Note: Descriptions are shown in the official language in which they were submitted.
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The invention relates to a process for cleaning adher-
ent aqueous surEace treatment agents from articles or objects
after galvanic and/or chemical surface treatment, preferably in
order to recover the valuable substances contained in these
agents.
Processes for rinsing galvanically or chemically
treated articles in orderto clean them for subsequent treatments
are already ~nown. The sole treatment agent used for this pur-
pose was water.
However, these processes have the disadvantage that
they involve relatively great losses of the valuable substances,
especially the metal salts, contained in the surface treatment
agents.
Great efforts were therefore made to prevent, as far
as possible, these losses of valuable metals and other treatment
substances for economic reasons and, more recently, to preserve
the environment.
Thus, the amount of water used for rinsing can be
minimised by tne ~nown process of so-called spray riilsing and
the use of multiple cascades. In addition, evaporation and
volatilisation processes have also been used.
A technique widely used in galvanising stations and in
anodising, phosp~atising and picklins plants is the recovery of
the rinsing water by ion exchange means which operate in the
circuit.
However, none of these processes gives satisfactory
results.
Thus, according to the process first mentioned, the
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valuable metallic substances can be recovered in a relatively
pure state only by means of a separate and expensive waste water
conveying arrangement and chemical precipitation of hydroxide
sludges. The disadvantage of the volatilisation and evaporation
processes is that they involve a particularly high degree of
energy consumption; the ion exchange columns bring about the
formation of neutral salks that render the waste water detrimental
to the environment.
Generally, it can also be established that none of the
]~nown processes permits an even remotely quantitative recovery
of the valuable substances.
The present invention thus provides a process which per-
mits both the thorough cleansing of objects or articles after the
completion of surface treatment of the type in question and also
a quantitative and technically simple recovery of the valuable
substances adhering to the objects as a result of treatment.
According to the present invention there is provided a
process for galvanic or electrolytic chemical treatment of articles
in a bath comprising an aqueous surface treatment agent including
~20 metals or metal alloys, said process comprising placing the
articles to be treated in said bath to form a deposit thereon
of said metals or metal alloys, removing the articles from the
bath and applying to the articles by spraying, squirting or pour-
ing a liquid, water immiscible solvent having a density substan-
tially different from that of water whereby residues of said
treatment agent adhering to the surface of the articles from the
preceding step are detached, said solvent additionally comprising
a wetting agent, said applying step being carried out in a rinsing
chamber, in a lower portion of which the solvent and residual
aqueous treatment agent discharged from said articles are col-
lected, permitting the solvent and treatment agent to separate
in the rinsing chamber by forming two phases, and withdrawing the
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~hase containing the treatment agent and passing the agent back
into said bath while separately recovering the solvent ~hase and
recycling the solvent for further treatment of said articles.
Thus in the present invention the articles or parts are
treated with a water-immiscible liquid solvent having a higher
or lower specific weight than the aqueous surface treatment agent.
In the process of the invention there is advantageously used as
the water-immiscible liquid solvent one having a specific weight
of more than 1.25 or less than 0.75 p/cm3. Preferably the solvent
is incombustible, inert to the surface treatment agents used,
non~toxic, and has a boiling point above 35C.
Advantageously the solvent is a halogenated hydrocarbon,
preferably a chlorofluorohydrocarbon, especially trichlorotri-
fluoroethane. Preferably the solvent contains a wetting agent
or a mixture of wetting agents, especially an amphoteric, non~
ionic, anion-active and/or cation-active wetting agent.
The articles are treated in a rinsing chamber, especially
a rinsing chamber provided with a cooling device. The solvent
collecting in the lower portion of the rinsing chamber below or
above the aqueous phase of the surface treatment agent is drawn
off and used again for the treatment of ob~ects, and the aqueous
surface treatment agent collecting in the lower portion of the
rinsing chamber below or above the solvent is drawn off and,
optionally after purification, preferably by filtration by means
of active carbon, is used for further surface treatment.
The process according to the invention may be applied in
all galvanic and/or chemical surface treatment processes where
it is necessary to purify and/or recover the aqueous surface treat-
ment agents still adhering to the objects after treatment.
The process of the invention is therefore suitable in
particular, for cleaning articles or ob~ects treated with chemical
or galvanising baths, for example based on chromium, nickel,
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1~)90Z38
cobalt, copper, cadmium, zinc, tin, lead, silver, gold or their
alloys, in the case of which articles economic
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application and environmental demands require a recovery of the
valuable substances that is as ~uantitative as possible.
These aims, which have hitherto been impossible to
fulfil by any of the known processes, are now surprisingly
achieved in a remarkable manner by the process according to
the invention, in that this process renders possible, with a
technically elegant procedure, both the thorough cleansing of
objects treated in the manner described and also the straight-
forward quantitative recovery of the treatment agents naturally
adhering to the objects after treatment.
The solvent must fulfil theconditions on the one hand
of being water--immiscible and, on the other, of havin~a specific
weight sufficiently different from water, even with substances
dissolved therein, that relatively rapid separation into two
phases can take place.
Solvents which can be used according to the invention
and which have these properties are, for example, trichlorotri-
fluoroethane and trichloromonofluoromethane.
Each of these solvents may be used alone or if desired
mixed with one another.
The solvents are, in particular for purposes of safe
application, to be preferably incombustible and have low, or
preferably no, toxicity and the most corrosive sur~ace treatment
agents must be incapable of destroying them or destroy them only
with great difficulty.
Advantageously the solvent should not have too low a
boiling point or, if it does, it should be used in conjunction
with suitable cooling devices.
Therefore, suitable solvents are those having boiling
points of, if possible, more than 35C.
It has also proved advantageous that a wetting agent
or a mixture of wetting agents is added to the solvent to be
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used according to the invention, to reduce, if necessary, the
surface ~ension and thereby to promote the downward migration
through the solvent of the film of water on the treated objects.
For this purpose, depending on the desired aim,
amphoteric, non-ionic, anion-active and cation-active wetting
agents or mixtures thereof may be used, wetting agents containing
fluorine or chlorine being particularly suitable.
The following may be mentioned by way of example:
Amphoteric wetting agents
N-laury-~-imino-dipropionic acid (Na-salt),
2-caprylimidazolinium-1-carboxymethyl-1-sodium ethoxylate,
lauroylamidopropyl-N-dimethylamino-acetic acid,
lauroylamidopropyl-N-dimetnylamine oxide, and
cetyl diethylamino tetraglycol ether sulphate.
Non-ionic wetting agents
Nonylphenol polyglycol ether,
glycol disterate,
ethoxylated polypropylene glycol,
perfluoroctylsulphonamido-polyglycol ether, and
oleic acld amido polyglycol ether.
Anion-active wetting agents
Sodium lauryl sulphate,
; perfluoroctylsulphonic acid (potassium salt),
coconut oil acid sarcoside (sodium salt),
dibutylnaphthalenesulphonic acid ~sodium salt), and
o-phosphoric acid ester of oleyl octaglycol ether (triethanol-
ammonium salt).
Cation-active wetting agents
Pentoxyethylstearylammonium chloride,
perfluoroctylsulphonamidopropyl-trimethyl-ammonium iodiae, a~d
cetyltrimethylammonium bromide.
When cleaning articles or parts thereof treated with
:~9~)Z3!3
agents or baths containing chromic acid, it is necessary to use
wetting agents which are inert to such agents or baths, particu-
larly fluorine-containing wetting agents.
The treatment of articles or parts according to the
process of the invention is effecked in a rinsing chamber. When
using solvents with low boiling points, this chamber, as mentioned
above, is advantageously provided with a cooling device which is
also appropriate in the case of surface treatments taking place
at relatively high temperatures, for example, with hot nickel
baths.
When carrying out the process of the invention, the
surface treatment agent adhering to the articles after appropri-
ate treatment processes is removed quantitatively by treatment
with the solvent, that is, by sprinkling, spraying or pouring
continuously or discontinuously, and can be collected in a
container, the rinsing chamber itself being the most suited to
this purpose.
Phase separation then takes place in the lower portion
of the container or rinsing chamber, the solvent separating
~20 either above or below the aqueous surface treatment agent,
depending on the specific weight of the solvent used.
The process of the present invention also includes, on
the one hand, drawing off the solvent by means of suitable
devices such, for example, as pumps and connecting systems, and
using it again for cleaning and, on the other, using the
separated aqueous surface treatment agent for further surface
treatment, optionally after purifying, preferably by filtration.
These measures therefore permit both the thorough
cleansing of objects after completed surface treatment and also
a quantitative recovery by a technically simple procedure of
the valuable substances used.
Further advantages result from this in individual
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cases, for example, the possibility of constructing smaller sur-
face treatment plants, for example, galvanising plants, and the
almost complete avoidance of waste water and thus the achieve-
ment of ideal environmental protection.
The following Examples illustrate the invention:
Example 1
Articles made of steel or iron, for example screws,
were treated galvanically at 55C in an aqueous nickel electro-
lyte of conventional composition in a tank, then removed from the
bath and transferred to a rinsin~ chamber. The articles were
then sprayed with a solution consisting of trichlorotrifluoro-
ethane tb.p.: 47.6C, specific weight 1.582 kp/m3) and 5 parts
by weight of a wetting agent based on perfluoroctylsulphonic
acid.
The spraying was effected at intervals with a total
duration of 2 to 5 minutes whereby the nickeled parts were
thoroughly cleansed of adherent bath solution.
Further articles were then cleaned in processes lasting
several hours with a similar effect and at the same time the mix-
ture, being formed, of the aqueous nickel electrolyte rinsedoff the articles and the solvent/wetting agent solution, was
collected in the lower portion of the rinsing chamber where
immediate separation into two layers took place in each case.
The lower solvent/wetting agent phase was then used, by means of
a pump connecting system and a pipe connecting system, to feed
the spray nozzles, and the upper aqueous electrolyte solution
was fed to the tank with the nickel electrolyte after undergoing
active carbon filtration.
The process involved no waste water and there were no
appreciable electrolyte losses.
The experiment was repeated with equal success using
a wetting agent based on ethoxylated polypropylene glycol.
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Example 2
The ~rocess described in Example 1 was carried out
using trichlorotrifluoroethane as the solvent without the addi-
tion of wetting agents. Although no wetting agents were involved,
this experiment, too, resulted in satisfactory cleansing of the
galvanised articles. The solvent and the entrained electrolyte
liquor were recovered practically quantitatively.
Example 3
The process described in Example 1 was carried out
using a conventional weakly acidic zinc electrolyte. Trichloro-
trifluoroethane containing, as the wetting agent, 3% by weight
of cetyldiethylamino polyglycol ether sulphate was used as the
solvent.
There was an optimum cleansing effect. After several
days' operation electrolyte losses as a result of entrainment
were not detected.
Example 4
The process described in Example 1 was carried out
using a conventional alkaline, cyanide-containing zinc electro-
lyte. Trichlorotrifluoroethane, containing, as the wetting
agent, 2% by weight of coconut oil acid sarcoside, was used
as the solvent. The articles were free of any residue. It
was possible to recover the solvent practically quantitatively
for re-use.
