JP2017127975A - Sinter molding method and sinter-molded object - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sinter molding method excellent in properties of removing a support part and maintaining a shape of a cured part and in degreasing property, and a sinter-molded object obtained by the method.SOLUTION: The sinter molding method includes: a molded layer forming step of forming a molded layer by using a sinter-molding material comprising inorganic particles and a first polyvinyl alcohol; an imparting step of imparting a liquid binder comprising a second polyvinyl alcohol having an average polymerization degree higher than that of the first polyvinyl alcohol to a desired region of the molded layer; a removing step of removing a region where the liquid binder is not imparted of the molded layer; and a sintering step of heating the molded layer to sinter the inorganic particles.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a sintered modeling method and a sintered model.

  As a conventional method for producing a three-dimensional layered object, a sintered layer is formed by irradiating a powder layer made of a powder material such as a metal with a laser to sinter, and on the sintered layer. By laying a new powder layer and irradiating the new powder layer with a beam to sinter, a new sintered layer joined to the lower sintered layer is formed, and by repeating this, a plurality of A method of manufacturing a desired three-dimensional layered product in which sintered layers are laminated and integrated is known (Patent Document 1).

Japanese Patent No. 2620353

  However, in the method disclosed in Patent Document 1, there is a problem in dimensional accuracy reduction and surface roughness due to excessive sintering other than in the substantial region, and in order to obtain a high-quality shaped object, further processing such as cutting and polishing is required. A process is required. Moreover, since the thickness of the powder layer is at least about 100 μm, and the particle size of the powder used is required to be 30 μm or more, there is a problem that a fine structure cannot be formed.

  On the other hand, the manufacturing method of the sintered molded article which does not use a laser is examined. For example, in order to deposit inorganic particles containing ceramic, metal, or the like in layers and bond the inorganic particles, a photo-curable binder material is applied to a selected region of the layer of inorganic particles and irradiated with light. Then, the binder material that has permeated into the voids between the inorganic particles bonds the inorganic particles to each other, thereby forming a three-dimensional object corresponding to the two-dimensional cross-sectional layer of the three-dimensional object. By alternately repeating the deposition of the inorganic particles and the application of the binder material, the two-dimensional cross-sectional layer is laminated, and a shaped article having a three-dimensional structure is formed (modeled). And after that, the inorganic particle which is not couple | bonded is remove | excluded and a modeling thing can be obtained by sintering the couple | bonded inorganic particle.

  However, even in the above method, the metal powder hardly transmits light, so that there is a problem that the bonding between the inorganic particles becomes insufficient. If the inorganic particles are not sufficiently bonded to each other, the inorganic particles that should have been bonded are removed at the stage of removing the inorganic particles that are not bonded, or after the inorganic particles that are not bonded are removed. In addition, there is a problem that the modeling shape cannot be maintained. Further, depending on the binder material, it cannot be sufficiently removed at the time of sintering, and it remains a problem that it remains in the shaped article.

  In the present specification, the portion removed in the removing step excluding the unbound inorganic particles is also referred to as “support portion”, and the property that the support portion is easily removed is also referred to as “support portion removability”. Moreover, after the support part is removed and before the sintering, the shape of the modeled object is maintained as “cured part shape maintainability”. Furthermore, the property that the binder material is sufficiently removed during sintering is also referred to as “degreasing”.

  The present invention has been made in order to solve at least a part of the above-described problems, and is a sintered modeling method excellent in support part removability, cured part shape maintainability, and degreasing property, and a fired product obtained by the method. The object is to provide a shaped object.

  The present inventors diligently studied to solve the above problems. As a result, by using a sintered modeling material containing inorganic particles and a first polyvinyl alcohol, and a liquid binder containing a second polyvinyl alcohol having an average degree of polymerization higher than that of the first polyvinyl alcohol, the above-mentioned The present invention has been completed by finding that the problems can be solved.

  That is, the present invention provides a modeling layer forming step of forming a modeling layer using a sintered modeling material containing inorganic particles and the first polyvinyl alcohol, and an average degree of polymerization is in the desired region of the modeling layer. An applying step of applying a liquid binder containing a second polyvinyl alcohol that is higher than the first polyvinyl alcohol, a removing step of removing an area of the modeling layer where the liquid binder is not applied, and the modeling layer. A sintering process comprising heating and sintering the inorganic particles. In this embodiment, the first polyvinyl alcohol and the second polyvinyl alcohol having an average degree of polymerization higher than that of the first polyvinyl alcohol, that is, two types of polyvinyl alcohol having different removability in the removing step are used. Thereby, the part with which the 2nd polyvinyl alcohol was provided has the solubility with respect to water compared with the part containing only 1st polyvinyl alcohol, for example. Therefore, in the removal process, the support part is easily removed. In addition, for example, compared to the case of using a photocurable compound, a curing step by light irradiation or the like is unnecessary, and the binding action of the second polyvinyl alcohol works to the inside, so that productivity and There is an advantage from the viewpoint of cost. Furthermore, by including the first polyvinyl alcohol that can also act as a rheology control agent, the formability of the modeling layer using the sintered modeling material can be further improved. In addition, if the degree of saponification other than the average degree of polymerization is controlled according to the conditions of the removal step, the method of this embodiment can be carried out, so that the removal of the region not provided with the liquid binder (developability) High degree of control freedom. In addition, the second polyvinyl alcohol has a sufficient effect on the binding of the inorganic particles, and after the support portion is removed, the shape of the modeled object can be maintained before sintering. Furthermore, since the second polyvinyl alcohol can be sufficiently removed in the sintering process, the result is excellent in degreasing properties.

  In the sintered modeling method of the present invention, the inorganic particles preferably include ceramic particles or metal particles, and the saponification degree of the first polyvinyl alcohol is preferably lower than the saponification degree of the second polyvinyl alcohol. . Furthermore, the sintered shaped article of the present invention is preferably a thing shaped by the above-described sintered shaping method.

It is a flowchart of the sintering modeling method of this embodiment. It is a schematic diagram explaining a sintering modeling apparatus.

  Hereinafter, an embodiment of the present invention (hereinafter referred to as “the present embodiment”) will be described in detail with reference to the drawings as necessary. However, the present invention is not limited to this, and the gist thereof is described below. Various modifications are possible without departing from the scope. In the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted. Further, positional relationships such as up, down, left and right are based on the positional relationships shown in the drawings unless otherwise specified. Further, the dimensional ratios in the drawings are not limited to the illustrated ratios.

[Sintering molding method]
In the sintered modeling method of the present embodiment, a modeling layer forming step of forming a modeling layer using a sintered modeling material containing inorganic particles and first polyvinyl alcohol, and an average in a desired region of the modeling layer An applying step of applying a liquid binder containing a second polyvinyl alcohol having a degree of polymerization higher than that of the first polyvinyl alcohol; and a removing step of removing a region of the modeling layer where the liquid binder is not applied; A sintering treatment step of heating the modeling layer to sinter the inorganic particles.

  In this embodiment, the first polyvinyl alcohol and the second polyvinyl alcohol having an average degree of polymerization higher than that of the first polyvinyl alcohol, that is, two types of polyvinyl alcohol having different removability in the removing step are used. Thereby, the part with which the 2nd polyvinyl alcohol was provided has the solubility with respect to water compared with the part containing only 1st polyvinyl alcohol, for example. Therefore, in the removal process, the support part is easily removed. In addition, for example, compared to the case of using a photocurable compound, a curing step by light irradiation or the like is unnecessary, and the binding action of the second polyvinyl alcohol works to the inside, so that productivity and There is an advantage from the viewpoint of cost. Furthermore, by including the first polyvinyl alcohol that can also act as a rheology control agent, the formability of the modeling layer using the sintered modeling material can be further improved. In addition, if the degree of saponification other than the average degree of polymerization is controlled according to the conditions of the removal step, the method of this embodiment can be carried out, so that the removal of the region not provided with the liquid binder (developability) High degree of control freedom.

  In addition, the second polyvinyl alcohol has a sufficient effect on the binding of the inorganic particles, and after the support portion is removed, the shape of the modeled object can be maintained before sintering. Furthermore, since the second polyvinyl alcohol can be sufficiently removed in the sintering process, the result is excellent in degreasing properties. Hereinafter, each process and components used in these processes will be described. FIG. 1 shows a flowchart of the sintering modeling method of the present embodiment.

[Modeling layer formation process]
A modeling layer formation process is a process of forming a modeling layer using the sintered modeling material containing an inorganic particle and 1st polyvinyl alcohol. Specifically, the sintered modeling material is spread on the stage so as to have a thickness corresponding to one modeling layer. At this time, the sintered modeling material may be preheated so as to have fluidity. Moreover, you may make it form a modeling layer by cooling the heated sintered modeling material on the stage maintained at low temperature than it.

[Sintered molding material]
The sintered modeling material contains inorganic particles and first polyvinyl alcohol, and may contain other components such as water as necessary. The sintered modeling material is preferably in the form of a paste rather than a powder. By being in the paste form, the formability of the modeling layer and the suppression of powder scattering tend to be further improved. This increases the accuracy of the model and the reliability of the device.

(Inorganic particles)
Although it does not specifically limit as an inorganic particle, For example, a ceramic particle or a metal particle is mentioned. By using such inorganic particles, the mechanical strength of sintered modeling tends to be further improved.

  Although it does not specifically limit as a metal particle, For example, stainless steel alloy copper, bronze (Cu / Sn), brass (Cu / Zn), tin, lead, gold, silver, platinum, palladium, iridium, titanium, tantalum, iron, Carbonyl iron, titanium alloy, cobalt alloy, aluminum alloy, magnesium alloy, iron alloy, nickel alloy, chromium alloy, silicon alloy, zirconium alloy, gold alloy, Fe / Ni, Fe / Si, Fe / Al, Fe / Si / Al , Fe / Co, Fe / Co / V, particles of titanium aluminum and the like.

  The ceramic particles are not particularly limited, and examples thereof include alumina and zirconia.

  The content of the inorganic particles is preferably 80 to 97.5% by mass, more preferably 85 to 97.5% by mass, and still more preferably 90 to 95% by mass with respect to the total amount of the sintered modeling material. It is.

(First polyvinyl alcohol)
The saponification degree of the first polyvinyl alcohol is preferably 76 to 92, more preferably 78 to 90, and still more preferably 80 to 88. When the degree of saponification of the first polyvinyl alcohol is within the above range, the support portion removability, the cured portion shape maintaining property, and the degreasing property tend to be further improved. The saponification degree can be determined by the method described in JIS K6726.

  The average degree of polymerization of the first polyvinyl alcohol is preferably 100 to 15000, more preferably 400 to 4000, and still more preferably 500 to 2000. When the average degree of polymerization of the first polyvinyl alcohol is within the above range, the support portion removability, the cured portion shape maintaining property, and the degreasing property tend to be further improved. The average degree of polymerization can be determined by the method described in JIS K6726.

  The content of the first polyvinyl alcohol is preferably 1 to 5% by mass, more preferably 2 to 3% by mass, and still more preferably 2.2 to 2.% by mass with respect to the total amount of the sintered modeling material. 8% by mass. When content of 1st polyvinyl alcohol exists in the said range, it exists in the tendency which support part removability, hardening part shape maintainability, and degreasing property improve more.

[Granting process]
The applying step is a step of applying a liquid binder containing the second polyvinyl alcohol to a desired region of the modeling layer. Specifically, a liquid binder containing the second polyvinyl alcohol is applied to a desired region of the modeling layer formed on the stage to form a desired image using the liquid binder. The method for applying the liquid binder is not particularly limited, but according to the image information of each cross-sectional layer constituting the sintered model, the liquid binder is discharged while moving the discharge head, A liquid binder is applied to a position corresponding to the cross-sectional shape.

  Next, the stage lifting mechanism lowers the stage according to the layer thickness of the modeling layer that is spread and formed on the stage. After the stage is lowered, the sintered modeling material is spread again on the already formed modeling layer, and a new modeling layer is laminated. Thereafter, the modeling layer is repeatedly stacked from the modeling layer forming step to the applying step, and the modeling layers are stacked. That is, the second and subsequent modeling layers are stacked on the previously formed modeling layer. In addition, the method of laminating | stacking by performing the process of extending a sintered modeling material and forming a modeling layer in places other than on a stage, and transferring a modeling layer to a stage sequentially may be sufficient.

[Liquid binder]
The liquid binder contains a second polyvinyl alcohol having an average degree of polymerization higher than that of the first polyvinyl alcohol, and may contain other components such as water as necessary.

(Second polyvinyl alcohol)
The saponification degree of the second polyvinyl alcohol is preferably 84 to 99, more preferably 86 to 99, and still more preferably 88 to 98. When the saponification degree of the second polyvinyl alcohol is within the above range, the support part removability, the cured part shape maintaining property, and the degreasing property tend to be further improved. The saponification degree can be determined by the method described in JIS K6726.

  The saponification degree of the first polyvinyl alcohol is preferably lower than the saponification degree of the second polyvinyl alcohol. Thereby, it exists in the tendency which support part removability, hardening part shape maintenance property, and degreasing property improve more. The difference between the saponification degree of the first polyvinyl alcohol and the saponification degree of the second polyvinyl alcohol described later is preferably 4 to 14, more preferably 8 to 14, and still more preferably 12 to 14 It is.

  The average degree of polymerization of the second polyvinyl alcohol is preferably 100 to 15000, more preferably 400 to 4000, and further preferably 500 to 2000. When the average degree of polymerization of the second polyvinyl alcohol is within the above range, the support portion removability, the cured portion shape maintaining property, and the degreasing property tend to be further improved. The average degree of polymerization can be determined by the method described in JIS K6726.

  The difference between the average degree of polymerization of the first polyvinyl alcohol and the average degree of polymerization of the second polyvinyl alcohol is preferably 750 to 1750, more preferably 900 to 1750, and further preferably 1100 to 1750. When the difference in the average degree of polymerization is within the above range, the support portion removability, the cured portion shape maintainability, and the degreasing property tend to be further improved.

  The content of the second polyvinyl alcohol is preferably 0.1 to 5% by mass, more preferably 0.1 to 3% by mass, and still more preferably 0.1 to 5% by mass with respect to the total amount of the sintered modeling material. It is 5-1.5 mass%. When the content of the second polyvinyl alcohol is within the above range, the support portion removability, the cured portion shape maintainability, and the degreasing property tend to be further improved.

[Removal process]
A removal process is a process of removing the area | region where the liquid binder of the modeling layer is not provided. Specifically, in the applying step, when the stacking of the modeling layers reaches a height corresponding to the modeling of the target modeled object and the stacking is completed, this is taken out from the modeling unit and the modeled object appears. For example, a modeled object (laminated layered product) is transported from the modeled part to the appearing part by the transport mechanism, and the modeled object (laminated) is removed by removing the support part to which the liquid binder is not applied by the support part removing unit. The modeled cross-sectional layer).

  The removal method is not particularly limited as long as it uses a difference in physical properties between the first polyvinyl alcohol and the second polyvinyl alcohol. For example, a method of removing a region to which no liquid binder is applied by washing with water. Is mentioned.

[Sintering process]
The sintering process is a process of heating the modeling layer and sintering the inorganic particles. Specifically, there is a method in which the modeled object revealed in the removing step is transferred to the degreasing and sintering section and subjected to degreasing treatment. First, a shaped article is conveyed from the exposed part to the inside of the degreasing sintering furnace by the conveying mechanism, and the shaped article is degreased. Degreasing is performed for the purpose of thermally decomposing and removing the first polyvinyl alcohol and the liquid binder (second polyvinyl alcohol). In the degreasing step, the first polyvinyl alcohol and the liquid binder (second polyvinyl alcohol) are heated in a temperature range where degreasing starts to degrease the first polyvinyl alcohol and liquid binder (second polyvinyl alcohol). To proceed. The decomposition component generated by thermal decomposition of the liquid binder is discharged from the exhaust facility by the degreasing gas supplied from the degreasing gas supply facility.

  Next, the degreased shaped product is sintered. Specifically, heating is performed gradually at a temperature that further exceeds the temperature at which the degreasing treatment is performed, and the inorganic particles are sintered. As a preferred example, for example, when a stainless alloy powder is used as the inorganic particles, the heating temperature is gradually increased to 1300 ° C. at which the stainless alloy is sintered. By completing the sintering of the inorganic particles, a desired sintered model is obtained.

[Sintered objects]
The sintered model according to the present embodiment is modeled by the above-described sintered modeling method. According to the sintered modeling method, it is possible to manufacture a sintered model with excellent dimensional accuracy and surface roughness and high reproducibility of a fine shape at low cost and high productivity.

[Sintering equipment]
Hereinafter, the sintering modeling apparatus used for the sintering modeling method of this embodiment is demonstrated. FIG. 2 shows a schematic diagram for explaining the sintering modeling apparatus. In addition, from the process after supplying the sintering modeling material 1 to the sintering modeling apparatus 100 to the process of performing the sintering process of the modeling object 7, it is performed by control of the control part with which the sintering modeling apparatus 100 is provided.

  First, the sintered modeling material 1 containing an inorganic particle and 1st polyvinyl alcohol is prepared, and it fills with the material supply part 10 (hopper 11). Each ratio is appropriately set according to the modeling specifications of the sintered model, such as the particle size of the inorganic particles, the particle size distribution, the volume filling rate of the inorganic particles, and the layer thickness of the modeling layer 5 formed by spreading. It is desirable. Moreover, it is preferable that each dispersion | distribution becomes uniform.

  In addition, the liquid binder 8 containing the second polyvinyl alcohol is prepared, filled in the ink cartridge, and set in the cartridge loading section 52.

  Next, the sintered modeling material 1 is supplied from the material supply unit 10 to the sintered modeling material holding unit 20. The amount of the sintered modeling material 1 supplied to the sintered modeling material holding unit 20 at a time is controlled to an amount commensurate with the amount of one layer of the modeling layer 5. The sintered modeling material holding part 20 may be heated as needed.

  Next, the sintered modeling material 1 is spread on the stage 41 by the spreading portion 30. Specifically, the squeegee 31 brought into contact with the + X side of the sintered modeling material 1 having fluidity is moved in the −X direction to be extended to the surface of the stage 41.

  The layer thickness of the modeling layer 5 is controlled by the specification of the spread by the squeegee 31. Specifically, the layer thickness of the modeling layer 5 is the size of the gap between the lower end of the squeegee 31 and the XY plane (for example, the surface of the stage 41 at the initial position), the moving speed of the squeegee 31, and the sintered modeling material 1. Therefore, it is desirable to set appropriately so as to obtain a desired thickness.

  Next, the drawing unit 50 applies the liquid binder 8 containing the second polyvinyl alcohol to a desired region of the modeling layer 5 formed on the stage 41, and forms a desired image using the liquid binder 8. . Specifically, the liquid binder 8 is ejected while moving the ejection head 51 in accordance with the image information of each cross-sectional layer constituting the sintered model that is input in advance to the control unit, and the sintered model A liquid binder 8 is applied at a position corresponding to the cross-sectional shape.

  The liquid binder 8 selectively applied to a desired position penetrates into the region containing the inorganic particles and the first polyvinyl alcohol (the void portion of the inorganic particles covered with the first polyvinyl alcohol), and the modeling portion is It is formed.

  Next, the stage elevating mechanism 42 lowers the stage 41 in accordance with the layer thickness of the modeling layer 5 that is spread and formed on the stage 41. As the stage 41 descends, the surface of the modeling layer 5 comes to be located in the same plane as the sintered modeling holding unit 20, and the sintered modeling material 1 is spread again by the squeegee 31 as the modeling layer 5. A stacked XY plane is formed.

  Thereafter, the steps from supplying the sintered modeling material 1 to the sintered modeling material holding unit 20 from the material supply unit 10 to the above steps are repeated, and the modeling layer 5 is laminated. That is, the second and subsequent modeling layers 5 are laminated on the modeling layer 5 formed in advance. In addition, the method of laminating | stacking by performing the process of extending the sintered modeling material 1 and forming the modeling layer 5 in places other than on the stage 41, and transferring the modeling layer 5 to the stage 41 sequentially may be sufficient.

  When the stacking of the modeling layer 5 reaches a height corresponding to the modeling of the modeled object 7 and the stacking is completed, the modeled layer 7 is taken out from the modeled part 40 and the modeled object 7 appears. Specifically, the non-modeling part 5b to which the modeling object (lamination of the modeling layer 5) is conveyed from the modeling part 40 to the appearing part 70 by the conveyance mechanism 43 and the liquid binder 8 is not applied by the unnecessary part removing means. The model 7 is made to appear by removing.

  Next, the revealed shaped article 7 is transferred to the degreasing and sintering unit 80 and subjected to degreasing treatment. Specifically, first, the model 7 is transported from the appearing unit 70 to the inside of the degreasing sintering furnace 81 by the transport mechanism 43, and the model 7 is degreased. Degreasing is performed for the purpose of thermally decomposing and removing the first polyvinyl alcohol and the liquid binder 8 (second polyvinyl alcohol). In the degreasing step, the first polyvinyl alcohol or the liquid binder 8 (second polyvinyl alcohol) is heated in a temperature range where degreasing starts, and the first polyvinyl alcohol and the liquid binder 8 (second polyvinyl alcohol) ) Degreasing. The decomposition component generated by the thermal decomposition of the first polyvinyl alcohol and the liquid binder 8 (second polyvinyl alcohol) is discharged from the exhaust facility 84 by the degreasing gas supplied from the degreasing gas supply facility 83. .

  Next, the degreased shaped article 7 is sintered. Specifically, heating is performed gradually at a temperature that further exceeds the temperature at which the degreasing treatment is performed, and the inorganic particles are sintered. As a preferred example, for example, when a stainless alloy powder is used as the inorganic particles, the heating temperature is gradually increased to 1300 ° C. at which the stainless alloy is sintered. By completing the sintering of the inorganic particles, a desired sintered model is obtained. In addition, although the main material (inorganic particles) is supported by the liquid binder, in the degreasing process, the liquid binder is gradually heated and decomposed, so that the force for binding the main material (inorganic particles) gradually decreases. .

  Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples. The present invention is not limited in any way by the following examples.

[Sintered molding material]
〔particle〕
Aluminum oxide SUS304L
(Water-soluble resin)
Low saponified polyvinyl alcohol (saponification degree 80, polymerization degree 500)
Partially saponified polyvinyl alcohol (saponification degree 88, polymerization degree 500)
Partially saponified polyvinyl alcohol (saponification degree 88, polymerization degree 1,700)
Highly saponified polyvinyl alcohol (saponification degree 98, polymerization degree 1,700)

  Hereinafter, the preparation method of the polyvinyl alcohol used in Example 2 is shown. The polyvinyl alcohol used in Example 1 and Comparative Examples 1 to 3 was prepared by the same method as the method for preparing polyvinyl alcohol used in Example 2, except that only the blending amount was changed in the following preparation method. .

[Synthesis of polyvinyl acetate]
A 6 L separable flask equipped with a stirrer, thermometer, nitrogen introduction tube, and reflux tube was previously deoxygenated, 1055 g of vinyl acetate containing 650 ppm acetaldehyde and 65 ppm acetaldehyde dimethyl acetal; 50 ppm acetaldehyde dimethyl acetal containing acetaldehyde 2445 g of methanol with a content of less than 1 ppm; 1% methanol solution of tartaric acid in an amount that makes the content of tartaric acid in vinyl acetate 20 ppm. While blowing nitrogen into the flask, the temperature inside the flask was adjusted to 60 ° C. In addition, -10 degreeC ethylene glycol / water solution was circulated through the reflux pipe. A 3.00 mass% methanol solution of di-n-propyl peroxydicarbonate was prepared, and 15.6 mL was added into the flask to initiate polymerization. A methanol solution of di-n-propyl peroxydicarbonate was sequentially added at a rate of 17.5 mL / hour until the completion of polymerization. During the polymerization, the temperature in the flask was kept at 60 ° C. 6 hours after the start of the polymerization, when the solid content concentration of the polymerization solution reached 22.1%, an amount corresponding to 3 molar equivalents of di-n-propyl peroxydicarbonate remaining undecomposed in the polymerization solution. After adding 1200 g of methanol containing sorbic acid, the polymerization solution was cooled to stop the polymerization. The polymerization rate of vinyl acetate when the polymerization was stopped was 75.0%. After the polymerization solution was cooled to room temperature, the pressure in the flask was reduced using a water flow aspirator to distill off vinyl acetate and methanol, thereby precipitating polyvinyl acetate. After 3000 g of methanol was added to the precipitated polyvinyl acetate and the polyvinyl acetate was dissolved while heating at 30 ° C., the pressure in the flask was reduced again using a water aspirator to distill off the vinyl acetate and methanol. Thus, polyvinyl acetate was precipitated. The operation of dissolving polyvinyl acetate in methanol and then precipitating it was further repeated twice. Methanol was added to the precipitated polyvinyl acetate to obtain a 40% by mass methanol solution of polyvinyl acetate with a vinyl acetate removal rate of 99.8%.

  The polymerization degree was measured using a part of the obtained methanol solution of polyvinyl acetate. A 10% methanol solution of sodium hydroxide was added to a methanol solution of polyvinyl acetate so that the molar ratio of sodium hydroxide to vinyl acetate monomer units in the polyvinyl acetate was 0.1. When the gelled product was formed, the gel was pulverized and subjected to Soxhlet extraction with methanol for 3 days. The obtained polyvinyl alcohol was dried and subjected to viscosity average polymerization degree measurement. The degree of polymerization was 500.

[Synthesis of polyvinyl alcohol]
The total solid concentration (saponification concentration) is 40% by mass with respect to a 40% by mass methanol solution of polyvinyl acetate, and the molar ratio of sodium hydroxide to vinyl acetate monomer units in the polyvinyl acetate is 0.00. Methanol and an 8% methanol solution of sodium hydroxide were added under stirring so as to be 01, and the saponification reaction was started at 40 ° C. The gel is pulverized when the gelated product is generated as the saponification reaction proceeds, and the crushed gel is transferred to a container at 40 ° C. When 60 minutes have elapsed from the start of the saponification reaction, methanol / methyl acetate / water ( 25/70/5 mass ratio) solution and neutralized. Centrifugation of the obtained swollen gel, adding twice the mass of methanol to the swollen gel, immersing it, leaving it for 30 minutes, and then centrifuging it three times, followed by drying at 60 ° C. for 1 hour And then dried at 100 ° C. for 2 hours to obtain polyvinyl alcohol.

  The polymerization degree and saponification degree of polyvinyl alcohol were determined by the method described in JIS-K6726. The degree of polymerization was 500, and the degree of saponification was 88.0 mol%.

[Preparation of sintered modeling material]
Each material was mixed with the composition shown in Table 1 below and stirred sufficiently to obtain each sintered modeling material. In Table 1 below, the numerical unit is mass%, and the total is 100.0 mass%.

[Liquid binder material]
(Water-soluble resin)
Low saponified polyvinyl alcohol (saponification degree 80, polymerization degree 500)
Partially saponified polyvinyl alcohol (saponification degree 88, polymerization degree 500)
Partially saponified polyvinyl alcohol (saponification degree 88, polymerization degree 1,700)
Highly saponified polyvinyl alcohol (saponification degree 98, polymerization degree 1,700)
〔solvent〕
Water (polymerizable compound)
Phenoxyethyl acrylate 2- (2-vinyloxyethoxy) ethyl acrylate 2-ethylhexyloxetane 3,4-epoxycyclohexanecarboxylic acid methyl ester [others]
Irgacure 819 (trade name, manufactured by BASF)
Irgacure 250 (BSF product name)
CXC-1616 (KING INDUSTRY product name)
Speedcure DETX (trade name, manufactured by Lambson)
MEHQ (p-methoxyphenol, manufactured by Tokyo Chemical Industry Co., Ltd.)
BYK-3500 (BIC Chemie Japan product name)

[Preparation of liquid binder]
Each material was mixed with the composition shown in Table 1 below and stirred sufficiently to obtain each liquid binder. In Table 1 below, the numerical unit is mass%, and the total is 100.0 mass%.

[Sintering molding method]
Using a squeegee, spread the sintered modeling material on the stage to a thickness of 50 μm, dry the sintered modeling material using a dryer (warm air), remove the water that is the solvent, A modeling layer was formed. Next, a liquid binder was applied to a desired region of the modeling layer using a piezoelectric inkjet head. Then, the water | moisture content in a liquid binder was dried using the dryer (warm air), and it washed with water, and removed the area | region (support part) to which the liquid binder was not provided. Finally, the inorganic particles were sintered under conditions of 1300 ° C. and 5 hours to obtain a sintered shaped product.

  When a liquid binder (Comparative Example 3), which is a UV curable composition, is used, a liquid binder is applied to a desired region of the modeling layer using a piezo ink jet head, and then UV is applied. The liquid binder was cured by irradiating a lamp. Then, it put into oven, post-cure (heat processing), and washed with water, and removed the area | region (support part) to which the liquid binder was not provided. Finally, the inorganic particles were sintered under conditions of 1300 ° C. and 5 hours to obtain a sintered shaped product.

[Support part removability]
The support part removability was evaluated according to the following criteria.
(Evaluation criteria)
○: When the support portion was removed in the removal step, only the portion to which the second polyvinyl alcohol was adhered remained clean.
X: When the support part was removed in the removal step, a part to which the second polyvinyl alcohol was adhered was also partially removed, or a part to which the second polyvinyl alcohol was not adhered was not completely removed .

[Hardened part shape maintainability]
The cured part shape maintainability was evaluated according to the following criteria.
(Evaluation criteria)
○: No change in the shape of the shaped article was observed after the removal step and before the sintering treatment step.
X: After the removing step and before the sintering treatment step, the shape of the model was not sufficiently maintained by polyvinyl alcohol, and a change in shape was observed.

[Degreasing]
Degreasing was evaluated according to the following criteria.
(Evaluation criteria)
○: Polyvinyl alcohol was completely removed after the sintering process.
X: After the sintering process, a residue of polyvinyl alcohol was observed on the surface of the molded article, and degreasing was not completed.

  DESCRIPTION OF SYMBOLS 1 ... Sintered modeling material, 5 ... Modeling layer, 5b ... Support part, 7 ... Modeling thing, 8 ... Liquid binder, 10 ... Material supply part, 11 ... Hopper, 20 ... Sintered modeling material holding part, 30 ... Exhibition Extension part, 31 ... Squeegee, 40 ... Modeling part, 41 ... Stage, 42 ... Stage lifting mechanism, 43 ... Conveying mechanism, 50 ... Drawing part, 51 ... Discharge head, 52 ... Cartridge loading part, 53 ... Carriage, 54 ... Carriage Moving mechanism, 70 ... revealing part, 80 ... degreasing and sintering part, 81 ... degreasing and sintering furnace, 83 ... degreasing gas supply equipment, 84 ... exhaust equipment, 100 ... sintering molding apparatus.

Claims (4)

A modeling layer forming step of forming a modeling layer using a sintered modeling material containing inorganic particles and first polyvinyl alcohol;
An application step of applying a liquid binder containing a second polyvinyl alcohol having an average polymerization degree higher than that of the first polyvinyl alcohol to a desired region of the modeling layer;
A removal step of removing a region of the modeling layer to which the liquid binder is not applied;
A sintering process step of heating the modeling layer to sinter the inorganic particles,
Sinter molding method.   The sintered modeling method according to claim 1, wherein the inorganic particles include ceramic particles or metal particles.   The sintering modeling method according to claim 1 or 2, wherein a saponification degree of the first polyvinyl alcohol is lower than a saponification degree of the second polyvinyl alcohol.   The sintered modeling thing modeled by the sintering modeling method of any one of Claims 1-3.

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