Gas separation: processes – Liquid contacting – Defoaming or antifoaming agent
Patent
1997-12-11
1999-07-06
Hruskoci, Peter A.
Gas separation: processes
Liquid contacting
Defoaming or antifoaming agent
95196, 134 38, 210765, 210930, 427331, B01D 1904
Patent
active
059192887
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a method of inhibiting bubbling of booth circulating water in a water-borne recycle coating system.
BACKGROUND ART
For spray-coating with a water-based paint, it is common practice to use a spray booth in order to prevent contamination of the working environment. The booth water is circulated in this spray booth so that the water-based paint which is not deposited on the substrate upon spraying may be trapped by the booth water (referred to as booth circulating water) as an over-spray paint and, therefore, not scattered. However, when the water-based paint finds its way into the booth circulating water, copious surface bubbles are formed and sometimes overflow to contaminate the spray booth and ancillary equipment.
Moreover, while the water-based paint trapped by the booth circulating water is generally recycled, the copious production of bubbles in the booth circulating water and overflows from the spray booth interfere with recovery of the water-based paint, thus causing the problem of a waste of materials. Therefore, in view of better workability and prevention of pollutions, inhibition of bubbling of the booth circulating water has been demanded by the industry.
Japanese Koukai Publication Hei-7-100415 discloses a water-based paint mist elimination device which recovers the bubbles formed on the surface of booth circulating water in one location, taking them out from the spray booth, and destroying the pooled bubbles. Since, in this technology, the bubbles formed in booth circulating water are removed from the spray booth to prevent overflowing, there must be provided a bubble recovery tank and a heater or other device for breaking up the bubbles, so that the equipment is of necessity large-scale.
SUMMARY OF THE INVENTION
Accomplished in view of the above state of the art, the present invention has for its object to provide a method for inhibiting bubbling of booth circulating water by which the bubbles formed in booth circulating water upon spray-coating a water-based paint can be effectively controlled to maintain the working environment in good condition.
The present invention is essentially directed to a method for inhibiting bubbling of booth circulating water in a water-borne recycle coating system wherein a substrate is spray-coated with a Fater-based paint in a spray booth and any over-spray paint trapped in the booth circulating water is concentrated and recovering for reuse in admixture with said water-based paint, which comprises that the booth circulating water contains a silicone antifoamer (A) and a hydrophilic high-boiling solvent (B).
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 shows a typical water-borne recycle coating system to which the method for inhibiting bubbling of booth circulating water according to the invention can be applied.
DETAILED DISCLOSURE OF THE INVENTION
The present invention is now described in detail.
In the water-borne recycle coating system to be used in the present invention, booth circulating water is circulated in a spray booth in order to trap an over-spray paint which is formed upon spray coating of a substrate with a water-based paint.
The substrate mentioned above is virtually unlimited in kind but includes a variety of substrates, e.g. vehicle components such as automotive bodies and engine blocks, metallic furniture such as lockers, etc., household electrical appliance housings, and architectural members, among others.
The water-based paint mentioned above is not limited in kind, either, but includes paints based on acrylic resin, polyester resin, alkyd resin, modified alkyd resin, e.g. epoxy-modified, rosin-modified, and phenol resin-modified alkyds, etc., and paints composed of a water-soluble or water-dispersible resin such as polyurethane resin in combination with a melamine resin, and epoxy resin or modified epoxy resin. Those paints may be whichever of the baking paint and the cold-setting paint.
The water-based paint for use is adequately selected according to the kind of substrate and in
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patent: 4125476 (1978-11-01), Dean
patent: 4378235 (1983-03-01), Cosper et al.
patent: 5282970 (1994-02-01), Wepf
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patent: 5330659 (1994-07-01), Schapira et al.
patent: 5419487 (1995-05-01), Nielson et al.
Kageyama Takao
Mashima Hiroshi
Uenoyama Kazuo
Hruskoci Peter A.
Nippon Paint Co. Ltd.
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