Patent FR-2771661-A1 (FR)
Title: Plastics container cleaning
Inventor: MORIN MICHEL
IPC: B08B3/12
Filed: 1997-11-28
Abstract: To clean the interior of plastics containers, with complex shape structures, the container is placed in an autoclave for the introduction of a supercritical fluid which is compatible with the polymer of the container material. The fluid is maintained in a supercritical state in an extraction zone, for a total absorption of impurities on the polymer material within the autoclave. To clean the interior of plastics containers, with complex shape structures, the container (1) is placed in an autoclave (12) for the introduction of a supercritical fluid (14) which is compatible with the polymer of the container material. The fluid (14) is maintained in a supercritical state in an extraction zone, for a total absorption of impurities on the polymer material within the autoclave. The fluid (14), soiled by the absorbed impurities, is extracted and cooled to ambient temp. levels to bring the supercritical state into a gas form in a monophase zone where the gas can be cleaned and the carried impurities separated by a particle filter and a mol. purification. The cleaned gas is frozen to a biphase condensation zone to bring the fluid (14) from a gas to a liquid state. The gas is heated to pass through a biphase compression zone to bring it from a liquid to a supercritical state, and returned to the autoclave for a further container cleaning cycle. The supercritical fluid is formed by carbon dioxide (CO2), or ammonia (NH3).  The fluid (14) is recycled continuously with a gas phase before the condensation and compression phases. An Independent claim is included for an apparatus as an autoclave (12) to take the container (10) for cleaning.  It has an inlet opening (16) for the injection of the supercritical fluid (14). A low pressure relief valve (20) links the outlet opening (18) at the autoclave with an outflow channel (17) for the soiled fluid, and the valve changes the fluid from a gas to a liquid.  A collection bottle (20) is linked to a closed circuit to regenerate the fluid.  A monophase purification stage (28) has a particle filter and a mol. cleaning action through the outlet of the low pressure relief valve (20).  A biphase compressor (42) gives the condensation of the chilled and cleaned gas and reheats the liquid to a supercritical state.  The regenerated fluid (14) is returned for injection into the autoclave entry (16) for a fresh cleaning cycle. Preferred Features: The bottle (20) is filled with CO2, and is linked to the closed regeneration circuit through a valve (27) and an auxiliary relief valve (25). The purification stage (28) has an initial filter (30) to retain the large impurities from the gas and an ion purifier (32), as a paddle washer in a watery medium, and a mol. sieve (34) for an anti-corrosive drying. After passing through the sieve (34), the fluid passes through a reduction purifier (36) and an oxidant purifier (38) to trap the carbonized and oxidized impurities by getters.  A further filter (40) gives a secondary filtration to the gas before the action of the biphase compressor (42). The biphase compressor (42) has condensers/reheaters (42A,42B) in tandem, connected by a feed circuit (44) to the entry opening (16) of the autoclave (12).