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Stretch blown or extrusion blown internal coated plastic container manufacture, involves pre-inflation with gas, followed by final inflation with ignited combustible gas containing substances to form barrier layer
Stretch blown or extrusion blown internal coated plastic container manufacture, involves pre-inflation with gas, followed by final inflation with ignited combustible gas containing substances to form barrier layer
A plastic preform is introduced into a tool and inflated with pressurized gas to create an intermediate container. Pressure in the container is then reduced to that of the surrounding environment. Barrier layer forming substances are added to a combustible gas which is introduced into the container and ignited to increase pressure and produce the final container shape. During ignition the layer-forming substances take the shortest path to the wall of the intermediate or final container to form an internal diffusion barrier. After reducing pressure in the intermediate container(1) a dry gas may be pumped in under pressure and then extracted. In a variation of the process a precursor layer comprising one or more layer forming substances in fluid, paste or melt form is applied onto the inside of the preform or the intermediate plastic container. Combustible gas burnt in the container forms a diffusion barrier layer. An independent claim is included for the process equipment which includes a gas igniter(3) extending into the intermediate or final containers with at least two ignition points(2,2', 21,22). Distribution of the ignition points over the length of the ignition lance depends on the container dimensions. Maximum spacing of individual ignition points from each other and from the adjacent wall is equal to the radius(41), but is preferably less than the radius length.
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