Process and device for coinjection molding multilayer products

Abstract

Multilayer products, such as vehicle trim panels, provided with an external skin layer and an internal core layer are co-injection molded by injecting external material (P) through a first plurality of points of injection ( 3 a - 3 c ) and injecting the core material (C) through a second plurality of points of injection ( 4 a - 4 g ), the points and nozzles of injection of one material being physically distinct from those of the other material.

1 . A process of co-injection molding multi-layer products, in which two or more materials (P,C; A,B) are injected from a plurality of injection points ( 3   a - 3   c ;  4   a - 4   g ) into the cavity ( 2 ) of a mold ( 1 ), characterized in that at least one of the said injection points only one of said materials is injected.  
     
     
         2 . A process according to  claim 1 , further comprising the steps of: 
 injecting a first material (P) through a first plurality of injection points ( 3   a - 3   c ) and injecting a second material (C) through a second plurality of injection points ( 4   a - 4   g ), the injection points of said second plurality being distinct from the injection points of said first plurality.    
     
     
         3 . A process according to  claim 1  or  2 , wherein said first (P) and/or said second (C) material is cascade injected.  
     
     
         4 . A process according to any previous claim, further comprising the steps of injecting a first material (P) from at least one first nozzle ( 3   a ); detecting when the said first material reaches pre-set positions and generating a corresponding signal; injecting a second material from at least one second nozzle ( 4   b ) on the basis of said signal or signals.  
     
     
         5 . A process according to any previous claim, wherein one of the materials injected (P) is prevented from flowing into pre-set zones ( 15 ) of the said mold.  
     
     
         6 . A process of co-injection molding a trim panel for motor-vehicle integral with retainers ( 13 ), studs ( 13   a ) and similar means of assembly, characterized by maintaining closed the portion of the mold ( 15 ) corresponding to the said means of assembly during the skin material injection step and allowing the entry into the said portions of the mold substantially to only the core material.  
     
     
         7 . A device for co-injection molding multi-layer products consisting of two or more materials, comprising a plurality of nozzles ( 3   a - 3   c ;  4   a - 4   g ) located in a corresponding plurality of distinct points on the same cavity ( 2 ) of a mold ( 1 ), characterized by at least one of the said nozzles being provided with means ( 5 - 10 ) of feeding only one of the said materials (P, C).  
     
     
         8 . A device according to  claim 7 , comprising at least one first nozzle ( 3 ) dedicated to the injection of a first material (P) and at least one second nozzle ( 4 ) dedicated to the injection of a second material (C).  
     
     
         9 . A device according to  claim 8 , comprising a first plurality of nozzles ( 3   a - 3   c ) for injecting said first material (P) and a second plurality of nozzles ( 4   a - 4   g ) for injecting said second material and means ( 22 , 23 ) for controlling in sequence the injection of the said first or second material from the corresponding plurality of nozzles ( 3   a - 3   c ;  4   a - 4   g ).  
     
     
         10 . A device according to  claim 8  or  9 , further comprising sensor means ( 23 ) for detecting when said first material (P) reaches preset positions and for generating a corresponding signal; and means of data processing ( 22 ) for receiving the said signal and for controlling the injection of said second material (C) from at least one second nozzle ( 4 ) on the basis of said signal or signals.  
     
     
         11 . A device according to any  claim 7  to  10 , wherein said nozzles ( 3 , 4 ) are provided with feeding channels ( 5 , 6 ) which extend through the wall of said mold ( 1 ) and with means ( 7 ) for heating the said channels.  
     
     
         12 . A device according to any  claim 7  to  11 , further comprising mechanisms ( 14 , 21 ;  18 , 19 ) for the temporary closure of pre-set portions ( 15 ;  20 , 20   a ) of the said mold cavity ( 2 ).  
     
     
         13 . A device according to  claim 12 , wherein said cavity is a cavity for an interior panel for motor vehicles and said preset portions are corresponding to means ( 13 , 13   a ) for the assembly of said panel.  
     
     
         14 . A multi-layer product comprising at least one portion provided with one external skin layer and one or more internal core layers, as obtainable with the process according to any of the claims from  1  to  6  and characterized by having a plurality of points of injection, at least one of the said points being dedicated to only one of the said materials.  
     
     
         15 . A multi-layer product according to  claim 14 , comprising some portions ( 13 , 13   a ) substantially consisting of core material alone.  
     
     
         16 . A multi-layer product comprising at least one portion provided with an external -skin layer and one or more internal core layers, characterized by comprising means of panel assembly such as retainers and studs made of core material.