P
USH2000HExpiredUtilityPatentIndex 89

Method for making polyolefin/filler films having increased WVTR

Assignee: EXXON CHEMICAL PATENTS INCPriority: Aug 1, 1996Filed: Aug 1, 1996Granted: Nov 6, 2001
Est. expiryAug 1, 2016(expired)· nominal 20-yr term from priority
Inventors:MIDDLESWORTH JEFFREY ALANBRADY KEVIN ARTHUR
B29C 55/005B32B 38/0032C08J 5/18B32B 2305/20B29K 2023/0641B32B 2307/31B32B 37/153B32B 27/32B32B 27/12B32B 5/022B29K 2023/06B29K 2023/083B32B 2038/0028C08J 2323/08B32B 27/20B32B 38/06B29K 2105/16B32B 38/0036
89
PatentIndex Score
39
Cited by
15
References
23
Claims

Abstract

Films, made of polyethylenes and filers, and articles made therefrom greater WVTR than previously available films based on conventional Zeigler-Natta based polyethylenes. The polyethylenes are produced in a metallocene-catalyzed production process. The films may be made by a cast film process, and may be made in widely varying filler content, generally polyethylene to filler ratios of 30/70 to 70/30. The metallocene based polyethylenes when combined with filler also permit the extrusion of thinner films leading to lighter weight and softer films. The m-polyethylenes utilized for making such films typically have a Composition Distribution Breadth Index above 50%, a M w /M n below 3, and a M z /M w below 2. The films may be used advantageously in composite structures with fabrics (either woven or non-woven) to fabricate such articles as house-wrap

Claims

exact text as granted — not AI-modified
We claim:  
     
       1. A method of preparing a laminate having good water vapor transmission rate (WVTR), said laminate including a filled film and a fabric bonded thereto, said filled film including an effective amount of filler and having a water vapor transmission rate at least 10% higher than the WVTR described by the equation: WVTR=−10,900+320(filler weight %) and the fabric having an elongation less than 30%, an Elmendorf tear strength of at least 300 g, and a breakload of at least 15 lb./in., the method comprising the steps of: 
       (a) stretching said film to form a stretched film; and  
       (b) bonding said stretched film to said fabric, to form said laminate;  
       (c) wherein said film is a polyethylene film including a metallocene catalyzed polyethylene having a M w /M n <3, and a composition distribution breadth index greater than 60%.  
     
     
       2. The method of claim  1  wherein said lamination is selected from the group consisting of heat lamination, adhesive lamination, extrusion lamination, mechanical bonding and combinations thereof. 
     
     
       3. A process of making a housewrap, comprising: 
       a) mixing a polyolefin with a filler to form a polyolefin/filler mixture;  
       b) extruding a film from the polyolefin/filler mixture to form an extruded filled film;  
       c) melt embossing the extruded filled film to form an embossed film having a pattern of different film thicknesses;  
       d) stretching the embossed film to impart greater water vapor transmission rate; and  
       e) melt bonding the stretched film to a nonwoven fabric comprising crosslaminated fibers at a temperature and pressure sufficient to bond the fabric and film to form a breathable laminate, wherein said polyolefin includes at least a majority of a metallocene catalyzed polyethylene having a M w /M n  <3, and a composition distribution breadth index above 60 percent; and wherein the breathable laminate has a water vapor transmission rate at least 10% higher than the WVTR described the equation: WVTR=−10,900+320 (filler weight %).  
     
     
       4. The method of claim  3 , further comprising heat setting the stretched film at a temperature above the stretching temperature and below the softening temperature of the stretched film. 
     
     
       5. The method of claim  3 , wherein the polyolefin is a copolymer of ethylene and a C 4 -C 10  alpha-olefin. 
     
     
       6. The method of claim  4 , wherein said filler is calcium carbonate surface treated with calcium stearate. 
     
     
       7. The method of claim  4 , wherein the precursor film is melt embossed with a diamond pattern. 
     
     
       8. The method of claim  4 , wherein the polyolefin/filler mixture contains between about 30 percent to about 65 percent filler by weight based on the total weight of said mixture. 
     
     
       9. The method of claim  3 , wherein the fabric is a nonwoven polyolefin fabric having a heat seal layer. 
     
     
       10. The method of claim  9 , wherein the lamination comprises heating the fabric and pressing the unheated film to the heated fabric. 
     
     
       11. A method of making a housewrap, comprising: 
       a) mixing a polyolefin comprising metallocene catalyzed polyethylene with a filler;  
       b) cast extruding a precursor film of the polyethylene/filler mixture onto at least one melt embossing roller to form a melt embossed precursor film having a pattern of different film thicknesses;  
       c) stretching the melt embossed precursor film in the transverse direction to impart greater water vapor transmission rate in the areas of reduced thickness thereof in comparison to the areas of greater thickness, said stretched melt embossed film having a water vapor transmission rate at least 10% higher than the WVTR described by the equation: WVTR=−10,900+320(filler weight %);  
       d) heating a nonwoven fabric comprising cross-laminated polyolefin fibers and an ethylene-vinyl acetate copolymer heat seal layer; and  
       e) pressing the heated fabric to the melt embossed precursor film at a temperature and pressure sufficient to bond the fabric and film to form a breathable laminate wherein said polyethylene has a M w /M n <3.  
     
     
       12. The method of claim  11 , further comprising heat setting the stretched film at a temperature above the stretching temperature and below the softening temperature of the stretched film, and wherein said polyethylene has a M w /M n <2.5. 
     
     
       13. The method of claim  11 , wherein the polyolefin is a copolymer of ethylene and a C 4 -C 10  alpha-olefin. 
     
     
       14. The method of claim  11 , wherein the filler is calcium carbonate surface treated with calcium stearate. 
     
     
       15. The method of claim  11 , wherein the precursor film is melt embossed with a diamond pattern. 
     
     
       16. The method of claim  11 , wherein the polyolefin/filler mixture contains between about 30 percent to about 65 percent filler by weight. 
     
     
       17. The method of claim  11  wherein said film has a WVTR of at at least 20% greater than the WVTR described by the equation: 
       
         
             WVTR=− 10,900+320 (filler weight %).  
         
       
     
     
       18. The method of claim  11  wherein said film has a WVTR of at at least 30% greater than the WVTR described by the equation: 
       
         
             WVTR=− 10,900+320 (filler weight %).  
         
       
     
     
       19. The method of claim  1 , wherein said laminate is a diaper. 
     
     
       20. The method of claim  1 , wherein said laminate is an adult incontinence device. 
     
     
       21. The method of claim  1 , wherein said laminate is a feminine hygiene article. 
     
     
       22. The method of claim  1 , wherein said laminate is a medical gown. 
     
     
       23. The method of claim  1 , wherein said laminate is a surgical gown.

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