SU1014870A1 - Method for cleaning metal structures from polyurethane coatings - Google Patents

Abstract

A METHOD FOR CLEANING METAL STRUCTURES FROM POLYURETHANE COATINGS by treating the latter with solvents when heated, characterized in that, with a chain to increase the cleaning efficiency and intensify the process, a mixture of the composition is used as a solvent. %: Shmetsh1formamidZO-9O WaterOther and processing is carried out at 11О - 15ОС and a pressure of 1.5 - 4.5 kg / cm. (Ls

Description

41 OD H

The invention of sunsm-gits for the utilization, destruction and processing of thermosetting polymers, in particular, for the removal of thermosetting polymers from knots and parts during repair, is transferred directly to polyurethanes.

The known method of thermal decomposition of cured polyurethanes at 250-400 1,

The disadvantage of this method is the large amount of toxic substances, energy intensity and the inability to use secondary waste. In addition, B repair work while burning port other components of Hsneraiui

Methods are known for the chemical decomposition of hardened polyurethanes, which consist in treating their amino-containing compounds with strong alkalis | acids or chlorinated hydrocarbons 12.

However, the use of chlorinated hydrocarbons requires the regeneration of large quantities of solvent and can be justified only in the case of using the resulting solution with the decomposition products of polyurethanes in repetition. nom production. The use of acids and alkalis leads to the destruction not only of hardened polyurethanes, but also of other ingredients of polyurethane storage compositions, metals, etc. Amine-containing compounds are toxic, therefore their use to decompose hardened polyurethanes requires

ensuring good sealing and air exchange.

The closest in technical essence to the present invention is a method of cleaning metal structures from polyurethane coatings by treating the latter with a solvent when heated, where dimethylformamide or its mixture with glycols is used as a solvent. As a result, the waste (coating) of polyurethanes is completely decomposed, forming a transparent fsj solution.

However, the high viscosity of such a solution makes it difficult to remove the degradation products of polyurethane from parts and structures; therefore, the method is unsuitable for cleaning metal products from polyurethane, a particularly complex configuration. walkie-talkies. The method can only be applied gfy decomposition of granular

FROM WASTES of polyurethanes, containing no fillers. The recovery of the solvent from the solution resulting from the decomposition is difficult, since the high boiling point components are included in the kompiz. In addition, during the boiling of dimethylformamite, its decomposition products (cietclamine and low molecular weight products of destructive polyurethanes — amines, isocyanates) evaporate, which makes the process toxic.

The purpose of the invention is to increase the cleaning efficiency and intensify the process.

This goal is achieved by the fact that when cleaning metal structures from polyurethane coatings by treating the latter with a solvent when heated, a mixture of composition weight is used as a solvent. %:

Dimethylformamide 30-9O

WaterEverything

and the treatment is carried out at 110 - and a pressure of 1.5 - 4.5 kg / cm.

With a decrease in the content of dimethylformamide in the destructive composition (30%), its effectiveness decreases, therefore, to ensure a sufficiently short technological cycle for decomposition of hardened polyurethanes, it is necessary to increase the temperature and pressure during decomposition, which is economically disadvantageous.

Work under low pressure promotes better penetration of the destructive solution into the mass of thick layers of hardened polyurethane, which reduces the processing time C h (according to the prototype) to 2–4 h.

Example 1. Steel plates coated with a polyurethane coating .0.5 0.7 mm thick on both sides are placed in an autoclave with a capacity of 30.0 ml, filled with 50 ml of an aqueous solution of dimethylformamide and (the concentration of the solutions is given in Table 1) at appropriate temperatures for 2 hours, Fr & This autoclave is opened and visually inspected. If the concentration and temperature were sufficient, the remaining plates are completely cleaned from the surface of the Tan.

The table shows the concentration of solutions and test results.

150

140

130 120 100 110

Plastana completely

.5 cleared, in solution

pe thin sediment

Plate completely.

3.5 It has taken place, in solution a thin white precipitate

W, o Same

.five

Coat-gae not solution 1 .0 elk, swollen 1.5 Plate i completely cleaned the precipitate is strongly swollen, gelatinous

EXAMPLE 2 A coil model of a transformer made from an enamelled wire in a frame made of glass fiber mowing tape, filled and impregnated with a polyurethane composition, cured at 30 for 6 hours and then 2 for the final curing was used in an autoclave with a capacity of 10 liters. , pour 30% aqueous solution of dimethylformamide and process at 130. and pressure of 3 kg / cm for 4 hours. After disassembling the autoclave, the coil is easily disassembled, the mica tape is easily wound, the CHHMaeiw wire from the coil. After 10 ° refining, the viscosity of the destructive composition does not change. A precipitate of 0.5 kg was collected from the bottom of the autoclave. The precipitate dissolves in chlorobenzene. Froze A semiconductor device, sealed with cast polyurethane sheath, obtained by pouring a polyurethane composition cured at 50 ° for 5 hours and aged for 48 hours, is placed in a 1 l autoclave. Pour with a 5O% aqueous solution of dimethylformamide and process at 120 and a pressure of 1.5 kg / cm for 3 hours. Then the autoclave is opened, the device is removed from the autoclave, and after drying it is tested for workability. The audit showed that the integrity of the installation scheme and that the processing was not violated; no polyuret-j residues on the device are not. detected. The simplicity of the technology and the availability of the solvent allow the proposed method to be used in the repair of electrical products with molded polyurethane insulation. The method gives a large extractive effect during large-scale work and a large number of processed products. In aqueous solutions of dimethylformamide at a concentration of less than 90%, the products of degradation of polyurethanes are slightly soluble. This is the basis for a more economical method of decomposing hardened polyurethanes, suitable for their removal from complex structures; The viscosity of the destructive composition of the proposed method does not increase with the accumulation of decomposition products of polyurethanes in it, so KfK the latter are deposited on the bottom of the reactor. therefore, mass and heat transfer processes do not deteriorate. The low viscosity of the medium contributes to the good cleaning of parts and structures, which makes it possible to reuse the same destructive bath. The use of aqueous solutions of dimethylformamide leads to a decrease in the decomposition temperature of polyurethanes.

S1014870. "

compared to the prototype, contributes to compoish. The decomposition products of nt toxicity reduction and fire-fighting liuregia are separated from it by simple

process bore .. In addition, it simplifies by decantation and can be utilized during the regeneration stage destructive by one of the known methods.

Claims (1)

METHOD FOR CLEANING METAL STRUCTURES FROM POLYURETHANE COATINGS by treating the latter with a solvent by heating, characterized in that, in order to increase the cleaning efficiency and intensify the process, a mixture of weight composition is used as a solvent. %: Dimethylformamide 30-90 Water Else ^! and the treatment is carried out at 110 - 150 ° Ο and a pressure of 1.5 - 4.5 kg / cm ^g . SU „„ 1014870