Method for the post-treatment of products made from lignin-containing pulp, especially paper and paperboard

Abstract

The present invention relates to a method for post-treatment of products, in particular paper and paperboard, made from pulp containing lignin, comprising the steps of: introducing the product into a product gap of a belt press having at least one belt, heating the product in the belt press to a temperature between 160°C and 350°C, and applying a line pressure of 30N / mm to 200N / mm and / or 50kN / m 2 (0.5bar)~600kN / m 2 (6bar), especially 200kN / m 2 (2bar)~600kN / m 2 (6 bar) surface pressure.

Description

[Technical field]

[0001] The present invention relates to a method for post-treatment of products made from lignin-containing pulp, particularly paper and paperboard. Summary of the Invention

[0002] The present invention allows for improved post-processing of products made from lignin-containing pulp, particularly paper and paperboard.

[0003] The above mentioned improvement is achieved by a method for the post-treatment of products made from lignin-containing pulp, in particular paper and paperboard, according to claim 1. Advantageous further developments in the present invention are described in the dependent claims.

[0004] The method for post-treatment of products, particularly paper and paperboard, made at least in part from pulp containing lignin comprises the steps of: introducing the product into a product gap of a belt press having at least one belt, heating the product in the belt press to a temperature between 160°C and 350°C, and applying a line pressure of 30N / mm to 200N / mm and / or 50kN / m 2 (0.5bar)~600kN / m 2 (6bar), especially 200kN / m 2 (2bar)~600kN / m 2 (6 bar) surface pressure.

[0005] The method of the present invention can improve the mechanical strength as well as the moisture resistance of products made from pulp containing lignin, in particular paper and paperboard. The products are at least partially made from pulp containing lignin, meaning that at least a component or at least a layer of the product is made from pulp containing lignin. The pulp contains lignin and usually also contains fibrous material. The pulp is preferably made at least partially from wood or plants containing lignin. The products are in particular thin products, such as paper and paperboard. Heating the paper to a temperature within the above range and placing it under pressure within the above range acts on the lignin in the product, thereby making it stronger and more resistant to humidity and moisture. It has been shown that the dry strength and wet strength can be improved. The dry strength is evaluated by the tensile index and the SCT (Short Crush Test) index. The wet strength is evaluated by the wet tensile index. In particular, the wet strength of the products, in particular paper and paperboard, is significantly increased by the method of the present invention, for example by a factor of 10. On the other hand, the dry strength is, for example, doubled. It should be noted that all the lignin is already contained in the product. Additional lignin can be added during the process of the invention, for example by applying a liquid or powder containing lignin to the product. This can be done by spraying or sprinkling, respectively. By using a band press, the process of the invention can be carried out very economically and quickly. However, the process of the invention does not require the formation of an in-line solution. That is, the process of the invention is not limited to being carried out downstream of or in the same papermaking machine. Rather, the process of the invention can be carried out offline, for example by a roll-to-roll process. According to the invention, the product is heated to a temperature of 160°C to 350°C. It is understood that the scope of the invention encompasses all temperatures in the ranges mentioned above. The exact temperature and the exact temperature range used depends on the type of paper, and in particular the pulp from which the product is made. Simple tests regarding the optimum temperature and temperature range can be carried out for a particular given product.According to the present invention, the product in the band press is subjected to a line pressure of 30N / mm to 200N / mm and / or 50kN / m. 2 ~600kN / m 2 The scope of the present invention encompasses all line pressures and surface pressures within each given range. The optimum line pressure and / or surface pressure depends on the type of product being post-processed, and in particular the type of pulp from which the product is made. Simple tests can be performed to determine the optimum line pressure and / or optimum surface pressure for a particular product being post-processed within the given ranges for line pressure and surface pressure.

[0006] According to one embodiment of the invention, before the product is introduced into the product gap, a step of moistening or drying the product is carried out so that the product contains a moisture content of between 2% and 40%, in particular a moisture content of between 10% and 40%.

[0007] According to one embodiment of the invention, the at least one belt is a steel belt or a plastic belt.

[0008] With a steel or plastic belt, the product to be post-treated can be reliably guided through the belt press and temperature and pressure can be provided to the product in a reproducible manner. In the case of a plastic belt, the belt can include, be made of, or be coated with Teflon. In the case of a steel belt, the belt can be polished or have a desired surface roughness.

[0009] According to one embodiment of the present invention, the belt press is a double belt press having at least an upper belt and a lower belt, where heating of the product and providing pressure to the product take place in a product gap between at least one upper belt and at least one lower belt of the double belt press.

[0010] The double belt press is particularly well suited for the post-treatment of thin products, especially paper: the product can be safely introduced into the product gap between the belts and pressure and temperature can be applied to the product.

[0011] A double belt press can have two or more steel belts forming at least a part of the product gap between them, two or more plastic belts forming at least a part of the product gap between them, and / or at least one steel belt and at least one plastic belt forming at least a part of the product gap between them. All the upper belts and all the lower belts are looped belts (endless belts) and are guided around at least two drums. The drums may be driven or may rotate freely, and the drums may be heated or cooled. Furthermore, the belts may also be heated or cooled.

[0012] According to one embodiment of the invention, two plastic belts form at least a portion of a product gap between them, and on the back side of at least one of the plastic belts, and for at least a portion of the product gap, a steel belt moves in a parallel direction to the plastic belt.

[0013] By using two plastic belts and additionally at least one steel belt, the advantages of both plastic and steel belts can be combined. The plastic belt can have a non-stick surface, i.e. Teflon. Furthermore, plastic belts are generally cheaper and easier to manufacture compared to steel belts. The steel belt, on the other hand, can be used to apply higher pressures and achieve a higher heat flux to the post-treated paper compared to the plastic belt. Furthermore, the heat capacity of the steel belt is very high compared to the plastic belt. Thereby, heat losses can be minimized when using a steel belt to introduce heat flow to the post-treated paper. According to one embodiment of the present invention, the upper belt of the double belt press is perforated.

[0014] The upper belt being perforated allows the vaporized gas or steam to escape from the product gap. This can be important and advantageous, since the product is heated and the moisture contained in the product evaporates in the product gap. The perforated belt gives the possibility for the vaporized gas or steam to escape from the product gap without adversely affecting the product quality. Even in that case, pressure can be provided by the perforated belt, whereby a high and constant product quality can be ensured.

[0015] According to one embodiment of the invention, the double belt press comprises a first upper belt and a second upper belt, where the first upper belt is arranged upstream of the second upper belt when viewed in the conveying direction of the double belt press in the product gap.

[0016] By means of the first and second upper belts, the product to be post-processed is pressurized and heated, and at the same time, the vaporized gases and steam generated in the product gap by the heating of the product can escape through the gap between the first and second upper belts. Moreover, the pressure is also released between the first and second upper belts and provided again by the second upper belt. This can also be an advantage in the method of the present invention. Such vaporized gases or steam are generated from the moisture contained in the product and the subsequent heating of the product inside the product gap. By allowing the vaporized gases or steam to escape, a very good and constant product quality can be ensured. Within the scope of the present invention, two or more separate upper belts can be provided, when viewed in the paper transport direction through the product gap, and between each pair of adjacent upper belts, a product gap is provided to allow the vaporized gases or steam to escape the product gap.

[0017] According to one embodiment of the invention, pressure is applied by at least one pressure roller, a rotating roller, at least one S-roller, at least one counter pressure roller, and / or at least one counter pressure belt.

[0018] Pressure rollers, rotating rollers, S-rollers, counter pressure rollers and / or counter pressure belts are advantageously combined with a belt press. Within the scope of the present invention, combinations of pressure rollers, rotating rollers, S-rollers, counter pressure rollers and / or counter pressure belts are possible. The optimal combination is determined for the pressure provided to the product, i.e. line pressure or surface pressure, and the amount of pressure or pressure range provided to the product.

[0019] According to one embodiment of the invention, pressure is applied directly to the product by at least one pressure roller, a rotating roller, at least one S-roller, at least one counter pressure roller, and / or at least one counter pressure belt.

[0020] According to one embodiment of the invention, at least one pressure roller, rotating roller, at least one S-roller, at least one counter pressure roller, and / or at least one counter pressure belt contacts the backside of at least one belt, where the backside of the belt faces away from the product to be post-treated.

[0021] Thereby, pressure is applied to the product indirectly, which can be an advantage.

[0022] According to one aspect of the invention, the desired temperature of the product in the belt press is achieved by heating at least one belt.

[0023] In particular, the product to be post-treated can simultaneously be heated by the belt and pressure can be applied to the product by the belt.

[0024] According to one embodiment of the invention, pressure is applied and at least partially released again in a belt press at least twice.

[0025] Applying pressure at least twice and releasing it again at least partially leads to an improvement in the product quality after post-treatment, i.e. increased mechanical strength and increased resistance to moisture. For example, pressure can be applied to the product in the product gap by a first pair of pressure rollers facing each other and a second pair of pressure rollers facing each other, the first pair of pressure rollers and the second pair of pressure rollers being arranged one behind the other in the conveying direction of the product through the belt press, and between the first pair of pressure rollers and the second pair of pressure rollers the pressure is at least partially released.

[0026] According to an exemplary embodiment, pressure can also be applied to the products in the product gap by at least one pair of pressure rollers, said pair of pressure rollers having an upper roller and a lower roller, the upper roller and the lower roller being arranged in the same longitudinal position when viewed in the conveying direction, the upper roller touching the rear surface of the first belt, the rear surface of the first belt facing the opposite side of the product gap, and the lower roller touching the rear surface of the second belt, the rear surface of the second belt facing the opposite side of the product gap. According to a further exemplary embodiment, pressure can be applied to the products in the product gap by a first upper arrangement of rotating rollers and a second lower arrangement of rotating rollers, the first arrangement of rotating rollers and the second arrangement of rotating rollers being arranged in the same longitudinal position when viewed in the conveying direction, the first arrangement of rotating rollers touching the rear surface of the first belt, the rear surface of the first belt facing the opposite side of the product gap, and the second arrangement of rotating rollers touching the rear surface of the second belt, the rear surface of the second belt facing the opposite side of the product gap. With the rotating rollers, pressure is applied and partially released again in the flow path of the rotating rollers on the product or on the part of the belt that the product touches.

[0027] According to one embodiment of the invention, the pulp is produced by mechanical pulping.

[0028] Mechanical pulping means that wood in the form of chips or logs is mechanically separated into pulp fibers by grinding stones or refiners. This includes that many of the naturally occurring wood components, such as cellulose, hemicellulose and lignin, remain intact, with some modifications. The properties of such products can be greatly improved by the inventive method for the post-treatment of this product. In particular, the mechanical strength of the product and the resistance of the product to moisture and water are greatly increased. At least components or layers of products, such as paper and paperboard, are produced from pulp containing lignin to achieve the results of the present invention.

[0029] According to one embodiment of the invention, the product is unwound from a first product coil and the product is introduced into a belt press, and after exiting the belt press the product is wound onto a second coil.

[0030] Thereby, a roll-to-roll method is realized. Such a roll-to-roll method is particularly advantageous since the method of the invention is designed as an offline solution, i.e. it is not intended to be implemented inside the paper machine or downstream and online of the paper machine.

[0031] According to one embodiment of the invention, at least two layers of products that are laminated to one another are introduced into the product gap.

[0032] The post-treatment of the product can be carried out simultaneously on at least two layers that are laminated together, thereby at least doubling the product productivity of the method of the invention. It has been found that no separation layer is required between two layers of the product that are post-treated simultaneously.

[0033] Further advantages and aspects of the present invention can be derived from the following description of preferred embodiments of the invention in conjunction with the drawings. The specific features of the present invention can be combined with other specific features described and / or shown in the drawings within the scope of the present invention. This also applies to combinations of specific features without other specific features described or shown in conjunction with the specific feature with which it is combined.

[0034] Exemplary embodiments of the present invention will now be described in detail with reference to the figures. [Brief description of the drawings]

[0035] [Figure 1] FIG. 1 is a schematic diagram of a first exemplary embodiment of a belt press for carrying out the invention. [Diagram 2] FIG. 2 is a schematic diagram of a second exemplary embodiment of a belt press for carrying out the invention. [Diagram 3] FIG. 3 is a schematic diagram of a third exemplary embodiment of a belt press for carrying out the invention. [Figure 4] FIG. 4 is a schematic diagram of a fourth exemplary embodiment of a belt press for carrying out the invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0036] FIG 1 shows a belt press 10 including an upper belt 12 and a lower belt 14. The upper belt 12 is guided by a first rotating drum 16 and a second rotating drum 18. Both drums 16 and 18 rotate counterclockwise, causing a lower portion of the upper belt 12 to move from left to right in FIG 1, i.e., in a conveying direction 20 indicated by an arrow in FIG 1.

[0037] The lower belt 14 is guided by a third rotating drum 22 and a fourth rotating drum 24. Two of the drums 22 and 24 can rotate in a clockwise direction, whereby the upper part of the lower belt 14 moves in the conveying direction 20. Between the lower part of the upper belt 12 and the upper part of the lower belt 14, a product gap 26 is provided.

[0038] The paper 28 to be post-treated is presented to the product gap 26 and is transported through the product gap in conveying direction 20 by the moving belts 12 and 14. Within the scope of the present invention, products made from lignin-containing pulp, in particular paper 28 and paperboard, can be post-treated. Moistening or drying of the paper to a moisture content of 2% to 40% can be carried out before introducing the paper into the product gap.

[0039] The paper 28 is unwound from a first paper coil 30. After being post-processed by the belt press 10 in the product gap 26, the paper is wound onto a second coil 32. The method of the invention is thereby implemented as a roll-to-roll process. The method of the invention is intended to form an off-line solution, i.e. the method of the invention is not intended to be implemented on-line and downstream of the papermaking device as an additional papermaking production step.

[0040] The paper 28 is guided into the product gap 26 from a first coil 30. The drums 16 and 22 may be heated.

[0041] The upper belt 12 and the lower belt 14 may be plastic belts or steel belts. For example, the upper belt 12 may be a plastic belt and the lower belt 14 may be a steel belt, or both belts 12 and 14 may be plastic belts or steel belts. In the exemplary embodiment shown in Figure 1, both belts 12 and 14 are steel belts, and drums 16 and 22 may be heated to heat the upper belt 12 and the lower belt 14 to a desired temperature at the beginning of the product gap 26.

[0042] At the beginning of the product gap 26, the upper belt 12 is guided over approximately half of the circumference of the first drum 16. The first drum 16 is heated by a heating liquid guided through the channel 40 into the interior of the first drum 16. As a result, the upper belt 12 is heated while in contact with the circumference of the first drum 16. Therefore, at the very beginning of the product gap 26, i.e. between the first drum 16 and the top of the second belt 14, the upper belt 12 has the desired temperature. The lower belt 14 is guided over approximately half of the circumference of the third drum 22, which is heated by the channel 54. Therefore, the lower belt 14 also has the desired temperature at the beginning of the product gap 26.

[0043] Downstream of the first drum 16, a set of six pressure rollers 42 is arranged. Each set of pressure rollers 42 consists of an upper pressure roller and a lower pressure roller, and when viewed in a vertical direction perpendicular to the conveying direction 20, each upper pressure roller is arranged above each lower pressure roller. Each upper pressure roller touches the lower back surface of the upper belt 12, and each lower pressure roller touches the upper back surface of the lower belt 14. That is, the upper pressure roller touches the back surface of the upper belt facing away from the product gap 26, and the lower pressure roller touches the back surface of the lower belt facing away from the product gap 26.

[0044] Between the two pressure rollers 42, a set of heaters 44 is disposed. Each set of heaters 44 includes an upper heater that blows hot air onto the back surface of the upper belt 12 between the two upper pressure rollers. Additionally, each set of heaters 44 also includes a lower heater that blows hot air onto the back surface of the lower belt 14 between the two lower pressure rollers. In total, five sets of heaters 44 are disposed to maintain the temperature in the product gap 26 at a desired value or within a desired range. The pressure rollers 42 are also heated by the heaters 44 sets.

[0045] The pressure rollers 42 form a pressure and heat application zone. The temperature applied to the paper 28 in said zone reaches 300° C. and the line pressure applied to the paper 28 in said zone reaches 40 N / mm. It has been found that a line pressure of 40 N / mm is applied by each set of pressure rollers 42. Downstream of a set of pressure rollers 42, pressure is at least partially released and then applied again by the next set of pressure rollers 42. Thus, pressure is applied and released by the pressure rollers 42 six times.

[0046] Downstream of the sixth set of pressure rollers 42, the upper belt 12 is guided around the second drum 18 and the lower belt 14 is guided around the fourth drum 24. Thus, between the second drum 18 and the fourth drum 24, the product gap 26 ends. The post-processed paper 28 is then wound onto a second coil 32 downstream of the product gap 26.

[0047] FIG. 2 shows diagrammatically a second exemplary embodiment of a belt press by means of which the method of the present invention can be carried out.

[0048] It has been recognized that the various methods of providing heat and pressure described in Figures 1, 2, 3, and 4 may be combined with one another without the need to combine every method of providing heat and pressure in Figure 1 with every method of providing heat and pressure in Figure 2. For example, pressure roller 42 of Figure 1 may be combined in a belt press with an S-roller and counter pressure belt as shown and described by Figure 4 and / or a rotating roller according to Figure 3.

[0049] The belt press 100 shown in FIG. 2 comprises a first upper belt 112 and a second upper belt 114. The first belt 112 is guided around two drums 118 and 120. The drums 118 and 120 can be heated. The second upper belt 114 is guided around two drums 122 and 124. The drums 122 and 124 can be heated or cooled. The drums 118 and 120 for the first upper belt 112 and the drums 122 and 124 for the second upper belt 114 are arranged at the same height and can only rotate in a counterclockwise direction. When viewed in the conveying direction 20, the second upper belt 114 is arranged downstream of the first upper belt 112. Between the first upper belt 112 and the second upper belt 114, a gap 140 is provided. This gap 140 is arranged between the drums 120 and 122. This gap 140 blocks the product gap 26, which is open to the upper side in the gap 140. This gap 140 is used to release vaporized gas or steam of the paper that is post-processed in the product gap 26. The paper that is post-processed by the double belt press 100 in the product gap 26 contains a moisture content between 30% and 70%. And the paper is heated in the product gap by the upper belts 112 and 114 and the lower belt 116 as well as by the pressure roller 42 and the heater 44. The paper in the product gap 26 is heated to a temperature between 160° C. and 350° C., whereby the moisture contained in the paper is at least partially evaporated. The vaporized gas or steam that is thereby generated can escape the product gap 26 in the gap 140. The vaporized gas or steam that is generated in the product gap 26 is thereby released much faster compared to the double belt press 10 of FIG. 1. In the double belt press shown in FIG. 1, vapor gas or steam can only escape from the product gap 26 to the side, ie, into the view of FIG. 1 and into the page.

[0050] The first upper belt 112 has the same length as the second upper belt 114. In the section of the first upper belt 112, two sets of pressure rollers 42 are arranged, and one set of heaters 44 is arranged between the two sets of pressure rollers 42. In the section of the second upper belt 114, two sets of pressure rollers 42 are also arranged, and one set of heaters 44 is arranged between the two sets of pressure rollers 42.

[0051] The lower belt 116 has approximately twice the length of the first upper belt 112 or the second upper belt 114. The first drum 126, which guides the lower belt 116 at the beginning of the product gap 26, is disposed directly below the drum 118, which guides the first upper belt 112 at the beginning of the product gap 26. The drum 128, which guides the lower belt 116 at the end of the product gap 26, is disposed directly below the drum 124, which guides the second upper belt 114 at the end of the product gap 26. In the section of the lower belt 116, two sets of pressure rollers 42 and one set of heaters 44 are disposed across the first upper belt 112. In the section of the lower belt 116, two sets of pressure rollers 42 and one set of heaters 44 are disposed across the second upper belt 114. An additional pressure roller 142 is arranged in the section of the gap 140 over the drum 120 which guides the first upper belt 112, and over the drum 122 which guides the second upper belt 114. The pressure roller 142 adjoins the rear surface of the lower belt 116 which faces away from the product gap 26. A heater 144 is arranged opposite the gap 140 which heats the drums 120 and 122 and the top of the lower belt 116.

[0052] A first layer 28 of paper is unwound from a first coil 130, guided through the product gap 26 and wound on a second coil 132 after the end of the product gap 26. At the same time, a second layer 128 of paper is unwound from a first coil 134, guided through the product gap 26 and wound on a second coil 136 after the end of the product gap 26. According to the double belt press 100 of FIG. 2, the two layers 28 and 128 of paper can be post-treated simultaneously. No separating layer is required between the two layers 28 and 128 of paper. Within the scope of the present invention, two or more layers of paper can be post-treated simultaneously.

[0053] 3 shows a belt press 200 according to a third exemplary embodiment of the present invention. The belt press 200 is a double belt press, having an upper belt 12 and a lower belt 14 forming a product gap 26 therebetween. The belt press 200 is very similar to the belt press 210 described in conjunction with FIG. 1, and only the differences will be described.

[0054] The paper 28 is unwound from a first coil 30 and guided through the product gap 26 where temperature and pressure are applied to the paper. After exiting the product gap 26, the paper is wound onto a second coil 32.

[0055] Disposed within the product gap 26 are three sets of pressure rollers 42. Between the two sets of pressure rollers 42 is a set of heaters 44.

[0056] Downstream of the third set of pressure rollers 42, two sets of circulating rollers 210 are arranged. Each set of circulating rollers 210 provides an upper circulating roller device 212 and a lower circulating roller device 214. The upper circulating roller device 212 provides a roller chain, which is guided and moves counterclockwise around a guide block. As can be seen in FIG. 3, approximately eight rollers of the circulating roller device 212 contact the back surface of the upper belt 12 at the same time. By each roller of the circulating roller device 212, pressure is provided to the paper 28 in the product gap 26. After passing through each roller, the pressure is shortly released and is provided again by the next roller. The lower circulating roller device 214 is arranged in the same manner as the upper circulating roller device 212, except that the roller chain moves clockwise. The guide block and / or the rollers of the upper circulating roller device 212 and the lower circulating roller device 214 can be heated and / or cooled. The second set of rotating rollers 210 are arranged in the same manner as the first set of rotating rollers 210 .

[0057] By the circulating roller 210, a temperature of up to 350° C. can be provided to the paper 28 in the product gap 26, and at the same time a pressure of 200 kN / m2 (2 bar) can be provided to the paper 28 in the product gap 26.

[0058] 4 shows a schematic diagram of a fourth exemplary embodiment of a belt press for carrying out the method of the present invention. The belt press 300 is very similar to the belt press 10 of FIG. 1 and only the differences will be described.

[0059] The belt press 300 includes an upper belt 12 and a lower belt 14. The lower part of the upper belt 12 and the upper part of the lower belt 14 form a product gap 26 therebetween. Paper 28 is unwound from a first coil 30 and guided in the conveying direction 20 through the product gap 26, whereupon the paper 28 is wound onto a second coil 32. The upper belt 12 is guided around the drums 16 and 18, and the lower belt 14 is guided around the drums 22 and 24.

[0060] Within the product gap, S-rollers 310 are arranged. The S-rollers 310 are arranged in such a way that they push the upper belt 12 downwards. At the same time, the lower belt 14 is also pushed downwards. This leads to the product gap 26 first curving downwards upstream of the S-rollers 310 and then curving upwards downstream of the S-rollers 310. The S-rollers 310 can be prestressed in the direction towards the product gap 26, for example by hydraulic cylinders. The S-rollers 310 can be heated or cooled.

[0061] Across the S-roller 310, a counter pressure roller 312 is arranged adjacent to the back surface of the lower belt 14. The counter pressure roller 312 is fixed in its position and touches the back surface of the lower belt 14 facing away from the product gap 26. The counter pressure roller 312 provides a counter pressure in the area of ​​the S-roller 310. As a result, the paper 28 in the product gap 26 is first guided downwards by the S-roller 310 and then line pressure or pressure by the counter pressure roller 312 and the S-roller 310 is applied. After that, the paper 28 in the product gap 26 is again guided upwards to the same height as the beginning of the product gap 26. Upstream of the S-roller 310, a set of pressure rollers 42 is arranged. This set of pressure rollers 42 is used to provide pressure to the paper 28 in the product gap, but is also used to guide the upper belt 12 and the lower belt 14.

[0062] A further set of pressure rollers 42 is arranged downstream of the S-roller 310. This set of pressure rollers 42 is used to provide pressure to the paper 28 in the product gap and to further guide the upper belt 12 and the lower belt 14. It can be seen that by the set of pressure rollers 42 upstream of the S-roller 310, by the S-roller 310 and the counter pressure roller 312, and by the pressure roller 42 downstream of the S-roller 310, pressure is provided and again at least partially relieved from the paper 28 three times. By the set of pressure rollers 42 upstream of the S-roller 310, a first pressure is provided with a first value. By the S-roller 310 and the counter pressure roller 312, a second pressure is provided with a second value, the second value being higher than the first value. By the set of pressure rollers 42 downstream of the S-roller 310, a third pressure is provided to the paper 28 with a third value, the third value being lower than the second value and having, for example, the same value as the first value.

[0063] Following the second set of pressure rollers downstream of the S-roller 310, a set of three heaters 44 are positioned such that the paper 28 in this region of the product gap is only heated and only a pressure of less than the third value provided by the set of pressure rollers 42 downstream of the S-roller 310 is applied to the paper 28. The lower belt 14 is guided by the support rollers 314 in this region within the product gap.

[0064] After exiting the product gap 26 , the paper 28 is wound onto a second coil 32 .

Claims

1. 1. A method for the post-treatment of products, in particular paper and paperboard, at least partly made from pulp containing lignin, comprising the steps of: introducing said product (28) into a product gap (26) of a belt press (10; 100) having at least one belt, heating the product in said belt press (10; 100) to a temperature of 160°C to 350°C, in particular 250°C to 350°C, and applying a line pressure of 30 N / mm to 200 N / mm and / or 50 kN / mm to said product (28) in said belt press. ２ (0.5bar)~600kN / m ２ (6 bar), especially 200 kN / m ２ (2bar)~600kN / m ２ (6 bar) surface pressure.

2. 2. The method of claim 1, comprising wetting or drying the product (28), in particular paper (28), so that the product (28) contains a moisture content of between 2% and 40%.

3. 3. The method of claim 1 or 2, wherein the at least one belt is a steel belt or a plastic belt.

4. 3. The method according to claim 1 or 2, wherein the belt press is a double belt press (10; 100) having at least one upper belt and at least one lower belt, and the heating of the product and the application of pressure to the product are carried out in a product gap (26) between the at least one upper belt and the at least one lower belt of the double belt press.

5. 5. The method according to claim 4, wherein the double belt press (10; 100) comprises two steel belts that form at least a part of the product gap (26) between them, the double belt press (10; 100) comprises two plastic belts that form at least a part of the product gap (26) between them, or the double belt press (10; 100) comprises a steel belt and a plastic belt that form at least a part of the product gap (26) between them.

6. 6. The method of claim 5, wherein two plastic belts define at least a portion of the product gap (26) therebetween, and the steel belt runs parallel to the plastic belt behind at least one of the plastic belts for at least a portion of the product gap (26).

7. 5. The method of claim 4, wherein the top belt of the double belt press is perforated.

8. 5. The method of claim 4, wherein the double belt press comprises a first upper belt and a second upper belt, the first belt being positioned upstream of the second belt when viewed in a conveying direction of the double belt press at the product gap.

9. 3. The method of claim 1 or 2, wherein the pressure is provided by at least one pressure roller (42, 48), circulating roller (44, 46, 50), at least one S-roller (124), at least one counter pressure roller (126), and / or at least one counter pressure belt (128).

10. 10. The method of claim 9, wherein the pressure is applied directly to the product by at least one pressure roller (42, 48), circulating roller (44, 46, 50), at least one S-roller (124), at least one counter-pressure roller (126), and / or at least one counter-pressure belt (128).

11. 10. The method of claim 9, wherein the at least one pressure roller (128), the circulating roller (44, 46, 50), the at least one S-roller (124), the at least one counter pressure roller (126), and / or the at least one counter pressure belt (128) contact a back surface of the at least one belt, the back surface of the belt facing away from the product gap (26).

12. 3. The method according to claim 1 or 2, wherein the desired temperature of the product (28) in the belt press (10; 100) is achieved by heating the at least one belt.

13. 3. The method according to claim 1 or 2, wherein the pressure is applied and at least partially released in the belt press (10; 100) at least twice.

14. 14. The method according to claim 13, wherein the pressure is released to a value less than 30%, in particular less than 10%, of the pressure provided immediately before the release of the pressure.

15. 3. The method of claim 1 or 2, wherein the pulp is produced by mechanical pulping.

16. 3. The method according to claim 1 or 2, wherein the product (28) is unwound from a first coil and the product (28) is introduced into the belt press (10; 100) and, after exiting the belt press (10; 100), the product is wound onto a second coil (32).

17. 3. The method according to claim 1 or 2, wherein at least two layers of the product, stacked on top of each other, are introduced into the product gap.

18. 3. The method of claim 1 or 2, wherein heating the paper to a temperature within the range and applying a pressure within the range to the product affects the lignin within the product, thereby making the product stronger and more resistant to moisture and water.

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