Use of molybdenum compounds for paint coagulation

Details Use of molybdenum compounds for paint coagulation Use of molybdenum compounds for paint coagulation

1993-02-12

1994-06-28

Green, Anthony

Liquid purification or separation

Processes

Making an insoluble substance or accreting suspended...

210728, 210729, 210730, 210734, 210725, 210735, 55DIG46, B03D 302, C02F 154

Patent

active

053244370

DESCRIPTION:

BRIEF SUMMARY
FIELD OF THE INVENTION

The present invention relates to the use of molybdenum compounds in circulating waters of wet precipitators of spray coating units and to a process for detackifying and coagulating paints, waxes and other organic coating compositions by means of molybdenum-containing coagulants.


STATEMENT OF RELATED ART

If paints, waxes or similar coating materials containing water-insoluble organic substances are applied, e.g. in the automotive industry, it is not practicable to apply the materials completely onto the parts to be coated without leaving behind any residual portions thereof. More specifically, if automobiles are being painted, as is conventionally carried out in closed compartments (paint spray booths) allowing an automatic application of the paints or coating compositions, there is formed the so-called "overspray" which is trapped by a water curtain drizzling down the walls of the paint spray booths and flushed into a so-called "stabilization basin". Chemicals for detackifying and coagulating said materials will have to be added to said water so that, on the one hand, malfunctions caused by sticking paint particles on the water-conducting conduits, nozzles and sprinkler systems will be avoided and, on the other hand, the ingredients entrained in the circulating water will be removed for the disposal thereof. It is desirable that detackifying of the paint particles spattered and present in the water and the agglomeration thereof such as to form a coagulum capable of being discharged will be effected in one operation.
For coagulating conventional paints used above all in the automotive industry, there is available a series of neutral and alkaline products. To accomplish a coagulation, i.e., detackifying of the paint particles and agglomeration thereof to form a coagulum capable of being discharged, powdery alkaline or liquid alkaline as well as powdery neutral products have been added to the water circulated in the paint spray booths and in the connected conduits and aggregates. Thus, in GB-A-1,512,022 there have been described flocculating agents, i.e. agents causing the particles to amalgamate under the action of intermolecular bridge-forming macromolecules. These are composed of inorganic metal salts acting as a clarifying agent {iron(II)chloride or aluminum sulfate} and organic cationic polymers such as polyvinylpyridine or polyamines in an aqueous solution.
From the teaching of DE-A-33 16 878 there have been known liquid one-component coagulants which contain calcium and/or magnesium nitrates, chlorides and/or sulfates as well as polyethyleneimines cationically modified by protonation or alkylation.
Particularly the disposal of two-component polyurethane varnishes in the past again and again gave rise to trouble. For disposing of the mist of such varnishes and coating compositions, in DE-A-34 12 763 there have been described agents which contain cyanamide and/or dicyanamide and/or cyanamide salts in combination with materials as conventionally contained in such coagulants.
Furthermore, layer silicates of various kinds have been more recently used to an increasing extent as paint coagulating and detackifying agents; these include, for example, 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 smectite (U.S. Pat. No. 4,701,220). According to the teaching of DE-C-38 17 251, also clay, especially boehmite or pseudo-boehmite, can be employed as a paint-detackifying and -sedimenting agent.
Furthermore, it has been known from the teachings of U.S. Pat. No. 4,496,374 and of EP-A-117 586 that talc may be employed in combination with calcium oxide, hydroxide, carbonate and/or zinc stearate for coagulating and depositing high-solid varnishes. Furthermore it has been known from the teachings of DE-C-34 21 289 and of DE-C-27 58 873 that wax, especially montan wax or carnauba wax, in combination with paraffin derivatives can be employed for coagulating and detackifying portions of synthetic resin

REFERENCES:
patent: 4220456 (1980-09-01), Block
patent: 4380495 (1983-04-01), Maher
patent: 4496374 (1985-01-01), Murphy
patent: 4541931 (1985-09-01), Geke et al.
patent: 4629477 (1986-12-01), Geke
patent: 4629572 (1986-12-01), Leitz et al.
patent: 4701220 (1987-10-01), Seng
patent: 4853132 (1989-08-01), Merrell et al.
patent: 4933091 (1990-06-01), Geke et al.

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