Cleaner paints

1989/11/01 Elhuyar Zientzia Iturria: Elhuyar aldizkaria

A U.S. chemical company has recently developed a process that substitutes organic solvents in gun paint for carbon dioxide. This advance can significantly reduce the emissions of organic solvents into the atmosphere.

These solvents include oxygenated compounds and chlorinated compounds such as hydrocarbons, alcohols, glycols, ketones and esters. These low-evaporation point solvents evaporate and disperse into the atmosphere during the application of paint. They react with nitrogen in the atmosphere and help increase photochemical smog.

This process, called UNICARB, has been developed by the unfortunate American company Union Carbide, with the collaboration of Professor Marc Donohue of John Hopkins. Carbon oxide (IV) has a special phase state between 35º-65º C and a pressure of 8 megapascals. This phase is called supercritical and acts as a solvent.

According to Union Carbide 1 kg of organic solvent is emitted into the atmosphere for 2 l of applied paint. Only 1.6 billion liters of paint and coating were applied in the US. Car manufacturers and straighteners use pistol paint the most and could be reduced by 30 to 70% if a UNICARB process was applied.

In conventional technique the paint is diluted with solvent until it is light enough to be applied. In the UNICARB process solvents are also used, but only enough to keep the paint in dissolution (polymers coatings, pigments and additives). In this situation the paint is not light enough to be applied with a gun. Carbon dioxide is added in the UNICARB process to make the paint applicable at this time. UNICARB does not require technological changes, as current equipment is available.

More than one might think that from an ecological point of view the system has no advantages. In fact, the emission of organic solvents into the atmosphere is avoided, while the emission of carbon dioxide (CO2) produced by the greenhouse effect is produced. What you think is wrong, as the new carbon oxide (IV) would not be synthesized, but the content in the atmosphere.

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