Material with a high degree of impermeability to gases and a method for the production thereof

Abstract

From a general point of view, the present invention relates to a material which has a high degree of impermeability to gases, especially to atmospheric oxygen, and which is particularly suitable for the manufacture of containers for easily oxidizable foods or beverages such as, for example, beer, milk, “soft drinks”, and fruit juices. In particular, the present invention relates to a method for the preparation of polymeric material with a high degree of impermeability to gases, the method comprising the step of subjecting the polymeric material to a high-pressure treatment.

1 . A method for the preparation of polymeric material with increased impermeability to gases, particularly to oxygen, the meth comprising the step of subjecting the polymeric material to hydrostatic pressure.  
     
     
         2 . A Method according to  claim 1  in which the hydrostatic pressure step is carried out at a pressure greater than 500 bar.  
     
     
         3 . A method according to  claim 1  in which the hydrostatic pressure step is carried out at a pressure of between 4000 bar and 9000 bar.  
     
     
         4 . A method according to  claim 1  in which the hydrostatic pressure step is carried out at a pressure of between 5000 bar and 7000 bar.  
     
     
         5 . A method according to any one of  claims 1  to  4  in which temperatures of between −10° C. and 60° C. are applied to the polymeric material.  
     
     
         6 . A meth according to  claim 5  in which temperatures of between 10° C. and 30° C. are applied to the material.  
     
     
         7 . A method according to any one of  claims 1  to  6  in which the polymeric material reaches temperatures of between 0° C. and 80° C.  
     
     
         8 . A method according to any one of  claims 1  to  7  in which the hydrostatic pressure treatment has a duration of between 1 second and 2 minutes.  
     
     
         9 . A method according to any one of  claims 1  to  8 , the method comprising the steps of: 
 a) inserting the polymeric material in a chamber for treatment at hydrostatic pressure,  
 b) filling the chamber for treatment at hydrostatic pressure with a substantially incompressible fluid such as water or oil,  
 c) applying a predetermined temperature to the substantially incompressible fluid,  
 d) raising the pressure in the chamber for treatment at hydrostatic pressure to a predetermined level and maintaining this hydrostatic pressure for a predetermined period of time,  
 e) reducing the pressure to atmospheric pressure, removing the substantially incompressible fluid, and extracting the polymeric material.  
 
     
     
         10 . A method according to  claim 9  in which the hydrostatic pressure treatment is implemented by means of a cycle of compressions/decompressions.  
     
     
         11 . A method according to any one of  claims 1  to  10  in which the polymeric material is a thermoplastic material, a synthetic fibre, or a non-woven fabric.  
     
     
         12 . A method according to  claim 11  in which the thermoplastic material is a single-layer or multi-layer, flexible or semi-rigid material closed of polymers, preferably selected from low-density and high-density polyethylene, polypropylene, PEN, EVOH, polyethylene terephthalate, copolymers and blends thereof, possibly additionally including nylon and/or scavangers and, most preferably, is a single layer of polyethlene terephthalate.  
     
     
         13 . A method according to  claim 11  or  claim 12  in which the polymeric material has previously undergone a deformation outside its elastic range.  
     
     
         14 . A method according to  claim 13  in which the polymeric material has undergone softening by heating immediately prior to the deformation outside its elastic range.  
     
     
         15 . A method according to  claim 13  or  claim 14  in which the deformation outside the elastic range is a deformation caused by a blowing, stretching, pressing, or injection-moulding process.  
     
     
         16 . A polymeric material obtainable by the method outlined in  claims 1  to  15 , wherein thi said polymeric material previously undergone a deformation outside its elastic range and has then be subjected to a hydrostatic pressure treatment at a pressure greater that 500 bar.  
     
     
         17 . A polymeric material according to  claim 16  in which the material has a microscopic structure which is substantially compact or with compacted or reduced spaces between the fibres.  
     
     
         18 . A polymeric material according to  claim 16  or  claim 17  in which the material is a thermoplastic material, a synthetic fibre, or a non-woven fabric.  
     
     
         19 . A polymeric material according to  claim 18  in which the thermoplastic material is a single-layer or multi-layer, flexible or semi-rigid material composed of polymers, preferably selected from low-density and high-density polyethylene, polypropylene, PEN, EVOH, polyethylene terephthalate, copolymers and blends thereof, possibly additionally including nylon and/or scavangers and, most preferably, is a single layer of polyethylene terephthalate.  
     
     
         20 . A polymeric material according to any one of  claims 16  to  19 , in which the polymeric material has undergone softening by heating immediately prior to the deformation outside its elastic range.  
     
     
         21 . An article comprising at least one layer of the polymeric material according to any one of  claims 16  to  20 .  
     
     
         22 . An article according to  claim 21 , the article being a container.  
     
     
         23 . An article according to  claim 22  in which the container is a container for liquids, in particular, a bottle including the closure.