The Dow Chemical Company

Kenneth J Cleereman

Walter J Schrenk

Ralph E Ayres

Ritchie A Wessling

Norbert L Bradley

John W McLaren

Alan F Burmester

Eckel R Lane

O Carl Raspor

Grant W Cheney

An improved, essentially scrap-free, solid-phase process for making thermoplastic articles directly from resinous powder. The process can be particularly advantageous to forming large parts from thermoplastic resinous powders. The method essentially comprises taking resinous powder, briquetting the powder, sintering the briquette, repressing the powder in a warm state and then shaping the briquette into a preform or a blank which can then be thermoformed into a resulting container or other product, assuming the blank itself is not the desired end product. Alternatively, sintering can take place after repressing with preheating of the briquette prior to the repressing step.

Method of forming blanks for the solid-phase forming of thermoplastic

A scrap-free, substantially solid phase, relatively low temperature economical process for rapidly making plastic articles from resinous powders wherein the resultant articles can comprise various polymers including oriented polymers; polymers with a high practical heat distortion temperature; expanded polymers; ultra high molecular weight polymers; blended structures of two or more materials; or multilayered structures. The resinous powders are initially compressed into briquettes, which briquettes are heated to a temperature in the range from about the alpha transition temperature to less than the melting point or melt temperature of the polymer therein to both somewhat soften and sinter the briquettes. The sintered briquettes are forged under conditions which permit substantial plug flow deformation into preforms whereby fusion of the sintered resin powder particles occurs. The resulting preforms can then be cooled for later thermoforming or can be directly transferred to thermoforming molds for forming into desired shaped articles. It is also possible to form at least shallow cans, lids or other items directly in the forging step.

Scrapless forming of plastic articles

Process for forming a plastic article

A method for manufacturing blown articles is disclosed wherein the article is manufactured from a parison having a high degree of multi-axial orientation. The method permits molecular orientation within the parison to be superposed with orientation imparted during the blowing step, whereby a blown article of greatly improved properties is manufactured.

Method of preparing blown thermoplastic articles having multiaxial

An injection mold cavity is sealed at the mold parting line using a highly exact, narrow annular gap or clearance which restricts flash through of the molten plastic. The seal is designed for molds having a rotatable pin and comprises a fixed seating ring which seats with the mold cavity element, and a journable seal ring having a precisely machined seal face which is narrowly spaced from the lip of the mold cavity and defines the gap dimension with the assistance of the seating ring. The rings float at a unit against a resilient component which controls the seating pressure of the assembly independently of the clamping force of the mold. The foregoing components are unitized within a clamp ring under a preload compressive force with the critical gap dimension precisely built into the unit. Variable compressive loading of the seal assembly in the injection mold is counteracted by the resilient component and floating motion of the seal and seating rings whereby highly exact preciseness can be obtained in the critical gap dimension over prolonged operating periods.

Injection mold

Apparatus for rapidly making thermoplastic containers wherein the resultant containers can, if desired, be multilayered for vapor or gas barrier or other reasons, or be oriented for toughness and improved stress crack resistance. The apparatus takes a measured amount of thermoplastic material which is lubricated, heated and forged into a desired shape preform with a predetermined lip configuration. The center portion of each said preform is maintained at a forming temperature while the peripheral portion thereof is clamped and rapidly brought below the softening point of the plastic resin. The preform can then be immediately thermoformed into a container having a desired shape and size, and cooled. If desired, the preform can be forged, cooled and recovered for a subsequent thermoforming operation or can be a finished article itself.

A scrap free process for rapidly making thermoplastic containers wherein the resultant containers can, if desired, be multilayered for vapor or gas barrier or other reasons, or be oriented for toughness and improved stress crack resistance. The containers can be formed from multilayered or homogeneous plastic sheets wherein a relatively thin thermoplastic blank is provided. This blank is lubricated, heated and forged into a desired shape preform with a predetermined lip configuration. The center portion of each said preform is maintained at a forming temperature while the peripheral portion thereof is rapidly brought below the softening point of the plastic resin. The preform is then immediately thermoformed into a container having a desired shape and size, and cooled. If desired, the preform can be forged, cooled and recovered from a subsequent thermoforming operation.

Growing community of inventors

Midland, MI, United States of America

Kenneth J Cleereman