US3446746A - Novel three phase aerosols - Google Patents

Description

United States Patent 5 Int. Cl. (509k 3/30 US. Cl. 252-30 7 Claims ABSTRACT OF THE DISCLOSURE Three phase aerosol systems for the propulsion of liquid solutions or suspensions wherein the liquid to be discharged (first or useful phase) is projected through a spray nozzle by the action of a liquefied propellant under pressure gelled with an aluminum salt of a fatty acid of 8 to 18 carbon atoms (second phase) having a lower density than the first phase and a gaseous phase of the said propellant (third phase) which increases in volume in proportion to the amount of the useful phase sprayed by vaporization of the liquid propellant. The useful phase is released by actuation of a control element which communicates with the useful phase and the outlet for discharging the said phase into the atmosphere. These conditions effect each spraying under a constant pressure equal to the pressure of liquefaction of the second phase. The liquid propellants are well known and may be liquified hydrocarbons or halogenated hydrocarbons or mixtures thereof such as propane and butane. The gelled liquified propellant has a viscosity suificient to clog the dip-tube opening when the first liquid phase has been discharged.

Prior art The problem of known aerosol systems is that the propellant is discharged from the apparatus in the gaseous phase through the dip-tube after the first or useful phase has been completely discharged, which is undesirable. For this reason, the said propellants have not been used for many spraying purposes, particularly for aqueous solutions of medicines such as for the treatment of ailments such as of rhinolaryngologic, vaginal, etc. The use of transparent containers to ascertain when the first phase has been used up has been suggested but this does not prevent a premature discharge of at least some of the liquefied propellant through the spray means in the form of gas.

Objects of the invention It is an object of the invention to provide a novel aerosol system which will not allow discharge of the propellant after the first phase has been used up.

This and other objects and advantages of the invention will become obvious from the following detailed description.

The invention The novel three phase aerosol system of the invention comprises a pressurized system of a first liquid phase to be discharged, a liquid and gelled gas propellant having a lower density than the first phase and immiscible therein and a gaseous phase of the said propellant. The second phase in gelled form performs its normal function of generating additional gaseous phase as the first phase is discharged to maintain the pressure in the system and performs the additional function of preventing the escape of the gaseous phase when all of the first liquid phase has been discharged. When the gelled liquefied propellant reaches the opening of the dip-tube, it automatically clogs the dip-tube due to the viscosity of the gel and the small diameter of the dip-tube.

3,446,746 Patented May 27, 1969 Examples of suitable liquefiable propellants useful for the invention are hydrocarbons such as propane, butane, mixtures of propane and butane, trichlorofiuoromethane, mixtures of trichlorofiuoromethane and propane and/or butane, dichlorodifluoromethane and/or dichlorotetrafiuoroethane alone or admixed with propane and/or butane. The selection of the specific propellant will depend upon the pressure required to discharge the first phase which pressure is determined by the characteristics of the first phase. The pressure required for the liquefaction of the propellant depends on the propellant and is not effected by the gelled state of the propellant.

The gelling of the liquid propellant gases can be effected by any suitable gelling agent, but aluminum salts of fatty acids having 8 to 18 carbon atoms are preferred. Examples of suitable fatty acids are 2-ethylhexanoic acid, dodecanoic acid, undecanoic acid, palmitic acid, stearic acid, nonanoic acid, etc. Aluminum 2-ethylhexanoate is particularly preferred. The amount of gelling agent required will vary depending upon the specific gelling agent and liquefied propellant, but is usually 1 to 15% by weight of the liquefied propellant.

The gelling of the liquefied propellant may be effected in a suitable vessel and the gelled propellant can then be introduced into the pressure container. However, the propellant is preferably gelled in the pressure container per se. The filling of the container is preferably effected by introducing the desired quantity of the first liquid phase which is to be discharged into the pressure container followed by the desired quantity of gelling agent. The plug or valve control element is then set on the pressure container and then the liquefied gas which is immiscible in the first phase is introduced into the first liquid phase in a larger quantity than that required to fill the container with a gaseous phase at the desired pressure after which the container is moderately agitated for a short time to assure even dispersion of the gelling agent in the liquid second phase. The gel formation occurs within a few minutes and a portion of the propellant vaporizes and settles above the liquid and gel phases. The output ferrule, usually an atomizer nozzle, is then attached unless it is already attached to the valve head. Any known type of pressurized or aerosol container may be used.

The space above the liquid first phase and gelled second phase is filled with the gaseous third phase under a pressure equal to the vapor pressure of the gelled second phase, which pressure is exerted on the first liquid phase through pressure on the intermediate gelled phase. When the control valve of the pressurized container is open, the first phase liquid is forced out of the container through the atomizer nozzle or other outlet ferrule by the said pressure. Each time the first phase is discharged, a portion of the gelled propellant vaporizes to keep the pressure in the container constant. As the first phase is discharged, the gelled second phase approaches the bottom of the container until the last of the first phase is discharged at which time the gelled propellant comes in contact with the discharge opening, usually the lower end of a dip-tube. Due to the high viscosity of the gelled propellant, it is not able to flow through the said opening and effectively closes it so that the propellant cannot leave the container in gaseous form.

The present invention is not only applicable for the discharge of medicinal solutions but for any liquid immiscible in the liquid second phase propellant. It allows the use of propellants which due to their properties such as toxicity and/or flammability have been avoided or restricted in their use.

In the following examples there are described several preferred embodiments to illustrate the invention. However, it should be understood that the invention is not intended to be limited to the specific embodiments.

3 Example I 40 cc. of an aqueous solution of a therapeutic and 0.1 gm. of alumuinm 2-ethylhexanoate were introduced in a 50 cc. aerosol container and then a conventional valve comprised of a valve head, a valve or plug and plunger tube extending almost to the bottom of the container was installed. Then 2 gm. of liquid butane were introduced into the container through the valve by means of an injector pump. The butane was slowly agitated for a short period of time to disperse the said aluminum salt therein and a gel formed in a few minutes which floated on the aqueous phase after which the valve control was mounted. Any conventional means could be used to introduce the liquiefied propellant into the aerosol container.

The useful liquid or first phase is emitted through the spray nozzle and the pressure in the container is kept constant by vaporization of the gelled propellant. As the first phase is used up, the gelled propellant goes lower in the container and when the last of the first phase is used up, the gelled propellant comes in contact with the lower orifice of the plunger tube. Because of the high viscosity of the gelled propellant, the propellant cannot pass through the said orifice and seals the orifice.

Example II Example I was repeated except the liquid propellant was 1 gm. of liquid butane, 0.2 gm. of liquid dichlorodifiuoromethane and 0.8 gm. of dichlorodifluoromethane. The said liquids could be added separately or as a mixture.

Example IV Example I was repeated except the liquid propellant was 1 gm. of liquid propane and 1 gm. of liquid trichlorofluoromethane. The said liquids could be added separately or as a mixture.

Example V Example I was repeated except the liquid propellant was 2 gm. of liquid propane and 0.2 gm. of aluminum 2-ethylhex-anoate was used.

Various modifications of the aerosol system of the invention may be made without departing from the spirit or scope thereof and it is to be understood that the invention is to be limited only as defined in the appended claims.

We claim:

-1. A three-phase system for the propulsion of liquids comprising a pressure system of a first liquid phase to be discharged, a liquefied propellant gelled with an aluminum salt of a fatty acid of 8 to 18 carbon atoms and having a lower density. than the first phase and immiscible therein and a gaseous phase of the said propellant, said gelled liquefied propellant having a viscosity sufficient to clog the dip-tube opening when the first liquid phase has been discharged.v

2. The system of claim 1 wherein the gelling agent is present in an amount of 1 to 15% by weight of the liquefied propellant. i l y 3. The system of claim butane.

4. The system of claim 1 wherein the propellant is propane.

5. The system of claim 1 wherein the propellant is a mixture of propane and butane.

6. The system of claim 1 wherein the propellant is a mixture of at least one chlorofiuorohydrocarbon selected from the group consisting of trichlorofluoromethane, dichlorodifluoromethane and dichlorotetrafluoroethane and at least one hydrocarbon selected from the group consisting of propane and butane.

7. The system of claim 2 whereinthe gelling agent is aluminum 2-ethylhexanoate.

1 wherein the propellant is References Cited UNITED STATES PATENTS 2,866,754 12/1958 Cardwell et a1 252-855 2,876,839 3/1959 Fast et al 166 -22 3,137,416 6/1964 Shepherd et a1. 252-305 X 3,148,127 9/1964 Marsh 2 252--305 X 3,218,263 11/1965 Boyle et al 252-305 RICHARD D. LOVERING, Primary Examiner.

US. Cl. X.R. 42445