A linear polyglycerol fatty acid ester and a cosmetic

Abstract

The application discloses a linear polyglycerol fatty acid ester and cosmetics, relates to the technical field of polyglycerol fatty acid esters, and the preparation raw material of the linear polyglycerol fatty acid ester comprises linear polyglycerol and fatty acid; the average polymerization degree of the linear polyglycerol is 3-40, the branching degree of the linear polyglycerol is less than 0.2, and the proportion of the number of primary hydroxyl groups in the linear polyglycerol in the number of all hydroxyl groups is greater than or equal to 90%; and the average esterification degree of the linear polyglycerol fatty acid ester is 0.5-3.0. The primary hydroxyl group proportion and the branching degree of the linear polyglycerol are controlled in a specific range, so that the linear polyglycerol fatty acid ester can achieve good emulsifying performance and solubilizing performance in cosmetics, and the use feeling of the cosmetics is good and the stability of the cosmetics is good.

Description

Technical Field

[0001] This invention relates to the field of polyglycerol fatty acid ester technology, and particularly to a linear polyglycerol fatty acid ester and cosmetics. Background Technology

[0002] Polyglycerol fatty acid esters, as nonionic surfactants, have high safety and biodegradability, and are therefore widely used as emulsifiers, solubilizers, dispersants, stabilizers, plasticizers, emollients and other ingredients in the food, cosmetics and pharmaceutical industries.

[0003] Currently, polyglycerol fatty acid esters are mainly prepared by esterification with fatty acids or their derivatives, using polyglycerol obtained from the high-temperature dehydration condensation reaction of glycerol or the ring-opening polymerization reaction of glycidyl glycerol as raw material. However, polyglycerol obtained by these methods is prone to contain 1,3-carbon bonds and 1,2-carbon bonds, and easily forms a branched nonlinear structure with primary and secondary hydroxyl groups distributed on the polyglycerol backbone.

[0004] When the types of hydroxyl groups on the polyglycerol backbone are not uniform, the difference in reactivity between primary and secondary hydroxyl groups during esterification with fatty acids makes it difficult to precisely control the introduction sites and quantities of fatty acids. This results in differences in the molecular structure of polyglycerol fatty acid esters even with the same average degree of esterification, leading to fluctuations in emulsification behavior, solubilization behavior, and the density and thickness of the adsorbed layer formed at the interface between batches. These structural fluctuations become a key obstacle to precisely controlling makeup removal power, rinseability, and post-wash skin feel (such as moisturizing or sticky sensation) in cleansing cosmetics. Summary of the Invention

[0005] The main objective of this invention is to propose a linear polyglycerol fatty acid ester and a cosmetic product, aiming to solve the problem of insufficient makeup removal effect of makeup removal products prepared from linear polyglycerol fatty acid esters in the prior art.

[0006] To achieve the above objectives, the present invention proposes a linear polyglycerol fatty acid ester, wherein the raw materials for preparing the linear polyglycerol fatty acid ester include linear polyglycerol and fatty acids; The linear polyglycerol has an average degree of polymerization of 3 to 40, a degree of branching of <0.2, and a primary hydroxyl group content of ≥90% of all hydroxyl groups. The linear polyglycerol fatty acid ester has an average degree of esterification of 0.5 to 3.0.

[0007] In one embodiment, the linear polyglycerol has an average degree of polymerization of 6 to 40; and / or, The degree of branching of the linear polyglycerol is ≤0.15; and / or, The linear polyglycerol contains primary hydroxyl groups accounting for 95% to 100% of all hydroxyl groups, and secondary hydroxyl groups accounting for ≤5% of all hydroxyl groups; and / or, The linear polyglycerol fatty acid ester has an average degree of esterification of 0.9 to 1.2.

[0008] The fatty acids include fatty acids with 6 to 24 carbon atoms.

[0009] In one embodiment, the fatty acid includes at least one selected from decanoic acid, lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, and isostearic acid.

[0010] This invention also provides a method for preparing linear polyglycerol fatty acid esters, wherein the linear polyglycerol fatty acid esters are prepared through the following steps: Provide linear polyglycerol; Under an inert atmosphere, the linear polyglycerol, catalyst, and fatty acid are mixed and subjected to an esterification reaction to obtain the linear polyglycerol fatty acid ester.

[0011] In one embodiment, the step of providing linear polyglycerol includes: Under an inert atmosphere, an initiator, an organic solvent, and ethoxyethyl glycidyl ether are mixed and polymerized at the polymerization temperature to obtain a reaction solution. The reaction solution was mixed with an aqueous hydrochloric acid solution to obtain an organic layer. The solvent in the organic layer was then removed to obtain an intermediate. The intermediate was mixed with an aqueous hydrochloric acid solution and subjected to a hydrolysis reaction to obtain the linear polyglycerol.

[0012] In one embodiment, the step of mixing the initiator, organic solvent, and ethoxyethyl glycidyl ether under an inert atmosphere and carrying out the polymerization reaction at the polymerization reaction temperature to obtain the reaction solution includes: The initiator includes tetrabutylammonium hydroxide, tetramethylammonium hydroxide, or benzyltriethylammonium hydroxide; and / or, The organic solvent includes tetrahydrofuran, N,N-dimethylformamide, or N-methyl-2-pyrrolidone; and / or The molar ratio of the initiator to the ethoxyethyl glycidyl ether is 1:0.8~1.2; and / or, The polymerization reaction temperature is 20~50℃; and / or, The polymerization reaction time is 3-5 hours.

[0013] In one embodiment, the step of mixing the intermediate with an aqueous hydrochloric acid solution and performing a hydrolysis reaction to obtain the linear polyglycerol includes: The concentration of the hydrochloric acid aqueous solution is 0.8~1.2 mol; and / or, The hydrolysis reaction is performed at a temperature of 40-45°C; and / or, The hydrolysis reaction takes 20-24 hours.

[0014] In one embodiment, the step of mixing the linear polyglycerol, catalyst, and fatty acid under an inert atmosphere to carry out an esterification reaction to obtain the linear polyglycerol fatty acid ester includes: The molar ratio of the linear polyglycerol to the fatty acid is 1:1 to 1:6; and / or, The catalyst includes sodium hydroxide or potassium hydroxide; and / or, The esterification reaction is carried out at a temperature of 160-180°C; and / or, The esterification reaction takes 3-5 hours.

[0015] The present invention also provides a cosmetic product comprising the aforementioned linear polyglycerol fatty acid ester or a linear polyglycerol fatty acid ester prepared by the aforementioned method for preparing linear polyglycerol fatty acid ester.

[0016] In one embodiment, the cosmetic includes at least one of cleansing cosmetics, emulsified creams, and solubilizing compositions.

[0017] In one embodiment, the cleansing cosmetic includes a makeup remover, wherein the linear polyglycerol fatty acid in the makeup remover comprises 1-30% by mass.

[0018] In one embodiment, the viscosity of the cosmetic product at 25°C is 100~5000 mPa·s.

[0019] In the technical solution of this invention, by controlling the proportion of primary hydroxyl groups and the degree of branching of linear polyglycerol within a specific range, the branching density and hydroxyl types of polyglycerol exhibit high consistency. This ensures that the linear polyglycerol fatty acid ester achieves good emulsifying and solubilizing properties in cosmetics, resulting in a better user experience and better stability. The linear polyglycerol fatty acid ester provided by this invention, when applied to makeup removal and cleansing, has a shorter compatibility time, is easy to rinse, and leaves less stickiness and tightness after rinsing. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0021] Figure 1 Five structures of polyglycerol; Figure 2 The image shows the 13C-NMR spectrum of polyglycerol in Example 1 of this invention. Figure 3 The image shows the 13C-NMR spectrum of polyglycerol in Example 2 of this invention. Figure 4 The image shows the 13C-NMR spectrum of polyglycerol in Example 3 of this invention. Figure 5 The image shows the 13C-NMR spectrum of polyglycerol in Example 4 of this invention. Figure 6 The image shows the 13C-NMR spectrum of polyglycerol in Comparative Example 1 of this invention. Figure 7 The image shows the 13C-NMR spectrum of polyglycerol in Comparative Example 2 of this invention. Figure 8 The image shows the 13C-NMR spectrum of polyglycerol in Comparative Example 3 of this invention.

[0022] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially. Furthermore, the meaning of "and / or" throughout the text includes three parallel solutions; for example, "A and / or B" includes solution A, or solution B, or a solution where both A and B are satisfied simultaneously. In addition, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] Traditional polyglycerol fatty acid esters are mainly prepared by esterification with fatty acids or their derivatives, using polyglycerol obtained from (i) the high-temperature dehydration condensation reaction of glycerol or (ii) the ring-opening polymerization reaction of glycidyl glycerol as raw material. However, polyglycerol obtained by these methods is prone to contain 1,3-carbon bonds and 1,2-carbon bonds, and easily forms a branched nonlinear structure. The glycerol backbone has primary and secondary hydroxyl groups distributed on it, with a high proportion of secondary hydroxyl groups, ranging from 30% to 70%. Specifically, in polyglycerol prepared by the alkali-catalyzed glycidyl glycerol method and the glycerol thermal condensation method, the proportion of primary hydroxyl groups is about 30%, the proportion of secondary hydroxyl groups is about 70%, and the degree of branching is 0 to 0.30. In contrast, polyglycerol prepared by the phosphoric acid-catalyzed glycidyl glycerol method has a three-dimensional highly branched structure, with a primary hydroxyl group proportion of about 64%, a secondary hydroxyl group proportion of about 36%, and a branching degree as high as 0.50 or more.

[0025] Traditional methods often result in polyglycerol fatty acid esters with a high proportion of secondary hydroxyl groups or a high degree of branching. Because secondary hydroxyl groups are less reactive than primary hydroxyl groups, and highly branched structures have greater steric hindrance, the introduction of fatty acids during polyglycerol fatty acid ester synthesis is dispersed along the polyglycerol backbone and around branching points. Even with the same average degree of esterification, the structural fluctuations between molecules become significant. Specifically, when the types of hydroxyl groups on the polyglycerol backbone are not uniform, the difference in reactivity between primary and secondary hydroxyl groups during esterification makes it difficult to precisely control the introduction sites and quantities of fatty acids. This results in differences in the molecular structure of polyglycerol fatty acid esters, even with the same average degree of esterification. This leads to fluctuations in emulsification behavior, solubilization behavior, and the density and thickness of the adsorbed layer formed at the interface between batches. These structural fluctuations become a key obstacle to precisely controlling makeup removal power, rinseability, and post-wash skin feel (such as moisturizing or sticky feeling) in cleansing cosmetics.

[0026] In view of this, the present invention proposes a linear polyglycerol fatty acid ester, wherein the raw materials for preparing the linear polyglycerol fatty acid ester include linear polyglycerol and fatty acids; the average degree of polymerization of the linear polyglycerol is 3~40, the degree of branching of the linear polyglycerol is <0.2, the proportion of primary hydroxyl groups in the linear polyglycerol to the total number of hydroxyl groups is ≥90%; and the average degree of esterification of the linear polyglycerol fatty acid ester is 0.5~3.0.

[0027] In the technical solution of this invention, by controlling the branching degree and primary hydroxyl ratio of linear polyglycerol within a specific range, the branching density and hydroxyl types of polyglycerol exhibit high consistency. This ensures that the obtained linear polyglycerol fatty acid ester achieves good emulsifying and solubilizing properties in cosmetics, resulting in a better user experience and stability. The linear polyglycerol fatty acid ester provided by this invention, when applied to makeup removal and cleansing, exhibits a shorter compatibility onset time, is easy to rinse, and leaves less stickiness and tightness after rinsing.

[0028] The linear polyglycerol can have an average degree of polymerization of 3, 10, 20, 30 or 40, and a degree of branching of 0.19, 0.15, 0.10, 0.05, 0.01 or even lower. The proportion of primary hydroxyl groups in the total number of hydroxyl groups (i.e., the proportion of primary hydroxyl groups) can be 90%, 94%, 98% or even higher. The linear polyglycerol fatty acid ester can have an average degree of esterification of 0.5, 1.0, 2.0 or 3.0.

[0029] Among them, the proportion of primary hydroxyl groups in linear polyglycerol is ≥90% (i.e., the proportion of primary hydroxyl groups is ≥90%) and the degree of branching is <0.2. This means that the polymerization reaction that forms linear polyglycerol has extremely high regioselectivity, and the product is a highly linear straight-chain structure, rather than a disordered mixture of branched chains or rings. This parameter reflects that almost all primary hydroxyl groups in polyglycerol have the same chemical environment, that is, the branching density and the consistency of hydroxyl types in polyglycerol are relatively high.

[0030] The average degree of polymerization (DOP) of linear polyglycerol ranges from 3 to 40, which is based on a balance between viscosity, feel, and solubilizing ability in cosmetic applications. If the average DOP is below 3, its low molecular weight, similar to polyols, makes its performance as a surfactant insufficient; if it exceeds 40, the melt viscosity or aqueous solution viscosity of polyglycerol becomes too high, potentially affecting its compatibility and usability. Compared to polyethylene glycol (PEG), linear polyglycerol has more hydroxyl groups per molecule. Therefore, with similar molecular weights, polyglycerol exhibits higher hydrophilicity and hydrogen bonding ability, which helps improve the rheological properties of emulsion and cleansing systems.

[0031] In this article, "polyglycerol" refers to a polymer formed by the polymerization of glycerol through ether bonds. Glycerol has three carbon atoms, namely at positions 1, 2, and 3. The hydroxyl groups attached to the carbon atoms at positions 1 and 3 are primary hydroxyl groups, while the hydroxyl group attached to the carbon atom at position 2 is a secondary hydroxyl group. The linear polyglycerol of this invention mainly has a linear structure with 1,2-glycerol bonds as repeating units, that is, the carbon at position 1 of the glycerol is connected to the carbon at position 2 of the next unit through an ether bond (C1-O-C2 bond). In this structure, the carbon at position 3 of each glycerol unit does not participate in bonding, so each glycerol unit forms a primary hydroxyl structure, and theoretically, all hydroxyl groups in the final polyglycerol are primary hydroxyl groups. Polyglycerols obtained by direct polymerization of glycidyl ether, thermal condensation of glycerol, and various glycidyl ether derivatives, in addition to 1,2-bonding, are prone to generating various bonding modes, including 1,3-bonding and branched bonding. This results in primary and secondary hydroxyl groups on the glycerol units existing in different proportions. Even if the average degree of polymerization and molecular weight distribution of these polyglycerols can be controlled within a specific range, the hydroxyl environment in their structure is still non-uniform. Therefore, the intermolecular homogeneity fluctuates greatly after fatty acid esterification.

[0032] In this paper, linear polyglycerol fatty acid esters are obtained by esterification of linear polyglycerol and fatty acids. Since the proportion of primary hydroxyl groups in linear polyglycerol is close to or equal to 100% and the degree of branching of linear polyglycerol is less than 0.2, the hydroxyl environment that reacts with fatty acids is relatively uniform, making it easy to uniformly control the position and amount of fatty acid introduction. In the end, a substance with highly uniform arrangement of hydrophobic groups of fatty acids is formed, thereby improving the emulsifying and solubilizing properties of linear polyglycerol fatty acid esters.

[0033] In this article, for linear polyglycerol: the degree of branching and the proportion of primary hydroxyl groups can be obtained by carbon NMR spectroscopy; the average degree of polymerization can be obtained by measuring the hydroxyl value; the hydrophilic-lipophilic balance value (HLB value) of linear polyglycerol fatty acid esters can be calculated by acid value and saponification value.

[0034] Preferably, the linear polyglycerol has an average degree of polymerization of 6 to 40; and / or, the degree of branching of the linear polyglycerol is ≤0.15; and / or, the proportion of primary hydroxyl groups in the linear polyglycerol is 95% to 100% of the total number of hydroxyl groups, and the proportion of secondary hydroxyl groups in the linear polyglycerol is ≤5% of the total number of hydroxyl groups; and / or, the average degree of esterification of the linear polyglycerol fatty acid ester is 0.9 to 1.2. Simultaneously controlling the above parameters within a suitable range can further improve the uniformity of the polyglycerol fatty acid ester's main chain length, branch density, and hydroxyl group types, thereby further improving the emulsifying and solubilizing properties of the polyglycerol fatty acid ester.

[0035] In this article, the number of carbon atoms in fatty acids can be 6, 8, 10, 12, 14, 16, 18, 20, 22, or 24. Fatty acids can be branched-chain saturated fatty acids, or they can be straight-chain saturated fatty acids or straight-chain unsaturated fatty acids. Straight-chain saturated fatty acids can be caprylic acid (C8), capric acid (C10), lauric acid (C12), myristic acid (C14), palmitic acid (C16), and stearic acid (C18); branched-chain fatty acids can be isononanoic acid (C9) and isostearic acid (C18); straight-chain unsaturated fatty acids can be oleic acid (C18:1), linoleic acid (C18:2), and linolenic acid (C18:3). The shorter the carbon chain of the fatty acid (C6~C10), the higher the overall hydrophilicity and the lower the melting point of the polyglycerol fatty acid ester formed; the longer the carbon chain (C16~C24), the higher the hydrophobicity and the higher the melting point of the polyglycerol fatty acid ester formed. On the other hand, introducing branched chains or unsaturated double bonds helps lower the melting point of polyglycerol fatty acid esters and improves fluidity and spreadability. Therefore, by rationally designing the types of fatty acids and the average degree of esterification, it is possible to balance the surface activity (wetting ability to remove makeup and dirt, i.e., the emulsifying and solubilizing properties of cleansing cosmetics) and the user experience (easy rinsing and reduced stickiness) required for cleansing purposes.

[0036] Preferably, in some embodiments, the fatty acid includes at least one selected from decanoic acid, lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, and isostearic acid. That is, the fatty acid can be any one of decanoic acid, lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, and isostearic acid, or two or more of these fatty acids, all within the scope of this invention. Selecting the above-mentioned fatty acids ensures superior emulsifying and solubilizing properties of the formed polyglycerol fatty acid ester, while also reducing cost.

[0037] The present invention also provides a method for preparing linear polyglycerol fatty acid esters, wherein the linear polyglycerol fatty acid esters are prepared by the following steps: providing linear polyglycerol; and mixing the linear polyglycerol, a catalyst, and fatty acids under an inert atmosphere to carry out an esterification reaction to obtain the linear polyglycerol fatty acid esters.

[0038] In some embodiments, the step of providing linear polyglycerol includes: mixing an initiator, an organic solvent, and ethoxyethyl glycidyl ether under an inert atmosphere, and carrying out a polymerization reaction at a polymerization reaction temperature to obtain a reaction solution; mixing the reaction solution with an aqueous hydrochloric acid solution to obtain an organic layer, removing the solvent from the organic layer to obtain an intermediate; and mixing the intermediate with an aqueous hydrochloric acid solution to carry out a hydrolysis reaction to obtain the linear polyglycerol.

[0039] In the technical solution of this invention, ethoxyethyl glycidyl ether (EEGE) is a glycidyl ether with an ethoxyethyl protecting group, also known as 3-(ethoxyethoxy)-1,2-epoxypropane. In the EEGE molecule, the primary hydroxyl group at position 3 is protected, and the carbon atoms at positions 1 and 2 form an ethylene oxide ring through an oxygen atom. Using ethoxyethyl glycidyl ether as the polymerization monomer, and under the action of an initiator, due to the higher reactivity of the ethylene oxide ring, the ethylene oxide ring in ethoxyethyl glycidyl ether undergoes anionic ring-opening polymerization. Because the primary hydroxyl group at position 3 is protected by the protecting group, it cannot participate in the polymerization process. Only the ether bond forms at position 1 after the ring-opening of the previous EEGE molecule and at position 2 after the ring-opening of the next EEGE molecule, thus obtaining a dimer. This process is repeated, forcibly generating a highly linear polymer backbone. Subsequently, the reaction solution is quenched and the residual alkaline initiator in the system is neutralized by a low-concentration hydrochloric acid aqueous solution. Since the generated polymer intermediate (polyether with ethoxyethyl protecting group) is a hydrophobic organic compound, it dissolves in the organic solvent layer, while the generated inorganic salts, catalyst residues and other impurities enter the aqueous phase to obtain the intermediate. Finally, the intermediate is mixed with a high concentration of hydrochloric acid aqueous solution for hydrolysis reaction, which causes the acid-sensitive "ethoxyethyl" ether bond to break, and the free primary hydroxyl group (-OH) at the 3 position is exposed again. In this case, almost all the residual polymer monomers are primary hydroxyl groups at the 3 position, so the final polymer has a linear structure and its hydroxyl group is highly consistent. Theoretically, all the hydroxyl groups in the final polyglycerol are primary hydroxyl groups.

[0040] In the preparation of polyglycerol esters, because the primary hydroxyl groups of linear polyglycerols are more reactive in esterification and have less steric hindrance than the secondary hydroxyl groups, fatty acids tend to be selectively and uniformly introduced onto the primary hydroxyl group at position 3. Therefore, not only is the amount of fatty acid introduced per molecule of polyglycerol precisely controlled, but the distribution of its introduction sites is also suppressed to a very narrow range, facilitating the formation of a surfactant backbone with a consistent spatial arrangement of hydrophobic groups.

[0041] In some embodiments, in the step of mixing an initiator, an organic solvent, and ethoxyethyl glycidyl ether under an inert atmosphere and carrying out a polymerization reaction at a polymerization temperature to obtain a reaction solution: the initiator includes tetrabutylammonium hydroxide, tetramethylammonium hydroxide, or benzyltriethylammonium hydroxide; and / or, the organic solvent includes tetrahydrofuran, N,N-dimethylformamide, or N-methyl-2-pyrrolidone; and / or, the molar ratio of the initiator to the ethoxyethyl glycidyl ether is 1:0.8~1.2; and / or, the polymerization reaction temperature is 20~50°C; and / or, the polymerization reaction time is 3~5 hours. That is, the molar ratio of initiator to ethoxyethyl glycidyl ether can be 0.8, 1 or 1.2, the polymerization temperature can be 20℃, 25℃ or 50℃, and the polymerization time can be 3h, 4h or 5h. By controlling the types of initiator and organic solvent, the molar ratio of initiator to ethoxyethyl glycidyl ether, the polymerization temperature and time within a suitable range, it can be ensured that ethoxyethyl glycidyl ether molecules undergo sufficient linear polymerization to form intermediates.

[0042] In some embodiments, in the step of mixing the intermediate with an aqueous hydrochloric acid solution and performing a hydrolysis reaction to obtain the linear polyglycerol: the concentration of the aqueous hydrochloric acid solution is 0.8~1.2 mol; and / or, the temperature of the hydrolysis reaction is 40~45℃; and / or, the time of the hydrolysis reaction is 20~24 h. That is, the concentration of the aqueous hydrochloric acid solution can be 0.8 mol, 1 mol, or 1.2 mol, the temperature of the hydrolysis reaction can be 40℃, 42℃, or 45℃, and the time of the hydrolysis reaction can be 20 h, 22 h, or 24 h. Controlling the above parameters within a suitable range can ensure that the residual ethoxyethyl ether bond in each polymerization unit in the intermediate is fully broken, re-exposing the free primary hydroxyl group at the 3-position, which facilitates the subsequent introduction of fatty acids.

[0043] In some embodiments, in the step of mixing the linear polyglycerol, catalyst, and fatty acid under an inert atmosphere and carrying out an esterification reaction to obtain the linear polyglycerol fatty acid ester: the molar ratio of the linear polyglycerol to the fatty acid is 1:1 to 1:6; and / or, the catalyst includes sodium hydroxide or potassium hydroxide; and / or, the temperature of the esterification reaction is 160 to 180°C; and / or, the time of the esterification reaction is 3 to 5 hours. That is, the molar ratio of the linear polyglycerol to the fatty acid can be 1:1, 1:2, or 1:6, the temperature of the esterification reaction can be 160°C, 170°C, or 180°C, and the time of the esterification reaction can be 3 hours, 4 hours, or 5 hours. Controlling these parameters within a suitable range ensures that relatively recombinant fatty acids are introduced into the polyglycerol backbone.

[0044] The present invention also provides a cosmetic product comprising the aforementioned linear polyglycerol fatty acid ester or a linear polyglycerol fatty acid ester prepared by the aforementioned method for preparing linear polyglycerol fatty acid esters. Therefore, this cosmetic product possesses all the beneficial effects of the aforementioned linear polyglycerol fatty acid ester or the aforementioned method for preparing linear polyglycerol fatty acid esters, which will not be elaborated further here.

[0045] In some embodiments, the cosmetic includes at least one of cleansing cosmetics, emulsifying creams, and solubilizing compositions. Cleansing cosmetics include makeup-removing and cleansing products such as cleansing gels and mild cleansing products such as facial cleansers; emulsifying creams can be used as skin creams; and the solubilizing compositions themselves can be used as emulsifiers in cosmetics. Using the linear polyglycerol fatty acid esters provided by this invention in makeup-removing and cleansing cosmetics exhibits good emulsifying and solubilizing properties, thereby achieving both high cleansing power and a pleasant user experience. Furthermore, the linear polyglycerol fatty acid esters have high structural uniformity, easily forming uniform lamellar liquid crystal structures or micelle particle sizes, thus significantly improving the skin permeability of cosmetic ingredients and enhancing their storage stability. Due to the lower irritation of the primary hydroxyl structure, it can also be applied to skincare products for sensitive skin and baby care products.

[0046] In some embodiments, the cleansing cosmetic includes a makeup remover, wherein the linear polyglycerol fatty acid in the makeup remover comprises 1-30% by mass. The mass percentage of linear polyglycerol fatty acid can be 1%, 10%, 20%, or 30%, thus making it suitable for various types of makeup removers and cleansing cosmetics, applicable to cosmetics with different cleansing levels, from auxiliary cleansing products to powerful makeup removers.

[0047] The technical solution of the present invention will be further described in detail below with reference to specific embodiments and accompanying drawings. It should be understood that the following embodiments are only used to explain the present invention and are not intended to limit the present invention.

[0048] Example 1 A linear polyglycerol fatty acid ester is first synthesized using ethoxyethyl glycidyl ether (EEGE) to produce polyglycerol A (average degree of polymerization 10, degree of branching 0.12, primary hydroxyl groups accounting for 98% of all hydroxyl groups, and secondary hydroxyl groups accounting for 2%). Subsequently, polyglycerol A and fatty acids are esterified to obtain a linear polyglycerol fatty acid ester (average degree of esterification 1.0). The specific steps are as follows: Step (1): Under a nitrogen atmosphere, 15.1 g (0.058 mol) of tetrabutylammonium hydroxide as an initiator was added to a dry three-necked flask, followed by 100 g of anhydrous tetrahydrofuran (THF), and the mixture was cooled to 0 °C. Subsequently, a total of 84.9 g (0.58 mol) of EEGE was added dropwise over 2 hours, and the mixture was stirred at 35 °C for 4 hours to confirm that the monomer was almost completely converted, thus obtaining the reaction solution. Step (2): Add a 20% dilute hydrochloric acid aqueous solution to the above reaction solution to neutralize the residual alkali, and then separate to obtain the organic layer. Remove the solvent from the organic layer by vacuum distillation, dissolve the obtained product in methanol, remove the salts using an ion exchange resin, and remove the solvent again by vacuum distillation to obtain an intermediate, which is a pale yellow viscous liquid with a yield of 90%. Step (3): Add 10 mL of 1 mol / L hydrochloric acid aqueous solution to the above intermediate and stir at 30 °C for 24 hours to carry out the hydrolysis reaction, so that the 1-ethoxyethyl protecting group is deprotected under acidic conditions. After the reaction is completed, the reaction solution is concentrated under reduced pressure, then diluted with ethanol, the acid in the reaction solution is removed by anion exchange resin, the solvent is removed by distillation, and the residue is dried under reduced pressure to obtain linear polyglycerol, namely polyglycerol A, which is a colorless viscous liquid with a yield of 85%. Step (4): In a stainless steel reactor, add 100.0g of polyglycerol A and 26.4g of lauric acid. Under stirring and a nitrogen atmosphere, gradually raise the temperature from room temperature to 170℃. Then add 0.2g of sodium hydroxide as a catalyst. Continuously remove the generated water from the reaction system through nitrogen bubbling and reduced pressure operation. The reaction time is 4 hours. During the reaction, continue the reaction until the acid value drops below 5mg KOH / g. After the reaction is complete, cool the reaction solution and neutralize it with acetic acid to obtain linear polyglycerol fatty acid ester. The linear polyglycerol fatty acid ester is a pale yellow viscous liquid with a yield of 90%.

[0049] Example 2 The difference between Example 2 and Example 1 is that: The linear polyglycerol fatty acid ester is obtained by esterification of polyglycerol B and lauric acid; wherein, the average degree of polymerization of polyglycerol B is 6, the degree of branching is 0.07, the number of primary hydroxyl groups accounts for 95% of the total number of hydroxyl groups, and the number of secondary hydroxyl groups accounts for 5% of the total number of hydroxyl groups; The preparation method of polyglycerol B described above is the same as in Example 1, except that the amount of initiator tetrabutylammonium hydroxide added is 0.097 mmol; and the final yield of polyglycerol B is 89%.

[0050] Example 3 The difference between Example 3 and Example 1 is that: Linear polyglycerol fatty acid esters are obtained by esterification of polyglycerol C and lauric acid; wherein, the average degree of polymerization of polyglycerol C is 20, the degree of branching is 0.10, the number of primary hydroxyl groups accounts for 98% of the total number of hydroxyl groups, and the number of secondary hydroxyl groups accounts for 2% of the total number of hydroxyl groups; The preparation method of polyglycerol C described above is the same as in Example 1, except that the amount of initiator tetrabutylammonium hydroxide added is 0.029 mmol; and the final yield of polyglycerol C is 87%.

[0051] Example 4 The difference between Example 4 and Example 1 is that: Linear polyglycerol fatty acid esters are obtained by esterification of polyglycerol D and lauric acid; wherein, the average degree of polymerization of polyglycerol D is 40, the degree of branching is 0.11, the number of primary hydroxyl groups accounts for 98% of the total number of hydroxyl groups, and the number of secondary hydroxyl groups accounts for 2% of the total number of hydroxyl groups; The preparation method of polyglycerol D described above is the same as in Example 1, except that the amount of initiator tetrabutylammonium hydroxide added is 0.0145 mmol; and the final yield of polyglycerol D is 82%.

[0052] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that: Polyglycerol fatty acid esters are obtained by esterification of polyglycerol E and lauric acid; wherein, the average degree of polymerization of polyglycerol E is 10, the degree of branching is 0.33, the number of primary hydroxyl groups accounts for 29% of the total number of hydroxyl groups, and the number of secondary hydroxyl groups accounts for 71% of the total number of hydroxyl groups; Polyglycerol E was prepared by the base-catalyzed glycidyl method, and the specific steps are as follows: Under a nitrogen atmosphere, 92 g (1 mol) of glycerol and 1.0 g (0.018 mol) of potassium hydroxide were added to a drying reactor, and the mixture was heated to 120 °C and dried for 30 minutes. Subsequently, a total of 667 g (9 mol) of glycidyl ether (i.e., glycidol) was added dropwise over 4 hours. After the addition was complete, the mixture was stirred at 140 °C for another 4 hours. During the reaction, low-boiling-point components were continuously removed by vacuum distillation. After the reaction was complete, the reaction solution was cooled to room temperature and neutralized with a 20% dilute hydrochloric acid solution. Water and volatile components were then removed by vacuum distillation. The resulting viscous liquid was filtered through a ceramic filter to remove insoluble matter, yielding pale yellow polyglycerol E in 80% yield.

[0053] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that: Polyglycerol fatty acid esters are obtained by esterification of polyglycerol F and lauric acid; wherein, polyglycerol F has an average degree of polymerization of 10, a degree of branching of 0.19, a primary hydroxyl group accounting for 36% of the total number of hydroxyl groups, and a secondary hydroxyl group accounting for 64% of the total number of hydroxyl groups; Polyglycerol F was prepared by the glycerol heat shrinking method, and the specific steps are as follows: 100.0 g of glycerol was placed in a four-necked flask, and 0.5 g of sodium hydroxide was added under a nitrogen atmosphere. A mechanical stirrer, thermometer, and reflux condenser with a Dean-Stark water separator were installed. The temperature was raised to 230 °C and the reaction was carried out for 6 hours, continuously removing the generated water during the reaction. After the reaction was complete, the system was cooled, and the residual acid was neutralized with an aqueous sodium carbonate solution. Subsequently, the system was distilled under reduced pressure to remove water and volatile components. The mixture was filtered to obtain a viscous liquid. Solids (derived from the catalyst) were removed from the viscous liquid to obtain polyglycerol F, which was light brown in color, with a yield of 75%.

[0054] Comparative Example 3 The difference between Comparative Example 3 and Example 1 is that: Polyglycerol fatty acid esters are obtained by esterification of polyglycerol G and lauric acid; wherein, the average degree of polymerization of polyglycerol G is 10, the degree of branching is 0.50, the number of primary hydroxyl groups accounts for 64% of the total number of hydroxyl groups, and the number of secondary hydroxyl groups accounts for 36% of the total number of hydroxyl groups; Polyglycerol G was prepared by the phosphoric acid-catalyzed glycidyl ether method, and the specific steps are as follows: Under a nitrogen atmosphere, 92 g (1 mol) of glycerol was added to a dry reactor, and the temperature was continuously increased from room temperature to 120 °C. Subsequently, a total of 666.7 g (9 mol) of glycidyl ether and 10 g of phosphoric acid were added dropwise over 12 hours. After the addition was complete, the mixture was stirred at 120 °C for another hour. After the reaction was completed, the reaction solution was cooled to room temperature to obtain polyglycerol G, which was pale yellow in color, with a yield of 80%.

[0055] Performance testing 1. Polyglycerol determination The following determinations were performed on the polyglycerols in Examples 1-4 and Comparative Examples 1-3: (1) Average degree of polymerization: The formula for calculating the average degree of polymerization is: Average degree of polymerization = (112.2 × 10) 3 -18×hydroxyl value) / (74×hydroxyl value-56.1×10 3 ); The hydroxyl value was determined using the phthalic anhydride method: based on the esterification reaction between phthalic anhydride and hydroxyl groups, excess phthalic anhydride was titrated with a standard sodium hydroxide solution, using phenolphthalein as an indicator, and the hydroxyl value was calculated based on the volume of sodium hydroxide solution consumed. The specific procedure was as follows: weigh wg (in grams) of sample, place it in an Erlenmeyer flask, add 25 mL of phthalic anhydride acylation reagent; shake the flask until the sample dissolves, connect an air condenser to each Erlenmeyer flask, and place it in an oil bath at (105±2)℃ for 30 min; after heating in the oil bath, remove the apparatus from the oil bath and cool it to room temperature. Rinse the condenser tube with 30 mL of pyridine and remove the condenser tube; titrate with 0.5 mol / L potassium hydroxide solution using phenolphthalein as an indicator; and perform a blank test under the same conditions. Let the volume of titrant consumed in the blank test be a (mL), the volume of titrant consumed in the sample solution be b (mL), and the sample volume be w (g). Calculate the hydroxyl value using hydroxyl value = (ab) × 28.05 / w. (2) Branching degree, primary hydroxyl ratio, and secondary hydroxyl ratio: First, the 13C-NMR spectrum of polyglycerol was obtained. The steps were as follows: 200 mg of polyglycerol was dissolved in 0.6 mL of heavy water. A 100 MHz 13C-NMR instrument was used, the measurement temperature was 30 °C, the measurement mode was single-pulse 1H decoupling (quantitative measurement mode), the pulse repetition time was more than 10 seconds, the cumulative number of times was more than 256, and the internal standard was acetone (30.89 ppm).

[0056] Subsequently, based on the carbon signal integral values ​​corresponding to the bonding mode with the polyglycerol backbone (including 1,3-bonded main chain, 1,2-bonded and branched structure), the degree of branching, primary hydroxyl ratio and secondary hydroxyl ratio were calculated respectively. Specifically, polyglycerol has five structures (D, L13, L14, T1, T2; see details for specific structures). Figure 1 In the carbon NMR spectrum, the peaks corresponding to A~H (e.g.) Figure 2 The peaks labeled A, B, C, D, E, F, and H were identified as carbon atoms at specific locations within each structure. The proportions of the five structures D, L13, L14, T1, and T2 were calculated using the integral ratios of each peak.

[0057] The proportion of D-structures: D = {C}, where {C} is the integral area of ​​peak C; The proportion of L13 structure: L13 = {I}, where {I} is the integral area of ​​peak I; The proportion of L14 structure: L14 = {D} / 2; where {D} is the integral area of ​​peak D; Branching degree is calculated using the following formula: DB = 2D / (2D + L13 + L14); Based on the proportions of each structure in polyglycerol, the proportion of primary hydroxyl groups is calculated as L13 / (L13+L14), and the proportion of secondary hydroxyl groups is calculated as L14 / (L13+L14).

[0058] The measurement results are shown in Table 1.

[0059] Table 1. Characterization results of polyglycerol in Examples 1-4 and Comparative Examples 1-3

[0060] As shown in Table 1, the linear polyglycerol obtained by ring-opening polymerization using the ethoxyethyl protecting group as described in this application has a branching degree of less than 0.15, a primary hydroxyl content of 95-98%, and a secondary hydroxyl content of 2-5% according to 13C-NMR spectroscopy. In contrast, conventional polyglycerols obtained by direct polymerization of glycidyl ether or high-temperature dehydration condensation (Comparative Examples 1-3) have a primary hydroxyl content of 29%-64%, a secondary hydroxyl content of 36%-71%, and a branching degree of 0.19-0.50.

[0061] 2. Determination of polyglycerol fatty acid esters The polyglycerol fatty acid esters in Examples 1-4 and Comparative Examples 1-3 were determined as follows: (1) Average degree of esterification: Average degree of esterification = number of moles of reacted fatty acids / number of moles of polyglycerol; (2) HLB value: The HLB value is determined by the formula HLB=20(1-S / A); where S is the saponification value and A is the acid value A of the raw material lauric acid. S is determined by the following steps: Weigh 2-10 g of polyglycerol fatty acid ester m1 into an Erlenmeyer flask, add 25 mL of ethanol and 25 mL of potassium hydroxide ethanol solution; attach a reflux condenser and maintain boiling for 60 min (2 h for flasks difficult to saponify); after slightly cooling, add 0.5 mL-1 mL of phenolphthalein indicator, and titrate the blank and sample to the phenolphthalein endpoint with standardized 0.5 mol / L hydrochloric acid solution; the volume difference (V0-V) between the hydrochloric acid used in the neutralization blank test and the test solution is the amount of potassium hydroxide consumed by the polyglycerol fatty acid ester, and the number of milligrams of potassium hydroxide required per gram of polyglycerol fatty acid ester is the saponification value; saponification value S = (V0-V) × 28.05 / mL; A was determined by the following steps: A sample m2 (5g~6g) of polyglycerol fatty acid ester was weighed into the conical flask described above, and the mass was recorded to an accuracy of 0.1g; (50±10)mL of isopropanol and 1mL of phenolphthalein indicator were added to the conical flask; the solution in the conical flask was shaken until the polyglycerol fatty acid ester was completely dissolved; the polyglycerol fatty acid ester solution was titrated with a 0.02 mol / L potassium hydroxide-methanol standard titration solution until a light pink color was obtained, and the titration was maintained for 30s as the endpoint. The volume consumed, V, was recorded; the acid value A = 1.12 × V / m2. The measurement results are shown in Table 2.

[0062] Table 2 Characterization results of polyglycerol fatty acid esters in Examples 1-4 and Comparative Examples 1-3

[0063] As shown in Table 2, under the same conditions, the average degree of esterification of the corresponding laurates prepared using the polyglycerols in Examples 1-4 and Comparative Examples 1-3 were all in the range of 0.9 to 1.2, and their HLB values ​​were also roughly equivalent. 13C-NMR analysis results showed that the fatty acids in the polyglycerol fatty acid esters of Example 1 were distributed on the primary hydroxyl groups, while the fatty acids in the polyglycerol fatty acid esters of Comparative Example 1 were more introduced into the secondary hydroxyl sites; and in the branched polyglycerol fatty acid esters of Comparative Examples 2 and 3, a large number of fatty acids were densely distributed around the branching points.

[0064] 3. Application of polyglycerol fatty acid esters in cleansing gels The polyglycerol fatty acid esters from Examples 1-4 and Comparative Examples 1-3 were used to prepare seven groups of cleansing gels according to the following formulations: Formula: 10.0wt% polyglycerol fatty acid ester, 10.0wt% glycerol, 5.0wt% 1,3-butanediol, 73.0wt% purified water, 0.1wt% disodium EDTA, 1.9wt% potassium sorbate; Preparation method: Pure water, glycerin, and 1,3-butanediol were added to a stainless steel mixing tank and mixed thoroughly at room temperature. Then, polyglycerol fatty acid esters were added, and the mixture was gradually heated from room temperature to 70°C while stirring, to prepare a homogeneous and transparent solution. After cooling to 40°C, preservatives were added, and the mixture was defoamed to obtain a cleansing gel.

[0065] The cleansing effects of the seven groups of cleansing gels prepared were tested, and the testing methods are as follows: Cleansing effect: The cleansing effect is characterized by the amount of makeup residue. That is, waterproof mascara (ukiss Fireworks Dance Mascara Primer) and liquid foundation (ukiss Oily Skin Foundation) are evenly applied to the surface of artificial leather substrate. After being left at room temperature for 30 minutes, 0.5g of cleansing gel is applied to it and gently massaged with fingers for 30 seconds. Then it is rinsed under running water at 35℃ for 10 seconds. The makeup residue rate is evaluated by visual observation (0-100%). After rinsing the makeup, the residual makeup on the surface of artificial leather substrate is evaluated by sensory evaluation. The standard is whether there is obvious stickiness and slipperiness (0~10 points). The initial compatibility time is the time from the initial application of cleansing gel to the time when the foundation begins to dissolve.

[0066] The determination methods are shown in Table 3.

[0067] Table 3. Performance characterization of the cleansing gels corresponding to Examples 1-4 and Comparative Examples 1-3

[0068] As shown in Table 3, for the cleansing gel, the viscosity change rate of Examples 1-4 after being stored at 40°C for 1 month was less than 10%, and there was no obvious change in appearance; while the viscosity change rate of Comparative Examples 1-3 after being stored at 40°C for 1 month fluctuated in the range of 20% to 40%, and slight phase separation or turbidity appeared in appearance.

[0069] The cleansing gels corresponding to Examples 1-4 had makeup residue rates equal to or lower than 10%, compatibility onset times as short as 5 seconds, and lower scores for stickiness and greasiness after rinsing. In contrast, the cleansing gels corresponding to Comparative Examples 1-3 all had makeup residue rates in the range of 20% to 30%, and compatibility onset times of 10 to 15 seconds, both higher than Example 1. Furthermore, regarding sensory evaluation of stickiness and greasiness after rinsing (by 10 panel members), Examples 1-4 received better sensory scores, while Comparative Examples 1-3 received worse scores.

[0070] 4. Application of polyglycerol fatty acid esters in emulsified creams Seven groups of emulsified creams were prepared by using the polyglycerol fatty acid esters from Examples 1-4 and Comparative Examples 1-3 according to the following formulations: Formula: 3.0wt% polyglycerol fatty acid ester, 5.0wt% squalane, 10.0wt% liquid paraffin, 2.0wt% stearic acid, 1.0wt% cetyl alcohol, 5.0wt% glycerol, 5.0wt% 1,3-butanediol, 0.2wt% carbomer, 0.2wt% triethanolamine, 68.4wt% purified water, 0.1wt% disodium EDTA, 0.1wt% potassium sorbate; Preparation method: The oil phase (polyglycerol fatty acid ester, squalane, liquid paraffin, stearic acid, cetyl alcohol) and the aqueous phase (pure water, glycerol, 1,3-butanediol, carbomer) were heated to 75°C respectively. Then, the oil phase was added to the aqueous phase, and emulsification was carried out under high-speed stirring at 1400 rpm. After emulsification, triethanolamine was added for neutralization to adjust the viscosity to 5000 mPa·s. After cooling to 40°C, preservatives and chelating agents were added to obtain a white emulsified cream.

[0071] Table 4 Characterization of the stability of emulsified creams in Examples 1-4 and Comparative Examples 1-3

[0072] As shown in Table 4, for emulsified creams, the initial appearance of emulsified creams in Examples 1-4 was milky white. After being stored at 25°C for 1 week, their appearance did not change significantly, and the viscosity change rate was 8%-10%. However, the emulsified cream in Comparative Example 2 showed slight turbidity immediately after preparation. After being stored at 25°C for 1 week, Comparative Example 1 showed the phenomenon of oil phase floating and separation, and the viscosity change rate was more than 30%.

[0073] 5. Application of polyglycerol fatty acid esters in solubilizing compositions Seven solubilizing compositions were prepared from the polyglycerol fatty acid esters in Examples 1-4 and Comparative Examples 1-3 according to the following formulations: Formula: 5.0wt% polyglycerol fatty acid ester, 10.0wt% ethanol, 5.0wt% glycerol, 5.0wt% 1,3-butanediol, 74wt% purified water, 0.1wt% disodium EDTA (chelating agent), 0.1wt% potassium sorbate (preservative); Preparation method: At room temperature, pure water, glycerol, and 1,3-butanediol are mixed evenly, followed by the addition of polyglycerol fatty acid esters and their dissolution. Then, ethanol is added and stirred, and finally, preservatives and chelating agents are added.

[0074] The above-mentioned solubilizing compositions were evaluated using the following methods: (1) The transmittance of the solubilized composition was tested by ultraviolet spectrophotometry at 25°C; (2) High temperature stability: The solubilized composition was stored at 40℃ for one month, and the sample condition was observed; (3) Low temperature stability: Freeze the solubilized composition at -5℃ and then thaw it at 25℃, and observe whether the sample becomes turbid.

[0075] The evaluation results are shown in Table 5.

[0076] Table 5. Characterization of the stability of the solubilized compositions corresponding to Examples 1-4 and Comparative Examples 1-3

[0077] As shown in Table 5, for the solubilizing compositions, the solubilizing compositions of Examples 1-4 are transparent solutions at 25°C with a transmittance of 97-98%; and no turbidity or precipitation was observed after the freeze-thaw test, and their stability is significantly higher than that of Comparative Examples 1-3.

[0078] The above are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the patent protection scope of the present invention.

Claims

1. A linear polyglycerol fatty acid ester, characterized in that, The raw materials for preparing the linear polyglycerol fatty acid ester include linear polyglycerol and fatty acids; The linear polyglycerol has an average degree of polymerization of 3 to 40, a degree of branching of <0.2, and a primary hydroxyl group content of ≥90% of all hydroxyl groups. The linear polyglycerol fatty acid ester has an average degree of esterification of 0.5 to 3.

0.

2. The linear polyglycerol fatty acid ester according to claim 1, characterized in that, The linear polyglycerol has an average degree of polymerization of 6 to 40; and / or, The degree of branching of the linear polyglycerol is ≤0.15; and / or, The linear polyglycerol contains primary hydroxyl groups accounting for 95% to 100% of all hydroxyl groups, and secondary hydroxyl groups accounting for ≤5% of all hydroxyl groups; and / or, The linear polyglycerol fatty acid ester has an average degree of esterification of 0.9 to 1.

2.

3. The linear polyglycerol fatty acid ester according to claim 1, characterized in that, The fatty acids include fatty acids with 6 to 24 carbon atoms.

4. The linear polyglycerol fatty acid ester according to claim 3, characterized in that, The fatty acids include at least one of decanoic acid, lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, and isostearic acid.

5. A method for preparing a linear polyglycerol fatty acid ester as described in any one of claims 1 to 4, characterized in that, The linear polyglycerol fatty acid ester is prepared by the following steps: Provide linear polyglycerol; Under an inert atmosphere, the linear polyglycerol, catalyst, and fatty acid are mixed and subjected to an esterification reaction to obtain the linear polyglycerol fatty acid ester.

6. The method for preparing linear polyglycerol fatty acid esters according to claim 5, characterized in that, The step of providing linear polyglycerol includes: Under an inert atmosphere, an initiator, an organic solvent, and ethoxyethyl glycidyl ether are mixed and polymerized at the polymerization temperature to obtain a reaction solution. The reaction solution was mixed with an aqueous hydrochloric acid solution to obtain an organic layer. The solvent in the organic layer was then removed to obtain an intermediate. The intermediate was mixed with an aqueous hydrochloric acid solution and subjected to a hydrolysis reaction to obtain the linear polyglycerol.

7. The method for preparing linear polyglycerol fatty acid esters according to claim 6, characterized in that, In the step of mixing the initiator, organic solvent, and ethoxyethyl glycidyl ether under an inert atmosphere and carrying out the polymerization reaction at the polymerization reaction temperature to obtain the reaction solution: The initiator includes tetrabutylammonium hydroxide, tetramethylammonium hydroxide, or benzyltriethylammonium hydroxide; and / or, The organic solvent includes tetrahydrofuran, N,N-dimethylformamide, or N-methyl-2-pyrrolidone; and / or The molar ratio of the initiator to the ethoxyethyl glycidyl ether is 1:0.8~1.2; and / or, The polymerization reaction temperature is 20~50℃; and / or, The polymerization reaction time is 3-5 hours.

8. The method for preparing linear polyglycerol fatty acid esters as described in claim 6, characterized in that, In the step of mixing the intermediate with an aqueous hydrochloric acid solution and carrying out a hydrolysis reaction to obtain the linear polyglycerol: The concentration of the hydrochloric acid aqueous solution is 0.8~1.2 mol; and / or, The hydrolysis reaction is performed at a temperature of 40-45°C; and / or, The hydrolysis reaction takes 20-24 hours.

9. The method for preparing linear polyglycerol fatty acid esters as described in claim 5, characterized in that, In the step of mixing the linear polyglycerol, catalyst, and fatty acid under an inert atmosphere and carrying out an esterification reaction to obtain the linear polyglycerol fatty acid ester: The molar ratio of the linear polyglycerol to the fatty acid is 1:1 to 1:6; and / or, The catalyst includes sodium hydroxide or potassium hydroxide; and / or, The esterification reaction is carried out at a temperature of 160-180°C; and / or, The esterification reaction takes 3-5 hours.

10. A cosmetic product, characterized in that, The cosmetic product includes linear polyglycerol fatty acid esters as described in any one of claims 1 to 4, or linear polyglycerol fatty acid esters prepared by the method for preparing linear polyglycerol fatty acid esters as described in any one of claims 5 to 9.

11. The cosmetic product as described in claim 10, characterized in that, The cosmetics include at least one of cleansing cosmetics, emulsified creams, and solubilizing compositions.

12. The cosmetic product as described in claim 11, characterized in that, The cleansing cosmetics include makeup remover cleansing cosmetics, wherein the linear polyglycerol fatty acid in the makeup remover cleansing cosmetics accounts for 1-30% by mass.

13. The cosmetic product as described in claim 10, characterized in that, The viscosity of the cosmetic product at 25°C is 100~5000 mPa·s.

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