Monophase gels of non-polar liquids with non-ionic surfactants

Abstract

The invention relates to a monophase gel consisting of a non-polar liquid mixed with a non-ionic surfactant selected from ester surfactants of formula ROC(O)R1 or RC(O)OR2 or ether surfactants of formula ROR2, wherein RO denotes the radical of a sugar or sugar alcohol, RC(O)O denotes a sugar acid, C(O)R1 denotes the radical of a fatty acid and R2 denotes the radical of a fatty acid alcohol. In the afore-mentioned non-ionic surfactants, the sugar is a C5 or C6 sugar, and the sugar acid and the sugar alcohol are a sugar acid derived therefrom or a sugar alcohol derived therefrom. The fatty acid or fatty acid alcohol has a C chain length of at least 6 and the non-ionic surfactant has an OH group to C atom ratio in the range of 1: 3 to 1: 8. The invention further relates to methods for producing corresponding monophase gels and to the use of corresponding gels for texturing food or cosmetic products or for formulating pharmaceuticals.

Description

[0001] Monophasic gels of non-polar liquids with non-ionic surfactants

[0002] Description

[0003] The present invention relates to a monophasic gel consisting of a non-polar liquid in a mixture with non-ionic surfactants selected from ester surfactants of the formula ROC(O)R 1 or RC(O)OR 2 or ether surfactants of the formula ROR 2 is formed, where RO is the residue of a sugar or sugar alcohol, RC(O)O is a sugar acid, C(O)R 1 the residue of a fatty acid and R 2denotes the residue of a fatty acid alcohol. In the nonionic surfactants specified, the sugar is a C5 or C6 sugar, and the sugar acid and the sugar alcohol are a sugar acid or a sugar alcohol derived therefrom. The fatty acid or fatty acid alcohol has a C chain length of at least 6, and the nonionic surfactant has an OH group to C atom ratio in the range from 1:3 to 1:8. The present invention further relates to processes for producing corresponding monophasic gels and the use of corresponding gels for texturizing food or cosmetic products or for formulating pharmaceuticals, as well as in paints and varnishes.

[0004] State of the art

[0005] Today's growing awareness of human health concerns has led to increased interest in reducing saturated fatty acids and eliminating trans fatty acids in liquid foods. Organogels made from vegetable oils, which are formed with comparatively low levels of trans fatty acids and saturated fatty acids, offer an alternative to conventional solid soap-based food products. To gel vegetable oils, so-called gelling agents must be added. Gelling largely prevents the release of oils from the system and improves the mechanical and physical properties as well as the organoleptic characteristics, such as consistency, texture, taste, and stability. Low molecular weight gelling agents, in particular, have recently experienced increased interest as a replacement for crystalline triglycerides in edible oils.

[0006] Important gelling agents for oils in this context include sterols, monoglycerides, fatty acids, natural waxes, and sugar alcohols. Most of these organogelators contain a nonpolar fatty acid residue and a hydrophilic alcohol group. The most commonly used gelling agents currently use hypercholesterolemic fatty acids such as stearic acid as structuring agents.

[0007] Pang et al. describe an erythritol-based sugar alcohol diester, specifically in the form of erythritol dioctanoate, in Eur. J. Lipid Sci. Technol. 2020, 12, pp. 1900-412, in which the two primary OH groups of erythritol are esterified with octanoic acid groups. This leaves two polar OH groups in the middle of the molecule. This compound has been used to gel vegetable oils.

[0008] Zhu et al. describe in Chem. Mater. 2006, 18, pp. 5988-95 trehalose diesters with acetic acid, butyric acid, decanoic acid, and myristic acid, in which the acid groups are also bonded to the primary OH groups of the sugar, and which can be used for the gelation of organic solvents.

[0009] The solvents gelled in Zhu are esters (such as ethyl or butyl acetates), ketones and comparatively polar solvents such as alcohols and acetonitrile.

[0010] US Patent No. 10,081,748 B1 deals with gelling agents for oils, particularly mineral oil. These gelling agents are said to be addable to water / oil mixtures and selectively generate an oil gel in this mixture. The gelling agents specified in US Patent No. 10,081,748 B1 are mono- or diesters of C6 sugar alcohols and medium-chain fatty acids such as octanoic acid, which are converted to the corresponding esters with the aid of an enzyme called "Novozyme 435." The gel is formed by the aggregation of the hydrophilic components of the molecules and the nonpolar components of the molecules.

[0011] The compounds specified in US Pat. No. 10,081,748 B1 allow gel formation with petroleum and vegetable oils. However, the compounds are not optimized for the formation of gels with high strength properties, as desired for some applications in the food and cosmetics sectors. Therefore, there is a need for agents for the production of gel-based formulations of vegetable oils or nonpolar organic solvents that form gels with high strength even with lower additive levels.

[0012] Murdan S. et al., J. Pharmaceutical Science, Vol. 88, No. 6, 1999, pp. 608 to 614, describes organogels based on sorbitan monostearate and sorbitan monopalmitate. It is stated that no stable gels could be obtained for sorbitan tristearate.

[0013] Shchipuov YA et al., J. Colloid and Interface Science 211, 1999, pp. 81-88, describes organogels with n-decane based on lecithin as the essential gel-forming component. In addition to lecithin, n-dodecyl-ß-D-lactobionamide and n-dodecyl-ß-D-glucopyranoside were used in amounts of up to 10 wt.% (based on the total amount of gelling agent) to investigate the effect of the additives on the properties of the gel.

[0014] The present invention addresses this need.

[0015] Description of the invention

[0016] In the investigations underlying this invention, it was surprisingly discovered that, on the one hand, the chain length of a non-polar moiety of a gel-forming additive and, on the other hand, the size of the polar moiety are of relevant importance for the gel properties to be achieved with this molecule. In particular, it was observed that a smaller polar moiety is favorable for the production of firmer gels (with an identical amount of added additive), and that particularly suitable gelling properties can be achieved by matching a non-polar moiety to the size of the polar moiety. Within the scope of the invention, the "size of the polar moiety" was determined via the number of OH groups in the moiety, while the size of the non-polar moiety was estimated indirectly via the number of carbon atoms in the compound.Furthermore, it was found that the gels produced with the non-ionic surfactants exhibit at least partially thixotropic properties.

[0017] Accordingly, in a first aspect, the present invention relates to a monophasic gel comprising a non-polar liquid and a non-ionic surfactant selected from ester surfactants of the formula ROC(O)R 1 or RC(O)OR 2 or ether surfactants of the formula ROR 2 wherein RO is the residue of a sugar or sugar alcohol, RC(O)O is a sugar acid, OC(O)R 1 a fatty acid and R 2 a fatty acid alcohol, wherein the sugar is a C5 or C6 sugar, the sugar acid and the sugar alcohol are a sugar acid or a sugar alcohol derived therefrom, and the fatty acid or the fatty acid alcohol has a C chain length of at least 6 and wherein the non-ionic surfactant has an OH groups to C atom ratio in the range of 1:3 to 1:8.

[0018] The term "non-polar liquid" in the present invention refers to aprotic chemical compounds that are in liquid form at room temperature. Preferably, the non-polar liquid has a polarity, determined as E T (30) is defined as the transition energy of the longest-wavelength Vis / NIR absorption band in a solution containing the negatively solvatochromic Reichardt dye (betaine 30) under standard conditions in kcal / mol, and has a transition energy of 145 kJ / mol or less, and preferably in the range of 140 to 120 kJ / mol. Suitable nonpolar solvents are therefore, in particular, linear or branched alkanes such as n-hexane or n-heptane, but also oils, particularly vegetable oils or alkanones.

[0019] In the present invention, the term "monophasic gel" refers to the fact that the non-polar liquid and the non-ionic surfactant form a single phase. This does not preclude the gel from containing other solid components, such as colorants or pigments, which are present as an additional phase in the gel, since the solid components do not dissolve in the gel. Such mixtures are also considered monophasic gels in the context of the invention described here. However, the specified monophasic gel does not contain a separate liquid phase in addition to the phase formed from the non-polar liquid.

[0020] The residue "OR" in the formula given above denotes the residue of a sugar or sugar alcohol, where the sugar is formed by adding a hydrogen atom from the residue to form "ROH". The residue "R" forms the remaining part of the sugar or sugar alcohol, in which a C5 sugar contains 5 carbon atoms, 3 OH groups and an aldehyde or keto function, and a C6 sugar contains 6 carbon atoms, 4 OH groups and an aldehyde or keto function. In a sugar alcohol, the aldehyde or keto function is reduced to another OH group. It is also possible for one or more of the OH groups to be deoxidized to form a CH2 group, as long as the sugar or sugar alcohol forms a non-ionic surfactant having an OH group to C atom ratio in the range of 1:3 to 1:8. According to the above definition, sugar anhydrides (i.e.Substances derived from sugar by elimination of water, such as sorbitan anhydride) are not considered to be sugars or sugar alcohols as they are present in the radical OR, so that ester and ether surfactants based on such substances are not encompassed by the present invention.

[0021] Sugar acid, whose residue forms "RC(O)O", is a sugar derivative in which a primary OH group of the sugar or the aldehyde group is oxidized to a carboxylic acid group.

[0022] In the context of the invention specified here, a fatty acid refers to a generally linear alkanecarboxylic acid, whereby, according to the invention, the term is also intended to encompass carboxylic acids that have one or more OH groups (preferably one) and / or one or more (preferably a maximum of two) short alkyl radicals (C1-C3), in particular in the form of methyl or ethyl, on the alkane acid chain. Furthermore, the term "fatty acid" includes unsaturated fatty acids that have one or more double bonds in their chain. A fatty acid alcohol is a derivative of a fatty acid, as specified above, in which the carboxylic acid function (-CO2H) has been converted into an alcohol function (-CH2OH) by reduction.

[0023] In the non-ionic surfactants used in the context of the invention specified here, the polar molecular parts (sugar / sugar alcohol / sugar acid) and the non-polar molecular parts (fatty acid or fatty acid alcohol) are covalently linked to one another via an ester (-C(O)OC) or ether bond (-COC-).

[0024] Examples of sugars that can be used in the non-ionic surfactants of the present invention include the C5 sugars arabinose, xylose, or ribose, and the C6 sugars glucose, mannose, or galactose, as well as fructose and sorbose. Examples of sugar alcohols that can be mentioned are arabitol, xylitol, ribitol, mannitol, sorbitol, dulcitol, or iditol. Examples of sugar acids that can be used in the non-ionic surfactants are glucuronic acid, galacturonic acid, xyluronic acid, and gluconic acid, galactonic acid, or xylonic acid. However, this list is not exhaustive, and further sugars, sugar alcohols, or sugar acids that can be used in the non-ionic surfactants of the present invention are mentioned below.

[0025] The fatty acids included in the non-ionic surfactants according to the present invention are preferably fatty acids substituted on the carboxylic acid function with an alkyl group selected from the group comprising n-pentyl, n-hexyl, n-heptyl, n-octyl (alkyl radical of caprylic acid), n-nonyl (alkyl radical of pelargonic acid), n-decyl (alkyl radical of capric acid), n-lauryl, iso-pentyl, iso-hexyl, iso-heptyl, iso-octyl, iso-nonyl, iso-decyl, iso-lauryl, 2,2-dimethylpropyl, 4-methyl-2-pentyl, 2,3-dimethylpentyl, 3-ethyl-2-pentyl and 3-ethyl-5-methyloctyl. Other examples of saturated groups include n-undecanyl, n-dodecanyl, n-tridecanyl (alkane residue of myristic acid), n-tetradecanyl, n-pentadecanyl (alkane residue of palmitic acid), n-hexadecanyl (alkane residue of margaric acid), n-heptadecanyl (alkane residue of stearic acid), n-octadecanyl, n-nonadecanyl (alkane residue of aracic acid), n-icosanyl, 4-methyldodecanyl, and 3-ethyl-5-methylpentadecanyl.Unsaturated fatty acids that can be used in the non-ionic surfactants include fatty acids that are substituted on the carboxylic acid function with an alkylene group selected from the group comprising n-pentenyl, n-hex-2-enyl, n-hept-3-enyl, n-oct-4-enyl, n-non-5-enyl, n-dec-6-enyl, n-dodec-3,6-dienyl, n-heptadec-9-enyl (alkene residue of oleic acid), isopentenyl, isohexenyl, isoheptenyl, isooctenyl, isononenyl, isodecenyl, isododecenyl, 3,3,3-trimethylpropenyl, 4-methyl-2-pentenyl, 2,3-Dimethylpent-2-enyl, 3-ethyl-2-pentenyl, 2-isopropyl-2,2-dimethylpentynyl, and 3-ethyl-5-methyloct-2,4-dienyl. Other examples of unsaturated alkyl groups include n-heptadec-3,6-dienyl, 3-isopropyl-2,4-dimethylpentynyl, and 3,3,3-trimethylheptadecynyl.

[0026] Also usable in the non-ionic surfactants are fatty acids which are substituted on the carboxylic acid function with a hydroxyalkyl group, wherein the hydroxyalkyl group is preferably selected from the group comprising hydroxypentyl, hydroxyhexyl, hydroxyheptyl, hydroxyoctyl, hydroxynonyl, hydroxydecyl, hydroxylauryl, hydroxyundecanyl, hydroxydodecanyl, hydroxytridecanyl, hydroxytetradecanyl, hydroxypentadecanyl, hydroxyhexadecanyl, hydroxyheptadecanyl, hydroxyoctadecanyl, hydroxynonadecanyl, and hydroxyicosanyl. For hydroxycarboxylic acids, it is advantageous if the hydroxy group is positioned at the α- or β-C atom to the carboxylic acid to ensure that a sufficiently long "nonpolar" residue is obtained for interactions with the nonpolar liquid.

[0027] The term "monophasic gel" in the context of the invention described herein refers to a gel with only one phase, which is usually formed by a network of non-ionic surfactants, in the free spaces of which the non-polar liquid is embedded. In particular, the network of non-ionic surfactants is formed by the non-ionic surfactants, and networks in which the non-ionic surfactants are present only as a supplement to other gel-forming agents (for example, in the form of lecithin) are not covered by the invention.

[0028] The term "thixotropic mixture" in the context given here refers to a mixture which has a lower viscosity immediately after shear than before shear, and where the viscosity increases to the pre-shear viscosity (or at least to a value close to this viscosity) after the end of the shearing action. This is also referred to as structural recovery in the rest phase (i.e. the flow properties of the mixture are time-dependent, with the viscosity decreasing as a result of ongoing external influences and only returning to the initial viscosity after the stress has ceased).

[0029] In a preferred embodiment, the specified monophasic gel contains as non-ionic surfactant a non-ionic ester surfactant of the formula ROC(O)R 1 , where R 1the residue of an unbranched or branched saturated or unsaturated fatty acid having a carbon chain length in the range of 8 to 20. Preferably, the unbranched or branched saturated or unsaturated fatty acid is selected from caprylic acid, pelargonic acid, capric acid, lauric acid, myristic acid, palmitic acid, margaric acid, stearic acid, arachidic acid, caproleic acid, undecylenic acid, myristoleic acid, palmitoleic acid, and oleic acid.

[0030] "RO" in this case can be a C5 or C6 sugar or a sugar alcohol derived therefrom, the surfactant having the formula ROC(O)R 1can be formed via conventional esterification of the two components. Since a sugar in the non-ionic surfactant has one fewer OH group than a corresponding sugar alcohol, it is preferred if the C-chain length of the fatty acid residue in this case is closer to the lower part of the specified range, e.g., in the range from 8 to 14 and preferably 8 to 12 or 6 to 12, whereas the C-chain length of the fatty acid residue in a corresponding sugar alcohol is somewhat longer, e.g., in the range from 10 to 18 or 10 to 16.

[0031] In another preferred embodiment, the specified monophasic gel contains as non-ionic surfactant a non-ionic ester surfactant of the formula ROC(O)R 1 , where R 1 the residue of a branched fatty acid with one or more methyl side chains or a ß-hydroxy fatty acid.

[0032] In yet another preferred embodiment, the specified monophasic gel contains as non-ionic surfactant a non-ionic ether surfactant of the formula ROR 2 , where R 2 the residue of an unbranched or branched saturated or unsaturated fatty acid alcohol having a C-chain length in the range of 10 to 20, preferably obtainable by reduction from capric acid, lauric acid, myristic acid, palmitic acid, margaric acid, stearic acid, arachidic acid, caproleic acid, undecylenic acid, myristoleic acid, palmitoleic acid, oleic acid, or hydroxydecanoic acid. For the C-chain length of the residue R 2 The information given above for the C-chain length of the fatty acid residue is analogously considered preferred.

[0033] "RO" in this case can be a C5 or C6 sugar or a sugar alcohol derived therefrom, the surfactant of the formula ROR 2can be formed via a conventional ether bond between the two components. To facilitate this, the OH group in the fatty acid alcohol can first be modified into a leaving group, such as a toluenesulfonate group or a halogen such as Br or I, and the appropriately modified fatty acid alcohol can then be reacted with the sugar or sugar alcohol under basic conditions. If "RO" is a sugar, the non-ionic ether surfactant can also be an "alkyl glycoside", in which the fatty acid alcohol is bonded to the sugar via a glycosidic bond. The bond thus formed points in the a-position to the COR 2 bond another oxygen atom.

[0034] In addition, if "RO" is a sugar, the residue R 2a fatty acid alcohol that, in addition to the alcohol function, has an acid group. Such residues are preferably derived from α- or β-hydroxycarboxylic acids; a particularly preferred hydroxycarboxylic acid in this context is, for example, β-hydroxydecanoic acid. In corresponding alkyl glycosides, the sugar is linked to the alcohol residue of the hydroxycarboxylic acid via a glycosidic bond; in this case, the alkyl group of the hydroxycarboxylic acid, which is opposite to the carboxylic acid function, forms a nonpolar molecular moiety, while the carboxylic acid function is assigned to the polar molecular moiety.

[0035] In yet another preferred embodiment, the specified monophasic gel contains a non-ionic surfactant of the formula RC(O)OR 2 , where R 2the residue of an unbranched or branched saturated or unsaturated fatty acid alcohol having a C chain length in the range of 10 to 20, which is preferably obtainable by reduction from capric acid, lauric acid, myristic acid, palmitic acid, margaric acid, stearic acid, arachidic acid, caproleic acid, undecylenic acid, myristoleic acid, palmitoleic acid, oleic acid, or hydroxydecanoic acid.

[0036] In this case, the residue RC(O) denotes the residue of a sugar acid that is linked by esterification to the unbranched or branched saturated or unsaturated fatty acid alcohol. Sugar acids that can be used in the context of the invention specified here include, for example, glucuronic acid, galacturonic acid, xyluronic acid, gluconic acid, galactonic acid, mannosugar acid, or xylonic acid, preferably in the respective D-form, and preferably D-gluconic acid, D-glucuronic acid, and D-mannosugar acid.

[0037] In general, it is preferred for the specified non-ionic surfactants if the C5 or C6 sugar, sugar acid, and sugar alcohol contained are selected from the group comprising xylose, arabinose, glucose, galactose, mannose, sorbose, fructose, glucuronic acid, xylitol, mannitol, and sorbitol. The specified sugars, sugar alcohols, and sugar acids are characterized by high natural availability and correspondingly low costs.

[0038] In a particularly preferred embodiment, the non-ionic surfactant is either a non-ionic ester surfactant of the formula ROR 2 or RC(O)OR 2 . In another particularly preferred embodiment, the non-ionic surfactant is a non-ionic ester surfactant of the formula ROCCOjR 1 or RC(O)OR 2 or a non-ionic ether surfactant of the formula ROR 2 , where RO denotes the residue of a C5 sugar or C5 sugar alcohol or C5 sugar acid.

[0039] It has already been pointed out above that the non-ionic surfactants used in the gels according to the invention should be designed in such a way that an OH group to C atom ratio in the range of 1:3 to 1:8 is established. The "number of OH groups" refers to the number of free OH groups in the non-ionic surfactant, i.e. if, for example, the non-ionic surfactant is formed from xylitol (5-OH groups) and lauric acid, one of the OH groups of the xylitol is bound as an ester, so that the resulting non-ionic surfactant has only 4 OH groups. A corresponding xylose-based non-ionic surfactant has 3 free OH groups because, in contrast to xylitol, xylose contains only 4 OH groups (and one aldehyde group) in its free form. Any CO2H present in the surfactant is regarded as OH groups. The number of C atoms is determined as the sum of the C atoms in the sugar, sugar alcohol or sugar acid and the number of C atoms in the residue R 1or R 2 A particularly preferred ratio can be specified as a range from 1:3.2 to 1:7, more preferably 1:3.5 to 1:6 and even more preferably 1:3.7 to 1:5.

[0040] In the investigations underlying this invention, it was found that at least some gels according to the invention have thixotropic properties. In a preferred embodiment, the gel according to the invention is therefore a gel with thixotropic properties, preferably with a structural recovery after 10 s (viscosity 10 s after termination of a shear load, which is higher than the viscosity at the shear load by the amount of x% of the difference between the viscosity before the shear load and the viscosity at the shear load) of at least 10%, and preferably at least 20%. In another embodiment, the thixotropic gel has a structural recovery after 60 s of at least 20%, preferably at least 30%, and even more preferably at least 50%.

[0041] Another important parameter of the non-ionic surfactant that influences the properties of the monophasic gel or thixotropic mixture is the HLB value of the non-ionic surfactant. Non-ionic surfactants preferably used in the specified gels and thixotropic mixtures have an HLB value in the range of approximately 6 to 14, and more preferably approximately 7 to 12. HLB values ​​for the non-ionic surfactants are calculated according to Griffin using the following formula:

[0042] ML HLB=20x(l - )

[0043] M where M is the molecular weight of the non-ionic surfactant and M L is the molecular weight of the lipophilic moiety. For ROC(O)R 1 the lipophilic part of the molecule is the alkyl chain of the fatty acid residue R 1from the C-atom from which the fatty acid contains no OH groups (i.e. from the first C-atom after the acid function in non-hydroxylated fatty acids and from the first C-atom after the CHOH group in hydroxylated fatty acids). For fatty acid alcohols in RC(O)OR 2 and ROR 2 the lipophilic molecular part is the alkyl chain from CI of the fatty acid alcohol residue “R 2 ", or if the fatty acid alcohol contains further OH groups, from the first C atom after the CHOH group.

[0044] With regard to the amount of non-ionic surfactant to be incorporated into the non-polar liquid to form the gel, the present invention is not subject to any relevant restrictions, although, not least for economic reasons, the liquid is generally present in a relevant excess to the non-ionic surfactant. In most cases, the non-ionic surfactant makes up no more than 10 wt.%, based on the total amount of non-ionic surfactant and non-polar liquid, of the monophasic gel. It is further preferred if the non-ionic surfactant makes up a proportion of 0.05 to 7 wt.%, preferably 0.1 to 6 wt.%, further preferably 0.25 to 5 wt.%, and even more preferably 0.5 to 3 wt.% of the monophasic gel or the thixotropic mixture.

[0045] The non-polar liquid in the monophasic gel according to the invention is preferably present as edible oil, vegetable oil, fish oil, insect fat, tallow, kerosene, isopropyl palmitate, isopropyl myristate, pentane, hexane, heptane, guanine, isooctane, decane, dibutyl ether, ethyl acetate, cyclohexane, cyclopentane, cyclooctane, isopropanol, terpenes, glycol ether, ethyl laurate, ethyl myristate, ethyl palmitate. In one embodiment, the non-polar liquid can also be present in the form of dimethyl sulfoxide. In a particularly preferred embodiment, the non-polar liquid in the monophasic gel is a renewable oil or fat, such as edible oil, vegetable oil, fish oil, or insect fat, as well as microbial oils.

[0046] Non-polar liquids in the form of alkanes, such as pentane, hexane, heptane, getane, iso-octane, decane, or even terpenes or glycol ethers are particularly relevant in the context of paints and varnishes, while oils or esters of oleic acids with C2 to C6 and especially C2 to C4 alcohols also find applications in areas where contact with the surface of the human body is intended, for example in cosmetic products or in the food sector.

[0047] In the monophasic gels according to the invention, the nonpolar liquid makes up the largest proportion of the composition, usually more than 80% by weight of the composition. In one embodiment, the nonpolar liquid makes up a proportion in the range of 80 to 99.9% by weight, in a preferred embodiment 90 to 99.75% by weight, and even more preferably 95 to 99.5% by weight.

[0048] In addition to the non-polar liquid and the non-ionic surfactant, the monophasic gel may contain other ingredients depending on the intended use of the gel. Substances that may be used include, but are not limited to, preservatives, dermatological agents, antioxidants, pigments or other colorants, etc.

[0049] Other advantageous active ingredients, particularly for cosmetic applications, are natural active ingredients and / or their derivatives, such as alpha-lipoic acid, phytoene, D-biotin, coenzyme Q10, alpha-glucosylrutin, carnitine, carnosine, natural and / or synthetic isoflavonoids, creatine, taurine and / or ß-alanine.

[0050] However, other pharmaceutically or dermatologically active substances, such as skin-soothing and skin-care substances, can also be incorporated into the non-polar gels according to the invention. These include, for example, panthenol, allantoin, tannin, antihistamines, anti-inflammatory drugs, glucocorticoids (e.g., hydrocortisone), as well as plant-based active ingredients such as azulene and bisabolol, glycyrrhizin, witch hazel, and plant extracts such as chamomile, aloe vera, witch hazel, and licorice root.

[0051] The amount of the aforementioned active ingredients, antioxidants, etc. (one or more compounds) in the non-polar gels is preferably 0.001 to 10 wt.%, particularly preferably 0.05 - 8 wt.%, in particular 1 - 5 wt.%, based on the total weight of the monophasic gel.

[0052] The rheological properties of the monophasic gel according to the invention are preferably adjusted such that the gel has a yield point after 24 hours with a shear stress in the range of more than 0.1 Pa, preferably in the range of 0.1 to 20 Pa. Alternatively or additionally, it is preferred if the gel has a storage modulus (determined at the yield point and in the linear viscoelastic range) of at least 5 Pa, and preferably in the range of 8 Pa to 500 Pa. The shear and storage moduli in question are determined in the context of the invention specified here using a shear rheometer (MCR 702e MultiDrive Rheometer from Anton Paar), as specified in the examples section.

[0053] The rheological properties of the thixotropic mixture according to the invention are preferably adjusted to achieve a structural recovery, as described in the examples, of at least 55%, preferably at least 60%, and more preferably at least 70%. Thixotropic properties are determined in the context of the invention specified here using a shear rheometer (MCR 702e MultiDrive Rheometer from Anton Paar), as specified in the examples.

[0054] In a further aspect, the present invention relates to a process for producing a monophasic gel as stated above, the process comprising the steps of i) providing a mixture of non-polar liquid and at least one non-ionic ester or ether surfactant as stated above; ii) heating the mixture, preferably to a temperature in the range of 30°C and 120°C, more preferably 40 to 100°C, for a period of time until a homogeneous mixture has formed; iii) allowing the mixture to rest to form a monophasic gel.

[0055] In the process, the mixture in step ii) is preferably heated for a period of 5 minutes to 2 hours, and preferably 10 minutes to 60 minutes. For this purpose, it may be advantageous if the formation of the homogeneous mixture in step ii) is assisted by a mechanical treatment selected from the group comprising shaking, stirring, grinding, in particular in a ball mill, ultrasound, and vibration.

[0056] The specification "allowing to stand" in the context of the process specified here means "allowing the mixture to stand without stirring or other movement". In one embodiment, the standing takes place under ambient conditions (20 to 25°C). In another embodiment, the standing takes place at a reduced temperature (e.g., 0 to 8°C and in particular 3 to 6°C). For such a treatment, it has been shown that, compared to standing under ambient conditions, gels with even further improved mechanical properties, or thixotropic mixtures with a higher structural recovery, can be produced.

[0057] In yet another aspect, the present invention relates to the use of a monophasic gel, as specified above, for texturizing food products, texturizing cosmetic products, pharmaceutical formulations, membranes, phase-transfer materials, evaporation barriers, paints and varnishes, 3D printing, or anti-fouling surface coatings. For an evaporation barrier, for example, a thin layer of a gel according to the invention can be applied to the surface of a water-containing substrate or a water-containing mixture in order to minimize water evaporation losses.

[0058] For paints and varnishes, thixotropic viscosity behavior is particularly desirable. For example, varnishes based on nonpolar solvents exhibit dynamic viscosities of approximately 3000 mPas.

[0059] Cosmetic products in which a gel according to the invention can be used include, for example, after-sun care gels, baby oil gels, body lotions, facial care products, gel lotions, creams, lip balms, lip gloss, shower gels, or tanning gels. Such a cosmetic product preferably has a yield point in the range of 0.5 to about 50 Pa, and preferably 0.5 to 30 Pa.

[0060] When texturing food products, the food product can be formed in one embodiment as a fat substitute, which preferably has a linear viscoelastic range of 100 to 10,000 Pa.

[0061] In the following, the present invention is illustrated in more detail using some embodiments, which, however, should not be construed in any way as limiting the scope of the claims or the application underlying this application:

[0062] Examples:

[0063] Production of non-ionic surfactants:

[0064] General procedure for the preparation of esters as non-ionic surfactants

[0065] The esters (e.g., sorbitol monolaurate) were produced enzymatically. Equimolar amounts of sugar / sugar alcohol and fatty acid were stirred with a lipase (e.g., Candida rugosa lipase or Candida antarctica lipase B) in 2-methyl-2-butanol in a stirred-tank reactor at 50°C for 24 hours. The reaction mixture was then filtered, the solvent was evaporated, and the resulting product was purified by silica gel chromatography.

[0066] 2) General procedure for the preparation of ethers as non-ionic surfactants

[0067] The ether compounds used for the following tests were obtained conventionally by reacting the sugar alcohols with fatty acid alcohols modified with leaving groups (where, for example, tosylate or a halide derived from the alcohol is used as the leaving group). The workup and purification of this compound was carried out analogously to the description for the preparation of the ester surfactants. The preparation of sugar glycosides from the sugars and sugar alcohols was carried out enzymatically by reacting the sugar with a ß-glucosidase and the fatty acid alcohol in a deep eutectic solvent, as described in Delavault, A. https: / / onlinelibrary.wiley.com / doi / 10.1002 / cite.202100150. The workup and purification were carried out analogously to the description for the preparation of the ester surfactants.

[0068] The surfactants octylxyloside, decylxyloside, laurylxyloside, myristylxyloside and carboxy-decylxyloside were purchased from Glycosurf (USA).

[0069] 3) Investigation of the non-ionic surfactants with regard to gel-forming ability and properties of the produced gels. The non-ionic surfactants were weighed and mixed with a non-polar liquid, adjusting the concentration of non-ionic surfactant to various concentrations. The resulting mixtures were heated to a temperature between 30 and 120°C to obtain a homogeneous phase. The mixtures were then allowed to stand for 1 to 24 hours at a temperature of 20 to 25°C, during which time a gel formed.

[0070] The resulting samples were subjected to rheological measurements. Shear and storage moduli were determined using a shear rheometer (MCR 702e MultiDrive Rheometer from Anton Paar). The measurements were carried out at a constant angular frequency of co = 10 rad / s with an oscillating shear strain with a logarithmic distribution between 0.05% and 15% shear strain. A PP25 measuring plate with a diameter of 25 mm and a temperature of 20 °C was used for the measurements.

[0071] The thixotropic properties were also determined using a shear rheometer (MCR 702e MultiDrive Rheometer from Anton Paar). For the measurement, the structural recovery was determined using a 3-interval thixotrophy test (3-ITT). For this purpose, the viscosity was measured in the first step at a low shear rate of 0.1 s -1over 10 measuring points with a measuring point duration of 5 s (viscosity step 1). In the second step, a shear of 100 s was used for the viscosity measurement. -1 over 10 measurement points with a measurement point duration of 1 s (viscosity step 2). After this interval, 4 s at 0 s -1 Shear was measured to avoid an interference signal in step 3. In step 3, the viscosity was measured at low shear of 0.1 s -1 Over 1000 measurement points with a measurement point duration of 0.5 s were determined. A PP25 measuring plate with a diameter of 25 mm and a temperature of 20 °C was used for the measurements.

[0072] The compositions of the tested mixtures of non-ionic surfactants with the respective non-polar solvents (vegetable oil, isopropyl palmitate, or n-pentane) are listed in the following tables. These also show the parameters relevant to the yield point, namely shear stress and storage modulus, as well as the linear viscoelastic range. Table 1: Gels of non-ionic ester and ether surfactants and vegetable oil.

[0073] 1 = Glycoside (alcohol bound to the Cl of the sugar)

[0074] Table 2: Gels made from non-ionic ester and ether surfactants and isopropyl palmitate or pentane

[0075] 1 = Glycoside (alcohol bound to the Cl of the sugar)

[0076] Table 3: Influence of cooling and C-chain length of fatty acid alcohols

[0077] 1 = Glycoside (alcohol bound to the Cl of the sugar)

[0078] Table 4: Determination of thixotropic properties for the gels

[0079] Table 1 shows that, for the same amount of non-ionic surfactant added to the non-polar liquid, the best gel strengths are achieved with surfactants with an OH / C atom ratio of approximately 4. It was also observed that the gel strengths depend on the amount of surfactant used, with higher strengths being achieved at higher amounts (results not shown). In Table 1, the storage modulus properties for all non-ionic surfactants based on C5 sugars and C5 sugar alcohols were better than for the analogous system based on the C6 sugar alcohol sorbitol. The samples also showed a high viscoelastic range, i.e., a range in which the sample structure is maintained before deformation (e.g., due to flow) occurs (i.e., gels with a high viscoelastic range are still stable at higher loads on the gel).

[0080] An improved viscoelastic range can, for example, improve the bite resistance / mouth feel of food, the strength of a color, the paste stability of sunscreen (to improve dosing), or the dimensional stability in 3D printing.

[0081] In Table 2, this result was confirmed for the gelation of isopropyl palmitate with non-ionic surfactants based on esters and ethers.

[0082] Table 3 shows that a cooling step increases the strength and elasticity of the gels. Yield stress and material elasticity can therefore be influenced by using a cooling step. Furthermore, Table 3 shows that for xylose, a higher viscoelastic range and higher shear stress and storage modulus values ​​are obtained at higher C / OH atomic ratios.

[0083] Table 4 shows viscoelastic behavior for all gels investigated.

Claims

Claims 1. Monophasic gel comprising a non-polar liquid and a non-ionic surfactant selected from ester surfactants of the formula ROC(O)R 1 or RC(O)OR 2 or ether surfactants of the formula ROR 2 , where RO is the residue of a sugar or sugar alcohol, RC(O)O is a sugar acid, OC(O)R 1 a fatty acid residue and R 2 a fatty acid alcohol residue, wherein the sugar is a C5 or C6 sugar, the sugar acid and the sugar alcohol are a sugar acid or a sugar alcohol derived therefrom, and the fatty acid or the fatty acid alcohol has a C chain length of at least 6 and wherein the non-ionic surfactant has an OH groups to C atom ratio in the range from 1:3 to 1:

8.

2. Monophasic gel according to claim 1, characterized in that the gel contains a non-ionic ester surfactant of the formula ROC(O)R 1 contains, where R 1the residue of an unbranched or branched saturated or unsaturated fatty acid having a C chain length in the range of 8 to 20, which is preferably selected from caprylic acid, pelargonic acid, capric acid, lauric acid, myristic acid, palmitic acid, margaric acid, stearic acid, arachidic acid, caproleic acid, undecylenic acid, myristoleic acid, palmitoleic acid and oleic acid or the residue of a branched fatty acid having one or more methyl side chains or the residue of a ß-hydroxy fatty acid.

3. Monophasic gel according to claim 1, characterized in that the gel contains a non-ionic ether surfactant of the formula ROR 2 contains, where R 2the rest unbranched or branched saturated or unsaturated fatty acid alcohols having a C chain length in the range from 10 to 20, preferably selected from fatty acid alcohols derived from capric acid, lauric acid, myristic acid, palmitic acid, margaric acid, stearic acid, arachidic acid, caproleic acid, undecylenic acid, myristoleic acid, palmitoleic acid, oleic acid, hydroxydecanoic acid.

4. Monophasic gel according to claim 1, characterized in that the gel contains a non-ionic ester surfactant of the formula RC(O)OR 2 contains, where R 2the residue of an unbranched or branched saturated or unsaturated fatty acid alcohol having a C chain length in the range from 10 to 20, which is preferably obtainable by reduction from capric acid, lauric acid, myristic acid, palmitic acid, margaric acid, stearic acid, arachidic acid, caproleic acid, undecylenic acid, myristoleic acid, palmitoleic acid, oleic acid, or hydroxydecanoic acid.

5. Monophasic gel according to at least one of the preceding claims, characterized in that the gel has thixotropic properties.

6. Monophasic gel according to at least one of the preceding claims, characterized in that the surfactant in the non-ionic ester of the formula ROC(O)R 1 or RC(O)OR 2 or ether surfactant of the formula ROR 2contained C5 or C6 sugar, the sugar acid and the sugar alcohol is selected from the group comprising xylose, arabinose, rhamnose, glucose, galactose, mannose, sorbose, fructose, xyluronic acid, glucuronic acid, galacturonic acid, xylitol, arabitol, mannitol, sorbitol, gluconic acid, galactonic acid and xylonic acid.

7. Monophasic gel according to at least one of the preceding claims, characterized in that the non-ionic ester or ether surfactant has an HLB value in the range of 6 to 14, preferably between 7 and 12.

8. Monophasic gel according to at least one of the preceding claims, characterized in that the non-ionic ester or ether surfactant makes up a proportion of 0.05 to 7 wt.%, preferably 0.25 to 5 wt.% and more preferably 0.5 to 3 wt.% of the monophasic gel.

9. Monophasic gel according to at least one of the preceding claims, characterized in that the non-polar liquid is selected from the group comprising edible oils, vegetable oils, fish oils, insect fats, tallow, kerosene, isopropyl palmitate, isopropyl myristate, pentane, hexane, gentian, iso-octane, decane, dibutyl ether, ethyl acetate, cyclohexane, cyclopentane, cyclooctane, isopropanol, ethyl laurate, ethyl myristate, ethyl palmitate, terpenes, glycol ethers and dimethyl sulfoxide.

10. Monophasic gel according to at least one of the preceding claims, characterized in that the non-polar liquid makes up a proportion of 80 to 99.9 wt.%, preferably 90 to 99.75 wt.% and more preferably 95 to 99.53 wt.% of the monophasic gel.

11. Monophasic gel according to at least one of the preceding claims, characterized in that the gel has a yield point after 24 hours with a shear stress in the range of more than 0.1 Pa, preferably in the range of 0.1 to 20 Pa and a storage modulus of at least 5 Pa, preferably in the range of 8 Pa to 500 Pa.

12. A process for producing a monophasic gel according to any one of claims 1 to 11, comprising the steps of i) providing a mixture of non-polar liquid and at least one non-ionic ester or ether surfactant as specified in claim 1; ii) heating the mixture, preferably to a temperature in the range of 30°C to 120°C, more preferably 40 to 100°C, for a period of time until a homogeneous mixture has formed; iii) allowing the mixture to rest to form a monophasic gel.

13. The process according to claim 12, wherein the mixture is heated to form a homogeneous mixture in step ii) for a period of 5 minutes to 2 hours, and preferably 10 minutes to 60 minutes.

14. The method according to claim 12 or 13, wherein the formation of the homogeneous mixture in step ii) is assisted by a mechanical treatment selected from the group comprising shaking, stirring, ultrasound, and vibration.

15. Use of a monophasic gel according to any one of claims 1 to 11 for texturizing food products, texturizing cosmetic products, pharmaceutical formulations, membranes, phase transfer materials, or anti-fouling surface coatings, evaporation barriers, paints and varnishes, 3D printing.

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