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

Abstract

A method for manufacturing a three-dimensional object, comprising the steps of (a) 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, and (b) impregnating the three-dimensional object obtained in step (a) with a thermosetting monomer mixture and curing it. This method can produce a three-dimensional object with good airtightness and reliability that does not leak even in high-temperature environments. Furthermore, it can produce a three-dimensional object with good airtightness that maintains the heat resistance and mechanical properties of the material itself.

Description

Technical Field

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

Background Art

[0002] Three-dimensional shaping enables designs with a high degree of freedom in shape, and thus has been widely applied in various fields 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 members are required. The shaping process of the powder bed fusion bonding method is a method of manufacturing by sequentially repeating a thin layer formation process of spreading resin powder in a thin layer and a cross-sectional shape formation 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 shaped 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 shaped 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 shaped object is formed by melting and sintering under normal pressure from a state filled with powder, it is known that it usually involves 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. Also, in Patent Document 2, a method of injecting a low melting point polymer into the shaped object to protect the shaped object and perform quality finishing is disclosed.

Prior Art Documents

Patent Documents

[0005] [Patent Document 1] Japanese Patent Publication No. 2023-014051 [Patent Document 2] Japanese Patent Publication No. 2019-130916 [Overview of the project] [Problems that the invention aims to solve]

[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. [Means for solving the problem]

[0008] To solve the aforementioned problems and achieve the objective, the present invention has the following configuration. [1] A method for manufacturing a three-dimensional object, comprising the following steps (a) and (b) in sequence. (a) A process for manufacturing a three-dimensional object by powder bed fusion bonding using a powder composition containing resin particles made of 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 object according to [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 [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 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. (b-2) A step of washing a three-dimensional molded object impregnated with a thermosetting monomer mixture to wash away any thermosetting resin adhering to the surface. (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. [4] A method for manufacturing a three-dimensional 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 manufacturing a three-dimensional object according to any one of [1] to [4], wherein the thermoplastic resin is a polyarylene sulfide resin. [6] A method for manufacturing a three-dimensional 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 object according to any one of [1] to [6], wherein the thermosetting monomer mixture comprises an acrylic monomer. [8] A three-dimensional object obtained by powder bed fusion bonding 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 increased to 500 kPa is 3 kPa / mm or less per unit thickness at the minimum thickness of the structural part. [9] A three-dimensional object as described in [8], having a water absorption rate of 1% or less.

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

[11] A three-dimensional object obtained by a powder bed fusion method using a powder composition containing polyarylene sulfide resin, which is then impregnated with a thermosetting monomer mixture and cured, as described in any of [8] to

[10] .

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

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

[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. [Modes for carrying out the invention]

[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 at a rate of 20°C / min from 50°C to a temperature 50°C higher than the endothermic peak indicating the melting point of the resin, using a differential scanning calorimeter in a nitrogen atmosphere.

[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 the melting point is 200°C or higher, and examples thereof include polyester, polyamide, polyarylene sulfide, polyether ether ketone, polyether ketone ketone, polyether imide, polyamide imide, polyether sulfone, polytetrafluoroethylene, or a mixture thereof. Among these, a polyarylene sulfide resin is preferable in terms of excellent heat resistance and low water absorption.

[0017] The D50 particle size of the powder composition of the present invention is preferably in the range of 1 to 100 μm. A more preferable lower limit of the D50 particle size is 3 μm, still more preferably 5 μm, particularly preferably 8 μm, extremely preferably 10 μm, and most preferably 15 μm. Also, a more preferable upper limit of the D50 particle size is 90 μm, still more preferably 85 μm, particularly preferably 80 μm, extremely preferably 75 μm, and most preferably 70 μm. When the D50 particle size exceeds 100 μm, the uniformity is impaired during powder lamination by the powder bed fusion bonding method, and the strength of the three-dimensional molded object decreases. On the other hand, when the D50 particle size is less than 1 μm, aggregation of particles occurs due to static electricity, and similarly, the uniformity is impaired during powder lamination, and the strength of the three-dimensional molded object decreases.

[0018] Incidentally, the D50 particle size of the powder composition is the particle size (D50 particle size) at which the cumulative frequency from the small particle size side of the particle size distribution measured by a laser diffraction particle size distribution analyzer becomes 50%. When the powder composition contains components such as an inorganic reinforcing material and a flow aid described later, the particle size measured in the state of the composition containing these is taken as the particle size of the powder composition.

[0019] The powder composition of the present invention may contain additives such as inorganic reinforcing materials within a range that does not impair the present invention. The blending amount of the 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 expanded glass beads; nepheline syenite fine powder; fired clays such as montmorillonite and bentonite; clays (aluminum silicate powder) such as silane-modified clay; talc; diatomaceous earth; silicon-containing compounds such as silica sand; pulverized products of 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 (carbon); silica (silicon dioxide) such as fused silica, crystalline silica, and amorphous silica; alumina (aluminum oxide); alumina colloids (alumina sols); alumina such as alumina white; calcium carbonate such as light calcium carbonate, heavy calcium carbonate, micronized calcium carbonate, and special calcium carbonate-based fillers; fly ash balls, 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 oxide, magnesium oxide, basic magnesium carbonate, dolomite, calcium sulfite, mica, asbestos, calcium silicate, molybdenum sulfide, boron fibers, silicon carbide fibers, etc. Glass-based fillers, minerals, and carbon fibers are preferred in terms of being hard and having a large effect on improving strength, and glass-based fillers are more preferred in terms of having a narrow particle size distribution and fiber diameter distribution. Examples of glass-based fillers include glass fibers, glass beads, glass flakes, and expanded glass beads. These inorganic reinforcing materials can be used alone or in combination of two or more.

[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 such a 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 manufacturing method for the three-dimensional object of the present invention is a powder bed fusion method. This powder bed fusion method is a 3D printing technique that obtains a three-dimensional object by repeatedly forming a layer of resin particles, selectively melting and welding the layers 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 performed 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 to wash away any 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 for efficient hardening of the thermosetting monomer. 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. A lower water absorption rate results in less change in the mechanical properties of the 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. Therefore, 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 desirable.

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

[0046] The three-dimensional molded object of the present invention, after being pressurized to an internal pressure of 500 kPa and left to stand for 1 hour, exhibits a pressure drop of 3 kPa / mm or less per unit thickness at the minimum thickness of the structural part. Nitrogen gas can be used as the pressurizing gas. The pressure drop occurs due to leakage from the structural part, and if the airtightness of the molded object is excellent, nitrogen will not leak, and the pressure drop will be small. 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. The lower limit is 0 kPa / mm, where there is no leakage.

[0047] The pressure drop per hour after pressurizing the three-dimensional object of the present invention to an internal pressure of 500 kPa and letting it stand for 1 hour can be observed from the change in the reading of the pressure gauge. The method of pressurizing the three-dimensional object can be appropriately changed depending on the shape of the object. For example, in the case of a pipe shape, all openings except the part that will be the pressurized port of the pipe are sealed with O-rings or the like, closed with a plug, and then pressurized to 500 kPa using a nitrogen cylinder or pump via a regulator from the pressurized port. In the case of a container shape, the opening is appropriately adjusted via an adjuster and pressurized in the same way. In the case of a plate shape, the pipe is covered with the plate-shaped object, and the pipe is pressurized in the same way. The pressurization method is illustrative and not limited to these. After pressurizing to an internal pressure of 500 kPa, the pressure value after letting it stand for 1 hour to stabilize the pressure was used as the starting point, and the pressure after 1 hour was measured to observe the pressure drop from the starting point. The minimum thickness part of the structural part refers to the thinnest part of the part under pressure.

[0048] The three-dimensional molded object of the present invention is preferably manufactured by powder bed fusion bonding, with a tensile test specimen (total length 170 mm, parallel section length 80 mm, parallel section width 10 mm, thickness 4 mm) conforming to ISO 527-1A, such that the longitudinal direction of the specimen is parallel to the direction (X direction) of the recoater's movement, and the tensile strength in the X direction of the specimen, measured according to JIS K7161 (2014), is 20 MPa or higher. For the use of the three-dimensional molded object with excellent airtightness in final product applications, a tensile strength of 25 MPa or higher is more preferable, 30 MPa or higher is even more preferable, 35 MPa or higher is particularly preferable, and 40 MPa or higher is significantly preferable. Furthermore, there is no particular upper limit.

[0049] In this invention, tensile strength can be measured by a tensile test in accordance with JIS K7161 (2014), with a gripping distance of 115 mm and a test speed of 0.5 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 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 × 10 mm × 4 mm) conforming to ISO 178 is prepared such that the longitudinal direction of the test specimen is parallel to the direction (X direction) of the recoater's movement, it is preferable that the bending modulus of elasticity in the X direction of the test 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 extremely preferable, as it provides high rigidity and resistance to deformation. Furthermore, there is no particular upper limit, but generally, if the elastic modulus becomes too high, it tends to become brittle and have low strength, so a modulus of elasticity of 20000 MPa or less is preferable, 17000 MPa or less is more preferable, 15000 MPa or less is even more preferable, and 12000 MPa or less is particularly preferable.

[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 object of the present invention is preferably 100°C or higher. The higher the load deflection temperature, the less the object is likely to deform in a high-temperature environment. Therefore, the load deflection temperature of the 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 measuring a test specimen with a width of 10 mm, a length of 80 mm, and a thickness of 4 mm, prepared by the powder bed fusion bonding method, such that the 80 mm length is parallel to the direction (X direction) in which the recoater moves, under a load of 1.8 MPa in accordance with the Japanese Industrial Standard (JIS standard) 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. [Examples]

[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 Methods] (1) Melting point of thermoplastic resin A sample obtained by cutting the edge of a three-dimensional 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 melting point of the thermoplastic resin was defined as the peak temperature of the endothermic peak during melting in the DSC curve. Approximately 8 mg of sample was required for the measurement.

[0057] (2) Water absorption rate of thermoplastic resins and three-dimensional molded objects In accordance with JIS K7209 (2000), thermoplastic resin 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 specimen in the water-absorbed state was then measured. These specimens were dried in a 50°C dryer for 24 hours, and then cooled to room temperature in a desiccator. The weight of the specimen in the dry state was measured again. The difference in weight between the water-absorbed and dry specimens was divided by the weight of the dry specimen and expressed as a percentage to determine the water absorption rate of the thermoplastic resin or three-dimensional molded object.

[0058] (3) Airtightness of three-dimensional objects The airtightness of the three-dimensional object was tested using an Aspect Co., Ltd. powder bed fusion 3D printer (RaFaElII 300-HT) to create 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 fitting, 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 pressure gauge reading. After pressurizing to 500 kPa, the internal pressure was allowed to stabilize for 1 hour. This value was used as the starting point, and the pressure was measured again after 1 hour. The amount of pressure drop from the starting point was observed, and this value was divided by the thickness to determine the pressure drop per hour per unit thickness at the thinnest part of the structure. The number of samples was n=3, and the average value was calculated. If the airtightness of the object is excellent, nitrogen will not leak, and the amount of pressure drop will be small.

[0059] (4) Measurement of the tensile strength of three-dimensional objects The tensile strength of the three-dimensionally fabricated object was measured using a powder bed fusion 3D printer (RaFaElII 300-HT) manufactured by Aspect Co., Ltd. A test specimen 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 was fabricated with the 170 mm length direction as the X direction. The tensile strength in the X direction was measured using a Tensilon universal tester (TENSIRON TRG-1250) manufactured by A&D Company, Limited. The tensile strength was determined according to JIS K7161 (2014), with a gripping distance of 115 mm and a test speed of 0.5 mm / min. The measurement temperature was room temperature (23°C), and the number of measurements was n=10. The average value was calculated.

[0060] [Manufacturing Example 1] In a 1-liter autoclave equipped with a stirrer, 1.00 mole of 47 wt% sodium hydroxide, 1.05 moles of 46 wt% 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 then 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 an 80-mesh sieve. The resulting solids were washed several times with 1 liter of warm water, 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] 10 kg 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, room temperature and pressure while rotating and revolving to obtain a powder composition.

[0065] [Manufacturing 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 fusion apparatus (RaFaElII 300-HT) manufactured by Aspect Co., Ltd. was used to produce three-dimensional molded objects of airtightness measurement piping, tensile test specimens, and bending test specimens at a powder surface temperature of 260°C, a side temperature of 200°C, and a bottom temperature of 200°C. The ends of these three-dimensional molded objects were 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℃)), 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 occur. 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℃ 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 form 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 Manufacturing Example 2 was used to manufacture the three-dimensional object. The obtained three-dimensional object, specifically the pipe-shaped object, exhibited 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] Three-dimensional printed objects were evaluated without impregnation treatment with a thermosetting monomer mixture. The pipe-shaped object exhibited 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. [Industrial applicability]

[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 process for 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 molded 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. The method for manufacturing a three-dimensional object according to claim 1, 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 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. (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. (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, and curing the impregnated thermosetting monomer.

4. The method for manufacturing a three-dimensional object according to claim 1, 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 claim 1, wherein the thermoplastic resin is a polyarylene sulfide resin.

6. The method for manufacturing a three-dimensional object according to claim 1, 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 claim 1, wherein the thermosetting monomer mixture includes an acrylic monomer.

8. A three-dimensional 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, wherein the three-dimensional object comprises a thermosetting resin.

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