Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D7/00—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials
  • B05D7/50—Multilayers
  • B05D7/56—Three layers or more
  • B05D7/58—No clear coat specified
  • B05D7/586—No clear coat specified each layer being cured, at least partially, separately
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D7/00—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials
  • B05D7/14—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials to metal, e.g. car bodies
  • B05D7/16—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials to metal, e.g. car bodies using synthetic lacquers or varnishes
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D7/00—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials
  • B05D7/50—Multilayers
  • B05D7/52—Two layers
  • B05D7/54—No clear coat specified
  • B05D7/546—No clear coat specified each layer being cured, at least partially, separately
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D1/00—Processes for applying liquids or other fluent materials
  • B05D1/02—Processes for applying liquids or other fluent materials performed by spraying
  • B05D1/04—Processes for applying liquids or other fluent materials performed by spraying involving the use of an electrostatic field
  • B05D1/06—Applying particulate materials
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D2451/00—Type of carrier, type of coating (Multilayers)
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D2601/00—Inorganic fillers
  • B05D2601/20—Inorganic fillers used for non-pigmentation effect
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D2601/00—Inorganic fillers
  • B05D2601/20—Inorganic fillers used for non-pigmentation effect
  • B05D2601/22—Silica
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D3/00—Pretreatment of surfaces to which liquids or other fluent materials are to be applied; After-treatment of applied coatings, e.g. intermediate treating of an applied coating preparatory to subsequent applications of liquids or other fluent materials
  • B05D3/02—Pretreatment of surfaces to which liquids or other fluent materials are to be applied; After-treatment of applied coatings, e.g. intermediate treating of an applied coating preparatory to subsequent applications of liquids or other fluent materials by baking
  • B05D3/0218—Pretreatment, e.g. heating the substrate
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D5/00—Processes for applying liquids or other fluent materials to surfaces to obtain special surface effects, finishes or structures
  • B05D5/08—Processes for applying liquids or other fluent materials to surfaces to obtain special surface effects, finishes or structures to obtain an anti-friction or anti-adhesive surface
  • B05D5/083—Processes for applying liquids or other fluent materials to surfaces to obtain special surface effects, finishes or structures to obtain an anti-friction or anti-adhesive surface involving the use of fluoropolymers

Definitions

• the invention relates to a method for coating high-temperature-resistant surfaces by the powder coating method by applying a base layer and a cover layer, each of which is made of a fluorothermoplastic that can be processed from the melt.
• pore-free coatings are produced from such fluorothermoplastics using the usual powder coating methods, such as electrostatic spraying or fluidized bed sintering, which can be processed from the melt.
• Fluoroplastics are characterized by excellent resistance to a variety of chemicals and are not attacked by strong acids and alkalis.
• fluoroplastic coatings have a permeability for gases, liquids and solutions.
• the permeation of aggressive media can lead to bubble formation, detachment from the substrate and finally attack the substrate.
• the permeability of such coatings is particularly dependent on their layer thickness; it decreases rapidly with increasing layer thickness. That is why one strives, if possible apply thick layers to protect the surface from attack by aggressive media. Such thick layers are attempted by repeated application and fusing of the fluoroplastic powder. However, this process cannot be repeated any number of times, since the melt of the fluorothermoplastic starts to flow from a certain layer thickness due to gravitation and drips off.
• the invention has for its object to produce coatings of fluorothermoplastics, which can be processed from the melt, with a uniform layer thickness.
• the layer thickness should be of a magnitude in which permeation-related influences, in particular also on edges with small radii, are practically meaningless.
• This object is achieved by a method of the type mentioned at the outset, which is characterized in that, in order to prevent the runoff during the coating process, the fluidity of the fluorothermoplast which forms the base layer is reduced by this base layer having 15 to 65% by volume of glass spheres with a diameter from 10 to 400 ⁇ m can be added.
• layer thicknesses can be produced in the powder coating process, which are twice to are three times as large as in the case of unfilled fluoropolymers, without the melt flowing off due to gravity when repeated application.
• a fluorothermoplastic top layer without a glass sphere filler is applied to the fused fluorothermoplastic base layer filled with glass spheres. Since - in accordance with the idea of this invention - the fluidity of the base layer is considerably reduced by the addition of the amount of glass spheres mentioned, the same fluorothermoplastic can preferably be used for the construction of the outer layer, if appropriate also one which has a somewhat lower fluidity.
• the fluorothermoplastic of the cover layer preferably has the same melting point and / or the same melt viscosity as that of the base layer; optionally the melting point of the cover layer material can be up to 20 ° C higher and / or the melt viscosity of the cover layer material in Pa s Factor 10 be greater than the corresponding values for the fluorothermoplastic of the base layer.
• the cover layer can optionally also be applied in several partial steps without problems up to a layer thickness which is just below the discharge limit of this fluorothermoplastic, without the entire layer flowing away.
• the run-off limit is understood to mean the limit layer thickness at which the melt of a given material (with a given fluidity) begins to flow at a certain temperature precisely under the influence of gravity. It is of particular advantage in the process according to the invention that the processing temperature at which the powder coating is applied and fused can be kept at approximately the same level for the base layer and the individual cover layers without flowing off. If necessary, the base layer is also applied beforehand in several partial steps. In this way, total layer thicknesses which are three to four times as large as with coatings of unfilled fluorothermoplastics alone can be achieved by the process according to the invention.
• the fluorothermoplastic layer filled with glass balls does not tend to retract on edges with small radii, so that sufficiently thick coatings can also be produced at these points.
• the radii of the edges are enlarged to such an extent that the top layers can be applied without any significant edge alignment.
• the mixtures of the fluorothermoplastic powder used and the glass balls should be as homogeneous as possible and can be produced in known mixing units for solids will.
• the glass spheres used should have an average particle diameter of 10 to 400 ⁇ m, preferably 20 to 200 ⁇ m. Both solid and hollow glass spheres as well as mixtures thereof can be used.
• the average particle diameter of the fluorothermoplastic powder used is usually 20 to 400 ⁇ m, preferably 30 to 200 ⁇ m.
• the same fluorothermoplastic can preferably be used for the application of the cover layer as for the application of the base layer filled with glass balls.
• fluorothermoplastics can also be selected which, with a different composition, have the same fluidity, that is to say the same melting point and / or the same melt viscosity.
• the fluidity of the fluorothermoplastic for the cover layer can even be somewhat less than the fluidity of the fluorothermoplastic for the Base layer (without glass spheres), i.e. the top layer material can have a melting point up to 20 ° C higher or a melt viscosity, measured in Pa s, which is up to ten times higher.
• the substrate must consist of a material which does not undergo any disadvantageous changes when the fluorothermoplastic layer melts and the thermal load associated therewith.
• the process is therefore suitable for the coating of metal, glass and ceramic surfaces, but also for the coating of high-temperature resistant plastics.
• the surface to be coated is degreased using customary methods, for example by vapor phase degreasing, treatment in alkaline baths or, if appropriate, also by heating the object to be coated to about 400 to 450 ° C.
• An improvement in the adhesion of the coating can be achieved by roughening the substrate, for example by sandblasting or etching, if necessary also by applying ceramic or metallic intermediate layers with a high surface roughness, for example by flame spraying or plasma coating. If very great demands are placed on the adhesion of the coating, an adhesion promoter layer, which is usually made of the same fluorothermoplastic with the addition, can be applied before the base layer filled with glass balls is applied adhesion-promoting substances.
• Suitable bonding agents for such fluorothermoplastics are high-temperature-resistant binder resins, such as epoxy resins, polyamides, polyamideimides, polyimides, polytriketoimidazolidines, polyphenylene sulfides, polyether sulfides, polyether ketones, polyhydantoins or else inorganic substances, such as, for example, alkali silicates, chromic acid or aluminum chloride, phosphorus.
• the adhesion promoter layer is applied as a powder by the customary powder coating methods or else in the form of dispersions, suspensions or solutions by spraying, dipping or brushing. After application, the adhesive layer is optionally dried and baked.
• the coating with the glass ball-containing fluorothermoplastic base layer can be carried out.
• Part of the fluorothermoplastic powder melts during the application.
• a complete fusion is achieved in the subsequent tempering in an oven at temperatures which are also 20 to 80 ° C above the melting point of the fluorothermoplastic used.
• layer thicknesses can be achieved that are two to three times as large as with the same fluorothermoplastic powder not provided with glass spheres, without the coating flowing off. Even on edges with a lot Small radii can be used to achieve sufficiently thick layers.
• the edges of the fluorothermoplastic layer filled with glass balls have substantially larger radii than the carrier material, so that when the top layer not filled with glass balls is later applied, the alignment of edges described above does not occur.
• the fluorothermoplastic top layer is applied without glass balls in the same way as that of the base layer provided with glass balls. Since both fluorothermoplastics have essentially the same fluidity on their own, the top and base layers can be fused without any problems. Nevertheless, under the influence of the glass ball filling of the base layer, there are no runoff phenomena, although the runoff limit for the layer thicknesses achieved for the entire layer has long been exceeded. Care must, of course, be taken to ensure that the surface layer alone remains below the discharge limit of the fluorothermoplastic used here.
• At least one additional layer can be applied to this top layer, whereby the fluidity of the fluorothermoplastic of each subsequent top layer must be higher than that of the previous and expediently only a partial layer (the layer thickness of which does not bring the previous top layer to the runoff limit) and after application with the previous cover layer is fused.
• the average particle diameter of the copolymer is 90 ⁇ m.
• the mixture is applied with an electrostatic powder spray gun to a vertically arranged steel plate with the dimensions 100 x 40 x 20 mm.
• the steel plate is preheated to 260 ° C before application.
• the coating is melted at 250 ° C.
• Four additional partial layers are then applied, the coating being melted at 250 ° C. after each application. In this way, a layer thickness of 4 mm is obtained without the coating running off at 250 ° C. during melting.
• the total layer thickness of the coating is now 6 mm and shows no tendency to flow off at the last fusion at 250 ° C.
• the fluoropolymer powder used in the previous example (without glass balls) is placed on a vertically arranged steel plate with the dimensions 100 x 40 x 20 mm in the same way applied five times using an electrostatic spray gun and fused at 250 ° C. The last time the coating melts, the coating begins to flow off.
• the layer thickness on the steel plate is only 2.5 mm in the lower area and 1.8 mm in the upper area, which is caused by gravity-induced drainage of the coating when it melts.

Landscapes

• Life Sciences & Earth Sciences (AREA)
• Engineering & Computer Science (AREA)
• Wood Science & Technology (AREA)
• Application Of Or Painting With Fluid Materials (AREA)
• Paints Or Removers (AREA)

Applications Claiming Priority (2)

Publications (2)

Family

ID=6348067

Family Applications (1)

Country Status (3)

Cited By (5)

Families Citing this family (5)

Family Cites Families (1)

• 1988
  • 1988-02-24 DE DE19883805766 patent/DE3805766A1/de not_active Withdrawn
• 1989
  • 1989-02-14 EP EP19890102470 patent/EP0330048A3/fr not_active Withdrawn
  • 1989-02-23 JP JP4197689A patent/JPH01258771A/ja active Pending

Also Published As

Similar Documents

Legal Events