Thermoplastic impermeable hollow body

Abstract

Impermeable hollow body suitable as a fuel tank, made of thermoplastic material comprising at least one polyolefin and coated with a polyvinyl alcohol film impermeable to and insoluble in water owing to its crosslinking by a chemical agent and/or owing to the presence of an epoxy protective layer. Two-step process for impermeabilizing a hollow body made of thermoplastic material comprising at least one polyolefin. In the first step, the surface of the hollow body is firstly coated with a polyvinyl alcohol film and, in the second step, the polyvinyl alcohol film is made insoluble and impermeable by crosslinking the polyvinyl alcohol molecules by means of a chemical agent and/or by depositing an epoxy coating on the film.

1 . Hollow body made of thermoplastic material, comprising at least one polyolefin and coated on at least one of its faces and at least part of its surface with a polyvinyl alcohol film, characterized in that the film has a water permeability and a water solubility that are greatly reduced owing to the crosslinked state of its molecules caused by means of a chemical agent chosen from esterification and acetalization agents and/or by the presence of a protective layer that covers it at its interface with the atmosphere.  
     
     
         2 . Hollow body according to the preceding claim, characterized in that the protective layer is chosen from those comprising a flexible epoxy, a polyurethane varnish and an acrylic paint.  
     
     
         3 . Hollow body according to  claim 1 , characterized in that the chemical crosslinking agent is an esterification agent chosen from at least one of the following compounds: acetic acid, ethylhexyl glycidyl ether, long-chain organic acids or diacids and acid chlorides thereof, isocyanates and urea.  
     
     
         4 . Hollow body according to the preceding claim, characterized in that the esterification agent is acetic acid.  
     
     
         5 . Process for impermeabilizing a hollow body made of thermoplastic material comprising at least one polyolefin, characterized in that, in a first step, at least part of the surface of at least one of the faces of the hollow body is firstly coated with a polyvinyl alcohol film and, in a second step, the solubility in water of the film is reduced by crosslinking its molecules by means of a chemical agent and/or by depositing an epoxy coating on the film.  
     
     
         6 . Process according to the preceding claim, characterized in that the thermoplastic material also contains an adhesion promoter for the polyvinyl alcohol film and in that the adhesion reaction is activated by localized heat generation.  
     
     
         7 . Process according to the preceding claim, characterized in that the localized heat generation takes place by scanning the surface with electromagnetic radiation of wavelength from 500 to 15 000 nm chosen from infrared radiation and laser radiation.  
     
     
         8 . Process according to  claim 6 , characterized in that the localized heat generation takes place by using an argon or nitrogen plasma.  
     
     
         9 . Process according to any one of  claims 6  to  8 , characterized in that the adhesion promoter is selected from polyolefins grafted by an anhydride, acid peroxides and acid sites produced by a CO 2  plasma.  
     
     
         10 . Process according to any one of  claims 5  to  9 , characterized in that the step of coating the surface of the hollow body with polyvinyl alcohol is carried out by spraying the surface with an aqueous polyvinyl alcohol solution followed by drying for the purpose of evaporating the water of the solvent.