Process for adjusting WVTR and other properties of a polyolefin film
AssigneeExxon Chemical Patents Inc.
InventorsKevin A. Brady, John H. Mackay
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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.
Claims18
A process for producing a breathable film having a WVTR greater than 200 g/m2/day at 38° C. and 90% relative humidity comprising a polyolefin and a filler, said process comprising:
- a) extruding a precursor film from a polyolefin blend comprising at least a first polymer composition and a second polymer composition and said filler, said filler having a concentration in a range of from about 16.5 to about 71.5 wt.% of said polyolefin blend;
- and
- b) passing said precursor film between at least one pair of interdigitating grooved rollers to stretch said precursor film, said rollers being heated to a temperature range of from 95° F. to 159° F., so that said precursor film contacting said rollers is heated and stretched to produce a breathable film having permanent elongation, said breathable film having a WVTR greater than 200 g/m2/day at 38° C. and 90% relative humidity, wherein said WVTR of said breathable film produced is higher when said rollers are heated to the highest temperature within said temperature range than said WVTR of said breathable film produced at the lowest temperature within said temperature range.
A process for producing a breathable film having a WVTR of at least 200 g/m2/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.% of said polyolefin blend, 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 to stretch said precursor film, said rollers being heated to a temperature range of from 95° F. to 159° F. so that said precursor film contacting said rollers is heated and stretched to produce said breathable film having permanent elongation, so that said breathable film has at least
- i) a WVTR in a range of from about 200 g/m2/day to about 10,000 g/m2/day at 38° C. and 90% relative humidity, wherein said WVTR of said breathable film produced is higher when said rollers are heated to the highest temperature within said temperature range than said WVTR of said breathable film produced at the lowest temperature within said temperature range,
- 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%.
Dependencies are inferred from the claim text.