Impregnated blade coating

Abstract

A blade for treating fibrous nonwoven webs having a base body and a coating covering at least a part of the surface of the base body. The coating forms at least that part of the blade surface which is provided to come into contact with the fibrous nonwoven web. At the contact surface, the coating has an open-pored material, the pores of which are filled at least partly with a polymer.

Description

CROSS REFERENCE TO RELATED APPLICATIONS[0001]This is a continuation of PCT application No. PCT / EP2011 / 070659, entitled “IMPREGNATED BLADE COATING”, filed Nov. 22, 2011, which is incorporated herein by reference.BACKGROUND OF THE INVENTION[0002]1. Field of the Invention[0003]The present invention relates to blades for machines for the production of paper and, in particular to the configuration of blades for use in creping or coating of a paper web.[0004]2. Description of the Related Art[0005]In order to produce the surface properties required for a particular application purpose of a given paper type, the fibrous nonwoven web, or the so-called raw paper web, produced in the paper manufacturing process must, as a rule, be subjected to a separate treatment. In this regard, high quality paper types are coated and hygienic papers are creped.[0006]The creping process produces paper types having surface structures. Normally a blade called a creping doctor is applied with its working edge a...

AI Technical Summary

Benefits of technology

[0014]According to one embodiment of the present invention, the polymer includes an epoxy resin, because this effectively moistens the open pored coating material in its non-cross-linked or partially cross-linked condition, thereby being able to penetrate deeply into the pores of the coating. In additional embodiments the polymer advantageously includes a silicone-polyester resin, since this combines very good anti-sticking properties and thereby sliding properties with an excellent dirt repellent effect. To improve the sliding or dirt-repelling properties of the contact surface of the coating, fillers may be embedded into the polymer, whereby the fillers of preferred design variations thereof contain poly fluorinated ethylene (PFE) and in particular polytetrafluoroethylene (PTFE). The fillers may, for example, be present in the form of particles and particularly in the form of particles having median diameters from within the range of approximately 0.1 to 5 micrometers (μm). Instead of consisting of an epoxide resin or silicone polyester resin with fillers containing PFE or PTFE, the polymer may also be formed directly of poly fluorinated ethylene and in particular of polytetrafluoroethylene or a polymer which includes such a substance. To bring polytetrafluoroethylene into the pores of the coating, polytetrafluoroethylene particles of sizes from within the range of approximately 50 to 100 nanometers (nm) are, for example, prepared into a slurry and the thus obtained dispersion is applied into the pores, for example with the assistance of immersion, spraying or application with a brush or another coating device. A polymer may be used for this which is present in the form of particles in various sizes, whereby at least 65 percent of the particles are of one or more sizes from the range of 50 to 100 nm.

[0015]The open-pored base material of the coating in all embodiments consists of an oxide ceramic or of a mixture of two or more oxide ceramics. Additional embodiments feature an open pored coating base material which includes one or more oxide ceramics. In some embodiments, the oxide ceramics are selected from aluminum oxide, zirconium dioxide, magnesium oxide, chromium (III) oxide, yttrium oxide and titanate, which combine good mechanical stability with high abrasion resistance and which can be applied with modern high speed spray methods, for example High Velocity Oxygen Fuel (HVOF) onto the base body of the blade. In additional embodiments the open pored material of the coating includes a hard metal, which can also combine good mechanical stability with high abrasion resistance and which can be effectively and economically applied with modern high speed spray methods. The porosity of the coating material is, for example, between approximately 2 and 10 percent, whereby these values reflect the area proportion of the pores interspersed cross-sectionally in the material. The median pore diameter of the pores of the coating base material may have a value from the range of 5 to 15 μm. To improve adhesion of the coating on the base body of the blade, an adhesive layer may be arranged between them.

Problems solved by technology

Since in the two processes strong forces act upon the blades, high demands are placed on the mechanical stability and wear resistance of the blades.

However, the wear and tear characteristics of these coating mediums do not permit extended standstills under the conditions prevailing during operation, so that creping doctors and doctor blades still need to be replaced in very short intervals in order to maintain the paper quality.

Particles and contaminants on and inside the paper web moreover lead to localized load peaks on the blades which regularly cause damage on the blade coating, thereby reducing the quality of the produced paper.

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