GB1587074A - Propellants for aerosol sprays - Google Patents

Description

(54) PROPELLANTS FOR AEROSOL SPRAYS (71) We, HOECHST AKTIENGESELLSCHAFT, a body corporate organised according to the laws of the Federal Republic of Germany, of 6230 Frankfurt/Main 80, Postfach 80 03 20, Federal Republic of Germany, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- Aerosol sprays use as propellants compressed or liqueified gases, for example CO2 and/or N2O, mixtures of chlorofluorohydrocarbons, or mixtures of propane and butane. Moreover, combinations of compressed and liquefied gases have been proposed and used for this purpose.

Each of these propellant types has several advantages and disadvantages, which depend mainly on the physical properties of the propellant. Compressed gases have the disadvantage that the pressure exerted by them is inversely proportional to the available volume in the container. This means that the pressure in the aerosol container is reduced as the aerosol is used, and thus the spray behaviour changes constantly. This effect is reduced if the compressed gas has a good solubility in the liquid containing the active ingredients, but it cannot be compensated for quantitatively.

Certain liquefied gases have the great disadvantage from the safety point of view that they form explosive mixtures with air; the use of certain other gases having suitable physical properties for use as aerosol propellants is forbidden for toxicological reasons.

Among non-combustible chlorofluorohydrocarbons used as propellants in aerosol sprays, trichlorofluoromethane CCl3F (FKW 11), dichlorodifluoromethane CCl2F2 (FKW 12) and dichlorotetrafluoroethane C2CI2F4 (FKW 114) have been used successfully in industry. Mixtures of FKW 11 and FKW 12 or of FKW 12 and FKW 14 can be used to prepare aerosol propellants which, at a temperature of 50"C, may have any excess pressure in the range of from 12 bars to the saturation pressure of the component having the higher boiling'point, the excess pressure depending on the proportion of each component in the mixture.

According to the technical regulations for compressed gases 300 (TRG 300, throw-away containers) in force in the Federal Republic of Germany, containers with compressed gas (aerosol containers) may have a pressure of no more than 12 bars at a temperature of 50"C. This requirement is excellently fulfilled by the above fluorochlorohydrocarbons.

A further compound of this type, namely chlorodifluoromethane CHCIF2 (FKW 22), an important refrigerant for compression-type refrigerating plants, is also industrially available. German Patent 859,202 discloses that FKW 22 can be used in principle in the same manner as FKW 11, 12 and 114 as a propellant in aerosols. In practice, however, it cannot normally be used as it has a vapour pressure of 18.3 bars at a temperature of 50"C, which is far in excess of the inaximum permitted overpressure in an aerosol fixed at 12 bars for safety reasons.

For most aerosol products (for example hair spray or lacquer spray) tin aerosol containers are used; the maximum admissible service overpressure of these at a temperature of 50"C is only 8 bars. Therefore FKW 22 cannot be used at all in these containers if FKW 22 concentrations of more than about 30 /O (calculated on the weight of the total aerosol mixture) are required to give an acceptable spray.

Even in relatively expensive aerosols made of aluminium and made to withstand a maximum operating overpressure of 12 bars, it has not been possible hitherto to use formulations containing more than 50% by weight of FKW 22, calculated on the total mixture, without exceeding the maximum admissible pressure (cf. Montford A.

Johnson: "The Aerosol Handbook", 1st edition, 1972, page 263).

Also in a number of countries there are legal regulations (for example the Federal Republic of Germany and other member countries of the European Community) which require the indication "combustible" to be present on aerosols if the proportion of non-combustible components is less than 55% by weight. In order to conform to these regulations by reducing the proportion of combustible components to no more than 45van by weight, an adequate quantity of FKW propellants must be used in most cases, especially in the field of cosmetic sprays, since the use of at least 550/, of non-combustible solvents should generally be avoided for reasons of toxicity.

The solvents customarily used in aerosol mixtures for dissolving the active ingredient (for example binder resin in hair spray) generally lead to a pressure reduction in the pressure exerted by the propellant as they affect the vapour pressure equilibrium. Montford A. Johnson has proposed the use of ethanol as a pressure-reducing component for FKW 22 (cf. Aerosol Report 14, (1975), 435). The pressure-reducing effect of solvents normally used (which include ethanol) is generally not sufficient to bring the total pressure in the container below the admissible maximum overpressure of 12 or 8 bars.

The present invention provides a composition which comprises chlorodifluoromethane and one or more carbonyl compound(s), wherein the weight ratio of chlorodifluoromethane to carbonyl compound is in the range of from 35:65 to 80:20 and wherein the carbonyl compound is a) an ester of a mono- or di-carboxylic acid having 1 or 2 carbon atoms and (i) an aliphatic monohydric alcohol having from 1 to 4 carbon atoms or (ii) an aliphatic monohydric ether alcohol having 3 or 4 carbon atoms and one ether oxygen atom, b) diethyl carbonate, c) a ketone or a mixture of any two or more thereof.

Compositions of the invention may be used in a pressurised vessel, especially an aerosol container, wherein the FKW 22 acts as a propellant, and the carbonyl compound may act as solvent for an active ingredient of the aerosol.

Accordingly the present invention also provides a pressurised vessel containing a composition of the invention and a process for the filling thereof.

Further, the present invention provides an aerosol propellant preparation comprising a composition of the invention and, if desired, one or more additional compounds being solvents for one or more active aerosol ingredients, wherein at least one of the carbonyl compounds and solvents if liquid at room temperature, preferably one wherein the proportion of FKW 22 is in the range of from 20 to 800/, more preferably 50 to 800/,, especially 50 to 60%, by weight based on the total weight of the aerosol propellant preparation. The terms "room temperature" and "room pressure" whenever used herein refer to a temperature of 20"C and a pressure of 1 atmosphere respectively.

The carbonyl compound present in a composition of the invention reduces the over pressure exerted by the FKW 22 so that is possible to use such a composition in a container which has a maximum permitted pressure of 8 bars at 500C, for example a tin aerosol container. Accordingly when used in an aerosol container the pressure therein is preferably greater than 1 and no more than 12 bars, especially no more than 8 bars, at 500 C. The composition of the invention is generally liquid when used in an aerosol.

When the composition of the invention consists only of FKW 22 and one or more carbonyl compounds then the FKW 22 is preferably present in an amount of at least 50% by weight. However, in any composition of the invention FKW 22 is preferably present in an amount of at least 55%, especially in the range of from 55 to 60%, by weight based on the total weight of the composition.

Preferably a ketone used in a composition of the invention is an aliphatic ketone having from 3 to 8, preferably 3 to 5, carbon atoms and which may be substituted by one or two hydroxyl groups.

Suitably the carbonyl compound is acetone, methyl ethyl ketone, diethyl ketone, methyl isobutyl ketone, diacetone alcohol, ethyl acetate, butyl acetate, ethyl glycol acetate or diethyl carbonate.

Mixtures of two or more carbonyl compounds and/or mixtures with other solvents, for example alcohols, petroleum hydrocarbons, chlorinated hydrocarbons and aromatic compounds, may be used.

The pressure reduction is greater, the higher the proportion of pressurereducing component in the total mixture. If the carbonyl compound used according to the invention is used solely for reducing the pressure and not as a solvent or dissolving intermediary, it should be present in such an amount that the maximum admissible pressure is not attained, and that the quality of the dispensed spray, which depends on the product used, is favourable. A content of chlorodifluoromethane of from 55 to 60% by weight in the total aerosol mixture is especially preferred; since chlorodifluoromethane is non-combustible, the aerosol container need not be marked "combustible" and other non-combustible solvents need not be used.

In most cases the use of FKW 22 as an aerosol propellant in combination with one or more carbonyl compounds according to the invention, has the technical and economic advantage over the more conventional chlorofluorohydrocarbons that it requires a considerably smaller amount of propellant to maintain the quality of the dispensed spray. Consequently the content of the active ingredient may be higher, which means that the output of dischargeable active ingredient is substantially increased while the size of the bottle remains the same.

The following Examples illustrate the invention; the ratios quoted there are all given on a weight basis.

EXAMPLE 1 A body deodorant spray was prepared by using as the solution, A, of active ingredients, the formulation: 0.5% by weight of 2,4,4' - trichloro - 2' - hydroxydiphenyl ether 3.0% by weight of isopropyl myristate 1.0% by weight of fragrant oil 90.0% by weight of ethanol (of 96% strength) 5.5% by weight of distilled water.

The aerosol contained 30% by weight of solution A of active ingredients and 70% by weight of propellant mixture, this mixture consisting of 40% by weight of dichlorodifluoromethane (FKW 12) and 60% by weight of dichlorotetrafluoroethane (FKW 114).

This aerosol has an overpressure of 3.5 bars at a temperature of 20"C and 7.6 bars at 50"C.

When replacing the propellant mixture consisting of FKW 12 and FKW 114 by chlorodifluoromethane (FKW 22), the proportion of propellant can be reduced considerably while maintaining the good spraying properties of the aerosol, owing to the higher pressure exerted by FKW 22. The proportion of propellant should not be reduced, however, to less than 55% by weight, as in this case the warning notice "combustible" would have to be marked on the aerosol container.When mixing, however, 55% by weight of FKW 22 with 45% by weight of solution A of active ingredients, the overpressure of the total mixture is increased to 12.2 bars at a temperature of 50"C. Even when using expensive aluminium containers which may contain an overpressure of at most 12 bars, the use of this formulation would result in an offence against certain the official safety regulations; i.e. the product must not be used for the preparation and distribution of aerosol containers.

However, when varying the solution of active ingredients by partial substitution of ethanol by acetone in the following manner: 0.5% by weight of 2,4,4' - trichloro - 2' - hydroxydiphenyl ether 3.0% by weight of isopropyl myristate 1.0% by weight of fragrant oil 65.0% by weight of ethanol (of 96% strength) 25.0% by weight of acetone 5.5% by weight of distilled water to give a solution B of active ingredients, and using 45% by weight of solution B of active ingredients and 55% by weight of chlorodifluoromethane (FKW 22), the overpressure was 4.3 bars at a temperature of 20"C and 9.9 bars at a temperature of 50"C.

Consequently, commercial aerosol containers having maximum permitted service overpressure of 10 bars can be used for aerosol mixtures having the above formulation. The quality of the dispensed spray is equivalent to that based on the conventional mixture of FKW 12 and FKW 114 4060 (ratio of the components of the mixture 40:60).

Both formulations may be classified as non-combustible according to the legal regulations in force in the Federal Republic of Germany and other countries. (For example TRG 300.) The formulation according to the invention has, however, the technical advantage that the aerosol mixture, for the same nominal quantity, contains 50% more of the solution of active ingredients and a smaller amount of propellant than the conventional mixture: i.e. the output of the aerosol is higher by about 50%.

EXAMPLE 2 The pressures of anhydrous formulations of body deodorants are generally lower than those of deodorants containing water. However, when replacing the FKW 11/12 5050 mixture in mixture 1 (ratio of the components of the mixture 50:50) normally used in such aerosols by FKW 22 (see mixture 2), the pressure is increased to a level considerably higher than 10 bars, at a temperature of 50"C and, consequently, only very expensive aerosol containers can be used.The addition of acetone (mixture 3) makes it possible to produce aerosols in considerably less expensive containers which can withstand a maximum working pressure of 8 bars, as may be seen from the following Table: Total Mixture Component 1 2 3 2,4,4'-trichloro-2'- 0.15 0.23 0.23% by weight hydroxydiphenylether Isopropyl myristate 0.30 0.45 0.45 by weight 1,2-propyleneglycol 0.60 0.90 0.90 /O by weight Fragrant oil 0.12 0.18 0.18% by weight Ethanol of 99.5% strength 28.83 43.24 18.24% by weight Acetone - 25.00 by weight FKWll/125050 70.0 - - FKW 22 - 55.0 55.0 /" by weight Excess working pressure (bars) at 20"C 3.5 6.2 3.5 at50 C 71 11.9 7.1 The output of the active ingredients is improved in the formulation according to the invention by 50% without influencing the quality of the dispensed aerosol spray because of the reduction of the proportion of propellants from 70 to 55% by weight.

EXAMPLE 3 The following Table shows how, in a dehydrating formulation (for use in electric distributors in automobiles) the exchange of FKW 11/12 5050 (formulation 1) for FKW 22 (formulation 2) or FKW 22/ethyl acetate (formulation 3) influences the vapour pressure of the aerosol mixture.

Total Mixture Number of Formulation Component 1 2 3 Emulsogen E (Trade Mark) 0.3 0.7 0.7 /" by weight White spirit (1 50--195 OC) 29.7 69.3 49.0% by weight Ethyl acetate - 20.30/, by weight FKWll/l25050 70.0 - - FKW 22 - 30.0 30.0 /,, by weight Excess working pressure (bars) at200C 2.7 4.8 2.1 at 50"C 5.8 9.2 5.0 Formulation 3makes it possible to use less expensive tin aerosol containers having a maximum permitted working overpressure of 6.6 bars while improving the output of the aerosol by 133%. Since the propellant in this case is the most expensive component of the aerosol, the price of the aerosol can be reduced considerably by modifying the formulation. FKW 22 is only about 50% more expensive than the FKW 11/12 5050 mixture. Moreover, the good quality of the dispensed spray using the conventional mixture is riot affected.

EXAMPLE 4 When exchanging an FKW 11/12 mixture (formulation 1) for FKW 22 a much smaller proportion of propellant is sufficient (formulation 2) to ensure that the spray behaviour remains unchanged, resulting in a considerable reduction in cost.

However, at 500C the overpressure of the formulation (7.3 bars) exceeds the permitted maximum pressure (6.66 bars). By using in addition ethyl acetate (formulation 3), the overpressure of the formulation at 500C can be reduced below this limit.

Leather impregnation agent: Number of Formulation Component 1 2 3 Silicon oil WL 8 a') 6.0 8.5 8.5% by weight Perchloro ethylene 54.0 76.6 61.5 /" by weight Ethyl acetate - - 15.0% by weight FKW 11/121090 40.0 - - FKW 22 15.0 15.0% by weight Excess working pressure (bars) at20 C 3.1 4.0 2.1 at 50"C 6.6 7.3 5.4 I) Producer: Wacker-Chemie GmbH, Germany.

The output of the aerosol is moreover increased as a consequence of the higher concentration of active ingredients.

EXAMPLE 5 The output and the economy of a conventional formulation for protective lacquers for chromium can also be improved by the exchange of FKW 11/12 for FKW 22. In this case, the pressure reduction required so that the normal containers having a maximum permitted working overpressure of 8 bars may be used is attained by means of ethyl glycol acetate for formulation 3 and methyl ethyl ketone of by means of for formulation 4. Formulation 2 is the same as a conventional formulation (formulation 1) but contains FKW 22 instead of FKW 11/12.

Total Mixture Number of Formulation Component 1 2 3 4 Plexigum P 26* (Trade Mark) 6.0 9.0 9.0 9.0% by weight Palatinol AH (Trade Mark) 0.8 1.2 1.2 1.2% by weight White spirit 20.0 30.0 12.0 30.0 /" by weight Xylene 6.0 9.0 9.0 Toluene 7.2 10.8 10.8 Ethyl glycol acetate - - 18.0 Butyl acetate - - - 9.0% by weight Methyl ethyl ketone - - - 10.8% by weight FKW 11/122575 60.0 - - - FKW 22 - 40.0 40.0 40.0% by weight Excess working pressure (bar) at 20"C 3.2 4.8 3.4 3.6 at 50"C 6.8 9.3 7.0 7.0 *Rohm GmbH, Darmstadt.

EXAMPLE 6 Aluminium containers were filled with a solvent, the air was displaced from the gas zone by introducing a sufficient quantity of an FKW component under pressure, the containers were closed by stem valves (and dishes) without ascending pipe and the remaining FKW was introduced under pressure through the valve.

The pressure was measured after having kept the mixtures in thermostats for one hour, at temperatures of 20"C and 50"C respectively, by means of a tube spring precision manometer (class 0.6) having a measuring range of from 0 to 16 bars of overpressure.

Tables 1 to 4 show the results of the measurements.

Table 1 shows the pressure reduction in mixtures consisting of 50 parts by weight of solvent and 50 parts by weight of FKW 22 at 500 C, Table 2 shows the corresponding pressure reduction at 200C. It can be seen that mixtures of FKW 22 and esters or ketones in a ratio of 50:50 have an overpressure of less than 8 bars, even at a temperature of 50"C. Tables 3 and 4 show the pressure reduction of FKW 12 by the same solvents, at 500C (Table 3) and at 20"C (Table 4). A pressure reduction comparable to that in the case of FKW 22 cannot be observed.

TABLE 1 Solvent Pressure (bars) FKW 22 18.3 Perchloroethylene 13.8 Shellsol T (Trade Mark) 13.5 FKW 113 12.5 FKW 11 11.8 n-propanol 11.6 Petroleum (100140 C) -11.3 Petroleum ether 11.2 1,1,1 -trichloroethane 11.1 Isopropanol 10.6 Xylene 10.1 Methylene chloride 9.8 Ethanol 9.2 Toluene 9.0 Methanol 8.5 Diacetone alcohol 7.9 Diethyl carbonate 7.7 Ethylglycol acetate 7.6 Methyl isobutyl ketone 7.1 Diethyl ketone 6.8 Butyl acetate 6.6 Ethyl acetate 5.5 Methyl ethyl ketone 4.5 Acetone 4.0 TABLE 2 Solvent Pressure (bars) FKW 22 8.1 Perchloroethylene 6.6 Shellsol T (Trade Mark) 6.8 FKW 113 5.4 FKW 11 5.2 n-propanol 5.6 Gasoline (! 00-140"C) 5.4 Petrol ether 6.5 1,11 -trichloroethane 5.2 Isopropanol 5.2 Xylene 4.8 Methylene chloride 4.2 Ethanol 4.0 Toluene 3.9 Methanol 4.1 Diacetone alcohol 3.5 Diethyl carbonate 3.6 Ethylglycol acetate 3.3 Methyl isobutyl ketone 3.0 Diethyl ketone 2.6 Butyl acetate 3.8 Ethyl acetate 2.1 Methyl ethyl ketone 1.5 Acetone 1.2 TABLE 3 Solvent Pressure (bars) FKW 12 11.2 Perchloroethylene 6.6 Shellsol T (Trade Mark) 6.4 FKW 113 7.1 FKW 11 6.8 n-propanol 8.7 Gasoline (100--140"C) 5.7 Petrol ether 5.5 1,1,1 -trichloroethane 5.9 Isopropanol 7.2 Xylene 7.9 Methylene chloride 6.8 Ethanol 7.6 Toluene ' 5.5 Methanol 10.5 Diacetone alcohol 8.8 Diethyl carbonate 6.6 Ethylglycol acetate 7.8 Methyl isobutyl ketone 8.4 Diethyl ketone 7.6 Butyl acetate 6.4 Ethyl acetate 5.5 Methyl ethyl ketone 5.5 Acetone 6.0 TABLE 4 Solvent Pressure (bars) FKW 12 4.7 Perchloroethylene 2.8 Shellsol T (Trade Mark) 2.8 FKW 113 2.9 FKW 11 2.7 n-propanol 3.9 Gasoline (100--140"C) 2.2 Petrol ether 2.4 1,1,1 -trichloroethane Isopropanol 3.0 Xylene 3.1 Methylene chloride 2.7 Ethanol 3.3 Toluene 2.6 Methanol 4.6 Diacetone alcohol 4.1 Diethyl carbonate 3.1 Ethylglycol acetate 3.6 Methyl isobutyl ketone 3.0 Diethyl ketone 2.0 Butyl acetate 2.4 Ethyl acetate 2.3 Methyl ethyl ketone 2.3 Acetone 2.4 WHAT WE CLAIM IS: 1. A composition which comprises chlorodifluoromethane and one or more carbonyl compound(s), wherein the weight ratio of chlorodifluoromethane to carbonyl compoundis in the range of from 35:65 to 80:20 and wherein the carbonyl compound is a) an ester of a mono- or di-carboxylic acid having I or 2 carbon atoms and (i) an aliphatic monohydric alcohol having from I to 4 carbon atoms or (ii) an aliphatic monohydric ether alcohol having 3 or 4 carbon atoms and one ether oxygen atom, b) diethyl carbonate, c) a ketone or a mixture of any two or more thereof.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (18)

**WARNING** start of CLMS field may overlap end of DESC **. TABLE 3 Solvent Pressure (bars) FKW 12 11.2 Perchloroethylene 6.6 Shellsol T (Trade Mark) 6.4 FKW 113 7.1 FKW 11 6.8 n-propanol 8.7 Gasoline (100--140"C) 5.7 Petrol ether 5.5 1,1,1 -trichloroethane 5.9 Isopropanol 7.2 Xylene 7.9 Methylene chloride 6.8 Ethanol 7.6 Toluene ' 5.5 Methanol 10.5 Diacetone alcohol 8.8 Diethyl carbonate 6.6 Ethylglycol acetate 7.8 Methyl isobutyl ketone 8.4 Diethyl ketone 7.6 Butyl acetate 6.4 Ethyl acetate 5.5 Methyl ethyl ketone 5.5 Acetone 6.0 TABLE 4 Solvent Pressure (bars) FKW 12 4.7 Perchloroethylene 2.8 Shellsol T (Trade Mark) 2.8 FKW 113 2.9 FKW 11 2.7 n-propanol 3.9 Gasoline (100--140"C) 2.2 Petrol ether 2.4 1,1,1 -trichloroethane Isopropanol 3.0 Xylene 3.1 Methylene chloride 2.7 Ethanol 3.3 Toluene 2.6 Methanol 4.6 Diacetone alcohol 4.1 Diethyl carbonate 3.1 Ethylglycol acetate 3.6 Methyl isobutyl ketone 3.0 Diethyl ketone 2.0 Butyl acetate 2.4 Ethyl acetate 2.3 Methyl ethyl ketone 2.3 Acetone 2.4 WHAT WE CLAIM IS:

1. A composition which comprises chlorodifluoromethane and one or more carbonyl compound(s), wherein the weight ratio of chlorodifluoromethane to carbonyl compoundis in the range of from 35:65 to 80:20 and wherein the carbonyl compound is a) an ester of a mono- or di-carboxylic acid having I or 2 carbon atoms and (i) an aliphatic monohydric alcohol having from I to 4 carbon atoms or (ii) an aliphatic monohydric ether alcohol having 3 or 4 carbon atoms and one ether oxygen atom, b) diethyl carbonate, c) a ketone or a mixture of any two or more thereof.

2. A composition as claimed in Claim 1, which also contains one or more

active ingredients for an aerosol spray and/or one or more non-carbonyl solvents therefor.

3. A composition as claimed in claim 1, which consists only of chlorodifluoromethane and one or more carbonyl compounds wherein the chlorodifluoromethane is present in an amount of at least 50 /O by weight.

4. A composition as claimed in any one of Claims 1 to 3, wherein the carbonyl compound is an aliphatic ketone having from 3 to 8 carbon atoms, which may be substituted by one or two hydroxyl groups.

5. A composition as claimed in Claim 4, wherein the carbonyl compound is an aliphatic ketone having from 3 to 5 carbon aroms.

6. A composition as claimed in any one of Claims 1 to 5, wherein the carbonyl compound is acetone, methyl ethyl ketone, diethyl ketone, methyl isobutyl ketone, diacetone alcohol, ethyl acetate, butyl acetate, ethyl glycol acetate or diethyl carbonate.

7. A composition as claimed in any one of Claims 1 to 6, wherein the chlorodifluoromethane is present in an amount of at least 55% by weight based on the total weight of composition.

8. A composition as claimed in Claim 7, wherein the chlorodifluoromethane comprises in the range of from 55 to 60% by weight of the composition.

9. A composition as claimed in Claim 1, substantially as described in any one of the Examples herein.

10. A pressurised vessel having contents which comprises a composition as claimed in any one of Claims 1 to 9.

11. A pressurised vessel as claimed in Claim 10, which is an aerosol.

12. A pressurised vessel as claimed in Claim 11, wherein the pressure in the aerosol is greater than 1 and no more than 12 bars at 500 C.

13. A pressurised vessel as claimed in Claim 12, wherein the pressure in the aerosol is greater than 1 and no more than 8 bars at 500C.

14. A process for filling a pressurised vessel as claimed in any one of Claims 10 to 13, which comprises introducing the component(s) which is liquid at room temperature and pressure (as hereinbefore defined) into the vessel and subsequently introducing liquefied chlorodifluoromethane under pressure.

15. An aerosol propellant preparation comprising a composition as claimed in any one of Claims 1 to 9 and, if desired, one or more additional compounds being solvents for one or more active aerosol ingredients, wherein at least one of the carbonyl compounds and solvents is liquid at room temperature.

16. An aerosol propellant preparation as claimed in Claim 15, wherein the proportion of chlorodifluoromethane is in the range of from 20 to 80%, by weight based on the total weight of preparation.

17. An aerosol propellant preparation as claimed in Claim 16, wherein the proportion of chlorodifluoromethane is in the range of from 50 to 80% by weight based on the total weight of preparation.

18. An aerosol propellant preparation as claimed in Claim 17 wherein the proportion of chlorodifluoromethane is in the range of from 55 to 60 /" by weight.