Heat set method for oval containers

A method for making a partially crystalline, biaxially oriented heat set hollow plastic container from a hollow parison having an open end and a closed end comprising engaging the open end of a poly(ethylene) terephthalate parison which is at a temperature within its molecular orientation temperature range ranging between 80.degree. C. and 110.degree. C., enclosing the hot parison in a hot mold, the mold being at heat setting temperature ranging between 180.degree. C. and 230.degree. C., expanding the plastic parison within the hot mold by internal pressurization to induce biaxial orientation of the plastic parison and force the plastic parison into intimate contact and conformance with the hot mold and to maintain contact between the mold and the biaxially oriented container for a time ranging between 0.5 and 10 seconds sufficient to induce partial crystallization in the biaxially oriented container and form a partially crystalline, biaxially oriented heat set container, thereafter exhausting the blow molding fluid while continuously introducing a cooling fluid into the interior of the biaxially oriented container, said cooling fluid being of a type which changes state to cool by the latent heat of vaporization when introduced into the mold and having a positive pressure, the cooling fluid being selected from the group consisting of liquid carbon dioxide, liquid nitrogen, and combined sub-zero temperature air and water mist, and the cooling fluid cooling the container from the interior while the container is held in contact with the hot mold by the positive pressure of the cooling fluid while the hot mold is closed for a time ranging between 0.5 to 9.5 seconds sufficient that the average temperature of the container is reduced until the container is in a condition such that it will not expand under the positive pressure of the cooling fluid and such that it would collapse in the absence of the positive pressure of the cooling fluid, the positive pressure of the cooling fluid preventing the container from collapsing when the hot mold is opened, and opening the hot mold after a time ranging between 0.5 and 9.5 seconds after introduction of cooling fluid into the container is begun and thereafter cooling the container under the positive pressure of the cooling fluid for a predetermined period of time to continue the cooling of the container from the interior until the container is cooled sufficiently to prevent significant shrinkage and is self sustaining.

A method for making a partially crystalline, biaxially oriented heat set hollow plastic container from a hollow parison having an open end and a closed end comprising engaging the open end of a polyethylene terephthalate parison which is at a temperature within its molecular orientation temperature range, enclosing the hot parison in a partible hot mold having a separate mold base which is separate from the partible mold, the mold being at heat setting temperature of 180.degree. C. to 230.degree. C., expanding the plastic parison within the hot mold by internal pressurization to induce biaxial orientation of the plastic parison and force the plastic parison into intimate contact and conformance with the hot mold and to maintain contact between the mold and the biaxially oriented container for a time sufficient to induce partial crystallization in the biaxially oriented container and form a partially crystalline, biaxially oriented heat set container, exhausting the blow molding fluid while continuously introducing a cooling fluid into the interior of the biaxially oriented container, the cooling fluid being of a type which changes state when introduced into the mold, and having a positive pressure, and being selected from the group consisting of liquid carbon dioxide, liquid nitrogen, and combined sub-zero temperature air and water mist, and continuously exhausting the cooling fluid from the container to cool the container from the interior while the container is held in contact with the hot mold by the positive pressure while the hot mold is closed for a period of time sufficient that the average temperature of the container is reduced until the container is in a condition such that it will not expand under the positive pressure of the cooling fluid but would collapse in the absence of the positive pressure of the cooling fluid so that the positive pressure of the continuously flowing cooling fluid prevents the container from collapsing when the hot mold is opened, opening the hot mold and maintaining engagement of the mold base with the base of the container and thereafter continuing to cool the container from the inside while preventing the container from collapsing when the mold is opened with partial pressure of the cooling fluid until the container is self sustaining.

A method for making a partially crystalline, biaxially oriented heat set hollow plastic container from a hollow parison having an open end and a closed end comprising engaging the open end of a polyethylene terephthalate parison which is at a temperature within its molecular orientation temperature range, enclosing the hot parison in a hot mold, the mold being at heat setting temperature of 180.degree. C. to 230.degree. C., expanding the plastic parison within the hot mold by internal pressurization to induce biaxial orientation of the plastic parison and force the plastic parison into intimate contact and conformance with the hot mold and to maintain contact between the mold and the biaxially oriented container for a time sufficient to induce partial crystallization in the biaxially oriented container and form a partially crystalline, biaxially oriented heat set container, thereafter exhausting the blow molding fluid while continuously introducing a cooling fluid into the interior of the biaxially oriented container, the cooling fluid being of a type which changes state to cool by the latent heat of vaporization, the cooling fluid having a positive pressure when introduced into the mold and into the biaxially oriented container, the cooling fluid being selected from the group consisting of liquid carbon dioxide, liquid nitrogen and combined sub-zero temperature air and water mist, and the cooling fluid cooling the container from the interior while the container is held in contact with the hot mold by the positive pressure of the cooling fluid while the hot mold is closed for a period of time of 0.5 to 9.5 seconds until the average temperature of the container is reduced until the container is in a condition such that it will not expand under the positive pressure of the cooling fluid but would collapse in the absence of positive pressure of the cooling fluid, the positive pressure of the cooling fluid preventing the container from collapsing when the hot mold is opened, and opening the hot mold and thereafter cooling the container under the positive pressure of the cooling fluid for a predetermined period of time to cool the container from the interior until the container is cooled sufficiently to prevent significant shrinkage and to obtain a self sustaining container.