Emulsion thickener with back-acid stability and method for preparing the same

Abstract

The application provides an emulsion thickener with acid recovery stability and a preparation method thereof, and relates to the technical field of thickener.The raw materials of the emulsion thickener include polymerized monomers, emulsifiers, initiators, crosslinking agents, water and structural additives; the polymerized monomers include first monomers and second monomers, the first monomers are alpha, beta-unsaturated acid monomers, the second monomers are alpha, beta-unsaturated ester monomers, and the structural additives are polypeptides including polar amino acid residues.The emulsion thickener with acid recovery stability can quickly recover to the viscosity in the alkaline condition and gradually increase when the system changes from the alkaline condition to the acidic condition, effectively improves the response rate of network reconstruction, and realizes the self-repairing function.The preparation method of the emulsion thickener with acid recovery stability is simple and easy to operate, has good stability, and can be implemented in industrialization.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of thickening agent, in particular to an emulsion thickening agent with acid recovery stability and a preparation method thereof. BACKGROUND

[0002] The acid recovery emulsion thickening agent with acid recovery stability has been widely used in various emulsion systems. This kind of thickening agent constructs a slightly cross-linked acrylic acid-acrylate multi-copolymer network structure, and the special molecular structure of the dense distribution of multiple carboxyl and multiple ester groups on the molecular chain enables it to produce synergistic stabilization with various ionic and non-ionic surfactants. After compounding and neutralization by alkali, the acid recovery emulsion thickening agent can significantly improve the suspension, stability and thickening effect of the emulsion system when the pH value of the system drops to acidic conditions, and gives the product a transparent and clear appearance.

[0003] Compared with the traditional acrylic thickening agent powder, the acid recovery emulsion thickening agent exists in the form of low viscosity liquid, which is easier to quickly mix with other formula raw materials, thereby solving the technical bottleneck of limited compatibility of surfactant system, and significantly improving the stability and suspension effect. In addition, the acid recovery emulsion thickening agent system can still tolerate the introduction of subsequent acidic substances after completing the alkali activation, and can still maintain high viscosity and rheological properties even when the system is adjusted back to weak acidity. The thickening agent can function within a wide pH range (4.0-11.0), breaking through the acid-base sensitivity limitation of traditional acrylic thickening agents in compounding process, so its application range is more extensive.

[0004] Studies have shown that the acid recovery mechanism of acid recovery emulsion thickening agent usually relies on the protonation / deprotonation balance of carboxylic acid groups to achieve static cross-linking. As the pH value of the system moves towards acidity, the carboxylic acid groups promote the contraction of the molecular chain and form a physical cross-linking network through protonation. However, when the pH value of the system falls back from alkaline to acidic, the reconstruction of the cross-linking network has a certain hysteresis, which is reflected in the significant slowing down of the system's recovery to high viscosity and the difficulty in returning to the viscosity in alkaline conditions. Therefore, the limitation of this traditional mechanism is increasingly prominent, and the acid recovery performance needs to be further optimized. SUMMARY

[0005] In view of the deficiencies in the prior art, the present application discloses an emulsion thickening agent with acid recovery stability and a preparation method thereof. The preparation method adds a compounded emulsifying system and a structure additive to the polymerization system, thereby enhancing the acid recovery performance of the prepared emulsion thickening agent.

[0006] To achieve the above technical purposes, in one aspect, the present application provides an emulsion thickener with acid return stability, raw materials of the emulsion thickener comprising polymerized monomers, emulsifiers, initiators, cross-linking agents, water and structural additives; the polymerized monomers comprising first monomers and second monomers, the first monomers being α, β-unsaturated acid monomers, the second monomers being α, β-unsaturated ester monomers, and the structural additives being polypeptides comprising polar amino acid residues.

[0007] The emulsion thickener with acid return stability of the present application comprises polypeptides with polar amino acid residues as structural additives, which enhances the acid return performance of the emulsion thickener and endows it with biocompatibility; specifically, the polypeptides assume an extended conformation in the alkaline polymerization stage and fold or self-assemble into a β-sheet / α-helix structure in the acid return stage, so that the structural additives can adjust the conformational change of the thickener molecules in the acidic environment by interacting with the thickener molecules, effectively improving the response rate of network reconstruction, promoting the system to realize self-repairing function, and endowing it with additional functions such as biocompatibility; in addition, the hydrophilic groups of the polypeptides improve the emulsification efficiency by interacting with the emulsifiers. The examples and comparative examples demonstrate that the emulsion thickener of the present application has excellent acid return stability and has wide application value.

[0008] Based on the above technical solution, the structural additives are polypeptides comprising charged amino acid residues, and the molecular weight of the structural additives is 500-5000 Dalton.

[0009] Based on the above technical solution, the mass of the structural additives is 0.5%-3% of the mass of the polymerized monomers, preferably 1%-2.5%, and further preferably 1%-2%.

[0010] Based on the above technical solution, the emulsifiers are composite emulsifiers of anionic emulsifiers and non-ionic emulsifiers, the mass of the emulsifiers is 0.1%-3% of the mass of the polymerized monomers, preferably 0.1%-1%, and further preferably 0.2%-1%; and the mass ratio of the non-ionic emulsifiers to the anionic emulsifiers is (1-4):1, preferably (1-3):1, and further preferably (1-2):1.

[0011] Based on the above technical solution, the cross-linking agents comprise one or more of pentaerythritol triacrylate, trimethylolpropane triacrylate, dipentaerythritol pentaacrylate, 1,6-hexanediol diacrylate, trimethylolpropane trimethacrylate, and diallyl phthalate, preferably pentaerythritol triacrylate and / or diallyl phthalate.

[0012] Based on the above technical scheme, the mass of the crosslinking agent is 0.1% to 3%, preferably 0.5% to 2%, further preferably 0.5% to 1%, preferably 0.05% to 0.5%, further preferably 0.05% to 0.2% of the mass of the polymerization monomer.

[0013] Based on the above technical scheme, the initiator includes a first initiator and a second initiator, and the first initiator and the second initiator are independently selected from one or more of potassium persulfate, sodium persulfate, ammonium persulfate, sodium thiosulfate, azobisdimethylamid hydrochloride, and azobisdimethylimidazoline hydrochloride, preferably potassium persulfate and / or sodium persulfate.

[0014] Based on the above technical scheme, the sum of the mass of the first initiator and the second initiator is 0.05% to 1% of the mass of the polymerization monomer; and the mass ratio of the first initiator to the second initiator is (0.2 to 5):1, preferably (0.2 to 2):1, further preferably (0.2 to 1):1.

[0015] The present application provides a preparation method of an emulsion thickener with back-acid stability, which comprises the following steps:

[0016] S1: under an inert atmosphere, heating a first material to a first temperature, then adding a second material and mixing uniformly to obtain a first reaction system; S2: adding a third material and a fourth material to the first reaction system respectively, and obtaining a second reaction system after the addition is completed; S3: heating the second reaction system to a second temperature for reaction to obtain the emulsion thickener with back-acid stability;

[0017] In the preparation method, the emulsifier is added in two parts; the first material is a mixture of part of the emulsifier and water; the second material is a mixture of the first initiator and water; the third material is a mixture of the polymerization monomer, the crosslinking agent, and the other part of the emulsifier and water; the fourth material is a mixture of the second initiator, the structural additive, and water; and the structural additive is a polypeptide including a polar amino acid residue.

[0018] In the technical solution, a polypeptide containing polar amino acid residues is added to the reaction system as a structure additive, which presents an extended conformation in the alkaline polymerization stage and is folded or self-assembled into a beta-sheet / alpha-helix structure in the acid recovery stage. By interacting with the thickener molecules, the conformation change of the thickener molecules in the acidic environment can be adjusted, the response rate of network reconstruction is effectively improved, the self-repairing function of the system is promoted, and additional functions such as biocompatibility are also provided. The hydrophilic group of the polypeptide interacts with the emulsifier to improve the emulsification efficiency. The polypeptide structure additive is a green additive, so the technical solution provides key technical support for green and efficient emulsion design. In addition, the emulsification stability can be improved by adding the emulsifier step by step, and the thickener emulsion particle size and its distribution can be controlled, so that the emulsion thickener has more excellent thickening effect.

[0019] It should be noted that the specific preparation methods of the first material, the second material, the third material and the fourth material are not limited in the present application. In an optional example of the present application, the first material is obtained by uniformly mixing a part of the emulsifier with water; the second material is obtained by uniformly mixing the first initiator with water; the third material is obtained by uniformly mixing the polymerization monomer, the crosslinking agent and another part of the emulsifier in water; and the fourth material is obtained by uniformly mixing the second initiator, the structure additive and water. It should be noted that the order of preparation of the first material, the second material, the third material and the fourth material is not limited.

[0020] The acid recovery stage of the present application refers to the process stage of gradually changing the pH value of the thickener system from the alkaline range to the acidic range. The acid recovery performance is used to characterize the performance of the thickener system in maintaining and restoring the viscosity of the system after the pH value gradually changes from the alkaline range to the acidic range. The acid recovery stability is used to characterize the performance of the thickener system in maintaining and restoring its viscosity to the viscosity of the alkaline polymerization stage.

[0021] In further examples of the present application, the composition and amount of the structure additive are explored and optimized.

[0022] Alternatively, the structure additive is a polypeptide containing charged amino acid residues. The charged amino acid residues in the polypeptide contain one or more of carboxyl groups (-COOH) or amino groups (-NH2), which can form hydrogen bonds, ionic bonds or participate in condensation reactions with amino groups, carboxyl groups or hydroxyl groups (-OH) in the thickener molecules. A large number of experiments of the present application have proved that the interaction between the charged amino acid residues and the thickener molecules helps to introduce the polypeptide into the structure of the thickener molecules or stabilize it in the system, thereby affecting the acid recovery performance of the thickener.

[0023] Optionally, the molecular weight of the structural additive is 500-5000 Dalton, and the polypeptide structural additive in the molecular weight range has good solubility and diffusivity in the emulsion thickener system, and can effectively interact with the thickener molecules, as demonstrated by the examples and comparative examples of the present application. In the optional examples of the present application, the molecular weight of the structural additive is 500-2000 Dalton.

[0024] Optionally, the structural additive is a polypeptide chain comprising at least one charged amino acid residue of lysine, arginine, histidine, glutamic acid or aspartic acid, and the optimization of the structural form of the polypeptide chain facilitates the exertion of the charged amino acid residue.

[0025] It should be noted that the present application is not limited to the source of the structural additive, which can be naturally extracted or artificially synthesized according to the design.

[0026] Further optionally, the polypeptide chain comprises at least one charged amino acid residue of histidine, and the imidazole group of histidine has special acid-base properties near the physiological pH value; the comparative examples of the present application show that the addition of the structural additive comprising the charged amino acid residue of histidine can effectively enhance the viscosity of the thickener under the condition of reduced pH value, and promote the obtaining of the cosmetic product with better skin feel. In the optional examples of the present application, the polypeptide chain comprises at least three charged amino acid residues of histidine.

[0027] Optionally, the mass of the structural additive is 0.5%-3% of the mass of the polymerized monomer, and the appropriate amount of the structural additive facilitates the interaction between the polypeptide and the emulsifier during the preparation process, and improves the acid return stability of the prepared emulsion thickener. In the optional examples of the present application, the mass of the structural additive is 1%-2.5% of the mass of the polymerized monomer, preferably 1%-2%.

[0028] In further examples of the present application, the composition and amount of the emulsifier are explored and optimized.

[0029] Optionally, the emulsifier is a composite emulsifier including an anionic emulsifier and a non-ionic emulsifier. In the polypeptide including a polar amino acid residue, the hydrophilic group can interact with the negative charge of the anionic emulsifier, or form a hydrogen bond with the hydrophilic segment of the non-ionic emulsifier, etc., thereby changing the arrangement of the emulsifier at the oil-water interface and improving the emulsification efficiency. In addition, the anionic emulsifier is dispersed efficiently by electrostatic repulsion under alkaline conditions, and the non-ionic emulsifier can maintain stability by steric hindrance in an acidic environment, avoiding the risk of emulsion breaking caused by pH fluctuation in a single emulsifier system. The examples and comparative examples of the present application demonstrate that the use of a composite emulsifier in the present application, the emulsion thickener prepared is especially suitable for systems that need to undergo dynamic changes in acidity and alkalinity, and is superior to a single emulsifier system in stability, thickening efficiency and applicable scenarios.

[0030] Optionally, the anionic emulsifier includes one or more of sodium dodecyl sulfate, sodium dodecyl benzene sulfonate, sodium dodecyl sulfonate, sodium dodecyl phosphate, sodium stearate, sodium lauroyl sarcosinate, sodium laureth sulfate, sodium myristyl sulfate, dioctyl sodium sulfosuccinate, preferably one or more of sodium dodecyl sulfate, sodium dodecyl benzene sulfonate, sodium dodecyl sulfonate, preferably one or more of sodium dodecyl sulfate, sodium dodecyl benzene sulfonate, sodium dodecyl sulfonate.

[0031] Optionally, the non-ionic emulsifier includes one or more of Tween-80, Span-80, Span-60, glyceryl laurate, polyglycerol fatty acid ester, sucrose fatty acid ester, alkyl glycoside, methyl glucoside polyoxyethylene ether, preferably one or more of Tween-80, Span-80, Span-60.

[0032] Optionally, in the emulsifier, the mass ratio of the non-ionic emulsifier to the anionic emulsifier is (1-4):1. Optimizing the mass ratio of the non-ionic emulsifier to the anionic emulsifier helps to improve the stability of the thickening agent when the pH value of the application system falls from alkaline to acidic. In optional examples of the present application, the mass ratio of the non-ionic emulsifier to the anionic emulsifier is (1-3):1, preferably (1-2):1.

[0033] Optionally, the mass of the emulsifier is 0.1%-3% of the mass of the polymerized monomers. Optimizing the amount of emulsifier can regulate the particle size and distribution of monomer droplets in the emulsion, and help to improve the rheological properties and stability of the thickening agent. In optional examples of the present application, the mass of the emulsifier is 0.1%-1% of the mass of the polymerized monomers, preferably 0.2%-1%.

[0034] Optionally, the mass ratio of the third material and the first material containing emulsifier is (0.2-5):1. In the present application, the step-by-step addition of emulsifier is realized by adding part of emulsifier to the third material and the first material, thereby improving the morphology and distribution of the thickener polymer particles prepared, and improving the operation stability. In the optional examples of the present application, the mass ratio of the third material and the first material containing emulsifier is (1-4):1, preferably (2-4):1.

[0035] In further examples of the present application, the types and amounts of the polymerization monomers are explored and optimized.

[0036] Optionally, the polymerization monomers are mixed monomers including a first monomer and a second monomer, the first monomer is an a,b-unsaturated acid monomer, and the second monomer is an a,b-unsaturated ester monomer.

[0037] Optionally, the first monomer includes one or more of acrylic acid, methacrylic acid, crotonic acid, maleic acid, cinnamic acid, fumaric acid, citraconic acid and mesaconic acid, preferably acrylic acid and / or methacrylic acid.

[0038] Optionally, the second monomer includes one or more of methyl acrylate, ethyl acrylate, butyl acrylate, methyl methacrylate, butyl methacrylate, hydroxyethyl methacrylate, glycidyl methacrylate, palmitoleic acid acrylate and ethylene glycol dimethacrylate, preferably one or more of butyl acrylate, ethyl methacrylate and glycidyl methacrylate.

[0039] Optionally, the mass concentration of the polymerization monomers in the second reaction system is 5%-50%. The exploration of the concentration of polymerization monomers is conducive to preparing a thickener with reasonable molecular weight distribution and stable structure, and improving the rheological properties of the prepared thickener. In the optional examples of the present application, the mass concentration of the polymerization monomers in the second reaction system is 10%-40%, preferably 30%-40%.

[0040] In further examples of the present application, the composition and amount of the initiator are explored and optimized.

[0041] Optionally, the first initiator and the second initiator are independently selected from one or more of potassium persulfate, sodium persulfate, ammonium persulfate, sodium thiosulfate, azobisdimethylaminoformamide hydrochloride and azobisdimethylimidazoline hydrochloride, preferably potassium persulfate and / or sodium persulfate.

[0042] In the above technical solution, the types of the first initiator and the second initiator can be the same or different. In the optional examples of the present application, the types of the first initiator and the second initiator are the same.

[0043] Optionally, the total mass of the first initiator and the second initiator is 0.05% to 1% of the mass of the polymerization monomers. Optimizing the amount of initiator is conducive to controlling the reaction process, improving the stability of the operation, and helping to obtain a structurally stable thickening agent product. In optional examples of the present application, the total mass of the first initiator and the second initiator is 0.05% to 0.5%, preferably 0.05% to 0.2%, of the mass of the polymerization monomers.

[0044] Optionally, the mass ratio of the first initiator to the second initiator is (0.2 to 5): 1. By combining the phased addition of initiators with the phased crosslinking reaction, the start and rate of the polymerization reaction can be gradually controlled, making the polymerization reaction more uniform and stable. In optional examples of the present application, the mass ratio of the first initiator to the second initiator is (0.2 to 2): 1, preferably (0.2 to 1): 1.

[0045] In further examples of the present application, the composition and amount of the crosslinking agent are explored and optimized.

[0046] Optionally, the crosslinking agent includes one or more of pentaerythritol triacrylate, trimethylolpropane triacrylate, dipentaerythritol pentaacrylate, 1,6-hexanediol diacrylate, trimethylolpropane trimethacrylate, diallyl phthalate, and pentaerythritol tetraacrylate, preferably pentaerythritol triacrylate and / or diallyl phthalate.

[0047] Optionally, the mass of the crosslinking agent is 0.1% to 3% of the mass of the polymerization monomers. Optimizing the amount of crosslinking agent can promote crosslinking polymerization between the polymerization monomers and improve efficiency. In optional examples of the present application, the mass of the crosslinking agent is 0.5% to 2%, preferably 0.5% to 1%, of the mass of the polymerization monomers.

[0048] In further examples of the present application, the first temperature is 50 to 80°C. In further examples of the present application, the second temperature is 70 to 90°C, and the reaction time at the second temperature is 1 to 5 hours. Controlling the temperature in different polymerization stages is conducive to forming a uniform and stable crosslinking network through crosslinking reactions in each stage, improving the operability of the method.

[0049] In the above technical solution, the relative dropping speed of the third material and the fourth material is not limited and can be the same or different. In further examples of the present application, in step S2, the dropping speed of the third material and the fourth material is the same, and the dropping operation of the two materials is completed within a time range of 0.5 to 3 hours.

[0050] It should be noted that in the present application, the inert atmosphere refers to a gas environment composed of a gas that does not chemically interact with the reactants, such as a nitrogen atmosphere, or an atmosphere formed by a zero group element gas in the periodic table (such as argon), etc.

[0051] Compared with the prior art, the emulsion thickener with acid recovery stability of the present application has the following beneficial effects: the emulsion thickener with acid recovery stability of the present application includes a structural additive containing polar amino acid residues, which enhances the acid recovery performance of the emulsion thickener and endows it with biocompatibility, so that the emulsion thickener of the present application can quickly restore to the viscosity in the alkaline condition and gradually increase when the system changes from an alkaline condition to an acidic condition, effectively improving the response rate of network reconstruction and realizing the self-repairing function, and can be applied in a wider range of pH conditions and formulations; in addition, the emulsion thickener with acid recovery stability of the present application can also promote the obtaining of cosmetic products with better skin feel in practical application.

[0052] The preparation method of the emulsion thickener with acid recovery stability of the present application adds a structural additive containing polar amino acid residues, and the step-by-step addition of the emulsifier forms a reversible dynamic crosslinking network, which enhances the acid recovery performance of the emulsion thickener and endows it with biocompatibility; the preparation method of the present application is simple and easy to implement, has good stability, and can be implemented in an industrialized manner. DETAILED DESCRIPTION

[0053] In order to facilitate the understanding of the present application, the present application will be described more fully below, and preferred embodiments of the present application will be given. However, it should be understood that these embodiments are only used for more detailed description, and should not be understood as limiting the present application in any form, i.e. not intended to limit the protection scope of the present application.

[0054] Unless otherwise defined, the technical terms used in the following examples have the same meaning as generally understood by those skilled in the art to which the present application belongs. The test reagents used in the following examples, unless otherwise specified, are conventional biochemical reagents; the experimental methods, unless otherwise specified, are conventional methods.

[0055] The test method for the viscosity of the emulsion thickener in the present application is the viscosity test of the shower gel formula, specifically: the emulsion thickener prepared in the examples and comparative examples is prepared into a transparent shower gel according to the formula shown in Table 1; the stirring state is maintained during the preparation process; the water, chelating agent, thickener and surfactant are added into a beaker in sequence, then 20% mass concentration sodium hydroxide aqueous solution is added into the solution under stirring to adjust the pH of the formula to about 7.0, and finally 50% citric acid is added to adjust the pH value to 5, 4 and 3, to obtain a hydrogel. When the viscosity is tested, the hydrogel is transferred to a centrifuge tube and centrifuged to remove bubbles at each pH value, and the viscosity of the hydrogel is determined at 25°C using a Brookfiled DV2T-RV type rotary viscometer, and the rotation speed is selected to be 20 revolutions per minute.

[0056] Table 1

[0057]

[0058] The smoothness of the prepared shower gel formula is tested by visually and manually touching the surface of the sample, and is divided into two grades of rough and smooth.

[0059] Example 1

[0060] A method for preparing an emulsion thickener with acid return stability, specifically: under a nitrogen atmosphere, 200 g of water, 0.1 g of sodium dodecyl sulfonate, and 0.1 g of Span-60 (first material) are added to a 1 L three-necked flask, stirred and mixed uniformly, and heated to 50°C; a beaker is taken and 20 g of water and 0.03 g of potassium persulfate (second material) are added, mixed uniformly, and added to the three-necked flask at one time. Two other beakers are taken to prepare the third material and the fourth material, respectively; the third material is composed of 0.2 g of sodium dodecyl sulfonate, 0.2 g of Span-60, 45 g of methacrylic acid, 105 g of glycidyl methacrylate, 0.75 g of pentaerythritol triacrylate, and 40 g of water, and the fourth material is composed of 0.12 g of potassium persulfate, 1.5 g of heptapeptide HSHGHEK (molecular weight 830 daltons, amino acid sequence: histidine-serine-histidine-glycine-histidine-glutamic acid-lysine), and 40 g of water, which are stirred uniformly and then added to the three-necked flask at the same speed, with a dropwise addition time of about 0.5-3 h; after the dropwise addition is completed, the reaction temperature is increased to 80°C and the reaction is continued for 2 h, and after cooling to room temperature, the target emulsion thickener is obtained by filtration. In Test Example 1, the emulsion thickener of the present example is used to prepare a transparent shower gel according to the formula of Table 1, and the viscosity is tested under different pH values subsequently, and the test results are shown in Table 2.

[0061] Example 2

[0062] A method for preparing an emulsion thickener with acid back stability, specifically: under a nitrogen atmosphere, 80 g of water, 0.05 g of sodium dodecyl sulfate and 0.1 g of Span-80 (first material) are added to a 1 L three-necked flask, stirred and mixed uniformly and heated to 80℃; a beaker is taken and 20 g of water and 0.05 g of potassium persulfate (second material) are added thereto, mixed uniformly and added to the three-necked flask at one time. Two other beakers are taken to prepare third material and fourth material respectively. The third material is composed of 0.2 g of sodium dodecyl sulfate, 0.3 g of Span-80, 28 g of acrylic acid, 44 g of ethyl methacrylate, 0.72 g of diallyl phthalate ether and 30 g of water, and the fourth material is composed of 0.05 g of potassium persulfate, 1.2 g of heptapeptide WLHAEQS (molecular weight 870 daltons, amino acid sequence: tryptophan-leucine-histidine-alanine-glutamic acid-glutamine-serine) and 30 g of water, which are stirred uniformly respectively and then added to the three-necked flask at a certain pump rate, with a dropwise adding time of about 0.5-3 h; after the dropwise adding is completed, the reaction temperature is increased to 90℃ and the reaction is continued for 4 h, and after cooling to room temperature, the target emulsion thickener is obtained by filtration. In Test Example 2, the emulsion thickener of the present embodiment is used to prepare a transparent shower gel according to the formulation of Table 1, and subsequent viscosity tests under different pH values are carried out, and the test results are shown in Table 2.

[0063] Example 3

[0064] A preparation method of an emulsion thickener with acid back stability, specifically: under a nitrogen atmosphere, 150 g of water, 0.2 g of sodium dodecyl benzene sulfonate, and 0.2 g of Tween-80 (first material) are added into a 1 L three-necked flask, stirred and mixed uniformly, and heated to 60°C; a beaker is taken, 20 g of water and 0.02 g of potassium persulfate (second material) are added into the beaker, mixed uniformly, and then added into the three-necked flask at one time. Two other beakers are taken, and a third material and a fourth material are prepared respectively. The third material is composed of 0.6 g of sodium dodecyl benzene sulfonate, 0.6 g of Tween-80, 64 g of methacrylic acid, 96 g of butyl acrylate, 0.8 g of diallyl phthalate ether, and 30 g of water, and the fourth material is composed of 0.06 g of potassium persulfate, 2 g of decapeptide GHDFRKYWQS (with a molecular weight of 1323 Dalton, and an amino acid sequence of: glycine-histidine-aspartic acid-phenylalanine-arginine-lysine-tyrosine-tryptophan-glutamine-serine), and 40 g of water, which are stirred uniformly respectively, and then the third material and the fourth material are added into the three-necked flask at a certain pump speed, and the dropping time is about 0.5-3 h; after the dropping is completed, the reaction temperature is increased to 70°C, and the reaction is continued for 5 h, and then the target emulsion thickener is obtained after being cooled to room temperature. In Test Example 3, the emulsion thickener of the present embodiment is used, a transparent shower gel is prepared according to the formula in Table 1, and then viscosity tests under different pH values are carried out, and the test results are shown in Table 2.

[0065] Comparative Example 1

[0066] A preparation method of an emulsion thickener, the parameter control and operation steps of the preparation method are the same as those of Example 1, except that the fourth material in the present comparative example does not contain a structural additive. In Test Example 4, the emulsion thickener prepared by the present comparative example is used, a transparent shower gel is prepared according to the formula in Table 1, and then viscosity tests under different pH values are carried out, and the test results are shown in Table 2.

[0067] Comparative Example 2

[0068] A preparation method of an emulsion thickener, the parameter control and operation steps of the preparation method are the same as those of Example 1, except that the emulsifier used in the present comparative example is sodium dodecyl sulfonate, and the fourth material does not contain a structural additive. In Test Example 5, the emulsion thickener prepared by the present comparative example is used, a transparent shower gel is prepared according to the formula in Table 1, and then viscosity tests under different pH values are carried out, and the test results are shown in Table 2.

[0069] Comparative Example 3

[0070] A method for preparing an emulsion thickening agent, the parameter control and operation steps of which are the same as those of Example 1, except that the structural additive used in the present comparative example is 50 peptide, the molecular weight of which is about 5900 Dalton, and the amino acid sequence of which is: WHLEQKLRASGLAEHLGALESWLHQEALERSQLEWLGALESWLRQEALER (tryptophan-histidine-leucine-glutamic acid-glutamine-lysine-leucine-arginine-alanine-serine-glycine-leucine-alanine-glutamic acid-histidine-leucine-glycine-alanine-leucine-glutamic acid-serine-tryptophan-leucine-histidine-glutamine-glutamic acid-alanine-leucine-glutamic acid-arginine-serine-glutamine-leucine-glutamic acid-tryptophan-leucine-glycine-alanine-leucine-glutamic acid-serine-tryptophan-leucine-arginine-glutamine-glutamic acid-alanine-leucine-glutamic acid-arginine). The emulsion thickening agent prepared in Test Example 6 using the present comparative example is formulated into a transparent shower gel according to the formulation of Table 1, and viscosity tests at different pH values are carried out subsequently, and the test results are shown in Table 2.

[0071] Comparative Example 4

[0072] A method for preparing an emulsion thickening agent, the parameter control and operation steps of which are the same as those of Example 1, except that the structural additive used in the present comparative example is 4 peptide, the molecular weight of which is about 400 Dalton, and the amino acid sequence of which is GAAS (glycine-alanine-alanine-serine). The emulsion thickening agent prepared in Test Example 7 using the present comparative example is formulated into a transparent shower gel according to the formulation of Table 1, and viscosity tests at different pH values are carried out subsequently, and the test results are shown in Table 2.

[0073] Comparative Example 5

[0074] A method for preparing an emulsion thickening agent, the parameter control and operation steps of which are the same as those of Example 1, except that the emulsifier used in the present comparative example is sodium dodecyl sulfonate. The emulsion thickening agent prepared in Test Example 8 using the present comparative example is formulated into a transparent shower gel according to the formulation of Table 1, and viscosity tests at different pH values are carried out subsequently, and the test results are shown in Table 2.

[0075] Comparative Example 6

[0076] A method for preparing an emulsion thickening agent, the parameter control and operation steps of which are the same as those of Example 1, except that the emulsifier used in the present comparative example is Span-60. The emulsion thickening agent prepared in Test Example 9 using the present comparative example is formulated into a transparent shower gel according to the formulation of Table 1, and viscosity tests at different pH values are carried out subsequently, and the test results are shown in Table 2.

[0077] Comparative Example 7

[0078] A preparation method of the emulsion thickening agent, the parameter control and operation steps of the preparation method are the same as those of Example 1, the difference is that the emulsifier used in the present comparative example is added at one time, and is contained in the first material. In test example 10, the emulsion thickening agent prepared by using the present comparative example is used to prepare transparent shower gel according to the formula in table 1, and the viscosity test under different pH values is carried out, and the test results are shown in table 2.

[0079] Table 2

[0080]

[0081] It can be proved by combining test examples 1-3 in table 2 that when the emulsion thickening agent prepared by the preparation method of the emulsion thickening agent with acid return stability of the present application is applied to the preparation of cosmetic shower gel, after neutralization by compounding alkali (pH=7), it can play an excellent suspension, stability and system thickening effect, and get a smooth skin feeling cosmetic product; When the pH value of the system decreases to the acidic direction, the shower gel containing the emulsion thickening agent of the present example can still maintain a relatively high viscosity and rheological property, and the system viscosity can quickly recover to the level at neutral and gradually increase, reflecting the excellent network reconstruction response rate and self-repairing function of the emulsion thickening agent of the present example, which has excellent acid return stability and can be applied to a wider range of pH value conditions and formulations.

[0082] By combining test example 1 with test examples 4, 6-7 in table 2, it is proved that the addition of polypeptide containing specific polar amino acid residues in the preparation method of the present application improves the acid return performance and thickening efficiency of the whole thickening agent system, and has better thickening performance under acidic conditions; The addition of structural additives with specific molecular weight in the preparation process makes the emulsion thickening agent have better acid return performance. Further combining test example 5 proves that the use of composite emulsifier and specific polypeptide structural additive in the preparation method of the present application synergistically improves the acid return performance of the system containing the emulsion thickening agent prepared, not only makes the skin feel of the system better, but also enhances the interfacial stability and rheological property of the system under acidic conditions.

[0083] By combining test example 1 with test examples 8-9, it is verified that the addition of composite emulsifier containing anionic emulsifier and nonionic emulsifier in the preparation method of the present application can effectively promote the formation of crosslinked network, not only improve the thickening performance of the emulsion thickening agent under alkaline activation, get a cosmetic product with high viscosity and better skin feel, but also efficiently promote the formation of reversible dynamic crosslinked network when the pH value of the system is acidic, maintain the viscosity and skin feel of the cosmetic. Combining test example 1 and test example 10, it is proved that the stepwise addition of emulsifier in the preparation method of the present application helps to control the particle size and its distribution of the thickening agent emulsion, and improves the thickening effect under acid return condition.

[0084] It should be noted that the above content is a further detailed description of the present application in combination with specific embodiments, and cannot be regarded as the specific implementation of the present application only limited to these descriptions. For ordinary skilled persons in the technical field of the present application, without departing from the concept of the present application, a number of simple improvements can be made, which should be regarded as belonging to the protection scope of the present application.

Claims

1. An emulsion thickener with acid stability, characterized in that: The raw materials of the emulsion thickener include polymer monomers, emulsifiers, initiators, cross-linking agents, water and structural additives; The polymerizable monomers include a first monomer and a second monomer, the first monomer is an α,β-unsaturated acid monomer, the second monomer is an α,β-unsaturated ester monomer, and the structural additive is a polypeptide including polar amino acid residues; The molecular weight of the structural additive is 500-5000 Daltons; the mass of the structural additive is 0.5%-3% of the mass of the polymerized monomer; the emulsifier is a composite emulsifier of anionic emulsifier and nonionic emulsifier; the mass ratio of the nonionic emulsifier to the anionic emulsifier is (1-4):1; the mass of the cross-linking agent is 0.1%-3% of the mass of the polymerized monomer; The initiator includes a first initiator and a second initiator; and the preparation method of the emulsion thickener includes the following steps: S1: Under an inert atmosphere, heating a first material to a first temperature, adding a second material and mixing them uniformly to obtain a first reaction system; S2: adding a third material and a fourth material dropwise to the first reaction system to obtain a second reaction system after the addition is completed; S3: heating the second reaction system to a second temperature for reaction to obtain the emulsion thickener with back acid stability; The emulsifier used in the preparation method is added in two parts; the first material is a mixture of a portion of the emulsifier and water; the second material is a mixture of the first initiator and water; the third material is a mixture of the polymerization monomer, the cross-linking agent, another portion of the emulsifier and water; and the fourth material is a mixture of the second initiator, the structural additive and water.

2. The acid-stable emulsion thickener according to claim 1, characterized in that The structural additive is a polypeptide comprising charged amino acid residues.

3. The acid-stable emulsion thickener according to claim 1, characterized in that The mass of the emulsifier is 0.1% to 3% of the mass of the polymerized monomer.

4. The acid-stable emulsion thickener according to claim 1, characterized in that The crosslinking agent includes one or more of pentaerythritol triacrylate, trimethylolpropane triacrylate, dipentaerythritol pentaacrylate, 1,6-hexanediol diacrylate, trimethylolpropane trimethacrylate, diallyl phthalate, and pentaerythritol tetraacrylate; And / or, the first initiator and the second initiator are independently selected from one or more of potassium persulfate, sodium persulfate, ammonium persulfate, sodium thiosulfate, azobisisobutylamidine hydrochloride and azobisisobutylimidazoline hydrochloride; the mass ratio of the first initiator to the second initiator is (0.2-5):1; the initiator accounts for 0.05%-1% of the mass of the polymerized monomer.

5. A method for preparing an emulsion thickener with acid stability, characterized in that: The raw materials of the emulsion thickener include polymerizable monomers, emulsifiers, initiators, crosslinking agents, water and structural additives, the polymerizable monomers include a first monomer and a second monomer, the first monomer is an α,β-unsaturated acid monomer, the second monomer is an α,β-unsaturated ester monomer, the structural additive is a polypeptide including polar amino acid residues, and the initiators include a first initiator and a second initiator; The preparation method comprises the following steps: S1: Under an inert atmosphere, heating a first material to a first temperature, adding a second material and mixing them uniformly to obtain a first reaction system; S2: adding a third material and a fourth material dropwise to the first reaction system to obtain a second reaction system after the addition is completed; S3: heating the second reaction system to a second temperature for reaction to obtain the emulsion thickener with back acid stability; The emulsifier used in the preparation method is added in two parts; the first material is a mixture of a portion of the emulsifier and water; the second material is a mixture of the first initiator and water; the third material is a mixture of the polymerizable monomer, the crosslinking agent, another portion of the emulsifier, and water; and the fourth material is a mixture of the second initiator, the structural additive, and water. The molecular weight of the structural additive is 500 to 5000 Daltons; the mass of the structural additive is 0.5% to 3% of the mass of the polymerized monomer; the emulsifier is a composite emulsifier of anionic emulsifier and nonionic emulsifier; in the emulsifier, the mass ratio of the nonionic emulsifier to the anionic emulsifier is (1 to 4): 1; and the mass of the cross-linking agent is 0.1% to 3% of the mass of the polymerized monomer.

6. The method for preparing an emulsion thickener having acid return stability according to claim 5, wherein: The structural additive is a polypeptide comprising charged amino acid residues; And / or, the structural additive is a polypeptide chain comprising at least one charged amino acid residue of lysine, arginine, histidine, glutamic acid or aspartic acid.

7. The method for preparing an emulsion thickener having acid return stability according to claim 5, wherein: The anionic emulsifier includes one or more of sodium lauryl sulfate, sodium dodecylbenzenesulfonate, sodium laurylsulfonate, sodium laurylphosphate, sodium stearate, sodium lauroyl sarcosinate, sodium laureth sulfate, sodium tetradecyl sulfate, and sodium dioctylsulfosuccinate; And / or, the nonionic emulsifier includes one or more of Tween-80, Span-80, Span-60, glyceryl laurate, polyglyceryl fatty acid ester, sucrose fatty acid ester, alkyl glycoside, and methyl glucoside polyoxyethylene ether; and / or, the mass of the emulsifier is 0.1% to 3% of the mass of the polymerized monomer; And / or, the mass ratio of the emulsifier contained in the third material to the first material is (0.2~5):

1.

8. The method for preparing an emulsion thickener having acid return stability according to claim 5, wherein: The first monomer comprises one or more of acrylic acid, methacrylic acid, crotonic acid, maleic acid, cinnamic acid, fumaric acid, citraconic acid and mesaconic acid; and / or, the second monomer comprises one or more of methyl acrylate, ethyl acrylate, butyl acrylate, ethyl methacrylate, butyl methacrylate, hydroxyethyl methacrylate, glycidyl methacrylate, palmitic acrylate and ethylene glycol dimethacrylate; And / or, the mass concentration of the polymerization monomer in the second reaction system is 5% to 50%.

9. The method for preparing an emulsion thickener having acid back stability according to claim 5, wherein: The first initiator and the second initiator are independently selected from one or more of potassium persulfate, sodium persulfate, ammonium persulfate, sodium thiosulfate, azobisisobutylamidine hydrochloride and azobisisobutylimidazoline hydrochloride; the sum of the mass of the first initiator and the second initiator is 0.05% to 1% of the mass of the polymerized monomer; the mass ratio of the first initiator to the second initiator is (0.2 to 5):1; And / or, the crosslinking agent includes one or more of pentaerythritol triacrylate, trimethylolpropane triacrylate, dipentaerythritol pentaacrylate, 1,6-hexanediol diacrylate, trimethylolpropane trimethacrylate, diallyl phthalate, and pentaerythritol tetraacrylate.

10. The method for preparing an emulsion thickener having acid return stability according to claim 5, characterized in that: The first temperature is 50-80°C; And / or, the second temperature is 70-90° C., and the reaction time under the second temperature condition is 1-5 hours; And / or, in step S2, the third material and the fourth material are added at the same speed, and the addition of the two materials is completed within a time range of 0.5 to 3 hours.

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