Polyglycerol partial esters, preparation and use thereof

The present invention relates to polyglycerol partial esters of a specific composition which are capable of solubilizing very hydrophobic, oil-soluble substances in aqueous solution. The present invention also relates to the preparation and use of these polyglycol ether-free solubilizers in cosmetic formulations.

Non-ionic surfactants having hardly any foam-generating effect are usually employed as solubilizers of oil-soluble, hydrophobic substances in water.

Polyethoxylated triglycerides, particularly based on castor oil, e.g., PEG-40 hydrogenated castor oil, are used as standard solubilizers. The latter is virtually able to clearly solubilize oil-soluble substances of a wide variety of structures and hydrophobicity in water. Polyglycol ether-free polyglycerol partial esters have also been used for some years as alternative solubilizers.

The disadvantage of all polyglycerol partial esters available to date is that their use as solubilizers of oil-soluble substances in water cannot cover as wide a substance spectrum as the previously mentioned polyethoxylated triglycerides. The polyglycerol esters are thus mainly suitable for solubilizing “small” molecules such as, for example, short-chain terpenes. In contrast, oils based on fatty acids and triglycerides of long-chain fatty acids such as jojoba oil, almond oil, soybean oil or avocado oil cannot, to date. be clearly solubilized in water using the commercial products based on polyglycerol partial esters.

JP 2008-119568 describes the use of polyglycerol partial esters as solubilizers of oils in which the polyglycerol partial esters are based on mixtures of saturated fatty acids having 8 to 22 carbon atoms and unsaturated fatty acids having 16 to 22 carbon atoms, wherein the molar ratio of saturated to unsaturated fatty acids is in a range of 0.2 to 0.8 to 0.8 to 0.2. In addition, polyglycerol partial esters of polyricinoleic acid may be admixed with this polyglycerol partial ester.

One object of the present invention is to provide solubilizers based on polyglycerol partial esters which, in contrast to the products available on the market to date, are able to clearly solubilize, in particular, hydrophobic, oil-soluble substances, such as long-chain triglycerides, in water and to solubilize cosmetic formulations.

It has been surprisingly found that the polyglycerol partial esters described in the present invention are able to rectify the disadvantages of the prior art and thus enable to achieve the object of the present invention mentioned above.

In one embodiment of the present invention, polyglycerol partial esters are provided which are prepared from polyglycerol by esterification of a specifically selected fatty acid mixture. The products are able to clearly solubilize very hydrophobic, oil-soluble substances, such as long-chain triglycerides, in water or to solubilize a cosmetic formulation. The preparation and use of these solubilizers in cosmetic formulations is also part of this invention.

An advantage of the present invention is that the polyglycerol partial esters described herein are able to clearly solubilize strongly hydrophobic, oil-soluble substances, such as long-chain triglycerides, in water or to solubilize a cosmetic formulation, which is not possible using the products based on polyglycerol esters available to date.

A further advantage of the present invention is that the polyglycerol partial esters described herein may be prepared exclusively from renewable raw materials in contrast to polyethoxylated triglycerides.

A yet further advantage of the present invention is that the polyglycerol partial esters described herein are liquid, and thus readily processable, in contrast to polyethoxylated triglycerides.

An even further advantage of the present invention compared to the polyethoxylated triglycerides is that the polyglyceryl esters described herein lead to particularly clear dispersions of the oil in the water, and also no cloudiness occurs on storage, in contrast to polyethoxylated triglycerides (PEG-40 hydrogenated castor oil).

Another advantage of the present invention is that formulations may be provided that are polyglycol ether-free.

A further advantage of the polyglycerol partial esters described herein is that the polyglycerol partial esters of the present invention can produce a pleasant skin sensation in cosmetic formulations.

Another advantage of the polyglycerol partial esters described herein is that the polyglycerol partial esters of the present invention exhibit only a very low foam formation on stirring in water.

A further advantage is that the polyglycerol partial esters described herein show only a very low effect on foamability and foam quantity in surfactant formulations, but the foam creaminess can, however, improve.

Another advantage is that the polyglycerol partial esters described in the present invention may lead to attenuation of the skin irritancy in surfactant formulations.

A further advantage of the polyglycerol partial esters described herein is that the polyglycerol partial esters of the present invention can have a stabilizing effect in emulsions.

A further advantage of the inventive products is that they are relatively stable to oxidation and more stable with respect to color, odor and appearance.

The present invention provides polyglycerol partial esters of general formula I

where

n=2 to 16, preferably 4 to 14, particularly preferably 5 to 11,

R 1 , R 2 , R 3 =independently of one another, identical or different, selected from H, R 4 and

R 5 , where

R 4 =saturated or unsaturated acyl residue having 6-22 carbon atoms, preferably 8-18 carbon atoms, comprising no hydroxyl groups,

R 5 =saturated or unsaturated acyl residue having 6-22 carbon atoms, preferably 14-22 carbon atoms, comprising at least one hydroxyl group or an acyl residue of an oligomer of saturated or unsaturated acyl residues having 6-22 carbon atoms, preferably 14-22 carbon atoms, comprising at least one hydroxyl group, in which the acyl residue of the oligomer preferably has 26 to 66 carbon atoms,

characterized in that the molar ratio of the acyl residues R 4 to R 5 is in a range of 95:5 to 5:95, preferably 85:15 to 15:85, particularly preferably 85:15 to 50:50.

A person skilled in the art is aware that the polyglycerol base skeleton present in general formula I, owing to its polymeric property, represents a random mixture of various compounds. Polyglycerol may have formed ether bonds between two primary, one primary and one secondary and also two secondary positions of the glycerol monomers. For this reason, the polyglycerol base skeleton does not usually consist exclusively of linearly linked glycerol units, but may also comprise branches and rings. For details see, e.g., “ Original synthesis of linear, branched and cyclic oligoglycerol standards ”, Cassel et al., J Org. Chem. 2001, 875-896.

Structures of this kind are covered in this respect in the simplified, general formula I.

From the term “the molar ratio of the acyl residues R 4 to R 5 is in a range of 95:5 to 5:95”, it is clear that residues R 4 and R 5 are present in the polyglycerol partial esters according to the invention.

Preferred polyglycerol partial esters according to the invention are characterized in that they comprise structures of general formula 1) each having at the same time at least one R 4 residue and one R 5 residue.

The acyl residues R 4 and R 5 can be randomly attached to the polyglycerol base skeleton both via primary and via secondary hydroxyl groups.

All conditions such as, for example, pressure and temperature, if not stated otherwise, are standard conditions (20° C., 1 bar). Percentages are indicated, if not described otherwise, in mass percent.

The degree of polymerisation ‘n’ can thus be determined, whereby the hydroxyl number of the polyglycerol used for the synthesis of the inventive ester is determined, in which the mean degree of polymerisation n is related to the hydroxyl number of the polyglycerol on which it is based via the following equation:

n = 2000 · M ⁡ ( KOH ) OHZ - M ⁡ ( Water ) [ [ M ⁡ ( Glycerol ) - M ⁡ ( Water ) ] - 1000 · M ⁡ ( KOH ) OHZ ]

where M=molar mass; OHZ=hydroxyl number of the free polyglycerol.

Alternatively, the degree of polymerisation ‘n’ can also be determined by determining the hydroxyl number of the polyglycerol obtained after complete ester hydrolysis.

Suitable methods for determining the hydroxyl number are particularly those according to DGF C-V 17 a (53), Ph. Eur. 2.5.3 Method A and DIN 53240.

The acyl residues R 4 and R 5 are preferably acyl residues of fatty acids. R 4 and R 5 may also represent mixtures of such acyl residues, particularly technical mixtures such as, in the case of R 4 , coconut fatty acid cuts.

For R 4 , it is with particular preference that at least 50 mol %, preferably at least 75 mol %, of the R 4 acyl residues are selected from capryloyl, caproyl and lauroyl residues, based on all R 4 residues in the polyglycerol partial ester.

R 5 is particularly preferably selected from ricinoyl and hydroxystearoyl residues, their oligomers and mixtures thereof, particularly preferably at least 90 mol % of the R 5 acyl residues comprise ricinoyl residues or a mixture of ricinoyl and hydroxystearoyl residues, based on all R 5 residues in the polyglycerol partial ester, in which it is preferred that the mixture of ricinoyl and hydroxystearoyl residues has a molar ratio of ricinoyl to hydroxystearoyl residues in a range of 100 to 0.1 to 50 to 50.

As an alternative, R 5 is preferably selected from ricinoyl residues.

Preferred polyglycerol partial esters according to the invention are characterized in that the weight ratio of the polyglyceryl residue to the sum total of the acyl residues R 4 and R 5 is 85:15 to 55:45, preferably 80:20 to 60:40, particularly preferably 75:25 to 65:35.

Preferred polyglycerol partial esters according to the invention are further characterized in that the molar ratio of saturated to unsaturated acyl residues in the sum total of all R 4 and R 5 residues is 99:1-1:99, preferably 95:5-50:50, particularly preferably 90:10-60:40.

The polyglycerol partial esters of the present invention can be prepared by classical esterification and transesterification methods, preferably by the inventive method described hereinafter.

The present invention further relates to a method for preparing polyglycerol partial esters comprising the method steps of:

A) providing a polyglycerol having a mean degree of polymerisation n=2 to 16, preferably 4-14, particularly preferably 5-11, B) acylation of some of the hydroxyl groups of the polyglycerol with at least one first carboxylic acid derivative of one or more first, saturated or unsaturated carboxylic acids having 6-22 carbon atoms, preferably 8-18 carbon atoms, comprising no hydroxyl groups and at least one second carboxylic acid derivative of one or more second, saturated or unsaturated carboxylic acids having 6-22 carbon atoms, preferably 14-22 carbon atoms, comprising at least one hydroxyl group or an oligomer of the second carboxylic acid, wherein the oligomer preferably has 26 to 66 carbon atoms, in which the carboxylic acid derivatives are selected from carboxylic acids and carboxylic esters, wherein triglycerides are preferred as carboxylic esters in accordance with the invention, wherein the molar ratio of the acyl residues of the first carboxylic acid derivative used in method step B) to those of the second carboxylic acid derivative is in a range of 95:5 to 5:95, preferably 85:5 to 15:85, particularly preferably 85:15 to 50:50.

The carboxylic acid derivatives preferably used in the method according to the invention are fatty acid derivatives.

In the method according to the invention, therefore, in method step B)

at least one first carboxylic acid and at least one second carboxylic acid, at least one first carboxylic ester and at least one second carboxylic acid, at least one first carboxylic acid and at least one second carboxylic ester, at least one first carboxylic ester and at least one second carboxylic ester, at least one first carboxylic acid and at least one first carboxylic ester and at least one second carboxylic acid, at least one first carboxylic acid and at least one first carboxylic ester and at least one second carboxylic ester, at least one first carboxylic acid and at least one second carboxylic acid and at least one second carboxylic ester, at least one first carboxylic ester and at least one second carboxylic acid and at least one second carboxylic ester, or at least one first carboxylic acid and at least one first carboxylic ester and at least one second carboxylic acid and at least one second carboxylic ester, may be used.

A preferred method according to the invention is characterized in that at least 50 mol %, preferably at least 75 mol %, of the first carboxylic acids are selected from caprylic acid, capric acid and lauric acid, based on the acyl residues of all the first carboxylic acid derivatives.

It is preferred in accordance with the invention, in the method according to the invention, that at least 90 mol % of the second carboxylic acids are selected from ricinoleic acid and hydroxystearic acid, based on the acyl residues of all the second carboxylic acid derivatives.

A preferred method according to the invention is characterized in that at least 90 mol % of the second carboxylic acids comprise ricinoleic acid and/or hydroxystearic acid, wherein the second carboxylic acids preferably have a molar ratio of ricinoleic acid residues to hydroxystearic acid residues in a range of 100 to 0.1 to 50 to 50, based on the acyl residues of all the second carboxylic acid derivatives.

Alternatively, the second carboxylic acid derivative is preferably selected from ricinoleic acid or castor oil.

It is preferred, in the method according to the invention, that the weight ratio of the polyglycerol to the calculated sum total of the acyl residues of the first and second carboxylic acid derivatives used is 85:15 to 55:45, preferably 80:20 to 60:40, particularly preferably 75:25 to 65:35.

A preferred method according to the invention is characterized in that the molar ratio of the acyl residues of saturated to those of the unsaturated carboxylic acid derivatives used in method step B) is 99:1-1:99, preferably 95:5-50:50, particularly preferably 90:10-60:40.

The present invention furthermore relates to polyglycerol partial esters, obtainable by the method according to the invention, wherein the preferred partial esters according to the invention are those which are obtainable by the preferred method according to the invention.

The present invention further relates to formulations, particularly cosmetic and pharmaceutical formulations, wherein particular preference is given to cosmetic formulations which comprise at least one polyglycerol partial ester according to the invention and/or at least one polyglycerol partial ester obtainable by the method according to the invention.

Particular preference is given to formulations which are essentially polyglycol ether-free and essentially free of alkoxylated compounds. The term “essentially free of alkoxylated compounds” and “essentially polyglycol ether-free”, in connection with the present invention, are understood to mean that the formulations have no notable amounts of alkoxylated compounds or compounds comprising polyglycol ethers which exert a surface-active effect. This is particularly understood to mean that these compounds are present in amounts of less than 1% by weight, preferably less than 0.1% by weight, particularly preferably less than 0.01% by weight, based on the total formulation, in particular no detectable amounts.

The polyglycerol partial esters of the present invention can be used advantageously for preparing care and cleaning formulations, particularly for skin and skin appendages, such as liquid soaps, shower gels, oil baths, make-up removers or shampoos, shower gels, foam baths, liquid soaps, hair shampoos, 2-in-1 shampoos, hair conditioners, permanent wave fixing solutions, hair colouring shampoos, hair setting compositions, hair treatments, hair arranging compositions, hair styling compositions, blow-drying lotions, setting foams, hair treatments, leave-in conditioners, hair smoothing compositions, shine improving compositions and compositions for colouring the hair. The present invention therefore also relates to such uses.

The present invention thus also provides care and cleaning formulations, in particular for skin and skin appendages, comprising polyglycerol partial esters according to the invention.

The term “care formulation” is herein understood to mean a formulation which satisfies the purpose of restoring an object to its original form, of reducing or avoiding the effects of external influences (e.g., time, light, temperature, pressure, soiling, chemical reaction with other reactive compounds that come into contact with the object) such as ageing, soiling, material fatigue, bleaching or even of improving desired positive properties of the object. For the last point, mention may be made for example of a shine of the object under consideration.

Cosmetic care and cleaning formulations according to the invention can, for example, comprise at least one additional component selected from the group of:

emollients, emulsifiers, thickeners/viscosity regulators/stabilizers, antioxidants, hydrotropes (or polyols), solids and fillers, pearlescence additives, deodorant and antiperspirant active ingredients, insect repellents, self-tanning agents, preservatives, conditioners, perfumes, dyes, cosmetic active ingredients, care additives, superfatting agents, solvents.

Substances which can be used as exemplary representatives of the individual groups are known to a person skilled in the art and can be found, for example, in EP2273966A1. This patent application is herewith incorporated as reference and thus forms part of the disclosure.

As regards to further optional components and the amounts of these components used, reference is made expressly to the relevant handbooks known to a person skilled in the art, e.g., K. Schrader, “Grundlagen and Rezepturen der Kosmetika [Fundamentals and Formulations of Cosmetics]”, 2nd edition, pages 329 to 341, Hüthig Buch Verlag Heidelberg.

The amounts of the particular additives are governed by the intended use. Typical guide formulations for the respective applications are known prior art and are contained for example in the brochures of the manufacturers of the particular basic materials and active ingredients. These existing formulations can usually be adopted unchanged. If necessary, the desired modifications can, however, be undertaken without complication by means of simple experiments for the purposes of adaptation and optimization.

Preferred formulation according to the invention comprise preferred polyglycerol partial esters according to the invention as set out above or preferred polyglycerol partial esters according to the invention obtainable by the method according to the invention as set out above.

It is preferred if the formulation according to the invention additionally comprise at least one oil-soluble substance and water.

In the present invention, oil-soluble substances are understood to mean substances having a log P (logarithm of n-octanol/water partition coefficient, also known as log K OW ) of at least 2.

Preference is given to oil-soluble substances having a log P of at least 5. Particular preference is given to oil-soluble substances selected from the group comprising oils based on fatty acids, triglycerides of long-chain fatty acids, cosmetic ester oils, pure hydrocarbons such as jojoba oil, almond oil, soybean oil, avocado oil, olive oil, argan oil, rapeseed oil, sunflower oil, neem oil, caprylic/capric acid triglyceride, shea butter, decyl cocoate, isopropyl palmitate, myristyl myristate and isohexadecane.

Particularly preferred formulations according to the invention comprise 0.1% by weight to 40% by weight, preferably 0.3% by weight to 35% by weight, particularly preferably 0.5% by weight to 10% by weight, of polyglycerol partial ester according to the invention and/or polyglycerol partial ester obtainable by the method according to the invention,0.01% by weight to 40% by weight, preferably 0.1% by weight to 30% by weight, particularly preferably 0.2% by weight to 2% by weight, of oil-soluble substance and 10% by weight to 98% by weight, preferably 20% by weight to 95% by weight, particularly preferably 45% by weight to 90% by weight, of water.

The present invention also relates to the use of at least one polyglycerol partial ester according to the invention and/or at least one polyglycerol partial ester obtainable by the method according to the invention for solubilizing at least one oil-soluble substance in water, wherein it is preferable in accordance with the invention that preferred polyglycerol partial esters according to the invention as set out above or preferred polyglycerol partial esters according to the invention obtainable by the method according to the invention as set out above are used.

The examples listed below describe the present invention by way of example, without any intention of restricting the invention, the scope of application of which is apparent from the entirety of the description and the claims, to the embodiments specified in the examples.