can be applied to the fibrous mat (8) on the first pressing contact line is less than the peak pressure that can be applied to the fibrous mat (8) on the second pressing contact line.

5. Press arrangement (10), according to any of the preceding claims, characterized in that the second press (1) is a shoe press comprising a press shoe (4) with a concave curved surface and a shoe press sleeve (6) rotatably mounted around the press shoe (4).

6. Press arrangement (10), according to claim 5, characterized in that the shoe press sleeve (6) consists at least partially of polyurethane, which is formed by the reaction of a prepolymer and a crosslinking component, wherein the prepolymer is a reaction product of 1,4-phenylene diisocyanate (PPDI) and a polyol component containing at least one polyether polyol and / or at least one polycarbonate polyol, and wherein the crosslinking component contains a C2-14-Diol.

7. Press arrangement (10), according to claim 6, characterized in that the polyol component of the prepolymer comprises polytetramethylene ether glycol (PTMEG) and at least one polycarbonate polyol.

8. Press arrangement (10), according to claim 6 or 7, characterized in that the crosslinking component comprises polytetramethylene ether glycol (PTMEG) and / or at least one polycarbonate polyol.

9. Machine for producing a fibrous blanket (8), preferably a Packaging Testliner, characterized in that it comprises a press arrangement (10), as defined in any of the preceding claims.

10. Method for pressing a fibrous blanket (8), in particular a continuous roll of packaging paper, preferably using an arrangement Petition 870250087501, dated 26 / 09 / 2025, page.32 / 44 3 / 4 press (10) as defined in any of claims 1 to 8, wherein the fibrous mat (8) is successively guided through at least two presses (11, 1), namely a first press (11) with a first pressing contact line and a subsequent second press (1) with a second pressing contact line, wherein the second pressing contact line is an extended pressing contact line and wherein the fibrous mat (8) is pressed in the second press (1) with a line load of at least 500 kN / m, characterized in that the fibrous mat (8) is pressed in the second press (1) such that the quotient between the average pressure and the peak pressure on the pressing contact line of the second press is less than 0.5, and wherein the fibrous mat (8) is pressed in the second press (1) with a peak pressure of at least 12 MPa.

11. Method, according to claim 10, characterized in that the ratio between the average pressure and the peak pressure is less than 0.46 and / or greater than 0.

3.

12. Method according to claim 10 or 11, characterized in that the fibrous blanket (8) is pressed in the second press (1) with a linear load of at least 1,000 kN / m, preferably at least 1,300 kN / m.

13. Method, according to any one of claims 10 to 12, characterized in that the first press (1) is operated in such a way that at least one of the following statements applies: a) a ratio between the average pressure and the peak pressure on the pressing contact line is greater than 0.5; b) the maximum line load with which the first press (1) is operated is less than the maximum line load with which the second press (11) is operated; c) the peak pressure applied to the fibrous blanket (8) on the first pressing contact line is less than the peak pressure applied to the fibrous blanket (8) on the second pressing contact line.

14. Method, according to any one of claims 10 to 13, characterized in that the fibrous mat (8) consists of at least 20% by weight, preferably at least 50% by weight of OCC fibers. Petition 870250087501, dated 09 / 26 / 2025, pp. 34 / 44

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