FR2927006A1 - LIQUID SUPPLY METHOD OF A NEBULIZATION DEVICE - Google Patents

Abstract

The invention relates to a method of nebulizing in air a first liquid (36a) comprising a solvent and an active product immiscible with the first liquid, the method comprising steps of contacting the first liquid ( 36a) with the active product, agitating the first liquid in contact with the active product to obtain a substantially homogeneous mixture (36) and unstable, and nebulizing the mixture before the liquid separates from the active product, during a cycle of nebulization.

Description

LIQUID SUPPLY METHOD OF A NEBULIZATION DEVICE

The present invention relates to the nebulization of liquids in the air, in particular to distribute sanitizers, deodorants, disinfectants, perfumes or pest control. The present invention relates more particularly to a liquid supply method of a liquid nebulizer apparatus projecting fine droplets into the air. The present invention is applicable to all types of nebulizing heads such as those described in EP 0 714 709 comprising ejection channels subjected to vibration, cu using piezoelectricity or electrostatic or Venturi effect. When the active product to be nebulized is an oily product such as perfumes and essential oils, the solvent used to dilute the product generally is an alcohol or a mixture of alcohols or other organic solvents more or less volatile. However, certain regulations prohibit the marketing of compositions containing perfumes with a concentration greater than 10% without particular labeling alerting the consumer of the dangers of the composition. Some regulations impose special and binding storage and transport conditions, and the application of a hazard warning logo to products containing a relatively large amount of alcohol because of the risk of explosion. The amount of alcohol that can be mixed with the active product is therefore small. On the other hand, it is preferable to avoid applying alcoholic compositions to the skin, even though the perfumes and toilet waters generally contain alcohol. Nor is it desirable to create stable solutions with water and surfactants as these are subject to stringent regulations.

It is desirable that the mixture of the active product with the solvent to be sprayed promotes nebulization and in particular that it does not increase or reduce the sensitivity of the device to ambient conditions, including temperature, pressure and humidity 10 and the nature of the active product to be sprayed. It turns out that with certain compositions, the amounts of liquid nebulized with each nebulization vary significantly depending on the ambient conditions. It is therefore also desirable to use a solvent that is chemically and physically neutral, inexpensive, environmentally friendly, and non-skin friendly, that can be used with all active ingredients. likely to be nebulized. The aim of the invention is to nebulise an active product in the air or towards the skin by using a carrier liquid which is not necessarily miscible or soluble with all the compositions, in particular hydrophobic compositions such as perfumes or essential oils, or compositions in powder form such as pigments. Thus, in one embodiment, there is provided a method of nebulizing in air a first liquid comprising a solvent and an immiscible and non-soluble active product with the first liquid. According to one embodiment, the method comprises the steps of: bringing the first liquid into contact with the active product, shaking the first liquid in contact with the active product to obtain a substantially homogeneous and unstable mixture, and nebulizing the mixture beforehand the first liquid separates from the active product during a nebulization cycle. According to one embodiment, the first liquid 5 comprises water. According to one embodiment, the active product is in liquid or powder form and comprises at least one component belonging to the assembly comprising perfumes, essential oils, pesticides, biocides, pheromones and cosmetic products. According to one embodiment, the first liquid in contact with the active product is stirred in an intermediate reservoir. According to one embodiment, the entire mixture in the intermediate reservoir is nebulized with each nebulization cycle. In one embodiment, the active product is in the form of a second liquid, the process comprising a step of adjusting the amount of each of the liquids contacted with each other in an intermediate reservoir. According to one embodiment, the process comprises, before the stirring step, a step of contacting the first liquid with a third liquid containing a concentrated active product to be nebulized. According to one embodiment, the third liquid is immiscible with the first liquid. According to one embodiment, the sono liquids introduced simultaneously into the intermediate reservoir 30 by spraying droplets of liquids into the intermediate reservoir, causing agitation and mixing of the liquids, to form an unstable and substantially homogeneous emulsion, the nebulization cycle mixing is started before the end of the filling of the intermediate tank.

According to one embodiment, the first liquid is a thixotropic gel in which the active product is trapped. According to one embodiment, the thixotropic gel is forced into a nebulization head and fluidized during nebulization. According to one embodiment, the thixotropic gel comprises water and polysaccharides. In one embodiment, the nebulization is effected to a surface so as to form a polysaccharide film containing the active product. one embodiment, there is provided a nebulization of liquids in the air a nebulizing nozzle, a first reservoir provided to contain a first liquid a solvent, supplying the nebulizing nozzle with liquid to be sprayed, and a control member of nebulization to trigger the ejection of liquid droplets into a nebulization jet by the nebulization nozzle, during nebulization cycles. According to one embodiment, the apparatus is configured to: agitate the first liquid previously brought into contact with an immiscible and non-soluble active product in the first liquid, to obtain a substantially homogeneous and unstable mixture, and to nebulize the mixture before the first liquid separates from the active product, during a nebulization cycle. According to one embodiment, the first liquid comprises water. According to one embodiment, the active product is in liquid or powder form and comprises at least one component belonging to the set comprising perfumes, essential oils, pesticides, biocides, pheromones and cosmetic products. In a main comprising apparatus comprising an embodiment, the apparatus comprises a nebulizing head having a capillary tube having one end forming the nebulizing nozzle, a vibrating member for driving the vibrating nebulizing head to eject liquid droplets in a nebulizing jet, and an excitation circuit for applying to the first vibrating member an excitation signal during each nebulization cycle. According to one embodiment, the apparatus is configured to nebulise all of the mixture produced in an intermediate reservoir, at each nebulization cycle. According to one embodiment, the apparatus comprises a second main reservoir containing the active product in liquid form, filling control devices configured to project into an intermediate reservoir droplets of liquids from main reservoirs, causing agitation and mixing the liquids, wherein the liquids form an unstable and substantially homogeneous emulsion, the apparatus being configured to start the nebulization cycle of the mixture before the end of the intermediate reservoir filling. According to one embodiment, each filling control device comprises a cavity that can be filled by gravity by the main tank and opening into the intermediate tank by at least one nozzle, and a vibrating member for driving the liquid into the cavity. vibration so that it is ejected in droplets by the nozzle in the intermediate reservoir, and excitation means for applying to the vibrating member an excitation signal. According to one embodiment, each control device comprises a plurality of nozzles projecting droplets into the intermediate tank.

According to one embodiment, the apparatus comprises a stirring device for agitating the liquids in an intermediate reservoir and obtaining a substantially homogeneous unstable emulsion, the apparatus being configured to start the nebulization cycle of the mixture during the stirring of the two liquids. According to one embodiment, the stirring device comprises an ultrasonic generator or a rotary stirrer driven by an electric motor or a piezoelectric vibrating member placed in contact with the liquids. According to one embodiment, the apparatus is configured to adjust the amount of each of the liquids introduced into the intermediate tank.

According to one embodiment, the apparatus comprises a third main reservoir adapted to contain a third liquid comprising a concentrated active product to be nebulized, and a third filling control device for controlling the filling of the intermediate reservoir from the second main reservoir, the apparatus being configured to introduce the third liquid into the intermediate reservoir to mix with the first liquid. According to one embodiment, the third liquid 25 is immiscible with the first liquid. According to one embodiment, the first liquid is a thixotropic gel in which the second liquid is trapped. According to one embodiment, the apparatus comprises a vibrating capillary tube, and a pump for forcing the thixotropic gel to penetrate into the capillary tube in which it is fluidized. According to one embodiment, the thixotropic gel comprises water and polysaccharides. Exemplary embodiments of the invention will be described in the following, without limitation in connection with the accompanying figures in which: - Figure 1 is a schematic sectional view in perspective of a nebulizing device according to a embodiment, - Figure 2 is a schematic sectional view in perspective of a nebulizing device according to another embodiment, - Figure 3 is a schematic sectional view in perspective of a nebulizing device according to FIG. 4 is a diagrammatic sectional view in perspective of a nebulizing device according to another embodiment, FIG. 5 is a diagrammatic sectional and perspective view of a device of FIG. nebulization according to another embodiment. FIG. 1 shows an embodiment of a nebulizer apparatus comprising two main reservoirs 1a, 1b containing liquids 36a, 36b to be sprayed, and an NBCT nebulization circuit fed by reservoirs 1a, 1b. The nebulization circuit NBCT comprises a nebulizing head 30, an intermediate reservoir 10 supplying the nebulizing head, lines 34a, 34b connecting the reservoir 10 to the tanks 1a, 1b, and filling control devices 12a, 12b to control filling the tank 10 from the tanks 1a, 1b. The nebulizing head 30 is for example of the vibrating capillary tube type. Thus the nebulizing head comprises a capillary tube 30-1 which can be horizontal, and a nozzle 30-2 ejection of the liquid. The nebulizing head generally has the shape of a hollow needle forming the capillary tube 30-1 and having an internal diameter less than a millimeter or of the order of 1 mm, and a length of a few centimeters. The distal end of the nebulization head is beveled and forms the ejection nozzle 30-2. The proximal end of the nebulizing head 30 opens directly into a lower region of the reservoir 10. The nebulizing head 30 is mechanically coupled to a vibrating means, for example a piezoelectric transducer TPE1 with a resonator. The transducer TPE1 is excited by an alternating signal Sv1 supplied by an excitation circuit EXCT. The EXCT circuit is controlled by a control circuit CNCT which defines the duration of nebulization cycles during which the nozzle 30-2 emits nebulized liquid, and the duration of periods of rest between the nebulization cycles. In one embodiment, the CNCT circuit controls the fill control devices 12a, 12b to adjust the level of the liquid 36 in the intermediate tank 10, which it monitors by means of a level meter 14. The reservoir It is intended to contain a solvent or a mixture of solvents and the reservoir lb, of smaller dimensions, a concentrated active product. The tanks 1a, 1b and 10 are subjected to atmospheric pressure.

When the excitation signal Sv1 is applied to the TPE transducer, the nebulizing head resonates and droplets 32 of the liquid 36 from the intermediate reservoir 10 are ejected, forming a kind of mist of droplets or "nebulizing jet". During nebulization, the nebulizing head 30 is supplied with liquid by capillarity and by gravity (effect of the hydrostatic overpressure). An air circulation means such as a fan (not shown) can be provided to increase the range of the jet. of nebulization.

At rest, when the nebulizing head 30 is not driven in vibration, the liquid 36 is retained in the nebulization head by capillarity, and the hydrostatic pressure is compensated by the appearance of a convex meniscus 32 of liquid 36 to the end of the nebulizing head, due to the surface tension forces acting on the liquid. Beyond a critical threshold of overpressure, the meniscus 32 breaks and the liquid 36 flows through the nebulizing head.

In the example of FIG. 1, each filling control device 12a, 12b is of the print head type = pet of piezoelectric ink. Thus each device 12e, 12b comprises a cavity 12- 1 fed by the main reservoir 12a, 12b corresponding. Each cavity 12-1 opens into the reservoir 10 via one or more nozzles 12-2. Each cavity 12-1 is closed by a plate 12-3 mechanically coupled to a vibrating means TPE2a, TPE2b, such as a piezoelectric transducer with resonator. Each vibrating means is controlled by a respective excitation signal SV2a, SV2b, derived from the excitation circuit EXCT. With the level measuring device 14, the control circuit CNCT1 can determine the volume of nebulized liquid during one or more nebulization cycles.

The CNCT control circuit is configured to calculate the number of drops to be extracted from each of the main tanks 1a, 1b so that the liquid contained in the intermediate tank 10 has a concentration of active product corresponding to a set value supplied. The control circuit then controls the filling control devices 12a, 12b to simultaneously transmit the numbers of calculated drops that mix in the intermediate tank 10.

The drop filling technique makes it possible to very finely adjust the concentration of active product of the nebulized liquid. The concentration of active product of the liquid in the tank 10 can thus be adjusted between 0 and 100 for example between 2.5% and 10%. According to one embodiment, the two liquids in the tanks 1a and 1b are not miscible with each other. For example, the liquid in the tank 1a comprises water and the liquid in the tank 1b comprises an oily active product, for example a perfume or an essential oil. Intermediate reservoir droplet filling technique, drop ejection speed and activation time of the fill control devices mix the two liquids from the two tanks 1a, 1b to obtain an unstable emulsion over time. . According to one embodiment, a nebulization cycle is triggered before the end of the filling of the intermediate tank 10. Thus, the liquid drops projected by the devices 12a, 12b into the tank 10 mix to form a substantially homogeneous and unstable emulsion, that is to say, whose constituents separate at rest in distinct phases. The unstable mixture is nebulized before the two liquids separate into two distinct phases. In this way, both the strong agitation of the liquids 36a, 36b caused by the devices 12a, 12b, and the settling dynamics of the two liquids are exploited so that the transfer time of the mixing zone in the Intermediate reservoir 10 at the nebulization zone in the capillary tube 30-1 is less than the separation time (settling or demixing) of the constituents of the mixture. In order for the nebulized liquid to be substantially homogeneous, the intermediate reservoir 10 is filled just at the beginning of a nebulization cycle and the entire mixture made in the reservoir 10 can be nebulized during the nebulization cycle. The arrangement of the nozzles 12-2 of the filling control devices 12e, 12b relative to one another in the tank 10 and the respective number of nozzles of each filling device can be adapted to make the effect more effective. agitating the liquids when introduced into the reservoir 10. It can thus be advantageous for the homogeneity of the emulsion obtained that the two nozzles are facing each other to emit droplets in directions opposed, or on the contrary that they open into the tank 1C by the same tank wall to emit the droplets in the same direction, or by two adjacent walls to emit the droplets in directions perpendicular to each other. It may also be advantageous for each control device 12e, 12b to open into the tank 10 by several smaller nozzles so that the droplets emitted into the tank are smaller. Other types of devices for controlling the filling of the intermediate reservoir 10 can be implemented. Thus, FIG. 2 shows a nebulizing apparatus according to another embodiment which differs from that represented in FIG. 1 in that the devices for controlling the filling of the intermediate reservoir from the main tanks are controlled valves 21a, 21b, for example piezoelectric tpe. The valves 21a, 21b are controlled by control signals SCa, SCb provided by the control circuit CNCT. In the apparatus of FIG. 2, the mixing of the immiscible two liquids 36a, 36b into a homogeneous and unstable emulsion is not carried out during the filling of the tank 10. There is then provided a stirring device 22 controlled by the CNCT1 control device and placed in contact with the liquids in the tank 10 to form the substantially homogeneous and unstable emulsion. Since agitation of the mixture of the two liquids is not carried out at the time of filling the intermediate tank 10, it is not necessary to empty the tank 10 during each nebulization cycle. The control circuit CNCT1 is thus configured to activate the stirring device 22 shortly before the start of each nebulization so that the two liquids are mixed at the beginning of a nebulization cycle. As a result, at the beginning of a nebulization cycle, the liquids possibly present in the capillary tube 30-1 are separated in the form of successive trains. After the nebulization of the contents of the capillary tube at the beginning of the nebulization cycle, the capillary tube is filled with the substantially homogeneous mixture present in the reservoir 10. If the stirring device is deactivated between the cycles of nebulization, the two liquids present in the the reservoir 10 separate into two distinct phases. The stirring device 22 may comprise an ultrasonic generator or a rotary stirrer driven by an electric motor, or a vibrating member disposed at the bottom or on a wall of the reservoir 10 in contact with the liquid. The vibrating member may thus be a cup or a piezoelectric membrane disposed inside the reservoir 10. In another embodiment, the vibrating member may be a piezoelectric resonator immersed in the reservoir 10.

Figure 3 shows a nebulizing apparatus according to another embodiment. In FIG. 3, the nebulizer apparatus differs from that shown in FIG. 1 in that it comprises a third main reservoir connected to the intermediate reservoir 10 via a pipe 34c and a control device. 12c identical to the control device 12b and controlled by a signal Sv2c provided by the excitation circuit EXCT.

The reservoir 1c may also be of small dimensions such as the reservoir 1b and contain an active product 36c to be nebulized alone with the solvent 36a contained in the reservoir 1a, or mixed in proportions adjusted with the active product 36b contained in the reservoir 1b and with the solvent. The active product 36c may or may not be miscible with the solvent 36a. Figure 4 shows a nebulizer apparatus according to another embodiment. In FIG. 4, the nebulizer apparatus differs from that shown in FIG. 2 in that it comprises only one main reservoir 1 which empties into the intermediate reservoir 10, without passing through a filling control device. . In this embodiment, the liquid to be nebulized is in the form of a highly viscous gel 36-1 at the usual conditions of temperature and pressure, but which has the characteristic of being thixotropic. A thixotropic gel has the particularity of becoming fluid substantially like water when it is subjected to shear forces caused for example by forcing in a pipeline or by mechanical agitation. A reasonable proportion of an active product in liquid or powder form, immiscible and insoluble with the gel components, is mixed with the gel 36-1. The active product is then trapped in the gel without being dissolved forming a substantially homogeneous mixture. The active product thus mixed with the gel 36-1 is fed from the single tank 1, and fluidified by stirring at the inlet of the nebulizing head 30, with the aid of the stirring device 22. The hydrostatic pressure brought by the gel column ensures the forcing of the fluidized gel 36 in the needle 30-1. It should be noted that the mixture formed during the agitation by the fluidized gel and the active product, is not stable. Indeed, if the stirring of the mixture is stopped, the fluidized gel found almost instantly its original viscosity. Consequently, it can no longer penetrate by gravity into the needle 30-1, and therefore it can no longer be nebulized.

Figure 5 shows a nebulizing apparatus according to another embodiment. In Figure 5, the nebulizer differs from that shown in Figure 4 in that it does not include an intermediate reservoir. Thus, the main reservoir 1, which is filled with a thixotropic gel 36-1, feeds directly the nebulizer head 30. The apparatus comprises a small pump 23 which forces the gel 36-1 to penetrate the nebulizing needle 30. -1. The flow velocity being low, the gel remains very viscous in the needle.

However, the acceleration of the tip of the needle during nebulization causes almost instant fluidization of the gel at the meniscus and nebulization of the fluidized gel. Again, in the absence of acceleration of the tip of the needle, the mixture would be too viscous to be nebulized. The thixotropic gel is for example composed of polysaccharides and water, the proportion of polysaccharide being limited to 0.5. This results in the dispersion in the air of a tiny amount of dry matter presenting no danger to health. If the nebulizing device is intended for a projection towards the skin for a cosmetic purpose, the polysaccharides form on the skin an imperceptible film which leads to an accentuation of the persistence of the active product. If the active product includes an insecticide, the nebulization aims to project the active product on insects. The remanence effect produced by the polysaccharides also enhances the effect of the insecticide. In the embodiments described above, the active product may comprise one or more of the following components, in liquid or powder form: perfumes, essential oils, pesticides, biocides, pheromones and cosmetic products. It will be apparent to those skilled in the art that the present invention is susceptible to various embodiments and applications. In particular, the invention can be applied to the use of any other solvent than water. Moreover, the invention is not limited to a nebulization head of the vibrating capillary tube type. Any other fogging head capable of being fed by an intermediate reservoir may be suitable for nebulizing an unstable mixture. The use of inkjet head type filling control devices does not preclude the use of a stirring device in the intermediate tank, at least to maintain the mixing in the state of emulsion during nebulization, or to avoid having to completely empty the intermediate reservoir with each nebulization.

Claims (6)

A method of nebulizing in air a first liquid (36a) comprising a solvent and an immiscible and non-soluble active product with the first liquid, characterized in that it comprises steps of: the first liquid (36a) in contact with the active product, shaking the first liquid in contact with the active product to obtain a substantially homogeneous (36) and unstable mixture, and nebulizing the mixture before the first liquid separates from the active product , during a nebulization cycle. 15 The method of claim 1, wherein the first liquid (36a) comprises water. 3. Method according to one of claims 1 and 2, wherein the active product is in liquid or powder form and comprises at least one component belonging to the set comprising perfumes, essential oils, pesticides, biocides , pheromones and cosmetics. 25 4. Method according to one of claims 1 to 3, wherein the first liquid (36a) in contact with the active product is stirred in an intermediate reservoir (10). 30 5. The method of claim 4, wherein the entire mixture (36) in the intermediate tank (10) is nebulized with each nebulization cycle. 16 30 6. Method according to one of claims 4 and 5, wherein the active product is in the form of a second liquid (36b), the method comprising a step of adjusting the amount of each of the liquids (36a, 36b ) brought into contact with each other in an intermediate reservoir (10). î. Process according to one of claims 6, comprising before the stirring step, a step of contacting the first liquid with a third liquid (36c) containing a concentrated active product to be nebulized. The method of claim 7, wherein the third liquid (36c) is immiscible with the first liquid (36a). 9. Method according to one of claims 6 to 8, wherein the liquids (36a, 36b) are introduced simultaneously into the intermediate tank (10) by the droplet projection of liquids into the intermediate tank, causing agitation and mixing the liquids, to form an unstable and substantially homogeneous emulsion, the nebulization cycle of the mixture being started before the end of the filling of the intermediate reservoir. 10. Method according to one of claims 1 to 5, wherein the first liquid (36a) is a thixotropic gel in which the active product is trapped. 11. The method of claim 10, wherein the thixotropic gel is forced into a nebulizing head (30) and fluidized during nebulization. The method of claim 10 or 11, wherein the thixotropic gel comprises water and polysaccharides. The method of claim 12, wherein the nebulization is effected to a surface so as to form a polysaccharide film containing the active product. 14. Apparatus for nebulizing liquids in the air comprising a nebulizing nozzle (30-2), a first main reservoir (la) provided for containing a first liquid (36a) comprising a solvent, supplying the nebulization nozzle with liquid to nebulizing, and a nebulizing control device (TPE) for triggering the ejection of liquid droplets into a nebulizing jet by the nebulization nozzle, during nebulization cycles, characterized in that the apparatus is configured to: agitating the first liquid previously contacted with an immiscible and non-soluble active product in the first liquid to obtain a substantially homogeneous (36) and unstable mixture, and nebulizing the mixture before the first liquid separates from the active product , during a nebulization cycle. The apparatus of claim 14, wherein the first liquid (36a) comprises water. 16. Apparatus according to one of claims 14 and 15, wherein the active product is in liquid or powder form and comprises at least one component belonging to the set comprising perfumes, essential oils, pesticides, biocides. , pheromones and cosmetics. 17. Apparatus according to one of claims 14 to 16, comprising a nebulizing head comprising a capillary tube (30-1), one end of which forms the nebulization nozzle (30-2), a vibrating member (TPE) for driving the vibration nebulizing head for ejecting droplets of liquid into a nebulizing jet, and an excitation circuit (EXCT) for applying to the first vibrating member an excitation signal (Sv) during each nebulization cycle. 18. Apparatus according to one of claims 14 to 17, configured to nebulise the entire mixture (36) made in an intermediate reservoir (10), each nebulization cycle. 19. Apparatus according to one of claims 14 to 18, comprising a second main tank (lb) containing the active product in liquid form (36b), filling control devices (12a, 12b, configured to project into an intermediate tank (10) liquid droplets (36a, 36b) from main reservoirs (1a, 1b) agitating and mixing the liquids, wherein the liquids form an unstable and substantially homogeneous emulsion, the apparatus being configured to starting the nebulization cycle of the mixture before the end of the filling of the intermediate reservoir 20. The apparatus of claim 19, wherein each filling control device (12a, 12b) comprises a cavity (12-1) which can be filled by gravity through the main tank (la, lb) and opening into the intermediate tank (10) by at least one nozzle (12-2), and a vibrating member (TPE2a, TPE2b) to entrain the liquid dan s the cavity vibrating so that it is ejected in droplets by the nozzle in the intermediate reservoir, and excitation means (EXCT) for applying to the vibrating member an excitation signal (Sv2a, Sv2b). 21. Apparatus according to one of claims 19 and 20, wherein each control device (12a, 12b) comprises a plurality of nozzles (12-2) projecting droplets into the intermediate reservoir (10). Apparatus according to one of claims 19 21, comprising a stirring device (22) for agitating the liquids in an intermediate reservoir (10) and obtaining a substantially homogeneous unstable emulsion, the apparatus being configured to start the nebulization cycle of the mixing while stirring the two liquids. Apparatus according to claim 22, wherein the stirring device (22) comprises an ultrasonic generator or a rotary stirrer driven by an electric motor or a piezoelectric vibrating member placed in contact with the liquids. 24. Apparatus according to one of claims 19 to 23, configured to adjust the amount of each of the liquids (36e, 36b) introduced into the intermediate tank (10). Apparatus according to one of claims 19 to 24, comprising a third main tank (1c) for containing a third liquid (36c) comprising a concentrated active product to be sprayed, and a third filling control device (12c) for controlling the filling of the intermediate tank (10) from the second main tank, the apparatus being configured to introduce the third liquid into the intermediate tank to mix with the first liquid (36a). Apparatus according to claim 25, wherein the third liquid (36c) is immiscible with the first liquid (36a). 27. Apparatus according to one of claims 19 to 18, wherein the first liquid (36a) is a thixotropic gel in which the second liquid is trapped. 28. Apparatus according to claim 27, comprising a vibrating capillary tube (30-1), and a pump for forcing the thixotropic gel into the capillary tube in which it is fluidized. Apparatus according to claim 27 or 28, wherein the thixotropic gel comprises water and polysaccharides. 25