A method for preparing core-shell rubber particles with magnetic function

Abstract

The application belongs to the technical field of polymer material preparation, and discloses a preparation method of core-shell rubber particles with magnetic function, which comprises the following steps: (1) preparing primary emulsion W11 / O1 and primary emulsion W12 / O1; (2) adding into deionized water in which emulsifier E2 is dispersed in advance to obtain a latex particle beam wrapping magnetic particles Fe3O4; (3) dropping the prepared grafting acrylate monomer mixture oil phase O2 to graft acrylate monomers on the outer layer of the latex particle beam wrapping magnetic particles Fe3O4; (4) removing the trichloromethane and dichloromethane solvents through condensation reflux, and then filtering, cleaning and drying the product to obtain the final product. The core-shell rubber particles with magnetic function have a core-shell structure, can provide excellent impact strength, and avoid many problems such as uneven dispersion and stratified settlement in the later use or storage process.

Description

Technical Field

[0001] This invention relates to a method for preparing core-shell rubber particles with magnetic properties, belonging to the field of polymer material preparation technology. Background Technology

[0002] Iron(III) oxide (Fe3O4), as a traditional magnetic material, has the advantages of high magnetic permeability, high absorption intensity, and simple preparation. However, it also has some disadvantages, such as easy particle agglomeration, and problems such as sedimentation and uneven dispersion when used directly in adhesives and coatings. These disadvantages limit its further application. Summary of the Invention

[0003] To address the shortcomings of existing technologies, this invention provides a method for preparing core-shell rubber particles with magnetic properties. The particle size is adjustable from 0.5 to 50 μm. When applied to conventional polymer structural materials, it can not only prevent brittle fracture and improve the toughness of the material, but also has the magnetic properties of iron(III) oxide. Furthermore, when dispersed in acrylate monomers, it has the advantage of preventing sedimentation.

[0004] To achieve the above objectives, the technical solution adopted is:

[0005] The purpose of this invention is to provide a method for preparing core-shell rubber particles with magnetic properties, comprising the following steps:

[0006] (1) Use deionized water to prepare an aqueous solution of FeCl2 and FeCl3 as the aqueous phase W11, use deionized water to prepare an aqueous solution of NaOH and reducing agent as the aqueous phase W12, and use chloroform and dichloromethane to prepare a rubber latex as the oil phase O1; mix the aqueous phase W11 and the oil phase O1, add emulsifier E1, and control the rotation speed, temperature and time to prepare a primary emulsion W11 / O1; mix the aqueous phase W12 and the oil phase O1, add emulsifier E1, and control the rotation speed, temperature and time to prepare a primary emulsion W12 / O1;

[0007] (2) Add the primary emulsion W11 / O1 and primary emulsion W12 / O1 to deionized water in which emulsifier E2 has been dispersed in advance, and after heating and reacting, latex particle bundles encapsulating magnetic particles Fe3O4 are obtained.

[0008] (3) Add the pre-prepared oil phase O2 of grafted acrylate monomer mixture to the latex particle bundles containing magnetic Fe3O4 particles described in step (2), control the reaction temperature, and graft acrylate monomers onto the outer layer of the latex particle bundles containing magnetic Fe3O4 particles; wherein, the preparation process of the oil phase O2 includes the following steps: dissolving the acrylate monomers and initiator in a mixed solution of chloroform and dichloroform;

[0009] (4) Heat to 60-100℃ and reflux to remove chloroform and dichloromethane solvents. Then filter, wash and dry the product to obtain the final product.

[0010] Further, in step (1), the mass ratio of FeCl2, FeCl3, and deionized water in aqueous phase W11 is 27-45:13-15:40-60; the mass ratio of NaOH, deionized water, and reducing agent in aqueous phase W12 is 20-45:52-79.5:0.5-3; the mass ratio of chloroform, dichloromethane, and rubber latex in oil phase O1 is 23-60:30-47:10-30; the mass ratio of aqueous phase W11, oil phase O1, and emulsifier E1 is 10-40:55-89:1-5; and the mass ratio of aqueous phase W12, oil phase O1, and emulsifier E1 is 10-45:50-89:1-5.

[0011] The beneficial effects of adopting the above technical solution are as follows: the role of emulsifier E1 is to make W11 and W12 exist stably in O1 and O2. The purpose of selecting trichloromethane and dichloromethane for oil phase O1 is to adjust the stability of oil phase O1 in W2 based on the difference in density extractability between the two.

[0012] Furthermore, the reducing agent is at least one of N,N-dimethyl-p-toluidine, tetramethylthiourea, and aldehyde-amine condensate; the rubber latex is at least one of natural rubber latex, epoxidized natural rubber latex, nitrile rubber latex, and acrylate latex; and the emulsifier E1 is at least one of sucrose fatty acid ester, polyglycerol fatty acid ester, and polyoxyethylene castor oil.

[0013] The beneficial effect of adopting the above technical solution is that the reducing agent promotes the decomposition of the initiator to generate free radicals, which initiates the grafting of acrylate monomers onto the latex particles that encapsulate the magnetic particles.

[0014] Furthermore, in step (1), the stirring speed is 500-1000 rpm / min, the temperature is 20-30℃, and the time is 10-30 min.

[0015] Furthermore, step (2) also includes the following steps: mixing deionized water and emulsifier E2 in advance at a stirring speed of 500-1000 rpm / min, a temperature of 20-30℃, and a time of 10-30 min, wherein the mass ratio of deionized water to emulsifier E2 is 95-99:1-5, and is denoted as W2; the mass ratios of W11 / O1, W12 / O1, and W2 are 10-20:10-20:60-80 respectively; the emulsifier E2 is at least one of glyceryl stearate PEG-100, Croda A165 emulsifier, ABIL CARE 85 siloxane emulsifier, EG emulsifier, Pruitsen 721 emulsifier, and BASF A25 emulsifier.

[0016] The beneficial effects of adopting the above technical solution are as follows: the role of emulsifier E2 is to make W11 / O1 and W12 / O1 exist stably in W2, and to prevent W11 and W12 from demulsifying in O1 and O2 respectively. At the same time, adjusting the ratio of (W11 / O1) and (W12 / O1) can control the content of magnetic Fe3O4 particles in latex particles.

[0017] Furthermore, in step (2), the temperature of the heating reaction is 40-70°C and the reaction time is 10-90 min.

[0018] Furthermore, step (3) also includes the following steps: chloroform, dichloromethane, acrylate monomer, and initiator are mixed in advance and designated as oil phase O2, with a stirring speed of 500–1000 rpm / min, a temperature of 20–30°C, and a time of 10–30 min. The mass ratio of chloroform, dichloromethane, acrylate monomer, and initiator in the oil phase O2 is 14–25: 26–49: 25–55: 1–5. The mixed oil phase O2 is then added dropwise to the latex particle bundles encapsulating magnetic Fe3O4 particles while stirring at a speed of 500–1000 rpm / min. The temperature of the latex particle bundles encapsulating magnetic Fe3O4 particles is 30–60°C during the dropwise addition.

[0019] Furthermore, the mass ratio of W11 / O1, W12 / O1, and W2 to the oil phase O2 is 60-80:20-40; the acrylate monomer is at least one of styrene (St), acrylonitrile (AN), and methyl methacrylate (MMA); and the initiator is at least one of benzoyl peroxide and cumene hydroperoxide.

[0020] The beneficial effects of adopting the above technical solution are as follows: the purpose of this reaction step is to graft acrylate monomers onto the outer layer of the latex particle bundles that encapsulate magnetic Fe3O4 particles. In this step, the purpose of using chloroform and dichloromethane in the oil phase O2 is to adjust the stability of the oil phase O2 in W2 based on the difference in their density extractability.

[0021] Furthermore, the cleaning in step (4) involves first washing the product with anhydrous ethanol 1 to 2 times, and then washing it with deionized water 3 to 4 times. The drying is carried out at 80°C for 2 hours.

[0022] The beneficial effect of adopting the above technical solution is that the purpose of using anhydrous ethanol for cleaning is to remove the excess unreacted acrylate monomers in step (3).

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0024] The magnetic core-shell rubber particles prepared by this invention not only have a core-shell structure, providing excellent impact resistance, but also differ from conventional magnetic materials and polymer resin physical blends. The inorganic magnetic particles in this invention are formed by the rubber core-shell structure being encapsulated during the emulsification grafting process, avoiding many problems such as uneven dispersion and stratification during later use or storage. Detailed Implementation

[0025] The principles and features of the present invention are described below. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0026] Example 1

[0027] First, weigh out 25.2g of FeCl2, 12.6g of FeCl3, and 52.2g of deionized water. Stir at 600 rpm / min and 25°C for 15 minutes, and record this as W11 for later use. Next, weigh out 22.4g of NaOH, 69.5g of deionized water, and 0.82g of N,N-dimethyl-p-toluidine. Stir at 600 rpm / min and 25°C for 15 minutes, and record this as W12 for later use. Then, weigh out 500g of chloroform, 300g of dichloromethane, and 200g of natural rubber latex. Stir at 600 rpm / min and 25°C for 15 minutes, and record this as O1 for later use. Finally, weigh out 85g of W11, 490g of O1, and 12g of sucrose fatty acid ester. Stir at 600 rpm / min... At a speed of 600 rpm / min and a temperature of 25℃, stir for 15 min and record as W11 / O1 for later use. Weigh out 100 g of W12, 480 g of O1, and 12 g of polyglycerol fatty acid ester, and stir at a speed of 600 rpm / min and a temperature of 25℃ for 15 min, and record as W12 / O1 for later use. In the second step, weigh out 3590 g of deionized water and 108 g of glycerol stearate PEG-100, and stir at a speed of 600 rpm / min and a temperature of 25℃ for 15 min, and record as W2 for later use. Weigh out 580 g of (W11 / O1), 580 g of (W12 / O1), and 2000 g of W2, and stir at a speed of 800 rpm / min and a temperature of 50℃ for 20 min to obtain a latex particle bundle encapsulating magnetic Fe3O4 particles. The third step involves weighing 200g of chloroform, 400g of dichloroform, 360g of styrene (St), and 36g of benzoyl peroxide. Stir at 600 rpm / min and 25°C for 15 minutes, recording this as O2 for later use. Then, take 900g of O2 and add it dropwise to the product from the second step while stirring at 800 rpm / min. The material temperature during addition is 45°C. This product is an acrylate monomer grafted onto the outer layer of latex particle bundles encapsulating magnetic Fe3O4 particles. The fourth step involves heating the product from the third step to 80°C and refluxing to remove the chloroform and dichloroform solvents. The product is then filtered, washed twice with anhydrous ethanol, and then three times with deionized water. Finally, it is dried at 80°C for 2 hours to obtain the final product.

[0028] Example 2

[0029] Step 1: Weigh out 25.8g of FeCl2, 12.0g of FeCl3, and 52.2g of deionized water. Stir at 600 rpm / min and 25℃ for 15 minutes, and record as W11 for later use. Weigh out 23.9g of NaOH, 68g of deionized water, and 2.2g of tetramethylthiourea. Stir at 600 rpm / min and 25℃ for 15 minutes, and record as W12 for later use. Weigh out 400g of chloroform, 400g of dichloromethane, and 200g of nitrile rubber latex. Stir at 600 rpm / min and 25℃ for 15 minutes, and record as O1 for later use. Weigh out 80g of W11, 485g of O1, and 12g of polyglycerol fatty acid ester. Stir at 600 rpm / min... For the first step, at a temperature of 25℃, stir for 15 minutes and record as W11 / O1 for later use. Weigh out 100g of W12, 480g of O1, and 12g of polyglycerol fatty acid ester, and stir at a speed of 600rpm / min and a temperature of 25℃ for 15 minutes, and record as W12 / O1 for later use. For the second step, weigh out 3590g of deionized water and 108g of Pruison 721 emulsifier, and stir at a speed of 600rpm / min and a temperature of 25℃ for 15 minutes, and record as W2 for later use. Weigh out 580g of (W11 / O1), 580g of (W12 / O1), and 2000g of W2, and stir at a speed of 800rpm / min and a temperature of 50℃ for 20 minutes to obtain a latex particle bundle encapsulating magnetic Fe3O4 particles. The third step involves weighing 200g of chloroform, 400g of dichloroform, 360g of acrylonitrile AN, and 36g of cumene hydrogen peroxide. The mixture is stirred at 600 rpm / min and 25°C for 15 minutes, and this mixture is recorded as O2 for later use. 900g of O2 is then added dropwise to the product from the second step while stirring at 800 rpm / min. The material temperature during addition is 45°C. This product is composed of latex particle bundles coated with magnetic Fe3O4 particles grafted with acrylate monomers. The fourth step involves heating the product from the third step to 80°C and refluxing it to remove the chloroform and dichloroform solvents. The product is then filtered, washed twice with anhydrous ethanol, and then three times with deionized water. Finally, it is dried at 80°C for 2 hours to obtain the final product.

[0030] Example 3

[0031] Step 1: Weigh out 24g of FeCl2, 13.8g of FeCl3, and 52.2g of deionized water. Stir at 600 rpm / min and 25°C for 15 minutes, and record this as W11 for later use. Weigh out 23g of NaOH, 68.9g of deionized water, and 0.82g of N,N-dimethyl-p-toluidine. Stir at 600 rpm / min and 25°C for 15 minutes, and record this as W12 for later use. Weigh out 450g of chloroform, 350g of dichloromethane, and 200g of acrylate emulsion. Stir at 600 rpm / min and 25°C for 15 minutes, and record this as O1 for later use. Weigh out 85g of W11, 490g of O1, and 12g of polyoxyethylene castor oil. Stir at 600 rpm / min for 15 minutes, and record this as O1 for later use. Stir at 600 rpm / min and 25℃ for 15 min, and record as W11 / O1 for later use; weigh out W12: 100 g, O1: 480 g, and polyglycerol fatty acid ester: 12 g, stir at 600 rpm / min and 25℃ for 15 min, and record as W12 / O1 for later use; in the second step, weigh out deionized water: 3590 g and BASF A25 emulsifier: 108 g, stir at 600 rpm / min and 25℃ for 15 min, and record as W2 for later use; weigh out (W11 / O1): 580 g, (W12 / O1): 580 g, and W2: 2000 g, stir at 800 rpm / min and 50℃ for 20 min, and obtain the product as a latex particle bundle encapsulating magnetic Fe3O4 particles. The third step involves weighing 180g of chloroform, 450g of dichloromethane, 360g of methyl methacrylate (MMA), and 36g of benzoyl peroxide. The mixture is stirred at 600 rpm / min and 25°C for 15 minutes, and this mixture is recorded as O2 for later use. 900g of O2 is then added dropwise to the product from the second step while stirring at 800 rpm / min. The material temperature during addition is 45°C. This product is composed of latex particle bundles coated with magnetic Fe3O4 particles grafted with acrylate monomers. The fourth step involves heating the product from the third step to 80°C and refluxing it to remove the chloroform and dichloromethane solvents. The product is then filtered, washed twice with anhydrous ethanol, and then three times with deionized water. Finally, it is dried at 80°C for 2 hours to obtain the final product.

[0032] Comparative Example 1

[0033] First, weigh out 26g of FeCl2, 15.2g of FeCl3, and 62g of deionized water. Stir at 600 rpm / min and 25°C for 15 minutes, and record this as W11 for later use. Next, weigh out 26g of NaOH and 68.9g of deionized water. Stir at 600 rpm / min and 25°C for 15 minutes, and record this as W12 for later use. Then, weigh out 200g of trichloromethane and 420g of dichloromethane. Stir at 600 rpm / min and 25°C for 15 minutes, and record this as O1 for later use. Finally, weigh out 85g of W11, 490g of O1, and 12g of polyoxyethylene castor oil. Stir at 600 rpm / min and 25°C for... For the first step, weigh out W12: 100g, O1: 480g, and polyglycerol fatty acid ester: 12g, and stir at 600rpm / min and 25℃ for 15min, then record it as W12 / O1 for later use. For the second step, weigh out deionized water: 3590g and BASF A25 emulsifier: 120g, and stir at 600rpm / min and 25℃ for 15min, then record it as W2 for later use. Weigh out (W11 / O1): 580g, (W12 / O1): 580g, and W2: 2000g, and stir at 800rpm / min and 50℃ for 20min to obtain a latex particle bundle encapsulating magnetic Fe3O4 particles. The third step involves heating the product from the second step to 80°C, condensing and refluxing to remove the chloroform and dichloromethane solvents, filtering the product, washing it twice with anhydrous ethanol, washing it three times with deionized water, and then drying it at 80°C for 2 hours to obtain the final product.

[0034] Comparative Example 2

[0035] Step 1: Weigh out 75g of deionized water and 1.0g of N,N-dimethyl-p-toluidine, and stir at 600 rpm / min and 25°C for 15 minutes. Record this as W1 for later use. Weigh out 450g of chloroform, 350g of dichloromethane, and 250g of acrylate emulsion, and stir at 600 rpm / min and 25°C for 15 minutes. Record this as O1 for later use. Weigh out 90g of W1, 500g of O1, and 12g of polyoxyethylene castor oil, and stir at a speed of... First, stir at 600 rpm / min and 25℃ for 15 min, and record this as W1 / O1 for later use. Second, weigh 3590 g of deionized water and 120 g of BASF A25 emulsifier, and stir at 600 rpm / min and 25℃ for 15 min, and record this as W2 for later use. Weigh 600 g of W1 / O1 and 2000 g of W2, and stir at 800 rpm / min and 50℃ for 20 min to obtain a latex particle bundle encapsulating the reducing agent. Third step: Weigh out 170g of chloroform, 420g of dichloromethane, 360g of methyl methacrylate (MMA), and 36g of benzoyl peroxide. Stir at 60 rpm / min and 25°C for 15 minutes, recording this as O2 for later use. Take 900g of O2 and add it dropwise to the product from step two while stirring at 800 rpm / min. The material temperature during addition is 45°C. This product is latex particle bundles grafted with acrylate monomers. Fourth step: Heat the product from step three to 80°C and reflux to remove the chloroform and dichloromethane solvents. Filter the product, wash it twice with anhydrous ethanol, then wash it three times with deionized water, and finally dry it at 80°C for 2 hours to obtain the final product.

[0036] Specific experimental verification plan:

[0037] In conducting specific experiments to verify the formulation, in order to more fully compare it with the Fe3O4 inorganic particles synthesized in Comparative Example 1 and the core-shell rubber particles synthesized in Comparative Example 2, commercially available Fe3O4 inorganic particles were selected as blank group 1, and commercially available Zhongyuan core-shell rubber particles M521 were selected as blank group 2. The formulations are shown in Table 1:

[0038] Table 1.

[0039] raw material Blank Group 1 Comparison Group 1 Blank Group 2 Comparison Group 2 Experimental group 1 Experimental group 2 Experimental group 3 Isoborneol acrylate 80 80 80 80 80 80 80 Commercially available Fe3O4 inorganic particles 20 - - - - - - Comparative Example 1: Synthesis of Inorganic Particles - 20 - - - - - Commercially available Zhongyuan core-shell rubber particles M521 - - 20 - - - - Comparative Example 2: Synthesis of Core-Shell Rubber Particles - - - 20 - - - In Embodiment 1 of this patent, magnetic core-shell rubber particles - - - - 20 - - In Embodiment 2 of this patent, magnetic core-shell rubber particles - - - - - 20 - In Embodiment 3 of this patent, magnetic core-shell rubber particles - - - - - - 20 total 100 100 100 100 100 100 100

[0040] The magnet adsorption and storage stability experiments were conducted sequentially, and the test data are shown in Table 2 below:

[0041] Table 2.

[0042] Experiment number Magnet adsorption Storage stability Blank Group 1 Fe3O4 adsorption and aggregation Fe3O4 precipitates at room temperature for 12 hours. Comparison Group 1 Synthesized inorganic particles adsorption and aggregation Inorganic particles settle at room temperature for 12 hours. Blank Group 2 No change No sedimentation after 7 days of storage at 40 degrees Celsius. Comparison Group 2 No change No sedimentation after 7 days of storage at 40 degrees Celsius. Experimental group 1 Adsorption and aggregation of core-shell rubber particles No sedimentation after 7 days of storage at 40 degrees Celsius. Experimental group 2 Adsorption and aggregation of core-shell rubber particles No sedimentation after 7 days of storage at 40 degrees Celsius. Experimental group 3 Adsorption and aggregation of core-shell rubber particles No sedimentation after 7 days of storage at 40 degrees Celsius.

[0043] As can be seen from the table above, the core-shell rubber particles with magnetic function prepared by this invention not only have magnetic function, but also differ from the conventional physical blending of magnetic materials and polymer resins. The inorganic magnetic particles in this invention are formed by the rubber core-shell structure being encapsulated during the emulsification and grafting process, which avoids many problems such as uneven dispersion and stratification during later use or storage.

[0044] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing core-shell rubber particles with magnetic properties, characterized in that, Includes the following steps: (1) Use deionized water to prepare an aqueous solution of FeCl2 and FeCl3 as the aqueous phase W11, use deionized water to prepare an aqueous solution of NaOH and reducing agent as the aqueous phase W12, and use chloroform and dichloromethane to prepare a rubber latex as the oil phase O1; mix the aqueous phase W11 and the oil phase O1, add emulsifier E1, and control the rotation speed, temperature and time to prepare a primary emulsion W11 / O1; mix the aqueous phase W12 and the oil phase O1, add emulsifier E1, and control the rotation speed, temperature and time to prepare a primary emulsion W12 / O1; (2) Add the primary emulsion W11 / O1 and primary emulsion W12 / O1 to deionized water in which emulsifier E2 has been dispersed in advance, and after heating and reacting, latex particle bundles encapsulating magnetic particles Fe3O4 are obtained. (3) Add the pre-prepared oil phase O2 of grafted acrylate monomer mixture to the latex particle bundles containing magnetic Fe3O4 as described in step (2), control the reaction temperature, and graft acrylate monomers onto the outer layer of the latex particle bundles containing magnetic Fe3O4; wherein, the preparation process of the oil phase O2 includes the following steps: dissolving the acrylate monomers and initiator in a mixed solution of chloroform and dichloromethane; (4) Heat to 60-100℃ and reflux to remove chloroform and dichloromethane solvents. Then filter, wash and dry the product to obtain the final product. In step (1), the mass ratio of FeCl2, FeCl3, and deionized water in aqueous phase W11 is 27-45:13-15:40-60; the mass ratio of NaOH, deionized water, and reducing agent in aqueous phase W12 is 20-45:52-79.5:0.5-3; the mass ratio of trichloromethane, dichloromethane, and rubber latex in oil phase O1 is 23-60:30-47:10-30; the mass ratio of aqueous phase W11, oil phase O1, and emulsifier E1 is 10-40:55-89:1-5; and the mass ratio of aqueous phase W12, oil phase O1, and emulsifier E1 is 10-45:50-89:1-5. The reducing agent is at least one of N,N-dimethyl-p-toluidine, tetramethylthiourea, and aldehyde-amine condensate; the rubber latex is at least one of natural rubber latex, epoxidized natural rubber latex, nitrile rubber latex, and acrylate latex; and the emulsifier E1 is at least one of sucrose fatty acid ester, polyglycerol fatty acid ester, and polyoxyethylene castor oil. Step (2) further includes the following steps: Pre-mix deionized water and emulsifier E2 at a stirring speed of 500–1000 rpm / min, a temperature of 20–30°C, and a time of 10–30 min, with the mass ratio of deionized water to emulsifier E2 being 95–99:1–5, and denoted as W2; the mass ratios of W11 / O1, W12 / O1, and W2 are respectively 10–20:10–20:60–80; the emulsifier E2 is at least one of glyceryl stearate PEG-100, Croda A165 emulsifier, ABIL CARE 85 siloxane emulsifier, EG emulsifier, Pruitsen 721 emulsifier, and BASF A25 emulsifier; Step (3) further includes the following steps: Pre-mixing chloroform, dichloromethane, acrylate monomers, and initiator at a stirring speed of 500–1000 rpm / min, a temperature of 20–30°C, and a time of 10–30 min, and designating this mixture as oil phase O2. The mass ratio of chloroform, dichloromethane, acrylate monomers, and initiator in oil phase O2 is 14–25: 26–49: 25–55: 1–5. The mixed oil phase O2... While stirring, the material is added dropwise to a latex particle bundle encapsulating magnetic Fe3O4 particles. The temperature of the latex particle bundle encapsulating Fe3O4 particles during the dropwise addition is 30-60℃. The mass ratio of W11 / O1, W12 / O1, and W2 to the oil phase O2 is 60-80:20-40. The acrylate monomer is at least one of styrene, acrylonitrile, and methyl methacrylate. The initiator is at least one of benzoyl peroxide and cumene hydroperoxide. The cleaning in step (4) involves first washing the product with anhydrous ethanol 1 to 2 times, and then washing it with deionized water 3 to 4 times. The drying is done at 80°C for 2 hours.