Polymer powder, its manufacturing method, and manufacturing method of three-dimensional object

Abstract

A polymer powder composed of a polyamide, characterized in that the melting point obtained by differential scanning calorimetry is 190°C or higher, the difference between the melting point and the melting start temperature obtained by differential scanning calorimetry is less than 30°C, and the D50 particle size is 1-100 μm inclusive; a method for producing the same; and a method for producing a 3-dimensional model object through a powder bed melt bonding process using the same. The polymer powder of the present invention can maintain the powder form in a non-laser irradiated area even in a large modeling device. By using the polymer powder in the production of a model object, a model object having small warpage can be provided.

Description

[Technical Field]

[0001] The present invention relates to a polymer powder, a method for producing the same, and a method for producing a three-dimensional object by powder bed fusion using the same. [Background technology]

[0002] Powder bed fusion (PFB) is a well-known technology for producing three-dimensional (3D) objects. Objects manufactured using PFB are produced by sequentially repeating a thin-layer formation process, in which powder is spread into thin layers, and a cross-sectional shape formation process, in which the formed thin layers are selectively melted into a shape corresponding to the cross-sectional shape of the object to bond the resin powder particles. Methods for selectively melting powder include selective laser sintering, in which a layer of powder is formed, and then selectively melted and solidified with a laser at locations corresponding to the object's cross-section, thereby bonding and laminating these layers. Other methods for selectively melting powder include selective absorption sintering and selective suppression sintering, in which a layer of powder is formed, and then electromagnetic radiation absorbers or suppressors are printed at locations corresponding to the object's cross-section, and then selectively melted and solidified with a laser or other light or heat source, thereby bonding and laminating these layers to form a molded object. These methods are expected to rapidly expand because they can achieve high dimensional accuracy and mechanical strength in molded objects.

[0003] Traditionally, polyamide 12 resin powder has been used primarily as a molding material, but there have been issues with heat resistance and strength, limiting its application. In addition, with the recent increase in demand for practical applications such as automobiles, the size of molded objects has increased, and there is a demand for technology to suppress warping of molded objects.

[0004] Numerous technical improvements have been attempted to obtain the above-mentioned powders. For example, Patent Document 1 discloses a polyamide powder obtained by copolymerizing a copolymer of polyamide 6I and polyamide 6T with a semicrystalline polyamide having a melting enthalpy of 45 J / g or more. Patent Document 2 also discloses a copolymerized polyamide obtained by anionic polymerization or hydrolytic polycondensation of a major monomer with 0.1 to 20 parts by weight of a minor comonomer. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Special Publication No. 2019-524939 [Patent Document 2] Special Publication No. 2011-518938 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in Patent Documents 1 and 2, the powder shape was non-uniform, resulting in a large difference between the melting point and melting initiation temperature of the polymer powder. Therefore, in large-scale modeling equipment prone to temperature variations, the powder shape could not be maintained in non-laser-irradiated areas. Furthermore, it was difficult to prevent warping of the modeled object when the polyamide powder was used.

[0007] Therefore, the present invention aims to provide a polymer powder that can maintain the shape of the powder in non-laser-irradiated areas even in large-scale molding equipment where temperature unevenness is likely to occur, and to provide a molded object that has little warping when made using this polymer powder. [Means for solving the problem]

[0008] In order to solve the above problems, the present inventors have conducted extensive research and have arrived at the following invention. That is, the present invention is "[1] A polymer powder composed of polyamide, characterized in that the melting point obtained by differential scanning calorimetry is 190°C or higher, the difference between the melting point obtained by differential scanning calorimetry and the melting onset temperature is less than 30°C, and the D50 particle size is 1 μm or more and 100 μm or less. [2] The polymer powder according to [1], wherein the difference between the melting onset temperature and the crystallization onset temperature obtained by differential scanning calorimetry is 3°C or more. [3] The polymer powder according to [1] or [2], wherein the polyamide having a molecular weight of 3,000 or less is 0.4 wt % or less of the total polyamide. [4] The polymer powder according to any one of [1] to [3], which has a weight average molecular weight of 40,000 or more. [5] The polymer powder according to any one of [1] to [4], wherein the weight average molecular weight / number average molecular weight is 1.8 or less. [6] The polymer powder according to any one of [1] to [5], wherein the ratio of the amount of terminal carboxyl groups to the amount of terminal amino groups in the polyamide is 0.001 or more and 0.8 or less. [7] The polymer powder according to any one of [1] to [6], wherein the particle size distribution D90 / D10 is less than 3.0. [8] The polymer powder according to any one of [1] to [7], which has a sphericity of 80 or more. [9] The polymer powder according to any one of [1] to [8], wherein the polyamide contains at least one of polyamide 6, polyamide 66, or a copolymer thereof.

[10] The polymer powder according to any one of [1] to [9], which contains a flow aid in an amount of 0.01 parts by mass or more and 5 parts by mass or less per 100 parts by mass of the polyamide.

[11] The polymer powder according to any one of [1] to

[10] , which contains an inorganic reinforcing material in an amount of 10 parts by mass or more and 200 parts by mass or less per 100 parts by mass of the polyamide.

[12] A method for producing a polymer powder comprising a polyamide by polymerizing a polyamide monomer in the presence of a polymer incompatible with the resulting polyamide, characterized in that the polyamide monomer and the polymer are uniformly dissolved at the start of polymerization, and polymerization is carried out at a temperature of at least 20°C above the crystallization temperature of the resulting polyamide but not exceeding the melting point, until the difference between the melting point and the melting initiation temperature of the resulting polyamide measured by differential scanning calorimetry becomes less than 30°C.

[13] The method for producing a polymer powder according to

[12] , wherein a terminal modifier is added in an amount of 0.001 mol% or more and 0.8 mol% or less at the start of polymerization.

[14] A method for producing a three-dimensional object by powder bed fusion, using the polymer powder according to any one of [1] to

[11] . [Effects of the Invention]

[0009] The polymer powder of the present invention can maintain the shape of the powder in the non-laser-irradiated areas even in a large-scale molding device that is prone to temperature unevenness.Furthermore, when the polymer powder is used to produce a molded object, it is possible to provide a molded object with minimal warping. DETAILED DESCRIPTION OF THE INVENTION

[0010] The present invention will be described in detail below with reference to embodiments. The polymer powder of the present invention is a polymer powder composed of polyamide, characterized in that it has a melting point of 190°C or higher as determined by differential scanning calorimetry, a difference between the melting point and the melting onset temperature as determined by differential scanning calorimetry of less than 30°C, and a D50 particle size of 1 μm or more and 100 μm or less.

[0011] In the production of objects using powder bed fusion, if the temperature inside the modeling machine drops below the crystallization temperature of the polymer powder after melting and cooling to obtain a uniform object, the object will crystallize and shrink, resulting in warping. A common method for preventing warping is to use the aforementioned polymer powder and set the modeling temperature at a temperature 15°C or more below the melting point, the upper limit at which the polymer powder will not melt. However, as the modeling machine becomes larger, the temperature inside the machine varies, resulting in high temperatures in some areas, causing the polymer powder to melt in areas not irradiated with the laser. While melting of the polymer powder can be prevented by further lowering the temperature during modeling, the risk of warping increases as the temperature is lowered. Therefore, in large-scale modeling, there is a trade-off between warping of the object and melting of the polymer powder in areas not irradiated with the laser, making it difficult to simultaneously prevent both.

[0012] The present inventors discovered that when manufacturing three-dimensional objects using powder bed fusion, using a polymer powder composed of polyamide, which has a difference between its melting point and melting onset temperature within a specific range, can eliminate the above-mentioned trade-off, maintain the shape of the polymer powder in the non-laser-irradiated areas, and suppress warping of the resulting object, leading to the present invention.

[0013] The polymer powder in the present invention is composed of a polyamide having a structure containing an amide group. Specific examples of polyamides include polycaproamide (polyamide 6), polyhexamethylene adipamide (polyamide 66), polyhexamethylene terephthalamide (polyamide 6T), polyhexamethylene sebacamide (polyamide 610), polyhexamethylene dodecamide (polyamide 612), polydecamethylene adipamide (polyamide 106), polydodecamethylene adipamide (polyamide 126), polynonanamide (polyamide 9), polydecamethylene terephthalamide (polyamide 10T), polydecamethylene sebacamide (polyamide 1010), polyundecaneamide (polyamide 11), polydodecamethylene terephthalamide (polyamide 12T), polycaproamide / polyhexamethylene adipamide copolymer (polyamide 6 / 66), and copolymers thereof. From the viewpoint of heat resistance during molding and the thermal properties of the molded object, polycaproamide (polyamide 6), polyhexamethylene adipamide (polyamide 66) or copolymers thereof are particularly preferred, polycaproamide (polyamide 6) or its copolymers are significantly more preferred, and polycaproamide (polyamide 6) is most preferred.

[0014] These may be copolymerized within the range that does not impair the effects of the present invention. As the copolymerizable component, an elastomer component such as a polyolefin or polyalkylene glycol that imparts flexibility, a rigid aromatic component that improves heat resistance and strength, or a terminal modifier that modifies the terminal group can be appropriately selected.

[0015] The melting point of the polymer powder in the present invention refers to the temperature at which all of the powder melts in the molding apparatus. The melting point was calculated from the endothermic peak observed when 10 mg of the powder was heated from 30°C at a rate of 20°C / min in a nitrogen atmosphere using a differential scanning calorimeter (DSCQ20) manufactured by TA Instruments, and the temperature at the top of the peak was taken as the melting point.

[0016] From the viewpoint of the heat resistance of the shaped product, the melting point of the polymer powder of the present invention is 190°C or higher. The lower limit is preferably 200°C or higher, more preferably 205°C or higher, even more preferably 210°C or higher, particularly preferably 215°C or higher, significantly more preferably 217°C or higher, and most preferably 218°C or higher. From the viewpoint of the heat resistance of the shaping apparatus, the upper limit is preferably 300°C or lower, more preferably 295°C or lower, even more preferably 290°C or lower, particularly preferably 285°C or lower, significantly more preferably 280°C or lower, and most preferably 260°C or lower.

[0017] In the present invention, the melting initiation temperature of a polymer powder refers to the temperature at which the powder begins to melt, even slightly, in a molding apparatus. Conventionally, the melting initiation temperature is determined by drawing a tangent to the first bending point, which is lower than the minimum temperature of the endothermic peak observed when the powder is heated at a constant rate using a differential scanning calorimeter, and defining the temperature at the intersection of this tangent with the tangent to the baseline. However, this definition does not allow for the evaluation of low-melting-point polymer powders present in small amounts. In large molding apparatuses that use large amounts of powder, the presence of even a small amount of low-melting-point powder can cause the powder in non-laser-irradiated areas to melt, so it is necessary to evaluate even small amounts of low-melting-point powder. Therefore, the melting onset temperature in the present invention was determined as the lowest temperature among the peak-top temperature of the endothermic peak observed when 10 mg of powder was heated from 30°C at a rate of 20°C / min in a nitrogen atmosphere using a TA Instruments Differential Scanning Calorimeter (DSCQ20) and the temperature at which the first temperature derivative of the heat flow (W / g) observed between the peak-top of the endothermic peak and a temperature point of -50°C was -0.2 (W / g·°C).

[0018] The difference between the melting point and melting initiation temperature of the polymer powder of the present invention is less than 30°C. Outside this range, variations in the melting temperature occur. Variations in the melting temperature result in a mixture of powders with low and high melting temperatures within the molding apparatus. Setting a low temperature for the molding apparatus in accordance with a powder with a low melting temperature makes the molded object more likely to warp. Furthermore, setting a high laser output for a powder with a high melting temperature makes it more likely that the powder in the non-laser-irradiated areas will melt. Therefore, variations in the melting temperature make it difficult to set molding conditions that suppress melting of the powder in the non-laser-irradiated areas and warping of the molded object in large molding apparatuses prone to temperature variations. The upper limit of the difference between the melting point and melting initiation temperature is preferably 29°C or less, more preferably 28°C or less, particularly preferably 27°C or less, and most preferably 26°C or less. Theoretically, the lower limit is 0°C.

[0019] The D50 particle size of the polymer powder of the present invention is in the range of 1 μm or more and 100 μm or less. If the D50 particle size exceeds 100 μm, the particle size will be greater than the thickness of the thin layer formed for shaping, resulting in a rough surface. If the D50 particle size is less than 1 μm, the particles will be too fine and will easily adhere to the coater during shaping, making it difficult to raise the temperature inside the shaping device to the required level. The upper limit of the D50 particle size of the polymer powder is preferably 90 μm or less, more preferably 80 μm or less, and even more preferably 75 μm or less. The lower limit is preferably 5 μm or more, more preferably 20 μm or more, and even more preferably 30 μm or more.

[0020] The D50 particle size of the polymer powder is the particle size (D50 particle size) at which the cumulative frequency from the small particle size side of the particle size distribution measured with a laser diffraction particle size distribution analyzer is 50%.

[0021] The crystallization onset temperature in this invention refers to the temperature below which a molded object immediately warps in a molding apparatus. Conventionally, the crystallization onset temperature is determined by drawing a tangent to the first bending point, which is higher than the maximum temperature of the exothermic peak observed when a powder is cooled at a constant rate using a differential scanning calorimeter, and determining the temperature at the intersection of this tangent and the tangent to the baseline. However, this definition does not allow for evaluation of small amounts of high-crystallization-temperature polymer powder. In large-scale molding apparatuses that use large amounts of powder, even small amounts of high-crystallization-temperature polymer powder can cause warping in the molded object, so it is necessary to evaluate even small amounts of high-crystallization-temperature powder. Therefore, in the present invention, the crystallization onset temperature was calculated using a differential scanning calorimeter (DSCQ20) manufactured by TA Instruments, based on the exothermic peak that appeared when the temperature was raised from 30°C at a rate of 20°C / min under a nitrogen atmosphere to a temperature 50°C higher than the peak top of the endothermic peak observed, held for 1 minute, and then cooled to 30°C at a rate of 20°C / min. The crystallization onset temperature was determined to be the highest temperature at which the first temperature derivative of Heat Flow (W / g) observed between the peak top temperature of the exothermic peak and a temperature point 50°C above the peak top of the exothermic peak was -0.1 (W / g °C).

[0022] In the present invention, the difference between the melting initiation temperature and the crystallization initiation temperature is preferably 3°C or more. If the difference between the melting initiation temperature and the crystallization initiation temperature is small, the temperature conditions for simultaneously suppressing melting of the powder in the non-laser-irradiated portions and warping of the molded object tend to be narrower. In particular, it may be difficult to set the conditions in large molding equipment where temperature variations occur. Therefore, the lower limit is preferably 4°C or more, more preferably 6°C or more, even more preferably 8°C or more, and particularly preferably 10°C or more. If the difference between the melting initiation temperature and the crystallization initiation temperature is large, it takes a long time to cool and solidify after melting, resulting in a decrease in productivity. Therefore, the upper limit is preferably 100°C or less, more preferably 90°C or less, even more preferably 80°C or less, particularly preferably 70°C or less, and most preferably 60°C or less.

[0023] The proportion of polyamides with a molecular weight of 3,000 or less in the polyamides constituting the polymer powder is preferably 0.4 wt% or less. The lower the proportion of polyamides with a molecular weight of 3,000 or less, the higher the melting initiation temperature and the smaller the difference between the melting point and the melting initiation temperature. This is preferable because melting of non-laser-irradiated powder areas and warping of the molded object can be suppressed even in large molding devices prone to temperature unevenness. The upper limit is preferably 0.4 wt% or less, more preferably 0.3 wt% or less, and even more preferably 0.2 wt% or less. If the proportion of polyamides with a molecular weight of 3,000 or less is low, the viscosity becomes high and powder fusion is more likely to proceed, so the proportion is preferably 0.001 wt% or more, and more preferably 0.005 wt% or more.

[0024] The weight-average molecular weight of the polyamide is preferably 40,000 or higher. The higher the weight-average molecular weight, the higher the melting initiation temperature and the smaller the difference between the melting point and the melting initiation temperature. This is advantageous because it prevents melting of non-laser-irradiated powder and warping of the molded object, even in large-scale molding equipment prone to temperature variations. Furthermore, in powder bed fusion, molded objects are produced using only a portion of the polymer powder used, leaving a large amount of polymer powder remaining. Reusing the remaining polymer powder is important from a cost perspective. To achieve this, it is important to maintain the properties of the polymer powder during the heating and molding process. The higher the weight-average molecular weight of the polyamide, the less terminal groups there are and the smaller the change in molecular weight before and after molding. Therefore, the lower limit is preferably 40,000 or higher, more preferably 46,000 or higher, even more preferably 50,000 or higher, particularly preferably 60,000 or higher, significantly more preferably 70,000 or higher, and most preferably 74,000 or higher. If the molecular weight is too high, the viscosity becomes high and the powder tends to fuse together, so the molecular weight is preferably 800,000 or less, more preferably 500,000 or less, and particularly preferably 300,000 or less.

[0025] The molecular weight distribution index of the polyamide, expressed as the ratio of the weight average molecular weight to the number average molecular weight (weight average molecular weight / number average molecular weight), is preferably 1.8 or less. A smaller molecular weight distribution index reduces the difference between the melting point and the melting onset temperature, eliminating variations in the melting temperature. This is preferable because it can prevent melting of the powder in non-laser-irradiated areas and warping of the molded product, even in large molding devices prone to temperature variations. Therefore, the molecular weight distribution index of the polyamide is preferably 1.7 or less, more preferably 1.6 or less, and even more preferably 1.5 or less. Theoretically, the lower limit is 1.

[0026] The weight average molecular weight and number average molecular weight of polyamide are measured by gel permeation chromatography using hexafluoroisopropanol as a solvent and converted into a weight average molecular weight and number average molecular weight in terms of polymethyl methacrylate.

[0027] The amount of terminal carboxyl groups and the amount of terminal amino groups of the polyamide are 9.5 × 10 -5 It is preferable that the amount of terminal carboxyl groups and the amount of amino groups are small, because when the powder is reused, the change in molecular weight before and after molding is small. The amount of terminal carboxyl groups and the amount of amino groups are each 8.5 × 10 -5 mol / g or less is preferable, and 6.5×10 -5 mol / g or less is more preferable, and 3.0×10 -5 mol / g or less is more preferable. On the other hand, if the amount of terminal carboxyl groups or amino groups is small, the adhesiveness to the inorganic reinforcing agent decreases, so it is necessary to maintain a certain amount of functional groups. The amount of terminal carboxyl groups and the amount of amino groups are each 1.0 × 10 -9 mol / g or more is preferable, and 1.0×10 -8 mol / g or more is more preferable, and 1.0×10 -7 More preferably, it is mol / g or more.

[0028] The amount of terminal carboxyl groups in polyamides can be determined by dissolving the polymer powder in benzyl alcohol and then neutralizing titrating it with an ethanolic potassium hydroxide solution, while the amount of terminal amino groups in polyamides can be determined by dissolving the polymer powder in PEA (phenol-ethanol solvent) and then neutralizing titrating it with an aqueous hydrochloric acid solution.

[0029] Methods for reducing the amount of terminal carboxyl groups and terminal amino groups include using high-molecular-weight polymer powders and adding monofunctional terminal modifiers, such as monoamines (e.g., hexylamine, octylamine, and aniline) or monocarboxylic acids (e.g., acetic acid, hexanoic acid, lauric acid, stearic acid, and benzoic acid) during polymerization of polyamide monomers. When amino acids or lactams are used as polyamide monomers, adding bifunctional terminal modifiers (e.g., diamines (e.g., hexamethylenediamine and phenylenediamine) or dicarboxylic acids (e.g., terephthalic acid and adipic acid) in addition to monofunctional terminal modifiers is also possible. The terminal modifiers added are preferably monocarboxylic acids (e.g., acetic acid, hexanoic acid, lauric acid, stearic acid, and benzoic acid), with aromatic monocarboxylic acids (e.g., benzoic acid) being more preferred, from the viewpoints of not inhibiting the polymerization reaction, producing high-molecular-weight polyamides, and suppressing coloration. When diamines or dicarboxylic acids are used as polyamide monomers, adjusting the feed ratios can reduce the amount of terminal groups.

[0030] When reusing the powder, a small ratio of the amount of terminal carboxyl groups to the amount of terminal amino groups in the polyamide is preferable because it further reduces the change in molecular weight before and after molding. The ratio of the amount of terminal carboxyl groups to the amount of terminal amino groups in the polyamide refers to the value obtained by dividing the amount of smaller functional groups by the amount of larger functional groups in the amount of terminal carboxyl groups and terminal amino groups in the polyamide. A small amount of terminal amino groups is preferable because it reduces the change in color tone of the powder before and after molding. The ratio of the amount of terminal carboxyl groups to the amount of terminal amino groups in the polyamide is preferably 0.8 or less. The ratio of the amount of terminal carboxyl groups to the amount of terminal amino groups in the polyamide is preferably 0.7 or less, more preferably 0.6 or less, even more preferably 0.4 or less, and most preferably 0.3 or less. On the other hand, particles with a small ratio of the amount of terminal carboxyl groups to the amount of terminal amino groups in the polyamide have a small molecular weight, which can cause melting of the powder in non-laser-irradiated areas and warping of the molded product. The ratio of the amount of terminal carboxyl groups to the amount of terminal amino groups in the polyamide is preferably 0.001 or more, more preferably 0.01 or more.

[0031] The polymer powder of the present invention has a small amount of terminal carboxyl groups and terminal amino groups, and furthermore, the ratio of the amount of terminal carboxyl groups to the amount of terminal amino groups in the polyamide is small, so that even if the powder is reused for molding, the molecular weight of the polyamide does not change. This index can be evaluated by calculating the rate of change in molecular weight before and after molding.

[0032] The rate of change in molecular weight before and after molding in the present invention refers to the amount of change in the molecular weight of polyamide after a test piece is molded using a large-scale molding device.

[0033] In the present invention, the molecular weight change rate before and after molding is preferably in the range of 0.8 or more and less than 1.6 when molding is performed for 5 hours or more using a large-scale molding apparatus. If it is outside this range, the change in molecular weight of the polyamide before and after molding will be large, which is undesirable in terms of reusing the powder. The upper limit of the molecular weight change rate before and after molding is preferably less than 1.5, more preferably less than 1.4. The lower limit is preferably 0.85 or more, more preferably 0.90 or more.

[0034] The rate of change in molecular weight before and after molding is calculated as the ratio of the weight average molecular weight of the polyamide that constitutes the polymer powder after molding (Mw. of the polyamide after molding) to the weight average molecular weight Mw. of the polyamide that constitutes the polymer powder before molding (Mw. of the polyamide before molding). The Mw. of the polyamide after molding is calculated by measuring the post-molding powder remaining in the molding device after specimen molding using gel permeation chromatography with hexafluoroisopropanol as a solvent, and converting the obtained value into polymethyl methacrylate.

[0035]

number

[0036] The particle size distribution index of the polymer powder is expressed as D90 / D10, which is the ratio of D90 to D10 in the particle size distribution, and is preferably less than 3.0. A smaller particle size distribution index reduces the difference between the melting point and the melting onset temperature, thereby preventing variations in the melting temperature. This is preferable because it can prevent melting of the powder in non-laser-irradiated areas and warping of the molded object, even in large molding devices where temperature variations are likely to occur. Therefore, D90 / D10 is preferably less than 2.8, more preferably less than 2.6, and even more preferably less than 2.4. Theoretically, the lower limit of D90 / D10 is 1.

[0037] The particle size distribution index D90 / D10 of the polymer powder in the present invention is a value obtained by dividing the particle size (D90) at which the cumulative frequency from the small particle size side of the particle size distribution measured by the laser diffraction particle size distribution meter described above is 90% by the particle size (D10) at which the cumulative frequency from the small particle size side is 10%.

[0038] The sphericity, which indicates the sphericity of the polymer powder of the present invention, is preferably 80 or more. High sphericity reduces the difference between the melting point and the melting initiation temperature, eliminating variations in the melting temperature. This is preferable because it can prevent melting of the powder in non-laser-irradiated areas and warping of the molded product, even in large molding devices that are prone to temperature variations. The sphericity is preferably 85 or more, more preferably 90 or more, and even more preferably 95 or more. The upper limit is 100.

[0039] The sphericity of the polyamide powder is calculated by observing 30 particles randomly selected from a scanning electron microscope photograph and averaging the ratio of the minor axis to the major axis of each particle.

[0040]

number

[0041] In the above formula, S is sphericity, a is major axis, b is minor axis, and n is the number of measurements (30).

[0042] The polymer powder of the present invention may contain a flow aid. The flow aid is preferably dry-blended with the polymer powder. In the present invention, the flow aid refers to a substance that suppresses aggregation of polymer powder due to adhesive forces between polymer powders. By including the flow aid, the fluidity of the polymer powder can be improved, and the polymer powder will be packed evenly when it is formed into a molded object. As a result, the warpage of the resulting molded object will be reduced.

[0043] Examples of such flow aids include silica (silicon dioxide) such as fused silica, crystalline silica, and amorphous silica; alumina (aluminum oxide), alumina colloid (alumina sol), and alumina white; calcium carbonate such as light calcium carbonate, heavy calcium carbonate, finely powdered calcium carbonate, and special calcium carbonate fillers; nepheline syenite fine powder, calcined clay such as montmorillonite and bentonite; clay (aluminum silicate powder) such as silane-modified clay; silicic acid-containing compounds such as talc, diatomaceous earth, and silica sand; and crushed natural minerals such as pumice powder, pumice balloons, slate powder, and mica powder. Examples of suitable fillers include minerals such as barium sulfate, lithopone, calcium sulfate, molybdenum disulfide, and graphite; glass fillers such as glass fibers, glass beads, glass flakes, and foamed glass beads; fly ash spheres, hollow volcanic glass, synthetic inorganic hollow bodies, single-crystal potassium titanate, carbon fibers, carbon nanotubes, hollow carbon spheres, fullerenes, anthracite powder, artificial cryolite, titanium oxide, magnesium oxide, basic magnesium carbonate, dolomite, potassium titanate, calcium sulfite, mica, asbestos, calcium silicate, molybdenum sulfide, boron fiber, and silicon carbide fiber. Silica, alumina, calcium carbonate powder, glass fillers, and titanium oxide are more preferred. Silica is particularly preferred.

[0044] Commercially available examples of such silica include the fumed silica "AEROSIL" (registered trademark) series manufactured by Nippon Aerosil Co., Ltd., the dry silica "Reolosil" (registered trademark) series manufactured by Tokuyama Corporation, and the sol-gel silica powder X-24 series manufactured by Shin-Etsu Chemical Co., Ltd.

[0045] The D50 particle size of such a flow aid is preferably 20 nm or more and 1 μm or less. The upper limit of the D50 particle size of the flow aid is preferably 1 μm or less, since the smaller the particle size and the larger the surface area, the more easily the resin powder can be prevented from agglomerating. It is more preferably 500 nm or less, even more preferably 400 nm or less, particularly preferably 300 nm or less, and extremely preferably 250 nm or less. The lower limit is preferably 20 nm or more, since an excessively large surface area inhibits filling properties and causes warping of the molded product. It is more preferably 30 nm or more, even more preferably 50 nm or more, and particularly preferably 100 nm or more. If the average particle size of the flow aid is within the above range, the fluidity of the polymer powder is improved and the flow aid tends to be uniformly dispersed in the polymer powder.

[0046] The D50 particle size of the flow aid in the present invention is the particle size (D50 particle size) at which the cumulative frequency from the small particle size side of the particle size distribution measured with a laser diffraction particle size distribution analyzer is 50%.

[0047] The blending amount of such flow aid is 0.01 to 5 parts by mass per 100 parts by mass of polyamide. The upper limit of the blending amount is preferably 4 parts by mass or less, more preferably 3 parts by mass or less, even more preferably 2 parts by mass or less, and particularly preferably 1 part by mass or less. The lower limit of the blending amount is preferably 0.02 parts by mass or more, more preferably 0.03 parts by mass or more, even more preferably 0.05 parts by mass or more, and particularly preferably 0.1 parts by mass or more. If the blending amount of the flow aid is less than 0.01 parts by mass, the fluidity is insufficient, and the resulting shaped product is likely to warp. If the blending amount of the flow aid exceeds 5 parts by mass, the surface of the resin powder is coated with the flow aid, inhibiting sintering and making it impossible to obtain a shaped product.

[0048] The polymer powder in the present invention may contain an inorganic reinforcing material composed of an inorganic compound. The inorganic reinforcing material may be dry-blended with the polymer powder or may be contained inside the polymer powder, but dry-blending is preferred from the viewpoint of controlling the polymer powder to have a spherical shape and improving flowability.

[0049] Examples of such inorganic reinforcing materials include glass fillers such as glass fiber, glass beads, glass flakes, and expanded glass beads; nepheline syenite fine powder, calcined clays such as montmorillonite and bentonite; clays (aluminum silicate powders) such as silane-modified clay; silicic acid-containing compounds such as talc, diatomaceous earth, and silica sand; crushed natural minerals such as pumice powder, pumice balloons, slate powder, and mica powder; minerals such as barium sulfate, lithopone, calcium sulfate, molybdenum disulfide, and graphite; silica (silicon dioxide) such as fused silica, crystalline silica, and amorphous silica; alumina (aluminum oxide); and alumina colloids (alumina). Examples of suitable inorganic reinforcing materials include alumina such as Luminasol and alumina white; calcium carbonate such as light calcium carbonate, heavy calcium carbonate, finely powdered calcium carbonate, and special calcium carbonate-based fillers; fly ash spheres; hollow volcanic glass bodies; synthetic inorganic hollow bodies; single-crystal potassium titanate; potassium titanate fibers; carbon fibers; carbon nanotubes; hollow carbon spheres; fullerenes; anthracite powder; cellulose nanofibers; artificial cryolite (cryolite); titanium oxide; magnesium oxide; basic magnesium carbonate; dolomite; calcium sulfite; mica; asbestos; calcium silicate; molybdenum sulfide; boron fibers; and silicon carbide fibers. Glass-based fillers, minerals, and carbon fibers are preferred due to their hardness and significant strength-enhancing effect, and glass-based fillers are even more preferred due to their narrow particle size and fiber size distributions. These inorganic reinforcing materials can be used alone or in combination of two or more.

[0050] Examples of glass-based fillers preferably used in the present invention include glass fibers, glass beads, glass flakes, and foamed glass beads. Glass fibers and glass beads are particularly preferred because they can suppress warping of three-dimensionally shaped objects. Among these, glass fibers are particularly preferred, and glass fibers may have a circular or flat cross section. Furthermore, glass beads are particularly preferred because they result in small anisotropic warping of shaped objects.

[0051] To improve the adhesion between the inorganic reinforcing material and the polymer powder, inorganic reinforcing materials that have been surface-treated can be used, as long as the effects of the present invention are not impaired. Examples of such surface treatments include silane coupling agents such as aminosilane, epoxysilane, and acrylicsilane. These surface treatment agents may be immobilized on the surface of the inorganic reinforcing material by a coupling reaction or may coat the surface of the inorganic reinforcing material. However, in terms of recycling the powder used in three-dimensional modeling, those immobilized by a coupling reaction are preferred because they are less likely to be modified by heat or the like.

[0052] The average major axis diameter of the inorganic reinforcing material of the present invention is preferably in the range of 3 to 300 μm. If the average major axis diameter exceeds 300 μm, uneven filling of the polymer powder occurs when the shaped product is formed, which is undesirable, and warping of the shaped product occurs. If the average major axis diameter is less than 3 μm, it is undesirable because it will not contribute to suppressing warping. The upper limit of the average major axis diameter of the inorganic reinforcing material is preferably 250 μm or less, more preferably 200 μm or less, even more preferably 150 μm or less, and particularly preferably 100 μm or less. The lower limit is preferably 5 μm or more, more preferably 8 μm or more, and even more preferably 10 μm or more.

[0053] The shape characteristics of the inorganic reinforcing material of the present invention are expressed by the ratio of the average major axis diameter to the average minor axis diameter, i.e., the average major axis diameter / average minor axis diameter, and are preferably 1 to 15. A ratio of the average major axis diameter / average minor axis diameter exceeding 15 is undesirable because the orientation in the X direction of the shaped object becomes significant, increasing the anisotropy of warpage relative to the Z direction. Therefore, the average major axis diameter / average minor axis diameter is preferably 12 or less, more preferably 10 or less, and even more preferably 8 or less. Theoretically, the lower limit is 1. Among these, from the viewpoint of increasing strength, a ratio of 2 to 8 is particularly preferable, and a ratio of 3 to 8 is extremely preferable. From the viewpoint of reducing anisotropy, a ratio of 1 to 5 is particularly preferable, and a ratio of 1 to 3 is extremely preferable.

[0054] In the present invention, the average major axis diameter and the average minor axis diameter of an inorganic reinforcing material are the number average values ​​of the major axis diameter and the minor axis diameter of 100 randomly selected fibers or particles observed in a photograph obtained by capturing an inorganic reinforcing material with a scanning electron microscope. The major axis diameter is the diameter at which the distance between two parallel lines is the largest when an image of a particle is sandwiched between two parallel lines in a direction perpendicular to the major axis diameter, and the minor axis diameter is the diameter at which the distance between two parallel lines is the smallest when an image of a particle is sandwiched between two parallel lines in a direction perpendicular to the major axis diameter.

[0055] The amount of inorganic reinforcing material added is preferably 10 to 200 parts by mass per 100 parts by mass of polyamide. The upper limit of the amount added is more preferably 150 parts by mass or less, even more preferably 100 parts by mass or less, and particularly preferably 75 parts by mass or less, in order to prevent deterioration of the flowability of the resin powder granules and to obtain a shaped product without warping. The lower limit of the amount added is more preferably 15 parts by mass or more, even more preferably 20 parts by mass or more, and particularly preferably 25 parts by mass or more, in order to prevent warping of the shaped product.

[0056] Other additives may also be contained, such as antioxidants for improving the stability of the polymer powder, heat stabilizers, weathering agents, lubricants, pigments, dyes, plasticizers, antistatic agents, flame retardants, carbon black, and titanium dioxide.

[0057] The polymer powder of the present invention has the effect of suppressing melting of the powder in the non-laser-irradiated areas and warping of the molded object, even in a large-scale modeling apparatus that is prone to temperature unevenness. This can be evaluated by calculating the degree of melting of the powder in the non-laser-irradiated areas when using the large-scale modeling apparatus and the amount of warping of the molded object obtained from the large-scale modeling apparatus.

[0058] The degree of powder melting in the non-laser-irradiated areas when using the above-mentioned large-scale modeling equipment refers to the weight percentage of powder that melts in the non-laser-irradiated areas when a test piece is manufactured using the large-scale modeling equipment for 5 hours or more.

[0059] In the present invention, when using a large-scale modeling apparatus, the powder melting degree of the non-laser-irradiated portions is preferably 30 wt% or less. The smaller the powder melting degree of the non-laser-irradiated portions, the less melting of the powder in the non-laser-irradiated portions occurs, and the desired model can be obtained, so it is preferable. The upper limit is more preferably 20 wt% or less, and even more preferably 5 wt% or less. Theoretically, the lower limit is 0 wt%.

[0060] The degree of powder melting in the non-laser-irradiated areas when using a large-scale modeling device was determined by taking 100 g of powder remaining in the device after forming test pieces using the large-scale modeling device for 5 hours or more, crushing it in a mortar and pestle, and passing it through a 500 μm sieve, and then calculating the percentage of the weight W of the powder remaining on the sieve.

[0061]

number

[0062] The amount of warpage of the object obtained using the large-scale modeling equipment mentioned above refers to the amount of warpage that actually occurs in the test piece when the test piece is manufactured using the large-scale modeling equipment for 5 hours or more.

[0063] The amount of warpage (measurement and evaluation methods are described below) of the object obtained by the large-scale modeling apparatus is preferably 0.3 mm / 10 cm or less. If the amount of warpage of the object is greater than 0.3 mm / 10 cm, the warpage becomes significant, and the desired object cannot be obtained. The smaller the amount of warpage of the object, the more preferable it is, since the desired object can be obtained without warpage. The upper limit is more preferably 0.2 mm / 10 cm or less, even more preferably 0.1 mm / 10 cm or less, and particularly preferably 0.05 mm / 10 cm or less. Theoretically, the lower limit is 0.0 mm / 10 cm.

[0064] The amount of warping of the object formed using the above-mentioned large-scale modeling equipment is measured after forming a test specimen for more than five hours by placing the resulting test specimen on a horizontal surface in an upward convex position and inserting a taper gauge into the gap between the horizontal surface and the test specimen.

[0065] Although there are no limitations on the method for producing the polymer powder of the present invention, a preferred method is described in International Publication WO 2018 / 207728, previously disclosed by the present inventors, in which the polyamide monomer of the present invention is polymerized in the presence of a polymer incompatible with the resulting polyamide, and the resulting polymer powder is washed and dried. The inventors discovered that by carrying out the polymerization at a polymerization temperature that is at least 20°C above the crystallization temperature of the resulting polyamide and below its melting point, and until the difference between the melting point and melting onset temperature of the resulting polyamide measured by differential scanning calorimetry is less than 30°C, the melting temperature does not vary, and a polymer powder can be produced that is less likely to melt in non-laser-irradiated areas of the powder or warp in the molded product, even in large-scale modeling equipment prone to temperature variations.

[0066] From the viewpoints of suppressing the production of low-molecular-weight polyamide in the polymer powder and reducing the difference between the melting and crystallization initiation temperatures, the polymerization temperature is preferably the crystallization temperature of the resulting polyamide +20°C or more, more preferably +25°C or more, and even more preferably +30°C or more. From the viewpoint of preventing the progression of side reactions of polyamide such as three-dimensional crosslinked products from increasing the molecular weight distribution index and widening the difference between the melting and crystallization initiation temperatures, the polymerization temperature is preferably the melting point of the resulting polyamide or lower, more preferably the melting point -3°C or lower, and even more preferably the melting point -5°C or lower. The melting point and crystallization temperature of the polyamide were determined using a differential scanning calorimeter (DSCQ20) manufactured by TA Instruments. The melting point was determined as the peak top temperature of the endothermic peak observed when the temperature was raised from 30°C at a rate of 20°C / min under a nitrogen atmosphere, and the crystallization temperature was determined as the peak top temperature of the exothermic peak that appeared when the temperature was raised to a temperature 50°C higher than the melting point, held for 1 minute, and then cooled to 30°C at a rate of 20°C / min.

[0067] In order to produce particles that can suppress melting of the powder in non-laser-irradiated areas and warping of the molded object in large-scale modeling equipment prone to temperature unevenness, polymerization is carried out until the difference between the melting point and melting onset temperature of the resulting polyamide measured by differential scanning calorimetry is less than 30°C. If the difference between the melting point and melting onset temperature exceeds 30°C, the melting temperature will vary, which will likely cause melting of the powder in non-laser-irradiated areas and warping of the molded object in large-scale modeling equipment prone to temperature unevenness. Polymerization is preferably carried out until the difference between the melting point and melting onset temperature is 29°C or less, more preferably 28°C or less, particularly preferably 27°C or less, and most preferably 26°C or less.

[0068] Furthermore, the polymer powder obtained by the manufacturing method of the present invention undergoes a polymerization reaction within small, uniform emulsions, and there is no variation in polymerization behavior within or between emulsions. This has been shown to result in a small molecular weight distribution index for the polyamide, and a small difference between the melting point and melting onset temperature measured by differential scanning calorimetry for the resulting polyamide. Because there is no variation in the melting temperature, this method is advantageous in that it can prevent melting of powder in non-laser-irradiated areas and warping of the molded product, even in large-scale modeling equipment where temperature unevenness is likely to occur.

[0069] Next, the method for producing the polymer powder of the present invention will be described in detail. A preferred method for producing polymer powder is to produce a polymer powder by polymerizing a polyamide monomer in the presence of a polymer incompatible with the resulting polyamide at a polymerization temperature that is at least 20°C above the crystallization temperature of the polyamide obtained by polymerizing the polyamide monomer and below the melting point, until the difference between the melting point and melting initiation temperature of the resulting polyamide measured by differential scanning calorimetry is less than 30°C. In this method, the polyamide monomer and the polymer incompatible with the resulting polyamide are uniformly dissolved at the start of polymerization, and after polymerization, a polymer powder with the desired melting point, melting initiation temperature, and particle size can be produced.

[0070] It is more preferable to avoid using organic solvents in the production process. This can prevent problems such as powder fusion caused by organic solvents that cannot be completely removed by washing or drying. In particular, organic solvents with high boiling points (100°C or higher) are not preferable because they are more difficult to remove.

[0071] To determine whether the polyamide monomer is uniformly dissolved in the resulting polyamide-immiscible polymer at the start of polymerization, visually confirm that the reaction vessel is a transparent solution. A suspension or two-phase separation at the start of polymerization indicates that the polyamide monomer and the resulting polyamide-immiscible polymer are incompatible, resulting in the formation of aggregates or the need for vigorous stirring. In this case, additional water can be added to homogenize the polyamide monomer and the resulting polyamide-immiscible polymer before starting polymerization. To determine whether polymer powder has precipitated after polymerization, visually confirm that the reaction vessel is a suspension. A homogeneous solution at the end of polymerization indicates that the polyamide and the resulting polyamide-immiscible polymer are uniformly dissolved, resulting in aggregates or a porous powder upon cooling.

[0072] Specific examples of polyamide monomers used in this method for producing polymer powder include mixtures or salts of amino acids such as aminohexanoic acid, 9-aminopelargonic acid, and 11-aminoundecanoic acid, lactams such as ε-caprolactam, dicarboxylic acids such as oxalic acid, succinic acid, adipic acid, terephthalic acid, isophthalic acid, 1,4-cyclohexanedicarboxylic acid, and 1,3-cyclohexanedicarboxylic acid, and diamines such as ethylenediamine, trimethylenediamine, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, 1,4-cyclohexanediamine, and 1,3-cyclohexanediamine. Two or more of these polyamide monomers may be used, and other copolymerizable components may be included, as long as the present invention is not impaired.

[0073] From the viewpoint of the heat resistance of the resulting polymer powder during molding and the thermal properties of the molded product, ε-caprolactam, aminohexanoic acid, adipic acid and hexamethylenediamine are particularly preferred.

[0074] The copolymerizable component can be selected appropriately from elastomer components such as polyolefins and polyalkylene glycols that impart flexibility, rigid aromatic components that improve heat resistance and strength, etc. Also, a terminal modifier that adjusts the end groups so that the polymer powder can be reused in the powder bed fusion bonding method can be selected appropriately.

[0075] When the resulting polymer powder is subjected to molding, it is preferable to add a terminal modifier from the viewpoint of being able to suppress changes in molecular weight, and the terminal modifier is selected depending on the polyamide monomer. When dicarboxylic acids or diamines are used as polyamide monomers, it is preferable to add a monofunctional terminal modifier, such as monoamines such as hexylamine, octylamine, and aniline, or monocarboxylic acids such as acetic acid, hexanoic acid, lauric acid, stearic acid, and benzoic acid.

[0076] When amino acids or lactams are used as the polyamide monomer, bifunctional terminal modifiers can be used in addition to monofunctional terminal modifiers, such as diamines (hexamethylenediamine, phenylenediamine, etc.) and dicarboxylic acids (terephthalic acid, adipic acid, etc.).

[0077] When dicarboxylic acids or diamines are used as the polyamide monomer, or when amino acids or lactams are used as the polyamide monomer, the preferred terminal modifiers are monofunctional terminal modifiers such as acetic acid, hexanoic acid, lauric acid, stearic acid, and benzoic acid, from the viewpoint of not inhibiting the polymerization, enabling the production of high-molecular-weight polyamides, and suppressing the formation of agglomerates, and aromatic monocarboxylic acids such as benzoic acid are more preferred.

[0078] The amount of monofunctional and bifunctional terminal modifiers is preferably 0.001 mol% or more and 0.8 mol% or less relative to the total amount of polyamide monomer added. Adding more than 0.8 mol% of the agent fails to increase the molecular weight of the polyamide, reduces the difference between the melting point and the melting onset temperature, and makes it difficult to maintain the powder shape in non-laser-irradiated areas in large-scale modeling equipment prone to temperature variations, and to produce models with minimal warpage when the polymer powder is used for modeling. This is also undesirable because the polyamide does not form spherical particles but instead becomes agglomerated. Adding less than 0.001 mol% of the agent fails to reduce the amount of terminal groups, resulting in changes in molecular weight before and after modeling, which is undesirable. The upper limit of the amount of the terminal modifier is preferably 0.5 mol% or less, more preferably 0.2 mol% or less, relative to the total amount of polyamide monomer added. The lower limit of the amount of the terminal modifier is preferably 0.005 mol % or more, more preferably 0.01 mol % or more, based on the total amount of polyamide monomers added.

[0079] The polymer incompatible with polyamide obtained in the present method for producing polymer powder is a polymer that is compatible with polyamide monomer at the start of polymerization, but is incompatible with polyamide after polymerization.

[0080] More specifically, from the viewpoint of precipitating a polymer powder from a homogeneous solution, it is preferable that the resulting polyamide-incompatible polymer be non-reactive with the polyamide monomer. Specifically, it is preferable that the resulting polyamide-incompatible polymer does not have a polar group reactive with the carboxyl or amino groups that form the amide groups contained in the polyamide, or that it has a polar group that is low in reactivity with the carboxyl or amino group. Examples of polar groups reactive with the carboxyl or amino group include amino, carboxy, epoxy, and isocyanate groups. Examples of polar groups that are low in reactivity with the carboxyl or amino group include hydroxyl and sulfur groups, with hydroxyl groups being the most preferred. From the viewpoint of suppressing crosslinking reactions, it is preferable that the resulting polyamide-incompatible polymer contain four or fewer polar groups, more preferably three or fewer, and most preferably two or fewer.

[0081] Specific examples of such polymers incompatible with the resulting polyamide include polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polypentamethylene glycol, polyhexamethylene glycol, polyethylene glycol-polypropylene glycol copolymer, polyethylene glycol-polytetramethylene glycol copolymer, and alkyl ethers in which the hydroxyl groups at one or both ends are blocked with methyl, ethyl, propyl, isopropyl, butyl, hexyl, octyl, decyl, dodecyl, hexadecyl, octadecyl, or the like, or alkyl phenyl ethers in which the hydroxyl groups are blocked with octylphenyl or the like. In particular, polyethylene glycol, polyethylene glycol-polypropylene glycol copolymer, polypropylene glycol, polytetramethylene glycol, and alkyl ethers thereof are preferred because of their excellent compatibility with polyamide monomers. From the viewpoint of also having excellent compatibility with water used in the ring-opening polymerization by hydrolysis of polyamide monomers, polyethylene glycol, polyethylene glycol-polypropylene glycol copolymer, and alkyl ethers thereof are more preferred, and polyethylene glycol is most preferred. Two or more of these may be used simultaneously as long as the present invention is not impaired.

[0082] The preferred upper limit of the weight-average molecular weight of the resulting polyamide-incompatible polymer is 200,000. If the weight-average molecular weight is too high, it becomes difficult to remove the resulting polyamide-incompatible polymer, and fusion of the non-laser-irradiated powder is likely to occur. Therefore, the weight-average molecular weight is more preferably 100,000 or less, even more preferably 50,000 or less, and particularly preferably 30,000 or less. If the molecular weight is 1,000 or less, fusion of particles cannot be suppressed during the polymerization process, and a fine powder cannot be produced. Therefore, the weight-average molecular weight of the resulting polyamide-incompatible polymer is preferably 4,000 or more, more preferably 5,000 or more.

[0083] These polyamide monomers are mixed with a polymer that is incompatible with the resulting polyamide to obtain a homogeneous solution, and then polymerization is initiated at a temperature above the crystallization temperature of the polyamide obtained by polymerizing the polyamide monomers, but below its melting point, to produce polymer powder. During this process, as the polyamide monomers are converted into polyamide in the homogeneous mixed solution, the polymer powder is induced homogeneously without crystallization, resulting in the precipitation of spherical, solid, smooth-surfaced, and polyamide powder with a small particle size distribution index after polymerization.

[0084] To achieve a moderate polymerization rate and smooth particle formation due to the occurrence of phase separation induced by polymerization, while preventing the formation of large amounts of aggregates due to particle formation occurring early in the polymerization, the mass ratio of the polyamide monomer to the polymer incompatible with the resulting polyamide during polymerization is preferably in the range of 5 / 95 to 95 / 5. The lower limit of the mass ratio of polyamide monomer to the polymer incompatible with the resulting polyamide is more preferably 10 / 90, even more preferably 20 / 80, and most preferably 30 / 70. Meanwhile, the upper limit of the mass ratio of polyamide monomer to the polymer incompatible with the resulting polyamide is more preferably 90 / 10, even more preferably 80 / 20, and particularly preferably 70 / 30.

[0085] Known methods can be used to polymerize polyamide monomers into polyamides. While the method varies depending on the type of polyamide monomer, in the case of lactams, anionic ring-opening polymerization using alkali metals such as sodium or potassium or organometallic compounds such as butyllithium or butylmagnesium as initiators, cationic ring-opening polymerization using acids as initiators, and hydrolytic ring-opening polymerization using water are commonly used. Cationic ring-opening polymerization and hydrolytic ring-opening polymerization are preferred because they allow for polymerization at temperatures between 20°C above the crystallization temperature of the polyamide and below its melting point, which facilitates the production of spherical, smooth-surfaced polyamide powder. Hydrolytic ring-opening polymerization is more preferred in polymerizations at temperatures between 20°C above the crystallization temperature of the polyamide and below its melting point, as they suppress coloration of the polyamide due to the initiator and gelation and decomposition due to crosslinking reactions. While known methods can be used to hydrolyze lactams, a preferred method involves applying pressure in the presence of water to promote lactam hydrolysis and generate amino acids, followed by ring-opening polymerization and polycondensation while removing the water.

[0086] In this case, the presence of water prevents the polycondensation reaction, and polymerization begins as soon as the water is discharged out of the reaction vessel. Therefore, there is no particular limitation on the amount of water used as long as the hydrolysis of lactams proceeds. However, it is generally preferable to use 100 parts by mass or less of water, assuming that the total amount of polyamide monomers and the polymer incompatible with the resulting polyamide is 100 parts by mass. To improve the production efficiency of polymer powder, the amount of water used is more preferably 70 parts by mass or less, even more preferably 50 parts by mass or less, and particularly preferably 30 parts by mass or less. To prevent the hydrolysis of lactams from proceeding unsuccessfully, the lower limit of the amount of water used is preferably 1 part by mass or more, more preferably 2 parts by mass or more, even more preferably 5 parts by mass or more, and particularly preferably 10 parts by mass or more. Water (condensation water) produced by condensation during polycondensation can be removed by any known method, such as by flowing an inert gas such as nitrogen at normal pressure or by reducing pressure.

[0087] Furthermore, when the polyamide monomer is an amino acid, a dicarboxylic acid and a diamine, or a salt thereof, a polycondensation reaction can be used as the polymerization method. On the other hand, when these are polyamide monomers, there are combinations that are incompatible with the resulting polyamide and that are not homogeneously soluble. In such a case, adding water to the polyamide monomer and the resulting polyamide-incompatible polymer makes it possible to produce a polymer powder.

[0088] The amount of water used is preferably 5 to 200 parts by mass, assuming that the total amount of the amino acid or dicarboxylic acid, diamine, and the resulting polymer incompatible with the polyamide is 100 parts by mass. From the viewpoint of preventing particle size from becoming coarse, the amount of water used is more preferably 150 parts by mass or less, and even more preferably 120 parts by mass or less. On the other hand, from the viewpoint of ensuring that water functions as a solvent, the amount of water used is more preferably 5 parts by mass or more, and even more preferably 10 parts by mass or more.

[0089] Two or more lactams and amino acids and / or dicarboxylic acids or diamines may be used in combination, but in this case water functions as a hydrolyzer or a solvent.

[0090] The polymerization time can be adjusted appropriately depending on the molecular weight of the polyamide to be obtained, and is preferably in the range of 1.5 to 70 hours. From the viewpoint of increasing the melting onset temperature of the resulting polymer powder and reducing the difference between the melting point and the melting onset temperature, and from the viewpoint of decreasing the crystallization onset temperature and increasing the difference between the melting onset temperature and the crystallization onset temperature, it is preferable to extend the reaction time to achieve a high molecular weight. The lower limit of the polymerization time is more preferably 2.0 hours or more, even more preferably 2.5 hours or more, and particularly preferably 3.0 hours or more. To ensure that the polymerization proceeds to obtain a high molecular weight polyamide while preventing side reactions of the polyamide, such as three-dimensional crosslinked products, coloration, and deterioration of polymers incompatible with the resulting polyamide, the upper limit of the polymerization time is more preferably 50 hours or less, even more preferably 25 hours or less, and particularly preferably 10 hours or less.

[0091] A polymerization accelerator may be added as long as it does not impair the effects of the present invention. Known accelerators can be used, including 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. Two or more of these may be used. The amount of the accelerator added can be selected appropriately, but it is preferable to add 1 part by mass or less per 100 parts by mass of polyamide monomer.

[0092] Other additives may also be added, such as surfactants and dispersants for controlling the particle size of the polymer powder, antioxidants, heat stabilizers, weathering agents, lubricants, pigments, dyes, plasticizers, antistatic agents, flame retardants, and fillers such as carbon black, silica, titanium dioxide, glass fiber, glass beads, and carbon fiber, to modify the properties of the polymer powder or improve the stability of the polymer that is incompatible with the resulting polyamide. Two or more of these may be used. Furthermore, two or more different additives may be used, one for modifying the polyamide monomer or polyamide and the other for modifying the polymer that is incompatible with the resulting polyamide. The amount added may be selected appropriately.

[0093] In the present invention, since polymer powder is homogeneously induced from a homogeneous solution, fine powder can be produced without stirring. However, stirring may be performed to better control particle size and achieve a uniform particle size distribution. Known stirring devices, such as impellers, melt kneaders, and homogenizers, can be used. Examples of impellers include propellers, paddles, flat blades, turbine blades, cones, anchor blades, screws, and helical blades. The stirring speed depends on the polyamide monomer and molecular weight, but is preferably in the range of 0 to 2,000 rpm to ensure uniform heat transfer even in large equipment while preventing liquid adhesion to the wall, which can cause changes in the blending ratio. The lower limit of the stirring speed is more preferably 10 rpm or higher, even more preferably 30 rpm or higher, and particularly preferably 50 rpm or higher. The upper limit of the stirring speed is more preferably 1,600 rpm or lower, even more preferably 1,200 rpm or lower, and particularly preferably 800 rpm or lower.

[0094] To isolate the polymer powder from a mixture of polymer powder after polymerization and the resulting polyamide-immiscible polymer, the mixture at the end of polymerization can be discharged into a poor solvent for the polymer powder, or a poor solvent for the polymer powder can be added to a reaction vessel. To prevent the polymer powders from melting and coalescing, which would increase the particle size distribution index, the mixture is preferably cooled to below the melting point of the polymer powder, more preferably below the crystallization temperature, and then discharged into a poor solvent for the polymer powder. Alternatively, a poor solvent for the polymer powder can be added to a reaction vessel. The isolation method can be selected from known methods such as reduced pressure or pressure filtration, decantation, centrifugation, and spray drying.

[0095] The poor solvent for the polymer powder is preferably a solvent that does not dissolve the polymer, and further dissolves the polyamide monomer and a polymer that is incompatible with the resulting polyamide. Such a solvent can be appropriately selected, but examples include alcohols such as methanol, ethanol, and isopropanol, and water, with water being preferred from the viewpoint of preventing the generation of voids in the molded product due to the organic solvent.

[0096] The washing, isolation, and drying of the polymer powder can be carried out by known methods. Washing methods for removing deposits and inclusions from the polymer powder include reslurry washing, which may be heated as appropriate. The solvent used for washing is not limited as long as it does not dissolve the polymer powder but dissolves the polyamide monomer and polymers incompatible with the resulting polyamide, and water is preferred from an economical standpoint. Isolation can be carried out by vacuum or pressure filtration, decantation, centrifugation, spray drying, or other suitable method. By this washing and isolation, the polymer incompatible with the resulting polyamide is removed to less than 0.001% by mass of the polymer powder. Drying is preferably carried out below the melting point of the polymer powder, and may be carried out under reduced pressure. Air drying, hot air drying, heat drying, reduced-pressure drying, freeze drying, and other suitable methods are available.

[0097] The production of three-dimensional objects by the powder bed fusion method of the present invention refers to a method of producing powder bed fusion layer-by-layer objects by selective laser sintering, which sequentially repeats a thin layer formation process in which polymer powder is spread into a thin layer, and a cross-sectional formation process in which this thin layer is irradiated with laser light in a shape corresponding to the cross-sectional shape of the object to be shaped to bond the polymer powder, or a selective absorption (or suppression) sintering, which sequentially repeats a thin layer formation process in which polymer powder is spread into a thin layer, a printing process in which an energy absorption promoter or energy absorption suppressor is printed on this thin layer in a shape corresponding to the cross-sectional shape of the object to be shaped, and a cross-sectional forming process in which the polymer powder is bonded using electromagnetic radiation.

[0098] The electromagnetic radiation used in selective absorption (suppression) sintering can be any radiation that does not impair the quality of the polymer powder or the molded object, but infrared radiation is preferred because it is relatively inexpensive and provides energy suitable for molding. The electromagnetic radiation can be coherent or incoherent.

[0099] The energy absorption enhancer is a substance that absorbs electromagnetic radiation. Examples of such substances include carbon black, carbon fiber, copper hydroxyphosphate, near-infrared absorbing dyes, near-infrared absorbing pigments, metal nanoparticles, polythiophene, poly(p-phenylene sulfide), polyaniline, poly(pyrrole), polyacetylene, poly(p-phenylene vinylene), polyparaphenylene, poly(styrene sulfonate), poly(3,4-ethylenedioxythiophene)-poly(styrene phosphonate) p-diethylaminobenzaldehyde diphenylhydrazone, anti-9-isopropylcarbazole-3-, and conjugated polymers formed from combinations thereof. These substances may be used alone or in combination.

[0100] The energy absorption inhibitor is a substance that does not easily absorb electromagnetic radiation. Examples of such substances include substances that reflect particle electromagnetic radiation, such as titanium, heat-insulating powders, such as mica powder and ceramic powder, and water. These substances may be used alone or in combination.

[0101] These selective absorbents or selective inhibitors may be used alone or in combination.

[0102] The selective absorbent or selective inhibitor can be printed in a shape corresponding to the cross-sectional shape of the object to be shaped by known methods such as inkjet printing. In this case, the selective absorbent or selective inhibitor may be used as is, or may be dispersed or dissolved in a solvent.

[0103] The molding apparatus of the present invention is a manufacturing apparatus for manufacturing three-dimensional objects by powder bed fusion. The small molding apparatus is a machine for manufacturing objects with a work size of 0.01 m. 3 A large-scale modeling device is one with a work size of 0.01 m or less. Specifically, the RaFaElII 150-HT (manufactured by Aspect Corporation) can be mentioned. 3 Specifically, the above-mentioned molding apparatuses include RaFaElII 300-HT (manufactured by Aspect Inc.) and RaFaElII 550-HT (manufactured by Aspect Inc.). [Example]

[0104] The present invention will be described below based on examples, but the present invention is not limited to these examples. (1) Melting point, melting onset temperature, crystallization onset temperature, and crystallization temperature of polymer powder Using a differential scanning calorimeter (DSCQ20) manufactured by TA Instruments, 10 mg of polymer powder was heated from 30°C at a rate of 20°C / min in a nitrogen atmosphere, and the endothermic peak observed was observed. The temperature was then raised to a temperature 50°C higher than the endothermic peak top, held for 1 minute, and then cooled to 30°C at a rate of 20°C / min. From these, the melting point, melting onset temperature, crystallization onset temperature, and crystallization temperature were calculated.

[0105] The melting point was determined as the peak top temperature of the endothermic peak observed when the temperature was increased. The melting onset temperature was determined as the lowest temperature among the temperatures at which the first temperature derivative of Heat Flow (W / g) observed between the endothermic peak top and a temperature point of -50°C is -0.2 (W / g·°C). The crystallization onset temperature was determined as the highest temperature among the temperatures at which the first temperature derivative of Heat Flow (W / g) observed between the exothermic peak top and a temperature point of +50°C is -0.1 (W / g·°C). change The temperature was determined as the temperature at the top of the exothermic peak observed when the temperature was lowered.

[0106] (2) D50 particle size and particle distribution index D90 / D10 A dispersion of approximately 100 mg of polymer powder in approximately 5 mL of deionized water was added to a Nikkiso Co., Ltd. laser diffraction particle size distribution analyzer (Microtrac MT3300EXII) until a measurable concentration was reached. After ultrasonic dispersion for 60 seconds at 30 W, the particle size distribution measured over a 10-second period was determined as the particle size at which the cumulative frequency from the small particle size end of the particle size distribution reached 50%. The particle size distribution index, D90 / D10, was calculated by dividing the particle size (D90) at which the cumulative frequency from the small particle size end of the particle size distribution measured by the above method reached 90% by the particle size (D10) at which the cumulative frequency from the small particle size end reached 10%. The refractive index used during the measurement was 1.52, and the refractive index of the medium (deionized water) was 1.333.

[0107] (3) Weight-average molecular weight and number-average molecular weight of the polyamide that makes up the polymer powder The weight-average and number-average molecular weights of polyamides were calculated by gel permeation chromatography using a calibration curve based on polymethyl methacrylate. The measurement sample was prepared by dissolving approximately 3 mg of polymer powder in approximately 3 g of hexafluoroisopropanol. Equipment: Waters e-Alliance GPC system Column: Showa Denko HFIP-806M x 2 Mobile phase: 5mmol / L sodium trifluoroacetate / hexafluoroisopropanol Flow rate: 1.0ml / min Temperature: 30℃ Detection: Differential refractometer.

[0108] (4) The proportion of polyamides having a molecular weight of 3,000 or less in the polyamides constituting the polymer powder After measuring the molecular weight by the method (3) above, the molecular weight and slice height of each slice were calculated, and the ratio of the cumulative slice height and the cumulative slice height for slice molecular weights of 3,000 or less was taken as the proportion of polyamides with a molecular weight of 3,000 or less.

[0109]

number

[0110] (5) Quantitative determination of terminal carboxyl groups in polyamides 0.5 g of polymer powder was dissolved in 20 mL of benzyl alcohol and heated to 190°C for 2 hours. After confirming dissolution, a few drops of phenolphthalein indicator were added. The solution was titrated with 1 / 50N KOH ethanol solution, and the point at which the solution turned red was defined as the endpoint.

[0111]

number

[0112] In the above formula, COOH is the amount of terminal carboxyl groups in the polyamide, T is the titration volume (mL) of the 1 / 50N-KOH ethanol solution, B is the titration volume (mL) of the 1 / 50N-KOH ethanol solution required for the blank, f is the titer of the 1 / 50N-KOH ethanol solution, and W is the weight of the sample (g).

[0113] (6) Quantitative determination of terminal amino groups in polyamides 0.5 g of polymer powder was dissolved in 25 mL of PEA (phenol-ethanol solvent). After confirming dissolution, a few drops of thymol blue indicator were added. The solution was titrated with 1 / 50 N HCl aqueous solution, and the endpoint was the point at which the solution turned pale pink.

[0114]

number

[0115] In the above formula, NH2 is the amount of terminal amino groups in the polyamide, A is the titration volume (mL) of the 1 / 50N HCl aqueous solution, B is the titration volume (mL) of the 1 / 50N HCl aqueous solution required for the blank, f is the titer of the 1 / 50N HCl aqueous solution, and W is the weight of the sample (g).

[0116] (7) Sphericity of polymer powder The sphericity of the polymer powder is calculated from the average value of the ratio of the minor axis to the major axis of each particle by observing 30 particles randomly selected from a photograph taken with a scanning electron microscope (JEOL Ltd., Scanning Electron Microscope JSM-6301NF).

[0117]

number

[0118] In the above formula, S is sphericity, a is major axis, b is minor axis, and n is the number of measurements (30).

[0119] (8) Powder melting degree in non-laser irradiated areas when using large-scale modeling equipment After the molding was completed, 100 g of the powder remaining in the molding device was collected and crushed in a mortar and pestle, then passed through a 500 μm sieve, and the weight of the powder that remained on the sieve was calculated. The ratio of the weight W of the powder that remained on the sieve to 100 g of the charged powder was taken as the powder melting degree of the non-laser-irradiated area.

[0120]

number

[0121] The evaluation was carried out according to the following criteria. A: The weight of the sieved powder is 5 wt% or less. B: The weight of the powder on the sieve is more than 5 wt% and not more than 20 wt%. C: The weight of the powder on the sieve is more than 20 wt% and not more than 30 wt%. D: The weight of the powder on the sieve is greater than 30 wt% or the molded object is fused. A to C are pass marks, D is fail marks.

[0122] (9) Evaluation of the amount of warpage of objects obtained from large-scale modeling equipment The obtained test piece was placed on a horizontal surface with the convex part facing upward, and a taper gauge was inserted into the gap between the horizontal surface and the test piece to measure the height of the gap. The value converted into per 10 cm of test piece length was calculated as the amount of warpage, and the amount of warpage was evaluated according to the following criteria. AA: Warpage is 0.05mm / 10cm or less. A: The amount of warping is greater than 0.05mm / 10cm and less than 0.1mm / 10cm. B: The amount of warping is greater than 0.1mm / 10cm and less than 0.2mm / 10cm. C: The amount of warping is greater than 0.2mm / 10cm and less than 0.3mm / 10cm. D: The amount of warping is greater than 0.3 mm / 10 cm. AA to C are passing grades, D is failing grades.

[0123] (10) Evaluation of molecular weight change rate before and after molding The powder after shaping was measured using the method (3) to calculate the weight average molecular weight of the polyamide constituting the polymer powder after shaping (Mw. of the polyamide after shaping). The value obtained by dividing the weight average molecular weight Mw. of the polyamide after shaping by the weight average molecular weight of the polyamide constituting the polymer powder measured in (3) (Mw. of the polyamide before shaping) was used as the rate of change in molecular weight before and after shaping.

[0124]

number

[0125] The evaluation was carried out according to the following criteria. A: The rate of change in molecular weight before and after molding is 0.90 or more and less than 1.40. B: The rate of change in molecular weight before and after molding is 1.40 or more and less than 1.50, or 0.85 or more and less than 0.90. C: The rate of change in molecular weight before and after molding is 1.50 or more and less than 1.60, or 0.80 or more and less than 0.85. D: The rate of change in molecular weight before and after molding is 1.60 or more or less than 0.80. A, B, C are pass, D is fail.

[0126] [Example 1] A 3-L autoclave was charged with 360 g of ε-caprolactam (special grade reagent, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) as a polyamide monomer, 240 g of polyethylene glycol (grade 1 polyethylene glycol 6,000, molecular weight 7,700, manufactured by Wako Pure Chemical Industries, Ltd.) as a polymer incompatible with the resulting polyamide (2.5 g of antioxidant (BASF "IRGANOX" (registered trademark) 1098), and 50 g of deionized water. After sealing, the autoclave was pressurized with nitrogen to 1 MPa and then released to 0.1 MPa three times. After replacing the inside of the vessel with nitrogen, the pressure was adjusted to 0.1 MPa and the vessel was sealed. The stirring speed was then set to 60 rpm and the temperature was raised to 230 °C. The pressure inside the system was 1.4 MPa, and stirring was continued at 60 rpm for 3 hours while maintaining the pressure and temperature. Next, the pressure was released at a rate of 0.02 MPa / min to set the internal pressure to 0 MPa. The polymerization temperature was then raised to 210°C, and nitrogen was circulated at a rate of 5 L / min for 1.5 hours. Finally, the mixture was poured into a 2000 g water bath to obtain a slurry. The slurry was thoroughly homogenized by stirring and then filtered. 2000 g of water was added to the filter cake, followed by washing at 80°C. The slurry was then passed through a 100 μm sieve to remove any aggregates. The filtered cake was then filtered again and the isolated cake was dried at 80°C for 12 hours to obtain 313 g of polymer powder (87% yield). The resulting polymer powder had a melting point of 217°C, a melting onset temperature of 189°C, a crystallization onset temperature of 186°C, and a crystallization temperature of 171°C. The D50 particle size was 55 μm, and the D90 / D10 ratio was 2.3. The weight-average molecular weight was 46,000, the proportion of polyamides with molecular weights of 3,000 or less was 0.3 wt%, and the weight-average molecular weight / number-average molecular weight ratio was 1.7. The amount of terminal carboxyl groups in polyamide is 7.8 x 10 -5 mol / g, the amount of terminal amino groups is 8.5×10 -5 The ratio of the amount of terminal carboxyl groups to the amount of terminal amino groups of the polyamide was 0.92 mol / g. The sphericity was 95. The properties of the polymer powder are shown in Table 1.

[0127] Next, the synthesis of the polymer powder was repeated, and 5 kg of the resulting polymer powder was used to fabricate an 80 mm x 10 mm x 4 mm test piece using a powder bed fusion system (RaFaElII 300-HT) manufactured by Aspect Corporation for 12 hours. The setup conditions were a 60W CO2 laser, a stacking height of 0.1 mm, a laser scanning interval of 0.1 mm, a laser scanning speed of 10 m / s, and a laser power of 16 W. The temperature settings were a supply tank temperature of -5°C below the crystallization temperature, and a part bed temperature of -15°C below the melting point. The powder melting rate in the non-laser-irradiated areas when using the large-scale modeling system was evaluated and found to be 25 wt%, with a rating of C. The warpage of the resulting model was evaluated and found to be 0.21 mm / 10 cm, with a rating of C. The rate of change in molecular weight before and after modeling was evaluated and found to be 69,000 Mw after modeling, with a rating of C. The modeling properties of the polymer powder are shown in Table 2.

[0128] [Example 2] A polymer powder was obtained in the same manner as in Example 1, except that the polymerization time was changed to 2 hours. Subsequently, 0.1 parts by mass of trimethylsilylated amorphous silica (X-24-9500 manufactured by Shin-Etsu Chemical Co., Ltd.) with an average particle size of 170 nm was added as a flow aid per 100 parts by mass of polyamide, followed by dry blending. The properties of the obtained polymer powder are shown in Table 1, and the moldability is shown in Table 2.

[0129] [Example 3] A polymer powder was obtained in the same manner as in Example 2, except that the polymerization time was changed to 3 hours. The properties of the obtained polymer powder are shown in Table 1, and the moldability is shown in Table 2.

[0130] [Example 4] A polymer powder was obtained in the same manner as in Example 2, except that the polymerization time was changed to 4 hours. The properties of the obtained polymer powder are shown in Table 1, and the moldability is shown in Table 2.

[0131] [Example 5] A polymer powder was obtained in the same manner as in Example 3, except that 3.11 g of benzoic acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added as a monofunctional terminal modifier. The properties of the obtained polymer powder are shown in Table 1, and the moldability is shown in Table 2.

[0132] [Example 6] A polymer powder was obtained in the same manner as in Example 3, except that 1.95 g of benzoic acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added as a monofunctional terminal modifier. The properties of the obtained polymer powder are shown in Table 1, and the moldability is shown in Table 2.

[0133] [Example 7] A polymer powder was obtained in the same manner as in Example 3, except that 2.37 g of aniline (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added as a monofunctional terminal modifier. The properties of the obtained polymer powder are shown in Table 1, and the moldability is shown in Table 2.

[0134] [Example 8] A polymer powder was obtained in the same manner as in Example 3, except that 0.3 parts by mass of trimethylsilylated amorphous silica (X-24-9500 manufactured by Shin-Etsu Chemical Co., Ltd.) having an average particle size of 170 nm was added as a flow aid relative to 100 parts by mass of polyamide, and 67 parts by mass of glass beads GB731A (manufactured by Potters Ballotini, average major axis diameter 27 μm, average minor axis diameter 26 μm) were dry-blended as an inorganic reinforcing agent relative to 100 parts by mass of polyamide. The properties of the obtained polymer powder are shown in Table 1, and the moldability is shown in Table 2.

[0135] [Example 9] A polymer powder was obtained in the same manner as in Example 8, except that 43 parts by mass of glass beads GB301S (manufactured by Potters Ballotini, average major axis diameter 41 μm, average minor axis diameter 40 μm) were added as the inorganic reinforcing agent instead of glass beads GB731A and dry blended. The properties of the obtained polymer powder are shown in Table 1, and the moldability is shown in Table 2.

[0136] [Example 10] A polymer powder was obtained in the same manner as in Example 8, except that 43 parts by mass of glass fiber EPG40M-10A (manufactured by Nippon Electric Glass Co., Ltd., average major axis diameter 43 μm, average minor axis diameter 10 μm) was added as the inorganic reinforcing agent instead of glass beads GB731A and dry blended. The properties of the obtained polymer powder are shown in Table 1, and the moldability is shown in Table 2.

[0137] [Example 11] A polymer powder was obtained in the same manner as in Example 8, except that 43 parts by mass of glass fiber EPG70M-01N (manufactured by Nippon Electric Glass Co., Ltd., average major axis diameter 73 μm, average minor axis diameter 10 μm) was added as the inorganic reinforcing agent instead of glass beads GB731A and dry blended. The properties of the obtained polymer powder are shown in Table 1, and the moldability is shown in Table 2.

[0138] [Example 12] A polymer powder was obtained in the same manner as in Example 4, except that ε-caprolactam was replaced with 201 g of adipic acid (manufactured by Tokyo Chemical Industry Co., Ltd.) and 318 g of a 50% aqueous solution of hexamethylenediamine (manufactured by Tokyo Chemical Industry Co., Ltd.) as the polyamide monomer, and the polymerization temperature was changed to 240° C. The properties of the obtained polymer powder are shown in Table 1, and the moldability is shown in Table 2.

[0139] [Example 13] A polymer powder was obtained in the same manner as in Example 4, except that the polyamide monomers for the polyamide were changed to 306 g of ε-caprolactam, 30 g of adipic acid, and 48 g of a 50% aqueous solution of hexamethylenediamine (manufactured by Tokyo Chemical Industry Co., Ltd.). The properties of the obtained polymer powder are shown in Table 1, and the moldability is shown in Table 2.

[0140] [Example 14] A 3L autoclave was charged with 300g of the polymer powder obtained in Example 3 and sealed. The process of pressurizing the vessel with nitrogen to 1 MPa and then releasing the pressure to 0.1 MPa was repeated three times. The atmosphere inside the vessel was then purged with nitrogen, after which the pressure was adjusted to 0.1 MPa and the vessel was sealed. The stirring speed was then set to 60 rpm, the temperature was raised to 250°C, and the mixture was stirred at 60 rpm for 3 hours before being discharged. The discharged polyamide 6 was pulverized for 120 minutes using a jet mill (Hosokawa Micron 100AFG) to obtain a polymer powder with a D50 particle size of 52μm. The properties of the obtained polymer powder are shown in Table 1, and the moldability is shown in Table 2.

[0141] [Comparative Example 1] Except for changing the polymerization time to 1 hour, a polymer powder was obtained in the same manner as in Example 1. The properties of the obtained polymer powder are shown in Table 1, and the moldability is shown in Table 2.

[0142] Comparative Example 2 A polymer powder was obtained in the same manner as in Example 3, except that 5.44 g of benzoic acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added as a monofunctional terminal modifier. A large amount of lumps were generated during this process. The properties of the obtained polymer powder are shown in Table 1, and the moldability is shown in Table 2.

[0143] Comparative Example 3 Polyamide 6 (BASF "Ultramid" (registered trademark) B27) was pulverized for 120 minutes using a jet mill (Hosokawa Micron 100AFG) to obtain a polymer powder with a D50 particle size of 55 μm. The properties of the obtained polymer powder are shown in Table 1, and the moldability is shown in Table 2.

[0144] Comparative Example 4 25 g of polyamide 6 (BASF "Ultramid" (registered trademark) B27) was dissolved in 250 g of 42.5 wt % ε-caprolactam (Fujifilm Wako Pure Chemical Industries, Ltd. special grade reagent) aqueous solution, and the solution was allowed to precipitate, yielding a polymer powder. The properties of the obtained polymer powder are shown in Table 1, and the moldability is shown in Table 2.

[0145] [Table 1]

[0146] Table 2

Claims

1. A polymer powder composed of polyamide obtained by polymerization of polyamide monomers, wherein the polyamide monomer is at least one selected from aminohexanoic acid, 9-aminopelargonic acid, 11-aminoundecanoic acid, and ε-caprolactam, or at least one selected from oxalic acid, succinic acid, adipic acid, 1,4-cyclohexanedicarboxylic acid, and 1,3-cyclohexanedicarboxylic acid, as well as ethylenediamine, trimethylenediamine, tetramethylenediamine, 1. A polymer powder for producing a three-dimensionally shaped object by powder bed fusion, comprising a mixture of at least one selected from pentamethylenediamine, hexamethylenediamine, 1,4-cyclohexanediamine, and 1,3-cyclohexanediamine, or a salt thereof, the mixture having a melting point of 190°C or higher as measured by differential scanning calorimetry, wherein the difference between the melting point and the melting onset temperature, which is the lowest temperature at which the first temperature derivative of Heat Flow (W / g) between the endothermic peak top temperature and a temperature point below -50°C becomes -0.2 (W / g °C), is less than 30°C, and the D50 particle size is 1 μm or more and 100 μm or less.

2. 2. The polymer powder according to claim 1, wherein the amount of polyamide having a molecular weight of 3,000 or less is 0.4 wt % or less of the total amount of polyamide.

3. 3. The polymer powder according to claim 1, wherein the weight average molecular weight is 40,000 or more.

4. 4. The polymer powder according to claim 1, wherein the weight average molecular weight / number average molecular weight is 1.8 or less.

5. 5. The polymer powder according to claim 1, wherein the ratio of the amount of terminal carboxyl groups to the amount of terminal amino groups in the polyamide is 0.001 or more and 0.8 or less.

6. 6. The polymer powder according to claim 1, wherein the particle size distribution D90 / D10 is less than 3.

0.

7. The polymer powder according to any one of claims 1 to 6, having a sphericity of 80 or more.

8. The polymer powder according to any one of claims 1 to 7, wherein the polyamide comprises at least one of polyamide 6, polyamide 66, or a copolymer thereof.

9. The polymer powder according to any one of claims 1 to 8, comprising a flow aid in an amount of 0.01 parts by mass or more and 5 parts by mass or less per 100 parts by mass of the polyamide.

10. The polymer powder according to any one of claims 1 to 9, comprising an inorganic reinforcing material in an amount of 10 parts by mass or more and 200 parts by mass or less per 100 parts by mass of the polyamide.

11. A method for producing a polymer powder comprising a polyamide by polymerizing a polyamide monomer in the presence of a polymer incompatible with the resulting polyamide, wherein the polyamide monomer is at least one selected from aminohexanoic acid, 9-aminopelargonic acid, 11-aminoundecanoic acid, and ε-caprolactam, or at least one selected from oxalic acid, succinic acid, adipic acid, 1,4-cyclohexanedicarboxylic acid, and 1,3-cyclohexanedicarboxylic acid, as well as ethylenediamine, trimethylenediamine, tetramethylenediamine, pentamethylenediamine, hexamethane, 9. A method for producing a polymer powder according to claim 1, wherein the polyamide is a mixture of at least one selected from ethylenediamine, 1,4-cyclohexanediamine, and 1,3-cyclohexanediamine, or a salt thereof, and the polyamide monomer and the polymer are uniformly dissolved at the start of polymerization. The method is characterized in that the polymerization is carried out at a temperature between the crystallization temperature of the resulting polyamide plus 20°C and the melting point of the resulting polyamide until the difference between the melting point of the resulting polyamide in differential scanning calorimetry and the melting initiation temperature, which is the lowest temperature at which the first temperature derivative of Heat Flow (W / g) between the endothermic peak top temperature and a temperature point below -50°C from the endothermic peak top becomes less than 30°C.

12. The method for producing a polymer powder according to claim 11, wherein the terminal modifier is added in an amount of 0.001 mol % or more and 0.8 mol % or less at the start of polymerization.

13. A method for producing a three-dimensional object by powder bed fusion using the polymer powder according to any one of claims 1 to 10.

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