US 5,393,390 AGranted

Treatment and recycling of overspray from the spray application of waterborne coatings

AssigneeAkzo Nobel N.V.

InventorsKarl-Heinz Freese, Gerhard Gunter

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Abstract

A process and apparatus for treating overspray from the spray application of waterborne coatings is provided, which includes at least an electrophoresis separation step (means) for recovering substantially all of solids and higher molecular weight water-soluble components and a second separation step (means) for recovering the remainder. The result of such treatment is a recyclable waterborne coating stream of substantially the same composition as the waterborne coating and a recyclable water stream containing substantially none of the resin or additive parts of the original waterborne coating. The process and apparatus are effective, efficient and relatively simple, and recycling is effected without the use of coagulants, detackifiers and other chemical additives which may complicate the recycling procedure and have a detrimental effect on the so recycled products.

Claims14

Dependent claims

A process for treating overspray collected from the spray coating of an object with a waterborne coating, which waterborne coating comprises:

(A) water,
(B) a resin part including at least one of a water-insoluble, water-dispersible and water-soluble component, and
(C) optionally, an additive part including at least one of a water insoluble, water dispersible and water-soluble component,
which process results in a recyclable waterborne coating stream of substantially the same composition as the waterborne coating and a recyclable water stream containing substantially none of the resin or additive parts of the waterborne coating, which process comprises the steps of:
(1) collecting at least a portion of the overspray in collection means;
(2) electrophoretically separating the collected over-spray with electrophoretic separating means into
(i) a concentrated fraction comprising
(a) substantially all of the resin part,
(b) substantially all of the water-insoluble and water-dispersible components of the additive part, if present, and
(c) at least a portion of the water-soluble component of the additive part, if present;
and
(ii) a water fraction comprising
(a) a substantial portion of the water,
(b) the residue of the resin and additive parts not contained in the concentrated fraction;
(3) separating the water fraction into
(i) the recyclable water stream and
(ii) a concentrated residue stream;
(4) recovering the concentrated fraction of step (2);
(5) recovering the concentrated residue stream of step (3);
and
(6) generating the recyclable waterborne coating stream by mixing the recovered concentrated fraction of step (2) and the recovered concentrated residue stream of step (3) in a manner and with other components necessary to result in a mixture having substantially the same composition as the waterborne coating of the overspray.

18 more elements

An apparatus for treating overspray produced from the spray coating of an object with a waterborne coating which comprises:

(A) water,
(B) a resin part including at least one of a water-insoluble, water-dispersible and/or water-soluble component, and
(C) optionally, an additive part including at least one of a water-insoluble, water-dispersible and water-soluble component,
which apparatus comprises:
(1a) means for collecting at least a portion of the overspray;
(1b) a catchment tank for holding the collected overspray;
(2b) electrophoretic separating means, connected to the catchment tank, for electrophoretically separating the collected overspray into
(i) a concentrated fraction comprising
(a) substantially all of the resin part,
(b) substantially all of the water-insoluble and water-dispersible components of the additive part, if present and
(c) at least a portion of the water-soluble component of the additive part;
and
(ii) a water fraction comprising
(a) a substantial portion of the water,
(b) the residue of the resin and additive parts not contained in the concentrated fraction;
(3) means, connected to the electrophoretic separation means, for separating the water fraction into
(i) a recyclable water stream and
(ii) a concentrated residue stream;
(4b) means, connected to the electrophoretic separation means, for recovering the concentrated fraction;
(5) means, connected to the means for separating the water fraction, for recovering the concentrated residue stream;
(6) mixing means for generating a recyclable waterborne coating stream from the concentrated fraction, the concentrated residue stream and other components necessary to result in a mixture having substantially the same composition as the waterborne coating,
wherein the recyclable waterborne coating stream comprises substantially the same composition as the waterborne coating, and the recyclable water stream contains substantially none of the resin or additive parts of the waterborne coating.

19 more elements

Dependencies are inferred from the claim text.