RU2058352C1 - Method of paint and varnish coating removal - Google Patents

Abstract

FIELD: cleansing high-precision members. SUBSTANCE: method involves the immersion of members in organic solvent in which at stirring the mixture is added. Mixture has, wt.-%: ethanol 78.1-80.0; ortho-phosphoric acid 13.8-15.6, and water 6.2-6.3. Mixture added quantity is 20-40% of solution volume. Member is kept up to coating swelling which then is removed mechanically, member is washed in pure organic solvent. EFFECT: improved method of coating removal. 2 tbl

Description

 The invention relates to the removal of paints, in particular to chemical methods for removing paint coatings from the surface of high-precision parts.

 To protect parts from atmospheric corrosion, a multilayer paint coating is widely used, consisting of layers of soil VP-02 and AK-070 and enamel layer XB-124.

 When carrying out some technological processes (control of quality control, repair work, elimination of marriage after painting, remelting of parts from other enterprises), it becomes necessary to remove the paintwork.

 In industrial conditions, the removal of paintwork can be carried out by mechanical, thermal or chemical methods.

 The mechanical method of removing coatings is similar to cleaning the surface of oxides. This method is unacceptable for removing paint coatings from the surface of high-precision parts due to changes in their geometric dimensions after this operation.

 The thermal method consists in treating the painted surface with a gas burner flame. This method is not acceptable for removing paint from the surface of high-precision parts due to the strong oxidation of their surface after this operation. Subsequent removal of the oxide layer leads to a change in the geometric dimensions of the parts.

 To remove paint coatings from the surface of high-precision parts, chemical methods were most widely used.

 To remove coatings by chemical methods, special types of flushing compounds are used: two types of alkali: alkali-based; based on organic solvents.

Smyvku based alkali is used at a temperature of 70-100 ^{° C,} so the removal of coatings from the surface of precision parts using smyvok based alkalis causes oxidation of the surface thereof, and subsequently removing the oxide layer leads to a change in geometric dimensions.

 In the mass production of high-precision parts, the removal of paintwork from their surface is carried out using organic solvents.

A known method of removing paint from the surface of high-precision parts, including holding them in a solvent until the coating swells, mechanical removal of paint residues with a brush, subsequent washing of the parts in a clean solvent [1]
The disadvantages of the method are low productivity due to the slow process of the destruction of the paint film, the presence of organic residues on the surface of individual parts after removal of the coating, which adversely affects the subsequent degreasing and painting of parts, high consumption of solvent.

 The purpose of the invention is to increase the productivity of the process and the quality of paint removal, reducing the consumption of solvent.

 The goal is achieved due to the fact that before immersion of the parts in an organic solvent, a mixture containing, by weight, is added, followed by stirring. ethyl alcohol 78.1-80.0; phosphoric acid 13.8-15.6; water 6.2-6.3, in an amount of 20-40% of the volume of the resulting solution.

 The method is suitable for removing coatings based on the following film-forming agents: cellulose nitrate and alkyd-epoxy resin, epoxy oligomer, acrylic and melamine-formaldehyde composition, vinyl chloride-vinyl acetate copolymer, perchlorovinyl, epoxy oligomer-coal varnish mixture, organosilicon polymer, polybutyl acrylate, organosilicon polymer polyvinyl butyral and others using the following organic solvents: 645, 646, 647, 648 according to GOST 18188-72, P-4, P-4A, P-5, P-5A according to GOS 7827-74, mineral spirits, GOST 3134-78, GOST technical acetone 12768-84.

Steel parts are machined with a diameter of 20 mm and a length of 120 mm. The parts are degreased in an MS-15 detergent using ultrasound and then dried. The coating is applied by pneumatic spraying in two layers. After application of the second coating layer is baked at 70-85 ^{° C} for 20 minutes, then every other day with parts removed coating as follows. Three parts for each option are immersed in a bath with a solvent mixed with the addition of an acid diluent of the primer VL-02, which is a mixture containing, by weight. ethyl alcohol 78.1-80.0; phosphoric acid 13.8-15.6; water 6.2-6.3. in an amount of 30% of the solution volume and maintained until the coating swells, the solution level in the bath is 10-15 mm higher than the level of the parts lying on the supports, then the remaining paint is removed from the parts with a hair brush, after which the parts are transferred to a clean bath solvent, washed them and dried. The research results are presented in table 1
Table 2 presents data illustrating the performance of the removal process, depending on the amount of added mixture of the above composition.

Claims (1)

 METHOD FOR REMOVING THE PAINT AND VARNISH COATING from the surface of the parts, including immersing the parts in an organic solvent and holding it until the coating swells, mechanically removing coating residues and subsequent washing of the parts in a pure organic solvent, characterized in that a mixture is added before the parts are immersed in an organic solvent, followed by stirring containing, by weight. Ethyl alcohol 78.1 80.0
Phosphoric acid 13.8 15.6
Water 6.2 6.3
in an amount of 20 to 40% of the volume of the resulting solution.

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