Composition, molding method, and molded article

Abstract

Provided is a composition capable of suppressing the occurrence of warpage during curing after melting by laser irradiation. The composition according to one embodiment of the present invention is used for three-dimensional modeling. The composition includes a resin powder. In an endothermic energy curve when differential scanning calorimetry is performed on the resin powder, if T1 is the temperature of the point of intersection between the baseline after melting and the endothermic energy curve before melting and T2 is the endothermic peak temperature during melting, (T2-T1) is 38-70 DEG C and T2 is 130-300 DEG C.

Description

Technical Field

[0001] The present invention relates to a composition, a shaping method and a shaped object. Background Art

[0002] As a modeling method for 3D printers, a method is known that uses a laser as a heat source to melt and solidify powder spread evenly layer by layer while laminating (powder bed fusion bonding (PBF)).

[0003] Patent Document 1 discloses a styrene-based resin as a molding powder for a powder bed fusion bonding method.

[0004] Prior art literature Patent Literature Patent Document 1: Japanese Patent Application Laid-Open No. 2019-130864 Summary of the Invention Problems to be solved by the invention Conventional modeling resin particles have a problem: after being melted by laser irradiation, the object undergoes thermal contraction due to the temperature difference between the object and the printer interior (typically 150°C), causing warping in the sintered film and preventing the desired size of the object. Furthermore, increasing the temperature inside the printer to prevent this thermal contraction causes the surface of the resin particles to melt, leading to sticking. This reduces the flowability of the particles during the powder coating process, making it difficult to achieve a uniform powder coating surface and resulting in poor modeling.

[0005] The present invention has been made in view of the above-mentioned problems, and an object thereof is to provide a composition capable of producing a molded object with excellent performance in a 3D printer molding method using a laser as a heat source.

[0006] Means used to solve problems One embodiment of the present invention is a composition for three-dimensional molding, comprising a resin powder. In a differential scanning calorimetry analysis of an endothermic energy curve of the resin powder, the temperature of the intersection of the baseline after melting and the endothermic energy curve before melting is defined as T1, and the endothermic peak temperature during melting is defined as T2. The result shows that (T2-T1) is 38-70°C, and T2 is 130-300°C.

[0007] In the composition of the above embodiment, the resin powder may be an aggregate of particles comprising two or more resins having different melting points. In a differential scanning calorimetry (DSC) endothermic energy curve of the resin powder, with the exothermic peak temperature during crystallization being defined as T3, the equation 30°C ≤ (T2 - T3) can be satisfied.

[0008] The resin powder may have a median particle size D50 (volume basis) of 30 to 150 μm.

[0009] The average sphericity of the resin powder may be 0.70-0.98.

[0010] The resin powder may have a bulk filling rate (bulk specific gravity / true specific gravity) of 25-60%, and a melt flow rate (MFR) of 5-100 (g / 10 minutes) at 230° C.

[0011] Another embodiment of the present invention is a molding method comprising the step of forming a cured resin layer in a predetermined pattern using the composition of any one of the above embodiments.

[0012] Another embodiment of the present invention is a shaped object obtained by using the composition of any of the above embodiments.

[0013] Effects of the Invention According to the present invention, it is possible to provide a technique related to a composition capable of producing a molded object having excellent performance in a 3D printer molding method using a laser as a heat source. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is a diagram schematically showing an endothermic energy curve obtained when a resin powder is subjected to differential scanning calorimetry. DETAILED DESCRIPTION

[0015] Hereinafter, embodiments of the present invention will be described in detail. In addition, in this specification, unless otherwise specified, the expression "a to b" in the description of a numerical range means a or more and b or less.

[0016] The composition of the embodiment is used for three-dimensional modeling. In other words, the composition of the embodiment is used as a resin powder for modeling in a so-called 3D printer. The composition of the embodiment contains resin powder.

[0017] Figure 1 This is a diagram schematically showing an endothermic energy curve when a resin powder (also referred to as a resin powder) is subjected to differential scanning calorimetry (DSC). Figure 1 As shown, in the endothermic energy curve when the resin powder is measured by differential scanning calorimetry, the temperature of the intersection of the base line after melting and the endothermic energy curve before melting is defined as T1, and the endothermic peak temperature during melting is defined as T2.

[0018] In this embodiment, (T2-T1) is 38 to 70°C, preferably 40 to 66°C, and more preferably 42 to 62°C.

[0019] By setting the lower limit of (T2-T1) above the above value, the resin particles will fully melt at the printer's internal temperature, reducing warping of the object. On the other hand, by setting the upper limit of (T2-T1) below the above value, the resin particles will melt appropriately, preventing surface sticking and a decrease in fluidity. This allows the printer's internal temperature to be increased, further reducing warping of the object.

[0020] T2 is 130 to 300°C, preferably 135 to 250°C, and more preferably 140 to 200°C.

[0021] By setting the lower limit of T2 above the above value, the mechanical and physical properties of the material itself can be improved, thereby increasing the strength of the molded object. On the other hand, by setting the upper limit of T2 below the above value, the temperature change during cooling to room temperature after molding will not be excessive, thereby suppressing shrinkage of the resin material and improving the dimensional accuracy of the molded object.

[0022] In an endothermic energy curve obtained by differential scanning calorimetry of the resin powder, assuming that the exothermic peak temperature during crystallization is T3, it is preferred that 30° C. ≤ (T2 − T3).

[0023] By setting the lower limit of (T2-T3) above the above value, the temperature inside the printer can be prevented from falling below the crystallization temperature of the resin. When cooling to the temperature inside the printer after laser irradiation, crystallization of the resin is difficult to occur, which suppresses shrinkage of the molded object and thus prevents warping.

[0024] The median particle size D50 (volume basis) of the resin powder is preferably 30 to 150 μm, more preferably 30 to 130 μm, and even more preferably 30 to 100 μm. The median particle size D50 (volume basis) of the resin powder can be measured using a laser diffraction particle size distribution analyzer.

[0025] By setting the lower limit of the D50 of the resin powder to be above the above-mentioned value, the gaps between the resin particles are reduced, making it easier to obtain a dense molded object, thereby improving the mechanical and physical properties and suppressing warping. In addition, the resin particles are difficult to dissolve in the printer, and the fluidity of the resin particles increases, which can make the powder surface smooth when spreading the powder and improve the density of the molded object. On the other hand, by setting the upper limit of the D50 of the resin powder to be below the above-mentioned value, it is difficult for the powder spreader used to spread the resin particles to get stuck when spreading the powder, and the generation of streaks on the powder surface can be suppressed. In addition, when irradiated with a laser, the cores of the resin particles are easy to melt, making it easier to obtain a dense molded object, thereby improving the mechanical and physical properties and suppressing the warping of the molded object.

[0026] The average sphericity of the resin powder is preferably 0.70 to 0.98, more preferably 0.80 to 0.90, and even more preferably 0.85 to 0.90.

[0027] By setting the lower limit of the average sphericity of the resin powder above the above value, the fluidity of the resin particles is increased, the powder surface becomes smoother during spreading, and the density of the shaped object is improved, thereby improving the mechanical and physical properties and suppressing warping of the shaped object. On the other hand, by setting the upper limit of the average sphericity of the resin powder below the above value, the fluidity of the resin particles is prevented from becoming excessively high. By appropriately filling the resin particles, the contact points between the powders are optimized. As a result, at the end of the laser irradiation area, the powders in the unirradiated area will not fuse to each other, and the shaped object of the target size can be obtained.

[0028] The bulk filling rate (bulk specific gravity / true specific gravity) of the resin powder is preferably 25 to 60%, more preferably 30 to 57%, and even more preferably 35 to 55%.

[0029] By setting the lower limit of the bulk filling to above the above value, the gaps between the resin particles are reduced, facilitating a dense structure, improving mechanical properties, and suppressing warping of the molded object. On the other hand, by setting the upper limit of the bulk filling to below the above value, the contact points between the resin particles can be appropriately controlled, preventing adhesion of the resin particles in non-molding areas (non-laser irradiated areas).

[0030] The melt flow rate (MFR) of the resin powder at 230° C. is preferably 5 to 100 (g / 10 minutes), more preferably 8 to 90 (g / 10 minutes), and even more preferably 10 to 80 (g / 10 minutes).

[0031] By setting the lower limit of the resin powder's MFR above the above value, the fluidity during melting is prevented from becoming excessively low, allowing the gaps between the resin particles to be filled, resulting in a dense molded object. This improves mechanical properties and prevents warping of the molded object. On the other hand, by setting the upper limit of the resin powder's MFR below the above value, the fluidity during melting is prevented from becoming excessively high, allowing the unirradiated portion at the end of the laser irradiation area to remain unmelted, thereby achieving a molded object of the target size.

[0032] The resin constituting the resin powder is not particularly limited as long as it satisfies the aforementioned temperature characteristics and physical properties, and examples thereof include thermoplastic resins. Examples of such thermoplastic resins include crystalline resins. Furthermore, when such crystalline resins are measured according to ISO 3146 (Method for Determination of Plastic Transition Temperature, JIS K7121), they exhibit a melting peak.

[0033] Examples of the crystalline resin include polymers such as polyolefin, polyamide, polyester, polyether, polyphenylene sulfide (PPS), liquid crystal polymer (LCP), polyacetal (POM), and polyimide.

[0034] Examples of the polyolefin include polyethylene and polypropylene, and these may be used alone or in combination of two or more.

[0035] Examples of the polypropylene include homopolypropylene, random polypropylene, and block polypropylene.

[0036] Examples of polyamides include polyamide 410 (PA410), polyamide 6 (PA6), polyamide 66 (PA66), polyamide 610 (PA610), polyamide 612 (PA612), polyamide 11 (PA11), and polyamide 12 (PA12); and semi-aromatic polyamide 4T (PA4T), polyamide MXD6 (PAMXD6), polyamide 6T (PA6T), polyamide 9T (PA9T), and polyamide 10T (PA10T). These can be used alone or in combination of two or more. Among these, PA9T, also known as polynonane terephthalamide, is composed of a diamine with nine carbon atoms and terephthalic acid monomers. Because the carboxylic acid side is aromatic, it is generally referred to as semi-aromatic. Furthermore, the polyamides disclosed herein also include fully aromatic polyamides composed of p-phenylenediamine and terephthalic acid monomers, known as aramids.

[0037] Examples of polyester include polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and polylactic acid (PLA).

[0038] Examples of polyethers include polyetheretherketone (PEEK), polyetherketone (PEK), polyetherketoneketone (PEKK), polyaryletherketone (PAEK), polyetheretherketoneketone (PEEKK), polyetherketoneetherketoneketone (PEKEKK), and polyethersulfone. Furthermore, from the perspectives of cost-effectiveness, availability, and energy conservation, polyolefins are preferred, with polypropylene being particularly preferred.

[0039] The resin powder is preferably an aggregate of particles containing two or more resins having different melting points. This allows rigidity to be obtained by the high-melting-point resin having a relatively high melting point, while ductility to be obtained by the low-melting-point resin having a relatively low melting point.

[0040] The combination of the high melting point resin and the low melting point resin is not particularly limited as long as it satisfies the above-mentioned temperature characteristics and physical properties. Examples thereof include homopolypropylene and random polypropylene, two random polypropylenes with different PE amounts, PPS and PA6, and the like.

[0041] In addition to the above-mentioned thermoplastic resin, the resin powder may also contain resin powder composed of a non-crystalline resin, a crystal nucleating agent, a compatibilizer, a plasticizer, an antioxidant, a stabilizer, a color-proofing agent, a pigment, a dye, an ultraviolet absorber, a release agent, a lubricant, a flame retardant, an antistatic agent, an inorganic fiber, an organic fiber, an inorganic particle, or an organic particle. These substances may be used alone or in combination of two or more. These substances may be mixed with the above-mentioned thermoplastic resin, included in the resin powder, or attached to the surface of the resin powder.

[0042] Methods for producing the resin powder of this embodiment include melt granulation, which forms fibers from a resin composition melted near its melting point and then cuts them; pulverization, which cuts or destroys the resin material composed of the resin composition by impact or shearing; and methods for producing resin particles by dispersing a resin immiscible with a matrix component in a meltable matrix component and then removing the matrix component. Furthermore, to improve the coating properties of the powder, a curved shape, i.e., a high degree of sphericity, is preferred. Therefore, to achieve such a preferred powder shape, it is preferable to select a preferred powdering method for the thermoplastic resin contained in the resin powder used in the powder lamination molding method of this embodiment.

[0043] When the powder is pulverized, it is preferable to perform a classification step after the pulverization from the viewpoint of removing elongated powder from the pulverized powder and increasing the sphericity.

[0044] In this case, examples of the classification method include wind classification and sieve classification.

[0045] The composition described above enables the production of three-dimensional objects at temperatures within the printer (e.g., 150°C) where the resin particles do not melt or cause sticking. Furthermore, thermal shrinkage of the resin during the laser irradiation process is mitigated, reducing warping of the sintered film and enabling the production of objects of the desired dimensions.

[0046] (Modeling method) The molding method of the embodiment includes the step of forming a resin cured layer in a predetermined pattern using the above-mentioned composition. The procedure of the molding method is shown below.

[0047] First, a thin layer is formed using the composition described above. Specifically, after the composition is supplied to a molding table, a powder spreader (a doctor blade or roller) evenly spreads the composition onto the molding table to form a thin layer. This thin layer can be formed directly on the molding table or laminated onto an already applied thin layer or a pre-formed sintered film.

[0048] The thickness of the thin layer can be adjusted according to the thickness of the sintered film or the precision of the object being made. The thickness of the thin layer is usually around 0.01 to 0.3 mm.

[0049] Next, within the stacked layers, the area where the object will be formed is selectively irradiated with laser light. The temperature inside the printer during laser irradiation can be between (T2-20)°C and (T2-10)°C. Laser irradiation fuses the resin powder within the layers, forming a sintered film. The resin powder not irradiated by the laser can be recovered as excess powder and reused as recycled powder.

[0050] Next, the formation stage is lowered by a height corresponding to the thickness of the sintered film obtained by laser irradiation, and thin layer formation and laser irradiation are repeated in this order.

[0051] According to the above method, a resin cured layer (3D object) with a predetermined pattern is produced.

[0052] (Sculpture) The molded object of this embodiment is obtained by the above-mentioned molding method using the above-mentioned composition. The molded object of this embodiment has high dimensional accuracy because the sintered film obtained by laser irradiation is less likely to warp.

[0053] As mentioned above, although embodiment of this invention was described, these are examples of this invention, and various structures other than the above-mentioned can also be adopted.

[0054] Example Hereinafter, the present invention will be described with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

[0055] Compositions (aggregates of resin powders) were prepared using the resin components and blending amounts shown in Table 1. The components of the main resin and the secondary resin shown in Table 1 are general-purpose products.

[0056] (Differential Scanning Calorimetry) A differential scanning calorimeter (SSC-5200 manufactured by Seiko Instruments Inc.) was used. The measurement was performed while blowing 50 ml of N2 gas in 1 minute. First, the temperature was raised from 10°C to 330°C at a rate of 5°C per minute, and maintained at 330°C for 4 minutes. Then, the temperature was lowered from 330°C to 10°C at a rate of 5°C per minute. The endothermic peak temperature during melting in the heating curve was set to T2, the heat at a temperature 30°C higher than T2 was set to the baseline, and the temperature of the intersection of the baseline and the heating curve before melting was set to T1. The exothermic peak during crystallization in the cooling curve was set to T3. The values ​​obtained based on the obtained endothermic energy curve are shown in Table 1.

[0057] (Median particle size D50 measurement (volume basis)) The powder particle size distribution was measured using a laser diffraction particle size analyzer (Malvern Mastersizer 3000, Hydro MV wet dispersion unit). The median diameter (D50) at which the volume fraction of the measured particle size distribution reached 50% was calculated. The obtained values ​​are shown in Table 1.

[0058] (Average sphericity determination) Using a circularity measuring instrument (FPIA-3000S, manufactured by Sysmex), the projected area and outline length (perimeter) of the particle projection were measured. Sphericity was calculated using the following formula. The sphericity was calculated for 1000 to 2000 particles, and the average of these sphericity values ​​was taken as the average sphericity of the composition (resin powder). The resulting values ​​are shown in Table 1.

[0059] Sphericity = (the circumference of a circle with the same area as the projected area of ​​the particle) / (the length of the outline of the particle's projected image) (Loose filling rate determination (bulk density / true density)) The bulk density was measured using a bulk density meter (compliant with JIS Z-2504, produced by Kurachi Scientific Instruments Co., Ltd.). The obtained bulk density was divided by the true density (true specific gravity) of the resin to calculate the "bulk filling rate" of the resin powder. The resulting values ​​are shown in Table 1.

[0060] (MFR measurement) The MFR of the resin powder was measured at 230° C. and a load of 2.16 kg according to JIS K7210 A method. The obtained values ​​are shown in Table 1.

[0061] (Warp evaluation) Using a powder bed fusion 3D printer (RaFaElII 150C-HT) manufactured by Aspect Co., Ltd., laser irradiation was performed on a 30 mm square of the composition at a printer internal temperature of (T2-15)°C to produce a single sintered film (test piece). The resulting test piece was placed horizontally in a downwardly convex position. A taper gauge was inserted into the gap between the horizontal surface and the test piece. The height of the gap was used as the warpage, and the warpage was evaluated according to the following criteria.

[0062] [Evaluation Criteria] AA: The warpage is less than 0.05 mm.

[0063] A: The warpage is greater than 0.05 mm and less than 0.1 mm.

[0064] B: The warpage amount is greater than 0.1 mm and less than 0.2 mm.

[0065] C: The warpage amount is greater than 0.2 mm and less than 0.3 mm.

[0066] D: The warping amount is greater than 0.3 mm.

[0067] AA~C are qualified, and D is unqualified.

[0068] (Physical properties of sculptures: Measurement of the flexural modulus of the sculptures) Using a powder bed fusion 3D printer (RaFaElII 150C-HT) manufactured by Aspect Co., Ltd., three-dimensional objects (test pieces) with a width of 10 mm, a length of 80 mm, and a thickness of 4 mm were produced from each composition. The flexural modulus of the three-dimensional objects in the thickness direction was measured using a TENSIRON universal testing machine (TENSIRON TRG-1250) manufactured by A&D. The flexural modulus was determined using 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 / minute. Measurements were made at room temperature (23°C) for 5 measurements, and the average value was calculated.

[0069] [Evaluation Criteria] A: 1500MPa or more.

[0070] B: 1200 or more and less than 1500 MPa.

[0071] C: 1000 or more and less than 1200 MPa.

[0072] D: less than 1000 MPa.

[0073] A~C are qualified, and D is unqualified.

[0074] (Tensile strain evaluation) The resulting three-dimensional object was subjected to a tensile test according to ISO 527. The testing machine used was an AGS-5kN (manufactured by Shimadzu Corporation). The test speed during the tensile test was 5 mm / minute. The tensile test was conducted five times, and the average stress at the maximum tensile point was measured as the tensile strength, while the average strain at the maximum tensile point was measured as the tensile strain. The tensile strength and tensile strain were evaluated based on the following evaluation criteria. The results are shown in Table 1. Strain is expressed as "(final length - initial length / initial length) × 100."

[0075] [Evaluation Criteria] A: The tensile strain is above 10%.

[0076] B: The tensile strain is 5% or more and less than 10%.

[0077] C: The tensile strain is greater than 3% and less than 5%.

[0078] D: Tensile strain is less than 3%.

[0079] A~C are qualified, and D is unqualified.

[0080] Dimensional accuracy Each composition (3D modeling resin powder) was stored at 27°C and 80% humidity for one week. Three-dimensional objects were produced using a powder bed fusion 3D printer (RaFaElII 150C-HT) manufactured by Aspect Co., Ltd. The conditions for producing the three-dimensional objects are shown below.

[0081] Average thickness of powder layer: 0.1mm Laser power: 10 watts or more and 150 watts or less Laser scanning space: 0.1mm Bed temperature: 15°C lower than the melting point of the resin The three-dimensional object used for dimensional accuracy evaluation is a cube with a side of 50 mm and an average thickness of 5 mm. This object is created based on CAD (Computer Aided Design) data. The difference in the length of each side between the CAD data and the real-time modeling of the object is calculated, and the average of these differences is used as the dimensional difference. "Dimensional accuracy" is evaluated based on the following evaluation criteria.

[0082] [Evaluation Criteria] A: The size difference is less than 0.02mm.

[0083] B: The dimensional difference is more than 0.02 mm and less than 0.05 mm.

[0084] C: The dimensional difference is more than 0.05 mm and less than 0.10 mm.

[0085] D: The dimensional difference is more than 0.10 mm and less than 0.15 mm.

[0086] A~C are qualified, and D is unqualified.

[0087] [Table 1] .

Claims

1. A composition for three-dimensional modeling, wherein: Contains resin powder, In an endothermic energy curve obtained by differential scanning calorimetry of the resin powder, the temperature of the intersection of the baseline after melting and the endothermic energy curve before melting is defined as T1, and the endothermic peak temperature during melting is defined as T2. Thus, (T2-T1) is 38-70° C., and T2 is 130-300° C.

2. The composition according to claim 1, wherein The resin powder is an aggregate of particles containing two or more resins having different melting points.

3. The composition according to claim 1 or 2, wherein In an endothermic energy curve obtained by differential scanning calorimetry of the resin powder, assuming that the exothermic peak temperature during crystallization is T3, 30° C. ≤ (T2−T3).

4. The composition according to claim 1 or 2, wherein The resin powder has a volume-based median particle size D50 of 30 to 150 μm.

5. The composition according to claim 1 or 2, wherein The average sphericity of the resin powder is 0.70-0.

98.

6. The composition according to claim 1 or 2, wherein The loose filling rate of the resin powder, that is, bulk density / true density, is 25-60%.

7. The composition according to claim 1 or 2, wherein The resin powder has a melt flow rate of 5 to 100 g / 10 minutes at 230° C.

8. A shaping method, wherein: The method comprises the step of forming a resin cured layer in a predetermined pattern using the composition according to claim 1 or 2.

9. A sculpture, wherein: The shaped object is obtained using the composition according to claim 1 or 2.

Images