JP2019116094A - Hydraulic composition for additive manufacturing device, and method for manufacturing mold - Google Patents

Abstract

To provide a hydraulic composition for an additive manufacturing device excellent in early strength development.SOLUTION: The present invention is a hydraulic composition for an additive manufacturing device, comprising a composite binder containing 1.5 to 12 parts by mass of a partially saponified polyvinyl alcohol per 100 parts by mass of an inorganic binder, and sand. The present invention is also a method for manufacturing a mold by using the hydraulic composition for additive manufacturing device.SELECTED DRAWING: None

Description

  The present invention relates to a hydraulic composition for an additive manufacturing apparatus (3D printer) which is excellent in early strength development, particularly early bending strength, and a method of manufacturing a mold using the composition.

Casting is a traditional metalworking method in which molten metal is poured into a mold to produce a casting. The self-hardening molds used for this casting are organic and inorganic, depending on the caking agent (binder) to be used. Among these, inorganics are mainly water glass and cement. However, in the cement-based self-hardening mold, depending on the casting temperature, the contained gypsum is thermally decomposed to generate a gas, causing a defect in the casting, and the appearance and the function are impaired. In addition, although the production of the mold requires the production of a model or a wood mold as a pre-process, this pre-process takes time and cost.
Then, the aesthetics etc. of a casting are not impaired but the manufacturing method of the casting_mold | template which does not need this front-end process is desired.

By the way, recently, the additive manufacturing apparatus has attracted attention as a rapid and precise forming means. Among the additional manufacturing apparatuses, for example, a powder lamination molding apparatus is an apparatus that forms a solidified product, which is obtained by laying a powder on a flat surface and then injecting an aqueous binder onto the powder to solidify, sequentially laminating in the vertical direction It is. The feature of this device is that the data of three-dimensional molding created by three-dimensional CAD or the like is divided into a large number of horizontal surfaces, and the shapes of these horizontal surfaces are sequentially laminated to produce a molded body.
Therefore, if the mold can be manufactured using the above-mentioned apparatus, it is expected that the above-mentioned pre-process becomes unnecessary and the working time and cost can be reduced.

  For example, in Patent Document 1, 15 to 50% of quick-hardening cement is blended with fireproof sand such as silica sand, olivine sand, and artificial sand as a hydraulic composition for an additive manufacturing apparatus suitable for a powder lamination molding method and kneaded. There is disclosed a technology for obtaining a molded body by adding an aqueous binder to the (mixed) material, solidifying and laminating. Here, the powder lamination molding method is a layer in which a molding liquid is dropped or sprayed through a nozzle such as an ink jet to solidify in a predetermined range of powder material placed on a loading table (base), and successively solidified Are laminated to form a desired shape.

  However, molded articles produced by the additive manufacturing apparatus using the materials described in Patent Document 1 are likely to be easily chipped because the early strength development, particularly bending strength, is not sufficient, and stable supply of the product is difficult, and molding by the additive manufacturing apparatus There are cases where it is difficult to manufacture a micro-shaped product which is a feature of technology.

JP, 2011-51010, A

  Then, an object of this invention is to provide the hydraulic composition for addition manufacturing apparatuses excellent in early stage strength development.

As a result of intensive studies to solve the above problems, the inventor of the present invention is able to achieve the above object by a hydraulic composition containing an inorganic binder such as calcium aluminates, polyvinyl alcohol, sand, and water in a specific ratio. It found and completed the present invention.
That is, the present invention is a hydraulic composition etc. for an additional manufacturing apparatus having the following constitution.

[1] A hydraulic composition for an additive manufacturing device, comprising a composite binder containing 1.5 to 12 parts by mass of partially saponified polyvinyl alcohol with respect to 100 parts by mass of an inorganic binder, and sand.
[2] The hydraulic composition for addition production devices according to the above [1], wherein the inorganic binder contains 50 to 100 mass% of calcium aluminates, based on 100 mass% of the entire inorganic binder.
[3] The hydraulic composition for addition production devices according to the above [1] or [2], wherein the inorganic binder contains 0.5 to 10 mass% of gypsum based on 100 mass% of the entire inorganic binder.
[4] The hydraulic composition for an additive manufacturing device according to any one of the above [1] to [3], wherein the inorganic binder contains 100% by mass of the entire inorganic binder and 0 to 50% by mass of rapid curing cement. object.
[5] The hydraulic composition for an addition manufacturing device according to any one of the above [1] to [4], wherein the average particle diameter of the polyvinyl alcohol is 150 μm or less.
[6] The hydraulic composition for an additive manufacturing device according to any one of the above [1] to [5], wherein the calcium aluminates are amorphous calcium aluminate.
[7] The hydraulic composition for addition production device according to any one of the above [1] to [6], further containing 28 to 60 parts by mass of water with respect to a total of 100 parts by mass of the composite binder.
[8] A method for producing a mold, which molds a mold using the additive production apparatus and the hydraulic composition for additive production apparatus according to any one of the above [1] to [7].
[9] The method for producing a mold according to the above [8], wherein the curing temperature of the mold is 10 to 80 ° C.

  The hydraulic composition for an additive manufacturing device of the present invention has high early strength development.

  The present invention, as described above, comprises a composite binder containing 1.5 to 12 parts by mass of polyvinyl alcohol partially saponified relative to 100 parts by mass of the inorganic binder, and sand, and a hydraulic composition for an additive manufacturing apparatus Sometimes abbreviated as “hydraulic composition”. Hereinafter, the present invention will be described separately for the inorganic binder, the composite binder, the hydraulic composition, and the method for producing a mold.

1. Inorganic Binder The inorganic binder is a binder which contains at least one selected from the following calcium aluminates as an essential component, and further contains, for example, gypsum and quick-hardening cement as an optional component.
Next, calcium aluminates, gypsum, quick-hardening cement and the like will be separately described in detail.

(1) Calcium aluminates wherein the calcium aluminates _{may, 3CaO · Al 2 O 3,} 2CaO · Al 2 O 3, 12CaO · 7Al 2 O 3, 5CaO · 3Al 2 O 3, CaO · Al 2 O 3, 3CaO · _5Al 2 _{O 3,} or calcium aluminate such as _{CaO · 2Al 2 O 3,;} 2CaO · Al 2 O 3 · Fe 2 O 3 , or calcium alumino ferrite etc. _{4CaO · Al 2 O 3 · Fe} 2 O 3,; calcium calcium halophosphate aluminate containing calcium fluoroalkyl aluminate such as _{3CaO · 3Al 2 O 3 · CaF} 2, and _{11CaO · 7Al 2 O 3 · CaF} 2 halogen is dissolved or substituted aluminate; 8CaO _· Na 2 O _· 3Al ₂ O _3, and _{3CaO · 2Na 2 O · 5Al 2} O 3 Calcium sodium aluminate; calcium lithium aluminate; alumina cement; and additionally, trace elements (including oxides, etc.) such as Na, K, Li, Ti, Fe, Mg, Cr, P, F, S etc. Or more selected from mineral minerals.
Among these inorganic binders, calcium aluminate is preferable, and amorphous calcium aluminate is particularly preferable, from the viewpoint of high strength development and little generation of gas when used as a template. Since amorphous calcium aluminate is produced by melting and quenching the raw material, it has substantially no crystal structure, and the vitrification rate is usually 80% or more, and the higher the vitrification rate Since the early strength development is high, the vitrification rate is preferably 90% or more.

The molar ratio of calcium aluminates to CaO / Al ₂ O ₃ is preferably 1.5 to 3.0, more preferably 1.7 to 2.4. When the molar ratio is 1.5 or more, the early development of the strength of the hydraulic composition is high, and when it is 3.0 or less, the heat resistance of the hydraulic composition is high.
Also, in order to obtain sufficient early strength development and to suppress the generation of dust, the brane specific surface area (powder degree specified in JIS R 5201) of calcium aluminates is preferably 1000 to 6000 cm ² / g, more preferably Preferably it is 1500-5000 cm < ² > / g. The brane specific surface area of the calcium aluminates is more preferably 1500 to 4000 cm ² / g, particularly preferably 2000, in order to ensure uniform spreading in the addition production apparatus and not to decrease the strength of the mold. It is ~ 3000 cm ² / g.
The content of calcium aluminates in the inorganic binder is preferably 50 to 100% by mass. When the value is 50% by mass or more, the early development of strength and heat resistance of the hydraulic composition are high. The value is preferably 60 to 100% by mass, more preferably 70 to 100% by mass, and still more preferably 80 to 95% by mass. Among calcium aluminates, amorphous calcium aluminate is preferred as described above.

(2) Gypsum The inorganic binder may further contain gypsum as an optional component in order to further improve early strength development. Examples of the gypsum include one or more selected from anhydrite, hemihydrate gypsum, and dihydrate gypsum. Among these, hemihydrate gypsum is preferable because it has higher early strength development. The content of gypsum in the inorganic binder improves the early development of strength and prevents the generation of gas and defects in the spheroidization of graphite at the time of manufacture of the casting. It is 0.5 to 10% by mass, more preferably 0.8 to 5% by mass or less, still more preferably 1 to 3% by mass or less in terms of gypsum.
The gypsum may be gypsum contained in cement. Gypsum in cement is generally present in the form of a mixture of gypsum dihydrate and gypsum hemihydrate (mixed gypsum). Since the hemihydrate gypsum is generated by dewatering from dihydrate gypsum by the heat generated by the grinding of cement, the content ratio of hemihydrate gypsum and dihydrate gypsum fluctuates under the influence of the milling conditions.

(3) Fast-Hardening Cement The inorganic binder may contain quick-hardening cement (super-fast-hardening cement) as an optional component to further improve early strength development, and the rapid-hardening cement is preferably JIS R 5210. It is a quick-hardening cement (super fast-hardening cement) or a water-stopping cement whose setting (initial development) measured according to the above is within 30 minutes. In addition, commercial products such as quick-hardening cement are Super Jet Cement (manufactured by Pacific Cement Co., Ltd.), Jet Cement (manufactured by Sumitomo Osaka Cement Co., Ltd.), Lion Shisui (registered trademark, manufactured by Sumitomo Osaka Cement Co., Ltd.), or Denka Super Cement (Denka Super Cement). Company company). Fast-hardening cement containing gypsum is preferable because it exhibits high early strength development and facilitates addition of a small amount of gypsum.
The content of quick-hardening cement in the inorganic binder improves the early development of strength and reduces gas generation when used as a mold, so the entire inorganic binder is preferably 100% by mass, preferably 0 to 50. It is mass%, more preferably 0-30 mass%, still more preferably 5-20 mass%.

(4) Other components in inorganic binder The inorganic binder may contain cement as another component (optional component).
It is preferable that the cement (crude oil) measured in accordance with JIS R 5210 is within 3 hours and 30 minutes because the early strength development after 3 hours from molding is high, and 1 hour or less is more preferable.
The cement may be one or more selected from ordinary Portland cement, early-strength Portland cement, moderate-heat Portland cement, low-thermal Portland cement, white Portland cement, eco cement, blast furnace cement, fly ash cement, and cement clinker powder. In the present invention, cement clinker powder is also included in cement. Moreover, the content rate of the calcium silicate in cement makes the whole cement 100 mass%, Preferably it is 25 mass% or more. If the content is 25% by mass or more, strength development after 1 day of material age is high, and if long-term strength development is required, the content is preferably 45% by mass or more.
The content of cement in the inorganic binder is preferably 0 to 50 mass%, more preferably 0 to 30 mass%, and still more preferably 100 mass% of the entire inorganic binder for the improvement of early strength development. It is 0-20 mass%.

2. Composite binder The composite binder is a binder including 1.5 to 12 parts by mass of partially saponified polyvinyl alcohol with respect to 100 parts by mass of the inorganic binder. If the blending ratio of polyvinyl alcohol is less than 1.5 parts by mass, the strength improvement effect is low, and if it exceeds 12 parts by mass, depending on the shape, deformation or cracking may occur due to shrinkage of the molded product, and a mold having a complicated shape is obtained. In addition to the production of the casting, gas may be generated during the production of the casting to cause defects such as blow holes in the casting, or an offensive odor at the production site. The blending ratio of polyvinyl alcohol is more preferably 2 to 10 parts by mass, and still more preferably 3 to 9 parts by mass with respect to 100 parts by mass of the inorganic binder.
The method of grinding and mixing the inorganic binder and polyvinyl alcohol includes separate grinding in which both are separately ground and then mixed, and mixed grinding in which both are mixed at the same time and simultaneously ground, but the time and effort of grinding is taken into consideration For example, mixing and grinding is preferred.
The degree of saponification of the polyvinyl alcohol is preferably 80 to 90 mol% because the solubility is high and the strength of the molded product is improved.
The average particle diameter (median diameter, D50) of polyvinyl alcohol is preferably 150 μm or less, more preferably 90 μm or less, and still more preferably 10 to 75 μm because high strength can be obtained. The content of particles of polyvinyl alcohol larger than 94 μm is preferably 90% by mass or less, more preferably 45% by mass or less, and still more preferably 30% by mass or less. Further, the content of polyvinyl alcohol larger than 77 μm is preferably 90% by mass or less, more preferably 60% by mass or less, and still more preferably 50% by mass or less.

3. Hydraulic composition The hydraulic composition is a composition comprising 28 to 60 parts by mass of water and sand with respect to a total of 100 parts by mass of the composite binder. If the mixing ratio of water is in the above range, strength development can be ensured. In addition, the compounding ratio of water is preferably 30 to 55 parts by mass, more preferably 35 to 46 parts by mass from the viewpoint of further enhancing the strength and dimensional accuracy of the mold.
In addition, the blending ratio of sand is preferably 100 to 600 parts by mass, more preferably 150 to 500 parts by mass, and still more preferably 200 to 400 parts by mass with respect to 100 parts by mass of the composite binder. If the blending ratio of sand is within the above range, similarly, strength development can be secured.
The sand is not particularly limited as long as it is refractory sand, and one or more types selected from silica sand, olivine sand, zircon sand, chromite sand, alumina sand, artificial sand and the like can be mentioned. As the water, normal tap water, well water and the like can be used. In addition, even if water is used in combination with one or more selected from thickeners, lubricants, fluidizers, surfactants, and surface tension reducing agents in order to impart various functions required. Good.

4. Other Components in Hydraulic Composition In order to facilitate the operation (depowdering) of removing the uncured powder of the hydraulic composition remaining after molding from the molded body, the hydraulic composition of the present invention further comprises The hydrophobic fumed silica can be contained as an optional component in an amount of 0.1 to 2 parts by mass, more preferably 0.5 to 1.5 parts by mass, based on 100 parts by mass of the composite binder. Here, the hydrophobic fumed silica is a silica powder in which the surface of fumed silica is treated with silane or siloxane to make the surface hydrophobic.
Moreover, in order to raise the removal efficiency of the powder of a hydraulic composition more, BET specific surface area of hydrophobic fumed silica becomes like this. Preferably it is 30-300 m < ² > / g. If the BET specific surface area of the hydrophobic fumed silica is within the above range, the flowability of the powder is improved, the surface spread by the additive manufacturing apparatus is flat, and the weight of the mold can be reduced without lowering the strength. . In addition, hydrophobic fumed silica is effective in preventing caking of powder and improving mixing properties.

  The hydraulic composition of the present invention may further contain optional components such as blast furnace slag, fly ash, silica fume, finely powdered silica, and limestone powder as a strength-increasing adjusting material or the like.

5. Method for Producing a Mold The production method is a method for producing a mold using an additive production apparatus and the hydraulic composition of the present invention. The additive manufacturing apparatus is not particularly limited, and commercially available products such as a powder laminate type additive manufacturing apparatus can be used. Also, the hydraulic composition prior to containing water is prepared by mixing the above-mentioned components with a commercially available mixer or manually. When a plurality of materials are used as the binder, the binder may be previously mixed by a commercially available mixer or by hand, or may be mixed and pulverized by a grinder.
As a method of curing the mold, there is a method of air curing alone, a method of air curing followed by water curing, or surface impregnation agent curing. Among these, air curing alone is preferable from the viewpoint of early development of strength and suppression of water vapor generated at the time of production of castings. Further, from the viewpoint of strength enhancement by calcium aluminate, cement, and polyvinyl alcohol, the temperature of atmospheric curing is preferably 10 to 100 ° C., more preferably 30 to 80 ° C. Further, the relative humidity of atmospheric curing is preferably 10 to 90%, more preferably 15 to 80%, and still more preferably 20 to 60%, in view of sufficient strength expression and production efficiency. Furthermore, the atmospheric curing time is preferably 1 hour to 1 week, more preferably 2 hours to 5 days, and still more preferably 3 hours to 4 days, in view of sufficient strength expression and production efficiency.

Hereinafter, the present invention will be described by way of examples, but the present invention is not limited to these examples.
1. Materials used (1) Calcium aluminates
(i) Amorphous calcium aluminate (abbreviation: CA)
The molar ratio of CaO / Al ₂ O ₃ is 2.2, the vitrification ratio is 95% or more, and the Blaine specific surface area is 2040 cm ² / g.
(ii) Alumina cement (abbreviation: AC)
Denka Alumina Cement No. 1 (trade name), with a specific surface area of 4570 cm ² / g, manufactured by Denka Co., Ltd.
(2) Quick-hardening cement
(i) Super jet cement (trade name), the content of calcium silicate is 47% by mass, setting (initial) is 30 minutes, and the specific surface area of blaine is 4700 cm ² / g. However, 14% by mass of anhydrous gypsum is included. Made by Pacific Cement Co., Ltd.
(ii) Water-stopping cement Lion Shisui 105 (trade name) manufactured by Sumitomo Osaka Cement Co., Ltd.
(3) Early-Strength Portland Cement The calcium silicate content is 75% by mass, the setting (initial) is 30 minutes, and the brane specific surface area is 4000 cm ² / g, manufactured by Pacific Cement Co., Ltd.
(4) Gypsum Natural anhydrous gypsum, produced in Thailand, has a specific surface area of 7200 cm ² / g.
(5) Sand The following two types of artificial casting sand were used in equal amounts by mixing.
Espar # 180 L (trade name), alumina-based, manufactured by Yamakawa Sangyo Co., Ltd.
NAIGAI THERABEADS # 1450 (registered trademark), Alumina-based, Itochu Celatech Co., Ltd.
(6) Polyvinyl alcohol (i) Polyvinyl alcohol a
Item No. 22-88S1 (PVA 217 SS), manufactured by Kuraray Co., Ltd.
The saponification degree is 87 to 89%, the average particle size (median diameter, D50) is 60 μm, the content of particles larger than 94 μm is 29% by mass, and the content of particles larger than 77 μm is 47% by mass, 10% The diameter (D10) is 25 μm, and the 90% diameter (D90) is 121 μm.
[Classification of polyvinyl alcohol]
The polyvinyl alcohol a is classified using a sieve and has an aperture of 75 μm and 150 μm (average particle diameter 106 μm), an aperture of 45 μm and 75 μm (average particle diameter 63 μm), and an aperture of 25 μm and 45 μm A classified product of polyvinyl alcohol having an average particle size of 38 μm was produced.
Furthermore, a ground product of polyvinyl alcohol a was also prepared by mixing calcium aluminate crushed to a particle size of 5 mm or less and polyvinyl alcohol a simultaneously and simultaneously grinding the calcium aluminate to a specific surface area of 2040 cm ² / g. did. However, the particle size of the pulverized product of polyvinyl alcohol a was mixed with calcium aluminate and could not be measured. However, the average particle diameter (median diameter, D50) of the calcium aluminate having a specific surface area of 2040 cm ² / g is 25 μm, and it is estimated to be smaller than 25 μm in view of the crushability.
(Ii) polyvinyl alcohol b
Product No. KP18-88S1, manufactured by Kuraray.
The saponification degree is 87 to 89%, the average particle size (median diameter, D50) is 57 μm, the content of particles larger than 94 μm is 30% by mass, and the content of particles larger than 77 μm is 44% by mass, 10% The diameter (D10) is 23 μm, and the 90% diameter (D90) is 123 μm.
(Iii) polyvinyl alcohol c
Product number 22-88 S1 (PVA 217 S), manufactured by Kuraray Co., Ltd.
The saponification degree is 87 to 89%, the average particle size (median diameter, D50) is 113 μm, the content of particles larger than 94 μm is 81% by mass, and the content of particles larger than 77 μm is 87% by mass, 10% The diameter (D10) is 57 μm, and the 90% diameter (D90) is 162 μm.
(Iv) polyvinyl alcohol d
Product number D5100, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.
The saponification degree is 87 to 89%, the average particle size (median diameter, D50) is 56 μm, the content of particles larger than 94 μm is 38% by mass, and the amount of particles larger than 77 μm is 46% by mass. D10) is 14 μm, and the 90% diameter (D90) is 155 μm.
(V) Polyvinyl alcohol e
Product number Elvanol 71-30, manufactured by Kuraray.
The degree of saponification is 100%, and the average particle size (median diameter, D50) is 110 μm.
(Vi) polyvinyl alcohol f
Product number Elvano 80-18, manufactured by Kuraray.
The degree of saponification is 100%, and the average particle size (median diameter, D50) is 98 μm.
The particle diameter of the polyvinyl alcohol was measured by SALD-2000J manufactured by Shimadzu Corporation using silicone oil as a medium.
(7) Water 3% by weight aqueous glycerol solution (binder solution for ProJet 660Pro), manufactured by 3D

2. Preparation of hydraulic composition and test pieces The test pieces of Examples 1 to 4 and Comparative Examples 1 to 5 were the amorphous calcium aluminate (CA), a fine mineral powder (Brene specific surface area of 2000 cm ² / g). The powder mixture (hydraulic composition containing no water) was prepared by mixing silica stone powder, super jet cement, polyvinyl alcohol not classified, and sand in the amounts shown in Table 1.
Next, using the powder mixture and a binder injection type powder layer forming apparatus (trade name: ProJet 660Pro, manufactured by 3D System Co., Ltd.) as an additive manufacturing apparatus, the cross section size is 10 mm long and 16 mm wide by a binder injection method. , And a molded body of 80 mm in length was produced. The molding conditions are such that the water amount setting value of the device is 65% outside (Shell) and 90% inside (Core) (water / composite binder ratio is 29 to 32% by mass), room temperature (20 ° C.), relative humidity 60 %Met. Further, the molded body was air cured under the conditions of 40 ° C. and relative humidity 30% for 3 hours to prepare a test body.
In the test pieces of Examples 5 to 28, 90 parts by mass of the amorphous calcium aluminate, 10 parts by mass of super jet cement, polyvinyl alcohol in an amount shown in Table 2, and 200 parts by mass of sand are mixed to obtain powder. A mixture (hydraulic composition containing no water) was prepared. Next, in the apparatus shown in Table 2, with the water amount setting value and the water / composite binder ratio, under the conditions of room temperature (20 ° C.) and relative humidity 60%, the dimension of the cross section is 10 mm long by the binder injection method. A compact having a width of 16 mm and a length of 80 mm was produced. Further, the molded body was air-cured for 3 hours under conditions of 20 ° C., 40 ° C., or 60 ° C. and a relative humidity of 30% to prepare a test body.
In the manufacture of a molded body by the above apparatus, a predetermined position of the powder mixture is selected, the water amount setting value of the apparatus is adjusted from the nozzle, and water is jetted to the outside and the inside of the powder mixture. The mixture solidified.

3. Measurement of Bending Strength of Specimen Next, using the above-mentioned specimen, a three-point bending test is conducted by a bending strength tester (model number: MODEL-2257, manufactured by EIKO ENGINEERING CO., LTD.), And the bending strength of the specimen and the specimen The width and height dimensions of the were measured. The results are shown in Table 1. From the viewpoint of practicality, bending strength of 1.0 N / mm ² or more was accepted (practical) at a material age of 3 hours as a target value.
As shown in Table 1, the test piece (comparative example 4) produced only with calcium aluminates does not satisfy the standard value. Moreover, although the test body (comparative examples 2 and 3) containing the completely saponified polyvinyl alcohol does not satisfy | fill a reference value, the test object (Examples 1-4) containing the partially saponified polyvinyl alcohol satisfies a reference value.

4. Preparation of hydraulic composition and test body According to the composition of Table 3, calcium aluminates, cement, gypsum, polyvinyl alcohol a and sand are mixed to obtain a powder mixture (water-free hydraulic composition) Made.
Next, using the powder mixture and a binder injection type powder layer forming apparatus (trade name: ProJet 660Pro, manufactured by 3D System Co., Ltd.) as an additive manufacturing apparatus, the cross section size is 10 mm long and 16 mm wide by a binder injection method. After preparing a molded body of 80 mm in length and 80 mm in length, the molded body was air-cured for 3 to 72 hours under the conditions of 40 ° C. and relative humidity 30% to manufacture a test body.
In the manufacture of a molded body by the above apparatus, a predetermined position of the powder mixture is selected, and water is jetted from the nozzle to the outside and the inside of the sample according to the water amount setting value of the apparatus shown in Table 3 The mixture solidified.

5. Bending Strength of Specimen Next, a three-point bending test was performed using the specimen and a bending strength tester (model number: MODEL-2257, manufactured by AIKO ENGINEERING CO., LTD.) To measure the bending strength of the specimen. The results are shown in Table 3. From the viewpoint of practicality, bending strength of 1.0 N / mm ² or more was accepted (practical) at a material age of 3 hours as a target value.
As shown in Table 3, the bending strengths of all the examples satisfy the above standard value. In addition, samples (Examples 29 to 37) in which calcium aluminates are mixed with quick-hardening cement and gypsum are more stronger than those containing calcium aluminates and partially saponified polyvinyl alcohol (Example 1). Is high. Among calcium aluminates, the strength of the test sample containing amorphous calcium aluminate (for example, Example 32) is higher than that of the test body containing alumina cement (Example 33).

Claims (9)

  The hydraulic composition for addition manufacturing apparatuses containing the composite binder which contains 1.5-12 mass parts of polyvinyl alcohol partially saponified with respect to 100 mass parts of inorganic binders, and sand.   The hydraulic composition for addition manufacturing devices according to claim 1, wherein the inorganic binder contains 50 to 100 mass% of calcium aluminates, based on 100 mass% of the entire inorganic binder.   The hydraulic composition for addition manufacturing devices according to claim 1 or 2, wherein the inorganic binder contains 0.5 to 10 mass% of gypsum based on 100 mass% of the entire inorganic binder.   The hydraulic composition for addition manufacturing devices according to any one of claims 1 to 3, wherein the inorganic binder contains 0 to 50 mass% of quick-hardening cement, based on 100 mass% of the entire inorganic binder.   The hydraulic composition for addition manufacturing apparatuses of any one of Claims 1-4 whose average particle diameter of the said polyvinyl alcohol is 150 micrometers or less.   The hydraulic composition for addition manufacturing devices according to any one of claims 2 to 5, wherein the calcium aluminates are amorphous calcium aluminate.   The hydraulic composition for addition manufacturing apparatuses of any one of Claims 1-6 which further contains 28-60 mass parts of water with respect to a total of 100 mass parts of the said composite binder.   The manufacturing method of a casting_mold | template which shape | molds a mold using an addition manufacturing apparatus and the hydraulic composition for addition manufacturing apparatuses of any one of Claims 1-7. The method for producing a mold according to claim 8, wherein a curing temperature of the mold is 10 to 80 ° C.