Microporous films having zoned breathability

Abstract

Breathable microporous films are provided having controlled regional breathability with high WVTR regions and thicker low WVTR regions. The zoned breathable microporous films are be made by selectively applying adhesive to the microporous film.

What is claimed is:  
     
       1. A method of making a film having regions of varied breathability comprising: providing a microporous film wherein said microporous film has a hydrohead of at least 50 mbars and a WVTR of at least 800 g/m 2 /24 hours; selectively applying adhesive to a portion of said film thereby creating first and second regions within said film, said second region having dimensions of at least 3 cm by 3 cm and wherein the porosity and the WVTR is decreased within said second region of the film relative to the WVTR of the first region. 
     
     
       2. The method of claim  1  wherein providing said microporous film comprises the steps of extruding a film comprising a thermoplastic polymer and a filler and stretching said film wherein a plurality of pores are created throughout said film. 
     
     
       3. The method of claim  2  wherein the application of adhesive decreases the WVTR of the second region by at least 25% and further wherein said second region has a minimum dimensions of 5 cm by 5 cm. 
     
     
       4. The method of claim  3  wherein said second region comprises from about 5% to about 75% of the area of said film. 
     
     
       5. The method of claim  4  wherein said thermoplastic polymer comprises a polyolefin polymer and wherein the basis weight of each of said first and second regions is below about 35 g/m 2 . 
     
     
       6. The method of claim  1  wherein said adhesive is selectively applied to said microporous film in a coat layer. 
     
     
       7. The method of claim  6  wherein said second region comprises between about 5% and 75% of the area of said film and further wherein said first and second regions of said microporous film each have a basis weight less than about 35 g/m 2 . 
     
     
       8. The method of claim  7  wherein providing said microporous film comprises the steps of extruding a film comprising a thermoplastic polymer and a filler and stretching said film wherein said stretched filled film has a basis weight less than about 35 g/m 2  and a WVTR in excess of 1500 g/m 2 /24 hours and further wherein said WVTR of said second region is decreased by at least 50%. 
     
     
       9. The method of claim  1  wherein said adhesive applied to said film comprises a first thickness and a second thickness wherein first, second, and third regions are created within said film with said third region having a WVTR intermediate to the WVTR of said first and second regions. 
     
     
       10. The method of claim  9  wherein said second region comprises from about 5% to about 75% of said film. 
     
     
       11. The method of claim  10  wherein said second and third regions are continuous. 
     
     
       12. The method of claim  11  wherein said film has a WVTR gradient. 
     
     
       13. The method of claim  4  further comprising the step of laminating a nonwoven web to said film prior to applying said adhesive.