Method and apparatus for delivering sequential shots to multiple cavities to form multilayer articles

Abstract

Method and apparatus for sequentially delivering multiple shots of polymer material to a plurality of mold cavities to form multilayer articles. A first shot of greater than 50% of the total article weight of a first polymer material is simultaneously delivered to a plurality of mold cavities using, at each cavity, a chamber of predetermined volume that is prefilled with the first polymer material. A second shot of no greater than 10% of the total article weight of a second material is simultaneously delivered to all of the cavities beginning subsequent to the step of delivering the start of the first shot delivery step. The second shot of second material is delivered through a manifold channel that fluidly communicates with each cavity, and is injected to all cavities under pressure exerted by a source of the second material that is common to all of the plurality of cavities.

1 . A method of sequentially delivering multiple shots of polymer material to a plurality of mold cavities to form injection-molded multilayer articles, the method comprising:
 delivering a first shot, forming an exterior article layer of a predetermined volume of greater than 50% of the total article weight of a first polymer material, simultaneously to a plurality of mold cavities using, at each cavity, a chamber that is pre-filled with the first polymer material to deliver the predetermined volume of the first material separately to each mold cavity;   delivering a second shot, forming an interior article layer comprising up to 10% of the total article weight of a second material, simultaneously to all of the cavities beginning subsequent to the start of the first shot delivery step; and   delivering one or more additional shots of material to form the multilayer article;   wherein the second shot delivery step comprises injecting the second shot of the second material through a manifold channel that fluidly communicates with each cavity, the second shot being injected to all cavities under pressure exerted by a source of the second material that is common to all of the plurality of cavities.   
   
   
       2 . The method of  claim 1 , wherein the step of delivering one or more additional shots comprises delivering a third shot of a third material through a manifold channel that fluidly communicates with each cavity, the third shot being injected under pressure exerted by a source of the third material that is common to all of the plurality of cavities. 
   
   
       3 . The method of  claim 1 , wherein the second shot delivery step begins upon completion of delivery of the first shot to all of the plurality of cavities. 
   
   
       4 . The method of  claim 3 , wherein the method includes a step of delivering a third shot of polymer material simultaneously to all of the plurality of cavities subsequent to the step of delivering the second material to each cavity. 
   
   
       5 . The method of  claim 4 , wherein the first shot delivery step delivers a structural polymer material as the first polymer material. 
   
   
       6 . The method of  claim 5 , wherein the second shot delivery step delivers a barrier polymer material as the second polymer material. 
   
   
       7 . The method of  claim 6 , wherein the third shot delivery step delivers at least one of a structural and recycled material as the third polymer material. 
   
   
       8 . The method of  claim 1 , wherein the second shot delivers up to 8% of the total article weight. 
   
   
       9 . The method of  claim 1 , wherein the second shot delivers up to 5% of the total article weight. 
   
   
       10 . The method of  claim 1 , wherein the article is a preform. 
   
   
       11 . The method of  claim 10 , wherein the second shot forms a core layer in the preform. 
   
   
       12 . The method of  claim 11 , wherein a third shot seals the core layer in the preform. 
   
   
       13 . The method of  claim 10 , wherein the second shot forms two intermediate layers in the preform. 
   
   
       14 . The method of  claim 13 , wherein a third shot forms a central core layer in the preform. 
   
   
       15 . The method of  claim 14 , wherein a fourth shot seals the core and intermediate layers in the preform. 
   
   
       16 . The method of  claim 1 , wherein the weight of the second shot is selected to achieve a predetermined minimum height of the second shot interior layer in the articles formed in all cavities. 
   
   
       17 . The method of  claim 16 , wherein the article is a preform and the minimum height extends into a neck portion of the preform. 
   
   
       18 . The method of  claim 1 , wherein the second shot delivery step begins prior to completion of the first shot delivery step. 
   
   
       19 . The method of  claim 18 , wherein a third shot delivery step begins with or after start of the second shot delivery step and prior to completion of the first delivery step. 
   
   
       20 . The method of  claim 19 , wherein the second shot delivery step delivers a barrier polymer material. 
   
   
       21 . The method of  claim 20 , wherein the first shot delivery step delivers a structural polymer material. 
   
   
       22 . The method of  claim 21 , wherein the first and third shot delivery steps deliver the same structural polymer material. 
   
   
       23 . An injection molding apparatus for sequential delivery of multiple shots of polymer material to a plurality of mold cavities to form multilayer articles, the apparatus comprising:
 a plurality of mold cavities, each cavity fluidly communicating with first, second and third fluid delivery channels that respectively deliver first, second and third shots of first, second and third polymer materials sequentially to each mold cavity;   the first fluid delivery channel having separate channel portions individually fluidly communicating with a separate corresponding cavity, each channel portion having a separate fluid injection chamber that separately communicates with a corresponding cavity and separately contains and delivers a predetermined volume of greater than 50% of the total article weight of the first material during the first shot to a corresponding cavity;   the second fluid delivery channel fluidly communicating with a common source of injection of the second material, the common source of injection exerting a pressure that simultaneously delivers a volume of up to 10% of the total article weight as the second shot to all of the plurality cavities beginning subsequent to the start of a delivery of the first shot to each cavity.   
   
   
       24 . The apparatus of  claim 23 , wherein the common source of injection of the second material comprises an injection screw or a fluid chamber that commonly communicates with and delivers the second material simultaneously to each cavity. 
   
   
       25 . The apparatus of  claim 23 , wherein at least one or the other of the second channel and each cavity includes a heating mechanism for independent control of the temperature of the second material flowing into or through each cavity. 
   
   
       26 . The apparatus of  claim 23 , wherein each cavity fluidly communicates with a separate corresponding nozzle, each nozzle having first and second bores respectively communicating with the first and second channels for delivering the first and second shots respectively and sequentially to a corresponding cavity. 
   
   
       27 . The apparatus of  claim 23 , wherein each of the separate fluid injection chambers include a first drive mechanism, the common source of injection of the second material includes a second drive mechanism, and the apparatus includes a controller that directs the operation of the first and second drive mechanisms to effect initiation of delivery of the second shot upon completion of delivery of the first shot to all cavities.