Thermal cell having an oxygen permeable top sheet and a method of making a gas permeable material

• US 6,158,427 A
• Filed: 03/30/1999
• Issued: 12/12/2000
• Est. Priority Date: 07/18/1997
• Status: Expired due to Term

• Current Assignee: Wyeth (Pfizer Inc.)
• Original Assignee: The Procter & Gamble Company
• Inventors: McGuire, Kenneth S., Hamilton, Peter W.
• Primary Examiner(s): Price, Carl D.
• Assistant Examiner(s): LEE, DAVID B
• Application Number:
  US09/281,372
• Time in Patent Office: 623 Days
• Field of Search: 126/263.02, 126/263.05, 126/263.01, 126/204, 607/114, 607/108, 607/109, 607/110, 607/111, 607/112
• US Class Current: 126/263.01
• CPC Class Codes: A61F 2007/0098 ways of manufacturing heating or cooling devices for therapy
• CPC Class Codes: A61F 2007/0268 having a plurality of compartments being filled with a heat carrier heat packs stored in pockets A61F2007/023, A61F2007/0238
• CPC Class Codes: A61F 7/034 Flameless
• CPC Class Codes: B32B 2262/0253 Polyolefin fibres vinyl or acrylic copolymers B32B2262/0223 or B32B2262/0246
• CPC Class Codes: B32B 2305/026 Porous
• CPC Class Codes: B32B 2307/724 Permeability to gases, adsorption
• CPC Class Codes: B32B 2323/046 LDPE, i.e. low density polyethylene
• CPC Class Codes: B32B 27/12 next to a fibrous or filamentary layer
• CPC Class Codes: B32B 27/32 comprising polyolefins comprising vinyl (co)polymers or acrylic (co)polymers B32B27/30
• CPC Class Codes: B32B 3/04 characterised by at least one layer folded at the edge, e.g. over another layer ; characterised by at least one layer enveloping or enclosing a material
• CPC Class Codes: B32B 5/022 Non-woven fabric
• CPC Class Codes: B32B 7/12 using interposed adhesives or interposed materials with bonding properties
• CPC Class Codes: B32B 7/14 applied in spaced arrangements, e.g. in stripes
• CPC Class Codes: D06M 23/16 Processes for the non-uniform application of treating agents, e.g. one-sided treatment; Differential treatment
• CPC Class Codes: D06N 2205/06 Melt
• CPC Class Codes: D06N 2209/121 Permeability to gases, adsorption
• CPC Class Codes: D06N 3/007 characterised by mechanical or physical treatments D06N3/0029, D06N3/0031 take precedence
• CPC Class Codes: D06N 7/0092 Non-continuous polymer coating on the fibrous substrate, e.g. plastic dots on fabrics

Abstract

A method of making a gas permeable material having a diffusive gas permeability at 0.21 atmosphere diffusive driving force in the range of about 0.5×10⁵ cm³ /100 square inches/day to about 2×10⁵ cm³ /100 square inches/day. The method comprises the step of coating a pattern of spots of a gas impermeable material onto a porous substrate, followed by a step of enlarging the pattern of spots to cover greater than about 95% of the porous substrate such that the gas permeability occurs only through openings between the pattern of spots. The gas impermeable material is preferably a hot melt adhesive and the porous substrate is preferably a nonwoven. The step of enlarging the pattern of spots includes smearing substantially circular spots into oblong spots as the pattern of spots is printed onto the porous substrate until the oblong spots partially overlap. The smearing is achieved by operating a printing screen at a surface speed higher than a draw rate of the porous substrate. Alternatively, the step of enlarging the pattern of spots includes calendering through a fixed gap the porous substrate after the pattern of spots is coated thereon.

Claims

1. A thermal cell comprising:

a) a bottom sheet formed to have a pocket, said bottom sheet being impermeable to oxygen;

b) a plurality of particles placed in said pocket, said plurality of particles reacting exothermally when exposed to oxygen; and

c) a top sheet sealed to said bottom sheet at a flange of said pocket to enclose said plurality of particles such that said particles cannot exit said pocket, said top sheet having a porous substrate, said substrate being coated with a pattern of spots made of hot melt adhesive, said hot melt adesive uniformly covering greater than about 95%of a surface of said porous substrate such that said top sheet has a diffusive oxygen permeability at 0.21 atmosphere diffusive driving force ranging from about 0.5×

10⁵ cm³ /100 square inches/day to about 2×

10⁵ cm³ /100 square inches/day.

2. The thermal cell of claim 1 wherein said porous substrate is a nonwoven.

3. The thermal cell of claim 1 wherein said hot melt adhesive is on a pocket-facing side of said porous substrate so that said hot melt adhesive may also serve to seal said top sheet to said bottom sheet.