Hollow polystyrene microsphere as well as preparation method and application thereof

Abstract

The invention discloses a hollow polystyrene microsphere as well as a preparation method and application thereof. The preparation method comprises the following steps: taking a copolymer containing an ester group cross-linking agent, such as n-butyl acrylate, methyl methacrylate, methacrylic acid and ethylene glycol dimethacrylate, as a hydrophilic core; copolymers containing carbon-carbon double bond cross-linking agents such as styrene, methyl methacrylate and divinyl benzene are used as hydrophobic shells, carboxyl in cores is ionized under the action of alkali to form carboxylate ions, and the hollow polymer microspheres with high light scattering rate and uniform hollow diameter distribution are synthesized. As the polymer has a high refractive index difference with air, the hollow microspheres have excellent covering performance, the hollow microspheres as a coating are widely applied to building coatings and replace part of titanium dioxide, while the cost is reduced, the white color and opaqueness of the coating can be enhanced, the performance of industrial coatings is also improved, and the application prospect is wide. The hollow microsphere material can also be used in light materials.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of functional coating technology, and more particularly to a kind of hollow polystyrene microspheres and its preparation method and application. BACKGROUND

[0002] Hollow polymer microspheres are a kind of polymer spheres with special structure, and the microspheres have excellent hiding performance and deformability due to the high refractive index difference between polymer and air and hollow structure. As fillers, the microspheres have been more and more widely used in high-grade light-shielding coatings, and are applied to building coatings to replace part of titanium dioxide, enhance the whiteness and opacity of the coatings, reduce the cost, and improve the performance of industrial coatings.

[0003] The development of hollow polymer microspheres is considered as one of the three greatest achievements in the past decades that have changed the paint industry. Although the research on the preparation method of hollow polymer microspheres is increasing, there are still some problems in production and use. For example, in Fusion Engineering and Design (1997, 34-35: 811-814), hollow polystyrene microspheres were prepared by encapsulation method. The principle of this method is to prepare a triple emulsion by a suitable method, and then gradually increase the oil phase concentration under certain conditions until the hollow polystyrene shell is completely solidified. Because of the limited process conditions, the single-pot yield is low, and the use of organic solvents in the preparation process has a certain impact on the environment and poses a fire hazard. In patent CN103387625A, hollow polystyrene microspheres were also prepared by encapsulation method. The difference is that the polystyrene is directly dissolved in the styrene monomer, without the use of organic solvents, which avoids the problems of solvent recovery and utilization, and the instability of the emulsion caused by the low viscosity of the monomer. Although this method can prepare hollow polymer microspheres with good morphology, the preparation process is complex and has certain limitations in practical application. In Chinese Journal of Inorganic Chemistry (2007, 23(11): 2003-2006), zinc sulfide nanohollow spheres were synthesized by self-assembly method. The basic principle is to use the electrostatic adsorption between different charged substances, layer-by-layer deposition, with negatively charged polystyrene colloidal particles as templates, three layers of polyelectrolyte are deposited on the surface of the colloidal particles to make the colloidal particles surface positively charged, and then the negatively charged silica nanoparticles are adsorbed on the colloidal surface. However, this method often requires expensive equipment for characterization, and the requirements for the reaction system are also high, which is difficult to realize industrialization. In Macromolecular Symposia (1996, 101: 509-516), hollow polymer microspheres were prepared by dynamic swelling method. This method can prepare monodisperse large particle size hollow polymer microspheres by polymerization of divinylbenzene inside the particles to form the shell of the hollow spheres. However, the reaction degree of this method is difficult to control, and the use of organic solvents also poses a threat to human health and pollutes the environment. The use of solvent volatilization and recovery device also greatly increases the production cost.

[0004] This invention synthesizes a copolymer with a three-layer core-shell structure via emulsion polymerization, and then swells the solid copolymer into hollow polymer microspheres using an alkali swelling technique. This method exhibits advantages such as being environmentally friendly, simple to operate, and easy to industrialize. It can yield hollow polymer microspheres with controllable structure, excellent performance, and low cost, and is a rapidly developing preparation technology in recent years. Summary of the Invention

[0005] The purpose of this invention is to solve the above problems by providing a hollow polystyrene microsphere with a simple preparation process, low production cost, and excellent covering performance, as well as its preparation method and application.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A hollow polystyrene microsphere comprises: a core layer monomer mixture, an intermediate layer monomer mixture, and a shell layer monomer mixture;

[0008] The core layer monomer mixture comprises the following components in parts by weight: 146-150 parts of n-butyl acrylate, 162-170 parts of methyl methacrylate, 100-140 parts of methacrylic acid, and 2.5-3 parts of crosslinking agent A;

[0009] The intermediate layer monomer mixture comprises the following components in parts by weight: 70-76 parts of methyl methacrylate, 8-10 parts of methacrylic acid, and 40-45 parts of styrene;

[0010] The shell monomer mixture comprises the following components in parts by weight: 230-250 parts of styrene and 6-10 parts of crosslinking agent B.

[0011] Preferably, the crosslinking agent A is one of ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, and diallyl phthalate; and the crosslinking agent B is divinylbenzene.

[0012] Another object of the present invention is to provide a method for preparing the above-mentioned hollow polystyrene microspheres, comprising the following steps:

[0013] (a) Preparation of monomer mixtures

[0014] Based on the components of the hollow polystyrene microspheres described above, prepare a core layer monomer mixture, an intermediate layer monomer mixture, and a shell layer monomer mixture, and divide the core layer monomer mixture into two parts: core layer monomer mixture A accounts for 5-20% of the total mass of the core layer monomer mixture, and core layer monomer mixture B accounts for 80-95% of the total mass of the core layer monomer mixture;

[0015] (b) Preparation of seed emulsion

[0016] Mixing the oil phase and the water phase homogeneously to carry out emulsion polymerization reaction to obtain emulsion A; the oil phase is the core layer monomer mixture A, and the water phase is emulsifier, initiator and deionized water;

[0017] (c) Preparation of core emulsion

[0018] Drop the core layer monomer mixture B into emulsion A within 2-5 hours, supplement 1-5 parts of initiator, and obtain emulsion B after reaction;

[0019] (d) Preparation of core / intermediate layer emulsion

[0020] Take 50-200 parts of emulsion B and add 200-500 parts of deionized water to obtain emulsion C after dilution, supplement 0.5-2 parts of initiator, drop the intermediate layer monomer mixture into emulsion C within 10-60 minutes, and obtain emulsion D after reaction;

[0021] (e) Preparation of core / intermediate layer / shell emulsion

[0022] Supplement 1-5 parts of initiator to emulsion D, drop the shell layer monomer mixture into emulsion D within 1-5 hours, and obtain emulsion E after reaction;

[0023] (f) Alkali swelling

[0024] Take 100-300 parts of emulsion E and add 500-1000 parts of deionized water to obtain emulsion F after dilution, add alkali solution to emulsion F to adjust pH value, and obtain hollow polystyrene microspheres after swelling for 1-5 hours.

[0025] Preferably, the water phase solution in step (b) comprises the following components by weight: 0.01-1 parts of emulsifier, 0.1-2 parts of initiator and 500-1000 parts of deionized water; wherein the emulsifier is sodium dodecyl sulfate or sodium dodecyl sulfonate; and the initiator is one of ammonium persulfate and potassium persulfate. Preferably, the reaction conditions of emulsion polymerization in step (b) are: rotation speed 150-500 rpm and reaction temperature 65-85℃.

[0026] Preferably, the reaction conditions in step (c) are: rotation speed 150-500 rpm, reaction temperature 65-85℃, temperature is raised to 90-95℃ after dropping is completed, and the temperature is kept for 30-60 minutes and then cooled to room temperature; wherein the initiator is the same as the above initiator.

[0027] Preferably, the reaction conditions in step (d) are: rotation speed 150-500 rpm and reaction temperature 65-85℃; wherein the initiator is the same as the above initiator.

[0028] Preferably, the reaction conditions in step (e) are: rotation speed 150-500 rpm, reaction temperature 90-95 DEG C, after the dropwise addition is completed, heat for 30-60 min, and then cool to room temperature; wherein the initiator is the same as the above initiator.

[0029] Preferably, the alkali solution in step (f) is one of ammonia, sodium hydroxide solution, and N-methyl diethanolamine solution; and the pH value is in the range of 9.0-12.5.

[0030] The swelling reaction conditions are: rotation speed 150-500 rpm, and reaction temperature 90-100 DEG C.

[0031] Compared with the prior art, the application has the following beneficial effects:

[0032] The hollow polystyrene microspheres prepared by the method have excellent hiding performance and low production cost, are green, environmentally friendly, and easy to operate and use in large scale. BRIEF DESCRIPTION OF DRAWINGS

[0033] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed in the embodiments or the prior art description will be briefly introduced as follows. Obviously, the drawings in the following description are only embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative effort on the basis of the provided drawings.

[0034] Figure 1 TEM photo of the hollow polystyrene microspheres prepared in Example 1.

[0035] Figure 2 TEM photo of the hollow polystyrene microspheres prepared in Example 2.

[0036] Figure 3 TEM photo of the hollow polystyrene microspheres prepared in Example 3.

[0037] Figure 4 TEM photo of the hollow polystyrene microspheres prepared in Example 4.

[0038] Figure 5 SEM photograph of the hollow polystyrene microspheres prepared in Example 3. DETAILED DESCRIPTION

[0039] The technical solutions in the embodiments of the present application will be apparently and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all the other embodiments obtained by a person of ordinary skill in the art without any creative work fall within the protection scope of the present application.

[0040] Example 1

[0041] (1) Preparation of core emulsion

[0042] With the mass of the polymerized monomers being 100 parts as the basis, 30 parts of polymerized monomer methacrylic acid, 36.5 parts of polymerized monomer methyl methacrylate, 33 parts of polymerized monomer n-butyl acrylate and 0.5 part of crosslinking agent ethylene glycol dimethacrylate were uniformly mixed to obtain a core layer monomer mixture. 200 parts of deionized water, 0.01 part of emulsifier sodium dodecyl sulfonate and 0.2 part of initiator ammonium persulfate were placed in a three-necked flask, uniformly mixed and heated to 80°C. 5 parts of the core layer monomer mixture were poured into the three-necked flask, stirred at a speed of 300 rpm, and a seed emulsion was obtained after 40 min of reaction. 0.6 part of initiator ammonium persulfate was completely dissolved in 22 parts of deionized water and poured into the seed emulsion, and then the remaining 95 parts of the core layer monomer mixture was added dropwise into the seed emulsion within 4.5 h, the temperature was maintained at 80°C, and after the dropwise addition was completed, the temperature was raised to 90°C, and after 30 min of incubation, the temperature was cooled to room temperature to obtain the core emulsion.

[0043] (2) Preparation of core / intermediate layer emulsion

[0044] With the mass of the polymerized monomers being 100 parts as the basis, 72 parts of polymerized monomer methyl methacrylate, 8 parts of polymerized monomer methacrylic acid and 20 parts of polymerized monomer styrene were uniformly mixed to obtain an intermediate layer monomer mixture. 200 parts of the core emulsion were placed in a three-necked flask, diluted with 500 parts of deionized water and heated to 80°C. 3 parts of initiator ammonium persulfate were completely dissolved in 100 parts of deionized water and poured into the three-necked flask, and then the intermediate layer monomer mixture was added dropwise into the three-necked flask within 40 min, stirred at a speed of 300 rpm, and the temperature was maintained at 80°C. The core / intermediate layer emulsion was obtained after the reaction was completed.

[0045] (3) Preparation of core / intermediate layer / shell emulsion

[0046] Based on a monomer mass of 100 parts, 86 parts of styrene monomer and 14 parts of divinylbenzene crosslinking agent were mixed evenly to obtain a shell monomer mixture. The core / intermediate layer emulsion prepared in step (2) was placed in a three-necked flask and heated to 90°C. 0.7 parts of ammonium persulfate initiator were completely dissolved in 36 parts of deionized water and poured into the three-necked flask. The shell monomer mixture was then added dropwise to the three-necked flask over 2 hours while stirring at 300 rpm. The temperature was maintained at 90°C. After the addition was complete, the temperature was raised to 90°C, held for 30 minutes, and then cooled to room temperature to obtain the core / intermediate layer / shell emulsion.

[0047] (4) Alkali swelling

[0048] 90 parts of the core / intermediate layer / shell emulsion prepared in step (3) were diluted with 364 parts of deionized water. 30wt% N-methyldiethanolamine was added to adjust the pH to 10. The mixture was then placed in a high-pressure reactor and heated to 95°C. The mixture was stirred at 300 rpm and swollen for 3 hours to obtain hollow polystyrene microspheres.

[0049] Example 2

[0050] (1) Preparation of nuclear emulsion

[0051] Based on a monomer mass of 100 parts, 32 parts of methacrylic acid, 40 parts of methyl methacrylate, 27.25 parts of n-butyl acrylate, and 0.25 parts of diethylene glycol dimethacrylate were mixed evenly to obtain a core layer monomer mixture. 200 parts of deionized water, 0.01 parts of sodium dodecyl sulfate emulsifier, and 0.4 parts of potassium persulfate initiator were placed in a three-necked flask, mixed evenly, and heated to 80°C. 5 parts of the core layer monomer mixture were added to the three-necked flask and stirred at 300 rpm. After reacting for 1 hour, a seed emulsion was obtained. 0.8 parts of potassium persulfate initiator were completely dissolved in 22 parts of deionized water and added to the seed emulsion. Then, the remaining 95 parts of the core layer monomer mixture were added dropwise to the seed emulsion over 5 hours, stirred at 300 rpm, and the temperature was maintained at 80°C. After the addition was complete, the temperature was raised to 90°C, held for 40 minutes, and then cooled to room temperature to obtain the core emulsion.

[0052] (2) Preparation of core / intermediate layer emulsion

[0053] With the mass of the polymerization monomer as 100 parts, 72 parts of the polymerization monomer methyl methacrylate, 8 parts of the polymerization monomer methacrylic acid and 20 parts of the polymerization monomer styrene were mixed uniformly to obtain an intermediate layer monomer mixture. 200 parts of the core emulsion were placed in a three-necked flask, diluted with 500 parts of deionized water and heated to 80°C. 5 parts of the initiator potassium persulfate was completely dissolved in 100 parts of deionized water and then poured into the three-necked flask. Then, the intermediate layer monomer mixture was added dropwise into the three-necked flask within 1 hour, stirred at a speed of 300 rpm and the temperature was maintained at 80°C. After the reaction was completed, a core / intermediate layer emulsion was obtained.

[0054] (3) Preparation of the core / intermediate layer / shell emulsion

[0055] With the mass of the polymerization monomer as 100 parts, 80 parts of the polymerization monomer styrene and 20 parts of the crosslinking agent divinylbenzene were mixed uniformly to obtain a shell layer monomer mixture. The core / intermediate layer emulsion prepared in step (2) was placed in a three-necked flask and heated to 90°C. 1.2 parts of the initiator potassium persulfate was completely dissolved in 36 parts of deionized water and then poured into the three-necked flask. Then, the shell layer monomer mixture was added dropwise into the three-necked flask within 2 hours, stirred at a speed of 300 rpm and the temperature was maintained at 90°C. After the dropwise addition was completed, the temperature was increased to 90°C, maintained at 90°C for 30 minutes and then cooled to room temperature, to obtain a core / intermediate layer / shell emulsion.

[0056] (4) Alkali swelling

[0057] 90 parts of the core / intermediate layer / shell emulsion prepared in step (3) was diluted with 364 parts of deionized water. After the pH value was adjusted to 10 by adding 25wt% ammonia water, the mixture was placed in a high-pressure reaction kettle and heated to 95°C, stirred at a speed of 300 rpm and swelled for 3 hours, to obtain hollow polystyrene microspheres.

[0058] Example 3

[0059] With the mass of the polymerization monomer as 100 parts, 33.2 parts of the polymerization monomer methacrylic acid, 32 parts of the polymerization monomer methyl methacrylate, 34 parts of the polymerization monomer n-butyl acrylate and 0.8 parts of the crosslinking agent diallyl phthalate were mixed uniformly to obtain a core layer monomer mixture. 200 parts of deionized water, 0.01 parts of the emulsifier sodium dodecyl sulfonate and 0.2 parts of the initiator ammonium persulfate were placed in a three-necked flask, mixed uniformly and heated to 80°C. 5 parts of the core layer monomer mixture was poured into the three-necked flask, stirred at a speed of 300 rpm and a seed emulsion was obtained after the reaction for 40 minutes. 0.6 parts of the initiator ammonium persulfate was completely dissolved in 22 parts of deionized water and then poured into the seed emulsion. Then, 95 parts of the remaining core layer monomer mixture was added dropwise into the seed emulsion within 4.5 hours, stirred at a speed of 300 rpm and the temperature was maintained at 80°C. After the dropwise addition was completed, the temperature was increased to 90°C, maintained at 90°C for 30 minutes and then cooled to room temperature, to obtain a core emulsion.

[0060] (2) Preparation of core / intermediate layer emulsion

[0061] The polymerization monomer methyl methacrylate 72 parts, polymerization monomer methacrylic acid 8 parts and polymerization monomer styrene 20 parts were mixed uniformly to obtain an intermediate layer monomer mixture, taking the core emulsion 200 parts into a three-necked flask, adding deionized water 500 parts for dilution and heating to 80°C. The initiator ammonium persulfate 3 parts was completely dissolved in deionized water 100 parts and poured into the three-necked flask, then the intermediate layer monomer mixture was added dropwise into the three-necked flask within 40 min, stirring at a speed of 300 rpm, the temperature was maintained at 80°C, and the core / intermediate layer emulsion was obtained after the reaction was completed.

[0062] (3) Preparation of core / intermediate layer / shell emulsion

[0063] The polymerization monomer styrene 86 parts and crosslinking agent divinylbenzene 14 parts were mixed uniformly to obtain a shell layer monomer mixture, the core / intermediate layer emulsion prepared in step (2) was placed in a three-necked flask and heated to 90°C. The initiator ammonium persulfate 0.7 parts was completely dissolved in deionized water 36 parts and poured into the three-necked flask, then the shell layer monomer mixture was added dropwise into the three-necked flask within 2 h, stirring at a speed of 300 rpm, the temperature was maintained at 90°C, after the dropwise addition was completed, the temperature was raised to 90°C, and after 30 min of incubation, the temperature was cooled to room temperature, to obtain the core / intermediate layer / shell emulsion.

[0064] (4) Alkali swelling

[0065] The core / intermediate layer / shell emulsion prepared in step (3) 90 parts was added to deionized water 364 parts for dilution, the pH value was adjusted to 10 by adding 25wt% ammonia solution, and then placed in a high-pressure reaction kettle and heated to 105°C, stirring at a speed of 300 rpm, and the hollow polystyrene microspheres were obtained after swelling for 3 h.

[0066] Example 4

[0067] (1) Preparation of core emulsion

[0068] With the mass of the polymerization monomer as 100 parts, 30 parts of the polymerization monomer methacrylic acid, 36.5 parts of the polymerization monomer methyl methacrylate, 33 parts of the polymerization monomer n-butyl acrylate and 0.5 parts of the crosslinking agent ethylene glycol dimethacrylate were uniformly mixed to obtain a core layer monomer mixture. 200 parts of deionized water, 0.01 parts of the emulsifier sodium dodecyl sulfonate and 0.2 parts of the initiator ammonium persulfate were placed in a three-necked flask, uniformly mixed and heated to 80°C. 5 parts of the core layer monomer mixture was poured into the three-necked flask, stirred at a speed of 300 rpm, and after 40 min of reaction, a seed emulsion was obtained. 0.6 parts of the initiator ammonium persulfate was completely dissolved in 22 parts of deionized water and poured into the seed emulsion, and then the remaining 95 parts of the core layer monomer mixture was added dropwise into the seed emulsion within 4.5 h, stirred at a speed of 300 rpm, and the temperature was maintained at 80°C. After the dropwise addition was completed, the temperature was increased to 90°C, and after 30 min of incubation, the temperature was cooled to room temperature to obtain a core emulsion.

[0069] (2) Preparation of the core / intermediate layer emulsion

[0070] With the mass of the polymerization monomer as 100 parts, 72 parts of the polymerization monomer methyl methacrylate, 8 parts of the polymerization monomer methacrylic acid and 20 parts of the polymerization monomer styrene were uniformly mixed to obtain an intermediate layer monomer mixture. 200 parts of the core emulsion was placed in a three-necked flask, diluted with 500 parts of deionized water and heated to 80°C. 3 parts of the initiator ammonium persulfate was completely dissolved in 100 parts of deionized water and poured into the three-necked flask, and then the intermediate layer monomer mixture was added dropwise into the three-necked flask within 40 min, stirred at a speed of 300 rpm, and the temperature was maintained at 80°C. After the reaction was completed, a core / intermediate layer emulsion was obtained.

[0071] (3) Preparation of the core / intermediate layer / shell emulsion

[0072] With the mass of the polymerization monomer as 100 parts, 86 parts of the polymerization monomer styrene and 14 parts of the crosslinking agent divinylbenzene were uniformly mixed to obtain a shell layer monomer mixture. The core / intermediate layer emulsion prepared in step (2) was placed in a three-necked flask and heated to 90°C. 0.7 parts of the initiator ammonium persulfate was completely dissolved in 36 parts of deionized water and poured into the three-necked flask, and then the shell layer monomer mixture was added dropwise into the three-necked flask within 2 h, stirred at a speed of 300 rpm, and the temperature was maintained at 90°C. After the dropwise addition was completed, the temperature was increased to 90°C, and after 30 min of incubation, the temperature was cooled to room temperature to obtain a core / intermediate layer / shell emulsion.

[0073] (4) Alkali swelling

[0074] 90 parts of the core / intermediate layer / shell emulsion prepared in step (3) was added to 364 parts of deionized water for dilution, and 15 wt% sodium hydroxide was added to adjust the pH value to 10, and then the mixture was placed in a high-pressure reaction kettle and heated to 95°C, stirred at a speed of 300 rpm, and after 3 h of swelling, hollow polystyrene microspheres were obtained.

[0075] The hollow polystyrene microspheres synthesized in the above Examples 1-4 were tested for pore volume using a specific surface area and pore size analyzer (BET, ASAP 2020 Plus, Micromeritics, USA), and the obtained data are shown in Table 1.

[0076] As can be seen from the table, by changing the alkali treatment conditions, hollow polystyrene microspheres with different pore volumes can be obtained. When the same alkali is used for alkali treatment of the polymer microspheres, keeping the pH value of the emulsion the same, the higher the temperature, the greater the pore volume of the hollow polymer microspheres. When the temperature reaches a certain value, further increasing the temperature will decrease the pore volume of the hollow polymer microspheres.

[0077] Table 1 Pore volume data of Examples 1-4

[0078] Pore volume / (mL g -1 )]]> Example 1 0.1308 Example 2 0.1277 Example 3 0.1670 Example 4 0.0595

[0079] The hollow polystyrene microspheres synthesized in Examples 1-4 were observed for morphology using a transmission electron microscope (TEM) (JEOL-1020, 100 kV, Japan) and a scanning electron microscope (SEM) (JSM-6510, Japan).

[0080] Figure 1 Figures 1-4 Figure 1 is a transmission electron microscope photograph of the hollow polystyrene microspheres prepared in Example 1. Figure 2 is a transmission electron microscope photograph of the hollow polystyrene microspheres prepared in Example 2. Figure 3 is a transmission electron microscope photograph of the hollow polystyrene microspheres prepared in Example 3. Figure 4 is a transmission electron microscope photograph of the hollow polystyrene microspheres prepared in Example 4. Figure 5 Figure 3 is a scanning electron microscope photograph of the hollow polystyrene microspheres prepared in Example 3. By observation, it can be found that if the polymer microspheres are excessively swollen, the shell layer will become thinner, and the excessively thin shell layer is difficult to support after drying, eventually leading to collapse of the hollow polymer microspheres, forming a "bowl-shaped" structure. By changing the alkali treatment conditions, hollow polystyrene microspheres with different hollow sizes and morphology can be obtained.

[0081] The various embodiments in the specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other. For the device disclosed in the embodiments, since it corresponds to the method disclosed in the embodiments, the description is relatively simple, and the relevant parts can be referred to the method part.

[0082] The above description of the disclosed embodiments enables a person skilled in the art to implement or use the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to these embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A hollow polystyrene microsphere, characterized in that, include: Core layer monomer mixture, intermediate layer monomer mixture, and shell layer monomer mixture; The core layer monomer mixture comprises the following components in parts by weight: 146-150 parts of n-butyl acrylate, 162-170 parts of methyl methacrylate, 100-140 parts of methacrylic acid, and 2.5-3 parts of crosslinking agent A; The intermediate layer monomer mixture comprises the following components in parts by weight: 70-76 parts of methyl methacrylate, 8-10 parts of methacrylic acid, and 40-45 parts of styrene; The shell monomer mixture comprises the following components in parts by weight: 230-250 parts of styrene and 6-10 parts of crosslinking agent B.

2. The hollow polystyrene microspheres according to claim 1, characterized in that, The crosslinking agent A is one of ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, and diallyl phthalate; the crosslinking agent B is divinylbenzene.

3. A method for preparing hollow polystyrene microspheres as described in claim 2, characterized in that, Includes the following steps: (a) Preparation of monomer mixtures According to the components of the hollow polystyrene microspheres described in claim 2, a core layer monomer mixture, an intermediate layer monomer mixture, and a shell layer monomer mixture are prepared, and the core layer monomer mixture is divided into two parts: core layer monomer mixture A accounts for 5-20% of the total mass of the core layer monomer mixture, and core layer monomer mixture B accounts for 80-95% of the total mass of the core layer monomer mixture; (b) Preparation of seed emulsion Emulsion A is obtained by uniformly mixing the oil phase and the aqueous phase and carrying out emulsion polymerization. The oil phase is a mixture of core layer monomers A, and the aqueous phase consists of emulsifier, initiator and deionized water. (c) Preparation of nuclear emulsion The core layer monomer mixture B is added dropwise to emulsion A within 2-5 hours, and 1-5 parts of initiator are added. After the reaction, emulsion B is obtained. (d) Preparation of core / intermediate layer emulsion Take 50-200 parts of emulsion B and add 200-500 parts of deionized water to dilute and obtain emulsion C. Add 0.5-2 parts of initiator and add the intermediate layer monomer mixture dropwise to emulsion C within 10-60 minutes. After the reaction is complete, emulsion D is obtained. (e) Preparation of core / intermediate layer / shell emulsion Add 1 to 5 parts of initiator to emulsion D, and add the shell monomer mixture dropwise to emulsion D within 1 to 5 hours. After the reaction is complete, emulsion E is obtained. (f) Alkali swelling Take 100-300 parts of emulsion E and add 500-1000 parts of deionized water to dilute and obtain emulsion F. Add alkali solution to emulsion F to adjust the pH value, and after swelling for 1-5 hours, hollow polystyrene microspheres are obtained.

4. The method for preparing hollow polystyrene microspheres according to claim 3, characterized in that, The aqueous solution in step (b) comprises the following components by weight: 0.01 to 1 part emulsifier, 0.1 to 2 parts initiator, and 500 to 1000 parts deionized water; wherein the emulsifier is sodium dodecyl sulfate or sodium dodecyl sulfonate; and the initiator is one of ammonium persulfate and potassium persulfate.

5. The method for preparing hollow polystyrene microspheres according to claim 3, characterized in that, The reaction conditions for emulsion polymerization in step (b) are: rotation speed 150-500 rpm and reaction temperature 65-85℃.

6. The method for preparing hollow polystyrene microspheres according to claim 4, characterized in that, The reaction conditions in step (c) are: rotation speed 150-500 rpm, reaction temperature 65-85℃, after the addition is complete, the temperature is raised to 95-100℃, kept at this temperature for 30-60 min, and then cooled to room temperature; wherein the initiator is the same as the initiator in claim 4.

7. The method for preparing hollow polystyrene microspheres according to claim 4, characterized in that, The reaction conditions in step (d) are: rotation speed 150-500 rpm, reaction temperature 65-85℃; wherein the initiator is the same as the initiator in claim 4.

8. The method for preparing hollow polystyrene microspheres according to claim 4, characterized in that, The reaction conditions in step (e) are: rotation speed 150-500 rpm, reaction temperature 90-95℃, and after the addition is completed, keep warm for 30-60 min and then cool to room temperature; wherein the initiator is the same as the initiator in claim 4.

9. The method for preparing hollow polystyrene microspheres according to claim 4, characterized in that, The alkaline solution mentioned in step (f) is one of ammonia water, sodium hydroxide solution, or N-methyldiethanolamine solution; the pH value ranges from 9.0 to 12.

5. The swelling reaction conditions are a rotation speed of 150–500 rpm and a reaction temperature of 90–100 °C.

10. Hollow polystyrene microspheres prepared by the method of claims 1-2 or claims 3-9 are used in architectural coatings or lightweight structural materials.

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