Paints and lacquers under control

Helmut Kaiser, Walter Sonntag

In combination with modern process control technology, automatic feeding systems introduce all raw materials into the production process at exactly the right time and in exactly the right quantity – regardless of whether bulk goods, small quantities or liquid components are involved. Feeding of raw materials is simplified and the supply of materials from sacks, which is both labour intensive and critical from a health point of view, is reduced. One result of this is a considerable increase in the precision of adherence to formulas. Intelligent process control technology also permits reliable and rapid production monitoring. This leads to a clear improvement in the quality of the end product. This is confirmed by several examples from the paint and lacquer industry.

In the field of paint production, considerable automation potential still exists in the raw materials feeding sector. Azo offers competent solutions for receiving and storing raw materials in powder form that have already proved their value in the production of powder coatings. The automation of titanium dioxide handling is one good instance of this. Special silo delivery systems ensure reliable delivery and stable conveyance for this particularly fine-grained raw material with difficult removal and conveying characteristics. The choice of suitable materials and the high-quality finish effectively prevent caking.

Azo dosing systems are particularly suitable for formulas with small components, which must be weighed in the mixing container with great precision and which also have poor flow properties, such as titanium dioxide. The negative weighing technique ensures dosing and weighing accuracy to the nearest gram. Dosing systems can be added to whenever necessary thanks to their modular design. The easy-to-clean Azodos devices combined with intelligent processing technology enable a complete change of formula in the shortest possible time.

Safe batch separation and freedom from contamination are obtained in interaction with the Componenter. Storage hoppers are filled by pneumatic conveyance from silos or directly via Big Bag loading stations. The various components are transported by the dosing system and weighed directly in the mixing container, which is driven under the Componenter on mobile scales. The special devices used for discharging and loading form unique conveyance and transport systems that ensure safe transport and precise positioning of the mixing container. At the loading station the container is detected using a barcode, automatically collected, filled according to its formula and then discharged again at the end of the dosing and weighing process. It is subsequently fed to the mixer or temporarily stored for later processing.

The automation of large and medium-sized components, some of which like carbon black have very low apparent densities, places particularly high demands on plant systems and processing technology. Production in a system that is closed to the greatest possible extent ensures dust-free production processes. The precondition for this is maximum automation of all raw materials from large, mostly hard components through to small components such as pigments and additives. The proven pneumatic systems are the basis for this in addition to reliable Big Bag loading stations and container emptying stations.

Pneumatic suction weighing systems are ideally suited to precise feeding of large and medium-sized components in powdered form for the production of printing inks. The individual components are weighed by conveyor scales and fed to the dissolver via a sluice or a dosing screw. Large components are fed pneumatically directly from silos during this process. Medium-sized components stored in Big Bags and containers, such as special carbon black types, are transported to the dissolver by pneumatic suction conveyance via Big Bag loading stations or container emptying stations and the conveyor scales. The advantages of pneumatic suction weighing systems are clear: a large number of components are conveyed to one or more dissolvers in the most economical way possible. Processing takes place in dust-free, closed systems and the special design of the suction weighing systems saves space and height.

The extensive and versatile raw materials spectrum with an abundance of components makes automation solutions for paint production a special challenge. Depending on the task, either volumetric flow meters are used for dosing large components or the fluids are filled directly into the mixing container, which stands on scales. Medium-sized components are dosed and weighed with these scales. Two different systems are used for this purpose, depending on the fluid. The precise negative weighing technique is particularly suited to the task of weighing highly viscous fluid components. The positive weighing technique is used for fluids that flow easily. The cyclone screening machine has proved itself when it comes to safe screening and the elimination of agglomerates in paint production. It excels in particular thanks to its easy-to-clean and easy-to-service design, simple operation and sturdy, high-quality workmanship at a reasonable price.

The Dosibox is ideal for automating small components delivered in vats, Big Bags and sacks. The external containers are transferred into the low-cost dosing containers in PE plastic at a special loading station. They enable automatic access to all small components. Identification systems determine the contents of each individual Dosibox. Closed access via the integrated dosing screw is dustproof and decisively increases production safety. The Dosinenter system, which is built in a linear manner from several Dosiboxes, allows transparent stock control, flexible formula changes and exactly reproducible formulas. The Mandos manual weighing system provides a good solution for very small quantities where automation is not worthwhile. Mandos additionally furnishes complete documentation.

A trend towards continuous production of lacquer is emerging at present. The main advantage of this is the dosed introduction of powders into fluids in closed dosing systems with no environmental damage. A further bonus is that larger quantities can be produced with small machines and low space requirements. A single machine handles several process steps, such as addition, wetting, pre-mixing and homogenisation. This saves time, investment costs and staff. The Dositainer system is an optimal solution for these requirements. It doses the dry products and delivers them to the continuous processes. Product changeover is effected with minimal residual quantities. The Dositainer’s special geometry and safe discharge system make it ideally suited to even the heaviest products.

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More information about feeding and dosing systems

Powtech 2005