SU670344A1 - Coating method - Google Patents

Description

powder, charge of its particles, as well as the transfer of particles in the interelectrode space and their deposition on the surface of the coated product in the ES field. However, coating by a known method does not allow excluding aggregation of polymer particles in the process of transfer to the ES field, therefore, it is practically impossible to obtain solid, equal-thickness coatings of thickness up to 50-100 microns. The closest to the invention in terms of technical dryness and the achieved result is a method of obtaining coatings by electrostatic coating a metal product of a mixture of polymer powder and electric wire виб, which is material fluidized under vibration conditions, and its material followed by fusion of powder 3. coating thickness. The purpose of the invention is to increase the density of the applied polymer and obtain a uniform thickness coating. This goal is achieved by the described method of producing coatings consisting in electrostatic coating of a mixture of polymer powder containing about 20-40 vol. % of electrically conductive material (iron, nickel, copper, zinc, etc.) with a density of 4-10 g / cm. An electrically conductive material is introduced into the polymeric material intended for coatings. The powdered two-component composition is then fluidized in the working chamber of a vibro-vortex type spraying apparatus, equipped with a high-voltage electrode in the lower part. The fluidization parameters are chosen in such a way that the polymer particles are fluidized by the combined action of vibration and gas, while the heavier particles of electrically conductive material are only in the mode of vibro-liquefaction. The acceleration of vibration should be within (5-10), where g is the acceleration of free fall. A grounded coated product is placed above the apparatus. Then a high voltage potential is applied to the electrode located at the bottom of the working chamber. When an electric field appears between the high voltage electrode and the workpiece above the fluidized bed, only polymer particles can be transported to the product, and the heavier electrically conductive particles will remain in the apparatus. Their density is chosen in such a way that, firstly, the electrically conductive particles cannot be carried by the gas stream from the apparatus, and, secondly, so that they can be vibro-liquefied by vibration. These requirements are satisfied by particles of a material with a density limited to 4-10 g / cm. The optimum content of the added additive is 20–40% of the polymer volume, because with the introduction of a smaller amount of an electrically conductive material, the improvement in the properties of the layer and coatings is not as significant as in the specified interval, and with the introduction of the additive more than 40 vol. % it is almost impossible to vibro-liquefy a composition with the specified process parameters. Example 1. In powdered low-pressure polyethylene (grade 209, GOST 13338-70, dispersion less than 200 microns) are introduced from the volume of the polymer of powdered bronze (VPK brand, dispersion less than 40 microns). The composition is placed in the working chamber of the apparatus of the vibro-vortex type, at the bottom of which a high-voltage electrode is fixed in the form of a perforated metal plate. Aluminum foil (grade A99, thickness 50 µm), which is grounded, is placed above the fluidized bed parallel to its surface as a coated product. The composition is fluidized at an air filtration rate of 0.04 m / s and acceleration of the vibration drip (7-10). A high voltage potential is then applied to the electrode and a layer of charged particles is deposited on the foil in an electrostatic field. The coating is melted at 200 ° C for 30 minutes. The density of the deposited layer is estimated as well as the quality of the coating (equal thickness) by the average relative error of measuring the thickness of the coatings at ten different points. In tab. 1 shows data on the density of the electrodeposited powder layer (p, g / cm) on the foil surface, as well as on the thickness ((i ± Ad, μm) and equal thickness of coatings (Ad / rfj%) formed at different values of the high-voltage potential on the electrode ( 160 mm inter-electrode distance. Table I: The results indicate a high density of the polymer, as well as a high degree of uniform thickness of the coating. Example 2. Polyamine butyral (LA grade, GOST 9439-60, dispersion less than 200 µm) is introduced into powdered form

25% of the volume of polymer powdered nickel (grade PNE-1, dispersibility less than 50 microns). Fluidization and electrodeposition of the polymer powder are carried out on the vibro-type device described. The composition is fluidized at an air filtration rate of 0.02 m / s and acceleration of the vibration of the powder (5-8). The electrodeposition of polyvinyl butyral powder onto the surface of the foil is carried out similarly to that noted. The coatings are fused at 230 ° C for 30 minutes.

The results are shown in Table. 2

table 2

Example 3. In powdered pentaplast (grade A, TU-605-1422-71, dispersion less than 200 microns) 35% of the volume of the polymer of powdered copper (grade PM.S-1, dispersion less than 40 microns) are introduced. Fluidization is dried on the device described, electrodeposition onto the foil is carried out in the same way. The composition is fluidized at an air filtration rate of 0.03 m / s and acceleration of the vibration of the powder (6-9) g. The coatings are melted at 250 ° C for 30 minutes.

The results of the evaluation of the precipitated pentaplast layer and the equal thickness of the coatings from it are given in Table. 3 indicate a high density of the coating obtained and uniformity in thickness.

T a b l II c a 3

Thus, the proposed method makes it possible to obtain coatings with improved qualities, namely, with an increased density of the applied polymer and an equal-width coating.

Claims (3)

Invention Formula The method of obtaining coatings by electrostatic coating on a metal product fluidized under conditions vibrations of the mixture of polymer powder and electrically conductive material followed by melting of the powder, characterized in that, in order to increase the density of the deposited polymer and obtain a uniform thickness coating, a mixture containing 20-40 vol. % of electrically conductive material with a density of 4-10 g / cm. Information sources, taken into account in the examination I. Yakovlev, AD, Zdor.V.F., Kaplan, V.I. Powder polymeric materials and coatings based on them. L., “Himi, 1971, p. 157. 2. Garin V.N., Dolgopolov N.N. Polymer protective and decorative coatings for building materials, M., Stroyizdat, 1975, p. 90-92. 3. USSR author's certificate No. 220478, cl. B 29C 13/00, 1965.