Thermally induced phase separation normal pressure special engineering plastic powder and preparation method thereof

Abstract

The present invention discloses a thermally induced phase separation atmospheric pressure special engineering plastic powder and a preparation method thereof, belonging to the field of polymer material technology. The method comprises: mixing special engineering plastic pellets, a diluent, and a functional additive, heating and dissolving in stages to form a homogeneous solution; then cooling at a rate of 10 to 300°C / min to induce solid-liquid phase separation, solidifying and precipitating powder particles; after removing the diluent with an extractant, the powder is obtained by vacuum filtration, solvent washing, and vacuum drying. Operating at atmospheric pressure, it breaks through the limitations of traditional high-pressure methods. By regulating the solubility parameters of the compound diluent, the cooling rate, and the functional additives, the phase separation process is synergistically optimized to achieve precise control of the powder morphology and particle size. The resulting powder exhibits high sphericity, a narrow particle size distribution, and excellent fluidity and melting properties. It is suitable for high-end fields such as laser sintering and electrostatic spraying, and the process is environmentally friendly.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer materials, and in particular relates to thermally induced phase separation normal pressure special engineering plastic powder and a preparation method thereof. Background Art

[0002] Selective laser sintering (SLS) and electrostatic spraying are cutting-edge additive manufacturing and surface engineering technologies, and their core performance is highly dependent on the physical and chemical properties of the powder material. In selective laser sintering, the powder must meet strict particle size distribution, high sphericity, and excellent fluidity to ensure uniform absorption of laser energy during the layer-by-layer sintering process, reduce porosity defects caused by unmelted particles, and thus improve the density and mechanical properties of the molded parts. In electrostatic spraying, the uniformity of the surface charge distribution and the regularity of the morphology of the powder directly affect the motion trajectory under the action of the electric field, thereby determining the thickness uniformity, adhesion, and functionality of the coating. Currently, nylon 12 (PA12), thermoplastic polyurethane (TPU), and 316L stainless steel powders have become the mainstream powder materials in these two fields due to their mature processing technology and moderate cost. However, the performance shortcomings of these materials under extreme operating conditions are becoming increasingly apparent. For example, PA12 has a long-term operating temperature limit of 120°C and is prone to thermal degradation in high-temperature environments. TPU has poor chemical resistance, especially in acidic and alkaline media, where it swells and fails. While metal powders offer high thermal conductivity, they are dense, expensive, and unsuitable for insulation or lightweighting applications. Therefore, developing new powder materials that can withstand extreme environments (such as high temperatures and severe corrosion) has become a key direction for overcoming technical bottlenecks.

[0003] Specialty engineering plastics (such as polyetheretherketone, polyimide, and polyphenylene sulfide) are considered ideal candidates for overcoming the limitations of existing materials due to their exceptional high-temperature resistance, mechanical strength, and chemical stability. For example, polyetheretherketone (PEEK) powder has been successfully used in SLS molding of high-temperature, aircraft engine brackets, and polyimide (PI) powder has been fabricated into high-insulation protective coatings for electronic components via electrostatic spraying. Furthermore, the chemical resistance of polyphenylene sulfide (PPS) (tolerance to acidic and alkaline environments with a pH range of 1-14) and the high transparency of polysulfone offer promising applications in automotive fuel systems and precision optical devices. However, the large-scale application of specialty engineering plastic powders has long been limited by the immaturity of their preparation technology. Currently, the preparation of specialty engineering plastic powders primarily involves cryogenic pulverization and solution precipitation. While cryogenic pulverization involves cryogenically embrittled polymers followed by mechanical crushing, a simple process that relies on high-energy cryogenic equipment. The resulting powders exhibit a wide particle size distribution, irregular morphology, and poor flowability, making them difficult to meet the stringent SLS requirements for uniform powder spreading. The solvent precipitation method uses high-temperature, high-pressure dissolution to achieve powder precipitation. Although it can produce powders with high sphericity, specialty engineering plastics have extremely poor solubility in conventional solvents and often rely on highly toxic solvents (such as concentrated sulfuric acid and chloroform) or extreme process conditions (such as supercritical fluids). Not only is the equipment cost high and energy consumption significant, but there are also risks of solvent residue and environmental pollution. Although specialty engineering plastic powders can be used to produce precision components suitable for use in extreme environments during selective laser sintering and can form corrosion-resistant, high-adhesion functional coatings during electrostatic spraying, bottlenecks in existing preparation technologies have resulted in a disconnect between powder performance and the needs of large-scale production, greatly limiting their penetration into high-end manufacturing. Therefore, there is an urgent need to develop new methods for preparing specialty engineering plastic powders that are both environmentally friendly and efficient and controllable. Summary of the Invention

[0004] In order to overcome the above shortcomings, the present invention provides a thermally induced phase separation normal pressure special engineering plastic powder and a preparation method thereof.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] The method for preparing thermally induced phase separation normal pressure special engineering plastic powder comprises the following steps:

[0007] 1) Mix the special engineering plastic granules, diluent and functional additives and dissolve them by increasing the temperature in stages:

[0008] a. Heating to a first temperature A, standing and heating for 0.5 to 1 hour, wherein the first temperature A is 5 to 50° C. higher than the melting temperature of the diluent, and standing and heating for 0.5 to 1 hour at this temperature;

[0009] b. Raise the temperature to a second temperature B, keep warm for 0.5 to 2 hours and stir until completely dissolved, wherein the second temperature B is 5 to 100°C lower than the melting temperature of the special engineering plastic pellets;

[0010] 2) cooling the homogeneous solution formed in step 1) at a rate of 10-300°C / min to a third temperature C that induces phase separation, thereby solidifying and precipitating powder particles;

[0011] 3) After the powder particles are cooled to room temperature, an extractant is used to remove the diluent from the powder particles. After solid-liquid separation, solvent washing and drying, special engineering plastic powder is obtained.

[0012] Further optimization, the special engineering plastic granules are selected from one or more of polyetheretherketone, polyetherketone, polyetherketoneketone, polyetheretherketoneketone, polyphenylene sulfide, liquid crystal polymer, polyimide, polysulfone, polyethersulfone, polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinylidene fluoride, polybutylene terephthalate, and polyethylene naphthalate granules.

[0013] Further optimization, the diluent is a compound diluent, selected from any two or three of ethylene carbonate, caprolactam, acetyl tributyl citrate, diphenyl sulfone, benzophenone, dimethyl sulfoxide, cyclohexyl pyrrolidone, N-methyl pyrrolidone, dibutyl sebacate, dibenzoyl ketone, triacetin, polyvinyl alcohol, polyethylene glycol, dimethyl phthalate, polyethylene glycol monomethyl ether, and acetamide.

[0014] Further optimization, the functional additive is a nano nucleating agent with a particle size of 50-500 nm, the nano nucleating agent is the functional additive is a nano nucleating agent with a particle size of 50-500 nm, the nano nucleating agent is one or more of nano silicon dioxide, nano zinc oxide, nano copper oxide, nano titanium dioxide, nano hydroxyapatite, nano calcium carbonate, nano talc, carbon nanotubes, and graphene, and the functional additive is 0-0.4% of the total mass of the special engineering plastic pellets, diluent and functional additive in step 1).

[0015] Further optimization is performed, in step 1), the special engineering plastic pellets in step 1) are 20-60% of the total mass of the special engineering plastic pellets, diluent and functional additives in step 1), the stirring rate of the phase separation process in step 2) is 10-100 rpm, and the curing time is 0.25-5 h.

[0016] Further optimization, the third temperature C is 0-10° C. lower than the crystallization temperature of the special engineering plastic pellets.

[0017] Further optimization is performed, in step 3), the extraction agent is selected from one or two of deionized water, methanol, ethanol, isopropanol, n-hexane or acetone, and the extraction time is 0.25-4 h; in step 3), the solvent washing adopts one or two of deionized water, ethanol, n-hexane or acetone, the washing times are 3-5 times, each washing time is 20 min, and the washing temperature is 30-60°C.

[0018] Further optimization is performed, in step 3), the drying temperature is 40-80° C., and the drying time is 2-6 h.

[0019] The plastic powder prepared by the thermally induced phase separation atmospheric pressure method is characterized in that the powder has a spherical structure, a particle size distribution of 10-100 μm, an angle of repose ≤30°, and a melt index not less than 20 g / 10 min.

[0020] The beneficial effects of the present invention are:

[0021] (1) The thermally induced phase separation method used in the present invention has more gentle and controllable process conditions. Compared with the traditional high-pressure solvent precipitation method (5-10 MPa) and cryogenic mechanical crushing method (-196°C), the present invention adopts the normal pressure thermally induced phase separation method, with the operating pressure being normal pressure and the temperature range being controlled within 100-350°C (adjusted according to the melting point of the special engineering plastic pellets), which significantly reduces equipment requirements and energy consumption costs. By precisely controlling the cooling rate and crystallization temperature, programmable control of the phase separation process can be achieved, avoiding the problem of unstable powder performance caused by process fluctuations in traditional methods;

[0022] (2) The particle size and morphology of the special engineering plastic powder prepared by the present invention can be precisely controlled. By optimizing the compounding ratio and solubility parameters of the compound diluent to actively induce controllable solid-liquid phase separation, a polymer-rich phase as a precursor micro-region is formed during the cooling process, and the cooling rate (controlling the establishment of supercooling and growth dynamics) and the amount of nucleating agent added (controlling the heterogeneous nucleation density and activation energy barrier) are coordinated to achieve a directional design of the morphology and particle size of the special engineering plastic powder; the optimized polymer concentration and the interaction force of the diluent ensure the spontaneous and uniform formation of the precursor micro-region; the precisely matched slower cooling rate allows the precursor micro-region to form a uniform and uniform phase. The regions are fully fused and spheroidized under the guidance of interfacial tension, significantly improving the sphericity of the powder. The quantitatively introduced nucleating agent significantly reduces the nucleation energy barrier and precisely controls the nucleation density. While inhibiting dendrite growth, it also cooperates with the cooling rate to control the diffusion-limited growth of particles, effectively constraining the final particle size and narrowing the particle size distribution. This method is different from traditional passive forming methods that rely on mechanical crushing or simple precipitation. It can controllably produce special engineering plastic powders with high sphericity (near true sphere), narrow particle size distribution and excellent fluidity. This type of powder material can meet the stringent requirements of special engineering plastic powder materials in the fields of automotive manufacturing, aerospace, electronic packaging, etc.

[0023] (3) The preparation process adopted by the present invention is green and environmentally friendly, and the diluent used can be completely phase-separated at room temperature and can be easily recycled;

[0024] (4) The special engineering plastic powder material prepared by the present invention can be applied to fields such as selective laser sintering and electrostatic spraying. The powder material can be used in extreme environments (such as high temperature and strong corrosion), providing a reliable material basis for the application of special engineering plastics in high-end fields such as aerospace and electronic packaging;

[0025] (5) The preparation process adopted by the present invention is adaptable to a variety of special engineering plastics, breaking through the limitations of existing technologies, and has potential application prospects in the field of polymer powder preparation and good potential for industrial scale-up application;

[0026] (6) The present invention prepares a homogeneous solution of special engineering plastics by adopting a staged heating and dissolving process, which significantly improves the preparation efficiency and reliability of the homogeneous solution of special engineering plastics. Specifically, the process is heated for 0.5 to 1 hour at a temperature range of 5 to 50°C higher than the melting temperature of the diluent, which ensures that the solid diluent is fully and evenly melted, creating favorable conditions for the subsequent dissolution of the special engineering plastic pellets, ensuring that the diluent can better play its role in the subsequent dissolution process, and improving the overall dissolution efficiency and quality. Subsequently, the temperature is raised to 5 to 100°C lower than the melting temperature of the special engineering plastic pellets and stirring is started. This optimization step utilizes the good liquid medium foundation formed in the early stage, combined with appropriate temperature and forced convection, to significantly accelerate the dissolution kinetics of the special engineering plastics, achieving rapid and sufficient dissolution. This method can effectively shorten the preparation time of the homogeneous solution of special engineering plastics, improve production efficiency, and at the same time ensure the quality and uniformity of the solution. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is an SEM image of the polyetheretherketone powder prepared in Example 1 of the present invention;

[0028] Figure 2 is the particle size distribution curve of the polyetheretherketone powder prepared in Example 1 of the present invention;

[0029] Figure 3 This is an SEM image of the polyetheretherketone powder prepared in Comparative Example 1 of the present invention;

[0030] Figure 4 This is an SEM image of the polyetheretherketone bulk material prepared in Comparative Example 2 of the present invention;

[0031] Figure 5 This is an SEM image of the polyetheretherketone powder prepared in Comparative Example 4 of the present invention. DETAILED DESCRIPTION

[0032] In order to more clearly understand the above-mentioned objects, features and advantages of the present invention, the present invention is described in detail below in conjunction with specific embodiments. The following embodiments are implemented based on the technical solutions of the present invention, and provide detailed implementation methods and specific operating procedures. However, the present invention can also be implemented in other ways different from those described herein. Therefore, the protection scope of the present invention is not limited to the following embodiments.

[0033] Example 1

[0034] 1) PEEK, a compound diluent (diphenyl sulfone and dibutyl sebacate in a ratio of 7:3), and 100 nm silica were added to a reaction vessel in a mass ratio of 30.0:69.9:0.1. The temperature was first raised to 150°C and allowed to stand for 0.5 h. The temperature was then raised to 270°C and stirred at 200 rpm to dissolve the PEEK pellets.

[0035] 2) The solution obtained in step 1) was kept warm for 2 hours to completely dissolve the polyetheretherketone pellets to obtain a homogeneous solution, and then the temperature of the homogeneous solution was reduced to 100° C. at a cooling rate of 10° C. / min to allow solid-liquid phase separation between the polyetheretherketone and the diluent in the homogeneous solution, and the polyetheretherketone was solidified and precipitated into powder particles, wherein the curing time during the curing process was 4 hours and the stirring rate was 50 rpm;

[0036] 3) After the solidified polyetheretherketone powder particles obtained in step 2) are further cooled to room temperature, they are placed in a composite extractant consisting of methanol and n-hexane in a volume ratio of 1:1 for 4 hours to remove the diluent. The particles precipitated in the solution are the primary polyetheretherketone powder;

[0037] 4) Separating the liquid from the polyetheretherketone primary powder obtained in step 3) by vacuum filtration, then washing the polyetheretherketone powder five times with ethanol and n-hexane at 30°C, each washing time being 20 min. After each washing, separating the polyetheretherketone powder by vacuum filtration, and finally drying the polyetheretherketone powder in vacuo at 60°C for 2 h to remove residual solvent, thereby obtaining polyetheretherketone powder.

[0038] After testing, polyetheretherketone powder has a regular spherical structure, such as Figure 1 As shown in the figure, the particle size distribution of the powder is narrow, mainly distributed in the range of 20~60μm, as shown in the figure. Figure 2 As shown, the angle of repose is 27.6° and the bulk density is 0.32 g / cm 3 , melt index 25g / 10min. The performance of polyetheretherketone powder can meet the performance requirements of its powder material in the fields of selective laser sintering and electrostatic spraying. The specific test method is as follows:

[0039] Selective laser sintering (SLS) testing methods: Prepared specialty engineering plastic powder was placed in an SLS machine for selective laser sintering (sintering into bar specimens for performance testing). The laser power was 50 W, the powder layer thickness was 0.3 mm, the powder feed cylinder was preheated to 335°C, and the forming cylinder was preheated to 355°C. The test results showed that the sintered PEEK bar exhibited a tensile strength of 78.2 MPa and an elongation at break of 9.1%.

[0040] Electrostatic spray testing methods: The prepared special engineering plastic powder was sprayed onto a steel plate using a spray gun, followed by curing at 400°C for 15 minutes. The spray voltage was 70 kV, the current was 15 μA, the spray distance was 20 cm, and the atomization pressure was 0.4 MPa. The test results showed that the polyetheretherketone coating had a Rockwell hardness of 115 and an adhesion of 34.7 MPa. The coating also exhibited excellent heat resistance, chemical stability, wear resistance, and corrosion resistance.

[0041] Example 2

[0042] Example 2 is identical to steps 1), 3) and 4) of Example 1. The only difference from step 2) of Example 1 is that the cooling rate is 300°C / min. Specifically:

[0043] 1) PEEK, a compound diluent (diphenyl sulfone and dibutyl sebacate in a ratio of 7:3), and 100 nm silica were added to a reaction vessel in a mass ratio of 30.0:69.9:0.1. The temperature was first raised to 150°C and allowed to stand for 0.5 h. The temperature was then raised to 270°C and stirred at 200 rpm to dissolve the PEEK pellets.

[0044] 2) The solution obtained in step 1) was kept warm for 2 hours to completely dissolve the polyetheretherketone pellets to obtain a homogeneous solution, and then the temperature of the homogeneous solution was reduced to 100° C. at a cooling rate of 300° C. / min to allow solid-liquid phase separation of the polyetheretherketone and the diluent in the homogeneous solution, and the polyetheretherketone was solidified and precipitated into powder particles, wherein the curing time during the curing process was 4 hours and the stirring rate was 50 rpm;

[0045] 3) After the solidified polyetheretherketone powder particles obtained in step 2) are further cooled to room temperature, they are placed in a composite extractant consisting of methanol and n-hexane in a volume ratio of 1:1 for 4 hours to remove the diluent. The particles precipitated in the solution are the primary polyetheretherketone powder;

[0046] 4) Separating the liquid from the polyetheretherketone primary powder obtained in step 3) by vacuum filtration, then washing the polyetheretherketone powder five times with ethanol and n-hexane at 30° C., each washing time being 20 min. After each washing, separating the polyetheretherketone powder by vacuum filtration, and finally drying the polyetheretherketone powder in vacuo at 60° C. for 2 h to remove the residual solvent, thereby obtaining polyetheretherketone powder.

[0047] The test results show that the polyetheretherketone powder has a regular spherical structure, and the particle size distribution range of the powder is narrow, mainly distributed in the range of 10~30μm, the angle of repose is 22.6°, and the bulk density is 0.41g / cm 3 , melt index 36g / 10min, which shows that the particle size and distribution of the powder can be controlled by adjusting the cooling rate, which is helpful for the targeted synthesis of required special engineering plastic powders.

[0048] Example 3

[0049] 1) Add polyethersulfone and a compound diluent (ethylene carbonate and benzoyl ketone, in a ratio of 9:1) in a mass ratio of 20:80 to a reaction vessel. First, heat the mixture to 140°C and allow to stand for 0.5 h. Then, heat the mixture to 200°C and stir at 50 rpm to dissolve the polyethersulfone pellets.

[0050] 2) The solution obtained in step 1) was kept warm for 1 hour to completely dissolve the polyethersulfone pellets to obtain a homogeneous solution, and then the temperature of the homogeneous solution was reduced to 40°C at a cooling rate of 50°C / min to allow solid-liquid phase separation of the polyethersulfone and the diluent in the homogeneous solution, and the polyethersulfone was solidified and precipitated into powder particles, wherein the curing time during the curing process was 5 hours and the stirring rate was 10 rpm;

[0051] 3) After the solidified polyethersulfone powder particles obtained in step 2) are further cooled to room temperature, they are placed in a composite extractant consisting of methanol and n-hexane in a volume ratio of 2:1 for 0.5 hours to remove the diluent. The particles precipitated in the solution are the primary polyethersulfone powder;

[0052] 4) Separating the liquid from the polyethersulfone primary powder obtained in step 3) by vacuum filtration, then washing the polyethersulfone powder three times with ethanol at 30°C, each washing time being 20 minutes. After each washing, separating the polyethersulfone powder by vacuum filtration, and finally drying the polyethersulfone powder in vacuo at 40°C for 5 hours to remove residual solvent, thereby obtaining polyethersulfone powder.

[0053] The test results show that the polyethersulfone powder has a regular spherical structure, and the particle size distribution range of the powder is narrow, mainly distributed in the range of 40~80μm, the angle of repose is 25.4°, and the bulk density is 0.44g / cm 3 , with a melt index of 42g / 10min. The properties of polyethersulfone powder meet the requirements for powder material performance in the fields of selective laser sintering and electrostatic spraying. Specifically, during the selective laser sintering process, with the powder feed cylinder preheated at 190°C and the build cylinder preheated at 225°C, the polyethersulfone sintered specimens achieved a tensile strength of 65.2 MPa and an elongation at break of 11.2%. During electrostatic spraying, with a curing temperature of 220°C, the polyethersulfone coating achieved a Rockwell hardness of 100 and an adhesion of 30.7 MPa. The coating also exhibits excellent heat resistance, chemical stability, wear resistance, and corrosion resistance.

[0054] Example 4

[0055] 1) Polychlorotrifluoroethylene (PTFE), a composite diluent (comprised of tributyl acetyl citrate, glyceryl triacetate, and acetamide in a ratio of 2:7:1), and 500 nm carbon nanotubes (CNTs) in a mass ratio of 45:54.6:0.4 were added to a reaction vessel. The temperature was first raised to 90°C and allowed to stand for 1 hour. The temperature was then raised to 190°C and stirred at 500 rpm to dissolve the PTFE pellets.

[0056] 2) The solution obtained in step 1) was kept warm for 0.5 h to completely dissolve the polytrifluorochloroethylene pellets to obtain a homogeneous solution, and then the temperature of the homogeneous solution was reduced to 60° C. at a cooling rate of 30° C. / min to allow solid-liquid phase separation of the polytrifluorochloroethylene and the diluent in the homogeneous solution, and the polytrifluorochloroethylene was solidified and precipitated into powder particles, wherein the curing time during the curing process was 0.25 h and the stirring rate was 60 rpm;

[0057] 3) After the solidified polychlorotrifluoroethylene powder particles obtained in step 2) are further cooled to room temperature, they are placed in a composite extractant consisting of deionized water and methanol in a volume ratio of 3:1 for 3 hours to remove the diluent. The particles precipitated in the solution are the primary polychlorotrifluoroethylene powder;

[0058] 4) separating the liquid from the primary polytrifluorochloroethylene powder obtained in step 3) by vacuum filtration, then washing the polytrifluorochloroethylene powder four times with deionized water at 60° C., each washing time being 20 min. After each washing, separating the polytrifluorochloroethylene powder by vacuum filtration, and finally drying the polytrifluorochloroethylene powder in vacuo at 80° C. for 6 h to remove residual solvent, thereby obtaining polytrifluorochloroethylene powder.

[0059] The test results show that polytrifluorochloroethylene powder has a regular spherical structure, and the particle size distribution range of the powder is narrow, mainly distributed in the range of 20~50μm, the angle of repose is 22.9°, and the bulk density is 0.38g / cm 3 , melt index 53g / 10min. The performance of polytrifluoroethylene powder can meet the performance requirements of its powder materials in the fields of selective laser sintering and electrostatic spraying. Specifically: in the selective laser sintering process, the preheating temperature of the powder feeding cylinder is 165℃, the preheating temperature of the forming cylinder is 190℃, the tensile strength of the polytrifluoroethylene sintered specimen is 73.4 MPa, and the elongation at break is 8.7%; in electrostatic spraying, the curing temperature is 210℃, the Rockwell hardness of the polytrifluoroethylene coating is 105, the adhesion is 29.9MPa, and the coating has excellent heat resistance, chemical stability, wear resistance and corrosion resistance.

[0060] Example 5

[0061] 1) Polybutylene terephthalate (PBTA), a compound diluent (cyclohexyl pyrrolidone and polyethylene glycol monomethyl ether, in a ratio of 6:4), and titanium dioxide with a particle size of 50 nm were added to a reaction vessel at a mass ratio of 60:39.95:0.05. The temperature was first raised to 50°C and allowed to stand for 0.5 h. The temperature was then raised to 210°C and stirred at 500 rpm to dissolve the PBTA pellets.

[0062] 2) The solution obtained in step 1) was kept warm for 2 hours to completely dissolve the polybutylene terephthalate pellets to obtain a homogeneous solution. The temperature of the homogeneous solution was then reduced to 50° C. at a cooling rate of 30° C. / min to allow solid-liquid phase separation of the polybutylene terephthalate and the diluent in the homogeneous solution. The polybutylene terephthalate solidified and precipitated into powder particles. The curing time during the curing process was 5 hours and the stirring rate was 100 rpm.

[0063] 3) After the solidified polybutylene terephthalate powder particles obtained in step 2) are further cooled to room temperature, they are placed in a composite extractant consisting of deionized water and isopropyl alcohol in a volume ratio of 3:1 for 0.25 hours to remove the diluent. The particles precipitated in the solution are the primary polybutylene terephthalate powder;

[0064] 4) separating the liquid from the primary polybutylene terephthalate powder obtained in step 3) by vacuum filtration, then washing the polybutylene terephthalate powder three times with water and isopropyl alcohol at 50° C., each washing time being 20 min. After each washing, separating the polybutylene terephthalate powder by vacuum filtration, and finally drying the polybutylene terephthalate powder in vacuo at 70° C. for 5 h to remove the residual solvent, thereby obtaining polybutylene terephthalate powder.

[0065] The test results show that polybutylene terephthalate powder has a regular spherical structure, and the particle size distribution range of the powder is narrow, mainly distributed in the range of 30~80μm, the angle of repose is 28.4°, and the bulk density is 0.24g / cm 3 , with a melt index of 37g / 10min. The properties of polybutylene terephthalate powder meet the requirements for powder material performance in selective laser sintering and electrostatic spraying. Specifically, during selective laser sintering, with the powder feed cylinder preheated at 160°C and the build cylinder preheated at 200°C, the sintered polybutylene terephthalate strips achieved a tensile strength of 57.4 MPa and an elongation at break of 13.7%. During electrostatic spraying, with a curing temperature of 235°C, the polybutylene terephthalate coating achieved a Rockwell hardness of 100 and an adhesion of 28.8 MPa. The coating also exhibits excellent heat resistance, chemical stability, wear resistance, and corrosion resistance.

[0066] Example 6

[0067] 1) Polyetherketoneketone (PEK), a composite diluent (comprised of acetyl tributyl citrate and benzoyl ketone in a ratio of 2:8), and hydroxyapatite with a particle size of 200 nm were added to a reaction vessel in a mass ratio of 15:84.7:0.3. The temperature was first raised to 150°C and allowed to stand for 0.8 h. The temperature was then raised to 290°C and stirred at 400 rpm to dissolve the PKK pellets.

[0068] 2) The solution obtained in step 1) was kept warm for 1.5 hours to completely dissolve the polyetherketoneketone granules to obtain a homogeneous solution, and then the temperature of the homogeneous solution was reduced to 120° C. at a cooling rate of 200° C. / min to allow solid-liquid phase separation between the polyetherketoneketone granules and the diluent in the homogeneous solution, and the polyetherketoneketone granules were solidified and precipitated into powder particles, wherein the curing time during the curing process was 2 hours and the stirring rate was 20 rpm;

[0069] 3) After the solidified polyetheretherketone powder particles obtained in step 2) are further cooled to room temperature, they are placed in a composite extractant consisting of deionized water and isopropyl alcohol in a volume ratio of 5:1 for 3 hours to remove the diluent. The particles precipitated in the solution are the primary polyetheretherketone powder;

[0070] 4) Separating the liquid from the polyetherketoneketone nascent powder obtained in step 3) by vacuum filtration, then washing the polyetherketoneketone nascent powder with ethanol and acetone at 40°C for 5 times, each washing time being 20 min. After each washing, separating the polyetherketoneketone nascent powder by vacuum filtration, and finally vacuum drying the polyetherketoneketone nascent powder at 60°C for 3 h to remove the residual solvent, thereby obtaining polyetherketoneketone nascent powder.

[0071] The test results show that the polyetherketone ketone powder has a regular spherical structure, and the particle size distribution range of the powder is narrow, mainly distributed in the range of 40~90μm, the angle of repose is 23.1°, and the bulk density is 0.35g / cm 3 , with a melt index of 21g / 10min. The performance of PEEK powder meets the requirements for powder material properties in both selective laser sintering and electrostatic spraying. Specifically, during selective laser sintering, with the powder feed cylinder preheated at 295°C and the build cylinder preheated at 315°C, the PEEK sintered strips achieved a tensile strength of 82.4 MPa and an elongation at break of 10.7%. During electrostatic spraying, with a curing temperature of 395°C, the PEEK coating achieved a Rockwell hardness of 120 and adhesion of 33.4 MPa. The coating also exhibits excellent heat resistance, chemical stability, wear resistance, and corrosion resistance.

[0072] Example 7

[0073] 1) Liquid crystal polymer, a compound diluent (diphenyl sulfone and polyethylene glycol monomethyl ether, in a ratio of 5:5), and zinc oxide with a particle size of 150 nm were added to a reaction vessel in a mass ratio of 35:64.9:0.1. The temperature was first raised to 160°C and allowed to stand for 1 hour. The temperature was then raised to 320°C and stirred at 300 rpm to dissolve the liquid crystal polymer particles.

[0074] 2) The solution obtained in step 1) was kept warm for 2 hours to completely dissolve the liquid crystal polymer pellets to obtain a homogeneous solution. The temperature of the homogeneous solution was then reduced to 120°C at a cooling rate of 15°C / min to allow solid-liquid phase separation between the liquid crystal polymer and the diluent in the homogeneous solution. The liquid crystal polymer was solidified and precipitated into powder particles. The curing time during the curing process was 5 hours and the stirring rate was 20 rpm.

[0075] 3) After the solidified liquid crystal polymer powder particles obtained in step 2) are further cooled to room temperature, they are placed in a composite extractant consisting of methanol and ethanol in a volume ratio of 1:1 for 3 hours to remove the diluent. The particles precipitated in the solution are the primary liquid crystal polymer powder;

[0076] 4) Separating the liquid from the primary liquid crystal polymer powder obtained in step 3) by vacuum filtration, then washing the liquid crystal polymer powder with ethanol at 30° C. for 5 times, each washing time being 20 min. After each washing, separating the liquid crystal polymer powder by vacuum filtration, and finally vacuum drying the liquid crystal polymer powder at 60° C. for 4 h to remove the residual solvent, thereby obtaining a liquid crystal polymer powder.

[0077] The test results show that the liquid crystal polymer powder has a regular spherical structure, and the particle size distribution range of the powder is narrow, mainly distributed in the range of 20~50μm, the angle of repose is 28.3°, and the bulk density is 0.42g / cm 3 , with a melt index of 34g / 10min. The properties of the liquid crystal polymer powder meet the requirements for powder material performance in the fields of selective laser sintering and electrostatic spraying. Specifically, during the selective laser sintering process, with the powder feed cylinder preheated at 245°C and the build cylinder preheated at 270°C, the sintered liquid crystal polymer strips achieved a tensile strength of 81.2 MPa and an elongation at break of 5.4%. During electrostatic spraying, with a curing temperature of 330°C, the liquid crystal polymer coating achieved a Rockwell hardness of 85 and an adhesion of 25.4 MPa. The coating also exhibits excellent heat resistance, chemical stability, flame retardancy, and corrosion resistance.

[0078] Example 8

[0079] 1) Add polyvinylidene fluoride, a compound diluent (diphenyl sulfone and polyethylene glycol, in a ratio of 7:3), and calcium carbonate with a particle size of 500 nm to a reaction vessel in a mass ratio of 30.0:69.9:0.1. First, heat the mixture to 70°C and allow it to stand for 0.5 h. Then, heat the mixture to 140°C and stir at 200 rpm to dissolve the polyvinylidene fluoride pellets.

[0080] 2) The solution obtained in step 1) was kept warm for 2 hours to completely dissolve the polyvinylidene fluoride pellets to obtain a homogeneous solution, and then the temperature of the homogeneous solution was reduced to 80°C at a cooling rate of 30°C / min to allow solid-liquid phase separation between the polyvinylidene fluoride and the diluent in the homogeneous solution, and the polyvinylidene fluoride was solidified and precipitated into powder particles, wherein the curing time during the curing process was 4 hours and the stirring rate was 80 rpm;

[0081] 3) After the solidified polyvinylidene fluoride powder particles obtained in step 2) are further cooled to room temperature, they are placed in a composite extractant consisting of deionized water and ethanol in a volume ratio of 1:1 for 3 hours to remove the diluent. The particles precipitated in the solution are the primary polyvinylidene fluoride powder;

[0082] 4) separating the liquid from the nascent polyvinylidene fluoride powder obtained in step 3) by vacuum filtration, then washing the polyvinylidene fluoride powder five times with deionized water and ethanol at 40° C., each washing time being 20 min. After each washing, separating the polyvinylidene fluoride powder by vacuum filtration, and finally vacuum drying the polyvinylidene fluoride powder at 50° C. for 6 h to remove residual solvent, thereby obtaining polyvinylidene fluoride powder.

[0083] The test results show that the polyvinylidene fluoride powder has a regular spherical structure, and the particle size distribution range of the powder is narrow, mainly distributed in the range of 30~60μm, the angle of repose is 24.3°, and the bulk density is 0.35g / cm 3 , with a melt index of 58g / 10min. The performance of PVDF powder meets the requirements for powder materials in selective laser sintering and electrostatic spraying. Specifically, during selective laser sintering, with the powder feed cylinder preheated at 125°C and the build cylinder preheated at 150°C, the PVDF sintered strips achieved a tensile strength of 62.7 MPa and an elongation at break of 14.5%. During electrostatic spraying, with a curing temperature of 170°C, the PVDF coating achieved a Rockwell hardness of 105 and adhesion of 30.6 MPa. The coating also exhibits excellent heat resistance, chemical stability, wear resistance, and corrosion resistance.

[0084] Example 9

[0085] 1) Polyethylene naphthalate (PEN), a compound diluent (benzophenone and dimethyl phthalate, in a ratio of 3:7), and talc with a particle size of 200 nm were added to a reaction vessel in a mass ratio of 25.0:74.9:0.1. The temperature was first raised to 100°C and allowed to stand for 0.5 h. The temperature was then raised to 240°C and stirred at 300 rpm to dissolve the PEN pellets.

[0086] 2) The solution obtained in step 1) was kept warm for 1.5 hours to completely dissolve the polyethylene naphthalate pellets to obtain a homogeneous solution. The temperature of the homogeneous solution was then reduced to 100° C. at a cooling rate of 50° C. / min to allow solid-liquid phase separation of the polyethylene naphthalate and the diluent in the homogeneous solution. The polyethylene naphthalate solidified and precipitated into powder particles. The curing time during the curing process was 4 hours and the stirring rate was 20 rpm.

[0087] 3) After the solidified polyethylene naphthalate powder particles obtained in step 2) are further cooled to room temperature, they are placed in a composite extractant consisting of deionized water and methanol in a volume ratio of 1:1 for 4 hours to remove the diluent. The particles precipitated in the solution are the primary polyethylene naphthalate powder;

[0088] 4) Separating the liquid from the primary polyethylene naphthalate powder obtained in step 3) by vacuum filtration, then washing the polyethylene naphthalate powder five times with methanol at 40° C., each washing time being 20 min. After each washing, separating the polyethylene naphthalate powder by vacuum filtration, and finally drying the polyethylene naphthalate powder under vacuum at 60° C. for 4 h to remove residual solvent, thereby obtaining polyethylene naphthalate powder.

[0089] The test results show that polyethylene naphthalate powder has a regular spherical structure, and the particle size distribution range of the powder is narrow, mainly distributed in the range of 40~90μm, the angle of repose is 25.7°, and the bulk density is 0.29g / cm 3 , with a melt index of 38g / 10min. The properties of polyethylene naphthalate powder meet the requirements for powder material performance in selective laser sintering and electrostatic spraying. Specifically, during selective laser sintering, with the powder feed cylinder preheated at 200°C and the build cylinder preheated at 235°C, the sintered polyethylene naphthalate strips achieved a tensile strength of 72.4 MPa and an elongation at break of 11.9%. During electrostatic spraying, with a curing temperature of 280°C, the polyethylene naphthalate coating achieved a Rockwell hardness of 110 and an adhesion of 32.1 MPa. The coating also exhibits excellent heat resistance, chemical stability, wear resistance, and corrosion resistance.

[0090] Comparative Example 1

[0091] Comparative Example 1 is identical to steps 2), 3), and 4) of Example 1. The only difference from step 1) of Example 1 is that a single diluent, dibutyl sebacate, is used. Specifically:

[0092] 1) Polyetheretherketone, dibutyl sebacate, and silica with a particle size of 100 nm were added to a reaction vessel in a mass ratio of 30.0:69.9:0.1. The temperature was first raised to 150°C and allowed to stand for 0.5 h. The temperature was then raised to 270°C and stirred at 200 rpm to dissolve the polyetheretherketone pellets.

[0093] 2) The solution obtained in step 1) was kept warm for 2 hours to completely dissolve the polyetheretherketone pellets to obtain a homogeneous solution, and then the temperature of the homogeneous solution was reduced to 100° C. at a cooling rate of 10° C. / min to allow solid-liquid phase separation between the polyetheretherketone and the diluent in the homogeneous solution, and the polyetheretherketone was solidified and precipitated into powder particles, wherein the curing time during the curing process was 4 hours and the stirring rate was 50 rpm;

[0094] 3) After the solidified polyetheretherketone powder particles obtained in step 2) are further cooled to room temperature, they are placed in a composite extractant consisting of methanol and n-hexane in a volume ratio of 1:1 for 4 hours to remove the diluent. The particles precipitated in the solution are the primary polyetheretherketone powder;

[0095] 4) Separating the liquid from the polyetheretherketone primary powder obtained in step 3) by vacuum filtration, then washing the polyetheretherketone powder five times with ethanol and n-hexane at 30° C., each washing time being 20 min. After each washing, separating the polyetheretherketone powder by vacuum filtration, and finally drying the polyetheretherketone powder in vacuo at 60° C. for 2 h to remove the residual solvent, thereby obtaining polyetheretherketone powder.

[0096] After testing, the polyetheretherketone powder showed an irregular morphology, such as Figure 3 As shown, the particle size distribution of the powder is too wide, the angle of repose is 42.8°, and the bulk density is 0.12 g / cm 3 , melt index 12g / 10min. PEEK prepared with a single diluent exhibits poor sphericity, a wide particle size distribution, and poor fluidity, which is due to the mismatched (weak) interaction between the single diluent and PEEK.

[0097] Comparative Example 2

[0098] Comparative Example 2 is identical to steps 2), 3), and 4) of Example 1. The only difference from step 1) of Example 1 is that the composite diluent used is glyceryl monooleate and dibutyl sebacate. Specifically:

[0099] 1) PEEK, a compound diluent (glycerol monooleate and dibutyl sebacate, in a ratio of 7:3), and 100 nm silica were added to a reaction vessel at a mass ratio of 30.0:69.9:0.1. The temperature was first raised to 150°C and allowed to stand for 0.5 h. The temperature was then raised to 270°C and stirred at 200 rpm to dissolve the PEEK pellets.

[0100] 2) The solution obtained in step 1) was kept warm for 2 hours to completely dissolve the polyetheretherketone pellets to obtain a homogeneous solution, and then the temperature of the homogeneous solution was reduced to 100° C. at a cooling rate of 300° C. / min. The polyetheretherketone and the diluent in the homogeneous solution underwent liquid-liquid phase separation, and the polyetheretherketone did not precipitate. After solidification, a block material was precipitated. The solidification time during the solidification process was 4 hours, and the stirring rate was 50 rpm.

[0101] 3) After the polyetheretherketone block material obtained in step 2) is further cooled to room temperature, it is placed in a composite extractant composed of methanol and n-hexane in a volume ratio of 1:1 for 4 hours to remove the diluent, and large blocks of polyetheretherketone block material are precipitated in the solution;

[0102] 4) Separate the liquid from the polyetheretherketone bulk material obtained in step 3) by vacuum filtration, then wash the polyetheretherketone bulk material five times with ethanol and n-hexane at 30°C, each washing time being 20 minutes, separate the polyetheretherketone bulk material by vacuum filtration after each washing, and finally vacuum dry the polyetheretherketone bulk material at 60°C for 2 hours to remove the residual solvent, thereby obtaining the polyetheretherketone bulk material.

[0103] After testing, the polyetheretherketone block material showed a network structure (such as Figure 4 (As shown in Figure 2), this network structure is typical of liquid-liquid phase separation. This indicates that an inappropriate diluent type or ratio causes liquid-liquid phase separation in the specialty engineering plastic solution, making it impossible to prepare specialty engineering plastic powder.

[0104] Comparative Example 3

[0105] Comparative Example 3 is exactly the same as steps 1), 3) and 4) of Example 1. The only difference from step 2) of Example 1 is that the cooling rate is 500°C / min.

[0106] 1) PEEK, a compound diluent (diphenyl sulfone and dibutyl sebacate in a ratio of 7:3), and 100 nm silica were added to a reaction vessel in a mass ratio of 30.0:69.9:0.1. The temperature was first raised to 150°C and allowed to stand for 0.5 h. The temperature was then raised to 270°C and stirred at 200 rpm to dissolve the PEEK pellets.

[0107] 2) The solution obtained in step 1) was kept warm for 2 hours to completely dissolve the polyetheretherketone pellets to obtain a homogeneous solution, and then the temperature of the homogeneous solution was reduced to 100° C. at a cooling rate of 500° C. / min to allow solid-liquid phase separation of the polyetheretherketone and the diluent in the homogeneous solution, and the polyetheretherketone was solidified and precipitated into powder particles, wherein the curing time during the curing process was 4 hours and the stirring rate was 50 rpm;

[0108] 3) After the solidified polyetheretherketone powder particles obtained in step 2) are further cooled to room temperature, they are placed in a composite extractant consisting of methanol and n-hexane in a volume ratio of 1:1 for 4 hours to remove the diluent. The particles precipitated in the solution are the primary polyetheretherketone powder;

[0109] 4) Separating the liquid from the polyetheretherketone primary powder obtained in step 3) by vacuum filtration, then washing the polyetheretherketone powder five times with ethanol and n-hexane at 30° C., each washing time being 20 min. After each washing, separating the polyetheretherketone powder by vacuum filtration, and finally drying the polyetheretherketone powder in vacuo at 60° C. for 2 h to remove the residual solvent, thereby obtaining polyetheretherketone powder.

[0110] The test results show that the polyetheretherketone powder has a regular spherical structure, and the particle size distribution range of the powder is narrow, mainly distributed in the range of 0.1~5 μm, the angle of repose is 34.2°, and the bulk density is 0.52g / cm 3 , the melt index is 24g / 10min, which indicates that too fast a cooling rate will result in the generated powder particle size being too small, which cannot meet the application of selective laser sintering and electrostatic spraying.

[0111] Comparative Example 4

[0112] Comparative Example 4 is exactly the same as steps 2), 3) and 4) of Example 1. The only difference from step 1) of Example 1 is the heating process.

[0113] 1) Add polyetheretherketone (PEEK), a compound diluent (diphenyl sulfone and dibutyl sebacate, in a ratio of 7:3), and 100 nm silica particles in a mass ratio of 30.0:69.9:0.1 to a reaction vessel. Raise the temperature to 270°C and stir at 200 rpm to dissolve the PEEK pellets.

[0114] 2) The solution obtained in step 1) was kept warm for 2 hours to completely dissolve the polyetheretherketone pellets to obtain a homogeneous solution, and then the temperature of the homogeneous solution was reduced to 100° C. at a cooling rate of 10° C. / min to allow solid-liquid phase separation between the polyetheretherketone and the diluent in the homogeneous solution, and the polyetheretherketone was solidified and precipitated into powder particles, wherein the curing time during the curing process was 4 hours and the stirring rate was 50 rpm;

[0115] 3) After the solidified polyetheretherketone powder particles obtained in step 2) are further cooled to room temperature, they are placed in a composite extractant consisting of methanol and n-hexane in a volume ratio of 1:1 for 4 hours to remove the diluent. The particles precipitated in the solution are the primary polyetheretherketone powder;

[0116] 4) Separating the liquid from the polyetheretherketone primary powder obtained in step 3) by vacuum filtration, then washing the polyetheretherketone powder five times with ethanol and n-hexane at 30° C., each washing time being 20 min. After each washing, separating the polyetheretherketone powder by vacuum filtration, and finally drying the polyetheretherketone powder in vacuo at 60° C. for 2 h to remove the residual solvent, thereby obtaining polyetheretherketone powder.

[0117] After testing, the polyetheretherketone powder did not show a regular spherical structure (such as Figure 5 The main distribution range is 20~90μm, the angle of repose is 38.7°, and the apparent density is 0.15g / cm 3 , the melt index is 11g / 10min, which shows that a single heating process is not conducive to the dissolution of special engineering plastics, and the quality and uniformity of the obtained homogeneous solution are poor.

[0118] The above shows and describes the main features, methods of use, basic principles, and advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and improvements may be made to the present invention based on actual circumstances without departing from the spirit and scope of the present invention. Such changes and improvements are intended to fall within the scope of the present invention. The scope of protection claimed in the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a thermally induced phase separation atmospheric pressure special engineering plastic powder, characterized in that: The following steps are involved: 1) mixing special engineering plastic pellets, diluents and functional additives, wherein the special engineering plastics are selected from one or more of polyetheretherketone, polyetherketone, polyetherketoneketone, polyetheretherketoneketone, polyphenylene sulfide, liquid crystal polymer, polyimide, polysulfone, polyethersulfone, polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinylidene fluoride, polybutylene terephthalate, and polyethylene naphthalate pellets; the diluent is a compound diluent selected from any two or three of ethylene carbonate, caprolactam, acetyl tributyl citrate, diphenyl sulfone, benzophenone, dimethyl sulfoxide, cyclohexyl pyrrolidone, N-methyl pyrrolidone, dibutyl sebacate, benzophenone, triacetin, polyvinyl alcohol, polyethylene glycol, dimethyl phthalate, polyethylene glycol monomethyl ether, and acetamide; and the functional additives are particles with a diameter of 50 to 500 μm. The nano nucleating agent is of size 0.01 nm, and the functional additive is 0-0.4% of the total mass of the special engineering plastic granules, diluent and functional additive. The mixed system is heated and dissolved in stages: a. Heating to a first temperature A, standing and heating for 0.5 to 1 hour, wherein the first temperature A is 5 to 50° C. higher than the melting temperature of the diluent, and standing and heating for 0.5 to 1 hour at this temperature; b. Raise the temperature to a second temperature B, keep warm for 0.5 to 2 hours and stir until completely dissolved, wherein the second temperature B is 5 to 100°C lower than the melting temperature of the special engineering plastic; 2) cooling the homogeneous solution formed in step 1) at a rate of 10-300°C / min to a third temperature C that induces phase separation, thereby solidifying and precipitating powder particles; 3) After the powder particles are cooled to room temperature, an extractant is used to remove the diluent from the powder particles. After solid-liquid separation, solvent washing and drying, special engineering plastic powder is obtained.

2. The method for preparing thermally induced phase separation normal pressure special engineering plastic powder according to claim 1, characterized in that: The nano nucleating agent is one or more of nano silicon dioxide, nano zinc oxide, nano copper oxide, nano titanium dioxide, nano hydroxyapatite, nano calcium carbonate, nano talc, carbon nanotubes, and graphene.

3. The method for preparing thermally induced phase separation atmospheric pressure special engineering plastic powder according to claim 1, characterized in that: The special engineering plastic in step 1) is 20-60% of the total mass of the special engineering plastic pellets, diluent and functional additives in step 1), the stirring rate of the phase separation process in step 2) is 10-100 rpm, and the curing time is 0.25-5h.

4. The method for preparing thermally induced phase separation normal pressure special engineering plastic powder according to claim 1, characterized in that: The third temperature C is 0-10° C. lower than the crystallization temperature of the special engineering plastic.

5. The method for preparing thermally induced phase separation normal pressure special engineering plastic powder according to claim 1, characterized in that: In step 3), the extraction agent is selected from one or two of deionized water, methanol, ethanol, isopropanol, n-hexane or acetone, and the extraction time is 0.25 to 4 hours. In step 3), the solvent cleaning adopts one or two of deionized water, ethanol, n-hexane or acetone, and the number of cleaning times is 3 to 5 times, each cleaning time is 20 minutes, and the cleaning temperature is 30 to 60°C.

6. The method for preparing thermally induced phase separation normal pressure special engineering plastic powder according to claim 1, characterized in that: In step 3), the drying temperature is 40-80° C., and the drying time is 2-6 hours.

7. The plastic powder prepared according to the method according to any one of claims 1 to 6, characterized in that: The powder has a spherical structure, a particle size distribution of 10-100 μm, an angle of repose ≤30°, and a melt index of not less than 20 g / 10 min.

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