Method for producing three-dimensional molded article and three-dimensional molded article

Abstract

Provided is a method for producing a three-dimensional molded article by sequentially performing (a) a step for producing a three-dimensional molded article by a powder bed fusion method by using a powder composition containing a resin powder composed of a thermoplastic resin having a melting point of 200°C or more and (b) a step for impregnating the three-dimensional molded article obtained in step (a) with a thermosetting monomer mixture and curing the mixture. A three-dimensional molded article having good airtightness and reliability can be obtained without the occurrence of leakage even under a high-temperature environment. Furthermore, a three-dimensional molded article having good airtightness can be obtained while maintaining the heat resistance and mechanical properties of the material itself.

Description

Method for manufacturing a three-dimensional object, and three-dimensional object

[0001] The present invention relates to a method for manufacturing a three-dimensional object (hereinafter sometimes referred to as a shaped object), and a three-dimensional object obtained thereby.

[0002] Three-dimensional shaping enables designs with a high degree of freedom in shape, and thus has been widely applied in applications such as automobiles, aerospace, industry, and medicine. As such a shaping method, the powder bed fusion bonding method is suitable in terms of achieving precision shaping and mechanical strength and the fact that no support member is required. The shaping process of the powder bed fusion bonding method is a method of manufacturing by sequentially repeating a thin layer forming process of spreading resin powder in a thin layer and a cross-sectional shape forming process of irradiating the formed thin layer with laser light in a shape corresponding to the cross-sectional shape of the object to be shaped to bond the powder.

[0003] The three-dimensional object obtained by the above method makes use of its good mechanical properties and dimensional accuracy, and is being considered for use in various fields such as mobility applications such as automobiles, aviation, and space, medical applications such as prosthetics, orthotics, hearing aids, and catheters, sports applications, and electrical and electronic materials. In these applications, it is very important for the three-dimensional object to have certain performance, that is, the stability of quality and reliability.

[0004] On the other hand, in the powder bed fusion bonding method, since the object is shaped by melting and sintering under normal pressure from a state filled with powder, it is generally known that it is accompanied by a density change due to shrinkage, and pores remain inside the shaped object during the process. In Patent Document 1, it is disclosed that by controlling the filling state of the powder composition, a shaped object having excellent mechanical properties and reliability can be obtained even in a shaped object having appropriate pores inside. Further, Patent Document 2 discloses a method of injecting a low-melting-point polymer into the shaped object to protect the shaped object and perform quality finishing. [[ID= fourteen]]

[0005] [ Japanese Patent Application Laid-Open No. 2023-014051 Japanese Patent Application Laid-Open No. 2019-130916

[0006] However, Patent Document 1 had the problem that voids remained in the molded object, so when the film thickness was thin, leakage would occur probabilistically in applications such as piping. Patent Document 2 had the problem that it could not be used at high temperatures because the voids were sealed with a low-melting-point polymer.

[0007] The present invention aims to provide a three-dimensionally fabricated object that exhibits good airtightness and reliability, and does not leak even in high-temperature environments. In particular, it aims to provide a three-dimensionally fabricated object that maintains the heat resistance and mechanical properties of the material itself while exhibiting good airtightness.

[0008] To solve the above-mentioned problems and achieve the objective, the present invention has the following configuration: [1] A method for manufacturing a three-dimensional molded object, comprising the following steps (a) and (b) in sequence: (a) A step of manufacturing a three-dimensional molded object by a powder bed fusion method using a powder composition containing resin particles made of a thermoplastic resin with a melting point of 200°C or higher; (b) A step of impregnating the three-dimensional molded object obtained in step (a) with a thermosetting monomer mixture and curing it; [2] The method for manufacturing a three-dimensional molded object according to [1], wherein the water absorption rate of the thermoplastic resin is 1% or less; [3] The method for manufacturing a three-dimensional molded object according to [1] or [2], wherein step (b) is performed sequentially with the following steps (b-1), (b-2), and (b-3): (b-1) A step of reducing the pressure of a container containing a three-dimensional molded object to 10 kPa or less, then introducing a thermosetting monomer mixture into the container to impregnate the three-dimensional molded object with the thermosetting monomer mixture; (b-2) A step of washing the three-dimensional molded object impregnated with a thermosetting monomer mixture and washing away the thermosetting resin adhering to the surface. (b-3) A step of immersing the three-dimensional molded object impregnated with a thermosetting monomer mixture in a liquid at a temperature above the curing temperature of the thermosetting monomer, and curing the impregnated thermosetting monomer. [4] A method for producing a three-dimensional molded object according to any one of [1] to [3], wherein in step (b), the viscosity of the thermosetting monomer mixture at 25°C is 1 mPa·s or more and 50 mPa·s or less. [5] A method for producing a three-dimensional molded object according to any one of [1] to [4], wherein the thermoplastic resin is a polyarylene sulfide resin. [6] A method for producing a three-dimensional molded object according to any one of [1] to [5], wherein the powder composition contains 20% by mass or more and 60% by mass or less of an inorganic reinforcing material. [7] A method for producing a three-dimensional molded object according to any one of [1] to [6], wherein the thermosetting monomer mixture contains an acrylic monomer. [8] A three-dimensional molded object obtained by a powder bed fusion method using a powder composition containing resin particles made of a thermoplastic resin with a melting point of 200°C or higher, characterized in that the pressure drop per hour when the internal pressure is pressurized to 500 kPa is 3 kPa / mm or less per unit thickness at the minimum thickness of the structural part. [9] The three-dimensional molded object according to [8], wherein the water absorption rate is 1% or less.

[10] A three-dimensional molded object according to [8] or [9], wherein the three-dimensional molded object comprises a thermosetting resin.

[11] A three-dimensional molded object according to any one of [8] to

[10] , wherein a three-dimensional molded object obtained by a powder bed fusion method using a powder composition containing a polyarylene sulfide resin is impregnated with a thermosetting monomer mixture and cured.

[12] A three-dimensional molded object according to any one of [8] to

[11] , wherein the powder composition comprises 20% by mass or more and 60% by mass or less of an inorganic reinforcing material.

[0009] According to the present invention, it is possible to obtain a three-dimensionally fabricated object that has good airtightness and reliability and does not leak even in high-temperature environments. Furthermore, it is possible to obtain a three-dimensionally fabricated object that has good airtightness while maintaining the heat resistance and mechanical properties of the material itself.

[0010] As a means of obtaining three-dimensional molded objects with good airtightness and reliability, the method of injecting the low-melting-point polymer described above is known. However, when high heat resistance is required for mobility applications or electrical and electronic materials applications, even if the resin forming the molded object has excellent heat resistance, it is difficult to maintain airtightness in high-temperature environments if the material sealing the voids has a low melting point. In response to this, the inventors of the present invention devised a method of forming a three-dimensional molded object with a high-heat-resistant thermoplastic resin, then impregnating it with a thermosetting monomer mixture and curing it, and found that a three-dimensional molded object with good airtightness can be obtained while maintaining the heat resistance and mechanical properties of the material itself, leading to the present invention. Furthermore, because the thermoplastic resin forming the three-dimensional molded object has a high heat resistance with a melting point of 200°C or higher, the thermoplastic resin does not deform or deteriorate even in the process of impregnating the three-dimensional molded object with a thermosetting monomer mixture and curing it, making it possible to obtain a three-dimensional molded object that achieves both mechanical properties and airtightness for the first time, leading to the present invention.

[0011] The method for manufacturing a three-dimensional object according to the present invention will be described in detail below. The present invention is characterized by sequentially performing the following steps: (a) manufacturing a three-dimensional object using a powder composition containing resin powder made of thermoplastic resin, and (b) impregnating the obtained three-dimensional object with a thermosetting monomer mixture and curing it.

[0012] The melting point of the thermoplastic resin constituting the resin powder of the present invention is 200°C or higher. A higher melting point provides superior heat resistance of the three-dimensional molded object, and furthermore, in order to prevent the thermoplastic resin from deforming or degrading when curing the thermosetting monomer mixture in step (b), a melting point of 210°C or higher is preferable, more preferably 220°C or higher, even more preferably 230°C or higher, and particularly preferable 250°C or higher. The upper limit is preferably 340°C or lower, more preferably 320°C or lower, even more preferably 310°C or lower, and particularly preferable 300°C or lower, in order to ensure that the equipment has high heat resistance and high power in step (a) for manufacturing the three-dimensional molded object.

[0013] Here, the melting point of the thermoplastic resin of the present invention was defined as the peak temperature of the endothermic peak during melting when a sample obtained by cutting the end of a three-dimensional molded object was heated in a nitrogen atmosphere using a differential scanning calorimeter from 50°C to a temperature 50°C higher than the endothermic peak indicating the melting point of the resin, at a rate of 20°C / min.

[0014] The thermoplastic resin constituting the resin powder of the present invention preferably has a water absorption rate of 1% or less in order to reduce the water absorption rate of the resulting molded object. A lower water absorption rate of the thermoplastic resin results in less change in the mechanical properties of the resulting three-dimensional molded object due to moisture absorption, and furthermore, even when the thermosetting monomer mixture is immersed in hot water to cure in step (b), the resin does not deform or deteriorate. For these reasons, a water absorption rate of 0.5% or less is more preferable, 0.3% or less is even more preferable, 0.2% or less is particularly preferable, and 0.1% or less is significantly preferable. The lower limit is preferably 0%, meaning no water absorption is preferable.

[0015] Here, the water absorption rate of the thermoplastic resin of the present invention is expressed as a percentage obtained by immersing the thermoplastic resin in water at 23°C for 24 hours, in accordance with JIS K7209 (2000), and dividing the weight difference of the thermoplastic resin before and after treatment by the weight of the thermoplastic resin before treatment.

[0016] The thermoplastic resin of the present invention is not limited as long as it has a melting point of 200°C or higher, and includes polyester, polyamide, polyarylene sulfide, polyetheretherketone, polyetherketoneketone, polyetherimide, polyamideimide, polyethersulfone, polytetrafluoroethylene, or mixtures thereof. Among these, polyarylene sulfide resin is preferred because it has excellent heat resistance and low water absorption.

[0017] The D50 particle diameter of the powder composition of the present invention is preferably in the range of 1 to 100 μm. A more preferable lower limit for the D50 particle diameter is 3 μm, even more preferably 5 μm, particularly preferably 8 μm, significantly preferably 10 μm, and most preferably 15 μm. A more preferable upper limit for the D50 particle diameter is 90 μm, even more preferably 85 μm, particularly preferably 80 μm, significantly preferably 75 μm, and most preferably 70 μm. If the D50 particle diameter exceeds 100 μm, uniformity is lost during powder bed fusion bonding, and the strength of the three-dimensional object is reduced. On the other hand, if the D50 particle diameter is less than 1 μm, particle aggregation occurs due to static electricity, similarly impairing uniformity during powder bed fusion and reducing the strength of the three-dimensional object.

[0018] The D50 particle size of the powder composition is the particle size (D50 particle size) at which the cumulative frequency from the smallest particle size side of the particle size distribution measured by a laser diffraction particle size distribution analyzer reaches 50%. If the powder composition contains components such as inorganic reinforcing materials and flow aids described later, the particle size measured in the state in which these components are included shall be considered the particle size of the powder composition.

[0019] The powder composition of the present invention may contain additives such as inorganic reinforcing materials, to the extent that it does not impair the present invention. The amount of inorganic reinforcing material is preferably 20% by mass or more and 60% by mass or less. Examples of such inorganic reinforcing materials include glass-based fillers such as glass fibers, glass beads, glass flakes, and foamed glass beads; clays such as nepheline syenite fine powder, calcined clay such as montmorillonite and bentonite, and silane-modified clay (aluminum silicate powder); silica-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 such as fused silica, crystalline silica, and amorphous silica (silicon dioxide); alumina (aluminum oxide); and alumina colloids. Examples of inorganic reinforcing materials include alumina (alumina sol), alumina white, light calcium carbonate, heavy calcium carbonate, finely powdered calcium carbonate, special calcium carbonate-based fillers, fly ash spheres, volcanic glass hollow bodies, synthetic inorganic hollow bodies, single-crystal potassium titanate, potassium titanate fibers, carbon fibers, carbon nanotubes, carbon hollow spheres, fullerenes, anthracite powder, cellulose nanofibers, artificial cryolite, titanium dioxide, 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, with glass-based fillers being even more preferred due to their narrow particle size distribution and fiber size distribution. Examples of glass-based fillers include glass fibers, glass beads, glass flakes, and foamed glass beads. These inorganic reinforcing materials can be used individually or in combination of two or more types.

[0020] Within the limits of not impairing the effects of the present invention, the powder composition preferably contains a flow aid in order to improve fluidity. A flow aid refers to a substance that suppresses the aggregation of powder due to the adhesive force between powder particles. By including such a flow aid, the fluidity of the powder composition can be improved, which tends to reduce defects that cause a decrease in mechanical properties and to further improve the appearance of the resulting molded object.

[0021] Examples of such fluidizing agents 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-based fillers; titanium dioxide, magnesium oxide, basic magnesium carbonate, potassium titanate fibers, boron fibers, silicon carbide fibers, and carbon black. More preferably, silica, alumina, calcium carbonate powder, titanium dioxide, and carbon black are used. Particularly preferred is silica, as it is hard and can contribute to improving strength and fluidity, and among these, amorphous silica particles, which have low toxicity to the human body, are industrially extremely preferred.

[0022] The D50 particle size of the fluidizing agent is preferably between 20 nm and 3000 nm. The upper limit of the D50 particle size of the fluidizing agent is more preferably 2000 nm, even more preferably 1000 nm, particularly preferably 500 nm, significantly preferably 300 nm, and most preferably 200 nm. The lower limit is more preferably 30 nm, even more preferably 50 nm, particularly preferably 100 nm, significantly preferably 120 nm, and most preferably 140 nm. When the D50 particle size of the fluidizing agent is within the above range, it tends to improve the fluidity of the powder composition and allow the fluidizing agent to be uniformly dispersed in the powder composition.

[0023] The amount of the fluidizing agent added is preferably 0.01% by mass or more and 2.0% by mass or less, relative to the total weight of the powder composition. The upper limit of the amount added is more preferably 1.5% by mass or less, even more preferably 1.0% by mass or less, particularly preferably 0.8% by mass or less, and significantly preferably 0.7% by mass or less. The lower limit of the amount added is more preferably 0.02% by mass or more, even more preferably 0.03% by mass or more, and particularly preferably 0.04% by mass or more. If the amount of the fluidizing agent added is above the lower limit, the fluidity of the powder composition is further improved, and the filling ability when forming the object is increased, so that voids that result in defects in mechanical properties are less likely to occur, and the resulting object tends to exhibit high strength. If the amount of the fluidizing agent added is below the upper limit, sintering is not inhibited by the fluidizing agent coating the surface of the thermoplastic resin particles, and the resulting object tends to have high strength.

[0024] Furthermore, the powder composition in the present invention may include powder that has been recycled from the powder composition that remained after the three-dimensional molding process without becoming a molded object. In the powder bed fusion method, it is preferable to reuse residual powder in the recycled molding process to reduce waste powder, and it is preferable that the recycled powder accounts for 30% to 100% by weight of the total weight of the powder composition, and more preferably 50% to 90% by weight.

[0025] The method for creating three-dimensional objects according to the present invention is a powder bed fusion method. This powder bed fusion method is a 3D printing method that obtains a three-dimensional object by repeatedly forming a layer of resin particles, selectively melting and welding the position corresponding to the cross-section of the desired object using a heat source, and then forming another layer of thermoplastic resin particles on top of it.

[0026] Methods for selective melting and sintering include, for example, selective laser sintering, which involves irradiating a laser into a shape corresponding to the cross-sectional shape of the object to be fabricated, thereby bonding the powder composition. Another example is selective absorption (or suppression) sintering, which involves a printing process in which an energy absorption enhancer or energy absorption inhibitor is printed into a shape corresponding to the cross-sectional shape of the object to be fabricated, and then bonding the resin powder using electromagnetic radiation.

[0027] The laser light used in selective laser sintering is not particularly limited as long as it does not impair the quality of the powder composition or the fabricated object. Examples include carbon dioxide lasers, YAG lasers, Yb fiber lasers, excimer lasers, He-Cd lasers, and semiconductor-pumped solid-state lasers. Among these, carbon dioxide lasers are preferred because they are easy to operate and control.

[0028] Furthermore, any electromagnetic radiation can be used in selective absorption (suppression) sintering as long as it does not impair the quality of the powder composition or the fabricated object, but infrared radiation is preferred because it is relatively inexpensive and provides energy suitable for fabrication. Also, the electromagnetic radiation may or may not be coherent.

[0029] Energy absorption enhancers are substances that absorb electromagnetic radiation. Examples of such substances include carbon black, carbon fibers, 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, or conjugated polymers consisting of combinations thereof. These may be used individually or in combination.

[0030] Energy absorption inhibitors are substances that do not readily absorb electromagnetic radiation. Examples of such substances include materials that reflect electromagnetic radiation, such as titanium, heat-insulating powders such as mica powder and ceramic powder, and water. These can be used individually or in combination.

[0031] These selective absorbers or selective inhibitors may be used individually or in combination.

[0032] In the process of printing a selective absorber or selective inhibitor in a shape corresponding to the cross-sectional shape of the object to be fabricated, known methods such as inkjet printing can be used. In this case, the selective absorber or selective inhibitor may be used as is, or it may be dispersed or dissolved in a solvent before use.

[0033] The thermosetting monomer of the present invention is not particularly limited as long as it can be impregnated into a three-dimensional molded object and hardened by heating. Examples of such thermosetting monomers include acrylic monomers, epoxy monomers, silicone monomers, urethane monomers, and cyanate monomers, but acrylic monomers are preferred due to their low viscosity and excellent impregnation properties.

[0034] The viscosity of the thermosetting monomer mixture of the present invention at 25°C is preferably 1 mPa·s or more and 50 mPa·s or less. The upper limit is more preferably 30 mPa·s or less, even more preferably 20 mPa·s or less, particularly preferably 15 mPa·s or less, and significantly preferably 12 mPa·s or less, as a lower viscosity makes it easier for the thermosetting monomer to impregnate the fine pores present in the three-dimensional molded object. The lower limit is more preferably 2 mPa·s or more, even more preferably 3 mPa·s or more, particularly preferably 4 mPa·s or more, and significantly preferably 5 mPa·s or more, as if the viscosity is too low, the thermosetting monomer will not settle in the three-dimensional molded object and it will be difficult to improve airtightness.

[0035] In the present invention, it is preferable that the step of impregnating the obtained three-dimensional molded object with a thermosetting monomer mixture and curing it is carried out sequentially using the following steps (b-1), (b-2), and (b-3).

[0036] (b-1) A step of reducing the pressure of the container containing the three-dimensional object to 10 kPa or less, then introducing a thermosetting monomer mixture into the container to impregnate the three-dimensional object with the thermosetting monomer mixture.

[0037] (b-2) A step of washing a three-dimensional molded object impregnated with a thermosetting monomer mixture and washing away the thermosetting resin adhering to the surface.

[0038] (b-3) A step of immersing a three-dimensional molded object impregnated with a thermosetting monomer mixture in a liquid at a temperature above the curing temperature of the thermosetting monomer, thereby curing the impregnated thermosetting monomer.

[0039] In step (b-1) of the present invention, it is preferable to reduce the pressure of the container containing the three-dimensional object to 10 kPa or less. The lower this pressure, the easier it is to create a vacuum in the voids present in the three-dimensional object, making it easier to impregnate with thermosetting monomers. Therefore, 7 kPa or less is more preferable, 5 kPa or less is even more preferable, and 3 kPa or less is particularly preferable.

[0040] In step (b-1) of the present invention, it is preferable to further pressurize the mixture after introducing the thermosetting monomer mixture to promote the impregnation of the thermosetting monomer. The pressurizing pressure is preferably 0.2 MPa or higher, and more preferably 0.3 MPa or higher.

[0041] In step (b-2) of the present invention, the liquid used to clean the three-dimensional molded object impregnated with the thermosetting monomer mixture is not particularly limited as long as it does not adversely affect the resin constituting the molded object and can wash away the thermosetting monomer mixture. However, in terms of the ease of removal of the cleaning liquid, water or an alcohol-based solvent is preferred, and water is particularly preferred.

[0042] In step (b-3) of the present invention, the liquid used to immerse the three-dimensional object is not particularly limited as long as its boiling point is higher than the thermosetting temperature, but water is preferred because it has a high affinity for thermosetting monomers and does not adversely affect the three-dimensional object.

[0043] In step (b-3) of the present invention, the temperature of the liquid into which the three-dimensional object is immersed is not particularly limited as long as it is above the temperature at which the thermosetting monomer hardens. However, a temperature of 60°C or higher is more preferable, 70°C or higher is even more preferable, and 80°C or higher is particularly preferable in that it allows the thermosetting monomer to harden efficiently. Furthermore, the upper limit is preferably 100°C or lower in that it does not adversely affect the three-dimensional object.

[0044] The water absorption rate of the three-dimensional molded object of the present invention is preferably 1% or less. When the water absorption rate is lower, the change in mechanical properties due to moisture absorption of the three-dimensional molded object is smaller. Furthermore, even when the thermosetting monomer mixture is cured by immersion in hot water in step (b), the resin does not denature or deteriorate. In this regard, 0.5% or less is more preferable, 0.3% or less is even more preferable, 0.2% or less is particularly preferable, and 0.1% or less is remarkably preferable. Also, the lower limit is preferably no water absorption, that is, 0%.

[0045] Here, the water absorption rate of the thermoplastic resin of the present invention is a value expressed as a percentage obtained by immersing the three-dimensional molded object in water at 23°C for 24 hours in accordance with JIS K7209 (2000) and dividing the weight difference of the three-dimensional molded object before and after the treatment by the weight of the three-dimensional molded object before the treatment.

[0046] The three-dimensional molded object of the present invention is pressurized to an internal pressure of 500 kPa, allowed to stand for 1 hour, and then the pressure drop per hour is 3 kPa / mm or less per unit thickness at the minimum thickness part of the structural part. Nitrogen gas can be used as the gas for pressurization. The pressure drop is generated due to leakage from the structural part. When the airtightness of the molded object is excellent, nitrogen does not leak and the pressure drop becomes smaller. Therefore, the pressure drop per hour is preferably 2.5 kPa / mm or less, more preferably 2 kPa / mm or less, even more preferably 1.5 kPa / mm or less, and particularly preferably 1 kPa / mm or less. Also, the lower limit is 0 kPa / mm without leakage.

[0047] Note that the pressure drop per hour after pressurizing the three-dimensional object of the present invention to an internal pressure of 500 kPa and leaving it standing for 1 hour can be observed from the change in the indicated value of the pressure gauge. Also, the method of pressurizing the three-dimensional object can be appropriately changed according to the shape of the three-dimensional object. For example, in the case of a piping shape, all openings other than the portion that becomes the pressurizing port of the pipe are sealed with an O-ring or the like, closed with a plug, and then pressurized to 500 kPa using a nitrogen cylinder or a pump via a regulator from the pressurizing port. In the case of a container shape, the opening is appropriately adjusted via an adjuster and pressurized in the same manner. In the case of a plate shape, the piping is configured to cover the plate-shaped object, and the piping is pressurized in the same manner. The method of pressurization is an example and is not limited thereto. After pressurizing to an internal pressure of 500 kPa and leaving it standing for 1 hour to stabilize the pressure, the pressure after 1 hour was measured starting from the pressure value after stabilization, and the pressure drop amount from the starting point was observed. Also, the minimum thickness part of the structural part indicates the part with the thinnest thickness among the parts to which pressure is applied.

[0048] The three-dimensional object of the present invention is produced by the powder bed fusion bonding method such that the longitudinal direction of a tensile test piece (total length 170 mm, parallel part length 80 mm, parallel part width 10 mm, thickness 4 mm) conforming to ISO 527-1A is parallel to the direction (X direction) in which the recoater moves. When produced, it is preferable that the tensile strength in the X direction measured according to JIS K7161 (2014) of the test piece is 20 MPa or more. For using a three-dimensional object with excellent airtightness for final product applications, in terms of being a three-dimensional object having high strength and being difficult to break, 25 MPa or more is more preferable, 30 MPa or more is further preferable, 35 MPa or more is particularly preferable, and 40 MPa or more is remarkably preferable. Also, the upper limit is not particularly limited.

[0049] In the present invention, the tensile strength can be measured by a tensile test under the conditions of a grip distance of 115 mm and a test speed of 0.5 mm / min according to JIS K7161 (2014). The measurement temperature is room temperature (23°C), the number of measurements is n = 10, and the average value thereof is taken as the tensile strength.

[0050] In the present invention, when a three-dimensional molded object is prepared by powder bed fusion bonding, and a bending test specimen (80 mm x 10 mm x 4 mm) conforming to ISO 178 is prepared such that the longitudinal direction of the specimen is parallel to the direction (X direction) in which the recoater moves, it is preferable that the bending modulus of elasticity in the X direction of the specimen, as measured according to JIS K7171 (2016), is 2000 MPa or more. For a three-dimensional molded object with excellent airtightness to be used in final product applications, a bending modulus of elasticity of 2500 MPa or more is more preferable, 3000 MPa or more is even more preferable, 3500 MPa or more is particularly preferable, and 4000 MPa or more is significantly preferable, in order to obtain a three-dimensional molded object with high rigidity and resistance to deformation. Furthermore, there is no particular upper limit, but generally, if the modulus of elasticity becomes too high, it tends to become brittle and lose strength. Therefore, 20,000 MPa or less is preferred, 17,000 MPa or less is more preferred, 15,000 MPa or less is even more preferred, and 12,000 MPa or less is particularly preferred.

[0051] In this invention, the flexural modulus can be measured by a three-point bending test in accordance with JIS K7171 (2016), with a support distance of 64 mm and a test speed of 2 mm / min. The measurement temperature is room temperature (23°C), the number of measurements is n=10, and the average value is taken as the flexural modulus.

[0052] The load deflection temperature of the three-dimensional molded object of the present invention is preferably 100°C or higher. The higher the load deflection temperature, the less the molded object is likely to deform in a high-temperature environment. Therefore, the load deflection temperature of the molded object is more preferably 110°C or higher, and even more preferably 120°C or higher.

[0053] In this invention, the load deflection temperature is the value obtained by preparing a test specimen with a width of 10 mm, a length of 80 mm, and a thickness of 4 mm using a powder bed fusion bonding method, such that the 80 mm length is parallel to the direction (X direction) in which the recoater moves, and measuring the said test specimen under a load of 1.8 MPa in accordance with the Japanese Industrial Standard (JIS) JIS K7191-1 (2015) "Plastics - Method for determining load deflection temperature".

[0054] The three-dimensional molded product of the present invention is obtained by crystallization under atmospheric pressure and a slow cooling process, compared to conventional melt molding. As a result, the crystalline state differs from that of conventional melt molding. However, it is difficult to express this as a characteristic of the product, so the invention is limited to the manufacturing method, specifically three-dimensional molding, preferably by powder bed fusion bonding. While it is known that conventional melt molding can yield molded products with excellent airtightness and heat resistance through careful consideration by those skilled in the art, it has not been possible to obtain molded products that achieve both airtightness and heat resistance in three-dimensional molding, which allows for the molding of complex shapes. This has only become possible with the present invention.

[0055] The present invention will be described in detail below with reference to examples. However, the present invention is not limited to these examples.

[0056] [Measurement and Evaluation Method] (1) Melting Point of Thermoplastic Resin A sample obtained by cutting the end of a three-dimensional molded object was heated from 50°C to 340°C at a rate of 20°C / min under a nitrogen atmosphere using a differential scanning calorimeter (DSCQ20) manufactured by TA Instruments Inc. The peak temperature of the endothermic peak during melting in the DSC curve was defined as the melting point of the thermoplastic resin. Approximately 8 mg of sample was required for the measurement.

[0057] (2) Water absorption rate of thermoplastic resins and three-dimensional molded objects According to JIS K7209 (2000), thermoplastic resins or three-dimensional molded objects were immersed in water at 23°C for 24 hours, and the surface moisture was wiped off. The weight of the test specimens was then measured and recorded as the weight in the water-absorbed state. These test specimens were dried in a dryer at 50°C for 24 hours, and then cooled to room temperature in a desiccator. The weight of the test specimens was then measured and recorded as the weight in the dry state. The difference in weight between the water-absorbed and dry test specimens was divided by the weight of the dry test specimen and expressed as a percentage. This value was defined as the water absorption rate of the thermoplastic resin or three-dimensional molded object.

[0058] (3) Airtightness of three-dimensionally fabricated objects The airtightness of three-dimensionally fabricated objects was tested by using an Aspect Co., Ltd. powder bed fusion 3D printer (RaFaElII 300-HT) to fabricate a cylindrical pipe with an outer diameter of 30 mm, a thickness of 4 mm, and a length of 200 mm, with a circular cross-section. One end was sealed with an O-ring and fittings, and the other end was connected to a metal pipe. The internal pressure was then increased to 500 kPa using a nitrogen cylinder while monitoring the reading of a pressure gauge. After pressurizing to 500 kPa, the internal pressure was allowed to stabilize for one hour. The pressure value after this time was taken as the starting point, and the pressure drop from the starting point was observed. The value obtained by dividing the observed pressure drop by the thickness was taken as the pressure drop per hour per unit thickness at the minimum thickness of the structural part, and the average value was calculated with n=3 samples. If the airtightness of the fabricated object is excellent, nitrogen will not leak, and the pressure drop will be small.

[0059] (4) Measurement of the tensile strength of three-dimensionally fabricated objects The tensile strength of three-dimensionally fabricated objects was measured using a powder bed fusion 3D printer (RaFaElII 300-HT) manufactured by Aspect Co., Ltd. Test specimens with a total length of 170 mm, a parallel section length of 80 mm, a parallel section width of 10 mm, and a thickness of 4 mm were fabricated so that the 170 mm length direction was the X direction, and the tensile strength in the X direction was measured using a Tensilon universal tester (TENSIRON TRG-1250) manufactured by A&D Co., Ltd. The tensile strength was determined by measuring under conditions of a gripping distance of 115 mm and a test speed of 0.5 mm / min in accordance with JIS K7161 (2014). The measurement temperature was room temperature (23°C), the number of measurements was n=10, and the average value was calculated.

[0060] [Production Example 1] In a 1-liter autoclave equipped with a stirrer, 1.00 mole of 47% by weight sodium hydroxide, 1.05 moles of 46% by weight sodium hydroxide, 1.65 moles of N-methyl-2-pyrrolidone (NMP), 0.45 moles of sodium acetate, and 5.55 moles of deionized water were charged. The mixture was gradually heated to 225°C over approximately 2 hours under atmospheric pressure while passing nitrogen through it. After distilling off 11.70 moles of water and 0.02 moles of NMP, the reaction vessel was cooled to 160°C.

[0061] Next, 1.02 moles of p-dichlorobenzene (p-DCB) and 1.32 moles of NMP were added. The reaction vessel was sealed under nitrogen gas, and the temperature was increased in two stages while stirring at 400 rpm: from 160°C to 240°C at a rate of 0.4°C / min, and from 240°C to 270°C at a rate of 0.4°C / min. Ten minutes after reaching 270°C, 0.75 moles of water were injected into the system over 15 minutes. After 120 minutes at 270°C, the mixture was cooled to 200°C at a rate of 1.0°C / min, and then rapidly cooled to near room temperature to remove the contents.

[0062] The contents were removed, diluted with 0.5 liters of NMP, and the solvent and solids were filtered off using a sieve (80 mesh). The resulting solids were washed several times with 1 liter of warm water, and then 800 g of 0.45% by weight of calcium acetate monohydrate was added to the polyarylene sulfide in the solids and washed again with 1 liter of warm water. The mixture was then filtered to obtain the cake.

[0063] The obtained cake was dried under a nitrogen atmosphere at 120°C and then pulverized to obtain a polyarylene sulfide resin powder with a gas generation amount of 0.34 wt%, a melt flow rate of 150 g / 10 min, a number-average particle size of 43 μm, a melting point of 294°C, and a recrystallization temperature of 178°C. The water absorption rate of this polyarylene sulfide resin was 0.01%.

[0064] Ten kilograms of the obtained polyarylene sulfide resin powder and 15 g of trimethylsilylated amorphous silica QSG-170 (manufactured by Shin-Etsu Chemical Co., Ltd., D50 particle size 170 nm) as a flow aid were added and mixed using a cross-rotary mixer under nitrogen atmosphere and room temperature and pressure while rotating and revolving to obtain a powder composition.

[0065] [Production Example 2] 7.5 kg of polyarylene sulfide resin powder obtained in Production Example 1, 2.5 kg of glass fiber EPG70M-01N (manufactured by Nippon Electric Glass Co., Ltd., average major axis diameter 71 μm) as an inorganic reinforcing material, and 20 g of trimethylsilylated amorphous silica QSG-170 as a flow aid were added and mixed using a cross-rotary mixer under nitrogen atmosphere, room temperature and pressure while rotating and revolving to obtain a powder composition.

[0066] [Example 1] Using 10 kg of the powder composition obtained in Production Example 1, a powder bed fusion apparatus (RaFaElII 300-HT) manufactured by Aspect Co., Ltd. was used to produce three-dimensional molded objects of a pipe for airtightness measurement, a tensile test specimen, and a bending test specimen at a powder surface temperature of 260°C, a side temperature of 200°C, and a bottom temperature of 200°C. The end of this three-dimensional molded object was cut, and the melting point of the polyarylene sulfide resin was measured to be 287°C.

[0067] The obtained three-dimensional object was placed in a beaker and then placed in a desiccator equipped with piping for introducing thermosetting monomer into the beaker. After reducing the pressure of the desiccator to less than 1 kPa using a pump, the three-dimensional object was immersed in an organic impregnation agent, Superseal P-401 (manufactured by Chuo Invention Research Institute Co., Ltd., viscosity 10 mPa·s (25°C)), which is an acrylic monomer, as the thermosetting monomer mixture. The pressure was then returned to normal and left to stand for 1 hour to allow the impregnation to penetrate the object. The beaker containing the three-dimensional object and the thermosetting monomer mixture was transferred to a pressurized container, pressurized to 0.5 MPa, and allowed to immerse for another 1 hour. The three-dimensional object impregnated with the thermosetting monomer mixture was removed from the beaker and washed by immersing it in a beaker filled with water and shaking it. After that, it was immersed in 90°C hot water for 5 minutes to cure by hot water immersion. The three-dimensional object, in which the impregnation agent had hardened, was dried to obtain the three-dimensional object of the present invention.

[0068] The resulting three-dimensional fabricated object, specifically the pipe-shaped object, exhibited good airtightness, with a pressure drop of 0.2 kPa / mm per hour. Its water absorption rate was 0.04%, and its tensile strength was 52 MPa.

[0069] [Example 2] A three-dimensional object of the present invention was obtained in the same manner as in Example 1, except that the organic impregnation agent Superseal P-601 (manufactured by Chuo Invention Research Institute Co., Ltd., viscosity 6 mPa·s (25℃)) was used as the thermosetting monomer mixture. The obtained three-dimensional object, in the shape of a pipe, showed good airtightness with a pressure drop of 0.8 kPa / mm per hour. The water absorption rate was 0.03%, and the tensile strength was 43 MPa.

[0070] [Example 3] A three-dimensional object of the present invention was obtained in the same manner as in Example 1, except that 10 kg of the powder composition obtained in Production Example 2 was used to produce the three-dimensional object. The obtained three-dimensional object, a pipe-shaped object, showed good airtightness, with a pressure drop of 0.3 kPa / mm per hour. The water absorption rate was 0.03%, and the tensile strength was 63 MPa.

[0071] [Comparative Example 1] A three-dimensional object was evaluated without impregnation treatment with a thermosetting monomer mixture. The pipe-shaped object had a pressure drop of 5 kPa / mm per hour, indicating poor airtightness. The water absorption rate was 0.02%, and the tensile strength was 48 MPa.

[0072] The three-dimensional fabricated object of the present invention can be obtained that has good airtightness and reliability, and does not leak even in high-temperature environments. Furthermore, it is possible to obtain a three-dimensional fabricated object that maintains the heat resistance and mechanical properties of the material itself and has good airtightness, making it suitable for use in final product applications, particularly in industrial applications such as automotive piping parts and electrical and electronic piping parts.

Claims

1. A method for manufacturing a three-dimensional object, comprising the following steps (a) and (b) in sequence: (a) A step of manufacturing a three-dimensional object by powder bed fusion bonding using a powder composition containing resin powder made of a thermoplastic resin with a melting point of 200°C or higher. (b) A step of impregnating the three-dimensional object obtained in step (a) with a thermosetting monomer mixture and curing it.

2. The method for manufacturing a three-dimensional object according to claim 1, wherein the water absorption rate of the thermoplastic resin is 1% or less.

3. A method for manufacturing a three-dimensional object according to claim 1 or 2, wherein step (b) is performed sequentially by steps (b-1), (b-2), and (b-3) below: (b-1) A step of reducing the pressure of a container containing the three-dimensional object to 10 kPa or less, then introducing a thermosetting monomer mixture into the container to impregnate the three-dimensional object with the thermosetting monomer mixture. (b-2) A step of washing the three-dimensional object impregnated with the thermosetting monomer mixture to wash away any thermosetting resin adhering to the surface. (b-3) A step of immersing the three-dimensional object impregnated with the thermosetting monomer mixture in a liquid at or above the temperature at which the thermosetting monomer hardens, to harden the impregnated thermosetting monomer.

4. The method for manufacturing a three-dimensional object according to any one of claims 1 to 3, wherein in step (b), the viscosity of the thermosetting monomer mixture at 25°C is 1 mPa·s or more and 50 mPa·s or less.

5. The method for manufacturing a three-dimensional object according to any one of claims 1 to 4, wherein the thermoplastic resin is a polyarylene sulfide resin.

6. The method for manufacturing a three-dimensional object according to any one of claims 1 to 5, wherein the powder composition contains 20% by mass or more and 60% by mass or less of an inorganic reinforcing material.

7. The method for producing a three-dimensional object according to any one of claims 1 to 6, wherein the thermosetting monomer mixture includes an acrylic monomer.

8. A three-dimensional molded object obtained by a powder bed fusion method using a powder composition containing resin powder made of a thermoplastic resin with a melting point of 200°C or higher, characterized in that the pressure drop per hour when the internal pressure is increased to 500 kPa is 3 kPa / mm or less per unit thickness at the minimum thickness of the structural part.

9. The three-dimensional object according to claim 8, wherein the water absorption rate is 1% or less.

10. The three-dimensional object according to claim 8 or 9, wherein the three-dimensional object comprises a thermosetting resin.

11. A three-dimensional object according to any one of claims 8 to 10, wherein a three-dimensional object obtained by a powder bed fusion method using a powder composition containing polyarylene sulfide resin is impregnated with a thermosetting monomer mixture and cured.

12. The three-dimensional molded object according to any one of claims 8 to 11, wherein the powder composition contains 20% by mass or more and 60% by mass or less of an inorganic reinforcing material.