"Polymeric pro-fragrance"

The present invention relates to pro-fragrance compounds obtainable by the reaction of at least one fragrance molecule comprising at least one ketone and/or aldehyde functionality, and at least one specific diol compound, the production and use thereof, as well as cleaning, fabric treatment and cosmetic compositions comprising said pro-fragrance compounds.

To most consumers the smell of a cleaning, fabric treatment, cosmetic or related product as well as the smell of a substrate treated with such product is an important product feature. For instance, they often assess the performance of a laundry detergent composition not only by the visual appearance of the laundered fabric but also by the smell thereof. Thus, a laundry detergent composition, in addition to cleaning fabric, must also provide a pleasing fragrance that is delivered to the laundered fabric during the laundering process. The same is true with regard to other cleaning, fabric treatment or cosmetic products. Hence, usually fragrance molecules or perfumes are added to such products.

Aldehydes and ketones are important classes of fragrance molecules. However, the intrinsic high volatility of most fragrance molecules, especially aldehydes and ketones, causes rapid loss of scent. Furthermore, aldehyde molecules are generally susceptible to oxidation by air.

To overcome this problem, it has been suggested to use so-called pro-fragrances. Pro-fragrances are compounds comprising a fragrance molecule covalently linked to a carrier which releases the fragrance molecule under defined conditions. Such pro-fragrances may be formulated by the reaction of a fragrance molecule and a compound comprising reactive groups like primary hydroxyl groups, primary amine groups and/or secondary amine groups. The most common derivatives of aldehydes and ketones, which may be used as pro-fragrances, are acetals. These acetals usually are acid labile and undergo hydrolysis, thereby releasing the original fragrance aldehyde or ketone. However, many of the known pro-fragrances are compounds of comparatively low molecular weight and hence comparatively high vapor pressure. To maintain a pleasing fragrance over a prolonged period of time it is necessary to provide pro-fragrances with reduced volatility.

WO 97/34986 A1 discloses acetal-type and ketal-type pro-fragrances having a molecular weight of at least about 350 and certain further specific characteristics. These pro-fragrances are still of comparatively low molecular weight and hence volatile. Moreover, they are rather hydrophobic. It is explicitly stated on page 2, lines 34-36 that this is important in order to enhance deposition onto surfaces in the wash solution and retention on the washed surface during rinsing.

Acetal-type pro-fragrances, which can be obtained by the reaction of an aldehyde and a hydrophilic alcohol, are known from WO 97/34578 A1. These pro-fragrances preferably have a molecular weight of at least about 170. Again, many of these compounds show a comparably high volatility.

Pro-fragrances of low volatility can be obtained by incorporation of the fragrance aldehyde or ketone into polymeric structures. US 3,818,107 discloses sustained flavor release compositions comprising a reaction product of a polymer backbone having pendant flavor moieties thereon. The flavor molecules are incorporated into the side chains of the main polymer. However, the polymer backbones, which will be released together with the flavor molecules upon hydrolysis of the pro- fragrance, are hydrophobic and hence the affinity to certain fabrics, in particular cotton, will be low. Moreover, these polymer backbones are not degradable which is disadvantageous from an environmental point of view.

Polymeric pro-fragrances, wherein the active ingredient is incorporated into the backbone of a copolymer, are disclosed in WO 99/16802 A1. The copolymer degrades upon release of the active ingredient, e.g. a fragrance molecule. However, the co-monomeric units used to polymerise the active ingredient are keto carboxylates, in particular glyoxylic units. These co-monomeric units have a strong specific smell that will alter the desired scent of the fragrance ingredient.

Therefore, there remains a need to provide pro-fragrances which provide a good perfume release from the treated substrate over a prolonged period of time, wherein the pro-fragrance is fully degradable and does not release any by-products which contaminate the scent of the fragrance molecule. Moreover, the pro-fragrances have to provide an initial good perfume performance immediately after application.

Surprisingly, it has been found that the above problems are overcome by pro-fragrances based on fragrance molecules comprising at least one ketone and/or aldehyde functionality, which are reacted with specific diols.

Hence, a first object of the invention is a pro-fragrance compound obtainable by the reaction of

- at least one fragrance molecule comprising at least one ketone and/or aldehyde functionality,

- at least one diol of formula (I) wherein

R ¹ is a linear or branched C ₂ -C ₂ o-alkyl, and

n is a number from 4 to 1000,

and, optionally, at least one diol of formula (II)

HO-R ² -OH (II)

wherein

R ² is a linear or branched C ₂ -C ₂ o-alkyl, optionally containing at least a functionality selected from ether, ester, amide, carbonate, carboxyl, carboxylic acid sodium salt, carboxylic acid amine salt, sulfone, sulfoxide, sulfonyl, sulfonic acid sodium salt, sulfonic acid amine salt, phosphonyl, phosphonic acid sodium salt, phosphonic acid amine salt, pyridinium, and ammonium groups.

Due to their polymeric nature pro-fragrance compounds of the invention have no or almost no vapor pressure which prevents their evaporation from products comprising them and from substrates treated with such pro-fragrance compounds. Moreover, the adhesion to certain substrates like textile fibers, in particular cotton, is good. This results in a good fragrance release from the treated substrate over a prolonged period of time. Moreover, they show an improved initial perfume performance immediately after application of the pro-fragrance to a substrate. Pro- fragrance compounds of the invention can be obtained very easily by reaction of the educts under well-known polycondensation conditions.

Pro-fragrance compounds according to the invention are based on diols of formula (I).

Preferred diols are diols of formula (I), wherein R ¹ is a linear or branched C ₂ -C ₁₀ -alkyl, preferably a linear or branched C ₂ -C ₅ -alkyl, particularly preferred a linear or branched C ₂ -C ₃ -alkyl. Examples of particularly preferred diols are poly(ethylene glycol)s and poly(propylene glycol)s of formula (Ia) and (Ib), respectively.

HC-(-CH ₂ -CH ₂ — O

(Ia) (Ib) n has the meaning defined with regard to formula (I) above.

In formula (I), (Ia) an (Ib) n is preferably a number from 4 to 100, particularly preferred from 4 to 20, and most particularly preferred from 4 to 10.

In a particular embodiment of the invention the pro-fragrances are based not only on at least one diol of formula (I) but on a combination of at least one diol of formula (I) and at least one diol of formula (II).

Preferred are diols of formula (II), wherein R ² is a linear or branched C ₂ -Ci ₀ -alkyl, preferably a linear or branched C ₂ -C ₅ -alkyl, particularly preferred a linear or branched C ₂ -C ₃ -alkyl.

Also preferred are diols of formula (II), wherein R ² contains at least one functionality selected from ether, ester, amide, carbonate, carboxyl, carboxylic acid sodium salt, carboxylic acid amine salt, sulfone, sulfoxide, sulfonyl, sulfonic acid sodium salt, sulfonic acid amine salt, phosphonyl, phosphonic acid sodium salt, phosphonic acid amine salt, pyridinium, and ammonium groups, preferably selected from carboxylic acid sodium salt, carboxylic acid amine salt, sulfonic acid sodium salt, sulfonic acid amine salt, phosphonic acid sodium salt, phosphonic acid amine salt, pyridinium, and ammonium groups, particularly preferred selected from ammonium groups.

Most preferred diols of formula (II) are ammonium compounds of formula (Ma)

wherein

R ³ is a linear or branched C _∑ -C _∑ o-alkyl, preferably a linear or branched C ₂ -C ₁₀ -alkyl, particularly preferred a linear or branched C ₂ -C ₅ -alkyl.

To obtain a pro-fragrance compound according to the invention the diol of formula (I) and, optionally, the diol of formula (M) is reacted with at least one fragrance molecule comprising at least one ketone and/or aldehyde functionality. Of course it is also possible to use a mixture of two or more diols of formula (I) or (M), provided that at least one diol is a diol of formula (I). Likewise, it is possible to use several different fragrance molecules.

Preferred pro-fragrance compounds according to the invention are obtained, if the molar ratio of fragrance molecules to diols of formula (I) and (M) is from 1 : 0.9 to 1 : 1.1 , preferably from 1 : 0.95 to 1 : 1.05, based on the total amount of fragrance molecules comprising at least one ketone and/or aldehyde functionality and the total amount of diols of formula (I) and of formula (II), respectively.

In case that no diol of formula (M) is used, the resulting copolymeric pro-fragrances will comprise repeating units represented by formula (III)

wherein

R ⁴ and R ⁵ are residues originating from the fragrance molecule comprising at least one ketone and/or aldehyde functionality,

R ¹ is the linear or branched C _∑ -C _∑ o-alkyl derived from the diol of formula (I), and m is a number of at least 2.

In case that a diol of formula (II) is used in addition to at least one diol of formula (I), the resulting copolymeric pro-fragrances will comprise repeating units represented by formula (III), wherein at least some of the residues R ¹ are replaced by residues R ² originating from the diol of formula (II).

Suitable fragrance molecules comprising at least one ketone and/or aldehyde functionality may be selected from the group of conventional fragrance aldehydes and fragrance ketones which are typically used to achieve a pleasant fragrance perception. Those skilled in the art are aware of such fragrance aldehydes and fragrance ketones, which are for example described in US 2003/0158079 A1 paragraphs [0154] and [0155]. Furthermore, reference may also be made to US 6,861 ,402 B1.

Fragrance ketones may include all ketones that can impart a desired fragrance or a fresh perception. Mixtures of different ketones may also be used. For example, the ketone may be selected from the group comprising buccoxime, iso jasmine, methyl-β-naphthyl ketone, musk indanone, tonalide/musk plus, α-damascone, β-damascone, δ-damascone, iso damascone, damascenone, damarose, methyl dihydrojasmonate, menthone, carvone, camphor, fenchone, α- ionone, β-ionone, dihydro-β-ionone, γ-methyl so-called ionone, fleuramone, dihydrojasmone, cis- jasmone, iso-E-super, methyl cedrenyl ketone or methyl cedrylone, acetophenone, methyl acetophenone, paramethoxyacetophenone, methyl-β-naphthyl ketone, benzylacetone, benzophenone, parahydroxy-phenylbutanone, celery ketone or livescone, 6-isopropyl- decahydro-2-naphthone, dimethyloctenone, freskomenthe, 4-(1-ethoxyvinyl)-3,3,5,5-tetramethyl- cyclohexanone, methylheptenone, 2-(2-(4-methyl-3-cyclohexen-1-yl)propyl)-cyclopentanone, 1-(p- menthen-6(2)-yl)-1-propanone, 4-(4-hydroxy-3-methoxyphenyl)-2-butanone, 2-acetyl-3,3dimethyl- norbornane, 6,7-dihydro-1 ,1 ,2,3,3-pentamethyl-4(5H)indanone, 4-damascole, dulcinyl or cassione, gelsone, hexalon, isocyclemon E, methyl cyclocitrone, methyl lavendel ketone, orivon, para-tert- butylcyclohexanone, verdone, delphone, muscone, neobutenone, plicatone, veloutone, 2,4,4, 7-tetramethyloct-6-en-3-one, tetrameran, hedione and mixtures thereof. The ketones may preferably be selected from α-damascone, δ-damascone, isodamascone, carvone, γ-methylionone,

iso-E-super, 2,4,4, 7-tetramethyloct-6-en-3-one, benzylacetone, β-damascone, damascenone, methyl dihydrojasmonate, methyl cedrylone, hedione and mixtures thereof. Suitable fragrance aldehydes may be any aldehydes, which impart a desired fragrance or a fresh perception. These may again be individual aldehydes or aldehyde mixtures. Suitable aldehydes include for example melonal, triplal, ligustral, adoxal, anisaldehyde, cymal, ethyl vanillin, florhydral, helional, heliotropin, hydroxycitronellal, koavone, lauryl aldehyde, lyral, methyl nonylacetaldehyde, p-tert.-bucinal, phenyl acetaldehyde, undecylene aldehyde, vanillin, 2,6,10-trimethyl-9-undecenal, 3-dodecen-l-al, α-n-amylcinnamaldehyde, 4-methoxybenzaldhyde, benzaldehyde, 3-(4-tert-butylphenyl)propanal, 2-methyl-3-(para-methoxyphenylpropanal), 2-methyl-4-(2,6,6-trimethyl-2(1 )-cyclohexen-1-yl)butanal, 3-phenyl-2-propenal, cis-/trans-3,7-dimethyl-2,6-octadien-1-al, 3,7-dimethyl-6- octen-1-al, [(3,7-dimethyl-6-octenyl)oxy]acetaldehyde, 4-isopropylbenzaldehyde, 1 ,2,3,4,5,6,7,8-octahydro-8,8-dimethyl-2-naphthaldehyde, 2,4-dimethyl-3-cyclo- hexen-1-carboxyaldehyde, 2-methyl-3(isopropylphenyl)propanal, decylaldehyde, 2,6-dimethyl-5- heptenal, 4-(tricyclo(5.2.1.0(2,6)]decylidene-8)butanal, octahydro-4,7-methano-1 H- indenecarboxaldehyde, 3-ethoxy-4-hydroxybenzaldehyde, para-ethyl-α,α- dimethylhydrocinnamaldehyde, α-methyl-3,4(methylenedioxy)hydrocinnamaldehyde, 3,4- methylenedioxybenzaldehyde, α-n-hexylcinnamaldehyde, m-cymene-7-carboxaldehyde, α-methyl- phenylacetaldehyde, 7-hydroxy-3,7-dimethyloctanal, undecenal, 2,4,6-trimethyl-3-cyclohexene-1- carboxaldehyde, 4-(3)(4-methyl-3-pentenyl)-3-cyclohexene carboxaldehyde, 1-dodecanal, 2,4- dimethylcyclohexene-3-carboxaldehyde, 4-(4-hydroxy-4-methylpentyl)-3-cyclohexene-1- carboxaldehyde, 7-methoxy-3,7-dimethyloctan-1-al, 2-methylundecanal, 2-methyldecanal, 1-nonanal, 1-octanal, 2,6,10-trimethyl-5,9-undecadienal, 2-methyl-3-(4-tert-butyl)propanal, dihydrocinnamaldehyde, i-methyW-^-methyl-S-pentenyO-S-cyclohexene-i-carboxaldehyde, 5- or 6- methoxyhexahydro-4,7-methanoindan-1- or 2-carboxyaldehyde; 3,7-dimethyloctan-1-al, 1- undecanal, 10-undecen-1-al, 4-hydroxy-3methoxybenzaldehyde, 1-methyl-3-(4-methylpentyl)-3- cyclohexenecarboxyaldehyde, 7-hydroxy-3,7dimethyloctanal, trans-4-decenal, 2,6-nonadienal, para-tolylacetaldehyde; 4-methylphenylacetaldehyde, 2-methyl-4-(2,6,6-trimethyl-1-cyclohexen-1- yl)-2-butenal, ortho-methoxycinnamaldehyde, S.δ.θ-trimethyl-S-cyclohexenecarboxaldehyde, 3,7- dimethyl-2-methylene-6-octenal, phenoxyacetaldehyde, 5,9-dimethyl-4,8-decadienal, peony aldehyde (6,10-dimethyl-3-oxa-5,9-undecadien-1-al), hexahydro-4,7-methanoindane-1- carboxaldehyde, 2-methyloctanal, α-methyl-4-(1-methylethyl)benzeneacetaldehyde, 6,6-dimethyl- 2-norpinene-2-propionaldehyde, para-methylphenoxyacetaldehyde, 2-methyl-3-phenyl-2-propen-1- al, 3,5,5-trimethylhexanal, hexahydro-8,8-dimethyl-2-naphthaldehyde, 3-propylbicyclo[2.2.1]-hept- 5-ene-2-carbaldehyde, 9-decenal, 3-methyl-5-phenyl-1-pentanal, methylnonylacetaldehyde, 1-p- menthene-q-carboxaldehyde, citral, lilial citral, 1-decanal, florhydral, 2,4-dimethyl-3-cyclohexene-1- carboxaldehyde, and mixtures thereof. Preferred aldehydes may be selected from cis/trans-3,7- dimethyl-2,6octadien-1-al, heliotropin, 2,4,6-trimethyl-3-cyclohexene-1-carboxaldehyde, 2,6-

nonadienal, α-n-amylcinnamaldehyde, α-n-hexylcinnamaldehyde, p-tert-bucinal, lyral, cymal, methyl-nonylacetaldehyde, trans-2-nonenal, lilial, trans-2-nonenal and mixtures thereof.

For additional suitable fragrance substances selected from aldehydes and ketones, reference is made to Steffen Arctander, published 1960 and 1969, respectively, reprinted 2000 ISBN: Aroma Chemicals, vol. 1 : 0-931710-37-5, Aroma Chemicals, vol. 2: 0-931710-38-3.

As can be seen from the above examples, the fragrance aldehydes and fragrance ketones may have an aliphatic, cycloaliphatic, aromatic, ethylenically unsaturated structure or a combination of these structures. Furthermore, additional heteroatoms or polycyclic structures may also be present. The structures may have suitable substituents such as hydroxyl groups or amino groups.

Preferably the fragrance molecule comprising at least one ketone and/or aldehyde functionality is selected from the group consisting of acetophenone, 4-methylacetophenone, A- methoxyacetophenone, 2-pentylcyclopentanone, jasmine, ionone, damascone and damascenone, menthone, carvone, Iso-E-Super, methyl-heptenone, cyclopentadecanone, fixolide, melonal, cymal, ethyl vanillin, helional, hydroxycitronellal, koavone, methyl-nonyl-acetaldehyde, phenylacetaldehyde, undecylenic aldehyde, 3-dodecen-1-al, alpha-n-amyl cinnamic aldehyde, benzaldehyde, 4-methoxybenzaldehyde, piperonal, 3-(4-tert-butylphenyl)-propanal, 2-(4-tert- butylbenzyl)-propanal, 2-methyl-3-(para-methoxyphenylpropanal), 2-methyl-4-(2,6,6-trimethyl-2(1 )- cyclohexen-1-yl)butanal, cinnamaldehyde, cis-/trans-3,7-dimethyl-2,6-octadien-1-al, 3,7-dimethyl-6- octen-1-al, [(3,7-dimethyl-6-octenyl)oxy]acetaldehyde, 4-isopropylbenzaldehyde, 2,4-dimethyl-3- cyclohexen-1-carboxaldehyde, 2-methyl-3-(isopropylphenyl)propanal, decylaldehyde, 2,6-Dimethyl- 5-heptenal, alpha-n-hexylcinnamic aldehyde, 7-hydroxy-3,7-dimethyl octanal, 2,4,6-trimethyl-3- cyclohexene-1-carboxaldehyde, 1-dodecanal, 2,4-dimethylcyclohexene-3-carboxaldehyde, 4-(4- hydroxy-4-methyl pentyl)-3-cylohexene-1-carboxaldehyde, 2-methyl undecanal, 2-methyl decanal, 1-nonanal, 1-octanal, 1-heptanal, 2,6,10-trimethyl-5,9-undecadienal, 2-methyl-3-(4- tertbutyl)propanal, dihydrocinnamic aldehyde, 3,7-dimethyloctan-1-al, 1-undecanal, 10-undecen-1- al, 4-hydroxy-3-methoxybenzaldehyde, trans-4-decenal, 2,6-nonadienal, para-tolylacetaldehyde, 3,7-dimethyl-2-methylene-6-octenal, 2-methyloctanal, alpha-methyl-4-(1-methylethyl)benzene acetaldehyde, 2-methyl-3-phenyl-2-propen-1-al, 3,5,5-trimethyl hexanal, 3-propyl- bicyclo[2.2.1]hept-5-ene-2-carbaldehyde, 9-decenal, 3-methyl-5-phenyl-1-pentanal, methylnonylacetaldehyde, citral, 1 -decanal, florhydral, heliotropin, 2,4-dimethyl-3-cyclohexen-1- carbaldehyde, and mixtures thereof.

Particularly preferred fragrance molecules comprising at least one ketone and/or aldehyde functionality are selected from the group consisting of acetophenone, 4-methylacetophenone, A- methoxyacetophenone, 2-pentylcyclopentanone, ionone, damascone, menthone,

cyclopentadecanone, fixolide, phenylacetaldehyde, benzaldehyde, 4-methoxybenzaldehyde, piperonal, 2-(4-tert-butylbenzyl)-propanal, cinnamaldehyde, 3,7-dimethyl-6-octen-1-al, alpha-n- hexylcinnamic aldehyde, 10-undecen-1-al, 1-octanal, 1-heptanal, 4-hydroxy-3- methoxybenzaldehyde, trans-4-decenal, methylnonylacetaldehyde, citral, 2,4-dimethyl-3- cyclohexen-1-carbaldehyde, and mixtures thereof.

A further object of the invention is a process for the production of a pro-fragrance according to the invention, wherein

- at least one fragrance molecule comprising at least one ketone and/or aldehyde functionality is reacted with

- at least one diol of formula (I) wherein

R ¹ is a linear or branched C ₂ -C ₂ o-alkyl, and n is a number from 4 to 1000,

- and, optionally, at least one diol of formula (II)

HO-R ² -OH (II)

wherein

R ² is a linear or branched C ₂ -C ₂ o-alkyl, optionally containing at least a functionality selected from ether, ester, amide, carbonate, carboxyl, carboxylic acid sodium salt, carboxylic acid amine salt, sulfone, sulfoxide, sulfonyl, sulfonic acid sodium salt, sulfonic acid amine salt, phosphonyl, phosphonic acid sodium salt, phosphonic acid amine salt, pyridinium, and ammonium groups.

The reaction of diol and fragrance molecule is conducted by well-known polycondensation technologies. Depending on the reactants involved, it may be sufficient to simply mix the reactants and to remove the water formed during the reaction from the reaction mixture. Removal of the water may be accomplished by known techniques, e.g. by addition of a water-binding salt or by heating the reaction mixture at reflux on a water separator.

However, the reaction is preferably performed in a suitable solvent. Suitable solvents include, for example, aliphatic and aromatic hydrocarbons like cyclohexane or toluene. Cyclohexane is preferred.

Furthermore, it is preferred to add a catalyst to the reaction mixture, which promotes the polycondensation. In general, acids are suitable polycondensation catalysts. Preferably, the reaction is conducted in the presence of a polycondensation catalyst selected from the group comprising hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, trifluoroacetic acid, p- toluenesulfonic acid, and supported sulfonic acid catalyst, for example Amberlyst 15.

p-Toluenesulfonic acid is a particularly preferred polycondensation catalyst.

The reaction is preferably performed at a temperature in the range of 80 to 150 ⁰ C, particularly preferred 100 to 140 ⁰ C. For example, the reactants and the catalyst may be added to the solvent and the resulting mixture be heated under a protective gas at reflux on a water separator. Suitable protective gases are for example nitrogen or argon. The resulting reaction product is isolated by conventional methods and purified if necessary.

Preferred diols of formula (I) and (II), as well as preferred fragrance molecules have already been disclosed above.

Pro-fragrance compounds of the invention show excellent characteristics. They provide an initial good perfume performance immediately after application as well as a good perfume release from the treated substrate over a prolonged period of time.

Hence, the pro-fragrances are very useful ingredients for any product which is expected to show superior fragrance characteristics.

A further object of the invention is therefore the use of a pro-fragrance compound according to the invention in a detergent, cleaning, fabric treatment or cosmetic composition.

Still a further object of the invention is a detergent, cleaning, fabric treatment or cosmetic composition comprising from 0.001 to 50% by weight of at least one pro-fragrance compound according to the invention.

Another object of the invention is a method of treating a substrate to impart thereto surface substantive, slow odor release perfume materials, which method comprises contacting the

substrate with a composition comprising from 0.001 to 50% by weight of at least one pro-fragrance compound according to the invention.

The pro-fragrances according to the invention may be used as the single fragrance substance, but it is also possible to use mixtures of fragrance substances, which comprise the pro-fragrances only partially. In particular fragrance substance mixtures containing 1 to 50 wt%, preferably 5 to 40 wt% and in particular max. 30 wt% of pro-fragrances may be used. In other embodiments in which the delayed fragrance effect of the pro-fragrance is of particular importance, advantageously at least 30 wt%, preferably at least 40 wt% and in particular at least 50 wt% of the total perfume contained in an agent is introduced into the agent via pro-fragrances according to the invention, whereas the remaining 70 wt%, preferably 60 wt% and in particular 50 wt% of the total perfume present in the agent is sprayed as usual or is otherwise introduced into the agent.

By splitting the total perfume content of an agent, e.g., a detergent or cleaning agent, into a perfume, which is present in the form of the inventive pro-fragrances and a perfume that has been incorporated traditionally, a variety of product characteristics can be implemented which become possible only through the use of pro-fragrances according to the invention. For example, it is possible to divide the total perfume content of an agent into two portions x and y, whereby the portion x comprises inventive pro-fragrances and the portion y comprises traditional perfume oils.

The fragrance substances that may be incorporated into the agents in the traditional way are not subject to any restrictions. Individual perfume substance compounds of natural or synthetic origin, e.g., of the type of esters, ethers, aldehydes, ketones, alcohols and hydrocarbons may thus be used as the perfume oils and/or fragrance substances. Perfume substance compounds of the ester type include, for example, benzyl acetate, phenoxyethyl isobutyrate, p-tert-butylcyclohexyl acetate, linalyl acetate, dimethylbenzylcarbinyl acetate (DMBCA), phenylethyl acetate, benzyl acetate, ethylmethyl phenyl glycinate, allylcyclohexyl propionate, styrallyl propionate, benzyl salicylate, cyclohexylsalicylate, floramat, melusat and jasmacyclate. The ethers include, for example, benzylethyl ether and ambroxan; the aldehydes include, for example, the linear alkanals with 8 to 18 carbon atoms, citral, citronellal, citronellyl oxyacetaldehyde, cyclamenaldehyde, lilial and bourgeonal; the ketones include, for example, the ionones, α-isomethylionone and methyl cedryl ketone; the alcohols include anethole, citronellol, eugenol, geraniol, linalool, phenylethyl alcohol and terpineol; the hydrocarbons include mainly terpenes such as limonene and pinene. However, mixtures of various perfume substances which jointly produce an attractive fragrance note are preferred.

Such perfume oils may also contain mixtures of natural perfume substances such as those accessible from plant sources, e.g., pine oil, citrus oil, jasmine oil, patchouli oil, rose oil or ylang-

ylang oil. Also suitable are muscatel sage oil, chamomile oil, clove oil, lemon balm oil, mint oil, cinnamon leaf oil, linden blossom oil, juniper berry oil, vetiver oil, olibanum oil, galbanum oil and labdanum oil as well as orange blossom oil, neroli oil, orange peel oil and sandalwood oil.

Other traditional perfume substances that may be used include, for example, the essential oils such as angelica root oil, anise oil, arnica blossom oil, sweet basil oil, bay oil, champaca blossom oil, silver fir oil, fir cone oil, elemi oil, eucalyptus oil, fennel oil, spruce needle oil, galbanum oil, geranium oil, ginger grass oil, guaiac wood oil, gurjun balsam oil, helichrysum oil, ho oil, ginger oil, iris oil, cajeput oil, calamus oil, chamomile oil, camphor oil, canaga oil, cardamon oil, cassia oil, pine needle oil, copaiba balsam oil, coriander oil, spearmint oil, caraway oil, cumin oil, lavender oil, lemon grass oil, lime oil, mandarin oil, lemon balm oil, ambrette seed oil, myrrh oil, clove oil, neroli oil, niaouli oil, olibanum oil, origanum oil, palmarosa oil, patchouli oil, Peru balsam oil, petitgrain oil, pepper oil, peppermint oil, allspice oil, pine oil, rose oil, rosemary oil, sandalwood oil, celery seed oil, spike lavender oil, star anise oil, turpentine oil, thuja oil, thyme oil, verbena oil, vetiver oil, juniper berry oil, vermouth oil, wintergreen oil, ylang-ylang oil, ysop oil, cinnamon oil, cinnamon leaf oil, citronella oil, lemon oil and cypress oil as well as ambrettolide, ambroxan, α-amylcinnamaldehyde, anethole, anise aldehyde, anise alcohol, anisole, anthranilic acid methyl ester, acetophenone, benzylacetone, benzaldehyde, benzoic acid ethyl ester, benzophenone, benzyl alcohol, benzyl acetate, benzyl benzoate, benzyl formate, benzyl valerate, borneol, bornyl acetate, boisambrene forte, α-bromostyrene, n-decylaldehyde, n-dodecylaldehyde, eugenol, eugenol methyl ether, eucalyptol, farnesol, fenchone, fenchyl acetate, geranyl acetate, geranyl formate, heliotropin, heptin carboxylic acid methyl ester, heptaldehyde, hydroquinone dimethyl ester, hydroxycinnamyl aldehyde, hydroxycinnamyl alcohol, indole, iron, isoeugenol, isoeugenol methyl ether, isosafrol, jasmine, camphor, carvacrol, carbon, p-cresol methyl ether, coumarin, p- methoxyacetophenone, methyl-n-amyl ketone, methyl anthranilic acid methyl ester, p- methylacetophenone, methyl chavicol, p-methylquinoline, methyl β-naphthyl ketone, methyl n- nonylaldehyde, nonyl alcohol, n-octylaldehyde, p-oxyacetphenone, pentadecanolide, β-phenylethyl alcohol, phenylacetaldehyde-dimethylacetal, phenylacetic acid, pulegon, safrole, salicylic acid isoamyl ester, salicylic acid methyl ester, salicylic acid hexyl ester, salicylic acid cyclohexyl ester, santalol, sandelice, skatol, terpineol, thyme, thymol, troenan, γ-undelactone, vanillin, veratrum aldehyde, cinnamyl aldehyde, cinnamyl alcohol, cinnamic acid, cinnamic acid ethyl ester, cinnamic acid benzyl ester, diphenyl oxide, limonene, linalool, linayl acetate and linalyl propionate, melusat, menthol, menthone, methyl-n-heptenone, pinene, phenyl acetaldehyde, terpinyl acetate, citral, citronellal and mixtures thereof.

The pro-fragrances are preferably used in detergents and cleaning compositions, fabric treatment compositions like fabric softeners and in cosmetics. These may be solid, gel or liquid formulations,

and solid formulations may be in the form of powder, granules, tablets or tabs. Liquid formulations may be solutions, emulsions or dispersions.

Detergents may be used for manual or machine washing of textiles in particular. They may be detergents or cleaning agents for industrial use or for the household area. Cleaning agents may be used for cleaning hard surfaces, for example. They may be dishwasher detergents, for example, which are used for manual or machine cleaning of dishes. They may also be conventional industrial or household cleaners with which hard surfaces such as furniture surfaces, flagstones, ceramic tiles, wall coverings and floor coverings are cleaned. Fabric softeners include in particular fabric softeners that are used for treating textiles during or after being laundered. The cosmetics may be pastes, ointments, creams, emulsions, lotions and solutions, in particular alcohol-based solutions, which are known from fine perfumery, for example. The individual agents may be applied in any suitable form. For example, these may be agents to be applied by spraying. The inventive pro- fragrances may also be used to cover bad odors, which adhere well to solid surfaces when combined with other absorbents, for example.

Detergents, cleaning, fabric treatment or cosmetic compositions according to the invention comprise a sufficient amount of at least a pro-fragrance compound according to the invention, usually from 0,001 to 50% by weight based on the total amount of the composition.

In most cases an amount of pro-fragrance compounds of clearly below 50% by weight is sufficient. Typically, ready-to-use products comprise less than 5% by weight of at least a pro-fragrance compound, preferably less than 2% by weight, particularly preferred less than 1 % by weight. Typical ranges are from 0.05 to 0.5% by weight, preferably from 0.1 to 0.2% by weight. However, perfumes may comprise a high concentration of the pro-fragrance compound, for example up to 40% by weight.

Detergents, cleaning, fabric treatment or cosmetic compositions according to the invention may contain any further necessary or additional ingredient. Such ingredients are well known to those skilled in the art.

Detergents and cleaning agents and fabric softeners may contain other conventional ingredients of detergents and cleaning compositions and fabric softeners, such as surfactants, builder substances, bleaching agents, other fragrance substances, enzymes and other active ingredients, but also disintegration aids, so-called tablet d is integrants, to facilitate the disintegration of highly compressed tablets and tabs and to shorten the disintegration times.

Surfactants in particular are among the essential ingredients of detergents and cleaning agents and fabric softeners.

The surfactant content will be selected to be higher or lower, depending on the intended use of the inventive agents. The surfactant content of detergents is usually between 10 and 40 wt%, preferably between 12.5 and 30 wt% and in particular between 15 and 25 wt%, whereas cleaning agents for dishwashing machines contain between 0.1 and 10 wt%, preferably between 0.5 and 7.5 wt% and in particular between 1 and 5 wt% surfactant, for example.

These surfactant substances may be selected from the group of anionic, nonionic, zwitterionic or cationic surfactants but for economic reasons and because of their performance spectrum, anionic surfactants are definitely preferred in washing and cleaning. With respect to surfactants and emulsifiers which are preferably used according the invention it is referred to the disclosure of WO 2008/107346.

With respect to builder substances which are preferably used according to the invention it is referred to the disclosure of WO2008/107346.

The compositions contain builders preferably in amounts, based on the composition, of 0 to 20 wt%, preferably 0.01 to 12 wt%, in particular 0.1 to 8 wt%, and most preferred 0.3 to 5 wt%.

In addition to the ingredients already listed, the inventive detergents and cleaning compositions may additionally contain one or more other substances, preferably selected from the group consisitng of bleaching agents, bleach activators, enzymes, pH adjusting agents, fluorescent agents, dyes, foam inhibitors, silicone oils, anti-redeposition agents, optical brighteners, graying inhibitors, dye transfer inhibitors, soil-release compounds, corrosion inhibitors and silver protectants. With respect to bleaching agnets, bleach activators, enzymes, pH adjusting agents, fluorescent agents, dyes, foam inhibitors, silicone oils, anti-redeposition agents, optical brighteners, graying inhibitors, dye transfer inhibitors, disintegration aids, corrosion inhibitors and silver protectants which are most preferably used and with respect to the preferred amounts of those substances it is referred to the disclosure of WO 2008/107346.

This list of ingredients of fabric softeners and detergents and cleaning agents is by no means conclusive but instead merely gives the most essential typical ingredients of such agents. In particular, inasmuch as they are liquid or gel preparations, these agents may also contain organic solvents. These are preferably monovalent or polyvalent alcohols with 1 to 4 carbon atoms. Preferred alcohols in such agents include ethanol, 1 ,2-propanediol, glycerol as well as mixtures of these alcohols. In preferred embodiments, such agents contain 2 to 12 wt% of such alcohols.

Essentially the agents may have different physical states. In another preferred embodiment, the fabric softeners, detergents or cleaning agents are liquid or gel agents, in particular liquid detergents or liquid dishwashing detergents or cleaning gels, and they may in particular also be cleaning agents in the form of gels for cleaning toilets.

These are preferably intrinsically viscous cleaning agents in the form of gels with a viscosity of 30,000-150,000 mPas, containing as the gelatinizing agent a polysaccharide, as the emulsifier and wetting-active component a C ₈ _io alkyl polyglycoside or C ₁₂ - _M alkyl polyglycoside (APG) and perfume oil. Fatty alcohol ether sulfates (FAEOS) and fatty alcohol sulfates (FAS) may also be present as additional co-surfactants. The ratio of APG to co-surfactant is then usually greater than 1 , preferably between 50:1 and 1 :1 , especially preferably between 10:1 and 1.5 to 1 and most especially preferably between 5:1 and 1.8:1. In particular these are stable, shear-diluting cleaning agents in the form of a gel containing a polysaccharide, a surfactant system and perfume components, which are characterized by the fact that

• they contain a polysaccharide, preferably a xanthan gum, in amounts between 1 and 5 wt%, preferably 1 to 5 wt%, especially preferably 1.5 to 3.5 wt% and most especially preferably 1.8 to 3 wt%,

• they contain as a component of the surfactant system a C ₈ - ₂₂ alkyl polyglycoside in amounts between 3 and 25 wt%, preferably 4 and 20 wt%, especially preferably 5 and 15 wt% and most especially preferably 5 and 12 wt%, and

• they contain the perfume component(s) up to 15 wt%, preferably 2 to 12 wt%, especially preferably 3 to 8 wt%,

• and they optionally contain other ingredients such as lime-dissolving agents, dyes, microbicidal agents (e.g., isothiazoline mixtures, sodium benzoate or salicylic acid), pearlescent agents, stabilizers, cleaning enhancers and odor absorbers,

• and that the agents have a viscosity of 30,000 to 150,000 mPas, measured with a Brookfield rotary viscometer, model RVT with a Helipath device and TA spindle at 1 rpm and 23°C.

If necessary, water-soluble and water-insoluble builders may also be present in the gels according to the invention. In that case water-soluble builders are preferred because they usually have less tendency to form insoluble residues on hard surfaces. The usual builders which may be present within the scope of the invention include the low-molecular polycarboxylic acids and their salts, the homopolymeric and copolymeric polycarboxylic acids and their salts, citric acid and its salts, carbonates, phosphates and silicates. The water-insoluble builders include the zeolite which may also be used as well as the mixtures of the aforementioned builder substances. The group of citrates is especially preferred.

Other typical cleaning agents which may contain the inventive pro-fragrances include liquid or gel cleaners for hard surfaces, in particular so-called all-purpose cleaners, glass cleaners, floor and bathroom cleaners as well as special embodiments of such cleaners, which include acidic or alkaline forms of all-purpose cleaners as well as glass cleaners with a so-called anti-rain effect. These liquid cleaning agents may also be present in one or more phases. In an especially preferred embodiment, the cleaners have two different phases.

"Cleaner" in the broadest sense is a term for formulations (usually containing a surfactant) with a very wide area of application and a very different composition, depending on the application. The most important market segments are household cleaners, industrial (technical) cleaners and institutional cleaners. Depending on the pH, a distinction is made between alkaline, neutral and acidic cleaners; according to the form in which it is offered, a distinction is made between liquid and solid cleaners (also in tablet form). These so-called cleaners for hard surfaces should yield an optimal profile of use (in contrast with dishwashing agents, which are also classified in the product group of cleaners) both in a concentrated state and in dilute aqueous solution when combined with mechanical energy. Low-temperature cleaners manifest their effect without elevated temperature. Surfactants and/or alkali carriers, alternatively acids, optionally also solvents such as glycol ethers and lower alcohols are crucial for the cleaning effect. In general, the formulations also contain builders and, depending on the type of cleaner, bleaching agents, enzymes, microbicidal or disinfecting additives as well as perfume oils and dyes. Cleaners may also be formulated as microemulsions. The success of cleaning depends to a great extent on the type of dirt - which may also vary greatly geographically - and the properties of the surfaces to be cleaned.

Household cleaners may be formulated as universal cleaners or as special cleaners for ceramics, tiles, windows, plastics, (carpet) floors, cooktops, baking ovens, microwave ovens, plumbing cleaners or bathroom or toilet cleaners. Pipe cleaners are adjusted to be alkaline and consist of, for example, solid sodium hydroxide and aluminum powder which, when dissolved, release hydrogen which ensures a corresponding turbulence in the pipe segments to be cleared. In addition to containing surfactant and builder, sanitary cleaners mainly contain active ingredients to reduce the microbe count, whereby sodium hypochlorite, which was used previously, has been partially replaced by hydrogen peroxide or other peracid compounds. Toilet cleaners are mainly acidic but may sometimes also be adjusted to be alkaline, whereby in the former case, the phosphoric acid originally used and sodium bisulfate are largely replaced by organic acids, mainly citric acid. Special cleaners also include automotive cleaners, automobile windshield cleaners, wheel rim cleaners, engine cleaners and paint application equipment cleaners in the do-it-yourself field.

In addition to the components already mentioned, the compositions according to the invention may also contain other additives and aids, such as those customary in such agents. These include in

particular polymers, soil-release active ingredients, solvents (e.g., ethanol, isopropanol, glycol ether), solubilizers, hydrotropes (e.g., cumenesulfonate, octyl sulfate, butyl glucoside, butyl glycol), cleaning enhancers, viscosity regulators (e.g., synthetic polymers, such as polysaccharides, polyacrylates, naturally occurring polymers and their derivatives such as xanthan gum, other polysaccharides and/or gelatins), pH regulators (e.g., citric acid, alkanolamines or NaOH), disinfectants, antistatics, preservatives, bleach systems, enzymes, dyes and opacifiers or skin protectants.

The amount of such additives is usually no more than 12 wt% in the cleaning agent. The lower limit for use depends on the type of additive and may be as low as 0.001 wt% or even less in the case of dyes. The amount of auxiliaries is preferably between 0.01 and 7 wt%, in particular 0.1 and 4 wt%.

The aforementioned compositions may also contain binders, which may be used alone or in mixture with other binders.

Cosmetic compositions according to the invention are preferably compositions for the treatment of hair and skin.

These cosmetic agents preferably contain the pro-fragrances according to the invention in amounts of 0.001 to 10 wt%, preferably from 0.01 to 5 wt%, especially preferably from 0.02 to 3 wt% and in particular in amounts of from 0.05 to 2 wt%, each based on the total cosmetic composition.

The total amount of fragrance substances in the cosmetic agents, including the pro-fragrances, is preferably between 0.01 and 5 wt%, especially preferably between 0.1 and 3 wt% and most especially preferably between 0.5 and 2 wt%, based on the total amount of the agent. Mixtures of various fragrance substances (from the various classes of fragrance substances mentioned above) which jointly produce an appealing fragrance note are preferably used. In this case, the total amount of the at least one fragrance substance is the amount of all fragrance substances in the mixture together, based on the total amount of the agent.

In a preferred embodiment, the cosmetic agents are aqueous, alcoholic or aqueous-alcoholic preparations that contain surfactant active ingredients and are suitable in particular for treatment of keratin fibers, in particular human hair, or for treatment of skin.

Said hair treatment agents include in particular agents for treatment of human head hair. The most conventional agents of this category can be divided into shampoo detergents, hair care agents, hair setting and permanent hair waving agents as well as hair dyes and depilatories. The agents that

are preferred according to this invention and contain surfactant active ingredients include in particular shampoos and treatment preparations. Such a hair washing agent or shampoo consists of 10 to 20 recipe ingredients, in individual cases up to 30 recipe ingredients. These preparations are usually in liquid form to pasty form.

Cosmetics (cosmetic agents, cosmetic compositions) according to the invention usually contain other ingredients that are conventional for these agents.

Preferably they contain surfactant active ingredients or detergent-active ingredients as additional ingredients. Fatty alcohol polyglycol ether sulfates (ether sulfates, alkyl ether sulfates) are preferably used here, partially in combination with other surfactants, usually anionics. In addition to the alkyl ether sulfates, preferred agents may additionally contain other surfactants such as alkyl sulfates, alkyl ether carboxylates, preferably with degrees of ethoxylation of 4 to 10, as well as surfactant protein-fatty acid condensates. Protein-abitic acid condensate should be mentioned here in particular. Sulfosuccinic acid esters, amidopropyl-betaines, amphoacetates and amphodiacetates as well as alkyl polyglycosides are surfactants that are preferably used in shampoos.

Another group of ingredients is summarized by the term auxiliary substances and is extremely varied: for example, nonionic surfactant additives such as ethoxylated sorbitan esters or protein hydrolysates increase the compatibility and/or have an irritation-reducing effect, e.g., in baby shampoo; e.g., natural oils or synthetic fatty acid esters serve as moisturizing agents to prevent excessive removal of oil in shampooing; humectants include glycerol, sorbitol, propylene glycol (see propanediols), polyethylene glycols and other polyols. To improve wet combability and to reduce electrostatic charge buildup on the hair after drying, cationic surfactants, e.g., quaternary ammonium compounds may be added to the shampoo. For a brilliant color appearance, dyes and/or pearlescent pigments may be added. To adjust the desired viscosity, thickeners of various substance classes may be used, and pH stability is achieved by buffers based on citrate, lactate or phosphate, for example. To ensure adequate stability and storage life, preservatives such as 4-hydroxybenzoic acid ester are added; oxidation-sensitive ingredients can be protected by adding antioxidants such as ascorbic acid, butylmethoxyphenol or tocopherol.

Another preferred group of ingredients includes special active ingredients for special shampoos, e.g., oils, herbal extracts, proteins, vitamins and lecithins in shampoos for hair that becomes oily rapidly, for especially dry hair, stressed or damaged hair. Active ingredients in shampoos for controlling dandruff usually have a broad growth-inhibiting effect against fungi and bacteria. The fungistatic properties of pyrithione salts in particular, have been shown to be the cause of the good antidandruff effect.

Cosmetic compositions according to the invention may be present in different preparation forms.

The most important are skin creams, skin lotions, skin oils and skin gels. The creams and lotions are based on emulsions in O/W (oil-in-water) form or VWO (water-in-oil) form. The main ingredients of the oil and/or fat or lipid phase include fatty alcohols, fatty acids, fatty acid esters, waxes, petrolatum, paraffins and other fat and oil components mainly of a natural origin. In addition to water, the aqueous phase contains moisture-regulating and moisture-preserving substances as the main skin care active ingredients plus agents to regulate consistency and/or viscosity. Additional additives such as preservatives, antioxidants, complexing agents, perfume oils, coloring agents as well as special active ingredients are added to one of the aforementioned phases, depending on their solubility and stability properties. The choice of the emulsifier system is essential for the emulsion type and its properties. It can be selected according to the HLB system.

In addition, the skin care agents may contain other special active ingredients, e.g., milk protein products, egg yolk, lecithins, lipoids, phosphatides, cereal seed oils, vitamins, especially vitamin F and biotin, which was previously referred to as the skin vitamin (vitamin H) as well as hormone-free placenta extracts.

The invention is further illustrated by the following examples in which all parts and percentages are by weight, unless otherwise stated. These examples were included for illustrative purposes only and shall not be construed as limiting the scope of the invention.

Examples

1. Synthesis of pro-fragrances

Comparative example 1 : Diethylene glycol / Octanal (Polyacetal A)

50 mmol diethylene glycol, 50 mmol octanal and 0.5 mmol p-toluenesulfonic acid were added to 120 ml cyclohexane in a 200 ml two necks round-bottom flask assembled with a Dean-Stark trap and condenser under argon atmosphere. The mixture was brought to reflux. After 48 hours, the theoretically amount of water had been accumulated in the Dean-Stark trap. After cooling, 5 ml of saturated sodium carbonate was added and the mixture was concentrated under vacuum. The resulting residue was dissolved in acetone and filtered to remove sodium carbonate. The filtrate was condensed and washed three times with hexane to obtain Polyacetal A having the following characteristics:

M _n = 580 MJM _n = 2.0

Amount of octanal incorporated into the obtained polyacetal: 59% by weight. Solubility in water: insoluble.

Example 1 : PEG 200 / Octanal (Polyacetal B)

50 mmol polyethylene glycol, represented by formula (Ia)

HO-(-CH _γ CH— O-^H (Ia)

wherein n is 4.3, commercially available e.g. under the tradename Carbowax PEG 200 from Dow Chemical Company (PEG 200), was added together with 50 mmol octanal and 0.5 mmol p- toluenesulfonic acid to 120 ml cyclohexane in a 200 ml two necks round-bottom flask assembled with a Dean-Stark trap and condenser under argon atmosphere. The mixture was brought to reflux. After 48 hours, the theoretically amount of water had been accumulated in the Dean-Stark trap. After cooling, 5 ml of saturated sodium carbonate was added and the mixture was concentrated under vacuum. The resulting residue was dissolved in acetone and filtered to remove sodium carbonate. The filtrate was condensed and washed three times with hexane to obtain Polyacetal B having the following characteristics:

M _n = 1 ,000

MJM _n = 1.9

Amount of octanal incorporated into the obtained polyacetal: 44% by weight.

Solubility in water: partially soluble.

Example 2: PEG 400 / Octanal (Polyacetal C)

50 mmol polyethylene glycol, represented by formula (Ia)

HO-(-CH _γ CH— O-^H (Ia)

wherein n is 8.9, commercially available e.g. under the tradename Carbowax PEG 400 from Dow Chemical Company (PEG 400), was added together with 50 mmol octanal and 0.5 mmol p- toluenesulfonic acid to 120 ml cyclohexane in a 200 ml two necks round-bottom flask assembled with a Dean-Stark trap and condenser under argon atmosphere. The mixture was brought to reflux.

After 48 hours, the theoretically amount of water had been accumulated in the Dean-Stark trap. After cooling, 5 ml of saturated sodium carbonate was added and the mixture was concentrated under vacuum. The resulting residue was dissolved in acetone and filtered to remove sodium carbonate. The filtrate was condensed and washed three times with hexane to obtain Polyacetal C having the following characteristics:

M _n = 1 ,200

MJM _n = 2.3

Amount of octanal incorporated into the obtained polyacetal: 20% by weight.

Solubility in water: soluble.

2. Fragrance characteristics:

To evaluate the fragrance characteristics hydrolysis tests as well as a sniff tests were performed.

Hydrolysis test:

Each of the pro-fragrances Polyacetal A, Polyacetal B and Polyacetal C were mixed at room temperature with pH-buffer solutions of pH 3, pH 5, pH 7, and pH 9, respectively. In each case the respective polyacetal was added to 20 ml of the respective pH-buffer solution to yield a molar concentration of 10 mmol/l based on the respective content of octanal. Each of the resulting 12 aqueous mixtures was overlayered with 20 ml of hexane and 10 mg dodecane, used as internal standard for quantification of the released octanal by gas chromatography. The octanal released due to hydrolysis transferred into the hexane layer. Over time small portions (each time about 0.1 ml) of the hexane solution were sampled. Each sample was diluted with hexane, and then analyzed by gas chromatography, using a Shimadzu GC-2014 with a J&W Scientific DB-5 capillary column. The injector and the detector were heated at 250 ⁰ C. During the measurement, the column oven was heated from 100 ⁰ C to 22O ⁰ C at a rate of 10°C/min.

Figure 1 shows the amount of released octanal in % by weight, based on the theoretically available amount of octanal in the pro-fragrance, versus the time of hydrolysis in hours for Polyacetal A (graph A), Polyacetal B (graph B), and Polyacetal C (graph C), respectively, each in a pH 3 buffer solution.

Figure 2 shows the amount of released octanal in % by weight, based on the theoretically available amount of octanal in the pro-fragrance, versus the time of hydrolysis in hours for Polyacetal A (graph A), Polyacetal B (graph B), and Polyacetal C (graph C), respectively, each in a pH 5 buffer solution.

As can be seen from Figures 1 and 2, the initial release rate of octanal is higher for pro-fragrances according to examples 1 and 2 compared to the pro-fragrance according to comparative example 1. Polyacetal A, the comparative pro-fragrance, shows only a very slight tendency to hydrolyze even under very acidic conditions indicating that Polyacetal A is not suitable as pro-fragrance due to the insufficient amount of released fragrance molecules. In contrast, polyacetal C underwent considerable hydrolysis even at pH 5, confirming its high ability as a pro-fragrance.

In pH-buffer solutions of pH 7 and pH 9, none of the polyacetals shows significant release of octanal over a period of 7 days, confirming the stability of the polyacetals under the practical washing and rinsing conditions if they are applied for instance to shampoos, hair conditioners, detergents and softeners.

The results indicate that pro-fragrances of the invention show an excellent initial perfume performance.

Sniff test:

Polyacetal B and Polyacetal C, respectively, were dissolved in ethanol. The concentration of the polyacetal was in each case 0.2 mol/l, based on the octanal content of the polyacetal. As reference solution octanal was dissolved in ethanol at a concentration of 0.2 mol/l. Cotton strips were dipped in each solution and dried. The strips soaked with polyacetal and pure octanal, respectively, were presented to an expert for evaluation of the odor grade. The evaluation was done after 1 , 2, 3, and 4 days, respectively, by smelling the strips in the dry state and wetted with water (pH = 7), a buffer solution of pH 3, and a buffer solution of pH 5, respectively.

In case of wetting the strips with a buffer solution of pH 3 the odor intensity of the pro-fragrances according to examples 1 and 2 was higher than or equal to the odor intensity of pure octanal. Wetting the strips with a buffer solution of pH 5 resulted in a slightly higher odor intensity of pure octanal after 1 day. However, after 2, 3 and 4 days, respectively, again the odor intensity of the pro-fragrances according to examples 1 and 2 was equal to or even higher than the odor intensity of pure octanal, indicating good fragrance durability.