JP7186004B2 - HYDRAULIC COMPOSITION FOR BINDER INJECTION TYPE POWDER LAYER MOLDING EQUIPMENT AND METHOD FOR MANUFACTURING MOLD - Google Patents

Description

TECHNICAL FIELD The present invention relates to a hydraulic composition for use in additive manufacturing equipment (3D printer), which exhibits good spreadability and excellent aesthetic appearance and dimensional accuracy of molded products, and a method for manufacturing a mold using the composition. .

Casting is a traditional metalworking method in which molten metal is poured into molds to produce castings. The self-hardening molds used for this casting are classified into organic and inorganic types depending on the caking material (binder) used. Of these, the inorganic types are mainly classified into water glass type and cement type. However, depending on the casting temperature, the gypsum contained in the cement-based self-hardening mold thermally decomposes to generate gas, which causes defects in the casting and impairs its appearance and function. In addition, the manufacture of this casting mold requires the preparation of models and wooden molds as a pre-process, which is time-consuming and costly.
Therefore, there is a demand for a casting mold manufacturing method that does not impair the appearance of castings and does not require such a pre-process.

By the way, recently, additive manufacturing equipment has attracted attention as a rapid and precise molding means. Among these additional manufacturing devices, for example, a powder lamination forming device is a device that, after spreading powder on a flat surface, sprays a water-based binder onto the powder and solidifies the powder, and then sequentially stacks and forms the solidified products in the vertical direction. is. The feature of this apparatus is that it divides three-dimensional molding data created by three-dimensional CAD or the like into a large number of horizontal planes, and successively stacks the shapes of these horizontal planes to produce a molded body.
Therefore, if the mold can be manufactured using the above-mentioned apparatus, the above-mentioned pre-process becomes unnecessary, and it is expected that the working time and cost can be reduced.

For example, in Patent Document 1, as a hydraulic composition for additive manufacturing equipment suitable for powder lamination molding, refractory sand such as silica sand, olivine sand, and artificial sand is blended with 15 to 50% of fast-hardening cement and kneaded. A technology is disclosed in which a water-based binder is added to (mixed) materials, solidified and laminated to obtain a molded body. Here, the powder lamination molding method means that the molding liquid is dropped or sprayed through a nozzle such as an inkjet to a predetermined range of the powder material placed on the loading table (pedestal) and solidified, and the layers are solidified one by one. is laminated to form a desired shape.

However, depending on the combination of the binder and sand, when the material is layered by the additional manufacturing equipment, the smoothed surface may not be flat, impairing the appearance of the molded product and impairing the dimensional accuracy. (See FIG. 4 below).

Japanese Patent Application Laid-Open No. 2011-51010

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a hydraulic composition or the like for use in an additive manufacturing apparatus, which is excellent in spreadability by the additive manufacturing apparatus and excellent in appearance and dimensional accuracy of molded articles.

As a result of intensive studies in order to solve the above problems, the inventors of the present invention have found that a hydraulic composition containing a binder such as calcium aluminate alone or a binder and sand and satisfying the following formula (1) is , found that the above object can be achieved, and completed the present invention.
That is, the present invention is a hydraulic composition for an addition manufacturing device, etc., having the following constitution.

[1] A hydraulic composition for a binder injection type powder lamination molding apparatus, which comprises a binder, sand and water and satisfies the following formula (1),
The binder contains 50 to 100% by mass of calcium aluminates having a molar ratio of CaO/Al ₂ O ₃ of 1.5 to 3.0, and 0 to 50% by mass of quick-hardening cement, with the total binder being 100% by mass. % by mass, and 0 to 50% by mass of cement,
The particle size of the binder is D10 4-7 μm, D50 24-40 μm and D90 60-140 μm,
The mixing ratio of sand is 50 to 600 parts by mass with respect to 100 parts by mass of the binder,
The mixing ratio of water is 28 to 60 parts by mass with respect to 100 parts by mass of the binder.
Hydraulic composition for binder injection type powder lamination molding equipment.
Mass of sand/mass of binding material ≥ 1.1 × 10 ^-3 × Blaine specific surface area of binding material - 2.2
…(1)
[2] The hydraulic composition for a binder injection type powder laminate molding apparatus according to [1], wherein the binder has a Blaine specific surface area of 1000 to 6000 cm ² /g.
[3] The hydraulic composition for a binder injection type powder laminate molding apparatus according to [1] or [2], wherein the sand has an average particle size of 40 to 200 μm.
[4] A mold manufacturing method, comprising forming a mold using a binder injection powder lamination molding apparatus and the hydraulic composition for a binder injection powder lamination molding apparatus according to any one of [1] to [3] above. .

ADVANTAGE OF THE INVENTION The hydraulic composition for the addition manufacturing apparatus of this invention can obtain a molded object with a favorable spreadability by an addition manufacturing apparatus, and a beautiful appearance and high dimensional accuracy.

FIG. 2 is a diagram showing the relationship between the mass ratio of sand/binder and Blaine's specific surface area of the binder, and the straight line in the figure represents the formula (1). FIG. 2 is a diagram showing the relationship between the mass ratio of sand/binder and Blaine's specific surface area of the binder, and the straight line in the figure represents the formula (2). FIG. 10 is a diagram showing a state after the hydraulic composition for an addition manufacturing device of Example 7 has been evened out using the addition manufacturing device. FIG. 10 is a view showing a state after the hydraulic composition for addition manufacturing equipment of Comparative Example 5 is evened out using the addition manufacturing equipment.

As described above, the present invention provides a hydraulic composition for additive manufacturing equipment (hereinafter referred to as "hydraulic composition It is sometimes abbreviated as “. Hereinafter, the present invention will be described separately for a binder, sand, a hydraulic composition, and a method for manufacturing a mold.

1. Binder The binder contains as an essential component one or more cementitious substances selected from calcium aluminates, fast-hardening cement, and cement, and is composed of polymers, gypsum, hydrophobic fumed silica, alkali metal salts, and the like. It is a binding material containing one or more selected as optional components.
The content of the cementitious substance, which is an essential component in the binder, is preferably 50% by mass or more, more preferably 60 to 100% by mass, based on 100% by mass of the entire binder, in order to improve early strength development. %, more preferably 70 to 95% by mass. Next, the description will be divided into calcium aluminates, fast-hardening cement, cement, polymer, gypsum, hydrophobic fumed silica, and alkali metal salts.

(1) Calcium aluminates The calcium aluminates are 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 and _3CaO . - calcium _{aluminates such as 5Al2O3} or _{CaO.2Al2O3 ;} calcium _{aluminoferrites such as 2CaO.Al2O3.Fe2O3 or 4CaO.Al2O3.Fe2O3} ; Calcium haloaluminates including calcium fluoroaluminates such as 3CaO.3Al ₂ O ₃ .CaF ₂ and 11CaO.7Al ₂ O ₃ .CaF ₂ in which halogen is dissolved or substituted in aluminate; 8CaO.Na ₂ O.3Al Calcium sodium aluminate such as _2O3 and _{3CaO.2Na2O.5Al2O3} ; _{calcium lithium} aluminate; _alumina cement; , S, and other trace elements (including oxides, etc.) are solid-dissolved in minerals.
Among these calcium aluminates, calcium aluminate is preferred, and amorphous calcium aluminate is particularly preferred, because it has high strength development and enables depowder and transportation immediately after production. Amorphous calcium aluminate is produced by melting a raw material and then quenching it. Therefore, it has substantially no crystalline structure. Since early strength development is high, the vitrification rate is preferably 90% or more.

The CaO/Al ₂ O ₃ molar ratio of the calcium aluminates is preferably 1.5-3.0, more preferably 1.7-2.4. When the molar ratio is 1.5 or more, the hydraulic composition exhibits high early strength, and when it is 3.0 or less, the hydraulic composition has high heat resistance.
The content of calcium aluminates in the binder is preferably 50-100% by mass. When this value is 50% by mass or more, the hydraulic composition exhibits high early strength development and high heat resistance. The value is preferably 60 to 100% by mass, more preferably 70 to 100% by mass, still more preferably 80 to 95% by mass. As described above, among calcium aluminates, amorphous calcium aluminate is preferred.
In addition, the Blaine specific surface area (fineness specified in JIS R 5201) of calcium aluminates is preferably 1000 to 6000 cm ² /g, more than It is preferably 1500 to 5000 cm ² /g.

(2) Fast-Hardening Cement The fast-hardening cement is a fast-hardening cement (ultra-fast-hardening cement) whose setting (initial setting) measured according to JIS R 5210 is within 30 minutes, or a water stop cement. Commercially available products such as fast-hardening cement include Super Jet Cement (manufactured by Taiheiyo Cement Co., Ltd.), Jet Cement (manufactured by Sumitomo Osaka Cement Co., Ltd.), Lion Shisui (registered trademark, manufactured by Sumitomo Osaka Cement Co., Ltd.), and Denka Super Cement (Denka company).
In order to improve early strength development, the content of the fast-hardening cement in the binder is preferably 50 to 100% by mass, more preferably 70 to 95% by mass, and still more preferably 80 to 90% by mass.
In addition, when used in combination with calcium aluminates, in order to improve early strength development and to reduce gas generation when used as a mold, the total binder is 100% by mass, preferably 0 to 50% by mass, more preferably 0 to 30% by mass, and even more preferably 5 to 20% by mass.

(3) Cement The cement preferably sets (initial) within 3 hours and 30 minutes as measured in accordance with JIS R 5210 because it has high early strength development 3 hours after molding, and within 1 hour. is more preferred.
The cement includes one or more selected from ordinary Portland cement, early-strength Portland cement, moderate heat Portland cement, low heat Portland cement, white Portland cement, ecocement, blast furnace cement, fly ash cement, and cement clinker powder. In the present invention, cement clinker powder is also included in cement.
In order to improve early strength development, the content of cement in the binder is preferably 0 to 50% by mass, more preferably 0 to 30% by mass, and still more preferably 0 to 50% by mass, based on 100% by mass of the entire binder. 20% by mass.

(4) Polymer The polymer is a polymer dispersion, a re-emulsified powder resin, or the like defined in JIS A 6203. In terms of polymer types, polyacrylic acid ester, ethylene/vinyl acetate copolymer, styrene/ At least one selected from butadiene copolymer, vinyl acetate/vinyl versatate copolymer, vinyl acetate/vinyl versatate/acrylate terpolymer, polyvinyl alcohol, maltodextrin, epoxy resin, and urethane resin is mentioned.
Among these, polyvinyl alcohol (partially saponified or completely saponified polyvinyl acetate) is preferable, and polyvinyl alcohol having a degree of saponification of 85 to 90 mol% is more preferable, since early strength development can be obtained. . Also, the average particle diameter (median diameter, D50) of polyvinyl alcohol is preferably 150 μm or less, more preferably 90 μm or less, still more preferably 10 to 75 μm, since high strength can be obtained. The content of polyvinyl alcohol particles larger than 94 μm is preferably 90% by mass or less, more preferably 45% by mass or less, and even more preferably 30% by mass or less. Also, the content of polyvinyl alcohol particles larger than 77 μm is preferably 90% by mass or less, more preferably 60% by mass or less, and even more preferably 50% by mass or less.

Moreover, the blending ratio of the polymer is preferably 2 to 12 parts by mass with respect to 100 parts by mass of the cementitious substance. If the blending ratio is less than 2 parts by mass, the effect of improving the strength is low, and if it exceeds 12 parts by mass, deformation or cracking may occur due to shrinkage of the molded product depending on the shape, and molds with complicated shapes may not be manufactured. In addition, there are cases in which gas is generated during the production of castings, causing defects such as blowholes in the castings, and producing offensive odors at the manufacturing site. The blending ratio of the polymer is more preferably 2 to 10 parts by mass, more preferably 3 to 9 parts by mass, per 100 parts by mass of the cementitious substance.
Cementitious substances and polymers can be pulverized and mixed in two ways: individual pulverization, in which both are pulverized separately and then mixed, and mixed pulverization, in which both are mixed and then pulverized simultaneously. , preferably mixed grinding.

(5) Gypsum The gypsum includes one or more selected from anhydrous gypsum, hemihydrate gypsum, and dihydrate gypsum. Among these, gypsum hemihydrate is preferred because of its higher early strength development. The content of gypsum in the binding material is preferably 0.5 to 5% by mass in terms of anhydrous gypsum, with the entire binding material being 100% by mass, in order to prevent gas and graphite spheroidization defects during the production of castings. It is more preferably 0.8 to 3% by mass, still more preferably 1 to 2% by mass.

(6) Other Additives In order to facilitate the work of removing the uncured powder of the hydraulic composition remaining after molding from the molded body (depowder), the hydraulic composition of the present invention further includes a binding Hydrophobic fumed silica can be included 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 a total of 100 parts by mass of the material. Here, hydrophobic fumed silica is silica powder obtained by treating the surface of fumed silica with silane or siloxane to make the surface hydrophobic.
Further, the BET specific surface area of the hydrophobic fumed silica is preferably 30 to 300 m ² /g in order to further increase the removal efficiency of the powder of the hydraulic composition. If the BET specific surface area of the hydrophobic fumed silica is within this range, the fluidity of the powder is improved, the surface spread by the additional manufacturing device is flat, and the weight of the mold can be reduced without lowering the strength. . Hydrophobic fumed silica is also effective in preventing caking of powder and improving mixability.
In addition, the hydraulic composition of the present invention may further include, as an adjusting material for strength development, any of alkali metal salts, alkaline earth metal salts, blast furnace slag, fly ash, silica fume, silica fine powder, and limestone powder. may contain components of

The Blaine specific surface area of the binder is preferably 1000 to 6000 cm ² /g, more preferably 1500 to 5000 cm ² /g, so that it can be evenly spread in the additional manufacturing device and the strength of the molded product does not decrease. is g. Each binder is prepared by mixing powders. The polymer may be used by dissolving it in water.

2. Sand The sand is natural sand or foundry sand that is coarser than the binding material. When the hydraulic composition is used for the mold, the sand is preferably refractory sand, such as silica sand, olivine sand, zircon sand, One or more selected from chromite sand, alumina sand, artificial sand, and the like can be used.
The average particle size of the sand is preferably 40-200 μm, more preferably 50-180 μm, still more preferably 60-150 μm, in order to obtain good spreadability when mixed with the binder.
Also, if the blending ratio of sand is within the range of the formula (1), the spreadability is good. If the blending ratio of sand is within the range of the following formula (2), the leveling property is better.
Mass of sand/mass of binding material ≧1.0×10 ⁻³ × Blaine specific surface area of binding material −1.6
…(2)
In order to obtain a high-strength hydraulic composition, the sand content is preferably 50 to 600 parts by mass, more preferably 100 to 500 parts by mass, and still more preferably 200 to 600 parts by mass with respect to 100 parts by mass of the binder. 400 parts by mass.

3. Hydraulic Composition The hydraulic composition preferably contains 28 to 60 parts by mass of water and sand with respect to a total of 100 parts by mass of the binder. If the content of water is within this range, strength development can be ensured. The mixing ratio of water is preferably 30 to 55 parts by mass, more preferably 32 to 45 parts by mass, from the viewpoint of increasing the strength and dimensional accuracy of the mold.

4. Manufacturing Method of Casting Mold This manufacturing method is a method of manufacturing a casting mold using an additive manufacturing apparatus and the hydraulic composition of the present invention. The additive manufacturing device is not particularly limited, and a commercially available product such as a powder lamination type additive manufacturing device can be used. Also, the hydraulic composition is prepared by mixing the above components with a commercially available mixer or by hand. When a plurality of materials are used as the binding material, the binding materials may be mixed in advance using a commercially available mixer or manually, or may be mixed and pulverized using a pulverizer. Usual tap water, well water, or the like can be used as water. In addition, water is used by mixing one or more selected from thickeners, lubricants, fluidizing agents, surfactants, polymers, and surface tension reducing agents in order to impart various required functions. may
Methods of curing the mold include air curing alone, air curing followed by water curing, and surface impregnation curing. Among these, air curing alone is preferable from the viewpoint of early development of strength and suppression of water vapor generated during casting production. The temperature for air curing is preferably 10 to 100.degree. C., more preferably 30 to 80.degree. The relative humidity during air curing is preferably 10 to 90%, more preferably 15 to 80%, still more preferably 20 to 60%, from the viewpoint of sufficient strength development and production efficiency. Furthermore, the air curing time is preferably 1 hour to 1 week, more preferably 2 hours to 5 days, still more preferably 3 hours to 4 days, from the viewpoint of sufficient strength development and production efficiency.

The surface impregnating agent curing is curing in which an alkali silicate aqueous solution is sprayed on the compact or the compact is immersed in the alkali silicate aqueous solution to increase the strength of the compact.
The alkali silicate in the alkali silicate aqueous solution is preferably sodium silicate and/or potassium silicate. The content of alkali silicate in the alkali silicate aqueous solution is preferably 10 to 40% by mass. If the content is less than 10% by mass, penetration of the alkali silicate is insufficient and the effect of increasing strength is low. The content is more preferably 20 to 35% by mass.

EXAMPLES The present invention will be described below with reference to Examples, but the present invention is not limited to these Examples.
1. Materials used (1) Calcium aluminate Amorphous calcium aluminate, which is a trial product.
The molar ratio of CaO/Al ₂ O ₃ is 2.2, and the vitrification rate is 95% or more.
Blaine specific surface area (JIS R 5201) is 1500 cm ² /g, 2040 cm ² /g, 3500 cm ² /g and 5000 cm ² /g.
The grain sizes of calcium aluminates and sand described later were measured by Microtrac MT3300EXII manufactured by Microtrac using ethanol as a solvent.
(2) Fast-hardening cement Super Jet Cement, manufactured by Taiheiyo Cement Co., Ltd.
The content of calcium silicate is 47% by mass, the coagulation (initial setting) is 30 minutes, and the Blaine specific surface area is 4700 cm ² /g.
(3) Sand
(i) Sand A: Natural casting sand/alumina sand #200, manufactured by Ace Sanshosha.
The average particle diameter (median diameter, D50) is 100 μm, the 10% diameter (D10) is 57 μm, and the 90% diameter (D90) is 155 μm.
(ii) Sand B: Alumina-based, trade name Espearl #180L, manufactured by Yamakawa Sangyo Co., Ltd.
The average particle diameter (median diameter, D50) is 75 μm, the 10% diameter (D10) is 45 μm, and the 90% diameter (D90) is 113 μm.
(iii) Sand C: Alumina-based, trade name: Naigai Cerabeads 60#1450 (registered trademark), manufactured by Itochu Ceratec.
The average particle diameter (median diameter, D50) is 124 μm, the 10% diameter (D10) is 95 μm, and the 90% diameter (D90) is 170 μm.
(iv) Sand D: Amorphous Calcium Aluminate Prototype.
The CaO/Al ₂ O ₃ molar ratio is 2.2, the vitrification rate is 95% or more, the average particle diameter (median diameter, D50) is 65 μm, the 10% diameter (D10) is 14 μm, and the 90% diameter (D90) is 184 μm.
(v) Sand E: Silica sand Product name: Tohoku Silica Sand No. 8 Manufactured by Tohoku Silica Sand Co., Ltd.
The average particle diameter (median diameter, D50) is 110 μm, the 10% diameter (D10) is 63 μm, and the 90% diameter (D90) is 160 μm.
When equal amounts of sand B and sand C are mixed and used, the average particle diameter (median diameter, D50) is 100 μm, the 10% diameter (D10) is 57 μm, and the 90% diameter (D90) is 155 μm.
(4) Water 3 mass% glycerol aqueous solution (binder solution for ProJet660Pro), manufactured by 3D System

2. Preparation of Hydraulic Composition and Specimen 90 parts by mass of the amorphous calcium aluminate and 10 parts by mass of quick-hardening cement, 100 parts by mass in total, were mixed with sand according to the formulation shown in Table 1 to form a powder mixture. (Hydraulic composition containing no water) was prepared. The Blaine specific surface area, average particle diameter (median diameter, D50), 10% diameter (D10), and 90% diameter (D90) of the binder (the mixture of amorphous calcium aluminate and fast-hardening cement) are shown. 1.
Next, a spreading test was conducted using the powder mixture and a binder injection type powder lamination molding apparatus (trade name: ProJet660Pro manufactured by 3D System Co., Ltd.) as an additional manufacturing apparatus. The leveling was visually observed. Photo 1 shows an example of good leveling, and Photo 2 shows an example of poor leveling.

As shown in Table 1, the greater the Blaine specific surface area of the binder, the greater the amount of sand required for good leveling. Fig. 1 shows the relationship between the Blaine specific surface area of the binder and the mass of the sand, which provides good leveling when the entire binder is 100 parts by mass. Therefore, if the hydraulic composition is blended so as to satisfy the formula (1), it is possible to obtain a molded article that is well laid out by an additional manufacturing apparatus and has a beautiful appearance and high dimensional accuracy.

Claims (4)

A hydraulic composition for a binder injection type powder lamination molding apparatus, which comprises a binder, sand and water and satisfies the following formula (1),
The binder contains 50 to 100% by mass of calcium aluminates having a molar ratio of CaO/Al ₂ O ₃ of 1.5 to 3.0, and 0 to 50% by mass of quick-hardening cement, with the total binder being 100% by mass. % by mass, and 0 to 50% by mass of cement,
The particle size of the binder is D10 4-7 μm, D50 24-40 μm and D90 60-140 μm,
The mixing ratio of sand is 50 to 600 parts by mass with respect to 100 parts by mass of the binder,
The mixing ratio of water is 28 to 60 parts by mass with respect to 100 parts by mass of the binder.
Hydraulic composition for binder injection type powder lamination molding equipment.
Mass of sand/mass of binding material ≥ 1.1 × 10 ^-3 × Blaine specific surface area of binding material - 2.2
…(1) 2. The hydraulic composition for a binder injection type powder lamination molding apparatus according to claim 1, wherein the binder has a Blaine specific surface area of 1000 to 6000 cm ² /g. 3. The hydraulic composition according to claim 1, wherein said sand has an average particle size of 40 to 200 μm. A mold manufacturing method, comprising molding a mold using a binder injection type powder lamination molding apparatus and the hydraulic composition for a binder injection type powder lamination molding apparatus according to any one of claims 1 to 3.

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