Abstract:
An aromatic thermal wrap comprises aromatic compounds such as camphor, menthol, essential oils and similar compounds, mixed with an absorbent material such as a silica powder and then combined with a superabsorbent polymer (SAP) to form a dry, aromatic mixture ( 200 ), and packaged in a flexible, water-permeable sachet ( 100 ). When suitably mixed with a silica powder, the aromatic compounds do not cause agglomeration or clumping of the superabsorbent polymer. Hydration of the sachet will cause the SAP to absorb water, forming a gel  210.  The sachet may be produced with multiple pockets ( 110 ) that can be separated into single packets or into sets of packets to accommodate the specific application. The end user hydrates the sachet, and optionally heats or freezes the hydrated package, to produce an aromatic, thermal wrap.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of U.S. Provisional Patent Application No. 60/238,368, filed Oct. 6, 2000. 
    
    
     FIELD OF THE INVENTION 
     A method for producing a thermal wrap utilizing a superabsorbent polymer and, more particularly, a method for producing an aromatic thermal wrap that can be packaged in porous sachets as a dry, hydratable mixture that can be hydrated by the user and then chilled or heated prior to use. 
     BACKGROUND OF THE INVENTION 
     Superabsorbent polymers, including, but not limited to polymers such as polysaccharides, polyacrylates, and carboxymethylcellulose, are well known in the art for their ability to absorb many times their own weight, and sometimes hundreds of times their own weight, in water. The hydrated superabsorbent polymer typically forms a gel that substantially retains the thermal properties of water while simultaneously immobilizing the water in the gel material. Such gels are frequently used in thermal wraps that can be warmed, typically by heating the gel in a microwave oven or other warming device, or frozen by placing the thermal pack in a freezer. 
     Cold and hot thermal wraps are commonly used as a first treatment for minor injuries, such as sprains and bruises. The thermal wrap is applied directly to the injured area. Lowering the local body temperature near a minor injury during the first few hours after the injury occurs will cause the blood vessels to contract, and limit internal bleeding and swelling near the injury situs. After the body has repaired itself sufficiently to stop undesirable internal bleeding, typically approximately 24 hours after the injury occurred, application of heat to the injured region will cause the blood vessels expand, thereby increasing the flow of blood to the site of the injury, and speeding the healing process. 
     The application of heat is also a common method of treating temporary or chronic pain. Such therapeutic heat treatments are used for conditions that include general body aches, stiffness in muscles and joints, nerve pain, rheumatism, and the like. Generally, the afflicted area is warmed by applying a heating element such as a thermal wrap directly to the aching area. 
     A common type of thermal wrap is produced by hydrating a superabsorbent polymer (SAP) to create a gel, and encapsulating the gel in an impermeable, sealed, plastic container. For example, in U.S. Pat. No. 3,545,230, Morse discloses a flexible cooling device comprising an insoluble hydrophilic gel (made from, e.g., carboxymethylcellulose) sealed in a flexible packaging material that can be frozen. A disadvantage of sealing the gel in a package is that the product must be hydrated during manufacture. The hydrated product is much heavier and voluminous than the unhydrated polymer, and therefore shipping, storing, and displaying the hydrated product is more difficult. 
     In U.S. Pat. No. 6,017,606, Sage et al. discloses a reusable thermal compress wherein a superabsorbent polymer is disposed within a water permeable fabric. The water permeable fabric is gel retaining, and so the user can hydrate the compress immediately prior to use. 
     In some situations, it may provide additional physical and/or psychological benefit and comfort to the user of a thermal wrap to additionally experience a pleasant and/or therapeutic aroma when using the thermal wrap. In addition to potential therapeutic benefits that certain aromatics might provide, if a pleasant aroma enhances the user&#39;s enjoyment of the thermal wrap, then the user is likely to beneficially continue application of the thermal wrap for a longer period of time. 
     The use of aromatic compounds with a SAP is known in the art. In U.S. Pat. No. 4,961,493 to Kaihatsu, for example, an aromatic package is disclosed wherein an aromatic liquid or powder is dissolved in a solvent comprising 50 wt % ethanol and 50 wt % water, and then combined with a gelling agent, such as a SAP, and placed in a gas permeable and liquid impermeable package. Kaihatsu does not contemplate or suggest the use of the aromatic package as a thermal wrap, however. A disadvantage of the aromatic package disclosed by Kaihatsu is that the aromatic compound must be dissolved in a solvent (in the disclosure, a water/ethanol mixture) prior to combining the solvent/aromatic compound mixture with the gelling agent. Therefore, the aromatic package must be hydrated during manufacture, complicating the shipping, storing, and displaying requirements for the product. Moreover, many aromatics, particularly oil-based aromatics, are not dissolvable in water, thereby requiring the use of an alternative solvent such as ethanol. 
     It would be useful to mix a SAP with an aromatic compound (or a mixture thereof), that could by hydrated by the user just prior to use. It has been found, however, that if liquid aromatic compounds such as camphor, menthol, eucalyptus, essential oils, and/or aromatic oils are combined with a SAP gelling agent directly, without first hydrating the SAP, the superabsorbent polymer tends to agglomerate or clump together, thereby preventing or hindering the ability of the SAP to absorb water and form a gel. 
     SUMMARY OF THE INVENTION 
     An aromatic thermal wrap comprises a mixture of one or more liquid aromatic compounds that are absorbed and/or adsorbed into a porous silica powder and then mixed with a superabsorbent polymer. The mixture is placed in water permeable sachets. The aromatic thermal wrap can be manufactured, shipped, and stored without hydrating the superabsorbent polymer, thereby significantly simplifying handling of the product. The end-user hydrates the thermal wrap, and optionally heats or cools it prior to application, producing a thermal wrap that also provides a pleasant, and potentially health-promoting aroma. 
     In one embodiment of the invention, the thermal wrap sachets are produced in a regular planar array having individually separable pockets that can be utilized individually or in any convenient combination. 
     The aromatic compounds usable in accordance with the present invention include camphor, menthol, and essential oils. A carrier oil may be combined with the essential oils to moderate the intensity of the aroma. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The foregoing aspects and many of the attendant advantages of this invention will become more readily appreciated as the same become better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein: 
     FIG. 1 is a perspective view of an embodiment of an aromatic thermal wrap according to the present invention; 
     FIG. 2 is a cross-sectional side view of the aromatic thermal wrap shown in FIG. 1 prior to hydration of the gel-forming aromatic mixture; 
     FIG. 3 is a perspective view of the aromatic thermal wrap shown in FIG. 1, after hydration of the gel-forming aromatic mixture; and 
     FIG. 4 is a cross-sectional side view of the aromatic thermal wrap shown in FIG. 3 after hydration of the gel-forming aromatic mixture. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to FIGS. 1 through 4, a preferred embodiment of an aromatic thermal wrap according to the present invention comprises a generally rectangular multi-compartment sachet  100  having a number of pockets  110 . The sachet  100  is formed from a nonporous back panel  112  affixed generally at its edge portions  114  to a liquid- and gas-permeable but gel- and solid-retaining front panel  116 . The back panel  112  and front panel  116  are also joined at a number of intermediate locations  118 , thereby forming a sheet having a plurality of pockets  110 . The back panel  112  and the front panel  116  may be affixed or joined in any of a number of means well known in the art, including but not limited to stitching, gluing, or heat bonding. 
     The back panel  112  and the front panel  116  may be made from any suitable materials that are capable of retaining a gel and are not damaged by soaking in water. Examples of suitable materials for the nonporous back panel  112  include, for example, polypropylene, polyester, or polyethylene films. Examples of suitable materials for the liquid- and gas-permeable front panel  116  include, for example, perforated or foraminous sheets made from polypropylene, polyester, polyethylene, and laminates thereof. The front panel  116  preferably has a number of pores or holes therethrough that are large enough to make the front panel  116  permeable to water and vapor, but small enough to substantially retain the aromatic gel-forming mixture  200  and the hydrated gel  210 , and to prevent or at least hinder the gel  210  from leaking out of the sachet  100  when the thermal wrap is in use. 
     In the preferred embodiment, the sachet  100  is produced as a flexible sheet having a plurality of pockets  110  containing the aromatic mixture  200 . Optionally, as shown in FIG. 1, the pockets  110  may be separated by perforations  120  or other zones of weakness in the intermediate portions  118 , so that individual pockets  110 , or a smaller set of pockets  110  may be separated to accommodate a particular application. It will be appreciated that although the illustrated preferred embodiment depicts a one-by-three array of pockets  110 , the sachets could be produced in any convenient planar array of pockets, including, for example, a large roll of pockets one wide by many long, or a sheet of pockets many wide by many long. Virtually any reasonably sized pocket may be produced, and in particular, a composite sachet utilizing a number or pockets with differing dimensions could be utilized to accommodate particular applications. 
     Prior to final sealing or joining of the edge portion  114 , a quantity of a gel-forming aromatic mixture  200  is inserted into each pocket  110 , the aromatic mixture  200  comprising one or more aromatic compounds that have been absorbed into a fine silica powder and a superabsorbent polymer (SAP). As used herein, a “superabsorbent polymer” refers to a polymeric material that is capable of absorbing large quantities of fluid by swelling and forming a hydrated gel (i.e., a hydrogel). In addition to absorbing large quantities of fluids, superabsorbent materials can also retain significant amounts of bodily fluids under moderate pressure. 
     Superabsorbent polymers generally fall into three classes: starch graft copolymers, cross-linked carboxymethylcellulose derivatives, and modified hydrophilic polyacrylates. Examples of such superabsorbent polymers include hydrolyzed starch-acrylonitrile graft copolymers, neutralized starch-acrylic acid graft copolymers, saponified acrylic acid ester-vinyl acetate copolymers, hydrolyzed acrylonitrile copolymers or acrylamide copolymers, modified crosslinked polyvinyl alcohol, neutralized self-crosslinking polyacrylic acids, crosslinked polyacrylate salts, carboxylated cellulose, and neutralized crosslinked isobutylene-maleic anhydride copolymers. 
     SAPs are available commercially, for example, polyacrylates from Clariant of Portsmouth, Va. These superabsorbent polymers come in a variety of sizes, morphologies, and absorbent properties (available from Clariant under trade designations such as IM 3500 and IM 3900). Other SAPs are marketed under the trademarks SANWET (supplied by Sanyo Kasei Kogyo Kabushiki Kaisha), and SXM77 (supplied by Stockhausen of Greensboro, N.C.). Still other SAPs are described in U.S. Pat. No. 4,160,059; U.S. Pat. No. 4,676,784; U.S. Pat. No. 4,673,402; U.S. Pat. No. 5,002,814; U.S. Pat. No. 5,057,166; U.S. Pat. No. 4,102,340; and U.S. Pat. No. 4,818,598—all expressly incorporated herein by reference. Products such as diapers that incorporate SAPs are described in U.S. Pat. No. 3,699,103 and U.S. Pat. No. 3,670,731. In the preferred embodiment of the present invention, a polysaccharide SAP is used. 
     As seen most clearly by comparing FIG. 2, showing a cross-sectional view of the non-hydrated sachet  100 , with FIG. 4, showing a cross-sectional view of the hydrated sachet  100 , the pockets  110  are sized to permit expansion of the aromatic mixture  200  upon absorption of water to form a gel  210 . Modem SAPs may absorb ten to a hundred or more times their weight in water, and so the pockets  110  must be large enough to accommodate the fully hydrated aromatic mixture  200  without causing the pockets to burst. 
     Most aromatic compounds are hydrophobic, and are frequently formulated in organic hydrocarbon bases or carrier oils. These compounds are not water soluble and, when mixed with a typical, unhydrated SAP, will cause undesirable clumping, which reduces the ability of the SAP to absorb water and form a gel. Thus the present invention uses an inert, absorbent compound, such as a porous silica powder, to absorb the aromatic compounds before mixing with the SAP. Although a porous silica powder is used in the preferred embodiment, it should be apparent that other inert absorbent compounds may also be used, including, for example, fine, porous, synthetic polymer particles such as clay, and zeolytes. A porous silica powder is generally less expensive than synthetic polymer particles, and more aesthetically appealing, and less prone to staining than zeolytes, however. 
     According to the present invention, the aromatic compounds are first absorbed into a porous silica powder at a sufficiently low loading that the aromatic compound/silica powder can be handled essentially as a powder. As used herein, “absorb” means the process of one substance taking up the matter of another substance, and so shall include without limitation, where appropriate, adsorption and/or absorption of one material by another. The impregnated silica powder can be mixed with a SAP without causing it to clump and without significantly interfering with the ability of the SAP to absorb water and form a gel. The preferred silica powder is 70 to 200 or 200 to 400 mesh size (corresponding to particle sized approximately 0.0015″ to 0.0083″ in diameter), and more preferably, 70 to 200 mesh size. A typical characteristic pore size in a suitable silica powder is about 60 Angstrom. 
     The dry mixture of aromatic compound/silica powder and SAP can therefore be sealed into the sachet pockets  110  without hydrating the SAP. The resulting sachets  100  can be easily packaged, stored, transported, displayed, and otherwise handled prior to delivery to the final user. 
     An aromatic product, such as the aromatic thermal wrap of the present invention, must generally be packaged for display in a manner that will not interfere with other neighboring products. In particular, the aromatic thermal wrap will generally be sealed in a package such that the scent from the aromatic compounds does not undesirably permeate the point of display. The sealed package will also hinder the vaporization of the volatile compounds, providing the product with a longer shelf life and protecting the thermal wrap from external damaging factors such as ultraviolet rays. Because the SAP can absorb ten to a hundred or more times its own weight in water, it will be appreciated that the ability to mix and package the unhydrated aromatic compound with the SAP for later use will greatly simplify the packaging and handling of the product. 
     When the sachet  100  is required for use as a thermal wrap, it can be soaked in water to hydrate the SAP, forming an aromatic gel  210 . The resulting gel  210  retains approximately the thermal properties of the absorbed water and the sachet  100  may be heated, as in a microwave oven, or frozen, depending on the desired application, prior to use. It has been found that the aromatic compounds in the gel  210  will evaporate over time, providing the thermal wrap of the present invention with the desired aromatic properties. 
     Specific formulae for the mixture of aromatic compounds that are absorbed into the silica powder can be tailored to produce a plethora of pleasant and potentially healthful scents. A non-aromatic carrier oil can be mixed with the aromatic compounds to moderate the intensity of the gel scent. In the preferred embodiment, the ratio of aromatic compounds, including the carrier oil, if any, to the silica powder, is preferably maintained in the range of 1:1 to 1:2, and more preferably approximately 1:1.5. This range of loading of the aromatic compounds into the silica has been found to maintain powder-like behavior in the impregnated silica while also enabling sufficient aromatic compounds to be incorporated in the gel  210  to produce the desired intensity of the aroma. 
     Although the preferred ratio of SAP to the aromatic compound and silica mixture will vary depending on the specific SAP that is used, as well as the selected aromatic compounds and desired intensity of the scent, when using a polysaccharide SAP, the SAP may be approximately 75 to 90 wt % of the mixture of aromatic compound/silica powder and SAP, and most preferably about 80 to 83 wt %. 
     EXAMPLE 1 
     In one embodiment of the present invention, the aromatic mixture  200  includes a polysaccharide SAP, silica, menthol, and camphor in the following proportions: 
     i) SAP, preferably 79 wt % to 87.5 wt %, most preferably 82.7 wt %; 
     ii) silica, preferably 7 wt % to 10 wt %, most preferably 10 wt %; 
     iii) I-menthol, preferably 4 wt % to 8 wt %, most preferably 5.5 wt %; and 
     iv) d-camphor, preferably 1.5 wt % to 3 wt %, most preferably 1.8 wt %. 
     EXAMPLE 2 
     In another embodiment, utilizing essential oils, the aromatic mixture includes approximately 80 wt % SAP, 12 wt % silica, and 8 wt % of essential oils including any carrier oil. Many different formulations of essential oils that have been found to produce pleasant scents, including: 
     Mix I: Atlas Cedarwood, Rosemary, Mandarin Lime, Nutmeg, Lavandin; 
     Mix II: Atlas Cedarwood, Benzoin, Guaiacwood, Rosemary, Sweet Birch, Scotch Pine, Silver Fir Needles; 
     Mix III: Atlas Cedarwood, Elemi, Ginger; and 
     Mix IV: Grapefruit, Jasmine, Sandalwood. 
     While the preferred embodiment of the invention has been illustrated and described, it will be appreciated that various changes can be made therein without departing from the spirit and scope of the invention. 
     While the preferred embodiment of the invention has been illustrated and described, it will be appreciated that various changes can be made therein without departing from the spirit and scope of the invention.