Heat cells comprising exothermic compositions having absorbent gelling material
View Patent ↗The present invention is directed to heat cells that are suitable for incorporation into disposable heating wraps. The heat cells comprise an exothermic composition comprising an absorbent gelling material, wherein the absorbent gelling material provides for improved heat application in the relief of temporary or chronic body aches and pains.
1. A heat cell comprising a particulate exothermic composition wherein the particulate exothermic composition comprises: (a) from about 10% to about 90% by weight of iron powder having a median particle size of from about 50 μm to about 400 μm; (b) from about 1% to about 25% by weight of a carbon selected from the group consisting of activated carbon, non-activated carbon, and mixtures thereof; (c) from about 1% to about 25% by weight of an absorbent gelling material having a median particle size of from about 300 μm to about 800 μm; and (d) from about 1% to about 35% by weight of water; wherein the particulate exothermic composition comprises a median particle size ratio range of absorbent gelling material to iron powder of less than 3:1 to 1:3; wherein the particles of the particulate exothermic composition are combined in a pocket, formed in a unified structure comprising at least two opposed surfaces, wherein at least one surface is oxygen permeable; and wherein the particulate exothermic composition in the pocket has interstitial particle void volume.
2. The heat cell of claim 1 wherein the particulate exothermic composition comprises a median particle size ratio of absorbent gelling material to iron powder of about 1:1.
3. The heat cell of claim 1 wherein the particulate exothermic composition comprises from about 50% to about 87% by weight of the iron powder.
4. The heat cell of claim 3 wherein the iron powder has a median particle size of from about 150 μm to about 300 μm.
5. The heat cell of claim 4 wherein the iron powder is selected from the group consisting of cast iron powder, reduced iron powder, electrolytic iron powder, scrap iron powder, pig iron, sponge iron, wrought iron, steel, iron alloy, and mixtures thereof.
6. The heat cell of claim 5 wherein the iron powder is sponge iron.
7. The heat cell of claim 1 wherein the particulate exothermic composition comprises from about 1% to about 10% by weight of the activated carbon, non-activated carbon, and mixtures thereof.
8. The heat cell of claim 7 wherein the activated carbon is prepared from materials selected from the group consisting of coconut shell, wood, charcoal, coal, bone coal, animal products, natural gas, fats, oils, resins, and mixtures thereof.
9. The heat cell of claim 1 wherein the particulate exothermic composition comprises from about 1% to about 15% by weight of the absorbent gelling material.
10. The heat cell of claim 9 wherein the absorbent gelling material is a hydrogel-forming polymeric material.
11. The heat cell of claim 10 wherein the hydrogel-forming polymeric material is selected from the group consisting of hydrolyzed acrylonitrile grafted starch, acrylic acid grafted starch, polyacrylate, maleic anhydride-based copolymer, and mixtures thereof.
12. The heat cell of claim 1 wherein the particulate exothermic composition further comprises from about 0.5% to about 10% by weight of a metal salt.
13. The heat cell of claim 12 wherein the metal salt is selected from the group consisting of alkali metal salts, alkaline earth metal salts, transition metal salts, and mixtures thereof.
14. The heat cell of claim 13 wherein the metal salt is selected from the group consisting of sodium chloride, cupric chloride, and mixtures thereof.
15. The heat cell of claim 1 wherein the heat cell has a cross-section area of from about 2 cm 2 to about 10 cm 2 .
16. The heat cell of claim 15 wherein the heat cell is in a shape selected from the group consisting of disk, triangle, pyramid, cone, sphere, square, cube, rectangle, rectangular parallelepiped, cylinder, ellipsoid, and combinations thereof.
17. The heat cell of claim 1 wherein the heat cell has a total cell weight of from about 0.8 grams to about 4.0 grams.
18. The heat cell of claim 17 wherein the heat cell is incorporated into disposable heating articles selected from the group consisting of back wraps, knee wraps, neck wraps, menstrual wraps, joint wraps, and neck-to-arm wraps.
19. The heat cell of claim 15 wherein the heat cell is elongated in shape and has a cell volume of about 1.25 to about 10 cm 3 .