Tube with head made of multilayer materials and manufacturing process

Abstract

A method for manufacturing a tube head including the steps of using a co-injection head having an annular outlet and which can be supplied simultaneously with a thermoplastic structure material A and a thermoplastic barrier material B is disclosed.

1 . Plastic tube head ( 2 ), designed to be assembled with a skirt ( 3 ) to form a tube ( 1 ), comprising a typically threaded orifice ( 20 ) and a shoulder ( 21 ) comprising an annular connection part ( 22 ) to the said skirt, characterized in that, 
 a) the said head ( 2 ) is formed by co-injection and comprises a thermoplastic multilayer material comprising an internal layer ( 24 ) and an external layer ( 23 ) in structure material A, and at least one inner layer ( 25 ) in barrier material B,    b) the said inner layer ( 25 ) is encased by the said internal layer ( 24 ) and external layer ( 23 ), including at the ends of the said head where the said internal and external layers are joined together in one layer, the distances “e” and “e′” between each of the ends ( 250 ,  251 ) of the said inner layer and the corresponding end of the said head being between 0.02 mm and 5 mm, such that the said inner layer made of a barrier material ( 25 ) extends over the greatest possible height, while its ends remain encased or encapsulated by the junction of the said internal layer ( 24 ) and external layer ( 23 ).    
   
   
       2 - 16 . (canceled)  
   
   
       17 . Process for manufacturing a tube head comprising followings steps: 
 a) using a co-injection head which has an annular outlet and which can be supplied simultaneously with a thermoplastic structure material A and a thermoplastic barrier material B,    b) in the time elapsing from 0 to τ, placing a mold having an annular cavity near the co-injection head such as said annular outlet is in communication with said cavity;    c) co-injecting said materials in said cavity during a time elapsing from τ to T 0 , by carrying out said following steps: 
 c1) injecting the structure material A from T to (τ+t),  
   c2) co-injecting structure material A and barrier material B between (τ+t) and (T 0 −t′) 
 c3) injecting the structure material A from (T 0 −t′) to T 0 , until the cavity is filled;  
   d) maintaining the injection pressure on the structure material A for an additional time T′, which is equal to at least T 0 , in order to stabilize the quantity of injected structure material;    e) opening the mold thus filled and extracting the molded piece that comprises an inner layer of said barrier material B, the ends of the said inner barrier being entirely encapsulated by said structure material A;    f) eliminating the injection gate.    
   
   
       18 . A process according to  claim 17 , wherein the annular cavity of the mold is formed by the cooperation of a die and a punch.  
   
   
       19 . A process according to  claim 17 , wherein the cavity of the mold has the shape of the tube head to be manufactured.  
   
   
       20 . A process according to  claim 19 , wherein elapsed times t and t′ are chosen such that the ends of the inner layer of material B are separated from the external medium by the structure material A, which has a thickness of at least 20 μm.  
   
   
       21 . A process according to  claim 17 , wherein: 
 T 0  is between 0.1 s and 1 s    T 0 +T′ is between 1 s and 3 s    t is between 0.01 T 0  and 0.1 T 0     t′ is between 0.02 T 0  and 0.2 T 0     
   
   
       22 . A process for manufacturing a collapsible tube comprising a tube head and a collapsible skirt, wherein said head is manufactured by the process of  claim 1  and welded on one end of said skirt.  
   
   
       23 . A process according to  claim 22 , wherein forming the said tube head and welding it on the end of the skirt are simultaneous.  
   
   
       24 . A process according to  claim 23 , wherein a plurality of n tube heads are manufactured simultaneously, n being typically between 2 and 16, by using n injection heads supplied with structure material A by means of an extruder for material A and a distributor with n arms, and supplied with barrier material B by means of an extruder for material B and a distributor with n arms.  
   
   
       25 . A process according to  claim 24 , wherein a turntable having a vertical axis of rotation, divided into p sectors, p being typically equal to 8, and indexed in rotation with an angular pitch equal to 360°/p, is rotated to successively bring each sector in front of at least three fixed stations, at different angular positions with respect to the said axis of rotation, that is a first skirt loading station on the said turntable sector, then a second station for co-injection molding of the said heads and simultaneous welding of said heads on the end of the skirts, and a third section at which the tubes are unloaded from the said turntable, the residence time of a sector facing each of the fixed stations being equal to the sum To+T′, preferably varying from 1 second to 3 seconds, and the time interval between two fixed stations being determined particularly by the angular offset between these two fixed stations.  
   
   
       26 . Process according to  claim 25 , wherein the angular offset α between the co-injection station and the unloading station, typically equal to 180°, is such that the tube cooling time between the co-injection station and the unloading station is approximately equal to (To+T′).(p/360°).α.  
   
   
       27 . A device for the manufacturing of tube heads or tubes, using the co-injection process according to  claim 19 , comprising 1 to n co-injection heads according to the number n of tube heads to be manufactured simultaneously in 1 to n corresponding cavities, wherein each of said co-injection heads comprises: 
 a) a co-injection nozzle, which is supplied with structure material A and barrier material B;    b) an annular outlet leading to the cavity of the mold, which may be supplied alternatively with material A via an external channel and with an annular flux of material A/B/A via the opening of said co-injection nozzle supplied with materials A and B, and    c) means for ensuring the programmed injection of material A or of said annular flux A/B/A/ into said cavity at predetermined times in the production cycle.    
   
   
       28 . Device according to  claim 27 , wherein said means for ensuring said programmed injection is a slide valve.  
   
   
       29 . Device according to  claim 28 , wherein said slide valve has 4 positions: 
 I. closing of opening of said co-injection nozzle and said external channel: in said position, no material flows;    II. placing said external channel in communication with the cavity of the mold: in said position, material A is injected into said cavity;    III. placing said opening of said co-injection nozzle in communication with said cavity: in said position, said annular flux of multilayer material A/B/A/ is injected into said cavity;    IV. placing the opening of said co-injection nozzle in communication with the outside for an optional draining of said opening.