MXPA98007542A - Mixed film to control the flow of oxygen to the inside of termi cells - Google Patents

Abstract

A mixed material for controlling the flow of oxygen into a thermal cell consisting of a lower sheet formed to have a bag, the lower sheet is impermeable to oxygen, a plurality of particles is placed in the bag, the plurality of The particles react exothermically when exposed to oxygen, an upper sheet is sealed to the lower sheet in the flange around the bag to enclose the plurality of particles in such a way that the particles can not fall out of the bag. The topsheet has a substrate that is highly permeable to oxygen, the substrate is coated with an oxygen-permeable silicone-based elastomer to a thickness that regulates an oxygen flow within the bag when the topsheet is exposed to oxygen. The composite material further comprises an oxygen impermeable barrier film bonded to the topsheet by means of pressure sensitive adhesive to prevent exposure of the topsheet to oxygen until the body heater is ready to be used. One method of making the upper sheet material includes covering a layer of silicone rubber on a flat surface by partially vulcanizing the silicone, pressing a porous substrate against the silicone rubber layer and fully vulcanizing the silicone rubber so that it adheres to the substra

Description

MIXED FILM TO CONTROL THE FLOW OF OXYGEN TO THE INSIDE OF THERMAL CELLS C? MQ PE THE I VENTION The present invention relates to oxygen permeable materials »and very particularly to materials of this type in which the thickness of the material is used to control the flow of oxygen from the ambient air into a thermal cell.

BACKGROUND OF THE INVENTION Thermal cells for body heaters are well known in the art, particularly those which use a reactive mixture of iron powder and activated carbon. Such cells require oxygen to produce a controlled exothermic reaction which provides heat for several hours. Typically the mixture is packed in an air permeable bag which is sealed in a waterproof outer bag until it is ready for use. The permeable bag can be a non-woven material or a perforated material. In any case, the particles of the mixture can be broken through perforations or between filaments of the nonwoven material when the assembly is being completed. Unnoticed leakage of the mixture, particularly coal, can contaminate the user's clothing and reduce the performance of the thermal cell. In a typical body heater »more than one thermal cell may be present. Placing smaller cells side by side with some substrate material between them allows the body heater to have more flexibility to mold itself to the contours of the body than a single cell can provide. The smaller the heat cell, the more critical will be the location and the number of perforations or the consistency of the nonwoven substrate placed on the cells »in order to control the flow of oxygen to the cells. Such control is required to ensure that the cells do not overheat and possibly burn the user or exhaust their heat potential too soon. Gas permeable membranes have been available for separation procedures. For example, U.S. Patent No. 5,102,552 to Callahan et al., Issued April 7, 1992, discloses a UV curable polymer coated on a microporous support having an average pore size of about 0.005 microns. almost 0.2 microns. The patent of E.U.A. No. 3,754,375 to Bouchilloux et al., Issued August 28, 1973, discloses an "anotropic membrane having excellent mechanical properties combined with good permeation characteristics." This consists of a polymer of vi or 1 triorganosi oo copollimer "which has a dense layer of 0.01 to 10 microns in average thickness and a porous layer of 2054 to 8054 of open area. Others have applied gas-permeable membranes to heat the cells, but with limited success. For example, the patent of E.U.A. No. 5,046,479 of Usu. issued on September 10, 1991. It details a method to control the penetration of oxygen through a microporous film which is subjected to a "heat fusion treatment" in order to restrict the permeability to oxygen to a water heater. disposable body. A loose bag containing an iron powder heat generating agent has an air permeable surface having an air permeability per unit of 5000 to 10,000 sec./100 cma. Microporous films. unfortunately "they are very expensive.

QB ETQS pe THE INVENTION An object of the present invention is to provide an economical mixed material and to have an excellent oxygen permeability control for use with a thermal cell. Another object of the present invention is to provide a mixed body material that has no perforations or voids through which the thermal mixing particles can leak from a bag containing said mixture. Still another object of the present invention is to provide a mixed material which is heat-sealable to the flange of a waterproof bag containing a thermal mixture and from which a waterproof cover sheet which does not allow the passage of oxygen is easily peelable. that the thermal cell is ready for use. It is a further object of the present invention to provide a method for making a mixed material having excellent oxygen permeability control for use with a thermal cell.

BRIEF DESCRIPTION OF THE INVENTION In practicing the present invention, a nonwoven substrate or other porous substrate is silicone coated and forms the top sheet of a thermal cell of a body heater. The slab-coated substrate is permeable to oxygen at a preferred rate, however it is non-porous to particular materials within the heat cell. The oxygen penetration rate is easily adjusted by varying the thickness of the silicone coating. The substrate provides structural integrity since the thin slab materials themselves are known to break easily. A barrier film "which is removed to initiate oxygen penetration and heat generation" can be easily peeled from the silicone coating »since the silicone coatings act as leaching surfaces for pressure sensitive adhesives.

In one aspect of the present invention, a mixed material for controlling the flow of oxygen into a thermal cell comprises a lower sheet formed to have a bag. The lower sheet is impermeable to oxygen. A plurality of particles is placed in the bag. The plurality of particles reacts exothermically when exposed to oxygen. A top sheet is sealed to the bottom sheet in the flange of the bag to enclose the plurality of particles in such a way that the particles can not fall out of the bag. The top sheet has a substrate which is highly permeable to oxygen. The substrate is covered with an oxygen-permeable elastomer based on a thickness that regulates an oxygen flow within the bag when the topsheet is exposed to oxygen. The mixed material further comprises a means for preventing exposure of the topsheet to oxygen until the body heater is ready for use. The medium may be an oxygen impermeable barrier film bonded to the topsheet by means of pressure sensitive adhesive. The medium can also be an oxygen-impermeable bag inside which a body heater having the thermal cell is placed for storage. The plurality of particles comprises a reactive mixture of iron. The mixture may include activated carbon »water and salts to increase the rate of exothermic reaction when the mixture is exposed to oxygen. The oxygen flow within the bag is preferably about 1.75 x 10ß cm 3 / S 45.15 cm * / day. The substrate comprises a non-woven material having openings of at least 2 microns and the silicone-based elastomer comprises poly i (dimethylsi loxane) printed on the substrate to a thickness of almost 0.000254 cm. In another aspect of the present invention, a method for making a mixed-body material for controlling oxygen flow within a thermal cell comprises the steps of coating a layer of silicone rubber over a smooth surface and partially vulcanizing the rubber layer. of silicone to improve its ability to detach from the smooth surface. Other steps include pressing a porous oxygen substrate against the silicone rubber layer and then fully vulcanizing the silicon rubber layer in such a way that it adheres to the substrate that is porous to oxygen. The method has one more step of stripping the porous substrate to oxygen and the rubber layer of the smooth surface. The smooth surface may be a drum and the oxygen porous substrate may be a continuous web wrapped around a part of the drum.

PftEYE DESCRIPTION PE IQS PIPWP5 Although the description concludes with claims that particularly indicate and distinctly claim the present invention, it is believed that the present invention will be better understood from the following description of the preferred embodiments "taken in conjunction with the accompanying drawings" in which Reference numerals identify identical elements and in which: Figure 1 is a top plan view of a preferred embodiment of a mixed material for controlling the oxygen flow within a thermal cell of the present invention, describing an inverted cylindrical bag projecting upwards from a flange of mixed material »Fig. 2 is a sectional side elevational view thereof» taken along section line 2-2 of Fig. 1 »showing the layers of mixed material and particles of a thermal mixture in the bag when the thermal cell is protected from oxygen by being placed in a waterproof bag; Figure 3 is a sectional side view similar to Figure 2 »but showing a removable impermeable barrier film bonded adhesively to the mixed material to protect the thermal mixture from oxygen; and Figure 4 is a side elevation view of a process for making the mixed material to control the oxygen flow within the thermal cell of the present invention, detailing a drum, heat lamps, an applicator roller, and a pair of Continuous cloth handling rollers.

DES RIOÓ PETAt TO PE ^ A INVECTION Referring now to the drawings, and more particularly to Figures 1 2 and 3, a first preferred embodiment of the present invention is shown. which provides at least one thermal cell 10. The thermal cell 10 has a lower sheet 12 »which is formed inside the bag 14. The lower sheet 12 is sealed in the flange 18 around the bag 14 to an upper sheet, generally being indicated as 16. The closed bag 14 preferably contains a thermal mixture 20. The topsheet 16 is a mixed material compressed to a substrate 22 and a silicone rubber cover 24. The substrate 22 is highly permeable to oxygen. Figure 2 shows a sectional side view of the thermal cell 10. In the embodiment of Figure 2 »the thermal cell 10 is enclosed in an oxygen-impermeable bag 26. The thermal mixture 20 is activated upon opening of the impermeable bag 26, thereby causing the oxygen to penetrate through the upper sheet 16 and into the thermal mixture 20. Figure 3 shows a sectioned side view similar to Figure 2 »but with the release film 28 attached with a pressure sensitive adhesive 27 to a silicone rubber cover 24. In this embodiment the release film 28 has a peelable tongue 30. When the peel tongue 30 is used to peel off the release film 28 of the silicone rubber cover 24, oxygen from the air passes through the silicone rubber liner 24 and the substrate 22 into the thermal mixture 20. The pressure sensitive adhesive 27 preferably adheres to the release film 28 in instead of the silicone rubber liner 24. Further details, related to the intended use of the present invention with a thermal cell of a body heater, can be found in the pending application serial number 08 / 496,373, entitled "Elastic back wrap with diamond pattern and means antiresbalosos ", filed on June 29, 1995, with the obligation to assign this request to the assignee of the present application, and which is incorporated herein by reference. In a particularly preferred embodiment of the present invention, the substrate 22 is a 0.65 μm Durapel microporous membrane available from the Millipore corporation of Bedford. MA. The silicone rubber 24 is applied to the substrate 22 by mixing first pol i (Dimeti Isi loxane) hydro-terminated »or PDMS. with a viscosity of about 1000 centistokes with a tin octoate catalyst in a mass ratio of 10: 0.25. The PDMS mixture is covered on the microporous membrane with a razor sharp to a thickness of almost 0.0000254 cm. The PDMS mixture is then exposed to tetraethoxysilane vapors, or TEOS, for 5 to 15 minutes.

Higher exposure times correspond to thicker coatings. The residual PDMS, which has not reacted, is washed with toluene and then with methanol. Oxygen penetration rates range from 3.5 x 10ß to 1.5 x 10ß cma / 645.1625 cm2 / day. for TEOS exposure times of 5 to 15 minutes. Although the microporous membranes provide a very uniform cover surface and a uniform pore size. They are considered very expensive. In comparison »expensive non-woven materials typically provide a reasonably uniform coating surface and reasonably uniform pore size. The inexpensive non-woven materials typically have a very rough coating surface and very large pores, which makes it very difficult to apply a 0.000254 cm thick layer of initially liquid silicone rubber over their surfaces when known coating techniques are used in the technique, such as rod-wrapped cable coating and gravure printing coating. When applying the liquid silicone rubber on a flat surface, putting the non-woven material in contact with the rubber of the partially vulcanized slone »and then fully vulcanizing the silicone rubber while it is in contact with the non-woven material» the silicone rubber it can be transferred from the flat surface to the non-woven material. This method results in a uniform coating of silicone rubber over the rough surface of the non-woven material. It is believed that a preferred method of coating, shown in Figure 4, could automate the coating of a 0.000254 cm thick layer of silicone rubber over the uneven surface of a cheap non-woven fabric. The method shown in Figure 4 could of course also be applicable to microporous expensive membranes. Figure 4 shows a process which is generally referred to as 29 for making the top sheet 16. The silicone rubber application system 32 deposits nearly 0.000254 cm of liquid silicone rubber »unvulcanized on a drum 36 as it rotates the drum 36. The surface of the drum 36 is preferably pulsed until it is smooth. It can be made of stainless steel, silver-plated material, or any other suitable smooth surface. The liquid silicone rubber may be partially vulcanized by means of the initial vulcanization source 37, which is preferably a heating mechanism used to heat the vulcanized silicone rubbers. Other vulcanization media, such as ultraviolet light, can also be used. The automated process 29 has a substrate web 22 screwed between the feed tension rod 38 and the drum 36. The substrate 22 is preferably a microporous film or a nonwoven material. In this process the liquid rubber 34 of the metal is preferably deposited first on the surface of the substrate 22. As the drum 36 rotates, the rubber 34 silicone liquid is partially vulcanized by the vulcanization mechanism 37. The vulcanization mechanism 37 is preferably a heater used to vulcanize heat-vulcanizable silicone rubbers. After the silicone liquid rubber 34 is transformed into solid silicone rubber 24, the substrate fabric 22 is pressed against the rubber rubber covering 24 by means of the feed tension roller 38. The tension in the fabric of substrate 22 keeps it in contact with the silicone rubber liner 24. The vulcanization source 40 is preferably a heater similar to the vulcanization source 37. The adhesion between the substrate 22 and the silicone rubber coating 24 occurs as the vulcanization is completed »by forming the upper sheet 16 of the mixed body. The upper sheet 16 is discharged after the drum 36 in the discharge guide rod 42. In a particularly preferred embodiment of the present invention, the heaters 37 and 40 heat the silicone rubber 34 and 24 between 37.7 and 93.3 ° C respectively »When the drum 36 has a surface velocity between 15.24 and 228.6 meters per minute. The drum 36 is preferably 15.24 to 91.44 cm. in diameter and has an outer surface made of stainless steel or chrome plated. Although particular embodiments of the present invention have been described and illustrated, it will be obvious to those skilled in the art that various modifications and changes can be made without departing from the spirit and scope of the invention, and it is intended to cover in the appended indications. all these modifications that are within the scope of the invention.

Claims (8)

NOVELTY OF THE INVENTION REIVIN ICATIONS

1. - A mixed material for controlling the oxygen flow into a thermal cell, comprising: (a) a lower sheet formed to have a bag »said bottom sheet being impermeable to oxygen» (b) a plurality of particles placed in said bag »said plurality of particles reacting exothermically when exposed to oxygen» and (c) an upper sheet sealed to said lower sheet in the tab around said bag to enclose said plurality of particles in such a way that said particles can not falling out of said bag, said top sheet having a substrate which is highly permeable to oxygen, said substrate being covered with an oxygen-permeable slurry-based elastomer at a thickness which regulates an oxygen flow within said bag when said bag Top sheet is exposed to oxygen.

2. The mixed material according to claim 1 further comprises: (d) means for preventing the exposure of said upper sheet to oxygen until said thermal cell is ready to be used.

3. The mixed material according to claim 2, further characterized in that the means for preventing exposure consist of an oxygen-impermeable barrier film bonded to said top sheet by means of pressure-sensitive adhesive, said barrier film. oxygen-impermeable being releasable from the oxygen-permeable silicone-based elastomer. A .- The mixed material according to claim 2 »further characterized in that the means for preventing exposure consist of an oxygen-impermeable bag inside which a body heater having said thermal cell is placed for storage. 5. The mixed material according to claim 1, further characterized in that said oxygen flow within the bag is about 1.75 x 10 ° cma / 645.1625 cm * / day. 6. The mixed material according to the re-indication 1 »further characterized in that said plurality of particles consists of a reactive mixture of iron» said mixture including activated carbon, water and salts to increase the rate of exothermic reaction when said mixture is exposed to oxygen. The mixed material according to claim 1 »further characterized in that said substrate consists of a non-woven material having openings of at least 2 microns, and the silicone-based elastomer consists of pol i (dimethylsi loxane) printed on the substrate to a thickness of almost 0.000254 c. 8. A mixed material to control the flow of oxygen into a thermal cell consisting of: (a) a lower sheet formed to have a bag »said lower sheet being impermeable to oxygen; (b) a plurality of particles placed in said bag, said plurality of particles reacting exothermically when exposed to oxygen "(c) a top sheet sealed to said bottom sheet in the flange of said bag to enclose said plurality of particles in such a way that said particles can not fall out of said bag »said upper sheet having a substrate which is highly permeable to oxygen» said substrate being covered with an oxygen-permeable silicone-based elastomer at a thickness which regulates an oxygen flow within said bag when said top sheet is exposed to oxygen "and < d) an oxygen impermeable barrier film adhered to said top sheet by pressure sensitive adhesive "said oxygen impermeable barrier film being peelable from the oxygen permeable silicone based elastomer to expose said upper sheet to oxygen. 9. The mixed material according to claim 8, further characterized in that the oxygen flow within said bag is about 1.75 x 10 ° cm3 / 645.1625 cm * / day. 10.- The mixed material in accordance with the rei indication 8, further characterized in that said plurality of particles consists of a reactive mixture of iron »said mixture including activated carbon» water and salts to increase the rate of exothermic reaction when said mixture is exposed to oxygen. 11. The mixed material according to claim 8 wherein said substrate consists of a non-woven material having openings of at least 2 microns "and the silicone-based elastomer consists of poly (dimeti 1-si loxane) printed on said substrate to a glosor of almost 0.000254 cm. 12.- A mixed material to control the oxygen flow inside a thermal cell that includes: <a) a lower sheet formed to have a bag, said lower sheet being impermeable to oxygen; (b) a plurality of particles placed in said bag, said plurality of particles including a reactive mixture of iron, said mixture including activated carbon, water and salts to increase the rate of exothermic reaction when said mixture is exposed to oxygen; and (c> a top sheet sealed to the bottom sheet in the flange of said bag to enclose said plurality of particles in such a way that said particles can not fall out of said bag, said top sheet including a nonwoven material having openings of at least 2 microns, which is highly permeable to oxygen, said non-woven material having an outer surface, said outer surface being printed with a poly i (Dimeti Is loxane) at a thickness of almost 0.000254 cm to regulate a flow of oxygen within the bag when said top sheet is exposed to oxygen 13.- The mixed material in accordance with claim 12, character Also curled because said oxygen flow inside said bag is almost 1.75 x 10ffl cma »/645.1625 cm ^ / day. 1

4. The mixed material according to claim 12, further characterized in that it further comprises: d) means for preventing the exposure of the upper sheet to oxygen until said thermal cell is ready to be used. 1

5. The mixed material in accordance with the rei indication 14, further characterized in that the means for preventing exposure consist of an oxygen impermeable barrier film bonded to the topsheet by pressure sensitive adhesive, "said impermeable barrier film to oxygen being removable from pol i (Dimeti Isi loxane). 1

6. The mixed material according to the rei indication 14, further characterized in that the means for preventing exposure consist of an oxygen-impermeable bag inside which a body heater having the thermal cell is placed for storage. 1

7. A method for making a mixed material to control the flow of oxygen into a thermal cell, said method consisting of the steps of: a) covering a layer of silicone rubber on a flat surface; b) partially vulcanizing said silicone rubber layer to improve its ability to detach from the flat surface; d) press a porous substrate to the oxygen against the rubber layer; and fully vulcanize said layer of silicone rubber from such that it adheres to the porous substrate to the oxygen »and e) releasing the porous substrate to the oxygen and the silicone rubber layer of said flat surface. 1

8. The method according to claim 17. further characterized in that said flat surface consists of a drum and the porous oxygen substrate comprising a continuous fabric entangled around a part of the drum.