DE1220129B - Process for the surface treatment of polyacetal moldings - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. Cl .:

C08g

German class: 39 b - 22/10

Number:
File number:
Registration date:
Display day:

1220129
F41084IVc / 39b October 25, 1963 June 30, 1966

Attempts to finish the surface of molded articles made of polyacetals chemically or with abrasive cloth and To mechanically roughen similar abrasives or to pre-treat the molded parts electronically to submit in a vacuum or to flame the surface with an oxidizing flame, resulted insufficient improvement in the adhesive strength of adhesives and paints.

Better results are obtained by immersing the molded parts in a solution containing oxidizing acid. Thus, it is known, for example, so roughen the surface of polyoxymethylene moldings by lOminutiges dipping in an approximately 20 ⁰ C. solution of 11 g of potassium bichromate in 400 parts of 95 to 98 ° / cent sulfuric acid and 14 parts of water, and they well water is made wettable and thus also gluable and paintable. The method can only be used if the shaped body does not contain any frozen or imposed stresses at the point to be treated, otherwise it tears under the influence of the acid. However, since molded parts are seldom without tension, it is necessary to temper all molded parts with oxidizing acids before treatment. In addition, it is difficult to limit the treatment with liquid acids to certain delimited parts of the surface.

It is known that moldings under tension can be mixed with a p-toluenesulfonic acid containing Mixture to be treated. For this purpose, the molded body is immersed in a temperature of 75 to 120 ° C. for 10 to 30 seconds hot mixture to be stirred of 0.3 percent by weight p-toluenesulfonic acid, 96.2 percent by weight perchlorethylene, 3.0 percent by weight of dioxane and 0.5 percent by weight of kieselguhr dipped and then Placed in an oven at 120 ° C for 1 minute, rinsed with water and air-dried. Man receives a surface that can be glued and painted, but is unevenly roughened because the after Amount of p-toluenesulfonic acid adhering to dipping despite the addition of kieselguhr, especially when it is complicated shaped bodies, is unevenly distributed. With this method, too, it is technically difficult to limit the pretreatment to certain areas of the surface.

The subject of the invention is a method for improving the bondability and paintability of the Surface of polyacetal moldings by treating the same at a higher temperature with a organic sulfonic acid. The inventive method is characterized in that the Process for the surface treatment of polyacetal moldings

Applicant:

Farbwerke Hoechst Aktiengesellschaft formerly Master Lucius & Brüning, Frankfurt / M.

Named as inventor:

Dipl.-Chem. Horst Neumann, Kelkheim (Taunus);

Dr. Fritz Höradler, Frankfurt / M.-Höchst

dry surface 15 seconds to 30 minutes at 70 to 150 ° C with a dry, fine powder Camphor sulfonic acid treated. The loosely adhering acid is z. B. eliminated by blowing over it. the The surface of the polyacetal molding looks evenly matt, can be wetted by water and has a good adhesion to adhesives and paints. It has been found to be particularly beneficial that by the process according to the invention also moldings that are subject to high stresses stand, can be treated without tempering or other pretreatment. Furthermore, it is easily possible to protect parts of the surface from acid attack by covering. For example Only pretreat the panels on one side by sprinkling them on or sticking adhesive foils on parts protection.

For special purposes, especially for the continuous treatment of large quantities of molded parts, it can be advantageous to do this by immersing it in dry, finely powdered camphor sulfonic acid, the with a hot carrier gas, ζ. Β. hot air being blown up to treat.

Surprisingly, the camphor sulfonic acid, which acts as a dry powder, is obtained a completely uniform etching of the surface without stress cracks occurring. the Etching is practically independent of the thickness of the scattered powder layer, so that it is also complicated shaped bodies can be uniformly etched without difficulty. Compared to before known methods, in which the work was carried out in solution or suspension, has the use of dry camphor sulfonic acid has advantages that could not be foreseen.

609 587/479

Claims (1)

3 4 Because camphor sulfonic acid is also at higher powder and rinsing off the still adhering acid temperatures Hardly decomposed, it can be repeatedly traced with water that had been dried in the open air of polyacetal moldings used Neten plates have a matt surface and can be will. With p-toluenesulfonic acid can also be used with each other and with panels made of wood, iron and a dry treatment of plastic surfaces 5 other plastics with a polyisocyanate-poly carried out will; however, it is disadvantageous that ester adhesives stick together. The adhesive connections the acid already decomposed after a single use had tensile shear strengths of 100 kp / cm, while and then washed off with water, untreated polyoxymethylene sheets are used got to. did not allow this glue to stick. According to the method according to the invention, io basically all claims made from polyacetals:
Shaped bodies are treated. Among polyacetals Both homo- and mixed-poly processes are used to improve bondability merisate understood. Particularly suitable, however, are and paintability of the surface of polyacetal Masses, the optionally esterified or etherified molded bodies by treating the same contain macromolecular polyoxymethylenes. higher temperature with an organic sulfone . . acid, characterized in that Example _{you let the} dry surface 15 seconds up Panels made of polyoxymethylene were heated to 70 to 150 ° C with a dry, fine-meshed sieve treated with camphor sulfonic acid powder 20 finely powdered camphor sulfonic acid. sprinkled so that the surface is covered evenly was. Subsequently, the sprinkled panels were considered publications: Heated to 120 ° C for 3 minutes. After removing the Modem Plastic, December 1961, p. 97ff. 609 587/479 6.66 © Bundesdruckerei Berlin