Multi-layer container blow molding

Abstract

A method for making a multi-layer blow molded container ( 10 ), the multi-layer preform ( 10 ′) from which the container is blow molded, and the apparatus ( 53 ) for making a liner ( 24 ) of the preform utilizes thermoforming of a heated sheet ( 34 ) of resin. A vacuum is drawn within a vacuum enclosure ( 54 ) at a first surface of the heated sheet of resin ( 34 ) and a male vacuum mold ( 56 ) engages the other surface of the heated sheet of resin which has a concave shape to provide the forming in a manner that prevents crystallinity of the lower freestanding base of the multi-layer container that is ultimately blow molded from the preform ( 10 ′) made with the thermoformed liner ( 24 ).

What is claimed is:  
     
         1 . A method for making a multi-layer blow molded container, comprising: 
 drawing a vacuum within a confined area at a first surface of a heated sheet of resin which has a second surface that faces in the opposite direction as the first surface such that the first surface has a convex shape and the second surface has a concave shape;    thermoforming the heated sheet of resin by engagement at the concave second surface thereof with a male vacuum mold through which a vacuum is drawn to form the sheet of resin into a preform liner;    injection molding an outer layer of resin around the preform liner to provide a multi-layer preform; and    blow molding the multi-layer preform to provide the multi-layer blow molded container.    
     
     
         2 . A method for making a multi-layer blow molded container as in    claim 1    wherein the vacuum is drawn at the first surface of the heated sheet of resin before the male vacuum mold engages the second surface of the heated sheet of resin.  
     
     
         3 . A method for making a multi-layer blow molded container as in    claim 2    wherein the vacuum is maintained at the first surface of the heated sheet of resin after the initial engagement of the male vacuum mold with the second surface thereof and while the male vacuum mold is thereafter moved to form the heated sheet of resin.  
     
     
         4 . A method for making a multi-layer blow molded container as in    claim 3    wherein the movement of the male vacuum mold is terminated and the vacuum drawn at the first surface of the heated sheet of resin is terminated, and the vacuum is then drawn through the male vacuum mold to complete the forming of the preform liner to the shape of the male vacuum mold.  
     
     
         5 . A method for making a multi-layer blow molded container as in    claim 1    wherein the preform liner is trimmed from the rest of the sheet of resin prior to the injection molding of the outer layer of resin.  
     
     
         6 . A method for making a multi-layer blow molded container as in    claim 1    wherein the injection molding of the outer layer of resin is performed with sufficient resin such that the outer layer by weight constitutes at least 75% of the total weight of the container.  
     
     
         7 . A method for making a multi-layer blow molded container as in    claim 1    wherein the thermoforming is performed on a sheet of virgin resin and the injection molding is performed with post consumer recycled resin.  
     
     
         8 . A method for making a multi-layer blow molded container as in    claim 1    wherein the thermoforming is performed on a sheet of resin that is a barrier material.  
     
     
         9 . A method for making a multi-layer blow molded container as in    claim 1    wherein the thermoforming is performed on a sheet of resin that includes more than one layer to provide a multi-layer liner around which the outer layer of resin is injection molded.  
     
     
         10 . Apparatus for making a preform liner for use in blow molding, comprising: 
 a vacuum enclosure for drawing a vacuum within a confined area at a first surface of a heated sheet of resin which has a second surface that faces in the opposite direction as the first surface such that the first surface assumes a convex shape and the second surface assumes a concave shape; and    a male vacuum mold for thermoforming the heated sheet of resin by engagement therewith at the concave second surface thereof and having passages through which a vacuum is drawn to form the sheet of resin to the shape thereof to provide the preform liner.    
     
     
         11 . Apparatus as in    claim 1    further including an actuator for moving the vacuum enclosure into and out of sealed engagement with the heated sheet of resin.  
     
     
         12 . Apparatus as in    claim 1    further including an actuator for moving the male vacuum mold into engagement with the heated sheet of resin.  
     
     
         13 . Apparatus as in    claim 1    further including an actuator for moving the enclosure into and out of sealed engagement with the heated sheet of resin, and an actuator for moving the male vacuum mold into engagement with the heated sheet of resin.  
     
     
         14 . A multi-layer blow molding preform comprising: 
 a liner that is thermoformed by applying a vacuum to one surface of a heated sheet of resin to provide a dome shape thereto and by engaging the other surface thereof with a male vacuum mold through which a vacuum is drawn to form the final shape of the liner; and    an injection molded outer layer extending around the liner and constituting at least 75% by weight of the total preform weight, and the outer layer having a closed end that has reduced crystallinity by virtue of the manner in which the liner is formed by the vacuum applied to the one surface of the heated sheet of resin and the engagement of the other surface by the male vacuum mold.    
     
     
         15 . A multi-layer blow molding preform as in    claim 14    wherein the liner is virgin resin and the outer layer is post consumer recycled resin.  
     
     
         16 . A multi-layer plastic blow molding preform as in    claim 14    wherein the liner is a barrier material.  
     
     
         17 . A multi-layer plastic blow molding preform as in    claim 14    wherein the liner includes more than one layer.  
     
     
         18 . A multi-layer plastic blow molded container comprising: 
 an inner layer blow molded from a liner that is thermoformed by applying a vacuum to one surface of a heated sheet of resin to provide a dome shape thereto and by engaging the other surface thereof with a male vacuum mold through which a vacuum is drawn to form the final liner shape;    an outer layer that is blow molded from an injection molded outer layer around the liner; and    the container including a body portion and an upper dispensing end located above the body portion, and a lower freestanding base that closes the lower extremity of the body portion and has reduced crystallinity by virtue of the manner in which the liner is formed by the vacuum applied to the one surface of the heated sheet of resin and the engagement of the other surface by the male vacuum mold.