Porous polymer microsphere as well as preparation method and application thereof

Abstract

The invention provides a porous polymer microsphere as well as a preparation method and application thereof. The particle size of the porous polymer microsphere is 0.5-5 mm, the porous polymer microsphere has rich pore structures on the surface and inside, has a temperature-sensitive characteristic, is subjected to wettability conversion from hydrophilic to hydrophobic at about 43 DEG C, is easy to desorb and regenerate after adsorption, has good oil removal performance and good cycle stability, and can be repeatedly used as a filter material.

Description

Technical Field

[0001] This invention belongs to the technical field, and particularly relates to a porous polymer microsphere, its preparation method, and its application. Background Technology

[0002] In recent years, smart materials have gradually emerged as a new type of functional polymer material, capable of responding to changes in the external environment (pH, temperature, electric field, magnetic field, light, etc.). Poly(N-isopropylacrylamide) (PNIPAM) is a temperature-sensitive polymer with a very high temperature responsiveness. The synthesis of temperature-sensitive polymers can be achieved through bulk polymerization, solution polymerization, suspension polymerization, and emulsion polymerization. Generally, solution polymerization is convenient and easy to perform, often employing free radical initiation in organic solvents and redox initiation in aqueous media. Other common methods include ultrasonic polymerization and microwave radiation.

[0003] However, the spherical polymer materials obtained by conventional emulsion polymerization methods have small particle sizes that are difficult to control, leading to problems such as high filtration resistance and filter material loss when used as filter media. Therefore, there is a need to develop a spherical polymer material with a simple preparation method, uniform particle size, interconnected macroporous structure, low filtration resistance and loss, and reusability. Summary of the Invention

[0004] One aspect of the present invention provides a method for preparing porous polymer microspheres, comprising the following steps:

[0005] 1) The temperature-sensitive monomer, hydrophilic monomer, crosslinking agent, emulsifier, first initiator and first solvent are mixed to obtain the oil phase;

[0006] 2) Mix the dispersant, the second initiator, and the second solvent to obtain the dispersed phase;

[0007] 3) Mix the aqueous phase and the oil phase to prepare a water-in-oil emulsion;

[0008] 4) Add the water-in-oil emulsion to the dispersed phase and react to obtain porous polymer microspheres.

[0009] The water-in-oil emulsion described in this invention consists of water and oil from the inside out.

[0010] According to a specific embodiment of the present invention, in step 1), the oil phase further includes hydrophobic monomers and / or reinforcing agents.

[0011] According to a specific embodiment of the present invention, the temperature-sensitive monomer is N-isopropylacrylamide; and / or

[0012] The hydrophilic monomer is selected from at least one of 2-hydroxyethyl methacrylate, hydroxypropyl methacrylate, tert-butyl methacrylate, and tert-butyl acrylate; and / or

[0013] The crosslinking agent is trimethylolpropane triacrylate; and / or

[0014] The emulsifier is emulsifier P123 or emulsifier 5800; and / or

[0015] The first initiator is an oil-soluble initiator; and / or the second initiator is a water-soluble initiator; and / or

[0016] The aqueous phase includes water; and / or

[0017] The dispersant is polyvinyl alcohol; and / or

[0018] The first solvent is toluene; and / or the second solvent is water;

[0019] Preferably, the hydrophilic monomer is selected from at least one of 2-hydroxyethyl methacrylate, hydroxypropyl methacrylate, and tert-butyl acrylate; and / or

[0020] The emulsifier is emulsifier P123; and / or

[0021] The first initiator is benzoyl peroxide and / or dodecyl peroxide; and / or the second initiator is ammonium persulfate and / or potassium persulfate.

[0022] According to a specific embodiment of the present invention, the hydrophobic monomer is selected from at least one of isobornyl methacrylate, methyl methacrylate, glycidyl methacrylate, and tetradecanoylphoryl acetate; and / or

[0023] The reinforcing agent is 3-(isobutenoyloxy)propyltrimethylsilane;

[0024] Preferably, the hydrophobic monomer is selected from at least one of isobornyl methacrylate, methyl methacrylate, and glycidyl methacrylate.

[0025] According to a specific embodiment of the present invention, the total mass of the thermosensitive monomer, hydrophilic monomer, and crosslinking agent is 100%, the amount of the thermosensitive monomer is 34 wt% to 44.5 wt%, the amount of the hydrophilic monomer is 3 wt% to 12.5 wt%, and the amount of the crosslinking agent is 50 wt% to 55 wt%; and / or

[0026] The total mass of the thermosensitive monomer, hydrophilic monomer, and crosslinking agent is 100%, the amount of the emulsifier is 1.8 wt% to 4.2 wt%; and / or the amount of the first initiator is 8.8 wt% to 9.7 wt%; and / or

[0027] The amount of the first solvent is 2 to 4 times the total mass of the temperature-sensitive monomer, hydrophilic monomer, and crosslinking agent; and / or

[0028] The dispersed phase, by mass 100%, comprises 1 wt% dispersant, 0.07 wt% second initiator, and the balance being a second solvent; and / or

[0029] The mass ratio of the first solvent to water in the aqueous phase is 1:(1.6 to 3.7); and / or

[0030] The mass ratio of the water-in-oil emulsion to the dispersed phase is 1:(7.6 to 8.6).

[0031] According to a specific embodiment of the present invention, the total mass of the thermosensitive monomer, the hydrophilic monomer and the crosslinking agent is 100%, the amount of the hydrophobic monomer is 0 to 21.2 wt%, and the amount of the reinforcing agent is 0 to 25 wt%.

[0032] It should be noted that the amounts of the hydrophobic monomer and the reinforcing agent are not both 0.

[0033] According to a specific embodiment of the present invention, in step 2), the dispersant, the second initiator, and the second solvent are mixed and deoxygenated to obtain the dispersed phase; and / or

[0034] In step 3), after adding the aqueous phase to the oil phase, a first reducing agent is added to prepare the water-in-oil emulsion; and / or

[0035] In step 4), the water-in-oil emulsion is added to the dispersed phase, a second reducing agent is added, and the reaction is then carried out. According to a specific embodiment of the present invention, the first reducing agent and the second reducing agent are independently N,N,N,N-tetramethylethylenediamine and / or N,N-dimethylaniline;

[0036] Preferably, the total mass of the temperature-sensitive monomer, hydrophilic monomer, and crosslinking agent is 100%, the amount of the first reducing agent is 1.8 wt% to 5.8 wt%, and / or the amount of the second reducing agent is 17.6 wt% to 19.4 wt%.

[0037] According to a specific embodiment of the present invention, step 3) is carried out entirely under ice bath conditions;

[0038] Preferably, in step 3), the aqueous phase is added to the oil phase under a stirring condition that gradually increases the speed from 3000 r / min to 9000 r / min; and / or

[0039] In step 4), the reaction is continuously stirred at a speed of 180 r / min to 280 r / min (e.g., 260 r / min); and / or

[0040] In step 4), the reaction product obtained from the reaction is filtered, washed, and dried to obtain the porous polymer microspheres;

[0041] More preferably, in step 3), the stirring conditions are: stirring at 3000 r / min for 1 to 3 minutes, increasing the speed to 5000 to 7000 r / min (e.g., 6000 r / min) for 2 to 4 minutes, and then increasing the speed to 9000 r / min for 4 to 6 minutes; and / or

[0042] In step 4), the filter residue obtained after filtration is washed with methanol; and / or

[0043] The drying conditions are as follows: drying at 60°C for 4 to 24 hours.

[0044] In one specific embodiment of the present invention, the reaction is a gradient temperature increase reaction;

[0045] Preferably, the temperature of the reaction is gradually increased from 65°C to 130°C; and / or the total duration of the reaction is 50 to 60 minutes.

[0046] More preferably, the reaction conditions are as follows: first, react at 65°C for 10 to 15 minutes, then raise the temperature to 80°C and react for 15 to 20 minutes, and then raise the temperature to 130°C and react for 20 to 30 minutes.

[0047] The second invention provides a porous polymer microsphere prepared by the method described in the first invention.

[0048] According to one specific embodiment of the present invention, the porous polymer microspheres have a particle size of 0.5 mm to 5 mm; and / or

[0049] The porous polymer microspheres have a porosity of 20% to 23%; and / or

[0050] The porous polymer microspheres have a surface pore size of 0.5 μm to 4 μm; and / or an internal pore size of 0.2 μm to 3.8 μm;

[0051] And / or the internal average pore size is 1.5 μm to 1.6 μm.

[0052] The porous polymer microspheres prepared by the method according to one of the present inventions or the porous polymer microspheres according to another of the present inventions are used in oil-water separation, especially as adsorption and filtration materials for emulsified oily wastewater.

[0053] The beneficial effects of this invention are:

[0054] To address the problems of high filtration resistance and filter media loss caused by the small and difficult-to-control particle size of conventionally prepared temperature-sensitive polymer filter media, this invention provides porous polymer microspheres, their preparation method, and applications. The method provided by this invention can control the particle size of the obtained porous polymer microspheres to be between 0.5 and 5 mm, maintaining good filtration performance, low filtration resistance, minimal filter media loss during filtration, and no impact on water quality. The porous polymer microspheres prepared by this invention have well-developed pore structures on both the surface and interior. The surface pore size is 0.5 to 4 μm, and the interior pore size is mainly distributed between 0.2 and 3.8 μm, allowing emulsified oil droplets to enter the interior of the porous polymer microspheres, improving adsorption efficiency. The porous polymer microspheres exhibit temperature-sensitive properties. When the ambient temperature is >43℃ (e.g., 43℃ ± 1℃), the wettability of the porous polymer microspheres changes from hydrophilic to hydrophobic, which is beneficial for oil droplet adsorption. When the ambient temperature is <43℃ (e.g., 43℃ ± 1℃), the wettability of the porous polymer microspheres decreases. The hydrophobic-to-hydrophilic transition of the porous polymer microspheres facilitates the desorption and regeneration of adsorbed oil droplets. The hydrophobic-hydrophilic transition exhibits good cyclic stability; in buoyancy tests conducted at 50°C for 1 to 5 cycles, the changes in the buoyancy rates of the 2nd, 3rd, 4th, and 5th cycles compared to the 1st cycle are all within 7%. The porous polymer microspheres also demonstrate good oil removal performance and cyclic stability: at 50°C, for emulsified wastewater with an initial oil content of 154 to 181 mg / L, the porous polymer microspheres achieve an equilibrium oil removal rate of over 70% after adsorption saturation. After desorption and regeneration in water at 20°C, the changes in the equilibrium oil removal rate of the porous polymer microspheres in the second, third, fourth, and fifth cycles compared to the first cycle are all within 6.5%. In summary, the porous polymer microspheres provided by this invention can effectively adsorb oil in oily emulsified wastewater as a filter medium, and can still maintain good oil removal performance after desorption and regeneration. They can be reused in oil removal operations, reducing filter medium wear. Attached Figure Description

[0055] Figure 1 DSC curves of porous polymer microspheres prepared in Example 2;

[0056] Figure 2 DSC curves of porous polymer microspheres prepared in Example 3;

[0057] Figure 3 DSC curves of porous polymer microspheres prepared in Example 4;

[0058] Figure 4A photograph of the porous polymer microspheres prepared in Example 3;

[0059] Figure 5 A photograph of the porous polymer microspheres prepared in Example 5;

[0060] Figure 6 A photograph of the porous polymer microspheres prepared in Example 6;

[0061] Figure 7 Scanning electron microscope image of the porous polymer microspheres prepared in Example 2;

[0062] Figure 8 Image of the pore structure on the surface of the porous polymer microspheres prepared in Example 2;

[0063] Figure 9 Image of the internal pore structure of the porous polymer microspheres prepared in Example 2. Detailed Implementation

[0064] The present invention will be further described below with reference to the embodiments. However, the embodiments of the present invention are merely illustrative examples and should not be construed as limiting the present invention under any circumstances.

[0065] Example 1

[0066] 1) Oil phase: Take 0.65g N-isopropylacrylamide, 0.15g tert-butyl acrylate, 0.15g methyl methacrylate, 0.1g glycidyl methacrylate, 0.1g isobornyl methacrylate, 0.85g trimethylolpropane triacrylate, 0.03g emulsifier P123 and 0.15g benzoyl peroxide and sonicate them in 7ml (6g) toluene to obtain the oil phase;

[0067] 2) Dispersed phase: Take 1.4g polyvinyl alcohol, 0.1g ammonium persulfate and 140ml deionized water, mix them evenly, put them into a 250ml three-necked flask with a stirrer, and purge with nitrogen for 10min while stirring to obtain the dispersed phase;

[0068] 3) Preparation of water-in-oil emulsion: Take 10 ml of deionized water as the aqueous phase; under ice bath conditions, the oil phase is stirred at a gradient speed: 3000 r / min for 1 min, 6000 r / min for 4 min, and 9000 r / min for 6 min. During this gradient stirring process, the aqueous phase is added dropwise to the oil phase, and then 0.03 g of N,N-dimethylaniline is added and stirred to obtain the water-in-oil emulsion.

[0069] 4) Preparation of porous polymer microspheres: The water-in-oil emulsion was added to the dispersed phase and stirred at 260 r / min to uniformly disperse the water-in-oil emulsion in the dispersed phase in a spherical shape. After the dispersion was stable, 0.3 g of N,N,N',N'-tetramethylethylenediamine was added to obtain a water-in-oil emulsion. The reaction was carried out in a gradient temperature manner: 65 °C for 10 min, 80 °C for 15 min, and then 130 °C for 30 min. The reaction product was filtered, and the solid product was collected, washed in methanol, filtered again, and dried in a 60 °C oven for 24 h to obtain porous polymer microspheres with a particle size of 0.5 to 2.0 mm.

[0070] Example 2

[0071] 1) Oil phase: 0.65g N-isopropylacrylamide, 0.05g tert-butyl acrylate, 0.1g methyl methacrylate, 0.15g 3-(isobutyrooxy)propyltrimethylsilane, 0.1g glycidyl methacrylate, 0.1g isobornyl methacrylate, 0.85g trimethylolpropane triacrylate, 0.03g emulsifier P123 and 0.15g benzoyl peroxide were ultrasonically dissolved in 7ml (6g) toluene to obtain the oil phase;

[0072] 2) Dispersed phase: Take 1.4g polyvinyl alcohol, 0.1g ammonium persulfate and 140ml deionized water, mix them evenly, put them into a 250ml three-necked flask with a stirrer, and purge with nitrogen for 10min while stirring to obtain the dispersed phase;

[0073] 3) Preparation of water-in-oil emulsion: Take 10 ml of deionized water as the aqueous phase; under ice bath conditions, the oil phase is stirred at a gradient speed: 3000 r / min for 3 min, 6000 r / min for 2 min, and 9000 r / min for 4 min. During this gradient stirring process, the aqueous phase is added dropwise to the oil phase, and then 0.09 g of N,N-dimethylaniline is added and stirred to obtain the water-in-oil emulsion.

[0074] 4) Preparation of porous polymer microspheres: The water-in-oil emulsion was poured into the dispersed phase and stirred at 260 r / min to uniformly disperse the water-in-oil emulsion in the dispersed phase in a spherical form. After the dispersion stabilized, 0.3 g of N,N,N',N'-tetramethylethylenediamine was added. The reaction was carried out in a gradient temperature manner: 65 °C for 10 min, 80 °C for 20 min, and then 130 °C for 20 min. The reaction product was filtered, and the solid product was collected, washed in methanol, filtered again, and dried in a 60 °C oven for 24 h to obtain porous polymer microspheres with a particle size of 0.5 to 2.0 mm.

[0075] Example 3

[0076] 1) Oil phase: 0.75g N-isopropylacrylamide, 0.15g isobornyl methacrylate, 0.15g glycidyl methacrylate, 0.07g hydroxypropyl methacrylate, 0.03g tert-butyl acrylate, 0.85g trimethylolpropane triacrylate, 0.07g P123 and 0.15g benzoyl peroxide were ultrasonically dissolved in 7ml (6g) toluene to obtain the oil phase;

[0077] 2) Dispersed phase: Take 1.4g polyvinyl alcohol, 0.1g ammonium persulfate and 140ml deionized water, mix them evenly, put them into a 250ml three-necked flask with a stirrer, and purge with nitrogen for 10min while stirring to obtain the dispersed phase;

[0078] 3) Preparation of water-in-oil emulsion: Take 10 ml of deionized water as the aqueous phase; under ice bath conditions, perform gradient stirring on the oil phase: stir at 3000 r / min for 2 min, stir at 6000 r / min for 3 min, and stir at 9000 r / min for 6 min. During this gradient stirring process, add the aqueous phase dropwise to the oil phase, and then add 0.09 g of N,N-dimethylaniline and stir to obtain the water-in-oil emulsion.

[0079] 4) Preparation of porous polymer microspheres: The water-in-oil emulsion was poured into the dispersed phase and stirred at 260 r / min to uniformly disperse the water-in-oil emulsion in the dispersed phase in a spherical form. After the dispersion was stable, 0.3 g of N,N,N',N'-tetramethylethylenediamine was added. The reaction was carried out at 65℃ for 15 min, then at 80℃ for 15 min, and then at 130℃ for 30 min in a gradient temperature increase reaction. The reaction product was filtered, and the solid product was collected, washed and filtered in methanol, and dried in a 60℃ oven for 24 h to obtain porous polymer microspheres with a particle size of 0.5 to 2.0 mm.

[0080] Example 4

[0081] 1) Oil phase: 0.55g N-isopropylacrylamide, 0.40g 3-(isobutyrooxy)propyltrimethylsilane (KH570), 0.2g 2-hydroxyethyl methacrylate (HEMA), 0.85g trimethylolpropane triacrylate (TMPTA), 0.03g P123 and 0.15g benzoyl peroxide were ultrasonically dissolved in 7ml (6g) toluene to obtain the oil phase;

[0082] 2) Dispersed phase: Take 1.4g polyvinyl alcohol, 0.1g ammonium persulfate and 140ml deionized water, mix them evenly, put them into a 250ml three-necked flask with a stirrer, and purge with nitrogen for 10min while stirring to obtain the dispersed phase;

[0083] 3) Preparation of water-in-oil emulsion: Take 10 ml of deionized water as the aqueous phase; under ice bath conditions, perform gradient stirring on the oil phase: stir at 3000 r / min for 1 min, stir at 6000 r / min for 3 min, and stir at 9000 r / min for 5 min. During this gradient stirring process, add the aqueous phase dropwise to the oil phase, and then add 0.09 g of N,N-dimethylaniline and stir to obtain the water-in-oil emulsion.

[0084] 4) Preparation of porous polymer microspheres: The water-in-oil emulsion was poured into the dispersed phase and stirred at 260 r / min to uniformly disperse the water-in-oil emulsion in the dispersed phase in a spherical form. After the dispersion was stable, 0.3 g of N,N,N',N'-tetramethylethylenediamine was added. The reaction was carried out at 65 °C for 15 min, then at 80 °C for 20 min, and then at 130 °C for 20 min in a gradient temperature increase reaction. The reaction product was filtered, and the solid product was collected, washed and filtered in methanol, and dried in a 60 °C oven for 24 h to obtain porous polymer microspheres with a particle size of 0.5 to 2.0 mm.

[0085] Example 5

[0086] 1) Oil phase: 0.75g N-isopropylacrylamide, 0.15g isobornyl methacrylate, 0.15g glycidyl methacrylate, 0.07g hydroxypropyl methacrylate, 0.03g tert-butyl acrylate, 0.85g trimethylolpropane triacrylate, 0.07g P123 and 0.15g benzoyl peroxide were ultrasonically dissolved in 4ml (3.5g) toluene to obtain the oil phase;

[0087] 2) Dispersed phase: Take 1.4g polyvinyl alcohol, 0.1g ammonium persulfate and 140ml deionized water, mix them evenly, put them into a 250ml three-necked flask with a stirrer, and purge with nitrogen for 10min while stirring to obtain the dispersed phase;

[0088] 3) Preparation of water-in-oil emulsion: Take 13 ml of deionized water as the aqueous phase; under ice bath conditions, the oil phase is stirred at a gradient speed: 3000 r / min for 3 min, 6000 r / min for 3 min, and 9000 r / min for 5 min. During this gradient stirring process, the aqueous phase is added dropwise to the oil phase, and then 0.09 g of N,N-dimethylaniline is added and stirred to obtain the water-in-oil emulsion.

[0089] 4) Preparation of porous polymer microspheres: The water-in-oil emulsion was poured into the dispersed phase and stirred at 260 r / min to uniformly disperse the water-in-oil emulsion in the dispersed phase in spherical form. After the dispersion was stable, 0.3 g of N,N,N',N'-tetramethylethylenediamine was added. The reaction was carried out in a gradient temperature manner: 65 °C for 13 min, 80 °C for 17 min, and then 130 °C for 28 min. The reaction product was filtered, and the solid product was collected, washed and filtered in methanol, and dried in a 60 °C oven for 24 h to obtain porous polymer microspheres with a particle size of 0.5 to 5 mm.

[0090] Example 6

[0091] 1) Oil phase: 0.75g N-isopropylacrylamide, 0.15g isobornyl methacrylate, 0.15g glycidyl methacrylate, 0.07g hydroxypropyl methacrylate, 0.03g tert-butyl acrylate, 0.85g trimethylolpropane triacrylate, 0.07g P123 and 0.15g benzoyl peroxide were ultrasonically dissolved in 5ml (4.5g) toluene to obtain the oil phase;

[0092] 2) Dispersed phase: Take 1.4g polyvinyl alcohol, 0.1g ammonium persulfate and 140ml deionized water, mix them evenly, put them into a 250ml three-necked flask with a stirrer, and purge with nitrogen for 10min while stirring to obtain the dispersed phase;

[0093] 3) Preparation of water-in-oil emulsion: Take 10 ml of deionized water as the aqueous phase; under ice bath conditions, the oil phase is stirred at a gradient speed: 3000 r / min for 1 min, 6000 r / min for 3 min, and 9000 r / min for 4 min. During this gradient stirring process, the aqueous phase is added dropwise to the oil phase, and then 0.09 g of N,N-dimethylaniline is added and stirred to obtain the water-in-oil emulsion.

[0094] 4) Preparation of porous polymer microspheres: The water-in-oil emulsion was poured into the dispersed phase and stirred at 260 r / min to uniformly disperse the water-in-oil emulsion in the dispersed phase in spherical form. After the dispersion was stable, 0.3 g of N,N,N',N'-tetramethylethylenediamine was added. The reaction was carried out at 65℃ for 14 min, then at 80℃ for 19 min, and then at 130℃ for 25 min in a gradient temperature increase reaction. The reaction product was filtered, and the solid product was collected, washed and filtered in methanol, and dried in a 60℃ oven for 24 h to obtain porous polymer microspheres with a particle size of 0.5 to 3 mm.

[0095] Experimental Evaluation

[0096] 1. DSC analysis of porous polymer microspheres

[0097] B. DSC Analysis

[0098] The porous polymer microspheres prepared in Examples 1 to 6 were analyzed using a TADSC Q2000 differential scanning calorimeter (USA). Examples 2, 3, and 4 are analyzed in detail here.

[0099] Figure 1 The DSC curve of the porous polymer microspheres prepared in Example 2 shows that the endothermic peak of the material appears at 43℃, which indicates that the temperature-sensitive phase transition temperature of the material is around 43℃.

[0100] Figure 2 The DSC curve of the porous polymer microspheres prepared in Example 3 shows that the endothermic peak of the material appears at 42℃, which indicates that the temperature-sensitive phase transition temperature of the material is around 42℃.

[0101] Figure 3 The DSC curve of the porous polymer microspheres prepared in Example 4 shows that the endothermic peak of the material appears at 44℃, which indicates that the temperature-sensitive phase transition temperature of the material is around 44℃.

[0102] The porous polymer microspheres prepared in Examples 1, 5, and 6 were analyzed by DSC and found to have thermosensitive phase transition temperatures of 43°C, 42°C, and 44°C, respectively.

[0103] 2. Morphological observation of porous polymer microspheres

[0104] First, observe the morphology of the porous polymer microspheres prepared in Examples 1 to 6 with the naked eye, taking Examples 3, 5, and 6 as examples: Figure 4 This is a photograph of the porous polymer microspheres prepared in Example 3. Figure 5 This is a photograph of the porous polymer microspheres prepared in Example 5. Figure 6 This is a photograph of the porous polymer microspheres prepared in Example 6. The formulations for preparing porous polymer microspheres in Examples 3, 5, and 6 are basically the same, the difference being the amount of toluene in the oil phase and water in the aqueous phase. The ratio of oil to water phase affects the viscosity of the water-in-oil emulsion, and thus the morphology of the porous polymer microspheres. Figures 4 to 6 As can be seen, the porous polymer microspheres prepared in the three examples have certain differences in particle size and uniformity.

[0105] The morphology, surface pore structure, and internal pore structure of the porous polymer microspheres prepared in Examples 1 to 6 were further observed using scanning electron microscopy. For observing the internal pore structure, the porous polymer microspheres were cut open from the middle and sputter-coated with gold before being observed under a scanning electron microscope. The porous polymer microspheres prepared in Example 2 are used as an example for detailed explanation here.

[0106] Figure 7The morphology of the porous polymer microspheres prepared in Example 2 is shown under a scanning electron microscope at a magnification of 285x. It can be seen that the porous polymer microspheres prepared in Example 2 are relatively regular spheres with a particle size of 0.5 to 2 mm and numerous pores distributed on their surface.

[0107] Figure 8 The pore structure of the surface of the porous polymer microspheres prepared in Example 2 is shown at a magnification of 2000x. It can be observed that the surface pore size is approximately 0.5 to 3.8 μm.

[0108] Under scanning electron microscopy, the porous polymer microspheres prepared in Examples 1, 3 to 6 were observed to be spheres with many pores distributed on their relatively regular surfaces. The particle sizes of the porous polymer microspheres prepared in Examples 1, 3 to 6 were 0.5 to 2 mm, 0.5 to 2 mm, 0.5 to 2 mm, 0.5 to 5 mm, and 0.5 to 3 mm, respectively, and the surface pore sizes were basically in the range of 0.5 to 4 μm.

[0109] Figure 9 The image shows the internal pore structure of the porous polymer microspheres prepared in Example 2, observed under a scanning electron microscope at a magnification of 10,000. It can be seen that the internal pores are well-developed and interconnected.

[0110] Under a scanning electron microscope, the well-developed pore structure inside the porous polymer microspheres prepared in Examples 1, 3 to 6 can also be observed, with the pores interconnected.

[0111] 3. Determination of internal pore size and porosity of porous polymer microspheres

[0112] The distribution of internal pore size and porosity of the porous polymer microspheres prepared in Examples 1 to 6 were determined using a quanta pore size analyzer. The distribution of internal pore size is shown in Table 1 and the porosity is shown in Table 2.

[0113] Table 1. Internal pore size distribution of porous polymer microspheres

[0114]

[0115] Table 2. Porosity of porous polymer microspheres

[0116] Example Porosity / % Example 1 21 Example 2 21 Example 3 20 Example 4 21 Example 5 23 Example 6 22

[0117] Table 1 shows the internal pore size distribution of the porous polymer microspheres prepared in Examples 1 to 6: the internal pore size of the porous polymer microspheres prepared in Examples 1 to 6 is mainly distributed between 1.1 and 2 μm. Specifically, the average internal pore size of the porous polymer microspheres prepared in Examples 1 and 3-6 is approximately 1.6 μm, and the average internal pore size of the porous polymer microspheres prepared in Example 2 is approximately 1.5 μm. Table 2 shows that the porosity of the porous polymer microspheres prepared in Examples 1-6 is 20%-23%.

[0118] Based on the above analysis of the morphology, internal pore size, and porosity of the porous polymer microspheres prepared in Examples 1 to 6, it can be concluded that the porous polymer microspheres prepared in Examples 1 to 6 have well-developed pore structures on both the surface and inside, which is beneficial for the emulsified oil droplet molecules to enter the interior of the porous polymer microspheres and improve the adsorption effect.

[0119] The hydrophilicity, hydrophobicity, thermosensitive properties, and cycle stability of porous polymer microspheres are evaluated below, including:

[0120] Sinking rate = (mass of porous polymer microspheres sinking to the bottom / initial mass of porous polymer microspheres) × 100%;

[0121] Buoyancy rate = (mass of porous polymer microspheres floating to the water surface / initial mass of porous polymer microspheres) × 100%;

[0122] The mass of the porous polymer microspheres that sank to the bottom of the water and the mass of the porous polymer microspheres that floated to the surface of the water are both after drying.

[0123] 4. Evaluation of the hydrophilicity, hydrophobicity, and thermosensitive properties of porous polymer microspheres

[0124] 1) Determination of sinking rate: 10g of porous polymer microspheres prepared in Example 1 were weighed and placed in 500mL of deionized water. The porous polymer microspheres were fully soaked by stirring at 20°C. After the porous polymer microspheres were almost no longer floating or sinking, the porous polymer microspheres floating on the water surface and those that sank to the bottom were collected respectively. After drying, they were weighed and the sinking rate was calculated to characterize the hydrophilicity of the porous polymer microspheres.

[0125] Following the same method, the settling rate of the porous polymer microspheres prepared in Examples 2 to 6 at 20°C was determined.

[0126] 2) Buoyancy determination: The porous polymer microspheres dried from the surface and bottom of the water in Experiment 1) were combined and placed in 500 mL of deionized water. The experiment was conducted in a water bath at 30 °C. The porous polymer microspheres were fully immersed by stirring. When the porous polymer microspheres were almost no longer floating or sinking, the porous polymer microspheres floating on the surface and sinking to the bottom were collected separately, dried, and weighed. The buoyancy at 30 °C was calculated. Then, in the same way, the buoyancy at 40 °C was determined by combining the dried porous polymer microspheres dried from the surface and bottom of the water after the buoyancy at 30 °C was determined. The buoyancy at 50 °C was determined by combining the dried porous polymer microspheres dried from the surface and bottom of the water after the buoyancy at 40 °C was determined. This was to characterize the hydrophobicity and temperature-sensitive properties of the porous polymer microspheres.

[0127] Following the above method, the buoyancy rates of the porous polymer microspheres prepared in Examples 2 to 6 at 30°C, 40°C, and 50°C were determined.

[0128] The sinking rate in Experiment 1) and the buoyancy rate at different temperatures in Experiment 2) are shown in Table 1.

[0129] Table 1. Sinking rate at 20℃ and buoyancy rate at 30 to 50℃

[0130]

[0131] As shown in Table 1, at 20℃, the sinking rate of the porous polymer microspheres prepared in Examples 1 to 6 can reach as high as 95%, proving that the porous polymer microspheres have good hydrophilicity. At 20℃, the water absorption density increases and they sink to the bottom. At 30℃ to 50℃, the buoyancy of the porous polymer microspheres prepared in Examples 1 to 6 is all greater than 0, indicating that the porous polymer microspheres undergo a hydrophilic-to-hydrophobic transition when the temperature increases. Furthermore, as the temperature increases from 30℃ to 50℃, the buoyancy of the porous polymer microspheres continuously increases, reaching a maximum of 88% at 50℃. This indicates that as the temperature increases, the hydrophilicity of the porous polymer microspheres weakens and the hydrophobicity increases, the probability of the transition from hydrophilic to hydrophobic increases, the water absorption decreases, the density decreases and they float, exhibiting excellent temperature-sensitive properties. This is beneficial for the porous polymer microspheres to absorb oil above the hydrophilic-to-hydrophobic transition temperature and to desorb oil below the hydrophilic-to-hydrophobic transition temperature, thus achieving regeneration.

[0132] 5. Evaluation of the cyclic stability of porous polymer microspheres

[0133] a. Weigh 10g of the porous polymer microspheres prepared in Example 1 and place them in 500mL of deionized water. In a water bath at 50°C, the porous polymer microspheres are fully soaked by stirring. When the porous polymer microspheres are almost no longer floating or sinking, collect the porous polymer microspheres floating on the water surface and those that have sunk to the bottom. After drying, weigh them and calculate the first buoyancy rate.

[0134] b. Then, the dried porous polymer microspheres on the water surface and at the bottom are combined and placed in 500 mL of deionized water. In a water bath at 50 °C, the porous polymer microspheres are fully immersed by stirring. After the porous polymer microspheres in the water have almost stopped floating or sinking, the porous polymer microspheres floating on the water surface and sinking at the bottom are collected separately, dried, weighed, and the second buoyancy rate is calculated.

[0135] c. Then, step b is performed three times in a row, and the buoyancy rate is measured for the third, fourth and fifth times. For example, the porous polymers on the water surface and bottom are combined after the second buoyancy rate is measured, and the buoyancy rate is measured for the third time. The porous polymer microspheres on the water surface and bottom are combined after the third buoyancy rate is measured, and the buoyancy rate is measured for the fourth time. The buoyancy rate is measured for the fifth time in the same way.

[0136] Following steps a to c, the cyclic stability of the porous polymer microspheres prepared in Examples 2 to 6 was evaluated, and the specific results are shown in Table 2.

[0137] Table 2. Rise Rate in the 5th Cycle

[0138]

[0139] As can be seen from Table 2, for the porous polymer microspheres prepared in any of Examples 1 to 6, the changes in the second, third, fourth, and fifth float rates compared to the first float rate are all within 7%, indicating that the hydrophilic-hydrophobic transition behavior of the porous polymer microspheres prepared in this invention has good cycle stability.

[0140] 6. Evaluation of the oil removal performance of porous polymer microspheres

[0141] (1) Preparation of emulsified wastewater and determination of oil content

[0142] ① Preparation of emulsified wastewater: First, mix polyacrylamide (molecular weight of 2 million to 10 million) and water to prepare a polyacrylamide aqueous solution with a concentration of 500 mg / L; then add 100 mg of paraffin oil, 25 mg of kaolin, and 10 mL of the 500 mg / L polyacrylamide aqueous solution to 500 mL of water, and stir at 10000 r / min until no oil droplets are observed. Then continue stirring for 3 hours to disperse the oil droplets evenly, and obtain emulsified wastewater with an oil content of approximately 200 mg / L (the accurate oil content needs to be determined by the method in step ②), a suspension concentration of 50 mg / L, and an oil droplet size of less than 5 μm.

[0143] ② Determination of oil content in emulsified wastewater by ultraviolet spectrophotometry: CCl4 solutions with concentrations of 5, 10, 20, 40, 60, 80, 120, 160, 200, and 240 mg / L were prepared using paraffin oil and CCl4, and ultraviolet absorption was measured to obtain a standard curve. When determining the oil content in emulsified wastewater, background measurement was first performed using CCl4, followed by ultraviolet absorption measurement of the emulsified wastewater. Combined with the standard curve, the accurate oil content of the emulsified wastewater, or what can be called the original oil content, was obtained.

[0144] (2) Degreasing test

[0145] 5g of porous polymer microspheres were packed into an adsorption column with a diameter of 2cm and a thermometer fixed in place. 100mL of the emulsified wastewater prepared in step (1) ① was added from the top of the adsorption column, ensuring that the liquid height was kept as consistent as possible each time and that the flow rate of the emulsified wastewater was 4mL / min. The emulsified wastewater flowing out from the bottom of the adsorption column was reinjected into the adsorption column for oil removal. The emulsified wastewater flowing out of the adsorption column was sampled periodically, and its oil content was determined by ultraviolet spectrophotometry according to the method provided in step (1) ②. The oil content was measured 50min after the start of the experiment. During the experiment, samples were taken every 10 minutes to measure the oil content. After 50 minutes, samples were taken every 20 minutes to measure the oil content until the measured oil content no longer changed significantly. At this point, the porous polymer microspheres in the adsorption column were considered to have reached adsorption saturation, and the oil content measured at this time was called the "equilibrium oil content" of the emulsified wastewater. Throughout the process, the emulsified wastewater was placed in an oil bath, and a heat tracing cable was wrapped around the adsorption column to maintain the required adsorption column temperature. After the porous polymer microspheres were saturated, they were removed from the adsorption column and placed in 100 ml of 20°C cold water for regeneration. Specifically, the water was changed after stirring for 15 minutes, and this process was repeated 4 times. The regeneration was considered complete, and the first cycle was thus completed.

[0146] After drying the regenerated porous polymer microspheres, they were backfilled into the adsorption column. Freshly prepared emulsified wastewater with original oil content determined by ultraviolet spectrophotometry was injected into the adsorption column at a flow rate of 4 mL / min. The oil removal test was then carried out for the next cycle. A total of 5 cycles of oil removal effect test were conducted.

[0147] According to the emulsified wastewater preparation method, oil content determination method and oil removal experiment method described in (1) and (2) above, each example uses an adsorption column alone, and the porous polymer microspheres prepared in Examples 1 to 6 are used to conduct experiments at an adsorption column temperature of 50°C. The specific results are shown in Table 3.

[0148] Table 3. Evaluation of oil removal performance

[0149]

[0150]

[0151] As can be seen from Table 3, for the porous polymer microspheres prepared in any of Examples 1 to 6, the change in the equilibrium oil removal rate of the second, third, fourth, and fifth cycles compared with the equilibrium oil removal rate of the first cycle is within 6.5%, indicating that the porous polymer microspheres provided by the present invention have good oil removal performance, can achieve good oil removal effect as filter media, and can be used multiple times.

[0152] While the present invention has been described with reference to specific embodiments, those skilled in the art will understand that various changes can be made without departing from the true spirit and scope of the invention. Furthermore, numerous modifications can be made to the subject, spirit, and scope of the invention to suit specific situations, materials, material compositions, and methods. All such modifications are included within the scope of the claims of the present invention.

Claims

1. A method for preparing porous polymer microspheres, comprising the following steps: 1) The temperature-sensitive monomer, hydrophilic monomer, crosslinking agent, emulsifier, first initiator and first solvent are mixed to obtain the oil phase; 2) Mix the dispersant, the second initiator, and the second solvent to obtain the dispersed phase; 3) Mix the aqueous phase and the oil phase to prepare a water-in-oil emulsion; 4) Add the water-in-oil emulsion to the dispersed phase and react to obtain porous polymer microspheres.

2. The method according to claim 1, characterized in that, In step 1), the oil phase further includes hydrophobic monomers and / or reinforcing agents.

3. The method according to claim 1 or 2, characterized in that, The temperature-sensitive monomer is N-isopropylacrylamide; and / or The hydrophilic monomer is selected from at least one of 2-hydroxyethyl methacrylate, hydroxypropyl methacrylate, tert-butyl methacrylate, and tert-butyl acrylate; and / or The crosslinking agent is trimethylolpropane triacrylate; and / or The emulsifier is emulsifier P123 or emulsifier 5800; and / or The first initiator is an oil-soluble initiator; and / or the second initiator is a water-soluble initiator; and / or The aqueous phase includes water; and / or The dispersant is polyvinyl alcohol; and / or The first solvent is toluene; and / or the second solvent is water.

4. The method according to claim 2, characterized in that, The hydrophobic monomer is selected from at least one of isobornyl methacrylate, methyl methacrylate, glycidyl methacrylate, and tetradecanoyl phorbol acetate; and / or The reinforcing agent is 3-(isobutenoyloxy)propyltrimethylsilane.

5. The method according to claim 1, characterized in that, The total mass of the thermosensitive monomer, hydrophilic monomer, and crosslinking agent is 100%, the amount of the thermosensitive monomer is 34 wt% to 44.5 wt%, the amount of the hydrophilic monomer is 3 wt% to 12.5 wt%, and the amount of the crosslinking agent is 50 wt% to 55 wt%; and / or The total mass of the thermosensitive monomer, hydrophilic monomer, and crosslinking agent is 100%, the amount of the emulsifier is 1.8 wt% to 4.2 wt%; and / or the amount of the first initiator is 8.8 wt% to 9.7 wt%; and / or The amount of the first solvent is 2 to 4 times the total mass of the temperature-sensitive monomer, hydrophilic monomer, and crosslinking agent; and / or The dispersed phase, by mass 100%, comprises 1 wt% dispersant, 0.07 wt% second initiator, and the balance being a second solvent; and / or The mass ratio of the first solvent to water in the aqueous phase is 1:(1.6 to 3.7); and / or The mass ratio of the water-in-oil emulsion to the dispersed phase is 1:(7.6 to 8.6).

6. The method according to claim 2, characterized in that, The total mass of the thermosensitive monomer, hydrophilic monomer, and crosslinking agent is 100%, the amount of the hydrophobic monomer is 0 to 21.2 wt%, and / or the amount of the reinforcing agent is 0 to 25 wt%.

7. The method according to any one of claims 1 to 6, characterized in that, In step 2), the dispersant, the second initiator, and the second solvent are mixed and deoxygenated to obtain the dispersed phase; and / or In step 3), after adding the aqueous phase to the oil phase, a first reducing agent is added to prepare the water-in-oil emulsion; and / or In step 4), the water-in-oil emulsion is added to the dispersed phase, a second reducing agent is added, and then the reaction is carried out.

8. The method according to claim 7, characterized in that, The first reducing agent and the second reducing agent are independently N,N,N,N-tetramethylethylenediamine and / or N,N-dimethylaniline; Preferably, the total mass of the temperature-sensitive monomer, hydrophilic monomer, and crosslinking agent is 100%, the amount of the first reducing agent is 1.8 wt% to 5.8 wt%, and / or the amount of the second reducing agent is 17.6 wt% to 19.4 wt%.

9. The method according to any one of claims 1 to 8, characterized in that, Step 3) is carried out entirely under ice bath conditions; Preferably, in step 3), the aqueous phase is added to the oil phase under a stirring condition that gradually increases the speed from 3000 r / min to 9000 r / min; and / or In step 4), the reaction is continuously stirred at a speed of 180 r / min to 280 r / min. and / or In step 4), the reaction product obtained from the reaction is filtered, washed, and dried to obtain the porous polymer microspheres.

10. The method according to any one of claims 1 to 9, characterized in that, The reaction is a gradient temperature increase reaction; Preferably, the temperature of the reaction is gradually increased from 65°C to 130°C; and / or the total duration of the reaction is 50 min to 60 min.

11. A porous polymer microsphere prepared by the method according to any one of claims 1 to 10.

12. The porous polymer microspheres according to claim 11, characterized in that, The porous polymer microspheres have a particle size of 0.5 mm to 5 mm; and / or The porous polymer microspheres have a porosity of 20% to 23%; and / or The porous polymer microspheres have a surface pore size of 0.5 μm to 4 μm; and / or an internal pore size of 0.2 μm to 3.8 μm; And / or the internal average pore size is 1.5 μm to 1.6 μm.

13. The porous polymer microspheres prepared by the method according to any one of claims 1 to 10, or the porous polymer microspheres according to claim 11 or 12, are used in oil-water separation, particularly as an adsorption and filtration material for emulsified oily wastewater.

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