Flexible tube, resistant to stress cracking and impermeable to water vapour

Abstract

The invention concerns a tube comprising a wall made of C 4 -C 10 linear ethylene-olefin copolymer or a mixture of C 4 -C 10 linear ethylene-olefin copolymer having a melt index ranging between 3 and 10 g/mn, and a density ranging between 0.880 g/cm 3 and 0.935 g/cm 3 inclusive. The skirt has a mid-height wall thickness ranging between 0.30 and 10 mm inclusive, and a length between 40 and 200 mm inclusive. Further-more, the skirt and the dispensing head are made in a single injection moulding operation in an injection mould. The invention is useful for making tube-like packages.

1 . A tube made up of a skirt and a distribution head, characterized by the fact that:—its wall is made of an ethylene-linear C 4 to 10  olefin copolymer or of a mixture of ethylene-linear C 4 to 10  olefin copolymers having a fluidity index (MFI) measured according to the ISO 1133 standard between 3 and 10 g/10 min, and preferably between 3.5 and 9 g/10 min inclusive, and a density between 0.880 g/cm 3  and 0.935 g/cm 3  inclusive, and preferably between 0.900 and 0.930 g/cm 3 , 
 by the fact that the skirt has a wall thickness at mid-height between 0.30 and 1.00 mm inclusive, and preferably between 0.35 and 0.95 mm inclusive, and a length between 40 and 200 mm inclusive,  
 and by the fact that  
 the skirt and the distribution head are manufactured in a single operation of injection in an injection mold, which has cavity insert ( 5 ) and insert ( 4 ), said insert having central part ( 8 ) whose free upper end ( 9 ) rests centered on cavity insert ( 5 ) during the phase of injection of the tube, from which it results that the tube is flexible, resistant to stress cracking and impermeable to water vapor.  
 
     
     
         2 . A tube according to  claim 1 , characterized by the fact that the mixture of ethylene-linear C 4 to 10  olefin copolymers is either a mixture of ethylene-linear C 4 to 5  olefin copolymers or a mixture of ethylene-linear C 6 to 10  olefin copolymers.  
     
     
         3 . A tube according to  claim 1  or  2 , characterized by the fact that the ethylene-linear C 4 to 10  olefin copolymer(s) is(are) ethylene-octene copolymer(s).  
     
     
         4 . A tube according to any one of the preceding claims, characterized by the fact that free upper end ( 9 ) of insert ( 4 ) has feed channels ( 10 ).  
     
     
         5 . A tube according to  claim 4 , characterized by the fact that said end ( 9 ) is in the shape of a reentrant cone, and by the fact that the angles α between channels ( 10 ) and the vertical axis of cavity insert ( 5 ) are less than 90°.  
     
     
         6 . A tube according to either of claims  4  and  5 , characterized by the fact that the total widths of channels ( 10 ) at their zones of connection (A) with the end piece of the head of the tube represent at least 15%, and preferably more than 25% of the perimeter of this end piece.  
     
     
         7 . A tube according to any one of  claims 4  to  6 , characterized by the fact that channels ( 10 ) have a width which increases from injection point ( 13 ) according to a centrifugal radial direction to their points of connection (A) with the end piece of the head of the tube.  
     
     
         8 . A tube according to any one of  claims 4  to  7 , characterized by the fact that the end piece of the distribution head has an annular zone of narrowing beyond the zone of connection (A) of channels ( 10 ) with the end piece of the head of the tube.  
     
     
         9 . A tube according to any one of the preceding claims, characterized by the fact that central part ( 8 ) of the insert of the injection mold is mobile, and by the fact that the upper wall of the head of the tube is injected after movement of mobile part ( 8 ) back a distance which is proportional to the desired wall thickness.  
     
     
         10 . A tube according to any one of the preceding claims, characterized by the fact that the fluidity index of the ethylene-linear C 4 to 10  olefin copolymer or mixture of these copolymers is between 5 and 10 g/10 min inclusive, and preferably between 5 and 9 g/10 min inclusive, and by the fact that the thickness of the wall at mid-height of the skirt is situated on the curve represented in FIG. 2, as a function of the length of the skirt, + or −0.05 mm, in order to obtain a tube with improved flexibility.  
     
     
         11 . A tube according to any one of  claims 1  to  9 , characterized by the fact that the fluidity index of the ethylene-linear C 4 to 10  olefin copolymer or mixture of these copolymers is between 3 and 6.5 g/10 min inclusive, and preferably between 3.5 and 6.5 g/10 min inclusive, and by the fact that the thickness of the wall at mid-height of the skirt is situated on the curve represented in FIG. 3, as a function of the length of the skirt, + or −0.05 mm, in order to obtain a tube with improved resistance to stress cracking, particularly in the presence of surfactant products.  
     
     
         12 . A tube according to any one of the preceding claims, characterized by the fact that the density of the ethylene-linear C 4 to 10  olefin copolymer or mixture of these copolymers is between 0.880 and 0.920 g/cm 3  inclusive, and preferably between 0.900 and 0.920 g/cm 3  inclusive, in order to obtain a tube with improved flexibility.  
     
     
         13 . A tube according to  claim 12 , characterized by the fact that the skirt has a length greater than or equal to 75 mm.  
     
     
         14 . A tube according to  claim 10  or  claim 12 , characterized by the fact that the fluidity index of the ethylene-linear C 4 to 10  olefin copolymer or mixture of these copolymers is between 5 and 10 g/10 min, and preferably between 5 and 9 g/10 min inclusive, and by the fact that the density of the ethylene-linear C 4 to 10  olefin copolymer or mixture of these copolymers is between 0.900 and 0.920 g/cm 3  inclusive.  
     
     
         15 . A tube according to  claim 12 , characterized by the fact that its wall is made of an ethylene-octene copolymer with a fluidity index between 5 and 6 g/ 10 min inclusive and a density equal to 0.919 g/cm 3 .  
     
     
         16 . A tube according to any one of  claims 1  to  11 , characterized by the fact that the density of the ethylene-linear C 4 to 10  olefin copolymer or mixture of these copolymers is 
 between 0.925 and 0.935 g/cm 3  inclusive for a thickness of the wall at mid-height of the skirt close to 0.45 mm,  
 between 0.920 and 0.930 g/cm 3  for a thickness of the wall at mid-height of the skirt close to 0.60 mm,  
 between 0.915 and 0.925 g/cm 3  for a thickness of the wall at mid-height of the skirt close to 0.75 mm,  
 in order to obtain a tube with reinforced impermeability to water vapor and with optimized flexibility as a function of the thickness of the wall at mid-height and of the length of the skirt.  
 
     
     
         17 . A tube according to  claim 16 , characterized by the fact that its wall is made of a mixture of: 
 a) 33 to 67 wt %, with respect to the total weight of the mixture, of an ethylene-linear C 4 to 10  olefin copolymer having a density between 0.900 and 0.920 g/cm 3  inclusive, and    b) 67 to 33 wt %, with respect to the total weight of the mixture, of an ethylene-linear C 4 to 10  olefin copolymer having a density between 0.920 and 0.935 g/cm 3  inclusive.    
     
     
         18 . A tube according to  claim 17 , characterized by the fact that its wall is made of a mixture of: 
 a) 33 to 67 wt %, with respect to the total weight of the mixture, of an ethylene-octene copolymer having a fluidity index between 3 and 6.5 g/10 min inclusive and a density between 0.900 and 0.920 g/cm 3  inclusive, and    b) 67 to 33 wt %, with respect to the total weight of the mixture, of an ethylene-octene copolymer having a fluidity index between 3 and 6.5 g/10 min inclusive and a density between 0.920 and 0.935 g/cm 3  inclusive,    in order to obtain simultaneously a tube with improved [sic; resistance to] stress cracking with reinforced impermeability to water vapor and optimized flexibility as a function of the thickness of the wall at mid-height and of the length of the skirt.    
     
     
         19 . A tube according to  claim 18 , characterized by the fact that its wall is made of a mixture of: 
 a) 33 to 67 wt %, with respect to the total weight of the mixture, of an ethylene-octene copolymer having a fluidity index between 5 and 6 g/10 min and a density equal to 0.919 g/cm 3 , and    b) 67 to 33 wt %, with respect to the total weight of the mixture, of an ethylene-octene copolymer having a fluidity index between 3 and 4 g/10 min and a density equal to 0.935 g/cm 3 .    
     
     
         20 . A tube according to  claim 19 , characterized by the fact that each ethylene-octene copolymer represents 50 wt % of said mixture.  
     
     
         21 . A tube according to  claim 18 , characterized by the fact that its wall is made of a mixture of: 
 a) 33 to 67 wt %, with respect to the total weight of the mixture, of an ethylene-octene copolymer having a fluidity index between 3 and 5 g/10 min and a density equal to 0.915 g/cm 3 , and    b) 67 to 33 wt %, with respect to the total weight of the mixture, of an ethylene-octene copolymer having a fluidity index between 3 and 4 g/10 min and a density equal to 0.935 g/cm 3 .