Preparation method of large-size polymer hollow microspheres with high crosslinking degrees

[0018] Example 1

[0019] (1) Preparation of seed emulsion: add 0.15g of emulsifier sodium dodecyl biphenyl sulfonate (DSB) and 260g of deionized water to 500ml four ports equipped with stirring, reflux condenser, thermometer and nitrogen inlet pipe In the bottle, after stirring for 10 minutes, add 21g methyl methacrylate (MMA), 7.5g butyl methacrylate (BA), 1.5g methacrylic acid (MAA) mixed monomer; increase the temperature to 70℃, add 0.165g An aqueous solution of ammonium persulfate (APS) and 5g of water and an aqueous solution of 0.075g of sodium bisulfite (SBS) and 5g of water are incubated and matured for 2 hours to obtain seed latex particles, which are cooled for later use.

[0020] (2) Preparation of core layer latex particles: 25g seed latex particles and 185g deionized water are added to a 500ml four-necked flask equipped with a stirring, reflux condenser, thermometer and nitrogen inlet tube, and 40.5g methyl methacrylate (MMA) ), 22.5g butyl methacrylate (BA) and 27g methacrylic acid (MAA) are mixed, 0.6188g ammonium persulfate (APS), 0.2813g sodium bisulfite (SBS) are mixed with 20g deionized water respectively, and heated to At 70°C, the monomer mixed solution and the initiator mixed solution were added dropwise at the same time, and the dropping was completed in 2 hours, and the core layer latex particles were obtained by heat preservation and curing for 2 hours, and the temperature was lowered for later use.

[0021] (3) Preparation of core-shell latex particles: 50g of core-shell latex particles and 147.5g of deionized water were added to a 500ml four-necked flask equipped with a stirring, reflux condenser, thermometer and nitrogen inlet tube, and 56.25g of styrene ( St), 6.25g butyl methacrylate (BA) and 0.31g tripropylene glycol diacrylate (TPGDA) were mixed, 0.4297g ammonium persulfate (APS), 0.1953g sodium sulfite (SBS) were mixed with 20g deionized water, and heated At 70°C, the monomer mixture solution and the initiator mixture solution were added dropwise at the same time, and the dripping was completed in 5 hours, and then the heat preservation and maturation were continued for 2 hours to obtain the core-shell latex particles, which were cooled for use.

[0022] (4) Alkali/acid gradual swelling: Take 15g core-shell latex particles and 285g deionized water into a 500ml four-necked flask equipped with stirring, reflux condenser and thermometer, stir well and add 25% ammonia The pH value of the system was adjusted to 10 by the aqueous solution, heated to 80°C, and reacted for 5 hours to reduce to room temperature; diluted hydrochloric acid was added to adjust the pH value to 3, heated to 80°C for 5 hours, and cooled to obtain polymer latex particles with hollow structure.

[0023] (5) Preparation of cross-linked shell layer: Take 5g hollow latex particles, 0.45g polyvinylpyrrolidone, 80g deionized water and 80g ethanol and add them to a 250ml four-necked flask equipped with stirring, reflux condenser, thermometer and nitrogen inlet pipe , Turn on the heating and vent nitrogen and condensed water. Mix 9g of methyl methacrylate (MMA) and 6g of divinylbenzene (DVB), 0.15g of ammonium persulfate (APS) and 20g of deionized water. The temperature is raised to 80°C, while the monomer mixture solution and the initiator are added dropwise. The mixed solution of the agent is dripped in 4 hours, and then heat preservation and curing for 2 hours to obtain a highly crosslinked hollow polymer emulsion.

[0024] (6) TEM test: Dilute the latex particles obtained in each stage with deionized water to a solid content of 5%, ultrasonically disperse for 15 minutes, and drop them on a special copper net, and observe and characterize with HITACHI-800 transmission electron microscope. figure 1 It is an electron micrograph of the core layer latex particles, it can be seen that the core layer latex particles are regular spherical, and the diameter measured is about 200nm; figure 2 So figure 1 As the core-shell structure latex particles prepared from seeds, it can be clearly seen that the particle diameter becomes larger, about 420nm, and the shape is still spherical, indicating that the shell monomer is completely wrapped on the seed surface. The latex particles are darker in color and lighter on the edges, showing a core-shell structure. The size of the core-shell latex particles is basically the same and is monodisperse; image 3 It is the latex particles obtained by alkali high temperature expansion. At this time, the latex particles have a relatively large cavity structure, and the shape is a regular spherical shape. The diameter of the latex particles is about 660nm and the cavity diameter is about 500nm, but there is still some core polymerization in the shell. Objects are not completely hollow structures. Figure 4 It is a latex particle obtained by swelling with acid and high temperature, showing a hollow structure, the diameter of the latex particle is about 450nm, and the diameter of the cavity is about 300nm. Figure 5 It is the microscopic morphology of latex particles with hollow microspheres as seeds and a highly crosslinked shell layer polymerized on their surface. The particle diameter is about 550nm, and the average cavity diameter is still 300nm, that is, the hollowness is about 16.2% (hollowness: the percentage of the volume of the cavity of the latex particle to the volume of the latex particle). Compared Figure 4 with Figure 5 It can be found that the particle size of the latex particles has increased by about 100 nm, while the cavity diameter remains the same, indicating that the monomer is polymerized on the shell of the hollow microspheres.

[0025] Example 2

[0026] (1) Preparation of seed latex particles: same as Example 1.

[0027] (2) Preparation of core layer latex particles: 25g seed latex particles and 185g deionized water are added to a 500ml four-necked flask equipped with a stirring, reflux condenser, thermometer and nitrogen inlet tube, and 40.5g methyl methacrylate (MMA) ), 22.5g butyl methacrylate (BA), 27g methacrylic acid (MAA) and 0.09g tripropylene glycol diacrylate (TPGDA) mixed, 0.6188g ammonium persulfate (APS), 0.2813g sodium sulfite (SBS) and Mix 20 g of deionized water, heat up to 70°C, and add the monomer mixture solution and the initiator mixture solution dropwise at the same time. After 2 hours of dripping, the core layer latex particles are obtained by heat preservation and curing for 2 hours, and the temperature is lowered for later use.

[0028] (3) Preparation of core-shell latex particles: 75g of core-shell latex particles and 128.75g of deionized water were added to a 500ml four-necked flask equipped with a stirring, reflux condenser, thermometer and nitrogen inlet tube, and 50.63g of styrene ( St), 5.63g butyl methacrylate (BA) and 0.56g tripropylene glycol diacrylate (TPGDA) were mixed, 0.3867g ammonium persulfate (APS), 0.1758g sodium sulfite (SBS) were mixed with 20g deionized water, and heated At 70°C, the monomer mixture solution and the initiator mixture solution were added dropwise at the same time, and the dripping was completed in 5 hours, and then the heat preservation and maturation were continued for 2 hours to obtain the core-shell latex particles, which were cooled for use.

[0029] (4) Alkali/acid gradual swelling: 15g core-shell latex particles and 285g deionized water are added to a 500ml four-necked flask equipped with a stirring, reflux condenser and thermometer, and after stirring, add 25% ammonia solution to adjust the system The pH value is 9.3, heated to 70°C, and the reaction is reduced to room temperature for 3 hours; diluted hydrochloric acid is added to adjust the pH value to 3, heated to 70°C for 3 hours, and the temperature is lowered to obtain polymer latex particles with a hollow structure.

[0030] (5) Preparation of cross-linked shell layer: the same as in Example 1.

[0031] (6) TEM test: Dilute the latex particles obtained by gradually swelling alkali/acid with deionized water to a solid content of 5%, ultrasonically disperse for 15 minutes, drop them on a special copper net, and observe and characterize with HITACHI-800 transmission electron microscope. The microscopic appearance of the particles is like Image 6 As shown, there is polymer in the cavity of the latex particles, and the thickness of part of the shell layer is uneven, indicating that the increase in the degree of cross-linking between the core layer and the shell layer will inhibit the outward migration of the chain segments, making the cavity not empty, and indicating that the shell monomer When the amount is small, it will cause incomplete shell coating and uneven distribution of shell thickness.

[0032] Example 3

[0033] (1) Preparation of seed latex particles: same as Example 1.

[0034] (2) Preparation of core layer latex particles: same as Example 2

[0035] (3) Preparation of core-shell latex particles: 60g of core-shell latex particles and 140g of deionized water were added to a 500ml four-necked flask equipped with stirring, reflux condenser, thermometer and nitrogen inlet, and 54g of styrene (St) , 6g butyl methacrylate (BA) and 0.6g tripropylene glycol diacrylate (TPGDA) mixed, 0.4125g ammonium persulfate (APS), 0.1875g sodium sulfite (SBS) + 0.06g sodium dodecyl biphenyl sulfonate (DSB) were mixed with 20g of deionized water, heated to 70°C, while dripping the monomer mixture solution and the initiator mixture solution, dripping in 2 hours, and then continued to heat and mature for 2 hours to obtain core-shell latex particles, which were cooled for later use.

[0036] (4) Alkali/acid swelling gradually: same as example 1.

[0037] (5) Preparation of cross-linked shell layer: the same as in Example 1.

[0038] (6) Particle size and distribution test: Dilute a small amount of core-shell latex particles with deionized water and place them in a cuvette. Use Zetasizer Nano-ZS, Malvern to measure the particle size of the latex particles, such as Figure 7 As shown, the particle size distribution curve is bimodal, indicating that the excessively fast rate of dropping monomer leads to secondary nucleation of latex particles.