3D printer slurry composition using si3n4

Abstract

Disclosed is a 3D printer slurry composition using Si3N4, which is based on the non-oxide ceramic material of Si3N4, is biocompatible, has excellent bacterial resistance, and has improved flexural strength, fracture toughness and the like. The disclosed 3D printer slurry composition using Si3N4 comprises 60 to 66 wt% of ceramic powder, 30 to 36 wt% of a photocurable binder, and 3 to 5 wt% of a dispersant, wherein the ceramic powder can comprise Si3N4 and a sintering additive.

Description

Slurry composition for 3D printers using SI3N4

[0001] The present invention relates to a slurry composition for a 3D printer using Si3N4, and more particularly, to a slurry composition for a 3D printer using Si3N4, a ceramic material, as a main raw material, and to a slurry composition for a 3D printer using Si3N4 that is biocompatible and has excellent mechanical properties when manufacturing orthopedic implants and the like using the same.

[0002]

[0003] Recently, 3D printing technology has been utilized to produce products with complex and intricate shapes without the use of molds. 3D printing technology selectively exposes a composite containing photocurable materials to ultraviolet or visible light, layering two-dimensional surfaces to create complex shapes.

[0004] According to a 2018 Gartner report, the use of 3D printing technology is expected to increase in the medical device, aircraft, consumer goods, and other manufacturing industries. Currently, 25% of medical devices in the healthcare industry use 3D printing technology. Accordingly, active research is underway to apply ceramic materials to 3D printing technology.

[0005] Ceramic materials are high value-added materials used in biomedical fields such as medical implants, artificial bones, and artificial teeth, as well as in structures, environments, and energy. Their application to 3D printing technology began in earnest in the 1980s with the development of the SLA (Stereolithography) method. However, commercialization has been limited to date due to the characteristics of ceramics compared to other materials (metals, polymers).

[0006] In other words, 3D printing technology using ceramic materials determines the size and mechanical properties of the final product through debinding and sintering. However, because excessive volume shrinkage and defects can occur during these processes, it has been difficult to commercialize compared to other materials.

[0007] However, while a lot of research has been conducted and commercialized recently, focusing on oxides such as zirconia (ZrO2), alumina (Al2O3), and calcium phosphate (HAP, TCP, etc.), mainly in the fields of orthopedics and dentistry, research on nitride and carbide ceramics such as Si3N4, SiC, and AlN, which are biocompatible and have excellent mechanical properties but are more difficult to laminate and sinter than oxide ceramics, is relatively lacking.

[0008] In addition, although research is actively being conducted to apply ceramic materials to 3D printing, the reality is that Spinal Cages as orthopedic implants are still manufactured using polymer or metal materials such as PEEK (Polyether ether ketone) or titanium (Ti).

[0009] Titanium material has excellent mechanical properties, so it does not break during the procedure. However, it is difficult to determine union with radiation due to X-ray scattering, and a stress shielding phenomenon can occur, which causes weakening and loss of bone tissue.

[0010] In addition, PEEK is a polymer material with excellent biocompatibility that can replace metal-based materials such as titanium, and can be manufactured through methods such as injection forming, molding, cutting, and extrusion. It is a thermoplastic resin with properties that are strong against impact and wear compared to general polymer materials, and has high mechanical strength, creep resistance, and fatigue resistance over a wide temperature range, and has excellent radiation stability. However, due to the limitations of polymer materials (relatively low mechanical properties), breakage may occur during surgery.

[0011] Therefore, there is a need to develop a ceramic material for 3D printers that is biocompatible, has excellent bacterial resistance, and has good mechanical properties like PEEK while maintaining mechanical properties similar to titanium.

[0012]

[0013] The present invention has been created in consideration of the above-described points, and is characterized by comprising 60 to 66 wt% of ceramic powder; 30 to 36 wt% of photocurable binder; and 3 to 5 wt% of dispersant, wherein the ceramic powder includes Si3N4 and a sintering additive, and the purpose of the present invention is to provide a slurry composition for a 3D printer using Si3N4, which is biocompatible, has excellent virus resistance, improves interlayer adhesion, and minimizes photocuring shrinkage, thereby having excellent mechanical properties when manufacturing an orthopedic implant using the same.

[0014]

[0015] In order to achieve the above-mentioned purpose, a slurry composition for a 3D printer utilizing Si3N4 according to the present invention comprises 60 to 66 wt% of ceramic powder; 30 to 36 wt% of a photocurable binder; and 3 to 5 wt% of a dispersant, wherein the ceramic powder comprises Si3N4 and a sintering additive.

[0016] In addition, the above Si3N4 and sintering additives are characterized in that they are included in an amount of 88 to 93 wt%: 7 to 12 wt% with respect to the total weight% of the ceramic.

[0017] In addition, the sintering additive is characterized by containing Al2O3 and Y2O3, or Al(NO3)39H2O and Y(NO3)36H2O.

[0018] In addition, the sintering additive is characterized in that it contains 2 to 5 wt%: 5 to 7 wt% of Al2O3 and Y2O3, or 2 to 5 wt%: 5 to 7 wt% of Al(NO3)39H2O and Y(NO3)36H2O, based on the total weight% of the ceramic powder.

[0019] In addition, the photocurable binder includes a photocurable initiator, a monofunctional monomer, a difunctional monomer, a monofunctional oligomer, and a difunctional oligomer,

[0020] The photocuring initiator, the monofunctional monomer, the difunctional monomer, the monofunctional oligomer, and the difunctional oligomer are characterized in that they are included in an amount of 0.5 to 1 wt%: 10 to 15 wt%: 10 to 15 wt%: 3 to 5 wt%: 3 to 5 wt% based on the total weight% of the slurry composition.

[0021] In addition, the monofunctional monomer and the difunctional monomer are included in a ratio of 1:1, and the monofunctional oligomer and the difunctional oligomer are also included in a ratio of 1:1.

[0022] In addition, the photocuring initiator is characterized in that it includes a long-wavelength initiator having a wavelength of 390 to 410 nm so that the slurry composition can laminate a thin film having a thickness of 30 to 50 μm per layer.

[0023] In addition, a sintered body manufactured using the slurry composition for a 3D printer of claims 1 to 8 is characterized in that it satisfies the conditions (a) to (c) below.

[0024] (a) Flexural strength of 500 MPa or more

[0025] (b) Vickers hardness of 1500 Hv or higher

[0026] (c) Fracture toughness 6.0 MPa·m 1 / 2 more

[0027]

[0028] The slurry composition for a 3D printer utilizing Si3N4 according to the present invention comprises 60 to 66 wt% of ceramic powder; 30 to 36 wt% of photocurable binder; and 3 to 5 wt% of dispersant, wherein the ceramic powder comprises Si3N4 and a sintering additive, and when using the same to manufacture an orthopedic implant, since it is based on Si3N4 as a non-oxide ceramic material, it is biocompatible, has high virus resistance, and provides excellent mechanical properties such as flexural strength and fracture toughness.

[0029]

[0030] Figure 1 is Si3N according to the present invention 4, A comparison of cell differentiation between Ti and PEEK is shown.

[0031] Figure 2 shows the curing thickness according to the photocuring initiator content of the monofunctional monomer according to the present invention.

[0032] Figure 3 shows the curing thickness according to the photocuring initiator content of the bifunctional monomer according to the present invention.

[0033] Figure 4 shows the curing thickness according to the photoinitiator content of the monofunctional monomer and the difunctional monomer according to the present invention.

[0034] Figure 5 shows a sample of a slurry composition for 3D printing according to the present invention stacked in the Z-axis direction.

[0035] Figure 6 shows the sintered density according to the content of the sintering additive according to the present invention.

[0036] Figure 7 shows the flexural strength according to the content of the sintering additive according to the present invention.

[0037] Figure 8 shows the Vickers hardness according to the content of the sintering additive according to the present invention.

[0038] Figure 9 shows the fracture toughness according to the content of the sintering additive according to the present invention.

[0039] Figure 10 shows XRD analysis according to the type of sintering additive of the present invention.

[0040] Figure 11 shows the sintering density according to the type of sintering additive of the present invention.

[0041] Figure 12 shows the viscosity according to the ceramic powder content of the present invention.

[0042] Figure 13 shows the density of a sintered body using the slurry composition of the present invention.

[0043] Figure 14 shows the flexural strength (horizontal stacked specimen) of a sintered body using the slurry composition of the present invention.

[0044] Figure 15 shows the flexural strength (vertical stacked specimen) of a sintered body using the slurry composition of the present invention.

[0045] Figure 16 shows the Vickers hardness of a sintered body using the slurry composition of the present invention.

[0046] Figure 17 shows the fracture toughness of a sintered body using the slurry composition of the present invention.

[0047] Figure 18 shows the flexural strength according to the layering thickness of a sintered body using the slurry composition of the present invention.

[0048]

[0049] All terms described in this specification are currently widely used and selected in consideration of the functions of the present invention. However, these terms may vary depending on the intentions of those skilled in the art, customs, or the emergence of new technologies. Furthermore, if the inventor specifies any term in the present invention, its meaning will be described in the description of the invention. Therefore, the terms used in the present invention should be interpreted based on the actual meaning of the term and the overall content described in the description of the present invention, rather than simply the name of the term.

[0050] Hereinafter, a slurry composition for a 3D printer utilizing Si3N4 according to an embodiment of the present invention will be described in detail with reference to the attached drawings. In order to clearly explain the present invention in the drawings, parts irrelevant to the description are omitted, and the same reference numerals will be used for identical or similar components throughout the specification.

[0051] The present invention provides a slurry composition for a 3D printer utilizing Si3N4.

[0052] A slurry composition for a 3D printer utilizing Si3N4 according to the present invention comprises 60 to 66 wt% of ceramic powder; 30 to 36 wt% of photocurable binder; and 3 to 5 wt% of dispersant, wherein the ceramic powder comprises Si3N4 and a sintering additive.

[0053] The present invention includes a ceramic powder. The ceramic powder is a main material used in manufacturing structures such as orthopedic implants using 3D printing. In addition, the ceramic powder includes Si3N4 and a sintering additive. Therefore, the ceramic composition may include 60 to 66 wt% based on the total weight% of the slurry composition. As another example, the ceramic powder may include 62 to 66 wt% based on the total weight% of the slurry composition. Therefore, when the content of the ceramic powder is below the range, mechanical properties may be deteriorated, and when it exceeds the range, it may cause a decrease in the content of other components, thereby deteriorating interlayer adhesion, etc. In addition, the Si3N4 and the sintering additive may be included in an amount of 88 to 93 wt%: 7 to 12 wt% based on the total weight% of the ceramic powder.

[0054] The above Si3N4 is included in the ceramic powder. The above Si3N4 is a chemically stable non-oxide ceramic material with excellent mechanical properties such as excellent corrosion resistance against wear and corrosion, flexural strength, and fracture toughness. Therefore, the above Si3N4 is mainly used in the automotive, aerospace, electronics, and medical industries.

[0055] In particular, in the medical industry, materials such as titanium and PEEK, which are compatible with the human body, are widely used in the manufacture of orthopedic implants. However, while titanium has excellent mechanical properties, it is difficult to judge union with radiation due to X-ray scattering, and a stress shielding phenomenon that causes bone tissue weakening and loss may occur. In addition, while PEEK (Polyether ether ketone) is an excellent biocompatible polymer, it has relatively low mechanical properties, which may cause breakage during surgery. Therefore, in the present invention, Si3N4, which is both biocompatible and has excellent mechanical properties, can be utilized.

[0056] Referring to Fig. 1, the Si3N4 material as an orthopedic implant material exhibits superior bacterial resistance compared to titanium or PEEK. In addition, it can be confirmed that the Si3N4 material exhibits excellent differentiation of osteoblasts on the surface.

[0057] Therefore, the Si3N4 may be included in an amount of 88 to 93 wt% based on the total weight of the ceramic powder. If the content of the Si3N4 is less than 88 wt%, the mechanical properties of the sintered body, such as flexural strength and fracture toughness, may deteriorate. In addition, if the content of the Si3N4 exceeds 93 wt%, the viscosity may increase, making it difficult to print a precise and defect-free laminate.

[0058] The above sintering additive is included in the ceramic powder to produce a dense sintered body. Any inorganic and organic acid salt containing aluminum and yttrium may be used as the sintering additive. In the present invention, the sintering additive is preferably Al2O3 and Y2O3, or may include Al(NO3)39H2O and Y(NO3)36H2O. In addition, the number of H2O contained in the Al(NO3)39H2O and Y(NO3)36H2O is not limited thereto. When Si3N4 is stabilized with the sintering additive, Si3N4 powder or the like can be produced in a granular form. The granular form can produce a dense sintered body by containing a relatively large amount of ceramic components in the slurry composition compared to the powder, thereby increasing the density.

[0059] Therefore, the sintering additive may be included in an amount of 7 to 12 wt% based on the total weight of the ceramic powder. If the content of the sintering additive is less than 7 wt%, it may be difficult to manufacture a dense sintered body, and if it exceeds 12 wt%, the mechanical properties of the sintered body, such as density, flexural strength, and fracture toughness, may deteriorate.

[0060] In addition, the Al2O3 and Y2O3 may be included in an amount of 2 to 5 wt%: 5 to 7 wt% based on the total weight% of the ceramic powder. Alternatively, the Al(NO3)39H2O and Y(NO3)36H2O may be included in an amount of 2 to 5 wt%: 5 to 7 wt% based on the total weight% of the ceramic powder. When the Al2O3 or the Al(NO3)39H2O is less than 2 wt%, it may be difficult to manufacture a dense sintered body, and when it exceeds 5 wt%, the liquid additive may remain at the grain boundaries, affecting the coarsening of the grains, which may deteriorate the mechanical properties. In addition, when the above Y2O3 or Y(NO3)36H2O is less than 5 wt%, it may be difficult to stabilize Si3N4, which may result in a deterioration in the mechanical properties of the sintered body, and when the Y2O3 or Y(NO3)36H2O is more than 7 wt%, it may be meaningless in terms of critical significance.

[0061] The present invention includes a photocurable binder. The photocurable binder can provide adhesion between a build plate and ceramic powder in a 3D printing process, control the viscosity of a slurry, and provide lamination stability. Accordingly, the photocurable binder includes a photocurable initiator, a monofunctional monomer, a difunctional monomer, a monofunctional oligomer, and a difunctional oligomer, and the photocurable initiator can be included in an amount of 0.5 to 1 wt% based on the total weight% of the slurry composition.

[0062] The above photocuring initiator is included in the photocuring binder to cure the lamination. The photocuring initiator can play a role in making a solid polymer by absorbing light when irradiated with ultraviolet rays or LED and emitting light in the form of radicals, thereby enabling bonding between monomers and oligomers. In particular, the photocuring initiator is greatly affected by the type of ceramic powder, and since non-oxide ceramic powder absorbs light during curing compared to oxide ceramic powder, an LED can be used as a light source for stable lamination, and a wavelength range of 390 to 410 nm can be selected. Therefore, the slurry composition of the present invention can include a long-wavelength initiator to laminate a thin film having a thickness of 30 to 50 μm per layer. When a long-wavelength initiator is used in the present invention, excellent interlayer adhesion can be secured by optimizing the thickness and curing speed of the thin film.

[0063] The above long-wavelength initiator may be selected from the phosphine oxide series. That is, the above long-wavelength initiator may be selected from at least one of 2,4,6-trimethylbenzoyl-diphenyl phosphine oxide or phosphine oxide.

[0064] Therefore, the photocuring initiator may be included in an amount of 0.5 to 1 wt% based on the total weight of the slurry composition. If the content of the photocuring initiator is less than 0.5 wt%, the adhesion of the laminated surface may be reduced due to insufficient bonding between the monomer and the oligomer. In addition, if the content of the photocuring initiator exceeds 1 wt%, the thickness of the thin film may increase, making it difficult to form a stable laminate.

[0065] The above photocurable monomer and photocurable oligomer are included in the photocurable binder. The photocurable monomer and photocurable oligomer may be included to form adhesive strength between ceramic powders. If only low-shrinkage photocurable monomers are included, the adhesive strength between the build plate (made of metal) and the ceramic powders is reduced, and if only the oligomer is used, the viscosity of the oligomer itself makes it difficult to contain a high content of ceramic powder, which may cause problems in increasing the packing density.

[0066] In addition, the photocurable monomer includes a monofunctional monomer and a difunctional monomer, and the photocurable oligomer includes a monofunctional oligomer and a difunctional oligomer. In the present invention, "monofunctional" and "difunctional" do not mean quantity, but refer to specific names. Since the monofunctional monomer, the difunctional monomer, the monofunctional oligomer, and the difunctional oligomer each include one functional group, the photocurable binder includes a total of four functional groups and can form cross-linked bonds. The cross-linked bond can significantly increase the bonding density between the monomer and the oligomer. Table 1 shows the viscosity of the photocurable monomer and the photocurable oligomer.

[0067] Photocurable monomer, photocurable oligomer, monofunctional monomer, bifunctional monomer, monofunctional oligomer, bifunctional oligomer, viscosity (cPs) at 20 ~ 25 ~ 10 ~ 204500 ~ 16000 10000 ~ 30000

[0068] Referring to Table 1, the viscosity of the monofunctional monomer and the difunctional monomer does not differ significantly, but the monofunctional monomer controls the curing speed, but there is a problem in that precise control is difficult because curing shrinkage occurs. The difunctional monomer has small curing shrinkage, but the thickness of the laminated thin film may be relatively low. Therefore, in order to solve the above problem, it may be preferable that the present invention includes the monofunctional monomer and the difunctional monomer in a ratio of 1:1.

[0069] In addition, the high viscosity monofunctional oligomer improves the adhesion between the build plate and the ceramic powder and between layers, but as the viscosity increases, it may be difficult to contain a high content of ceramic powder, which may make it difficult to increase the packing density. In addition, the high viscosity difunctional oligomer can control the viscosity of the slurry composition of the present invention to provide lamination stability. Therefore, in order to solve the above problem, it may be preferable that the present invention includes the monofunctional oligomer and the difunctional oligomer in a ratio of 1:1.

[0070] The above monofunctional monomer and difunctional monomer can be selected from products with excellent compatibility among the acrylate series. That is, the monofunctional monomer and the difunctional monomer are respectively stearyl acrylate, tetrahydrofufuryl acrylate, lauryl acrylate, ethoxylate(n) nonyl phenol acrylate, isodecyl acrylate, cycloaliphatic acrylate, methoxy polyethylene glycol monoacrylate, alkoxylated phenol acrylate, 1,6-hexanediol diacrylate, bisphenol A (EO)n diacrylate, and cyclohexane dimethanol. One or more of diacrylate (Cyclohexane dimethanol diacrylate) can be selected.

[0071] The above monofunctional oligomer and difunctional oligomer may each be selected from at least one of a urethane oligomer (e.g., urethane acrylate), an oligomer containing a phosphoric acid group (e.g., phosphoric acid-modified acrylate), an oligomer containing a carboxylic acid group (e.g., carboxylic acid-modified acrylate), and an epoxy oligomer (e.g., epoxy acrylate). In the present invention, in order to improve the adhesion between the build plate (made of metal) and the material during 3D printing and to provide lamination stability by controlling the viscosity of the slurry composition, the oligomer containing an acidic group may be selected from at least one of an oligomer containing a phosphoric acid group (e.g., phosphoric acid-modified acrylate), or an oligomer containing a carboxylic acid group (e.g., carboxylic acid-modified acrylate).

[0072] Therefore, the monofunctional monomer, the difunctional monomer, the monofunctional oligomer, and the difunctional oligomer may be included in an amount of 10 to 15 wt%: 10 to 15 wt%: 3 to 5 wt%: 3 to 5 wt% based on the total weight% of the slurry composition. When the content of the monofunctional monomer, the difunctional monomer, the difunctional oligomer, and the difunctional oligomer is less than the range, the adhesion between layers may decrease and curing shrinkage may occur during curing, thereby deteriorating mechanical properties. In addition, when the content of the monofunctional monomer, the difunctional monomer, the difunctional oligomer, and the difunctional oligomer exceeds the range, the viscosity increases, making it difficult to increase the content of the ceramic powder, thereby lowering the density, and thus deteriorating mechanical properties.

[0073] The present invention includes a dispersant. The dispersant may be included to uniformly disperse fine ceramic powder in a photocurable binder and prevent re-agglomeration. The dispersant is a conventional dispersant in the art, and may be selected from at least one of a copolymer compound having an acidic group, or a polyester or polyether compound having a phosphoric acid group and an amine group.

[0074] Therefore, the dispersant may be included in an amount of 3 to 5 wt% based on the total weight of the slurry composition. If the content of the dispersant is less than 3 wt%, the ceramic powder cannot be uniformly dispersed, which may make it difficult to produce a dense sintered body. In addition, if the content of the dispersant exceeds 5 wt%, the viscosity may decrease, thereby increasing the content of the ceramic powder, thereby producing a dense sintered body. However, this may cause a decrease in the content of other components, which may deteriorate mechanical properties such as flexural strength and fracture toughness.

[0075]

[0076] In this way, the slurry composition of the present invention is based on Si3N4, a non-oxide ceramic material that is biocompatible, has excellent virus resistance, and has excellent mechanical properties, and uses a photocurable binder to optimize adhesion between the build plate and the material during 3D printing, adhesion between layers, control of the thickness of the thin film according to curing, and viscosity control, thereby providing appropriate flowability and excellent interlayer adhesion in the 3D printed output, and can impart excellent flexural strength and fracture toughness when manufacturing orthopedic implants.

[0077]

[0078] Below, manufacturing examples and examples are provided. The following manufacturing examples and examples are provided solely to aid in understanding the present invention.

[0079]

[0080] <Manufacturing and testing examples>

[0081] [Manufacturing Examples 1 to 9]

[0082] A photoinitiator was mixed with a monofunctional monomer and a difunctional monomer according to the contents in Table 2 below, and then stirred in a stirrer at 300 rpm or more for 2 h to completely dissolve the photoinitiator, thereby preparing a mixture. The mixture and Si3N4 were mixed in a 1:1 ratio, and mixed using a paste mixer at 500 rpm for 10 min, and then mixed using an attrition mill at 500 rpm for 30 min to prepare a slurry composition. The slurry composition was laminated using a DLP 3D printing method to produce a 3D molded body.

[0083] Table 2 shows the contents of a photoinitiator, a monofunctional monomer, a difunctional monomer, and Si3N4. In the present invention, "MA-2" means a manufacturing example including 2 wt% of a photoinitiator in a monofunctional monomer, "MB-2" means a manufacturing example including 2 wt% of a photoinitiator in a difunctional monomer, and "M-AB-2" means a manufacturing example including 2 wt% of a photoinitiator in a monofunctional monomer and a difunctional monomer.

[0084] Photocurable binder Si3N4 (wt%) Photocurable initiator (wt%) Monofunctional monomer (wt%) Bifunctional monomer (wt%) Preparation example 1 (MA-2) 2980 100 Preparation example 2 (MA-3) 3970 100 Preparation example 3 (MA-4) 4960 100 Preparation example 4 (MB-2) 2098 100 Preparation example 5 (MB-3) 3097 100 Preparation example 6 (MB-4) 4096 100 Preparation example 7 (M-AB-2) 24949 100 Preparation example 8 (M-AB-3) 348.5 48.5 100 Preparation example 9 (M-AB-4) 44848 100

[0085]

[0086] [Experimental Example 1] - Optimization of photocurable initiators, monofunctional monomers, and difunctional monomers

[0087] Test method: In order to optimize the content of the photocuring initiator and monomer, the curing thickness of the 3D molded bodies manufactured in Manufacturing Examples 1 to 9 was measured according to a test conducted by an authorized certification agency to select the monomer composition.

[0088] [Test results]: Fig. 2 shows the curing thickness according to the photoinitiator content of the monofunctional monomer according to the present invention, Fig. 3 shows the curing thickness according to the photoinitiator content of the bifunctional monomer according to the present invention, and Fig. 4 shows the curing thickness according to the photoinitiator content of the monofunctional monomer and bifunctional monomer according to the present invention.

[0089] Referring to FIGS. 2 to 4, in Manufacturing Examples 1 to 9, it was confirmed that the difunctional monomer cured faster than the monofunctional monomer and that the cured thickness was thicker by 15 μm or more, but a lot of curing shrinkage occurred. On the other hand, it was confirmed that the monofunctional monomer had small curing shrinkage and relatively low curing thickness. Therefore, in the present invention, it was found that in Manufacturing Examples 7 to 9, in which the monofunctional monomer and the difunctional monomer were mixed at a 1:1 ratio, it was preferable to prevent curing shrinkage during 3D printing and to manufacture an output having an optimal curing thickness.

[0090] In addition, it was confirmed that the cured thickness increased as the content of the photocuring initiator increased. Therefore, it was confirmed that Manufacturing Examples 7 to 9, which included 0.5 to 1 wt% (in comparison to 100 wt% of the slurry composition of the present invention) of the photocuring initiator with respect to the total weight% of the slurry composition for stable lamination, were ideal, and Manufacturing Example 8 was the most preferable.

[0091]

[0092] [Manufacturing Examples 10 to 21]

[0093] Manufacturing Examples 10 to 15 were prepared by mixing a photoinitiator (0.7 wt% added relative to the total weight% of Table 2) with a monofunctional monomer, a difunctional monomer, a monofunctional oligomer, and a dispersant according to the contents of Table 3 below, and then stirring in a stirrer at 300 rpm or more for 2 h to completely dissolve the photoinitiator, and adding ceramic powder (Si3N) to the mixture. 4, A slurry composition was prepared by mixing (including sintering additives) and mixing at 500 rpm for 10 min using a paste mixer, and then mixing at 500 rpm for 30 min using an attrition mill. The slurry composition was laminated using a DLP 3D printing method to produce a 3D molded body.

[0094] In addition, Manufacturing Examples 16 to 21 were manufactured in the same manner as Manufacturing Examples 10 to 15, except that they were manufactured according to the contents in Table 4 below.

[0095] Tables 3 and 4 show the contents of ceramic powder, dispersant, monomer, and oligomer, as well as the viscosity and flexural strength. In the present invention, "Oli-A-2" means a manufacturing example including 2 wt% of a monofunctional oligomer, "Oli-AB-1" means a manufacturing example including 1 wt% of a difunctional oligomer, and "Oli-AB-4" means a manufacturing example including 4 wt% of a difunctional oligomer.

[0096] Ceramic powder (wt%) Dispersant (wt%) Monofunctional and bifunctional monomers (wt%) Monofunctional oligomer (wt%) Viscosity (cPs) Flexural strength (wt%) Manufacturing example 10 (Oli-A-0) 6043605,240 Manufacturing example 11 (Oli-A-2) 6043426,280 Manufacturing example 12 (Oli-A-4) 6043247,01038 Manufacturing example 13 (Oli-A-6) 6043067,99096 Manufacturing example 14 (Oli-A-8) 6042889,100122 Manufacturing example 15 (Oli-A-10) 604261010,70083

[0097] Ceramic powder (wt%) Dispersant (wt%) Monofunctional and bifunctional monomer (wt%) Monofunctional oligomer (wt%) Bifunctional oligomer (wt%) Viscosity (cPs) Flexural strength (wt%) Manufacturing example 16 (Oli-AB-0) 60428809, 100, 122 Manufacturing example 17 (Oli-AB-1) 60428719, 080, 153 Manufacturing example 18 (Oli-AB-2) 60428627, 820, 141 Manufacturing example 19 (Oli-AB-3) 60428537, 350, 146 Manufacturing example 20 (Oli-AB-4) 60428447, 000, 154 Manufacturing example 21 (Oli-AB-5) 60428356, 480, 133

[0098]

[0099] [Experimental Example 2] - Optimization of monofunctional and bifunctional oligomers

[0100] Test method: To optimize the oligomer content, 3*4*40mm specimens manufactured according to Table 3 below were stacked in the z-axis direction, and the viscosity and flexural strength (KS L ISO 14704) were measured.

[0101] Test results: Fig. 5 shows a specimen of a slurry composition for 3D printing according to the present invention laminated in the Z-axis direction.

[0102] Referring to FIG. 5 and Table 3, it was found that the viscosity of the slurry compositions of Preparation Examples 10 to 15 tended to increase as the content of the monofunctional oligomer increased. Preparation Examples 10 to 15 also showed that the flexural strength increased up to 8 wt% of the monofunctional oligomer content and then converged at 10 wt%. In addition, Preparation Examples 10 and 11 showed lamination failure, indicating that adhesion to the build plate was not achieved. Therefore, as the viscosity increases, it is difficult to increase the content of ceramic powder, which makes it impossible to increase the packing density, and post-lamination processes such as washing become difficult. Therefore, it was found that Preparation Example 14, in which the content of the monofunctional oligomer was 8 wt%, was the most ideal.

[0103] Also, referring to Table 4, the viscosity and flexural strength of Preparation Examples 16 to 21, in which a high-viscosity difunctional oligomer was added to control the viscosity of the slurry composition of the present invention, were evaluated, and it was confirmed that Preparation Example 20, in which a monofunctional oligomer and a difunctional oligomer were mixed in a 1:1 ratio, had a low viscosity of 7,000 cPs and excellent flexural strength. Therefore, it was confirmed that mixing a monofunctional oligomer and a difunctional oligomer in a 1:1 ratio is most ideal, and since the viscosity is low, it was confirmed that the slurry composition of the present invention can be manufactured with a higher packing density by adding more ceramic powder.

[0104]

[0105] [Manufacturing Examples 22 to 25]

[0106] Manufacturing Examples 22 to 25 were prepared by mixing a ceramic powder, a photocurable binder, and a dispersant according to the contents of Table 5 below, and then mixing ethanol as a solvent in a ratio of 1:1 with the mixture, and mixing for 12 h using a ball mill to prepare a slurry composition. The slurry composition was heated and stirred on a hot plate, sufficiently dried in a 90°C dryer, and then the dried powder was screened using a 325 mesh sieve. The powder was charged into a molding mold to form a 1 ton / cm 2 A sintered specimen was made by forming it using a uniaxial pressing method under pressure. The formed specimen was subjected to pressureless sintering at 1750°C to 1850°C for 2 h in a nitrogen atmosphere, and the pressure-sintered specimen was subjected to gas pressure sintering (GPS) at 1900°C for 2 h in a nitrogen atmosphere to produce a sintered body.

[0107] Table 5 shows the composition and contents of the slurry composition.

[0108] Composition of slurry composition Manufacturing example 22 (1A) Manufacturing example 23 (3A) Manufacturing example 24 (5A) Manufacturing example 25 (7A) Ceramic powder (wt%) Si3N46094609260906088 Sintering additive (wt%) Al2O31357Y2O35555 Photocurable binder (wt%) Photocurable initiator 0.50.50.50.51 Functional monomer 14.2514.2514.2514.252 Functional monomer 14.2514.2514.2514.2514.251 Functional oligomer 44442 Functional oligomer 44444 Dispersant (wt%) 3333

[0109]

[0110] [Experimental Example 3] - Optimization of Sintering Additives for Manufacturing Dense Sintered Bodies

[0111] Test method: Sintered density, flexural strength (KS L ISO 14704), Vickers hardness (KS L ISO 14705), and fracture toughness (KS L 1600) were measured according to the content of sintering additives.

[0112] Test results: Fig. 6 shows the sintered density according to the content of the sintering additive according to the present invention, Fig. 7 shows the flexural strength according to the content of the sintering additive according to the present invention, Fig. 8 shows the Vickers hardness according to the content of the sintering additive according to the present invention, and Fig. 9 shows the fracture toughness according to the content of the sintering additive according to the present invention.

[0113] Referring to FIG. 6 and Table 5, in Manufacturing Examples 22 to 25, Manufacturing Example 22 with 1 wt% Al2O3 had a relatively low sintered density, whereas Manufacturing Examples 23 to 25, which added 3 wt% or more of Al2O3 as a sintering additive, exhibited high sintered densities even at low temperatures, and it was confirmed that all Al2O3 compositions exhibited a high sintered density of 98% or more under 1900℃ GPS conditions. Therefore, it was found that the sintering additive was effective in improving the sinterability of Si3N4. On the other hand, Manufacturing Example 25 with 7 wt% Al2O3 showed that the excessive amount of sintering additive affected the coarsening of crystal grains, which could be the cause of the deterioration of mechanical properties. Therefore, it was found that Manufacturing Examples 23 and 24, which included 2 to 5 wt% of Al2O3 with respect to the total weight% of the ceramic powder, had excellent sintered density and mechanical properties.

[0114] Referring to FIGS. 7 to 9 and Table 5, it was found that, except for Manufacturing Example 22 with 1 wt% Al2O3, Manufacturing Examples 23 to 25 had excellent flexural strength, Vickers hardness, and fracture toughness. Specifically, the flexural strength of the sintered body of the slurry composition of the present invention showed a maximum of 1083 MPa in Manufacturing Example 24 with 5 wt% Al2O3 when the GPS process was applied, and it was confirmed that all other Manufacturing Examples showed a tendency to increase as the sintering temperature increased. In particular, it was confirmed that the strength was rapidly increased due to the increase in density in the specimens to which the GPS process was applied. The Vickers hardness showed a similar pattern to the sintered density, and was measured as 1521 Hv in Manufacturing Example 25 with 7 wt% Al2O3. On the other hand, fracture toughness showed a tendency to increase at a sintering temperature of 1750℃ to 1850℃ in all manufacturing examples, but it was confirmed that it decreased rapidly in the specimens applied with the GPS process. Therefore, when sintering using the slurry composition of the present invention, it was found that the sintering temperature was ideally 1750℃ to 1800℃ and the sintering additive Al2O3 was ideally 2 to 5 wt% based on the total weight% of the ceramic powder, considering the energy efficiency aspect.

[0115]

[0116] [Manufacturing Examples 26 and 27]

[0117] Manufacturing Examples 26 and 27 manufactured sintered bodies according to the contents of Table 6 below. However, Manufacturing Example 26 performed normal pressure sintering at 1600°C to 1800°C for 2 h in a nitrogen atmosphere, and Manufacturing Example 27 manufactured a sintered molded specimen, then performed a calcination process at 500°C for 1 h in a nitrogen atmosphere, and then performed normal pressure sintering at 1600°C to 1800°C for 2 h in a nitrogen atmosphere. Except this, the sintered bodies were manufactured in the same manner as Manufacturing Examples 22 to 25.

[0118] Table 6 shows the composition and contents of the slurry composition.

[0119] Composition of slurry composition Manufacturing example 26 (AY) Manufacturing example 27 (ANYN) Ceramic powder (wt%) Si3N4 (wt%) 60936093 Sintering additive (wt%) Al2O3 20 Y2O3 50 Al(NO3)39H2O0 2 Y(NO3)36H2O0 5 Photocurable binder (wt%) Photocurable initiator 0.5 0.5 1 Functional monomer 14.25 14.25 2 Functional monomer 14.25 14.25 1 Functional oligomer 44 2 Functional oligomer 44 Dispersant (wt%) 33

[0120]

[0121] [Test Example 4] - Sintered density according to sintering additives

[0122] Test method: Crystal phase analysis (XRD) and sintered density were measured according to the content of sintering additives. The sintering additives included Al2O3 and Y2O3, or Al(NO3)39H2O and Y(NO3)36H2O.

[0123] Test results: Fig. 10 shows XRD analysis according to the type of sintering additive of the present invention, and Fig. 11 shows sintered density according to the type of sintering additive of the present invention.

[0124] Referring to Fig. 10 and Table 6, in Manufacturing Examples 26 and 27, α and β phases coexisted until 1800°C, but after sintering, it was confirmed that most of the crystal phase transitioned to the β phase at 1800°C. In Manufacturing Examples 26 and 27, the change in crystal phase according to composition was not large, and it was confirmed that the transition from α to β was successful. In addition, it was found that the fraction of the β phase increased according to the sintering temperature.

[0125] Also, referring to FIG. 11 and Table 6, it was confirmed that in Manufacturing Examples 26 and 27, the sintered density greatly increased as the sintering temperature increased, and at 1800℃, a dense sintered body was manufactured with a relative density of 99% or more. In addition, Manufacturing Example 27 showed a relatively high sintered density compared to Manufacturing Example 26, and it was found that this was the result of smooth material movement during sintering of Si3N4 with a nitrate-based additive rather than an oxide-based additive. Therefore, in the present invention, the sintering additive may include 2 to 5 wt%: 5 to 7 wt% of the Al2O3 and Y2O3, or 2 to 5 wt%: 5 to 7 wt% of the Al(NO3)39H2O and Y(NO3)36H2O, based on the total weight% of the ceramic powder.

[0126]

[0127] [Manufacturing Examples 28 and 32] - Sintered body using slurry composition for 3D printer

[0128] In Manufacturing Examples 28 to 29, a photoinitiator was mixed with a monofunctional monomer, a difunctional monomer, a monofunctional oligomer, a difunctional oligomer, and a dispersant according to the contents in Table 7 below, and then the mixture was stirred in a stirrer at 300 rpm or more for 2 h to completely dissolve the photoinitiator, and a ceramic powder was mixed with the mixture, and mixed for 10 min at 500 rpm using a paste mixer, and then mixed for 30 min at 500 rpm using an attrition mill to prepare a slurry composition. The slurry composition was laminated using a DLP 3D printing method to manufacture a 3D molded body and separated. The separated molded body was first washed for 20 sec with a vacuum cleaner using ethanol as a washing solution, and then washed for 20 min with an ultrasonic cleaner. The washed molded body was degreased at 600°C for 1 h, and sintered at 1,700 to 1,850°C for each sintering temperature to manufacture a dense sintered body. Afterwards, sintering was performed at 1,500°C for 2 h for densification.

[0129] Table 7 shows the composition and contents of the slurry composition.

[0130] Composition of slurry composition Manufacturing example 28 (S_62) Manufacturing example 29 (S_64) Manufacturing example 30 (S_66) Manufacturing example 31 (S_68) Manufacturing example 32 (S_70) Ceramic powder (wt%) Si3N4 629 364 9366 9368 9370 93 Sintering additive Al2O3 22222 Y2O3 55555 Photocurable binder (wt%) Photocurable initiator Photocurable initiator 0.8 0.76 0.72 0.68 0.64 1 Functional monomer 1 Functional monomer 12.9 12. 2211.5410.8610.182Functional monomer2Functional monomer12.912.2211.5410.8610.181Functional oligomer1Functional oligomer3.83.63.43.232Functional oligomer2Functional oligomer3.83.63.43.23Dispersant(wt%)3.83.63.43.23

[0131]

[0132] [Test Example 5] - Viscosity

[0133] Test method: During the production of sintered bodies of Manufacturing Examples 28 to 32, before manufacturing a 3D molded body by laminating using the DLP 3D printing method, the viscosity of the slurry composition mixed using a paste mixer and an attrition mill was measured. The viscosity was measured using a rotational viscometer at a spindle rotation speed of 10 rpm and a torque value of 15%.

[0134] Test results: Fig. 12 shows the viscosity according to the ceramic powder content of the present invention.

[0135] Referring to FIG. 12 and Table 7, it was confirmed that the viscosity of Preparation Examples 28 to 32 increased as the content of the ceramic powder increased, and Preparation Examples 31 and 32, in which the content of the ceramic powder was 68 wt% or more, showed a viscosity of 20,000 cPs or more. Specifically, Preparation Examples 28 to 30, in which the content of the ceramic powder was 66 wt% or less, showed a small increase in viscosity, but Preparation Examples 31 and 32, in which the content of the ceramic powder was more than 66 wt, showed a viscosity increase of about 33% or more. Therefore, since a viscosity of 20,000 cPs or less is recommended in order to print a defect-free laminate, the content of the ceramic powder in the present invention may include 60 to 66 wt% with respect to the total weight% of the slurry composition.

[0136]

[0137] [Test Example 6] - Sintered body density

[0138] Test method: The density of the sintered bodies of Manufacturing Examples 29 to 31 was measured. The density of the sintered bodies was measured by measuring the density and apparent pores of fine ceramic sintered bodies (KS L ISO 18754).

[0139] Test results: Fig. 13 shows the density of a sintered body using the slurry composition of the present invention.

[0140] Referring to Fig. 13 and Table 7, it was found that the relative density of Manufacturing Examples 29 to 31 was 99% or higher at a sintering temperature of 1800°C or higher. This was because the distance between ceramic powder particles became closer as the content of ceramic powder increased, facilitating material transfer. On the other hand, Manufacturing Example 31, in which the content of ceramic powder was outside the range of the present invention, showed the highest relative density, but had a problem of delamination occurring between layers during lamination, which was found to affect the flexural strength.

[0141]

[0142] [Test Example 7] - Flexural Strength

[0143] Test method: The flexural strength specimens of Manufacturing Examples 29 to 31 were post-processed to a thickness of 3 mm and a width of 4 mm to remove surface defects after sintering. The post-processed specimens were measured for strength (KS L ISO 14704) of 10 specimens with a span distance of 20 mm using equipment (UTM), and the average and standard deviation were obtained.

[0144] Test results: Fig. 14 shows the flexural strength (horizontal stacked specimen) of a sintered body using the slurry composition of the present invention, and Fig. 15 shows the flexural strength (vertical stacked specimen) of a sintered body using the slurry composition of the present invention.

[0145] Referring to FIGS. 14 and 15 and Table 7, it was found that the flexural strength of Manufacturing Examples 29 to 31 tended to increase as the sintering temperature increased. In addition, it was found that the flexural strength converged to a maximum value at a sintering temperature of 1800°C. Therefore, it was found that the sintering temperature was ideally 1750 to 1800°C to exhibit excellent flexural strength. Specifically, it was confirmed that the flexural strength of the vertically laminated specimen (FIG. 15) was reduced by about 5% compared to the horizontally laminated specimen (FIG. 14). On the other hand, in the case of Manufacturing Example 31 with a ceramic powder content of 68 wt%, it was found that the flexural strength of the vertically laminated specimen (FIG. 15) was reduced by about 30 to 40% compared to the horizontally laminated specimen (FIG. 14). It was found that this was because the high ceramic powder content caused the interlayer adhesion to decrease during lamination, resulting in defects.

[0146] Therefore, it was found that the flexural strength of the sintered bodies of Manufacturing Examples 29 and 30 using the slurry composition of the present invention was 500 MPa or more.

[0147]

[0148] [Test Example 8] - Vickers hardness and fracture toughness

[0149] Test method: In order to measure the Vickers hardness (KS L ISO 14705) and fracture toughness (KS L 1600) of the sintered bodies of Manufacturing Examples 29 to 31, the surface of the sintered bodies was polished to a mirror-like state using diamond paste to prepare specimens, and then the hardness was measured using a Vickers hardness tester. The fracture toughness was measured using the IF method using a Vickers hardness tester.

[0150] Test results: Fig. 16 shows the Vickers hardness of a sintered body using the slurry composition of the present invention, and Fig. 17 shows the fracture toughness of a sintered body using the slurry composition of the present invention.

[0151] Referring to FIGS. 16, 17, and Table 7, the Vickers hardness of the sintered bodies of Manufacturing Examples 29 to 31 showed a similar trend to the density, and it was confirmed that they were all 1500 Hv or higher at a sintering temperature of 1750°C or higher. In addition, the fracture toughness of Manufacturing Examples 29 to 31 showed a tendency to slightly decrease after increasing with the sintering temperature from 1700 to 1800°C, while it was confirmed that it significantly decreased at a sintering temperature of 1850°C. This was found to be due to an increase in the brittleness of the material as the hardness increased at a sintering temperature higher than 1800°C.

[0152] Therefore, when the sintering temperature of Manufacturing Examples 29 and 30 using the slurry composition of the present invention is 1750 to 1800°C, the Vickers hardness of the sintered body is 1500 Hv or more, and the fracture toughness is 6.0 MPa·m 1 / 2 I could tell it was abnormal.

[0153]

[0154] [Test Example 9] - Flexural strength (depending on laminate thickness)

[0155] Test method: In order to analyze the effect of the laminated layer thickness on the strength, sintered bodies having laminated thicknesses of 30 ㎛, 40 ㎛, 50 ㎛, and 60 ㎛ were manufactured using the composition of Manufacturing Example 30, and then the flexural strength (KS L ISO 14704) was measured.

[0156] Test results: Fig. 18 shows the flexural strength according to the laminated thickness of a sintered body using the slurry composition of the present invention.

[0157] Referring to Fig. 18 and Table 7, the strength of the horizontally laminated specimens did not show a significant difference depending on the thickness of the laminate, but in the case of the vertically laminated specimens, it was confirmed that the strength was reduced by approximately 45% at a laminate thickness of 60 μm. This was found to be due to the occurrence of delamination when laminating 60 μm thick slurry with a cured thickness of 60 μm under the lamination conditions.

[0158] Therefore, when manufacturing a sintered body using the slurry composition of the present invention, it was found that laminating with a hardening thickness of 30 to 50 ㎛ resulted in excellent mechanical properties.

[0159]

[0160] [Example 10] - Washing

[0161] Test method: During the manufacture of the sintered body of Manufacturing Example 30, a 3D molded body was manufactured by laminating using the DLP 3D printing method, and then separated. A cleaning process test was conducted using an ultrasonic cleaner and a vacuum cleaner, using ethanol as the cleaning liquid. The ultrasonic cleaner was set to a frequency of 40 kHz and an output of 200 W, and the vacuum cleaner was set to a rotation speed of 1000 rpm.

[0162] Test results: Referring to Table 8, in the case of ultrasonic cleaning, it was confirmed that the strength decreased when it was performed for more than 25 minutes. In addition, in the case of the pre-vacuum cleaner, there was no significant decrease in strength, but it was confirmed that chipping occurred at the corners of the specimen after 30 seconds. It was found that the cleaning power of the ultrasonic cleaner is reduced in structures with micro-holes, but it was easy to clean in the pre-vacuum cleaner. Therefore, in the case of spinal cages, which are sintered bodies and are orthopedic implants, it was found that it is desirable to first clean them using a pre-vacuum cleaner and then second clean them with an ultrasonic cleaner because they have less chipping due to the lack of sharp corners.

[0163] Table 8 shows the strength according to washing time.

[0164] Ultrasonic cleaner time (min) 510 1520 2530 Intensity (MPa) 896 876 90 582 175 6719 Ultrasonic cleaner time (sec) 5 sec 10 sec 15 sec 20 sec 25 sec 30 sec Intensity (MPa) 873 853 887 872 84 1815 Note-----chipping

[0165]

[0166] In this way, the slurry composition for a 3D printer utilizing Si3N4 according to an embodiment of the present invention is a composition that is biocompatible, has excellent virus resistance, and has excellent mechanical properties, and is an excellent composition for manufacturing orthopedic implants such as spinal cages.

[0167]

[0168] The embodiments described above are merely illustrative, and those skilled in the art will readily appreciate various modifications and equivalent alternative embodiments. Therefore, the true scope of technical protection of the present invention should be determined by the technical spirit of the invention as set forth in the claims.

Claims

1. In the slurry composition for 3D printer, Ceramic powder 60 to 66 wt%; 30 to 36 wt% of photocurable binder; and Contains 3 to 5 wt% of dispersant, A slurry composition for a 3D printer utilizing Si3N4, characterized in that the above ceramic powder comprises Si3N4 and a sintering additive.

2. In paragraph 1, A slurry composition for a 3D printer utilizing Si3N4, characterized in that the above Si3N4 and sintering additives are included in an amount of 88 to 93 wt%: 7 to 12 wt% based on the total weight% of the ceramic powder.

3. In paragraph 1, A slurry composition for a 3D printer utilizing Si3N4, characterized in that the sintering additive comprises Al2O3 and Y2O3, or Al(NO3)39H2O and Y(NO3)36H2O.

4. In paragraph 3, A slurry composition for a 3D printer utilizing Si3N4, characterized in that the sintering additive comprises 2 to 5 wt%: 5 to 7 wt% of the Al2O3 and Y2O3, or 2 to 5 wt%: 5 to 7 wt% of the Al(NO3)39H2O and Y(NO3)36H2O, based on the total weight% of the ceramic powder.

5. In paragraph 1, The above photocurable binder comprises a photocurable initiator, a monofunctional monomer, a difunctional monomer, a monofunctional oligomer, and a difunctional oligomer, A slurry composition for a 3D printer utilizing Si3N4, characterized in that the photocuring initiator, the monofunctional monomer, the difunctional monomer, the monofunctional oligomer, and the difunctional oligomer are included in an amount of 0.5 to 1 wt%: 10 to 15 wt%: 10 to 15 wt%: 3 to 5 wt%: 3 to 5 wt% based on the total weight % of the slurry composition.

6. In paragraph 5, A slurry composition for a 3D printer utilizing Si3N4, characterized in that the monofunctional monomer and the difunctional monomer are included in a ratio of 1:1, and the monofunctional oligomer and the difunctional oligomer are also included in a ratio of 1:

1.

7. In paragraph 5, A slurry composition for a 3D printer utilizing Si3N4, characterized in that the photocuring initiator includes a long-wavelength initiator having a wavelength of 390 to 410 nm, so that the slurry composition can laminate a thin film having a thickness of 30 to 50 μm per layer.

8. A sintered body manufactured using the slurry composition for a 3D printer according to any one of claims 1 to 8, characterized in that it satisfies the conditions (a) to (c) below. A slurry composition for a 3D printer utilizing Si3N4. (a) Flexural strength of 500 MPa or more (b) Vickers hardness of 1500 Hv or higher (c) Fracture toughness 6.0 MPa·m 1 / 2 more

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