WO2000028142A1

WO2000028142A1 - Coating bar

Info

Publication number: WO2000028142A1
Application number: PCT/FI1999/000922
Authority: WO
Inventors: Timo Lintula; Ilkka Rata
Original assignee: Metso Paper, Inc.
Priority date: 1998-11-09
Filing date: 1999-11-05
Publication date: 2000-05-18
Also published as: AU1273500A; FI982424A; FI104103B; FI982424A0; DE29980220U1; FI104103B1; WO2000028142A8

Abstract

The invention concerns a coating bar for a bar coater used in coating of paper or board and in particular a coating bar suited for surface-sizing, pigmenting, and film coating as well as a method for manufacture of the coating bar. The coating bar in accordance with the invention comprises a fibre-reinforced composite body, onto whose face a wear-resistant face has been prepared electrolytically, auto-catalytically, by means of thermal spraying, or by means of physical vapour deposition.

Description

Coating bar

The invention concerns a coating bar for a bar coater used in coating of paper or board and in particular a coating bar suited for surface-sizing, pigmenting, and film coating.

Bar coaters are used for coating of paper, board, or of a moving base with the desired coating agent, which coater comprises a revolving coating bar, which rests against the moving base, which extends across the machine width, which has been supported in a cradle substantially over its entire length, and which coating bar has been fitted to spread and to smooth a coating agent on the moving base, which coating agent has been introduced into the coating device before the coating bar, as viewed in the running direction of the moving base. The material of the coating bars is often steel, which has been coated with a chromium plating in order to increase its service life. In particular the face of a bar used in surface-sizing is provided either with grooves, or onto the bar a steel wire has been wound, which forms a solution similar to grooves on the face of the bar. By means of the depth of the grooves, it is possible to determine the thickness of the size film to be applied to the base to be coated in surface sizing. However, it is a problem of grooved bars that they are worn very rapidly, and pigmenting has proved uneconomical with these bars, because the dry solids content of the paste used for pigmenting is high, and it results in excessive wear of the bars. Metal bars and in particular steel bars are worn very intensively in pigmenting, for which reason materials to be substituted for metal have started being looked for. When the diameter of the bar is increased, an increased resistance to wear is achieved, but, in the case of metal bars, a problem is increased weight of the bar. This results in problems of handling and construction, and the proportion of material costs becomes higher. Bars made of a ceramic material are considerably more durable, and occasionally also of lower weight, but they are also very much more expensive, and their manufacture and machining to an adequate smoothness of the face and to adequate precision of tolerance are problematic. A rough face of the bar requires polishing before use, in which connection, moreover, considerable costs arise in the stage of finishing.

In the FI Patent 93,885, a large-diameter, grooved, and favourably tubular coating bar is described, whose diameter is at least 18 mm and whose material is chromium- plated copper, steel or equivalent. In the FI Patent 100,672, a doctor bar is described, which is meant in particular for metering of coating pastes onto moving webs consisting of paper or board or onto rubber coatings on rolls and which doctor bar consists, at least in the area of the doctor face or metering face, of acrylic glass fibres or carbon fibres or of glass-reinforced or carbon-reinforced plastic fibres, or the whole of the doctor bar can be made of acrylic glass. The core of the bar can consist of metal, epoxy resin and carbon fibres, of a sintered material or plastic, and a glass coating layer has been applied onto the core part of the bar. One of the problems in such a bar is poor resistance to wear; when the matrix is worn, the fibre is separated from the face, and it is difficult to obtain an adequate surface quality.

The object of the present invention is a coating bar whose construction is of lower weight than the prior-art bars, which is easy to machine in compliance with the application of use, which is advantageous to manufacture, and which has excellent resistance to wear and corrosion. A further object of the present invention is to provide a solution by whose means the drawbacks involved in the prior art are avoided and by whose means a considerable improvement is achieved in particular in coating bars suitable for surface-sizing, pigmenting and film coating.

The coating bar in accordance with the invention is characterized in what is stated in the patent claims.

It has been noticed that the objectives given above are achieved by making use of a solution in which the coating bar comprises a composite body, onto which a wear- resistant coating has been prepared. The invention will be illustrated in more detail by means of some preferred embodiments of the invention with reference to the figures in the accompanying drawings.

List of illustrations:

Figure 1. Axial sectional view and cross-sectional view of coating bar.

Figure 2. Axial sectional view and cross-sectional view of a hollow coating bar.

Figure 3. Axial sectional view and cross-sectional view of a grooved coating bar.

Figure 4. Axial sectional view and cross-sectional view of a metal-faced coating bar.

Fig. 1 is an axial sectional view of a coating bar 1 in accordance with the invention and a cross-sectional view of the body of the bar. The bar comprises a solid, fibre- reinforced plastic composite body 11, onto whose face 12 a durable coating has been applied electrolytically, auto-catalytically, or by means of thermal spraying.

Fig. 2 is a similar illustration of a fibre-reinforced plastic composite coating bar 1, whose construction comprises a hollow tube. Onto the hollow tubular plastic composite body 11, a durable face 12 has been prepared electrolytically, auto- catalytically, or by means of thermal spraying.

Fig. 3 illustrates a coating bar 1, which is provided with a fibre-reinforced plastic composite body 11, which body can be either solid or hollow, and onto which body 11 grooves 13 have been prepared by means of a carbon- fibre, fibreglass or metal profile band and in which the band windings have been interlocked with each other optionally by means of shaped projections 14. Fig. 4 illustrates a fibre-reinforced coating bar 1 with a plastic composite body, which bar can be either hollow or solid and in which bar a smooth metallic face is accomplished by means of a metal band or net or wire 15 to be wound and glued onto the composite body 11.

The basic material, i.e. the core, of the coating bar comprises a fibre-reinforced composite body, which is manufactured appropriately by means of a pultrusion, extrusion, or filament-winding method. The bar can be either solid or hollow; advantages of a hollow bar include lower weight, resilience, and favourable cost. Suitable fibres are glass fibres, carbon fibres, boron fibres, aramide fibres, and synthetic fibres or combinations of same; favourable fibres are carbon fibres and glass fibres or their combinations so that the necessary torsional strength is achieved. As a matrix in a composite material, it is possible to use conventional thermosetting plastics, epoxy, vinylester and polyester resins, and most advantageously polyester and epoxy resins. Onto the face of the composite body, it is also possible to prepare grooves by around the body winding carbon-fibre, glass-fibre or metal yarn or wire or profile band, which can be glued or expoxidized onto the base body. A yarn or wire winding can also be interlocked with a second winding by means of a shaped projection provided in the cross-sectional face of the yarn or wire or band. Onto the face of the composite body, it is also optionally possible to prepare an intermediate layer, i.e. an anchor structure, in order to improve the adhesion of the topmost coating material, in particular in cases in which problems are encountered in the adhesion of the topmost coating material. The anchor structure can be placed on the face of the composite material, partly in the composite structure, or as fully sub- merged in the composite structure very close to the surface. The anchor structure is prepared so that onto the composite face or to among the face, a metal wire, metal fillet, metal net, metal foil, metal powder, metal-plastic composites, plastic-ceramic powder is/are fixed, or onto the composite bar a metal sleeve is prepared which permits adhesion of a ceramic onto the face of the composite or, if the anchor structure is placed below the surface, to under the surface. Onto a groove formation that has been applied onto a metallic intermediate layer or onto the composite body or onto the face of the composite body, a wear-resistant face is prepared electrolytically, auto-catalytically, by means of thermal spraying, or by means of physical vapour deposition (PVD). Suitable coating materials include hard chromium, chemical nickel, aluminium oxide, chromium oxide, titanium oxide, zirconium oxide, or combinations of same, titanium nitride, titanium carbonitride, titanium aluminonitride, molybdenum sulphide, diamond-like coating, combinations of same, and multi-layer coatings. In particular the preparation and the adhesion of a thermally sprayed coating on the composite body can be improved so that an anchor structure is prepared onto the composite structure. A ceramic coating can be applied onto the face of a composite by means of thermal spraying at a temperature lower than 150°C, in which case the polymer matrix of the composite does not melt to a substantial extent or is not otherwise damaged.

The construction of a coating bar in accordance with the present invention is of very low weight, and it is easy to handle. The coating bar can be profiled readily, the longitudinal modulus of the base bar can be regulated by means of orientation and quantity of the reinforcement fibres, and likewise it is possible to regulate the coefficient of thermal expansion of the base bar. The cost of a bar in accordance with the invention is also favourable, its resistance to wear and corrosion is good, and the materials needed for manufacture are readily available. With a high dimen- sional and balancing precision, it is possible to manufacture bars of different diameters.

Claims

1. A coating bar for use in coating of paper or board, characterized in that the bar comprises a fibre-reinforced composite body, onto whose face a wear-resistant face has been prepared electrolytically, auto-catalytically, by means of thermal spraying, or by means of physical vapour deposition.

2. A coating bar as claimed in claim 1, characterized in that the bar comprises a composite body, an intermediate layer or anchor structure prepared onto the body, and a wear-resistant layer that has been prepared onto the intermediate layer electrolytically, auto-catalytically, by means of thermal spraying, or by means of physical vapour deposition.

3. A coating bar as claimed in claim 1 or 2, characterized in that the fibre- reinforced composite body comprises thermosetting plastics, preferably epoxy, vinylester or polyester resins.

4. A coating bar as claimed in any of the claims 1 to 3, characterized in that the wear-resistant coating comprises hard chromium, nickel, aluminium oxide, chro- mium oxide, zirconium oxide, titanium oxide, combinations of same, titanium nitride, titanium carbonitride, titanium aluminonitride, molybdenum sulphide, diamond-like coating, combinations of same and multi-layer coatings.

5. A coating bar as claimed in any of the claims 1 to 4, characterized in that the intermediate layer comprises metal wire, metal fillet, metal net, metal foil, metal powder, a metal-plastic combination, plastic-ceramic powder, or a metal sleeve.

6. A coating bar as claimed in any of the claims 1 to 5, characterized in that on the face of the composite body, there are grooves, which have been prepared by onto the face of the composite body winding wire or yarn or profile band, and favourably the band has been interlocked with a second band by means of a shaped projection.

7. The use of a coating bar as claimed in any of the claims 1 to 6 for surface- sizing, pigmenting, and film coating of paper or board.

8. A method for manufacture of a coating bar as claimed in claim 1, characterized in that the bar body is made of a fibre-reinforced composite material by means of a pultrusion, extrusion, or filament-winding method, and a wear-resistant coating is prepared onto the outer face of the bar body electrolytically, auto-catalytically, by means of thermal spraying, or by means of physical vapour deposition.

9. A method as claimed in claim 8, characterized in that, onto the bar body, an intermediate layer is prepared, onto which layer the wear-resistant coating is applied.

10. A method as claimed in claim 8, characterized in that, onto the bar body, grooves are prepared by around the body winding a wire or yarn or a profile band, and onto said grooves a wear-resistant coating is applied.