Brief introduction of several main molding processes for heat-resistant PET bottles

Heat-resistant PET bottles, also known as hot-fill PET bottles, began their industrial production in the late 1980s. They have been widely used in foreign countries. In recent years, domestic production and applications have also gradually increased, and new production routes are still being developed. Among them. The production of heat-resistant PET bottles includes heat setting technology, material blending modification method, multi-layer co-blow molding, and liquid nitrogen cooling technology.
Through the heat-setting technology, the crystallinity of PET biaxially stretched blow-molded bottles can be increased, the oriented PET macromolecules can be shaped, and the heat-resistance of heat-set high-crystallinity PET biaxially stretched blow-molded bottles is significantly improved. Hot-fillable to 80°C or higher. Since the PET macromolecules are in the stretch orientation during the heat-setting process, large-sized PET spherulites may not be formed during heat-setting, so despite the increased degree of crystallinity of the heat-set PET bottles, the transparency remains high. .
The so-called liquid nitrogen cooling technology still performs heat setting treatment by directly contacting the stretch blow-molded bottle with the high-temperature mold, but the heat-set PET bottle is not made by lowering the mold temperature but by supplying liquid nitrogen to the PET bottle. The PET bottle was quenched and the cooled PET bottle was removed from the hot mold to give a product. With the liquid nitrogen cooling technology, the temperature of the blow mold can be as high as 200°C, thus having a better treatment effect. The obtained PET bottle can withstand hot water at 100°C and high temperature filling of 110°C salad oil just because of this The current high cost of this method and the problem of process stability control have yet to be solved and there is still a certain distance from industrial production.
With the high heat resistance of polyethylene naphthalate (PEN) and its good compatibility with PET resin, a certain amount of PEN resin is incorporated into the PET resin, and the PET biaxially stretch blow molded is used. Conventional equipment and processes can produce PET bottles with good heat resistance and can be used for hot filling. If they are heat-treated in the production process, they are more effective.
Using polyarylate (u-polymer) molding properties similar to PET and high heat resistance, a multi-layer preform of PET/polyarylate/PET structure was first prepared using a multi-layered method of polyarylate and PET. , Then the multi-layered PET bottle with PET as the main layer produced by biaxial stretch blow molding can meet the requirement of 85°C hot filling without heat setting treatment.
At present, practical heat-resistant PET bottles are still generally produced using a heat-setting process route. When we develop hot-fill PET bottles, we should focus on heat-setting methods.

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