Copolyamide microparticles, method of preparation and shaped articles thereof

Abstract

The present invention provides a method for producing polyamide fine particles having a controlled particle size, a narrow particle size distribution, and a high degree of sphericity. The method is characterized by polymerizing monomer A and monomer B of polyamide in the presence of a polymer C, and precipitating fine particles containing a copolyamide in a state in which the copolyamide is dissolved in the polymer C or the copolyamide is dispersed in the polymer C in the form of droplets. The present invention also provides fine particles of a copolyamide having a narrow particle size distribution, a high degree of sphericity, and a melting point of 210°C or lower.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials, specifically relating to a copolyamide microparticle, its preparation method, and its molded product. Background Technology

[0002] Polyamide microparticles possess characteristics such as high toughness, flexibility, and high heat resistance, and are therefore used in various applications such as powders and coatings. For example, in recent years, with the development of 3D printing technology, polyamide microparticles with a spherical shape, solid structure, and smooth surface, made from polyamides such as polyamide 12, are beneficial for the flatness of powder spreading in powder bed fusion molding technology, resulting in a smooth surface of the molded product.

[0003] Patent documents 1 and 2 disclose methods for manufacturing porous polyamide microparticles by dissolving polyamide in a solvent and then adding a non-solvent and water. The resulting polyamide microparticles have a wide particle size distribution and a porous structure. Patent documents 3 and 4 disclose methods for vigorously stirring polyamide in a medium such as polyethylene glycol at a temperature above its melting point and methods for carrying out polycondensation reactions of polyamide raw materials in a silicone oil medium. However, since these methods involve mechanically dispersing polyamide within a polymer to manufacture particles, only microparticles with a wide particle size distribution can be produced.

[0004] Patent document 5 discloses anionic polymerization in a paraffin medium to provide amorphous polyamide microparticles. Patent document 6 further discloses a method for preparing anionic polymerized polyamide microparticles in ethylbenzene and chlorobenzene. However, the anionic polymerization technique is difficult to perform at high temperatures due to the flammability of the initiator and the use of flammable media and solvents. This reduces solubility and causes polyamide to precipitate in the solvent, resulting in amorphous microparticles. Furthermore, removing various media and solvents requires large amounts of organic solvents and various complex processes.

[0005] Furthermore, Patent Document 7 discloses a method of polymerizing polyamide monomers in polymers such as polyethylene glycol at a temperature above the crystallization temperature of polyamide to obtain polyamide microparticles. While the technology in Patent Document 7 solves some of the problems of Patent Documents 1-6, its preparation process still has shortcomings in controlling particle size, microparticle sphericity, and preventing particle aggregation. Moreover, the resulting polyamide microparticles still need improvement in terms of particle size, particle size distribution, and sphericity.

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent Document 1: Japanese Patent Application Publication No. 2002-080629

[0009] Patent Document 2: Japanese Patent Application Publication No. 2010-053272

[0010] Patent Document 3: Japanese Patent Application Publication No. 60-040134

[0011] Patent Document 4: Japanese Patent Application Publication No. 10-316750

[0012] Patent Document 5: Japanese Patent Application Publication No. 61-181826

[0013] Patent Document 6: Japanese Patent Application Publication No. 08-073602

[0014] Patent Document 7: Japanese Patent Application Publication No. 2019-167545 Summary of the Invention

[0015] The problem that the invention aims to solve

[0016] In view of the above problems, the present invention aims to provide a method for manufacturing copolyamide microparticles, which can polymerize and precipitate copolyamide microparticles in a polymer solvent. The microparticles have easily adjustable particle size, narrow particle size distribution, high sphericity, and the powder formed by the microparticles has good flowability. Furthermore, the crystallinity of the copolyamide in the microparticles is maintained to a certain extent, and the crystallinity of the copolyamide in the microparticles remains relatively good. In addition, the present invention also aims to provide copolyamide microparticles with narrow particle size distribution, high sphericity, good powder flowability, and high crystallinity, and to provide applications of the above-mentioned copolyamide microparticles in powder bed fusion bonding 3D printing technology and corresponding 3D printed products.

[0017] After repeated and in-depth research, the inventors discovered that when monomer A of polyamide is polymerized in the presence of polymer C, by adding monomer B to copolymerize with monomer A, and in the state where the copolyamide is dissolved in polymer C or the copolyamide forms droplets dispersed in polymer C, copolyamide-containing microparticles are precipitated. This allows for easy adjustment of particle size and particle size distribution, the precipitation of copolyamide microparticles with high sphericity, a certain melting point, and a certain degree of crystallinity, while also preventing the copolyamide microparticles from agglomerating.

[0018] The inventors have also discovered copolyamide microparticles with corresponding positive sphericity and melting point within a specific range, which can achieve a narrow particle size distribution and have high number-average molecular weight and crystallinity.

[0019] This invention comprises the following:

[0020] 1. A method for preparing copolyamide microparticles, characterized in that monomer A and monomer B of polyamide are polymerized in the presence of polymer C, and microparticles containing copolyamide are precipitated in the state where the copolyamide is dissolved in polymer C or in the state where the copolyamide forms droplets dispersed in polymer C; wherein monomer A is selected from one of a diamine having 8-20 carbon atoms and a diacid having 8-20 carbon atoms; monomer B is different from monomer A and is selected from one of a diamine having 2-20 carbon atoms, or a diacid having 2-20 carbon atoms, or an aminoalkyl acid having 3-12 carbon atoms, or a lactam having 3-12 carbon atoms.

[0021] 2. According to the preparation method of the copolyamide microparticles described in 1, the monomer A of the polyamide is selected from decanediamine and sebacic acid, or decanediamine and dodecanoic acid.

[0022] 3. According to the preparation method of the copolyamide microparticles described in 1, the monomer B of the polyamide is selected from a diamine having 2-20 carbon atoms, or a diacid having 2-20 carbon atoms and is different from both the diamine and the diacid in monomer A.

[0023] 4. According to the preparation method of the copolyamide microparticles described in 3, the monomer B of the polyamide is selected from one of butanediamine, pentanediamine, hexanediamine, adipic acid, azelaic acid or sebacic acid and is different from the diamine and dicarboxylic acid in monomer A.

[0024] 5. According to the preparation method of the copolyamide microparticles described in 3, the total molar amount of monomer A and monomer B is 100 mol%, and the amount of monomer B added is 1.0 to 45.0 mol%.

[0025] 6. According to the method for preparing copolyamide microparticles described in 5, the total molar amount of monomer A and monomer B is 100 mol%, and the amount of monomer B added is 5.0-20.0 mol% or 30.0-45.0 mol%.

[0026] 7. According to the method for preparing copolyamide microparticles described in 1, the monomer B of the polyamide is selected from one of aminoalkyl acids having 3-12 carbon atoms or lactams having 3-12 carbon atoms.

[0027] 8. According to the preparation method of copolyamide microparticles described in 7, the total molar amount of monomer A and monomer B is 100 mol%, and the amount of monomer B added is 1.0 to 90.0 mol%.

[0028] 9. According to the preparation method of the copolyamide microparticles described in 8, the total molar amount of monomer A and monomer B is 100 mol%, and the amount of monomer B added is 5.0-25.0 mol% or 70.0-90.0 mol%.

[0029] 10. According to the preparation method of copolyamide microparticles described in 1, the final polymerization temperature is above the melting point of the obtained copolyamide.

[0030] 11. According to the method for preparing copolyamide microparticles described in 1, the total weight W of monomer A and monomer B of the polyamide is... AB The weight W of the polymer C c The ratio of W AB / W c The value ranges from 0.25 to 2.50.

[0031] 12. According to the method for preparing copolyamide microparticles described in 1, the polymer C is at least one of polyethylene glycol, polypropylene glycol, poly1,4-butanediol, polyethylene glycol-polypropylene glycol copolymer, and polymers whose hydroxyl-terminal -OH is hydroxyalkylated.

[0032] 13. A copolyamide microparticle obtained by the preparation method described in 1-12, characterized in that the sphericity of the copolyamide microparticle is 70-100, and the melting point of the copolyamide microparticle is below 210°C.

[0033] 14. The copolyamide microparticles according to 13, characterized in that the copolyamide is composed of a first structural unit derived from a diamine having 8-20 carbon atoms, a second structural unit derived from a diacid having 8-20 carbon atoms, and a third structural unit derived from a diamine having 2-20 carbon atoms or a diacid having 2-20 carbon atoms, which is different from the two mentioned above.

[0034] 15. The copolyamide microparticles according to 13, characterized in that the copolyamide is composed of a first structural unit derived from a diamine having 8-20 carbon atoms, a second structural unit derived from a dicarboxylic acid having 8-20 carbon atoms, and a fourth structural unit derived from an aminoalkyl acid having 3-12 carbon atoms or a lactam having 3-12 carbon atoms.

[0035] 16. The copolyamide microparticles according to 13, characterized in that the volume-based average particle size MV of the copolyamide microparticles is 10 micrometers to 150 micrometers.

[0036] 17. The copolyamide microparticles according to 13, characterized in that the volume-based average particle size / number-based average particle size of the copolyamide microparticles is 1.00 to 2.50.

[0037] 18. The copolyamide microparticles according to 13, characterized in that the (D90-D10) / D50 of the copolyamide microparticles is less than 2.0.

[0038] 19. The copolyamide microparticles according to 13, characterized in that the copolyamide microparticles undergo a heating-cooling-reheating process at a rate of 20°C / min within the range of 0°C to 30°C above the melting point, wherein the enthalpy of fusion measured during the reheating process is 40 J / g or higher.

[0039] 20. The copolyamide microparticles according to 13, characterized in that the powder formed by the copolyamide microparticles has an angle of repose of less than 50° as measured according to ISO 902:1976.

[0040] 21. The use of the copolyamide microparticles of any one of 13-20 for powder bed fusion bonding 3D printing.

[0041] 22. A 3D printed product obtained by powder containing copolyamide microparticles as described in any one of 13-20 through a powder bed fusion bonding method.

[0042] 23. The 3D printed article according to 22, characterized in that the surface roughness Ra value of the 3D printed article is less than 20 μm.

[0043] 24. The 3D printed article according to 22, characterized in that the warpage value of the 3D printed article is less than 3mm / 10cm.

[0044] The effects of the invention

[0045] This invention involves polymerizing polyamide monomers A and B in the presence of polymer C. The resulting copolyamide is dissolved in polymer C or dispersed as droplets within polymer C, precipitating copolyamide-containing microparticles. This manufacturing method suppresses the aggregation of copolyamide droplets within polymer C and prevents polymer C from being trapped inside the copolyamide droplets, making them impossible to remove in subsequent steps. This results in copolyamide microparticles with easily adjustable particle size range, narrow particle size distribution, high sphericity, smooth particle surface, good powder flowability, and good crystallinity. When using powder containing these copolyamide microparticles for powder bed fusion bonding 3D printing, 3D printed products with smooth surfaces and low warpage values ​​can be obtained. Detailed Implementation

[0046] The present invention is a method for obtaining copolyamide microparticles by polymerizing polyamide monomer A and polyamide monomer B in the presence of polymer C, wherein the polymerized copolyamide is dissolved in polymer C or dispersed as droplets in polymer C.

[0047] The inventors discovered in their experiments that, without the addition of polyamide monomer B, during the polymerization of polyamide monomer A, as the polymerization reaction proceeds, the molecular weight of the polyamide increases, forming droplets that separate from polymer C. After a suitable polymerization time, cooling the mixture of polyamide and polymer C, for example by immersing it in water, causes the polyamide droplets to solidify into polyamide microparticles due to cooling. Since the polyamide and polymer C have separated, removing polymer C allows for the separation of polyamide microparticles. However, the separation of polyamide and polymer C during polymerization is influenced by many factors, and the separation of polyamide and polymer C into droplets is a crucial step in the final formation of polyamide microparticles, affecting the final particle size, particle size distribution, and other properties of the polyamide microparticles. Influenced by factors such as the ratio of polyamide monomer A to polymer C, the compatibility of different types of polyamide with polymer C, and viscosity differences, polyamide often fails to separate from polymer C, or although the polyamide droplets separate from polymer C, they aggregate, or even the aggregation of polyamide leads to the encapsulation of polymer C within them. The above situation can cause polyamide microparticles to stick together, making it difficult to control the particle size and resulting in a wide particle size distribution. It also greatly reduces the sphericity of the polyamide microparticles, and may even cause the polyamide microparticles to agglomerate into flocculent form, making it impossible to separate them at all.

[0048] To address this problem, the inventors conducted extensive experiments and discovered that copolymerizing polyamide monomer B with monomer A could inhibit polyamide droplet aggregation, allowing the copolyamide droplets to smoothly separate from polymer C and form copolyamide microparticles. Unexpectedly, they also found that after adding a certain amount of monomer B for copolymerization, the copolyamide microparticles consistently maintained a narrow particle size distribution, and the polyamide microparticles were spherical with consistently high sphericity. Therefore, by uniformly dissolving polyamide monomers A and B in polymer C and precipitating copolyamide microparticles after polymerization, the problems of irregular shape and wide particle size distribution caused by polyamide microparticle aggregation in previous preparation methods can be solved, resulting in copolyamide microparticles with high sphericity, smooth surface, good powder flowability, fine size, and narrow particle size distribution. The powder formed from such copolyamide microparticles is particularly suitable for powder bed fusion bonding 3D printing technology, and the resulting 3D printed products have smooth surfaces and low warpage.

[0049] The copolyamide constituting the copolyamide microparticles of the present invention refers to a copolymer containing an amide group, which comprises structural units from monomer A and monomer B. Monomer A, which forms the copolyamide structure, is selected from one diamine having 8-20 carbon atoms and one diacid having 8-20 carbon atoms. Examples of diamines include aliphatic diamines such as octanediamine, nonanediamine, decanediamine, undecanediamine, dodecanediamine, tridecanediamine, tetradecanediamine, pentadecanediamine, hexadecanediamine, heptadecanediamine, octadecanediamine, nonadecanediamine, eicosanediamine, or 2-methyl-1,8-octanediamine; alicyclic diamines such as 4,4'-diaminodicyclohexylmethane or 4,4'-methylenebis(2-methylcyclohexylamine); and aromatic diamines such as phenylenediamine. Considering the melting point and crystallinity of the copolyamide, the diamine in monomer A is preferably octanediamine, nonanediamine, decanediamine, undecanediamine, or dodecanediamine, with decanediamine being the most preferred. Examples of dicarboxylic acids in monomer A include aliphatic dicarboxylic acids such as octanoic acid, azelaic acid, sebacic acid, or dodecanoic acid; aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, 2-chloro-1,4-phthalic acid, 2-methyl-1,4-phthalic acid, 5-methylisophthalic acid, or sodium 5-sulfonate isophthalic acid; and alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid. Considering the melting point and crystallinity of the copolyamide, the aforementioned dicarboxylic acids are preferably octanoic acid, azelaic acid, sebacic acid, or dodecanoic acid, with sebacic acid or dodecanoic acid being the most preferred.

[0050] Monomer B, which forms the copolyamide structure, is selected from one of the following: a diamine having 2-20 carbon atoms, a diacid having 2-20 carbon atoms, an aminoalkyl acid having 3-12 carbon atoms, or a lactam having 3-12 carbon atoms, and is different from both the diamine and diacid in monomer A. Specific examples of diamines include ethylenediamine, propylenediamine, butanediamine, pentanediamine, hexanediamine, heptadecanediamine, octanediamine, nonanediamine, decanediamine, undecanediamine, dodecanediamine, tridecanediamine, tetradecanediamine, pentadecanediamine, hexadecanediamine, heptadecanediamine, octadecanediamine, nonadecanediamine, eicosanediamine, 2-methyl-1,5-pentanediamine, or 2-methyl-1,8-octanediamine, etc.; alicyclic diamines such as cyclohexanediamine, 4,4'-diaminodicyclohexylmethane, or 4,4'-methylenebis(2-methylcyclohexylamine); and aromatic diamines such as phenylenediamine. Monomer B can include aliphatic dicarboxylic acids such as oxalic acid, succinic acid, adipic acid, octanoic acid, azelaic acid, sebacic acid, or dodecanoic acid; aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, 2-chloro-1,4-phthalic acid, 2-methyl-1,4-phthalic acid, 5-methylisophthalic acid, or sodium isophthalic acid sulfonate; and alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid. Monomer B containing 3-12 carbon atoms can include aminoalkyl acids such as β-alanine, γ-aminobutyric acid, 5-aminovaleric acid, 6-aminohexanoic acid, 7-aminoheptanoic acid, 8-aminooctanoic acid, 9-aminononanoic acid, 10-aminodecanoic acid, 11-aminoundecanoic acid, or 12-aminododecanoic acid. Lactams with 3-12 carbon atoms in monomer B can be specifically categorized as γ-butyrolactam, δ-valeractam, ε-caprolactam, ω-heptylactam, ω-octylactam, ω-undecaprolactam, or ω-dodecylactam.

[0051] Considering the effects of improving solubility with polymer C, and obtaining polyamide microparticles with fine particle size, narrow particle size distribution, high sphericity, prevention of microparticle aggregation, and maintenance of crystallinity, the monomer B is preferably ethylenediamine, propylenediamine, butanediamine, pentanediamine, hexanediamine, heptamethamine, octanediamine, nonanediamine, decanediamine, oxalic acid, adipic acid, azelaic acid, sebacic acid, dodecanoic acid, β-alanine, γ-aminobutyric acid, 5-aminovaleric acid, 6-aminohexanoic acid, 11-aminoundecanoic acid, γ-butyrolactam, δ-valeractam, ε-caprolactam, ω-undecanoic acid, or ω-dodecanoic acid. More preferably, it is butanediamine, pentanediamine, hexanediamine, adipic acid, azelaic acid, sebacic acid, or ε-caprolactam. Even more preferably, it is butanediamine, pentanediamine, hexanediamine, adipic acid, azelaic acid, or sebacic acid. Most preferably, it is pentanediamine or azelaic acid.

[0052] When monomer B is a diamine or diacid, considering the control of particle size and particle size distribution, reduction of melting point, and maintenance of crystallinity of the resulting copolyamide microparticles, the addition amount is preferably 1.0–45.0 mol%, more preferably 5.0–20.0 mol% or 30.0–45.0 mol%, with a total molar percentage of monomer A and monomer B of 100 mol%. By controlling the addition amount of monomer B within the above range, it is easier to control the sphericity, particle size, and particle size distribution of the copolyamide microparticles, avoid particle aggregation, and better maintain the crystallinity of the copolyamide microparticles.

[0053] When monomer B is an aminoalkyl acid or lactam, considering the control of particle size and particle size distribution, reduction of melting point, and maintenance of crystallinity of the resulting copolyamide microparticles, the addition amount is preferably 1.0–90.0 mol%, more preferably 5.0–25.0 mol% or 70.0–90.0 mol%, with a total molar percentage of monomer A and monomer B of 100 mol%. By controlling the addition amount of monomer B within the above range, it is easier to control the sphericity, particle size, and particle size distribution of the copolyamide microparticles, avoid particle aggregation, and better maintain the crystallinity of the copolyamide microparticles.

[0054] Polyamide monomers A and B contain carboxyl and amino groups. The total molar amount N of amino groups in monomers A and B is as follows. AB And the molar amount of total carboxyl groups C AB The molar ratio can be calculated based on the masses of monomers A and B of the polyamide, the relative molecular masses of monomers A and B, and the molar amounts of carboxyl and amino groups in one molecule of monomer A and monomer B. When monomer B of the polyamide is a lactam, the molar ratio is calculated using the amounts of amino and carboxyl groups obtained from the hydrolysis of the amide groups. From the viewpoint of increasing the polymerization rate and thus increasing the molecular weight, the preferred molar ratio N of the total amino group amount to the total carboxyl group amount of monomers A and B of the polyamide is... AB / C AB The value ranges from 0.90 to 1.10, and the N value can be adjusted as needed depending on the target molecular weight. AB / C AB The value is adjusted within the above range, with N being the preferred value. AB / C AB The value is 0.980 to 1.035, with N being more preferred. AB / C AB The value is 0.985 or higher, and more preferably 0.990 or higher. More preferably, N... AB / C AB The value is below 1.030, and is further preferred to be below 1.020.

[0055] In this invention, the melting point of the resulting copolyamide varies depending on the selection and proportion of monomers A and B in the polyamide. To prevent polymer C from being encapsulated within the formed copolyamide particles at the end of polymerization, which would prevent its removal during subsequent processing, the final polymerization temperature is preferably above the melting point of the resulting copolyamide. When the final polymerization temperature is higher than the melting point of the copolyamide, polymer C is less likely to be encapsulated within the copolyamide particles, making it easier to remove during subsequent processing and thus not affecting the properties of the copolyamide particles. Furthermore, from the viewpoint of preventing the polyamide and polymer C from being difficult to decompose, the polymerization temperature is preferably below the melting point of the desired polyamide + 100°C, more preferably below the melting point of the desired polyamide + 50°C, and even more preferably below the melting point of the desired polyamide + 20°C.

[0056] In this invention, in order to ensure that polyamide monomers A and B dissolve more uniformly in polymer C while maintaining reaction efficiency, the total weight W of monomers A and B is [not specified]. AB The weight W of the polymer C c The ratio of W AB / W c Preferably, it is 0.25 to 2.50. Weight ratio W AB / W c Too low a concentration will result in excessively low polyamide microparticle yield; the lower limit is more preferably 0.25 or higher, and even more preferably 0.67 or higher. On the other hand, the weight ratio W... AB / W c Excessive concentration can prevent polyamide monomers from dissolving uniformly in polymer C. The upper limit is more preferably below 1.50, and even more preferably below 1.

[0057] In this invention, to ensure that polyamide monomers A and B dissolve more uniformly in polymer C, the melting point of polymer C is preferably between 30°C and 200°C. Within this temperature range, degradation of polymer C during polymerization can be prevented, while also improving the solubility of polyamide monomers A and B. From this perspective, the melting point of polymer C is more preferably above 40°C, and even more preferably above 50°C. The melting point of polymer C is more preferably below 150°C, and even more preferably below 100°C.

[0058] Similar to the above, from the viewpoint that polyamide monomers A and B are uniformly dissolved in polymer C, the number average molecular weight of polymer C is preferably 500 to 500,000. Within this molecular weight range, polymer C can prevent degradation while facilitating the dissolution of polyamide monomers A and B. More preferably, the molecular weight of polymer C is 1,000 or more, and even more preferably 5,000 or more. More preferably, it is 100,000 or less, and even more preferably 50,000 or less. Furthermore, polymer C can be a mixture of polymers with different number average molecular weights.

[0059] The copolyamide microparticles of the present invention are obtained by precipitating out copolyamide dissolved in polymer C or by forming droplets dispersed in polymer C. From this point of view, it is preferable that polymer C and the monomers of the polyamide are non-reactive and that polymer C readily dissolves polyamide monomers A and B.

[0060] Specific examples of such polymer C include polyethylene glycol, polypropylene glycol, poly1,4-butanediol, poly1,5-pentanediol, poly1,6-hexanediol, polyethylene glycol-polypropylene glycol copolymers, polyethylene glycol-poly1,4-butanediol copolymers, and polymers in which the single- or double-terminal hydroxyl groups are hydroxyalkylated with alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, hexyl, octyl, decyl, dodecyl, hexadecyl, or octadecyl, or polymers hydroxyalkylated with octylphenyl, etc. In particular, from the viewpoint of excellent compatibility with polyamide monomer A and monomer B, polyethylene glycol, polyethylene glycol-polypropylene glycol copolymers, polypropylene glycol, poly1,4-butanediol, and polymers in which the -OH-terminal hydroxyl groups are hydroxyalkylated are preferred, further preferred are polyethylene glycol and polyethylene glycol-polypropylene glycol copolymers, and most preferred is polyethylene glycol. Polymer C can be used alone or in combination of two or more.

[0061] Regarding the polymerization of monomers A and B, known methods such as the condensation polymerization of aminoalkyl acids, anionic ring-opening polymerization of lactams and initiators, cationic ring-opening polymerization, condensation polymerization of aminoalkyl acids obtained from lactam hydrolysis, and condensation polymerization of diacids with diamines or their salts can be cited.

[0062] In the later stages of the polymerization reaction described above, inactive gases such as nitrogen can be circulated or the water generated during the polymerization reaction can be removed from the polymerization system more efficiently under reduced pressure, thereby promoting the polymerization process.

[0063] In the preparation method of the present invention, solvent D may be added to better form a homogeneous solution of polyamide monomer A, monomer B, and polymer C. Preferably, solvent D is water, diethyl ether, tetrahydrofuran, dimethyl sulfoxide, ethanol, methanol, or N-methylpyrrolidone. Considering the need to dissolve monomer A, monomer B, and polymer C, and the requirement to remove condensation water from the system to allow the polycondensation reaction to proceed, the solvent D is more preferably water. The total weight W of the polyamide monomers A and B is used as the reference. AB The solvent D is preferably added in amounts of 5 to 900 parts by weight per 100 parts by weight. To ensure a better homogeneous solution formation in the initial stages of polymerization, the amount of solvent D added is more preferably 10 parts by weight or more, and even more preferably 20 parts by weight or more. Furthermore, considering polymerization efficiency, the amount of solvent D added is more preferably 200 parts by weight or less, and even more preferably 100 parts by weight or less. When the polyamide monomer B is a lactam and the solvent D is water, the water also has the effect of hydrolyzing the lactam.

[0064] The polymerization time can be appropriately adjusted according to the molecular weight of the polyamide microparticles to be obtained. From the viewpoint of increasing the degree of polymerization of the polyamide while preventing its decomposition, a range of 0.1 to 70 hours is generally preferred. As a lower limit for the polymerization time, 0.2 hours or more is more preferred, 0.3 hours or more is even more preferred, and 0.5 hours or more is particularly preferred. As an upper limit for the polymerization time, 50 hours or less is more preferred, 25 hours or less is even more preferred, and 10 hours or less is particularly preferred.

[0065] In this invention, since polyamide microparticles can be homogenized from a uniform solution, fine microparticles can be produced even without stirring. However, stirring can be performed to control particle size and achieve a more uniform particle size distribution. Known devices such as stirring blades, melt mixers, and homogenizers can be used as stirring devices. For example, in the case of stirring blades, propellers, paddles, flat blades, turbines, conical blades, anchor blades, screws, or spiral blades can be used. The stirring speed is determined based on the type and molecular weight of polymer B, but from the viewpoint of ensuring homogeneous heat transfer even in large-scale equipment, and from the viewpoint of preventing changes in the mix proportions due to liquid adhesion to the wall surface, a range of 0 to 2000 rpm is preferred. The lower limit of the stirring speed is more preferably 10 rpm or more, further preferably 30 rpm or more, and particularly preferably 50 rpm or more. The upper limit of the stirring speed is more preferably 1600 rpm or less, further preferably 1200 rpm or less, and particularly preferably 800 rpm or less.

[0066] To separate the polyamide microparticles from the mixture of copolyamide microparticles and polymer C after polymerization, the mixture at the end of polymerization can be added to a poor solvent containing the copolyamide microparticles, and then the copolyamide microparticles can be separated from the mixture by any of the known methods such as reduced pressure filtration, pressure filtration, decantation, centrifugation, or spray drying. This separation operation can be performed by discharging the mixture into a poor solvent containing the copolyamide microparticles, or by adding a poor solvent containing the copolyamide microparticles to the reaction tank before separation. From the viewpoint of preventing the copolyamide microparticles from melting and agglomerating, thus expanding the particle size distribution, it is preferable to perform the separation method after cooling to below the melting point of the copolyamide microparticles, and more preferably below the crystallization temperature.

[0067] The term "unsuitable solvent" refers to a solvent with an interaction parameter χ of 0.5 or higher with the copolyamide. It is acceptable as long as it can dissolve monomer A, monomer B, and polymer C without dissolving the polyamide particles. Examples of such solvents include alcohols such as methanol, ethanol, and isopropanol, or water.

[0068] In this invention, the copolyamide microparticles can be washed after separation using known methods to remove adhering substances and inclusions. The washing can be performed using slurry washing or similar methods, and heating can be applied as needed. As a solvent used for washing, there are no limitations as long as it dissolves monomer A, monomer B, and polymer C without dissolving the copolyamide; from an economic point of view, methanol, ethanol, isopropanol, or water are preferred, with water being the most preferred. Furthermore, the washed copolyamide microparticles can be dried. Known drying methods such as air drying, hot air drying, heat drying, vacuum drying, or freeze drying can be selected. In the copolyamide microparticles of this invention, the content of byproducts used in the copolyamide microparticle manufacturing process, such as polymer C and washing solvent, is less than 0.1 wt% (based on 100 wt% of the copolyamide mass). Such byproducts reduce the flowability of the powder composition formed from the microparticles; therefore, it is more preferable to be less than 0.05 wt%, and even more preferably less than 0.01 wt%. It should be noted that the content of such byproducts can be analyzed using known methods. For example, they can be extracted from polyamide powder using water or organic solvents, the solvent can be removed, and then water can be used as a solvent for quantification using gel permeation chromatography.

[0069] Using the methods described above, it is possible to manufacture copolyamide microparticles of various sizes, with narrow particle size distribution, high sphericity, and melting points below 210°C. The following is a description of these copolyamide microparticles.

[0070] The copolyamide microparticles of this invention are spherical or nearly spherical in shape. Therefore, powder containing these copolyamide microparticles exhibits good flowability, meeting the powder flowability requirements of powder bed fusion bonding 3D printing. Preferably, the sphericity of the polyamide microparticles of this invention is 70 or higher. In powder bed fusion bonding 3D printing applications, the higher the sphericity of the microparticles, the better the flowability of the resulting powder, the higher the uniformity of powder spreading, and the lower the surface roughness, the higher the surface smoothness, and the less warpage of the obtained 3D printed product. From this perspective, the sphericity is preferably 80 or higher, more preferably 90 or higher, and even more preferably 95 or higher. Furthermore, its upper limit is 100.

[0071] The melting point of the copolyamide microparticles of the present invention varies depending on the composition of the structural units constituting the copolyamide. The upper limit of the melting point is 210°C, and it is preferably below 205°C, more preferably below 200°C. Controlling the melting point of the copolyamide within this range ensures that it can be 3D printed on a general-purpose 3D printer without failing to melt, thus not affecting its 3D printability. The melting point of the copolyamide is preferably above 100°C, more preferably above 120°C, and even more preferably above 160°C.

[0072] The structural unit of the copolyamide microparticle can be composed of a first structural unit derived from a diamine having 8-20 carbon atoms, a second structural unit derived from a diacid having 8-20 carbon atoms, a third structural unit derived from a diamine or diacid having 2-20 carbon atoms (different from the two mentioned above), or a fourth structural unit derived from an aminoalkyl acid or lactam having 3-12 carbon atoms.

[0073] Examples of diamines having 8-20 carbon atoms that constitute the first structural unit include aliphatic diamines such as octanediamine, nonanediamine, decanediamine, undecanediamine, dodecanediamine, tridecanediamine, tetradecanediamine, pentadecanediamine, hexadecanediamine, heptadecanediamine, octadecanediamine, nonadecanediamine, eicosanediamine, or 2-methyl-1,8-octanediamine; alicyclic diamines such as 4,4'-diaminodicyclohexylmethane or 4,4'-methylenebis(2-methylcyclohexylamine); or aromatic diamines such as phenylenediamine; preferably octanediamine, nonanediamine, decanediamine, undecanediamine, or dodecanediamine, with decanediamine being the most preferred.

[0074] Examples of dicarboxylic acids having 8-20 carbon atoms constituting the second structural unit include aliphatic dicarboxylic acids such as octanoic acid, azelaic acid, sebacic acid, or dodecanoic acid; aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, 2-chloro-1,4-phthalic acid, 2-methyl-1,4-phthalic acid, 5-methylisophthalic acid, or sodium 5-sulfonate isophthalic acid; or alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid; octanoic acid, azelaic acid, sebacic acid, or dodecanoic acid are preferred, and sebacic acid or dodecanoic acid are most preferred.

[0075] Specific examples of diamines or dicarboxylic acids having 2-20 carbon atoms, which are different from the aforementioned diamines and dicarboxylic acids having 8-20 carbon atoms and constitute the third structural unit, include ethylenediamine, propylenediamine, butanediamine, pentanediamine, hexanediamine, heptadecanediamine, octanediamine, nonanediamine, decanedanediamine, undecanediamine, dodecanediamine, tridecanediamine, tetradecanediamine, pentadecanediamine, hexadecanediamine, heptanediamine, octadecanediamine, nonadecananediamine, eicosanediamine, and 2-methyl-1,5-pentanediamine. Aliphatic diamines such as 2-methyl-1,8-octanediamine; alicyclic diamines such as cyclohexanediamine, 4,4'-diaminodicyclohexylmethane, or 4,4'-methylenebis(2-methylcyclohexylamine); aromatic diamines such as phenylenediamine; aliphatic dicarboxylic acids such as oxalic acid, succinic acid, adipic acid, octanoic acid, azelaic acid, sebacic acid, or dodecanoic acid; aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, 2-chloro-1,4-phthalic acid, 2-methyl-1,4-phthalic acid, 5-methylisophthalic acid, or sodium isophthalic acid 5-sulfonate; and alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid.

[0076] Specific examples of aminoalkyl acids or lactams having 3-12 carbon atoms that constitute the fourth structural unit include β-alanine, γ-aminobutyric acid, 5-aminovaleric acid, 6-aminohexanoic acid, 7-aminoheptanoic acid, 8-aminooctanoic acid, 9-aminononanoic acid, 10-aminodecanoic acid, 11-aminoundecanoic acid, 12-aminododecanoic acid; lactams such as γ-butyrolactam, δ-valeractam, ε-caprolactam, ω-heptanolactam, ω-octanolactam, ω-undecanolactam, or ω-dodecanolactam.

[0077] Considering the effects of producing copolyamide microparticles with fine particle size and narrow particle size distribution, high sphericity, and preventing microparticle aggregation, the third structural unit is preferably derived from ethylenediamine, propylenediamine, butanediamine, pentanediamine, hexanediamine, heptaethylenediamine, octanediamine, nonanediamine, decanediamine, oxalic acid, adipic acid, azelaic acid, sebacic acid, dodecanoic acid, 6-aminohexanoic acid, 11-aminoundecanoic acid, or 12-aminododecanoic acid. More preferably, it is derived from one of butanediamine, pentanediamine, hexanediamine, adipic acid, azelaic acid, or sebacic acid. Most preferably, it is derived from a structural unit derived from pentanediamine or azelaic acid. The fourth structural unit is preferably derived from one of ε-caprolactam, ω-undecanoic acid, or ω-dodecanoic acid. More preferably, it is derived from a structural unit derived from ε-caprolactam.

[0078] Regarding the content of the third structural unit in the copolyamide, with the total molar number of the first and second structural units being 100 mol%, the content is preferably 1.0 to 45.0 mol%. Considering the control of particle size, sphericity, melting point, and crystallinity of the copolyamide particles, the content of the third structural unit is further preferably 5.0 to 20.0 mol% or 30.0 to 45.0 mol%.

[0079] Regarding the content of the fourth structural unit in the copolyamide, with the total molar number of the first and second structural units being 100 mol%, the content is preferably 1.0 to 90.0 mol%. Considering the control of particle size, sphericity, melting point, and crystallinity of the copolyamide particles, the content of the fourth structural unit is further preferably 5.0 to 25.0 mol% or 70.0 to 90.0 mol%.

[0080] The copolyamide microparticles of the present invention, considering the particle size requirements of copolyamide microparticles in practical applications, preferably have a volume-based average particle size (MV) of 10 to 150 micrometers. The lower limit of the volume-based average particle size (MV) is more preferably 20 micrometers or more, and even more preferably 30 micrometers or more. Furthermore, the upper limit of the volume-based average particle size (MV) is more preferably 115 micrometers or less, and even more preferably 94 micrometers or less. In applications where microparticles are used in powder bed fusion bonding 3D printing, excessively large or small particle sizes can lead to uneven melting and poor powder flowability, thereby affecting the surface smoothness of the molded product. By maintaining the particle size within the above-mentioned range, the powder formed by the microparticles maintains good flowability and can melt uniformly during the 3D printing process, resulting in a smooth surface and resistance to warping of the 3D printed product.

[0081] The volume-based average particle size / number-based average particle size distribution of the copolyamide microparticles in this invention is 1.00 to 2.50. A volume-based average particle size / number-based average particle size of less than 2.50 indicates a narrow particle size distribution and good microparticle flowability, which meets the requirements for subsequent applications. For example, when copolyamide microparticles are used in powder bed fusion bonding 3D printing, uniform particle filling is necessary. Within the aforementioned range, the microparticles exhibit good flowability, enabling uniform filling and melting, resulting in a smooth surface and reduced warping of the 3D printed product. The volume-based average particle size / number-based average particle size is preferably less than 2.00, more preferably less than 1.50. Furthermore, its lower limit is theoretically 1.00.

[0082] Regarding the particle size distribution of the copolyamide microparticles, in addition to the evaluation criterion of volume-based average particle size / number-based average particle size, there is also the evaluation criterion of (D90-D10) / D50. The (D90-D10) / D50 of the copolyamide microparticles in this invention is preferably below 2.0. D50, D90, and D10 in (D90-D10) / D50 are all measured on a volume basis. The evaluation criteria for (D90-D10) / D50 and volume-based average particle size / number-based average particle size are different and cannot be converted to each other. When using (D90-D10) / D50 to evaluate particle size distribution, the smaller the value of (D90-D10) / D50, the more uniform the microparticles. When microparticles are used in powder bed fusion bonding 3D printing, uniform filling of the microparticles is necessary. Within the above range, the microparticles have good flowability, can fill uniformly, and melt uniformly, resulting in a smooth surface of the 3D printed product and resistance to warping. From this perspective, the (D90-D10) / D50 ratio of the copolyamide microparticles is preferably 1.6 or less.

[0083] The volume-based average particle size MV, number-based average particle size MN, particle size D50 at 50% frequency cumulativeity, particle size D90 at 90% frequency cumulativeity, and particle size D10 at 10% frequency cumulativeity of the aforementioned polyamide microparticles can be determined using laser diffraction particle size analysis. The instrument used was a Microtrace S3500, and deionized water was used as the dispersant.

[0084] The number-average molecular weight of the copolyamide microparticles described in this invention is preferably between 5,000 and 50,000. Controlling this range is beneficial for various subsequent applications. For example, in powder bed fused deposition modeling (FDM) 3D printing, copolyamide microparticles within this range can melt uniformly and the molded product can maintain high mechanical strength. The upper limit of the number-average molecular weight of the copolyamide microparticles is more preferably below 30,000, and even more preferably below 25,000. Furthermore, the lower limit of the number-average molecular weight of the copolyamide microparticles is more preferably above 8,000, and even more preferably above 10,000.

[0085] The copolyamide microparticles of this invention exhibit good crystallinity. Using a differential scanning calorimeter, the copolyamide is subjected to a heating-cooling-reheating process at a rate of 20°C / min within the range of 0°C to 30°C above its melting point. During the reheating process, the enthalpy of fusion of the copolyamide is preferably 40 J / g or higher, more preferably 50 J / g or higher, and even more preferably 60 J / g or higher. When the enthalpy of fusion of the copolyamide is within the above-mentioned preferred range, its crystallinity is good, and it easily forms microparticles with high sphericity during polymerization. Because the crystallinity of the copolyamide is well maintained, the final molded product possesses high mechanical strength, heat resistance, and solvent resistance.

[0086] The copolyamide microparticles of this invention have a narrow particle size distribution, high sphericity, and smooth surface, resulting in powder with good flowability. Powder flowability can be characterized by the angle of repose measured according to ISO 902:1976. A smaller angle of repose indicates better powder flowability; preferably, the angle of repose is below 50°, more preferably below 40°. The lower limit of the angle of repose is typically above 20°.

[0087] This invention is particularly suitable for powder bed fused deposition modeling (PDM) 3D printing because it can produce polyamide microparticles with suitable particle size, narrow particle size distribution, high sphericity, good crystallinity, and high powder flowability. Without impairing the beneficial effects of this invention, other compounds can be added to the polymer powder of this invention to form a powder composition for PDM 3D printing. Examples of additives include antioxidants and heat stabilizers to suppress thermal degradation caused by heating during PDM 3D printing. Examples of antioxidants and heat stabilizers include hindered phenols, hydroquinone, phosphites, their substitutes, phosphites, or hypophosphites. Other products include pigments and dyes for coloring, plasticizers for adjusting viscosity, flow promoters for improving powder flowability, antistatic agents for adding functionality, flame retardants, and fillers such as carbon black, silica, titanium dioxide, glass fiber, and glass microspheres. The above additives can be commercially available products from various manufacturers, and they can be present inside or outside the copolyamide microparticles.

[0088] In the 3D printing process, due to the suitable particle size and narrow particle size distribution, the powder can melt uniformly during the powder bed fusion 3D printing process. Simultaneously, the powder has good flowability, allowing for uniform filling and resulting in a high surface smoothness of the molded product. The smaller the surface roughness Ra, the higher the surface smoothness. The surface roughness Ra value of the molded product is preferably below 20 μm, more preferably below 15 μm, and even more preferably below 10 μm.

[0089] Furthermore, due to its suitable particle size and narrow particle size distribution, the powder can melt uniformly during the powder bed fusion bonding 3D printing process. Simultaneously, the powder has good flowability, allowing for uniform filling during printing, resulting in lower warpage in the final product. The warpage value can be measured using a printed standard spline. Preferably, the warpage value is below 3 mm / 10 cm, more preferably below 2.5 mm / 10 cm, and even more preferably below 2 mm / 10 cm. When the microparticles of this invention are used in 3D printing with a mixed powder formed from reinforcing materials such as glass fiber and copolyamide microparticles, the warpage value can be further reduced to below 0.3 mm / 10 cm.

[0090] The present invention will be further described below with reference to the embodiments, but this does not mean that the present invention is limited to these embodiments.

[0091] The tests involved in the embodiments and comparative examples are described below:

[0092] (1) Method for determining the molar concentration of amino acids

[0093] The polyamide microparticles obtained in each example and comparative example were accurately weighed and dissolved in a phenol / ethanol mixture with a volume ratio of 85 / 15 to prepare a 0.01 g / mL solution. This solution was then titrated with 0.02 mol / L hydrochloric acid at 25°C. The molar concentration of the amino group is expressed as C0. NH2 The unit is ×10 -5 mol / g. The above test was repeated twice for each sample, and the average value of the results was taken as the amino molar concentration. (2) Method for determining the carboxyl molar concentration:

[0094] The polyamide microparticles obtained in each example and comparative example were accurately weighed and dissolved in benzyl alcohol to prepare a 0.01 g / mL solution, which was then titrated at 190°C with a 0.02 mol / L potassium hydroxide ethanol solution. The molar concentration of carboxyl groups is expressed as C0. COOH The unit is ×10 -5 mol / g. The above test was repeated twice for each sample, and the average value of the results was taken as the amino molar concentration.

[0095] (3) The number-average molecular weight Mn of polyamide microparticles is determined by the molar concentration C of amino groups in the polyamide microparticles. NH2- molar concentration of carboxyl groups C COOH The calculation is as follows:

[0096] [Number 1]

[0097]

[0098] (4) Thermal properties of polyamide microparticles: Using a differential scanning calorimeter (DSCQ2000) from TA Corporation, approximately 3 mg of polyamide microparticles obtained in each example and comparative example were accurately weighed. Under a nitrogen atmosphere, the temperature was increased from 20°C to a temperature 30°C higher than the temperature T0 where the endothermic peak appeared at a heating rate of 20°C / min, and held at this temperature for 2 min. Subsequently, the temperature was increased at 20°C / min.

[0099] The temperature was lowered to 20℃ at a cooling rate of 20℃ / min, held at 20℃ for 2 min, and then raised again at a heating rate of 20℃ / min to a temperature 30℃ higher than T0, yielding the melting point Tm. Tm is the temperature corresponding to the peak tip of the endothermic peak during the second heating process, and the enthalpy of fusion is automatically calculated by software from the peak area corresponding to the endothermic peak and the sample mass.

[0100] (5) Methods for determining the particle size and particle size distribution of polyamide microparticles:

[0101] Laser diffraction particle size analysis was used. The instrument used was a Microtrace S3500, and deionized water was used as the dispersant. This method can measure the volume-based average particle size MV, the number-based average particle size MN, the particle size D50 at 50% frequency accumulation, the particle size D90 at 90% frequency accumulation, and the particle size D10 at 10% frequency accumulation.

[0102] (6) Method for determining the positive sphericity of polyamide microparticles:

[0103] Select 30 particles from scanning electron microscope images and determine their minor and major axes according to the following mathematical formula.

[0104] [Number 2]

[0105]

[0106] Where S: positive sphericity, a: major axis, b: minor axis, n: number of measurements (30).

[0107] (7) Evaluation methods for the dispersibility of polyamide droplets in polymer C and the yield of polyamide particles:

[0108] After polymerization, the mixture of polyamide and polymer C from the examples and comparative examples was discharged into water and stirred. Polymer C dissolved in the water while the polyamide microparticles dispersed in the water. If the microparticles were substantially uniformly dispersed in the water, and the mass of solids remaining on the sieve after passing through a 1 mm sieve accounted for less than 10% of the mass of the polyamide microparticles, then the dispersion of the polyamide droplets in polymer C during polymerization was good, and the evaluation was 0.

[0109] If most of the particles are uniformly dispersed in water, and after the dispersion passes through a sieve with a pore size of 1 mm, the mass of solids left on the sieve is more than 10% and less than 50% of the mass of the polyamide particles, then the dispersion of polyamide droplets in polymer C during the polymerization process is evaluated as △.

[0110] If, after the dispersion passes through a sieve with a pore size of 1 mm, the mass of solids remaining on the sieve accounts for more than 50% of the mass of the polyamide microparticles, or even if no microparticles can be recovered from the dispersion, then the dispersibility of the polyamide microparticles in polymer C is evaluated as ×.

[0111] The collected polyamide particles were dispersed again in hot water at 80°C, stirred and washed, filtered again, dried and weighed. The weight of the particles was divided by the theoretical yield of copolyamide calculated based on the number of moles of monomer A and monomer B and their molar molecular weight. The resulting ratio was the polyamide particle yield.

[0112] (8) Method for determining the number-average molecular weight of polymer C:

[0113] The number-average molecular weight of polymer C was calculated using gel permeation chromatography, by comparing it with a calibration curve obtained from polyethylene glycol. The sample was prepared by dissolving approximately 3 mg of polymer C in approximately 6 g of water.

[0114] Device: LC-10A series manufactured by Shimadzu Corporation

[0115] Chromatographic column: TSKgelG3000PWXL manufactured by Tosei Co., Ltd.

[0116] Mobile phase: 100 mmol / L sodium chloride aqueous solution

[0117] Flow rate: 0.8 ml / min

[0118] Temperature: 40℃

[0119] Test: Differential refractometer.

[0120] (9) Method for determining the angle of repose:

[0121] The XF-6609A alumina angle of repose measuring instrument manufactured by Xiamen Xiongfa Instrument Co., Ltd. was used to test the powder according to the method specified in ISO902:1976. The powder was loaded into a funnel with an internal 1mm sieve, gradually increasing the amount of powder and allowing it to flow from the funnel's inlet (inner diameter di = 6mm) onto a graduated base plate. The powder was added until the highest point of the cone formed by the powder accumulation on the base plate reached the height of the funnel's inlet (40mm), i.e., the height of the cone formed by the powder was h = 40mm. The radii of the bottom of the cone-shaped powder accumulation on the base plate were recorded in eight different directions at this point, and the average diameter was calculated by taking the average value. according to Calculate the angle of repose.

[0122] (10) Surface roughness Ra test

[0123] The surface of the 3D printed product was observed using a KEYENCE optical microscope (VHX-5000) with a VH-ZST (ZS-20) objective lens and 200x magnification. The accompanying software (System Version 1.04) was used in automatic synthesis mode to create a 3D image of the surface texture. The height profile of the cross-section was calculated along lengths greater than 1 mm, and the surface roughness Ra was calculated using an arithmetic mean. Three different locations were selected for testing each sample, and the average value was taken as the surface roughness of the product. A smaller surface roughness Ra indicates a smoother surface.

[0124] (11) Warpage test

[0125] The obtained specimen is placed on a horizontal surface with its upward convex shape. A precision cone gauge is inserted into the gap between the horizontal surface and the specimen to measure the height of the gap and calculate the warping value per 10 cm of specimen length.

[0126] The raw materials used in the examples and comparative examples are as follows:

[0127] Sebacdiamine: Wuxi Xingda Nylon Co., Ltd.

[0128] Sebacic acid: Hebei Kaide Biomaterials Co., Ltd.

[0129] Pentylenediamine, Dodecanoic Acid: Shanghai Kaisai Biotechnology Co., Ltd.

[0130] Hexamethylenediamine: Shanghai Aladdin Biochemical Technology Co., Ltd.

[0131] Adipic acid: Thermo Fisher Scientific (China) Co., Ltd.

[0132] Azelaic acid, 11-aminoundecanoic acid: TCI (Shanghai) Chemical Industry Development Co., Ltd.

[0133] Polyethylene glycol 20000 (Mn=20000): Aoki Oils & Fats Co., Ltd.

[0134] Polyethylene glycol 10000 (Mn = 10000): Sigma-Aldrich (Shanghai) Trading Co., Ltd. ε-Caprolactam: BASF (China) Co., Ltd.

[0135] [Example 1]

[0136] 85.3g of decanediamine, 102.1g of dodecanoic acid, 1.0g of pentanediamine, 188g of polyethylene glycol 20000, and 177g of deionized water were added to a reactor. The reactor was sealed and purged three times with nitrogen. The heater temperature of the reactor was set to 230℃ and heating began. When the pressure inside the reactor reached 1.0MPa, the water vapor inside the reactor was released through the vent valve while maintaining the pressure at 1.0MPa until the temperature inside the reactor rose to 190℃. After the temperature inside the reactor reached 190℃, the pressure inside the reactor was gradually reduced from 1.0MPa to atmospheric pressure over 50 minutes (the temperature inside the reactor was 210℃ when atmospheric pressure was reached). Then, a nitrogen stream was introduced into the reactor, and melt polymerization was carried out under nitrogen flow for 120 minutes (the temperature inside the reactor was maintained at around 210℃ during melt polymerization). After polymerization, the mixture was discharged into water through the reactor's discharge valve. The resulting slurry was passed through a 1mm sieve to remove agglomerates. The slurry was filtered after sieving, and the filtrate was recovered. It was then redispersed in hot water at 80°C, stirred, washed, and filtered again. The washed filtrate was recovered. The filtrate was dried at 80°C for 12 hours to obtain 88.5 g of copolyamide 1010 / 510 powder (yield 52%). Additionally, 65 g of agglomerates remained on a 1 mm sieve. The amino molar concentration of the obtained powder was 2.9 × 10⁻⁶. -5 mol / g, carboxyl molar concentration is 10.0 × 10⁻⁶ -5 The number-average molecular weight of the copolyamide powder was calculated to be 15400 mol / g. Scanning electron microscopy revealed that the copolyamide powder consisted of perfectly spherical particles with a sphericity of 90. Laser diffraction particle size analysis yielded the following particle sizes: volume-based average particle size (MV) of 143.3 μm, number-based average particle size (MN) of 61.0 μm, particle size D50 at 50% frequency accumulation of 101.0 μm, particle size D90 at 90% frequency accumulation of 260.7 μm, and particle size D10 at 10% frequency accumulation of 60.1 μm. The ratio of volume-based average particle size to number-based average particle size was 2.35, and (D90-D10) / D50 was 1.99. The angle of repose was 48°. The characteristics of the obtained copolyamide particles are summarized in Table 1.

[0137] [Examples 2-11, Comparative Example 1, Comparative Example 3]

[0138] The types and amounts of comonomers were changed as shown in Table 1, except that all other operations were the same as in Example 1. The properties of the resulting copolyamide microparticles are shown in Table 1.

[0139] [Example 12, Comparative Example 2]

[0140] Apart from changing the type and amount of comonomer as shown in Table 1, the polymerization temperature was controlled at around 190°C in the later stage by adjusting the set temperature. All other operations were the same as in Example 1. The properties of the obtained polyamide microparticles are shown in Table 1.

[0141] [Table 1]

[0142]

[0143] Compared to Comparative Example 1, Examples 1-11 show that in Comparative Example 1, without the addition of polyamide monomer B, the dispersion of the microparticles is very poor, with a particle yield of only 48%, and the sphericity of the microparticles is 80° and the angle of repose is 51°. In Examples 1-11, by adding a diacid or diamine as monomer B for copolymerization, particle aggregation during polymerization is reduced, particle size and particle size distribution are improved, and the sphericity, powder flowability, and particle yield are increased. Simultaneously, the decrease in melting enthalpy is suppressed, and crystallinity is maintained to a certain extent. In Examples 12 and Comparative Example 2, the final polymerization temperature is lowered below the melting point of the copolyamide microparticles. The resulting polyamide microparticles contain PEG that cannot be removed. Thermal property tests show the melting point of PEG. Furthermore, the inability to remove PEG leads to a decrease in the surface smoothness of the microparticles, significantly affecting the flowability of the powder formed from the polyamide microparticles, with the angle of repose exceeding 50°. However, compared to Comparative Example 2, Example 12 yields higher copolyamide microparticles and exhibits better sphericity. In addition, in Comparative Example 3, two monomers, hexamethylenediamine and adipic acid, were added for copolymerization. The resulting copolyamide microparticles had excessively small particle size, low particle yield, and poor sphericity and crystallinity.

[0144] Approximately 1.5 kg of polyamide powder obtained from Examples 5, 6, 7, 8, and Comparative Example 1 were 3D printed using an Aspect powder bed melt sintering apparatus RaFaElII 300-HT. The surface roughness Ra value of the molded product obtained in Example 5 was 20 μm, and the warpage value was 3 mm / 10 cm; the surface roughness Ra value of the molded product obtained in Example 6 was 15 μm, and the warpage value was 2.5 mm / 10 cm; the surface roughness Ra value of the molded product obtained in Example 7 was 13 μm, and the warpage value was 2.3 mm / 10 cm; the surface roughness Ra value of the molded product obtained in Example 8 was 10 μm, and the warpage value was 1.9 mm / 10 cm; while the surface roughness of the molded product obtained in Comparative Example 1 was 30 μm, and the warpage value was 3.8 mm / 10 cm.

[0145] [Examples 13-21, Comparative Example 4]

[0146] Except for the raw materials, which were changed as shown in Table 2, all other operations were the same as in Example 1. The properties of the resulting polyamide microparticles are shown in Table 2.

[0147] [Table 2]

[0148]

[0149] Based on a comparison of Examples 13-16 and Comparative Example 4, Examples 17-21 and Comparative Example 1, it can be seen that adding aminoalkyl acid or lactam as monomer B for copolymerization can improve particle yield and sphericity, thereby controlling the particle size and particle size distribution of polyamide microparticles. At the same time, by controlling the amount added, the crystallinity of the copolyamide can be maintained to a certain extent.

[0150] [Examples 22-25, Comparative Example 5]

[0151] Except for the raw materials, which were changed as shown in Table 3, all other operations were the same as in Example 1. The properties of the resulting polyamide microparticles are shown in Table 3.

[0152] [Table 3]

[0153]

[0154] Compared with Comparative Example 5, Examples 3 and 22-25 do not contain polymer C, and the polyamide cannot form microparticles.

Claims

1. A method for preparing copolyamide microparticles, characterized in that, Polymers A and B of polyamide are polymerized in the presence of polymer C, and copolyamide-containing microparticles are precipitated when the copolyamide is dissolved in polymer C or when the copolyamide forms droplets dispersed in polymer C. Monomer A is selected from one of a diamine having 8-20 carbon atoms and one of a diacid having 8-20 carbon atoms; Monomer B is different from monomer A and is selected from one of a diamine having 2-20 carbon atoms, or a diacid having 2-20 carbon atoms, or an aminoalkyl acid having 3-12 carbon atoms, or a lactam having 3-12 carbon atoms.

2. The method for preparing copolyamide microparticles according to claim 1, wherein the monomer A of the polyamide is selected from decanediamine and sebacic acid, or decanediamine and dodecanoic acid.

3. The method for preparing copolyamide microparticles according to claim 1, wherein the monomer B of the polyamide is selected from a diamine having 2-20 carbon atoms, or a diacid having 2-20 carbon atoms and is different from both the diamine and the diacid in monomer A.

4. The method for preparing copolyamide microparticles according to claim 3, wherein the monomer B of the polyamide is selected from one of butanediamine, pentanediamine, hexanediamine, adipic acid, azelaic acid or sebacic acid and is different from the diamine and dicarboxylic acid in monomer A.

5. The method for preparing copolyamide microparticles according to claim 3, wherein the total molar amount of monomer A and monomer B is 100 mol%, and the amount of monomer B added is 1.0 to 45.0 mol%.

6. The method for preparing copolyamide microparticles according to claim 5, wherein the total molar amount of monomer A and monomer B is 100 mol%, and the amount of monomer B added is 5.0–20.0 mol% or 30.0–45.0 mol%.

7. The method for preparing copolyamide microparticles according to claim 1, wherein the monomer B of the polyamide is selected from aminoalkyl acids having 3-12 carbon atoms, or lactams having 3-12 carbon atoms.

8. The method for preparing copolyamide microparticles according to claim 7, wherein the total molar amount of monomer A and monomer B is 100 mol%, and the amount of monomer B added is 1.0 to 90.0 mol%.

9. The method for preparing copolyamide microparticles according to claim 8, wherein the total molar amount of monomer A and monomer B is 100 mol%, and the amount of monomer B added is 5.0–25.0 mol% or 70.0–90.0 mol%.

10. The method for preparing copolyamide microparticles according to claim 1, wherein the final polymerization temperature is above the melting point of the obtained copolyamide.

11. The method for preparing copolyamide microparticles according to claim 1, wherein the total weight W of monomer A and monomer B of the polyamide is... AB The weight W of the polymer C c ratio W AB / W c The value ranges from 0.25 to 2.

50.

12. The method for preparing copolyamide microparticles according to claim 1, wherein the polymer C is at least one of polyethylene glycol, polypropylene glycol, poly1,4-butanediol, polyethylene glycol-polypropylene glycol copolymer, and polymers whose hydroxyl-terminal -OH is hydroxyalkylated.

13. A copolyamide microparticle obtained by the preparation method according to any one of claims 1-12, characterized in that, The copolyamide microparticles have a sphericity of 70 to 100 and a melting point below 210°C.

14. The copolyamide microparticles according to claim 13, characterized in that, The structural unit of the copolyamide microparticle consists of a first structural unit derived from a diamine having 8-20 carbon atoms, a second structural unit derived from a diacid having 8-20 carbon atoms, and a third structural unit derived from a diamine having 2-20 carbon atoms or a diacid having 2-20 carbon atoms, which is different from the two mentioned above.

15. The copolyamide microparticles according to claim 13, characterized in that, The copolyamide is composed of a first structural unit derived from a diamine having 8-20 carbon atoms, a second structural unit derived from a dicarboxylic acid having 8-20 carbon atoms, and a fourth structural unit derived from an aminoalkyl acid having 3-12 carbon atoms or a lactam having 3-12 carbon atoms.

16. The copolyamide microparticles according to claim 13, characterized in that, The volume-based average particle size (MV) of the copolyamide microparticles is 10 micrometers to 150 micrometers.

17. The copolyamide microparticles according to claim 13, characterized in that, The volume-based average particle size / number-based average particle size of the copolyamide microparticles is 1.00 to 2.

50.

18. The copolyamide microparticles according to claim 13, characterized in that, The (D90-D10) / D50 of the copolyamide microparticles is below 2.

0.

19. The copolyamide microparticles according to claim 13, characterized in that, The copolyamide microparticles were subjected to a heating-cooling-reheating process at a rate of 20°C / min within the range of 0°C to 30°C above the melting point. The enthalpy of fusion measured during the reheating process was above 40 J / g.

20. The copolyamide microparticles according to claim 13, characterized in that, The powder formed from the copolyamide microparticles has an angle of repose of less than 50° as measured according to ISO 902:1976.

21. Use of the copolyamide microparticle powder according to any one of claims 13-20 for powder bed fusion bonding 3D printing.

22. A 3D printed product obtained by powder containing copolyamide microparticles as described in any one of claims 13-20 through a powder bed melt bonding method.

23. The 3D printed article according to claim 22, characterized in that, The surface roughness Ra value of the 3D printed product is below 20 μm.

24. The 3D printed article according to claim 22, characterized in that, The warpage value of the 3D printed product is less than 3mm / 10cm.

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