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The present is in the field of cosmetic spray products and methods of generating sprays. In particular, the invention concerns the generation of a spray from a liquid cosmetic composition without the use of a volatile propellant.
Cosmetic spray devices of the prior art have utilised a variety of means for creating the spray. A widely used option has been to formulate a liquid cosmetic composition with a volatile propellant, such as a liquefied hydrocarbon or chlorofluorocarbon. However, it is increasingly recognised that the addition to the atmosphere of VOCs/greenhouse gases may have detrimental environmental consequences and alternative means of spray generation have been sought.
As an alternative to the use of a volatile propellant, mechanical pressure may be used to expel a liquid cosmetic composition through a nozzle, thereby creating a cosmetic spray. Currently marketed cosmetic spray devices that operate in this manner are squeeze sprays and trigger sprays. Unfortunately, such devices tend not to produce good quality sprays, partly as a result of limited pressure that may be applied to the composition. The poor spray quality often results in poor sensory properties on application to the human body.
Higher pressures may be generating by spring-driven mechanisms. Devices incorporating such mechanisms have been used as ‘inhalers’, intended for the delivery of medicaments via the respiratory tract. Such devices are described in U.S. Pat. No. 5,331,954 (1994, Novo Nordisk, A/S), U.S. Pat. No. 6,109,479 (2000, Bespak plc), and WO 91/14468 (1991, Dunne Miller Weston Ltd.) together with references cited therein.
Unfortunately, these publications contain no description of how a cosmetic spray suitable for application to the surface of the human body might be generated. The devices described in these publications operate at pressures that are higher than would be desired in a cosmetic spray applicator and/or would not deliver the spray at sufficient rate or spray quality for cosmetic application.
In a first aspect of the present invention, there is provided a method of spraying a liquid cosmetic composition onto the surface of the human body comprising:
In a second aspect of the present invention, there is provided a product comprising a free-flowing liquid cosmetic composition and a hand-held spraying device suitable for spraying the same onto the human body, said device comprising a pre-atomisation chamber for the cosmetic composition, a means for subjecting the cosmetic composition to a pressure of from 1.0 to less than 5.0 MPa, a transfer conduit for the cosmetic composition leading from the pre-atomisation chamber to a swirl chamber, the swirl chamber having a 100-200 micron outlet nozzle for the spray created from the cosmetic composition.
Throughout this specification, references to application to the surface of the human body should be understood to mean application to the skin and/or hair exclusively.
Preferably, such application should be direct. The products and methods of the present invention are particularly suited for application to the human skin.
The present invention describes a method of creating a cosmetic spray that has good sensory properties on application to the human body, without the use of a volatile propellant. The good sensory properties result from the good spray quality attained by the combination of suitable device components and suitable mechanical pressurisation as described herein. In addition, the invention enables the cosmetic spray to be applied to the surface of the human body at a flow rate that is appropriate.
The benefit of appropriate flow rate and good spray quality is of great advantage in the application of liquid cosmetic compositions to the surface of the human body. Consumers greatly desire the often rapid application of product achievable at appropriate flow rates and the good spray quality gives a sensory or “comfort in use” benefit. Poor quality sprays, comprising large droplets, often feel cold and wet on application to the human body, whereas sprays produced according to the present invention have good sensory properties.
The mechanical pressurisation of the liquid cosmetic composition requires mechanical force to be applied to the composition in some way. It is not sufficient that the composition is put under pressure merely by the presence of a liquified volatile propellant as a component of the composition. Indeed, it is preferred that the composition does not comprise such a component. The pressure generated must be at least 1.0 MPa, preferably at least 1.5 MPa, and more preferably at least 2.0 MPa; yet the maximum pressure must be less than 5.0 MPa, preferably no higher than 4.5 MPa, and more preferably no higher than 3.5 MPa.
In the second aspect of the invention, the liquid cosmetic composition is held in a pre-atomisation chamber immediately before it is forced into a swirl chamber via a transfer conduit. Typically, the liquid cosmetic composition in the pre-atomisation chamber is not under pressure until a latching means is released, resulting in pressure being exerted and the composition being forced from the pre-atomisation chamber.
In many embodiments, the mechanical pressurisation of the liquid cosmetic composition is achieved by means of a tensioned spring. The consumer may tension the spring, typically before each use of the product to create a cosmetic spray. In preferred embodiments, the spring is tensioned by the operation of a lever; flexing of the lever putting the spring under tension. In such embodiments, the spring may be held in its tensioned state by a latching means; the latching means being released when it is desired to put pressure upon the liquid cosmetic composition using the tensioned spring.
The swirl chamber is an important element of the present invention. It causes the liquid cosmetic composition to swirl around and thereby enhances its atomisation on exit from the outlet nozzle. A typical swirl chamber has one or more radial inlet holes or slots. Preferably, such holes or slots are tangentially disposed to the cross-section of the swirl chamber; the cross-section preferably being essentially circular. For optimum efficacy, the holes or slots, of which there are preferably two or more, in particular from two to four, are present in the bottom of the swirl chamber, i.e. the part furthest from the outlet nozzle. Multiple inlets, when present, are arranged to all promote swirling in the same direction, whether that be clockwise or counter-clockwise.
The outlet nozzle from the swirl chamber is typically of circular cross-section having a diameter of from 100 to 200 microns. The outlet nozzle represents the exit orifice from the swirl chamber and causes the atomisation of the pressurised, swirling, liquid cosmetic composition exiting therefrom.
The relative dimensions of the inlet(s) to and outlet from the swirl chamber can effect the quality of the spray produced. It is preferred that the total cross-sectional area of the inlet(s) is greater than that of the outlet nozzle; in particular, it is preferred that the inlet:outlet area ratio, i.e. the ratio of the total cross-sectional area of the inlet(s) to the area of the outlet nozzle, is from 2.5:1 to 3:1. In measuring the cross-sectional areas referred to, one should take the minimum inlet/outlet areas linking the swirl chamber with the non-swirl chamber space.
The liquid cosmetic compositions used in accordance with the present invention are free-flowing. Free-flowing in the context of this invention should be understood to refer to liquid cosmetic compositions that will swirl when introduced under a pressure of a pressure of from 1.0 to less than 5.0 MPa into a swirl chamber at a temperature of 20° C. Suitable compositions have a viscosity of from 0.8 mPa·s to 200 mPa·s, in particular from 1 mPa·s to 100 mPa·s, and especially from 1 mPa·s to 50 mPa·s, when measured at a shear rate of 100/s and a temperature of 20° C. The surface tension of the liquid cosmetic composition, at a temperature of 20° C., is typically from 23 to 100, in particular from 30 to 80, and especially from 30 to 50 mN/m.
Liquid cosmetic compositions sprayed according to the present invention frequently comprise a C2 to C4 alcohol, for example ethanol, propylene glycol, propanol, or iso-propanol. Particularly good sensory benefits may be achieved when such compositions are used. Compositions may comprise C2 to C4 alcohol at a level of from 1% to 99%, in particular from 1% to 50%, and especially from 5% to 15% by weight of the composition.
The composition may comprise water in an amount from 1% to 99%, particularly from 25% to 99%, and especially from 50% to 99% by weight. When the especially preferred minimum level of water of 50% by weight is employed, the maximum level is preferably up to 95% by weight. The compositions used may be solutions or emulsions, in particular oil-in-water emulsions.
Suitable cosmetic compositions include hair sprays, body sprays, deodorants, antiperspirants, and perfumes. Body sprays are particularly suitable.
High flow rates, for example from 0.1 g/s to 1.0 g/s, and, in particular, from 0.2/s to 0.6 g/s, can be achieved, whilst still maintaining good spray quality. Spray quality may be defined by the fineness of the droplets achieved and/or by the narrowness of the droplet size distribution of said droplets. For many applications, it desirable to achieve a Sauter D[4,3] mean droplet size of from 7 μm to 60 μm, in particular from 10 μm to 50 μm, and especially from 15 μm to 35 μm. It is further preferred that for each of the Sauter D[4,3] preferred ranges indicated above, that the Sauter D[3,2] mean droplet size is also within the same range. Measurement have also been made of the median volume droplet size (Sauter D[v,0.5]) and it is preferred that this value is from 7 μm to 60 μm, in particular from 10 μm to 50 μm, and especially from 15 μm to 35 μm. With regard to the narrowness of the droplet size distribution, it is preferred that the gap between the Sauter D[v,0.1] value and the Sauter D[v,0.9] value is 50 microns or less, more preferably 45 microns or less, and especially 40 microns or less.
The droplet size measurements referred in this specification may be made using standard instrumentation based on light scattering technology.
The invention will now be further illustrated by a description of a specific embodiment of a suitable spraying device and a description of a specific embodiment of a suitable nozzle assembly (defined below). Reference will be made to FIGS. 1 to 5, wherein:
FIG. 1 is a schematic of a specific embodiment of a spraying device suitable for use according to the invention;
FIG. 2 is a vertical cross-section through the centre of a specific embodiment of a nozzle assembly suitable for use according to the invention;
FIG. 3 is a vertical cross-section through the centre of the upper portion (22) of the nozzle assembly illustrated in FIG. 2;
FIG. 4 is a vertical cross-section through the centre of the lower portion (23) of the nozzle assembly illustrated in FIG. 2;
FIG. 5 is a top view of the lower portion (23) of the nozzle assembly illustrated in FIG. 4.
The spray device illustrated in FIG. 1 is in many respects similar to a device described in the aforementioned WO 91/14468. It comprises a body (1) in which there is defined a cylinder (2) of circular cross-section, in which a piston (3) is mounted for reciprocating movement. The cylinder (2) communicates with a pre-atomisation chamber (4) of reduced cross-section. The piston (3) has a reduced diameter portion (5) which sealingly engages within the pre-atomisation chamber (4), by means of a plastic sealing cap or ring provided on the piston portion (5).
A compression spring (6) is located in the cylinder (2), between the enlarged head of the piston (3) and an opposite end wall of the cylinder (2). An operating rod (7) is connected to the piston (3), and passes through the spring (7) and through a passageway (8) in the body (1). A latching means (9) attached to the body (1) engages with the rod (7) to latch the rod (7) in a position in which the surrounding spring (6) is compressed, i.e. tensioned. The rod (7) is linked at a point outside of the body (1) of the device to one end of a lever (10) by a pivot (11). The lever (8) passes over a fulcrum (12) attached to the body (1) at a position close to the latching means (9). An actuating or trigger button (13) is provided, for releasing the latching means (9).
Also defined within the body (1) is a cavity (14) in which there is located a collapsible bag (15) containing the liquid cosmetic composition (16). The interior of the bag (15) communicates with an inlet passage (17) which, in turn, communicates with the chamber (4) via a non-return valve (18).
Also connected to the chamber (4) is an outlet passage or transfer conduit (19) running to the nozzle assembly (20) via a valve (21) which functions as a non-return valve and as a pressure release valve.
The nozzle assembly illustrated in FIGS. 2 to 5 is one that would be suitable for use with the spray device illustrated in FIG. 1. The nozzle assembly has a circular cross-section and comprises an upper portion (22) and a lower portion (23). The bottom surface (29) of the upper portion (22) fits tightly against the top surface (38) of the lower portion (23). A swirl chamber (30), comprising a lower cylindrical portion (37) and an upper frusto-conical portion (31) is defined between the upper portion (22) and the lower portion (23) of the nozzle assembly, as described below.
The upper portion (22) of the nozzle assembly is illustrated in FIG. 3 and comprises a cylinder (24) of circular cross-section into which the lower portion (23) snugly fits. Above the cylinder (24) is the top (25) of the upper portion (22), in the top surface (26) of which there is defined a conical indentation (27) at the centre of which there is an outlet orifice/nozzle (28). In the bottom surface (29) of the upper portion (22) there is defined a smaller frusto-conical indentation (30) terminating as the outlet orifice/nozzle (28) in the centre. The smaller conical indentation (30) defines the upper portion of the swirl chamber (31) shown in FIG. 2.
The lower portion (23) of the nozzle assembly is illustrated in FIGS. 4 and 5. It comprises a body (32) of circular cross-section, bevelled on its outer side at the top (33) and of reduced diameter at a portion at its lower end (34). The liquid cosmetic composition passes from the pre-atomisation chamber (4) into a chamber (35) in the lower portion (23) of the nozzle assembly via the transfer conduit (19) and an aperture in the lower face (36) of the lower portion (23) of the nozzle assembly. From this latter chamber (35), the liquid cosmetic composition is forced upwards via transfer tubes (39) and (40) of circular cross-section. At their lower ends, the outer portions of the transfer tubes (39) and (40) are continuous with semi-circular indentations (41A) and (41B) which slope into the sidewall of the chamber (35).
The transfer tubes (39 and 40) open into a depressed portion (42) of the top surface (38) of the nozzle assembly lower portion (23), as illustrated in FIG. 5. The depressed portion (42), together with the bottom surface (29) of the nozzle assembly upper portion (22), define two passageways (43 and 44) of rectangular cross-section that lead into the lower portion (37) of the swirl chamber (31) via two tangential inlet slots (45 and 46) arranged to promote swirling in the same direction (clockwise, as viewed from the top, as in FIG. 5). The ratio of the total cross-sectional area of the two inlet slots (45 and 46) to the area of the outlet nozzle (28) is 2.7:1.
A series of experiments was performed using the swirl chamber illustrated in FIGS. 2 to 5, using output nozzle sizes of 100, 150, and 200 microns. The following model liquid cosmetic compositions were employed (details in Table 1):
1: deodorant base composition;
2: aqueous-alcohol solution antiperspirant composition;
3: oil-in-water emulsion antiperspirant composition;
4: 50 mPa·s standard.
|Model Liquid Cosmetic Compositions|
|Composition (% w/w)|
|Reach 501 ACH||—||36.00||—||—|
|Emulgade SE PF||—||—||4.50||—|
|(50% aqu. solution)|
Each of the liquid compositions was subjecting to the pressures indicated in Table 2 using a G15 DVE Maximator® high pressure pump from Schmidt, Kranz & Co. GmbH. Table 2 shows the spray data on use of the 100 micron nozzle with compositions 1 and 3, on use of the 200 micron nozzle with compositions 2, and on use of the 150 micron nozzle with composition 4. The particle size determinations were made using a Malvern Mastersizer light scattering instrument.
|Spray data on liquid cosmetic compositions|
|as a function of pressure|
|Compn., nozzle||D[v, 0.9]|
|MPa)||(g/s)||D[4, 3]||D[v, 0.5]||D[v, 0.1]|
|1, 100 micron|
|2, 200 micron|
|3, 100 micron|
|4, 150 micron|
Results in italics (top line of each row) are from operation outside the scope of the invention. Droplet size values are in microns.
Table 2 shows the excellent spray quality attainable by use of the present invention. Significantly, the flow rate and the spray quality, both in terms of the fineness of the droplets and the narrowness of the droplet size distribution, is poorer when operating at 0.69 MPa, i.e., outside the scope of the present invention. Good results were also obtained when operating within the scope of the invention with each of the compositions of Table 1 with any of the nozzles investigated.
Analogous experiments to those described above were performed in order to contrast the spray quality achieved according to the invention with that achieved using a standard nozzle having a 270 micron nozzle. In these experiments, ethanol was used as a model liquid cosmetic composition. The results are shown in Table 3 and indicate the superior spray quality achieved by the method of the invention.
|Particle size as a function of nozzle diameter and pressure|
|Pressure||100 micron||150 micron||Standard (270 micron)|
|(MPa)||Median droplet size [d(v, 0.5)]|
Results in italics (column on far right) are from operation outside the scope of the invention. Droplet size values are in microns.