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Casein & Levelling

Casein-containing Levelling Compounds

It is instructive to look at the example of casein containing levelling compounds, when considering the role of levelling compounds in the indoor environment. In the late 1970s, a new technique of levelling floors was introduced in Scandinavia. Instead of manually levelling the substrate with paste- like compounds, new materials with self-levelling properties were introduced. The new materials improved on the manual methods by a factor of 10 and very rapidly took over most of the market. Since the market at the beginning of the 1980s consisted mainly of new buildings, several million m² of self-levelling compound was being used each year. BR>

But there was a problem that no one had considered. The additive responsible for the self-levelling properties was casein. This is extracted from milk and consists of amino acids. The problem is that casein is not stable in the moist alkaline environment created cement. It is degraded and the process emits not only ammonia, but also bad smelling amines. This should have been noticed at building sites, but no one paid any attention. There are many sources of smells at building sites…

The first sign that something was wrong came in 1980 when the main producer of cork tiles noticed blackening at the edges of tiles to an extent that had not been seen before. A year later, similar blackening of parquet floors was noticed. Since it was known that ammonia blackens tannic acid in oak, it was natural to look for a source of ammonia in the floor construction. This was found to be the new casein-containing levelling compounds. The answer was to avoid cork tiles on casein- containing levelling compounds, and to protect oak parquet with a plastic sheet-isolating layer.

However the problems were not over. The question of SBS, "sick building syndrome", received more and more attention. One research group claimed that the cause was bacteria living on the casein, but this theory was proved to be false. Other ideas included the presence of mould on the underside of the flooring, and the emission of

2-ethylhexanol, an alcohol formed from degrading PVC plasticiser (more about that later). However in 1983, a pattern was emerging that indicated a statistical connection between casein- containing levelling compounds and SBS. This patter was statistical. It was not known – and it is still not known – by what mechanism the casein had caused the health problems.

In view of the statistical evidence, the main producers in Scandinavia stopped using casein in 1983 and as a result, the occurrence of SBS in new buildings dropped markedly. This is further evidence that casein was a factor in SBS. Casein was replaced with other flow agents, and new formulations were developed.

The lesson from the casein story has been to focus on emissions, and primarily to ensure that the products do not emit ammonia. An official approval system was introduced to regulate this.

This may seem like fussing about something that happened a long time ago, but we at maxit think that the story is worth telling. There are still many producers around the world using casein. They may not have heard of the Scandinavian experience, or they may not believe in it. It is worth pointing out that the cost to restore floors with casein-containing levelling compounds has amounted to several hundreds of million Euros over the years.