VOC-free color change for 2K clearcoats thanks to new technology

A VOC-free color change for 2K clear coats is made possible by a new technology in which mixed 2K materials are fed directly into the recirculation system. Rinsing and color changes no longer introduce VOCs into the paint booth.

A new development from Dürr makes it possible for the first time to feed mixed 2K paint systems directly into the recirculation system in the atomizer. This means that rinsing processes and color changes no longer introduce VOCs into the paint booth. The new solution has been used successfully in two top coat lines for a year now. When using mixed paint systems with two components (2K), a lot of VOC (Volatile Organic Compound) has so far entered the paint booth during rinsing and color changes. Rinsing processes in which the residual paint flows forwards via the atomizer into a funnel or directly into the washout are still widespread in industrial painting. With this procedure, over 70 percent of the booth air is contaminated with volatile organic compounds. The EcoBell PurgeBox collection system, which is equipped with special filter mats, is more environmentally friendly and emits up to 60 percent less VOC.

Dürr's new development reduces VOC pollution even further by making it possible for the first time to recycle 2-component clear coats, as is usual in the classic 1-component process. This was previously unthinkable for mixed systems consisting of hardener and basecoat, e.g. clearcoat. Thanks to a patented process sequence with precisely coordinated parameters, mixed 2K materials can be fed back into a collecting line via a recirculation system integrated into the atomizer without curing. This is made technically possible by, among other things, up to two main needles in the atomizer and the established diaphragm valve technology, which delivers the highest mixing quality with the lowest mixing volume. A minimal 5% VOC emission only occurs when cleaning the bell plate in the EcoBell Cleaner D2. No more VOCs are released during the rinsing process and color change.

Effect coatings within normal cycle times

Recirculation for mixed 2K materials is not only environmentally friendly, but also advantageous in other respects: it saves time. While the bell cup and the surface of the atomizer are being cleaned in the EcoBell Cleaner D2, the bell cup can be rinsed and pressed on at the same time. These work steps, which previously took place one after the other, are now carried out in parallel within a maximum of 15 seconds. Depending on the requirements and system, this halves the time required for the color change, which increases the overall capacity of a system and allows more time for the painting process, resulting in better painting quality. Tinted clearcoats can now also be applied without any loss of cycle time. This enables car manufacturers to use effect coatings, which were previously limited to exclusive areas, much more widely in future.

Application setups in combination with an EcoBell4 Pro offer maximum flexibility. Two recirculation systems for 2K material (2x2K) are integrated into each robot arm. This means that while one body is being painted, the paint and hardener for the next body can be prepared in parallel on the second channel. Even if manufacturers use several master coats and hardeners that are not chemically compatible with each other, these can be applied via the separate channels. To ensure that everything works smoothly for the customer later on, Dürr checks in advance at its own test center whether the customer's clear coat systems are compatible with the new technology. Until now, all 2K clear coats could be returned and collected via the atomizers.

Recirculation reduces costs for fixtures

The EcoBell4 Pro rotary atomizer is available in 2x2K and 1x2K recirculation versions. The EcoBell3 can be retrofitted with 1x2K. A further system with the new development is currently being put into operation. In addition to the advantages of completely eliminating VOC input during rinsing and color changes and significantly reducing solvent consumption, the low investment costs are also impressive. This is because recirculation eliminates the need for hoppers or EcoBell PurgeBoxes and other installations in the paint booth.

For a year now, the recirculation system for mixed 2K material has been proving its functionality at a leading manufacturer of electric cars on two top coat lines with 42 high-speed rotary atomizers. (OM-12/24)

Contact

Dürr AG
Carl-Benz-Str. 34
74321 Bietigheim-Bissingen (Germany)
Phone +49 71 42 78 0
E-mail: corpcom@durr.com
www.durr.com

About Dürr

The Dürr Group is one of the world's leading mechanical and plant engineering companies with strong expertise in the areas of automation and digitalization/Industry 4.0. Its products, systems and services enable highly efficient and resource-saving manufacturing processes in various industries.

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