Monday, November 23, 2015

Importance of hot end coating with Butyltin chloride in Glass production

Butyltin trichloride

Monobutyltin trichloride, also known as MBTC, is an organotin compound(organometallic compound). Monobutyltin trichloride is commonly used in Chemical vapor deposition (CVD) to deposit a tin-based coating onto flat and hollow glass
In Glass coating
Monobutyltin trichloride is primarily used to deposit tin dioxide coatings on glass, which are low-emssivity and transparent to visible light, reflect infrared light, and provide a high conductance and a low sheet resistance. The tin dioxide coatings are typically doped with other materials, like fluorine or antimony to increase the surface strength and abrasion resistance of the finished glass


MBTC is used in the manufacturing process of glass containers such as those used for beers, spirits, and juices. These glass-making processes heat raw materials (sand, soda-ash,
limestone, and recycled glass) to produce molten glass. The molten glob is cut into smaller pieces of uniform size, and are then pressed in a mold. MBTC is applied on the external surface of these containers, and then, the glass is annealed and coated with polyethylene
MBTC is a commonly used organotin compound for on-line chemical vapor deposition because it readily decomposes at or close to the hot glass surface. The tin dioxide coatings formed are transparent to visible light, reflect infrared light, and are highly conductive. If these coatings are doped with fluorine from a source like trifluoroacetic acid (TFA), the coating will also have a lowered emissivity.
PVC stabilizer

Monobutyltin trichloride is used as a polyvinyl chloride (PVC) stabilizer. PVC is used in mass production for various objects. One such object is a PVC based container for various wines and brandies (especially those produced in Canada). Consequently, the MBTC leaches into the wine along with other organotin compounds (some of which are used as wood preservatives for the wine barrels). These compounds are toxic to the human body, and the amount of organotin compounds, especially MBTC, have been the subject of a lot of food-safety based research.[9]
Another object PVC is used in is pipe production. Since these pipes are used to carry drinking water, the MBTC is leeching into the drinking water supply. The EPA believes this is a great threat.[10]

Safety

Monobutyltin trichloride is strongly corrosive, and can cause severe burns to the eyes and blindness as well as burns to the skin. Organotin compounds can act as delayed poisons, and consequently, they can cause headaches, dizziness, psycho-neurologic disturbances, sore throat, vomiting, urine retention, vision impairment, skin burns, and liver and kidney damage.

Monobutyltin trichloride is a serious safety concern, for it is found in many unexpected places. It is found in drinking water, for it leaches out of PVC piping into drinking streams. It is also found in white wine and brandies that are stored in PVC containers.

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