Aerosol Composition And Method For Producing Same

Abstract

A sprayable aerosol composition is prepared by encapsulating a material in a microcapsule and introducing into said microcapsule a fluid under a pressure essentially equal to the pressure in the aerosol container from which said composition is dispensed. Also provided is an aerosol dispenser containing under pressure said microcapsules dispersed in an aerosol propellant.

Description

This invention relates to a method for producing a sprayable aerosol composition containing a self-releasable encapsulated material and to an aerosol dispenser containing said encapsulated material dispersed in a propellant.

More particularly, the present invention relates to the production of an aerosol composition containing an encapsulated material which can be released therefrom without the need of mechanical, chemical or thermal means.

The present invention has been found to be particularly useful in the cosmetic and pharmaceutical industry and in the packaging of maintenance products, for projecting active ingredients onto the surface where they are to act, and to obtain automatic liberation of these ingredients on the said support.

The present invention is a method for producing a sprayable aerosol composition containing a self-releasable encapsulated material which comprises encapsulating the material to be sprayed in the form of an aerosol in a rupturable microcapsule having a size ranging from about 50 to 1000 microns in diameter and introducing into said microcapsule a fluid under sufficient pressure so that when said microcapsule, dispersed in an aerosol propellant, is sprayed into an atmosphere having a pressure less than the pressure of the fluid in said microcapsule, the microcapsule ruptures, thereby releasing the material contained therein.

Preferably, in the present invention the propellant in which the microcapsules are dispersed and stored and the fluid contained in the microcapsules under pressure are essentially the same. Thus, this fluid and propellant can conveniently be a fluorinated hydrocarbon and particularly a fluorochloroalkane such as trichlorofluoromethane and dichlorofluoromethane or their mixtures. Moreover, the propellant can be a saturated aliphatic hydrocarbon such as propane, isobutane, n-butane or the like. The aerosol dispenser in which the propellant and microcapsules are packaged will have a valve provided with a diaphragm, having a diameter greater than the maximum diameter of the microcapsules.

In one embodiment of the present invention, a fluid having sufficient pressure to rupture the micro-capsule when sprayed into the atmosphere is introduced into the microcapsule in the liquid state in admixture with the material to be released therefrom on rupturing. In this case, microencapsulation is carried out at a sufficiently low temperature and pressure so that the fluid is in the liquid. When the material being encapsulated is itself a liquid, it must be miscible with the liquified pressuring medium, especially when the releasable material is an alcohol solution, and the liquified pressuring medium gas is a mixture of fluorochloroalkanes.

In another embodiment of the present invention, the material to be released is initially microencapsulated in the absence of any pressurizing medium, and the micro-capsules are then placed in an atmosphere of the desired pressurizing medium at a pressure sufficient for the said pressurizing medium to permeate the microcapsule walls in a time ranging from a few minutes to a few days.

The present invention is also related to an aerosol dispenser containing a suitable propellant and the microcapsules defined above. Thus, when these components are sprayed from the pressurized dispenser, it will be evident that when the user depresses the valve of the dispenser, the microcapsules, having dispersed therein the propellant having an internal pressure at least equal to the pressure of the propellant in the dispenser but greater than the atmosphere into which they are sprayed will rupture as soon as they come in contact with the atmosphere. Packaging will thus be achieved in which the microcapsules exist during storage and which do not have to be destroyed by any independent action of the user at the time of dispensing the same onto the desired surface.

The microcapsules used in the present invention can be made of any conventionally employed material in the microencapsulation field. Representative of polymeric materials to produce the microcapsules are such polymers as polyvinyl alcohol, polyethylene, polypropylene, polystyrene, polyacrylamides, polyethers, polyesters, polyamides, polybutadiene, polyisoprene, epoxy resins, polyurethanes, ethylcellulose, carboxymethylcellulose and the like. Preferably, the microcapsules are made from a thermoplastic polymer such as low melting polyethylene; the latter is particularly applicable when the pressurizing gas is a mixture of fluorochloroalkanes and when this mixture of fluorochloroalkanes is introduced into the microcapsules by using the permeability characteristics of the wall. The nature of the walls will generally be chosen for its compatibility with the propellant in which the microcapsules are placed. Generally, the ratio of the weight of the wall to the total weight of the filled microcapsule ranges between 3-10:100.

Any convenient technique of microcapsule fabrication can be used, particularly microencapsulation by mechanical means such as centrifugal microencapsulation. In this method droplets of the material to be encapsulated are formed by the centrifugal force of a turntable which then traverse by means of the velocity which they thus acquire, a thin film of fluid product designed to form the wall of the microcapsule. A conventional wall-hardening treatment can be employed which, in the case where the wall is prepared from a thermoplastic material, can simply be a sudden cooling of the microcapsules formed. Representative suitable microencapsulation operations can be found in the literature, for instance in U.S. Pat. No. 3,015,128.

The material encapsulated in the microcapsules can be, for instance, such cosmetic preparations as hair dyes, bleaches, dressing composition or the like, pharmaceutical preparations including antiseptics, topical anesthetics, or such products as stain-removing agents, finely divided solid inorganic absorbents such as talc and the like.

In order to gain a better understanding of the invention, the following example is provided.

EXAMPLE

Mechanical centrifuging is used to prepare microcapsules with average dimensions of approximately 400 microns from low melting polyethylene. The microencapsulated liquid has the following composition:

nonylphenol condensed with 4 molecules of ethylene oxide 23 g nonylphenol condensed with 9 molecules of ethylene oxide 25 g copra diethanolamide 6 g butyl glycol 2 g propylene glycol 16 g 20% ammonia 12 ml paratoylenediamine 0.9 g paraaminophenol 0.9 g m-diaminoanisole sulfate 0.06 g m-aminophenol 0.2 g resorcinol 0.5 g nitroparaphenylenediamine 0.002 g hydroquinone 0.10 g sodium salt of diethylene- triaminepentaacetic acid 1.5 g sodium bisulfite 1.2 ml water 100 g

The microcapsules thus formed are placed in a atmosphere of a fluorochloralkane at a relative pressure of 1.5 kg/cm.sup.2. This pressure is maintained for several days, after which the microcapsules are transferred, the external pressure being kept the same, to a liquid medium compatible with the wall, such as, for example, trichlorofluoromethane, dichlorodifluoromethane, or dichlorotetrafluoromethane. The liquid medium containing the microcapsules is then placed in a pressurized "aerosol can" type container at a pressure above 1.5 kg/cm.sup.2 by means of a fluorochloroalkane. The liquid present in the pressurized container is dispensed directly onto hair to be dyed by the action of the container valve; the diaphragm associated with the valve having an aperture 1 mm in diameter. An oxidant is added to the dye thus placed on the hair. Alternatively, an oxidant can be included in the propellant. After 15 minutes, a chestnut brown coloration is obtained on 70 percent white hair.

Claims

What is claimed is:

1. An aerosol dispenser provided with a valve through which the contents thereof are discharged therefrom and containing a propellant under pressure and sprayable microcapsules dispersed therein, said microcapsules encapsulating a liquid cosmetic or pharmaceutical material and a fluid under pressure to provide a liquefied encapsulated pressuring medium, said microcapsules having walls compatible with and permeable to said aerosol propellant and having a size ranging from about 50 - 1000 microns in diameter and being less than the diameter of the valve of said aerosol dispenser in which said propellant and microcapsules are packaged; said fluid encapsulated in said microcapsules under pressure and said propellant in which said microcapsules are dispersed and stored being essentially the same and comprising a liquefied gas of a fluorinated hydrocarbon selected from the group consisting of trichlorofluoromethane, dichlorofluoromethane and mixtures thereof or a saturated aliphatic hydrocarbon selected from the group consisting of propane, isobutane, n-butane and mixtures thereof, said liquid cosmetic or pharmaceutical material being miscible with said liquefied pressuring medium and the internal pressure of said microcapsules containing said liquid cosmetic or pharmaceutical material and said liquefied pressuring medium being essentially equal to the pressure of said propellant in said dispenser but greater than the atmosphere into which said microcapsules are to be sprayed so that said microcapsules without any independent action of the user upon actuating the valve of the dispenser to discharge said microcapsules into the atmosphere through the valve of the dispenser, rupture as soon as said microcapsules come into contact with the atmosphere thereby releasing said liquid cosmetic or pharmaceutical material therefrom.

2. An aerosol dispenser provided with a valve through which the contents thereof are discharged therefrom and containing a propellant under pressure and sprayable microcapsules dispersed therein, said microcapsules encapsulating a liquid cosmetic or pharmaceutical material and a fluid under pressure to provide a liquefied encapsulated pressuring medium, said microcapsules having walls compatible with said aerosol propellant and having a size ranging from about 50 - 1000 microns in diameter and being less than the diameter of the valve of said aerosol dispenser in which said propellant and microcapsules are packaged; said fluid encapsulated in said microcapsules under pressure and said propellant in which said microcapsules are dispersed and stored being essentially the same and comprising a liquefied gas of a fluorinated hydrocarbon selected from the group consisting of trichlorofluoromethane, dichlorofluoromethane and mixtures thereof or a saturated aliphatic hydrocarbon selected from the group consisting of propane, isobutane, n-butane and mixtures thereof, said liquid cosmetic or pharmaceutical material being miscible with said liquefied pressuring medium and the internal pressure of said microcapsules containing said liquid cosmetic or pharmaceutical material and said liquefied pressuring medium being essentially equal to the pressure of said propellant in said dispenser but greater than the atmosphere into which said microcapsules are to be sprayed so that said microcapsules without any independent action of the user upon actuating the valve of the dispenser to discharge said microcapsules into the atmosphere through the valve of the dispenser, rupture as soon as said microcapsules come into contact with the atmosphere thereby releasing said liquid cosmetic or pharmaceutical material therefrom.

3. A method for producing and dispensing a sprayable aerosol composition contained under pressure in an aerosol dispenser provided with a valve through which the contents thereof are discharged therefrom into an atmosphere having a pressure less than the pressure in said aerosol dispenser, said composition comprising an aerosol propellant and sprayable microcapsules dispersed therein, said microcapsules encapsulating a liquid cosmetic or pharmaceutical material and a fluid under pressure to provide a liquefied encapsulated pressuring medium, said microcapsules having walls compatible with and permeable to said aerosol propellant and having a size ranging from about 50 - 1000 microns in diameter and being less than the diameter of the valve of said aerosol dispenser in which said propellant and microcapsules are contained, the steps comprising microencapsulating said liquid cosmetic or pharmaceutical material in said microcapsules; placing said microcapsules in an atmosphere containing said fluid at a pressure sufficient for said fluid to permeate the microcapsule walls so that fluid is contained within said microcapsules as a liquid to provide a liquefied encapsulated pressuring medium; dispersing at said pressure the resulting microcapsules containing said liquid cosmetic or pharmaceutical material and liquefied pressuring medium in an aerosol propellant, liquefied pressuring medium and said aerosol propellant in which said microcapsules are dispersed and stored being essentially the same and comprising a liquefied gas of a fluorinated hydrocarbon selected from the group consisting of trichlorofluoromethane, dichlorofluoromethane and mixtures thereof or a saturated aliphatic hydrocarbon selected from the group consisting of propane, isobutane, n-butane and mixtures thereof, said liquid cosmetic or pharmaceutical material being miscible with said liquefied pressuring medium; and confining under pressure said microcapsules, containing said liquefied cosmetic or pharmaceutical material and liquefied pressuring medium, dispersed in said aerosol propellant in said aerosol dispenser, the internal pressure of said microcapsules containing said liquefied cosmetic or pharmaceutical material and said liquefied pressuring medium being essentially equal to the pressure of said aerosol propellant in said dispenser but greater than the atmosphere into which said microcapsules are to be sprayed so that said microcapsules without any independent action of the user upon actuating the valve of the dispenser rupture as soon as said microcapsules come into contact with the atmosphere thereby releasing said liquid cosmetic or pharmaceutical material therefrom.

4. A method for producing and dispensing a sprayable aerosol composition contained under pressure in an aerosol dispenser provided with a valve through which the contents thereof are discharged therefrom into an atmosphere having a pressure less than the pressure in said aerosol dispenser, said composition comprising an aerosol propellant and sprayable microcapsules dispersed therein, said microcapsules encapsulating a liquid cosmetic or pharmaceutical material and a fluid under pressure to provide a liquefied encapsulated pressuring medium, said microcapsules having walls compatible with said aerosol propellant and having a size ranging from about 50 - 1000 microns in diameter and being less than the diameter of the valve of said aerosol dispenser in which said propellant and microcapsules are contained, the steps comprising microencapsulating said liquid cosmetic or pharmaceutical material in admixture with said fluid in said microcapsules at a sufficiently low temperature and at a pressure so that said fluid provides a liquefied pressuring medium encapsulated therein; dispersing the resulting microcapsules, containing said liquid cosmetic or pharmaceutical material and liquefied pressuring medium, in an aerosol propellant, said liquefied pressuring medium and said aerosol propellant in which said microcapsules are dispersed and stored being essentially the same and comprising a liquefied gas of a fluorinated hydrocarbon selected from the group consisting of trichlorofluoromethane, dichlorofluoromethane and mixtures thereof or a saturated aliphatic hydrocarbon selected from the group consisting of propane, isobutane, n-butane and mixtures thereof, said liquid cosmetic or pharmaceutical material being miscible with said liquefied pressuring medium; and confining, under pressure, said microcapsules, containing said liquid cosmetic or pharmaceutical material and liquefied pressuring medium, dispersed in said aerosol propellant in said aerosol dispenser, the internal pressure of said microcapsules containing said liquid cosmetic or pharmaceutical material and said liquefied pressuring medium being essentially equal to the pressure of said aerosol propellant in said dispenser but greater than the atmosphere into which said microcapsules are to be sprayed so that said microcapsules without any independent action of the user upon actuating the valve of the dispenser to discharge said microcapsules into the atmosphere through the valve of the dispenser, rupture as soon as said microcapsules come into contact with the atmosphere thereby releasing said liquid cosmetic or pharmaceutical material therefrom.