WO2013004732A1

WO2013004732A1 - Roll having a wear-resistant non-stick surface

Info

Publication number: WO2013004732A1
Application number: PCT/EP2012/062998
Authority: WO
Inventors: Jürgen ABRAHAM; Alexander Etschmaier
Original assignee: Voith Patent Gmbh
Priority date: 2011-07-06
Filing date: 2012-07-04
Publication date: 2013-01-10
Also published as: EP2729613A1; CN103649411A; DE102011078759A1

Abstract

The invention relates to a roll cover for rolls (10) for use in a web-producing and/or web-processing machine, such as a paper machine or film machine, wherein the roll cover (12) has an inner cover layer (121, 122) and an outer cover layer (123, 124) arranged at least on part of the cylindrical surface of the inner cover layer (121, 122), and wherein the inner cover layer (121, 122) has a polymer composite material and the outer cover layer (123, 124) is composed of a metal or ceramic spray coating (123) having a polymer material (124) applied thereto.

Description

ROLLER WITH VERSCHLEISSBESTANDIGER nonstick surface The present invention relates to covers for rolls having cores preferably made from carbon fiber reinforced plastic ^¬ materials and particularly relates to a robust, easy to clean surface of such rolls.

Rolling with rolling seeds on the basis of carbon fiber reinforced plastics, so-called carbon fiber rolls generally have a higher rigidity than rolls Walzenker ^¬ NEN steel base. While the modulus of elasticity of steel rolls is about 220 GPa, CFRP rolls having moduli of elasticity of about 240 to about 700 GPa can be made and thus are much stiffer for the same diameter. Their composite construction also dampens vibrations. Compared to steel rollers, with CFRP rollers in web-processing machines such as paper machines, higher rotational speeds can be achieved without bringing the rollers into a critical speed and thereby causing vibrations. In contrast to steel rolls, CFRP rolls do not require a start-up time to be uniformly heated, which reduces the paper scrap at the beginning of a production run.

The stiffness of CFRP rollers can be adjusted by selecting a suitable fiber cross-section and by appropriate design of the carbon fiber windings over a wide Be ^¬ kingdom and thus be "tailored" for the particular operation ^¬ purpose of the roller. Since the specifi ^¬ specific weight of carbon fiber reinforced plastics (CFRP) speaks only in about one-fifth of that of steel corresponds, CFRP rolls are easily used in web-processing machines, such as paper machines and draw also characterized by a lower energy consumption.

As a result, CFRP rolls are increasingly being used as a replacement for steel rolls in existing web-processing machines. For use as guide rolls, z. As for screens and felts, the running surfaces of the CFRP rollers are coated with a so-called composite material, which guarantees a high mechanical resistance and in particular Ver ^¬ wear resistance of the respective screen or the respective felt contacting roller surface. As composite materials, polymers are frequently used in which fillers are embedded in order to achieve specific elasticities and abrasion properties. CFRP rolls provided with such composite covers have a life comparable to steel rolls.

However, it has been found that impurities accumulating on the composite surfaces during the operation of CFRP rollers are difficult to remove again.

It is therefore desirable to specify a roll cover based on egg ^¬ nes composite material on the surface impurities can accumulate with only low adhesive force.

Embodiments of such a roll cover for rolls for use in a papermaking machine have an inner reference ply and an outer ply disposed at least on a portion of the peripheral surface of the inner ply. The inner reference layer in this case has a poly ^¬ mer composite material, while the outer reference layer is formed by a metallic or ceramic sprayed coating having applied thereto polymeric material. It should be noted in this regard that the descriptions in this specification and claims are intended to be exhaustive Features used include "comprising", "having", "including", "containing" and "having", as well as their grammatical modifications, generally as a non-exhaustive Auf ^¬ counting of features, such as components, process steps, facilities, areas, sizes and the like, and in no way exclude the presence of other or additional features or groupings of other or additional features. Roll covers with the specified features combine a wear-resistant cover surface with a non-stick effect, which makes it difficult to adhere to impurities arising during paper production, thus guaranteeing an easily cleanable reference surface.

To achieve a positive connection between the spray coating and the polymeric material applied thereon, the outer surface of the metallic or ceramic spray coating advantageously has a roughness in the range of 5 to 8 μm and in particular in the range of 6 to 7 μm.

In advantageous embodiments, the polymeric material comprises an epoxy resin, since this wets well the spray coating in the non-crosslinked or partially crosslinked state and thereby not only a cohesive connection, but also creates a positive connection by penetrating depressions in the spray coating. In further embodiments, the polymeric material advantageously comprises a silicone-polyester resin because it combines very good non-stick properties with an excellent stain-resistant effect. In order to improve the non-stick and dirt-repellent properties of the outer reference layer of the coating, filling materials can be embedded in the polymeric material, the fillers of preferred Embodiments thereof include polyfluoroethylene (PFE) and in particular polytetrafluoroethylene (PTFE). In advantageous embodiments, the fillers are present in the form of particles and in particular in the form of particles with average diameters in the range from 0.01 to 5 μm. Instead of an epoxy resin or silicone polyester resin with PFE or PTFE-containing fillers, the polymeric material may also be formed directly from polyfluoroethylene and in particular polytetrafluoroethylene or from a polymer comprising such a substance.

For reliable filling of pores or pores formed in the spray layer when using polytetrafluoroethylene as the polymeric material, polytetrafluoroethylene particles having sizes in the range from about 50 to 100 nm are preferably slurried and the resulting dispersion applied to the spray coating, for example with the aid of a Immersion bath, by spraying or by applying with a brush or another brush. For this purpose, a polymer is USAGE ^¬ det, preferably that is in the form of particles having a size distribution in which at least 65 percent of the particles have one or more values from the range of 50 to 100 nm.

In embodiments, the spray coating on a metallic material containing hard materials, wherein the hard materials on the basis of metal-type carbides, me ^¬ metallic nitrides and borides, and mixtures thereof formed, and the binder of the metallic composite ^¬ substance of cobalt, iron, nickel, copper , Chromium or at least one of these metals containing alloy may be formed. Other embodiments include ceramic spray coating comprising one or more oxide ceramics. The Oxide ceramics can be selected from alumina, zirconium oxide, magnesium oxide, chromium (III) oxide, yttrium oxide and titanates. Further preferred embodiments have a porous metallic or ceramic sprayed coating whose pores are at least partially filled with the polymeric material in order to ensure the non-stick properties of the reference surface even after further wear of the sprayed coating.

The roll covers described above are preferably used at Wal ^¬ zen with roll cores made of carbon fiber reinforced plastic.

Further features of the invention will become apparent from the following description of exemplary embodiments in conjunction with the claims and the figures. It should be noted that the invention is not limited to the embodiments of the described embodiments, but is determined by the scope of the appended claims. In particular, the individual features in embodiments according to the invention can be realized in a different number and combination than in the examples given below. In the following explanation of some embodiments of the invention, reference is made to the accompanying Figure 1, which illustrates the structure ei ^¬ ner roller using a schematic cross section through a roller segment.

The schematized representation of Figure 1 illustrates the structure of a roller 10 based on a cross section through a roller segment. The roller 10 has a formed in the shape of a ^¬ ro tationssymmetrischen hollow body roll core 11, its outer surface at least in the region in which the roll to another medium such. B. a sieve o- which acts on a felt is provided with a roll cover 12. The roll cover 12 has a plurality of layers, the number and physical properties of the individual reference layers depending on the particular application of the roller 10 in a papermaking machine. The collective term "paper" in this document denotes all pulp-containing fibrous webs, so that this term encompasses, for example, also cartons and nonwovens in addition to the various types of papers.

The roll core of CFRP rolls is formed in embodiments by helical or helical winding impregnated with Epo ^¬ xidharzen carbon fibers or fiber strands with certain and possibly different from layer to layer pitches. The epoxy resins may be added to achieve certain properties fillers. After curing, the epoxy resins form the matrix in which the carbon fibers are embedded. The matrix additionally strengthens the roller and reduces vibration energy. Due to the aggressive vapors occurring in the production of paper, epoxy resins are preferably used for embedding the carbon fibers, which form a temperature- and hydrolysis-resistant matrix after curing.

In the embodiment illustrated in FIG. 1, the cover 12 of the roller 10 has an inner reference layer which is subdivided into a base layer 121 and a functional layer 122 arranged thereon.

The base layer 121 serves the Her ^¬ provide a dynamically fixed connection of the roller core 11 and roll cover 12 is composed essentially of a provided with fillers fiber reinforced Harzimprägnie- tion wound on the roll core 11, or molded, cured, and then the in primarily Shape is ground. overall At the present time, predominantly glass fiber fabrics or glass short fibers are used for the production of the base layer.

The elastic properties of the roll cover are for the most part determined by the functional layer 122, which as a rule is likewise formed by a composite material comprising a polymer matrix. The composite preferably contains fibrous materials such as aramid fibers, glass fibers or carbon fibers, which may be used as a laminate of e.g. B. non-woven rovings (fiber bundles or fiber strands) or may be formed as a tissue. Material, diameter and laying type of the fibers used have a significant influence on the elasticity, mechanical stability and thermal conductivity 15 of the functional layer. In particular fibers may be combined with various ^¬ Dener materials and diameters. For example, the thermal conductivity of the composite ^¬ material can be improved by the use of carbon fibers, while aramid fibers give the composite material 20 a high mechanical resistance. In USAGE ^¬ dung of fiber fabrics and / or layups also an anisotropic elasticity of the functional layer 122 can be ge ^¬ create over the pitch of a helical or helical winding, in which the elasticity in the circumferential direction 25, for example, larger than in the direction along the symmetry ^¬ axis the roll cover is.

Elasticity and strength of the functional layer 122 may also be enhanced by embedding fillers in the polymer layer.

30 matrix can be improved. Oxides, Car ^¬ bide, nitrides or borides, such as silica, alumina, titanium dioxide, silicon carbide, titanium carbide or chalk, but also short fibers of the above fiber materials can be used as fillers. For the formation of the polymer

In particular, epoxy resins, phenolic resins, polyurethanes, polyethers and polyesters are suitable. lyetheretherketones.

In embodiments, the thickness of the base layer 121 is selected from a range of about 1 to 3 mm, the functional layer 122 is selected from a range of about 4 to 8 mm, so that total thicknesses of the inner reference layer from a range of about 5 to 11 mm. Of course, have other embodiments, other thicknesses of the internal reference position or it forming base layer 121 and the functional layer 122, and layer structures are preferred, with a total thickness from a range from about 2 to 35 mm and into ^¬ particular from about 2 to 10 mm.

On the outside in the radial direction of the roll 10 mantle surface of the inner reference position of an outer cover ^¬ layer is arranged, on the one hand further improves the wear resistance of the roll cover 12 and the other hand reduces the probability of adhesion of impurities on the running surface of a roller 10, the. The outer covering layer is subdivided into two components, wherein the first of the two components is formed by a metallic or ceramic spray material and the second of the two components by a polymer or a polymer composite on which the impurities occurring in a papermaking process are poor be liable. The first component is designed as a coating of the inner Be ^¬ zugslage.

In preferred embodiments, a thermal spraying process is used to produce the first component 123. The spray coating is preferably carried out in several strokes, for example with 10 to 100 strokes. Each stroke produces a thin sub-layer of the coating material, the first sub-layer being applied directly to the outer surface of the inner coating layer, and further sub-layers applied to the previously applied sub-layer. Be sprayed on. The physical homogeneity of the coating forming the first component 123 can be adjusted via the parameters of the method used. In the case of the acronym HVOF (High Velocity Oxygen Fuel) designated spraying method z. For example, the formation of pores in the sublayers can be adjusted or avoided by choosing a suitable ratio of fuel to oxygen and a suitable delivery rate of the powder material used for layer formation. Further towards also the method of electric arc spraying can be ^¬ Wandt.

Commercially available metals, alloys and hard metal powder with about 8-10% cobalt as binder and tungsten monocarbide as hard material can be used as materials for producing a metallic spray coating 123. The cemented carbide powder is preferably applied so as to obtain a surface roughness on the outer surface of the sprayed coating 123 in the range of about 5 to 8 μm and in particular in the range of 6 to 7 μm. As Ma ^¬ materials for the preparation of a ceramic spray coating 123 commercially available ceramic powder materials based on z. For example, alumina, zirconia, magnesia, crom (III) oxide, yttria and titanates can be used.

A spray coating forming the first component 123 is substantially thinner than the inner roll cover. At Off ^¬ guide, the thickness of the spray coating is A maximum of 3 mm, with thicknesses are preferably from the range of 0.05 to 2 mm and in particular from the range from 0.3 to 1 mm. Corresponding spray coatings, due to their hardness and toughness with a steel rolling vergleichba ^¬ re wear resistance of the surface and can the elastic deformation of the inner roll cover position without affecting its mechanical strength strength yet follow suit.

After application of the first component 123, a polymer or Po is applied to the surface of its outer circumferential surface lymerverbundwerkstoff ^¬ be applied as the second component 124th The second component 124 fills to the details given by the surface roughness of the first component Vertie ^¬ levies, whereby in addition, a positive connection of the two compo- results in a material-locking components.

Suitable polymers are thermosets and thermoplastics, which can be prepared on the basis of one-component and two-component systems. Particularly suitable are castings whose decomposition temperature is so far above the starting temperature of the second component 124 that the thermoset behaves elastically. In an analogous manner, thermoplastics whose glass transition temperature is so far above the starting temperature of the second component 124, that when using a roller 10, no disturbing softening of the polymer can occur. As a rough guideline for the minimum difference between Einsatztempera ^¬ temperature and decomposition or glass transition temperature 20 ° C can be specified. The operating temperature is understood to mean the operating temperature of the second component 124 during the intended use of a roller 10.

As polymers or polymer composites are the ^¬ special epoxy resins and epoxy resins is of Embedded th filler, such as polyfluoroethylene (PFE), and in particular of polytetrafluoroethylene (PTFE). Since epoxy resin shows a good wetting of the first component 123 in the non-crosslinked or partially crosslinked state, it has good adhesion to it.

The viscosity of the epoxy resin can be increased by adding be reduced, for example, alcohols or ketones, for example, to allow spraying or casting of the polymer. At higher viscosities, application of the polymer with the aid of coating tools, such as, e.g. As brushing or filling preferably. When using an immersion bath, the coating of the surface of the first component can also be done by immersion in a still liquid polymer. In a preferred embodiment, the polymer starting material used is a mixture of epoxy resin and isobutanol containing PTFE particles with mean diameters of 0.1 to 5 μm. The proportions of the epoxy resin in the poly ^¬ merausgangsmaterial be between 40 and 70 wt .-%, the isobutanol of between 10 and 60 wt .-%, and the PTFE particles is between 2 and 20 wt .-%. The ^polymer / solvent mixture is preferably sprayed onto the first component, which is preferably formed by a spray coating of NiCrBSi.

Another preferred embodiment differs from that described above in the choice of starting polymer material, wherein an isobutanol mixed with Si ^¬ licon polyester resin is used which contains PTFE particles having average sizes of 0.1 to 5 ym. The proportions of the silicone-polyester resin in the polymer starting material are again between 40 and 70 wt .-%, that of isobutanol between 10 and 60 wt .-% and that of the PTFE particles between 2 and 20 wt .-%. The polymer / solvent mixture is preferably sprayed upstream to the first component before Trains t ^¬ of a spray coating of NiCrBSi formed.

After applying the polymer base material to the first component 123, it is preferably thermally crosslinked, whereby the formation of the polymeric second component 124 is completed. Instead of or in conjunction with the polymer materials described above, silicones may also be used to form the second component 124. Low viscosity polymer starting materials are preferably used to form relatively thin coatings as a second component, for example, for thicknesses of from 20 to about 50 ym, higher viscosity polymer starting materials for correspondingly thicker coatings of, for example, up to 80 ym.

After a removal of such a layer-applied second component 124, for example due to wear remain due to the surface roughness of the first component 123 in the recesses residues of the second component 124 forming polymeric material, whereby the non-stick effect of the roll reference surface over a removal of the second component layer addition remains .

To maintain the anti-adhesive effect of the roll surface and to ei ^¬ nem certain wear of the first component 123 bil ^¬ Denden spray coating, the latter is sprayed in advantageous embodiments, a porous coating. The pores of the coating are then filled with the polymeric material of the second component whereby the first component 123 serves as a matrix for ^¬ On acquisition of the second component 124th In such embodiments, the wear and strength properties of the roll surface are determined by the properties of the spray coating, ie the properties of the first component 123, while the adhesion of fouling is determined on the roll surface substantially via the polymeric second component. The pores are, as already mentioned previously generated processing material during application of the coating, wherein the pore density is set on the parame- ters of the spray coating method ^¬ the can, and preferably leads to a porosity of the Be ^¬ range from 2 to 10%.

The invention makes it possible to form wear-resistant roll-covering surfaces which at the same time has an anti-adhesion effect for impurities arising during paper production and is thus easy to keep clean.

Claims

claims

1. roll cover for rolls (10) for use in a machine for producing and / or finishing a fibrous or film web, in particular in a Papierma ^¬ machine, wherein the roll cover (12) an inner cover ^¬ position (121, 122) and a at least on a part of the lateral surface of the inner reference layer (121, 122) angeord ^¬ Nete outer reference layer (123, 124), and wherein the inner reference layer (121, 122 has a polymeric composite material and

the external reference position (123, 124) from a metalli ^¬ rule or ceramic spray coating (123) is formed with out-applied polymer material (124).

2. roll cover according to claim 1, wherein the outer Oberflä ^¬ surface of the metallic or ceramic spray coating (123) has a roughness in the range of 2 to 12 ym and in particular from the range of 4 to 7 ym ^¬ .

A roll cover according to claim 1 or 2, wherein the polymeric material (124) comprises an epoxy resin.

A roll cover according to claim 1 or 2, wherein the polymeric material (124) comprises a silicone-polyester resin.

5. roll cover according to one of the preceding claims, wherein the polymeric material (124) comprises a polymer with embedded therein ^¬ fillers.

6. roll cover according to claim 5, wherein the fillers polyfluoroethylene and in particular polytetrafluoroethylene contain .

7. roll cover according to claim 5 or 6, wherein the Füllstof ^¬ fe in the form of particles and in particular in the form of particles with average diameters in the range of 0.01 to 5 ym present.

8. roll cover according to claim 1, wherein the polymeric material (124) of polyfluoroethylene and in particular polytetrafluoroethylene is formed.

9. Roll cover according to one of the preceding claims, wherein the metallic or ceramic spray coating (123) comprises a metal compound containing hard materials.

10. roll cover according to claim 9, wherein the hard materials are formed as hard material grains based on metal-type carbides, metallic nitrides and borides, and mixtures thereof, and the binder of the metallic

Composite of cobalt, iron, nickel, copper o- or at least one of these metals containing alloy is formed.

11. Roll cover according to one of the preceding claims, wherein the metallic or ceramic spray coating (123) comprises an oxide ceramic or a plurality of oxide ceramics.

A roll cover according to claim 11, wherein the oxide ceramics are selected from alumina, zirconia, magnesia, chromia, yttria and titanates. 13. roll cover according to one of the preceding claims, wherein the metallic or ceramic Spritzbeschich- Device (123) is formed porous and the polymeric material ^¬ (124) at least partially filled the pores of the spray coating.

Roller with a roller core (11) made of carbon fiber reinforced plastic ^¬ and a roll cover (12) according to any one of claims 1 to 13.