Self-heating Composition

Abstract

The present invention is concerned with self-heating compositions and more specifically with self-heating cosmetic compositions such as aqueous shaving creams. In the compositions disclosed herein, at least one of the components of a heat-generating combination are encapsulated in rupturable capsules and dispersed in the composition. In especially useful embodiments, the capsules have melting points at or below the temperatures which will be generated in the composition.

Description

One object of the present invention is to provide self-heating compositions.

Another object of the present invention is to provide self-heating compositions which provide heat over a prolonged period.

Still another object of the present invention is to provide self-heating compositions which are also self-foaming.

A further object of the present invention is to provide compositions such as set forth above which can be packaged in low-pressure containers or single-use packets.

Other objects should be clear from the following detailed description, claims and drawing, wherein:

FIG. 1 is a perspective front view showing a single-use packet containing a composition within the scope of the present invention, and

FIG. 2 is a perspective front view of another single-use packet containing a composition within the scope of the present invention.

Self-heating compositions such as shaving creams are presently available in aerosol containers. Generally such compositions involve the use of a combination of heat-generating components which effect an exothermic reaction when in contact with one another. The aerosol containers which are used for such compositions generally comprise at least two separate compartments wherein the heat-generating components can be stored separately, along with the other ingredients, until time of use. Upon use, the heat-generating components are dispensed from the separate compartments through concurrently operated valves into a common discharge passageway where they come together to effect the exothermic reaction and thereby elevate the temperature of the composition. Although such aerosol-dispensed, self-heating compositions have met with considerable success, they require multicompartment containers and close tolerance valving systems in order to store the heat-generating components separately and to dispense said components in the proper stoichiometric amounts under a myriad of operating modes and conditions. The compositions of the present invention eliminate the need for such multicompartment containers and close tolerance valving systems.

In the self-heating compositions of the present invention the need for multicompartment containers and close tolerance valving systems is eliminated by encapsulating at least one of the heat-generating components in frangible capsules and dispersing the capsules in the composition. The second heat-generating component may be added directly to the composition or it may also be encapsulated and dispersed in the composition. During use, the capsules are ruptured by mechanical force, e.g. by rubbing the composition in one's hands to release the heat-generating components and bring them together to effect the exothermic reaction. Generally, the present invention is broadly applicable to a wide range of hydrophilic and hydrophobic compositions. It is particularly useful in aqueous-based pharmaceutical and cosmetic compositions such as shaving creams wherein heat is desired to increase the effectiveness of the composition.

Processes for encapsulating the heat-generating components are known. As examples of such processes, mention may be made of chemical methods such as disclosed in U.S. Pat. Nos. 2,800,457, 2,800,458, and 3,155,590 mechanical methods such as disclosed in U.S. Pat. Nos. 3,015,128, and 3,423,489 and electrostatic processes such as disclosed in U.S. Pat. No. 3,159,874. Generally, such processes comprise forming a continuous wall of the encapsulating material around the material to be encapsulated and thereafter solidifying the encapsulating material. A wide variety of substances have been found useful as encapsulating materials. Such materials, in addition to being capable of being deposited around the material to be encapsulated, also have to be inert and impermeable with respect to both the compositions in which they are to be dispersed as well as the encapsulated material. Generally, if the encapsulated material and the composition in which it is to be dispersed are hydrophilic, the encapsulating material will be of a hydrophobic nature and if the encapsulated material and the composition in which it is to be dispersed are hydrophobic, the encapsulating material will be of a hydrophilic nature. As examples of typical encapsulating materials, mention may be made of gelatin, ethyl cellulose, polymethylmethacrylate, wax, gum arabic, starch, paraffin, polyethylene, polyvinyl alcohol, and polystyrene.

Generally, encapsulation processes such as set forth above are capable of producing capsules having diameters varying from about a few microns up to about 4000 microns and even larger. In the compositions of the present invention, the size of the capsules may be chosen to fit the particular need. In embodiments wherein the capsules are intended to be ruptured by hand, the rupturing can be facilitated by using the larger diameter capsules, e.g. 2000 microns and above.

The heat-generating components for use in the compositions of the present invention may be broadly selected from the various combinations of materials which effect an exothermic reaction when in contact with one another. As can be appreciated, when the composition is to be topically applied, the heat-generating components and the byproducts of the exothermic reaction should be nontoxic and nonirritating. As examples of types of heat-generating combinations, mention may be made of the combination of an acid and base and the combination of a solvent and a solute having an appreciable heat of solution or dilution in the solvent, e.g. the combination of water and ethylene glycol and the combination of water and salts such as aluminum sulfate, calcium chloride, copper sulfate, ferric chloride, magnesium chloride, magnesium sulfate, etc. The latter combinations may be conveniently used in aqueous-based composition by merely encapsulating the salt in a water-insoluble, water-impermeable encapsulating material and dispersing the capsules in the composition.

In preferred embodiments of the present invention, the combination of an oxidizing reagent and a reducing reagent are used as the heat-generating components. Such oxidizing and reducing reagents may be selected broadly from the various compounds of this nature available. As examples of oxidizing agents, mention may be made of chlorates, perchlorates, permanganates, persulfates, peroxides, nitrates, metal oxides, such as copper oxide, lead oxide, and iron oxide, and perborates. The preferred oxidizing agents include hydrogen peroxide, urea peroxide, sodium peroxide, sodium perborate, sodium persulfate, ammonium persulfate, potassium persulfate, and mixtures of any of two or more of the foregoing. As examples of reducing reagents mention may be made of metals such as magnesium, zinc, aluminum and iron; sulfites, thio-sulfates, thioureas, imidazolinethiones, thiotriazoles, thiopyridines, thio-pyrimidines, thiols, thio-acids, sulfoxides, xanthates, ortho- and para-polyhydroxy benzenes, aldehydes, and glycols. A preferred class of reductants for use in compositions which are to be topically applied is disclosed in U.S. Pat. No. 3,341,418. Such compounds may be represented by the structure: ##SPC1##

in which R.sub.1 may be hydrogen, lower alkyl, lower hydroxyalkyl, lower alkoxy, or lower alkanoyl, and R.sub.2 may be any of the foregoing except hydrogen and may in addition be phenyl. Among such compounds, are 1-phenyl-2-thio-barbituric acid, 1-phenyl-5-ethyl-2-thio-barbituric acid, 1-methyl-2-thiobarbituric acid, 1-methyl-5-methyl-2-thio-barbituric acid, 1-methyl-5-ethyl-2-thiobarbituric acid, 1-ethyl-5-ethyl-2-thiobarbituric acid, 1-phenyl-5-methyl-2-thiobarbituric acid, and the like.

Generally, the amounts of heat-generating components employed in the compositions will vary depending upon factors such as the heat of reaction of the components; the specific heat of the composition and the ultimate temperature desired. Usually, the heat-generating components will be used in amounts which will provide a sensible temperature rise to the composition (e.g. a rise of 25.degree. F. from room temperature in a minute). As can be appreciated, the amounts which will produce such a rise will vary from system to system but can be readily calculated or empirically determined. In aqueous systems, such as shaving creams, when employing the heat-generating components disclosed in U.S. Pat. No. 3,342,418 as little as 0.8 percent by weight of oxidant based on the total weight of the aqueous composition will suffice to produce a sensible temperature rise when a stoichiometrically equivalent amount of reductant is used. In preferred embodiments of such aqueous compositions, at least 1 percent by weight of the oxidant, with a stoichiometrically equivalent amount of the reductant, is employed.

When desired, catalysts or amounts of one of the heat-generating components in excess of the stoichiometric amount may be used to promote or accelerate the heat-generating reaction. When employing catalysts such materials may be separately encapsulated or they may be added to the phase of the composition in which they are inactive. As can be appreciated, the type of catalyst will depend upon the nature of the heat-generating components. As examples of catalysts which can be employed in oxidant-reductant systems such as disclosed in U.S. Pat. No. 3,341,418 mention may be made of the alkali metal and ammonium salts of molybdates and tungstates.

In especially useful embodiments of the present invention, the compositions are self-foaming as well as self-heating. This is accomplished by incorporating into the foamable composition a foam-generating material which is insoluble or only slightly soluble in the composition e.g. less than 2 gms. per 100 cc. and which is a liquid at room temperature, e.g. 25.degree. C. but boils at the elevated temperature which will result from the reaction of the heat-generating components. In preferred embodiments of the present invention, the foam-generating materials will have boiling points between about 95.degree. F. to about 160.degree. F. As examples of foam-generating materials mention may be made of pentane, hexane, dichlorotetrafluoroethane and trichlorotrifluoroethane. When the compositions are to be marketed in single use, packets, or in containers which will be open to the atmosphere, only for short periods of time during the dispensing of the composition, the foam-generating materials may be added directly to the compositions. In uses wherein the compositions may be exposed to the atmosphere for extended periods, the foam-generating materials may be encapsulated. At time of use, the capsules containing the foam-generating materials are ruptured along with those containing the heat-generating components to provide a self-heating, self-foaming composition.

In preferred embodiments of the present invention, the heat-generating components are encapsulated in thermoplastic materials which have melting points at or below the temperature which will be generated in the compositions. Such embodiments make it possible to provide compositions which are able to generate heat over a prolonged period and thus may be called self-sustaining. Generally, in such self-sustaining compositions the heat-generating components are present in amounts in excess of that which is necessary to bring the composition to the desired or specified temperature. In using such self-sustaining compositions, at least that portion of the capsules are ruptured which will bring the composition or a portion of it to the temperature at which the walls of the unruptured capsules will melt. As the composition or portions of it reach such temperatures, the walls of unruptured capsules in the composition or adjacent to the heated portion of it will gradually melt over a prolonged period and continuously release additional quantities of the heat-generating components; thus sustaining the evolution of heat. In compositions which are self-foaming, as well as self-heating, the foaming action may be similarly sustained by also incorporating the foam-generating materials into similar capsules.

In still another preferred embodiment of this invention, the compositions are compounded so that they may be elevated to the desired temperature over a prolonged period. This is accomplished by incorporating the heat-generating components in a plurality of thermoplastic capsules which have sequentially higher melting points e.g. a first portion of the heat-generating components are incapsulated in an encapsulating material which melts at e.g. 120.degree. F., a second portion is encapsulated in a material which melts at 140.degree. F., and so on. Generally, the melting points of the encapsulating materials will lie in a range of temperatures which are above the temperature at which the composition will normally be stored and at or below the desired temperature to which the composition is to be heated. When it is desired that the compositions also be self-sustaining, this is readily accomplished by using an excess of the heat-generating components and incorporating the excess components in the highest melting encapsulating material.

The self-sustaining and/or gradually elevatable compositions disclosed above are especially useful in heating pads, garments, etc.

In certain end uses of the compositions of the present invention, e.g. cosmetics such as shaving creams, the fragments of the ruptured capsules give the compositions a gritty feel and are undesirable. Such undesirable characteristics may be substantially reduced by encapsulating the reagents in thermoplastic materials, such as taught above, which have melting points at or below the temperature which will be generated in the compositions by the reaction of the heat-generating components. In the melted state such encapsulating materials are usually readily dispersible in the compositions and thereby provide a convenient mode of eliminating the undesirable feel of the solid shell fragments. In some compositions, such as shaving creams, there will be surface active agents present which will facilitate such dispersion. In compositions where such surface active agents are not present, it is preferable, if the formulation will tolerate it, to add such surface active agents to aid in the dispersion.

Generally, the thermoplastic encapsulating materials for use in this invention may be selected from the low melting forms of the encapsulating materials previously mentioned above. A particularly useful class of thermoplastic materials for use in such embodiments are the waxes and especially beeswax (solidification point 60.5.degree. to 62.degree. C). Such waxes, in addition to providing a means of accomplishing the objectives set forth above may also, in some instances, be a useful ingredient in the composition or provide it with desirable characteristics such as body.

Thermoplastic capsules for use in the above embodiments may be readily prepared by known processes. In one such process, the thermoplastic encapsulating material is dispersed in an external phase which is a nonsolvent for both the encapsulating material and the material to be encapsulated. The system is heated to melt the encapsulating material and the material to be encapsulated is then added. As the system is cooled, the encapsulating material solidifies around the material to be encapsulated and thereby forms the capsules. The capsules, thus produced, are removed from the system by filtration.

As can be appreciated from the above, the concepts of the present invention are applicable to a broad range of compositions. Such compositions may be illustrated by the following shaving cream formulation which is prepared as set forth below.

An 8.2 percent aqueous hydrogen peroxide solution (the oxidant) is encapsulated in beeswax by methods such as set forth above, to provide capsules having an average diameter of at least 2000 microns. The capsules are uniformly dispersed in a shaving cream formulation having the following composition by weight: ##SPC2## ##SPC3##

The capsules are added to the formulation in amounts such that there will be about one part by weight of the aqueous peroxide solution present for each three parts of the shaving cream formulation.

In using the above composition for shaving, an amount of it, sufficient for one shave, is applied to the hand and rubbed to rupture the capsules and release the aqueous peroxide solution. Upon release, the peroxide reacts with the 1-phenyl-5-ethyl-2-thiobarbituric acid reductant to elevate the temperature of the composition. The rubbing is continued until the melted capsule fragments are dispersed in the composition and the resulting hot shaving cream is then applied to the beard.

If it is desired to make the above shaving formulation self-foaming as well as self-heating, this can be readily accomplished by adding a foam-generating material, such as described above, to the composition. Usually, the use of about 0.75 to about 2.0 gram molecular weights of the foam-generating material per 1000 gms of the aqueous composition will provide a useful foam. If it is desired to sustain the heat-generating action, this is accomplished by using an excess of the heat-generating components and initially rupturing that portion of the capsules which will bring the composition or a portion of it to a temperature which will gradually melt the remaining unruptured capsules.

In packaging the compositions of the present invention, it is generally not advisable to use squeeze-type tubes because a certain portion of the capsules in the unused portion of the composition will be ruptured during the dispensing operation. If it is desired to package the compositions in bulk, it is best to use wide-necked jars which will enable the user to gingerly remove the portion he wishes to use without rupturing the capsules in the unused portion of the composition.

When using such bulk packaging, the viscosity of the compositions should preferrably be such that the capsules will remain uniformly suspended in the composition until time of use and will not require stirring. Such suspension of the capsules may be achieved by employing in the compositions one or more of the many thickening and suspending reagents which are commercially available.

The compositions of the present invention are particularly useful in single use packets such as shown in FIGS. 1 and 2. Referring to FIG. 1, the packet 1 comprises a completely enclosed chamber 3 which is bounded by resilient sidewalls 4 which are sealed to each other along their peripheries. The chamber opens into a narrow dispensing channel 7 which is closed off by a tear-off cap 9. Within the chamber, there is provided a shaving cream composition 5 containing a plurality of first 11 and second 13 capsules. The first capsules 11 contain a heat-generating material which is reactive with another heat-generating material which is disposed in the shaving cream composition and the second capsules 13 contain a foam-generating material. In use, the sidewalls 4 of the packet 1 are pressed together to rupture the capsules 11 and 13. When the capsules 11 and 13 are ruptured and the composition becomes hot and begins to foam, the tear-off cap is removed. Under the pressure of the foam-generating material, the hot shaving composition is forced out of the packet 1 for use.

In FIG. 2, there is shown a packet similar to that shown in claim 1, except that it is encased by a rigid protective sheath 15 which prevents the accidental rupturing of the capsules 11 and 13. The sheath 15 is provided with an opening 17 in its top through which the capped dispensing channel 7 protrudes and in its 15 sidewalls there are positioned openings 21 which provide access to the resilient sidewalls 4 so that they may be pressed together during use to rupture the capsules 11 and 13.

It should be appreciated that in single-use packets, such as shown in FIGS. 1 and 2, the foam-generating material, when desired, may be disposed directly in the composition. Similarly, the heat-generating materials and the foam-generating materials may be disposed in single large frangible capsules which are positioned contiguous to the composition.

In embodiments of the present invention where the heat-generating component and the foam-generating material are inert with respect to each other, it should be understood that they may be encapsulated in the same capsules.

Claims

Having thus described the invention, what I claim is:

1. An aqueous self-heating composition comprising a combination of at least first and second heat-generating components which when in contact with one another effect an exothermic reaction; at least one of said components which is nonaqueous being encapsulated into a plurality of frangible capsules which are dispersed in said aqueous composition, the encapsulating material for said capsules being both inert and impermeable with respect to the aqueous composition and the heat-generating components.

2. A self-heating composition as defined in claim 1 wherein the encapsulating material has a melting point which is at or below the temperature which is generated in the composition when said heat-generating components effect the exothermic reaction.

3. A self-heating composition as defined in claim 2 which includes a foam-generating material, said foam-generating material being a liquid at room temperature and having a boiling point which is below the temperature which is generated in the composition when said heat-generating components effect the exothermic reaction.

4. A self-heating composition as defined in claim 1 which includes a foam-generating material, said foam-generating material being a liquid at room temperature and having a boiling point which is below the temperature which is generated in the composition when said heat-generating components effect the exothermic reaction.

5. A self-heating composition as defined in claim 1 in which said composition is a shaving cream.

6. A self-heating composition as defined in claim 4 wherein said composition is a shaving cream.

7. A self-heating composition as defined in claim 4 wherein said foam-generating material is encapsulated into a plurality of frangible capsules which are dispersed in said composition, the encapsulating material for said capsules being both inert and impermeable with respect to said composition and said foam-generating material.

8. A single-use packet containing a self-heating composition, said packet comprising an enclosed chamber in which said composition is disposed, said chamber being bound by at least one resilient wall and having a dispensing opening which is closed off by a removable closure, said composition comprising a combination of at least first and second heat-generating components which when in contact with one another effect an exothermic reaction; at least one of said components being encapsulated in at least one frangible capsule which is positioned in the packet contiguous with the composition, the wall material of said capsule being both inert and impermeable with respect to said composition and said heat-generating components.

9. A packet as defined in claim 8 wherein said composition also comprises a foam-generating material, said foam-generating material being a liquid at room temperature and having a boiling point below the temperature which is generated in the composition when said heat-generating components effect the exothermic reaction.

10. A packet as defined in claim 9 in which said composition is a shaving cream.

11. A packet as defined in claim 9 wherein said foam-generating material is encapsulated in at least one frangible capsule which is positioned within the packet contiguous said composition, the encapsulating material for said capsule being both inert and impermeable with respect to said composition and said heat-generating composition.

12. A packet as defined in claim 11 in which said composition is a shaving cream.

13. A packet as defined in claim 8 in which said composition is a shaving cream.

14. An aqueous self-heating composition which is capable of evolving heat over a prolonged period, said composition comprising a combination of at least first and second heat-generating components which in contact with one another effect an exothermic reaction said combination of heat-generating components being present in amounts in excess of that which is required to bring the composition to a desired specified temperature, at least one of said components which is nonaqueous being encapsulated into a plurality of frangible capsules which are dispersed in said composition, the encapsulating material for said capsules being both inert and impermeable with respect to the aqueous composition and the heat-generating components and having a melting point at or below said specified temperature whereby upon rupturing at least that portion of the capsules which will bring at least a portion of the composition above said melting point, the unruptured capsules will gradually melt over a prolonged period and continuously release additional quantities of the heat-generating component.

15. A self-heating composition as defined in claim 14 which includes a foam-generating material which is encapsulated into a plurality of frangible capsules which are dispersed in said composition, the encapsulating material for said capsules being both inert and impermeable with respect to said composition and having a melting point at or below said specified temperature whereby said capsules will be melted over a prolonged period and continuously release additional quantities of said foam-generating material.

16. An aqueous self-heating composition which rises gradually to a specified temperature over a prolonged period said composition comprising a combination of at least first and second heat-generating components which in contact with one another effect an exothermic reaction, at least one of said heat-generating components which is nonaqueous being encapsulated in a plurality of encapsulating materials, said plurality of encapsulating materials being inert and impermeable with respect to said composition and said heat-generating components and having sequentially higher melting points which are above the temperature at which the aqueous composition is normally stored and at or below said specified temperature.

17. A self-heating composition as defined in claim 16 which evolves heat over a prolonged period when said composition reaches the specified temperature said composition comprising said heat-generating components in amounts in excess of that required to elevate the composition to said specified temperature, the excess of heat-generating components being encapsulated in the encapsulating material which has the highest melting point in said plurality of encapsulating materials.