A thermosensitive emulsifier, a preparation method thereof, and its application in emulsion polymerization self-demulsification

Abstract

The invention discloses a kind of temperature-sensitive emulsifier and its preparation method and its application in emulsion polymerization self-demulsification, belong to functional polymer surfactant application field.The temperature-sensitive emulsifier of the present invention, it includes hydrophilic component A and temperature-sensitive component B, the hydrophilic component A includes polyethylene glycol with a polymerization degree of 10~100, and the temperature-sensitive component includes poly-N-isopropylacrylamide with a polymerization degree of 10~150, connected by a covalent bond.The temperature-sensitive emulsifier of the present invention can be used for preparing high polymer by emulsion polymerization, and as an emulsifier under relatively high temperature conditions, it can demulsify under relatively low temperature conditions.The temperature-sensitive emulsifier of the present invention has temperature-controlled surface activity ability, contributes to the advantages such as emulsion polymerization process self-demulsification.

Description

Technical Field

[0001] The invention belongs to the application field of functional polymer surfactants, and particularly relates to a temperature-sensitive emulsifier, a preparation method thereof, and application thereof in emulsion polymerization self-demulsification. Background Art

[0002] At present, emulsion polymerization products, such as styrene-butadiene rubber, nitrile rubber, polyacrylate emulsion, etc., have been widely used in our daily life. The revenue of emulsion polymerization market has also shown an increasing trend year by year. It can be seen that emulsion polymerization has become an important field of polymer science and technology and is one of the important methods for producing polymers.

[0003] Emulsion polymerization offers advantages such as using non-toxic water as a solvent, easy heat dissipation, avoiding local overheating, fast polymerization reaction rates, and high polymer molecular weight. However, it also suffers from disadvantages such as complex polymer separation and precipitation processes, requiring the addition of demulsifiers or coagulants. Because emulsifiers in emulsion polymerization systems reduce the interfacial tension between the oil and water phases, they are crucial for both emulsification and demulsification. Therefore, the development of a temperature-sensitive emulsifier for use in emulsion polymerization is an attempt to address this issue.

[0004] The development of thermosensitive emulsifiers began in the 1970s, when scientists began exploring reversible phase transfer systems and used compounds such as ampholytes, polymers, and low-molecular-weight organic compounds to construct thermosensitive emulsifiers. In recent years, the performance and application of thermosensitive emulsifiers have been further enhanced with the development and application of new materials.

[0005] N-isopropylacrylamide (NIPAM) is a commonly used thermosensitive polymer. Its most notable characteristic is its temperature responsiveness, meaning it undergoes a reversible phase transition between an aqueous solution and an aggregated state at a specific temperature. Its phase transition temperature is approximately 32°C. Above this temperature, hydrogen bonds formed with water molecules break, while below this temperature, hydrogen bonds re-form. Therefore, it has the potential to be used in emulsion polymerization. Summary of the Invention

[0006] In view of this, the purpose of the present invention is to provide a temperature-sensitive emulsifier, a preparation method thereof, and its application in emulsion polymerization self-demulsification. The temperature-sensitive emulsifier of the present invention has temperature-controllable surface activity, which is conducive to the self-demulsification of the emulsion polymerization process.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] A temperature-sensitive emulsifier with the following structure:

[0009]

[0010] Here, n is an integer from 10 to 100, and m is an integer from 10 to 150.

[0011] The preparation process includes the following steps:

[0012] (1) Add a certain amount of polyethylene glycol monomethyl ether to a flask and dissolve it in chloroform at a molar ratio of 200, heat it to 40-50 °C to completely dissolve it, then add a certain amount of triethylamine, and then place the flask in a cold trap for ice bath treatment; weigh 2-bromoisobutyryl bromide and dissolve it in chloroform at a molar ratio of 30, and add it dropwise to the above flask under nitrogen protection. After the addition is completed, wait for 10 minutes and then place the flask at room temperature to react for 12 hours; when the reaction is completed, use a rotary evaporator to distill the solvent, and the remaining product is purified by reprecipitation with ether, and dried to obtain polyethylene glycol monomethyl ether 2-bromoisobutyl ester.

[0013] (2) Weigh a certain amount of N-isopropylacrylamide and polyethylene glycol monomethyl ether 2-bromoisobutyl ester obtained in step (1) in a corresponding proportion and dissolve them in a certain amount of mixed solvent. Weigh a certain amount of cuprous bromide (CuBr) and pentamethyldiethylenetriamine (PMDETA) and dissolve them in a small amount of mixed solvent. Under nitrogen protection, add the latter mixed solution to the former and react at 35°C for 12-24 hours. After the reaction is terminated, dialyze the reaction solution with distilled water using a dialysis bag with a specific molecular weight cut-off for 72-96 hours, and then remove water using a freeze dryer to obtain the product temperature-sensitive emulsifier.

[0014] The degree of polymerization of polyethylene glycol monomethyl ether used in the above step (1) is 10-100.

[0015] The molar ratio of polyethylene glycol monomethyl ether, triethylamine and 2-bromoisobutyryl bromide used in the above step (1) is 1:2~3:1~5.

[0016] The mixed solvent described in the above step (2) is a mixed solvent of deionized water and dimethylformamide, and the volume ratio of deionized water to dimethylformamide is 3:1.

[0017] The molar ratio of the polyethylene glycol macroinitiator (polyethylene glycol monomethyl ether 2-bromoisobutyl ester), N-isopropylacrylamide, cuprous bromide and pentamethyldiethylenetriamine used in the above step (2) is 1:10-150:1.2-1.5:3-5.

[0018] Application: The temperature-sensitive emulsifier is used for preparing polymers by emulsion polymerization. It acts as an emulsifier at relatively high temperatures (40-75°C) and can break the emulsion at relatively low temperatures (5-30°C).

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] 1. The thermosensitive emulsifier prepared by the present invention is a temperature-responsive surfactant that can be used as an emulsifier for emulsion polymerization. Under relatively high temperature conditions (40-50°C), it can form stable latex particles in an aqueous solvent as an emulsifier, and can demulsify under relatively low temperature conditions (5-30°C).

[0021] 2. The preparation method of the temperature-sensitive emulsifier of the present invention has the advantages of simple synthesis route, simple operation, low material cost, no need for complex equipment, environmentally friendly solvents, and convenience for industrial scale-up production.

[0022] 3. The temperature-sensitive emulsifier of the present invention has the advantages of temperature-controlled emulsification and demulsification and recyclable use in the application of emulsion polymerization self-demulsification. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a synthetic scheme for temperature-sensitive emulsifiers.

[0024] Figure 2 This is the hydrogen nuclear magnetic resonance spectrum of the temperature-sensitive emulsifier obtained in Example 1.

[0025] Figure 3 The surface tension diagram of the thermosensitive emulsifier obtained in Example 1 at different concentrations at 50 °C shows that the critical micelle concentration of the thermosensitive emulsifier is 3.95×10 -6 mol / L.

[0026] Figure 4 This figure compares the emulsions formed by emulsion polymerization using the temperature-sensitive emulsifier obtained in Example 1 (left) and the common emulsifier sodium lauryl sulfate (right), both centrifuged at room temperature without the addition of a demulsifier. This demonstrates that the temperature-sensitive emulsifier synthesized in this invention can achieve temperature-controlled demulsification without the addition of a demulsifier. DETAILED DESCRIPTION

[0027] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0028] Example 1

[0029] (1) Weigh 10.0 g of polyethylene glycol monomethyl ether (Macklin, average molecular weight 2000, 0.005 mol) and dissolve it in 120 g (1.0 mol) of chloroform. Heat it to 40 °C to dissolve it completely. Add 1.0 g of triethylamine (0.01 mol) and then place the flask in a cold trap for ice bath treatment. Weigh 2.0 g (0.0087 mol) of 2-bromoisobutyryl bromide and dissolve it in 30 g (0.25 mol) of chloroform. Add the solution dropwise to the flask under nitrogen protection. After the addition is complete, wait for 10 minutes and then place the flask at room temperature to react for 12 hours. After the reaction is completed, distill the solvent using a rotary evaporator. The remaining product is purified by reprecipitation with ether and dried to obtain polyethylene glycol monomethyl ether 2-bromoisobutyl ester.

[0030] (2) Weigh 17.0 g (0.15 mol) of N-isopropylacrylamide and 11.0 g (0.005 mol) of polyethylene glycol monomethyl ether 2-bromoisobutyl ester obtained in step (1) and dissolve them in 80 mL of a mixed solvent of deionized water and dimethylformamide (volume ratio of deionized water: dimethylformamide = 3:1). Weigh 0.86 g (0.006 mol) of cuprous bromide and 1.73 g (0.01 mol) of pentamethyldiethylenetriamine and dissolve them in 20 mL of a mixed solvent of deionized water and dimethylformamide (volume ratio of deionized water: dimethylformamide = 3:1). Under nitrogen protection, the latter mixed solution is added to the former, and the mixture is reacted at 35 °C for 12 h. After the reaction is terminated, the reaction solution is dialyzed with distilled water using a dialysis bag with a molecular weight cutoff of 2500 for 72 h, and then dehydrated using a freeze dryer to obtain the product temperature-sensitive emulsifier.

[0031] Example 2

[0032] (1) Weigh 7.5 g of polyethylene glycol monomethyl ether (Macklin, average molecular weight of 1500, 0.005 mol) and dissolve it in 120 g (1.0 mol) of chloroform. Heat it to 40 °C to dissolve it completely. Add 1.0 g of triethylamine (0.01 mol) and then place the flask in a cold trap for ice bath treatment. Weigh 2.0 g (0.0087 mol) of 2-bromoisobutyryl bromide and dissolve it in 30 g (0.25 mol) of chloroform. Add the solution dropwise to the flask under nitrogen protection. After the addition is complete, wait for 10 minutes and then place the flask at room temperature to react for 12 hours. After the reaction is completed, distill the solvent using a rotary evaporator. The remaining product is purified by reprecipitation with ether and dried to obtain polyethylene glycol monomethyl ether 2-bromoisobutyl ester.

[0033] (2) Weigh 17.0 g (0.15 mol) of N-isopropylacrylamide and 8.5 g (0.005 mol) of polyethylene glycol monomethyl ether 2-bromoisobutyl ester obtained in step (1) and dissolve them in 80 mL of a mixed solvent of deionized water and dimethylformamide (volume ratio of deionized water: dimethylformamide = 3:1). Weigh 0.86 g (0.006 mol) of cuprous bromide and 1.73 g (0.01 mol) of pentamethyldiethylenetriamine and dissolve them in 20 mL of a mixed solvent of deionized water and dimethylformamide (volume ratio of deionized water: dimethylformamide = 3:1). Under nitrogen protection, the latter mixed solution is added to the former, and the reaction is carried out at 35 °C for 12 h. After the reaction is terminated, the reaction solution is dialyzed with distilled water using a dialysis bag with a specific molecular weight cutoff for 72 h, and then dehydrated using a freeze dryer to obtain the product temperature-sensitive emulsifier.

[0034] Example 3

[0035] (1) Weigh 5.0 g of polyethylene glycol monomethyl ether (Macklin, average molecular weight of 1000, 0.005 mol) and dissolve it in 120 g (1.0 mol) of chloroform. Heat it to 40 °C to dissolve it completely. Add 1.0 g of triethylamine (0.01 mol) and then place the flask in a cold trap for ice bath treatment. Weigh 2.0 g (0.0087 mol) of 2-bromoisobutyryl bromide and dissolve it in 30 g (0.25 mol) of chloroform. Add the solution dropwise to the flask under nitrogen protection. After the addition is complete, wait for 10 minutes and then place the flask at room temperature to react for 12 hours. After the reaction is completed, distill the solvent using a rotary evaporator. The remaining product is purified by reprecipitation with ether and dried to obtain polyethylene glycol monomethyl ether 2-bromoisobutyl ester.

[0036] (2) Weigh 17.0 g (0.15 mol) of N-isopropylacrylamide and 6.0 g (0.005 mol) of polyethylene glycol monomethyl ether 2-bromoisobutyl ester obtained in step (1) and dissolve them in 80 mL of a mixed solvent of deionized water and dimethylformamide (volume ratio of deionized water: dimethylformamide = 3:1). Weigh 0.86 g (0.006 mol) of cuprous bromide and 1.73 g (0.0075 mol) of tris[2-(dimethylamino)ethyl]amine and dissolve them in 20 mL of a mixed solvent of deionized water and dimethylformamide (volume ratio of deionized water: dimethylformamide = 3:1). Under nitrogen protection, the latter mixed solution is added to the former, and the reaction is carried out at 35 °C for 12 h. After the reaction is terminated, the reaction solution is dialyzed with distilled water using a dialysis bag with a specific molecular weight cutoff for 72 h, and then dehydrated using a freeze dryer to obtain the product temperature-sensitive emulsifier.

[0037] Application Example 1

[0038] 0.2 g (0.00012 mol) of the temperature-sensitive emulsifier prepared in Example 1 of the present invention and 20 mL (0.18 mol) of styrene monomer from which the polymerization inhibitor was removed were weighed and added to 80 mL of deionized water. 0.5 g (0.0018 mol) of potassium persulfate as an initiator was weighed and added to 20 mL of deionized water with stirring. After the initiator was completely dissolved, the mixture was poured into the aforementioned solution. Under nitrogen protection, the reaction was carried out at 70°C for 6 h. After the reaction was terminated, the emulsion was cooled to room temperature and the emulsion was repeatedly centrifuged (9000 rpm, 10 min) until the supernatant was clear. The supernatant was poured out and dried at 60°C to obtain the product polystyrene.

[0039] Application Example 2

[0040] 0.2 g (0.00012 mol) of the temperature-sensitive emulsifier prepared in Example 1 of the present invention and 20 mL (0.19 mol) of methyl methacrylate monomer from which the polymerization inhibitor was removed were weighed and added to 80 mL of deionized water. 0.5 g (0.0018 mol) of potassium persulfate as an initiator was weighed and added to 20 mL of deionized water with stirring. After the initiator was completely dissolved, the mixture was poured into the aforementioned solution and reacted at 70°C for 6 h under nitrogen protection. After the reaction was terminated, the emulsion was cooled to room temperature and repeatedly centrifuged (9000 rpm, 10 min) until the supernatant was clear. The supernatant was poured out and dried at 60°C to obtain the product, polymethyl methacrylate.

[0041] Comparative Example 1

[0042] 0.20 g (0.0007 mol) of sodium dodecyl sulfate (SDS) as an emulsifier and 20 mL (0.18 mol) of styrene monomer (excluding the polymerization inhibitor) were weighed and added to 80 mL of deionized water. 0.5 g (0.0018 mol) of potassium persulfate as an initiator was weighed and added to 20 mL of deionized water with stirring. After it was completely dissolved, the mixture was poured into the above solution and reacted at 70°C for 6 h under nitrogen protection. After the reaction was terminated, sodium chloride was added to break the emulsion, and the mixture was repeatedly washed with anhydrous ethanol and centrifuged (9000 rpm, 10 min) until the supernatant was clear. The supernatant was poured out and dried at 60°C to obtain the product polystyrene.

[0043] Comparative Example 2

[0044] 0.20 g (0.0007 mol) of sodium dodecyl sulfate (SDS) as an emulsifier and 20 mL (0.19 mol) of methyl methacrylate monomer (excluding the polymerization inhibitor) were weighed and added to 80 mL of deionized water. 0.5 g (0.0018 mol) of potassium persulfate as an initiator was weighed and added to 20 mL of deionized water with stirring. After it was completely dissolved, it was poured into the above solution and reacted at 70°C for 6 h under nitrogen protection. After the reaction was terminated, sodium chloride was added to break the emulsion, and the mixture was repeatedly washed with anhydrous ethanol and centrifuged (9000 rpm, 10 min) until the supernatant was clear. The supernatant was poured out and dried at 60°C to obtain the product polymethyl methacrylate.

[0045] As can be seen from Application Example 1 and Comparative Example 1, and Application Example 2 and Comparative Example 2, Comparative Examples 1 and 2 require the addition of sodium chloride and anhydrous ethanol for demulsification, which adds additional reagents and processes and requires a large amount of cleaning, which is time-consuming and labor-intensive. The temperature-sensitive emulsifier prepared by the present invention can achieve temperature-controlled emulsion polymerization self-demulsification, significantly reducing the number of operating steps and raw material consumption.

[0046] Characterization and testing:

[0047] In order to characterize the performance of the thermosensitive emulsifier of the present invention, the surface tension of the thermosensitive emulsifier synthesized in Example 1 was tested at different concentrations. The results are as follows: Figure 2 As shown. It can be concluded that the critical micelle concentration of the thermosensitive emulsifier is 3.95×10 -6 mol / L.

[0048] In order to characterize the self-demulsification performance of the thermosensitive emulsifier of the present invention, the emulsion formed by the emulsion polymerization of the thermosensitive emulsifier synthesized in Example 1 was centrifuged without adding a demulsifier. At the same time, the emulsion formed by the emulsion polymerization of the common emulsifier sodium lauryl sulfate was centrifuged under the same conditions. The results are shown in FIG. Figure 4 It can be seen that the temperature-sensitive emulsifier synthesized in the present invention can achieve temperature-controlled demulsification without adding a demulsifier.

[0049] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the same. Although the present invention has been described in detail with reference to the above embodiments, a person skilled in the art may still modify or make equivalent substitutions for the specific implementation schemes of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention are within the scope of protection of the claims of the present invention.

Claims

1. A temperature-sensitive emulsifier, characterized in that: The structure is as follows: Here, n is an integer from 10 to 100, and m is an integer from 10 to 150.

2. The method for preparing the temperature-sensitive emulsifier according to claim 1, wherein: The following steps are involved: (1) Add a certain amount of polyethylene glycol monomethyl ether to a flask and dissolve it in chloroform at a molar ratio of 200 times, heat it to 40-50°C to completely dissolve it, then add a certain amount of triethylamine, and then place the flask in a cold trap for ice bath treatment; weigh 2-bromoisobutyryl bromide and dissolve it in chloroform at a molar ratio of 30 times, and add it dropwise to the above flask under nitrogen protection. After 10 minutes of addition, place the flask at room temperature to react for 12 hours; after the reaction is completed, use a rotary evaporator to distill the solvent, and the remaining product is purified by reprecipitation with ether, and dried to obtain polyethylene glycol monomethyl ether 2-bromoisobutyl ester; (2) Weigh a certain amount of N-isopropylacrylamide and polyethylene glycol monomethyl ether 2-bromoisobutyl ester and dissolve them in a mixed solvent. Under nitrogen protection, add a solution of cuprous bromide and pentamethyldiethylenetriamine dissolved in a small amount of the mixed solvent and react at 35 °C for 12-24 h. After the reaction is terminated, dialyze the reaction solution with distilled water using a dialysis bag with a specific molecular weight cutoff for 72-96 h, and then remove water using a freeze dryer to obtain the product temperature-sensitive emulsifier.

3. The method for preparing a temperature-sensitive emulsifier according to claim 2, wherein: The degree of polymerization of polyethylene glycol monomethyl ether used in step (1) is 10-100.

4. The method for preparing a temperature-sensitive emulsifier according to claim 2, wherein: The molar ratio of polyethylene glycol monomethyl ether, triethylamine and 2-bromoisobutyryl bromide used in step (1) is 1:2~3:1~5.

5. The method for preparing a temperature-sensitive emulsifier according to claim 2, wherein: The mixed solvent described in step (2) is a mixed solvent of deionized water and dimethylformamide, and the volume ratio of deionized water to dimethylformamide is 3:

1.

6. The method for preparing a temperature-sensitive emulsifier according to claim 2, wherein: The molar ratio of polyethylene glycol monomethyl ether 2-bromoisobutyl ester, N-isopropylacrylamide, cuprous bromide and pentamethyldiethylenetriamine used in step (2) is 1:10-150:1.2-1.5:3-5.

7. The use of a temperature-sensitive emulsifier according to claim 1, characterized in that: The temperature-sensitive emulsifier is used for preparing high polymers by emulsion polymerization, acts as an emulsifier at 40-75°C, and can break the emulsion at 5-30°C.

Images