PROCESS OF PREPARING GEL

Provided are a process of producing a gel adapted to hold and release into an atmosphere a volatile liquid, and a gel thus produced.

Gels, that is, solid or semi-solid substances having a three-dimensional polymer network and produced by cross-linking reactions, have been known for some time and have been widely used in a number of applications. One such application is the storage and releasing into an atmosphere of a volatile liquid. The liquid is typically fragrance, but it can be any other volatile liquid whose presence in an atmosphere is desired, for example, deodorants, insecticides and insect repellents, fungicides, disinfectants and antimicrobial agents. Because such gels can be attractively coloured, and because their shrinkage gives a clear end-of-life indication, gel-based air-fresheners containing fragrance have proved very popular and successful.

In production, the materials that react to form the gel (hereinafter referred to as "the gel components", usually a functionalized polymer and a cross-linking agent, are mixed and the resultant mixture is poured into moulds and allowed to set. In order to ensure a viscosity that allows easy mixing, it is a common practice to mix into one or both of the gel components a proportion of the volatile liquid. A problem frequently encountered when this is done is reaction between the components of the volatile liquid and the cross-linking groups of one or both of the gel components. This can slow down cross-linking, resulting in longer reaction times, or, in the case of production on a moving production line, the potential gels arriving at the end of the line still in a partially liquid state, making handling and packing difficult or impossible. This is especially the case with fragrances, which are often complex mixtures of different molecules, some of which are capable of reaction with some type of gel component; some indeed are highly reactive. Aldehydes and ketones are typical examples of such molecules and they can react with polyamines, one of the more common gel components. Another example is polyisocyanate, used in the manufacture of polyurethane, which can react with fragrance materials such as alcohols.

In the particular case of fragrances, it has been proposed to mix into the individual gel components not the whole fragrance but only those fragrance components that do not react with the particular gel component. While this is useful up to a point, it does not solve the problem completely. For example, there are common fragrance components that react with both gel components, meaning that a compromise should be sought to minimise reaction in such cases. Another problem is that, if taken to its extreme, it can result in most of the fragrance components going into one gel component. This can bring about handling problems; many gel components are inherently quite viscous, and the presence of fluid fragrance components therein can allow their easier handling. Remove the fragrance components and it may be necessary to dilute the affected gel component with solvent, something that may not be desirable or even possible, as it may affect the achievement of the desired gel structure.

It has now been found that it is possible to overcome these problems substantially or even completely and to produce volatile liquid-containing gels by a process that is easy to operate. There is therefore provided a process of producing a gel containing a volatile liquid to be released into an atmosphere, comprising the blending of a polymeric component and a cross- linking agent therefor ( hereinafter referred to as "the gel components") and a volatile liquid, all or part of which liquid is inherently reactive with at least one of the gel components (hereinafter referred to as "the reactive component", any liquid that does not form part of the reactive component being considered "non-reactive component"), at least the major portion of the reactive component being incorporated into the gel in the form of a solution in an organic solvent, any minor portion of reactive component, plus any non-reactive component, of the volatile liquid being premixed into at least one of the gel components, such that the minor reactive component is premixed into that gel component with which it reacts less.

The gel components for use in this process and composition may be any such components known to the art and useful for forming a gelled structure suitable for loading with volatile liquid and then releasing it into the atmosphere. As hereinabove mentioned, the gel components are usually a functionalized polymeric component and a cross-linking component, the gel components comprising complementary reactive groups that react to form a three-dimensional gel structure.

A functionalized polymer is one that comprises a plurality of functional groups capable of participating in a cross-linking reaction. Such polymers are well known to the art and readily available commercially. Typical examples of suitable functionalized polymers include maleinised polybutadiene and polyisoprene. Maleinised polybutadienes having a molecular weight of from 5000-20,000 are commercially available, e.g. those sold under the trade name "Lithene' by Revertex Limited. Such polymers containing acid or anhydride or acid chloride groups can be cross-linked with amines or alcohols. Cross-linking agents include, but are not limited to, compounds that contain amine, alcohol or thio functional groups.

Suitable cross-linking agents can also contain a combination of one or more thio, amine and alcohol functional groups, one particular example being polyamines. Suitable polyamine cross-linking agents include diamines, including polyoxypropylenediamine (such as Jeffamine™ D-400, available from Huntsman Corp., Salt Lake City, Utah) and triethyleneglycoldiamine (such as Jeffamine XTJ-504), and triamines, such as polyoxypropylenetriamine (such as Jeffamine T-403 and XTJ-509).

Another suitable combination of functionalized polymer and cross-linking agent is one in which the functionalized polymer is a modified polyamide, cross-linkable by reaction with a polyisocyanate. A typical polymer of this type is Sylvaclear™ of Arizona Chemicals and a typical polyisocyanate is one of the Desmodur™ range of Bayer Material Science.

The volatile liquid may be any suitable volatile liquid whose presence in the atmosphere is desired. One volatile liquid of particular interest is fragrance, as used in air fresheners. This is a particularly complex problem, as fragrances are usually combinations of individual perfumery ingredients (often a great many of these).

The remainder of this description will be mainly concerned with the particular embodiment of fragrances, but the principles involved are generally applicable to any volatile liquid and the skilled person in the art will have no difficulty moving from one volatile liquid to another, based on the teachings of this specification. Examples of non-fragrance volatile liquids include, but are not restricted to:

- insect repellents, such as pyrethroid insecticides, citronella, citronellol, nerol, geraniol, and N, N-Diethyl-m-toluamide (DEET);

- antimicrobials such as oxygenated monoterpenes cineole, fenchone and menthol, as well as several aromatic aldehydes and alcohols, including thymol, hydrocinnamaldehyde, cuminaldehyde, salicylaldehyde, cinnamaldehyde, and benzaldehyde. 5

Perfumes and perfumery ingredients useful in the present compositions and process comprise a wide variety of natural and synthetic chemical ingredients. One of the features of this process is that an unusually wide variety of such materials may be used. Typical examples include, but are not limited to, synthetic materials such as hydrocarbons, alcohols, 10 aldehydes, ketones, ethers, acids, esters, acetals, ketals, nitriles, oxides, etc., including saturated and unsaturated compounds, aliphatic, carbocyclic, and heterocyclic compounds. The molecular weights range from around 90 to 320. Such fragrance materials are mentioned, for example, in S. Arctander, Perfume and Flavour Chemicals (Montclair, NJ., 1969), in S. Arctander, perfume and Flavour Materials of Natural Origin (Elizabeth, NJ., 15 1960) and in "Flavour and Fragrance Materials-1991", Allured Publishing Co. Wheaton, 111. USA.. Also included are various natural extracts and essences which can comprise complex mixtures of ingredients, such as orange oil, lemon oil, rose extract, lavender, musk, patchouli, balsamic essence, sandalwood oil, pine oil, cedar, and the like.

20 Many fragrances contain substantial quantities of materials that are to some degree reactive with many gel components. Such components comprise, for the purposes of this specification the "reactive components", and they include fragrant aldehydes and ketones. Those materials that are not reactive or are only slightly reactive to one or both of the gel components may be added to the gel components. While it is generally clear to the skilled

25 person what is reactive or non-reactive in any given fragrance/gel formulation, in cases of doubt, the borderline between reactive and non-reactive for the purposes of this process and compositions may be determined by a simple test. A non-reactive organic solvent is added to the functionalized polymer phase and the cross-linker phase, respectively in such proportion that the polymer and cross-linking agent are individually of a viscosity that permits ready

30 mixing and that allows the components to be pumped and mixed by conventional techniques. This proportion will differ, depending on the natures of the solvent and the gel system, but the skilled person can readily determine a suitable proportion in every case. By way of example only, in a system in which the gel components are a maleinised polybutadiene

polyamine and a polyamine (such as respectively the Lithene and Jeffamine materials hereinabove described) and the solvent is an organic liquid such as isopropyl myristate, the proportion of solvent will be typically from about 35% to about 60% in the case of the Lithene and from about 8% to about 20% of the Jeffamine (both by weight of the gel component + solvent). The phases are stirred for 30 minutes. A gel is prepared by mixing the two phases. The set time is measured, set time being the time from mixing to the point when the mixture ceases to be flowable, by which is meant that the viscosity is above 5000cps and more, in certain embodiments above 10,000cps. (Brookfield Viscometer LV with LV4 spindle at 30 rpm). This is repeated, replacing the solvent with a mixture of 90% non-reactive solvent and 10% of a fragrance component whose reactivity is to be determined. The gel set time is measured. If the fragrance component causes an extension of the gelling time of more than 40%, in comparison with the gelling time without the perfume material, that perfume component is considered reactive. A perfume component that gives a gelling time extension of 30% maximum is non-reactive for the purposes of this process and compositions.

The major proportion of reactive components is incorporated into an organic solvent separate from either of the gel components. In a particular embodiment, all of the reactive components are incorporated into the solvent. However, a certain flexibility is possible here. It is well known that many of the gel components are quite viscous and hard to mix. This can be eased by incorporating thereinto the non-reactive part of the fragrance formulation; this imparts more fluidity to the gel component. It is also possible to add to at least one gel component some reactive component, provided the reactive component is added to that gel component with which it does not react. Thus, if a particular perfume material reacts with the cross-linking agent, it may be incorporated into the functionalized polymer, and the reverse if it reacts with the polymer. This is not always possible to realise in practice, because some requirements, for example, that of maintaining a flowable mixture, may dictate that a reactive component be added to a gel component with which it is reactive. While not desirable (and to be avoided whenever possible), very small amounts of reactive material can exceptionally be tolerated.

In a further particular embodiment, the non-reactive part of the fragrance is added to both gel components, and in a particular embodiment of this, the composition of the non-reactive part

added to the individual gel components is identical. The quantity thereof need not be identical, but can be allocated depending on the desired viscosity of the individual components.

Organic solvent useful for the phase containing the fragrance may be selected from many classes of volatile compounds that are known to the art, for example, ethers; straight or branched chain alcohols and diols; volatile silicones; dipropylene glycol, triethyl citrate, ethanol, isopropanol, diethyleneglycol monoethyl ether, dipropylene glycol, diethyl phthalate, triethyl citrate, isopropyl myristate, etc., hydrocarbon solvents such as Isopar™ series by ExxonMobile Chemical Company or the Dowanol series by Dow Chemicals, such as Dowanol TPM, TPnP, DPnB, DPnP, TPnB, PPh, DPM, DPMA, DB, and others.

These solvents in general may have a molecular weight between 20 and 400. They are selected specifically for each volatile liquid to achieve the performance and safety, (e.g. VOC and flash point) specified.

In a particular embodiment, the solvent may additionally comprise surfactant. Suitable surfactants include non-ionic surfactants, zwitterionic surfactants, cationic surfactants, anionic surfactants and combinations thereof. Particular examples of surfactants are non- ionic and anionic surfactants. Examples of non-ionic surfactants include ethoxylated nonylphenol containing 4 moles of ethylene oxide (such as Surfonic™ N40, available from Huntsman Corp., Salt Lake City, Utah) and ethoxylated alcohols containing 3 moles of ethylene oxide (such as Surfonic L243 and Tergitol™15-S-3, available from Dow Chemical Co., Midland, Mich.). Examples of anionic surfactants are ethoxylated alkyl sulfates (such as Steol™ CS-460, available from Stephan Company, Northfield, 111.). Surfactant may be present to the extent of from about 0.01 to about 25 wt. %, in some embodiments from about 0.5 to about 10 wt. % of the final gel.

In addition to the incorporation of surfactant into the solvent, surfactants that are themselves liquid (either by being inherently liquid or by being normally available in a liquid form by being dissolved or dispersed in a liquid) can act as solvents, without the need to add solvents of the types hereinabove described. An example of this is the abovementioned Steol CS-460,

an aqueous dispersion. For the purposes of this specification, such liquid surfactants are considered to fall within the scope of the term "solvent".

In addition to the abovementioned components, the gel compositions prepared by the subject process may also comprise other known ingredients, present in art-recognised quantities for the attainment of specific purposes. These include colorants, antioxidants, UV screens, denaturants, preservatives, catalysts and the like.

The subject process may be performed by simply mixing the three components of the gel composition (polymer, cross-linking agent and reactive component solvent phase), adding them to moulds and allowing them to set. There are several ways of accomplishing this. For example, should the reactive components of a fragrance react only with one of the gel components, that gel component can be completely fragrance-free, the fragrance being contained entirely in the other gel component and the solution of reactive components. The fragrance-containing gel component can then be mixed with the solution and the other

(fragrance-free) gel component added. In the most typical case, the cross-linking agent is the gel component more likely to react, and so it is fragrance-free.

It should be noted that, while it is sometimes possible to use gel components in a solvent- free state, addition of some solvent to one of the phases is generally necessary to add solvent to ensure good flowability and mixing. In the case of a maleinised polybutadiene/polyamine gel system (such as the Lithene /Jeffamine system mentioned hereinabove), the polybutadiene will typically be used with a solvent addition of from about 35% to about 60% by weight, (in some embodiments from about 40% to about 60% by weight) of polybutadiene + solvent/solution and an addition of from about 8% to about 20% (in some embodiments from about 10% to about 20% by weight for the polyamine.

In a further embodiment, the two gel components are mixed together prior to adding the reactive component solution. In this embodiment, the addition of the solution should be undertaken relatively quickly after the gel component mixing. How quick this needs to be before the gelling reaction proceeds too far to ensure efficient mixing will depend on the particular system and the skilled person can readily determine a suitable timing, but as a general rule, the time elapsed between mixing and the addition of the reactive component

solvent phase should be no longer than 5 minutes, in some embodiments no longer than 3 minutes. The optimum way to do this is on a continuous production plant in which the polymer phase and the cross-linking phase are brought together in an in-line mixer which then feeds into another in-line mixer to which the solution is added in the correct proportion. The resultant mixture is dosed into moulds and allowed to set.

These methods and others not mentioned but within the skill of the art are easily achieved by means of conventional equipment. The subject process is not only easy and efficient in its production of gels, but it also allows the use of an unusually wide variety of volatile liquids - this is especially true of fragrances.

There now follows a series of non-limiting examples that serve to illustrate the subject process and compositions.

Example 1.

Determination of Reactivity

Premix A was prepared by mixing 18.7 g of Lithene™ N4-9000-10MA (from Synthomer) and 73.54 g of the inert solvent in a 120 ml glass beaker using a magnetic stirrer until the Lithene had completely dissolved.

Premix B was prepared by mixing 1.93 g of Jeffamine™ D-400 (from Huntsman), 0.83 g of Jeffamine XTJ-504 and 17.54 g of the inert solvent in a 50 ml glass vial.

Premix A and premix B, respectively were stirred with a magnetic stirrer for half an hour. The end of this stirring was time t=0. After 30 minutes, 14.94 g of the Lithene/solvent mixture was transferred to a 100 ml glass beaker, and continually mixed with a magnetic stirrer. 4.06 g of the perfume/cross-linking composition was then added and 1 g of Steol™ CS-460 under constant stirring. The setting time of the gel thus produced was then measured.

This process was repeated using a blend of 90% (wt) solvent and 10% of the fragrance under test, after a period of 30 minutes had elapsed. The gel setting times recorded are shown in Table 1.

Table 1. Gelling Time

Example 2

The following fragrance was created (quantities are by weight):

Table 2 Fragrance Composition

Dihydromyrcenol 10

Isobornyl acetate 15 p-t-butyl cyclohexyl acetate 10

Orange terpene 15

Allyl caproate 5

Verdyl acetate 5

Citral 2

Aldehyde C8 2

Citronellal 1

Hexyl acetate 5

Citronellyl Nitrile 5

Teφinyl acetate 5

Cyclal C 5

B Ionone 5

Isopropyl myristate 10

A Premix A was prepared by mixing 18.7 g of Lithene™ N4-9000-10MA polymer and 73.54 g of the entire fragrance in a 120 ml glass beaker using a magnetic stirrer until the polymer had completely dissolved.

A Premix B was prepared by mixing 1.93 g of Jeffamine™ D-400 (from Huntsman) polyamine, 0.83 g of Jeffamine XTJ-504 polyamine and 17.54 g of the entire fragrance in a 50 ml glass vial. The time was then recorded (t=0).

After 10 minutes had elapsed 14.94 g of the polymer/perfume mixture was transferred to a 100 ml glass beaker, and continually mixed with a magnetic stirrer. 4.06 g of the perfume/cross-linking composition was then added and 1 g of Steol™ CS-460 surfactant under constant stirring. The setting time of the gel thus produced was then measured. This process was repeated when after, 4 hours and seven hours, respectively had elapsed. The gel setting times recorded are shown in Table3.

Table 3. Gelling Time

Example 3

The fragrance composition of Example 2 was prepared as two separate compositions, in which all of the highly reactive components as defined by the method in Example 1 were in Part B. These are shown in Table 4.

Table 4. Fragrance Compositions for Parts A/B and C.

Fragrance 1 Fragrance 2

Dihydromyrcenol 5 -

Isobornyl acetate 7.5 - p-t-butyl cyclohexyl acetate 5 -

Orange terpene 2.5 12.5

AHyI caproate 2.5 -

Verdyl acetate 2.5 -

Citral - 2

Aldehyde C8 - 2

Citronellal - 1

Hexyl acetate 2.5 -

Citronellyl Nitrile - 2.5

Terpinyl acetate 2.5 -

Cyclal C - 5

B Ionone _ 5

Isopropyl myristate 5

Premix A was prepared by mixing 14.55 g of Lithene N4-B-10MA polymer and 52.46 g of Fragrance 1 in a closed 120 ml glass jar using a magnetic stirrer until the polymer had completely dissolved.

Premix B was prepared by mixing 1.93 g of Jeffamine D-400 polyamide, 0.83 g of Jeffamine XTJ-504 polyamide and 17.54 of Fragrance 1 in a 50 ml glass vial. The time was then recorded (t=0).

Premix C was prepared by mixing 5 g of solvent (Steol CS-460) and 30 g of Fragrance 2 in a 50 ml glass vial.

After 10 minutes had elapsed 17.492 g of the polymer/perfume mixture was transferred to a 100 ml glass beaker, and continually mixed with a magnetic stirrer. 4.06 g of the perfume/cross-linking agent was then added and 7 g of solvent/surfactant/perfume mix under constant stirring. The setting time of the gel thus produced was then measured.

This process was repeated after holding batches for 4 hours and seven hours, respectively. The gel setting times recorded are shown in Table 5.

Table 5.

Example 3 Examples of use with different fragrances.

The olfactive themes shown in Table 6 were created by and the resulting fragrance compositions then divided into two parts as follows:

Part 1 contains fragrance materials that were not reactive to either of the gel components (the gel components being those described in Example 1).

Part 2 Contains components that are reactive to the gel components.

Part 1 was blended into the individual gel components in the proportions given in Example 2, to form Pre-mix A and Pre-mix B, respectively. Part 2 of the fragrance was mixed with solvent Steol CS-460 to form Pre-mix C.

The gelled fragrance was prepared by mixing Phase A and C together and then adding Phase B with mixing. The gel set time was measured, and the results are shown in Table 6.

The fragrances were compounded in one formulation and the gels made as given in Example 2. The gel set time was measured and the results are shown in Table 6.

Table 6 Gelling Set time using 3-Part Process of Different Olfactive themes

If the subject process is used then the set time of the fragrances is significantly reduced over a wide range of fragrance types.

Although the process and compositions have been described in detail through the above detailed description and the preceding examples, these examples are for the purpose of illustration only and it is understood that variations and modifications can be made by one skilled in the art without departing from the scope of the invention. It should be understood that the embodiments described above are not only in the alternative, but can be combined.