Process for adjusting WVTR and other properties of a polyolefin film

Abstract

A process for rendering films, film composites, and articles made therefrom less resistant to passage of water vapor by passing a filled precursor film or film composite through the nip of interdigitating grooved rollers. The films or film composites are generally formed using a precursor film of a film forming polyolefin or polyolefin blend, with a relatively high filler loading and optionally an elastomer. A process is disclosed for making diapers or other disposable items where a relatively high water vapor is coupled with a resistance to liquid strikethrough. In one embodiment of the invention, the interdigitating grooved rollers are maintained in a temperature range of from about 91° F. to about 159° F.

We claim:  
     
         1 . A process for producing a film having a WVTR greater than 200 g/m 2 /day at 38° C. and 90% relative humidity comprising a polyolefin and a filler, said process comprising: 
 a) extruding a precursor film from said polyolefin blend comprising said first and said second polymer compositions and said filler, said filler concentration being in a range of from about 16.5 to about 71.5 wt. %; and  
 b) passing said precursor film between at least one pair of interdigitating grooved rollers, said rollers being maintained in a temperature range of from about 91° F. to about 159° F., so that said film is heated to produce said film having a WVTR greater than 200 g/m 2 /day at 38 ° C. and 90% relative humidity.  
 
     
     
         2 . The process of    claim 1    wherein said polyolefin is selected from the group consisting of polypropylene, polyethylene, ethylene polar comonomer polymers, ethylene α-olefin copolymers and combinations thereof.  
     
     
         3 . The process of    claim 1    further comprising cooling said precursor film to a temperature of at least 75° F. or less after step a) but prior to step b).  
     
     
         4 . The process of    claim 1    wherein said rollers are maintained in a temperature range of from about 95° F. to about 159° F.  
     
     
         5 . A process for producing a film having a WVTR of at least 200 g/m 2 /day at 38° C. and 90% relative humidity comprising a polyolefin blend, said polyolefin blend having at least a first and a second polymer composition, and a filler, said process comprising: 
 a) extruding a precursor film from said polyolefin blend comprising said first and said second polymer compositions and said filler, said filler concentration being in a range of from about 16.5 to about 71.5 wt. %, wherein, 
 i) said first polymer composition is a polypropylene and  
 ii) said second polymer composition is selected from the group consisting of elastomers, plastomers, styrenic block copolymers, ethylene-maleic anhydride copolymers, ethylene ethyl acetate, and combinations thereof, and  
 b) passing said precursor film between at least one pair of interdigitating grooved rollers so that said film has at least  
 i) a WVTR in a range of from about 200 g/m 2 /day to about 10,000 g/m 2 /day at 38° C. and 90% relative humidity,  
 ii) a dart drop impact in a range of from about 100 grams to about 300 grams, and  
 iii) an elongation selected from the group consisting of machine direction, transverse direction and combinations thereof in a range of from about 150% to about 550%.  
 
 
     
     
         6 . The process of    claim 5    wherein said polypropylene is selected from the group consisting of random copolymer polypropylene, impact copolymer polypropylene, polypropylene produced with a metallocene catalyst and combinations thereof.  
     
     
         7 . The process of    claim 5    wherein said elastomer is selected from the group consisting of styrene-isoprene-styrene, styrene-butadiene-styrene, styrene-ethylene -butylene-styrene, ethylene alpha-olefin rubber, ethylene propylene diene monomer rubber, butyl rubber, vulcanized natural rubber and combinations thereof.  
     
     
         8 . The process of    claim 5    wherein said plastomer is at least one ethylene α-olefin copolymer selected from the group consisting of ethylene α-olefin copolymers wherein the α-olefin comonomer is selected from the group consisting butene, pentene, hexene, and combinations thereof.  
     
     
         9 . The process of    claim 5    wherein a non-woven polymeric material is laminated to said precursor film, after step a) but prior to step b), using a lamination means selected from the group consisting of adhesive, heat, ultrasonic radiation and combinations thereof.  
     
     
         10 . The process of    claim 5    wherein said interdigitating grooved rollers are positioned in a direction selected from the group consisting of machine direction, transverse direction and combinations thereof.  
     
     
         11 . The process of    claim 5    further comprising forming said film of step b) into a fabricated article selected from the group consisting of diapers, adult incontinence devices, surgical apparel, surgical drapes, sports apparel, industrial apparel, house wrap, filtration media and controlled atmosphere packaging.