# US 5,344,851 A · Process for recovering binder components from lacquer sludge

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- Number: US 5,344,851 A
- Document ID: US5344851A
- Status: Granted
- Kind: A
- Application number: 08/054,931
- Filed: 1993-04-28
- Granted: 1994-09-06
- Earliest claimed: 1992-05-06
- Assignees: Bayer Aktiengesellschaft
- Inventors: Wieland Hovestadt; Jochen Bruck; Volker Schneider
- Web page: https://patentgrep.com/patent/US5344851A

## CPC

- C08J 11/00: Recovery or working-up of waste materials (recovery of plastics B29B17/00; polymerisation processes involving purification or recycling of waste polymers or their depolymerisation products C08B, C08C, C08F, C08G, C08H)
- C09D 7/71: {Paint detackifiers or coagulants, e.g. for the treatment of oversprays in paint spraying installations (chemical paint removers C09D9/00)}
- C08J 2375/04: Polyurethanes
- C08J: WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H (working, e.g. shaping, of plastics B29)
- C09D: COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR (cosmetics A61K; processes for applying liquids or other fluent materials to surfaces, in general, B05D; staining wood B27K5/02; glazes or vitreous enamels C03C; natural resins, French polish, drying-oils, driers, turpentine, per se, C09F; polishing compositions other than French polish, ski waxes C09G; adhesives or use of materials as adhesives C09J; materials for sealing or packing joints or covers C09K3/10; materials for stopping leaks C09K3/12; processes for the electrolytic or electrophoretic production of coatings C25D)

## Abstract

The present invention relates to a process for recovering and recycling the organic binder components accumulating as overspray during the spraying of a solvent-containing, two-component polyurethane lacquer or a solvent-containing, moisture-curing, one-component polyurethane lacquer by i) washing the overspray out of the exhaust air of a coating plant with the aid of an aqueous medium which a) contains in dissolved or dispersed form compounds that exhibit greater reactivity towards isocyanate groups than either water or the isocyanate-reactive groups present in two-component polyurethane lacquers, and b) may contain emulsifiers, ii) isolating the chemically modified overspray formed in step (i) in the form of lacquer sludge by treatment with coagulating agents, which may be present in the aqueous medium, iii) mixing the lacquer sludge, containing fully reacted lacquer constituents, coagulating agents and water, optionally after a portion of the water is removed, with an organic solvent and iv) separating the organic phase accumulating in step iii) from the aqueous phase and insoluble-constituents which may be present and recovering the solution of modified organic binder components dissolved in the organic phase.

## Claims

### Claim 1

A process for recovering and recycling the organic binder components accumulating as overspray during the spraying of a solvent-containing, two-component polyurethane lacquer or a solvent-containing, moisture-curing, one-component polyurethane lacquer which comprises
i) washing the overspray out of the exhaust air of a coating plant with the aid of an aqueous medium which a) contains in dissolved or dispersed form a compound that exhibits greater reactivity towards isocyanate groups than either water or the isocyanate-reactive groups present in a two-component polyurethane lacquer, and b) may contain an emulsifier,
ii) isolating the chemically modified overspray formed in step (i) in the form of lacquer sludge by treatment with a coagulating agent, which may be present in said aqueous medium,
iii) mixing the lacquer sludge, containing fully reacted lacquer constituents, coagulating agents and water, optionally after a portion of the water is removed, with an organic solvent and
iv) separating the organic phase accumulating in step iii) from the aqueous phase and insoluble constituents which may be present and recovering the solution of the modified binder components dissolved in the organic phase.

### Claim 2 (depends on 1)

The process of claim 1 wherein said compound of process step i) comprises a primary or secondary monoamine having aliphatically or cycloaliphatically bound amino groups.

### Claim 3 (depends on 1)

The process of claim 1 wherein said compound of process step i) comprises an oxime.

### Claim 4 (depends on 1)

The process of claim 1 wherein said compound of process step i) comprises an amino alcohol.

### Claim 5 (depends on 1)

The process of claim 1 which comprises blending the modified binder components recovered in process step iv) with a polyisocyanate to form a two-component polyurethane lacquer.

### Claim 6 (depends on 1)

The process of claim 1 wherein the modified binder components recovered in process step iv) are suitable for use as a one-component polyurethane lacquer which may be crosslinked at elevated temperature to form a solvent resistant coating.

### Claim 7 (depends on 1)

The process of claim 1 which comprises removing the solvent from the organic binder components recovered in process step iv) to form a powder lacquer which may be crosslinked at elevated temperature to form a solvent resistant coating.

### Claim 8 (depends on 1)

The process of claim 1 which comprises treating the water and/or insoluble constituents separated according to process step (iv) with a solvent to recover additional modified binder components and combining the resulting solvent phase with the organic phase obtained according to process step iv).