Apparatus and method for producing a polyolefinic transpiring film
AssigneeNuova Pansac S.P.A.
InventorsFabrizio Lori, Graziano Bortoletto
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Abstract
The invention relates to a method and a plant for producing polyolefinic transpiring films by means of bubble extrusion of a LLDPE and filler mix, flattening of the extruded tube to obtain a double layer flat film and transversely and/or longitudinally stretching of the double layer flat film.
Claims16
A method for producing a polyolefinic double layer transpiring film which allows vapour and air to pass therethrough while being impermeable to liquids, said method comprising the steps of:
- bubble extruding a mix of a filler, which filler imparts transpirability upon stretching, and a polyolefin to form a tube;
- flattening the tube to obtain a double layer flat film having two layers;
- heating the double layer flat film to its softening temperature, wherein said heating of the double layer flat film to its softening temperature comprises first heating by conduction and then heating by irradiation;
- compressing the heated double layer flat film to unite the layers of the double layer film and thereby form a double layer laminate;
- then cooling the double layer flat film having united layers to a temperature between 8–30° C.;
- and then
- transversely and longitudinally stretching the cooled double layer flat film to impart transpirability to the double layer flat film.
An apparatus for producing a stretched double layer polyolefinic transpiring film which allows vapour and air to pass therethrough while being impermeable to liquids, said apparatus comprising, arranged successively in series;
- a bubble extruder for extruding a tube;
- a first calender for flattening the extruded tube to obtain a double layer flat film;
- heating means for heating the double layer flat film to its softening temperature, said heating means comprising, arranged in series, conductive heating means for heating the double layer flat film by conduction and radiant heating means for heating the double layer flat film by irradiation;
- a second calender for compressing the heated double layer flat film to unite the layers of the double layer flat film;
- cooling means for quickly cooling the double layer flat film with united layers to a temperature between 8–30° C.;
- and
- stretching means for transversely and longitudinally stretching the double layer flat film to impart transpirability to the double layer flat film.
Dependencies are inferred from the claim text.