WO2001062308A1

WO2001062308A1 - Liquid nonaqueous composition for use with hydrophobic membrane air fresheners

Info

Publication number: WO2001062308A1
Application number: PCT/IB2000/000206
Authority: WO
Inventors: Nicholas O'leary
Original assignee: Firmenich S.A.
Priority date: 2000-02-25
Filing date: 2000-02-25
Publication date: 2001-08-30

Abstract

The invention provides a liquid non-aqueous air freshener composition comprising at least 20 % by weight of a polar solvent; at least 10 % by weight of a non-polar solvent; and an active substance. According to a preferred embodiment of the invention, the active substance is a perfume. The composition is particularly useful for diffusing active substances such as fragrances, insect repellents or attractants, and the like, into the surrounding air from air freshener articles or devices of the type possessing hydrophobic diffusion membranes.

Description

NON AQUEOUS COMPOSITION FOR HYDROPHOBIC MEMBRANE AIR FRESHENERS

Technical Field and Background Art

The present invention relates to liquid nonaqueous compositions suitable for use with air fresheners of the type in which the active composition is contained in a chamber having at least one wall formed of a material that is permeable to the vapours of the composition, thereby allowing controlled release of the vapours over a period of time. The invention also relates to the air freshener devices or articles comprising such compositions.

Conventionally, there are essentially two types of liquid airfreshener systems. One system generally comprises a container for the air freshening composition and a wick serving as a carrier for the diffusion of the airfreshening composition into the surroundings of the airfreshener device. Typically, the active compositions adapted to this type of airfreshener are essentially water-based and often require the use of surfactants to incorporate the active substance, namely a perfume, in the aqueous medium.

The other current system comprises a reservoir for the liquid composition, which reservoir is provided with at least one diffusion wall or element typically made of polymeric material which is impervious to liquids but permeable to the vapours of the liquid volatile airfreshening composition lodged in the reservoir, such that the latter can evaporate slowly therough the diffusion wall or element into the surroundings of the airfreshener. Such an arrangement is described for example in US 4,534,509, in which the fragrance is enclosed in an impermeable bag with a weak seal along one edge, which prevents escape of the vapours as long as the package is sealed. This is then contained within a larger pouch of a suitable permeable membrane. When sufficient pressure is applied by the user, the weak seal ruptures and the volatile composition flows from the inner pouch into the outer permeable pouch, thereby allowing release of the vapours.

An alternative arrangement of similar type is described in US 4,634,614 in which the permeable wall is covered with a thin layer of paper coated with a polymer sheet to which adheres a protection sheet which is impermeable to the vapours of the composition. The paper layer tears when subjected to a peeling force such that the protective layer is readily removed, and the volatile substance is covered only by a layer of material which is permeable to the vapours, thereby allowing release of the vapours.

Yet another arrangement is described in WO 98/23304, which comprises a membrane laminate having plural layers. The outer layers of the laminate are impermeable to the composition and it's vapours, and thus prevent escape of the vapours as long as the package is sealed. Upon opening to activate the device, delamination occurs at the interface between two selected layers of the laminate, such that the composition is covered only by a layer of material which is permeable to the vapours. EP-B1-662 845 and US 5,518,790 report yet other more recent examples of this type of air fresheners and relate in particular to modified membrane systems intended to provide improved diffusion of the active composition's vapours as compared to prior known devices.

In the air freshener devices described here-above severe constraints are placed on the active composition contained within the chamber. The device must be capable of being stored for a long period of time without the composition affecting the permeable wall or other parts of the chamber prior to activation. Also, the composition must be able to evaporate satisfactorily through the permeable wall at a relatively constant rate throughout the lifetime of the device after activation by the consumer. A typical lifetime of such a device is between 30 and 60 days. It is desirable that after this period a suitable end of life indicator is provided, so that the consumer can see when it is appropriate to buy a new device, or refill composition for such a device. One such suitable indication is a visible reduction in the amount of the composition in the device.

In these prior art devices there is a relatively small amount, for example from 2 to 5 g, of active composition present. In order to provide effective fragrancing or other activity such as insect repellency or attractancy during the product's lifetime, it is necessary for the composition to have a high concentration of active substance, e.g. fragrance, and consequently only a small amount of solvent present. The solvent is chosen so as to aid diffusion of the fragrance through the permeable wall of the chamber. As is described for example in GB 2 066 665, EP 141 266 or yet in US 5,711,955, non- polar or weakly polar solvents are generally used, since such solvents have good diffusion properties through the polymer diffusion walls of the air fresheners. It is now desirable to produce devices of this type which are capable of carrying a larger amount of active composition so as to provide enhanced delivery of the active substance within the desired life time of the air freshener product. In order to do this, it is necessary to increase the rate at which the volatile composition evaporates from the device. This can be achieved by increasing the surface area of the permeable wall or by heating the device, ideally to between 40-60°C.

Alternatively, or simultaneously, the rate of evaporation of the active composition can be increased by increasing significantly the amount of volatile non-polar solvent present in the composition, typically to a concentration greater than 50% by weight of composition. It has been found however that compositions comprising such high levels of non-polar solvents present problems during prolonged storage prior to activation. For example, if the permeable wall is of the laminated membrane type such as described in WO 98/23304 or US 4,145,001 for example, premature de-lamination may occur. The present invention provides a new active composition which brings precisely a solution to this problem and has improved diffusion properties when used in an air freshener of the type described here-above comprising a diffusion membrane or element impervious to the liquid active composition but permeable to its vapours.

Disclosure of the Invention

The invention provides a liquid non-aqueous air freshener composition comprising : a) at least 20% by weight of a polar solvent ; b) at least 10% by weight of a non-polar solvent ; and c) an active substance.

We have surprisingly discovered that such a composition can be used in larger quantities than prior known volatile active compositions in permeable membrane air freshener devices and has the appropriate evaporation characteristics, without however causing any damage to membrane laminates during storage or use of the devices.

This is an unexpected result since it is well-known in the art that, in order to obviate the de-lamination problems mentioned above, it is not possible to simply replace non-polar solvents with polar solvents. It is known that polar solvents by themselves do not easily pass through the permeable membrane walls of the type used in air fresheners, and therefore do not provide the adequate evaporation characteristics. This is clearly demonstrated by Figure 1, which shows the evaporation profile of a polar solvent (propylene glycol n-butyl ether) compared to that of a non-polar solvent (Cπ to Cj isoparaffm) of similar vapour pressure, from a membrane air freshener device comprising a permeable membrane of the type described in WO 98/23304. It is clearly apparent from this figure that the evaporation of propylene glycol n-butyl ether with time is very poor compared to that of isoparaffm, in spite of the fact that these two solvents have similar vapour pressures. However, we have now surprisingly found that, when used in combination with a suitable non-polar solvent, in the relative proportions above-mentioned, the polar solvent is able to diffuse through the membrane wall. This surprising synergistic effect will become clearly apparent from the examples presented further on, and three to fourfold increases in the mass of a polar solvent evaporated were observed upon the combined use of the latter with the adequate non-polar solvents current in prior known devices.

It has been found that by using a mixture of a polar solvent and a non-polar solvent, the evaporation characteristics of the composition can be controlled, by altering the relative proportions of the solvents and by an appropriate choice of the solvents. The amount of non-polar solvent remains limited, such that the membrane wall is not damaged during storage and use.

The polar solvent may be selected from a wide range of solvents such as glycol ethers and glycol esters. Desirably, the glycol ether is a (C alkyl) glycol (C_1-4 alkyl) ether, a di (C alkyl) glycol (C alkyl) ether, (C_M alkyl) glycol di (C_M alkyl) ether or di (CM alkyl) glycol di (CM alkyl) ether.

For example the polar solvent may be ethylene glycol mono propyl ether (e.g. "propyl cellosolve" ; origin : Union Carbide), ethylene glycol mono n-butyl ether (e.g. "Dowanol EB" ; origin : Dow Chemical Company), diethylene glycol mono methyl ether (e.g. "methyl carbitol" ; origin : Union Carbide), diethylene glycol mono ethyl ether (e.g. "Dowanol DE" ; origin : Dow Chemical Company), diethylene glycol mono propyl ether (e.g. "propyl carbitol" ; origin : Union Carbide), diethylene glycol mono n-butyl ether (e.g. "Dowanol DB" ; origin : Dow Chemical Company), propylene glycol mono methyl ether (e.g. "Dowanol PM" ; origin : Dow Chemical Company), propylene glycol mono propyl ether (e.g. "Dowanol PnP" ; origin : Dow Chemical Company), propylene glycol mono n-butyl ether (e.g. "Dowanol PnB" ; origin : Dow Chemical Company), dipropylene glycol mono methyl ether (e.g. "Dowanol DPM" ; origin : Dow Chemical Company), dipropylene glycol mono propyl ether (e.g. "Dowanol DPnP" ; origin : Dow Chemical Company), or dipropylene glycol dimethyl ether (e.g. "Proglyde DMM" ; origin : Dow Chemical Company). A suitable glycol ester is propylene glycol diacetate (e.g. "Dowanol PGDA" ; origin : Dow Chemical Company).

A single polar solvent, or a mixture of two or more polar solvents, may be used. The non-polar solvent may also be selected from a wide range of such solvents. In particular, this non-polar solvent can be selected amongst the prior known substances which act as diffusion agents of the active compositions traditionally used in these membrane air fresheners and which are described for example in in GB 2 066 665, EP 141 266 or US 5,711,955. The contents of these documents and their teachings with regard to the substances which can be used as diffusion agents acting as the non-polar solvent in the composition of the invention, are hereby included by reference.

According to preferred embodiments of the invention, there will be used as the non-polar solvent, linear or branched chain hydrocarbons. Preferred hydrocarbons include linear or branched chain alkanes or alkenes such as Cio-is alkanes or alkenes. A single non-polar solvent, or a mixture of two or more non-polar solvents, may be used. A mixture of hydrocarbons is often used since it is not necessary to use a single hydrocarbon and separation of different hydrocarbons is costly.

The composition comprises at least 20% w/w of the polar solvent and at least 10% of the non-polar solvent, preferably from 20 to 40% w/w of the polar solvent and from 10 to 30% w/w of the non-polar solvent.

The weight ratio of polar solvent to non-polar solvent is preferably from 1 :3 to 3:1, preferably from 1:1 to 3:1. The skilled person in the art is well able to adjust the amount of each solvent component and their weight ratio without undue effort to provide a composition with appropriate characteristics and able to achieve the aim of the invention.

The composition of the invention also comprises an active substance, typically selected selected from the group consisting of a perfuming substance, a substance having insect repellent, insect attractant or insecticidal activity and a substance having antimicrobial activity

According to a preferred embodiment, the composition of the invention shall comprise a fragrance as the active substance. Air freshener fragrances suitable for use in permeable membrane air fresheners are well known to those skilled in the art. These are typically one or more ingredients capable of developing an odour and thus capable of perfuming the ambient air or closed spaces in which the air freshener will be used. The nature and variety of such perfuming ingredients does not require a more detailed description here, which moreover, could not be exhaustive, and the person skilled in the art is well able to select these ingredients as a function of the desired perfuming and/or freshening effect. These perfuming ingredients belong to chemical classes as varied as alcohols, ketones, aldehydes, ethers, esters, acetates, nitriles, lactones, terpene hydrocarbons, sulfur- nitrogen- and oxygen-containing heterocyclic, polycyclic and macrocyclic compounds, as well essential oils of natural or synthetic origin. A large number of such ingredients is moreover disclosed in reference textbooks such as the book of S. Arctander, Perfume and Flavor Chemicals, 1969, Montclair, New Jersey, USA, or its more recent versions, or in other works of similar nature.

The fragrance composition may also contain non-odorous polar or non-polar solvents. Any such solvent in the fragrance composition is to be taken into account when calculating the level of such solvents present in the final liquid non-aqueous composition according to the invention.

The fragrance is desirably present in an amount of from 40 to 70% by weight, preferably of 50 to 60% by weight, relative to the total weight of the composition.

The composition may also comprise other components conventionally used in the art such as thickeners or dyes.

The liquid non-aqueous air freshener compositions of the invention are particularly suitable for use in air freshener articles or devices comprising diffusion membranes or elements impervious to the liquid composition but permeable to the vapours of the same, and the invention also relates to such articles and devices. The nature or form of these devices can be any and there is not restriction in the type, size, colour, material or shape of such air fresheners comprising the compositions of the invention. The amount of composition which can be contained in the device is not limited and is only dependent on the size of the air freshener article or device, more precisely on the size of the chamber or reservoirs of the latter intended to contain the active composition. However, since the composition evaporates at a higher rate than conventional compositions, whilst being compatible with the membrane wall, larger amounts of non-aqueous composition of the invention can be used for the same size of device, when compared to the prior known air freshener compositions. For example, from 5 to 20 g can typically be used, more preferably about 10 g of composition, for devices having reservoirs or chambers of an average volume. The nature of the diffusion membrane in the air freshener is also immaterial for the working of the invention. This membrane can take any of the forms, compositions or arrangements currently known in the art and described at length in the prior art of common knowledge to the skilled person.

The air freshener articles and devices containing the compositions of the invention can be formed of any of the materials and according to any of the technologies known in the prior art, in particular that cited in detail above. The contents of all the prior art documents cited above in connection with prior known air freshener devices comprising diffusion membranes are hereby included by reference. In particular, the contents of GB 2 066 665, US 4,534,5098, EP 141 266, US 4,534,509, US 4,634,614, WO 98/23304, US 4,145,001, EP-B1-662 845 and US 5,518,790 and US 5,711,955 and their teachings are hereby included in the present disclosure.

Brief Description of Drawings

FIG. 1 shows the relative rate of evaporation of two solvents, one polar (propylene glycol n-butyl ether) and one non-polar (isoparaffm), measured as weight loss from a membrane air freshener of the type described in WO 98/23304.

FIG. 2 shows the comparative evaporation characteristics of solvents, one of which consists of a mixture of compounds suitable for use in a liquid non-aqueous composition according to the invention, from a membrane air-freshener of the type described in WO 98/23304. FIG. 3 shows another comparative example of the evaporation characteristics of solvents, one of which consists of a mixture of compounds suitable for use in a liquid non-aqueous composition according to the invention, from a membrane air-freshener of the type described in WO 98/23304.

FIG. 4 shows the rate of evaporation, from a membrane air freshener of the type described in US 4,634,614, of a solvent mixture for use in a liquid non-aqueous air freshener composition according to the invention and as a function of the amount of polar solvent, in this case propylene glycol n-butyl ether, present in the mixture.

FIG. 5 shows the rate of evaporation, from a membrane air freshener of the type described in US 4,634,614, of a solvent mixture for use in a liquid non-aqueous air freshener composition according to the invention and as a function of the amount of polar solvent, in this case propylene glycol monomethyl ether, present in the mixture.

Embodiments of the Invention

Example 1

This example demonstrates the improved evaporation characteristics of a mixture of a polar solvent and a non-polar solvent, which is used in a liquid non-aqueous air freshener composition of the invention, from a permeable membrane type air freshener of the type described in WO 98/23304.

Table 1 herebelow summarises the data used to draft Figure 2.

TABLE 1 - Evaporation of a solvent mixture comprising 50% w/w dipropylene glycol dimethyl ether and 50%) w/w of C_11-13 isoparaffm from a permeable membrane air freshener of the type described in WO 98/23304, with a surface area of 23cm² and a solvent fill mass of 1 Og.

With reference to Table 1 and Figure 2, it can be clearly seen that a solvent mixture having equal amounts of Cn to C₁₃ isoparaffm and dipropylene glycol dimethyl ether (the polar solvent) has a consistently higher evaporation rate with time than either of these solvents when used on their own in the same air freshener and under the same conditions, i.e. the same surface area of the reservoir or chamber of the air freshener device containing the solvent mixture and the same mass charge of solvent in said reservoir.

Moreover, it is also apparent from Figure 2 that the combined use of the polar and non- polar solvent according to the invention provides a synergistic diffusion effect, since the evaporation rate of this solvent mixture is consistently and significantly enhanced with regard to the expected behaviour if the evaporation of this solvent mixture had simply been the average of the evaporation rates observed for each of the two pure components (average line)

Example 2

This example demonstrates the improved evaporation characteristics of a mixture of a polar solvent and a non-polar solvent, which is used in a liquid non-aqueous air freshener composition of the invention, from a permeable membrane type air freshener of the type described in WO 98/23304. Table 2 herebelow summarises the data used to draft Figure 3.

TABLE 2 - Evaporation of a solvent mixture comprising 50% w/w dipropylene glycol dimethyl ether and 50% w/w of Cj_2-ι isoparaffm from a permeable membrane air freshener of the type described in WO 98/23304, with a surface area of 23 cm² and a solvent fill mass of 10 g.

With reference to Table 2 and Figure 3, it can be clearly seen that a solvent mixture having equal amounts of C₁ to isoparaffm and dipropylene glycol dimethyl ether (the polar solvent) has a consistently higher evaporation rate with time than either of these solvents when used on their own in the same air freshener and under the same conditions, i.e. the same surface area of the reservoir or chamber of the air freshener device containing the solvent mixture and the same mass charge of solvent in said reservoir.

Moreover, it is also apparent from Figure 3 that the combined use of the polar and non- polar solvent according to the invention provides a synergistic diffusion effect, since the evaporation rate of this solvent mixture is consistently and significantly enhanced with regard to the expected behaviour if the evaporation of this solvent mixture had simply been the average of the evaporation rates observed for each of the two pure components (average line). Example 3

This example illustrates the evaporation characteristics of mixture of a polar solvent and a non-polar solvent, used in a liquid non-aqueous air freshener composition of the invention, from a permeable membrane type air freshener of the type described in WO 98/23304.

Table 3 herebelow summarises the data measured reflecting the evaporation of a mixture having equal weight amounts of the two solvent components from the reservoir, as well as the evaporation of the glycol ether (the polar solvent) component of the mixture.

TABLE 3 - Evaporation of a solvent mixture comprising 50%) w/w propylene glycol n- butyl ether and 50%) w/w of C_12-ι₄ isoparaffm from a permeable membrane air freshener of the type described in WO 98/23304, with a surface area of 23 cm² and a solvent fill mass of 10 g.

* Concentration of glycol ether remaining in the compartment determined by GC analysis.

When the non polar Cj₂ - Cι isoparaffm is replaced by Cπ - Cj₃ isoparaffm, still using propylene glycol n-butyl ether as the polar component in the solvent mixture, the results obtained are summarised in table 4 herebelow. TABLE 4 - Evaporation of a solvent mixture comprising 50% w/w propylene glycol n- butyl ether and 50% w/w of Cπ-₁₃ isoparaffm from a permeable membrane air freshener of the type described in WO 98/23304, with a surface area of 23 cm² and a solvent fill mass of 10 g.

These results show that the glycol ether evaporates smoothly, and at least at the same evaporation rate as that of the solvent mixture, through the permeable membrane. When compared to what was observed when this glycol ether was used on its own (see Figure 1 and Table 5 herebelow) as the only solvent in the permeable membrane air freshener, a clear 3 to 4 fold increase in the mass of polar solvent evaporating can be observed.

TABLE 5 - Data for Figure 1

Example 4

This example illustrates the effect of the concentration of glycol ether in the solvent mixture used in the air freshener compositions of the invention.

The experimental rate of evaporation of a solvent mixture containing propylene glycol n- butyl ether and C₁₂ - Cι₄ isoparaffm, over a period of 28 days, from a membrane air freshener of the type described in US 4,634,614, and as a function of the weight of glycol ether in the mixture, was compared to the evaporation behaviour of the same mixture that would have been predicted on the assumption that the solvent mixture evaporated at an evaporation rate which was simply an average of the individual evaporation rates of the two pure individual components of the mixture.

Table 6 and Figure 4 summarise the results obtained, represented as the average evaporation rate in the first 7 days of use of the air freshener device, as a function of weight content (%) of the solvent mixture in propylene glycol n-butyl ether. TABLE 6

Example 5

The experimental rate of evaporation of a solvent mixture containing propylene glycol monomethyl ether and Cπ - Cι isoparaffm, over a period of 28 days, from a membrane air freshener of the type described in US 4,634,614, and as a function of the weight of glycol ether in the mixture, was compared to the evaporation behaviour of the same mixture that would have been predicted on the assumption that the solvent mixture evaporated at an evaporation rate which was simply an average of the individual evaporation rates of the two pure individual components of the mixture.

Table 7 and Figure 5 summarise the results obtained, represented as the average evaporation rate in the first 7 days of use of the air freshener device, as a function of weight content (%) of the solvent mixture in propylene glycol monomethyl ether. TABLE 7

This example, together with the preceding ones, shows that the solvent mixtures used in the liquid non-aqueous air freshener compositions of the invention have an evaporation rate which is significantly higher than would have been expected as a result of mixing a polar and non polar solvent. In fact, the mass of solvent mixture evaporated from the membrane air fresheners of the invention, containing the above-mentioned compositions, is significantly and consistently higher than that of either of the individual solvent components, or indeed of their averaged sum, and this under identical evaporation conditions.

Claims

1. A liquid non-aqueous air-freshener composition comprising : a) at least 20% by weight of a polar solvent ; b) at least 10%) by weight of a non-polar solvent ; and c) an active substance.

2. A liquid non-aqueous air-freshener composition according to claim 1, wherein the polar solvent is present in an amount of 20 to 40%) by weight.

3. A liquid non-aqueous air-freshener composition according to claim 1 or 2, wherein the non-polar solvent is present in an amount of 10 to 30% by weight.

4. A liquid non-aqueous air-freshener composition according to any one of claims 1 to 3, wherein the active substance is selected from the group consisting of a perfuming substance, a substance having insect repellent, insect attractant or insecticidal activity and a substance having antimicrobial activity.

5. A liquid non-aqueous air-freshener composition according to claim 4, wherein the active substance is a fragrance.

6. A liquid non-aqueous air-freshener composition according to claim 5, wherein the fragrance is present in an amount of at least 40% by weight, preferably in an amount of 50 to 60% by weight.

7. A liquid non-aqueous air-freshener composition according to claim 1 or 4, wherein the weight ratio of polar solvent to non-polar solvent is from 1 :3 to 3:1, preferably 1.1 to 3:1.

A liquid non-aqueous air-freshener composition according to any one of the preceding claims, wherein the polar solvent is selected from the group consisting of glycol ethers, glycol esters and mixtures thereof.

9. A liquid non-aqueous air-freshener composition according to claim 8, wherein the polar solvent is selected from the group consisting of ethylene glycol monomethyl or monoethyl ether ; diethylene glycol monobutyl ether, propylene glycol monomethyl or monoethyl ether ; propylene glycol n-butyl ether, dipropylene glycol monomethyl or monoethyl ether ; dipropylene glycol dimethyl ether or diethyl ether ; propylene glycol diacetate ; and mixtures thereof.

10. A liquid non-aqueous air-freshener composition according to any one of claims 1 to 9, wherein the non-polar solvent is a linear or branched chain hydrocarbon, preferably an alkane or alkene having 10 to 18 carbon atoms in the chain.

11. An air freshener article or device comprising a liquid non-aqueous air-freshener composition according to any one of claims 1 to 10.