WO1994001511A1

WO1994001511A1 - Pressurised aerosol formulation

Info

Publication number: WO1994001511A1
Application number: PCT/GB1993/001419
Authority: WO
Inventors: David John Page
Original assignee: Smithkline Beecham Plc
Priority date: 1992-07-11
Filing date: 1993-07-06
Publication date: 1994-01-20
Also published as: GB9214765D0

Abstract

A pressurised aerosol formulation in a pressurised container which is in the form of a compressed gas, a liquefied hydrocarbon propellant and also active compound(s) and carrier(s) which are in the form of a suspension or a solution and which contains at least 0.05 per cent by weight of compressed gas and at least 0.5 per cent by weight of liquefied hydrocarbon propellant.

Description

PRESSURISED AEROSOL FORMULATION

The present invention relates to propellants used in pressurised spray containers particularly those of the type known as aerosol cans.

Traditionally these systems use liquefied propellants, which have the ability to change from the gaseous to liquid state (below the critical temperature) when pressure is applied. Examples of liquefied propellants are hydrocarbon and chlorofluorocarbons. The liquefied propellant is contained in the packaging and it divides between the liquid and gaseous phases, with the liquid phase forming a reserve. On spraying the container, part of the gaseous phase is expelled. Immediately a part of the liquid phase vaporises, returning the internal pressure almost to its original starting pressure. The pressure remains substantially constant throughout the life of the container. The pressurised containers are equipped with a dispensing head and valve and pressurised with the liquefied propellant. Upon discharge of the concentrate through the dispensing head the volatilisation of the dispensed liquid propellant particles assists the dispensed product to form aerosol droplets. This change from the liquid to gaseous phase may also have a self cleaning action to remove any residual concentrate which may have remained within the expansion chamber and channels of the dispensing head after spraying has ceased.

A disadvantage of hydrocarbon propellants is that they are by nature flammable and the possibility of an explosion exists if the hydrocarbon/air ratio is between the upper and lower explosive limits. Products using hydrocarbon propellants therefore require careful handling, storage and transportation. Also, for environmental reasons, the future use of hydrocarbon propellants may be restricted.

One alternative to using liquefied gases is to use compressed gas as the propellant system. Various compressed gas containing products have been successfully marketed using carbon dioxide. However, the use of carbon dioxide may also in the future be restricted for environmental reasons. Nitrogen is suitable for use as a compressed gas propellant, it is non toxic, non-flammable and environmentally friendly. There are, however, some disadvantages to using nitrogen as an aerosol propellant. Because the nitrogen is only present as a gas, there is no liquid state present (unlike the liquefied propellants) to form a pressure reserve. Typically only 1 - 2 g of nitrogen can be filled into an aerosol package. Any misuse of the aerosol package resulting in loss of the nitrogen propellant may prevent total evacuation of the contents. Nitrogen propellant systems rely on the use of mechanical means involving the use of small diameter channels in the dispensing head to create the aerosol particles. This is because there is no liquid to gas transformation as with the liquefied propellants. Nitrogen does not have the self cleaning action of the the liquefied propellants and therefore any product remaining in the channels after spraying will quickly lead to impaired performance and may even result in total blockage.

The nitrogen is added to the aerosol container by filling to a typical pressure of 120 psig. As the contents are dispensed there is a pressure drop within the can to around 30 - 40 psig after total evacuation of the contents. This pressure drop may affect the break up characteristics of the valve with a gradual transition from fine to coarse aerosol particles as the pressure decreases.

The use of nitrogen as the sole aerosol propellant also results in performance differences compared to a liquefied propellant system e.g. hairspray formulation gives a significantly wetter spray, taking longer to dry, forming globules of product on the hair and generally giving an inferior performance.

For these reasons we have found it desirable to provide a mixture of compressed gas and liquefied propellant which are to be sprayed from a pressurised gas container as a cosmetic, household or medicinal spray of propellant gases to:-

1) Provide a small reservoir of liquefied propellant to ensure total evacuation of the contents in the case of misuse.

2) Provide the self cleaning action of liquefied propellants to prevent blockage of the dispensing head.

3) Ensure constant spray characteristics throughout the life of the can.

4) Improve the product's performance to give parity with that of a typical liquefied propellant system.

5) Reduce the flammability of the product in comparison to a liquefied propellant system.

The present invention therefore provides a pressurised aerosol formulation in a pressurised container which is in the form of a compressed gas, a liquefied hydrocarbon propellant and also active compound(s) and carrier(s) which are in the form of a suspension or a solution and which contains at least 0.05 per cent by weight of compressed gas and at least 0.5 per cent by weight of liquefied hydrocarbon propellant.

Suitable compressed gases are nitrogen, carbon dioxide, compressed air, oxygen, xenon, argon or mixtures thereof.

Suitable liquefied hydrocarbon propellants are methane, ethane, butane, propane, isobutane, dimethyl ether, pentane, hexane, heptane, octane, nonane, decane, chlorodifluoromethane, 1,1 dichloro, 2,2,2 trifluroethane, 1,2 dichloro, 2,2, difluoroethane, 2 chloro, 2,2 difluoroethane, 1,2,2,2 tetrafluoroethane, 2,2,2 trifluoroethane, 1,1,1 trichloroethane, dichloromethane, or mixtures thereof.

Suitable carriers are volatile compounds, for example alcohols, and include ethyl alcohol, n-propanol, iso-propanol, n-pentane, iso-pentane, water, acetone, ethyl, methyl ketone, diethyl ether, volatile silicone compounds, fluoro surfactants, dimethoxy methane, diethyl carbonate, methoxy acetone, hydroxy acetone, methyl isopropyl ketone, diethyl ketone, diisopropyl ketone, dipropyl ketone, diacetone alcohol, or mixtures thereof. The formulation according to this invention can be formulated with cosmetic, hygienically or medicinally active constituents (active compounds) and give formulations for different purposes eg. cosmetic spray.

Active compounds which can be contained in the formulation are eg. hair spray resin, hair care substances, deodorants, antiperspirants, perfume, bactericidal agents and fungicides.

Examples of such actives being 2,4,4'trichloro-2'-hydroxydiphenylether which is sold by Ciba Geigy and is known internationally under the non-proprietary name of Triclosan, and octylamide/ acrylate/ butylaminoethyl methacrylate, a hairspray resin which is sold by National Starch Ltd. and is sold under the name Amphomer LV71. It may also be necessary to include in certain formulations other ingredients such are conventional in the art, for example neutralisers for hairspray resins such as amino-methylpropanol, otherwise known as AMP.

A typical aerosol formulation preferably contains as propellant gases 0.05 to 2.5 per cent by weight of nitrogen and 1.0 to 12.0 per cent by weight of liquified hydrocarbon, the percentages by weight being based on the total weight of the constituents of the filled container.

The aerosol formulation preferably contains 80 - 95 per cent by weight of a carrier, suitably an organic carrier for the propellant gases and/or active compound(s), the percentages by weight being based on the total weight of the constituents of the filled container.

Ideally the aerosol formulation is characterised in that it contains 0.7 - 1.4 per cent by weight of nitrogen, 4 - 9 per cent by weight of liquified hydrocarbon, 85 - 93 per cent by weight of an organic carrier, suitably alcohol, and 1 to 4 per cent of active compound by weight. The nature and the amount of the required active compound, organic solvent for the propellant gases and/or active compound, and nitrogen are so matched Qualitatively and quantitatively in a sample batch taking into account the intended use and taking into account the ranges given above for the percentages by weight that a suspension or solution is obtained which can be sprayed without blocking nozzles or channels as a ready to use aerosol.

The present invention also provides a process for the manufacture of an aerosol formulation which is characterised in that the active compound(s), and carrier(s) are processed such that a requisite partial amount is filled into a pressurised spray container and subsequently sealed with a valve. After the liquefied hydrocarbon propellant and nitrogen have been filled through the valve into the container under pressure, the liquid product is in the form of a suspension or homogeneous solution under a pressure of about 120 psig.

The invention is illustrated by the following Examples wherein all figures refer to % w/w.

EXAMPLES Hairsprays

Deodorant Sprays

Claims

1. A pressurised aerosol formulation in a pressurised container which is in the form of a compressed gas, a liquefied hydrocarbon propellant and also active compound(s) and carrier(s) which are in the form of a suspension or a solution and which contains at least 0.05 per cent by weight of compressed gas and at least 0.5 per cent by weight of liquefied hydrocarbon propellant.

2. An aerosol formulation according to claim 1, wherein the compressed gas is nitrogen, carbon dioxide, compressed air, oxygen, xenon, argon or mixtures thereof.

3. An aerosol formulation according to claim 2, wherein the liquefied hydrocarbon propellant is methane, ethane, butane, propane, isobutane, dimethyl ether, pentane, hexane, heptane, octane, nonane, decane, chlorodifluoromethane, 1,1 dichloro, 2,2,2 trifluroethane, 1,2 dichloro, 2,2, difluoroethane, 2 chloro, 2,2 difluoroethane, 1,2,2,2 tetrafluoroethane, 2,2,2 trifluoroethane, 1,1,1 trichloroethane, dichloromethane, or mixtures thereof.

4. An aerosol formulation according to claim 3, comprising 80-95 per cent by weight of carrier(s), the carrier(s) being volatile compound(s).

5. An aerosol formulation according to claim 4, wherein the carrier(s) are ethyl alcohol, n-propanol, iso-propanol, n-pentane, iso-pentane, water, acetone, ethyl, methyl ketone, diethyl ether, volatile silicone compounds, fluoro surfactants, dimethoxy methane, diethyl carbonate, methoxy acetone, hydroxy acetone, methyl isopropyl ketone, diethyl ketone, diisopropyl ketone, dipropyl ketone, diacetone alcohol, or mixtures thereof.

6. An aerosol formulation according to any one of claims 1 to 5 comprising 0.05 to 2.5 per cent by weight of nitrogen and 1.0 to 12.0 per cent by weight of liquified hydrocarbon.

7. An aerosol formulation according to claim 6 comprising as active compound(s), hair spray resin, hair care substances, deodorants, antiperspirants, perfume, bactericidal agents or fungicides.

8. An aerosol formulation according to claim 7 comprising 2,4,4'trichloro-2'- hydroxydiphenylether.

9. A process for the manufacture of an aerosol formulation which is characterised in that the active compound, and carrier(s) are processed such that a requisite partial amount is filled into a pressurised spray container, sealed with a valve and thereafter the liquified hydrocarbon propellant and compressed gas introduced into the liquid product.

10. A process according to claim 11, wherein the liquid product is in the form of a suspension or homogeneous solution under a pressure of about 120 psig.

11. An aerosol formulation according to any one of claims 1 to 8, for use with cosmetic, hygienically or medicinally active constituents.

12. An aerosol formulation according to claim 11 for use as a cosmetic, household or medicinal spray.