JP2022153896A - Core resin composition and method for producing sintered body - Google Patents

Abstract

To provide a resin composition for a core that can form cavity part in the inside of a sintered body.SOLUTION: The core resin composition according to the embodiment is used, when producing a sintered body by molding a laminate structure using a 3-dimensional printer using a composition for sintered body containing an inorganic powder and an organic binder, and degreasing and sintering the laminate structure to produce a sintered body, as a material for a core for forming cavity part in the inside of the sintered body. The core resin composition contains a crosslinked polymer particle (A) and an organic binder (B) comprising a thermoplastic resin (B1).SELECTED DRAWING: None

Description

An embodiment of the present invention relates to a core resin composition used as a core material for forming a cavity inside a sintered body, and a method for producing a sintered body using the same.

As a technology for manufacturing ceramic products and metal products by a three-dimensional printer, the material extrusion laminating method (MEX) (also referred to as the hot melt lamination method: FDM) is known. For example, in Patent Document 1, a compound for a three-dimensional printer made by adding an organic binder to an inorganic powder such as a ceramic powder or a metal powder is used to form a laminated structure with a three-dimensional printer using a material extrusion lamination method. , followed by degreasing and sintering to obtain a sintered body.

WO2020/003901

When forming a laminated structure with a three-dimensional printer that uses a material extrusion lamination method to obtain a sintered body with an internal cavity, the forming path along which the nozzle that ejects the molten material moves is drawn in the form of a bridge. A cavity can be formed by In that case, however, gravity causes the ejected material to sag. In addition, when the laminated structure is softened during degreasing after molding, the cavity may sag. Therefore, it is conceivable to use a core that supports the shape of the hollow portion so as not to cause sagging. It is desirable that such a core be molded together with the laminated structure by a three-dimensional printer and removed in a degreasing or sintering process after molding.

In view of the above points, an embodiment of the present invention can form a cavity inside the sintered body when manufacturing a sintered body by degreasing and sintering a laminated structure with a three-dimensional printer, An object of the present invention is to provide a resin composition from which a core suitable for degreasing can be obtained.

The present invention includes embodiments shown below.
[1] When manufacturing a sintered body by modeling a laminated structure with a three-dimensional printer using a sintered body composition containing an inorganic powder and an organic binder, and degreasing and sintering the laminated structure , a resin composition used as a core material for forming a cavity inside the sintered body, the organic binder (B) containing crosslinked polymer particles (A) and a thermoplastic resin (B1) and a core resin composition containing:
[2] The core resin according to [1], wherein the thermoplastic resin (B1) contains a thermoplastic resin (B10) having a thermal decomposition temperature lower than that of the crosslinked polymer particles (A). Composition.
[3] The crosslinked polymer particles (A) have a thermal decomposition temperature higher than the thermal decomposition temperature of at least one thermoplastic resin contained in the organic binder of the sintered body composition [1] or The core resin composition according to [2].
[4] The core according to any one of [1] to [3], wherein the crosslinked polymer particles (A) have a thermal decomposition temperature lower than the maximum temperature at which the laminated structure is degreased. Resin composition.
[5] Any one of [1] to [4], wherein the mass ratio of the crosslinked polymer particles (A) and the organic binder (B) is (A)/(B) = 100/35 to 100/105 1. The core resin composition according to claim 1.
[6] The core resin composition according to any one of [1] to [5], which has a residue of less than 0.1% by mass when heated at 1000° C. in air.
[7] A method for producing a sintered body made of ceramics, cermet or metal, wherein a laminated structure is formed by a three-dimensional printer using a sintered body composition containing an inorganic powder and an organic binder, [ 1] to shape a core with a three-dimensional printer using the resin composition for a core according to any one of [6]; A method for producing a sintered body, comprising heating and degreasing the laminated structure together with the core, and sintering the degreased laminated structure to obtain a sintered body having a cavity inside.
[8] Using the composition for a sintered body and the resin composition for a core, a three-dimensional printer is used to shape the core arranged inside the laminated structure together with the laminated structure, [7] The method for producing a sintered body according to 1.

In the core resin composition according to the embodiment of the present invention, by blending crosslinked polymer particles together with an organic binder containing a thermoplastic resin, sagging during degreasing is suppressed and a cavity is formed inside the sintered body. It can be formed and can provide a core suitable for degreasing.

(A) is a plan view of a laminated structure in an example, and (B) is a side view.

A core resin composition according to an embodiment contains crosslinked polymer particles (A) and an organic binder (B) containing a thermoplastic resin (B1), and contains an inorganic powder and an organic binder. A cavity is formed inside the sintered body when a laminated structure is formed by a three-dimensional printer using a composition for a sintered body, and the laminated structure is degreased and sintered to produce a sintered body. It is used as a core material for By providing the core, it is possible to support the inner wall surface of the laminated structure, which becomes the hollow portion, and to prevent sagging during molding.

Further, degreasing is a process of heating the laminated structure to thermally decompose and remove the organic binder in the laminated structure. While the body becomes more deformable, as the degreasing process approaches the end of the degreasing process, the laminated structure is given a strength capable of maintaining its shape even without a core. According to the present embodiment, the crosslinked polymer particles (A) are used for the core, and unlike thermoplastic resins, the crosslinked polymer particles (A) are not plasticized by heating, so the laminated structure is easily deformed in the degreasing process. The body can be supported, and deformation of the laminated structure can be suppressed. Moreover, since the crosslinked polymer particles (A) and the organic binder (B) that constitute the core are organic substances, they can be removed by thermal decomposition in the degreasing step or the sintering step.

The crosslinked polymer particles (A) are resin fine particles having a crosslinked structure, and examples thereof include crosslinked acrylic resin particles, crosslinked urethane resin particles, crosslinked styrene resin particles, and the like. can be used.

The crosslinked acrylic resin particles are crosslinked particles having a (meth)acrylic acid ester monomer as a main structural unit (50% by mass or more of the structural unit; the same shall apply hereinafter). Examples of the crosslinked acrylic resin particles include crosslinked poly(meth)acrylates such as crosslinked polymethyl(meth)acrylate, crosslinked polyethyl(meth)acrylate, crosslinked poly(meth)acrylate, and crosslinked poly(meth)acrylate). ) particles of alkyl acrylate (the alkyl group preferably has 4 or less carbon atoms), and may be crosslinked acrylic copolymer particles containing other monomers such as styrene as a copolymerization component. Here, "(meth)acrylate" represents acrylate or methacrylate, and "(meth)acrylic acid" represents acrylic acid or methacrylic acid.

Crosslinked urethane resin particles are crosslinked particles composed of a urethane resin having a urethane bond and/or a urea bond. Crosslinked styrene resin particles are crosslinked particles having a styrene-based monomer as a main structural unit.

The crosslinked polymer particles (A) are preferably spherical particles, that is, crosslinked polymer beads, more preferably spherical particles. Although the average particle size of the crosslinked polymer particles (A) is not particularly limited, it is preferably 1 to 200 μm, more preferably 1 to 50 μm, still more preferably 1 to 30 μm. As used herein, the average particle size means the particle size at an integrated value of 50% in the particle size distribution obtained using a Coulter counter (for example, a precision particle size distribution analyzer sold by Beckman Coulter, Inc.). .

The crosslinked polymer particles (A) preferably have a thermal decomposition temperature higher than the thermal decomposition temperature of at least one thermoplastic resin contained in the organic binder (D) of the composition for sintered bodies described below. That is, the organic binder (D) of the composition for a sintered body contains one or more thermoplastic resins, and the crosslinked polymer particles (A) are more thermoplastic than at least one thermoplastic resin. A high decomposition temperature is preferred. With such a high thermal decomposition temperature, when degreasing a laminated structure formed from the composition for a sintered body, it is possible to support the laminated structure to a temperature at which it does not deform, and deformation of the laminated structure can be achieved. can be effectively suppressed.

The thermal decomposition temperature of the crosslinked polymer particles (A) is preferably lower than the maximum temperature at which the laminated structure is degreased. Thereby, the crosslinked polymer particles (A) can be removed by thermal decomposition in the degreasing step of the laminated structure.

The thermal decomposition temperature of the crosslinked polymer particles (A) is preferably 200 to 600°C, more preferably 230 to 550°C, still more preferably 250 to 500°C. In this specification, the thermal decomposition temperature is measured using a differential thermal analysis device (for example, a thermogravimetric analysis/differential thermal analysis measurement device sold by Rigaku Co., Ltd.), diameter 5 mm × height 2.5 mm aluminum pan under an air flow of 200 mL/min with a temperature rise of 10° C./min, and the value of 50% by mass of the total weight loss can be determined as the thermal decomposition temperature.

The organic binder (B) contained in the core resin composition contains a thermoplastic resin (B1). Examples of the thermoplastic resin (B1) include acrylic resins, atactic polystyrene (atactic PS), polycarbonate (PC), amorphous polyolefins, acrylonitrile-butadiene-styrene (ABS) and other amorphous polymers, and ethylene-vinyl acetate. Crystalline polymers such as copolymer (EVA), polyethylene (PE), polypropylene (PP), polyacetal (POM), polyamide (PA), polybutylene terephthalate (PBT), polyethylene terephthalate (PET), polylactic acid (PLA) is mentioned. These can be used either singly or in combination of two or more.

Among these, as the thermoplastic resin (B1), it is preferable to use at least one thermoplastic resin (B11) selected from amorphous polymers and EVA, and the thermoplastic resin (B11) is used as a main component. , and at least one thermoplastic resin (B12) selected from crystalline polymers other than EVA may be used in combination.

Although the ratio of the thermoplastic resin (B11) contained in the thermoplastic resin (B1) is not particularly limited, it is preferably 50% by mass or more, more preferably 70% by mass or more, and still more preferably 90% by mass. or more, and particularly preferably 95% by mass or more.

As the thermoplastic resin (B11), it is preferable to use two or more types selected from the group consisting of acrylic resin, atactic PS, amorphous polyolefin, and EVA. More preferably, acrylic resin and at least one selected from the group consisting of atactic PS, amorphous polyolefin and EVA are used.

PP and/or POM are preferably used as the thermoplastic resin (B12).

The thermoplastic resin (B1) used in the core resin composition is preferably of the same type as the thermoplastic resin used in the sintered body composition described below. Therefore, when ceramic powder such as metal oxide powder or cermet powder is used as the inorganic powder for the sintered body composition, it is preferable to use an acrylic resin and atactic PS together as the thermoplastic resin (B1). EVA and/or amorphous polyolefin may be combined with this, and more preferably, acrylic resin, atactic PS and EVA are used together. The mass ratio of these is preferably 20 to 100 parts by mass, more preferably 30 to 80 parts by mass, of the atactic PS with respect to 100 parts by mass of the acrylic resin. When EVA is used, it is preferably 5 to 200 parts by mass, more preferably 10 to 50 parts by mass, with respect to 100 parts by mass of the acrylic resin.

Further, when a metal powder is used as the inorganic powder of the composition for a sintered body, it is preferable to use an acrylic resin and EVA in combination as the thermoplastic resin (B1), and further atactic PS and/or PP can be combined. preferable. The mass ratio of EVA is preferably 10 to 200 parts by mass, more preferably 80 to 150 parts by mass, with respect to 100 parts by mass of the acrylic resin, and the atactic PS is 0 to 200 parts by mass. It is preferably 50 to 150 parts by mass, and 0 to 200 parts by mass of PP, more preferably 30 to 100 parts by mass.

Examples of acrylic resins include polymers of (meth)acrylic esters, which are esters of (meth)acrylic acid and alcohols having 1 to 8 carbon atoms, and copolymers of (meth)acrylic esters with other monomers. A polymer etc. are mentioned. The weight average molecular weight (Mw) of the acrylic resin is not particularly limited, and may be, for example, about 10,000 to 350,000 or about 20,000 to 100,000. In this specification, the weight average molecular weight can be determined using GPC (gel permeation chromatography).

Specific examples of (meth)acrylates include n-alkyl (meth)acrylates having 1 to 8 carbon atoms in the alkyl group, isopropyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate and the like. Among these, n-alkyl (meth)acrylates having 1 to 4 carbon atoms in the alkyl group such as methyl (meth)acrylate and n-butyl (meth)acrylate, isopropyl (meth)acrylate, and isobutyl (meth)acrylate At least one selected from the group consisting of acrylates is preferred.

Copolymers of (meth)acrylic acid esters and other monomers include, for example, ethylene-vinyl acetate copolymers and ethylene-ethyl acrylate copolymers as described in JP-A-2000-303103. A polymer, (meth)acrylic acid ester alone or a mixture of (meth)acrylic acid ester and styrenic monomer, and a polymerization initiator solution are dispersed and suspended in an aqueous medium containing a dispersant. Composite acrylic resins obtained by polymerization may be mentioned.

As the atactic PS, those having a weight average molecular weight (Mw) of about 100,000 to 300,000 are preferably used, and those having a weight average molecular weight of about 150,000 to 250,000 are more preferably used.

It is more preferable to use EVA with a low degree of crystallinity (for example, one with a degree of crystallinity of 25% or less). Since the crystallinity of EVA correlates with the vinyl acetate (VA) content, preferable EVA has a vinyl acetate content (mass percentage: JISK7192:1999) of 20% to 50%, more preferably 25% to 40%. of EVA. Further, it is preferable to use one having a weight average molecular weight of about 30,000 to 120,000, more preferably about 50,000 to 100,000.

PP having a weight average molecular weight of about 100,000 to 400,000, more preferably about 200,000 to 300,000 is used.

As the thermoplastic resin (B1), it is preferable to use a thermoplastic resin (B10) having a thermal decomposition temperature lower than that of the crosslinked polymer particles (A). Since the thermal decomposition temperature of the crosslinked polymer particles (A) is high in this way, it is possible to support the laminated structure up to a temperature at which the laminated structure is not deformed when the laminated structure is degreased. can be effectively suppressed. When using a plurality of types of thermoplastic resins (B1), all the thermoplastic resins (B1) may be the thermoplastic resin (B10), but have a thermal decomposition temperature higher than the thermal decomposition temperature of the crosslinked polymer particles (A). A thermoplastic resin (B100) may be partially included. In that case, the thermoplastic resin (B10) preferably accounts for 30% by mass or more of the thermoplastic resin (B1), more preferably 35% by mass or more of the thermoplastic resin (B1), and 40 to 70% by mass. may be the thermoplastic resin (B10).

The content ratio of the thermoplastic resin (B1) contained in the organic binder (B) is not particularly limited. It is preferably 35 to 85% by mass, more preferably 40 to 80% by mass, from the viewpoint of suppressing stringing when moving to a position and suppressing deformation in the degreasing step.

The organic binder (B) preferably contains a wax (B2) in order to improve the fluidity of the core resin composition. The wax (B2) may be synthetic or natural, and specific examples thereof include paraffin wax, microcrystalline wax, polyethylene wax, beeswax, carnauba wax, montan wax, polyalkylene glycol, and the like. can be used either singly or in combination of two or more. The content of the wax (B2) contained in the organic binder (B) is not particularly limited, and may be 7 to 40% by mass, 7 to 35% by mass, 10 to 30% by mass, or 15 to 25% by mass. % by mass may be used.

The organic binder (B) may contain a lubricant (B3) in order to improve the fluidity of the core resin composition. Specific examples of the lubricant (B3) include fatty acids and their derivatives (esters, amides, etc.), and these can be used singly or in combination of two or more. Preferred lubricants include stearic acid and its esters (eg, sorbitan monostearate). The content of the lubricant (B3) contained in the organic binder (B) is not particularly limited, and may be 0 to 18% by mass, 0 to 16% by mass, or 0 to 15% by mass.

The organic binder (B) may contain other additives (B4). Other additives (B4) include, for example, plasticizers, antioxidants, metal deactivators, ultraviolet absorbers, and nucleating agents.

Examples of plasticizers include phthalates, adipates, trimellitates, diisononyl 1,2-cyclohexanedicarboxylate, bis(2-ethylhexyl) 4-cyclohexene-1,2-dicarboxylate, and glycol benzoate. esters, phosphate esters, and the like. Antioxidants include, for example, phenolic antioxidants.

In the core resin composition, the mass ratio of the crosslinked polymer particles (A) and the organic binder (B) is preferably (A)/(B)=100/35 to 100/105. When the amount of the organic binder (B) is 35 parts by mass or more relative to 100 parts by mass of the crosslinked polymer particles (A), the fluidity of the core resin composition can be increased during lamination molding by a three-dimensional printer. In addition, the adhesiveness between the core resin compositions can be enhanced, and the adhesiveness between the core resin composition and the sintered body composition can be enhanced, and the formability by a three-dimensional printer can be improved. can. Further, when the amount of the organic binder (B) is 105 parts by mass or less, the support property in the degreasing step can be improved. A more preferable mass ratio is (A)/(B)=100/40 to 100/100, and more preferably (A)/(B)=100/45 to 100/95.

The core resin composition preferably has a residue (heated residue) of less than 0.1% by mass, more preferably 0, under heating conditions of 1000° C. in the atmosphere so that no residue remains after the sintering process. less than 0.05% by weight. As a result, it is possible to reduce the residue inside the cavity after the sintering process. Especially when forming a closed space as the cavity, it is impossible to remove the residue in the cavity after sintering. Therefore, it is preferable that the heating residue is as small as possible. In order to reduce or eliminate the heating residue, the amount of inorganic elements contained in the core resin composition should be reduced to eliminate the inorganic elements. For example, the content of inorganic elements determined by a standard addition method using ICP-MS (inductively coupled plasma mass spectrometer) is preferably less than 0.1% by mass, more preferably less than 0.05% by mass. Here, the inorganic elements are elements other than oxygen, carbon, hydrogen and nitrogen, and include elements such as sodium, potassium, calcium, magnesium, phosphorus and sulfur that remain as residues after sintering.

The method for producing the core resin composition is not particularly limited, and it can be prepared by melt-kneading the crosslinked polymer particles (A) and the organic binder (B). Examples of the kneader used for melt-kneading include a pressure kneader, a twin-arm kneader kneader, a Banbury kneader, and a single-screw or twin-screw kneading extruder.

The shape of the core resin composition is not particularly limited, but in one embodiment, it may be in the form of pellets. For example, pelletization is performed by cutting the extruded melt after kneading into pellets in air with a rotary cutter. may be

The core resin composition according to the present embodiment is used to form a laminated structure with a three-dimensional printer using the sintered body composition for manufacturing a sintered body made of an inorganic material such as ceramics, cermet, or metal. It is used as a core material when

A composition containing an inorganic powder (C) and an organic binder (D) is used as the sintered body composition, and is not particularly limited, but as an embodiment, the composition described in Patent Document 1 can be used. can be done.

Specifically, examples of the inorganic powder (C) include metal powder, ceramic powder, and cermet powder. Specific examples of metal powders include powders of pure iron, iron-nickel, iron-cobalt, iron-silicon, iron-based alloys such as stainless steel, tungsten, aluminum alloys, copper, and copper alloys. Ceramic powders include oxides such as _{Al2O3 ,} BeO and ZrO2; carbides such as TiC, ZrC, _B4C and tungsten carbide ₍ WC); borides such as CrB and _ZrB2 ; Powders such as nitrides can be mentioned. Examples of cermet powders include powders of cemented carbide (WC--Co based alloys, etc.), Al ₂ O ₃ -Fe-based, TiC--Ni-based, TiC--Co-based, and B ₄ C--Fe-based powders. These may be used singly or in combination of two or more.

The average particle size of the inorganic powder (C) is not particularly limited, and may be, for example, 0.05 to 30 μm or 0.1 to 10 μm. In this specification, the average particle size of the inorganic powder (C) means the particle size at an integrated value of 50% in the particle size distribution determined using a laser diffraction/scattering method (Microtrac particle size measuring device: MT3100II). .

The organic binder (D) contains a thermoplastic resin (D1) and may further contain wax (D2), lubricant (D3) and other additives (D4). In order to match the degreasing patterns of the laminated structure made of the sintered body composition and the core made of the core resin composition, the organic binder (D) of the sintered body composition and the core resin composition It is preferable that the organic binder (B) in the above consists of the same components.

Examples of the thermoplastic resin (D1) include acrylic resins, atactic PS, PC, amorphous polyolefins, non-crystalline polymers such as ABS, EVA, and the like, similar to the thermoplastic resin (B1) used in the core resin composition. Crystalline polymers such as PE, PP, POM, PA, PBT, PET, PLA are included. As described above, the thermoplastic resin (D1) used in the sintered body composition and the thermoplastic resin (B1) used in the core resin composition preferably have the same component. ) and combinations thereof are as described for the thermoplastic resin (B1).

As an example, when ceramic powder such as metal oxide powder or cermet powder is used as inorganic powder (C), acrylic resin and atactic PS are preferably used in combination as thermoplastic resin (D1), and EVA is used as the thermoplastic resin (D1). And/or amorphous polyolefin may be used in combination, and more preferably, acrylic resin, atactic PS and EVA are used in combination. The mass ratio of these is preferably 20 to 100 parts by mass, more preferably 30 to 80 parts by mass, of the atactic PS with respect to 100 parts by mass of the acrylic resin. Further, when EVA is used, it is preferably 5 to 200 parts by mass, more preferably 7 to 100 parts by mass, and further preferably 10 to 50 parts by mass with respect to 100 parts by mass of the acrylic resin. preferable.

When a metal powder is used as the inorganic powder (C), the thermoplastic resin (D1) is preferably an acrylic resin and EVA, and more preferably atactic PS and/or PP. The mass ratio of these is preferably 30 to 200 parts by mass, more preferably 80 to 150 parts by mass, for EVA with respect to 100 parts by mass for acrylic resin, and 0 to 200 parts by mass for atactic PS. It is preferably 50 to 150 parts by mass, and 0 to 200 parts by mass of PP, more preferably 30 to 100 parts by mass.

Concerning the wax (D2), the lubricant (D3) and other additives (D4), the specific examples and content ratio thereof are described in the wax (B2), the lubricant (B3) and other additives used in the core resin composition. It is as having explained about the agent (B4).

In the composition for sintered bodies, the mass ratio of the inorganic powder (C) and the organic binder (D) is preferably (C)/(D)=100/3 to 100/30. For example, when the inorganic powder (A) is a ceramic powder, the mass ratio (A)/(B) is preferably 100/10 to 100/25, more preferably 100/12 to 100/20. is. When the inorganic powder (A) is a metal powder or a cermet powder, the mass ratio (A)/(B) is preferably 100/3 to 100/13, more preferably 100/4 to 100/ 10.

The resin composition for a core according to the embodiment is used to form a core for forming a cavity with a three-dimensional printer when forming a laminated structure using a composition for a sintered body with a three-dimensional printer. be done. Therefore, in the method for producing a sintered body according to the embodiment, a laminated structure is formed by a three-dimensional printer using a composition for a sintered body, and a core is formed by a three-dimensional printer using a core resin composition. heating and degreasing the laminated structure together with the core in a state where the core is arranged inside the laminated structure; and sintering the degreased laminated structure to form a cavity inside obtaining a sintered body having a

Preferably, the core is a thermal decomposition type core that is shaped together with the laminated structure by a three-dimensional printer so as to be arranged inside the laminated structure, and is thermally decomposed in a degreasing or sintering step after modeling. , a cavity can be formed inside the sintered body. Accordingly, a method for manufacturing a sintered body according to a preferred embodiment includes the following steps.
(1) A step of forming a laminate structure together with a core by a three-dimensional printer using the resin composition for a core and the composition for a sintered compact;
(2) a step of heating and degreasing the laminated structure together with the core;
(3) A step of sintering the degreased laminated structure.

As a three-dimensional printer, for example, it is possible to use a printer that can form a three-dimensional structure while heating and fluidizing a molding material and discharging it from a nozzle to laminate it. (Thermal fusion lamination method: FDM) various three-dimensional printers.

In step (1), a three-dimensional printer having a plurality of nozzles is used to heat and fluidize the composition for sintered bodies and the resin composition for cores, and discharge the sintered bodies from the respective nozzles. Based on the data, the layered structure and the core are formed using the composition for the core and the resin composition for the core, respectively, based on the data. As a result, a laminated structure in which a core is arranged in a portion to be a hollow portion inside the laminated structure can be obtained, and sagging of the inner wall surface of the laminated structure during modeling can be suppressed. In one embodiment, when forming a closed space cut off from the outside as a cavity, the core is formed in a state of being buried in the laminated structure so as not to appear on the surface of the laminated structure.

The heating temperature for fluidizing the composition for a sintered body and the resin composition for a core is not particularly limited as long as the composition can be fluidized without thermal decomposition, and may be, for example, 100 to 200°C. .

In step (2), the laminated structure having the core thus obtained is heated to be degreased. Since the degreasing step is usually a step of removing organic substances by thermal decomposition, the organic binder (D) contained in the laminated structure, the crosslinked polymer particles (A) and the organic binder (B) contained in the core are also heated. Removed by decomposition. The crosslinked polymer particles (A) may remain after the degreasing step as long as they can be eliminated in the subsequent sintering step, but preferably disappear after the degreasing step.

In the degreasing step, the softening of the thermoplastic resin (D1) contained in the laminated structure makes the laminated structure more susceptible to deformation. On the other hand, as the degreasing process comes to an end, the laminated structure is given strength enough to maintain its shape without the core. According to the present embodiment, since the crosslinked polymer particles (A) used for the core are not plasticized by heating, the inner wall surface of the laminated structure can be supported to a temperature at which the laminated structure is less likely to deform in the degreasing step. It is possible to suppress the sagging. In addition, since the crosslinked polymer particles (A) and the organic binder (B) that constitute the core can be removed by thermal decomposition in the degreasing process or the sintering process, a process for removing the core is not necessary.

The degreasing conditions can be appropriately set according to the type of the inorganic powder (C) contained in the laminated structure. For example, when the inorganic powder (C) is a ceramic powder such as zirconia or alumina, degreasing may be performed by raising the temperature to around 450 to 550° C. at a rate of 5 to 20° C./h in air. When the inorganic powder (C) is a metal powder, degreasing may be performed by raising the temperature to around 450 to 550° C. at a rate of 5 to 20° C./h in an inert gas atmosphere.

In step (3), the laminated structure after the degreasing step is sintered. The sintering conditions can be appropriately set according to the type of inorganic powder (C) and the like. For example, when the inorganic powder (C) is a ceramic powder such as zirconia or aluminum, sintering may be performed by raising the temperature to 1300 to 1700° C. at a rate of 40 to 120° C./h in the air. When the inorganic powder is metal powder or cermet powder, sintering may be performed by raising the temperature to 1300 to 1400° C. at a temperature elevation rate of 40 to 160° C./h in an inert gas atmosphere.

By performing sintering in this way, a sintered body made of ceramics, cermet or metal is obtained.

According to this embodiment, by using the core as described above, support can be provided not only during modeling with a three-dimensional printer but also during degreasing. After sintering, the core disappears due to thermal decomposition, so that a cavity corresponding to the shape of the core can be formed inside the sintered body. Therefore, it is possible to form even a hermetic cavity having a complicated shape.

In addition, various numerical ranges including the above-described compounding amounts and viscosities can be arbitrarily combined with their upper and lower limits, and all combinations thereof are described herein as preferred numerical ranges. It is assumed that there is

The present invention will be described in more detail with reference to examples below, but the present invention is not limited to the following examples.

<Raw materials used>
Raw materials used in Examples and Comparative Examples are as follows.

[Crosslinked polymer particles]
・ Crosslinked acrylic resin particles 1: “MBX-20” manufactured by Sekisui Plastics Co., Ltd. (average particle size: 20 μm, thermal decomposition temperature: 270 ° C.)
- Crosslinked acrylic resin particles 2: "MBX-30" manufactured by Sekisui Plastics Co., Ltd. (average particle size: 30 μm, thermal decomposition temperature: 270 ° C.)
・ Crosslinked acrylic resin particles 3: “SSX-102” manufactured by Sekisui Plastics Co., Ltd. (average particle size: 2 μm, thermal decomposition temperature: 270 ° C.)
・Crosslinked acrylic resin particles 4: “Crosslinked acrylic beads J-6PF” manufactured by Negami Kogyo Co., Ltd. (average particle size: 4 μm, thermal decomposition temperature: 270 ° C.)
・Crosslinked acrylic resin particles 5: “Crosslinked acrylic beads SE-020T” manufactured by Negami Kogyo Co., Ltd. (average particle diameter: 20 μm, thermal decomposition temperature: 300 ° C.)
・Crosslinked urethane resin particles: “Crosslinked urethane beads C-400T” manufactured by Negami Kogyo Co., Ltd. (average particle size: 15 μm, thermal decomposition temperature: 320 ° C.)
・ Crosslinked styrene resin particles: “SBX-12” manufactured by Sekisui Plastics Co., Ltd. (average particle size: 12 μm, thermal decomposition temperature: 300 ° C.)

[Thermoplastic resin]
・Acrylic resin: n-butyl methacrylate, weight average molecular weight 50,000, thermal decomposition temperature 250°C
・Atactic PS: weight average molecular weight 190,000, thermal decomposition temperature 350°C
・EVA: vinyl acetate content 28% by mass, weight average molecular weight 70,000, thermal decomposition temperature 400°C
・PP: weight average molecular weight 240,000, thermal decomposition temperature 250°C

[wax]
・Paraffin wax: molecular weight 472, melting point 70°C
[Lubricant]
・Stearic acid: molecular weight 284
[Other additives]
・Plasticizer: bis(2-ethylhexyl) 4-cyclohexene-1,2-dicarboxylate, molecular weight 394

[Inorganic powder]
・Alumina powder: BET specific surface area is 6 m ² /g, average particle diameter D ₅₀ is 0.52 μm
Zirconia powder: yttria partially stabilized zirconia powder containing ₃ mol% of Y2O3, BET specific surface area of _{15 m2} /g, average particle diameter ^D50 of 0.15 µm
・Stainless steel powder: SUS316L, average particle size _D50 is 7.1 μm, tap density 4.6 g/cm ³ )
・WC-Co powder: Average particle size _D50 is 1.4 μm

<Preparation of composition for sintered body>
A composition for a sintered body was prepared according to the formulation (parts by mass) shown in Table 1 below. Specifically, the components listed in Table 1 were melt-kneaded at 170° C. using a pressurized kneader, and pellets were produced from the resulting melt using a pelletizer-type plunger extruder.

<Preparation of core resin composition>
A core resin composition was prepared according to the composition (parts by mass) shown in Table 2 below. Specifically, the components shown in Table 2 were melt-kneaded at 170° C. using a pressurized kneader, and pellets were produced from the resulting melt using a pelletizer-type plunger extruder.

The heating residue was measured for the obtained core resin composition. The heating residue was obtained by heating the core resin composition at 1000° C. for 2 hours in the air, and calculating the ratio of the mass after heating to the mass before heating as the heating residue (% by mass).

<Modeling of laminated structure by 3D printer>
In order to produce a sintered body provided with a cavity (flow path), each pellet of the sintered body composition and core resin composition prepared above was used to insert a core inside shown in FIG. was formed by a three-dimensional printer.

Specifically, a MEX-type three-dimensional printer (CERA#P3 manufactured by S.Lab Co., Ltd., molding range X150 mm × Y150 mm × Z150 mm, screw diameter φ20 mm), and the composition for the sintered body was put into the first inlet, and the resin composition for the core was put into the second inlet. A three-dimensional structure including a laminated structure made of the composition for the sintered body and a core made of the resin composition for the core while discharging the composition for the sintered body and the resin composition for the core from nozzles respectively. was laminate-molded. The produced three-dimensional structure was obtained by integrating a cross-shaped core with a width of 10 mm and a height of 2 mm inside the laminated structure of 50 mm×50 mm×6 mm in thickness shown in FIG. Nozzle diameter: 1.0 mm, nozzle temperature: 150 to 190° C., lamination pitch: 0.2 mm, molding speed: 2000 mm/min. Combinations of the sintered body composition and the core resin composition are shown in Table 2.

As the evaluation of the core resin composition, the adhesiveness during lamination molding was evaluated. Adhesiveness evaluation is based on whether or not there is adhesion between core resin compositions during lamination molding, and whether or not the core resin composition has adhesion to the composition for sintered bodies. gone. Judgment criteria are as follows.
○: Adhesion between the core resin compositions and adhesion between the core resin composition and the sintered body composition are both good.
Δ: Poor adhesion of the resin composition for the core to the composition for the sintered compact occurs.
×: Poor adhesion occurs between core resin compositions

<Degreasing of laminated structure>
The three-dimensional structure provided with the core obtained above was degreased. At that time, for those using alumina powder and zirconia powder as the inorganic powder of the laminated structure, the temperature was raised to 500° C. at a temperature elevation rate of 10° C./h in the air for degreasing. For those using SUS powder and WC—Co powder as the inorganic powder of the laminated structure, the temperature was raised to 500° C. at a rate of 10° C./h in a nitrogen gas atmosphere for degreasing.

<Sintering of laminate-molded body>
After degreasing the laminated structure, sintering was performed. For those using alumina powder as the inorganic powder for the laminated structure, the laminate was fired in the atmosphere in such a manner that the temperature was raised to a maximum temperature of 1600° C. at a temperature elevation rate of 100° C./h and kept at 1600° C. for 2 hours. For those using zirconia powder, the temperature was raised to a maximum temperature of 1350° C. at a rate of temperature increase of 100° C./h in the air, and fired at a temperature of 1350° C. for 2 hours. For those using SUS powder as the inorganic powder of the laminated structure, the temperature was raised to 1000°C at a temperature elevation rate of 150°C/h in vacuum, and from 1000°C, the temperature was raised at a temperature elevation rate of 150°C/h in an argon atmosphere. The temperature was raised to 1,350° C., and firing was performed in a pattern of keeping at 1,350° C. for 2 hours. For those using WC—Co powder, the temperature was raised to 1000° C. at a heating rate of 150° C./h in vacuum, and from 1000° C. to 1390° C. at a heating rate of 150° C./h in an argon atmosphere. and baked in a pattern of keeping at 1390° C. for 2 hours.

As an evaluation of the supportability by the core, it was evaluated whether or not the cavity was accurately formed after sintering. For the evaluation, it was measured how much the upper wall of the hollow part was deformed downward from the shape before degreasing. Judgment criteria are as follows.
○: Deformation after sintering is 0.5 mm or less.
Δ: Deformation of more than 0.5 mm and less than 2 mm is observed after sintering.
x: After sintering, the upper wall of the hollow portion is attached to the bottom surface, and deformation of 2 mm or more is observed.

After degreasing, the amount of residue of the core resin composition was measured to determine the mass ratio of the residue to the core resin composition before degreasing.

The results are shown in Table 2. In Comparative Examples 1 and 2, in which the crosslinked polymer particles were not blended in the core resin composition, the supportability of the core during degreasing and sintering was impaired. , deformation was observed in the cavity. On the other hand, in Examples 1 to 10 in which the crosslinked polymer particles and the organic binder are blended in the resin composition for the core, the adhesiveness during lamination molding is excellent, and the support by the core during degreasing and sintering is excellent. It was possible to produce a sintered body having a cavity inside. Further, in Examples 1 to 10, it was possible to produce cores with less residue after degreasing and excellent extinguishing properties.

Although several embodiments of the invention have been described above, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and modifications can be made without departing from the scope of the invention. These embodiments, their omissions, replacements, modifications, etc., are included in the invention described in the scope of claims and equivalents thereof, as well as being included in the scope and gist of the invention.

Claims (8)

When manufacturing a sintered body by modeling a laminated structure with a three-dimensional printer using a sintered body composition containing an inorganic powder and an organic binder, degreasing and sintering the laminated structure, the sintered body A resin composition used as a material for a core for forming a cavity inside a joint,
A core resin composition containing crosslinked polymer particles (A) and an organic binder (B) containing a thermoplastic resin (B1). The core resin composition according to claim 1, wherein the thermoplastic resin (B1) contains a thermoplastic resin (B10) having a thermal decomposition temperature lower than that of the crosslinked polymer particles (A). 3. The crosslinked polymer particles (A) according to claim 1, wherein the thermal decomposition temperature is higher than the thermal decomposition temperature of at least one thermoplastic resin contained in the organic binder of the sintered body composition. core resin composition. The core resin composition according to any one of claims 1 to 3, wherein the crosslinked polymer particles (A) have a thermal decomposition temperature lower than the maximum temperature at which the laminated structure is degreased. The mass ratio of the crosslinked polymer particles (A) and the organic binder (B) is (A)/(B) = 100/35 to 100/105, according to any one of claims 1 to 4. core resin composition. The core resin composition according to any one of claims 1 to 5, which has a residue of less than 0.1% by mass when heated at 1000°C in air. A method for producing a sintered body made of ceramics, cermet or metal,
Using a composition for a sintered body containing an inorganic powder and an organic binder to form a laminated structure with a three-dimensional printer, using the core resin composition according to any one of claims 1 to 6. forming a core with a three-dimensional printer using a three-dimensional printer; heating and degreasing the laminated structure together with the core in a state where the core is arranged inside the laminated structure; and degreasing the laminated structure A method for producing a sintered body, comprising sintering the body to obtain a sintered body having a cavity inside. 8. The core according to claim 7, wherein the sintered body composition and the core resin composition are used to form the core arranged inside the laminated structure together with the laminated structure by a three-dimensional printer. A method for producing a sintered body.

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