JP2018153820A - Manufacturing method of laminated mold - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an improved manufacturing method of a laminated mold in which a spray solution is easily settled into dry-coated sand by improving wettability with respect to a water component in the dry-coated sand using water glass as a binder.SOLUTION: A thin sand layer 20 is formed on a surface of a fire-resistance aggregate by using dry-coated sand which is obtained by forming a coating layer containing a surfactant together with water glass as a binder, and after that, the sand layer 20 is heated after being sprayed with an aqueous medium. By repeating work for forming prescribed two-dimensional pattern mold layers 34, a purposed three-dimensional laminated mold is manufactured by laminating the mold layers 34.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a method for producing a laminated mold, and in particular, by forming a thin sand layer and repeatedly curing it into a predetermined shape one by one, It relates to a method for producing a three-dimensional sand mold.

  In recent years, a lamination molding technique using a three-dimensional printing method has been actively studied and put into practical use. In addition, such lamination molding technology is applied to mold molding, and trial production of molds and production of molds for high-mix low-volume production are being studied all over the world. A mold forming method has been proposed. Among these laser systems and ink jet systems, the ink jet system manufacturing apparatus has an advantage that the apparatus is less expensive than the laser system.

  By the way, as a conventional method for layered modeling of a mold by a laser method, for example, a sand mold modeling method by a layering method as disclosed in Japanese Patent Laid-Open No. 9-168840 (Patent Document 1) has been proposed. ing. In the method, a resin layer-coated sand (resin coated sand) is sprayed to form a thin sand layer, and a predetermined step of the thinly layered sand layer is cured by laser irradiation. In this way, one layer of the sand mold is formed, and these steps are repeated in sequence, and a hardened sand layer corresponding to each cross-sectional shape of the target sand mold is sequentially laminated. A sand mold is shaped.

  However, in such a sand mold molding method using a laser laminating method, the resin-coated sand is heated and cured by heating by laser irradiation. In addition, the problem that organic odor is generated is inherent. Further, since a temperature difference is generated in the sand layer depending on the presence or absence of laser irradiation, internal stress is likely to occur, and there is a problem that warpage and distortion occur in the sand mold when stored for a long period of time. Furthermore, in order to heat and cure a predetermined part by laser irradiation, high output and precise control are required, and an expensive laser irradiation apparatus is required, and much energy is required for heating. The problem of becoming is also inherent.

  On the other hand, as a layered modeling method of a mold by an ink jet method, in Japanese Patent Application Laid-Open No. 2011-230421 (Patent Document 2), a layer forming step of forming a layer with a three-dimensional modeling powder containing a water-soluble polymer, and this layer formation A generation step of generating a layer having a product generated by dissolving the three-dimensional modeling powder in the modeling liquid by discharging a modeling liquid using water as a solvent from the inkjet head to the layer formed in the step. The manufacturing method of the three-dimensional molded object provided is clarified.

  Then, while suppressing evaporation of water, a thickening wetting agent that thickens the modeling liquid and a surfactant are contained in the used modeling liquid, and the pH is further adjusted to 7-9. It is said that the target three-dimensional model can be modeled according to the desired shape, but when this modeling liquid is sprayed from the inkjet head onto the three-dimensional model powder layer, it becomes dry There is a problem that it takes time for the modeling liquid to penetrate into the powder without the powder and the modeling liquid becoming familiar. In particular, when coated sand (coated sand) made of water glass as a binder is coated with refractory aggregate, the coated sand has the action of repelling water. Due to the delay, the molding time becomes long and molding defects are likely to occur. In addition, measures to increase the amount of modeling liquid can be considered as a countermeasure against the delay in penetration, but bleeding due to excessive modeling liquid occurs, resulting in a change in the shape of the molded mold, and deterioration in dimensional accuracy. Problems will be raised.

JP-A-9-168840 JP 2011-230421 A

  Here, the present invention has been made in the background as described above, and the problem to be solved is a dry-coated material using water glass as a binder in the additive manufacturing. An object of the present invention is to provide an improved method for producing a laminated mold, which makes it easier for the sprayed liquid to become familiar with such dry coated sand by improving the wettability of the sand (coated sand) with moisture. Another problem is that a method for producing a laminated mold that can shorten the molding cycle and reduce the amount of heat used by minimizing the amount of aqueous medium applied and reducing the heating time. Is to provide.

  Under such circumstances, as a result of intensive studies on the additive manufacturing method, the present inventors, as foundry sand, coated sand having a refractory aggregate coated with a coating layer containing water glass and a surfactant. The present inventors have found that the above-mentioned problems can be solved by solidifying or curing the formed mold layer by spraying an aqueous medium and heating, and have completed the present invention.

  And in order to solve the subject mentioned above, this invention can be implemented suitably in the various aspects as enumerated below. In addition, each aspect described below can be employed in any combination. In addition, it should be understood that the aspects and technical features of the present invention are not limited to those described below, but are recognized based on the description of the entire specification and the inventive concept described in the drawings. is there.

(1) After forming a thin sand layer using a coated sand formed by coating a fireproof aggregate with a binder, an aqueous medium is sprayed on the sand layer and heated to form a solidified layer having a predetermined two-dimensional pattern. In a method for producing a target three-dimensional laminated mold by repeating the operation of forming a hardened layer and laminating the solidified layer or hardened layer, the surface of the refractory aggregate is used as the coated sand. And a method for producing a laminated mold characterized by using dry coated sand obtained by forming a coating layer containing a surfactant together with water glass as a binder.
(2) The surfactant comprises a cationic surfactant, an anionic surfactant, an amphoteric surfactant, a nonionic surfactant, a silicone surfactant, and a fluorosurfactant. The method for producing a laminated mold according to the aspect (1), which is selected from the above.
(3) The said aspect characterized by the content of the said surfactant being a ratio of 0.1-20.0 mass parts with respect to 100 mass parts of solid content of the water glass in the said coated sand. The manufacturing method of the lamination | stacking casting_mold | template as described in aspect (1) or the said aspect (2).
(4) The method for producing a laminated mold according to any one of the above aspects (1) to (3), wherein the aqueous medium contains a surfactant.
(5) The laminate according to the aspect (4), wherein the aqueous medium further contains at least one of a curing accelerator, a humectant, a drying accelerator, and a preservative. Mold manufacturing method.
(6) In any one of the above aspects (1) to (5), the aqueous medium has a viscosity of 0.1 to 50 cP and a surface tension of 15 to 50 mN / m. The manufacturing method of the lamination mold of description.
(7) The method for producing a laminated mold according to any one of the aspects (1) to (6), wherein the coated sand further contains a lubricant on the surface thereof.
(8) The aspect (1), wherein the content of the lubricant is 0.1 to 10.0 parts by mass with respect to 100 parts by mass of the solid content of water glass in the coated sand. The manufacturing method of the lamination | stacking mold as described in any one of the said aspect (7).
(9) Moisture content in the coated sand is 5 to 55% by mass of the solid content of water glass. The layer according to any one of modes (1) to (8), Mold manufacturing method.
(10) The laminated casting according to any one of the aspects (1) to (9), wherein the dispersion of the aqueous medium on the sand layer is performed using an ink jet type spraying device. Mold manufacturing method.

According to such a method for producing a laminated mold according to the present invention, various effects as listed below can be achieved.
(A) Since wettability with respect to moisture in the coated sand is improved, the sprayed liquid is easily adapted to the dry coated sand, and the penetration of the aqueous medium into the coated sand can be improved.
(B) Because the coated sand has good wettability, the bonding between the layers in the laminate is strengthened, and there is no variation in the curing of each layer, so that stable lamination is achieved. , The strength of the mold is improved.
(C) Due to the wettability of the coated sand to moisture, the amount of aqueous medium sprayed can be minimized.
(D) Since the amount of aqueous medium sprayed becomes the minimum necessary, the heating time can be shortened, the molding cycle can be shortened, and the advantage is obtained that less heat is consumed.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic explanatory drawing which shows the 1st process employ | adopted in an example of the manufacturing method of the lamination mold | type according to this invention, Comprising: (a) is the state which has spread | coated the coated sand, (b) is a plane of the coated coated sand. Each of the expanded states is shown. It is a schematic explanatory drawing which shows the 2nd process employ | adopted in an example of the manufacturing method of the lamination mold | type according to this invention. It is a schematic explanatory drawing which shows the 3rd process employ | adopted in an example of the manufacturing method of the lamination mold | type according to this invention. It is a schematic explanatory drawing which shows the form after the process of 1 turn which consists of a process shown by FIGS. It is a schematic explanatory drawing which shows the state which repeated each process of the manufacturing method of the lamination mold | type according to this invention, and laminated | stacked the multiple-layered mold layer. It is a schematic explanatory drawing which shows the lamination mold obtained in embodiment of the manufacturing method of the lamination mold according to this invention shown by FIGS.

  Hereinafter, in order to clarify the configuration of the present invention more specifically, representative embodiments of the present invention will be described in detail with reference to the drawings.

  First, the coated sand used in the present invention is generally mixed with water glass in the form of an aqueous solution as a binder to the refractory aggregate, and further mixed with a surfactant, and It is produced by evaporating moisture from the resulting mixture, in other words, by evaporating the moisture in the water glass in the form of an aqueous solution or the moisture brought in by the surfactant. A dry coating layer containing a solid content of a water glass and a surfactant is formed on the surface of such a refractory aggregate at a predetermined thickness, and has a good room temperature fluidity. It is what has.

  Here, the “dry coated sand having room temperature fluidity” in the present invention means a coated sand from which a measured value is obtained when the dynamic angle of repose is measured regardless of the moisture content. This dynamic angle of repose means that the coated sand to be measured is accommodated in a cylinder whose one end in the axial direction is closed with a transparent plate (for example, 7.2 cm in diameter × 10 cm in height). Put the coated sand into the container to half of its volume), hold the shaft center in the horizontal direction, and rotate around the horizontal shaft center at a constant speed (for example, 25 rpm) to flow in the cylinder The angle formed between the slope and the horizontal plane when the slope of the coated sand layer is flat. On the other hand, for example, when the coated sand is moist, the coated sand layer does not flow as a flat surface without flowing in the cylinder, and as a result, the dynamic angle of repose can be measured. What cannot be done is called wet coated sand.

  The dry coated sand having room temperature fluidity according to the present invention has a moisture content of 5 to 55 with respect to the solid content of water glass contained in the coating layer covering the surface of the refractory aggregate. The amount is preferably an amount corresponding to the proportion of mass%, more preferably 10 to 50 mass%, and most preferably 20 to 50 mass%. When the moisture content in the coated sand is less than the amount corresponding to 5% by mass with respect to the solid content of the water glass in the coating layer, the water glass is vitrified, and water is added again during mold forming. However, when the amount exceeds 55% by mass, the coated sand may not be in a dry state. In addition, it does not specifically limit as a measuring method of the moisture content in a coated sand, The method according to types, such as water glass and surfactant, can be employ | adopted suitably. Specifically, the measuring method described in the column of Examples described later can be exemplified.

  The refractory aggregate constituting the coated sand used in the present invention is a refractory substance that functions as a base material of a mold, and various refractory granules or powders conventionally used for molds. Any material can be used, specifically, silica sand, recycled silica sand, special sand such as alumina sand, olivine sand, zircon sand, chromite sand, ferrochrome slag, ferronickel slag, Examples thereof include slag-based particles such as converter slag; artificial particles such as alumina-based particles and mullite-based particles and regenerated particles thereof; alumina balls, magnesia clinker, and the like. These refractory aggregates may be fresh sand, or reclaimed sand or recovered sand that has been used once or a plurality of times as a molding sand for molding a mold. Even mixed sand made by adding fresh sand to sand or recovered sand and mixing them can be used. And such a refractory aggregate will generally be used as an AFS index with a particle size of about 40 to 200, preferably with a particle size of about 50 to 150.

  Moreover, in the coated sand used for this invention, what has water glass as a main component will be used as a binder which coat | covers the above refractory aggregates. Here, water glass is a water-soluble silicate compound. Examples of such a silicate compound include sodium silicate, potassium silicate, sodium metasilicate, potassium metasilicate, lithium silicate, and silicate. Although ammonium etc. can be mentioned, Among these, especially sodium silicate (sodium silicate) will be used advantageously in this invention. As a binder, as long as water glass is used as a main component, other known water-soluble binders such as thermosetting resins, saccharides, proteins, synthetic polymers, salts and inorganic polymers are used in combination. Is possible. When such other water-soluble binder is used in combination with water glass, the proportion of water glass in the whole binder is preferably 60% by mass or more, more preferably 80% by mass or more, most preferably. It is 90% mass or more.

Here, sodium silicate is usually classified into Nos. 1 to 5 according to the molar ratio of SiO ₂ / Na ₂ O and used. Specifically, sodium silicate No. 1 has a SiO ₂ / Na ₂ O molar ratio of 2.0 to 2.3, and sodium silicate No. 2 is SiO ₂ / Na ₂ O ₂ . The molar ratio is 2.4 to 2.6, and sodium silicate No. 3 has a SiO ₂ / Na ₂ O molar ratio of 2.8 to 3.3. In addition, sodium silicate No. 4 has a SiO ₂ / Na ₂ O molar ratio of 3.3 to 3.5, and sodium silicate No. 5 has a SiO ₂ / Na ₂ O molar ratio. Is 3.6 to 3.8. Among these, sodium silicate Nos. 1 to 3 are also defined in JIS-K-1408. In the present invention, these various sodium silicates may be used alone or in combination, and the molar ratio of SiO ₂ / Na ₂ O may be adjusted by mixing. Is possible.

In the present invention, in order to advantageously obtain a dry coated sand, the sodium silicate constituting the water glass used as a binder has a molar ratio of SiO ₂ / Na ₂ O of generally 1.9 or more, Preferably, it is 2.0 or more, more preferably 2.1 or more. In the above-mentioned classification of sodium silicate, sodium silicate corresponding to No. 1 and No. 2 is particularly advantageously used. Become. Such sodium silicates No. 1 and No. 2 provide dry coated sand having stable and good characteristics even when the sodium silicate concentration in the water glass is wide. Further, the upper limit of the molar ratio of SiO ₂ / Na ₂ O in such sodium silicate is appropriately selected according to the characteristics of the water glass in the form of an aqueous solution, but generally 3.5 or less. , Preferably 3.2 or less, more preferably 2.7 or less. Here, when the molar ratio of SiO ₂ / Na ₂ O is smaller than 1.9, the viscosity of the water glass is lowered, and it becomes difficult to make the coated sand dry unless the water content is considerably reduced. On the other hand, if it exceeds 3.5, the solubility in water decreases, the adhesion area cannot be gained, and the strength of the mold finally obtained may decrease.

  The water glass used in the present invention means a solution of a silicate compound in a state dissolved in water. In addition to being used in a stock solution as purchased in the market, water is added to such a stock solution. It is also possible to add and use in a diluted state. And, from such water glass, the non-volatile content (water glass component) excluding volatile substances such as water and solvent is called solid content, which corresponds to the above-described soluble silicate compound such as sodium silicate. To do. Moreover, the higher the proportion of such solid content (nonvolatile content), the higher the concentration of the silicate compound in the water glass. Therefore, the solid content of the water glass used in the present invention corresponds to the amount excluding the amount of water in the stock solution when it is composed only of the stock solution, while the stock solution is converted into water. When the diluted solution obtained by dilution is used, the amount excluding the amount of water in the stock solution and the amount of water used for dilution corresponds to the solid content of the water glass used. It becomes.

  Further, the solid content in the water glass is set to an appropriate ratio depending on the type of the water glass component (soluble silicate compound) and the like, but preferably a ratio of 20 to 50% by mass. It is desirable to be contained in By making the water glass component corresponding to the solid content appropriately present in the aqueous solution, the water glass component can be uniformly and uniformly applied to the fire resistant aggregate during mixing (kneading) with the fire resistant aggregate. Thus, it becomes possible to advantageously shape the target mold. If the concentration of the water glass component in the water glass is too low and the total amount of solids is less than 20% by mass, the heating temperature is increased or the heating time is increased for drying the coated sand. For this reason, problems such as energy loss are caused. In addition, if the ratio of the solid content in the water glass becomes too high, it becomes difficult to uniformly coat the surface of the refractory aggregate with the water glass component, which causes a problem in improving the properties of the target mold. Therefore, it is desirable to prepare water glass in the form of an aqueous solution so that the solid content is 50% by mass or less, and thus the water content is 50% by mass or more.

And it is desirable that such water glass is used in a proportion of 0.1 to 5.0 parts by mass in terms of solid content when considered as only non-volatile content with respect to 100 parts by mass of the refractory aggregate. The ratio of 0.3 to 4.0 parts by mass is particularly advantageously employed, and a predetermined coating layer is formed on the surface of the refractory aggregate. Here, the measurement of solid content is implemented as follows. That is, 10 g of a sample was weighed and contained in an aluminum foil dish (length: 90 mm, width: 90 mm, height: 15 mm), placed on a heating plate maintained at 180 ± 1 ° C., and left for 20 minutes. Invert the sample pan and leave it on the heating plate for another 20 minutes. Thereafter, the sample dish is taken out from the heating plate, allowed to cool in a desiccator, weighed, and the solid content (% by mass) is calculated by the following formula.
Solid content (mass%) = [mass after drying (g) / mass before drying (g)] × 100

  In the present invention, if the amount of water glass used is too small, it is difficult to form a coating layer on the surface of the refractory aggregate, and the solidification or hardening of the coated sand at the time of mold molding may not proceed sufficiently. There is. In addition, even if the amount of water glass used is excessive, an excessive amount of water glass adheres to the surface of the refractory aggregate, making it difficult to form a uniform coating layer, and the coated sand adheres to each other. This may cause agglomeration (composite particles), which adversely affects the physical properties of the final mold and makes it difficult to remove the sand from the core after casting the molten metal. There is also a risk of triggering.

  By the way, in the coated sand used in the present invention, the coating layer covering the surface of the refractory aggregate has a great feature in that a surfactant is further contained together with water glass. It is. Thus, the coated sand according to the present invention has excellent water permeability, in other words, wettability to water, by further including a surfactant in the coating layer containing water glass. It has become a thing. For this reason, when moisture is supplied to the coated sand during molding, the surfactant mediates between the supplied moisture and water glass, so that the entire coated sand can be obtained even with a small amount of moisture. 1) Moisture supply time to the coated sand (for example, when water is supplied by ink jet, water is sprayed on the sand layer and penetrates into the sand layer). 2) It is possible to suppress the time until the required minimum), and 2) it has excellent wettability to water, so that the bond between the layers in the laminate becomes stronger and the interlayer strength (Strength against delamination between layers) is further improved, and 3) Molding is performed by shortening the heating time (time for drying the water sprayed by heating) to a necessary minimum by applying a small amount of water. With shortening the cycle, it is possible to effect the like can be minimized the amount of heat to be used, advantageously enjoyed.

  Here, in this invention, the quantity of surfactant contained in the coating layer containing water glass is 0.1-20.0 mass parts with respect to 100 mass parts of solid content of the water glass in a coating layer. The ratio is preferably 0.5 to 15.0 parts by mass, and particularly preferably 0.75 to 12.5 parts by mass. In this case, if the amount of the surfactant to be contained is too small, there is a possibility that the above-described effects cannot be enjoyed advantageously. On the other hand, if the amount of the surfactant is too large, the surfactant may be used again. The improvement of the effect according to the amount is not recognized, and depending on the surfactant, the water glass does not solidify when it is dried, and the coated sand may become wet. From the point of view, it is not a good idea. In the present invention, as the surfactant, any of a cationic surfactant, an anionic surfactant, an amphoteric surfactant, a nonionic surfactant, a silicone surfactant and a fluorine surfactant is used. Can also be used.

  Specifically, examples of the cationic surfactant include aliphatic amine salts, aliphatic quaternary ammonium salts, benzalkonium salts, benzethonium chloride, pyridinium salts, imidazolinium salts, and the like. Examples of the anionic surfactant include fatty acid soap, N-acyl-N-methylglycine salt, N-acyl-N-methyl-β-alanine salt, N-acyl glutamate, alkyl ether carboxylate, acyl Peptide, alkyl sulfonate, alkyl benzene sulfonate, alkyl naphthalene sulfonate, dialkyl sulfosuccinate, alkyl sulfoacetate, α-olefin sulfonate, N-acylmethyl taurine, sulfated oil, higher alcohol Sulfate, secondary higher alcohol sulfate, alkyl ether sulfate, secondary higher alcohol ethoxy sulfate, polyoxyethylene alkyl phenyl ether sulfate, monoglyculate, fatty acid alkylolamide sulfate, alkyl ether phosphorus Acid Examples include stealth salts and alkyl phosphate ester salts. Furthermore, examples of the amphoteric surfactant include carboxybetaine type, sulfobetaine type, aminocarboxylate, imidazolinium betaine and the like. In addition, nonionic surfactants include polyoxyethylene alkyl ether, polyoxyethylene secondary alcohol ether, polyoxyethylene alkylphenyl ether (eg, Emulgen 911), polyoxyethylene sterol ether, polyoxyethylene lanolin derivative , Polyoxyethylene polyoxypropylene alkyl ether (for example, Newpol PE-62), polyoxyethylene glycerin fatty acid ester, polyoxyethylene castor oil, hydrogenated castor oil, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene sorbitol fatty acid ester, Polyethylene glycol fatty acid ester, fatty acid monoglyceride, polyglycerin fatty acid ester, sorbitan fatty acid ester, propylene glycol fat Esters, sucrose fatty acid esters, fatty acid alkanolamides, polyoxyethylene fatty acid amides, polyoxyethylene alkyl amines, alkyl amine oxides, acetylene glycol, acetylene alcohol, and the like.

  Further, among conventionally known surfactants, those having a siloxane structure as a nonpolar site are referred to as silicone surfactants, and those having a perfluoroalkyl group are referred to as fluorine surfactants. In the invention, all of them are targeted. Examples of the silicone surfactant include polyester-modified silicone, acrylic-terminated polyester-modified silicone, polyether-modified silicone, acrylic-terminated polyether-modified silicone, polyglycerin-modified silicone, and aminopropyl-modified silicone. In addition, as fluorosurfactants, perfluoroalkyl sulfonates, perfluoroalkyl carboxylates, perfluoroalkyl phosphates, perfluoroalkyltrimethylammonium salts, perfluoroalkylethylene oxide adducts, perfluoroalkyl groups Containing oligomers and the like. These various surfactants are used alone or in admixture of two or more.

  Furthermore, in the coated sand used in the present invention, in addition to the above-described surfactant, it is also effective to add a moisturizer as a further additive to the coating layer. By further adding a moisturizing agent to the coating layer containing water glass or a surfactant, the swellability of the coated sand wetted by moisture during mold molding is solidified or cured by heating. , Can be maintained stably. The content of the humectant in the present invention is desirably 0.1 to 20.0 parts by mass with respect to 100 parts by mass of the solid content of the water glass in the coating layer, and in particular 0.5 to 15. 0 parts by mass is more desirable, and 0.75 to 12.5 parts by mass is most desirable. Moreover, as such a humectant, a polyhydric alcohol, a water-soluble polymer compound, hydrocarbons, saccharides, protein, an inorganic compound, etc. can be selected and used.

  Specifically, as the polyhydric alcohol, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, polypropylene glycol, dipropylene glycol, propylene glycol, butylene glycol, 1,2-butanediol, 1,2-pentanediol, 1,5-pentanediol, 1,2-hexanediol, 2-ethyl-1,3-hexanediol, 1,6-hexanediol, 1,2-heptanediol, 1,2-octanediol, 1,2, Examples include 6-hexanetriol, thioglycol, hexylene glycol, glycerin, trimethylolethane, and trimethylolpropane. The water-soluble polymer compound particularly refers to a compound having 5 to 25 alcoholic hydroxyl groups per 1000 molecular weight. Examples of such water-soluble polymer compounds include vinyl alcohol polymers such as polyvinyl alcohol and various modified products thereof; celluloses such as alkyl cellulose, hydroxyalkyl cellulose, alkyl hydroxyalkyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, and hydroxypropyl methyl cellulose. Derivatives; starch derivatives such as alkyl starch, carboxymethyl starch and oxidized starch; and water-absorbing polymers such as sodium polyacrylate. Examples of the hydrocarbons include aliphatic hydrocarbons, alicyclic hydrocarbons, aromatic hydrocarbons, petroleum ether, petroleum benzyl, tetralin, decalin, tertiary amylbenzene, dimethylnaphthalene and the like. Examples of saccharides include polysaccharides such as monosaccharides, oligosaccharides, and dextrins. Among them, monosaccharides are saccharides that are not decomposed into simpler saccharides by hydrolysis. Carbon dioxide (monosaccharide having 3 carbon atoms) to decacarbonose (monosaccharide having 10 carbon atoms), more preferably hexose sugar (monosaccharide having 6 carbon atoms). Examples of proteins include gelatin. In addition, examples of inorganic compounds include sodium chloride, sodium sulfate, calcium chloride, magnesium chloride, and silicate. These various humectants are used alone or in admixture of two or more.

  In addition, various conventionally known moisturizers include those that are water-soluble to those that are sparingly water-soluble. In the present invention, the viscosity increases when poured into water at room temperature (25 ° C.). A moisturizing agent with a low is advantageously used. Specifically, in the case of a water-soluble humectant, an amount of humectant corresponding to 20% of the mass of water is added to water at room temperature, and the mixture is stirred for 1 hour. A moisturizing agent of 8-10 cP, preferably 0.8-5 cP, will be used advantageously. On the other hand, a poorly water-soluble humectant exhibits an effect as a humectant when dispersed in water. Even a poorly water-soluble humectant has a mass of 20 It is advantageous that a moisturizing agent in an amount corresponding to% is added, stirred for 1 hour, the stirred solution (mixture of water and moisturizing agent) is filtered, and the viscosity of the obtained filtrate is within the above range. Used for. From the above, the humectant advantageously used in the present invention includes cellulose derivatives such as glycerin and hydroxypropylmethylcellulose, water-absorbing polymers such as sodium polyacrylate, polysaccharides such as dextrin, and vinyl alcohols such as polyvinyl alcohol. And polyethylene glycol (polyethylene oxide) having a weight average molecular weight of 50,000 or more.

  Moreover, the coating layer in the coated sand according to the present invention has spherical particles having a particle diameter smaller than that of the refractory aggregate, specifically, an average particle diameter of 0.1 to 20 μm, preferably an average particle diameter of 0. Spherical particles having a diameter of 5 to 10.0 μm may be contained. By including such predetermined spherical particles in the coating layer, it is possible to more advantageously improve the filling property of the coated sand into the molding die (molding cavity) during molding. The content of such spherical particles is preferably 0.1 to 500 parts by mass, more preferably 0.3 to 300 parts by mass with respect to 100 parts by mass of the solid content of water glass in the coating layer. Yes, more preferably 0.5 to 200 parts by mass, and most preferably 0.75 to 150 parts by mass. The average particle diameter of the spherical particles can be determined from the particle size distribution measured by a laser diffraction type particle size distribution measuring device or the like.

  Furthermore, the spherical particles used in the present invention are not particularly limited as long as they have a spherical shape and are not necessarily required to have a true spherical shape. Usually, those having a sphericity of 0.5 or more are preferably 0. Those of 0.7 or more, more preferably 0.9 or more, are advantageously used. Here, the sphericity is the average value of the aspect ratio (minor axis / major axis ratio) obtained from the projection shape of 10 single particles randomly selected in scanning electron microscope observation. I mean. The material constituting the spherical particles is not particularly limited, but preferably, spherical particles such as silicon dioxide, aluminum oxide, and titanium oxide are preferably used.

  In addition, in the coated sand of the present invention, in addition to the surfactant, moisturizer and spherical particles described above, various known additives may be appropriately contained in the coating layer as necessary. Is possible.

  In addition, as such an additive, there is a lubricant, and it is desirable to include such a lubricant in the sand surface of the coated sand. In the present invention, since it is necessary to form a thin sand layer by thinly spreading the coated sand to a certain thickness, it is desirable to add a lubricant in order to improve the fluidity of the coated sand. . In addition, since the lubricant has water repellency, when the aqueous medium is sprayed on the dry sand layer, if it is a conventional coated sand, the dry coated sand and the aqueous medium are not easily adapted by the water repellency of the lubricant. However, according to the configuration of the present invention, since the water repellency of the lubricant is suppressed by the wettability by the surfactant, it is possible to simultaneously improve the fluidity and wettability of the coated sand.

  Moreover, as the usage-amount of this lubricant made to mention above, it is desirable that it is 0.1-10 mass parts with respect to 100 mass parts of solid content of the water glass in a coating layer, and 0.3-8 mass parts especially Is preferable, and 0.5 to 5 parts by mass is particularly preferable. If the amount of the lubricant contained is too small, the above-described effects may not be enjoyed advantageously.On the other hand, if the amount of the lubricant is too large, the mold strength may decrease, Furthermore, it is not a good idea from the viewpoint of cost effectiveness.

  Examples of the lubricant used in the present invention include waxes such as paraffin wax, synthetic polyethylene wax, and montanic acid wax; fatty acid amides such as stearic acid amide, oleic acid amide, erucic acid amide; methylene bis stearic acid amide, ethylene Alkylene fatty acid amides such as bis-stearic acid amide; stearic acid, stearyl alcohol; stearic acid metal salts such as lead stearate, zinc stearate, calcium stearate, magnesium stearate; stearic acid monoglyceride, stearyl stearate, hydrogenated oil, graphite It is possible to use molybdenum disulfide, talc, mica and the like. Among these, calcium stearate is particularly preferable.

  In the present invention, solid oxides and salts are also advantageously used as one of the additives. By containing these solid oxides and salts, it is possible to advantageously improve the moisture resistance of the coated sand. In addition, as solid oxide, use of oxides, such as silicon, zinc, magnesium, aluminum, calcium, lead, boron, is effective, for example. Among these, the use of silicon dioxide, zinc oxide, aluminum oxide, and boron oxide is particularly desirable. Of silicon dioxide, precipitated silicic acid and exothermic silicic acid are preferably used. On the other hand, examples of the salt include silicic fluoride, silicate, phosphate, borate, tetraborate, carbonate, etc. Among them, zinc carbonate, basic zinc carbonate, metaboric acid The use of potassium, sodium tetraborate or potassium tetraborate is preferred. These solid oxides and salts are generally used in such an amount that the ratio is about 0.5 to 5% by mass with respect to the solid content of the water glass in the coating layer of the coated sand.

  Furthermore, it is also effective to include a coupling agent that strengthens the bond between the refractory aggregate and water glass as other additives, such as silane coupling agents, zircon coupling agents, titanium coupling agents, etc. Can be used. In addition, release of paraffin, wax, light oil, machine oil, spindle oil, insulating oil, waste oil, vegetable oil, fatty acid ester, organic acid, fine graphite particles, mica, meteorite, fluorine release agent, silicone release agent, etc. Molds can also be used. Each of these various additives is generally in an amount such that the ratio is 5% by mass or less, preferably 3% by mass or less, based on the solid content of the water glass in the coated sand coating layer. It is contained in

By the way, when manufacturing a dry coated sand having room temperature fluidity used in the present invention, generally, water glass as a binder is used for a fireproof aggregate, a surfactant or as required. Kneading or mixing with the additives used in this process, and mixing uniformly to cover the surface of the refractory aggregate with water glass. Additives such as surfactants to the coating layer A method of forming a coating layer containing water glass, a surfactant or the like on the surface of the refractory aggregate by incorporating and watering off the water of such water glass is employed. In such a technique, the water vapor in the coating layer needs to be rapidly evaporated before the water glass solidifies or hardens, so that the water glass in the form of an aqueous solution is used against the refractory aggregate. In general, it is desirable to remove the water content within 5 minutes, more preferably within 3 minutes, after adding (mixing) and additives, to obtain dry powder coated sand. If the transpiration time becomes longer, the mixing (kneading) cycle becomes longer, the productivity of the coated sand is lowered, and the time that the water glass is in contact with CO ₂ in the air becomes longer, resulting in inactivation. This is because there is a high risk of occurrence.

  Moreover, in the manufacturing process of the above-mentioned coated sand, as one of effective means for rapidly evaporating the water in the water glass, the refractory aggregate is preheated and water in the form of an aqueous solution is added. A technique of kneading or mixing glass and additives and mixing them is preferably employed. By mixing or mixing water glass and additives with this preheated refractory aggregate, the water in the water glass is very quickly heated by the heat of such refractory aggregate. Since the amount of water in the coated sand obtained can be effectively reduced, a dry powder having room temperature fluidity can be advantageously obtained. is there. In order to quickly evaporate moisture at this time, it is also effective to employ a method of blowing hot air into the kneading vessel, a method of heating the kneading vessel, and a method of reducing the pressure inside the kneading vessel. Here, the preheating temperature of the refractory aggregate is appropriately selected according to the water content of the water glass, the blending amount thereof, etc., but generally a temperature of about 100 to 200 ° C. is preferable. A temperature of about 120 to 180 ° C. is employed. If the preheating temperature is too low, it is not possible to effectively evaporate water, and it takes time to dry. Therefore, it is desirable to employ a temperature of 100 ° C. or higher. If the coating sand is too high, the water glass component is hardened when the resulting coated sand is cooled, and in addition, the formation of composite particles progresses, so the function as the coated sand, especially the strength of the final mold obtained. This causes problems in physical properties.

  In the coated sand used in the present invention, the surfactant contained in the coating layer containing water glass and other additives used as necessary, such as humectants and spherical particles, are previously added to the water glass. It may be added to the refractory aggregate in a mixed state and kneaded. At the time of kneading, it may be added and kneaded separately from the water glass. May be added and kneaded with a time difference. Therefore, the coating layer in the coated sand according to the present invention is, for example, in a state in which the water glass and the surfactant are integrally integrated, or from the surface of the refractory aggregate to the outside, the solid content of the water glass. While the concentration of (non-volatile content) gradually decreases or increases, the concentration of the additive such as a surfactant gradually increases or decreases.

(Layered modeling method)
By the way, the method for manufacturing a laminated mold according to the present invention is carried out using the coated sand obtained as described above, for example, as shown in FIGS. That is, first, as shown in FIG. 1, the mold forming apparatus used in the present invention has a rectangular table 12 that can be slid vertically in a vertical direction in a container-like frame 10 having a square planar shape. Is arranged. Further, as shown in FIGS. 1 to 3, the modeling apparatus is provided in a storage tank 16 that supplies the coated sand 14 positioned above the frame 10 and a lower part of the storage tank 16. The coated sand 14 supplied from the discharge port 18 to the upper surface of the table 12 is thinly spread on a flat surface to have a constant thickness, and a thin layer of sand 20 is formed. An inkjet spraying device 26 serving as a selective spraying means for spraying on a predetermined portion and a heater 30 provided with a heating wire 32 as a heating element are provided, which are selectively used in accordance with each process of manufacturing the mold layer. It is switched to and is arranged.

  The ink jet spraying device 26 has a nozzle 28 that can move along the upper surface of the sand layer 20 as shown in FIG. 2 together with a storage device and a control device (not shown), and can spray the aqueous medium to be used. It has become. The storage device stores a predetermined two-dimensional pattern (planar shape) of a predetermined mold layer 34 (see FIG. 5) formed in each sand layer 20 as an image signal. While controlling the operation according to the image signal, a predetermined aqueous medium can be ejected (spread) in a predetermined plane shape (pattern) to each sand layer 20. Here, the switching of the equipment in each process is automatically performed, but of course, it is also possible to perform the switching by a manual or semi-automatic method.

  In addition, the heater 30 shown in FIG. 3 can be heated by using the heating wire 32 as a heating element. As the heating element for such a heating wire 32, various known types of heating elements can be used. Can be selected and used, for example, using metal heating elements (Nichrome wire, Kanthal wire, platinum wire, etc.), silicon carbide, molybdenum disilicide, lanthanum chromite, molybdenum, carbon, etc. It is also possible to heat. The heater 30 is not particularly limited as long as it can be heated, and an infrared generator, a microwave generator, or the like can also be used.

  In the above-described embodiment, the selective spraying means configured by the ink jet spraying device 26 is a device that can selectively spray a predetermined aqueous medium to a predetermined position on the sand layer 20. In addition, an ink jet type spraying apparatus as illustrated is advantageously used, but in addition, a mask in which a predetermined aqueous medium is sprayed only on a necessary portion of the sand layer 20 using a mask. A system-type spraying device or the like can also be employed as appropriate.

  Then, as one method for manufacturing the target laminated mold according to the present invention using the apparatus as described above, the following manufacturing procedure is adopted to manufacture the mold layer 34, and the mold layer is further manufactured. As a result of stacking and integrating 34, a three-dimensional stacked mold 36 (target mold) is formed.

<First step>
First, in the stage before manufacture, the upper surface of the frame 10 of the modeling apparatus and the upper surface of the table 12 are positioned on the same plane. Then, when the modeling process starts, the table 12 is slid downward by the height of the sand layer 20. Next, the coated sand 14 stored in the storage tank 16 is supplied so as to be evenly spread on the table 12 with a substantially uniform thickness while the supply amount from the discharge port 18 is controlled [FIG. ) State]. At this time, the height per one layer of the sand layer 20 is formed as a step corresponding to the distance that the table 12 slides downward, for example, a step of 0.3 mm. In addition, this level | step difference is formed so that it may become always uniform height for every layer laminated | stacked, and generally it is desirable to set it as a level | step difference of about 0.1 mm-3 mm.

  Then, when the supply of the coated sand 14 onto the table 12 is finished, the extending member 24 is moved in the horizontal direction along the upper surface of the frame 10, and the excess coated sand 14 is scraped off. Thereby, the sand layer 20 thinly developed on the table 12 is formed in a predetermined thickness [state of FIG. 1 (b)].

<Second step>
Next, as shown in FIG. 2, droplets, a liquid or mist-like aqueous medium 22 are sprayed from the nozzles 28 of the inkjet spraying device 26 toward the sand layer 20 for each minute region in a predetermined planar shape. Is done. Here, the determined planar shape is obtained by dividing the shape of the mold to be manufactured into a plurality of regions at equal intervals about the thickness of the sand layer, and depending on the mold to be manufactured. For each sand layer, the aqueous medium 22 is sprayed in order from the bottom based on the planar shape of each layer. For example, by obtaining sand mold shape data from CAD data of the product shape and using this as cross-sectional shape data for each thickness of the sand layer, a predetermined planar shape of each layer can be set. In this inkjet spraying device 26, the nozzle diameter of the nozzle 28 for ejecting the aqueous medium 22 is extremely small, for example, about 20 to 100 μm. However, since the liquid to be ejected is an aqueous medium, the nozzle There is no such problem as clogging.

  In this way, the coated sand 14 is moistened by the aqueous medium 22 sprayed onto the specific area of the sand layer 20, so that the water glass of the coating layer in the coated sand 14 is dissolved in the aqueous medium 22 in the fire resistance. Covering the aggregate, the water glass will aggregate between the sand grains. At this time, since the coated sand 14 contains water glass and a surfactant, the wettability of the water is improved by such a surfactant, so that the liquid can easily be adapted to the dry coated sand. Thus, the aqueous medium can be rapidly penetrated into the coated sand. Thereby, the application quantity of an aqueous medium can be reduced to the minimum necessary.

  Here, as a spraying method of the aqueous medium 22, the method is particularly limited as long as an appropriate amount of the aqueous medium 22 can be sprayed on the sand layer 20 so as to wet the coated sand 14 so as not to increase too much. For example, in addition to the method of spraying the aqueous medium, a method of dropping the aqueous medium or spraying the aqueous medium in a mist form using a sprayer or the like is appropriately employed.

  Further, since it is necessary to dry the coated sand 14 after the coated sand 14 is moistened with the aqueous medium 22, it is desirable that the aqueous medium 22 to be sprayed is at a room temperature or a temperature higher than the room temperature. For this reason, it is desirable that the temperature of the aqueous medium is generally in the temperature range of about 20 to 100 ° C, more preferably about 30 to 95 ° C. In addition, when using the vapor | steam of an aqueous medium, it is preferable that it is 80-100 degreeC vapor | steam.

  In the present invention, water is typically used as the aqueous medium 22, and such water must be mixed with dust, dust, etc., such as pure water, tap water, distilled water, industrial water, and the like. For example, although not particularly limited, pure water or distilled water is preferable from the viewpoint of preventing clogging of the nozzle. Further, it is preferable to add a surfactant to the aqueous medium 22. By adding a surfactant in the aqueous medium 22, in addition to improving the wettability of the surfactant contained in the coated sand 14, the phase of the coated sand 14 is increased by the action of the surfactant in the aqueous medium 22. The solubility is further improved. The surfactant to be added to the aqueous medium 22 is not particularly limited, but the same surfactant as that contained in the coated sand 14 is preferably used because the compatibility is improved.

  Further, the water may contain an acid or an ester as a curing agent or a curing accelerator. Among them, as the acid, sulfuric acid, hydrochloric acid, carbonic acid, and sulfonic acids are preferable, and as the ester, γ-butyrolactone, Lactones such as ε-caprolactone and esters derived from a C 1-10 alcohol and a C 1-10 carboxylic acid such as ethylene glycol diacetate, triacetin, diethylene glycol diacetate and triethylene glycol diacetate are preferred. . The alcohol having 1 to 10 carbon atoms may be monovalent or polyvalent. Moreover, drying accelerators such as alcohols such as methanol and ketones such as acetone and diacetone alcohol, which are organic solvents, PROXEL GXL (1,2-benzoisothiazole, manufactured by Lonza Japan Co., Ltd.) -3 (2H) -one) and PROXEL IB (polyhexamethylene biguanidine) can be added in a small amount. In this case, the viscosity of the aqueous medium is generally 0.1 to 50 cP, and more preferably 0.3 to 40 cP, since problems such as clogging from the nozzle occur when the viscosity increases. Furthermore, the surface tension may be 15 to 50 mN / m, and 20 to 40 mN / m is more desirable in order to make the aqueous medium 22 easily adapted to the sand layer 22.

<Third step>
For the sand layer 20 after the aqueous medium 22 is sprayed, a heater 30 provided with a heating wire 32 is disposed above the sand layer 20 at a predetermined interval, and the sand layer 20 is heated by the heat of the heater 30. Thus, the wet coated sand 14 is dried (the state of FIG. 3). Thereby, the coated sand 14 is moistened with the aqueous medium 22 in the second step, the water glass of the coating layer is melted, and the moisture of the coated sand 14 moistened in the third step is evaporated from the adhered state. Thus, the refractory aggregate to which the water glass is applied is solidified or hardened in a state of being bonded to each other, whereby one mold layer 34 is formed. Further, since the portion wetted with the aqueous medium 22 has better heat conductivity than the portion not wetted, only the portion wetted with the aqueous medium 22 of the coated sand 14 is efficiently solidified or cured by heating. Will be able to. Further, the improvement of the wettability of the coated sand 14 can reduce the amount of the aqueous medium sprayed to the minimum necessary, so that the heating time can be shortened and distortion due to heating can be suppressed. Furthermore, the time from spraying the aqueous medium to the heating time can be shortened, and the molding cycle can be shortened. At this time, the heating by the heater 30 dries the coated sand 14 and solidifies or hardens it, so that the sand layer 20 is about 30 to 180 ° C, preferably 60 to 150 ° C, more preferably 80 to 140 ° C. As long as it can be heated to about 100 ° C., more preferably about 100 to 120 ° C., and this does not cause a significant temperature difference in the sand layer 20, it is possible to effectively suppress warping of the hardened sand layer (20). I can do it. Moreover, since the heating temperature at this time can be solidified or cured at a low temperature of about 100 ° C., the odor generated by heating the conventional coated sand to a high temperature (about 200 to 300 ° C.) is also effectively suppressed. It can be done. For this reason, the heater 30 does not need to have a high output, and exhibits features such as less energy consumption for heating.

  Here, when the sand layer 20 is heated and dried, the drying can be promoted by performing it in an atmosphere of heated air. As another method, curing can be promoted by heating and drying in an atmosphere containing carbon dioxide or gasified ester or in an atmosphere of an inert gas such as nitrogen. The method for implementing the above-described promotion means is not particularly limited as long as heating and drying can be performed in a predetermined gas atmosphere. For example, the inside of the apparatus is sealed and the internal atmosphere is changed. There are techniques such as replacement with heated air, carbon dioxide, gasified ester or inert gas, and modeling in the atmosphere in which the gas is replaced. It is also possible to adjust the heating temperature inside the apparatus.

  In addition, before or after the heating, a gas such as air, heated air, superheated steam, carbon dioxide gas, gasified ester or inert gas may be blown or ventilated. Furthermore, drying of the coated sand 14 can be promoted by flowing the gas. The method for spraying or venting gas is not particularly limited as long as the coated sand 14 can be carried out without being blown away by the gas to be sprayed or by ventilation. There is a method of ventilating by blowing a gas from a jet outlet installed on the top of the apparatus or circulating the atmosphere inside the apparatus.

  Furthermore, in order to prevent water vapor | steam remaining in an apparatus, the process of attracting | sucking the gas in an apparatus and exhausting it out of the system may be included. The gas suction is preferably performed after the sand layer is heated and dried in the third step. However, as long as each step is not adversely affected, it may be performed during the third step or during all the steps. Good.

<Repetition process>
Then, using the series of mold layer 34 forming steps including the first step, the second step, and the third step as one turn (cycle), the table 12 is further slid downward by the height of one sand layer. 4 (state of FIG. 4), by repeating the turn of the forming process of the template layer 34, a new template layer 34 is integrally formed on the already formed template layer 34. Thus, a laminated structure is realized. Further, by repeating the formation of the template layer 34 several times, the template layer 34 is sequentially laminated and integrated (the state shown in FIG. 5), and thus is constituted by an appropriate number of template layers 34. A laminated mold 36 having a desired three-dimensional shape is manufactured. At this time, because the wetness of the coated sand to moisture is stable without any variation in the curing of each layer in the lamination, the strength between the formed layers is increased, and the strength of the mold is advantageously improved. It can be done. Then, the target mold | type (36) will be taken out by removing the sand which has not been hardened or hardened from the modeling apparatus (frame 10) (state of FIG. 6). Further, the obtained mold (36) may be further subjected to secondary firing in order to suppress variation in strength. The conditions for the secondary firing are 5 minutes to 2 hours, preferably 10 minutes to 1 hour in a thermostatic chamber heated to 100 to 200 ° C, preferably 120 to 180 ° C.

  In the mold layer forming process including the first process, the second process, and the third process described above, the switching of the equipment in each process is automatically performed, but of course, manually or semi-automatically. Even if the switching is performed, there is no problem.

  Hereinafter, the present invention will be more specifically clarified by using some examples, but the present invention is not construed as being limited in any way by the description of such examples. Should be understood. In the following examples and comparative examples, “%” and “parts” are shown on a mass basis unless otherwise specified. Moreover, the water content of the coated sand (CS) obtained in Examples and Comparative Examples, water permeability, bending strength, and evaluation of the breaking state were evaluated as follows.

-Measurement of water content with respect to solid content of water glass-
10g of each CS is weighed and stored in a crucible that has been baked and weighed, and the mass loss (%) after exposure to heat at 900 ° C for 1 hour is used to determine the amount of water in the CS and the organic content. Total amount [hereinafter referred to as “(moisture + organic content) amount”], and is referred to as “W1”. ] Is calculated from the following equation (1). Here, the organic content is the total amount of the surfactant and other liquid additives (hereinafter referred to as organic content). The weighing is measured to the fourth decimal place. Next, the solid content (B1) of the water glass with respect to CS is calculated using the following formula (2). And (water + organic content) amount (W1) in CS, solid content amount (B1) of water glass with respect to CS, addition amount (A) of organic content with respect to 100 parts of solid content of water glass, and later described. From the solid content ratio (C) in the organic content measured according to the method, the water content with respect to the solid content of the water glass (CS water content with respect to the solid content of the water glass in the coating layer: W2) is expressed by the following equation (3). Use to calculate. W2 calculated as described above is shown as “moisture content (mass%)” in Table 1 below.
W1 = [(M1-M2) / M3] × 100 (1)
[W1: (water + organic content) amount (%) in CS, M1: total mass (g) of crucible and CS before firing, M2: total mass (g) of crucible and CS after firing, M3: firing Mass of previous CS (g)]
B1 = [B2 / (100 + B2)] × (100−W1) (2)
[B1: solid content (%) of water glass relative to CS, B2: solid content (part) of water glass added to 100 parts of sand, W1: (water + organic content) amount (%) in CS W2 = [(W1 / B1) × 100] − (A × C / 100) (3)
[W2: CS moisture content (%) with respect to solid content of water glass in coating layer, W1: (water + organic content) content (%) in CS, B1: solid content of water glass with respect to CS (%)
%), A: addition amount (parts) of organic component to 100 parts of solid content of water glass, C: solid content ratio (%) in organic component in CS]

-Measurement of solid content in organic content-
First, a sample is prepared which is composed of a surfactant and other liquid additives, and whose blending ratio is the same as the ratio of addition to sand (fireproof aggregate). Next, 10 g of the previously prepared sample was placed in an aluminum foil dish (length: 90 mm, width: 90 mm, height: 15 mm), weighed, and heated on a heating plate held at 180 ± 1 ° C. Place the dish and let it stand for 20 minutes, then let it cool in a desiccator. Then, the aluminum foil dish after cooling is weighed, and the solid content ratio (C) in the organic content is calculated from the following formula (4).
C = [mass of aluminum foil dish after drying (g) / mass of aluminum foil dish before drying (g)]
× 100 (4)

−Measurement of bending strength−
About a test piece having a size of width: 1.0 cm × height: 1.0 cm × length: 6.0 cm obtained by layered modeling using each CS, a load was applied perpendicularly to the stacking direction, The breaking load is measured using a measuring device (manufactured by Takachiho Seiki Co., Ltd .: Digital foundry sand strength tester). Then, using this measured breaking load, the bending strength is calculated by the following equation (5).
Folding strength (N / cm ² ) = 1.5 × LW / ab ² (5)
[L: distance between fulcrums (cm), W: breaking load (N), a: width of test piece (cm), b: thickness of test piece (cm)]

-Evaluation of water permeability in coated sand-
Cotton is packed into a glass tube having an outer diameter of 10 mmφ and an inner diameter of 9 mmφ to produce a simple column. Into it, 22 g of CS is put and vibrated for 1 minute to close-pack. Next, 2 g of the liquid to be infiltrated (water) is put into this sand-filled column, and when the liquid has infiltrated 20 mm from the top surface of the packed sand, the measurement is started. Five minutes after the start of this measurement, the distance (mm) that has further penetrated from the position of 20 mm is measured, and that distance is taken as the penetration amount.

-Observation of fracture state of bending strength-
After measuring the above bending strength, the fracture surface is visually observed and evaluated according to the following criteria.
Delamination: A phenomenon in which the test piece cracks in the same direction as the laminated surface was observed.
No peeling: The phenomenon that the test piece cracks in the same direction as the laminated surface was not observed.
It should be noted that delamination is a phenomenon that occurs when the strength between the layers at the time of lamination is weak and occurs because the liquid has not sufficiently permeated.

-Production Example 1 of Dry CS-
Lunamos # 110 (trade name: manufactured by Kao Quaker Co., Ltd.), a commercially available artificial sand for casting, is prepared as a fireproof aggregate, and a commercially available product: No. 2 sodium silicate (product) Name: Fuji Chemical Co., Ltd., SiO ₂ / Na ₂ O molar ratio: 2.5, solid component: 41.3%) were prepared. And after heating said lunamos # 110 to the temperature of about 180 degreeC, it introduce | transduces into a whirl mixer (made by Enshu Iron Works Co., Ltd.), Furthermore, the said water glass is 7.26 with respect to 100 parts of lunamos # 110. Parts (solid component: 3.0 parts) and then added as an anionic surfactant (anionic surfactant): commercially available Olfine PD-301 (trade name: manufactured by Nissin Chemical Industry Co., Ltd.) This was added at a ratio of 0.03 parts (100 parts of solid content of water glass) to 100 parts of Lunamos # 110 and kneaded for 3 minutes to obtain moisture. The mixture was stirred and mixed until the lump of sand collapsed, 0.03 part of calcium stearate was further added, stirred and mixed, and then taken out to obtain dry CS1 having room temperature fluidity. When the moisture content of CS1 after such kneading was calculated, it was an amount corresponding to 28% by mass of the solid content of water glass in the coating layer.

-Production Example 2- of Dry CS
A dry state having room temperature fluidity according to the same procedure as in Production Example 1 except that the addition amount of the anionic surfactant was 0.12 part (4 parts with respect to 100 parts of the solid content of water glass). Coated sand: CS2 was obtained. When the moisture content of the obtained CS2 was calculated, it was an amount corresponding to 29% by mass of the solid content of water glass in the coating layer.

-Production example of dry CS 3-
A dry state having room temperature fluidity according to the same procedure as in Production Example 1 except that the anionic surfactant was added in an amount of 0.3 part (10 parts relative to 100 parts of water glass solids). Coated sand: CS3 was obtained. When the moisture content of the obtained CS3 was calculated, it was an amount corresponding to 30% by mass of the solid content of water glass in the coating layer.

-Production Example 4- of Dry CS
As a surfactant, a commercially available silicone surfactant: KF643 (trade name: manufactured by Shin-Etsu Chemical Co., Ltd.) was used, and this was added to 100 parts of fire-resistant aggregate (Lunamos # 110). Except that it was added at a ratio of 09 parts (3 parts with respect to 100 parts of the solid content of water glass), dry coated sand: CS4 having room temperature fluidity was obtained according to the same procedure as in Production Example 1 above. . When the moisture content of the obtained CS4 was calculated, it was an amount corresponding to 29% by mass of the solid content of water glass in the coating layer.

-Production example of dry CS-
As a surfactant, a commercially available nonionic surfactant: Surfynol 485 (trade name: manufactured by Nissin Chemical Industry Co., Ltd.) is used, and this is added to 100 parts of fire-resistant aggregate (Lunamos # 110). , 0.12 parts (4 parts with respect to 100 parts of the solid content of water glass) in the same manner as in Production Example 1 above, dry coated sand having room temperature fluidity: CS5 Got. When the moisture content of the obtained CS5 was calculated, it was an amount corresponding to 29% by mass of the solid content of water glass in the coating layer.

-Production example 6 of dry CS-
Commercially available product: No. 1 sodium silicate (trade name: manufactured by Fuji Chemical Co., Ltd., molar ratio of SiO ₂ / Na ₂ O: 2.1, solid component: 48.5%) is used as the water glass for the binder. Moreover, the procedure similar to the said manufacture example 2 except the addition amount having been 6.19 parts (solid component: 3.0 parts) with respect to 100 parts of fireproof aggregates (Lunamos # 110). Thus, dry coated sand CS6 having room temperature fluidity was obtained. And when the moisture content of obtained CS6 was computed, it was the quantity equivalent to 31 mass% of solid content of the water glass in a coating layer.

-Production Example 7 of Dry CS-
As the water glass for the binder, a commercially available product: No. 3 sodium silicate (trade name: manufactured by Fuji Chemical Co., Ltd., molar ratio of SiO ₂ / Na ₂ O: 3.2, solid component: 38%) is used. The addition amount was 7.89 parts (solid component: 3.0 parts) with respect to 100 parts of the refractory aggregate (Lunamos # 110), according to the same procedure as in Production Example 2 above. Dry coated sand: CS7 having room temperature fluidity was obtained. When the moisture content of the obtained CS7 was calculated, it was an amount corresponding to 30% by mass of the solid content of water glass in the coating layer.

-Production Example 8 of Dry CS-
Except not adding a surfactant, according to the procedure similar to the said manufacture example 2, dry coated sand: CS8 which has normal temperature fluidity was obtained. When the moisture content of the obtained CS8 was calculated, it was an amount corresponding to 29% by mass of the solid content of water glass in the coating layer.

-Production example 9 of dry CS-
A dry coated sand CS9 having room temperature fluidity was obtained in the same manner as in Production Example 6 except that the surfactant was not added. When the moisture content of the obtained CS9 was calculated, it was an amount corresponding to 31% by mass of the solid content of water glass in the coating layer.

-Production example 10 of dry CS-
A dry coated sand: CS10 was obtained according to the same procedure as in Production Example 7 except that the surfactant was not added. When the moisture content of the obtained CS10 was calculated, it was an amount corresponding to 29% by mass of the solid content of water glass in the coating layer.

  Next, using the dry CS1-10 obtained above, in Examples 1-7 and Comparative Examples 1-3, the above-described permeability evaluation was performed, and the results are shown in Table 1. On the other hand, a laminated mold was formed from each CS, and its strength was evaluated.

Example 1
Using the previously prepared CS 1, a predetermined laminated mold was formed by the laminated mold manufacturing apparatus according to the embodiment shown in FIGS. 1 to 5. That is, first, in the first step, the table (12) is slid downward by 0.3 mm, and then CS1 is thinly developed on the table (12) to form a sand layer (20). In the process, by spraying a mist-like aqueous medium (22) by an ink jet method for each minute region so as to give a predetermined planar shape of 203 mm × 254 mm, such an aqueous medium (22 ) In the sprayed area of the sand layer (20). Thereafter, using a halogen lamp as a heater (30), a predetermined planar shape portion was heated and cured or solidified to obtain a mold layer (34) having a shape corresponding to the portion. The aqueous medium (22) used there had a composition of 93% by weight of water, 6% by weight of a humectant and 1% by weight of a surfactant (viscosity 1.1 mPa · s / 25 ° C., surface tension 31.5 mN). / M) and was used at a temperature of 25 ° C.

  Then, using the series of processes including the first process and the second process as one turn, the mold layer (34) until the thickness (height) of the laminated mold (modeled object 36) becomes 10 mm. The additive manufacturing operation was repeated. Then, CS1 which is not solidified or hardened is removed from the laminated mold manufacturing apparatus, and the shaped article (36) is taken out and baked at a temperature of 150 ° C. for 10 minutes, whereby the target laminated mold (36) is obtained. Manufactured. And the bending strength and fracture state of this obtained laminated mold were observed, and the results are shown in Table 1 below.

-Examples 2-7, Comparative Examples 1-3
CS1 is replaced with CS2 to 10 respectively, and the layered modeling of the mold is performed in the same manner as in Example 1, and the modeled product obtained is baked at a temperature of 150 ° C. for 10 minutes to achieve the desired layered structure. A mold (36) was produced. And the bending strength and fracture state of the obtained laminated mold were observed, and the results are shown in Table 1 below.

  From the results of Table 1, it is recognized that in Examples 1 to 7, the water permeability in the coated sand is improved. And by this, when forming each layer at the time of additive manufacturing, it is possible to form a stable layer by spreading the aqueous medium evenly, and also improve the strength between layers from the fractured state of Examples 1-7. From the viewpoint of bending strength, it can be seen that the strength of the entire mold can be improved.

DESCRIPTION OF SYMBOLS 10 Frame 12 Table 14 Coated sand 16 Storage tank 18 Discharge port 20 Sand layer 22 Aqueous medium 24 Extension member 26 Inkjet spraying device 28 Nozzle 30 Heater 32 Heating wire 34 Mold layer 36 Molded article (lamination mold)

Claims (10)

A thin sand layer is formed using a coated sand formed by coating a fireproof aggregate with a binder, and then an aqueous medium is sprayed on the sand layer and heated to form a solidified layer or a hardened layer having a predetermined two-dimensional pattern. In the method for producing the target three-dimensional laminated mold by laminating the solidified layer or the cured layer by repeating the operation of forming
As the coated sand, dry coated sand obtained by forming a coating layer containing a surfactant together with water glass as a binder on the surface of the refractory aggregate is used. A method for producing a laminated mold.   The surfactant is selected from the group consisting of a cationic surfactant, an anionic surfactant, an amphoteric surfactant, a nonionic surfactant, a silicone surfactant, and a fluorosurfactant. The method for producing a laminated mold according to claim 1.   The content of the surfactant is a ratio of 0.1 to 20.0 parts by mass with respect to 100 parts by mass of the solid content of water glass in the coated sand. 3. A method for producing a laminated mold according to 2.   The method for producing a laminated mold according to any one of claims 1 to 3, wherein the aqueous medium contains a surfactant.   The method for producing a laminated mold according to claim 4, wherein the aqueous medium further contains at least one of a curing accelerator, a humectant, a drying accelerator, and a preservative.   The method for producing a laminated mold according to any one of claims 1 to 5, wherein the aqueous medium has a viscosity of 0.1 to 50 cP and a surface tension of 15 to 50 mN / m. .   The method for producing a laminated mold according to any one of claims 1 to 6, wherein the coated sand further contains a lubricant on the surface thereof.   The content of the lubricant is 0.1 to 10.0 parts by mass with respect to 100 parts by mass of the solid content of water glass in the coated sand. The manufacturing method of the lamination | stacking casting_mold | template of any one.   The method for producing a laminated mold according to any one of claims 1 to 8, wherein a moisture content in the coated sand is 5 to 55 mass% of a solid content of water glass. The method for producing a laminated mold according to any one of claims 1 to 9, wherein the dispersion of the aqueous medium on the sand layer is performed using an ink jet type spraying device.

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