Roller, use and method

Abstract

Roller and its use in a machine for the production or processing of a fibrous web, wherein the roller has at least one coating which provides the radial outer surface of the roller, wherein the coating comprises a first component of metallic, ceramic or cermet-based material and a second component of a polysiloxane-based polymer material, and wherein the radial outer surface comprises both material of the first component and of the second component, as well as a manufacturing process for such a roller.

Description

[0001] The invention relates to a roller and its use in a machine for the production or processing of a fibrous web according to the preamble of claim 1, and to a method for the production or processing of a roller according to the preamble of claim 10.

[0002] Coated rollers with a non-porous structure are used in paper machines for the production of a wide variety of papers (e.g., packaging, food, hygiene, graphic arts, etc.). The coating is produced using methods such as arc spraying, HVOF, HVAF, plasma spraying, flame spraying, laser cladding, or high-speed metal arc welding, among others.

[0003] These layers are characterized by the fact that substances from the papermaking process agglomerate on the surface of these rollers and consequently lead to problems in the manufacturing process, including corrosion of the coating and / or the roller base, fouling and / or wear of the coating and / or the roller base, and damage to the screen, felt, or fabric and / or paper web.

[0004] To minimize these effects and to maintain the longevity of the roller coverings or rollers, these non-porous layers are coated with sealants. A variety of polymer materials are suitable for this purpose. For example, epoxy resins are used when high mechanical stability of the covering is required, or poly- and perfluorinated alkyl compounds (so-called PFAS substances) are used to achieve non-stick properties.

[0005] Such a non-stick coating made of Teflon is described, for example, in DE 103 54 507 A1.

[0006] Increased awareness of perfluorinated substances is now leading to changes in regulations and / or legal requirements, as well as a new awareness among paper product manufacturers, in the availability of raw materials for the aforementioned sealants, and, last but not least, to more conscious behavior among end consumers. Therefore, these perfluorinated substances are increasingly considered problematic from both an ecological and economic perspective, and restrictive legislation is to be expected in many areas in the future.

[0007] The object of the invention is to propose alternatives to the use of PFAS which are less harmful to health and with which good anti-stick properties can still be achieved.

[0008] In particular, the object of the invention is to propose polymer-based alternative materials for anti-stick applications on thermal coatings of rollers in paper machines.

[0009] The problem is solved according to the invention by an embodiment according to the independent claims. Further advantageous embodiments of the present invention are found in the dependent claims.

[0010] A roller is proposed for use in a machine for the production or processing of a fibrous web, which has at least one coating providing the radial outer surface of the roller, wherein the coating comprises a first component of metallic, ceramic or cermet-based material and a second component of a polysiloxane-based polymer material, and wherein the radial outer surface comprises material of both the first component and the second component.

[0011] The metallic, ceramic, or cermet-based component of the roller surface is nowadays usually applied to a roller base body in the form of a thermal spray coating. The provision of the second component, made of polymer material, can be described as a sealant. In rollers according to aspects of the invention, this sealant material comprises a polysiloxane-based polymer material.

[0012] The covering and / or paper rests primarily on the abrasion-resistant coating peaks of the first component for most of its service life. The polysiloxane-based polymer in the recesses of the coating structure provides the anti-adhesion properties against organic and / or inorganic substances. Upon delivery, the coating may have a protrusion of the polysiloxane-based polymer sealant, so that the peaks of the first component only reach the surface through wear during operation of the second component. Alternatively, the protrusion can be removed before delivery, for example by sanding, or the quantity of the second component can be selected so that no protrusion occurs at all.

[0013] Advantageously, it can be provided that the polysiloxane-based polymer material is cross-linked or already is.

[0014] The polysiloxyane-based polymer material can be selected differently depending on the intended use and operating conditions.

[0015] For example, the polysiloxane-based polymer material may comprise or consist of a polysiloxane oligomer or polysiloxane polymer of the composition -[(SiR 1< R 2< )-O-] n -, wherein the polysiloxane oligomer or polysiloxane polymer has a linear, branched / dendritic or cyclic architecture and R 1< and R 2< are independently H, CH 3 , C 2 -C 15 alkyl groups (linear, branched or cyclic) or C 5 -C 14 aromatics, and wherein n is an integer between 2 and 10,000, preferably between 5 and 1,000, most preferably between 10 and 100.

[0016] The alkyl substituents and / or the aromatic substituents in R 1< and R 2< may be equipped with functional groups such as halogens, alkenyl groups, alkynyl groups, alkaryl groups, heteroalkyl groups, heteroaryl groups, hydroxy groups, amine groups (primary, secondary, tertiary and quaternary amine or ammonium groups), sulfides, disulfides, ethers, thioethers, carboxylic acids and their salts, sulfonic acids and their salts, esters or amides.

[0017] In particular, further reagents can be added to further improve cross-linking or cross-linkability.

[0018] Alternatively or additionally, the polysiloxane-based polymer material may comprise or consist of a copolymer with the composition -{[(SiR 1< R 2< )-O-] n -[Y] m -} x, where Y is a monomer from the class of substances acrylates, methacrylates, urethanes, epoxides, amides or ethers; R1< and R2< are independently H, CH3, C2-C15 alkyl groups (linear, branched or cyclic) or C5-C14 aromatics, and wherein n is an integer between 2 and 10,000, preferably between 5 and 1,000, most preferably between 10 and 100, and m is an integer between 2 and 10,000, preferably between 10 and 1,000, most preferably between 25 and 100, and wherein the ratio m:n spans the range 100:5 to 100:500, preferably the range 100:10 to 100:100, and most preferably the range 100:20 to 100:50.

[0019] The copolymer can be a static copolymer, a block polymer, a dendritic copolymer, a hyperbranched copolymer, an alternating copolymer, a gradient copolymer, or a graft copolymer (x = stat, block, dend, alt, grad, or graft). In such copolymers with a dendritic architecture or graft structure, the polysiloxane blocks can advantageously be arranged in the outer region; conversely, copolymers with a dendritic architecture or graft structure can also be used in which the polysiloxane blocks are located in the inner region.

[0020] The formulation of the polysiloxane oligomer or polysiloxane polymer or the copolymer with polysiloxane structural units can be carried out as a 1-component or 2-component system.

[0021] The crosslinking of the polysiloxane oligomer or polysiloxane polymer or copolymer with polysiloxane structural units can occur either intrinsically after mixing all raw materials under standard conditions / room temperature (particularly relevant for 2-component systems) or stimuli-induced, for example by heating, by adding reagents such as catalysts or water / humidity, or radiation-induced (particularly relevant for 1-component systems).

[0022] Preferably, the crosslinking of the polysiloxane oligomer or polysiloxane polymer or copolymer with polysiloxane structural units can be carried out by polycondensation, particularly with the addition of crosslinking agents. Optionally, organometallic catalysts, for example based on tin, titanium, or magnesium, can also be used.

[0023] The crosslinking agents can thereby change the composition Z 3 SiR 3< or Z 4 SiR 3< can be chosen from H, CH 3 , C 2 -C 15 alkyl groups (linear, branched or cyclic) or C 5 -C 14 aromatics.

[0024] The alkyl substituents and / or the aromatic substituents in R 3< can be equipped with functional groups such as halogens, alkenyl groups, alkynyl groups, alkaryl groups, heteroalkyl groups, heteroaryl groups, hydroxy groups, amine groups (primary, secondary, tertiary and quaternary amine or ammonium groups), sulfides, disulfides, ethers, thioethers, carboxylic acids and their salts, sulfonic acids and their salts, esters or amides.

[0025] The structural units Z can each contain a hydrolyzable group such as a carboxylic acid chloride, a carboxylic acid ester (especially an acetate), a carboxylic acid anhydride, a lactone or a benzyl chloride.

[0026] Alternatively, the crosslinking of the polysiloxane oligomer or polysiloxane polymer or copolymer with polysiloxane structural units can be achieved by hydrosilylation, particularly with the addition of catalysts. These can be, for example, catalysts based on organometallic platinum compounds. Crosslinking agents, such as oligosilanes (compounds containing at least three SiH silane structural units) or oligoalkenes (compounds containing at least three C=C double bonds), can also be used.

[0027] Alternatively, the crosslinking of the polysiloxane oligomer or polysiloxane polymer or copolymer with polysiloxane structural units can be carried out by radical crosslinking, especially after the addition of radical initiators such as benzoyl peroxide, dicumyl peroxide, etc.

[0028] It has been shown that sealing the roller surface with a hardened polysiloxane-based polymer (polysiloxane coating) results in a roller with low surface energy and thus good anti-stick properties. While the addition of additives to the polysiloxane coating is possible, it is not necessary to achieve the desired anti-stick properties.

[0029] It is possible to obtain rollers with very low surface energy by varying the sealing material and / or other parameters.

[0030] In advantageous embodiments, the surface may have a surface energy of less than 25 mN / m, in particular 20 mN / m or less. Alternatively or additionally, the surface may have a contact angle of at least 100°, in particular 110° or more, when wetted with the test liquid water (contact angle H2O [°]). Example 1: Surface energy of native steel substrates or of arc-coated steel substrates, which may have a further coating with a polysiloxane-based sealing layer.

[0031] The following table shows the influence of the polysiloxane-based sealer layer on the surface energy (OE) and the contact angle. The surface energies were calculated according to the Owens-Wendt-Rabel-Kaelble method based on contact angle measurements with the test liquids water and diiodomethane. Table 1: Surface energy (OE) of unsealed and sealed surfaces. substrate Sealing layer cut Contact angle H₂O [°] Contact angle CH 2 I 2 [°] OE total [mN / m] OE disp [mN / m] OE pol [mN / m] th. spray layer no no 62 41 50,6 39,0 11,5 th. spray layer no Yes 54 45 54,1 37,2 17,0 blasted steel Yes no 113 91 12,9 12,2 0,6 th. spray layer Yes no 112 90 13,6 12,9 0,7 th. spray layer Yes Yes 143 105 7,6 7,1 0,5

[0032] All polysiloxane-sealed surfaces exhibit surface energies below 20 mN / m, in contrast to an unsealed thermal spray coating, which has surface energies above 50 mN / m (Table 1). While the polysiloxane-coated steel substrates show surface energies of 19.5 mN / m and 12.9 mN / m, respectively, various arc-sprayed thermal spray coatings impregnated with polysiloxane sealants have surface energies of 13.6 mN / m (as-sprayed) and 7.6 mN / m (in the ground condition), respectively.

[0033] The first component, made of metallic, ceramic, or cermet-based material, can exhibit various structural properties.

[0034] For example, this first component can be designed as a non-porous layer onto which the polysiloxane-based second component is applied.

[0035] In preferred embodiments, the roller surface may have a stochastic structure. This means that neither the material of the first component nor the material of the second component exhibits a regular structure with repeating uniform elements on the radially outer surface.

[0036] Since the roller's surface consists of two very different materials (metallic, ceramic, or cermet-based material of the first component versus polysiloxane-based polymer material of the second component), it cannot be ruled out that these materials will affect the fiber web differently upon direct contact (e.g., with regard to gloss or roughness). Even if the differences are small, they are often noticeable to the eye if they occur in regular patterns. This is then perceived as a quality defect in the fiber web. If, on the other hand, the roller has a stochastic surface in which neither material component exhibits regular and repeating elements, the differences in gloss, smoothness, etc., in the fiber web are equally stochastic and far less noticeable to the observer.

[0037] In further advantageous embodiments, it can also be provided that the first component forms a porous layer, and the sealant, in the form of the polysiloxane-based second component, penetrates this porous layer completely or at least partially and is embedded in the pores of the porous layer.

[0038] Versions in which the first component forms a porous layer always exhibit a stochastic structure as described above due to the irregular pore structure of the first components.

[0039] What is particularly surprising is that the low surface energy of the sealing polysiloxane layer is also guaranteed in the case of low polysiloxane layer heights.

[0040] The polysiloxane-based polymer material used in this sealant advantageously exhibits low-viscosity properties, enabling penetration into the pores of the roller surface. This ensures effective bonding of the sealant to the coating. Due to this low viscosity, the formulation of the sealant can be formulated without, or at least almost entirely without, the use of solvents. (The collective term "solvent" here includes both organic solvents and water.)

[0041] The thickness of the coating layer can vary greatly depending on the application.

[0042] The layer heights can be, in particular, between 30 µm and 2000 µm, preferably between 50 µm and 700 µm, and especially preferably between 50 µm and 400 µm.

[0043] In cases where the first components have non-porous structures, the sealing layer will remain only on the surface of the coating. However, in porous structures, the polysiloxane-based polymer penetrates deeper into the coating structure. For example, it may be provided that the second component (viewed from the roller surface) penetrates at least 50 µm, in particular more than 100 µm, and preferably more than 150 µm, into the first component.

[0044] Surprisingly, it has been shown that even at very low heights of the polysiloxane-based polymer, the desired low surface energies and high contact angles can be achieved. Additional additives to the polysiloxane material are not necessary.

[0045] A preferred application area for rollers according to aspects of the present invention are rollers in the drying section of a paper machine.

[0046] In some applications, it is advantageous if the sealant, made of polysiloxane-based polymer, is distributed over the entire surface of the roller. This is the case, for example, with conventional drying cylinders or guide rollers.

[0047] However, there are also applications where it is advantageous or sufficient for the surface to contain material of the second component only on a portion of the roller surface, particularly in the area of ​​the end faces, while the entire outer surface contains material of the first component. Yankee cylinders, used, for example, in the production of tissue paper, represent such an application. Here, the edge areas are particularly susceptible to the adhesion of dirt particles, making the use of a polysiloxane-based sealer highly advantageous in these areas, while such a sealer can be omitted in the web center.

[0048] Furthermore, a method for manufacturing or processing a roller for use in a machine for manufacturing or processing a fibrous web is proposed, comprising the following steps: a. Providing a roller base body b. Applying a second component made of a polysiloxane-based polymer material.

[0049] The roller body can be the roller surface itself. Alternatively, the provided roller body can already have one or more coatings, particularly made of a metallic, ceramic, or cermet-based material, whereby these coatings are applied, for example, by thermal spraying.

[0050] Preferably, the process further comprises the step of cross-linking the polysiloxane-based polymer material, wherein the cross-linking is either inherent to the system after mixing all raw materials or stimuli-induced, for example by heating, by adding reagents such as catalysts, water / humidity, or radiation-induced.

[0051] It may be provided that the crosslinking is carried out by polycondensation with the addition of crosslinking agents, wherein the crosslinking agents have the composition Z 3 SiR 3< or Z 4 Si, and R 3< is chosen from H, CH 3 , C 2 -C 15 alkyl groups (linear, branched or cyclic) or C 5 -C 14 aromatics and the structural units Z contain a hydrolyzable group such as a carboxylic acid chloride, a carboxylic acid ester, in particular an acetate, a carboxylic acid anhydride, a lactone or a benzyl chloride.

[0052] Alternatively, it can also be provided that cross-linking is carried out by hydrosilylation with the addition of catalysts or by radical cross-linking after the addition of radical initiators.

[0053] The first component can, for example, be applied by thermal spraying. In this case, the process further comprises step: a2. Applying a first component made of a metallic, ceramic, or cermet-based material, wherein the application is carried out in particular by thermal spraying, with step a2 being performed before step b.

[0054] Methods according to aspects of the invention can be used for the initial production of a roller.

[0055] Rollers used in a machine for producing or processing a fibrous web are subject to constant wear during operation, so their surface coating must be renewed regularly. This renewal of the coating can also be carried out using methods according to aspects of the present invention.

[0056] The invention will be explained below with the aid of figures. The figures show, in detail: Figure 1 Schematic section of a roller according to one aspect of the invention. Figure 2a Schematic section of a roller according to another aspect of the invention. Figure 2b Microscopic view of a coating for a roller according to another aspect of the invention. Figure 3 Roller according to further aspects of the invention.

[0057] Figure 1Figure 1 schematically shows the structure of a coating with a non-porous structure consisting of the first component 2 and a sealant 10. The first component 2, made of a metallic, ceramic, or cermet-based material, is applied to a roller surface 1. This first component has a largely closed internal structure and is, in particular, non-porous. The top surface of this first component 2 is not completely smooth but exhibits a certain topography. The second component 10, in the form of a polysiloxane-based polymer 10, is applied according to the design shown. Figure 1 applied to this top surface, it completely or largely fills in the topography of the top surface.

[0058] As can be seen, the radial outer surface of the roller contains material of both the first component 2 and the second component 10.

[0059] The covering and / or the paper web essentially rests on the abrasion-resistant coating peaks 12. The polysiloxane-based polymer / sealant in the recesses of the layer structure provides the anti-adhesion properties 11 against organic and / or inorganic substances.

[0060] Neither the material of the first component 2 nor the material of the second component 3 has a regular structure with repeating uniform elements. The structure of the roller surface 1 is therefore a stochastic structure within the meaning of this application.

[0061] In contrast, it shows Figure 2a The illustration shows a layer structure with a porous structure of the first component 3 and a sealant 10. The polysiloxane-based polymer 10 can completely (as shown here) or to a large extent fill the existing (open) porosity.

[0062] Figure 2bFigure 1 shows a microscopic image of such a coating for further illustration. The polysiloxane-based polymer 10 can be seen here as dark spots in the significantly lighter metallic, ceramic and / or cermet-based porous coating / first component 3.

[0063] The coating thickness can vary considerably depending on the application. Specifically, the layer thickness can range from 30 µm to 2000 µm, preferably from 50 µm to 700 µm, and most preferably from 50 µm to 400 µm.

[0064] The polysiloxane-based polymer 10 can remain not only near the surface of a porous first component 3. Figure 2a The polysiloxane-based polymer 10 has penetrated as an example up to the roller surface 1.

[0065] At the in Figure 2bIn the real-world example shown, the polysiloxane-based polymer 10 can still be detected at a distance of 150 µm from the surface. It is even possible to achieve penetration depths of 350 µm or more.

[0066] Such penetration depths are not necessary to achieve the desired effect of reducing surface energy. However, they can have a positive impact on the stability of polysiloxane-based sealing layers.

[0067] Tests have shown that even when used in paper machines, the low surface energy and, consequently, the dirt-repellent effect are maintained despite the continuous abrasive processes.

[0068] In this test, a paper-contacting guide roller still showed a surface energy of 18.6 mN / m after several months of operation (determined according to the Owens-Wendt-Rabel-Kaelble method based on contact angle measurements with the test liquids water and diiodomethane).

[0069] The in the Figure 1 and 2a The examples shown each depict a single-layer structure of the coating, where a metallic, ceramic and / or cermet-based first component 2, 3 and a polysiloxane-based polymer 10 are applied as a sealer to the roller surface 1.

[0070] In Figure 3 This example demonstrates that this coating can also be produced in a multi-layer structure. Several layers of metallic, ceramic, and / or cermet-based coating 2, 3 are applied one on top of the other to the roller surface 1. In the example of the Figure 3These are three layers. These three layers can be the same or different. In particular, they can be porous coatings (3) or non-porous coatings (2).

[0071] In the case of several superimposed layers of porous coating 3, it is possible that the polysiloxane-based polymer 10 completely penetrates the top layer of the first component 3 and also penetrates into the pores of the underlying layer(s). Here too, it can happen that the polysiloxane-based polymer 10 (as in Figure 2a (shown) penetrates to the roller surface 1. Reference symbol list

[0072] 1 Roller surface / substrate 2 Metallic, ceramic and / or cermet-based non-porous coating / first component 3 Metallic, ceramic and / or cermet-based porous coating / first component 10 Polysiloxane-based polymer / sealer / second component 11 Anti-adhesion properties 12 Coating peaks (summits)

Claims

1. Roller for use in a machine for producing or processing a fibrous web, having at least one coating which provides the radial outer surface of the roller, wherein the coating comprises a first component (2, 3) of metallic, ceramic or cermet-based material, and a second component of a polysiloxane-based polymer material (10), and wherein the radial outer surface comprises material of both the first component (2, 3) and the second component (10).

2. Roller according to one of the preceding claims, characterized by the fact that the polysiloxane-based polymer material is cross-linked or is cross-linked.

3. Roller according to one of the preceding claims, characterized by the fact thatthe roller has a stochastic structure such that on the radial outer surface neither the material of the first component (2) nor the material of the second component (2) has a regular structure with repeating uniform elements.

4. Roller according to one of the preceding claims, characterized by the fact that the polysiloxane-based polymer material is a polysiloxane oligomer or polysiloxane polymer of the composition -[(SiR 1 R 2 )-O-] n - comprises or consists of, wherein the polysiloxane oligomer or polysiloxane polymer has a linear, branched / dendritic or cyclic architecture and R 1 and R 2 independently of each other H, CH3, C2-C 15 -Alkyl groups (linear, branched or cyclic) or C5-C 14 -aromatics are and where n is an integer between 2 and 10,000, preferably between 5 and 1,000, most preferably between 10 and 100.

5. Roller according to any of the preceding claims, characterized by the fact that the polysiloxane-based polymer material is a copolymer with the composition -{[(SiR 1 R 2 )-O-] n -[Y] m -} x comprising or consisting of, wherein Y is a monomer from the class of substances acrylates, methacrylates, urethanes, epoxides, amides or ethers; R 1 and R 2 independently of each other H, CH3, C2-C 15 -Alkyl groups (linear, branched or cyclic) or C5-C 14 -aromatics and where n is an integer between 2 and 10,000, preferably between 5 and 1,000, most preferably between 10 and 100 and m is an integer between 2 and 10,000, preferably between 10 and 1,000, most preferably between 25 and 100, and where the ratio m:n spans the range 100:5 to 100:500, preferably the range from 100:10 to 100:100, and most preferably the range from 100:20 to 100:

50.

6. Roller according to any of the preceding claims, characterized by the fact that the surface has a surface energy of less than 25 mN / m, in particular 20 mN / m or less, and / or the surface has a contact angle of at least 100°, in particular 110° or more, when wetted with the test liquid water.

7. Roller according to any of the preceding claims, characterized by the fact that the first component (3) forms a porous structure, and the second component (10) is at least partially embedded in the pores of the porous structure.

8. Roller according to claim 7, characterized by the fact that The second component, viewed from the roller surface, has penetrated at least 50 µm, in particular more than 100 µm, preferably more than 150 µm deep into the first component.

9. Roller according to any of the preceding claims, characterized by the fact thatthe radial outer surface has material of the second component (10) only on a part of the roller surface, in particular in the area of ​​the end face edges, while it has material of the first component (2, 3) on the entire outer surface.

10. Method for manufacturing or processing a roller for use in a machine for manufacturing or processing a fibrous web, comprising the steps of: a. providing a roller body b. applying a second component of a polysiloxane-based polymer material (10) 11. The method of claim 10, wherein the method further comprises the step of cross-linking the polysiloxane-based polymer material (10), wherein the cross-linking is either inherent in the system after mixing all raw materials or stimuli-induced, for example by heating, by adding reagents such as catalysts, water / humidity, or radiation-induced.

12. Method according to claim 11, characterized by the fact that Cross-linking occurs through polycondensation with the addition of cross-linking agents, the cross-linking agents having the composition Z3SiR 3 or have a Z4Si, and R 3 from H, CH3, C2-C 15 -Alkyl groups (linear, branched or cyclic) or C5-C 14 -aromatics is chosen and the structural units Z contain a hydrolyzable group such as a carboxylic acid chloride, a carboxylic acid ester, in particular an acetate, a carboxylic acid anhydride, a lactone or a benzyl chloride.

13. Method according to claim 11 characterized by the fact that Cross-linking occurs through hydrosilylation with the addition of catalysts or through radical cross-linking after the addition of radical initiators.

14. Method according to any one of claims 10 to 13, further comprising step a2. Applying a first component (2, 3) made of a metallic, ceramic or cermet-based material, wherein the application is carried out in particular by thermal spraying, wherein step a2. is carried out before step b.

15. Use of a roller according to any one of claims 1 to 9 in the drying section of a machine for the production or processing of a fibrous web, in particular as a guide roller, drying cylinder or Yankee cylinder.

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