WO1995017340A1

WO1995017340A1 - Method and apparatus for release of sorbed gas

Info

Publication number: WO1995017340A1
Application number: PCT/US1994/013854
Authority: WO
Inventors: Anatoli Y. Stolyarevski; Alexandre S. Doronin; Poi Sik Tan; Hwai Chiang Lam
Original assignee: Acma Limited
Priority date: 1993-12-22
Filing date: 1994-12-06
Publication date: 1995-06-29
Also published as: AU1334295A

Abstract

Apparatus and methods for dispensing and cooling fluids (70) utilize a pressurized capsule (10) having a propellant gas sorbed in a sorbent matrix (18) therein. The capsules (10) are sealed so that the propellant gas is maintained until the capsule (10) is immersed in a liquid (70) or exposed to another environmental change. Such pressurized capsules (10) are useful for pressurizing aerosol delivery packages (62) and for cooling liquids (70) under ambient conditions.

Description

METHOD AND APPARATUS FOR RELEASE OF SORBED GAS

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to systems for pressurized delivery and cooling of liquids. More particularly the present invention relates to apparatus and methods for releasing sorbed gases within a liquid environment for pressurized delivery or cooling of the liquid.

Pressurized containers are in wide use for delivery of numerous consumer and industrial products including shaving cream, hair spray, paints, insecticides, cleaning substances, and the like. Such pressurized delivery systems are generally referred to as "aerosols" based on the aerosolized nature of the material being delivered. Such delivery systems usually include (1) the product to be dispensed, which may be a liquid, solid (powder) or gas, (2) a propellant, and (3) a container having a valve actuator. The material to be dispensed and the propellant are combined within the interior of the container, where the propellant pressurizes the interior to expel product through the valve. The valve is designed with an orifice or nozzle which can dispense the product as a liquid spray, powder, foam, or the like, depending on the material and pressure. Heretofore, the propellant has usually been a material which is a gas under ambient conditions but a liquid under the mildly elevated pressure within the container. The use of such liquified propellant gases is desirable since, as a liquid, they displace a very small volume within the pressurized container, maximizing the volume available for the product to be delivered. Moreover, because of the minimum volume required, it is easy to provide sufficient propellant to maintain a substantially constant pressure within the container as the product is dispensed. Preferred propellants which are gases under ambient conditions but which may be readily liquified at moderate pressures include low molecular weight hydrocarbons, such as propane, butane, and isobutane, as well as chlorofluorocarbons (CFCs) .

Such liquid propellants, however, suffer from certain disadvantages. Hydrocarbon propellants are flammable and therefore present a risk during manufacture and use. CFCs, moreover, are environmentally destructive and are believed to have an adverse impact on the ozone layer in the atmosphere. Thus, the use of CFCs has been or is being discontinued throughout the world. As an alternative to such liquid propellants, the use of compressed "safe" gas propellants, such as nitrous oxide, nitrogen, and carbon dioxide, has been proposed. These gases are non-toxic, low in cost, and present minimum impact on the environment. Unfortunately, none of these gases are readily liquified at moderate pressures, thus requiring that they be maintained within the pressurized delivery container as a compressed gas. The degree of gas compression, however, is limited by the pressure within the container, so that there is a significant trade-off between the ability to maintain pressure (by providing a relatively large amount of compressed gas) and the ability to provide an adequate amount of product within the container.

In an effort to improve the amount of gas propellant which may be stored within a unit volume at a given pressure, it has been proposed to reversibly sorb such gas propellant within a liquid and/or porous solid sorbent. Such sorbed gas is released from the sorbent to maintain a pressure equilibrium as product is dispensed from the container. Thus, such sorbent system decreases the internal volume required for storing propellant gas within a pressurized delivery container. Although a significant improvement in terms of product safety and lessened environmental impact, the use of sorbent systems for maintaining gaseous propellants in pressurized aerosol containers suffers from certain disadvantages, particularly with regard to the manufacturing process. At least most proposed manufacturing processes require that the gaseous propellant be introduced to the aerosol container in a high pressure filling line. Such a high pressure filling line requires a greater capital investment and present a somewhat greater risk of industrial accident. Moreover, certain sorbent materials can be incompatible with a particular product to be delivered, thus limiting the use of many sorbents in certain applications.

For these reasons, it would be desirable to provide improved sorbed propellant gas systems for use in pressurized aerosol delivery packages and elsewhere. It would be particularly desirable to provide sorbed propellant gas systems which could be handled under ambient conditions, both for pressurizing aerosol delivery packages and for other purposes, such as liquid cooling. Such sorbed propellant gas systems will preferably be in the form of capsules which can be transported, manipulated, and placed into aerosol delivery packages under ambient conditions.

2. Description of the Background Art

The use of various sorbent systems for releasing propellant gases into aerosol dispensing devices is described in a number of references. See, e.g., U.S. Patent Nos. 3,964,649; 5,032,619; and 5,256,400; published European patent applications 385 773 and 502 678. PCT publications WO 92/14091 and 93/00277; and Netherlands published application NL 7501277. A commercial system for sorbing propellant gases, such as carbon dioxide-acetone, is available from The BOC Group, Guildford, United Kingdom, under the tradename Polygas. The system is described in a release entitled "New Green Aerosol - BOC Launch Enviro-friendly Propellant System," Packaging, February 1992, page 20, and Fruitin, "Polygas - The Alternative Propellant," Packaging, April 1992, page 23. U.S. Patent No. 3,815,793, discloses a valved container holding a pressurizing fluid for use within pressurized delivery packages. Gas generating systems for pressurized dispensers are described in U.S. Patent Nos. 4,491,250, 4,909,420; and 5,054,651. Self- cooling beverage and other cans are described in U.S. Patent Nos. 4,319,464; 4,679,407; 4,784,678; 4,802,343; and 4,993,237.

SUMMARY OF THE INVENTION According to the present invention, pressurization or cooling of liquids is achieved using a pressurization capsule containing a gaseous propellant reversibly sorbed in a sorbent material. The capsules comprise a capsule wall defining an interior volume (which contains the reversibly sorbed propellant) , wherein the gaseous propellant may be released through the capsule wall in response to a change in the exterior environment, such as exposure to a liquid, change in temperature or pressure, mechanical shock, or the like.

Preferably, release of the gaseous propellant occurs in response to immersion of the pressurization capsule in a liquid, such as a liquid to be dispensed from pressurized aerosol delivery package or a liquid to be cooled. In such cases, the capsule wall will include a passageway therethrough which is blocked so long as the capsule is dry (or exposed to a liquid which does not effect dissolution or solubilization of a blocking material, as described below) . The passageway will typically be in the form of either a discrete aperture or a porous portion of the wall and is blocked with a barrier which is soluble in the liquid to be delivered or cooled. In the case of discrete apertures, the barrier will typically be in the form of a plug which is inserted into the aperture and which is dissolved or released from the aperture in response to immersion in the liquid. In the case of a porous capsule wall or portion thereof, the barrier will typically be a layer of liquid-soluble material impregnated into or coated over a fabric or mesh reinforcement layer. In both cases, the propellant gas will be retained within the capsule up until the time the capsule is immersed into the liquid. After such immersion, the passageway will be opened, permitting the propellant gas to desorb and enter the lower pressure environment of the liquid. Generally, the sorbent material will continue to be retained within the capsule.

In a particular aspect of the present invention, capsules which contain discrete aperture passageways will further comprise a sorbent retaining element over the aperture to permit loss of sorbent after the aperture is opened. Such retaining means can be in the form of a screen, mesh, fabric, or the like. In cases where it is desired to isolate the sorbent material from the external liquid, the barrier may be in the form of a semi-permeable membrane which permits the passage of gases (i.e. the propellant gas which is being released from the capsule) but prevents the passage of liquids, such as porous PTFE fabrics. Pressurized aerosol delivery packages according to the present invention will comprise a shell defining a pressure-tight interior volume containing a material, usually a liquid, to be dispensed. The shell will further include a valve to release the material to be dispensed and a pressurization capsule as described above. Manufacture of suc aerosol delivery packages is facilitated since the liquid and pressurization capsule can be combined within the shell under ambient conditions. The shell may then be closed and the interior of the shell pressurized after the pressurization capsule is opened, typically by dissolution or solubilization of a barrier as discussed above. Alternatively, the capsule can be opened by the application of mechanical shock to fracture the pressurization capsule, by the application of hea to open the pressurization capsule, or the like. Pressurization capsules can also be used to cool a liquid simply by immersing the pressurization capsule into a liquid under ambient conditions. The pressurization capsules intended for liquid cooling will be designed to release the sorbed "propellant" gas at a fairly rapid rate, requiring sufficient enthalpy of desorption to effect the desired cooling. The present invention further provides for self- cooling liquid packages containing a "propellant" gas in a sorbent within the package. The package will include means fo abruptly opening the package to ambient conditions, such as a pull-top on a beverage can. By substantially immediately exposing the liquid to ambient pressure, the propellant gas will be desorbed sufficiently rapidly to provide the desired cooling.

The present invention further provides methods for pressurizing aerosol delivery packages, where a pressurization capsule as described above is combined with material to be dispensed. The package is then sealed and the propellant subsequently released from the capsule, either by dissolution of a barrier, fracture of the capsule, heat-mediated opening o the capsule, or the like.

A further understanding of the nature and advantages of the invention will become apparent by reference to the remaining portions of the specification and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 illustrates a first exemplary pressurization capsule constructed in accordance with principles of the present invention, where the capsule includes discrete apertures sealed by liquid-soluble or heat-releasable plugs.

Fig. 2 illustrates a second exemplary embodiment of pressurization capsule constructed in accordance with the principles of the present invention, where the capsule is frangible so that it may be broken at its midpoint during or after introduction to a pressurized aerosol delivery package o other container according to the present invention.

Fig. 2A is an alternative configuration of the secon exemplary embodiment of Fig. 2, where a frangible stem extends from one end thereof. Fig. 2B is an alternative configuration of the secon exemplary embodiment of Fig. 2, where a reciprocatable pin is disposed to puncture a frangible barrier and where the entire pressurization capsule is disposed within an expandable bag. Fig. 3 illustrates a third exemplary embodiment of the pressurization capsule constructed in accordance with the principles of the present invention, where the capsule comprises a fabric coated or impregnated with a liquid soluble material.

Fig. 4 is a detail of the capsule fabric of Fig. 3. Fig. 5 illustrates a pressurized aerosol delivery package incorporating the pressurization capsule of Fig. 3. Fig. 6 illustrates a self-cooling liquid beverage container employing the pressurization capsule of Fig. 1.

Fig. 7 illustrates a pressurization capsule employed in the experimental section of the present application. Fig. 8 illustrates the internal pressure of an aerosol delivery package incorporating the pressurization capsule of Fig. 7 as a function of filled volume. DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS The present invention provides apparatus and methods for providing pressurization gas or propellant to pressurized aerosol delivery packages under controlled conditions. The present invention is also suitable for cooling liquids, either as part of pre-packaged, pressurized liquid containers, such a beverage cans, or by adding a pressurization capsule to a liquid maintained under ambient conditions. The present invention still further provides pressurized aerosol delivery packages and self-cooling liquid containers which incorporate pressurization capsule according to the present invention. Th pressurization capsules of the present invention provide propellant gases reversibly sorbed within a sorbent matrix, whereby relatively large amounts of the propellant gas may be stored and manipulated under ambient conditions. The propellant gas is optionally dissolved in a solvent, and the propellant and optionally solvent gas are absorbed, adsorbed, or otherwise taken up in the sorbent matrix, which is typicall a porous solid material which increases the amount of sorbed material which can be stored at a given pressure.

The present invention is suitable for dispensing virtually any product which is dispensable from a pressurized container. It will be appreciated, of course, that the produc must be compatible with the propellant gas and the sorbent matrix which are employed in the pressurization capsule, as described hereinbelow. Materials to be dispensed will usually be liquids, or soluble in a liquid carrier, and will thus be dispensed from the package as a liquid spray, emulsion, foam, or the like. In some cases, however, it may also be possible to deliver dry powder materials from the pressurized aerosol containers, although such dry powders may not be compatible with pressurized capsules which require a liquid material to release propellant gas therefrom. Exemplary products to be dispensed include cosmetics, hair sprays, shaving creams, cleaning materials, pharmaceutical substances (such as from etered dose inhalers), lubricants, paints, insecticides, furniture polish, and the like. Often, the propellant will be dispensed with the product and in some cases may even be necessary to provide the desired consistency of the product. For example, in shaving creams and other foam products, the propellant gas may be necessary to impart the foam. In other cases, the propellant gas may form a primary component of the product being delivered, such as providing an inflation gas for inflating articles such as tires and balloons, or providing oxygen or oxidizer for breathing, chemical reaction, combustion, and the like.

A wide variety of conventional propellant gases may be employed in the pressurized capsules of the present invention. Preferred are non-toxic, non-flammable, environmentally benign gases such as carbon dioxide, nitrous oxide, and the like. The present invention can also employ other conventional propellants, including ammonia, sulphur dioxide, low molecular weight hydrocarbons (e.g. propane, butane, and isobutane) , CFCs, and the like. In most cases, industrial-grade or commercial-grade gases containing minor impurities will be suitable. In the case of pharmaceuticals and other biologically active materials, it may be necessary to provide a higher level of purity.

The propellant gas may optionally be dissolved in a liquid solvent or mixture of solvents to enhance sorption capacity of the sorbent matrix, as described hereinafter.

Suitable solvents will be able to dissolve the propellant gas and will be compatible with the porous, solid phase sorbent material. For example, acetone in various low molecular weight alcohols may be used as a solvent for carbon dioxide propellant. Lower weight alcohols are also suitable for nitrous oxide propellants. In some cases, it may be possible to employ such liquid solvents as the sorbent material, without a solid phase, porous matrix. In such cases, it will usually be necessary to provide a pressurization capsule which can release the propellant gas while containing the liquid solvent. For example, containment barriers can be employed using selective membranes which pass gases but block passage of liquids, for example polytetrafluoroethylene (PTFE) fabrics may be employed. Suitable PTFE fabrics are sold under the tradename Gore-Tex®, by W.L. Gore Associates, Inc.

The sorbent matrix will usually be composed of a porous, particulate material, such as activated charcoal, a natural zeolite, a synthetic zeolite (i.e. cross-linked polymeric ion gas exchange beads, such as those described in U.S. Patent Nos. 4,458,990; 4,224,415; and 4,221,871) silicas, methylated silicas, precipitated silicas, fumed amorphous silicas, alumina, powdered alumina, molecular sieve materials, and the like. Particular sorbent matrices which may be used in the pressurization capsules in the present invention are described in U.S. Patent Nos. 5,032,619 and 3,964,649, the disclosures of which are incorporated herein by reference. The propellant gas will be maintained within the sorbent matrix at an elevated pressure, typically in the range from 2-10 atmospheres, usually from 4-10 atmospheres, and more usually from 5-10 atmospheres. The amount of propellant gas sorbed within the matrix may vary widely, depending primarily on the porosity of the sorbent matrix and the pressure at which the sorbent gas is maintained. The volume of propellant gas (at standard temperature and pressure) stored in a gram of sorbent matrix will usually be between about 0.05 liters and 0.5 liters, more usually between about 0.1 liters and 0.3 liters. Higher volumes are generally preferred since they permit the use of smaller pressurization capsules to maintain internal pressure in pressurized delivery packages. It should be understood, of course, that less than the entire stored volume of propellant gas will be released from the capsule at a nominal residual pressure, e.g., 2 atmospheres, in a headspace of a pressurized delivery container.

The propellant gas will generally be sorbed within the sorbent matrix by exposure of the gas to the matrix at elevated pressure for a time sufficient for the gas pressure within the sorbent to reach equilibrium with the external pressure. Typically, the exposure time will be at least about an hour, and may be longer. Once the sorbent matrix is charged with the propellant gas, the matrix material will be introduced to the capsule which is then sealed so that the propellant- sorbent matrix system will maintain the elevated pressure, even when the capsule is exposed to ambient conditions. As described in detail hereinbelow, the resulting pressurized capsule will be constructed so that the propellant gas can be released after the capsule is introduced to a pressurized aerosol delivery package or liquid to be cooled.

Compatible gaseous propellant-sorbent matrix systems for use in the present invention are set forth in Table 1 as follows: Table 1

Sorbent Propellant Compatibility Material co₂ CFCs SF₆ N₂0

Activated Carbon E G G G

Natural Zeolite E G G G

Molecular Sieve E E E E

Methylated Silica G G F G

Alumina G F F G

E = excellent

G = good

F = fair

Referring now to Fig. 1 a first exemplary pressurization capsule 10 constructed in accordance with the principles of the present invention will be described. The pressurization capsule 10 includes a cylindrical capsule wall 12 formed of a rigid material, such as metal, plastic, glass, ceramic, or the like, which is impermeable to liquids and gases except for an aperture 14 at each end. The apertures 14 are closed by plugs 16 which will be composed of a material which is dissolved or otherwise disrupted when the capsule 10 is introduced into a liquid or exposed to another environmental event, such as heat, mechanical shock, or the like. In a preferred embodiment, the plug 16 will be composed of a liquid- soluble material, such as a solid gelatin or carbohydrate

(sugar) , which will dissolve when immersed in an aqueous or organic (e.g., alcoholic) solution. Alternatively, the plug can be formed from any material which is then secured in the aperture 14 using an adhesive which is dissolved or disrupted when immersed in a liquid, exposed to heat, or the like. While two plugs 16 are illustrated, it will be appreciated that capsules having only a single plug could also be constructed. Capsule 10 includes a sorbent matrix 18 which contains a desired propellant gas, generally as described above. The sorbent matrix is maintained within the capsule, and prevented from escaping through aperture 14 when plug 16 has been dissolved or otherwise removed, by the screen or mesh element 20.

The volume of the capsule 10 may vary widely depending on the amount of compressed propellant gas which is desired to be delivered. Typically, the capsule 10 will have an internal volume capable of holding from about 20 ml to 150 ml of sorbent matrix, usually from about 50 ml to 100 ml. The second exemplary embodiment 30 of a pressurized capsule according to the present invention is illustrated in Fig. 2. Pressurized capsule 30 is generally solid and impermeable over its entire capsule wall 32, typically in the form of a cylinder. The capsule 30, however, will be designed to be frangible so that the capsule will open when subjected to mechanical shock, typically when the capsule is introduced to a liquid to be dispensed or cooled. Most simply, the capsule 30 may include a thinned or scored region 34 circumscribing the capsule wall 32, which permits the capsule to be broken open to expose sorbent matrix 36 held behind screens or meshes 38. It may also be desirable to form the cylindrical wall 32 from a material which is readily fractured, such as glass or ceramic. Referring now to Fig. 2A, a pressurized capsule 300 also comprises a solid, impermeable cylindrical wall 302.

Rather than being designed to fracture at its midsection (as with capsule 30) , the capsule 300 includes a stem 304 which has a much narrowed diameter than the cylindrical wall 302. The stem 304 defines a passage 306 which is exposed when the stem is broken from the rest of the capsule 300. In this way, sorbent matrix 308 can be exposed through screen or mesh 310. The cylindrical wall 302 and stem 304 will usually be formed from a readily fracturable material, and this design is particular useful when opening is to be effected by mechanical shock which is by shaking a sealed pressurized delivery package.

Referring to Fig. 2B, another pressurized capsule 400 will be described. The capsule 400 also comprises a solid, impermeable cylindrical wall 402. The wall 402 includes a frangible barrier 404 at one end. A reciprocatable pin 406 is mounted at the same end and disposed to puncture the barrier 404 when depressed. Puncturing the barrier 404 releases propellant gas from the sorbent 408 disposed behind mesh or screen 410. Optionally, the entire capsule 400 structure may be enclosed in an expandable bag 412. The bag 412 will have a sufficient volume, when expanded, to displace most or all of the internal volume of a pressurized delivery package into which it is to be placed. Use of the bag 412 is advantageous when it is desired to isolate the released propellant gas from the material to be delivered from the package. Such expandable bags (or other known isolation structures, such as movable pistons) may be employed with any of the pressurized capsule structures of the present invention which do not require contact between the capsule and a liquid to release the propellant gas.

A third specific embodiment 50 of the pressurized capsule of the present invention is illustrated in Figs. 3 and 4. The capsule 50 comprises a fabric 52 (Fig. 4) impregnated with a barrier material 54 containing sorbent matrix 56 therein. The barrier material 54 is a liquid-soluble or heat-sensitive material which will be solubilized or otherwise removed when exposed to appropriate conditions. The capsule 50 is particularly advantageous since it may be readily manufactured by employing a continuous tube of the coated or impregnated fabric. The tube may be filled with desired amounts of the sorbent matrix 56 with lengths of the tube being cut and ends of the cut lengths being sealed to form the capsules 50. The entire manufacturing process may be contained under elevated pressure or reduced temperature in order to achieve a desired amount of sorbed propellant gas within the matrix 56. Once the capsules 50 are sealed, however, they may be stored and manipulated under ambient conditions without significant loss of the propellant gas.

Referring now to Fig. 5, a pressurized aerosol delivery container 60 comprises a shell 62 having a mounting cap 64 with an actuator 66 mounted thereon. The actuator is attached to valve stem 68 which in turn is attached to dip tube 70. The dip tube 70 is immersed within a liquid product 72 to be dispensed. The pressurized capsule 50 of Figs. 3 and 4 may be introduced into the shell 62 through the upper opening, either before, after, or simultaneously with introduction of the liquid 72 to be dispensed. The shell 62 will then be sealed with the mounting cap 64 and, after time, barrier material 54 will dissolve, releasing propellant gas from the capsule 50. Gas will be released until pressure in head space 74 comes into equilibrium with the effective pressure within the pressurized capsule 50. As product is released through the actuator 66, the volume of head space 74 will increase. Additional propellant gas will be released from the pressurized capsule 50 in order to maintain a relatively uniform pressure within the head space 74.

Referring now to Fig. 6, self-cooling beverage can employing the pressurized capsule 10 of Fig. 1 will be described. Beverage can 80 may be a conventional beverage can employing a continuous aluminum wall 82 having a pull-top 84 at its upper end. The pressurized capsule 10 will be introduced before, after, or at the same time the liquid beverage is introduced. As the head space 84 will be minimum, the pressure will quickly reach equilibrium with the internal pressure within capsule 10. When pull-top 84 is open, however, pressure in the head space will quickly lower to ambient. Propellant gas from capsule 10 will then rapidly desorb, requiring enthalpy of desorption. The necessary heat for the enthalpy will be absorbed from the liquid beverage contained in the container, thus causing cooling. In addition to self-cooling liquid packages where cooling is initiated upon opening of the package, the pressurized capsules of the present invention will also be useful for cooling any liquid present in an open container. The capsules will simply be immersed in a liquid, initiating release of the propellant gases therefrom. As the gases desorb, enthalpy of desorption will cause cooling.

It should be noted, that when used in cooling applications, the term "propellant" is a misnomer. The propellant gases do not actually act to propel anything in such cooling applications. Suitable gases for cooling, however, will be identical to those which are useful as propellants as described above. Thus, for consistency, the term propellant gas will be used even in conjunction with cooling applications according to the present invention.

The following examples are offered by way of illustration, not by way of limitation.

EXPERIMENTAL Pressurized capsules 100, as illustrated in Fig. 7, were prepared as follows. Each capsule comprised a shell 101 having a fill-valve 102 at one end and an open aperture 104 at the other end. One capsule was filled with activated charcoal and a second capsule was filled with a natural zeolite. Both capsules were charged with carbon dioxide at 6.5 atmospheres

(95 psig) for 1.5 hours. Prior to charging, the capsules were evacuated to minus 0.7 atmospheres (-11 psig) for a short time. The capsules were sealed using a porous plug 106 and a bead of molten sugar 108. The sugar, after hardening, will seal the aperture 104 and prevent loss of propellant gas from the sorbent matrix. Porous padding will prevent loss of the sorbent material after the plug has been removed. Each pressurized capsule 100 was placed in a conventional aerosol can having an internal volume of 300 ml, with a liquid volume of 220 ml, and a head space of 10 ml. The pressurized capsule 100 displaced a volume of 70 ml. The soluble sugar plug dissolved in less than 30 minutes, allowing release of the propellant gas to pressurize again. Both pressurized capsules were able to achieve an equilibrium pressurization of about 4 atmospheres (59 psig) .

The cans were then discharged periodically releasing liquid through the actuator. It was found that the pressurized capsule was able to maintain a generally uniform pressure as the product is dispensed. The internal can pressure as a function of fill volume (percent of liquid product remaining) is illustrated in Fig. 8. Fig. 8 is a generalized representation of a number of actual trials and is not meant t represent a single test result.

Although the foregoing invention has been described in some detail by way of illustration and example, for purpose of clarity of understanding, it will be obvious that certain changes and modifications may be practiced within the scope of the appended claims.

Claims

WHAT IS CLAIMED IS:

1. A pressurization capsule comprising: a capsule wall defining an interior volume and exterior environment; a propellant sorbed within a sorbent and contained within the interior volume of the capsule; and means on the capsule for releasing the propellant in response to a change in the exterior environment.

2. A pressurization capsule as in claim 1, wherein the releasing means comprises passages means formed in the capsule wall for transporting gas from the interior volume to the exterior environment and further comprising a barrier which blocks gas transport through said passage means, wherein said barrier is soluble in a liquid.

3. A pressurization capsule as in claim 2, wherein the capsule wall is non-permeable and the passage means comprises one or more apertures, wherein the barrier comprises a liquid-soluble plug in said aperture to define the passage means.

4. A pressurization capsule as in claim 3, further comprising a porous retainer disposed adjacent the aperture to contain the sorbent and permit transport of the propellant to define the passage means.

5. A pressurization capsule as in claim 2, wherein at least a portion of the capsule wall is gas permeable to define the passage means and wherein the barrier comprises a liquid soluble layer which occludes said gas permeable portion.

6. A pressurization capsule as in claim 1, wherein the propellant-releasing means comprises at least a portion of the capsule wall which is mechanically frangible.

7. A pressurization capsule as in claim 1, wherein the propellant-releasing means comprises at least a portion of the capsule wall which is heat frangible.

8. A pressurization capsule as in claim 1, wherein the barrier is soluble in an aqueous or organic liquid and is composed of a material selected from the group consisting of carbohydrates and gelatin.

9. A pressurization capsule as in claim 1, wherein the propellant is selected from the group consisting of carbon dioxide, nitrous oxide, ammonia, sulfur dioxide, low molecular weight hydrocarbons, and chlorinated fluorocarbons.

10. A pressurized capsule as in claim 1, wherein the sorbent is composed of a material selected from the group consisting of activated charcoal, natural zeolite, synthetic zeolite, silicates, and molecular sieve materials.

11. A pressurization capsule as in claim 1, further comprising an expandable bag, wherein the releasing is disposed to release propellant into said bag.

12. An aerosol delivery package comprising: a shell defining a pressure-tight interior volume containing a liquid to be dispensed; an actuator in the shell; and a pressurization capsule as in any of claims 1-11 disposed the interior volume of the shell.

13. A self-cooling liquid package comprising: a shell defining a pressure-tight interior volume; means for opening the shell to abruptly establish pressure equilibrium between said interior volume and ambient conditions; and a pressurization capsule as in any of claims 1-11 disposed in the interior volume of the shell.

14. A self-cooling liquid package comprising: a shell defining a pressure-tight interior volume; means for opening the shell to abruptly establish pressure equilibrium between said interior volume and ambient conditions; a sorbent material within said interior volume, said sorbent having a propellant sorbed therein which is in pressur equilibrium with an elevated interior volume pressure, and a liquid in said interior volume and in thermal contact with said sorbent material, wherein opening said opening means cause propellant desorption from said sorbent thereby cooling said liquid.

15. A method for pressurizing an aerosol delivery package, said method comprising: combining a capsule and a material to be dispensed i said package, wherein said capsule contains a propellant sorbe within a sorbent and includes means for releasing the propellant in response to an environmental event; and sealing the package, whereby pressure will increase as the propellant is released from the capsule.

16. A method as in claim 15, wherein the material t be dispensed is a liquid and the means for releasing comprises a barrier on the capsule which is soluble in said liquid, whereby the propellant is released from the capsule after the barrier dissolves in the presence of the liquid.

17. A method as in claim 15, wherein the capsule comprises a non-permeable wall having at least one aperture, wherein the barrier comprises a liquid soluble plug in said aperture.

18. A method as in any of claims 16 or 17, wherein the liquid to be dispensed comprises an aqueous or organic bas and the barrier is composed of a material selected from the group consisting of carbohydrates and gelatin.

19. A method as in claim 15, wherein the means for releasing is a mechanically frangible barrier on the capsule and said method further comprises subjecting the package to sufficient mechanical shock to break the barrier to release th propellant.

20. A method'as in claim 15, wherein the means for releasing is a heat frangible barrier on the capsule and said method further comprises subjecting the package to an elevated temperature for a time sufficient to break the barrier to release the propellant.

21. A method as in any of claims 19 or 20 wherein the propellant is released into an expandable bag, whereby the bag expands as the propellant is released and the propellant i isolated from the material to be dispersed.

22. A method for cooling a liquid maintained under ambient pressure, said method comprising: combining the liquid with a capsule, wherein said capsule contains a propellant sorbed within a sorbent; and releasing propellant from said capsule sufficiently rapidly so that the enthalpy of desorption absorbs heat from the liquid to reduce the temperature by a desired amount.

23. A method as in claim 22, wherein the capsule is combined with the liquid in an open container under ambient pressure, wherein the propellant is released substantially immediately after contact with the liquid to cool the liquid.

24. A method as in claim 22, wherein the capsule is combined with the liquid in a pressure-tight container so that the propellant is in pressure equilibrium, wherein propellant is released by abruptly opening said container to the ambient.

25. A method as in any of claims 23 or 24, wherein the capsule includes means for releasing propellant in respons to an environmental event.

26. A method as in claim 25, wherein the means for releasing comprises a barrier on the capsule which is soluble in said liquid, whereby the propellant is released from the capsule after the barrier dissolves in the presence of the liquid.

27. A method as in claim 25, wherein the capsule comprises a non-permeable wall having at least one aperture, wherein the barrier comprises a liquid soluble plug in said aperture.

28. A method as in claim 25, wherein the liquid to be cooled comprises an aqueous or organic base and the barrier is composed of a material selected from the group consisting of carbohydrates and gelatin.

29. A method as in claim 25, wherein the means for releasing is a mechanically frangible barrier on the capsule and said method further comprises subjecting the package to sufficient mechanical shock to break the barrier to release the propellant.

30. A method as in claim 25, wherein the means for releasing is a heat frangible barrier on the capsule and said method further comprises subjecting the package to an elevated temperature for a time sufficient to break the barrier to release the propellant.

31. A method as in claim 25, wherein the means for releasing is a mechanically frangible barrier on the capsule and the capsule is disposed in an expandable bag which isolates released propellant from the material to be dispensed.