IL30766A - Push-button dispenser with separated phases - Google Patents

Description

ί PUSH-BUTTQH DISPENSES WITH S EPA BATED PHASES T is invention relates to push-button dispenser of the aerosol bomb type, in which the liquefied gas constituting the propellant and the active agent are physically separated from one another.

More precisely, the dispensers of the kind to which the invention relates comprise in known manner : - a reservoir provided with a push-button valve and containing a liquefied gas acting as propellant, - an ejector system comprising a spray nozzle controlled by a push-button and ensuring, under the action of the propellant the suction, discharge and atomization of a liquid phase, or in some cases a fluent solid phase, containing at least ene active agent, - a second reservoir containing the liquid or fluent solid phase which reservoir may be exterior to the first reservoir and in particular may contain it or be adjacent to it.

Dispensers of the above kind differ from push-button dispensers of the conventional type in that these latter have only a single container containing both the propellant and also the active agent phase. In a single container so arranged the mixture of the agent to be sprayed and the propellant occurs in the form of a liquid subjected to the pressure of the vapour phase of the propellant. The drawing off of the agent from its reservoir, must of course be effected in the liquid phase, or otherwise the active agent would not be dispensed. Dispensers of the conventional type are therefore arranged so as to meet this imperative requirement, and they work either head upwards if the valve is extended by a dip tube which descends to the bottom of the container, or head downwards if the valve does not have a dip tube, or even in any position if certain devices are employed,, many forms of which are known.

These two classes of push-button dispensers, with differing structures, act on principles which are likewise In. separate-phase dispensers, the propellant necessarily has to be drawn off in the form of a gas. If this were not so, and the propellant only became gaseous at the instant of its arrival in the spray nozzle, there would be no suction of the active agent, but on the contrary, there would be a backflow of part of the gas into the container holding the active agent, and the said container would suffer a forced expansion. The separate-phase dispenser can only be used therefore head upwards and this necessity may be a drawback under certain conditions of use.

One of the objects of this invention is to obviate this restriction and to permit the use of separate-phase aerosol dispensers in all positions.

Another object of the invention is to regularise the evaporation of the propellant and consequently to improve the functioning of these dispensers.

According to the invention there is provided a push-button dispenser having separate phases, respectively consisting of an active agent to be dispensed and a propellant under pressure which has to be drawn off in the gaseous state, these two phases being accomodated in different containers connected to a valve controlled by a push-button, characterized in that the container for the propellant contains a lacunar carrier ensuring the retention of the propellant in such a way that there is no propellant in the said container capable of flowing in the liquid state.

In this way, when the valve is opened, the propellant is transformed into gas in or at the surface of the carrier with which it is in contact and it cannot flow in the liquid state through the valve. The dispenser can therefore be used in any position without inconvenience, and can even function head downwards.

By the term "lacunar carrier" is meant materials which may be porous, spongy or finely-divided, and in particular may be in powder form, the said materials being prefera In a first embodiment of the invention the lacunar carrier consists of at least one of the following materials : absorbent cotton, felt, fibre mats, pumice stone, expanded vermiculite, porous minerals, or cellular plastics materials such as polyurethane foam.

Such materials ensure the retention of the propellant in the mean proportions of 2 to 3 grammes of propellant per gramme of lacunar product, in the case where the propellant is dichlorodifluoromethane (3? 12).

In a preferred embodiment of the invention, the lacunar carrier consists of a product in powdery form in which the propellant is dispersed.

In powder form, certain substances have the remarkable property of adsorbing considerable quantities of liquid with which they are mixed. This power of retention is a result of the large surface of contact of the powdery body and increases with the fineness of its particles.

Experience has shown further that certain powdery bodies have a particularly noteworthy power of retention in respect of the liquefied propellants used in push-button dispensers. This power of retention may reach a level such that the volume of the mixture of adsorbent substance and liquefied propellant is not noticeably increased by comparison with a corresponding volume of the same mass of liquefied propellant in the pure state. Preferably the powdery carrier consists of pure precipitated silica occurring in the form of fine particles.

It is also advan ageously possible to utilize activated fossil silica, hydrated light alumina or a precipi-tated pure silica.

It is also possible to use a powdery carrier consisting of precipitated pure silica associated with activated fossil silica or hydrated light alumina. Preferably the quantity of silica present in the adsorbent mixture is between 25$ and 0$.

The invention also applies to a separate-phase push-button dispenser, in which a lacunar carrier stop grid is provided in the valve body at the inlet of the orifice leading to the high pressure obturator. In this way any risk of obstruction of the valve by particles of the lacunar carrier is avoided.

The invention will now be described in greater detail by may of example, with reference to the accompanying drawings wherein ; Figure 1 represents in axial section a separate- phase push-button dispenser embodying the invention.

Figure 2 represents on a larger scale an axial section of the stop grid for the powdery carrier, provided in the dispenser in Figure 1, Figure 3 is a corresponding horizontal section taken on the line III-III in Figure 2, Figure represents a comparative graph of the flow rates obtained with dichlorodifluoromethane as propellant, in the free state and adsorbed state respectively, and Figure 5 represents a comparative graph of the flow rates obtained under the same conditions with butane as propellant.

Referring to Figure 1 there can be seen an outer container 1 of an aerosol dispenser containing a liquid active agent 2 to be sprayed.

The outer container 1 is obturated by a plug 3 carrying interiorly, in its central part, a valve body 4 on which is fixed a reservoir 5 containing a powdery carrier 6 in wich- the liquid propellant is dispersed. The kinetic energy of the gas arising from the evaporation of the liquid propellant makes possible the atomization of the active agent 2. The plug 5 contains a high pressure valve (no shown) comprising the obturator or obturators necessary for proper functioning of the appliance, and there passes through it an ejector carrying a push-button 8 containing a spray nozzle having an orifice 9. The active agent 2 is fed to the ejector through a dip tube 10.

The valve body 4 carries at its lower part a stop grid 11 to catch particles of the powdery carrier 6 which might be entrained towards the high pressure valve passing round the rod 7 of the push-button controlling the high pressure valve.

The stop grid 11 (Figures 2 and 3) which is integral with the valve body 4 consists of a cylindrical body 12 obturated at its free end by a solid disc 13 which is secured in place. Slots 14» whose width is smaller than the smallest orifice of the valve, are uniformly distributed over the whole lateral surface of the cylindrical body 12.

In accordance with this preferred embodiment of the invention, the powdery carrier, whic is precipitated pure silica, is present in the form of an amorphous powder, white in colour, extremely finely-divided and very light.

Its preferred physical properties are as follows : Unheaped density (or apparent density) : 0.03 to 0.12 Heaped density % 0.20 to 0.25 Specific surface sq.m. per gramme s 90 to 420 Micron size of particles s about 0.007 Its great specific surface gives it a high power of retention of liquids. With propellents it forms a kind of gel and when the propellant is evaporated the silica is not regenerated in its initial form ; there is a more or less voluminous formation of agglomerate.

But in this preferred embodiment of the invention it is also possible to use another powdery carrier which may be ; activated fossil silica, or hydrated light alumina obtained from a gel of a precipitated silicate such as aluminium silicate, or magnesium silicate.

All these carriers occur in granular form in a high degree of fineness, comparable to that of precipitated pure silica grains. Their apparent densities are preferably as follows ί Activated fossil silica : from 0.10 to 0.16 Hydrated light alumina and precipitated silicates Ϊ not more than 0.17 Their special feature is that they preserve their original powdery condition after adsorption of the liquefied propellants in respect of which they have excellent powers of re ention.

Likewise, in this preferred embodiment of the invention, it is possible to utilize precipitated pure silica in association either with activated fossil silica, or with hydrated light alumina. In this association the gel formed by the precipitated pure silica which is impr¾iated with propellant covers the particles of fossil silica or alumina to form agglomerates.

In a preferred form of application, the dispersion of the liquefied propellant is effected by filling the inner reservoir 5 beforehand with the powdery carrier 6, then injecting the propellant under pressure, after placing the valve body 4 in position.

It is also possible to effect this dispersion by producing beforehand the mixture of the powdery carrier with the liquefied propellant, after which the mixture obtained is injected at low temperature into the inner reservoir 5 of the dispenser, before placing the valve body 4 in position.

In a series of practical tests of the invention using the abovementioned powdery carriers, singly or in mixtures, the following results were obtained, with dichlorodifluorome-thane (F12) as propellant s Constituents of the Percentage Apparent Quantity of carrier of each of density P12 in grammes the absorbed by constituents 1 gramme of carrier (power of retention) Activated fossil silica 100 0.16 3.3 ditto - 100$ 0.14 3.4 ditto. 100$ 0.12 4.5 ditto. 100$ 0.10 5.5 Light alumina 100$ 0.17 4.4 Precipitated silica 100$ 0.17 4.4 ditto. 100$ 0.12 7 ditto 100$ 0.05 19 (Activated fossil silica 75$ ( 0.12 6.5 (Precipitated silica 25$ (Light alumina 75$ ( 0.10 7 (Precipitated silica 25$ (Activated fossil silica 75$ ( 0.10 8.5 (Precipitated silica 25$ (Light alumina 50$ ( 0.07 11 (Precipitated silica 50$ (Activated fossil silica 50$ ( 0.07 11 (Precipitated silica 50$ If liquefied propellants such as hydrocarbone, butane and propane are used, the power of retention of the above powdery carriers is substantially the same in volume as with dichlorodifluoromethane, which corresponds in weight, for 1 gramme of each of these propellants, to the following powers of retention determined : Constituents of Apparent Quantity of Quantity of the carrier density "butane in propane in g. grammes absorbed per 1 g. absorbed per of carrier 1 g. of carrier Activated fossil silica 0.16 1.4 1.3 ditto. 0.14 1.4 1.3 ditto. 0.12 1.9 1.7 ditto. 0.10 2.3 2.1 light alumina 0.17 1.8 1.7 Precipitated silica 0.17 1.8 1.7 ditto. 0.12 3 2.7 ditto. 0.05 8 7.3 The powers of retention shown in the two tables above and which are given for guidance, were measured in the following way ; A given weight of powdery carrier was inserted in a transparent container hermetically closed by a valve, after which the propellant was injected in the liquid state through the valve.

In the first stage of injection it was found that the carrier and the propellant form a single mass of solid appearance j when the operation is continued further it is found that in a second stage a second phase in the liquid state appears. The measure of the power of retention consists in determining the limit between these two stages, that is to say the appearance of the first liquid drop.

The results shown in the two tables above were obtained at a temperature close to 20°C. lying between 15 and 25°C It can be seen that the power of retention of the carriers used in accordance with the invention is greater than 3 grammes per gramme of adsorbent.

Furthermore the numerical analysis of the results shows that the retentivity of the carriers is practically inversely proportional to their apparent density. The highest pover of retention belongs to precipitated silica which can be supplied in the lowest apparent densities.

In this preferred embodiment of the invention where the propellant is dispersed in a powdery carrier 6 placed i ide the inner reservoir 5, the separate-phase aerosol dispenser can advantageously be used in any position. The propellant Itiquid can only be drawn off when it is ccmpletely dispersed or adsorbed. The drawing off therefore always takes place starting from the gaseous phase of the propellant which surmounts the carrier 6 and is constantly renewed b quantities of vapour fed to it from the outer layer and also from the interior of the mass. The fine particles arriving are checked by the stop grid 11 placed at the bottom of the valve body 4 so that these particles, or possibly agglomerates with a precipitated silica base, do not enter the valve and there is no danger therefore of them blocking the ducts leading to the spray nozzle.

The presence of the powdery carrier 6 further produces a remarkable technical effect. In known aerosols when the gaseous propellant is drawn off above the said liquid propellant in the non-dispersed condition, the transformation of the liquid into gas takes place at the surface of separation of the two phases. This surface cools rapidly, the speed of evaporation decreases and there is thus found a considerable decrease in the vapour phase pressure, which detracts from the quality of the a omization of the active agent 2· By contrast, with the carrier 6 in accordance with the invention, the transformation of liquid into gas of the same propellant takes place at the surface of separation but likewise in the actual interior of the carrier. The surface of evaporation is therefore considerably increased and any fall in pressure is very much reduced.

The important property of the containers holding the separate-phase aerosol propellants is not the actual pressure in the container but the rate of flow of gas which it is capable of releasing per unit of time (this rate of flow being of course a function of the pressure).

Keeping this in mind, the effectiveness of the preferred embodiment of the invention has been verified in the course cf comparative experiments relating to measurements of the rate of flow effected between containers filled with propellant alone and containers filled with propellants adsorbed by precipitated pure silica.

The results of these experiments are shown in the graphs in Figures 4 and 5j where the rates of flow d in grammes per second are plotted as ordinates and the time £ in seconds as abscissae. The propellant corresponding to the graph in Figure 4 is dichlorodifluoromethane, and that corresponding to the graph in Figure 5 is butane.

The rates of flow of a venturi valve having an orifice of 0.30 mm diameter for the gas, were measured, at test temperature, at the beginning of atomization, first of all at 20°C and then at 25°C, this valve being carried in each case by a propellant container provided with a valve and consisting of a small aluminium reservoir with a capacity of 55ml. The spray times varied from 5 to 60 seconds.

Tho rates of flow found with dichlorofluoromethane (Figure 4) were plotted on curves (at 20°C) and (at °C) when the reservoir only contained the propellant by itself, and on curves Dk^ (at 20°C) and DA^ (at 25°C) when the said reservoir contained the propellant in the adsorbed state.

Similarly the rates of flow found with butane (Figure 5) are respectively plotted on the curves (at 20°C), 332 (at 25°C), BA^ (at 20°C) and BA2 (at 25°C).

It is easy to see that for either of these test temperatures, the instantaneous rate of flow from the reser of impregnation in accordance with the invention.

This property is very advantageous in the case of separate-phase dispensers. In fact the fineness of their atomization, which is directly proportional to the velocity of the propellant gas, and hence to its instantaneous rate of flow, can be considerably increased.

The separate-phase dispenser, improved in accordance with the invention, makes it possible in a remarkable manners either to obtain a finer atomization starting from a given propellant and at a given temperature of use 5 or to obtain an atomization of the same fineness starting from a propellant with a lower vapour pressure ; or to lower the limit temperature at which a given propellant can supply an acceptable atomization ; or to permit utilizations of longer duration while maintaining an acceptable fineness.

This form of embodiment can of course be given modifications which do not go outside the scope of the invention. In particular, to avoid the arrival of agglomerates • from the carrier 6 at the inlet of the valve it is possible to use filters formed by a metal mesh screen or a cloth screen or by a pad of fibres such as a plug of cotton or felt.

Similarly the stop grid 11 provided in the embodiment in accordance with the invention may be provided with holes instead of the slots 14·

Claims (2)

WHAT IS CLAIMED B:

1. An aerosol dispenser having two distinct containers, one of which contains liquefied aerosol propellent, while the other contains the material to be dispensed, a push-button being provided controlling the dispensing nozzle, the arrangement being that by actuating the said push-button gaseous propellent flows rom the propellant container through nozzle, sucking in material from the container of material and vaporizing it, characterised thereby that the liquefied phase which is contained in the propellant container (5) is held in a carrier? hich is preferably composed of cotton wool, felt, fibrous flakes, pumice stone, vermiculite foam, absorptive or adsorptive minerals such as pure precipitated or activated silica, light weight hydrated aluminum oxide and/or precipitated aluminum or magnesium silicate, or of cellular synthetic material such as polyurethane oam (6) which carrier is of such a nature that it is adapted to absorb or adsorb the propellant under pressure and to release gaseous propellant whenever the pressure lowers and thereby that the absorbate or adsorbate composed of propellant and carrier is in the form of a powder o a gel and that in the case of' use of a pulverulent carrier a grid is provided at the outlet of the propellant container which grid retains the powder.

2. An aerosol dispenser according to claim 1, characterised thereby that the propellant is dichloroflu or methane, propane and/or butane. 3, Aerosol dispenser according to claims 1 or 2 characterised thereby that the carrier (6) is pure precipitated diatomaceous earth with a density between 0*03 and 0,12 g/cm3* 4« An aerosol dispenser according to claims 1 or 2 diatomaceous earth, with an addition of activated fossile kieselguhr or light weight hydrated aluminum oxide. 8· Aerosol dispenser according to any of the preceding claims characterised thereby that the grid which is provided at the outlet of the propellant container (ll) has passages the width of which is smaller than the smallest diameter of the conduit for the propellant from the container (5) to the nozzle (9)· P.O. Box 33116, TEL AVIT Attorneys for Applicant*