DE740357C - Process for the temperature treatment of lacquer coatings - Google Patents

Description

Process for the temperature treatment of lacquer coatings during manufacture > Coatings often use substances that only take effect at elevated temperatures go to the desired state. Also in the production of coatings with Air-drying paints are often used to achieve the final state accelerated increased temperature. Such temperature treatments are mostly in heated drying cabinets, less often by exposure to a heating sun or, z. B. with incandescent paints, made by electrical heating of the workpieces. External coatings on pipe sections, e.g. B. on radiators, can also be dried, when steam is passed through the pipe sections.

The heat transfer in heated drying cabinets or baking ovens on the workpieces takes place mainly through direct heat emission from the hot air to the workpieces and only to a minor extent by radiation from the hot ones Furnace walls. This is consistently the temperature treatment of the various places the workpieces are uneven. In the case of hardening by inflation, which is sometimes carried out Even temperature treatment can hardly be achieved with hot air.

It has now been found that the temperature treatment of paint coatings, which consist entirely or partially of substances that during the transition to the Final stage of a polymerization or further polymerization, a condensation or Further condensation or several such conversions are advantageous is carried out in such a way that the predried in a known manner, the Workpieces bearing coatings under the normal pressure of the action of hot organic substances Liquids (including those that are liquid at working temperature and ordinary ones temperature solid substances are to be understood) that the coatings do not attack, suspends. This does not damage the still soft layer of the coating or replaced. Rather, a fraction of the hardening of the coatings is achieved the time required in the drying cabinet. Other advantages of the process consist in the fact that all parts of the surface of the workpieces are uniform Subject to temperature treatment and that the treatment temperature is easy and reliable can be regulated, because due to its large heat content, the liquid is easy to keep at a desired temperature. After all, the finishes own the coatings have particularly favorable properties, for which the interface ratios can be revealed are decisive; the surface tensions that cause the formation of the surfaces or significantly influence, are here significantly different from the circumstances in baking or drying ovens. By using particularly suitable liquids can one still favor the formation of good surfaces; for example you can by choosing a liquid of which small amounts remain in the coating without damage can effect the filling of any microscopic pores that may still be present. That too The escape of volatile constituents and the prevention of gas and oxygen uptake can be brought about by a suitable choice of the liquid.

You bring the painted objects with the hot liquids in any way in contact, e.g. B. by immersion in baths of the liquids or by passing through such baths. You can also use the liquids on it pour or spray the painted objects or let them flow over them. The hot liquid can also be poured into objects whose shape allows it will. The duration of the action is measured according to the desired properties of the Coatings.

In the manner indicated, you can, for example, paint coatings Phenol aldehyde resins, urea aldehyde resins, alkyd resins and polymerizable Dry or harden oils.

The following liquids may be mentioned: molten bitumen or molten Paraffin, mineral oils, tar oils, paraffin oils, fatty oils, melted waxes, aryl phosphates, such as tricresyl phosphate, chlorinated and sulphurized compounds such as chloronaphthalene, and molten asphalt heated with sulfur, and also molten resins. With Water-miscible substances, such as glycerine, can be anhydrous or diluted with water use. The workpieces can be immersed in the liquid in any way take place. Single items or mass-produced items can be used, for. B. by basket diving, drumming or automatic hurdle dipping dried «earth. The short duration of treatment makes it easy to work continuously; for example wires, Foils, endless sheet metal, fabrics, tapes, threads, etc. through the hot liquid bath be pulled through at a suitable speed.

The adhering residues of the liquid can, for example, through Drainage, stripping, centrifugation or extraction with a suitable solvent removed. If necessary, residues of the liquid can also be left on the painted Workpiece remain.

You already have bodies covered with resin varnish in a liquid, in which the coating is insoluble, put under pressure, with the resin varnish in part the body is pressed into the upper layer; with this treatment can in the case of curable resin varnishes, the curing can be combined. Working under But printing is, especially with large workpieces, cumbersome and in some cases, z. B. with continuous treatment, such as coated wire, practically impracticable.

Furthermore, one already has when painting objects with cellulose ester lacquers containing the objects provided with lacquer still containing solvent by rinsing with water or immersing solvent residues in warm water freed. In this way, hardening lacquers cannot be cured satisfactorily, since the temperature required for rapid hardening cannot be reached in this way. After all, you already have objects with cellulose ester paint in bathrooms treated by gasoline, benzene or vegetable oils to cause film formation and to remove adhering solvent. But this is not about the hardening of an already formed and freed from the main amount of solvent curable paint film. Example i Wire is coated with a q.5% solution of a Lacquer obtained by mixing 7o parts of curable phenol-formaldehyde resin with a Solution of 3o parts - # Idipinsäuretrimethyloläthanester or -trimethy lolpropanester is made in ethylene glycol monoethyl ether. After going through a heated The enamelled wire runs through a bath of high-boiling point in the ventilation section 2200 heated mineral oil, in which he i bis 2 minutes (of exposure of the bath. Adhering oil is removed in a stripping device. The finished painted wire is wound onto a drum.

Example 2 Metal objects are painted with a solution of a synthetic resin, by combining a urea-formaldehyde condensation product with trimethylolethane adipate or atrimethylolpropane ester in a ratio of 7: 3. The work pieces are made by immersing them in a bath heated to 80 ° for about 5 minutes Hardened paraffin.

Claims (1)

PATENT CLAIM: Process for the temperature treatment of paint coatings, which consist in whole or in part of substances that during the transition to 'the Final state of a polymerisation or further polymerisation, a condensation or Further condensation or subject to several such conversions, characterized in that d.that the pre-dried workpieces bearing the coatings were kept under normal conditions Pressure from the action of hot, organic liquids that do not attack the coatings, suspends.