CS243969B1 - Thermoreactive polyepoxy resins removal destructive process - Google Patents

Abstract

The solution relates to the removal of polyepoxide resins from encapsulated electronic or electrical components, for fault diagnosis or recovering the closed parts by sweeping pieces. Destruction is performed by action phenol in a sealed pressure vessel at a temperature of 80 to 230 ° C and a pressure of 0.11 to 1.5 MPa followed by neutralization of the residue destructive substances in alcohol or alkaline hydroxide.

Description

The present invention relates to a destructive process for removing thermoreactive polyepoxide resins from metal parts, glass and ceramics.

Epoxy resins with hardeners, fillers and possibly other additives (catalysts, accelerators, pigments, etc.) are encapsulating or molding materials used for the technology of stamping and embedding the elements of used electronics and electrical engineering, eg for encapsulation of semiconductor diodes, thyristors, integrated circuits, modules, as well as electrical resistors, capacitors, transformers, etc.

In practice, there is a requirement to reseal such encapsulated electrical and mechanical components. This circumstance is motivated by the loss of functionality of the electrical elements during enclosure or other technological defect leading to the disintegration of the encapsulated components. The decoupling procedure should lead to the recovery of the built-in components and their use for assembly or to the elimination of faults.

Until now, this issue has been addressed using chemical compounds such as concentrated sulfuric acid, concentrated nitric acid, dimethylformamide. dimethylsulfoxide, monomethyl ethers, cresols, ethylene glycol-N-methyl-2 * pyrrolidole and the like.

These substances act very slowly on the cross-linked thermosetting plastics at 18 to 25 ° C, while at elevated temperatures the removal process is accompanied by a number of health and hygiene problems.

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Other problems arise with the disposal of liquid wastes, and the necessity of replacing a destructive agent frequently when the destruction of a plastic is accompanied by a chemical reaction of the destructing agent with metal surfaces or with the plastic itself, with the destructive substance degrading *

These problems are solved by the present invention, according to which the destructive process for removing thermoreactive polyepoxide resins from metal parts, glass and ceramics is essentially carried out by the action of phenol in a pressure vessel at 80 to 230 ° C and a pressure of 0.11 to 1.5 MPa. at the end of the reaction time, the phenol is cooled below the melting point of the phenol to 18 to 41 ° C, the pressure is reduced to 0.1 MPa *

After removal of thermoreactive polyepoxide resins, the phenols adhering to the components are neutralized in alcohol or alkaline hydroxide *

Advantages of the destructive process of removing thermoreactive polyepoxide resins from the metal surfaces, glass and ceramics according to the invention are the process safety, reduced destruction time and also the absence of liquid waste disposal problems: for example, phenol can be recovered from the alkaline phenolate application * From the health point of view it is advantageous that after opening the pressure vessel and removing the metal or other parts, the operator comes into contact only with the solid phase of the destructive substance, since this has a melting point of 41 ° 0. when using phenol, the destructive substance is not degraded *

Example 1

A basket with encapsulated electronic components in a 20 mm epoxy molding material is immersed in molten phenol at 45 ° C. * After closing the pressure vessel, the temperature / pressure is increased to 210 ° 0 / 1.2 MPa and this value is maintained for 6 hours * After cooling to 50 ° 0 and reducing the pressure to 0.1 MPa, the basket with the cleaned elements is placed above the surface and after the eaves and the phenol solidify on cooling to 40 ° C the container is opened and the basket with the components is transferred to the container with a solution of 10-15% sodium hydroxide when _t at 40 to 50 ° C is converted to phenol adhering sodium phenolate and the recovered components are separated by mechanical separation *

Example 2 ^{243 999}

Electronic components coated with palm-type epoxy resin cured with an aliphatic amine and wall thickness of 0.2 mm are placed in a basket in a molten phenol pressure vessel at 45 ° C * After closing the pressure vessel, maintain the temperature at 90 ° C and pressure at 0.15 MPa for 2.5 hours · Reduced pressure to 0.1 MPa, eject basket with parts above surface, reduce temperature to 30 ° C, open pressure vessel, remove baskets with components, neutralize destructive residues in ethanol and manually separate backwards parts obtained.

Claims (2)

Object of the invention 1 · Destructive process for removing thermoreactive polyepoxide resins from metal parts, glass and ceramics ₍ characterized in that epoxy resin cast parts are treated in a pressure vessel with phenol at a temperature of 80 to 230 ° C and a pressure of 0.11 to 1.5 MPa then, after the reaction time, the phenol is cooled below the melting point of the phenol to 18 to 41 ° C and the pressure is reduced to 0.1 MPa · 2. Destruction process according to claim 1, characterized in that after removal of the thermoreactive pelyepoxide resins, the phenols adhering to the components are neutralized in alcohol or alkaline hydroxide *.