DE4207425A1 - Treating over-spray collected from coating of object with waterborne coating - Google Patents

Abstract

Object is spray coated with waterborne coating comprising water, a resin part including water-insol., water-dispersible and/or water-soluble component, and, opt. an additive part including at least a water-insol., water-dispersible, and/or water-soluble component and the overspray is collected and treated to provide a recyclable, waterborne coating stream of the same compsn. as the original coating and a recyclable water stream contg. no resin or additive parts. The collected overspray is treated by electrophoterically separating it into a concentrated fraction comprising all of the resin part, all of the water-insoluble and water-dispersible components of the additive part, and at least a part of the water-soluble component of the additive part and a water fraction comprising a major portion of the water and the residue of the resin and additive parts, the water fraction subsequently being sepd. into the recyclable water stream and a concentrated residue stream. The concentrated fraction and concentrated residue stream are recovered and the recyclable waterborne coating stream is generated by mixing them with other components necessary to produce a mixt. the same as the original compsn.

Description

The invention relates to a recycling process according to the preamble of claim 1 and  a device principle according to the related, partly alternative claims.

Which arise when spraying water-based paint in a cabin de overspray is usually and such as known from DE-OS 41 23 296, by water areas tion of the spray chamber walls and with a so-called wet wash out from the extracted cabin exhaust air to catch. Here, in the cabin circulation water Solids content of paint components at max. 2% ge keep to within the required or permissible Emission values remain in the exhaust air; to do that ensure and recover the paint, the overlying solid content from the cabin water be separated. So far this has been narrowed low-cost systems such as centrifuges or ultra filtration made, with each system on its own used as a precursor of a solid concentration can be.

Although such facilities are already increasing in general the present Er finding the task nevertheless, here with egg another method and corresponding devices a further optimization of the previously known water to achieve paint recovery systems.  

This task is solved in a general way by the method specified in claim 1 wise; the sub or subsequent claims include here to advantageous process developments and pre directional features of alternative systems to the process execution.

In the drawings, Figure 1 and Figure 2, two different procedures are shown schematically and explained in more detail below in connection with the claims. Figs. 3 to 5 also purely schematically indicate different devices for carrying out the process.

In both process representations, the respective spray booth is followed by a system tank equipped with an agitator for receiving the booth circulating water enriched with overspray, and an ultrafiltration device with a concentrate container as shown in Fig. 1, whereby in Fig. 2 a centrifuge with intermediate storage is connected upstream of the ultrafiltration device.

New to the embodiment shown in Figures 1 and 2 process example is now an additional step for the deposition of the collected in the circulating water paint composition in a separate operation on electrophoretic manner, depending on the coating material, the polarity of the electric voltage of the separation electrodes is maintained anodic or cathodic. One makes use of the known technique of EP coating of workpieces to discharge paint from the circulating water of the cabin, in principle, however, by controlling the deposition process in such a way that a loose, mechanically easily stripped paint layer forms on the electrode surface. Important for an optimal process flow is still influencing the liquid flow in the EP bath of the type that in the area of the separating electrodes neither foaming nor accumulation of paint material is successful and cooling of the EP bath, at least in the loading area of the separating electrodes. As cabin water, preferably demineralized water is to be used, the particular advantages of which for the process sequence are already sufficiently described in DE-OS 34 28 300.

Since it has been shown in practice that optimal paint Separation conditions in the present process ma material-specific, must also correspond here  appropriate settings or adjustments to the separator duration, the size and ripple of each applied DC voltage as well as current limitation and pH value control tion by adding amine or the like. be it is also preferred to return the paint material freed water in the spray booth water circuit.

Devices for carrying out the new method are generally characterized according to the representations in Figures 3 to 5 by a separate container 1 for the booster circulation water enriched with the overspray, electrode 2 suspended in the container 1 and as a counter-pole separating surfaces A, which mechanical stripping elements AB for the paint material adhering to the separating surfaces A are assigned to an adjacent Sam mel container 3 . In a special design, it can be provided that the separating surfaces A and the respectively assigned mechanical wiper elements AB have the following alternative configurations:

• a. Periodically immerse in the paint water tank 1 and to the collecting tank 3 together with its wipers AB z. B. Swinging out, parallel plates Figure 3.
• b. Rotating disks immersed in the container 1 as shown in FIG. 4, the paint wipers AB also representing the drainage surface F for the paint material 3 .
• c. As under b .; but with rotating roller as Separation area A.
• d. Circulating, vertical or inclined and lying out of the container 1 is partially outstanding circumferential steel strip as a separator A with ent speaking stripper AB and flow area F accelerator as Image 1, 2 and 5. FIG.

A defined roughness can also be advantageous speed of the separating surfaces A to improve the port effect of the paint material, as well as the assignment of drying elements (not shown) such as Warm air nozzles, infrared heaters or similar to the separator elements A.

Finally, the heating caused by electrical leakage currents in the bathroom has to be compensated. This is done in such a way that the required bath cooling in the container 1 takes place by means of cooling elements arranged in the region of the separating element A; this can be done with a roller as a separating element by internal cooling of the same or by cooling coils on or in the container.

The anla described can be completed ultimately through a post-drainage of the Paint material after the stripping process on mechanical Way, so z. B. by nip rolls with any Forwarding of the deposited paint material using Screw conveyor or the like to a catchment or storage area holder.

Reference numeral

1 container for cabin spray water enriched with overspray
2 electrodes
3 paint collection containers
A separator, separation surface
AB scraper
F discharge surface, paint drain surface
P Swivel or rotation direction of the separating surfaces
E footprint, floor space

Claims (10)

1. A process for the recovery of waterborne paint from the booth circulating water containing the overspray in industrial spray applications, characterized by separating the paint mass captured in the circulating water in a separate operation in an electrophoretic manner, the polarity of the electrical voltage of the separating electrodes being anodic depending on the paint used or is kept cathodic. 2. The method according to claim 1, marked by Control of the deposition process in such a way that the electrode surface a loose, mechanical easily strippable paint layer forms. 3. The method according to claims 1 and 2, marked by Influencing the liquid flow in the EP bath such that neither in the area of the separating electrodes Foaming or accumulation of paint material consequences. 4. The method according to claims 1 to 3, marked by  Cooling of the EP bath, at least in the area of the Ab cutting electrodes. 5. The method according to several of the preceding claims, marked by Use of the new separation system in conjunction with an ultrafiltration and / or with a Zen trifuge level within the same facility; as before stage for concentrating the circulating water in the cabin. 6. Device for performing the method according to the preceding claims, characterized by a separate container ( 1 ) for the enriched with the over spray cabin circulation water, in the loading container ( 1 ) suspended electrode ( 2 ) and as a counter-pole separating surfaces (A), which mechanical wiping elements (AB) for the paint material adhering to the separating surfaces (A) are assigned to a secondary collecting container ( 3 ). 7. The device according to claim 6, characterized in that the separating surfaces (A) and the respectively assigned mechanical wiper elements (AB) have the following alternative configurations:

• a. Periodically immersed in the paint water tank ( 1 ) and to the collecting tank ( 3 ) together with its wipers (AB) z. B. swinging out, parallel plates ( picture 3).
• b. Rotating disks immersed in the container ( 1 ) up to approximately the revolving axis ( 4 ), whereby the paint wipers (AB) are the same guide surface (F) for the paint material as the paint collecting container ( 3 ) ( Fig. 4).
• c. As under b.), But with a rotating roller as separation surface (A).
• d. Circumferential, vertical or inclined are the and from the container ( 1 ) partially protruding, circumferential steel strip as a separator (A) with a corresponding scraper (AB with F) ( Fig. 1, 2 and 5).

8. Device according to claims 6 and 7, marked by a defined roughness of the separating surfaces (A) to improve the adhesion of the paint material. 9. The device according to one or more of the preceding claims, characterized in that the required bath cooling in the container ( 1 ) by in the region of the separating elements (A) is arranged cooling elements. 10. Device according to one or more of the above claims,  marked by Assignment of drying (not shown) elements such as warm air nozzles, infrared radiators or the like to the separating elements (A).