A hydrophobically modified thickener and its preparation method and application

Abstract

The present invention belongs to the field of new materials and discloses a method for preparing a hydrophobically modified thickener. The method comprises the following steps: Step 1: subjecting a portion of a hydrophobically associating monomer, a portion of a hydrophilic monomer, a portion of a hydrophobic monomer, and a reactive emulsifier to a free radical emulsion polymerization reaction, and after completion of the reaction, adjusting the pH of the reaction system to 4 to 7; Step 2: adding the remaining hydrophobically associating monomer, hydrophilic monomer, and hydrophobic monomer to the reaction system to conduct a free radical emulsion polymerization reaction. This method produces a polymer emulsion with excellent stability, which can maintain long-term stability under high and low temperature conditions. The present invention also discloses a hydrophobically modified thickener and its application.

Description

Technical Field

[0001] The present invention relates to the field of new materials, and in particular to a hydrophobically modified thickener, a preparation method thereof, and an application thereof. Background Art

[0002] Thickeners are polymers used to increase system viscosity and improve rheological properties. Currently, the most widely used synthetic thickener is the alkali-swellable polyacrylic acid thickener. Later, building on this alkali-swelling property, a new type of hydrophobically associating acrylic thickener was developed. This thickener incorporates hydrophobic side chains into the original acrylic backbone. This allows the polymer backbone to swell in alkali, while the hydrophobic groups in the side chains associate to form a physical crosslinking network, significantly enhancing the thickening effect.

[0003] Traditional emulsion polymerization requires a considerable amount of emulsifier to maintain emulsion stability. These emulsifiers are only physically adsorbed onto the exterior of the latex particles. High or low ambient temperatures can cause the emulsion to become unstable and cause sedimentation. Furthermore, the use of large amounts of conventional emulsifiers also poses safety risks. Reactive emulsifiers contain reactive functional groups that can chemically bind to the polymer, making them less susceptible to migration than traditional emulsifiers and improving the stability of the finished emulsion. However, some reactive emulsifiers, such as allyl or acrylamide, are easily embedded within the latex particles due to their short chain lengths, resulting in decreased emulsion stability.

[0004] That is, traditional emulsion-type thickeners generally have the problem of poor storage stability under high and low temperature conditions. Summary of the Invention

[0005] The present invention aims to provide a method for preparing a hydrophobically modified thickener. The hydrophobically modified thickener prepared by the method has excellent storage stability under high and low temperature conditions. The present invention also discloses a hydrophobically modified thickener and its application.

[0006] To achieve the above objectives, this application discloses:

[0007] A method for preparing a hydrophobically modified thickener comprises the following steps:

[0008] Step 1: adding part of the hydrophobic associating monomer, part of the hydrophilic monomer, part of the hydrophobic monomer, a reactive emulsifier and deionized water into a reaction vessel to carry out a free radical emulsion polymerization reaction in the presence of an initiator, and adjusting the pH of the reaction system to 4-7 after the reaction is completed;

[0009] Step 2: adding the remaining hydrophobically associating monomer, hydrophilic monomer, and hydrophobic monomer to the reaction system obtained in step 1 to carry out free radical emulsion polymerization in the presence of an initiator;

[0010] The weight of the hydrophobically associating monomer used in step 1 is equivalent to 20.0 wt % to 60.0 wt % of the total weight of the hydrophobically associating monomers used in steps 1 and 2;

[0011] The weight of the hydrophilic monomer used in step 1 is equivalent to 20.0 wt% to 40.0 wt% of the total weight of the hydrophilic monomers used in steps 1 and 2;

[0012] The weight of the hydrophobic monomer used in step 1 is equivalent to 20.0 wt% to 40.0 wt% of the total weight of the hydrophobic monomers used in steps 1 and 2;

[0013] The weight ratio of the total weight of the hydrophobic associating monomers in steps 1 and 2, the total weight of the hydrophilic monomers in steps 1 and 2, the total weight of the hydrophobic monomers in steps 1 and 2, and the weight of the reactive emulsifier is: 4.0-25.0:15.5-32:55.5-80.0:0.5-5.0.

[0014] Existing emulsion thickeners are prepared by using reactive emulsifier monomers or non-reactive emulsifiers. When using reactive emulsifier monomers to synthesize polymers, the reactive emulsifier monomers are added to the polymer chain through copolymerization. After the reaction is completed, the polymer is distributed in the thickener solution in the form of particles. Most of the reactive emulsifier monomers are embedded inside the particles and cannot fully exert their emulsification effect, resulting in particle precipitation under high or low temperature storage conditions. The present invention synthesizes the polymer by adopting two-step free radical emulsion polymerization. The first step of free radical emulsion polymerization is used to add the reactive emulsifier to the polymer chain segment, and then the reaction is terminated and the polymer is neutralized. The second step of free radical emulsion polymerization continues the reaction to synthesize the polymer.

[0015] Since the neutralization operation is carried out after the first step of free radical emulsion polymerization, the carboxyl group in the monomer is ionized to form -COO - The carboxylate groups in the polymer form a repulsive force with the cations (related to the type of cations in the alkali solution used for neutralization). The intramolecular repulsion of the polymer causes the polymer chain to unfold, thereby allowing the reactive emulsifier on the polymer chain to extend into the aqueous phase and continue to play the role of an emulsifier.

[0016] The second-step free-radical emulsion polymerization, based on the superior emulsification system obtained in the first step, allows for the smooth synthesis of the remaining monomers. In this step, the reactive emulsifier is attached to the polymer, meaning that the monomers in the second step react within the micelles formed by the first-step polymer, forming an entrapment structure. This entrapment structure may result in a core-shell structure in the resulting polymer particles. This entrapment structure maintains its emulsification function and maintains stability during the long-term storage of the polymer emulsion.

[0017] The polymer obtained by the above method has the advantage of good high-temperature and low-temperature storage stability. At the same time, the polymer does not require the use of a non-reactive emulsifier and is more friendly to the environment and the human body.

[0018] In the above preparation method, the ratio of the total weight of the hydrophobically associating monomers in steps 1 and 2, the total weight of the hydrophilic monomers in steps 1 and 2, the total weight of the hydrophobic monomers in steps 1 and 2, and the weight of the reactive emulsifier is: 7.0-25.0: 21.5-32: 55.5-70.0: 0.5-5.0;

[0019] Preferably, in step 2, the hydrophobic associating monomer, the hydrophilic monomer and the hydrophobic monomer are added to the reaction system obtained in step 1 by dropwise addition or batchwise addition.

[0020] The ratio of the total weight of the hydrophobically associating monomers in steps 1 and 2, the total weight of the hydrophilic monomers in steps 1 and 2, the total weight of the hydrophobic monomers in steps 1 and 2, and the weight of the reactive emulsifier is a reasonable ratio range for preparing a thickener with thickening and rheological properties;

[0021] In the present invention, controlling the ratio of the hydrophobically associating monomer, the hydrophilic monomer, and the hydrophobic monomer in step 1 has a certain influence on at least one of the storage stability, reaction stability, thickening performance, light transmittance, and rheological properties of the product;

[0022] If the ratio of each monomer in step 1 is reduced to a lower level, such as 10%, and the reaction is carried out by adding the remaining monomers without neutralization, the reaction process will be close to that of seed emulsion polymerization. The polymer uniformity of the product obtained by seed emulsion polymerization will definitely be better than that of the polymer of the present invention, but the negative impact thereof is lower viscosity.

[0023] If the ratio of each monomer in step 1 is reduced to a lower level, such as 10%, and the remaining monomers are added dropwise during the reaction while neutralized, the number of polymer particles produced will be small, and the relative proportion of the reactive emulsifier will increase, which will reduce the stability of the second step reaction and affect the viscosity and transmittance of the product.

[0024] If the ratio of monomers in step 1 is increased to above the upper limit and the reaction is carried out by adding the remaining monomers dropwise during neutralization, it is close to the traditional emulsion polymerization method. As the ratio increases, its storage stability and viscosity will decrease.

[0025] Therefore, regulating the content and ratio of each monomer in step 1 and step 2 can effectively improve stability, viscosity and transmittance.

[0026] In the above preparation method, in step 2, the remaining hydrophobic associating monomer, hydrophilic monomer, hydrophobic monomer, and crosslinking agent are added to the reaction system obtained in step 1 and reacted in the presence of an initiator; the ratio of the weight of the crosslinking agent to the total weight of the hydrophobic monomers in steps 1 and 2 is 0-3.0:25.0-80.0;

[0027] The crosslinking agent is one or more of diallyl phthalate, diacetone acrylamide, and trimethylolpropane triacrylate.

[0028] At the same time, it is not recommended to use a cross-linking agent in step 1, because this will affect the swelling of the polymer after neutralization in step 1, reduce the emulsification performance, and have a significant impact on the reaction stability and storage stability.

[0029] In the above preparation method, the hydrophobic associating monomer is a polyoxyethylene ether acrylate with a long-chain alkyl group, and the number of carbon atoms of the long-chain alkyl group is 16 to 22;

[0030] The hydrophilic monomer is one or more of acrylic acid, methacrylic acid, maleic anhydride, acrylamide, hydroxyethyl acrylate, and itaconic acid;

[0031] The hydrophobic monomer is one or more of methyl methacrylate, ethyl acrylate, butyl acrylate, styrene, isooctyl acrylate, and isooctyl methacrylate;

[0032] The reactive emulsifier is one or more of sodium vinyl sulfonate, allyloxy fatty alcohol oxyethylene ether ammonium sulfate, and acrylamide isopropyl sulfonate.

[0033] In the above preparation method, the total weight of the initiator used in step 1 and step 2 is equivalent to 0.1-2.0 wt % of the total weight of the monomers used in step 1 and step 2;

[0034] The initiator is one or more of ammonium persulfate, potassium persulfate, sodium bisulfite, tert-butyl hydroperoxide, and isoascorbic acid.

[0035] It should be noted that the use of the initiator is recommended to be compatible with the monomer distribution ratio of step 1 and step 2, but this does not mean that strict adaptation is required. The initiator in step 1 and step 2 can be flexibly adjusted according to actual conditions, and the purpose of the present invention can be achieved as long as the reaction can be stably carried out and the degree of non-explosion is controlled.

[0036] In the above preparation method, the reaction time of step 1 is 30-60 min, and the reaction temperature is 80-90°C; the reaction time of step 2 is 60-240 min, and the reaction temperature is 80-90°C.

[0037] Preferably, the dropwise addition or batchwise addition operation takes 60 to 120 minutes, and the temperature is kept for 60 to 120 minutes after the dropwise addition or batchwise addition operation is completed.

[0038] In the above preparation method, the ratio of the total weight of the monomers used in step 1 and step 2 to the total weight of the deionized water used in step 1 and step 2 is 28.0-32.0:68.0-72.0.

[0039] Most of the deionized water is used in step 1. In step 2, a small amount of deionized water is needed to dissolve the initiator.

[0040] In addition, the present invention also discloses a hydrophobically modified thickener, which is prepared by any of the above methods.

[0041] Finally, the present invention also discloses the use of the hydrophobically modified thickener in preparing cosmetics.

[0042] The hydrophobically modified thickener of the present invention is used in the above-mentioned cosmetics for thickening, and the dosage form of the cosmetics can be emulsion, cream, etc.;

[0043] The hydrophobically modified thickener of the present invention can also be used in the fields of food, medicine and the like.

[0044] This application has at least the following beneficial effects:

[0045] 1. The emulsifiers involved in the present invention are all reactive emulsifiers, and non-reactive emulsifiers are not used, which can avoid the safety risks brought by traditional non-reactive emulsifiers.

[0046] 2. The present invention synthesizes the thickener of the present invention through two-step free radical emulsion polymerization, and terminates the reaction and neutralizes after the first step of free radical emulsion polymerization to relax the polymer chain segments, avoid embedding the reactive emulsifier, and allow the reactive emulsifier to continue to play an emulsifying role, providing an emulsification basic environment for the second step of free radical emulsion polymerization. The obtained thickener has the advantages of high storage stability and high and low temperature resistance.

[0047] 3. In addition to the storage stability advantage, the emulsifier synthesized by the method of the present invention also has excellent thickening performance and light transmittance. DETAILED DESCRIPTION

[0048] Below in conjunction with embodiments of the present invention, the present invention is clearly and completely described, in description of the present invention, it should be noted that, in the embodiment, the unrecited specific conditions person, carry out according to the condition of normal condition or manufacturer's suggestion. Reagents therefor or instrument are not recited manufacturer person, are the conventional products that can be obtained by commercial purchase. When not making special instructions, used part in the embodiments of the present invention is all weight part.

[0049] Examples and Comparative Examples

[0050] Example 1 to Example 12

[0051] Step 1: Add 300 g of deionized water, a reactive emulsifier (sodium vinyl sulfonate), a portion of a hydrophobic monomer (ethyl acrylate), a portion of a hydrophilic monomer (methacrylic acid), and a portion of a hydrophobic associating monomer (behenyl polyoxyethylene ether methacrylate) into a reaction vessel, stir for 30 minutes, and heat the system to 85°C.

[0052] Dissolve 2.5 g of initiator (ammonium persulfate) in 50 g of deionized water to prepare an initiator solution;

[0053] Step 2: Add 50% of the initiator solution to the reaction vessel at once, keep the temperature at 85°C and allow the material to react for 30 minutes. After 30 minutes, slowly add a 5wt% sodium hydroxide solution and measure the pH at this time. The addition should be completed within 15 minutes, at which point the material in the system gradually becomes viscous.

[0054] Step 3: Add the remaining hydrophobic monomer, the remaining hydrophilic monomer, the remaining hydrophobic associating monomer, and the crosslinking monomer (trimethylolpropane triacrylate) into the external monomer tank and stir for 30 minutes;

[0055] Step 4: Add the mixed monomers from step 3 and the remaining 50% initiator solution to the reaction vessel from step 2 dropwise at a uniform rate until the materials are consumed after 60 minutes of dropwise addition, and keep the mixture at 87°C for 60 minutes;

[0056] Step 5: After the insulation is completed, 120 g of deionized water is added to adjust the solid content to 30 wt%, and the material is cooled and discharged to obtain an associative thickener emulsion.

[0057] The relevant formula can be found in Table 1;

[0058] Table 1 Recipe

[0059]

[0060] It should be noted that the types of monomers used in Examples 1 to 12 are exactly the same, and the difference lies in the different amounts of the substances recorded in Table 1 above.

[0061] Example 13

[0062] The composition is substantially the same as in Example 1, except that the hydrophobic associating monomer is octadecyl polyoxyethylene methacrylate, the hydrophilic monomer is acrylic acid, the hydrophobic monomer is butyl acrylate, the reactive emulsifier is ammonium allyloxy fatty alcohol oxyethylene ether sulfate, and the crosslinking agent is diallyl phthalate. The weights of the various monomers are the same as in Example 1.

[0063] Example 14

[0064] The weights of the various monomers were the same as those in Example 1, except that the hydrophobic associating monomer was hexadecyl polyoxyethylene methacrylate, the hydrophilic monomer was maleic anhydride, the hydrophobic monomer was methyl methacrylate, the reactive emulsifier was allyloxy fatty alcohol oxyethylene ether ammonium sulfate, and the crosslinking agent was diacetone acrylamide.

[0065] The total ratio of monomers in the above embodiments is shown in Table 2 below;

[0066] Table 2 Monomer ratio table

[0067]

[0068] Comparative Example 1

[0069] After emulsifying all the monomers in Example 1, 1 / 4 of the monomers were added to the reaction bottle at one time, and 1 / 2 of the initiator solution was added at one time. After reacting for 30 minutes, the remaining monomers and initiator solution were added dropwise.

[0070] In the second half of the reaction, the viscosity of the emulsion in the reaction bottle is very high. It may be that as the latex particles grow, the emulsifier is not enough to cover all the particles, resulting in an unstable system and a certain amount of gel residue in the final product.

[0071] Comparative Example 2

[0072] Comparative Example 2 is substantially the same as Comparative Example 1, except that the emulsifier used is a conventional non-reactive emulsifier of equal weight, and the conventional non-reactive emulsifier is sodium lauryl sulfate.

[0073] In the second half of the reaction, the viscosity of the emulsion in the reaction bottle is very high. It may be that as the latex particles grow, the emulsifier is not enough to cover all the particles, resulting in an unstable system and a certain amount of gel residue in the final product.

[0074] Performance Testing

[0075] All the embodiments and comparative examples of the present invention have acceptable stability at room temperature, so only the high and low temperature storage stability performance is tested.

[0076] Test item 1: High temperature storage stability test;

[0077] 150 g of the emulsion from each example and comparative example was placed in a 200 mL transparent bottle and placed in a 48°C incubator. After two weeks, the bottle was removed and the bottom of the bottle was inverted to observe the precipitation. If the emulsion is inherently unstable, some emulsion will break and precipitate, which will then settle at the bottom over time, resulting in a decrease in solids content.

[0078] For samples that sink to the bottom, take 1.0±0.1 g of the upper emulsion and test the actual solid content using a rapid moisture tester at 105°C.

[0079] Test item 2: low temperature storage stability test;

[0080] Place 150 g of the emulsion from each example and comparative example in a 200 mL transparent bottle and place in a refrigerator at 5°C. After two weeks, remove the bottle and invert the bottom to observe the precipitation. If the emulsion is inherently unstable, some demulsification will occur, resulting in precipitation. This will then settle over time, leading to a decrease in solids content.

[0081] Test Item 3: Viscosity and transmittance test

[0082] After preparing 200 g of the formula according to Table 3, the emulsion of each embodiment and comparative example was added to a formula base containing a fixed ratio of anionic surfactant and nonionic surfactant at an actual solid content of 0.67%, and the pH of the system was adjusted to 7.0-8.0 with an 18% KOH aqueous solution. The emulsion was bottled and centrifuged for defoaming, and the viscosity was tested using a unified measurement method after being kept in a constant temperature incubator at 25°C for more than two hours.

[0083] For the rotational viscometer test, select a No. 5 rotor at 20 rpm. Turn the instrument's lift knob to slowly lower the rotor into the sample until the rotor groove is flush with the sample's liquid surface. After 1 minute, when the viscosity reading on the instrument stabilizes, record the value.

[0084] Meanwhile, the above formula was placed in a 1 cm cuvette and centrifuged to eliminate bubbles. The cuvette was then placed in a UV spectrophotometer and its transmittance was measured at 420 nm.

[0085] The formula is shown in Table 3 below;

[0086] Table 3 Application formula table Unit: wt%

[0087]

[0088] The emulsions in Table 3 above are the emulsions corresponding to the examples and comparative examples of the present invention;

[0089] TC-MAB 40LDL: disodium lauroamphodiacetate;

[0090] AES (70%): sodium alkyl polyoxyethylene ether sulfate with a concentration of 70wt%;

[0091] CAB 35: Cocamidopropyl Betaine;

[0092] CMMEA: Coco Methyl Monoethanolamide.

[0093] The test results can be seen in Table 4;

[0094] Table 4 Test results

[0095] High temperature storage stability Low temperature storage stability Viscosity Light transmittance Example 1 Stable and non-stratified Stable and non-stratified 12980 95% Example 2 Slight precipitation, solid content decreased by 1.2% Slight precipitation, solid content decreased by 0.8% 12700 96% Example 3 Stable and non-stratified Stable and non-stratified 11320 93% Example 4 Stable and non-stratified Stable and non-stratified 8500 87% Example 5 Slight precipitation, solid content decreased by 2.1% Slight precipitation, solid content decreased by 1.8% 8820 93% Example 6 Slight precipitation, solid content decreased by 1% Stable and non-stratified 10880 92% Example 7 Stable and non-stratified Stable and non-stratified 10020 97% Example 8 Stable and non-stratified Stable and non-stratified 12700 96% Example 9 - - - - Example 10 Stable and non-stratified Stable and non-stratified 16800 92% Example 11 Stable and non-stratified Stable and non-stratified 13560 95% Example 12 Precipitation, solid content decreased by 4.3% Precipitation, solid content decreased by 4.4% 7100 94% Example 13 Stable and non-stratified Stable and non-stratified 11250 95% Example 14 Slight precipitation, solid content decreased by 1.0% Slight precipitation, solid content decreased by 1.3% 10030 96% Comparative Example 1 Precipitation, solid content decreased by 4.8% Precipitation, solid content decreased by 4.7% 10160 92% Comparative Example 2 Precipitation, solid content decreased by 4.0% Precipitation, solid content decreased by 4.0% 9350 94%

[0096] Result analysis:

[0097] From the comparison of all the examples (except Example 9 and Example 12) and Comparative Examples 1 and 2, it can be seen that the path of the present invention is very important. In most cases, it maintains the high and low temperature stability of the system. Even if precipitation occurs, the precipitation is small.

[0098] The reason for the above phenomenon is that the present invention adds a reactive emulsifier to the polymer chain segment during the first step of free radical emulsion polymerization, and then neutralizes the polymer to allow the chain segment of the reactive emulsifier to relax, thereby avoiding the hydrophilic groups and hydrophobic segments of the reactive emulsifier in the polymer in the traditional method being embedded in the polymer and losing the emulsification stabilization effect. In Comparative Example 1, segmented emulsion polymerization was performed, but the polymer was not neutralized after the first stage of polymerization, and the purpose of the present invention could not be achieved, resulting in high and low temperature instability. In Comparative Example 2, no reactive emulsifier was used, and it could not participate in the self-emulsification stabilization process of the polymer, resulting in poor high and low temperature performance.

[0099] In several examples of the present invention, Example 9 exhibited obvious stratification after the reaction, preventing subsequent experiments from being conducted. This was due to the excessive amount of hydrophilic monomer used in Example 9, resulting in demulsification. Examples 2, 5, 6, 12, and 14 also exhibited precipitation, each due to the following reasons: Example 2 exhibited precipitation due to the insufficient use of emulsifier; Example 5 used too little total monomer in the first free radical polymerization stage, resulting in too few relaxed segments after neutralization, negatively impacting subsequent high and low temperature emulsification stability; Example 6 used an excessive amount of monomer in the first stage, causing the entire reaction to become an emulsion polymerization reaction, which had a slight negative impact on stability; Example 12 used too little hydrophobic associating monomer in the first stage; and Example 14 used maleic anhydride as the hydrophilic monomer, which may have weakened its stability.

[0100] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as illustrative and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Equivalents to the claims are intended to be encompassed. All variations within the meaning and scope of the elements are intended to be included in the present invention.

Claims

1. A method for preparing a hydrophobically modified thickener, characterized in that: The steps include: Step 1: adding part of the hydrophobic associating monomer, part of the hydrophilic monomer, part of the hydrophobic monomer, a reactive emulsifier and deionized water into a reaction vessel to carry out a free radical emulsion polymerization reaction in the presence of an initiator, and adjusting the pH of the reaction system to 4-7 after the reaction is completed; Step 2: adding the remaining hydrophobically associating monomer, hydrophilic monomer, and hydrophobic monomer to the reaction system obtained in step 1 to carry out free radical emulsion polymerization in the presence of an initiator; The weight of the hydrophobic associating monomer used in step 1 is equivalent to 20.0wt% to 60.0wt% of the total weight of the hydrophobic associating monomers used in step 1 and step 2; the weight of the hydrophilic monomer used in step 1 is equivalent to 20.0wt% to 35.0wt% of the total weight of the hydrophilic monomers used in step 1 and step 2; the weight of the hydrophobic monomer used in step 1 is equivalent to 20.0wt% to 35.0wt% of the total weight of the hydrophobic monomers used in step 1 and step 2; The ratio of the total weight of the hydrophobically associating monomers in steps 1 and 2, the total weight of the hydrophilic monomers in steps 1 and 2, the total weight of the hydrophobic monomers in steps 1 and 2, and the weight of the reactive emulsifier is: 4.0-25.0:15.5-32:55.5-80.0:0.5-5.0; The hydrophobic associating monomer is a polyoxyethylene ether acrylate with a long-chain alkyl group, wherein the number of carbon atoms of the long-chain alkyl group is 16 to 22; the hydrophilic monomer is one or more of acrylic acid, methacrylic acid, maleic anhydride, acrylamide, hydroxyethyl acrylate, and itaconic acid; the hydrophobic monomer is one or more of methyl methacrylate, ethyl acrylate, butyl acrylate, styrene, isooctyl acrylate, and isooctyl methacrylate; and the reactive emulsifier is one or more of sodium vinyl sulfonate, allyloxy fatty alcohol oxyethylene ether ammonium sulfate, and acrylamido isopropyl sulfonate.

2. The preparation method according to claim 1, characterized in that The ratio of the total weight of the hydrophobically associating monomers in steps 1 and 2, the total weight of the hydrophilic monomers in steps 1 and 2, the total weight of the hydrophobic monomers in steps 1 and 2, and the weight of the reactive emulsifier is: 7.0-25.0: 21.5-32: 55.5-70.0: 0.5-5.0; In the step 2, the hydrophobic associating monomer, the hydrophilic monomer, and the hydrophobic monomer are added to the reaction system obtained in the step 1 by dropwise addition or batchwise addition.

3. The preparation method according to claim 1, characterized in that In the step 2, a hydrophobic associating monomer, a hydrophilic monomer, a hydrophobic monomer, and a crosslinking agent are added to the reaction system obtained in the step 1 in the presence of an initiator to carry out a reaction; the ratio of the weight of the crosslinking agent to the total weight of the hydrophobic monomers in steps 1 and 2 is 0-3.0:55.5-80.0; The crosslinking agent is one or more of diallyl phthalate, diacetone acrylamide, and trimethylolpropane triacrylate.

4. The preparation method according to claim 1, characterized in that The total weight of the initiators used in step 1 and step 2 is equivalent to 0.1-2.0 wt % of the total weight of the monomers used in step 1 and step 2; The initiator is one or more of ammonium persulfate, potassium persulfate, sodium bisulfite, tert-butyl hydroperoxide, and isoascorbic acid.

5. The preparation method according to claim 1, characterized in that The reaction time of step 1 is 30-60 min, and the reaction temperature is 80-90°C; the reaction time of step 2 is 60-240 min, and the reaction temperature is 80-90°C.

6. The preparation method according to claim 2, characterized in that The time for the dropwise addition or the batchwise addition is 60 to 120 minutes, and the temperature is kept for 60 to 120 minutes after the dropwise addition or the batchwise addition is completed.

7. The preparation method according to claim 1, characterized in that The ratio of the total weight of the monomers used in step 1 and step 2 to the total weight of the deionized water used in step 1 and step 2 is 28.0-32.0:68.0-72.

0.

8. A hydrophobically modified thickener, characterized in that The method is prepared by any one of claims 1 to 7.

9. Use of the hydrophobically modified thickener according to claim 8 in preparing cosmetics.

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