Process and plant for making a breathable, elastic polyolefin film

1 . A process for preparing breathable, elastic polyolefin films, including the steps of:

blow molding a mixture of olefins, styrenic thermoplastic elastomers and filler to facilitate the generation of porosity by stretching;

squeezing the tubular to obtain a flat film composed of two superposed layers;

heating the flat film to the softening point;

pressing the flat film in order to join the two original layers together;

cooling the flat film to a temperature of 8 to 30° C.;

stretching the film in the transverse and/or longitudinal directions to make it breathable.

2 . A process as claimed in claim 1 , further comprising the steps of:

coupling a separating material to the breathable elastic film;

winding the film coupled with the separating material, into a roll.

3 . A process as claimed in claim 1 or 2 , wherein said mixture comprises 30% to 70% by weight fillers, 10% to 40% by weight styrenic thermoplastic elastomers and 10% to 50% by weight olefins.

4 . A process as claimed in claim 1 , 2 or 3 , wherein said separating material has a continuous structure.

5 . A process as claimed in claim 4 , wherein said separating material is a paper or nonwoven fabric film.

6 . A process as claimed in claim 5 , wherein said paper or nonwoven fabric film is coupled to said extruded film by an adhesive.

7 . A process as claimed in claim 5 , wherein said paper or nonwoven fabric film is coupled to said extruded film ( 11 ) without using adhesives.

8 . A process as claimed in claim 1 , 2 or 3 , wherein said separating layer has a discontinuous structure.

9 . A process as claimed in claim 8 , wherein said separating layer is made of a powdered material.

10 . A plant for producing a breathable elastomeric polyolefin film, including, in succession:

a blow molding extruder ( 1 ) for extruding a tubular ( 11 );

a calender ( 2 ) for squeezing the extruded tubular ( 11 ) fed from the blow molding extruder in order to obtain two superposed layers;

means ( 3 , 4 ) for heating the squeezed extruded tubular film to the softening point;

a calender ( 5 ) to press the film that was previously heated to the softening point in order to join the two original layers together;

means ( 5 ) for cooling the compressed film to a temperature of 8 to 30° C.;

means ( 6 , 8 ) for stretching the film ( 11 ) in the transverse and/or longitudinal directions;

means for stretch stabilization by cooling the extruded film ( 11 );

means ( 12 , 13 , 14 ) for coupling the extruded film ( 11 ) to a separating material;

a reeling machine ( 9 ) for winding the film ( 11 ) coupled to said separating material into a roll ( 18 ).

11 . A use of a mixture of olefins, styrenic thermoplastic elastomers and filler to produce a breathable elastic film wherein the amount of styrenic thermoplastic elastomers is of 20% to 30% by weight, the amount of filler is of 30% to 70% by weight and the amount of olefins is of 27% to 34% by weight.