Two-phase Aerosol Spraying System

Abstract

The invention concerns a two-phase system, comprising an aerosol pressure container which contains a sprayable mixture therein, consisting essentially of a liquid phase of active ingredients; a propellant, liquefiable under pressure which may be either carbon dioxide and/or nitrous oxide and a liquid dimethoxymethane as an effective propellant dissolving agent for the carbon dioxide - nitrous oxide propellants.

Description

The present invention relates to improved two-phase aerosol spraying systems consisting of a pressure vessel and a mixture which can be sprayed under pressure contained therein, this mixture consisting of a liquid phase to be sprayed containing active ingredient and carbon dioxide and / or nitrous oxide partly dissolved therein and partly in gas form, as propellant.

Up to the present, the use of carbon dioxide (CO.sub.2) and nitrous oxide (N.sub.2 O) as propellants in the aerosol industry has been limited mainly to pressure packings from which it is simple to remove the contents in the form of foam, paste or liquid; the principal contents of these pressure packings have been foodstuffs such as, e.g. cream, cosmetic preparations such as, e.g. toothpaste, or pharmaceuticals such as, e.g. syrups. Because of the relatively bad solubility of these gases in the mainly aqueous products to be taken from these packings, the modest gas reserve which is formed under pressure is sufficient in the above cases to empty the packings completely. However, if it is desired to bring the product to be removed into a more or less finely distributed form, i.e. to attain a spray mist, then the proportion of propellant in the product to be sprayed must be considerably increased and the propellant must be excellently soluble therein. While, normally, it is quite possible to incorporate a sufficiently high proportion of propellant in the contents of the packing to attain a fine spray thereof with the aid of propellants which liquefy under pressure such as, e.g. dichlorodifluoromethane, dichlorotetrafluoroethane, vinyl chloride, propane, butane, etc., the greatest difficulties are encountered with carbon dioxide and nitrous oxide because of their slight solubility in the phase to be sprayed. In particular, these difficulties occur with aqueous products because the solubility of carbon dioxide and nitrous oxide in aqueous media is very slight. When using spray button, such mixtures can usually be sprayed well initially, but the gas pressure drops so strongly as the aerosol is emptied, that the spray pattern changes to an undesirable extent, while the apparatus is in use, the fog becoming more and more coarsely dispersed and the amount of material leaving the valve becoming smaller with time. In addition, on using carbon dioxide and nitrous oxide, the small gas reserve present in the known mixtures has a disadvantageous effect as such aerosol packings lose their pressure to a great extent even with the slightest leak and faulty manipulations and become quickly unusable.

In view of their attractive price and also because of their slight toxicity and high stability, there has been no lack of attempts to find ways of using these gases (CO.sub.2 and N.sub.2 O) for the fine spraying of products in spite of the difficulties mentioned above. In particular, attempts have been made to find substances having particularly good solubility powers for carbon dioxide and nitrous oxide from among the organic solvents. The solvents which have been suggested up to now are mainly alcohols, ketones, esters and chlorinated hydrocarbons such as, e.g. ethanol, isopropanol, acetone, methyl acetate, ethyl acetate, methylene chloride etc. For use in the most finely sprayable aerosols, these solvents either have too slight a solubility for carbon dioxide and nitrous oxide, a too pronounced odor, too high a toxicity, they attack the elastomers of the aerosol packing excessively or they have insufficient chemical stability in the presence of water.

It has now surprisingly been found that dimethoxy-methane has a previously unknown, remarkably good solubility for gaseous CO.sub.2, N.sub.2 O, and mixtures thereof in a random ratio of CO.sub.2 : NO.sub.2, and, as solvent for these gases, is superior in every way to the organic solvents mentioned above in its suitability for formulation in aerosols as can be seen from the following Table:

solvent lowest proportion- toxic pract- behavior towards ality thresh- ical elastomers constant.sup.1 hold concen- (weight take-up value tration in %) .sup.k CO.sub.2 .sup.k N.sub.2 O (ml.sup./ m.sup.3) in air (g/m.sup.3).sup.(2) "Buna N" "Neoprene" __________________________________________________________________________ dimethoxy- methane 1.45 1.20 1000 119 21.5 11.8 isopro- panol 0.44 0.51 400 67 0.0 0.0 methylene chloride.sup.3 0.56 0.62 500 -- 122.0 161.0 dioxan 1.02 0.73 100 79 67.0 64.0 ethyl acetate.sup. 3 1.00 1.01 400 79 31.0 39.0 methyl acetate.sup. 3 1.21 1.04 200 103 41.0 45.5 acetone 1.26 1.15 500 56 41.0 48.0 diethyl ether 1.26 1.11 400 59 -- -- __________________________________________________________________________

From the Table it is clearly seen that, on the whole, dimethoxy-methane combines most of the positive properties required of a solvent for propellants namely:

1. superior solubility powers for the propellant gases

expressed by the proportionality constant k in Henry's law, c = k. p. in which c is the concentration of the dissolved gases (in percent by weight) and p is the equilibrium pressure (in kg/cm.sup.2);

2. slight toxicity

expressed as the toxic threshold value in milliliter of solvent, in vapor form, per cubic meter of air.

3. small danger of explosion

expressed as the lowest practical concentration in the air in grams of solvent per cubic meter of air, and

4. slight attack on the elastomers used as aerosol container material

expressed in the percentual take-up of solvent by the elastomers on storing in the solvent tested for 7 days.

It has further been found that, unexpectedly, a much quicker, finer distribution of the spray particles is obtained which is probably due to a much quicker release of the propellant dissolved with the aid of dimethoxymethane, directly after the spray has left the valve, than when using another propellant-dissolving agent, for instance isopropanol or dioxane. As a further advantage dimethoxymethane has an ignition point of 470.degree. C. which distinguishes it especially from diethyl ether whose ignition point of 180.degree. C. makes it too dangerous for using. It could be determined from the tests that dimethoxymethane saturated with carbon dioxide or nitrous oxide at equilibrium pressures of over 2 atmospheres excess pressure attains an aerosol effect which is at least equal in practice to that of the conventional pressure liquefied propellant gases such as Freon.

In principle, the phase to be sprayed in the apparatus according to the invention, can contain in addition to the active substances only dimethoxymethane with carbon dioxide or nitrous oxide dissolved under pressure, or it may further contain other organic solvents in combination with dimethoxymethane.

The sprayable phase in the apparatus according to the invention can contain active ingredients of any type such as, e.g. pest control agents, weed killers, pharmaceuticals, cosmetics, household chemicals etc. in dissolved or dispersed form except, of course, active ingredients which react with carbon dioxide or nitrous oxide, in an amount of 0.01 to 50 percent preferably 0.05 to 20 percent by weight.

The following examples illustrate a few preferred forms of the mixture according to the invention. Where not otherwise stated, parts are given as parts by weight. The relationship of parts by weight to parts by volume is as that of grams to cubic centimeters.

EXAMPLE 1

2-isopropyl-4-methyl-6-pyrimidyl-0,0 -diethyl-thiophosphate 3.75 parts hexachlorocyclohexane 1.00 part dimethoxymethane 222.50 parts carbon dioxide 22.50 parts epichlorohydrin 0.25 part

2-Isopropyl-4-methyl-6-pyrimidyl-0,0-diethyl thiophosphate, hexachlorocyclohexane and epichlorohydrin as stabilizer for the thiophosphate are dissolved in dimethoxymethane. 227.5 Parts of this mixture are put into an aerosol container of 350 parts by volume capacity and then the valve is fixed. 22.5 Parts of carbon dioxide are introduced through the valve while shaking, which amount of gas corresponds to about 33 times the total volume of the container under normal conditions. The mixture formed, (at an initial inner pressure of about 5.5 atmospheres excess pressure/20.degree. C. and an end pressure of about 4.0 atmospheres excess pressure/20.degree. C.) can be perfectly and completely sprayed as a dry mist and is excellently suitable for the combatting of flying insects.

EXAMPLE 2

propylene glycol 0.75 part triethylene glycol 0.75 part methylene chloride 27.75 parts dimethoxymethane 108.00 parts nitrous oxide 12.00 parts.

The liquid components of the mixture are dissolved in each other. 138 Parts of this mixture are then put into an aerosol container of 220 parts by volume capacity and the valve is fixed. 12 Parts of nitrous oxide are introduced through the valve while shaking, which amount of gas corresponds to 28 times the total volume of the container under normal conditions. The mixture formed can be perfectly and completely sprayed as a dry mist (at an initial pressure of about 6.4 atmospheres excess pressure/20.degree. C and an end pressure of about 4.3 atmospheres excess pressure/20.degree. C). It can be used as a room deodorant.

EXAMPLE 3

highly dispersed silicic acid 2.5 parts 1,1,1-trichloroethane 10.0 parts acetone 10.0 parts xylene 10.0 parts dimethoxymethane 61.5 parts carbon dioxide 6.0 parts

The silicic acid is pasted in the liquid components. 94 Parts of the mixture are put into an aerosol container of 220 parts by volume capacity and 6 parts of carbon dioxide are introduced through the valve while shaking. The amount of gas corresponds to about 14 times the total volume of the container under normal conditions. The mixture formed can be perfectly and completely sprayed (at an initial inner pressure of about 3.8 atmospheres excess pressure/20.degree. C and an end pressure of about 2.5 atmospheres excess pressure/20.degree. C) and can be used to remove stains on textiles.

EXAMPLE 4

o-chlorobenzoyl diethylamine 9.0 parts benzoyl diethylamine 9.0 parts isopropanol 12.0 parts dimethoxymethane 111.0 parts nitrous oxide 9.0 parts

o-Chlorobenzoyl diethylamine and benzoyl diethylamine are dissolved in the isopropanol and dimethoxymethane. 141 Parts of this mixture are then put into an aerosol container of 220 parts by volume capacity and the valve is fixed. 9 Parts of nitrous oxide are introduced through the valve while shaking, which amount of gas corresponds to about 21 times the total volume of the container under normal conditions. The mixture formed can be perfectly and completely sprayed (at an initial inner pressure of about 5.0 atmospheres excess pressure/20.degree. C and an end pressure of about 3.1 atmospheres excess pressure/20.degree. C) and is excellently suitable as a repellant for mosquitoes.

EXAMPLE 5

dichloroxyquinaldine 2.0 parts isopropyl myristate 10.0 parts isopropanol 28.0 parts dimethoxymethane 146.0 parts carbon dioxide 14.0 parts

Dichloroxyquinaldine is dissolved in isopropyl myristate, ethanol and dimethoxymethane. 186 Parts of this mixture are put into an aerosol container of 350 parts by volume capacity and then the valve is fixed. 14 Parts of carbon dioxide are introduced through the valve while shaking, which amount of gas corresponds to about 20 times the total volume of the container under normal conditions. The mixture formed can be perfectly and completely sprayed (at an initial inner pressure of about 4.9 atmospheres excess pressure/20.degree. C. and an end pressure of about 3.4 atmospheres excess pressure/20.degree. C.) and is excellently suitable for the disinfection of external wounds as well as for combatting foot mycosis.

EXAMPLE 6

carnauba wax 4.0 parts beeswax, bleached 6.0 parts paraffin 50/52.degree.C 8.0 parts terpentine oil 41.0 parts silicone oil (500 centistokes) 1.0 part dimethoxymethane 130.0 parts carbon dioxide 10.0 parts

Carnauba wax, beeswax and paraffin are heated with the terpentine oil to 110.degree. C. until solution occurs; the solution is then quickly cooled to 20.degree. C. while stirring and the paste formed is homogeneously mixed with dimethoxymethane. 190 Parts of this mixture are put into an aerosol container of 350 parts by volume capacity and the valve is fixed. 10 Parts of carbon dioxide are introduced through the valve while shaking, which amount of gas corresponds to about 15 times the total volume of the container under normal conditions. The mixture formed can be perfectly and completely sprayed (at an initial inner pressure of about 3.9 atmospheres excess pressure /20.degree. C. and an end pressure of about 2.6 atmospheres excess pressure/20.degree. C.) and is excellently suitable as a floor polish.

EXAMPLE 7

o-chlorobenzoyl diethylamine 9.0 parts benzoyl diethylamine 9.0 parts isopropanol 12.0 parts dimethoxymethane 111.0 parts nitrous oxide 5.0 parts carbon dioxide 4.0 parts

o-Chlorobenzoyl diethylamine and benzoyl diethylamine are dissolved in the isopropanol and dimethoxymethane. 141 Parts of this mixture are then put into an aerosol container of 220 parts by volume capacity and the valve is fixed. 9 Parts of a mixture consisting of 5.0 parts of nitrous oxide and 4.0 parts of carbon dioxide are introduced through the valve while shaking, which amount of gas corresponds to about 21 times the total volume of the container under normal conditions. The mixture formed can be perfectly and completely sprayed (at an initial inner pressure of about 5.0 atmospheres excess pressure/20.degree. C. and an end pressure of about 3.1 atmospheres excess pressure/20.degree. C.) and is excellently suitable as a repellant for mosquitoes.

Claims

What we claim is:

1. In a two-phase aerosol spraying system comprising an aerosol pressure container and a sprayable mixture contained in said vessel under pressure, which mixture consists essentially of a non-aqueous liquid phase to be sprayed containing an effective amount of the active ingredients, said ingredients being non-reactive with carbon dioxide or nitrous oxide, a propellant dissolved therein and gasified under normal pressure, and the gaseous phase of the propellant, the improvement wherein said mixture contains 25 to 95 percent by weight of dimethoxymethane calculated on the total weight of the mixture and 5 to 15 percent by weight of a member selected from the group consisting of carbon dioxide and nitrous oxide.

2. In a two-phase aerosol spraying system comprising an aerosol pressure container and a sprayable mixture contained in said vessel under pressure, which mixture consists essentially of a non-aqueous liquid phase to be sprayed containing an effective amount of the active ingredients, said ingredients being non-reactive with carbon dioxide or nitrous oxide, a propellant dissolved therein and gasified under normal pressure, and the gaseous phase of the propellant, the improvement wherein said mixture contains 60 to 75 percent by weight of dimethoxymethane calculated on the total weight of the mixture and 8 to 10 percent by weight of a member selected from the group consisting of carbon dioxide and nitrous oxide.