Resin particle for three-dimensional printer

Abstract

The present invention provides resin particles for a three-dimensional printer that make it possible to obtain a three-dimensional shaped object with excellent rigidity and elasticity. The resin particles for a three-dimensional printer according to the present invention comprise first resin particles and second resin particles. The first resin particles include: a homopolyolefin HP1b obtained using a monomer M1b having 3 to 4 carbon atoms; a homopolyolefin HP1a that is obtained using a monomer M1a having 2 to 3 carbon atoms and is present in a lump-like form within the homopolyolefin HP1b; and a random copolymer of the monomer M1a and the monomer M1b that coats the homopolyolefin HP1a. The second resin particles include: a random copolymer of a monomer M2a having 2 to 3 carbon atoms and a monomer M2b having 3 to 4 carbon atoms; and a homopolyolefin HP2b that is incompatible with a homopolyolefin HP2a obtained using the monomer M2a and is obtained using the monomer M2b having 3 to 4 carbon atoms. The content of the homopolyolefin HP1a in the first resin particles is 2-25 mass%. The sum of the content of the random copolymer and the content of the homopolyolefin HP2b in the second resin particles is more than 92 mass%. The monomer M1b has more carbon atoms than the monomer M1a.

Description

Resin particles for 3D printers

[0001] The present invention relates to resin particles for three-dimensional printers.

[0002] Three-dimensional printers, which create three-dimensional objects using additive manufacturing technology based on three-dimensional digital data, are expected to be put to practical use in a variety of fields. One method for manufacturing three-dimensional objects using a 3D printer is the additive manufacturing method using powder sintering.

[0003] Resin particles used in the powder sintering lamination method are known to be those obtained by melt-kneading a thermoplastic resin and a styrene-based resin (see, for example, Patent Document 1).

[0004] JP 2009-040870 A

[0005] In resin particles in which a thermoplastic resin and a styrene-based resin are melt-kneaded, the thermoplastic resin and the styrene-based resin are highly compatible with each other and are mixed together, so the resulting three-dimensional object has high yield elongation, impact resistance, and flexural modulus, but does not have sufficient tensile strength.

[0006] The present invention has been made in view of the above-mentioned problems, and has as its object to provide resin particles for use in three-dimensional printers that can produce three-dimensional objects having excellent rigidity and elasticity.

[0007] One aspect of the present invention is resin particles for a three-dimensional printer, the resin particles for a three-dimensional printer comprising first resin particles and second resin particles, the first resin particles comprising homopolyolefin HP1b obtained using a monomer M1b having 3 to 4 carbon atoms, homopolyolefin HP1a present in the homopolyolefin HP1b in the form of clumps and obtained using a monomer M1a having 2 to 3 carbon atoms, and a random copolymer of the monomer M1a and the monomer M1b coating the homopolyolefin HP1a, and the second resin particles comprising a monomer M2a having 2 to 3 carbon atoms and a random copolymer of the monomer M2a having 3 to 3 carbon atoms. and a homopolyolefin HP2b obtained using a monomer M2b having 3 to 4 carbon atoms and which is incompatible with the homopolyolefin HP2a obtained using the monomer M2a, wherein the content of the homopolyolefin HP1a in the first resin particles is 2 to 25% by mass, the sum of the content of the random copolymer and the content of the homopolyolefin HP2b in the second resin particles exceeds 92% by mass, and the monomer M1b has a larger number of carbon atoms than the monomer M1a.

[0008] In the resin particles for a three-dimensional printer of the above aspect, the mixing ratio of the first resin particles to the second resin particles may be 20 / 80 to 70 / 30. The ratio of the particle size of the first resin particles to the particle size of the second resin particles may be 1 / 3 to 3 / 1. The mixing ratio of the random copolymer to the homopolyolefin HP2b in the second resin particles may be 3 / 97 to 50 / 50.

[0009] The second resin particles may contain a compatibilizer. The content of the compatibilizer relative to the total amount of the second resin particles may be 0.5 to 5.0 mass %. The compatibilizer may be one or more selected from the group consisting of acid-modified polypropylene, acid-modified polyethylene, and acid-modified ethylene-butene copolymer.

[0010] The second resin particles may contain a sintering aid. The content of the sintering aid relative to the total amount of the second resin particles may be 0.1 to 3.0 mass %. The sintering aid may be carbon particles. The average particle size of the carbon particles may be 10 to 50 nm.

[0011] The second resin particles may contain a fluidity-imparting agent. The content of the fluidity-imparting agent relative to the total mass of the second resin particles may be 0.1 to 5.0 mass %. The fluidity-imparting agent may be one or more selected from the group consisting of silica, mica, talc, titanium oxide, and fatty acid salts.

[0012] According to the present invention, it is possible to provide a technology relating to resin particles for use in three-dimensional printers, which can produce three-dimensional objects having excellent rigidity and elasticity.

[0013] Hereinafter, embodiments of the present invention will be described in detail. In this specification, the expression "a to b" in the description of a range of values ​​means that the range is from a to b, unless otherwise specified.

[0014] (Resin Particles for Three-Dimensional Printers) Resin particles for three-dimensional printers according to the embodiment include first resin particles and second resin particles.

[0015] <First Resin Particles> The first resin particles contain homopolyolefin HP1b obtained using a monomer M1b having 3 to 4 carbon atoms, homopolyolefin HP1a which is present in the form of chunks in the homopolyolefin HP1b and which is obtained using a monomer M1a having 2 to 3 carbon atoms, and a random copolymer of the monomer M1a and the monomer M1b which coats the homopolyolefin HP1a.

[0016] By using a monomer M1a having 2 to 3 carbon atoms, the crystallinity can be reduced, which makes it easier to relax stress in a three-dimensional object (hereinafter, sometimes referred to as a "formed object") obtained using the resin particles for a 3D printer according to the embodiment, and thereby increases elasticity. Examples of the monomer M1a include ethylene and propylene.

[0017] The use of a monomer M1b having 3 to 4 carbon atoms can enhance the rigidity and elasticity of the resulting shaped object. Examples of the monomer M1b include propylene and butene.

[0018] The content of homopolyolefin HP1a in the first resin particles is 2 to 25% by mass. By setting the lower limit of the content within the above range, the elasticity of the resulting shaped object can be increased. By setting the upper limit of the content within the above range, the rigidity of the resulting shaped object can be increased. Furthermore, the powder flowability during heating can be made sufficient, which in turn allows the resulting shaped object to be denser.

[0019] The monomer M1b has a larger number of carbon atoms than the monomer M1a, which makes it easier for crazes to form when an external stress is applied to the resulting shaped object, and as a result, impact energy is absorbed, resulting in increased elasticity.

[0020] <Second Resin Particles> The second resin particles contain a random copolymer of a monomer M2a having 2 to 3 carbon atoms and a monomer M2b having 3 to 4 carbon atoms, and a homopolyolefin HP2b which is incompatible with the homopolyolefin HP2a obtained using the monomer M2a and which is obtained using the monomer M2b having 3 to 4 carbon atoms.

[0021] By using a monomer M2a having 2 to 3 carbon atoms, the elasticity of the resulting shaped article can be increased and warping of the shaped article can be suppressed. Examples of the monomer M2a include ethylene and propylene.

[0022] The use of a monomer M2b having 3 to 4 carbon atoms can enhance the rigidity and elasticity of the resulting shaped object. Examples of the monomer M2b include propylene and butene.

[0023] The sum of the content of the random copolymer and the content of the homopolyolefin HP2b in the second resin particles is more than 92 mass %, which can increase the rigidity of the resulting shaped article.

[0024] The mixing ratio of the first resin particles to the second resin particles (content of first resin particles / content of second resin particles) is preferably 20 / 80 to 70 / 30, more preferably 20 / 80 to 60 / 40, and even more preferably 20 / 80 to 50 / 50. By keeping the mixing ratio within the above range, the elasticity of the resulting shaped object can be improved.

[0025] The ratio of the particle size of the first resin particles to the particle size of the second resin particles is preferably 1 / 3 to 3 / 1, and more preferably 1 / 2 to 2 / 1. By setting the lower limit of this ratio to the above value, it is possible to obtain a sufficient restoring force due to interfacial tension, thereby improving rigidity. By setting the upper limit of this ratio to the above value, stress concentration is reduced, making it easier to obtain elasticity. The particle sizes of the first resin particles and the second resin particles can be measured using a laser diffraction particle size distribution analyzer (Malvern Instruments, Mastersizer 3000, wet dispersion unit Hydro MV).

[0026] The mixing ratio of the random copolymer to the homopolyolefin HP2b in the second resin particles is preferably 3 / 97 to 50 / 50, more preferably 5 / 95 to 40 / 60, and even more preferably 7 / 93 to 35 / 70. By setting the lower limit of the mixing ratio within the above range, the elasticity of the resulting shaped object can be increased and warpage can be suppressed. By setting the upper limit of the mixing ratio within the above range, the rigidity of the resulting shaped object can be increased.

[0027] (Compatibilizer) The second resin particles preferably contain a compatibilizer. Examples of the compatibilizer include one or more selected from the group consisting of acid-modified polypropylene, acid-modified polyethylene, and acid-modified ethylene-butene copolymer. The content of the compatibilizer relative to the total amount of the second resin particles is preferably 0.5 to 5.0 mass%, more preferably 0.5 to 3.0 mass%, and even more preferably 0.5 to 2.0 mass%. By setting the lower limit of the content to the above value, compatibility with fillers such as sintering aids can be improved, thereby increasing the rigidity of the resulting shaped object. By setting the upper limit of the content to the above value, the rigidity and elasticity of the second resin particles themselves can be increased.

[0028] (Sintering Aid) The second resin particles preferably contain a sintering aid. Examples of sintering aids include carbon particles such as carbon black. This improves laser absorption and increases the amount of heat generated, making it easier to melt adjacent resin particles. Furthermore, by making it easier to melt the resin, the resulting molded object can be made denser and have increased rigidity and elasticity.

[0029] The average particle size (volume average diameter D50) of the carbon particles is preferably 10 to 50 nm. The average particle size of the carbon particles can be measured using the Otsuka Electronics Co., Ltd. Zeta Potential / Particle Size Measurement System ELS-Z Series. By setting the lower limit of the average particle size to the above value, the dispersibility of the carbon particles can be improved. Furthermore, by preventing the specific surface area of ​​the carbon particles from becoming too large, the melt viscosity of the carbon particles can be maintained at an appropriate level. As a result, gaps between resin particles for 3D printers are more easily filled during modeling, thereby increasing the strength of the resulting modeled object. Furthermore, the number or area of ​​interfaces with the resin that serve as the starting point for fracture can be reduced, thereby increasing the strength of the resulting modeled object. By setting the upper limit of the average particle size to the above value, heat can be more easily transferred uniformly to the resin during laser irradiation. Furthermore, stress concentration on the carbon particles is reduced, thereby increasing the strength of the resulting modeled object.

[0030] The content of the sintering aid relative to the total amount of the second resin particles is preferably 0.1 to 3.0 mass%, more preferably 0.2 to 2.0 mass%, and even more preferably 0.3 to 1.0 mass%. By setting the lower limit of the content within the above range, it is possible to enhance laser absorption, make the structure of the resulting shaped object denser, and increase the strength of the resulting shaped object. By setting the upper limit of the content within the above range, it is possible to reduce the likelihood of fracture at the interface between the sintering aid and the resin, thereby increasing the strength of the resulting shaped object.

[0031] (Fluidity-imparting material) The second resin particles preferably contain a fluidity-imparting material. Examples of the fluidity-imparting material include one or more selected from the group consisting of silica, mica, talc, titanium oxide, and fatty acid salts. The inclusion of such a fluidity-imparting material can enhance the fluidity of the powder made of resin particles for 3D printers, making it easier for the resin particles for 3D printers to be densely packed. As a result, a dense structure can be more easily obtained after modeling, and the elasticity and rigidity of the modeled object can be increased.

[0032] The content of the fluidity-imparting agent relative to the total amount of the second resin particles is preferably 0.1 to 5.0% by mass, more preferably 0.2 to 3.0% by mass, and even more preferably 0.3 to 2.0% by mass. By setting the lower limit of the content to the above value, the fluidity of the powder made of resin particles for 3D printers can be increased, making it easier to densely pack the resin particles for 3D printers. As a result, a dense structure can be easily obtained after modeling, and the elasticity and rigidity of the model can be increased. By setting the upper limit of the content to the above value, the fluidity-imparting agent can be prevented from interfering with the fusion of the resin particles for 3D printers, thereby increasing the strength of the model.

[0033] (Method for Producing Resin Particles for 3D Printers) Regarding methods for producing resin particles for 3D printers according to the embodiment, there are various methods, including a melt granulation method in which a resin composition melted near its melting point is fibrous and then cut; a pulverization method in which a resin material composed of a resin composition is cut or destroyed by applying impact or shear; and a method in which a resin incompatible with a fusible matrix component is dispersed in the matrix component and then the matrix component is removed to produce resin particles. To improve the flowability of the powder, it is preferable that the powder has a rounded shape, i.e., a high degree of circularity. Therefore, to obtain powders with such a suitable shape, it is preferable to select a powdering method suitable for the thermoplastic resin contained in the resin powder for the powder additive manufacturing method of this embodiment. Furthermore, when powdering is performed by pulverization, a classification process may be performed after pulverization to remove elongated powder from the pulverized powder and increase the circularity. In this case, classification methods include air classification and sieve classification.

[0034] (Production of Modeled Object) The resin particles for 3D printers according to the embodiment are suitable for use in producing a three-dimensional model by the powder sintering lamination method, which includes the following steps: <Powder Spreading Step> Using a mechanism such as a wiper, the resin particles for 3D printers stored in a tank are moved onto the stage of the printer, and a thin layer of the resin particles for 3D printers is formed on the stage. <Laser Irradiation Step> The resin particles for 3D printers on the stage are irradiated with laser light in accordance with the 3D data of the model, causing the resin particles for 3D printers to melt and sinter together. <Lamination Step> After the stage is lowered by one layer, the step of forming a thin layer of the resin particles for 3D printers and the laser irradiation step are sequentially repeated, similar to the powder spreading step, to obtain the desired three-dimensional model.

[0035] Although the embodiments of the present invention have been described above, these are merely examples of the present invention, and various other configurations can also be adopted.

[0036] EXAMPLES The present invention will be described below with reference to examples and comparative examples, but the present invention is not limited to these.

[0037] Resin particles for 3D printers were prepared using the blending amounts of each component shown in Tables 2 and 3. Specifically, for the first resin particles, the monomer M1a was selected from ethylene, propylene, and butene. The monomer M1b was selected from ethylene, propylene, butene, and pentene. The content of homopolyolefin HP1a was selected from 1.0 mass%, 5.0 mass%, 20.0 mass%, and 30.0 mass%. The combination of monomer M1a and monomer M1b in the random copolymer was selected from ethylene-ethylene, propylene-propylene, ethylene-propylene, ethylene-butene, propylene-butene, and ethylene-pentene. For the second resin particles, the monomer M2a was selected from ethylene and propylene. The monomer M2b was selected from ethylene, propylene, butene, and pentene. The combination of monomer M1a and monomer M1b in the random copolymer was selected from ethylene-ethylene, propylene-propylene, ethylene-propylene, ethylene-butene, propylene-butene, and ethylene-pentene. The sum of the content of the random copolymer and the content of homopolyolefin HP2b was selected from 90.5% by mass and 98.5% by mass. The mixing ratio of the random copolymer to homopolyolefin HP2b was selected from 0.02, 0.05, 0.23, 0.97, and 1.19. The type of compatibilizer was acid-modified polypropylene, and the content was selected from 0.2% by mass, 1.0% by mass, 4.0% by mass, and 6.0% by mass. The type of sintering aid was carbon black, and the average particle size was selected from 6 nm, 26 nm, and 60 nm, and the content was selected from 0.05% by mass, 0.5% by mass, 2.0% by mass, and 4.0% by mass. Silica was selected as the fluidity imparting agent, and the content was selected from 0.05 mass%, 0.5 mass%, 4.0 mass%, and 6.0 mass%. The mixing ratio of the first resin particles to the second resin particles was selected from 0.2, 0.5, 2.0, and 2.5. The particle size combinations of the first resin particles and the second resin particles were selected from 12 μm-62 μm, 31 μm-62 μm, 62 μm-62 μm, 155 μm-62 μm, and 217 μm-62 μm.

[0038] (Flexural modulus) A test piece with a width of 10 mm, a length of 80 mm (X direction), and a thickness of 4 mm was prepared using a powder bed fusion 3D printer (RaFaEl II 150C-HT) manufactured by Aspect Inc. The flexural modulus in the X direction was measured using a Tensilon universal testing machine (TENSIRON TRG-1250) manufactured by A&D Co., Ltd. Specifically, in accordance with JIS K7171 (2016), a three-point bending test was performed under conditions of a support distance of 64 mm and a test speed of 2 mm / min to determine the flexural modulus. The measurement temperature was room temperature (23 ° C), the number of measurements was n = 5, and the average value was calculated. Based on the results obtained for the flexural modulus, evaluation was performed according to the following evaluation criteria. The results obtained for the flexural modulus are shown in Tables 2 and 3. A: 1500 MPa or more B: 1300 or more and less than 1500 MPa C: 1000 or more and less than 1300 MPa D: Less than 1000 MPa

[0039] (Charpy Impact Strength) Unnotched Charpy impact strength was measured using a Charpy impact tester manufactured by Shimadzu Corporation in accordance with K7111-1 (2012). The measurement temperature was room temperature (23°C), the number of measurements was n=5, and the average value was calculated. Based on the results obtained for Charpy impact strength, evaluation was performed according to the following evaluation criteria. The results obtained for Charpy impact strength are shown in Tables 2 and 3. A: 10 kJ / m ２ More than B: 8kJ / m ２ 10kJ / m or more ２ Less than C: 6 kJ / m ２ 8kJ / m or more ２ Less than D: 6 kJ / m ２ less than

[0040] (Overall Evaluation) The resin particles for three-dimensional printers of each Example and each Comparative Example were subjected to an overall evaluation according to the evaluation criteria shown in Table 1. The results of the overall evaluation are shown in Tables 2 and 3.

[0041]

[0042]

[0043]

[0044] By using the resin particles for three-dimensional printers of the present invention as a printing material for a three-dimensional printer, a three-dimensional object having excellent rigidity and elasticity can be obtained. CROSS-REFERENCE TO RELATED APPLICATIONS

[0045] This application claims priority based on Japanese Patent Application No. 2023-222391, filed with the Japan Patent Office on December 28, 2023, the entire disclosure of which is incorporated herein by reference in its entirety.

Claims

1. It has first resin particles and second resin particles, the first resin particles include a homopolyolefin HP1b obtained using a monomer M1b having 3 to 4 carbon atoms, a homopolyolefin HP1a obtained using a monomer M1a having 2 to 3 carbon atoms and present in a lump in the homopolyolefin HP1b, and a random copolymer of the monomer M1a covering the homopolyolefin HP1a and the monomer M1b; the second resin particles include a random copolymer of a monomer M2a having 2 to 3 carbon atoms and a monomer M2b having 3 to 4 carbon atoms, and are incompatible with a homopolyolefin HP2a obtained using the monomer M2a, and include a homopolyolefin HP2b obtained using the monomer M2b having 3 to 4 carbon atoms; the content of the homopolyolefin HP1a in the first resin particles is 2 to 25% by mass; the sum of the content of the random copolymer and the content of the homopolyolefin HP2b in the second resin particles is more than 92% by mass; the monomer M1b has more carbon atoms than the monomer M1a; resin particles for a 3D printer.

2. The resin particles for a 3D printer according to claim 1, wherein the mixing ratio of the first resin particles and the second resin particles is 20 / 80 to 70 / 30.

3. The resin particles for a 3D printer according to claim 1 or 2, wherein the ratio of the particle size of the first resin particles to the particle size of the second resin particles is 1 / 3 to 3 / 1.

4. The resin particles for a 3D printer according to claim 1 or 2, wherein the mixing ratio of the random copolymer and the homopolyolefin HP2b in the second resin particles is 3 / 97 to 50 / 50.

5. The resin particles for a 3D printer according to claim 1 or 2, wherein the second resin particles contain a compatibilizer.

6. The resin particles for a 3D printer according to claim 5, wherein the content of the compatibilizer with respect to the entire second resin particles is 0.5 to 5.0% by mass.

7. The resin particles for a 3D printer according to claim 5, wherein the compatibilizer is one or more selected from the group consisting of acid-modified polypropylene, acid-modified polyethylene, and acid-modified ethylene-butene copolymer.

8. The resin particles for a 3D printer according to claim 1 or 2, wherein the second resin particles contain a sintering aid.

9. The resin particles for a 3D printer according to claim 8, wherein the content of the sintering aid with respect to the entire amount of the second resin particles is 0.1 to 3.0% by mass.

10. The resin particles for a 3D printer according to claim 8, wherein the sintering aid is carbon particles.

11. The resin particles for a 3D printer according to claim 10, wherein the average particle diameter of the carbon particles is 10 to 50 nm.

12. The resin particles for a 3D printer according to claim 1 or 2, wherein the second resin particles contain a flowability-imparting material.

13. The resin particles for a 3D printer according to claim 12, wherein the content of the flowability-imparting material with respect to the entire amount of the second resin particles is 0.1 to 5.0% by mass.

14. The resin particles for a 3D printer according to claim 12, wherein the flowability-imparting material is at least one selected from the group consisting of silica, mica, talc, titanium oxide, and fatty acid salts.

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