PET bottles are produced by injection stretch blow molding of preforms. The preforms are heated using quartz infrared heaters which have a maximum peak output at 1100 – 1200 nm. Since PET absorbs this wavelength poorly, additives are put into the PET to improve the absorption of this energy. These additives are typically carbon black, iron oxide or other so-called black body absorbers. These additives improve the heat absorption of the polymer, reducing the processing time and energy required for blow molding. However, these additives are all black or dark and decrease the color of the PET considerably, leading to unattractive containers.
NYACOL has developed an alternative technology using antimony doped tin oxide (ATO). ATO is part of a class of materials described as transparent conductive oxides. These materials are transparent in the visible wavelength range, but absorb in the near IR range. This balance of properties is ideal for use as a clear fast reheat agent.
NYACOL ATO is produced in a patented process. Particles of 15 – 20 nm tin oxide are prepared and then doped with Sb. The dopant amount has been optimized to provide the best balance of color and reheat performance. The particles are crystallized to prepare a dark blue sol and transferred to EG. The current commercial product is designated SN902. The material is 20 percent ATO in EG with a measured dispersed size of 50-90 nm. The small dispersed size enables high transparency and excellent color in PET bottles while the optimized dopant level provides excellent coupling with the quartz IR heater output — leading to fast reheat performance and reduced energy consumption in ISBM.
NYACOL SN902 has been approved by the FDA under FCN1437 for use in PET at dosing levels up to 0.05%, though typical use levels are less than 0.005%. The use of SN902 is approved for all conditions of use.