A micron-sized PA6 microsphere, preparation method and application

Abstract

The invention discloses a micron-sized PA6 microsphere, a preparation method and an application thereof. The preparation method comprises: adding a block copolymer of polyacrylamide and polyethylene oxide to molten caprolactam and stirring in the presence of vacuum or protective atmosphere; adding an initiator and removing water in vacuum, then adding an activator to carry out anionic ring-opening polymerization, and the experimental system undergoes a phase inversion to obtain a PA6 alloy; and washing after crushing to obtain micron-sized PA6 microspheres. The invention has no special equipment requirements, is simple, environmentally friendly, and has a high microsphere yield. The amount of the block copolymer is only 3 to 10 wt% of the total mass of the caprolactam and the block copolymer. The size of the prepared PA6 microspheres is controllable and has good application prospects.

Description

Technical Field

[0001] The invention belongs to the technical field of organic polymer materials, and specifically relates to micron-sized PA6 microspheres, a preparation method and applications thereof. Background Art

[0002] PA6 microspheres not only have high strength, wear resistance and excellent chemical resistance, but also contain amino, carboxyl and amide functional groups, which are easy to carry out functional treatments such as grafting. Therefore, PA6 microspheres have broad application prospects in powder spraying, sewage treatment, 3D printing, bioengineering and other fields.

[0003] At present, the preparation methods of PA6 microspheres can be summarized into two categories: physical method and chemical method. Among them, the physical method mainly includes mechanical crushing and solution precipitation. Among these methods, mechanical crushing has the disadvantages of high energy consumption, high processing cost, and irregular microsphere morphology; while solution precipitation generally requires the use of a large amount of organic solvents, and the operating conditions are harsh, and some processes need to be carried out under high temperature and high pressure. The chemical method mainly involves the use of caprolactam monomers to directly polymerize PA6 microspheres, which mainly includes precipitation polymerization, emulsion polymerization, suspension polymerization, and reaction-induced phase separation. However, the above-mentioned chemical method has a complex process, a very low microsphere yield, and the post-processing process also requires a large amount of organic solvents, which pollutes the environment. For example, the publication number CN101077910A proposes to prepare nylon microspheres by a dual in-situ reaction-induced phase separation method, but this method requires two-step reactions of styrene free radical polymerization and caprolactam anion polymerization, which takes a long time. In addition, a large amount of toxic solvents are required in the subsequent removal of the polystyrene phase, which is time-consuming and energy-consuming, and the processing cost is high and not environmentally friendly. Summary of the invention

[0004] The first object of the present invention is to provide an efficient preparation method of micron-sized PA6 microspheres in order to overcome the defects of the prior art.

[0005] The second object of the present invention is to provide a micron-sized PA6 microsphere prepared by the above method. To achieve the above object, the present invention adopts the following technical solution:

[0006] A method for preparing micron-sized PA6 microspheres comprises the following steps:

[0007] (1) adding a block copolymer of polyacrylamide and polyethylene oxide to molten caprolactam under vacuum or protective atmosphere, and stirring magnetically at 70 to 90° C. for 20 to 40 minutes to obtain a mixed solution;

[0008] (2) adding an initiator to the mixed solution obtained in step (1), and performing vacuum dehydration at 100 to 120° C.;

[0009] (3) adding an activator, and performing anionic ring-opening polymerization of caprolactam at 140-160° C. for 5-30 min, and the experimental system undergoes phase inversion to obtain a PA6 alloy;

[0010] (4) The PA6 alloy obtained in step (3) is crushed and immersed in deionized water or distilled water for thorough washing to obtain micron-sized PA6 microspheres.

[0011] In a further embodiment, the amount of the block copolymer of polyacrylamide and polyethylene oxide is 3-10 wt % of the total mass of all raw materials of caprolactam and the block copolymer of polyacrylamide and polyethylene oxide.

[0012] In a further embodiment, the initiator is an alkali metal hydride, an alkali metal hydroxide, an alkali metal alcoholate or an alkali metal carbonate, preferably sodium hydroxide.

[0013] In a further embodiment, the initiator is added in an amount of 0.5 to 1 wt% of the mass of caprolactam and block copolymer (block copolymer of polyacrylamide and polyethylene oxide); the activator is added in an amount of 0.5 to 1 wt% of the total mass of caprolactam and block copolymer (block copolymer of polyacrylamide and polyethylene oxide).

[0014] In a further embodiment, the activator is isocyanate, acyl chloride, acid anhydride or acyl caprolactam, preferably toluene diisocyanate.

[0015] In a further embodiment, the washing time is 24 to 48 hours.

[0016] In a further embodiment, the protective atmosphere is at least one of hydrogen, argon, methane and nitrogen.

[0017] Another object of the present invention is to provide micron-sized PA6 microspheres prepared by the above-mentioned preparation method, wherein the particle size of the micron-sized PA6 microspheres is 10 to 100 μm.

[0018] The third invention object of the present invention is to provide an application of the above-mentioned micron-sized PA6 microspheres, wherein the micron-sized PA6 microspheres are used as 3D printing materials or raw materials for the production of cosmetics and powder coatings.

[0019] In the present application, anionic ring-opening polymerization refers to the reaction of caprolactam with an initiator to generate caprolactam anion, and the caprolactam anion and the block copolymer of polyacrylamide and polyethylene oxide continue to undergo nucleophilic addition reaction. In order to increase the polymerization rate, an activator needs to be added to the reaction system.

[0020] The phase inversion of the experimental system in the present application refers to the two main raw materials in the experimental system, caprolactam and block copolymer of polyacrylamide and polyethylene oxide. Since the amount of caprolactam is much larger than the block copolymer, caprolactam is a continuous phase before the reaction, and after the reaction is completed, caprolactam becomes a dispersed phase.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1. The present invention uses a block copolymer of caprolactam / polyacrylamide and polyethylene oxide as a raw material. If the total mass of all raw materials in the experimental system is used as a benchmark, when the block copolymer of polyacrylamide and polyethylene oxide accounts for only 3 to 10 wt%, the caprolactam anionic polymerization can be used to induce phase separation in the experimental system to prepare micron-sized PA6 microspheres, and the yield of the microspheres is very high, reaching 90% to 97%.

[0023] 2. Since the block copolymer of polyacrylamide and polyethylene oxide is easily soluble in water, alcohol or other organic solvents, the PA6 alloy prepared after the reaction is completed can be eluted with water, which is easy to operate and environmentally friendly.

[0024] 3. The particle size of the PA6 microspheres prepared by the present invention is 10 to 100 μm, which is in the micron range and can be used in the field of 3D printing or as raw materials for the production of cosmetics and powder coatings.

[0025] 4. The preparation process of the present invention is simple and does not require special equipment such as an extruder for processing, so the production cost is low and suitable for industrial production. In addition, the size of the prepared micron-sized PA6 microspheres is controllable and has good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a scanning electron microscope image of the PA6 microspheres obtained in Example 1 of the present invention.

[0027] Figure 2 This is a scanning electron microscope image of the PA6 microspheres obtained in Example 2 of the present invention.

[0028] Figure 3 This is a scanning electron microscope image of the PA6 microspheres obtained in Example 3 of the present invention.

[0029] Figure 4 This is a scanning electron microscope image of the PA6 microspheres obtained in Example 4 of the present invention.

[0030] Figure 5 This is a scanning electron microscope image of the PA6 microspheres obtained in Example 5 of the present invention.

[0031] Figure 6 This is the particle size distribution diagram of PA6 microspheres obtained in Example 1 of the present invention.

[0032] Figure 7 This is the particle size distribution diagram of PA6 microspheres obtained in Example 5 of the present invention.

[0033] Figure 8 This is a scanning electron microscope image of the PA6 microspheres obtained in Comparative Example 1 of the present invention.

[0034] Fig. 9 This is a scanning electron microscope image of the PA6 microspheres obtained in Comparative Example 2 of the present invention.

[0035] Fig.10 This is a scanning electron microscope image of the PA6 microspheres obtained in Comparative Example 3 of the present invention. DETAILED DESCRIPTION

[0036] For ease of understanding of the present invention, the present invention will be described more fully below in conjunction with specific embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present invention more thoroughly understood.

[0037] Unless otherwise defined, all scientific and technological terms used herein have the same meanings as those of ordinary skill in the art to which the present invention belongs. In the event of a conflict, the present specification including the definitions shall prevail. The terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0038] Suitable methods and materials are described herein, although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention.

[0039] The specific information of the raw materials used in the following examples and comparative examples is as follows:

[0040] Caprolactam, technical grade, purchased from China Petrochemical Corporation;

[0041] The block copolymer of polyacrylamide and polyethylene oxide was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.;

[0042] Initiator, sodium hydroxide, analytical grade, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.;

[0043] Activator, 2,4-toluene diisocyanate, analytical grade, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.; isophorone diisocyanate, analytical grade, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.;

[0044] All materials are commercially available conventional products.

[0045] It can be understood that the above raw materials and reagents are only examples of some specific embodiments of the present invention, which makes the technical solution of the present invention clearer, and does not mean that the present invention can only adopt the above reagents. The specific scope shall be subject to the scope in the claims.

[0046] Example 1

[0047] Under nitrogen protection, 95 g of caprolactam was melted at 70° C., and then 5 g of a block copolymer of polyacrylamide and polyethylene oxide was added to the molten caprolactam to obtain a uniform liquid, which was maintained at 70° C. with magnetic stirring for 30 min.

[0048] 0.8 g of sodium hydroxide was added to the mixed solution, and the mixture was distilled under reduced pressure at 100° C. for about 30 min to remove the remaining trace water.

[0049] Then, 0.87 g of toluene diisocyanate was added, the mixture was quickly shaken and immediately poured into a mold preheated at 150° C. to carry out anionic ring-opening polymerization for 30 minutes. The experimental system underwent a phase inversion to obtain a PA6 alloy.

[0050] The PA6 alloy was crushed, immersed in distilled water for 24 hours to fully dissolve and wash, filtered and dried to obtain PA6 microspheres, with a microsphere yield of up to 95%. Figure 1 As shown in Figure 2, the obtained particles are PA6 microspheres with a particle size distribution of 10 to 65 μm. Figure 6 shown.

[0051] The particle size of the PA6 microspheres prepared in this embodiment is 10 to 65 μm, which is in the micron range and can be used in the field of 3D printing or as raw materials for the production of cosmetics and powder coatings.

[0052] Example 2

[0053] A micron-sized PA6 microsphere and a preparation method thereof, comprising the following steps:

[0054] Under nitrogen protection, 92g of caprolactam was melted at 70°C, and 8g of block copolymer of polyacrylamide and polyethylene oxide was added to the molten caprolactam to obtain a uniform liquid, which was kept at 70°C with magnetic stirring for 40min. After that, 0.5g of sodium hydroxide was added to the above solution, and it was distilled at 110°C under reduced pressure for about 30min to remove residual trace water. Then, 0.55g of toluene diisocyanate was added, shaken quickly, and immediately poured into a mold preheated to 160°C for anionic ring-opening polymerization for 10min. The experimental system was inverted to obtain PA6 alloy. After the obtained PA6 alloy was crushed, it was fully dissolved and washed with distilled water for 24h, filtered and dried to obtain PA6 microspheres, with a microsphere yield of 92%. The scanning electron microscope image is shown as follows Figure 2 As shown, the particle size distribution ranges from about 10 to 100 μm.

[0055] Example 3

[0056] A micron-sized PA6 microsphere and a preparation method thereof, comprising the following steps:

[0057] Under nitrogen protection, 72g of caprolactam was melted at 80°C, and 8g of block copolymer of polyacrylamide and polyethylene oxide was added to the molten caprolactam to obtain a uniform liquid, which was maintained at 80°C with magnetic stirring for 30 minutes. After that, 0.48g of sodium hydroxide was added to the above solution, and it was distilled under reduced pressure at 110°C for about 30 minutes to remove residual trace water. Then, 0.52g of toluene diisocyanate was added, shaken quickly, and immediately poured into a mold preheated to 150°C for anionic ring-opening polymerization for 20 minutes. The obtained PA6 alloy was crushed, fully dissolved and washed with deionized water for 24 hours, filtered and dried to obtain PA6 microspheres, with a microsphere yield of 90%. The scanning electron microscope image is as follows Figure 3 As shown, the particle size distribution ranges from about 10 to 80 μm.

[0058] Example 4

[0059] A micron-sized PA6 microsphere and a preparation method thereof, comprising the following steps:

[0060] Under vacuum conditions, 64.4g of caprolactam was melted at 80°C, and 5.6g of block copolymer of polyacrylamide and polyethylene oxide was added to the molten caprolactam to obtain a uniform liquid, which was maintained at 80°C with magnetic stirring for 30 minutes. After that, 0.56g of sodium hydroxide was added to the above solution, and the solution was distilled at 120°C under reduced pressure for about 30 minutes to remove residual trace water. Then, 0.61g of toluene diisocyanate was added, shaken quickly, and immediately poured into a mold preheated to 160°C for anionic ring-opening polymerization for 30 minutes. The obtained PA6 alloy was crushed, fully dissolved and washed with distilled water for 24 hours, filtered and dried to obtain PA6 microspheres, with a microsphere yield of 92%. The scanning electron microscope image is as follows Figure 4 As shown, the particle size distribution ranges from 10 to 90 μm.

[0061] Example 5

[0062] A micron-sized PA6 microsphere and a preparation method thereof, comprising the following steps:

[0063] Under argon protection, 97g of caprolactam was melted at 70°C, and then 3g of block copolymer of polyacrylamide and polyethylene oxide was added to the molten caprolactam to obtain a uniform liquid, which was maintained at 70°C with magnetic stirring for 30 minutes. Afterwards, 0.8g of sodium hydroxide was added to the above mixed melt, and the mixture was distilled at 100°C under reduced pressure for about 30 minutes to remove residual trace water. Then, 0.87g of toluene diisocyanate was added, shaken quickly, and immediately poured into a mold preheated to 150°C for anionic ring-opening polymerization for 30 minutes to obtain PA6 alloy. After the obtained PA6 alloy was crushed, it was fully dissolved and washed with distilled water for 24 hours, filtered and dried to obtain PA6 microspheres, with a microsphere yield of about 97%. The scanning electron microscope image is as follows Figure 5 As shown in the figure, the obtained particles are PA6 balls with a particle size distribution of 10 to 65 μm. Figure 7 shown.

[0064] Comparative Example 1

[0065] Under nitrogen protection, 92g of caprolactam was melted at 70°C, and 8g of block copolymer of polyacrylamide and polyethylene oxide was added to the molten caprolactam to obtain a uniform liquid, which was maintained at 70°C with magnetic stirring for 40min. Afterwards, 0.5g of sodium hydroxide was added to the above solution, and it was distilled under reduced pressure at 110°C for about 30min to remove residual trace water. Then, 0.71g of isophorone diisocyanate was added, shaken quickly, and immediately poured into a mold preheated to 160°C to react for 10min. After the obtained PA6 alloy was crushed, it was fully dissolved and washed with distilled water for 24h, filtered and dried to obtain PA6 microspheres, with a microsphere yield of 30%. The scanning electron microscope image is shown as follows Figure 8 As shown, the particle size of the microspheres is uneven, with a size distribution of 500 nm to 10 μm, which is significantly smaller than the particle size of the microspheres prepared in Example 2.

[0066] Comparative Example 2

[0067] Under nitrogen protection, 72g of caprolactam was melted at 80°C, and 8g of block copolymer of polyacrylamide and polyethylene oxide was added to the molten caprolactam to obtain a uniform liquid, which was maintained at 80°C with magnetic stirring for 30 minutes. Afterwards, 0.48g of sodium hydroxide was added to the above solution, and it was distilled under reduced pressure at 110°C for about 30 minutes to remove residual trace water. Then, 0.66g of isophorone diisocyanate was added, shaken quickly, and immediately poured into a mold preheated to 150°C to react for 20 minutes. After the obtained PA6 alloy was crushed, it was fully dissolved and washed with distilled water for 24 hours, filtered and dried to obtain PA6 microspheres with a microsphere yield of 35%. The scanning electron microscope image is as follows Fig. 9 As shown, the microspheres are uneven in size, with a size distribution of 500 nm to 10 μm, which is significantly smaller than the particle size of the microspheres in Example 3.

[0068] SEM images Figure 8 and Fig. 9 In comparative examples 1 and 2, isophorone diisocyanate is used as the activator, and the experimental system cannot be completely inverted. The PA6 microspheres obtained are not completely dispersed. Many large and small microspheres coexist, and the size is about 500nm to 10μm. The microspheres are adhered to each other, and it is impossible to obtain dispersed microspheres. The yield of microspheres is very low. This is very different from the SEM results of the experimental sample using toluene diisocyanate as the activator. It can be seen that in the present invention, the activator is an important factor affecting the microscopic morphology of the product PA6.

[0069] Comparative Example 3

[0070] Under nitrogen protection, 72g of caprolactam was melted at 70°C, and then 8g of block copolymer of polystyrene and polyacrylic acid was added to the molten caprolactam to obtain a uniform liquid, which was maintained at 80°C with magnetic stirring for 30 minutes. After that, 0.48g of sodium hydroxide was added to the mixed melt, and the mixture was distilled at 100°C under reduced pressure for about 30 minutes to remove residual trace water. Then, 0.52g of toluene diisocyanate was added, shaken quickly, and immediately poured into a mold preheated to 150°C for anionic ring-opening polymerization for 30 minutes to obtain a PA6 alloy. The obtained PA6 alloy was fractured with liquid nitrogen, and the cross section was fully dissolved and cleaned with distilled water for 24 hours. The scanning electron microscope image is as follows Fig.10 As shown, the PA6 continuous phase and PA6 balls with an average particle size of 1 μm were obtained. Compared with Example 3, the experimental system of Comparative Example 3 could not undergo a complete phase inversion, and most of the PA6 obtained was in a continuous phase, with only a small amount of PA6 balls with a small particle size, that is, the yield of PA6 balls was extremely low, indicating that the block copolymer was an important factor affecting the microscopic morphology of the product PA6.

[0071] The above description of the embodiments is to facilitate the understanding and application of the present invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the embodiments herein, and improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the protection scope of the present invention.

Claims

1. A method for preparing micron-sized PA6 microspheres, characterized in that: The steps include: (1) adding a block copolymer of polyacrylamide and polyethylene oxide to molten caprolactam under vacuum or protective atmosphere, and stirring magnetically at 70 to 90° C. for 20 to 40 minutes to obtain a mixed solution; (2) adding an initiator to the mixed solution obtained in step (1), and performing vacuum dehydration at 100 to 120° C.; (3) adding an activator, and performing anionic ring-opening polymerization of caprolactam at 140-160° C. for 5-30 min, and the experimental system undergoes phase inversion to obtain a PA6 alloy; the activator is toluene diisocyanate; (4) The PA6 alloy obtained in step (3) is crushed and washed to obtain micron-sized PA6 microspheres.

2. The method according to claim 1, characterized in that: The amount of the block copolymer of polyacrylamide and polyethylene oxide is 3-10 wt % of the total mass of caprolactam and the block copolymer of polyacrylamide and polyethylene oxide.

3. The method according to claim 1, characterized in that: The initiator is an alkali metal hydride, an alkali metal hydroxide, an alkali metal alcoholate or an alkali metal carbonate.

4. The method according to claim 1, characterized in that: The added amount of the initiator is 0.5-1wt% of the total mass of the block copolymer of caprolactam, polyacrylamide and polyethylene oxide; the added amount of the activator is 0.5-1wt% of the total mass of the block copolymer of caprolactam, polyacrylamide and polyethylene oxide.

5. The method according to claim 1, characterized in that: The washing time is 24 to 48 hours.

6. The method according to claim 1, characterized in that: The protective atmosphere is at least one of hydrogen, argon, methane and nitrogen.

7. A micron-sized PA6 microsphere prepared by the preparation method according to any one of claims 1 to 6, characterized in that: The particle size of the micron-sized PA6 microspheres is 10 to 100 μm.

8. The use of micron-sized PA6 microspheres as claimed in claim 7, characterized in that: The micron-sized PA6 microspheres are used as 3D printing materials or raw materials for the production of cosmetics and powder coatings.

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