GB2421184A - Air freshener powered by the heat of a light bulb - Google Patents

Abstract

An apparatus adapted to disseminate volatile liquid into an atmosphere by heating and evaporation, and simultaneously to provide illumination, comprising <SL> <LI>(a) a source of heat and light comprising at least one electric light bulb 4; <LI>(b) a reservoir 2 for holding the liquid 7, having <SL> <LI>(i) an upper end comprising an opening leading to the atmosphere, this opening being covered by a mesh 11 defining a series of apertures; <LI>(ii) a lower end in which is formed a re-entrant portion whose shape conforms closely to the exterior form of the bulb, such that, in place, most of the glass surface of the bulb is surrounded, at least that part of the reservoir in the vicinity of the bulb being translucent or transparent; and </SL> <LI>(c) a volatile liquid that is transparent or translucent, and that has a viscosity under conditions of use such that it will be retained by a mesh of having apertures of the same size as those of the mesh in the upper end. </SL> The apparatus provides an effective and aesthetically attractive method of disseminating liquids such as fragrances and insecticides into the atmosphere, and it has the added advantage of safety when inadvertently knocked over.

Description

CONTAINER This invention relates to methods for the dissemination of volatile liquid into an atmosphere, to an apparatus and a formulation for achieving this. A refill for use with an air freshener powered by the heat from a light bulb consisting of a container with a particular shape, a mesh over the top opening of a particular aperture size and formulations of specific composition and properties to be used in the system. The use of heat.to disseminate volatile material, for example fragrance or insecticide, is well known. Typically, such devices use a porous wick in contact or close proximity to a resistor, thermistor or naked flame. Electric light bulbs have also been used, in such a way that they provide heat and give light in an aesthetically pleasing manner. Such devices are limited in the properties of the volatile material that can be used and the way that it is presented to the light bulb. The material should ideally be clear or translucent and free-flowing to ensure both a uniform delivery of volatile material from the material and also no detrimental effects on the appearance of the material (such as the central portion of the material nearest the heat source drying out and forming a crust while the outermost portion is still fluid).The use of free-flowing materials is also limiting in that they are prone to spillage if tipped over. This can be solved by sealing the top of the container with a permeable membrane but this restricts the amount of material that can be dispensed during use. What is needed is a container and corresponding formulation that allows the passage of light through the container, does not leak on tipping, permits adequate and controllable release of volatile material and is sufficiently free-flowing to prevent non-uniform evaporation. In practical terms, the system should remain clear and provide effective release of volatile material throughout the majority of the lifespan of the system in regular use. The material should remain transparent or translucent and uniform in appearance (though, the volume of material will gradually reduce) throughout the same period.It is not deemed to be a problem, . if at the end of the usage of the device that the material opacifies; indeed, such a property would provide a useful indication that the material needs replacing or replenishing a The invention therefore provides an apparatus adapted to disseminate volatile liquid into an atmosphere by heating and evaporation, and simultaneously to provide illumination, comprising (a) a source of heat and light comprising at least one electric light bulb; (b) a reservoir for holding the liquid, having (i) an upper end comprising an opening leading to the atmosphere, this opening being covered by a mesh defining a series of apertures;(ii) a lower end in which is formed a re-entrant portion whose shape conforms closely to the exterior form of the bulb, such that, in place, most of the glass surface of the bulb is surrounded, at least that part of the reservoir in the vicinity of the bulb being translucent or transparent; and (c) a volatile liquid that is transparent or translucent, and that has a viscosity under conditions of use such that it will be retained by a mesh of having apertures of the same size as those of the mesh in the upper end. The invention additionally provides a method of providing simultaneously illumination and a dissemination of a volatile liquid into an atmosphere, comprising the steps of (a) providing a volatile liquid that is transparent or translucent, and that has a viscosity under conditions of use such that it will be retained by a mesh of having apertures of the same size as those of the mesh in the upper end (b) heating this liquid to cause it to evaporate, heating being by means of at least one electric light bulb, the liquid being heated in a reservoir having an upper portion and a lower portion, the lower portion having formed therein a re-entrant depression whose shape conforms closely to the exterior form of the bulbs, and such that, in place, the glass of the bulb is substantially completely surrounded at least that part of which in the vicinity of the bulb being translucent or transparent. The heating and lighting element is at least one electric bulb. Preferably, for convenience of manufacture, this is a single bulb of substantially spherical shape, but the bulb may also be other shapes, for example, elongate and pointed, better to resemble a flame. In addition, there can be more than one bulb, for example, a cluster of two, three or more. In such a case, the shape of the re-entrant portion (further discussed hereinunder) will conform to the external shape of the cluster as a whole. The bulb may be selected from any known type. It is preferably a tungsten filament incandescent type, but other types, such as small electricity-saving fluorescents and H4-type quartz halogen bulbs, may also be used, although the former does not generate very much heat. The reservoir has an upper and a lower portion. The upper portion has an opening, to allow volatilised material to escape. In a preferred embodiment, this opening is partially closed by a mesh grille. By "mesh grille" is meant an essentially planar entity that has the form of at least two series of parallel, thin, elongate members, which series intersect at an angle and are connected at the points of intersections, so as to define a series of apertures. Many such types are available, for example, wire mesh made of interwoven metal wire and single-piece moulded or extruded plastics mesh. The mesh may cover the entire opening of the upper portion, or only a part thereof. For example, it may form part of an otherwise solid plate. Thus, choice of mesh size and total area of mesh in conjunction with a particular apparatus and liquid can regulate the dissemination of the liquid into the atmosphere. A further function of the mesh is to prevent leakage of the liquid in the event of the apparatus being knocked over. The prevention of spillage by a mesh is a function of the mesh size and the viscosity of the liquid. As a general indication, the apertures of the mesh have a minimum size of 50 micrometres (smaller sizes impede effective evaporation), and sizes of from 50-150 micrometres are generally preferred. However, it is simply not possible to give an indication as to what mesh size is suitable for what liquid in every case, as there are other factors, for example the temperature of the heating will affect the viscosity and that will vary between types of apparatus. Thus, mesh with aperture sizes greater than 150 micrometres could be useful with some liquids. However, the skilled person can readily determine by simple experimentation a suitable mesh size for any given liquid.The following table gives some indication of the interrelationship between mesh aperture and viscosity.

In the lower end of the reservoir is formed a re-entrant portion into which fits the bulb or bulbs. The shape of this re-entrant portion is such that it matches the shape of the bulb and covers the glass area thereof to such an extent that adequate heat for evaporation is provided. The necessary design will be different in each case, but as a general rule, the shape should be such as to allow a close fit to the bulb and the close fit should involve most of the glass area of the bulb. As the bulb should provide both heat for the evaporation and light for practical or aesthetic effect, that part of the reservoir in close proximity to the bulb should be transparent or translucent. The extent of any such transparency or translucency is dependent on the nature of the apparatus and the effect desired. In most cases, for practical reasons, the entire reservoir is made from transparent or translucent material. Typical suitable materials include glass or plastics that can be made transparent or translucent, such as PET, polycarbonate, polypropylene and polyethylene. As well as being transparent, the material should be resistant to the heat generated by the bulb and also resistant to attack by the fluid. The shape of the reservoir is not narrowly critical, and provided the practical requirements mentioned hereinabove mentioned are met, it can basically be any practical and/or aesthetic shape desired. An essential factor in the apparatus of the invention is the use of a particular formulation of volatile liquid, as not all liquids will give good results in the apparatus (some in fact give very poor results or do not work at all). As hereinabove described, the essential properties are that the liquid be transparent or translucent, and that it have a viscosity under conditions of use such that it will be retained by a mesh of having apertures of the same size as those of the mesh in the upper end. The formulation should preferably be transparent or translucent during use up to at least the point where it has lost 80% of its weight through evaporation of active and solvent. For safety reasons, it is also preferable for the formula to have an overall flash point in excess of 61[deg]C. The material whose presence in the atmosphere is desired should be soluble or dispersible (with, if necessary, any auxiliary materials, such as emulsifiers and co-solvents) to give the necessary clarity or translucency. As previously mentioned, it is impossible to set out precisely aperture sizes and viscosities, because these will vary according to temperature, but the skilled person can readily find out by simple experimentation whether a particular combination is suitable for any given application. A typical method for measuring whether a liquid is of sufficiently high viscosity that it will not pass through the mesh at an operational temperature of 50[deg]C is as follows: 30g of gel is placed in a container (total volume 40ml) and a mesh of suitable pore size fixed into place. The container is placed in a temperature-controlled oven at 50 degrees centigrade for one hour to bring the gel to operational temperature. The container is then tipped over 90 degrees (so that the mesh is vertical) and observed regularly up to 2 hours and then again after 24 hours. A gel is deemed to have passed the test if it does not emerge from the outer side of the mesh and flow beyond the extent of the mesh. For a 100 micron mesh a suitable formula would have a viscosity of at least 56,000 centipoise (as measured with a Brookfield RVT, spindle number 5 at 2.5 rpm rotation). In order to achieve the necessary viscosity, there is generally required a thickener that will thicken aqueous or water-alcohol mixtures (including aqueous systems of glycol ethers) to the desired level, while retaining sufficient optical transparency or translucency. Examples of such thickeners include commercially-available acrylic polymers (such as the Carbopol range) and carboxymethylcellulose (such as Blanose ). A typical formulation for a fragrance system would be as follows (all figures %w/w):

* Depending on the system the formula could contain no water or no co-solvent ** e.g. neutralizing agent for the thickener, pH buffer, preservative, dye, optical enhancers. A typical formulation for an insecticide is as follows:

The apparatus of this invention can be manufactured easily and cheaply by known methods. They are easy and cheap to maintain, using standard light bulbs as their source of heat and light. In use, they provide an effective and aesthetically attractive method of disseminating liquids such as fragrances and insecticides into the atmosphere. In addition, they have considerable safety advantages over known apparatus. There is no naked flame, so any fire hazard is reduced almost to nothing, and they are spill-proof, should the apparatus be accidentally knocked over. The invention is further described with reference to the drawings and the following examples, all of which are non-limiting. Figure 1 is a schematic, perspective, part-cutaway view of an embodiment of the invention. Figure 2 depicts three different reservoir configurations in a schematic vertical crosssection. Figure 3 is a graph, showing the effect of the reservoir configurations of Figure 2 on the rate of liquid weight loss. Figure 4 is a graph, showing the effect of different areas of mesh on the rate of liquid weight loss. In Figure 1, an apparatus generally indicated as 1 has a generally cylindrical reservoir 2 seated on a base unit 3. On the base unit is mounted a light bulb 4 in a holder 5, the necessary electrical components for powering the bulb being installed within the base. This light bulb fits within a re-entrant recess 6 formed in a lower end of the reservoir, the surface of the recess fitting sufficiently closely around the bulb so that sufficient heat is transferred. The reservoir contains a volatile liquid 7, whose evaporation into the atmosphere is required. There is formed at the top of the reservoir 2 a lip 8, on which fits a cap 9. This cap has an opening in which is positioned a cross-hatched support grid 10, cap and grid being moulded in one piece. This grid serves to confer rigidity on the cap and provide support for a plastics mesh 11 of 100 micrometre aperture size that forms part of the cap and that is positioned immediately below the support grid. In operation, heat from the bulb 4 heats the liquid and causes it to evaporate into the atmosphere. The plastics mesh 11 has an aperture size that allows evaporation to take place, but that will prevent liquid from running out of the reservoir, should the apparatus be knocked over. Figure 2 shows three different reservoirs, one tall in relation to its diameter, a second with diameter and height about equal, and a third with a diameter considerably larger than the height. These three are used to illustrate the effect of these physical dimensions on evaporation. All three have a capacity of 60ml and all three are loaded with 50ml of a volatile liquid (the liquid used is that of Example 3 below). In each case, the reservoir top is covered with a plastics mesh of 100 micrometres aperture size. All three are then mounted on identical test rigs. Each bulb is run at 3W for two hours daily and the reservoirs measured for weight loss over a period of several days. The results are shown in the graph of Figure 3. In this graph, it can be seen that the short, wide reservoir lost liquid at the fastest rate and that the tall, narrow reservoir lost it at the slowest rate. A suitable choice of reservoir dimensions can therefore help determine the rate of dissemination into the atmosphere. A further way of determining this rate is by adjusting the area of mesh in the cap. The effect is tested by replacing a cap in which the opening is 100% mesh by caps in which the proportion of mesh is smaller, the opening in this case being covered by a higher proportion of non-porous material. Figure 4 shows the rates of loss with time of a series of otherwise identical reservoirs with caps in which the areas of the openings have the following percentages of 100 micrometre mesh; 100, 53, 32, 19 and 5. The liquid is the same as is used for the reservoirs of Fig.2. The reservoirs are heated on identical apparatus by a 3W bulb for two hours a day. As can be seen, the area of mesh has a marked effect on the rate of loss of liquid. Testing of effect of volatile materials on clarity A selection of fragrance raw materials with known water solubility (in ppm) are added to the following test formulae; 1) Unthickened Test Formula

1. Emulsifier (primary alcohol ethoxylate) ex Surfachem Group Limited 2) Thickened Test Formula

2. Acrylic thickener ex Noveon Europe B.V The following fragrance raw materials are used: Water Solubility ClogP (ppm)

Formulations are prepared as described above with ingredients being added in the order listed. The clarity of the resulting liquid or gel is measured using a L*a*b* scale (using the CIELAB colour model). The deviation of each sample from the water control is calculated using the formula:

where L is the lightness, a is the redness/greenness and b the yellowness/blueness. The results for the test raw materials are as follows:

From this test, for the given test formulae, fragrance raw materials with a solubility greater than 600ppm (or a ClogP lower than 3.3) are required to achieve a clear formula.

Example 1 A typical solvent-free volatile liquid formulation for use with a fragrance:

Example 2

Two solvent-based fragrance systems.

Note: for Carbopol systems the optimum pH is 4.0 - 5.5 Systems containing glycol ethers are preferable for good clarity of the gel.

Example 3 3. Acrylic thickener ex Noveon Europe B.V Fragrance formula with different thickener.

4. Thickener (sodium carboxymethylcellulose) ex Hercules S.A. 5. Preservative (mixture of 5 -chloro-2-methyl-4-isothiazolin-3 -one and 2-methyl-4isothiazolin-3-one) ex Rohm & Haas (UK) Ltd 6. Emulsifier (ethoxylated / hydrogenated castor oil) ex BASF pic

Claims (3)

Claims:

1. An apparatus adapted to disseminate volatile liquid into an atmosphere by heating and evaporation, and simultaneously provide illumination, comprising (a) a source of heat and light comprising at least one electric light bulb; (b) a reservoir for holding the liquid, having (i) an upper end comprising an opening leading to the atmosphere, this opening being covered by a mesh defining a series of apertures; (ii) a lower end in which is formed a re-entrant portion whose shape conforms closely to the exterior form of the bulb, such that, in place, most of the glass surface of the bulb is surrounded, at least that part of the reservoir in the vicinity of the bulb being translucent or transparent; and (c) a volatile liquid that is transparent or translucent, and that has a viscosity under conditions of use such that it will be retained by a mesh of having apertures of the same size as those of the mesh in the upper end.

2. An apparatus according to claim 1, in which the aperture size is from 50-150 micrometres.

3. A method of providing simultaneously illumination and a dissemination of a volatile liquid into an atmosphere, comprising the steps of (a) providing a volatile liquid that is transparent or translucent, and that has a viscosity under conditions of use such that it will be retained by a mesh of having apertures of the same size as those of the mesh in the upper end; and (b) heating this liquid to cause it to evaporate, heating being by means of at least one electric light bulb, the liquid being heated in a reservoir having an upper portion and a lower portion, the lower portion having formed therein a re-entrant depression whose shape conforms closely to the exterior form of the bulbs, and such that, in place, the glass of the bulb is substantially completely surrounded at least that part of which in the vicinity of the bulb being translucent or transparent.