High-temperature-resistant monodisperse thermoplastic polystyrene nanoscale microsphere and preparation method thereof

Abstract

The invention belongs to the technical field of polymer microspheres, and particularly relates to a high-temperature-resistant monodisperse thermoplastic polystyrene nanoscale microsphere and a preparation method thereof. The high-temperature-resistant monodisperse thermoplastic polystyrene nanoscale microsphere provided by the invention is prepared from the following raw materials: a styrene monomer, a heat-resistant modified monomer, a stabilization-assisting monomer, a free radical initiator, an emulsifier and water, the total mass percentage content of the styrene monomer, the heat-resistant modified monomer and the stabilization-assisting monomer is 100%, the styrene monomer accounts for 5%-94.9%, the heat-resistant modified monomer accounts for 5%-85%, and the stabilization-assisting monomer accounts for 0.1%-10%; the mass of the free radical initiator is 0.5-5% of the total mass of the styrene monomer, the heat-resistant modified monomer and the stabilization-assisting monomer, and the mass of the emulsifier is 0-2% of the total mass of the styrene monomer, the heat-resistant modified monomer and the stabilization-assisting monomer. The high-temperature-resistant monodisperse thermoplastic polystyrene nanoscale microsphere provided by the invention has the characteristics of controllable particle size and good monodispersity.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer microspheres, and in particular relates to high temperature resistant monodisperse thermoplastic polystyrene nano-scale microspheres and a preparation method thereof. Background Art

[0002] Monodisperse polymer microspheres refer to polymer spherical particles whose average particle size distribution of at least 90% of the particles is within a range of 5%. The coefficient of variation (CV) is usually used to describe the monodispersity of the microspheres. Monodisperse polymer microspheres have many advantages, such as uniform physical and chemical properties, good agglutination, large specific surface area, strong adsorption, strong binding force with affinity ligands, proteins, dyes and other substances, and controllable particle size. They are widely used in immunomedicine, biochemistry, standard metrology, analytical chemistry and other fields.

[0003] Polystyrene microspheres are a common type of polymer microspheres, the main component of which is polystyrene. Early monodisperse polystyrene microspheres were all thermoplastic structures. Affected by the glass transition temperature of polystyrene itself (Tg≤105℃), the long-term use temperature of thermoplastic polystyrene microspheres is usually required to be lower than 80℃. Nowadays, some specific application environments, such as catalyst carriers and functional fillers, require polymer microspheres to have good heat resistance, and their working temperatures are often greater than 100℃, and some even require higher than 200℃. In order to meet the working temperature requirements, the cross-linking method is often used in the preparation of polystyrene microspheres. However, the cross-linked polystyrene microspheres prepared by the cross-linking method are thermosetting and can only be incinerated after use, and cannot be recycled and reused, which does not meet the current green environmental protection requirements; especially when it is used as a functional particle, it will spread its own non-recyclable and non-reusable characteristics to the entire material component, causing the original thermoplastic matrix to lose its recyclability, which in turn causes greater waste and environmental pollution. Moreover, when cross-linking polystyrene microspheres are prepared by a cross-linking method, it is usually necessary to add a cross-linking monomer during the polymerization process, thereby reducing the monodispersity of the polystyrene microspheres. Summary of the invention

[0004] The purpose of the present invention is to provide a high temperature resistant monodisperse thermoplastic polystyrene nano-scale microsphere and a preparation method thereof. The high temperature resistant monodisperse thermoplastic polystyrene nano-scale microsphere provided by the present invention has good thermoplasticity, monodispersity and heat resistance.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] A high temperature resistant monodisperse thermoplastic polystyrene nano-scale microsphere, comprising the following raw materials:

[0007] Styrene monomer, heat-resistant modified monomer, stabilizing monomer, free radical initiator, emulsifier and water; based on the total mass percentage of styrene monomer, heat-resistant modified monomer and stabilizing monomer as 100%, styrene monomer is 5% to 94.9%, heat-resistant modified monomer is 5% to 85%, and stabilizing monomer is 0.1% to 10%; the free radical initiator is 0.5% to 5% of the total mass of styrene monomer, heat-resistant modified monomer and stabilizing monomer, and the emulsifier is 0% to 2% of the total mass of styrene monomer, heat-resistant modified monomer and stabilizing monomer.

[0008] Preferably, the styrene monomers include styrene and / or α-methylstyrene.

[0009] Preferably, the heat-resistant modified monomer includes one or more of N-(1-phenylethyl)maleimide, N-methylmaleimide, N-phenylethylmaleimide, N-ethylmaleimide, N-phenylmaleimide and N-benzylmaleimide.

[0010] Preferably, the auxiliary stabilizing monomer includes one or more of acrylic acid, methacrylic acid, sodium acrylate, acrylonitrile, methacrylonitrile, acrylamide, N-isopropylacrylamide and N-benzylacrylamide.

[0011] Preferably, the free radical initiator includes one or more of potassium persulfate, ammonium persulfate, sodium persulfate and 2,2'-azo(2-methylpropylamidine) dihydrochloride.

[0012] Preferably, the emulsifier includes one or more of ammonium dodecyl sulfate, sodium dodecyl sulfate, sodium dodecylbenzene sulfonate and hexadecyltrimethylammonium bromide.

[0013] Preferably, the particle size of the high temperature resistant monodisperse thermoplastic polystyrene nano-scale microspheres is 100-600 nm, the coefficient of variation is 0.031-0.043, and the glass transition temperature is 113-184°C.

[0014] The present invention provides a method for preparing high temperature resistant monodisperse thermoplastic polystyrene nanoscale microspheres according to the above technical solution, comprising the following steps:

[0015] The raw materials of high temperature resistant monodisperse thermoplastic polystyrene nano-scale microspheres are mixed and polymerized to obtain the high temperature resistant monodisperse thermoplastic polystyrene nano-scale microspheres.

[0016] Preferably, the polymerization reaction temperature is 50 to 90° C.; the polymerization reaction time is 5 to 24 hours.

[0017] Preferably, the polymerization reaction is carried out under stirring conditions.

[0018] The present invention provides a high temperature resistant monodisperse thermoplastic polystyrene nanometer microsphere, comprising the following raw materials: styrene monomer, heat resistant modified monomer, auxiliary stabilizing monomer, free radical initiator, emulsifier and water; taking the total mass percentage of styrene monomer, heat resistant modified monomer and auxiliary stabilizing monomer as 100%, styrene monomer is 5% to 94.9%, heat resistant modified monomer is 5% to 85%, and auxiliary stabilizing monomer is 0.1% to 10%; free radical initiator is 0.5% to 5% of the total mass of styrene monomer, heat resistant modified monomer and auxiliary stabilizing monomer, and emulsifier is 0% to 2% of the total mass of styrene monomer, heat resistant modified monomer and auxiliary stabilizing monomer. The present invention adopts styrene monomer as the main raw material for preparing polystyrene microsphere; adopting heat resistant modified monomer can improve the glass transition temperature of polystyrene microsphere, thereby improving the heat resistance of polystyrene microsphere; adopting auxiliary stabilizing monomer can improve the stability of polystyrene microsphere; free radical initiator of the present invention is used to initiate and promote the polymerization reaction of monomer. The high temperature resistant monodisperse thermoplastic polystyrene nano-scale microspheres provided by the present invention have both the thermoplastic characteristics of thermoplastic polystyrene microspheres and the heat resistance characteristics of cross-linked polystyrene microspheres, while avoiding the problems that thermoplastic polystyrene cannot be used in high temperature occasions and that cross-linked polystyrene microspheres cannot be recycled after use. The microspheres have the characteristics of controllable particle size and monodispersity, and are environmentally friendly, high temperature resistant monodisperse thermoplastic polystyrene microspheres.

[0019] Furthermore, the present invention uses an emulsifier to stabilize the emulsion formed by mixing the raw materials, making the emulsion uniform.

[0020] Furthermore, the high temperature resistant monodisperse thermoplastic polystyrene nano-scale microspheres prepared by the present invention have a nano-scale particle size, good monodispersity, and controllable and uniform particle size.

[0021] Furthermore, the preparation method of the high temperature resistant monodisperse thermoplastic polystyrene nano-scale microspheres provided by the present invention is emulsion polymerization, which has the characteristics of simple preparation method, mild reaction conditions, and water as the medium, and has the characteristics of high preparation safety, low pollution, and environmental friendliness. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a scanning electron microscope photograph of the high temperature resistant monodisperse thermoplastic polystyrene nanoscale microspheres prepared in Example 1;

[0023] Figure 2 This is a scanning electron microscope photograph of the high temperature resistant monodisperse thermoplastic polystyrene nano-scale microspheres prepared in Example 2;

[0024] Figure 3 This is a scanning electron microscope photograph of the high temperature resistant monodisperse thermoplastic polystyrene nano-scale microspheres prepared in Example 3;

[0025] Figure 4This is a scanning electron microscope photograph of the high temperature resistant monodisperse thermoplastic polystyrene nano-scale microspheres prepared in Example 4;

[0026] Figure 5 This is a scanning electron microscope photograph of the high temperature resistant monodisperse thermoplastic polystyrene nanoscale microspheres prepared in Example 5. DETAILED DESCRIPTION

[0027] The present invention provides a high temperature resistant monodisperse thermoplastic polystyrene nano-scale microsphere, comprising the following raw materials:

[0028] Styrene monomer, heat-resistant modified monomer, stabilizing monomer, free radical initiator, emulsifier and water; based on the total mass percentage of styrene monomer, heat-resistant modified monomer and stabilizing monomer as 100%, styrene monomer is 5% to 94.9%, heat-resistant modified monomer is 5% to 85%, and stabilizing monomer is 0.1% to 10%; the free radical initiator is 0.5% to 5% of the total mass of styrene monomer, heat-resistant modified monomer and stabilizing monomer, and the emulsifier is 0% to 2% of the total mass of styrene monomer, heat-resistant modified monomer and stabilizing monomer.

[0029] In the present invention, unless otherwise specified, all preparation raw materials / components are commercially available products well known to those skilled in the art.

[0030] Taking the total mass percentage of styrene monomers, heat-resistant modified monomers and stabilizing monomers as 100%, the raw materials of the high-temperature resistant monodisperse thermoplastic polystyrene nano-microspheres of the present invention include 5% to 94.9% styrene monomers, further 30% to 90%, and specifically 50% to 80%.

[0031] As an embodiment of the present invention, the styrene-based monomer may include styrene and / or α-methylstyrene, specifically styrene or α-methylstyrene.

[0032] Taking the total mass percentage of styrene monomers, heat-resistant modified monomers and stabilizing monomers as 100%, the raw materials of the high-temperature resistant monodisperse thermoplastic polystyrene nano-scale microspheres of the present invention include 5% to 85% of heat-resistant modified monomers, further 9% to 60%, and specifically 20% to 45%.

[0033] As an embodiment of the present invention, the heat-resistant modified monomer may include one or more of N-(1-phenylethyl)maleimide, N-methylmaleimide, N-phenylethylmaleimide, N-ethylmaleimide, N-phenylmaleimide and N-benzylmaleimide; when there are two heat-resistant modified monomers, specifically, N-benzylmaleimide and N-(1-phenylethyl)maleimide are mixed, and the mixed mass ratio is 29.5:20 or N-phenylmaleimide and N-methylmaleimide are mixed, and the mixed mass ratio is 28:30.

[0034] Taking the total mass percentage of styrene monomers, heat-resistant modified monomers and stabilizing monomers as 100%, the raw materials of the high-temperature resistant monodisperse thermoplastic polystyrene nano-scale microspheres of the present invention include 0.1% to 10% of stabilizing monomers, specifically 0.1% to 5%.

[0035] As an embodiment of the present invention, the auxiliary stabilizing monomer may include one or more of acrylic acid, methacrylic acid, sodium acrylate, acrylonitrile, methacrylonitrile, acrylamide, N-isopropylacrylamide and N-benzylacrylamide.

[0036] The present invention mixes a heat-resistant modified monomer and a stabilizing monomer with a styrene monomer, and the heat-resistant modified monomer and the stabilizing monomer play a synergistic role together, thereby improving the heat resistance of polystyrene microspheres while improving chemical stability; the range of the particle size distribution of the polystyrene microspheres can also be reduced, and the particle size of the polystyrene microspheres is controlled to be nanometer-level, which is beneficial to improving the monodispersity of the polystyrene microspheres.

[0037] The raw materials of the high temperature resistant monodisperse thermoplastic polystyrene nano-scale microspheres of the present invention include free radical initiators, which account for 0.5% to 5% of the total mass of styrene monomers, heat-resistant modified monomers and stabilizing monomers, and specifically 0.5% to 3%.

[0038] As an embodiment of the present invention, the free radical initiator may include one or more of potassium persulfate, ammonium persulfate, sodium persulfate and 2,2'-azo(2-methylpropylamidine) dihydrochloride.

[0039] The raw materials of the high temperature resistant monodisperse thermoplastic polystyrene nano-scale microspheres of the present invention include an emulsifier, which accounts for 0% to 2% of the total mass of styrene monomers, heat-resistant modified monomers and stabilizing monomers, and specifically can be 0% to 1%.

[0040] As an embodiment of the present invention, the emulsifier may include one or more of ammonium dodecyl sulfate, sodium dodecyl sulfate, sodium dodecylbenzene sulfonate and hexadecyltrimethylammonium bromide.

[0041] The raw material of the high temperature resistant monodisperse thermoplastic polystyrene nano-scale microspheres of the present invention includes water.

[0042] As an embodiment of the present invention, the mass ratio of water to the styrene monomer, the heat-resistant modified monomer and the stabilizing monomer can be 20:1 to 1:1, specifically 3:1.

[0043] As an embodiment of the present invention, the particle size of the high temperature resistant monodisperse thermoplastic polystyrene nano-scale microspheres can be 100-600 nm, specifically 180-336 nm; the coefficient of variation can be 0.031-0.043, and the glass transition temperature can be 113-184°C.

[0044] The present invention provides a method for preparing high temperature resistant monodisperse thermoplastic polystyrene nanoscale microspheres according to the above technical solution, comprising the following steps:

[0045] The raw materials of high temperature resistant monodisperse thermoplastic polystyrene nano-scale microspheres are mixed and polymerized to obtain the high temperature resistant monodisperse thermoplastic polystyrene nano-scale microspheres.

[0046] As an embodiment of the present invention, the mixing may include: first mixing styrene monomers, heat-resistant modified monomers and stabilizing monomers to obtain a first mixture; second mixing a free radical initiator, an emulsifier and water to obtain a second mixture (when no emulsifier is contained, the step of adding the emulsifier is omitted); third mixing the first mixture and the second mixture. The present invention has no special restrictions on the first mixing and the second mixing, and it is sufficient to mix the raw materials evenly. As an embodiment of the present invention, specifically, the first mixture is added to the second mixture for the third mixing; the third mixing is carried out under stirring conditions, and the stirring rate can be 100 to 500 rpm. The present invention has no special restrictions on the stirring time, and it is sufficient to stir evenly; in the embodiment of the present invention, an emulsion is obtained by the third mixing, and then the polymerization reaction is carried out.

[0047] As an embodiment of the present invention, the polymerization reaction temperature can be 50-90°C, specifically 70-90°C; the polymerization reaction time can be 5-24h, specifically 5-10h; the polymerization reaction can be carried out under stirring conditions, and the stirring rate can be 100-500rpm.

[0048] The temperature and time of the polymerization reaction of the present invention can promote the polymerization of monomers and increase the rate of the polymerization reaction; at the same time, the particle size of the polystyrene microspheres can be controlled to be nanometer-level, so that the particle size of the obtained polystyrene microspheres is uniform, which is beneficial to improving the monodispersity of the polystyrene microspheres.

[0049] As an embodiment of the present invention, after the polymerization reaction is completed, a drying operation may be performed, and the drying operation may be drying in a blast oven, and the drying temperature may be 70°C.

[0050] In order to further illustrate the present invention, the technical solutions provided by the present invention are described in detail below in conjunction with embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0051] Example 1

[0052] 90 g of styrene, 9 g of N-phenylmaleimide and 1 g of acrylic acid were mixed evenly and added into 300 g of water containing 1 g of potassium persulfate to form an emulsion under the action of mechanical stirring; the emulsion was heated to 80° C., free radical polymerization was carried out for 6 hours at a stirring rate of 300 rpm, and dried in a forced air oven at 70° C. to obtain high temperature resistant monodisperse thermoplastic polystyrene nano-scale microspheres.

[0053] Figure 1 This is a scanning electron microscope photograph of the high temperature resistant monodisperse thermoplastic polystyrene nanoscale microspheres prepared in Example 1. Figure 1 The characterization results showed that the average particle size of the obtained microspheres was 320 nm, the CV value was 0.034, and they were highly monodisperse. The glass transition temperature was 113 °C.

[0054] Example 2

[0055] 70 g of styrene, 29 g of N-phenylethylmaleimide and 1 g of methacrylic acid were mixed evenly and added into 300 g of water containing 0.5 g of potassium persulfate to form an emulsion under the action of mechanical stirring; the emulsion was heated to 70° C., free radical polymerization was carried out for 10 hours at a stirring rate of 250 rpm, and dried in a blast oven at 70° C. to obtain high temperature resistant monodisperse thermoplastic polystyrene nano-scale microspheres.

[0056] Figure 2 This is a scanning electron microscope photograph of the high temperature resistant monodisperse thermoplastic polystyrene nanoscale microspheres prepared in Example 2. Figure 2 The characterization results showed that the average particle size of the obtained microspheres was 336 nm, the CV value was 0.031, and they were highly monodisperse. The glass transition temperature was 141 °C.

[0057] Example 3

[0058] 60 g of α-methylstyrene, 39 g of N-benzylmaleimide and 1 g of methacrylic acid were mixed evenly and added into 300 g of water containing 1 g of potassium persulfate and 1 g of sodium dodecyl sulfate to form an emulsion under the action of mechanical stirring; the emulsion was heated to 90° C., free radical polymerization was carried out for 5 h at a stirring rate of 200 rpm, and dried in a blast oven at 70° C. to obtain high temperature resistant monodisperse thermoplastic polystyrene nano-scale microspheres.

[0059] Figure 3 This is a scanning electron microscope photograph of the high temperature resistant monodisperse thermoplastic polystyrene nanoscale microspheres prepared in Example 3. Figure 3 The characterization results showed that the average particle size of the obtained microspheres was 180 nm, the CV value was 0.043, and they were highly monodisperse. The glass transition temperature was 155°C.

[0060] Example 4

[0061] 50 g of styrene, 29.5 g of N-benzylmaleimide, 20 g of N-(1-phenylethyl)maleimide and 0.5 g of methacrylic acid were uniformly mixed and added into 300 g of water containing 1 g of potassium persulfate and 1 g of sodium dodecylbenzenesulfonate to form an emulsion under the action of mechanical stirring; the emulsion was heated to 80° C., free radical polymerization was carried out for 8 hours at a stirring rate of 400 rpm, and the emulsion was dried in a blast oven at 70° C. to obtain high temperature resistant monodisperse thermoplastic polystyrene nano-scale microspheres.

[0062] Figure 4 This is a scanning electron microscope photograph of the high temperature resistant monodisperse thermoplastic polystyrene nanoscale microspheres prepared in Example 4. Figure 4 Characterization results show that the average particle size of the obtained microspheres is 250nm, the CV value is 0.035, and they are highly monodisperse. The glass transition temperature is 170℃.

[0063] Example 5

[0064] 40g of styrene, 28g of N-phenylmaleimide, 30g of N-methylmaleimide and 2g of methacrylic acid were mixed evenly and added into 300g of water containing 1g of potassium persulfate and 0.5g of sodium dodecylbenzene sulfonate to form an emulsion under the action of mechanical stirring; the emulsion was heated to 80°C, free radical polymerization was carried out for 8h at a stirring rate of 300rpm, and dried in a blast oven at 70°C to obtain high temperature resistant monodisperse thermoplastic polystyrene nano-scale microspheres.

[0065] Figure 5 This is a scanning electron microscope photograph of the high temperature resistant monodisperse thermoplastic polystyrene nanoscale microspheres prepared in Example 5. Figure 5The characterization results showed that the average particle size of the obtained microspheres was 206 nm, the CV value was 0.040, and they were highly monodisperse. The glass transition temperature was 184 °C.

[0066] According to the characterization results of Examples 1 to 5 of the present invention, the average particle size of the high temperature resistant monodisperse thermoplastic polystyrene nano-scale microspheres prepared by the preparation method of the present invention is a nano-scale particle size, the particle size range is 180 to 336 nm, and the value range of the coefficient of variation is 0.031 to 0.043, and the CV value is very small, indicating that the particle size of the high temperature resistant monodisperse thermoplastic polystyrene nano-scale microspheres is uniform and has good monodispersity. The glass transition temperature range of the prepared high temperature resistant monodisperse thermoplastic polystyrene nano-scale microspheres is 113 to 184 ° C, which is higher than the glass transition temperature Tg≤105 ° C of polystyrene itself, indicating that the heat resistance of the high temperature resistant monodisperse thermoplastic polystyrene nano-scale microspheres prepared by the present invention is significantly improved, which has a decisive influence on the application of the microspheres in high temperature molding plastic film additives and the like. The use of high temperature resistant monodisperse thermoplastic polystyrene nano-scale microspheres not only improves the performance of the film, but also well maintains its original thermoplasticity, which is of great significance for green production and recycling of products after use.

[0067] The embodiments described above are only descriptions of the preferred implementation modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should fall within the protection scope determined by the claims of the present invention.

Claims

1. A high temperature resistant monodisperse thermoplastic polystyrene nano-scale microsphere comprising the following raw materials: Styrene monomer, heat-resistant modified monomer, stabilizing monomer, free radical initiator, emulsifier and water; based on the total mass percentage of styrene monomer, heat-resistant modified monomer and stabilizing monomer as 100%, styrene monomer is 5% to 94.9%, heat-resistant modified monomer is 5% to 85%, and stabilizing monomer is 0.1% to 10%; free radical initiator is 0.5% to 5% of the total mass of styrene monomer, heat-resistant modified monomer and stabilizing monomer, and emulsifier is 0% to 2% of the total mass of styrene monomer, heat-resistant modified monomer and stabilizing monomer.

2. The high temperature resistant monodisperse thermoplastic polystyrene nano-scale microspheres according to claim 1, characterized in that: The styrene monomers include styrene and / or α-methylstyrene.

3. The high temperature resistant monodisperse thermoplastic polystyrene nano-scale microspheres according to claim 1, characterized in that: The heat-resistant modified monomer includes one or more of N-(1-phenylethyl)maleimide, N-methylmaleimide, N-phenylethylmaleimide, N-ethylmaleimide, N-phenylmaleimide and N-benzylmaleimide.

4. The high temperature resistant monodisperse thermoplastic polystyrene nano-scale microspheres according to claim 1, characterized in that: The auxiliary stabilizing monomer includes one or more of acrylic acid, methacrylic acid, sodium acrylate, acrylonitrile, methacrylonitrile, acrylamide, N-isopropylacrylamide and N-benzylacrylamide.

5. The high temperature resistant monodisperse thermoplastic polystyrene nano-scale microspheres according to claim 1, characterized in that: The free radical initiator includes one or more of potassium persulfate, ammonium persulfate, sodium persulfate and 2,2'-azo(2-methylpropylamidine) dihydrochloride.

6. The high temperature resistant monodisperse thermoplastic polystyrene nano-scale microspheres according to claim 1, characterized in that: The emulsifier includes one or more of ammonium dodecyl sulfate, sodium dodecyl sulfate, sodium dodecylbenzene sulfonate and hexadecyltrimethylammonium bromide.

7. The high temperature resistant monodisperse thermoplastic polystyrene nano-scale microspheres according to any one of claims 1 to 6, characterized in that: The particle size of the high temperature resistant monodisperse thermoplastic polystyrene nano-scale microspheres is 100-600nm, the coefficient of variation is 0.031-0.043, and the glass transition temperature is 113-184°C.

8. The method for preparing the high temperature resistant monodisperse thermoplastic polystyrene nano-scale microspheres according to any one of claims 1 to 7, comprising the following steps: The raw materials of high temperature resistant monodisperse thermoplastic polystyrene nano-scale microspheres are mixed and polymerized to obtain the high temperature resistant monodisperse thermoplastic polystyrene nano-scale microspheres.

9. The preparation method according to claim 8, characterized in that: The polymerization reaction temperature is 50-90° C., and the polymerization reaction time is 5-24 hours.

10. The preparation method according to claim 9, characterized in that: The polymerization reaction is carried out under stirring conditions.

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