Chemistry: electrical and wave energy – Processes and products – Electrostatic field or electrical discharge
Patent
1986-06-11
1988-03-01
Tufariello, T. M.
Chemistry: electrical and wave energy
Processes and products
Electrostatic field or electrical discharge
C02F 146
Patent
active
047284030
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a process for the regeneration of used cleaning and degreasing baths in an electrolysis cell powered by direct current and the apparatus for carrying out the method.
With the cleaning and simultaneous degreasing of metallic materials or plastic materials, which are subsequently coated, galvanized or coated by galvanic or an electro-immersion process, after a certain period of time used baths arise which contain in addition to portions of the components for cleaning and degreasing, emulsified oils and fats and dispersed soiled materials which have to be worked up for the following reasons.
Cleaning and degreasing baths are, as is known, watery fluids containing mainly sodium hydroxide, potassium hydroxide, carbonates, phosphates, silicates, wetting agents, emulsifiers and dispersants. Besides these, as far as is required by the processes which follow the cleaning and degreasing of the surfaces, there may also be nitrides, fluorides and complex salts present in the baths.
The action of the cleaning fluids is based, above all, on peptizing and dispersing the impurities present on the surfaces of the work pieces or parts being treated, particularly the adherent oils and fats, and subsequent stabilization of the emulsion as well as the saponification of the saponifiable fats.
With the typical emulsifiers that are present in the fluids, the hydrophyle-lipophyle equilibrium is decisive, depending on the composition of the fats and oils that are to be dissolved by these processes.
Since mainly poorly biologically degradable sulphonates, wetting agents and tensides are also added to the described cleaning and degreasing fluids, they are always with environmentally hostile fluids whose removal, after their cleaning power has been exhausted, is possible only after the addition of special agents and the associated high expenses. Used cleaning and degreasing baths are emulsions, i.e. dispersed systems of two immiscible or partially miscible fluids and phases, the one phase of which is finely divided in the other phase. Typical examples of these are the water/oil and oil/water emulsions i.e. water-oil systems where the water as well as the oil can form the inner phase.
As a result of the customary replenishment of the cleaning baths, i.e. the continuous addition of fresh salts to the cleaning baths in use, further wetting agents, tensides and emulsifiers are added to the solution, so that the critical colloidal salt concentration is partially largely exceeded and thereby forms extremely stable aggregates whose decomposition thereafter is extremely difficult.
Since however, as is known, only small emounts of free, dissolved or emulsified oils can be passed to the sewers, it is necessary to work up the used cleaning and degreasing baths at a pH of about 4.5 to decompose the emulsions. With this measure, however, all functional components of the baths are destroyed simultaneously. Hence, it is necessary when working up the baths in this way, for the treatment of the used fluids to close down the whole cleaning and degreasing plant, so that a continuous operation of the cleaning and degreasing plant is not possible. Regeneration of the used cleaning and degreasing baths is therefore of special significance for numerous reasons.
The processes known up to now for working up used cleaning and degreasing baths, are, it is true, suitable to a greater or lesser extent for separating the emulsified oils and fats from these baths, but up to now they have not succeeded in removing the environmentally harmful bath additivies entirely from the baths nor do they recover the useful constituents of the baths which are removed together with the oils and greases. Moreover, it is necessary to mention, as an additional disadvantage of the known processes, the fact that the plant used for cleaning and degreasing of components has to be closed down when working up the baths.
The invention has set out to eliminate the described difficulties and to provide a continuous as possible process for cleaning and degreasing of w
REFERENCES:
patent: 4439290 (1984-03-01), Marfurt
Schellin Eric P.
Tufariello T. M.
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