Liquid purification or separation – Processes – Preventing – decreasing – or delaying precipitation,...
Patent
1994-11-18
1996-08-20
Hruskoci, Peter A.
Liquid purification or separation
Processes
Preventing, decreasing, or delaying precipitation,...
95152, 95189, 210687, 210697, 210698, 210699, 210725, 210728, 210735, 210930, 134 38, 427331, C02F 510
Patent
active
055475876
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to a process for denaturing and coagulating paints and other organic coating materials, more particularly water-based systems, so-called "water-based paints", in circuit waters of wet separators for spray painting installations, more particularly of the type with sidestream disposal.
BACKGROUND OF THE INVENTION
In the application of paints and other organic coating materials to metal surfaces or plastic surfaces, for example in the automotive industry, it is not possible to apply the paints or coating materials completely to the parts to be coated. So-called overspray collects in the paint spraying booths, particularly in the painting of motor vehicles, and is taken up with water and flushed into so-called system basins. In order, on the one hand, not to disturb the operation of water-carrying pipe, nozzle and sprinkler systems, for example by tacky paint particles, and other hand to free the circulating water from the paint ingredients taken up, chemicals known as coagulants have to be added to the circuit water to coagulate the ingredients in question.
Various neutral and alkaline products are available for denaturing and coagulating conventional paints, above all paints used in the automotive industry.
In known process for coagulating paints and coating materials, the technical installations present largely determine whether a paint coagulant which floats the coagulate in the settling basin is used or whether a coagulant which sediments the coagulate is used. In the first case, the coagulate can be stripped from the surface of the water whereas, in the second case, the sedimented coagulates are removed from the bottom of the basin by means of a scraping belt. However, paint disposal lines where the denatured paint particles have to be kept in a uniform dispersion or suspension in the circuit water without precipitating the paint are being used to increasing extent. Accordingly, depending on the type and quality of paint, the specific behavior of the paint particles has to be influenced in each individual case in such a way that paint particles with a tendency towards flotation or sedimentation form a uniform dispersion or suspension. An overview of the problems involved in the coagulation of paints is provided by J. Geke in "Oberflache+JOT", 1986, No. 11, pages 43 to 46.
RELATED ART
Various paint coagulants are available for coagulating conventional paints, particularly for use in the automotive industry. To coagulate and denature the paint particles and to agglomerate them into a dischargeable coagulate, powder-form or liquid, alkaline or neutral products are added to the circulating water in the prior art.
Thus, GB-A-1,512,022 describes flocculating agents, i.e. agents which agglomerate the particles under the effect of intermolecular bridge-forming macromolecules. These flocculating agents are made up of inorganic metal salts (iron chloride or aluminium sulfate), which act as precipitants, and organic cationic polymers, such as polyvinyl pyridine or polyamines, in aqueous solution.
DE-A-33 16 878 describes liquid one-component coagulants containing calcium and/or magnesium nitrates, chlorides and/or sulfates and also polyethylene imines cationically modified by protonation or alkylation.
Hitherto, the disposal of two-component polyurethane paints in particular has always presented difficulties. To dispose of mists of such paints and coating materials, DE-A-34 12 763 proposes coagulants containing cyanamide and/or dicyanodiamide and/or cyanamide salts in conjunction with materials typically used in paint coagulants.
Recently, layer silicates of various types, such as bentonites (U.S. Pat. No. 4,220,456), hectorites (EP-B-193 668), montmorillonites (U.S. Pat. No. 4,629,572), kaolins (U.S. Pat. No 4,380,495) or smectites (U.S. Pat. No. 4,701,220), have bee used for denaturing and coagulating paints. According to DE-C-38 17 251, other types of alumina, particularly boehmite or pseudoboehmite, may also be used for denaturing and sedimenting paints.
In a
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Geke Juergen
Molz Thomas
Rehm Hans-Joergen
Vogt Toni
Henkel Kommanditgesellschaft auf Aktien
Hruskoci Peter A.
Jaeschke Wayne C.
Oritz Daniel S.
Szoke Ernest G.
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