Method for preparing coacervate dispersion controllable emulsion by using acrylic macromolecular emulsifier
By using RAFT polymerization and pH control of acrylic macromolecular emulsifiers, the problems of poor stability of small molecule emulsifiers and complex synthesis of traditional macromolecular emulsifiers have been solved, achieving stability and reversible control of high solids content emulsions, and improving the storage stability and preparation efficiency of emulsions.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- CHANGCHUN UNIV OF TECH
- Filing Date
- 2023-04-04
- Publication Date
- 2026-06-19
AI Technical Summary
Existing small molecule emulsifiers have poor stability in emulsion systems, especially under high solid content conditions, they are prone to demulsification, which affects product performance and is difficult to recycle, leading to environmental pollution. Meanwhile, traditional large molecule emulsifiers are complex to synthesize and costly.
A method for preparing emulsions with controllable coagulation and dispersion is achieved by constructing emulsions using acrylic macromolecular emulsifiers via RAFT polymerization and combining pH adjustment. The method includes synthesizing acrylic macromolecular emulsifiers, emulsion polymerization, and pH adjustment to achieve emulsion stability and reversible control.
The prepared emulsion exhibits good stability during storage and transportation, with minimal variation in latex particle size, shortening the polymerization cycle of high-solids-content emulsions and providing a stable and reversible control pathway.
Smart Images
Figure FT_1 
Figure FT_2
Abstract
Description
Technical Field
[0001] This invention belongs to the field of emulsion polymerization technology, specifically relating to a method for preparing a coagulation and dispersion controllable emulsion using acrylic macromolecular emulsifiers. Background Technology
[0002] An emulsion is typically a liquid system in which two immiscible components exist as dispersed micro-regions within a continuous phase under the influence of an emulsifier interface. The thermodynamic instability of emulsion systems is affected by the hydrophilic-lipophilic balance, electrostatic repulsion, and physical barriers of the emulsifier. Small molecule emulsifiers accumulate on the surface of the dispersed phase through physical adsorption in emulsion systems. The relative stability maintained by the emulsifier is easily disrupted by mechanical forces, temperature, or the action of anti-ion reactions. Furthermore, emulsion stability deteriorates during long-term storage or the synthesis of high-solids-content emulsions, and may even lead to coagulation and demulsification. Adding emulsifiers to maintain emulsion stability increases manufacturing costs. Moreover, for polymerization processes requiring demulsification to obtain solid products, residual emulsifiers not only affect product performance but are also difficult to recover and degrade in the aqueous phase, easily causing environmental pollution.
[0003] Small molecule emulsifiers are easily eluted under external force, and the coagulation process is irreversible. Furthermore, large amounts of emulsifier are required when preparing high-solids-content emulsions, which negatively impacts product performance. Macromolecular emulsifiers, as an effective means to solve these problems, have received widespread attention. The paper *Science*, 2006, 958, reported an alkylamidine compound that reacts with carbon dioxide to become an ionic surfactant. The reaction is reversed and the surface activity is lost upon the introduction of nitrogen or other inert gases. Based on this research, ZL201110126690.1 disclosed a method for preparing latex by achieving emulsion coagulation through alkaline solutions or inert gases and redispersing it by introducing carbon dioxide. The aforementioned reversible coagulation and redispersibility effects are all achieved through the reaction of the amidine group with CO2. However, amidine compounds are easily hydrolyzed, which inevitably affects their stability in the aqueous phase. Moreover, the synthesis of amidine compounds is difficult, with cumbersome steps and high costs. Macromolecules (2015, 1313) reported a method for preparing emulsions from a polystyrene-polybutyl acrylate diblock polymer. While this method achieved reversible control over aggregation and dispersion, the dispersed latex particles exhibited partial and irreversible agglomeration in size, resulting in a near doubling of particle size and a wider particle size distribution. Summary of the Invention
[0004] This invention addresses the shortcomings of existing technologies by providing a method for preparing coagulation-dispersion controllable emulsions based on acrylic macromolecular emulsifiers.
[0005] The objective of this invention is achieved through the following steps:
[0006] Step 1 provides a synthesis scheme for an acrylic macromolecular emulsifier. Under nitrogen protection, RAFT reagent and hydrophilic acrylic monomers are dissolved in a solvent. The reaction temperature is controlled at 60-80℃. 0.1-3 wt% of the polymerization monomer is added as an initiator. After reacting for 3-8 hours, a hydrophobic acrylic monomer is added. At the same time, 0.05-0.2 wt% of the hydrophobic monomer, initiator, and solvent are added to continue the reaction for 2-5 hours. After the reaction is completed, the acrylic macromolecular emulsifier is obtained after sedimentation, filtration, and drying.
[0007] Step 2 provides an emulsion polymerization scheme based on acrylic macromolecular emulsifiers: the above-mentioned acrylic macromolecular emulsifiers are dissolved in deionized water and then polymerized monomers are added. The polymerized monomers account for 20-40% of the total emulsion mass. Under nitrogen protection, the mixture is stirred thoroughly and heated to the reaction temperature of 65-80°C. Then, an initiator accounting for 0.5-3% of the total emulsion mass is added. After polymerization for 0.5-3 hours, an emulsion with high conversion rate is obtained.
[0008] Step 3 provides a method for controlling the coagulation and dispersion of an emulsion: an acidic solution is added to the above emulsion to adjust the pH value of the emulsion to 1-3, causing the emulsion to coagulate; the supernatant of the coagulated sample is removed, and deionized water and alkaline solution are added until the solid content before demulsification is reached, controlling the pH of the emulsion between 9 and 10, and a stable emulsion is obtained after sufficient dispersion.
[0009] Furthermore, in step 1, the hydrophilic monomer is one or more of acrylic acid, methacrylic acid, hydroxyethyl acrylate, and hydroxypropyl acrylate; the hydrophobic monomer is one or more of methyl acrylate, methyl methacrylate, propyl methacrylate, and n-butyl acrylate.
[0010] Furthermore, in step 1, the molar ratio of the hydrophilic monomer to the hydrophobic monomer is 1.5 to 6.5:1.
[0011] Further, the RAFT reagent in step 1 is at least one of S-tert-butyl-S′-(α-methyl-α′-acetic acid) trithiocarbonate, S,S′-bis(α,α′-dimethyl-α"-acetic acid) trithiocarbonate, and S-1-dodecyl-S′-(α,α′-dimethyl-α"-acetic acid) trithiocarbonate.
[0012] Furthermore, in step 1, the initiator is one or more of azobisisobutyronitrile or azobisisoheptanenitrile; the solvent used is 1,4-dioxane.
[0013] Furthermore, in step 1, the initiator accounts for 0.5% to 1.5% of the total mass of the monomer, and the molar ratio of RAFT reagent to initiator is 3 to 9:1.
[0014] Furthermore, in step 2, the initiator is one or more of potassium persulfate or ammonium persulfate, and the polymerizing monomer is one or more of methyl methacrylate, propyl methacrylate, and n-butyl acrylate.
[0015] Furthermore, in step 2, the monomer accounts for 20-40% of the total emulsion mass, the initiator is used at 0.4-1% of the monomer mass, and the macromolecular emulsifier is used at 0.5-0.9% of the monomer molar mass.
[0016] Furthermore, in step 3, the alkaline solution can be either an aqueous solution of sodium hydroxide or potassium hydroxide, and the acidic solution can be an aqueous solution of hydrochloric acid.
[0017] Furthermore, in step 3, the emulsion obtained can undergo at least three coagulation and dispersion cycles by adjusting the pH value, wherein the average particle size change rate of the polymer particles in the emulsion does not exceed 10%.
[0018] The present invention provides a method for preparing a coagulation-dispersion controllable emulsion based on an acrylic macromolecular emulsifier. This method uses RAFT polymerization to construct an emulsion based on an acrylic macromolecular emulsifier and applies it to traditional emulsion polymerization to prepare an emulsion whose coagulation and dispersion states can be repeatedly controlled by pH. After cycles of coagulation and dispersion, the latex particles in the resulting emulsion exhibit good stability and are essentially consistent with the initial emulsion particle size. The emulsion prepared by this invention shows good stability during storage and transportation, and can significantly shorten the preparation cycle of high-solids-content emulsion polymerization, providing an effective approach to expanding the preparation and application of water-dispersible polymers. Attached Figure Description
[0019] Figure 1 Three-stage coagulation and dispersion diagram of emulsion 1.
[0020] Figure 2 Particle size diagram of latex particles in emulsion 1 and the dispersed emulsion after coagulation. Detailed Implementation
[0021] To further illustrate the present invention, the technical solution provided by the present invention will be described in detail below with reference to the embodiments. The reagents or instruments involved in the embodiments are all conventional products that can be purchased commercially.
[0022] Example 1
[0023] Synthesis of acrylic macromolecular emulsifiers
[0024] In a three-necked flask, 7.5 parts of the hydrophilic monomer acrylic acid and 0.9 parts of RAFT reagent S,S′-bis(α,α′-dimethyl-α"-acetic acid) trithiocarbonate were dissolved in 67 parts of solvent 1,4-dioxane. After purging with nitrogen to remove oxygen for 20 minutes and stirring until homogeneous, 0.08 parts of initiator AIBN were added and reacted for 3 hours at a constant temperature of 70°C. Then, 2.5 parts of the hydrophobic monomer methyl methacrylate were added to the three-necked flask, along with 0.02 parts of initiator AIBN and 22 parts of solvent 1,4-dioxane. The reaction was continued for 5 hours. The resulting solution was then precipitated in n-hexane, filtered, and dried in a vacuum oven to obtain the acrylic macromolecular emulsifier PAA-b-PMMA-1, with a number-average molecular weight of 2665 and a polydispersity index of 1.0039. The molar ratio of hydrophilic monomer to hydrophobic monomer in PAA-b-PMMA-1 was 4:1.
[0025] Coagulation and dispersion can regulate the synthesis of emulsions.
[0026] Take 1.8 parts of the macromolecular emulsifier PAA-b-PMMA-1 obtained above and dissolve it completely in 70 parts of deionized water. Then add 28 parts of methyl methacrylate monomer to the reactor. After purging with nitrogen to remove oxygen for 20 minutes, stir at 180 r / min at 80℃ for 30 minutes to pre-emulsify. Then add 0.2 parts of potassium persulfate to start the reaction. After 1 hour, emulsion 1 is obtained.
[0027] At room temperature, a suitable amount of 0.2M HCl was added dropwise to adjust the pH of emulsion 1 to 1-3. Under these conditions, the emulsion coagulated and demulsified. After standing, the supernatant was removed, and the emulsion was rinsed with deionized water until near neutral. 1M NaOH solution and deionized water were added to the coagulated sample to adjust the emulsion solids content back to that before demulsification, while simultaneously controlling the pH to between 9 and 10. The emulsion was then sonicated until completely dispersed, resulting in a stable emulsion. This coagulation and dispersion process was repeated three times, and the latex particle size distribution in the emulsion was characterized using a dynamic light scattering particle size analyzer. The particle sizes of the original emulsion and the dispersed emulsions after three coagulations were 118 nm, 123 nm, 113 nm, and 125 nm, respectively. The coagulation and dispersion state of the emulsion and the particle size distribution of the latex particles are shown in the figure below. Figure 1 , Figure 2 As shown.
[0028] Example 2
[0029] An acrylate macromolecular emulsifier was prepared according to the method in Example 1, except that the amount of hydrophobic monomer was adjusted to 2 parts, and the total amount of solvent 1,4-dioxane was 88.6 parts, wherein the molar ratio of hydrophilic monomer to hydrophobic monomer was 5:1. The resulting macromolecular emulsifier was PAA-b-PMMA-2, with a number-average molecular weight of 2832 and a polydispersity index of 1.0138. The molar ratio of hydrophilic monomer to hydrophobic monomer in PAA-b-PMMA-1 was 5:1.
[0030] Emulsions with adjustable coagulation and dispersion were prepared according to the method of Example 1, except that emulsion 2 was prepared using the macromolecular emulsifier PAA-b-PMMA-2.
[0031] The coagulation and dispersion process of emulsion 2 was repeated three times according to the method in Example 1, and the particle size of latex particles in the emulsion was characterized using a dynamic light scattering particle size analyzer. The particle sizes of emulsion 3 and the dispersed emulsion after three coagulations were 146 nm, 152 nm, 160 nm, and 155 nm, respectively.
[0032] Example 3
[0033] An acrylic macromolecular emulsifier was prepared according to the method of Example 1 for the preparation of coagulation and dispersion controllable emulsions. The difference was that the amount of potassium persulfate initiator used in the emulsion polymerization process was 0.15 parts, and the resulting emulsion was emulsion 3.
[0034] The coagulation and dispersion process of emulsion 3 was repeated three times according to the method in Example 1, and the particle size of latex particles in the emulsion was characterized using a dynamic light scattering particle size analyzer. The particle sizes of emulsion 3 and the dispersed emulsion after three coagulations were 165 nm, 158 nm, 160 nm, and 172 nm, respectively.
[0035] Example 4
[0036] An acrylic macromolecular emulsifier was prepared according to the method in Example 1, except that the polymerization temperature was set to 75°C. The resulting macromolecular emulsifier was PAA-b-PMMA-3. Its number-average molecular weight was 2564, and its polydispersity index was 1.2016.
[0037] Emulsions with adjustable coagulation and dispersion were prepared according to the method of Example 1, except that emulsion 4 was prepared using the macromolecular emulsifier PAA-b-PMMA-3.
[0038] The coagulation and dispersion process of emulsion 4 was repeated three times according to the method in Example 1, and the particle size of latex particles in the emulsion was characterized using a dynamic light scattering particle size analyzer. The particle sizes of emulsion 3 and the dispersed emulsion after three coagulations were 132 nm, 138 nm, 144 nm, and 142 nm, respectively.
[0039] Example 5
[0040] An acrylic macromolecular emulsifier was prepared according to the method of Example 1 and used to prepare a coagulation-dispersion controllable emulsion, except that the emulsion polymerization temperature was set to 75°C, and the resulting emulsion was denoted as emulsion 5.
[0041] The coagulation and dispersion process of emulsion 4 was repeated three times according to the method in Example 1, and the particle size of latex particles in the emulsion was characterized using a dynamic light scattering particle size analyzer. The particle sizes of emulsion 5 and the dispersed emulsion after three coagulations were 118 nm, 112 nm, 121 nm, and 126 nm, respectively.
[0042] Example 6
[0043] The acrylic macromolecular emulsifier PAA-b-PMMA-1 was prepared according to the method of Example 1 and used to prepare a coagulation and dispersion controllable emulsion. The difference was that the monomers used in the emulsion polymerization were a mixture of 14 parts methyl methacrylate and 14 parts n-butyl acrylate. The resulting emulsion was designated as emulsion 6.
[0044] The coagulation and dispersion process of emulsion 6 was repeated three times according to the method in Example 1, and the particle size of latex particles in the emulsion was characterized using a dynamic light scattering particle size analyzer. The particle sizes of emulsion 4 and the dispersed emulsion after three coagulations were 198 nm, 204 nm, 213 nm, and 209 nm, respectively.
[0045] As can be seen from the above embodiments, the present invention constructs an acrylic macromolecular emulsifier through the RAFT reaction, and achieves performance regulation by controlling the ratio of hydrophobic and hydrophilic segments in the emulsifier structure. This emulsifier is then used as an emulsifier for further emulsion polymerization. The resulting emulsion has good stability, and the aggregation and dispersion states can be controlled by adjusting the pH of the emulsion. The solid content of the emulsion can be rapidly increased, and a good redispersion effect can be achieved. After three aggregation and dispersion cycles, the particle size of the latex particles in the emulsion does not change by more than 10% compared with the initial particle size.
[0046] The above embodiments are merely examples for clear explanation and are not intended to limit the implementation. Any changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention should be considered equivalent substitutions and are all included within the protection scope of the present invention.
Claims
1. A method for preparing a coagulation-dispersion controllable emulsion based on acrylic macromolecular emulsifiers, characterized in that, The method includes the following steps: Step 1, Synthesis of acrylic macromolecular emulsifier: Under nitrogen protection, RAFT reagent and hydrophilic acrylic monomers are dissolved in a solvent, wherein the hydrophilic acrylic monomer is at least one of acrylic acid, methacrylic acid, hydroxyethyl acrylate, and hydroxypropyl acrylate. The temperature is controlled at 60~80℃. 0.1~3wt% of initiator of hydrophilic acrylic monomer is added. After reacting for 3~8h, a hydrophobic monomer is added, wherein the hydrophobic monomer is at least one of methyl acrylate, methyl methacrylate, propyl methacrylate, and n-butyl acrylate. At the same time, 0.05-0.2wt% of initiator and solvent of hydrophobic monomer are added to continue the reaction for 2~5h. In this reaction, the molar ratio of hydrophilic acrylic monomer to hydrophobic monomer is 1.5~6.5:
1. After the reaction is completed, after sedimentation, filtration and drying, the acrylic macromolecular emulsifier is obtained. Step 2, Coagulation and Dispersion Controllable Emulsion Polymerization: The above-mentioned acrylic macromolecular emulsifier is dissolved in deionized water and then polymerized monomers are added, wherein the polymerized monomers account for 20-40 wt% of the total emulsion. The polymerized monomers used are at least one of methyl methacrylate and n-butyl acrylate. Under nitrogen protection, the mixture is stirred thoroughly and heated to the reaction temperature of 65-80°C. Then, an initiator accounting for 0.4%-1 wt% of the total polymerized monomers is added and polymerized for 0.5-3 hours, wherein the initiator is one of ammonium persulfate and potassium persulfate. Finally, a reversible coagulation and dispersion emulsion with high conversion rate is obtained. Step 3, Coagulation and Dispersion Control: Add an acidic solution to the above emulsion to adjust the pH value of the emulsion to 1-3, so that the emulsion coagulates; remove the supernatant of the sample after coagulation, add deionized water and alkaline solution to the solid content before demulsification, control the pH value of the emulsion between 9 and 10, and obtain a stable emulsion after sufficient dispersion.
2. The method according to claim 1, characterized in that, The RAFT reagent in step 1 is one of S-tert-butyl-S′-(α-methyl-α′-acetic acid) trithiocarbonate, S,S′-bis(α,α′-dimethyl-α"-acetic acid) trithiocarbonate, and S-1-dodecyl-S′-(α,α′-dimethyl-α"-acetic acid) trithiocarbonate.
3. The method according to claim 1, characterized in that, In step 1, the initiator is one of azobisisobutyronitrile (AIBN) and azobisisoheptanenitrile (AIHH), and the solvent is 1,4-dioxane.
4. The method according to claim 1, characterized in that, In step 1, the initiator accounts for 0.5% to 1.5 wt% of the total monomer mass, and the molar ratio of RAFT reagent to initiator is 3 to 9:
1.
5. The method of claim 1, wherein, In step 3, the alkaline solution can be either sodium hydroxide or potassium hydroxide aqueous solution, and the acidic solution can be hydrochloric acid aqueous solution.
6. The method of claim 1, wherein, In step 3, the emulsion can complete at least three coagulation and dispersion cycles by adjusting the pH value, wherein the average particle size change rate of the polymer particles in the emulsion does not exceed 10%.