Perfect pigments with the help of flake-ice

Citation

(2001), "Perfect pigments with the help of flake-ice", Pigment & Resin Technology, Vol. 30 No. 3. https://doi.org/10.1108/prt.2001.12930cad.001

Perfect pigments with the help of flake-ice

Perfect pigments with the help of flake-ice

Keywords Cappelle, Pigments

Known throughout the world simply as "Cappelle", Etn Gebroeders Cappelle N.V. of Kortrijkstraat, Belgium, has an excellent reputation for quality pigments used by the paint, ink, plastics and other industries. Their quality standards have enabled them to continue to grow as an independent supplier of pigments alongside the large international chemical groups. The business has been in family ownership for four generations.

A mixture of chemicals in vats produces dyes and pigments and this process can generate considerable heat that has to be controlled – technically this process is defined as an explosive exothermic effect. At certain critical times in the process, it is essential that the rapidly increasing heat is reduced and specific temperatures are required to sustain the quality of the end product. In the past chilled water had been used but the industry has long accepted that water is not suitable and ice has been used for a number of years. This has raised the question: "What sort of ice?" Cappelle used to buy in block ice and break it up and this had two problems: some of the sharper lumps could damage the walls of the mixing vats and inconsistent lump size made accurate prediction of cooling time impossible. Later, flake-ice machines were installed but Cappelle's production started to outpace the ice supply.

In Spring 2000, after a review of many options available, Cappelle took delivery from Vanderbeke sa, the Belgian distributors, of a Geneglace F900 flake-ice machine, which produces 25 tonnes in 24 hours of sub-cooled ice at –6°C (Plate 1).

Plate 1 Cappelle uses Geneglace F900 flake-ice machine

There are two principal benefits claimed of Geneglace flake-ice. First, compared to chips, blocks or granules of ice, the flake-ice has a much larger surface area and consequently provides much more efficient thermal exchange from the mixture within the vats and this ensures faster cooling. There is no water mixed with the ice, and this "ice only" feature of the flake-ice manufacture means that the latent heat, the principal source of the cooling energy, is 100 per cent available and 1kg of ice will draw 350kJ of heat from the mix. Thus, the consistency of the dry flake-ice enables precise calculations to be made of its cooling input by production directors in the dye and pigment industries and other processes.

The second principal benefit, reported to be endorsed by Cappelle, is the reliability of the Geneglace F900 flake-ice machine which uses the "greener" R507 refrigerant.

At the Cappelle plant, which employs 230, there is continuous shift working six days a week. At the critical mixing stage the sizes of vats employed range from 10M³ to 40M³. It is a convention in the pigments industry that the many formulae of chemicals to match specific pigment requirements are closely guarded trade secrets and at Cappelle there is no exception to this principle. However, a typical application for the flake-ice might be to reduce the temperature of a mix which has reached 24°C (and is still rising) to 5°C. At Cappelle the flake-ice is taken from a holding silo in bins by trolley to the vats and experienced operators manually introduce the appropriate amount. This enables the mix to go forward to the next stages of the process at the optimum temperature and with the added advantage of less water in the mix, which reduces time at the later crystallisation stage.

Quality control is stringent at Cappelle at every stage of production. One of the important tests of batches of the finished products is continuous exposure to the sun over several weeks (Plate 2).

Plate 2 Testing time at Cappelle - rigorous outdoor exposure of samples

Details available from: Frigofrance s.a., Tel: + 33 2 40 32 0606, Fax: +33 2 40 65 04 88, e-mail: contact@geneglace.com