A method for preparing an aqueous acrylic suspension thickening emulsion

Abstract

The application discloses a preparation method of an aqueous acrylic acid suspension thickening emulsion. When the residual monomer of a soft monomer is 200-1000 ppm in the preparation process, the soft monomer is supplemented into a reaction kettle, and then the reaction is continuously carried out. By using the method, the production stability and product performance are fully balanced, the obtained emulsion has good repeatability in industrial production, and the thickening agent prepared through the process has excellent suspension thickening performance and transparency.

Description

Technical Field

[0001] This invention relates to the field of thickener preparation processes, specifically to a method for preparing an aqueous acrylic suspension thickening emulsion and its application. Background Technology

[0002] With the continuous improvement of living standards, people have placed new demands on personal care products. For example, in pursuit of a more aesthetically pleasing appearance, they may request the addition of elements such as pearlescent powder, flower petals, microbeads, or walnut particles. Suspension thickeners, as rheology modifiers widely used in shampoos, shower gels, and other personal care products, play a crucial role, especially in the hair care industry. Thanks to their excellent compatibility and good transparency, they can be compounded with anionic, nonionic, and amphoteric surfactants, as well as commonly used additives and conditioners, for the production of shampoos, shower gels, and other cleaning products. Furthermore, suspension thickeners can also suspend colored exfoliating particles and show broad application potential in creams and serums.

[0003] Most commonly used suspending and thickening agents in personal care products are acrylate copolymers, such as liquid carbomer, which are anionic polymers. They impart excellent suspending and thickening properties to shampoos and conditioners, ensuring that the ingredients remain evenly suspended and do not easily settle. However, commonly available suspending and thickening agents often electrostatically bind with cationic conditioning agents in the formula, significantly reducing the formula's conditioning effect. Furthermore, the addition of polymeric copolymers can also affect the transparency of the formula to some extent.

[0004] To address this issue, patent CN103772625A discloses an antifreeze acrylate suspension thickening emulsion that improves suspension thickening performance by introducing hydrophobically modified surface-active monomers while also possessing excellent antifreeze properties. However, it still suffers from the aforementioned drawback: while maintaining its basic suspension thickening performance, it excessively sacrifices transparency.

[0005] Patents CN103772625A and CN107641167A both improve suspension thickening properties by introducing long-chain hydrophobic monomers. However, due to the strong hydrophobicity of these long-chain alkyl monomers, their solubility in water is too low. During emulsion polymerization, they are difficult to migrate into the latex particles and remain within the chain segments. While this can improve suspension thickening properties, it results in significant loss of transparency and noticeably leads to instability in emulsion polymerization. Furthermore, large-scale reactor production is more difficult to control, and existing industrial production processes are highly volatile, making stable production difficult. Therefore, how to produce stable suspension thickeners that meet performance requirements is an urgent problem to be solved. Summary of the Invention

[0006] To address the challenges of poor transparency, suspension performance, and instability in industrial production of waterborne acrylic suspension thickener emulsions, this invention aims to provide a method for preparing waterborne acrylic suspension thickener emulsions. The resulting emulsion exhibits high transparency, good suspension performance, high batch-to-batch stability during industrial production, and stable performance, achieving a perfect balance between performance and industrial production.

[0007] To achieve the above objectives, the present invention adopts the following technical solution.

[0008] A method for preparing an aqueous acrylic suspension thickening emulsion includes the following steps:

[0009] (1) Add water to the reactor, heat it to 70-95℃, and add bottom emulsifier I and additives;

[0010] (2) At 70-95℃, initiator I is added to the reactor. After 5-10 min, pre-emulsion, initiator II and emulsifier II are added to the reactor simultaneously. When the amount of pre-emulsion added is 75%-95% of its mass, chain transfer agent is added to the pre-emulsion. After stirring for 5-15 min, the pre-emulsion is continued to be added until all the pre-emulsion is added. The total addition time is 120-240 min.

[0011] (3) Maintain the temperature for 30-90 min, then cool to 65-80℃. During the maintenance process, monitor the residual amount of soft monomers. When the residual amount of soft monomers is 200-1000 ppm, add the soft monomers to the reactor. Stir for 5-20 min, then add oxidant I and reductant I, with an interval of less than 5 min between the addition of oxidant I and reductant I. Maintain the temperature for 30-60 min, then start adding oxidant II and reductant II, which takes 60-120 min. After the addition is complete, maintain the temperature for 60-120 min.

[0012] All of the above processes are carried out in a polymerization reactor. After the heat preservation is completed, the temperature is lowered to 50-60℃, the reactor is transferred, defoamer and preservative are added, and the product is filtered and discharged.

[0013] Preferably, in the preparation method, the amount of each component added is:

[0014] The pre-emulsion comprises 220-630 parts by weight, preferably 270-490 parts by weight.

[0015] Emulsifier: 2-10 parts by weight, preferably 3-9 parts by weight.

[0016] The additive is 0.3-3 parts by weight, preferably 0.5-2 parts by weight.

[0017] Chain transfer agent, 0.1-3 parts by weight, preferably 0.2-1.5 parts by weight.

[0018] The initiator is used in amounts of 0.1-2 parts by weight, preferably 0.1-1.5 parts by weight.

[0019] Oxidizing agent: 0.5-6 parts by weight, preferably 0.8-4 parts by weight.

[0020] The reducing agent is 0.4-2 parts by weight, preferably 0.5-1.5 parts by weight.

[0021] The defoamer is used in an amount of 0-1 parts by weight, preferably 0.2-0.8 parts by weight.

[0022] Preservative: 0-4 parts by weight, preferably 1.5-3.5 parts by weight.

[0023] Water 340-775 parts by weight, preferably 450-750 parts by weight;

[0024] The total mass of the above components is 1000 parts.

[0025] The amount of emulsifier added refers to the total amount of emulsifier I and emulsifier II. The ratio of emulsifier I to emulsifier II can be selected based on common knowledge known to those skilled in the art, such as a mass ratio of emulsifier I to emulsifier II of 1:20-20:1.

[0026] The amount of initiator added refers to the total amount of initiator I and initiator II. The ratio of initiator I to initiator II can be selected according to common knowledge known to those skilled in the art, such as the mass ratio of initiator I to initiator II being 1:20-20:1.

[0027] The amount of oxidant added refers to the total amount of oxidant I and oxidant II. The ratio of oxidant I to oxidant II can be selected according to common knowledge known to those skilled in the art, such as a mass ratio of oxidant I to oxidant II of 1:20-20:1.

[0028] The amount of reducing agent added refers to the total amount of reducing agent I and reducing agent II. The ratio of reducing agent I to reducing agent II can be selected based on common knowledge known to those skilled in the art, such as a mass ratio of reducing agent I to reducing agent II of 1:20-20:1.

[0029] In this invention, emulsifier I and emulsifier II are each independently selected from one or more of sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, alkyl polyoxyethylene ether, sodium p-styrene sulfonate, fatty alcohol polyoxyethylene ether and its salts, and fatty alcohol ether phosphate and its salts, preferably sodium dodecyl sulfate and sodium p-styrene sulfonate. In step (1) of this invention, the auxiliary agent is one or more of alkali metal carbonate, alkali metal bicarbonate, and alcohol, preferably one or more of sodium bicarbonate, sodium carbonate, potassium bicarbonate, potassium carbonate, methanol, and ethanol.

[0030] In step (2) of the present invention, the initiator is a peroxide, preferably one or more of ammonium persulfate, sodium persulfate, potassium persulfate, cumene hydrogen peroxide, and tert-butyl hydrogen peroxide.

[0031] In step (2) of this invention, the pre-emulsion comprises the following components, calculated based on a total pre-emulsion mass of 100 parts by weight:

[0032] 18-40 parts by weight of hard monomer, preferably 20-35 parts by weight;

[0033] 45-65 parts by weight of the soft monomer, preferably 45-58 parts by weight;

[0034] 0-3 parts by weight of functional monomer, preferably 0-1.5 parts by weight;

[0035] Emulsifier III: 0-1.2 parts by weight, preferably 0-1 parts by weight;

[0036] 10-30 parts by weight of water, preferably 13-27 parts by weight.

[0037] The preparation method of the pre-emulsion includes the following steps: adding water and emulsifier to the pre-emulsion kettle 1, stirring evenly, and then adding soft monomer, optional functional monomer, and hard monomer in sequence, and stirring.

[0038] The pre-emulsion contains one or more of the following: sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, alkyl polyoxyethylene ether, sodium p-styrene sulfonate, fatty alcohol polyoxyethylene ether and its salts, and fatty alcohol ether phosphate and its salts.

[0039] The hard monomers in the pre-emulsion include one or more of styrene, methacrylic acid, acrylic acid, and methyl methacrylate, preferably methacrylic acid and methyl methacrylate.

[0040] The soft monomers in the pre-emulsion include one or more of isooctyl acrylate, butyl acrylate, ethyl acrylate, isooctyl methacrylate, 2-ethylhexyl acrylate, and lauryl methacrylate.

[0041] The functional monomers in the pre-emulsion include one or more of hydroxyethyl acrylate, β-acryloyloxypropionic acid, diallyl phthalate, allyl methacrylate, ethylene glycol dimethacrylate, and 1,3-butanediol dimethacrylate.

[0042] In step (2) of the present invention, the chain transfer agent is one or more of n-dodecyl mercaptobutyl ester, mercaptopropionic acid, and mercaptoethanol.

[0043] In step (3) of the present invention, the amount of soft monomer added is 0.5%-10% of the total monomer mass, preferably 0.5%-5%.

[0044] In step (3) of this invention, the soft monomer is added at once or quickly within 5 minutes.

[0045] In step (3) of this invention, oxidant I is added all at once or rapidly within 5 minutes, and reducing agent solution I is added all at once or rapidly within 5 minutes. In step (3) of this invention, initiator I and initiator II are each independently selected from peroxides, preferably from one or more of sodium persulfate, ammonium persulfate, tert-butyl hydroperoxide, cumene hydroperoxide, and hydrogen peroxide, preferably tert-butyl hydroperoxide.

[0046] In step (3) of the present invention, reducing agent I and reducing agent II are each independently selected from one or more of sodium metabisulfite, disodium metabisulfite, ascorbic acid, and sodium formaldehyde sulfoxylate, with ascorbic acid being preferred.

[0047] In step (3) of this invention, the defoamer is one or more of the following: silicone defoamer, mineral oil defoamer, and polyether defoamer, preferably silicone defoamer, such as one or more of Evonik Degussa Tego1488, Tego825, BYK028, and BYK024, preferably Evonik Degussa Tego-825 and / or Tego-1488.

[0048] In step (3) of the present invention, the preservative is one or more of triazine preservatives, bisoxazoline preservatives, isothiazolinone preservatives, and broad-spectrum preservatives, preferably a broad-spectrum preservative, such as PHCG preservative.

[0049] The aqueous acrylic suspension thickening emulsion of the present invention has a solid content of 25%-40% and an average particle size of 90-150 nm.

[0050] In this application, the hard monomers and soft monomers are designed with corresponding differences in their polymerization rates to achieve a large distribution of acid in the inner layer. The acid concentration is also designed to gradually decrease from the inside to the outside, ensuring that the high internal osmotic pressure makes it easier to absorb water and expand, and that the water retention is stronger. At the same time, this method can avoid abnormal fluctuations caused by other complex process operations.

[0051] This formula inserts thiols into the outer layer, allowing the alkali to enter the interior during neutralization. The internal neutralization creates high osmotic pressure, causing the particles to absorb water and swell. This reduces the transparency of the latex particles while instantly and significantly increasing the viscosity of the thickener.

[0052] In industrial production, due to the scale-up of reaction vessels, the efficiency of the three-stage transfer and one-stage reaction is far inferior to that of laboratory-scale tests. This can lead to deviations from the expected reaction structure, incomplete encapsulation of the internal acid, and ultimately, large fluctuations in product performance, making it impossible to provide customers with a stable product. Therefore, this formulation adjusts the process by using a certain amount of soft monomers for explosive polymerization on the outer layer to achieve comprehensive encapsulation of the internal acid. The amount of encapsulation is strictly controlled. If the amount of encapsulated soft monomers is too small, the internal acid is exposed to the outside and cannot be completely encapsulated. The hydrophilic segments extend excessively, and the latex spheres break down, resulting in a significant increase in viscosity, but ultimately failing to provide good suspension properties in the final application. If the amount of encapsulated soft monomers is too large, the outer shell is too thick, and the latex spheres cannot expand after neutralization, resulting in poor suspension properties. In addition, the presence of more hydrophobic monomers on the outside leads to poor transparency in the finished product.

[0053] In summary, this invention, through a special production process and ingenious overall formula design, simplifies the process route and improves industrial repeatability while ensuring excellent transparency and suspension, thus solving the problems of fluctuations in industrial production operations and performance. Detailed Implementation

[0054] The present invention will be further illustrated by the following examples. In the following examples, portions are by weight unless otherwise specified.

[0055] Table 1. Raw materials used in the preparation of acrylic suspension thickener emulsions

[0056] Abbreviation Chemical types MMA Methyl methacrylate EA Ethyl acrylate BA Butyl acrylate EHA Isooctyl acrylate AA acrylic acid MAA methacrylic acid APS ammonium persulfate SDS Sodium dodecyl sulfate SSS Sodium p-styrenesulfonate ALMA Allyl methacrylate DAP diallyl phthalate N-DM n-dodecanethiol NaHCO3 Sodium bicarbonate AE ethanol T-BHP tert-butyl hydroperoxide IAA Isoascorbic acid Tego825 Defoamer PHCG Phenoxyethanol DIW Deionized water

[0057] Example 1: Emulsion 1-1

[0058] Pre-emulsion preparation:

[0059] Add 0.8 parts SSS and 3.5 parts SDS to 80 parts deionized water and stir for 30 minutes. Add 70 parts MAA, 6 parts AA, 116.5 parts EA, 28 parts EHA, and 3 parts DAP to the mixture, and place it in a pre-emulsification vessel and stir thoroughly.

[0060] Weigh 0.5 parts of ammonium persulfate (APS) and dissolve it in 10 parts of deionized water (DIW) to prepare initiator solution I;

[0061] Weigh 0.9 parts ammonium persulfate (APS), 0.8 parts SSS, and 2 parts SDS, and dissolve them in 40 parts deionized water (DIW) to prepare initiator solution II;

[0062] Add 540 parts of deionized water to the reactor and heat to 83-88℃. Add 1.5 parts of SDS, 1.5 parts of anhydrous ethanol, and 0.5 parts of NaHCO3. Add initiator solution I to the reactor. After 3 minutes, add the pre-emulsion (85% of the total mass) and initiator solution II dropwise, controlling the reaction temperature at 85-89℃ and adding at a uniform rate for 120 minutes. When the addition reaches 102 minutes, stop the addition, add 0.8 parts by mass of NDM to the pre-emulsion, stir for 10 minutes, and then continue the addition until the pre-emulsion is completely added. Keep the reactor at this temperature for 60 minutes.

[0063] Weigh out 15 parts of TBHP dissolved in deionized water to prepare 3 parts of oxidant solution I; weigh out 20 parts of TBHP dissolved in deionized water to prepare oxidant solution II;

[0064] Weigh out 15 parts of IAA dissolved in deionized water to prepare reducing agent solution I; weigh out 2 parts of IAA dissolved in deionized water to prepare reducing agent solution II;

[0065] When the residual EA in the polymerization reactor was detected to be 550 ppm, the reactor was rapidly cooled to 75°C. 3.7 parts by weight of EA were quickly added to the reactor and stirred for 5 minutes. Oxidizing agent solution I and reducing agent solution I were then added sequentially and rapidly, with an interval of less than 5 minutes between each addition. The mixture was kept at this temperature for 60 minutes. Oxidizing agent solution II and reducing agent solution II were then added dropwise simultaneously over 60 minutes, followed by another 60 minutes of temperature maintenance. The temperature was then lowered to below 50°C. 0.5 parts by weight of Tego825 defoamer dissolved in 7 parts of deionized water and 2 parts by weight of PHCG were added. Water was added to adjust the solid content to 30%, and the mixture was filtered out. Emulsion 1-1 was obtained.

[0066] Example 2: Emulsion 1-2

[0067] Pre-emulsion preparation:

[0068] Add 0.8 parts SSS and 3.5 parts SDS to 80 parts deionized water and stir for 30 minutes. Add 53.5 parts MAA, 5.5 parts AA, 131 parts EA, 30.5 parts EHA, and 3 parts DAP to the mixture, and place it in a pre-emulsification vessel and stir thoroughly.

[0069] Weigh 0.5 parts of ammonium persulfate (APS) and dissolve it in 10 parts of deionized water (DIW) to prepare initiator solution I;

[0070] Weigh 0.9 parts ammonium persulfate (APS), 0.8 parts SSS, and 2 parts SDS, and dissolve them in 40 parts deionized water (DIW) to prepare initiator solution II;

[0071] Add 540 parts of deionized water to the reactor and heat to 83-88℃. Add 1.5 parts of SDS, 1.5 parts of anhydrous ethanol, and 0.5 parts of NaHCO3. Add initiator solution I to the reactor. After 3 minutes, add the pre-emulsion and initiator solution II dropwise, controlling the reaction temperature at 85-89℃ and adding at a uniform rate for 120 minutes. When the addition reaches 102 minutes, stop the addition, add 0.8 parts by mass of NDM to the pre-emulsion, stir for 10 minutes, and continue adding dropwise until the addition is complete. Keep the reactor at this temperature for 60 minutes.

[0072] Weigh out 15 parts of TBHP dissolved in deionized water to prepare 3 parts of oxidant solution I; weigh out 20 parts of TBHP dissolved in deionized water to prepare oxidant solution II;

[0073] Weigh out 15 parts of IAA dissolved in deionized water to prepare reducing agent solution I; weigh out 2 parts of IAA dissolved in deionized water to prepare reducing agent solution II;

[0074] When the residual EA in the polymerization reactor was detected to be 250 ppm, the reactor was rapidly cooled to 75°C. 3.7 parts by weight of EA were quickly added to the reactor and stirred for 5 minutes. Then, oxidant solution I and reducing agent solution I were added sequentially and rapidly, with an interval of less than 5 minutes between each addition. The mixture was kept at this temperature for 60 minutes. Oxidant solution II and reducing agent solution II were then added dropwise simultaneously over 60 minutes, followed by another 60 minutes of temperature maintenance. The temperature was then lowered to below 50°C. 0.5 parts by weight of Tego825 defoamer dissolved in 7 parts of deionized water and 2 parts by weight of PHCG were added. Water was added to adjust the solid content to 30%, and the mixture was filtered out. Emulsion 1-2 was obtained.

[0075] Example 3: Emulsion 1-3

[0076] Pre-emulsion preparation:

[0077] Add 0.8 parts SSS and 3.5 parts SDS to 80 parts deionized water and stir for 30 minutes. Add 89 parts MAA, 6.5 parts AA, 99 parts EA, 26 parts EHA, 2 parts DAP, and 1 part ALMA to the mixture, and place it in a pre-emulsification vessel and stir thoroughly.

[0078] Weigh 0.5 parts of ammonium persulfate (APS) and dissolve it in 10 parts of deionized water (DIW) to prepare initiator solution I;

[0079] Weigh 0.9 parts ammonium persulfate (APS), 0.8 parts SSS, and 2 parts SDS, and dissolve them in 40 parts deionized water (DIW) to prepare initiator solution II;

[0080] Add 540 parts of deionized water to the reactor and heat to 83-88℃. Add 1.5 parts of SDS, 1.5 parts of anhydrous ethanol, and 0.5 parts of NaHCO3. Add initiator solution I to the reactor. After 3 minutes, add the pre-emulsion and initiator solution II dropwise, controlling the reaction temperature at 85-89℃ and adding at a uniform rate for 120 minutes. When the addition reaches 102 minutes, stop the addition, add 0.8 parts by mass of NDM to the pre-emulsion, stir for 10 minutes, and continue adding dropwise until the addition is complete. Keep the reactor at this temperature for 60 minutes.

[0081] Weigh out 15 parts of TBHP dissolved in deionized water to prepare 3 parts of oxidant solution I; weigh out 20 parts of TBHP dissolved in deionized water to prepare oxidant solution II;

[0082] Weigh out 15 parts of IAA dissolved in deionized water to prepare reducing agent solution I; weigh out 2 parts of IAA dissolved in deionized water to prepare reducing agent solution II;

[0083] When the residual EA in the polymerization reactor was detected to be 380 ppm, the reactor was rapidly cooled to 75°C. 3.7 parts by weight of EA were quickly added to the reactor and stirred for 5 minutes. Then, oxidant solution I and reducing agent solution I were added sequentially and rapidly, with an interval of less than 5 minutes between each addition. The mixture was kept at this temperature for 60 minutes. Oxidant solution II and reducing agent solution II were then added dropwise simultaneously over 60 minutes, followed by another 60 minutes of temperature maintenance. The temperature was then lowered to below 50°C. 0.5 parts by weight of Tego825 defoamer dissolved in 7 parts of deionized water and 2 parts by weight of PHCG were added. Water was added to adjust the solid content to 30%, and the mixture was filtered out. Emulsion 1-3 was obtained.

[0084] Example 4: Emulsion 1-4

[0085] Pre-emulsion preparation:

[0086] Add 0.8 parts SSS and 3.5 parts SDS to 80 parts deionized water and stir for 30 minutes. Add 70 parts MAA, 6 parts AA, 116.5 parts EA, 28 parts EHA, and 3 parts DAP to the mixture, and place it in a pre-emulsification vessel and stir thoroughly.

[0087] Weigh 0.5 parts of ammonium persulfate (APS) and dissolve it in 10 parts of deionized water (DIW) to prepare initiator solution I;

[0088] Weigh 0.9 parts ammonium persulfate (APS), 0.8 parts SSS, and 2 parts SDS, and dissolve them in 40 parts deionized water (DIW) to prepare initiator solution II;

[0089] Add 540 parts of deionized water to the reactor and heat to 83-88℃. Add 1.5 parts of SDS, 1.5 parts of anhydrous ethanol, and 0.5 parts of NaHCO3. Add initiator solution I to the reactor. After 3 minutes, add the pre-emulsion and initiator solution II dropwise, controlling the reaction temperature at 85-89℃ and adding at a uniform rate for 120 minutes. When the addition reaches 90 minutes, stop the addition, add 0.8 parts by mass of NDM to the pre-emulsion, stir for 10 minutes, and then continue the addition until it is complete. Keep the reactor at this temperature for 60 minutes.

[0090] Weigh out 15 parts of TBHP dissolved in deionized water to prepare 3 parts of oxidant solution I; weigh out 20 parts of TBHP dissolved in deionized water to prepare oxidant solution II;

[0091] Weigh out 15 parts of IAA dissolved in deionized water to prepare reducing agent solution I; weigh out 2 parts of IAA dissolved in deionized water to prepare reducing agent solution II;

[0092] When the residual EA in the polymerization reactor was detected to be 480 ppm, the reactor was rapidly cooled to 75°C. 3.7 parts by weight of EA were quickly added to the reactor and stirred for 5 minutes. Then, oxidant solution I and reducing agent solution I were added sequentially and rapidly, with an interval of less than 5 minutes between each addition. The mixture was kept at this temperature for 60 minutes. Oxidant solution II and reducing agent solution II were then added dropwise simultaneously over 60 minutes, followed by another 60 minutes of temperature maintenance. The temperature was then lowered to below 50°C. 0.5 parts by weight of Tego825 defoamer dissolved in 7 parts of deionized water and 2 parts by weight of PHCG were added. Water was added to adjust the solid content to 30%, and the mixture was filtered out. Emulsion 1-4 was obtained.

[0093] Example 5: Emulsion 1-5

[0094] Pre-emulsion preparation:

[0095] Add 0.8 parts SSS and 3.5 parts SDS to 80 parts deionized water and stir for 30 minutes. Add 105 parts MAA, 9 parts AA, 175 parts EA, 42 parts EHA, 2.25 parts DAP, and 2.25 parts ALMA to the mixture and prepare it in a pre-emulsification vessel and stir thoroughly.

[0096] Weigh 0.5 parts of ammonium persulfate (APS) and dissolve it in 10 parts of deionized water (DIW) to prepare initiator solution I;

[0097] Weigh 0.9 parts ammonium persulfate (APS), 0.8 parts SSS, and 2 parts SDS, and dissolve them in 40 parts deionized water (DIW) to prepare initiator solution II;

[0098] Add 440 parts of deionized water to the reactor and heat to 83-88℃. Add 1.5 parts of SDS, 1.5 parts of anhydrous ethanol, and 0.5 parts of NaHCO3. Add initiator solution II to the reactor. After 3 minutes, add the pre-emulsion and initiator solution II dropwise, controlling the reaction temperature at 85-89℃ and adding at a uniform rate for 120 minutes. When the addition reaches 114 minutes, stop the addition, add 1.2 parts by mass of NDM to the pre-emulsion, stir for 10 minutes, and continue adding dropwise until the addition is complete. Keep the reactor at this temperature for 60 minutes.

[0099] Weigh out 3 parts of TBHP dissolved in 15 parts of deionized water to prepare oxidizing agent solution I; weigh out 4 parts of TBHP dissolved in 15 parts of deionized water to prepare oxidizing agent solution II;

[0100] Weigh out 1.5 parts of IAA dissolved in 15 parts of deionized water to prepare reducing agent solution I; weigh out 2 parts of IAA dissolved in 15 parts of deionized water to prepare reducing agent solution II;

[0101] When the residual EA in the polymerization reactor was detected to be 690 ppm, the reactor was rapidly cooled to 75°C. 3.7 parts by weight of EA were quickly added to the reactor and stirred for 5 minutes. Then, oxidant solution I and reducing agent solution I were added sequentially and rapidly, with an interval of less than 5 minutes between each addition. The mixture was kept at this temperature for 60 minutes. Oxidant solution II and reducing agent solution II were then added dropwise simultaneously over 60 minutes, followed by another 60 minutes of temperature maintenance. The temperature was then lowered to below 50°C. 0.1 parts by weight of Tego825 defoamer dissolved in 7 parts of deionized water and 2 parts by weight of PHCG were added. Water was added to adjust the solid content to 35%, and the mixture was filtered out. Emulsion 1-5 was obtained.

[0102] Example 6: Emulsion 1-6

[0103] Pre-emulsion preparation:

[0104] Add 0.8 parts SSS and 3.5 parts SDS to 80 parts deionized water and stir for 30 minutes. Add 70 parts MAA, 6 parts AA, 119 parts EA, 28 parts EHA, and 3 parts DAP to the mixture, and place it in a pre-emulsification vessel and stir thoroughly.

[0105] Weigh 0.5 parts of ammonium persulfate (APS) and dissolve it in 10 parts of deionized water (DIW) to prepare initiator solution I;

[0106] Weigh 0.9 parts ammonium persulfate (APS), 0.8 parts SSS, and 2 parts SDS, and dissolve them in 40 parts deionized water (DIW) to prepare initiator solution II;

[0107] Add 540 parts of deionized water to the reactor and heat to 83-88℃. Add 1.5 parts of SDS, 1.5 parts of anhydrous ethanol, and 0.5 parts of NaHCO3. Add initiator solution II to the reactor. After 3 minutes, add the pre-emulsion and initiator solution II dropwise, controlling the reaction temperature at 85-89℃ and adding at a uniform rate for 120 minutes. When the addition reaches 102 minutes, stop the addition, add 0.8 parts by mass of NDM to the pre-emulsion, stir for 10 minutes, and then continue the addition until it is complete. Keep the reactor at this temperature for 60 minutes.

[0108] Weigh out 15 parts of TBHP dissolved in deionized water to prepare 3 parts of oxidant solution I; weigh out 20 parts of TBHP dissolved in deionized water to prepare oxidant solution II;

[0109] Weigh out 15 parts of IAA dissolved in deionized water to prepare reducing agent solution I; weigh out 2 parts of IAA dissolved in deionized water to prepare reducing agent solution II;

[0110] When the residual EA in the polymerization reactor was detected to be 800 ppm, the reactor was rapidly cooled to 75°C. 1.2 parts by weight of EA were quickly added to the reactor and stirred for 5 minutes. Then, oxidant solution I and reducing agent solution I were added sequentially and rapidly, with an interval of less than 5 minutes between each addition. The mixture was kept at this temperature for 60 minutes. Oxidant solution II and reducing agent solution II were then added dropwise simultaneously over 60 minutes, followed by another 60 minutes of temperature maintenance. The temperature was then lowered to below 50°C. 0.5 parts by weight of Tego825 defoamer dissolved in 7 parts of deionized water and 2 parts by weight of PHCG were added. Water was added to adjust the solid content to 30%, and the mixture was filtered out. Emulsion 1-6 was obtained.

[0111] Example 7: Emulsion 1-7

[0112] Pre-emulsion preparation:

[0113] Add 0.8 parts SSS and 3.5 parts SDS to 80 parts deionized water and stir for 30 minutes. Add 70 parts MAA, 6 parts AA, 105.6 parts EA, 28 parts EHA, and 3 parts DAP to the mixture, and place it in a pre-emulsification vessel and stir thoroughly.

[0114] Weigh 0.5 parts of ammonium persulfate (APS) and dissolve it in 10 parts of deionized water (DIW) to prepare initiator solution I;

[0115] Weigh 0.9 parts ammonium persulfate (APS), 0.8 parts SSS, and 2 parts SDS, and dissolve them in 40 parts deionized water (DIW) to prepare initiator solution II;

[0116] Add 540 parts of deionized water to the reactor and heat to 83-88℃. Add 1.5 parts of SDS, 1.5 parts of anhydrous ethanol, and 0.5 parts of NaHCO3. Add initiator solution II to the reactor. After 3 minutes, add the pre-emulsion and initiator solution II dropwise, controlling the reaction temperature at 85-89℃ and adding at a uniform rate for 120 minutes. When the addition reaches 102 minutes, stop the addition, add 0.8 parts by mass of NDM to the pre-emulsion, stir for 10 minutes, and then continue the addition until it is complete. Keep the reactor at this temperature for 60 minutes.

[0117] Weigh out 15 parts of TBHP dissolved in deionized water to prepare 3 parts of oxidant solution I; weigh out 20 parts of TBHP dissolved in deionized water to prepare oxidant solution II;

[0118] Weigh out 15 parts of IAA dissolved in deionized water to prepare reducing agent solution I; weigh out 2 parts of IAA dissolved in deionized water to prepare reducing agent solution II;

[0119] When the residual EA in the polymerization reactor was detected to be 980 ppm, the reactor was rapidly cooled to 75°C. 14.6 parts by weight of EA were quickly added to the reactor and stirred for 5 minutes. Then, oxidant solution I and reducing agent solution I were added sequentially and rapidly, with an interval of less than 5 minutes between each addition. The mixture was kept at this temperature for 60 minutes. Oxidant solution II and reducing agent solution II were then added dropwise simultaneously over 60 minutes, followed by another 60 minutes of temperature maintenance. The temperature was then lowered to below 50°C. 0.5 parts by weight of Tego825 defoamer dissolved in 7 parts of deionized water and 2 parts by weight of PHCG were added. Water was added to adjust the solid content to 30%, and the mixture was filtered out. Emulsion 1-7 was obtained.

[0120] Comparative Example 1: Emulsion 2-1

[0121] Pre-emulsion preparation:

[0122] Add 0.8 parts SSS and 3.5 parts SDS to 80 parts deionized water and stir for 30 minutes. Add 70 parts MAA, 6 parts AA, 120.2 parts EA, 28 parts EHA, and 3 parts DAP to the mixture, and place it in a pre-emulsification vessel and stir thoroughly.

[0123] Weigh 0.5 parts of ammonium persulfate (APS) and dissolve it in 10 parts of deionized water (DIW) to prepare initiator solution I;

[0124] Weigh 0.9 parts ammonium persulfate (APS), 0.8 parts SSS, and 2 parts SDS, and dissolve them in 40 parts deionized water (DIW) to prepare initiator solution II;

[0125] Add 540 parts of deionized water to the reactor and heat to 83-88℃. Add 1.5 parts of SDS, 1.5 parts of anhydrous ethanol, and 0.5 parts of NaHCO3. Add initiator solution I to the reactor. After 3 minutes, add the pre-emulsion and initiator solution II dropwise, controlling the reaction temperature at 85-89℃ and adding at a uniform rate for 120 minutes. When the addition reaches 102 minutes, stop the addition, add 0.8 parts by mass of NDM to the pre-emulsion, stir for 10 minutes, and continue adding dropwise until the addition is complete. Keep the reactor at this temperature for 60 minutes.

[0126] Weigh out 15 parts of TBHP dissolved in deionized water to prepare 3 parts of oxidant solution I; weigh out 20 parts of TBHP dissolved in deionized water to prepare oxidant solution II;

[0127] Weigh out 15 parts of IAA dissolved in deionized water to prepare reducing agent solution I; weigh out 2 parts of IAA dissolved in deionized water to prepare reducing agent solution II;

[0128] When the residual EA in the polymerization reactor was detected to be 100 ppm, the reactor was rapidly cooled to 75°C. 3.7 parts by weight of EA were quickly added to the reactor and stirred for 5 minutes. Then, oxidant solution I and reducing agent solution I were added sequentially and rapidly, with an interval of less than 5 minutes between each addition. The mixture was kept at this temperature for 60 minutes. Oxidant solution II and reducing agent solution II were then added dropwise simultaneously over 60 minutes, followed by another 60 minutes of temperature maintenance. The temperature was then lowered to below 50°C. 0.5 parts by weight of Tego825 defoamer dissolved in 7 parts of deionized water and 2 parts by weight of PHCG were added. Water was added to adjust the solid content to 30%, and the mixture was filtered out. Emulsion 2-1 was obtained.

[0129] Comparative Example 2: Emulsion 2-2

[0130] Pre-emulsion preparation:

[0131] Add 0.8 parts SSS and 3.5 parts SDS to 80 parts deionized water and stir for 30 minutes. Add 70 parts MAA, 6 parts AA, 116.5 parts EA, 28 parts EHA, and 3 parts DAP to the mixture, and place it in a pre-emulsification vessel and stir thoroughly.

[0132] Weigh 0.5 parts of ammonium persulfate (APS) and dissolve it in 10 parts of deionized water (DIW) to prepare initiator solution I;

[0133] Weigh 0.9 parts ammonium persulfate (APS), 0.8 parts SSS, and 2 parts SDS, and dissolve them in 40 parts deionized water (DIW) to prepare initiator solution I;

[0134] Add 540 parts of deionized water to the reactor and heat to 83-88℃. Add 1.5 parts of SDS, 1.5 parts of anhydrous ethanol, and 0.5 parts of NaHCO3. Add initiator solution I to the reactor. After 3 minutes, add the pre-emulsion and initiator solution II dropwise, controlling the reaction temperature at 85-89℃ and adding at a uniform rate for 120 minutes. When the addition reaches 102 minutes, stop the addition, add 0.8 parts by mass of NDM to the pre-emulsion, stir for 10 minutes, and continue adding dropwise until the addition is complete. Keep the reactor at this temperature for 60 minutes.

[0135] Weigh out 15 parts of TBHP dissolved in deionized water to prepare 3 parts of oxidant solution I; weigh out 20 parts of TBHP dissolved in deionized water to prepare oxidant solution II;

[0136] Weigh out 15 parts of IAA dissolved in deionized water to prepare reducing agent solution I; weigh out 2 parts of IAA dissolved in deionized water to prepare reducing agent solution II;

[0137] When the residual EA in the polymerization reactor was detected to be 1200 ppm, the reactor was rapidly cooled to 75°C. 3.7 parts by weight of EA were quickly added to the reactor and stirred for 5 minutes. Then, oxidant solution I and reducing agent solution I were added sequentially and rapidly, with an interval of less than 5 minutes between each addition. The mixture was kept at this temperature for 60 minutes. Oxidant solution II and reducing agent solution II were then added dropwise simultaneously over 60 minutes, followed by another 60 minutes of temperature maintenance. The temperature was then lowered to below 50°C. 0.5 parts by weight of Tego825 defoamer dissolved in 7 parts of deionized water and 2 parts by weight of PHCG were added. Water was added to adjust the solid content to 30%, and the mixture was filtered out. Emulsion 2-2 was obtained.

[0138] In one specific embodiment, the acrylate suspending thickener used in the preparation of shampoo may comprise the following components in parts by weight:

[0139] Water 66-77.7 parts, thickener 7.0-9.0 parts, surfactant 15-20 parts, cationic compound 0-1.0 parts, fragrance 0-1.0 parts, pigment 0-1.0 parts, pearlescent agent 0-1.0 parts, neutralizer 0.3-1.0 parts. Depending on the application and performance requirements, those skilled in the art can adjust the composition and content of other components besides the thickener.

[0140] In a specific embodiment of this application, the acrylate suspending thickener used in the formulation for preparing shampoo includes:

[0141] 71 parts by weight of water, 8.2 parts by weight of sodium alginate (thickener), 18 parts by weight of chlorinated 2-hydroxy-3-(trimethylamino)propyl polyethylene oxide cellulose ether (surfactant), 0.5 parts by weight of ammonium lauryl sulfate (cationic compound), 0.5 parts by weight of fragrance, 0.6 parts by weight of pigment, 0.4 parts by weight of ethylene glycol stearate, and 0.8 parts by weight of sodium hydroxide (neutralizing agent).

[0142] (1) The suspension and thickening properties of acrylic emulsions in shampoo formulations are mainly characterized by the viscosity and yield value of the shampoo formulation. The test methods are as follows:

[0143] ① The viscosity values ​​at 20 r were measured using a Brookfeald viscometer with a 64# rotor.

[0144] ② The yield value is characterized by subtracting the viscosity value measured at 1r from the viscosity value measured at 0.5r and then dividing by 100. The larger the yield value, the better the suspension.

[0145] (2) The transparency of acrylic emulsion in shampoo formulation is mainly characterized by ultraviolet spectrophotometer. The test methods are as follows: using ultraviolet spectrophotometer, at a wavelength of 420nm, after zero calibration with pure water as reference, the transmittance of the sample is tested. The higher the transmittance, the better the transparency of the shampoo formulation.

[0146] Table 3 Experimental conditions for the examples and comparative examples

[0147]

[0148] Table 4 Comparison of Emulsion Performance Tests

[0149]

[0150] Among them, the samples of Example 1-1 showed good performance repeatability during industrialization, while the performance of Comparative Example 2-1 fluctuated during industrialization. This invention, through a special production process and ingenious overall formulation design, ensures high transparency while maintaining good suspension properties, and the resulting emulsion of Example 1-1 solves the problem of performance fluctuations in industrial production.

[0151] The comparison of the examples and comparative examples shows that the timing of soft monomer insertion has a significant impact on the suspension and transparency of the product. When the residual soft monomer content is between 200ppm and 1000ppm, the emulsion production can achieve good stability and excellent performance.

[0152] Finally, it should be noted that the above examples of water-based acrylic suspension thickeners are only used to describe preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that various modifications and improvements made to the technical solutions of the present invention by means of modifications or equivalent substitutions should fall within the scope of protection defined by the claims of the present invention.

Claims

1. A method for preparing an aqueous acrylic suspension thickening emulsion, characterized in that, Includes the following steps: (1) Add water to the reactor, heat it to 70-95℃, and add bottom emulsifier I and additives; (2) At 70-95℃, initiator I is added to the reactor. After 5-10 min, pre-emulsion, initiator II and emulsifier II are added to the reactor simultaneously. When the amount of pre-emulsion added is 75%-95% of its mass, chain transfer agent is added to the pre-emulsion. After stirring for 5-15 min, the pre-emulsion is added until all the pre-emulsion is added. The total addition time is 120-240 min. (3) Keep warm for 30-90 min, then cool down to 65-80℃. During the heat preservation process, detect the residual soft monomer. When the residual soft monomer is 200-1000 ppm, add the soft monomer to the reactor. Stir for 5-20 min and then add oxidant I and reductant I. The interval between adding oxidant I and reductant I is less than 5 min. Keep warm for 30-60 minutes, then start adding oxidant II and reducing agent II, which takes 60-120 minutes. After adding, keep warm for 60-120 minutes. In step (2), the pre-emulsion comprises the following components, calculated based on a total pre-emulsion mass of 100 parts by weight: 18-40 parts by weight of hard monomer; 45-65 parts by weight of soft monomer; 0-3 parts by weight of functional monomer; Emulsifier III 0-1.2 parts by weight; 10-30 parts by weight of water; In step (2), the chain transfer agent is one or more of n-dodecyl mercaptobutyl ester, mercaptopropionic acid, and mercaptoethanol; In step (3), the amount of soft monomer added is 0.5%-10% of the total monomer mass; The soft monomers in the pre-emulsion include one or more of isooctyl acrylate, butyl acrylate, ethyl acrylate, isooctyl methacrylate, 2-ethylhexyl acrylate, and lauryl methacrylate. In step (1), the auxiliary agent is one or more of alkali metal carbonates, alkali metal bicarbonates, and alcohols.

2. The preparation method according to claim 1, characterized in that, After the heat preservation is completed, the temperature is lowered to 50-60℃, then the reactor is rotated, defoamer and preservative are added, and the material is filtered and discharged.

3. The preparation method according to claim 1 or 2, characterized in that, In the preparation method described above, the amounts of each component added are as follows: 220-630 parts by weight of pre-emulsion Emulsifier 2-10 parts by weight, Additives 0.3-3 parts by weight, Chain transfer agent 0.1-3 parts by weight, Initiator 0.1-2 parts by weight, Oxidizing agent 0.5-6 parts by weight, Reducing agent 0.4-2 parts by weight, 0-1 parts by weight of defoamer Preservative 0-4 parts by weight 340-775 parts by weight of water; The total mass of the above components shall be 1000 parts. The amount of emulsifier added refers to the total amount of emulsifier I and emulsifier II; the mass ratio of emulsifier I to emulsifier II is 1:20-20:

1. The amount of initiator added refers to the total amount of initiator I and initiator II; the mass ratio of initiator I to initiator II is 1:20-20:1; The amount of oxidant added refers to the total amount of oxidant I and oxidant II; the mass ratio of oxidant I to oxidant II is 1:20-20:

1. The amount of reducing agent added refers to the total amount of reducing agent I and reducing agent II; the mass ratio of reducing agent I to reducing agent II is 1:20-20:

1.

4. The preparation method according to claim 3, characterized in that, In the preparation method described above, the amounts of each component added are as follows: Pre-emulsion 270-490 parts by weight, Emulsifier 3-9 parts by weight 0.5-2 parts by weight of additives Chain transfer agent 0.2-1.5 parts by weight, Initiator 0.1-1.5 parts by weight, Oxidizing agent 0.8-4 parts by weight, Reducing agent 0.5-1.5 parts by weight, Defoamer 0.2-0.8 parts by weight, Preservative 1.5-3.5 parts by weight, 450-750 parts by weight of water; The total mass of the above components is 1000 parts.

5. The preparation method according to claim 1, characterized in that, Emulsifier I and emulsifier II are each independently selected from one or more of sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, alkyl polyoxyethylene ether, sodium p-styrene sulfonate, fatty alcohol polyoxyethylene ether and its salts, and fatty alcohol ether phosphate and its salts.

6. The preparation method according to claim 5, characterized in that, Emulsifier I and emulsifier II are independently selected from sodium dodecyl sulfate and sodium p-styrene sulfonate, respectively.

7. The preparation method according to claim 1, characterized in that, In step (1), the auxiliary agent is one or more of sodium bicarbonate, sodium carbonate, potassium bicarbonate, potassium carbonate, methanol, and ethanol.

8. The preparation method according to claim 1, characterized in that, In step (2), initiator I and initiator II are each an initiator, and are each an initiator, and are initiators ... respectively.

9. The preparation method according to claim 8, characterized in that, In step (2), initiator I and initiator II are each independently one or more of ammonium sulfate, sodium persulfate, potassium persulfate, cumene hydrogen peroxide, and tert-butyl hydrogen peroxide.

10. The preparation method according to claim 1, characterized in that, In step (2), the pre-emulsion comprises the following components, calculated based on a total pre-emulsion mass of 100 parts by weight: 20-35 parts by weight of hard monomer; 45-58 parts by weight of soft monomer; 0-1.5 parts by weight of functional monomer; Emulsifier III 0-1 parts by weight; 13-27 parts by weight of water.

11. The preparation method according to claim 1, characterized in that, The method for preparing the pre-emulsion includes the following steps: adding water and emulsifier to the pre-emulsion kettle 1, stirring evenly, and then adding soft monomers, optionally functional monomers, and hard monomers, and stirring.

12. The preparation method according to claim 1, characterized in that, The pre-emulsifier III in the pre-emulsified liquid is one or more of sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, alkyl polyoxyethylene ether, sodium p-styrene sulfonate, fatty alcohol polyoxyethylene ether and its salts, and fatty alcohol ether phosphate and its salts.

13. The preparation method according to claim 1, characterized in that, The hard monomers in the pre-emulsion include one or more of styrene, methacrylic acid, acrylic acid, and methyl methacrylate.

14. The preparation method according to claim 13, characterized in that, The hard monomers in the pre-emulsion include methacrylic acid and methyl methacrylate.

15. The preparation method according to claim 1, characterized in that, The functional monomers in the pre-emulsion include one or more of hydroxyethyl acrylate, β-acryloyloxypropionic acid, diallyl phthalate, allyl methacrylate, ethylene glycol dimethacrylate, and 1,3-butanediol dimethacrylate.

16. The preparation method according to claim 1, characterized in that, In step (3), the amount of soft monomer added is 0.5%-5% of the total monomer mass.

17. The preparation method according to claim 1, characterized in that, In step (3), the soft monomer is added all at once or quickly within 5 minutes.

18. The preparation method according to claim 1, characterized in that, In step (3), oxidant I is added at once or quickly within 5 minutes, and reducing agent solution I is added at once or quickly within 5 minutes.

19. The preparation method according to claim 1, characterized in that, In step (3), the oxidant I and oxidant II are each independently selected from peroxides.

20. The preparation method according to claim 19, characterized in that, The oxidant I and oxidant II are each independently selected from one or more of sodium persulfate, ammonium persulfate, tert-butyl hydroperoxide, cumene hydroperoxide, and hydrogen peroxide.

21. The preparation method according to claim 20, characterized in that, The oxidant I and oxidant II are each independently selected from tert-butyl hydroperoxide.

22. The preparation method according to claim 1, characterized in that, In step (3), reducing agent I and reducing agent II are each independently selected from one or more of sodium metabisulfite, disodium metabisulfite, ascorbic acid, and sodium formaldehyde sulfoxylate.

23. The preparation method according to claim 22, characterized in that, In step (3), reducing agent I and reducing agent II are independently selected from ascorbic acid.

24. The preparation method according to claim 2, characterized in that, In step (3), the defoamer is one or more of the following: silicone defoamer, mineral oil defoamer, and polyether defoamer.

25. The preparation method according to claim 24, characterized in that, In step (3), the defoamer is an organosilicon defoamer.

26. The preparation method according to claim 2, characterized in that, In step (3), the preservative is one or more of the following: triazine preservative, bisoxazoline preservative, isothiazolinone preservative, and broad-spectrum preservative.

27. The preparation method according to claim 1, characterized in that, The aqueous acrylic suspension thickening emulsion has a solid content of 25%-40% and an average particle size of 90-150 nm.

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