Rollers and devices used in the manufacture of paper, paperboard, and tissue paper.

Abstract

This invention relates to a roller for manufacturing paper, paperboard, tissue paper, etc. The roller has a first end and a second end, and includes a cylindrical roller body having a hollow internal space and an outer protective surface. The roller also includes a roller coating layer, which at least includes a base layer disposed on the outer protective surface of the roller body and an elastomer layer disposed on the base layer. The elastomer layer forms the outer surface of the roller coating layer. The first and second ends of the roller have protective zones in which the base layer is not covered by the elastomer layer and forms the outer surface of the roller. The invention also relates to an apparatus including such a roller.

Description

Technical Field

[0001] This invention relates to rollers and apparatus for manufacturing paper, paperboard, household paper, etc. Background Technology

[0002] Various polymer-coated rolls are used in the manufacture of fiber webs (such as paper, paperboard, and tissue paper). For example, press rolls and suction rolls are used in the press sections of paper machines, paperboard machines, or tissue paper machines to remove water from the fiber web by pressing. These rolls typically consist of a hollow roll body and a soft elastomer cover, usually polyurethane, arranged to form the outer surface of the roll body. Elastomer-coated rolls are used, for example, as counter rolls in heated drying cylinders (such as Yankee drying cylinders), and the surfaces of these rolls are typically exposed to heat and / or moisture. However, because the roll body is typically internally cooled, the roll has a relatively cool roll body surface, i.e., the mantle surface. For example, the sealing elements of suction rolls are lubricated with water, typically unheated circulating water from the mill. The lubricating water simultaneously cools the surface of the roll body's protective cover, creating a temperature gradient between the roll body surface and the surface of the elastomer coating layer exposed to ambient heat and moisture through the roll cover. The same phenomenon occurs when the roll body is intentionally cooled with water.

[0003] However, if the ambient temperature and / or moisture content becomes excessively high, the elastomeric coating may exhibit rapid degradation. In particular, when the elastomeric coating comes into direct contact with the heated surface of another cylinder, or when it is subjected to a large temperature gradient, there is a risk of coating failure manifested as swelling, structural degradation, and loss of strength and / or abrasion resistance. In the worst case, this could even lead to debonding and fragmentation of the coating. Therefore, new solutions are needed to improve the durability of elastomeric-coated rollers under adverse conditions. Summary of the Invention

[0004] The purpose of this invention is to minimize or even completely eliminate the drawbacks of the prior art.

[0005] Another object of the present invention is to provide a roller and a device having improved durability, increased reliability and extended service life, especially in hot and / or humid environments.

[0006] Various embodiments of the invention will be shown below. Features in all the described embodiments are applicable to all aspects of the invention, whether rollers or apparatus, as long as applicable, even if not always stated as such.

[0007] A typical roller according to the invention for manufacturing paper, paperboard, tissue paper, etc., has a first end and a second end, and includes:

[0008] The cylindrical roller body has a hollow internal space and an outer protective cover surface.

[0009] The roller coating layer includes at least a base layer disposed on the outer protective surface of the roller body, and an elastomer layer disposed on the base layer, the elastomer layer forming the outer surface of the roller coating layer, and

[0010] Optionally, multiple suction holes extend from the outer surface of the roller to the hollow interior space of the roller body.

[0011] The first and second ends of the roller have protection zones in which the base layer is not covered by the elastomer layer and forms the outer surface of the roller.

[0012] A typical apparatus according to the present invention for manufacturing paper, paperboard, tissue paper, etc., includes:

[0013] Heated cylinders, such as Yankee drying cylinders, etc.

[0014] According to the invention, the rollers are arranged to serve as opposing rollers relative to the heating cylinder, thereby forming a pressure zone between the heating cylinder and the rollers.

[0015] The fabric is arranged to pass through the pressure zone and has a first fabric edge and a second fabric edge.

[0016] It has been surprisingly found that when the first and second ends of the roll have protected zones, the service life of the elastomer layer of the roll coating increases and the risk of coating failure is significantly reduced, where the base layer of the roll coating forms the outer surface of the roll. This means that at the protected zones, the base layer is not covered by the elastomer layer and is freely visible. In this way, the direct exposure of the elastomer layer to excessive heat and large temperature gradients is minimized, and the likelihood of the elastomer layer failing due to expansion, degradation, debonding, loss of strength and / or abrasion resistance is reduced.

[0017] The roll-coated layer includes at least one base layer and at least one elastomer layer, said at least one elastomer layer being disposed on top of the base layer, preferably in direct and immediate contact with the base layer. Preferably, the base layer is less heat-sensitive than the elastomer layer. The roll-coated layer may also include one or more intermediate layers between the base layer and the elastomer layer.

[0018] In this document, the term "protected area" refers to the area on the outer cover surface of the roller body covered only by the base layer of the roller coating. Thus, the base layer forms the outer surface of the roller or roller coating at the protected area. The protected area is located at both the first and second ends of the roller. Preferably, the protected area is arranged on the area of ​​the outer cover surface of the roller body that is not covered by the fabric, i.e., in the area between the roller end and the fabric edge. The protected area can have a width of at least 10 mm, i.e., its length along the axial direction of the roller as viewed from the fabric edge, and a maximum possible width that can extend to the roller end. The width of the protected area depends on the roller width. The width of the protected area is preferably large enough to allow for slight wandering of the fabric edge. In practice, the position of the fabric edge is unstable, but due to fabric aging and / or fabric width variations caused by uneven stretching, the fabric edge may be offset to some extent in the cross-machine direction, i.e., relative to the centerline of the machine / roller. Sometimes, the fabric can even be deliberately oscillated. In any case, by means of the present invention, the area of ​​the roller surface exposed to heat from the heating cylinder (such as a Yankee dryer) is covered only by the base layer, and the risk of elastomeric layer failure can be minimized. However, the contact area between the base layer and the outer cover surface of the roll body remains essentially the same as that in a conventional roll, thus providing a similar bonding area between the base layer and the outer cover surface. Therefore, the presence of the protection zone does not negatively affect the bonding between the roll coating and the roll body.

[0019] Generally, the roller according to the invention is suitable for manufacturing paper, paperboard, tissue paper, etc. The roller can be, for example, a press roller with a solid, unperforated surface, or a suction roller with a perforated surface. The roller has a first end and a second end, and the longitudinal axis of the roller extends from the first end to the second end. The roller comprises a cylindrical roller body having a hollow internal space, an inner protective surface, and an outer protective surface. The roller body, and therefore its inner and outer protective surfaces, are made of metals such as cast iron, stainless steel, hardened steel, bronze, etc. Typically, the length of the roller body can range from 2.5 to 12 m, and is typically in the range of 48 m.

[0020] The roller may include means located inside the roller body for supplying, circulating and / or conveying cooling and / or lubricating liquid media (such as water).

[0021] According to a preferred embodiment of the invention, the roller is a suction roller. The suction roller includes a stationary suction box disposed within a hollow space inside a cylindrical roller body, wherein the roller body is arranged to rotate about the suction box. This rotation is provided by a drive device that can be arranged to functionally contact the roller body. The suction box includes seals that restrict the suction area longitudinally within the hollow space of the roller body and at the ends of the roller body. These seals are typically lubricated with a liquid medium (such as water) to reduce seal wear and improve sealing performance. Therefore, the suction roller includes means for providing a liquid medium between the surface of the seals and the surface of the inner shroud of the roller body.

[0022] When the roller is a suction roller, it includes a plurality of suction holes arranged through the roller coating layer and the roller body. The suction holes extend from the outer surface of the roller to the hollow interior space of the roller body. According to a preferred embodiment of the invention, the elastomeric layer of the roller coating layer may have a first edge region and a second edge region, the first and second edge regions including a plurality of blind holes extending from the outer surface of the roller and located only partially within the elastomeric layer. The edge region includes a solid portion and a blind-drilled portion with blind holes along the radial direction of the roller. It has been observed that the edge region with blind holes further reduces the negative effects caused by high temperature gradients, temperature, and moisture exposure. In the absence of perfect fabric coverage and protection of the elastomeric layer, the edge region of the elastomeric layer can be considered as an additional safety zone. Viewed from the first end of the roller along the longitudinal axis of the roller toward the second end, the roller surface may include a first protection zone, a first edge region of the elastomeric layer, an elastomeric layer with suction holes, a second edge region of the elastomeric layer, and a second protection zone.

[0023] According to one embodiment of the invention, the first edge region and the second edge region may include a plurality of blind holes with a depth of up to 90%, preferably up to 80%, and more preferably up to 60% of the total thickness of the elastomeric layer. The blind holes in the edge regions may be arranged to follow a hole pattern that is generally the same as that of the holes in the elastomeric layer, or they may be arranged to follow a different pattern or form surface profiles, such as grooving. The widths of the first edge region and the second edge region may correspond to the thickness of one or more elastomeric layers, or be less than the thickness of one or more elastomeric layers. In some embodiments, the edge regions may have a width of, for example, 5 mm to 15 mm. The widths of the first edge region and the second edge region are typically the same.

[0024] According to one embodiment of the invention, the roller may further include bare regions in which the outer protective surface of the roller body is exposed, i.e., uncovered and without any coated layer or roller coating layer. The bare regions presenting the uncovered outer protective surface of the roller body are preferably located between the protected zone and the end of the roller. This means that, viewed from the first end to the second end of the roller along the longitudinal axis of the roller, the roller surface includes an optional first bare region, a first protected zone, an optional first edge region, an elastomer layer, an optional second edge region, a second protected zone, and an optional second bare region. The width of the elastomer layer is typically consistent with the width of the fabric used in the device. The bare regions typically have a width of 0-50 mm or 0.5-50 mm.

[0025] The roller according to the invention includes a roller coating layer, which at least includes a base layer and an elastomer layer. The roller coating layer may include multiple elastomer layers stacked on top of each other. The total thickness of the roller coating layer is typically 15-50 mm. The total thickness of the roller coating layer includes the base layer and all possible elastomer layers included in the roller coating layer.

[0026] The base layer is disposed on the outer cover surface of the roller body, in direct and immediate contact with the outer cover surface. The base layer is heat-resistant and / or insensitive to heat. According to one embodiment of the invention, the base layer may be made of a composite material comprising reinforcing fibers in an epoxy resin matrix. The reinforcing fibers may be glass fibers or carbon fibers embedded in a continuous epoxy resin matrix. The thickness of the base layer may be 10-20 mm. The base layer is arranged to surround the outer cover surface of the roller body or the aforementioned overlay layer, and forms a continuous sleeve around the outer cover surface of the roller body. Thus, the base layer forms a continuous layer on the outer cover surface of the roller body, extending from a first end of the roller to a second end.

[0027] At least one elastomer layer is also disposed on the base layer, forming the outer surface of the roller. The elastomer layer is typically a heat-sensitive layer. According to one embodiment of the invention, the elastomer layer may include at least two or more sublayers. The sublayers may be chemically different and / or have different mechanical properties, such as abrasion resistance or flexibility.

[0028] The elastomer layer may preferably comprise or may be a polyurethane elastomer layer. The polyurethane elastomer suitable for this invention can be formed by the chemical reaction of elastomer precursors based on polyols and isocyanates, i.e., polyol precursors and isocyanate precursors, with a chain extender. The chain extender cures the polyurethane elastomer formed by the reaction between the isocyanate precursor and the polyol precursor. The chain extender may be selected from diols and diamines with a weight average molecular weight ≤4000 g / mol, for example 60-4000 g / mol. Examples of suitable chain extenders are 1,4-butanediol, hydroquinone bis(2-hydroxyethyl) ether, diethyltoluene diamine, and 4,4'-methylenebis(3-chloro-2,6-diethylaniline).

[0029] The isocyanate precursors used in polyurethane elastomers can be selected from aromatic isocyanates, aliphatic isocyanates, or mixtures thereof. It is also possible that the elastomer layer can be formed from two or more different isocyanate precursors based on aliphatic or aromatic isocyanates. By selecting one or more isocyanate precursors used, the chemical and / or mechanical properties of the formed elastomer layer can be tailored. The aromatic isocyanate precursor may be selected from 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 4,4'-methylene diphenyl diisocyanate, 2,4'-methylene diphenyl diisocyanate, 2,2'-methylene diphenyl diisocyanate, 1,5-naphthalene diisocyanate, para-phenylene diisocyanate, 3,3'-dimethyl-4,4'-biphenyl diisocyanate, 1,4-benzene diisocyanate, 1,3-xylylene diisocyanate, 4,6-xylylene diisocyanate, and tetramethylxylylene diisocyanate. Aliphatic isocyanate precursors can be selected from 1,6-hexamethylene diisocyanate, isophorone diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, tetramethylxylidene diisocyanate, trimethylhexamethylene diisocyanate, 1,3-bis(isocyanatomethyl)cyclohexane, 1,4-cyclohexyl diisocyanate, and cyclohexamethylene diisocyanate.

[0030] The polyol precursors for polyurethane elastomers can be selected from polyesters, polyethers, polycarbonate polyols, and polycaprolactone polyols. The elastomer layer can be formed using one polyol precursor or two or more different polyol precursors.

[0031] The roller according to the invention is particularly suitable for use as a pair of rollers in a heating cylinder, such as a steam-heated cylinder, like a Yankee drying cylinder. During operation, a fiber web supported by a fabric (such as a blanket) is arranged to pass through a pressure zone formed between the heating cylinder and the roller. While supporting the fiber web, the fabric simultaneously protects the roller's rubber coating from excessive heat and moisture. Preferably, the protective zone of the roller is arranged in areas at the fabric edges where the outer protective surface of the roller body is not covered and protected by the fabric, i.e., at least in the area between the roller end and the fabric edge. Edge areas with blind holes are preferably located at the fabric edges. Attached Figure Description

[0032] The following schematic, non-limiting drawings further illustrate certain aspects of the invention. A better understanding of the invention can be achieved by referring to the accompanying drawings and the detailed description of the embodiments presented herein.

[0033] Figure 1 A side view of a Yankee dryer cylinder during tissue paper manufacturing.

[0034] Figure 2 This is a partial schematic diagram of an apparatus according to an embodiment of the present invention, viewed along the machine direction. Detailed Implementation

[0035] Figure 1 A Yankee drying cylinder 1 is shown, rotating about axis A in the direction of arrow R. The Yankee drying cylinder 1 is a large-diameter cylinder and has a rotating journal 24 and bearing 25. The Yankee drying cylinder 1 is heated internally by hot steam, possibly overpressurized, or by other internal or external heating devices such as infrared heaters, hot oil, or induction. A wet fiber web W travels on fabric 30, which can be, for example, an endless absorbent blanket running in a loop around guide rollers (not shown), or in some cases, a non-absorbent but textured fabric, thereby imprinting a three-dimensional structure onto the fiber web W. Figure 1 In the diagram, the direction of movement of fabric 30 is indicated by arrow C.

[0036] The rollers 31 are placed within the loop of the fabric 30 and arranged to form a pressure zone together with the outer surface of the Yankee dryer 1. The rollers 31 can be suction rollers with perforated surfaces, or press rollers with grooved or non-grooved surfaces. If the rollers 31 are suction rollers, a suction box D is provided inside the rollers 31. Figure 1(Illustrated schematically) to improve the dehydration of the web W and enhance the separation of the fabric 30 from the web W in the pressing zone. Roller 31 has an elastic coating on its outer surface. In the pressing zone, the fiber web W and fabric 30 are sandwiched between roller 31 and Yankee dryer 1, and the fiber web W is conveyed to the smooth outer surface of Yankee dryer 1. Then, as Yankee dryer 1 rotates in the direction of arrow R, the fiber web W will reliably travel on the outer surface of Yankee dryer 1. As the initially relatively wet fiber web W travels in contact with the very hot outer surface of Yankee dryer 1, the fiber web is dried by evaporation during its travel and can then be crepeed off from Yankee dryer 1 by scraper 29.

[0037] The pressing performance is important for the reliable operation of the manufacturing process and for the production of fiber webs W with desired properties. To ensure that the web W follows the Yankee dryer 1 across its full width, rather than remaining wholly or partially on the fabric 30, the pressing pressure profile between the Yankee dryer 1 and the elastic coating of the roller 31 should be sufficiently uniform. Therefore, the primary purpose of the elastic coating of the roller 31 is to provide an elastic roller surface that conforms to the surface of the Yankee dryer 1 under a given pressing load condition. This can be achieved through… Figure 2 The apparatus of the present invention is illustrated in the schematic diagram.

[0038] Figure 2 This is a schematic cross-sectional view of an apparatus according to an embodiment of the present invention, viewed along the machine direction. Figure 2 This is a partial view of the device, which means that in Figure 2 Only half of the device is visible in the image. The device 40 includes a heating cylinder 1, which is a Yankee-style drying cylinder, and rollers 31 arranged to serve as opposite rollers to the heating cylinder 1. A pressure zone is formed between the heating cylinder 1 and the rollers 31, and the fabric 30 and the fiber web W are arranged as a web-fabric sandwich to pass through the pressure zone.

[0039] Roller 31 includes a cylindrical roller body 41 having a hollow internal space S and an outer protective surface 41'. The hollow internal space S may include a suction box, a seal for sealing the suction area of ​​the suction box, and / or means for supplying lubricating water / cooling water (not shown). Roller 31 also includes a roller coating layer, which includes at least a base layer 42 and an elastomer layer 43. The base layer is arranged to be in direct and immediate contact with the outer protective surface 41' of the roller body 41. The base layer 42 attaches the roller coating layer to the roller body 41. One or more elastomer layers 43 are arranged on top of the base layer 42 to form the outer surface of the roller coating layer.

[0040] from Figure 2As can be seen, a protection zone 44 exists at the end of roller 31, where the dirt-resistant base layer 42 is exposed, i.e., not covered by the heat-sensitive elastomer layer 43, and forms the actual outer surface of roller 31. A similar protection zone is arranged at the other end of roller 31 (not shown). The protection zone minimizes the area of ​​the elastomer layer 43 directly exposed to heat radiated from the heating cylinder 1. Most of the elastomer layer 43 is protected by the heat-dissipating fiber web W and fabric 30. In this way, the risk of large temperature gradients through the roller coating is reduced, and the possibility of the elastomer layer 43 failing due to expansion, degradation, delamination, loss of strength and / or abrasion resistance is reduced.

[0041] Multiple suction holes (schematically indicated by stripes) extend from the outer surface of the roll through the roll coating layer and the roll body 31 to the hollow interior space S of the roll body 41. Furthermore, the elastomer layer 43 has an edge region 43' comprising multiple blind-drilled holes extending from the outer surface of the roll and located only partially within the elastomer layer. The edge region 43' provides another safety zone where the blind-drilled holes further reduce the negative effects caused by high temperature gradients, temperature, and moisture exposure. The solid portion of the edge region 43' may have a width equal to that of the blind-drilled portion above it; however, preferably, the solid portion of the edge region 43' may be formed slightly longer by reducing the width of the blind-drilled portion, for example, by chamfering, rounding, or beveling the edge of the outermost elastomer layer 43.

[0042] To provide full-width support and uniform thickness and moisture profile for the fiber web, the fabric needs to be wider than the fiber web to ensure uniform compression of the web-fabric interlayer in the pressing zone and at the web edge areas. The elastomeric layer of the roll-coated layer is wider than the maximum width of the fabric, so that the fabric edge remains in contact with the elastomeric layer in the pressing zone, regardless of inaccuracies in the precise positioning of the fabric edge. However, even when the fabric is at its narrowest, the elastomeric layer does not extend too far from the fabric edge to remain present under the heat load from the heating cylinder. Ideally, the thermosensitive elastomeric layer extends beyond the fabric edge by a maximum of 5 mm to 15 mm. According to a preferred embodiment of the invention, the heat-resistant base layer extends at least 10 mm beyond the edge of the thermosensitive elastomeric layer to protect the elastomeric layer, thereby protecting the entire roll-coated layer from excessive heat.

[0043] Even though the invention has been described with reference to what appears to be the most practical and preferred embodiments, it should be understood that the invention is not limited to the embodiments described above, but is also intended to cover various modifications and equivalents within the scope of the appended claims.

Claims

1. A roller for manufacturing fiber webs, the roller having a first end and a second end, and arranged as a pair of rollers relative to a heating cylinder, the roller further comprising: The cylindrical roller body has a hollow internal space and an outer protective cover surface. The roller coating layer includes at least a base layer disposed on the outer protective surface of the roller body and an elastomer layer disposed on the base layer, wherein the elastomer layer forms the outer surface of the roller coating layer. Its features are, The first and second ends of the roller have protection zones in which the base layer is not covered by the elastomer layer and forms the outer surface of the roller, and the length of the heating cylinder is greater than the length of the elastomer layer.

2. The roller according to claim 1, characterized in that, The roller includes a plurality of suction holes that extend from the outer surface of the roller to the hollow interior space of the roller body.

3. The roller according to claim 1 or 2, characterized in that, The base layer has lower thermal sensitivity than the elastomer layer.

4. The roller according to claim 1 or 2, characterized in that, The elastomer layer has a first edge region and a second edge region, the first edge region and the second edge region including a plurality of blind holes, the plurality of blind holes extending from the outer surface of the roller and located only partially within the elastomer layer.

5. The roller according to claim 4, characterized in that, The depth of the blind hole is at most 90% of the thickness of the elastomer layer.

6. The roller according to claim 4, characterized in that, The depth of the blind hole is at most 80% of the thickness of the elastomer layer.

7. The roller according to claim 4, characterized in that, The depth of the blind hole is at most 60% of the thickness of the elastomer layer.

8. The roller according to claim 1 or 2, characterized in that, The first and second ends of the roller present an exposed area of ​​uncovered shield surface between the protected area and the end of the roller.

9. The roller according to claim 1 or 2, characterized in that, The elastomer layer comprises polyurethane.

10. The roller according to claim 1 or 2, characterized in that, The elastomer layer comprises at least two sublayers.

11. The roller according to claim 1 or 2, characterized in that, The base layer is made of a composite material comprising reinforcing fibers in an epoxy resin matrix.

12. The roller according to claim 1 or 2, characterized in that, The roller is a suction roller, which includes a fixed suction box arranged in a hollow space inside the cylindrical roller body.

13. The roller according to claim 1 or 2, characterized in that, The roller includes means located inside the roller body for supplying, circulating and / or conveying cooling and / or lubricating liquid media.

14. The roller according to claim 13, characterized in that, The cooling and / or lubricating liquid medium is water.

15. An apparatus for manufacturing fiber webs, the apparatus comprising: Heating cylinder, The rollers according to any one of claims 1 to 11 are arranged as opposing rollers relative to the heating cylinder, thereby forming a pressure zone between the heating cylinder and the rollers. The fabric is arranged to pass through the pressure zone and has a first fabric edge and a second fabric edge, and the length of the heating cylinder is greater than the length of the elastomer layer.

16. The apparatus according to claim 15, characterized in that, The heating cylinder is a Yankee drying cylinder.

17. The apparatus according to claim 15, characterized in that, The protection zone of the roller is arranged in the area between the end of the roller and the edge of the fabric.

18. The apparatus according to any one of claims 15 to 17, characterized in that, The elastomer layer includes an edge region with blind holes, wherein the edge region is located at the edge of the fabric.

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