Device for Dispensing Volatile Fragrances

FIG. 1 is a perspective view of a silicone rubber device made in accordance with the invention;

FIG. 2 is a cross-sectional view long lines 2--2 of the silicone rubber device depicted in FIG. 1;

FIG. 3 is a cross-sectional side view of a hollow silicone rubber device, wherein the walls are reinforced by a wire or plastic screen.

Referring now to FIG. 1, there is seen a hollow, silicone-rubber dispenser shown in the form of a designer styled container 10 which is representative of the articles of the invention. In its simplest construction, the container may comprise a section of silicone rubber hollow tubing. The container 10 has a generally tubular body 12 having a first, closed end 16 and a second, open end 18. As shown in FIG. 2, a cross-sectional view along lines 2--2 of the FIG. 1, the body 12 together with ends 16,18 define a hollow or chamber 20 containing a liquid volatile composition 22. The open end 18 of body 12 is closed by a removable closure member 40 thereby completely closing the chamber 20. The closure member 40 may be a non-removable plug made, of for example, silicone rubber or a fluid impervious material such as polyethylene, polyvinyl chloride, or the like, inserted into the open end 18 of the hollow body 12 to provide a completely closed volatile fragrance reservoir (chamber 20). Optionally, the closure member 40 may be made to be removed so that the original charge of chamber 20 can be refilled after depletion of the original change of volatile composition 22, as described more fully hereinafter. The member 40 may be held in an interference fit in the open end 18 of body 12.

The body 12 of container 10 is made of a silicone rubber which is generally impermeable to the volatilized form of composition 22 due to its thickness. The body of silicone rubber advantageously exhibits a relatively low gas permeability. A silicone rubber is herein defined as a cross-linked silicone elastomer, preferably of the type vulcanized at room temperature (RTV) or at elevated temperatures (HTV). Such silicone rubbers are well known, as are methods of their preparation; see for example the descriptions given in the U.S. Pat. Nos. 3,664,997; 3,674,738; 4,180,642; 4,216,140; and 4,419,484, all of which are incorporated herein by reference thereto. Dimethyl siloxanediol with silicone resin or alkyl silicate as cross-linking agents are advantageously used. Generally, fillers such as silica, calcium carbonate, titanium oxide, and the like may be added to the polymer. The filler materials provide rigidity. Mica fillers can also be used to control porosity of the silicone rubber. Higher mica contents reduce vapor and gas transmission rates.

One example of a preferred silicone rubber used in the invention is the commercially available Dow Corning 3110 RTV silicone rubber. This material may be cross-linked at room temperature with Dow Corning RTV catalyst No. 4. When allowed to cure in a suitable mold, this material will give a hollow body 12 which may be used as described herein. Also, commercially available silicone tubing (generally free of filler materials) may be end-capped to provide an article of the invention.

Silicone rubber articles of this invention may also be made by injection molding processes. An injection molding process is particularly advantageous because it can be automated and will allow for the cost effective rapid production of th articles described herein.

Typically, the silicone rubber articles of the invention may be designed to contain between about 1 to 50 g of a liquid volatile composition, preferably between about 3 to 25 g.

We have found that the silicone rubber wall thickness of body 12 is a limiting variable, in that hollow bodies having relatively thick walls, as thick as about 1-2 mm to about 5 mm, will give uniform and high rates of release of volatile fragrance compositions. Variable wall thickness, such as depicted for the container 10 in FIGS. 1 and 2 will also give acceptable results provided they are within the range of 1-2 mm to about 5 mm. Thinner walls tend to allow the passage of gases, including the volatilized form of the fragrance composition. As described above, this is undesirable, and may result in a non-linear dispensing of the fragrance composition. Also, as wall thickness is reduced, additional materials, for example, wire or plastic screen, may be required to provide the hollow body with additional rigidity, as shown in FIG. 3 and described below.

In actual use the liquid fragrance composition is brought into contact with the thick body of silicone rubber. The uniform mixture of the fragrance composition charges up the silicone rubber and travels to the outer surface where it can be exposed, unchanged, to the air. A uniform mixture of the fragrance composition constantly volatilizes from the outer surface and is replenished with fresh liquid fragrance composition from within the body of the silicone rubber. It has been found that over the course of the entire use of a container having the thick silicone rubber body that there is a uniform linear emission of the fragrance composition.

It will be appreciated that the liquid porosity of the silicone rubber is a factor to be adjusted for in relation to the fluidity and penetration of the fragrance composition 22 and the rate at which it will transfer across the wall of body 12. If the rate of travel is too fast, the liquid will accumulate on the outer surface of body 12 faster than volatilization occurs. As mentioned above, this is a problem with many of the prior art devices. To avoid this, some trial and error testing may be necessary for specific combinations of silicone rubber (thickness and porosity) and fragrance compositions. In general however the silicone rubber may be selected from those having a water vapor transmission rate at 38.degree. C., under a 90 percent room humidity of from 5 to 50 gms/24 hours/m.sup.2 in a 70 mil. thick section (as determined by ASTM test method E-96-66, Condition E) and a gas (N) permeability coefficient of 50-1,000 gms/24 hours/m.sup.2 at 23.degree. C. and atmospheric pressure.

FIG. 3 is a cross-sectional side elevation of an alternative embodiment container 10 of the invention wherein features similar to the structural features of the container 10 shown in FIGS. 1 and 2 are assigned numerical identifications identical to those used in the FIGS. 1 and 2. The difference between the container of FIGS. 1 and 2 and the container of FIG. 3 is found in the presence of a wire screen 60 on the inner aspect of the walls of body 12, as a means of giving additional rigidity and wall support. The wire or plastic screen or other reinforcing material 60 may be either imbedded in the silicone rubber or inserted inside the chamber 20, butted against the inner wall of the body 12 as depicted in FIG. 3. An advantage of the use of a enforcing material 60 is that it will reduce the cost of the silicone rubber by allowing the use of lesser amounts of the silicone rubber (a thinner wall).

While there have been shown and described preferred embodiments of a silicone rubber, hollow body 12 for dispensing volatile compositions in accordance with the invention, it will be appreciated that many changes and modifications may be made without departing from the spirit of the invention. For example, the article of container 10 may be packaged for transportation and storage before use within an impermeable barrier layer or film such as a metal foil to inhibit dispensing of the contained composition 22 prior to the time when release is desired. The container 10 is particularly useful for the dispensing of complex fragrance composition 22. Fragrances which may be included in the complex compositions 22 are represented by natural essential oils such as lemon oil, mandarin oil, clove leaf oil, petitgrain oil, cedar wood oil patchouli oil, lavandin oil, neroli oil, ylang oil, rose absolute or jasmin absolute; natural resins such as labdanum resin or olibanum resin; single perfumery chemicals which may be isolated from natural sources or manufactured synthetically, as for example alcohols such as geraniol, nerol, citronellol, linalool, tetrahydrogeraniol, betaphenylethyl alcohol, methyl phenyl carbinol, dimethyl benzyl carbinol, menthol or cedrol; acetates and other esters derived from such alcohols-aldehydes such as citral, citronellal, hydroxycitronellal, lauric aldehyde, undecylenic aldehyde, cinnamaldehyde, amyl cinnamic aldehyde, vanillin or heliotropin; acetals derived from such aldehydes; ketones such as methyl hexyl ketone, the ionones and the methylionones; phenolic compounds such as eugenol and isoeugenol; synthetic musks such as musk xylene, musk ketone and ethylene brassylate and the like.

Generally, the fragrances as represented above are compounded in mixtures with perfumery acceptable carriers to obtain the compositions 22.

Perfumery acceptable carriers are well known and are represented by a volatile liquid, such as a non-toxic alcohol (e.g. ethyl alcohol), a non-toxic glycol (e.g. 1,2-propylene glycol) and the like.

The compositions 22 as part of the articles of the invention may be prepared by a simple, homogeneous admixture of the carrier and the fragrance ingredient or ingredients.

The following example describes the manner and process of making and using the invention and sets forth the best mode contemplated by the inventor for carrying out the invention but are non-limiting of the invention. All parts are by weight unless otherwise stated. Where reported, the following test methods are employed: Tensile strength, ASTM test method D-638; elongation, ASTM test method D-638; Shore A hardness, ASTM test method D-2240; moisture vapor transmission rate, ASTM test method E-96-66 (condition E).

There is mixed with 480 parts of silanol end-stopped dimethylpolysiloxane of 4200 centipoise viscosity at 25.degree. C., 120 parts of trimethylsiloxy end-stopped, silanol end-stopped polysiloxane oil, and 18 parts of a cyclicsiloxane treated fumed silica and 480 parts of 160 mesh mica which is treated with 4% by weight of stearic acid. To 100 parts of the above composition there is added 10 parts of a catalyst composition prepared by mixing 102 parts of a vinyl terminated dimethylpolysiloxane of 3,000 cps at 25.degree. C., 120 parts of CaCo.sub.3, parts of gamma aminopropyltriethoxysilane, 24 parts of partially hydrolyzed ethyl silicate and 3.6 parts of dibutyl tin dilaurate.

Sample sheets of the compositions which have cured for 24 hour at 25.degree. C. give the following physicals and moisture vapor transmission rate (MVTR):

Tensile Strength psi: 330

Elongation %: 70

Shore A Hardness: 62

MVTR--8.25 grams/M.sup.2 on sheet 74 mils thick.

A container article as shown in the accompanying drawing of FIG. 1 is molded from the above described silicone rubber, having a minimum wall thickness of about 1 mm and a maximum wall thickness of about 4.8 mm. and a container capacity of about 25 gms of a liquid fragrance composition prepared by simple admixture of the following ingredients.

The fragrance composition, which has a woody, amber character, is charged to the container and the container is placed in an open room for a period of about 6 weeks. At that time, a second container is charged with a freshly prepared fragrance composition as described above. A panel of odor analysts is assembled and asked to evaluate the odor emanating from the two containers and from the freshly prepared composition. A majority of the panel will agree that they cannot distinguish the three sources of fragrance.

In perfume compositions, it is the individual components which contribute their particular olfactory characteristics. However, the overall sensory effect of the perfume composition will be at least the sum total of the effects of each of the ingredients. It can be concluded that the volatilized and dispensed fragrances described in this example are unchanged in their passage to the atmosphere. There is a linear release.