Process for molding multilayer articles

Claim 2

A PROCESS FOR MOLDING MULTI-LAYER PLASTIC ARTICLES FORMED FROM AT LEAST TWO THERMOPLASTIC MATERIALS WHICH COMPRISES THE STEPS OF: A. PROVIDING A FIRST INJECTION MOLD ABOUT A MANDREL; B. THEREAFTER INJECTING A FIRST HEAT-PLASTICIZED THERMOPLASTIC MATERIAL INTO SAID MOLD AND INTO SAID MANDREL TO FORM A FIRST PARISON; C. THEREAFTER WITHDRAWING SAID MANDREL AND FIRST PARISON FROM SAID FIRST INJECTION MOLD AFTER THE PARISON IS FORMED D. THEREAFTER COOLING AT LEAST A PORTION OF SAID PARISON ON WHICH A SECOND LAYER IS TO BE INJECTED, TO A TEMPERATURE BELOW THE NORMAL WORKING RANGE OF SAID FIRST THERMOPLASTIC MATERIAL IN ORDER TO PREVENT EROSION OT THE FIRST PARSION BY SUBSEQUENT INJECTION OF A SECOND LAYER THEREON; E. THEREAFTER PROVIDING A SECOND INJECTION MOLD ABOUT SAID MANDREL AND FIRST PARISON; F. THEREAFTER INJECTING A HEAT-PLASTICIZED THERMOPLASTIC MATERIAL ONTO SAID FIRST PARISON TO FORM A SECOND LAYER PARISON; G. THEREAFTER TRANSFERRING SAID SECOND LAYER PARISON ON SAID MANDREL AND FIRST PARISON; H. THEREAFTER BLOW MOLDING SAID SECOND LAYER PARISON IN SAID BLOW MOLD TO FORM AN ARTICLE; AND I. THEREAFTER REMOVING SAID ARTICLE FROM SAID MANDREL.

Claim 3

The process of claim 1, including the step, after the second layer parison is formed on said mandrel, of withdrawing said mandrel and second layer parison from said second injection mold and thereafter heating said second layer parison so that said first thermoplastic material and said second thermoplastic material are both at a temperature that is high enough for subsequent blow molding thereof.

Claim 4

The process of claim 1, wherein said first layer parison is cooled by a chill plate located at said cooling stage.

Claim 5

The process of claim 1, wherein said first layer parison is cooled by circulating fluid through said mandrel at said cooling stage.

Claim 6

The process of claim 1, wherein said first layer parison is cooled by refrigeration at said cooling stage.

Claim 7

The process of claim 1, wherein said first layer parison is air cooled at said cooling stage.

Claim 8

A process for molding multi-layer plastic articles formed from at least two thermoplastic materials which comprises the steps of: injecting a first heat-plasticized thermoplastic material onto a mandrel in an injection mold to form a parison; removing said injection mold after the parison is formed; thereafter cooling at least a portion of said parison on which another layer is to be injected, to a temperature below the normal working range of said first thermoplastic material in order to prevent erosion of the first parison by subsequent injection of another parison layer thereon; transferring said parison to at least One additional injection mold; injecting a heat-plasticized thermoplastic material onto said parison at each additional injection molding step to form a multi-layer parison; after each parison is formed removing the injection mold and cooling at least a portion of the parison formed between each injection step so that at least a portion of the top layer, prior to injection of the next injected layer, is at a temperature below the normal working range of the thermoplastic material from which the parison is formed in order to prevent erosion of the formed parison by subsequent injection of another parison layer thereon; transferring said multi-layer parison on said mandrel to a blow mold; blow molding said multi-layer parison in said blow mold to form an article; and removing said article from said mandrel.

Claim 9

A process for molding multi-layer plastic articles formed from at least two thermoplastic materials which comprises the steps of: injecting a first heat-plasticized thermoplastic material onto a mandrel in an injection mold to form a parison; removing said injection mold after the parison is formed; thereafter cooling at least a portion of said parison on which another layer is to be injected, to a temperature below the normal working range of said first thermoplastic material in order to prevent erosion of the first parison by subsequent injection of another parison layer thereon; transferring said parison to at least One additional injection mold; injecting a heat-plasticized thermoplastic material onto said parison at each additional injection molding step to form a multi-layer parison; after each parison is formed removing the injection mold and cooling at least a portion of the parison formed between each injection step so that at least a portion of the top layer, prior to injection of the next injected layer, is at a temperature below the normal working range of the thermoplastic material from which the parison is formed in order to prevent erosion of the formed parison by subsequent injection of another parison layer thereon; transferring said multi-layer parison on said mandrel to a blow mold; blow molding said multi-layer parison in said blow mold to form an article; and removing said article from said mandrel.