Formaldehyde-free liquifier for
plasterboard manufacture
Manufacturing plasterboardA plasterboard panel is made of a paper liner wrapped around an inner gypsum core. In the manufacturing process, plaster is mixed with water to obtain a homogeneous slurry. The water needed to rehydrate plaster is about 18 parts per 100 parts of plaster by weight. However in practice 60-80 parts of water are used so that the plaster can easily be poured between the paper liners. Organic dispersants, called liquefiers, are used to reduce the amount of water, and hence reduce the drying energy and time, needed to produce a flowable gypsum slurry during wallboard manufacture.
Release of formaldehydeResults from indoor air quality studies in Europe show that volatile organic compounds (VOC) are released from a variety of construction products, including plasterboard. These emissions may cause health complaints in new buildings. For plasterboards the concerns are directed towards both total VOC and towards formaldehyde specifically. Formaldehyde may be present in several components of a plasterboard including the gypsum core itself coming from the liquefier. The level of formaldehyde in Poly-Naphthalene Sulfonate anionic polymers is usually higher
Use of Poly-Naphthalene
Sulfonate (PNS)The most efficient liquefiers presently available are constituted by calcium salts of Poly-Naphthalene Sulfonate anionic polymers. These polymers allow an important reduction of water at equal slurry flowability. To produce boards with good mechanical properties the influence of the liquefier on the size and shape of the gypsum crystals shall be as limited as possible.
than 300 ppm, a level posing issues not only on the indoor air quality but on the workplace hygiene as well. Experimentally a large variability of the measured emissions is observed, with an average long term (28 days) formaldehyde release of 39 µg·m-2·h-1. A recent French regulation labels construction products according to their emission potential, and to be granted the A+ label the formaldehyde emitted shall reach a concentration less than 10 µg·m-3.To cope with such requirements Bozzetto has developed a liquefier containing no free formaldehyde, FLUPLAST 40, which consequently does not contribute to emissions. As more experimental data on formaldehyde emission will become available in the future, and all the European countries will adopt regulatory legislation, such a product will enforce its status as the reference material to which all plasterboard manufacturers shall revert.
