Process for forming liquid impermeable sheet material having a fibrous surface and products formed thereby

• US 5,783,290 A
• Filed: 05/22/1995
• Issued: 07/21/1998
• Est. Priority Date: 11/30/1993
• Status: Expired due to Fees

• Current Assignee: Kimberly-Clark Worldwide Incorporated (Kimberly-Clark Corporation)
• Original Assignee: Kimberly-Clark Worldwide Incorporated (Kimberly-Clark Corporation)
• Inventors: Isaac, Robert Lewis, Cohen, Bernard, Jameson, Lee Kirby
• Primary Examiner(s): Page, Thurman K.
• Assistant Examiner(s): Shelborne, Kathryne E.
• Application Number:
  US08/445,961
• Time in Patent Office: 1,156 Days
• Field of Search: 428/273, 428/284, 428/286, 428/287, 428/288, 428/296, 428/297, 428/298, 428/299, 428/326, 428/131, 428/137, 428/138, 428/198, 428/903, 428/913, 604/378, 604/366, 604/370, 604/372, 604/283, 427/245, 156/296, 156/308.2, 156/309.6, 156/253, 156/268
• US Class Current: 428/198
• CPC Class Codes: A61F 13/00991 for treating webs, e.g. for moisturising, coating, impregnating or applying powder
• CPC Class Codes: B29C 43/006 Pressing and sintering powders, granules or fibres
• CPC Class Codes: B29K 2105/06 containing reinforcements, fillers or inserts
• CPC Class Codes: B29K 2105/25 Solid
• CPC Class Codes: B29K 2995/0065 Permeability to gases
• CPC Class Codes: B29K 2995/0067 non-permeable
• CPC Class Codes: B29K 2995/0069 non-permeable
• CPC Class Codes: B32B 37/04 characterised by the partial melting of at least one layer
• CPC Class Codes: D04H 1/54 by welding together the fibres, e.g. by partially melting or dissolving in combination with needling D04H1/485
• CPC Class Codes: D04H 1/559 the fibres being within layered webs
• CPC Class Codes: D04H 1/56 in association with fibre formation, e.g. immediately following extrusion of staple fibres
• CPC Class Codes: Y10T 156/1057 Subsequent to assembly of laminae
• CPC Class Codes: Y10T 428/24273 including aperture
• CPC Class Codes: Y10T 428/24322 Composite web or sheet
• CPC Class Codes: Y10T 428/24331 including nonapertured component
• CPC Class Codes: Y10T 428/24826 Spot bonds connect components
• CPC Class Codes: Y10T 442/20 Coated or impregnated woven, knit, or nonwoven fabric which is not [a] associated with another preformed layer or fiber layer or, [b] with respect to woven and knit, characterized, respectively, by a particular or differential weave or knit, wherein the coating or impregnation is neither a foamed material nor a free metal or alloy layer
• CPC Class Codes: Y10T 442/2139 Coating or impregnation specified as porous or permeable to a specific substance [e.g., water vapor, air, etc.]
• CPC Class Codes: Y10T 442/2893 Coated or impregnated polyamide fiber fabric
• CPC Class Codes: Y10T 442/2918 Polypropylene fiber fabric
• CPC Class Codes: Y10T 442/68 : Melt-blown nonwoven fabric
• CPC Class Codes: Y10T 442/681 : Spun-bonded nonwoven fabric

Abstract

Disclosed are a number of processes for forming a liquid-impermeable sheet having a fibrous cloth-like surface. In one embodiment the process includes the steps of: (1) forming a sheet having first and second fibrous surfaces; and subjecting the sheet to pressure and a z-gradient temperature differential sufficient to melt the fibers of the first surface and form the melt into a liquid impermeable skin without significantly altering the fibers of the second surface. In another embodiment, the process includes the steps of: (1) forming a sheet having first and second fibrous surfaces wherein, upon the sheet being subjected to a sufficient temperature, the fibers forming the first fibrous surface are adapted to substantially completely melt prior to the fibers forming the second fibrous surface significantly melting; and (2) subjecting the sheet to a sufficient pressure and temperature to melt the fibers of the first surface and form the melt into a liquid impermeable skin without significantly altering the fibers of the second surface. In some embodiments the liquid impermeable skin is subsequently apertured to make the sheet breathable. Products formed by these processes are also disclosed.

Claims

1. A liquid-impermeable, water vapor permeable sheet having a fibrous surface and a liquid impermeable skin, the sheet being formed by a process comprising the steps of:

forming a sheet having a first fibrous surface and a second fibrous surface;

subjecting the sheet to pressure and a z-gradient temperature differential sufficient to melt the fibers of the first surface and form the melt into a liquid impermeable skin without significantly altering the fibers of the second surface; and

aperturing the liquid impermeable skin.

2. The product of claim 1, wherein the product has a water vapor transmission rate of at least about 500 grams per square meter per day when measured in accordance with ASTM 96-80.

3. The product of claim 1, wherein the product has a hydrohead of at least about 50 centimeters of water when measured in accordance with Federal Test Method 55-14 (standard number 191A).

4. A liquid-impermeable, water vapor permeable sheet having a fibrous surface and a liquid impermeable skin, the sheet being formed by a process comprising the steps of:

forming a sheet of polymeric fibers, said sheet having a first fibrous surface and a second fibrous surface wherein, upon the sheet being subjected to a sufficient temperature, the fibers comprising the first fibrous surface are adapted to substantially completely melt prior to the fibers comprising the second fibrous surface significantly melting; and

subjecting the sheet to a sufficient pressure and, generally uniform, temperature to melt the fibers of the first surface and form the melt into a liquid impermeable skin without significantly altering the fibers of the second surface; and

aperturing the liquid impermeable skin.

5. The product of claim 4, wherein the product has a water vapor transmission rate of at least about 500 grams per square meter per day when measured in accordance with ASTM 96-80.

6. The product of claim 4, wherein the product has a hydrohead of at least about 50 centimeters of water when measured in accordance with Federal Test Method 55-14 (standard number 191A).

7. A sheet comprising:

a first fibrous layer including first polymeric fibers; and

a second fibrous layer including second polymeric fibers, said second fibrous layer situated adjacent to said first fibrous layer such that said first fibrous layer forms a first fibrous surface of said sheet and said second fibrous layer forms a second fibrous surface of said sheet, said first polymeric fibers and said second polymeric fibers a disparate melt characteristic selected from the group consisting of (1) the fibers forming the first surface are formed from a material having a melt flow rate which is at least 25 per cent greater than the material forming the fibers and (2) the fibers forming the first surface having an average diameter at least about 50 per cent less than the average diameter of the fibers forming the second surface; and

wherein, upon the sheet being subjected to a sufficient, generally uniform, temperature, the fibers comprising the first fibrous surface are adapted to substantially completely melt prior to the fibers comprising the second fibrous surface significantly melting.

8. The sheet according to claim 7, wherein the fibers forming the first surface are formed from a material having a melt flow rate which is at least 25 percent greater than the melt flow rate of the material forming the fibers of the second surface.

9. The sheet according to claim 7, wherein the fibers forming the first surface are formed from a material having a melt flow rate which is at least 50 percent greater than the melt flow rate of the material forming the fibers of the second surface.

10. The sheet according to claim 7, wherein the fibers forming the first surface are formed from a material having a melt flow rate which is at least 100 percent greater than the melt flow rate of the material forming the fibers of the second surface.

11. The sheet according to claim 7, wherein the fibers forming the first surface are formed from one or more materials selected from the group consisting of polyolefins, polyesters, polyamides, polyurethanes and polyetheresters.

12. The sheet according to claim 7, wherein the fibers forming the first surface have an average diameter which is at least about 90 percent less than the average diameter of the fibers forming the second surface.

13. The sheet according to claim 7, wherein the fibers forming the first surface have an average diameter which is at least about 75 percent less than the average diameter of the fibers forming the second surface.

14. The sheet according to claim 7, wherein the fibers forming the first surface have an average diameter which is at least about 50 percent less than the average diameter of the fibers forming the second surface.