Polyamide resin powder, its manufacturing method, and manufacturing method of three-dimensional object using polyamide resin powder

Abstract

To provide branched polyamide resin granular powder which is polyamide composed of a monomer (A) that has an average particle diameter of more than 1 μm and 100 μm or less and is composed of an aminocarboxylic acid and a lactam or at least one of diamine and a dicarboxylic acid, and a monomer (B) containing three functional groups capable of reacting with an amino group or a carboxyl group, and has a molar ratio (molar ratio of monomer (A): molar ratio of monomer (B)) of the monomer (A) to the monomer (B) of 99:1 to 85:15.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to polyamide resin powder suitable as a material powder for producing three-dimensional objects using powder bed fusion, which is suitable for a wide range of applications such as automotive, aerospace, and industrial / medical machinery, a method for producing the same, and a method for producing three-dimensional objects using polyamide resin powder. [Background technology]

[0002] In recent years, three-dimensional printing (hereinafter sometimes referred to as 3D printers) has attracted attention as a technology with the potential to bring about manufacturing innovation because it is useful for freely creating three-dimensional shapes that are difficult to create using injection molding, and for producing parts consisting of welded parts, divided components, and complex parts in a single unit.

[0003] Known methods for creating these objects include fused deposition molding, UV-curable inkjet printing, stereolithography, powder bed fusion (hereinafter sometimes referred to as the PBF method), and inkjet binder printing. Among these, the PBF method is expected to expand rapidly because it can achieve high dimensional accuracy and mechanical strength in three-dimensional objects.

[0004] In the PBF process, a powder bed is formed by spreading the powder using rollers or blades, and a laser beam is scanned over the powder bed to melt and solidify the powder, so it is necessary to control the crystallization rate after irradiation with the laser beam and suppress warping of the 3D object caused by volumetric shrinkage during melting and solidification. Conventionally, polyamide resin powder has been mainly used as the modeling material for the PBF method, but polyamide resin powder has a fast crystallization rate, and in order to suppress warping of the 3D object, a polyamide resin powder with a slow crystallization rate is required.

[0005] Numerous technical improvements have been attempted so far as a technique for obtaining such polyamide resins. For example, Patent Document 1 discloses a method for obtaining a crosslinked polyamide with a low degree of crystallinity by using a polyisocyanate as an activator for polyamide polymerization by anionic polymerization. Patent Document 2 discloses a method for obtaining a crosslinked polyamide for the PBF method with excellent thermomechanical properties by introducing a crosslinkable functional group into the polyamide by grafting. Patent Document 3 discloses a method for obtaining an amorphous hyperbranched polyamide with a controlled crystallization rate by polymerization of a multifunctional monomer and a bifunctional monomer. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Special Publication No. 2014-528018 [Patent Document 2] Special Publication No. 2020-514457 [Patent Document 3] Special Publication No. 2002-544307 Summary of the Invention [Problem to be solved by the invention]

[0007] In the method of Patent Document 1, since it is a cast polymerization, it is difficult to powderize, and it is not possible to obtain polyamide resin powder having an average particle size suitable for the PBF method. In addition, since an anionic catalyst is required to obtain a branched polyamide resin by anionic polymerization, it is economically disadvantageous. Furthermore, the examples of Patent Document 1 disclose only a very small amount of crosslinker ratio, but anionic polymerization has a fast reaction rate, and since the crosslinker polyisocyanate acts as an activator, it was difficult to control the reaction. In addition, when the crosslinker ratio is increased, it is difficult to control the degree of polymerization and crosslinking to an appropriate level, and the degree of crystallization is significantly reduced due to excessive crosslinking, and when a three-dimensional object is produced by the PBF method, there is a risk of causing a decrease in mechanical properties and gelation.

[0008] In the method of Patent Document 2, the reduction in the crystallization rate of the polyamide resin is insufficient to suppress warping of a three-dimensional object in the PBF method, and it is necessary to perform a grafting treatment after polymerization of the polyamide resin to reduce the crystallization rate, which is economically disadvantageous. In addition, there is no disclosure of the hyperbranched polyamide obtained by the method of Patent Document 3 being used for 3D printers, and since it is not in powder form, it is unsuitable for the PBF method. Furthermore, since the crystallinity of hyperbranched polyamide is extremely low, there are problems with reduced mechanical properties and gelation when a three-dimensional object is produced by the PBF method.

[0009] Therefore, an object of the present invention is to provide a three-dimensional object that has an appropriately controlled crystallization rate, is capable of forming a smooth powder surface when used in a powder bed fusion 3D printer, does not warp when irradiated with a laser, and has good tensile strength. [Means for solving the problem]

[0010] As a result of intensive research aimed at solving the above problems, the present inventors have arrived at the following invention.

[0011] That is, the present invention is as follows. (1) The average particle size is more than 1 μm and not more than 100 μm, and the aminocarboxylic acid or Rakuta M and a monomer (A) consisting of an amino group. and Carboxyl group Sum up A polyamide made of three or more monomers (B), and the molar ratio of monomers (A) to (B) (the molar ratio of monomers (A): (B)) is 99:1 to 85:15. Constructed from polyamide Branched polyamide resin powder. (2) The branched polyamide resin powder particles according to (1), wherein the monomer (A) is ε-aminocaproic acid or ε-caprolactam. (3) The branched polyamide resin powder particles according to (1) or (2), characterized in that the monomer (B) is L-lysine. (4) A branched polyamide resin powder or granule according to any one of (1) to (3), characterized in that the difference between the melting point and the crystallization temperature upon cooling measured by differential scanning calorimetry at a temperature increase / decrease rate of 20°C / min is 50°C or more. (5) The branched polyamide resin granule according to any one of (1) to (4), characterized in that the sphericity is 0.80 or more. (6) Aminocarboxylic acids or Rakuta M and a monomer (A) consisting of an amino group. and Carboxyl group Sum up The method for producing a branched polyamide resin powder granule according to any one of (1) to (5), characterized in that a monomer (B) containing three or more groups is polymerized without using an anionic catalyst, and the obtained polymer is pulverized to obtain a polyamide powder granule. (7) Aminocarboxylic acids or Rakuta M and a monomer (A) consisting of an amino group. and Carboxyl group Sum up The method for producing a branched polyamide resin powder particle according to any one of (1) to (5), characterized in that a monomer (B) containing three or more of the above is polymerized in the presence of at least one polymer (C) that is compatible with the monomers (A) and (B) and undergoes phase separation from the polyamide resin, and a polyamide resin powder particle is precipitated after the polymerization. (8) The method for producing a branched polyamide resin powder or granule according to (7), wherein the polymer (C) is polyethylene glycol, polypropylene glycol, polytetramethylene glycol, a polyethylene glycol-polypropylene glycol copolymer, or an alkyl ether form thereof. (9)(1)~( 5 ) of A method for manufacturing a three-dimensional object, comprising supplying any one of the branched polyamide resin powders to a powder bed fusion 3D printer. Effect of the Invention

[0012] According to the present invention, it is possible to obtain a three-dimensional object having an appropriately controlled crystallization rate, which, when used in a powder bed fusion 3D printer, can form a smooth powder surface, is free from warping upon laser irradiation, and has good tensile strength. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, the present invention will be described in detail with reference to embodiments.

[0014] The present invention relates to a branched polyamide resin powdery product having an average particle size of more than 1 μm and not more than 100 μm, which is a polyamide composed of monomer (A) consisting of at least one of aminocarboxylic acid, lactam, or diamine and dicarboxylic acid, and monomer (B) containing three or more functional groups capable of reacting with a reactive functional group of monomer (A), and wherein the molar ratio of monomer (A) to monomer (B) (molar ratio of monomer (A):molar ratio of monomer (B)) is 99:1 to 85:15.

[0015] Generally, a method of controlling the crystallization rate using the above-mentioned crosslinking agent or the like is known as a means of suppressing warpage of a three-dimensional object. In response to this, the inventors of the present application focused on the mechanism of warpage of a three-dimensional object and came up with the idea that warpage can be suppressed by inhibiting molecular orientation caused by hydrogen bonds between molecular chains due to amide bonds of polyamide by introducing a branched structure into the molecular chain. However, generally, when a branched structure is introduced into the molecular chain, the ratio of amorphous structures in the three-dimensional object also increases, and conversely, the strength of the object tends to decrease.

[0016] Therefore, the inventors of the present application discovered that by using a branched polyamide resin powder that is in the form of fine particles and has a specific monomer structure, the above-mentioned trade-off can be eliminated, the crystallization rate can be appropriately controlled, and when used in a powder bed fusion 3D printer, a smooth powder surface can be formed, there is no warping when irradiated with a laser, and the tensile strength of the molded object can be improved, thereby arriving at the present invention.

[0017] [Branched polyamide resin] The monomer (A) of the branched polyamide resin used in the present invention is either an aminocarboxylic acid, a lactam, or a diamine and a dicarboxylic acid, and refers to a compound that produces a polyamide by polymerization. Specific examples of the monomer (A) include lactams such as 4-butane lactam, ε-caprolactam, and ω-laurolactam, amino acids such as 4-aminobutyric acid, ε-aminocaproic acid, and 12-aminododecanoic acid, and dicarboxylic acids and diamines such as 1,4-diaminobutane, hexamethylenediamine, 1,10-diaminodecane, succinic acid, adipic acid, sebacic acid, dodecanedioic acid, terephthalic acid, isophthalic acid, decanediamine, undecanediamine, and dodecanediamine. Two or more of these monomers (A) may be used as long as they do not impair the present invention. In addition, these components may contain other components that can be copolymerized.

[0018] The monomer (B) of the branched polyamide resin used in the present invention refers to a compound that contains three or more functional groups that can react with the reactive functional group of the monomer (A) and forms a branched structure by polymerizing with the monomer (A). Examples of the functional group that can react with the reactive functional group of the monomer (A) include an amino group, a carboxyl group, an epoxy group, and an isocyanate group. Specific examples of the monomer (B) include L-lysine, D-lysine, DL-lysine, L-aspartic acid, D-aspartic acid, DL-aspartic acid, serine, cysteine, L-glutamic acid, D-glutamic acid, DL-glutamic acid, 5-aminoisophthalic acid, 5-aminoundecanedioic acid, 3,5-diaminobenzoic acid, 3,4-diaminobenzoic acid, 4,4'-diaminobiphenyl-3,3'-dicarboxylic acid, and triglycidyl isocyanurate. Two or more kinds of these monomers (B) may be used in combination as long as the present invention is not impaired.

[0019] The branched polyamide resin of the present invention refers to a polymer having a structure containing an amide group. The branched polyamide resin is produced by, for example, a polycondensation reaction of amino acids, ring-opening polymerization after hydrolysis of lactams with water, or a polycondensation reaction of dicarboxylic acid and diamine or their salts, or a combination of these. From an economical point of view, hydrolysis-type ring-opening polymerization is preferred, and the method of ring-opening polymerization of lactams by hydrolysis is not limited as long as it is a known method, but a preferred method is to pressurize in the presence of water to generate amino acids while promoting hydrolysis of lactams, and then perform ring-opening polymerization and polycondensation while removing water.

[0020] Specific examples of the branched polyamide resin obtained by polymerizing the monomer (A) and the monomer (B) of the present invention include polyamide 4, polyamide 5, polyamide 6, polyamide 11, polyamide 12, polyamide 44, polyamide 46, polyamide 410, polyamide 411, polyamide 412, polyamide 56, polyamide 510, polyamide 511, polyamide 512, polyamide 64, polyamide 65, polyamide 66, polyamide 610, polyamide 611, polyamide 62, Examples of such polyamides include polyamide 612, polyamide 104, polyamide 106, polyamide 1010, polyamide 1011, polyamide 1012, polyamide 124, polyamide 125, polyamide 126, polyamide 1210, polyamide 1212, polyamide 6T, polyamide 10T, polyamide 12T, polyamide 6I, polyamide 10I, polyamide 12I, and further copolymers of these polyamides, such as polyamide 6 / polyamide 66 copolymer.

[0021] The molar ratio of monomer (A) and monomer (B) constituting the branched polyamide resin of the present invention is in the range of 99:1 to 85:15. The molar ratio of monomer (A) and monomer (B) is calculated from the amounts of monomer (A) and monomer (B) charged when polymerizing the branched polyamide resin. If the molar ratio of monomer (B) is less than 99:1, the effect of lowering the crystallization rate is not sufficiently obtained, and if the molar ratio of monomer (B) is more than 85:15, the crystallization degree of the branched polyamide resin powder is significantly reduced, and various physical properties of the three-dimensional object, including the tensile strength of the three-dimensional object formed by the PBF method 3D printer, are reduced.

[0022] The difference between the melting point and the crystallization temperature of the branched polyamide resin of the present invention is preferably 50°C or more. If the difference between the melting point and the crystallization temperature of the branched polyamide resin is less than 50°C, the resin melted by laser irradiation may crystallize, causing shrinkage and warping. In the powder bed fusion method, if the molten resin warps, the warped molten resin may be dragged when a powder layer is laminated on top of the molten resin, and a three-dimensional object of a desired shape may not be obtained. Here, the crystallization temperature of the branched polyamide resin refers to the apex temperature of the exothermic peak during crystallization when the branched polyamide resin is heated in a nitrogen atmosphere using a differential scanning calorimeter from 50°C to a temperature 40°C higher than the melting point at 20°C / min, held for 5 minutes, and cooled to 50°C at 20°C / min. When there are multiple peaks, the apex of the peak on the highest temperature side was taken as the melting point and the crystallization temperature of the temperature.

[0023] [Branched polyamide resin powder] The average particle size of the branched polyamide resin powder of the present invention must be more than 1 μm and not more than 100 μm. The lower limit of the average particle size of the branched polyamide resin powder is preferably 5 μm, more preferably 10 μm. The upper limit of the average particle size is preferably 95 μm, more preferably 90 μm, and even more preferably 80 μm. If the average particle size of the branched polyamide resin powder exceeds 100 μm, a uniform powder surface cannot be formed during powder lamination in a powder bed fusion 3D printer. Also, if the average particle size of the branched polyamide resin powder is less than 1 μm, aggregation of the powder occurs, and a uniform powder surface cannot be formed.

[0024] The average particle size of the branched polyamide resin powder particles in the present invention is the particle size (d50) at which the cumulative curve from the small particle side becomes 50% when the cumulative curve is calculated with the total volume of the microparticles obtained by analyzing scattered laser light using the Microtrack method as 100%.

[0025] The sphericity of the branched polyamide resin powder particles in the present invention is preferably 0.80 or more from the viewpoint of powder flowability. The sphericity of the branched polyamide resin powder particles was calculated by observing the particles with a scanning electron microscope, and calculating the sphericity of 30 randomly selected particles using the following formula, where the major axis of the particle is a and the minor axis is b.

number

[0026] Here, S is sphericity, and n is the number of measurements, 30. The preferred lower limit of sphericity is 0.82, and more preferably 0.85. In particular, when using branched polyamide resin powder particles having high sphericity to produce a three-dimensional object with a powder bed fusion 3D printer, this is preferred because a very smooth powder surface can be formed when the powder is spread.

[0027] [Method of manufacturing branched polyamide resin powder] The method for producing the branched polyamide resin powder in the present invention is not particularly limited, and examples thereof include a method in which polyamide resin pellets obtained by melt polymerization are pulverized, and a method in which polymerization is carried out in the presence of monomer (A) and polymer (C) that is compatible with monomer (B) while stirring at a predetermined rotation speed, and the produced branched polyamide resin is phase-separated from polymer (C) to precipitate in the form of particles.

[0028] In the method for obtaining branched polyamide resin pellets by melt polymerization, the polymerization temperature is preferably the melting point of the branched polyamide resin +20° C. or more and the melting point +100° C. or less. The pressure during polymerization is preferably normal pressure or reduced pressure, and reduced pressure is more preferable in order to improve the reaction rate. The pressure during polymerization under reduced pressure is preferably -80 kPa or more and -10 kPa or less in gauge pressure.

[0029] The branched polyamide resin pellets obtained by melt polymerization can be washed to remove the remaining monomer (A) and monomer (B). The branched polyamide resin pellets can be washed by a known method. As a washing method for removing deposits and inclusions from the branched polyamide resin pellets, reslurry washing or the like can be used, and heating is preferable to efficiently remove the remaining monomer (A) and monomer (B) in the pellets. There is no limitation on the solvent used for washing, so long as it does not dissolve the branched polyamide resin pellets but dissolves the monomer (A) and monomer (B). From the viewpoint of economy, methanol, ethanol, isopropanol and water are preferable, and water is most preferable.

[0030] The method for pulverizing the branched polyamide resin pellets is not particularly limited, but by cooling to -40°C or less and pulverizing by brittle fracture utilizing low-temperature brittleness, branched polyamide resin powder particles can be obtained efficiently. The pulverization method is not particularly limited, and includes jet mills, bead mills, hammer mills, ball mills, sand mills, turbo mills, and pin mills. Dry pulverization using turbo mills and jet mills is preferable. Examples of the method for cooling to -40°C or less include a method of cooling with liquid nitrogen or dry ice before pulverization, and a method of cooling from the raw material inlet to the pulverizer with liquid nitrogen or dry ice. The average particle size of the branched polyamide resin powder particles after pulverization can be controlled by adjusting the pulverization time.

[0031] In a method in which polymerization is carried out in the presence of monomer (A) and polymer (C) compatible with monomer (B) while stirring at a prescribed rotation speed, and the branched polyamide resin thus produced is phase-separated from polymer (C) and precipitated in particulate form, the polymerization temperature is preferably at least the melting point of the polyamide resin minus 50° C. and at most the melting point plus 20° C. The pressure during polymerization is preferably normal pressure.

[0032] After polymerization and precipitation of the branched polyamide resin powder, washing can be carried out to remove the remaining monomers (A), (B) and (C). The branched polyamide resin powder can be washed by a known method. As a washing method for removing deposits and inclusions on the branched polyamide resin powder, reslurry washing or the like can be used, and heating may be used as appropriate. There is no limitation on the solvent used for washing, so long as it does not dissolve the branched polyamide resin powder but dissolves the monomers (A), (B) and (C), and from the viewpoint of economy, methanol, ethanol, isopropanol and water are preferred, and water is the most preferred.

[0033] Polymer (C) is a polymer that is compatible with monomer (A) and monomer (B) of the branched polyamide resin at the start of polymerization, but is not compatible with polyamide after polymerization. Compatibility is determined by whether polymer (C) is dissolved uniformly with monomer (A) and monomer (B) under the temperature and pressure conditions at which polymerization is started. Incompatibility between polymer (C) and polyamide resin is determined by whether it is a suspension or separates into two phases under the temperature and pressure conditions after polymerization. Whether it is a homogeneous solution, suspension, or two-phase separation can be determined by visually inspecting the reaction vessel. The average particle size of the branched polyamide resin powder after precipitation can be controlled by adjusting the stirring speed during polymerization, the weight ratio of monomer (A) and monomer (B) to polymer (C), and the molecular weight of polymer (C).

[0034] From the viewpoint of precipitating branched polyamide powder particles from a homogeneous solution, it is preferable that the polymer (C) is non-reactive with the monomer (A) and the monomer (B). Specifically, it is preferable that the polymer (C) does not have a polar group that reacts with a carboxyl group or an amino group that forms an amide group contained in the polyamide, or has a polar group that is low in reactivity with a carboxyl group or an amino group. Examples of polar groups that react with a carboxyl group or an amino group include an amino group, a carboxyl group, an epoxy group, and an isocyanate group. Examples of polar groups that are low in reactivity with a carboxyl group or an amino group include a hydroxyl group and a hydrosulfur group, and among these, a hydroxyl group is the most preferable. From the viewpoint of suppressing the crosslinking reaction, it is preferable that the number of polar groups in the polymer (C) is 4 or less, more preferably 3 or less, and most preferably 2 or less.

[0035] Specific examples of such polymers (C) include polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polypentamethylene glycol, polyhexamethylene glycol, polyethylene glycol-polypropylene glycol copolymers, polyethylene glycol-polytetramethylene glycol copolymers, alkyl ethers in which the hydroxyl groups at one or both ends of these are blocked with a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a hexyl group, an octyl group, a decyl group, a dodecyl group, a hexadecyl group, an octadecyl group or the like, and alkyl phenyl ethers in which the hydroxyl groups at one or both ends are blocked with an octylphenyl group or the like. In particular, polyethylene glycol, polyethylene glycol-polypropylene glycol copolymer, polypropylene glycol, polytetramethylene glycol, and their alkyl ethers are preferred because they have excellent compatibility with monomer (A) and monomer (B) and can be produced using a high concentration of polyamide monomer. From the viewpoint of excellent compatibility with water used in ring-opening polymerization by hydrolysis of monomer (A), polyethylene glycol, polyethylene glycol-polypropylene glycol copolymer, and their alkyl ethers are more preferred, and polyethylene glycol is the most preferred. Two or more of these may be used simultaneously as long as they do not impair the present invention. The amount of polymer (C) blended during polymerization is preferably in the range of 10 parts by mass or more and less than 70 parts by mass per 100 parts by mass of monomer (A), monomer (B), and polymer (C). In addition to monomer (A), monomer (B), and polymer (C), water may be present to improve the compatibility of these, and the amount of water is preferably 1 part by mass or more and 600 parts by mass or less per 100 parts by mass of monomer (A), monomer (B), and polymer (C).

[0036] In the method for obtaining the branched polyamide resin pellets or branched polyamide resin powder particles, a polymerization accelerator can be added during polymerization as necessary. As the polymerization accelerator, for example, inorganic phosphorus compounds such as phosphoric acid, phosphorous acid, hypophosphorous acid, pyrophosphoric acid, polyphosphoric acid, and their alkali metal salts and alkaline earth metal salts are preferable, and sodium phosphite and sodium hypophosphite are particularly preferably used. The polymerization accelerator is preferably used in the range of 0.001 to 1 part by mass relative to 100 parts by mass of the raw material of the polyamide resin.

[0037] Furthermore, when polymerizing the branched polyamide resin or the branched polyamide resin powder or granule, the following additives may be used: end-capping agents (monocarboxylic acids such as acetic acid and benzoic acid, and monoamines such as aniline), antioxidants (hindered phenols, hydroquinones, phosphites and their substitutes, copper halides, iodine compounds, etc.), weathering agents (resorcinols, salicylates, benzotriazoles, benzophenones, etc.), pigments (cadmium sulfide, phthalocyanine, carbon black, etc.), dyes (nigrosine, aniline black, etc.), band-forming agents (polyvinyl chloride, phenyl phthalate ... Antistatic agents (alkyl sulfate-type anionic antistatic agents, quaternary ammonium salt-type cationic antistatic agents, nonionic antistatic agents such as polyoxyethylene sorbitan monostearate, betaine-type amphoteric antistatic agents, etc.), and flame retardants (hydroxides such as magnesium hydroxide and aluminum hydroxide, ammonium polyphosphate, brominated polystyrene, brominated polyphenylene oxide, brominated polycarbonate, brominated epoxy resin, or combinations of these brominated flame retardants with antimony trioxide, etc.) may be blended. EXAMPLES

[0038] The method of the present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to these examples. Various measurement methods are as follows.

[0039] [Average particle size of branched polyamide resin powder] The average particle size of the branched polyamide resin powder was measured using a MicrotracBEL laser diffraction / scattering particle size distribution analyzer MT3300EX2, using a 0.5 wt% aqueous solution of polyoxyethylene cumylphenyl ether (trade name Nonal 912A, manufactured by Toho Chemical Industry Co., Ltd., hereafter referred to as Nonal 912A) as a dispersion medium. Specifically, a cumulative curve was obtained by analyzing the scattered light of a laser using the Microtrac method, with the total volume of the fine particles obtained being 100%, and the particle size (median diameter: d50) at the point where the cumulative curve from the small particle size side becomes 50% was taken as the average particle size of the branched polyamide resin powder.

[0040] [Melting point and crystallization temperature of branched polyamide resin] The temperature-lowering crystallization temperature of the branched polyamide resin was measured using about 5 mg of powder particles in a nitrogen atmosphere under the following measurement conditions using a PerkinElmer DSC7. 50℃ x 1 minute -Heating from 50℃ to 40℃ above the melting point, heating rate 20℃ / min Hold for 5 minutes - From 40℃ higher than the melting point to 50℃, the temperature drop rate is 20℃ / min. The apex of the endothermic peak accompanying melting during heating was taken as the melting point, and the apex of the exothermic peak accompanying crystallization during cooling was taken as the cooling crystallization temperature.

[0041] [Sphericity of branched polyamide resin powder particles] The sphericity of the branched polyamide resin powder was calculated by observing the particles with a scanning electron microscope manufactured by JEOL Ltd. and calculating the sphericity of 30 randomly selected particles according to the following formula.

number

[0042] In addition, S: sphericity, a: major axis of the particle, b: minor axis of the particle, and n: number of measurements (30).

[0043] [Tensile strength of 3D objects] The tensile strength of the three-dimensional model made using the branched polyamide resin powder was measured by creating ISO1A type test pieces using a powder bed fusion 3D printer (Rafael2 300HT, Aspect Corporation) and using a universal testing machine (Tensilon universal testing machine RTG-1250, A&D Corporation). The measurement method was in accordance with ISO-527, and the average value of five measurements was taken as the tensile strength.

[0044] [Number average molecular weight of polymer (C)] The number average molecular weight of the polymer (C) was calculated by gel permeation chromatography in comparison with a calibration curve using polyethylene glycol. The measurement sample was prepared by dissolving about 3 mg of the polymer (C) in about 6 g of water. Equipment: Shimadzu Corporation LC-10A series Column: Tosoh Corporation TSKgel G3000PWXL Mobile phase: 100mmol / L sodium chloride aqueous solution Flow rate: 0.8mL / min Temperature: 40℃ Detection: Differential refractometer

[0045] [Example 1] In a 3L autoclave equipped with a stirrer, 566g (5 mol) of ε-caprolactam, 7.38g (0.05 mol) of L-lysine, 3.95g (0.03 mol) of benzoic acid, and 141g (7.85 mol) of ion-exchanged water were charged. The molar ratio of monomer (A) to monomer (B) was monomer (A):monomer (B) = 99:1. The inside of the vessel was replaced with nitrogen, sealed, and gradually heated to an internal temperature of 200°C over about 120 minutes while stirring at 120 rpm, and maintained for 120 minutes. The internal pressure at this time was 1.0 MPa.

[0046] Next, the tank was heated to an internal temperature of 240°C over 60 minutes, and at the same time, the pressure was released to normal pressure while distilling off water by controlling the opening of the pressure release valve. After that, the tank was depressurized to a gauge pressure of -20 kPa, and polymerization was carried out by holding the tank for 1 hour. After 1 hour, the agitator was stopped, nitrogen was sealed in to pressurize the tank to a gauge pressure of 0.2 MPa, and the strand discharged from the die was passed through a cooling bath filled with water to cool it, and cut into pellets of 1 to 3 mm while being taken out with a cutter to obtain pellets of branched polyamide resin (1). The melting point of the obtained branched polyamide resin (1) was 217°C, and the crystallization temperature upon cooling was 165°C. The pellets of branched polyamide resin (1) were cooled to -192°C with liquid nitrogen, and pulverized to an average particle size of 50 μm with a turbo mill to obtain branched polyamide resin powder (1). The sphericity of the obtained branched polyamide resin powder (1) was 0.80. This branched polyamide resin powder (1) was used to create a three-dimensional object using a powder bed fusion 3D printer (Rafael2 300HT, manufactured by Aspect Corporation). No roughening of the powder surface during powder layering or warping during laser irradiation occurred, resulting in a good three-dimensional object. The tensile strength of the three-dimensional object was 70 MPa.

[0047] [Example 2] Pellets of branched polyamide resin (2) were obtained in the same manner as in Example 1, except that the amount of L-lysine charged was 38.5 g (0.263 mol). The molar ratio of monomer (A) to monomer (B) was monomer (A):monomer (B)=95:5. The melting point of the obtained branched polyamide resin (2) was 208°C, and the temperature-reducing crystallization temperature was 153°C. The pellets of branched polyamide resin (2) were cooled to -192°C with liquid nitrogen and pulverized to an average particle size of 50 μm with a turbo mill to obtain branched polyamide resin powder particles. The sphericity of the obtained branched polyamide resin powder particles (2) was 0.81. A three-dimensional model was produced using this branched polyamide resin powder particles (2) by a powder bed fusion 3D printer (Rafael2 300HT manufactured by Aspect Co., Ltd.). No roughness of the powder surface during powder lamination or warping during laser irradiation occurred, and a good three-dimensional model was obtained. The tensile strength of the three-dimensional object was 66 MPa.

[0048] [Example 3] Pellets of branched polyamide resin (5) were obtained in the same manner as in Example 1, except that the amount of L-lysine charged was 99.7 g (0.682 mol). The molar ratio of monomer (A) to monomer (B) was monomer (A):monomer (B)=88:12. The melting point of the obtained branched polyamide resin (3) was 202°C, and the temperature-reducing crystallization temperature was 146°C. The pellets of branched polyamide resin (3) were cooled to -192°C with liquid nitrogen and pulverized to an average particle size of 50 μm with a turbo mill to obtain branched polyamide resin powder particles. The sphericity of the obtained branched polyamide resin powder particles (3) was 0.81. A three-dimensional model was produced using this branched polyamide resin powder particles (3) by a powder bed fusion 3D printer (Rafael2 300HT manufactured by Aspect Co., Ltd.). No roughness of the powder surface during powder lamination or warping during laser irradiation occurred, and a good three-dimensional model was obtained. The tensile strength of the three-dimensional object was 64 MPa.

[0049] [Example 4] In a 3L autoclave equipped with a stirrer, 200g (1.52 mol) of ε-aminocaproic acid, 11.7g (0.08 mol) of L-lysine, 800g of polyethylene glycol (Wako Pure Chemical Industries, Ltd. Grade 1 polyethylene glycol 6,000, weight average molecular weight 7,700), and 1000g (55.6 mol) of ion-exchanged water were charged. The molar ratio of monomer (A) to monomer (B) was monomer (A):monomer (B) = 95:5. The inside of the vessel was replaced with nitrogen, sealed, and heated to an internal temperature of 210°C while stirring at 30 rpm. At this time, after the pressure of the system reached a gauge pressure of 1 MPa, the internal pressure was controlled by releasing steam so as to maintain the gauge pressure of 1 MPa.

[0050] Next, the opening of the pressure release valve was controlled, and the pressure was released to normal pressure while distilling water over 50 minutes. After that, the polymerization was carried out by holding for 1 hour while aerating nitrogen. After 1 hour, the agitator was stopped, and the contents were discharged into 2 L of water to obtain a branched polyamide resin powder (4) slurry. The obtained slurry was filtered, 2000 mL of water was added to the filtered product, and washed at 80 ° C. Then, the slurry liquid was filtered through a 200 μm sieve, and the filtered product was isolated and vacuum dried at 80 ° C. for 12 hours to obtain a branched polyamide resin powder (4). The obtained branched polyamide resin powder (4) had a melting point of 209 ° C, a cooling crystallization temperature of 156 ° C, an average particle size of 48 μm, and a sphericity of 0.94. Using this branched polyamide resin powder (4), a three-dimensional model was produced by a powder bed fusion 3D printer (Rafael2 300HT manufactured by Aspect Co., Ltd.). The powder surface during powder lamination was very smooth, and no warping occurred during laser irradiation, resulting in a good 3D object. The tensile strength of the 3D object was 74 MPa.

[0051] [Comparative Example 1] Pellets of polyamide resin (5) were obtained in the same manner as in Example 1, except that L-lysine was not added. The molar ratio of monomer (A) to monomer (B) was monomer (A):monomer (B)=100:0. The melting point of the obtained polyamide resin (5) was 219°C, and the crystallization temperature was 176°C. The pellets of polyamide resin (5) were cooled to -192°C with liquid nitrogen and pulverized to an average particle size of 50 μm with a turbo mill to obtain polyamide resin powder particles. The sphericity of the obtained polyamide resin powder particles (5) was 0.81. A three-dimensional model was produced using this polyamide resin powder particles (5) with a powder bed fusion 3D printer (Rafael2 300HT manufactured by Aspect Co., Ltd.). No powder surface roughness occurred during powder lamination, but a three-dimensional model could not be obtained due to warping during laser irradiation.

[0052] [Comparative Example 2] A branched polyamide resin powder (6) was obtained in the same manner as in Example 1, except that the branched polyamide resin powder was pulverized with a turbo mill so that the average particle size was 200 μm. The sphericity of the obtained branched polyamide resin powder (6) was 0.73. A three-dimensional object was produced using this branched polyamide resin powder (6) with a powder bed fusion 3D printer (Rafael2 300HT manufactured by Aspect Corporation). The powder surface was roughened during powder layering, and a three-dimensional object could not be obtained.

[0053] [Comparative Example 3] Pellets of branched polyamide resin (7) were obtained in the same manner as in Example 1, except that the amount of L-lysine charged was 150 g (1.02 mol). The molar ratio of monomer (A) to monomer (B) was monomer (A):monomer (B)=83:17. The melting point of the obtained branched polyamide resin (7) was 199°C, and the temperature-reducing crystallization temperature was 142°C. The pellets of branched polyamide resin (7) were cooled to -192°C with liquid nitrogen and pulverized in a turbo mill to an average particle size of 50 μm to obtain branched polyamide resin powder particles (7). The sphericity of the obtained branched polyamide resin powder particles (7) was 0.82. A three-dimensional model was produced using this branched polyamide resin powder particles (7) by a powder bed fusion 3D printer (Rafael2 300HT manufactured by Aspect Co., Ltd.). No roughening of the powder surface during powder lamination or warping during laser irradiation occurred, and a good three-dimensional model was obtained. The tensile strength of the three-dimensional object was 46 MPa.

[0054] [Comparative Example 4] Polyamide resin powder particles (2) obtained in the same manner as in Comparative Example 1 were mixed with 5 wt% of glycidoxypropyltrimethoxysilane Silquest A187 (manufactured by Momentive Performance Materials) until a paste was formed. The paste obtained was placed in a sealed container and kept in an oven at 80°C for 3 hours, and then kept at 130°C for 8 hours to obtain a branched polyamide resin powder particle (8) by grafting a silane coupling agent. The melting point of the obtained branched polyamide resin powder particle (8) was 219°C, the cooling crystallization temperature was 173°C, the average particle size was 50 μm, and the sphericity was 0.81. This branched polyamide resin powder particle (8) was used to produce a three-dimensional object using a powder bed fusion 3D printer (Rafael2 300HT manufactured by Aspect Co., Ltd.). Although no roughness of the powder surface occurred during powder lamination, a three-dimensional object could not be obtained due to warping during laser irradiation.

[0055] [Table 1]

[0056] [Table 2] [Industrial Applicability]

[0057] The branched polyamide resin granule of the present invention has a moderately controlled crystallization rate, and therefore can be suitably used in powder bed fusion 3D printers, etc. Furthermore, when used in powder bed fusion 3D printers, a smooth powder surface can be formed, there is no warping during laser irradiation, and a molded object with good tensile strength can be obtained.

Claims

1. A branched polyamide resin powder granule is formed from a polyamide having an average particle size of more than 1 μm and not more than 100 μm, the polyamide being composed of a monomer (A) consisting of an aminocarboxylic acid or a lactam, and a monomer (B) containing a total of three or more amino groups and carboxyl groups, and the molar ratio of monomer (A) to monomer (B) (molar ratio of monomer (A):molar ratio of monomer (B)) is 99:1 to 85:

15.

2. 2. The branched polyamide resin powder according to claim 1, wherein the monomer (A) is ε-aminocaproic acid or ε-caprolactam.

3. 3. The branched polyamide resin powder according to claim 1, wherein the monomer (B) is L-lysine.

4. 4. The branched polyamide resin powder according to claim 1, wherein the difference between the melting point and the crystallization temperature upon cooling measured by differential scanning calorimetry at a temperature increase / decrease rate of 20° C. / min is 50° C. or more.

5. 5. The branched polyamide resin powder according to claim 1, having a sphericity of 0.80 or more.

6. The method for producing a branched polyamide resin powder granule according to any one of claims 1 to 5, characterized in that a monomer (A) consisting of an aminocarboxylic acid or a lactam and a monomer (B) containing a total of three or more amino groups and carboxyl groups are polymerized without using an anionic catalyst, and the obtained polymer is pulverized to obtain a polyamide powder granule.

7. 6. A method for producing a branched polyamide resin powder granule according to claim 1, characterized in that a monomer (A) consisting of an aminocarboxylic acid or a lactam and a monomer (B) containing a total of three or more amino groups and carboxyl groups are polymerized in the presence of at least one polymer (C) which is compatible with the monomers (A) and (B) and undergoes phase separation from the polyamide resin, and a polyamide resin powder granule is precipitated after the polymerization.

8. 8. The method for producing branched polyamide resin powder particles according to claim 7, wherein the polymer (C) is polyethylene glycol, polypropylene glycol, polytetramethylene glycol, a polyethylene glycol-polypropylene glycol copolymer, or an alkyl ether thereof.

9. A method for producing a three-dimensional object, comprising supplying the branched polyamide resin powder or granule according to any one of claims 1 to 5 to a powder bed fusion 3D printer.

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